From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH v3 3/4] dm: add infrastructure for DAX support Date: Fri, 24 Jun 2016 11:44:47 -0400 Message-ID: <20160624154446.GB13898@redhat.com> References: <1466715953-40692-1-git-send-email-snitzer@redhat.com> <1466715953-40692-4-git-send-email-snitzer@redhat.com> <1466724984.3504.380.camel@hpe.com> <20160624014930.GA10540@redhat.com> <1466782822.3504.391.camel@hpe.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <1466782822.3504.391.camel-ZPxbGqLxI0U@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: "Kani, Toshimitsu" Cc: "axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org" , "linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , "viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org" List-Id: dm-devel.ids On Fri, Jun 24 2016 at 11:40am -0400, Kani, Toshimitsu wrote: > On Thu, 2016-06-23 at 21:49 -0400, Mike Snitzer wrote: > > On Thu, Jun 23 2016 at=A0=A07:36pm -0400, > > Kani, Toshimitsu wrote: > =A0: > > > Thanks for the update. =A0I have a question about the above change. = =A0Targets > > > may have their own parameters. =A0For instance, dm-stripe has 'chunk_= size', > > > which is checked in stripe_ctr(). =A0DAX adds additional restriction = that > > > chunk_size needs to be aligned by page size. =A0So, I think we need t= o keep > > > target responsible to verify if DAX can be supported. =A0What do you = think? > > > > We've never had to concern the dm-stripe target with hardware > > specific chunk_size validation.=A0=A0The user is able to specify the > > chunk_size via lvm2's lvcreate -I argument.=A0=A0Yes this gives users e= nough > > rope to hang themselves but it is very easy to configure a dm-stripe > > device with the appropriate chunk size (PAGE_SIZE) from userspace. > > = > > But lvm2 could even be trained to make sure the chunk_size is a factor > > of physical_block_size (PAGE_SIZE in the case of pmem) if the underlying > > devices export queue/dax=3D1 > = > lvcreate=A0-I only allows multiple of page size, so we are OK with lvm2. = =A0I was > wondering if the check in lvm2 is enough. =A0Are there any other tools th= at may > be used to configure stripe size? =A0Can we trust userspace on this? Other than lvm2, I'm not aware of any other userspace tool that is driving the dm-stripe target configuration. So I think we can trust userspace here until proven otherwise. Good news is that any misconfiguration will simply not work right? Errors would result from improperly sized IO right? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751665AbcFXPvS (ORCPT ); Fri, 24 Jun 2016 11:51:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36547 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751546AbcFXPvQ (ORCPT ); Fri, 24 Jun 2016 11:51:16 -0400 Date: Fri, 24 Jun 2016 11:44:47 -0400 From: Mike Snitzer To: "Kani, Toshimitsu" Cc: "axboe@kernel.dk" , "linux-nvdimm@ml01.01.org" , "linux-kernel@vger.kernel.org" , "dm-devel@redhat.com" , "viro@zeniv.linux.org.uk" , "yigal@plexistor.com" , "dan.j.williams@intel.com" , "ross.zwisler@linux.intel.com" Subject: Re: [PATCH v3 3/4] dm: add infrastructure for DAX support Message-ID: <20160624154446.GB13898@redhat.com> References: <1466715953-40692-1-git-send-email-snitzer@redhat.com> <1466715953-40692-4-git-send-email-snitzer@redhat.com> <1466724984.3504.380.camel@hpe.com> <20160624014930.GA10540@redhat.com> <1466782822.3504.391.camel@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1466782822.3504.391.camel@hpe.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Fri, 24 Jun 2016 15:44:49 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 24 2016 at 11:40am -0400, Kani, Toshimitsu wrote: > On Thu, 2016-06-23 at 21:49 -0400, Mike Snitzer wrote: > > On Thu, Jun 23 2016 at  7:36pm -0400, > > Kani, Toshimitsu wrote: >  : > > > Thanks for the update.  I have a question about the above change.  Targets > > > may have their own parameters.  For instance, dm-stripe has 'chunk_size', > > > which is checked in stripe_ctr().  DAX adds additional restriction that > > > chunk_size needs to be aligned by page size.  So, I think we need to keep > > > target responsible to verify if DAX can be supported.  What do you think? > > > > We've never had to concern the dm-stripe target with hardware > > specific chunk_size validation.  The user is able to specify the > > chunk_size via lvm2's lvcreate -I argument.  Yes this gives users enough > > rope to hang themselves but it is very easy to configure a dm-stripe > > device with the appropriate chunk size (PAGE_SIZE) from userspace. > > > > But lvm2 could even be trained to make sure the chunk_size is a factor > > of physical_block_size (PAGE_SIZE in the case of pmem) if the underlying > > devices export queue/dax=1 > > lvcreate -I only allows multiple of page size, so we are OK with lvm2.  I was > wondering if the check in lvm2 is enough.  Are there any other tools that may > be used to configure stripe size?  Can we trust userspace on this? Other than lvm2, I'm not aware of any other userspace tool that is driving the dm-stripe target configuration. So I think we can trust userspace here until proven otherwise. Good news is that any misconfiguration will simply not work right? Errors would result from improperly sized IO right?