On Sun, 28 Jan 2007 19:47:27 -0600
Robert Hancock <hancockr@xxxxxxx> wrote:
> Here's a patch for sd.c I've cooked up which issues a START STOP UNIT
> command to stop the drive when the SCSI disk is removed or the machine
> is powered down. The rationale behind this is that apparently on many
> drives, simply cutting power to the spinning disk forces it to do an
> emergency head park/unload which creates more wear on the drive then a
> controlled park/unload with power still applied. This change ensures
> that the drive will be spun down if the user shuts down the machine or
> if they are about to hot-unplug the drive and have done "scsiadd -r" first.
>
> The main potential concern I have about this implementation is that if
> the drive is used in a multi-initiator, iSCSI, etc. environment,
> stopping the drive may be undesirable as another initiator may still be
> accessing it. I'm not familiar enough with these setups to know if this
> problem is likely to come up or not. For this and other reasons we may
> want to make this behavior controllable - I'm open to suggestions on how
> to do this or whether it's needed.
>
> I've tested that this does work on SATA disks through libata (with my
> patch "libata: fix translation for START STOP UNIT" applied). I also
> tested with some external USB-to-IDE drive enclosures. The support for
> START STOP UNIT on those seems rather poor though, on one enclosure with
> a Genesys bridge chip it returned a check condition with "Invalid field
> in CDB", and on another with a JMicron chip the request succeeded but it
> didn't actually spin the drive down.
>
What we don't want to happen is for those disks to spin down during a reboot.
It seems that this is OK with this patch.
Also, we probably don't want them to be spun down during a kexec_load, but
I expect that's OK too.
triviata:
> --- linux-2.6.20-rc6nv/drivers/scsi/sd.c 2007-01-28 17:00:00.000000000 -0600
> +++ linux-2.6.20-rc6nvedit/drivers/scsi/sd.c 2007-01-28 18:08:53.000000000 -0600
> @@ -821,6 +821,39 @@ static int sd_sync_cache(struct scsi_dev
> return res;
> }
>
> +static int sd_stop_unit(struct scsi_device *sdp, struct scsi_disk* sdkp)
s/* / */
> +{
> + int res;
> + struct scsi_sense_hdr sshdr;
> + unsigned char cmd[10] = { 0 };
I don't think this initialisation-to-all-zeroes is needed, is it?
> + if (!scsi_device_online(sdp))
> + return -ENODEV;
> +
> + cmd[0] = START_STOP;
> + /*
> + * Leave the rest of the command zero to indicate
> + * transition to stopped power condition and return
> + * on completion.
> + */
> + printk(KERN_NOTICE "Stopping SCSI disk %s\n",
> + sdkp->disk->disk_name);
> + res = scsi_execute_req(sdp, cmd, DMA_NONE, NULL, 0, &sshdr,
> + SD_TIMEOUT, SD_MAX_RETRIES);
> +
> + if (res) {
> + printk(KERN_WARNING "sd stop failed: status = %x, message = %02x, "
> + "host = %d, driver = %02x\n",
> + status_byte(res), msg_byte(res),
> + host_byte(res), driver_byte(res));
> + if (driver_byte(res) & DRIVER_SENSE)
> + scsi_print_sense_hdr("sd", &sshdr);
> + }
> +
> + return res;
> +}
> +
> +
> static int sd_issue_flush(struct device *dev, sector_t *error_sector)
> {
> int ret = 0;
> @@ -1727,11 +1760,13 @@ static int sd_probe(struct device *dev)
> **/
> static int sd_remove(struct device *dev)
> {
> + struct scsi_device *sdp = to_scsi_device(dev);
> struct scsi_disk *sdkp = dev_get_drvdata(dev);
>
> class_device_del(&sdkp->cdev);
> del_gendisk(sdkp->disk);
> sd_shutdown(dev);
> + sd_stop_unit(sdp,sdkp);
>
> mutex_lock(&sd_ref_mutex);
> dev_set_drvdata(dev, NULL);
> @@ -1784,6 +1819,9 @@ static void sd_shutdown(struct device *d
> sdkp->disk->disk_name);
> sd_sync_cache(sdp);
> }
> + if(system_state == SYSTEM_POWER_OFF)
s/if(/if (/
> + sd_stop_unit(sdp,sdkp);
> +
> scsi_disk_put(sdkp);
> }
>
>
>
>
>
>
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