[PATCHv3 1/9] nvme: Sync request queues on reset

[keith.busch@intel.com (Keith Busch)]

This patch fixes races that occur with simultaneous controller
resets by synchronizing request queues prior to initializing the
controller. Without this, a timeout thread may attempt disabling a
controller at the same time as we're trying to enable it.

Signed-off-by: Keith Busch <keith.busch at intel.com>
---
 drivers/nvme/host/core.c | 21 +++++++++++++++++++--
 drivers/nvme/host/nvme.h |  1 +
 drivers/nvme/host/pci.c  | 11 +++++++----
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index dc8aa2c1c22a..33034e469bbc 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3469,6 +3469,12 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
 }
 EXPORT_SYMBOL_GPL(nvme_init_ctrl);
 
+static void nvme_start_queue(struct nvme_ns *ns)
+{
+	blk_mq_unquiesce_queue(ns->queue);
+	blk_mq_kick_requeue_list(ns->queue);
+}
+
 /**
  * nvme_kill_queues(): Ends all namespace queues
  * @ctrl: the dead controller that needs to end
@@ -3497,7 +3503,7 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 		blk_set_queue_dying(ns->queue);
 
 		/* Forcibly unquiesce queues to avoid blocking dispatch */
-		blk_mq_unquiesce_queue(ns->queue);
+		nvme_start_queue(ns);
 	}
 	up_read(&ctrl->namespaces_rwsem);
 }
@@ -3567,11 +3573,22 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
 
 	down_read(&ctrl->namespaces_rwsem);
 	list_for_each_entry(ns, &ctrl->namespaces, list)
-		blk_mq_unquiesce_queue(ns->queue);
+		nvme_start_queue(ns);
 	up_read(&ctrl->namespaces_rwsem);
 }
 EXPORT_SYMBOL_GPL(nvme_start_queues);
 
+void nvme_sync_queues(struct nvme_ctrl *ctrl)
+{
+	struct nvme_ns *ns;
+
+	down_read(&ctrl->namespaces_rwsem);
+	list_for_each_entry(ns, &ctrl->namespaces, list)
+		blk_sync_queue(ns->queue);
+	up_read(&ctrl->namespaces_rwsem);
+}
+EXPORT_SYMBOL_GPL(nvme_sync_queues);
+
 int nvme_reinit_tagset(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set)
 {
 	if (!ctrl->ops->reinit_request)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index ec6e4acc4d48..4f43918cd902 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -403,6 +403,7 @@ int nvme_sec_submit(void *data, u16 spsp, u8 secp, void *buffer, size_t len,
 void nvme_complete_async_event(struct nvme_ctrl *ctrl, __le16 status,
 		volatile union nvme_result *res);
 
+void nvme_sync_queues(struct nvme_ctrl *ctrl);
 void nvme_stop_queues(struct nvme_ctrl *ctrl);
 void nvme_start_queues(struct nvme_ctrl *ctrl);
 void nvme_kill_queues(struct nvme_ctrl *ctrl);
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 917e1714f7d9..9da28e10d942 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2317,11 +2317,14 @@ static void nvme_reset_work(struct work_struct *work)
 		goto out;
 
 	/*
-	 * If we're called to reset a live controller first shut it down before
-	 * moving on.
+	 * Ensure there are no timeout work in progress prior to forcefully
+	 * disabling the queue. There is no harm in disabling the device even
+	 * when it was already disabled, as this will forcefully reclaim any
+	 * IOs that are stuck due to blk-mq's timeout handling that prevents
+	 * timed out requests from completing.
 	 */
-	if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
-		nvme_dev_disable(dev, false);
+	nvme_sync_queues(&dev->ctrl);
+	nvme_dev_disable(dev, false);
 
 	/*
 	 * Introduce CONNECTING state from nvme-fc/rdma transports to mark the
-- 
2.14.3