blk-mq-sched: allow setting of default IO scheduler

Add Kconfig entries to manage what devices get assigned an MQ
scheduler, and add a blk-mq flag for drivers to opt out of scheduling.
The latter is useful for admin type queues that still allocate a blk-mq
queue and tag set, but aren't use for normal IO.

Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>

1 files changed, 50 insertions, 6 deletions

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 490ef2850fae..0715ce93daef 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -32,12 +32,6 @@ config IOSCHED_CFQ
 
           This is the default I/O scheduler.
 
-config MQ_IOSCHED_DEADLINE
-        tristate "MQ deadline I/O scheduler"
-        default y
-        ---help---
-          MQ version of the deadline IO scheduler.
-
 config CFQ_GROUP_IOSCHED
         bool "CFQ Group Scheduling support"
         depends on IOSCHED_CFQ && BLK_CGROUP
@@ -69,6 +63,56 @@ config DEFAULT_IOSCHED
         default "cfq" if DEFAULT_CFQ
         default "noop" if DEFAULT_NOOP
 
+config MQ_IOSCHED_DEADLINE
+        tristate "MQ deadline I/O scheduler"
+        default y
+        ---help---
+          MQ version of the deadline IO scheduler.
+
+config MQ_IOSCHED_NONE
+        bool
+        default y
+
+choice
+        prompt "Default single-queue blk-mq I/O scheduler"
+        default DEFAULT_SQ_NONE
+        help
+          Select the I/O scheduler which will be used by default for blk-mq
+          managed block devices with a single queue.
+
+        config DEFAULT_SQ_DEADLINE
+                bool "MQ Deadline" if MQ_IOSCHED_DEADLINE=y
+
+        config DEFAULT_SQ_NONE
+                bool "None"
+
+endchoice
+
+config DEFAULT_SQ_IOSCHED
+        string
+        default "mq-deadline" if DEFAULT_SQ_DEADLINE
+        default "none" if DEFAULT_SQ_NONE
+
+choice
+        prompt "Default multi-queue blk-mq I/O scheduler"
+        default DEFAULT_MQ_NONE
+        help
+          Select the I/O scheduler which will be used by default for blk-mq
+          managed block devices with multiple queues.
+
+        config DEFAULT_MQ_DEADLINE
+                bool "MQ Deadline" if MQ_IOSCHED_DEADLINE=y
+
+        config DEFAULT_MQ_NONE
+                bool "None"
+
+endchoice
+
+config DEFAULT_MQ_IOSCHED
+        string
+        default "mq-deadline" if DEFAULT_MQ_DEADLINE
+        default "none" if DEFAULT_MQ_NONE
+
 endmenu
 
 endif