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

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Message-ID: <7c5fdd14-5c59-4292-b4b5-b0d49ba1bce6@oracle.com>
Date: Thu, 22 Aug 2024 19:04:02 +0100
From: John Garry <john.g.garry@...cle.com>
To: "Darrick J. Wong" <djwong@...nel.org>
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 21/08/2024 18:11, Darrick J. Wong wrote:
> 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.

Do you mean that add a new member to xfs_inode to record this? If yes, 
it sounds ok, but we need to maintain consistency (of that member) 
whenever anything which can affect it changes, which is always a bit 
painful.

John