Re: [PATCH] btrfs: clear free space tree state on rebuild failure

[Qu Wenruo]

在 2026/9/16 00:18, Guanghui Yang 写道:
> btrfs_rebuild_free_space_tree() sets
> BTRFS_FS_CREATING_FREE_SPACE_TREE and
> BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED before rebuilding the free space
> tree. Several error paths return without clearing these flags.
>
> This leaves the flags set on the live filesystem and affects delayed
> reference processing and free-space caching.

What kind of effect?

> Clear both flags on all
> free space tree rebuild failure paths.
>
> Fixes: 1d6a4fc85717 ("btrfs: make clear_cache mount option to rebuild FST without disabling it")
> Cc: stable@xxxxxxxxxxxxxxx # 6.4+
> Assisted-by: Codex:gpt-5
> Tested: make -j$(nproc) fs/btrfs/free-space-tree.o

That's not helpful, you should run the full fstests instead.

> Signed-off-by: Guanghui Yang <3497809730@xxxxxx>
> ---
>   fs/btrfs/free-space-tree.c | 15 +++++++++++----
>   1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c
> index 1b3d82ae3de8..1410da2766a9 100644
> --- a/fs/btrfs/free-space-tree.c
> +++ b/fs/btrfs/free-space-tree.c
> @@ -1353,7 +1353,7 @@ int btrfs_rebuild_free_space_tree(struct btrfs_fs_info *fs_info)
>   	if (unlikely(ret)) {
>   		btrfs_abort_transaction(trans, ret);
>   		btrfs_end_transaction(trans);
> -		return ret;
> +		goto out_clear;
>   	}
>   
>   	node = rb_first_cached(&fs_info->block_group_cache_tree);
> @@ -1371,14 +1371,16 @@ int btrfs_rebuild_free_space_tree(struct btrfs_fs_info *fs_info)
>   		if (unlikely(ret)) {
>   			btrfs_abort_transaction(trans, ret);
>   			btrfs_end_transaction(trans);
> -			return ret;
> +			goto out_clear;
>   		}
>   next:
>   		if (btrfs_should_end_transaction(trans)) {
>   			btrfs_end_transaction(trans);
>   			trans = btrfs_start_transaction(free_space_root, 1);
> -			if (IS_ERR(trans))
> -				return PTR_ERR(trans);
> +			if (IS_ERR(trans)) {
> +				ret = PTR_ERR(trans);
> +				goto out_clear;
> +			}
>   		}
>   		node = rb_next(node);
>   	}
> @@ -1390,6 +1392,11 @@ int btrfs_rebuild_free_space_tree(struct btrfs_fs_info *fs_info)
>   	ret = btrfs_commit_transaction(trans);
>   	clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
>   	return ret;
> +
> +out_clear:
> +	clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
> +	clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);

The free space tree is not properly rebuilt, thus we can not trust it 
anymore.

Why you want to clear the UNTRUSTED flag?

> +	return ret;
>   }
>   
>   static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
>
> base-commit: 587858367581b9c55c3690f4e63382ad622719d4