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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) 2011, 2012 STRATO.  All rights reserved.
  */
 
 #include <linux/blkdev.h>
 #include <linux/ratelimit.h>
 #include <linux/sched/mm.h>
 #include <crypto/hash.h>
 #include "ctree.h"
 #include "discard.h"
 #include "volumes.h"
 #include "disk-io.h"
 #include "ordered-data.h"
 #include "transaction.h"
 #include "backref.h"
 #include "extent_io.h"
 #include "dev-replace.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
 #include "raid56.h"
 #include "block-group.h"
 #include "zoned.h"
 
 /*
  * This is only the first step towards a full-features scrub. It reads all
  * extent and super block and verifies the checksums. In case a bad checksum
  * is found or the extent cannot be read, good data will be written back if
  * any can be found.
  *
  * Future enhancements:
  *  - In case an unrepairable extent is encountered, track which files are
  *    affected and report them
  *  - track and record media errors, throw out bad devices
  *  - add a mode to also read unallocated space
  */
 
 struct scrub_block;
 struct scrub_ctx;
 
 /*
  * The following three values only influence the performance.
  *
  * The last one configures the number of parallel and outstanding I/O
  * operations. The first one configures an upper limit for the number
  * of (dynamically allocated) pages that are added to a bio.
  */
 #define SCRUB_SECTORS_PER_BIO   32  /* 128KiB per bio for 4KiB pages */
 #define SCRUB_BIOS_PER_SCTX 64  /* 8MiB per device in flight for 4KiB pages */
 
 /*
  * The following value times PAGE_SIZE needs to be large enough to match the
  * largest node/leaf/sector size that shall be supported.
  */
 #define SCRUB_MAX_SECTORS_PER_BLOCK (BTRFS_MAX_METADATA_BLOCKSIZE / SZ_4K)
 
 struct scrub_recover {
     refcount_t      refs;
     struct btrfs_io_context *bioc;
     u64         map_length;
 };
 
 struct scrub_sector {
     struct scrub_block  *sblock;
     struct page     *page;
     struct btrfs_device *dev;
     struct list_head    list;
     u64         flags;  /* extent flags */
     u64         generation;
     u64         logical;
     u64         physical;
     u64         physical_for_dev_replace;
     atomic_t        refs;
     u8          mirror_num;
     unsigned int        have_csum:1;
     unsigned int        io_error:1;
     u8          csum[BTRFS_CSUM_SIZE];
 
     struct scrub_recover    *recover;
 };
 
 struct scrub_bio {
     int         index;
     struct scrub_ctx    *sctx;
     struct btrfs_device *dev;
     struct bio      *bio;
     blk_status_t        status;
     u64         logical;
     u64         physical;
     struct scrub_sector *sectors[SCRUB_SECTORS_PER_BIO];
     int         sector_count;
     int         next_free;
     struct work_struct  work;
 };
 
 struct scrub_block {
     struct scrub_sector *sectors[SCRUB_MAX_SECTORS_PER_BLOCK];
     int         sector_count;
     atomic_t        outstanding_sectors;
     refcount_t      refs; /* free mem on transition to zero */
     struct scrub_ctx    *sctx;
     struct scrub_parity *sparity;
     struct {
         unsigned int    header_error:1;
         unsigned int    checksum_error:1;
         unsigned int    no_io_error_seen:1;
         unsigned int    generation_error:1; /* also sets header_error */
 
         /* The following is for the data used to check parity */
         /* It is for the data with checksum */
         unsigned int    data_corrected:1;
     };
     struct work_struct  work;
 };
 
 /* Used for the chunks with parity stripe such RAID5/6 */
 struct scrub_parity {
     struct scrub_ctx    *sctx;
 
     struct btrfs_device *scrub_dev;
 
     u64         logic_start;
 
     u64         logic_end;
 
     int         nsectors;
 
     u32         stripe_len;
 
     refcount_t      refs;
 
     struct list_head    sectors_list;
 
     /* Work of parity check and repair */
     struct work_struct  work;
 
     /* Mark the parity blocks which have data */
     unsigned long       dbitmap;
 
     /*
      * Mark the parity blocks which have data, but errors happen when
      * read data or check data
      */
     unsigned long       ebitmap;
 };
 
 struct scrub_ctx {
     struct scrub_bio    *bios[SCRUB_BIOS_PER_SCTX];
     struct btrfs_fs_info    *fs_info;
     int         first_free;
     int         curr;
     atomic_t        bios_in_flight;
     atomic_t        workers_pending;
     spinlock_t      list_lock;
     wait_queue_head_t   list_wait;
     struct list_head    csum_list;
     atomic_t        cancel_req;
     int         readonly;
     int         sectors_per_bio;
 
     /* State of IO submission throttling affecting the associated device */
     ktime_t         throttle_deadline;
     u64         throttle_sent;
 
     int         is_dev_replace;
     u64         write_pointer;
 
     struct scrub_bio        *wr_curr_bio;
     struct mutex            wr_lock;
     struct btrfs_device     *wr_tgtdev;
     bool                    flush_all_writes;
 
     /*
      * statistics
      */
     struct btrfs_scrub_progress stat;
     spinlock_t      stat_lock;
 
     /*
      * Use a ref counter to avoid use-after-free issues. Scrub workers
      * decrement bios_in_flight and workers_pending and then do a wakeup
      * on the list_wait wait queue. We must ensure the main scrub task
      * doesn't free the scrub context before or while the workers are
      * doing the wakeup() call.
      */
     refcount_t              refs;
 };
 
 struct scrub_warning {
     struct btrfs_path   *path;
     u64         extent_item_size;
     const char      *errstr;
     u64         physical;
     u64         logical;
     struct btrfs_device *dev;
 };
 
 struct full_stripe_lock {
     struct rb_node node;
     u64 logical;
     u64 refs;
     struct mutex mutex;
 };
 
 static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
                      struct scrub_block *sblocks_for_recheck);
 static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
                 struct scrub_block *sblock,
                 int retry_failed_mirror);
 static void scrub_recheck_block_checksum(struct scrub_block *sblock);
 static int scrub_repair_block_from_good_copy(struct scrub_block *sblock_bad,
                          struct scrub_block *sblock_good);
 static int scrub_repair_sector_from_good_copy(struct scrub_block *sblock_bad,
                         struct scrub_block *sblock_good,
                         int sector_num, int force_write);
 static void scrub_write_block_to_dev_replace(struct scrub_block *sblock);
 static int scrub_write_sector_to_dev_replace(struct scrub_block *sblock,
                          int sector_num);
 static int scrub_checksum_data(struct scrub_block *sblock);
 static int scrub_checksum_tree_block(struct scrub_block *sblock);
 static int scrub_checksum_super(struct scrub_block *sblock);
 static void scrub_block_put(struct scrub_block *sblock);
 static void scrub_sector_get(struct scrub_sector *sector);
 static void scrub_sector_put(struct scrub_sector *sector);
 static void scrub_parity_get(struct scrub_parity *sparity);
 static void scrub_parity_put(struct scrub_parity *sparity);
 static int scrub_sectors(struct scrub_ctx *sctx, u64 logical, u32 len,
              u64 physical, struct btrfs_device *dev, u64 flags,
              u64 gen, int mirror_num, u8 *csum,
              u64 physical_for_dev_replace);
 static void scrub_bio_end_io(struct bio *bio);
 static void scrub_bio_end_io_worker(struct work_struct *work);
 static void scrub_block_complete(struct scrub_block *sblock);
 static void scrub_find_good_copy(struct btrfs_fs_info *fs_info,
                  u64 extent_logical, u32 extent_len,
                  u64 *extent_physical,
                  struct btrfs_device **extent_dev,
                  int *extent_mirror_num);
 static int scrub_add_sector_to_wr_bio(struct scrub_ctx *sctx,
                       struct scrub_sector *sector);
 static void scrub_wr_submit(struct scrub_ctx *sctx);
 static void scrub_wr_bio_end_io(struct bio *bio);
 static void scrub_wr_bio_end_io_worker(struct work_struct *work);
 static void scrub_put_ctx(struct scrub_ctx *sctx);
 
 static inline int scrub_is_page_on_raid56(struct scrub_sector *sector)
 {
     return sector->recover &&
            (sector->recover->bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK);
 }
 
 static void scrub_pending_bio_inc(struct scrub_ctx *sctx)
 {
     refcount_inc(&sctx->refs);
     atomic_inc(&sctx->bios_in_flight);
 }
 
 static void scrub_pending_bio_dec(struct scrub_ctx *sctx)
 {
     atomic_dec(&sctx->bios_in_flight);
     wake_up(&sctx->list_wait);
     scrub_put_ctx(sctx);
 }
 
 static void __scrub_blocked_if_needed(struct btrfs_fs_info *fs_info)
 {
     while (atomic_read(&fs_info->scrub_pause_req)) {
         mutex_unlock(&fs_info->scrub_lock);
         wait_event(fs_info->scrub_pause_wait,
            atomic_read(&fs_info->scrub_pause_req) == 0);
         mutex_lock(&fs_info->scrub_lock);
     }
 }
 
 static void scrub_pause_on(struct btrfs_fs_info *fs_info)
 {
     atomic_inc(&fs_info->scrubs_paused);
     wake_up(&fs_info->scrub_pause_wait);
 }
 
 static void scrub_pause_off(struct btrfs_fs_info *fs_info)
 {
     mutex_lock(&fs_info->scrub_lock);
     __scrub_blocked_if_needed(fs_info);
     atomic_dec(&fs_info->scrubs_paused);
     mutex_unlock(&fs_info->scrub_lock);
 
     wake_up(&fs_info->scrub_pause_wait);
 }
 
 static void scrub_blocked_if_needed(struct btrfs_fs_info *fs_info)
 {
     scrub_pause_on(fs_info);
     scrub_pause_off(fs_info);
 }
 
 /*
  * Insert new full stripe lock into full stripe locks tree
  *
  * Return pointer to existing or newly inserted full_stripe_lock structure if
  * everything works well.
  * Return ERR_PTR(-ENOMEM) if we failed to allocate memory
  *
  * NOTE: caller must hold full_stripe_locks_root->lock before calling this
  * function
  */
 static struct full_stripe_lock *insert_full_stripe_lock(
         struct btrfs_full_stripe_locks_tree *locks_root,
         u64 fstripe_logical)
 {
     struct rb_node **p;
     struct rb_node *parent = NULL;
     struct full_stripe_lock *entry;
     struct full_stripe_lock *ret;
 
     lockdep_assert_held(&locks_root->lock);
 
     p = &locks_root->root.rb_node;
     while (*p) {
         parent = *p;
         entry = rb_entry(parent, struct full_stripe_lock, node);
         if (fstripe_logical < entry->logical) {
             p = &(*p)->rb_left;
         } else if (fstripe_logical > entry->logical) {
             p = &(*p)->rb_right;
         } else {
             entry->refs++;
             return entry;
         }
     }
 
     /*
      * Insert new lock.
      */
     ret = kmalloc(sizeof(*ret), GFP_KERNEL);
     if (!ret)
         return ERR_PTR(-ENOMEM);
     ret->logical = fstripe_logical;
     ret->refs = 1;
     mutex_init(&ret->mutex);
 
     rb_link_node(&ret->node, parent, p);
     rb_insert_color(&ret->node, &locks_root->root);
     return ret;
 }
 
 /*
  * Search for a full stripe lock of a block group
  *
  * Return pointer to existing full stripe lock if found
  * Return NULL if not found
  */
 static struct full_stripe_lock *search_full_stripe_lock(
         struct btrfs_full_stripe_locks_tree *locks_root,
         u64 fstripe_logical)
 {
     struct rb_node *node;
     struct full_stripe_lock *entry;
 
     lockdep_assert_held(&locks_root->lock);
 
     node = locks_root->root.rb_node;
     while (node) {
         entry = rb_entry(node, struct full_stripe_lock, node);
         if (fstripe_logical < entry->logical)
             node = node->rb_left;
         else if (fstripe_logical > entry->logical)
             node = node->rb_right;
         else
             return entry;
     }
     return NULL;
 }
 
 /*
  * Helper to get full stripe logical from a normal bytenr.
  *
  * Caller must ensure @cache is a RAID56 block group.
  */
 static u64 get_full_stripe_logical(struct btrfs_block_group *cache, u64 bytenr)
 {
     u64 ret;
 
     /*
      * Due to chunk item size limit, full stripe length should not be
      * larger than U32_MAX. Just a sanity check here.
      */
     WARN_ON_ONCE(cache->full_stripe_len >= U32_MAX);
 
     /*
      * round_down() can only handle power of 2, while RAID56 full
      * stripe length can be 64KiB * n, so we need to manually round down.
      */
     ret = div64_u64(bytenr - cache->start, cache->full_stripe_len) *
             cache->full_stripe_len + cache->start;
     return ret;
 }
 
 /*
  * Lock a full stripe to avoid concurrency of recovery and read
  *
  * It's only used for profiles with parities (RAID5/6), for other profiles it
  * does nothing.
  *
  * Return 0 if we locked full stripe covering @bytenr, with a mutex held.
  * So caller must call unlock_full_stripe() at the same context.
  *
  * Return <0 if encounters error.
  */
 static int lock_full_stripe(struct btrfs_fs_info *fs_info, u64 bytenr,
                 bool *locked_ret)
 {
     struct btrfs_block_group *bg_cache;
     struct btrfs_full_stripe_locks_tree *locks_root;
     struct full_stripe_lock *existing;
     u64 fstripe_start;
     int ret = 0;
 
     *locked_ret = false;
     bg_cache = btrfs_lookup_block_group(fs_info, bytenr);
     if (!bg_cache) {
         ASSERT(0);
         return -ENOENT;
     }
 
     /* Profiles not based on parity don't need full stripe lock */
     if (!(bg_cache->flags & BTRFS_BLOCK_GROUP_RAID56_MASK))
         goto out;
     locks_root = &bg_cache->full_stripe_locks_root;
 
     fstripe_start = get_full_stripe_logical(bg_cache, bytenr);
 
     /* Now insert the full stripe lock */
     mutex_lock(&locks_root->lock);
     existing = insert_full_stripe_lock(locks_root, fstripe_start);
     mutex_unlock(&locks_root->lock);
     if (IS_ERR(existing)) {
         ret = PTR_ERR(existing);
         goto out;
     }
     mutex_lock(&existing->mutex);
     *locked_ret = true;
 out:
     btrfs_put_block_group(bg_cache);
     return ret;
 }
 
 /*
  * Unlock a full stripe.
  *
  * NOTE: Caller must ensure it's the same context calling corresponding
  * lock_full_stripe().
  *
  * Return 0 if we unlock full stripe without problem.
  * Return <0 for error
  */
 static int unlock_full_stripe(struct btrfs_fs_info *fs_info, u64 bytenr,
                   bool locked)
 {
     struct btrfs_block_group *bg_cache;
     struct btrfs_full_stripe_locks_tree *locks_root;
     struct full_stripe_lock *fstripe_lock;
     u64 fstripe_start;
     bool freeit = false;
     int ret = 0;
 
     /* If we didn't acquire full stripe lock, no need to continue */
     if (!locked)
         return 0;
 
     bg_cache = btrfs_lookup_block_group(fs_info, bytenr);
     if (!bg_cache) {
         ASSERT(0);
         return -ENOENT;
     }
     if (!(bg_cache->flags & BTRFS_BLOCK_GROUP_RAID56_MASK))
         goto out;
 
     locks_root = &bg_cache->full_stripe_locks_root;
     fstripe_start = get_full_stripe_logical(bg_cache, bytenr);
 
     mutex_lock(&locks_root->lock);
     fstripe_lock = search_full_stripe_lock(locks_root, fstripe_start);
     /* Unpaired unlock_full_stripe() detected */
     if (!fstripe_lock) {
         WARN_ON(1);
         ret = -ENOENT;
         mutex_unlock(&locks_root->lock);
         goto out;
     }
 
     if (fstripe_lock->refs == 0) {
         WARN_ON(1);
         btrfs_warn(fs_info, "full stripe lock at %llu refcount underflow",
             fstripe_lock->logical);
     } else {
         fstripe_lock->refs--;
     }
 
     if (fstripe_lock->refs == 0) {
         rb_erase(&fstripe_lock->node, &locks_root->root);
         freeit = true;
     }
     mutex_unlock(&locks_root->lock);
 
     mutex_unlock(&fstripe_lock->mutex);
     if (freeit)
         kfree(fstripe_lock);
 out:
     btrfs_put_block_group(bg_cache);
     return ret;
 }
 
 static void scrub_free_csums(struct scrub_ctx *sctx)
 {
     while (!list_empty(&sctx->csum_list)) {
         struct btrfs_ordered_sum *sum;
         sum = list_first_entry(&sctx->csum_list,
                        struct btrfs_ordered_sum, list);
         list_del(&sum->list);
         kfree(sum);
     }
 }
 
 static noinline_for_stack void scrub_free_ctx(struct scrub_ctx *sctx)
 {
     int i;
 
     if (!sctx)
         return;
 
     /* this can happen when scrub is cancelled */
     if (sctx->curr != -1) {
         struct scrub_bio *sbio = sctx->bios[sctx->curr];
 
         for (i = 0; i < sbio->sector_count; i++) {
             WARN_ON(!sbio->sectors[i]->page);
             scrub_block_put(sbio->sectors[i]->sblock);
         }
         bio_put(sbio->bio);
     }
 
     for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
         struct scrub_bio *sbio = sctx->bios[i];
 
         if (!sbio)
             break;
         kfree(sbio);
     }
 
     kfree(sctx->wr_curr_bio);
     scrub_free_csums(sctx);
     kfree(sctx);
 }
 
 static void scrub_put_ctx(struct scrub_ctx *sctx)
 {
     if (refcount_dec_and_test(&sctx->refs))
         scrub_free_ctx(sctx);
 }
 
 static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
         struct btrfs_fs_info *fs_info, int is_dev_replace)
 {
     struct scrub_ctx *sctx;
     int     i;
 
     sctx = kzalloc(sizeof(*sctx), GFP_KERNEL);
     if (!sctx)
         goto nomem;
     refcount_set(&sctx->refs, 1);
     sctx->is_dev_replace = is_dev_replace;
     sctx->sectors_per_bio = SCRUB_SECTORS_PER_BIO;
     sctx->curr = -1;
     sctx->fs_info = fs_info;
     INIT_LIST_HEAD(&sctx->csum_list);
     for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
         struct scrub_bio *sbio;
 
         sbio = kzalloc(sizeof(*sbio), GFP_KERNEL);
         if (!sbio)
             goto nomem;
         sctx->bios[i] = sbio;
 
         sbio->index = i;
         sbio->sctx = sctx;
         sbio->sector_count = 0;
         INIT_WORK(&sbio->work, scrub_bio_end_io_worker);
 
         if (i != SCRUB_BIOS_PER_SCTX - 1)
             sctx->bios[i]->next_free = i + 1;
         else
             sctx->bios[i]->next_free = -1;
     }
     sctx->first_free = 0;
     atomic_set(&sctx->bios_in_flight, 0);
     atomic_set(&sctx->workers_pending, 0);
     atomic_set(&sctx->cancel_req, 0);
 
     spin_lock_init(&sctx->list_lock);
     spin_lock_init(&sctx->stat_lock);
     init_waitqueue_head(&sctx->list_wait);
     sctx->throttle_deadline = 0;
 
     WARN_ON(sctx->wr_curr_bio != NULL);
     mutex_init(&sctx->wr_lock);
     sctx->wr_curr_bio = NULL;
     if (is_dev_replace) {
         WARN_ON(!fs_info->dev_replace.tgtdev);
         sctx->wr_tgtdev = fs_info->dev_replace.tgtdev;
         sctx->flush_all_writes = false;
     }
 
     return sctx;
 
 nomem:
     scrub_free_ctx(sctx);
     return ERR_PTR(-ENOMEM);
 }
 
 static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root,
                      void *warn_ctx)
 {
     u32 nlink;
     int ret;
     int i;
     unsigned nofs_flag;
     struct extent_buffer *eb;
     struct btrfs_inode_item *inode_item;
     struct scrub_warning *swarn = warn_ctx;
     struct btrfs_fs_info *fs_info = swarn->dev->fs_info;
     struct inode_fs_paths *ipath = NULL;
     struct btrfs_root *local_root;
     struct btrfs_key key;
 
     local_root = btrfs_get_fs_root(fs_info, root, true);
     if (IS_ERR(local_root)) {
         ret = PTR_ERR(local_root);
         goto err;
     }
 
     /*
      * this makes the path point to (inum INODE_ITEM ioff)
      */
     key.objectid = inum;
     key.type = BTRFS_INODE_ITEM_KEY;
     key.offset = 0;
 
     ret = btrfs_search_slot(NULL, local_root, &key, swarn->path, 0, 0);
     if (ret) {
         btrfs_put_root(local_root);
         btrfs_release_path(swarn->path);
         goto err;
     }
 
     eb = swarn->path->nodes[0];
     inode_item = btrfs_item_ptr(eb, swarn->path->slots[0],
                     struct btrfs_inode_item);
     nlink = btrfs_inode_nlink(eb, inode_item);
     btrfs_release_path(swarn->path);
 
     /*
      * init_path might indirectly call vmalloc, or use GFP_KERNEL. Scrub
      * uses GFP_NOFS in this context, so we keep it consistent but it does
      * not seem to be strictly necessary.
      */
     nofs_flag = memalloc_nofs_save();
     ipath = init_ipath(4096, local_root, swarn->path);
     memalloc_nofs_restore(nofs_flag);
     if (IS_ERR(ipath)) {
         btrfs_put_root(local_root);
         ret = PTR_ERR(ipath);
         ipath = NULL;
         goto err;
     }
     ret = paths_from_inode(inum, ipath);
 
     if (ret < 0)
         goto err;
 
     /*
      * we deliberately ignore the bit ipath might have been too small to
      * hold all of the paths here
      */
     for (i = 0; i < ipath->fspath->elem_cnt; ++i)
         btrfs_warn_in_rcu(fs_info,
 "%s at logical %llu on dev %s, physical %llu, root %llu, inode %llu, offset %llu, length %u, links %u (path: %s)",
                   swarn->errstr, swarn->logical,
                   rcu_str_deref(swarn->dev->name),
                   swarn->physical,
                   root, inum, offset,
                   fs_info->sectorsize, nlink,
                   (char *)(unsigned long)ipath->fspath->val[i]);
 
     btrfs_put_root(local_root);
     free_ipath(ipath);
     return 0;
 
 err:
     btrfs_warn_in_rcu(fs_info,
               "%s at logical %llu on dev %s, physical %llu, root %llu, inode %llu, offset %llu: path resolving failed with ret=%d",
               swarn->errstr, swarn->logical,
               rcu_str_deref(swarn->dev->name),
               swarn->physical,
               root, inum, offset, ret);
 
     free_ipath(ipath);
     return 0;
 }
 
 static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 {
     struct btrfs_device *dev;
     struct btrfs_fs_info *fs_info;
     struct btrfs_path *path;
     struct btrfs_key found_key;
     struct extent_buffer *eb;
     struct btrfs_extent_item *ei;
     struct scrub_warning swarn;
     unsigned long ptr = 0;
     u64 extent_item_pos;
     u64 flags = 0;
     u64 ref_root;
     u32 item_size;
     u8 ref_level = 0;
     int ret;
 
     WARN_ON(sblock->sector_count < 1);
     dev = sblock->sectors[0]->dev;
     fs_info = sblock->sctx->fs_info;
 
     path = btrfs_alloc_path();
     if (!path)
         return;
 
     swarn.physical = sblock->sectors[0]->physical;
     swarn.logical = sblock->sectors[0]->logical;
     swarn.errstr = errstr;
     swarn.dev = NULL;
 
     ret = extent_from_logical(fs_info, swarn.logical, path, &found_key,
                   &flags);
     if (ret < 0)
         goto out;
 
     extent_item_pos = swarn.logical - found_key.objectid;
     swarn.extent_item_size = found_key.offset;
 
     eb = path->nodes[0];
     ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
     item_size = btrfs_item_size(eb, path->slots[0]);
 
     if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
         do {
             ret = tree_backref_for_extent(&ptr, eb, &found_key, ei,
                               item_size, &ref_root,
                               &ref_level);
             btrfs_warn_in_rcu(fs_info,
 "%s at logical %llu on dev %s, physical %llu: metadata %s (level %d) in tree %llu",
                 errstr, swarn.logical,
                 rcu_str_deref(dev->name),
                 swarn.physical,
                 ref_level ? "node" : "leaf",
                 ret < 0 ? -1 : ref_level,
                 ret < 0 ? -1 : ref_root);
         } while (ret != 1);
         btrfs_release_path(path);
     } else {
         btrfs_release_path(path);
         swarn.path = path;
         swarn.dev = dev;
         iterate_extent_inodes(fs_info, found_key.objectid,
                     extent_item_pos, 1,
                     scrub_print_warning_inode, &swarn, false);
     }
 
 out:
     btrfs_free_path(path);
 }
 
 static inline void scrub_get_recover(struct scrub_recover *recover)
 {
     refcount_inc(&recover->refs);
 }
 
 static inline void scrub_put_recover(struct btrfs_fs_info *fs_info,
                      struct scrub_recover *recover)
 {
     if (refcount_dec_and_test(&recover->refs)) {
         btrfs_bio_counter_dec(fs_info);
         btrfs_put_bioc(recover->bioc);
         kfree(recover);
     }
 }
 
 /*
  * scrub_handle_errored_block gets called when either verification of the
  * sectors failed or the bio failed to read, e.g. with EIO. In the latter
  * case, this function handles all sectors in the bio, even though only one
  * may be bad.
  * The goal of this function is to repair the errored block by using the
  * contents of one of the mirrors.
  */
 static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
 {
     struct scrub_ctx *sctx = sblock_to_check->sctx;
     struct btrfs_device *dev;
     struct btrfs_fs_info *fs_info;
     u64 logical;
     unsigned int failed_mirror_index;
     unsigned int is_metadata;
     unsigned int have_csum;
     struct scrub_block *sblocks_for_recheck; /* holds one for each mirror */
     struct scrub_block *sblock_bad;
     int ret;
     int mirror_index;
     int sector_num;
     int success;
     bool full_stripe_locked;
     unsigned int nofs_flag;
     static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
                       DEFAULT_RATELIMIT_BURST);
 
     BUG_ON(sblock_to_check->sector_count < 1);
     fs_info = sctx->fs_info;
     if (sblock_to_check->sectors[0]->flags & BTRFS_EXTENT_FLAG_SUPER) {
         /*
          * if we find an error in a super block, we just report it.
          * They will get written with the next transaction commit
          * anyway
          */
         spin_lock(&sctx->stat_lock);
         ++sctx->stat.super_errors;
         spin_unlock(&sctx->stat_lock);
         return 0;
     }
     logical = sblock_to_check->sectors[0]->logical;
     BUG_ON(sblock_to_check->sectors[0]->mirror_num < 1);
     failed_mirror_index = sblock_to_check->sectors[0]->mirror_num - 1;
     is_metadata = !(sblock_to_check->sectors[0]->flags &
             BTRFS_EXTENT_FLAG_DATA);
     have_csum = sblock_to_check->sectors[0]->have_csum;
     dev = sblock_to_check->sectors[0]->dev;
 
     if (!sctx->is_dev_replace && btrfs_repair_one_zone(fs_info, logical))
         return 0;
 
     /*
      * We must use GFP_NOFS because the scrub task might be waiting for a
      * worker task executing this function and in turn a transaction commit
      * might be waiting the scrub task to pause (which needs to wait for all
      * the worker tasks to complete before pausing).
      * We do allocations in the workers through insert_full_stripe_lock()
      * and scrub_add_sector_to_wr_bio(), which happens down the call chain of
      * this function.
      */
     nofs_flag = memalloc_nofs_save();
     /*
      * For RAID5/6, race can happen for a different device scrub thread.
      * For data corruption, Parity and Data threads will both try
      * to recovery the data.
      * Race can lead to doubly added csum error, or even unrecoverable
      * error.
      */
     ret = lock_full_stripe(fs_info, logical, &full_stripe_locked);
     if (ret < 0) {
         memalloc_nofs_restore(nofs_flag);
         spin_lock(&sctx->stat_lock);
         if (ret == -ENOMEM)
             sctx->stat.malloc_errors++;
         sctx->stat.read_errors++;
         sctx->stat.uncorrectable_errors++;
         spin_unlock(&sctx->stat_lock);
         return ret;
     }
 
     /*
      * read all mirrors one after the other. This includes to
      * re-read the extent or metadata block that failed (that was
      * the cause that this fixup code is called) another time,
      * sector by sector this time in order to know which sectors
      * caused I/O errors and which ones are good (for all mirrors).
      * It is the goal to handle the situation when more than one
      * mirror contains I/O errors, but the errors do not
      * overlap, i.e. the data can be repaired by selecting the
      * sectors from those mirrors without I/O error on the
      * particular sectors. One example (with blocks >= 2 * sectorsize)
      * would be that mirror #1 has an I/O error on the first sector,
      * the second sector is good, and mirror #2 has an I/O error on
      * the second sector, but the first sector is good.
      * Then the first sector of the first mirror can be repaired by
      * taking the first sector of the second mirror, and the
      * second sector of the second mirror can be repaired by
      * copying the contents of the 2nd sector of the 1st mirror.
      * One more note: if the sectors of one mirror contain I/O
      * errors, the checksum cannot be verified. In order to get
      * the best data for repairing, the first attempt is to find
      * a mirror without I/O errors and with a validated checksum.
      * Only if this is not possible, the sectors are picked from
      * mirrors with I/O errors without considering the checksum.
      * If the latter is the case, at the end, the checksum of the
      * repaired area is verified in order to correctly maintain
      * the statistics.
      */
 
     sblocks_for_recheck = kcalloc(BTRFS_MAX_MIRRORS,
                       sizeof(*sblocks_for_recheck), GFP_KERNEL);
     if (!sblocks_for_recheck) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.malloc_errors++;
         sctx->stat.read_errors++;
         sctx->stat.uncorrectable_errors++;
         spin_unlock(&sctx->stat_lock);
         btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
         goto out;
     }
 
     /* Setup the context, map the logical blocks and alloc the sectors */
     ret = scrub_setup_recheck_block(sblock_to_check, sblocks_for_recheck);
     if (ret) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.read_errors++;
         sctx->stat.uncorrectable_errors++;
         spin_unlock(&sctx->stat_lock);
         btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
         goto out;
     }
     BUG_ON(failed_mirror_index >= BTRFS_MAX_MIRRORS);
     sblock_bad = sblocks_for_recheck + failed_mirror_index;
 
     /* build and submit the bios for the failed mirror, check checksums */
     scrub_recheck_block(fs_info, sblock_bad, 1);
 
     if (!sblock_bad->header_error && !sblock_bad->checksum_error &&
         sblock_bad->no_io_error_seen) {
         /*
          * The error disappeared after reading sector by sector, or
          * the area was part of a huge bio and other parts of the
          * bio caused I/O errors, or the block layer merged several
          * read requests into one and the error is caused by a
          * different bio (usually one of the two latter cases is
          * the cause)
          */
         spin_lock(&sctx->stat_lock);
         sctx->stat.unverified_errors++;
         sblock_to_check->data_corrected = 1;
         spin_unlock(&sctx->stat_lock);
 
         if (sctx->is_dev_replace)
             scrub_write_block_to_dev_replace(sblock_bad);
         goto out;
     }
 
     if (!sblock_bad->no_io_error_seen) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.read_errors++;
         spin_unlock(&sctx->stat_lock);
         if (__ratelimit(&rs))
             scrub_print_warning("i/o error", sblock_to_check);
         btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
     } else if (sblock_bad->checksum_error) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.csum_errors++;
         spin_unlock(&sctx->stat_lock);
         if (__ratelimit(&rs))
             scrub_print_warning("checksum error", sblock_to_check);
         btrfs_dev_stat_inc_and_print(dev,
                          BTRFS_DEV_STAT_CORRUPTION_ERRS);
     } else if (sblock_bad->header_error) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.verify_errors++;
         spin_unlock(&sctx->stat_lock);
         if (__ratelimit(&rs))
             scrub_print_warning("checksum/header error",
                         sblock_to_check);
         if (sblock_bad->generation_error)
             btrfs_dev_stat_inc_and_print(dev,
                 BTRFS_DEV_STAT_GENERATION_ERRS);
         else
             btrfs_dev_stat_inc_and_print(dev,
                 BTRFS_DEV_STAT_CORRUPTION_ERRS);
     }
 
     if (sctx->readonly) {
         ASSERT(!sctx->is_dev_replace);
         goto out;
     }
 
     /*
      * now build and submit the bios for the other mirrors, check
      * checksums.
      * First try to pick the mirror which is completely without I/O
      * errors and also does not have a checksum error.
      * If one is found, and if a checksum is present, the full block
      * that is known to contain an error is rewritten. Afterwards
      * the block is known to be corrected.
      * If a mirror is found which is completely correct, and no
      * checksum is present, only those sectors are rewritten that had
      * an I/O error in the block to be repaired, since it cannot be
      * determined, which copy of the other sectors is better (and it
      * could happen otherwise that a correct sector would be
      * overwritten by a bad one).
      */
     for (mirror_index = 0; ;mirror_index++) {
         struct scrub_block *sblock_other;
 
         if (mirror_index == failed_mirror_index)
             continue;
 
         /* raid56's mirror can be more than BTRFS_MAX_MIRRORS */
         if (!scrub_is_page_on_raid56(sblock_bad->sectors[0])) {
             if (mirror_index >= BTRFS_MAX_MIRRORS)
                 break;
             if (!sblocks_for_recheck[mirror_index].sector_count)
                 break;
 
             sblock_other = sblocks_for_recheck + mirror_index;
         } else {
             struct scrub_recover *r = sblock_bad->sectors[0]->recover;
             int max_allowed = r->bioc->num_stripes - r->bioc->num_tgtdevs;
 
             if (mirror_index >= max_allowed)
                 break;
             if (!sblocks_for_recheck[1].sector_count)
                 break;
 
             ASSERT(failed_mirror_index == 0);
             sblock_other = sblocks_for_recheck + 1;
             sblock_other->sectors[0]->mirror_num = 1 + mirror_index;
         }
 
         /* build and submit the bios, check checksums */
         scrub_recheck_block(fs_info, sblock_other, 0);
 
         if (!sblock_other->header_error &&
             !sblock_other->checksum_error &&
             sblock_other->no_io_error_seen) {
             if (sctx->is_dev_replace) {
                 scrub_write_block_to_dev_replace(sblock_other);
                 goto corrected_error;
             } else {
                 ret = scrub_repair_block_from_good_copy(
                         sblock_bad, sblock_other);
                 if (!ret)
                     goto corrected_error;
             }
         }
     }
 
     if (sblock_bad->no_io_error_seen && !sctx->is_dev_replace)
         goto did_not_correct_error;
 
     /*
      * In case of I/O errors in the area that is supposed to be
      * repaired, continue by picking good copies of those sectors.
      * Select the good sectors from mirrors to rewrite bad sectors from
      * the area to fix. Afterwards verify the checksum of the block
      * that is supposed to be repaired. This verification step is
      * only done for the purpose of statistic counting and for the
      * final scrub report, whether errors remain.
      * A perfect algorithm could make use of the checksum and try
      * all possible combinations of sectors from the different mirrors
      * until the checksum verification succeeds. For example, when
      * the 2nd sector of mirror #1 faces I/O errors, and the 2nd sector
      * of mirror #2 is readable but the final checksum test fails,
      * then the 2nd sector of mirror #3 could be tried, whether now
      * the final checksum succeeds. But this would be a rare
      * exception and is therefore not implemented. At least it is
      * avoided that the good copy is overwritten.
      * A more useful improvement would be to pick the sectors
      * without I/O error based on sector sizes (512 bytes on legacy
      * disks) instead of on sectorsize. Then maybe 512 byte of one
      * mirror could be repaired by taking 512 byte of a different
      * mirror, even if other 512 byte sectors in the same sectorsize
      * area are unreadable.
      */
     success = 1;
     for (sector_num = 0; sector_num < sblock_bad->sector_count;
          sector_num++) {
         struct scrub_sector *sector_bad = sblock_bad->sectors[sector_num];
         struct scrub_block *sblock_other = NULL;
 
         /* Skip no-io-error sectors in scrub */
         if (!sector_bad->io_error && !sctx->is_dev_replace)
             continue;
 
         if (scrub_is_page_on_raid56(sblock_bad->sectors[0])) {
             /*
              * In case of dev replace, if raid56 rebuild process
              * didn't work out correct data, then copy the content
              * in sblock_bad to make sure target device is identical
              * to source device, instead of writing garbage data in
              * sblock_for_recheck array to target device.
              */
             sblock_other = NULL;
         } else if (sector_bad->io_error) {
             /* Try to find no-io-error sector in mirrors */
             for (mirror_index = 0;
                  mirror_index < BTRFS_MAX_MIRRORS &&
                  sblocks_for_recheck[mirror_index].sector_count > 0;
                  mirror_index++) {
                 if (!sblocks_for_recheck[mirror_index].
                     sectors[sector_num]->io_error) {
                     sblock_other = sblocks_for_recheck +
                                mirror_index;
                     break;
                 }
             }
             if (!sblock_other)
                 success = 0;
         }
 
         if (sctx->is_dev_replace) {
             /*
              * Did not find a mirror to fetch the sector from.
              * scrub_write_sector_to_dev_replace() handles this
              * case (sector->io_error), by filling the block with
              * zeros before submitting the write request
              */
             if (!sblock_other)
                 sblock_other = sblock_bad;
 
             if (scrub_write_sector_to_dev_replace(sblock_other,
                                   sector_num) != 0) {
                 atomic64_inc(
                     &fs_info->dev_replace.num_write_errors);
                 success = 0;
             }
         } else if (sblock_other) {
             ret = scrub_repair_sector_from_good_copy(sblock_bad,
                                  sblock_other,
                                  sector_num, 0);
             if (0 == ret)
                 sector_bad->io_error = 0;
             else
                 success = 0;
         }
     }
 
     if (success && !sctx->is_dev_replace) {
         if (is_metadata || have_csum) {
             /*
              * need to verify the checksum now that all
              * sectors on disk are repaired (the write
              * request for data to be repaired is on its way).
              * Just be lazy and use scrub_recheck_block()
              * which re-reads the data before the checksum
              * is verified, but most likely the data comes out
              * of the page cache.
              */
             scrub_recheck_block(fs_info, sblock_bad, 1);
             if (!sblock_bad->header_error &&
                 !sblock_bad->checksum_error &&
                 sblock_bad->no_io_error_seen)
                 goto corrected_error;
             else
                 goto did_not_correct_error;
         } else {
 corrected_error:
             spin_lock(&sctx->stat_lock);
             sctx->stat.corrected_errors++;
             sblock_to_check->data_corrected = 1;
             spin_unlock(&sctx->stat_lock);
             btrfs_err_rl_in_rcu(fs_info,
                 "fixed up error at logical %llu on dev %s",
                 logical, rcu_str_deref(dev->name));
         }
     } else {
 did_not_correct_error:
         spin_lock(&sctx->stat_lock);
         sctx->stat.uncorrectable_errors++;
         spin_unlock(&sctx->stat_lock);
         btrfs_err_rl_in_rcu(fs_info,
             "unable to fixup (regular) error at logical %llu on dev %s",
             logical, rcu_str_deref(dev->name));
     }
 
 out:
     if (sblocks_for_recheck) {
         for (mirror_index = 0; mirror_index < BTRFS_MAX_MIRRORS;
              mirror_index++) {
             struct scrub_block *sblock = sblocks_for_recheck +
                              mirror_index;
             struct scrub_recover *recover;
             int i;
 
             for (i = 0; i < sblock->sector_count; i++) {
                 sblock->sectors[i]->sblock = NULL;
                 recover = sblock->sectors[i]->recover;
                 if (recover) {
                     scrub_put_recover(fs_info, recover);
                     sblock->sectors[i]->recover = NULL;
                 }
                 scrub_sector_put(sblock->sectors[i]);
             }
         }
         kfree(sblocks_for_recheck);
     }
 
     ret = unlock_full_stripe(fs_info, logical, full_stripe_locked);
     memalloc_nofs_restore(nofs_flag);
     if (ret < 0)
         return ret;
     return 0;
 }
 
 static inline int scrub_nr_raid_mirrors(struct btrfs_io_context *bioc)
 {
     if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID5)
         return 2;
     else if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID6)
         return 3;
     else
         return (int)bioc->num_stripes;
 }
 
 static inline void scrub_stripe_index_and_offset(u64 logical, u64 map_type,
                          u64 *raid_map,
                          int nstripes, int mirror,
                          int *stripe_index,
                          u64 *stripe_offset)
 {
     int i;
 
     if (map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
         /* RAID5/6 */
         for (i = 0; i < nstripes; i++) {
             if (raid_map[i] == RAID6_Q_STRIPE ||
                 raid_map[i] == RAID5_P_STRIPE)
                 continue;
 
             if (logical >= raid_map[i] &&
                 logical < raid_map[i] + BTRFS_STRIPE_LEN)
                 break;
         }
 
         *stripe_index = i;
         *stripe_offset = logical - raid_map[i];
     } else {
         /* The other RAID type */
         *stripe_index = mirror;
         *stripe_offset = 0;
     }
 }
 
 static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
                      struct scrub_block *sblocks_for_recheck)
 {
     struct scrub_ctx *sctx = original_sblock->sctx;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     u64 length = original_sblock->sector_count << fs_info->sectorsize_bits;
     u64 logical = original_sblock->sectors[0]->logical;
     u64 generation = original_sblock->sectors[0]->generation;
     u64 flags = original_sblock->sectors[0]->flags;
     u64 have_csum = original_sblock->sectors[0]->have_csum;
     struct scrub_recover *recover;
     struct btrfs_io_context *bioc;
     u64 sublen;
     u64 mapped_length;
     u64 stripe_offset;
     int stripe_index;
     int sector_index = 0;
     int mirror_index;
     int nmirrors;
     int ret;
 
     /*
      * Note: the two members refs and outstanding_sectors are not used (and
      * not set) in the blocks that are used for the recheck procedure.
      */
 
     while (length > 0) {
         sublen = min_t(u64, length, fs_info->sectorsize);
         mapped_length = sublen;
         bioc = NULL;
 
         /*
          * With a length of sectorsize, each returned stripe represents
          * one mirror
          */
         btrfs_bio_counter_inc_blocked(fs_info);
         ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS,
                        logical, &mapped_length, &bioc);
         if (ret || !bioc || mapped_length < sublen) {
             btrfs_put_bioc(bioc);
             btrfs_bio_counter_dec(fs_info);
             return -EIO;
         }
 
         recover = kzalloc(sizeof(struct scrub_recover), GFP_NOFS);
         if (!recover) {
             btrfs_put_bioc(bioc);
             btrfs_bio_counter_dec(fs_info);
             return -ENOMEM;
         }
 
         refcount_set(&recover->refs, 1);
         recover->bioc = bioc;
         recover->map_length = mapped_length;
 
         ASSERT(sector_index < SCRUB_MAX_SECTORS_PER_BLOCK);
 
         nmirrors = min(scrub_nr_raid_mirrors(bioc), BTRFS_MAX_MIRRORS);
 
         for (mirror_index = 0; mirror_index < nmirrors;
              mirror_index++) {
             struct scrub_block *sblock;
             struct scrub_sector *sector;
 
             sblock = sblocks_for_recheck + mirror_index;
             sblock->sctx = sctx;
 
             sector = kzalloc(sizeof(*sector), GFP_NOFS);
             if (!sector) {
 leave_nomem:
                 spin_lock(&sctx->stat_lock);
                 sctx->stat.malloc_errors++;
                 spin_unlock(&sctx->stat_lock);
                 scrub_put_recover(fs_info, recover);
                 return -ENOMEM;
             }
             scrub_sector_get(sector);
             sblock->sectors[sector_index] = sector;
             sector->sblock = sblock;
             sector->flags = flags;
             sector->generation = generation;
             sector->logical = logical;
             sector->have_csum = have_csum;
             if (have_csum)
                 memcpy(sector->csum,
                        original_sblock->sectors[0]->csum,
                        sctx->fs_info->csum_size);
 
             scrub_stripe_index_and_offset(logical,
                               bioc->map_type,
                               bioc->raid_map,
                               bioc->num_stripes -
                               bioc->num_tgtdevs,
                               mirror_index,
                               &stripe_index,
                               &stripe_offset);
             sector->physical = bioc->stripes[stripe_index].physical +
                      stripe_offset;
             sector->dev = bioc->stripes[stripe_index].dev;
 
             BUG_ON(sector_index >= original_sblock->sector_count);
             sector->physical_for_dev_replace =
                 original_sblock->sectors[sector_index]->
                 physical_for_dev_replace;
             /* For missing devices, dev->bdev is NULL */
             sector->mirror_num = mirror_index + 1;
             sblock->sector_count++;
             sector->page = alloc_page(GFP_NOFS);
             if (!sector->page)
                 goto leave_nomem;
 
             scrub_get_recover(recover);
             sector->recover = recover;
         }
         scrub_put_recover(fs_info, recover);
         length -= sublen;
         logical += sublen;
         sector_index++;
     }
 
     return 0;
 }
 
 static void scrub_bio_wait_endio(struct bio *bio)
 {
     complete(bio->bi_private);
 }
 
 static int scrub_submit_raid56_bio_wait(struct btrfs_fs_info *fs_info,
                     struct bio *bio,
                     struct scrub_sector *sector)
 {
     DECLARE_COMPLETION_ONSTACK(done);
 
     bio->bi_iter.bi_sector = sector->logical >> 9;
     bio->bi_private = &done;
     bio->bi_end_io = scrub_bio_wait_endio;
     raid56_parity_recover(bio, sector->recover->bioc,
                   sector->sblock->sectors[0]->mirror_num, false);
 
     wait_for_completion_io(&done);
     return blk_status_to_errno(bio->bi_status);
 }
 
 static void scrub_recheck_block_on_raid56(struct btrfs_fs_info *fs_info,
                       struct scrub_block *sblock)
 {
     struct scrub_sector *first_sector = sblock->sectors[0];
     struct bio *bio;
     int i;
 
     /* All sectors in sblock belong to the same stripe on the same device. */
     ASSERT(first_sector->dev);
     if (!first_sector->dev->bdev)
         goto out;
 
     bio = bio_alloc(first_sector->dev->bdev, BIO_MAX_VECS, REQ_OP_READ, GFP_NOFS);
 
     for (i = 0; i < sblock->sector_count; i++) {
         struct scrub_sector *sector = sblock->sectors[i];
 
         WARN_ON(!sector->page);
         bio_add_page(bio, sector->page, PAGE_SIZE, 0);
     }
 
     if (scrub_submit_raid56_bio_wait(fs_info, bio, first_sector)) {
         bio_put(bio);
         goto out;
     }
 
     bio_put(bio);
 
     scrub_recheck_block_checksum(sblock);
 
     return;
 out:
     for (i = 0; i < sblock->sector_count; i++)
         sblock->sectors[i]->io_error = 1;
 
     sblock->no_io_error_seen = 0;
 }
 
 /*
  * This function will check the on disk data for checksum errors, header errors
  * and read I/O errors. If any I/O errors happen, the exact sectors which are
  * errored are marked as being bad. The goal is to enable scrub to take those
  * sectors that are not errored from all the mirrors so that the sectors that
  * are errored in the just handled mirror can be repaired.
  */
 static void scrub_recheck_block(struct btrfs_fs_info *fs_info,
                 struct scrub_block *sblock,
                 int retry_failed_mirror)
 {
     int i;
 
     sblock->no_io_error_seen = 1;
 
     /* short cut for raid56 */
     if (!retry_failed_mirror && scrub_is_page_on_raid56(sblock->sectors[0]))
         return scrub_recheck_block_on_raid56(fs_info, sblock);
 
     for (i = 0; i < sblock->sector_count; i++) {
         struct scrub_sector *sector = sblock->sectors[i];
         struct bio bio;
         struct bio_vec bvec;
 
         if (sector->dev->bdev == NULL) {
             sector->io_error = 1;
             sblock->no_io_error_seen = 0;
             continue;
         }
 
         WARN_ON(!sector->page);
         bio_init(&bio, sector->dev->bdev, &bvec, 1, REQ_OP_READ);
         bio_add_page(&bio, sector->page, fs_info->sectorsize, 0);
         bio.bi_iter.bi_sector = sector->physical >> 9;
 
         btrfsic_check_bio(&bio);
         if (submit_bio_wait(&bio)) {
             sector->io_error = 1;
             sblock->no_io_error_seen = 0;
         }
 
         bio_uninit(&bio);
     }
 
     if (sblock->no_io_error_seen)
         scrub_recheck_block_checksum(sblock);
 }
 
 static inline int scrub_check_fsid(u8 fsid[], struct scrub_sector *sector)
 {
     struct btrfs_fs_devices *fs_devices = sector->dev->fs_devices;
     int ret;
 
     ret = memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
     return !ret;
 }
 
 static void scrub_recheck_block_checksum(struct scrub_block *sblock)
 {
     sblock->header_error = 0;
     sblock->checksum_error = 0;
     sblock->generation_error = 0;
 
     if (sblock->sectors[0]->flags & BTRFS_EXTENT_FLAG_DATA)
         scrub_checksum_data(sblock);
     else
         scrub_checksum_tree_block(sblock);
 }
 
 static int scrub_repair_block_from_good_copy(struct scrub_block *sblock_bad,
                          struct scrub_block *sblock_good)
 {
     int i;
     int ret = 0;
 
     for (i = 0; i < sblock_bad->sector_count; i++) {
         int ret_sub;
 
         ret_sub = scrub_repair_sector_from_good_copy(sblock_bad,
                                  sblock_good, i, 1);
         if (ret_sub)
             ret = ret_sub;
     }
 
     return ret;
 }
 
 static int scrub_repair_sector_from_good_copy(struct scrub_block *sblock_bad,
                           struct scrub_block *sblock_good,
                           int sector_num, int force_write)
 {
     struct scrub_sector *sector_bad = sblock_bad->sectors[sector_num];
     struct scrub_sector *sector_good = sblock_good->sectors[sector_num];
     struct btrfs_fs_info *fs_info = sblock_bad->sctx->fs_info;
     const u32 sectorsize = fs_info->sectorsize;
 
     BUG_ON(sector_bad->page == NULL);
     BUG_ON(sector_good->page == NULL);
     if (force_write || sblock_bad->header_error ||
         sblock_bad->checksum_error || sector_bad->io_error) {
         struct bio bio;
         struct bio_vec bvec;
         int ret;
 
         if (!sector_bad->dev->bdev) {
             btrfs_warn_rl(fs_info,
                 "scrub_repair_page_from_good_copy(bdev == NULL) is unexpected");
             return -EIO;
         }
 
         bio_init(&bio, sector_bad->dev->bdev, &bvec, 1, REQ_OP_WRITE);
         bio.bi_iter.bi_sector = sector_bad->physical >> 9;
         __bio_add_page(&bio, sector_good->page, sectorsize, 0);
 
         btrfsic_check_bio(&bio);
         ret = submit_bio_wait(&bio);
         bio_uninit(&bio);
 
         if (ret) {
             btrfs_dev_stat_inc_and_print(sector_bad->dev,
                 BTRFS_DEV_STAT_WRITE_ERRS);
             atomic64_inc(&fs_info->dev_replace.num_write_errors);
             return -EIO;
         }
     }
 
     return 0;
 }
 
 static void scrub_write_block_to_dev_replace(struct scrub_block *sblock)
 {
     struct btrfs_fs_info *fs_info = sblock->sctx->fs_info;
     int i;
 
     /*
      * This block is used for the check of the parity on the source device,
      * so the data needn't be written into the destination device.
      */
     if (sblock->sparity)
         return;
 
     for (i = 0; i < sblock->sector_count; i++) {
         int ret;
 
         ret = scrub_write_sector_to_dev_replace(sblock, i);
         if (ret)
             atomic64_inc(&fs_info->dev_replace.num_write_errors);
     }
 }
 
 static int scrub_write_sector_to_dev_replace(struct scrub_block *sblock, int sector_num)
 {
     struct scrub_sector *sector = sblock->sectors[sector_num];
 
     BUG_ON(sector->page == NULL);
     if (sector->io_error)
         clear_page(page_address(sector->page));
 
     return scrub_add_sector_to_wr_bio(sblock->sctx, sector);
 }
 
 static int fill_writer_pointer_gap(struct scrub_ctx *sctx, u64 physical)
 {
     int ret = 0;
     u64 length;
 
     if (!btrfs_is_zoned(sctx->fs_info))
         return 0;
 
     if (!btrfs_dev_is_sequential(sctx->wr_tgtdev, physical))
         return 0;
 
     if (sctx->write_pointer < physical) {
         length = physical - sctx->write_pointer;
 
         ret = btrfs_zoned_issue_zeroout(sctx->wr_tgtdev,
                         sctx->write_pointer, length);
         if (!ret)
             sctx->write_pointer = physical;
     }
     return ret;
 }
 
 static int scrub_add_sector_to_wr_bio(struct scrub_ctx *sctx,
                       struct scrub_sector *sector)
 {
     struct scrub_bio *sbio;
     int ret;
     const u32 sectorsize = sctx->fs_info->sectorsize;
 
     mutex_lock(&sctx->wr_lock);
 again:
     if (!sctx->wr_curr_bio) {
         sctx->wr_curr_bio = kzalloc(sizeof(*sctx->wr_curr_bio),
                           GFP_KERNEL);
         if (!sctx->wr_curr_bio) {
             mutex_unlock(&sctx->wr_lock);
             return -ENOMEM;
         }
         sctx->wr_curr_bio->sctx = sctx;
         sctx->wr_curr_bio->sector_count = 0;
     }
     sbio = sctx->wr_curr_bio;
     if (sbio->sector_count == 0) {
         ret = fill_writer_pointer_gap(sctx, sector->physical_for_dev_replace);
         if (ret) {
             mutex_unlock(&sctx->wr_lock);
             return ret;
         }
 
         sbio->physical = sector->physical_for_dev_replace;
         sbio->logical = sector->logical;
         sbio->dev = sctx->wr_tgtdev;
         if (!sbio->bio) {
             sbio->bio = bio_alloc(sbio->dev->bdev, sctx->sectors_per_bio,
                           REQ_OP_WRITE, GFP_NOFS);
         }
         sbio->bio->bi_private = sbio;
         sbio->bio->bi_end_io = scrub_wr_bio_end_io;
         sbio->bio->bi_iter.bi_sector = sbio->physical >> 9;
         sbio->status = 0;
     } else if (sbio->physical + sbio->sector_count * sectorsize !=
            sector->physical_for_dev_replace ||
            sbio->logical + sbio->sector_count * sectorsize !=
            sector->logical) {
         scrub_wr_submit(sctx);
         goto again;
     }
 
     ret = bio_add_page(sbio->bio, sector->page, sectorsize, 0);
     if (ret != sectorsize) {
         if (sbio->sector_count < 1) {
             bio_put(sbio->bio);
             sbio->bio = NULL;
             mutex_unlock(&sctx->wr_lock);
             return -EIO;
         }
         scrub_wr_submit(sctx);
         goto again;
     }
 
     sbio->sectors[sbio->sector_count] = sector;
     scrub_sector_get(sector);
     sbio->sector_count++;
     if (sbio->sector_count == sctx->sectors_per_bio)
         scrub_wr_submit(sctx);
     mutex_unlock(&sctx->wr_lock);
 
     return 0;
 }
 
 static void scrub_wr_submit(struct scrub_ctx *sctx)
 {
     struct scrub_bio *sbio;
 
     if (!sctx->wr_curr_bio)
         return;
 
     sbio = sctx->wr_curr_bio;
     sctx->wr_curr_bio = NULL;
     scrub_pending_bio_inc(sctx);
     /* process all writes in a single worker thread. Then the block layer
      * orders the requests before sending them to the driver which
      * doubled the write performance on spinning disks when measured
      * with Linux 3.5 */
     btrfsic_check_bio(sbio->bio);
     submit_bio(sbio->bio);
 
     if (btrfs_is_zoned(sctx->fs_info))
         sctx->write_pointer = sbio->physical + sbio->sector_count *
             sctx->fs_info->sectorsize;
 }
 
 static void scrub_wr_bio_end_io(struct bio *bio)
 {
     struct scrub_bio *sbio = bio->bi_private;
     struct btrfs_fs_info *fs_info = sbio->dev->fs_info;
 
     sbio->status = bio->bi_status;
     sbio->bio = bio;
 
     INIT_WORK(&sbio->work, scrub_wr_bio_end_io_worker);
     queue_work(fs_info->scrub_wr_completion_workers, &sbio->work);
 }
 
 static void scrub_wr_bio_end_io_worker(struct work_struct *work)
 {
     struct scrub_bio *sbio = container_of(work, struct scrub_bio, work);
     struct scrub_ctx *sctx = sbio->sctx;
     int i;
 
     ASSERT(sbio->sector_count <= SCRUB_SECTORS_PER_BIO);
     if (sbio->status) {
         struct btrfs_dev_replace *dev_replace =
             &sbio->sctx->fs_info->dev_replace;
 
         for (i = 0; i < sbio->sector_count; i++) {
             struct scrub_sector *sector = sbio->sectors[i];
 
             sector->io_error = 1;
             atomic64_inc(&dev_replace->num_write_errors);
         }
     }
 
     for (i = 0; i < sbio->sector_count; i++)
         scrub_sector_put(sbio->sectors[i]);
 
     bio_put(sbio->bio);
     kfree(sbio);
     scrub_pending_bio_dec(sctx);
 }
 
 static int scrub_checksum(struct scrub_block *sblock)
 {
     u64 flags;
     int ret;
 
     /*
      * No need to initialize these stats currently,
      * because this function only use return value
      * instead of these stats value.
      *
      * Todo:
      * always use stats
      */
     sblock->header_error = 0;
     sblock->generation_error = 0;
     sblock->checksum_error = 0;
 
     WARN_ON(sblock->sector_count < 1);
     flags = sblock->sectors[0]->flags;
     ret = 0;
     if (flags & BTRFS_EXTENT_FLAG_DATA)
         ret = scrub_checksum_data(sblock);
     else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
         ret = scrub_checksum_tree_block(sblock);
     else if (flags & BTRFS_EXTENT_FLAG_SUPER)
         (void)scrub_checksum_super(sblock);
     else
         WARN_ON(1);
     if (ret)
         scrub_handle_errored_block(sblock);
 
     return ret;
 }
 
 static int scrub_checksum_data(struct scrub_block *sblock)
 {
     struct scrub_ctx *sctx = sblock->sctx;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
     u8 csum[BTRFS_CSUM_SIZE];
     struct scrub_sector *sector;
     char *kaddr;
 
     BUG_ON(sblock->sector_count < 1);
     sector = sblock->sectors[0];
     if (!sector->have_csum)
         return 0;
 
     kaddr = page_address(sector->page);
 
     shash->tfm = fs_info->csum_shash;
     crypto_shash_init(shash);
 
     /*
      * In scrub_sectors() and scrub_sectors_for_parity() we ensure each sector
      * only contains one sector of data.
      */
     crypto_shash_digest(shash, kaddr, fs_info->sectorsize, csum);
 
     if (memcmp(csum, sector->csum, fs_info->csum_size))
         sblock->checksum_error = 1;
     return sblock->checksum_error;
 }
 
 static int scrub_checksum_tree_block(struct scrub_block *sblock)
 {
     struct scrub_ctx *sctx = sblock->sctx;
     struct btrfs_header *h;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
     u8 calculated_csum[BTRFS_CSUM_SIZE];
     u8 on_disk_csum[BTRFS_CSUM_SIZE];
     /*
      * This is done in sectorsize steps even for metadata as there's a
      * constraint for nodesize to be aligned to sectorsize. This will need
      * to change so we don't misuse data and metadata units like that.
      */
     const u32 sectorsize = sctx->fs_info->sectorsize;
     const int num_sectors = fs_info->nodesize >> fs_info->sectorsize_bits;
     int i;
     struct scrub_sector *sector;
     char *kaddr;
 
     BUG_ON(sblock->sector_count < 1);
 
     /* Each member in sectors is just one sector */
     ASSERT(sblock->sector_count == num_sectors);
 
     sector = sblock->sectors[0];
     kaddr = page_address(sector->page);
     h = (struct btrfs_header *)kaddr;
     memcpy(on_disk_csum, h->csum, sctx->fs_info->csum_size);
 
     /*
      * we don't use the getter functions here, as we
      * a) don't have an extent buffer and
      * b) the page is already kmapped
      */
     if (sector->logical != btrfs_stack_header_bytenr(h))
         sblock->header_error = 1;
 
     if (sector->generation != btrfs_stack_header_generation(h)) {
         sblock->header_error = 1;
         sblock->generation_error = 1;
     }
 
     if (!scrub_check_fsid(h->fsid, sector))
         sblock->header_error = 1;
 
     if (memcmp(h->chunk_tree_uuid, fs_info->chunk_tree_uuid,
            BTRFS_UUID_SIZE))
         sblock->header_error = 1;
 
     shash->tfm = fs_info->csum_shash;
     crypto_shash_init(shash);
     crypto_shash_update(shash, kaddr + BTRFS_CSUM_SIZE,
                 sectorsize - BTRFS_CSUM_SIZE);
 
     for (i = 1; i < num_sectors; i++) {
         kaddr = page_address(sblock->sectors[i]->page);
         crypto_shash_update(shash, kaddr, sectorsize);
     }
 
     crypto_shash_final(shash, calculated_csum);
     if (memcmp(calculated_csum, on_disk_csum, sctx->fs_info->csum_size))
         sblock->checksum_error = 1;
 
     return sblock->header_error || sblock->checksum_error;
 }
 
 static int scrub_checksum_super(struct scrub_block *sblock)
 {
     struct btrfs_super_block *s;
     struct scrub_ctx *sctx = sblock->sctx;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
     u8 calculated_csum[BTRFS_CSUM_SIZE];
     struct scrub_sector *sector;
     char *kaddr;
     int fail_gen = 0;
     int fail_cor = 0;
 
     BUG_ON(sblock->sector_count < 1);
     sector = sblock->sectors[0];
     kaddr = page_address(sector->page);
     s = (struct btrfs_super_block *)kaddr;
 
     if (sector->logical != btrfs_super_bytenr(s))
         ++fail_cor;
 
     if (sector->generation != btrfs_super_generation(s))
         ++fail_gen;
 
     if (!scrub_check_fsid(s->fsid, sector))
         ++fail_cor;
 
     shash->tfm = fs_info->csum_shash;
     crypto_shash_init(shash);
     crypto_shash_digest(shash, kaddr + BTRFS_CSUM_SIZE,
             BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE, calculated_csum);
 
     if (memcmp(calculated_csum, s->csum, sctx->fs_info->csum_size))
         ++fail_cor;
 
     if (fail_cor + fail_gen) {
         /*
          * if we find an error in a super block, we just report it.
          * They will get written with the next transaction commit
          * anyway
          */
         spin_lock(&sctx->stat_lock);
         ++sctx->stat.super_errors;
         spin_unlock(&sctx->stat_lock);
         if (fail_cor)
             btrfs_dev_stat_inc_and_print(sector->dev,
                 BTRFS_DEV_STAT_CORRUPTION_ERRS);
         else
             btrfs_dev_stat_inc_and_print(sector->dev,
                 BTRFS_DEV_STAT_GENERATION_ERRS);
     }
 
     return fail_cor + fail_gen;
 }
 
 static void scrub_block_get(struct scrub_block *sblock)
 {
     refcount_inc(&sblock->refs);
 }
 
 static void scrub_block_put(struct scrub_block *sblock)
 {
     if (refcount_dec_and_test(&sblock->refs)) {
         int i;
 
         if (sblock->sparity)
             scrub_parity_put(sblock->sparity);
 
         for (i = 0; i < sblock->sector_count; i++)
             scrub_sector_put(sblock->sectors[i]);
         kfree(sblock);
     }
 }
 
 static void scrub_sector_get(struct scrub_sector *sector)
 {
     atomic_inc(&sector->refs);
 }
 
 static void scrub_sector_put(struct scrub_sector *sector)
 {
     if (atomic_dec_and_test(&sector->refs)) {
         if (sector->page)
             __free_page(sector->page);
         kfree(sector);
     }
 }
 
 /*
  * Throttling of IO submission, bandwidth-limit based, the timeslice is 1
  * second.  Limit can be set via /sys/fs/UUID/devinfo/devid/scrub_speed_max.
  */
 static void scrub_throttle(struct scrub_ctx *sctx)
 {
     const int time_slice = 1000;
     struct scrub_bio *sbio;
     struct btrfs_device *device;
     s64 delta;
     ktime_t now;
     u32 div;
     u64 bwlimit;
 
     sbio = sctx->bios[sctx->curr];
     device = sbio->dev;
     bwlimit = READ_ONCE(device->scrub_speed_max);
     if (bwlimit == 0)
         return;
 
     /*
      * Slice is divided into intervals when the IO is submitted, adjust by
      * bwlimit and maximum of 64 intervals.
      */
     div = max_t(u32, 1, (u32)(bwlimit / (16 * 1024 * 1024)));
     div = min_t(u32, 64, div);
 
     /* Start new epoch, set deadline */
     now = ktime_get();
     if (sctx->throttle_deadline == 0) {
         sctx->throttle_deadline = ktime_add_ms(now, time_slice / div);
         sctx->throttle_sent = 0;
     }
 
     /* Still in the time to send? */
     if (ktime_before(now, sctx->throttle_deadline)) {
         /* If current bio is within the limit, send it */
         sctx->throttle_sent += sbio->bio->bi_iter.bi_size;
         if (sctx->throttle_sent <= div_u64(bwlimit, div))
             return;
 
         /* We're over the limit, sleep until the rest of the slice */
         delta = ktime_ms_delta(sctx->throttle_deadline, now);
     } else {
         /* New request after deadline, start new epoch */
         delta = 0;
     }
 
     if (delta) {
         long timeout;
 
         timeout = div_u64(delta * HZ, 1000);
         schedule_timeout_interruptible(timeout);
     }
 
     /* Next call will start the deadline period */
     sctx->throttle_deadline = 0;
 }
 
 static void scrub_submit(struct scrub_ctx *sctx)
 {
     struct scrub_bio *sbio;
 
     if (sctx->curr == -1)
         return;
 
     scrub_throttle(sctx);
 
     sbio = sctx->bios[sctx->curr];
     sctx->curr = -1;
     scrub_pending_bio_inc(sctx);
     btrfsic_check_bio(sbio->bio);
     submit_bio(sbio->bio);
 }
 
 static int scrub_add_sector_to_rd_bio(struct scrub_ctx *sctx,
                       struct scrub_sector *sector)
 {
     struct scrub_block *sblock = sector->sblock;
     struct scrub_bio *sbio;
     const u32 sectorsize = sctx->fs_info->sectorsize;
     int ret;
 
 again:
     /*
      * grab a fresh bio or wait for one to become available
      */
     while (sctx->curr == -1) {
         spin_lock(&sctx->list_lock);
         sctx->curr = sctx->first_free;
         if (sctx->curr != -1) {
             sctx->first_free = sctx->bios[sctx->curr]->next_free;
             sctx->bios[sctx->curr]->next_free = -1;
             sctx->bios[sctx->curr]->sector_count = 0;
             spin_unlock(&sctx->list_lock);
         } else {
             spin_unlock(&sctx->list_lock);
             wait_event(sctx->list_wait, sctx->first_free != -1);
         }
     }
     sbio = sctx->bios[sctx->curr];
     if (sbio->sector_count == 0) {
         sbio->physical = sector->physical;
         sbio->logical = sector->logical;
         sbio->dev = sector->dev;
         if (!sbio->bio) {
             sbio->bio = bio_alloc(sbio->dev->bdev, sctx->sectors_per_bio,
                           REQ_OP_READ, GFP_NOFS);
         }
         sbio->bio->bi_private = sbio;
         sbio->bio->bi_end_io = scrub_bio_end_io;
         sbio->bio->bi_iter.bi_sector = sbio->physical >> 9;
         sbio->status = 0;
     } else if (sbio->physical + sbio->sector_count * sectorsize !=
            sector->physical ||
            sbio->logical + sbio->sector_count * sectorsize !=
            sector->logical ||
            sbio->dev != sector->dev) {
         scrub_submit(sctx);
         goto again;
     }
 
     sbio->sectors[sbio->sector_count] = sector;
     ret = bio_add_page(sbio->bio, sector->page, sectorsize, 0);
     if (ret != sectorsize) {
         if (sbio->sector_count < 1) {
             bio_put(sbio->bio);
             sbio->bio = NULL;
             return -EIO;
         }
         scrub_submit(sctx);
         goto again;
     }
 
     scrub_block_get(sblock); /* one for the page added to the bio */
     atomic_inc(&sblock->outstanding_sectors);
     sbio->sector_count++;
     if (sbio->sector_count == sctx->sectors_per_bio)
         scrub_submit(sctx);
 
     return 0;
 }
 
 static void scrub_missing_raid56_end_io(struct bio *bio)
 {
     struct scrub_block *sblock = bio->bi_private;
     struct btrfs_fs_info *fs_info = sblock->sctx->fs_info;
 
     if (bio->bi_status)
         sblock->no_io_error_seen = 0;
 
     bio_put(bio);
 
     queue_work(fs_info->scrub_workers, &sblock->work);
 }
 
 static void scrub_missing_raid56_worker(struct work_struct *work)
 {
     struct scrub_block *sblock = container_of(work, struct scrub_block, work);
     struct scrub_ctx *sctx = sblock->sctx;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     u64 logical;
     struct btrfs_device *dev;
 
     logical = sblock->sectors[0]->logical;
     dev = sblock->sectors[0]->dev;
 
     if (sblock->no_io_error_seen)
         scrub_recheck_block_checksum(sblock);
 
     if (!sblock->no_io_error_seen) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.read_errors++;
         spin_unlock(&sctx->stat_lock);
         btrfs_err_rl_in_rcu(fs_info,
             "IO error rebuilding logical %llu for dev %s",
             logical, rcu_str_deref(dev->name));
     } else if (sblock->header_error || sblock->checksum_error) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.uncorrectable_errors++;
         spin_unlock(&sctx->stat_lock);
         btrfs_err_rl_in_rcu(fs_info,
             "failed to rebuild valid logical %llu for dev %s",
             logical, rcu_str_deref(dev->name));
     } else {
         scrub_write_block_to_dev_replace(sblock);
     }
 
     if (sctx->is_dev_replace && sctx->flush_all_writes) {
         mutex_lock(&sctx->wr_lock);
         scrub_wr_submit(sctx);
         mutex_unlock(&sctx->wr_lock);
     }
 
     scrub_block_put(sblock);
     scrub_pending_bio_dec(sctx);
 }
 
 static void scrub_missing_raid56_pages(struct scrub_block *sblock)
 {
     struct scrub_ctx *sctx = sblock->sctx;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     u64 length = sblock->sector_count << fs_info->sectorsize_bits;
     u64 logical = sblock->sectors[0]->logical;
     struct btrfs_io_context *bioc = NULL;
     struct bio *bio;
     struct btrfs_raid_bio *rbio;
     int ret;
     int i;
 
     btrfs_bio_counter_inc_blocked(fs_info);
     ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS, logical,
                    &length, &bioc);
     if (ret || !bioc || !bioc->raid_map)
         goto bioc_out;
 
     if (WARN_ON(!sctx->is_dev_replace ||
             !(bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK))) {
         /*
          * We shouldn't be scrubbing a missing device. Even for dev
          * replace, we should only get here for RAID 5/6. We either
          * managed to mount something with no mirrors remaining or
          * there's a bug in scrub_find_good_copy()/btrfs_map_block().
          */
         goto bioc_out;
     }
 
     bio = bio_alloc(NULL, BIO_MAX_VECS, REQ_OP_READ, GFP_NOFS);
     bio->bi_iter.bi_sector = logical >> 9;
     bio->bi_private = sblock;
     bio->bi_end_io = scrub_missing_raid56_end_io;
 
     rbio = raid56_alloc_missing_rbio(bio, bioc);
     if (!rbio)
         goto rbio_out;
 
     for (i = 0; i < sblock->sector_count; i++) {
         struct scrub_sector *sector = sblock->sectors[i];
 
         /*
          * For now, our scrub is still one page per sector, so pgoff
          * is always 0.
          */
         raid56_add_scrub_pages(rbio, sector->page, 0, sector->logical);
     }
 
     INIT_WORK(&sblock->work, scrub_missing_raid56_worker);
     scrub_block_get(sblock);
     scrub_pending_bio_inc(sctx);
     raid56_submit_missing_rbio(rbio);
     return;
 
 rbio_out:
     bio_put(bio);
 bioc_out:
     btrfs_bio_counter_dec(fs_info);
     btrfs_put_bioc(bioc);
     spin_lock(&sctx->stat_lock);
     sctx->stat.malloc_errors++;
     spin_unlock(&sctx->stat_lock);
 }
 
 static int scrub_sectors(struct scrub_ctx *sctx, u64 logical, u32 len,
                u64 physical, struct btrfs_device *dev, u64 flags,
                u64 gen, int mirror_num, u8 *csum,
                u64 physical_for_dev_replace)
 {
     struct scrub_block *sblock;
     const u32 sectorsize = sctx->fs_info->sectorsize;
     int index;
 
     sblock = kzalloc(sizeof(*sblock), GFP_KERNEL);
     if (!sblock) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.malloc_errors++;
         spin_unlock(&sctx->stat_lock);
         return -ENOMEM;
     }
 
     /* one ref inside this function, plus one for each page added to
      * a bio later on */
     refcount_set(&sblock->refs, 1);
     sblock->sctx = sctx;
     sblock->no_io_error_seen = 1;
 
     for (index = 0; len > 0; index++) {
         struct scrub_sector *sector;
         /*
          * Here we will allocate one page for one sector to scrub.
          * This is fine if PAGE_SIZE == sectorsize, but will cost
          * more memory for PAGE_SIZE > sectorsize case.
          */
         u32 l = min(sectorsize, len);
 
         sector = kzalloc(sizeof(*sector), GFP_KERNEL);
         if (!sector) {
 leave_nomem:
             spin_lock(&sctx->stat_lock);
             sctx->stat.malloc_errors++;
             spin_unlock(&sctx->stat_lock);
             scrub_block_put(sblock);
             return -ENOMEM;
         }
         ASSERT(index < SCRUB_MAX_SECTORS_PER_BLOCK);
         scrub_sector_get(sector);
         sblock->sectors[index] = sector;
         sector->sblock = sblock;
         sector->dev = dev;
         sector->flags = flags;
         sector->generation = gen;
         sector->logical = logical;
         sector->physical = physical;
         sector->physical_for_dev_replace = physical_for_dev_replace;
         sector->mirror_num = mirror_num;
         if (csum) {
             sector->have_csum = 1;
             memcpy(sector->csum, csum, sctx->fs_info->csum_size);
         } else {
             sector->have_csum = 0;
         }
         sblock->sector_count++;
         sector->page = alloc_page(GFP_KERNEL);
         if (!sector->page)
             goto leave_nomem;
         len -= l;
         logical += l;
         physical += l;
         physical_for_dev_replace += l;
     }
 
     WARN_ON(sblock->sector_count == 0);
     if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state)) {
         /*
          * This case should only be hit for RAID 5/6 device replace. See
          * the comment in scrub_missing_raid56_pages() for details.
          */
         scrub_missing_raid56_pages(sblock);
     } else {
         for (index = 0; index < sblock->sector_count; index++) {
             struct scrub_sector *sector = sblock->sectors[index];
             int ret;
 
             ret = scrub_add_sector_to_rd_bio(sctx, sector);
             if (ret) {
                 scrub_block_put(sblock);
                 return ret;
             }
         }
 
         if (flags & BTRFS_EXTENT_FLAG_SUPER)
             scrub_submit(sctx);
     }
 
     /* last one frees, either here or in bio completion for last page */
     scrub_block_put(sblock);
     return 0;
 }
 
 static void scrub_bio_end_io(struct bio *bio)
 {
     struct scrub_bio *sbio = bio->bi_private;
     struct btrfs_fs_info *fs_info = sbio->dev->fs_info;
 
     sbio->status = bio->bi_status;
     sbio->bio = bio;
 
     queue_work(fs_info->scrub_workers, &sbio->work);
 }
 
 static void scrub_bio_end_io_worker(struct work_struct *work)
 {
     struct scrub_bio *sbio = container_of(work, struct scrub_bio, work);
     struct scrub_ctx *sctx = sbio->sctx;
     int i;
 
     ASSERT(sbio->sector_count <= SCRUB_SECTORS_PER_BIO);
     if (sbio->status) {
         for (i = 0; i < sbio->sector_count; i++) {
             struct scrub_sector *sector = sbio->sectors[i];
 
             sector->io_error = 1;
             sector->sblock->no_io_error_seen = 0;
         }
     }
 
     /* Now complete the scrub_block items that have all pages completed */
     for (i = 0; i < sbio->sector_count; i++) {
         struct scrub_sector *sector = sbio->sectors[i];
         struct scrub_block *sblock = sector->sblock;
 
         if (atomic_dec_and_test(&sblock->outstanding_sectors))
             scrub_block_complete(sblock);
         scrub_block_put(sblock);
     }
 
     bio_put(sbio->bio);
     sbio->bio = NULL;
     spin_lock(&sctx->list_lock);
     sbio->next_free = sctx->first_free;
     sctx->first_free = sbio->index;
     spin_unlock(&sctx->list_lock);
 
     if (sctx->is_dev_replace && sctx->flush_all_writes) {
         mutex_lock(&sctx->wr_lock);
         scrub_wr_submit(sctx);
         mutex_unlock(&sctx->wr_lock);
     }
 
     scrub_pending_bio_dec(sctx);
 }
 
 static inline void __scrub_mark_bitmap(struct scrub_parity *sparity,
                        unsigned long *bitmap,
                        u64 start, u32 len)
 {
     u64 offset;
     u32 nsectors;
     u32 sectorsize_bits = sparity->sctx->fs_info->sectorsize_bits;
 
     if (len >= sparity->stripe_len) {
         bitmap_set(bitmap, 0, sparity->nsectors);
         return;
     }
 
     start -= sparity->logic_start;
     start = div64_u64_rem(start, sparity->stripe_len, &offset);
     offset = offset >> sectorsize_bits;
     nsectors = len >> sectorsize_bits;
 
     if (offset + nsectors <= sparity->nsectors) {
         bitmap_set(bitmap, offset, nsectors);
         return;
     }
 
     bitmap_set(bitmap, offset, sparity->nsectors - offset);
     bitmap_set(bitmap, 0, nsectors - (sparity->nsectors - offset));
 }
 
 static inline void scrub_parity_mark_sectors_error(struct scrub_parity *sparity,
                            u64 start, u32 len)
 {
     __scrub_mark_bitmap(sparity, &sparity->ebitmap, start, len);
 }
 
 static inline void scrub_parity_mark_sectors_data(struct scrub_parity *sparity,
                           u64 start, u32 len)
 {
     __scrub_mark_bitmap(sparity, &sparity->dbitmap, start, len);
 }
 
 static void scrub_block_complete(struct scrub_block *sblock)
 {
     int corrupted = 0;
 
     if (!sblock->no_io_error_seen) {
         corrupted = 1;
         scrub_handle_errored_block(sblock);
     } else {
         /*
          * if has checksum error, write via repair mechanism in
          * dev replace case, otherwise write here in dev replace
          * case.
          */
         corrupted = scrub_checksum(sblock);
         if (!corrupted && sblock->sctx->is_dev_replace)
             scrub_write_block_to_dev_replace(sblock);
     }
 
     if (sblock->sparity && corrupted && !sblock->data_corrected) {
         u64 start = sblock->sectors[0]->logical;
         u64 end = sblock->sectors[sblock->sector_count - 1]->logical +
               sblock->sctx->fs_info->sectorsize;
 
         ASSERT(end - start <= U32_MAX);
         scrub_parity_mark_sectors_error(sblock->sparity,
                         start, end - start);
     }
 }
 
 static void drop_csum_range(struct scrub_ctx *sctx, struct btrfs_ordered_sum *sum)
 {
     sctx->stat.csum_discards += sum->len >> sctx->fs_info->sectorsize_bits;
     list_del(&sum->list);
     kfree(sum);
 }
 
 /*
  * Find the desired csum for range [logical, logical + sectorsize), and store
  * the csum into @csum.
  *
  * The search source is sctx->csum_list, which is a pre-populated list
  * storing bytenr ordered csum ranges.  We're responsible to cleanup any range
  * that is before @logical.
  *
  * Return 0 if there is no csum for the range.
  * Return 1 if there is csum for the range and copied to @csum.
  */
 static int scrub_find_csum(struct scrub_ctx *sctx, u64 logical, u8 *csum)
 {
     bool found = false;
 
     while (!list_empty(&sctx->csum_list)) {
         struct btrfs_ordered_sum *sum = NULL;
         unsigned long index;
         unsigned long num_sectors;
 
         sum = list_first_entry(&sctx->csum_list,
                        struct btrfs_ordered_sum, list);
         /* The current csum range is beyond our range, no csum found */
         if (sum->bytenr > logical)
             break;
 
         /*
          * The current sum is before our bytenr, since scrub is always
          * done in bytenr order, the csum will never be used anymore,
          * clean it up so that later calls won't bother with the range,
          * and continue search the next range.
          */
         if (sum->bytenr + sum->len <= logical) {
             drop_csum_range(sctx, sum);
             continue;
         }
 
         /* Now the csum range covers our bytenr, copy the csum */
         found = true;
         index = (logical - sum->bytenr) >> sctx->fs_info->sectorsize_bits;
         num_sectors = sum->len >> sctx->fs_info->sectorsize_bits;
 
         memcpy(csum, sum->sums + index * sctx->fs_info->csum_size,
                sctx->fs_info->csum_size);
 
         /* Cleanup the range if we're at the end of the csum range */
         if (index == num_sectors - 1)
             drop_csum_range(sctx, sum);
         break;
     }
     if (!found)
         return 0;
     return 1;
 }
 
 /* scrub extent tries to collect up to 64 kB for each bio */
 static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
             u64 logical, u32 len,
             u64 physical, struct btrfs_device *dev, u64 flags,
             u64 gen, int mirror_num)
 {
     struct btrfs_device *src_dev = dev;
     u64 src_physical = physical;
     int src_mirror = mirror_num;
     int ret;
     u8 csum[BTRFS_CSUM_SIZE];
     u32 blocksize;
 
     if (flags & BTRFS_EXTENT_FLAG_DATA) {
         if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
             blocksize = map->stripe_len;
         else
             blocksize = sctx->fs_info->sectorsize;
         spin_lock(&sctx->stat_lock);
         sctx->stat.data_extents_scrubbed++;
         sctx->stat.data_bytes_scrubbed += len;
         spin_unlock(&sctx->stat_lock);
     } else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
         if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
             blocksize = map->stripe_len;
         else
             blocksize = sctx->fs_info->nodesize;
         spin_lock(&sctx->stat_lock);
         sctx->stat.tree_extents_scrubbed++;
         sctx->stat.tree_bytes_scrubbed += len;
         spin_unlock(&sctx->stat_lock);
     } else {
         blocksize = sctx->fs_info->sectorsize;
         WARN_ON(1);
     }
 
     /*
      * For dev-replace case, we can have @dev being a missing device.
      * Regular scrub will avoid its execution on missing device at all,
      * as that would trigger tons of read error.
      *
      * Reading from missing device will cause read error counts to
      * increase unnecessarily.
      * So here we change the read source to a good mirror.
      */
     if (sctx->is_dev_replace && !dev->bdev)
         scrub_find_good_copy(sctx->fs_info, logical, len, &src_physical,
                      &src_dev, &src_mirror);
     while (len) {
         u32 l = min(len, blocksize);
         int have_csum = 0;
 
         if (flags & BTRFS_EXTENT_FLAG_DATA) {
             /* push csums to sbio */
             have_csum = scrub_find_csum(sctx, logical, csum);
             if (have_csum == 0)
                 ++sctx->stat.no_csum;
         }
         ret = scrub_sectors(sctx, logical, l, src_physical, src_dev,
                     flags, gen, src_mirror,
                     have_csum ? csum : NULL, physical);
         if (ret)
             return ret;
         len -= l;
         logical += l;
         physical += l;
         src_physical += l;
     }
     return 0;
 }
 
 static int scrub_sectors_for_parity(struct scrub_parity *sparity,
                   u64 logical, u32 len,
                   u64 physical, struct btrfs_device *dev,
                   u64 flags, u64 gen, int mirror_num, u8 *csum)
 {
     struct scrub_ctx *sctx = sparity->sctx;
     struct scrub_block *sblock;
     const u32 sectorsize = sctx->fs_info->sectorsize;
     int index;
 
     ASSERT(IS_ALIGNED(len, sectorsize));
 
     sblock = kzalloc(sizeof(*sblock), GFP_KERNEL);
     if (!sblock) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.malloc_errors++;
         spin_unlock(&sctx->stat_lock);
         return -ENOMEM;
     }
 
     /* one ref inside this function, plus one for each page added to
      * a bio later on */
     refcount_set(&sblock->refs, 1);
     sblock->sctx = sctx;
     sblock->no_io_error_seen = 1;
     sblock->sparity = sparity;
     scrub_parity_get(sparity);
 
     for (index = 0; len > 0; index++) {
         struct scrub_sector *sector;
 
         sector = kzalloc(sizeof(*sector), GFP_KERNEL);
         if (!sector) {
 leave_nomem:
             spin_lock(&sctx->stat_lock);
             sctx->stat.malloc_errors++;
             spin_unlock(&sctx->stat_lock);
             scrub_block_put(sblock);
             return -ENOMEM;
         }
         ASSERT(index < SCRUB_MAX_SECTORS_PER_BLOCK);
         /* For scrub block */
         scrub_sector_get(sector);
         sblock->sectors[index] = sector;
         /* For scrub parity */
         scrub_sector_get(sector);
         list_add_tail(&sector->list, &sparity->sectors_list);
         sector->sblock = sblock;
         sector->dev = dev;
         sector->flags = flags;
         sector->generation = gen;
         sector->logical = logical;
         sector->physical = physical;
         sector->mirror_num = mirror_num;
         if (csum) {
             sector->have_csum = 1;
             memcpy(sector->csum, csum, sctx->fs_info->csum_size);
         } else {
             sector->have_csum = 0;
         }
         sblock->sector_count++;
         sector->page = alloc_page(GFP_KERNEL);
         if (!sector->page)
             goto leave_nomem;
 
 
         /* Iterate over the stripe range in sectorsize steps */
         len -= sectorsize;
         logical += sectorsize;
         physical += sectorsize;
     }
 
     WARN_ON(sblock->sector_count == 0);
     for (index = 0; index < sblock->sector_count; index++) {
         struct scrub_sector *sector = sblock->sectors[index];
         int ret;
 
         ret = scrub_add_sector_to_rd_bio(sctx, sector);
         if (ret) {
             scrub_block_put(sblock);
             return ret;
         }
     }
 
     /* Last one frees, either here or in bio completion for last sector */
     scrub_block_put(sblock);
     return 0;
 }
 
 static int scrub_extent_for_parity(struct scrub_parity *sparity,
                    u64 logical, u32 len,
                    u64 physical, struct btrfs_device *dev,
                    u64 flags, u64 gen, int mirror_num)
 {
     struct scrub_ctx *sctx = sparity->sctx;
     int ret;
     u8 csum[BTRFS_CSUM_SIZE];
     u32 blocksize;
 
     if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state)) {
         scrub_parity_mark_sectors_error(sparity, logical, len);
         return 0;
     }
 
     if (flags & BTRFS_EXTENT_FLAG_DATA) {
         blocksize = sparity->stripe_len;
     } else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
         blocksize = sparity->stripe_len;
     } else {
         blocksize = sctx->fs_info->sectorsize;
         WARN_ON(1);
     }
 
     while (len) {
         u32 l = min(len, blocksize);
         int have_csum = 0;
 
         if (flags & BTRFS_EXTENT_FLAG_DATA) {
             /* push csums to sbio */
             have_csum = scrub_find_csum(sctx, logical, csum);
             if (have_csum == 0)
                 goto skip;
         }
         ret = scrub_sectors_for_parity(sparity, logical, l, physical, dev,
                          flags, gen, mirror_num,
                          have_csum ? csum : NULL);
         if (ret)
             return ret;
 skip:
         len -= l;
         logical += l;
         physical += l;
     }
     return 0;
 }
 
 /*
  * Given a physical address, this will calculate it's
  * logical offset. if this is a parity stripe, it will return
  * the most left data stripe's logical offset.
  *
  * return 0 if it is a data stripe, 1 means parity stripe.
  */
 static int get_raid56_logic_offset(u64 physical, int num,
                    struct map_lookup *map, u64 *offset,
                    u64 *stripe_start)
 {
     int i;
     int j = 0;
     u64 stripe_nr;
     u64 last_offset;
     u32 stripe_index;
     u32 rot;
     const int data_stripes = nr_data_stripes(map);
 
     last_offset = (physical - map->stripes[num].physical) * data_stripes;
     if (stripe_start)
         *stripe_start = last_offset;
 
     *offset = last_offset;
     for (i = 0; i < data_stripes; i++) {
         *offset = last_offset + i * map->stripe_len;
 
         stripe_nr = div64_u64(*offset, map->stripe_len);
         stripe_nr = div_u64(stripe_nr, data_stripes);
 
         /* Work out the disk rotation on this stripe-set */
         stripe_nr = div_u64_rem(stripe_nr, map->num_stripes, &rot);
         /* calculate which stripe this data locates */
         rot += i;
         stripe_index = rot % map->num_stripes;
         if (stripe_index == num)
             return 0;
         if (stripe_index < num)
             j++;
     }
     *offset = last_offset + j * map->stripe_len;
     return 1;
 }
 
 static void scrub_free_parity(struct scrub_parity *sparity)
 {
     struct scrub_ctx *sctx = sparity->sctx;
     struct scrub_sector *curr, *next;
     int nbits;
 
     nbits = bitmap_weight(&sparity->ebitmap, sparity->nsectors);
     if (nbits) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.read_errors += nbits;
         sctx->stat.uncorrectable_errors += nbits;
         spin_unlock(&sctx->stat_lock);
     }
 
     list_for_each_entry_safe(curr, next, &sparity->sectors_list, list) {
         list_del_init(&curr->list);
         scrub_sector_put(curr);
     }
 
     kfree(sparity);
 }
 
 static void scrub_parity_bio_endio_worker(struct work_struct *work)
 {
     struct scrub_parity *sparity = container_of(work, struct scrub_parity,
                             work);
     struct scrub_ctx *sctx = sparity->sctx;
 
     scrub_free_parity(sparity);
     scrub_pending_bio_dec(sctx);
 }
 
 static void scrub_parity_bio_endio(struct bio *bio)
 {
     struct scrub_parity *sparity = bio->bi_private;
     struct btrfs_fs_info *fs_info = sparity->sctx->fs_info;
 
     if (bio->bi_status)
         bitmap_or(&sparity->ebitmap, &sparity->ebitmap,
               &sparity->dbitmap, sparity->nsectors);
 
     bio_put(bio);
 
     INIT_WORK(&sparity->work, scrub_parity_bio_endio_worker);
     queue_work(fs_info->scrub_parity_workers, &sparity->work);
 }
 
 static void scrub_parity_check_and_repair(struct scrub_parity *sparity)
 {
     struct scrub_ctx *sctx = sparity->sctx;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     struct bio *bio;
     struct btrfs_raid_bio *rbio;
     struct btrfs_io_context *bioc = NULL;
     u64 length;
     int ret;
 
     if (!bitmap_andnot(&sparity->dbitmap, &sparity->dbitmap,
                &sparity->ebitmap, sparity->nsectors))
         goto out;
 
     length = sparity->logic_end - sparity->logic_start;
 
     btrfs_bio_counter_inc_blocked(fs_info);
     ret = btrfs_map_sblock(fs_info, BTRFS_MAP_WRITE, sparity->logic_start,
                    &length, &bioc);
     if (ret || !bioc || !bioc->raid_map)
         goto bioc_out;
 
     bio = bio_alloc(NULL, BIO_MAX_VECS, REQ_OP_READ, GFP_NOFS);
     bio->bi_iter.bi_sector = sparity->logic_start >> 9;
     bio->bi_private = sparity;
     bio->bi_end_io = scrub_parity_bio_endio;
 
     rbio = raid56_parity_alloc_scrub_rbio(bio, bioc,
                           sparity->scrub_dev,
                           &sparity->dbitmap,
                           sparity->nsectors);
     if (!rbio)
         goto rbio_out;
 
     scrub_pending_bio_inc(sctx);
     raid56_parity_submit_scrub_rbio(rbio);
     return;
 
 rbio_out:
     bio_put(bio);
 bioc_out:
     btrfs_bio_counter_dec(fs_info);
     btrfs_put_bioc(bioc);
     bitmap_or(&sparity->ebitmap, &sparity->ebitmap, &sparity->dbitmap,
           sparity->nsectors);
     spin_lock(&sctx->stat_lock);
     sctx->stat.malloc_errors++;
     spin_unlock(&sctx->stat_lock);
 out:
     scrub_free_parity(sparity);
 }
 
 static void scrub_parity_get(struct scrub_parity *sparity)
 {
     refcount_inc(&sparity->refs);
 }
 
 static void scrub_parity_put(struct scrub_parity *sparity)
 {
     if (!refcount_dec_and_test(&sparity->refs))
         return;
 
     scrub_parity_check_and_repair(sparity);
 }
 
 /*
  * Return 0 if the extent item range covers any byte of the range.
  * Return <0 if the extent item is before @search_start.
  * Return >0 if the extent item is after @start_start + @search_len.
  */
 static int compare_extent_item_range(struct btrfs_path *path,
                      u64 search_start, u64 search_len)
 {
     struct btrfs_fs_info *fs_info = path->nodes[0]->fs_info;
     u64 len;
     struct btrfs_key key;
 
     btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
     ASSERT(key.type == BTRFS_EXTENT_ITEM_KEY ||
            key.type == BTRFS_METADATA_ITEM_KEY);
     if (key.type == BTRFS_METADATA_ITEM_KEY)
         len = fs_info->nodesize;
     else
         len = key.offset;
 
     if (key.objectid + len <= search_start)
         return -1;
     if (key.objectid >= search_start + search_len)
         return 1;
     return 0;
 }
 
 /*
  * Locate one extent item which covers any byte in range
  * [@search_start, @search_start + @search_length)
  *
  * If the path is not initialized, we will initialize the search by doing
  * a btrfs_search_slot().
  * If the path is already initialized, we will use the path as the initial
  * slot, to avoid duplicated btrfs_search_slot() calls.
  *
  * NOTE: If an extent item starts before @search_start, we will still
  * return the extent item. This is for data extent crossing stripe boundary.
  *
  * Return 0 if we found such extent item, and @path will point to the extent item.
  * Return >0 if no such extent item can be found, and @path will be released.
  * Return <0 if hit fatal error, and @path will be released.
  */
 static int find_first_extent_item(struct btrfs_root *extent_root,
                   struct btrfs_path *path,
                   u64 search_start, u64 search_len)
 {
     struct btrfs_fs_info *fs_info = extent_root->fs_info;
     struct btrfs_key key;
     int ret;
 
     /* Continue using the existing path */
     if (path->nodes[0])
         goto search_forward;
 
     if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
         key.type = BTRFS_METADATA_ITEM_KEY;
     else
         key.type = BTRFS_EXTENT_ITEM_KEY;
     key.objectid = search_start;
     key.offset = (u64)-1;
 
     ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
     if (ret < 0)
         return ret;
 
     ASSERT(ret > 0);
     /*
      * Here we intentionally pass 0 as @min_objectid, as there could be
      * an extent item starting before @search_start.
      */
     ret = btrfs_previous_extent_item(extent_root, path, 0);
     if (ret < 0)
         return ret;
     /*
      * No matter whether we have found an extent item, the next loop will
      * properly do every check on the key.
      */
 search_forward:
     while (true) {
         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
         if (key.objectid >= search_start + search_len)
             break;
         if (key.type != BTRFS_METADATA_ITEM_KEY &&
             key.type != BTRFS_EXTENT_ITEM_KEY)
             goto next;
 
         ret = compare_extent_item_range(path, search_start, search_len);
         if (ret == 0)
             return ret;
         if (ret > 0)
             break;
 next:
         path->slots[0]++;
         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
             ret = btrfs_next_leaf(extent_root, path);
             if (ret) {
                 /* Either no more item or fatal error */
                 btrfs_release_path(path);
                 return ret;
             }
         }
     }
     btrfs_release_path(path);
     return 1;
 }
 
 static void get_extent_info(struct btrfs_path *path, u64 *extent_start_ret,
                 u64 *size_ret, u64 *flags_ret, u64 *generation_ret)
 {
     struct btrfs_key key;
     struct btrfs_extent_item *ei;
 
     btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
     ASSERT(key.type == BTRFS_METADATA_ITEM_KEY ||
            key.type == BTRFS_EXTENT_ITEM_KEY);
     *extent_start_ret = key.objectid;
     if (key.type == BTRFS_METADATA_ITEM_KEY)
         *size_ret = path->nodes[0]->fs_info->nodesize;
     else
         *size_ret = key.offset;
     ei = btrfs_item_ptr(path->nodes[0], path->slots[0], struct btrfs_extent_item);
     *flags_ret = btrfs_extent_flags(path->nodes[0], ei);
     *generation_ret = btrfs_extent_generation(path->nodes[0], ei);
 }
 
 static bool does_range_cross_boundary(u64 extent_start, u64 extent_len,
                       u64 boundary_start, u64 boudary_len)
 {
     return (extent_start < boundary_start &&
         extent_start + extent_len > boundary_start) ||
            (extent_start < boundary_start + boudary_len &&
         extent_start + extent_len > boundary_start + boudary_len);
 }
 
 static int scrub_raid56_data_stripe_for_parity(struct scrub_ctx *sctx,
                            struct scrub_parity *sparity,
                            struct map_lookup *map,
                            struct btrfs_device *sdev,
                            struct btrfs_path *path,
                            u64 logical)
 {
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     struct btrfs_root *extent_root = btrfs_extent_root(fs_info, logical);
     struct btrfs_root *csum_root = btrfs_csum_root(fs_info, logical);
     u64 cur_logical = logical;
     int ret;
 
     ASSERT(map->type & BTRFS_BLOCK_GROUP_RAID56_MASK);
 
     /* Path must not be populated */
     ASSERT(!path->nodes[0]);
 
     while (cur_logical < logical + map->stripe_len) {
         struct btrfs_io_context *bioc = NULL;
         struct btrfs_device *extent_dev;
         u64 extent_start;
         u64 extent_size;
         u64 mapped_length;
         u64 extent_flags;
         u64 extent_gen;
         u64 extent_physical;
         u64 extent_mirror_num;
 
         ret = find_first_extent_item(extent_root, path, cur_logical,
                          logical + map->stripe_len - cur_logical);
         /* No more extent item in this data stripe */
         if (ret > 0) {
             ret = 0;
             break;
         }
         if (ret < 0)
             break;
         get_extent_info(path, &extent_start, &extent_size, &extent_flags,
                 &extent_gen);
 
         /* Metadata should not cross stripe boundaries */
         if ((extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) &&
             does_range_cross_boundary(extent_start, extent_size,
                           logical, map->stripe_len)) {
             btrfs_err(fs_info,
     "scrub: tree block %llu spanning stripes, ignored. logical=%llu",
                   extent_start, logical);
             spin_lock(&sctx->stat_lock);
             sctx->stat.uncorrectable_errors++;
             spin_unlock(&sctx->stat_lock);
             cur_logical += extent_size;
             continue;
         }
 
         /* Skip hole range which doesn't have any extent */
         cur_logical = max(extent_start, cur_logical);
 
         /* Truncate the range inside this data stripe */
         extent_size = min(extent_start + extent_size,
                   logical + map->stripe_len) - cur_logical;
         extent_start = cur_logical;
         ASSERT(extent_size <= U32_MAX);
 
         scrub_parity_mark_sectors_data(sparity, extent_start, extent_size);
 
         mapped_length = extent_size;
         ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, extent_start,
                       &mapped_length, &bioc, 0);
         if (!ret && (!bioc || mapped_length < extent_size))
             ret = -EIO;
         if (ret) {
             btrfs_put_bioc(bioc);
             scrub_parity_mark_sectors_error(sparity, extent_start,
                             extent_size);
             break;
         }
         extent_physical = bioc->stripes[0].physical;
         extent_mirror_num = bioc->mirror_num;
         extent_dev = bioc->stripes[0].dev;
         btrfs_put_bioc(bioc);
 
         ret = btrfs_lookup_csums_range(csum_root, extent_start,
                            extent_start + extent_size - 1,
                            &sctx->csum_list, 1);
         if (ret) {
             scrub_parity_mark_sectors_error(sparity, extent_start,
                             extent_size);
             break;
         }
 
         ret = scrub_extent_for_parity(sparity, extent_start,
                           extent_size, extent_physical,
                           extent_dev, extent_flags,
                           extent_gen, extent_mirror_num);
         scrub_free_csums(sctx);
 
         if (ret) {
             scrub_parity_mark_sectors_error(sparity, extent_start,
                             extent_size);
             break;
         }
 
         cond_resched();
         cur_logical += extent_size;
     }
     btrfs_release_path(path);
     return ret;
 }
 
 static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
                           struct map_lookup *map,
                           struct btrfs_device *sdev,
                           u64 logic_start,
                           u64 logic_end)
 {
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     struct btrfs_path *path;
     u64 cur_logical;
     int ret;
     struct scrub_parity *sparity;
     int nsectors;
 
     path = btrfs_alloc_path();
     if (!path) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.malloc_errors++;
         spin_unlock(&sctx->stat_lock);
         return -ENOMEM;
     }
     path->search_commit_root = 1;
     path->skip_locking = 1;
 
     ASSERT(map->stripe_len <= U32_MAX);
     nsectors = map->stripe_len >> fs_info->sectorsize_bits;
     ASSERT(nsectors <= BITS_PER_LONG);
     sparity = kzalloc(sizeof(struct scrub_parity), GFP_NOFS);
     if (!sparity) {
         spin_lock(&sctx->stat_lock);
         sctx->stat.malloc_errors++;
         spin_unlock(&sctx->stat_lock);
         btrfs_free_path(path);
         return -ENOMEM;
     }
 
     ASSERT(map->stripe_len <= U32_MAX);
     sparity->stripe_len = map->stripe_len;
     sparity->nsectors = nsectors;
     sparity->sctx = sctx;
     sparity->scrub_dev = sdev;
     sparity->logic_start = logic_start;
     sparity->logic_end = logic_end;
     refcount_set(&sparity->refs, 1);
     INIT_LIST_HEAD(&sparity->sectors_list);
 
     ret = 0;
     for (cur_logical = logic_start; cur_logical < logic_end;
          cur_logical += map->stripe_len) {
         ret = scrub_raid56_data_stripe_for_parity(sctx, sparity, map,
                               sdev, path, cur_logical);
         if (ret < 0)
             break;
     }
 
     scrub_parity_put(sparity);
     scrub_submit(sctx);
     mutex_lock(&sctx->wr_lock);
     scrub_wr_submit(sctx);
     mutex_unlock(&sctx->wr_lock);
 
     btrfs_free_path(path);
     return ret < 0 ? ret : 0;
 }
 
 static void sync_replace_for_zoned(struct scrub_ctx *sctx)
 {
     if (!btrfs_is_zoned(sctx->fs_info))
         return;
 
     sctx->flush_all_writes = true;
     scrub_submit(sctx);
     mutex_lock(&sctx->wr_lock);
     scrub_wr_submit(sctx);
     mutex_unlock(&sctx->wr_lock);
 
     wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
 }
 
 static int sync_write_pointer_for_zoned(struct scrub_ctx *sctx, u64 logical,
                     u64 physical, u64 physical_end)
 {
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     int ret = 0;
 
     if (!btrfs_is_zoned(fs_info))
         return 0;
 
     wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
 
     mutex_lock(&sctx->wr_lock);
     if (sctx->write_pointer < physical_end) {
         ret = btrfs_sync_zone_write_pointer(sctx->wr_tgtdev, logical,
                             physical,
                             sctx->write_pointer);
         if (ret)
             btrfs_err(fs_info,
                   "zoned: failed to recover write pointer");
     }
     mutex_unlock(&sctx->wr_lock);
     btrfs_dev_clear_zone_empty(sctx->wr_tgtdev, physical);
 
     return ret;
 }
 
 /*
  * Scrub one range which can only has simple mirror based profile.
  * (Including all range in SINGLE/DUP/RAID1/RAID1C*, and each stripe in
  *  RAID0/RAID10).
  *
  * Since we may need to handle a subset of block group, we need @logical_start
  * and @logical_length parameter.
  */
 static int scrub_simple_mirror(struct scrub_ctx *sctx,
                    struct btrfs_root *extent_root,
                    struct btrfs_root *csum_root,
                    struct btrfs_block_group *bg,
                    struct map_lookup *map,
                    u64 logical_start, u64 logical_length,
                    struct btrfs_device *device,
                    u64 physical, int mirror_num)
 {
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     const u64 logical_end = logical_start + logical_length;
     /* An artificial limit, inherit from old scrub behavior */
     const u32 max_length = SZ_64K;
     struct btrfs_path path = { 0 };
     u64 cur_logical = logical_start;
     int ret;
 
     /* The range must be inside the bg */
     ASSERT(logical_start >= bg->start && logical_end <= bg->start + bg->length);
 
     path.search_commit_root = 1;
     path.skip_locking = 1;
     /* Go through each extent items inside the logical range */
     while (cur_logical < logical_end) {
         u64 extent_start;
         u64 extent_len;
         u64 extent_flags;
         u64 extent_gen;
         u64 scrub_len;
 
         /* Canceled? */
         if (atomic_read(&fs_info->scrub_cancel_req) ||
             atomic_read(&sctx->cancel_req)) {
             ret = -ECANCELED;
             break;
         }
         /* Paused? */
         if (atomic_read(&fs_info->scrub_pause_req)) {
             /* Push queued extents */
             sctx->flush_all_writes = true;
             scrub_submit(sctx);
             mutex_lock(&sctx->wr_lock);
             scrub_wr_submit(sctx);
             mutex_unlock(&sctx->wr_lock);
             wait_event(sctx->list_wait,
                    atomic_read(&sctx->bios_in_flight) == 0);
             sctx->flush_all_writes = false;
             scrub_blocked_if_needed(fs_info);
         }
         /* Block group removed? */
         spin_lock(&bg->lock);
         if (bg->removed) {
             spin_unlock(&bg->lock);
             ret = 0;
             break;
         }
         spin_unlock(&bg->lock);
 
         ret = find_first_extent_item(extent_root, &path, cur_logical,
                          logical_end - cur_logical);
         if (ret > 0) {
             /* No more extent, just update the accounting */
             sctx->stat.last_physical = physical + logical_length;
             ret = 0;
             break;
         }
         if (ret < 0)
             break;
         get_extent_info(&path, &extent_start, &extent_len,
                 &extent_flags, &extent_gen);
         /* Skip hole range which doesn't have any extent */
         cur_logical = max(extent_start, cur_logical);
 
         /*
          * Scrub len has three limits:
          * - Extent size limit
          * - Scrub range limit
          *   This is especially imporatant for RAID0/RAID10 to reuse
          *   this function
          * - Max scrub size limit
          */
         scrub_len = min(min(extent_start + extent_len,
                     logical_end), cur_logical + max_length) -
                 cur_logical;
 
         if (extent_flags & BTRFS_EXTENT_FLAG_DATA) {
             ret = btrfs_lookup_csums_range(csum_root, cur_logical,
                     cur_logical + scrub_len - 1,
                     &sctx->csum_list, 1);
             if (ret)
                 break;
         }
         if ((extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) &&
             does_range_cross_boundary(extent_start, extent_len,
                           logical_start, logical_length)) {
             btrfs_err(fs_info,
 "scrub: tree block %llu spanning boundaries, ignored. boundary=[%llu, %llu)",
                   extent_start, logical_start, logical_end);
             spin_lock(&sctx->stat_lock);
             sctx->stat.uncorrectable_errors++;
             spin_unlock(&sctx->stat_lock);
             cur_logical += scrub_len;
             continue;
         }
         ret = scrub_extent(sctx, map, cur_logical, scrub_len,
                    cur_logical - logical_start + physical,
                    device, extent_flags, extent_gen,
                    mirror_num);
         scrub_free_csums(sctx);
         if (ret)
             break;
         if (sctx->is_dev_replace)
             sync_replace_for_zoned(sctx);
         cur_logical += scrub_len;
         /* Don't hold CPU for too long time */
         cond_resched();
     }
     btrfs_release_path(&path);
     return ret;
 }
 
 /* Calculate the full stripe length for simple stripe based profiles */
 static u64 simple_stripe_full_stripe_len(const struct map_lookup *map)
 {
     ASSERT(map->type & (BTRFS_BLOCK_GROUP_RAID0 |
                 BTRFS_BLOCK_GROUP_RAID10));
 
     return map->num_stripes / map->sub_stripes * map->stripe_len;
 }
 
 /* Get the logical bytenr for the stripe */
 static u64 simple_stripe_get_logical(struct map_lookup *map,
                      struct btrfs_block_group *bg,
                      int stripe_index)
 {
     ASSERT(map->type & (BTRFS_BLOCK_GROUP_RAID0 |
                 BTRFS_BLOCK_GROUP_RAID10));
     ASSERT(stripe_index < map->num_stripes);
 
     /*
      * (stripe_index / sub_stripes) gives how many data stripes we need to
      * skip.
      */
     return (stripe_index / map->sub_stripes) * map->stripe_len + bg->start;
 }
 
 /* Get the mirror number for the stripe */
 static int simple_stripe_mirror_num(struct map_lookup *map, int stripe_index)
 {
     ASSERT(map->type & (BTRFS_BLOCK_GROUP_RAID0 |
                 BTRFS_BLOCK_GROUP_RAID10));
     ASSERT(stripe_index < map->num_stripes);
 
     /* For RAID0, it's fixed to 1, for RAID10 it's 0,1,0,1... */
     return stripe_index % map->sub_stripes + 1;
 }
 
 static int scrub_simple_stripe(struct scrub_ctx *sctx,
                    struct btrfs_root *extent_root,
                    struct btrfs_root *csum_root,
                    struct btrfs_block_group *bg,
                    struct map_lookup *map,
                    struct btrfs_device *device,
                    int stripe_index)
 {
     const u64 logical_increment = simple_stripe_full_stripe_len(map);
     const u64 orig_logical = simple_stripe_get_logical(map, bg, stripe_index);
     const u64 orig_physical = map->stripes[stripe_index].physical;
     const int mirror_num = simple_stripe_mirror_num(map, stripe_index);
     u64 cur_logical = orig_logical;
     u64 cur_physical = orig_physical;
     int ret = 0;
 
     while (cur_logical < bg->start + bg->length) {
         /*
          * Inside each stripe, RAID0 is just SINGLE, and RAID10 is
          * just RAID1, so we can reuse scrub_simple_mirror() to scrub
          * this stripe.
          */
         ret = scrub_simple_mirror(sctx, extent_root, csum_root, bg, map,
                       cur_logical, map->stripe_len, device,
                       cur_physical, mirror_num);
         if (ret)
             return ret;
         /* Skip to next stripe which belongs to the target device */
         cur_logical += logical_increment;
         /* For physical offset, we just go to next stripe */
         cur_physical += map->stripe_len;
     }
     return ret;
 }
 
 static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
                        struct btrfs_block_group *bg,
                        struct extent_map *em,
                        struct btrfs_device *scrub_dev,
                        int stripe_index)
 {
     struct btrfs_path *path;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     struct btrfs_root *root;
     struct btrfs_root *csum_root;
     struct blk_plug plug;
     struct map_lookup *map = em->map_lookup;
     const u64 profile = map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK;
     const u64 chunk_logical = bg->start;
     int ret;
     u64 physical = map->stripes[stripe_index].physical;
     const u64 dev_stripe_len = btrfs_calc_stripe_length(em);
     const u64 physical_end = physical + dev_stripe_len;
     u64 logical;
     u64 logic_end;
     /* The logical increment after finishing one stripe */
     u64 increment;
     /* Offset inside the chunk */
     u64 offset;
     u64 stripe_logical;
     u64 stripe_end;
     int stop_loop = 0;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     /*
      * work on commit root. The related disk blocks are static as
      * long as COW is applied. This means, it is save to rewrite
      * them to repair disk errors without any race conditions
      */
     path->search_commit_root = 1;
     path->skip_locking = 1;
     path->reada = READA_FORWARD;
 
     wait_event(sctx->list_wait,
            atomic_read(&sctx->bios_in_flight) == 0);
     scrub_blocked_if_needed(fs_info);
 
     root = btrfs_extent_root(fs_info, bg->start);
     csum_root = btrfs_csum_root(fs_info, bg->start);
 
     /*
      * collect all data csums for the stripe to avoid seeking during
      * the scrub. This might currently (crc32) end up to be about 1MB
      */
     blk_start_plug(&plug);
 
     if (sctx->is_dev_replace &&
         btrfs_dev_is_sequential(sctx->wr_tgtdev, physical)) {
         mutex_lock(&sctx->wr_lock);
         sctx->write_pointer = physical;
         mutex_unlock(&sctx->wr_lock);
         sctx->flush_all_writes = true;
     }
 
     /*
      * There used to be a big double loop to handle all profiles using the
      * same routine, which grows larger and more gross over time.
      *
      * So here we handle each profile differently, so simpler profiles
      * have simpler scrubbing function.
      */
     if (!(profile & (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID10 |
              BTRFS_BLOCK_GROUP_RAID56_MASK))) {
         /*
          * Above check rules out all complex profile, the remaining
          * profiles are SINGLE|DUP|RAID1|RAID1C*, which is simple
          * mirrored duplication without stripe.
          *
          * Only @physical and @mirror_num needs to calculated using
          * @stripe_index.
          */
         ret = scrub_simple_mirror(sctx, root, csum_root, bg, map,
                 bg->start, bg->length, scrub_dev,
                 map->stripes[stripe_index].physical,
                 stripe_index + 1);
         offset = 0;
         goto out;
     }
     if (profile & (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID10)) {
         ret = scrub_simple_stripe(sctx, root, csum_root, bg, map,
                       scrub_dev, stripe_index);
         offset = map->stripe_len * (stripe_index / map->sub_stripes);
         goto out;
     }
 
     /* Only RAID56 goes through the old code */
     ASSERT(map->type & BTRFS_BLOCK_GROUP_RAID56_MASK);
     ret = 0;
 
     /* Calculate the logical end of the stripe */
     get_raid56_logic_offset(physical_end, stripe_index,
                 map, &logic_end, NULL);
     logic_end += chunk_logical;
 
     /* Initialize @offset in case we need to go to out: label */
     get_raid56_logic_offset(physical, stripe_index, map, &offset, NULL);
     increment = map->stripe_len * nr_data_stripes(map);
 
     /*
      * Due to the rotation, for RAID56 it's better to iterate each stripe
      * using their physical offset.
      */
     while (physical < physical_end) {
         ret = get_raid56_logic_offset(physical, stripe_index, map,
                           &logical, &stripe_logical);
         logical += chunk_logical;
         if (ret) {
             /* it is parity strip */
             stripe_logical += chunk_logical;
             stripe_end = stripe_logical + increment;
             ret = scrub_raid56_parity(sctx, map, scrub_dev,
                           stripe_logical,
                           stripe_end);
             if (ret)
                 goto out;
             goto next;
         }
 
         /*
          * Now we're at a data stripe, scrub each extents in the range.
          *
          * At this stage, if we ignore the repair part, inside each data
          * stripe it is no different than SINGLE profile.
          * We can reuse scrub_simple_mirror() here, as the repair part
          * is still based on @mirror_num.
          */
         ret = scrub_simple_mirror(sctx, root, csum_root, bg, map,
                       logical, map->stripe_len,
                       scrub_dev, physical, 1);
         if (ret < 0)
             goto out;
 next:
         logical += increment;
         physical += map->stripe_len;
         spin_lock(&sctx->stat_lock);
         if (stop_loop)
             sctx->stat.last_physical =
                 map->stripes[stripe_index].physical + dev_stripe_len;
         else
             sctx->stat.last_physical = physical;
         spin_unlock(&sctx->stat_lock);
         if (stop_loop)
             break;
     }
 out:
     /* push queued extents */
     scrub_submit(sctx);
     mutex_lock(&sctx->wr_lock);
     scrub_wr_submit(sctx);
     mutex_unlock(&sctx->wr_lock);
 
     blk_finish_plug(&plug);
     btrfs_free_path(path);
 
     if (sctx->is_dev_replace && ret >= 0) {
         int ret2;
 
         ret2 = sync_write_pointer_for_zoned(sctx,
                 chunk_logical + offset,
                 map->stripes[stripe_index].physical,
                 physical_end);
         if (ret2)
             ret = ret2;
     }
 
     return ret < 0 ? ret : 0;
 }
 
 static noinline_for_stack int scrub_chunk(struct scrub_ctx *sctx,
                       struct btrfs_block_group *bg,
                       struct btrfs_device *scrub_dev,
                       u64 dev_offset,
                       u64 dev_extent_len)
 {
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     struct extent_map_tree *map_tree = &fs_info->mapping_tree;
     struct map_lookup *map;
     struct extent_map *em;
     int i;
     int ret = 0;
 
     read_lock(&map_tree->lock);
     em = lookup_extent_mapping(map_tree, bg->start, bg->length);
     read_unlock(&map_tree->lock);
 
     if (!em) {
         /*
          * Might have been an unused block group deleted by the cleaner
          * kthread or relocation.
          */
         spin_lock(&bg->lock);
         if (!bg->removed)
             ret = -EINVAL;
         spin_unlock(&bg->lock);
 
         return ret;
     }
     if (em->start != bg->start)
         goto out;
     if (em->len < dev_extent_len)
         goto out;
 
     map = em->map_lookup;
     for (i = 0; i < map->num_stripes; ++i) {
         if (map->stripes[i].dev->bdev == scrub_dev->bdev &&
             map->stripes[i].physical == dev_offset) {
             ret = scrub_stripe(sctx, bg, em, scrub_dev, i);
             if (ret)
                 goto out;
         }
     }
 out:
     free_extent_map(em);
 
     return ret;
 }
 
 static int finish_extent_writes_for_zoned(struct btrfs_root *root,
                       struct btrfs_block_group *cache)
 {
     struct btrfs_fs_info *fs_info = cache->fs_info;
     struct btrfs_trans_handle *trans;
 
     if (!btrfs_is_zoned(fs_info))
         return 0;
 
     btrfs_wait_block_group_reservations(cache);
     btrfs_wait_nocow_writers(cache);
     btrfs_wait_ordered_roots(fs_info, U64_MAX, cache->start, cache->length);
 
     trans = btrfs_join_transaction(root);
     if (IS_ERR(trans))
         return PTR_ERR(trans);
     return btrfs_commit_transaction(trans);
 }
 
 static noinline_for_stack
 int scrub_enumerate_chunks(struct scrub_ctx *sctx,
                struct btrfs_device *scrub_dev, u64 start, u64 end)
 {
     struct btrfs_dev_extent *dev_extent = NULL;
     struct btrfs_path *path;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
     struct btrfs_root *root = fs_info->dev_root;
     u64 chunk_offset;
     int ret = 0;
     int ro_set;
     int slot;
     struct extent_buffer *l;
     struct btrfs_key key;
     struct btrfs_key found_key;
     struct btrfs_block_group *cache;
     struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     path->reada = READA_FORWARD;
     path->search_commit_root = 1;
     path->skip_locking = 1;
 
     key.objectid = scrub_dev->devid;
     key.offset = 0ull;
     key.type = BTRFS_DEV_EXTENT_KEY;
 
     while (1) {
         u64 dev_extent_len;
 
         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
         if (ret < 0)
             break;
         if (ret > 0) {
             if (path->slots[0] >=
                 btrfs_header_nritems(path->nodes[0])) {
                 ret = btrfs_next_leaf(root, path);
                 if (ret < 0)
                     break;
                 if (ret > 0) {
                     ret = 0;
                     break;
                 }
             } else {
                 ret = 0;
             }
         }
 
         l = path->nodes[0];
         slot = path->slots[0];
 
         btrfs_item_key_to_cpu(l, &found_key, slot);
 
         if (found_key.objectid != scrub_dev->devid)
             break;
 
         if (found_key.type != BTRFS_DEV_EXTENT_KEY)
             break;
 
         if (found_key.offset >= end)
             break;
 
         if (found_key.offset < key.offset)
             break;
 
         dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
         dev_extent_len = btrfs_dev_extent_length(l, dev_extent);
 
         if (found_key.offset + dev_extent_len <= start)
             goto skip;
 
         chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
 
         /*
          * get a reference on the corresponding block group to prevent
          * the chunk from going away while we scrub it
          */
         cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 
         /* some chunks are removed but not committed to disk yet,
          * continue scrubbing */
         if (!cache)
             goto skip;
 
         ASSERT(cache->start <= chunk_offset);
         /*
          * We are using the commit root to search for device extents, so
          * that means we could have found a device extent item from a
          * block group that was deleted in the current transaction. The
          * logical start offset of the deleted block group, stored at
          * @chunk_offset, might be part of the logical address range of
          * a new block group (which uses different physical extents).
          * In this case btrfs_lookup_block_group() has returned the new
          * block group, and its start address is less than @chunk_offset.
          *
          * We skip such new block groups, because it's pointless to
          * process them, as we won't find their extents because we search
          * for them using the commit root of the extent tree. For a device
          * replace it's also fine to skip it, we won't miss copying them
          * to the target device because we have the write duplication
          * setup through the regular write path (by btrfs_map_block()),
          * and we have committed a transaction when we started the device
          * replace, right after setting up the device replace state.
          */
         if (cache->start < chunk_offset) {
             btrfs_put_block_group(cache);
             goto skip;
         }
 
         if (sctx->is_dev_replace && btrfs_is_zoned(fs_info)) {
             spin_lock(&cache->lock);
             if (!cache->to_copy) {
                 spin_unlock(&cache->lock);
                 btrfs_put_block_group(cache);
                 goto skip;
             }
             spin_unlock(&cache->lock);
         }
 
         /*
          * Make sure that while we are scrubbing the corresponding block
          * group doesn't get its logical address and its device extents
          * reused for another block group, which can possibly be of a
          * different type and different profile. We do this to prevent
          * false error detections and crashes due to bogus attempts to
          * repair extents.
          */
         spin_lock(&cache->lock);
         if (cache->removed) {
             spin_unlock(&cache->lock);
             btrfs_put_block_group(cache);
             goto skip;
         }
         btrfs_freeze_block_group(cache);
         spin_unlock(&cache->lock);
 
         /*
          * we need call btrfs_inc_block_group_ro() with scrubs_paused,
          * to avoid deadlock caused by:
          * btrfs_inc_block_group_ro()
          * -> btrfs_wait_for_commit()
          * -> btrfs_commit_transaction()
          * -> btrfs_scrub_pause()
          */
         scrub_pause_on(fs_info);
 
         /*
          * Don't do chunk preallocation for scrub.
          *
          * This is especially important for SYSTEM bgs, or we can hit
          * -EFBIG from btrfs_finish_chunk_alloc() like:
          * 1. The only SYSTEM bg is marked RO.
          *    Since SYSTEM bg is small, that's pretty common.
          * 2. New SYSTEM bg will be allocated
          *    Due to regular version will allocate new chunk.
          * 3. New SYSTEM bg is empty and will get cleaned up
          *    Before cleanup really happens, it's marked RO again.
          * 4. Empty SYSTEM bg get scrubbed
          *    We go back to 2.
          *
          * This can easily boost the amount of SYSTEM chunks if cleaner
          * thread can't be triggered fast enough, and use up all space
          * of btrfs_super_block::sys_chunk_array
          *
          * While for dev replace, we need to try our best to mark block
          * group RO, to prevent race between:
          * - Write duplication
          *   Contains latest data
          * - Scrub copy
          *   Contains data from commit tree
          *
          * If target block group is not marked RO, nocow writes can
          * be overwritten by scrub copy, causing data corruption.
          * So for dev-replace, it's not allowed to continue if a block
          * group is not RO.
          */
         ret = btrfs_inc_block_group_ro(cache, sctx->is_dev_replace);
         if (!ret && sctx->is_dev_replace) {
             ret = finish_extent_writes_for_zoned(root, cache);
             if (ret) {
                 btrfs_dec_block_group_ro(cache);
                 scrub_pause_off(fs_info);
                 btrfs_put_block_group(cache);
                 break;
             }
         }
 
         if (ret == 0) {
             ro_set = 1;
         } else if (ret == -ENOSPC && !sctx->is_dev_replace) {
             /*
              * btrfs_inc_block_group_ro return -ENOSPC when it
              * failed in creating new chunk for metadata.
              * It is not a problem for scrub, because
              * metadata are always cowed, and our scrub paused
              * commit_transactions.
              */
             ro_set = 0;
         } else if (ret == -ETXTBSY) {
             btrfs_warn(fs_info,
            "skipping scrub of block group %llu due to active swapfile",
                    cache->start);
             scrub_pause_off(fs_info);
             ret = 0;
             goto skip_unfreeze;
         } else {
             btrfs_warn(fs_info,
                    "failed setting block group ro: %d", ret);
             btrfs_unfreeze_block_group(cache);
             btrfs_put_block_group(cache);
             scrub_pause_off(fs_info);
             break;
         }
 
         /*
          * Now the target block is marked RO, wait for nocow writes to
          * finish before dev-replace.
          * COW is fine, as COW never overwrites extents in commit tree.
          */
         if (sctx->is_dev_replace) {
             btrfs_wait_nocow_writers(cache);
             btrfs_wait_ordered_roots(fs_info, U64_MAX, cache->start,
                     cache->length);
         }
 
         scrub_pause_off(fs_info);
         down_write(&dev_replace->rwsem);
         dev_replace->cursor_right = found_key.offset + dev_extent_len;
         dev_replace->cursor_left = found_key.offset;
         dev_replace->item_needs_writeback = 1;
         up_write(&dev_replace->rwsem);
 
         ret = scrub_chunk(sctx, cache, scrub_dev, found_key.offset,
                   dev_extent_len);
 
         /*
          * flush, submit all pending read and write bios, afterwards
          * wait for them.
          * Note that in the dev replace case, a read request causes
          * write requests that are submitted in the read completion
          * worker. Therefore in the current situation, it is required
          * that all write requests are flushed, so that all read and
          * write requests are really completed when bios_in_flight
          * changes to 0.
          */
         sctx->flush_all_writes = true;
         scrub_submit(sctx);
         mutex_lock(&sctx->wr_lock);
         scrub_wr_submit(sctx);
         mutex_unlock(&sctx->wr_lock);
 
         wait_event(sctx->list_wait,
                atomic_read(&sctx->bios_in_flight) == 0);
 
         scrub_pause_on(fs_info);
 
         /*
          * must be called before we decrease @scrub_paused.
          * make sure we don't block transaction commit while
          * we are waiting pending workers finished.
          */
         wait_event(sctx->list_wait,
                atomic_read(&sctx->workers_pending) == 0);
         sctx->flush_all_writes = false;
 
         scrub_pause_off(fs_info);
 
         if (sctx->is_dev_replace &&
             !btrfs_finish_block_group_to_copy(dev_replace->srcdev,
                               cache, found_key.offset))
             ro_set = 0;
 
         down_write(&dev_replace->rwsem);
         dev_replace->cursor_left = dev_replace->cursor_right;
         dev_replace->item_needs_writeback = 1;
         up_write(&dev_replace->rwsem);
 
         if (ro_set)
             btrfs_dec_block_group_ro(cache);
 
         /*
          * We might have prevented the cleaner kthread from deleting
          * this block group if it was already unused because we raced
          * and set it to RO mode first. So add it back to the unused
          * list, otherwise it might not ever be deleted unless a manual
          * balance is triggered or it becomes used and unused again.
          */
         spin_lock(&cache->lock);
         if (!cache->removed && !cache->ro && cache->reserved == 0 &&
             cache->used == 0) {
             spin_unlock(&cache->lock);
             if (btrfs_test_opt(fs_info, DISCARD_ASYNC))
                 btrfs_discard_queue_work(&fs_info->discard_ctl,
                              cache);
             else
                 btrfs_mark_bg_unused(cache);
         } else {
             spin_unlock(&cache->lock);
         }
 skip_unfreeze:
         btrfs_unfreeze_block_group(cache);
         btrfs_put_block_group(cache);
         if (ret)
             break;
         if (sctx->is_dev_replace &&
             atomic64_read(&dev_replace->num_write_errors) > 0) {
             ret = -EIO;
             break;
         }
         if (sctx->stat.malloc_errors > 0) {
             ret = -ENOMEM;
             break;
         }
 skip:
         key.offset = found_key.offset + dev_extent_len;
         btrfs_release_path(path);
     }
 
     btrfs_free_path(path);
 
     return ret;
 }
 
 static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx,
                        struct btrfs_device *scrub_dev)
 {
     int i;
     u64 bytenr;
     u64 gen;
     int ret;
     struct btrfs_fs_info *fs_info = sctx->fs_info;
 
     if (BTRFS_FS_ERROR(fs_info))
         return -EROFS;
 
     /* Seed devices of a new filesystem has their own generation. */
     if (scrub_dev->fs_devices != fs_info->fs_devices)
         gen = scrub_dev->generation;
     else
         gen = fs_info->last_trans_committed;
 
     for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
         bytenr = btrfs_sb_offset(i);
         if (bytenr + BTRFS_SUPER_INFO_SIZE >
             scrub_dev->commit_total_bytes)
             break;
         if (!btrfs_check_super_location(scrub_dev, bytenr))
             continue;
 
         ret = scrub_sectors(sctx, bytenr, BTRFS_SUPER_INFO_SIZE, bytenr,
                     scrub_dev, BTRFS_EXTENT_FLAG_SUPER, gen, i,
                     NULL, bytenr);
         if (ret)
             return ret;
     }
     wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
 
     return 0;
 }
 
 static void scrub_workers_put(struct btrfs_fs_info *fs_info)
 {
     if (refcount_dec_and_mutex_lock(&fs_info->scrub_workers_refcnt,
                     &fs_info->scrub_lock)) {
         struct workqueue_struct *scrub_workers = fs_info->scrub_workers;
         struct workqueue_struct *scrub_wr_comp =
                         fs_info->scrub_wr_completion_workers;
         struct workqueue_struct *scrub_parity =
                         fs_info->scrub_parity_workers;
 
         fs_info->scrub_workers = NULL;
         fs_info->scrub_wr_completion_workers = NULL;
         fs_info->scrub_parity_workers = NULL;
         mutex_unlock(&fs_info->scrub_lock);
 
         if (scrub_workers)
             destroy_workqueue(scrub_workers);
         if (scrub_wr_comp)
             destroy_workqueue(scrub_wr_comp);
         if (scrub_parity)
             destroy_workqueue(scrub_parity);
     }
 }
 
 /*
  * get a reference count on fs_info->scrub_workers. start worker if necessary
  */
 static noinline_for_stack int scrub_workers_get(struct btrfs_fs_info *fs_info,
                         int is_dev_replace)
 {
     struct workqueue_struct *scrub_workers = NULL;
     struct workqueue_struct *scrub_wr_comp = NULL;
     struct workqueue_struct *scrub_parity = NULL;
     unsigned int flags = WQ_FREEZABLE | WQ_UNBOUND;
     int max_active = fs_info->thread_pool_size;
     int ret = -ENOMEM;
 
     if (refcount_inc_not_zero(&fs_info->scrub_workers_refcnt))
         return 0;
 
     scrub_workers = alloc_workqueue("btrfs-scrub", flags,
                     is_dev_replace ? 1 : max_active);
     if (!scrub_workers)
         goto fail_scrub_workers;
 
     scrub_wr_comp = alloc_workqueue("btrfs-scrubwrc", flags, max_active);
     if (!scrub_wr_comp)
         goto fail_scrub_wr_completion_workers;
 
     scrub_parity = alloc_workqueue("btrfs-scrubparity", flags, max_active);
     if (!scrub_parity)
         goto fail_scrub_parity_workers;
 
     mutex_lock(&fs_info->scrub_lock);
     if (refcount_read(&fs_info->scrub_workers_refcnt) == 0) {
         ASSERT(fs_info->scrub_workers == NULL &&
                fs_info->scrub_wr_completion_workers == NULL &&
                fs_info->scrub_parity_workers == NULL);
         fs_info->scrub_workers = scrub_workers;
         fs_info->scrub_wr_completion_workers = scrub_wr_comp;
         fs_info->scrub_parity_workers = scrub_parity;
         refcount_set(&fs_info->scrub_workers_refcnt, 1);
         mutex_unlock(&fs_info->scrub_lock);
         return 0;
     }
     /* Other thread raced in and created the workers for us */
     refcount_inc(&fs_info->scrub_workers_refcnt);
     mutex_unlock(&fs_info->scrub_lock);
 
     ret = 0;
     destroy_workqueue(scrub_parity);
 fail_scrub_parity_workers:
     destroy_workqueue(scrub_wr_comp);
 fail_scrub_wr_completion_workers:
     destroy_workqueue(scrub_workers);
 fail_scrub_workers:
     return ret;
 }
 
 int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
             u64 end, struct btrfs_scrub_progress *progress,
             int readonly, int is_dev_replace)
 {
     struct btrfs_dev_lookup_args args = { .devid = devid };
     struct scrub_ctx *sctx;
     int ret;
     struct btrfs_device *dev;
     unsigned int nofs_flag;
 
     if (btrfs_fs_closing(fs_info))
         return -EAGAIN;
 
     if (fs_info->nodesize > BTRFS_STRIPE_LEN) {
         /*
          * in this case scrub is unable to calculate the checksum
          * the way scrub is implemented. Do not handle this
          * situation at all because it won't ever happen.
          */
         btrfs_err(fs_info,
                "scrub: size assumption nodesize <= BTRFS_STRIPE_LEN (%d <= %d) fails",
                fs_info->nodesize,
                BTRFS_STRIPE_LEN);
         return -EINVAL;
     }
 
     if (fs_info->nodesize >
         SCRUB_MAX_SECTORS_PER_BLOCK << fs_info->sectorsize_bits ||
         fs_info->sectorsize > PAGE_SIZE * SCRUB_MAX_SECTORS_PER_BLOCK) {
         /*
          * Would exhaust the array bounds of sectorv member in
          * struct scrub_block
          */
         btrfs_err(fs_info,
 "scrub: nodesize and sectorsize <= SCRUB_MAX_SECTORS_PER_BLOCK (%d <= %d && %d <= %d) fails",
                fs_info->nodesize, SCRUB_MAX_SECTORS_PER_BLOCK,
                fs_info->sectorsize, SCRUB_MAX_SECTORS_PER_BLOCK);
         return -EINVAL;
     }
 
     /* Allocate outside of device_list_mutex */
     sctx = scrub_setup_ctx(fs_info, is_dev_replace);
     if (IS_ERR(sctx))
         return PTR_ERR(sctx);
 
     ret = scrub_workers_get(fs_info, is_dev_replace);
     if (ret)
         goto out_free_ctx;
 
     mutex_lock(&fs_info->fs_devices->device_list_mutex);
     dev = btrfs_find_device(fs_info->fs_devices, &args);
     if (!dev || (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) &&
              !is_dev_replace)) {
         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
         ret = -ENODEV;
         goto out;
     }
 
     if (!is_dev_replace && !readonly &&
         !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state)) {
         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
         btrfs_err_in_rcu(fs_info,
             "scrub on devid %llu: filesystem on %s is not writable",
                  devid, rcu_str_deref(dev->name));
         ret = -EROFS;
         goto out;
     }
 
     mutex_lock(&fs_info->scrub_lock);
     if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
         test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &dev->dev_state)) {
         mutex_unlock(&fs_info->scrub_lock);
         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
         ret = -EIO;
         goto out;
     }
 
     down_read(&fs_info->dev_replace.rwsem);
     if (dev->scrub_ctx ||
         (!is_dev_replace &&
          btrfs_dev_replace_is_ongoing(&fs_info->dev_replace))) {
         up_read(&fs_info->dev_replace.rwsem);
         mutex_unlock(&fs_info->scrub_lock);
         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
         ret = -EINPROGRESS;
         goto out;
     }
     up_read(&fs_info->dev_replace.rwsem);
 
     sctx->readonly = readonly;
     dev->scrub_ctx = sctx;
     mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
     /*
      * checking @scrub_pause_req here, we can avoid
      * race between committing transaction and scrubbing.
      */
     __scrub_blocked_if_needed(fs_info);
     atomic_inc(&fs_info->scrubs_running);
     mutex_unlock(&fs_info->scrub_lock);
 
     /*
      * In order to avoid deadlock with reclaim when there is a transaction
      * trying to pause scrub, make sure we use GFP_NOFS for all the
      * allocations done at btrfs_scrub_sectors() and scrub_sectors_for_parity()
      * invoked by our callees. The pausing request is done when the
      * transaction commit starts, and it blocks the transaction until scrub
      * is paused (done at specific points at scrub_stripe() or right above
      * before incrementing fs_info->scrubs_running).
      */
     nofs_flag = memalloc_nofs_save();
     if (!is_dev_replace) {
         btrfs_info(fs_info, "scrub: started on devid %llu", devid);
         /*
          * by holding device list mutex, we can
          * kick off writing super in log tree sync.
          */
         mutex_lock(&fs_info->fs_devices->device_list_mutex);
         ret = scrub_supers(sctx, dev);
         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
     }
 
     if (!ret)
         ret = scrub_enumerate_chunks(sctx, dev, start, end);
     memalloc_nofs_restore(nofs_flag);
 
     wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
     atomic_dec(&fs_info->scrubs_running);
     wake_up(&fs_info->scrub_pause_wait);
 
     wait_event(sctx->list_wait, atomic_read(&sctx->workers_pending) == 0);
 
     if (progress)
         memcpy(progress, &sctx->stat, sizeof(*progress));
 
     if (!is_dev_replace)
         btrfs_info(fs_info, "scrub: %s on devid %llu with status: %d",
             ret ? "not finished" : "finished", devid, ret);
 
     mutex_lock(&fs_info->scrub_lock);
     dev->scrub_ctx = NULL;
     mutex_unlock(&fs_info->scrub_lock);
 
     scrub_workers_put(fs_info);
     scrub_put_ctx(sctx);
 
     return ret;
 out:
     scrub_workers_put(fs_info);
 out_free_ctx:
     scrub_free_ctx(sctx);
 
     return ret;
 }
 
 void btrfs_scrub_pause(struct btrfs_fs_info *fs_info)
 {
     mutex_lock(&fs_info->scrub_lock);
     atomic_inc(&fs_info->scrub_pause_req);
     while (atomic_read(&fs_info->scrubs_paused) !=
            atomic_read(&fs_info->scrubs_running)) {
         mutex_unlock(&fs_info->scrub_lock);
         wait_event(fs_info->scrub_pause_wait,
                atomic_read(&fs_info->scrubs_paused) ==
                atomic_read(&fs_info->scrubs_running));
         mutex_lock(&fs_info->scrub_lock);
     }
     mutex_unlock(&fs_info->scrub_lock);
 }
 
 void btrfs_scrub_continue(struct btrfs_fs_info *fs_info)
 {
     atomic_dec(&fs_info->scrub_pause_req);
     wake_up(&fs_info->scrub_pause_wait);
 }
 
 int btrfs_scrub_cancel(struct btrfs_fs_info *fs_info)
 {
     mutex_lock(&fs_info->scrub_lock);
     if (!atomic_read(&fs_info->scrubs_running)) {
         mutex_unlock(&fs_info->scrub_lock);
         return -ENOTCONN;
     }
 
     atomic_inc(&fs_info->scrub_cancel_req);
     while (atomic_read(&fs_info->scrubs_running)) {
         mutex_unlock(&fs_info->scrub_lock);
         wait_event(fs_info->scrub_pause_wait,
                atomic_read(&fs_info->scrubs_running) == 0);
         mutex_lock(&fs_info->scrub_lock);
     }
     atomic_dec(&fs_info->scrub_cancel_req);
     mutex_unlock(&fs_info->scrub_lock);
 
     return 0;
 }
 
 int btrfs_scrub_cancel_dev(struct btrfs_device *dev)
 {
     struct btrfs_fs_info *fs_info = dev->fs_info;
     struct scrub_ctx *sctx;
 
     mutex_lock(&fs_info->scrub_lock);
     sctx = dev->scrub_ctx;
     if (!sctx) {
         mutex_unlock(&fs_info->scrub_lock);
         return -ENOTCONN;
     }
     atomic_inc(&sctx->cancel_req);
     while (dev->scrub_ctx) {
         mutex_unlock(&fs_info->scrub_lock);
         wait_event(fs_info->scrub_pause_wait,
                dev->scrub_ctx == NULL);
         mutex_lock(&fs_info->scrub_lock);
     }
     mutex_unlock(&fs_info->scrub_lock);
 
     return 0;
 }
 
 int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
              struct btrfs_scrub_progress *progress)
 {
     struct btrfs_dev_lookup_args args = { .devid = devid };
     struct btrfs_device *dev;
     struct scrub_ctx *sctx = NULL;
 
     mutex_lock(&fs_info->fs_devices->device_list_mutex);
     dev = btrfs_find_device(fs_info->fs_devices, &args);
     if (dev)
         sctx = dev->scrub_ctx;
     if (sctx)
         memcpy(progress, &sctx->stat, sizeof(*progress));
     mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
     return dev ? (sctx ? 0 : -ENOTCONN) : -ENODEV;
 }
 
 static void scrub_find_good_copy(struct btrfs_fs_info *fs_info,
                  u64 extent_logical, u32 extent_len,
                  u64 *extent_physical,
                  struct btrfs_device **extent_dev,
                  int *extent_mirror_num)
 {
     u64 mapped_length;
     struct btrfs_io_context *bioc = NULL;
     int ret;
 
     mapped_length = extent_len;
     ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, extent_logical,
                   &mapped_length, &bioc, 0);
     if (ret || !bioc || mapped_length < extent_len ||
         !bioc->stripes[0].dev->bdev) {
         btrfs_put_bioc(bioc);
         return;
     }
 
     *extent_physical = bioc->stripes[0].physical;
     *extent_mirror_num = bioc->mirror_num;
     *extent_dev = bioc->stripes[0].dev;
     btrfs_put_bioc(bioc);
 }