[SCSI] Allow error handling timeout to be specified

Introduce eh_timeout which can be used for error handling purposes. This
was previously hardcoded to 10 seconds in the SCSI error handling
code. However, for some fast-fail scenarios it is necessary to be able
to tune this as it can take several iterations (bus device, target, bus,
controller) before we give up.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/scsi_sysfs.c

@@ -559,6 +559,35 @@ sdev_store_timeout (struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR(timeout, S_IRUGO | S_IWUSR, sdev_show_timeout, sdev_store_timeout);
 
+static ssize_t
+sdev_show_eh_timeout(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct scsi_device *sdev;
+	sdev = to_scsi_device(dev);
+	return snprintf(buf, 20, "%u\n", sdev->eh_timeout / HZ);
+}
+
+static ssize_t
+sdev_store_eh_timeout(struct device *dev, struct device_attribute *attr,
+		    const char *buf, size_t count)
+{
+	struct scsi_device *sdev;
+	unsigned int eh_timeout;
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	sdev = to_scsi_device(dev);
+	err = kstrtouint(buf, 10, &eh_timeout);
+	if (err)
+		return err;
+	sdev->eh_timeout = eh_timeout * HZ;
+
+	return count;
+}
+static DEVICE_ATTR(eh_timeout, S_IRUGO | S_IWUSR, sdev_show_eh_timeout, sdev_store_eh_timeout);
+
 static ssize_t
 store_rescan_field (struct device *dev, struct device_attribute *attr,
 		    const char *buf, size_t count)
@@ -723,6 +752,7 @@ static struct attribute *scsi_sdev_attrs[] = {
 	&dev_attr_delete.attr,
 	&dev_attr_state.attr,
 	&dev_attr_timeout.attr,
+	&dev_attr_eh_timeout.attr,
 	&dev_attr_iocounterbits.attr,
 	&dev_attr_iorequest_cnt.attr,
 	&dev_attr_iodone_cnt.attr,