NVMe: Async IO queue deletion

This attempts to delete all IO queues at the same time asynchronously on
shutdown. This is necessary for a present device that is not responding;
a shutdown operation previously would take 2 minutes per queue-pair
to timeout before moving on to the next queue, making a device removal
appear to take a very long time or "hung" as reported by users.

In the previous worst case, a removal may be stuck forever until a kill
signal is given if there are more than 32 queue pairs since it would run
out of admin command IDs after over an hour of timed out sync commands
(admin queue depth is 64).

This patch will wait for the admin command timeout for all commands to
complete, so the worst case now for an unresponsive controller is 60
seconds, though that still seems like a long time.

Since this adds another way to take queues offline, some duplicate code
resulted so I moved these into more convienient functions.
Signed-off-by: Keith Busch <keith.busch@intel.com>
[make functions static, correct line length and whitespace issues]
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

drivers/block/nvme-core.c

@@ -62,6 +62,14 @@ static struct workqueue_struct *nvme_workq;
 
 static void nvme_reset_failed_dev(struct work_struct *ws);
 
+struct async_cmd_info {
+	struct kthread_work work;
+	struct kthread_worker *worker;
+	u32 result;
+	int status;
+	void *ctx;
+};
+
 /*
  * An NVM Express queue.  Each device has at least two (one for admin
  * commands and one for I/O commands).
@@ -87,6 +95,7 @@ struct nvme_queue {
 	u8 cq_phase;
 	u8 cqe_seen;
 	u8 q_suspended;
+	struct async_cmd_info cmdinfo;
 	unsigned long cmdid_data[];
 };
 
@@ -208,6 +217,15 @@ static void special_completion(struct nvme_dev *dev, void *ctx,
 	dev_warn(&dev->pci_dev->dev, "Unknown special completion %p\n", ctx);
 }
 
+static void async_completion(struct nvme_dev *dev, void *ctx,
+						struct nvme_completion *cqe)
+{
+	struct async_cmd_info *cmdinfo = ctx;
+	cmdinfo->result = le32_to_cpup(&cqe->result);
+	cmdinfo->status = le16_to_cpup(&cqe->status) >> 1;
+	queue_kthread_work(cmdinfo->worker, &cmdinfo->work);
+}
+
 /*
  * Called with local interrupts disabled and the q_lock held.  May not sleep.
  */
@@ -898,12 +916,34 @@ int nvme_submit_sync_cmd(struct nvme_queue *nvmeq, struct nvme_command *cmd,
 	return cmdinfo.status;
 }
 
+static int nvme_submit_async_cmd(struct nvme_queue *nvmeq,
+			struct nvme_command *cmd,
+			struct async_cmd_info *cmdinfo, unsigned timeout)
+{
+	int cmdid;
+
+	cmdid = alloc_cmdid_killable(nvmeq, cmdinfo, async_completion, timeout);
+	if (cmdid < 0)
+		return cmdid;
+	cmdinfo->status = -EINTR;
+	cmd->common.command_id = cmdid;
+	nvme_submit_cmd(nvmeq, cmd);
+	return 0;
+}
+
 int nvme_submit_admin_cmd(struct nvme_dev *dev, struct nvme_command *cmd,
 								u32 *result)
 {
 	return nvme_submit_sync_cmd(dev->queues[0], cmd, result, ADMIN_TIMEOUT);
 }
 
+static int nvme_submit_admin_cmd_async(struct nvme_dev *dev,
+		struct nvme_command *cmd, struct async_cmd_info *cmdinfo)
+{
+	return nvme_submit_async_cmd(dev->queues[0], cmd, cmdinfo,
+								ADMIN_TIMEOUT);
+}
+
 static int adapter_delete_queue(struct nvme_dev *dev, u8 opcode, u16 id)
 {
 	int status;
@@ -1124,15 +1164,20 @@ static void nvme_free_queues(struct nvme_dev *dev)
 	}
 }
 
-static void nvme_disable_queue(struct nvme_dev *dev, int qid)
+/**
+ * nvme_suspend_queue - put queue into suspended state
+ * @nvmeq - queue to suspend
+ *
+ * Returns 1 if already suspended, 0 otherwise.
+ */
+static int nvme_suspend_queue(struct nvme_queue *nvmeq)
 {
-	struct nvme_queue *nvmeq = dev->queues[qid];
-	int vector = dev->entry[nvmeq->cq_vector].vector;
+	int vector = nvmeq->dev->entry[nvmeq->cq_vector].vector;
 
 	spin_lock_irq(&nvmeq->q_lock);
 	if (nvmeq->q_suspended) {
 		spin_unlock_irq(&nvmeq->q_lock);
-		return;
+		return 1;
 	}
 	nvmeq->q_suspended = 1;
 	spin_unlock_irq(&nvmeq->q_lock);
@@ -1140,17 +1185,33 @@ static void nvme_disable_queue(struct nvme_dev *dev, int qid)
 	irq_set_affinity_hint(vector, NULL);
 	free_irq(vector, nvmeq);
 
+	return 0;
+}
+
+static void nvme_clear_queue(struct nvme_queue *nvmeq)
+{
+	spin_lock_irq(&nvmeq->q_lock);
+	nvme_process_cq(nvmeq);
+	nvme_cancel_ios(nvmeq, false);
+	spin_unlock_irq(&nvmeq->q_lock);
+}
+
+static void nvme_disable_queue(struct nvme_dev *dev, int qid)
+{
+	struct nvme_queue *nvmeq = dev->queues[qid];
+
+	if (!nvmeq)
+		return;
+	if (nvme_suspend_queue(nvmeq))
+		return;
+
 	/* Don't tell the adapter to delete the admin queue.
 	 * Don't tell a removed adapter to delete IO queues. */
 	if (qid && readl(&dev->bar->csts) != -1) {
 		adapter_delete_sq(dev, qid);
 		adapter_delete_cq(dev, qid);
 	}
-
-	spin_lock_irq(&nvmeq->q_lock);
-	nvme_process_cq(nvmeq);
-	nvme_cancel_ios(nvmeq, false);
-	spin_unlock_irq(&nvmeq->q_lock);
+	nvme_clear_queue(nvmeq);
 }
 
 static struct nvme_queue *nvme_alloc_queue(struct nvme_dev *dev, int qid,
@@ -2089,20 +2150,164 @@ static void nvme_dev_unmap(struct nvme_dev *dev)
 		pci_disable_device(dev->pci_dev);
 }
 
+struct nvme_delq_ctx {
+	struct task_struct *waiter;
+	struct kthread_worker *worker;
+	atomic_t refcount;
+};
+
+static void nvme_wait_dq(struct nvme_delq_ctx *dq, struct nvme_dev *dev)
+{
+	dq->waiter = current;
+	mb();
+
+	for (;;) {
+		set_current_state(TASK_KILLABLE);
+		if (!atomic_read(&dq->refcount))
+			break;
+		if (!schedule_timeout(ADMIN_TIMEOUT) ||
+					fatal_signal_pending(current)) {
+			set_current_state(TASK_RUNNING);
+
+			nvme_disable_ctrl(dev, readq(&dev->bar->cap));
+			nvme_disable_queue(dev, 0);
+
+			send_sig(SIGKILL, dq->worker->task, 1);
+			flush_kthread_worker(dq->worker);
+			return;
+		}
+	}
+	set_current_state(TASK_RUNNING);
+}
+
+static void nvme_put_dq(struct nvme_delq_ctx *dq)
+{
+	atomic_dec(&dq->refcount);
+	if (dq->waiter)
+		wake_up_process(dq->waiter);
+}
+
+static struct nvme_delq_ctx *nvme_get_dq(struct nvme_delq_ctx *dq)
+{
+	atomic_inc(&dq->refcount);
+	return dq;
+}
+
+static void nvme_del_queue_end(struct nvme_queue *nvmeq)
+{
+	struct nvme_delq_ctx *dq = nvmeq->cmdinfo.ctx;
+
+	nvme_clear_queue(nvmeq);
+	nvme_put_dq(dq);
+}
+
+static int adapter_async_del_queue(struct nvme_queue *nvmeq, u8 opcode,
+						kthread_work_func_t fn)
+{
+	struct nvme_command c;
+
+	memset(&c, 0, sizeof(c));
+	c.delete_queue.opcode = opcode;
+	c.delete_queue.qid = cpu_to_le16(nvmeq->qid);
+
+	init_kthread_work(&nvmeq->cmdinfo.work, fn);
+	return nvme_submit_admin_cmd_async(nvmeq->dev, &c, &nvmeq->cmdinfo);
+}
+
+static void nvme_del_cq_work_handler(struct kthread_work *work)
+{
+	struct nvme_queue *nvmeq = container_of(work, struct nvme_queue,
+							cmdinfo.work);
+	nvme_del_queue_end(nvmeq);
+}
+
+static int nvme_delete_cq(struct nvme_queue *nvmeq)
+{
+	return adapter_async_del_queue(nvmeq, nvme_admin_delete_cq,
+						nvme_del_cq_work_handler);
+}
+
+static void nvme_del_sq_work_handler(struct kthread_work *work)
+{
+	struct nvme_queue *nvmeq = container_of(work, struct nvme_queue,
+							cmdinfo.work);
+	int status = nvmeq->cmdinfo.status;
+
+	if (!status)
+		status = nvme_delete_cq(nvmeq);
+	if (status)
+		nvme_del_queue_end(nvmeq);
+}
+
+static int nvme_delete_sq(struct nvme_queue *nvmeq)
+{
+	return adapter_async_del_queue(nvmeq, nvme_admin_delete_sq,
+						nvme_del_sq_work_handler);
+}
+
+static void nvme_del_queue_start(struct kthread_work *work)
+{
+	struct nvme_queue *nvmeq = container_of(work, struct nvme_queue,
+							cmdinfo.work);
+	allow_signal(SIGKILL);
+	if (nvme_delete_sq(nvmeq))
+		nvme_del_queue_end(nvmeq);
+}
+
+static void nvme_disable_io_queues(struct nvme_dev *dev)
+{
+	int i;
+	DEFINE_KTHREAD_WORKER_ONSTACK(worker);
+	struct nvme_delq_ctx dq;
+	struct task_struct *kworker_task = kthread_run(kthread_worker_fn,
+					&worker, "nvme%d", dev->instance);
+
+	if (IS_ERR(kworker_task)) {
+		dev_err(&dev->pci_dev->dev,
+			"Failed to create queue del task\n");
+		for (i = dev->queue_count - 1; i > 0; i--)
+			nvme_disable_queue(dev, i);
+		return;
+	}
+
+	dq.waiter = NULL;
+	atomic_set(&dq.refcount, 0);
+	dq.worker = &worker;
+	for (i = dev->queue_count - 1; i > 0; i--) {
+		struct nvme_queue *nvmeq = dev->queues[i];
+
+		if (nvme_suspend_queue(nvmeq))
+			continue;
+		nvmeq->cmdinfo.ctx = nvme_get_dq(&dq);
+		nvmeq->cmdinfo.worker = dq.worker;
+		init_kthread_work(&nvmeq->cmdinfo.work, nvme_del_queue_start);
+		queue_kthread_work(dq.worker, &nvmeq->cmdinfo.work);
+	}
+	nvme_wait_dq(&dq, dev);
+	kthread_stop(kworker_task);
+}
+
 static void nvme_dev_shutdown(struct nvme_dev *dev)
 {
 	int i;
 
 	dev->initialized = 0;
-	for (i = dev->queue_count - 1; i >= 0; i--)
-		nvme_disable_queue(dev, i);
 
 	spin_lock(&dev_list_lock);
 	list_del_init(&dev->node);
 	spin_unlock(&dev_list_lock);
 
-	if (dev->bar)
+	if (!dev->bar || (dev->bar && readl(&dev->bar->csts) == -1)) {
+		for (i = dev->queue_count - 1; i >= 0; i--) {
+			struct nvme_queue *nvmeq = dev->queues[i];
+			nvme_suspend_queue(nvmeq);
+			nvme_clear_queue(nvmeq);
+		}
+	} else {
+		nvme_disable_io_queues(dev);
 		nvme_shutdown_ctrl(dev);
+		nvme_disable_queue(dev, 0);
+	}
 	nvme_dev_unmap(dev);
 }