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

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Message-ID: <87plnvglck.fsf@gmail.com>
Date: Sun, 20 Oct 2024 15:14:11 +0530
From: Ritesh Harjani (IBM) <ritesh.list@...il.com>
To: John Garry <john.g.garry@...cle.com>, axboe@...nel.dk, brauner@...nel.org, djwong@...nel.org, viro@...iv.linux.org.uk, jack@...e.cz, dchinner@...hat.com, hch@....de, cem@...nel.org
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, hare@...e.de, martin.petersen@...cle.com, catherine.hoang@...cle.com, mcgrof@...nel.org, ojaswin@...ux.ibm.com, John Garry <john.g.garry@...cle.com>
Subject: Re: [PATCH v10 7/8] xfs: Validate atomic writes

John Garry <john.g.garry@...cle.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@....de>
> Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>
> Signed-off-by: John Garry <john.g.garry@...cle.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