Re: [PATCH v6 12/31] ext4: pass out extent seq counter when mapping da blocks

[sashiko-bot@kernel.org]

> From: Zhang Yi <yi.zhang@huawei.com>
> 
> The iomap buffered write path does not hold the folio lock between
> mapping the inode extent and copying data. Therefore, it can race
> with writeback that modifies the extent type (e.g., from unwritten to
> written). This can lead to data corruption on partial writes, as
> iomap_block_needs_zeroing() may return a false positive based on a
> stale extent. The iomap infrastructure uses the sequence counter
> stored in the inode to detect such stale mappings.
> 
> Commit 07c440e8da8f ("ext4: pass out extent seq counter when mapping
> blocks") added the m_seq field to ext4_map_blocks to pass out extent
> sequence numbers, but it missed two callsites within
> ext4_da_map_blocks(). These callsites are on the delayed allocation
> path, which is needed in the iomap buffered write path. Pass out the
> sequence counter to ensure stale mappings can be detected.
> 
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20260903123543.2302999-1-yi.zhang@huaweicloud.com?part=12