Date:	Fri, 22 Mar 2013 13:14:32 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	dm-devel@...hat.com, linux-kernel@...r.kernel.org,
	Heinz Mauelshagen <heinzm@...hat.com>,
	Joe Thornber <ejt@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>,
	Mikulas Patocka <mpatocka@...hat.com>,
	Paul Taysom <taysom@...omium.org>,
	Randy Dunlap <rdunlap@...radead.org>, stable@...r.kernel.org
Subject: Re: [dm-devel] [git pull] device-mapper fixes for 3.9

On Fri, Mar 22, 2013 at 11:53:26AM -0700, Darrick J. Wong wrote:
> On Thu, Mar 21, 2013 at 02:26:26AM +0000, Alasdair G Kergon wrote:
> > Please pull from:
> > 
> >   git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm tags/dm-3.9-fixes
> > 
> > to get the following device-mapper fixes for 3.9.
> > 
> > Thanks,
> > Alasdair
> > 
> > ----------------------------------------------------------------
> > A set of device-mapper fixes for 3.9.
> > 
> > Fix reported data loss with discards and thin snapshots; avoid a
> > deadlock observed in dm verity; fix a race in the new dm cache code
> > along with some other minor bugs; store the cache policy version on disk
> > to make the stored hints format future-proof.
> > 
> > ----------------------------------------------------------------
> > Heinz Mauelshagen (2):
> >       dm cache: detect cache_create failure
> >       dm cache: avoid calling policy destructor twice on error
> > 
> > Joe Thornber (5):
> >       dm thin: fix discard corruption
> >       dm thin: fix non power of two discard granularity calc
> >       dm cache: avoid 64 bit division on 32 bit
> >       dm cache: metadata clear dirty bits on clean shutdown
> >       dm cache: fix race in writethrough implementation
> 
> I think I've found a bug in this new WT implementation.  /dev/sdb is an SSD,
> /dev/sda is a spinny disk, and both have been zeroed prior to running the
> following:
> 
> # pvcreate /dev/sdb
> # vgcreate -s 256K moocache /dev/sdb
> # lvcreate -n metadata moocache -l 17
> # lvcreate -n blocks moocache -l 2030
> # echo '0 67108864 cache /dev/mapper/moocache-metadata /dev/mapper/moocache-blocks /dev/sda 512 1 writethrough default 4 random_threshold 4 sequential_threshold 32768' | dmsetup create moocache
> # mkfs.ext4 /dev/mapper/moocache -U deadbeef-cafe-dead-beef-cafedeadbeef 
> 
> If I then run blkid, I only see this:
> /dev/sdb: UUID="jlKkqi-L3W1-QQqf-7HKR-jmjU-GL79-qDOdvP" TYPE="LVM2_member" 
> /dev/sda: UUID="deadbeef-cafe-dead-beef-cafedeadbeef" TYPE="ext4" 
> 
> Curious -- it didn't find anything on /dev/mapper/moocache.  e2fsck/mount also
> see nothing, and dumping the first 256K shows zeroes.  Sometimes it finds no
> ext4 at all.
> 
> If I create the cache in WB mode, I see that blkid finds the deadbeef fs on
> /dev/sda and /dev/mapper/moocache, like I'd expect:
> 
> /dev/sdb: UUID="9hYUEh-OOKT-KuqF-6eDy-2cEZ-2eEa-y17lhN" TYPE="LVM2_member" 
> /dev/mapper/moocache-blocks: UUID="deadbeef-cafe-dead-beef-cafedeadbeef" TYPE="ext4" 
> /dev/mapper/moocache: UUID="deadbeef-cafe-dead-beef-cafedeadbeef" TYPE="ext4" 

It looks like dm-cache issues the bio first to the origin device with bi_sector
== N and bi_size == S, but then fails to reset these values when reissuing the
bio to the cache device.  Therefore, the second issue of the bio goes out with
bi_size == 0 and bi_sector == N + (S >> 512), which is incorrect.  I'll send a
patch.

--D
> 
> --D
> 
> > 
> > Mike Snitzer (2):
> >       dm cache: policy change version from string to integer set
> >       dm cache: policy ignore hints if generated by different version
> > 
> > Mikulas Patocka (1):
> >       dm verity: avoid deadlock
> > 
> >  drivers/md/dm-bufio.c                        |    2 +
> >  drivers/md/dm-cache-metadata.c               |   64 ++++++++--
> >  drivers/md/dm-cache-metadata.h               |    2 +-
> >  drivers/md/dm-cache-policy-cleaner.c         |    7 +-
> >  drivers/md/dm-cache-policy-internal.h        |    2 +
> >  drivers/md/dm-cache-policy-mq.c              |    8 +-
> >  drivers/md/dm-cache-policy.c                 |    8 ++
> >  drivers/md/dm-cache-policy.h                 |    2 +
> >  drivers/md/dm-cache-target.c                 |  169 +++++++++++++++++---------
> >  drivers/md/dm-thin.c                         |   11 +-
> >  drivers/md/dm-verity.c                       |   39 +++++-
> >  drivers/md/persistent-data/dm-btree-remove.c |   46 +++----
> >  12 files changed, 252 insertions(+), 108 deletions(-)
> > 
> 
> --
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