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| author |   Joe Thornber <ejt@redhat.com> | 2014-04-03 16:16:44 +0100 |
|---|---|---|
| committer |   Mike Snitzer <snitzer@redhat.com> | 2014-04-04 14:53:05 -0400 |
| commit | 0596661f0a16d9d69bf1033320e70b6ff52b5e81 (patch) | |
| tree | 5f2393ddece9f82f9fa7853c7aa6f9d9dbffddd1 /drivers/md/dm-cache-metadata.h | |
| parent | dm thin: sort the per thin deferred bios using an rb_tree (diff) | |
| download | linux-dev-0596661f0a16d9d69bf1033320e70b6ff52b5e81.tar.xz linux-dev-0596661f0a16d9d69bf1033320e70b6ff52b5e81.zip | |
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
Diffstat (limited to 'drivers/md/dm-cache-metadata.h')
| -rw-r--r-- | drivers/md/dm-cache-metadata.h | 9 |
1 files changed, 1 insertions, 8 deletions
diff --git a/drivers/md/dm-cache-metadata.h b/drivers/md/dm-cache-metadata.h index ce8468bb616e..cd70a78623a3 100644 --- a/drivers/md/dm-cache-metadata.h +++ b/drivers/md/dm-cache-metadata.h @@ -128,14 +128,7 @@ void dm_cache_dump(struct dm_cache_metadata *cmd); * rather than querying the policy for each cblock, we let it walk its data * structures and fill in the hints in whatever order it wishes. */ - -int dm_cache_begin_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *p); - -/* - * requests hints for every cblock and stores in the metadata device. - */ -int dm_cache_save_hint(struct dm_cache_metadata *cmd, - dm_cblock_t cblock, uint32_t hint); +int dm_cache_write_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *p); /* * Query method. Are all the blocks in the cache clean? |