blkio: Export some symbols from blkio as its user CFQ can be a module

o blkio controller is inside the kernel and cfq makes use of interfaces
  exported by blkio. CFQ can be a module too, hence export symbols used
  by CFQ.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 257dc6a..4f89b96 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -43,6 +43,9 @@
 	unsigned long sectors;
 };
 
+extern bool blkiocg_css_tryget(struct blkio_cgroup *blkcg);
+extern void blkiocg_css_put(struct blkio_cgroup *blkcg);
+
 #else
 
 struct blkio_group {