linux-kernel - Re: [PATCH 2/4] libata: Implement disk shock protection support

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Message-ID: <874p4eoksc.fsf@denkblock.local>
Date:	Wed, 17 Sep 2008 17:26:59 +0200
From:	Elias Oltmanns <eo@...ensachen.de>
To:	Tejun Heo <htejun@...il.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Jeff Garzik <jeff@...zik.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] libata: Implement disk shock protection support

Elias Oltmanns <eo@...ensachen.de> wrote:
> What about the following patch?
>
> From: Elias Oltmanns <eo@...ensachen.de>
> Subject: [PATCH] libata: Implement disk shock protection support
>
> On user request (through sysfs), the IDLE IMMEDIATE command with UNLOAD
> FEATURE as specified in ATA-7 is issued to the device and processing of
> the request queue is stopped thereafter until the specified timeout
> expires or user space asks to resume normal operation. This is supposed
> to prevent the heads of a hard drive from accidentally crashing onto the
> platter when a heavy shock is anticipated (like a falling laptop
> expected to hit the floor). In fact, the whole port stops processing
> commands until the timeout has expired in order to avoid any resets due
> to failed commands on another device.
>
> Signed-off-by: Elias Oltmanns <eo@...ensachen.de>
> ---

Apart from addressing the issue with timeouts exceeding the limit of
30000 msec discussed lately, I have also simplified the crucial
if-clause in ata_scsi_park_show(). Both changes are given below.
Assuming that you don't have any objections, I'll just go ahead and
submit the updated patch series shortly.

Regards,

Elias

> +static ssize_t ata_scsi_park_show(struct device *device,
> +				  struct device_attribute *attr, char *buf)
> +{
> +	struct scsi_device *sdev = to_scsi_device(device);
> +	struct ata_port *ap;
> +	struct ata_link *link;
> +	struct ata_device *dev;
> +	unsigned long flags;
> +	unsigned int uninitialized_var(msecs);
> +	int rc = 0;
> +
> +	ap = ata_shost_to_port(sdev->host);
> +
> +	spin_lock_irqsave(ap->lock, flags);
> +	dev = ata_scsi_find_dev(ap, sdev);
> +	if (!dev) {
> +		rc = -ENODEV;
> +		goto unlock;
> +	}
> +	if (dev->flags & ATA_DFLAG_NO_UNLOAD) {
> +		rc = -EOPNOTSUPP;
> +		goto unlock;
> +	}
> +
> +	link = dev->link;
> +	if (((ap->pflags & ATA_PFLAG_EH_IN_PROGRESS &&
> +	      (link->eh_context.i.dev_action[dev->devno] & ATA_EH_PARK ||
> +	       link->eh_info.dev_action[dev->devno] & ATA_EH_PARK)) ||
> +	     (ap->pflags & ATA_PFLAG_EH_PENDING &&
> +	      link->eh_info.dev_action[dev->devno])) &&
> +	    time_after(dev->unpark_deadline, jiffies))

Changed to:

	if (ap->pflags & ATA_PFLAG_EH_IN_PROGRESS &&
	    link->eh_context.unloaded_mask & (1 << dev->devno) &&
	    time_after(dev->unpark_deadline, jiffies))

> +		msecs = jiffies_to_msecs(dev->unpark_deadline - jiffies);
> +	else
> +		msecs = 0;
> +
> +unlock:
> +	spin_unlock_irq(ap->lock);
> +
> +	return rc ? rc : snprintf(buf, 20, "%u\n", msecs);
> +}
> +
> +static ssize_t ata_scsi_park_store(struct device *device,
> +				   struct device_attribute *attr,
> +				   const char *buf, size_t len)
> +{
> +	struct scsi_device *sdev = to_scsi_device(device);
> +	struct ata_port *ap;
> +	struct ata_device *dev;
> +	long int input;
> +	unsigned long flags;
> +	int rc;
> +
> +	rc = strict_strtol(buf, 10, &input);
> +	if (rc || input < -2 || input > ATA_TMOUT_MAX_PARK)
> +		return -EINVAL;

Changed to:

	if (rc || input < -2)
		return -EINVAL;
	if (input > ATA_TMOUT_MAX_PARK) {
		rc = -EOVERFLOW;
		input = ATA_TMOUT_MAX_PARK;
	}

> +
> +	ap = ata_shost_to_port(sdev->host);
> +
> +	spin_lock_irqsave(ap->lock, flags);
> +	dev = ata_scsi_find_dev(ap, sdev);
> +	if (unlikely(!dev)) {
> +		rc = -ENODEV;
> +		goto unlock;
> +	}
> +	if (dev->class != ATA_DEV_ATA) {
> +		rc = -EOPNOTSUPP;
> +		goto unlock;
> +	}
> +
> +	if (input >= 0) {
> +		if (dev->flags & ATA_DFLAG_NO_UNLOAD) {
> +			rc = -EOPNOTSUPP;
> +			goto unlock;
> +		}
> +
> +		dev->unpark_deadline = ata_deadline(jiffies, input);
> +		dev->link->eh_info.dev_action[dev->devno] |= ATA_EH_PARK;
> +		ata_port_schedule_eh(ap);
> +		wake_up_all(&ata_scsi_park_wq);
> +	} else {
> +		switch (input) {
> +		case -1:
> +			dev->flags &= ~ATA_DFLAG_NO_UNLOAD;
> +			break;
> +		case -2:
> +			dev->flags |= ATA_DFLAG_NO_UNLOAD;
> +			break;
> +		}
> +	}
> +unlock:
> +	spin_unlock_irqrestore(ap->lock, flags);
> +
> +	return rc ? rc : len;
> +}
> +DEVICE_ATTR(unload_heads, S_IRUGO | S_IWUSR,
> +	    ata_scsi_park_show, ata_scsi_park_store);
> +EXPORT_SYMBOL_GPL(dev_attr_unload_heads);
> +
>  static void ata_scsi_set_sense(struct scsi_cmnd *cmd, u8 sk, u8 asc, u8 ascq)
>  {
>  	cmd->result = (DRIVER_SENSE << 24) | SAM_STAT_CHECK_CONDITION;
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