USB: handle errors in power/level attribute

This patch (as906) improves the error handling for the USB power/level
attribute file.  If an error occurs, the original power-level settings
will be restored.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/sysfs.c

@@ -232,12 +232,15 @@ set_level(struct device *dev, struct device_attribute *attr,
 	int len = count;
 	char *cp;
 	int rc = 0;
+	int old_autosuspend_disabled, old_autoresume_disabled;
 
 	cp = memchr(buf, '\n', count);
 	if (cp)
 		len = cp - buf;
 
 	usb_lock_device(udev);
+	old_autosuspend_disabled = udev->autosuspend_disabled;
+	old_autoresume_disabled = udev->autoresume_disabled;
 
 	/* Setting the flags without calling usb_pm_lock is a subject to
 	 * races, but who cares...
@@ -263,6 +266,10 @@ set_level(struct device *dev, struct device_attribute *attr,
 	} else
 		rc = -EINVAL;
 
+	if (rc) {
+		udev->autosuspend_disabled = old_autosuspend_disabled;
+		udev->autoresume_disabled = old_autoresume_disabled;
+	}
 	usb_unlock_device(udev);
 	return (rc < 0 ? rc : count);
 }