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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
 
 #include <linux/list_sort.h>
 #include "misc.h"
 #include "ctree.h"
 #include "block-group.h"
 #include "space-info.h"
 #include "disk-io.h"
 #include "free-space-cache.h"
 #include "free-space-tree.h"
 #include "volumes.h"
 #include "transaction.h"
 #include "ref-verify.h"
 #include "sysfs.h"
 #include "tree-log.h"
 #include "delalloc-space.h"
 #include "discard.h"
 #include "raid56.h"
 #include "zoned.h"
 
 /*
  * Return target flags in extended format or 0 if restripe for this chunk_type
  * is not in progress
  *
  * Should be called with balance_lock held
  */
 static u64 get_restripe_target(struct btrfs_fs_info *fs_info, u64 flags)
 {
     struct btrfs_balance_control *bctl = fs_info->balance_ctl;
     u64 target = 0;
 
     if (!bctl)
         return 0;
 
     if (flags & BTRFS_BLOCK_GROUP_DATA &&
         bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) {
         target = BTRFS_BLOCK_GROUP_DATA | bctl->data.target;
     } else if (flags & BTRFS_BLOCK_GROUP_SYSTEM &&
            bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) {
         target = BTRFS_BLOCK_GROUP_SYSTEM | bctl->sys.target;
     } else if (flags & BTRFS_BLOCK_GROUP_METADATA &&
            bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) {
         target = BTRFS_BLOCK_GROUP_METADATA | bctl->meta.target;
     }
 
     return target;
 }
 
 /*
  * @flags: available profiles in extended format (see ctree.h)
  *
  * Return reduced profile in chunk format.  If profile changing is in progress
  * (either running or paused) picks the target profile (if it's already
  * available), otherwise falls back to plain reducing.
  */
 static u64 btrfs_reduce_alloc_profile(struct btrfs_fs_info *fs_info, u64 flags)
 {
     u64 num_devices = fs_info->fs_devices->rw_devices;
     u64 target;
     u64 raid_type;
     u64 allowed = 0;
 
     /*
      * See if restripe for this chunk_type is in progress, if so try to
      * reduce to the target profile
      */
     spin_lock(&fs_info->balance_lock);
     target = get_restripe_target(fs_info, flags);
     if (target) {
         spin_unlock(&fs_info->balance_lock);
         return extended_to_chunk(target);
     }
     spin_unlock(&fs_info->balance_lock);
 
     /* First, mask out the RAID levels which aren't possible */
     for (raid_type = 0; raid_type < BTRFS_NR_RAID_TYPES; raid_type++) {
         if (num_devices >= btrfs_raid_array[raid_type].devs_min)
             allowed |= btrfs_raid_array[raid_type].bg_flag;
     }
     allowed &= flags;
 
     if (allowed & BTRFS_BLOCK_GROUP_RAID6)
         allowed = BTRFS_BLOCK_GROUP_RAID6;
     else if (allowed & BTRFS_BLOCK_GROUP_RAID5)
         allowed = BTRFS_BLOCK_GROUP_RAID5;
     else if (allowed & BTRFS_BLOCK_GROUP_RAID10)
         allowed = BTRFS_BLOCK_GROUP_RAID10;
     else if (allowed & BTRFS_BLOCK_GROUP_RAID1)
         allowed = BTRFS_BLOCK_GROUP_RAID1;
     else if (allowed & BTRFS_BLOCK_GROUP_RAID0)
         allowed = BTRFS_BLOCK_GROUP_RAID0;
 
     flags &= ~BTRFS_BLOCK_GROUP_PROFILE_MASK;
 
     return extended_to_chunk(flags | allowed);
 }
 
 u64 btrfs_get_alloc_profile(struct btrfs_fs_info *fs_info, u64 orig_flags)
 {
     unsigned seq;
     u64 flags;
 
     do {
         flags = orig_flags;
         seq = read_seqbegin(&fs_info->profiles_lock);
 
         if (flags & BTRFS_BLOCK_GROUP_DATA)
             flags |= fs_info->avail_data_alloc_bits;
         else if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
             flags |= fs_info->avail_system_alloc_bits;
         else if (flags & BTRFS_BLOCK_GROUP_METADATA)
             flags |= fs_info->avail_metadata_alloc_bits;
     } while (read_seqretry(&fs_info->profiles_lock, seq));
 
     return btrfs_reduce_alloc_profile(fs_info, flags);
 }
 
 void btrfs_get_block_group(struct btrfs_block_group *cache)
 {
     refcount_inc(&cache->refs);
 }
 
 void btrfs_put_block_group(struct btrfs_block_group *cache)
 {
     if (refcount_dec_and_test(&cache->refs)) {
         WARN_ON(cache->pinned > 0);
         /*
          * If there was a failure to cleanup a log tree, very likely due
          * to an IO failure on a writeback attempt of one or more of its
          * extent buffers, we could not do proper (and cheap) unaccounting
          * of their reserved space, so don't warn on reserved > 0 in that
          * case.
          */
         if (!(cache->flags & BTRFS_BLOCK_GROUP_METADATA) ||
             !BTRFS_FS_LOG_CLEANUP_ERROR(cache->fs_info))
             WARN_ON(cache->reserved > 0);
 
         /*
          * A block_group shouldn't be on the discard_list anymore.
          * Remove the block_group from the discard_list to prevent us
          * from causing a panic due to NULL pointer dereference.
          */
         if (WARN_ON(!list_empty(&cache->discard_list)))
             btrfs_discard_cancel_work(&cache->fs_info->discard_ctl,
                           cache);
 
         /*
          * If not empty, someone is still holding mutex of
          * full_stripe_lock, which can only be released by caller.
          * And it will definitely cause use-after-free when caller
          * tries to release full stripe lock.
          *
          * No better way to resolve, but only to warn.
          */
         WARN_ON(!RB_EMPTY_ROOT(&cache->full_stripe_locks_root.root));
         kfree(cache->free_space_ctl);
         kfree(cache->physical_map);
         kfree(cache);
     }
 }
 
 /*
  * This adds the block group to the fs_info rb tree for the block group cache
  */
 static int btrfs_add_block_group_cache(struct btrfs_fs_info *info,
                        struct btrfs_block_group *block_group)
 {
     struct rb_node **p;
     struct rb_node *parent = NULL;
     struct btrfs_block_group *cache;
     bool leftmost = true;
 
     ASSERT(block_group->length != 0);
 
     write_lock(&info->block_group_cache_lock);
     p = &info->block_group_cache_tree.rb_root.rb_node;
 
     while (*p) {
         parent = *p;
         cache = rb_entry(parent, struct btrfs_block_group, cache_node);
         if (block_group->start < cache->start) {
             p = &(*p)->rb_left;
         } else if (block_group->start > cache->start) {
             p = &(*p)->rb_right;
             leftmost = false;
         } else {
             write_unlock(&info->block_group_cache_lock);
             return -EEXIST;
         }
     }
 
     rb_link_node(&block_group->cache_node, parent, p);
     rb_insert_color_cached(&block_group->cache_node,
                    &info->block_group_cache_tree, leftmost);
 
     write_unlock(&info->block_group_cache_lock);
 
     return 0;
 }
 
 /*
  * This will return the block group at or after bytenr if contains is 0, else
  * it will return the block group that contains the bytenr
  */
 static struct btrfs_block_group *block_group_cache_tree_search(
         struct btrfs_fs_info *info, u64 bytenr, int contains)
 {
     struct btrfs_block_group *cache, *ret = NULL;
     struct rb_node *n;
     u64 end, start;
 
     read_lock(&info->block_group_cache_lock);
     n = info->block_group_cache_tree.rb_root.rb_node;
 
     while (n) {
         cache = rb_entry(n, struct btrfs_block_group, cache_node);
         end = cache->start + cache->length - 1;
         start = cache->start;
 
         if (bytenr < start) {
             if (!contains && (!ret || start < ret->start))
                 ret = cache;
             n = n->rb_left;
         } else if (bytenr > start) {
             if (contains && bytenr <= end) {
                 ret = cache;
                 break;
             }
             n = n->rb_right;
         } else {
             ret = cache;
             break;
         }
     }
     if (ret)
         btrfs_get_block_group(ret);
     read_unlock(&info->block_group_cache_lock);
 
     return ret;
 }
 
 /*
  * Return the block group that starts at or after bytenr
  */
 struct btrfs_block_group *btrfs_lookup_first_block_group(
         struct btrfs_fs_info *info, u64 bytenr)
 {
     return block_group_cache_tree_search(info, bytenr, 0);
 }
 
 /*
  * Return the block group that contains the given bytenr
  */
 struct btrfs_block_group *btrfs_lookup_block_group(
         struct btrfs_fs_info *info, u64 bytenr)
 {
     return block_group_cache_tree_search(info, bytenr, 1);
 }
 
 struct btrfs_block_group *btrfs_next_block_group(
         struct btrfs_block_group *cache)
 {
     struct btrfs_fs_info *fs_info = cache->fs_info;
     struct rb_node *node;
 
     read_lock(&fs_info->block_group_cache_lock);
 
     /* If our block group was removed, we need a full search. */
     if (RB_EMPTY_NODE(&cache->cache_node)) {
         const u64 next_bytenr = cache->start + cache->length;
 
         read_unlock(&fs_info->block_group_cache_lock);
         btrfs_put_block_group(cache);
         return btrfs_lookup_first_block_group(fs_info, next_bytenr);
     }
     node = rb_next(&cache->cache_node);
     btrfs_put_block_group(cache);
     if (node) {
         cache = rb_entry(node, struct btrfs_block_group, cache_node);
         btrfs_get_block_group(cache);
     } else
         cache = NULL;
     read_unlock(&fs_info->block_group_cache_lock);
     return cache;
 }
 
 /**
  * Check if we can do a NOCOW write for a given extent.
  *
  * @fs_info:       The filesystem information object.
  * @bytenr:        Logical start address of the extent.
  *
  * Check if we can do a NOCOW write for the given extent, and increments the
  * number of NOCOW writers in the block group that contains the extent, as long
  * as the block group exists and it's currently not in read-only mode.
  *
  * Returns: A non-NULL block group pointer if we can do a NOCOW write, the caller
  *          is responsible for calling btrfs_dec_nocow_writers() later.
  *
  *          Or NULL if we can not do a NOCOW write
  */
 struct btrfs_block_group *btrfs_inc_nocow_writers(struct btrfs_fs_info *fs_info,
                           u64 bytenr)
 {
     struct btrfs_block_group *bg;
     bool can_nocow = true;
 
     bg = btrfs_lookup_block_group(fs_info, bytenr);
     if (!bg)
         return NULL;
 
     spin_lock(&bg->lock);
     if (bg->ro)
         can_nocow = false;
     else
         atomic_inc(&bg->nocow_writers);
     spin_unlock(&bg->lock);
 
     if (!can_nocow) {
         btrfs_put_block_group(bg);
         return NULL;
     }
 
     /* No put on block group, done by btrfs_dec_nocow_writers(). */
     return bg;
 }
 
 /**
  * Decrement the number of NOCOW writers in a block group.
  *
  * @bg:       The block group.
  *
  * This is meant to be called after a previous call to btrfs_inc_nocow_writers(),
  * and on the block group returned by that call. Typically this is called after
  * creating an ordered extent for a NOCOW write, to prevent races with scrub and
  * relocation.
  *
  * After this call, the caller should not use the block group anymore. It it wants
  * to use it, then it should get a reference on it before calling this function.
  */
 void btrfs_dec_nocow_writers(struct btrfs_block_group *bg)
 {
     if (atomic_dec_and_test(&bg->nocow_writers))
         wake_up_var(&bg->nocow_writers);
 
     /* For the lookup done by a previous call to btrfs_inc_nocow_writers(). */
     btrfs_put_block_group(bg);
 }
 
 void btrfs_wait_nocow_writers(struct btrfs_block_group *bg)
 {
     wait_var_event(&bg->nocow_writers, !atomic_read(&bg->nocow_writers));
 }
 
 void btrfs_dec_block_group_reservations(struct btrfs_fs_info *fs_info,
                     const u64 start)
 {
     struct btrfs_block_group *bg;
 
     bg = btrfs_lookup_block_group(fs_info, start);
     ASSERT(bg);
     if (atomic_dec_and_test(&bg->reservations))
         wake_up_var(&bg->reservations);
     btrfs_put_block_group(bg);
 }
 
 void btrfs_wait_block_group_reservations(struct btrfs_block_group *bg)
 {
     struct btrfs_space_info *space_info = bg->space_info;
 
     ASSERT(bg->ro);
 
     if (!(bg->flags & BTRFS_BLOCK_GROUP_DATA))
         return;
 
     /*
      * Our block group is read only but before we set it to read only,
      * some task might have had allocated an extent from it already, but it
      * has not yet created a respective ordered extent (and added it to a
      * root's list of ordered extents).
      * Therefore wait for any task currently allocating extents, since the
      * block group's reservations counter is incremented while a read lock
      * on the groups' semaphore is held and decremented after releasing
      * the read access on that semaphore and creating the ordered extent.
      */
     down_write(&space_info->groups_sem);
     up_write(&space_info->groups_sem);
 
     wait_var_event(&bg->reservations, !atomic_read(&bg->reservations));
 }
 
 struct btrfs_caching_control *btrfs_get_caching_control(
         struct btrfs_block_group *cache)
 {
     struct btrfs_caching_control *ctl;
 
     spin_lock(&cache->lock);
     if (!cache->caching_ctl) {
         spin_unlock(&cache->lock);
         return NULL;
     }
 
     ctl = cache->caching_ctl;
     refcount_inc(&ctl->count);
     spin_unlock(&cache->lock);
     return ctl;
 }
 
 void btrfs_put_caching_control(struct btrfs_caching_control *ctl)
 {
     if (refcount_dec_and_test(&ctl->count))
         kfree(ctl);
 }
 
 /*
  * When we wait for progress in the block group caching, its because our
  * allocation attempt failed at least once.  So, we must sleep and let some
  * progress happen before we try again.
  *
  * This function will sleep at least once waiting for new free space to show
  * up, and then it will check the block group free space numbers for our min
  * num_bytes.  Another option is to have it go ahead and look in the rbtree for
  * a free extent of a given size, but this is a good start.
  *
  * Callers of this must check if cache->cached == BTRFS_CACHE_ERROR before using
  * any of the information in this block group.
  */
 void btrfs_wait_block_group_cache_progress(struct btrfs_block_group *cache,
                        u64 num_bytes)
 {
     struct btrfs_caching_control *caching_ctl;
 
     caching_ctl = btrfs_get_caching_control(cache);
     if (!caching_ctl)
         return;
 
     wait_event(caching_ctl->wait, btrfs_block_group_done(cache) ||
            (cache->free_space_ctl->free_space >= num_bytes));
 
     btrfs_put_caching_control(caching_ctl);
 }
 
 static int btrfs_caching_ctl_wait_done(struct btrfs_block_group *cache,
                        struct btrfs_caching_control *caching_ctl)
 {
     wait_event(caching_ctl->wait, btrfs_block_group_done(cache));
     return cache->cached == BTRFS_CACHE_ERROR ? -EIO : 0;
 }
 
 static int btrfs_wait_block_group_cache_done(struct btrfs_block_group *cache)
 {
     struct btrfs_caching_control *caching_ctl;
     int ret;
 
     caching_ctl = btrfs_get_caching_control(cache);
     if (!caching_ctl)
         return (cache->cached == BTRFS_CACHE_ERROR) ? -EIO : 0;
     ret = btrfs_caching_ctl_wait_done(cache, caching_ctl);
     btrfs_put_caching_control(caching_ctl);
     return ret;
 }
 
 #ifdef CONFIG_BTRFS_DEBUG
 static void fragment_free_space(struct btrfs_block_group *block_group)
 {
     struct btrfs_fs_info *fs_info = block_group->fs_info;
     u64 start = block_group->start;
     u64 len = block_group->length;
     u64 chunk = block_group->flags & BTRFS_BLOCK_GROUP_METADATA ?
         fs_info->nodesize : fs_info->sectorsize;
     u64 step = chunk << 1;
 
     while (len > chunk) {
         btrfs_remove_free_space(block_group, start, chunk);
         start += step;
         if (len < step)
             len = 0;
         else
             len -= step;
     }
 }
 #endif
 
 /*
  * This is only called by btrfs_cache_block_group, since we could have freed
  * extents we need to check the pinned_extents for any extents that can't be
  * used yet since their free space will be released as soon as the transaction
  * commits.
  */
 u64 add_new_free_space(struct btrfs_block_group *block_group, u64 start, u64 end)
 {
     struct btrfs_fs_info *info = block_group->fs_info;
     u64 extent_start, extent_end, size, total_added = 0;
     int ret;
 
     while (start < end) {
         ret = find_first_extent_bit(&info->excluded_extents, start,
                         &extent_start, &extent_end,
                         EXTENT_DIRTY | EXTENT_UPTODATE,
                         NULL);
         if (ret)
             break;
 
         if (extent_start <= start) {
             start = extent_end + 1;
         } else if (extent_start > start && extent_start < end) {
             size = extent_start - start;
             total_added += size;
             ret = btrfs_add_free_space_async_trimmed(block_group,
                                  start, size);
             BUG_ON(ret); /* -ENOMEM or logic error */
             start = extent_end + 1;
         } else {
             break;
         }
     }
 
     if (start < end) {
         size = end - start;
         total_added += size;
         ret = btrfs_add_free_space_async_trimmed(block_group, start,
                              size);
         BUG_ON(ret); /* -ENOMEM or logic error */
     }
 
     return total_added;
 }
 
 static int load_extent_tree_free(struct btrfs_caching_control *caching_ctl)
 {
     struct btrfs_block_group *block_group = caching_ctl->block_group;
     struct btrfs_fs_info *fs_info = block_group->fs_info;
     struct btrfs_root *extent_root;
     struct btrfs_path *path;
     struct extent_buffer *leaf;
     struct btrfs_key key;
     u64 total_found = 0;
     u64 last = 0;
     u32 nritems;
     int ret;
     bool wakeup = true;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     last = max_t(u64, block_group->start, BTRFS_SUPER_INFO_OFFSET);
     extent_root = btrfs_extent_root(fs_info, last);
 
 #ifdef CONFIG_BTRFS_DEBUG
     /*
      * If we're fragmenting we don't want to make anybody think we can
      * allocate from this block group until we've had a chance to fragment
      * the free space.
      */
     if (btrfs_should_fragment_free_space(block_group))
         wakeup = false;
 #endif
     /*
      * We don't want to deadlock with somebody trying to allocate a new
      * extent for the extent root while also trying to search the extent
      * root to add free space.  So we skip locking and search the commit
      * root, since its read-only
      */
     path->skip_locking = 1;
     path->search_commit_root = 1;
     path->reada = READA_FORWARD;
 
     key.objectid = last;
     key.offset = 0;
     key.type = BTRFS_EXTENT_ITEM_KEY;
 
 next:
     ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
     if (ret < 0)
         goto out;
 
     leaf = path->nodes[0];
     nritems = btrfs_header_nritems(leaf);
 
     while (1) {
         if (btrfs_fs_closing(fs_info) > 1) {
             last = (u64)-1;
             break;
         }
 
         if (path->slots[0] < nritems) {
             btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
         } else {
             ret = btrfs_find_next_key(extent_root, path, &key, 0, 0);
             if (ret)
                 break;
 
             if (need_resched() ||
                 rwsem_is_contended(&fs_info->commit_root_sem)) {
                 if (wakeup)
                     caching_ctl->progress = last;
                 btrfs_release_path(path);
                 up_read(&fs_info->commit_root_sem);
                 mutex_unlock(&caching_ctl->mutex);
                 cond_resched();
                 mutex_lock(&caching_ctl->mutex);
                 down_read(&fs_info->commit_root_sem);
                 goto next;
             }
 
             ret = btrfs_next_leaf(extent_root, path);
             if (ret < 0)
                 goto out;
             if (ret)
                 break;
             leaf = path->nodes[0];
             nritems = btrfs_header_nritems(leaf);
             continue;
         }
 
         if (key.objectid < last) {
             key.objectid = last;
             key.offset = 0;
             key.type = BTRFS_EXTENT_ITEM_KEY;
 
             if (wakeup)
                 caching_ctl->progress = last;
             btrfs_release_path(path);
             goto next;
         }
 
         if (key.objectid < block_group->start) {
             path->slots[0]++;
             continue;
         }
 
         if (key.objectid >= block_group->start + block_group->length)
             break;
 
         if (key.type == BTRFS_EXTENT_ITEM_KEY ||
             key.type == BTRFS_METADATA_ITEM_KEY) {
             total_found += add_new_free_space(block_group, last,
                               key.objectid);
             if (key.type == BTRFS_METADATA_ITEM_KEY)
                 last = key.objectid +
                     fs_info->nodesize;
             else
                 last = key.objectid + key.offset;
 
             if (total_found > CACHING_CTL_WAKE_UP) {
                 total_found = 0;
                 if (wakeup)
                     wake_up(&caching_ctl->wait);
             }
         }
         path->slots[0]++;
     }
     ret = 0;
 
     total_found += add_new_free_space(block_group, last,
                 block_group->start + block_group->length);
     caching_ctl->progress = (u64)-1;
 
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 static noinline void caching_thread(struct btrfs_work *work)
 {
     struct btrfs_block_group *block_group;
     struct btrfs_fs_info *fs_info;
     struct btrfs_caching_control *caching_ctl;
     int ret;
 
     caching_ctl = container_of(work, struct btrfs_caching_control, work);
     block_group = caching_ctl->block_group;
     fs_info = block_group->fs_info;
 
     mutex_lock(&caching_ctl->mutex);
     down_read(&fs_info->commit_root_sem);
 
     if (btrfs_test_opt(fs_info, SPACE_CACHE)) {
         ret = load_free_space_cache(block_group);
         if (ret == 1) {
             ret = 0;
             goto done;
         }
 
         /*
          * We failed to load the space cache, set ourselves to
          * CACHE_STARTED and carry on.
          */
         spin_lock(&block_group->lock);
         block_group->cached = BTRFS_CACHE_STARTED;
         spin_unlock(&block_group->lock);
         wake_up(&caching_ctl->wait);
     }
 
     /*
      * If we are in the transaction that populated the free space tree we
      * can't actually cache from the free space tree as our commit root and
      * real root are the same, so we could change the contents of the blocks
      * while caching.  Instead do the slow caching in this case, and after
      * the transaction has committed we will be safe.
      */
     if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
         !(test_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags)))
         ret = load_free_space_tree(caching_ctl);
     else
         ret = load_extent_tree_free(caching_ctl);
 done:
     spin_lock(&block_group->lock);
     block_group->caching_ctl = NULL;
     block_group->cached = ret ? BTRFS_CACHE_ERROR : BTRFS_CACHE_FINISHED;
     spin_unlock(&block_group->lock);
 
 #ifdef CONFIG_BTRFS_DEBUG
     if (btrfs_should_fragment_free_space(block_group)) {
         u64 bytes_used;
 
         spin_lock(&block_group->space_info->lock);
         spin_lock(&block_group->lock);
         bytes_used = block_group->length - block_group->used;
         block_group->space_info->bytes_used += bytes_used >> 1;
         spin_unlock(&block_group->lock);
         spin_unlock(&block_group->space_info->lock);
         fragment_free_space(block_group);
     }
 #endif
 
     caching_ctl->progress = (u64)-1;
 
     up_read(&fs_info->commit_root_sem);
     btrfs_free_excluded_extents(block_group);
     mutex_unlock(&caching_ctl->mutex);
 
     wake_up(&caching_ctl->wait);
 
     btrfs_put_caching_control(caching_ctl);
     btrfs_put_block_group(block_group);
 }
 
 int btrfs_cache_block_group(struct btrfs_block_group *cache, bool wait)
 {
     struct btrfs_fs_info *fs_info = cache->fs_info;
     struct btrfs_caching_control *caching_ctl = NULL;
     int ret = 0;
 
     /* Allocator for zoned filesystems does not use the cache at all */
     if (btrfs_is_zoned(fs_info))
         return 0;
 
     caching_ctl = kzalloc(sizeof(*caching_ctl), GFP_NOFS);
     if (!caching_ctl)
         return -ENOMEM;
 
     INIT_LIST_HEAD(&caching_ctl->list);
     mutex_init(&caching_ctl->mutex);
     init_waitqueue_head(&caching_ctl->wait);
     caching_ctl->block_group = cache;
     caching_ctl->progress = cache->start;
     refcount_set(&caching_ctl->count, 2);
     btrfs_init_work(&caching_ctl->work, caching_thread, NULL, NULL);
 
     spin_lock(&cache->lock);
     if (cache->cached != BTRFS_CACHE_NO) {
         kfree(caching_ctl);
 
         caching_ctl = cache->caching_ctl;
         if (caching_ctl)
             refcount_inc(&caching_ctl->count);
         spin_unlock(&cache->lock);
         goto out;
     }
     WARN_ON(cache->caching_ctl);
     cache->caching_ctl = caching_ctl;
     cache->cached = BTRFS_CACHE_STARTED;
     cache->has_caching_ctl = 1;
     spin_unlock(&cache->lock);
 
     write_lock(&fs_info->block_group_cache_lock);
     refcount_inc(&caching_ctl->count);
     list_add_tail(&caching_ctl->list, &fs_info->caching_block_groups);
     write_unlock(&fs_info->block_group_cache_lock);
 
     btrfs_get_block_group(cache);
 
     btrfs_queue_work(fs_info->caching_workers, &caching_ctl->work);
 out:
     if (wait && caching_ctl)
         ret = btrfs_caching_ctl_wait_done(cache, caching_ctl);
     if (caching_ctl)
         btrfs_put_caching_control(caching_ctl);
 
     return ret;
 }
 
 static void clear_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
 {
     u64 extra_flags = chunk_to_extended(flags) &
                 BTRFS_EXTENDED_PROFILE_MASK;
 
     write_seqlock(&fs_info->profiles_lock);
     if (flags & BTRFS_BLOCK_GROUP_DATA)
         fs_info->avail_data_alloc_bits &= ~extra_flags;
     if (flags & BTRFS_BLOCK_GROUP_METADATA)
         fs_info->avail_metadata_alloc_bits &= ~extra_flags;
     if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
         fs_info->avail_system_alloc_bits &= ~extra_flags;
     write_sequnlock(&fs_info->profiles_lock);
 }
 
 /*
  * Clear incompat bits for the following feature(s):
  *
  * - RAID56 - in case there's neither RAID5 nor RAID6 profile block group
  *            in the whole filesystem
  *
  * - RAID1C34 - same as above for RAID1C3 and RAID1C4 block groups
  */
 static void clear_incompat_bg_bits(struct btrfs_fs_info *fs_info, u64 flags)
 {
     bool found_raid56 = false;
     bool found_raid1c34 = false;
 
     if ((flags & BTRFS_BLOCK_GROUP_RAID56_MASK) ||
         (flags & BTRFS_BLOCK_GROUP_RAID1C3) ||
         (flags & BTRFS_BLOCK_GROUP_RAID1C4)) {
         struct list_head *head = &fs_info->space_info;
         struct btrfs_space_info *sinfo;
 
         list_for_each_entry_rcu(sinfo, head, list) {
             down_read(&sinfo->groups_sem);
             if (!list_empty(&sinfo->block_groups[BTRFS_RAID_RAID5]))
                 found_raid56 = true;
             if (!list_empty(&sinfo->block_groups[BTRFS_RAID_RAID6]))
                 found_raid56 = true;
             if (!list_empty(&sinfo->block_groups[BTRFS_RAID_RAID1C3]))
                 found_raid1c34 = true;
             if (!list_empty(&sinfo->block_groups[BTRFS_RAID_RAID1C4]))
                 found_raid1c34 = true;
             up_read(&sinfo->groups_sem);
         }
         if (!found_raid56)
             btrfs_clear_fs_incompat(fs_info, RAID56);
         if (!found_raid1c34)
             btrfs_clear_fs_incompat(fs_info, RAID1C34);
     }
 }
 
 static int remove_block_group_item(struct btrfs_trans_handle *trans,
                    struct btrfs_path *path,
                    struct btrfs_block_group *block_group)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_root *root;
     struct btrfs_key key;
     int ret;
 
     root = btrfs_block_group_root(fs_info);
     key.objectid = block_group->start;
     key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
     key.offset = block_group->length;
 
     ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
     if (ret > 0)
         ret = -ENOENT;
     if (ret < 0)
         return ret;
 
     ret = btrfs_del_item(trans, root, path);
     return ret;
 }
 
 int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
                  u64 group_start, struct extent_map *em)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_path *path;
     struct btrfs_block_group *block_group;
     struct btrfs_free_cluster *cluster;
     struct inode *inode;
     struct kobject *kobj = NULL;
     int ret;
     int index;
     int factor;
     struct btrfs_caching_control *caching_ctl = NULL;
     bool remove_em;
     bool remove_rsv = false;
 
     block_group = btrfs_lookup_block_group(fs_info, group_start);
     BUG_ON(!block_group);
     BUG_ON(!block_group->ro);
 
     trace_btrfs_remove_block_group(block_group);
     /*
      * Free the reserved super bytes from this block group before
      * remove it.
      */
     btrfs_free_excluded_extents(block_group);
     btrfs_free_ref_tree_range(fs_info, block_group->start,
                   block_group->length);
 
     index = btrfs_bg_flags_to_raid_index(block_group->flags);
     factor = btrfs_bg_type_to_factor(block_group->flags);
 
     /* make sure this block group isn't part of an allocation cluster */
     cluster = &fs_info->data_alloc_cluster;
     spin_lock(&cluster->refill_lock);
     btrfs_return_cluster_to_free_space(block_group, cluster);
     spin_unlock(&cluster->refill_lock);
 
     /*
      * make sure this block group isn't part of a metadata
      * allocation cluster
      */
     cluster = &fs_info->meta_alloc_cluster;
     spin_lock(&cluster->refill_lock);
     btrfs_return_cluster_to_free_space(block_group, cluster);
     spin_unlock(&cluster->refill_lock);
 
     btrfs_clear_treelog_bg(block_group);
     btrfs_clear_data_reloc_bg(block_group);
 
     path = btrfs_alloc_path();
     if (!path) {
         ret = -ENOMEM;
         goto out;
     }
 
     /*
      * get the inode first so any iput calls done for the io_list
      * aren't the final iput (no unlinks allowed now)
      */
     inode = lookup_free_space_inode(block_group, path);
 
     mutex_lock(&trans->transaction->cache_write_mutex);
     /*
      * Make sure our free space cache IO is done before removing the
      * free space inode
      */
     spin_lock(&trans->transaction->dirty_bgs_lock);
     if (!list_empty(&block_group->io_list)) {
         list_del_init(&block_group->io_list);
 
         WARN_ON(!IS_ERR(inode) && inode != block_group->io_ctl.inode);
 
         spin_unlock(&trans->transaction->dirty_bgs_lock);
         btrfs_wait_cache_io(trans, block_group, path);
         btrfs_put_block_group(block_group);
         spin_lock(&trans->transaction->dirty_bgs_lock);
     }
 
     if (!list_empty(&block_group->dirty_list)) {
         list_del_init(&block_group->dirty_list);
         remove_rsv = true;
         btrfs_put_block_group(block_group);
     }
     spin_unlock(&trans->transaction->dirty_bgs_lock);
     mutex_unlock(&trans->transaction->cache_write_mutex);
 
     ret = btrfs_remove_free_space_inode(trans, inode, block_group);
     if (ret)
         goto out;
 
     write_lock(&fs_info->block_group_cache_lock);
     rb_erase_cached(&block_group->cache_node,
             &fs_info->block_group_cache_tree);
     RB_CLEAR_NODE(&block_group->cache_node);
 
     /* Once for the block groups rbtree */
     btrfs_put_block_group(block_group);
 
     write_unlock(&fs_info->block_group_cache_lock);
 
     down_write(&block_group->space_info->groups_sem);
     /*
      * we must use list_del_init so people can check to see if they
      * are still on the list after taking the semaphore
      */
     list_del_init(&block_group->list);
     if (list_empty(&block_group->space_info->block_groups[index])) {
         kobj = block_group->space_info->block_group_kobjs[index];
         block_group->space_info->block_group_kobjs[index] = NULL;
         clear_avail_alloc_bits(fs_info, block_group->flags);
     }
     up_write(&block_group->space_info->groups_sem);
     clear_incompat_bg_bits(fs_info, block_group->flags);
     if (kobj) {
         kobject_del(kobj);
         kobject_put(kobj);
     }
 
     if (block_group->has_caching_ctl)
         caching_ctl = btrfs_get_caching_control(block_group);
     if (block_group->cached == BTRFS_CACHE_STARTED)
         btrfs_wait_block_group_cache_done(block_group);
     if (block_group->has_caching_ctl) {
         write_lock(&fs_info->block_group_cache_lock);
         if (!caching_ctl) {
             struct btrfs_caching_control *ctl;
 
             list_for_each_entry(ctl,
                     &fs_info->caching_block_groups, list)
                 if (ctl->block_group == block_group) {
                     caching_ctl = ctl;
                     refcount_inc(&caching_ctl->count);
                     break;
                 }
         }
         if (caching_ctl)
             list_del_init(&caching_ctl->list);
         write_unlock(&fs_info->block_group_cache_lock);
         if (caching_ctl) {
             /* Once for the caching bgs list and once for us. */
             btrfs_put_caching_control(caching_ctl);
             btrfs_put_caching_control(caching_ctl);
         }
     }
 
     spin_lock(&trans->transaction->dirty_bgs_lock);
     WARN_ON(!list_empty(&block_group->dirty_list));
     WARN_ON(!list_empty(&block_group->io_list));
     spin_unlock(&trans->transaction->dirty_bgs_lock);
 
     btrfs_remove_free_space_cache(block_group);
 
     spin_lock(&block_group->space_info->lock);
     list_del_init(&block_group->ro_list);
 
     if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
         WARN_ON(block_group->space_info->total_bytes
             < block_group->length);
         WARN_ON(block_group->space_info->bytes_readonly
             < block_group->length - block_group->zone_unusable);
         WARN_ON(block_group->space_info->bytes_zone_unusable
             < block_group->zone_unusable);
         WARN_ON(block_group->space_info->disk_total
             < block_group->length * factor);
         WARN_ON(block_group->zone_is_active &&
             block_group->space_info->active_total_bytes
             < block_group->length);
     }
     block_group->space_info->total_bytes -= block_group->length;
     if (block_group->zone_is_active)
         block_group->space_info->active_total_bytes -= block_group->length;
     block_group->space_info->bytes_readonly -=
         (block_group->length - block_group->zone_unusable);
     block_group->space_info->bytes_zone_unusable -=
         block_group->zone_unusable;
     block_group->space_info->disk_total -= block_group->length * factor;
 
     spin_unlock(&block_group->space_info->lock);
 
     /*
      * Remove the free space for the block group from the free space tree
      * and the block group's item from the extent tree before marking the
      * block group as removed. This is to prevent races with tasks that
      * freeze and unfreeze a block group, this task and another task
      * allocating a new block group - the unfreeze task ends up removing
      * the block group's extent map before the task calling this function
      * deletes the block group item from the extent tree, allowing for
      * another task to attempt to create another block group with the same
      * item key (and failing with -EEXIST and a transaction abort).
      */
     ret = remove_block_group_free_space(trans, block_group);
     if (ret)
         goto out;
 
     ret = remove_block_group_item(trans, path, block_group);
     if (ret < 0)
         goto out;
 
     spin_lock(&block_group->lock);
     block_group->removed = 1;
     /*
      * At this point trimming or scrub can't start on this block group,
      * because we removed the block group from the rbtree
      * fs_info->block_group_cache_tree so no one can't find it anymore and
      * even if someone already got this block group before we removed it
      * from the rbtree, they have already incremented block_group->frozen -
      * if they didn't, for the trimming case they won't find any free space
      * entries because we already removed them all when we called
      * btrfs_remove_free_space_cache().
      *
      * And we must not remove the extent map from the fs_info->mapping_tree
      * to prevent the same logical address range and physical device space
      * ranges from being reused for a new block group. This is needed to
      * avoid races with trimming and scrub.
      *
      * An fs trim operation (btrfs_trim_fs() / btrfs_ioctl_fitrim()) is
      * completely transactionless, so while it is trimming a range the
      * currently running transaction might finish and a new one start,
      * allowing for new block groups to be created that can reuse the same
      * physical device locations unless we take this special care.
      *
      * There may also be an implicit trim operation if the file system
      * is mounted with -odiscard. The same protections must remain
      * in place until the extents have been discarded completely when
      * the transaction commit has completed.
      */
     remove_em = (atomic_read(&block_group->frozen) == 0);
     spin_unlock(&block_group->lock);
 
     if (remove_em) {
         struct extent_map_tree *em_tree;
 
         em_tree = &fs_info->mapping_tree;
         write_lock(&em_tree->lock);
         remove_extent_mapping(em_tree, em);
         write_unlock(&em_tree->lock);
         /* once for the tree */
         free_extent_map(em);
     }
 
 out:
     /* Once for the lookup reference */
     btrfs_put_block_group(block_group);
     if (remove_rsv)
         btrfs_delayed_refs_rsv_release(fs_info, 1);
     btrfs_free_path(path);
     return ret;
 }
 
 struct btrfs_trans_handle *btrfs_start_trans_remove_block_group(
         struct btrfs_fs_info *fs_info, const u64 chunk_offset)
 {
     struct btrfs_root *root = btrfs_block_group_root(fs_info);
     struct extent_map_tree *em_tree = &fs_info->mapping_tree;
     struct extent_map *em;
     struct map_lookup *map;
     unsigned int num_items;
 
     read_lock(&em_tree->lock);
     em = lookup_extent_mapping(em_tree, chunk_offset, 1);
     read_unlock(&em_tree->lock);
     ASSERT(em && em->start == chunk_offset);
 
     /*
      * We need to reserve 3 + N units from the metadata space info in order
      * to remove a block group (done at btrfs_remove_chunk() and at
      * btrfs_remove_block_group()), which are used for:
      *
      * 1 unit for adding the free space inode's orphan (located in the tree
      * of tree roots).
      * 1 unit for deleting the block group item (located in the extent
      * tree).
      * 1 unit for deleting the free space item (located in tree of tree
      * roots).
      * N units for deleting N device extent items corresponding to each
      * stripe (located in the device tree).
      *
      * In order to remove a block group we also need to reserve units in the
      * system space info in order to update the chunk tree (update one or
      * more device items and remove one chunk item), but this is done at
      * btrfs_remove_chunk() through a call to check_system_chunk().
      */
     map = em->map_lookup;
     num_items = 3 + map->num_stripes;
     free_extent_map(em);
 
     return btrfs_start_transaction_fallback_global_rsv(root, num_items);
 }
 
 /*
  * Mark block group @cache read-only, so later write won't happen to block
  * group @cache.
  *
  * If @force is not set, this function will only mark the block group readonly
  * if we have enough free space (1M) in other metadata/system block groups.
  * If @force is not set, this function will mark the block group readonly
  * without checking free space.
  *
  * NOTE: This function doesn't care if other block groups can contain all the
  * data in this block group. That check should be done by relocation routine,
  * not this function.
  */
 static int inc_block_group_ro(struct btrfs_block_group *cache, int force)
 {
     struct btrfs_space_info *sinfo = cache->space_info;
     u64 num_bytes;
     int ret = -ENOSPC;
 
     spin_lock(&sinfo->lock);
     spin_lock(&cache->lock);
 
     if (cache->swap_extents) {
         ret = -ETXTBSY;
         goto out;
     }
 
     if (cache->ro) {
         cache->ro++;
         ret = 0;
         goto out;
     }
 
     num_bytes = cache->length - cache->reserved - cache->pinned -
             cache->bytes_super - cache->zone_unusable - cache->used;
 
     /*
      * Data never overcommits, even in mixed mode, so do just the straight
      * check of left over space in how much we have allocated.
      */
     if (force) {
         ret = 0;
     } else if (sinfo->flags & BTRFS_BLOCK_GROUP_DATA) {
         u64 sinfo_used = btrfs_space_info_used(sinfo, true);
 
         /*
          * Here we make sure if we mark this bg RO, we still have enough
          * free space as buffer.
          */
         if (sinfo_used + num_bytes <= sinfo->total_bytes)
             ret = 0;
     } else {
         /*
          * We overcommit metadata, so we need to do the
          * btrfs_can_overcommit check here, and we need to pass in
          * BTRFS_RESERVE_NO_FLUSH to give ourselves the most amount of
          * leeway to allow us to mark this block group as read only.
          */
         if (btrfs_can_overcommit(cache->fs_info, sinfo, num_bytes,
                      BTRFS_RESERVE_NO_FLUSH))
             ret = 0;
     }
 
     if (!ret) {
         sinfo->bytes_readonly += num_bytes;
         if (btrfs_is_zoned(cache->fs_info)) {
             /* Migrate zone_unusable bytes to readonly */
             sinfo->bytes_readonly += cache->zone_unusable;
             sinfo->bytes_zone_unusable -= cache->zone_unusable;
             cache->zone_unusable = 0;
         }
         cache->ro++;
         list_add_tail(&cache->ro_list, &sinfo->ro_bgs);
     }
 out:
     spin_unlock(&cache->lock);
     spin_unlock(&sinfo->lock);
     if (ret == -ENOSPC && btrfs_test_opt(cache->fs_info, ENOSPC_DEBUG)) {
         btrfs_info(cache->fs_info,
             "unable to make block group %llu ro", cache->start);
         btrfs_dump_space_info(cache->fs_info, cache->space_info, 0, 0);
     }
     return ret;
 }
 
 static bool clean_pinned_extents(struct btrfs_trans_handle *trans,
                  struct btrfs_block_group *bg)
 {
     struct btrfs_fs_info *fs_info = bg->fs_info;
     struct btrfs_transaction *prev_trans = NULL;
     const u64 start = bg->start;
     const u64 end = start + bg->length - 1;
     int ret;
 
     spin_lock(&fs_info->trans_lock);
     if (trans->transaction->list.prev != &fs_info->trans_list) {
         prev_trans = list_last_entry(&trans->transaction->list,
                          struct btrfs_transaction, list);
         refcount_inc(&prev_trans->use_count);
     }
     spin_unlock(&fs_info->trans_lock);
 
     /*
      * Hold the unused_bg_unpin_mutex lock to avoid racing with
      * btrfs_finish_extent_commit(). If we are at transaction N, another
      * task might be running finish_extent_commit() for the previous
      * transaction N - 1, and have seen a range belonging to the block
      * group in pinned_extents before we were able to clear the whole block
      * group range from pinned_extents. This means that task can lookup for
      * the block group after we unpinned it from pinned_extents and removed
      * it, leading to a BUG_ON() at unpin_extent_range().
      */
     mutex_lock(&fs_info->unused_bg_unpin_mutex);
     if (prev_trans) {
         ret = clear_extent_bits(&prev_trans->pinned_extents, start, end,
                     EXTENT_DIRTY);
         if (ret)
             goto out;
     }
 
     ret = clear_extent_bits(&trans->transaction->pinned_extents, start, end,
                 EXTENT_DIRTY);
 out:
     mutex_unlock(&fs_info->unused_bg_unpin_mutex);
     if (prev_trans)
         btrfs_put_transaction(prev_trans);
 
     return ret == 0;
 }
 
 /*
  * Process the unused_bgs list and remove any that don't have any allocated
  * space inside of them.
  */
 void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_block_group *block_group;
     struct btrfs_space_info *space_info;
     struct btrfs_trans_handle *trans;
     const bool async_trim_enabled = btrfs_test_opt(fs_info, DISCARD_ASYNC);
     int ret = 0;
 
     if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
         return;
 
     /*
      * Long running balances can keep us blocked here for eternity, so
      * simply skip deletion if we're unable to get the mutex.
      */
     if (!mutex_trylock(&fs_info->reclaim_bgs_lock))
         return;
 
     spin_lock(&fs_info->unused_bgs_lock);
     while (!list_empty(&fs_info->unused_bgs)) {
         int trimming;
 
         block_group = list_first_entry(&fs_info->unused_bgs,
                            struct btrfs_block_group,
                            bg_list);
         list_del_init(&block_group->bg_list);
 
         space_info = block_group->space_info;
 
         if (ret || btrfs_mixed_space_info(space_info)) {
             btrfs_put_block_group(block_group);
             continue;
         }
         spin_unlock(&fs_info->unused_bgs_lock);
 
         btrfs_discard_cancel_work(&fs_info->discard_ctl, block_group);
 
         /* Don't want to race with allocators so take the groups_sem */
         down_write(&space_info->groups_sem);
 
         /*
          * Async discard moves the final block group discard to be prior
          * to the unused_bgs code path.  Therefore, if it's not fully
          * trimmed, punt it back to the async discard lists.
          */
         if (btrfs_test_opt(fs_info, DISCARD_ASYNC) &&
             !btrfs_is_free_space_trimmed(block_group)) {
             trace_btrfs_skip_unused_block_group(block_group);
             up_write(&space_info->groups_sem);
             /* Requeue if we failed because of async discard */
             btrfs_discard_queue_work(&fs_info->discard_ctl,
                          block_group);
             goto next;
         }
 
         spin_lock(&block_group->lock);
         if (block_group->reserved || block_group->pinned ||
             block_group->used || block_group->ro ||
             list_is_singular(&block_group->list)) {
             /*
              * We want to bail if we made new allocations or have
              * outstanding allocations in this block group.  We do
              * the ro check in case balance is currently acting on
              * this block group.
              */
             trace_btrfs_skip_unused_block_group(block_group);
             spin_unlock(&block_group->lock);
             up_write(&space_info->groups_sem);
             goto next;
         }
         spin_unlock(&block_group->lock);
 
         /* We don't want to force the issue, only flip if it's ok. */
         ret = inc_block_group_ro(block_group, 0);
         up_write(&space_info->groups_sem);
         if (ret < 0) {
             ret = 0;
             goto next;
         }
 
         ret = btrfs_zone_finish(block_group);
         if (ret < 0) {
             btrfs_dec_block_group_ro(block_group);
             if (ret == -EAGAIN)
                 ret = 0;
             goto next;
         }
 
         /*
          * Want to do this before we do anything else so we can recover
          * properly if we fail to join the transaction.
          */
         trans = btrfs_start_trans_remove_block_group(fs_info,
                              block_group->start);
         if (IS_ERR(trans)) {
             btrfs_dec_block_group_ro(block_group);
             ret = PTR_ERR(trans);
             goto next;
         }
 
         /*
          * We could have pending pinned extents for this block group,
          * just delete them, we don't care about them anymore.
          */
         if (!clean_pinned_extents(trans, block_group)) {
             btrfs_dec_block_group_ro(block_group);
             goto end_trans;
         }
 
         /*
          * At this point, the block_group is read only and should fail
          * new allocations.  However, btrfs_finish_extent_commit() can
          * cause this block_group to be placed back on the discard
          * lists because now the block_group isn't fully discarded.
          * Bail here and try again later after discarding everything.
          */
         spin_lock(&fs_info->discard_ctl.lock);
         if (!list_empty(&block_group->discard_list)) {
             spin_unlock(&fs_info->discard_ctl.lock);
             btrfs_dec_block_group_ro(block_group);
             btrfs_discard_queue_work(&fs_info->discard_ctl,
                          block_group);
             goto end_trans;
         }
         spin_unlock(&fs_info->discard_ctl.lock);
 
         /* Reset pinned so btrfs_put_block_group doesn't complain */
         spin_lock(&space_info->lock);
         spin_lock(&block_group->lock);
 
         btrfs_space_info_update_bytes_pinned(fs_info, space_info,
                              -block_group->pinned);
         space_info->bytes_readonly += block_group->pinned;
         block_group->pinned = 0;
 
         spin_unlock(&block_group->lock);
         spin_unlock(&space_info->lock);
 
         /*
          * The normal path here is an unused block group is passed here,
          * then trimming is handled in the transaction commit path.
          * Async discard interposes before this to do the trimming
          * before coming down the unused block group path as trimming
          * will no longer be done later in the transaction commit path.
          */
         if (!async_trim_enabled && btrfs_test_opt(fs_info, DISCARD_ASYNC))
             goto flip_async;
 
         /*
          * DISCARD can flip during remount. On zoned filesystems, we
          * need to reset sequential-required zones.
          */
         trimming = btrfs_test_opt(fs_info, DISCARD_SYNC) ||
                 btrfs_is_zoned(fs_info);
 
         /* Implicit trim during transaction commit. */
         if (trimming)
             btrfs_freeze_block_group(block_group);
 
         /*
          * Btrfs_remove_chunk will abort the transaction if things go
          * horribly wrong.
          */
         ret = btrfs_remove_chunk(trans, block_group->start);
 
         if (ret) {
             if (trimming)
                 btrfs_unfreeze_block_group(block_group);
             goto end_trans;
         }
 
         /*
          * If we're not mounted with -odiscard, we can just forget
          * about this block group. Otherwise we'll need to wait
          * until transaction commit to do the actual discard.
          */
         if (trimming) {
             spin_lock(&fs_info->unused_bgs_lock);
             /*
              * A concurrent scrub might have added us to the list
              * fs_info->unused_bgs, so use a list_move operation
              * to add the block group to the deleted_bgs list.
              */
             list_move(&block_group->bg_list,
                   &trans->transaction->deleted_bgs);
             spin_unlock(&fs_info->unused_bgs_lock);
             btrfs_get_block_group(block_group);
         }
 end_trans:
         btrfs_end_transaction(trans);
 next:
         btrfs_put_block_group(block_group);
         spin_lock(&fs_info->unused_bgs_lock);
     }
     spin_unlock(&fs_info->unused_bgs_lock);
     mutex_unlock(&fs_info->reclaim_bgs_lock);
     return;
 
 flip_async:
     btrfs_end_transaction(trans);
     mutex_unlock(&fs_info->reclaim_bgs_lock);
     btrfs_put_block_group(block_group);
     btrfs_discard_punt_unused_bgs_list(fs_info);
 }
 
 void btrfs_mark_bg_unused(struct btrfs_block_group *bg)
 {
     struct btrfs_fs_info *fs_info = bg->fs_info;
 
     spin_lock(&fs_info->unused_bgs_lock);
     if (list_empty(&bg->bg_list)) {
         btrfs_get_block_group(bg);
         trace_btrfs_add_unused_block_group(bg);
         list_add_tail(&bg->bg_list, &fs_info->unused_bgs);
     }
     spin_unlock(&fs_info->unused_bgs_lock);
 }
 
 /*
  * We want block groups with a low number of used bytes to be in the beginning
  * of the list, so they will get reclaimed first.
  */
 static int reclaim_bgs_cmp(void *unused, const struct list_head *a,
                const struct list_head *b)
 {
     const struct btrfs_block_group *bg1, *bg2;
 
     bg1 = list_entry(a, struct btrfs_block_group, bg_list);
     bg2 = list_entry(b, struct btrfs_block_group, bg_list);
 
     return bg1->used > bg2->used;
 }
 
 static inline bool btrfs_should_reclaim(struct btrfs_fs_info *fs_info)
 {
     if (btrfs_is_zoned(fs_info))
         return btrfs_zoned_should_reclaim(fs_info);
     return true;
 }
 
 void btrfs_reclaim_bgs_work(struct work_struct *work)
 {
     struct btrfs_fs_info *fs_info =
         container_of(work, struct btrfs_fs_info, reclaim_bgs_work);
     struct btrfs_block_group *bg;
     struct btrfs_space_info *space_info;
 
     if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
         return;
 
     if (!btrfs_should_reclaim(fs_info))
         return;
 
     sb_start_write(fs_info->sb);
 
     if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) {
         sb_end_write(fs_info->sb);
         return;
     }
 
     /*
      * Long running balances can keep us blocked here for eternity, so
      * simply skip reclaim if we're unable to get the mutex.
      */
     if (!mutex_trylock(&fs_info->reclaim_bgs_lock)) {
         btrfs_exclop_finish(fs_info);
         sb_end_write(fs_info->sb);
         return;
     }
 
     spin_lock(&fs_info->unused_bgs_lock);
     /*
      * Sort happens under lock because we can't simply splice it and sort.
      * The block groups might still be in use and reachable via bg_list,
      * and their presence in the reclaim_bgs list must be preserved.
      */
     list_sort(NULL, &fs_info->reclaim_bgs, reclaim_bgs_cmp);
     while (!list_empty(&fs_info->reclaim_bgs)) {
         u64 zone_unusable;
         int ret = 0;
 
         bg = list_first_entry(&fs_info->reclaim_bgs,
                       struct btrfs_block_group,
                       bg_list);
         list_del_init(&bg->bg_list);
 
         space_info = bg->space_info;
         spin_unlock(&fs_info->unused_bgs_lock);
 
         /* Don't race with allocators so take the groups_sem */
         down_write(&space_info->groups_sem);
 
         spin_lock(&bg->lock);
         if (bg->reserved || bg->pinned || bg->ro) {
             /*
              * We want to bail if we made new allocations or have
              * outstanding allocations in this block group.  We do
              * the ro check in case balance is currently acting on
              * this block group.
              */
             spin_unlock(&bg->lock);
             up_write(&space_info->groups_sem);
             goto next;
         }
         spin_unlock(&bg->lock);
 
         /* Get out fast, in case we're unmounting the filesystem */
         if (btrfs_fs_closing(fs_info)) {
             up_write(&space_info->groups_sem);
             goto next;
         }
 
         /*
          * Cache the zone_unusable value before turning the block group
          * to read only. As soon as the blog group is read only it's
          * zone_unusable value gets moved to the block group's read-only
          * bytes and isn't available for calculations anymore.
          */
         zone_unusable = bg->zone_unusable;
         ret = inc_block_group_ro(bg, 0);
         up_write(&space_info->groups_sem);
         if (ret < 0)
             goto next;
 
         btrfs_info(fs_info,
             "reclaiming chunk %llu with %llu%% used %llu%% unusable",
                 bg->start, div_u64(bg->used * 100, bg->length),
                 div64_u64(zone_unusable * 100, bg->length));
         trace_btrfs_reclaim_block_group(bg);
         ret = btrfs_relocate_chunk(fs_info, bg->start);
         if (ret) {
             btrfs_dec_block_group_ro(bg);
             btrfs_err(fs_info, "error relocating chunk %llu",
                   bg->start);
         }
 
 next:
         btrfs_put_block_group(bg);
         spin_lock(&fs_info->unused_bgs_lock);
     }
     spin_unlock(&fs_info->unused_bgs_lock);
     mutex_unlock(&fs_info->reclaim_bgs_lock);
     btrfs_exclop_finish(fs_info);
     sb_end_write(fs_info->sb);
 }
 
 void btrfs_reclaim_bgs(struct btrfs_fs_info *fs_info)
 {
     spin_lock(&fs_info->unused_bgs_lock);
     if (!list_empty(&fs_info->reclaim_bgs))
         queue_work(system_unbound_wq, &fs_info->reclaim_bgs_work);
     spin_unlock(&fs_info->unused_bgs_lock);
 }
 
 void btrfs_mark_bg_to_reclaim(struct btrfs_block_group *bg)
 {
     struct btrfs_fs_info *fs_info = bg->fs_info;
 
     spin_lock(&fs_info->unused_bgs_lock);
     if (list_empty(&bg->bg_list)) {
         btrfs_get_block_group(bg);
         trace_btrfs_add_reclaim_block_group(bg);
         list_add_tail(&bg->bg_list, &fs_info->reclaim_bgs);
     }
     spin_unlock(&fs_info->unused_bgs_lock);
 }
 
 static int read_bg_from_eb(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
                struct btrfs_path *path)
 {
     struct extent_map_tree *em_tree;
     struct extent_map *em;
     struct btrfs_block_group_item bg;
     struct extent_buffer *leaf;
     int slot;
     u64 flags;
     int ret = 0;
 
     slot = path->slots[0];
     leaf = path->nodes[0];
 
     em_tree = &fs_info->mapping_tree;
     read_lock(&em_tree->lock);
     em = lookup_extent_mapping(em_tree, key->objectid, key->offset);
     read_unlock(&em_tree->lock);
     if (!em) {
         btrfs_err(fs_info,
               "logical %llu len %llu found bg but no related chunk",
               key->objectid, key->offset);
         return -ENOENT;
     }
 
     if (em->start != key->objectid || em->len != key->offset) {
         btrfs_err(fs_info,
             "block group %llu len %llu mismatch with chunk %llu len %llu",
             key->objectid, key->offset, em->start, em->len);
         ret = -EUCLEAN;
         goto out_free_em;
     }
 
     read_extent_buffer(leaf, &bg, btrfs_item_ptr_offset(leaf, slot),
                sizeof(bg));
     flags = btrfs_stack_block_group_flags(&bg) &
         BTRFS_BLOCK_GROUP_TYPE_MASK;
 
     if (flags != (em->map_lookup->type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
         btrfs_err(fs_info,
 "block group %llu len %llu type flags 0x%llx mismatch with chunk type flags 0x%llx",
               key->objectid, key->offset, flags,
               (BTRFS_BLOCK_GROUP_TYPE_MASK & em->map_lookup->type));
         ret = -EUCLEAN;
     }
 
 out_free_em:
     free_extent_map(em);
     return ret;
 }
 
 static int find_first_block_group(struct btrfs_fs_info *fs_info,
                   struct btrfs_path *path,
                   struct btrfs_key *key)
 {
     struct btrfs_root *root = btrfs_block_group_root(fs_info);
     int ret;
     struct btrfs_key found_key;
 
     btrfs_for_each_slot(root, key, &found_key, path, ret) {
         if (found_key.objectid >= key->objectid &&
             found_key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
             return read_bg_from_eb(fs_info, &found_key, path);
         }
     }
     return ret;
 }
 
 static void set_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
 {
     u64 extra_flags = chunk_to_extended(flags) &
                 BTRFS_EXTENDED_PROFILE_MASK;
 
     write_seqlock(&fs_info->profiles_lock);
     if (flags & BTRFS_BLOCK_GROUP_DATA)
         fs_info->avail_data_alloc_bits |= extra_flags;
     if (flags & BTRFS_BLOCK_GROUP_METADATA)
         fs_info->avail_metadata_alloc_bits |= extra_flags;
     if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
         fs_info->avail_system_alloc_bits |= extra_flags;
     write_sequnlock(&fs_info->profiles_lock);
 }
 
 /**
  * Map a physical disk address to a list of logical addresses
  *
  * @fs_info:       the filesystem
  * @chunk_start:   logical address of block group
  * @bdev:      physical device to resolve, can be NULL to indicate any device
  * @physical:      physical address to map to logical addresses
  * @logical:       return array of logical addresses which map to @physical
  * @naddrs:    length of @logical
  * @stripe_len:    size of IO stripe for the given block group
  *
  * Maps a particular @physical disk address to a list of @logical addresses.
  * Used primarily to exclude those portions of a block group that contain super
  * block copies.
  */
 int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
              struct block_device *bdev, u64 physical, u64 **logical,
              int *naddrs, int *stripe_len)
 {
     struct extent_map *em;
     struct map_lookup *map;
     u64 *buf;
     u64 bytenr;
     u64 data_stripe_length;
     u64 io_stripe_size;
     int i, nr = 0;
     int ret = 0;
 
     em = btrfs_get_chunk_map(fs_info, chunk_start, 1);
     if (IS_ERR(em))
         return -EIO;
 
     map = em->map_lookup;
     data_stripe_length = em->orig_block_len;
     io_stripe_size = map->stripe_len;
     chunk_start = em->start;
 
     /* For RAID5/6 adjust to a full IO stripe length */
     if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
         io_stripe_size = map->stripe_len * nr_data_stripes(map);
 
     buf = kcalloc(map->num_stripes, sizeof(u64), GFP_NOFS);
     if (!buf) {
         ret = -ENOMEM;
         goto out;
     }
 
     for (i = 0; i < map->num_stripes; i++) {
         bool already_inserted = false;
         u64 stripe_nr;
         u64 offset;
         int j;
 
         if (!in_range(physical, map->stripes[i].physical,
                   data_stripe_length))
             continue;
 
         if (bdev && map->stripes[i].dev->bdev != bdev)
             continue;
 
         stripe_nr = physical - map->stripes[i].physical;
         stripe_nr = div64_u64_rem(stripe_nr, map->stripe_len, &offset);
 
         if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
                  BTRFS_BLOCK_GROUP_RAID10)) {
             stripe_nr = stripe_nr * map->num_stripes + i;
             stripe_nr = div_u64(stripe_nr, map->sub_stripes);
         }
         /*
          * The remaining case would be for RAID56, multiply by
          * nr_data_stripes().  Alternatively, just use rmap_len below
          * instead of map->stripe_len
          */
 
         bytenr = chunk_start + stripe_nr * io_stripe_size + offset;
 
         /* Ensure we don't add duplicate addresses */
         for (j = 0; j < nr; j++) {
             if (buf[j] == bytenr) {
                 already_inserted = true;
                 break;
             }
         }
 
         if (!already_inserted)
             buf[nr++] = bytenr;
     }
 
     *logical = buf;
     *naddrs = nr;
     *stripe_len = io_stripe_size;
 out:
     free_extent_map(em);
     return ret;
 }
 
 static int exclude_super_stripes(struct btrfs_block_group *cache)
 {
     struct btrfs_fs_info *fs_info = cache->fs_info;
     const bool zoned = btrfs_is_zoned(fs_info);
     u64 bytenr;
     u64 *logical;
     int stripe_len;
     int i, nr, ret;
 
     if (cache->start < BTRFS_SUPER_INFO_OFFSET) {
         stripe_len = BTRFS_SUPER_INFO_OFFSET - cache->start;
         cache->bytes_super += stripe_len;
         ret = btrfs_add_excluded_extent(fs_info, cache->start,
                         stripe_len);
         if (ret)
             return ret;
     }
 
     for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
         bytenr = btrfs_sb_offset(i);
         ret = btrfs_rmap_block(fs_info, cache->start, NULL,
                        bytenr, &logical, &nr, &stripe_len);
         if (ret)
             return ret;
 
         /* Shouldn't have super stripes in sequential zones */
         if (zoned && nr) {
             btrfs_err(fs_info,
             "zoned: block group %llu must not contain super block",
                   cache->start);
             return -EUCLEAN;
         }
 
         while (nr--) {
             u64 len = min_t(u64, stripe_len,
                 cache->start + cache->length - logical[nr]);
 
             cache->bytes_super += len;
             ret = btrfs_add_excluded_extent(fs_info, logical[nr],
                             len);
             if (ret) {
                 kfree(logical);
                 return ret;
             }
         }
 
         kfree(logical);
     }
     return 0;
 }
 
 static void link_block_group(struct btrfs_block_group *cache)
 {
     struct btrfs_space_info *space_info = cache->space_info;
     int index = btrfs_bg_flags_to_raid_index(cache->flags);
 
     down_write(&space_info->groups_sem);
     list_add_tail(&cache->list, &space_info->block_groups[index]);
     up_write(&space_info->groups_sem);
 }
 
 static struct btrfs_block_group *btrfs_create_block_group_cache(
         struct btrfs_fs_info *fs_info, u64 start)
 {
     struct btrfs_block_group *cache;
 
     cache = kzalloc(sizeof(*cache), GFP_NOFS);
     if (!cache)
         return NULL;
 
     cache->free_space_ctl = kzalloc(sizeof(*cache->free_space_ctl),
                     GFP_NOFS);
     if (!cache->free_space_ctl) {
         kfree(cache);
         return NULL;
     }
 
     cache->start = start;
 
     cache->fs_info = fs_info;
     cache->full_stripe_len = btrfs_full_stripe_len(fs_info, start);
 
     cache->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
 
     refcount_set(&cache->refs, 1);
     spin_lock_init(&cache->lock);
     init_rwsem(&cache->data_rwsem);
     INIT_LIST_HEAD(&cache->list);
     INIT_LIST_HEAD(&cache->cluster_list);
     INIT_LIST_HEAD(&cache->bg_list);
     INIT_LIST_HEAD(&cache->ro_list);
     INIT_LIST_HEAD(&cache->discard_list);
     INIT_LIST_HEAD(&cache->dirty_list);
     INIT_LIST_HEAD(&cache->io_list);
     INIT_LIST_HEAD(&cache->active_bg_list);
     btrfs_init_free_space_ctl(cache, cache->free_space_ctl);
     atomic_set(&cache->frozen, 0);
     mutex_init(&cache->free_space_lock);
     btrfs_init_full_stripe_locks_tree(&cache->full_stripe_locks_root);
 
     return cache;
 }
 
 /*
  * Iterate all chunks and verify that each of them has the corresponding block
  * group
  */
 static int check_chunk_block_group_mappings(struct btrfs_fs_info *fs_info)
 {
     struct extent_map_tree *map_tree = &fs_info->mapping_tree;
     struct extent_map *em;
     struct btrfs_block_group *bg;
     u64 start = 0;
     int ret = 0;
 
     while (1) {
         read_lock(&map_tree->lock);
         /*
          * lookup_extent_mapping will return the first extent map
          * intersecting the range, so setting @len to 1 is enough to
          * get the first chunk.
          */
         em = lookup_extent_mapping(map_tree, start, 1);
         read_unlock(&map_tree->lock);
         if (!em)
             break;
 
         bg = btrfs_lookup_block_group(fs_info, em->start);
         if (!bg) {
             btrfs_err(fs_info,
     "chunk start=%llu len=%llu doesn't have corresponding block group",
                      em->start, em->len);
             ret = -EUCLEAN;
             free_extent_map(em);
             break;
         }
         if (bg->start != em->start || bg->length != em->len ||
             (bg->flags & BTRFS_BLOCK_GROUP_TYPE_MASK) !=
             (em->map_lookup->type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
             btrfs_err(fs_info,
 "chunk start=%llu len=%llu flags=0x%llx doesn't match block group start=%llu len=%llu flags=0x%llx",
                 em->start, em->len,
                 em->map_lookup->type & BTRFS_BLOCK_GROUP_TYPE_MASK,
                 bg->start, bg->length,
                 bg->flags & BTRFS_BLOCK_GROUP_TYPE_MASK);
             ret = -EUCLEAN;
             free_extent_map(em);
             btrfs_put_block_group(bg);
             break;
         }
         start = em->start + em->len;
         free_extent_map(em);
         btrfs_put_block_group(bg);
     }
     return ret;
 }
 
 static int read_one_block_group(struct btrfs_fs_info *info,
                 struct btrfs_block_group_item *bgi,
                 const struct btrfs_key *key,
                 int need_clear)
 {
     struct btrfs_block_group *cache;
     struct btrfs_space_info *space_info;
     const bool mixed = btrfs_fs_incompat(info, MIXED_GROUPS);
     int ret;
 
     ASSERT(key->type == BTRFS_BLOCK_GROUP_ITEM_KEY);
 
     cache = btrfs_create_block_group_cache(info, key->objectid);
     if (!cache)
         return -ENOMEM;
 
     cache->length = key->offset;
     cache->used = btrfs_stack_block_group_used(bgi);
     cache->flags = btrfs_stack_block_group_flags(bgi);
     cache->global_root_id = btrfs_stack_block_group_chunk_objectid(bgi);
 
     set_free_space_tree_thresholds(cache);
 
     if (need_clear) {
         /*
          * When we mount with old space cache, we need to
          * set BTRFS_DC_CLEAR and set dirty flag.
          *
          * a) Setting 'BTRFS_DC_CLEAR' makes sure that we
          *    truncate the old free space cache inode and
          *    setup a new one.
          * b) Setting 'dirty flag' makes sure that we flush
          *    the new space cache info onto disk.
          */
         if (btrfs_test_opt(info, SPACE_CACHE))
             cache->disk_cache_state = BTRFS_DC_CLEAR;
     }
     if (!mixed && ((cache->flags & BTRFS_BLOCK_GROUP_METADATA) &&
         (cache->flags & BTRFS_BLOCK_GROUP_DATA))) {
             btrfs_err(info,
 "bg %llu is a mixed block group but filesystem hasn't enabled mixed block groups",
                   cache->start);
             ret = -EINVAL;
             goto error;
     }
 
     ret = btrfs_load_block_group_zone_info(cache, false);
     if (ret) {
         btrfs_err(info, "zoned: failed to load zone info of bg %llu",
               cache->start);
         goto error;
     }
 
     /*
      * We need to exclude the super stripes now so that the space info has
      * super bytes accounted for, otherwise we'll think we have more space
      * than we actually do.
      */
     ret = exclude_super_stripes(cache);
     if (ret) {
         /* We may have excluded something, so call this just in case. */
         btrfs_free_excluded_extents(cache);
         goto error;
     }
 
     /*
      * For zoned filesystem, space after the allocation offset is the only
      * free space for a block group. So, we don't need any caching work.
      * btrfs_calc_zone_unusable() will set the amount of free space and
      * zone_unusable space.
      *
      * For regular filesystem, check for two cases, either we are full, and
      * therefore don't need to bother with the caching work since we won't
      * find any space, or we are empty, and we can just add all the space
      * in and be done with it.  This saves us _a_lot_ of time, particularly
      * in the full case.
      */
     if (btrfs_is_zoned(info)) {
         btrfs_calc_zone_unusable(cache);
         /* Should not have any excluded extents. Just in case, though. */
         btrfs_free_excluded_extents(cache);
     } else if (cache->length == cache->used) {
         cache->last_byte_to_unpin = (u64)-1;
         cache->cached = BTRFS_CACHE_FINISHED;
         btrfs_free_excluded_extents(cache);
     } else if (cache->used == 0) {
         cache->last_byte_to_unpin = (u64)-1;
         cache->cached = BTRFS_CACHE_FINISHED;
         add_new_free_space(cache, cache->start,
                    cache->start + cache->length);
         btrfs_free_excluded_extents(cache);
     }
 
     ret = btrfs_add_block_group_cache(info, cache);
     if (ret) {
         btrfs_remove_free_space_cache(cache);
         goto error;
     }
     trace_btrfs_add_block_group(info, cache, 0);
     btrfs_update_space_info(info, cache->flags, cache->length,
                 cache->used, cache->bytes_super,
                 cache->zone_unusable, cache->zone_is_active,
                 &space_info);
 
     cache->space_info = space_info;
 
     link_block_group(cache);
 
     set_avail_alloc_bits(info, cache->flags);
     if (btrfs_chunk_writeable(info, cache->start)) {
         if (cache->used == 0) {
             ASSERT(list_empty(&cache->bg_list));
             if (btrfs_test_opt(info, DISCARD_ASYNC))
                 btrfs_discard_queue_work(&info->discard_ctl, cache);
             else
                 btrfs_mark_bg_unused(cache);
         }
     } else {
         inc_block_group_ro(cache, 1);
     }
 
     return 0;
 error:
     btrfs_put_block_group(cache);
     return ret;
 }
 
 static int fill_dummy_bgs(struct btrfs_fs_info *fs_info)
 {
     struct extent_map_tree *em_tree = &fs_info->mapping_tree;
     struct btrfs_space_info *space_info;
     struct rb_node *node;
     int ret = 0;
 
     for (node = rb_first_cached(&em_tree->map); node; node = rb_next(node)) {
         struct extent_map *em;
         struct map_lookup *map;
         struct btrfs_block_group *bg;
 
         em = rb_entry(node, struct extent_map, rb_node);
         map = em->map_lookup;
         bg = btrfs_create_block_group_cache(fs_info, em->start);
         if (!bg) {
             ret = -ENOMEM;
             break;
         }
 
         /* Fill dummy cache as FULL */
         bg->length = em->len;
         bg->flags = map->type;
         bg->last_byte_to_unpin = (u64)-1;
         bg->cached = BTRFS_CACHE_FINISHED;
         bg->used = em->len;
         bg->flags = map->type;
         ret = btrfs_add_block_group_cache(fs_info, bg);
         /*
          * We may have some valid block group cache added already, in
          * that case we skip to the next one.
          */
         if (ret == -EEXIST) {
             ret = 0;
             btrfs_put_block_group(bg);
             continue;
         }
 
         if (ret) {
             btrfs_remove_free_space_cache(bg);
             btrfs_put_block_group(bg);
             break;
         }
 
         btrfs_update_space_info(fs_info, bg->flags, em->len, em->len,
                     0, 0, false, &space_info);
         bg->space_info = space_info;
         link_block_group(bg);
 
         set_avail_alloc_bits(fs_info, bg->flags);
     }
     if (!ret)
         btrfs_init_global_block_rsv(fs_info);
     return ret;
 }
 
 int btrfs_read_block_groups(struct btrfs_fs_info *info)
 {
     struct btrfs_root *root = btrfs_block_group_root(info);
     struct btrfs_path *path;
     int ret;
     struct btrfs_block_group *cache;
     struct btrfs_space_info *space_info;
     struct btrfs_key key;
     int need_clear = 0;
     u64 cache_gen;
 
     if (!root)
         return fill_dummy_bgs(info);
 
     key.objectid = 0;
     key.offset = 0;
     key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     cache_gen = btrfs_super_cache_generation(info->super_copy);
     if (btrfs_test_opt(info, SPACE_CACHE) &&
         btrfs_super_generation(info->super_copy) != cache_gen)
         need_clear = 1;
     if (btrfs_test_opt(info, CLEAR_CACHE))
         need_clear = 1;
 
     while (1) {
         struct btrfs_block_group_item bgi;
         struct extent_buffer *leaf;
         int slot;
 
         ret = find_first_block_group(info, path, &key);
         if (ret > 0)
             break;
         if (ret != 0)
             goto error;
 
         leaf = path->nodes[0];
         slot = path->slots[0];
 
         read_extent_buffer(leaf, &bgi, btrfs_item_ptr_offset(leaf, slot),
                    sizeof(bgi));
 
         btrfs_item_key_to_cpu(leaf, &key, slot);
         btrfs_release_path(path);
         ret = read_one_block_group(info, &bgi, &key, need_clear);
         if (ret < 0)
             goto error;
         key.objectid += key.offset;
         key.offset = 0;
     }
     btrfs_release_path(path);
 
     list_for_each_entry(space_info, &info->space_info, list) {
         int i;
 
         for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
             if (list_empty(&space_info->block_groups[i]))
                 continue;
             cache = list_first_entry(&space_info->block_groups[i],
                          struct btrfs_block_group,
                          list);
             btrfs_sysfs_add_block_group_type(cache);
         }
 
         if (!(btrfs_get_alloc_profile(info, space_info->flags) &
               (BTRFS_BLOCK_GROUP_RAID10 |
                BTRFS_BLOCK_GROUP_RAID1_MASK |
                BTRFS_BLOCK_GROUP_RAID56_MASK |
                BTRFS_BLOCK_GROUP_DUP)))
             continue;
         /*
          * Avoid allocating from un-mirrored block group if there are
          * mirrored block groups.
          */
         list_for_each_entry(cache,
                 &space_info->block_groups[BTRFS_RAID_RAID0],
                 list)
             inc_block_group_ro(cache, 1);
         list_for_each_entry(cache,
                 &space_info->block_groups[BTRFS_RAID_SINGLE],
                 list)
             inc_block_group_ro(cache, 1);
     }
 
     btrfs_init_global_block_rsv(info);
     ret = check_chunk_block_group_mappings(info);
 error:
     btrfs_free_path(path);
     /*
      * We've hit some error while reading the extent tree, and have
      * rescue=ibadroots mount option.
      * Try to fill the tree using dummy block groups so that the user can
      * continue to mount and grab their data.
      */
     if (ret && btrfs_test_opt(info, IGNOREBADROOTS))
         ret = fill_dummy_bgs(info);
     return ret;
 }
 
 /*
  * This function, insert_block_group_item(), belongs to the phase 2 of chunk
  * allocation.
  *
  * See the comment at btrfs_chunk_alloc() for details about the chunk allocation
  * phases.
  */
 static int insert_block_group_item(struct btrfs_trans_handle *trans,
                    struct btrfs_block_group *block_group)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_block_group_item bgi;
     struct btrfs_root *root = btrfs_block_group_root(fs_info);
     struct btrfs_key key;
 
     spin_lock(&block_group->lock);
     btrfs_set_stack_block_group_used(&bgi, block_group->used);
     btrfs_set_stack_block_group_chunk_objectid(&bgi,
                            block_group->global_root_id);
     btrfs_set_stack_block_group_flags(&bgi, block_group->flags);
     key.objectid = block_group->start;
     key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
     key.offset = block_group->length;
     spin_unlock(&block_group->lock);
 
     return btrfs_insert_item(trans, root, &key, &bgi, sizeof(bgi));
 }
 
 static int insert_dev_extent(struct btrfs_trans_handle *trans,
                 struct btrfs_device *device, u64 chunk_offset,
                 u64 start, u64 num_bytes)
 {
     struct btrfs_fs_info *fs_info = device->fs_info;
     struct btrfs_root *root = fs_info->dev_root;
     struct btrfs_path *path;
     struct btrfs_dev_extent *extent;
     struct extent_buffer *leaf;
     struct btrfs_key key;
     int ret;
 
     WARN_ON(!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state));
     WARN_ON(test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state));
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     key.objectid = device->devid;
     key.type = BTRFS_DEV_EXTENT_KEY;
     key.offset = start;
     ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*extent));
     if (ret)
         goto out;
 
     leaf = path->nodes[0];
     extent = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_extent);
     btrfs_set_dev_extent_chunk_tree(leaf, extent, BTRFS_CHUNK_TREE_OBJECTID);
     btrfs_set_dev_extent_chunk_objectid(leaf, extent,
                         BTRFS_FIRST_CHUNK_TREE_OBJECTID);
     btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset);
 
     btrfs_set_dev_extent_length(leaf, extent, num_bytes);
     btrfs_mark_buffer_dirty(leaf);
 out:
     btrfs_free_path(path);
     return ret;
 }
 
 /*
  * This function belongs to phase 2.
  *
  * See the comment at btrfs_chunk_alloc() for details about the chunk allocation
  * phases.
  */
 static int insert_dev_extents(struct btrfs_trans_handle *trans,
                    u64 chunk_offset, u64 chunk_size)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_device *device;
     struct extent_map *em;
     struct map_lookup *map;
     u64 dev_offset;
     u64 stripe_size;
     int i;
     int ret = 0;
 
     em = btrfs_get_chunk_map(fs_info, chunk_offset, chunk_size);
     if (IS_ERR(em))
         return PTR_ERR(em);
 
     map = em->map_lookup;
     stripe_size = em->orig_block_len;
 
     /*
      * Take the device list mutex to prevent races with the final phase of
      * a device replace operation that replaces the device object associated
      * with the map's stripes, because the device object's id can change
      * at any time during that final phase of the device replace operation
      * (dev-replace.c:btrfs_dev_replace_finishing()), so we could grab the
      * replaced device and then see it with an ID of BTRFS_DEV_REPLACE_DEVID,
      * resulting in persisting a device extent item with such ID.
      */
     mutex_lock(&fs_info->fs_devices->device_list_mutex);
     for (i = 0; i < map->num_stripes; i++) {
         device = map->stripes[i].dev;
         dev_offset = map->stripes[i].physical;
 
         ret = insert_dev_extent(trans, device, chunk_offset, dev_offset,
                        stripe_size);
         if (ret)
             break;
     }
     mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 
     free_extent_map(em);
     return ret;
 }
 
 /*
  * This function, btrfs_create_pending_block_groups(), belongs to the phase 2 of
  * chunk allocation.
  *
  * See the comment at btrfs_chunk_alloc() for details about the chunk allocation
  * phases.
  */
 void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_block_group *block_group;
     int ret = 0;
 
     while (!list_empty(&trans->new_bgs)) {
         int index;
 
         block_group = list_first_entry(&trans->new_bgs,
                            struct btrfs_block_group,
                            bg_list);
         if (ret)
             goto next;
 
         index = btrfs_bg_flags_to_raid_index(block_group->flags);
 
         ret = insert_block_group_item(trans, block_group);
         if (ret)
             btrfs_abort_transaction(trans, ret);
         if (!block_group->chunk_item_inserted) {
             mutex_lock(&fs_info->chunk_mutex);
             ret = btrfs_chunk_alloc_add_chunk_item(trans, block_group);
             mutex_unlock(&fs_info->chunk_mutex);
             if (ret)
                 btrfs_abort_transaction(trans, ret);
         }
         ret = insert_dev_extents(trans, block_group->start,
                      block_group->length);
         if (ret)
             btrfs_abort_transaction(trans, ret);
         add_block_group_free_space(trans, block_group);
 
         /*
          * If we restriped during balance, we may have added a new raid
          * type, so now add the sysfs entries when it is safe to do so.
          * We don't have to worry about locking here as it's handled in
          * btrfs_sysfs_add_block_group_type.
          */
         if (block_group->space_info->block_group_kobjs[index] == NULL)
             btrfs_sysfs_add_block_group_type(block_group);
 
         /* Already aborted the transaction if it failed. */
 next:
         btrfs_delayed_refs_rsv_release(fs_info, 1);
         list_del_init(&block_group->bg_list);
     }
     btrfs_trans_release_chunk_metadata(trans);
 }
 
 /*
  * For extent tree v2 we use the block_group_item->chunk_offset to point at our
  * global root id.  For v1 it's always set to BTRFS_FIRST_CHUNK_TREE_OBJECTID.
  */
 static u64 calculate_global_root_id(struct btrfs_fs_info *fs_info, u64 offset)
 {
     u64 div = SZ_1G;
     u64 index;
 
     if (!btrfs_fs_incompat(fs_info, EXTENT_TREE_V2))
         return BTRFS_FIRST_CHUNK_TREE_OBJECTID;
 
     /* If we have a smaller fs index based on 128MiB. */
     if (btrfs_super_total_bytes(fs_info->super_copy) <= (SZ_1G * 10ULL))
         div = SZ_128M;
 
     offset = div64_u64(offset, div);
     div64_u64_rem(offset, fs_info->nr_global_roots, &index);
     return index;
 }
 
 struct btrfs_block_group *btrfs_make_block_group(struct btrfs_trans_handle *trans,
                          u64 bytes_used, u64 type,
                          u64 chunk_offset, u64 size)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_block_group *cache;
     int ret;
 
     btrfs_set_log_full_commit(trans);
 
     cache = btrfs_create_block_group_cache(fs_info, chunk_offset);
     if (!cache)
         return ERR_PTR(-ENOMEM);
 
     cache->length = size;
     set_free_space_tree_thresholds(cache);
     cache->used = bytes_used;
     cache->flags = type;
     cache->last_byte_to_unpin = (u64)-1;
     cache->cached = BTRFS_CACHE_FINISHED;
     cache->global_root_id = calculate_global_root_id(fs_info, cache->start);
 
     if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
         cache->needs_free_space = 1;
 
     ret = btrfs_load_block_group_zone_info(cache, true);
     if (ret) {
         btrfs_put_block_group(cache);
         return ERR_PTR(ret);
     }
 
     ret = exclude_super_stripes(cache);
     if (ret) {
         /* We may have excluded something, so call this just in case */
         btrfs_free_excluded_extents(cache);
         btrfs_put_block_group(cache);
         return ERR_PTR(ret);
     }
 
     add_new_free_space(cache, chunk_offset, chunk_offset + size);
 
     btrfs_free_excluded_extents(cache);
 
 #ifdef CONFIG_BTRFS_DEBUG
     if (btrfs_should_fragment_free_space(cache)) {
         u64 new_bytes_used = size - bytes_used;
 
         bytes_used += new_bytes_used >> 1;
         fragment_free_space(cache);
     }
 #endif
     /*
      * Ensure the corresponding space_info object is created and
      * assigned to our block group. We want our bg to be added to the rbtree
      * with its ->space_info set.
      */
     cache->space_info = btrfs_find_space_info(fs_info, cache->flags);
     ASSERT(cache->space_info);
 
     ret = btrfs_add_block_group_cache(fs_info, cache);
     if (ret) {
         btrfs_remove_free_space_cache(cache);
         btrfs_put_block_group(cache);
         return ERR_PTR(ret);
     }
 
     /*
      * Now that our block group has its ->space_info set and is inserted in
      * the rbtree, update the space info's counters.
      */
     trace_btrfs_add_block_group(fs_info, cache, 1);
     btrfs_update_space_info(fs_info, cache->flags, size, bytes_used,
                 cache->bytes_super, cache->zone_unusable,
                 cache->zone_is_active, &cache->space_info);
     btrfs_update_global_block_rsv(fs_info);
 
     link_block_group(cache);
 
     list_add_tail(&cache->bg_list, &trans->new_bgs);
     trans->delayed_ref_updates++;
     btrfs_update_delayed_refs_rsv(trans);
 
     set_avail_alloc_bits(fs_info, type);
     return cache;
 }
 
 /*
  * Mark one block group RO, can be called several times for the same block
  * group.
  *
  * @cache:      the destination block group
  * @do_chunk_alloc: whether need to do chunk pre-allocation, this is to
  *          ensure we still have some free space after marking this
  *          block group RO.
  */
 int btrfs_inc_block_group_ro(struct btrfs_block_group *cache,
                  bool do_chunk_alloc)
 {
     struct btrfs_fs_info *fs_info = cache->fs_info;
     struct btrfs_trans_handle *trans;
     struct btrfs_root *root = btrfs_block_group_root(fs_info);
     u64 alloc_flags;
     int ret;
     bool dirty_bg_running;
 
     /*
      * This can only happen when we are doing read-only scrub on read-only
      * mount.
      * In that case we should not start a new transaction on read-only fs.
      * Thus here we skip all chunk allocations.
      */
     if (sb_rdonly(fs_info->sb)) {
         mutex_lock(&fs_info->ro_block_group_mutex);
         ret = inc_block_group_ro(cache, 0);
         mutex_unlock(&fs_info->ro_block_group_mutex);
         return ret;
     }
 
     do {
         trans = btrfs_join_transaction(root);
         if (IS_ERR(trans))
             return PTR_ERR(trans);
 
         dirty_bg_running = false;
 
         /*
          * We're not allowed to set block groups readonly after the dirty
          * block group cache has started writing.  If it already started,
          * back off and let this transaction commit.
          */
         mutex_lock(&fs_info->ro_block_group_mutex);
         if (test_bit(BTRFS_TRANS_DIRTY_BG_RUN, &trans->transaction->flags)) {
             u64 transid = trans->transid;
 
             mutex_unlock(&fs_info->ro_block_group_mutex);
             btrfs_end_transaction(trans);
 
             ret = btrfs_wait_for_commit(fs_info, transid);
             if (ret)
                 return ret;
             dirty_bg_running = true;
         }
     } while (dirty_bg_running);
 
     if (do_chunk_alloc) {
         /*
          * If we are changing raid levels, try to allocate a
          * corresponding block group with the new raid level.
          */
         alloc_flags = btrfs_get_alloc_profile(fs_info, cache->flags);
         if (alloc_flags != cache->flags) {
             ret = btrfs_chunk_alloc(trans, alloc_flags,
                         CHUNK_ALLOC_FORCE);
             /*
              * ENOSPC is allowed here, we may have enough space
              * already allocated at the new raid level to carry on
              */
             if (ret == -ENOSPC)
                 ret = 0;
             if (ret < 0)
                 goto out;
         }
     }
 
     ret = inc_block_group_ro(cache, 0);
     if (!do_chunk_alloc || ret == -ETXTBSY)
         goto unlock_out;
     if (!ret)
         goto out;
     alloc_flags = btrfs_get_alloc_profile(fs_info, cache->space_info->flags);
     ret = btrfs_chunk_alloc(trans, alloc_flags, CHUNK_ALLOC_FORCE);
     if (ret < 0)
         goto out;
     /*
      * We have allocated a new chunk. We also need to activate that chunk to
      * grant metadata tickets for zoned filesystem.
      */
     ret = btrfs_zoned_activate_one_bg(fs_info, cache->space_info, true);
     if (ret < 0)
         goto out;
 
     ret = inc_block_group_ro(cache, 0);
     if (ret == -ETXTBSY)
         goto unlock_out;
 out:
     if (cache->flags & BTRFS_BLOCK_GROUP_SYSTEM) {
         alloc_flags = btrfs_get_alloc_profile(fs_info, cache->flags);
         mutex_lock(&fs_info->chunk_mutex);
         check_system_chunk(trans, alloc_flags);
         mutex_unlock(&fs_info->chunk_mutex);
     }
 unlock_out:
     mutex_unlock(&fs_info->ro_block_group_mutex);
 
     btrfs_end_transaction(trans);
     return ret;
 }
 
 void btrfs_dec_block_group_ro(struct btrfs_block_group *cache)
 {
     struct btrfs_space_info *sinfo = cache->space_info;
     u64 num_bytes;
 
     BUG_ON(!cache->ro);
 
     spin_lock(&sinfo->lock);
     spin_lock(&cache->lock);
     if (!--cache->ro) {
         if (btrfs_is_zoned(cache->fs_info)) {
             /* Migrate zone_unusable bytes back */
             cache->zone_unusable =
                 (cache->alloc_offset - cache->used) +
                 (cache->length - cache->zone_capacity);
             sinfo->bytes_zone_unusable += cache->zone_unusable;
             sinfo->bytes_readonly -= cache->zone_unusable;
         }
         num_bytes = cache->length - cache->reserved -
                 cache->pinned - cache->bytes_super -
                 cache->zone_unusable - cache->used;
         sinfo->bytes_readonly -= num_bytes;
         list_del_init(&cache->ro_list);
     }
     spin_unlock(&cache->lock);
     spin_unlock(&sinfo->lock);
 }
 
 static int update_block_group_item(struct btrfs_trans_handle *trans,
                    struct btrfs_path *path,
                    struct btrfs_block_group *cache)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     int ret;
     struct btrfs_root *root = btrfs_block_group_root(fs_info);
     unsigned long bi;
     struct extent_buffer *leaf;
     struct btrfs_block_group_item bgi;
     struct btrfs_key key;
 
     key.objectid = cache->start;
     key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
     key.offset = cache->length;
 
     ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
     if (ret) {
         if (ret > 0)
             ret = -ENOENT;
         goto fail;
     }
 
     leaf = path->nodes[0];
     bi = btrfs_item_ptr_offset(leaf, path->slots[0]);
     btrfs_set_stack_block_group_used(&bgi, cache->used);
     btrfs_set_stack_block_group_chunk_objectid(&bgi,
                            cache->global_root_id);
     btrfs_set_stack_block_group_flags(&bgi, cache->flags);
     write_extent_buffer(leaf, &bgi, bi, sizeof(bgi));
     btrfs_mark_buffer_dirty(leaf);
 fail:
     btrfs_release_path(path);
     return ret;
 
 }
 
 static int cache_save_setup(struct btrfs_block_group *block_group,
                 struct btrfs_trans_handle *trans,
                 struct btrfs_path *path)
 {
     struct btrfs_fs_info *fs_info = block_group->fs_info;
     struct btrfs_root *root = fs_info->tree_root;
     struct inode *inode = NULL;
     struct extent_changeset *data_reserved = NULL;
     u64 alloc_hint = 0;
     int dcs = BTRFS_DC_ERROR;
     u64 cache_size = 0;
     int retries = 0;
     int ret = 0;
 
     if (!btrfs_test_opt(fs_info, SPACE_CACHE))
         return 0;
 
     /*
      * If this block group is smaller than 100 megs don't bother caching the
      * block group.
      */
     if (block_group->length < (100 * SZ_1M)) {
         spin_lock(&block_group->lock);
         block_group->disk_cache_state = BTRFS_DC_WRITTEN;
         spin_unlock(&block_group->lock);
         return 0;
     }
 
     if (TRANS_ABORTED(trans))
         return 0;
 again:
     inode = lookup_free_space_inode(block_group, path);
     if (IS_ERR(inode) && PTR_ERR(inode) != -ENOENT) {
         ret = PTR_ERR(inode);
         btrfs_release_path(path);
         goto out;
     }
 
     if (IS_ERR(inode)) {
         BUG_ON(retries);
         retries++;
 
         if (block_group->ro)
             goto out_free;
 
         ret = create_free_space_inode(trans, block_group, path);
         if (ret)
             goto out_free;
         goto again;
     }
 
     /*
      * We want to set the generation to 0, that way if anything goes wrong
      * from here on out we know not to trust this cache when we load up next
      * time.
      */
     BTRFS_I(inode)->generation = 0;
     ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
     if (ret) {
         /*
          * So theoretically we could recover from this, simply set the
          * super cache generation to 0 so we know to invalidate the
          * cache, but then we'd have to keep track of the block groups
          * that fail this way so we know we _have_ to reset this cache
          * before the next commit or risk reading stale cache.  So to
          * limit our exposure to horrible edge cases lets just abort the
          * transaction, this only happens in really bad situations
          * anyway.
          */
         btrfs_abort_transaction(trans, ret);
         goto out_put;
     }
     WARN_ON(ret);
 
     /* We've already setup this transaction, go ahead and exit */
     if (block_group->cache_generation == trans->transid &&
         i_size_read(inode)) {
         dcs = BTRFS_DC_SETUP;
         goto out_put;
     }
 
     if (i_size_read(inode) > 0) {
         ret = btrfs_check_trunc_cache_free_space(fs_info,
                     &fs_info->global_block_rsv);
         if (ret)
             goto out_put;
 
         ret = btrfs_truncate_free_space_cache(trans, NULL, inode);
         if (ret)
             goto out_put;
     }
 
     spin_lock(&block_group->lock);
     if (block_group->cached != BTRFS_CACHE_FINISHED ||
         !btrfs_test_opt(fs_info, SPACE_CACHE)) {
         /*
          * don't bother trying to write stuff out _if_
          * a) we're not cached,
          * b) we're with nospace_cache mount option,
          * c) we're with v2 space_cache (FREE_SPACE_TREE).
          */
         dcs = BTRFS_DC_WRITTEN;
         spin_unlock(&block_group->lock);
         goto out_put;
     }
     spin_unlock(&block_group->lock);
 
     /*
      * We hit an ENOSPC when setting up the cache in this transaction, just
      * skip doing the setup, we've already cleared the cache so we're safe.
      */
     if (test_bit(BTRFS_TRANS_CACHE_ENOSPC, &trans->transaction->flags)) {
         ret = -ENOSPC;
         goto out_put;
     }
 
     /*
      * Try to preallocate enough space based on how big the block group is.
      * Keep in mind this has to include any pinned space which could end up
      * taking up quite a bit since it's not folded into the other space
      * cache.
      */
     cache_size = div_u64(block_group->length, SZ_256M);
     if (!cache_size)
         cache_size = 1;
 
     cache_size *= 16;
     cache_size *= fs_info->sectorsize;
 
     ret = btrfs_check_data_free_space(BTRFS_I(inode), &data_reserved, 0,
                       cache_size);
     if (ret)
         goto out_put;
 
     ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, cache_size,
                           cache_size, cache_size,
                           &alloc_hint);
     /*
      * Our cache requires contiguous chunks so that we don't modify a bunch
      * of metadata or split extents when writing the cache out, which means
      * we can enospc if we are heavily fragmented in addition to just normal
      * out of space conditions.  So if we hit this just skip setting up any
      * other block groups for this transaction, maybe we'll unpin enough
      * space the next time around.
      */
     if (!ret)
         dcs = BTRFS_DC_SETUP;
     else if (ret == -ENOSPC)
         set_bit(BTRFS_TRANS_CACHE_ENOSPC, &trans->transaction->flags);
 
 out_put:
     iput(inode);
 out_free:
     btrfs_release_path(path);
 out:
     spin_lock(&block_group->lock);
     if (!ret && dcs == BTRFS_DC_SETUP)
         block_group->cache_generation = trans->transid;
     block_group->disk_cache_state = dcs;
     spin_unlock(&block_group->lock);
 
     extent_changeset_free(data_reserved);
     return ret;
 }
 
 int btrfs_setup_space_cache(struct btrfs_trans_handle *trans)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_block_group *cache, *tmp;
     struct btrfs_transaction *cur_trans = trans->transaction;
     struct btrfs_path *path;
 
     if (list_empty(&cur_trans->dirty_bgs) ||
         !btrfs_test_opt(fs_info, SPACE_CACHE))
         return 0;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     /* Could add new block groups, use _safe just in case */
     list_for_each_entry_safe(cache, tmp, &cur_trans->dirty_bgs,
                  dirty_list) {
         if (cache->disk_cache_state == BTRFS_DC_CLEAR)
             cache_save_setup(cache, trans, path);
     }
 
     btrfs_free_path(path);
     return 0;
 }
 
 /*
  * Transaction commit does final block group cache writeback during a critical
  * section where nothing is allowed to change the FS.  This is required in
  * order for the cache to actually match the block group, but can introduce a
  * lot of latency into the commit.
  *
  * So, btrfs_start_dirty_block_groups is here to kick off block group cache IO.
  * There's a chance we'll have to redo some of it if the block group changes
  * again during the commit, but it greatly reduces the commit latency by
  * getting rid of the easy block groups while we're still allowing others to
  * join the commit.
  */
 int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_block_group *cache;
     struct btrfs_transaction *cur_trans = trans->transaction;
     int ret = 0;
     int should_put;
     struct btrfs_path *path = NULL;
     LIST_HEAD(dirty);
     struct list_head *io = &cur_trans->io_bgs;
     int loops = 0;
 
     spin_lock(&cur_trans->dirty_bgs_lock);
     if (list_empty(&cur_trans->dirty_bgs)) {
         spin_unlock(&cur_trans->dirty_bgs_lock);
         return 0;
     }
     list_splice_init(&cur_trans->dirty_bgs, &dirty);
     spin_unlock(&cur_trans->dirty_bgs_lock);
 
 again:
     /* Make sure all the block groups on our dirty list actually exist */
     btrfs_create_pending_block_groups(trans);
 
     if (!path) {
         path = btrfs_alloc_path();
         if (!path) {
             ret = -ENOMEM;
             goto out;
         }
     }
 
     /*
      * cache_write_mutex is here only to save us from balance or automatic
      * removal of empty block groups deleting this block group while we are
      * writing out the cache
      */
     mutex_lock(&trans->transaction->cache_write_mutex);
     while (!list_empty(&dirty)) {
         bool drop_reserve = true;
 
         cache = list_first_entry(&dirty, struct btrfs_block_group,
                      dirty_list);
         /*
          * This can happen if something re-dirties a block group that
          * is already under IO.  Just wait for it to finish and then do
          * it all again
          */
         if (!list_empty(&cache->io_list)) {
             list_del_init(&cache->io_list);
             btrfs_wait_cache_io(trans, cache, path);
             btrfs_put_block_group(cache);
         }
 
 
         /*
          * btrfs_wait_cache_io uses the cache->dirty_list to decide if
          * it should update the cache_state.  Don't delete until after
          * we wait.
          *
          * Since we're not running in the commit critical section
          * we need the dirty_bgs_lock to protect from update_block_group
          */
         spin_lock(&cur_trans->dirty_bgs_lock);
         list_del_init(&cache->dirty_list);
         spin_unlock(&cur_trans->dirty_bgs_lock);
 
         should_put = 1;
 
         cache_save_setup(cache, trans, path);
 
         if (cache->disk_cache_state == BTRFS_DC_SETUP) {
             cache->io_ctl.inode = NULL;
             ret = btrfs_write_out_cache(trans, cache, path);
             if (ret == 0 && cache->io_ctl.inode) {
                 should_put = 0;
 
                 /*
                  * The cache_write_mutex is protecting the
                  * io_list, also refer to the definition of
                  * btrfs_transaction::io_bgs for more details
                  */
                 list_add_tail(&cache->io_list, io);
             } else {
                 /*
                  * If we failed to write the cache, the
                  * generation will be bad and life goes on
                  */
                 ret = 0;
             }
         }
         if (!ret) {
             ret = update_block_group_item(trans, path, cache);
             /*
              * Our block group might still be attached to the list
              * of new block groups in the transaction handle of some
              * other task (struct btrfs_trans_handle->new_bgs). This
              * means its block group item isn't yet in the extent
              * tree. If this happens ignore the error, as we will
              * try again later in the critical section of the
              * transaction commit.
              */
             if (ret == -ENOENT) {
                 ret = 0;
                 spin_lock(&cur_trans->dirty_bgs_lock);
                 if (list_empty(&cache->dirty_list)) {
                     list_add_tail(&cache->dirty_list,
                               &cur_trans->dirty_bgs);
                     btrfs_get_block_group(cache);
                     drop_reserve = false;
                 }
                 spin_unlock(&cur_trans->dirty_bgs_lock);
             } else if (ret) {
                 btrfs_abort_transaction(trans, ret);
             }
         }
 
         /* If it's not on the io list, we need to put the block group */
         if (should_put)
             btrfs_put_block_group(cache);
         if (drop_reserve)
             btrfs_delayed_refs_rsv_release(fs_info, 1);
         /*
          * Avoid blocking other tasks for too long. It might even save
          * us from writing caches for block groups that are going to be
          * removed.
          */
         mutex_unlock(&trans->transaction->cache_write_mutex);
         if (ret)
             goto out;
         mutex_lock(&trans->transaction->cache_write_mutex);
     }
     mutex_unlock(&trans->transaction->cache_write_mutex);
 
     /*
      * Go through delayed refs for all the stuff we've just kicked off
      * and then loop back (just once)
      */
     if (!ret)
         ret = btrfs_run_delayed_refs(trans, 0);
     if (!ret && loops == 0) {
         loops++;
         spin_lock(&cur_trans->dirty_bgs_lock);
         list_splice_init(&cur_trans->dirty_bgs, &dirty);
         /*
          * dirty_bgs_lock protects us from concurrent block group
          * deletes too (not just cache_write_mutex).
          */
         if (!list_empty(&dirty)) {
             spin_unlock(&cur_trans->dirty_bgs_lock);
             goto again;
         }
         spin_unlock(&cur_trans->dirty_bgs_lock);
     }
 out:
     if (ret < 0) {
         spin_lock(&cur_trans->dirty_bgs_lock);
         list_splice_init(&dirty, &cur_trans->dirty_bgs);
         spin_unlock(&cur_trans->dirty_bgs_lock);
         btrfs_cleanup_dirty_bgs(cur_trans, fs_info);
     }
 
     btrfs_free_path(path);
     return ret;
 }
 
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_block_group *cache;
     struct btrfs_transaction *cur_trans = trans->transaction;
     int ret = 0;
     int should_put;
     struct btrfs_path *path;
     struct list_head *io = &cur_trans->io_bgs;
 
     path = btrfs_alloc_path();
     if (!path)
         return -ENOMEM;
 
     /*
      * Even though we are in the critical section of the transaction commit,
      * we can still have concurrent tasks adding elements to this
      * transaction's list of dirty block groups. These tasks correspond to
      * endio free space workers started when writeback finishes for a
      * space cache, which run inode.c:btrfs_finish_ordered_io(), and can
      * allocate new block groups as a result of COWing nodes of the root
      * tree when updating the free space inode. The writeback for the space
      * caches is triggered by an earlier call to
      * btrfs_start_dirty_block_groups() and iterations of the following
      * loop.
      * Also we want to do the cache_save_setup first and then run the
      * delayed refs to make sure we have the best chance at doing this all
      * in one shot.
      */
     spin_lock(&cur_trans->dirty_bgs_lock);
     while (!list_empty(&cur_trans->dirty_bgs)) {
         cache = list_first_entry(&cur_trans->dirty_bgs,
                      struct btrfs_block_group,
                      dirty_list);
 
         /*
          * This can happen if cache_save_setup re-dirties a block group
          * that is already under IO.  Just wait for it to finish and
          * then do it all again
          */
         if (!list_empty(&cache->io_list)) {
             spin_unlock(&cur_trans->dirty_bgs_lock);
             list_del_init(&cache->io_list);
             btrfs_wait_cache_io(trans, cache, path);
             btrfs_put_block_group(cache);
             spin_lock(&cur_trans->dirty_bgs_lock);
         }
 
         /*
          * Don't remove from the dirty list until after we've waited on
          * any pending IO
          */
         list_del_init(&cache->dirty_list);
         spin_unlock(&cur_trans->dirty_bgs_lock);
         should_put = 1;
 
         cache_save_setup(cache, trans, path);
 
         if (!ret)
             ret = btrfs_run_delayed_refs(trans,
                              (unsigned long) -1);
 
         if (!ret && cache->disk_cache_state == BTRFS_DC_SETUP) {
             cache->io_ctl.inode = NULL;
             ret = btrfs_write_out_cache(trans, cache, path);
             if (ret == 0 && cache->io_ctl.inode) {
                 should_put = 0;
                 list_add_tail(&cache->io_list, io);
             } else {
                 /*
                  * If we failed to write the cache, the
                  * generation will be bad and life goes on
                  */
                 ret = 0;
             }
         }
         if (!ret) {
             ret = update_block_group_item(trans, path, cache);
             /*
              * One of the free space endio workers might have
              * created a new block group while updating a free space
              * cache's inode (at inode.c:btrfs_finish_ordered_io())
              * and hasn't released its transaction handle yet, in
              * which case the new block group is still attached to
              * its transaction handle and its creation has not
              * finished yet (no block group item in the extent tree
              * yet, etc). If this is the case, wait for all free
              * space endio workers to finish and retry. This is a
              * very rare case so no need for a more efficient and
              * complex approach.
              */
             if (ret == -ENOENT) {
                 wait_event(cur_trans->writer_wait,
                    atomic_read(&cur_trans->num_writers) == 1);
                 ret = update_block_group_item(trans, path, cache);
             }
             if (ret)
                 btrfs_abort_transaction(trans, ret);
         }
 
         /* If its not on the io list, we need to put the block group */
         if (should_put)
             btrfs_put_block_group(cache);
         btrfs_delayed_refs_rsv_release(fs_info, 1);
         spin_lock(&cur_trans->dirty_bgs_lock);
     }
     spin_unlock(&cur_trans->dirty_bgs_lock);
 
     /*
      * Refer to the definition of io_bgs member for details why it's safe
      * to use it without any locking
      */
     while (!list_empty(io)) {
         cache = list_first_entry(io, struct btrfs_block_group,
                      io_list);
         list_del_init(&cache->io_list);
         btrfs_wait_cache_io(trans, cache, path);
         btrfs_put_block_group(cache);
     }
 
     btrfs_free_path(path);
     return ret;
 }
 
 static inline bool should_reclaim_block_group(struct btrfs_block_group *bg,
                           u64 bytes_freed)
 {
     const struct btrfs_space_info *space_info = bg->space_info;
     const int reclaim_thresh = READ_ONCE(space_info->bg_reclaim_threshold);
     const u64 new_val = bg->used;
     const u64 old_val = new_val + bytes_freed;
     u64 thresh;
 
     if (reclaim_thresh == 0)
         return false;
 
     thresh = div_factor_fine(bg->length, reclaim_thresh);
 
     /*
      * If we were below the threshold before don't reclaim, we are likely a
      * brand new block group and we don't want to relocate new block groups.
      */
     if (old_val < thresh)
         return false;
     if (new_val >= thresh)
         return false;
     return true;
 }
 
 int btrfs_update_block_group(struct btrfs_trans_handle *trans,
                  u64 bytenr, u64 num_bytes, bool alloc)
 {
     struct btrfs_fs_info *info = trans->fs_info;
     struct btrfs_block_group *cache = NULL;
     u64 total = num_bytes;
     u64 old_val;
     u64 byte_in_group;
     int factor;
     int ret = 0;
 
     /* Block accounting for super block */
     spin_lock(&info->delalloc_root_lock);
     old_val = btrfs_super_bytes_used(info->super_copy);
     if (alloc)
         old_val += num_bytes;
     else
         old_val -= num_bytes;
     btrfs_set_super_bytes_used(info->super_copy, old_val);
     spin_unlock(&info->delalloc_root_lock);
 
     while (total) {
         bool reclaim;
 
         cache = btrfs_lookup_block_group(info, bytenr);
         if (!cache) {
             ret = -ENOENT;
             break;
         }
         factor = btrfs_bg_type_to_factor(cache->flags);
 
         /*
          * If this block group has free space cache written out, we
          * need to make sure to load it if we are removing space.  This
          * is because we need the unpinning stage to actually add the
          * space back to the block group, otherwise we will leak space.
          */
         if (!alloc && !btrfs_block_group_done(cache))
             btrfs_cache_block_group(cache, true);
 
         byte_in_group = bytenr - cache->start;
         WARN_ON(byte_in_group > cache->length);
 
         spin_lock(&cache->space_info->lock);
         spin_lock(&cache->lock);
 
         if (btrfs_test_opt(info, SPACE_CACHE) &&
             cache->disk_cache_state < BTRFS_DC_CLEAR)
             cache->disk_cache_state = BTRFS_DC_CLEAR;
 
         old_val = cache->used;
         num_bytes = min(total, cache->length - byte_in_group);
         if (alloc) {
             old_val += num_bytes;
             cache->used = old_val;
             cache->reserved -= num_bytes;
             cache->space_info->bytes_reserved -= num_bytes;
             cache->space_info->bytes_used += num_bytes;
             cache->space_info->disk_used += num_bytes * factor;
             spin_unlock(&cache->lock);
             spin_unlock(&cache->space_info->lock);
         } else {
             old_val -= num_bytes;
             cache->used = old_val;
             cache->pinned += num_bytes;
             btrfs_space_info_update_bytes_pinned(info,
                     cache->space_info, num_bytes);
             cache->space_info->bytes_used -= num_bytes;
             cache->space_info->disk_used -= num_bytes * factor;
 
             reclaim = should_reclaim_block_group(cache, num_bytes);
             spin_unlock(&cache->lock);
             spin_unlock(&cache->space_info->lock);
 
             set_extent_dirty(&trans->transaction->pinned_extents,
                      bytenr, bytenr + num_bytes - 1,
                      GFP_NOFS | __GFP_NOFAIL);
         }
 
         spin_lock(&trans->transaction->dirty_bgs_lock);
         if (list_empty(&cache->dirty_list)) {
             list_add_tail(&cache->dirty_list,
                       &trans->transaction->dirty_bgs);
             trans->delayed_ref_updates++;
             btrfs_get_block_group(cache);
         }
         spin_unlock(&trans->transaction->dirty_bgs_lock);
 
         /*
          * No longer have used bytes in this block group, queue it for
          * deletion. We do this after adding the block group to the
          * dirty list to avoid races between cleaner kthread and space
          * cache writeout.
          */
         if (!alloc && old_val == 0) {
             if (!btrfs_test_opt(info, DISCARD_ASYNC))
                 btrfs_mark_bg_unused(cache);
         } else if (!alloc && reclaim) {
             btrfs_mark_bg_to_reclaim(cache);
         }
 
         btrfs_put_block_group(cache);
         total -= num_bytes;
         bytenr += num_bytes;
     }
 
     /* Modified block groups are accounted for in the delayed_refs_rsv. */
     btrfs_update_delayed_refs_rsv(trans);
     return ret;
 }
 
 /**
  * btrfs_add_reserved_bytes - update the block_group and space info counters
  * @cache:  The cache we are manipulating
  * @ram_bytes:  The number of bytes of file content, and will be same to
  *              @num_bytes except for the compress path.
  * @num_bytes:  The number of bytes in question
  * @delalloc:   The blocks are allocated for the delalloc write
  *
  * This is called by the allocator when it reserves space. If this is a
  * reservation and the block group has become read only we cannot make the
  * reservation and return -EAGAIN, otherwise this function always succeeds.
  */
 int btrfs_add_reserved_bytes(struct btrfs_block_group *cache,
                  u64 ram_bytes, u64 num_bytes, int delalloc)
 {
     struct btrfs_space_info *space_info = cache->space_info;
     int ret = 0;
 
     spin_lock(&space_info->lock);
     spin_lock(&cache->lock);
     if (cache->ro) {
         ret = -EAGAIN;
     } else {
         cache->reserved += num_bytes;
         space_info->bytes_reserved += num_bytes;
         trace_btrfs_space_reservation(cache->fs_info, "space_info",
                           space_info->flags, num_bytes, 1);
         btrfs_space_info_update_bytes_may_use(cache->fs_info,
                               space_info, -ram_bytes);
         if (delalloc)
             cache->delalloc_bytes += num_bytes;
 
         /*
          * Compression can use less space than we reserved, so wake
          * tickets if that happens
          */
         if (num_bytes < ram_bytes)
             btrfs_try_granting_tickets(cache->fs_info, space_info);
     }
     spin_unlock(&cache->lock);
     spin_unlock(&space_info->lock);
     return ret;
 }
 
 /**
  * btrfs_free_reserved_bytes - update the block_group and space info counters
  * @cache:      The cache we are manipulating
  * @num_bytes:  The number of bytes in question
  * @delalloc:   The blocks are allocated for the delalloc write
  *
  * This is called by somebody who is freeing space that was never actually used
  * on disk.  For example if you reserve some space for a new leaf in transaction
  * A and before transaction A commits you free that leaf, you call this with
  * reserve set to 0 in order to clear the reservation.
  */
 void btrfs_free_reserved_bytes(struct btrfs_block_group *cache,
                    u64 num_bytes, int delalloc)
 {
     struct btrfs_space_info *space_info = cache->space_info;
 
     spin_lock(&space_info->lock);
     spin_lock(&cache->lock);
     if (cache->ro)
         space_info->bytes_readonly += num_bytes;
     cache->reserved -= num_bytes;
     space_info->bytes_reserved -= num_bytes;
     space_info->max_extent_size = 0;
 
     if (delalloc)
         cache->delalloc_bytes -= num_bytes;
     spin_unlock(&cache->lock);
 
     btrfs_try_granting_tickets(cache->fs_info, space_info);
     spin_unlock(&space_info->lock);
 }
 
 static void force_metadata_allocation(struct btrfs_fs_info *info)
 {
     struct list_head *head = &info->space_info;
     struct btrfs_space_info *found;
 
     list_for_each_entry(found, head, list) {
         if (found->flags & BTRFS_BLOCK_GROUP_METADATA)
             found->force_alloc = CHUNK_ALLOC_FORCE;
     }
 }
 
 static int should_alloc_chunk(struct btrfs_fs_info *fs_info,
                   struct btrfs_space_info *sinfo, int force)
 {
     u64 bytes_used = btrfs_space_info_used(sinfo, false);
     u64 thresh;
 
     if (force == CHUNK_ALLOC_FORCE)
         return 1;
 
     /*
      * in limited mode, we want to have some free space up to
      * about 1% of the FS size.
      */
     if (force == CHUNK_ALLOC_LIMITED) {
         thresh = btrfs_super_total_bytes(fs_info->super_copy);
         thresh = max_t(u64, SZ_64M, div_factor_fine(thresh, 1));
 
         if (sinfo->total_bytes - bytes_used < thresh)
             return 1;
     }
 
     if (bytes_used + SZ_2M < div_factor(sinfo->total_bytes, 8))
         return 0;
     return 1;
 }
 
 int btrfs_force_chunk_alloc(struct btrfs_trans_handle *trans, u64 type)
 {
     u64 alloc_flags = btrfs_get_alloc_profile(trans->fs_info, type);
 
     return btrfs_chunk_alloc(trans, alloc_flags, CHUNK_ALLOC_FORCE);
 }
 
 static struct btrfs_block_group *do_chunk_alloc(struct btrfs_trans_handle *trans, u64 flags)
 {
     struct btrfs_block_group *bg;
     int ret;
 
     /*
      * Check if we have enough space in the system space info because we
      * will need to update device items in the chunk btree and insert a new
      * chunk item in the chunk btree as well. This will allocate a new
      * system block group if needed.
      */
     check_system_chunk(trans, flags);
 
     bg = btrfs_create_chunk(trans, flags);
     if (IS_ERR(bg)) {
         ret = PTR_ERR(bg);
         goto out;
     }
 
     ret = btrfs_chunk_alloc_add_chunk_item(trans, bg);
     /*
      * Normally we are not expected to fail with -ENOSPC here, since we have
      * previously reserved space in the system space_info and allocated one
      * new system chunk if necessary. However there are three exceptions:
      *
      * 1) We may have enough free space in the system space_info but all the
      *    existing system block groups have a profile which can not be used
      *    for extent allocation.
      *
      *    This happens when mounting in degraded mode. For example we have a
      *    RAID1 filesystem with 2 devices, lose one device and mount the fs
      *    using the other device in degraded mode. If we then allocate a chunk,
      *    we may have enough free space in the existing system space_info, but
      *    none of the block groups can be used for extent allocation since they
      *    have a RAID1 profile, and because we are in degraded mode with a
      *    single device, we are forced to allocate a new system chunk with a
      *    SINGLE profile. Making check_system_chunk() iterate over all system
      *    block groups and check if they have a usable profile and enough space
      *    can be slow on very large filesystems, so we tolerate the -ENOSPC and
      *    try again after forcing allocation of a new system chunk. Like this
      *    we avoid paying the cost of that search in normal circumstances, when
      *    we were not mounted in degraded mode;
      *
      * 2) We had enough free space info the system space_info, and one suitable
      *    block group to allocate from when we called check_system_chunk()
      *    above. However right after we called it, the only system block group
      *    with enough free space got turned into RO mode by a running scrub,
      *    and in this case we have to allocate a new one and retry. We only
      *    need do this allocate and retry once, since we have a transaction
      *    handle and scrub uses the commit root to search for block groups;
      *
      * 3) We had one system block group with enough free space when we called
      *    check_system_chunk(), but after that, right before we tried to
      *    allocate the last extent buffer we needed, a discard operation came
      *    in and it temporarily removed the last free space entry from the
      *    block group (discard removes a free space entry, discards it, and
      *    then adds back the entry to the block group cache).
      */
     if (ret == -ENOSPC) {
         const u64 sys_flags = btrfs_system_alloc_profile(trans->fs_info);
         struct btrfs_block_group *sys_bg;
 
         sys_bg = btrfs_create_chunk(trans, sys_flags);
         if (IS_ERR(sys_bg)) {
             ret = PTR_ERR(sys_bg);
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
 
         ret = btrfs_chunk_alloc_add_chunk_item(trans, sys_bg);
         if (ret) {
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
 
         ret = btrfs_chunk_alloc_add_chunk_item(trans, bg);
         if (ret) {
             btrfs_abort_transaction(trans, ret);
             goto out;
         }
     } else if (ret) {
         btrfs_abort_transaction(trans, ret);
         goto out;
     }
 out:
     btrfs_trans_release_chunk_metadata(trans);
 
     if (ret)
         return ERR_PTR(ret);
 
     btrfs_get_block_group(bg);
     return bg;
 }
 
 /*
  * Chunk allocation is done in 2 phases:
  *
  * 1) Phase 1 - through btrfs_chunk_alloc() we allocate device extents for
  *    the chunk, the chunk mapping, create its block group and add the items
  *    that belong in the chunk btree to it - more specifically, we need to
  *    update device items in the chunk btree and add a new chunk item to it.
  *
  * 2) Phase 2 - through btrfs_create_pending_block_groups(), we add the block
  *    group item to the extent btree and the device extent items to the devices
  *    btree.
  *
  * This is done to prevent deadlocks. For example when COWing a node from the
  * extent btree we are holding a write lock on the node's parent and if we
  * trigger chunk allocation and attempted to insert the new block group item
  * in the extent btree right way, we could deadlock because the path for the
  * insertion can include that parent node. At first glance it seems impossible
  * to trigger chunk allocation after starting a transaction since tasks should
  * reserve enough transaction units (metadata space), however while that is true
  * most of the time, chunk allocation may still be triggered for several reasons:
  *
  * 1) When reserving metadata, we check if there is enough free space in the
  *    metadata space_info and therefore don't trigger allocation of a new chunk.
  *    However later when the task actually tries to COW an extent buffer from
  *    the extent btree or from the device btree for example, it is forced to
  *    allocate a new block group (chunk) because the only one that had enough
  *    free space was just turned to RO mode by a running scrub for example (or
  *    device replace, block group reclaim thread, etc), so we can not use it
  *    for allocating an extent and end up being forced to allocate a new one;
  *
  * 2) Because we only check that the metadata space_info has enough free bytes,
  *    we end up not allocating a new metadata chunk in that case. However if
  *    the filesystem was mounted in degraded mode, none of the existing block
  *    groups might be suitable for extent allocation due to their incompatible
  *    profile (for e.g. mounting a 2 devices filesystem, where all block groups
  *    use a RAID1 profile, in degraded mode using a single device). In this case
  *    when the task attempts to COW some extent buffer of the extent btree for
  *    example, it will trigger allocation of a new metadata block group with a
  *    suitable profile (SINGLE profile in the example of the degraded mount of
  *    the RAID1 filesystem);
  *
  * 3) The task has reserved enough transaction units / metadata space, but when
  *    it attempts to COW an extent buffer from the extent or device btree for
  *    example, it does not find any free extent in any metadata block group,
  *    therefore forced to try to allocate a new metadata block group.
  *    This is because some other task allocated all available extents in the
  *    meanwhile - this typically happens with tasks that don't reserve space
  *    properly, either intentionally or as a bug. One example where this is
  *    done intentionally is fsync, as it does not reserve any transaction units
  *    and ends up allocating a variable number of metadata extents for log
  *    tree extent buffers;
  *
  * 4) The task has reserved enough transaction units / metadata space, but right
  *    before it tries to allocate the last extent buffer it needs, a discard
  *    operation comes in and, temporarily, removes the last free space entry from
  *    the only metadata block group that had free space (discard starts by
  *    removing a free space entry from a block group, then does the discard
  *    operation and, once it's done, it adds back the free space entry to the
  *    block group).
  *
  * We also need this 2 phases setup when adding a device to a filesystem with
  * a seed device - we must create new metadata and system chunks without adding
  * any of the block group items to the chunk, extent and device btrees. If we
  * did not do it this way, we would get ENOSPC when attempting to update those
  * btrees, since all the chunks from the seed device are read-only.
  *
  * Phase 1 does the updates and insertions to the chunk btree because if we had
  * it done in phase 2 and have a thundering herd of tasks allocating chunks in
  * parallel, we risk having too many system chunks allocated by many tasks if
  * many tasks reach phase 1 without the previous ones completing phase 2. In the
  * extreme case this leads to exhaustion of the system chunk array in the
  * superblock. This is easier to trigger if using a btree node/leaf size of 64K
  * and with RAID filesystems (so we have more device items in the chunk btree).
  * This has happened before and commit eafa4fd0ad0607 ("btrfs: fix exhaustion of
  * the system chunk array due to concurrent allocations") provides more details.
  *
  * Allocation of system chunks does not happen through this function. A task that
  * needs to update the chunk btree (the only btree that uses system chunks), must
  * preallocate chunk space by calling either check_system_chunk() or
  * btrfs_reserve_chunk_metadata() - the former is used when allocating a data or
  * metadata chunk or when removing a chunk, while the later is used before doing
  * a modification to the chunk btree - use cases for the later are adding,
  * removing and resizing a device as well as relocation of a system chunk.
  * See the comment below for more details.
  *
  * The reservation of system space, done through check_system_chunk(), as well
  * as all the updates and insertions into the chunk btree must be done while
  * holding fs_info->chunk_mutex. This is important to guarantee that while COWing
  * an extent buffer from the chunks btree we never trigger allocation of a new
  * system chunk, which would result in a deadlock (trying to lock twice an
  * extent buffer of the chunk btree, first time before triggering the chunk
  * allocation and the second time during chunk allocation while attempting to
  * update the chunks btree). The system chunk array is also updated while holding
  * that mutex. The same logic applies to removing chunks - we must reserve system
  * space, update the chunk btree and the system chunk array in the superblock
  * while holding fs_info->chunk_mutex.
  *
  * This function, btrfs_chunk_alloc(), belongs to phase 1.
  *
  * If @force is CHUNK_ALLOC_FORCE:
  *    - return 1 if it successfully allocates a chunk,
  *    - return errors including -ENOSPC otherwise.
  * If @force is NOT CHUNK_ALLOC_FORCE:
  *    - return 0 if it doesn't need to allocate a new chunk,
  *    - return 1 if it successfully allocates a chunk,
  *    - return errors including -ENOSPC otherwise.
  */
 int btrfs_chunk_alloc(struct btrfs_trans_handle *trans, u64 flags,
               enum btrfs_chunk_alloc_enum force)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_space_info *space_info;
     struct btrfs_block_group *ret_bg;
     bool wait_for_alloc = false;
     bool should_alloc = false;
     bool from_extent_allocation = false;
     int ret = 0;
 
     if (force == CHUNK_ALLOC_FORCE_FOR_EXTENT) {
         from_extent_allocation = true;
         force = CHUNK_ALLOC_FORCE;
     }
 
     /* Don't re-enter if we're already allocating a chunk */
     if (trans->allocating_chunk)
         return -ENOSPC;
     /*
      * Allocation of system chunks can not happen through this path, as we
      * could end up in a deadlock if we are allocating a data or metadata
      * chunk and there is another task modifying the chunk btree.
      *
      * This is because while we are holding the chunk mutex, we will attempt
      * to add the new chunk item to the chunk btree or update an existing
      * device item in the chunk btree, while the other task that is modifying
      * the chunk btree is attempting to COW an extent buffer while holding a
      * lock on it and on its parent - if the COW operation triggers a system
      * chunk allocation, then we can deadlock because we are holding the
      * chunk mutex and we may need to access that extent buffer or its parent
      * in order to add the chunk item or update a device item.
      *
      * Tasks that want to modify the chunk tree should reserve system space
      * before updating the chunk btree, by calling either
      * btrfs_reserve_chunk_metadata() or check_system_chunk().
      * It's possible that after a task reserves the space, it still ends up
      * here - this happens in the cases described above at do_chunk_alloc().
      * The task will have to either retry or fail.
      */
     if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
         return -ENOSPC;
 
     space_info = btrfs_find_space_info(fs_info, flags);
     ASSERT(space_info);
 
     do {
         spin_lock(&space_info->lock);
         if (force < space_info->force_alloc)
             force = space_info->force_alloc;
         should_alloc = should_alloc_chunk(fs_info, space_info, force);
         if (space_info->full) {
             /* No more free physical space */
             if (should_alloc)
                 ret = -ENOSPC;
             else
                 ret = 0;
             spin_unlock(&space_info->lock);
             return ret;
         } else if (!should_alloc) {
             spin_unlock(&space_info->lock);
             return 0;
         } else if (space_info->chunk_alloc) {
             /*
              * Someone is already allocating, so we need to block
              * until this someone is finished and then loop to
              * recheck if we should continue with our allocation
              * attempt.
              */
             wait_for_alloc = true;
             force = CHUNK_ALLOC_NO_FORCE;
             spin_unlock(&space_info->lock);
             mutex_lock(&fs_info->chunk_mutex);
             mutex_unlock(&fs_info->chunk_mutex);
         } else {
             /* Proceed with allocation */
             space_info->chunk_alloc = 1;
             wait_for_alloc = false;
             spin_unlock(&space_info->lock);
         }
 
         cond_resched();
     } while (wait_for_alloc);
 
     mutex_lock(&fs_info->chunk_mutex);
     trans->allocating_chunk = true;
 
     /*
      * If we have mixed data/metadata chunks we want to make sure we keep
      * allocating mixed chunks instead of individual chunks.
      */
     if (btrfs_mixed_space_info(space_info))
         flags |= (BTRFS_BLOCK_GROUP_DATA | BTRFS_BLOCK_GROUP_METADATA);
 
     /*
      * if we're doing a data chunk, go ahead and make sure that
      * we keep a reasonable number of metadata chunks allocated in the
      * FS as well.
      */
     if (flags & BTRFS_BLOCK_GROUP_DATA && fs_info->metadata_ratio) {
         fs_info->data_chunk_allocations++;
         if (!(fs_info->data_chunk_allocations %
               fs_info->metadata_ratio))
             force_metadata_allocation(fs_info);
     }
 
     ret_bg = do_chunk_alloc(trans, flags);
     trans->allocating_chunk = false;
 
     if (IS_ERR(ret_bg)) {
         ret = PTR_ERR(ret_bg);
     } else if (from_extent_allocation) {
         /*
          * New block group is likely to be used soon. Try to activate
          * it now. Failure is OK for now.
          */
         btrfs_zone_activate(ret_bg);
     }
 
     if (!ret)
         btrfs_put_block_group(ret_bg);
 
     spin_lock(&space_info->lock);
     if (ret < 0) {
         if (ret == -ENOSPC)
             space_info->full = 1;
         else
             goto out;
     } else {
         ret = 1;
         space_info->max_extent_size = 0;
     }
 
     space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
 out:
     space_info->chunk_alloc = 0;
     spin_unlock(&space_info->lock);
     mutex_unlock(&fs_info->chunk_mutex);
 
     return ret;
 }
 
 static u64 get_profile_num_devs(struct btrfs_fs_info *fs_info, u64 type)
 {
     u64 num_dev;
 
     num_dev = btrfs_raid_array[btrfs_bg_flags_to_raid_index(type)].devs_max;
     if (!num_dev)
         num_dev = fs_info->fs_devices->rw_devices;
 
     return num_dev;
 }
 
 static void reserve_chunk_space(struct btrfs_trans_handle *trans,
                 u64 bytes,
                 u64 type)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     struct btrfs_space_info *info;
     u64 left;
     int ret = 0;
 
     /*
      * Needed because we can end up allocating a system chunk and for an
      * atomic and race free space reservation in the chunk block reserve.
      */
     lockdep_assert_held(&fs_info->chunk_mutex);
 
     info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
     spin_lock(&info->lock);
     left = info->total_bytes - btrfs_space_info_used(info, true);
     spin_unlock(&info->lock);
 
     if (left < bytes && btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
         btrfs_info(fs_info, "left=%llu, need=%llu, flags=%llu",
                left, bytes, type);
         btrfs_dump_space_info(fs_info, info, 0, 0);
     }
 
     if (left < bytes) {
         u64 flags = btrfs_system_alloc_profile(fs_info);
         struct btrfs_block_group *bg;
 
         /*
          * Ignore failure to create system chunk. We might end up not
          * needing it, as we might not need to COW all nodes/leafs from
          * the paths we visit in the chunk tree (they were already COWed
          * or created in the current transaction for example).
          */
         bg = btrfs_create_chunk(trans, flags);
         if (IS_ERR(bg)) {
             ret = PTR_ERR(bg);
         } else {
             /*
              * We have a new chunk. We also need to activate it for
              * zoned filesystem.
              */
             ret = btrfs_zoned_activate_one_bg(fs_info, info, true);
             if (ret < 0)
                 return;
 
             /*
              * If we fail to add the chunk item here, we end up
              * trying again at phase 2 of chunk allocation, at
              * btrfs_create_pending_block_groups(). So ignore
              * any error here. An ENOSPC here could happen, due to
              * the cases described at do_chunk_alloc() - the system
              * block group we just created was just turned into RO
              * mode by a scrub for example, or a running discard
              * temporarily removed its free space entries, etc.
              */
             btrfs_chunk_alloc_add_chunk_item(trans, bg);
         }
     }
 
     if (!ret) {
         ret = btrfs_block_rsv_add(fs_info,
                       &fs_info->chunk_block_rsv,
                       bytes, BTRFS_RESERVE_NO_FLUSH);
         if (!ret)
             trans->chunk_bytes_reserved += bytes;
     }
 }
 
 /*
  * Reserve space in the system space for allocating or removing a chunk.
  * The caller must be holding fs_info->chunk_mutex.
  */
 void check_system_chunk(struct btrfs_trans_handle *trans, u64 type)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     const u64 num_devs = get_profile_num_devs(fs_info, type);
     u64 bytes;
 
     /* num_devs device items to update and 1 chunk item to add or remove. */
     bytes = btrfs_calc_metadata_size(fs_info, num_devs) +
         btrfs_calc_insert_metadata_size(fs_info, 1);
 
     reserve_chunk_space(trans, bytes, type);
 }
 
 /*
  * Reserve space in the system space, if needed, for doing a modification to the
  * chunk btree.
  *
  * @trans:      A transaction handle.
  * @is_item_insertion:  Indicate if the modification is for inserting a new item
  *          in the chunk btree or if it's for the deletion or update
  *          of an existing item.
  *
  * This is used in a context where we need to update the chunk btree outside
  * block group allocation and removal, to avoid a deadlock with a concurrent
  * task that is allocating a metadata or data block group and therefore needs to
  * update the chunk btree while holding the chunk mutex. After the update to the
  * chunk btree is done, btrfs_trans_release_chunk_metadata() should be called.
  *
  */
 void btrfs_reserve_chunk_metadata(struct btrfs_trans_handle *trans,
                   bool is_item_insertion)
 {
     struct btrfs_fs_info *fs_info = trans->fs_info;
     u64 bytes;
 
     if (is_item_insertion)
         bytes = btrfs_calc_insert_metadata_size(fs_info, 1);
     else
         bytes = btrfs_calc_metadata_size(fs_info, 1);
 
     mutex_lock(&fs_info->chunk_mutex);
     reserve_chunk_space(trans, bytes, BTRFS_BLOCK_GROUP_SYSTEM);
     mutex_unlock(&fs_info->chunk_mutex);
 }
 
 void btrfs_put_block_group_cache(struct btrfs_fs_info *info)
 {
     struct btrfs_block_group *block_group;
     u64 last = 0;
 
     while (1) {
         struct inode *inode;
 
         block_group = btrfs_lookup_first_block_group(info, last);
         while (block_group) {
             btrfs_wait_block_group_cache_done(block_group);
             spin_lock(&block_group->lock);
             if (block_group->iref)
                 break;
             spin_unlock(&block_group->lock);
             block_group = btrfs_next_block_group(block_group);
         }
         if (!block_group) {
             if (last == 0)
                 break;
             last = 0;
             continue;
         }
 
         inode = block_group->inode;
         block_group->iref = 0;
         block_group->inode = NULL;
         spin_unlock(&block_group->lock);
         ASSERT(block_group->io_ctl.inode == NULL);
         iput(inode);
         last = block_group->start + block_group->length;
         btrfs_put_block_group(block_group);
     }
 }
 
 /*
  * Must be called only after stopping all workers, since we could have block
  * group caching kthreads running, and therefore they could race with us if we
  * freed the block groups before stopping them.
  */
 int btrfs_free_block_groups(struct btrfs_fs_info *info)
 {
     struct btrfs_block_group *block_group;
     struct btrfs_space_info *space_info;
     struct btrfs_caching_control *caching_ctl;
     struct rb_node *n;
 
     write_lock(&info->block_group_cache_lock);
     while (!list_empty(&info->caching_block_groups)) {
         caching_ctl = list_entry(info->caching_block_groups.next,
                      struct btrfs_caching_control, list);
         list_del(&caching_ctl->list);
         btrfs_put_caching_control(caching_ctl);
     }
     write_unlock(&info->block_group_cache_lock);
 
     spin_lock(&info->unused_bgs_lock);
     while (!list_empty(&info->unused_bgs)) {
         block_group = list_first_entry(&info->unused_bgs,
                            struct btrfs_block_group,
                            bg_list);
         list_del_init(&block_group->bg_list);
         btrfs_put_block_group(block_group);
     }
 
     while (!list_empty(&info->reclaim_bgs)) {
         block_group = list_first_entry(&info->reclaim_bgs,
                            struct btrfs_block_group,
                            bg_list);
         list_del_init(&block_group->bg_list);
         btrfs_put_block_group(block_group);
     }
     spin_unlock(&info->unused_bgs_lock);
 
     spin_lock(&info->zone_active_bgs_lock);
     while (!list_empty(&info->zone_active_bgs)) {
         block_group = list_first_entry(&info->zone_active_bgs,
                            struct btrfs_block_group,
                            active_bg_list);
         list_del_init(&block_group->active_bg_list);
         btrfs_put_block_group(block_group);
     }
     spin_unlock(&info->zone_active_bgs_lock);
 
     write_lock(&info->block_group_cache_lock);
     while ((n = rb_last(&info->block_group_cache_tree.rb_root)) != NULL) {
         block_group = rb_entry(n, struct btrfs_block_group,
                        cache_node);
         rb_erase_cached(&block_group->cache_node,
                 &info->block_group_cache_tree);
         RB_CLEAR_NODE(&block_group->cache_node);
         write_unlock(&info->block_group_cache_lock);
 
         down_write(&block_group->space_info->groups_sem);
         list_del(&block_group->list);
         up_write(&block_group->space_info->groups_sem);
 
         /*
          * We haven't cached this block group, which means we could
          * possibly have excluded extents on this block group.
          */
         if (block_group->cached == BTRFS_CACHE_NO ||
             block_group->cached == BTRFS_CACHE_ERROR)
             btrfs_free_excluded_extents(block_group);
 
         btrfs_remove_free_space_cache(block_group);
         ASSERT(block_group->cached != BTRFS_CACHE_STARTED);
         ASSERT(list_empty(&block_group->dirty_list));
         ASSERT(list_empty(&block_group->io_list));
         ASSERT(list_empty(&block_group->bg_list));
         ASSERT(refcount_read(&block_group->refs) == 1);
         ASSERT(block_group->swap_extents == 0);
         btrfs_put_block_group(block_group);
 
         write_lock(&info->block_group_cache_lock);
     }
     write_unlock(&info->block_group_cache_lock);
 
     btrfs_release_global_block_rsv(info);
 
     while (!list_empty(&info->space_info)) {
         space_info = list_entry(info->space_info.next,
                     struct btrfs_space_info,
                     list);
 
         /*
          * Do not hide this behind enospc_debug, this is actually
          * important and indicates a real bug if this happens.
          */
         if (WARN_ON(space_info->bytes_pinned > 0 ||
                 space_info->bytes_may_use > 0))
             btrfs_dump_space_info(info, space_info, 0, 0);
 
         /*
          * If there was a failure to cleanup a log tree, very likely due
          * to an IO failure on a writeback attempt of one or more of its
          * extent buffers, we could not do proper (and cheap) unaccounting
          * of their reserved space, so don't warn on bytes_reserved > 0 in
          * that case.
          */
         if (!(space_info->flags & BTRFS_BLOCK_GROUP_METADATA) ||
             !BTRFS_FS_LOG_CLEANUP_ERROR(info)) {
             if (WARN_ON(space_info->bytes_reserved > 0))
                 btrfs_dump_space_info(info, space_info, 0, 0);
         }
 
         WARN_ON(space_info->reclaim_size > 0);
         list_del(&space_info->list);
         btrfs_sysfs_remove_space_info(space_info);
     }
     return 0;
 }
 
 void btrfs_freeze_block_group(struct btrfs_block_group *cache)
 {
     atomic_inc(&cache->frozen);
 }
 
 void btrfs_unfreeze_block_group(struct btrfs_block_group *block_group)
 {
     struct btrfs_fs_info *fs_info = block_group->fs_info;
     struct extent_map_tree *em_tree;
     struct extent_map *em;
     bool cleanup;
 
     spin_lock(&block_group->lock);
     cleanup = (atomic_dec_and_test(&block_group->frozen) &&
            block_group->removed);
     spin_unlock(&block_group->lock);
 
     if (cleanup) {
         em_tree = &fs_info->mapping_tree;
         write_lock(&em_tree->lock);
         em = lookup_extent_mapping(em_tree, block_group->start,
                        1);
         BUG_ON(!em); /* logic error, can't happen */
         remove_extent_mapping(em_tree, em);
         write_unlock(&em_tree->lock);
 
         /* once for us and once for the tree */
         free_extent_map(em);
         free_extent_map(em);
 
         /*
          * We may have left one free space entry and other possible
          * tasks trimming this block group have left 1 entry each one.
          * Free them if any.
          */
         __btrfs_remove_free_space_cache(block_group->free_space_ctl);
     }
 }
 
 bool btrfs_inc_block_group_swap_extents(struct btrfs_block_group *bg)
 {
     bool ret = true;
 
     spin_lock(&bg->lock);
     if (bg->ro)
         ret = false;
     else
         bg->swap_extents++;
     spin_unlock(&bg->lock);
 
     return ret;
 }
 
 void btrfs_dec_block_group_swap_extents(struct btrfs_block_group *bg, int amount)
 {
     spin_lock(&bg->lock);
     ASSERT(!bg->ro);
     ASSERT(bg->swap_extents >= amount);
     bg->swap_extents -= amount;
     spin_unlock(&bg->lock);
 }