blk-stat: don't use this_cpu_ptr() in a preemptable section

If PREEMPT_RCU is enabled, rcu_read_lock() isn't strong enough for us to use this_cpu_ptr() in that section. Use the safer get/put_cpu_ptr() variants instead. Reported-by: Mike Galbraith <[email protected]> Fixes: 34dbad5 ("blk-stat: convert to callback-based statistics reporting") Signed-off-by: Jens Axboe <[email protected]>
trax85 · May 10, 2017 · d373812 · d373812
1 parent 340ff32
commit d373812
Showing 1 changed file with 10 additions and 7 deletions.
diff --git a/block/blk-stat.c b/block/blk-stat.c
@@ -96,13 +96,16 @@ void blk_stat_add(struct request *rq)
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
-		if (blk_stat_is_active(cb)) {
-			bucket = cb->bucket_fn(rq);
-			if (bucket < 0)
-				continue;
-			stat = &this_cpu_ptr(cb->cpu_stat)[bucket];
-			__blk_stat_add(stat, value);
-		}
+		if (!blk_stat_is_active(cb))
+			continue;
+
+		bucket = cb->bucket_fn(rq);
+		if (bucket < 0)
+			continue;
+
+		stat = &get_cpu_ptr(cb->cpu_stat)[bucket];
+		__blk_stat_add(stat, value);
+		put_cpu_ptr(cb->cpu_stat);
 	}
 	rcu_read_unlock();
 }