scsi: block: pm: Simplify resume handling

Commit 05d18ae1cc ("scsi: pm: Balance pm_only counter of request queue
during system resume") fixed a problem in the block layer's runtime-PM
code: blk_set_runtime_active() failed to call blk_clear_pm_only().
However, the commit's implementation was awkward; it forced the SCSI
system-resume handler to choose whether to call blk_post_runtime_resume()
or blk_set_runtime_active(), depending on whether or not the SCSI device
had previously been runtime suspended.

This patch simplifies the situation considerably by adding the missing
function call directly into blk_set_runtime_active() (under the condition
that the queue is not already in the RPM_ACTIVE state).  This allows the
SCSI routine to revert back to its original form.  Furthermore, making this
change reveals that blk_post_runtime_resume() (in its success pathway) does
exactly the same thing as blk_set_runtime_active().  The duplicate code is
easily removed by making one routine call the other.

No functional changes are intended.

Link: https://lore.kernel.org/r/20200706151436.GA702867@rowland.harvard.edu
CC: Can Guo <cang@codeaurora.org>
CC: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

block/blk-pm.c

@@ -164,9 +164,8 @@ EXPORT_SYMBOL(blk_pre_runtime_resume);
  *
  * Description:
  *    Update the queue's runtime status according to the return value of the
- *    device's runtime_resume function. If it is successfully resumed, process
- *    the requests that are queued into the device's queue when it is resuming
- *    and then mark last busy and initiate autosuspend for it.
+ *    device's runtime_resume function. If the resume was successful, call
+ *    blk_set_runtime_active() to do the real work of restarting the queue.
  *
  *    This function should be called near the end of the device's
  *    runtime_resume callback.
@@ -175,19 +174,13 @@ void blk_post_runtime_resume(struct request_queue *q, int err)
 {
 	if (!q->dev)
 		return;
-
-	spin_lock_irq(&q->queue_lock);
 	if (!err) {
-		q->rpm_status = RPM_ACTIVE;
-		pm_runtime_mark_last_busy(q->dev);
-		pm_request_autosuspend(q->dev);
+		blk_set_runtime_active(q);
 	} else {
+		spin_lock_irq(&q->queue_lock);
 		q->rpm_status = RPM_SUSPENDED;
-	}
 		spin_unlock_irq(&q->queue_lock);
-
-	if (!err)
-		blk_clear_pm_only(q);
+	}
 }
 EXPORT_SYMBOL(blk_post_runtime_resume);
 
@@ -204,15 +197,25 @@ EXPORT_SYMBOL(blk_post_runtime_resume);
  * This function can be used in driver's resume hook to correct queue
  * runtime PM status and re-enable peeking requests from the queue. It
  * should be called before first request is added to the queue.
+ *
+ * This function is also called by blk_post_runtime_resume() for successful
+ * runtime resumes.  It does everything necessary to restart the queue.
  */
 void blk_set_runtime_active(struct request_queue *q)
 {
-	if (q->dev) {
+	int old_status;
+
+	if (!q->dev)
+		return;
+
 	spin_lock_irq(&q->queue_lock);
+	old_status = q->rpm_status;
 	q->rpm_status = RPM_ACTIVE;
 	pm_runtime_mark_last_busy(q->dev);
 	pm_request_autosuspend(q->dev);
 	spin_unlock_irq(&q->queue_lock);
-	}
+
+	if (old_status != RPM_ACTIVE)
+		blk_clear_pm_only(q);
 }
 EXPORT_SYMBOL(blk_set_runtime_active);

drivers/scsi/scsi_pm.c

@@ -80,10 +80,6 @@ static int scsi_dev_type_resume(struct device *dev,
 	dev_dbg(dev, "scsi resume: %d\n", err);
 
 	if (err == 0) {
-		bool was_runtime_suspended;
-
-		was_runtime_suspended = pm_runtime_suspended(dev);
-
 		pm_runtime_disable(dev);
 		err = pm_runtime_set_active(dev);
 		pm_runtime_enable(dev);
@@ -97,9 +93,7 @@ static int scsi_dev_type_resume(struct device *dev,
 		 */
 		if (!err && scsi_is_sdev_device(dev)) {
 			struct scsi_device *sdev = to_scsi_device(dev);
-			if (was_runtime_suspended)
-				blk_post_runtime_resume(sdev->request_queue, 0);
-			else
+
 			blk_set_runtime_active(sdev->request_queue);
 		}
 	}