block: ensure cached plug request matches the current queue

If we're driving multiple devices, we could have pre-populated the cache
for a different device. Ensure that the empty request matches the current
queue.

Fixes: 47c122e35d7e ("block: pre-allocate requests if plug is started and is a batch")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5fe40c8..bbe1fb2 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2540,7 +2540,7 @@ static inline struct request *blk_mq_get_request(struct request_queue *q,
                struct request *rq;
 
                rq = rq_list_peek(&plug->cached_rq);
-               if (rq) {
+               if (rq && rq->q == q) {
                        if (unlikely(!submit_bio_checks(bio)))
                                return NULL;
                        if (blk_attempt_bio_merge(q, bio, nsegs, same_queue_rq))