blk-mq-sched: check for successful allocation before assigning tag

We don't trigger this from the normal IO path, since we always use
blocking allocations from there. But Bart saw it testing multipath
dm, since that is a heavy user of atomic request allocations in
the map and clone path.

Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 56b92db944aeb722f55db02e0ea74471caef8ec2..4cee060a292dff406d93c724da85a9e07f1a74ec 100644 (file)
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -134,7 +134,8 @@ struct request *blk_mq_sched_get_request(struct request_queue *q,
                        rq = __blk_mq_alloc_request(data, op);
        } else {
                rq = __blk_mq_alloc_request(data, op);
-               data->hctx->tags->rqs[rq->tag] = rq;
+               if (rq)
+                       data->hctx->tags->rqs[rq->tag] = rq;
        }
 
        if (rq) {