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Subject[PATCH 10/10] blk-mq-sched: allow setting of default IO scheduler
Date
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>
---
block/Kconfig.iosched | 56 +++++++++++++++++++++++++++++++++++++++++++------
block/blk-mq-sched.c | 20 ++++++++++++++++++
block/blk-mq-sched.h | 2 ++
block/blk-mq.c | 8 +++++++
block/elevator.c | 8 ++++++-
drivers/nvme/host/pci.c | 1 +
include/linux/blk-mq.h | 1 +
7 files changed, 89 insertions(+), 7 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
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 44cf30eb1589..26e9e20f67ce 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -332,3 +332,23 @@ int blk_mq_sched_teardown(struct request_queue *q)

return 0;
}
+
+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 68d6a202b827..77859eae19c9 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -25,6 +25,8 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx);
int blk_mq_sched_setup(struct request_queue *q);
int 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 3180b5fac88c..0dcd593e4ddd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2227,6 +2227,14 @@ 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 79e74da26343..b3ea721e51b4 100644
--- 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 19beeb7b2ac2..e1b4e603b1cf 100644
--- 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 63569eb46d15..8e4df3d6c8cd 100644
--- 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,

--
2.7.4
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