Re: [PATCH 1/3] ext2: drain in-flight DIO before buffered write fallback

[sashiko-bot@kernel.org]

> An asynchronous direct write can remain in flight after the inode lock is
> released.  If another direct write falls back to buffered I/O while the
> first write is still pending, generic_perform_write() can dirty pages
> before the first write completes its post-I/O page cache invalidation.
> The invalidation then finds dirty pages, reports a page cache invalidation
> failure, and records -EIO in the mapping error sequence.  A later fsync()
> therefore returns -EIO.
> 
> Commit 15cdefd0c0522f9d5e12d947fa04f4c11649b699 ("ext4: drain
> in-flight DIO before buffered write fallback") fixed the same race in
> ext4.  Ext2 has an equivalent fallback after iomap_dio_rw() returns
> -ENOTBLK or a short write, but does not drain other in-flight DIO before
> dirtying the page cache.
> 
> Wait for in-flight DIO before calling generic_perform_write() in the
> fallback path.
> 
> A reproducer using concurrent AIO direct writes and buffered fallback
> triggered the following warning and made a subsequent fsync() return
> -EIO:
> 
>   Page cache invalidation failure on direct I/O.  Possible data corruption
>   due to collision with buffered I/O!
> 
> Fixes: fb5de4358e1a ("ext2: Move direct-io to use iomap")
> Link: https://lore.kernel.org/r/20260629113827.4074335-3-libaokun@linux.alibaba.com
> Signed-off-by: Jiale Yao <yaojiale02@163.com>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20260924105125.577714-2-yaojiale02@163.com?part=1