text: // SPDX-License-Identifier: GPL-2.0-only
  #include "cgroup-internal.h"
  
  #include <linux/ctype.h>
  #include <linux/kmod.h>
  #include <linux/sort.h>
  #include <linux/delay.h>
  #include <linux/mm.h>
  #include <linux/sched/signal.h>
  #include <linux/sched/task.h>
  #include <linux/magic.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
  #include <linux/delayacct.h>
  #include <linux/pid_namespace.h>
  #include <linux/cgroupstats.h>
  #include <linux/fs_parser.h>
  
  #include <trace/events/cgroup.h>
  
  /*
   * pidlists linger the following amount before being destroyed.  The goal
   * is avoiding frequent destruction in the middle of consecutive read calls
   * Expiring in the middle is a performance problem not a correctness one.
   * 1 sec should be enough.
   */
  #define CGROUP_PIDLIST_DESTROY_DELAY	HZ
  
  /* Controllers blocked by the commandline in v1 */
  static u16 cgroup_no_v1_mask;
  
  /* disable named v1 mounts */
  static bool cgroup_no_v1_named;
  
  /*
   * pidlist destructions need to be flushed on cgroup destruction.  Use a
   * separate workqueue as flush domain.
   */
  static struct workqueue_struct *cgroup_pidlist_destroy_wq;
  
  /* protects cgroup_subsys->release_agent_path */
  static DEFINE_SPINLOCK(release_agent_path_lock);
  
  bool cgroup1_ssid_disabled(int ssid)
  {
  	return cgroup_no_v1_mask & (1 << ssid);
  }
  
  /**
   * 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
   *
   * Return: %0 on success or a negative errno code on failure
   */
  int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
  {
  	struct cgroup_root *root;
  	int retval = 0;
  
  	mutex_lock(&cgroup_mutex);
  	percpu_down_write(&cgroup_threadgroup_rwsem);
  	for_each_root(root) {
  		struct cgroup *from_cgrp;
  
  		if (root == &cgrp_dfl_root)
  			continue;
  
  		spin_lock_irq(&css_set_lock);
  		from_cgrp = task_cgroup_from_root(from, root);
  		spin_unlock_irq(&css_set_lock);
  
  		retval = cgroup_attach_task(from_cgrp, tsk, false);
  		if (retval)
  			break;
  	}
  	percpu_up_write(&cgroup_threadgroup_rwsem);
  	mutex_unlock(&cgroup_mutex);
  
  	return retval;
  }
  EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
  
  /**
   * cgroup_transfer_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
   *
   * Locking rules between cgroup_post_fork() and the migration path
   * guarantee that, if a task is forking while being migrated, the new child
   * is guaranteed to be either visible in the source cgroup after the
   * parent's migration is complete or put into the target cgroup.  No task
   * can slip out of migration through forking.
   *
   * Return: %0 on success or a negative errno code on failure
   */
  int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
  {
  	DEFINE_CGROUP_MGCTX(mgctx);
  	struct cgrp_cset_link *link;
  	struct css_task_iter it;
  	struct task_struct *task;
  	int ret;
  
  	if (cgroup_on_dfl(to))
  		return -EINVAL;
  
  	ret = cgroup_migrate_vet_dst(to);
  	if (ret)
  		return ret;
  
  	mutex_lock(&cgroup_mutex);
  
  	percpu_down_write(&cgroup_threadgroup_rwsem);
  
  	/* all tasks in @from are being moved, all csets are source */
  	spin_lock_irq(&css_set_lock);
  	list_for_each_entry(link, &from->cset_links, cset_link)
  		cgroup_migrate_add_src(link->cset, to, &mgctx);
  	spin_unlock_irq(&css_set_lock);
  
  	ret = cgroup_migrate_prepare_dst(&mgctx);
  	if (ret)
  		goto out_err;
  
  	/*
  	 * Migrate tasks one-by-one until @from is empty.  This fails iff
  	 * ->can_attach() fails.
  	 */
  	do {
  		css_task_iter_start(&from->self, 0, &it);
  
  		do {
  			task = css_task_iter_next(&it);
  		} while (task && (task->flags & PF_EXITING));
  
  		if (task)
  			get_task_struct(task);
  		css_task_iter_end(&it);
  
  		if (task) {
  			ret = cgroup_migrate(task, false, &mgctx);
  			if (!ret)
  				TRACE_CGROUP_PATH(transfer_tasks, to, task, false);
  			put_task_struct(task);
  		}
  	} while (task && !ret);
  out_err:
  	cgroup_migrate_finish(&mgctx);
  	percpu_up_write(&cgroup_threadgroup_rwsem);
  	mutex_unlock(&cgroup_mutex);
  	return ret;
  }
  
  /*
   * Stuff for reading the 'tasks'/'procs' files.
   *
   * 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.
   *
   */
  
  /* 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;
  	/* 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;
  	/* for delayed destruction */
  	struct delayed_work destroy_dwork;
  };
  
  /*
   * Used to destroy all pidlists lingering waiting for destroy timer.  None
   * should be left afterwards.
   */
  void cgroup1_pidlist_destroy_all(struct cgroup *cgrp)
  {
  	struct cgroup_pidlist *l, *tmp_l;
  
  	mutex_lock(&cgrp->pidlist_mutex);
  	list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
  		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
  	mutex_unlock(&cgrp->pidlist_mutex);
  
  	flush_workqueue(cgroup_pidlist_destroy_wq);
  	BUG_ON(!list_empty(&cgrp->pidlists));
  }
  
  static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
  {
  	struct delayed_work *dwork = to_delayed_work(work);
  	struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
  						destroy_dwork);
  	struct cgroup_pidlist *tofree = NULL;
  
  	mutex_lock(&l->owner->pidlist_mutex);
  
  	/*
  	 * Destroy iff we didn't get queued again.  The state won't change
  	 * as destroy_dwork can only be queued while locked.
  	 */
  	if (!delayed_work_pending(dwork)) {
  		list_del(&l->links);
  		kvfree(l->list);
  		put_pid_ns(l->key.ns);
  		tofree = l;
  	}
  
  	mutex_unlock(&l->owner->pidlist_mutex);
  	kfree(tofree);
  }
  
  /*
   * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
   * Returns the number of unique elements.
   */
  static int pidlist_uniq(pid_t *list, int length)
  {
  	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;
  }
  
  /*
   * The two pid files - task and cgroup.procs - guaranteed that the result
   * is sorted, which forced this whole pidlist fiasco.  As pid order is
   * different per namespace, each namespace needs differently sorted list,
   * making it impossible to use, for example, single rbtree of member tasks
   * sorted by task pointer.  As pidlists can be fairly large, allocating one
   * per open file is dangerous, so cgroup had to implement shared pool of
   * pidlists keyed by cgroup and namespace.
   */
  static int cmppid(const void *a, const void *b)
  {
  	return *(pid_t *)a - *(pid_t *)b;
  }
  
  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 */
  	struct pid_namespace *ns = task_active_pid_ns(current);
  
  	lockdep_assert_held(&cgrp->pidlist_mutex);
  
  	list_for_each_entry(l, &cgrp->pidlists, links)
  		if (l->key.type == type && l->key.ns == ns)
  			return l;
  	return NULL;
  }
  
  /*
   * 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_create(struct cgroup *cgrp,
  						enum cgroup_filetype type)
  {
  	struct cgroup_pidlist *l;
  
  	lockdep_assert_held(&cgrp->pidlist_mutex);
  
  	l = cgroup_pidlist_find(cgrp, type);
  	if (l)
  		return l;
  
  	/* entry not found; create a new one */
  	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
  	if (!l)
  		return l;
  
  	INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
  	l->key.type = type;
  	/* don't need task_nsproxy() if we're looking at ourself */
  	l->key.ns = get_pid_ns(task_active_pid_ns(current));
  	l->owner = cgrp;
  	list_add(&l->links, &cgrp->pidlists);
  	return l;
  }
  
  /*
   * Load a cgroup's pidarray with either procs' tgids or tasks' pids
   */
  static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
  			      struct cgroup_pidlist **lp)
  {
  	pid_t *array;
  	int length;
  	int pid, n = 0; /* used for populating the array */
  	struct css_task_iter it;
  	struct task_struct *tsk;
  	struct cgroup_pidlist *l;
  
  	lockdep_assert_held(&cgrp->pidlist_mutex);
  
  	/*
  	 * 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);
  	array = kvmalloc_array(length, sizeof(pid_t), GFP_KERNEL);
  	if (!array)
  		return -ENOMEM;
  	/* now, populate the array */
  	css_task_iter_start(&cgrp->self, 0, &it);
  	while ((tsk = css_task_iter_next(&it))) {
  		if (unlikely(n == length))
  			break;
  		/* get tgid or pid for procs or tasks file respectively */
  		if (type == CGROUP_FILE_PROCS)
  			pid = task_tgid_vnr(tsk);
  		else
  			pid = task_pid_vnr(tsk);
  		if (pid > 0) /* make sure to only use valid results */
  			array[n++] = pid;
  	}
  	css_task_iter_end(&it);
  	length = n;
  	/* now sort & (if procs) strip out duplicates */
  	sort(array, length, sizeof(pid_t), cmppid, NULL);
  	if (type == CGROUP_FILE_PROCS)
  		length = pidlist_uniq(array, length);
  
  	l = cgroup_pidlist_find_create(cgrp, type);
  	if (!l) {
  		kvfree(array);
  		return -ENOMEM;
  	}
  
  	/* store array, freeing old if necessary */
  	kvfree(l->list);
  	l->list = array;
  	l->length = length;
  	*lp = l;
  	return 0;
  }
  
  /*
   * seq_file methods for the tasks/procs files. The seq_file position is the
   * next pid to display; the seq_file iterator is a pointer to the pid
   * in the cgroup->l->list array.
   */
  
  static void *cgroup_pidlist_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 kernfs_open_file *of = s->private;
  	struct cgroup *cgrp = seq_css(s)->cgroup;
  	struct cgroup_pidlist *l;
  	enum cgroup_filetype type = seq_cft(s)->private;
  	int index = 0, pid = *pos;
  	int *iter, ret;
  
  	mutex_lock(&cgrp->pidlist_mutex);
  
  	/*
  	 * !NULL @of->priv indicates that this isn't the first start()
  	 * after open.  If the matching pidlist is around, we can use that.
  	 * Look for it.  Note that @of->priv can't be used directly.  It
  	 * could already have been destroyed.
  	 */
  	if (of->priv)
  		of->priv = cgroup_pidlist_find(cgrp, type);
  
  	/*
  	 * Either this is the first start() after open or the matching
  	 * pidlist has been destroyed inbetween.  Create a new one.
  	 */
  	if (!of->priv) {
  		ret = pidlist_array_load(cgrp, type,
  					 (struct cgroup_pidlist **)&of->priv);
  		if (ret)
  			return ERR_PTR(ret);
  	}
  	l = of->priv;
  
  	if (pid) {
  		int end = l->length;
  
  		while (index < end) {
  			int mid = (index + end) / 2;
  			if (l->list[mid] == pid) {
  				index = mid;
  				break;
  			} else if (l->list[mid] <= pid)
  				index = mid + 1;
  			else
  				end = mid;
  		}
  	}
  	/* If we're off the end of the array, we're done */
  	if (index >= l->length)
  		return NULL;
  	/* Update the abstract position to be the actual pid that we found */
  	iter = l->list + index;
  	*pos = *iter;
  	return iter;
  }
  
  static void cgroup_pidlist_stop(struct seq_file *s, void *v)
  {
  	struct kernfs_open_file *of = s->private;
  	struct cgroup_pidlist *l = of->priv;
  
  	if (l)
  		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
  				 CGROUP_PIDLIST_DESTROY_DELAY);
  	mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
  }
  
  static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
  {
  	struct kernfs_open_file *of = s->private;
  	struct cgroup_pidlist *l = of->priv;
  	pid_t *p = v;
  	pid_t *end = l->list + l->length;
  	/*
  	 * Advance to the next pid in the array. If this goes off the
  	 * end, we're done
  	 */
  	p++;
  	if (p >= end) {
  		(*pos)++;
  		return NULL;
  	} else {
  		*pos = *p;
  		return p;
  	}
  }
  
  static int cgroup_pidlist_show(struct seq_file *s, void *v)
  {
  	seq_printf(s, "%d\n", *(int *)v);
  
  	return 0;
  }
  
  static ssize_t __cgroup1_procs_write(struct kernfs_open_file *of,
  				     char *buf, size_t nbytes, loff_t off,
  				     bool threadgroup)
  {
  	struct cgroup *cgrp;
  	struct task_struct *task;
  	const struct cred *cred, *tcred;
  	ssize_t ret;
  	bool locked;
  
  	cgrp = cgroup_kn_lock_live(of->kn, false);
  	if (!cgrp)
  		return -ENODEV;
  
  	task = cgroup_procs_write_start(buf, threadgroup, &locked);
  	ret = PTR_ERR_OR_ZERO(task);
  	if (ret)
  		goto out_unlock;
  
  	/*
  	 * Even if we're attaching all tasks in the thread group, we only
  	 * need to check permissions on one of them.
  	 */
  	cred = current_cred();
  	tcred = get_task_cred(task);
  	if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
  	    !uid_eq(cred->euid, tcred->uid) &&
  	    !uid_eq(cred->euid, tcred->suid))
  		ret = -EACCES;
  	put_cred(tcred);
  	if (ret)
  		goto out_finish;
  
  	ret = cgroup_attach_task(cgrp, task, threadgroup);
  
  out_finish:
  	cgroup_procs_write_finish(task, locked);
  out_unlock:
  	cgroup_kn_unlock(of->kn);
  
  	return ret ?: nbytes;
  }
  
  static ssize_t cgroup1_procs_write(struct kernfs_open_file *of,
  				   char *buf, size_t nbytes, loff_t off)
  {
  	return __cgroup1_procs_write(of, buf, nbytes, off, true);
  }
  
  static ssize_t cgroup1_tasks_write(struct kernfs_open_file *of,
  				   char *buf, size_t nbytes, loff_t off)
  {
  	return __cgroup1_procs_write(of, buf, nbytes, off, false);
  }
  
  static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
  					  char *buf, size_t nbytes, loff_t off)
  {
  	struct cgroup *cgrp;
  
  	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
  
  	cgrp = cgroup_kn_lock_live(of->kn, false);
  	if (!cgrp)
  		return -ENODEV;
  	spin_lock(&release_agent_path_lock);
  	strlcpy(cgrp->root->release_agent_path, strstrip(buf),
  		sizeof(cgrp->root->release_agent_path));
  	spin_unlock(&release_agent_path_lock);
  	cgroup_kn_unlock(of->kn);
  	return nbytes;
  }
  
  static int cgroup_release_agent_show(struct seq_file *seq, void *v)
  {
  	struct cgroup *cgrp = seq_css(seq)->cgroup;
  
  	spin_lock(&release_agent_path_lock);
  	seq_puts(seq, cgrp->root->release_agent_path);
  	spin_unlock(&release_agent_path_lock);
  	seq_putc(seq, '\n');
  	return 0;
  }
  
  static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
  {
  	seq_puts(seq, "0\n");
  	return 0;
  }
  
  static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
  					 struct cftype *cft)
  {
  	return notify_on_release(css->cgroup);
  }
  
  static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
  					  struct cftype *cft, u64 val)
  {
  	if (val)
  		set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
  	else
  		clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
  	return 0;
  }
  
  static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
  				      struct cftype *cft)
  {
  	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
  }
  
  static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
  				       struct cftype *cft, u64 val)
  {
  	if (val)
  		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
  	else
  		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
  	return 0;
  }
  
  /* cgroup core interface files for the legacy hierarchies */
  struct cftype cgroup1_base_files[] = {
  	{
  		.name = "cgroup.procs",
  		.seq_start = cgroup_pidlist_start,
  		.seq_next = cgroup_pidlist_next,
  		.seq_stop = cgroup_pidlist_stop,
  		.seq_show = cgroup_pidlist_show,
  		.private = CGROUP_FILE_PROCS,
  		.write = cgroup1_procs_write,
  	},
  	{
  		.name = "cgroup.clone_children",
  		.read_u64 = cgroup_clone_children_read,
  		.write_u64 = cgroup_clone_children_write,
  	},
  	{
  		.name = "cgroup.sane_behavior",
  		.flags = CFTYPE_ONLY_ON_ROOT,
  		.seq_show = cgroup_sane_behavior_show,
  	},
  	{
  		.name = "tasks",
  		.seq_start = cgroup_pidlist_start,
  		.seq_next = cgroup_pidlist_next,
  		.seq_stop = cgroup_pidlist_stop,
  		.seq_show = cgroup_pidlist_show,
  		.private = CGROUP_FILE_TASKS,
  		.write = cgroup1_tasks_write,
  	},
  	{
  		.name = "notify_on_release",
  		.read_u64 = cgroup_read_notify_on_release,
  		.write_u64 = cgroup_write_notify_on_release,
  	},
  	{
  		.name = "release_agent",
  		.flags = CFTYPE_ONLY_ON_ROOT,
  		.seq_show = cgroup_release_agent_show,
  		.write = cgroup_release_agent_write,
  		.max_write_len = PATH_MAX - 1,
  	},
  	{ }	/* terminate */
  };
  
  /* Display information about each subsystem and each hierarchy */
  int proc_cgroupstats_show(struct seq_file *m, void *v)
  {
  	struct cgroup_subsys *ss;
  	int i;
  
  	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
  	/*
  	 * 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.
  	 */
  	mutex_lock(&cgroup_mutex);
  
  	for_each_subsys(ss, i)
  		seq_printf(m, "%s\t%d\t%d\t%d\n",
  			   ss->legacy_name, ss->root->hierarchy_id,
  			   atomic_read(&ss->root->nr_cgrps),
  			   cgroup_ssid_enabled(i));
  
  	mutex_unlock(&cgroup_mutex);
  	return 0;
  }
  
  /**
   * 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.
   *
   * Return: %0 on success or a negative errno code on failure
   */
  int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
  {
  	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
  	struct cgroup *cgrp;
  	struct css_task_iter it;
  	struct task_struct *tsk;
  
  	/* it should be kernfs_node belonging to cgroupfs and is a directory */
  	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
  	    kernfs_type(kn) != KERNFS_DIR)
  		return -EINVAL;
  
  	mutex_lock(&cgroup_mutex);
  
  	/*
  	 * We aren't being called from kernfs and there's no guarantee on
  	 * @kn->priv's validity.  For this and css_tryget_online_from_dir(),
  	 * @kn->priv is RCU safe.  Let's do the RCU dancing.
  	 */
  	rcu_read_lock();
  	cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
  	if (!cgrp || cgroup_is_dead(cgrp)) {
  		rcu_read_unlock();
  		mutex_unlock(&cgroup_mutex);
  		return -ENOENT;
  	}
  	rcu_read_unlock();
  
  	css_task_iter_start(&cgrp->self, 0, &it);
  	while ((tsk = css_task_iter_next(&it))) {
  		switch (READ_ONCE(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 (tsk->in_iowait)
  				stats->nr_io_wait++;
  			break;
  		}
  	}
  	css_task_iter_end(&it);
  
  	mutex_unlock(&cgroup_mutex);
  	return 0;
  }
  
  void cgroup1_check_for_release(struct cgroup *cgrp)
  {
  	if (notify_on_release(cgrp) && !cgroup_is_populated(cgrp) &&
  	    !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
  		schedule_work(&cgrp->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.
   */
  void cgroup1_release_agent(struct work_struct *work)
  {
  	struct cgroup *cgrp =
  		container_of(work, struct cgroup, release_agent_work);
  	char *pathbuf, *agentbuf;
  	char *argv[3], *envp[3];
  	int ret;
  
  	/* snoop agent path and exit early if empty */
  	if (!cgrp->root->release_agent_path[0])
  		return;
  
  	/* prepare argument buffers */
  	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
  	agentbuf = kmalloc(PATH_MAX, GFP_KERNEL);
  	if (!pathbuf || !agentbuf)
  		goto out_free;
  
  	spin_lock(&release_agent_path_lock);
  	strlcpy(agentbuf, cgrp->root->release_agent_path, PATH_MAX);
  	spin_unlock(&release_agent_path_lock);
  	if (!agentbuf[0])
  		goto out_free;
  
  	ret = cgroup_path_ns(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
  	if (ret < 0 || ret >= PATH_MAX)
  		goto out_free;
  
  	argv[0] = agentbuf;
  	argv[1] = pathbuf;
  	argv[2] = NULL;
  
  	/* minimal command environment */
  	envp[0] = "HOME=/";
  	envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
  	envp[2] = NULL;
  
  	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
  out_free:
  	kfree(agentbuf);
  	kfree(pathbuf);
  }
  
  /*
   * cgroup_rename - Only allow simple rename of directories in place.
   */
  static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
  			  const char *new_name_str)
  {
  	struct cgroup *cgrp = kn->priv;
  	int ret;
  
  	/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
  	if (strchr(new_name_str, '\n'))
  		return -EINVAL;
  
  	if (kernfs_type(kn) != KERNFS_DIR)
  		return -ENOTDIR;
  	if (kn->parent != new_parent)
  		return -EIO;
  
  	/*
  	 * We're gonna grab cgroup_mutex which nests outside kernfs
  	 * active_ref.  kernfs_rename() doesn't require active_ref
  	 * protection.  Break them before grabbing cgroup_mutex.
  	 */
  	kernfs_break_active_protection(new_parent);
  	kernfs_break_active_protection(kn);
  
  	mutex_lock(&cgroup_mutex);
  
  	ret = kernfs_rename(kn, new_parent, new_name_str);
  	if (!ret)
  		TRACE_CGROUP_PATH(rename, cgrp);
  
  	mutex_unlock(&cgroup_mutex);
  
  	kernfs_unbreak_active_protection(kn);
  	kernfs_unbreak_active_protection(new_parent);
  	return ret;
  }
  
  static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
  {
  	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
  	struct cgroup_subsys *ss;
  	int ssid;
  
  	for_each_subsys(ss, ssid)
  		if (root->subsys_mask & (1 << ssid))
  			seq_show_option(seq, ss->legacy_name, NULL);
  	if (root->flags & CGRP_ROOT_NOPREFIX)
  		seq_puts(seq, ",noprefix");
  	if (root->flags & CGRP_ROOT_XATTR)
  		seq_puts(seq, ",xattr");
  	if (root->flags & CGRP_ROOT_CPUSET_V2_MODE)
  		seq_puts(seq, ",cpuset_v2_mode");
  
  	spin_lock(&release_agent_path_lock);
  	if (strlen(root->release_agent_path))
  		seq_show_option(seq, "release_agent",
  				root->release_agent_path);
  	spin_unlock(&release_agent_path_lock);
  
  	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
  		seq_puts(seq, ",clone_children");
  	if (strlen(root->name))
  		seq_show_option(seq, "name", root->name);
  	return 0;
  }
  
  enum cgroup1_param {
  	Opt_all,
  	Opt_clone_children,
  	Opt_cpuset_v2_mode,
  	Opt_name,
  	Opt_none,
  	Opt_noprefix,
  	Opt_release_agent,
  	Opt_xattr,
  };
  
  const struct fs_parameter_spec cgroup1_fs_parameters[] = {
  	fsparam_flag  ("all",		Opt_all),
  	fsparam_flag  ("clone_children", Opt_clone_children),
  	fsparam_flag  ("cpuset_v2_mode", Opt_cpuset_v2_mode),
  	fsparam_string("name",		Opt_name),
  	fsparam_flag  ("none",		Opt_none),
  	fsparam_flag  ("noprefix",	Opt_noprefix),
  	fsparam_string("release_agent",	Opt_release_agent),
  	fsparam_flag  ("xattr",		Opt_xattr),
  	{}
  };
  
  int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param)
  {
  	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
  	struct cgroup_subsys *ss;
  	struct fs_parse_result result;
  	int opt, i;
  
  	opt = fs_parse(fc, cgroup1_fs_parameters, param, &result);
  	if (opt == -ENOPARAM) {
  		int ret;
  
  		ret = vfs_parse_fs_param_source(fc, param);
  		if (ret != -ENOPARAM)
  			return ret;
  		for_each_subsys(ss, i) {
  			if (strcmp(param->key, ss->legacy_name))
  				continue;
  			if (!cgroup_ssid_enabled(i) || cgroup1_ssid_disabled(i))
  				return invalfc(fc, "Disabled controller '%s'",
  					       param->key);
  			ctx->subsys_mask |= (1 << i);
  			return 0;
  		}
  		return invalfc(fc, "Unknown subsys name '%s'", param->key);
  	}
  	if (opt < 0)
  		return opt;
  
  	switch (opt) {
  	case Opt_none:
  		/* Explicitly have no subsystems */
  		ctx->none = true;
  		break;
  	case Opt_all:
  		ctx->all_ss = true;
  		break;
  	case Opt_noprefix:
  		ctx->flags |= CGRP_ROOT_NOPREFIX;
  		break;
  	case Opt_clone_children:
  		ctx->cpuset_clone_children = true;
  		break;
  	case Opt_cpuset_v2_mode:
  		ctx->flags |= CGRP_ROOT_CPUSET_V2_MODE;
  		break;
  	case Opt_xattr:
  		ctx->flags |= CGRP_ROOT_XATTR;
  		break;
  	case Opt_release_agent:
  		/* Specifying two release agents is forbidden */
  		if (ctx->release_agent)
  			return invalfc(fc, "release_agent respecified");
  		ctx->release_agent = param->string;
  		param->string = NULL;
  		break;
  	case Opt_name:
  		/* blocked by boot param? */
  		if (cgroup_no_v1_named)
  			return -ENOENT;
  		/* Can't specify an empty name */
  		if (!param->size)
  			return invalfc(fc, "Empty name");
  		if (param->size > MAX_CGROUP_ROOT_NAMELEN - 1)
  			return invalfc(fc, "Name too long");
  		/* Must match [\w.-]+ */
  		for (i = 0; i < param->size; i++) {
  			char c = param->string[i];
  			if (isalnum(c))
  				continue;
  			if ((c == '.') || (c == '-') || (c == '_'))
  				continue;
  			return invalfc(fc, "Invalid name");
  		}
  		/* Specifying two names is forbidden */
  		if (ctx->name)
  			return invalfc(fc, "name respecified");
  		ctx->name = param->string;
  		param->string = NULL;
  		break;
  	}
  	return 0;
  }
  
  static int check_cgroupfs_options(struct fs_context *fc)
  {
  	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
  	u16 mask = U16_MAX;
  	u16 enabled = 0;
  	struct cgroup_subsys *ss;
  	int i;
  
  #ifdef CONFIG_CPUSETS
  	mask = ~((u16)1 << cpuset_cgrp_id);
  #endif
  	for_each_subsys(ss, i)
  		if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i))
  			enabled |= 1 << i;
  
  	ctx->subsys_mask &= enabled;
  
  	/*
  	 * In absence of 'none', 'name=' and subsystem name options,
  	 * let's default to 'all'.
  	 */
  	if (!ctx->subsys_mask && !ctx->none && !ctx->name)
  		ctx->all_ss = true;
  
  	if (ctx->all_ss) {
  		/* Mutually exclusive option 'all' + subsystem name */
  		if (ctx->subsys_mask)
  			return invalfc(fc, "subsys name conflicts with all");
  		/* 'all' => select all the subsystems */
  		ctx->subsys_mask = enabled;
  	}
  
  	/*
  	 * We either have to specify by name or by subsystems. (So all
  	 * empty hierarchies must have a name).
  	 */
  	if (!ctx->subsys_mask && !ctx->name)
  		return invalfc(fc, "Need name or subsystem set");
  
  	/*
  	 * Option noprefix was introduced just for backward compatibility
  	 * with the old cpuset, so we allow noprefix only if mounting just
  	 * the cpuset subsystem.
  	 */
  	if ((ctx->flags & CGRP_ROOT_NOPREFIX) && (ctx->subsys_mask & mask))
  		return invalfc(fc, "noprefix used incorrectly");
  
  	/* Can't specify "none" and some subsystems */
  	if (ctx->subsys_mask && ctx->none)
  		return invalfc(fc, "none used incorrectly");
  
  	return 0;
  }
  
  int cgroup1_reconfigure(struct fs_context *fc)
  {
  	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
  	struct kernfs_root *kf_root = kernfs_root_from_sb(fc->root->d_sb);
  	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
  	int ret = 0;
  	u16 added_mask, removed_mask;
  
  	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
  
  	/* See what subsystems are wanted */
  	ret = check_cgroupfs_options(fc);
  	if (ret)
  		goto out_unlock;
  
  	if (ctx->subsys_mask != root->subsys_mask || ctx->release_agent)
  		pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
  			task_tgid_nr(current), current->comm);
  
  	added_mask = ctx->subsys_mask & ~root->subsys_mask;
  	removed_mask = root->subsys_mask & ~ctx->subsys_mask;
  
  	/* Don't allow flags or name to change at remount */
  	if ((ctx->flags ^ root->flags) ||
  	    (ctx->name && strcmp(ctx->name, root->name))) {
  		errorfc(fc, "option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"",
  		       ctx->flags, ctx->name ?: "", root->flags, root->name);
  		ret = -EINVAL;
  		goto out_unlock;
  	}
  
  	/* remounting is not allowed for populated hierarchies */
  	if (!list_empty(&root->cgrp.self.children)) {
  		ret = -EBUSY;
  		goto out_unlock;
  	}
  
  	ret = rebind_subsystems(root, added_mask);
  	if (ret)
  		goto out_unlock;
  
  	WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));
  
  	if (ctx->release_agent) {
  		spin_lock(&release_agent_path_lock);
  		strcpy(root->release_agent_path, ctx->release_agent);
  		spin_unlock(&release_agent_path_lock);
  	}
  
  	trace_cgroup_remount(root);
  
   out_unlock:
  	mutex_unlock(&cgroup_mutex);
  	return ret;
  }
  
  struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
  	.rename			= cgroup1_rename,
  	.show_options		= cgroup1_show_options,
  	.mkdir			= cgroup_mkdir,
  	.rmdir			= cgroup_rmdir,
  	.show_path		= cgroup_show_path,
  };
  
  /*
   * The guts of cgroup1 mount - find or create cgroup_root to use.
   * Called with cgroup_mutex held; returns 0 on success, -E... on
   * error and positive - in case when the candidate is busy dying.
   * On success it stashes a reference to cgroup_root into given
   * cgroup_fs_context; that reference is *NOT* counting towards the
   * cgroup_root refcount.
   */
  static int cgroup1_root_to_use(struct fs_context *fc)
  {
  	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
  	struct cgroup_root *root;
  	struct cgroup_subsys *ss;
  	int i, ret;
  
  	/* First find the desired set of subsystems */
  	ret = check_cgroupfs_options(fc);
  	if (ret)
  		return ret;
  
  	/*
  	 * Destruction of cgroup root is asynchronous, so subsystems may
  	 * still be dying after the previous unmount.  Let's drain the
  	 * dying subsystems.  We just need to ensure that the ones
  	 * unmounted previously finish dying and don't care about new ones
  	 * starting.  Testing ref liveliness is good enough.
  	 */
  	for_each_subsys(ss, i) {
  		if (!(ctx->subsys_mask & (1 << i)) ||
  		    ss->root == &cgrp_dfl_root)
  			continue;
  
  		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt))
  			return 1;	/* restart */
  		cgroup_put(&ss->root->cgrp);
  	}
  
  	for_each_root(root) {
  		bool name_match = false;
  
  		if (root == &cgrp_dfl_root)
  			continue;
  
  		/*
  		 * If we asked for a name then it must match.  Also, if
  		 * name matches but sybsys_mask doesn't, we should fail.
  		 * Remember whether name matched.
  		 */
  		if (ctx->name) {
  			if (strcmp(ctx->name, root->name))
  				continue;
  			name_match = true;
  		}
  
  		/*
  		 * If we asked for subsystems (or explicitly for no
  		 * subsystems) then they must match.
  		 */
  		if ((ctx->subsys_mask || ctx->none) &&
  		    (ctx->subsys_mask != root->subsys_mask)) {
  			if (!name_match)
  				continue;
  			return -EBUSY;
  		}
  
  		if (root->flags ^ ctx->flags)
  			pr_warn("new mount options do not match the existing superblock, will be ignored\n");
  
  		ctx->root = root;
  		return 0;
  	}
  
  	/*
  	 * No such thing, create a new one.  name= matching without subsys
  	 * specification is allowed for already existing hierarchies but we
  	 * can't create new one without subsys specification.
  	 */
  	if (!ctx->subsys_mask && !ctx->none)
  		return invalfc(fc, "No subsys list or none specified");
  
  	/* Hierarchies may only be created in the initial cgroup namespace. */
  	if (ctx->ns != &init_cgroup_ns)
  		return -EPERM;
  
  	root = kzalloc(sizeof(*root), GFP_KERNEL);
  	if (!root)
  		return -ENOMEM;
  
  	ctx->root = root;
  	init_cgroup_root(ctx);
  
  	ret = cgroup_setup_root(root, ctx->subsys_mask);
  	if (ret)
  		cgroup_free_root(root);
  	return ret;
  }
  
  int cgroup1_get_tree(struct fs_context *fc)
  {
  	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
  	int ret;
  
  	/* Check if the caller has permission to mount. */
  	if (!ns_capable(ctx->ns->user_ns, CAP_SYS_ADMIN))
  		return -EPERM;
  
  	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
  
  	ret = cgroup1_root_to_use(fc);
  	if (!ret && !percpu_ref_tryget_live(&ctx->root->cgrp.self.refcnt))
  		ret = 1;	/* restart */
  
  	mutex_unlock(&cgroup_mutex);
  
  	if (!ret)
  		ret = cgroup_do_get_tree(fc);
  
  	if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) {
  		fc_drop_locked(fc);
  		ret = 1;
  	}
  
  	if (unlikely(ret > 0)) {
  		msleep(10);
  		return restart_syscall();
  	}
  	return ret;
  }
  
  static int __init cgroup1_wq_init(void)
  {
  	/*
  	 * Used to destroy pidlists and separate to serve as flush domain.
  	 * Cap @max_active to 1 too.
  	 */
  	cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
  						    0, 1);
  	BUG_ON(!cgroup_pidlist_destroy_wq);
  	return 0;
  }
  core_initcall(cgroup1_wq_init);
  
  static int __init cgroup_no_v1(char *str)
  {
  	struct cgroup_subsys *ss;
  	char *token;
  	int i;
  
  	while ((token = strsep(&str, ",")) != NULL) {
  		if (!*token)
  			continue;
  
  		if (!strcmp(token, "all")) {
  			cgroup_no_v1_mask = U16_MAX;
  			continue;
  		}
  
  		if (!strcmp(token, "named")) {
  			cgroup_no_v1_named = true;
  			continue;
  		}
  
  		for_each_subsys(ss, i) {
  			if (strcmp(token, ss->name) &&
  			    strcmp(token, ss->legacy_name))
  				continue;
  
  			cgroup_no_v1_mask |= 1 << i;
  		}
  	}
  	return 1;
  }
  __setup("cgroup_no_v1=", cgroup_no_v1);
  