[PATCH 3/3] blk-mq: allow the driver to pass in an affinity mask

[Christoph Hellwig]

Allow drivers to pass in the affinity mask from the generic interrupt
layer, and spread queues based on that.  If the driver doesn't pass in
a mask we will create it using the genirq helper.  As this helper was
modelled after the blk-mq algorithm there should be no change in
behavior.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 block/Makefile         |   2 +-
 block/blk-mq-cpumap.c  | 120 -------------------------------------------------
 block/blk-mq.c         |  68 +++++++++++++++++++++++++---
 block/blk-mq.h         |   8 ----
 include/linux/blk-mq.h |   1 +
 5 files changed, 65 insertions(+), 134 deletions(-)
 delete mode 100644 block/blk-mq-cpumap.c

diff --git a/block/Makefile b/block/Makefile
index 9eda232..aeb318d 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -6,7 +6,7 @@ obj-$(CONFIG_BLOCK) := bio.o elevator.o blk-core.o blk-tag.o blk-sysfs.o \
 			blk-flush.o blk-settings.o blk-ioc.o blk-map.o \
 			blk-exec.o blk-merge.o blk-softirq.o blk-timeout.o \
 			blk-lib.o blk-mq.o blk-mq-tag.o \
-			blk-mq-sysfs.o blk-mq-cpu.o blk-mq-cpumap.o ioctl.o \
+			blk-mq-sysfs.o blk-mq-cpu.o ioctl.o \
 			genhd.o scsi_ioctl.o partition-generic.o ioprio.o \
 			badblocks.o partitions/
 
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
deleted file mode 100644
index d0634bc..0000000
--- a/block/blk-mq-cpumap.c
+++ /dev/null
@@ -1,120 +0,0 @@
-/*
- * CPU <-> hardware queue mapping helpers
- *
- * Copyright (C) 2013-2014 Jens Axboe
- */
-#include <linux/kernel.h>
-#include <linux/threads.h>
-#include <linux/module.h>
-#include <linux/mm.h>
-#include <linux/smp.h>
-#include <linux/cpu.h>
-
-#include <linux/blk-mq.h>
-#include "blk.h"
-#include "blk-mq.h"
-
-static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
-			      const int cpu)
-{
-	return cpu * nr_queues / nr_cpus;
-}
-
-static int get_first_sibling(unsigned int cpu)
-{
-	unsigned int ret;
-
-	ret = cpumask_first(topology_sibling_cpumask(cpu));
-	if (ret < nr_cpu_ids)
-		return ret;
-
-	return cpu;
-}
-
-int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
-			    const struct cpumask *online_mask)
-{
-	unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
-	cpumask_var_t cpus;
-
-	if (!alloc_cpumask_var(&cpus, GFP_ATOMIC))
-		return 1;
-
-	cpumask_clear(cpus);
-	nr_cpus = nr_uniq_cpus = 0;
-	for_each_cpu(i, online_mask) {
-		nr_cpus++;
-		first_sibling = get_first_sibling(i);
-		if (!cpumask_test_cpu(first_sibling, cpus))
-			nr_uniq_cpus++;
-		cpumask_set_cpu(i, cpus);
-	}
-
-	queue = 0;
-	for_each_possible_cpu(i) {
-		if (!cpumask_test_cpu(i, online_mask)) {
-			map[i] = 0;
-			continue;
-		}
-
-		/*
-		 * Easy case - we have equal or more hardware queues. Or
-		 * there are no thread siblings to take into account. Do
-		 * 1:1 if enough, or sequential mapping if less.
-		 */
-		if (nr_queues >= nr_cpus || nr_cpus == nr_uniq_cpus) {
-			map[i] = cpu_to_queue_index(nr_cpus, nr_queues, queue);
-			queue++;
-			continue;
-		}
-
-		/*
-		 * Less then nr_cpus queues, and we have some number of
-		 * threads per cores. Map sibling threads to the same
-		 * queue.
-		 */
-		first_sibling = get_first_sibling(i);
-		if (first_sibling == i) {
-			map[i] = cpu_to_queue_index(nr_uniq_cpus, nr_queues,
-							queue);
-			queue++;
-		} else
-			map[i] = map[first_sibling];
-	}
-
-	free_cpumask_var(cpus);
-	return 0;
-}
-
-unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set)
-{
-	unsigned int *map;
-
-	/* If cpus are offline, map them to first hctx */
-	map = kzalloc_node(sizeof(*map) * nr_cpu_ids, GFP_KERNEL,
-				set->numa_node);
-	if (!map)
-		return NULL;
-
-	if (!blk_mq_update_queue_map(map, set->nr_hw_queues, cpu_online_mask))
-		return map;
-
-	kfree(map);
-	return NULL;
-}
-
-/*
- * We have no quick way of doing reverse lookups. This is only used at
- * queue init time, so runtime isn't important.
- */
-int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
-{
-	int i;
-
-	for_each_possible_cpu(i) {
-		if (index == mq_map[i])
-			return local_memory_node(cpu_to_node(i));
-	}
-
-	return NUMA_NO_NODE;
-}
diff --git a/block/blk-mq.c b/block/blk-mq.c
index c4adaa2..1053b7b 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -22,6 +22,7 @@
 #include <linux/sched/sysctl.h>
 #include <linux/delay.h>
 #include <linux/crash_dump.h>
+#include <linux/interrupt.h>
 
 #include <trace/events/block.h>
 
@@ -1996,6 +1997,22 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 }
 EXPORT_SYMBOL(blk_mq_init_queue);
 
+/*
+ * We have no quick way of doing reverse lookups. This is only used at
+ * queue init time, so runtime isn't important.
+ */
+static int blk_mq_hw_queue_to_node(unsigned int *mq_map, unsigned int index)
+{
+	int i;
+
+	for_each_possible_cpu(i) {
+		if (index == mq_map[i])
+			return local_memory_node(cpu_to_node(i));
+	}
+
+	return NUMA_NO_NODE;
+}
+
 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 						struct request_queue *q)
 {
@@ -2295,6 +2312,30 @@ struct cpumask *blk_mq_tags_cpumask(struct blk_mq_tags *tags)
 }
 EXPORT_SYMBOL_GPL(blk_mq_tags_cpumask);
 
+static int blk_mq_create_mq_map(struct blk_mq_tag_set *set,
+		const struct cpumask *affinity_mask)
+{
+	int queue = -1, cpu = 0;
+
+	set->mq_map = kzalloc_node(sizeof(*set->mq_map) * nr_cpu_ids,
+			GFP_KERNEL, set->numa_node);
+	if (!set->mq_map)
+		return -ENOMEM;
+
+	if (!affinity_mask)
+		return 0;	/* map all cpus to queue 0 */
+
+	/* If cpus are offline, map them to first hctx */
+	for_each_online_cpu(cpu) {
+		if (cpumask_test_cpu(cpu, affinity_mask))
+			queue++;
+		if (queue >= 0)
+			set->mq_map[cpu] = queue;
+	}
+
+	return 0;
+}
+
 /*
  * Alloc a tag set to be associated with one or more request queues.
  * May fail with EINVAL for various error conditions. May adjust the
@@ -2303,6 +2344,8 @@ EXPORT_SYMBOL_GPL(blk_mq_tags_cpumask);
  */
 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 {
+	int ret;
+
 	BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
 
 	if (!set->nr_hw_queues)
@@ -2341,11 +2384,26 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 	if (!set->tags)
 		return -ENOMEM;
 
-	set->mq_map = blk_mq_make_queue_map(set);
-	if (!set->mq_map)
-		goto out_free_tags;
+	/*
+	 * Use the passed in affinity mask if the driver provided one.
+	 */
+	if (set->affinity_mask) {
+		ret = blk_mq_create_mq_map(set, set->affinity_mask);
+		if (!set->mq_map)
+			goto out_free_tags;
+	} else {
+		struct cpumask *affinity_mask;
+
+		affinity_mask = irq_create_affinity_mask(&set->nr_hw_queues);
+		ret = blk_mq_create_mq_map(set, affinity_mask);
+		kfree(affinity_mask);
+
+		if (!set->mq_map)
+			goto out_free_tags;
+	}
 
-	if (blk_mq_alloc_rq_maps(set))
+	ret = blk_mq_alloc_rq_maps(set);
+	if (ret)
 		goto out_free_mq_map;
 
 	mutex_init(&set->tag_list_lock);
@@ -2359,7 +2417,7 @@ out_free_mq_map:
 out_free_tags:
 	kfree(set->tags);
 	set->tags = NULL;
-	return -ENOMEM;
+	return ret;
 }
 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
 
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 9087b11..fe7e21f 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -45,14 +45,6 @@ void blk_mq_enable_hotplug(void);
 void blk_mq_disable_hotplug(void);
 
 /*
- * CPU -> queue mappings
- */
-extern unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set);
-extern int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
-				   const struct cpumask *online_mask);
-extern int blk_mq_hw_queue_to_node(unsigned int *map, unsigned int);
-
-/*
  * sysfs helpers
  */
 extern int blk_mq_sysfs_register(struct request_queue *q);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a572227..0809966 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -75,6 +75,7 @@ struct blk_mq_tag_set {
 	unsigned int		timeout;
 	unsigned int		flags;		/* BLK_MQ_F_* */
 	void			*driver_data;
+	struct cpumask		*affinity_mask;
 
 	struct blk_mq_tags	**tags;
 
-- 
2.1.4