Re: [PATCH] ext4: fix race between inline dir conversion and folio read

[sashiko-bot@kernel.org]

> Commit 90f097b1403f ("ext4: refactor the inline directory conversion and
> new directory codepaths") moved directory block initialization in
> ext4_convert_inline_data_nolock() into ext4_init_dirblock(), unlocking
> data_bh before setting BH_Uptodate.
> 
> When block size is smaller than PAGE_SIZE, multiple buffer heads share a
> single block device folio. If a concurrent read on that folio runs via
> block_read_full_folio() while data_bh is unlocked and not uptodate, it
> locks data_bh and submits a disk read for the uninitialized block.
> 
> Because ext4_init_dirblock() initializes bh->b_data without holding the
> buffer lock, the disk read races with and overwrites the initialized
> directory entries and checksum tail, corrupting the directory block:
> 
>   EXT4-fs warning: ext4_dirblock_csum_verify:375: inode #...:
>     No space for directory leaf checksum. Please run e2fsck -D.
>   EXT4-fs error: __ext4_find_entry:1626: inode #...:
>     checksumming directory block 0
> 
> To fix this, mark data_bh uptodate before unlocking it in
> ext4_convert_inline_data_nolock(), just like the regular file path
> does. Additionally, hold lock_buffer(bh) in ext4_init_dirblock() while
> populating the directory entries and checksum tail so any buffer
> modifications are properly serialized.
> 
> Fixes: 90f097b1403f ("ext4: refactor the inline directory conversion and new directory codepaths")
> Cc: stable@vger.kernel.org
> Assisted-by: Antigravity:gemini-3.8-flash
> Signed-off-by: Sandeep Dhavale <dhavale@google.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260918025416.604297-1-dhavale@google.com?part=1