1 files changed, 17 insertions, 16 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index e6c05a97ee2b..3a78b00edd71 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -642,7 +642,7 @@ static inline void blk_free_request(struct request_queue *q, struct request *rq)
         if (rq->cmd_flags & REQ_ELVPRIV) {
                 elv_put_request(q, rq);
                 if (rq->elv.icq)
-                        put_io_context(rq->elv.icq->ioc, q);
+                        put_io_context(rq->elv.icq->ioc);
         }
 
         mempool_free(rq, q->rq.rq_pool);
@@ -872,13 +872,15 @@ retry:
         spin_unlock_irq(q->queue_lock);
 
         /* create icq if missing */
-        if (unlikely(et->icq_cache && !icq))
+        if ((rw_flags & REQ_ELVPRIV) && unlikely(et->icq_cache && !icq)) {
                 icq = ioc_create_icq(q, gfp_mask);
+                if (!icq)
+                        goto fail_icq;
+        }
 
-        /* rqs are guaranteed to have icq on elv_set_request() if requested */
-        if (likely(!et->icq_cache || icq))
-                rq = blk_alloc_request(q, icq, rw_flags, gfp_mask);
+        rq = blk_alloc_request(q, icq, rw_flags, gfp_mask);
 
+fail_icq:
         if (unlikely(!rq)) {
                 /*
                  * Allocation failed presumably due to memory. Undo anything
@@ -1210,7 +1212,6 @@ static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
         req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
 
         drive_stat_acct(req, 0);
-        elv_bio_merged(q, req, bio);
         return true;
 }
 
@@ -1241,7 +1242,6 @@ static bool bio_attempt_front_merge(struct request_queue *q,
         req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
 
         drive_stat_acct(req, 0);
-        elv_bio_merged(q, req, bio);
         return true;
 }
 
@@ -1255,13 +1255,12 @@ static bool bio_attempt_front_merge(struct request_queue *q,
  * on %current's plugged list.  Returns %true if merge was successful,
  * otherwise %false.
  *
- * This function is called without @q->queue_lock; however, elevator is
- * accessed iff there already are requests on the plugged list which in
- * turn guarantees validity of the elevator.
- *
- * Note that, on successful merge, elevator operation
- * elevator_bio_merged_fn() will be called without queue lock.  Elevator
- * must be ready for this.
+ * Plugging coalesces IOs from the same issuer for the same purpose without
+ * going through @q->queue_lock.  As such it's more of an issuing mechanism
+ * than scheduling, and the request, while may have elvpriv data, is not
+ * added on the elevator at this point.  In addition, we don't have
+ * reliable access to the elevator outside queue lock.  Only check basic
+ * merging parameters without querying the elevator.
  */
 static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
                                unsigned int *request_count)
@@ -1280,10 +1279,10 @@ static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
 
                 (*request_count)++;
 
-                if (rq->q != q)
+                if (rq->q != q || !blk_rq_merge_ok(rq, bio))
                         continue;
 
-                el_ret = elv_try_merge(rq, bio);
+                el_ret = blk_try_merge(rq, bio);
                 if (el_ret == ELEVATOR_BACK_MERGE) {
                         ret = bio_attempt_back_merge(q, rq, bio);
                         if (ret)
@@ -1345,12 +1344,14 @@ void blk_queue_bio(struct request_queue *q, struct bio *bio)
         el_ret = elv_merge(q, &req, bio);
         if (el_ret == ELEVATOR_BACK_MERGE) {
                 if (bio_attempt_back_merge(q, req, bio)) {
+                        elv_bio_merged(q, req, bio);
                         if (!attempt_back_merge(q, req))
                                 elv_merged_request(q, req, el_ret);
                         goto out_unlock;
                 }
         } else if (el_ret == ELEVATOR_FRONT_MERGE) {
                 if (bio_attempt_front_merge(q, req, bio)) {
+                        elv_bio_merged(q, req, bio);
                         if (!attempt_front_merge(q, req))
                                 elv_merged_request(q, req, el_ret);
                         goto out_unlock;