Merge tag 'dm-4.7-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper updates from Mike Snitzer:

 - based on Jens' 'for-4.7/core' to have DM thinp's discard support use
   bio_inc_remaining() and the block core's new async __blkdev_issue_discard()
   interface

 - make DM multipath's fast code-paths lockless, using lockless_deference,
   to significantly improve large NUMA performance when using blk-mq.
   The m->lock spinlock contention was a serious bottleneck.

 - a few other small code cleanups and Documentation fixes

* tag 'dm-4.7-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm thin: unroll issue_discard() to create longer discard bio chains
  dm thin: use __blkdev_issue_discard for async discard support
  dm thin: remove __bio_inc_remaining() and switch to using bio_inc_remaining()
  dm raid: make sure no feature flags are set in metadata
  dm ioctl: drop use of __GFP_REPEAT in copy_params()'s __vmalloc() call
  dm stats: fix spelling mistake in Documentation
  dm cache: update cache-policies.txt now that mq is an alias for smq
  dm mpath: eliminate use of spinlock in IO fast-paths
  dm mpath: move trigger_event member to the end of 'struct multipath'
  dm mpath: use atomic_t for counting members of 'struct multipath'
  dm mpath: switch to using bitops for state flags
  dm thin: Remove return statement from void function
  dm: remove unused mapped_device argument from free_tio()

2 files changed, 17 insertions, 19 deletions

diff --git a/Documentation/device-mapper/cache-policies.txt b/Documentation/device-mapper/cache-policies.txt
index e5062ad18717..d3ca8af21a31 100644
--- a/Documentation/device-mapper/cache-policies.txt
+++ b/Documentation/device-mapper/cache-policies.txt
@@ -11,7 +11,7 @@ Every bio that is mapped by the target is referred to the policy.
 The policy can return a simple HIT or MISS or issue a migration.
 
 Currently there's no way for the policy to issue background work,
-e.g. to start writing back dirty blocks that are going to be evicte
+e.g. to start writing back dirty blocks that are going to be evicted
 soon.
 
 Because we map bios, rather than requests it's easy for the policy
@@ -48,7 +48,7 @@ with the multiqueue (mq) policy.
 
 The smq policy (vs mq) offers the promise of less memory utilization,
 improved performance and increased adaptability in the face of changing
-workloads.  SMQ also does not have any cumbersome tuning knobs.
+workloads.  smq also does not have any cumbersome tuning knobs.
 
 Users may switch from "mq" to "smq" simply by appropriately reloading a
 DM table that is using the cache target.  Doing so will cause all of the
@@ -57,47 +57,45 @@ degrade slightly until smq recalculates the origin device's hotspots
 that should be cached.
 
 Memory usage:
-The mq policy uses a lot of memory; 88 bytes per cache block on a 64
+The mq policy used a lot of memory; 88 bytes per cache block on a 64
 bit machine.
 
-SMQ uses 28bit indexes to implement it's data structures rather than
+smq uses 28bit indexes to implement it's data structures rather than
 pointers.  It avoids storing an explicit hit count for each block.  It
-has a 'hotspot' queue rather than a pre cache which uses a quarter of
+has a 'hotspot' queue, rather than a pre-cache, which uses a quarter of
 the entries (each hotspot block covers a larger area than a single
 cache block).
 
-All these mean smq uses ~25bytes per cache block.  Still a lot of
+All this means smq uses ~25bytes per cache block.  Still a lot of
 memory, but a substantial improvement nontheless.
 
 Level balancing:
-MQ places entries in different levels of the multiqueue structures
-based on their hit count (~ln(hit count)).  This means the bottom
-levels generally have the most entries, and the top ones have very
-few.  Having unbalanced levels like this reduces the efficacy of the
+mq placed entries in different levels of the multiqueue structures
+based on their hit count (~ln(hit count)).  This meant the bottom
+levels generally had the most entries, and the top ones had very
+few.  Having unbalanced levels like this reduced the efficacy of the
 multiqueue.
 
-SMQ does not maintain a hit count, instead it swaps hit entries with
-the least recently used entry from the level above.  The over all
+smq does not maintain a hit count, instead it swaps hit entries with
+the least recently used entry from the level above.  The overall
 ordering being a side effect of this stochastic process.  With this
 scheme we can decide how many entries occupy each multiqueue level,
 resulting in better promotion/demotion decisions.
 
 Adaptability:
-The MQ policy maintains a hit count for each cache block.  For a
+The mq policy maintained a hit count for each cache block.  For a
 different block to get promoted to the cache it's hit count has to
-exceed the lowest currently in the cache.  This means it can take a
+exceed the lowest currently in the cache.  This meant it could take a
 long time for the cache to adapt between varying IO patterns.
-Periodically degrading the hit counts could help with this, but I
-haven't found a nice general solution.
 
-SMQ doesn't maintain hit counts, so a lot of this problem just goes
+smq doesn't maintain hit counts, so a lot of this problem just goes
 away.  In addition it tracks performance of the hotspot queue, which
 is used to decide which blocks to promote.  If the hotspot queue is
 performing badly then it starts moving entries more quickly between
 levels.  This lets it adapt to new IO patterns very quickly.
 
 Performance:
-Testing SMQ shows substantially better performance than MQ.
+Testing smq shows substantially better performance than mq.
 
 cleaner
 -------
diff --git a/Documentation/device-mapper/statistics.txt b/Documentation/device-mapper/statistics.txt
index 6f5ef944ca4c..170ac02a1f50 100644
--- a/Documentation/device-mapper/statistics.txt
+++ b/Documentation/device-mapper/statistics.txt
@@ -205,7 +205,7 @@ statistics on them:
 
   dmsetup message vol 0 @stats_create - /100
 
-Set the auxillary data string to "foo bar baz" (the escape for each
+Set the auxiliary data string to "foo bar baz" (the escape for each
 space must also be escaped, otherwise the shell will consume them):
 
   dmsetup message vol 0 @stats_set_aux 0 foo\\ bar\\ baz