Re: [PATCH v10 7/8] xfs: Validate atomic writes

[IBM]

John Garry <john.g.garry@xxxxxxxxxx> 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@xxxxxx>
> Reviewed-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
> Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
> ---
>  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