isci: kill isci_remote_device_change_state()

Now that "stopping/stopped" are one in the same and signalled by a NULL device
pointer the rest of the device status infrastructure can be removed (->status
and ->state_lock).  The "not ready for i/o state" is replaced with a state
flag, and is evaluated under scic_lock so that we don't see transients from
taking the device reference to submitting the i/o.

This also fixes a potential leakage of can_queue slots in the rare case that
SAS_TASK_ABORTED is set at submission.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

4 files changed, 27 insertions, 97 deletions

diff --git a/drivers/scsi/isci/host.c b/drivers/scsi/isci/host.c
index 40f35fa..b08455f 100644
--- a/drivers/scsi/isci/host.c
+++ b/drivers/scsi/isci/host.c
@@ -2504,7 +2504,6 @@ int isci_host_init(struct isci_host *isci_host)
 
 		INIT_LIST_HEAD(&idev->reqs_in_process);
 		INIT_LIST_HEAD(&idev->node);
-		spin_lock_init(&idev->state_lock);
 	}
 
 	return 0;
diff --git a/drivers/scsi/isci/remote_device.c b/drivers/scsi/isci/remote_device.c
index ab5f986..c2e5c05 100644
--- a/drivers/scsi/isci/remote_device.c
+++ b/drivers/scsi/isci/remote_device.c
@@ -62,24 +62,6 @@
 #include "task.h"
 
 /**
- * isci_remote_device_change_state() - This function gets the status of the
- *    remote_device object.
- * @isci_device: This parameter points to the isci_remote_device object
- *
- * status of the object as a isci_status enum.
- */
-void isci_remote_device_change_state(
-	struct isci_remote_device *isci_device,
-	enum isci_status status)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&isci_device->state_lock, flags);
-	isci_device->status = status;
-	spin_unlock_irqrestore(&isci_device->state_lock, flags);
-}
-
-/**
  * isci_remote_device_not_ready() - This function is called by the scic when
  *    the remote device is not ready. We mark the isci device as ready (not
  *    "ready_for_io") and signal the waiting proccess.
@@ -96,8 +78,7 @@ static void isci_remote_device_not_ready(struct isci_host *ihost,
 	if (reason == SCIC_REMOTE_DEVICE_NOT_READY_STOP_REQUESTED)
 		set_bit(IDEV_GONE, &idev->flags);
 	else
-		/* device ready is actually a "not ready for io" state. */
-		isci_remote_device_change_state(idev, isci_ready);
+		clear_bit(IDEV_IO_READY, &idev->flags);
 }
 
 /**
@@ -113,7 +94,7 @@ static void isci_remote_device_ready(struct isci_host *ihost, struct isci_remote
 	dev_dbg(&ihost->pdev->dev,
 		"%s: idev = %p\n", __func__, idev);
 
-	isci_remote_device_change_state(idev, isci_ready_for_io);
+	set_bit(IDEV_IO_READY, &idev->flags);
 	if (test_and_clear_bit(IDEV_START_PENDING, &idev->flags))
 		wake_up(&ihost->eventq);
 }
@@ -871,26 +852,6 @@ static void isci_remote_device_deconstruct(struct isci_host *ihost, struct isci_
 	isci_put_device(idev);
 }
 
-/**
- * isci_remote_device_stop_complete() - This function is called by the scic
- *    when the remote device stop has completed. We mark the isci device as not
- *    ready and remove the isci remote device.
- * @ihost: This parameter specifies the isci host object.
- * @idev: This parameter specifies the remote device.
- * @status: This parameter specifies status of the completion.
- *
- */
-static void isci_remote_device_stop_complete(struct isci_host *ihost,
-					     struct isci_remote_device *idev)
-{
-	dev_dbg(&ihost->pdev->dev, "%s: complete idev = %p\n", __func__, idev);
-
-	isci_remote_device_change_state(idev, isci_stopped);
-
-	/* after stop, we can tear down resources. */
-	isci_remote_device_deconstruct(ihost, idev);
-}
-
 static void scic_sds_remote_device_stopped_state_enter(struct sci_base_state_machine *sm)
 {
 	struct scic_sds_remote_device *sci_dev = container_of(sm, typeof(*sci_dev), sm);
@@ -903,7 +864,7 @@ static void scic_sds_remote_device_stopped_state_enter(struct sci_base_state_mac
 	 */
 	prev_state = sci_dev->sm.previous_state_id;
 	if (prev_state == SCI_DEV_STOPPING)
-		isci_remote_device_stop_complete(scic_to_ihost(scic), idev);
+		isci_remote_device_deconstruct(scic_to_ihost(scic), idev);
 
 	scic_sds_controller_remote_device_stopped(scic, sci_dev);
 }
@@ -1301,8 +1262,6 @@ isci_remote_device_alloc(struct isci_host *ihost, struct isci_port *iport)
 	if (WARN_ONCE(!list_empty(&idev->node), "found non-idle remote device\n"))
 		return NULL;
 
-	isci_remote_device_change_state(idev, isci_freed);
-
 	return idev;
 }
 
@@ -1315,6 +1274,7 @@ void isci_remote_device_release(struct kref *kref)
 	idev->isci_port = NULL;
 	clear_bit(IDEV_START_PENDING, &idev->flags);
 	clear_bit(IDEV_STOP_PENDING, &idev->flags);
+	clear_bit(IDEV_IO_READY, &idev->flags);
 	clear_bit(IDEV_GONE, &idev->flags);
 	clear_bit(IDEV_EH, &idev->flags);
 	smp_mb__before_clear_bit();
@@ -1341,7 +1301,6 @@ enum sci_status isci_remote_device_stop(struct isci_host *ihost, struct isci_rem
 	spin_lock_irqsave(&ihost->scic_lock, flags);
 	idev->domain_dev->lldd_dev = NULL; /* disable new lookups */
 	set_bit(IDEV_GONE, &idev->flags);
-	isci_remote_device_change_state(idev, isci_stopping);
 	spin_unlock_irqrestore(&ihost->scic_lock, flags);
 
 	/* Kill all outstanding requests. */
@@ -1430,7 +1389,6 @@ int isci_remote_device_found(struct domain_device *domain_dev)
 	spin_lock_irq(&isci_host->scic_lock);
 	isci_device->domain_dev = domain_dev;
 	isci_device->isci_port = isci_port;
-	isci_remote_device_change_state(isci_device, isci_starting);
 	list_add_tail(&isci_device->node, &isci_port->remote_dev_list);
 
 	set_bit(IDEV_START_PENDING, &isci_device->flags);
diff --git a/drivers/scsi/isci/remote_device.h b/drivers/scsi/isci/remote_device.h
index 05842b5..33f0114 100644
--- a/drivers/scsi/isci/remote_device.h
+++ b/drivers/scsi/isci/remote_device.h
@@ -130,19 +130,18 @@ struct scic_sds_remote_device {
 };
 
 struct isci_remote_device {
-	enum isci_status status;
 	#define IDEV_START_PENDING 0
 	#define IDEV_STOP_PENDING 1
 	#define IDEV_ALLOCATED 2
 	#define IDEV_EH 3
 	#define IDEV_GONE 4
+	#define IDEV_IO_READY 5
 	unsigned long flags;
 	struct kref kref;
 	struct isci_port *isci_port;
 	struct domain_device *domain_dev;
 	struct list_head node;
 	struct list_head reqs_in_process;
-	spinlock_t state_lock;
 	struct scic_sds_remote_device sci;
 };
 
@@ -178,8 +177,6 @@ bool isci_device_is_reset_pending(struct isci_host *ihost,
 				  struct isci_remote_device *idev);
 void isci_device_clear_reset_pending(struct isci_host *ihost,
 				     struct isci_remote_device *idev);
-void isci_remote_device_change_state(struct isci_remote_device *idev,
-				     enum isci_status status);
 /**
  * scic_remote_device_stop() - This method will stop both transmission and
  *    reception of link activity for the supplied remote device.  This method
diff --git a/drivers/scsi/isci/task.c b/drivers/scsi/isci/task.c
index dd5e9de..c313bc1 100644
--- a/drivers/scsi/isci/task.c
+++ b/drivers/scsi/isci/task.c
@@ -147,10 +147,10 @@ int isci_task_execute_task(struct sas_task *task, int num, gfp_t gfp_flags)
 {
 	struct isci_host *ihost = dev_to_ihost(task->dev);
 	struct isci_remote_device *idev;
+	enum sci_status status;
 	unsigned long flags;
+	bool io_ready;
 	int ret;
-	enum sci_status status;
-	enum isci_status device_status;
 
 	dev_dbg(&ihost->pdev->dev, "%s: num=%d\n", __func__, num);
 
@@ -163,64 +163,40 @@ int isci_task_execute_task(struct sas_task *task, int num, gfp_t gfp_flags)
 	}
 
 	for_each_sas_task(num, task) {
-		dev_dbg(&ihost->pdev->dev,
-			"task = %p, num = %d; dev = %p; cmd = %p\n",
-			    task, num, task->dev, task->uldd_task);
 		spin_lock_irqsave(&ihost->scic_lock, flags);
 		idev = isci_lookup_device(task->dev);
+		io_ready = idev ? test_bit(IDEV_IO_READY, &idev->flags) : 0;
 		spin_unlock_irqrestore(&ihost->scic_lock, flags);
 
-		if (idev)
-			device_status = idev->status;
-		else
-			device_status = isci_freed;
-
-		/* From this point onward, any process that needs to guarantee
-		 * that there is no kernel I/O being started will have to wait
-		 * for the quiesce spinlock.
-		 */
-
-		if (device_status != isci_ready_for_io) {
+		dev_dbg(&ihost->pdev->dev,
+			"task: %p, num: %d dev: %p idev: %p:%#lx cmd = %p\n",
+			task, num, task->dev, idev, idev ? idev->flags : 0,
+			task->uldd_task);
 
-			/* Forces a retry from scsi mid layer. */
-			dev_dbg(&ihost->pdev->dev,
-				"%s: task %p: isci_host->status = %d, "
-				"device = %p; device_status = 0x%x\n\n",
-				__func__,
-				task,
-				isci_host_get_state(ihost),
-				idev,
-				device_status);
-
-			if (device_status == isci_ready) {
-				/* Indicate QUEUE_FULL so that the scsi midlayer
-				* retries.
-				*/
-				isci_task_refuse(ihost, task,
-						 SAS_TASK_COMPLETE,
-						 SAS_QUEUE_FULL);
-			} else {
-				/* Else, the device is going down. */
-				isci_task_refuse(ihost, task,
-						 SAS_TASK_UNDELIVERED,
-						 SAS_DEVICE_UNKNOWN);
-			}
+		if (!idev) {
+			isci_task_refuse(ihost, task, SAS_TASK_UNDELIVERED,
+					 SAS_DEVICE_UNKNOWN);
+			isci_host_can_dequeue(ihost, 1);
+		} else if (!io_ready) {
+			/* Indicate QUEUE_FULL so that the scsi midlayer
+			 * retries.
+			  */
+			isci_task_refuse(ihost, task, SAS_TASK_COMPLETE,
+					 SAS_QUEUE_FULL);
 			isci_host_can_dequeue(ihost, 1);
 		} else {
 			/* There is a device and it's ready for I/O. */
 			spin_lock_irqsave(&task->task_state_lock, flags);
 
 			if (task->task_state_flags & SAS_TASK_STATE_ABORTED) {
-
+				/* The I/O was aborted. */
 				spin_unlock_irqrestore(&task->task_state_lock,
 						       flags);
 
 				isci_task_refuse(ihost, task,
 						 SAS_TASK_UNDELIVERED,
 						 SAM_STAT_TASK_ABORTED);
-
-				/* The I/O was aborted. */
-
+				isci_host_can_dequeue(ihost, 1);
 			} else {
 				task->task_state_flags |= SAS_TASK_AT_INITIATOR;
 				spin_unlock_irqrestore(&task->task_state_lock, flags);
@@ -323,11 +299,11 @@ int isci_task_execute_tmf(struct isci_host *ihost,
 	/* sanity check, return TMF_RESP_FUNC_FAILED
 	 * if the device is not there and ready.
 	 */
-	if (!isci_device || isci_device->status != isci_ready_for_io) {
+	if (!isci_device || !test_bit(IDEV_IO_READY, &isci_device->flags)) {
 		dev_dbg(&ihost->pdev->dev,
-			"%s: isci_device = %p not ready (%d)\n",
+			"%s: isci_device = %p not ready (%#lx)\n",
 			__func__,
-			isci_device, isci_device->status);
+			isci_device, isci_device ? isci_device->flags : 0);
 		return TMF_RESP_FUNC_FAILED;
 	} else
 		dev_dbg(&ihost->pdev->dev,