block: fix peeking requests during PM

We need to look for an active PM request until the next softbarrier
instead of looking for the first non-PM request.  Otherwise any cause
of request reordering might starve the PM request(s).

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 395bfb10d65819a8602664312e1c152156f686b2..223f32826e62d6e236ee5ce259091bd26d36348b 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2511,20 +2511,22 @@ void blk_account_io_done(struct request *req)
  * Don't process normal requests when queue is suspended
  * or in the process of suspending/resuming
  */
-static struct request *blk_pm_peek_request(struct request_queue *q,
-                                          struct request *rq)
+static bool blk_pm_allow_request(struct request *rq)
 {
-       if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
-           (q->rpm_status != RPM_ACTIVE && !(rq->rq_flags & RQF_PM))))
-               return NULL;
-       else
-               return rq;
+       switch (rq->q->rpm_status) {
+       case RPM_RESUMING:
+       case RPM_SUSPENDING:
+               return rq->rq_flags & RQF_PM;
+       case RPM_SUSPENDED:
+               return false;
+       }
+
+       return true;
 }
 #else
-static inline struct request *blk_pm_peek_request(struct request_queue *q,
-                                                 struct request *rq)
+static bool blk_pm_allow_request(struct request *rq)
 {
-       return rq;
+       return true;
 }
 #endif
 
@@ -2572,9 +2574,12 @@ static struct request *elv_next_request(struct request_queue *q)
        WARN_ON_ONCE(q->mq_ops);
 
        while (1) {
-               if (!list_empty(&q->queue_head)) {
-                       rq = list_entry_rq(q->queue_head.next);
-                       return rq;
+               list_for_each_entry(rq, &q->queue_head, queuelist) {
+                       if (blk_pm_allow_request(rq))
+                               return rq;
+
+                       if (rq->rq_flags & RQF_SOFTBARRIER)
+                               break;
                }
 
                /*
@@ -2625,10 +2630,6 @@ struct request *blk_peek_request(struct request_queue *q)
        WARN_ON_ONCE(q->mq_ops);
 
        while ((rq = elv_next_request(q)) != NULL) {
-               rq = blk_pm_peek_request(q, rq);
-               if (!rq)
-                       break;
-
                if (!(rq->rq_flags & RQF_STARTED)) {
                        /*
                         * This is the first time the device driver