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From: "Kani, Toshimitsu" <toshi.kani-ZPxbGqLxI0U@public.gmane.org>
To: "snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org"
	<snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: "axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org"
	<axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>,
	"linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org"
	<linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org"
	<dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	"viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org"
	<viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Subject: Re: [PATCH v3 3/4] dm: add infrastructure for DAX support
Date: Fri, 24 Jun 2016 15:40:24 +0000	[thread overview]
Message-ID: <1466782822.3504.391.camel@hpe.com> (raw)
In-Reply-To: <20160624014930.GA10540-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

On Thu, 2016-06-23 at 21:49 -0400, Mike Snitzer wrote:
> On Thu, Jun 23 2016 at  7:36pm -0400,
> Kani, Toshimitsu <toshi.kani@hpe.com> 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?

Thanks,
-Toshi
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  parent reply	other threads:[~2016-06-24 15:40 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-23 21:05 [PATCH v3 0/4] Support DAX for device-mapper linear devices Mike Snitzer
     [not found] ` <1466715953-40692-1-git-send-email-snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-06-23 21:05   ` [PATCH v3 1/4] block: add QUEUE_FLAG_DAX for devices to advertise their DAX support Mike Snitzer
2016-06-23 21:05   ` [PATCH v3 2/4] block: expose QUEUE_FLAG_DAX in sysfs Mike Snitzer
2016-06-23 21:05   ` [PATCH v3 3/4] dm: add infrastructure for DAX support Mike Snitzer
     [not found]     ` <1466715953-40692-4-git-send-email-snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-06-23 23:36       ` Kani, Toshimitsu
     [not found]         ` <1466724984.3504.380.camel-ZPxbGqLxI0U@public.gmane.org>
2016-06-24  1:49           ` Mike Snitzer
     [not found]             ` <20160624014930.GA10540-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-06-24 15:40               ` Kani, Toshimitsu [this message]
     [not found]                 ` <1466782822.3504.391.camel-ZPxbGqLxI0U@public.gmane.org>
2016-06-24 15:44                   ` Mike Snitzer
     [not found]                     ` <20160624154446.GB13898-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-06-24 15:56                       ` Kani, Toshimitsu
2016-06-23 21:05   ` [PATCH v3 4/4] dm linear: add " Mike Snitzer
2016-06-30 17:00   ` [PATCH v3 0/4] Support DAX for device-mapper linear devices Mike Snitzer
     [not found]     ` <20160630170053.GA20750-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-07-08 19:30       ` Mike Snitzer

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