[linux-block.git] / kernel / cgroup / pids.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Process number limiting controller for cgroups.
 *
 * Used to allow a cgroup hierarchy to stop any new processes from fork()ing
 * after a certain limit is reached.
 *
 * Since it is trivial to hit the task limit without hitting any kmemcg limits
 * in place, PIDs are a fundamental resource. As such, PID exhaustion must be
 * preventable in the scope of a cgroup hierarchy by allowing resource limiting
 * of the number of tasks in a cgroup.
 *
 * In order to use the `pids` controller, set the maximum number of tasks in
 * pids.max (this is not available in the root cgroup for obvious reasons). The
 * number of processes currently in the cgroup is given by pids.current.
 * Organisational operations are not blocked by cgroup policies, so it is
 * possible to have pids.current > pids.max. However, it is not possible to
 * violate a cgroup policy through fork(). fork() will return -EAGAIN if forking
 * would cause a cgroup policy to be violated.
 *
 * To set a cgroup to have no limit, set pids.max to "max". This is the default
 * for all new cgroups (N.B. that PID limits are hierarchical, so the most
 * stringent limit in the hierarchy is followed).
 *
 * pids.current tracks all child cgroup hierarchies, so parent/pids.current is
 * a superset of parent/child/pids.current.
 *
 * Copyright (C) 2015 Aleksa Sarai <cyphar@cyphar.com>
 */

#include <linux/kernel.h>
#include <linux/threads.h>
#include <linux/atomic.h>
#include <linux/cgroup.h>
#include <linux/slab.h>
#include <linux/sched/task.h>

#define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
#define PIDS_MAX_STR "max"

struct pids_cgroup {
	struct cgroup_subsys_state	css;

	/*
	 * Use 64-bit types so that we can safely represent "max" as
	 * %PIDS_MAX = (%PID_MAX_LIMIT + 1).
	 */
	atomic64_t			counter;
	atomic64_t			limit;
	int64_t				watermark;

	/* Handle for "pids.events" */
	struct cgroup_file		events_file;

	/* Number of times fork failed because limit was hit. */
	atomic64_t			events_limit;
};

static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
{
	return container_of(css, struct pids_cgroup, css);
}

static struct pids_cgroup *parent_pids(struct pids_cgroup *pids)
{
	return css_pids(pids->css.parent);
}

static struct cgroup_subsys_state *
pids_css_alloc(struct cgroup_subsys_state *parent)
{
	struct pids_cgroup *pids;

	pids = kzalloc(sizeof(struct pids_cgroup), GFP_KERNEL);
	if (!pids)
		return ERR_PTR(-ENOMEM);

	atomic64_set(&pids->counter, 0);
	atomic64_set(&pids->limit, PIDS_MAX);
	atomic64_set(&pids->events_limit, 0);
	return &pids->css;
}

static void pids_css_free(struct cgroup_subsys_state *css)
{
	kfree(css_pids(css));
}

static void pids_update_watermark(struct pids_cgroup *p, int64_t nr_pids)
{
	/*
	 * This is racy, but we don't need perfectly accurate tallying of
	 * the watermark, and this lets us avoid extra atomic overhead.
	 */
	if (nr_pids > READ_ONCE(p->watermark))
		WRITE_ONCE(p->watermark, nr_pids);
}

/**
 * pids_cancel - uncharge the local pid count
 * @pids: the pid cgroup state
 * @num: the number of pids to cancel
 *
 * This function will WARN if the pid count goes under 0, because such a case is
 * a bug in the pids controller proper.
 */
static void pids_cancel(struct pids_cgroup *pids, int num)
{
	/*
	 * A negative count (or overflow for that matter) is invalid,
	 * and indicates a bug in the `pids` controller proper.
	 */
	WARN_ON_ONCE(atomic64_add_negative(-num, &pids->counter));
}

/**
 * pids_uncharge - hierarchically uncharge the pid count
 * @pids: the pid cgroup state
 * @num: the number of pids to uncharge
 */
static void pids_uncharge(struct pids_cgroup *pids, int num)
{
	struct pids_cgroup *p;

	for (p = pids; parent_pids(p); p = parent_pids(p))
		pids_cancel(p, num);
}

/**
 * pids_charge - hierarchically charge the pid count
 * @pids: the pid cgroup state
 * @num: the number of pids to charge
 *
 * This function does *not* follow the pid limit set. It cannot fail and the new
 * pid count may exceed the limit. This is only used for reverting failed
 * attaches, where there is no other way out than violating the limit.
 */
static void pids_charge(struct pids_cgroup *pids, int num)
{
	struct pids_cgroup *p;

	for (p = pids; parent_pids(p); p = parent_pids(p)) {
		int64_t new = atomic64_add_return(num, &p->counter);

		pids_update_watermark(p, new);
	}
}

/**
 * pids_try_charge - hierarchically try to charge the pid count
 * @pids: the pid cgroup state
 * @num: the number of pids to charge
 *
 * This function follows the set limit. It will fail if the charge would cause
 * the new value to exceed the hierarchical limit. Returns 0 if the charge
 * succeeded, otherwise -EAGAIN.
 */
static int pids_try_charge(struct pids_cgroup *pids, int num)
{
	struct pids_cgroup *p, *q;

	for (p = pids; parent_pids(p); p = parent_pids(p)) {
		int64_t new = atomic64_add_return(num, &p->counter);
		int64_t limit = atomic64_read(&p->limit);

		/*
		 * Since new is capped to the maximum number of pid_t, if
		 * p->limit is %PIDS_MAX then we know that this test will never
		 * fail.
		 */
		if (new > limit)
			goto revert;

		/*
		 * Not technically accurate if we go over limit somewhere up
		 * the hierarchy, but that's tolerable for the watermark.
		 */
		pids_update_watermark(p, new);
	}

	return 0;

revert:
	for (q = pids; q != p; q = parent_pids(q))
		pids_cancel(q, num);
	pids_cancel(p, num);

	return -EAGAIN;
}

static int pids_can_attach(struct cgroup_taskset *tset)
{
	struct task_struct *task;
	struct cgroup_subsys_state *dst_css;

	cgroup_taskset_for_each(task, dst_css, tset) {
		struct pids_cgroup *pids = css_pids(dst_css);
		struct cgroup_subsys_state *old_css;
		struct pids_cgroup *old_pids;

		/*
		 * No need to pin @old_css between here and cancel_attach()
		 * because cgroup core protects it from being freed before
		 * the migration completes or fails.
		 */
		old_css = task_css(task, pids_cgrp_id);
		old_pids = css_pids(old_css);

		pids_charge(pids, 1);
		pids_uncharge(old_pids, 1);
	}

	return 0;
}

static void pids_cancel_attach(struct cgroup_taskset *tset)
{
	struct task_struct *task;
	struct cgroup_subsys_state *dst_css;

	cgroup_taskset_for_each(task, dst_css, tset) {
		struct pids_cgroup *pids = css_pids(dst_css);
		struct cgroup_subsys_state *old_css;
		struct pids_cgroup *old_pids;

		old_css = task_css(task, pids_cgrp_id);
		old_pids = css_pids(old_css);

		pids_charge(old_pids, 1);
		pids_uncharge(pids, 1);
	}
}

/*
 * task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
 * on cgroup_threadgroup_change_begin() held by the copy_process().
 */
static int pids_can_fork(struct task_struct *task, struct css_set *cset)
{
	struct cgroup_subsys_state *css;
	struct pids_cgroup *pids;
	int err;

	if (cset)
		css = cset->subsys[pids_cgrp_id];
	else
		css = task_css_check(current, pids_cgrp_id, true);
	pids = css_pids(css);
	err = pids_try_charge(pids, 1);
	if (err) {
		/* Only log the first time events_limit is incremented. */
		if (atomic64_inc_return(&pids->events_limit) == 1) {
			pr_info("cgroup: fork rejected by pids controller in ");
			pr_cont_cgroup_path(css->cgroup);
			pr_cont("\n");
		}
		cgroup_file_notify(&pids->events_file);
	}
	return err;
}

static void pids_cancel_fork(struct task_struct *task, struct css_set *cset)
{
	struct cgroup_subsys_state *css;
	struct pids_cgroup *pids;

	if (cset)
		css = cset->subsys[pids_cgrp_id];
	else
		css = task_css_check(current, pids_cgrp_id, true);
	pids = css_pids(css);
	pids_uncharge(pids, 1);
}

static void pids_release(struct task_struct *task)
{
	struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id));

	pids_uncharge(pids, 1);
}

static ssize_t pids_max_write(struct kernfs_open_file *of, char *buf,
			      size_t nbytes, loff_t off)
{
	struct cgroup_subsys_state *css = of_css(of);
	struct pids_cgroup *pids = css_pids(css);
	int64_t limit;
	int err;

	buf = strstrip(buf);
	if (!strcmp(buf, PIDS_MAX_STR)) {
		limit = PIDS_MAX;
		goto set_limit;
	}

	err = kstrtoll(buf, 0, &limit);
	if (err)
		return err;

	if (limit < 0 || limit >= PIDS_MAX)
		return -EINVAL;

set_limit:
	/*
	 * Limit updates don't need to be mutex'd, since it isn't
	 * critical that any racing fork()s follow the new limit.
	 */
	atomic64_set(&pids->limit, limit);
	return nbytes;
}

static int pids_max_show(struct seq_file *sf, void *v)
{
	struct cgroup_subsys_state *css = seq_css(sf);
	struct pids_cgroup *pids = css_pids(css);
	int64_t limit = atomic64_read(&pids->limit);

	if (limit >= PIDS_MAX)
		seq_printf(sf, "%s\n", PIDS_MAX_STR);
	else
		seq_printf(sf, "%lld\n", limit);

	return 0;
}

static s64 pids_current_read(struct cgroup_subsys_state *css,
			     struct cftype *cft)
{
	struct pids_cgroup *pids = css_pids(css);

	return atomic64_read(&pids->counter);
}

static s64 pids_peak_read(struct cgroup_subsys_state *css,
			  struct cftype *cft)
{
	struct pids_cgroup *pids = css_pids(css);

	return READ_ONCE(pids->watermark);
}

static int pids_events_show(struct seq_file *sf, void *v)
{
	struct pids_cgroup *pids = css_pids(seq_css(sf));

	seq_printf(sf, "max %lld\n", (s64)atomic64_read(&pids->events_limit));
	return 0;
}

static struct cftype pids_files[] = {
	{
		.name = "max",
		.write = pids_max_write,
		.seq_show = pids_max_show,
		.flags = CFTYPE_NOT_ON_ROOT,
	},
	{
		.name = "current",
		.read_s64 = pids_current_read,
		.flags = CFTYPE_NOT_ON_ROOT,
	},
	{
		.name = "peak",
		.flags = CFTYPE_NOT_ON_ROOT,
		.read_s64 = pids_peak_read,
	},
	{
		.name = "events",
		.seq_show = pids_events_show,
		.file_offset = offsetof(struct pids_cgroup, events_file),
		.flags = CFTYPE_NOT_ON_ROOT,
	},
	{ }	/* terminate */
};

struct cgroup_subsys pids_cgrp_subsys = {
	.css_alloc	= pids_css_alloc,
	.css_free	= pids_css_free,
	.can_attach 	= pids_can_attach,
	.cancel_attach 	= pids_cancel_attach,
	.can_fork	= pids_can_fork,
	.cancel_fork	= pids_cancel_fork,
	.release	= pids_release,
	.legacy_cftypes	= pids_files,
	.dfl_cftypes	= pids_files,
	.threaded	= true,
};
Commit	Line	Data
f85d2086	1	// SPDX-License-Identifier: GPL-2.0-only
49b786ea AS	2	/*
	3	* Process number limiting controller for cgroups.
	4	*
	5	* Used to allow a cgroup hierarchy to stop any new processes from fork()ing
	6	* after a certain limit is reached.
	7	*
	8	* Since it is trivial to hit the task limit without hitting any kmemcg limits
	9	* in place, PIDs are a fundamental resource. As such, PID exhaustion must be
	10	* preventable in the scope of a cgroup hierarchy by allowing resource limiting
	11	* of the number of tasks in a cgroup.
	12	*
	13	* In order to use the `pids` controller, set the maximum number of tasks in
	14	* pids.max (this is not available in the root cgroup for obvious reasons). The
	15	* number of processes currently in the cgroup is given by pids.current.
	16	* Organisational operations are not blocked by cgroup policies, so it is
	17	* possible to have pids.current > pids.max. However, it is not possible to
	18	* violate a cgroup policy through fork(). fork() will return -EAGAIN if forking
	19	* would cause a cgroup policy to be violated.
	20	*
	21	* To set a cgroup to have no limit, set pids.max to "max". This is the default
	22	* for all new cgroups (N.B. that PID limits are hierarchical, so the most
	23	* stringent limit in the hierarchy is followed).
	24	*
	25	* pids.current tracks all child cgroup hierarchies, so parent/pids.current is
	26	* a superset of parent/child/pids.current.
	27	*
	28	* Copyright (C) 2015 Aleksa Sarai <cyphar@cyphar.com>
49b786ea AS	29	*/
	30
	31	#include <linux/kernel.h>
	32	#include <linux/threads.h>
	33	#include <linux/atomic.h>
	34	#include <linux/cgroup.h>
	35	#include <linux/slab.h>
ef2c41cf	36	#include <linux/sched/task.h>
49b786ea AS	37
	38	#define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
	39	#define PIDS_MAX_STR "max"
	40
	41	struct pids_cgroup {
	42	struct cgroup_subsys_state css;
	43
	44	/*
	45	* Use 64-bit types so that we can safely represent "max" as
	46	* %PIDS_MAX = (%PID_MAX_LIMIT + 1).
	47	*/
	48	atomic64_t counter;
a713af39	49	atomic64_t limit;
5251c6c4	50	int64_t watermark;
135b8b37 KY	51
	52	/* Handle for "pids.events" */
	53	struct cgroup_file events_file;
	54
	55	/* Number of times fork failed because limit was hit. */
	56	atomic64_t events_limit;
49b786ea AS	57	};
	58
	59	static struct pids_cgroup css_pids(struct cgroup_subsys_state css)
	60	{
	61	return container_of(css, struct pids_cgroup, css);
	62	}
	63
	64	static struct pids_cgroup parent_pids(struct pids_cgroup pids)
	65	{
	66	return css_pids(pids->css.parent);
	67	}
	68
	69	static struct cgroup_subsys_state *
	70	pids_css_alloc(struct cgroup_subsys_state *parent)
	71	{
	72	struct pids_cgroup *pids;
	73
	74	pids = kzalloc(sizeof(struct pids_cgroup), GFP_KERNEL);
	75	if (!pids)
	76	return ERR_PTR(-ENOMEM);
	77
49b786ea	78	atomic64_set(&pids->counter, 0);
a713af39	79	atomic64_set(&pids->limit, PIDS_MAX);
135b8b37	80	atomic64_set(&pids->events_limit, 0);
49b786ea AS	81	return &pids->css;
	82	}
	83
	84	static void pids_css_free(struct cgroup_subsys_state *css)
	85	{
	86	kfree(css_pids(css));
	87	}
	88
5251c6c4 JD	89	static void pids_update_watermark(struct pids_cgroup *p, int64_t nr_pids)
	90	{
	91	/*
	92	* This is racy, but we don't need perfectly accurate tallying of
	93	* the watermark, and this lets us avoid extra atomic overhead.
	94	*/
	95	if (nr_pids > READ_ONCE(p->watermark))
	96	WRITE_ONCE(p->watermark, nr_pids);
	97	}
	98
49b786ea AS	99	/**
	100	* pids_cancel - uncharge the local pid count
	101	* @pids: the pid cgroup state
	102	* @num: the number of pids to cancel
	103	*
	104	* This function will WARN if the pid count goes under 0, because such a case is
	105	* a bug in the pids controller proper.
	106	*/
	107	static void pids_cancel(struct pids_cgroup *pids, int num)
	108	{
	109	/*
	110	* A negative count (or overflow for that matter) is invalid,
	111	* and indicates a bug in the `pids` controller proper.
	112	*/
	113	WARN_ON_ONCE(atomic64_add_negative(-num, &pids->counter));
	114	}
	115
	116	/**
	117	* pids_uncharge - hierarchically uncharge the pid count
	118	* @pids: the pid cgroup state
	119	* @num: the number of pids to uncharge
	120	*/
	121	static void pids_uncharge(struct pids_cgroup *pids, int num)
	122	{
	123	struct pids_cgroup *p;
	124
67cde9c4	125	for (p = pids; parent_pids(p); p = parent_pids(p))
49b786ea AS	126	pids_cancel(p, num);
	127	}
	128
	129	/**
	130	* pids_charge - hierarchically charge the pid count
	131	* @pids: the pid cgroup state
	132	* @num: the number of pids to charge
	133	*
	134	* This function does not follow the pid limit set. It cannot fail and the new
	135	* pid count may exceed the limit. This is only used for reverting failed
	136	* attaches, where there is no other way out than violating the limit.
	137	*/
	138	static void pids_charge(struct pids_cgroup *pids, int num)
	139	{
	140	struct pids_cgroup *p;
	141
5251c6c4 JD	142	for (p = pids; parent_pids(p); p = parent_pids(p)) {
	143	int64_t new = atomic64_add_return(num, &p->counter);
	144
	145	pids_update_watermark(p, new);
	146	}
49b786ea AS	147	}
	148
	149	/**
	150	* pids_try_charge - hierarchically try to charge the pid count
	151	* @pids: the pid cgroup state
	152	* @num: the number of pids to charge
	153	*
	154	* This function follows the set limit. It will fail if the charge would cause
	155	* the new value to exceed the hierarchical limit. Returns 0 if the charge
fccd3af5	156	* succeeded, otherwise -EAGAIN.
49b786ea AS	157	*/
	158	static int pids_try_charge(struct pids_cgroup *pids, int num)
	159	{
	160	struct pids_cgroup p, q;
	161
67cde9c4	162	for (p = pids; parent_pids(p); p = parent_pids(p)) {
49b786ea	163	int64_t new = atomic64_add_return(num, &p->counter);
a713af39	164	int64_t limit = atomic64_read(&p->limit);
49b786ea AS	165
	166	/*
	167	* Since new is capped to the maximum number of pid_t, if
	168	* p->limit is %PIDS_MAX then we know that this test will never
	169	* fail.
	170	*/
a713af39	171	if (new > limit)
49b786ea	172	goto revert;
5251c6c4 JD	173
	174	/*
	175	* Not technically accurate if we go over limit somewhere up
	176	* the hierarchy, but that's tolerable for the watermark.
	177	*/
	178	pids_update_watermark(p, new);
49b786ea AS	179	}
	180
	181	return 0;
	182
	183	revert:
	184	for (q = pids; q != p; q = parent_pids(q))
	185	pids_cancel(q, num);
	186	pids_cancel(p, num);
	187
	188	return -EAGAIN;
	189	}
	190
1f7dd3e5	191	static int pids_can_attach(struct cgroup_taskset *tset)
49b786ea	192	{
49b786ea	193	struct task_struct *task;
1f7dd3e5	194	struct cgroup_subsys_state *dst_css;
49b786ea	195
1f7dd3e5 TH	196	cgroup_taskset_for_each(task, dst_css, tset) {
1f7dd3e5 TH	197	struct pids_cgroup *pids = css_pids(dst_css);
49b786ea AS	198	struct cgroup_subsys_state *old_css;
	199	struct pids_cgroup *old_pids;
	200
	201	/*
ce523995 AS	202	* No need to pin @old_css between here and cancel_attach()
	203	* because cgroup core protects it from being freed before
	204	* the migration completes or fails.
49b786ea	205	*/
ce523995	206	old_css = task_css(task, pids_cgrp_id);
49b786ea AS	207	old_pids = css_pids(old_css);
	208
	209	pids_charge(pids, 1);
	210	pids_uncharge(old_pids, 1);
	211	}
	212
	213	return 0;
	214	}
	215
1f7dd3e5	216	static void pids_cancel_attach(struct cgroup_taskset *tset)
49b786ea	217	{
49b786ea	218	struct task_struct *task;
1f7dd3e5	219	struct cgroup_subsys_state *dst_css;
49b786ea	220
1f7dd3e5 TH	221	cgroup_taskset_for_each(task, dst_css, tset) {
1f7dd3e5 TH	222	struct pids_cgroup *pids = css_pids(dst_css);
49b786ea AS	223	struct cgroup_subsys_state *old_css;
	224	struct pids_cgroup *old_pids;
	225
	226	old_css = task_css(task, pids_cgrp_id);
	227	old_pids = css_pids(old_css);
	228
	229	pids_charge(old_pids, 1);
	230	pids_uncharge(pids, 1);
49b786ea AS	231	}
	232	}
	233
afbcb364 ON	234	/*
afbcb364 ON	235	* task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
780de9dd	236	* on cgroup_threadgroup_change_begin() held by the copy_process().
afbcb364	237	*/
ef2c41cf	238	static int pids_can_fork(struct task_struct task, struct css_set cset)
49b786ea AS	239	{
	240	struct cgroup_subsys_state *css;
	241	struct pids_cgroup *pids;
135b8b37	242	int err;
49b786ea	243
ef2c41cf CB	244	if (cset)
	245	css = cset->subsys[pids_cgrp_id];
	246	else
	247	css = task_css_check(current, pids_cgrp_id, true);
49b786ea	248	pids = css_pids(css);
135b8b37 KY	249	err = pids_try_charge(pids, 1);
	250	if (err) {
	251	/* Only log the first time events_limit is incremented. */
	252	if (atomic64_inc_return(&pids->events_limit) == 1) {
	253	pr_info("cgroup: fork rejected by pids controller in ");
1d18c274	254	pr_cont_cgroup_path(css->cgroup);
135b8b37 KY	255	pr_cont("\n");
	256	}
	257	cgroup_file_notify(&pids->events_file);
	258	}
	259	return err;
49b786ea AS	260	}
49b786ea AS	261
ef2c41cf	262	static void pids_cancel_fork(struct task_struct task, struct css_set cset)
49b786ea	263	{
afbcb364 ON	264	struct cgroup_subsys_state *css;
afbcb364 ON	265	struct pids_cgroup *pids;
49b786ea	266
ef2c41cf CB	267	if (cset)
	268	css = cset->subsys[pids_cgrp_id];
	269	else
	270	css = task_css_check(current, pids_cgrp_id, true);
afbcb364	271	pids = css_pids(css);
49b786ea	272	pids_uncharge(pids, 1);
49b786ea AS	273	}
49b786ea AS	274
51bee5ab	275	static void pids_release(struct task_struct *task)
49b786ea	276	{
2e91fa7f	277	struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id));
49b786ea AS	278
	279	pids_uncharge(pids, 1);
	280	}
	281
	282	static ssize_t pids_max_write(struct kernfs_open_file of, char buf,
	283	size_t nbytes, loff_t off)
	284	{
	285	struct cgroup_subsys_state *css = of_css(of);
	286	struct pids_cgroup *pids = css_pids(css);
	287	int64_t limit;
	288	int err;
	289
	290	buf = strstrip(buf);
	291	if (!strcmp(buf, PIDS_MAX_STR)) {
	292	limit = PIDS_MAX;
	293	goto set_limit;
	294	}
	295
	296	err = kstrtoll(buf, 0, &limit);
	297	if (err)
	298	return err;
	299
	300	if (limit < 0 \|\| limit >= PIDS_MAX)
	301	return -EINVAL;
	302
	303	set_limit:
	304	/*
	305	* Limit updates don't need to be mutex'd, since it isn't
	306	* critical that any racing fork()s follow the new limit.
	307	*/
a713af39	308	atomic64_set(&pids->limit, limit);
49b786ea AS	309	return nbytes;
	310	}
	311
	312	static int pids_max_show(struct seq_file sf, void v)
	313	{
	314	struct cgroup_subsys_state *css = seq_css(sf);
	315	struct pids_cgroup *pids = css_pids(css);
a713af39	316	int64_t limit = atomic64_read(&pids->limit);
49b786ea AS	317
	318	if (limit >= PIDS_MAX)
	319	seq_printf(sf, "%s\n", PIDS_MAX_STR);
	320	else
	321	seq_printf(sf, "%lld\n", limit);
	322
	323	return 0;
	324	}
	325
	326	static s64 pids_current_read(struct cgroup_subsys_state *css,
	327	struct cftype *cft)
	328	{
	329	struct pids_cgroup *pids = css_pids(css);
	330
	331	return atomic64_read(&pids->counter);
	332	}
	333
5251c6c4 JD	334	static s64 pids_peak_read(struct cgroup_subsys_state *css,
	335	struct cftype *cft)
	336	{
	337	struct pids_cgroup *pids = css_pids(css);
	338
	339	return READ_ONCE(pids->watermark);
	340	}
	341
135b8b37 KY	342	static int pids_events_show(struct seq_file sf, void v)
	343	{
	344	struct pids_cgroup *pids = css_pids(seq_css(sf));
	345
9f6870dd	346	seq_printf(sf, "max %lld\n", (s64)atomic64_read(&pids->events_limit));
135b8b37 KY	347	return 0;
	348	}
	349
49b786ea AS	350	static struct cftype pids_files[] = {
	351	{
	352	.name = "max",
	353	.write = pids_max_write,
	354	.seq_show = pids_max_show,
	355	.flags = CFTYPE_NOT_ON_ROOT,
	356	},
	357	{
	358	.name = "current",
	359	.read_s64 = pids_current_read,
67cde9c4	360	.flags = CFTYPE_NOT_ON_ROOT,
49b786ea	361	},
5251c6c4 JD	362	{
	363	.name = "peak",
	364	.flags = CFTYPE_NOT_ON_ROOT,
	365	.read_s64 = pids_peak_read,
	366	},
135b8b37 KY	367	{
	368	.name = "events",
	369	.seq_show = pids_events_show,
	370	.file_offset = offsetof(struct pids_cgroup, events_file),
	371	.flags = CFTYPE_NOT_ON_ROOT,
	372	},
49b786ea AS	373	{ } /* terminate */
	374	};
	375
	376	struct cgroup_subsys pids_cgrp_subsys = {
	377	.css_alloc = pids_css_alloc,
	378	.css_free = pids_css_free,
49b786ea AS	379	.can_attach = pids_can_attach,
	380	.cancel_attach = pids_cancel_attach,
	381	.can_fork = pids_can_fork,
	382	.cancel_fork = pids_cancel_fork,
51bee5ab	383	.release = pids_release,
49b786ea AS	384	.legacy_cftypes = pids_files,
49b786ea AS	385	.dfl_cftypes = pids_files,
8cfd8147	386	.threaded = true,
49b786ea	387	};