[PATCH] nvme: unquiesce the queue before cleaup it

[Jianchao Wang]

There is race between nvme_remove and nvme_reset_work that can
lead to io hang.

nvme_remove                    nvme_reset_work
-> change state to DELETING
                               -> fail to change state to LIVE
                               -> nvme_remove_dead_ctrl
                                 -> nvme_dev_disable
                                   -> quiesce request_queue
                                 -> queue remove_work
-> cancel_work_sync reset_work
-> nvme_remove_namespaces
  -> splice ctrl->namespaces
                               nvme_remove_dead_ctrl_work
                               -> nvme_kill_queues
  -> nvme_ns_remove               do nothing
    -> blk_cleanup_queue
      -> blk_freeze_queue
Finally, the request_queue is quiesced state when wait freeze,
we will get io hang here.

To fix it, unquiesce the request_queue directly before nvme_ns_remove.
We have spliced the ctrl->namespaces, so nobody could access them
and quiesce the queue any more.

Signed-off-by: Jianchao Wang <jianchao.w.wang at oracle.com>
---
 drivers/nvme/host/core.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 9df4f71..0e95082 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3249,8 +3249,15 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
 	list_splice_init(&ctrl->namespaces, &ns_list);
 	up_write(&ctrl->namespaces_rwsem);
 
-	list_for_each_entry_safe(ns, next, &ns_list, list)
+	/*
+	 * After splice the namespaces list from the ctrl->namespaces,
+	 * nobody could get them anymore, let's unquiesce the request_queue
+	 * forcibly to avoid io hang.
+	 */
+	list_for_each_entry_safe(ns, next, &ns_list, list) {
+		blk_mq_unquiesce_queue(ns->queue);
 		nvme_ns_remove(ns);
+	}
 }
 EXPORT_SYMBOL_GPL(nvme_remove_namespaces);
 
-- 
2.7.4