Re: [PATCH 2/6] ext4: Check for atomic writes support in write iter

[John Garry <john.g.garry@oracle.com>]

On 25/10/2024 04:45, Ritesh Harjani (IBM) wrote:
> Let's validate using generic_atomic_write_valid() in
> ext4_file_write_iter() if the write request has IOCB_ATOMIC set.
> 
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> ---
>   fs/ext4/file.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index f14aed14b9cf..b06c5d34bbd2 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>   	if (IS_DAX(inode))
>   		return ext4_dax_write_iter(iocb, from);
>   #endif
> +
> +	if (iocb->ki_flags & IOCB_ATOMIC) {
> +		size_t len = iov_iter_count(from);
> +		int ret;
> +
> +		if (!IS_ALIGNED(len, EXT4_SB(inode->i_sb)->fs_awu_min) ||
> +			len > EXT4_SB(inode->i_sb)->fs_awu_max)
> +			return -EINVAL;

this looks ok, but the IS_ALIGNED() check looks odd. I am not sure why 
you don't just check that fs_awu_max >= len >= fs_awu_min

> +
> +		ret = generic_atomic_write_valid(iocb, from);
> +		if (ret)
> +			return ret;
> +	}
> +
>   	if (iocb->ki_flags & IOCB_DIRECT)
>   		return ext4_dio_write_iter(iocb, from);
>   	else