block: optimise blk_flush_plug_list

Don't call flush_plug_callbacks if there are no plug callbacks. Signed-off-by: Pavel Begunkov <[email protected]> [hch: split from a larger patch] Signed-off-by: Christoph Hellwig <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Jens Axboe <[email protected]>
ambv · Oct 20, 2021 · b600455 · b600455
1 parent dbb6f76
commit b600455
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/block/blk-core.c b/block/blk-core.c
@@ -1639,8 +1639,8 @@ EXPORT_SYMBOL(blk_check_plugged);
 
 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 {
-	flush_plug_callbacks(plug, from_schedule);
-
+	if (!list_empty(&plug->cb_list))
+		flush_plug_callbacks(plug, from_schedule);
 	if (!rq_list_empty(plug->mq_list))
 		blk_mq_flush_plug_list(plug, from_schedule);
 	if (unlikely(!from_schedule && plug->cached_rq))