2 files changed, 34 insertions, 21 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 1efabf829c53..b03d88013e1e 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -88,7 +88,7 @@ unsigned blk_ordered_req_seq(struct request *rq)
                 return QUEUE_ORDSEQ_DONE;
 }
 
-void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
+bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
 {
         struct request *rq;
 
@@ -99,7 +99,7 @@ void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
         q->ordseq |= seq;
 
         if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
-                return;
+                return false;
 
         /*
          * Okay, sequence complete.
@@ -109,6 +109,8 @@ void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
 
         if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq)))
                 BUG();
+
+        return true;
 }
 
 static void pre_flush_end_io(struct request *rq, int error)
@@ -151,9 +153,11 @@ static void queue_flush(struct request_queue *q, unsigned which)
         elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
 }
 
-static inline struct request *start_ordered(struct request_queue *q,
-                                            struct request *rq)
+static inline bool start_ordered(struct request_queue *q, struct request **rqp)
 {
+        struct request *rq = *rqp;
+        unsigned skip = 0;
+
         q->orderr = 0;
         q->ordered = q->next_ordered;
         q->ordseq |= QUEUE_ORDSEQ_STARTED;
@@ -177,7 +181,7 @@ static inline struct request *start_ordered(struct request_queue *q,
                 queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
                 rq = &q->post_flush_rq;
         } else
-                q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
+                skip |= QUEUE_ORDSEQ_POSTFLUSH;
 
         if (q->ordered & QUEUE_ORDERED_DO_BAR) {
                 rq = &q->bar_rq;
@@ -193,35 +197,40 @@ static inline struct request *start_ordered(struct request_queue *q,
 
                 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
         } else
-                q->ordseq |= QUEUE_ORDSEQ_BAR;
+                skip |= QUEUE_ORDSEQ_BAR;
 
         if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
                 queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
                 rq = &q->pre_flush_rq;
         } else
-                q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
+                skip |= QUEUE_ORDSEQ_PREFLUSH;
 
         if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && q->in_flight)
                 rq = NULL;
         else
-                q->ordseq |= QUEUE_ORDSEQ_DRAIN;
+                skip |= QUEUE_ORDSEQ_DRAIN;
+
+        *rqp = rq;
 
-        return rq;
+        /*
+         * Complete skipped sequences.  If whole sequence is complete,
+         * return false to tell elevator that this request is gone.
+         */
+        return !blk_ordered_complete_seq(q, skip, 0);
 }
 
-int blk_do_ordered(struct request_queue *q, struct request **rqp)
+bool blk_do_ordered(struct request_queue *q, struct request **rqp)
 {
         struct request *rq = *rqp;
         const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
 
         if (!q->ordseq) {
                 if (!is_barrier)
-                        return 1;
+                        return true;
 
-                if (q->next_ordered != QUEUE_ORDERED_NONE) {
-                        *rqp = start_ordered(q, rq);
-                        return 1;
-                } else {
+                if (q->next_ordered != QUEUE_ORDERED_NONE)
+                        return start_ordered(q, rqp);
+                else {
                         /*
                          * Queue ordering not supported.  Terminate
                          * with prejudice.
@@ -231,7 +240,7 @@ int blk_do_ordered(struct request_queue *q, struct request **rqp)
                                               blk_rq_bytes(rq)))
                                 BUG();
                         *rqp = NULL;
-                        return 0;
+                        return false;
                 }
         }
 
@@ -242,7 +251,7 @@ int blk_do_ordered(struct request_queue *q, struct request **rqp)
         /* Special requests are not subject to ordering rules. */
         if (!blk_fs_request(rq) &&
             rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
-                return 1;
+                return true;
 
         if (q->ordered & QUEUE_ORDERED_BY_TAG) {
                 /* Ordered by tag.  Blocking the next barrier is enough. */
@@ -255,7 +264,7 @@ int blk_do_ordered(struct request_queue *q, struct request **rqp)
                         *rqp = NULL;
         }
 
-        return 1;
+        return true;
 }
 
 static void bio_end_empty_barrier(struct bio *bio, int err)
diff --git a/block/elevator.c b/block/elevator.c
index 86836dd179c0..261ffaaf47bd 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -944,10 +944,14 @@ void elv_completed_request(struct request_queue *q, struct request *rq)
          * drained for flush sequence.
          */
         if (unlikely(q->ordseq)) {
-                struct request *first_rq = list_entry_rq(q->queue_head.next);
-                if (q->in_flight == 0 &&
+                struct request *next = NULL;
+
+                if (!list_empty(&q->queue_head))
+                        next = list_entry_rq(q->queue_head.next);
+
+                if (!q->in_flight &&
                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
-                    blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
+                    (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {
                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
                         blk_start_queueing(q);
                 }