Patch "Revert "SCSI: Fix NULL pointer dereference in runtime PM"" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

Revert "SCSI: Fix NULL pointer dereference in runtime PM"

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
revert-scsi-fix-null-pointer-dereference-in-runtime-pm.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ken Xue <[email protected]>
Date: Tue, 1 Dec 2015 14:45:23 +0800
Subject: Revert "SCSI: Fix NULL pointer dereference in runtime PM"

From: Ken Xue <[email protected]>

commit 1c69d3b6eb73e466ecbb8edaf1bc7fd585b288da upstream.

This reverts commit 49718f0fb8c9 ("SCSI: Fix NULL pointer dereference in runtime PM")

The old commit may lead to a issue that blk_{pre|post}_runtime_suspend and blk_{pre|post}_runtime_resume may not be called in pairs.

Take sr device as example, when sr device goes to runtime suspend, blk_{pre|post}_runtime_suspend will be called since sr device defined pm->runtime_suspend. But blk_{pre|post}_runtime_resume will not be called since sr device doesn't have pm->runtime_resume. so, sr device can not resume correctly anymore.

More discussion can be found from below link.
http://marc.info/?l=linux-scsi&m=144163730531875&w=2

---
 drivers/scsi/scsi_pm.c |   20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

@@ -151,13 +151,13 @@ static int sdev_runtime_suspend(struct d
 	struct scsi_device *sdev = to_scsi_device(dev);
 	int err = 0;
 
-	if (pm && pm->runtime_suspend) {
-		err = blk_pre_runtime_suspend(sdev->request_queue);
-		if (err)
-			return err;
+	err = blk_pre_runtime_suspend(sdev->request_queue);
+	if (err)
+		return err;
+	if (pm && pm->runtime_suspend)
 		err = pm->runtime_suspend(dev);
-		blk_post_runtime_suspend(sdev->request_queue, err);
-	}
+	blk_post_runtime_suspend(sdev->request_queue, err);
+
 	return err;
 }
 

@@ -180,11 +180,11 @@ static int sdev_runtime_resume(struct de
 	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
 	int err = 0;
 
-	if (pm && pm->runtime_resume) {
-		blk_pre_runtime_resume(sdev->request_queue);
+	blk_pre_runtime_resume(sdev->request_queue);
+	if (pm && pm->runtime_resume)
 		err = pm->runtime_resume(dev);
-		blk_post_runtime_resume(sdev->request_queue, err);
-	}
+	blk_post_runtime_resume(sdev->request_queue, err);
+
 	return err;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/scsi-fix-null-pointer-dereference-in-runtime-pm.patch queue-3.14/revert-scsi-fix-null-pointer-dereference-in-runtime-pm.patch