From: Dan Williams <dan.j.williams@intel.com>
To: "Kani, Toshimitsu" <toshi.kani@hpe.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"agk@redhat.com" <agk@redhat.com>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"snitzer@redhat.com" <snitzer@redhat.com>,
"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
"ross.zwisler@linux.intel.com" <ross.zwisler@linux.intel.com>,
"dm-devel@redhat.com" <dm-devel@redhat.com>
Subject: Re: [PATCH 0/6] Support DAX for device-mapper dm-linear devices
Date: Mon, 13 Jun 2016 17:02:39 -0700 [thread overview]
Message-ID: <CAPcyv4hnKRc6qrPPuKo1r3=YmuAAaeSSv7xBOpDMAy5UuUhoHw@mail.gmail.com> (raw)
In-Reply-To: <1465861755.3504.185.camel@hpe.com>
On Mon, Jun 13, 2016 at 4:59 PM, Kani, Toshimitsu <toshi.kani@hpe.com> wrote:
> 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.
Hmm, but we already violate this with badblocks. The device is DAX
capable, but certain LBAs will return an error if direct_access is
attempted.
next prev parent reply other threads:[~2016-06-14 0:02 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-13 22:21 [PATCH 0/6] Support DAX for device-mapper dm-linear devices Toshi Kani
2016-06-13 22:21 ` [PATCH 1/6] genhd: Add GENHD_FL_DAX to gendisk flags Toshi Kani
2016-06-13 22:21 ` [PATCH 2/6] block: Check GENHD_FL_DAX for DAX capability Toshi Kani
2016-06-13 22:21 ` [PATCH 3/6] dm: Add dm_blk_direct_access() for mapped device Toshi Kani
2016-06-13 22:21 ` [PATCH 4/6] dm-linear: Add linear_direct_access() Toshi Kani
2016-06-13 22:21 ` [PATCH 5/6] dm, dm-linear: Add dax_supported to dm_target Toshi Kani
2016-06-13 22:21 ` [PATCH 6/6] dm: Enable DAX support for mapper device Toshi Kani
2016-06-13 22:57 ` [PATCH 0/6] Support DAX for device-mapper dm-linear devices Mike Snitzer
2016-06-20 18:00 ` Mike Snitzer
2016-06-20 18:31 ` Kani, Toshimitsu
2016-06-20 19:40 ` Mike Snitzer
2016-06-20 19:52 ` Mike Snitzer
2016-06-20 20:11 ` Kani, Toshimitsu
2016-06-20 21:28 ` Kani, Toshimitsu
2016-06-20 22:22 ` Mike Snitzer
2016-06-21 13:41 ` Mike Snitzer
2016-06-21 15:44 ` Kani, Toshimitsu
2016-06-21 15:50 ` Kani, Toshimitsu
2016-06-21 16:25 ` Dan Williams
2016-06-21 16:35 ` Kani, Toshimitsu
2016-06-21 16:45 ` Dan Williams
2016-06-21 16:56 ` Kani, Toshimitsu
2016-06-21 18:17 ` Mike Snitzer
2016-06-22 17:44 ` Kani, Toshimitsu
2016-06-22 19:15 ` Dan Williams
2016-06-22 20:16 ` Kani, Toshimitsu
2016-06-22 22:38 ` Mike Snitzer
2016-06-22 22:59 ` Kani, Toshimitsu
2016-06-13 23:18 ` Dan Williams
2016-06-13 23:59 ` Kani, Toshimitsu
2016-06-14 0:02 ` Dan Williams [this message]
2016-06-14 7:30 ` Dan Williams
2016-06-14 13:50 ` Jeff Moyer
2016-06-14 15:41 ` Mike Snitzer
2016-06-14 18:00 ` Kani, Toshimitsu
2016-06-14 20:19 ` Jeff Moyer
2016-06-15 1:46 ` Mike Snitzer
2016-06-15 2:07 ` Dan Williams
2016-06-15 2:35 ` Mike Snitzer
2016-06-14 15:53 ` Kani, Toshimitsu
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