[PATCH] fix queue stalling while barrier sequencing
If ordered tag isn't supported, request ordering for barrier
sequencing is performed by queue draining, which basically hangs the
request queue until elv_completed_request() reports completion of all
previous fs requests.
The condition check in elv_completed_request() was only performed for
fs requests. If a special request is queued between the last
to-be-drained request and the barrier sequence, draining is never
completed and the queue is stalled forever.
This patch moves the end-of-draining condition check such that it's
performed for all requests.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/block/elevator.c b/block/elevator.c
index 99a4d7b..1d075917 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -610,23 +610,23 @@
* request is released from the driver, io must be done
*/
if (blk_account_rq(rq)) {
- struct request *first_rq = list_entry_rq(q->queue_head.next);
-
q->in_flight--;
+ if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
+ e->ops->elevator_completed_req_fn(q, rq);
+ }
- /*
- * Check if the queue is waiting for fs requests to be
- * drained for flush sequence.
- */
- if (q->ordseq && q->in_flight == 0 &&
+ /*
+ * Check if the queue is waiting for fs requests to be
+ * drained for flush sequence.
+ */
+ if (unlikely(q->ordseq)) {
+ struct request *first_rq = list_entry_rq(q->queue_head.next);
+ if (q->in_flight == 0 &&
blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
q->request_fn(q);
}
-
- if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
- e->ops->elevator_completed_req_fn(q, rq);
}
}