Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices

[Kani, Toshimitsu]

On Tue, 2016-06-21 at 09:25 -0700, Dan Williams wrote:
> On Tue, Jun 21, 2016 at 8:44 AM, Kani, Toshimitsu <toshi.kani@xxxxxxx>
> wrote:
> > 
> > On Tue, 2016-06-21 at 09:41 -0400, Mike Snitzer wrote:
> > > 
> > > On Mon, Jun 20 2016 atÂÂ6:22pm -0400,
> > > Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
> > > > 
> > > > On Mon, Jun 20 2016 atÂÂ5:28pm -0400,
> > > > Kani, Toshimitsu <toshi.kani@xxxxxxx> wrote:
> > Â:
> > > > Looks good, I folded it in and tested it to work.ÂÂPushed to my 'wip'
> > > > branch.
> > > > 
> > > > No longer seeing any corruption in my test that was using partitions
> > > > to span pmem devices with a dm-linear device.
> > > > 
> > > > Jens, any chance you'd be open to picking up the first 2 patches in
> > > > this series?ÂÂOr would you like to see them folded or something
> > > > different?
> > >
> > > I'm now wondering if we'd be better off setting a new QUEUE_FLAG_DAX
> > > rather than establish GENHD_FL_DAX on the genhd?
> > > 
> > > It'd be quite a bit easier to allow upper layers (e.g. XFS and ext4) to
> > > check for a queue flag.
> >
> > I think GENHD_FL_DAX is more appropriate since DAX does not use a request
> > queue, except for protecting the underlining device being disabled while
> > direct_access() is called (b2e0d1625e19).
> > 
> > About protecting direct_access, this patch assumes that the underlining
> > device cannot be disabled until dtr() is called.ÂÂIs this correct?ÂÂIf
> > not, I will need to call dax_map_atomic().
>
> Kernel internal usages of dax should be using dax_map_atomic() to
> safely resolve device removal races.

Will do. ÂIn such case, shall I moveÂdax_[un]map_atomic() to block_dev.c and
rename them to bdev_dax_[un]map_atomic()?

Thanks,
-Toshi