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>

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 490ef2850faee1f6682e112a7876c35340794502..0715ce93daef42001407f690912a1b2a437e5a6e 100644 (file)
--- 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

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 26759798a0b392ed778f9148968cc983e2c656fe..d05061f27bb1ffd8e859c5d2354a9f983478abaf 100644 (file)
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -366,3 +366,23 @@ void blk_mq_sched_teardown(struct request_queue *q)
        queue_for_each_hw_ctx(q, hctx, i)
                blk_mq_sched_free_tags(set, hctx, i);
 }
+
+int blk_mq_sched_init(struct request_queue *q)
+{
+       int ret;
+
+#if defined(CONFIG_DEFAULT_SQ_NONE)
+       if (q->nr_hw_queues == 1)
+               return 0;
+#endif
+#if defined(CONFIG_DEFAULT_MQ_NONE)
+       if (q->nr_hw_queues > 1)
+               return 0;
+#endif
+
+       mutex_lock(&q->sysfs_lock);
+       ret = elevator_init(q, NULL);
+       mutex_unlock(&q->sysfs_lock);
+
+       return ret;
+}

diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 35c49e2e008a2d785d5067d007f40e7788888d5b..6b465bc7014c38b1b5d789e1b331125eb7f8d968 100644 (file)
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -28,6 +28,8 @@ void blk_mq_sched_move_to_dispatch(struct blk_mq_hw_ctx *hctx,
 int blk_mq_sched_setup(struct request_queue *q);
 void blk_mq_sched_teardown(struct request_queue *q);
 
+int blk_mq_sched_init(struct request_queue *q);
+
 static inline bool
 blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
 {

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 45e1707a9f8652027eaa59347cb4006df1de5a79..fa1f8619bfe7dbbba9422288d7ddb07011a6e919 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2285,6 +2285,14 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
        mutex_unlock(&all_q_mutex);
        put_online_cpus();
 
+       if (!(set->flags & BLK_MQ_F_NO_SCHED)) {
+               int ret;
+
+               ret = blk_mq_sched_init(q);
+               if (ret)
+                       return ERR_PTR(ret);
+       }
+
        return q;
 
 err_hctxs:

diff --git a/block/elevator.c b/block/elevator.c
index 0e1ccddab8a26db70513b7fa566b1d0f39ff4859..bcba2dd5cb5c0812b76d2aaf2afff48ee0e207e6 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -219,7 +219,13 @@ int elevator_init(struct request_queue *q, char *name)
        }
 
        if (!e) {
-               e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
+               if (q->mq_ops && q->nr_hw_queues == 1)
+                       e = elevator_get(CONFIG_DEFAULT_SQ_IOSCHED, false);
+               else if (q->mq_ops)
+                       e = elevator_get(CONFIG_DEFAULT_MQ_IOSCHED, false);
+               else
+                       e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
+
                if (!e) {
                        printk(KERN_ERR
                                "Default I/O scheduler not found. " \

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 19beeb7b2ac26a5bf0f81bf4e8b995bf29dba195..e1b4e603b1cf7f9ee756344c08c1cf6fece2827e 100644 (file)
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1181,6 +1181,7 @@ static int nvme_alloc_admin_tags(struct nvme_dev *dev)
                dev->admin_tagset.timeout = ADMIN_TIMEOUT;
                dev->admin_tagset.numa_node = dev_to_node(dev->dev);
                dev->admin_tagset.cmd_size = nvme_cmd_size(dev);
+               dev->admin_tagset.flags = BLK_MQ_F_NO_SCHED;
                dev->admin_tagset.driver_data = dev;
 
                if (blk_mq_alloc_tag_set(&dev->admin_tagset))

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 63569eb46d150abb6aa9b4283a1320d2a1b02bf0..8e4df3d6c8cd9dbd1ddd96e25e1abae9a4aa4b6f 100644 (file)
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -153,6 +153,7 @@ enum {
        BLK_MQ_F_SG_MERGE       = 1 << 2,
        BLK_MQ_F_DEFER_ISSUE    = 1 << 4,
        BLK_MQ_F_BLOCKING       = 1 << 5,
+       BLK_MQ_F_NO_SCHED       = 1 << 6,
        BLK_MQ_F_ALLOC_POLICY_START_BIT = 8,
        BLK_MQ_F_ALLOC_POLICY_BITS = 1,