bblum

/* *  Generic process-grouping system. * *  Based originally on the cpuset system, extracted by Paul Menage *  Copyright (C) 2006 Google, Inc * *  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>#include <linux/errno.h>#include <linux/fs.h>#include <linux/kernel.h>#include <linux/list.h>#include <linux/mm.h>#include <linux/mutex.h>#include <linux/mount.h>#include <linux/pagemap.h>#include <linux/proc_fs.h>#include <linux/rcupdate.h>#include <linux/sched.h>#include <linux/backing-dev.h>#include <linux/seq_file.h>#include <linux/slab.h>#include <linux/magic.h>#include <linux/spinlock.h>#include <linux/string.h>#include <linux/sort.h>#include <linux/kmod.h>#include <linux/delayacct.h>#include <linux/cgroupstats.h>#include <linux/hash.h>#include <linux/namei.h>#include <asm/atomic.h>static DEFINE_MUTEX(cgroup_mutex);/* Generate an array of cgroup subsystem pointers */#define SUBSYS(_x) &_x ## _subsys,static struct cgroup_subsys *subsys[] = {#include <linux/cgroup_subsys.h>};/* * A cgroupfs_root represents the root of a cgroup hierarchy, * and may be associated with a superblock to form an active * hierarchy */struct cgroupfs_root {	struct super_block *sb;	/*	 * The bitmask of subsystems intended to be attached to this	 * hierarchy	 */	unsigned long subsys_bits;	/* The bitmask of subsystems currently attached to this hierarchy */	unsigned long actual_subsys_bits;	/* A list running through the attached subsystems */	struct list_head subsys_list;	/* The root cgroup for this hierarchy */	struct cgroup top_cgroup;	/* Tracks how many cgroups are currently defined in hierarchy.*/	int number_of_cgroups;	/* A list running through the active hierarchies */	struct list_head root_list;	/* Hierarchy-specific flags */	unsigned long flags;	/* The path to use for release notifications. */	char release_agent_path[PATH_MAX];};/* * The "rootnode" hierarchy is 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. */static struct cgroupfs_root rootnode;/* The list of hierarchy roots */static LIST_HEAD(roots);static int root_count;/* dummytop is a shorthand for the dummy hierarchy's top cgroup */#define dummytop (&rootnode.top_cgroup)/* This flag indicates whether tasks in the fork and exit paths should * check for fork/exit handlers to call. This avoids us having to do * extra work in the fork/exit path if none of the subsystems need to * be called. */static int need_forkexit_callback __read_mostly;/* convenient tests for these bits */inline int cgroup_is_removed(const struct cgroup *cgrp){	return test_bit(CGRP_REMOVED, &cgrp->flags);}/* bits in struct cgroupfs_root flags field */enum {	ROOT_NOPREFIX, /* mounted subsystems have no named prefix */};static int cgroup_is_releasable(const struct cgroup *cgrp){	const int bits =		(1 << CGRP_RELEASABLE) |		(1 << CGRP_NOTIFY_ON_RELEASE);	return (cgrp->flags & bits) == bits;}static int notify_on_release(const struct cgroup *cgrp){	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);}/* * for_each_subsys() allows you to iterate on each subsystem attached to * an active hierarchy */#define for_each_subsys(_root, _ss) \list_for_each_entry(_ss, &_root->subsys_list, sibling)/* for_each_active_root() allows you to iterate across the active hierarchies */#define for_each_active_root(_root) \list_for_each_entry(_root, &roots, root_list)/* the list of cgroups eligible for automatic release. Protected by * release_list_lock */static LIST_HEAD(release_list);static DEFINE_SPINLOCK(release_list_lock);static void cgroup_release_agent(struct work_struct *work);static DECLARE_WORK(release_agent_work, cgroup_release_agent);static void check_for_release(struct cgroup *cgrp);/* Link structure for associating css_set objects with cgroups */struct cg_cgroup_link {	/*	 * List running through cg_cgroup_links associated with a	 * cgroup, anchored on cgroup->css_sets	 */	struct list_head cgrp_link_list;	/*	 * List running through cg_cgroup_links pointing at a	 * single css_set object, anchored on css_set->cg_links	 */	struct list_head cg_link_list;	struct css_set *cg;};/* 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;static struct cg_cgroup_link init_css_set_link;/* 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;/* hash table for cgroup groups. This improves the performance to * find an existing css_set */#define CSS_SET_HASH_BITS	7#define CSS_SET_TABLE_SIZE	(1 << CSS_SET_HASH_BITS)static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[]){	int i;	int index;	unsigned long tmp = 0UL;	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)		tmp += (unsigned long)css[i];	tmp = (tmp >> 16) ^ tmp;	index = hash_long(tmp, CSS_SET_HASH_BITS);	return &css_set_table[index];}/* 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 */static int use_task_css_set_links __read_mostly;/* When we create or destroy a css_set, the operation simply * takes/releases a reference count on all the cgroups referenced * by subsystems in this css_set. This can end up multiple-counting * some cgroups, but that's OK - the ref-count is just a * busy/not-busy indicator; ensuring that we only count each cgroup * once would require taking a global lock to ensure that no * subsystems moved between hierarchies while we were doing so. * * Possible TODO: decide at boot time based on the number of * registered subsystems and the number of CPUs or NUMA nodes whether * it's better for performance to ref-count every subsystem, or to * take a global lock and only add one ref count to each hierarchy. *//* * unlink a css_set from the list and free it */static void unlink_css_set(struct css_set *cg){	struct cg_cgroup_link *link;	struct cg_cgroup_link *saved_link;	hlist_del(&cg->hlist);	css_set_count--;	list_for_each_entry_safe(link, saved_link, &cg->cg_links,				 cg_link_list) {		list_del(&link->cg_link_list);		list_del(&link->cgrp_link_list);		kfree(link);	}}static void __put_css_set(struct css_set *cg, int taskexit){	int i;	/*	 * Ensure that the refcount doesn't hit zero while any readers	 * can see it. Similar to atomic_dec_and_lock(), but for an	 * rwlock	 */	if (atomic_add_unless(&cg->refcount, -1, 1))		return;	write_lock(&css_set_lock);	if (!atomic_dec_and_test(&cg->refcount)) {		write_unlock(&css_set_lock);		return;	}	unlink_css_set(cg);	write_unlock(&css_set_lock);	rcu_read_lock();	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup *cgrp = rcu_dereference(cg->subsys[i]->cgroup);		if (atomic_dec_and_test(&cgrp->count) &&		    notify_on_release(cgrp)) {			if (taskexit)				set_bit(CGRP_RELEASABLE, &cgrp->flags);			check_for_release(cgrp);		}	}	rcu_read_unlock();	kfree(cg);}/* * refcounted get/put for css_set objects */static inline void get_css_set(struct css_set *cg){	atomic_inc(&cg->refcount);}static inline void put_css_set(struct css_set *cg){	__put_css_set(cg, 0);}static inline void put_css_set_taskexit(struct css_set *cg){	__put_css_set(cg, 1);}/* * find_existing_css_set() is a helper for * find_css_set(), and checks to see whether an existing * css_set is suitable. * * oldcg: the cgroup group that we're using before the cgroup * transition * * cgrp: the cgroup that we're moving into * * template: location in which to build the desired set of subsystem * state objects for the new cgroup group */static struct css_set *find_existing_css_set(	struct css_set *oldcg,	struct cgroup *cgrp,	struct cgroup_subsys_state *template[]){	int i;	struct cgroupfs_root *root = cgrp->root;	struct hlist_head *hhead;	struct hlist_node *node;	struct css_set *cg;	/* Built the set of subsystem state objects that we want to	 * see in the new css_set */	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		if (root->subsys_bits & (1UL << i)) {			/* Subsystem is in this hierarchy. So we want			 * the subsystem state from the new			 * cgroup */			template[i] = cgrp->subsys[i];		} else {			/* Subsystem is not in this hierarchy, so we			 * don't want to change the subsystem state */			template[i] = oldcg->subsys[i];		}	}	hhead = css_set_hash(template);	hlist_for_each_entry(cg, node, hhead, hlist) {		if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) {			/* All subsystems matched */			return cg;		}	}	/* No existing cgroup group matched */	return NULL;}static void free_cg_links(struct list_head *tmp){	struct cg_cgroup_link *link;	struct cg_cgroup_link *saved_link;	list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {		list_del(&link->cgrp_link_list);		kfree(link);	}}/* * allocate_cg_links() allocates "count" cg_cgroup_link structures * and chains them on tmp through their cgrp_link_list fields. Returns 0 on * success or a negative error */static int allocate_cg_links(int count, struct list_head *tmp){	struct cg_cgroup_link *link;	int i;	INIT_LIST_HEAD(tmp);	for (i = 0; i < count; i++) {		link = kmalloc(sizeof(*link), GFP_KERNEL);		if (!link) {			free_cg_links(tmp);			return -ENOMEM;		}		list_add(&link->cgrp_link_list, tmp);	}	return 0;}/** * link_css_set - a helper function to link a css_set to a cgroup * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links() * @cg: the css_set to be linked * @cgrp: the destination cgroup */static void link_css_set(struct list_head *tmp_cg_links,			 struct css_set *cg, struct cgroup *cgrp){	struct cg_cgroup_link *link;	BUG_ON(list_empty(tmp_cg_links));	link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,				cgrp_link_list);	link->cg = cg;	list_move(&link->cgrp_link_list, &cgrp->css_sets);	list_add(&link->cg_link_list, &cg->cg_links);}/* * find_css_set() takes an existing cgroup group and a * cgroup object, and returns a css_set object that's * equivalent to the old group, but with the given cgroup * substituted into the appropriate hierarchy. Must be called with * cgroup_mutex held */static struct css_set *find_css_set(	struct css_set *oldcg, struct cgroup *cgrp){	struct css_set *res;	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];	int i;	struct list_head tmp_cg_links;	struct hlist_head *hhead;	/* First see if we already have a cgroup group that matches	 * the desired set */	read_lock(&css_set_lock);	res = find_existing_css_set(oldcg, cgrp, template);	if (res)		get_css_set(res);	read_unlock(&css_set_lock);	if (res)		return res;	res = kmalloc(sizeof(*res), GFP_KERNEL);	if (!res)		return NULL;	/* Allocate all the cg_cgroup_link objects that we'll need */	if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {		kfree(res);		return NULL;	}	atomic_set(&res->refcount, 1);	INIT_LIST_HEAD(&res->cg_links);	INIT_LIST_HEAD(&res->tasks);	INIT_HLIST_NODE(&res->hlist);	/* Copy the set of subsystem state objects generated in	 * find_existing_css_set() */	memcpy(res->subsys, template, sizeof(res->subsys));	write_lock(&css_set_lock);	/* Add reference counts and links from the new css_set. */	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup *cgrp = res->subsys[i]->cgroup;		struct cgroup_subsys *ss = subsys[i];		atomic_inc(&cgrp->count);		/*		 * We want to add a link once per cgroup, so we		 * only do it for the first subsystem in each		 * hierarchy		 */		if (ss->root->subsys_list.next == &ss->sibling)			link_css_set(&tmp_cg_links, res, cgrp);	}	if (list_empty(&rootnode.subsys_list))		link_css_set(&tmp_cg_links, res, dummytop);	BUG_ON(!list_empty(&tmp_cg_links));	css_set_count++;	/* Add this cgroup group to the hash table */	hhead = css_set_hash(res->subsys);	hlist_add_head(&res->hlist, hhead);	write_unlock(&css_set_lock);	return res;}/* * 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 * cgroup_attach_task() can increment it again.  Because a count of zero * 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 * to the release agent with the name of the cgroup (path relative to * the root of cgroup file system) as the argument. * * 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 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with * another.  It does so using cgroup_mutex, however there are * 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 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use * 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 * update of a tasks cgroup pointer by cgroup_attach_task() *//** * cgroup_lock - lock out any changes to cgroup structures * */void cgroup_lock(void){	mutex_lock(&cgroup_mutex);}/** * cgroup_unlock - release lock on cgroup changes * * Undo the lock taken in a previous cgroup_lock() call. */void cgroup_unlock(void){	mutex_unlock(&cgroup_mutex);}/* * 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. */static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);static int cgroup_populate_dir(struct cgroup *cgrp);static struct inode_operations cgroup_dir_inode_operations;static struct file_operations proc_cgroupstats_operations;static struct backing_dev_info cgroup_backing_dev_info = {	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,};static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb){	struct inode *inode = new_inode(sb);	if (inode) {		inode->i_mode = mode;		inode->i_uid = current_fsuid();		inode->i_gid = current_fsgid();		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;	}	return inode;}/* * Call subsys's pre_destroy handler. * This is called before css refcnt check. */static void cgroup_call_pre_destroy(struct cgroup *cgrp){	struct cgroup_subsys *ss;	for_each_subsys(cgrp->root, ss)		if (ss->pre_destroy)			ss->pre_destroy(ss, cgrp);	return;}static void free_cgroup_rcu(struct rcu_head *obj){	struct cgroup *cgrp = container_of(obj, struct cgroup, rcu_head);	kfree(cgrp);}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)) {		struct cgroup *cgrp = dentry->d_fsdata;		struct cgroup_subsys *ss;		BUG_ON(!(cgroup_is_removed(cgrp)));		/* It's possible for external users to be holding css		 * reference counts on a cgroup; css_put() needs to		 * be able to access the cgroup after decrementing		 * the reference count in order to know if it needs to		 * queue the cgroup to be handled by the release		 * agent */		synchronize_rcu();		mutex_lock(&cgroup_mutex);		/*		 * Release the subsystem state objects.		 */		for_each_subsys(cgrp->root, ss)			ss->destroy(ss, cgrp);		cgrp->root->number_of_cgroups--;		mutex_unlock(&cgroup_mutex);		/*		 * Drop the active superblock reference that we took when we		 * created the cgroup		 */		deactivate_super(cgrp->root->sb);		call_rcu(&cgrp->rcu_head, free_cgroup_rcu);	}	iput(inode);}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);}static void cgroup_clear_directory(struct dentry *dentry){	struct list_head *node;	BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));	spin_lock(&dcache_lock);	node = dentry->d_subdirs.next;	while (node != &dentry->d_subdirs) {		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);		list_del_init(node);		if (d->d_inode) {			/* This should never be called on a cgroup			 * directory with child cgroups */			BUG_ON(d->d_inode->i_mode & S_IFDIR);			d = dget_locked(d);			spin_unlock(&dcache_lock);			d_delete(d);			simple_unlink(dentry->d_inode, d);			dput(d);			spin_lock(&dcache_lock);		}		node = dentry->d_subdirs.next;	}	spin_unlock(&dcache_lock);}/* * NOTE : the dentry must have been dget()'ed */static void cgroup_d_remove_dir(struct dentry *dentry){	cgroup_clear_directory(dentry);	spin_lock(&dcache_lock);	list_del_init(&dentry->d_u.d_child);	spin_unlock(&dcache_lock);	remove_dir(dentry);}static int rebind_subsystems(struct cgroupfs_root *root,			      unsigned long final_bits){	unsigned long added_bits, removed_bits;	struct cgroup *cgrp = &root->top_cgroup;	int i;	removed_bits = root->actual_subsys_bits & ~final_bits;	added_bits = final_bits & ~root->actual_subsys_bits;	/* Check that any added subsystems are currently free */	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		unsigned long bit = 1UL << i;		struct cgroup_subsys *ss = subsys[i];		if (!(bit & added_bits))			continue;		if (ss->root != &rootnode) {			/* 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 */	if (root->number_of_cgroups > 1)		return -EBUSY;	/* Process each subsystem */	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup_subsys *ss = subsys[i];		unsigned long bit = 1UL << i;		if (bit & added_bits) {			/* We're binding this subsystem to this hierarchy */			BUG_ON(cgrp->subsys[i]);			BUG_ON(!dummytop->subsys[i]);			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);			mutex_lock(&ss->hierarchy_mutex);			cgrp->subsys[i] = dummytop->subsys[i];			cgrp->subsys[i]->cgroup = cgrp;			list_move(&ss->sibling, &root->subsys_list);			ss->root = root;			if (ss->bind)				ss->bind(ss, cgrp);			mutex_unlock(&ss->hierarchy_mutex);		} else if (bit & removed_bits) {			/* We're removing this subsystem */			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);			mutex_lock(&ss->hierarchy_mutex);			if (ss->bind)				ss->bind(ss, dummytop);			dummytop->subsys[i]->cgroup = dummytop;			cgrp->subsys[i] = NULL;			subsys[i]->root = &rootnode;			list_move(&ss->sibling, &rootnode.subsys_list);			mutex_unlock(&ss->hierarchy_mutex);		} else if (bit & final_bits) {			/* Subsystem state should already exist */			BUG_ON(!cgrp->subsys[i]);		} else {			/* Subsystem state shouldn't exist */			BUG_ON(cgrp->subsys[i]);		}	}	root->subsys_bits = root->actual_subsys_bits = final_bits;	synchronize_rcu();	return 0;}static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs){	struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;	struct cgroup_subsys *ss;	mutex_lock(&cgroup_mutex);	for_each_subsys(root, ss)		seq_printf(seq, ",%s", ss->name);	if (test_bit(ROOT_NOPREFIX, &root->flags))		seq_puts(seq, ",noprefix");	if (strlen(root->release_agent_path))		seq_printf(seq, ",release_agent=%s", root->release_agent_path);	mutex_unlock(&cgroup_mutex);	return 0;}struct cgroup_sb_opts {	unsigned long subsys_bits;	unsigned long flags;	char *release_agent;};/* Convert a hierarchy specifier into a bitmask of subsystems and * flags. */static int parse_cgroupfs_options(char *data,				     struct cgroup_sb_opts *opts){	char *token, *o = data ?: "all";	opts->subsys_bits = 0;	opts->flags = 0;	opts->release_agent = NULL;	while ((token = strsep(&o, ",")) != NULL) {		if (!*token)			return -EINVAL;		if (!strcmp(token, "all")) {			/* Add all non-disabled subsystems */			int i;			opts->subsys_bits = 0;			for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {				struct cgroup_subsys *ss = subsys[i];				if (!ss->disabled)					opts->subsys_bits |= 1ul << i;			}		} else if (!strcmp(token, "noprefix")) {			set_bit(ROOT_NOPREFIX, &opts->flags);		} else if (!strncmp(token, "release_agent=", 14)) {			/* Specifying two release agents is forbidden */			if (opts->release_agent)				return -EINVAL;			opts->release_agent = kzalloc(PATH_MAX, GFP_KERNEL);			if (!opts->release_agent)				return -ENOMEM;			strncpy(opts->release_agent, token + 14, PATH_MAX - 1);			opts->release_agent[PATH_MAX - 1] = 0;		} else {			struct cgroup_subsys *ss;			int i;			for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {				ss = subsys[i];				if (!strcmp(token, ss->name)) {					if (!ss->disabled)						set_bit(i, &opts->subsys_bits);					break;				}			}			if (i == CGROUP_SUBSYS_COUNT)				return -ENOENT;		}	}	/* We can't have an empty hierarchy */	if (!opts->subsys_bits)		return -EINVAL;	return 0;}static int cgroup_remount(struct super_block *sb, int *flags, char *data){	int ret = 0;	struct cgroupfs_root *root = sb->s_fs_info;	struct cgroup *cgrp = &root->top_cgroup;	struct cgroup_sb_opts opts;	mutex_lock(&cgrp->dentry->d_inode->i_mutex);	mutex_lock(&cgroup_mutex);	/* See what subsystems are wanted */	ret = parse_cgroupfs_options(data, &opts);	if (ret)		goto out_unlock;	/* Don't allow flags to change at remount */	if (opts.flags != root->flags) {		ret = -EINVAL;		goto out_unlock;	}	ret = rebind_subsystems(root, opts.subsys_bits);	/* (re)populate subsystem files */	if (!ret)		cgroup_populate_dir(cgrp);	if (opts.release_agent)		strcpy(root->release_agent_path, opts.release_agent); out_unlock:	if (opts.release_agent)		kfree(opts.release_agent);	mutex_unlock(&cgroup_mutex);	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);	return ret;}static struct super_operations cgroup_ops = {	.statfs = simple_statfs,	.drop_inode = generic_delete_inode,	.show_options = cgroup_show_options,	.remount_fs = cgroup_remount,};static void init_cgroup_housekeeping(struct cgroup *cgrp){	INIT_LIST_HEAD(&cgrp->sibling);	INIT_LIST_HEAD(&cgrp->children);	INIT_LIST_HEAD(&cgrp->css_sets);	INIT_LIST_HEAD(&cgrp->release_list);	init_rwsem(&cgrp->pids_mutex);}static void init_cgroup_root(struct cgroupfs_root *root){	struct cgroup *cgrp = &root->top_cgroup;	INIT_LIST_HEAD(&root->subsys_list);	INIT_LIST_HEAD(&root->root_list);	root->number_of_cgroups = 1;	cgrp->root = root;	cgrp->top_cgroup = cgrp;	init_cgroup_housekeeping(cgrp);}static int cgroup_test_super(struct super_block *sb, void *data){	struct cgroupfs_root *new = data;	struct cgroupfs_root *root = sb->s_fs_info;	/* First check subsystems */	if (new->subsys_bits != root->subsys_bits)	    return 0;	/* Next check flags */	if (new->flags != root->flags)		return 0;	return 1;}static int cgroup_set_super(struct super_block *sb, void *data){	int ret;	struct cgroupfs_root *root = data;	ret = set_anon_super(sb, NULL);	if (ret)		return ret;	sb->s_fs_info = root;	root->sb = sb;	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){	struct inode *inode =		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);	struct dentry *dentry;	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);	dentry = d_alloc_root(inode);	if (!dentry) {		iput(inode);		return -ENOMEM;	}	sb->s_root = dentry;	return 0;}static int cgroup_get_sb(struct file_system_type *fs_type,			 int flags, const char *unused_dev_name,			 void *data, struct vfsmount *mnt){	struct cgroup_sb_opts opts;	int ret = 0;	struct super_block *sb;	struct cgroupfs_root *root;	struct list_head tmp_cg_links;	/* First find the desired set of subsystems */	ret = parse_cgroupfs_options(data, &opts);	if (ret) {		if (opts.release_agent)			kfree(opts.release_agent);		return ret;	}	root = kzalloc(sizeof(*root), GFP_KERNEL);	if (!root) {		if (opts.release_agent)			kfree(opts.release_agent);		return -ENOMEM;	}	init_cgroup_root(root);	root->subsys_bits = opts.subsys_bits;	root->flags = opts.flags;	if (opts.release_agent) {		strcpy(root->release_agent_path, opts.release_agent);		kfree(opts.release_agent);	}	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root);	if (IS_ERR(sb)) {		kfree(root);		return PTR_ERR(sb);	}	if (sb->s_fs_info != root) {		/* Reusing an existing superblock */		BUG_ON(sb->s_root == NULL);		kfree(root);		root = NULL;	} else {		/* New superblock */		struct cgroup *root_cgrp = &root->top_cgroup;		struct inode *inode;		int i;		BUG_ON(sb->s_root != NULL);		ret = cgroup_get_rootdir(sb);		if (ret)			goto drop_new_super;		inode = sb->s_root->d_inode;		mutex_lock(&inode->i_mutex);		mutex_lock(&cgroup_mutex);		/*		 * 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		 */		ret = allocate_cg_links(css_set_count, &tmp_cg_links);		if (ret) {			mutex_unlock(&cgroup_mutex);			mutex_unlock(&inode->i_mutex);			goto drop_new_super;		}		ret = rebind_subsystems(root, root->subsys_bits);		if (ret == -EBUSY) {			mutex_unlock(&cgroup_mutex);			mutex_unlock(&inode->i_mutex);			goto free_cg_links;		}		/* EBUSY should be the only error here */		BUG_ON(ret);		list_add(&root->root_list, &roots);		root_count++;		sb->s_root->d_fsdata = root_cgrp;		root->top_cgroup.dentry = sb->s_root;		/* Link the top cgroup in this hierarchy into all		 * the css_set objects */		write_lock(&css_set_lock);		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {			struct hlist_head *hhead = &css_set_table[i];			struct hlist_node *node;			struct css_set *cg;			hlist_for_each_entry(cg, node, hhead, hlist)				link_css_set(&tmp_cg_links, cg, root_cgrp);		}		write_unlock(&css_set_lock);		free_cg_links(&tmp_cg_links);		BUG_ON(!list_empty(&root_cgrp->sibling));		BUG_ON(!list_empty(&root_cgrp->children));		BUG_ON(root->number_of_cgroups != 1);		cgroup_populate_dir(root_cgrp);		mutex_unlock(&inode->i_mutex);		mutex_unlock(&cgroup_mutex);	}	return simple_set_mnt(mnt, sb); free_cg_links:	free_cg_links(&tmp_cg_links); drop_new_super:	up_write(&sb->s_umount);	deactivate_super(sb);	return ret;}static void cgroup_kill_sb(struct super_block *sb) {	struct cgroupfs_root *root = sb->s_fs_info;	struct cgroup *cgrp = &root->top_cgroup;	int ret;	struct cg_cgroup_link *link;	struct cg_cgroup_link *saved_link;	BUG_ON(!root);	BUG_ON(root->number_of_cgroups != 1);	BUG_ON(!list_empty(&cgrp->children));	BUG_ON(!list_empty(&cgrp->sibling));	mutex_lock(&cgroup_mutex);	/* Rebind all subsystems back to the default hierarchy */	ret = rebind_subsystems(root, 0);	/* Shouldn't be able to fail ... */	BUG_ON(ret);	/*	 * Release all the links from css_sets to this hierarchy's	 * root cgroup	 */	write_lock(&css_set_lock);	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,				 cgrp_link_list) {		list_del(&link->cg_link_list);		list_del(&link->cgrp_link_list);		kfree(link);	}	write_unlock(&css_set_lock);	if (!list_empty(&root->root_list)) {		list_del(&root->root_list);		root_count--;	}	mutex_unlock(&cgroup_mutex);	kill_litter_super(sb);	kfree(root);}static struct file_system_type cgroup_fs_type = {	.name = "cgroup",	.get_sb = cgroup_get_sb,	.kill_sb = cgroup_kill_sb,};static inline struct cgroup *__d_cgrp(struct dentry *dentry){	return dentry->d_fsdata;}static inline struct cftype *__d_cft(struct dentry *dentry){	return dentry->d_fsdata;}/** * 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 * * Called with cgroup_mutex held or else with an RCU-protected cgroup * reference.  Writes path of cgroup into buf.  Returns 0 on success, * -errno on error. */int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen){	char *start;	struct dentry *dentry = rcu_dereference(cgrp->dentry);	if (!dentry || cgrp == dummytop) {		/*		 * Inactive subsystems have no dentry for their root		 * cgroup		 */		strcpy(buf, "/");		return 0;	}	start = buf + buflen;	*--start = '\0';	for (;;) {		int len = dentry->d_name.len;		if ((start -= len) < buf)			return -ENAMETOOLONG;		memcpy(start, cgrp->dentry->d_name.name, len);		cgrp = cgrp->parent;		if (!cgrp)			break;		dentry = rcu_dereference(cgrp->dentry);		if (!cgrp->parent)			continue;		if (--start < buf)			return -ENAMETOOLONG;		*start = '/';	}	memmove(buf, start, buf + buflen - start);	return 0;}/* * Return the first subsystem attached to a cgroup's hierarchy, and * its subsystem id. */static void get_first_subsys(const struct cgroup *cgrp,			struct cgroup_subsys_state **css, int *subsys_id){	const struct cgroupfs_root *root = cgrp->root;	const struct cgroup_subsys *test_ss;	BUG_ON(list_empty(&root->subsys_list));	test_ss = list_entry(root->subsys_list.next,			     struct cgroup_subsys, sibling);	if (css) {		*css = cgrp->subsys[test_ss->subsys_id];		BUG_ON(!*css);	}	if (subsys_id)		*subsys_id = test_ss->subsys_id;}/** * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp' * @cgrp: the cgroup the task is attaching to * @tsk: the task to be attached * * Call holding cgroup_mutex. May take task_lock of * the task 'tsk' during call. */int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk){	int retval = 0;	struct cgroup_subsys *ss;	struct cgroup *oldcgrp;	struct css_set *cg;	struct css_set *newcg;	struct cgroupfs_root *root = cgrp->root;	int subsys_id;	get_first_subsys(cgrp, NULL, &subsys_id);	/* Nothing to do if the task is already in that cgroup */	oldcgrp = task_cgroup(tsk, subsys_id);	if (cgrp == oldcgrp)		return 0;	for_each_subsys(root, ss) {		if (ss->can_attach) {			retval = ss->can_attach(ss, cgrp, tsk);			if (retval)				return retval;		}	}	task_lock(tsk);	cg = tsk->cgroups;	get_css_set(cg);	task_unlock(tsk);	/*	 * Locate or allocate a new css_set for this task,	 * based on its final set of cgroups	 */	newcg = find_css_set(cg, cgrp);	put_css_set(cg);	if (!newcg)		return -ENOMEM;	task_lock(tsk);	if (tsk->flags & PF_EXITING) {		task_unlock(tsk);		put_css_set(newcg);		return -ESRCH;	}	rcu_assign_pointer(tsk->cgroups, newcg);	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)) {		list_del(&tsk->cg_list);		list_add(&tsk->cg_list, &newcg->tasks);	}	write_unlock(&css_set_lock);	for_each_subsys(root, ss) {		if (ss->attach)			ss->attach(ss, cgrp, oldcgrp, tsk);	}	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);	synchronize_rcu();	put_css_set(cg);	return 0;}/* * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex * held. May take task_lock of task */static int attach_task_by_pid(struct cgroup *cgrp, u64 pid){	struct task_struct *tsk;	const struct cred *cred = current_cred(), *tcred;	int ret;	if (pid) {		rcu_read_lock();		tsk = find_task_by_vpid(pid);		if (!tsk || tsk->flags & PF_EXITING) {			rcu_read_unlock();			return -ESRCH;		}		tcred = __task_cred(tsk);		if (cred->euid &&		    cred->euid != tcred->uid &&		    cred->euid != tcred->suid) {			rcu_read_unlock();			return -EACCES;		}		get_task_struct(tsk);		rcu_read_unlock();	} else {		tsk = current;		get_task_struct(tsk);	}	ret = cgroup_attach_task(cgrp, tsk);	put_task_struct(tsk);	return ret;}static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid){	int ret;	if (!cgroup_lock_live_group(cgrp))		return -ENODEV;	ret = attach_task_by_pid(cgrp, pid);	cgroup_unlock();	return ret;}/* The various types of files and directories in a cgroup file system */enum cgroup_filetype {	FILE_ROOT,	FILE_DIR,	FILE_TASKLIST,	FILE_NOTIFY_ON_RELEASE,	FILE_RELEASE_AGENT,};/** * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive. * @cgrp: the cgroup to be checked for liveness * * On success, returns true; the lock should be later released with * cgroup_unlock(). On failure returns false with no lock held. */bool cgroup_lock_live_group(struct cgroup *cgrp){	mutex_lock(&cgroup_mutex);	if (cgroup_is_removed(cgrp)) {		mutex_unlock(&cgroup_mutex);		return false;	}	return true;}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);	if (!cgroup_lock_live_group(cgrp))		return -ENODEV;	strcpy(cgrp->root->release_agent_path, buffer);	cgroup_unlock();	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');	cgroup_unlock();	return 0;}/* A buffer size big enough for numbers or short strings */#define CGROUP_LOCAL_BUFFER_SIZE 64static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,				struct file *file,				const char __user *userbuf,				size_t nbytes, loff_t *unused_ppos){	char buffer[CGROUP_LOCAL_BUFFER_SIZE];	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 */	strstrip(buffer);	if (cft->write_u64) {		u64 val = simple_strtoull(buffer, &end, 0);		if (*end)			return -EINVAL;		retval = cft->write_u64(cgrp, cft, val);	} else {		s64 val = simple_strtoll(buffer, &end, 0);		if (*end)			return -EINVAL;		retval = cft->write_s64(cgrp, cft, val);	}	if (!retval)		retval = nbytes;	return retval;}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){	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];	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;	}	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {		retval = -EFAULT;		goto out;	}	buffer[nbytes] = 0;     /* nul-terminate */	strstrip(buffer);	retval = cft->write_string(cgrp, cft, buffer);	if (!retval)		retval = nbytes;out:	if (buffer != local_buffer)		kfree(buffer);	return retval;}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);	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);	if (cgroup_is_removed(cgrp))		return -ENODEV;	if (cft->write)		return cft->write(cgrp, cft, file, buf, nbytes, ppos);	if (cft->write_u64 || cft->write_s64)		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);	if (cft->write_string)		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);	if (cft->trigger) {		int ret = cft->trigger(cgrp, (unsigned int)cft->private);		return ret ? ret : nbytes;	}	return -EINVAL;}static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,			       struct file *file,			       char __user *buf, size_t nbytes,			       loff_t *ppos){	char tmp[CGROUP_LOCAL_BUFFER_SIZE];	u64 val = cft->read_u64(cgrp, cft);	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);}static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,			       struct file *file,			       char __user *buf, size_t nbytes,			       loff_t *ppos){	char tmp[CGROUP_LOCAL_BUFFER_SIZE];	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);}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);	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);	if (cgroup_is_removed(cgrp))		return -ENODEV;	if (cft->read)		return cft->read(cgrp, cft, file, buf, nbytes, ppos);	if (cft->read_u64)		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);	if (cft->read_s64)		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);	return -EINVAL;}/* * 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;	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);}static int cgroup_seqfile_release(struct inode *inode, struct file *file){	struct seq_file *seq = file->private_data;	kfree(seq->private);	return single_release(inode, file);}static struct file_operations cgroup_seqfile_operations = {	.read = seq_read,	.write = cgroup_file_write,	.llseek = seq_lseek,	.release = cgroup_seqfile_release,};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);	if (cft->read_map || cft->read_seq_string) {		struct cgroup_seqfile_state *state =			kzalloc(sizeof(*state), GFP_USER);		if (!state)			return -ENOMEM;		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)		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){	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;	return simple_rename(old_dir, old_dentry, new_dir, new_dentry);}static struct file_operations cgroup_file_operations = {	.read = cgroup_file_read,	.write = cgroup_file_write,	.llseek = generic_file_llseek,	.open = cgroup_file_open,	.release = cgroup_file_release,};static struct inode_operations cgroup_dir_inode_operations = {	.lookup = simple_lookup,	.mkdir = cgroup_mkdir,	.rmdir = cgroup_rmdir,	.rename = cgroup_rename,};static int cgroup_create_file(struct dentry *dentry, int mode,				struct super_block *sb){	static struct dentry_operations cgroup_dops = {		.d_iput = cgroup_diput,	};	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);		/* start with the directory inode held, so that we can		 * populate it without racing with another mkdir */		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);	} else if (S_ISREG(mode)) {		inode->i_size = 0;		inode->i_fop = &cgroup_file_operations;	}	dentry->d_op = &cgroup_dops;	d_instantiate(dentry, inode);	dget(dentry);	/* Extra count - pin the dentry in core */	return 0;}/* * cgroup_create_dir - create a directory for an object. * @cgrp: the cgroup we create the directory for. It must have a valid *        ->parent field. And we are going to fill its ->dentry field. * @dentry: dentry of the new cgroup * @mode: mode to set on new directory. */static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,				int mode){	struct dentry *parent;	int error = 0;	parent = cgrp->parent->dentry;	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);	if (!error) {		dentry->d_fsdata = cgrp;		inc_nlink(parent->d_inode);		rcu_assign_pointer(cgrp->dentry, dentry);		dget(dentry);	}	dput(dentry);	return error;}int cgroup_add_file(struct cgroup *cgrp,		       struct cgroup_subsys *subsys,		       const struct cftype *cft){	struct dentry *dir = cgrp->dentry;	struct dentry *dentry;	int error;	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {		strcpy(name, subsys->name);		strcat(name, ".");	}	strcat(name, cft->name);	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));	dentry = lookup_one_len(name, dir, strlen(name));	if (!IS_ERR(dentry)) {		error = cgroup_create_file(dentry, 0644 | S_IFREG,						cgrp->root->sb);		if (!error)			dentry->d_fsdata = (void *)cft;		dput(dentry);	} else		error = PTR_ERR(dentry);	return error;}int cgroup_add_files(struct cgroup *cgrp,			struct cgroup_subsys *subsys,			const struct cftype cft[],			int count){	int i, err;	for (i = 0; i < count; i++) {		err = cgroup_add_file(cgrp, subsys, &cft[i]);		if (err)			return err;	}	return 0;}/** * cgroup_task_count - count the number of tasks in a cgroup. * @cgrp: the cgroup in question * * Return the number of tasks in the cgroup. */int cgroup_task_count(const struct cgroup *cgrp){	int count = 0;	struct cg_cgroup_link *link;	read_lock(&css_set_lock);	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {		count += atomic_read(&link->cg->refcount);	}	read_unlock(&css_set_lock);	return count;}/* * Advance a list_head iterator.  The iterator should be positioned at * the start of a css_set */static void cgroup_advance_iter(struct cgroup *cgrp,					  struct cgroup_iter *it){	struct list_head *l = it->cg_link;	struct cg_cgroup_link *link;	struct css_set *cg;	/* Advance to the next non-empty css_set */	do {		l = l->next;		if (l == &cgrp->css_sets) {			it->cg_link = NULL;			return;		}		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);		cg = link->cg;	} while (list_empty(&cg->tasks));	it->cg_link = l;	it->task = cg->tasks.next;}/* * 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(). * * The tasklist_lock is not held here, as do_each_thread() and * while_each_thread() are protected by RCU. */static void cgroup_enable_task_cg_lists(void){	struct task_struct *p, *g;	write_lock(&css_set_lock);	use_task_css_set_links = 1;	do_each_thread(g, p) {		task_lock(p);		/*		 * 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))			list_add(&p->cg_list, &p->cgroups->tasks);		task_unlock(p);	} while_each_thread(g, p);	write_unlock(&css_set_lock);}void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it){	/*	 * 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.	 */	if (!use_task_css_set_links)		cgroup_enable_task_cg_lists();	read_lock(&css_set_lock);	it->cg_link = &cgrp->css_sets;	cgroup_advance_iter(cgrp, it);}struct task_struct *cgroup_iter_next(struct cgroup *cgrp,					struct cgroup_iter *it){	struct task_struct *res;	struct list_head *l = it->task;	struct cg_cgroup_link *link;	/* If the iterator cg is NULL, we have no tasks */	if (!it->cg_link)		return NULL;	res = list_entry(l, struct task_struct, cg_list);	/* Advance iterator to find next entry */	l = l->next;	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);	if (l == &link->cg->tasks) {		/* We reached the end of this task list - move on to		 * the next cg_cgroup_link */		cgroup_advance_iter(cgrp, it);	} else {		it->task = l;	}	return res;}void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it){	read_unlock(&css_set_lock);}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++) {			struct task_struct *q = heap->ptrs[i];			if (i == 0) {				latest_time = q->start_time;				latest_task = q;			}			/* Process the task per the caller's callback */			scan->process_task(q, scan);			put_task_struct(q);		}		/*		 * 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;}/* * Stuff for reading the 'tasks' file. * * 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. * *//* * Load into 'pidarray' up to 'npids' of the tasks using cgroup * 'cgrp'.  Return actual number of pids loaded.  No need to * task_lock(p) when reading out p->cgroup, since we're in an RCU * read section, so the css_set can't go away, and is * immutable after creation. */static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cgrp){	int n = 0, pid;	struct cgroup_iter it;	struct task_struct *tsk;	cgroup_iter_start(cgrp, &it);	while ((tsk = cgroup_iter_next(cgrp, &it))) {		if (unlikely(n == npids))			break;		pid = task_pid_vnr(tsk);		if (pid > 0)			pidarray[n++] = pid;	}	cgroup_iter_end(cgrp, &it);	return n;}/** * cgroupstats_build - build and fill cgroupstats * @stats: cgroupstats to fill information into * @dentry: A dentry entry belonging to the cgroup for which stats have * been requested. * * Build and fill cgroupstats so that taskstats can export it to user * space. */int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry){	int ret = -EINVAL;	struct cgroup *cgrp;	struct cgroup_iter it;	struct task_struct *tsk;	/*	 * Validate dentry by checking the superblock operations,	 * and make sure it's a directory.	 */	if (dentry->d_sb->s_op != &cgroup_ops ||	    !S_ISDIR(dentry->d_inode->i_mode))		 goto err;	ret = 0;	cgrp = dentry->d_fsdata;	cgroup_iter_start(cgrp, &it);	while ((tsk = cgroup_iter_next(cgrp, &it))) {		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;		}	}	cgroup_iter_end(cgrp, &it);err:	return ret;}static int cmppid(const void *a, const void *b){	return *(pid_t *)a - *(pid_t *)b;}/* * seq_file methods for the "tasks" file. The seq_file position is the * next pid to display; the seq_file iterator is a pointer to the pid * in the cgroup->tasks_pids array. */static void *cgroup_tasks_start(struct seq_file *s, loff_t *pos){	/*	 * 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	 */	struct cgroup *cgrp = s->private;	int index = 0, pid = *pos;	int *iter;	down_read(&cgrp->pids_mutex);	if (pid) {		int end = cgrp->pids_length;		while (index < end) {			int mid = (index + end) / 2;			if (cgrp->tasks_pids[mid] == pid) {				index = mid;				break;			} else if (cgrp->tasks_pids[mid] <= pid)				index = mid + 1;			else				end = mid;		}	}	/* If we're off the end of the array, we're done */	if (index >= cgrp->pids_length)		return NULL;	/* Update the abstract position to be the actual pid that we found */	iter = cgrp->tasks_pids + index;	*pos = *iter;	return iter;}static void cgroup_tasks_stop(struct seq_file *s, void *v){	struct cgroup *cgrp = s->private;	up_read(&cgrp->pids_mutex);}static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos){	struct cgroup *cgrp = s->private;	int *p = v;	int *end = cgrp->tasks_pids + cgrp->pids_length;	/*	 * 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;	}}static int cgroup_tasks_show(struct seq_file *s, void *v){	return seq_printf(s, "%d\n", *(int *)v);}static struct seq_operations cgroup_tasks_seq_operations = {	.start = cgroup_tasks_start,	.stop = cgroup_tasks_stop,	.next = cgroup_tasks_next,	.show = cgroup_tasks_show,};static void release_cgroup_pid_array(struct cgroup *cgrp){	down_write(&cgrp->pids_mutex);	BUG_ON(!cgrp->pids_use_count);	if (!--cgrp->pids_use_count) {		kfree(cgrp->tasks_pids);		cgrp->tasks_pids = NULL;		cgrp->pids_length = 0;	}	up_write(&cgrp->pids_mutex);}static int cgroup_tasks_release(struct inode *inode, struct file *file){	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);	if (!(file->f_mode & FMODE_READ))		return 0;	release_cgroup_pid_array(cgrp);	return seq_release(inode, file);}static struct file_operations cgroup_tasks_operations = {	.read = seq_read,	.llseek = seq_lseek,	.write = cgroup_file_write,	.release = cgroup_tasks_release,};/* * Handle an open on 'tasks' file.  Prepare an array containing the * process id's of tasks currently attached to the cgroup being opened. */static int cgroup_tasks_open(struct inode *unused, struct file *file){	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);	pid_t *pidarray;	int npids;	int retval;	/* Nothing to do for write-only files */	if (!(file->f_mode & FMODE_READ))		return 0;	/*	 * 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.	 */	npids = cgroup_task_count(cgrp);	pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);	if (!pidarray)		return -ENOMEM;	npids = pid_array_load(pidarray, npids, cgrp);	sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);	/*	 * Store the array in the cgroup, freeing the old	 * array if necessary	 */	down_write(&cgrp->pids_mutex);	kfree(cgrp->tasks_pids);	cgrp->tasks_pids = pidarray;	cgrp->pids_length = npids;	cgrp->pids_use_count++;	up_write(&cgrp->pids_mutex);	file->f_op = &cgroup_tasks_operations;	retval = seq_open(file, &cgroup_tasks_seq_operations);	if (retval) {		release_cgroup_pid_array(cgrp);		return retval;	}	((struct seq_file *)file->private_data)->private = cgrp;	return 0;}static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,					    struct cftype *cft){	return notify_on_release(cgrp);}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;}/* * for the common functions, 'private' gives the type of file */static struct cftype files[] = {	{		.name = "tasks",		.open = cgroup_tasks_open,		.write_u64 = cgroup_tasks_write,		.release = cgroup_tasks_release,		.private = FILE_TASKLIST,	},	{		.name = "notify_on_release",		.read_u64 = cgroup_read_notify_on_release,		.write_u64 = cgroup_write_notify_on_release,		.private = FILE_NOTIFY_ON_RELEASE,	},};static struct cftype cft_release_agent = {	.name = "release_agent",	.read_seq_string = cgroup_release_agent_show,	.write_string = cgroup_release_agent_write,	.max_write_len = PATH_MAX,	.private = FILE_RELEASE_AGENT,};static int cgroup_populate_dir(struct cgroup *cgrp){	int err;	struct cgroup_subsys *ss;	/* First clear out any existing files */	cgroup_clear_directory(cgrp->dentry);	err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));	if (err < 0)		return err;	if (cgrp == cgrp->top_cgroup) {		if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)			return err;	}	for_each_subsys(cgrp->root, ss) {		if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)			return err;	}	return 0;}static void init_cgroup_css(struct cgroup_subsys_state *css,			       struct cgroup_subsys *ss,			       struct cgroup *cgrp){	css->cgroup = cgrp;	atomic_set(&css->refcnt, 1);	css->flags = 0;	if (cgrp == dummytop)		set_bit(CSS_ROOT, &css->flags);	BUG_ON(cgrp->subsys[ss->subsys_id]);	cgrp->subsys[ss->subsys_id] = css;}static void cgroup_lock_hierarchy(struct cgroupfs_root *root){	/* We need to take each hierarchy_mutex in a consistent order */	int i;	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup_subsys *ss = subsys[i];		if (ss->root == root)			mutex_lock(&ss->hierarchy_mutex);	}}static void cgroup_unlock_hierarchy(struct cgroupfs_root *root){	int i;	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup_subsys *ss = subsys[i];		if (ss->root == root)			mutex_unlock(&ss->hierarchy_mutex);	}}/* * 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 * * Must be called with the mutex on the parent inode held */static long cgroup_create(struct cgroup *parent, struct dentry *dentry,			     int mode){	struct cgroup *cgrp;	struct cgroupfs_root *root = parent->root;	int err = 0;	struct cgroup_subsys *ss;	struct super_block *sb = root->sb;	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);	if (!cgrp)		return -ENOMEM;	/* 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);	mutex_lock(&cgroup_mutex);	init_cgroup_housekeeping(cgrp);	cgrp->parent = parent;	cgrp->root = parent->root;	cgrp->top_cgroup = parent->top_cgroup;	if (notify_on_release(parent))		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);	for_each_subsys(root, ss) {		struct cgroup_subsys_state *css = ss->create(ss, cgrp);		if (IS_ERR(css)) {			err = PTR_ERR(css);			goto err_destroy;		}		init_cgroup_css(css, ss, cgrp);	}	cgroup_lock_hierarchy(root);	list_add(&cgrp->sibling, &cgrp->parent->children);	cgroup_unlock_hierarchy(root);	root->number_of_cgroups++;	err = cgroup_create_dir(cgrp, dentry, mode);	if (err < 0)		goto err_remove;	/* The cgroup directory was pre-locked for us */	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));	err = cgroup_populate_dir(cgrp);	/* If err < 0, we have a half-filled directory - oh well ;) */	mutex_unlock(&cgroup_mutex);	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);	return 0; err_remove:	cgroup_lock_hierarchy(root);	list_del(&cgrp->sibling);	cgroup_unlock_hierarchy(root);	root->number_of_cgroups--; err_destroy:	for_each_subsys(root, ss) {		if (cgrp->subsys[ss->subsys_id])			ss->destroy(ss, cgrp);	}	mutex_unlock(&cgroup_mutex);	/* Release the reference count that we took on the superblock */	deactivate_super(sb);	kfree(cgrp);	return err;}static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode){	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);}static int cgroup_has_css_refs(struct cgroup *cgrp){	/* Check the reference count on each subsystem. Since we	 * already established that there are no tasks in the	 * cgroup, if the css refcount is also 1, then there should	 * be no outstanding references, so the subsystem is safe to	 * destroy. We scan across all subsystems rather than using	 * the per-hierarchy linked list of mounted subsystems since	 * we can be called via check_for_release() with no	 * synchronization other than RCU, and the subsystem linked	 * list isn't RCU-safe */	int i;	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup_subsys *ss = subsys[i];		struct cgroup_subsys_state *css;		/* Skip subsystems not in this hierarchy */		if (ss->root != cgrp->root)			continue;		css = cgrp->subsys[ss->subsys_id];		/* When called from check_for_release() it's possible		 * that by this point the cgroup has been removed		 * and the css deleted. But a false-positive doesn't		 * matter, since it can only happen if the cgroup		 * has been deleted and hence no longer needs the		 * release agent to be called anyway. */		if (css && (atomic_read(&css->refcnt) > 1))			return 1;	}	return 0;}/* * Atomically mark all (or else none) of the cgroup's CSS objects as * CSS_REMOVED. Return true on success, or false if the cgroup has * busy subsystems. Call with cgroup_mutex held */static int cgroup_clear_css_refs(struct cgroup *cgrp){	struct cgroup_subsys *ss;	unsigned long flags;	bool failed = false;	local_irq_save(flags);	for_each_subsys(cgrp->root, ss) {		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];		int refcnt;		while (1) {			/* We can only remove a CSS with a refcnt==1 */			refcnt = atomic_read(&css->refcnt);			if (refcnt > 1) {				failed = true;				goto done;			}			BUG_ON(!refcnt);			/*			 * Drop the refcnt to 0 while we check other			 * subsystems. This will cause any racing			 * css_tryget() to spin until we set the			 * CSS_REMOVED bits or abort			 */			if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)				break;			cpu_relax();		}	} done:	for_each_subsys(cgrp->root, ss) {		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];		if (failed) {			/*			 * Restore old refcnt if we previously managed			 * to clear it from 1 to 0			 */			if (!atomic_read(&css->refcnt))				atomic_set(&css->refcnt, 1);		} else {			/* Commit the fact that the CSS is removed */			set_bit(CSS_REMOVED, &css->flags);		}	}	local_irq_restore(flags);	return !failed;}static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry){	struct cgroup *cgrp = dentry->d_fsdata;	struct dentry *d;	struct cgroup *parent;	/* the vfs holds both inode->i_mutex already */	mutex_lock(&cgroup_mutex);	if (atomic_read(&cgrp->count) != 0) {		mutex_unlock(&cgroup_mutex);		return -EBUSY;	}	if (!list_empty(&cgrp->children)) {		mutex_unlock(&cgroup_mutex);		return -EBUSY;	}	mutex_unlock(&cgroup_mutex);	/*	 * Call pre_destroy handlers of subsys. Notify subsystems	 * that rmdir() request comes.	 */	cgroup_call_pre_destroy(cgrp);	mutex_lock(&cgroup_mutex);	parent = cgrp->parent;	if (atomic_read(&cgrp->count)	    || !list_empty(&cgrp->children)	    || !cgroup_clear_css_refs(cgrp)) {		mutex_unlock(&cgroup_mutex);		return -EBUSY;	}	spin_lock(&release_list_lock);	set_bit(CGRP_REMOVED, &cgrp->flags);	if (!list_empty(&cgrp->release_list))		list_del(&cgrp->release_list);	spin_unlock(&release_list_lock);	cgroup_lock_hierarchy(cgrp->root);	/* delete this cgroup from parent->children */	list_del(&cgrp->sibling);	cgroup_unlock_hierarchy(cgrp->root);	spin_lock(&cgrp->dentry->d_lock);	d = dget(cgrp->dentry);	spin_unlock(&d->d_lock);	cgroup_d_remove_dir(d);	dput(d);	set_bit(CGRP_RELEASABLE, &parent->flags);	check_for_release(parent);	mutex_unlock(&cgroup_mutex);	return 0;}static void __init cgroup_init_subsys(struct cgroup_subsys *ss){	struct cgroup_subsys_state *css;	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);	/* Create the top cgroup state for this subsystem */	list_add(&ss->sibling, &rootnode.subsys_list);	ss->root = &rootnode;	css = ss->create(ss, dummytop);	/* We don't handle early failures gracefully */	BUG_ON(IS_ERR(css));	init_cgroup_css(css, ss, dummytop);	/* Update the init_css_set to contain a subsys	 * pointer to this state - since the subsystem is	 * newly registered, all tasks and hence the	 * init_css_set is in the subsystem's top cgroup. */	init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];	need_forkexit_callback |= ss->fork || ss->exit;	/* 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));	mutex_init(&ss->hierarchy_mutex);	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);	ss->active = 1;}/** * cgroup_init_early - cgroup initialization at system boot * * Initialize cgroups at system boot, and initialize any * subsystems that request early init. */int __init cgroup_init_early(void){	int i;	atomic_set(&init_css_set.refcount, 1);	INIT_LIST_HEAD(&init_css_set.cg_links);	INIT_LIST_HEAD(&init_css_set.tasks);	INIT_HLIST_NODE(&init_css_set.hlist);	css_set_count = 1;	init_cgroup_root(&rootnode);	root_count = 1;	init_task.cgroups = &init_css_set;	init_css_set_link.cg = &init_css_set;	list_add(&init_css_set_link.cgrp_link_list,		 &rootnode.top_cgroup.css_sets);	list_add(&init_css_set_link.cg_link_list,		 &init_css_set.cg_links);	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)		INIT_HLIST_HEAD(&css_set_table[i]);	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup_subsys *ss = subsys[i];		BUG_ON(!ss->name);		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);		BUG_ON(!ss->create);		BUG_ON(!ss->destroy);		if (ss->subsys_id != i) {			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",			       ss->name, ss->subsys_id);			BUG();		}		if (ss->early_init)			cgroup_init_subsys(ss);	}	return 0;}/** * cgroup_init - cgroup initialization * * Register cgroup filesystem and /proc file, and initialize * any subsystems that didn't request early init. */int __init cgroup_init(void){	int err;	int i;	struct hlist_head *hhead;	err = bdi_init(&cgroup_backing_dev_info);	if (err)		return err;	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup_subsys *ss = subsys[i];		if (!ss->early_init)			cgroup_init_subsys(ss);	}	/* Add init_css_set to the hash table */	hhead = css_set_hash(init_css_set.subsys);	hlist_add_head(&init_css_set.hlist, hhead);	err = register_filesystem(&cgroup_fs_type);	if (err < 0)		goto out;	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);out:	if (err)		bdi_destroy(&cgroup_backing_dev_info);	return err;}/* * 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, *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it *    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 */static int proc_cgroup_show(struct seq_file *m, void *v){	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);	for_each_active_root(root) {		struct cgroup_subsys *ss;		struct cgroup *cgrp;		int subsys_id;		int count = 0;		seq_printf(m, "%lu:", root->subsys_bits);		for_each_subsys(root, ss)			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);		seq_putc(m, ':');		get_first_subsys(&root->top_cgroup, NULL, &subsys_id);		cgrp = task_cgroup(tsk, subsys_id);		retval = cgroup_path(cgrp, buf, PAGE_SIZE);		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;}static int cgroup_open(struct inode *inode, struct file *file){	struct pid *pid = PROC_I(inode)->pid;	return single_open(file, proc_cgroup_show, pid);}struct file_operations proc_cgroup_operations = {	.open		= cgroup_open,	.read		= seq_read,	.llseek		= seq_lseek,	.release	= single_release,};/* Display information about each subsystem and each hierarchy */static int proc_cgroupstats_show(struct seq_file *m, void *v){	int i;	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");	mutex_lock(&cgroup_mutex);	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {		struct cgroup_subsys *ss = subsys[i];		seq_printf(m, "%s\t%lu\t%d\t%d\n",			   ss->name, ss->root->subsys_bits,			   ss->root->number_of_cgroups, !ss->disabled);	}	mutex_unlock(&cgroup_mutex);	return 0;}static int cgroupstats_open(struct inode *inode, struct file *file){	return single_open(file, proc_cgroupstats_show, NULL);}static struct file_operations proc_cgroupstats_operations = {	.open = cgroupstats_open,	.read = seq_read,	.llseek = seq_lseek,	.release = single_release,};/** * cgroup_fork - attach newly forked task to its parents cgroup. * @child: pointer to task_struct of forking parent process. * * 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 * 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. * * 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){	task_lock(current);	child->cgroups = current->cgroups;	get_css_set(child->cgroups);	task_unlock(current);	INIT_LIST_HEAD(&child->cg_list);}/** * cgroup_fork_callbacks - run fork callbacks * @child: the new task * * Called on a new task very soon before adding it to the * tasklist. No need to take any locks since no-one can * be operating on this task. */void cgroup_fork_callbacks(struct task_struct *child){	if (need_forkexit_callback) {		int i;		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {			struct cgroup_subsys *ss = subsys[i];			if (ss->fork)				ss->fork(ss, child);		}	}}/** * cgroup_post_fork - called on a new task after adding it to the task list * @child: the task in question * * Adds the task to the list running through its css_set if necessary. * 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. */void cgroup_post_fork(struct task_struct *child){	if (use_task_css_set_links) {		write_lock(&css_set_lock);		task_lock(child);		if (list_empty(&child->cg_list))			list_add(&child->cg_list, &child->cgroups->tasks);		task_unlock(child);		write_unlock(&css_set_lock);	}}/** * cgroup_exit - detach cgroup from exiting task * @tsk: pointer to task_struct of exiting process * @run_callback: run exit callbacks? * * 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, *    which wards off any cgroup_attach_task() attempts, or task is a failed *    fork, never visible to cgroup_attach_task. */void cgroup_exit(struct task_struct *tsk, int run_callbacks){	int i;	struct css_set *cg;	if (run_callbacks && need_forkexit_callback) {		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {			struct cgroup_subsys *ss = subsys[i];			if (ss->exit)				ss->exit(ss, tsk);		}	}	/*	 * 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))			list_del(&tsk->cg_list);		write_unlock(&css_set_lock);	}	/* Reassign the task to the init_css_set. */	task_lock(tsk);	cg = tsk->cgroups;	tsk->cgroups = &init_css_set;	task_unlock(tsk);	if (cg)		put_css_set_taskexit(cg);}/** * cgroup_clone - clone the cgroup the given subsystem is attached to * @tsk: the task to be moved * @subsys: the given subsystem * @nodename: the name for the new cgroup * * Duplicate the current cgroup in the hierarchy that the given * subsystem is attached to, and move this task into the new * child. */int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,							char *nodename){	struct dentry *dentry;	int ret = 0;	struct cgroup *parent, *child;	struct inode *inode;	struct css_set *cg;	struct cgroupfs_root *root;	struct cgroup_subsys *ss;	/* We shouldn't be called by an unregistered subsystem */	BUG_ON(!subsys->active);	/* First figure out what hierarchy and cgroup we're dealing	 * with, and pin them so we can drop cgroup_mutex */	mutex_lock(&cgroup_mutex); again:	root = subsys->root;	if (root == &rootnode) {		mutex_unlock(&cgroup_mutex);		return 0;	}	/* Pin the hierarchy */	if (!atomic_inc_not_zero(&root->sb->s_active)) {		/* We race with the final deactivate_super() */		mutex_unlock(&cgroup_mutex);		return 0;	}	/* Keep the cgroup alive */	task_lock(tsk);	parent = task_cgroup(tsk, subsys->subsys_id);	cg = tsk->cgroups;	get_css_set(cg);	task_unlock(tsk);	mutex_unlock(&cgroup_mutex);	/* Now do the VFS work to create a cgroup */	inode = parent->dentry->d_inode;	/* Hold the parent directory mutex across this operation to	 * stop anyone else deleting the new cgroup */	mutex_lock(&inode->i_mutex);	dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));	if (IS_ERR(dentry)) {		printk(KERN_INFO		       "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,		       PTR_ERR(dentry));		ret = PTR_ERR(dentry);		goto out_release;	}	/* Create the cgroup directory, which also creates the cgroup */	ret = vfs_mkdir(inode, dentry, 0755);	child = __d_cgrp(dentry);	dput(dentry);	if (ret) {		printk(KERN_INFO		       "Failed to create cgroup %s: %d\n", nodename,		       ret);		goto out_release;	}	/* The cgroup now exists. Retake cgroup_mutex and check	 * that we're still in the same state that we thought we	 * were. */	mutex_lock(&cgroup_mutex);	if ((root != subsys->root) ||	    (parent != task_cgroup(tsk, subsys->subsys_id))) {		/* Aargh, we raced ... */		mutex_unlock(&inode->i_mutex);		put_css_set(cg);		deactivate_super(root->sb);		/* The cgroup is still accessible in the VFS, but		 * we're not going to try to rmdir() it at this		 * point. */		printk(KERN_INFO		       "Race in cgroup_clone() - leaking cgroup %s\n",		       nodename);		goto again;	}	/* do any required auto-setup */	for_each_subsys(root, ss) {		if (ss->post_clone)			ss->post_clone(ss, child);	}	/* All seems fine. Finish by moving the task into the new cgroup */	ret = cgroup_attach_task(child, tsk);	mutex_unlock(&cgroup_mutex); out_release:	mutex_unlock(&inode->i_mutex);	mutex_lock(&cgroup_mutex);	put_css_set(cg);	mutex_unlock(&cgroup_mutex);	deactivate_super(root->sb);	return ret;}/** * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp * @cgrp: the cgroup in question * * See if @cgrp is a descendant of the current task's cgroup in * the appropriate hierarchy. * * If we are sending in dummytop, then presumably we are creating * the top cgroup in the subsystem. * * Called only by the ns (nsproxy) cgroup. */int cgroup_is_descendant(const struct cgroup *cgrp){	int ret;	struct cgroup *target;	int subsys_id;	if (cgrp == dummytop)		return 1;	get_first_subsys(cgrp, NULL, &subsys_id);	target = task_cgroup(current, subsys_id);	while (cgrp != target && cgrp!= cgrp->top_cgroup)		cgrp = cgrp->parent;	ret = (cgrp == target);	return ret;}static void check_for_release(struct cgroup *cgrp){	/* All of these checks rely on RCU to keep the cgroup	 * structure alive */	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {		/* Control Group is currently removeable. If it's not		 * already queued for a userspace notification, queue		 * it now */		int need_schedule_work = 0;		spin_lock(&release_list_lock);		if (!cgroup_is_removed(cgrp) &&		    list_empty(&cgrp->release_list)) {			list_add(&cgrp->release_list, &release_list);			need_schedule_work = 1;		}		spin_unlock(&release_list_lock);		if (need_schedule_work)			schedule_work(&release_agent_work);	}}void __css_put(struct cgroup_subsys_state *css){	struct cgroup *cgrp = css->cgroup;	rcu_read_lock();	if ((atomic_dec_return(&css->refcnt) == 1) &&	    notify_on_release(cgrp)) {		set_bit(CGRP_RELEASABLE, &cgrp->flags);		check_for_release(cgrp);	}	rcu_read_unlock();}/* * 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);	spin_lock(&release_list_lock);	while (!list_empty(&release_list)) {		char *argv[3], *envp[3];		int i;		char *pathbuf = NULL, *agentbuf = NULL;		struct cgroup *cgrp = list_entry(release_list.next,						    struct cgroup,						    release_list);		list_del_init(&cgrp->release_list);		spin_unlock(&release_list_lock);		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);		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;		i = 0;		argv[i++] = agentbuf;		argv[i++] = pathbuf;		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); continue_free:		kfree(pathbuf);		kfree(agentbuf);		spin_lock(&release_list_lock);	}	spin_unlock(&release_list_lock);	mutex_unlock(&cgroup_mutex);}static int __init cgroup_disable(char *str){	int i;	char *token;	while ((token = strsep(&str, ",")) != NULL) {		if (!*token)			continue;		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {			struct cgroup_subsys *ss = subsys[i];			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);