nvme-multipath: fix lockdep WARN due to partition scan work

Blktests test cases nvme/014, 057 and 058 fail occasionally due to a
lockdep WARN. As reported in the Closes tag URL, the WARN indicates that
a deadlock can happen due to the dependency among disk->open_mutex,
kblockd workqueue completion and partition_scan_work completion.

To avoid the lockdep WARN and the potential deadlock, cut the dependency
by running the partition_scan_work not by kblockd workqueue but by
nvme_wq.

Reported-by: Yi Zhang <[email protected]>
Closes: https://lore.kernel.org/linux-block/CAHj4cs8mJ+R_GmQm9R8ebResKAWUE8kF5+_WVg0v8zndmqd6BQ@mail.gmail.com/
Link: https://lore.kernel.org/linux-block/oeyzci6ffshpukpfqgztsdeke5ost5hzsuz4rrsjfmvpqcevax@5nhnwbkzbrpa/
Fixes: 1f02134 ("nvme-multipath: defer partition scanning")
Signed-off-by: Shin'ichiro Kawasaki <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Keith Busch <[email protected]>

Author: kawasaki

drivers/nvme/host/multipath.c

@@ -793,7 +793,7 @@ static void nvme_mpath_set_live(struct nvme_ns *ns)
 			return;
 		}
 		nvme_add_ns_head_cdev(head);
-		kblockd_schedule_work(&head->partition_scan_work);
+		queue_work(nvme_wq, &head->partition_scan_work);
 	}
 
 	nvme_mpath_add_sysfs_link(ns->head);