From: Ming Lei <ming.lei@redhat.com>
Date: Sat, 15 Apr 2017 12:38:22 +0000 (+0800)
Subject: block: respect BLK_MQ_F_NO_SCHED
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3a5088c8c11ac9d56f7e90acaaae9e0e98c1ff94;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

block: respect BLK_MQ_F_NO_SCHED

If one driver claims that it doesn't support io scheduler via
BLK_MQ_F_NO_SCHED, we should not allow to change and show the
availabe io schedulers.

This patch adds check to enhance this behaviour.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/block/elevator.c b/block/elevator.c
index dbeecf7be719..4d9084a14c10 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -1098,12 +1098,20 @@ int elevator_change(struct request_queue *q, const char *name)
 }
 EXPORT_SYMBOL(elevator_change);
 
+static inline bool elv_support_iosched(struct request_queue *q)
+{
+	if (q->mq_ops && q->tag_set && (q->tag_set->flags &
+				BLK_MQ_F_NO_SCHED))
+		return false;
+	return true;
+}
+
 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
 			  size_t count)
 {
 	int ret;
 
-	if (!(q->mq_ops || q->request_fn))
+	if (!(q->mq_ops || q->request_fn) || !elv_support_iosched(q))
 		return count;
 
 	ret = __elevator_change(q, name);
@@ -1135,7 +1143,7 @@ ssize_t elv_iosched_show(struct request_queue *q, char *name)
 			len += sprintf(name+len, "[%s] ", elv->elevator_name);
 			continue;
 		}
-		if (__e->uses_mq && q->mq_ops)
+		if (__e->uses_mq && q->mq_ops && elv_support_iosched(q))
 			len += sprintf(name+len, "%s ", __e->elevator_name);
 		else if (!__e->uses_mq && !q->mq_ops)
 			len += sprintf(name+len, "%s ", __e->elevator_name);