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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2007 Oracle.  All rights reserved.
  */
 
 #include <linux/sched.h>
 #include <linux/sched/mm.h>
 #include <linux/bio.h>
 #include <linux/slab.h>
 #include <linux/blkdev.h>
 #include <linux/ratelimit.h>
 #include <linux/kthread.h>
 #include <linux/raid/pq.h>
 #include <linux/semaphore.h>
 #include <linux/uuid.h>
 #include <linux/list_sort.h>
 #include <linux/namei.h>
 #include "misc.h"
 #include "ctree.h"
 #include "extent_map.h"
 #include "disk-io.h"
 #include "transaction.h"
 #include "print-tree.h"
 #include "volumes.h"
 #include "raid56.h"
 #include "async-thread.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
 #include "dev-replace.h"
 #include "sysfs.h"
 #include "tree-checker.h"
 #include "space-info.h"
 #include "block-group.h"
 #include "discard.h"
 #include "zoned.h"
 
 #define BTRFS_BLOCK_GROUP_STRIPE_MASK   (BTRFS_BLOCK_GROUP_RAID0 | \
                      BTRFS_BLOCK_GROUP_RAID10 | \
                      BTRFS_BLOCK_GROUP_RAID56_MASK)
 
 const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
     [BTRFS_RAID_RAID10] = {
         .sub_stripes    = 2,
         .dev_stripes    = 1,
         .devs_max   = 0,    /* 0 == as many as possible */
         .devs_min   = 2,
         .tolerated_failures = 1,
         .devs_increment = 2,
         .ncopies    = 2,
         .nparity        = 0,
         .raid_name  = "raid10",
         .bg_flag    = BTRFS_BLOCK_GROUP_RAID10,
         .mindev_error   = BTRFS_ERROR_DEV_RAID10_MIN_NOT_MET,
     },
     [BTRFS_RAID_RAID1] = {
         .sub_stripes    = 1,
         .dev_stripes    = 1,
         .devs_max   = 2,
         .devs_min   = 2,
         .tolerated_failures = 1,
         .devs_increment = 2,
         .ncopies    = 2,
         .nparity        = 0,
         .raid_name  = "raid1",
         .bg_flag    = BTRFS_BLOCK_GROUP_RAID1,
         .mindev_error   = BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET,
     },
     [BTRFS_RAID_RAID1C3] = {
         .sub_stripes    = 1,
         .dev_stripes    = 1,
         .devs_max   = 3,
         .devs_min   = 3,
         .tolerated_failures = 2,
         .devs_increment = 3,
         .ncopies    = 3,
         .nparity        = 0,
         .raid_name  = "raid1c3",
         .bg_flag    = BTRFS_BLOCK_GROUP_RAID1C3,
         .mindev_error   = BTRFS_ERROR_DEV_RAID1C3_MIN_NOT_MET,
     },
     [BTRFS_RAID_RAID1C4] = {
         .sub_stripes    = 1,
         .dev_stripes    = 1,
         .devs_max   = 4,
         .devs_min   = 4,
         .tolerated_failures = 3,
         .devs_increment = 4,
         .ncopies    = 4,
         .nparity        = 0,
         .raid_name  = "raid1c4",
         .bg_flag    = BTRFS_BLOCK_GROUP_RAID1C4,
         .mindev_error   = BTRFS_ERROR_DEV_RAID1C4_MIN_NOT_MET,
     },
     [BTRFS_RAID_DUP] = {
         .sub_stripes    = 1,
         .dev_stripes    = 2,
         .devs_max   = 1,
         .devs_min   = 1,
         .tolerated_failures = 0,
         .devs_increment = 1,
         .ncopies    = 2,
         .nparity        = 0,
         .raid_name  = "dup",
         .bg_flag    = BTRFS_BLOCK_GROUP_DUP,
         .mindev_error   = 0,
     },
     [BTRFS_RAID_RAID0] = {
         .sub_stripes    = 1,
         .dev_stripes    = 1,
         .devs_max   = 0,
         .devs_min   = 1,
         .tolerated_failures = 0,
         .devs_increment = 1,
         .ncopies    = 1,
         .nparity        = 0,
         .raid_name  = "raid0",
         .bg_flag    = BTRFS_BLOCK_GROUP_RAID0,
         .mindev_error   = 0,
     },
     [BTRFS_RAID_SINGLE] = {
         .sub_stripes    = 1,
         .dev_stripes    = 1,
         .devs_max   = 1,
         .devs_min   = 1,
         .tolerated_failures = 0,
         .devs_increment = 1,
         .ncopies    = 1,
         .nparity        = 0,
         .raid_name  = "single",
         .bg_flag    = 0,
         .mindev_error   = 0,
     },
     [BTRFS_RAID_RAID5] = {
         .sub_stripes    = 1,
         .dev_stripes    = 1,
         .devs_max   = 0,
         .devs_min   = 2,
         .tolerated_failures = 1,
         .devs_increment = 1,
         .ncopies    = 1,
         .nparity        = 1,
         .raid_name  = "raid5",
         .bg_flag    = BTRFS_BLOCK_GROUP_RAID5,
         .mindev_error   = BTRFS_ERROR_DEV_RAID5_MIN_NOT_MET,
     },
     [BTRFS_RAID_RAID6] = {
         .sub_stripes    = 1,
         .dev_stripes    = 1,
         .devs_max   = 0,
         .devs_min   = 3,
         .tolerated_failures = 2,
         .devs_increment = 1,
         .ncopies    = 1,
         .nparity        = 2,
         .raid_name  = "raid6",
         .bg_flag    = BTRFS_BLOCK_GROUP_RAID6,
         .mindev_error   = BTRFS_ERROR_DEV_RAID6_MIN_NOT_MET,
     },
 };
 
 /*
  * Convert block group flags (BTRFS_BLOCK_GROUP_*) to btrfs_raid_types, which
  * can be used as index to access btrfs_raid_array[].
  */
 enum btrfs_raid_types __attribute_const__ btrfs_bg_flags_to_raid_index(u64 flags)
 {
     const u64 profile = (flags & BTRFS_BLOCK_GROUP_PROFILE_MASK);
 
     if (!profile)
         return BTRFS_RAID_SINGLE;
 
     return BTRFS_BG_FLAG_TO_INDEX(profile);
 }
 
 const char *btrfs_bg_type_to_raid_name(u64 flags)
 {
     const int index = btrfs_bg_flags_to_raid_index(flags);
 
     if (index >= BTRFS_NR_RAID_TYPES)
         return NULL;
 
     return btrfs_raid_array[index].raid_name;
 }
 
 int btrfs_nr_parity_stripes(u64 type)
 {
     enum btrfs_raid_types index = btrfs_bg_flags_to_raid_index(type);
 
     return btrfs_raid_array[index].nparity;
 }
 
 /*
  * Fill @buf with textual description of @bg_flags, no more than @size_buf
  * bytes including terminating null byte.
  */
 void btrfs_describe_block_groups(u64 bg_flags, char *buf, u32 size_buf)
 {
     int i;
     int ret;
     char *bp = buf;
     u64 flags = bg_flags;
     u32 size_bp = size_buf;
 
     if (!flags) {
         strcpy(bp, "NONE");
         return;
     }
 
 #define DESCRIBE_FLAG(flag, desc)                       \
     do {                                \
         if (flags & (flag)) {                   \
             ret = snprintf(bp, size_bp, "%s|", (desc)); \
             if (ret < 0 || ret >= size_bp)          \
                 goto out_overflow;          \
             size_bp -= ret;                 \
             bp += ret;                  \
             flags &= ~(flag);               \
         }                           \
     } while (0)
 
     DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_DATA, "data");
     DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_SYSTEM, "system");
     DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_METADATA, "metadata");
 
     DESCRIBE_FLAG(BTRFS_AVAIL_ALLOC_BIT_SINGLE, "single");
     for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
         DESCRIBE_FLAG(btrfs_raid_array[i].bg_flag,
                   btrfs_raid_array[i].raid_name);
 #undef DESCRIBE_FLAG
 
     if (flags) {
         ret = snprintf(bp, size_bp, "0x%llx|", flags);
         size_bp -= ret;
     }
 
     if (size_bp < size_buf)
         buf[size_buf - size_bp - 1] = '\0'; /* remove last | */
 
     /*
      * The text is trimmed, it's up to the caller to provide sufficiently
      * large buffer
      */
 out_overflow:;
 }
 
 static int init_first_rw_device(struct btrfs_trans_handle *trans);
 static int btrfs_relocate_sys_chunks(struct btrfs_fs_info *fs_info);
 static void btrfs_dev_stat_print_on_load(struct btrfs_device *device);
 static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
                  enum btrfs_map_op op,
                  u64 logical, u64 *length,
                  struct btrfs_io_context **bioc_ret,
                  int mirror_num, int need_raid_map);
 
 /*
  * Device locking
  * ==============
  *
  * There are several mutexes that protect manipulation of devices and low-level
  * structures like chunks but not block groups, extents or files
  *
  * uuid_mutex (global lock)
  * ------------------------
  * protects the fs_uuids list that tracks all per-fs fs_devices, resulting from
  * the SCAN_DEV ioctl registration or from mount either implicitly (the first
  * device) or requested by the device= mount option
  *
  * the mutex can be very coarse and can cover long-running operations
  *
  * protects: updates to fs_devices counters like missing devices, rw devices,
  * seeding, structure cloning, opening/closing devices at mount/umount time
  *
  * global::fs_devs - add, remove, updates to the global list
  *
  * does not protect: manipulation of the fs_devices::devices list in general
  * but in mount context it could be used to exclude list modifications by eg.
  * scan ioctl
  *
  * btrfs_device::name - renames (write side), read is RCU
  *
  * fs_devices::device_list_mutex (per-fs, with RCU)
  * ------------------------------------------------
  * protects updates to fs_devices::devices, ie. adding and deleting
  *
  * simple list traversal with read-only actions can be done with RCU protection
  *
  * may be used to exclude some operations from running concurrently without any
  * modifications to the list (see write_all_supers)
  *
  * Is not required at mount and close times, because our device list is
  * protected by the uuid_mutex at that point.
  *
  * balance_mutex
  * -------------
  * protects balance structures (status, state) and context accessed from
  * several places (internally, ioctl)
  *
  * chunk_mutex
  * -----------
  * protects chunks, adding or removing during allocation, trim or when a new
  * device is added/removed. Additionally it also protects post_commit_list of
  * individual devices, since they can be added to the transaction's
  * post_commit_list only with chunk_mutex held.
  *
  * cleaner_mutex
  * -------------
  * a big lock that is held by the cleaner thread and prevents running subvolume
  * cleaning together with relocation or delayed iputs
  *
  *
  * Lock nesting
  * ============
  *
  * uuid_mutex
  *   device_list_mutex
  *     chunk_mutex
  *   balance_mutex
  *
  *
  * Exclusive operations
  * ====================
  *
  * Maintains the exclusivity of the following operations that apply to the
  * whole filesystem and cannot run in parallel.
  *
  * - Balance (*)
  * - Device add
  * - Device remove
  * - Device replace (*)
  * - Resize
  *
  * The device operations (as above) can be in one of the following states:
  *
  * - Running state
  * - Paused state
  * - Completed state
  *
  * Only device operations marked with (*) can go into the Paused state for the
  * following reasons:
  *
  * - ioctl (only Balance can be Paused through ioctl)
  * - filesystem remounted as read-only
  * - filesystem unmounted and mounted as read-only
  * - system power-cycle and filesystem mounted as read-only
  * - filesystem or device errors leading to forced read-only
  *
  * The status of exclusive operation is set and cleared atomically.
  * During the course of Paused state, fs_info::exclusive_operation remains set.
  * A device operation in Paused or Running state can be canceled or resumed
  * either by ioctl (Balance only) or when remounted as read-write.
  * The exclusive status is cleared when the device operation is canceled or
  * completed.
  */
 
 DEFINE_MUTEX(uuid_mutex);
 static LIST_HEAD(fs_uuids);
 struct list_head * __attribute_const__ btrfs_get_fs_uuids(void)
 {
     return &fs_uuids;
 }
 
 /*
  * alloc_fs_devices - allocate struct btrfs_fs_devices
  * @fsid:       if not NULL, copy the UUID to fs_devices::fsid
  * @metadata_fsid:  if not NULL, copy the UUID to fs_devices::metadata_fsid
  *
  * Return a pointer to a new struct btrfs_fs_devices on success, or ERR_PTR().
  * The returned struct is not linked onto any lists and can be destroyed with
  * kfree() right away.
  */
 static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid,
                          const u8 *metadata_fsid)
 {
     struct btrfs_fs_devices *fs_devs;
 
     fs_devs = kzalloc(sizeof(*fs_devs), GFP_KERNEL);
     if (!fs_devs)
         return ERR_PTR(-ENOMEM);
 
     mutex_init(&fs_devs->device_list_mutex);
 
     INIT_LIST_HEAD(&fs_devs->devices);
     INIT_LIST_HEAD(&fs_devs->alloc_list);
     INIT_LIST_HEAD(&fs_devs->fs_list);
     INIT_LIST_HEAD(&fs_devs->seed_list);
     if (fsid)
         memcpy(fs_devs->fsid, fsid, BTRFS_FSID_SIZE);
 
     if (metadata_fsid)
         memcpy(fs_devs->metadata_uuid, metadata_fsid, BTRFS_FSID_SIZE);
     else if (fsid)
         memcpy(fs_devs->metadata_uuid, fsid, BTRFS_FSID_SIZE);
 
     return fs_devs;
 }
 
 void btrfs_free_device(struct btrfs_device *device)
 {
     WARN_ON(!list_empty(&device->post_commit_list));
     rcu_string_free(device->name);
     extent_io_tree_release(&device->alloc_state);
     btrfs_destroy_dev_zone_info(device);
     kfree(device);
 }
 
 static void free_fs_devices(struct btrfs_fs_devices *fs_devices)
 {
     struct btrfs_device *device;
     WARN_ON(fs_devices->opened);
     while (!list_empty(&fs_devices->devices)) {
         device = list_entry(fs_devices->devices.next,
                     struct btrfs_device, dev_list);
         list_del(&device->dev_list);
         btrfs_free_device(device);
     }
     kfree(fs_devices);
 }
 
 void __exit btrfs_cleanup_fs_uuids(void)
 {
     struct btrfs_fs_devices *fs_devices;
 
     while (!list_empty(&fs_uuids)) {
         fs_devices = list_entry(fs_uuids.next,
                     struct btrfs_fs_devices, fs_list);
         list_del(&fs_devices->fs_list);
         free_fs_devices(fs_devices);
     }
 }
 
 static noinline struct btrfs_fs_devices *find_fsid(
         const u8 *fsid, const u8 *metadata_fsid)
 {
     struct btrfs_fs_devices *fs_devices;
 
     ASSERT(fsid);
 
     /* Handle non-split brain cases */
     list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
         if (metadata_fsid) {
             if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0
                 && memcmp(metadata_fsid, fs_devices->metadata_uuid,
                       BTRFS_FSID_SIZE) == 0)
                 return fs_devices;
         } else {
             if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0)
                 return fs_devices;
         }
     }
     return NULL;
 }
 
 static struct btrfs_fs_devices *find_fsid_with_metadata_uuid(
                 struct btrfs_super_block *disk_super)
 {
 
     struct btrfs_fs_devices *fs_devices;
 
     /*
      * Handle scanned device having completed its fsid change but
      * belonging to a fs_devices that was created by first scanning
      * a device which didn't have its fsid/metadata_uuid changed
      * at all and the CHANGING_FSID_V2 flag set.
      */
     list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
         if (fs_devices->fsid_change &&
             memcmp(disk_super->metadata_uuid, fs_devices->fsid,
                BTRFS_FSID_SIZE) == 0 &&
             memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
                BTRFS_FSID_SIZE) == 0) {
             return fs_devices;
         }
     }
     /*
      * Handle scanned device having completed its fsid change but
      * belonging to a fs_devices that was created by a device that
      * has an outdated pair of fsid/metadata_uuid and
      * CHANGING_FSID_V2 flag set.
      */
     list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
         if (fs_devices->fsid_change &&
             memcmp(fs_devices->metadata_uuid,
                fs_devices->fsid, BTRFS_FSID_SIZE) != 0 &&
             memcmp(disk_super->metadata_uuid, fs_devices->metadata_uuid,
                BTRFS_FSID_SIZE) == 0) {
             return fs_devices;
         }
     }
 
     return find_fsid(disk_super->fsid, disk_super->metadata_uuid);
 }
 
 
 static int
 btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder,
               int flush, struct block_device **bdev,
               struct btrfs_super_block **disk_super)
 {
     int ret;
 
     *bdev = blkdev_get_by_path(device_path, flags, holder);
 
     if (IS_ERR(*bdev)) {
         ret = PTR_ERR(*bdev);
         goto error;
     }
 
     if (flush)
         sync_blockdev(*bdev);
     ret = set_blocksize(*bdev, BTRFS_BDEV_BLOCKSIZE);
     if (ret) {
         blkdev_put(*bdev, flags);
         goto error;
     }
     invalidate_bdev(*bdev);
     *disk_super = btrfs_read_dev_super(*bdev);
     if (IS_ERR(*disk_super)) {
         ret = PTR_ERR(*disk_super);
         blkdev_put(*bdev, flags);
         goto error;
     }
 
     return 0;
 
 error:
     *bdev = NULL;
     return ret;
 }
 
 /**
  *  Search and remove all stale devices (which are not mounted).
  *  When both inputs are NULL, it will search and release all stale devices.
  *
  *  @devt:  Optional. When provided will it release all unmounted devices
  *      matching this devt only.
  *  @skip_device:  Optional. Will skip this device when searching for the stale
  *      devices.
  *
  *  Return: 0 for success or if @devt is 0.
  *      -EBUSY if @devt is a mounted device.
  *      -ENOENT if @devt does not match any device in the list.
  */
 static int btrfs_free_stale_devices(dev_t devt, struct btrfs_device *skip_device)
 {
     struct btrfs_fs_devices *fs_devices, *tmp_fs_devices;
     struct btrfs_device *device, *tmp_device;
     int ret = 0;
 
     lockdep_assert_held(&uuid_mutex);
 
     if (devt)
         ret = -ENOENT;
 
     list_for_each_entry_safe(fs_devices, tmp_fs_devices, &fs_uuids, fs_list) {
 
         mutex_lock(&fs_devices->device_list_mutex);
         list_for_each_entry_safe(device, tmp_device,
                      &fs_devices->devices, dev_list) {
             if (skip_device && skip_device == device)
                 continue;
             if (devt && devt != device->devt)
                 continue;
             if (fs_devices->opened) {
                 /* for an already deleted device return 0 */
                 if (devt && ret != 0)
                     ret = -EBUSY;
                 break;
             }
 
             /* delete the stale device */
             fs_devices->num_devices--;
             list_del(&device->dev_list);
             btrfs_free_device(device);
 
             ret = 0;
         }
         mutex_unlock(&fs_devices->device_list_mutex);
 
         if (fs_devices->num_devices == 0) {
             btrfs_sysfs_remove_fsid(fs_devices);
             list_del(&fs_devices->fs_list);
             free_fs_devices(fs_devices);
         }
     }
 
     return ret;
 }
 
 /*
  * This is only used on mount, and we are protected from competing things
  * messing with our fs_devices by the uuid_mutex, thus we do not need the
  * fs_devices->device_list_mutex here.
  */
 static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
             struct btrfs_device *device, fmode_t flags,
             void *holder)
 {
     struct block_device *bdev;
     struct btrfs_super_block *disk_super;
     u64 devid;
     int ret;
 
     if (device->bdev)
         return -EINVAL;
     if (!device->name)
         return -EINVAL;
 
     ret = btrfs_get_bdev_and_sb(device->name->str, flags, holder, 1,
                     &bdev, &disk_super);
     if (ret)
         return ret;
 
     devid = btrfs_stack_device_id(&disk_super->dev_item);
     if (devid != device->devid)
         goto error_free_page;
 
     if (memcmp(device->uuid, disk_super->dev_item.uuid, BTRFS_UUID_SIZE))
         goto error_free_page;
 
     device->generation = btrfs_super_generation(disk_super);
 
     if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING) {
         if (btrfs_super_incompat_flags(disk_super) &
             BTRFS_FEATURE_INCOMPAT_METADATA_UUID) {
             pr_err(
         "BTRFS: Invalid seeding and uuid-changed device detected\n");
             goto error_free_page;
         }
 
         clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
         fs_devices->seeding = true;
     } else {
         if (bdev_read_only(bdev))
             clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
         else
             set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
     }
 
     if (!bdev_nonrot(bdev))
         fs_devices->rotating = true;
 
     device->bdev = bdev;
     clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
     device->mode = flags;
 
     fs_devices->open_devices++;
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
         device->devid != BTRFS_DEV_REPLACE_DEVID) {
         fs_devices->rw_devices++;
         list_add_tail(&device->dev_alloc_list, &fs_devices->alloc_list);
     }
     btrfs_release_disk_super(disk_super);
 
     return 0;
 
 error_free_page:
     btrfs_release_disk_super(disk_super);
     blkdev_put(bdev, flags);
 
     return -EINVAL;
 }
 
 /*
  * Handle scanned device having its CHANGING_FSID_V2 flag set and the fs_devices
  * being created with a disk that has already completed its fsid change. Such
  * disk can belong to an fs which has its FSID changed or to one which doesn't.
  * Handle both cases here.
  */
 static struct btrfs_fs_devices *find_fsid_inprogress(
                     struct btrfs_super_block *disk_super)
 {
     struct btrfs_fs_devices *fs_devices;
 
     list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
         if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
                BTRFS_FSID_SIZE) != 0 &&
             memcmp(fs_devices->metadata_uuid, disk_super->fsid,
                BTRFS_FSID_SIZE) == 0 && !fs_devices->fsid_change) {
             return fs_devices;
         }
     }
 
     return find_fsid(disk_super->fsid, NULL);
 }
 
 
 static struct btrfs_fs_devices *find_fsid_changed(
                     struct btrfs_super_block *disk_super)
 {
     struct btrfs_fs_devices *fs_devices;
 
     /*
      * Handles the case where scanned device is part of an fs that had
      * multiple successful changes of FSID but currently device didn't
      * observe it. Meaning our fsid will be different than theirs. We need
      * to handle two subcases :
      *  1 - The fs still continues to have different METADATA/FSID uuids.
      *  2 - The fs is switched back to its original FSID (METADATA/FSID
      *  are equal).
      */
     list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
         /* Changed UUIDs */
         if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
                BTRFS_FSID_SIZE) != 0 &&
             memcmp(fs_devices->metadata_uuid, disk_super->metadata_uuid,
                BTRFS_FSID_SIZE) == 0 &&
             memcmp(fs_devices->fsid, disk_super->fsid,
                BTRFS_FSID_SIZE) != 0)
             return fs_devices;
 
         /* Unchanged UUIDs */
         if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
                BTRFS_FSID_SIZE) == 0 &&
             memcmp(fs_devices->fsid, disk_super->metadata_uuid,
                BTRFS_FSID_SIZE) == 0)
             return fs_devices;
     }
 
     return NULL;
 }
 
 static struct btrfs_fs_devices *find_fsid_reverted_metadata(
                 struct btrfs_super_block *disk_super)
 {
     struct btrfs_fs_devices *fs_devices;
 
     /*
      * Handle the case where the scanned device is part of an fs whose last
      * metadata UUID change reverted it to the original FSID. At the same
      * time * fs_devices was first created by another constitutent device
      * which didn't fully observe the operation. This results in an
      * btrfs_fs_devices created with metadata/fsid different AND
      * btrfs_fs_devices::fsid_change set AND the metadata_uuid of the
      * fs_devices equal to the FSID of the disk.
      */
     list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
         if (memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
                BTRFS_FSID_SIZE) != 0 &&
             memcmp(fs_devices->metadata_uuid, disk_super->fsid,
                BTRFS_FSID_SIZE) == 0 &&
             fs_devices->fsid_change)
             return fs_devices;
     }
 
     return NULL;
 }
 /*
  * Add new device to list of registered devices
  *
  * Returns:
  * device pointer which was just added or updated when successful
  * error pointer when failed
  */
 static noinline struct btrfs_device *device_list_add(const char *path,
                struct btrfs_super_block *disk_super,
                bool *new_device_added)
 {
     struct btrfs_device *device;
     struct btrfs_fs_devices *fs_devices = NULL;
     struct rcu_string *name;
     u64 found_transid = btrfs_super_generation(disk_super);
     u64 devid = btrfs_stack_device_id(&disk_super->dev_item);
     dev_t path_devt;
     int error;
     bool has_metadata_uuid = (btrfs_super_incompat_flags(disk_super) &
         BTRFS_FEATURE_INCOMPAT_METADATA_UUID);
     bool fsid_change_in_progress = (btrfs_super_flags(disk_super) &
                     BTRFS_SUPER_FLAG_CHANGING_FSID_V2);
 
     error = lookup_bdev(path, &path_devt);
     if (error)
         return ERR_PTR(error);
 
     if (fsid_change_in_progress) {
         if (!has_metadata_uuid)
             fs_devices = find_fsid_inprogress(disk_super);
         else
             fs_devices = find_fsid_changed(disk_super);
     } else if (has_metadata_uuid) {
         fs_devices = find_fsid_with_metadata_uuid(disk_super);
     } else {
         fs_devices = find_fsid_reverted_metadata(disk_super);
         if (!fs_devices)
             fs_devices = find_fsid(disk_super->fsid, NULL);
     }
 
 
     if (!fs_devices) {
         if (has_metadata_uuid)
             fs_devices = alloc_fs_devices(disk_super->fsid,
                               disk_super->metadata_uuid);
         else
             fs_devices = alloc_fs_devices(disk_super->fsid, NULL);
 
         if (IS_ERR(fs_devices))
             return ERR_CAST(fs_devices);
 
         fs_devices->fsid_change = fsid_change_in_progress;
 
         mutex_lock(&fs_devices->device_list_mutex);
         list_add(&fs_devices->fs_list, &fs_uuids);
 
         device = NULL;
     } else {
         struct btrfs_dev_lookup_args args = {
             .devid = devid,
             .uuid = disk_super->dev_item.uuid,
         };
 
         mutex_lock(&fs_devices->device_list_mutex);
         device = btrfs_find_device(fs_devices, &args);
 
         /*
          * If this disk has been pulled into an fs devices created by
          * a device which had the CHANGING_FSID_V2 flag then replace the
          * metadata_uuid/fsid values of the fs_devices.
          */
         if (fs_devices->fsid_change &&
             found_transid > fs_devices->latest_generation) {
             memcpy(fs_devices->fsid, disk_super->fsid,
                     BTRFS_FSID_SIZE);
 
             if (has_metadata_uuid)
                 memcpy(fs_devices->metadata_uuid,
                        disk_super->metadata_uuid,
                        BTRFS_FSID_SIZE);
             else
                 memcpy(fs_devices->metadata_uuid,
                        disk_super->fsid, BTRFS_FSID_SIZE);
 
             fs_devices->fsid_change = false;
         }
     }
 
     if (!device) {
         if (fs_devices->opened) {
             mutex_unlock(&fs_devices->device_list_mutex);
             return ERR_PTR(-EBUSY);
         }
 
         device = btrfs_alloc_device(NULL, &devid,
                         disk_super->dev_item.uuid);
         if (IS_ERR(device)) {
             mutex_unlock(&fs_devices->device_list_mutex);
             /* we can safely leave the fs_devices entry around */
             return device;
         }
 
         name = rcu_string_strdup(path, GFP_NOFS);
         if (!name) {
             btrfs_free_device(device);
             mutex_unlock(&fs_devices->device_list_mutex);
             return ERR_PTR(-ENOMEM);
         }
         rcu_assign_pointer(device->name, name);
         device->devt = path_devt;
 
         list_add_rcu(&device->dev_list, &fs_devices->devices);
         fs_devices->num_devices++;
 
         device->fs_devices = fs_devices;
         *new_device_added = true;
 
         if (disk_super->label[0])
             pr_info(
     "BTRFS: device label %s devid %llu transid %llu %s scanned by %s (%d)\n",
                 disk_super->label, devid, found_transid, path,
                 current->comm, task_pid_nr(current));
         else
             pr_info(
     "BTRFS: device fsid %pU devid %llu transid %llu %s scanned by %s (%d)\n",
                 disk_super->fsid, devid, found_transid, path,
                 current->comm, task_pid_nr(current));
 
     } else if (!device->name || strcmp(device->name->str, path)) {
         /*
          * When FS is already mounted.
          * 1. If you are here and if the device->name is NULL that
          *    means this device was missing at time of FS mount.
          * 2. If you are here and if the device->name is different
          *    from 'path' that means either
          *      a. The same device disappeared and reappeared with
          *         different name. or
          *      b. The missing-disk-which-was-replaced, has
          *         reappeared now.
          *
          * We must allow 1 and 2a above. But 2b would be a spurious
          * and unintentional.
          *
          * Further in case of 1 and 2a above, the disk at 'path'
          * would have missed some transaction when it was away and
          * in case of 2a the stale bdev has to be updated as well.
          * 2b must not be allowed at all time.
          */
 
         /*
          * For now, we do allow update to btrfs_fs_device through the
          * btrfs dev scan cli after FS has been mounted.  We're still
          * tracking a problem where systems fail mount by subvolume id
          * when we reject replacement on a mounted FS.
          */
         if (!fs_devices->opened && found_transid < device->generation) {
             /*
              * That is if the FS is _not_ mounted and if you
              * are here, that means there is more than one
              * disk with same uuid and devid.We keep the one
              * with larger generation number or the last-in if
              * generation are equal.
              */
             mutex_unlock(&fs_devices->device_list_mutex);
             return ERR_PTR(-EEXIST);
         }
 
         /*
          * We are going to replace the device path for a given devid,
          * make sure it's the same device if the device is mounted
          *
          * NOTE: the device->fs_info may not be reliable here so pass
          * in a NULL to message helpers instead. This avoids a possible
          * use-after-free when the fs_info and fs_info->sb are already
          * torn down.
          */
         if (device->bdev) {
             if (device->devt != path_devt) {
                 mutex_unlock(&fs_devices->device_list_mutex);
                 btrfs_warn_in_rcu(NULL,
     "duplicate device %s devid %llu generation %llu scanned by %s (%d)",
                           path, devid, found_transid,
                           current->comm,
                           task_pid_nr(current));
                 return ERR_PTR(-EEXIST);
             }
             btrfs_info_in_rcu(NULL,
     "devid %llu device path %s changed to %s scanned by %s (%d)",
                       devid, rcu_str_deref(device->name),
                       path, current->comm,
                       task_pid_nr(current));
         }
 
         name = rcu_string_strdup(path, GFP_NOFS);
         if (!name) {
             mutex_unlock(&fs_devices->device_list_mutex);
             return ERR_PTR(-ENOMEM);
         }
         rcu_string_free(device->name);
         rcu_assign_pointer(device->name, name);
         if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
             fs_devices->missing_devices--;
             clear_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
         }
         device->devt = path_devt;
     }
 
     /*
      * Unmount does not free the btrfs_device struct but would zero
      * generation along with most of the other members. So just update
      * it back. We need it to pick the disk with largest generation
      * (as above).
      */
     if (!fs_devices->opened) {
         device->generation = found_transid;
         fs_devices->latest_generation = max_t(u64, found_transid,
                         fs_devices->latest_generation);
     }
 
     fs_devices->total_devices = btrfs_super_num_devices(disk_super);
 
     mutex_unlock(&fs_devices->device_list_mutex);
     return device;
 }
 
 static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
 {
     struct btrfs_fs_devices *fs_devices;
     struct btrfs_device *device;
     struct btrfs_device *orig_dev;
     int ret = 0;
 
     lockdep_assert_held(&uuid_mutex);
 
     fs_devices = alloc_fs_devices(orig->fsid, NULL);
     if (IS_ERR(fs_devices))
         return fs_devices;
 
     fs_devices->total_devices = orig->total_devices;
 
     list_for_each_entry(orig_dev, &orig->devices, dev_list) {
         struct rcu_string *name;
 
         device = btrfs_alloc_device(NULL, &orig_dev->devid,
                         orig_dev->uuid);
         if (IS_ERR(device)) {
             ret = PTR_ERR(device);
             goto error;
         }
 
         /*
          * This is ok to do without rcu read locked because we hold the
          * uuid mutex so nothing we touch in here is going to disappear.
          */
         if (orig_dev->name) {
             name = rcu_string_strdup(orig_dev->name->str,
                     GFP_KERNEL);
             if (!name) {
                 btrfs_free_device(device);
                 ret = -ENOMEM;
                 goto error;
             }
             rcu_assign_pointer(device->name, name);
         }
 
         list_add(&device->dev_list, &fs_devices->devices);
         device->fs_devices = fs_devices;
         fs_devices->num_devices++;
     }
     return fs_devices;
 error:
     free_fs_devices(fs_devices);
     return ERR_PTR(ret);
 }
 
 static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices,
                       struct btrfs_device **latest_dev)
 {
     struct btrfs_device *device, *next;
 
     /* This is the initialized path, it is safe to release the devices. */
     list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
         if (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state)) {
             if (!test_bit(BTRFS_DEV_STATE_REPLACE_TGT,
                       &device->dev_state) &&
                 !test_bit(BTRFS_DEV_STATE_MISSING,
                       &device->dev_state) &&
                 (!*latest_dev ||
                  device->generation > (*latest_dev)->generation)) {
                 *latest_dev = device;
             }
             continue;
         }
 
         /*
          * We have already validated the presence of BTRFS_DEV_REPLACE_DEVID,
          * in btrfs_init_dev_replace() so just continue.
          */
         if (device->devid == BTRFS_DEV_REPLACE_DEVID)
             continue;
 
         if (device->bdev) {
             blkdev_put(device->bdev, device->mode);
             device->bdev = NULL;
             fs_devices->open_devices--;
         }
         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
             list_del_init(&device->dev_alloc_list);
             clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
             fs_devices->rw_devices--;
         }
         list_del_init(&device->dev_list);
         fs_devices->num_devices--;
         btrfs_free_device(device);
     }
 
 }
 
 /*
  * After we have read the system tree and know devids belonging to this
  * filesystem, remove the device which does not belong there.
  */
 void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices)
 {
     struct btrfs_device *latest_dev = NULL;
     struct btrfs_fs_devices *seed_dev;
 
     mutex_lock(&uuid_mutex);
     __btrfs_free_extra_devids(fs_devices, &latest_dev);
 
     list_for_each_entry(seed_dev, &fs_devices->seed_list, seed_list)
         __btrfs_free_extra_devids(seed_dev, &latest_dev);
 
     fs_devices->latest_dev = latest_dev;
 
     mutex_unlock(&uuid_mutex);
 }
 
 static void btrfs_close_bdev(struct btrfs_device *device)
 {
     if (!device->bdev)
         return;
 
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
         sync_blockdev(device->bdev);
         invalidate_bdev(device->bdev);
     }
 
     blkdev_put(device->bdev, device->mode);
 }
 
 static void btrfs_close_one_device(struct btrfs_device *device)
 {
     struct btrfs_fs_devices *fs_devices = device->fs_devices;
 
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
         device->devid != BTRFS_DEV_REPLACE_DEVID) {
         list_del_init(&device->dev_alloc_list);
         fs_devices->rw_devices--;
     }
 
     if (device->devid == BTRFS_DEV_REPLACE_DEVID)
         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 
     if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
         clear_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
         fs_devices->missing_devices--;
     }
 
     btrfs_close_bdev(device);
     if (device->bdev) {
         fs_devices->open_devices--;
         device->bdev = NULL;
     }
     clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
     btrfs_destroy_dev_zone_info(device);
 
     device->fs_info = NULL;
     atomic_set(&device->dev_stats_ccnt, 0);
     extent_io_tree_release(&device->alloc_state);
 
     /*
      * Reset the flush error record. We might have a transient flush error
      * in this mount, and if so we aborted the current transaction and set
      * the fs to an error state, guaranteeing no super blocks can be further
      * committed. However that error might be transient and if we unmount the
      * filesystem and mount it again, we should allow the mount to succeed
      * (btrfs_check_rw_degradable() should not fail) - if after mounting the
      * filesystem again we still get flush errors, then we will again abort
      * any transaction and set the error state, guaranteeing no commits of
      * unsafe super blocks.
      */
     device->last_flush_error = 0;
 
     /* Verify the device is back in a pristine state  */
     ASSERT(!test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state));
     ASSERT(!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state));
     ASSERT(list_empty(&device->dev_alloc_list));
     ASSERT(list_empty(&device->post_commit_list));
 }
 
 static void close_fs_devices(struct btrfs_fs_devices *fs_devices)
 {
     struct btrfs_device *device, *tmp;
 
     lockdep_assert_held(&uuid_mutex);
 
     if (--fs_devices->opened > 0)
         return;
 
     list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list)
         btrfs_close_one_device(device);
 
     WARN_ON(fs_devices->open_devices);
     WARN_ON(fs_devices->rw_devices);
     fs_devices->opened = 0;
     fs_devices->seeding = false;
     fs_devices->fs_info = NULL;
 }
 
 void btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 {
     LIST_HEAD(list);
     struct btrfs_fs_devices *tmp;
 
     mutex_lock(&uuid_mutex);
     close_fs_devices(fs_devices);
     if (!fs_devices->opened)
         list_splice_init(&fs_devices->seed_list, &list);
 
     list_for_each_entry_safe(fs_devices, tmp, &list, seed_list) {
         close_fs_devices(fs_devices);
         list_del(&fs_devices->seed_list);
         free_fs_devices(fs_devices);
     }
     mutex_unlock(&uuid_mutex);
 }
 
 static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
                 fmode_t flags, void *holder)
 {
     struct btrfs_device *device;
     struct btrfs_device *latest_dev = NULL;
     struct btrfs_device *tmp_device;
 
     flags |= FMODE_EXCL;
 
     list_for_each_entry_safe(device, tmp_device, &fs_devices->devices,
                  dev_list) {
         int ret;
 
         ret = btrfs_open_one_device(fs_devices, device, flags, holder);
         if (ret == 0 &&
             (!latest_dev || device->generation > latest_dev->generation)) {
             latest_dev = device;
         } else if (ret == -ENODATA) {
             fs_devices->num_devices--;
             list_del(&device->dev_list);
             btrfs_free_device(device);
         }
     }
     if (fs_devices->open_devices == 0)
         return -EINVAL;
 
     fs_devices->opened = 1;
     fs_devices->latest_dev = latest_dev;
     fs_devices->total_rw_bytes = 0;
     fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_REGULAR;
     fs_devices->read_policy = BTRFS_READ_POLICY_PID;
 
     return 0;
 }
 
 static int devid_cmp(void *priv, const struct list_head *a,
              const struct list_head *b)
 {
     const struct btrfs_device *dev1, *dev2;
 
     dev1 = list_entry(a, struct btrfs_device, dev_list);
     dev2 = list_entry(b, struct btrfs_device, dev_list);
 
     if (dev1->devid < dev2->devid)
         return -1;
     else if (dev1->devid > dev2->devid)
         return 1;
     return 0;
 }
 
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                fmode_t flags, void *holder)
 {
     int ret;
 
     lockdep_assert_held(&uuid_mutex);
     /*
      * The device_list_mutex cannot be taken here in case opening the
      * underlying device takes further locks like open_mutex.
      *
      * We also don't need the lock here as this is called during mount and
      * exclusion is provided by uuid_mutex
      */
 
     if (fs_devices->opened) {
         fs_devices->opened++;
         ret = 0;
     } else {
         list_sort(NULL, &fs_devices->devices, devid_cmp);
         ret = open_fs_devices(fs_devices, flags, holder);
     }
 
     return ret;
 }
 
 void btrfs_release_disk_super(struct btrfs_super_block *super)
 {
     struct page *page = virt_to_page(super);
 
     put_page(page);
 }
 
 static struct btrfs_super_block *btrfs_read_disk_super(struct block_device *bdev,
                                u64 bytenr, u64 bytenr_orig)
 {
     struct btrfs_super_block *disk_super;
     struct page *page;
     void *p;
     pgoff_t index;
 
     /* make sure our super fits in the device */
     if (bytenr + PAGE_SIZE >= bdev_nr_bytes(bdev))
         return ERR_PTR(-EINVAL);
 
     /* make sure our super fits in the page */
     if (sizeof(*disk_super) > PAGE_SIZE)
         return ERR_PTR(-EINVAL);
 
     /* make sure our super doesn't straddle pages on disk */
     index = bytenr >> PAGE_SHIFT;
     if ((bytenr + sizeof(*disk_super) - 1) >> PAGE_SHIFT != index)
         return ERR_PTR(-EINVAL);
 
     /* pull in the page with our super */
     page = read_cache_page_gfp(bdev->bd_inode->i_mapping, index, GFP_KERNEL);
 
     if (IS_ERR(page))
         return ERR_CAST(page);
 
     p = page_address(page);
 
     /* align our pointer to the offset of the super block */
     disk_super = p + offset_in_page(bytenr);
 
     if (btrfs_super_bytenr(disk_super) != bytenr_orig ||
         btrfs_super_magic(disk_super) != BTRFS_MAGIC) {
         btrfs_release_disk_super(p);
         return ERR_PTR(-EINVAL);
     }
 
     if (disk_super->label[0] && disk_super->label[BTRFS_LABEL_SIZE - 1])
         disk_super->label[BTRFS_LABEL_SIZE - 1] = 0;
 
     return disk_super;
 }
 
 int btrfs_forget_devices(dev_t devt)
 {
     int ret;
 
     mutex_lock(&uuid_mutex);
     ret = btrfs_free_stale_devices(devt, NULL);
     mutex_unlock(&uuid_mutex);
 
     return ret;
 }
 
 /*
  * Look for a btrfs signature on a device. This may be called out of the mount path
  * and we are not allowed to call set_blocksize during the scan. The superblock
  * is read via pagecache
  */
 struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
                        void *holder)
 {
     struct btrfs_super_block *disk_super;
     bool new_device_added = false;
     struct btrfs_device *device = NULL;
     struct block_device *bdev;
     u64 bytenr, bytenr_orig;
     int ret;
 
     lockdep_assert_held(&uuid_mutex);
 
     /*
      * we would like to check all the supers, but that would make
      * a btrfs mount succeed after a mkfs from a different FS.
      * So, we need to add a special mount option to scan for
      * later supers, using BTRFS_SUPER_MIRROR_MAX instead
      */
     flags |= FMODE_EXCL;
 
     bdev = blkdev_get_by_path(path, flags, holder);
     if (IS_ERR(bdev))
         return ERR_CAST(bdev);
 
     bytenr_orig = btrfs_sb_offset(0);
     ret = btrfs_sb_log_location_bdev(bdev, 0, READ, &bytenr);
     if (ret) {
         device = ERR_PTR(ret);
         goto error_bdev_put;
     }
 
     disk_super = btrfs_read_disk_super(bdev, bytenr, bytenr_orig);
     if (IS_ERR(disk_super)) {
         device = ERR_CAST(disk_super);
         goto error_bdev_put;
     }
 
     device = device_list_add(path, disk_super, &new_device_added);
     if (!IS_ERR(device) && new_device_added)
         btrfs_free_stale_devices(device->devt, device);
 
     btrfs_release_disk_super(disk_super);
 
 error_bdev_put:
     blkdev_put(bdev, flags);
 
     return device;
 }
 
 /*
  * Try to find a chunk that intersects [start, start + len] range and when one
  * such is found, record the end of it in *start
  */
 static bool contains_pending_extent(struct btrfs_device *device, u64 *start,
                     u64 len)
 {
     u64 physical_start, physical_end;
 
     lockdep_assert_held(&device->fs_info->chunk_mutex);
 
     if (!find_first_extent_bit(&device->alloc_state, *start,
                    &physical_start, &physical_end,
                    CHUNK_ALLOCATED, NULL)) {
 
         if (in_range(physical_start, *start, len) ||
             in_range(*start, physical_start,
                  physical_end - physical_start)) {
             *start = physical_end + 1;
             return true;
         }
     }
     return false;
 }
 
 static u64 dev_extent_search_start(struct btrfs_device *device, u64 start)
 {
     switch (device->fs_devices->chunk_alloc_policy) {
     case BTRFS_CHUNK_ALLOC_REGULAR:
         return max_t(u64, start, BTRFS_DEVICE_RANGE_RESERVED);
     case BTRFS_CHUNK_ALLOC_ZONED:
         /*
          * We don't care about the starting region like regular
          * allocator, because we anyway use/reserve the first two zones
          * for superblock logging.
          */
         return ALIGN(start, device->zone_info->zone_size);
     default:
         BUG();
     }
 }
 
 static bool dev_extent_hole_check_zoned(struct btrfs_device *device,
                     u64 *hole_start, u64 *hole_size,
                     u64 num_bytes)
 {
     u64 zone_size = device->zone_info->zone_size;
     u64 pos;
     int ret;
     bool changed = false;
 
     ASSERT(IS_ALIGNED(*hole_start, zone_size));
 
     while (*hole_size > 0) {
         pos = btrfs_find_allocatable_zones(device, *hole_start,
                            *hole_start + *hole_size,
                            num_bytes);
         if (pos != *hole_start) {
             *hole_size = *hole_start + *hole_size - pos;
             *hole_start = pos;
             changed = true;
             if (*hole_size < num_bytes)
                 break;
         }
 
         ret = btrfs_ensure_empty_zones(device, pos, num_bytes);
 
         /* Range is ensured to be empty */
         if (!ret)
             return changed;
 
         /* Given hole range was invalid (outside of device) */
         if (ret == -ERANGE) {
             *hole_start += *hole_size;
             *hole_size = 0;
             return true;
         }
 
         *hole_start += zone_size;
         *hole_size -= zone_size;
         changed = true;
     }
 
     return changed;
 }
 
 /**
  * dev_extent_hole_check - check if specified hole is suitable for allocation
  * @device: the device which we have the hole
  * @hole_start: starting position of the hole
  * @hole_size:  the size of the hole
  * @num_bytes:  the size of the free space that we need
  *
  * This function may modify @hole_start and @hole_size to reflect the suitable
  * position for allocation. Returns 1 if hole position is updated, 0 otherwise.
  */
 static bool dev_extent_hole_check(struct btrfs_device *device, u64 *hole_start,
                   u64 *hole_size, u64 num_bytes)
 {
     bool changed = false;
     u64 hole_end = *hole_start + *hole_size;
 
     for (;;) {
         /*
          * Check before we set max_hole_start, otherwise we could end up
          * sending back this offset anyway.
          */
         if (contains_pending_extent(device, hole_start, *hole_size)) {
             if (hole_end >= *hole_start)
                 *hole_size = hole_end - *hole_start;
             else
                 *hole_size = 0;
             changed = true;
         }
 
         switch (device->fs_devices->chunk_alloc_policy) {
         case BTRFS_CHUNK_ALLOC_REGULAR:
             /* No extra check */
             break;
         case BTRFS_CHUNK_ALLOC_ZONED:
             if (dev_extent_hole_check_zoned(device, hole_start,
                             hole_size, num_bytes)) {
                 changed = true;
                 /*
                  * The changed hole can contain pending extent.
                  * Loop again to check that.
                  */
                 continue;
             }
             break;
         default:
             BUG();
         }
 
         break;
     }
 
     return changed;
 }
 
 /*
  * find_free_dev_extent_start - find free space in the specified device
  * @device:   the device which we search the free space in
  * @num_bytes:    the size of the free space that we need
  * @search_start: the position from which to begin the search
  * @start:    store the start of the free space.
  * @len:      the size of the free space. that we find, or the size
  *        of the max free space if we don't find suitable free space
  *
  * this uses a pretty simple search, the expectation is that it is
  * called very infrequently and that a given device has a small number
  * of extents
  *
  * @start is used to store the start of the free space if we find. But if we
  * don't find suitable free space, it will be used to store the start position
  * of the max free space.
  *
  * @len is used to store the size of the free space that we find.
  * But if we don't find suitable free space, it is used to store the size of
  * the max free space.
  *
  * NOTE: This function will search *commit* root of device tree, and does extra
  * check to ensure dev extents are not double allocated.
  * This makes the function safe to allocate dev extents but may not report
  * correct usable device space, as device extent freed in current transaction
  * is not reported as available.
  */
 static int find_free_dev_extent_start(struct btrfs_device *device,
                 u64 num_bytes, u64 search_start, u64 *start,
                 u64 *len)
 {
     struct btrfs_fs_info *fs_info = device->fs_info;
     struct btrfs_root *root = fs_info->dev_root;
     struct btrfs_key key;
     struct btrfs_dev_extent *dev_extent;
     struct btrfs_path *path;
     u64 hole_size;
     u64 max_hole_start;
     u64 max_hole_size;
     u64 extent_end;
     u64 search_end = device->total_bytes;
     int ret;
     int slot;
     struct extent_buffer *l;
 
     search_start = dev_extent_search_start(device, search_start);
 
     WARN_ON(device->zone_info &&
         !IS_ALIGNED(num_bytes, device->zone_info->zone_size));
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     max_hole_start = search_start;
     max_hole_size = 0;
 
 again:
     if (search_start >= search_end ||
         test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
         ret = -ENOSPC;
         goto out;
     }
 
     path->reada = READA_FORWARD;
     path->search_commit_root = 1;
     path->skip_locking = 1;
 
     key.objectid = device->devid;
     key.offset = search_start;
     key.type = BTRFS_DEV_EXTENT_KEY;
 
     ret = btrfs_search_backwards(root, &key, path);
     if (ret < 0)
         goto out;
 
     while (1) {
         l = path->nodes[0];
         slot = path->slots[0];
         if (slot >= btrfs_header_nritems(l)) {
             ret = btrfs_next_leaf(root, path);
             if (ret == 0)
                 continue;
             if (ret < 0)
                 goto out;
 
             break;
         }
         btrfs_item_key_to_cpu(l, &key, slot);
 
         if (key.objectid < device->devid)
             goto next;
 
         if (key.objectid > device->devid)
             break;
 
         if (key.type != BTRFS_DEV_EXTENT_KEY)
             goto next;
 
         if (key.offset > search_start) {
             hole_size = key.offset - search_start;
             dev_extent_hole_check(device, &search_start, &hole_size,
                           num_bytes);
 
             if (hole_size > max_hole_size) {
                 max_hole_start = search_start;
                 max_hole_size = hole_size;
             }
 
             /*
              * If this free space is greater than which we need,
              * it must be the max free space that we have found
              * until now, so max_hole_start must point to the start
              * of this free space and the length of this free space
              * is stored in max_hole_size. Thus, we return
              * max_hole_start and max_hole_size and go back to the
              * caller.
              */
             if (hole_size >= num_bytes) {
                 ret = 0;
                 goto out;
             }
         }
 
         dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
         extent_end = key.offset + btrfs_dev_extent_length(l,
                                   dev_extent);
         if (extent_end > search_start)
             search_start = extent_end;
 next:
         path->slots[0]++;
         cond_resched();
     }
 
     /*
      * At this point, search_start should be the end of
      * allocated dev extents, and when shrinking the device,
      * search_end may be smaller than search_start.
      */
     if (search_end > search_start) {
         hole_size = search_end - search_start;
         if (dev_extent_hole_check(device, &search_start, &hole_size,
                       num_bytes)) {
             btrfs_release_path(path);
             goto again;
         }
 
         if (hole_size > max_hole_size) {
             max_hole_start = search_start;
             max_hole_size = hole_size;
         }
     }
 
     /* See above. */
     if (max_hole_size < num_bytes)
         ret = -ENOSPC;
     else
         ret = 0;
 
 out:
     btrfs_free_path(path);
     *start = max_hole_start;
     if (len)
         *len = max_hole_size;
     return ret;
 }
 
 int find_free_dev_extent(struct btrfs_device *device, u64 num_bytes,
              u64 *start, u64 *len)
 {
     /* FIXME use last free of some kind */
     return find_free_dev_extent_start(device, num_bytes, 0, start, len);
 }
 
 static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
               struct btrfs_device *device,
               u64 start, u64 *dev_extent_len)
 {
     struct btrfs_fs_info *fs_info = device->fs_info;
     struct btrfs_root *root = fs_info->dev_root;
     int ret;
     struct btrfs_path *path;
     struct btrfs_key key;
     struct btrfs_key found_key;
     struct extent_buffer *leaf = NULL;
     struct btrfs_dev_extent *extent = NULL;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = device->devid;
     key.offset = start;
     key.type = BTRFS_DEV_EXTENT_KEY;
 again:
     ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
     if (ret > 0) {
         ret = btrfs_previous_item(root, path, key.objectid,
                       BTRFS_DEV_EXTENT_KEY);
         if (ret)
             goto out;
         leaf = path->nodes[0];
         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
         extent = btrfs_item_ptr(leaf, path->slots[0],
                     struct btrfs_dev_extent);
         BUG_ON(found_key.offset > start || found_key.offset +
                btrfs_dev_extent_length(leaf, extent) < start);
         key = found_key;
         btrfs_release_path(path);
         goto again;
     } else if (ret == 0) {
         leaf = path->nodes[0];
         extent = btrfs_item_ptr(leaf, path->slots[0],
                     struct btrfs_dev_extent);
     } else {
         goto out;
     }
 
     *dev_extent_len = btrfs_dev_extent_length(leaf, extent);
 
     ret = btrfs_del_item(trans, root, path);
     if (ret == 0)
         set_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags);
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 static u64 find_next_chunk(struct btrfs_fs_info *fs_info)
 {
     struct extent_map_tree *em_tree;
     struct extent_map *em;
     struct rb_node *n;
     u64 ret = 0;
 
     em_tree = &fs_info->mapping_tree;
     read_lock(&em_tree->lock);
     n = rb_last(&em_tree->map.rb_root);
     if (n) {
         em = rb_entry(n, struct extent_map, rb_node);
         ret = em->start + em->len;
     }
     read_unlock(&em_tree->lock);
 
     return ret;
 }
 
 static noinline int find_next_devid(struct btrfs_fs_info *fs_info,
                     u64 *devid_ret)
 {
     int ret;
     struct btrfs_key key;
     struct btrfs_key found_key;
     struct btrfs_path *path;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
     key.type = BTRFS_DEV_ITEM_KEY;
     key.offset = (u64)-1;
 
     ret = btrfs_search_slot(NULL, fs_info->chunk_root, &key, path, 0, 0);
     if (ret < 0)
         goto error;
 
     if (ret == 0) {
         /* Corruption */
         btrfs_err(fs_info, "corrupted chunk tree devid -1 matched");
         ret = -EUCLEAN;
         goto error;
     }
 
     ret = btrfs_previous_item(fs_info->chunk_root, path,
                   BTRFS_DEV_ITEMS_OBJECTID,
                   BTRFS_DEV_ITEM_KEY);
     if (ret) {
         *devid_ret = 1;
     } else {
         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                       path->slots[0]);
         *devid_ret = found_key.offset + 1;
     }
     ret = 0;
 error:
     btrfs_free_path(path);
     return ret;
 }
 
 /*
  * the device information is stored in the chunk root
  * the btrfs_device struct should be fully filled in
  */
 static int btrfs_add_dev_item(struct btrfs_trans_handle *trans,
                 struct btrfs_device *device)
 {
     int ret;
     struct btrfs_path *path;
     struct btrfs_dev_item *dev_item;
     struct extent_buffer *leaf;
     struct btrfs_key key;
     unsigned long ptr;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
     key.type = BTRFS_DEV_ITEM_KEY;
     key.offset = device->devid;
 
     btrfs_reserve_chunk_metadata(trans, true);
     ret = btrfs_insert_empty_item(trans, trans->fs_info->chunk_root, path,
                       &key, sizeof(*dev_item));
     btrfs_trans_release_chunk_metadata(trans);
     if (ret)
         goto out;
 
     leaf = path->nodes[0];
     dev_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_item);
 
     btrfs_set_device_id(leaf, dev_item, device->devid);
     btrfs_set_device_generation(leaf, dev_item, 0);
     btrfs_set_device_type(leaf, dev_item, device->type);
     btrfs_set_device_io_align(leaf, dev_item, device->io_align);
     btrfs_set_device_io_width(leaf, dev_item, device->io_width);
     btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
     btrfs_set_device_total_bytes(leaf, dev_item,
                      btrfs_device_get_disk_total_bytes(device));
     btrfs_set_device_bytes_used(leaf, dev_item,
                     btrfs_device_get_bytes_used(device));
     btrfs_set_device_group(leaf, dev_item, 0);
     btrfs_set_device_seek_speed(leaf, dev_item, 0);
     btrfs_set_device_bandwidth(leaf, dev_item, 0);
     btrfs_set_device_start_offset(leaf, dev_item, 0);
 
     ptr = btrfs_device_uuid(dev_item);
     write_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);
     ptr = btrfs_device_fsid(dev_item);
     write_extent_buffer(leaf, trans->fs_info->fs_devices->metadata_uuid,
                 ptr, BTRFS_FSID_SIZE);
     btrfs_mark_buffer_dirty(leaf);
 
     ret = 0;
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 /*
  * Function to update ctime/mtime for a given device path.
  * Mainly used for ctime/mtime based probe like libblkid.
  *
  * We don't care about errors here, this is just to be kind to userspace.
  */
 static void update_dev_time(const char *device_path)
 {
     struct path path;
     struct timespec64 now;
     int ret;
 
     ret = kern_path(device_path, LOOKUP_FOLLOW, &path);
     if (ret)
         return;
 
     now = current_time(d_inode(path.dentry));
     inode_update_time(d_inode(path.dentry), &now, S_MTIME | S_CTIME);
     path_put(&path);
 }
 
 static int btrfs_rm_dev_item(struct btrfs_trans_handle *trans,
                  struct btrfs_device *device)
 {
     struct btrfs_root *root = device->fs_info->chunk_root;
     int ret;
     struct btrfs_path *path;
     struct btrfs_key key;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
     key.type = BTRFS_DEV_ITEM_KEY;
     key.offset = device->devid;
 
     btrfs_reserve_chunk_metadata(trans, false);
     ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
     btrfs_trans_release_chunk_metadata(trans);
     if (ret) {
         if (ret > 0)
             ret = -ENOENT;
         goto out;
     }
 
     ret = btrfs_del_item(trans, root, path);
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 /*
  * Verify that @num_devices satisfies the RAID profile constraints in the whole
  * filesystem. It's up to the caller to adjust that number regarding eg. device
  * replace.
  */
 static int btrfs_check_raid_min_devices(struct btrfs_fs_info *fs_info,
         u64 num_devices)
 {
     u64 all_avail;
     unsigned seq;
     int i;
 
     do {
         seq = read_seqbegin(&fs_info->profiles_lock);
 
         all_avail = fs_info->avail_data_alloc_bits |
                 fs_info->avail_system_alloc_bits |
                 fs_info->avail_metadata_alloc_bits;
     } while (read_seqretry(&fs_info->profiles_lock, seq));
 
     for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
         if (!(all_avail & btrfs_raid_array[i].bg_flag))
             continue;
 
         if (num_devices < btrfs_raid_array[i].devs_min)
             return btrfs_raid_array[i].mindev_error;
     }
 
     return 0;
 }
 
 static struct btrfs_device * btrfs_find_next_active_device(
         struct btrfs_fs_devices *fs_devs, struct btrfs_device *device)
 {
     struct btrfs_device *next_device;
 
     list_for_each_entry(next_device, &fs_devs->devices, dev_list) {
         if (next_device != device &&
             !test_bit(BTRFS_DEV_STATE_MISSING, &next_device->dev_state)
             && next_device->bdev)
             return next_device;
     }
 
     return NULL;
 }
 
 /*
  * Helper function to check if the given device is part of s_bdev / latest_dev
  * and replace it with the provided or the next active device, in the context
  * where this function called, there should be always be another device (or
  * this_dev) which is active.
  */
 void __cold btrfs_assign_next_active_device(struct btrfs_device *device,
                         struct btrfs_device *next_device)
 {
     struct btrfs_fs_info *fs_info = device->fs_info;
 
     if (!next_device)
         next_device = btrfs_find_next_active_device(fs_info->fs_devices,
                                 device);
     ASSERT(next_device);
 
     if (fs_info->sb->s_bdev &&
             (fs_info->sb->s_bdev == device->bdev))
         fs_info->sb->s_bdev = next_device->bdev;
 
     if (fs_info->fs_devices->latest_dev->bdev == device->bdev)
         fs_info->fs_devices->latest_dev = next_device;
 }
 
 /*
  * Return btrfs_fs_devices::num_devices excluding the device that's being
  * currently replaced.
  */
 static u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
 {
     u64 num_devices = fs_info->fs_devices->num_devices;
 
     down_read(&fs_info->dev_replace.rwsem);
     if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
         ASSERT(num_devices > 1);
         num_devices--;
     }
     up_read(&fs_info->dev_replace.rwsem);
 
     return num_devices;
 }
 
 void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
                    struct block_device *bdev,
                    const char *device_path)
 {
     struct btrfs_super_block *disk_super;
     int copy_num;
 
     if (!bdev)
         return;
 
     for (copy_num = 0; copy_num < BTRFS_SUPER_MIRROR_MAX; copy_num++) {
         struct page *page;
         int ret;
 
         disk_super = btrfs_read_dev_one_super(bdev, copy_num);
         if (IS_ERR(disk_super))
             continue;
 
         if (bdev_is_zoned(bdev)) {
             btrfs_reset_sb_log_zones(bdev, copy_num);
             continue;
         }
 
         memset(&disk_super->magic, 0, sizeof(disk_super->magic));
 
         page = virt_to_page(disk_super);
         set_page_dirty(page);
         lock_page(page);
         /* write_on_page() unlocks the page */
         ret = write_one_page(page);
         if (ret)
             btrfs_warn(fs_info,
                 "error clearing superblock number %d (%d)",
                 copy_num, ret);
         btrfs_release_disk_super(disk_super);
 
     }
 
     /* Notify udev that device has changed */
     btrfs_kobject_uevent(bdev, KOBJ_CHANGE);
 
     /* Update ctime/mtime for device path for libblkid */
     update_dev_time(device_path);
 }
 
 int btrfs_rm_device(struct btrfs_fs_info *fs_info,
             struct btrfs_dev_lookup_args *args,
             struct block_device **bdev, fmode_t *mode)
 {
     struct btrfs_trans_handle *trans;
     struct btrfs_device *device;
     struct btrfs_fs_devices *cur_devices;
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
     u64 num_devices;
     int ret = 0;
 
     if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
         btrfs_err(fs_info, "device remove not supported on extent tree v2 yet");
         return -EINVAL;
     }
 
     /*
      * The device list in fs_devices is accessed without locks (neither
      * uuid_mutex nor device_list_mutex) as it won't change on a mounted
      * filesystem and another device rm cannot run.
      */
     num_devices = btrfs_num_devices(fs_info);
 
     ret = btrfs_check_raid_min_devices(fs_info, num_devices - 1);
     if (ret)
         return ret;
 
     device = btrfs_find_device(fs_info->fs_devices, args);
     if (!device) {
         if (args->missing)
             ret = BTRFS_ERROR_DEV_MISSING_NOT_FOUND;
         else
             ret = -ENOENT;
         return ret;
     }
 
     if (btrfs_pinned_by_swapfile(fs_info, device)) {
         btrfs_warn_in_rcu(fs_info,
           "cannot remove device %s (devid %llu) due to active swapfile",
                   rcu_str_deref(device->name), device->devid);
         return -ETXTBSY;
     }
 
     if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
         return BTRFS_ERROR_DEV_TGT_REPLACE;
 
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
         fs_info->fs_devices->rw_devices == 1)
         return BTRFS_ERROR_DEV_ONLY_WRITABLE;
 
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
         mutex_lock(&fs_info->chunk_mutex);
         list_del_init(&device->dev_alloc_list);
         device->fs_devices->rw_devices--;
         mutex_unlock(&fs_info->chunk_mutex);
     }
 
     ret = btrfs_shrink_device(device, 0);
     if (ret)
         goto error_undo;
 
     trans = btrfs_start_transaction(fs_info->chunk_root, 0);
     if (IS_ERR(trans)) {
         ret = PTR_ERR(trans);
         goto error_undo;
     }
 
     ret = btrfs_rm_dev_item(trans, device);
     if (ret) {
         /* Any error in dev item removal is critical */
         btrfs_crit(fs_info,
                "failed to remove device item for devid %llu: %d",
                device->devid, ret);
         btrfs_abort_transaction(trans, ret);
         btrfs_end_transaction(trans);
         return ret;
     }
 
     clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
     btrfs_scrub_cancel_dev(device);
 
     /*
      * the device list mutex makes sure that we don't change
      * the device list while someone else is writing out all
      * the device supers. Whoever is writing all supers, should
      * lock the device list mutex before getting the number of
      * devices in the super block (super_copy). Conversely,
      * whoever updates the number of devices in the super block
      * (super_copy) should hold the device list mutex.
      */
 
     /*
      * In normal cases the cur_devices == fs_devices. But in case
      * of deleting a seed device, the cur_devices should point to
      * its own fs_devices listed under the fs_devices->seed_list.
      */
     cur_devices = device->fs_devices;
     mutex_lock(&fs_devices->device_list_mutex);
     list_del_rcu(&device->dev_list);
 
     cur_devices->num_devices--;
     cur_devices->total_devices--;
     /* Update total_devices of the parent fs_devices if it's seed */
     if (cur_devices != fs_devices)
         fs_devices->total_devices--;
 
     if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
         cur_devices->missing_devices--;
 
     btrfs_assign_next_active_device(device, NULL);
 
     if (device->bdev) {
         cur_devices->open_devices--;
         /* remove sysfs entry */
         btrfs_sysfs_remove_device(device);
     }
 
     num_devices = btrfs_super_num_devices(fs_info->super_copy) - 1;
     btrfs_set_super_num_devices(fs_info->super_copy, num_devices);
     mutex_unlock(&fs_devices->device_list_mutex);
 
     /*
      * At this point, the device is zero sized and detached from the
      * devices list.  All that's left is to zero out the old supers and
      * free the device.
      *
      * We cannot call btrfs_close_bdev() here because we're holding the sb
      * write lock, and blkdev_put() will pull in the ->open_mutex on the
      * block device and it's dependencies.  Instead just flush the device
      * and let the caller do the final blkdev_put.
      */
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
         btrfs_scratch_superblocks(fs_info, device->bdev,
                       device->name->str);
         if (device->bdev) {
             sync_blockdev(device->bdev);
             invalidate_bdev(device->bdev);
         }
     }
 
     *bdev = device->bdev;
     *mode = device->mode;
     synchronize_rcu();
     btrfs_free_device(device);
 
     /*
      * This can happen if cur_devices is the private seed devices list.  We
      * cannot call close_fs_devices() here because it expects the uuid_mutex
      * to be held, but in fact we don't need that for the private
      * seed_devices, we can simply decrement cur_devices->opened and then
      * remove it from our list and free the fs_devices.
      */
     if (cur_devices->num_devices == 0) {
         list_del_init(&cur_devices->seed_list);
         ASSERT(cur_devices->opened == 1);
         cur_devices->opened--;
         free_fs_devices(cur_devices);
     }
 
     ret = btrfs_commit_transaction(trans);
 
     return ret;
 
 error_undo:
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
         mutex_lock(&fs_info->chunk_mutex);
         list_add(&device->dev_alloc_list,
              &fs_devices->alloc_list);
         device->fs_devices->rw_devices++;
         mutex_unlock(&fs_info->chunk_mutex);
     }
     return ret;
 }
 
 void btrfs_rm_dev_replace_remove_srcdev(struct btrfs_device *srcdev)
 {
     struct btrfs_fs_devices *fs_devices;
 
     lockdep_assert_held(&srcdev->fs_info->fs_devices->device_list_mutex);
 
     /*
      * in case of fs with no seed, srcdev->fs_devices will point
      * to fs_devices of fs_info. However when the dev being replaced is
      * a seed dev it will point to the seed's local fs_devices. In short
      * srcdev will have its correct fs_devices in both the cases.
      */
     fs_devices = srcdev->fs_devices;
 
     list_del_rcu(&srcdev->dev_list);
     list_del(&srcdev->dev_alloc_list);
     fs_devices->num_devices--;
     if (test_bit(BTRFS_DEV_STATE_MISSING, &srcdev->dev_state))
         fs_devices->missing_devices--;
 
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &srcdev->dev_state))
         fs_devices->rw_devices--;
 
     if (srcdev->bdev)
         fs_devices->open_devices--;
 }
 
 void btrfs_rm_dev_replace_free_srcdev(struct btrfs_device *srcdev)
 {
     struct btrfs_fs_devices *fs_devices = srcdev->fs_devices;
 
     mutex_lock(&uuid_mutex);
 
     btrfs_close_bdev(srcdev);
     synchronize_rcu();
     btrfs_free_device(srcdev);
 
     /* if this is no devs we rather delete the fs_devices */
     if (!fs_devices->num_devices) {
         /*
          * On a mounted FS, num_devices can't be zero unless it's a
          * seed. In case of a seed device being replaced, the replace
          * target added to the sprout FS, so there will be no more
          * device left under the seed FS.
          */
         ASSERT(fs_devices->seeding);
 
         list_del_init(&fs_devices->seed_list);
         close_fs_devices(fs_devices);
         free_fs_devices(fs_devices);
     }
     mutex_unlock(&uuid_mutex);
 }
 
 void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
 {
     struct btrfs_fs_devices *fs_devices = tgtdev->fs_info->fs_devices;
 
     mutex_lock(&fs_devices->device_list_mutex);
 
     btrfs_sysfs_remove_device(tgtdev);
 
     if (tgtdev->bdev)
         fs_devices->open_devices--;
 
     fs_devices->num_devices--;
 
     btrfs_assign_next_active_device(tgtdev, NULL);
 
     list_del_rcu(&tgtdev->dev_list);
 
     mutex_unlock(&fs_devices->device_list_mutex);
 
     btrfs_scratch_superblocks(tgtdev->fs_info, tgtdev->bdev,
                   tgtdev->name->str);
 
     btrfs_close_bdev(tgtdev);
     synchronize_rcu();
     btrfs_free_device(tgtdev);
 }
 
 /**
  * Populate args from device at path
  *
  * @fs_info:    the filesystem
  * @args:   the args to populate
  * @path:   the path to the device
  *
  * This will read the super block of the device at @path and populate @args with
  * the devid, fsid, and uuid.  This is meant to be used for ioctls that need to
  * lookup a device to operate on, but need to do it before we take any locks.
  * This properly handles the special case of "missing" that a user may pass in,
  * and does some basic sanity checks.  The caller must make sure that @path is
  * properly NUL terminated before calling in, and must call
  * btrfs_put_dev_args_from_path() in order to free up the temporary fsid and
  * uuid buffers.
  *
  * Return: 0 for success, -errno for failure
  */
 int btrfs_get_dev_args_from_path(struct btrfs_fs_info *fs_info,
                  struct btrfs_dev_lookup_args *args,
                  const char *path)
 {
     struct btrfs_super_block *disk_super;
     struct block_device *bdev;
     int ret;
 
     if (!path || !path[0])
         return -EINVAL;
     if (!strcmp(path, "missing")) {
         args->missing = true;
         return 0;
     }
 
     args->uuid = kzalloc(BTRFS_UUID_SIZE, GFP_KERNEL);
     args->fsid = kzalloc(BTRFS_FSID_SIZE, GFP_KERNEL);
     if (!args->uuid || !args->fsid) {
         btrfs_put_dev_args_from_path(args);
         return -ENOMEM;
     }
 
     ret = btrfs_get_bdev_and_sb(path, FMODE_READ, fs_info->bdev_holder, 0,
                     &bdev, &disk_super);
     if (ret) {
         btrfs_put_dev_args_from_path(args);
         return ret;
     }
 
     args->devid = btrfs_stack_device_id(&disk_super->dev_item);
     memcpy(args->uuid, disk_super->dev_item.uuid, BTRFS_UUID_SIZE);
     if (btrfs_fs_incompat(fs_info, METADATA_UUID))
         memcpy(args->fsid, disk_super->metadata_uuid, BTRFS_FSID_SIZE);
     else
         memcpy(args->fsid, disk_super->fsid, BTRFS_FSID_SIZE);
     btrfs_release_disk_super(disk_super);
     blkdev_put(bdev, FMODE_READ);
     return 0;
 }
 
 /*
  * Only use this jointly with btrfs_get_dev_args_from_path() because we will
  * allocate our ->uuid and ->fsid pointers, everybody else uses local variables
  * that don't need to be freed.
  */
 void btrfs_put_dev_args_from_path(struct btrfs_dev_lookup_args *args)
 {
     kfree(args->uuid);
     kfree(args->fsid);
     args->uuid = NULL;
     args->fsid = NULL;
 }
 
 struct btrfs_device *btrfs_find_device_by_devspec(
         struct btrfs_fs_info *fs_info, u64 devid,
         const char *device_path)
 {
     BTRFS_DEV_LOOKUP_ARGS(args);
     struct btrfs_device *device;
     int ret;
 
     if (devid) {
         args.devid = devid;
         device = btrfs_find_device(fs_info->fs_devices, &args);
         if (!device)
             return ERR_PTR(-ENOENT);
         return device;
     }
 
     ret = btrfs_get_dev_args_from_path(fs_info, &args, device_path);
     if (ret)
         return ERR_PTR(ret);
     device = btrfs_find_device(fs_info->fs_devices, &args);
     btrfs_put_dev_args_from_path(&args);
     if (!device)
         return ERR_PTR(-ENOENT);
     return device;
 }
 
 static struct btrfs_fs_devices *btrfs_init_sprout(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
     struct btrfs_fs_devices *old_devices;
     struct btrfs_fs_devices *seed_devices;
 
     lockdep_assert_held(&uuid_mutex);
     if (!fs_devices->seeding)
         return ERR_PTR(-EINVAL);
 
     /*
      * Private copy of the seed devices, anchored at
      * fs_info->fs_devices->seed_list
      */
     seed_devices = alloc_fs_devices(NULL, NULL);
     if (IS_ERR(seed_devices))
         return seed_devices;
 
     /*
      * It's necessary to retain a copy of the original seed fs_devices in
      * fs_uuids so that filesystems which have been seeded can successfully
      * reference the seed device from open_seed_devices. This also supports
      * multiple fs seed.
      */
     old_devices = clone_fs_devices(fs_devices);
     if (IS_ERR(old_devices)) {
         kfree(seed_devices);
         return old_devices;
     }
 
     list_add(&old_devices->fs_list, &fs_uuids);
 
     memcpy(seed_devices, fs_devices, sizeof(*seed_devices));
     seed_devices->opened = 1;
     INIT_LIST_HEAD(&seed_devices->devices);
     INIT_LIST_HEAD(&seed_devices->alloc_list);
     mutex_init(&seed_devices->device_list_mutex);
 
     return seed_devices;
 }
 
 /*
  * Splice seed devices into the sprout fs_devices.
  * Generate a new fsid for the sprouted read-write filesystem.
  */
 static void btrfs_setup_sprout(struct btrfs_fs_info *fs_info,
                    struct btrfs_fs_devices *seed_devices)
 {
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
     struct btrfs_super_block *disk_super = fs_info->super_copy;
     struct btrfs_device *device;
     u64 super_flags;
 
     /*
      * We are updating the fsid, the thread leading to device_list_add()
      * could race, so uuid_mutex is needed.
      */
     lockdep_assert_held(&uuid_mutex);
 
     /*
      * The threads listed below may traverse dev_list but can do that without
      * device_list_mutex:
      * - All device ops and balance - as we are in btrfs_exclop_start.
      * - Various dev_list readers - are using RCU.
      * - btrfs_ioctl_fitrim() - is using RCU.
      *
      * For-read threads as below are using device_list_mutex:
      * - Readonly scrub btrfs_scrub_dev()
      * - Readonly scrub btrfs_scrub_progress()
      * - btrfs_get_dev_stats()
      */
     lockdep_assert_held(&fs_devices->device_list_mutex);
 
     list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices,
                   synchronize_rcu);
     list_for_each_entry(device, &seed_devices->devices, dev_list)
         device->fs_devices = seed_devices;
 
     fs_devices->seeding = false;
     fs_devices->num_devices = 0;
     fs_devices->open_devices = 0;
     fs_devices->missing_devices = 0;
     fs_devices->rotating = false;
     list_add(&seed_devices->seed_list, &fs_devices->seed_list);
 
     generate_random_uuid(fs_devices->fsid);
     memcpy(fs_devices->metadata_uuid, fs_devices->fsid, BTRFS_FSID_SIZE);
     memcpy(disk_super->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
 
     super_flags = btrfs_super_flags(disk_super) &
               ~BTRFS_SUPER_FLAG_SEEDING;
     btrfs_set_super_flags(disk_super, super_flags);
 }
 
 /*
  * Store the expected generation for seed devices in device items.
  */
 static int btrfs_finish_sprout(struct btrfs_trans_handle *trans)
 {
     BTRFS_DEV_LOOKUP_ARGS(args);
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_root *root = fs_info->chunk_root;
     struct btrfs_path *path;
     struct extent_buffer *leaf;
     struct btrfs_dev_item *dev_item;
     struct btrfs_device *device;
     struct btrfs_key key;
     u8 fs_uuid[BTRFS_FSID_SIZE];
     u8 dev_uuid[BTRFS_UUID_SIZE];
     int ret;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
     key.offset = 0;
     key.type = BTRFS_DEV_ITEM_KEY;
 
     while (1) {
         btrfs_reserve_chunk_metadata(trans, false);
         ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
         btrfs_trans_release_chunk_metadata(trans);
         if (ret < 0)
             goto error;
 
         leaf = path->nodes[0];
 next_slot:
         if (path->slots[0] >= btrfs_header_nritems(leaf)) {
             ret = btrfs_next_leaf(root, path);
             if (ret > 0)
                 break;
             if (ret < 0)
                 goto error;
             leaf = path->nodes[0];
             btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
             btrfs_release_path(path);
             continue;
         }
 
         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
         if (key.objectid != BTRFS_DEV_ITEMS_OBJECTID ||
             key.type != BTRFS_DEV_ITEM_KEY)
             break;
 
         dev_item = btrfs_item_ptr(leaf, path->slots[0],
                       struct btrfs_dev_item);
         args.devid = btrfs_device_id(leaf, dev_item);
         read_extent_buffer(leaf, dev_uuid, btrfs_device_uuid(dev_item),
                    BTRFS_UUID_SIZE);
         read_extent_buffer(leaf, fs_uuid, btrfs_device_fsid(dev_item),
                    BTRFS_FSID_SIZE);
         args.uuid = dev_uuid;
         args.fsid = fs_uuid;
         device = btrfs_find_device(fs_info->fs_devices, &args);
         BUG_ON(!device); /* Logic error */
 
         if (device->fs_devices->seeding) {
             btrfs_set_device_generation(leaf, dev_item,
                             device->generation);
             btrfs_mark_buffer_dirty(leaf);
         }
 
         path->slots[0]++;
         goto next_slot;
     }
     ret = 0;
 error:
     btrfs_free_path(path);
     return ret;
 }
 
 int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path)
 {
     struct btrfs_root *root = fs_info->dev_root;
     struct btrfs_trans_handle *trans;
     struct btrfs_device *device;
     struct block_device *bdev;
     struct super_block *sb = fs_info->sb;
     struct rcu_string *name;
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
     struct btrfs_fs_devices *seed_devices;
     u64 orig_super_total_bytes;
     u64 orig_super_num_devices;
     int ret = 0;
     bool seeding_dev = false;
     bool locked = false;
 
     if (sb_rdonly(sb) && !fs_devices->seeding)
         return -EROFS;
 
     bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
                   fs_info->bdev_holder);
     if (IS_ERR(bdev))
         return PTR_ERR(bdev);
 
     if (!btrfs_check_device_zone_type(fs_info, bdev)) {
         ret = -EINVAL;
         goto error;
     }
 
     if (fs_devices->seeding) {
         seeding_dev = true;
         down_write(&sb->s_umount);
         mutex_lock(&uuid_mutex);
         locked = true;
     }
 
     sync_blockdev(bdev);
 
     rcu_read_lock();
     list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) {
         if (device->bdev == bdev) {
             ret = -EEXIST;
             rcu_read_unlock();
             goto error;
         }
     }
     rcu_read_unlock();
 
     device = btrfs_alloc_device(fs_info, NULL, NULL);
     if (IS_ERR(device)) {
         /* we can safely leave the fs_devices entry around */
         ret = PTR_ERR(device);
         goto error;
     }
 
     name = rcu_string_strdup(device_path, GFP_KERNEL);
     if (!name) {
         ret = -ENOMEM;
         goto error_free_device;
     }
     rcu_assign_pointer(device->name, name);
 
     device->fs_info = fs_info;
     device->bdev = bdev;
     ret = lookup_bdev(device_path, &device->devt);
     if (ret)
         goto error_free_device;
 
     ret = btrfs_get_dev_zone_info(device, false);
     if (ret)
         goto error_free_device;
 
     trans = btrfs_start_transaction(root, 0);
     if (IS_ERR(trans)) {
         ret = PTR_ERR(trans);
         goto error_free_zone;
     }
 
     set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
     device->generation = trans->transid;
     device->io_width = fs_info->sectorsize;
     device->io_align = fs_info->sectorsize;
     device->sector_size = fs_info->sectorsize;
     device->total_bytes =
         round_down(bdev_nr_bytes(bdev), fs_info->sectorsize);
     device->disk_total_bytes = device->total_bytes;
     device->commit_total_bytes = device->total_bytes;
     set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
     clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
     device->mode = FMODE_EXCL;
     device->dev_stats_valid = 1;
     set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 
     if (seeding_dev) {
         btrfs_clear_sb_rdonly(sb);
 
         /* GFP_KERNEL allocation must not be under device_list_mutex */
         seed_devices = btrfs_init_sprout(fs_info);
         if (IS_ERR(seed_devices)) {
             ret = PTR_ERR(seed_devices);
             btrfs_abort_transaction(trans, ret);
             goto error_trans;
         }
     }
 
     mutex_lock(&fs_devices->device_list_mutex);
     if (seeding_dev) {
         btrfs_setup_sprout(fs_info, seed_devices);
         btrfs_assign_next_active_device(fs_info->fs_devices->latest_dev,
                         device);
     }
 
     device->fs_devices = fs_devices;
 
     mutex_lock(&fs_info->chunk_mutex);
     list_add_rcu(&device->dev_list, &fs_devices->devices);
     list_add(&device->dev_alloc_list, &fs_devices->alloc_list);
     fs_devices->num_devices++;
     fs_devices->open_devices++;
     fs_devices->rw_devices++;
     fs_devices->total_devices++;
     fs_devices->total_rw_bytes += device->total_bytes;
 
     atomic64_add(device->total_bytes, &fs_info->free_chunk_space);
 
     if (!bdev_nonrot(bdev))
         fs_devices->rotating = true;
 
     orig_super_total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
     btrfs_set_super_total_bytes(fs_info->super_copy,
         round_down(orig_super_total_bytes + device->total_bytes,
                fs_info->sectorsize));
 
     orig_super_num_devices = btrfs_super_num_devices(fs_info->super_copy);
     btrfs_set_super_num_devices(fs_info->super_copy,
                     orig_super_num_devices + 1);
 
     /*
      * we've got more storage, clear any full flags on the space
      * infos
      */
     btrfs_clear_space_info_full(fs_info);
 
     mutex_unlock(&fs_info->chunk_mutex);
 
     /* Add sysfs device entry */
     btrfs_sysfs_add_device(device);
 
     mutex_unlock(&fs_devices->device_list_mutex);
 
     if (seeding_dev) {
         mutex_lock(&fs_info->chunk_mutex);
         ret = init_first_rw_device(trans);
         mutex_unlock(&fs_info->chunk_mutex);
         if (ret) {
             btrfs_abort_transaction(trans, ret);
             goto error_sysfs;
         }
     }
 
     ret = btrfs_add_dev_item(trans, device);
     if (ret) {
         btrfs_abort_transaction(trans, ret);
         goto error_sysfs;
     }
 
     if (seeding_dev) {
         ret = btrfs_finish_sprout(trans);
         if (ret) {
             btrfs_abort_transaction(trans, ret);
             goto error_sysfs;
         }
 
         /*
          * fs_devices now represents the newly sprouted filesystem and
          * its fsid has been changed by btrfs_sprout_splice().
          */
         btrfs_sysfs_update_sprout_fsid(fs_devices);
     }
 
     ret = btrfs_commit_transaction(trans);
 
     if (seeding_dev) {
         mutex_unlock(&uuid_mutex);
         up_write(&sb->s_umount);
         locked = false;
 
         if (ret) /* transaction commit */
             return ret;
 
         ret = btrfs_relocate_sys_chunks(fs_info);
         if (ret < 0)
             btrfs_handle_fs_error(fs_info, ret,
                     "Failed to relocate sys chunks after device initialization. This can be fixed using the \"btrfs balance\" command.");
         trans = btrfs_attach_transaction(root);
         if (IS_ERR(trans)) {
             if (PTR_ERR(trans) == -ENOENT)
                 return 0;
             ret = PTR_ERR(trans);
             trans = NULL;
             goto error_sysfs;
         }
         ret = btrfs_commit_transaction(trans);
     }
 
     /*
      * Now that we have written a new super block to this device, check all
      * other fs_devices list if device_path alienates any other scanned
      * device.
      * We can ignore the return value as it typically returns -EINVAL and
      * only succeeds if the device was an alien.
      */
     btrfs_forget_devices(device->devt);
 
     /* Update ctime/mtime for blkid or udev */
     update_dev_time(device_path);
 
     return ret;
 
 error_sysfs:
     btrfs_sysfs_remove_device(device);
     mutex_lock(&fs_info->fs_devices->device_list_mutex);
     mutex_lock(&fs_info->chunk_mutex);
     list_del_rcu(&device->dev_list);
     list_del(&device->dev_alloc_list);
     fs_info->fs_devices->num_devices--;
     fs_info->fs_devices->open_devices--;
     fs_info->fs_devices->rw_devices--;
     fs_info->fs_devices->total_devices--;
     fs_info->fs_devices->total_rw_bytes -= device->total_bytes;
     atomic64_sub(device->total_bytes, &fs_info->free_chunk_space);
     btrfs_set_super_total_bytes(fs_info->super_copy,
                     orig_super_total_bytes);
     btrfs_set_super_num_devices(fs_info->super_copy,
                     orig_super_num_devices);
     mutex_unlock(&fs_info->chunk_mutex);
     mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 error_trans:
     if (seeding_dev)
         btrfs_set_sb_rdonly(sb);
     if (trans)
         btrfs_end_transaction(trans);
 error_free_zone:
     btrfs_destroy_dev_zone_info(device);
 error_free_device:
     btrfs_free_device(device);
 error:
     blkdev_put(bdev, FMODE_EXCL);
     if (locked) {
         mutex_unlock(&uuid_mutex);
         up_write(&sb->s_umount);
     }
     return ret;
 }
 
 static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
                     struct btrfs_device *device)
 {
     int ret;
     struct btrfs_path *path;
     struct btrfs_root *root = device->fs_info->chunk_root;
     struct btrfs_dev_item *dev_item;
     struct extent_buffer *leaf;
     struct btrfs_key key;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
     key.type = BTRFS_DEV_ITEM_KEY;
     key.offset = device->devid;
 
     ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
     if (ret < 0)
         goto out;
 
     if (ret > 0) {
         ret = -ENOENT;
         goto out;
     }
 
     leaf = path->nodes[0];
     dev_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_item);
 
     btrfs_set_device_id(leaf, dev_item, device->devid);
     btrfs_set_device_type(leaf, dev_item, device->type);
     btrfs_set_device_io_align(leaf, dev_item, device->io_align);
     btrfs_set_device_io_width(leaf, dev_item, device->io_width);
     btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
     btrfs_set_device_total_bytes(leaf, dev_item,
                      btrfs_device_get_disk_total_bytes(device));
     btrfs_set_device_bytes_used(leaf, dev_item,
                     btrfs_device_get_bytes_used(device));
     btrfs_mark_buffer_dirty(leaf);
 
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 int btrfs_grow_device(struct btrfs_trans_handle *trans,
               struct btrfs_device *device, u64 new_size)
 {
     struct btrfs_fs_info *fs_info = device->fs_info;
     struct btrfs_super_block *super_copy = fs_info->super_copy;
     u64 old_total;
     u64 diff;
     int ret;
 
     if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
         return -EACCES;
 
     new_size = round_down(new_size, fs_info->sectorsize);
 
     mutex_lock(&fs_info->chunk_mutex);
     old_total = btrfs_super_total_bytes(super_copy);
     diff = round_down(new_size - device->total_bytes, fs_info->sectorsize);
 
     if (new_size <= device->total_bytes ||
         test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
         mutex_unlock(&fs_info->chunk_mutex);
         return -EINVAL;
     }
 
     btrfs_set_super_total_bytes(super_copy,
             round_down(old_total + diff, fs_info->sectorsize));
     device->fs_devices->total_rw_bytes += diff;
 
     btrfs_device_set_total_bytes(device, new_size);
     btrfs_device_set_disk_total_bytes(device, new_size);
     btrfs_clear_space_info_full(device->fs_info);
     if (list_empty(&device->post_commit_list))
         list_add_tail(&device->post_commit_list,
                   &trans->transaction->dev_update_list);
     mutex_unlock(&fs_info->chunk_mutex);
 
     btrfs_reserve_chunk_metadata(trans, false);
     ret = btrfs_update_device(trans, device);
     btrfs_trans_release_chunk_metadata(trans);
 
     return ret;
 }
 
 static int btrfs_free_chunk(struct btrfs_trans_handle *trans, u64 chunk_offset)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_root *root = fs_info->chunk_root;
     int ret;
     struct btrfs_path *path;
     struct btrfs_key key;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
     key.offset = chunk_offset;
     key.type = BTRFS_CHUNK_ITEM_KEY;
 
     ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
     if (ret < 0)
         goto out;
     else if (ret > 0) { /* Logic error or corruption */
         btrfs_handle_fs_error(fs_info, -ENOENT,
                       "Failed lookup while freeing chunk.");
         ret = -ENOENT;
         goto out;
     }
 
     ret = btrfs_del_item(trans, root, path);
     if (ret < 0)
         btrfs_handle_fs_error(fs_info, ret,
                       "Failed to delete chunk item.");
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 static int btrfs_del_sys_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
 {
     struct btrfs_super_block *super_copy = fs_info->super_copy;
     struct btrfs_disk_key *disk_key;
     struct btrfs_chunk *chunk;
     u8 *ptr;
     int ret = 0;
     u32 num_stripes;
     u32 array_size;
     u32 len = 0;
     u32 cur;
     struct btrfs_key key;
 
     lockdep_assert_held(&fs_info->chunk_mutex);
     array_size = btrfs_super_sys_array_size(super_copy);
 
     ptr = super_copy->sys_chunk_array;
     cur = 0;
 
     while (cur < array_size) {
         disk_key = (struct btrfs_disk_key *)ptr;
         btrfs_disk_key_to_cpu(&key, disk_key);
 
         len = sizeof(*disk_key);
 
         if (key.type == BTRFS_CHUNK_ITEM_KEY) {
             chunk = (struct btrfs_chunk *)(ptr + len);
             num_stripes = btrfs_stack_chunk_num_stripes(chunk);
             len += btrfs_chunk_item_size(num_stripes);
         } else {
             ret = -EIO;
             break;
         }
         if (key.objectid == BTRFS_FIRST_CHUNK_TREE_OBJECTID &&
             key.offset == chunk_offset) {
             memmove(ptr, ptr + len, array_size - (cur + len));
             array_size -= len;
             btrfs_set_super_sys_array_size(super_copy, array_size);
         } else {
             ptr += len;
             cur += len;
         }
     }
     return ret;
 }
 
 /*
  * btrfs_get_chunk_map() - Find the mapping containing the given logical extent.
  * @logical: Logical block offset in bytes.
  * @length: Length of extent in bytes.
  *
  * Return: Chunk mapping or ERR_PTR.
  */
 struct extent_map *btrfs_get_chunk_map(struct btrfs_fs_info *fs_info,
                        u64 logical, u64 length)
 {
     struct extent_map_tree *em_tree;
     struct extent_map *em;
 
     em_tree = &fs_info->mapping_tree;
     read_lock(&em_tree->lock);
     em = lookup_extent_mapping(em_tree, logical, length);
     read_unlock(&em_tree->lock);
 
     if (!em) {
         btrfs_crit(fs_info, "unable to find logical %llu length %llu",
                logical, length);
         return ERR_PTR(-EINVAL);
     }
 
     if (em->start > logical || em->start + em->len < logical) {
         btrfs_crit(fs_info,
                "found a bad mapping, wanted %llu-%llu, found %llu-%llu",
                logical, length, em->start, em->start + em->len);
         free_extent_map(em);
         return ERR_PTR(-EINVAL);
     }
 
     /* callers are responsible for dropping em's ref. */
     return em;
 }
 
 static int remove_chunk_item(struct btrfs_trans_handle *trans,
                  struct map_lookup *map, u64 chunk_offset)
 {
     int i;
 
     /*
      * Removing chunk items and updating the device items in the chunks btree
      * requires holding the chunk_mutex.
      * See the comment at btrfs_chunk_alloc() for the details.
      */
     lockdep_assert_held(&trans->fs_info->chunk_mutex);
 
     for (i = 0; i < map->num_stripes; i++) {
         int ret;
 
         ret = btrfs_update_device(trans, map->stripes[i].dev);
         if (ret)
             return ret;
     }
 
     return btrfs_free_chunk(trans, chunk_offset);
 }
 
 int btrfs_remove_chunk(struct btrfs_trans_handle *trans, u64 chunk_offset)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct extent_map *em;
     struct map_lookup *map;
     u64 dev_extent_len = 0;
     int i, ret = 0;
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 
     em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
     if (IS_ERR(em)) {
         /*
          * This is a logic error, but we don't want to just rely on the
          * user having built with ASSERT enabled, so if ASSERT doesn't
          * do anything we still error out.
          */
         ASSERT(0);
         return PTR_ERR(em);
     }
     map = em->map_lookup;
 
     /*
      * First delete the device extent items from the devices btree.
      * We take the device_list_mutex to avoid racing with the finishing phase
      * of a device replace operation. See the comment below before acquiring
      * fs_info->chunk_mutex. Note that here we do not acquire the chunk_mutex
      * because that can result in a deadlock when deleting the device extent
      * items from the devices btree - COWing an extent buffer from the btree
      * may result in allocating a new metadata chunk, which would attempt to
      * lock again fs_info->chunk_mutex.
      */
     mutex_lock(&fs_devices->device_list_mutex);
     for (i = 0; i < map->num_stripes; i++) {
         struct btrfs_device *device = map->stripes[i].dev;
         ret = btrfs_free_dev_extent(trans, device,
                         map->stripes[i].physical,
                         &dev_extent_len);
         if (ret) {
             mutex_unlock(&fs_devices->device_list_mutex);
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
 
         if (device->bytes_used > 0) {
             mutex_lock(&fs_info->chunk_mutex);
             btrfs_device_set_bytes_used(device,
                     device->bytes_used - dev_extent_len);
             atomic64_add(dev_extent_len, &fs_info->free_chunk_space);
             btrfs_clear_space_info_full(fs_info);
             mutex_unlock(&fs_info->chunk_mutex);
         }
     }
     mutex_unlock(&fs_devices->device_list_mutex);
 
     /*
      * We acquire fs_info->chunk_mutex for 2 reasons:
      *
      * 1) Just like with the first phase of the chunk allocation, we must
      *    reserve system space, do all chunk btree updates and deletions, and
      *    update the system chunk array in the superblock while holding this
      *    mutex. This is for similar reasons as explained on the comment at
      *    the top of btrfs_chunk_alloc();
      *
      * 2) Prevent races with the final phase of a device replace operation
      *    that replaces the device object associated with the map's stripes,
      *    because the device object's id can change at any time during that
      *    final phase of the device replace operation
      *    (dev-replace.c:btrfs_dev_replace_finishing()), so we could grab the
      *    replaced device and then see it with an ID of
      *    BTRFS_DEV_REPLACE_DEVID, which would cause a failure when updating
      *    the device item, which does not exists on the chunk btree.
      *    The finishing phase of device replace acquires both the
      *    device_list_mutex and the chunk_mutex, in that order, so we are
      *    safe by just acquiring the chunk_mutex.
      */
     trans->removing_chunk = true;
     mutex_lock(&fs_info->chunk_mutex);
 
     check_system_chunk(trans, map->type);
 
     ret = remove_chunk_item(trans, map, chunk_offset);
     /*
      * Normally we should not get -ENOSPC since we reserved space before
      * through the call to check_system_chunk().
      *
      * Despite our system space_info having enough free space, we may not
      * be able to allocate extents from its block groups, because all have
      * an incompatible profile, which will force us to allocate a new system
      * block group with the right profile, or right after we called
      * check_system_space() above, a scrub turned the only system block group
      * with enough free space into RO mode.
      * This is explained with more detail at do_chunk_alloc().
      *
      * So if we get -ENOSPC, allocate a new system chunk and retry once.
      */
     if (ret == -ENOSPC) {
         const u64 sys_flags = btrfs_system_alloc_profile(fs_info);
         struct btrfs_block_group *sys_bg;
 
         sys_bg = btrfs_create_chunk(trans, sys_flags);
         if (IS_ERR(sys_bg)) {
             ret = PTR_ERR(sys_bg);
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
 
         ret = btrfs_chunk_alloc_add_chunk_item(trans, sys_bg);
         if (ret) {
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
 
         ret = remove_chunk_item(trans, map, chunk_offset);
         if (ret) {
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
     } else if (ret) {
         btrfs_abort_transaction(trans, ret);
         goto out;
     }
 
     trace_btrfs_chunk_free(fs_info, map, chunk_offset, em->len);
 
     if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
         ret = btrfs_del_sys_chunk(fs_info, chunk_offset);
         if (ret) {
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
     }
 
     mutex_unlock(&fs_info->chunk_mutex);
     trans->removing_chunk = false;
 
     /*
      * We are done with chunk btree updates and deletions, so release the
      * system space we previously reserved (with check_system_chunk()).
      */
     btrfs_trans_release_chunk_metadata(trans);
 
     ret = btrfs_remove_block_group(trans, chunk_offset, em);
     if (ret) {
         btrfs_abort_transaction(trans, ret);
         goto out;
     }
 
 out:
     if (trans->removing_chunk) {
         mutex_unlock(&fs_info->chunk_mutex);
         trans->removing_chunk = false;
     }
     /* once for us */
     free_extent_map(em);
     return ret;
 }
 
 int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
 {
     struct btrfs_root *root = fs_info->chunk_root;
     struct btrfs_trans_handle *trans;
     struct btrfs_block_group *block_group;
     u64 length;
     int ret;
 
     if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
         btrfs_err(fs_info,
               "relocate: not supported on extent tree v2 yet");
         return -EINVAL;
     }
 
     /*
      * Prevent races with automatic removal of unused block groups.
      * After we relocate and before we remove the chunk with offset
      * chunk_offset, automatic removal of the block group can kick in,
      * resulting in a failure when calling btrfs_remove_chunk() below.
      *
      * Make sure to acquire this mutex before doing a tree search (dev
      * or chunk trees) to find chunks. Otherwise the cleaner kthread might
      * call btrfs_remove_chunk() (through btrfs_delete_unused_bgs()) after
      * we release the path used to search the chunk/dev tree and before
      * the current task acquires this mutex and calls us.
      */
     lockdep_assert_held(&fs_info->reclaim_bgs_lock);
 
     /* step one, relocate all the extents inside this chunk */
     btrfs_scrub_pause(fs_info);
     ret = btrfs_relocate_block_group(fs_info, chunk_offset);
     btrfs_scrub_continue(fs_info);
     if (ret)
         return ret;
 
     block_group = btrfs_lookup_block_group(fs_info, chunk_offset);
     if (!block_group)
         return -ENOENT;
     btrfs_discard_cancel_work(&fs_info->discard_ctl, block_group);
     length = block_group->length;
     btrfs_put_block_group(block_group);
 
     /*
      * On a zoned file system, discard the whole block group, this will
      * trigger a REQ_OP_ZONE_RESET operation on the device zone. If
      * resetting the zone fails, don't treat it as a fatal problem from the
      * filesystem's point of view.
      */
     if (btrfs_is_zoned(fs_info)) {
         ret = btrfs_discard_extent(fs_info, chunk_offset, length, NULL);
         if (ret)
             btrfs_info(fs_info,
                 "failed to reset zone %llu after relocation",
                 chunk_offset);
     }
 
     trans = btrfs_start_trans_remove_block_group(root->fs_info,
                              chunk_offset);
     if (IS_ERR(trans)) {
         ret = PTR_ERR(trans);
         btrfs_handle_fs_error(root->fs_info, ret, NULL);
         return ret;
     }
 
     /*
      * step two, delete the device extents and the
      * chunk tree entries
      */
     ret = btrfs_remove_chunk(trans, chunk_offset);
     btrfs_end_transaction(trans);
     return ret;
 }
 
 static int btrfs_relocate_sys_chunks(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_root *chunk_root = fs_info->chunk_root;
     struct btrfs_path *path;
     struct extent_buffer *leaf;
     struct btrfs_chunk *chunk;
     struct btrfs_key key;
     struct btrfs_key found_key;
     u64 chunk_type;
     bool retried = false;
     int failed = 0;
     int ret;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
 again:
     key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
     key.offset = (u64)-1;
     key.type = BTRFS_CHUNK_ITEM_KEY;
 
     while (1) {
         mutex_lock(&fs_info->reclaim_bgs_lock);
         ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
         if (ret < 0) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             goto error;
         }
         BUG_ON(ret == 0); /* Corruption */
 
         ret = btrfs_previous_item(chunk_root, path, key.objectid,
                       key.type);
         if (ret)
             mutex_unlock(&fs_info->reclaim_bgs_lock);
         if (ret < 0)
             goto error;
         if (ret > 0)
             break;
 
         leaf = path->nodes[0];
         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 
         chunk = btrfs_item_ptr(leaf, path->slots[0],
                        struct btrfs_chunk);
         chunk_type = btrfs_chunk_type(leaf, chunk);
         btrfs_release_path(path);
 
         if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM) {
             ret = btrfs_relocate_chunk(fs_info, found_key.offset);
             if (ret == -ENOSPC)
                 failed++;
             else
                 BUG_ON(ret);
         }
         mutex_unlock(&fs_info->reclaim_bgs_lock);
 
         if (found_key.offset == 0)
             break;
         key.offset = found_key.offset - 1;
     }
     ret = 0;
     if (failed && !retried) {
         failed = 0;
         retried = true;
         goto again;
     } else if (WARN_ON(failed && retried)) {
         ret = -ENOSPC;
     }
 error:
     btrfs_free_path(path);
     return ret;
 }
 
 /*
  * return 1 : allocate a data chunk successfully,
  * return <0: errors during allocating a data chunk,
  * return 0 : no need to allocate a data chunk.
  */
 static int btrfs_may_alloc_data_chunk(struct btrfs_fs_info *fs_info,
                       u64 chunk_offset)
 {
     struct btrfs_block_group *cache;
     u64 bytes_used;
     u64 chunk_type;
 
     cache = btrfs_lookup_block_group(fs_info, chunk_offset);
     ASSERT(cache);
     chunk_type = cache->flags;
     btrfs_put_block_group(cache);
 
     if (!(chunk_type & BTRFS_BLOCK_GROUP_DATA))
         return 0;
 
     spin_lock(&fs_info->data_sinfo->lock);
     bytes_used = fs_info->data_sinfo->bytes_used;
     spin_unlock(&fs_info->data_sinfo->lock);
 
     if (!bytes_used) {
         struct btrfs_trans_handle *trans;
         int ret;
 
         trans = btrfs_join_transaction(fs_info->tree_root);
         if (IS_ERR(trans))
             return PTR_ERR(trans);
 
         ret = btrfs_force_chunk_alloc(trans, BTRFS_BLOCK_GROUP_DATA);
         btrfs_end_transaction(trans);
         if (ret < 0)
             return ret;
         return 1;
     }
 
     return 0;
 }
 
 static int insert_balance_item(struct btrfs_fs_info *fs_info,
                    struct btrfs_balance_control *bctl)
 {
     struct btrfs_root *root = fs_info->tree_root;
     struct btrfs_trans_handle *trans;
     struct btrfs_balance_item *item;
     struct btrfs_disk_balance_args disk_bargs;
     struct btrfs_path *path;
     struct extent_buffer *leaf;
     struct btrfs_key key;
     int ret, err;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     trans = btrfs_start_transaction(root, 0);
     if (IS_ERR(trans)) {
         btrfs_free_path(path);
         return PTR_ERR(trans);
     }
 
     key.objectid = BTRFS_BALANCE_OBJECTID;
     key.type = BTRFS_TEMPORARY_ITEM_KEY;
     key.offset = 0;
 
     ret = btrfs_insert_empty_item(trans, root, path, &key,
                       sizeof(*item));
     if (ret)
         goto out;
 
     leaf = path->nodes[0];
     item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_balance_item);
 
     memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
 
     btrfs_cpu_balance_args_to_disk(&disk_bargs, &bctl->data);
     btrfs_set_balance_data(leaf, item, &disk_bargs);
     btrfs_cpu_balance_args_to_disk(&disk_bargs, &bctl->meta);
     btrfs_set_balance_meta(leaf, item, &disk_bargs);
     btrfs_cpu_balance_args_to_disk(&disk_bargs, &bctl->sys);
     btrfs_set_balance_sys(leaf, item, &disk_bargs);
 
     btrfs_set_balance_flags(leaf, item, bctl->flags);
 
     btrfs_mark_buffer_dirty(leaf);
 out:
     btrfs_free_path(path);
     err = btrfs_commit_transaction(trans);
     if (err && !ret)
         ret = err;
     return ret;
 }
 
 static int del_balance_item(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_root *root = fs_info->tree_root;
     struct btrfs_trans_handle *trans;
     struct btrfs_path *path;
     struct btrfs_key key;
     int ret, err;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     trans = btrfs_start_transaction_fallback_global_rsv(root, 0);
     if (IS_ERR(trans)) {
         btrfs_free_path(path);
         return PTR_ERR(trans);
     }
 
     key.objectid = BTRFS_BALANCE_OBJECTID;
     key.type = BTRFS_TEMPORARY_ITEM_KEY;
     key.offset = 0;
 
     ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
     if (ret < 0)
         goto out;
     if (ret > 0) {
         ret = -ENOENT;
         goto out;
     }
 
     ret = btrfs_del_item(trans, root, path);
 out:
     btrfs_free_path(path);
     err = btrfs_commit_transaction(trans);
     if (err && !ret)
         ret = err;
     return ret;
 }
 
 /*
  * This is a heuristic used to reduce the number of chunks balanced on
  * resume after balance was interrupted.
  */
 static void update_balance_args(struct btrfs_balance_control *bctl)
 {
     /*
      * Turn on soft mode for chunk types that were being converted.
      */
     if (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT)
         bctl->data.flags |= BTRFS_BALANCE_ARGS_SOFT;
     if (bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT)
         bctl->sys.flags |= BTRFS_BALANCE_ARGS_SOFT;
     if (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT)
         bctl->meta.flags |= BTRFS_BALANCE_ARGS_SOFT;
 
     /*
      * Turn on usage filter if is not already used.  The idea is
      * that chunks that we have already balanced should be
      * reasonably full.  Don't do it for chunks that are being
      * converted - that will keep us from relocating unconverted
      * (albeit full) chunks.
      */
     if (!(bctl->data.flags & BTRFS_BALANCE_ARGS_USAGE) &&
         !(bctl->data.flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
         !(bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
         bctl->data.flags |= BTRFS_BALANCE_ARGS_USAGE;
         bctl->data.usage = 90;
     }
     if (!(bctl->sys.flags & BTRFS_BALANCE_ARGS_USAGE) &&
         !(bctl->sys.flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
         !(bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
         bctl->sys.flags |= BTRFS_BALANCE_ARGS_USAGE;
         bctl->sys.usage = 90;
     }
     if (!(bctl->meta.flags & BTRFS_BALANCE_ARGS_USAGE) &&
         !(bctl->meta.flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
         !(bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
         bctl->meta.flags |= BTRFS_BALANCE_ARGS_USAGE;
         bctl->meta.usage = 90;
     }
 }
 
 /*
  * Clear the balance status in fs_info and delete the balance item from disk.
  */
 static void reset_balance_state(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_balance_control *bctl = fs_info->balance_ctl;
     int ret;
 
     BUG_ON(!fs_info->balance_ctl);
 
     spin_lock(&fs_info->balance_lock);
     fs_info->balance_ctl = NULL;
     spin_unlock(&fs_info->balance_lock);
 
     kfree(bctl);
     ret = del_balance_item(fs_info);
     if (ret)
         btrfs_handle_fs_error(fs_info, ret, NULL);
 }
 
 /*
  * Balance filters.  Return 1 if chunk should be filtered out
  * (should not be balanced).
  */
 static int chunk_profiles_filter(u64 chunk_type,
                  struct btrfs_balance_args *bargs)
 {
     chunk_type = chunk_to_extended(chunk_type) &
                 BTRFS_EXTENDED_PROFILE_MASK;
 
     if (bargs->profiles & chunk_type)
         return 0;
 
     return 1;
 }
 
 static int chunk_usage_range_filter(struct btrfs_fs_info *fs_info, u64 chunk_offset,
                   struct btrfs_balance_args *bargs)
 {
     struct btrfs_block_group *cache;
     u64 chunk_used;
     u64 user_thresh_min;
     u64 user_thresh_max;
     int ret = 1;
 
     cache = btrfs_lookup_block_group(fs_info, chunk_offset);
     chunk_used = cache->used;
 
     if (bargs->usage_min == 0)
         user_thresh_min = 0;
     else
         user_thresh_min = div_factor_fine(cache->length,
                           bargs->usage_min);
 
     if (bargs->usage_max == 0)
         user_thresh_max = 1;
     else if (bargs->usage_max > 100)
         user_thresh_max = cache->length;
     else
         user_thresh_max = div_factor_fine(cache->length,
                           bargs->usage_max);
 
     if (user_thresh_min <= chunk_used && chunk_used < user_thresh_max)
         ret = 0;
 
     btrfs_put_block_group(cache);
     return ret;
 }
 
 static int chunk_usage_filter(struct btrfs_fs_info *fs_info,
         u64 chunk_offset, struct btrfs_balance_args *bargs)
 {
     struct btrfs_block_group *cache;
     u64 chunk_used, user_thresh;
     int ret = 1;
 
     cache = btrfs_lookup_block_group(fs_info, chunk_offset);
     chunk_used = cache->used;
 
     if (bargs->usage_min == 0)
         user_thresh = 1;
     else if (bargs->usage > 100)
         user_thresh = cache->length;
     else
         user_thresh = div_factor_fine(cache->length, bargs->usage);
 
     if (chunk_used < user_thresh)
         ret = 0;
 
     btrfs_put_block_group(cache);
     return ret;
 }
 
 static int chunk_devid_filter(struct extent_buffer *leaf,
                   struct btrfs_chunk *chunk,
                   struct btrfs_balance_args *bargs)
 {
     struct btrfs_stripe *stripe;
     int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
     int i;
 
     for (i = 0; i < num_stripes; i++) {
         stripe = btrfs_stripe_nr(chunk, i);
         if (btrfs_stripe_devid(leaf, stripe) == bargs->devid)
             return 0;
     }
 
     return 1;
 }
 
 static u64 calc_data_stripes(u64 type, int num_stripes)
 {
     const int index = btrfs_bg_flags_to_raid_index(type);
     const int ncopies = btrfs_raid_array[index].ncopies;
     const int nparity = btrfs_raid_array[index].nparity;
 
     return (num_stripes - nparity) / ncopies;
 }
 
 /* [pstart, pend) */
 static int chunk_drange_filter(struct extent_buffer *leaf,
                    struct btrfs_chunk *chunk,
                    struct btrfs_balance_args *bargs)
 {
     struct btrfs_stripe *stripe;
     int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
     u64 stripe_offset;
     u64 stripe_length;
     u64 type;
     int factor;
     int i;
 
     if (!(bargs->flags & BTRFS_BALANCE_ARGS_DEVID))
         return 0;
 
     type = btrfs_chunk_type(leaf, chunk);
     factor = calc_data_stripes(type, num_stripes);
 
     for (i = 0; i < num_stripes; i++) {
         stripe = btrfs_stripe_nr(chunk, i);
         if (btrfs_stripe_devid(leaf, stripe) != bargs->devid)
             continue;
 
         stripe_offset = btrfs_stripe_offset(leaf, stripe);
         stripe_length = btrfs_chunk_length(leaf, chunk);
         stripe_length = div_u64(stripe_length, factor);
 
         if (stripe_offset < bargs->pend &&
             stripe_offset + stripe_length > bargs->pstart)
             return 0;
     }
 
     return 1;
 }
 
 /* [vstart, vend) */
 static int chunk_vrange_filter(struct extent_buffer *leaf,
                    struct btrfs_chunk *chunk,
                    u64 chunk_offset,
                    struct btrfs_balance_args *bargs)
 {
     if (chunk_offset < bargs->vend &&
         chunk_offset + btrfs_chunk_length(leaf, chunk) > bargs->vstart)
         /* at least part of the chunk is inside this vrange */
         return 0;
 
     return 1;
 }
 
 static int chunk_stripes_range_filter(struct extent_buffer *leaf,
                    struct btrfs_chunk *chunk,
                    struct btrfs_balance_args *bargs)
 {
     int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
 
     if (bargs->stripes_min <= num_stripes
             && num_stripes <= bargs->stripes_max)
         return 0;
 
     return 1;
 }
 
 static int chunk_soft_convert_filter(u64 chunk_type,
                      struct btrfs_balance_args *bargs)
 {
     if (!(bargs->flags & BTRFS_BALANCE_ARGS_CONVERT))
         return 0;
 
     chunk_type = chunk_to_extended(chunk_type) &
                 BTRFS_EXTENDED_PROFILE_MASK;
 
     if (bargs->target == chunk_type)
         return 1;
 
     return 0;
 }
 
 static int should_balance_chunk(struct extent_buffer *leaf,
                 struct btrfs_chunk *chunk, u64 chunk_offset)
 {
     struct btrfs_fs_info *fs_info = leaf->fs_info;
     struct btrfs_balance_control *bctl = fs_info->balance_ctl;
     struct btrfs_balance_args *bargs = NULL;
     u64 chunk_type = btrfs_chunk_type(leaf, chunk);
 
     /* type filter */
     if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) &
           (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) {
         return 0;
     }
 
     if (chunk_type & BTRFS_BLOCK_GROUP_DATA)
         bargs = &bctl->data;
     else if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM)
         bargs = &bctl->sys;
     else if (chunk_type & BTRFS_BLOCK_GROUP_METADATA)
         bargs = &bctl->meta;
 
     /* profiles filter */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_PROFILES) &&
         chunk_profiles_filter(chunk_type, bargs)) {
         return 0;
     }
 
     /* usage filter */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE) &&
         chunk_usage_filter(fs_info, chunk_offset, bargs)) {
         return 0;
     } else if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
         chunk_usage_range_filter(fs_info, chunk_offset, bargs)) {
         return 0;
     }
 
     /* devid filter */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_DEVID) &&
         chunk_devid_filter(leaf, chunk, bargs)) {
         return 0;
     }
 
     /* drange filter, makes sense only with devid filter */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_DRANGE) &&
         chunk_drange_filter(leaf, chunk, bargs)) {
         return 0;
     }
 
     /* vrange filter */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_VRANGE) &&
         chunk_vrange_filter(leaf, chunk, chunk_offset, bargs)) {
         return 0;
     }
 
     /* stripes filter */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_STRIPES_RANGE) &&
         chunk_stripes_range_filter(leaf, chunk, bargs)) {
         return 0;
     }
 
     /* soft profile changing mode */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_SOFT) &&
         chunk_soft_convert_filter(chunk_type, bargs)) {
         return 0;
     }
 
     /*
      * limited by count, must be the last filter
      */
     if ((bargs->flags & BTRFS_BALANCE_ARGS_LIMIT)) {
         if (bargs->limit == 0)
             return 0;
         else
             bargs->limit--;
     } else if ((bargs->flags & BTRFS_BALANCE_ARGS_LIMIT_RANGE)) {
         /*
          * Same logic as the 'limit' filter; the minimum cannot be
          * determined here because we do not have the global information
          * about the count of all chunks that satisfy the filters.
          */
         if (bargs->limit_max == 0)
             return 0;
         else
             bargs->limit_max--;
     }
 
     return 1;
 }
 
 static int __btrfs_balance(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_balance_control *bctl = fs_info->balance_ctl;
     struct btrfs_root *chunk_root = fs_info->chunk_root;
     u64 chunk_type;
     struct btrfs_chunk *chunk;
     struct btrfs_path *path = NULL;
     struct btrfs_key key;
     struct btrfs_key found_key;
     struct extent_buffer *leaf;
     int slot;
     int ret;
     int enospc_errors = 0;
     bool counting = true;
     /* The single value limit and min/max limits use the same bytes in the */
     u64 limit_data = bctl->data.limit;
     u64 limit_meta = bctl->meta.limit;
     u64 limit_sys = bctl->sys.limit;
     u32 count_data = 0;
     u32 count_meta = 0;
     u32 count_sys = 0;
     int chunk_reserved = 0;
 
     path = btrfs_alloc_path();
     if (!path) {
         ret = -ENOMEM;
         goto error;
     }
 
     /* zero out stat counters */
     spin_lock(&fs_info->balance_lock);
     memset(&bctl->stat, 0, sizeof(bctl->stat));
     spin_unlock(&fs_info->balance_lock);
 again:
     if (!counting) {
         /*
          * The single value limit and min/max limits use the same bytes
          * in the
          */
         bctl->data.limit = limit_data;
         bctl->meta.limit = limit_meta;
         bctl->sys.limit = limit_sys;
     }
     key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
     key.offset = (u64)-1;
     key.type = BTRFS_CHUNK_ITEM_KEY;
 
     while (1) {
         if ((!counting && atomic_read(&fs_info->balance_pause_req)) ||
             atomic_read(&fs_info->balance_cancel_req)) {
             ret = -ECANCELED;
             goto error;
         }
 
         mutex_lock(&fs_info->reclaim_bgs_lock);
         ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
         if (ret < 0) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             goto error;
         }
 
         /*
          * this shouldn't happen, it means the last relocate
          * failed
          */
         if (ret == 0)
             BUG(); /* FIXME break ? */
 
         ret = btrfs_previous_item(chunk_root, path, 0,
                       BTRFS_CHUNK_ITEM_KEY);
         if (ret) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             ret = 0;
             break;
         }
 
         leaf = path->nodes[0];
         slot = path->slots[0];
         btrfs_item_key_to_cpu(leaf, &found_key, slot);
 
         if (found_key.objectid != key.objectid) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             break;
         }
 
         chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
         chunk_type = btrfs_chunk_type(leaf, chunk);
 
         if (!counting) {
             spin_lock(&fs_info->balance_lock);
             bctl->stat.considered++;
             spin_unlock(&fs_info->balance_lock);
         }
 
         ret = should_balance_chunk(leaf, chunk, found_key.offset);
 
         btrfs_release_path(path);
         if (!ret) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             goto loop;
         }
 
         if (counting) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             spin_lock(&fs_info->balance_lock);
             bctl->stat.expected++;
             spin_unlock(&fs_info->balance_lock);
 
             if (chunk_type & BTRFS_BLOCK_GROUP_DATA)
                 count_data++;
             else if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM)
                 count_sys++;
             else if (chunk_type & BTRFS_BLOCK_GROUP_METADATA)
                 count_meta++;
 
             goto loop;
         }
 
         /*
          * Apply limit_min filter, no need to check if the LIMITS
          * filter is used, limit_min is 0 by default
          */
         if (((chunk_type & BTRFS_BLOCK_GROUP_DATA) &&
                     count_data < bctl->data.limit_min)
                 || ((chunk_type & BTRFS_BLOCK_GROUP_METADATA) &&
                     count_meta < bctl->meta.limit_min)
                 || ((chunk_type & BTRFS_BLOCK_GROUP_SYSTEM) &&
                     count_sys < bctl->sys.limit_min)) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             goto loop;
         }
 
         if (!chunk_reserved) {
             /*
              * We may be relocating the only data chunk we have,
              * which could potentially end up with losing data's
              * raid profile, so lets allocate an empty one in
              * advance.
              */
             ret = btrfs_may_alloc_data_chunk(fs_info,
                              found_key.offset);
             if (ret < 0) {
                 mutex_unlock(&fs_info->reclaim_bgs_lock);
                 goto error;
             } else if (ret == 1) {
                 chunk_reserved = 1;
             }
         }
 
         ret = btrfs_relocate_chunk(fs_info, found_key.offset);
         mutex_unlock(&fs_info->reclaim_bgs_lock);
         if (ret == -ENOSPC) {
             enospc_errors++;
         } else if (ret == -ETXTBSY) {
             btrfs_info(fs_info,
        "skipping relocation of block group %llu due to active swapfile",
                    found_key.offset);
             ret = 0;
         } else if (ret) {
             goto error;
         } else {
             spin_lock(&fs_info->balance_lock);
             bctl->stat.completed++;
             spin_unlock(&fs_info->balance_lock);
         }
 loop:
         if (found_key.offset == 0)
             break;
         key.offset = found_key.offset - 1;
     }
 
     if (counting) {
         btrfs_release_path(path);
         counting = false;
         goto again;
     }
 error:
     btrfs_free_path(path);
     if (enospc_errors) {
         btrfs_info(fs_info, "%d enospc errors during balance",
                enospc_errors);
         if (!ret)
             ret = -ENOSPC;
     }
 
     return ret;
 }
 
 /**
  * alloc_profile_is_valid - see if a given profile is valid and reduced
  * @flags: profile to validate
  * @extended: if true @flags is treated as an extended profile
  */
 static int alloc_profile_is_valid(u64 flags, int extended)
 {
     u64 mask = (extended ? BTRFS_EXTENDED_PROFILE_MASK :
                    BTRFS_BLOCK_GROUP_PROFILE_MASK);
 
     flags &= ~BTRFS_BLOCK_GROUP_TYPE_MASK;
 
     /* 1) check that all other bits are zeroed */
     if (flags & ~mask)
         return 0;
 
     /* 2) see if profile is reduced */
     if (flags == 0)
         return !extended; /* "0" is valid for usual profiles */
 
     return has_single_bit_set(flags);
 }
 
 static inline int balance_need_close(struct btrfs_fs_info *fs_info)
 {
     /* cancel requested || normal exit path */
     return atomic_read(&fs_info->balance_cancel_req) ||
         (atomic_read(&fs_info->balance_pause_req) == 0 &&
          atomic_read(&fs_info->balance_cancel_req) == 0);
 }
 
 /*
  * Validate target profile against allowed profiles and return true if it's OK.
  * Otherwise print the error message and return false.
  */
 static inline int validate_convert_profile(struct btrfs_fs_info *fs_info,
         const struct btrfs_balance_args *bargs,
         u64 allowed, const char *type)
 {
     if (!(bargs->flags & BTRFS_BALANCE_ARGS_CONVERT))
         return true;
 
     /* Profile is valid and does not have bits outside of the allowed set */
     if (alloc_profile_is_valid(bargs->target, 1) &&
         (bargs->target & ~allowed) == 0)
         return true;
 
     btrfs_err(fs_info, "balance: invalid convert %s profile %s",
             type, btrfs_bg_type_to_raid_name(bargs->target));
     return false;
 }
 
 /*
  * Fill @buf with textual description of balance filter flags @bargs, up to
  * @size_buf including the terminating null. The output may be trimmed if it
  * does not fit into the provided buffer.
  */
 static void describe_balance_args(struct btrfs_balance_args *bargs, char *buf,
                  u32 size_buf)
 {
     int ret;
     u32 size_bp = size_buf;
     char *bp = buf;
     u64 flags = bargs->flags;
     char tmp_buf[128] = {'\0'};
 
     if (!flags)
         return;
 
 #define CHECK_APPEND_NOARG(a)                       \
     do {                                \
         ret = snprintf(bp, size_bp, (a));           \
         if (ret < 0 || ret >= size_bp)              \
             goto out_overflow;              \
         size_bp -= ret;                     \
         bp += ret;                      \
     } while (0)
 
 #define CHECK_APPEND_1ARG(a, v1)                    \
     do {                                \
         ret = snprintf(bp, size_bp, (a), (v1));         \
         if (ret < 0 || ret >= size_bp)              \
             goto out_overflow;              \
         size_bp -= ret;                     \
         bp += ret;                      \
     } while (0)
 
 #define CHECK_APPEND_2ARG(a, v1, v2)                    \
     do {                                \
         ret = snprintf(bp, size_bp, (a), (v1), (v2));       \
         if (ret < 0 || ret >= size_bp)              \
             goto out_overflow;              \
         size_bp -= ret;                     \
         bp += ret;                      \
     } while (0)
 
     if (flags & BTRFS_BALANCE_ARGS_CONVERT)
         CHECK_APPEND_1ARG("convert=%s,",
                   btrfs_bg_type_to_raid_name(bargs->target));
 
     if (flags & BTRFS_BALANCE_ARGS_SOFT)
         CHECK_APPEND_NOARG("soft,");
 
     if (flags & BTRFS_BALANCE_ARGS_PROFILES) {
         btrfs_describe_block_groups(bargs->profiles, tmp_buf,
                         sizeof(tmp_buf));
         CHECK_APPEND_1ARG("profiles=%s,", tmp_buf);
     }
 
     if (flags & BTRFS_BALANCE_ARGS_USAGE)
         CHECK_APPEND_1ARG("usage=%llu,", bargs->usage);
 
     if (flags & BTRFS_BALANCE_ARGS_USAGE_RANGE)
         CHECK_APPEND_2ARG("usage=%u..%u,",
                   bargs->usage_min, bargs->usage_max);
 
     if (flags & BTRFS_BALANCE_ARGS_DEVID)
         CHECK_APPEND_1ARG("devid=%llu,", bargs->devid);
 
     if (flags & BTRFS_BALANCE_ARGS_DRANGE)
         CHECK_APPEND_2ARG("drange=%llu..%llu,",
                   bargs->pstart, bargs->pend);
 
     if (flags & BTRFS_BALANCE_ARGS_VRANGE)
         CHECK_APPEND_2ARG("vrange=%llu..%llu,",
                   bargs->vstart, bargs->vend);
 
     if (flags & BTRFS_BALANCE_ARGS_LIMIT)
         CHECK_APPEND_1ARG("limit=%llu,", bargs->limit);
 
     if (flags & BTRFS_BALANCE_ARGS_LIMIT_RANGE)
         CHECK_APPEND_2ARG("limit=%u..%u,",
                 bargs->limit_min, bargs->limit_max);
 
     if (flags & BTRFS_BALANCE_ARGS_STRIPES_RANGE)
         CHECK_APPEND_2ARG("stripes=%u..%u,",
                   bargs->stripes_min, bargs->stripes_max);
 
 #undef CHECK_APPEND_2ARG
 #undef CHECK_APPEND_1ARG
 #undef CHECK_APPEND_NOARG
 
 out_overflow:
 
     if (size_bp < size_buf)
         buf[size_buf - size_bp - 1] = '\0'; /* remove last , */
     else
         buf[0] = '\0';
 }
 
 static void describe_balance_start_or_resume(struct btrfs_fs_info *fs_info)
 {
     u32 size_buf = 1024;
     char tmp_buf[192] = {'\0'};
     char *buf;
     char *bp;
     u32 size_bp = size_buf;
     int ret;
     struct btrfs_balance_control *bctl = fs_info->balance_ctl;
 
     buf = kzalloc(size_buf, GFP_KERNEL);
     if (!buf)
         return;
 
     bp = buf;
 
 #define CHECK_APPEND_1ARG(a, v1)                    \
     do {                                \
         ret = snprintf(bp, size_bp, (a), (v1));         \
         if (ret < 0 || ret >= size_bp)              \
             goto out_overflow;              \
         size_bp -= ret;                     \
         bp += ret;                      \
     } while (0)
 
     if (bctl->flags & BTRFS_BALANCE_FORCE)
         CHECK_APPEND_1ARG("%s", "-f ");
 
     if (bctl->flags & BTRFS_BALANCE_DATA) {
         describe_balance_args(&bctl->data, tmp_buf, sizeof(tmp_buf));
         CHECK_APPEND_1ARG("-d%s ", tmp_buf);
     }
 
     if (bctl->flags & BTRFS_BALANCE_METADATA) {
         describe_balance_args(&bctl->meta, tmp_buf, sizeof(tmp_buf));
         CHECK_APPEND_1ARG("-m%s ", tmp_buf);
     }
 
     if (bctl->flags & BTRFS_BALANCE_SYSTEM) {
         describe_balance_args(&bctl->sys, tmp_buf, sizeof(tmp_buf));
         CHECK_APPEND_1ARG("-s%s ", tmp_buf);
     }
 
 #undef CHECK_APPEND_1ARG
 
 out_overflow:
 
     if (size_bp < size_buf)
         buf[size_buf - size_bp - 1] = '\0'; /* remove last " " */
     btrfs_info(fs_info, "balance: %s %s",
            (bctl->flags & BTRFS_BALANCE_RESUME) ?
            "resume" : "start", buf);
 
     kfree(buf);
 }
 
 /*
  * Should be called with balance mutexe held
  */
 int btrfs_balance(struct btrfs_fs_info *fs_info,
           struct btrfs_balance_control *bctl,
           struct btrfs_ioctl_balance_args *bargs)
 {
     u64 meta_target, data_target;
     u64 allowed;
     int mixed = 0;
     int ret;
     u64 num_devices;
     unsigned seq;
     bool reducing_redundancy;
     int i;
 
     if (btrfs_fs_closing(fs_info) ||
         atomic_read(&fs_info->balance_pause_req) ||
         btrfs_should_cancel_balance(fs_info)) {
         ret = -EINVAL;
         goto out;
     }
 
     allowed = btrfs_super_incompat_flags(fs_info->super_copy);
     if (allowed & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
         mixed = 1;
 
     /*
      * In case of mixed groups both data and meta should be picked,
      * and identical options should be given for both of them.
      */
     allowed = BTRFS_BALANCE_DATA | BTRFS_BALANCE_METADATA;
     if (mixed && (bctl->flags & allowed)) {
         if (!(bctl->flags & BTRFS_BALANCE_DATA) ||
             !(bctl->flags & BTRFS_BALANCE_METADATA) ||
             memcmp(&bctl->data, &bctl->meta, sizeof(bctl->data))) {
             btrfs_err(fs_info,
       "balance: mixed groups data and metadata options must be the same");
             ret = -EINVAL;
             goto out;
         }
     }
 
     /*
      * rw_devices will not change at the moment, device add/delete/replace
      * are exclusive
      */
     num_devices = fs_info->fs_devices->rw_devices;
 
     /*
      * SINGLE profile on-disk has no profile bit, but in-memory we have a
      * special bit for it, to make it easier to distinguish.  Thus we need
      * to set it manually, or balance would refuse the profile.
      */
     allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
     for (i = 0; i < ARRAY_SIZE(btrfs_raid_array); i++)
         if (num_devices >= btrfs_raid_array[i].devs_min)
             allowed |= btrfs_raid_array[i].bg_flag;
 
     if (!validate_convert_profile(fs_info, &bctl->data, allowed, "data") ||
         !validate_convert_profile(fs_info, &bctl->meta, allowed, "metadata") ||
         !validate_convert_profile(fs_info, &bctl->sys,  allowed, "system")) {
         ret = -EINVAL;
         goto out;
     }
 
     /*
      * Allow to reduce metadata or system integrity only if force set for
      * profiles with redundancy (copies, parity)
      */
     allowed = 0;
     for (i = 0; i < ARRAY_SIZE(btrfs_raid_array); i++) {
         if (btrfs_raid_array[i].ncopies >= 2 ||
             btrfs_raid_array[i].tolerated_failures >= 1)
             allowed |= btrfs_raid_array[i].bg_flag;
     }
     do {
         seq = read_seqbegin(&fs_info->profiles_lock);
 
         if (((bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
              (fs_info->avail_system_alloc_bits & allowed) &&
              !(bctl->sys.target & allowed)) ||
             ((bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
              (fs_info->avail_metadata_alloc_bits & allowed) &&
              !(bctl->meta.target & allowed)))
             reducing_redundancy = true;
         else
             reducing_redundancy = false;
 
         /* if we're not converting, the target field is uninitialized */
         meta_target = (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
             bctl->meta.target : fs_info->avail_metadata_alloc_bits;
         data_target = (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
             bctl->data.target : fs_info->avail_data_alloc_bits;
     } while (read_seqretry(&fs_info->profiles_lock, seq));
 
     if (reducing_redundancy) {
         if (bctl->flags & BTRFS_BALANCE_FORCE) {
             btrfs_info(fs_info,
                "balance: force reducing metadata redundancy");
         } else {
             btrfs_err(fs_info,
     "balance: reduces metadata redundancy, use --force if you want this");
             ret = -EINVAL;
             goto out;
         }
     }
 
     if (btrfs_get_num_tolerated_disk_barrier_failures(meta_target) <
         btrfs_get_num_tolerated_disk_barrier_failures(data_target)) {
         btrfs_warn(fs_info,
     "balance: metadata profile %s has lower redundancy than data profile %s",
                 btrfs_bg_type_to_raid_name(meta_target),
                 btrfs_bg_type_to_raid_name(data_target));
     }
 
     ret = insert_balance_item(fs_info, bctl);
     if (ret && ret != -EEXIST)
         goto out;
 
     if (!(bctl->flags & BTRFS_BALANCE_RESUME)) {
         BUG_ON(ret == -EEXIST);
         BUG_ON(fs_info->balance_ctl);
         spin_lock(&fs_info->balance_lock);
         fs_info->balance_ctl = bctl;
         spin_unlock(&fs_info->balance_lock);
     } else {
         BUG_ON(ret != -EEXIST);
         spin_lock(&fs_info->balance_lock);
         update_balance_args(bctl);
         spin_unlock(&fs_info->balance_lock);
     }
 
     ASSERT(!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
     set_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
     describe_balance_start_or_resume(fs_info);
     mutex_unlock(&fs_info->balance_mutex);
 
     ret = __btrfs_balance(fs_info);
 
     mutex_lock(&fs_info->balance_mutex);
     if (ret == -ECANCELED && atomic_read(&fs_info->balance_pause_req)) {
         btrfs_info(fs_info, "balance: paused");
         btrfs_exclop_balance(fs_info, BTRFS_EXCLOP_BALANCE_PAUSED);
     }
     /*
      * Balance can be canceled by:
      *
      * - Regular cancel request
      *   Then ret == -ECANCELED and balance_cancel_req > 0
      *
      * - Fatal signal to "btrfs" process
      *   Either the signal caught by wait_reserve_ticket() and callers
      *   got -EINTR, or caught by btrfs_should_cancel_balance() and
      *   got -ECANCELED.
      *   Either way, in this case balance_cancel_req = 0, and
      *   ret == -EINTR or ret == -ECANCELED.
      *
      * So here we only check the return value to catch canceled balance.
      */
     else if (ret == -ECANCELED || ret == -EINTR)
         btrfs_info(fs_info, "balance: canceled");
     else
         btrfs_info(fs_info, "balance: ended with status: %d", ret);
 
     clear_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
 
     if (bargs) {
         memset(bargs, 0, sizeof(*bargs));
         btrfs_update_ioctl_balance_args(fs_info, bargs);
     }
 
     if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
         balance_need_close(fs_info)) {
         reset_balance_state(fs_info);
         btrfs_exclop_finish(fs_info);
     }
 
     wake_up(&fs_info->balance_wait_q);
 
     return ret;
 out:
     if (bctl->flags & BTRFS_BALANCE_RESUME)
         reset_balance_state(fs_info);
     else
         kfree(bctl);
     btrfs_exclop_finish(fs_info);
 
     return ret;
 }
 
 static int balance_kthread(void *data)
 {
     struct btrfs_fs_info *fs_info = data;
     int ret = 0;
 
     sb_start_write(fs_info->sb);
     mutex_lock(&fs_info->balance_mutex);
     if (fs_info->balance_ctl)
         ret = btrfs_balance(fs_info, fs_info->balance_ctl, NULL);
     mutex_unlock(&fs_info->balance_mutex);
     sb_end_write(fs_info->sb);
 
     return ret;
 }
 
 int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
 {
     struct task_struct *tsk;
 
     mutex_lock(&fs_info->balance_mutex);
     if (!fs_info->balance_ctl) {
         mutex_unlock(&fs_info->balance_mutex);
         return 0;
     }
     mutex_unlock(&fs_info->balance_mutex);
 
     if (btrfs_test_opt(fs_info, SKIP_BALANCE)) {
         btrfs_info(fs_info, "balance: resume skipped");
         return 0;
     }
 
     spin_lock(&fs_info->super_lock);
     ASSERT(fs_info->exclusive_operation == BTRFS_EXCLOP_BALANCE_PAUSED);
     fs_info->exclusive_operation = BTRFS_EXCLOP_BALANCE;
     spin_unlock(&fs_info->super_lock);
     /*
      * A ro->rw remount sequence should continue with the paused balance
      * regardless of who pauses it, system or the user as of now, so set
      * the resume flag.
      */
     spin_lock(&fs_info->balance_lock);
     fs_info->balance_ctl->flags |= BTRFS_BALANCE_RESUME;
     spin_unlock(&fs_info->balance_lock);
 
     tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
     return PTR_ERR_OR_ZERO(tsk);
 }
 
 int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_balance_control *bctl;
     struct btrfs_balance_item *item;
     struct btrfs_disk_balance_args disk_bargs;
     struct btrfs_path *path;
     struct extent_buffer *leaf;
     struct btrfs_key key;
     int ret;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = BTRFS_BALANCE_OBJECTID;
     key.type = BTRFS_TEMPORARY_ITEM_KEY;
     key.offset = 0;
 
     ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
     if (ret < 0)
         goto out;
     if (ret > 0) { /* ret = -ENOENT; */
         ret = 0;
         goto out;
     }
 
     bctl = kzalloc(sizeof(*bctl), GFP_NOFS);
     if (!bctl) {
         ret = -ENOMEM;
         goto out;
     }
 
     leaf = path->nodes[0];
     item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_balance_item);
 
     bctl->flags = btrfs_balance_flags(leaf, item);
     bctl->flags |= BTRFS_BALANCE_RESUME;
 
     btrfs_balance_data(leaf, item, &disk_bargs);
     btrfs_disk_balance_args_to_cpu(&bctl->data, &disk_bargs);
     btrfs_balance_meta(leaf, item, &disk_bargs);
     btrfs_disk_balance_args_to_cpu(&bctl->meta, &disk_bargs);
     btrfs_balance_sys(leaf, item, &disk_bargs);
     btrfs_disk_balance_args_to_cpu(&bctl->sys, &disk_bargs);
 
     /*
      * This should never happen, as the paused balance state is recovered
      * during mount without any chance of other exclusive ops to collide.
      *
      * This gives the exclusive op status to balance and keeps in paused
      * state until user intervention (cancel or umount). If the ownership
      * cannot be assigned, show a message but do not fail. The balance
      * is in a paused state and must have fs_info::balance_ctl properly
      * set up.
      */
     if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE_PAUSED))
         btrfs_warn(fs_info,
     "balance: cannot set exclusive op status, resume manually");
 
     btrfs_release_path(path);
 
     mutex_lock(&fs_info->balance_mutex);
     BUG_ON(fs_info->balance_ctl);
     spin_lock(&fs_info->balance_lock);
     fs_info->balance_ctl = bctl;
     spin_unlock(&fs_info->balance_lock);
     mutex_unlock(&fs_info->balance_mutex);
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 int btrfs_pause_balance(struct btrfs_fs_info *fs_info)
 {
     int ret = 0;
 
     mutex_lock(&fs_info->balance_mutex);
     if (!fs_info->balance_ctl) {
         mutex_unlock(&fs_info->balance_mutex);
         return -ENOTCONN;
     }
 
     if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
         atomic_inc(&fs_info->balance_pause_req);
         mutex_unlock(&fs_info->balance_mutex);
 
         wait_event(fs_info->balance_wait_q,
                !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
 
         mutex_lock(&fs_info->balance_mutex);
         /* we are good with balance_ctl ripped off from under us */
         BUG_ON(test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
         atomic_dec(&fs_info->balance_pause_req);
     } else {
         ret = -ENOTCONN;
     }
 
     mutex_unlock(&fs_info->balance_mutex);
     return ret;
 }
 
 int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
 {
     mutex_lock(&fs_info->balance_mutex);
     if (!fs_info->balance_ctl) {
         mutex_unlock(&fs_info->balance_mutex);
         return -ENOTCONN;
     }
 
     /*
      * A paused balance with the item stored on disk can be resumed at
      * mount time if the mount is read-write. Otherwise it's still paused
      * and we must not allow cancelling as it deletes the item.
      */
     if (sb_rdonly(fs_info->sb)) {
         mutex_unlock(&fs_info->balance_mutex);
         return -EROFS;
     }
 
     atomic_inc(&fs_info->balance_cancel_req);
     /*
      * if we are running just wait and return, balance item is
      * deleted in btrfs_balance in this case
      */
     if (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
         mutex_unlock(&fs_info->balance_mutex);
         wait_event(fs_info->balance_wait_q,
                !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
         mutex_lock(&fs_info->balance_mutex);
     } else {
         mutex_unlock(&fs_info->balance_mutex);
         /*
          * Lock released to allow other waiters to continue, we'll
          * reexamine the status again.
          */
         mutex_lock(&fs_info->balance_mutex);
 
         if (fs_info->balance_ctl) {
             reset_balance_state(fs_info);
             btrfs_exclop_finish(fs_info);
             btrfs_info(fs_info, "balance: canceled");
         }
     }
 
     BUG_ON(fs_info->balance_ctl ||
         test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
     atomic_dec(&fs_info->balance_cancel_req);
     mutex_unlock(&fs_info->balance_mutex);
     return 0;
 }
 
 int btrfs_uuid_scan_kthread(void *data)
 {
     struct btrfs_fs_info *fs_info = data;
     struct btrfs_root *root = fs_info->tree_root;
     struct btrfs_key key;
     struct btrfs_path *path = NULL;
     int ret = 0;
     struct extent_buffer *eb;
     int slot;
     struct btrfs_root_item root_item;
     u32 item_size;
     struct btrfs_trans_handle *trans = NULL;
     bool closing = false;
 
     path = btrfs_alloc_path();
     if (!path) {
         ret = -ENOMEM;
         goto out;
     }
 
     key.objectid = 0;
     key.type = BTRFS_ROOT_ITEM_KEY;
     key.offset = 0;
 
     while (1) {
         if (btrfs_fs_closing(fs_info)) {
             closing = true;
             break;
         }
         ret = btrfs_search_forward(root, &key, path,
                 BTRFS_OLDEST_GENERATION);
         if (ret) {
             if (ret > 0)
                 ret = 0;
             break;
         }
 
         if (key.type != BTRFS_ROOT_ITEM_KEY ||
             (key.objectid < BTRFS_FIRST_FREE_OBJECTID &&
              key.objectid != BTRFS_FS_TREE_OBJECTID) ||
             key.objectid > BTRFS_LAST_FREE_OBJECTID)
             goto skip;
 
         eb = path->nodes[0];
         slot = path->slots[0];
         item_size = btrfs_item_size(eb, slot);
         if (item_size < sizeof(root_item))
             goto skip;
 
         read_extent_buffer(eb, &root_item,
                    btrfs_item_ptr_offset(eb, slot),
                    (int)sizeof(root_item));
         if (btrfs_root_refs(&root_item) == 0)
             goto skip;
 
         if (!btrfs_is_empty_uuid(root_item.uuid) ||
             !btrfs_is_empty_uuid(root_item.received_uuid)) {
             if (trans)
                 goto update_tree;
 
             btrfs_release_path(path);
             /*
              * 1 - subvol uuid item
              * 1 - received_subvol uuid item
              */
             trans = btrfs_start_transaction(fs_info->uuid_root, 2);
             if (IS_ERR(trans)) {
                 ret = PTR_ERR(trans);
                 break;
             }
             continue;
         } else {
             goto skip;
         }
 update_tree:
         btrfs_release_path(path);
         if (!btrfs_is_empty_uuid(root_item.uuid)) {
             ret = btrfs_uuid_tree_add(trans, root_item.uuid,
                           BTRFS_UUID_KEY_SUBVOL,
                           key.objectid);
             if (ret < 0) {
                 btrfs_warn(fs_info, "uuid_tree_add failed %d",
                     ret);
                 break;
             }
         }
 
         if (!btrfs_is_empty_uuid(root_item.received_uuid)) {
             ret = btrfs_uuid_tree_add(trans,
                           root_item.received_uuid,
                          BTRFS_UUID_KEY_RECEIVED_SUBVOL,
                           key.objectid);
             if (ret < 0) {
                 btrfs_warn(fs_info, "uuid_tree_add failed %d",
                     ret);
                 break;
             }
         }
 
 skip:
         btrfs_release_path(path);
         if (trans) {
             ret = btrfs_end_transaction(trans);
             trans = NULL;
             if (ret)
                 break;
         }
 
         if (key.offset < (u64)-1) {
             key.offset++;
         } else if (key.type < BTRFS_ROOT_ITEM_KEY) {
             key.offset = 0;
             key.type = BTRFS_ROOT_ITEM_KEY;
         } else if (key.objectid < (u64)-1) {
             key.offset = 0;
             key.type = BTRFS_ROOT_ITEM_KEY;
             key.objectid++;
         } else {
             break;
         }
         cond_resched();
     }
 
 out:
     btrfs_free_path(path);
     if (trans && !IS_ERR(trans))
         btrfs_end_transaction(trans);
     if (ret)
         btrfs_warn(fs_info, "btrfs_uuid_scan_kthread failed %d", ret);
     else if (!closing)
         set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);
     up(&fs_info->uuid_tree_rescan_sem);
     return 0;
 }
 
 int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_trans_handle *trans;
     struct btrfs_root *tree_root = fs_info->tree_root;
     struct btrfs_root *uuid_root;
     struct task_struct *task;
     int ret;
 
     /*
      * 1 - root node
      * 1 - root item
      */
     trans = btrfs_start_transaction(tree_root, 2);
     if (IS_ERR(trans))
         return PTR_ERR(trans);
 
     uuid_root = btrfs_create_tree(trans, BTRFS_UUID_TREE_OBJECTID);
     if (IS_ERR(uuid_root)) {
         ret = PTR_ERR(uuid_root);
         btrfs_abort_transaction(trans, ret);
         btrfs_end_transaction(trans);
         return ret;
     }
 
     fs_info->uuid_root = uuid_root;
 
     ret = btrfs_commit_transaction(trans);
     if (ret)
         return ret;
 
     down(&fs_info->uuid_tree_rescan_sem);
     task = kthread_run(btrfs_uuid_scan_kthread, fs_info, "btrfs-uuid");
     if (IS_ERR(task)) {
         /* fs_info->update_uuid_tree_gen remains 0 in all error case */
         btrfs_warn(fs_info, "failed to start uuid_scan task");
         up(&fs_info->uuid_tree_rescan_sem);
         return PTR_ERR(task);
     }
 
     return 0;
 }
 
 /*
  * shrinking a device means finding all of the device extents past
  * the new size, and then following the back refs to the chunks.
  * The chunk relocation code actually frees the device extent
  */
 int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
 {
     struct btrfs_fs_info *fs_info = device->fs_info;
     struct btrfs_root *root = fs_info->dev_root;
     struct btrfs_trans_handle *trans;
     struct btrfs_dev_extent *dev_extent = NULL;
     struct btrfs_path *path;
     u64 length;
     u64 chunk_offset;
     int ret;
     int slot;
     int failed = 0;
     bool retried = false;
     struct extent_buffer *l;
     struct btrfs_key key;
     struct btrfs_super_block *super_copy = fs_info->super_copy;
     u64 old_total = btrfs_super_total_bytes(super_copy);
     u64 old_size = btrfs_device_get_total_bytes(device);
     u64 diff;
     u64 start;
 
     new_size = round_down(new_size, fs_info->sectorsize);
     start = new_size;
     diff = round_down(old_size - new_size, fs_info->sectorsize);
 
     if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
         return -EINVAL;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     path->reada = READA_BACK;
 
     trans = btrfs_start_transaction(root, 0);
     if (IS_ERR(trans)) {
         btrfs_free_path(path);
         return PTR_ERR(trans);
     }
 
     mutex_lock(&fs_info->chunk_mutex);
 
     btrfs_device_set_total_bytes(device, new_size);
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
         device->fs_devices->total_rw_bytes -= diff;
         atomic64_sub(diff, &fs_info->free_chunk_space);
     }
 
     /*
      * Once the device's size has been set to the new size, ensure all
      * in-memory chunks are synced to disk so that the loop below sees them
      * and relocates them accordingly.
      */
     if (contains_pending_extent(device, &start, diff)) {
         mutex_unlock(&fs_info->chunk_mutex);
         ret = btrfs_commit_transaction(trans);
         if (ret)
             goto done;
     } else {
         mutex_unlock(&fs_info->chunk_mutex);
         btrfs_end_transaction(trans);
     }
 
 again:
     key.objectid = device->devid;
     key.offset = (u64)-1;
     key.type = BTRFS_DEV_EXTENT_KEY;
 
     do {
         mutex_lock(&fs_info->reclaim_bgs_lock);
         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
         if (ret < 0) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             goto done;
         }
 
         ret = btrfs_previous_item(root, path, 0, key.type);
         if (ret) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             if (ret < 0)
                 goto done;
             ret = 0;
             btrfs_release_path(path);
             break;
         }
 
         l = path->nodes[0];
         slot = path->slots[0];
         btrfs_item_key_to_cpu(l, &key, path->slots[0]);
 
         if (key.objectid != device->devid) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             btrfs_release_path(path);
             break;
         }
 
         dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
         length = btrfs_dev_extent_length(l, dev_extent);
 
         if (key.offset + length <= new_size) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             btrfs_release_path(path);
             break;
         }
 
         chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
         btrfs_release_path(path);
 
         /*
          * We may be relocating the only data chunk we have,
          * which could potentially end up with losing data's
          * raid profile, so lets allocate an empty one in
          * advance.
          */
         ret = btrfs_may_alloc_data_chunk(fs_info, chunk_offset);
         if (ret < 0) {
             mutex_unlock(&fs_info->reclaim_bgs_lock);
             goto done;
         }
 
         ret = btrfs_relocate_chunk(fs_info, chunk_offset);
         mutex_unlock(&fs_info->reclaim_bgs_lock);
         if (ret == -ENOSPC) {
             failed++;
         } else if (ret) {
             if (ret == -ETXTBSY) {
                 btrfs_warn(fs_info,
            "could not shrink block group %llu due to active swapfile",
                        chunk_offset);
             }
             goto done;
         }
     } while (key.offset-- > 0);
 
     if (failed && !retried) {
         failed = 0;
         retried = true;
         goto again;
     } else if (failed && retried) {
         ret = -ENOSPC;
         goto done;
     }
 
     /* Shrinking succeeded, else we would be at "done". */
     trans = btrfs_start_transaction(root, 0);
     if (IS_ERR(trans)) {
         ret = PTR_ERR(trans);
         goto done;
     }
 
     mutex_lock(&fs_info->chunk_mutex);
     /* Clear all state bits beyond the shrunk device size */
     clear_extent_bits(&device->alloc_state, new_size, (u64)-1,
               CHUNK_STATE_MASK);
 
     btrfs_device_set_disk_total_bytes(device, new_size);
     if (list_empty(&device->post_commit_list))
         list_add_tail(&device->post_commit_list,
                   &trans->transaction->dev_update_list);
 
     WARN_ON(diff > old_total);
     btrfs_set_super_total_bytes(super_copy,
             round_down(old_total - diff, fs_info->sectorsize));
     mutex_unlock(&fs_info->chunk_mutex);
 
     btrfs_reserve_chunk_metadata(trans, false);
     /* Now btrfs_update_device() will change the on-disk size. */
     ret = btrfs_update_device(trans, device);
     btrfs_trans_release_chunk_metadata(trans);
     if (ret < 0) {
         btrfs_abort_transaction(trans, ret);
         btrfs_end_transaction(trans);
     } else {
         ret = btrfs_commit_transaction(trans);
     }
 done:
     btrfs_free_path(path);
     if (ret) {
         mutex_lock(&fs_info->chunk_mutex);
         btrfs_device_set_total_bytes(device, old_size);
         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
             device->fs_devices->total_rw_bytes += diff;
         atomic64_add(diff, &fs_info->free_chunk_space);
         mutex_unlock(&fs_info->chunk_mutex);
     }
     return ret;
 }
 
 static int btrfs_add_system_chunk(struct btrfs_fs_info *fs_info,
                struct btrfs_key *key,
                struct btrfs_chunk *chunk, int item_size)
 {
     struct btrfs_super_block *super_copy = fs_info->super_copy;
     struct btrfs_disk_key disk_key;
     u32 array_size;
     u8 *ptr;
 
     lockdep_assert_held(&fs_info->chunk_mutex);
 
     array_size = btrfs_super_sys_array_size(super_copy);
     if (array_size + item_size + sizeof(disk_key)
             > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE)
         return -EFBIG;
 
     ptr = super_copy->sys_chunk_array + array_size;
     btrfs_cpu_key_to_disk(&disk_key, key);
     memcpy(ptr, &disk_key, sizeof(disk_key));
     ptr += sizeof(disk_key);
     memcpy(ptr, chunk, item_size);
     item_size += sizeof(disk_key);
     btrfs_set_super_sys_array_size(super_copy, array_size + item_size);
 
     return 0;
 }
 
 /*
  * sort the devices in descending order by max_avail, total_avail
  */
 static int btrfs_cmp_device_info(const void *a, const void *b)
 {
     const struct btrfs_device_info *di_a = a;
     const struct btrfs_device_info *di_b = b;
 
     if (di_a->max_avail > di_b->max_avail)
         return -1;
     if (di_a->max_avail < di_b->max_avail)
         return 1;
     if (di_a->total_avail > di_b->total_avail)
         return -1;
     if (di_a->total_avail < di_b->total_avail)
         return 1;
     return 0;
 }
 
 static void check_raid56_incompat_flag(struct btrfs_fs_info *info, u64 type)
 {
     if (!(type & BTRFS_BLOCK_GROUP_RAID56_MASK))
         return;
 
     btrfs_set_fs_incompat(info, RAID56);
 }
 
 static void check_raid1c34_incompat_flag(struct btrfs_fs_info *info, u64 type)
 {
     if (!(type & (BTRFS_BLOCK_GROUP_RAID1C3 | BTRFS_BLOCK_GROUP_RAID1C4)))
         return;
 
     btrfs_set_fs_incompat(info, RAID1C34);
 }
 
 /*
  * Structure used internally for btrfs_create_chunk() function.
  * Wraps needed parameters.
  */
 struct alloc_chunk_ctl {
     u64 start;
     u64 type;
     /* Total number of stripes to allocate */
     int num_stripes;
     /* sub_stripes info for map */
     int sub_stripes;
     /* Stripes per device */
     int dev_stripes;
     /* Maximum number of devices to use */
     int devs_max;
     /* Minimum number of devices to use */
     int devs_min;
     /* ndevs has to be a multiple of this */
     int devs_increment;
     /* Number of copies */
     int ncopies;
     /* Number of stripes worth of bytes to store parity information */
     int nparity;
     u64 max_stripe_size;
     u64 max_chunk_size;
     u64 dev_extent_min;
     u64 stripe_size;
     u64 chunk_size;
     int ndevs;
 };
 
 static void init_alloc_chunk_ctl_policy_regular(
                 struct btrfs_fs_devices *fs_devices,
                 struct alloc_chunk_ctl *ctl)
 {
     struct btrfs_space_info *space_info;
 
     space_info = btrfs_find_space_info(fs_devices->fs_info, ctl->type);
     ASSERT(space_info);
 
     ctl->max_chunk_size = READ_ONCE(space_info->chunk_size);
     ctl->max_stripe_size = ctl->max_chunk_size;
 
     if (ctl->type & BTRFS_BLOCK_GROUP_SYSTEM)
         ctl->devs_max = min_t(int, ctl->devs_max, BTRFS_MAX_DEVS_SYS_CHUNK);
 
     /* We don't want a chunk larger than 10% of writable space */
     ctl->max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
                   ctl->max_chunk_size);
     ctl->dev_extent_min = BTRFS_STRIPE_LEN * ctl->dev_stripes;
 }
 
 static void init_alloc_chunk_ctl_policy_zoned(
                       struct btrfs_fs_devices *fs_devices,
                       struct alloc_chunk_ctl *ctl)
 {
     u64 zone_size = fs_devices->fs_info->zone_size;
     u64 limit;
     int min_num_stripes = ctl->devs_min * ctl->dev_stripes;
     int min_data_stripes = (min_num_stripes - ctl->nparity) / ctl->ncopies;
     u64 min_chunk_size = min_data_stripes * zone_size;
     u64 type = ctl->type;
 
     ctl->max_stripe_size = zone_size;
     if (type & BTRFS_BLOCK_GROUP_DATA) {
         ctl->max_chunk_size = round_down(BTRFS_MAX_DATA_CHUNK_SIZE,
                          zone_size);
     } else if (type & BTRFS_BLOCK_GROUP_METADATA) {
         ctl->max_chunk_size = ctl->max_stripe_size;
     } else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
         ctl->max_chunk_size = 2 * ctl->max_stripe_size;
         ctl->devs_max = min_t(int, ctl->devs_max,
                       BTRFS_MAX_DEVS_SYS_CHUNK);
     } else {
         BUG();
     }
 
     /* We don't want a chunk larger than 10% of writable space */
     limit = max(round_down(div_factor(fs_devices->total_rw_bytes, 1),
                    zone_size),
             min_chunk_size);
     ctl->max_chunk_size = min(limit, ctl->max_chunk_size);
     ctl->dev_extent_min = zone_size * ctl->dev_stripes;
 }
 
 static void init_alloc_chunk_ctl(struct btrfs_fs_devices *fs_devices,
                  struct alloc_chunk_ctl *ctl)
 {
     int index = btrfs_bg_flags_to_raid_index(ctl->type);
 
     ctl->sub_stripes = btrfs_raid_array[index].sub_stripes;
     ctl->dev_stripes = btrfs_raid_array[index].dev_stripes;
     ctl->devs_max = btrfs_raid_array[index].devs_max;
     if (!ctl->devs_max)
         ctl->devs_max = BTRFS_MAX_DEVS(fs_devices->fs_info);
     ctl->devs_min = btrfs_raid_array[index].devs_min;
     ctl->devs_increment = btrfs_raid_array[index].devs_increment;
     ctl->ncopies = btrfs_raid_array[index].ncopies;
     ctl->nparity = btrfs_raid_array[index].nparity;
     ctl->ndevs = 0;
 
     switch (fs_devices->chunk_alloc_policy) {
     case BTRFS_CHUNK_ALLOC_REGULAR:
         init_alloc_chunk_ctl_policy_regular(fs_devices, ctl);
         break;
     case BTRFS_CHUNK_ALLOC_ZONED:
         init_alloc_chunk_ctl_policy_zoned(fs_devices, ctl);
         break;
     default:
         BUG();
     }
 }
 
 static int gather_device_info(struct btrfs_fs_devices *fs_devices,
                   struct alloc_chunk_ctl *ctl,
                   struct btrfs_device_info *devices_info)
 {
     struct btrfs_fs_info *info = fs_devices->fs_info;
     struct btrfs_device *device;
     u64 total_avail;
     u64 dev_extent_want = ctl->max_stripe_size * ctl->dev_stripes;
     int ret;
     int ndevs = 0;
     u64 max_avail;
     u64 dev_offset;
 
     /*
      * in the first pass through the devices list, we gather information
      * about the available holes on each device.
      */
     list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list) {
         if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
             WARN(1, KERN_ERR
                    "BTRFS: read-only device in alloc_list\n");
             continue;
         }
 
         if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
                     &device->dev_state) ||
             test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
             continue;
 
         if (device->total_bytes > device->bytes_used)
             total_avail = device->total_bytes - device->bytes_used;
         else
             total_avail = 0;
 
         /* If there is no space on this device, skip it. */
         if (total_avail < ctl->dev_extent_min)
             continue;
 
         ret = find_free_dev_extent(device, dev_extent_want, &dev_offset,
                        &max_avail);
         if (ret && ret != -ENOSPC)
             return ret;
 
         if (ret == 0)
             max_avail = dev_extent_want;
 
         if (max_avail < ctl->dev_extent_min) {
             if (btrfs_test_opt(info, ENOSPC_DEBUG))
                 btrfs_debug(info,
             "%s: devid %llu has no free space, have=%llu want=%llu",
                         __func__, device->devid, max_avail,
                         ctl->dev_extent_min);
             continue;
         }
 
         if (ndevs == fs_devices->rw_devices) {
             WARN(1, "%s: found more than %llu devices\n",
                  __func__, fs_devices->rw_devices);
             break;
         }
         devices_info[ndevs].dev_offset = dev_offset;
         devices_info[ndevs].max_avail = max_avail;
         devices_info[ndevs].total_avail = total_avail;
         devices_info[ndevs].dev = device;
         ++ndevs;
     }
     ctl->ndevs = ndevs;
 
     /*
      * now sort the devices by hole size / available space
      */
     sort(devices_info, ndevs, sizeof(struct btrfs_device_info),
          btrfs_cmp_device_info, NULL);
 
     return 0;
 }
 
 static int decide_stripe_size_regular(struct alloc_chunk_ctl *ctl,
                       struct btrfs_device_info *devices_info)
 {
     /* Number of stripes that count for block group size */
     int data_stripes;
 
     /*
      * The primary goal is to maximize the number of stripes, so use as
      * many devices as possible, even if the stripes are not maximum sized.
      *
      * The DUP profile stores more than one stripe per device, the
      * max_avail is the total size so we have to adjust.
      */
     ctl->stripe_size = div_u64(devices_info[ctl->ndevs - 1].max_avail,
                    ctl->dev_stripes);
     ctl->num_stripes = ctl->ndevs * ctl->dev_stripes;
 
     /* This will have to be fixed for RAID1 and RAID10 over more drives */
     data_stripes = (ctl->num_stripes - ctl->nparity) / ctl->ncopies;
 
     /*
      * Use the number of data stripes to figure out how big this chunk is
      * really going to be in terms of logical address space, and compare
      * that answer with the max chunk size. If it's higher, we try to
      * reduce stripe_size.
      */
     if (ctl->stripe_size * data_stripes > ctl->max_chunk_size) {
         /*
          * Reduce stripe_size, round it up to a 16MB boundary again and
          * then use it, unless it ends up being even bigger than the
          * previous value we had already.
          */
         ctl->stripe_size = min(round_up(div_u64(ctl->max_chunk_size,
                             data_stripes), SZ_16M),
                        ctl->stripe_size);
     }
 
     /* Stripe size should not go beyond 1G. */
     ctl->stripe_size = min_t(u64, ctl->stripe_size, SZ_1G);
 
     /* Align to BTRFS_STRIPE_LEN */
     ctl->stripe_size = round_down(ctl->stripe_size, BTRFS_STRIPE_LEN);
     ctl->chunk_size = ctl->stripe_size * data_stripes;
 
     return 0;
 }
 
 static int decide_stripe_size_zoned(struct alloc_chunk_ctl *ctl,
                     struct btrfs_device_info *devices_info)
 {
     u64 zone_size = devices_info[0].dev->zone_info->zone_size;
     /* Number of stripes that count for block group size */
     int data_stripes;
 
     /*
      * It should hold because:
      *    dev_extent_min == dev_extent_want == zone_size * dev_stripes
      */
     ASSERT(devices_info[ctl->ndevs - 1].max_avail == ctl->dev_extent_min);
 
     ctl->stripe_size = zone_size;
     ctl->num_stripes = ctl->ndevs * ctl->dev_stripes;
     data_stripes = (ctl->num_stripes - ctl->nparity) / ctl->ncopies;
 
     /* stripe_size is fixed in zoned filesysmte. Reduce ndevs instead. */
     if (ctl->stripe_size * data_stripes > ctl->max_chunk_size) {
         ctl->ndevs = div_u64(div_u64(ctl->max_chunk_size * ctl->ncopies,
                          ctl->stripe_size) + ctl->nparity,
                      ctl->dev_stripes);
         ctl->num_stripes = ctl->ndevs * ctl->dev_stripes;
         data_stripes = (ctl->num_stripes - ctl->nparity) / ctl->ncopies;
         ASSERT(ctl->stripe_size * data_stripes <= ctl->max_chunk_size);
     }
 
     ctl->chunk_size = ctl->stripe_size * data_stripes;
 
     return 0;
 }
 
 static int decide_stripe_size(struct btrfs_fs_devices *fs_devices,
                   struct alloc_chunk_ctl *ctl,
                   struct btrfs_device_info *devices_info)
 {
     struct btrfs_fs_info *info = fs_devices->fs_info;
 
     /*
      * Round down to number of usable stripes, devs_increment can be any
      * number so we can't use round_down() that requires power of 2, while
      * rounddown is safe.
      */
     ctl->ndevs = rounddown(ctl->ndevs, ctl->devs_increment);
 
     if (ctl->ndevs < ctl->devs_min) {
         if (btrfs_test_opt(info, ENOSPC_DEBUG)) {
             btrfs_debug(info,
     "%s: not enough devices with free space: have=%d minimum required=%d",
                     __func__, ctl->ndevs, ctl->devs_min);
         }
         return -ENOSPC;
     }
 
     ctl->ndevs = min(ctl->ndevs, ctl->devs_max);
 
     switch (fs_devices->chunk_alloc_policy) {
     case BTRFS_CHUNK_ALLOC_REGULAR:
         return decide_stripe_size_regular(ctl, devices_info);
     case BTRFS_CHUNK_ALLOC_ZONED:
         return decide_stripe_size_zoned(ctl, devices_info);
     default:
         BUG();
     }
 }
 
 static struct btrfs_block_group *create_chunk(struct btrfs_trans_handle *trans,
             struct alloc_chunk_ctl *ctl,
             struct btrfs_device_info *devices_info)
 {
     struct btrfs_fs_info *info = trans->fs_info;
     struct map_lookup *map = NULL;
     struct extent_map_tree *em_tree;
     struct btrfs_block_group *block_group;
     struct extent_map *em;
     u64 start = ctl->start;
     u64 type = ctl->type;
     int ret;
     int i;
     int j;
 
     map = kmalloc(map_lookup_size(ctl->num_stripes), GFP_NOFS);
     if (!map)
         return ERR_PTR(-ENOMEM);
     map->num_stripes = ctl->num_stripes;
 
     for (i = 0; i < ctl->ndevs; ++i) {
         for (j = 0; j < ctl->dev_stripes; ++j) {
             int s = i * ctl->dev_stripes + j;
             map->stripes[s].dev = devices_info[i].dev;
             map->stripes[s].physical = devices_info[i].dev_offset +
                            j * ctl->stripe_size;
         }
     }
     map->stripe_len = BTRFS_STRIPE_LEN;
     map->io_align = BTRFS_STRIPE_LEN;
     map->io_width = BTRFS_STRIPE_LEN;
     map->type = type;
     map->sub_stripes = ctl->sub_stripes;
 
     trace_btrfs_chunk_alloc(info, map, start, ctl->chunk_size);
 
     em = alloc_extent_map();
     if (!em) {
         kfree(map);
         return ERR_PTR(-ENOMEM);
     }
     set_bit(EXTENT_FLAG_FS_MAPPING, &em->flags);
     em->map_lookup = map;
     em->start = start;
     em->len = ctl->chunk_size;
     em->block_start = 0;
     em->block_len = em->len;
     em->orig_block_len = ctl->stripe_size;
 
     em_tree = &info->mapping_tree;
     write_lock(&em_tree->lock);
     ret = add_extent_mapping(em_tree, em, 0);
     if (ret) {
         write_unlock(&em_tree->lock);
         free_extent_map(em);
         return ERR_PTR(ret);
     }
     write_unlock(&em_tree->lock);
 
     block_group = btrfs_make_block_group(trans, 0, type, start, ctl->chunk_size);
     if (IS_ERR(block_group))
         goto error_del_extent;
 
     for (i = 0; i < map->num_stripes; i++) {
         struct btrfs_device *dev = map->stripes[i].dev;
 
         btrfs_device_set_bytes_used(dev,
                         dev->bytes_used + ctl->stripe_size);
         if (list_empty(&dev->post_commit_list))
             list_add_tail(&dev->post_commit_list,
                       &trans->transaction->dev_update_list);
     }
 
     atomic64_sub(ctl->stripe_size * map->num_stripes,
              &info->free_chunk_space);
 
     free_extent_map(em);
     check_raid56_incompat_flag(info, type);
     check_raid1c34_incompat_flag(info, type);
 
     return block_group;
 
 error_del_extent:
     write_lock(&em_tree->lock);
     remove_extent_mapping(em_tree, em);
     write_unlock(&em_tree->lock);
 
     /* One for our allocation */
     free_extent_map(em);
     /* One for the tree reference */
     free_extent_map(em);
 
     return block_group;
 }
 
 struct btrfs_block_group *btrfs_create_chunk(struct btrfs_trans_handle *trans,
                         u64 type)
 {
     struct btrfs_fs_info *info = trans->fs_info;
     struct btrfs_fs_devices *fs_devices = info->fs_devices;
     struct btrfs_device_info *devices_info = NULL;
     struct alloc_chunk_ctl ctl;
     struct btrfs_block_group *block_group;
     int ret;
 
     lockdep_assert_held(&info->chunk_mutex);
 
     if (!alloc_profile_is_valid(type, 0)) {
         ASSERT(0);
         return ERR_PTR(-EINVAL);
     }
 
     if (list_empty(&fs_devices->alloc_list)) {
         if (btrfs_test_opt(info, ENOSPC_DEBUG))
             btrfs_debug(info, "%s: no writable device", __func__);
         return ERR_PTR(-ENOSPC);
     }
 
     if (!(type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
         btrfs_err(info, "invalid chunk type 0x%llx requested", type);
         ASSERT(0);
         return ERR_PTR(-EINVAL);
     }
 
     ctl.start = find_next_chunk(info);
     ctl.type = type;
     init_alloc_chunk_ctl(fs_devices, &ctl);
 
     devices_info = kcalloc(fs_devices->rw_devices, sizeof(*devices_info),
                    GFP_NOFS);
     if (!devices_info)
         return ERR_PTR(-ENOMEM);
 
     ret = gather_device_info(fs_devices, &ctl, devices_info);
     if (ret < 0) {
         block_group = ERR_PTR(ret);
         goto out;
     }
 
     ret = decide_stripe_size(fs_devices, &ctl, devices_info);
     if (ret < 0) {
         block_group = ERR_PTR(ret);
         goto out;
     }
 
     block_group = create_chunk(trans, &ctl, devices_info);
 
 out:
     kfree(devices_info);
     return block_group;
 }
 
 /*
  * This function, btrfs_chunk_alloc_add_chunk_item(), typically belongs to the
  * phase 1 of chunk allocation. It belongs to phase 2 only when allocating system
  * chunks.
  *
  * See the comment at btrfs_chunk_alloc() for details about the chunk allocation
  * phases.
  */
 int btrfs_chunk_alloc_add_chunk_item(struct btrfs_trans_handle *trans,
                      struct btrfs_block_group *bg)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_root *chunk_root = fs_info->chunk_root;
     struct btrfs_key key;
     struct btrfs_chunk *chunk;
     struct btrfs_stripe *stripe;
     struct extent_map *em;
     struct map_lookup *map;
     size_t item_size;
     int i;
     int ret;
 
     /*
      * We take the chunk_mutex for 2 reasons:
      *
      * 1) Updates and insertions in the chunk btree must be done while holding
      *    the chunk_mutex, as well as updating the system chunk array in the
      *    superblock. See the comment on top of btrfs_chunk_alloc() for the
      *    details;
      *
      * 2) To prevent races with the final phase of a device replace operation
      *    that replaces the device object associated with the map's stripes,
      *    because the device object's id can change at any time during that
      *    final phase of the device replace operation
      *    (dev-replace.c:btrfs_dev_replace_finishing()), so we could grab the
      *    replaced device and then see it with an ID of BTRFS_DEV_REPLACE_DEVID,
      *    which would cause a failure when updating the device item, which does
      *    not exists, or persisting a stripe of the chunk item with such ID.
      *    Here we can't use the device_list_mutex because our caller already
      *    has locked the chunk_mutex, and the final phase of device replace
      *    acquires both mutexes - first the device_list_mutex and then the
      *    chunk_mutex. Using any of those two mutexes protects us from a
      *    concurrent device replace.
      */
     lockdep_assert_held(&fs_info->chunk_mutex);
 
     em = btrfs_get_chunk_map(fs_info, bg->start, bg->length);
     if (IS_ERR(em)) {
         ret = PTR_ERR(em);
         btrfs_abort_transaction(trans, ret);
         return ret;
     }
 
     map = em->map_lookup;
     item_size = btrfs_chunk_item_size(map->num_stripes);
 
     chunk = kzalloc(item_size, GFP_NOFS);
     if (!chunk) {
         ret = -ENOMEM;
         btrfs_abort_transaction(trans, ret);
         goto out;
     }
 
     for (i = 0; i < map->num_stripes; i++) {
         struct btrfs_device *device = map->stripes[i].dev;
 
         ret = btrfs_update_device(trans, device);
         if (ret)
             goto out;
     }
 
     stripe = &chunk->stripe;
     for (i = 0; i < map->num_stripes; i++) {
         struct btrfs_device *device = map->stripes[i].dev;
         const u64 dev_offset = map->stripes[i].physical;
 
         btrfs_set_stack_stripe_devid(stripe, device->devid);
         btrfs_set_stack_stripe_offset(stripe, dev_offset);
         memcpy(stripe->dev_uuid, device->uuid, BTRFS_UUID_SIZE);
         stripe++;
     }
 
     btrfs_set_stack_chunk_length(chunk, bg->length);
     btrfs_set_stack_chunk_owner(chunk, BTRFS_EXTENT_TREE_OBJECTID);
     btrfs_set_stack_chunk_stripe_len(chunk, map->stripe_len);
     btrfs_set_stack_chunk_type(chunk, map->type);
     btrfs_set_stack_chunk_num_stripes(chunk, map->num_stripes);
     btrfs_set_stack_chunk_io_align(chunk, map->stripe_len);
     btrfs_set_stack_chunk_io_width(chunk, map->stripe_len);
     btrfs_set_stack_chunk_sector_size(chunk, fs_info->sectorsize);
     btrfs_set_stack_chunk_sub_stripes(chunk, map->sub_stripes);
 
     key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
     key.type = BTRFS_CHUNK_ITEM_KEY;
     key.offset = bg->start;
 
     ret = btrfs_insert_item(trans, chunk_root, &key, chunk, item_size);
     if (ret)
         goto out;
 
     bg->chunk_item_inserted = 1;
 
     if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
         ret = btrfs_add_system_chunk(fs_info, &key, chunk, item_size);
         if (ret)
             goto out;
     }
 
 out:
     kfree(chunk);
     free_extent_map(em);
     return ret;
 }
 
 static noinline int init_first_rw_device(struct btrfs_trans_handle *trans)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     u64 alloc_profile;
     struct btrfs_block_group *meta_bg;
     struct btrfs_block_group *sys_bg;
 
     /*
      * When adding a new device for sprouting, the seed device is read-only
      * so we must first allocate a metadata and a system chunk. But before
      * adding the block group items to the extent, device and chunk btrees,
      * we must first:
      *
      * 1) Create both chunks without doing any changes to the btrees, as
      *    otherwise we would get -ENOSPC since the block groups from the
      *    seed device are read-only;
      *
      * 2) Add the device item for the new sprout device - finishing the setup
      *    of a new block group requires updating the device item in the chunk
      *    btree, so it must exist when we attempt to do it. The previous step
      *    ensures this does not fail with -ENOSPC.
      *
      * After that we can add the block group items to their btrees:
      * update existing device item in the chunk btree, add a new block group
      * item to the extent btree, add a new chunk item to the chunk btree and
      * finally add the new device extent items to the devices btree.
      */
 
     alloc_profile = btrfs_metadata_alloc_profile(fs_info);
     meta_bg = btrfs_create_chunk(trans, alloc_profile);
     if (IS_ERR(meta_bg))
         return PTR_ERR(meta_bg);
 
     alloc_profile = btrfs_system_alloc_profile(fs_info);
     sys_bg = btrfs_create_chunk(trans, alloc_profile);
     if (IS_ERR(sys_bg))
         return PTR_ERR(sys_bg);
 
     return 0;
 }
 
 static inline int btrfs_chunk_max_errors(struct map_lookup *map)
 {
     const int index = btrfs_bg_flags_to_raid_index(map->type);
 
     return btrfs_raid_array[index].tolerated_failures;
 }
 
 bool btrfs_chunk_writeable(struct btrfs_fs_info *fs_info, u64 chunk_offset)
 {
     struct extent_map *em;
     struct map_lookup *map;
     int miss_ndevs = 0;
     int i;
     bool ret = true;
 
     em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
     if (IS_ERR(em))
         return false;
 
     map = em->map_lookup;
     for (i = 0; i < map->num_stripes; i++) {
         if (test_bit(BTRFS_DEV_STATE_MISSING,
                     &map->stripes[i].dev->dev_state)) {
             miss_ndevs++;
             continue;
         }
         if (!test_bit(BTRFS_DEV_STATE_WRITEABLE,
                     &map->stripes[i].dev->dev_state)) {
             ret = false;
             goto end;
         }
     }
 
     /*
      * If the number of missing devices is larger than max errors, we can
      * not write the data into that chunk successfully.
      */
     if (miss_ndevs > btrfs_chunk_max_errors(map))
         ret = false;
 end:
     free_extent_map(em);
     return ret;
 }
 
 void btrfs_mapping_tree_free(struct extent_map_tree *tree)
 {
     struct extent_map *em;
 
     while (1) {
         write_lock(&tree->lock);
         em = lookup_extent_mapping(tree, 0, (u64)-1);
         if (em)
             remove_extent_mapping(tree, em);
         write_unlock(&tree->lock);
         if (!em)
             break;
         /* once for us */
         free_extent_map(em);
         /* once for the tree */
         free_extent_map(em);
     }
 }
 
 int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len)
 {
     struct extent_map *em;
     struct map_lookup *map;
     enum btrfs_raid_types index;
     int ret = 1;
 
     em = btrfs_get_chunk_map(fs_info, logical, len);
     if (IS_ERR(em))
         /*
          * We could return errors for these cases, but that could get
          * ugly and we'd probably do the same thing which is just not do
          * anything else and exit, so return 1 so the callers don't try
          * to use other copies.
          */
         return 1;
 
     map = em->map_lookup;
     index = btrfs_bg_flags_to_raid_index(map->type);
 
     /* Non-RAID56, use their ncopies from btrfs_raid_array. */
     if (!(map->type & BTRFS_BLOCK_GROUP_RAID56_MASK))
         ret = btrfs_raid_array[index].ncopies;
     else if (map->type & BTRFS_BLOCK_GROUP_RAID5)
         ret = 2;
     else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
         /*
          * There could be two corrupted data stripes, we need
          * to loop retry in order to rebuild the correct data.
          *
          * Fail a stripe at a time on every retry except the
          * stripe under reconstruction.
          */
         ret = map->num_stripes;
     free_extent_map(em);
 
     down_read(&fs_info->dev_replace.rwsem);
     if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace) &&
         fs_info->dev_replace.tgtdev)
         ret++;
     up_read(&fs_info->dev_replace.rwsem);
 
     return ret;
 }
 
 unsigned long btrfs_full_stripe_len(struct btrfs_fs_info *fs_info,
                     u64 logical)
 {
     struct extent_map *em;
     struct map_lookup *map;
     unsigned long len = fs_info->sectorsize;
 
     if (!btrfs_fs_incompat(fs_info, RAID56))
         return len;
 
     em = btrfs_get_chunk_map(fs_info, logical, len);
 
     if (!WARN_ON(IS_ERR(em))) {
         map = em->map_lookup;
         if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
             len = map->stripe_len * nr_data_stripes(map);
         free_extent_map(em);
     }
     return len;
 }
 
 int btrfs_is_parity_mirror(struct btrfs_fs_info *fs_info, u64 logical, u64 len)
 {
     struct extent_map *em;
     struct map_lookup *map;
     int ret = 0;
 
     if (!btrfs_fs_incompat(fs_info, RAID56))
         return 0;
 
     em = btrfs_get_chunk_map(fs_info, logical, len);
 
     if(!WARN_ON(IS_ERR(em))) {
         map = em->map_lookup;
         if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
             ret = 1;
         free_extent_map(em);
     }
     return ret;
 }
 
 static int find_live_mirror(struct btrfs_fs_info *fs_info,
                 struct map_lookup *map, int first,
                 int dev_replace_is_ongoing)
 {
     int i;
     int num_stripes;
     int preferred_mirror;
     int tolerance;
     struct btrfs_device *srcdev;
 
     ASSERT((map->type &
          (BTRFS_BLOCK_GROUP_RAID1_MASK | BTRFS_BLOCK_GROUP_RAID10)));
 
     if (map->type & BTRFS_BLOCK_GROUP_RAID10)
         num_stripes = map->sub_stripes;
     else
         num_stripes = map->num_stripes;
 
     switch (fs_info->fs_devices->read_policy) {
     default:
         /* Shouldn't happen, just warn and use pid instead of failing */
         btrfs_warn_rl(fs_info,
                   "unknown read_policy type %u, reset to pid",
                   fs_info->fs_devices->read_policy);
         fs_info->fs_devices->read_policy = BTRFS_READ_POLICY_PID;
         fallthrough;
     case BTRFS_READ_POLICY_PID:
         preferred_mirror = first + (current->pid % num_stripes);
         break;
     }
 
     if (dev_replace_is_ongoing &&
         fs_info->dev_replace.cont_reading_from_srcdev_mode ==
          BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID)
         srcdev = fs_info->dev_replace.srcdev;
     else
         srcdev = NULL;
 
     /*
      * try to avoid the drive that is the source drive for a
      * dev-replace procedure, only choose it if no other non-missing
      * mirror is available
      */
     for (tolerance = 0; tolerance < 2; tolerance++) {
         if (map->stripes[preferred_mirror].dev->bdev &&
             (tolerance || map->stripes[preferred_mirror].dev != srcdev))
             return preferred_mirror;
         for (i = first; i < first + num_stripes; i++) {
             if (map->stripes[i].dev->bdev &&
                 (tolerance || map->stripes[i].dev != srcdev))
                 return i;
         }
     }
 
     /* we couldn't find one that doesn't fail.  Just return something
      * and the io error handling code will clean up eventually
      */
     return preferred_mirror;
 }
 
 /* Bubble-sort the stripe set to put the parity/syndrome stripes last */
 static void sort_parity_stripes(struct btrfs_io_context *bioc, int num_stripes)
 {
     int i;
     int again = 1;
 
     while (again) {
         again = 0;
         for (i = 0; i < num_stripes - 1; i++) {
             /* Swap if parity is on a smaller index */
             if (bioc->raid_map[i] > bioc->raid_map[i + 1]) {
                 swap(bioc->stripes[i], bioc->stripes[i + 1]);
                 swap(bioc->raid_map[i], bioc->raid_map[i + 1]);
                 again = 1;
             }
         }
     }
 }
 
 static struct btrfs_io_context *alloc_btrfs_io_context(struct btrfs_fs_info *fs_info,
                                int total_stripes,
                                int real_stripes)
 {
     struct btrfs_io_context *bioc = kzalloc(
          /* The size of btrfs_io_context */
         sizeof(struct btrfs_io_context) +
         /* Plus the variable array for the stripes */
         sizeof(struct btrfs_io_stripe) * (total_stripes) +
         /* Plus the variable array for the tgt dev */
         sizeof(int) * (real_stripes) +
         /*
          * Plus the raid_map, which includes both the tgt dev
          * and the stripes.
          */
         sizeof(u64) * (total_stripes),
         GFP_NOFS|__GFP_NOFAIL);
 
     atomic_set(&bioc->error, 0);
     refcount_set(&bioc->refs, 1);
 
     bioc->fs_info = fs_info;
     bioc->tgtdev_map = (int *)(bioc->stripes + total_stripes);
     bioc->raid_map = (u64 *)(bioc->tgtdev_map + real_stripes);
 
     return bioc;
 }
 
 void btrfs_get_bioc(struct btrfs_io_context *bioc)
 {
     WARN_ON(!refcount_read(&bioc->refs));
     refcount_inc(&bioc->refs);
 }
 
 void btrfs_put_bioc(struct btrfs_io_context *bioc)
 {
     if (!bioc)
         return;
     if (refcount_dec_and_test(&bioc->refs))
         kfree(bioc);
 }
 
 /*
  * Please note that, discard won't be sent to target device of device
  * replace.
  */
 struct btrfs_discard_stripe *btrfs_map_discard(struct btrfs_fs_info *fs_info,
                            u64 logical, u64 *length_ret,
                            u32 *num_stripes)
 {
     struct extent_map *em;
     struct map_lookup *map;
     struct btrfs_discard_stripe *stripes;
     u64 length = *length_ret;
     u64 offset;
     u64 stripe_nr;
     u64 stripe_nr_end;
     u64 stripe_end_offset;
     u64 stripe_cnt;
     u64 stripe_len;
     u64 stripe_offset;
     u32 stripe_index;
     u32 factor = 0;
     u32 sub_stripes = 0;
     u64 stripes_per_dev = 0;
     u32 remaining_stripes = 0;
     u32 last_stripe = 0;
     int ret;
     int i;
 
     em = btrfs_get_chunk_map(fs_info, logical, length);
     if (IS_ERR(em))
         return ERR_CAST(em);
 
     map = em->map_lookup;
 
     /* we don't discard raid56 yet */
     if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
         ret = -EOPNOTSUPP;
         goto out_free_map;
 }
 
     offset = logical - em->start;
     length = min_t(u64, em->start + em->len - logical, length);
     *length_ret = length;
 
     stripe_len = map->stripe_len;
     /*
      * stripe_nr counts the total number of stripes we have to stride
      * to get to this block
      */
     stripe_nr = div64_u64(offset, stripe_len);
 
     /* stripe_offset is the offset of this block in its stripe */
     stripe_offset = offset - stripe_nr * stripe_len;
 
     stripe_nr_end = round_up(offset + length, map->stripe_len);
     stripe_nr_end = div64_u64(stripe_nr_end, map->stripe_len);
     stripe_cnt = stripe_nr_end - stripe_nr;
     stripe_end_offset = stripe_nr_end * map->stripe_len -
                 (offset + length);
     /*
      * after this, stripe_nr is the number of stripes on this
      * device we have to walk to find the data, and stripe_index is
      * the number of our device in the stripe array
      */
     *num_stripes = 1;
     stripe_index = 0;
     if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
              BTRFS_BLOCK_GROUP_RAID10)) {
         if (map->type & BTRFS_BLOCK_GROUP_RAID0)
             sub_stripes = 1;
         else
             sub_stripes = map->sub_stripes;
 
         factor = map->num_stripes / sub_stripes;
         *num_stripes = min_t(u64, map->num_stripes,
                     sub_stripes * stripe_cnt);
         stripe_nr = div_u64_rem(stripe_nr, factor, &stripe_index);
         stripe_index *= sub_stripes;
         stripes_per_dev = div_u64_rem(stripe_cnt, factor,
                           &remaining_stripes);
         div_u64_rem(stripe_nr_end - 1, factor, &last_stripe);
         last_stripe *= sub_stripes;
     } else if (map->type & (BTRFS_BLOCK_GROUP_RAID1_MASK |
                 BTRFS_BLOCK_GROUP_DUP)) {
         *num_stripes = map->num_stripes;
     } else {
         stripe_nr = div_u64_rem(stripe_nr, map->num_stripes,
                     &stripe_index);
     }
 
     stripes = kcalloc(*num_stripes, sizeof(*stripes), GFP_NOFS);
     if (!stripes) {
         ret = -ENOMEM;
         goto out_free_map;
     }
 
     for (i = 0; i < *num_stripes; i++) {
         stripes[i].physical =
             map->stripes[stripe_index].physical +
             stripe_offset + stripe_nr * map->stripe_len;
         stripes[i].dev = map->stripes[stripe_index].dev;
 
         if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
                  BTRFS_BLOCK_GROUP_RAID10)) {
             stripes[i].length = stripes_per_dev * map->stripe_len;
 
             if (i / sub_stripes < remaining_stripes)
                 stripes[i].length += map->stripe_len;
 
             /*
              * Special for the first stripe and
              * the last stripe:
              *
              * |-------|...|-------|
              *     |----------|
              *    off     end_off
              */
             if (i < sub_stripes)
                 stripes[i].length -= stripe_offset;
 
             if (stripe_index >= last_stripe &&
                 stripe_index <= (last_stripe +
                          sub_stripes - 1))
                 stripes[i].length -= stripe_end_offset;
 
             if (i == sub_stripes - 1)
                 stripe_offset = 0;
         } else {
             stripes[i].length = length;
         }
 
         stripe_index++;
         if (stripe_index == map->num_stripes) {
             stripe_index = 0;
             stripe_nr++;
         }
     }
 
     free_extent_map(em);
     return stripes;
 out_free_map:
     free_extent_map(em);
     return ERR_PTR(ret);
 }
 
 /*
  * In dev-replace case, for repair case (that's the only case where the mirror
  * is selected explicitly when calling btrfs_map_block), blocks left of the
  * left cursor can also be read from the target drive.
  *
  * For REQ_GET_READ_MIRRORS, the target drive is added as the last one to the
  * array of stripes.
  * For READ, it also needs to be supported using the same mirror number.
  *
  * If the requested block is not left of the left cursor, EIO is returned. This
  * can happen because btrfs_num_copies() returns one more in the dev-replace
  * case.
  */
 static int get_extra_mirror_from_replace(struct btrfs_fs_info *fs_info,
                      u64 logical, u64 length,
                      u64 srcdev_devid, int *mirror_num,
                      u64 *physical)
 {
     struct btrfs_io_context *bioc = NULL;
     int num_stripes;
     int index_srcdev = 0;
     int found = 0;
     u64 physical_of_found = 0;
     int i;
     int ret = 0;
 
     ret = __btrfs_map_block(fs_info, BTRFS_MAP_GET_READ_MIRRORS,
                 logical, &length, &bioc, 0, 0);
     if (ret) {
         ASSERT(bioc == NULL);
         return ret;
     }
 
     num_stripes = bioc->num_stripes;
     if (*mirror_num > num_stripes) {
         /*
          * BTRFS_MAP_GET_READ_MIRRORS does not contain this mirror,
          * that means that the requested area is not left of the left
          * cursor
          */
         btrfs_put_bioc(bioc);
         return -EIO;
     }
 
     /*
      * process the rest of the function using the mirror_num of the source
      * drive. Therefore look it up first.  At the end, patch the device
      * pointer to the one of the target drive.
      */
     for (i = 0; i < num_stripes; i++) {
         if (bioc->stripes[i].dev->devid != srcdev_devid)
             continue;
 
         /*
          * In case of DUP, in order to keep it simple, only add the
          * mirror with the lowest physical address
          */
         if (found &&
             physical_of_found <= bioc->stripes[i].physical)
             continue;
 
         index_srcdev = i;
         found = 1;
         physical_of_found = bioc->stripes[i].physical;
     }
 
     btrfs_put_bioc(bioc);
 
     ASSERT(found);
     if (!found)
         return -EIO;
 
     *mirror_num = index_srcdev + 1;
     *physical = physical_of_found;
     return ret;
 }
 
 static bool is_block_group_to_copy(struct btrfs_fs_info *fs_info, u64 logical)
 {
     struct btrfs_block_group *cache;
     bool ret;
 
     /* Non zoned filesystem does not use "to_copy" flag */
     if (!btrfs_is_zoned(fs_info))
         return false;
 
     cache = btrfs_lookup_block_group(fs_info, logical);
 
     spin_lock(&cache->lock);
     ret = cache->to_copy;
     spin_unlock(&cache->lock);
 
     btrfs_put_block_group(cache);
     return ret;
 }
 
 static void handle_ops_on_dev_replace(enum btrfs_map_op op,
                       struct btrfs_io_context **bioc_ret,
                       struct btrfs_dev_replace *dev_replace,
                       u64 logical,
                       int *num_stripes_ret, int *max_errors_ret)
 {
     struct btrfs_io_context *bioc = *bioc_ret;
     u64 srcdev_devid = dev_replace->srcdev->devid;
     int tgtdev_indexes = 0;
     int num_stripes = *num_stripes_ret;
     int max_errors = *max_errors_ret;
     int i;
 
     if (op == BTRFS_MAP_WRITE) {
         int index_where_to_add;
 
         /*
          * A block group which have "to_copy" set will eventually
          * copied by dev-replace process. We can avoid cloning IO here.
          */
         if (is_block_group_to_copy(dev_replace->srcdev->fs_info, logical))
             return;
 
         /*
          * duplicate the write operations while the dev replace
          * procedure is running. Since the copying of the old disk to
          * the new disk takes place at run time while the filesystem is
          * mounted writable, the regular write operations to the old
          * disk have to be duplicated to go to the new disk as well.
          *
          * Note that device->missing is handled by the caller, and that
          * the write to the old disk is already set up in the stripes
          * array.
          */
         index_where_to_add = num_stripes;
         for (i = 0; i < num_stripes; i++) {
             if (bioc->stripes[i].dev->devid == srcdev_devid) {
                 /* write to new disk, too */
                 struct btrfs_io_stripe *new =
                     bioc->stripes + index_where_to_add;
                 struct btrfs_io_stripe *old =
                     bioc->stripes + i;
 
                 new->physical = old->physical;
                 new->dev = dev_replace->tgtdev;
                 bioc->tgtdev_map[i] = index_where_to_add;
                 index_where_to_add++;
                 max_errors++;
                 tgtdev_indexes++;
             }
         }
         num_stripes = index_where_to_add;
     } else if (op == BTRFS_MAP_GET_READ_MIRRORS) {
         int index_srcdev = 0;
         int found = 0;
         u64 physical_of_found = 0;
 
         /*
          * During the dev-replace procedure, the target drive can also
          * be used to read data in case it is needed to repair a corrupt
          * block elsewhere. This is possible if the requested area is
          * left of the left cursor. In this area, the target drive is a
          * full copy of the source drive.
          */
         for (i = 0; i < num_stripes; i++) {
             if (bioc->stripes[i].dev->devid == srcdev_devid) {
                 /*
                  * In case of DUP, in order to keep it simple,
                  * only add the mirror with the lowest physical
                  * address
                  */
                 if (found &&
                     physical_of_found <= bioc->stripes[i].physical)
                     continue;
                 index_srcdev = i;
                 found = 1;
                 physical_of_found = bioc->stripes[i].physical;
             }
         }
         if (found) {
             struct btrfs_io_stripe *tgtdev_stripe =
                 bioc->stripes + num_stripes;
 
             tgtdev_stripe->physical = physical_of_found;
             tgtdev_stripe->dev = dev_replace->tgtdev;
             bioc->tgtdev_map[index_srcdev] = num_stripes;
 
             tgtdev_indexes++;
             num_stripes++;
         }
     }
 
     *num_stripes_ret = num_stripes;
     *max_errors_ret = max_errors;
     bioc->num_tgtdevs = tgtdev_indexes;
     *bioc_ret = bioc;
 }
 
 static bool need_full_stripe(enum btrfs_map_op op)
 {
     return (op == BTRFS_MAP_WRITE || op == BTRFS_MAP_GET_READ_MIRRORS);
 }
 
 /*
  * Calculate the geometry of a particular (address, len) tuple. This
  * information is used to calculate how big a particular bio can get before it
  * straddles a stripe.
  *
  * @fs_info: the filesystem
  * @em:      mapping containing the logical extent
  * @op:      type of operation - write or read
  * @logical: address that we want to figure out the geometry of
  * @io_geom: pointer used to return values
  *
  * Returns < 0 in case a chunk for the given logical address cannot be found,
  * usually shouldn't happen unless @logical is corrupted, 0 otherwise.
  */
 int btrfs_get_io_geometry(struct btrfs_fs_info *fs_info, struct extent_map *em,
               enum btrfs_map_op op, u64 logical,
               struct btrfs_io_geometry *io_geom)
 {
     struct map_lookup *map;
     u64 len;
     u64 offset;
     u64 stripe_offset;
     u64 stripe_nr;
     u32 stripe_len;
     u64 raid56_full_stripe_start = (u64)-1;
     int data_stripes;
 
     ASSERT(op != BTRFS_MAP_DISCARD);
 
     map = em->map_lookup;
     /* Offset of this logical address in the chunk */
     offset = logical - em->start;
     /* Len of a stripe in a chunk */
     stripe_len = map->stripe_len;
     /*
      * Stripe_nr is where this block falls in
      * stripe_offset is the offset of this block in its stripe.
      */
     stripe_nr = div64_u64_rem(offset, stripe_len, &stripe_offset);
     ASSERT(stripe_offset < U32_MAX);
 
     data_stripes = nr_data_stripes(map);
 
     /* Only stripe based profiles needs to check against stripe length. */
     if (map->type & BTRFS_BLOCK_GROUP_STRIPE_MASK) {
         u64 max_len = stripe_len - stripe_offset;
 
         /*
          * In case of raid56, we need to know the stripe aligned start
          */
         if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
             unsigned long full_stripe_len = stripe_len * data_stripes;
             raid56_full_stripe_start = offset;
 
             /*
              * Allow a write of a full stripe, but make sure we
              * don't allow straddling of stripes
              */
             raid56_full_stripe_start = div64_u64(raid56_full_stripe_start,
                     full_stripe_len);
             raid56_full_stripe_start *= full_stripe_len;
 
             /*
              * For writes to RAID[56], allow a full stripeset across
              * all disks. For other RAID types and for RAID[56]
              * reads, just allow a single stripe (on a single disk).
              */
             if (op == BTRFS_MAP_WRITE) {
                 max_len = stripe_len * data_stripes -
                       (offset - raid56_full_stripe_start);
             }
         }
         len = min_t(u64, em->len - offset, max_len);
     } else {
         len = em->len - offset;
     }
 
     io_geom->len = len;
     io_geom->offset = offset;
     io_geom->stripe_len = stripe_len;
     io_geom->stripe_nr = stripe_nr;
     io_geom->stripe_offset = stripe_offset;
     io_geom->raid56_stripe_offset = raid56_full_stripe_start;
 
     return 0;
 }
 
 static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
                  enum btrfs_map_op op,
                  u64 logical, u64 *length,
                  struct btrfs_io_context **bioc_ret,
                  int mirror_num, int need_raid_map)
 {
     struct extent_map *em;
     struct map_lookup *map;
     u64 stripe_offset;
     u64 stripe_nr;
     u64 stripe_len;
     u32 stripe_index;
     int data_stripes;
     int i;
     int ret = 0;
     int num_stripes;
     int max_errors = 0;
     int tgtdev_indexes = 0;
     struct btrfs_io_context *bioc = NULL;
     struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
     int dev_replace_is_ongoing = 0;
     int num_alloc_stripes;
     int patch_the_first_stripe_for_dev_replace = 0;
     u64 physical_to_patch_in_first_stripe = 0;
     u64 raid56_full_stripe_start = (u64)-1;
     struct btrfs_io_geometry geom;
 
     ASSERT(bioc_ret);
     ASSERT(op != BTRFS_MAP_DISCARD);
 
     em = btrfs_get_chunk_map(fs_info, logical, *length);
     ASSERT(!IS_ERR(em));
 
     ret = btrfs_get_io_geometry(fs_info, em, op, logical, &geom);
     if (ret < 0)
         return ret;
 
     map = em->map_lookup;
 
     *length = geom.len;
     stripe_len = geom.stripe_len;
     stripe_nr = geom.stripe_nr;
     stripe_offset = geom.stripe_offset;
     raid56_full_stripe_start = geom.raid56_stripe_offset;
     data_stripes = nr_data_stripes(map);
 
     down_read(&dev_replace->rwsem);
     dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace);
     /*
      * Hold the semaphore for read during the whole operation, write is
      * requested at commit time but must wait.
      */
     if (!dev_replace_is_ongoing)
         up_read(&dev_replace->rwsem);
 
     if (dev_replace_is_ongoing && mirror_num == map->num_stripes + 1 &&
         !need_full_stripe(op) && dev_replace->tgtdev != NULL) {
         ret = get_extra_mirror_from_replace(fs_info, logical, *length,
                             dev_replace->srcdev->devid,
                             &mirror_num,
                         &physical_to_patch_in_first_stripe);
         if (ret)
             goto out;
         else
             patch_the_first_stripe_for_dev_replace = 1;
     } else if (mirror_num > map->num_stripes) {
         mirror_num = 0;
     }
 
     num_stripes = 1;
     stripe_index = 0;
     if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
         stripe_nr = div_u64_rem(stripe_nr, map->num_stripes,
                 &stripe_index);
         if (!need_full_stripe(op))
             mirror_num = 1;
     } else if (map->type & BTRFS_BLOCK_GROUP_RAID1_MASK) {
         if (need_full_stripe(op))
             num_stripes = map->num_stripes;
         else if (mirror_num)
             stripe_index = mirror_num - 1;
         else {
             stripe_index = find_live_mirror(fs_info, map, 0,
                         dev_replace_is_ongoing);
             mirror_num = stripe_index + 1;
         }
 
     } else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
         if (need_full_stripe(op)) {
             num_stripes = map->num_stripes;
         } else if (mirror_num) {
             stripe_index = mirror_num - 1;
         } else {
             mirror_num = 1;
         }
 
     } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
         u32 factor = map->num_stripes / map->sub_stripes;
 
         stripe_nr = div_u64_rem(stripe_nr, factor, &stripe_index);
         stripe_index *= map->sub_stripes;
 
         if (need_full_stripe(op))
             num_stripes = map->sub_stripes;
         else if (mirror_num)
             stripe_index += mirror_num - 1;
         else {
             int old_stripe_index = stripe_index;
             stripe_index = find_live_mirror(fs_info, map,
                           stripe_index,
                           dev_replace_is_ongoing);
             mirror_num = stripe_index - old_stripe_index + 1;
         }
 
     } else if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
         ASSERT(map->stripe_len == BTRFS_STRIPE_LEN);
         if (need_raid_map && (need_full_stripe(op) || mirror_num > 1)) {
             /* push stripe_nr back to the start of the full stripe */
             stripe_nr = div64_u64(raid56_full_stripe_start,
                     stripe_len * data_stripes);
 
             /* RAID[56] write or recovery. Return all stripes */
             num_stripes = map->num_stripes;
             max_errors = btrfs_chunk_max_errors(map);
 
             /* Return the length to the full stripe end */
             *length = min(logical + *length,
                       raid56_full_stripe_start + em->start +
                       data_stripes * stripe_len) - logical;
             stripe_index = 0;
             stripe_offset = 0;
         } else {
             /*
              * Mirror #0 or #1 means the original data block.
              * Mirror #2 is RAID5 parity block.
              * Mirror #3 is RAID6 Q block.
              */
             stripe_nr = div_u64_rem(stripe_nr,
                     data_stripes, &stripe_index);
             if (mirror_num > 1)
                 stripe_index = data_stripes + mirror_num - 2;
 
             /* We distribute the parity blocks across stripes */
             div_u64_rem(stripe_nr + stripe_index, map->num_stripes,
                     &stripe_index);
             if (!need_full_stripe(op) && mirror_num <= 1)
                 mirror_num = 1;
         }
     } else {
         /*
          * after this, stripe_nr is the number of stripes on this
          * device we have to walk to find the data, and stripe_index is
          * the number of our device in the stripe array
          */
         stripe_nr = div_u64_rem(stripe_nr, map->num_stripes,
                 &stripe_index);
         mirror_num = stripe_index + 1;
     }
     if (stripe_index >= map->num_stripes) {
         btrfs_crit(fs_info,
                "stripe index math went horribly wrong, got stripe_index=%u, num_stripes=%u",
                stripe_index, map->num_stripes);
         ret = -EINVAL;
         goto out;
     }
 
     num_alloc_stripes = num_stripes;
     if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL) {
         if (op == BTRFS_MAP_WRITE)
             num_alloc_stripes <<= 1;
         if (op == BTRFS_MAP_GET_READ_MIRRORS)
             num_alloc_stripes++;
         tgtdev_indexes = num_stripes;
     }
 
     bioc = alloc_btrfs_io_context(fs_info, num_alloc_stripes, tgtdev_indexes);
     if (!bioc) {
         ret = -ENOMEM;
         goto out;
     }
 
     for (i = 0; i < num_stripes; i++) {
         bioc->stripes[i].physical = map->stripes[stripe_index].physical +
             stripe_offset + stripe_nr * map->stripe_len;
         bioc->stripes[i].dev = map->stripes[stripe_index].dev;
         stripe_index++;
     }
 
     /* Build raid_map */
     if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK && need_raid_map &&
         (need_full_stripe(op) || mirror_num > 1)) {
         u64 tmp;
         unsigned rot;
 
         /* Work out the disk rotation on this stripe-set */
         div_u64_rem(stripe_nr, num_stripes, &rot);
 
         /* Fill in the logical address of each stripe */
         tmp = stripe_nr * data_stripes;
         for (i = 0; i < data_stripes; i++)
             bioc->raid_map[(i + rot) % num_stripes] =
                 em->start + (tmp + i) * map->stripe_len;
 
         bioc->raid_map[(i + rot) % map->num_stripes] = RAID5_P_STRIPE;
         if (map->type & BTRFS_BLOCK_GROUP_RAID6)
             bioc->raid_map[(i + rot + 1) % num_stripes] =
                 RAID6_Q_STRIPE;
 
         sort_parity_stripes(bioc, num_stripes);
     }
 
     if (need_full_stripe(op))
         max_errors = btrfs_chunk_max_errors(map);
 
     if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL &&
         need_full_stripe(op)) {
         handle_ops_on_dev_replace(op, &bioc, dev_replace, logical,
                       &num_stripes, &max_errors);
     }
 
     *bioc_ret = bioc;
     bioc->map_type = map->type;
     bioc->num_stripes = num_stripes;
     bioc->max_errors = max_errors;
     bioc->mirror_num = mirror_num;
 
     /*
      * this is the case that REQ_READ && dev_replace_is_ongoing &&
      * mirror_num == num_stripes + 1 && dev_replace target drive is
      * available as a mirror
      */
     if (patch_the_first_stripe_for_dev_replace && num_stripes > 0) {
         WARN_ON(num_stripes > 1);
         bioc->stripes[0].dev = dev_replace->tgtdev;
         bioc->stripes[0].physical = physical_to_patch_in_first_stripe;
         bioc->mirror_num = map->num_stripes + 1;
     }
 out:
     if (dev_replace_is_ongoing) {
         lockdep_assert_held(&dev_replace->rwsem);
         /* Unlock and let waiting writers proceed */
         up_read(&dev_replace->rwsem);
     }
     free_extent_map(em);
     return ret;
 }
 
 int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
               u64 logical, u64 *length,
               struct btrfs_io_context **bioc_ret, int mirror_num)
 {
     return __btrfs_map_block(fs_info, op, logical, length, bioc_ret,
                  mirror_num, 0);
 }
 
 /* For Scrub/replace */
 int btrfs_map_sblock(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
              u64 logical, u64 *length,
              struct btrfs_io_context **bioc_ret)
 {
     return __btrfs_map_block(fs_info, op, logical, length, bioc_ret, 0, 1);
 }
 
 static struct workqueue_struct *btrfs_end_io_wq(struct btrfs_io_context *bioc)
 {
     if (bioc->orig_bio->bi_opf & REQ_META)
         return bioc->fs_info->endio_meta_workers;
     return bioc->fs_info->endio_workers;
 }
 
 static void btrfs_end_bio_work(struct work_struct *work)
 {
     struct btrfs_bio *bbio =
         container_of(work, struct btrfs_bio, end_io_work);
 
     bio_endio(&bbio->bio);
 }
 
 static void btrfs_end_bioc(struct btrfs_io_context *bioc, bool async)
 {
     struct bio *orig_bio = bioc->orig_bio;
     struct btrfs_bio *bbio = btrfs_bio(orig_bio);
 
     bbio->mirror_num = bioc->mirror_num;
     orig_bio->bi_private = bioc->private;
     orig_bio->bi_end_io = bioc->end_io;
 
     /*
      * Only send an error to the higher layers if it is beyond the tolerance
      * threshold.
      */
     if (atomic_read(&bioc->error) > bioc->max_errors)
         orig_bio->bi_status = BLK_STS_IOERR;
     else
         orig_bio->bi_status = BLK_STS_OK;
 
     if (btrfs_op(orig_bio) == BTRFS_MAP_READ && async) {
         INIT_WORK(&bbio->end_io_work, btrfs_end_bio_work);
         queue_work(btrfs_end_io_wq(bioc), &bbio->end_io_work);
     } else {
         bio_endio(orig_bio);
     }
 
     btrfs_put_bioc(bioc);
 }
 
 static void btrfs_end_bio(struct bio *bio)
 {
     struct btrfs_io_stripe *stripe = bio->bi_private;
     struct btrfs_io_context *bioc = stripe->bioc;
 
     if (bio->bi_status) {
         atomic_inc(&bioc->error);
         if (bio->bi_status == BLK_STS_IOERR ||
             bio->bi_status == BLK_STS_TARGET) {
             if (btrfs_op(bio) == BTRFS_MAP_WRITE)
                 btrfs_dev_stat_inc_and_print(stripe->dev,
                         BTRFS_DEV_STAT_WRITE_ERRS);
             else if (!(bio->bi_opf & REQ_RAHEAD))
                 btrfs_dev_stat_inc_and_print(stripe->dev,
                         BTRFS_DEV_STAT_READ_ERRS);
             if (bio->bi_opf & REQ_PREFLUSH)
                 btrfs_dev_stat_inc_and_print(stripe->dev,
                         BTRFS_DEV_STAT_FLUSH_ERRS);
         }
     }
 
     if (bio != bioc->orig_bio)
         bio_put(bio);
 
     btrfs_bio_counter_dec(bioc->fs_info);
     if (atomic_dec_and_test(&bioc->stripes_pending))
         btrfs_end_bioc(bioc, true);
 }
 
 static void submit_stripe_bio(struct btrfs_io_context *bioc,
                   struct bio *orig_bio, int dev_nr, bool clone)
 {
     struct btrfs_fs_info *fs_info = bioc->fs_info;
     struct btrfs_device *dev = bioc->stripes[dev_nr].dev;
     u64 physical = bioc->stripes[dev_nr].physical;
     struct bio *bio;
 
     if (!dev || !dev->bdev ||
         test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) ||
         (btrfs_op(orig_bio) == BTRFS_MAP_WRITE &&
          !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))) {
         atomic_inc(&bioc->error);
         if (atomic_dec_and_test(&bioc->stripes_pending))
             btrfs_end_bioc(bioc, false);
         return;
     }
 
     if (clone) {
         bio = bio_alloc_clone(dev->bdev, orig_bio, GFP_NOFS, &fs_bio_set);
     } else {
         bio = orig_bio;
         bio_set_dev(bio, dev->bdev);
         btrfs_bio(bio)->device = dev;
     }
 
     bioc->stripes[dev_nr].bioc = bioc;
     bio->bi_private = &bioc->stripes[dev_nr];
     bio->bi_end_io = btrfs_end_bio;
     bio->bi_iter.bi_sector = physical >> 9;
     /*
      * For zone append writing, bi_sector must point the beginning of the
      * zone
      */
     if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
         if (btrfs_dev_is_sequential(dev, physical)) {
             u64 zone_start = round_down(physical, fs_info->zone_size);
 
             bio->bi_iter.bi_sector = zone_start >> SECTOR_SHIFT;
         } else {
             bio->bi_opf &= ~REQ_OP_ZONE_APPEND;
             bio->bi_opf |= REQ_OP_WRITE;
         }
     }
     btrfs_debug_in_rcu(fs_info,
     "%s: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
         __func__, bio_op(bio), bio->bi_opf, bio->bi_iter.bi_sector,
         (unsigned long)dev->bdev->bd_dev, rcu_str_deref(dev->name),
         dev->devid, bio->bi_iter.bi_size);
 
     btrfs_bio_counter_inc_noblocked(fs_info);
 
     btrfsic_check_bio(bio);
     submit_bio(bio);
 }
 
 void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror_num)
 {
     u64 logical = bio->bi_iter.bi_sector << 9;
     u64 length = bio->bi_iter.bi_size;
     u64 map_length = length;
     int ret;
     int dev_nr;
     int total_devs;
     struct btrfs_io_context *bioc = NULL;
 
     btrfs_bio_counter_inc_blocked(fs_info);
     ret = __btrfs_map_block(fs_info, btrfs_op(bio), logical,
                 &map_length, &bioc, mirror_num, 1);
     if (ret) {
         btrfs_bio_counter_dec(fs_info);
         bio->bi_status = errno_to_blk_status(ret);
         bio_endio(bio);
         return;
     }
 
     total_devs = bioc->num_stripes;
     bioc->orig_bio = bio;
     bioc->private = bio->bi_private;
     bioc->end_io = bio->bi_end_io;
     atomic_set(&bioc->stripes_pending, total_devs);
 
     if ((bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) &&
         ((btrfs_op(bio) == BTRFS_MAP_WRITE) || (mirror_num > 1))) {
         if (btrfs_op(bio) == BTRFS_MAP_WRITE)
             raid56_parity_write(bio, bioc);
         else
             raid56_parity_recover(bio, bioc, mirror_num, true);
         return;
     }
 
     if (map_length < length) {
         btrfs_crit(fs_info,
                "mapping failed logical %llu bio len %llu len %llu",
                logical, length, map_length);
         BUG();
     }
 
     for (dev_nr = 0; dev_nr < total_devs; dev_nr++) {
         const bool should_clone = (dev_nr < total_devs - 1);
 
         submit_stripe_bio(bioc, bio, dev_nr, should_clone);
     }
     btrfs_bio_counter_dec(fs_info);
 }
 
 static bool dev_args_match_fs_devices(const struct btrfs_dev_lookup_args *args,
                       const struct btrfs_fs_devices *fs_devices)
 {
     if (args->fsid == NULL)
         return true;
     if (memcmp(fs_devices->metadata_uuid, args->fsid, BTRFS_FSID_SIZE) == 0)
         return true;
     return false;
 }
 
 static bool dev_args_match_device(const struct btrfs_dev_lookup_args *args,
                   const struct btrfs_device *device)
 {
     ASSERT((args->devid != (u64)-1) || args->missing);
 
     if ((args->devid != (u64)-1) && device->devid != args->devid)
         return false;
     if (args->uuid && memcmp(device->uuid, args->uuid, BTRFS_UUID_SIZE) != 0)
         return false;
     if (!args->missing)
         return true;
     if (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state) &&
         !device->bdev)
         return true;
     return false;
 }
 
 /*
  * Find a device specified by @devid or @uuid in the list of @fs_devices, or
  * return NULL.
  *
  * If devid and uuid are both specified, the match must be exact, otherwise
  * only devid is used.
  */
 struct btrfs_device *btrfs_find_device(const struct btrfs_fs_devices *fs_devices,
                        const struct btrfs_dev_lookup_args *args)
 {
     struct btrfs_device *device;
     struct btrfs_fs_devices *seed_devs;
 
     if (dev_args_match_fs_devices(args, fs_devices)) {
         list_for_each_entry(device, &fs_devices->devices, dev_list) {
             if (dev_args_match_device(args, device))
                 return device;
         }
     }
 
     list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
         if (!dev_args_match_fs_devices(args, seed_devs))
             continue;
         list_for_each_entry(device, &seed_devs->devices, dev_list) {
             if (dev_args_match_device(args, device))
                 return device;
         }
     }
 
     return NULL;
 }
 
 static struct btrfs_device *add_missing_dev(struct btrfs_fs_devices *fs_devices,
                         u64 devid, u8 *dev_uuid)
 {
     struct btrfs_device *device;
     unsigned int nofs_flag;
 
     /*
      * We call this under the chunk_mutex, so we want to use NOFS for this
      * allocation, however we don't want to change btrfs_alloc_device() to
      * always do NOFS because we use it in a lot of other GFP_KERNEL safe
      * places.
      */
     nofs_flag = memalloc_nofs_save();
     device = btrfs_alloc_device(NULL, &devid, dev_uuid);
     memalloc_nofs_restore(nofs_flag);
     if (IS_ERR(device))
         return device;
 
     list_add(&device->dev_list, &fs_devices->devices);
     device->fs_devices = fs_devices;
     fs_devices->num_devices++;
 
     set_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
     fs_devices->missing_devices++;
 
     return device;
 }
 
 /**
  * btrfs_alloc_device - allocate struct btrfs_device
  * @fs_info:    used only for generating a new devid, can be NULL if
  *      devid is provided (i.e. @devid != NULL).
  * @devid:  a pointer to devid for this device.  If NULL a new devid
  *      is generated.
  * @uuid:   a pointer to UUID for this device.  If NULL a new UUID
  *      is generated.
  *
  * Return: a pointer to a new &struct btrfs_device on success; ERR_PTR()
  * on error.  Returned struct is not linked onto any lists and must be
  * destroyed with btrfs_free_device.
  */
 struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,
                     const u64 *devid,
                     const u8 *uuid)
 {
     struct btrfs_device *dev;
     u64 tmp;
 
     if (WARN_ON(!devid && !fs_info))
         return ERR_PTR(-EINVAL);
 
     dev = kzalloc(sizeof(*dev), GFP_KERNEL);
     if (!dev)
         return ERR_PTR(-ENOMEM);
 
     INIT_LIST_HEAD(&dev->dev_list);
     INIT_LIST_HEAD(&dev->dev_alloc_list);
     INIT_LIST_HEAD(&dev->post_commit_list);
 
     atomic_set(&dev->dev_stats_ccnt, 0);
     btrfs_device_data_ordered_init(dev);
     extent_io_tree_init(fs_info, &dev->alloc_state,
                 IO_TREE_DEVICE_ALLOC_STATE, NULL);
 
     if (devid)
         tmp = *devid;
     else {
         int ret;
 
         ret = find_next_devid(fs_info, &tmp);
         if (ret) {
             btrfs_free_device(dev);
             return ERR_PTR(ret);
         }
     }
     dev->devid = tmp;
 
     if (uuid)
         memcpy(dev->uuid, uuid, BTRFS_UUID_SIZE);
     else
         generate_random_uuid(dev->uuid);
 
     return dev;
 }
 
 static void btrfs_report_missing_device(struct btrfs_fs_info *fs_info,
                     u64 devid, u8 *uuid, bool error)
 {
     if (error)
         btrfs_err_rl(fs_info, "devid %llu uuid %pU is missing",
                   devid, uuid);
     else
         btrfs_warn_rl(fs_info, "devid %llu uuid %pU is missing",
                   devid, uuid);
 }
 
 u64 btrfs_calc_stripe_length(const struct extent_map *em)
 {
     const struct map_lookup *map = em->map_lookup;
     const int data_stripes = calc_data_stripes(map->type, map->num_stripes);
 
     return div_u64(em->len, data_stripes);
 }
 
 #if BITS_PER_LONG == 32
 /*
  * Due to page cache limit, metadata beyond BTRFS_32BIT_MAX_FILE_SIZE
  * can't be accessed on 32bit systems.
  *
  * This function do mount time check to reject the fs if it already has
  * metadata chunk beyond that limit.
  */
 static int check_32bit_meta_chunk(struct btrfs_fs_info *fs_info,
                   u64 logical, u64 length, u64 type)
 {
     if (!(type & BTRFS_BLOCK_GROUP_METADATA))
         return 0;
 
     if (logical + length < MAX_LFS_FILESIZE)
         return 0;
 
     btrfs_err_32bit_limit(fs_info);
     return -EOVERFLOW;
 }
 
 /*
  * This is to give early warning for any metadata chunk reaching
  * BTRFS_32BIT_EARLY_WARN_THRESHOLD.
  * Although we can still access the metadata, it's not going to be possible
  * once the limit is reached.
  */
 static void warn_32bit_meta_chunk(struct btrfs_fs_info *fs_info,
                   u64 logical, u64 length, u64 type)
 {
     if (!(type & BTRFS_BLOCK_GROUP_METADATA))
         return;
 
     if (logical + length < BTRFS_32BIT_EARLY_WARN_THRESHOLD)
         return;
 
     btrfs_warn_32bit_limit(fs_info);
 }
 #endif
 
 static struct btrfs_device *handle_missing_device(struct btrfs_fs_info *fs_info,
                           u64 devid, u8 *uuid)
 {
     struct btrfs_device *dev;
 
     if (!btrfs_test_opt(fs_info, DEGRADED)) {
         btrfs_report_missing_device(fs_info, devid, uuid, true);
         return ERR_PTR(-ENOENT);
     }
 
     dev = add_missing_dev(fs_info->fs_devices, devid, uuid);
     if (IS_ERR(dev)) {
         btrfs_err(fs_info, "failed to init missing device %llu: %ld",
               devid, PTR_ERR(dev));
         return dev;
     }
     btrfs_report_missing_device(fs_info, devid, uuid, false);
 
     return dev;
 }
 
 static int read_one_chunk(struct btrfs_key *key, struct extent_buffer *leaf,
               struct btrfs_chunk *chunk)
 {
     BTRFS_DEV_LOOKUP_ARGS(args);
     struct btrfs_fs_info *fs_info = leaf->fs_info;
     struct extent_map_tree *map_tree = &fs_info->mapping_tree;
     struct map_lookup *map;
     struct extent_map *em;
     u64 logical;
     u64 length;
     u64 devid;
     u64 type;
     u8 uuid[BTRFS_UUID_SIZE];
     int num_stripes;
     int ret;
     int i;
 
     logical = key->offset;
     length = btrfs_chunk_length(leaf, chunk);
     type = btrfs_chunk_type(leaf, chunk);
     num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
 
 #if BITS_PER_LONG == 32
     ret = check_32bit_meta_chunk(fs_info, logical, length, type);
     if (ret < 0)
         return ret;
     warn_32bit_meta_chunk(fs_info, logical, length, type);
 #endif
 
     /*
      * Only need to verify chunk item if we're reading from sys chunk array,
      * as chunk item in tree block is already verified by tree-checker.
      */
     if (leaf->start == BTRFS_SUPER_INFO_OFFSET) {
         ret = btrfs_check_chunk_valid(leaf, chunk, logical);
         if (ret)
             return ret;
     }
 
     read_lock(&map_tree->lock);
     em = lookup_extent_mapping(map_tree, logical, 1);
     read_unlock(&map_tree->lock);
 
     /* already mapped? */
     if (em && em->start <= logical && em->start + em->len > logical) {
         free_extent_map(em);
         return 0;
     } else if (em) {
         free_extent_map(em);
     }
 
     em = alloc_extent_map();
     if (!em)
         return -ENOMEM;
     map = kmalloc(map_lookup_size(num_stripes), GFP_NOFS);
     if (!map) {
         free_extent_map(em);
         return -ENOMEM;
     }
 
     set_bit(EXTENT_FLAG_FS_MAPPING, &em->flags);
     em->map_lookup = map;
     em->start = logical;
     em->len = length;
     em->orig_start = 0;
     em->block_start = 0;
     em->block_len = em->len;
 
     map->num_stripes = num_stripes;
     map->io_width = btrfs_chunk_io_width(leaf, chunk);
     map->io_align = btrfs_chunk_io_align(leaf, chunk);
     map->stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
     map->type = type;
     map->sub_stripes = btrfs_chunk_sub_stripes(leaf, chunk);
     map->verified_stripes = 0;
     em->orig_block_len = btrfs_calc_stripe_length(em);
     for (i = 0; i < num_stripes; i++) {
         map->stripes[i].physical =
             btrfs_stripe_offset_nr(leaf, chunk, i);
         devid = btrfs_stripe_devid_nr(leaf, chunk, i);
         args.devid = devid;
         read_extent_buffer(leaf, uuid, (unsigned long)
                    btrfs_stripe_dev_uuid_nr(chunk, i),
                    BTRFS_UUID_SIZE);
         args.uuid = uuid;
         map->stripes[i].dev = btrfs_find_device(fs_info->fs_devices, &args);
         if (!map->stripes[i].dev) {
             map->stripes[i].dev = handle_missing_device(fs_info,
                                     devid, uuid);
             if (IS_ERR(map->stripes[i].dev)) {
                 free_extent_map(em);
                 return PTR_ERR(map->stripes[i].dev);
             }
         }
 
         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
                 &(map->stripes[i].dev->dev_state));
     }
 
     write_lock(&map_tree->lock);
     ret = add_extent_mapping(map_tree, em, 0);
     write_unlock(&map_tree->lock);
     if (ret < 0) {
         btrfs_err(fs_info,
               "failed to add chunk map, start=%llu len=%llu: %d",
               em->start, em->len, ret);
     }
     free_extent_map(em);
 
     return ret;
 }
 
 static void fill_device_from_item(struct extent_buffer *leaf,
                  struct btrfs_dev_item *dev_item,
                  struct btrfs_device *device)
 {
     unsigned long ptr;
 
     device->devid = btrfs_device_id(leaf, dev_item);
     device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
     device->total_bytes = device->disk_total_bytes;
     device->commit_total_bytes = device->disk_total_bytes;
     device->bytes_used = btrfs_device_bytes_used(leaf, dev_item);
     device->commit_bytes_used = device->bytes_used;
     device->type = btrfs_device_type(leaf, dev_item);
     device->io_align = btrfs_device_io_align(leaf, dev_item);
     device->io_width = btrfs_device_io_width(leaf, dev_item);
     device->sector_size = btrfs_device_sector_size(leaf, dev_item);
     WARN_ON(device->devid == BTRFS_DEV_REPLACE_DEVID);
     clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 
     ptr = btrfs_device_uuid(dev_item);
     read_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);
 }
 
 static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info,
                           u8 *fsid)
 {
     struct btrfs_fs_devices *fs_devices;
     int ret;
 
     lockdep_assert_held(&uuid_mutex);
     ASSERT(fsid);
 
     /* This will match only for multi-device seed fs */
     list_for_each_entry(fs_devices, &fs_info->fs_devices->seed_list, seed_list)
         if (!memcmp(fs_devices->fsid, fsid, BTRFS_FSID_SIZE))
             return fs_devices;
 
 
     fs_devices = find_fsid(fsid, NULL);
     if (!fs_devices) {
         if (!btrfs_test_opt(fs_info, DEGRADED))
             return ERR_PTR(-ENOENT);
 
         fs_devices = alloc_fs_devices(fsid, NULL);
         if (IS_ERR(fs_devices))
             return fs_devices;
 
         fs_devices->seeding = true;
         fs_devices->opened = 1;
         return fs_devices;
     }
 
     /*
      * Upon first call for a seed fs fsid, just create a private copy of the
      * respective fs_devices and anchor it at fs_info->fs_devices->seed_list
      */
     fs_devices = clone_fs_devices(fs_devices);
     if (IS_ERR(fs_devices))
         return fs_devices;
 
     ret = open_fs_devices(fs_devices, FMODE_READ, fs_info->bdev_holder);
     if (ret) {
         free_fs_devices(fs_devices);
         return ERR_PTR(ret);
     }
 
     if (!fs_devices->seeding) {
         close_fs_devices(fs_devices);
         free_fs_devices(fs_devices);
         return ERR_PTR(-EINVAL);
     }
 
     list_add(&fs_devices->seed_list, &fs_info->fs_devices->seed_list);
 
     return fs_devices;
 }
 
 static int read_one_dev(struct extent_buffer *leaf,
             struct btrfs_dev_item *dev_item)
 {
     BTRFS_DEV_LOOKUP_ARGS(args);
     struct btrfs_fs_info *fs_info = leaf->fs_info;
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
     struct btrfs_device *device;
     u64 devid;
     int ret;
     u8 fs_uuid[BTRFS_FSID_SIZE];
     u8 dev_uuid[BTRFS_UUID_SIZE];
 
     devid = btrfs_device_id(leaf, dev_item);
     args.devid = devid;
     read_extent_buffer(leaf, dev_uuid, btrfs_device_uuid(dev_item),
                BTRFS_UUID_SIZE);
     read_extent_buffer(leaf, fs_uuid, btrfs_device_fsid(dev_item),
                BTRFS_FSID_SIZE);
     args.uuid = dev_uuid;
     args.fsid = fs_uuid;
 
     if (memcmp(fs_uuid, fs_devices->metadata_uuid, BTRFS_FSID_SIZE)) {
         fs_devices = open_seed_devices(fs_info, fs_uuid);
         if (IS_ERR(fs_devices))
             return PTR_ERR(fs_devices);
     }
 
     device = btrfs_find_device(fs_info->fs_devices, &args);
     if (!device) {
         if (!btrfs_test_opt(fs_info, DEGRADED)) {
             btrfs_report_missing_device(fs_info, devid,
                             dev_uuid, true);
             return -ENOENT;
         }
 
         device = add_missing_dev(fs_devices, devid, dev_uuid);
         if (IS_ERR(device)) {
             btrfs_err(fs_info,
                 "failed to add missing dev %llu: %ld",
                 devid, PTR_ERR(device));
             return PTR_ERR(device);
         }
         btrfs_report_missing_device(fs_info, devid, dev_uuid, false);
     } else {
         if (!device->bdev) {
             if (!btrfs_test_opt(fs_info, DEGRADED)) {
                 btrfs_report_missing_device(fs_info,
                         devid, dev_uuid, true);
                 return -ENOENT;
             }
             btrfs_report_missing_device(fs_info, devid,
                             dev_uuid, false);
         }
 
         if (!device->bdev &&
             !test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
             /*
              * this happens when a device that was properly setup
              * in the device info lists suddenly goes bad.
              * device->bdev is NULL, and so we have to set
              * device->missing to one here
              */
             device->fs_devices->missing_devices++;
             set_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
         }
 
         /* Move the device to its own fs_devices */
         if (device->fs_devices != fs_devices) {
             ASSERT(test_bit(BTRFS_DEV_STATE_MISSING,
                             &device->dev_state));
 
             list_move(&device->dev_list, &fs_devices->devices);
             device->fs_devices->num_devices--;
             fs_devices->num_devices++;
 
             device->fs_devices->missing_devices--;
             fs_devices->missing_devices++;
 
             device->fs_devices = fs_devices;
         }
     }
 
     if (device->fs_devices != fs_info->fs_devices) {
         BUG_ON(test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state));
         if (device->generation !=
             btrfs_device_generation(leaf, dev_item))
             return -EINVAL;
     }
 
     fill_device_from_item(leaf, dev_item, device);
     if (device->bdev) {
         u64 max_total_bytes = bdev_nr_bytes(device->bdev);
 
         if (device->total_bytes > max_total_bytes) {
             btrfs_err(fs_info,
             "device total_bytes should be at most %llu but found %llu",
                   max_total_bytes, device->total_bytes);
             return -EINVAL;
         }
     }
     set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
     if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
        !test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
         device->fs_devices->total_rw_bytes += device->total_bytes;
         atomic64_add(device->total_bytes - device->bytes_used,
                 &fs_info->free_chunk_space);
     }
     ret = 0;
     return ret;
 }
 
 int btrfs_read_sys_array(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_super_block *super_copy = fs_info->super_copy;
     struct extent_buffer *sb;
     struct btrfs_disk_key *disk_key;
     struct btrfs_chunk *chunk;
     u8 *array_ptr;
     unsigned long sb_array_offset;
     int ret = 0;
     u32 num_stripes;
     u32 array_size;
     u32 len = 0;
     u32 cur_offset;
     u64 type;
     struct btrfs_key key;
 
     ASSERT(BTRFS_SUPER_INFO_SIZE <= fs_info->nodesize);
 
     /*
      * We allocated a dummy extent, just to use extent buffer accessors.
      * There will be unused space after BTRFS_SUPER_INFO_SIZE, but
      * that's fine, we will not go beyond system chunk array anyway.
      */
     sb = alloc_dummy_extent_buffer(fs_info, BTRFS_SUPER_INFO_OFFSET);
     if (!sb)
         return -ENOMEM;
     set_extent_buffer_uptodate(sb);
 
     write_extent_buffer(sb, super_copy, 0, BTRFS_SUPER_INFO_SIZE);
     array_size = btrfs_super_sys_array_size(super_copy);
 
     array_ptr = super_copy->sys_chunk_array;
     sb_array_offset = offsetof(struct btrfs_super_block, sys_chunk_array);
     cur_offset = 0;
 
     while (cur_offset < array_size) {
         disk_key = (struct btrfs_disk_key *)array_ptr;
         len = sizeof(*disk_key);
         if (cur_offset + len > array_size)
             goto out_short_read;
 
         btrfs_disk_key_to_cpu(&key, disk_key);
 
         array_ptr += len;
         sb_array_offset += len;
         cur_offset += len;
 
         if (key.type != BTRFS_CHUNK_ITEM_KEY) {
             btrfs_err(fs_info,
                 "unexpected item type %u in sys_array at offset %u",
                   (u32)key.type, cur_offset);
             ret = -EIO;
             break;
         }
 
         chunk = (struct btrfs_chunk *)sb_array_offset;
         /*
          * At least one btrfs_chunk with one stripe must be present,
          * exact stripe count check comes afterwards
          */
         len = btrfs_chunk_item_size(1);
         if (cur_offset + len > array_size)
             goto out_short_read;
 
         num_stripes = btrfs_chunk_num_stripes(sb, chunk);
         if (!num_stripes) {
             btrfs_err(fs_info,
             "invalid number of stripes %u in sys_array at offset %u",
                   num_stripes, cur_offset);
             ret = -EIO;
             break;
         }
 
         type = btrfs_chunk_type(sb, chunk);
         if ((type & BTRFS_BLOCK_GROUP_SYSTEM) == 0) {
             btrfs_err(fs_info,
             "invalid chunk type %llu in sys_array at offset %u",
                   type, cur_offset);
             ret = -EIO;
             break;
         }
 
         len = btrfs_chunk_item_size(num_stripes);
         if (cur_offset + len > array_size)
             goto out_short_read;
 
         ret = read_one_chunk(&key, sb, chunk);
         if (ret)
             break;
 
         array_ptr += len;
         sb_array_offset += len;
         cur_offset += len;
     }
     clear_extent_buffer_uptodate(sb);
     free_extent_buffer_stale(sb);
     return ret;
 
 out_short_read:
     btrfs_err(fs_info, "sys_array too short to read %u bytes at offset %u",
             len, cur_offset);
     clear_extent_buffer_uptodate(sb);
     free_extent_buffer_stale(sb);
     return -EIO;
 }
 
 /*
  * Check if all chunks in the fs are OK for read-write degraded mount
  *
  * If the @failing_dev is specified, it's accounted as missing.
  *
  * Return true if all chunks meet the minimal RW mount requirements.
  * Return false if any chunk doesn't meet the minimal RW mount requirements.
  */
 bool btrfs_check_rw_degradable(struct btrfs_fs_info *fs_info,
                     struct btrfs_device *failing_dev)
 {
     struct extent_map_tree *map_tree = &fs_info->mapping_tree;
     struct extent_map *em;
     u64 next_start = 0;
     bool ret = true;
 
     read_lock(&map_tree->lock);
     em = lookup_extent_mapping(map_tree, 0, (u64)-1);
     read_unlock(&map_tree->lock);
     /* No chunk at all? Return false anyway */
     if (!em) {
         ret = false;
         goto out;
     }
     while (em) {
         struct map_lookup *map;
         int missing = 0;
         int max_tolerated;
         int i;
 
         map = em->map_lookup;
         max_tolerated =
             btrfs_get_num_tolerated_disk_barrier_failures(
                     map->type);
         for (i = 0; i < map->num_stripes; i++) {
             struct btrfs_device *dev = map->stripes[i].dev;
 
             if (!dev || !dev->bdev ||
                 test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) ||
                 dev->last_flush_error)
                 missing++;
             else if (failing_dev && failing_dev == dev)
                 missing++;
         }
         if (missing > max_tolerated) {
             if (!failing_dev)
                 btrfs_warn(fs_info,
     "chunk %llu missing %d devices, max tolerance is %d for writable mount",
                    em->start, missing, max_tolerated);
             free_extent_map(em);
             ret = false;
             goto out;
         }
         next_start = extent_map_end(em);
         free_extent_map(em);
 
         read_lock(&map_tree->lock);
         em = lookup_extent_mapping(map_tree, next_start,
                        (u64)(-1) - next_start);
         read_unlock(&map_tree->lock);
     }
 out:
     return ret;
 }
 
 static void readahead_tree_node_children(struct extent_buffer *node)
 {
     int i;
     const int nr_items = btrfs_header_nritems(node);
 
     for (i = 0; i < nr_items; i++)
         btrfs_readahead_node_child(node, i);
 }
 
 int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_root *root = fs_info->chunk_root;
     struct btrfs_path *path;
     struct extent_buffer *leaf;
     struct btrfs_key key;
     struct btrfs_key found_key;
     int ret;
     int slot;
     int iter_ret = 0;
     u64 total_dev = 0;
     u64 last_ra_node = 0;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     /*
      * uuid_mutex is needed only if we are mounting a sprout FS
      * otherwise we don't need it.
      */
     mutex_lock(&uuid_mutex);
 
     /*
      * It is possible for mount and umount to race in such a way that
      * we execute this code path, but open_fs_devices failed to clear
      * total_rw_bytes. We certainly want it cleared before reading the
      * device items, so clear it here.
      */
     fs_info->fs_devices->total_rw_bytes = 0;
 
     /*
      * Lockdep complains about possible circular locking dependency between
      * a disk's open_mutex (struct gendisk.open_mutex), the rw semaphores
      * used for freeze procection of a fs (struct super_block.s_writers),
      * which we take when starting a transaction, and extent buffers of the
      * chunk tree if we call read_one_dev() while holding a lock on an
      * extent buffer of the chunk tree. Since we are mounting the filesystem
      * and at this point there can't be any concurrent task modifying the
      * chunk tree, to keep it simple, just skip locking on the chunk tree.
      */
     ASSERT(!test_bit(BTRFS_FS_OPEN, &fs_info->flags));
     path->skip_locking = 1;
 
     /*
      * Read all device items, and then all the chunk items. All
      * device items are found before any chunk item (their object id
      * is smaller than the lowest possible object id for a chunk
      * item - BTRFS_FIRST_CHUNK_TREE_OBJECTID).
      */
     key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
     key.offset = 0;
     key.type = 0;
     btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
         struct extent_buffer *node = path->nodes[1];
 
         leaf = path->nodes[0];
         slot = path->slots[0];
 
         if (node) {
             if (last_ra_node != node->start) {
                 readahead_tree_node_children(node);
                 last_ra_node = node->start;
             }
         }
         if (found_key.type == BTRFS_DEV_ITEM_KEY) {
             struct btrfs_dev_item *dev_item;
             dev_item = btrfs_item_ptr(leaf, slot,
                           struct btrfs_dev_item);
             ret = read_one_dev(leaf, dev_item);
             if (ret)
                 goto error;
             total_dev++;
         } else if (found_key.type == BTRFS_CHUNK_ITEM_KEY) {
             struct btrfs_chunk *chunk;
 
             /*
              * We are only called at mount time, so no need to take
              * fs_info->chunk_mutex. Plus, to avoid lockdep warnings,
              * we always lock first fs_info->chunk_mutex before
              * acquiring any locks on the chunk tree. This is a
              * requirement for chunk allocation, see the comment on
              * top of btrfs_chunk_alloc() for details.
              */
             chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
             ret = read_one_chunk(&found_key, leaf, chunk);
             if (ret)
                 goto error;
         }
     }
     /* Catch error found during iteration */
     if (iter_ret < 0) {
         ret = iter_ret;
         goto error;
     }
 
     /*
      * After loading chunk tree, we've got all device information,
      * do another round of validation checks.
      */
     if (total_dev != fs_info->fs_devices->total_devices) {
         btrfs_warn(fs_info,
 "super block num_devices %llu mismatch with DEV_ITEM count %llu, will be repaired on next transaction commit",
               btrfs_super_num_devices(fs_info->super_copy),
               total_dev);
         fs_info->fs_devices->total_devices = total_dev;
         btrfs_set_super_num_devices(fs_info->super_copy, total_dev);
     }
     if (btrfs_super_total_bytes(fs_info->super_copy) <
         fs_info->fs_devices->total_rw_bytes) {
         btrfs_err(fs_info,
     "super_total_bytes %llu mismatch with fs_devices total_rw_bytes %llu",
               btrfs_super_total_bytes(fs_info->super_copy),
               fs_info->fs_devices->total_rw_bytes);
         ret = -EINVAL;
         goto error;
     }
     ret = 0;
 error:
     mutex_unlock(&uuid_mutex);
 
     btrfs_free_path(path);
     return ret;
 }
 
 void btrfs_init_devices_late(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs;
     struct btrfs_device *device;
 
     fs_devices->fs_info = fs_info;
 
     mutex_lock(&fs_devices->device_list_mutex);
     list_for_each_entry(device, &fs_devices->devices, dev_list)
         device->fs_info = fs_info;
 
     list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
         list_for_each_entry(device, &seed_devs->devices, dev_list)
             device->fs_info = fs_info;
 
         seed_devs->fs_info = fs_info;
     }
     mutex_unlock(&fs_devices->device_list_mutex);
 }
 
 static u64 btrfs_dev_stats_value(const struct extent_buffer *eb,
                  const struct btrfs_dev_stats_item *ptr,
                  int index)
 {
     u64 val;
 
     read_extent_buffer(eb, &val,
                offsetof(struct btrfs_dev_stats_item, values) +
                 ((unsigned long)ptr) + (index * sizeof(u64)),
                sizeof(val));
     return val;
 }
 
 static void btrfs_set_dev_stats_value(struct extent_buffer *eb,
                       struct btrfs_dev_stats_item *ptr,
                       int index, u64 val)
 {
     write_extent_buffer(eb, &val,
                 offsetof(struct btrfs_dev_stats_item, values) +
                  ((unsigned long)ptr) + (index * sizeof(u64)),
                 sizeof(val));
 }
 
 static int btrfs_device_init_dev_stats(struct btrfs_device *device,
                        struct btrfs_path *path)
 {
     struct btrfs_dev_stats_item *ptr;
     struct extent_buffer *eb;
     struct btrfs_key key;
     int item_size;
     int i, ret, slot;
 
     if (!device->fs_info->dev_root)
         return 0;
 
     key.objectid = BTRFS_DEV_STATS_OBJECTID;
     key.type = BTRFS_PERSISTENT_ITEM_KEY;
     key.offset = device->devid;
     ret = btrfs_search_slot(NULL, device->fs_info->dev_root, &key, path, 0, 0);
     if (ret) {
         for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
             btrfs_dev_stat_set(device, i, 0);
         device->dev_stats_valid = 1;
         btrfs_release_path(path);
         return ret < 0 ? ret : 0;
     }
     slot = path->slots[0];
     eb = path->nodes[0];
     item_size = btrfs_item_size(eb, slot);
 
     ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_stats_item);
 
     for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
         if (item_size >= (1 + i) * sizeof(__le64))
             btrfs_dev_stat_set(device, i,
                        btrfs_dev_stats_value(eb, ptr, i));
         else
             btrfs_dev_stat_set(device, i, 0);
     }
 
     device->dev_stats_valid = 1;
     btrfs_dev_stat_print_on_load(device);
     btrfs_release_path(path);
 
     return 0;
 }
 
 int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs;
     struct btrfs_device *device;
     struct btrfs_path *path = NULL;
     int ret = 0;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     mutex_lock(&fs_devices->device_list_mutex);
     list_for_each_entry(device, &fs_devices->devices, dev_list) {
         ret = btrfs_device_init_dev_stats(device, path);
         if (ret)
             goto out;
     }
     list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
         list_for_each_entry(device, &seed_devs->devices, dev_list) {
             ret = btrfs_device_init_dev_stats(device, path);
             if (ret)
                 goto out;
         }
     }
 out:
     mutex_unlock(&fs_devices->device_list_mutex);
 
     btrfs_free_path(path);
     return ret;
 }
 
 static int update_dev_stat_item(struct btrfs_trans_handle *trans,
                 struct btrfs_device *device)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_root *dev_root = fs_info->dev_root;
     struct btrfs_path *path;
     struct btrfs_key key;
     struct extent_buffer *eb;
     struct btrfs_dev_stats_item *ptr;
     int ret;
     int i;
 
     key.objectid = BTRFS_DEV_STATS_OBJECTID;
     key.type = BTRFS_PERSISTENT_ITEM_KEY;
     key.offset = device->devid;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
     ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
     if (ret < 0) {
         btrfs_warn_in_rcu(fs_info,
             "error %d while searching for dev_stats item for device %s",
                   ret, rcu_str_deref(device->name));
         goto out;
     }
 
     if (ret == 0 &&
         btrfs_item_size(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
         /* need to delete old one and insert a new one */
         ret = btrfs_del_item(trans, dev_root, path);
         if (ret != 0) {
             btrfs_warn_in_rcu(fs_info,
                 "delete too small dev_stats item for device %s failed %d",
                       rcu_str_deref(device->name), ret);
             goto out;
         }
         ret = 1;
     }
 
     if (ret == 1) {
         /* need to insert a new item */
         btrfs_release_path(path);
         ret = btrfs_insert_empty_item(trans, dev_root, path,
                           &key, sizeof(*ptr));
         if (ret < 0) {
             btrfs_warn_in_rcu(fs_info,
                 "insert dev_stats item for device %s failed %d",
                 rcu_str_deref(device->name), ret);
             goto out;
         }
     }
 
     eb = path->nodes[0];
     ptr = btrfs_item_ptr(eb, path->slots[0], struct btrfs_dev_stats_item);
     for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
         btrfs_set_dev_stats_value(eb, ptr, i,
                       btrfs_dev_stat_read(device, i));
     btrfs_mark_buffer_dirty(eb);
 
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 /*
  * called from commit_transaction. Writes all changed device stats to disk.
  */
 int btrfs_run_dev_stats(struct btrfs_trans_handle *trans)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
     struct btrfs_device *device;
     int stats_cnt;
     int ret = 0;
 
     mutex_lock(&fs_devices->device_list_mutex);
     list_for_each_entry(device, &fs_devices->devices, dev_list) {
         stats_cnt = atomic_read(&device->dev_stats_ccnt);
         if (!device->dev_stats_valid || stats_cnt == 0)
             continue;
 
 
         /*
          * There is a LOAD-LOAD control dependency between the value of
          * dev_stats_ccnt and updating the on-disk values which requires
          * reading the in-memory counters. Such control dependencies
          * require explicit read memory barriers.
          *
          * This memory barriers pairs with smp_mb__before_atomic in
          * btrfs_dev_stat_inc/btrfs_dev_stat_set and with the full
          * barrier implied by atomic_xchg in
          * btrfs_dev_stats_read_and_reset
          */
         smp_rmb();
 
         ret = update_dev_stat_item(trans, device);
         if (!ret)
             atomic_sub(stats_cnt, &device->dev_stats_ccnt);
     }
     mutex_unlock(&fs_devices->device_list_mutex);
 
     return ret;
 }
 
 void btrfs_dev_stat_inc_and_print(struct btrfs_device *dev, int index)
 {
     btrfs_dev_stat_inc(dev, index);
 
     if (!dev->dev_stats_valid)
         return;
     btrfs_err_rl_in_rcu(dev->fs_info,
         "bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u",
                rcu_str_deref(dev->name),
                btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
                btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
                btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),
                btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_CORRUPTION_ERRS),
                btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_GENERATION_ERRS));
 }
 
 static void btrfs_dev_stat_print_on_load(struct btrfs_device *dev)
 {
     int i;
 
     for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
         if (btrfs_dev_stat_read(dev, i) != 0)
             break;
     if (i == BTRFS_DEV_STAT_VALUES_MAX)
         return; /* all values == 0, suppress message */
 
     btrfs_info_in_rcu(dev->fs_info,
         "bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u",
            rcu_str_deref(dev->name),
            btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
            btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
            btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),
            btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_CORRUPTION_ERRS),
            btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_GENERATION_ERRS));
 }
 
 int btrfs_get_dev_stats(struct btrfs_fs_info *fs_info,
             struct btrfs_ioctl_get_dev_stats *stats)
 {
     BTRFS_DEV_LOOKUP_ARGS(args);
     struct btrfs_device *dev;
     struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
     int i;
 
     mutex_lock(&fs_devices->device_list_mutex);
     args.devid = stats->devid;
     dev = btrfs_find_device(fs_info->fs_devices, &args);
     mutex_unlock(&fs_devices->device_list_mutex);
 
     if (!dev) {
         btrfs_warn(fs_info, "get dev_stats failed, device not found");
         return -ENODEV;
     } else if (!dev->dev_stats_valid) {
         btrfs_warn(fs_info, "get dev_stats failed, not yet valid");
         return -ENODEV;
     } else if (stats->flags & BTRFS_DEV_STATS_RESET) {
         for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
             if (stats->nr_items > i)
                 stats->values[i] =
                     btrfs_dev_stat_read_and_reset(dev, i);
             else
                 btrfs_dev_stat_set(dev, i, 0);
         }
         btrfs_info(fs_info, "device stats zeroed by %s (%d)",
                current->comm, task_pid_nr(current));
     } else {
         for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
             if (stats->nr_items > i)
                 stats->values[i] = btrfs_dev_stat_read(dev, i);
     }
     if (stats->nr_items > BTRFS_DEV_STAT_VALUES_MAX)
         stats->nr_items = BTRFS_DEV_STAT_VALUES_MAX;
     return 0;
 }
 
 /*
  * Update the size and bytes used for each device where it changed.  This is
  * delayed since we would otherwise get errors while writing out the
  * superblocks.
  *
  * Must be invoked during transaction commit.
  */
 void btrfs_commit_device_sizes(struct btrfs_transaction *trans)
 {
     struct btrfs_device *curr, *next;
 
     ASSERT(trans->state == TRANS_STATE_COMMIT_DOING);
 
     if (list_empty(&trans->dev_update_list))
         return;
 
     /*
      * We don't need the device_list_mutex here.  This list is owned by the
      * transaction and the transaction must complete before the device is
      * released.
      */
     mutex_lock(&trans->fs_info->chunk_mutex);
     list_for_each_entry_safe(curr, next, &trans->dev_update_list,
                  post_commit_list) {
         list_del_init(&curr->post_commit_list);
         curr->commit_total_bytes = curr->disk_total_bytes;
         curr->commit_bytes_used = curr->bytes_used;
     }
     mutex_unlock(&trans->fs_info->chunk_mutex);
 }
 
 /*
  * Multiplicity factor for simple profiles: DUP, RAID1-like and RAID10.
  */
 int btrfs_bg_type_to_factor(u64 flags)
 {
     const int index = btrfs_bg_flags_to_raid_index(flags);
 
     return btrfs_raid_array[index].ncopies;
 }
 
 
 
 static int verify_one_dev_extent(struct btrfs_fs_info *fs_info,
                  u64 chunk_offset, u64 devid,
                  u64 physical_offset, u64 physical_len)
 {
     struct btrfs_dev_lookup_args args = { .devid = devid };
     struct extent_map_tree *em_tree = &fs_info->mapping_tree;
     struct extent_map *em;
     struct map_lookup *map;
     struct btrfs_device *dev;
     u64 stripe_len;
     bool found = false;
     int ret = 0;
     int i;
 
     read_lock(&em_tree->lock);
     em = lookup_extent_mapping(em_tree, chunk_offset, 1);
     read_unlock(&em_tree->lock);
 
     if (!em) {
         btrfs_err(fs_info,
 "dev extent physical offset %llu on devid %llu doesn't have corresponding chunk",
               physical_offset, devid);
         ret = -EUCLEAN;
         goto out;
     }
 
     map = em->map_lookup;
     stripe_len = btrfs_calc_stripe_length(em);
     if (physical_len != stripe_len) {
         btrfs_err(fs_info,
 "dev extent physical offset %llu on devid %llu length doesn't match chunk %llu, have %llu expect %llu",
               physical_offset, devid, em->start, physical_len,
               stripe_len);
         ret = -EUCLEAN;
         goto out;
     }
 
     /*
      * Very old mkfs.btrfs (before v4.1) will not respect the reserved
      * space. Although kernel can handle it without problem, better to warn
      * the users.
      */
     if (physical_offset < BTRFS_DEVICE_RANGE_RESERVED)
         btrfs_warn(fs_info,
         "devid %llu physical %llu len %llu inside the reserved space",
                devid, physical_offset, physical_len);
 
     for (i = 0; i < map->num_stripes; i++) {
         if (map->stripes[i].dev->devid == devid &&
             map->stripes[i].physical == physical_offset) {
             found = true;
             if (map->verified_stripes >= map->num_stripes) {
                 btrfs_err(fs_info,
                 "too many dev extents for chunk %llu found",
                       em->start);
                 ret = -EUCLEAN;
                 goto out;
             }
             map->verified_stripes++;
             break;
         }
     }
     if (!found) {
         btrfs_err(fs_info,
     "dev extent physical offset %llu devid %llu has no corresponding chunk",
             physical_offset, devid);
         ret = -EUCLEAN;
     }
 
     /* Make sure no dev extent is beyond device boundary */
     dev = btrfs_find_device(fs_info->fs_devices, &args);
     if (!dev) {
         btrfs_err(fs_info, "failed to find devid %llu", devid);
         ret = -EUCLEAN;
         goto out;
     }
 
     if (physical_offset + physical_len > dev->disk_total_bytes) {
         btrfs_err(fs_info,
 "dev extent devid %llu physical offset %llu len %llu is beyond device boundary %llu",
               devid, physical_offset, physical_len,
               dev->disk_total_bytes);
         ret = -EUCLEAN;
         goto out;
     }
 
     if (dev->zone_info) {
         u64 zone_size = dev->zone_info->zone_size;
 
         if (!IS_ALIGNED(physical_offset, zone_size) ||
             !IS_ALIGNED(physical_len, zone_size)) {
             btrfs_err(fs_info,
 "zoned: dev extent devid %llu physical offset %llu len %llu is not aligned to device zone",
                   devid, physical_offset, physical_len);
             ret = -EUCLEAN;
             goto out;
         }
     }
 
 out:
     free_extent_map(em);
     return ret;
 }
 
 static int verify_chunk_dev_extent_mapping(struct btrfs_fs_info *fs_info)
 {
     struct extent_map_tree *em_tree = &fs_info->mapping_tree;
     struct extent_map *em;
     struct rb_node *node;
     int ret = 0;
 
     read_lock(&em_tree->lock);
     for (node = rb_first_cached(&em_tree->map); node; node = rb_next(node)) {
         em = rb_entry(node, struct extent_map, rb_node);
         if (em->map_lookup->num_stripes !=
             em->map_lookup->verified_stripes) {
             btrfs_err(fs_info,
             "chunk %llu has missing dev extent, have %d expect %d",
                   em->start, em->map_lookup->verified_stripes,
                   em->map_lookup->num_stripes);
             ret = -EUCLEAN;
             goto out;
         }
     }
 out:
     read_unlock(&em_tree->lock);
     return ret;
 }
 
 /*
  * Ensure that all dev extents are mapped to correct chunk, otherwise
  * later chunk allocation/free would cause unexpected behavior.
  *
  * NOTE: This will iterate through the whole device tree, which should be of
  * the same size level as the chunk tree.  This slightly increases mount time.
  */
 int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_path *path;
     struct btrfs_root *root = fs_info->dev_root;
     struct btrfs_key key;
     u64 prev_devid = 0;
     u64 prev_dev_ext_end = 0;
     int ret = 0;
 
     /*
      * We don't have a dev_root because we mounted with ignorebadroots and
      * failed to load the root, so we want to skip the verification in this
      * case for sure.
      *
      * However if the dev root is fine, but the tree itself is corrupted
      * we'd still fail to mount.  This verification is only to make sure
      * writes can happen safely, so instead just bypass this check
      * completely in the case of IGNOREBADROOTS.
      */
     if (btrfs_test_opt(fs_info, IGNOREBADROOTS))
         return 0;
 
     key.objectid = 1;
     key.type = BTRFS_DEV_EXTENT_KEY;
     key.offset = 0;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     path->reada = READA_FORWARD;
     ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
     if (ret < 0)
         goto out;
 
     if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
         ret = btrfs_next_leaf(root, path);
         if (ret < 0)
             goto out;
         /* No dev extents at all? Not good */
         if (ret > 0) {
             ret = -EUCLEAN;
             goto out;
         }
     }
     while (1) {
         struct extent_buffer *leaf = path->nodes[0];
         struct btrfs_dev_extent *dext;
         int slot = path->slots[0];
         u64 chunk_offset;
         u64 physical_offset;
         u64 physical_len;
         u64 devid;
 
         btrfs_item_key_to_cpu(leaf, &key, slot);
         if (key.type != BTRFS_DEV_EXTENT_KEY)
             break;
         devid = key.objectid;
         physical_offset = key.offset;
 
         dext = btrfs_item_ptr(leaf, slot, struct btrfs_dev_extent);
         chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dext);
         physical_len = btrfs_dev_extent_length(leaf, dext);
 
         /* Check if this dev extent overlaps with the previous one */
         if (devid == prev_devid && physical_offset < prev_dev_ext_end) {
             btrfs_err(fs_info,
 "dev extent devid %llu physical offset %llu overlap with previous dev extent end %llu",
                   devid, physical_offset, prev_dev_ext_end);
             ret = -EUCLEAN;
             goto out;
         }
 
         ret = verify_one_dev_extent(fs_info, chunk_offset, devid,
                         physical_offset, physical_len);
         if (ret < 0)
             goto out;
         prev_devid = devid;
         prev_dev_ext_end = physical_offset + physical_len;
 
         ret = btrfs_next_item(root, path);
         if (ret < 0)
             goto out;
         if (ret > 0) {
             ret = 0;
             break;
         }
     }
 
     /* Ensure all chunks have corresponding dev extents */
     ret = verify_chunk_dev_extent_mapping(fs_info);
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 /*
  * Check whether the given block group or device is pinned by any inode being
  * used as a swapfile.
  */
 bool btrfs_pinned_by_swapfile(struct btrfs_fs_info *fs_info, void *ptr)
 {
     struct btrfs_swapfile_pin *sp;
     struct rb_node *node;
 
     spin_lock(&fs_info->swapfile_pins_lock);
     node = fs_info->swapfile_pins.rb_node;
     while (node) {
         sp = rb_entry(node, struct btrfs_swapfile_pin, node);
         if (ptr < sp->ptr)
             node = node->rb_left;
         else if (ptr > sp->ptr)
             node = node->rb_right;
         else
             break;
     }
     spin_unlock(&fs_info->swapfile_pins_lock);
     return node != NULL;
 }
 
 static int relocating_repair_kthread(void *data)
 {
     struct btrfs_block_group *cache = data;
     struct btrfs_fs_info *fs_info = cache->fs_info;
     u64 target;
     int ret = 0;
 
     target = cache->start;
     btrfs_put_block_group(cache);
 
     sb_start_write(fs_info->sb);
     if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) {
         btrfs_info(fs_info,
                "zoned: skip relocating block group %llu to repair: EBUSY",
                target);
         sb_end_write(fs_info->sb);
         return -EBUSY;
     }
 
     mutex_lock(&fs_info->reclaim_bgs_lock);
 
     /* Ensure block group still exists */
     cache = btrfs_lookup_block_group(fs_info, target);
     if (!cache)
         goto out;
 
     if (!cache->relocating_repair)
         goto out;
 
     ret = btrfs_may_alloc_data_chunk(fs_info, target);
     if (ret < 0)
         goto out;
 
     btrfs_info(fs_info,
            "zoned: relocating block group %llu to repair IO failure",
            target);
     ret = btrfs_relocate_chunk(fs_info, target);
 
 out:
     if (cache)
         btrfs_put_block_group(cache);
     mutex_unlock(&fs_info->reclaim_bgs_lock);
     btrfs_exclop_finish(fs_info);
     sb_end_write(fs_info->sb);
 
     return ret;
 }
 
 bool btrfs_repair_one_zone(struct btrfs_fs_info *fs_info, u64 logical)
 {
     struct btrfs_block_group *cache;
 
     if (!btrfs_is_zoned(fs_info))
         return false;
 
     /* Do not attempt to repair in degraded state */
     if (btrfs_test_opt(fs_info, DEGRADED))
         return true;
 
     cache = btrfs_lookup_block_group(fs_info, logical);
     if (!cache)
         return true;
 
     spin_lock(&cache->lock);
     if (cache->relocating_repair) {
         spin_unlock(&cache->lock);
         btrfs_put_block_group(cache);
         return true;
     }
     cache->relocating_repair = 1;
     spin_unlock(&cache->lock);
 
     kthread_run(relocating_repair_kthread, cache,
             "btrfs-relocating-repair");
 
     return true;
 }