blk-mq: skip zero-queue maps in blk_mq_map_swqueue

Ming Lei · axboe · commit e5edd5f298fa · 2018-12-17T11:19:55.000-07:00
From 7e849dd ("nvme-pci: don't share queue maps"), the mapping table won't be initialized actually if map->nr_queues is zero, so we can't use blk_mq_map_queue_type() to retrieve hctx any more. This way still may cause broken mapping, fix it by skipping zero-queues maps in blk_mq_map_swqueue(). Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-mq.c b/block/blk-mq.c
@@ -2438,6 +2438,9 @@ static void blk_mq_map_swqueue(struct request_queue *q)
 
 		ctx = per_cpu_ptr(q->queue_ctx, i);
 		for (j = 0; j < set->nr_maps; j++) {
+			if (!set->map[j].nr_queues)
+				continue;
+
 			hctx = blk_mq_map_queue_type(q, j, i);
 
 			/*
