cgroup: always use cgroup_css()

cgroup_css() is the accessor for cgroup->subsys[] but is not used
consistently.  cgroup->subsys[] will become RCU protected and
cgroup_css() will grow synchronization sanity checks.  In preparation,
make all cgroup->subsys[] dereferences use cgroup_css() consistently.

This patch doesn't introduce any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 29 insertions, 29 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 52f0498db946..49ad96ee08e1 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -574,7 +574,7 @@ static struct css_set *find_existing_css_set(struct css_set *old_cset,
                         /* Subsystem is in this hierarchy. So we want
                          * the subsystem state from the new
                          * cgroup */
-                        template[i] = cgrp->subsys[i];
+                        template[i] = cgroup_css(cgrp, i);
                 } else {
                         /* Subsystem is not in this hierarchy, so we
                          * don't want to change the subsystem state */
@@ -871,7 +871,7 @@ static void cgroup_free_fn(struct work_struct *work)
          * Release the subsystem state objects.
          */
         for_each_root_subsys(cgrp->root, ss) {
-                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+                struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
 
                 ss->css_free(css);
         }
@@ -1067,27 +1067,27 @@ static int rebind_subsystems(struct cgroupfs_root *root,
 
                 if (bit & added_mask) {
                         /* We're binding this subsystem to this hierarchy */
-                        BUG_ON(cgrp->subsys[i]);
-                        BUG_ON(!cgroup_dummy_top->subsys[i]);
-                        BUG_ON(cgroup_dummy_top->subsys[i]->cgroup != cgroup_dummy_top);
+                        BUG_ON(cgroup_css(cgrp, i));
+                        BUG_ON(!cgroup_css(cgroup_dummy_top, i));
+                        BUG_ON(cgroup_css(cgroup_dummy_top, i)->cgroup != cgroup_dummy_top);
 
                         cgrp->subsys[i] = cgroup_dummy_top->subsys[i];
-                        cgrp->subsys[i]->cgroup = cgrp;
+                        cgroup_css(cgrp, i)->cgroup = cgrp;
                         list_move(&ss->sibling, &root->subsys_list);
                         ss->root = root;
                         if (ss->bind)
-                                ss->bind(cgrp->subsys[i]);
+                                ss->bind(cgroup_css(cgrp, i));
 
                         /* refcount was already taken, and we're keeping it */
                         root->subsys_mask |= bit;
                 } else if (bit & removed_mask) {
                         /* We're removing this subsystem */
-                        BUG_ON(cgrp->subsys[i] != cgroup_dummy_top->subsys[i]);
-                        BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
+                        BUG_ON(cgroup_css(cgrp, i) != cgroup_css(cgroup_dummy_top, i));
+                        BUG_ON(cgroup_css(cgrp, i)->cgroup != cgrp);
 
                         if (ss->bind)
-                                ss->bind(cgroup_dummy_top->subsys[i]);
-                        cgroup_dummy_top->subsys[i]->cgroup = cgroup_dummy_top;
+                                ss->bind(cgroup_css(cgroup_dummy_top, i));
+                        cgroup_css(cgroup_dummy_top, i)->cgroup = cgroup_dummy_top;
                         cgrp->subsys[i] = NULL;
                         cgroup_subsys[i]->root = &cgroup_dummy_root;
                         list_move(&ss->sibling, &cgroup_dummy_root.subsys_list);
@@ -2072,7 +2072,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
          * step 1: check that we can legitimately attach to the cgroup.
          */
         for_each_root_subsys(root, ss) {
-                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+                struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
 
                 if (ss->can_attach) {
                         retval = ss->can_attach(css, &tset);
@@ -2114,7 +2114,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
          * step 4: do subsystem attach callbacks.
          */
         for_each_root_subsys(root, ss) {
-                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+                struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
 
                 if (ss->attach)
                         ss->attach(css, &tset);
@@ -2136,7 +2136,7 @@ out_put_css_set_refs:
 out_cancel_attach:
         if (retval) {
                 for_each_root_subsys(root, ss) {
-                        struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+                        struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
 
                         if (ss == failed_ss)
                                 break;
@@ -2308,7 +2308,7 @@ static struct cgroup_subsys_state *cgroup_file_css(struct cfent *cfe)
         struct cgroup *cgrp = __d_cgrp(cfe->dentry->d_parent);
 
         if (cft->ss)
-                return cgrp->subsys[cft->ss->subsys_id];
+                return cgroup_css(cgrp, cft->ss->subsys_id);
         return &cgrp->dummy_css;
 }
 
@@ -4241,7 +4241,7 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 
         /* This cgroup is ready now */
         for_each_root_subsys(cgrp->root, ss) {
-                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+                struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
                 struct css_id *id = rcu_dereference_protected(css->id, true);
 
                 /*
@@ -4285,7 +4285,7 @@ static void init_cgroup_css(struct cgroup_subsys_state *css,
         css->id = NULL;
         if (cgrp == cgroup_dummy_top)
                 css->flags |= CSS_ROOT;
-        BUG_ON(cgrp->subsys[ss->subsys_id]);
+        BUG_ON(cgroup_css(cgrp, ss->subsys_id));
         cgrp->subsys[ss->subsys_id] = css;
 
         /*
@@ -4300,7 +4300,7 @@ static void init_cgroup_css(struct cgroup_subsys_state *css,
 /* invoke ->css_online() on a new CSS and mark it online if successful */
 static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
 {
-        struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+        struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
         int ret = 0;
 
         lockdep_assert_held(&cgroup_mutex);
@@ -4315,7 +4315,7 @@ static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
 static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
 {
-        struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+        struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
 
         lockdep_assert_held(&cgroup_mutex);
 
@@ -4400,7 +4400,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
         for_each_root_subsys(root, ss) {
                 struct cgroup_subsys_state *css;
 
-                css = ss->css_alloc(parent->subsys[ss->subsys_id]);
+                css = ss->css_alloc(cgroup_css(parent, ss->subsys_id));
                 if (IS_ERR(css)) {
                         err = PTR_ERR(css);
                         goto err_free_all;
@@ -4477,7 +4477,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 
 err_free_all:
         for_each_root_subsys(root, ss) {
-                struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
+                struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);