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

[Hyunchul Lee]

On Sat, Oct 03, 2026 at 05:30:34PM +0800, Jiale Yao 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>

Looks good to me.

Reviewed-by: Hyunchul Lee <hyc.lee@xxxxxxxxx>

> ---
>  fs/ntfs/file.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
> index 007d1614b9ac..8bbfa842889a 100644
> --- a/fs/ntfs/file.c
> +++ b/fs/ntfs/file.c
> @@ -525,8 +525,21 @@ static ssize_t ntfs_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  		ssize_t written;
>  		int ret2;
>  
> +		if (iocb->ki_flags & IOCB_NOWAIT) {
> +			if (!ret)
> +				ret = -EAGAIN;
> +			goto out;
> +		}
> +
>  		offset = iocb->ki_pos;
>  		iocb->ki_flags &= ~IOCB_DIRECT;
> +
> +		/*
> +		 * Prevent concurrent direct I/O and buffered I/O to the same file
> +		 * range. Wait for in-flight DIO to finish before dirtying pages.
> +		 */
> +		inode_dio_wait(file_inode(iocb->ki_filp));
> +
>  		written = iomap_file_buffered_write(iocb, from,
>  				&ntfs_write_iomap_ops, &ntfs_iomap_folio_ops,
>  				NULL);
> -- 
> 2.34.1
> 
> 

-- 
Thanks,
Hyunchul