On Tue, Jun 26, 2018 at 02:58:30PM -0400, Mike Snitzer wrote: > On Tue, Jun 26 2018 at 2:52pm -0400, > Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > > On Tue, Jun 26, 2018 at 10:59 AM, Ross Zwisler > > <ross.zwisler@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx> > > > Suggested-by: Mike Snitzer <snitzer@xxxxxxxxxx> > > > Cc: stable@xxxxxxxxxxxxxxx > > > > 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 Because in patch 3 of this series we now use the full bdev_dax_supported() instead of just checking the queue flag in device_supports_dax(), I agree that this isn't strictly necessary for stable. device_supports_dax() will still notice that the raw/sector namespaces don't support DAX because bdev_dax_supported() will fail, and we'll end up doing the right thing and not setting QUEUE_FLAG_DAX on the DM device. I think maybe it's good to have in stable for completeness (and it's a very small change), but if we drop it from stable the code will still do the right thing AFAICT.
