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>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 52f0498..49ad96e 100644 (file)
--- 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);
 }