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

From: "Kani, Toshimitsu" <toshi.kani-ZPxbGqLxI0U@public.gmane.org>
To: "snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org"
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Subject: Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices
Date: Wed, 22 Jun 2016 22:59:10 +0000	[thread overview]
Message-ID: <1466635735.3504.344.camel@hpe.com> (raw)
In-Reply-To: <20160622223842.GA34512-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

On Wed, 2016-06-22 at 18:38 -0400, Mike Snitzer wrote:
> On Wed, Jun 22 2016 at  4:16P -0400,
> Kani, Toshimitsu <toshi.kani@hpe.com> wrote:
> > 
> > On Wed, 2016-06-22 at 12:15 -0700, Dan Williams wrote:
> > > 
> > > On Wed, Jun 22, 2016 at 10:44 AM, Kani, Toshimitsu <toshi.kani@hpe.com>
> > > wrote:
> > > > 
> > > > On Tue, 2016-06-21 at 14:17 -0400, Mike Snitzer wrote:
> > > > > 
> > > > > On Tue, Jun 21 2016 at 11:44am -0400,
> > > > > Kani, Toshimitsu <toshi.kani@hpe.com> wrote:
> > > > > > 
> > > > > > On Tue, 2016-06-21 at 09:41 -0400, Mike Snitzer wrote:
> > > > > > > 
> > > > > The devices in question have a request_queue.  All bio-based device
> > > > > have a request_queue.
> > > > 
> > > > DAX-capable devices have two operation modes, bio-based and DAX.  I
> > > > agree that bio-based operation is associated with a request queue, and
> > > > its capabilities should be set to it.  DAX, on the other hand, is
> > > > rather independent from a request queue.
> > > > 
> > > > > 
> > > > > I don't have a big problem with GENHD_FL_DAX.  Just wanted to point
> > > > > out that such block device capabilities are generally advertised in
> > > > > terms of a QUEUE_FLAG.
> > > > 
> > > > I do not have a strong opinion, but feel a bit odd to associate DAX to
> > > > a request queue.
> > >
> > > Given that we do not support dax to a raw block device [1] it seems a
> > > gendisk flag is more misleading than request_queue flag that specifies
> > > what requests can be made of the device.
> > > 
> > > [1]: acc93d30d7d4 Revert "block: enable dax for raw block devices"
> >
> > Oh, I see.  I will change to use request_queue flag.
>
> I implemented the block patch for this yesterday but based on your
> feedback I stopped there (didn't carry the change through to the DM core
> and DM linear -- can easily do so tomorrow though).
> 
> Feel free to use this as a starting point and fix/extend and add a
> proper header:

Thanks Mike! I made similar changes as well. I will take yours and finish up
the rest. :)
-Toshi
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