Re: [PATCH v4 2/3] ntfs: drain in-flight DIO before buffered write fallback

[Namjae Jeon]

On Sat, Oct 3, 2026 at 6:30 PM Jiale Yao <yaojiale02@xxxxxxx> wrote:
>
> 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, iomap_file_buffered_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.  NTFS 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 iomap_file_buffered_write() in the
> fallback path.  Since NTFS supports IOCB_NOWAIT, do not enter the blocking
> fallback for such requests.  Return -EAGAIN if no bytes were written, or
> preserve the positive short-write result if the direct write made partial
> progress.
>
> 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: 9c87959601e8 ("ntfs: update file operations")
> Link: https://lore.kernel.org/r/20260629113827.4074335-3-libaokun@xxxxxxxxxxxxxxxxx
> Reviewed-by: Baolin Liu <liubaolin@xxxxxxxxxx>
> Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
Applied it to #ntfs-next.
Thanks!