Re: [PATCH]SCSI:Refine the way to fix NULL pointer dereference in runtime PM

[Huang Rui <ray.huang@amd.com>]

On Wed, Sep 09, 2015 at 03:02:11PM +0800, Ken Xue wrote:
> From 844ebfcecad7ddaf7206e0474c600b0146b4ef21 Mon Sep 17 00:00:00 2001
> From: Ken Xue <Ken.Xue@amd.com>
> Date: Wed, 9 Sep 2015 14:55:21 +0800
> Subject: [PATCH] SCSI:Refine the way to fix NULL pointer dereference in
>  runtime PM
> 
> There was a patch about Bugzilla #101371.

Which Bugzilla? I guess you should put a link or oops message of NULL
pointer dereference here. Then other guys can know detail infomation
of this fix.

Thanks,
Rui

> That patch introduced a possibility that can not call
> blk_{pre|post}_runtime_suspend and blk_{pre|post}_runtime_resume in
> pairs.
> 
> Signed-off-by: Ken Xue <Ken.Xue@amd.com>
> ---
>  block/blk-core.c       | 12 ++++++++++++
>  drivers/scsi/scsi_pm.c | 20 ++++++++++----------
>  2 files changed, 22 insertions(+), 10 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 60912e9..a07ab18 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -3280,6 +3280,9 @@ int blk_pre_runtime_suspend(struct request_queue *q)
>  {
>  	int ret = 0;
>  
> +	if (!q->dev)
> +		return ret;
> +
>  	spin_lock_irq(q->queue_lock);
>  	if (q->nr_pending) {
>  		ret = -EBUSY;
> @@ -3307,6 +3310,9 @@ EXPORT_SYMBOL(blk_pre_runtime_suspend);
>   */
>  void blk_post_runtime_suspend(struct request_queue *q, int err)
>  {
> +	if (!q->dev)
> +		return;
> +
>  	spin_lock_irq(q->queue_lock);
>  	if (!err) {
>  		q->rpm_status = RPM_SUSPENDED;
> @@ -3331,6 +3337,9 @@ EXPORT_SYMBOL(blk_post_runtime_suspend);
>   */
>  void blk_pre_runtime_resume(struct request_queue *q)
>  {
> +	if (!q->dev)
> +		return;
> +
>  	spin_lock_irq(q->queue_lock);
>  	q->rpm_status = RPM_RESUMING;
>  	spin_unlock_irq(q->queue_lock);
> @@ -3353,6 +3362,9 @@ EXPORT_SYMBOL(blk_pre_runtime_resume);
>   */
>  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;
> diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> index e4b7998..459abe1 100644
> --- 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;
>  }
>  
> -- 
> 1.9.1
> 
> 
>