blk-mq: skip unmapped queues in blk_mq_alloc_request_hctx

This provides the caller a feedback that a given hctx is not mapped and thus
no command can be sent on it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 13f5a6c1de76827c3aa2eaab28061581971e0c5c..c207fa9870ebcaaed6bfb02efa70b5f7333954f8 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -296,17 +296,29 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, int rw,
        if (ret)
                return ERR_PTR(ret);
 
+       /*
+        * Check if the hardware context is actually mapped to anything.
+        * If not tell the caller that it should skip this queue.
+        */
        hctx = q->queue_hw_ctx[hctx_idx];
+       if (!blk_mq_hw_queue_mapped(hctx)) {
+               ret = -EXDEV;
+               goto out_queue_exit;
+       }
        ctx = __blk_mq_get_ctx(q, cpumask_first(hctx->cpumask));
 
        blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx);
        rq = __blk_mq_alloc_request(&alloc_data, rw, 0);
        if (!rq) {
-               blk_queue_exit(q);
-               return ERR_PTR(-EWOULDBLOCK);
+               ret = -EWOULDBLOCK;
+               goto out_queue_exit;
        }
 
        return rq;
+
+out_queue_exit:
+       blk_queue_exit(q);
+       return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);