Validate that an atomic write adheres to length/offset rules. Currently
we can only write a single FS block.

For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_write_iter(),
FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this,
ATOMICWRITES flags would also need to be set for the inode.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 fs/xfs/xfs_file.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index b19916b11fd5..1ccbc1eb75c9 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -852,6 +852,20 @@ xfs_file_write_iter(
 	if (IS_DAX(inode))
 		return xfs_file_dax_write(iocb, from);
 
+	if (iocb->ki_flags & IOCB_ATOMIC) {
+		/*
+		 * Currently only atomic writing of a single FS block is
+		 * supported. It would be possible to atomic write smaller than
+		 * a FS block, but there is no requirement to support this.
+		 * Note that iomap also does not support this yet.
+		 */
+		if (ocount != ip->i_mount->m_sb.sb_blocksize)
+			return -EINVAL;
+		ret = generic_atomic_write_valid(iocb, from);
+		if (ret)
+			return ret;
+	}
+
 	if (iocb->ki_flags & IOCB_DIRECT) {
 		/*
 		 * Allow a directio write to fall back to a buffered
-- 
2.31.1

John Garry <john.g.garry@oracle.com> writes:

> Validate that an atomic write adheres to length/offset rules. Currently
> we can only write a single FS block.
>
> For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_write_iter(),
> FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this,
> ATOMICWRITES flags would also need to be set for the inode.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
>  fs/xfs/xfs_file.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index b19916b11fd5..1ccbc1eb75c9 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -852,6 +852,20 @@ xfs_file_write_iter(
>  	if (IS_DAX(inode))
>  		return xfs_file_dax_write(iocb, from);
>  
> +	if (iocb->ki_flags & IOCB_ATOMIC) {
> +		/*
> +		 * Currently only atomic writing of a single FS block is
> +		 * supported. It would be possible to atomic write smaller than
> +		 * a FS block, but there is no requirement to support this.
> +		 * Note that iomap also does not support this yet.
> +		 */
> +		if (ocount != ip->i_mount->m_sb.sb_blocksize)
> +			return -EINVAL;

Shouldn't we "return -ENOTSUPP" ? 
Given we are later going to add support for ocount > sb_blocksize.

-ritesh

On 20/10/2024 10:44, Ritesh Harjani (IBM) wrote:
>> +	if (iocb->ki_flags & IOCB_ATOMIC) {
>> +		/*
>> +		 * Currently only atomic writing of a single FS block is
>> +		 * supported. It would be possible to atomic write smaller than
>> +		 * a FS block, but there is no requirement to support this.
>> +		 * Note that iomap also does not support this yet.
>> +		 */
>> +		if (ocount != ip->i_mount->m_sb.sb_blocksize)
>> +			return -EINVAL;
> Shouldn't we "return -ENOTSUPP" ?
> Given we are later going to add support for ocount > sb_blocksize.

So far we have been reporting -EINVAL for an invalid atomic write size 
(according to atomic write unit min and max reported for that inode).

-ENOTSUPP is used for times when we just don't support atomic writes, 
like non-DIO.

Thanks,
John

John Garry <john.g.garry@oracle.com> writes:

> On 20/10/2024 10:44, Ritesh Harjani (IBM) wrote:
>>> +	if (iocb->ki_flags & IOCB_ATOMIC) {
>>> +		/*
>>> +		 * Currently only atomic writing of a single FS block is
>>> +		 * supported. It would be possible to atomic write smaller than
>>> +		 * a FS block, but there is no requirement to support this.
>>> +		 * Note that iomap also does not support this yet.
>>> +		 */
>>> +		if (ocount != ip->i_mount->m_sb.sb_blocksize)
>>> +			return -EINVAL;
>> Shouldn't we "return -ENOTSUPP" ?
>> Given we are later going to add support for ocount > sb_blocksize.
>
> So far we have been reporting -EINVAL for an invalid atomic write size 
> (according to atomic write unit min and max reported for that inode).
>
> -ENOTSUPP is used for times when we just don't support atomic writes, 
> like non-DIO.
>

Sure make sense. 

-ritesh