Re: [PATCH] ext4: propagate errors from fast commit create replay

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] ext4: fast commit mount failure due to broken idempotent directory replay
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commit 4015b43a7d3a20549b784ebf5a4fb9ffc38d14b9
Author: lty <781735889@qq.com>
ext4: propagate errors from fast commit create replay

This commit updates the fast-commit replay for directory creation to
propagate errors from parent lookup, directory initialization, and inode
dirtying. Previously, some of these errors were either ignored or masked.

> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
> index 0cac890cf3702..a6230f4411ed5 100644
> --- a/fs/ext4/fast_commit.c
> +++ b/fs/ext4/fast_commit.c
> @@ -2062,12 +2062,12 @@ static int ext4_fc_replay_create(struct super_block *sb,

[ ... ]

>  		ret = ext4_init_new_dir(NULL, dir, inode);
>  		iput(dir);
>  		if (ret) {
> -			ret = 0;

[Severity: High]
Does this removal break idempotent replays of directory creation?

Fast commit log replay must be idempotent because a directory's blocks might
have been flushed to disk by background writeback before the crash.

In ext4_fc_replay_create(), if the directory already exists on disk,
ext4_init_new_dir() forcefully sets its in-memory i_size to 0 and calls
ext4_append(). ext4_append() then computes logical block 0 and checks if
it is already allocated via ext4_map_blocks().

Since the directory was already fully persisted, the extent tree still maps
block 0, causing ext4_map_blocks() to return a positive value. ext4_append()
interprets this as a corruption ("Logical block already allocated") and
returns -EFSCORRUPTED.

Before this patch, this specific error was safely bypassed (ret = 0) since
the directory was already on disk. By propagating this error, it appears
journal recovery will abort with -EFSCORRUPTED whenever it encounters a
previously persisted directory without inline data, which might cause valid
mounts to fail.

>  			goto out;
>  		}
>  	}

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Sashiko AI review · https://sashiko.dev/#/patchset/tencent_1289C5B99FB98002A71088AC49394474B20A@qq.com?part=1