Re: [PATCH v2 14/14] fs: xfs: Support setting FMODE_CAN_ATOMIC_WRITE

From: John Garry <john.g.garry@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: djwong@kernel.org, hch@lst.de, viro@zeniv.linux.org.uk,
	brauner@kernel.org, jack@suse.cz, chandan.babu@oracle.com,
	axboe@kernel.dk, martin.petersen@oracle.com,
	linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com,
	ojaswin@linux.ibm.com, ritesh.list@gmail.com,
	linux-block@vger.kernel.org
Subject: Re: [PATCH v2 14/14] fs: xfs: Support setting FMODE_CAN_ATOMIC_WRITE
Date: Thu, 7 Mar 2024 11:55:59 +0000	[thread overview]
Message-ID: <5e7eb717-d810-4dc3-80b0-3baaa20ca41f@oracle.com> (raw)
In-Reply-To: <ZejhNMW5o0JSCgqW@dread.disaster.area>

On 06/03/2024 21:33, Dave Chinner wrote:
>> +static bool xfs_file_open_can_atomicwrite(
>> +	struct inode		*inode,
>> +	struct file		*file)
>> +{
>> +	struct xfs_inode	*ip = XFS_I(inode);
>> +	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
>> +
>> +	if (!(file->f_flags & O_DIRECT))
>> +		return false;
>> +
>> +	if (!xfs_inode_atomicwrites(ip))
>> +		return false;
>> +
>> +	if (!bdev_can_atomic_write(target->bt_bdev))
>> +		return false;
> Again, this is static blockdev information - the inode atomic write
> flag should not be set if the bdev cannot do atomic writes. It
> should be checked at mount time

ok

> - the filesystem probably should
> only mount read-only if it is configured to allow atomic writes and
> the underlying blockdev does not support atomic writes...

Let me know if you really would like to see that change also. It does 
seem a bit drastic, considering we can just disallow atomic writes.

Thanks,
John