staging: lustre: obdclass: eliminate NULL error return

Always return an ERR_PTR() on errors, never return a NULL,
in lu_object_find_slice().  Also clean up callers who
no longer need special case handling of NULL returns.
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5858
Reviewed-on: http://review.whamcloud.com/12554Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/obdclass/lu_object.c

@@ -767,13 +767,15 @@ struct lu_object *lu_object_find_slice(const struct lu_env *env,
 	struct lu_object *obj;
 
 	top = lu_object_find(env, dev, f, conf);
-	if (!IS_ERR(top)) {
-		obj = lu_object_locate(top->lo_header, dev->ld_type);
-		if (!obj)
-			lu_object_put(env, top);
-	} else {
-		obj = top;
+	if (IS_ERR(top))
+		return top;
+
+	obj = lu_object_locate(top->lo_header, dev->ld_type);
+	if (unlikely(!obj)) {
+		lu_object_put(env, top);
+		obj = ERR_PTR(-ENOENT);
 	}
+
 	return obj;
 }
 EXPORT_SYMBOL(lu_object_find_slice);