Re: [git pull] device-mapper fixes for 3.9

["Darrick J. Wong" <darrick.wong@oracle.com>]

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" 

--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(-)
>