2 files changed, 1 insertions, 284 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 3561d305b1e0..39c1d9469677 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -612,11 +612,6 @@ struct cgroup_subsys {
         int subsys_id;
         int disabled;
         int early_init;
-        /*
-         * True if this subsys uses ID. ID is not available before cgroup_init()
-         * (not available in early_init time.)
-         */
-        bool use_id;
 
         /*
          * If %false, this subsystem is properly hierarchical -
@@ -642,9 +637,6 @@ struct cgroup_subsys {
          */
         struct cgroupfs_root *root;
         struct list_head sibling;
-        /* used when use_id == true */
-        struct idr idr;
-        spinlock_t id_lock;
 
         /* list of cftype_sets */
         struct list_head cftsets;
@@ -875,35 +867,6 @@ int css_scan_tasks(struct cgroup_subsys_state *css,
 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
 
-/*
- * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
- * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
- * CSS ID is assigned at cgroup allocation (create) automatically
- * and removed when subsys calls free_css_id() function. This is because
- * the lifetime of cgroup_subsys_state is subsys's matter.
- *
- * Looking up and scanning function should be called under rcu_read_lock().
- * Taking cgroup_mutex is not necessary for following calls.
- * But the css returned by this routine can be "not populated yet" or "being
- * destroyed". The caller should check css and cgroup's status.
- */
-
-/*
- * Typically Called at ->destroy(), or somewhere the subsys frees
- * cgroup_subsys_state.
- */
-void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
-
-/* Find a cgroup_subsys_state which has given ID */
-
-struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
-
-/* Returns true if root is ancestor of cg */
-bool css_is_ancestor(struct cgroup_subsys_state *cg,
-                     const struct cgroup_subsys_state *root);
-
-/* Get id and depth of css */
-unsigned short css_id(struct cgroup_subsys_state *css);
 struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
                                          struct cgroup_subsys *ss);
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2418b6e71a85..a5629f1df13a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -125,38 +125,6 @@ struct cfent {
 };
 
 /*
- * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
- * cgroup_subsys->use_id != 0.
- */
-#define CSS_ID_MAX      (65535)
-struct css_id {
-        /*
-         * The css to which this ID points. This pointer is set to valid value
-         * after cgroup is populated. If cgroup is removed, this will be NULL.
-         * This pointer is expected to be RCU-safe because destroy()
-         * is called after synchronize_rcu(). But for safe use, css_tryget()
-         * should be used for avoiding race.
-         */
-        struct cgroup_subsys_state __rcu *css;
-        /*
-         * ID of this css.
-         */
-        unsigned short id;
-        /*
-         * Depth in hierarchy which this ID belongs to.
-         */
-        unsigned short depth;
-        /*
-         * ID is freed by RCU. (and lookup routine is RCU safe.)
-         */
-        struct rcu_head rcu_head;
-        /*
-         * Hierarchy of CSS ID belongs to.
-         */
-        unsigned short stack[0]; /* Array of Length (depth+1) */
-};
-
-/*
  * cgroup_event represents events which userspace want to receive.
  */
 struct cgroup_event {
@@ -387,9 +355,6 @@ struct cgrp_cset_link {
 static struct css_set init_css_set;
 static struct cgrp_cset_link init_cgrp_cset_link;
 
-static int cgroup_init_idr(struct cgroup_subsys *ss,
-                           struct cgroup_subsys_state *css);
-
 /*
  * css_set_lock protects the list of css_set objects, and the chain of
  * tasks off each css_set.  Nests outside task->alloc_lock due to
@@ -841,8 +806,6 @@ static struct backing_dev_info cgroup_backing_dev_info = {
         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
-static int alloc_css_id(struct cgroup_subsys_state *child_css);
-
 static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
 {
         struct inode *inode = new_inode(sb);
@@ -4242,21 +4205,6 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
                                 goto err;
                 }
         }
-
-        /* This cgroup is ready now */
-        for_each_root_subsys(cgrp->root, ss) {
-                struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
-                struct css_id *id = rcu_dereference_protected(css->id, true);
-
-                /*
-                 * Update id->css pointer and make this css visible from
-                 * CSS ID functions. This pointer will be dereferened
-                 * from RCU-read-side without locks.
-                 */
-                if (id)
-                        rcu_assign_pointer(id->css, css);
-        }
-
         return 0;
 err:
         cgroup_clear_dir(cgrp, subsys_mask);
@@ -4325,7 +4273,6 @@ static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
         css->cgroup = cgrp;
         css->ss = ss;
         css->flags = 0;
-        css->id = NULL;
 
         if (cgrp->parent)
                 css->parent = cgroup_css(cgrp->parent, ss);
@@ -4457,12 +4404,6 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
                         goto err_free_all;
 
                 init_css(css, ss, cgrp);
-
-                if (ss->use_id) {
-                        err = alloc_css_id(css);
-                        if (err)
-                                goto err_free_all;
-                }
         }
 
         /*
@@ -4927,12 +4868,6 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
 
         /* our new subsystem will be attached to the dummy hierarchy. */
         init_css(css, ss, cgroup_dummy_top);
-        /* init_idr must be after init_css() because it sets css->id. */
-        if (ss->use_id) {
-                ret = cgroup_init_idr(ss, css);
-                if (ret)
-                        goto err_unload;
-        }
 
         /*
          * Now we need to entangle the css into the existing css_sets. unlike
@@ -4998,9 +4933,6 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
 
         offline_css(cgroup_css(cgroup_dummy_top, ss));
 
-        if (ss->use_id)
-                idr_destroy(&ss->idr);
-
         /* deassign the subsys_id */
         cgroup_subsys[ss->subsys_id] = NULL;
 
@@ -5027,8 +4959,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
         /*
          * remove subsystem's css from the cgroup_dummy_top and free it -
          * need to free before marking as null because ss->css_free needs
-         * the cgrp->subsys pointer to find their state. note that this
-         * also takes care of freeing the css_id.
+         * the cgrp->subsys pointer to find their state.
          */
         ss->css_free(cgroup_css(cgroup_dummy_top, ss));
         RCU_INIT_POINTER(cgroup_dummy_top->subsys[ss->subsys_id], NULL);
@@ -5099,8 +5030,6 @@ int __init cgroup_init(void)
         for_each_builtin_subsys(ss, i) {
                 if (!ss->early_init)
                         cgroup_init_subsys(ss);
-                if (ss->use_id)
-                        cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
         }
 
         /* allocate id for the dummy hierarchy */
@@ -5520,181 +5449,6 @@ static int __init cgroup_disable(char *str)
 }
 __setup("cgroup_disable=", cgroup_disable);
 
-/*
- * Functons for CSS ID.
- */
-
-/* to get ID other than 0, this should be called when !cgroup_is_dead() */
-unsigned short css_id(struct cgroup_subsys_state *css)
-{
-        struct css_id *cssid;
-
-        /*
-         * This css_id() can return correct value when somone has refcnt
-         * on this or this is under rcu_read_lock(). Once css->id is allocated,
-         * it's unchanged until freed.
-         */
-        cssid = rcu_dereference_raw(css->id);
-
-        if (cssid)
-                return cssid->id;
-        return 0;
-}
-EXPORT_SYMBOL_GPL(css_id);
-
-/**
- *  css_is_ancestor - test "root" css is an ancestor of "child"
- * @child: the css to be tested.
- * @root: the css supporsed to be an ancestor of the child.
- *
- * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
- * this function reads css->id, the caller must hold rcu_read_lock().
- * But, considering usual usage, the csses should be valid objects after test.
- * Assuming that the caller will do some action to the child if this returns
- * returns true, the caller must take "child";s reference count.
- * If "child" is valid object and this returns true, "root" is valid, too.
- */
-
-bool css_is_ancestor(struct cgroup_subsys_state *child,
-                    const struct cgroup_subsys_state *root)
-{
-        struct css_id *child_id;
-        struct css_id *root_id;
-
-        child_id  = rcu_dereference(child->id);
-        if (!child_id)
-                return false;
-        root_id = rcu_dereference(root->id);
-        if (!root_id)
-                return false;
-        if (child_id->depth < root_id->depth)
-                return false;
-        if (child_id->stack[root_id->depth] != root_id->id)
-                return false;
-        return true;
-}
-
-void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
-{
-        struct css_id *id = rcu_dereference_protected(css->id, true);
-
-        /* When this is called before css_id initialization, id can be NULL */
-        if (!id)
-                return;
-
-        BUG_ON(!ss->use_id);
-
-        rcu_assign_pointer(id->css, NULL);
-        rcu_assign_pointer(css->id, NULL);
-        spin_lock(&ss->id_lock);
-        idr_remove(&ss->idr, id->id);
-        spin_unlock(&ss->id_lock);
-        kfree_rcu(id, rcu_head);
-}
-EXPORT_SYMBOL_GPL(free_css_id);
-
-/*
- * This is called by init or create(). Then, calls to this function are
- * always serialized (By cgroup_mutex() at create()).
- */
-
-static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
-{
-        struct css_id *newid;
-        int ret, size;
-
-        BUG_ON(!ss->use_id);
-
-        size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
-        newid = kzalloc(size, GFP_KERNEL);
-        if (!newid)
-                return ERR_PTR(-ENOMEM);
-
-        idr_preload(GFP_KERNEL);
-        spin_lock(&ss->id_lock);
-        /* Don't use 0. allocates an ID of 1-65535 */
-        ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
-        spin_unlock(&ss->id_lock);
-        idr_preload_end();
-
-        /* Returns error when there are no free spaces for new ID.*/
-        if (ret < 0)
-                goto err_out;
-
-        newid->id = ret;
-        newid->depth = depth;
-        return newid;
-err_out:
-        kfree(newid);
-        return ERR_PTR(ret);
-
-}
-
-static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
-                                            struct cgroup_subsys_state *rootcss)
-{
-        struct css_id *newid;
-
-        spin_lock_init(&ss->id_lock);
-        idr_init(&ss->idr);
-
-        newid = get_new_cssid(ss, 0);
-        if (IS_ERR(newid))
-                return PTR_ERR(newid);
-
-        newid->stack[0] = newid->id;
-        RCU_INIT_POINTER(newid->css, rootcss);
-        RCU_INIT_POINTER(rootcss->id, newid);
-        return 0;
-}
-
-static int alloc_css_id(struct cgroup_subsys_state *child_css)
-{
-        struct cgroup_subsys_state *parent_css = css_parent(child_css);
-        struct css_id *child_id, *parent_id;
-        int i, depth;
-
-        parent_id = rcu_dereference_protected(parent_css->id, true);
-        depth = parent_id->depth + 1;
-
-        child_id = get_new_cssid(child_css->ss, depth);
-        if (IS_ERR(child_id))
-                return PTR_ERR(child_id);
-
-        for (i = 0; i < depth; i++)
-                child_id->stack[i] = parent_id->stack[i];
-        child_id->stack[depth] = child_id->id;
-        /*
-         * child_id->css pointer will be set after this cgroup is available
-         * see cgroup_populate_dir()
-         */
-        rcu_assign_pointer(child_css->id, child_id);
-
-        return 0;
-}
-
-/**
- * css_lookup - lookup css by id
- * @ss: cgroup subsys to be looked into.
- * @id: the id
- *
- * Returns pointer to cgroup_subsys_state if there is valid one with id.
- * NULL if not. Should be called under rcu_read_lock()
- */
-struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
-{
-        struct css_id *cssid = NULL;
-
-        BUG_ON(!ss->use_id);
-        cssid = idr_find(&ss->idr, id);
-
-        if (unlikely(!cssid))
-                return NULL;
-
-        return rcu_dereference(cssid->css);
-}
-EXPORT_SYMBOL_GPL(css_lookup);
-
 /**
  * css_from_dir - get corresponding css from the dentry of a cgroup dir
  * @dentry: directory dentry of interest