Merge tag 'block-5.7-2020-05-29' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "Two small fixes:

   - Revert a block change that mixed up the return values for non-mq
     devices

   - NVMe poll race fix"

* tag 'block-5.7-2020-05-29' of git://git.kernel.dk/linux-block:
  Revert "block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ_NOWAIT"
  nvme-pci: avoid race between nvme_reap_pending_cqes() and nvme_poll()

Author: torvalds

block/blk-core.c

@@ -891,14 +891,11 @@ generic_make_request_checks(struct bio *bio)
 	}
 
 	/*
-	 * Non-mq queues do not honor REQ_NOWAIT, so complete a bio
-	 * with BLK_STS_AGAIN status in order to catch -EAGAIN and
-	 * to give a chance to the caller to repeat request gracefully.
+	 * For a REQ_NOWAIT based request, return -EOPNOTSUPP
+	 * if queue is not a request based queue.
 	 */
-	if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q)) {
-		status = BLK_STS_AGAIN;
-		goto end_io;
-	}
+	if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q))
+		goto not_supported;
 
 	if (should_fail_bio(bio))
 		goto end_io;

drivers/nvme/host/pci.c

@@ -1382,16 +1382,19 @@ static void nvme_disable_admin_queue(struct nvme_dev *dev, bool shutdown)
 
 /*
  * Called only on a device that has been disabled and after all other threads
- * that can check this device's completion queues have synced. This is the
- * last chance for the driver to see a natural completion before
- * nvme_cancel_request() terminates all incomplete requests.
+ * that can check this device's completion queues have synced, except
+ * nvme_poll(). This is the last chance for the driver to see a natural
+ * completion before nvme_cancel_request() terminates all incomplete requests.
  */
 static void nvme_reap_pending_cqes(struct nvme_dev *dev)
 {
 	int i;
 
-	for (i = dev->ctrl.queue_count - 1; i > 0; i--)
+	for (i = dev->ctrl.queue_count - 1; i > 0; i--) {
+		spin_lock(&dev->queues[i].cq_poll_lock);
 		nvme_process_cq(&dev->queues[i]);
+		spin_unlock(&dev->queues[i].cq_poll_lock);
+	}
 }
 
 static int nvme_cmb_qdepth(struct nvme_dev *dev, int nr_io_queues,