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-rw-r--r--include/linux/cgroup.h971
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diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
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index 000000000..b9cb94c31
--- /dev/null
+++ b/include/linux/cgroup.h
@@ -0,0 +1,971 @@
+#ifndef _LINUX_CGROUP_H
+#define _LINUX_CGROUP_H
+/*
+ * cgroup interface
+ *
+ * Copyright (C) 2003 BULL SA
+ * Copyright (C) 2004-2006 Silicon Graphics, Inc.
+ *
+ */
+
+#include <linux/sched.h>
+#include <linux/cpumask.h>
+#include <linux/nodemask.h>
+#include <linux/rcupdate.h>
+#include <linux/rculist.h>
+#include <linux/cgroupstats.h>
+#include <linux/rwsem.h>
+#include <linux/idr.h>
+#include <linux/workqueue.h>
+#include <linux/fs.h>
+#include <linux/percpu-refcount.h>
+#include <linux/seq_file.h>
+#include <linux/kernfs.h>
+#include <linux/wait.h>
+
+#ifdef CONFIG_CGROUPS
+
+struct cgroup_root;
+struct cgroup_subsys;
+struct cgroup;
+
+extern int cgroup_init_early(void);
+extern int cgroup_init(void);
+extern void cgroup_fork(struct task_struct *p);
+extern void cgroup_post_fork(struct task_struct *p);
+extern void cgroup_exit(struct task_struct *p);
+extern int cgroupstats_build(struct cgroupstats *stats,
+ struct dentry *dentry);
+
+extern int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *tsk);
+
+/* define the enumeration of all cgroup subsystems */
+#define SUBSYS(_x) _x ## _cgrp_id,
+enum cgroup_subsys_id {
+#include <linux/cgroup_subsys.h>
+ CGROUP_SUBSYS_COUNT,
+};
+#undef SUBSYS
+
+/*
+ * Per-subsystem/per-cgroup state maintained by the system. This is the
+ * fundamental structural building block that controllers deal with.
+ *
+ * Fields marked with "PI:" are public and immutable and may be accessed
+ * directly without synchronization.
+ */
+struct cgroup_subsys_state {
+ /* PI: the cgroup that this css is attached to */
+ struct cgroup *cgroup;
+
+ /* PI: the cgroup subsystem that this css is attached to */
+ struct cgroup_subsys *ss;
+
+ /* reference count - access via css_[try]get() and css_put() */
+ struct percpu_ref refcnt;
+
+ /* PI: the parent css */
+ struct cgroup_subsys_state *parent;
+
+ /* siblings list anchored at the parent's ->children */
+ struct list_head sibling;
+ struct list_head children;
+
+ /*
+ * PI: Subsys-unique ID. 0 is unused and root is always 1. The
+ * matching css can be looked up using css_from_id().
+ */
+ int id;
+
+ unsigned int flags;
+
+ /*
+ * Monotonically increasing unique serial number which defines a
+ * uniform order among all csses. It's guaranteed that all
+ * ->children lists are in the ascending order of ->serial_nr and
+ * used to allow interrupting and resuming iterations.
+ */
+ u64 serial_nr;
+
+ /* percpu_ref killing and RCU release */
+ struct rcu_head rcu_head;
+ struct work_struct destroy_work;
+};
+
+/* bits in struct cgroup_subsys_state flags field */
+enum {
+ CSS_NO_REF = (1 << 0), /* no reference counting for this css */
+ CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
+ CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */
+};
+
+/**
+ * css_get - obtain a reference on the specified css
+ * @css: target css
+ *
+ * The caller must already have a reference.
+ */
+static inline void css_get(struct cgroup_subsys_state *css)
+{
+ if (!(css->flags & CSS_NO_REF))
+ percpu_ref_get(&css->refcnt);
+}
+
+/**
+ * css_get_many - obtain references on the specified css
+ * @css: target css
+ * @n: number of references to get
+ *
+ * The caller must already have a reference.
+ */
+static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n)
+{
+ if (!(css->flags & CSS_NO_REF))
+ percpu_ref_get_many(&css->refcnt, n);
+}
+
+/**
+ * css_tryget - try to obtain a reference on the specified css
+ * @css: target css
+ *
+ * Obtain a reference on @css unless it already has reached zero and is
+ * being released. This function doesn't care whether @css is on or
+ * offline. The caller naturally needs to ensure that @css is accessible
+ * but doesn't have to be holding a reference on it - IOW, RCU protected
+ * access is good enough for this function. Returns %true if a reference
+ * count was successfully obtained; %false otherwise.
+ */
+static inline bool css_tryget(struct cgroup_subsys_state *css)
+{
+ if (!(css->flags & CSS_NO_REF))
+ return percpu_ref_tryget(&css->refcnt);
+ return true;
+}
+
+/**
+ * css_tryget_online - try to obtain a reference on the specified css if online
+ * @css: target css
+ *
+ * Obtain a reference on @css if it's online. The caller naturally needs
+ * to ensure that @css is accessible but doesn't have to be holding a
+ * reference on it - IOW, RCU protected access is good enough for this
+ * function. Returns %true if a reference count was successfully obtained;
+ * %false otherwise.
+ */
+static inline bool css_tryget_online(struct cgroup_subsys_state *css)
+{
+ if (!(css->flags & CSS_NO_REF))
+ return percpu_ref_tryget_live(&css->refcnt);
+ return true;
+}
+
+/**
+ * css_put - put a css reference
+ * @css: target css
+ *
+ * Put a reference obtained via css_get() and css_tryget_online().
+ */
+static inline void css_put(struct cgroup_subsys_state *css)
+{
+ if (!(css->flags & CSS_NO_REF))
+ percpu_ref_put(&css->refcnt);
+}
+
+/**
+ * css_put_many - put css references
+ * @css: target css
+ * @n: number of references to put
+ *
+ * Put references obtained via css_get() and css_tryget_online().
+ */
+static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
+{
+ if (!(css->flags & CSS_NO_REF))
+ percpu_ref_put_many(&css->refcnt, n);
+}
+
+/* bits in struct cgroup flags field */
+enum {
+ /* Control Group requires release notifications to userspace */
+ CGRP_NOTIFY_ON_RELEASE,
+ /*
+ * Clone the parent's configuration when creating a new child
+ * cpuset cgroup. For historical reasons, this option can be
+ * specified at mount time and thus is implemented here.
+ */
+ CGRP_CPUSET_CLONE_CHILDREN,
+};
+
+struct cgroup {
+ /* self css with NULL ->ss, points back to this cgroup */
+ struct cgroup_subsys_state self;
+
+ unsigned long flags; /* "unsigned long" so bitops work */
+
+ /*
+ * idr allocated in-hierarchy ID.
+ *
+ * ID 0 is not used, the ID of the root cgroup is always 1, and a
+ * new cgroup will be assigned with a smallest available ID.
+ *
+ * Allocating/Removing ID must be protected by cgroup_mutex.
+ */
+ int id;
+
+ /*
+ * If this cgroup contains any tasks, it contributes one to
+ * populated_cnt. All children with non-zero popuplated_cnt of
+ * their own contribute one. The count is zero iff there's no task
+ * in this cgroup or its subtree.
+ */
+ int populated_cnt;
+
+ struct kernfs_node *kn; /* cgroup kernfs entry */
+ struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */
+
+ /*
+ * The bitmask of subsystems enabled on the child cgroups.
+ * ->subtree_control is the one configured through
+ * "cgroup.subtree_control" while ->child_subsys_mask is the
+ * effective one which may have more subsystems enabled.
+ * Controller knobs are made available iff it's enabled in
+ * ->subtree_control.
+ */
+ unsigned int subtree_control;
+ unsigned int child_subsys_mask;
+
+ /* Private pointers for each registered subsystem */
+ struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
+
+ struct cgroup_root *root;
+
+ /*
+ * List of cgrp_cset_links pointing at css_sets with tasks in this
+ * cgroup. Protected by css_set_lock.
+ */
+ struct list_head cset_links;
+
+ /*
+ * On the default hierarchy, a css_set for a cgroup with some
+ * susbsys disabled will point to css's which are associated with
+ * the closest ancestor which has the subsys enabled. The
+ * following lists all css_sets which point to this cgroup's css
+ * for the given subsystem.
+ */
+ struct list_head e_csets[CGROUP_SUBSYS_COUNT];
+
+ /*
+ * list of pidlists, up to two for each namespace (one for procs, one
+ * for tasks); created on demand.
+ */
+ struct list_head pidlists;
+ struct mutex pidlist_mutex;
+
+ /* used to wait for offlining of csses */
+ wait_queue_head_t offline_waitq;
+
+ /* used to schedule release agent */
+ struct work_struct release_agent_work;
+};
+
+#define MAX_CGROUP_ROOT_NAMELEN 64
+
+/* cgroup_root->flags */
+enum {
+ CGRP_ROOT_SANE_BEHAVIOR = (1 << 0), /* __DEVEL__sane_behavior specified */
+ CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
+ CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
+};
+
+/*
+ * A cgroup_root represents the root of a cgroup hierarchy, and may be
+ * associated with a kernfs_root to form an active hierarchy. This is
+ * internal to cgroup core. Don't access directly from controllers.
+ */
+struct cgroup_root {
+ struct kernfs_root *kf_root;
+
+ /* The bitmask of subsystems attached to this hierarchy */
+ unsigned int subsys_mask;
+
+ /* Unique id for this hierarchy. */
+ int hierarchy_id;
+
+ /* The root cgroup. Root is destroyed on its release. */
+ struct cgroup cgrp;
+
+ /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
+ atomic_t nr_cgrps;
+
+ /* A list running through the active hierarchies */
+ struct list_head root_list;
+
+ /* Hierarchy-specific flags */
+ unsigned int flags;
+
+ /* IDs for cgroups in this hierarchy */
+ struct idr cgroup_idr;
+
+ /* The path to use for release notifications. */
+ char release_agent_path[PATH_MAX];
+
+ /* The name for this hierarchy - may be empty */
+ char name[MAX_CGROUP_ROOT_NAMELEN];
+};
+
+/*
+ * A css_set is a structure holding pointers to a set of
+ * cgroup_subsys_state objects. This saves space in the task struct
+ * object and speeds up fork()/exit(), since a single inc/dec and a
+ * list_add()/del() can bump the reference count on the entire cgroup
+ * set for a task.
+ */
+
+struct css_set {
+
+ /* Reference count */
+ atomic_t refcount;
+
+ /*
+ * List running through all cgroup groups in the same hash
+ * slot. Protected by css_set_lock
+ */
+ struct hlist_node hlist;
+
+ /*
+ * Lists running through all tasks using this cgroup group.
+ * mg_tasks lists tasks which belong to this cset but are in the
+ * process of being migrated out or in. Protected by
+ * css_set_rwsem, but, during migration, once tasks are moved to
+ * mg_tasks, it can be read safely while holding cgroup_mutex.
+ */
+ struct list_head tasks;
+ struct list_head mg_tasks;
+
+ /*
+ * List of cgrp_cset_links pointing at cgroups referenced from this
+ * css_set. Protected by css_set_lock.
+ */
+ struct list_head cgrp_links;
+
+ /* the default cgroup associated with this css_set */
+ struct cgroup *dfl_cgrp;
+
+ /*
+ * Set of subsystem states, one for each subsystem. This array is
+ * immutable after creation apart from the init_css_set during
+ * subsystem registration (at boot time).
+ */
+ struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
+
+ /*
+ * List of csets participating in the on-going migration either as
+ * source or destination. Protected by cgroup_mutex.
+ */
+ struct list_head mg_preload_node;
+ struct list_head mg_node;
+
+ /*
+ * If this cset is acting as the source of migration the following
+ * two fields are set. mg_src_cgrp is the source cgroup of the
+ * on-going migration and mg_dst_cset is the destination cset the
+ * target tasks on this cset should be migrated to. Protected by
+ * cgroup_mutex.
+ */
+ struct cgroup *mg_src_cgrp;
+ struct css_set *mg_dst_cset;
+
+ /*
+ * On the default hierarhcy, ->subsys[ssid] may point to a css
+ * attached to an ancestor instead of the cgroup this css_set is
+ * associated with. The following node is anchored at
+ * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
+ * iterate through all css's attached to a given cgroup.
+ */
+ struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
+
+ /* For RCU-protected deletion */
+ struct rcu_head rcu_head;
+};
+
+/*
+ * struct cftype: handler definitions for cgroup control files
+ *
+ * When reading/writing to a file:
+ * - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
+ * - the 'cftype' of the file is file->f_path.dentry->d_fsdata
+ */
+
+/* cftype->flags */
+enum {
+ CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
+ CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
+ CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
+
+ /* internal flags, do not use outside cgroup core proper */
+ __CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */
+ __CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */
+};
+
+#define MAX_CFTYPE_NAME 64
+
+struct cftype {
+ /*
+ * By convention, the name should begin with the name of the
+ * subsystem, followed by a period. Zero length string indicates
+ * end of cftype array.
+ */
+ char name[MAX_CFTYPE_NAME];
+ int private;
+ /*
+ * If not 0, file mode is set to this value, otherwise it will
+ * be figured out automatically
+ */
+ umode_t mode;
+
+ /*
+ * The maximum length of string, excluding trailing nul, that can
+ * be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
+ */
+ size_t max_write_len;
+
+ /* CFTYPE_* flags */
+ unsigned int flags;
+
+ /*
+ * Fields used for internal bookkeeping. Initialized automatically
+ * during registration.
+ */
+ struct cgroup_subsys *ss; /* NULL for cgroup core files */
+ struct list_head node; /* anchored at ss->cfts */
+ struct kernfs_ops *kf_ops;
+
+ /*
+ * read_u64() is a shortcut for the common case of returning a
+ * single integer. Use it in place of read()
+ */
+ u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
+ /*
+ * read_s64() is a signed version of read_u64()
+ */
+ s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
+
+ /* generic seq_file read interface */
+ int (*seq_show)(struct seq_file *sf, void *v);
+
+ /* optional ops, implement all or none */
+ void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
+ void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
+ void (*seq_stop)(struct seq_file *sf, void *v);
+
+ /*
+ * write_u64() is a shortcut for the common case of accepting
+ * a single integer (as parsed by simple_strtoull) from
+ * userspace. Use in place of write(); return 0 or error.
+ */
+ int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
+ u64 val);
+ /*
+ * write_s64() is a signed version of write_u64()
+ */
+ int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
+ s64 val);
+
+ /*
+ * write() is the generic write callback which maps directly to
+ * kernfs write operation and overrides all other operations.
+ * Maximum write size is determined by ->max_write_len. Use
+ * of_css/cft() to access the associated css and cft.
+ */
+ ssize_t (*write)(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lock_class_key lockdep_key;
+#endif
+};
+
+extern struct cgroup_root cgrp_dfl_root;
+extern struct css_set init_css_set;
+
+/**
+ * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
+ * @cgrp: the cgroup of interest
+ *
+ * The default hierarchy is the v2 interface of cgroup and this function
+ * can be used to test whether a cgroup is on the default hierarchy for
+ * cases where a subsystem should behave differnetly depending on the
+ * interface version.
+ *
+ * The set of behaviors which change on the default hierarchy are still
+ * being determined and the mount option is prefixed with __DEVEL__.
+ *
+ * List of changed behaviors:
+ *
+ * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
+ * and "name" are disallowed.
+ *
+ * - When mounting an existing superblock, mount options should match.
+ *
+ * - Remount is disallowed.
+ *
+ * - rename(2) is disallowed.
+ *
+ * - "tasks" is removed. Everything should be at process granularity. Use
+ * "cgroup.procs" instead.
+ *
+ * - "cgroup.procs" is not sorted. pids will be unique unless they got
+ * recycled inbetween reads.
+ *
+ * - "release_agent" and "notify_on_release" are removed. Replacement
+ * notification mechanism will be implemented.
+ *
+ * - "cgroup.clone_children" is removed.
+ *
+ * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
+ * and its descendants contain no task; otherwise, 1. The file also
+ * generates kernfs notification which can be monitored through poll and
+ * [di]notify when the value of the file changes.
+ *
+ * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
+ * take masks of ancestors with non-empty cpus/mems, instead of being
+ * moved to an ancestor.
+ *
+ * - cpuset: a task can be moved into an empty cpuset, and again it takes
+ * masks of ancestors.
+ *
+ * - memcg: use_hierarchy is on by default and the cgroup file for the flag
+ * is not created.
+ *
+ * - blkcg: blk-throttle becomes properly hierarchical.
+ *
+ * - debug: disallowed on the default hierarchy.
+ */
+static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
+{
+ return cgrp->root == &cgrp_dfl_root;
+}
+
+/* no synchronization, the result can only be used as a hint */
+static inline bool cgroup_has_tasks(struct cgroup *cgrp)
+{
+ return !list_empty(&cgrp->cset_links);
+}
+
+/* returns ino associated with a cgroup */
+static inline ino_t cgroup_ino(struct cgroup *cgrp)
+{
+ return cgrp->kn->ino;
+}
+
+/* cft/css accessors for cftype->write() operation */
+static inline struct cftype *of_cft(struct kernfs_open_file *of)
+{
+ return of->kn->priv;
+}
+
+struct cgroup_subsys_state *of_css(struct kernfs_open_file *of);
+
+/* cft/css accessors for cftype->seq_*() operations */
+static inline struct cftype *seq_cft(struct seq_file *seq)
+{
+ return of_cft(seq->private);
+}
+
+static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
+{
+ return of_css(seq->private);
+}
+
+/*
+ * Name / path handling functions. All are thin wrappers around the kernfs
+ * counterparts and can be called under any context.
+ */
+
+static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
+{
+ return kernfs_name(cgrp->kn, buf, buflen);
+}
+
+static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
+ size_t buflen)
+{
+ return kernfs_path(cgrp->kn, buf, buflen);
+}
+
+static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
+{
+ pr_cont_kernfs_name(cgrp->kn);
+}
+
+static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
+{
+ pr_cont_kernfs_path(cgrp->kn);
+}
+
+char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
+
+int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
+int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
+int cgroup_rm_cftypes(struct cftype *cfts);
+
+bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
+
+/*
+ * Control Group taskset, used to pass around set of tasks to cgroup_subsys
+ * methods.
+ */
+struct cgroup_taskset;
+struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
+struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
+
+/**
+ * cgroup_taskset_for_each - iterate cgroup_taskset
+ * @task: the loop cursor
+ * @tset: taskset to iterate
+ */
+#define cgroup_taskset_for_each(task, tset) \
+ for ((task) = cgroup_taskset_first((tset)); (task); \
+ (task) = cgroup_taskset_next((tset)))
+
+/*
+ * Control Group subsystem type.
+ * See Documentation/cgroups/cgroups.txt for details
+ */
+
+struct cgroup_subsys {
+ struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
+ int (*css_online)(struct cgroup_subsys_state *css);
+ void (*css_offline)(struct cgroup_subsys_state *css);
+ void (*css_released)(struct cgroup_subsys_state *css);
+ void (*css_free)(struct cgroup_subsys_state *css);
+ void (*css_reset)(struct cgroup_subsys_state *css);
+ void (*css_e_css_changed)(struct cgroup_subsys_state *css);
+
+ int (*can_attach)(struct cgroup_subsys_state *css,
+ struct cgroup_taskset *tset);
+ void (*cancel_attach)(struct cgroup_subsys_state *css,
+ struct cgroup_taskset *tset);
+ void (*attach)(struct cgroup_subsys_state *css,
+ struct cgroup_taskset *tset);
+ void (*fork)(struct task_struct *task);
+ void (*exit)(struct cgroup_subsys_state *css,
+ struct cgroup_subsys_state *old_css,
+ struct task_struct *task);
+ void (*bind)(struct cgroup_subsys_state *root_css);
+
+ int disabled;
+ int early_init;
+
+ /*
+ * If %false, this subsystem is properly hierarchical -
+ * configuration, resource accounting and restriction on a parent
+ * cgroup cover those of its children. If %true, hierarchy support
+ * is broken in some ways - some subsystems ignore hierarchy
+ * completely while others are only implemented half-way.
+ *
+ * It's now disallowed to create nested cgroups if the subsystem is
+ * broken and cgroup core will emit a warning message on such
+ * cases. Eventually, all subsystems will be made properly
+ * hierarchical and this will go away.
+ */
+ bool broken_hierarchy;
+ bool warned_broken_hierarchy;
+
+ /* the following two fields are initialized automtically during boot */
+ int id;
+#define MAX_CGROUP_TYPE_NAMELEN 32
+ const char *name;
+
+ /* link to parent, protected by cgroup_lock() */
+ struct cgroup_root *root;
+
+ /* idr for css->id */
+ struct idr css_idr;
+
+ /*
+ * List of cftypes. Each entry is the first entry of an array
+ * terminated by zero length name.
+ */
+ struct list_head cfts;
+
+ /*
+ * Base cftypes which are automatically registered. The two can
+ * point to the same array.
+ */
+ struct cftype *dfl_cftypes; /* for the default hierarchy */
+ struct cftype *legacy_cftypes; /* for the legacy hierarchies */
+
+ /*
+ * A subsystem may depend on other subsystems. When such subsystem
+ * is enabled on a cgroup, the depended-upon subsystems are enabled
+ * together if available. Subsystems enabled due to dependency are
+ * not visible to userland until explicitly enabled. The following
+ * specifies the mask of subsystems that this one depends on.
+ */
+ unsigned int depends_on;
+};
+
+#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
+#include <linux/cgroup_subsys.h>
+#undef SUBSYS
+
+/**
+ * task_css_set_check - obtain a task's css_set with extra access conditions
+ * @task: the task to obtain css_set for
+ * @__c: extra condition expression to be passed to rcu_dereference_check()
+ *
+ * A task's css_set is RCU protected, initialized and exited while holding
+ * task_lock(), and can only be modified while holding both cgroup_mutex
+ * and task_lock() while the task is alive. This macro verifies that the
+ * caller is inside proper critical section and returns @task's css_set.
+ *
+ * The caller can also specify additional allowed conditions via @__c, such
+ * as locks used during the cgroup_subsys::attach() methods.
+ */
+#ifdef CONFIG_PROVE_RCU
+extern struct mutex cgroup_mutex;
+extern struct rw_semaphore css_set_rwsem;
+#define task_css_set_check(task, __c) \
+ rcu_dereference_check((task)->cgroups, \
+ lockdep_is_held(&cgroup_mutex) || \
+ lockdep_is_held(&css_set_rwsem) || \
+ ((task)->flags & PF_EXITING) || (__c))
+#else
+#define task_css_set_check(task, __c) \
+ rcu_dereference((task)->cgroups)
+#endif
+
+/**
+ * task_css_check - obtain css for (task, subsys) w/ extra access conds
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ * @__c: extra condition expression to be passed to rcu_dereference_check()
+ *
+ * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
+ * synchronization rules are the same as task_css_set_check().
+ */
+#define task_css_check(task, subsys_id, __c) \
+ task_css_set_check((task), (__c))->subsys[(subsys_id)]
+
+/**
+ * task_css_set - obtain a task's css_set
+ * @task: the task to obtain css_set for
+ *
+ * See task_css_set_check().
+ */
+static inline struct css_set *task_css_set(struct task_struct *task)
+{
+ return task_css_set_check(task, false);
+}
+
+/**
+ * task_css - obtain css for (task, subsys)
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ *
+ * See task_css_check().
+ */
+static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
+ int subsys_id)
+{
+ return task_css_check(task, subsys_id, false);
+}
+
+/**
+ * task_css_is_root - test whether a task belongs to the root css
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ *
+ * Test whether @task belongs to the root css on the specified subsystem.
+ * May be invoked in any context.
+ */
+static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
+{
+ return task_css_check(task, subsys_id, true) ==
+ init_css_set.subsys[subsys_id];
+}
+
+static inline struct cgroup *task_cgroup(struct task_struct *task,
+ int subsys_id)
+{
+ return task_css(task, subsys_id)->cgroup;
+}
+
+struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
+ struct cgroup_subsys_state *parent);
+
+struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
+
+/**
+ * css_for_each_child - iterate through children of a css
+ * @pos: the css * to use as the loop cursor
+ * @parent: css whose children to walk
+ *
+ * Walk @parent's children. Must be called under rcu_read_lock().
+ *
+ * If a subsystem synchronizes ->css_online() and the start of iteration, a
+ * css which finished ->css_online() is guaranteed to be visible in the
+ * future iterations and will stay visible until the last reference is put.
+ * A css which hasn't finished ->css_online() or already finished
+ * ->css_offline() may show up during traversal. It's each subsystem's
+ * responsibility to synchronize against on/offlining.
+ *
+ * It is allowed to temporarily drop RCU read lock during iteration. The
+ * caller is responsible for ensuring that @pos remains accessible until
+ * the start of the next iteration by, for example, bumping the css refcnt.
+ */
+#define css_for_each_child(pos, parent) \
+ for ((pos) = css_next_child(NULL, (parent)); (pos); \
+ (pos) = css_next_child((pos), (parent)))
+
+struct cgroup_subsys_state *
+css_next_descendant_pre(struct cgroup_subsys_state *pos,
+ struct cgroup_subsys_state *css);
+
+struct cgroup_subsys_state *
+css_rightmost_descendant(struct cgroup_subsys_state *pos);
+
+/**
+ * css_for_each_descendant_pre - pre-order walk of a css's descendants
+ * @pos: the css * to use as the loop cursor
+ * @root: css whose descendants to walk
+ *
+ * Walk @root's descendants. @root is included in the iteration and the
+ * first node to be visited. Must be called under rcu_read_lock().
+ *
+ * If a subsystem synchronizes ->css_online() and the start of iteration, a
+ * css which finished ->css_online() is guaranteed to be visible in the
+ * future iterations and will stay visible until the last reference is put.
+ * A css which hasn't finished ->css_online() or already finished
+ * ->css_offline() may show up during traversal. It's each subsystem's
+ * responsibility to synchronize against on/offlining.
+ *
+ * For example, the following guarantees that a descendant can't escape
+ * state updates of its ancestors.
+ *
+ * my_online(@css)
+ * {
+ * Lock @css's parent and @css;
+ * Inherit state from the parent;
+ * Unlock both.
+ * }
+ *
+ * my_update_state(@css)
+ * {
+ * css_for_each_descendant_pre(@pos, @css) {
+ * Lock @pos;
+ * if (@pos == @css)
+ * Update @css's state;
+ * else
+ * Verify @pos is alive and inherit state from its parent;
+ * Unlock @pos;
+ * }
+ * }
+ *
+ * As long as the inheriting step, including checking the parent state, is
+ * enclosed inside @pos locking, double-locking the parent isn't necessary
+ * while inheriting. The state update to the parent is guaranteed to be
+ * visible by walking order and, as long as inheriting operations to the
+ * same @pos are atomic to each other, multiple updates racing each other
+ * still result in the correct state. It's guaranateed that at least one
+ * inheritance happens for any css after the latest update to its parent.
+ *
+ * If checking parent's state requires locking the parent, each inheriting
+ * iteration should lock and unlock both @pos->parent and @pos.
+ *
+ * Alternatively, a subsystem may choose to use a single global lock to
+ * synchronize ->css_online() and ->css_offline() against tree-walking
+ * operations.
+ *
+ * It is allowed to temporarily drop RCU read lock during iteration. The
+ * caller is responsible for ensuring that @pos remains accessible until
+ * the start of the next iteration by, for example, bumping the css refcnt.
+ */
+#define css_for_each_descendant_pre(pos, css) \
+ for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
+ (pos) = css_next_descendant_pre((pos), (css)))
+
+struct cgroup_subsys_state *
+css_next_descendant_post(struct cgroup_subsys_state *pos,
+ struct cgroup_subsys_state *css);
+
+/**
+ * css_for_each_descendant_post - post-order walk of a css's descendants
+ * @pos: the css * to use as the loop cursor
+ * @css: css whose descendants to walk
+ *
+ * Similar to css_for_each_descendant_pre() but performs post-order
+ * traversal instead. @root is included in the iteration and the last
+ * node to be visited.
+ *
+ * If a subsystem synchronizes ->css_online() and the start of iteration, a
+ * css which finished ->css_online() is guaranteed to be visible in the
+ * future iterations and will stay visible until the last reference is put.
+ * A css which hasn't finished ->css_online() or already finished
+ * ->css_offline() may show up during traversal. It's each subsystem's
+ * responsibility to synchronize against on/offlining.
+ *
+ * Note that the walk visibility guarantee example described in pre-order
+ * walk doesn't apply the same to post-order walks.
+ */
+#define css_for_each_descendant_post(pos, css) \
+ for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
+ (pos) = css_next_descendant_post((pos), (css)))
+
+bool css_has_online_children(struct cgroup_subsys_state *css);
+
+/* A css_task_iter should be treated as an opaque object */
+struct css_task_iter {
+ struct cgroup_subsys *ss;
+
+ struct list_head *cset_pos;
+ struct list_head *cset_head;
+
+ struct list_head *task_pos;
+ struct list_head *tasks_head;
+ struct list_head *mg_tasks_head;
+};
+
+void css_task_iter_start(struct cgroup_subsys_state *css,
+ struct css_task_iter *it);
+struct task_struct *css_task_iter_next(struct css_task_iter *it);
+void css_task_iter_end(struct css_task_iter *it);
+
+int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
+int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
+
+struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
+ struct cgroup_subsys *ss);
+struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
+ struct cgroup_subsys *ss);
+
+#else /* !CONFIG_CGROUPS */
+
+struct cgroup_subsys_state;
+
+static inline int cgroup_init_early(void) { return 0; }
+static inline int cgroup_init(void) { return 0; }
+static inline void cgroup_fork(struct task_struct *p) {}
+static inline void cgroup_post_fork(struct task_struct *p) {}
+static inline void cgroup_exit(struct task_struct *p) {}
+
+static inline int cgroupstats_build(struct cgroupstats *stats,
+ struct dentry *dentry)
+{
+ return -EINVAL;
+}
+
+static inline void css_put(struct cgroup_subsys_state *css) {}
+
+/* No cgroups - nothing to do */
+static inline int cgroup_attach_task_all(struct task_struct *from,
+ struct task_struct *t)
+{
+ return 0;
+}
+
+#endif /* !CONFIG_CGROUPS */
+
+#endif /* _LINUX_CGROUP_H */