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1// SPDX-License-Identifier: GPL-2.0-only
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>
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>
36#include <linux/sched/task.h>
37
38#define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
39#define PIDS_MAX_STR "max"
40
41enum pidcg_event {
42 /* Fork failed in subtree because this pids_cgroup limit was hit. */
43 PIDCG_MAX,
44 /* Fork failed in this pids_cgroup because ancestor limit was hit. */
45 PIDCG_FORKFAIL,
46 NR_PIDCG_EVENTS,
47};
48
49struct pids_cgroup {
50 struct cgroup_subsys_state css;
51
52 /*
53 * Use 64-bit types so that we can safely represent "max" as
54 * %PIDS_MAX = (%PID_MAX_LIMIT + 1).
55 */
56 atomic64_t counter;
57 atomic64_t limit;
58 int64_t watermark;
59
60 /* Handles for pids.events[.local] */
61 struct cgroup_file events_file;
62 struct cgroup_file events_local_file;
63
64 atomic64_t events[NR_PIDCG_EVENTS];
65 atomic64_t events_local[NR_PIDCG_EVENTS];
66};
67
68static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
69{
70 return container_of(css, struct pids_cgroup, css);
71}
72
73static struct pids_cgroup *parent_pids(struct pids_cgroup *pids)
74{
75 return css_pids(pids->css.parent);
76}
77
78static struct cgroup_subsys_state *
79pids_css_alloc(struct cgroup_subsys_state *parent)
80{
81 struct pids_cgroup *pids;
82
83 pids = kzalloc(sizeof(struct pids_cgroup), GFP_KERNEL);
84 if (!pids)
85 return ERR_PTR(-ENOMEM);
86
87 atomic64_set(&pids->limit, PIDS_MAX);
88 return &pids->css;
89}
90
91static void pids_css_free(struct cgroup_subsys_state *css)
92{
93 kfree(css_pids(css));
94}
95
96static void pids_update_watermark(struct pids_cgroup *p, int64_t nr_pids)
97{
98 /*
99 * This is racy, but we don't need perfectly accurate tallying of
100 * the watermark, and this lets us avoid extra atomic overhead.
101 */
102 if (nr_pids > READ_ONCE(p->watermark))
103 WRITE_ONCE(p->watermark, nr_pids);
104}
105
106/**
107 * pids_cancel - uncharge the local pid count
108 * @pids: the pid cgroup state
109 * @num: the number of pids to cancel
110 *
111 * This function will WARN if the pid count goes under 0, because such a case is
112 * a bug in the pids controller proper.
113 */
114static void pids_cancel(struct pids_cgroup *pids, int num)
115{
116 /*
117 * A negative count (or overflow for that matter) is invalid,
118 * and indicates a bug in the `pids` controller proper.
119 */
120 WARN_ON_ONCE(atomic64_add_negative(-num, &pids->counter));
121}
122
123/**
124 * pids_uncharge - hierarchically uncharge the pid count
125 * @pids: the pid cgroup state
126 * @num: the number of pids to uncharge
127 */
128static void pids_uncharge(struct pids_cgroup *pids, int num)
129{
130 struct pids_cgroup *p;
131
132 for (p = pids; parent_pids(p); p = parent_pids(p))
133 pids_cancel(p, num);
134}
135
136/**
137 * pids_charge - hierarchically charge the pid count
138 * @pids: the pid cgroup state
139 * @num: the number of pids to charge
140 *
141 * This function does *not* follow the pid limit set. It cannot fail and the new
142 * pid count may exceed the limit. This is only used for reverting failed
143 * attaches, where there is no other way out than violating the limit.
144 */
145static void pids_charge(struct pids_cgroup *pids, int num)
146{
147 struct pids_cgroup *p;
148
149 for (p = pids; parent_pids(p); p = parent_pids(p)) {
150 int64_t new = atomic64_add_return(num, &p->counter);
151
152 pids_update_watermark(p, new);
153 }
154}
155
156/**
157 * pids_try_charge - hierarchically try to charge the pid count
158 * @pids: the pid cgroup state
159 * @num: the number of pids to charge
160 * @fail: storage of pid cgroup causing the fail
161 *
162 * This function follows the set limit. It will fail if the charge would cause
163 * the new value to exceed the hierarchical limit. Returns 0 if the charge
164 * succeeded, otherwise -EAGAIN.
165 */
166static int pids_try_charge(struct pids_cgroup *pids, int num, struct pids_cgroup **fail)
167{
168 struct pids_cgroup *p, *q;
169
170 for (p = pids; parent_pids(p); p = parent_pids(p)) {
171 int64_t new = atomic64_add_return(num, &p->counter);
172 int64_t limit = atomic64_read(&p->limit);
173
174 /*
175 * Since new is capped to the maximum number of pid_t, if
176 * p->limit is %PIDS_MAX then we know that this test will never
177 * fail.
178 */
179 if (new > limit) {
180 *fail = p;
181 goto revert;
182 }
183 /*
184 * Not technically accurate if we go over limit somewhere up
185 * the hierarchy, but that's tolerable for the watermark.
186 */
187 pids_update_watermark(p, new);
188 }
189
190 return 0;
191
192revert:
193 for (q = pids; q != p; q = parent_pids(q))
194 pids_cancel(q, num);
195 pids_cancel(p, num);
196
197 return -EAGAIN;
198}
199
200static int pids_can_attach(struct cgroup_taskset *tset)
201{
202 struct task_struct *task;
203 struct cgroup_subsys_state *dst_css;
204
205 cgroup_taskset_for_each(task, dst_css, tset) {
206 struct pids_cgroup *pids = css_pids(dst_css);
207 struct cgroup_subsys_state *old_css;
208 struct pids_cgroup *old_pids;
209
210 /*
211 * No need to pin @old_css between here and cancel_attach()
212 * because cgroup core protects it from being freed before
213 * the migration completes or fails.
214 */
215 old_css = task_css(task, pids_cgrp_id);
216 old_pids = css_pids(old_css);
217
218 pids_charge(pids, 1);
219 pids_uncharge(old_pids, 1);
220 }
221
222 return 0;
223}
224
225static void pids_cancel_attach(struct cgroup_taskset *tset)
226{
227 struct task_struct *task;
228 struct cgroup_subsys_state *dst_css;
229
230 cgroup_taskset_for_each(task, dst_css, tset) {
231 struct pids_cgroup *pids = css_pids(dst_css);
232 struct cgroup_subsys_state *old_css;
233 struct pids_cgroup *old_pids;
234
235 old_css = task_css(task, pids_cgrp_id);
236 old_pids = css_pids(old_css);
237
238 pids_charge(old_pids, 1);
239 pids_uncharge(pids, 1);
240 }
241}
242
243static void pids_event(struct pids_cgroup *pids_forking,
244 struct pids_cgroup *pids_over_limit)
245{
246 struct pids_cgroup *p = pids_forking;
247
248 /* Only log the first time limit is hit. */
249 if (atomic64_inc_return(&p->events_local[PIDCG_FORKFAIL]) == 1) {
250 pr_info("cgroup: fork rejected by pids controller in ");
251 pr_cont_cgroup_path(p->css.cgroup);
252 pr_cont("\n");
253 }
254 if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
255 cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
256 cgroup_file_notify(&p->events_local_file);
257 return;
258 }
259
260 atomic64_inc(&pids_over_limit->events_local[PIDCG_MAX]);
261 cgroup_file_notify(&pids_over_limit->events_local_file);
262
263 for (p = pids_over_limit; parent_pids(p); p = parent_pids(p)) {
264 atomic64_inc(&p->events[PIDCG_MAX]);
265 cgroup_file_notify(&p->events_file);
266 }
267}
268
269/*
270 * task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
271 * on cgroup_threadgroup_change_begin() held by the copy_process().
272 */
273static int pids_can_fork(struct task_struct *task, struct css_set *cset)
274{
275 struct pids_cgroup *pids, *pids_over_limit;
276 int err;
277
278 pids = css_pids(cset->subsys[pids_cgrp_id]);
279 err = pids_try_charge(pids, 1, &pids_over_limit);
280 if (err)
281 pids_event(pids, pids_over_limit);
282
283 return err;
284}
285
286static void pids_cancel_fork(struct task_struct *task, struct css_set *cset)
287{
288 struct pids_cgroup *pids;
289
290 pids = css_pids(cset->subsys[pids_cgrp_id]);
291 pids_uncharge(pids, 1);
292}
293
294static void pids_release(struct task_struct *task)
295{
296 struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id));
297
298 pids_uncharge(pids, 1);
299}
300
301static ssize_t pids_max_write(struct kernfs_open_file *of, char *buf,
302 size_t nbytes, loff_t off)
303{
304 struct cgroup_subsys_state *css = of_css(of);
305 struct pids_cgroup *pids = css_pids(css);
306 int64_t limit;
307 int err;
308
309 buf = strstrip(buf);
310 if (!strcmp(buf, PIDS_MAX_STR)) {
311 limit = PIDS_MAX;
312 goto set_limit;
313 }
314
315 err = kstrtoll(buf, 0, &limit);
316 if (err)
317 return err;
318
319 if (limit < 0 || limit >= PIDS_MAX)
320 return -EINVAL;
321
322set_limit:
323 /*
324 * Limit updates don't need to be mutex'd, since it isn't
325 * critical that any racing fork()s follow the new limit.
326 */
327 atomic64_set(&pids->limit, limit);
328 return nbytes;
329}
330
331static int pids_max_show(struct seq_file *sf, void *v)
332{
333 struct cgroup_subsys_state *css = seq_css(sf);
334 struct pids_cgroup *pids = css_pids(css);
335 int64_t limit = atomic64_read(&pids->limit);
336
337 if (limit >= PIDS_MAX)
338 seq_printf(sf, "%s\n", PIDS_MAX_STR);
339 else
340 seq_printf(sf, "%lld\n", limit);
341
342 return 0;
343}
344
345static s64 pids_current_read(struct cgroup_subsys_state *css,
346 struct cftype *cft)
347{
348 struct pids_cgroup *pids = css_pids(css);
349
350 return atomic64_read(&pids->counter);
351}
352
353static s64 pids_peak_read(struct cgroup_subsys_state *css,
354 struct cftype *cft)
355{
356 struct pids_cgroup *pids = css_pids(css);
357
358 return READ_ONCE(pids->watermark);
359}
360
361static int __pids_events_show(struct seq_file *sf, bool local)
362{
363 struct pids_cgroup *pids = css_pids(seq_css(sf));
364 enum pidcg_event pe = PIDCG_MAX;
365 atomic64_t *events;
366
367 if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
368 cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
369 pe = PIDCG_FORKFAIL;
370 local = true;
371 }
372 events = local ? pids->events_local : pids->events;
373
374 seq_printf(sf, "max %lld\n", (s64)atomic64_read(&events[pe]));
375 return 0;
376}
377
378static int pids_events_show(struct seq_file *sf, void *v)
379{
380 __pids_events_show(sf, false);
381 return 0;
382}
383
384static int pids_events_local_show(struct seq_file *sf, void *v)
385{
386 __pids_events_show(sf, true);
387 return 0;
388}
389
390static struct cftype pids_files[] = {
391 {
392 .name = "max",
393 .write = pids_max_write,
394 .seq_show = pids_max_show,
395 .flags = CFTYPE_NOT_ON_ROOT,
396 },
397 {
398 .name = "current",
399 .read_s64 = pids_current_read,
400 .flags = CFTYPE_NOT_ON_ROOT,
401 },
402 {
403 .name = "peak",
404 .flags = CFTYPE_NOT_ON_ROOT,
405 .read_s64 = pids_peak_read,
406 },
407 {
408 .name = "events",
409 .seq_show = pids_events_show,
410 .file_offset = offsetof(struct pids_cgroup, events_file),
411 .flags = CFTYPE_NOT_ON_ROOT,
412 },
413 {
414 .name = "events.local",
415 .seq_show = pids_events_local_show,
416 .file_offset = offsetof(struct pids_cgroup, events_local_file),
417 .flags = CFTYPE_NOT_ON_ROOT,
418 },
419 { } /* terminate */
420};
421
422static struct cftype pids_files_legacy[] = {
423 {
424 .name = "max",
425 .write = pids_max_write,
426 .seq_show = pids_max_show,
427 .flags = CFTYPE_NOT_ON_ROOT,
428 },
429 {
430 .name = "current",
431 .read_s64 = pids_current_read,
432 .flags = CFTYPE_NOT_ON_ROOT,
433 },
434 {
435 .name = "peak",
436 .flags = CFTYPE_NOT_ON_ROOT,
437 .read_s64 = pids_peak_read,
438 },
439 {
440 .name = "events",
441 .seq_show = pids_events_show,
442 .file_offset = offsetof(struct pids_cgroup, events_file),
443 .flags = CFTYPE_NOT_ON_ROOT,
444 },
445 { } /* terminate */
446};
447
448
449struct cgroup_subsys pids_cgrp_subsys = {
450 .css_alloc = pids_css_alloc,
451 .css_free = pids_css_free,
452 .can_attach = pids_can_attach,
453 .cancel_attach = pids_cancel_attach,
454 .can_fork = pids_can_fork,
455 .cancel_fork = pids_cancel_fork,
456 .release = pids_release,
457 .legacy_cftypes = pids_files_legacy,
458 .dfl_cftypes = pids_files,
459 .threaded = true,
460};
1/*
2 * Process number limiting controller for cgroups.
3 *
4 * Used to allow a cgroup hierarchy to stop any new processes from fork()ing
5 * after a certain limit is reached.
6 *
7 * Since it is trivial to hit the task limit without hitting any kmemcg limits
8 * in place, PIDs are a fundamental resource. As such, PID exhaustion must be
9 * preventable in the scope of a cgroup hierarchy by allowing resource limiting
10 * of the number of tasks in a cgroup.
11 *
12 * In order to use the `pids` controller, set the maximum number of tasks in
13 * pids.max (this is not available in the root cgroup for obvious reasons). The
14 * number of processes currently in the cgroup is given by pids.current.
15 * Organisational operations are not blocked by cgroup policies, so it is
16 * possible to have pids.current > pids.max. However, it is not possible to
17 * violate a cgroup policy through fork(). fork() will return -EAGAIN if forking
18 * would cause a cgroup policy to be violated.
19 *
20 * To set a cgroup to have no limit, set pids.max to "max". This is the default
21 * for all new cgroups (N.B. that PID limits are hierarchical, so the most
22 * stringent limit in the hierarchy is followed).
23 *
24 * pids.current tracks all child cgroup hierarchies, so parent/pids.current is
25 * a superset of parent/child/pids.current.
26 *
27 * Copyright (C) 2015 Aleksa Sarai <cyphar@cyphar.com>
28 *
29 * This file is subject to the terms and conditions of version 2 of the GNU
30 * General Public License. See the file COPYING in the main directory of the
31 * Linux distribution for more details.
32 */
33
34#include <linux/kernel.h>
35#include <linux/threads.h>
36#include <linux/atomic.h>
37#include <linux/cgroup.h>
38#include <linux/slab.h>
39
40#define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
41#define PIDS_MAX_STR "max"
42
43struct pids_cgroup {
44 struct cgroup_subsys_state css;
45
46 /*
47 * Use 64-bit types so that we can safely represent "max" as
48 * %PIDS_MAX = (%PID_MAX_LIMIT + 1).
49 */
50 atomic64_t counter;
51 int64_t limit;
52
53 /* Handle for "pids.events" */
54 struct cgroup_file events_file;
55
56 /* Number of times fork failed because limit was hit. */
57 atomic64_t events_limit;
58};
59
60static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
61{
62 return container_of(css, struct pids_cgroup, css);
63}
64
65static struct pids_cgroup *parent_pids(struct pids_cgroup *pids)
66{
67 return css_pids(pids->css.parent);
68}
69
70static struct cgroup_subsys_state *
71pids_css_alloc(struct cgroup_subsys_state *parent)
72{
73 struct pids_cgroup *pids;
74
75 pids = kzalloc(sizeof(struct pids_cgroup), GFP_KERNEL);
76 if (!pids)
77 return ERR_PTR(-ENOMEM);
78
79 pids->limit = PIDS_MAX;
80 atomic64_set(&pids->counter, 0);
81 atomic64_set(&pids->events_limit, 0);
82 return &pids->css;
83}
84
85static void pids_css_free(struct cgroup_subsys_state *css)
86{
87 kfree(css_pids(css));
88}
89
90/**
91 * pids_cancel - uncharge the local pid count
92 * @pids: the pid cgroup state
93 * @num: the number of pids to cancel
94 *
95 * This function will WARN if the pid count goes under 0, because such a case is
96 * a bug in the pids controller proper.
97 */
98static void pids_cancel(struct pids_cgroup *pids, int num)
99{
100 /*
101 * A negative count (or overflow for that matter) is invalid,
102 * and indicates a bug in the `pids` controller proper.
103 */
104 WARN_ON_ONCE(atomic64_add_negative(-num, &pids->counter));
105}
106
107/**
108 * pids_uncharge - hierarchically uncharge the pid count
109 * @pids: the pid cgroup state
110 * @num: the number of pids to uncharge
111 */
112static void pids_uncharge(struct pids_cgroup *pids, int num)
113{
114 struct pids_cgroup *p;
115
116 for (p = pids; parent_pids(p); p = parent_pids(p))
117 pids_cancel(p, num);
118}
119
120/**
121 * pids_charge - hierarchically charge the pid count
122 * @pids: the pid cgroup state
123 * @num: the number of pids to charge
124 *
125 * This function does *not* follow the pid limit set. It cannot fail and the new
126 * pid count may exceed the limit. This is only used for reverting failed
127 * attaches, where there is no other way out than violating the limit.
128 */
129static void pids_charge(struct pids_cgroup *pids, int num)
130{
131 struct pids_cgroup *p;
132
133 for (p = pids; parent_pids(p); p = parent_pids(p))
134 atomic64_add(num, &p->counter);
135}
136
137/**
138 * pids_try_charge - hierarchically try to charge the pid count
139 * @pids: the pid cgroup state
140 * @num: the number of pids to charge
141 *
142 * This function follows the set limit. It will fail if the charge would cause
143 * the new value to exceed the hierarchical limit. Returns 0 if the charge
144 * succeeded, otherwise -EAGAIN.
145 */
146static int pids_try_charge(struct pids_cgroup *pids, int num)
147{
148 struct pids_cgroup *p, *q;
149
150 for (p = pids; parent_pids(p); p = parent_pids(p)) {
151 int64_t new = atomic64_add_return(num, &p->counter);
152
153 /*
154 * Since new is capped to the maximum number of pid_t, if
155 * p->limit is %PIDS_MAX then we know that this test will never
156 * fail.
157 */
158 if (new > p->limit)
159 goto revert;
160 }
161
162 return 0;
163
164revert:
165 for (q = pids; q != p; q = parent_pids(q))
166 pids_cancel(q, num);
167 pids_cancel(p, num);
168
169 return -EAGAIN;
170}
171
172static int pids_can_attach(struct cgroup_taskset *tset)
173{
174 struct task_struct *task;
175 struct cgroup_subsys_state *dst_css;
176
177 cgroup_taskset_for_each(task, dst_css, tset) {
178 struct pids_cgroup *pids = css_pids(dst_css);
179 struct cgroup_subsys_state *old_css;
180 struct pids_cgroup *old_pids;
181
182 /*
183 * No need to pin @old_css between here and cancel_attach()
184 * because cgroup core protects it from being freed before
185 * the migration completes or fails.
186 */
187 old_css = task_css(task, pids_cgrp_id);
188 old_pids = css_pids(old_css);
189
190 pids_charge(pids, 1);
191 pids_uncharge(old_pids, 1);
192 }
193
194 return 0;
195}
196
197static void pids_cancel_attach(struct cgroup_taskset *tset)
198{
199 struct task_struct *task;
200 struct cgroup_subsys_state *dst_css;
201
202 cgroup_taskset_for_each(task, dst_css, tset) {
203 struct pids_cgroup *pids = css_pids(dst_css);
204 struct cgroup_subsys_state *old_css;
205 struct pids_cgroup *old_pids;
206
207 old_css = task_css(task, pids_cgrp_id);
208 old_pids = css_pids(old_css);
209
210 pids_charge(old_pids, 1);
211 pids_uncharge(pids, 1);
212 }
213}
214
215/*
216 * task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
217 * on cgroup_threadgroup_change_begin() held by the copy_process().
218 */
219static int pids_can_fork(struct task_struct *task)
220{
221 struct cgroup_subsys_state *css;
222 struct pids_cgroup *pids;
223 int err;
224
225 css = task_css_check(current, pids_cgrp_id, true);
226 pids = css_pids(css);
227 err = pids_try_charge(pids, 1);
228 if (err) {
229 /* Only log the first time events_limit is incremented. */
230 if (atomic64_inc_return(&pids->events_limit) == 1) {
231 pr_info("cgroup: fork rejected by pids controller in ");
232 pr_cont_cgroup_path(css->cgroup);
233 pr_cont("\n");
234 }
235 cgroup_file_notify(&pids->events_file);
236 }
237 return err;
238}
239
240static void pids_cancel_fork(struct task_struct *task)
241{
242 struct cgroup_subsys_state *css;
243 struct pids_cgroup *pids;
244
245 css = task_css_check(current, pids_cgrp_id, true);
246 pids = css_pids(css);
247 pids_uncharge(pids, 1);
248}
249
250static void pids_free(struct task_struct *task)
251{
252 struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id));
253
254 pids_uncharge(pids, 1);
255}
256
257static ssize_t pids_max_write(struct kernfs_open_file *of, char *buf,
258 size_t nbytes, loff_t off)
259{
260 struct cgroup_subsys_state *css = of_css(of);
261 struct pids_cgroup *pids = css_pids(css);
262 int64_t limit;
263 int err;
264
265 buf = strstrip(buf);
266 if (!strcmp(buf, PIDS_MAX_STR)) {
267 limit = PIDS_MAX;
268 goto set_limit;
269 }
270
271 err = kstrtoll(buf, 0, &limit);
272 if (err)
273 return err;
274
275 if (limit < 0 || limit >= PIDS_MAX)
276 return -EINVAL;
277
278set_limit:
279 /*
280 * Limit updates don't need to be mutex'd, since it isn't
281 * critical that any racing fork()s follow the new limit.
282 */
283 pids->limit = limit;
284 return nbytes;
285}
286
287static int pids_max_show(struct seq_file *sf, void *v)
288{
289 struct cgroup_subsys_state *css = seq_css(sf);
290 struct pids_cgroup *pids = css_pids(css);
291 int64_t limit = pids->limit;
292
293 if (limit >= PIDS_MAX)
294 seq_printf(sf, "%s\n", PIDS_MAX_STR);
295 else
296 seq_printf(sf, "%lld\n", limit);
297
298 return 0;
299}
300
301static s64 pids_current_read(struct cgroup_subsys_state *css,
302 struct cftype *cft)
303{
304 struct pids_cgroup *pids = css_pids(css);
305
306 return atomic64_read(&pids->counter);
307}
308
309static int pids_events_show(struct seq_file *sf, void *v)
310{
311 struct pids_cgroup *pids = css_pids(seq_css(sf));
312
313 seq_printf(sf, "max %lld\n", (s64)atomic64_read(&pids->events_limit));
314 return 0;
315}
316
317static struct cftype pids_files[] = {
318 {
319 .name = "max",
320 .write = pids_max_write,
321 .seq_show = pids_max_show,
322 .flags = CFTYPE_NOT_ON_ROOT,
323 },
324 {
325 .name = "current",
326 .read_s64 = pids_current_read,
327 .flags = CFTYPE_NOT_ON_ROOT,
328 },
329 {
330 .name = "events",
331 .seq_show = pids_events_show,
332 .file_offset = offsetof(struct pids_cgroup, events_file),
333 .flags = CFTYPE_NOT_ON_ROOT,
334 },
335 { } /* terminate */
336};
337
338struct cgroup_subsys pids_cgrp_subsys = {
339 .css_alloc = pids_css_alloc,
340 .css_free = pids_css_free,
341 .can_attach = pids_can_attach,
342 .cancel_attach = pids_cancel_attach,
343 .can_fork = pids_can_fork,
344 .cancel_fork = pids_cancel_fork,
345 .free = pids_free,
346 .legacy_cftypes = pids_files,
347 .dfl_cftypes = pids_files,
348 .threaded = true,
349};