@@ -1065,10 +1065,35 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
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_put_group;
+
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 = -EIO;
+ if (ret < 0)
+ goto out;
+
+ ret = btrfs_del_item(trans, root, path);
+ if (ret)
+ goto out;
+
mutex_lock(&fs_info->chunk_mutex);
spin_lock(&block_group->lock);
block_group->removed = 1;
@@ -1103,23 +1128,9 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
mutex_unlock(&fs_info->chunk_mutex);
- ret = remove_block_group_free_space(trans, block_group);
- if (ret)
- goto out_put_group;
-
/* Once for the block groups rbtree */
btrfs_put_block_group(block_group);
- ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
- if (ret > 0)
- ret = -EIO;
- if (ret < 0)
- goto out;
-
- ret = btrfs_del_item(trans, root, path);
- if (ret)
- goto out;
-
if (remove_em) {
struct extent_map_tree *em_tree;