blk-mq: fix dereference of rq->mq_ctx if allocation fails

If __GFP_WAIT isn't set and we fail allocating, when we go
to drop the reference on the ctx, we will attempt to dereference
the NULL rq. Fix that.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index cdc629c..70fd6f9 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -202,10 +202,12 @@ static struct request *blk_mq_alloc_request_pinned(struct request_queue *q,
                if (rq) {
                        blk_mq_rq_ctx_init(q, ctx, rq, rw);
                        break;
-               } else if (!(gfp & __GFP_WAIT))
-                       break;
+               }
 
                blk_mq_put_ctx(ctx);
+               if (!(gfp & __GFP_WAIT))
+                       break;
+
                __blk_mq_run_hw_queue(hctx);
                blk_mq_wait_for_tags(hctx->tags);
        } while (1);
@@ -222,7 +224,8 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw,
                return NULL;
 
        rq = blk_mq_alloc_request_pinned(q, rw, gfp, reserved);
-       blk_mq_put_ctx(rq->mq_ctx);
+       if (rq)
+               blk_mq_put_ctx(rq->mq_ctx);
        return rq;
 }
 
@@ -235,7 +238,8 @@ struct request *blk_mq_alloc_reserved_request(struct request_queue *q, int rw,
                return NULL;
 
        rq = blk_mq_alloc_request_pinned(q, rw, gfp, true);
-       blk_mq_put_ctx(rq->mq_ctx);
+       if (rq)
+               blk_mq_put_ctx(rq->mq_ctx);
        return rq;
 }
 EXPORT_SYMBOL(blk_mq_alloc_reserved_request);