3 files changed, 13 insertions, 27 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index fa697bf691eb..3a78b00edd71 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1212,7 +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;
 }
 
@@ -1243,7 +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;
 }
 
@@ -1257,13 +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)
@@ -1282,7 +1279,7 @@ static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
 
                 (*request_count)++;
 
-                if (rq->q != q || !elv_rq_merge_ok(rq, bio))
+                if (rq->q != q || !blk_rq_merge_ok(rq, bio))
                         continue;
 
                 el_ret = blk_try_merge(rq, bio);
@@ -1347,12 +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;
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 5684df6848bc..d0ba50533668 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1699,18 +1699,11 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 
         /*
          * Lookup the cfqq that this bio will be queued with and allow
-         * merge only if rq is queued there.  This function can be called
-         * from plug merge without queue_lock.  In such cases, ioc of @rq
-         * and %current are guaranteed to be equal.  Avoid lookup which
-         * requires queue_lock by using @rq's cic.
+         * merge only if rq is queued there.
          */
-        if (current->io_context == RQ_CIC(rq)->icq.ioc) {
-                cic = RQ_CIC(rq);
-        } else {
-                cic = cfq_cic_lookup(cfqd, current->io_context);
-                if (!cic)
-                        return false;
-        }
+        cic = cfq_cic_lookup(cfqd, current->io_context);
+        if (!cic)
+                return false;
 
         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
         return cfqq == RQ_CFQQ(rq);
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index d6dfb65c8885..7d4e0356f329 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -42,12 +42,6 @@ struct elevator_ops
         elevator_merged_fn *elevator_merged_fn;
         elevator_merge_req_fn *elevator_merge_req_fn;
         elevator_allow_merge_fn *elevator_allow_merge_fn;
-
-        /*
-         * Used for both plugged list and elevator merging and in the
-         * former case called without queue_lock.  Read comment on top of
-         * attempt_plug_merge() for details.
-         */
         elevator_bio_merged_fn *elevator_bio_merged_fn;
 
         elevator_dispatch_fn *elevator_dispatch_fn;