blkcg: remove blkio_group->stats_lock

With recent plug merge updates, all non-percpu stat updates happen
under queue_lock making stats_lock unnecessary to synchronize stat
updates.  The only synchronization necessary is stat reading, which
can be done using u64_stats_sync instead.

This patch removes blkio_group->stats_lock and adds
blkio_group_stats->syncp for reader synchronization.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 2 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 8bdcf504f94b..9df5ab04b6d6 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -119,6 +119,7 @@ struct blkio_cgroup {
 };
 
 struct blkio_group_stats {
+        struct u64_stats_sync syncp;
         /* total disk time and nr sectors dispatched by this group */
         uint64_t time;
         uint64_t stat_arr[BLKIO_STAT_ARR_NR][BLKIO_STAT_TOTAL];
@@ -200,8 +201,6 @@ struct blkio_group {
         /* reference count */
         int refcnt;
 
-        /* Need to serialize the stats in the case of reset/update */
-        spinlock_t stats_lock;
         struct blkg_policy_data *pd[BLKIO_NR_POLICIES];
 
         /* List of blkg waiting for per cpu stats memory to be allocated */