[BLOCK] Implement elv_drain_elevator for improved switch error detection
This patch adds request_queue->nr_sorted which keeps the number of
requests in the iosched and implement elv_drain_elevator which
performs forced dispatching. elv_drain_elevator checks whether
iosched actually dispatches all requests it has and prints error
message if it doesn't. As buggy forced dispatching can result in
wrong barrier operations, I think this extra check is worthwhile.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 025a7f0..a33a31e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -406,6 +406,7 @@
atomic_t refcnt;
+ unsigned int nr_sorted;
unsigned int in_flight;
/*
@@ -631,6 +632,7 @@
{
if (q->last_merge == rq)
q->last_merge = NULL;
+ q->nr_sorted--;
q->end_sector = rq_end_sector(rq);
q->boundary_rq = rq;