[PATCH v2 3/6] block: Introduce get_current_ioprio()

[Damien Le Moal <damien.lemoal@wdc.com>]

Define get_current_ioprio() as an inline helper to obtain the caller
I/O priority from its task I/O context. Use this helper in
blk_init_request_from_bio() to set a request ioprio.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/blk-core.c       |  6 +-----
 include/linux/ioprio.h | 13 +++++++++++++
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 492648c96992..4450d3c08f25 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -813,18 +813,14 @@ unsigned int blk_plug_queued_count(struct request_queue *q)
 
 void blk_init_request_from_bio(struct request *req, struct bio *bio)
 {
-	struct io_context *ioc = current->io_context;
-
 	if (bio->bi_opf & REQ_RAHEAD)
 		req->cmd_flags |= REQ_FAILFAST_MASK;
 
 	req->__sector = bio->bi_iter.bi_sector;
 	if (ioprio_valid(bio_prio(bio)))
 		req->ioprio = bio_prio(bio);
-	else if (ioc)
-		req->ioprio = ioc->ioprio;
 	else
-		req->ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+		req->ioprio = get_current_ioprio();
 	req->write_hint = bio->bi_write_hint;
 	blk_rq_bio_prep(req->q, req, bio);
 }
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 9e30ed6443db..e9bfe6972aed 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -70,6 +70,19 @@ static inline int task_nice_ioclass(struct task_struct *task)
 		return IOPRIO_CLASS_BE;
 }
 
+/*
+ * If the calling process has set an I/O priority, use that. Otherwise, return
+ * the default I/O priority.
+ */
+static inline int get_current_ioprio(void)
+{
+	struct io_context *ioc = current->io_context;
+
+	if (ioc)
+		return ioc->ioprio;
+	return IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+}
+
 /*
  * For inheritance, return the highest of the two given priorities
  */
-- 
2.19.1