nvme-pci: fix queue_rqs list splitting

If command prep fails, current handling will orphan subsequent requests
in the list. Consider a simple example:

  rqlist = [ 1 -> 2 ]

When prep for request '1' fails, it will be appended to the
'requeue_list', leaving request '2' disconnected from the original
rqlist and no longer tracked. Meanwhile, rqlist is still pointing to the
failed request '1' and will attempt to submit the unprepped command.

Fix this by updating the rqlist accordingly using the request list
helper functions.

Fixes: d62cbcf ("nvme: add support for mq_ops->queue_rqs()")
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220105170518.3181469-5-kbusch@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/pci.c

@@ -999,30 +999,30 @@ static bool nvme_prep_rq_batch(struct nvme_queue *nvmeq, struct request *req)
 
 static void nvme_queue_rqs(struct request **rqlist)
 {
-	struct request *req = rq_list_peek(rqlist), *prev = NULL;
+	struct request *req, *next, *prev = NULL;
 	struct request *requeue_list = NULL;
 
-	do {
+	rq_list_for_each_safe(rqlist, req, next) {
 		struct nvme_queue *nvmeq = req->mq_hctx->driver_data;
 
 		if (!nvme_prep_rq_batch(nvmeq, req)) {
 			/* detach 'req' and add to remainder list */
-			if (prev)
-				prev->rq_next = req->rq_next;
-			rq_list_add(&requeue_list, req);
-		} else {
-			prev = req;
+			rq_list_move(rqlist, &requeue_list, req, prev);
+
+			req = prev;
+			if (!req)
+				continue;
 		}
 
-		req = rq_list_next(req);
-		if (!req || (prev && req->mq_hctx != prev->mq_hctx)) {
+		if (!next || req->mq_hctx != next->mq_hctx) {
 			/* detach rest of list, and submit */
-			if (prev)
-				prev->rq_next = NULL;
+			req->rq_next = NULL;
 			nvme_submit_cmds(nvmeq, rqlist);
-			*rqlist = req;
-		}
-	} while (req);
+			*rqlist = next;
+			prev = NULL;
+		} else
+			prev = req;
+	}
 
 	*rqlist = requeue_list;
 }