block: cleanup the flush plug helpers

Consolidate the various helpers into a single blk_flush_plug helper that
takes a plk_plug and the from_scheduler bool and switch all callsites to
call it directly.  Checks that the plug is non-NULL must be performed by
the caller, something that most already do anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211020144119.142582-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -1089,7 +1089,7 @@ int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags)
 		return 0;
 
 	if (current->plug)
-		blk_flush_plug_list(current->plug, false);
+		blk_flush_plug(current->plug, false);
 
 	if (blk_queue_enter(q, BLK_MQ_REQ_NOWAIT))
 		return 0;
@@ -1637,7 +1637,7 @@ struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
 }
 EXPORT_SYMBOL(blk_check_plugged);
 
-void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
+void blk_flush_plug(struct blk_plug *plug, bool from_schedule)
 {
 	if (!list_empty(&plug->cb_list))
 		flush_plug_callbacks(plug, from_schedule);
@@ -1659,11 +1659,10 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
  */
 void blk_finish_plug(struct blk_plug *plug)
 {
-	if (plug != current->plug)
-		return;
-	blk_flush_plug_list(plug, false);
-
-	current->plug = NULL;
+	if (plug == current->plug) {
+		blk_flush_plug(plug, false);
+		current->plug = NULL;
+	}
 }
 EXPORT_SYMBOL(blk_finish_plug);
 

fs/fs-writeback.c

@@ -1893,7 +1893,8 @@ static long writeback_sb_inodes(struct super_block *sb,
 			 * unplug, so get our IOs out the door before we
 			 * give up the CPU.
 			 */
-			blk_flush_plug(current);
+			if (current->plug)
+				blk_flush_plug(current->plug, false);
 			cond_resched();
 		}
 
@@ -2291,7 +2292,7 @@ void wakeup_flusher_threads(enum wb_reason reason)
 	 * If we are expecting writeback progress we must submit plugged IO.
 	 */
 	if (blk_needs_flush_plug(current))
-		blk_schedule_flush_plug(current);
+		blk_flush_plug(current->plug, true);
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)

include/linux/blkdev.h

@@ -725,9 +725,8 @@ extern void blk_set_queue_dying(struct request_queue *);
  * as the lock contention for request_queue lock is reduced.
  *
  * It is ok not to disable preemption when adding the request to the plug list
- * or when attempting a merge, because blk_schedule_flush_list() will only flush
- * the plug list when the task sleeps by itself. For details, please see
- * schedule() where blk_schedule_flush_plug() is called.
+ * or when attempting a merge. For details, please see schedule() where
+ * blk_flush_plug() is called.
  */
 struct blk_plug {
 	struct request *mq_list; /* blk-mq requests */
@@ -757,23 +756,8 @@ extern struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug,
 extern void blk_start_plug(struct blk_plug *);
 extern void blk_start_plug_nr_ios(struct blk_plug *, unsigned short);
 extern void blk_finish_plug(struct blk_plug *);
-extern void blk_flush_plug_list(struct blk_plug *, bool);
 
-static inline void blk_flush_plug(struct task_struct *tsk)
-{
-	struct blk_plug *plug = tsk->plug;
-
-	if (plug)
-		blk_flush_plug_list(plug, false);
-}
-
-static inline void blk_schedule_flush_plug(struct task_struct *tsk)
-{
-	struct blk_plug *plug = tsk->plug;
-
-	if (plug)
-		blk_flush_plug_list(plug, true);
-}
+void blk_flush_plug(struct blk_plug *plug, bool from_schedule);
 
 static inline bool blk_needs_flush_plug(struct task_struct *tsk)
 {
@@ -802,15 +786,10 @@ static inline void blk_finish_plug(struct blk_plug *plug)
 {
 }
 
-static inline void blk_flush_plug(struct task_struct *task)
-{
-}
-
-static inline void blk_schedule_flush_plug(struct task_struct *task)
+static inline void blk_flush_plug(struct blk_plug *plug, bool async)
 {
 }
 
-
 static inline bool blk_needs_flush_plug(struct task_struct *tsk)
 {
 	return false;

kernel/sched/core.c

@@ -6343,7 +6343,7 @@ static inline void sched_submit_work(struct task_struct *tsk)
 	 * make sure to submit it to avoid deadlocks.
 	 */
 	if (blk_needs_flush_plug(tsk))
-		blk_schedule_flush_plug(tsk);
+		blk_flush_plug(tsk->plug, true);
 }
 
 static void sched_update_worker(struct task_struct *tsk)
@@ -8354,7 +8354,8 @@ int io_schedule_prepare(void)
 	int old_iowait = current->in_iowait;
 
 	current->in_iowait = 1;
-	blk_schedule_flush_plug(current);
+	if (current->plug)
+		blk_flush_plug(current->plug, true);
 
 	return old_iowait;
 }