Add wait_for_completion_killable

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
diff --git a/include/linux/completion.h b/include/linux/completion.h
index 33d6aaf..d2961b6 100644
--- a/include/linux/completion.h
+++ b/include/linux/completion.h
@@ -44,6 +44,7 @@
 
 extern void wait_for_completion(struct completion *);
 extern int wait_for_completion_interruptible(struct completion *x);
+extern int wait_for_completion_killable(struct completion *x);
 extern unsigned long wait_for_completion_timeout(struct completion *x,
 						   unsigned long timeout);
 extern unsigned long wait_for_completion_interruptible_timeout(