Commit 1bc691d3 authored by Tejun Heo's avatar Tejun Heo Committed by Linus Torvalds
Browse files

[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: default avatarTejun Heo <>
Signed-off-by: default avatarJens Axboe <>
Signed-off-by: default avatarLinus Torvalds <>
parent 593195f9
...@@ -610,23 +610,23 @@ void elv_completed_request(request_queue_t *q, struct request *rq) ...@@ -610,23 +610,23 @@ void elv_completed_request(request_queue_t *q, struct request *rq)
* request is released from the driver, io must be done * request is released from the driver, io must be done
*/ */
if (blk_account_rq(rq)) { if (blk_account_rq(rq)) {
struct request *first_rq = list_entry_rq(q->;
q->in_flight--; 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 * Check if the queue is waiting for fs requests to be
* drained for flush sequence. * drained for flush sequence.
*/ */
if (q->ordseq && q->in_flight == 0 && if (unlikely(q->ordseq)) {
struct request *first_rq = list_entry_rq(q->;
if (q->in_flight == 0 &&
blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN && blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) { blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0); blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
q->request_fn(q); q->request_fn(q);
} }
if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
e->ops->elevator_completed_req_fn(q, rq);
} }
} }
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