[PATCH V3 7/8] nvme: pci: recover controller reliably

[Ming Lei]

During draining IO in resetting controller, error still may happen
and timeout can be triggered, the current implementation can't recover
controller any more for this situation, this patch fixes the issue
by the following approach:

- introduces eh_reset_work, and moves draining IO and updating controller
state into this work function.

- resets controller just after nvme_dev_disable(), then schedule
eh_reset_work for draining IO & updating controller state

- introduce reset lock to sync between the above two parts

- move nvme_start_queues() into the part for resetting controller,
so that timeout even won't quiesce queue any more during draining
IO

Cc: Jianchao Wang <jianchao.w.wang at oracle.com>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Sagi Grimberg <sagi at grimberg.me>
Cc: linux-nvme at lists.infradead.org
Cc: Laurence Oberman <loberman at redhat.com>
Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 drivers/nvme/host/pci.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 16d7507bfd79..64bbccdb5091 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -71,6 +71,7 @@ struct nvme_queue;
 static void nvme_process_cq(struct nvme_queue *nvmeq);
 static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown, bool
 		freeze_queue);
+static int nvme_eh_reset(struct nvme_dev *dev);
 
 /*
  * Represents an NVM Express device.  Each nvme_dev is a PCI function.
@@ -113,6 +114,10 @@ struct nvme_dev {
 	dma_addr_t host_mem_descs_dma;
 	struct nvme_host_mem_buf_desc *host_mem_descs;
 	void **host_mem_desc_bufs;
+
+	/* reset for timeout */
+	struct mutex reset_lock;
+	struct work_struct eh_reset_work;
 };
 
 static int io_queue_depth_set(const char *val, const struct kernel_param *kp)
@@ -1199,7 +1204,7 @@ static enum blk_eh_timer_return nvme_timeout(struct request *req, bool reserved)
 	if (nvme_should_reset(dev, csts)) {
 		nvme_warn_reset(dev, csts);
 		nvme_dev_disable(dev, false, true);
-		nvme_reset_ctrl(&dev->ctrl);
+		nvme_eh_reset(dev);
 		return BLK_EH_HANDLED;
 	}
 
@@ -1242,7 +1247,7 @@ static enum blk_eh_timer_return nvme_timeout(struct request *req, bool reserved)
 			 "I/O %d QID %d timeout, reset controller\n",
 			 req->tag, nvmeq->qid);
 		nvme_dev_disable(dev, false, true);
-		nvme_reset_ctrl(&dev->ctrl);
+		nvme_eh_reset(dev);
 
 		/*
 		 * Mark the request as handled, since the inline shutdown
@@ -2424,6 +2429,10 @@ static int nvme_pre_reset_dev(struct nvme_dev *dev)
 	}
 
 	result = nvme_setup_io_queues(dev);
+	if (result)
+		goto out;
+
+	nvme_start_queues(&dev->ctrl);
  out:
 	return result;
 }
@@ -2432,6 +2441,7 @@ static void nvme_post_reset_dev(struct nvme_dev *dev)
 {
 	enum nvme_ctrl_state new_state = NVME_CTRL_LIVE;
 
+	mutex_lock(&dev->reset_lock);
 	/*
 	 * Keep the controller around but remove all namespaces if we don't have
 	 * any working I/O queue.
@@ -2442,8 +2452,12 @@ static void nvme_post_reset_dev(struct nvme_dev *dev)
 		nvme_remove_namespaces(&dev->ctrl);
 		new_state = NVME_CTRL_ADMIN_ONLY;
 	} else {
-		nvme_start_queues(&dev->ctrl);
+		mutex_unlock(&dev->reset_lock);
+
+		/* error may happen during draining IO again */
 		nvme_wait_freeze(&dev->ctrl);
+
+		mutex_lock(&dev->reset_lock);
 		/* hit this only when allocate tagset fails */
 		if (nvme_dev_add(dev))
 			new_state = NVME_CTRL_ADMIN_ONLY;
@@ -2461,10 +2475,12 @@ static void nvme_post_reset_dev(struct nvme_dev *dev)
 	}
 
 	nvme_start_ctrl(&dev->ctrl);
+	mutex_unlock(&dev->reset_lock);
 	return;
 
  out:
 	nvme_remove_dead_ctrl(dev, 0);
+	mutex_unlock(&dev->reset_lock);
 }
 
 static void nvme_reset_work(struct work_struct *work)
@@ -2485,6 +2501,43 @@ static void nvme_reset_work(struct work_struct *work)
 	nvme_post_reset_dev(dev);
 }
 
+static void nvme_eh_reset_work(struct work_struct *work)
+{
+	struct nvme_dev *dev =
+		container_of(work, struct nvme_dev, eh_reset_work);
+
+	nvme_post_reset_dev(dev);
+}
+
+static int nvme_eh_reset(struct nvme_dev *dev)
+{
+	int ret = -EBUSY;
+
+	mutex_lock(&dev->reset_lock);
+	if (dev->ctrl.state != NVME_CTRL_RESETTING &&
+	    dev->ctrl.state != NVME_CTRL_CONNECTING) {
+	    if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING))
+		goto exit;
+	}
+
+	ret = nvme_pre_reset_dev(dev);
+	if (ret) {
+		dev_warn(dev->ctrl.device,
+			"failed to pre-reset controller: %d\n", ret);
+		nvme_remove_dead_ctrl(dev, ret);
+		goto exit;
+	}
+
+	mutex_unlock(&dev->reset_lock);
+
+	queue_work(nvme_reset_wq, &dev->eh_reset_work);
+
+	return 0;
+ exit:
+	mutex_unlock(&dev->reset_lock);
+	return ret;
+}
+
 static void nvme_remove_dead_ctrl_work(struct work_struct *work)
 {
 	struct nvme_dev *dev = container_of(work, struct nvme_dev, remove_work);
@@ -2606,6 +2659,8 @@ static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (result)
 		goto put_pci;
 
+	mutex_init(&dev->reset_lock);
+	INIT_WORK(&dev->eh_reset_work, nvme_eh_reset_work);
 	INIT_WORK(&dev->ctrl.reset_work, nvme_reset_work);
 	INIT_WORK(&dev->remove_work, nvme_remove_dead_ctrl_work);
 	mutex_init(&dev->shutdown_lock);
-- 
2.9.5