Re: [PATCH 3/3] ext4: fix directory link counts after fast commit replay

[sashiko-bot@kernel.org]

> From: Mani Tofigh <mt4022@columbia.edu>
> 
> After a crash, the fast commit replay of a mkdir leaves the new
> directory with one link and its parent with one link too few.  e2fsck
> then reports:
> 
>   Inode 2 ref count is 3, should be 4.
>   Inode 14 ref count is 1, should be 2.
> 
> Fast commits don't track directories, so the replay of a CREAT tag has
> to redo what ext4_mkdir() does.  ext4_fc_replay_create() sets the
> link count of the new inode to 1 even for a directory, and nothing
> counts the new ".." in the parent.  The replay of an rmdir has the
> opposite problem.  __ext4_unlink() drops only one link of the directory
> and the parent keeps the link of the removed "..":
> 
>   Inode 2 ref count is 4, should be 3.
> 
> Give a new directory 2 links and count it in its parent once its entry
> is added.  When an UNLINK tag removes a directory, drop all its links
> and one link of the parent like ext4_rmdir() does.  Both halves have to
> go together since today a mkdir and an rmdir replayed in sequence
> cancel out.
> 
> With the fix, e2fsck doesn't find wrong link counts after the replay
> anymore.
> 
> Fixes: 8016e29f4362 ("ext4: fast commit recovery path")
> Cc: stable@vger.kernel.org
> Signed-off-by: Mani Tofigh <mt4022@columbia.edu>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261111-ext4-fc-replay-mkdir-v1-0-4b20be29aed8@columbia.edu?part=3