block: add comment on why we save and disable interrupts in flush_plug_list()

It's done at the top to avoid doing it for every queue we unplug. Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

block: add comment on why we save and disable interrupts in flush_plug_list()
It's done at the top to avoid doing it for every queue we unplug. Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Jens Axboe
1 parent 94b5eb28b4
Showing 1 changed file with 5 additions and 0 deletions Side-by-side Diff
block/blk-core.c
@@ -2696,6 +2696,11 @@
  
 	q = NULL;
 	depth = 0;
+
+	/*
+	 * Save and disable interrupts here, to avoid doing it for every
+	 * queue lock we have to take.
+	 */
 	local_irq_save(flags);
 	while (!list_empty(&list)) {
 		rq = list_entry_rq(list.next);
...	...	@@ -2696,6 +2696,11 @@
2696	2696
2697	2697	q = NULL;
2698	2698	depth = 0;
	2699	+
	2700	+ /*
	2701	+ * Save and disable interrupts here, to avoid doing it for every
	2702	+ * queue lock we have to take.
	2703	+ */
2699	2704	local_irq_save(flags);
2700	2705	while (!list_empty(&list)) {
2701	2706	rq = list_entry_rq(list.next);