[PATCH v3 1/2] row: Adding support for reinsert already dispatched req

[Tanya 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>
---
v3: Update error handling when row queue is not set for a request  
v2: Nothing changed. Resend
v1: Initial version

diff --git a/block/row-iosched.c b/block/row-iosched.c
index 1f50180..b3204d6 100644
--- a/block/row-iosched.c
+++ b/block/row-iosched.c
@@ -274,7 +274,39 @@ static void row_add_request(struct request_queue *q,
 	row_log_rowq(rd, rqueue->prio, "added request");
 }
 
-/*
+/**
+ * row_reinsert_req() - Reinsert request back to the scheduler
+ * @q:	requests 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 */
+	if (rqueue->prio >= ROWQ_MAX_PRIO) {
+		pr_err("\n\nROW BUG: row_reinsert_req() rqueue->prio = %d\n",
+			   rqueue->prio);
+		blk_dump_rq_flags(rq, "");
+		return -EIO;
+	}
+
+	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
@@ -664,6 +696,7 @@ 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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