[PATCH 1/1] scsi: Add allow_restart sysfs class attribute

[PATCH 1/1] scsi: Add allow_restart sysfs class attribute

[Brian King]

This is a resend of a patch I generated in response to an email sent
by Ruben Faelens <parasietje@gmail.com>. His original email to
linux-scsi requested a method in which he could spin down a scsi disk
when not in use and have the kernel automatically spin it back up when
an I/O was generated to the disk. The infrastructure to automatically
spin a disk up has been in the scsi error handler for some time now,
but it is not enabled by default. This patch adds an sd sysfs attribute
which allows userspace to enable this behavior.

Signed-off-by: Brian King <brking@us.ibm.com>
---

 linux-2.6-bjking1/drivers/scsi/sd.c |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+)

diff -puN drivers/scsi/sd.c~sd_allow_restart_sysfs_attr drivers/scsi/sd.c
--- linux-2.6/drivers/scsi/sd.c~sd_allow_restart_sysfs_attr	2006-06-26 14:07:59.000000000 -0500
+++ linux-2.6-bjking1/drivers/scsi/sd.c	2006-06-26 14:07:59.000000000 -0500
@@ -208,6 +208,23 @@ static ssize_t sd_store_cache_type(struc
 	return count;
 }
 
+static ssize_t sd_store_allow_restart(struct class_device *cdev, const char *buf,
+				      size_t count)
+{
+	struct scsi_disk *sdkp = to_scsi_disk(cdev);
+	struct scsi_device *sdp = sdkp->device;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	if (sdp->type != TYPE_DISK)
+		return -EINVAL;
+
+	sdp->allow_restart = simple_strtoul(buf, NULL, 10);
+
+	return count;
+}
+
 static ssize_t sd_show_cache_type(struct class_device *cdev, char *buf)
 {
 	struct scsi_disk *sdkp = to_scsi_disk(cdev);
@@ -223,10 +240,19 @@ static ssize_t sd_show_fua(struct class_
 	return snprintf(buf, 20, "%u\n", sdkp->DPOFUA);
 }
 
+static ssize_t sd_show_allow_restart(struct class_device *cdev, char *buf)
+{
+	struct scsi_disk *sdkp = to_scsi_disk(cdev);
+
+	return snprintf(buf, 40, "%d\n", sdkp->device->allow_restart);
+}
+
 static struct class_device_attribute sd_disk_attrs[] = {
 	__ATTR(cache_type, S_IRUGO|S_IWUSR, sd_show_cache_type,
 	       sd_store_cache_type),
 	__ATTR(FUA, S_IRUGO, sd_show_fua, NULL),
+	__ATTR(allow_restart, S_IRUGO|S_IWUSR, sd_show_allow_restart,
+	       sd_store_allow_restart),
 	__ATTR_NULL,
 };
 
_

Re: [PATCH 1/1] scsi: Add allow_restart sysfs class attribute

[Stefan Richter]

Brian King wrote:
> This is a resend of a patch I generated in response to an email sent
> by Ruben Faelens <parasietje@gmail.com>. His original email to
> linux-scsi requested a method in which he could spin down a scsi disk
> when not in use and have the kernel automatically spin it back up when
> an I/O was generated to the disk. The infrastructure to automatically
> spin a disk up has been in the scsi error handler for some time now,

I am positively surprised that this code is actually already there --- I 
didn't notice...

> but it is not enabled by default. This patch adds an sd sysfs attribute
> which allows userspace to enable this behavior.

What is the reason that the code is not enabled by default? Are there 
dependencies on command set or transport, or firmwares which won't react 
properly?

There were a few requests for auto-spinup for SBP-2 HDDs during the last 
months, e.g. https://bugzilla.novell.com/show_bug.cgi?id=183011 . Maybe 
sbp2 should switch on sdev->allow_restart for all SBP-2 direct access 
and RBC devices, or at least for those that are known to require it.
-- 
Stefan Richter
-=====-=-==- -==- ==-==
http://arcgraph.de/sr/

Re: [PATCH 1/1] scsi: Add allow_restart sysfs class attribute

[Brian King]

Stefan Richter wrote:
> Brian King wrote:
>> This is a resend of a patch I generated in response to an email sent
>> by Ruben Faelens <parasietje@gmail.com>. His original email to
>> linux-scsi requested a method in which he could spin down a scsi disk
>> when not in use and have the kernel automatically spin it back up when
>> an I/O was generated to the disk. The infrastructure to automatically
>> spin a disk up has been in the scsi error handler for some time now,
> 
> I am positively surprised that this code is actually already there --- I 
> didn't notice...
> 
>> but it is not enabled by default. This patch adds an sd sysfs attribute
>> which allows userspace to enable this behavior.
> 
> What is the reason that the code is not enabled by default? Are there 
> dependencies on command set or transport, or firmwares which won't react 
> properly?

There was concern when the patch went in that if it was enabled by default
it would break a bunch of USB devices.

http://marc.theaimsgroup.com/?l=linux-scsi&m=107702811830956&w=2


-- 
Brian King
eServer Storage I/O
IBM Linux Technology Center