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);
 
                 if (css) {
                         percpu_ref_cancel_init(&css->refcnt);
@@ -4590,7 +4590,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
          */
         atomic_set(&cgrp->css_kill_cnt, 1);
         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);
 
                 /*
                  * Killing would put the base ref, but we need to keep it
@@ -4676,7 +4676,7 @@ static void cgroup_offline_fn(struct work_struct *work)
          * destruction happens only after all css's are released.
          */
         for_each_root_subsys(cgrp->root, ss)
-                css_put(cgrp->subsys[ss->subsys_id]);
+                css_put(cgroup_css(cgrp, ss->subsys_id));
 
         /* delete this cgroup from parent->children */
         list_del_rcu(&cgrp->sibling);
@@ -4741,7 +4741,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
         /* Create the top cgroup state for this subsystem */
         list_add(&ss->sibling, &cgroup_dummy_root.subsys_list);
         ss->root = &cgroup_dummy_root;
-        css = ss->css_alloc(cgroup_dummy_top->subsys[ss->subsys_id]);
+        css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss->subsys_id));
         /* We don't handle early failures gracefully */
         BUG_ON(IS_ERR(css));
         init_cgroup_css(css, ss, cgroup_dummy_top);
@@ -4820,7 +4820,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
          * struct, so this can happen first (i.e. before the dummy root
          * attachment).
          */
-        css = ss->css_alloc(cgroup_dummy_top->subsys[ss->subsys_id]);
+        css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss->subsys_id));
         if (IS_ERR(css)) {
                 /* failure case - need to deassign the cgroup_subsys[] slot. */
                 cgroup_subsys[ss->subsys_id] = NULL;
@@ -4936,7 +4936,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
          * the cgrp->subsys pointer to find their state. note that this
          * also takes care of freeing the css_id.
          */
-        ss->css_free(cgroup_dummy_top->subsys[ss->subsys_id]);
+        ss->css_free(cgroup_css(cgroup_dummy_top, ss->subsys_id));
         cgroup_dummy_top->subsys[ss->subsys_id] = NULL;
 
         mutex_unlock(&cgroup_mutex);
@@ -5562,8 +5562,8 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
         struct css_id *child_id, *parent_id;
 
         subsys_id = ss->subsys_id;
-        parent_css = parent->subsys[subsys_id];
-        child_css = child->subsys[subsys_id];
+        parent_css = cgroup_css(parent, subsys_id);
+        child_css = cgroup_css(child, subsys_id);
         parent_id = rcu_dereference_protected(parent_css->id, true);
         depth = parent_id->depth + 1;
 
@@ -5624,7 +5624,7 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
 
         /* get cgroup */
         cgrp = __d_cgrp(f->f_dentry);
-        css = cgrp->subsys[id];
+        css = cgroup_css(cgrp, id);
         return css ? css : ERR_PTR(-ENOENT);
 }