4 files changed, 81 insertions, 31 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 8713c2fbc4f6..0ab81a0a7502 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -180,7 +180,7 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
         }
 
         /* stash away the original request */
-        elv_dequeue_request(q, rq);
+        blk_dequeue_request(rq);
         q->orig_bar_rq = rq;
         rq = NULL;
 
@@ -248,7 +248,7 @@ bool blk_do_ordered(struct request_queue *q, struct request **rqp)
                          * Queue ordering not supported.  Terminate
                          * with prejudice.
                          */
-                        elv_dequeue_request(q, rq);
+                        blk_dequeue_request(rq);
                         __blk_end_request_all(rq, -EOPNOTSUPP);
                         *rqp = NULL;
                         return false;
diff --git a/block/blk-core.c b/block/blk-core.c
index 6226a380fb6d..93691d2ac5a0 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -902,6 +902,8 @@ EXPORT_SYMBOL(blk_get_request);
  */
 void blk_requeue_request(struct request_queue *q, struct request *rq)
 {
+        BUG_ON(blk_queued_rq(rq));
+
         blk_delete_timer(rq);
         blk_clear_rq_complete(rq);
         trace_block_rq_requeue(q, rq);
@@ -1610,28 +1612,6 @@ int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
 }
 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
 
-/**
- * blkdev_dequeue_request - dequeue request and start timeout timer
- * @req: request to dequeue
- *
- * Dequeue @req and start timeout timer on it.  This hands off the
- * request to the driver.
- *
- * Block internal functions which don't want to start timer should
- * call elv_dequeue_request().
- */
-void blkdev_dequeue_request(struct request *req)
-{
-        elv_dequeue_request(req->q, req);
-
-        /*
-         * We are now handing the request to the hardware, add the
-         * timeout handler.
-         */
-        blk_add_timer(req);
-}
-EXPORT_SYMBOL(blkdev_dequeue_request);
-
 static void blk_account_io_completion(struct request *req, unsigned int bytes)
 {
         if (blk_do_io_stat(req)) {
@@ -1671,7 +1651,23 @@ static void blk_account_io_done(struct request *req)
         }
 }
 
-struct request *elv_next_request(struct request_queue *q)
+/**
+ * blk_peek_request - peek at the top of a request queue
+ * @q: request queue to peek at
+ *
+ * Description:
+ *     Return the request at the top of @q.  The returned request
+ *     should be started using blk_start_request() before LLD starts
+ *     processing it.
+ *
+ * Return:
+ *     Pointer to the request at the top of @q if available.  Null
+ *     otherwise.
+ *
+ * Context:
+ *     queue_lock must be held.
+ */
+struct request *blk_peek_request(struct request_queue *q)
 {
         struct request *rq;
         int ret;
@@ -1748,10 +1744,12 @@ struct request *elv_next_request(struct request_queue *q)
 
         return rq;
 }
-EXPORT_SYMBOL(elv_next_request);
+EXPORT_SYMBOL(blk_peek_request);
 
-void elv_dequeue_request(struct request_queue *q, struct request *rq)
+void blk_dequeue_request(struct request *rq)
 {
+        struct request_queue *q = rq->q;
+
         BUG_ON(list_empty(&rq->queuelist));
         BUG_ON(ELV_ON_HASH(rq));
 
@@ -1767,6 +1765,58 @@ void elv_dequeue_request(struct request_queue *q, struct request *rq)
 }
 
 /**
+ * blk_start_request - start request processing on the driver
+ * @req: request to dequeue
+ *
+ * Description:
+ *     Dequeue @req and start timeout timer on it.  This hands off the
+ *     request to the driver.
+ *
+ *     Block internal functions which don't want to start timer should
+ *     call blk_dequeue_request().
+ *
+ * Context:
+ *     queue_lock must be held.
+ */
+void blk_start_request(struct request *req)
+{
+        blk_dequeue_request(req);
+
+        /*
+         * We are now handing the request to the hardware, add the
+         * timeout handler.
+         */
+        blk_add_timer(req);
+}
+EXPORT_SYMBOL(blk_start_request);
+
+/**
+ * blk_fetch_request - fetch a request from a request queue
+ * @q: request queue to fetch a request from
+ *
+ * Description:
+ *     Return the request at the top of @q.  The request is started on
+ *     return and LLD can start processing it immediately.
+ *
+ * Return:
+ *     Pointer to the request at the top of @q if available.  Null
+ *     otherwise.
+ *
+ * Context:
+ *     queue_lock must be held.
+ */
+struct request *blk_fetch_request(struct request_queue *q)
+{
+        struct request *rq;
+
+        rq = blk_peek_request(q);
+        if (rq)
+                blk_start_request(rq);
+        return rq;
+}
+EXPORT_SYMBOL(blk_fetch_request);
+
+/**
  * blk_update_request - Special helper function for request stacking drivers
  * @rq:       the request being processed
  * @error:    %0 for success, < %0 for error
@@ -1937,12 +1987,11 @@ static bool blk_update_bidi_request(struct request *rq, int error,
  */
 static void blk_finish_request(struct request *req, int error)
 {
+        BUG_ON(blk_queued_rq(req));
+
         if (blk_rq_tagged(req))
                 blk_queue_end_tag(req->q, req);
 
-        if (blk_queued_rq(req))
-                elv_dequeue_request(req->q, req);
-
         if (unlikely(laptop_mode) && blk_fs_request(req))
                 laptop_io_completion();
 
diff --git a/block/blk-tag.c b/block/blk-tag.c
index 3c518e3303ae..c260f7c30dda 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -374,7 +374,7 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
         rq->cmd_flags |= REQ_QUEUED;
         rq->tag = tag;
         bqt->tag_index[tag] = rq;
-        blkdev_dequeue_request(rq);
+        blk_start_request(rq);
         list_add(&rq->queuelist, &q->tag_busy_list);
         return 0;
 }
diff --git a/block/blk.h b/block/blk.h
index ab54529103c0..9e0042ca9495 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -13,6 +13,7 @@ extern struct kobj_type blk_queue_ktype;
 void init_request_from_bio(struct request *req, struct bio *bio);
 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
                         struct bio *bio);
+void blk_dequeue_request(struct request *rq);
 void __blk_queue_free_tags(struct request_queue *q);
 
 void blk_unplug_work(struct work_struct *work);