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

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

Signed-off-by: Ken Xue <Ken.Xue@amd.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Xiangliang Yu <Xiangliang.Yu@amd.com>
Cc: James E.J. Bottomley <JBottomley@odin.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Terry <Michael.terry@canonical.com>
Cc: stable@vger.kernel.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
index e4b7998379485454d26e39f6a5a91917a155ffbb..459abe1dcc87a6dfc1beca5672dc3d59d88bdbd2 100644 (file)
--- a/drivers/scsi/scsi_pm.c
+++ b/drivers/scsi/scsi_pm.c
@@ -219,13 +219,13 @@ static int sdev_runtime_suspend(struct device *dev)
        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;
 }
 
@@ -248,11 +248,11 @@ static int sdev_runtime_resume(struct device *dev)
        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;
 }