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

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Date:   Wed, 22 Jul 2020 17:18:54 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     Bart Van Assche <bvanassche@....org>
CC:     <linux-scsi@...r.kernel.org>, <martin.petersen@...cle.com>,
        <avri.altman@....com>, <alim.akhtar@...sung.com>,
        <jejb@...ux.ibm.com>, <beanhuo@...ron.com>,
        <asutoshd@...eaurora.org>, <cang@...eaurora.org>,
        <matthias.bgg@...il.com>, <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kuohong.wang@...iatek.com>,
        <peter.wang@...iatek.com>, <chun-hung.wu@...iatek.com>,
        <andy.teng@...iatek.com>, <chaotian.jing@...iatek.com>,
        <cc.chou@...iatek.com>
Subject: Re: [RFC PATCH v3] scsi: ufs: Quiesce all scsi devices before
 shutdown

Hi Bart,

On Sat, 2020-07-11 at 20:21 -0700, Bart Van Assche wrote:
> 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.

Got it.

So may I focus on fixing racing first by quiecsing all SCSI devices only
and do not touch blk_cleanup_queue() in UFS driver, just like v2?


> >  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?

ufshcd_shutdown() configures below things different from or more than
what sd_suspend_common() can do now,

- Set link as OFF state
- Regulator and clock toggling according to required low-power state for
shutdown
- Auto BKOP toggling
- Vendor-specific shutdown flow ...etc.

Therefore UFS shutdown callback would be still required.

Thanks,
Stanley Chu