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

[Mike Snitzer]

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.

Mike