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

From	"Kani, Toshimitsu" <toshi.kani@hpe.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices
Date	2016-06-14 02:00 +0200
Message-ID	<rJJVT-554-1@gated-at.bofh.it> (permalink)
References	<rJIGt-4a0-1@gated-at.bofh.it> <rJJjb-4NW-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Mon, 2016-06-13 at 16:18 -0700, Dan Williams wrote:
> Thanks Toshi!
> 
> On Mon, Jun 13, 2016 at 3:21 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
> > 
> > This patch-set adds DAX support to device-mapper dm-linear devices
> > used by LVM.  It works with LVM commands as follows:
> >  - Creation of a logical volume with all DAX capable devices (such
> >    as pmem) sets the logical volume DAX capable as well.
> >  - Once a logical volume is set to DAX capable, the volume may not
> >    be extended with non-DAX capable devices.
>
> I don't mind this, but it seems a policy decision that the kernel does
> not need to make.  A sufficiently sophisticated user could cope with
> DAX being available at varying LBAs.  Would it be sufficient to move
> this policy decision to userspace tooling?

I think this is a kernel restriction.  When a block device is declared as
DAX capable, it should mean that the whole device is DAX capable.  So, I
think we need to assure the same to a mapped device.

In LVM level, a volume group may contain both DAX and non-DAX capable
devices.  There is no restriction for creating/extending a volume group.

> > The direct_access interface is added to dm and dm-linear to map
> > a request to a target device.
>
> I had dm-linear and md-raid0 support on my list of things to look at,
> did you have raid0 in your plans?

Yes, I hope to extend further and raid0 is a good candidate.   

Thanks,
-Toshi

Thread

[PATCH 0/6] Support DAX for device-mapper dm-linear devices Toshi Kani <toshi.kani@hpe.com> - 2016-06-14 00:40 +0200
  [PATCH 1/6] genhd: Add GENHD_FL_DAX to gendisk flags Toshi Kani <toshi.kani@hpe.com> - 2016-06-14 00:40 +0200
  [PATCH 4/6] dm-linear: Add linear_direct_access() Toshi Kani <toshi.kani@hpe.com> - 2016-06-14 00:40 +0200
  [PATCH 6/6] dm: Enable DAX support for mapper device Toshi Kani <toshi.kani@hpe.com> - 2016-06-14 00:40 +0200
  [PATCH 3/6] dm: Add dm_blk_direct_access() for mapped device Toshi Kani <toshi.kani@hpe.com> - 2016-06-14 00:40 +0200
  [PATCH 2/6] block: Check GENHD_FL_DAX for DAX capability Toshi Kani <toshi.kani@hpe.com> - 2016-06-14 00:40 +0200
  [PATCH 5/6] dm, dm-linear: Add dax_supported to dm_target Toshi Kani <toshi.kani@hpe.com> - 2016-06-14 00:40 +0200
  Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-14 01:00 +0200
    Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-20 20:30 +0200
      Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-20 21:50 +0200
        Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-20 23:50 +0200
          Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-21 00:10 +0200
            Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-21 00:40 +0200
              Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-21 15:50 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-21 18:00 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-21 18:10 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Dan Williams <dan.j.williams@intel.com> - 2016-06-21 18:30 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Dan Williams <dan.j.williams@intel.com> - 2016-06-21 18:50 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-21 19:20 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-21 19:00 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-21 20:30 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-22 19:50 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Dan Williams <dan.j.williams@intel.com> - 2016-06-22 21:20 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-22 22:20 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-23 00:40 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-23 01:20 +0200
          Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-21 00:50 +0200
      Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-20 23:10 +0200
  Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Dan Williams <dan.j.williams@intel.com> - 2016-06-14 01:20 +0200
    Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-14 02:00 +0200
      Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Dan Williams <dan.j.williams@intel.com> - 2016-06-14 02:10 +0200
        Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Dan Williams <dan.j.williams@intel.com> - 2016-06-14 09:40 +0200
      Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Jeff Moyer <jmoyer@redhat.com> - 2016-06-14 16:00 +0200
        Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-14 17:50 +0200
          Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-14 20:10 +0200
          Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Jeff Moyer <jmoyer@redhat.com> - 2016-06-14 22:20 +0200
            Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-15 03:50 +0200
              Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Dan Williams <dan.j.williams@intel.com> - 2016-06-15 04:10 +0200
                Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer <snitzer@redhat.com> - 2016-06-15 04:40 +0200
        Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2016-06-14 18:00 +0200

csiph-web