diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c index cef2f080fdcd..a2111eab614f 100644 --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -639,7 +639,15 @@ static noinline void caching_thread(struct btrfs_work *work) mutex_lock(&caching_ctl->mutex); down_read(&fs_info->commit_root_sem); - if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) + /* + * 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); diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index e01545538e07..30ea9780725f 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -146,6 +146,9 @@ enum { BTRFS_FS_STATE_DEV_REPLACING, /* The btrfs_fs_info created for self-tests */ BTRFS_FS_STATE_DUMMY_FS_INFO, + + /* Indicate that we can't trust the free space tree for caching yet */ + BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, }; #define BTRFS_BACKREF_REV_MAX 256 diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c index 6b9faf3b0e96..6cf2f7bb30c2 100644 --- a/fs/btrfs/free-space-tree.c +++ b/fs/btrfs/free-space-tree.c @@ -1152,6 +1152,7 @@ int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info) return PTR_ERR(trans); set_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags); + set_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags); free_space_root = btrfs_create_tree(trans, BTRFS_FREE_SPACE_TREE_OBJECTID); if (IS_ERR(free_space_root)) { @@ -1173,11 +1174,18 @@ int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info) btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE); btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID); clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags); + ret = btrfs_commit_transaction(trans); - return btrfs_commit_transaction(trans); + /* + * Now that we've committed the transaction any reading of our commit + * root will be safe, so we can cache from the free space tree now. + */ + clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags); + return ret; abort: clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags); + clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags); btrfs_abort_transaction(trans, ret); btrfs_end_transaction(trans); return ret;