blk-mq: don't dump CPU -> hw queue map on driver load

Now that we are out of initial debug/bringup mode, remove
the verbose dump of the mapping table.

Provide the mapping table in sysfs, under the hardware queue
directory, in the cpu_list file.
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq-cpumap.c

@@ -9,15 +9,6 @@
 #include "blk.h"
 #include "blk-mq.h"
 
-static void show_map(unsigned int *map, unsigned int nr)
-{
-	int i;
-
-	pr_info("blk-mq: CPU -> queue map\n");
-	for_each_online_cpu(i)
-		pr_info("  CPU%2u -> Queue %u\n", i, map[i]);
-}
-
 static int cpu_to_queue_index(unsigned int nr_cpus, unsigned int nr_queues,
 			      const int cpu)
 {
@@ -85,7 +76,6 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
 			map[i] = map[first_sibling];
 	}
 
-	show_map(map, nr_cpus);
 	free_cpumask_var(cpus);
 	return 0;
 }

block/blk-mq-sysfs.c

@@ -244,6 +244,32 @@ static ssize_t blk_mq_hw_sysfs_tags_show(struct blk_mq_hw_ctx *hctx, char *page)
 	return blk_mq_tag_sysfs_show(hctx->tags, page);
 }
 
+static ssize_t blk_mq_hw_sysfs_cpus_show(struct blk_mq_hw_ctx *hctx, char *page)
+{
+	unsigned int i, queue_num, first = 1;
+	ssize_t ret = 0;
+
+	blk_mq_disable_hotplug();
+
+	for_each_online_cpu(i) {
+		queue_num = hctx->queue->mq_map[i];
+		if (queue_num != hctx->queue_num)
+			continue;
+
+		if (first)
+			ret += sprintf(ret + page, "%u", i);
+		else
+			ret += sprintf(ret + page, ", %u", i);
+
+		first = 0;
+	}
+
+	blk_mq_enable_hotplug();
+
+	ret += sprintf(ret + page, "\n");
+	return ret;
+}
+
 static struct blk_mq_ctx_sysfs_entry blk_mq_sysfs_dispatched = {
 	.attr = {.name = "dispatched", .mode = S_IRUGO },
 	.show = blk_mq_sysfs_dispatched_show,
@@ -294,6 +320,10 @@ static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_tags = {
 	.attr = {.name = "tags", .mode = S_IRUGO },
 	.show = blk_mq_hw_sysfs_tags_show,
 };
+static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_cpus = {
+	.attr = {.name = "cpu_list", .mode = S_IRUGO },
+	.show = blk_mq_hw_sysfs_cpus_show,
+};
 
 static struct attribute *default_hw_ctx_attrs[] = {
 	&blk_mq_hw_sysfs_queued.attr,
@@ -302,6 +332,7 @@ static struct attribute *default_hw_ctx_attrs[] = {
 	&blk_mq_hw_sysfs_pending.attr,
 	&blk_mq_hw_sysfs_ipi.attr,
 	&blk_mq_hw_sysfs_tags.attr,
+	&blk_mq_hw_sysfs_cpus.attr,
 	NULL,
 };
 

block/blk-mq.c

@@ -1532,6 +1532,16 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
 	return NOTIFY_OK;
 }
 
+void blk_mq_disable_hotplug(void)
+{
+	mutex_lock(&all_q_mutex);
+}
+
+void blk_mq_enable_hotplug(void)
+{
+	mutex_unlock(&all_q_mutex);
+}
+
 static int __init blk_mq_init(void)
 {
 	blk_mq_cpu_init();

block/blk-mq.h

@@ -40,6 +40,8 @@ void blk_mq_init_cpu_notifier(struct blk_mq_cpu_notifier *notifier,
 void blk_mq_register_cpu_notifier(struct blk_mq_cpu_notifier *notifier);
 void blk_mq_unregister_cpu_notifier(struct blk_mq_cpu_notifier *notifier);
 void blk_mq_cpu_init(void);
+void blk_mq_enable_hotplug(void);
+void blk_mq_disable_hotplug(void);
 
 /*
  * CPU -> queue mappings