bcache: add the missing comments for smp_mb()/smp_wmb()

Checkpatch.pl warns there are 2 locations of smp_mb() and smp_wmb()
without code comment. This patch adds the missing code comments for
these memory barrier calls.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Shenghui Wang <shhuiw@foxmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 4 insertions, 2 deletions

diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h
index 7f3594c0be14..eca0d496b686 100644
--- a/drivers/md/bcache/closure.h
+++ b/drivers/md/bcache/closure.h
@@ -289,10 +289,12 @@ static inline void closure_init_stack(struct closure *cl)
 }
 
 /**
- * closure_wake_up - wake up all closures on a wait list.
+ * closure_wake_up - wake up all closures on a wait list,
+ *                   with memory barrier
  */
 static inline void closure_wake_up(struct closure_waitlist *list)
 {
+        /* Memory barrier for the wait list */
         smp_mb();
         __closure_wake_up(list);
 }
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index e637d74e2908..94c756c66bd7 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1136,11 +1136,11 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
         list_move(&dc->list, &c->cached_devs);
         calc_cached_dev_sectors(c);
 
-        smp_wmb();
         /*
          * dc->c must be set before dc->count != 0 - paired with the mb in
          * cached_dev_get()
          */
+        smp_wmb();
         refcount_set(&dc->count, 1);
 
         /* Block writeback thread, but spawn it */