From: Jan Kara <jack@suse.cz>
To: linux-nvdimm@lists.01.org
Cc: Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, linux-fsdevel@vger.kernel.org
Subject: Snapshot target and DAX-capable devices
Date: Mon, 27 Aug 2018 18:07:44 +0200 [thread overview]
Message-ID: <20180827160744.GE4002@quack2.suse.cz> (raw)
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.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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next reply other threads:[~2018-08-27 16:07 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-27 16:07 Jan Kara [this message]
2018-08-27 16:43 ` Snapshot target and DAX-capable devices Kani, Toshi
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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