Re: [RFC PATCH v3] scsi: ufs: Quiesce all scsi devices before shutdown

[Bart Van Assche <bvanassche@acm.org>]

On 2020-07-06 06:22, Stanley Chu wrote:
> +static void ufshcd_cleanup_queue(struct scsi_device *sdev, void *data)
> +{
> +	if (sdev->request_queue)
> +		blk_cleanup_queue(sdev->request_queue);
> +}

No SCSI LLD should ever call blk_cleanup_queue() directly for
sdev->request_queue. Only the SCSI core should call blk_cleanup_queue()
directly for that queue.

>  int ufshcd_shutdown(struct ufs_hba *hba)
>  {
>  	int ret = 0;
> +	struct scsi_target *starget;
>  
>  	if (!hba->is_powered)
>  		goto out;
> @@ -8612,7 +8632,25 @@ int ufshcd_shutdown(struct ufs_hba *hba)
>  			goto out;
>  	}
>  
> +	/*
> +	 * Quiesce all SCSI devices to prevent any non-PM requests sending
> +	 * from block layer during and after shutdown.
> +	 *
> +	 * Here we can not use blk_cleanup_queue() since PM requests
> +	 * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent
> +	 * through block layer. Therefore SCSI command queued after the
> +	 * scsi_target_quiesce() call returned will block until
> +	 * blk_cleanup_queue() is called.
> +	 *
> +	 * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can
> +	 * be ignored since shutdown is one-way flow.
> +	 */
> +	ufshcd_scsi_for_each_sdev(ufshcd_quiece_sdev);
> +
>  	ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
> +
> +	/* Set queue as dying to not block queueing commands */
> +	ufshcd_scsi_for_each_sdev(ufshcd_cleanup_queue);
>  out:
>  	if (ret)
>  		dev_err(hba->dev, "%s failed, err %d\n", __func__, ret);
> 

What is the purpose of ufshcd_shutdown()? Why does this function exist?
How about removing the calls to ufshcd_shutdown() and invoking power down
code from inside sd_suspend_common() instead?

Thanks,

Bart.