[PATCH] Consolidate SCSI requeueing and add blk elevator hook

This patch removes the scsi mid layer dependency on __elv_add_request
and introduces a new blk_requeue_request() function so the block
layer specificially knows a requeue is in progress.

It also adds an elevator hook for elevators like AS which need to
hook into the requeue for correct adjustment of internal counters.

2 files changed, 31 insertions, 0 deletions

diff --git a/drivers/block/elevator.c b/drivers/block/elevator.c
index 00b56d022b0e..272bcb34195b 100644
--- a/drivers/block/elevator.c
+++ b/drivers/block/elevator.c
@@ -214,6 +214,18 @@ void elv_merge_requests(request_queue_t *q, struct request *rq,
 		e->elevator_merge_req_fn(q, rq, next);
 }
 
+void elv_requeue_request(request_queue_t *q, struct request *rq)
+{
+	/*
+	 * if iosched has an explicit requeue hook, then use that. otherwise
+	 * just put the request at the front of the queue
+	 */
+	if (q->elevator.elevator_requeue_req_fn)
+		q->elevator.elevator_requeue_req_fn(q, rq);
+	else
+		__elv_add_request(q, rq, 0, 0);
+}
+
 void __elv_add_request(request_queue_t *q, struct request *rq, int at_end,
 		       int plug)
 {
@@ -405,6 +417,7 @@ EXPORT_SYMBOL(elevator_noop);
 
 EXPORT_SYMBOL(elv_add_request);
 EXPORT_SYMBOL(__elv_add_request);
+EXPORT_SYMBOL(elv_requeue_request);
 EXPORT_SYMBOL(elv_next_request);
 EXPORT_SYMBOL(elv_remove_request);
 EXPORT_SYMBOL(elv_queue_empty);
diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index 0f11567e5277..db399409909d 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -1355,6 +1355,23 @@ struct request *blk_get_request(request_queue_t *q, int rw, int gfp_mask)
 
 	return rq;
 }
+/**
+ * blk_requeue_request - put a request back on queue
+ * @q:		request queue where request should be inserted
+ * @rq:		request to be inserted
+ *
+ * Description:
+ *    Drivers often keep queueing requests until the hardware cannot accept
+ *    more, when that condition happens we need to put the request back
+ *    on the queue. Must be called with queue lock held.
+ */
+void blk_requeue_request(request_queue_t *q, struct request *rq)
+{
+	if (blk_rq_tagged(rq))
+		blk_queue_end_tag(q, rq);
+
+	elv_requeue_request(q, rq);
+}
 
 /**
  * blk_insert_request - insert a special request in to a request queue
@@ -2339,6 +2356,7 @@ EXPORT_SYMBOL(blk_hw_contig_segment);
 EXPORT_SYMBOL(blk_get_request);
 EXPORT_SYMBOL(blk_put_request);
 EXPORT_SYMBOL(blk_insert_request);
+EXPORT_SYMBOL(blk_requeue_request);
 
 EXPORT_SYMBOL(blk_queue_prep_rq);
 EXPORT_SYMBOL(blk_queue_merge_bvec);