Date:	Fri, 15 Apr 2016 18:35:49 -0700
From:	Christoph Hellwig <hch@....de>
To:	tglx@...utronix.de, linux-block@...r.kernel.org,
	linux-pci@...r.kernel.org
Cc:	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5/8] blk-mq: allow the driver to pass in an affinity mask

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.

XXX: Just as with the core IRQ spreading code this doesn't handle CPU
hotplug yet.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 block/Makefile         |   2 +-
 block/blk-mq-cpumap.c  | 120 -------------------------------------------------
 block/blk-mq.c         |  60 ++++++++++++++++++++++++-
 block/blk-mq.h         |   8 ----
 include/linux/blk-mq.h |   1 +
 5 files changed, 60 insertions(+), 131 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 1699baf..ab156bb 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>
 
@@ -1954,6 +1955,22 @@ 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)
 {
@@ -2013,6 +2030,30 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 	blk_mq_sysfs_register(q);
 }
 
+static unsigned int *
+affinity_mask_to_queue_map(const struct cpumask *affinity_mask, int node)
+{
+	unsigned int *map;
+	int queue = -1, cpu = 0;
+
+	map = kzalloc_node(sizeof(*map) * nr_cpu_ids, GFP_KERNEL, node);
+	if (!map)
+		return NULL;
+
+	if (!affinity_mask)
+		return map;	/* 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)
+			map[cpu] = queue;
+	}
+
+	return map;
+}
+
 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 						  struct request_queue *q)
 {
@@ -2028,7 +2069,21 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	if (!q->queue_hw_ctx)
 		goto err_percpu;
 
-	q->mq_map = blk_mq_make_queue_map(set);
+	if (set->affinity_mask) {
+		q->mq_map = affinity_mask_to_queue_map(set->affinity_mask,
+				set->numa_node);
+	} else {
+		struct cpumask *affinity_mask;
+		int ret;
+
+		ret = irq_create_affinity_mask(&affinity_mask, set->nr_hw_queues);
+		if (ret)
+			goto err_map;
+
+		q->mq_map = affinity_mask_to_queue_map(affinity_mask, set->numa_node);
+		kfree(affinity_mask);
+	}
+
 	if (!q->mq_map)
 		goto err_map;
 
@@ -2111,7 +2166,8 @@ static void blk_mq_queue_reinit(struct request_queue *q,
 
 	blk_mq_sysfs_unregister(q);
 
-	blk_mq_update_queue_map(q->mq_map, q->nr_hw_queues, online_mask);
+//	XXX: figure out what to do about cpu hotplug in the new world order
+//	blk_mq_update_queue_map(q->mq_map, q->nr_hw_queues, online_mask);
 
 	/*
 	 * redo blk_mq_init_cpu_queues and blk_mq_init_hw_queues. FIXME: maybe
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 2498fdf..21ffe10 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -74,6 +74,7 @@ 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

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