kref: minor cleanup

 - make warning smp-safe
 - result of atomic _unless_zero functions should be checked by caller
   to avoid use-after-free error
 - trivial whitespace fix.

Link: https://lkml.org/lkml/2013/4/12/391

Tested: compile x86, boot machine and run xfstests
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
[ Removed line-break, changed to use WARN_ON_ONCE()  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/kobject.c b/lib/kobject.c
index a654866..b7e29a6 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -529,7 +529,7 @@
 	return kobj;
 }
 
-static struct kobject *kobject_get_unless_zero(struct kobject *kobj)
+static struct kobject * __must_check kobject_get_unless_zero(struct kobject *kobj)
 {
 	if (!kref_get_unless_zero(&kobj->kref))
 		kobj = NULL;