cgroup: remove css_parent()

cgroup in general is moving towards using cgroup_subsys_state as the
fundamental structural component and css_parent() was introduced to
convert from using cgroup->parent to css->parent.  It was quite some
time ago and we're moving forward with making css more prominent.

This patch drops the trivial wrapper css_parent() and let the users
dereference css->parent.  While at it, explicitly mark fields of css
which are public and immutable.

v2: New usage from device_cgroup.c converted.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Johannes Weiner <hannes@cmpxchg.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 7dbac4061b1c..ce14a31b1337 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -182,7 +182,7 @@ static inline bool is_devcg_online(const struct dev_cgroup *devcg)
 static int devcgroup_online(struct cgroup_subsys_state *css)
 {
         struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
-        struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css_parent(css));
+        struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent);
         int ret = 0;
 
         mutex_lock(&devcgroup_mutex);
@@ -455,7 +455,7 @@ static bool verify_new_ex(struct dev_cgroup *dev_cgroup,
 static int parent_has_perm(struct dev_cgroup *childcg,
                                   struct dev_exception_item *ex)
 {
-        struct dev_cgroup *parent = css_to_devcgroup(css_parent(&childcg->css));
+        struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
 
         if (!parent)
                 return 1;
@@ -476,7 +476,7 @@ static int parent_has_perm(struct dev_cgroup *childcg,
 static bool parent_allows_removal(struct dev_cgroup *childcg,
                                   struct dev_exception_item *ex)
 {
-        struct dev_cgroup *parent = css_to_devcgroup(css_parent(&childcg->css));
+        struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
 
         if (!parent)
                 return true;
@@ -614,7 +614,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
         char temp[12];          /* 11 + 1 characters needed for a u32 */
         int count, rc = 0;
         struct dev_exception_item ex;
-        struct dev_cgroup *parent = css_to_devcgroup(css_parent(&devcgroup->css));
+        struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
 
         if (!capable(CAP_SYS_ADMIN))
                 return -EPERM;