cgroup.c 152.1 KB
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/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
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 *  Notifications support
 *  Copyright (C) 2009 Nokia Corporation
 *  Author: Kirill A. Shutemov
 *
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 *  Copyright notices from the original cpuset code:
 *  --------------------------------------------------
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  ---------------------------------------------------
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.  See the file COPYING in the main directory of the Linux
 *  distribution for more details.
 */

#include <linux/cgroup.h>
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#include <linux/cred.h>
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#include <linux/ctype.h>
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#include <linux/errno.h>
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#include <linux/init_task.h>
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#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
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#include <linux/proc_fs.h>
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#include <linux/rcupdate.h>
#include <linux/sched.h>
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#include <linux/backing-dev.h>
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#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
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#include <linux/sort.h>
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#include <linux/kmod.h>
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#include <linux/module.h>
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#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
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#include <linux/hashtable.h>
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#include <linux/namei.h>
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#include <linux/pid_namespace.h>
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#include <linux/idr.h>
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#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
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#include <linux/eventfd.h>
#include <linux/poll.h>
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#include <linux/flex_array.h> /* used in cgroup_attach_task */
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#include <linux/kthread.h>
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#include <linux/atomic.h>
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/*
 * cgroup_mutex is the master lock.  Any modification to cgroup or its
 * hierarchy must be performed while holding it.
 *
 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
 * release_agent_path and so on.  Modifying requires both cgroup_mutex and
 * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
 * break the following locking order cycle.
 *
 *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
 *  B. namespace_sem -> cgroup_mutex
 *
 * B happens only through cgroup_show_options() and using cgroup_root_mutex
 * breaks it.
 */
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#ifdef CONFIG_PROVE_RCU
DEFINE_MUTEX(cgroup_mutex);
EXPORT_SYMBOL_GPL(cgroup_mutex);	/* only for task_subsys_state_check() */
#else
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static DEFINE_MUTEX(cgroup_mutex);
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#endif

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static DEFINE_MUTEX(cgroup_root_mutex);
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/*
 * Generate an array of cgroup subsystem pointers. At boot time, this is
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 * populated with the built in subsystems, and modular subsystems are
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 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
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#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
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#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
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static struct cgroup_subsys *cgroup_subsys[CGROUP_SUBSYS_COUNT] = {
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#include <linux/cgroup_subsys.h>
};

/*
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 * The dummy hierarchy, reserved for the subsystems that are otherwise
 * unattached - it never has more than a single cgroup, and all tasks are
 * part of that cgroup.
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 */
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static struct cgroupfs_root cgroup_dummy_root;

/* dummy_top is a shorthand for the dummy hierarchy's top cgroup */
static struct cgroup * const cgroup_dummy_top = &cgroup_dummy_root.top_cgroup;
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/*
 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
 */
struct cfent {
	struct list_head		node;
	struct dentry			*dentry;
	struct cftype			*type;
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	/* file xattrs */
	struct simple_xattrs		xattrs;
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};

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/*
 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
 * cgroup_subsys->use_id != 0.
 */
#define CSS_ID_MAX	(65535)
struct css_id {
	/*
	 * The css to which this ID points. This pointer is set to valid value
	 * after cgroup is populated. If cgroup is removed, this will be NULL.
	 * This pointer is expected to be RCU-safe because destroy()
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	 * is called after synchronize_rcu(). But for safe use, css_tryget()
	 * should be used for avoiding race.
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	 */
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	struct cgroup_subsys_state __rcu *css;
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	/*
	 * ID of this css.
	 */
	unsigned short id;
	/*
	 * Depth in hierarchy which this ID belongs to.
	 */
	unsigned short depth;
	/*
	 * ID is freed by RCU. (and lookup routine is RCU safe.)
	 */
	struct rcu_head rcu_head;
	/*
	 * Hierarchy of CSS ID belongs to.
	 */
	unsigned short stack[0]; /* Array of Length (depth+1) */
};

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/*
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 * cgroup_event represents events which userspace want to receive.
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 */
struct cgroup_event {
	/*
	 * Cgroup which the event belongs to.
	 */
	struct cgroup *cgrp;
	/*
	 * Control file which the event associated.
	 */
	struct cftype *cft;
	/*
	 * eventfd to signal userspace about the event.
	 */
	struct eventfd_ctx *eventfd;
	/*
	 * Each of these stored in a list by the cgroup.
	 */
	struct list_head list;
	/*
	 * All fields below needed to unregister event when
	 * userspace closes eventfd.
	 */
	poll_table pt;
	wait_queue_head_t *wqh;
	wait_queue_t wait;
	struct work_struct remove;
};
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/* The list of hierarchy roots */

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static LIST_HEAD(cgroup_roots);
static int cgroup_root_count;
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/*
 * Hierarchy ID allocation and mapping.  It follows the same exclusion
 * rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
 * writes, either for reads.
 */
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static DEFINE_IDR(cgroup_hierarchy_idr);
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static struct cgroup_name root_cgroup_name = { .name = "/" };

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/*
 * Assign a monotonically increasing serial number to cgroups.  It
 * guarantees cgroups with bigger numbers are newer than those with smaller
 * numbers.  Also, as cgroups are always appended to the parent's
 * ->children list, it guarantees that sibling cgroups are always sorted in
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 * the ascending serial number order on the list.  Protected by
 * cgroup_mutex.
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 */
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static u64 cgroup_serial_nr_next = 1;
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/* This flag indicates whether tasks in the fork and exit paths should
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 * 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.
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 */
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static int need_forkexit_callback __read_mostly;
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static void cgroup_offline_fn(struct work_struct *work);
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static int cgroup_destroy_locked(struct cgroup *cgrp);
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static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			      struct cftype cfts[], bool is_add);
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/* convenient tests for these bits */
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static inline bool cgroup_is_dead(const struct cgroup *cgrp)
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{
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	return test_bit(CGRP_DEAD, &cgrp->flags);
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}

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/**
 * cgroup_is_descendant - test ancestry
 * @cgrp: the cgroup to be tested
 * @ancestor: possible ancestor of @cgrp
 *
 * Test whether @cgrp is a descendant of @ancestor.  It also returns %true
 * if @cgrp == @ancestor.  This function is safe to call as long as @cgrp
 * and @ancestor are accessible.
 */
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
{
	while (cgrp) {
		if (cgrp == ancestor)
			return true;
		cgrp = cgrp->parent;
	}
	return false;
}
EXPORT_SYMBOL_GPL(cgroup_is_descendant);
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static int cgroup_is_releasable(const struct cgroup *cgrp)
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{
	const int bits =
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		(1 << CGRP_RELEASABLE) |
		(1 << CGRP_NOTIFY_ON_RELEASE);
	return (cgrp->flags & bits) == bits;
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}

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static int notify_on_release(const struct cgroup *cgrp)
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{
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	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
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}

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/**
 * for_each_subsys - iterate all loaded cgroup subsystems
 * @ss: the iteration cursor
 * @i: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
 *
 * Should be called under cgroup_mutex.
 */
#define for_each_subsys(ss, i)						\
	for ((i) = 0; (i) < CGROUP_SUBSYS_COUNT; (i)++)			\
		if (({ lockdep_assert_held(&cgroup_mutex);		\
		       !((ss) = cgroup_subsys[i]); })) { }		\
		else

/**
 * for_each_builtin_subsys - iterate all built-in cgroup subsystems
 * @ss: the iteration cursor
 * @i: the index of @ss, CGROUP_BUILTIN_SUBSYS_COUNT after reaching the end
 *
 * Bulit-in subsystems are always present and iteration itself doesn't
 * require any synchronization.
 */
#define for_each_builtin_subsys(ss, i)					\
	for ((i) = 0; (i) < CGROUP_BUILTIN_SUBSYS_COUNT &&		\
	     (((ss) = cgroup_subsys[i]) || true); (i)++)

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/* iterate each subsystem attached to a hierarchy */
#define for_each_root_subsys(root, ss)					\
	list_for_each_entry((ss), &(root)->subsys_list, sibling)
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/* iterate across the active hierarchies */
#define for_each_active_root(root)					\
	list_for_each_entry((root), &cgroup_roots, root_list)
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static inline struct cgroup *__d_cgrp(struct dentry *dentry)
{
	return dentry->d_fsdata;
}

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static inline struct cfent *__d_cfe(struct dentry *dentry)
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{
	return dentry->d_fsdata;
}

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static inline struct cftype *__d_cft(struct dentry *dentry)
{
	return __d_cfe(dentry)->type;
}

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/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
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 * On success, returns true; the mutex should be later unlocked.  On
 * failure returns false with no lock held.
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 */
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static bool cgroup_lock_live_group(struct cgroup *cgrp)
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{
	mutex_lock(&cgroup_mutex);
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	if (cgroup_is_dead(cgrp)) {
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		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}

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/* the list of cgroups eligible for automatic release. Protected by
 * release_list_lock */
static LIST_HEAD(release_list);
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static DEFINE_RAW_SPINLOCK(release_list_lock);
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static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
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static void check_for_release(struct cgroup *cgrp);
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/*
 * A cgroup can be associated with multiple css_sets as different tasks may
 * belong to different cgroups on different hierarchies.  In the other
 * direction, a css_set is naturally associated with multiple cgroups.
 * This M:N relationship is represented by the following link structure
 * which exists for each association and allows traversing the associations
 * from both sides.
 */
struct cgrp_cset_link {
	/* the cgroup and css_set this link associates */
	struct cgroup		*cgrp;
	struct css_set		*cset;

	/* list of cgrp_cset_links anchored at cgrp->cset_links */
	struct list_head	cset_link;

	/* list of cgrp_cset_links anchored at css_set->cgrp_links */
	struct list_head	cgrp_link;
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};

/* The default css_set - used by init and its children prior to any
 * hierarchies being mounted. It contains a pointer to the root state
 * for each subsystem. Also used to anchor the list of css_sets. Not
 * reference-counted, to improve performance when child cgroups
 * haven't been created.
 */

static struct css_set init_css_set;
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static struct cgrp_cset_link init_cgrp_cset_link;
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static int cgroup_init_idr(struct cgroup_subsys *ss,
			   struct cgroup_subsys_state *css);
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/* css_set_lock protects the list of css_set objects, and the
 * chain of tasks off each css_set.  Nests outside task->alloc_lock
 * due to cgroup_iter_start() */
static DEFINE_RWLOCK(css_set_lock);
static int css_set_count;

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/*
 * hash table for cgroup groups. This improves the performance to find
 * an existing css_set. This hash doesn't (currently) take into
 * account cgroups in empty hierarchies.
 */
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#define CSS_SET_HASH_BITS	7
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static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
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static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
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{
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	unsigned long key = 0UL;
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	struct cgroup_subsys *ss;
	int i;
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	for_each_subsys(ss, i)
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		key += (unsigned long)css[i];
	key = (key >> 16) ^ key;
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	return key;
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}

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/* We don't maintain the lists running through each css_set to its
 * task until after the first call to cgroup_iter_start(). This
 * reduces the fork()/exit() overhead for people who have cgroups
 * compiled into their kernel but not actually in use */
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static int use_task_css_set_links __read_mostly;
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static void __put_css_set(struct css_set *cset, int taskexit)
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{
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	struct cgrp_cset_link *link, *tmp_link;
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	/*
	 * Ensure that the refcount doesn't hit zero while any readers
	 * can see it. Similar to atomic_dec_and_lock(), but for an
	 * rwlock
	 */
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	if (atomic_add_unless(&cset->refcount, -1, 1))
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		return;
	write_lock(&css_set_lock);
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	if (!atomic_dec_and_test(&cset->refcount)) {
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		write_unlock(&css_set_lock);
		return;
	}
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	/* This css_set is dead. unlink it and release cgroup refcounts */
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	hash_del(&cset->hlist);
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	css_set_count--;

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	list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
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		struct cgroup *cgrp = link->cgrp;
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		list_del(&link->cset_link);
		list_del(&link->cgrp_link);
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		/* @cgrp can't go away while we're holding css_set_lock */
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		if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) {
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			if (taskexit)
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				set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
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		}
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		kfree(link);
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	}
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	write_unlock(&css_set_lock);
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	kfree_rcu(cset, rcu_head);
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}

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/*
 * refcounted get/put for css_set objects
 */
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static inline void get_css_set(struct css_set *cset)
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{
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	atomic_inc(&cset->refcount);
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}

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static inline void put_css_set(struct css_set *cset)
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{
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	__put_css_set(cset, 0);
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}

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static inline void put_css_set_taskexit(struct css_set *cset)
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{
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	__put_css_set(cset, 1);
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}

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/**
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 * compare_css_sets - helper function for find_existing_css_set().
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 * @cset: candidate css_set being tested
 * @old_cset: existing css_set for a task
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 * @new_cgrp: cgroup that's being entered by the task
 * @template: desired set of css pointers in css_set (pre-calculated)
 *
 * Returns true if "cg" matches "old_cg" except for the hierarchy
 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
 */
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static bool compare_css_sets(struct css_set *cset,
			     struct css_set *old_cset,
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			     struct cgroup *new_cgrp,
			     struct cgroup_subsys_state *template[])
{
	struct list_head *l1, *l2;

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	if (memcmp(template, cset->subsys, sizeof(cset->subsys))) {
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		/* Not all subsystems matched */
		return false;
	}

	/*
	 * Compare cgroup pointers in order to distinguish between
	 * different cgroups in heirarchies with no subsystems. We
	 * could get by with just this check alone (and skip the
	 * memcmp above) but on most setups the memcmp check will
	 * avoid the need for this more expensive check on almost all
	 * candidates.
	 */

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	l1 = &cset->cgrp_links;
	l2 = &old_cset->cgrp_links;
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	while (1) {
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		struct cgrp_cset_link *link1, *link2;
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		struct cgroup *cgrp1, *cgrp2;
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		l1 = l1->next;
		l2 = l2->next;
		/* See if we reached the end - both lists are equal length. */
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		if (l1 == &cset->cgrp_links) {
			BUG_ON(l2 != &old_cset->cgrp_links);
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			break;
		} else {
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			BUG_ON(l2 == &old_cset->cgrp_links);
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		}
		/* Locate the cgroups associated with these links. */
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		link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
		link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
		cgrp1 = link1->cgrp;
		cgrp2 = link2->cgrp;
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		/* Hierarchies should be linked in the same order. */
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		BUG_ON(cgrp1->root != cgrp2->root);
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		/*
		 * If this hierarchy is the hierarchy of the cgroup
		 * that's changing, then we need to check that this
		 * css_set points to the new cgroup; if it's any other
		 * hierarchy, then this css_set should point to the
		 * same cgroup as the old css_set.
		 */
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		if (cgrp1->root == new_cgrp->root) {
			if (cgrp1 != new_cgrp)
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				return false;
		} else {
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			if (cgrp1 != cgrp2)
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				return false;
		}
	}
	return true;
}

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/**
 * find_existing_css_set - init css array and find the matching css_set
 * @old_cset: the css_set that we're using before the cgroup transition
 * @cgrp: the cgroup that we're moving into
 * @template: out param for the new set of csses, should be clear on entry
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 */
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static struct css_set *find_existing_css_set(struct css_set *old_cset,
					struct cgroup *cgrp,
					struct cgroup_subsys_state *template[])
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{
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	struct cgroupfs_root *root = cgrp->root;
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	struct cgroup_subsys *ss;
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	struct css_set *cset;
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	unsigned long key;
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	int i;
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	/*
	 * Build the set of subsystem state objects that we want to see in the
	 * new css_set. while subsystems can change globally, the entries here
	 * won't change, so no need for locking.
	 */
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	for_each_subsys(ss, i) {
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		if (root->subsys_mask & (1UL << i)) {
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			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
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			template[i] = cgrp->subsys[i];
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		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
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			template[i] = old_cset->subsys[i];
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		}
	}

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	key = css_set_hash(template);
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	hash_for_each_possible(css_set_table, cset, hlist, key) {
		if (!compare_css_sets(cset, old_cset, cgrp, template))
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			continue;

		/* This css_set matches what we need */
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		return cset;
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	}
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	/* No existing cgroup group matched */
	return NULL;
}

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static void free_cgrp_cset_links(struct list_head *links_to_free)
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{
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	struct cgrp_cset_link *link, *tmp_link;
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	list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
		list_del(&link->cset_link);
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		kfree(link);
	}
}

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/**
 * allocate_cgrp_cset_links - allocate cgrp_cset_links
 * @count: the number of links to allocate
 * @tmp_links: list_head the allocated links are put on
 *
 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
 * through ->cset_link.  Returns 0 on success or -errno.
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 */
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static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
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{
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	struct cgrp_cset_link *link;
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	int i;
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	INIT_LIST_HEAD(tmp_links);

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	for (i = 0; i < count; i++) {
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		link = kzalloc(sizeof(*link), GFP_KERNEL);
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		if (!link) {
607
			free_cgrp_cset_links(tmp_links);
608 609
			return -ENOMEM;
		}
610
		list_add(&link->cset_link, tmp_links);
611 612 613 614
	}
	return 0;
}

615 616
/**
 * link_css_set - a helper function to link a css_set to a cgroup
617
 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
618
 * @cset: the css_set to be linked
619 620
 * @cgrp: the destination cgroup
 */
621 622
static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
			 struct cgroup *cgrp)
623
{
624
	struct cgrp_cset_link *link;
625

626 627 628
	BUG_ON(list_empty(tmp_links));
	link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
	link->cset = cset;
629
	link->cgrp = cgrp;
630
	list_move(&link->cset_link, &cgrp->cset_links);
631 632 633 634
	/*
	 * Always add links to the tail of the list so that the list
	 * is sorted by order of hierarchy creation
	 */
635
	list_add_tail(&link->cgrp_link, &cset->cgrp_links);
636 637
}

638 639 640 641 642 643 644
/**
 * find_css_set - return a new css_set with one cgroup updated
 * @old_cset: the baseline css_set
 * @cgrp: the cgroup to be updated
 *
 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
 * substituted into the appropriate hierarchy.
645
 */
646 647
static struct css_set *find_css_set(struct css_set *old_cset,
				    struct cgroup *cgrp)
648
{
649
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
650
	struct css_set *cset;
651 652
	struct list_head tmp_links;
	struct cgrp_cset_link *link;
653
	unsigned long key;
654

655 656
	lockdep_assert_held(&cgroup_mutex);

657 658
	/* First see if we already have a cgroup group that matches
	 * the desired set */
659
	read_lock(&css_set_lock);
660 661 662
	cset = find_existing_css_set(old_cset, cgrp, template);
	if (cset)
		get_css_set(cset);
663
	read_unlock(&css_set_lock);
664

665 666
	if (cset)
		return cset;
667

668
	cset = kzalloc(sizeof(*cset), GFP_KERNEL);
669
	if (!cset)
670 671
		return NULL;

672
	/* Allocate all the cgrp_cset_link objects that we'll need */
673
	if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
674
		kfree(cset);
675 676 677
		return NULL;
	}

678
	atomic_set(&cset->refcount, 1);
679
	INIT_LIST_HEAD(&cset->cgrp_links);
680 681
	INIT_LIST_HEAD(&cset->tasks);
	INIT_HLIST_NODE(&cset->hlist);
682 683 684

	/* Copy the set of subsystem state objects generated in
	 * find_existing_css_set() */
685
	memcpy(cset->subsys, template, sizeof(cset->subsys));
686 687 688

	write_lock(&css_set_lock);
	/* Add reference counts and links from the new css_set. */
689
	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
690
		struct cgroup *c = link->cgrp;
691

692 693
		if (c->root == cgrp->root)
			c = cgrp;
694
		link_css_set(&tmp_links, cset, c);
695
	}
696

697
	BUG_ON(!list_empty(&tmp_links));
698 699

	css_set_count++;
700 701

	/* Add this cgroup group to the hash table */
702 703
	key = css_set_hash(cset->subsys);
	hash_add(css_set_table, &cset->hlist, key);
704

705 706
	write_unlock(&css_set_lock);

707
	return cset;
708 709
}

710 711 712 713 714 715 716
/*
 * Return the cgroup for "task" from the given hierarchy. Must be
 * called with cgroup_mutex held.
 */
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
					    struct cgroupfs_root *root)
{
717
	struct css_set *cset;
718 719 720 721 722 723 724 725 726
	struct cgroup *res = NULL;

	BUG_ON(!mutex_is_locked(&cgroup_mutex));
	read_lock(&css_set_lock);
	/*
	 * No need to lock the task - since we hold cgroup_mutex the
	 * task can't change groups, so the only thing that can happen
	 * is that it exits and its css is set back to init_css_set.
	 */
727
	cset = task_css_set(task);
728
	if (cset == &init_css_set) {
729 730
		res = &root->top_cgroup;
	} else {
731 732 733
		struct cgrp_cset_link *link;

		list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
734
			struct cgroup *c = link->cgrp;
735

736 737 738 739 740 741 742 743 744 745 746
			if (c->root == root) {
				res = c;
				break;
			}
		}
	}
	read_unlock(&css_set_lock);
	BUG_ON(!res);
	return res;
}

747 748 749 750 751 752 753 754 755 756
/*
 * There is one global cgroup mutex. We also require taking
 * task_lock() when dereferencing a task's cgroup subsys pointers.
 * See "The task_lock() exception", at the end of this comment.
 *
 * A task must hold cgroup_mutex to modify cgroups.
 *
 * Any task can increment and decrement the count field without lock.
 * So in general, code holding cgroup_mutex can't rely on the count
 * field not changing.  However, if the count goes to zero, then only
757
 * cgroup_attach_task() can increment it again.  Because a count of zero
758 759 760 761 762 763 764 765 766 767 768 769 770
 * means that no tasks are currently attached, therefore there is no
 * way a task attached to that cgroup can fork (the other way to
 * increment the count).  So code holding cgroup_mutex can safely
 * assume that if the count is zero, it will stay zero. Similarly, if
 * a task holds cgroup_mutex on a cgroup with zero count, it
 * knows that the cgroup won't be removed, as cgroup_rmdir()
 * needs that mutex.
 *
 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
 * (usually) take cgroup_mutex.  These are the two most performance
 * critical pieces of code here.  The exception occurs on cgroup_exit(),
 * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
 * is taken, and if the cgroup count is zero, a usermode call made
L
Li Zefan 已提交
771 772
 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
773 774 775 776 777 778 779 780 781 782 783
 *
 * A cgroup can only be deleted if both its 'count' of using tasks
 * is zero, and its list of 'children' cgroups is empty.  Since all
 * tasks in the system use _some_ cgroup, and since there is always at
 * least one task in the system (init, pid == 1), therefore, top_cgroup
 * always has either children cgroups and/or using tasks.  So we don't
 * need a special hack to ensure that top_cgroup cannot be deleted.
 *
 *	The task_lock() exception
 *
 * The need for this exception arises from the action of
784
 * cgroup_attach_task(), which overwrites one task's cgroup pointer with
L
Li Zefan 已提交
785
 * another.  It does so using cgroup_mutex, however there are
786 787 788
 * several performance critical places that need to reference
 * task->cgroup without the expense of grabbing a system global
 * mutex.  Therefore except as noted below, when dereferencing or, as
789
 * in cgroup_attach_task(), modifying a task's cgroup pointer we use
790 791 792 793
 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
 * the task_struct routinely used for such matters.
 *
 * P.S.  One more locking exception.  RCU is used to guard the
794
 * update of a tasks cgroup pointer by cgroup_attach_task()
795 796 797 798 799 800 801 802 803
 */

/*
 * A couple of forward declarations required, due to cyclic reference loop:
 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
 * -> cgroup_mkdir.
 */

804
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
A
Al Viro 已提交
805
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
806
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
807 808
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask);
809
static const struct inode_operations cgroup_dir_inode_operations;
810
static const struct file_operations proc_cgroupstats_operations;
811 812

static struct backing_dev_info cgroup_backing_dev_info = {
813
	.name		= "cgroup",
814
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
815
};
816

K
KAMEZAWA Hiroyuki 已提交
817 818 819
static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

A
Al Viro 已提交
820
static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
821 822 823 824
{
	struct inode *inode = new_inode(sb);

	if (inode) {
825
		inode->i_ino = get_next_ino();
826
		inode->i_mode = mode;
827 828
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
829 830 831 832 833 834
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

835 836 837 838 839 840 841 842 843 844 845
static struct cgroup_name *cgroup_alloc_name(struct dentry *dentry)
{
	struct cgroup_name *name;

	name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL);
	if (!name)
		return NULL;
	strcpy(name->name, dentry->d_name.name);
	return name;
}

846 847
static void cgroup_free_fn(struct work_struct *work)
{
848
	struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
849 850 851 852 853 854
	struct cgroup_subsys *ss;

	mutex_lock(&cgroup_mutex);
	/*
	 * Release the subsystem state objects.
	 */
855
	for_each_root_subsys(cgrp->root, ss)
856 857 858 859 860
		ss->css_free(cgrp);

	cgrp->root->number_of_cgroups--;
	mutex_unlock(&cgroup_mutex);

861 862 863 864 865 866 867
	/*
	 * We get a ref to the parent's dentry, and put the ref when
	 * this cgroup is being freed, so it's guaranteed that the
	 * parent won't be destroyed before its children.
	 */
	dput(cgrp->parent->dentry);

868 869
	ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);

870 871
	/*
	 * Drop the active superblock reference that we took when we
872 873
	 * created the cgroup. This will free cgrp->root, if we are
	 * holding the last reference to @sb.
874 875 876 877 878 879 880 881 882 883 884
	 */
	deactivate_super(cgrp->root->sb);

	/*
	 * if we're getting rid of the cgroup, refcount should ensure
	 * that there are no pidlists left.
	 */
	BUG_ON(!list_empty(&cgrp->pidlists));

	simple_xattrs_free(&cgrp->xattrs);

885
	kfree(rcu_dereference_raw(cgrp->name));
886 887 888 889 890 891 892
	kfree(cgrp);
}

static void cgroup_free_rcu(struct rcu_head *head)
{
	struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);

893 894
	INIT_WORK(&cgrp->destroy_work, cgroup_free_fn);
	schedule_work(&cgrp->destroy_work);
895 896
}

897 898 899 900
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
	/* is dentry a directory ? if so, kfree() associated cgroup */
	if (S_ISDIR(inode->i_mode)) {
901
		struct cgroup *cgrp = dentry->d_fsdata;
902

903
		BUG_ON(!(cgroup_is_dead(cgrp)));
904
		call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
T
Tejun Heo 已提交
905 906 907 908 909 910 911
	} else {
		struct cfent *cfe = __d_cfe(dentry);
		struct cgroup *cgrp = dentry->d_parent->d_fsdata;

		WARN_ONCE(!list_empty(&cfe->node) &&
			  cgrp != &cgrp->root->top_cgroup,
			  "cfe still linked for %s\n", cfe->type->name);
L
Li Zefan 已提交
912
		simple_xattrs_free(&cfe->xattrs);
T
Tejun Heo 已提交
913
		kfree(cfe);
914 915 916 917
	}
	iput(inode);
}

918 919 920 921 922
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

923 924 925 926 927 928 929 930 931
static void remove_dir(struct dentry *d)
{
	struct dentry *parent = dget(d->d_parent);

	d_delete(d);
	simple_rmdir(parent->d_inode, d);
	dput(parent);
}

932
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
T
Tejun Heo 已提交
933 934 935 936 937 938
{
	struct cfent *cfe;

	lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

939 940 941 942
	/*
	 * If we're doing cleanup due to failure of cgroup_create(),
	 * the corresponding @cfe may not exist.
	 */
T
Tejun Heo 已提交
943 944 945 946 947 948 949 950
	list_for_each_entry(cfe, &cgrp->files, node) {
		struct dentry *d = cfe->dentry;

		if (cft && cfe->type != cft)
			continue;

		dget(d);
		d_delete(d);
951
		simple_unlink(cgrp->dentry->d_inode, d);
T
Tejun Heo 已提交
952 953 954
		list_del_init(&cfe->node);
		dput(d);

955
		break;
956
	}
T
Tejun Heo 已提交
957 958
}

959 960 961 962 963 964 965 966
/**
 * cgroup_clear_directory - selective removal of base and subsystem files
 * @dir: directory containing the files
 * @base_files: true if the base files should be removed
 * @subsys_mask: mask of the subsystem ids whose files should be removed
 */
static void cgroup_clear_directory(struct dentry *dir, bool base_files,
				   unsigned long subsys_mask)
T
Tejun Heo 已提交
967 968
{
	struct cgroup *cgrp = __d_cgrp(dir);
969
	struct cgroup_subsys *ss;
T
Tejun Heo 已提交
970

971
	for_each_root_subsys(cgrp->root, ss) {
972 973 974 975
		struct cftype_set *set;
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
		list_for_each_entry(set, &ss->cftsets, node)
976
			cgroup_addrm_files(cgrp, NULL, set->cfts, false);
977 978 979 980 981
	}
	if (base_files) {
		while (!list_empty(&cgrp->files))
			cgroup_rm_file(cgrp, NULL);
	}
982 983 984 985 986 987 988
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
Nick Piggin 已提交
989
	struct dentry *parent;
990
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
N
Nick Piggin 已提交
991

992
	cgroup_clear_directory(dentry, true, root->subsys_mask);
993

N
Nick Piggin 已提交
994 995
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
996
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
997
	list_del_init(&dentry->d_u.d_child);
N
Nick Piggin 已提交
998 999
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
1000 1001 1002
	remove_dir(dentry);
}

B
Ben Blum 已提交
1003
/*
B
Ben Blum 已提交
1004 1005 1006
 * Call with cgroup_mutex held. Drops reference counts on modules, including
 * any duplicate ones that parse_cgroupfs_options took. If this function
 * returns an error, no reference counts are touched.
B
Ben Blum 已提交
1007
 */
1008
static int rebind_subsystems(struct cgroupfs_root *root,
1009
			     unsigned long added_mask, unsigned removed_mask)
1010
{
1011
	struct cgroup *cgrp = &root->top_cgroup;
1012
	struct cgroup_subsys *ss;
1013 1014
	int i;

B
Ben Blum 已提交
1015
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
1016
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
1017

1018
	/* Check that any added subsystems are currently free */
1019
	for_each_subsys(ss, i) {
L
Li Zefan 已提交
1020
		unsigned long bit = 1UL << i;
1021

1022
		if (!(bit & added_mask))
1023
			continue;
1024

1025
		if (ss->root != &cgroup_dummy_root) {
1026 1027 1028 1029 1030 1031 1032 1033 1034
			/* Subsystem isn't free */
			return -EBUSY;
		}
	}

	/* Currently we don't handle adding/removing subsystems when
	 * any child cgroups exist. This is theoretically supportable
	 * but involves complex error handling, so it's being left until
	 * later */
1035
	if (root->number_of_cgroups > 1)
1036 1037 1038
		return -EBUSY;

	/* Process each subsystem */
1039
	for_each_subsys(ss, i) {
1040
		unsigned long bit = 1UL << i;
1041

1042
		if (bit & added_mask) {
1043
			/* We're binding this subsystem to this hierarchy */
1044
			BUG_ON(cgrp->subsys[i]);
1045 1046
			BUG_ON(!cgroup_dummy_top->subsys[i]);
			BUG_ON(cgroup_dummy_top->subsys[i]->cgroup != cgroup_dummy_top);
1047

1048
			cgrp->subsys[i] = cgroup_dummy_top->subsys[i];
1049
			cgrp->subsys[i]->cgroup = cgrp;
1050
			list_move(&ss->sibling, &root->subsys_list);
1051
			ss->root = root;
1052
			if (ss->bind)
1053
				ss->bind(cgrp);
1054

B
Ben Blum 已提交
1055
			/* refcount was already taken, and we're keeping it */
1056
			root->subsys_mask |= bit;
1057
		} else if (bit & removed_mask) {
1058
			/* We're removing this subsystem */
1059
			BUG_ON(cgrp->subsys[i] != cgroup_dummy_top->subsys[i]);
1060
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1061

1062
			if (ss->bind)
1063 1064
				ss->bind(cgroup_dummy_top);
			cgroup_dummy_top->subsys[i]->cgroup = cgroup_dummy_top;
1065
			cgrp->subsys[i] = NULL;
1066 1067
			cgroup_subsys[i]->root = &cgroup_dummy_root;
			list_move(&ss->sibling, &cgroup_dummy_root.subsys_list);
1068

B
Ben Blum 已提交
1069 1070
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1071 1072
			root->subsys_mask &= ~bit;
		} else if (bit & root->subsys_mask) {
1073
			/* Subsystem state should already exist */
1074
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1075 1076 1077 1078 1079 1080 1081 1082
			/*
			 * a refcount was taken, but we already had one, so
			 * drop the extra reference.
			 */
			module_put(ss->module);
#ifdef CONFIG_MODULE_UNLOAD
			BUG_ON(ss->module && !module_refcount(ss->module));
#endif
1083 1084
		} else {
			/* Subsystem state shouldn't exist */
1085
			BUG_ON(cgrp->subsys[i]);
1086 1087 1088
		}
	}

1089 1090 1091 1092 1093 1094
	/*
	 * Mark @root has finished binding subsystems.  @root->subsys_mask
	 * now matches the bound subsystems.
	 */
	root->flags |= CGRP_ROOT_SUBSYS_BOUND;

1095 1096 1097
	return 0;
}

1098
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1099
{
1100
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1101 1102
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1103
	mutex_lock(&cgroup_root_mutex);
1104
	for_each_root_subsys(root, ss)
1105
		seq_printf(seq, ",%s", ss->name);
1106 1107
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
		seq_puts(seq, ",sane_behavior");
1108
	if (root->flags & CGRP_ROOT_NOPREFIX)
1109
		seq_puts(seq, ",noprefix");
1110
	if (root->flags & CGRP_ROOT_XATTR)
A
Aristeu Rozanski 已提交
1111
		seq_puts(seq, ",xattr");
1112 1113
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1114
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1115
		seq_puts(seq, ",clone_children");
1116 1117
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
1118
	mutex_unlock(&cgroup_root_mutex);
1119 1120 1121 1122
	return 0;
}

struct cgroup_sb_opts {
1123
	unsigned long subsys_mask;
1124
	unsigned long flags;
1125
	char *release_agent;
1126
	bool cpuset_clone_children;
1127
	char *name;
1128 1129
	/* User explicitly requested empty subsystem */
	bool none;
1130 1131

	struct cgroupfs_root *new_root;
1132

1133 1134
};

B
Ben Blum 已提交
1135
/*
1136 1137 1138 1139
 * Convert a hierarchy specifier into a bitmask of subsystems and
 * flags. Call with cgroup_mutex held to protect the cgroup_subsys[]
 * array. This function takes refcounts on subsystems to be used, unless it
 * returns error, in which case no refcounts are taken.
B
Ben Blum 已提交
1140
 */
B
Ben Blum 已提交
1141
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1142
{
1143 1144
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1145
	unsigned long mask = (unsigned long)-1;
B
Ben Blum 已提交
1146
	bool module_pin_failed = false;
1147 1148
	struct cgroup_subsys *ss;
	int i;
1149

B
Ben Blum 已提交
1150 1151
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1152 1153 1154
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1155

1156
	memset(opts, 0, sizeof(*opts));
1157 1158 1159 1160

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1161
		if (!strcmp(token, "none")) {
1162 1163
			/* Explicitly have no subsystems */
			opts->none = true;
1164 1165 1166 1167 1168 1169 1170 1171 1172
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
1173 1174 1175 1176
		if (!strcmp(token, "__DEVEL__sane_behavior")) {
			opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
			continue;
		}
1177
		if (!strcmp(token, "noprefix")) {
1178
			opts->flags |= CGRP_ROOT_NOPREFIX;
1179 1180 1181
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1182
			opts->cpuset_clone_children = true;
1183 1184
			continue;
		}
A
Aristeu Rozanski 已提交
1185
		if (!strcmp(token, "xattr")) {
1186
			opts->flags |= CGRP_ROOT_XATTR;
A
Aristeu Rozanski 已提交
1187 1188
			continue;
		}
1189
		if (!strncmp(token, "release_agent=", 14)) {
1190 1191 1192
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1193
			opts->release_agent =
1194
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1195 1196
			if (!opts->release_agent)
				return -ENOMEM;
1197 1198 1199
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216
			const char *name = token + 5;
			/* Can't specify an empty name */
			if (!strlen(name))
				return -EINVAL;
			/* Must match [\w.-]+ */
			for (i = 0; i < strlen(name); i++) {
				char c = name[i];
				if (isalnum(c))
					continue;
				if ((c == '.') || (c == '-') || (c == '_'))
					continue;
				return -EINVAL;
			}
			/* Specifying two names is forbidden */
			if (opts->name)
				return -EINVAL;
			opts->name = kstrndup(name,
1217
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1218 1219 1220
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1221 1222 1223 1224

			continue;
		}

1225
		for_each_subsys(ss, i) {
1226 1227 1228 1229 1230 1231 1232 1233
			if (strcmp(token, ss->name))
				continue;
			if (ss->disabled)
				continue;

			/* Mutually exclusive option 'all' + subsystem name */
			if (all_ss)
				return -EINVAL;
1234
			set_bit(i, &opts->subsys_mask);
1235 1236 1237 1238 1239 1240 1241 1242 1243 1244
			one_ss = true;

			break;
		}
		if (i == CGROUP_SUBSYS_COUNT)
			return -ENOENT;
	}

	/*
	 * If the 'all' option was specified select all the subsystems,
1245 1246
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1247
	 */
1248 1249 1250 1251
	if (all_ss || (!one_ss && !opts->none && !opts->name))
		for_each_subsys(ss, i)
			if (!ss->disabled)
				set_bit(i, &opts->subsys_mask);
1252

1253 1254
	/* Consistency checks */

1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268
	if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
		pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");

		if (opts->flags & CGRP_ROOT_NOPREFIX) {
			pr_err("cgroup: sane_behavior: noprefix is not allowed\n");
			return -EINVAL;
		}

		if (opts->cpuset_clone_children) {
			pr_err("cgroup: sane_behavior: clone_children is not allowed\n");
			return -EINVAL;
		}
	}

1269 1270 1271 1272 1273
	/*
	 * Option noprefix was introduced just for backward compatibility
	 * with the old cpuset, so we allow noprefix only if mounting just
	 * the cpuset subsystem.
	 */
1274
	if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1275 1276
		return -EINVAL;

1277 1278

	/* Can't specify "none" and some subsystems */
1279
	if (opts->subsys_mask && opts->none)
1280 1281 1282 1283 1284 1285
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1286
	if (!opts->subsys_mask && !opts->name)
1287 1288
		return -EINVAL;

B
Ben Blum 已提交
1289 1290 1291 1292 1293 1294
	/*
	 * Grab references on all the modules we'll need, so the subsystems
	 * don't dance around before rebind_subsystems attaches them. This may
	 * take duplicate reference counts on a subsystem that's already used,
	 * but rebind_subsystems handles this case.
	 */
1295 1296
	for_each_subsys(ss, i) {
		if (!(opts->subsys_mask & (1UL << i)))
B
Ben Blum 已提交
1297
			continue;
1298
		if (!try_module_get(cgroup_subsys[i]->module)) {
B
Ben Blum 已提交
1299 1300 1301 1302 1303 1304 1305 1306 1307 1308
			module_pin_failed = true;
			break;
		}
	}
	if (module_pin_failed) {
		/*
		 * oops, one of the modules was going away. this means that we
		 * raced with a module_delete call, and to the user this is
		 * essentially a "subsystem doesn't exist" case.
		 */
1309
		for (i--; i >= 0; i--) {
B
Ben Blum 已提交
1310 1311 1312
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

1313
			if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1314
				continue;
1315
			module_put(cgroup_subsys[i]->module);
B
Ben Blum 已提交
1316 1317 1318 1319
		}
		return -ENOENT;
	}

1320 1321 1322
	return 0;
}

1323
static void drop_parsed_module_refcounts(unsigned long subsys_mask)
B
Ben Blum 已提交
1324
{
1325
	struct cgroup_subsys *ss;
B
Ben Blum 已提交
1326 1327
	int i;

1328 1329 1330 1331 1332
	mutex_lock(&cgroup_mutex);
	for_each_subsys(ss, i)
		if (subsys_mask & (1UL << i))
			module_put(cgroup_subsys[i]->module);
	mutex_unlock(&cgroup_mutex);
B
Ben Blum 已提交
1333 1334
}

1335 1336 1337 1338
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1339
	struct cgroup *cgrp = &root->top_cgroup;
1340
	struct cgroup_sb_opts opts;
1341
	unsigned long added_mask, removed_mask;
1342

1343 1344 1345 1346 1347
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
		pr_err("cgroup: sane_behavior: remount is not allowed\n");
		return -EINVAL;
	}

1348
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1349
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1350
	mutex_lock(&cgroup_root_mutex);
1351 1352 1353 1354 1355 1356

	/* See what subsystems are wanted */
	ret = parse_cgroupfs_options(data, &opts);
	if (ret)
		goto out_unlock;

1357
	if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
1358 1359 1360
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

1361 1362
	added_mask = opts.subsys_mask & ~root->subsys_mask;
	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1363

B
Ben Blum 已提交
1364
	/* Don't allow flags or name to change at remount */
1365
	if (((opts.flags ^ root->flags) & CGRP_ROOT_OPTION_MASK) ||
B
Ben Blum 已提交
1366
	    (opts.name && strcmp(opts.name, root->name))) {
1367 1368 1369
		pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
		       opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "",
		       root->flags & CGRP_ROOT_OPTION_MASK, root->name);
1370 1371 1372 1373
		ret = -EINVAL;
		goto out_unlock;
	}

1374 1375 1376 1377 1378 1379 1380
	/*
	 * Clear out the files of subsystems that should be removed, do
	 * this before rebind_subsystems, since rebind_subsystems may
	 * change this hierarchy's subsys_list.
	 */
	cgroup_clear_directory(cgrp->dentry, false, removed_mask);

1381
	ret = rebind_subsystems(root, added_mask, removed_mask);
B
Ben Blum 已提交
1382
	if (ret) {
1383 1384
		/* rebind_subsystems failed, re-populate the removed files */
		cgroup_populate_dir(cgrp, false, removed_mask);
1385
		goto out_unlock;
B
Ben Blum 已提交
1386
	}
1387

1388
	/* re-populate subsystem files */
1389
	cgroup_populate_dir(cgrp, false, added_mask);
1390

1391 1392
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1393
 out_unlock:
1394
	kfree(opts.release_agent);
1395
	kfree(opts.name);
T
Tejun Heo 已提交
1396
	mutex_unlock(&cgroup_root_mutex);
1397
	mutex_unlock(&cgroup_mutex);
1398
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1399 1400
	if (ret)
		drop_parsed_module_refcounts(opts.subsys_mask);
1401 1402 1403
	return ret;
}

1404
static const struct super_operations cgroup_ops = {
1405 1406 1407 1408 1409 1410
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1411 1412 1413 1414
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1415
	INIT_LIST_HEAD(&cgrp->files);
1416
	INIT_LIST_HEAD(&cgrp->cset_links);
1417
	INIT_LIST_HEAD(&cgrp->release_list);
1418 1419
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1420 1421
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
A
Aristeu Rozanski 已提交
1422
	simple_xattrs_init(&cgrp->xattrs);
1423
}
1424

1425 1426
static void init_cgroup_root(struct cgroupfs_root *root)
{
1427
	struct cgroup *cgrp = &root->top_cgroup;
1428

1429 1430 1431
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
	root->number_of_cgroups = 1;
1432
	cgrp->root = root;
1433
	RCU_INIT_POINTER(cgrp->name, &root_cgroup_name);
1434
	init_cgroup_housekeeping(cgrp);
1435 1436
}

1437
static int cgroup_init_root_id(struct cgroupfs_root *root, int start, int end)
1438
{
1439
	int id;
1440

T
Tejun Heo 已提交
1441 1442 1443
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&cgroup_root_mutex);

1444 1445
	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, start, end,
			      GFP_KERNEL);
1446 1447 1448 1449
	if (id < 0)
		return id;

	root->hierarchy_id = id;
1450 1451 1452 1453 1454
	return 0;
}

static void cgroup_exit_root_id(struct cgroupfs_root *root)
{
T
Tejun Heo 已提交
1455 1456 1457
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&cgroup_root_mutex);

1458
	if (root->hierarchy_id) {
1459
		idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1460 1461
		root->hierarchy_id = 0;
	}
1462 1463
}

1464 1465
static int cgroup_test_super(struct super_block *sb, void *data)
{
1466
	struct cgroup_sb_opts *opts = data;
1467 1468
	struct cgroupfs_root *root = sb->s_fs_info;

1469 1470 1471
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1472

1473 1474 1475 1476
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
1477 1478
	if ((opts->subsys_mask || opts->none)
	    && (opts->subsys_mask != root->subsys_mask))
1479 1480 1481 1482 1483
		return 0;

	return 1;
}

1484 1485 1486 1487
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1488
	if (!opts->subsys_mask && !opts->none)
1489 1490 1491 1492 1493 1494 1495
		return NULL;

	root = kzalloc(sizeof(*root), GFP_KERNEL);
	if (!root)
		return ERR_PTR(-ENOMEM);

	init_cgroup_root(root);
1496

1497 1498 1499 1500 1501 1502 1503 1504
	/*
	 * We need to set @root->subsys_mask now so that @root can be
	 * matched by cgroup_test_super() before it finishes
	 * initialization; otherwise, competing mounts with the same
	 * options may try to bind the same subsystems instead of waiting
	 * for the first one leading to unexpected mount errors.
	 * SUBSYS_BOUND will be set once actual binding is complete.
	 */
1505
	root->subsys_mask = opts->subsys_mask;
1506
	root->flags = opts->flags;
T
Tejun Heo 已提交
1507
	ida_init(&root->cgroup_ida);
1508 1509 1510 1511
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1512 1513
	if (opts->cpuset_clone_children)
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1514 1515 1516
	return root;
}

1517
static void cgroup_free_root(struct cgroupfs_root *root)
1518
{
1519 1520 1521
	if (root) {
		/* hierarhcy ID shoulid already have been released */
		WARN_ON_ONCE(root->hierarchy_id);
1522

1523 1524 1525
		ida_destroy(&root->cgroup_ida);
		kfree(root);
	}
1526 1527
}

1528 1529 1530
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1531 1532 1533 1534 1535 1536
	struct cgroup_sb_opts *opts = data;

	/* If we don't have a new root, we can't set up a new sb */
	if (!opts->new_root)
		return -EINVAL;

1537
	BUG_ON(!opts->subsys_mask && !opts->none);
1538 1539 1540 1541 1542

	ret = set_anon_super(sb, NULL);
	if (ret)
		return ret;

1543 1544
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555

	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
	sb->s_magic = CGROUP_SUPER_MAGIC;
	sb->s_op = &cgroup_ops;

	return 0;
}

static int cgroup_get_rootdir(struct super_block *sb)
{
A
Al Viro 已提交
1556 1557
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1558
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1559 1560
	};

1561 1562 1563 1564 1565 1566 1567 1568 1569 1570
	struct inode *inode =
		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);

	if (!inode)
		return -ENOMEM;

	inode->i_fop = &simple_dir_operations;
	inode->i_op = &cgroup_dir_inode_operations;
	/* directories start off with i_nlink == 2 (for "." entry) */
	inc_nlink(inode);
1571 1572
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1573
		return -ENOMEM;
A
Al Viro 已提交
1574 1575
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1576 1577 1578
	return 0;
}

A
Al Viro 已提交
1579
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1580
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1581
			 void *data)
1582 1583
{
	struct cgroup_sb_opts opts;
1584
	struct cgroupfs_root *root;
1585 1586
	int ret = 0;
	struct super_block *sb;
1587
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1588
	struct inode *inode;
1589 1590

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1591
	mutex_lock(&cgroup_mutex);
1592
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1593
	mutex_unlock(&cgroup_mutex);
1594 1595
	if (ret)
		goto out_err;
1596

1597 1598 1599 1600 1601 1602 1603
	/*
	 * Allocate a new cgroup root. We may not need it if we're
	 * reusing an existing hierarchy.
	 */
	new_root = cgroup_root_from_opts(&opts);
	if (IS_ERR(new_root)) {
		ret = PTR_ERR(new_root);
B
Ben Blum 已提交
1604
		goto drop_modules;
1605
	}
1606
	opts.new_root = new_root;
1607

1608
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1609
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1610
	if (IS_ERR(sb)) {
1611
		ret = PTR_ERR(sb);
1612
		cgroup_free_root(opts.new_root);
B
Ben Blum 已提交
1613
		goto drop_modules;
1614 1615
	}

1616 1617 1618 1619
	root = sb->s_fs_info;
	BUG_ON(!root);
	if (root == opts.new_root) {
		/* We used the new root structure, so this is a new hierarchy */
1620
		struct list_head tmp_links;
1621
		struct cgroup *root_cgrp = &root->top_cgroup;
1622
		struct cgroupfs_root *existing_root;
1623
		const struct cred *cred;
1624
		int i;
1625
		struct css_set *cset;
1626 1627 1628 1629 1630 1631

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1632
		inode = sb->s_root->d_inode;
1633

1634
		mutex_lock(&inode->i_mutex);
1635
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1636
		mutex_lock(&cgroup_root_mutex);
1637

T
Tejun Heo 已提交
1638 1639 1640 1641 1642 1643
		/* Check for name clashes with existing mounts */
		ret = -EBUSY;
		if (strlen(root->name))
			for_each_active_root(existing_root)
				if (!strcmp(existing_root->name, root->name))
					goto unlock_drop;
1644

1645 1646 1647 1648 1649 1650 1651
		/*
		 * We're accessing css_set_count without locking
		 * css_set_lock here, but that's OK - it can only be
		 * increased by someone holding cgroup_lock, and
		 * that's us. The worst that can happen is that we
		 * have some link structures left over
		 */
1652
		ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
T
Tejun Heo 已提交
1653 1654
		if (ret)
			goto unlock_drop;
1655

1656 1657
		/* ID 0 is reserved for dummy root, 1 for unified hierarchy */
		ret = cgroup_init_root_id(root, 2, 0);
1658 1659 1660
		if (ret)
			goto unlock_drop;

1661
		ret = rebind_subsystems(root, root->subsys_mask, 0);
1662
		if (ret == -EBUSY) {
1663
			free_cgrp_cset_links(&tmp_links);
T
Tejun Heo 已提交
1664
			goto unlock_drop;
1665
		}
B
Ben Blum 已提交
1666 1667 1668 1669 1670
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1671 1672 1673 1674

		/* EBUSY should be the only error here */
		BUG_ON(ret);

1675 1676
		list_add(&root->root_list, &cgroup_roots);
		cgroup_root_count++;
1677

1678
		sb->s_root->d_fsdata = root_cgrp;
1679 1680
		root->top_cgroup.dentry = sb->s_root;

1681 1682 1683
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1684
		hash_for_each(css_set_table, i, cset, hlist)
1685
			link_css_set(&tmp_links, cset, root_cgrp);
1686 1687
		write_unlock(&css_set_lock);

1688
		free_cgrp_cset_links(&tmp_links);
1689

1690
		BUG_ON(!list_empty(&root_cgrp->children));
1691 1692
		BUG_ON(root->number_of_cgroups != 1);

1693
		cred = override_creds(&init_cred);
1694
		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1695
		revert_creds(cred);
T
Tejun Heo 已提交
1696
		mutex_unlock(&cgroup_root_mutex);
1697
		mutex_unlock(&cgroup_mutex);
1698
		mutex_unlock(&inode->i_mutex);
1699 1700 1701 1702 1703
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1704
		cgroup_free_root(opts.new_root);
1705

1706
		if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) {
1707 1708 1709 1710 1711 1712 1713
			if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
				pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
				ret = -EINVAL;
				goto drop_new_super;
			} else {
				pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
			}
1714 1715
		}

B
Ben Blum 已提交
1716
		/* no subsys rebinding, so refcounts don't change */
1717
		drop_parsed_module_refcounts(opts.subsys_mask);
1718 1719
	}

1720 1721
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1722
	return dget(sb->s_root);
1723

T
Tejun Heo 已提交
1724
 unlock_drop:
1725
	cgroup_exit_root_id(root);
T
Tejun Heo 已提交
1726 1727 1728
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1729
 drop_new_super:
1730
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1731
 drop_modules:
1732
	drop_parsed_module_refcounts(opts.subsys_mask);
1733 1734 1735
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1736
	return ERR_PTR(ret);
1737 1738 1739 1740
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1741
	struct cgroup *cgrp = &root->top_cgroup;
1742
	struct cgrp_cset_link *link, *tmp_link;
1743 1744 1745 1746 1747
	int ret;

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1748
	BUG_ON(!list_empty(&cgrp->children));
1749 1750

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1751
	mutex_lock(&cgroup_root_mutex);
1752 1753

	/* Rebind all subsystems back to the default hierarchy */
1754 1755 1756 1757 1758
	if (root->flags & CGRP_ROOT_SUBSYS_BOUND) {
		ret = rebind_subsystems(root, 0, root->subsys_mask);
		/* Shouldn't be able to fail ... */
		BUG_ON(ret);
	}
1759

1760
	/*
1761
	 * Release all the links from cset_links to this hierarchy's
1762 1763 1764
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1765

1766 1767 1768
	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
		list_del(&link->cset_link);
		list_del(&link->cgrp_link);
1769 1770 1771 1772
		kfree(link);
	}
	write_unlock(&css_set_lock);

1773 1774
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
1775
		cgroup_root_count--;
1776
	}
1777

1778 1779
	cgroup_exit_root_id(root);

T
Tejun Heo 已提交
1780
	mutex_unlock(&cgroup_root_mutex);
1781 1782
	mutex_unlock(&cgroup_mutex);

A
Aristeu Rozanski 已提交
1783 1784
	simple_xattrs_free(&cgrp->xattrs);

1785
	kill_litter_super(sb);
1786
	cgroup_free_root(root);
1787 1788 1789 1790
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1791
	.mount = cgroup_mount,
1792 1793 1794
	.kill_sb = cgroup_kill_sb,
};

1795 1796
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1797 1798 1799 1800 1801 1802
/**
 * cgroup_path - generate the path of a cgroup
 * @cgrp: the cgroup in question
 * @buf: the buffer to write the path into
 * @buflen: the length of the buffer
 *
1803 1804 1805 1806 1807 1808
 * Writes path of cgroup into buf.  Returns 0 on success, -errno on error.
 *
 * We can't generate cgroup path using dentry->d_name, as accessing
 * dentry->name must be protected by irq-unsafe dentry->d_lock or parent
 * inode's i_mutex, while on the other hand cgroup_path() can be called
 * with some irq-safe spinlocks held.
1809
 */
1810
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1811
{
1812
	int ret = -ENAMETOOLONG;
1813
	char *start;
1814

1815 1816 1817
	if (!cgrp->parent) {
		if (strlcpy(buf, "/", buflen) >= buflen)
			return -ENAMETOOLONG;
1818 1819 1820
		return 0;
	}

1821 1822
	start = buf + buflen - 1;
	*start = '\0';
1823

1824
	rcu_read_lock();
1825
	do {
1826 1827 1828 1829
		const char *name = cgroup_name(cgrp);
		int len;

		len = strlen(name);
1830
		if ((start -= len) < buf)
1831 1832
			goto out;
		memcpy(start, name, len);
1833

1834
		if (--start < buf)
1835
			goto out;
1836
		*start = '/';
1837 1838

		cgrp = cgrp->parent;
1839
	} while (cgrp->parent);
1840
	ret = 0;
1841
	memmove(buf, start, buf + buflen - start);
1842 1843 1844
out:
	rcu_read_unlock();
	return ret;
1845
}
B
Ben Blum 已提交
1846
EXPORT_SYMBOL_GPL(cgroup_path);
1847

1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879
/**
 * task_cgroup_path_from_hierarchy - cgroup path of a task on a hierarchy
 * @task: target task
 * @hierarchy_id: the hierarchy to look up @task's cgroup from
 * @buf: the buffer to write the path into
 * @buflen: the length of the buffer
 *
 * Determine @task's cgroup on the hierarchy specified by @hierarchy_id and
 * copy its path into @buf.  This function grabs cgroup_mutex and shouldn't
 * be used inside locks used by cgroup controller callbacks.
 */
int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,
				    char *buf, size_t buflen)
{
	struct cgroupfs_root *root;
	struct cgroup *cgrp = NULL;
	int ret = -ENOENT;

	mutex_lock(&cgroup_mutex);

	root = idr_find(&cgroup_hierarchy_idr, hierarchy_id);
	if (root) {
		cgrp = task_cgroup_from_root(task, root);
		ret = cgroup_path(cgrp, buf, buflen);
	}

	mutex_unlock(&cgroup_mutex);

	return ret;
}
EXPORT_SYMBOL_GPL(task_cgroup_path_from_hierarchy);

1880 1881 1882
/*
 * Control Group taskset
 */
1883 1884 1885
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1886
	struct css_set		*cg;
1887 1888
};

1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959
struct cgroup_taskset {
	struct task_and_cgroup	single;
	struct flex_array	*tc_array;
	int			tc_array_len;
	int			idx;
	struct cgroup		*cur_cgrp;
};

/**
 * cgroup_taskset_first - reset taskset and return the first task
 * @tset: taskset of interest
 *
 * @tset iteration is initialized and the first task is returned.
 */
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
{
	if (tset->tc_array) {
		tset->idx = 0;
		return cgroup_taskset_next(tset);
	} else {
		tset->cur_cgrp = tset->single.cgrp;
		return tset->single.task;
	}
}
EXPORT_SYMBOL_GPL(cgroup_taskset_first);

/**
 * cgroup_taskset_next - iterate to the next task in taskset
 * @tset: taskset of interest
 *
 * Return the next task in @tset.  Iteration must have been initialized
 * with cgroup_taskset_first().
 */
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
{
	struct task_and_cgroup *tc;

	if (!tset->tc_array || tset->idx >= tset->tc_array_len)
		return NULL;

	tc = flex_array_get(tset->tc_array, tset->idx++);
	tset->cur_cgrp = tc->cgrp;
	return tc->task;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_next);

/**
 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
 * @tset: taskset of interest
 *
 * Return the cgroup for the current (last returned) task of @tset.  This
 * function must be preceded by either cgroup_taskset_first() or
 * cgroup_taskset_next().
 */
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
{
	return tset->cur_cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);

/**
 * cgroup_taskset_size - return the number of tasks in taskset
 * @tset: taskset of interest
 */
int cgroup_taskset_size(struct cgroup_taskset *tset)
{
	return tset->tc_array ? tset->tc_array_len : 1;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_size);


B
Ben Blum 已提交
1960 1961 1962
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
1963
 * Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1964
 */
1965 1966 1967
static void cgroup_task_migrate(struct cgroup *old_cgrp,
				struct task_struct *tsk,
				struct css_set *new_cset)
B
Ben Blum 已提交
1968
{
1969
	struct css_set *old_cset;
B
Ben Blum 已提交
1970 1971

	/*
1972 1973 1974
	 * 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.
B
Ben Blum 已提交
1975
	 */
1976
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
1977
	old_cset = task_css_set(tsk);
B
Ben Blum 已提交
1978 1979

	task_lock(tsk);
1980
	rcu_assign_pointer(tsk->cgroups, new_cset);
B
Ben Blum 已提交
1981 1982 1983 1984 1985
	task_unlock(tsk);

	/* Update the css_set linked lists if we're using them */
	write_lock(&css_set_lock);
	if (!list_empty(&tsk->cg_list))
1986
		list_move(&tsk->cg_list, &new_cset->tasks);
B
Ben Blum 已提交
1987 1988 1989
	write_unlock(&css_set_lock);

	/*
1990 1991 1992
	 * We just gained a reference on old_cset by taking it from the
	 * task. As trading it for new_cset is protected by cgroup_mutex,
	 * we're safe to drop it here; it will be freed under RCU.
B
Ben Blum 已提交
1993
	 */
1994 1995
	set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
	put_css_set(old_cset);
B
Ben Blum 已提交
1996 1997
}

L
Li Zefan 已提交
1998
/**
1999
 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
B
Ben Blum 已提交
2000
 * @cgrp: the cgroup to attach to
2001 2002
 * @tsk: the task or the leader of the threadgroup to be attached
 * @threadgroup: attach the whole threadgroup?
B
Ben Blum 已提交
2003
 *
2004
 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
2005
 * task_lock of @tsk or each thread in the threadgroup individually in turn.
B
Ben Blum 已提交
2006
 */
T
Tejun Heo 已提交
2007 2008
static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
			      bool threadgroup)
B
Ben Blum 已提交
2009 2010 2011 2012 2013
{
	int retval, i, group_size;
	struct cgroup_subsys *ss, *failed_ss = NULL;
	struct cgroupfs_root *root = cgrp->root;
	/* threadgroup list cursor and array */
2014
	struct task_struct *leader = tsk;
2015
	struct task_and_cgroup *tc;
2016
	struct flex_array *group;
2017
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2018 2019 2020 2021 2022

	/*
	 * step 0: in order to do expensive, possibly blocking operations for
	 * every thread, we cannot iterate the thread group list, since it needs
	 * rcu or tasklist locked. instead, build an array of all threads in the
2023 2024
	 * group - group_rwsem prevents new threads from appearing, and if
	 * threads exit, this will just be an over-estimate.
B
Ben Blum 已提交
2025
	 */
2026 2027 2028 2029
	if (threadgroup)
		group_size = get_nr_threads(tsk);
	else
		group_size = 1;
2030
	/* flex_array supports very large thread-groups better than kmalloc. */
2031
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2032 2033
	if (!group)
		return -ENOMEM;
2034
	/* pre-allocate to guarantee space while iterating in rcu read-side. */
2035
	retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
2036 2037
	if (retval)
		goto out_free_group_list;
B
Ben Blum 已提交
2038 2039

	i = 0;
2040 2041 2042 2043 2044 2045
	/*
	 * Prevent freeing of tasks while we take a snapshot. Tasks that are
	 * already PF_EXITING could be freed from underneath us unless we
	 * take an rcu_read_lock.
	 */
	rcu_read_lock();
B
Ben Blum 已提交
2046
	do {
2047 2048
		struct task_and_cgroup ent;

2049 2050 2051 2052
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2053 2054
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2055 2056
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2057 2058 2059
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2060 2061 2062 2063
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2064
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2065
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2066
		i++;
2067 2068 2069

		if (!threadgroup)
			break;
B
Ben Blum 已提交
2070
	} while_each_thread(leader, tsk);
2071
	rcu_read_unlock();
B
Ben Blum 已提交
2072 2073
	/* remember the number of threads in the array for later. */
	group_size = i;
2074 2075
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2076

2077 2078
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2079
	if (!group_size)
2080
		goto out_free_group_list;
2081

B
Ben Blum 已提交
2082 2083 2084
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
2085
	for_each_root_subsys(root, ss) {
B
Ben Blum 已提交
2086
		if (ss->can_attach) {
2087
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099
			if (retval) {
				failed_ss = ss;
				goto out_cancel_attach;
			}
		}
	}

	/*
	 * step 2: make sure css_sets exist for all threads to be migrated.
	 * we use find_css_set, which allocates a new one if necessary.
	 */
	for (i = 0; i < group_size; i++) {
2100 2101
		struct css_set *old_cset;

2102
		tc = flex_array_get(group, i);
2103 2104
		old_cset = task_css_set(tc->task);
		tc->cg = find_css_set(old_cset, cgrp);
2105 2106 2107
		if (!tc->cg) {
			retval = -ENOMEM;
			goto out_put_css_set_refs;
B
Ben Blum 已提交
2108 2109 2110 2111
		}
	}

	/*
2112 2113 2114
	 * step 3: now that we're guaranteed success wrt the css_sets,
	 * proceed to move all tasks to the new cgroup.  There are no
	 * failure cases after here, so this is the commit point.
B
Ben Blum 已提交
2115 2116
	 */
	for (i = 0; i < group_size; i++) {
2117
		tc = flex_array_get(group, i);
2118
		cgroup_task_migrate(tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2119 2120 2121 2122
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2123
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2124
	 */
2125
	for_each_root_subsys(root, ss) {
B
Ben Blum 已提交
2126
		if (ss->attach)
2127
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2128 2129 2130 2131 2132 2133
	}

	/*
	 * step 5: success! and cleanup
	 */
	retval = 0;
2134 2135 2136 2137 2138 2139 2140 2141
out_put_css_set_refs:
	if (retval) {
		for (i = 0; i < group_size; i++) {
			tc = flex_array_get(group, i);
			if (!tc->cg)
				break;
			put_css_set(tc->cg);
		}
B
Ben Blum 已提交
2142 2143 2144
	}
out_cancel_attach:
	if (retval) {
2145
		for_each_root_subsys(root, ss) {
2146
			if (ss == failed_ss)
B
Ben Blum 已提交
2147 2148
				break;
			if (ss->cancel_attach)
2149
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2150 2151 2152
		}
	}
out_free_group_list:
2153
	flex_array_free(group);
B
Ben Blum 已提交
2154 2155 2156 2157 2158
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2159 2160
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2161
 */
B
Ben Blum 已提交
2162
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2163 2164
{
	struct task_struct *tsk;
2165
	const struct cred *cred = current_cred(), *tcred;
2166 2167
	int ret;

B
Ben Blum 已提交
2168 2169 2170
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2171 2172
retry_find_task:
	rcu_read_lock();
2173
	if (pid) {
2174
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2175 2176
		if (!tsk) {
			rcu_read_unlock();
2177 2178
			ret= -ESRCH;
			goto out_unlock_cgroup;
2179
		}
B
Ben Blum 已提交
2180 2181 2182 2183
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2184
		tcred = __task_cred(tsk);
2185 2186 2187
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2188
			rcu_read_unlock();
2189 2190
			ret = -EACCES;
			goto out_unlock_cgroup;
2191
		}
2192 2193
	} else
		tsk = current;
2194 2195

	if (threadgroup)
2196
		tsk = tsk->group_leader;
2197 2198

	/*
2199
	 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2200 2201 2202
	 * trapped in a cpuset, or RT worker may be born in a cgroup
	 * with no rt_runtime allocated.  Just say no.
	 */
2203
	if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2204 2205 2206 2207 2208
		ret = -EINVAL;
		rcu_read_unlock();
		goto out_unlock_cgroup;
	}

2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225
	get_task_struct(tsk);
	rcu_read_unlock();

	threadgroup_lock(tsk);
	if (threadgroup) {
		if (!thread_group_leader(tsk)) {
			/*
			 * a race with de_thread from another thread's exec()
			 * may strip us of our leadership, if this happens,
			 * there is no choice but to throw this task away and
			 * try again; this is
			 * "double-double-toil-and-trouble-check locking".
			 */
			threadgroup_unlock(tsk);
			put_task_struct(tsk);
			goto retry_find_task;
		}
2226 2227 2228 2229
	}

	ret = cgroup_attach_task(cgrp, tsk, threadgroup);

2230 2231
	threadgroup_unlock(tsk);

2232
	put_task_struct(tsk);
2233
out_unlock_cgroup:
T
Tejun Heo 已提交
2234
	mutex_unlock(&cgroup_mutex);
2235 2236 2237
	return ret;
}

2238 2239 2240 2241 2242 2243 2244 2245 2246 2247
/**
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
 * @tsk: the task to be attached
 */
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
{
	struct cgroupfs_root *root;
	int retval = 0;

T
Tejun Heo 已提交
2248
	mutex_lock(&cgroup_mutex);
2249 2250 2251 2252 2253 2254 2255
	for_each_active_root(root) {
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk, false);
		if (retval)
			break;
	}
T
Tejun Heo 已提交
2256
	mutex_unlock(&cgroup_mutex);
2257 2258 2259 2260 2261

	return retval;
}
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);

2262
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2263 2264 2265 2266 2267
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2268
{
2269
	return attach_task_by_pid(cgrp, tgid, true);
2270 2271
}

2272 2273 2274 2275
static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
				      const char *buffer)
{
	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2276 2277
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2278 2279
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2280
	mutex_lock(&cgroup_root_mutex);
2281
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2282
	mutex_unlock(&cgroup_root_mutex);
T
Tejun Heo 已提交
2283
	mutex_unlock(&cgroup_mutex);
2284 2285 2286 2287 2288 2289 2290 2291 2292 2293
	return 0;
}

static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
				     struct seq_file *seq)
{
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
	seq_puts(seq, cgrp->root->release_agent_path);
	seq_putc(seq, '\n');
T
Tejun Heo 已提交
2294
	mutex_unlock(&cgroup_mutex);
2295 2296 2297
	return 0;
}

2298 2299 2300 2301
static int cgroup_sane_behavior_show(struct cgroup *cgrp, struct cftype *cft,
				     struct seq_file *seq)
{
	seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
2302 2303 2304
	return 0;
}

2305 2306 2307
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2308
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2309 2310 2311
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2312
{
2313
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324
	int retval = 0;
	char *end;

	if (!nbytes)
		return -EINVAL;
	if (nbytes >= sizeof(buffer))
		return -E2BIG;
	if (copy_from_user(buffer, userbuf, nbytes))
		return -EFAULT;

	buffer[nbytes] = 0;     /* nul-terminate */
2325
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2326
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2327 2328 2329 2330
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2331
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2332 2333 2334 2335
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2336 2337 2338 2339 2340
	if (!retval)
		retval = nbytes;
	return retval;
}

2341 2342 2343 2344 2345
static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
				   struct file *file,
				   const char __user *userbuf,
				   size_t nbytes, loff_t *unused_ppos)
{
2346
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360
	int retval = 0;
	size_t max_bytes = cft->max_write_len;
	char *buffer = local_buffer;

	if (!max_bytes)
		max_bytes = sizeof(local_buffer) - 1;
	if (nbytes >= max_bytes)
		return -E2BIG;
	/* Allocate a dynamic buffer if we need one */
	if (nbytes >= sizeof(local_buffer)) {
		buffer = kmalloc(nbytes + 1, GFP_KERNEL);
		if (buffer == NULL)
			return -ENOMEM;
	}
L
Li Zefan 已提交
2361 2362 2363 2364
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2365 2366

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2367
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2368 2369
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2370
out:
2371 2372 2373 2374 2375
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2376 2377 2378 2379
static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
						size_t nbytes, loff_t *ppos)
{
	struct cftype *cft = __d_cft(file->f_dentry);
2380
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2381

2382
	if (cgroup_is_dead(cgrp))
2383
		return -ENODEV;
2384
	if (cft->write)
2385
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2386 2387
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2388 2389
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2390 2391 2392 2393
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2394
	return -EINVAL;
2395 2396
}

2397 2398 2399 2400
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2401
{
2402
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2403
	u64 val = cft->read_u64(cgrp, cft);
2404 2405 2406 2407 2408
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}

2409 2410 2411 2412 2413
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2414
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2415 2416 2417 2418 2419 2420
	s64 val = cft->read_s64(cgrp, cft);
	int len = sprintf(tmp, "%lld\n", (long long) val);

	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}

2421 2422 2423 2424
static ssize_t cgroup_file_read(struct file *file, char __user *buf,
				   size_t nbytes, loff_t *ppos)
{
	struct cftype *cft = __d_cft(file->f_dentry);
2425
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2426

2427
	if (cgroup_is_dead(cgrp))
2428 2429 2430
		return -ENODEV;

	if (cft->read)
2431
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2432 2433
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2434 2435
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2436 2437 2438
	return -EINVAL;
}

2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458
/*
 * seqfile ops/methods for returning structured data. Currently just
 * supports string->u64 maps, but can be extended in future.
 */

struct cgroup_seqfile_state {
	struct cftype *cft;
	struct cgroup *cgroup;
};

static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
{
	struct seq_file *sf = cb->state;
	return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
}

static int cgroup_seqfile_show(struct seq_file *m, void *arg)
{
	struct cgroup_seqfile_state *state = m->private;
	struct cftype *cft = state->cft;
2459 2460 2461 2462 2463 2464 2465 2466
	if (cft->read_map) {
		struct cgroup_map_cb cb = {
			.fill = cgroup_map_add,
			.state = m,
		};
		return cft->read_map(state->cgroup, cft, &cb);
	}
	return cft->read_seq_string(state->cgroup, cft, m);
2467 2468
}

2469
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2470 2471 2472 2473 2474 2475
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2476
static const struct file_operations cgroup_seqfile_operations = {
2477
	.read = seq_read,
2478
	.write = cgroup_file_write,
2479 2480 2481 2482
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2483 2484 2485 2486 2487 2488 2489 2490 2491
static int cgroup_file_open(struct inode *inode, struct file *file)
{
	int err;
	struct cftype *cft;

	err = generic_file_open(inode, file);
	if (err)
		return err;
	cft = __d_cft(file->f_dentry);
2492

2493
	if (cft->read_map || cft->read_seq_string) {
2494 2495 2496
		struct cgroup_seqfile_state *state;

		state = kzalloc(sizeof(*state), GFP_USER);
2497 2498
		if (!state)
			return -ENOMEM;
2499

2500 2501 2502 2503 2504 2505 2506
		state->cft = cft;
		state->cgroup = __d_cgrp(file->f_dentry->d_parent);
		file->f_op = &cgroup_seqfile_operations;
		err = single_open(file, cgroup_seqfile_show, state);
		if (err < 0)
			kfree(state);
	} else if (cft->open)
2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527
		err = cft->open(inode, file);
	else
		err = 0;

	return err;
}

static int cgroup_file_release(struct inode *inode, struct file *file)
{
	struct cftype *cft = __d_cft(file->f_dentry);
	if (cft->release)
		return cft->release(inode, file);
	return 0;
}

/*
 * cgroup_rename - Only allow simple rename of directories in place.
 */
static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
			    struct inode *new_dir, struct dentry *new_dentry)
{
2528 2529 2530 2531 2532 2533 2534 2535 2536 2537
	int ret;
	struct cgroup_name *name, *old_name;
	struct cgroup *cgrp;

	/*
	 * It's convinient to use parent dir's i_mutex to protected
	 * cgrp->name.
	 */
	lockdep_assert_held(&old_dir->i_mutex);

2538 2539 2540 2541 2542 2543
	if (!S_ISDIR(old_dentry->d_inode->i_mode))
		return -ENOTDIR;
	if (new_dentry->d_inode)
		return -EEXIST;
	if (old_dir != new_dir)
		return -EIO;
2544 2545 2546

	cgrp = __d_cgrp(old_dentry);

2547 2548 2549 2550 2551 2552 2553
	/*
	 * This isn't a proper migration and its usefulness is very
	 * limited.  Disallow if sane_behavior.
	 */
	if (cgroup_sane_behavior(cgrp))
		return -EPERM;

2554 2555 2556 2557 2558 2559 2560 2561 2562 2563
	name = cgroup_alloc_name(new_dentry);
	if (!name)
		return -ENOMEM;

	ret = simple_rename(old_dir, old_dentry, new_dir, new_dentry);
	if (ret) {
		kfree(name);
		return ret;
	}

2564
	old_name = rcu_dereference_protected(cgrp->name, true);
2565 2566 2567 2568
	rcu_assign_pointer(cgrp->name, name);

	kfree_rcu(old_name, rcu_head);
	return 0;
2569 2570
}

A
Aristeu Rozanski 已提交
2571 2572 2573 2574 2575
static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
{
	if (S_ISDIR(dentry->d_inode->i_mode))
		return &__d_cgrp(dentry)->xattrs;
	else
L
Li Zefan 已提交
2576
		return &__d_cfe(dentry)->xattrs;
A
Aristeu Rozanski 已提交
2577 2578 2579 2580 2581
}

static inline int xattr_enabled(struct dentry *dentry)
{
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
2582
	return root->flags & CGRP_ROOT_XATTR;
A
Aristeu Rozanski 已提交
2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628
}

static bool is_valid_xattr(const char *name)
{
	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
	    !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
		return true;
	return false;
}

static int cgroup_setxattr(struct dentry *dentry, const char *name,
			   const void *val, size_t size, int flags)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
}

static int cgroup_removexattr(struct dentry *dentry, const char *name)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_remove(__d_xattrs(dentry), name);
}

static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
			       void *buf, size_t size)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
}

static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	return simple_xattr_list(__d_xattrs(dentry), buf, size);
}

2629
static const struct file_operations cgroup_file_operations = {
2630 2631 2632 2633 2634 2635 2636
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

A
Aristeu Rozanski 已提交
2637 2638 2639 2640 2641 2642 2643
static const struct inode_operations cgroup_file_inode_operations = {
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
};

2644
static const struct inode_operations cgroup_dir_inode_operations = {
2645
	.lookup = cgroup_lookup,
2646 2647 2648
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
A
Aristeu Rozanski 已提交
2649 2650 2651 2652
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
2653 2654
};

A
Al Viro 已提交
2655
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2656 2657 2658 2659 2660 2661 2662
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2663 2664 2665 2666 2667
/*
 * Check if a file is a control file
 */
static inline struct cftype *__file_cft(struct file *file)
{
A
Al Viro 已提交
2668
	if (file_inode(file)->i_fop != &cgroup_file_operations)
2669 2670 2671 2672
		return ERR_PTR(-EINVAL);
	return __d_cft(file->f_dentry);
}

A
Al Viro 已提交
2673
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2674 2675
				struct super_block *sb)
{
2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692
	struct inode *inode;

	if (!dentry)
		return -ENOENT;
	if (dentry->d_inode)
		return -EEXIST;

	inode = cgroup_new_inode(mode, sb);
	if (!inode)
		return -ENOMEM;

	if (S_ISDIR(mode)) {
		inode->i_op = &cgroup_dir_inode_operations;
		inode->i_fop = &simple_dir_operations;

		/* start off with i_nlink == 2 (for "." entry) */
		inc_nlink(inode);
T
Tejun Heo 已提交
2693
		inc_nlink(dentry->d_parent->d_inode);
2694

2695 2696 2697 2698 2699 2700 2701 2702 2703
		/*
		 * Control reaches here with cgroup_mutex held.
		 * @inode->i_mutex should nest outside cgroup_mutex but we
		 * want to populate it immediately without releasing
		 * cgroup_mutex.  As @inode isn't visible to anyone else
		 * yet, trylock will always succeed without affecting
		 * lockdep checks.
		 */
		WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
2704 2705 2706
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
A
Aristeu Rozanski 已提交
2707
		inode->i_op = &cgroup_file_inode_operations;
2708 2709 2710 2711 2712 2713
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

L
Li Zefan 已提交
2714 2715 2716 2717 2718 2719 2720 2721 2722
/**
 * cgroup_file_mode - deduce file mode of a control file
 * @cft: the control file in question
 *
 * returns cft->mode if ->mode is not 0
 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
 * returns S_IRUGO if it has only a read handler
 * returns S_IWUSR if it has only a write hander
 */
A
Al Viro 已提交
2723
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2724
{
A
Al Viro 已提交
2725
	umode_t mode = 0;
L
Li Zefan 已提交
2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740

	if (cft->mode)
		return cft->mode;

	if (cft->read || cft->read_u64 || cft->read_s64 ||
	    cft->read_map || cft->read_seq_string)
		mode |= S_IRUGO;

	if (cft->write || cft->write_u64 || cft->write_s64 ||
	    cft->write_string || cft->trigger)
		mode |= S_IWUSR;

	return mode;
}

T
Tejun Heo 已提交
2741
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2742
			   struct cftype *cft)
2743
{
2744
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2745
	struct cgroup *parent = __d_cgrp(dir);
2746
	struct dentry *dentry;
T
Tejun Heo 已提交
2747
	struct cfent *cfe;
2748
	int error;
A
Al Viro 已提交
2749
	umode_t mode;
2750
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2751

2752
	if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
2753 2754 2755 2756
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2757

2758
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2759 2760 2761 2762 2763

	cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
	if (!cfe)
		return -ENOMEM;

2764
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2765
	if (IS_ERR(dentry)) {
2766
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2767 2768 2769
		goto out;
	}

2770 2771 2772 2773 2774
	cfe->type = (void *)cft;
	cfe->dentry = dentry;
	dentry->d_fsdata = cfe;
	simple_xattrs_init(&cfe->xattrs);

T
Tejun Heo 已提交
2775 2776 2777 2778 2779 2780 2781 2782 2783
	mode = cgroup_file_mode(cft);
	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
	if (!error) {
		list_add_tail(&cfe->node, &parent->files);
		cfe = NULL;
	}
	dput(dentry);
out:
	kfree(cfe);
2784 2785 2786
	return error;
}

2787
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2788
			      struct cftype cfts[], bool is_add)
2789
{
A
Aristeu Rozanski 已提交
2790
	struct cftype *cft;
T
Tejun Heo 已提交
2791 2792 2793
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2794
		/* does cft->flags tell us to skip this file on @cgrp? */
2795 2796
		if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
			continue;
2797 2798 2799 2800 2801
		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
			continue;
		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
			continue;

2802
		if (is_add) {
2803
			err = cgroup_add_file(cgrp, subsys, cft);
2804 2805 2806
			if (err)
				pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
					cft->name, err);
T
Tejun Heo 已提交
2807
			ret = err;
2808 2809
		} else {
			cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2810
		}
2811
	}
T
Tejun Heo 已提交
2812
	return ret;
2813 2814
}

2815
static void cgroup_cfts_prepare(void)
2816
	__acquires(&cgroup_mutex)
2817 2818 2819 2820
{
	/*
	 * Thanks to the entanglement with vfs inode locking, we can't walk
	 * the existing cgroups under cgroup_mutex and create files.
2821 2822
	 * Instead, we use cgroup_for_each_descendant_pre() and drop RCU
	 * read lock before calling cgroup_addrm_files().
2823 2824 2825 2826 2827
	 */
	mutex_lock(&cgroup_mutex);
}

static void cgroup_cfts_commit(struct cgroup_subsys *ss,
A
Aristeu Rozanski 已提交
2828
			       struct cftype *cfts, bool is_add)
2829
	__releases(&cgroup_mutex)
2830 2831
{
	LIST_HEAD(pending);
2832
	struct cgroup *cgrp, *root = &ss->root->top_cgroup;
2833
	struct super_block *sb = ss->root->sb;
2834 2835
	struct dentry *prev = NULL;
	struct inode *inode;
2836
	u64 update_before;
2837 2838

	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2839
	if (!cfts || ss->root == &cgroup_dummy_root ||
2840 2841 2842
	    !atomic_inc_not_zero(&sb->s_active)) {
		mutex_unlock(&cgroup_mutex);
		return;
2843 2844 2845
	}

	/*
2846 2847
	 * All cgroups which are created after we drop cgroup_mutex will
	 * have the updated set of files, so we only need to update the
2848
	 * cgroups created before the current @cgroup_serial_nr_next.
2849
	 */
2850
	update_before = cgroup_serial_nr_next;
2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873

	mutex_unlock(&cgroup_mutex);

	/* @root always needs to be updated */
	inode = root->dentry->d_inode;
	mutex_lock(&inode->i_mutex);
	mutex_lock(&cgroup_mutex);
	cgroup_addrm_files(root, ss, cfts, is_add);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);

	/* add/rm files for all cgroups created before */
	rcu_read_lock();
	cgroup_for_each_descendant_pre(cgrp, root) {
		if (cgroup_is_dead(cgrp))
			continue;

		inode = cgrp->dentry->d_inode;
		dget(cgrp->dentry);
		rcu_read_unlock();

		dput(prev);
		prev = cgrp->dentry;
2874 2875 2876

		mutex_lock(&inode->i_mutex);
		mutex_lock(&cgroup_mutex);
2877
		if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp))
2878
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2879 2880 2881
		mutex_unlock(&cgroup_mutex);
		mutex_unlock(&inode->i_mutex);

2882
		rcu_read_lock();
2883
	}
2884 2885 2886
	rcu_read_unlock();
	dput(prev);
	deactivate_super(sb);
2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902
}

/**
 * cgroup_add_cftypes - add an array of cftypes to a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Register @cfts to @ss.  Files described by @cfts are created for all
 * existing cgroups to which @ss is attached and all future cgroups will
 * have them too.  This function can be called anytime whether @ss is
 * attached or not.
 *
 * Returns 0 on successful registration, -errno on failure.  Note that this
 * function currently returns 0 as long as @cfts registration is successful
 * even if some file creation attempts on existing cgroups fail.
 */
A
Aristeu Rozanski 已提交
2903
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2904 2905 2906 2907 2908 2909 2910 2911 2912 2913
{
	struct cftype_set *set;

	set = kzalloc(sizeof(*set), GFP_KERNEL);
	if (!set)
		return -ENOMEM;

	cgroup_cfts_prepare();
	set->cfts = cfts;
	list_add_tail(&set->node, &ss->cftsets);
2914
	cgroup_cfts_commit(ss, cfts, true);
2915 2916 2917 2918 2919

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932
/**
 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Unregister @cfts from @ss.  Files described by @cfts are removed from
 * all existing cgroups to which @ss is attached and all future cgroups
 * won't have them either.  This function can be called anytime whether @ss
 * is attached or not.
 *
 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
 * registered with @ss.
 */
A
Aristeu Rozanski 已提交
2933
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2934 2935 2936 2937 2938 2939 2940
{
	struct cftype_set *set;

	cgroup_cfts_prepare();

	list_for_each_entry(set, &ss->cftsets, node) {
		if (set->cfts == cfts) {
2941 2942
			list_del(&set->node);
			kfree(set);
2943 2944 2945 2946 2947 2948 2949 2950 2951
			cgroup_cfts_commit(ss, cfts, false);
			return 0;
		}
	}

	cgroup_cfts_commit(ss, NULL, false);
	return -ENOENT;
}

L
Li Zefan 已提交
2952 2953 2954 2955 2956 2957
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2958
int cgroup_task_count(const struct cgroup *cgrp)
2959 2960
{
	int count = 0;
2961
	struct cgrp_cset_link *link;
2962 2963

	read_lock(&css_set_lock);
2964 2965
	list_for_each_entry(link, &cgrp->cset_links, cset_link)
		count += atomic_read(&link->cset->refcount);
2966
	read_unlock(&css_set_lock);
2967 2968 2969
	return count;
}

2970 2971 2972 2973
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2974
static void cgroup_advance_iter(struct cgroup *cgrp, struct cgroup_iter *it)
2975
{
2976 2977
	struct list_head *l = it->cset_link;
	struct cgrp_cset_link *link;
2978
	struct css_set *cset;
2979 2980 2981 2982

	/* Advance to the next non-empty css_set */
	do {
		l = l->next;
2983 2984
		if (l == &cgrp->cset_links) {
			it->cset_link = NULL;
2985 2986
			return;
		}
2987 2988
		link = list_entry(l, struct cgrp_cset_link, cset_link);
		cset = link->cset;
2989
	} while (list_empty(&cset->tasks));
2990
	it->cset_link = l;
2991
	it->task = cset->tasks.next;
2992 2993
}

2994 2995 2996 2997 2998 2999
/*
 * To reduce the fork() overhead for systems that are not actually
 * using their cgroups capability, we don't maintain the lists running
 * through each css_set to its tasks until we see the list actually
 * used - in other words after the first call to cgroup_iter_start().
 */
3000
static void cgroup_enable_task_cg_lists(void)
3001 3002 3003 3004
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
3005 3006 3007 3008 3009 3010 3011 3012
	/*
	 * We need tasklist_lock because RCU is not safe against
	 * while_each_thread(). Besides, a forking task that has passed
	 * cgroup_post_fork() without seeing use_task_css_set_links = 1
	 * is not guaranteed to have its child immediately visible in the
	 * tasklist if we walk through it with RCU.
	 */
	read_lock(&tasklist_lock);
3013 3014
	do_each_thread(g, p) {
		task_lock(p);
3015 3016 3017 3018 3019 3020
		/*
		 * We should check if the process is exiting, otherwise
		 * it will race with cgroup_exit() in that the list
		 * entry won't be deleted though the process has exited.
		 */
		if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
3021
			list_add(&p->cg_list, &task_css_set(p)->tasks);
3022 3023
		task_unlock(p);
	} while_each_thread(g, p);
3024
	read_unlock(&tasklist_lock);
3025 3026 3027
	write_unlock(&css_set_lock);
}

3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045
/**
 * cgroup_next_sibling - find the next sibling of a given cgroup
 * @pos: the current cgroup
 *
 * This function returns the next sibling of @pos and should be called
 * under RCU read lock.  The only requirement is that @pos is accessible.
 * The next sibling is guaranteed to be returned regardless of @pos's
 * state.
 */
struct cgroup *cgroup_next_sibling(struct cgroup *pos)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/*
	 * @pos could already have been removed.  Once a cgroup is removed,
	 * its ->sibling.next is no longer updated when its next sibling
3046 3047 3048 3049 3050 3051 3052
	 * changes.  As CGRP_DEAD assertion is serialized and happens
	 * before the cgroup is taken off the ->sibling list, if we see it
	 * unasserted, it's guaranteed that the next sibling hasn't
	 * finished its grace period even if it's already removed, and thus
	 * safe to dereference from this RCU critical section.  If
	 * ->sibling.next is inaccessible, cgroup_is_dead() is guaranteed
	 * to be visible as %true here.
3053
	 */
3054
	if (likely(!cgroup_is_dead(pos))) {
3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077
		next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
		if (&next->sibling != &pos->parent->children)
			return next;
		return NULL;
	}

	/*
	 * Can't dereference the next pointer.  Each cgroup is given a
	 * monotonically increasing unique serial number and always
	 * appended to the sibling list, so the next one can be found by
	 * walking the parent's children until we see a cgroup with higher
	 * serial number than @pos's.
	 *
	 * While this path can be slow, it's taken only when either the
	 * current cgroup is removed or iteration and removal race.
	 */
	list_for_each_entry_rcu(next, &pos->parent->children, sibling)
		if (next->serial_nr > pos->serial_nr)
			return next;
	return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_sibling);

3078 3079 3080 3081 3082 3083 3084
/**
 * cgroup_next_descendant_pre - find the next descendant for pre-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_pre().  Find the next
 * descendant to visit for pre-order traversal of @cgroup's descendants.
3085 3086 3087 3088 3089
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct next descendant as long as both @pos
 * and @cgroup are accessible and @pos is a descendant of @cgroup.
3090 3091 3092 3093 3094 3095 3096 3097 3098
 */
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
					  struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* if first iteration, pretend we just visited @cgroup */
3099
	if (!pos)
3100 3101 3102 3103 3104 3105 3106 3107
		pos = cgroup;

	/* visit the first child if exists */
	next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
	if (next)
		return next;

	/* no child, visit my or the closest ancestor's next sibling */
3108
	while (pos != cgroup) {
3109 3110
		next = cgroup_next_sibling(pos);
		if (next)
3111 3112
			return next;
		pos = pos->parent;
3113
	}
3114 3115 3116 3117 3118

	return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);

3119 3120 3121 3122 3123 3124 3125
/**
 * cgroup_rightmost_descendant - return the rightmost descendant of a cgroup
 * @pos: cgroup of interest
 *
 * Return the rightmost descendant of @pos.  If there's no descendant,
 * @pos is returned.  This can be used during pre-order traversal to skip
 * subtree of @pos.
3126 3127 3128 3129 3130
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct rightmost descendant as long as @pos is
 * accessible.
3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149
 */
struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos)
{
	struct cgroup *last, *tmp;

	WARN_ON_ONCE(!rcu_read_lock_held());

	do {
		last = pos;
		/* ->prev isn't RCU safe, walk ->next till the end */
		pos = NULL;
		list_for_each_entry_rcu(tmp, &last->children, sibling)
			pos = tmp;
	} while (pos);

	return last;
}
EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);

3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169
static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
{
	struct cgroup *last;

	do {
		last = pos;
		pos = list_first_or_null_rcu(&pos->children, struct cgroup,
					     sibling);
	} while (pos);

	return last;
}

/**
 * cgroup_next_descendant_post - find the next descendant for post-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_post().  Find the next
 * descendant to visit for post-order traversal of @cgroup's descendants.
3170 3171 3172 3173 3174
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct next descendant as long as both @pos
 * and @cgroup are accessible and @pos is a descendant of @cgroup.
3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189
 */
struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
					   struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* if first iteration, visit the leftmost descendant */
	if (!pos) {
		next = cgroup_leftmost_descendant(cgroup);
		return next != cgroup ? next : NULL;
	}

	/* if there's an unvisited sibling, visit its leftmost descendant */
3190 3191
	next = cgroup_next_sibling(pos);
	if (next)
3192 3193 3194 3195 3196 3197 3198 3199
		return cgroup_leftmost_descendant(next);

	/* no sibling left, visit parent */
	next = pos->parent;
	return next != cgroup ? next : NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);

3200
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3201
	__acquires(css_set_lock)
3202 3203 3204 3205 3206 3207
{
	/*
	 * The first time anyone tries to iterate across a cgroup,
	 * we need to enable the list linking each css_set to its
	 * tasks, and fix up all existing tasks.
	 */
3208 3209 3210
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

3211
	read_lock(&css_set_lock);
3212
	it->cset_link = &cgrp->cset_links;
3213
	cgroup_advance_iter(cgrp, it);
3214 3215
}

3216
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3217 3218 3219 3220
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
3221
	struct cgrp_cset_link *link;
3222 3223

	/* If the iterator cg is NULL, we have no tasks */
3224
	if (!it->cset_link)
3225 3226 3227 3228
		return NULL;
	res = list_entry(l, struct task_struct, cg_list);
	/* Advance iterator to find next entry */
	l = l->next;
3229 3230
	link = list_entry(it->cset_link, struct cgrp_cset_link, cset_link);
	if (l == &link->cset->tasks) {
3231 3232
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
3233
		cgroup_advance_iter(cgrp, it);
3234 3235 3236 3237 3238 3239
	} else {
		it->task = l;
	}
	return res;
}

3240
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3241
	__releases(css_set_lock)
3242 3243 3244 3245
{
	read_unlock(&css_set_lock);
}

3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382
static inline int started_after_time(struct task_struct *t1,
				     struct timespec *time,
				     struct task_struct *t2)
{
	int start_diff = timespec_compare(&t1->start_time, time);
	if (start_diff > 0) {
		return 1;
	} else if (start_diff < 0) {
		return 0;
	} else {
		/*
		 * Arbitrarily, if two processes started at the same
		 * time, we'll say that the lower pointer value
		 * started first. Note that t2 may have exited by now
		 * so this may not be a valid pointer any longer, but
		 * that's fine - it still serves to distinguish
		 * between two tasks started (effectively) simultaneously.
		 */
		return t1 > t2;
	}
}

/*
 * This function is a callback from heap_insert() and is used to order
 * the heap.
 * In this case we order the heap in descending task start time.
 */
static inline int started_after(void *p1, void *p2)
{
	struct task_struct *t1 = p1;
	struct task_struct *t2 = p2;
	return started_after_time(t1, &t2->start_time, t2);
}

/**
 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
 * @scan: struct cgroup_scanner containing arguments for the scan
 *
 * Arguments include pointers to callback functions test_task() and
 * process_task().
 * Iterate through all the tasks in a cgroup, calling test_task() for each,
 * and if it returns true, call process_task() for it also.
 * The test_task pointer may be NULL, meaning always true (select all tasks).
 * Effectively duplicates cgroup_iter_{start,next,end}()
 * but does not lock css_set_lock for the call to process_task().
 * The struct cgroup_scanner may be embedded in any structure of the caller's
 * creation.
 * It is guaranteed that process_task() will act on every task that
 * is a member of the cgroup for the duration of this call. This
 * function may or may not call process_task() for tasks that exit
 * or move to a different cgroup during the call, or are forked or
 * move into the cgroup during the call.
 *
 * Note that test_task() may be called with locks held, and may in some
 * situations be called multiple times for the same task, so it should
 * be cheap.
 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
 * pre-allocated and will be used for heap operations (and its "gt" member will
 * be overwritten), else a temporary heap will be used (allocation of which
 * may cause this function to fail).
 */
int cgroup_scan_tasks(struct cgroup_scanner *scan)
{
	int retval, i;
	struct cgroup_iter it;
	struct task_struct *p, *dropped;
	/* Never dereference latest_task, since it's not refcounted */
	struct task_struct *latest_task = NULL;
	struct ptr_heap tmp_heap;
	struct ptr_heap *heap;
	struct timespec latest_time = { 0, 0 };

	if (scan->heap) {
		/* The caller supplied our heap and pre-allocated its memory */
		heap = scan->heap;
		heap->gt = &started_after;
	} else {
		/* We need to allocate our own heap memory */
		heap = &tmp_heap;
		retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
		if (retval)
			/* cannot allocate the heap */
			return retval;
	}

 again:
	/*
	 * Scan tasks in the cgroup, using the scanner's "test_task" callback
	 * to determine which are of interest, and using the scanner's
	 * "process_task" callback to process any of them that need an update.
	 * Since we don't want to hold any locks during the task updates,
	 * gather tasks to be processed in a heap structure.
	 * The heap is sorted by descending task start time.
	 * If the statically-sized heap fills up, we overflow tasks that
	 * started later, and in future iterations only consider tasks that
	 * started after the latest task in the previous pass. This
	 * guarantees forward progress and that we don't miss any tasks.
	 */
	heap->size = 0;
	cgroup_iter_start(scan->cg, &it);
	while ((p = cgroup_iter_next(scan->cg, &it))) {
		/*
		 * Only affect tasks that qualify per the caller's callback,
		 * if he provided one
		 */
		if (scan->test_task && !scan->test_task(p, scan))
			continue;
		/*
		 * Only process tasks that started after the last task
		 * we processed
		 */
		if (!started_after_time(p, &latest_time, latest_task))
			continue;
		dropped = heap_insert(heap, p);
		if (dropped == NULL) {
			/*
			 * The new task was inserted; the heap wasn't
			 * previously full
			 */
			get_task_struct(p);
		} else if (dropped != p) {
			/*
			 * The new task was inserted, and pushed out a
			 * different task
			 */
			get_task_struct(p);
			put_task_struct(dropped);
		}
		/*
		 * Else the new task was newer than anything already in
		 * the heap and wasn't inserted
		 */
	}
	cgroup_iter_end(scan->cg, &it);

	if (heap->size) {
		for (i = 0; i < heap->size; i++) {
3383
			struct task_struct *q = heap->ptrs[i];
3384
			if (i == 0) {
3385 3386
				latest_time = q->start_time;
				latest_task = q;
3387 3388
			}
			/* Process the task per the caller's callback */
3389 3390
			scan->process_task(q, scan);
			put_task_struct(q);
3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405
		}
		/*
		 * If we had to process any tasks at all, scan again
		 * in case some of them were in the middle of forking
		 * children that didn't get processed.
		 * Not the most efficient way to do it, but it avoids
		 * having to take callback_mutex in the fork path
		 */
		goto again;
	}
	if (heap == &tmp_heap)
		heap_free(&tmp_heap);
	return 0;
}

3406 3407 3408 3409 3410
static void cgroup_transfer_one_task(struct task_struct *task,
				     struct cgroup_scanner *scan)
{
	struct cgroup *new_cgroup = scan->data;

T
Tejun Heo 已提交
3411
	mutex_lock(&cgroup_mutex);
3412
	cgroup_attach_task(new_cgroup, task, false);
T
Tejun Heo 已提交
3413
	mutex_unlock(&cgroup_mutex);
3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433
}

/**
 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
 * @to: cgroup to which the tasks will be moved
 * @from: cgroup in which the tasks currently reside
 */
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
	struct cgroup_scanner scan;

	scan.cg = from;
	scan.test_task = NULL; /* select all tasks in cgroup */
	scan.process_task = cgroup_transfer_one_task;
	scan.heap = NULL;
	scan.data = to;

	return cgroup_scan_tasks(&scan);
}

3434
/*
3435
 * Stuff for reading the 'tasks'/'procs' files.
3436 3437 3438 3439 3440 3441 3442 3443
 *
 * Reading this file can return large amounts of data if a cgroup has
 * *lots* of attached tasks. So it may need several calls to read(),
 * but we cannot guarantee that the information we produce is correct
 * unless we produce it entirely atomically.
 *
 */

3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475
/* which pidlist file are we talking about? */
enum cgroup_filetype {
	CGROUP_FILE_PROCS,
	CGROUP_FILE_TASKS,
};

/*
 * A pidlist is a list of pids that virtually represents the contents of one
 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
 * a pair (one each for procs, tasks) for each pid namespace that's relevant
 * to the cgroup.
 */
struct cgroup_pidlist {
	/*
	 * used to find which pidlist is wanted. doesn't change as long as
	 * this particular list stays in the list.
	*/
	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
	/* array of xids */
	pid_t *list;
	/* how many elements the above list has */
	int length;
	/* how many files are using the current array */
	int use_count;
	/* each of these stored in a list by its cgroup */
	struct list_head links;
	/* pointer to the cgroup we belong to, for list removal purposes */
	struct cgroup *owner;
	/* protects the other fields */
	struct rw_semaphore mutex;
};

3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496
/*
 * The following two functions "fix" the issue where there are more pids
 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
 * TODO: replace with a kernel-wide solution to this problem
 */
#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
static void *pidlist_allocate(int count)
{
	if (PIDLIST_TOO_LARGE(count))
		return vmalloc(count * sizeof(pid_t));
	else
		return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
}
static void pidlist_free(void *p)
{
	if (is_vmalloc_addr(p))
		vfree(p);
	else
		kfree(p);
}

3497
/*
3498
 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3499
 * Returns the number of unique elements.
3500
 */
3501
static int pidlist_uniq(pid_t *list, int length)
3502
{
3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531
	int src, dest = 1;

	/*
	 * we presume the 0th element is unique, so i starts at 1. trivial
	 * edge cases first; no work needs to be done for either
	 */
	if (length == 0 || length == 1)
		return length;
	/* src and dest walk down the list; dest counts unique elements */
	for (src = 1; src < length; src++) {
		/* find next unique element */
		while (list[src] == list[src-1]) {
			src++;
			if (src == length)
				goto after;
		}
		/* dest always points to where the next unique element goes */
		list[dest] = list[src];
		dest++;
	}
after:
	return dest;
}

static int cmppid(const void *a, const void *b)
{
	return *(pid_t *)a - *(pid_t *)b;
}

3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542
/*
 * find the appropriate pidlist for our purpose (given procs vs tasks)
 * returns with the lock on that pidlist already held, and takes care
 * of the use count, or returns NULL with no locks held if we're out of
 * memory.
 */
static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
						  enum cgroup_filetype type)
{
	struct cgroup_pidlist *l;
	/* don't need task_nsproxy() if we're looking at ourself */
3543
	struct pid_namespace *ns = task_active_pid_ns(current);
3544

3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560
	/*
	 * We can't drop the pidlist_mutex before taking the l->mutex in case
	 * the last ref-holder is trying to remove l from the list at the same
	 * time. Holding the pidlist_mutex precludes somebody taking whichever
	 * list we find out from under us - compare release_pid_array().
	 */
	mutex_lock(&cgrp->pidlist_mutex);
	list_for_each_entry(l, &cgrp->pidlists, links) {
		if (l->key.type == type && l->key.ns == ns) {
			/* make sure l doesn't vanish out from under us */
			down_write(&l->mutex);
			mutex_unlock(&cgrp->pidlist_mutex);
			return l;
		}
	}
	/* entry not found; create a new one */
3561
	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3562 3563 3564 3565 3566 3567 3568
	if (!l) {
		mutex_unlock(&cgrp->pidlist_mutex);
		return l;
	}
	init_rwsem(&l->mutex);
	down_write(&l->mutex);
	l->key.type = type;
3569
	l->key.ns = get_pid_ns(ns);
3570 3571 3572 3573 3574 3575
	l->owner = cgrp;
	list_add(&l->links, &cgrp->pidlists);
	mutex_unlock(&cgrp->pidlist_mutex);
	return l;
}

3576 3577 3578
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3579 3580
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3581 3582 3583 3584
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3585 3586
	struct cgroup_iter it;
	struct task_struct *tsk;
3587 3588 3589 3590 3591 3592 3593 3594 3595
	struct cgroup_pidlist *l;

	/*
	 * If cgroup gets more users after we read count, we won't have
	 * enough space - tough.  This race is indistinguishable to the
	 * caller from the case that the additional cgroup users didn't
	 * show up until sometime later on.
	 */
	length = cgroup_task_count(cgrp);
3596
	array = pidlist_allocate(length);
3597 3598 3599
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3600 3601
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3602
		if (unlikely(n == length))
3603
			break;
3604
		/* get tgid or pid for procs or tasks file respectively */
3605 3606 3607 3608
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3609 3610
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3611
	}
3612
	cgroup_iter_end(cgrp, &it);
3613 3614 3615
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3616
	if (type == CGROUP_FILE_PROCS)
3617
		length = pidlist_uniq(array, length);
3618 3619
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3620
		pidlist_free(array);
3621
		return -ENOMEM;
3622
	}
3623
	/* store array, freeing old if necessary - lock already held */
3624
	pidlist_free(l->list);
3625 3626 3627 3628
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3629
	*lp = l;
3630
	return 0;
3631 3632
}

B
Balbir Singh 已提交
3633
/**
L
Li Zefan 已提交
3634
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3635 3636 3637
 * @stats: cgroupstats to fill information into
 * @dentry: A dentry entry belonging to the cgroup for which stats have
 * been requested.
L
Li Zefan 已提交
3638 3639 3640
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3641 3642 3643 3644
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3645
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3646 3647
	struct cgroup_iter it;
	struct task_struct *tsk;
3648

B
Balbir Singh 已提交
3649
	/*
3650 3651
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3652
	 */
3653 3654
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3655 3656 3657
		 goto err;

	ret = 0;
3658
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3659

3660 3661
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680
		switch (tsk->state) {
		case TASK_RUNNING:
			stats->nr_running++;
			break;
		case TASK_INTERRUPTIBLE:
			stats->nr_sleeping++;
			break;
		case TASK_UNINTERRUPTIBLE:
			stats->nr_uninterruptible++;
			break;
		case TASK_STOPPED:
			stats->nr_stopped++;
			break;
		default:
			if (delayacct_is_task_waiting_on_io(tsk))
				stats->nr_io_wait++;
			break;
		}
	}
3681
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3682 3683 3684 3685 3686

err:
	return ret;
}

3687

3688
/*
3689
 * seq_file methods for the tasks/procs files. The seq_file position is the
3690
 * next pid to display; the seq_file iterator is a pointer to the pid
3691
 * in the cgroup->l->list array.
3692
 */
3693

3694
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3695
{
3696 3697 3698 3699 3700 3701
	/*
	 * Initially we receive a position value that corresponds to
	 * one more than the last pid shown (or 0 on the first call or
	 * after a seek to the start). Use a binary-search to find the
	 * next pid to display, if any
	 */
3702
	struct cgroup_pidlist *l = s->private;
3703 3704 3705
	int index = 0, pid = *pos;
	int *iter;

3706
	down_read(&l->mutex);
3707
	if (pid) {
3708
		int end = l->length;
S
Stephen Rothwell 已提交
3709

3710 3711
		while (index < end) {
			int mid = (index + end) / 2;
3712
			if (l->list[mid] == pid) {
3713 3714
				index = mid;
				break;
3715
			} else if (l->list[mid] <= pid)
3716 3717 3718 3719 3720 3721
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3722
	if (index >= l->length)
3723 3724
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3725
	iter = l->list + index;
3726 3727 3728 3729
	*pos = *iter;
	return iter;
}

3730
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3731
{
3732 3733
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3734 3735
}

3736
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3737
{
3738 3739 3740
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753
	/*
	 * Advance to the next pid in the array. If this goes off the
	 * end, we're done
	 */
	p++;
	if (p >= end) {
		return NULL;
	} else {
		*pos = *p;
		return p;
	}
}

3754
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3755 3756 3757
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3758

3759 3760 3761 3762 3763 3764 3765 3766 3767
/*
 * seq_operations functions for iterating on pidlists through seq_file -
 * independent of whether it's tasks or procs
 */
static const struct seq_operations cgroup_pidlist_seq_operations = {
	.start = cgroup_pidlist_start,
	.stop = cgroup_pidlist_stop,
	.next = cgroup_pidlist_next,
	.show = cgroup_pidlist_show,
3768 3769
};

3770
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3771
{
3772 3773 3774 3775 3776 3777 3778
	/*
	 * the case where we're the last user of this particular pidlist will
	 * have us remove it from the cgroup's list, which entails taking the
	 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
	 * pidlist_mutex, we have to take pidlist_mutex first.
	 */
	mutex_lock(&l->owner->pidlist_mutex);
3779 3780 3781
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3782 3783 3784
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3785
		pidlist_free(l->list);
3786 3787 3788 3789
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3790
	}
3791
	mutex_unlock(&l->owner->pidlist_mutex);
3792
	up_write(&l->mutex);
3793 3794
}

3795
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3796
{
3797
	struct cgroup_pidlist *l;
3798 3799
	if (!(file->f_mode & FMODE_READ))
		return 0;
3800 3801 3802 3803 3804 3805
	/*
	 * the seq_file will only be initialized if the file was opened for
	 * reading; hence we check if it's not null only in that case.
	 */
	l = ((struct seq_file *)file->private_data)->private;
	cgroup_release_pid_array(l);
3806 3807 3808
	return seq_release(inode, file);
}

3809
static const struct file_operations cgroup_pidlist_operations = {
3810 3811 3812
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3813
	.release = cgroup_pidlist_release,
3814 3815
};

3816
/*
3817 3818 3819
 * The following functions handle opens on a file that displays a pidlist
 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
 * in the cgroup.
3820
 */
3821
/* helper function for the two below it */
3822
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3823
{
3824
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3825
	struct cgroup_pidlist *l;
3826
	int retval;
3827

3828
	/* Nothing to do for write-only files */
3829 3830 3831
	if (!(file->f_mode & FMODE_READ))
		return 0;

3832
	/* have the array populated */
3833
	retval = pidlist_array_load(cgrp, type, &l);
3834 3835 3836 3837
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3838

3839
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3840
	if (retval) {
3841
		cgroup_release_pid_array(l);
3842
		return retval;
3843
	}
3844
	((struct seq_file *)file->private_data)->private = l;
3845 3846
	return 0;
}
3847 3848
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3849
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3850 3851 3852
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3853
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3854
}
3855

3856
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3857 3858
					    struct cftype *cft)
{
3859
	return notify_on_release(cgrp);
3860 3861
}

3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873
static int cgroup_write_notify_on_release(struct cgroup *cgrp,
					  struct cftype *cft,
					  u64 val)
{
	clear_bit(CGRP_RELEASABLE, &cgrp->flags);
	if (val)
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
	else
		clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
	return 0;
}

3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890
/*
 * When dput() is called asynchronously, if umount has been done and
 * then deactivate_super() in cgroup_free_fn() kills the superblock,
 * there's a small window that vfs will see the root dentry with non-zero
 * refcnt and trigger BUG().
 *
 * That's why we hold a reference before dput() and drop it right after.
 */
static void cgroup_dput(struct cgroup *cgrp)
{
	struct super_block *sb = cgrp->root->sb;

	atomic_inc(&sb->s_active);
	dput(cgrp->dentry);
	deactivate_super(sb);
}

3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901
/*
 * Unregister event and free resources.
 *
 * Gets called from workqueue.
 */
static void cgroup_event_remove(struct work_struct *work)
{
	struct cgroup_event *event = container_of(work, struct cgroup_event,
			remove);
	struct cgroup *cgrp = event->cgrp;

3902 3903
	remove_wait_queue(event->wqh, &event->wait);

3904 3905
	event->cft->unregister_event(cgrp, event->cft, event->eventfd);

3906 3907 3908
	/* Notify userspace the event is going away. */
	eventfd_signal(event->eventfd, 1);

3909 3910
	eventfd_ctx_put(event->eventfd);
	kfree(event);
3911
	cgroup_dput(cgrp);
3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928
}

/*
 * Gets called on POLLHUP on eventfd when user closes it.
 *
 * Called with wqh->lock held and interrupts disabled.
 */
static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
		int sync, void *key)
{
	struct cgroup_event *event = container_of(wait,
			struct cgroup_event, wait);
	struct cgroup *cgrp = event->cgrp;
	unsigned long flags = (unsigned long)key;

	if (flags & POLLHUP) {
		/*
3929 3930 3931 3932 3933 3934 3935
		 * If the event has been detached at cgroup removal, we
		 * can simply return knowing the other side will cleanup
		 * for us.
		 *
		 * We can't race against event freeing since the other
		 * side will require wqh->lock via remove_wait_queue(),
		 * which we hold.
3936
		 */
3937 3938 3939 3940 3941 3942 3943 3944 3945 3946
		spin_lock(&cgrp->event_list_lock);
		if (!list_empty(&event->list)) {
			list_del_init(&event->list);
			/*
			 * We are in atomic context, but cgroup_event_remove()
			 * may sleep, so we have to call it in workqueue.
			 */
			schedule_work(&event->remove);
		}
		spin_unlock(&cgrp->event_list_lock);
3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971
	}

	return 0;
}

static void cgroup_event_ptable_queue_proc(struct file *file,
		wait_queue_head_t *wqh, poll_table *pt)
{
	struct cgroup_event *event = container_of(pt,
			struct cgroup_event, pt);

	event->wqh = wqh;
	add_wait_queue(wqh, &event->wait);
}

/*
 * Parse input and register new cgroup event handler.
 *
 * Input must be in format '<event_fd> <control_fd> <args>'.
 * Interpretation of args is defined by control file implementation.
 */
static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
				      const char *buffer)
{
	struct cgroup_event *event = NULL;
3972
	struct cgroup *cgrp_cfile;
3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016
	unsigned int efd, cfd;
	struct file *efile = NULL;
	struct file *cfile = NULL;
	char *endp;
	int ret;

	efd = simple_strtoul(buffer, &endp, 10);
	if (*endp != ' ')
		return -EINVAL;
	buffer = endp + 1;

	cfd = simple_strtoul(buffer, &endp, 10);
	if ((*endp != ' ') && (*endp != '\0'))
		return -EINVAL;
	buffer = endp + 1;

	event = kzalloc(sizeof(*event), GFP_KERNEL);
	if (!event)
		return -ENOMEM;
	event->cgrp = cgrp;
	INIT_LIST_HEAD(&event->list);
	init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
	init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
	INIT_WORK(&event->remove, cgroup_event_remove);

	efile = eventfd_fget(efd);
	if (IS_ERR(efile)) {
		ret = PTR_ERR(efile);
		goto fail;
	}

	event->eventfd = eventfd_ctx_fileget(efile);
	if (IS_ERR(event->eventfd)) {
		ret = PTR_ERR(event->eventfd);
		goto fail;
	}

	cfile = fget(cfd);
	if (!cfile) {
		ret = -EBADF;
		goto fail;
	}

	/* the process need read permission on control file */
A
Al Viro 已提交
4017
	/* AV: shouldn't we check that it's been opened for read instead? */
A
Al Viro 已提交
4018
	ret = inode_permission(file_inode(cfile), MAY_READ);
4019 4020 4021 4022 4023 4024 4025 4026 4027
	if (ret < 0)
		goto fail;

	event->cft = __file_cft(cfile);
	if (IS_ERR(event->cft)) {
		ret = PTR_ERR(event->cft);
		goto fail;
	}

4028 4029 4030 4031 4032 4033 4034 4035 4036 4037
	/*
	 * The file to be monitored must be in the same cgroup as
	 * cgroup.event_control is.
	 */
	cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
	if (cgrp_cfile != cgrp) {
		ret = -EINVAL;
		goto fail;
	}

4038 4039 4040 4041 4042 4043 4044 4045 4046 4047
	if (!event->cft->register_event || !event->cft->unregister_event) {
		ret = -EINVAL;
		goto fail;
	}

	ret = event->cft->register_event(cgrp, event->cft,
			event->eventfd, buffer);
	if (ret)
		goto fail;

4048
	efile->f_op->poll(efile, &event->pt);
4049

4050 4051 4052 4053 4054 4055 4056
	/*
	 * Events should be removed after rmdir of cgroup directory, but before
	 * destroying subsystem state objects. Let's take reference to cgroup
	 * directory dentry to do that.
	 */
	dget(cgrp->dentry);

4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080
	spin_lock(&cgrp->event_list_lock);
	list_add(&event->list, &cgrp->event_list);
	spin_unlock(&cgrp->event_list_lock);

	fput(cfile);
	fput(efile);

	return 0;

fail:
	if (cfile)
		fput(cfile);

	if (event && event->eventfd && !IS_ERR(event->eventfd))
		eventfd_ctx_put(event->eventfd);

	if (!IS_ERR_OR_NULL(efile))
		fput(efile);

	kfree(event);

	return ret;
}

4081 4082 4083
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
4084
	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4085 4086 4087 4088 4089 4090 4091
}

static int cgroup_clone_children_write(struct cgroup *cgrp,
				     struct cftype *cft,
				     u64 val)
{
	if (val)
4092
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4093
	else
4094
		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4095 4096 4097
	return 0;
}

4098
static struct cftype cgroup_base_files[] = {
4099
	{
4100
		.name = "cgroup.procs",
4101
		.open = cgroup_procs_open,
B
Ben Blum 已提交
4102
		.write_u64 = cgroup_procs_write,
4103
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
4104
		.mode = S_IRUGO | S_IWUSR,
4105
	},
4106
	{
4107
		.name = "cgroup.event_control",
4108 4109 4110
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
4111 4112
	{
		.name = "cgroup.clone_children",
4113
		.flags = CFTYPE_INSANE,
4114 4115 4116
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
4117 4118 4119 4120 4121
	{
		.name = "cgroup.sane_behavior",
		.flags = CFTYPE_ONLY_ON_ROOT,
		.read_seq_string = cgroup_sane_behavior_show,
	},
4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141

	/*
	 * Historical crazy stuff.  These don't have "cgroup."  prefix and
	 * don't exist if sane_behavior.  If you're depending on these, be
	 * prepared to be burned.
	 */
	{
		.name = "tasks",
		.flags = CFTYPE_INSANE,		/* use "procs" instead */
		.open = cgroup_tasks_open,
		.write_u64 = cgroup_tasks_write,
		.release = cgroup_pidlist_release,
		.mode = S_IRUGO | S_IWUSR,
	},
	{
		.name = "notify_on_release",
		.flags = CFTYPE_INSANE,
		.read_u64 = cgroup_read_notify_on_release,
		.write_u64 = cgroup_write_notify_on_release,
	},
4142 4143
	{
		.name = "release_agent",
4144
		.flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
4145 4146 4147 4148
		.read_seq_string = cgroup_release_agent_show,
		.write_string = cgroup_release_agent_write,
		.max_write_len = PATH_MAX,
	},
T
Tejun Heo 已提交
4149
	{ }	/* terminate */
4150 4151
};

4152 4153 4154 4155 4156 4157 4158 4159
/**
 * cgroup_populate_dir - selectively creation of files in a directory
 * @cgrp: target cgroup
 * @base_files: true if the base files should be added
 * @subsys_mask: mask of the subsystem ids whose files should be added
 */
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask)
4160 4161 4162 4163
{
	int err;
	struct cgroup_subsys *ss;

4164
	if (base_files) {
4165
		err = cgroup_addrm_files(cgrp, NULL, cgroup_base_files, true);
4166 4167 4168
		if (err < 0)
			return err;
	}
4169

4170
	/* process cftsets of each subsystem */
4171
	for_each_root_subsys(cgrp->root, ss) {
4172
		struct cftype_set *set;
4173 4174
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
4175

T
Tejun Heo 已提交
4176
		list_for_each_entry(set, &ss->cftsets, node)
4177
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
4178
	}
4179

K
KAMEZAWA Hiroyuki 已提交
4180
	/* This cgroup is ready now */
4181
	for_each_root_subsys(cgrp->root, ss) {
K
KAMEZAWA Hiroyuki 已提交
4182
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4183 4184
		struct css_id *id = rcu_dereference_protected(css->id, true);

K
KAMEZAWA Hiroyuki 已提交
4185 4186 4187 4188 4189
		/*
		 * Update id->css pointer and make this css visible from
		 * CSS ID functions. This pointer will be dereferened
		 * from RCU-read-side without locks.
		 */
4190 4191
		if (id)
			rcu_assign_pointer(id->css, css);
K
KAMEZAWA Hiroyuki 已提交
4192
	}
4193 4194 4195 4196

	return 0;
}

4197 4198 4199 4200 4201
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);

4202
	cgroup_dput(css->cgroup);
4203 4204
}

4205 4206 4207 4208 4209 4210 4211 4212
static void css_release(struct percpu_ref *ref)
{
	struct cgroup_subsys_state *css =
		container_of(ref, struct cgroup_subsys_state, refcnt);

	schedule_work(&css->dput_work);
}

4213 4214
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
4215
			       struct cgroup *cgrp)
4216
{
4217
	css->cgroup = cgrp;
4218
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
4219
	css->id = NULL;
4220
	if (cgrp == cgroup_dummy_top)
4221
		css->flags |= CSS_ROOT;
4222 4223
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
4224 4225

	/*
4226 4227 4228 4229
	 * css holds an extra ref to @cgrp->dentry which is put on the last
	 * css_put().  dput() requires process context, which css_put() may
	 * be called without.  @css->dput_work will be used to invoke
	 * dput() asynchronously from css_put().
4230 4231
	 */
	INIT_WORK(&css->dput_work, css_dput_fn);
4232 4233
}

T
Tejun Heo 已提交
4234 4235
/* invoke ->post_create() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4236
{
T
Tejun Heo 已提交
4237 4238
	int ret = 0;

4239 4240
	lockdep_assert_held(&cgroup_mutex);

4241 4242
	if (ss->css_online)
		ret = ss->css_online(cgrp);
T
Tejun Heo 已提交
4243 4244 4245
	if (!ret)
		cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
	return ret;
4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258
}

/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];

	lockdep_assert_held(&cgroup_mutex);

	if (!(css->flags & CSS_ONLINE))
		return;

4259
	if (ss->css_offline)
4260
		ss->css_offline(cgrp);
4261 4262 4263 4264

	cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
}

4265
/*
L
Li Zefan 已提交
4266 4267 4268 4269
 * cgroup_create - create a cgroup
 * @parent: cgroup that will be parent of the new cgroup
 * @dentry: dentry of the new cgroup
 * @mode: mode to set on new inode
4270
 *
L
Li Zefan 已提交
4271
 * Must be called with the mutex on the parent inode held
4272 4273
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
4274
			     umode_t mode)
4275
{
4276
	struct cgroup *cgrp;
4277
	struct cgroup_name *name;
4278 4279 4280 4281 4282
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

T
Tejun Heo 已提交
4283
	/* allocate the cgroup and its ID, 0 is reserved for the root */
4284 4285
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
4286 4287
		return -ENOMEM;

4288 4289 4290 4291 4292
	name = cgroup_alloc_name(dentry);
	if (!name)
		goto err_free_cgrp;
	rcu_assign_pointer(cgrp->name, name);

T
Tejun Heo 已提交
4293 4294
	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
	if (cgrp->id < 0)
4295
		goto err_free_name;
T
Tejun Heo 已提交
4296

4297 4298 4299 4300 4301 4302 4303 4304 4305
	/*
	 * Only live parents can have children.  Note that the liveliness
	 * check isn't strictly necessary because cgroup_mkdir() and
	 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
	 * anyway so that locking is contained inside cgroup proper and we
	 * don't get nasty surprises if we ever grow another caller.
	 */
	if (!cgroup_lock_live_group(parent)) {
		err = -ENODEV;
T
Tejun Heo 已提交
4306
		goto err_free_id;
4307 4308
	}

4309 4310 4311 4312 4313 4314 4315
	/* Grab a reference on the superblock so the hierarchy doesn't
	 * get deleted on unmount if there are child cgroups.  This
	 * can be done outside cgroup_mutex, since the sb can't
	 * disappear while someone has an open control file on the
	 * fs */
	atomic_inc(&sb->s_active);

4316
	init_cgroup_housekeeping(cgrp);
4317

4318 4319 4320
	dentry->d_fsdata = cgrp;
	cgrp->dentry = dentry;

4321 4322
	cgrp->parent = parent;
	cgrp->root = parent->root;
4323

4324 4325 4326
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

4327 4328
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4329

4330
	for_each_root_subsys(root, ss) {
4331
		struct cgroup_subsys_state *css;
4332

4333
		css = ss->css_alloc(cgrp);
4334 4335
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
4336
			goto err_free_all;
4337
		}
4338 4339 4340 4341 4342

		err = percpu_ref_init(&css->refcnt, css_release);
		if (err)
			goto err_free_all;

4343
		init_cgroup_css(css, ss, cgrp);
4344

4345 4346 4347
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
4348
				goto err_free_all;
4349
		}
4350 4351
	}

4352 4353 4354 4355 4356
	/*
	 * Create directory.  cgroup_create_file() returns with the new
	 * directory locked on success so that it can be populated without
	 * dropping cgroup_mutex.
	 */
T
Tejun Heo 已提交
4357
	err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
4358
	if (err < 0)
4359
		goto err_free_all;
4360
	lockdep_assert_held(&dentry->d_inode->i_mutex);
4361

4362
	cgrp->serial_nr = cgroup_serial_nr_next++;
4363

4364 4365 4366
	/* allocation complete, commit to creation */
	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
	root->number_of_cgroups++;
T
Tejun Heo 已提交
4367

T
Tejun Heo 已提交
4368
	/* each css holds a ref to the cgroup's dentry */
4369
	for_each_root_subsys(root, ss)
4370
		dget(dentry);
4371

4372 4373 4374
	/* hold a ref to the parent's dentry */
	dget(parent->dentry);

T
Tejun Heo 已提交
4375
	/* creation succeeded, notify subsystems */
4376
	for_each_root_subsys(root, ss) {
T
Tejun Heo 已提交
4377 4378 4379
		err = online_css(ss, cgrp);
		if (err)
			goto err_destroy;
4380 4381 4382 4383 4384 4385 4386 4387 4388

		if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
		    parent->parent) {
			pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
				   current->comm, current->pid, ss->name);
			if (!strcmp(ss->name, "memory"))
				pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
			ss->warned_broken_hierarchy = true;
		}
4389 4390
	}

4391
	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4392 4393
	if (err)
		goto err_destroy;
4394 4395

	mutex_unlock(&cgroup_mutex);
4396
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4397 4398 4399

	return 0;

4400
err_free_all:
4401
	for_each_root_subsys(root, ss) {
4402 4403 4404 4405
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];

		if (css) {
			percpu_ref_cancel_init(&css->refcnt);
4406
			ss->css_free(cgrp);
4407
		}
4408 4409 4410 4411
	}
	mutex_unlock(&cgroup_mutex);
	/* Release the reference count that we took on the superblock */
	deactivate_super(sb);
T
Tejun Heo 已提交
4412 4413
err_free_id:
	ida_simple_remove(&root->cgroup_ida, cgrp->id);
4414 4415
err_free_name:
	kfree(rcu_dereference_raw(cgrp->name));
4416
err_free_cgrp:
4417
	kfree(cgrp);
4418
	return err;
4419 4420 4421 4422 4423 4424

err_destroy:
	cgroup_destroy_locked(cgrp);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&dentry->d_inode->i_mutex);
	return err;
4425 4426
}

4427
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4428 4429 4430 4431 4432 4433 4434
{
	struct cgroup *c_parent = dentry->d_parent->d_fsdata;

	/* the vfs holds inode->i_mutex already */
	return cgroup_create(c_parent, dentry, mode | S_IFDIR);
}

4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476
static void cgroup_css_killed(struct cgroup *cgrp)
{
	if (!atomic_dec_and_test(&cgrp->css_kill_cnt))
		return;

	/* percpu ref's of all css's are killed, kick off the next step */
	INIT_WORK(&cgrp->destroy_work, cgroup_offline_fn);
	schedule_work(&cgrp->destroy_work);
}

static void css_ref_killed_fn(struct percpu_ref *ref)
{
	struct cgroup_subsys_state *css =
		container_of(ref, struct cgroup_subsys_state, refcnt);

	cgroup_css_killed(css->cgroup);
}

/**
 * cgroup_destroy_locked - the first stage of cgroup destruction
 * @cgrp: cgroup to be destroyed
 *
 * css's make use of percpu refcnts whose killing latency shouldn't be
 * exposed to userland and are RCU protected.  Also, cgroup core needs to
 * guarantee that css_tryget() won't succeed by the time ->css_offline() is
 * invoked.  To satisfy all the requirements, destruction is implemented in
 * the following two steps.
 *
 * s1. Verify @cgrp can be destroyed and mark it dying.  Remove all
 *     userland visible parts and start killing the percpu refcnts of
 *     css's.  Set up so that the next stage will be kicked off once all
 *     the percpu refcnts are confirmed to be killed.
 *
 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
 *     rest of destruction.  Once all cgroup references are gone, the
 *     cgroup is RCU-freed.
 *
 * This function implements s1.  After this step, @cgrp is gone as far as
 * the userland is concerned and a new cgroup with the same name may be
 * created.  As cgroup doesn't care about the names internally, this
 * doesn't cause any problem.
 */
4477 4478
static int cgroup_destroy_locked(struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4479
{
4480
	struct dentry *d = cgrp->dentry;
4481
	struct cgroup_event *event, *tmp;
4482
	struct cgroup_subsys *ss;
4483
	bool empty;
4484

4485 4486 4487
	lockdep_assert_held(&d->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

4488
	/*
T
Tejun Heo 已提交
4489 4490
	 * css_set_lock synchronizes access to ->cset_links and prevents
	 * @cgrp from being removed while __put_css_set() is in progress.
4491 4492
	 */
	read_lock(&css_set_lock);
T
Tejun Heo 已提交
4493
	empty = list_empty(&cgrp->cset_links) && list_empty(&cgrp->children);
4494 4495
	read_unlock(&css_set_lock);
	if (!empty)
4496
		return -EBUSY;
L
Li Zefan 已提交
4497

4498
	/*
4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511
	 * Block new css_tryget() by killing css refcnts.  cgroup core
	 * guarantees that, by the time ->css_offline() is invoked, no new
	 * css reference will be given out via css_tryget().  We can't
	 * simply call percpu_ref_kill() and proceed to offlining css's
	 * because percpu_ref_kill() doesn't guarantee that the ref is seen
	 * as killed on all CPUs on return.
	 *
	 * Use percpu_ref_kill_and_confirm() to get notifications as each
	 * css is confirmed to be seen as killed on all CPUs.  The
	 * notification callback keeps track of the number of css's to be
	 * killed and schedules cgroup_offline_fn() to perform the rest of
	 * destruction once the percpu refs of all css's are confirmed to
	 * be killed.
4512
	 */
4513
	atomic_set(&cgrp->css_kill_cnt, 1);
4514
	for_each_root_subsys(cgrp->root, ss) {
4515
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4516

4517 4518 4519 4520 4521 4522 4523 4524
		/*
		 * Killing would put the base ref, but we need to keep it
		 * alive until after ->css_offline.
		 */
		percpu_ref_get(&css->refcnt);

		atomic_inc(&cgrp->css_kill_cnt);
		percpu_ref_kill_and_confirm(&css->refcnt, css_ref_killed_fn);
4525
	}
4526
	cgroup_css_killed(cgrp);
4527 4528 4529 4530 4531 4532 4533 4534

	/*
	 * Mark @cgrp dead.  This prevents further task migration and child
	 * creation by disabling cgroup_lock_live_group().  Note that
	 * CGRP_DEAD assertion is depended upon by cgroup_next_sibling() to
	 * resume iteration after dropping RCU read lock.  See
	 * cgroup_next_sibling() for details.
	 */
4535
	set_bit(CGRP_DEAD, &cgrp->flags);
4536

4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561
	/* CGRP_DEAD is set, remove from ->release_list for the last time */
	raw_spin_lock(&release_list_lock);
	if (!list_empty(&cgrp->release_list))
		list_del_init(&cgrp->release_list);
	raw_spin_unlock(&release_list_lock);

	/*
	 * Remove @cgrp directory.  The removal puts the base ref but we
	 * aren't quite done with @cgrp yet, so hold onto it.
	 */
	dget(d);
	cgroup_d_remove_dir(d);

	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
	 * directory to avoid race between userspace and kernelspace.
	 */
	spin_lock(&cgrp->event_list_lock);
	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
		list_del_init(&event->list);
		schedule_work(&event->remove);
	}
	spin_unlock(&cgrp->event_list_lock);

4562 4563 4564
	return 0;
};

4565 4566 4567 4568 4569 4570 4571 4572 4573 4574
/**
 * cgroup_offline_fn - the second step of cgroup destruction
 * @work: cgroup->destroy_free_work
 *
 * This function is invoked from a work item for a cgroup which is being
 * destroyed after the percpu refcnts of all css's are guaranteed to be
 * seen as killed on all CPUs, and performs the rest of destruction.  This
 * is the second step of destruction described in the comment above
 * cgroup_destroy_locked().
 */
4575 4576 4577 4578 4579 4580 4581 4582 4583
static void cgroup_offline_fn(struct work_struct *work)
{
	struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
	struct cgroup *parent = cgrp->parent;
	struct dentry *d = cgrp->dentry;
	struct cgroup_subsys *ss;

	mutex_lock(&cgroup_mutex);

4584 4585 4586 4587
	/*
	 * css_tryget() is guaranteed to fail now.  Tell subsystems to
	 * initate destruction.
	 */
4588
	for_each_root_subsys(cgrp->root, ss)
4589
		offline_css(ss, cgrp);
4590 4591

	/*
4592 4593 4594 4595 4596
	 * Put the css refs from cgroup_destroy_locked().  Each css holds
	 * an extra reference to the cgroup's dentry and cgroup removal
	 * proceeds regardless of css refs.  On the last put of each css,
	 * whenever that may be, the extra dentry ref is put so that dentry
	 * destruction happens only after all css's are released.
4597
	 */
4598
	for_each_root_subsys(cgrp->root, ss)
T
Tejun Heo 已提交
4599
		css_put(cgrp->subsys[ss->subsys_id]);
4600

4601
	/* delete this cgroup from parent->children */
4602
	list_del_rcu(&cgrp->sibling);
4603

4604 4605
	dput(d);

4606
	set_bit(CGRP_RELEASABLE, &parent->flags);
4607 4608
	check_for_release(parent);

4609
	mutex_unlock(&cgroup_mutex);
4610 4611
}

4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
	int ret;

	mutex_lock(&cgroup_mutex);
	ret = cgroup_destroy_locked(dentry->d_fsdata);
	mutex_unlock(&cgroup_mutex);

	return ret;
}

4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636
static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
{
	INIT_LIST_HEAD(&ss->cftsets);

	/*
	 * base_cftset is embedded in subsys itself, no need to worry about
	 * deregistration.
	 */
	if (ss->base_cftypes) {
		ss->base_cftset.cfts = ss->base_cftypes;
		list_add_tail(&ss->base_cftset.node, &ss->cftsets);
	}
}

4637
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4638 4639
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4640 4641

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4642

4643 4644
	mutex_lock(&cgroup_mutex);

4645 4646 4647
	/* init base cftset */
	cgroup_init_cftsets(ss);

4648
	/* Create the top cgroup state for this subsystem */
4649 4650 4651
	list_add(&ss->sibling, &cgroup_dummy_root.subsys_list);
	ss->root = &cgroup_dummy_root;
	css = ss->css_alloc(cgroup_dummy_top);
4652 4653
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
4654
	init_cgroup_css(css, ss, cgroup_dummy_top);
4655

L
Li Zefan 已提交
4656
	/* Update the init_css_set to contain a subsys
4657
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4658 4659
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
4660
	init_css_set.subsys[ss->subsys_id] = css;
4661 4662 4663

	need_forkexit_callback |= ss->fork || ss->exit;

L
Li Zefan 已提交
4664 4665 4666 4667 4668
	/* At system boot, before all subsystems have been
	 * registered, no tasks have been forked, so we don't
	 * need to invoke fork callbacks here. */
	BUG_ON(!list_empty(&init_task.tasks));

4669
	BUG_ON(online_css(ss, cgroup_dummy_top));
4670

4671 4672
	mutex_unlock(&cgroup_mutex);

4673 4674 4675 4676 4677 4678 4679 4680 4681 4682
	/* this function shouldn't be used with modular subsystems, since they
	 * need to register a subsys_id, among other things */
	BUG_ON(ss->module);
}

/**
 * cgroup_load_subsys: load and register a modular subsystem at runtime
 * @ss: the subsystem to load
 *
 * This function should be called in a modular subsystem's initcall. If the
T
Thomas Weber 已提交
4683
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4684 4685 4686 4687 4688 4689
 * up for use. If the subsystem is built-in anyway, work is delegated to the
 * simpler cgroup_init_subsys.
 */
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
	struct cgroup_subsys_state *css;
4690
	int i, ret;
4691
	struct hlist_node *tmp;
4692
	struct css_set *cset;
4693
	unsigned long key;
4694 4695 4696

	/* check name and function validity */
	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4697
	    ss->css_alloc == NULL || ss->css_free == NULL)
4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713
		return -EINVAL;

	/*
	 * we don't support callbacks in modular subsystems. this check is
	 * before the ss->module check for consistency; a subsystem that could
	 * be a module should still have no callbacks even if the user isn't
	 * compiling it as one.
	 */
	if (ss->fork || ss->exit)
		return -EINVAL;

	/*
	 * an optionally modular subsystem is built-in: we want to do nothing,
	 * since cgroup_init_subsys will have already taken care of it.
	 */
	if (ss->module == NULL) {
4714
		/* a sanity check */
4715
		BUG_ON(cgroup_subsys[ss->subsys_id] != ss);
4716 4717 4718
		return 0;
	}

4719 4720 4721
	/* init base cftset */
	cgroup_init_cftsets(ss);

4722
	mutex_lock(&cgroup_mutex);
4723
	cgroup_subsys[ss->subsys_id] = ss;
4724 4725

	/*
4726
	 * no ss->css_alloc seems to need anything important in the ss
4727
	 * struct, so this can happen first (i.e. before the dummy root
4728
	 * attachment).
4729
	 */
4730
	css = ss->css_alloc(cgroup_dummy_top);
4731
	if (IS_ERR(css)) {
4732 4733
		/* failure case - need to deassign the cgroup_subsys[] slot. */
		cgroup_subsys[ss->subsys_id] = NULL;
4734 4735 4736 4737
		mutex_unlock(&cgroup_mutex);
		return PTR_ERR(css);
	}

4738 4739
	list_add(&ss->sibling, &cgroup_dummy_root.subsys_list);
	ss->root = &cgroup_dummy_root;
4740 4741

	/* our new subsystem will be attached to the dummy hierarchy. */
4742
	init_cgroup_css(css, ss, cgroup_dummy_top);
4743 4744
	/* init_idr must be after init_cgroup_css because it sets css->id. */
	if (ss->use_id) {
4745 4746 4747
		ret = cgroup_init_idr(ss, css);
		if (ret)
			goto err_unload;
4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758
	}

	/*
	 * Now we need to entangle the css into the existing css_sets. unlike
	 * in cgroup_init_subsys, there are now multiple css_sets, so each one
	 * will need a new pointer to it; done by iterating the css_set_table.
	 * furthermore, modifying the existing css_sets will corrupt the hash
	 * table state, so each changed css_set will need its hash recomputed.
	 * this is all done under the css_set_lock.
	 */
	write_lock(&css_set_lock);
4759
	hash_for_each_safe(css_set_table, i, tmp, cset, hlist) {
4760
		/* skip entries that we already rehashed */
4761
		if (cset->subsys[ss->subsys_id])
4762 4763
			continue;
		/* remove existing entry */
4764
		hash_del(&cset->hlist);
4765
		/* set new value */
4766
		cset->subsys[ss->subsys_id] = css;
4767
		/* recompute hash and restore entry */
4768 4769
		key = css_set_hash(cset->subsys);
		hash_add(css_set_table, &cset->hlist, key);
4770 4771 4772
	}
	write_unlock(&css_set_lock);

4773
	ret = online_css(ss, cgroup_dummy_top);
T
Tejun Heo 已提交
4774 4775
	if (ret)
		goto err_unload;
4776

4777 4778 4779
	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4780 4781 4782 4783 4784 4785

err_unload:
	mutex_unlock(&cgroup_mutex);
	/* @ss can't be mounted here as try_module_get() would fail */
	cgroup_unload_subsys(ss);
	return ret;
4786
}
4787
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4788

B
Ben Blum 已提交
4789 4790 4791 4792 4793 4794 4795 4796 4797 4798
/**
 * cgroup_unload_subsys: unload a modular subsystem
 * @ss: the subsystem to unload
 *
 * This function should be called in a modular subsystem's exitcall. When this
 * function is invoked, the refcount on the subsystem's module will be 0, so
 * the subsystem will not be attached to any hierarchy.
 */
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
4799
	struct cgrp_cset_link *link;
B
Ben Blum 已提交
4800 4801 4802 4803 4804 4805 4806 4807

	BUG_ON(ss->module == NULL);

	/*
	 * we shouldn't be called if the subsystem is in use, and the use of
	 * try_module_get in parse_cgroupfs_options should ensure that it
	 * doesn't start being used while we're killing it off.
	 */
4808
	BUG_ON(ss->root != &cgroup_dummy_root);
B
Ben Blum 已提交
4809 4810

	mutex_lock(&cgroup_mutex);
4811

4812
	offline_css(ss, cgroup_dummy_top);
4813

T
Tejun Heo 已提交
4814
	if (ss->use_id)
4815 4816
		idr_destroy(&ss->idr);

B
Ben Blum 已提交
4817
	/* deassign the subsys_id */
4818
	cgroup_subsys[ss->subsys_id] = NULL;
B
Ben Blum 已提交
4819

4820
	/* remove subsystem from the dummy root's list of subsystems */
4821
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4822 4823

	/*
4824 4825 4826
	 * disentangle the css from all css_sets attached to the dummy
	 * top. as in loading, we need to pay our respects to the hashtable
	 * gods.
B
Ben Blum 已提交
4827 4828
	 */
	write_lock(&css_set_lock);
4829
	list_for_each_entry(link, &cgroup_dummy_top->cset_links, cset_link) {
4830
		struct css_set *cset = link->cset;
4831
		unsigned long key;
B
Ben Blum 已提交
4832

4833 4834 4835 4836
		hash_del(&cset->hlist);
		cset->subsys[ss->subsys_id] = NULL;
		key = css_set_hash(cset->subsys);
		hash_add(css_set_table, &cset->hlist, key);
B
Ben Blum 已提交
4837 4838 4839 4840
	}
	write_unlock(&css_set_lock);

	/*
4841 4842 4843 4844
	 * remove subsystem's css from the cgroup_dummy_top and free it -
	 * need to free before marking as null because ss->css_free needs
	 * the cgrp->subsys pointer to find their state. note that this
	 * also takes care of freeing the css_id.
B
Ben Blum 已提交
4845
	 */
4846 4847
	ss->css_free(cgroup_dummy_top);
	cgroup_dummy_top->subsys[ss->subsys_id] = NULL;
B
Ben Blum 已提交
4848 4849 4850 4851 4852

	mutex_unlock(&cgroup_mutex);
}
EXPORT_SYMBOL_GPL(cgroup_unload_subsys);

4853
/**
L
Li Zefan 已提交
4854 4855 4856 4857
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4858 4859 4860
 */
int __init cgroup_init_early(void)
{
4861
	struct cgroup_subsys *ss;
4862
	int i;
4863

4864
	atomic_set(&init_css_set.refcount, 1);
4865
	INIT_LIST_HEAD(&init_css_set.cgrp_links);
4866
	INIT_LIST_HEAD(&init_css_set.tasks);
4867
	INIT_HLIST_NODE(&init_css_set.hlist);
4868
	css_set_count = 1;
4869 4870
	init_cgroup_root(&cgroup_dummy_root);
	cgroup_root_count = 1;
4871
	RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
4872

4873
	init_cgrp_cset_link.cset = &init_css_set;
4874 4875
	init_cgrp_cset_link.cgrp = cgroup_dummy_top;
	list_add(&init_cgrp_cset_link.cset_link, &cgroup_dummy_top->cset_links);
4876
	list_add(&init_cgrp_cset_link.cgrp_link, &init_css_set.cgrp_links);
4877

4878 4879
	/* at bootup time, we don't worry about modular subsystems */
	for_each_builtin_subsys(ss, i) {
4880 4881
		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4882 4883
		BUG_ON(!ss->css_alloc);
		BUG_ON(!ss->css_free);
4884
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4885
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896
			       ss->name, ss->subsys_id);
			BUG();
		}

		if (ss->early_init)
			cgroup_init_subsys(ss);
	}
	return 0;
}

/**
L
Li Zefan 已提交
4897 4898 4899 4900
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4901 4902 4903
 */
int __init cgroup_init(void)
{
4904
	struct cgroup_subsys *ss;
4905
	unsigned long key;
4906
	int i, err;
4907 4908 4909 4910

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4911

4912
	for_each_builtin_subsys(ss, i) {
4913 4914
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4915
		if (ss->use_id)
4916
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4917 4918
	}

4919
	/* allocate id for the dummy hierarchy */
T
Tejun Heo 已提交
4920 4921 4922
	mutex_lock(&cgroup_mutex);
	mutex_lock(&cgroup_root_mutex);

4923 4924 4925 4926
	/* Add init_css_set to the hash table */
	key = css_set_hash(init_css_set.subsys);
	hash_add(css_set_table, &init_css_set.hlist, key);

4927
	BUG_ON(cgroup_init_root_id(&cgroup_dummy_root, 0, 1));
4928

T
Tejun Heo 已提交
4929 4930 4931
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);

4932 4933 4934 4935 4936 4937
	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
	if (!cgroup_kobj) {
		err = -ENOMEM;
		goto out;
	}

4938
	err = register_filesystem(&cgroup_fs_type);
4939 4940
	if (err < 0) {
		kobject_put(cgroup_kobj);
4941
		goto out;
4942
	}
4943

L
Li Zefan 已提交
4944
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4945

4946
out:
4947 4948 4949
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4950 4951
	return err;
}
4952

4953 4954 4955 4956 4957 4958
/*
 * proc_cgroup_show()
 *  - Print task's cgroup paths into seq_file, one line for each hierarchy
 *  - Used for /proc/<pid>/cgroup.
 *  - No need to task_lock(tsk) on this tsk->cgroup reference, as it
 *    doesn't really matter if tsk->cgroup changes after we read it,
4959
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4960 4961 4962 4963 4964 4965
 *    anyway.  No need to check that tsk->cgroup != NULL, thanks to
 *    the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
 *    cgroup to top_cgroup.
 */

/* TODO: Use a proper seq_file iterator */
4966
int proc_cgroup_show(struct seq_file *m, void *v)
4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988
{
	struct pid *pid;
	struct task_struct *tsk;
	char *buf;
	int retval;
	struct cgroupfs_root *root;

	retval = -ENOMEM;
	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!buf)
		goto out;

	retval = -ESRCH;
	pid = m->private;
	tsk = get_pid_task(pid, PIDTYPE_PID);
	if (!tsk)
		goto out_free;

	retval = 0;

	mutex_lock(&cgroup_mutex);

4989
	for_each_active_root(root) {
4990
		struct cgroup_subsys *ss;
4991
		struct cgroup *cgrp;
4992 4993
		int count = 0;

4994
		seq_printf(m, "%d:", root->hierarchy_id);
4995
		for_each_root_subsys(root, ss)
4996
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4997 4998 4999
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
5000
		seq_putc(m, ':');
5001
		cgrp = task_cgroup_from_root(tsk, root);
5002
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020
		if (retval < 0)
			goto out_unlock;
		seq_puts(m, buf);
		seq_putc(m, '\n');
	}

out_unlock:
	mutex_unlock(&cgroup_mutex);
	put_task_struct(tsk);
out_free:
	kfree(buf);
out:
	return retval;
}

/* Display information about each subsystem and each hierarchy */
static int proc_cgroupstats_show(struct seq_file *m, void *v)
{
5021
	struct cgroup_subsys *ss;
5022 5023
	int i;

5024
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
5025 5026 5027 5028 5029
	/*
	 * ideally we don't want subsystems moving around while we do this.
	 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
	 * subsys/hierarchy state.
	 */
5030
	mutex_lock(&cgroup_mutex);
5031 5032

	for_each_subsys(ss, i)
5033 5034
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
5035
			   ss->root->number_of_cgroups, !ss->disabled);
5036

5037 5038 5039 5040 5041 5042
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
5043
	return single_open(file, proc_cgroupstats_show, NULL);
5044 5045
}

5046
static const struct file_operations proc_cgroupstats_operations = {
5047 5048 5049 5050 5051 5052
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

5053 5054
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
5055
 * @child: pointer to task_struct of forking parent process.
5056 5057 5058 5059 5060
 *
 * Description: A task inherits its parent's cgroup at fork().
 *
 * A pointer to the shared css_set was automatically copied in
 * fork.c by dup_task_struct().  However, we ignore that copy, since
5061 5062 5063 5064
 * it was not made under the protection of RCU or cgroup_mutex, so
 * might no longer be a valid cgroup pointer.  cgroup_attach_task() might
 * have already changed current->cgroups, allowing the previously
 * referenced cgroup group to be removed and freed.
5065 5066 5067 5068 5069 5070
 *
 * At the point that cgroup_fork() is called, 'current' is the parent
 * task, and the passed argument 'child' points to the child task.
 */
void cgroup_fork(struct task_struct *child)
{
5071
	task_lock(current);
5072
	get_css_set(task_css_set(current));
5073
	child->cgroups = current->cgroups;
5074
	task_unlock(current);
5075
	INIT_LIST_HEAD(&child->cg_list);
5076 5077
}

5078
/**
L
Li Zefan 已提交
5079 5080 5081
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
5082 5083 5084 5085 5086
 * Adds the task to the list running through its css_set if necessary and
 * call the subsystem fork() callbacks.  Has to be after the task is
 * visible on the task list in case we race with the first call to
 * cgroup_iter_start() - to guarantee that the new task ends up on its
 * list.
L
Li Zefan 已提交
5087
 */
5088 5089
void cgroup_post_fork(struct task_struct *child)
{
5090
	struct cgroup_subsys *ss;
5091 5092
	int i;

5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103
	/*
	 * use_task_css_set_links is set to 1 before we walk the tasklist
	 * under the tasklist_lock and we read it here after we added the child
	 * to the tasklist under the tasklist_lock as well. If the child wasn't
	 * yet in the tasklist when we walked through it from
	 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
	 * should be visible now due to the paired locking and barriers implied
	 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
	 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
	 * lock on fork.
	 */
5104 5105
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
5106 5107
		task_lock(child);
		if (list_empty(&child->cg_list))
5108
			list_add(&child->cg_list, &task_css_set(child)->tasks);
5109
		task_unlock(child);
5110 5111
		write_unlock(&css_set_lock);
	}
5112 5113 5114 5115 5116 5117 5118

	/*
	 * Call ss->fork().  This must happen after @child is linked on
	 * css_set; otherwise, @child might change state between ->fork()
	 * and addition to css_set.
	 */
	if (need_forkexit_callback) {
5119 5120 5121 5122 5123 5124 5125 5126
		/*
		 * fork/exit callbacks are supported only for builtin
		 * subsystems, and the builtin section of the subsys
		 * array is immutable, so we don't need to lock the
		 * subsys array here. On the other hand, modular section
		 * of the array can be freed at module unload, so we
		 * can't touch that.
		 */
5127
		for_each_builtin_subsys(ss, i)
5128 5129 5130
			if (ss->fork)
				ss->fork(child);
	}
5131
}
5132

5133 5134 5135
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
5136
 * @run_callback: run exit callbacks?
5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164
 *
 * Description: Detach cgroup from @tsk and release it.
 *
 * Note that cgroups marked notify_on_release force every task in
 * them to take the global cgroup_mutex mutex when exiting.
 * This could impact scaling on very large systems.  Be reluctant to
 * use notify_on_release cgroups where very high task exit scaling
 * is required on large systems.
 *
 * the_top_cgroup_hack:
 *
 *    Set the exiting tasks cgroup to the root cgroup (top_cgroup).
 *
 *    We call cgroup_exit() while the task is still competent to
 *    handle notify_on_release(), then leave the task attached to the
 *    root cgroup in each hierarchy for the remainder of its exit.
 *
 *    To do this properly, we would increment the reference count on
 *    top_cgroup, and near the very end of the kernel/exit.c do_exit()
 *    code we would add a second cgroup function call, to drop that
 *    reference.  This would just create an unnecessary hot spot on
 *    the top_cgroup reference count, to no avail.
 *
 *    Normally, holding a reference to a cgroup without bumping its
 *    count is unsafe.   The cgroup could go away, or someone could
 *    attach us to a different cgroup, decrementing the count on
 *    the first cgroup that we never incremented.  But in this case,
 *    top_cgroup isn't going away, and either task has PF_EXITING set,
5165 5166
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
5167 5168 5169
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
5170
	struct cgroup_subsys *ss;
5171
	struct css_set *cset;
5172
	int i;
5173 5174 5175 5176 5177 5178 5179 5180 5181

	/*
	 * Unlink from the css_set task list if necessary.
	 * Optimistically check cg_list before taking
	 * css_set_lock
	 */
	if (!list_empty(&tsk->cg_list)) {
		write_lock(&css_set_lock);
		if (!list_empty(&tsk->cg_list))
5182
			list_del_init(&tsk->cg_list);
5183 5184 5185
		write_unlock(&css_set_lock);
	}

5186 5187
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
5188 5189
	cset = task_css_set(tsk);
	RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
5190 5191

	if (run_callbacks && need_forkexit_callback) {
5192 5193 5194 5195
		/*
		 * fork/exit callbacks are supported only for builtin
		 * subsystems, see cgroup_post_fork() for details.
		 */
5196
		for_each_builtin_subsys(ss, i) {
5197
			if (ss->exit) {
5198
				struct cgroup *old_cgrp = cset->subsys[i]->cgroup;
5199
				struct cgroup *cgrp = task_cgroup(tsk, i);
5200

5201
				ss->exit(cgrp, old_cgrp, tsk);
5202 5203 5204
			}
		}
	}
5205
	task_unlock(tsk);
5206

5207
	put_css_set_taskexit(cset);
5208
}
5209

5210
static void check_for_release(struct cgroup *cgrp)
5211
{
5212
	if (cgroup_is_releasable(cgrp) &&
T
Tejun Heo 已提交
5213
	    list_empty(&cgrp->cset_links) && list_empty(&cgrp->children)) {
5214 5215
		/*
		 * Control Group is currently removeable. If it's not
5216
		 * already queued for a userspace notification, queue
5217 5218
		 * it now
		 */
5219
		int need_schedule_work = 0;
5220

5221
		raw_spin_lock(&release_list_lock);
5222
		if (!cgroup_is_dead(cgrp) &&
5223 5224
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
5225 5226
			need_schedule_work = 1;
		}
5227
		raw_spin_unlock(&release_list_lock);
5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

/*
 * Notify userspace when a cgroup is released, by running the
 * configured release agent with the name of the cgroup (path
 * relative to the root of cgroup file system) as the argument.
 *
 * Most likely, this user command will try to rmdir this cgroup.
 *
 * This races with the possibility that some other task will be
 * attached to this cgroup before it is removed, or that some other
 * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
 * unused, and this cgroup will be reprieved from its death sentence,
 * to continue to serve a useful existence.  Next time it's released,
 * we will get notified again, if it still has 'notify_on_release' set.
 *
 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
 * means only wait until the task is successfully execve()'d.  The
 * separate release agent task is forked by call_usermodehelper(),
 * then control in this thread returns here, without waiting for the
 * release agent task.  We don't bother to wait because the caller of
 * this routine has no use for the exit status of the release agent
 * task, so no sense holding our caller up for that.
 */
static void cgroup_release_agent(struct work_struct *work)
{
	BUG_ON(work != &release_agent_work);
	mutex_lock(&cgroup_mutex);
5260
	raw_spin_lock(&release_list_lock);
5261 5262 5263
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
5264
		char *pathbuf = NULL, *agentbuf = NULL;
5265
		struct cgroup *cgrp = list_entry(release_list.next,
5266 5267
						    struct cgroup,
						    release_list);
5268
		list_del_init(&cgrp->release_list);
5269
		raw_spin_unlock(&release_list_lock);
5270
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5271 5272 5273 5274 5275 5276 5277
		if (!pathbuf)
			goto continue_free;
		if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
			goto continue_free;
		agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
		if (!agentbuf)
			goto continue_free;
5278 5279

		i = 0;
5280 5281
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295
		argv[i] = NULL;

		i = 0;
		/* minimal command environment */
		envp[i++] = "HOME=/";
		envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
		envp[i] = NULL;

		/* Drop the lock while we invoke the usermode helper,
		 * since the exec could involve hitting disk and hence
		 * be a slow process */
		mutex_unlock(&cgroup_mutex);
		call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
		mutex_lock(&cgroup_mutex);
5296 5297 5298
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
5299
		raw_spin_lock(&release_list_lock);
5300
	}
5301
	raw_spin_unlock(&release_list_lock);
5302 5303
	mutex_unlock(&cgroup_mutex);
}
5304 5305 5306

static int __init cgroup_disable(char *str)
{
5307
	struct cgroup_subsys *ss;
5308
	char *token;
5309
	int i;
5310 5311 5312 5313

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
5314

5315 5316 5317 5318 5319
		/*
		 * cgroup_disable, being at boot time, can't know about
		 * module subsystems, so we don't worry about them.
		 */
		for_each_builtin_subsys(ss, i) {
5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330
			if (!strcmp(token, ss->name)) {
				ss->disabled = 1;
				printk(KERN_INFO "Disabling %s control group"
					" subsystem\n", ss->name);
				break;
			}
		}
	}
	return 1;
}
__setup("cgroup_disable=", cgroup_disable);
K
KAMEZAWA Hiroyuki 已提交
5331 5332 5333 5334 5335

/*
 * Functons for CSS ID.
 */

5336
/* to get ID other than 0, this should be called when !cgroup_is_dead() */
K
KAMEZAWA Hiroyuki 已提交
5337 5338
unsigned short css_id(struct cgroup_subsys_state *css)
{
5339 5340 5341 5342 5343 5344 5345
	struct css_id *cssid;

	/*
	 * This css_id() can return correct value when somone has refcnt
	 * on this or this is under rcu_read_lock(). Once css->id is allocated,
	 * it's unchanged until freed.
	 */
5346
	cssid = rcu_dereference_raw(css->id);
K
KAMEZAWA Hiroyuki 已提交
5347 5348 5349 5350 5351

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5352
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5353

5354 5355 5356 5357 5358 5359
/**
 *  css_is_ancestor - test "root" css is an ancestor of "child"
 * @child: the css to be tested.
 * @root: the css supporsed to be an ancestor of the child.
 *
 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5360
 * this function reads css->id, the caller must hold rcu_read_lock().
5361 5362 5363 5364 5365 5366
 * But, considering usual usage, the csses should be valid objects after test.
 * Assuming that the caller will do some action to the child if this returns
 * returns true, the caller must take "child";s reference count.
 * If "child" is valid object and this returns true, "root" is valid, too.
 */

K
KAMEZAWA Hiroyuki 已提交
5367
bool css_is_ancestor(struct cgroup_subsys_state *child,
5368
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5369
{
5370 5371
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5372

5373
	child_id  = rcu_dereference(child->id);
5374 5375
	if (!child_id)
		return false;
5376
	root_id = rcu_dereference(root->id);
5377 5378 5379 5380 5381 5382 5383
	if (!root_id)
		return false;
	if (child_id->depth < root_id->depth)
		return false;
	if (child_id->stack[root_id->depth] != root_id->id)
		return false;
	return true;
K
KAMEZAWA Hiroyuki 已提交
5384 5385 5386 5387
}

void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
{
5388 5389
	struct css_id *id = rcu_dereference_protected(css->id, true);

K
KAMEZAWA Hiroyuki 已提交
5390 5391 5392 5393 5394 5395 5396 5397
	/* When this is called before css_id initialization, id can be NULL */
	if (!id)
		return;

	BUG_ON(!ss->use_id);

	rcu_assign_pointer(id->css, NULL);
	rcu_assign_pointer(css->id, NULL);
5398
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5399
	idr_remove(&ss->idr, id->id);
5400
	spin_unlock(&ss->id_lock);
5401
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5402
}
B
Ben Blum 已提交
5403
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
5404 5405 5406 5407 5408 5409 5410 5411 5412

/*
 * This is called by init or create(). Then, calls to this function are
 * always serialized (By cgroup_mutex() at create()).
 */

static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
{
	struct css_id *newid;
T
Tejun Heo 已提交
5413
	int ret, size;
K
KAMEZAWA Hiroyuki 已提交
5414 5415 5416 5417 5418 5419 5420

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
T
Tejun Heo 已提交
5421 5422

	idr_preload(GFP_KERNEL);
5423
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5424
	/* Don't use 0. allocates an ID of 1-65535 */
T
Tejun Heo 已提交
5425
	ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
5426
	spin_unlock(&ss->id_lock);
T
Tejun Heo 已提交
5427
	idr_preload_end();
K
KAMEZAWA Hiroyuki 已提交
5428 5429

	/* Returns error when there are no free spaces for new ID.*/
T
Tejun Heo 已提交
5430
	if (ret < 0)
K
KAMEZAWA Hiroyuki 已提交
5431 5432
		goto err_out;

T
Tejun Heo 已提交
5433
	newid->id = ret;
K
KAMEZAWA Hiroyuki 已提交
5434 5435 5436 5437
	newid->depth = depth;
	return newid;
err_out:
	kfree(newid);
T
Tejun Heo 已提交
5438
	return ERR_PTR(ret);
K
KAMEZAWA Hiroyuki 已提交
5439 5440 5441

}

5442 5443
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
5444 5445 5446
{
	struct css_id *newid;

5447
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5448 5449 5450 5451 5452 5453 5454
	idr_init(&ss->idr);

	newid = get_new_cssid(ss, 0);
	if (IS_ERR(newid))
		return PTR_ERR(newid);

	newid->stack[0] = newid->id;
5455 5456
	RCU_INIT_POINTER(newid->css, rootcss);
	RCU_INIT_POINTER(rootcss->id, newid);
K
KAMEZAWA Hiroyuki 已提交
5457 5458 5459 5460 5461 5462 5463 5464
	return 0;
}

static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
			struct cgroup *child)
{
	int subsys_id, i, depth = 0;
	struct cgroup_subsys_state *parent_css, *child_css;
5465
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
5466 5467 5468 5469

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
5470
	parent_id = rcu_dereference_protected(parent_css->id, true);
5471
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508

	child_id = get_new_cssid(ss, depth);
	if (IS_ERR(child_id))
		return PTR_ERR(child_id);

	for (i = 0; i < depth; i++)
		child_id->stack[i] = parent_id->stack[i];
	child_id->stack[depth] = child_id->id;
	/*
	 * child_id->css pointer will be set after this cgroup is available
	 * see cgroup_populate_dir()
	 */
	rcu_assign_pointer(child_css->id, child_id);

	return 0;
}

/**
 * css_lookup - lookup css by id
 * @ss: cgroup subsys to be looked into.
 * @id: the id
 *
 * Returns pointer to cgroup_subsys_state if there is valid one with id.
 * NULL if not. Should be called under rcu_read_lock()
 */
struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
{
	struct css_id *cssid = NULL;

	BUG_ON(!ss->use_id);
	cssid = idr_find(&ss->idr, id);

	if (unlikely(!cssid))
		return NULL;

	return rcu_dereference(cssid->css);
}
B
Ben Blum 已提交
5509
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5510

S
Stephane Eranian 已提交
5511 5512 5513 5514 5515 5516 5517 5518 5519
/*
 * get corresponding css from file open on cgroupfs directory
 */
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
{
	struct cgroup *cgrp;
	struct inode *inode;
	struct cgroup_subsys_state *css;

A
Al Viro 已提交
5520
	inode = file_inode(f);
S
Stephane Eranian 已提交
5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533
	/* check in cgroup filesystem dir */
	if (inode->i_op != &cgroup_dir_inode_operations)
		return ERR_PTR(-EBADF);

	if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
		return ERR_PTR(-EINVAL);

	/* get cgroup */
	cgrp = __d_cgrp(f->f_dentry);
	css = cgrp->subsys[id];
	return css ? css : ERR_PTR(-ENOENT);
}

5534
#ifdef CONFIG_CGROUP_DEBUG
L
Li Zefan 已提交
5535
static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cgrp)
5536 5537 5538 5539 5540 5541 5542 5543 5544
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

	if (!css)
		return ERR_PTR(-ENOMEM);

	return css;
}

L
Li Zefan 已提交
5545
static void debug_css_free(struct cgroup *cgrp)
5546
{
L
Li Zefan 已提交
5547
	kfree(cgrp->subsys[debug_subsys_id]);
5548 5549
}

L
Li Zefan 已提交
5550
static u64 debug_taskcount_read(struct cgroup *cgrp, struct cftype *cft)
5551
{
L
Li Zefan 已提交
5552
	return cgroup_task_count(cgrp);
5553 5554
}

L
Li Zefan 已提交
5555
static u64 current_css_set_read(struct cgroup *cgrp, struct cftype *cft)
5556 5557 5558 5559
{
	return (u64)(unsigned long)current->cgroups;
}

L
Li Zefan 已提交
5560 5561
static u64 current_css_set_refcount_read(struct cgroup *cgrp,
					 struct cftype *cft)
5562 5563 5564 5565
{
	u64 count;

	rcu_read_lock();
5566
	count = atomic_read(&task_css_set(current)->refcount);
5567 5568 5569 5570
	rcu_read_unlock();
	return count;
}

L
Li Zefan 已提交
5571
static int current_css_set_cg_links_read(struct cgroup *cgrp,
5572 5573 5574
					 struct cftype *cft,
					 struct seq_file *seq)
{
5575
	struct cgrp_cset_link *link;
5576
	struct css_set *cset;
5577 5578 5579

	read_lock(&css_set_lock);
	rcu_read_lock();
5580
	cset = rcu_dereference(current->cgroups);
5581
	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
5582 5583 5584 5585 5586 5587 5588
		struct cgroup *c = link->cgrp;
		const char *name;

		if (c->dentry)
			name = c->dentry->d_name.name;
		else
			name = "?";
5589 5590
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5591 5592 5593 5594 5595 5596 5597
	}
	rcu_read_unlock();
	read_unlock(&css_set_lock);
	return 0;
}

#define MAX_TASKS_SHOWN_PER_CSS 25
L
Li Zefan 已提交
5598
static int cgroup_css_links_read(struct cgroup *cgrp,
5599 5600 5601
				 struct cftype *cft,
				 struct seq_file *seq)
{
5602
	struct cgrp_cset_link *link;
5603 5604

	read_lock(&css_set_lock);
L
Li Zefan 已提交
5605
	list_for_each_entry(link, &cgrp->cset_links, cset_link) {
5606
		struct css_set *cset = link->cset;
5607 5608
		struct task_struct *task;
		int count = 0;
5609 5610
		seq_printf(seq, "css_set %p\n", cset);
		list_for_each_entry(task, &cset->tasks, cg_list) {
5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623
			if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
				seq_puts(seq, "  ...\n");
				break;
			} else {
				seq_printf(seq, "  task %d\n",
					   task_pid_vnr(task));
			}
		}
	}
	read_unlock(&css_set_lock);
	return 0;
}

5624 5625 5626 5627 5628 5629 5630 5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644
static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
{
	return test_bit(CGRP_RELEASABLE, &cgrp->flags);
}

static struct cftype debug_files[] =  {
	{
		.name = "taskcount",
		.read_u64 = debug_taskcount_read,
	},

	{
		.name = "current_css_set",
		.read_u64 = current_css_set_read,
	},

	{
		.name = "current_css_set_refcount",
		.read_u64 = current_css_set_refcount_read,
	},

5645 5646 5647 5648 5649 5650 5651 5652 5653 5654
	{
		.name = "current_css_set_cg_links",
		.read_seq_string = current_css_set_cg_links_read,
	},

	{
		.name = "cgroup_css_links",
		.read_seq_string = cgroup_css_links_read,
	},

5655 5656 5657 5658 5659
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

5660 5661
	{ }	/* terminate */
};
5662 5663 5664

struct cgroup_subsys debug_subsys = {
	.name = "debug",
5665 5666
	.css_alloc = debug_css_alloc,
	.css_free = debug_css_free,
5667
	.subsys_id = debug_subsys_id,
5668
	.base_cftypes = debug_files,
5669 5670
};
#endif /* CONFIG_CGROUP_DEBUG */