blkcg: Make blkg_root_lookup() work for queues in bypass mode

KAGA-KOKO · axboe · commit b86d865cb1ca · 2018-08-11T15:41:25.000-06:00
For legacy queues the only call of blkg_root_lookup() happens after bypass mode has been enabled. Since blkg_lookup() returns NULL for queues in bypass mode, modify the blkg_root_lookup() such that it no longer depends on bypass mode. Rename the function into blk_queue_root_blkg() as suggested by Tejun. Suggested-by: Tejun Heo <tj@kernel.org> Fixes: 6bad9b2 ("blkcg: Introduce blkg_root_lookup()") Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
@@ -813,7 +813,7 @@ static void __blk_release_queue(struct work_struct *work)
 		blk_exit_queue(q);
 	}
 
-	WARN(blkg_root_lookup(q),
+	WARN(blk_queue_root_blkg(q),
 	     "request queue %p is being released but it has not yet been removed from the blkcg controller\n",
 	     q);
 
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
@@ -342,20 +342,14 @@ static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
 }
 
 /**
- * blkg_lookup - look up blkg for the specified request queue
+ * blk_queue_root_blkg - return blkg for the (blkcg_root, @q) pair
  * @q: request_queue of interest
  *
  * Lookup blkg for @q at the root level. See also blkg_lookup().
  */
-static inline struct blkcg_gq *blkg_root_lookup(struct request_queue *q)
+static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
 {
-	struct blkcg_gq *blkg;
-
-	rcu_read_lock();
-	blkg = blkg_lookup(&blkcg_root, q);
-	rcu_read_unlock();
-
-	return blkg;
+	return q->root_blkg;
 }
 
 /**
@@ -881,7 +875,8 @@ static inline bool blk_cgroup_congested(void) { return false; }
 static inline void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay) { }
 
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
-static inline struct blkcg_gq *blkg_root_lookup(struct request_queue *q) { return NULL; }
+static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
+{ return NULL; }
 static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
 static inline void blkcg_drain_queue(struct request_queue *q) { }
 static inline void blkcg_exit_queue(struct request_queue *q) { }

Original file line number	Diff line number	Diff line change
`@@ -813,7 +813,7 @@ static void __blk_release_queue(struct work_struct *work)`
`813`	`813`	`blk_exit_queue(q);`
`814`	`814`	`}`
`815`	`815`
`816`		`- WARN(blkg_root_lookup(q),`
	`816`	`+ WARN(blk_queue_root_blkg(q),`
`817`	`817`	`"request queue %p is being released but it has not yet been removed from the blkcg controller\n",`
`818`	`818`	`q);`
`819`	`819`