blk-mq: introduce blk_mq_map_hw_queues

blk_mq_pci_map_queues and blk_mq_virtio_map_queues will create a CPU to
hardware queue mapping based on affinity information. These two function
share common code and only differ on how the affinity information is
retrieved. Also, those functions are located in the block subsystem
where it doesn't really fit in. They are virtio and pci subsystem
specific.

Thus introduce provide a generic mapping function which uses the
irq_get_affinity callback from bus_type.

Originally idea from Ming Lei <ming.lei@redhat.com>

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Daniel Wagner <wagi@kernel.org>
Link: https://lore.kernel.org/r/20241202-refactor-blk-affinity-helpers-v6-4-27211e9c2cd5@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 37 insertions, 0 deletions

diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 9638b25fd521..ad8d6a363f24 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -11,6 +11,7 @@
 #include <linux/smp.h>
 #include <linux/cpu.h>
 #include <linux/group_cpus.h>
+#include <linux/device/bus.h>
 
 #include "blk.h"
 #include "blk-mq.h"
@@ -54,3 +55,39 @@ int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)
 
 	return NUMA_NO_NODE;
 }
+
+/**
+ * blk_mq_map_hw_queues - Create CPU to hardware queue mapping
+ * @qmap:	CPU to hardware queue map
+ * @dev:	The device to map queues
+ * @offset:	Queue offset to use for the device
+ *
+ * Create a CPU to hardware queue mapping in @qmap. The struct bus_type
+ * irq_get_affinity callback will be used to retrieve the affinity.
+ */
+void blk_mq_map_hw_queues(struct blk_mq_queue_map *qmap,
+			  struct device *dev, unsigned int offset)
+
+{
+	const struct cpumask *mask;
+	unsigned int queue, cpu;
+
+	if (!dev->bus->irq_get_affinity)
+		goto fallback;
+
+	for (queue = 0; queue < qmap->nr_queues; queue++) {
+		mask = dev->bus->irq_get_affinity(dev, queue + offset);
+		if (!mask)
+			goto fallback;
+
+		for_each_cpu(cpu, mask)
+			qmap->mq_map[cpu] = qmap->queue_offset + queue;
+	}
+
+	return;
+
+fallback:
+	WARN_ON_ONCE(qmap->nr_queues > 1);
+	blk_mq_clear_mq_map(qmap);
+}
+EXPORT_SYMBOL_GPL(blk_mq_map_hw_queues);