[PATCH V2 2/5] blk-mq: introduce .complete_queue_affinity

[Ming Lei <ming.lei@redhat.com>]

Some SCSI devices support single hw queue(tags), meantime allow
multiple private complete queues for handling request delivery &
completion. And mapping between CPU and private completion queue is
setup via pci_alloc_irq_vectors_affinity(PCI_IRQ_AFFINITY), just
like normal blk-mq's queue mapping.

Introduce .complete_queue_affinity callback for getting the
complete queue's affinity, so that we can drain in-flight requests
delivered from the complete queue if last CPU of the completion queue
becomes offline.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/blk-mq.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 15d1aa53d96c..56f2e2ed62a7 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -140,7 +140,8 @@ typedef int (poll_fn)(struct blk_mq_hw_ctx *);
 typedef int (map_queues_fn)(struct blk_mq_tag_set *set);
 typedef bool (busy_fn)(struct request_queue *);
 typedef void (complete_fn)(struct request *);
-
+typedef const struct cpumask *(hctx_complete_queue_affinity_fn)(
+		struct blk_mq_hw_ctx *, int);
 
 struct blk_mq_ops {
 	/*
@@ -207,6 +208,15 @@ struct blk_mq_ops {
 
 	map_queues_fn		*map_queues;
 
+	/*
+	 * Some SCSI devices support private complete queue, returns
+	 * affinity of the complete queue, and the passed 'cpu' parameter
+	 * has to be included in the complete queue's affinity cpumask, and
+	 * used to figure out the mapped reply queue. If NULL is returns,
+	 * it means this hctx hasn't private completion queues.
+	 */
+	hctx_complete_queue_affinity_fn *complete_queue_affinity;
+
 #ifdef CONFIG_BLK_DEBUG_FS
 	/*
 	 * Used by the debugfs implementation to show driver-specific
-- 
2.20.1