Re: [PATCH v3 3/3] xfs: reject max_atomic_write mount option for no reflink

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

On 24/07/2025 17:32, Darrick J. Wong wrote:
> On Thu, Jul 24, 2025 at 08:12:15AM +0000, John Garry wrote:
>> If the FS has no reflink, then atomic writes greater than 1x block are not
>> supported. As such, for no reflink it is pointless to accept setting
>> max_atomic_write when it cannot be supported, so reject max_atomic_write
>> mount option in this case.
>>
>> It could be still possible to accept max_atomic_write option of size 1x
>> block if HW atomics are supported, so check for this specifically.
>>
>> Fixes: 4528b9052731 ("xfs: allow sysadmins to specify a maximum atomic write limit at mount time")
>> Signed-off-by: John Garry<john.g.garry@oracle.com>
> /me wonders if "mkfs: allow users to configure the desired maximum
> atomic write size" needs a similar filter?
> 

Yeah, probably. But I am wondering if we should always require reflink 
for setting that max atomic mkfs option, and not have a special case of 
HW atomics available for 1x blocksize atomic writes.

> Reviewed-by: "Darrick J. Wong"<djwong@kernel.org>

cheers