Commit Graph

18 Commits

Author SHA1 Message Date
Joe Thornber 766a78882d dm cache: fix missing ERR_PTR returns and handling
Commit 9b1cc9f251 ("dm cache: share cache-metadata object across
inactive and active DM tables") mistakenly ignored the use of ERR_PTR
returns.  Restore missing IS_ERR checks and ERR_PTR returns where
appropriate.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
2015-01-28 09:59:20 -05:00
Joe Thornber 9b1cc9f251 dm cache: share cache-metadata object across inactive and active DM tables
If a DM table is reloaded with an inactive table when the device is not
suspended (normal procedure for LVM2), then there will be two dm-bufio
objects that can diverge.  This can lead to a situation where the
inactive table uses bufio to read metadata at the same time the active
table writes metadata -- resulting in the inactive table having stale
metadata buffers once it is promoted to the active table slot.

Fix this by using reference counting and a global list of cache metadata
objects to ensure there is only one metadata object per metadata device.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
2015-01-23 10:57:15 -05:00
Joe Thornber 1bad9bc4ee dm cache: revert "remove remainder of distinct discard block size"
This reverts commit 64ab346a36 because we
actually do want to allow the discard blocksize to be larger than the
cache blocksize.  Further dm-cache discard changes will make this
possible.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-11-10 15:25:30 -05:00
Mike Snitzer 895b47d798 dm cache metadata: use dm-space-map-metadata.h defined size limits
Commit 7d48935e cleaned up the persistent-data's space-map-metadata
limits by elevating them to dm-space-map-metadata.h.  Update
dm-cache-metadata to use these same limits.

The calculation for DM_CACHE_METADATA_MAX_SECTORS didn't account for the
sizeof the disk_bitmap_header.  So the supported maximum metadata size
is a bit smaller (reduced from 33423360 to 33292800 sectors).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
2014-08-01 12:30:33 -04:00
Mike Snitzer 048e5a07f2 dm cache metadata: do not allow the data block size to change
The block size for the dm-cache's data device must remained fixed for
the life of the cache.  Disallow any attempt to change the cache's data
block size.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Cc: stable@vger.kernel.org
2014-07-15 14:07:50 -04:00
Joe Thornber 0596661f0a dm cache: fix a lock-inversion
When suspending a cache the policy is walked and the individual policy
hints written to the metadata via sync_metadata().  This led to this
lock order:

      policy->lock
        cache_metadata->root_lock

When loading the cache target the policy is populated while the metadata
lock is held:

      cache_metadata->root_lock
         policy->lock

Fix this potential lock-inversion (ABBA) deadlock in sync_metadata() by
ensuring the cache_metadata root_lock is held whilst all the hints are
written, rather than being repeatedly locked while policy->lock is held
(as was the case with each callout that policy_walk_mappings() made to
the old save_hint() method).

Found by turning on the CONFIG_PROVE_LOCKING ("Lock debugging: prove
locking correctness") build option.  However, it is not clear how the
LOCKDEP reported paths can lead to a deadlock since the two paths,
suspending a target and loading a target, never occur at the same time.
But that doesn't mean the same lock-inversion couldn't have occurred
elsewhere.

Reported-by: Marian Csontos <mcsontos@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
2014-04-04 14:53:05 -04:00
Joe Thornber 5a32083d03 dm: take care to copy the space map roots before locking the superblock
In theory copying the space map root can fail, but in practice it never
does because we're careful to check what size buffer is needed.

But make certain we're able to copy the space map roots before
locking the superblock.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # drop dm-era and dm-cache changes as needed
2014-03-27 16:56:23 -04:00
Joe Thornber a9d45396f5 dm transaction manager: fix corruption due to non-atomic transaction commit
The persistent-data library used by dm-thin, dm-cache, etc is
transactional.  If anything goes wrong, such as an io error when writing
new metadata or a power failure, then we roll back to the last
transaction.

Atomicity when committing a transaction is achieved by:

a) Never overwriting data from the previous transaction.
b) Writing the superblock last, after all other metadata has hit the
   disk.

This commit and the following commit ("dm: take care to copy the space
map roots before locking the superblock") fix a bug associated with (b).
When committing it was possible for the superblock to still be written
in spite of an io error occurring during the preceeding metadata flush.
With these commits we're careful not to take the write lock out on the
superblock until after the metadata flush has completed.

Change the transaction manager's semantics for dm_tm_commit() to assume
all data has been flushed _before_ the single superblock that is passed
in.

As a prerequisite, split the block manager's block unlocking and
flushing by simplifying dm_bm_flush_and_unlock() to dm_bm_flush().  Now
the unlocking must be done separately.

This issue was discovered by forcing io errors at the crucial time
using dm-flakey.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
2014-03-27 16:56:23 -04:00
Heinz Mauelshagen 64ab346a36 dm cache: remove remainder of distinct discard block size
Discard block size not being equal to cache block size causes data
corruption by erroneously avoiding migrations in issue_copy() because
the discard state is being cleared for a group of cache blocks when it
should not.

Completely remove all code that enabled a distinction between the
cache block size and discard block size.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-03-27 16:56:23 -04:00
Joe Thornber 53d498198d dm cache metadata: check the metadata version when reading the superblock
Need to check the version to verify on-disk metadata is supported.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-11-11 11:37:49 -05:00
Joe Thornber 2ee57d5873 dm cache: add passthrough mode
"Passthrough" is a dm-cache operating mode (like writethrough or
writeback) which is intended to be used when the cache contents are not
known to be coherent with the origin device.  It behaves as follows:

* All reads are served from the origin device (all reads miss the cache)
* All writes are forwarded to the origin device; additionally, write
  hits cause cache block invalidates

This mode decouples cache coherency checks from cache device creation,
largely to avoid having to perform coherency checks while booting.  Boot
scripts can create cache devices in passthrough mode and put them into
service (mount cached filesystems, for example) without having to worry
about coherency.  Coherency that exists is maintained, although the
cache will gradually cool as writes take place.

Later, applications can perform coherency checks, the nature of which
will depend on the type of the underlying storage.  If coherency can be
verified, the cache device can be transitioned to writethrough or
writeback mode while still warm; otherwise, the cache contents can be
discarded prior to transitioning to the desired operating mode.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Morgan Mears <Morgan.Mears@netapp.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-11-11 11:37:49 -05:00
Joe Thornber f494a9c6b1 dm cache: cache shrinking support
Allow a cache to shrink if the blocks being removed from the cache are
not dirty.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-11-11 11:37:45 -05:00
Joe Thornber dd8b0c2096 dm cache metadata: return bool from __superblock_all_zeroes
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-11-09 18:20:17 -05:00
Joe Thornber 8c5008fac4 dm cache: replace memcpy with struct assignment
Use struct assignment rather than memcpy in dm cache.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-05-10 14:37:18 +01:00
Mike Snitzer ea2dd8c1ed dm cache: policy ignore hints if generated by different version
When reading the dm cache metadata from disk, ignore the policy hints
unless they were generated by the same major version number of the same
policy module.

The hints are considered to be private data belonging to the specific
module that generated them and there is no requirement for them to make
sense to different versions of the policy that generated them.
Policy modules are all required to work fine if no previous hints are
supplied (or if existing hints are lost).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-03-20 17:21:28 +00:00
Mike Snitzer 4e7f506f64 dm cache: policy change version from string to integer set
Separate dm cache policy version string into 3 unsigned numbers
corresponding to major, minor and patchlevel and store them at the end
of the on-disk metadata so we know which version of the policy generated
the hints in case a future version wants to use them differently.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-03-20 17:21:27 +00:00
Joe Thornber 79ed9caffc dm cache: metadata clear dirty bits on clean shutdown
When writing the dirty bitset to the metadata device on a clean
shutdown, clear the dirty bits.  Previously they were left indicating
the cache was dirty. This led to confusion about whether there really
was dirty data in the cache or not.  (This was a harmless bug.)

Reported-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-03-20 17:21:27 +00:00
Joe Thornber c6b4fcbad0 dm: add cache target
Add a target that allows a fast device such as an SSD to be used as a
cache for a slower device such as a disk.

A plug-in architecture was chosen so that the decisions about which data
to migrate and when are delegated to interchangeable tunable policy
modules.  The first general purpose module we have developed, called
"mq" (multiqueue), follows in the next patch.  Other modules are
under development.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-03-01 22:45:51 +00:00