block: Add rdma affinity based queue mapping helper

[mirror_ubuntu-bionic-kernel.git] / block / blk-mq-rdma.c

diff --git a/block/blk-mq-rdma.c b/block/blk-mq-rdma.c
new file mode 100644 (file)
index 0000000..996167f
--- /dev/null
+++ b/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);