[PATCH v2 01/15] block: Make bio_set_ioprio() modify fewer bio->bi_ioprio bits

[Bart Van Assche <bvanassche@acm.org>]

A later patch will store the data lifetime in the bio->bi_ioprio member
before bio_set_ioprio() is called. Make sure that bio_set_ioprio()
doesn't clear more bits than necessary.

Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk-mq.c         |  3 ++-
 include/linux/ioprio.h | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index e2d11183f62e..bc086660ffd3 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2926,7 +2926,8 @@ static void bio_set_ioprio(struct bio *bio)
 {
 	/* Nobody set ioprio so far? Initialize it based on task's nice value */
 	if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) == IOPRIO_CLASS_NONE)
-		bio->bi_ioprio = get_current_ioprio();
+		ioprio_set_class_and_level(&bio->bi_ioprio,
+					   get_current_ioprio());
 	blkcg_set_ioprio(bio);
 }
 
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 7578d4f6a969..f2e768ab4b35 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -71,4 +71,14 @@ static inline int ioprio_check_cap(int ioprio)
 }
 #endif /* CONFIG_BLOCK */
 
+#define IOPRIO_CLASS_LEVEL_MASK ((IOPRIO_CLASS_MASK << IOPRIO_CLASS_SHIFT) | \
+				 (IOPRIO_LEVEL_MASK << 0))
+
+static inline void ioprio_set_class_and_level(u16 *prio, u16 class_level)
+{
+	WARN_ON_ONCE(class_level & ~IOPRIO_CLASS_LEVEL_MASK);
+	*prio &= ~IOPRIO_CLASS_LEVEL_MASK;
+	*prio |= class_level;
+}
+
 #endif