Re: [PATCH 3/6] ext4: prevent stale data exposure after fatal mapping errors

[sashiko-bot@kernel.org]

> When the block size is smaller than the folio size, a folio can contain
> several extents that need mapping. Mapping an earlier extent can succeed
> before mapping a later extent fails with a fatal error such as -EIO.
> 
> mpage_map_and_submit_extent() submits the mapped part of the folio only
> for retryable errors. On a fatal error it discards the whole folio,
> including dirty buffers whose mapping has already succeeded. This loses
> data that could still be submitted.
> 
> With dioread_nolock, the mapped ranges can also remain in io_end's
> unwritten conversion list. Conversion can then mark those extents
> written without their data ever being submitted, exposing stale data.
> 
> Also submit the mapped buffers after a fatal mapping error when the
> filesystem is not in an emergency state. Discard buffers still marked
> [ ... ]
> retry behavior for transient errors.
> 
> Fixes: c8cc88163f40 ("ext4: Add support for blocksize < pagesize in dioread_nolock")
> Cc: stable@vger.kernel.org
> Signed-off-by: Julian Sun <sunjunchao@bytedance.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261022145241.2950379-1-sunjunchao@bytedance.com?part=3