[SCSI] sd: Allow protection_type to be overridden

We have encountered a few devices that misbehaved when operating in T10
PI mode. Allow T10 PI protection type to be overridden from userland.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/sd.c

@@ -261,6 +261,28 @@ sd_show_protection_type(struct device *dev, struct device_attribute *attr,
 	return snprintf(buf, 20, "%u\n", sdkp->protection_type);
 }
 
+static ssize_t
+sd_store_protection_type(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	struct scsi_disk *sdkp = to_scsi_disk(dev);
+	unsigned int val;
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	err = kstrtouint(buf, 10, &val);
+
+	if (err)
+		return err;
+
+	if (val >= 0 && val <= SD_DIF_TYPE3_PROTECTION)
+		sdkp->protection_type = val;
+
+	return count;
+}
+
 static ssize_t
 sd_show_protection_mode(struct device *dev, struct device_attribute *attr,
 			char *buf)
@@ -381,7 +403,8 @@ static struct device_attribute sd_disk_attrs[] = {
 	       sd_store_allow_restart),
 	__ATTR(manage_start_stop, S_IRUGO|S_IWUSR, sd_show_manage_start_stop,
 	       sd_store_manage_start_stop),
-	__ATTR(protection_type, S_IRUGO, sd_show_protection_type, NULL),
+	__ATTR(protection_type, S_IRUGO|S_IWUSR, sd_show_protection_type,
+	       sd_store_protection_type),
 	__ATTR(protection_mode, S_IRUGO, sd_show_protection_mode, NULL),
 	__ATTR(app_tag_own, S_IRUGO, sd_show_app_tag_own, NULL),
 	__ATTR(thin_provisioning, S_IRUGO, sd_show_thin_provisioning, NULL),