blkcg: minor updates around blkcg_policy_data

* Rename blkcg->pd[] to blkcg->cpd[] so that cpd is consistently used
  for blkcg_policy_data.

* Make blkcg_policy->cpd_init_fn() take blkcg_policy_data instead of
  blkcg.  This makes it consistent with blkg_policy_data methods and
  to-be-added cpd alloc/free methods.

* blkcg_policy_data->blkcg and cpd_to_blkcg() added so that
  cpd_init_fn() can determine the associated blkcg from
  blkcg_policy_data.

v2: blkcg_policy_data->blkcg initializations were missing.  Added.

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

1 files changed, 13 insertions, 11 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 8343450cffe2..247c42c8c83b 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -821,7 +821,7 @@ static void blkcg_css_free(struct cgroup_subsys_state *css)
         mutex_unlock(&blkcg_pol_mutex);
 
         for (i = 0; i < BLKCG_MAX_POLS; i++)
-                kfree(blkcg->pd[i]);
+                kfree(blkcg->cpd[i]);
         kfree(blkcg);
 }
 
@@ -857,15 +857,16 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
                 if (!pol || !pol->cpd_size)
                         continue;
 
-                BUG_ON(blkcg->pd[i]);
+                BUG_ON(blkcg->cpd[i]);
                 cpd = kzalloc(pol->cpd_size, GFP_KERNEL);
                 if (!cpd) {
                         ret = ERR_PTR(-ENOMEM);
                         goto free_pd_blkcg;
                 }
-                blkcg->pd[i] = cpd;
+                blkcg->cpd[i] = cpd;
+                cpd->blkcg = blkcg;
                 cpd->plid = i;
-                pol->cpd_init_fn(blkcg);
+                pol->cpd_init_fn(cpd);
         }
 
         spin_lock_init(&blkcg->lock);
@@ -881,7 +882,7 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 
 free_pd_blkcg:
         for (i--; i >= 0; i--)
-                kfree(blkcg->pd[i]);
+                kfree(blkcg->cpd[i]);
 free_blkcg:
         kfree(blkcg);
         mutex_unlock(&blkcg_pol_mutex);
@@ -1168,9 +1169,10 @@ int blkcg_policy_register(struct blkcg_policy *pol)
                                 goto err_free_cpds;
                         }
 
-                        blkcg->pd[pol->plid] = cpd;
+                        blkcg->cpd[pol->plid] = cpd;
+                        cpd->blkcg = blkcg;
                         cpd->plid = pol->plid;
-                        pol->cpd_init_fn(blkcg);
+                        pol->cpd_init_fn(cpd);
                 }
         }
 
@@ -1186,8 +1188,8 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 err_free_cpds:
         if (pol->cpd_size) {
                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
-                        kfree(blkcg->pd[pol->plid]);
-                        blkcg->pd[pol->plid] = NULL;
+                        kfree(blkcg->cpd[pol->plid]);
+                        blkcg->cpd[pol->plid] = NULL;
                 }
         }
         blkcg_policy[pol->plid] = NULL;
@@ -1222,8 +1224,8 @@ void blkcg_policy_unregister(struct blkcg_policy *pol)
 
         if (pol->cpd_size) {
                 list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
-                        kfree(blkcg->pd[pol->plid]);
-                        blkcg->pd[pol->plid] = NULL;
+                        kfree(blkcg->cpd[pol->plid]);
+                        blkcg->cpd[pol->plid] = NULL;
                 }
         }
         blkcg_policy[pol->plid] = NULL;