blkcg: remove unnecessary blkcg_root handling from css_alloc/free paths

blkcg_css_alloc() bypasses policy data allocation and blkcg_css_free()
bypasses policy data and blkcg freeing for blkcg_root.  There's no
reason to to treat policy data any differently for blkcg_root.  If the
root css gets allocated after policies are registered, policy
registration path will add policy data; otherwise, the alloc path
will.  The free path isn't never invoked for root csses.

This patch removes the unnecessary special handling of blkcg_root from
css_alloc/free paths.

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 cd251830038a6066d80176e0382552dd6d25b1d1..f91a4e09e0c9bf6c265dbe82fee333b2e432780d 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -823,18 +823,15 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css)
 static void blkcg_css_free(struct cgroup_subsys_state *css)
 {
        struct blkcg *blkcg = css_to_blkcg(css);
+       int i;
 
        mutex_lock(&blkcg_pol_mutex);
        list_del(&blkcg->all_blkcgs_node);
        mutex_unlock(&blkcg_pol_mutex);
 
-       if (blkcg != &blkcg_root) {
-               int i;
-
-               for (i = 0; i < BLKCG_MAX_POLS; i++)
-                       kfree(blkcg->pd[i]);
-               kfree(blkcg);
-       }
+       for (i = 0; i < BLKCG_MAX_POLS; i++)
+               kfree(blkcg->pd[i]);
+       kfree(blkcg);
 }
 
 static struct cgroup_subsys_state *
@@ -848,13 +845,12 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 
        if (!parent_css) {
                blkcg = &blkcg_root;
-               goto done;
-       }
-
-       blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
-       if (!blkcg) {
-               ret = ERR_PTR(-ENOMEM);
-               goto free_blkcg;
+       } else {
+               blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
+               if (!blkcg) {
+                       ret = ERR_PTR(-ENOMEM);
+                       goto free_blkcg;
+               }
        }
 
        for (i = 0; i < BLKCG_MAX_POLS ; i++) {
@@ -881,7 +877,6 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
                pol->cpd_init_fn(blkcg);
        }
 
-done:
        spin_lock_init(&blkcg->lock);
        INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT);
        INIT_HLIST_HEAD(&blkcg->blkg_list);