1 files changed, 96 insertions, 0 deletions
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
new file mode 100644
index 000000000..3db84d319
--- /dev/null
+++ b/block/blk-mq-cpumap.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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 queue_index(struct blk_mq_queue_map *qmap,
+		       unsigned int nr_queues, const int q)
+{
+	return qmap->queue_offset + (q % nr_queues);
+}
+
+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_map_queues(struct blk_mq_queue_map *qmap)
+{
+	unsigned int *map = qmap->mq_map;
+	unsigned int nr_queues = qmap->nr_queues;
+	unsigned int cpu, first_sibling, q = 0;
+
+	for_each_possible_cpu(cpu)
+		map[cpu] = -1;
+
+	/*
+	 * Spread queues among present CPUs first for minimizing
+	 * count of dead queues which are mapped by all un-present CPUs
+	 */
+	for_each_present_cpu(cpu) {
+		if (q >= nr_queues)
+			break;
+		map[cpu] = queue_index(qmap, nr_queues, q++);
+	}
+
+	for_each_possible_cpu(cpu) {
+		if (map[cpu] != -1)
+			continue;
+		/*
+		 * First do sequential mapping between CPUs and queues.
+		 * In case we still have CPUs to map, and we have some number of
+		 * threads per cores then map sibling threads to the same queue
+		 * for performance optimizations.
+		 */
+		if (q < nr_queues) {
+			map[cpu] = queue_index(qmap, nr_queues, q++);
+		} else {
+			first_sibling = get_first_sibling(cpu);
+			if (first_sibling == cpu)
+				map[cpu] = queue_index(qmap, nr_queues, q++);
+			else
+				map[cpu] = map[first_sibling];
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(blk_mq_map_queues);
+
+/**
+ * blk_mq_hw_queue_to_node - Look up the memory node for a hardware queue index
+ * @qmap: CPU to hardware queue map.
+ * @index: hardware queue index.
+ *
+ * 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(struct blk_mq_queue_map *qmap, unsigned int index)
+{
+	int i;
+
+	for_each_possible_cpu(i) {
+		if (index == qmap->mq_map[i])
+			return cpu_to_node(i);
+	}
+
+	return NUMA_NO_NODE;
+}