[PATCH v2 0/3] fs: drain in-flight DIO before buffered write fallback

[PATCH v2 0/3] fs: drain in-flight DIO before buffered write fallback

[Jiale Yao]

An asynchronous direct write can remain in flight after its submitting
thread releases the inode lock.  If another direct write falls back to
buffered I/O in the meantime, the buffered write can dirty page cache
before the first write completes post-I/O invalidation.  The invalidation
then finds dirty pages, emits a page cache invalidation failure warning,
and records -EIO in the mapping error sequence.  A later fsync() returns
-EIO.

Commit 15cdefd0c0522f9d5e12d947fa04f4c11649b699 ("ext4: drain
in-flight DIO before buffered write fallback") fixed this race in ext4.
The same ordering is missing from the buffered fallback paths in ext2,
NTFS, and exFAT.

This series adds inode_dio_wait() before each fallback dirties page cache.
Each patch fixes one filesystem and remains independently buildable.  The
NTFS patch also avoids entering the blocking fallback for IOCB_NOWAIT
requests: it returns -EAGAIN if DIO made no progress and preserves a
positive result after a partial direct write.

A reproducer using concurrent AIO direct writes and buffered fallback
triggered the following warning on all three filesystems 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!

Changes in v2:
- Handle IOCB_NOWAIT before the potentially blocking NTFS fallback,
  returning -EAGAIN before any bytes are written and preserving a positive
  short-write result otherwise, as requested in review.

Jiale Yao (3):
  ext2: drain in-flight DIO before buffered write fallback
  ntfs: drain in-flight DIO before buffered write fallback
  exfat: drain in-flight DIO before buffered write fallback

 fs/exfat/file.c |  6 ++++++
 fs/ext2/file.c  |  7 +++++++
 fs/ntfs/file.c  | 13 +++++++++++++
 3 files changed, 26 insertions(+)

-- 
2.34.1

[PATCH v2 1/3] ext2: drain in-flight DIO before buffered write fallback

[Jiale Yao]

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>
---
 fs/ext2/file.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index b9020df7d89e..67fe423c3828 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -135,6 +135,13 @@ static ssize_t ext2_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		int ret2;
 
 		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(inode);
+
 		pos = iocb->ki_pos;
 		status = generic_perform_write(iocb, from);
 		if (unlikely(status < 0)) {
-- 
2.34.1

[PATCH v2 2/3] ntfs: drain in-flight DIO before buffered write fallback

[Jiale Yao]

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@linux.alibaba.com
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 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

[PATCH v2 3/3] exfat: drain in-flight DIO before buffered write fallback

[Jiale Yao]

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.  ExFAT 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.

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: 867b9c96dc83 ("exfat: add iomap direct I/O support")
Link: https://lore.kernel.org/r/20260629113827.4074335-3-libaokun@linux.alibaba.com
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 fs/exfat/file.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index a2a9ee1a2004..cf5ccbd54823 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -807,6 +807,12 @@ static ssize_t exfat_fallback_buffered_write(struct kiocb *iocb,
 
 	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, &exfat_write_iomap_ops,
 			NULL, NULL);
 	if (written < 0)
-- 
2.34.1

Re: [PATCH v2 2/3] ntfs: drain in-flight DIO before buffered write fallback

[liubaolin]

在 2026/9/26 15:26, Jiale Yao 写道:
> 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@linux.alibaba.com
> Signed-off-by: Jiale Yao <yaojiale02@163.com>
> ---
>   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);

Looks good to me.

Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>

Re: [PATCH v2 3/3] exfat: drain in-flight DIO before buffered write fallback

[Chi Zhiling]

On 9/26/26 3:26 PM, Jiale Yao wrote:
> diff --git a/fs/exfat/file.c b/fs/exfat/file.c
> index a2a9ee1a2004..cf5ccbd54823 100644
> --- a/fs/exfat/file.c
> +++ b/fs/exfat/file.c
> @@ -807,6 +807,12 @@ static ssize_t exfat_fallback_buffered_write(struct kiocb *iocb,
>   
>   	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));

This change is correct, but the comment is not accurate because the 
function you modified is not part of the buffered I/O path in exFAT.

You can add inode_dio_wait() to both exfat_file_write_iter() and 
exfat_fallback_buffered_write(), and move the comment to 
exfat_file_write_iter().

> +
>   	written = iomap_file_buffered_write(iocb, from, &exfat_write_iomap_ops,
>   			NULL, NULL);
>   	if (written < 0)

Re: [PATCH v2 3/3] exfat: drain in-flight DIO before buffered write fallback

[jiale yao]

Hi Zhiling,

At 2026-09-27 21:04:58, "Chi Zhiling" <chizhiling@163.com> wrote:
>On 9/26/26 3:26 PM, Jiale Yao wrote:
>> diff --git a/fs/exfat/file.c b/fs/exfat/file.c
>> index a2a9ee1a2004..cf5ccbd54823 100644
>> --- a/fs/exfat/file.c
>> +++ b/fs/exfat/file.c
>> @@ -807,6 +807,12 @@ static ssize_t exfat_fallback_buffered_write(struct kiocb *iocb,
>>   
>>   	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));
>
>This change is correct, but the comment is not accurate because the 
>function you modified is not part of the buffered I/O path in exFAT.
>
>You can add inode_dio_wait() to both exfat_file_write_iter() and 
>exfat_fallback_buffered_write(), and move the comment to 
>exfat_file_write_iter().
>
>> +
>>   	written = iomap_file_buffered_write(iocb, from, &exfat_write_iomap_ops,
>>   			NULL, NULL);
>>   	if (written < 0)

Thanks for your review. See v3 in:
https://lore.kernel.org/all/20260928085412.2221055-1-yaojiale02@163.com/

Re: [PATCH v2 1/3] ext2: drain in-flight DIO before buffered write fallback

[Jan Kara]

On Sat 26-09-26 15:26:10, 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, 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>

This patch is already merged in my tree. You can drop it from the series.

								Honza

> ---
>  fs/ext2/file.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/ext2/file.c b/fs/ext2/file.c
> index b9020df7d89e..67fe423c3828 100644
> --- a/fs/ext2/file.c
> +++ b/fs/ext2/file.c
> @@ -135,6 +135,13 @@ static ssize_t ext2_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  		int ret2;
>  
>  		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(inode);
> +
>  		pos = iocb->ki_pos;
>  		status = generic_perform_write(iocb, from);
>  		if (unlikely(status < 0)) {
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR