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Subject: Re: [PATCH v7] scsi: ufs: Quiesce all scsi devices before shutdown
To:     Stanley Chu <stanley.chu@mediatek.com>, linux-scsi@vger.kernel.org,
        martin.petersen@oracle.com, avri.altman@wdc.com,
        alim.akhtar@samsung.com, jejb@linux.ibm.com, cang@codeaurora.org
Cc:     beanhuo@micron.com, asutoshd@codeaurora.org,
        matthias.bgg@gmail.com, linux-mediatek@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        kuohong.wang@mediatek.com, peter.wang@mediatek.com,
        chun-hung.wu@mediatek.com, andy.teng@mediatek.com,
        chaotian.jing@mediatek.com, cc.chou@mediatek.com,
        jiajie.hao@mediatek.com
References: <20200803100448.2738-1-stanley.chu@mediatek.com>
From:   Bart Van Assche <bvanassche@acm.org>
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Date:   Mon, 3 Aug 2020 09:04:40 -0700
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On 2020-08-03 03:04, Stanley Chu wrote:
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 307622284239..7cb220b3fde0 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -8640,6 +8640,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle);
>  int ufshcd_shutdown(struct ufs_hba *hba)
>  {
>  	int ret = 0;
> +	struct scsi_target *starget;
>  
>  	if (!hba->is_powered)
>  		goto out;
> @@ -8647,11 +8648,27 @@ int ufshcd_shutdown(struct ufs_hba *hba)
>  	if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba))
>  		goto out;
>  
> -	if (pm_runtime_suspended(hba->dev)) {
> -		ret = ufshcd_runtime_resume(hba);
> -		if (ret)
> -			goto out;
> -	}
> +	/*
> +	 * Let runtime PM framework manage and prevent concurrent runtime
> +	 * operations with shutdown flow.
> +	 */
> +	pm_runtime_get_sync(hba->dev);
> +
> +	/*
> +	 * 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.
> +	 */
> +	list_for_each_entry(starget, &hba->host->__targets, siblings)
> +		scsi_target_quiesce(starget);
>  
>  	ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM);
>  out:

This seems wrong to me. Since ufshcd_shutdown() shuts down the link I think
it should call scsi_remove_device() instead of scsi_target_quiesce().

Thanks,

Bart.