blkcg: add blkg_policy_data->plid

Add pd->plid so that the policy a pd belongs to can be identified
easily.  This will be used to implement hierarchical blkg_[rw]stats.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

2 files changed, 4 insertions, 1 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 10e1df9da46e..3a8de321d1f6 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -113,6 +113,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 
                 blkg->pd[i] = pd;
                 pd->blkg = blkg;
+                pd->plid = i;
 
                 /* invoke per-policy init */
                 if (pol->pd_init_fn)
@@ -908,6 +909,7 @@ int blkcg_activate_policy(struct request_queue *q,
 
                 blkg->pd[pol->plid] = pd;
                 pd->blkg = blkg;
+                pd->plid = pol->plid;
                 pol->pd_init_fn(blkg);
 
                 spin_unlock(&blkg->blkcg->lock);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 24462258200e..40f5b9768aac 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -81,8 +81,9 @@ struct blkg_rwstat {
  * beginning and pd_size can't be smaller than pd.
  */
 struct blkg_policy_data {
-        /* the blkg this per-policy data belongs to */
+        /* the blkg and policy id this per-policy data belongs to */
         struct blkcg_gq                 *blkg;
+        int                             plid;
 
         /* used during policy activation */
         struct list_head                alloc_node;