From: "Kani, Toshi" <toshi.kani@hpe.com>
To: "jack@suse.cz" <jack@suse.cz>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
Cc: "dm-devel@redhat.com" <dm-devel@redhat.com>,
"ross.zwisler@linux.intel.com" <ross.zwisler@linux.intel.com>,
"dan.j.williams@intel.com" <dan.j.williams@intel.com>,
"snitzer@redhat.com" <snitzer@redhat.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: Snapshot target and DAX-capable devices
Date: Mon, 27 Aug 2018 16:43:28 +0000 [thread overview]
Message-ID: <e38303902267d2d8bae8b0c88da84a4ed668e9fb.camel@hpe.com> (raw)
In-Reply-To: <20180827160744.GE4002@quack2.suse.cz>
On Mon, 2018-08-27 at 18:07 +0200, Jan Kara wrote:
> Hi,
>
> I've been analyzing why fstest generic/081 fails when the backing device is
> capable of DAX. The problem boils down to the failure of:
>
> lvm vgcreate -f vg0 /dev/pmem0
> lvm lvcreate -L 128M -n lv0 vg0
> lvm lvcreate -s -L 4M -n snap0 vg0/lv0
>
> The last command fails like:
>
> device-mapper: reload ioctl on (253:0) failed: Invalid argument
> Failed to lock logical volume vg0/lv0.
> Aborting. Manual intervention required.
>
> And the core of the problem is that volume vg0/lv0 is originally of
> DM_TYPE_DAX_BIO_BASED type but when the snapshot gets created, we try to
> switch it to DM_TYPE_BIO_BASED because now the device stops supporting DAX.
> The problem seems to be introduced by Ross' commit dbc626597 "dm: prevent
> DAX mounts if not supported".
>
> The question is whether / how this should be fixed. The current inability
> to create snapshots of DAX-capable devices looks weird and the cryptic
> failure makes it even worse (it took me quite a while to understand what is
> failing and why). OTOH I see the rationale behind Ross' change as well.
Here are the dm-snap changes that went along with the original DAX
support.
commit b5ab4a9ba55
commit f6e629bd237
Basically, snapshots can be added/removed to DAX-capable devices, but
snapshots need to be mounted without dax option.
Thanks,
-Toshi
next prev parent reply other threads:[~2018-08-27 20:30 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-27 16:07 Snapshot target and DAX-capable devices Jan Kara
2018-08-27 16:43 ` Kani, Toshi [this message]
2018-08-28 7:50 ` Jan Kara
2018-08-28 17:56 ` Mike Snitzer
2018-08-28 22:38 ` Kani, Toshi
2018-08-30 9:30 ` Jan Kara
2018-08-30 18:49 ` Mike Snitzer
2018-08-30 19:32 ` Jeff Moyer
2018-08-30 19:47 ` Mikulas Patocka
2018-08-30 19:53 ` Jeff Moyer
2018-08-30 23:38 ` Dave Chinner
2018-08-31 9:42 ` Jan Kara
2018-09-05 1:25 ` Dave Chinner
2018-12-12 16:11 ` Huaisheng Ye
2018-12-12 16:12 ` Christoph Hellwig
2018-12-12 17:50 ` Mike Snitzer
2018-12-12 19:49 ` Kani, Toshi
2018-12-12 21:15 ` Theodore Y. Ts'o
2018-12-12 22:43 ` Mike Snitzer
2018-12-14 4:11 ` [dm-devel] " Theodore Y. Ts'o
2018-12-14 8:24 ` [External] " Huaisheng HS1 Ye
2018-12-18 19:49 ` Mike Snitzer
2018-08-30 19:44 ` Mikulas Patocka
2018-08-31 10:01 ` Jan Kara
2018-08-30 22:55 ` Dave Chinner
2018-08-31 9:54 ` Jan Kara
2018-08-30 19:17 ` [dm-devel] " Jeff Moyer
2018-08-31 9:14 ` Jan Kara
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