blkcg: move blkio_group_conf->weight to cfq

blkio_group_conf->weight is owned by cfq and has no reason to be
defined in blkcg core.  Replace it with cfq_group->dev_weight and let
conf setting functions directly set it.  If dev_weight is zero, the
cfqg doesn't have device specific weight configured.

Also, rename BLKIO_WEIGHT_* constants to CFQ_WEIGHT_* and rename
blkio_cgroup->weight to blkio_cgroup->cfq_weight.  We eventually want
per-policy storage in blkio_cgroup but just mark the ownership of the
field for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 16f6ee6..c0e239b 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -30,7 +30,7 @@
 static DEFINE_MUTEX(all_q_mutex);
 static LIST_HEAD(all_q_list);
 
-struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
+struct blkio_cgroup blkio_root_cgroup = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT };
 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
 static struct blkio_policy_type *blkio_policy[BLKIO_NR_POLICIES];
@@ -611,7 +611,7 @@
 	if (!blkcg)
 		return ERR_PTR(-ENOMEM);
 
-	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
+	blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
 	blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
 done:
 	spin_lock_init(&blkcg->lock);