[PATCH v4 1/4] block: Add iocontext priority to request

[Adam Manzanares <adam.manzanares@hgst.com>]

Patch adds an association between iocontext ioprio and the ioprio of a
request. This value is set in blk_rq_set_prio which takes the request and
the ioc as arguments. If the ioc is valid in blk_rq_set_prio then the
iopriority of the request is set as the iopriority of the ioc. In
init_request_from_bio a check is made to see if the ioprio of the bio is
valid and if so then the request prio comes from the bio.

Signed-off-by: Adam Manzananares <adam.manzanares@wdc.com>
---
 block/blk-core.c       |  4 +++-
 include/linux/blkdev.h | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 14d7c07..361b1b9 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1153,6 +1153,7 @@ static struct request *__get_request(struct request_list *rl, int op,
 
 	blk_rq_init(q, rq);
 	blk_rq_set_rl(rq, rl);
+	blk_rq_set_prio(rq, ioc);
 	req_set_op_attrs(rq, op, op_flags | REQ_ALLOCED);
 
 	/* init elvpriv */
@@ -1656,7 +1657,8 @@ void init_request_from_bio(struct request *req, struct bio *bio)
 
 	req->errors = 0;
 	req->__sector = bio->bi_iter.bi_sector;
-	req->ioprio = bio_prio(bio);
+	if (ioprio_valid(bio_prio(bio)))
+		req->ioprio = bio_prio(bio);
 	blk_rq_bio_prep(req->q, req, bio);
 }
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c47c358..9a0ceaa 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -934,6 +934,20 @@ static inline unsigned int blk_rq_count_bios(struct request *rq)
 }
 
 /*
+ * blk_rq_set_prio - associate a request with prio from ioc
+ * @rq: request of interest
+ * @ioc: target iocontext
+ *
+ * Assocate request prio with ioc prio so request based drivers
+ * can leverage priority information.
+ */
+static inline void blk_rq_set_prio(struct request *rq, struct io_context *ioc)
+{
+	if (ioc)
+		rq->ioprio = ioc->ioprio;
+}
+
+/*
  * Request issue related functions.
  */
 extern struct request *blk_peek_request(struct request_queue *q);
-- 
2.1.4

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