linux-kernel - Re: [PATCH v5 7/7] xfs: Support setting FMODE_CAN_ATOMIC

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Message-ID: <20240821171142.GM865349@frogsfrogsfrogs>
Date: Wed, 21 Aug 2024 10:11:42 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: John Garry <john.g.garry@...cle.com>
Cc: axboe@...nel.dk, brauner@...nel.org, viro@...iv.linux.org.uk,
	jack@...e.cz, chandan.babu@...cle.com, dchinner@...hat.com,
	hch@....de, 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,
	kbusch@...nel.org
Subject: Re: [PATCH v5 7/7] xfs: Support setting FMODE_CAN_ATOMIC_WRITE

On Sat, Aug 17, 2024 at 09:48:00AM +0000, John Garry wrote:
> For when an inode is enabled for atomic writes, set FMODE_CAN_ATOMIC_WRITE
> flag. Only direct IO is currently supported, so check for that also.
> 
> We rely on the block layer to reject atomic writes which exceed the bdev
> request_queue limits, so don't bother checking any such thing here.
> 
> 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 9b6530a4eb4a..3489d478809e 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1149,6 +1149,18 @@ xfs_file_remap_range(
>  	return remapped > 0 ? remapped : ret;
>  }
>  
> +static bool xfs_file_open_can_atomicwrite(
> +	struct inode		*inode,
> +	struct file		*file)
> +{
> +	struct xfs_inode	*ip = XFS_I(inode);
> +
> +	if (!(file->f_flags & O_DIRECT))
> +		return false;
> +
> +	return xfs_inode_has_atomicwrites(ip);

...and here too.  I do like the shift to having an incore flag that
controls whether you get untorn write support or not.

--D

> +}
> +
>  STATIC int
>  xfs_file_open(
>  	struct inode	*inode,
> @@ -1157,6 +1169,8 @@ xfs_file_open(
>  	if (xfs_is_shutdown(XFS_M(inode->i_sb)))
>  		return -EIO;
>  	file->f_mode |= FMODE_NOWAIT | FMODE_CAN_ODIRECT;
> +	if (xfs_file_open_can_atomicwrite(inode, file))
> +		file->f_mode |= FMODE_CAN_ATOMIC_WRITE;
>  	return generic_file_open(inode, file);
>  }
>  
> -- 
> 2.31.1
> 
>