[RFC/PATCH 1/2] row: Adding support for reinsert already dispatched req

[Tatyana Brokhman]

Add support for reinserting already dispatched request back to the
schedulers internal data structures.
The request will be reinserted back to the queue (head) it was
dispatched from as if it was never dispatched.

Signed-off-by: Tatyana Brokhman <tlinder@xxxxxxxxxxxxxx>

---
 block/row-iosched.c |   28 ++++++++++++++++++++++++++++
 1 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/block/row-iosched.c b/block/row-iosched.c
index c99863a..9135416 100644
--- a/block/row-iosched.c
+++ b/block/row-iosched.c
@@ -273,6 +273,33 @@ static void row_add_request(struct request_queue *q,
 }
 
 /*
+ * row_reinsert_req() - Reinsert request back to the scheduler
+ * @q:	dispatch queue
+ * @rq:	request to add
+ *
+ * Reinsert the given request back to the queue it was
+ * dispatched from as if it was never dispatched.
+ *
+ * Returns 0 on success, error code otherwise
+ */
+static int row_reinsert_req(struct request_queue *q,
+			    struct request *rq)
+{
+	struct row_data    *rd = q->elevator->elevator_data;
+	struct row_queue   *rqueue = RQ_ROWQ(rq);
+
+	/* Verify rqueue is legitimate */
+	BUG_ON(rqueue != &rd->row_queues[rqueue->prio].rqueue);
+
+	list_add(&rq->queuelist, &rqueue->fifo);
+	rd->nr_reqs[rq_data_dir(rq)]++;
+
+	row_log_rowq(rd, rqueue->prio, "request reinserted");
+
+	return 0;
+}
+
+/**
  * row_remove_request() -  Remove given request from scheduler
  * @q:	requests queue
  * @rq:	request to remove
@@ -650,6 +677,7 @@ static struct elevator_type iosched_row = {
 		.elevator_merge_req_fn		= row_merged_requests,
 		.elevator_dispatch_fn		= row_dispatch_requests,
 		.elevator_add_req_fn		= row_add_request,
+		.elevator_reinsert_req_fn	= row_reinsert_req,
 		.elevator_former_req_fn		= elv_rb_former_request,
 		.elevator_latter_req_fn		= elv_rb_latter_request,
 		.elevator_set_req_fn		= row_set_request,
-- 
1.7.6
--
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