blkcg: make blkcg_activate_policy() allow NULL ->pd_init_fn

blkg_create() allows NULL ->pd_init_fn() but blkcg_activate_policy()
doesn't.  As both in-kernel policies implement ->pd_init_fn, it
currently doesn't break anything.  Update blkcg_activate_policy() so
that its behavior is consistent with blkg_create().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9e9b0df339ee6c53d2c6adefede7730f01b9c24a..4defbbabc0ff20d2fd1caca44e266f20578db65d 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1083,7 +1083,8 @@ pd_prealloc:
                blkg->pd[pol->plid] = pd;
                pd->blkg = blkg;
                pd->plid = pol->plid;
-               pol->pd_init_fn(blkg);
+               if (pol->pd_init_fn)
+                       pol->pd_init_fn(blkg);
        }
 
        __set_bit(pol->plid, q->blkcg_pols);