[dm-devel] [PATCH v3 1/3] pmem: only set QUEUE_FLAG_DAX for fsdax mode

[Dan Williams]

On Tue, Jun 26, 2018 at 11:58 AM, Mike Snitzer <snitzer at redhat.com> wrote:
> On Tue, Jun 26 2018 at  2:52pm -0400,
> Dan Williams <dan.j.williams at intel.com> wrote:
>
>> On Tue, Jun 26, 2018 at 10:59 AM, Ross Zwisler
>> <ross.zwisler at linux.intel.com> wrote:
>> > QUEUE_FLAG_DAX is an indication that a given block device supports
>> > filesystem DAX and should not be set for PMEM namespaces which are in "raw"
>> > or "sector" modes.  These namespaces lack struct page and are prevented
>> > from participating in filesystem DAX.
>> >
>> > Signed-off-by: Ross Zwisler <ross.zwisler at linux.intel.com>
>> > Suggested-by: Mike Snitzer <snitzer at redhat.com>
>> > Cc: stable at vger.kernel.org
>>
>> Why is this cc: stable? What is the user visible impact of this change
>> especially given the requirement to validate QUEUE_FLAG_DAX with
>> bdev_dax_supported()? Patch looks good, but it's just a cosmetic fixup
>> afaics.
>
> This isn't cosmetic when you consider that stacking up a DM device is
> looking at this flag to determine whether a table does or does _not_
> support DAX.
>
> So this patch, in conjunction with the other changes in the series, is
> certainly something I'd consider appropriate for stable.

I think this classifies as something that never worked correctly and
is not a regression. It does not identify which commit it is repairing
or the user visible failure mode.