block: Add rdma affinity based queue mapping helper

Like pci and virtio, we add a rdma helper for affinity
spreading. This achieves optimal mq affinity assignments
according to the underlying rdma device affinity maps.

Reviewed-by: Jens Axboe <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Max Gurtovoy <[email protected]>
Signed-off-by: Sagi Grimberg <[email protected]>
Signed-off-by: Doug Ledford <[email protected]>

block/Kconfig

@@ -206,4 +206,9 @@ config BLK_MQ_VIRTIO
  depends on BLOCK && VIRTIO
  default y
 
+config BLK_MQ_RDMA
+ bool
+ depends on BLOCK && INFINIBAND
+ default y
+
 source block/Kconfig.iosched

block/Makefile

@@ -29,6 +29,7 @@ obj-$(CONFIG_BLK_CMDLINE_PARSER) += cmdline-parser.o
 obj-$(CONFIG_BLK_DEV_INTEGRITY) += bio-integrity.o blk-integrity.o t10-pi.o
 obj-$(CONFIG_BLK_MQ_PCI) += blk-mq-pci.o
 obj-$(CONFIG_BLK_MQ_VIRTIO) += blk-mq-virtio.o
+obj-$(CONFIG_BLK_MQ_RDMA) += blk-mq-rdma.o
 obj-$(CONFIG_BLK_DEV_ZONED) += blk-zoned.o
 obj-$(CONFIG_BLK_WBT) += blk-wbt.o
 obj-$(CONFIG_BLK_DEBUG_FS) += blk-mq-debugfs.o

block/blk-mq-rdma.c

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2017 Sagi Grimberg.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ */
+#include <linux/blk-mq.h>
+#include <linux/blk-mq-rdma.h>
+#include <rdma/ib_verbs.h>
+
+/**
+ * blk_mq_rdma_map_queues - provide a default queue mapping for rdma device
+ * @set: tagset to provide the mapping for
+ * @dev: rdma device associated with @set.
+ * @first_vec: first interrupt vectors to use for queues (usually 0)
+ *
+ * This function assumes the rdma device @dev has at least as many available
+ * interrupt vetors as @set has queues. It will then query it's affinity mask
+ * and built queue mapping that maps a queue to the CPUs that have irq affinity
+ * for the corresponding vector.
+ *
+ * In case either the driver passed a @dev with less vectors than
+ * @set->nr_hw_queues, or @dev does not provide an affinity mask for a
+ * vector, we fallback to the naive mapping.
+ */
+int blk_mq_rdma_map_queues(struct blk_mq_tag_set *set,
+ struct ib_device *dev, int first_vec)
+{
+ const struct cpumask *mask;
+ unsigned int queue, cpu;
+
+ for (queue = 0; queue < set->nr_hw_queues; queue++) {
+ mask = ib_get_vector_affinity(dev, first_vec + queue);
+ if (!mask)
+ goto fallback;
+
+ for_each_cpu(cpu, mask)
+ set->mq_map[cpu] = queue;
+ }
+
+ return 0;
+
+fallback:
+ return blk_mq_map_queues(set);
+}
+EXPORT_SYMBOL_GPL(blk_mq_rdma_map_queues);

include/linux/blk-mq-rdma.h

@@ -0,0 +1,10 @@
+#ifndef _LINUX_BLK_MQ_RDMA_H
+#define _LINUX_BLK_MQ_RDMA_H
+
+struct blk_mq_tag_set;
+struct ib_device;
+
+int blk_mq_rdma_map_queues(struct blk_mq_tag_set *set,
+ struct ib_device *dev, int first_vec);
+
+#endif /* _LINUX_BLK_MQ_RDMA_H */