From b4a04ab7a37b490cad48e69abfe14288cacb669c Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 15:38:40 -0400
Subject: cgroup: separate out include/linux/cgroup-defs.h

From 2d728f74bfc071df06773e2fd7577dd5dab6425d Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 15:37:01 -0400

This patch separates out cgroup-defs.h from cgroup.h which has grown a
lot of dependencies.  cgroup-defs.h currently only contains constant
and type definitions and can be used to break circular include
dependency.  While moving, definitions are reordered so that
cgroup-defs.h has consistent logical structure.

This patch is pure reorganization.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 include/linux/cgroup-defs.h | 464 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/cgroup.h      | 455 +------------------------------------------
 2 files changed, 466 insertions(+), 453 deletions(-)
 create mode 100644 include/linux/cgroup-defs.h

(limited to 'include')

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
new file mode 100644
index 000000000000..55f3120fb952
--- /dev/null
+++ b/include/linux/cgroup-defs.h
@@ -0,0 +1,464 @@
+/*
+ * linux/cgroup-defs.h - basic definitions for cgroup
+ *
+ * This file provides basic type and interface.  Include this file directly
+ * only if necessary to avoid cyclic dependencies.
+ */
+#ifndef _LINUX_CGROUP_DEFS_H
+#define _LINUX_CGROUP_DEFS_H
+
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/idr.h>
+#include <linux/wait.h>
+#include <linux/mutex.h>
+#include <linux/rcupdate.h>
+#include <linux/percpu-refcount.h>
+#include <linux/workqueue.h>
+
+#ifdef CONFIG_CGROUPS
+
+struct cgroup;
+struct cgroup_root;
+struct cgroup_subsys;
+struct cgroup_taskset;
+struct kernfs_node;
+struct kernfs_ops;
+struct kernfs_open_file;
+
+#define MAX_CGROUP_TYPE_NAMELEN 32
+#define MAX_CGROUP_ROOT_NAMELEN 64
+#define MAX_CFTYPE_NAME		64
+
+/* 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
+
+/* 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 */
+};
+
+/* 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,
+};
+
+/* 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 */
+};
+
+/* 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 */
+};
+
+/*
+ * 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;
+};
+
+/*
+ * 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 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;
+};
+
+/*
+ * 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];
+};
+
+/*
+ * 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
+ */
+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
+};
+
+/*
+ * 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;
+	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;
+};
+
+#endif	/* CONFIG_CGROUPS */
+#endif	/* _LINUX_CGROUP_DEFS_H */
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index b9cb94c3102a..96a2ecd5aa69 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -11,23 +11,16 @@
 #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
+#include <linux/cgroup-defs.h>
 
-struct cgroup_root;
-struct cgroup_subsys;
-struct cgroup;
+#ifdef CONFIG_CGROUPS
 
 extern int cgroup_init_early(void);
 extern int cgroup_init(void);
@@ -40,66 +33,6 @@ extern int cgroupstats_build(struct cgroupstats *stats,
 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
@@ -185,307 +118,6 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
 		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;
 
@@ -612,11 +244,6 @@ 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);
 
@@ -629,84 +256,6 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *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
-- 
cgit v1.2.3-59-g8ed1b


From c326aa2bb2209e10df4a381801bb34ca0f923038 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 16:24:16 -0400
Subject: cgroup: reorganize include/linux/cgroup.h

From c4d440938b5e2015c70594fe6666a099c844f929 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 16:21:40 -0400

Over time, cgroup.h grew organically and doesn't have much logical
structure at this point.  Separation of cgroup-defs.h in the previous
patch gives us a good chance for reorganizing cgroup.h as changes to
the header are likely to cause conflicts anyway.

This patch reorganizes cgroup.h so that it has consistent logical
grouping.

This is pure reorganization.

v2: Relocating #ifdef CONFIG_CGROUPS caused build failure when cgroup
    is disabled.  Dropped.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 include/linux/cgroup.h | 552 ++++++++++++++++++++++++-------------------------
 1 file changed, 271 insertions(+), 281 deletions(-)

(limited to 'include')

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 96a2ecd5aa69..82319fb31cfe 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -22,16 +22,189 @@
 
 #ifdef CONFIG_CGROUPS
 
-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);
+/* 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;
+};
+
+extern struct cgroup_root cgrp_dfl_root;
+extern struct css_set init_css_set;
+
+#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
+#include <linux/cgroup_subsys.h>
+#undef SUBSYS
+
+bool css_has_online_children(struct cgroup_subsys_state *css);
+struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
+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);
+
+bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
+int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
+int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
+
+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);
+
+char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
+int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
+int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
+		     struct pid *pid, struct task_struct *tsk);
+
+void cgroup_fork(struct task_struct *p);
+void cgroup_post_fork(struct task_struct *p);
+void cgroup_exit(struct task_struct *p);
+
+int cgroup_init_early(void);
+int cgroup_init(void);
+
+/*
+ * Iteration helpers and macros.
+ */
+
+struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
+					   struct cgroup_subsys_state *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);
+struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos,
+						     struct cgroup_subsys_state *css);
+
+struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
+struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
+
+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);
+
+/**
+ * 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)))
+
+/**
+ * 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)))
+
+/**
+ * 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)))
+
+/**
+ * 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)))
 
-extern int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
-			    struct pid *pid, struct task_struct *tsk);
+/*
+ * Inline functions.
+ */
 
 /**
  * css_get - obtain a reference on the specified css
@@ -118,8 +291,87 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
 		percpu_ref_put_many(&css->refcnt, n);
 }
 
-extern struct cgroup_root cgrp_dfl_root;
-extern struct css_set init_css_set;
+/**
+ * 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;
+}
 
 /**
  * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
@@ -236,284 +488,22 @@ 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);
-
-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)))
-
-#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 css_put(struct cgroup_subsys_state *css) {}
+static inline int cgroup_attach_task_all(struct task_struct *from,
+					 struct task_struct *t) { return 0; }
+static inline int cgroupstats_build(struct cgroupstats *stats,
+				    struct dentry *dentry) { return -EINVAL; }
+
 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;
-}
+static inline int cgroup_init_early(void) { return 0; }
+static inline int cgroup_init(void) { return 0; }
 
 #endif /* !CONFIG_CGROUPS */
 
-- 
cgit v1.2.3-59-g8ed1b


From 7d7efec368d537226142cbe559f45797f18672f9 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 16:35:16 -0400
Subject: sched, cgroup: reorganize threadgroup locking

threadgroup_change_begin/end() are used to mark the beginning and end
of threadgroup modifying operations to allow code paths which require
a threadgroup to stay stable across blocking operations to synchronize
against those sections using threadgroup_lock/unlock().

It's currently implemented as a general mechanism in sched.h using
per-signal_struct rwsem; however, this never grew non-cgroup use cases
and becomes noop if !CONFIG_CGROUPS.  It turns out that cgroups is
gonna be better served with a different sycnrhonization scheme and is
a bit silly to keep cgroups specific details as a general mechanism.

What's general here is identifying the places where threadgroups are
modified.  This patch restructures threadgroup locking so that
threadgroup_change_begin/end() become a place where subsystems which
need to sycnhronize against threadgroup changes can hook into.

cgroup_threadgroup_change_begin/end() which operate on the
per-signal_struct rwsem are created and threadgroup_lock/unlock() are
moved to cgroup.c and made static.

This is pure reorganization which doesn't cause any functional
changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 include/linux/cgroup-defs.h | 10 +++++++++
 include/linux/sched.h       | 53 +++++++++++++++------------------------------
 kernel/cgroup.c             | 42 +++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+), 36 deletions(-)

(limited to 'include')

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 55f3120fb952..1b8c93806dbd 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -14,6 +14,7 @@
 #include <linux/mutex.h>
 #include <linux/rcupdate.h>
 #include <linux/percpu-refcount.h>
+#include <linux/percpu-rwsem.h>
 #include <linux/workqueue.h>
 
 #ifdef CONFIG_CGROUPS
@@ -460,5 +461,14 @@ struct cgroup_subsys {
 	unsigned int depends_on;
 };
 
+void cgroup_threadgroup_change_begin(struct task_struct *tsk);
+void cgroup_threadgroup_change_end(struct task_struct *tsk);
+
+#else	/* CONFIG_CGROUPS */
+
+static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) {}
+static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
+
 #endif	/* CONFIG_CGROUPS */
+
 #endif	/* _LINUX_CGROUP_DEFS_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8222ae40ecb0..5ee290003470 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -58,6 +58,7 @@ struct sched_param {
 #include <linux/uidgid.h>
 #include <linux/gfp.h>
 #include <linux/magic.h>
+#include <linux/cgroup-defs.h>
 
 #include <asm/processor.h>
 
@@ -2648,53 +2649,33 @@ static inline void unlock_task_sighand(struct task_struct *tsk,
 	spin_unlock_irqrestore(&tsk->sighand->siglock, *flags);
 }
 
-#ifdef CONFIG_CGROUPS
-static inline void threadgroup_change_begin(struct task_struct *tsk)
-{
-	down_read(&tsk->signal->group_rwsem);
-}
-static inline void threadgroup_change_end(struct task_struct *tsk)
-{
-	up_read(&tsk->signal->group_rwsem);
-}
-
 /**
- * threadgroup_lock - lock threadgroup
- * @tsk: member task of the threadgroup to lock
- *
- * Lock the threadgroup @tsk belongs to.  No new task is allowed to enter
- * and member tasks aren't allowed to exit (as indicated by PF_EXITING) or
- * change ->group_leader/pid.  This is useful for cases where the threadgroup
- * needs to stay stable across blockable operations.
+ * threadgroup_change_begin - mark the beginning of changes to a threadgroup
+ * @tsk: task causing the changes
  *
- * fork and exit paths explicitly call threadgroup_change_{begin|end}() for
- * synchronization.  While held, no new task will be added to threadgroup
- * and no existing live task will have its PF_EXITING set.
- *
- * de_thread() does threadgroup_change_{begin|end}() when a non-leader
- * sub-thread becomes a new leader.
+ * All operations which modify a threadgroup - a new thread joining the
+ * group, death of a member thread (the assertion of PF_EXITING) and
+ * exec(2) dethreading the process and replacing the leader - are wrapped
+ * by threadgroup_change_{begin|end}().  This is to provide a place which
+ * subsystems needing threadgroup stability can hook into for
+ * synchronization.
  */
-static inline void threadgroup_lock(struct task_struct *tsk)
+static inline void threadgroup_change_begin(struct task_struct *tsk)
 {
-	down_write(&tsk->signal->group_rwsem);
+	might_sleep();
+	cgroup_threadgroup_change_begin(tsk);
 }
 
 /**
- * threadgroup_unlock - unlock threadgroup
- * @tsk: member task of the threadgroup to unlock
+ * threadgroup_change_end - mark the end of changes to a threadgroup
+ * @tsk: task causing the changes
  *
- * Reverse threadgroup_lock().
+ * See threadgroup_change_begin().
  */
-static inline void threadgroup_unlock(struct task_struct *tsk)
+static inline void threadgroup_change_end(struct task_struct *tsk)
 {
-	up_write(&tsk->signal->group_rwsem);
+	cgroup_threadgroup_change_end(tsk);
 }
-#else
-static inline void threadgroup_change_begin(struct task_struct *tsk) {}
-static inline void threadgroup_change_end(struct task_struct *tsk) {}
-static inline void threadgroup_lock(struct task_struct *tsk) {}
-static inline void threadgroup_unlock(struct task_struct *tsk) {}
-#endif
 
 #ifndef __HAVE_THREAD_FUNCTIONS
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b91177f93416..980b1f52f39f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -848,6 +848,48 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 	return cset;
 }
 
+void cgroup_threadgroup_change_begin(struct task_struct *tsk)
+{
+	down_read(&tsk->signal->group_rwsem);
+}
+
+void cgroup_threadgroup_change_end(struct task_struct *tsk)
+{
+	up_read(&tsk->signal->group_rwsem);
+}
+
+/**
+ * threadgroup_lock - lock threadgroup
+ * @tsk: member task of the threadgroup to lock
+ *
+ * Lock the threadgroup @tsk belongs to.  No new task is allowed to enter
+ * and member tasks aren't allowed to exit (as indicated by PF_EXITING) or
+ * change ->group_leader/pid.  This is useful for cases where the threadgroup
+ * needs to stay stable across blockable operations.
+ *
+ * fork and exit explicitly call threadgroup_change_{begin|end}() for
+ * synchronization.  While held, no new task will be added to threadgroup
+ * and no existing live task will have its PF_EXITING set.
+ *
+ * de_thread() does threadgroup_change_{begin|end}() when a non-leader
+ * sub-thread becomes a new leader.
+ */
+static void threadgroup_lock(struct task_struct *tsk)
+{
+	down_write(&tsk->signal->group_rwsem);
+}
+
+/**
+ * threadgroup_unlock - unlock threadgroup
+ * @tsk: member task of the threadgroup to unlock
+ *
+ * Reverse threadgroup_lock().
+ */
+static inline void threadgroup_unlock(struct task_struct *tsk)
+{
+	up_write(&tsk->signal->group_rwsem);
+}
+
 static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
 {
 	struct cgroup *root_cgrp = kf_root->kn->priv;
-- 
cgit v1.2.3-59-g8ed1b


From d59cfc09c32a2ae31f1c3bc2983a0cd79afb3f14 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 16:35:17 -0400
Subject: sched, cgroup: replace signal_struct->group_rwsem with a global
 percpu_rwsem

The cgroup side of threadgroup locking uses signal_struct->group_rwsem
to synchronize against threadgroup changes.  This per-process rwsem
adds small overhead to thread creation, exit and exec paths, forces
cgroup code paths to do lock-verify-unlock-retry dance in a couple
places and makes it impossible to atomically perform operations across
multiple processes.

This patch replaces signal_struct->group_rwsem with a global
percpu_rwsem cgroup_threadgroup_rwsem which is cheaper on the reader
side and contained in cgroups proper.  This patch converts one-to-one.

This does make writer side heavier and lower the granularity; however,
cgroup process migration is a fairly cold path, we do want to optimize
thread operations over it and cgroup migration operations don't take
enough time for the lower granularity to matter.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 include/linux/cgroup-defs.h | 27 ++++++++++++++--
 include/linux/init_task.h   |  8 -----
 include/linux/sched.h       | 12 -------
 init/Kconfig                |  1 +
 kernel/cgroup.c             | 77 ++++++++++++---------------------------------
 kernel/fork.c               |  4 ---
 6 files changed, 46 insertions(+), 83 deletions(-)

(limited to 'include')

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 1b8c93806dbd..7d83d7f73420 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -461,8 +461,31 @@ struct cgroup_subsys {
 	unsigned int depends_on;
 };
 
-void cgroup_threadgroup_change_begin(struct task_struct *tsk);
-void cgroup_threadgroup_change_end(struct task_struct *tsk);
+extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
+
+/**
+ * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
+ * @tsk: target task
+ *
+ * Called from threadgroup_change_begin() and allows cgroup operations to
+ * synchronize against threadgroup changes using a percpu_rw_semaphore.
+ */
+static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
+{
+	percpu_down_read(&cgroup_threadgroup_rwsem);
+}
+
+/**
+ * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
+ * @tsk: target task
+ *
+ * Called from threadgroup_change_end().  Counterpart of
+ * cgroup_threadcgroup_change_begin().
+ */
+static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
+{
+	percpu_up_read(&cgroup_threadgroup_rwsem);
+}
 
 #else	/* CONFIG_CGROUPS */
 
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 696d22312b31..0cc0bbf20022 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -25,13 +25,6 @@
 extern struct files_struct init_files;
 extern struct fs_struct init_fs;
 
-#ifdef CONFIG_CGROUPS
-#define INIT_GROUP_RWSEM(sig)						\
-	.group_rwsem = __RWSEM_INITIALIZER(sig.group_rwsem),
-#else
-#define INIT_GROUP_RWSEM(sig)
-#endif
-
 #ifdef CONFIG_CPUSETS
 #define INIT_CPUSET_SEQ(tsk)							\
 	.mems_allowed_seq = SEQCNT_ZERO(tsk.mems_allowed_seq),
@@ -56,7 +49,6 @@ extern struct fs_struct init_fs;
 	},								\
 	.cred_guard_mutex =						\
 		 __MUTEX_INITIALIZER(sig.cred_guard_mutex),		\
-	INIT_GROUP_RWSEM(sig)						\
 }
 
 extern struct nsproxy init_nsproxy;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5ee290003470..add524a910bd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -743,18 +743,6 @@ struct signal_struct {
 	unsigned audit_tty_log_passwd;
 	struct tty_audit_buf *tty_audit_buf;
 #endif
-#ifdef CONFIG_CGROUPS
-	/*
-	 * group_rwsem prevents new tasks from entering the threadgroup and
-	 * member tasks from exiting,a more specifically, setting of
-	 * PF_EXITING.  fork and exit paths are protected with this rwsem
-	 * using threadgroup_change_begin/end().  Users which require
-	 * threadgroup to remain stable should use threadgroup_[un]lock()
-	 * which also takes care of exec path.  Currently, cgroup is the
-	 * only user.
-	 */
-	struct rw_semaphore group_rwsem;
-#endif
 
 	oom_flags_t oom_flags;
 	short oom_score_adj;		/* OOM kill score adjustment */
diff --git a/init/Kconfig b/init/Kconfig
index dc24dec60232..b9b824bf8f6b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -938,6 +938,7 @@ config NUMA_BALANCING_DEFAULT_ENABLED
 menuconfig CGROUPS
 	bool "Control Group support"
 	select KERNFS
+	select PERCPU_RWSEM
 	help
 	  This option adds support for grouping sets of processes together, for
 	  use with process control subsystems such as Cpusets, CFS, memory
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 980b1f52f39f..77578a169b8c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -46,6 +46,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/rwsem.h>
+#include <linux/percpu-rwsem.h>
 #include <linux/string.h>
 #include <linux/sort.h>
 #include <linux/kmod.h>
@@ -103,6 +104,8 @@ static DEFINE_SPINLOCK(cgroup_idr_lock);
  */
 static DEFINE_SPINLOCK(release_agent_path_lock);
 
+struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
+
 #define cgroup_assert_mutex_or_rcu_locked()				\
 	rcu_lockdep_assert(rcu_read_lock_held() ||			\
 			   lockdep_is_held(&cgroup_mutex),		\
@@ -848,48 +851,6 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 	return cset;
 }
 
-void cgroup_threadgroup_change_begin(struct task_struct *tsk)
-{
-	down_read(&tsk->signal->group_rwsem);
-}
-
-void cgroup_threadgroup_change_end(struct task_struct *tsk)
-{
-	up_read(&tsk->signal->group_rwsem);
-}
-
-/**
- * threadgroup_lock - lock threadgroup
- * @tsk: member task of the threadgroup to lock
- *
- * Lock the threadgroup @tsk belongs to.  No new task is allowed to enter
- * and member tasks aren't allowed to exit (as indicated by PF_EXITING) or
- * change ->group_leader/pid.  This is useful for cases where the threadgroup
- * needs to stay stable across blockable operations.
- *
- * fork and exit explicitly call threadgroup_change_{begin|end}() for
- * synchronization.  While held, no new task will be added to threadgroup
- * and no existing live task will have its PF_EXITING set.
- *
- * de_thread() does threadgroup_change_{begin|end}() when a non-leader
- * sub-thread becomes a new leader.
- */
-static void threadgroup_lock(struct task_struct *tsk)
-{
-	down_write(&tsk->signal->group_rwsem);
-}
-
-/**
- * threadgroup_unlock - unlock threadgroup
- * @tsk: member task of the threadgroup to unlock
- *
- * Reverse threadgroup_lock().
- */
-static inline void threadgroup_unlock(struct task_struct *tsk)
-{
-	up_write(&tsk->signal->group_rwsem);
-}
-
 static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
 {
 	struct cgroup *root_cgrp = kf_root->kn->priv;
@@ -2095,9 +2056,9 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
 	lockdep_assert_held(&css_set_rwsem);
 
 	/*
-	 * We are synchronized through threadgroup_lock() against PF_EXITING
-	 * setting such that we can't race against cgroup_exit() changing the
-	 * css_set to init_css_set and dropping the old one.
+	 * We are synchronized through cgroup_threadgroup_rwsem against
+	 * PF_EXITING setting such that we can't race against cgroup_exit()
+	 * changing the css_set to init_css_set and dropping the old one.
 	 */
 	WARN_ON_ONCE(tsk->flags & PF_EXITING);
 	old_cset = task_css_set(tsk);
@@ -2154,10 +2115,11 @@ static void cgroup_migrate_finish(struct list_head *preloaded_csets)
  * @src_cset and add it to @preloaded_csets, which should later be cleaned
  * up by cgroup_migrate_finish().
  *
- * This function may be called without holding threadgroup_lock even if the
- * target is a process.  Threads may be created and destroyed but as long
- * as cgroup_mutex is not dropped, no new css_set can be put into play and
- * the preloaded css_sets are guaranteed to cover all migrations.
+ * This function may be called without holding cgroup_threadgroup_rwsem
+ * even if the target is a process.  Threads may be created and destroyed
+ * but as long as cgroup_mutex is not dropped, no new css_set can be put
+ * into play and the preloaded css_sets are guaranteed to cover all
+ * migrations.
  */
 static void cgroup_migrate_add_src(struct css_set *src_cset,
 				   struct cgroup *dst_cgrp,
@@ -2260,7 +2222,7 @@ err:
  * @threadgroup: whether @leader points to the whole process or a single task
  *
  * Migrate a process or task denoted by @leader to @cgrp.  If migrating a
- * process, the caller must be holding threadgroup_lock of @leader.  The
+ * process, the caller must be holding cgroup_threadgroup_rwsem.  The
  * caller is also responsible for invoking cgroup_migrate_add_src() and
  * cgroup_migrate_prepare_dst() on the targets before invoking this
  * function and following up with cgroup_migrate_finish().
@@ -2388,7 +2350,7 @@ out_release_tset:
  * @leader: the task or the leader of the threadgroup to be attached
  * @threadgroup: attach the whole threadgroup?
  *
- * Call holding cgroup_mutex and threadgroup_lock of @leader.
+ * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
  */
 static int cgroup_attach_task(struct cgroup *dst_cgrp,
 			      struct task_struct *leader, bool threadgroup)
@@ -2481,7 +2443,7 @@ retry_find_task:
 	get_task_struct(tsk);
 	rcu_read_unlock();
 
-	threadgroup_lock(tsk);
+	percpu_down_write(&cgroup_threadgroup_rwsem);
 	if (threadgroup) {
 		if (!thread_group_leader(tsk)) {
 			/*
@@ -2491,7 +2453,7 @@ retry_find_task:
 			 * try again; this is
 			 * "double-double-toil-and-trouble-check locking".
 			 */
-			threadgroup_unlock(tsk);
+			percpu_up_write(&cgroup_threadgroup_rwsem);
 			put_task_struct(tsk);
 			goto retry_find_task;
 		}
@@ -2499,7 +2461,7 @@ retry_find_task:
 
 	ret = cgroup_attach_task(cgrp, tsk, threadgroup);
 
-	threadgroup_unlock(tsk);
+	percpu_up_write(&cgroup_threadgroup_rwsem);
 
 	put_task_struct(tsk);
 out_unlock_cgroup:
@@ -2704,17 +2666,17 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
 				goto out_finish;
 			last_task = task;
 
-			threadgroup_lock(task);
+			percpu_down_write(&cgroup_threadgroup_rwsem);
 			/* raced against de_thread() from another thread? */
 			if (!thread_group_leader(task)) {
-				threadgroup_unlock(task);
+				percpu_up_write(&cgroup_threadgroup_rwsem);
 				put_task_struct(task);
 				continue;
 			}
 
 			ret = cgroup_migrate(src_cset->dfl_cgrp, task, true);
 
-			threadgroup_unlock(task);
+			percpu_up_write(&cgroup_threadgroup_rwsem);
 			put_task_struct(task);
 
 			if (WARN(ret, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret))
@@ -5032,6 +4994,7 @@ int __init cgroup_init(void)
 	unsigned long key;
 	int ssid, err;
 
+	BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem));
 	BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
 	BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 03c1eaaa6ef5..9531275e12a9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1144,10 +1144,6 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 	tty_audit_fork(sig);
 	sched_autogroup_fork(sig);
 
-#ifdef CONFIG_CGROUPS
-	init_rwsem(&sig->group_rwsem);
-#endif
-
 	sig->oom_score_adj = current->signal->oom_score_adj;
 	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 
-- 
cgit v1.2.3-59-g8ed1b


From c80ef9e0c021ff86771fdd72583c75d8f7b6a720 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd@arndb.de>
Date: Fri, 29 May 2015 10:52:59 +0200
Subject: cgroup: add seq_file forward declaration for struct cftype

Recent header file changes for cgroup caused lots of warnings
about a missing struct seq_file form declaration for every
inclusion of include/linux/cgroup-defs.h.

As some files are built with -Werror, this leads to build
failure like:

                 from /git/arm-soc/drivers/gpu/drm/tilcdc/tilcdc_crtc.c:18:
/git/arm-soc/include/linux/cgroup-defs.h:354:25: error: 'struct seq_file' declared inside parameter list [-Werror]
cc1: all warnings being treated as errors
make[6]: *** [drivers/gpu/drm/tilcdc/tilcdc_crtc.o] Error 1

This patch adds the declaration, which resolves both the
warnings and the drm failure.

tj: Moved it where other type declarations are.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b4a04ab7a37b ("cgroup: separate out include/linux/cgroup-defs.h")
Signed-off-by: Tejun Heo <tj@kernel.org>
---
 include/linux/cgroup-defs.h | 1 +
 1 file changed, 1 insertion(+)

(limited to 'include')

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 7d83d7f73420..26d1cea7929f 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -26,6 +26,7 @@ struct cgroup_taskset;
 struct kernfs_node;
 struct kernfs_ops;
 struct kernfs_open_file;
+struct seq_file;
 
 #define MAX_CGROUP_TYPE_NAMELEN 32
 #define MAX_CGROUP_ROOT_NAMELEN 64
-- 
cgit v1.2.3-59-g8ed1b


From cb4a316752709be4a644f070440a8be470d92b7d Mon Sep 17 00:00:00 2001
From: Aleksa Sarai <cyphar@cyphar.com>
Date: Sat, 6 Jun 2015 10:02:14 +1000
Subject: cgroup: use bitmask to filter for_each_subsys

Add a new macro for_each_subsys_which that allows all enabled cgroup
subsystems to be filtered by a bitmask, such that mask & (1 << ssid)
determines if the subsystem is to be processed in the loop body (where
ssid is the unique id of the subsystem).

Also replace the need_forkexit_callback with two separate bitmasks for
each callback to make (ss->{fork,exit}) checks unnecessary.

tj: add a short comment for "if (!CGROUP_SUBSYS_COUNT)".

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
---
 include/linux/cgroup-defs.h |  2 ++
 kernel/cgroup.c             | 53 ++++++++++++++++++++++++++++-----------------
 2 files changed, 35 insertions(+), 20 deletions(-)

(limited to 'include')

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 26d1cea7929f..c5588c438448 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -490,6 +490,8 @@ static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
 
 #else	/* CONFIG_CGROUPS */
 
+#define CGROUP_SUBSYS_COUNT 0
+
 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) {}
 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0fd5227958fe..3a973519068f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -178,12 +178,13 @@ static DEFINE_IDR(cgroup_hierarchy_idr);
  */
 static u64 css_serial_nr_next = 1;
 
-/* This flag indicates whether tasks in the fork and exit paths should
- * check for fork/exit handlers to call. This avoids us having to do
- * extra work in the fork/exit path if none of the subsystems need to
- * be called.
+/*
+ * These bitmask flags indicate whether tasks in the fork and exit paths have
+ * fork/exit handlers to call. This avoids us having to do extra work in the
+ * fork/exit path to check which subsystems have fork/exit callbacks.
  */
-static int need_forkexit_callback __read_mostly;
+static unsigned long have_fork_callback __read_mostly;
+static unsigned long have_exit_callback __read_mostly;
 
 static struct cftype cgroup_dfl_base_files[];
 static struct cftype cgroup_legacy_base_files[];
@@ -412,6 +413,24 @@ static int notify_on_release(const struct cgroup *cgrp)
 	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT &&		\
 	     (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
 
+/**
+ * for_each_subsys_which - filter for_each_subsys with a bitmask
+ * @ss: the iteration cursor
+ * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
+ * @ss_maskp: a pointer to the bitmask
+ *
+ * The block will only run for cases where the ssid-th bit (1 << ssid) of
+ * mask is set to 1.
+ */
+#define for_each_subsys_which(ss, ssid, ss_maskp)			\
+	if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */	\
+		;							\
+	else								\
+		for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT)	\
+			if (((ss) = cgroup_subsys[ssid]) && false)	\
+				break;					\
+			else
+
 /* iterate across the hierarchies */
 #define for_each_root(root)						\
 	list_for_each_entry((root), &cgroup_roots, root_list)
@@ -4914,7 +4933,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
 	 * init_css_set is in the subsystem's root cgroup. */
 	init_css_set.subsys[ss->id] = css;
 
-	need_forkexit_callback |= ss->fork || ss->exit;
+	have_fork_callback |= (bool)ss->fork << ss->id;
+	have_exit_callback |= (bool)ss->exit << ss->id;
 
 	/* At system boot, before all subsystems have been
 	 * registered, no tasks have been forked, so we don't
@@ -5225,11 +5245,8 @@ void cgroup_post_fork(struct task_struct *child)
 	 * css_set; otherwise, @child might change state between ->fork()
 	 * and addition to css_set.
 	 */
-	if (need_forkexit_callback) {
-		for_each_subsys(ss, i)
-			if (ss->fork)
-				ss->fork(child);
-	}
+	for_each_subsys_which(ss, i, &have_fork_callback)
+		ss->fork(child);
 }
 
 /**
@@ -5273,16 +5290,12 @@ void cgroup_exit(struct task_struct *tsk)
 	cset = task_css_set(tsk);
 	RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
 
-	if (need_forkexit_callback) {
-		/* see cgroup_post_fork() for details */
-		for_each_subsys(ss, i) {
-			if (ss->exit) {
-				struct cgroup_subsys_state *old_css = cset->subsys[i];
-				struct cgroup_subsys_state *css = task_css(tsk, i);
+	/* see cgroup_post_fork() for details */
+	for_each_subsys_which(ss, i, &have_exit_callback) {
+		struct cgroup_subsys_state *old_css = cset->subsys[i];
+		struct cgroup_subsys_state *css = task_css(tsk, i);
 
-				ss->exit(css, old_css, tsk);
-			}
-		}
+		ss->exit(css, old_css, tsk);
 	}
 
 	if (put_cset)
-- 
cgit v1.2.3-59-g8ed1b


From fb02915f47181e824339d91f8e385fd4bd746d6a Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Thu, 18 Jun 2015 16:54:28 -0400
Subject: kernfs: make kernfs_get_inode() public

Move kernfs_get_inode() prototype from fs/kernfs/kernfs-internal.h to
include/linux/kernfs.h.  It obtains the matching inode for a
kernfs_node.

It will be used by cgroup for inode based permission checks for now
but is generally useful.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/kernfs/kernfs-internal.h | 1 -
 include/linux/kernfs.h      | 5 +++++
 2 files changed, 5 insertions(+), 1 deletion(-)

(limited to 'include')

diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index af9fa7499919..6762bfbd8207 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -76,7 +76,6 @@ extern struct kmem_cache *kernfs_node_cache;
 /*
  * inode.c
  */
-struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
 void kernfs_evict_inode(struct inode *inode);
 int kernfs_iop_permission(struct inode *inode, int mask);
 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr);
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 71ecdab1671b..e6b2f7db9c0c 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -277,6 +277,7 @@ void kernfs_put(struct kernfs_node *kn);
 
 struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
+struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn);
 
 struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
 				       unsigned int flags, void *priv);
@@ -352,6 +353,10 @@ static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
 static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
 { return NULL; }
 
+static inline struct inode *
+kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
+{ return NULL; }
+
 static inline struct kernfs_root *
 kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
 		   void *priv)
-- 
cgit v1.2.3-59-g8ed1b


From 187fe84067bd377047cfcb7f2bbc7c9dc12d290c Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Thu, 18 Jun 2015 16:54:28 -0400
Subject: cgroup: require write perm on common ancestor when moving processes
 on the default hierarchy

On traditional hierarchies, if a task has write access to "tasks" or
"cgroup.procs" file of a cgroup and its euid agrees with the target,
it can move the target to the cgroup; however, consider the following
scenario.  The owner of each cgroup is in the parentheses.

 R (root) - 0 (root) - 00 (user1) - 000 (user1)
          |                       \ 001 (user1)
          \ 1 (root) - 10 (user1)

The subtrees of 00 and 10 are delegated to user1; however, while both
subtrees may belong to the same user, it is clear that the two
subtrees are to be isolated - they're under completely separate
resource limits imposed by 0 and 1, respectively.  Note that 0 and 1
aren't strictly necessary but added to ease illustrating the issue.

If user1 is allowed to move processes between the two subtrees, the
intention of the hierarchy - keeping a given group of processes under
a subtree with certain resource restrictions while delegating
management of the subtree - can be circumvented by user1.

This happens because migration permission check doesn't consider the
hierarchical nature of cgroups.  To fix the issue, this patch adds an
extra permission requirement when userland tries to migrate a process
in the default hierarchy - the issuing task must have write access to
the common ancestor of "cgroup.procs" file of the ancestor in addition
to the destination's.

Conceptually, the issuer must be able to move the target process from
the source cgroup to the common ancestor of source and destination
cgroups and then to the destination.  As long as delegation is done in
a proper top-down way, this guarantees that a delegatee can't smuggle
processes across disjoint delegation domains.

The next patch will add documentation on the delegation model on the
default hierarchy.

v2: Fixed missing !ret test.  Spotted by Li Zefan.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
---
 include/linux/cgroup-defs.h |  1 +
 kernel/cgroup.c             | 30 +++++++++++++++++++++++++++---
 2 files changed, 28 insertions(+), 3 deletions(-)

(limited to 'include')

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index c5588c438448..93755a629299 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -220,6 +220,7 @@ struct cgroup {
 	int populated_cnt;
 
 	struct kernfs_node *kn;		/* cgroup kernfs entry */
+	struct kernfs_node *procs_kn;	/* kn for "cgroup.procs" */
 	struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */
 
 	/*
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4504d64f91e1..9ef9fc8a774b 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2392,7 +2392,9 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
 	return ret;
 }
 
-static int cgroup_procs_write_permission(struct task_struct *task)
+static int cgroup_procs_write_permission(struct task_struct *task,
+					 struct cgroup *dst_cgrp,
+					 struct kernfs_open_file *of)
 {
 	const struct cred *cred = current_cred();
 	const struct cred *tcred = get_task_cred(task);
@@ -2407,6 +2409,26 @@ static int cgroup_procs_write_permission(struct task_struct *task)
 	    !uid_eq(cred->euid, tcred->suid))
 		ret = -EACCES;
 
+	if (!ret && cgroup_on_dfl(dst_cgrp)) {
+		struct super_block *sb = of->file->f_path.dentry->d_sb;
+		struct cgroup *cgrp;
+		struct inode *inode;
+
+		down_read(&css_set_rwsem);
+		cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
+		up_read(&css_set_rwsem);
+
+		while (!cgroup_is_descendant(dst_cgrp, cgrp))
+			cgrp = cgroup_parent(cgrp);
+
+		ret = -ENOMEM;
+		inode = kernfs_get_inode(sb, cgrp->procs_kn);
+		if (inode) {
+			ret = inode_permission(inode, MAY_WRITE);
+			iput(inode);
+		}
+	}
+
 	put_cred(tcred);
 	return ret;
 }
@@ -2459,7 +2481,7 @@ static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
 	get_task_struct(tsk);
 	rcu_read_unlock();
 
-	ret = cgroup_procs_write_permission(tsk);
+	ret = cgroup_procs_write_permission(tsk, cgrp, of);
 	if (!ret)
 		ret = cgroup_attach_task(cgrp, tsk, threadgroup);
 
@@ -3087,7 +3109,9 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
 		return ret;
 	}
 
-	if (cft->seq_show == cgroup_populated_show)
+	if (cft->write == cgroup_procs_write)
+		cgrp->procs_kn = kn;
+	else if (cft->seq_show == cgroup_populated_show)
 		cgrp->populated_kn = kn;
 	return 0;
 }
-- 
cgit v1.2.3-59-g8ed1b