Line data Source code
1 : /*
2 : * Generic process-grouping system.
3 : *
4 : * Based originally on the cpuset system, extracted by Paul Menage
5 : * Copyright (C) 2006 Google, Inc
6 : *
7 : * Notifications support
8 : * Copyright (C) 2009 Nokia Corporation
9 : * Author: Kirill A. Shutemov
10 : *
11 : * Copyright notices from the original cpuset code:
12 : * --------------------------------------------------
13 : * Copyright (C) 2003 BULL SA.
14 : * Copyright (C) 2004-2006 Silicon Graphics, Inc.
15 : *
16 : * Portions derived from Patrick Mochel's sysfs code.
17 : * sysfs is Copyright (c) 2001-3 Patrick Mochel
18 : *
19 : * 2003-10-10 Written by Simon Derr.
20 : * 2003-10-22 Updates by Stephen Hemminger.
21 : * 2004 May-July Rework by Paul Jackson.
22 : * ---------------------------------------------------
23 : *
24 : * This file is subject to the terms and conditions of the GNU General Public
25 : * License. See the file COPYING in the main directory of the Linux
26 : * distribution for more details.
27 : */
28 :
29 : #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
30 :
31 : #include <linux/cgroup.h>
32 : #include <linux/cred.h>
33 : #include <linux/ctype.h>
34 : #include <linux/errno.h>
35 : #include <linux/init_task.h>
36 : #include <linux/kernel.h>
37 : #include <linux/list.h>
38 : #include <linux/magic.h>
39 : #include <linux/mm.h>
40 : #include <linux/mutex.h>
41 : #include <linux/mount.h>
42 : #include <linux/pagemap.h>
43 : #include <linux/proc_fs.h>
44 : #include <linux/rcupdate.h>
45 : #include <linux/sched.h>
46 : #include <linux/slab.h>
47 : #include <linux/spinlock.h>
48 : #include <linux/rwsem.h>
49 : #include <linux/string.h>
50 : #include <linux/sort.h>
51 : #include <linux/kmod.h>
52 : #include <linux/delayacct.h>
53 : #include <linux/cgroupstats.h>
54 : #include <linux/hashtable.h>
55 : #include <linux/pid_namespace.h>
56 : #include <linux/idr.h>
57 : #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
58 : #include <linux/kthread.h>
59 : #include <linux/delay.h>
60 :
61 : #include <linux/atomic.h>
62 :
63 : /*
64 : * pidlists linger the following amount before being destroyed. The goal
65 : * is avoiding frequent destruction in the middle of consecutive read calls
66 : * Expiring in the middle is a performance problem not a correctness one.
67 : * 1 sec should be enough.
68 : */
69 : #define CGROUP_PIDLIST_DESTROY_DELAY HZ
70 :
71 : #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
72 : MAX_CFTYPE_NAME + 2)
73 :
74 : /*
75 : * cgroup_mutex is the master lock. Any modification to cgroup or its
76 : * hierarchy must be performed while holding it.
77 : *
78 : * css_set_rwsem protects task->cgroups pointer, the list of css_set
79 : * objects, and the chain of tasks off each css_set.
80 : *
81 : * These locks are exported if CONFIG_PROVE_RCU so that accessors in
82 : * cgroup.h can use them for lockdep annotations.
83 : */
84 : #ifdef CONFIG_PROVE_RCU
85 : DEFINE_MUTEX(cgroup_mutex);
86 : DECLARE_RWSEM(css_set_rwsem);
87 : EXPORT_SYMBOL_GPL(cgroup_mutex);
88 : EXPORT_SYMBOL_GPL(css_set_rwsem);
89 : #else
90 : static DEFINE_MUTEX(cgroup_mutex);
91 : static DECLARE_RWSEM(css_set_rwsem);
92 : #endif
93 :
94 : /*
95 : * Protects cgroup_idr and css_idr so that IDs can be released without
96 : * grabbing cgroup_mutex.
97 : */
98 : static DEFINE_SPINLOCK(cgroup_idr_lock);
99 :
100 : /*
101 : * Protects cgroup_subsys->release_agent_path. Modifying it also requires
102 : * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
103 : */
104 : static DEFINE_SPINLOCK(release_agent_path_lock);
105 :
106 : #define cgroup_assert_mutex_or_rcu_locked() \
107 : rcu_lockdep_assert(rcu_read_lock_held() || \
108 : lockdep_is_held(&cgroup_mutex), \
109 : "cgroup_mutex or RCU read lock required");
110 :
111 : /*
112 : * cgroup destruction makes heavy use of work items and there can be a lot
113 : * of concurrent destructions. Use a separate workqueue so that cgroup
114 : * destruction work items don't end up filling up max_active of system_wq
115 : * which may lead to deadlock.
116 : */
117 : static struct workqueue_struct *cgroup_destroy_wq;
118 :
119 : /*
120 : * pidlist destructions need to be flushed on cgroup destruction. Use a
121 : * separate workqueue as flush domain.
122 : */
123 : static struct workqueue_struct *cgroup_pidlist_destroy_wq;
124 :
125 : /* generate an array of cgroup subsystem pointers */
126 : #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
127 : static struct cgroup_subsys *cgroup_subsys[] = {
128 : #include <linux/cgroup_subsys.h>
129 : };
130 : #undef SUBSYS
131 :
132 : /* array of cgroup subsystem names */
133 : #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
134 : static const char *cgroup_subsys_name[] = {
135 : #include <linux/cgroup_subsys.h>
136 : };
137 : #undef SUBSYS
138 :
139 : /*
140 : * The default hierarchy, reserved for the subsystems that are otherwise
141 : * unattached - it never has more than a single cgroup, and all tasks are
142 : * part of that cgroup.
143 : */
144 : struct cgroup_root cgrp_dfl_root;
145 :
146 : /*
147 : * The default hierarchy always exists but is hidden until mounted for the
148 : * first time. This is for backward compatibility.
149 : */
150 : static bool cgrp_dfl_root_visible;
151 :
152 : /*
153 : * Set by the boot param of the same name and makes subsystems with NULL
154 : * ->dfl_files to use ->legacy_files on the default hierarchy.
155 : */
156 : static bool cgroup_legacy_files_on_dfl;
157 :
158 : /* some controllers are not supported in the default hierarchy */
159 : static unsigned int cgrp_dfl_root_inhibit_ss_mask;
160 :
161 : /* The list of hierarchy roots */
162 :
163 : static LIST_HEAD(cgroup_roots);
164 : static int cgroup_root_count;
165 :
166 : /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
167 : static DEFINE_IDR(cgroup_hierarchy_idr);
168 :
169 : /*
170 : * Assign a monotonically increasing serial number to csses. It guarantees
171 : * cgroups with bigger numbers are newer than those with smaller numbers.
172 : * Also, as csses are always appended to the parent's ->children list, it
173 : * guarantees that sibling csses are always sorted in the ascending serial
174 : * number order on the list. Protected by cgroup_mutex.
175 : */
176 : static u64 css_serial_nr_next = 1;
177 :
178 : /* This flag indicates whether tasks in the fork and exit paths should
179 : * check for fork/exit handlers to call. This avoids us having to do
180 : * extra work in the fork/exit path if none of the subsystems need to
181 : * be called.
182 : */
183 : static int need_forkexit_callback __read_mostly;
184 :
185 : static struct cftype cgroup_dfl_base_files[];
186 : static struct cftype cgroup_legacy_base_files[];
187 :
188 : static int rebind_subsystems(struct cgroup_root *dst_root,
189 : unsigned int ss_mask);
190 : static int cgroup_destroy_locked(struct cgroup *cgrp);
191 : static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
192 : bool visible);
193 : static void css_release(struct percpu_ref *ref);
194 : static void kill_css(struct cgroup_subsys_state *css);
195 : static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
196 : bool is_add);
197 :
198 : /* IDR wrappers which synchronize using cgroup_idr_lock */
199 8 : static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
200 : gfp_t gfp_mask)
201 : {
202 : int ret;
203 :
204 8 : idr_preload(gfp_mask);
205 : spin_lock_bh(&cgroup_idr_lock);
206 8 : ret = idr_alloc(idr, ptr, start, end, gfp_mask);
207 : spin_unlock_bh(&cgroup_idr_lock);
208 : idr_preload_end();
209 8 : return ret;
210 : }
211 :
212 0 : static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
213 : {
214 : void *ret;
215 :
216 : spin_lock_bh(&cgroup_idr_lock);
217 0 : ret = idr_replace(idr, ptr, id);
218 : spin_unlock_bh(&cgroup_idr_lock);
219 0 : return ret;
220 : }
221 :
222 0 : static void cgroup_idr_remove(struct idr *idr, int id)
223 : {
224 : spin_lock_bh(&cgroup_idr_lock);
225 0 : idr_remove(idr, id);
226 : spin_unlock_bh(&cgroup_idr_lock);
227 0 : }
228 :
229 : static struct cgroup *cgroup_parent(struct cgroup *cgrp)
230 : {
231 : struct cgroup_subsys_state *parent_css = cgrp->self.parent;
232 :
233 11 : if (parent_css)
234 : return container_of(parent_css, struct cgroup, self);
235 : return NULL;
236 : }
237 :
238 : /**
239 : * cgroup_css - obtain a cgroup's css for the specified subsystem
240 : * @cgrp: the cgroup of interest
241 : * @ss: the subsystem of interest (%NULL returns @cgrp->self)
242 : *
243 : * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
244 : * function must be called either under cgroup_mutex or rcu_read_lock() and
245 : * the caller is responsible for pinning the returned css if it wants to
246 : * keep accessing it outside the said locks. This function may return
247 : * %NULL if @cgrp doesn't have @subsys_id enabled.
248 : */
249 : static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
250 : struct cgroup_subsys *ss)
251 : {
252 30 : if (ss)
253 30 : return rcu_dereference_check(cgrp->subsys[ss->id],
254 : lockdep_is_held(&cgroup_mutex));
255 : else
256 0 : return &cgrp->self;
257 : }
258 :
259 : /**
260 : * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
261 : * @cgrp: the cgroup of interest
262 : * @ss: the subsystem of interest (%NULL returns @cgrp->self)
263 : *
264 : * Similar to cgroup_css() but returns the effctive css, which is defined
265 : * as the matching css of the nearest ancestor including self which has @ss
266 : * enabled. If @ss is associated with the hierarchy @cgrp is on, this
267 : * function is guaranteed to return non-NULL css.
268 : */
269 0 : static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
270 : struct cgroup_subsys *ss)
271 : {
272 : lockdep_assert_held(&cgroup_mutex);
273 :
274 0 : if (!ss)
275 0 : return &cgrp->self;
276 :
277 0 : if (!(cgrp->root->subsys_mask & (1 << ss->id)))
278 : return NULL;
279 :
280 : /*
281 : * This function is used while updating css associations and thus
282 : * can't test the csses directly. Use ->child_subsys_mask.
283 : */
284 0 : while (cgroup_parent(cgrp) &&
285 0 : !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id)))
286 : cgrp = cgroup_parent(cgrp);
287 :
288 0 : return cgroup_css(cgrp, ss);
289 : }
290 :
291 : /**
292 : * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
293 : * @cgrp: the cgroup of interest
294 : * @ss: the subsystem of interest
295 : *
296 : * Find and get the effective css of @cgrp for @ss. The effective css is
297 : * defined as the matching css of the nearest ancestor including self which
298 : * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
299 : * the root css is returned, so this function always returns a valid css.
300 : * The returned css must be put using css_put().
301 : */
302 0 : struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
303 : struct cgroup_subsys *ss)
304 : {
305 : struct cgroup_subsys_state *css;
306 :
307 : rcu_read_lock();
308 :
309 : do {
310 : css = cgroup_css(cgrp, ss);
311 :
312 0 : if (css && css_tryget_online(css))
313 : goto out_unlock;
314 : cgrp = cgroup_parent(cgrp);
315 0 : } while (cgrp);
316 :
317 0 : css = init_css_set.subsys[ss->id];
318 : css_get(css);
319 : out_unlock:
320 : rcu_read_unlock();
321 0 : return css;
322 : }
323 :
324 : /* convenient tests for these bits */
325 : static inline bool cgroup_is_dead(const struct cgroup *cgrp)
326 : {
327 8 : return !(cgrp->self.flags & CSS_ONLINE);
328 : }
329 :
330 0 : struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
331 : {
332 0 : struct cgroup *cgrp = of->kn->parent->priv;
333 : struct cftype *cft = of_cft(of);
334 :
335 : /*
336 : * This is open and unprotected implementation of cgroup_css().
337 : * seq_css() is only called from a kernfs file operation which has
338 : * an active reference on the file. Because all the subsystem
339 : * files are drained before a css is disassociated with a cgroup,
340 : * the matching css from the cgroup's subsys table is guaranteed to
341 : * be and stay valid until the enclosing operation is complete.
342 : */
343 0 : if (cft->ss)
344 0 : return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
345 : else
346 0 : return &cgrp->self;
347 : }
348 : EXPORT_SYMBOL_GPL(of_css);
349 :
350 : /**
351 : * cgroup_is_descendant - test ancestry
352 : * @cgrp: the cgroup to be tested
353 : * @ancestor: possible ancestor of @cgrp
354 : *
355 : * Test whether @cgrp is a descendant of @ancestor. It also returns %true
356 : * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
357 : * and @ancestor are accessible.
358 : */
359 0 : bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
360 : {
361 0 : while (cgrp) {
362 0 : if (cgrp == ancestor)
363 : return true;
364 : cgrp = cgroup_parent(cgrp);
365 : }
366 : return false;
367 : }
368 :
369 : static int notify_on_release(const struct cgroup *cgrp)
370 : {
371 : return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
372 : }
373 :
374 : /**
375 : * for_each_css - iterate all css's of a cgroup
376 : * @css: the iteration cursor
377 : * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
378 : * @cgrp: the target cgroup to iterate css's of
379 : *
380 : * Should be called under cgroup_[tree_]mutex.
381 : */
382 : #define for_each_css(css, ssid, cgrp) \
383 : for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
384 : if (!((css) = rcu_dereference_check( \
385 : (cgrp)->subsys[(ssid)], \
386 : lockdep_is_held(&cgroup_mutex)))) { } \
387 : else
388 :
389 : /**
390 : * for_each_e_css - iterate all effective css's of a cgroup
391 : * @css: the iteration cursor
392 : * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
393 : * @cgrp: the target cgroup to iterate css's of
394 : *
395 : * Should be called under cgroup_[tree_]mutex.
396 : */
397 : #define for_each_e_css(css, ssid, cgrp) \
398 : for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
399 : if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
400 : ; \
401 : else
402 :
403 : /**
404 : * for_each_subsys - iterate all enabled cgroup subsystems
405 : * @ss: the iteration cursor
406 : * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
407 : */
408 : #define for_each_subsys(ss, ssid) \
409 : for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
410 : (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
411 :
412 : /* iterate across the hierarchies */
413 : #define for_each_root(root) \
414 : list_for_each_entry((root), &cgroup_roots, root_list)
415 :
416 : /* iterate over child cgrps, lock should be held throughout iteration */
417 : #define cgroup_for_each_live_child(child, cgrp) \
418 : list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
419 : if (({ lockdep_assert_held(&cgroup_mutex); \
420 : cgroup_is_dead(child); })) \
421 : ; \
422 : else
423 :
424 : static void cgroup_release_agent(struct work_struct *work);
425 : static void check_for_release(struct cgroup *cgrp);
426 :
427 : /*
428 : * A cgroup can be associated with multiple css_sets as different tasks may
429 : * belong to different cgroups on different hierarchies. In the other
430 : * direction, a css_set is naturally associated with multiple cgroups.
431 : * This M:N relationship is represented by the following link structure
432 : * which exists for each association and allows traversing the associations
433 : * from both sides.
434 : */
435 : struct cgrp_cset_link {
436 : /* the cgroup and css_set this link associates */
437 : struct cgroup *cgrp;
438 : struct css_set *cset;
439 :
440 : /* list of cgrp_cset_links anchored at cgrp->cset_links */
441 : struct list_head cset_link;
442 :
443 : /* list of cgrp_cset_links anchored at css_set->cgrp_links */
444 : struct list_head cgrp_link;
445 : };
446 :
447 : /*
448 : * The default css_set - used by init and its children prior to any
449 : * hierarchies being mounted. It contains a pointer to the root state
450 : * for each subsystem. Also used to anchor the list of css_sets. Not
451 : * reference-counted, to improve performance when child cgroups
452 : * haven't been created.
453 : */
454 : struct css_set init_css_set = {
455 : .refcount = ATOMIC_INIT(1),
456 : .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
457 : .tasks = LIST_HEAD_INIT(init_css_set.tasks),
458 : .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
459 : .mg_preload_node = LIST_HEAD_INIT(init_css_set.mg_preload_node),
460 : .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
461 : };
462 :
463 : static int css_set_count = 1; /* 1 for init_css_set */
464 :
465 : /**
466 : * cgroup_update_populated - updated populated count of a cgroup
467 : * @cgrp: the target cgroup
468 : * @populated: inc or dec populated count
469 : *
470 : * @cgrp is either getting the first task (css_set) or losing the last.
471 : * Update @cgrp->populated_cnt accordingly. The count is propagated
472 : * towards root so that a given cgroup's populated_cnt is zero iff the
473 : * cgroup and all its descendants are empty.
474 : *
475 : * @cgrp's interface file "cgroup.populated" is zero if
476 : * @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt
477 : * changes from or to zero, userland is notified that the content of the
478 : * interface file has changed. This can be used to detect when @cgrp and
479 : * its descendants become populated or empty.
480 : */
481 2 : static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
482 : {
483 : lockdep_assert_held(&css_set_rwsem);
484 :
485 : do {
486 : bool trigger;
487 :
488 1 : if (populated)
489 1 : trigger = !cgrp->populated_cnt++;
490 : else
491 0 : trigger = !--cgrp->populated_cnt;
492 :
493 1 : if (!trigger)
494 : break;
495 :
496 1 : if (cgrp->populated_kn)
497 0 : kernfs_notify(cgrp->populated_kn);
498 : cgrp = cgroup_parent(cgrp);
499 1 : } while (cgrp);
500 1 : }
501 :
502 : /*
503 : * hash table for cgroup groups. This improves the performance to find
504 : * an existing css_set. This hash doesn't (currently) take into
505 : * account cgroups in empty hierarchies.
506 : */
507 : #define CSS_SET_HASH_BITS 7
508 : static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
509 :
510 : static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
511 : {
512 : unsigned long key = 0UL;
513 : struct cgroup_subsys *ss;
514 : int i;
515 :
516 15 : for_each_subsys(ss, i)
517 7 : key += (unsigned long)css[i];
518 1 : key = (key >> 16) ^ key;
519 :
520 : return key;
521 : }
522 :
523 0 : static void put_css_set_locked(struct css_set *cset)
524 : {
525 : struct cgrp_cset_link *link, *tmp_link;
526 : struct cgroup_subsys *ss;
527 : int ssid;
528 :
529 : lockdep_assert_held(&css_set_rwsem);
530 :
531 0 : if (!atomic_dec_and_test(&cset->refcount))
532 0 : return;
533 :
534 : /* This css_set is dead. unlink it and release cgroup refcounts */
535 0 : for_each_subsys(ss, ssid)
536 0 : list_del(&cset->e_cset_node[ssid]);
537 : hash_del(&cset->hlist);
538 0 : css_set_count--;
539 :
540 0 : list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
541 0 : struct cgroup *cgrp = link->cgrp;
542 :
543 : list_del(&link->cset_link);
544 : list_del(&link->cgrp_link);
545 :
546 : /* @cgrp can't go away while we're holding css_set_rwsem */
547 0 : if (list_empty(&cgrp->cset_links)) {
548 0 : cgroup_update_populated(cgrp, false);
549 0 : check_for_release(cgrp);
550 : }
551 :
552 0 : kfree(link);
553 : }
554 :
555 0 : kfree_rcu(cset, rcu_head);
556 : }
557 :
558 887 : static void put_css_set(struct css_set *cset)
559 : {
560 : /*
561 : * Ensure that the refcount doesn't hit zero while any readers
562 : * can see it. Similar to atomic_dec_and_lock(), but for an
563 : * rwlock
564 : */
565 1774 : if (atomic_add_unless(&cset->refcount, -1, 1))
566 887 : return;
567 :
568 0 : down_write(&css_set_rwsem);
569 0 : put_css_set_locked(cset);
570 0 : up_write(&css_set_rwsem);
571 : }
572 :
573 : /*
574 : * refcounted get/put for css_set objects
575 : */
576 : static inline void get_css_set(struct css_set *cset)
577 : {
578 965 : atomic_inc(&cset->refcount);
579 : }
580 :
581 : /**
582 : * compare_css_sets - helper function for find_existing_css_set().
583 : * @cset: candidate css_set being tested
584 : * @old_cset: existing css_set for a task
585 : * @new_cgrp: cgroup that's being entered by the task
586 : * @template: desired set of css pointers in css_set (pre-calculated)
587 : *
588 : * Returns true if "cset" matches "old_cset" except for the hierarchy
589 : * which "new_cgrp" belongs to, for which it should match "new_cgrp".
590 : */
591 0 : static bool compare_css_sets(struct css_set *cset,
592 : struct css_set *old_cset,
593 : struct cgroup *new_cgrp,
594 : struct cgroup_subsys_state *template[])
595 : {
596 : struct list_head *l1, *l2;
597 :
598 : /*
599 : * On the default hierarchy, there can be csets which are
600 : * associated with the same set of cgroups but different csses.
601 : * Let's first ensure that csses match.
602 : */
603 0 : if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
604 : return false;
605 :
606 : /*
607 : * Compare cgroup pointers in order to distinguish between
608 : * different cgroups in hierarchies. As different cgroups may
609 : * share the same effective css, this comparison is always
610 : * necessary.
611 : */
612 0 : l1 = &cset->cgrp_links;
613 0 : l2 = &old_cset->cgrp_links;
614 : while (1) {
615 : struct cgrp_cset_link *link1, *link2;
616 : struct cgroup *cgrp1, *cgrp2;
617 :
618 0 : l1 = l1->next;
619 0 : l2 = l2->next;
620 : /* See if we reached the end - both lists are equal length. */
621 0 : if (l1 == &cset->cgrp_links) {
622 : BUG_ON(l2 != &old_cset->cgrp_links);
623 : break;
624 : } else {
625 : BUG_ON(l2 == &old_cset->cgrp_links);
626 : }
627 : /* Locate the cgroups associated with these links. */
628 : link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
629 : link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
630 0 : cgrp1 = link1->cgrp;
631 0 : cgrp2 = link2->cgrp;
632 : /* Hierarchies should be linked in the same order. */
633 : BUG_ON(cgrp1->root != cgrp2->root);
634 :
635 : /*
636 : * If this hierarchy is the hierarchy of the cgroup
637 : * that's changing, then we need to check that this
638 : * css_set points to the new cgroup; if it's any other
639 : * hierarchy, then this css_set should point to the
640 : * same cgroup as the old css_set.
641 : */
642 0 : if (cgrp1->root == new_cgrp->root) {
643 0 : if (cgrp1 != new_cgrp)
644 : return false;
645 : } else {
646 0 : if (cgrp1 != cgrp2)
647 : return false;
648 : }
649 : }
650 : return true;
651 : }
652 :
653 : /**
654 : * find_existing_css_set - init css array and find the matching css_set
655 : * @old_cset: the css_set that we're using before the cgroup transition
656 : * @cgrp: the cgroup that we're moving into
657 : * @template: out param for the new set of csses, should be clear on entry
658 : */
659 0 : static struct css_set *find_existing_css_set(struct css_set *old_cset,
660 : struct cgroup *cgrp,
661 : struct cgroup_subsys_state *template[])
662 : {
663 0 : struct cgroup_root *root = cgrp->root;
664 : struct cgroup_subsys *ss;
665 : struct css_set *cset;
666 : unsigned long key;
667 : int i;
668 :
669 : /*
670 : * Build the set of subsystem state objects that we want to see in the
671 : * new css_set. while subsystems can change globally, the entries here
672 : * won't change, so no need for locking.
673 : */
674 0 : for_each_subsys(ss, i) {
675 0 : if (root->subsys_mask & (1UL << i)) {
676 : /*
677 : * @ss is in this hierarchy, so we want the
678 : * effective css from @cgrp.
679 : */
680 0 : template[i] = cgroup_e_css(cgrp, ss);
681 : } else {
682 : /*
683 : * @ss is not in this hierarchy, so we don't want
684 : * to change the css.
685 : */
686 0 : template[i] = old_cset->subsys[i];
687 : }
688 : }
689 :
690 : key = css_set_hash(template);
691 0 : hash_for_each_possible(css_set_table, cset, hlist, key) {
692 0 : if (!compare_css_sets(cset, old_cset, cgrp, template))
693 0 : continue;
694 :
695 : /* This css_set matches what we need */
696 : return cset;
697 : }
698 :
699 : /* No existing cgroup group matched */
700 : return NULL;
701 : }
702 :
703 1 : static void free_cgrp_cset_links(struct list_head *links_to_free)
704 : {
705 : struct cgrp_cset_link *link, *tmp_link;
706 :
707 1 : list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
708 : list_del(&link->cset_link);
709 0 : kfree(link);
710 : }
711 1 : }
712 :
713 : /**
714 : * allocate_cgrp_cset_links - allocate cgrp_cset_links
715 : * @count: the number of links to allocate
716 : * @tmp_links: list_head the allocated links are put on
717 : *
718 : * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
719 : * through ->cset_link. Returns 0 on success or -errno.
720 : */
721 1 : static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
722 : {
723 : struct cgrp_cset_link *link;
724 : int i;
725 :
726 : INIT_LIST_HEAD(tmp_links);
727 :
728 2 : for (i = 0; i < count; i++) {
729 : link = kzalloc(sizeof(*link), GFP_KERNEL);
730 1 : if (!link) {
731 0 : free_cgrp_cset_links(tmp_links);
732 0 : return -ENOMEM;
733 : }
734 1 : list_add(&link->cset_link, tmp_links);
735 : }
736 : return 0;
737 : }
738 :
739 : /**
740 : * link_css_set - a helper function to link a css_set to a cgroup
741 : * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
742 : * @cset: the css_set to be linked
743 : * @cgrp: the destination cgroup
744 : */
745 1 : static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
746 1 : struct cgroup *cgrp)
747 : {
748 : struct cgrp_cset_link *link;
749 :
750 : BUG_ON(list_empty(tmp_links));
751 :
752 1 : if (cgroup_on_dfl(cgrp))
753 1 : cset->dfl_cgrp = cgrp;
754 :
755 1 : link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
756 1 : link->cset = cset;
757 1 : link->cgrp = cgrp;
758 :
759 2 : if (list_empty(&cgrp->cset_links))
760 1 : cgroup_update_populated(cgrp, true);
761 1 : list_move(&link->cset_link, &cgrp->cset_links);
762 :
763 : /*
764 : * Always add links to the tail of the list so that the list
765 : * is sorted by order of hierarchy creation
766 : */
767 1 : list_add_tail(&link->cgrp_link, &cset->cgrp_links);
768 1 : }
769 :
770 : /**
771 : * find_css_set - return a new css_set with one cgroup updated
772 : * @old_cset: the baseline css_set
773 : * @cgrp: the cgroup to be updated
774 : *
775 : * Return a new css_set that's equivalent to @old_cset, but with @cgrp
776 : * substituted into the appropriate hierarchy.
777 : */
778 0 : static struct css_set *find_css_set(struct css_set *old_cset,
779 : struct cgroup *cgrp)
780 : {
781 0 : struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
782 : struct css_set *cset;
783 : struct list_head tmp_links;
784 : struct cgrp_cset_link *link;
785 : struct cgroup_subsys *ss;
786 : unsigned long key;
787 : int ssid;
788 :
789 : lockdep_assert_held(&cgroup_mutex);
790 :
791 : /* First see if we already have a cgroup group that matches
792 : * the desired set */
793 0 : down_read(&css_set_rwsem);
794 0 : cset = find_existing_css_set(old_cset, cgrp, template);
795 0 : if (cset)
796 : get_css_set(cset);
797 0 : up_read(&css_set_rwsem);
798 :
799 0 : if (cset)
800 : return cset;
801 :
802 : cset = kzalloc(sizeof(*cset), GFP_KERNEL);
803 0 : if (!cset)
804 : return NULL;
805 :
806 : /* Allocate all the cgrp_cset_link objects that we'll need */
807 0 : if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
808 0 : kfree(cset);
809 0 : return NULL;
810 : }
811 :
812 0 : atomic_set(&cset->refcount, 1);
813 0 : INIT_LIST_HEAD(&cset->cgrp_links);
814 0 : INIT_LIST_HEAD(&cset->tasks);
815 0 : INIT_LIST_HEAD(&cset->mg_tasks);
816 0 : INIT_LIST_HEAD(&cset->mg_preload_node);
817 0 : INIT_LIST_HEAD(&cset->mg_node);
818 : INIT_HLIST_NODE(&cset->hlist);
819 :
820 : /* Copy the set of subsystem state objects generated in
821 : * find_existing_css_set() */
822 0 : memcpy(cset->subsys, template, sizeof(cset->subsys));
823 :
824 0 : down_write(&css_set_rwsem);
825 : /* Add reference counts and links from the new css_set. */
826 0 : list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
827 0 : struct cgroup *c = link->cgrp;
828 :
829 0 : if (c->root == cgrp->root)
830 : c = cgrp;
831 0 : link_css_set(&tmp_links, cset, c);
832 : }
833 :
834 : BUG_ON(!list_empty(&tmp_links));
835 :
836 0 : css_set_count++;
837 :
838 : /* Add @cset to the hash table */
839 : key = css_set_hash(cset->subsys);
840 0 : hash_add(css_set_table, &cset->hlist, key);
841 :
842 0 : for_each_subsys(ss, ssid)
843 0 : list_add_tail(&cset->e_cset_node[ssid],
844 0 : &cset->subsys[ssid]->cgroup->e_csets[ssid]);
845 :
846 0 : up_write(&css_set_rwsem);
847 :
848 0 : return cset;
849 : }
850 :
851 : static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
852 : {
853 0 : struct cgroup *root_cgrp = kf_root->kn->priv;
854 :
855 0 : return root_cgrp->root;
856 : }
857 :
858 1 : static int cgroup_init_root_id(struct cgroup_root *root)
859 : {
860 : int id;
861 :
862 : lockdep_assert_held(&cgroup_mutex);
863 :
864 1 : id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
865 1 : if (id < 0)
866 : return id;
867 :
868 1 : root->hierarchy_id = id;
869 1 : return 0;
870 : }
871 :
872 : static void cgroup_exit_root_id(struct cgroup_root *root)
873 : {
874 : lockdep_assert_held(&cgroup_mutex);
875 :
876 0 : if (root->hierarchy_id) {
877 0 : idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
878 0 : root->hierarchy_id = 0;
879 : }
880 : }
881 :
882 0 : static void cgroup_free_root(struct cgroup_root *root)
883 : {
884 0 : if (root) {
885 : /* hierarhcy ID shoulid already have been released */
886 : WARN_ON_ONCE(root->hierarchy_id);
887 :
888 0 : idr_destroy(&root->cgroup_idr);
889 0 : kfree(root);
890 : }
891 0 : }
892 :
893 0 : static void cgroup_destroy_root(struct cgroup_root *root)
894 : {
895 : struct cgroup *cgrp = &root->cgrp;
896 : struct cgrp_cset_link *link, *tmp_link;
897 :
898 0 : mutex_lock(&cgroup_mutex);
899 :
900 0 : BUG_ON(atomic_read(&root->nr_cgrps));
901 : BUG_ON(!list_empty(&cgrp->self.children));
902 :
903 : /* Rebind all subsystems back to the default hierarchy */
904 0 : rebind_subsystems(&cgrp_dfl_root, root->subsys_mask);
905 :
906 : /*
907 : * Release all the links from cset_links to this hierarchy's
908 : * root cgroup
909 : */
910 0 : down_write(&css_set_rwsem);
911 :
912 0 : list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
913 : list_del(&link->cset_link);
914 : list_del(&link->cgrp_link);
915 0 : kfree(link);
916 : }
917 0 : up_write(&css_set_rwsem);
918 :
919 0 : if (!list_empty(&root->root_list)) {
920 : list_del(&root->root_list);
921 0 : cgroup_root_count--;
922 : }
923 :
924 : cgroup_exit_root_id(root);
925 :
926 0 : mutex_unlock(&cgroup_mutex);
927 :
928 0 : kernfs_destroy_root(root->kf_root);
929 0 : cgroup_free_root(root);
930 0 : }
931 :
932 : /* look up cgroup associated with given css_set on the specified hierarchy */
933 : static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
934 : struct cgroup_root *root)
935 : {
936 : struct cgroup *res = NULL;
937 :
938 : lockdep_assert_held(&cgroup_mutex);
939 : lockdep_assert_held(&css_set_rwsem);
940 :
941 0 : if (cset == &init_css_set) {
942 0 : res = &root->cgrp;
943 : } else {
944 : struct cgrp_cset_link *link;
945 :
946 0 : list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
947 0 : struct cgroup *c = link->cgrp;
948 :
949 0 : if (c->root == root) {
950 : res = c;
951 : break;
952 : }
953 : }
954 : }
955 :
956 : BUG_ON(!res);
957 : return res;
958 : }
959 :
960 : /*
961 : * Return the cgroup for "task" from the given hierarchy. Must be
962 : * called with cgroup_mutex and css_set_rwsem held.
963 : */
964 : static struct cgroup *task_cgroup_from_root(struct task_struct *task,
965 : struct cgroup_root *root)
966 : {
967 : /*
968 : * No need to lock the task - since we hold cgroup_mutex the
969 : * task can't change groups, so the only thing that can happen
970 : * is that it exits and its css is set back to init_css_set.
971 : */
972 : return cset_cgroup_from_root(task_css_set(task), root);
973 : }
974 :
975 : /*
976 : * A task must hold cgroup_mutex to modify cgroups.
977 : *
978 : * Any task can increment and decrement the count field without lock.
979 : * So in general, code holding cgroup_mutex can't rely on the count
980 : * field not changing. However, if the count goes to zero, then only
981 : * cgroup_attach_task() can increment it again. Because a count of zero
982 : * means that no tasks are currently attached, therefore there is no
983 : * way a task attached to that cgroup can fork (the other way to
984 : * increment the count). So code holding cgroup_mutex can safely
985 : * assume that if the count is zero, it will stay zero. Similarly, if
986 : * a task holds cgroup_mutex on a cgroup with zero count, it
987 : * knows that the cgroup won't be removed, as cgroup_rmdir()
988 : * needs that mutex.
989 : *
990 : * A cgroup can only be deleted if both its 'count' of using tasks
991 : * is zero, and its list of 'children' cgroups is empty. Since all
992 : * tasks in the system use _some_ cgroup, and since there is always at
993 : * least one task in the system (init, pid == 1), therefore, root cgroup
994 : * always has either children cgroups and/or using tasks. So we don't
995 : * need a special hack to ensure that root cgroup cannot be deleted.
996 : *
997 : * P.S. One more locking exception. RCU is used to guard the
998 : * update of a tasks cgroup pointer by cgroup_attach_task()
999 : */
1000 :
1001 : static int cgroup_populate_dir(struct cgroup *cgrp, unsigned int subsys_mask);
1002 : static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1003 : static const struct file_operations proc_cgroupstats_operations;
1004 :
1005 3 : static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
1006 : char *buf)
1007 : {
1008 3 : if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
1009 0 : !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
1010 0 : snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
1011 0 : cft->ss->name, cft->name);
1012 : else
1013 3 : strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
1014 3 : return buf;
1015 : }
1016 :
1017 : /**
1018 : * cgroup_file_mode - deduce file mode of a control file
1019 : * @cft: the control file in question
1020 : *
1021 : * returns cft->mode if ->mode is not 0
1022 : * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
1023 : * returns S_IRUGO if it has only a read handler
1024 : * returns S_IWUSR if it has only a write hander
1025 : */
1026 3 : static umode_t cgroup_file_mode(const struct cftype *cft)
1027 : {
1028 : umode_t mode = 0;
1029 :
1030 3 : if (cft->mode)
1031 : return cft->mode;
1032 :
1033 2 : if (cft->read_u64 || cft->read_s64 || cft->seq_show)
1034 : mode |= S_IRUGO;
1035 :
1036 2 : if (cft->write_u64 || cft->write_s64 || cft->write)
1037 1 : mode |= S_IWUSR;
1038 :
1039 2 : return mode;
1040 : }
1041 :
1042 7 : static void cgroup_get(struct cgroup *cgrp)
1043 : {
1044 : WARN_ON_ONCE(cgroup_is_dead(cgrp));
1045 : css_get(&cgrp->self);
1046 7 : }
1047 :
1048 0 : static bool cgroup_tryget(struct cgroup *cgrp)
1049 : {
1050 0 : return css_tryget(&cgrp->self);
1051 : }
1052 :
1053 0 : static void cgroup_put(struct cgroup *cgrp)
1054 : {
1055 : css_put(&cgrp->self);
1056 0 : }
1057 :
1058 : /**
1059 : * cgroup_calc_child_subsys_mask - calculate child_subsys_mask
1060 : * @cgrp: the target cgroup
1061 : * @subtree_control: the new subtree_control mask to consider
1062 : *
1063 : * On the default hierarchy, a subsystem may request other subsystems to be
1064 : * enabled together through its ->depends_on mask. In such cases, more
1065 : * subsystems than specified in "cgroup.subtree_control" may be enabled.
1066 : *
1067 : * This function calculates which subsystems need to be enabled if
1068 : * @subtree_control is to be applied to @cgrp. The returned mask is always
1069 : * a superset of @subtree_control and follows the usual hierarchy rules.
1070 : */
1071 0 : static unsigned int cgroup_calc_child_subsys_mask(struct cgroup *cgrp,
1072 : unsigned int subtree_control)
1073 : {
1074 : struct cgroup *parent = cgroup_parent(cgrp);
1075 : unsigned int cur_ss_mask = subtree_control;
1076 : struct cgroup_subsys *ss;
1077 : int ssid;
1078 :
1079 : lockdep_assert_held(&cgroup_mutex);
1080 :
1081 0 : if (!cgroup_on_dfl(cgrp))
1082 : return cur_ss_mask;
1083 :
1084 : while (true) {
1085 : unsigned int new_ss_mask = cur_ss_mask;
1086 :
1087 0 : for_each_subsys(ss, ssid)
1088 0 : if (cur_ss_mask & (1 << ssid))
1089 0 : new_ss_mask |= ss->depends_on;
1090 :
1091 : /*
1092 : * Mask out subsystems which aren't available. This can
1093 : * happen only if some depended-upon subsystems were bound
1094 : * to non-default hierarchies.
1095 : */
1096 0 : if (parent)
1097 0 : new_ss_mask &= parent->child_subsys_mask;
1098 : else
1099 0 : new_ss_mask &= cgrp->root->subsys_mask;
1100 :
1101 0 : if (new_ss_mask == cur_ss_mask)
1102 : break;
1103 : cur_ss_mask = new_ss_mask;
1104 : }
1105 :
1106 : return cur_ss_mask;
1107 : }
1108 :
1109 : /**
1110 : * cgroup_refresh_child_subsys_mask - update child_subsys_mask
1111 : * @cgrp: the target cgroup
1112 : *
1113 : * Update @cgrp->child_subsys_mask according to the current
1114 : * @cgrp->subtree_control using cgroup_calc_child_subsys_mask().
1115 : */
1116 : static void cgroup_refresh_child_subsys_mask(struct cgroup *cgrp)
1117 : {
1118 0 : cgrp->child_subsys_mask =
1119 0 : cgroup_calc_child_subsys_mask(cgrp, cgrp->subtree_control);
1120 : }
1121 :
1122 : /**
1123 : * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1124 : * @kn: the kernfs_node being serviced
1125 : *
1126 : * This helper undoes cgroup_kn_lock_live() and should be invoked before
1127 : * the method finishes if locking succeeded. Note that once this function
1128 : * returns the cgroup returned by cgroup_kn_lock_live() may become
1129 : * inaccessible any time. If the caller intends to continue to access the
1130 : * cgroup, it should pin it before invoking this function.
1131 : */
1132 0 : static void cgroup_kn_unlock(struct kernfs_node *kn)
1133 : {
1134 : struct cgroup *cgrp;
1135 :
1136 0 : if (kernfs_type(kn) == KERNFS_DIR)
1137 0 : cgrp = kn->priv;
1138 : else
1139 0 : cgrp = kn->parent->priv;
1140 :
1141 0 : mutex_unlock(&cgroup_mutex);
1142 :
1143 0 : kernfs_unbreak_active_protection(kn);
1144 0 : cgroup_put(cgrp);
1145 0 : }
1146 :
1147 : /**
1148 : * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1149 : * @kn: the kernfs_node being serviced
1150 : *
1151 : * This helper is to be used by a cgroup kernfs method currently servicing
1152 : * @kn. It breaks the active protection, performs cgroup locking and
1153 : * verifies that the associated cgroup is alive. Returns the cgroup if
1154 : * alive; otherwise, %NULL. A successful return should be undone by a
1155 : * matching cgroup_kn_unlock() invocation.
1156 : *
1157 : * Any cgroup kernfs method implementation which requires locking the
1158 : * associated cgroup should use this helper. It avoids nesting cgroup
1159 : * locking under kernfs active protection and allows all kernfs operations
1160 : * including self-removal.
1161 : */
1162 0 : static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
1163 : {
1164 0 : struct cgroup *cgrp;
1165 :
1166 0 : if (kernfs_type(kn) == KERNFS_DIR)
1167 0 : cgrp = kn->priv;
1168 : else
1169 0 : cgrp = kn->parent->priv;
1170 :
1171 : /*
1172 : * We're gonna grab cgroup_mutex which nests outside kernfs
1173 : * active_ref. cgroup liveliness check alone provides enough
1174 : * protection against removal. Ensure @cgrp stays accessible and
1175 : * break the active_ref protection.
1176 : */
1177 0 : if (!cgroup_tryget(cgrp))
1178 : return NULL;
1179 0 : kernfs_break_active_protection(kn);
1180 :
1181 0 : mutex_lock(&cgroup_mutex);
1182 :
1183 0 : if (!cgroup_is_dead(cgrp))
1184 : return cgrp;
1185 :
1186 0 : cgroup_kn_unlock(kn);
1187 0 : return NULL;
1188 : }
1189 :
1190 0 : static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1191 : {
1192 : char name[CGROUP_FILE_NAME_MAX];
1193 :
1194 : lockdep_assert_held(&cgroup_mutex);
1195 0 : kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
1196 0 : }
1197 :
1198 : /**
1199 : * cgroup_clear_dir - remove subsys files in a cgroup directory
1200 : * @cgrp: target cgroup
1201 : * @subsys_mask: mask of the subsystem ids whose files should be removed
1202 : */
1203 0 : static void cgroup_clear_dir(struct cgroup *cgrp, unsigned int subsys_mask)
1204 : {
1205 : struct cgroup_subsys *ss;
1206 : int i;
1207 :
1208 0 : for_each_subsys(ss, i) {
1209 : struct cftype *cfts;
1210 :
1211 0 : if (!(subsys_mask & (1 << i)))
1212 0 : continue;
1213 0 : list_for_each_entry(cfts, &ss->cfts, node)
1214 0 : cgroup_addrm_files(cgrp, cfts, false);
1215 : }
1216 0 : }
1217 :
1218 1 : static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask)
1219 : {
1220 : struct cgroup_subsys *ss;
1221 : unsigned int tmp_ss_mask;
1222 : int ssid, i, ret;
1223 :
1224 : lockdep_assert_held(&cgroup_mutex);
1225 :
1226 8 : for_each_subsys(ss, ssid) {
1227 7 : if (!(ss_mask & (1 << ssid)))
1228 7 : continue;
1229 :
1230 : /* if @ss has non-root csses attached to it, can't move */
1231 0 : if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)))
1232 : return -EBUSY;
1233 :
1234 : /* can't move between two non-dummy roots either */
1235 0 : if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1236 : return -EBUSY;
1237 : }
1238 :
1239 : /* skip creating root files on dfl_root for inhibited subsystems */
1240 : tmp_ss_mask = ss_mask;
1241 1 : if (dst_root == &cgrp_dfl_root)
1242 1 : tmp_ss_mask &= ~cgrp_dfl_root_inhibit_ss_mask;
1243 :
1244 1 : ret = cgroup_populate_dir(&dst_root->cgrp, tmp_ss_mask);
1245 1 : if (ret) {
1246 0 : if (dst_root != &cgrp_dfl_root)
1247 : return ret;
1248 :
1249 : /*
1250 : * Rebinding back to the default root is not allowed to
1251 : * fail. Using both default and non-default roots should
1252 : * be rare. Moving subsystems back and forth even more so.
1253 : * Just warn about it and continue.
1254 : */
1255 0 : if (cgrp_dfl_root_visible) {
1256 0 : pr_warn("failed to create files (%d) while rebinding 0x%x to default root\n",
1257 : ret, ss_mask);
1258 0 : pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
1259 : }
1260 : }
1261 :
1262 : /*
1263 : * Nothing can fail from this point on. Remove files for the
1264 : * removed subsystems and rebind each subsystem.
1265 : */
1266 7 : for_each_subsys(ss, ssid)
1267 7 : if (ss_mask & (1 << ssid))
1268 0 : cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
1269 :
1270 7 : for_each_subsys(ss, ssid) {
1271 : struct cgroup_root *src_root;
1272 : struct cgroup_subsys_state *css;
1273 : struct css_set *cset;
1274 :
1275 7 : if (!(ss_mask & (1 << ssid)))
1276 7 : continue;
1277 :
1278 0 : src_root = ss->root;
1279 : css = cgroup_css(&src_root->cgrp, ss);
1280 :
1281 0 : WARN_ON(!css || cgroup_css(&dst_root->cgrp, ss));
1282 :
1283 0 : RCU_INIT_POINTER(src_root->cgrp.subsys[ssid], NULL);
1284 0 : rcu_assign_pointer(dst_root->cgrp.subsys[ssid], css);
1285 0 : ss->root = dst_root;
1286 0 : css->cgroup = &dst_root->cgrp;
1287 :
1288 0 : down_write(&css_set_rwsem);
1289 0 : hash_for_each(css_set_table, i, cset, hlist)
1290 0 : list_move_tail(&cset->e_cset_node[ss->id],
1291 : &dst_root->cgrp.e_csets[ss->id]);
1292 0 : up_write(&css_set_rwsem);
1293 :
1294 0 : src_root->subsys_mask &= ~(1 << ssid);
1295 0 : src_root->cgrp.subtree_control &= ~(1 << ssid);
1296 0 : cgroup_refresh_child_subsys_mask(&src_root->cgrp);
1297 :
1298 : /* default hierarchy doesn't enable controllers by default */
1299 0 : dst_root->subsys_mask |= 1 << ssid;
1300 0 : if (dst_root != &cgrp_dfl_root) {
1301 0 : dst_root->cgrp.subtree_control |= 1 << ssid;
1302 : cgroup_refresh_child_subsys_mask(&dst_root->cgrp);
1303 : }
1304 :
1305 0 : if (ss->bind)
1306 0 : ss->bind(css);
1307 : }
1308 :
1309 1 : kernfs_activate(dst_root->cgrp.kn);
1310 1 : return 0;
1311 : }
1312 :
1313 0 : static int cgroup_show_options(struct seq_file *seq,
1314 0 : struct kernfs_root *kf_root)
1315 : {
1316 : struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1317 : struct cgroup_subsys *ss;
1318 : int ssid;
1319 :
1320 0 : for_each_subsys(ss, ssid)
1321 0 : if (root->subsys_mask & (1 << ssid))
1322 0 : seq_printf(seq, ",%s", ss->name);
1323 0 : if (root->flags & CGRP_ROOT_NOPREFIX)
1324 0 : seq_puts(seq, ",noprefix");
1325 0 : if (root->flags & CGRP_ROOT_XATTR)
1326 0 : seq_puts(seq, ",xattr");
1327 :
1328 : spin_lock(&release_agent_path_lock);
1329 0 : if (strlen(root->release_agent_path))
1330 0 : seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1331 : spin_unlock(&release_agent_path_lock);
1332 :
1333 0 : if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
1334 0 : seq_puts(seq, ",clone_children");
1335 0 : if (strlen(root->name))
1336 0 : seq_printf(seq, ",name=%s", root->name);
1337 0 : return 0;
1338 : }
1339 :
1340 : struct cgroup_sb_opts {
1341 : unsigned int subsys_mask;
1342 : unsigned int flags;
1343 : char *release_agent;
1344 : bool cpuset_clone_children;
1345 : char *name;
1346 : /* User explicitly requested empty subsystem */
1347 : bool none;
1348 : };
1349 :
1350 1 : static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1351 : {
1352 1 : char *token, *o = data;
1353 : bool all_ss = false, one_ss = false;
1354 : unsigned int mask = -1U;
1355 : struct cgroup_subsys *ss;
1356 : int nr_opts = 0;
1357 : int i;
1358 :
1359 : #ifdef CONFIG_CPUSETS
1360 : mask = ~(1U << cpuset_cgrp_id);
1361 : #endif
1362 :
1363 1 : memset(opts, 0, sizeof(*opts));
1364 :
1365 2 : while ((token = strsep(&o, ",")) != NULL) {
1366 1 : nr_opts++;
1367 :
1368 1 : if (!*token)
1369 : return -EINVAL;
1370 1 : if (!strcmp(token, "none")) {
1371 : /* Explicitly have no subsystems */
1372 0 : opts->none = true;
1373 0 : continue;
1374 : }
1375 1 : if (!strcmp(token, "all")) {
1376 : /* Mutually exclusive option 'all' + subsystem name */
1377 0 : if (one_ss)
1378 : return -EINVAL;
1379 : all_ss = true;
1380 0 : continue;
1381 : }
1382 1 : if (!strcmp(token, "__DEVEL__sane_behavior")) {
1383 0 : opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
1384 0 : continue;
1385 : }
1386 1 : if (!strcmp(token, "noprefix")) {
1387 0 : opts->flags |= CGRP_ROOT_NOPREFIX;
1388 0 : continue;
1389 : }
1390 1 : if (!strcmp(token, "clone_children")) {
1391 0 : opts->cpuset_clone_children = true;
1392 0 : continue;
1393 : }
1394 1 : if (!strcmp(token, "xattr")) {
1395 0 : opts->flags |= CGRP_ROOT_XATTR;
1396 0 : continue;
1397 : }
1398 1 : if (!strncmp(token, "release_agent=", 14)) {
1399 : /* Specifying two release agents is forbidden */
1400 0 : if (opts->release_agent)
1401 : return -EINVAL;
1402 0 : opts->release_agent =
1403 0 : kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1404 0 : if (!opts->release_agent)
1405 : return -ENOMEM;
1406 0 : continue;
1407 : }
1408 1 : if (!strncmp(token, "name=", 5)) {
1409 0 : const char *name = token + 5;
1410 : /* Can't specify an empty name */
1411 0 : if (!strlen(name))
1412 : return -EINVAL;
1413 : /* Must match [\w.-]+ */
1414 0 : for (i = 0; i < strlen(name); i++) {
1415 0 : char c = name[i];
1416 0 : if (isalnum(c))
1417 0 : continue;
1418 0 : if ((c == '.') || (c == '-') || (c == '_'))
1419 0 : continue;
1420 : return -EINVAL;
1421 : }
1422 : /* Specifying two names is forbidden */
1423 0 : if (opts->name)
1424 : return -EINVAL;
1425 0 : opts->name = kstrndup(name,
1426 : MAX_CGROUP_ROOT_NAMELEN - 1,
1427 : GFP_KERNEL);
1428 0 : if (!opts->name)
1429 : return -ENOMEM;
1430 :
1431 0 : continue;
1432 : }
1433 :
1434 7 : for_each_subsys(ss, i) {
1435 7 : if (strcmp(token, ss->name))
1436 6 : continue;
1437 1 : if (ss->disabled)
1438 1 : continue;
1439 :
1440 : /* Mutually exclusive option 'all' + subsystem name */
1441 0 : if (all_ss)
1442 : return -EINVAL;
1443 0 : opts->subsys_mask |= (1 << i);
1444 : one_ss = true;
1445 :
1446 0 : break;
1447 : }
1448 1 : if (i == CGROUP_SUBSYS_COUNT)
1449 : return -ENOENT;
1450 : }
1451 :
1452 0 : if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
1453 0 : pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1454 0 : if (nr_opts != 1) {
1455 0 : pr_err("sane_behavior: no other mount options allowed\n");
1456 0 : return -EINVAL;
1457 : }
1458 : return 0;
1459 : }
1460 :
1461 : /*
1462 : * If the 'all' option was specified select all the subsystems,
1463 : * otherwise if 'none', 'name=' and a subsystem name options were
1464 : * not specified, let's default to 'all'
1465 : */
1466 0 : if (all_ss || (!one_ss && !opts->none && !opts->name))
1467 0 : for_each_subsys(ss, i)
1468 0 : if (!ss->disabled)
1469 0 : opts->subsys_mask |= (1 << i);
1470 :
1471 : /*
1472 : * We either have to specify by name or by subsystems. (So all
1473 : * empty hierarchies must have a name).
1474 : */
1475 0 : if (!opts->subsys_mask && !opts->name)
1476 : return -EINVAL;
1477 :
1478 : /*
1479 : * Option noprefix was introduced just for backward compatibility
1480 : * with the old cpuset, so we allow noprefix only if mounting just
1481 : * the cpuset subsystem.
1482 : */
1483 0 : if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1484 : return -EINVAL;
1485 :
1486 : /* Can't specify "none" and some subsystems */
1487 0 : if (opts->subsys_mask && opts->none)
1488 : return -EINVAL;
1489 :
1490 0 : return 0;
1491 : }
1492 :
1493 0 : static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
1494 : {
1495 : int ret = 0;
1496 : struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1497 : struct cgroup_sb_opts opts;
1498 : unsigned int added_mask, removed_mask;
1499 :
1500 0 : if (root == &cgrp_dfl_root) {
1501 0 : pr_err("remount is not allowed\n");
1502 0 : return -EINVAL;
1503 : }
1504 :
1505 0 : mutex_lock(&cgroup_mutex);
1506 :
1507 : /* See what subsystems are wanted */
1508 0 : ret = parse_cgroupfs_options(data, &opts);
1509 0 : if (ret)
1510 : goto out_unlock;
1511 :
1512 0 : if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
1513 0 : pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1514 : task_tgid_nr(current), current->comm);
1515 :
1516 0 : added_mask = opts.subsys_mask & ~root->subsys_mask;
1517 0 : removed_mask = root->subsys_mask & ~opts.subsys_mask;
1518 :
1519 : /* Don't allow flags or name to change at remount */
1520 0 : if ((opts.flags ^ root->flags) ||
1521 0 : (opts.name && strcmp(opts.name, root->name))) {
1522 0 : pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1523 : opts.flags, opts.name ?: "", root->flags, root->name);
1524 : ret = -EINVAL;
1525 0 : goto out_unlock;
1526 : }
1527 :
1528 : /* remounting is not allowed for populated hierarchies */
1529 0 : if (!list_empty(&root->cgrp.self.children)) {
1530 : ret = -EBUSY;
1531 : goto out_unlock;
1532 : }
1533 :
1534 0 : ret = rebind_subsystems(root, added_mask);
1535 0 : if (ret)
1536 : goto out_unlock;
1537 :
1538 0 : rebind_subsystems(&cgrp_dfl_root, removed_mask);
1539 :
1540 0 : if (opts.release_agent) {
1541 : spin_lock(&release_agent_path_lock);
1542 0 : strcpy(root->release_agent_path, opts.release_agent);
1543 : spin_unlock(&release_agent_path_lock);
1544 : }
1545 : out_unlock:
1546 0 : kfree(opts.release_agent);
1547 0 : kfree(opts.name);
1548 0 : mutex_unlock(&cgroup_mutex);
1549 0 : return ret;
1550 : }
1551 :
1552 : /*
1553 : * To reduce the fork() overhead for systems that are not actually using
1554 : * their cgroups capability, we don't maintain the lists running through
1555 : * each css_set to its tasks until we see the list actually used - in other
1556 : * words after the first mount.
1557 : */
1558 : static bool use_task_css_set_links __read_mostly;
1559 :
1560 1 : static void cgroup_enable_task_cg_lists(void)
1561 : {
1562 : struct task_struct *p, *g;
1563 :
1564 1 : down_write(&css_set_rwsem);
1565 :
1566 1 : if (use_task_css_set_links)
1567 : goto out_unlock;
1568 :
1569 1 : use_task_css_set_links = true;
1570 :
1571 : /*
1572 : * We need tasklist_lock because RCU is not safe against
1573 : * while_each_thread(). Besides, a forking task that has passed
1574 : * cgroup_post_fork() without seeing use_task_css_set_links = 1
1575 : * is not guaranteed to have its child immediately visible in the
1576 : * tasklist if we walk through it with RCU.
1577 : */
1578 1 : read_lock(&tasklist_lock);
1579 58 : do_each_thread(g, p) {
1580 112 : WARN_ON_ONCE(!list_empty(&p->cg_list) ||
1581 : task_css_set(p) != &init_css_set);
1582 :
1583 : /*
1584 : * We should check if the process is exiting, otherwise
1585 : * it will race with cgroup_exit() in that the list
1586 : * entry won't be deleted though the process has exited.
1587 : * Do it while holding siglock so that we don't end up
1588 : * racing against cgroup_exit().
1589 : */
1590 : spin_lock_irq(&p->sighand->siglock);
1591 56 : if (!(p->flags & PF_EXITING)) {
1592 : struct css_set *cset = task_css_set(p);
1593 :
1594 56 : list_add(&p->cg_list, &cset->tasks);
1595 : get_css_set(cset);
1596 : }
1597 : spin_unlock_irq(&p->sighand->siglock);
1598 56 : } while_each_thread(g, p);
1599 2 : read_unlock(&tasklist_lock);
1600 : out_unlock:
1601 1 : up_write(&css_set_rwsem);
1602 1 : }
1603 :
1604 1 : static void init_cgroup_housekeeping(struct cgroup *cgrp)
1605 : {
1606 : struct cgroup_subsys *ss;
1607 : int ssid;
1608 :
1609 1 : INIT_LIST_HEAD(&cgrp->self.sibling);
1610 1 : INIT_LIST_HEAD(&cgrp->self.children);
1611 1 : INIT_LIST_HEAD(&cgrp->cset_links);
1612 1 : INIT_LIST_HEAD(&cgrp->pidlists);
1613 1 : mutex_init(&cgrp->pidlist_mutex);
1614 1 : cgrp->self.cgroup = cgrp;
1615 1 : cgrp->self.flags |= CSS_ONLINE;
1616 :
1617 8 : for_each_subsys(ss, ssid)
1618 7 : INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
1619 :
1620 1 : init_waitqueue_head(&cgrp->offline_waitq);
1621 2 : INIT_WORK(&cgrp->release_agent_work, cgroup_release_agent);
1622 1 : }
1623 :
1624 1 : static void init_cgroup_root(struct cgroup_root *root,
1625 : struct cgroup_sb_opts *opts)
1626 : {
1627 1 : struct cgroup *cgrp = &root->cgrp;
1628 :
1629 1 : INIT_LIST_HEAD(&root->root_list);
1630 1 : atomic_set(&root->nr_cgrps, 1);
1631 1 : cgrp->root = root;
1632 1 : init_cgroup_housekeeping(cgrp);
1633 1 : idr_init(&root->cgroup_idr);
1634 :
1635 1 : root->flags = opts->flags;
1636 1 : if (opts->release_agent)
1637 0 : strcpy(root->release_agent_path, opts->release_agent);
1638 1 : if (opts->name)
1639 0 : strcpy(root->name, opts->name);
1640 1 : if (opts->cpuset_clone_children)
1641 : set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
1642 1 : }
1643 :
1644 1 : static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask)
1645 : {
1646 1 : LIST_HEAD(tmp_links);
1647 1 : struct cgroup *root_cgrp = &root->cgrp;
1648 : struct cftype *base_files;
1649 : struct css_set *cset;
1650 : int i, ret;
1651 :
1652 : lockdep_assert_held(&cgroup_mutex);
1653 :
1654 1 : ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_NOWAIT);
1655 1 : if (ret < 0)
1656 : goto out;
1657 1 : root_cgrp->id = ret;
1658 :
1659 1 : ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release, 0,
1660 : GFP_KERNEL);
1661 1 : if (ret)
1662 : goto out;
1663 :
1664 : /*
1665 : * We're accessing css_set_count without locking css_set_rwsem here,
1666 : * but that's OK - it can only be increased by someone holding
1667 : * cgroup_lock, and that's us. The worst that can happen is that we
1668 : * have some link structures left over
1669 : */
1670 1 : ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
1671 1 : if (ret)
1672 : goto cancel_ref;
1673 :
1674 1 : ret = cgroup_init_root_id(root);
1675 1 : if (ret)
1676 : goto cancel_ref;
1677 :
1678 1 : root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
1679 : KERNFS_ROOT_CREATE_DEACTIVATED,
1680 : root_cgrp);
1681 1 : if (IS_ERR(root->kf_root)) {
1682 : ret = PTR_ERR(root->kf_root);
1683 0 : goto exit_root_id;
1684 : }
1685 1 : root_cgrp->kn = root->kf_root->kn;
1686 :
1687 1 : if (root == &cgrp_dfl_root)
1688 : base_files = cgroup_dfl_base_files;
1689 : else
1690 : base_files = cgroup_legacy_base_files;
1691 :
1692 1 : ret = cgroup_addrm_files(root_cgrp, base_files, true);
1693 1 : if (ret)
1694 : goto destroy_root;
1695 :
1696 1 : ret = rebind_subsystems(root, ss_mask);
1697 1 : if (ret)
1698 : goto destroy_root;
1699 :
1700 : /*
1701 : * There must be no failure case after here, since rebinding takes
1702 : * care of subsystems' refcounts, which are explicitly dropped in
1703 : * the failure exit path.
1704 : */
1705 1 : list_add(&root->root_list, &cgroup_roots);
1706 1 : cgroup_root_count++;
1707 :
1708 : /*
1709 : * Link the root cgroup in this hierarchy into all the css_set
1710 : * objects.
1711 : */
1712 1 : down_write(&css_set_rwsem);
1713 2 : hash_for_each(css_set_table, i, cset, hlist)
1714 1 : link_css_set(&tmp_links, cset, root_cgrp);
1715 1 : up_write(&css_set_rwsem);
1716 :
1717 : BUG_ON(!list_empty(&root_cgrp->self.children));
1718 1 : BUG_ON(atomic_read(&root->nr_cgrps) != 1);
1719 :
1720 1 : kernfs_activate(root_cgrp->kn);
1721 : ret = 0;
1722 1 : goto out;
1723 :
1724 : destroy_root:
1725 0 : kernfs_destroy_root(root->kf_root);
1726 0 : root->kf_root = NULL;
1727 : exit_root_id:
1728 : cgroup_exit_root_id(root);
1729 : cancel_ref:
1730 0 : percpu_ref_exit(&root_cgrp->self.refcnt);
1731 : out:
1732 1 : free_cgrp_cset_links(&tmp_links);
1733 1 : return ret;
1734 : }
1735 :
1736 1 : static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1737 : int flags, const char *unused_dev_name,
1738 : void *data)
1739 : {
1740 : struct super_block *pinned_sb = NULL;
1741 : struct cgroup_subsys *ss;
1742 : struct cgroup_root *root;
1743 : struct cgroup_sb_opts opts;
1744 : struct dentry *dentry;
1745 : int ret;
1746 : int i;
1747 : bool new_sb;
1748 :
1749 : /*
1750 : * The first time anyone tries to mount a cgroup, enable the list
1751 : * linking each css_set to its tasks and fix up all existing tasks.
1752 : */
1753 1 : if (!use_task_css_set_links)
1754 1 : cgroup_enable_task_cg_lists();
1755 :
1756 1 : mutex_lock(&cgroup_mutex);
1757 :
1758 : /* First find the desired set of subsystems */
1759 1 : ret = parse_cgroupfs_options(data, &opts);
1760 1 : if (ret)
1761 : goto out_unlock;
1762 :
1763 : /* look for a matching existing root */
1764 0 : if (opts.flags & CGRP_ROOT_SANE_BEHAVIOR) {
1765 0 : cgrp_dfl_root_visible = true;
1766 : root = &cgrp_dfl_root;
1767 0 : cgroup_get(&root->cgrp);
1768 : ret = 0;
1769 0 : goto out_unlock;
1770 : }
1771 :
1772 : /*
1773 : * Destruction of cgroup root is asynchronous, so subsystems may
1774 : * still be dying after the previous unmount. Let's drain the
1775 : * dying subsystems. We just need to ensure that the ones
1776 : * unmounted previously finish dying and don't care about new ones
1777 : * starting. Testing ref liveliness is good enough.
1778 : */
1779 0 : for_each_subsys(ss, i) {
1780 0 : if (!(opts.subsys_mask & (1 << i)) ||
1781 0 : ss->root == &cgrp_dfl_root)
1782 0 : continue;
1783 :
1784 0 : if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
1785 0 : mutex_unlock(&cgroup_mutex);
1786 0 : msleep(10);
1787 : ret = restart_syscall();
1788 0 : goto out_free;
1789 : }
1790 0 : cgroup_put(&ss->root->cgrp);
1791 : }
1792 :
1793 0 : for_each_root(root) {
1794 : bool name_match = false;
1795 :
1796 0 : if (root == &cgrp_dfl_root)
1797 0 : continue;
1798 :
1799 : /*
1800 : * If we asked for a name then it must match. Also, if
1801 : * name matches but sybsys_mask doesn't, we should fail.
1802 : * Remember whether name matched.
1803 : */
1804 0 : if (opts.name) {
1805 0 : if (strcmp(opts.name, root->name))
1806 0 : continue;
1807 : name_match = true;
1808 : }
1809 :
1810 : /*
1811 : * If we asked for subsystems (or explicitly for no
1812 : * subsystems) then they must match.
1813 : */
1814 0 : if ((opts.subsys_mask || opts.none) &&
1815 0 : (opts.subsys_mask != root->subsys_mask)) {
1816 0 : if (!name_match)
1817 0 : continue;
1818 : ret = -EBUSY;
1819 : goto out_unlock;
1820 : }
1821 :
1822 0 : if (root->flags ^ opts.flags)
1823 0 : pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1824 :
1825 : /*
1826 : * We want to reuse @root whose lifetime is governed by its
1827 : * ->cgrp. Let's check whether @root is alive and keep it
1828 : * that way. As cgroup_kill_sb() can happen anytime, we
1829 : * want to block it by pinning the sb so that @root doesn't
1830 : * get killed before mount is complete.
1831 : *
1832 : * With the sb pinned, tryget_live can reliably indicate
1833 : * whether @root can be reused. If it's being killed,
1834 : * drain it. We can use wait_queue for the wait but this
1835 : * path is super cold. Let's just sleep a bit and retry.
1836 : */
1837 0 : pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
1838 0 : if (IS_ERR(pinned_sb) ||
1839 : !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
1840 0 : mutex_unlock(&cgroup_mutex);
1841 0 : if (!IS_ERR_OR_NULL(pinned_sb))
1842 0 : deactivate_super(pinned_sb);
1843 0 : msleep(10);
1844 : ret = restart_syscall();
1845 0 : goto out_free;
1846 : }
1847 :
1848 : ret = 0;
1849 : goto out_unlock;
1850 : }
1851 :
1852 : /*
1853 : * No such thing, create a new one. name= matching without subsys
1854 : * specification is allowed for already existing hierarchies but we
1855 : * can't create new one without subsys specification.
1856 : */
1857 0 : if (!opts.subsys_mask && !opts.none) {
1858 : ret = -EINVAL;
1859 : goto out_unlock;
1860 : }
1861 :
1862 : root = kzalloc(sizeof(*root), GFP_KERNEL);
1863 0 : if (!root) {
1864 : ret = -ENOMEM;
1865 : goto out_unlock;
1866 : }
1867 :
1868 0 : init_cgroup_root(root, &opts);
1869 :
1870 0 : ret = cgroup_setup_root(root, opts.subsys_mask);
1871 0 : if (ret)
1872 0 : cgroup_free_root(root);
1873 :
1874 : out_unlock:
1875 1 : mutex_unlock(&cgroup_mutex);
1876 : out_free:
1877 1 : kfree(opts.release_agent);
1878 1 : kfree(opts.name);
1879 :
1880 1 : if (ret)
1881 1 : return ERR_PTR(ret);
1882 :
1883 0 : dentry = kernfs_mount(fs_type, flags, root->kf_root,
1884 : CGROUP_SUPER_MAGIC, &new_sb);
1885 0 : if (IS_ERR(dentry) || !new_sb)
1886 0 : cgroup_put(&root->cgrp);
1887 :
1888 : /*
1889 : * If @pinned_sb, we're reusing an existing root and holding an
1890 : * extra ref on its sb. Mount is complete. Put the extra ref.
1891 : */
1892 0 : if (pinned_sb) {
1893 : WARN_ON(new_sb);
1894 0 : deactivate_super(pinned_sb);
1895 : }
1896 :
1897 0 : return dentry;
1898 : }
1899 :
1900 0 : static void cgroup_kill_sb(struct super_block *sb)
1901 : {
1902 0 : struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
1903 : struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1904 :
1905 : /*
1906 : * If @root doesn't have any mounts or children, start killing it.
1907 : * This prevents new mounts by disabling percpu_ref_tryget_live().
1908 : * cgroup_mount() may wait for @root's release.
1909 : *
1910 : * And don't kill the default root.
1911 : */
1912 0 : if (!list_empty(&root->cgrp.self.children) ||
1913 : root == &cgrp_dfl_root)
1914 0 : cgroup_put(&root->cgrp);
1915 : else
1916 0 : percpu_ref_kill(&root->cgrp.self.refcnt);
1917 :
1918 0 : kernfs_kill_sb(sb);
1919 0 : }
1920 :
1921 : static struct file_system_type cgroup_fs_type = {
1922 : .name = "cgroup",
1923 : .mount = cgroup_mount,
1924 : .kill_sb = cgroup_kill_sb,
1925 : };
1926 :
1927 : static struct kobject *cgroup_kobj;
1928 :
1929 : /**
1930 : * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1931 : * @task: target task
1932 : * @buf: the buffer to write the path into
1933 : * @buflen: the length of the buffer
1934 : *
1935 : * Determine @task's cgroup on the first (the one with the lowest non-zero
1936 : * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1937 : * function grabs cgroup_mutex and shouldn't be used inside locks used by
1938 : * cgroup controller callbacks.
1939 : *
1940 : * Return value is the same as kernfs_path().
1941 : */
1942 0 : char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
1943 : {
1944 : struct cgroup_root *root;
1945 : struct cgroup *cgrp;
1946 0 : int hierarchy_id = 1;
1947 : char *path = NULL;
1948 :
1949 0 : mutex_lock(&cgroup_mutex);
1950 0 : down_read(&css_set_rwsem);
1951 :
1952 0 : root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
1953 :
1954 0 : if (root) {
1955 : cgrp = task_cgroup_from_root(task, root);
1956 : path = cgroup_path(cgrp, buf, buflen);
1957 : } else {
1958 : /* if no hierarchy exists, everyone is in "/" */
1959 0 : if (strlcpy(buf, "/", buflen) < buflen)
1960 : path = buf;
1961 : }
1962 :
1963 0 : up_read(&css_set_rwsem);
1964 0 : mutex_unlock(&cgroup_mutex);
1965 0 : return path;
1966 : }
1967 : EXPORT_SYMBOL_GPL(task_cgroup_path);
1968 :
1969 : /* used to track tasks and other necessary states during migration */
1970 : struct cgroup_taskset {
1971 : /* the src and dst cset list running through cset->mg_node */
1972 : struct list_head src_csets;
1973 : struct list_head dst_csets;
1974 :
1975 : /*
1976 : * Fields for cgroup_taskset_*() iteration.
1977 : *
1978 : * Before migration is committed, the target migration tasks are on
1979 : * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1980 : * the csets on ->dst_csets. ->csets point to either ->src_csets
1981 : * or ->dst_csets depending on whether migration is committed.
1982 : *
1983 : * ->cur_csets and ->cur_task point to the current task position
1984 : * during iteration.
1985 : */
1986 : struct list_head *csets;
1987 : struct css_set *cur_cset;
1988 : struct task_struct *cur_task;
1989 : };
1990 :
1991 : /**
1992 : * cgroup_taskset_first - reset taskset and return the first task
1993 : * @tset: taskset of interest
1994 : *
1995 : * @tset iteration is initialized and the first task is returned.
1996 : */
1997 0 : struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1998 : {
1999 0 : tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
2000 0 : tset->cur_task = NULL;
2001 :
2002 0 : return cgroup_taskset_next(tset);
2003 : }
2004 :
2005 : /**
2006 : * cgroup_taskset_next - iterate to the next task in taskset
2007 : * @tset: taskset of interest
2008 : *
2009 : * Return the next task in @tset. Iteration must have been initialized
2010 : * with cgroup_taskset_first().
2011 : */
2012 0 : struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
2013 : {
2014 0 : struct css_set *cset = tset->cur_cset;
2015 0 : struct task_struct *task = tset->cur_task;
2016 :
2017 0 : while (&cset->mg_node != tset->csets) {
2018 0 : if (!task)
2019 0 : task = list_first_entry(&cset->mg_tasks,
2020 : struct task_struct, cg_list);
2021 : else
2022 0 : task = list_next_entry(task, cg_list);
2023 :
2024 0 : if (&task->cg_list != &cset->mg_tasks) {
2025 0 : tset->cur_cset = cset;
2026 0 : tset->cur_task = task;
2027 0 : return task;
2028 : }
2029 :
2030 0 : cset = list_next_entry(cset, mg_node);
2031 : task = NULL;
2032 : }
2033 :
2034 : return NULL;
2035 : }
2036 :
2037 : /**
2038 : * cgroup_task_migrate - move a task from one cgroup to another.
2039 : * @old_cgrp: the cgroup @tsk is being migrated from
2040 : * @tsk: the task being migrated
2041 : * @new_cset: the new css_set @tsk is being attached to
2042 : *
2043 : * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
2044 : */
2045 0 : static void cgroup_task_migrate(struct cgroup *old_cgrp,
2046 : struct task_struct *tsk,
2047 : struct css_set *new_cset)
2048 : {
2049 : struct css_set *old_cset;
2050 :
2051 : lockdep_assert_held(&cgroup_mutex);
2052 : lockdep_assert_held(&css_set_rwsem);
2053 :
2054 : /*
2055 : * We are synchronized through threadgroup_lock() against PF_EXITING
2056 : * setting such that we can't race against cgroup_exit() changing the
2057 : * css_set to init_css_set and dropping the old one.
2058 : */
2059 : WARN_ON_ONCE(tsk->flags & PF_EXITING);
2060 : old_cset = task_css_set(tsk);
2061 :
2062 : get_css_set(new_cset);
2063 0 : rcu_assign_pointer(tsk->cgroups, new_cset);
2064 :
2065 : /*
2066 : * Use move_tail so that cgroup_taskset_first() still returns the
2067 : * leader after migration. This works because cgroup_migrate()
2068 : * ensures that the dst_cset of the leader is the first on the
2069 : * tset's dst_csets list.
2070 : */
2071 0 : list_move_tail(&tsk->cg_list, &new_cset->mg_tasks);
2072 :
2073 : /*
2074 : * We just gained a reference on old_cset by taking it from the
2075 : * task. As trading it for new_cset is protected by cgroup_mutex,
2076 : * we're safe to drop it here; it will be freed under RCU.
2077 : */
2078 0 : put_css_set_locked(old_cset);
2079 0 : }
2080 :
2081 : /**
2082 : * cgroup_migrate_finish - cleanup after attach
2083 : * @preloaded_csets: list of preloaded css_sets
2084 : *
2085 : * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2086 : * those functions for details.
2087 : */
2088 0 : static void cgroup_migrate_finish(struct list_head *preloaded_csets)
2089 : {
2090 : struct css_set *cset, *tmp_cset;
2091 :
2092 : lockdep_assert_held(&cgroup_mutex);
2093 :
2094 0 : down_write(&css_set_rwsem);
2095 0 : list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
2096 0 : cset->mg_src_cgrp = NULL;
2097 0 : cset->mg_dst_cset = NULL;
2098 : list_del_init(&cset->mg_preload_node);
2099 0 : put_css_set_locked(cset);
2100 : }
2101 0 : up_write(&css_set_rwsem);
2102 0 : }
2103 :
2104 : /**
2105 : * cgroup_migrate_add_src - add a migration source css_set
2106 : * @src_cset: the source css_set to add
2107 : * @dst_cgrp: the destination cgroup
2108 : * @preloaded_csets: list of preloaded css_sets
2109 : *
2110 : * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2111 : * @src_cset and add it to @preloaded_csets, which should later be cleaned
2112 : * up by cgroup_migrate_finish().
2113 : *
2114 : * This function may be called without holding threadgroup_lock even if the
2115 : * target is a process. Threads may be created and destroyed but as long
2116 : * as cgroup_mutex is not dropped, no new css_set can be put into play and
2117 : * the preloaded css_sets are guaranteed to cover all migrations.
2118 : */
2119 0 : static void cgroup_migrate_add_src(struct css_set *src_cset,
2120 : struct cgroup *dst_cgrp,
2121 : struct list_head *preloaded_csets)
2122 : {
2123 : struct cgroup *src_cgrp;
2124 :
2125 : lockdep_assert_held(&cgroup_mutex);
2126 : lockdep_assert_held(&css_set_rwsem);
2127 :
2128 0 : src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
2129 :
2130 0 : if (!list_empty(&src_cset->mg_preload_node))
2131 0 : return;
2132 :
2133 : WARN_ON(src_cset->mg_src_cgrp);
2134 : WARN_ON(!list_empty(&src_cset->mg_tasks));
2135 : WARN_ON(!list_empty(&src_cset->mg_node));
2136 :
2137 0 : src_cset->mg_src_cgrp = src_cgrp;
2138 : get_css_set(src_cset);
2139 : list_add(&src_cset->mg_preload_node, preloaded_csets);
2140 : }
2141 :
2142 : /**
2143 : * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2144 : * @dst_cgrp: the destination cgroup (may be %NULL)
2145 : * @preloaded_csets: list of preloaded source css_sets
2146 : *
2147 : * Tasks are about to be moved to @dst_cgrp and all the source css_sets
2148 : * have been preloaded to @preloaded_csets. This function looks up and
2149 : * pins all destination css_sets, links each to its source, and append them
2150 : * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
2151 : * source css_set is assumed to be its cgroup on the default hierarchy.
2152 : *
2153 : * This function must be called after cgroup_migrate_add_src() has been
2154 : * called on each migration source css_set. After migration is performed
2155 : * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2156 : * @preloaded_csets.
2157 : */
2158 0 : static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
2159 : struct list_head *preloaded_csets)
2160 : {
2161 0 : LIST_HEAD(csets);
2162 : struct css_set *src_cset, *tmp_cset;
2163 :
2164 : lockdep_assert_held(&cgroup_mutex);
2165 :
2166 : /*
2167 : * Except for the root, child_subsys_mask must be zero for a cgroup
2168 : * with tasks so that child cgroups don't compete against tasks.
2169 : */
2170 0 : if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
2171 0 : dst_cgrp->child_subsys_mask)
2172 : return -EBUSY;
2173 :
2174 : /* look up the dst cset for each src cset and link it to src */
2175 0 : list_for_each_entry_safe(src_cset, tmp_cset, preloaded_csets, mg_preload_node) {
2176 : struct css_set *dst_cset;
2177 :
2178 0 : dst_cset = find_css_set(src_cset,
2179 : dst_cgrp ?: src_cset->dfl_cgrp);
2180 0 : if (!dst_cset)
2181 : goto err;
2182 :
2183 : WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
2184 :
2185 : /*
2186 : * If src cset equals dst, it's noop. Drop the src.
2187 : * cgroup_migrate() will skip the cset too. Note that we
2188 : * can't handle src == dst as some nodes are used by both.
2189 : */
2190 0 : if (src_cset == dst_cset) {
2191 0 : src_cset->mg_src_cgrp = NULL;
2192 : list_del_init(&src_cset->mg_preload_node);
2193 0 : put_css_set(src_cset);
2194 0 : put_css_set(dst_cset);
2195 0 : continue;
2196 : }
2197 :
2198 0 : src_cset->mg_dst_cset = dst_cset;
2199 :
2200 0 : if (list_empty(&dst_cset->mg_preload_node))
2201 : list_add(&dst_cset->mg_preload_node, &csets);
2202 : else
2203 0 : put_css_set(dst_cset);
2204 : }
2205 :
2206 : list_splice_tail(&csets, preloaded_csets);
2207 : return 0;
2208 : err:
2209 0 : cgroup_migrate_finish(&csets);
2210 0 : return -ENOMEM;
2211 : }
2212 :
2213 : /**
2214 : * cgroup_migrate - migrate a process or task to a cgroup
2215 : * @cgrp: the destination cgroup
2216 : * @leader: the leader of the process or the task to migrate
2217 : * @threadgroup: whether @leader points to the whole process or a single task
2218 : *
2219 : * Migrate a process or task denoted by @leader to @cgrp. If migrating a
2220 : * process, the caller must be holding threadgroup_lock of @leader. The
2221 : * caller is also responsible for invoking cgroup_migrate_add_src() and
2222 : * cgroup_migrate_prepare_dst() on the targets before invoking this
2223 : * function and following up with cgroup_migrate_finish().
2224 : *
2225 : * As long as a controller's ->can_attach() doesn't fail, this function is
2226 : * guaranteed to succeed. This means that, excluding ->can_attach()
2227 : * failure, when migrating multiple targets, the success or failure can be
2228 : * decided for all targets by invoking group_migrate_prepare_dst() before
2229 : * actually starting migrating.
2230 : */
2231 0 : static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader,
2232 : bool threadgroup)
2233 : {
2234 0 : struct cgroup_taskset tset = {
2235 : .src_csets = LIST_HEAD_INIT(tset.src_csets),
2236 : .dst_csets = LIST_HEAD_INIT(tset.dst_csets),
2237 : .csets = &tset.src_csets,
2238 : };
2239 : struct cgroup_subsys_state *css, *failed_css = NULL;
2240 : struct css_set *cset, *tmp_cset;
2241 : struct task_struct *task, *tmp_task;
2242 : int i, ret;
2243 :
2244 : /*
2245 : * Prevent freeing of tasks while we take a snapshot. Tasks that are
2246 : * already PF_EXITING could be freed from underneath us unless we
2247 : * take an rcu_read_lock.
2248 : */
2249 0 : down_write(&css_set_rwsem);
2250 : rcu_read_lock();
2251 : task = leader;
2252 : do {
2253 : /* @task either already exited or can't exit until the end */
2254 0 : if (task->flags & PF_EXITING)
2255 : goto next;
2256 :
2257 : /* leave @task alone if post_fork() hasn't linked it yet */
2258 0 : if (list_empty(&task->cg_list))
2259 : goto next;
2260 :
2261 : cset = task_css_set(task);
2262 0 : if (!cset->mg_src_cgrp)
2263 : goto next;
2264 :
2265 : /*
2266 : * cgroup_taskset_first() must always return the leader.
2267 : * Take care to avoid disturbing the ordering.
2268 : */
2269 0 : list_move_tail(&task->cg_list, &cset->mg_tasks);
2270 0 : if (list_empty(&cset->mg_node))
2271 : list_add_tail(&cset->mg_node, &tset.src_csets);
2272 0 : if (list_empty(&cset->mg_dst_cset->mg_node))
2273 : list_move_tail(&cset->mg_dst_cset->mg_node,
2274 : &tset.dst_csets);
2275 : next:
2276 0 : if (!threadgroup)
2277 : break;
2278 0 : } while_each_thread(leader, task);
2279 : rcu_read_unlock();
2280 0 : up_write(&css_set_rwsem);
2281 :
2282 : /* methods shouldn't be called if no task is actually migrating */
2283 0 : if (list_empty(&tset.src_csets))
2284 : return 0;
2285 :
2286 : /* check that we can legitimately attach to the cgroup */
2287 0 : for_each_e_css(css, i, cgrp) {
2288 0 : if (css->ss->can_attach) {
2289 0 : ret = css->ss->can_attach(css, &tset);
2290 0 : if (ret) {
2291 : failed_css = css;
2292 : goto out_cancel_attach;
2293 : }
2294 : }
2295 : }
2296 :
2297 : /*
2298 : * Now that we're guaranteed success, proceed to move all tasks to
2299 : * the new cgroup. There are no failure cases after here, so this
2300 : * is the commit point.
2301 : */
2302 0 : down_write(&css_set_rwsem);
2303 0 : list_for_each_entry(cset, &tset.src_csets, mg_node) {
2304 0 : list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list)
2305 0 : cgroup_task_migrate(cset->mg_src_cgrp, task,
2306 : cset->mg_dst_cset);
2307 : }
2308 0 : up_write(&css_set_rwsem);
2309 :
2310 : /*
2311 : * Migration is committed, all target tasks are now on dst_csets.
2312 : * Nothing is sensitive to fork() after this point. Notify
2313 : * controllers that migration is complete.
2314 : */
2315 0 : tset.csets = &tset.dst_csets;
2316 :
2317 0 : for_each_e_css(css, i, cgrp)
2318 0 : if (css->ss->attach)
2319 0 : css->ss->attach(css, &tset);
2320 :
2321 : ret = 0;
2322 : goto out_release_tset;
2323 :
2324 : out_cancel_attach:
2325 0 : for_each_e_css(css, i, cgrp) {
2326 0 : if (css == failed_css)
2327 : break;
2328 0 : if (css->ss->cancel_attach)
2329 0 : css->ss->cancel_attach(css, &tset);
2330 : }
2331 : out_release_tset:
2332 0 : down_write(&css_set_rwsem);
2333 : list_splice_init(&tset.dst_csets, &tset.src_csets);
2334 0 : list_for_each_entry_safe(cset, tmp_cset, &tset.src_csets, mg_node) {
2335 0 : list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2336 : list_del_init(&cset->mg_node);
2337 : }
2338 0 : up_write(&css_set_rwsem);
2339 0 : return ret;
2340 : }
2341 :
2342 : /**
2343 : * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2344 : * @dst_cgrp: the cgroup to attach to
2345 : * @leader: the task or the leader of the threadgroup to be attached
2346 : * @threadgroup: attach the whole threadgroup?
2347 : *
2348 : * Call holding cgroup_mutex and threadgroup_lock of @leader.
2349 : */
2350 0 : static int cgroup_attach_task(struct cgroup *dst_cgrp,
2351 : struct task_struct *leader, bool threadgroup)
2352 : {
2353 0 : LIST_HEAD(preloaded_csets);
2354 : struct task_struct *task;
2355 : int ret;
2356 :
2357 : /* look up all src csets */
2358 0 : down_read(&css_set_rwsem);
2359 : rcu_read_lock();
2360 : task = leader;
2361 : do {
2362 0 : cgroup_migrate_add_src(task_css_set(task), dst_cgrp,
2363 : &preloaded_csets);
2364 0 : if (!threadgroup)
2365 : break;
2366 0 : } while_each_thread(leader, task);
2367 : rcu_read_unlock();
2368 0 : up_read(&css_set_rwsem);
2369 :
2370 : /* prepare dst csets and commit */
2371 0 : ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets);
2372 0 : if (!ret)
2373 0 : ret = cgroup_migrate(dst_cgrp, leader, threadgroup);
2374 :
2375 0 : cgroup_migrate_finish(&preloaded_csets);
2376 0 : return ret;
2377 : }
2378 :
2379 : /*
2380 : * Find the task_struct of the task to attach by vpid and pass it along to the
2381 : * function to attach either it or all tasks in its threadgroup. Will lock
2382 : * cgroup_mutex and threadgroup.
2383 : */
2384 0 : static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
2385 : size_t nbytes, loff_t off, bool threadgroup)
2386 : {
2387 : struct task_struct *tsk;
2388 0 : const struct cred *cred = current_cred(), *tcred;
2389 : struct cgroup *cgrp;
2390 : pid_t pid;
2391 : int ret;
2392 :
2393 0 : if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
2394 : return -EINVAL;
2395 :
2396 0 : cgrp = cgroup_kn_lock_live(of->kn);
2397 0 : if (!cgrp)
2398 : return -ENODEV;
2399 :
2400 : retry_find_task:
2401 : rcu_read_lock();
2402 0 : if (pid) {
2403 0 : tsk = find_task_by_vpid(pid);
2404 0 : if (!tsk) {
2405 : rcu_read_unlock();
2406 : ret = -ESRCH;
2407 : goto out_unlock_cgroup;
2408 : }
2409 : /*
2410 : * even if we're attaching all tasks in the thread group, we
2411 : * only need to check permissions on one of them.
2412 : */
2413 0 : tcred = __task_cred(tsk);
2414 0 : if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2415 0 : !uid_eq(cred->euid, tcred->uid) &&
2416 : !uid_eq(cred->euid, tcred->suid)) {
2417 : rcu_read_unlock();
2418 : ret = -EACCES;
2419 : goto out_unlock_cgroup;
2420 : }
2421 : } else
2422 0 : tsk = current;
2423 :
2424 0 : if (threadgroup)
2425 0 : tsk = tsk->group_leader;
2426 :
2427 : /*
2428 : * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2429 : * trapped in a cpuset, or RT worker may be born in a cgroup
2430 : * with no rt_runtime allocated. Just say no.
2431 : */
2432 0 : if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2433 : ret = -EINVAL;
2434 : rcu_read_unlock();
2435 : goto out_unlock_cgroup;
2436 : }
2437 :
2438 0 : get_task_struct(tsk);
2439 : rcu_read_unlock();
2440 :
2441 : threadgroup_lock(tsk);
2442 0 : if (threadgroup) {
2443 0 : if (!thread_group_leader(tsk)) {
2444 : /*
2445 : * a race with de_thread from another thread's exec()
2446 : * may strip us of our leadership, if this happens,
2447 : * there is no choice but to throw this task away and
2448 : * try again; this is
2449 : * "double-double-toil-and-trouble-check locking".
2450 : */
2451 : threadgroup_unlock(tsk);
2452 : put_task_struct(tsk);
2453 : goto retry_find_task;
2454 : }
2455 : }
2456 :
2457 0 : ret = cgroup_attach_task(cgrp, tsk, threadgroup);
2458 :
2459 : threadgroup_unlock(tsk);
2460 :
2461 : put_task_struct(tsk);
2462 : out_unlock_cgroup:
2463 0 : cgroup_kn_unlock(of->kn);
2464 0 : return ret ?: nbytes;
2465 : }
2466 :
2467 : /**
2468 : * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2469 : * @from: attach to all cgroups of a given task
2470 : * @tsk: the task to be attached
2471 : */
2472 0 : int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2473 : {
2474 : struct cgroup_root *root;
2475 : int retval = 0;
2476 :
2477 0 : mutex_lock(&cgroup_mutex);
2478 0 : for_each_root(root) {
2479 : struct cgroup *from_cgrp;
2480 :
2481 0 : if (root == &cgrp_dfl_root)
2482 0 : continue;
2483 :
2484 0 : down_read(&css_set_rwsem);
2485 : from_cgrp = task_cgroup_from_root(from, root);
2486 0 : up_read(&css_set_rwsem);
2487 :
2488 0 : retval = cgroup_attach_task(from_cgrp, tsk, false);
2489 0 : if (retval)
2490 : break;
2491 : }
2492 0 : mutex_unlock(&cgroup_mutex);
2493 :
2494 0 : return retval;
2495 : }
2496 : EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2497 :
2498 0 : static ssize_t cgroup_tasks_write(struct kernfs_open_file *of,
2499 : char *buf, size_t nbytes, loff_t off)
2500 : {
2501 0 : return __cgroup_procs_write(of, buf, nbytes, off, false);
2502 : }
2503 :
2504 0 : static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
2505 : char *buf, size_t nbytes, loff_t off)
2506 : {
2507 0 : return __cgroup_procs_write(of, buf, nbytes, off, true);
2508 : }
2509 :
2510 0 : static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
2511 : char *buf, size_t nbytes, loff_t off)
2512 : {
2513 : struct cgroup *cgrp;
2514 :
2515 : BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2516 :
2517 0 : cgrp = cgroup_kn_lock_live(of->kn);
2518 0 : if (!cgrp)
2519 : return -ENODEV;
2520 : spin_lock(&release_agent_path_lock);
2521 0 : strlcpy(cgrp->root->release_agent_path, strstrip(buf),
2522 : sizeof(cgrp->root->release_agent_path));
2523 : spin_unlock(&release_agent_path_lock);
2524 0 : cgroup_kn_unlock(of->kn);
2525 0 : return nbytes;
2526 : }
2527 :
2528 0 : static int cgroup_release_agent_show(struct seq_file *seq, void *v)
2529 : {
2530 0 : struct cgroup *cgrp = seq_css(seq)->cgroup;
2531 :
2532 : spin_lock(&release_agent_path_lock);
2533 0 : seq_puts(seq, cgrp->root->release_agent_path);
2534 : spin_unlock(&release_agent_path_lock);
2535 0 : seq_putc(seq, '\n');
2536 0 : return 0;
2537 : }
2538 :
2539 0 : static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
2540 : {
2541 0 : seq_puts(seq, "0\n");
2542 0 : return 0;
2543 : }
2544 :
2545 0 : static void cgroup_print_ss_mask(struct seq_file *seq, unsigned int ss_mask)
2546 : {
2547 : struct cgroup_subsys *ss;
2548 : bool printed = false;
2549 : int ssid;
2550 :
2551 0 : for_each_subsys(ss, ssid) {
2552 0 : if (ss_mask & (1 << ssid)) {
2553 0 : if (printed)
2554 0 : seq_putc(seq, ' ');
2555 0 : seq_printf(seq, "%s", ss->name);
2556 : printed = true;
2557 : }
2558 : }
2559 0 : if (printed)
2560 0 : seq_putc(seq, '\n');
2561 0 : }
2562 :
2563 : /* show controllers which are currently attached to the default hierarchy */
2564 0 : static int cgroup_root_controllers_show(struct seq_file *seq, void *v)
2565 : {
2566 0 : struct cgroup *cgrp = seq_css(seq)->cgroup;
2567 :
2568 0 : cgroup_print_ss_mask(seq, cgrp->root->subsys_mask &
2569 0 : ~cgrp_dfl_root_inhibit_ss_mask);
2570 0 : return 0;
2571 : }
2572 :
2573 : /* show controllers which are enabled from the parent */
2574 0 : static int cgroup_controllers_show(struct seq_file *seq, void *v)
2575 : {
2576 0 : struct cgroup *cgrp = seq_css(seq)->cgroup;
2577 :
2578 0 : cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->subtree_control);
2579 0 : return 0;
2580 : }
2581 :
2582 : /* show controllers which are enabled for a given cgroup's children */
2583 0 : static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
2584 : {
2585 0 : struct cgroup *cgrp = seq_css(seq)->cgroup;
2586 :
2587 0 : cgroup_print_ss_mask(seq, cgrp->subtree_control);
2588 0 : return 0;
2589 : }
2590 :
2591 : /**
2592 : * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2593 : * @cgrp: root of the subtree to update csses for
2594 : *
2595 : * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
2596 : * css associations need to be updated accordingly. This function looks up
2597 : * all css_sets which are attached to the subtree, creates the matching
2598 : * updated css_sets and migrates the tasks to the new ones.
2599 : */
2600 0 : static int cgroup_update_dfl_csses(struct cgroup *cgrp)
2601 : {
2602 0 : LIST_HEAD(preloaded_csets);
2603 : struct cgroup_subsys_state *css;
2604 : struct css_set *src_cset;
2605 : int ret;
2606 :
2607 : lockdep_assert_held(&cgroup_mutex);
2608 :
2609 : /* look up all csses currently attached to @cgrp's subtree */
2610 0 : down_read(&css_set_rwsem);
2611 0 : css_for_each_descendant_pre(css, cgroup_css(cgrp, NULL)) {
2612 : struct cgrp_cset_link *link;
2613 :
2614 : /* self is not affected by child_subsys_mask change */
2615 0 : if (css->cgroup == cgrp)
2616 0 : continue;
2617 :
2618 0 : list_for_each_entry(link, &css->cgroup->cset_links, cset_link)
2619 0 : cgroup_migrate_add_src(link->cset, cgrp,
2620 : &preloaded_csets);
2621 : }
2622 0 : up_read(&css_set_rwsem);
2623 :
2624 : /* NULL dst indicates self on default hierarchy */
2625 0 : ret = cgroup_migrate_prepare_dst(NULL, &preloaded_csets);
2626 0 : if (ret)
2627 : goto out_finish;
2628 :
2629 0 : list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) {
2630 : struct task_struct *last_task = NULL, *task;
2631 :
2632 : /* src_csets precede dst_csets, break on the first dst_cset */
2633 0 : if (!src_cset->mg_src_cgrp)
2634 : break;
2635 :
2636 : /*
2637 : * All tasks in src_cset need to be migrated to the
2638 : * matching dst_cset. Empty it process by process. We
2639 : * walk tasks but migrate processes. The leader might even
2640 : * belong to a different cset but such src_cset would also
2641 : * be among the target src_csets because the default
2642 : * hierarchy enforces per-process membership.
2643 : */
2644 : while (true) {
2645 0 : down_read(&css_set_rwsem);
2646 0 : task = list_first_entry_or_null(&src_cset->tasks,
2647 : struct task_struct, cg_list);
2648 0 : if (task) {
2649 0 : task = task->group_leader;
2650 : WARN_ON_ONCE(!task_css_set(task)->mg_src_cgrp);
2651 0 : get_task_struct(task);
2652 : }
2653 0 : up_read(&css_set_rwsem);
2654 :
2655 0 : if (!task)
2656 : break;
2657 :
2658 : /* guard against possible infinite loop */
2659 0 : if (WARN(last_task == task,
2660 : "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
2661 : goto out_finish;
2662 : last_task = task;
2663 :
2664 : threadgroup_lock(task);
2665 : /* raced against de_thread() from another thread? */
2666 0 : if (!thread_group_leader(task)) {
2667 : threadgroup_unlock(task);
2668 : put_task_struct(task);
2669 0 : continue;
2670 : }
2671 :
2672 0 : ret = cgroup_migrate(src_cset->dfl_cgrp, task, true);
2673 :
2674 : threadgroup_unlock(task);
2675 : put_task_struct(task);
2676 :
2677 0 : if (WARN(ret, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret))
2678 : goto out_finish;
2679 : }
2680 : }
2681 :
2682 : out_finish:
2683 0 : cgroup_migrate_finish(&preloaded_csets);
2684 0 : return ret;
2685 : }
2686 :
2687 : /* change the enabled child controllers for a cgroup in the default hierarchy */
2688 0 : static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
2689 : char *buf, size_t nbytes,
2690 : loff_t off)
2691 : {
2692 : unsigned int enable = 0, disable = 0;
2693 : unsigned int css_enable, css_disable, old_sc, new_sc, old_ss, new_ss;
2694 0 : struct cgroup *cgrp, *child;
2695 : struct cgroup_subsys *ss;
2696 : char *tok;
2697 : int ssid, ret;
2698 :
2699 : /*
2700 : * Parse input - space separated list of subsystem names prefixed
2701 : * with either + or -.
2702 : */
2703 0 : buf = strstrip(buf);
2704 0 : while ((tok = strsep(&buf, " "))) {
2705 0 : if (tok[0] == '\0')
2706 0 : continue;
2707 0 : for_each_subsys(ss, ssid) {
2708 0 : if (ss->disabled || strcmp(tok + 1, ss->name) ||
2709 0 : ((1 << ss->id) & cgrp_dfl_root_inhibit_ss_mask))
2710 0 : continue;
2711 :
2712 0 : if (*tok == '+') {
2713 0 : enable |= 1 << ssid;
2714 0 : disable &= ~(1 << ssid);
2715 0 : } else if (*tok == '-') {
2716 0 : disable |= 1 << ssid;
2717 0 : enable &= ~(1 << ssid);
2718 : } else {
2719 : return -EINVAL;
2720 : }
2721 : break;
2722 : }
2723 0 : if (ssid == CGROUP_SUBSYS_COUNT)
2724 : return -EINVAL;
2725 : }
2726 :
2727 0 : cgrp = cgroup_kn_lock_live(of->kn);
2728 0 : if (!cgrp)
2729 : return -ENODEV;
2730 :
2731 0 : for_each_subsys(ss, ssid) {
2732 0 : if (enable & (1 << ssid)) {
2733 0 : if (cgrp->subtree_control & (1 << ssid)) {
2734 0 : enable &= ~(1 << ssid);
2735 0 : continue;
2736 : }
2737 :
2738 : /* unavailable or not enabled on the parent? */
2739 0 : if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
2740 0 : (cgroup_parent(cgrp) &&
2741 0 : !(cgroup_parent(cgrp)->subtree_control & (1 << ssid)))) {
2742 : ret = -ENOENT;
2743 : goto out_unlock;
2744 : }
2745 0 : } else if (disable & (1 << ssid)) {
2746 0 : if (!(cgrp->subtree_control & (1 << ssid))) {
2747 0 : disable &= ~(1 << ssid);
2748 0 : continue;
2749 : }
2750 :
2751 : /* a child has it enabled? */
2752 0 : cgroup_for_each_live_child(child, cgrp) {
2753 0 : if (child->subtree_control & (1 << ssid)) {
2754 : ret = -EBUSY;
2755 : goto out_unlock;
2756 : }
2757 : }
2758 : }
2759 : }
2760 :
2761 0 : if (!enable && !disable) {
2762 : ret = 0;
2763 : goto out_unlock;
2764 : }
2765 :
2766 : /*
2767 : * Except for the root, subtree_control must be zero for a cgroup
2768 : * with tasks so that child cgroups don't compete against tasks.
2769 : */
2770 0 : if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
2771 : ret = -EBUSY;
2772 : goto out_unlock;
2773 : }
2774 :
2775 : /*
2776 : * Update subsys masks and calculate what needs to be done. More
2777 : * subsystems than specified may need to be enabled or disabled
2778 : * depending on subsystem dependencies.
2779 : */
2780 0 : old_sc = cgrp->subtree_control;
2781 0 : old_ss = cgrp->child_subsys_mask;
2782 0 : new_sc = (old_sc | enable) & ~disable;
2783 0 : new_ss = cgroup_calc_child_subsys_mask(cgrp, new_sc);
2784 :
2785 0 : css_enable = ~old_ss & new_ss;
2786 0 : css_disable = old_ss & ~new_ss;
2787 0 : enable |= css_enable;
2788 0 : disable |= css_disable;
2789 :
2790 : /*
2791 : * Because css offlining is asynchronous, userland might try to
2792 : * re-enable the same controller while the previous instance is
2793 : * still around. In such cases, wait till it's gone using
2794 : * offline_waitq.
2795 : */
2796 0 : for_each_subsys(ss, ssid) {
2797 0 : if (!(css_enable & (1 << ssid)))
2798 0 : continue;
2799 :
2800 0 : cgroup_for_each_live_child(child, cgrp) {
2801 0 : DEFINE_WAIT(wait);
2802 :
2803 0 : if (!cgroup_css(child, ss))
2804 0 : continue;
2805 :
2806 0 : cgroup_get(child);
2807 0 : prepare_to_wait(&child->offline_waitq, &wait,
2808 : TASK_UNINTERRUPTIBLE);
2809 0 : cgroup_kn_unlock(of->kn);
2810 0 : schedule();
2811 0 : finish_wait(&child->offline_waitq, &wait);
2812 0 : cgroup_put(child);
2813 :
2814 0 : return restart_syscall();
2815 : }
2816 : }
2817 :
2818 0 : cgrp->subtree_control = new_sc;
2819 0 : cgrp->child_subsys_mask = new_ss;
2820 :
2821 : /*
2822 : * Create new csses or make the existing ones visible. A css is
2823 : * created invisible if it's being implicitly enabled through
2824 : * dependency. An invisible css is made visible when the userland
2825 : * explicitly enables it.
2826 : */
2827 0 : for_each_subsys(ss, ssid) {
2828 0 : if (!(enable & (1 << ssid)))
2829 0 : continue;
2830 :
2831 0 : cgroup_for_each_live_child(child, cgrp) {
2832 0 : if (css_enable & (1 << ssid))
2833 0 : ret = create_css(child, ss,
2834 0 : cgrp->subtree_control & (1 << ssid));
2835 : else
2836 0 : ret = cgroup_populate_dir(child, 1 << ssid);
2837 0 : if (ret)
2838 : goto err_undo_css;
2839 : }
2840 : }
2841 :
2842 : /*
2843 : * At this point, cgroup_e_css() results reflect the new csses
2844 : * making the following cgroup_update_dfl_csses() properly update
2845 : * css associations of all tasks in the subtree.
2846 : */
2847 0 : ret = cgroup_update_dfl_csses(cgrp);
2848 0 : if (ret)
2849 : goto err_undo_css;
2850 :
2851 : /*
2852 : * All tasks are migrated out of disabled csses. Kill or hide
2853 : * them. A css is hidden when the userland requests it to be
2854 : * disabled while other subsystems are still depending on it. The
2855 : * css must not actively control resources and be in the vanilla
2856 : * state if it's made visible again later. Controllers which may
2857 : * be depended upon should provide ->css_reset() for this purpose.
2858 : */
2859 0 : for_each_subsys(ss, ssid) {
2860 0 : if (!(disable & (1 << ssid)))
2861 0 : continue;
2862 :
2863 0 : cgroup_for_each_live_child(child, cgrp) {
2864 : struct cgroup_subsys_state *css = cgroup_css(child, ss);
2865 :
2866 0 : if (css_disable & (1 << ssid)) {
2867 0 : kill_css(css);
2868 : } else {
2869 0 : cgroup_clear_dir(child, 1 << ssid);
2870 0 : if (ss->css_reset)
2871 0 : ss->css_reset(css);
2872 : }
2873 : }
2874 : }
2875 :
2876 : /*
2877 : * The effective csses of all the descendants (excluding @cgrp) may
2878 : * have changed. Subsystems can optionally subscribe to this event
2879 : * by implementing ->css_e_css_changed() which is invoked if any of
2880 : * the effective csses seen from the css's cgroup may have changed.
2881 : */
2882 0 : for_each_subsys(ss, ssid) {
2883 : struct cgroup_subsys_state *this_css = cgroup_css(cgrp, ss);
2884 : struct cgroup_subsys_state *css;
2885 :
2886 0 : if (!ss->css_e_css_changed || !this_css)
2887 0 : continue;
2888 :
2889 0 : css_for_each_descendant_pre(css, this_css)
2890 0 : if (css != this_css)
2891 0 : ss->css_e_css_changed(css);
2892 : }
2893 :
2894 0 : kernfs_activate(cgrp->kn);
2895 : ret = 0;
2896 : out_unlock:
2897 0 : cgroup_kn_unlock(of->kn);
2898 0 : return ret ?: nbytes;
2899 :
2900 : err_undo_css:
2901 0 : cgrp->subtree_control = old_sc;
2902 0 : cgrp->child_subsys_mask = old_ss;
2903 :
2904 0 : for_each_subsys(ss, ssid) {
2905 0 : if (!(enable & (1 << ssid)))
2906 0 : continue;
2907 :
2908 0 : cgroup_for_each_live_child(child, cgrp) {
2909 : struct cgroup_subsys_state *css = cgroup_css(child, ss);
2910 :
2911 0 : if (!css)
2912 0 : continue;
2913 :
2914 0 : if (css_enable & (1 << ssid))
2915 0 : kill_css(css);
2916 : else
2917 0 : cgroup_clear_dir(child, 1 << ssid);
2918 : }
2919 : }
2920 : goto out_unlock;
2921 : }
2922 :
2923 0 : static int cgroup_populated_show(struct seq_file *seq, void *v)
2924 : {
2925 0 : seq_printf(seq, "%d\n", (bool)seq_css(seq)->cgroup->populated_cnt);
2926 0 : return 0;
2927 : }
2928 :
2929 0 : static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
2930 : size_t nbytes, loff_t off)
2931 : {
2932 0 : struct cgroup *cgrp = of->kn->parent->priv;
2933 0 : struct cftype *cft = of->kn->priv;
2934 : struct cgroup_subsys_state *css;
2935 : int ret;
2936 :
2937 0 : if (cft->write)
2938 0 : return cft->write(of, buf, nbytes, off);
2939 :
2940 : /*
2941 : * kernfs guarantees that a file isn't deleted with operations in
2942 : * flight, which means that the matching css is and stays alive and
2943 : * doesn't need to be pinned. The RCU locking is not necessary
2944 : * either. It's just for the convenience of using cgroup_css().
2945 : */
2946 : rcu_read_lock();
2947 0 : css = cgroup_css(cgrp, cft->ss);
2948 : rcu_read_unlock();
2949 :
2950 0 : if (cft->write_u64) {
2951 : unsigned long long v;
2952 0 : ret = kstrtoull(buf, 0, &v);
2953 0 : if (!ret)
2954 0 : ret = cft->write_u64(css, cft, v);
2955 0 : } else if (cft->write_s64) {
2956 : long long v;
2957 0 : ret = kstrtoll(buf, 0, &v);
2958 0 : if (!ret)
2959 0 : ret = cft->write_s64(css, cft, v);
2960 : } else {
2961 : ret = -EINVAL;
2962 : }
2963 :
2964 0 : return ret ?: nbytes;
2965 : }
2966 :
2967 0 : static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
2968 : {
2969 0 : return seq_cft(seq)->seq_start(seq, ppos);
2970 : }
2971 :
2972 0 : static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
2973 : {
2974 0 : return seq_cft(seq)->seq_next(seq, v, ppos);
2975 : }
2976 :
2977 0 : static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
2978 : {
2979 0 : seq_cft(seq)->seq_stop(seq, v);
2980 0 : }
2981 :
2982 0 : static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2983 : {
2984 : struct cftype *cft = seq_cft(m);
2985 : struct cgroup_subsys_state *css = seq_css(m);
2986 :
2987 0 : if (cft->seq_show)
2988 0 : return cft->seq_show(m, arg);
2989 :
2990 0 : if (cft->read_u64)
2991 0 : seq_printf(m, "%llu\n", cft->read_u64(css, cft));
2992 0 : else if (cft->read_s64)
2993 0 : seq_printf(m, "%lld\n", cft->read_s64(css, cft));
2994 : else
2995 : return -EINVAL;
2996 : return 0;
2997 : }
2998 :
2999 : static struct kernfs_ops cgroup_kf_single_ops = {
3000 : .atomic_write_len = PAGE_SIZE,
3001 : .write = cgroup_file_write,
3002 : .seq_show = cgroup_seqfile_show,
3003 : };
3004 :
3005 : static struct kernfs_ops cgroup_kf_ops = {
3006 : .atomic_write_len = PAGE_SIZE,
3007 : .write = cgroup_file_write,
3008 : .seq_start = cgroup_seqfile_start,
3009 : .seq_next = cgroup_seqfile_next,
3010 : .seq_stop = cgroup_seqfile_stop,
3011 : .seq_show = cgroup_seqfile_show,
3012 : };
3013 :
3014 : /*
3015 : * cgroup_rename - Only allow simple rename of directories in place.
3016 : */
3017 0 : static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
3018 : const char *new_name_str)
3019 : {
3020 0 : struct cgroup *cgrp = kn->priv;
3021 : int ret;
3022 :
3023 0 : if (kernfs_type(kn) != KERNFS_DIR)
3024 : return -ENOTDIR;
3025 0 : if (kn->parent != new_parent)
3026 : return -EIO;
3027 :
3028 : /*
3029 : * This isn't a proper migration and its usefulness is very
3030 : * limited. Disallow on the default hierarchy.
3031 : */
3032 0 : if (cgroup_on_dfl(cgrp))
3033 : return -EPERM;
3034 :
3035 : /*
3036 : * We're gonna grab cgroup_mutex which nests outside kernfs
3037 : * active_ref. kernfs_rename() doesn't require active_ref
3038 : * protection. Break them before grabbing cgroup_mutex.
3039 : */
3040 0 : kernfs_break_active_protection(new_parent);
3041 0 : kernfs_break_active_protection(kn);
3042 :
3043 0 : mutex_lock(&cgroup_mutex);
3044 :
3045 : ret = kernfs_rename(kn, new_parent, new_name_str);
3046 :
3047 0 : mutex_unlock(&cgroup_mutex);
3048 :
3049 0 : kernfs_unbreak_active_protection(kn);
3050 0 : kernfs_unbreak_active_protection(new_parent);
3051 0 : return ret;
3052 : }
3053 :
3054 : /* set uid and gid of cgroup dirs and files to that of the creator */
3055 3 : static int cgroup_kn_set_ugid(struct kernfs_node *kn)
3056 : {
3057 6 : struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
3058 3 : .ia_uid = current_fsuid(),
3059 : .ia_gid = current_fsgid(), };
3060 :
3061 3 : if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
3062 : gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
3063 : return 0;
3064 :
3065 0 : return kernfs_setattr(kn, &iattr);
3066 : }
3067 :
3068 3 : static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
3069 : {
3070 : char name[CGROUP_FILE_NAME_MAX];
3071 : struct kernfs_node *kn;
3072 : struct lock_class_key *key = NULL;
3073 : int ret;
3074 :
3075 : #ifdef CONFIG_DEBUG_LOCK_ALLOC
3076 : key = &cft->lockdep_key;
3077 : #endif
3078 6 : kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
3079 3 : cgroup_file_mode(cft), 0, cft->kf_ops, cft,
3080 : NULL, false, key);
3081 3 : if (IS_ERR(kn))
3082 0 : return PTR_ERR(kn);
3083 :
3084 3 : ret = cgroup_kn_set_ugid(kn);
3085 3 : if (ret) {
3086 0 : kernfs_remove(kn);
3087 0 : return ret;
3088 : }
3089 :
3090 3 : if (cft->seq_show == cgroup_populated_show)
3091 0 : cgrp->populated_kn = kn;
3092 : return 0;
3093 : }
3094 :
3095 : /**
3096 : * cgroup_addrm_files - add or remove files to a cgroup directory
3097 : * @cgrp: the target cgroup
3098 : * @cfts: array of cftypes to be added
3099 : * @is_add: whether to add or remove
3100 : *
3101 : * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3102 : * For removals, this function never fails. If addition fails, this
3103 : * function doesn't remove files already added. The caller is responsible
3104 : * for cleaning up.
3105 : */
3106 52 : static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
3107 : bool is_add)
3108 : {
3109 : struct cftype *cft;
3110 : int ret;
3111 :
3112 : lockdep_assert_held(&cgroup_mutex);
3113 :
3114 54 : for (cft = cfts; cft->name[0] != '\0'; cft++) {
3115 : /* does cft->flags tell us to skip this file on @cgrp? */
3116 45 : if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
3117 0 : continue;
3118 85 : if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
3119 40 : continue;
3120 7 : if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
3121 2 : continue;
3122 4 : if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
3123 0 : continue;
3124 :
3125 3 : if (is_add) {
3126 3 : ret = cgroup_add_file(cgrp, cft);
3127 3 : if (ret) {
3128 0 : pr_warn("%s: failed to add %s, err=%d\n",
3129 : __func__, cft->name, ret);
3130 0 : return ret;
3131 : }
3132 : } else {
3133 0 : cgroup_rm_file(cgrp, cft);
3134 : }
3135 : }
3136 : return 0;
3137 : }
3138 :
3139 8 : static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
3140 : {
3141 8 : LIST_HEAD(pending);
3142 8 : struct cgroup_subsys *ss = cfts[0].ss;
3143 8 : struct cgroup *root = &ss->root->cgrp;
3144 : struct cgroup_subsys_state *css;
3145 : int ret = 0;
3146 :
3147 : lockdep_assert_held(&cgroup_mutex);
3148 :
3149 : /* add/rm files for all cgroups created before */
3150 16 : css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
3151 8 : struct cgroup *cgrp = css->cgroup;
3152 :
3153 8 : if (cgroup_is_dead(cgrp))
3154 0 : continue;
3155 :
3156 8 : ret = cgroup_addrm_files(cgrp, cfts, is_add);
3157 8 : if (ret)
3158 : break;
3159 : }
3160 :
3161 8 : if (is_add && !ret)
3162 8 : kernfs_activate(root->kn);
3163 8 : return ret;
3164 : }
3165 :
3166 0 : static void cgroup_exit_cftypes(struct cftype *cfts)
3167 : {
3168 : struct cftype *cft;
3169 :
3170 0 : for (cft = cfts; cft->name[0] != '\0'; cft++) {
3171 : /* free copy for custom atomic_write_len, see init_cftypes() */
3172 0 : if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
3173 0 : kfree(cft->kf_ops);
3174 0 : cft->kf_ops = NULL;
3175 0 : cft->ss = NULL;
3176 :
3177 : /* revert flags set by cgroup core while adding @cfts */
3178 0 : cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
3179 : }
3180 0 : }
3181 :
3182 10 : static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3183 : {
3184 : struct cftype *cft;
3185 :
3186 61 : for (cft = cfts; cft->name[0] != '\0'; cft++) {
3187 : struct kernfs_ops *kf_ops;
3188 :
3189 : WARN_ON(cft->ss || cft->kf_ops);
3190 :
3191 51 : if (cft->seq_start)
3192 : kf_ops = &cgroup_kf_ops;
3193 : else
3194 : kf_ops = &cgroup_kf_single_ops;
3195 :
3196 : /*
3197 : * Ugh... if @cft wants a custom max_write_len, we need to
3198 : * make a copy of kf_ops to set its atomic_write_len.
3199 : */
3200 51 : if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
3201 1 : kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
3202 1 : if (!kf_ops) {
3203 0 : cgroup_exit_cftypes(cfts);
3204 0 : return -ENOMEM;
3205 : }
3206 1 : kf_ops->atomic_write_len = cft->max_write_len;
3207 : }
3208 :
3209 51 : cft->kf_ops = kf_ops;
3210 51 : cft->ss = ss;
3211 : }
3212 :
3213 : return 0;
3214 : }
3215 :
3216 0 : static int cgroup_rm_cftypes_locked(struct cftype *cfts)
3217 : {
3218 : lockdep_assert_held(&cgroup_mutex);
3219 :
3220 0 : if (!cfts || !cfts[0].ss)
3221 : return -ENOENT;
3222 :
3223 : list_del(&cfts->node);
3224 0 : cgroup_apply_cftypes(cfts, false);
3225 0 : cgroup_exit_cftypes(cfts);
3226 0 : return 0;
3227 : }
3228 :
3229 : /**
3230 : * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3231 : * @cfts: zero-length name terminated array of cftypes
3232 : *
3233 : * Unregister @cfts. Files described by @cfts are removed from all
3234 : * existing cgroups and all future cgroups won't have them either. This
3235 : * function can be called anytime whether @cfts' subsys is attached or not.
3236 : *
3237 : * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3238 : * registered.
3239 : */
3240 0 : int cgroup_rm_cftypes(struct cftype *cfts)
3241 : {
3242 : int ret;
3243 :
3244 0 : mutex_lock(&cgroup_mutex);
3245 0 : ret = cgroup_rm_cftypes_locked(cfts);
3246 0 : mutex_unlock(&cgroup_mutex);
3247 0 : return ret;
3248 : }
3249 :
3250 : /**
3251 : * cgroup_add_cftypes - add an array of cftypes to a subsystem
3252 : * @ss: target cgroup subsystem
3253 : * @cfts: zero-length name terminated array of cftypes
3254 : *
3255 : * Register @cfts to @ss. Files described by @cfts are created for all
3256 : * existing cgroups to which @ss is attached and all future cgroups will
3257 : * have them too. This function can be called anytime whether @ss is
3258 : * attached or not.
3259 : *
3260 : * Returns 0 on successful registration, -errno on failure. Note that this
3261 : * function currently returns 0 as long as @cfts registration is successful
3262 : * even if some file creation attempts on existing cgroups fail.
3263 : */
3264 14 : static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3265 : {
3266 : int ret;
3267 :
3268 14 : if (ss->disabled)
3269 : return 0;
3270 :
3271 14 : if (!cfts || cfts[0].name[0] == '\0')
3272 : return 0;
3273 :
3274 8 : ret = cgroup_init_cftypes(ss, cfts);
3275 8 : if (ret)
3276 : return ret;
3277 :
3278 8 : mutex_lock(&cgroup_mutex);
3279 :
3280 8 : list_add_tail(&cfts->node, &ss->cfts);
3281 8 : ret = cgroup_apply_cftypes(cfts, true);
3282 8 : if (ret)
3283 0 : cgroup_rm_cftypes_locked(cfts);
3284 :
3285 8 : mutex_unlock(&cgroup_mutex);
3286 8 : return ret;
3287 : }
3288 :
3289 : /**
3290 : * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3291 : * @ss: target cgroup subsystem
3292 : * @cfts: zero-length name terminated array of cftypes
3293 : *
3294 : * Similar to cgroup_add_cftypes() but the added files are only used for
3295 : * the default hierarchy.
3296 : */
3297 6 : int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3298 : {
3299 : struct cftype *cft;
3300 :
3301 6 : for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
3302 0 : cft->flags |= __CFTYPE_ONLY_ON_DFL;
3303 6 : return cgroup_add_cftypes(ss, cfts);
3304 : }
3305 :
3306 : /**
3307 : * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3308 : * @ss: target cgroup subsystem
3309 : * @cfts: zero-length name terminated array of cftypes
3310 : *
3311 : * Similar to cgroup_add_cftypes() but the added files are only used for
3312 : * the legacy hierarchies.
3313 : */
3314 8 : int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3315 : {
3316 : struct cftype *cft;
3317 :
3318 : /*
3319 : * If legacy_flies_on_dfl, we want to show the legacy files on the
3320 : * dfl hierarchy but iff the target subsystem hasn't been updated
3321 : * for the dfl hierarchy yet.
3322 : */
3323 8 : if (!cgroup_legacy_files_on_dfl ||
3324 0 : ss->dfl_cftypes != ss->legacy_cftypes) {
3325 40 : for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
3326 40 : cft->flags |= __CFTYPE_NOT_ON_DFL;
3327 : }
3328 :
3329 8 : return cgroup_add_cftypes(ss, cfts);
3330 : }
3331 :
3332 : /**
3333 : * cgroup_task_count - count the number of tasks in a cgroup.
3334 : * @cgrp: the cgroup in question
3335 : *
3336 : * Return the number of tasks in the cgroup.
3337 : */
3338 0 : static int cgroup_task_count(const struct cgroup *cgrp)
3339 : {
3340 : int count = 0;
3341 : struct cgrp_cset_link *link;
3342 :
3343 0 : down_read(&css_set_rwsem);
3344 0 : list_for_each_entry(link, &cgrp->cset_links, cset_link)
3345 0 : count += atomic_read(&link->cset->refcount);
3346 0 : up_read(&css_set_rwsem);
3347 0 : return count;
3348 : }
3349 :
3350 : /**
3351 : * css_next_child - find the next child of a given css
3352 : * @pos: the current position (%NULL to initiate traversal)
3353 : * @parent: css whose children to walk
3354 : *
3355 : * This function returns the next child of @parent and should be called
3356 : * under either cgroup_mutex or RCU read lock. The only requirement is
3357 : * that @parent and @pos are accessible. The next sibling is guaranteed to
3358 : * be returned regardless of their states.
3359 : *
3360 : * If a subsystem synchronizes ->css_online() and the start of iteration, a
3361 : * css which finished ->css_online() is guaranteed to be visible in the
3362 : * future iterations and will stay visible until the last reference is put.
3363 : * A css which hasn't finished ->css_online() or already finished
3364 : * ->css_offline() may show up during traversal. It's each subsystem's
3365 : * responsibility to synchronize against on/offlining.
3366 : */
3367 8 : struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
3368 : struct cgroup_subsys_state *parent)
3369 : {
3370 : struct cgroup_subsys_state *next;
3371 :
3372 : cgroup_assert_mutex_or_rcu_locked();
3373 :
3374 : /*
3375 : * @pos could already have been unlinked from the sibling list.
3376 : * Once a cgroup is removed, its ->sibling.next is no longer
3377 : * updated when its next sibling changes. CSS_RELEASED is set when
3378 : * @pos is taken off list, at which time its next pointer is valid,
3379 : * and, as releases are serialized, the one pointed to by the next
3380 : * pointer is guaranteed to not have started release yet. This
3381 : * implies that if we observe !CSS_RELEASED on @pos in this RCU
3382 : * critical section, the one pointed to by its next pointer is
3383 : * guaranteed to not have finished its RCU grace period even if we
3384 : * have dropped rcu_read_lock() inbetween iterations.
3385 : *
3386 : * If @pos has CSS_RELEASED set, its next pointer can't be
3387 : * dereferenced; however, as each css is given a monotonically
3388 : * increasing unique serial number and always appended to the
3389 : * sibling list, the next one can be found by walking the parent's
3390 : * children until the first css with higher serial number than
3391 : * @pos's. While this path can be slower, it happens iff iteration
3392 : * races against release and the race window is very small.
3393 : */
3394 8 : if (!pos) {
3395 8 : next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
3396 0 : } else if (likely(!(pos->flags & CSS_RELEASED))) {
3397 0 : next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
3398 : } else {
3399 0 : list_for_each_entry_rcu(next, &parent->children, sibling)
3400 0 : if (next->serial_nr > pos->serial_nr)
3401 : break;
3402 : }
3403 :
3404 : /*
3405 : * @next, if not pointing to the head, can be dereferenced and is
3406 : * the next sibling.
3407 : */
3408 8 : if (&next->sibling != &parent->children)
3409 0 : return next;
3410 : return NULL;
3411 : }
3412 :
3413 : /**
3414 : * css_next_descendant_pre - find the next descendant for pre-order walk
3415 : * @pos: the current position (%NULL to initiate traversal)
3416 : * @root: css whose descendants to walk
3417 : *
3418 : * To be used by css_for_each_descendant_pre(). Find the next descendant
3419 : * to visit for pre-order traversal of @root's descendants. @root is
3420 : * included in the iteration and the first node to be visited.
3421 : *
3422 : * While this function requires cgroup_mutex or RCU read locking, it
3423 : * doesn't require the whole traversal to be contained in a single critical
3424 : * section. This function will return the correct next descendant as long
3425 : * as both @pos and @root are accessible and @pos is a descendant of @root.
3426 : *
3427 : * If a subsystem synchronizes ->css_online() and the start of iteration, a
3428 : * css which finished ->css_online() is guaranteed to be visible in the
3429 : * future iterations and will stay visible until the last reference is put.
3430 : * A css which hasn't finished ->css_online() or already finished
3431 : * ->css_offline() may show up during traversal. It's each subsystem's
3432 : * responsibility to synchronize against on/offlining.
3433 : */
3434 : struct cgroup_subsys_state *
3435 16 : css_next_descendant_pre(struct cgroup_subsys_state *pos,
3436 : struct cgroup_subsys_state *root)
3437 : {
3438 : struct cgroup_subsys_state *next;
3439 :
3440 : cgroup_assert_mutex_or_rcu_locked();
3441 :
3442 : /* if first iteration, visit @root */
3443 16 : if (!pos)
3444 : return root;
3445 :
3446 : /* visit the first child if exists */
3447 8 : next = css_next_child(NULL, pos);
3448 8 : if (next)
3449 : return next;
3450 :
3451 : /* no child, visit my or the closest ancestor's next sibling */
3452 8 : while (pos != root) {
3453 0 : next = css_next_child(pos, pos->parent);
3454 0 : if (next)
3455 : return next;
3456 0 : pos = pos->parent;
3457 : }
3458 :
3459 : return NULL;
3460 : }
3461 :
3462 : /**
3463 : * css_rightmost_descendant - return the rightmost descendant of a css
3464 : * @pos: css of interest
3465 : *
3466 : * Return the rightmost descendant of @pos. If there's no descendant, @pos
3467 : * is returned. This can be used during pre-order traversal to skip
3468 : * subtree of @pos.
3469 : *
3470 : * While this function requires cgroup_mutex or RCU read locking, it
3471 : * doesn't require the whole traversal to be contained in a single critical
3472 : * section. This function will return the correct rightmost descendant as
3473 : * long as @pos is accessible.
3474 : */
3475 : struct cgroup_subsys_state *
3476 0 : css_rightmost_descendant(struct cgroup_subsys_state *pos)
3477 : {
3478 : struct cgroup_subsys_state *last, *tmp;
3479 :
3480 : cgroup_assert_mutex_or_rcu_locked();
3481 :
3482 : do {
3483 : last = pos;
3484 : /* ->prev isn't RCU safe, walk ->next till the end */
3485 : pos = NULL;
3486 0 : css_for_each_child(tmp, last)
3487 : pos = tmp;
3488 0 : } while (pos);
3489 :
3490 0 : return last;
3491 : }
3492 :
3493 : static struct cgroup_subsys_state *
3494 : css_leftmost_descendant(struct cgroup_subsys_state *pos)
3495 : {
3496 : struct cgroup_subsys_state *last;
3497 :
3498 : do {
3499 : last = pos;
3500 0 : pos = css_next_child(NULL, pos);
3501 0 : } while (pos);
3502 :
3503 : return last;
3504 : }
3505 :
3506 : /**
3507 : * css_next_descendant_post - find the next descendant for post-order walk
3508 : * @pos: the current position (%NULL to initiate traversal)
3509 : * @root: css whose descendants to walk
3510 : *
3511 : * To be used by css_for_each_descendant_post(). Find the next descendant
3512 : * to visit for post-order traversal of @root's descendants. @root is
3513 : * included in the iteration and the last node to be visited.
3514 : *
3515 : * While this function requires cgroup_mutex or RCU read locking, it
3516 : * doesn't require the whole traversal to be contained in a single critical
3517 : * section. This function will return the correct next descendant as long
3518 : * as both @pos and @cgroup are accessible and @pos is a descendant of
3519 : * @cgroup.
3520 : *
3521 : * If a subsystem synchronizes ->css_online() and the start of iteration, a
3522 : * css which finished ->css_online() is guaranteed to be visible in the
3523 : * future iterations and will stay visible until the last reference is put.
3524 : * A css which hasn't finished ->css_online() or already finished
3525 : * ->css_offline() may show up during traversal. It's each subsystem's
3526 : * responsibility to synchronize against on/offlining.
3527 : */
3528 : struct cgroup_subsys_state *
3529 0 : css_next_descendant_post(struct cgroup_subsys_state *pos,
3530 : struct cgroup_subsys_state *root)
3531 : {
3532 : struct cgroup_subsys_state *next;
3533 :
3534 : cgroup_assert_mutex_or_rcu_locked();
3535 :
3536 : /* if first iteration, visit leftmost descendant which may be @root */
3537 0 : if (!pos)
3538 : return css_leftmost_descendant(root);
3539 :
3540 : /* if we visited @root, we're done */
3541 0 : if (pos == root)
3542 : return NULL;
3543 :
3544 : /* if there's an unvisited sibling, visit its leftmost descendant */
3545 0 : next = css_next_child(pos, pos->parent);
3546 0 : if (next)
3547 : return css_leftmost_descendant(next);
3548 :
3549 : /* no sibling left, visit parent */
3550 0 : return pos->parent;
3551 : }
3552 :
3553 : /**
3554 : * css_has_online_children - does a css have online children
3555 : * @css: the target css
3556 : *
3557 : * Returns %true if @css has any online children; otherwise, %false. This
3558 : * function can be called from any context but the caller is responsible
3559 : * for synchronizing against on/offlining as necessary.
3560 : */
3561 0 : bool css_has_online_children(struct cgroup_subsys_state *css)
3562 : {
3563 : struct cgroup_subsys_state *child;
3564 : bool ret = false;
3565 :
3566 : rcu_read_lock();
3567 0 : css_for_each_child(child, css) {
3568 0 : if (child->flags & CSS_ONLINE) {
3569 : ret = true;
3570 : break;
3571 : }
3572 : }
3573 : rcu_read_unlock();
3574 0 : return ret;
3575 : }
3576 :
3577 : /**
3578 : * css_advance_task_iter - advance a task itererator to the next css_set
3579 : * @it: the iterator to advance
3580 : *
3581 : * Advance @it to the next css_set to walk.
3582 : */
3583 0 : static void css_advance_task_iter(struct css_task_iter *it)
3584 : {
3585 0 : struct list_head *l = it->cset_pos;
3586 : struct cgrp_cset_link *link;
3587 : struct css_set *cset;
3588 :
3589 : /* Advance to the next non-empty css_set */
3590 : do {
3591 0 : l = l->next;
3592 0 : if (l == it->cset_head) {
3593 0 : it->cset_pos = NULL;
3594 0 : return;
3595 : }
3596 :
3597 0 : if (it->ss) {
3598 0 : cset = container_of(l, struct css_set,
3599 : e_cset_node[it->ss->id]);
3600 : } else {
3601 : link = list_entry(l, struct cgrp_cset_link, cset_link);
3602 0 : cset = link->cset;
3603 : }
3604 0 : } while (list_empty(&cset->tasks) && list_empty(&cset->mg_tasks));
3605 :
3606 0 : it->cset_pos = l;
3607 :
3608 0 : if (!list_empty(&cset->tasks))
3609 0 : it->task_pos = cset->tasks.next;
3610 : else
3611 0 : it->task_pos = cset->mg_tasks.next;
3612 :
3613 0 : it->tasks_head = &cset->tasks;
3614 0 : it->mg_tasks_head = &cset->mg_tasks;
3615 : }
3616 :
3617 : /**
3618 : * css_task_iter_start - initiate task iteration
3619 : * @css: the css to walk tasks of
3620 : * @it: the task iterator to use
3621 : *
3622 : * Initiate iteration through the tasks of @css. The caller can call
3623 : * css_task_iter_next() to walk through the tasks until the function
3624 : * returns NULL. On completion of iteration, css_task_iter_end() must be
3625 : * called.
3626 : *
3627 : * Note that this function acquires a lock which is released when the
3628 : * iteration finishes. The caller can't sleep while iteration is in
3629 : * progress.
3630 : */
3631 0 : void css_task_iter_start(struct cgroup_subsys_state *css,
3632 : struct css_task_iter *it)
3633 : __acquires(css_set_rwsem)
3634 : {
3635 : /* no one should try to iterate before mounting cgroups */
3636 : WARN_ON_ONCE(!use_task_css_set_links);
3637 :
3638 0 : down_read(&css_set_rwsem);
3639 :
3640 0 : it->ss = css->ss;
3641 :
3642 0 : if (it->ss)
3643 0 : it->cset_pos = &css->cgroup->e_csets[css->ss->id];
3644 : else
3645 0 : it->cset_pos = &css->cgroup->cset_links;
3646 :
3647 0 : it->cset_head = it->cset_pos;
3648 :
3649 0 : css_advance_task_iter(it);
3650 0 : }
3651 :
3652 : /**
3653 : * css_task_iter_next - return the next task for the iterator
3654 : * @it: the task iterator being iterated
3655 : *
3656 : * The "next" function for task iteration. @it should have been
3657 : * initialized via css_task_iter_start(). Returns NULL when the iteration
3658 : * reaches the end.
3659 : */
3660 0 : struct task_struct *css_task_iter_next(struct css_task_iter *it)
3661 : {
3662 : struct task_struct *res;
3663 0 : struct list_head *l = it->task_pos;
3664 :
3665 : /* If the iterator cg is NULL, we have no tasks */
3666 0 : if (!it->cset_pos)
3667 : return NULL;
3668 : res = list_entry(l, struct task_struct, cg_list);
3669 :
3670 : /*
3671 : * Advance iterator to find next entry. cset->tasks is consumed
3672 : * first and then ->mg_tasks. After ->mg_tasks, we move onto the
3673 : * next cset.
3674 : */
3675 0 : l = l->next;
3676 :
3677 0 : if (l == it->tasks_head)
3678 0 : l = it->mg_tasks_head->next;
3679 :
3680 0 : if (l == it->mg_tasks_head)
3681 0 : css_advance_task_iter(it);
3682 : else
3683 0 : it->task_pos = l;
3684 :
3685 0 : return res;
3686 : }
3687 :
3688 : /**
3689 : * css_task_iter_end - finish task iteration
3690 : * @it: the task iterator to finish
3691 : *
3692 : * Finish task iteration started by css_task_iter_start().
3693 : */
3694 0 : void css_task_iter_end(struct css_task_iter *it)
3695 : __releases(css_set_rwsem)
3696 : {
3697 0 : up_read(&css_set_rwsem);
3698 0 : }
3699 :
3700 : /**
3701 : * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
3702 : * @to: cgroup to which the tasks will be moved
3703 : * @from: cgroup in which the tasks currently reside
3704 : *
3705 : * Locking rules between cgroup_post_fork() and the migration path
3706 : * guarantee that, if a task is forking while being migrated, the new child
3707 : * is guaranteed to be either visible in the source cgroup after the
3708 : * parent's migration is complete or put into the target cgroup. No task
3709 : * can slip out of migration through forking.
3710 : */
3711 0 : int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
3712 : {
3713 0 : LIST_HEAD(preloaded_csets);
3714 : struct cgrp_cset_link *link;
3715 : struct css_task_iter it;
3716 : struct task_struct *task;
3717 : int ret;
3718 :
3719 0 : mutex_lock(&cgroup_mutex);
3720 :
3721 : /* all tasks in @from are being moved, all csets are source */
3722 0 : down_read(&css_set_rwsem);
3723 0 : list_for_each_entry(link, &from->cset_links, cset_link)
3724 0 : cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
3725 0 : up_read(&css_set_rwsem);
3726 :
3727 0 : ret = cgroup_migrate_prepare_dst(to, &preloaded_csets);
3728 0 : if (ret)
3729 : goto out_err;
3730 :
3731 : /*
3732 : * Migrate tasks one-by-one until @form is empty. This fails iff
3733 : * ->can_attach() fails.
3734 : */
3735 : do {
3736 0 : css_task_iter_start(&from->self, &it);
3737 0 : task = css_task_iter_next(&it);
3738 0 : if (task)
3739 0 : get_task_struct(task);
3740 : css_task_iter_end(&it);
3741 :
3742 0 : if (task) {
3743 0 : ret = cgroup_migrate(to, task, false);
3744 : put_task_struct(task);
3745 : }
3746 0 : } while (task && !ret);
3747 : out_err:
3748 0 : cgroup_migrate_finish(&preloaded_csets);
3749 0 : mutex_unlock(&cgroup_mutex);
3750 0 : return ret;
3751 : }
3752 :
3753 : /*
3754 : * Stuff for reading the 'tasks'/'procs' files.
3755 : *
3756 : * Reading this file can return large amounts of data if a cgroup has
3757 : * *lots* of attached tasks. So it may need several calls to read(),
3758 : * but we cannot guarantee that the information we produce is correct
3759 : * unless we produce it entirely atomically.
3760 : *
3761 : */
3762 :
3763 : /* which pidlist file are we talking about? */
3764 : enum cgroup_filetype {
3765 : CGROUP_FILE_PROCS,
3766 : CGROUP_FILE_TASKS,
3767 : };
3768 :
3769 : /*
3770 : * A pidlist is a list of pids that virtually represents the contents of one
3771 : * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3772 : * a pair (one each for procs, tasks) for each pid namespace that's relevant
3773 : * to the cgroup.
3774 : */
3775 : struct cgroup_pidlist {
3776 : /*
3777 : * used to find which pidlist is wanted. doesn't change as long as
3778 : * this particular list stays in the list.
3779 : */
3780 : struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3781 : /* array of xids */
3782 : pid_t *list;
3783 : /* how many elements the above list has */
3784 : int length;
3785 : /* each of these stored in a list by its cgroup */
3786 : struct list_head links;
3787 : /* pointer to the cgroup we belong to, for list removal purposes */
3788 : struct cgroup *owner;
3789 : /* for delayed destruction */
3790 : struct delayed_work destroy_dwork;
3791 : };
3792 :
3793 : /*
3794 : * The following two functions "fix" the issue where there are more pids
3795 : * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3796 : * TODO: replace with a kernel-wide solution to this problem
3797 : */
3798 : #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3799 0 : static void *pidlist_allocate(int count)
3800 : {
3801 0 : if (PIDLIST_TOO_LARGE(count))
3802 0 : return vmalloc(count * sizeof(pid_t));
3803 : else
3804 0 : return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3805 : }
3806 :
3807 0 : static void pidlist_free(void *p)
3808 : {
3809 0 : if (is_vmalloc_addr(p))
3810 0 : vfree(p);
3811 : else
3812 0 : kfree(p);
3813 0 : }
3814 :
3815 : /*
3816 : * Used to destroy all pidlists lingering waiting for destroy timer. None
3817 : * should be left afterwards.
3818 : */
3819 0 : static void cgroup_pidlist_destroy_all(struct cgroup *cgrp)
3820 : {
3821 : struct cgroup_pidlist *l, *tmp_l;
3822 :
3823 0 : mutex_lock(&cgrp->pidlist_mutex);
3824 0 : list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
3825 0 : mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
3826 0 : mutex_unlock(&cgrp->pidlist_mutex);
3827 :
3828 0 : flush_workqueue(cgroup_pidlist_destroy_wq);
3829 : BUG_ON(!list_empty(&cgrp->pidlists));
3830 0 : }
3831 :
3832 0 : static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
3833 : {
3834 : struct delayed_work *dwork = to_delayed_work(work);
3835 0 : struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
3836 : destroy_dwork);
3837 : struct cgroup_pidlist *tofree = NULL;
3838 :
3839 0 : mutex_lock(&l->owner->pidlist_mutex);
3840 :
3841 : /*
3842 : * Destroy iff we didn't get queued again. The state won't change
3843 : * as destroy_dwork can only be queued while locked.
3844 : */
3845 0 : if (!delayed_work_pending(dwork)) {
3846 : list_del(&l->links);
3847 0 : pidlist_free(l->list);
3848 0 : put_pid_ns(l->key.ns);
3849 : tofree = l;
3850 : }
3851 :
3852 0 : mutex_unlock(&l->owner->pidlist_mutex);
3853 0 : kfree(tofree);
3854 0 : }
3855 :
3856 : /*
3857 : * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3858 : * Returns the number of unique elements.
3859 : */
3860 0 : static int pidlist_uniq(pid_t *list, int length)
3861 : {
3862 : int src, dest = 1;
3863 :
3864 : /*
3865 : * we presume the 0th element is unique, so i starts at 1. trivial
3866 : * edge cases first; no work needs to be done for either
3867 : */
3868 0 : if (length == 0 || length == 1)
3869 : return length;
3870 : /* src and dest walk down the list; dest counts unique elements */
3871 0 : for (src = 1; src < length; src++) {
3872 : /* find next unique element */
3873 0 : while (list[src] == list[src-1]) {
3874 0 : src++;
3875 0 : if (src == length)
3876 : goto after;
3877 : }
3878 : /* dest always points to where the next unique element goes */
3879 0 : list[dest] = list[src];
3880 0 : dest++;
3881 : }
3882 : after:
3883 : return dest;
3884 : }
3885 :
3886 : /*
3887 : * The two pid files - task and cgroup.procs - guaranteed that the result
3888 : * is sorted, which forced this whole pidlist fiasco. As pid order is
3889 : * different per namespace, each namespace needs differently sorted list,
3890 : * making it impossible to use, for example, single rbtree of member tasks
3891 : * sorted by task pointer. As pidlists can be fairly large, allocating one
3892 : * per open file is dangerous, so cgroup had to implement shared pool of
3893 : * pidlists keyed by cgroup and namespace.
3894 : *
3895 : * All this extra complexity was caused by the original implementation
3896 : * committing to an entirely unnecessary property. In the long term, we
3897 : * want to do away with it. Explicitly scramble sort order if on the
3898 : * default hierarchy so that no such expectation exists in the new
3899 : * interface.
3900 : *
3901 : * Scrambling is done by swapping every two consecutive bits, which is
3902 : * non-identity one-to-one mapping which disturbs sort order sufficiently.
3903 : */
3904 : static pid_t pid_fry(pid_t pid)
3905 : {
3906 0 : unsigned a = pid & 0x55555555;
3907 0 : unsigned b = pid & 0xAAAAAAAA;
3908 :
3909 0 : return (a << 1) | (b >> 1);
3910 : }
3911 :
3912 0 : static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
3913 : {
3914 0 : if (cgroup_on_dfl(cgrp))
3915 : return pid_fry(pid);
3916 : else
3917 : return pid;
3918 : }
3919 :
3920 0 : static int cmppid(const void *a, const void *b)
3921 : {
3922 0 : return *(pid_t *)a - *(pid_t *)b;
3923 : }
3924 :
3925 0 : static int fried_cmppid(const void *a, const void *b)
3926 : {
3927 0 : return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
3928 : }
3929 :
3930 0 : static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3931 : enum cgroup_filetype type)
3932 : {
3933 : struct cgroup_pidlist *l;
3934 : /* don't need task_nsproxy() if we're looking at ourself */
3935 0 : struct pid_namespace *ns = task_active_pid_ns(current);
3936 :
3937 : lockdep_assert_held(&cgrp->pidlist_mutex);
3938 :
3939 0 : list_for_each_entry(l, &cgrp->pidlists, links)
3940 0 : if (l->key.type == type && l->key.ns == ns)
3941 : return l;
3942 : return NULL;
3943 : }
3944 :
3945 : /*
3946 : * find the appropriate pidlist for our purpose (given procs vs tasks)
3947 : * returns with the lock on that pidlist already held, and takes care
3948 : * of the use count, or returns NULL with no locks held if we're out of
3949 : * memory.
3950 : */
3951 0 : static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
3952 : enum cgroup_filetype type)
3953 : {
3954 : struct cgroup_pidlist *l;
3955 :
3956 : lockdep_assert_held(&cgrp->pidlist_mutex);
3957 :
3958 0 : l = cgroup_pidlist_find(cgrp, type);
3959 0 : if (l)
3960 : return l;
3961 :
3962 : /* entry not found; create a new one */
3963 : l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3964 0 : if (!l)
3965 : return l;
3966 :
3967 0 : INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
3968 0 : l->key.type = type;
3969 : /* don't need task_nsproxy() if we're looking at ourself */
3970 0 : l->key.ns = get_pid_ns(task_active_pid_ns(current));
3971 0 : l->owner = cgrp;
3972 0 : list_add(&l->links, &cgrp->pidlists);
3973 0 : return l;
3974 : }
3975 :
3976 : /*
3977 : * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3978 : */
3979 0 : static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3980 : struct cgroup_pidlist **lp)
3981 : {
3982 : pid_t *array;
3983 : int length;
3984 : int pid, n = 0; /* used for populating the array */
3985 : struct css_task_iter it;
3986 : struct task_struct *tsk;
3987 : struct cgroup_pidlist *l;
3988 :
3989 : lockdep_assert_held(&cgrp->pidlist_mutex);
3990 :
3991 : /*
3992 : * If cgroup gets more users after we read count, we won't have
3993 : * enough space - tough. This race is indistinguishable to the
3994 : * caller from the case that the additional cgroup users didn't
3995 : * show up until sometime later on.
3996 : */
3997 0 : length = cgroup_task_count(cgrp);
3998 0 : array = pidlist_allocate(length);
3999 0 : if (!array)
4000 : return -ENOMEM;
4001 : /* now, populate the array */
4002 0 : css_task_iter_start(&cgrp->self, &it);
4003 0 : while ((tsk = css_task_iter_next(&it))) {
4004 0 : if (unlikely(n == length))
4005 : break;
4006 : /* get tgid or pid for procs or tasks file respectively */
4007 0 : if (type == CGROUP_FILE_PROCS)
4008 : pid = task_tgid_vnr(tsk);
4009 : else
4010 : pid = task_pid_vnr(tsk);
4011 0 : if (pid > 0) /* make sure to only use valid results */
4012 0 : array[n++] = pid;
4013 : }
4014 : css_task_iter_end(&it);
4015 : length = n;
4016 : /* now sort & (if procs) strip out duplicates */
4017 0 : if (cgroup_on_dfl(cgrp))
4018 0 : sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
4019 : else
4020 0 : sort(array, length, sizeof(pid_t), cmppid, NULL);
4021 0 : if (type == CGROUP_FILE_PROCS)
4022 0 : length = pidlist_uniq(array, length);
4023 :
4024 0 : l = cgroup_pidlist_find_create(cgrp, type);
4025 0 : if (!l) {
4026 0 : pidlist_free(array);
4027 0 : return -ENOMEM;
4028 : }
4029 :
4030 : /* store array, freeing old if necessary */
4031 0 : pidlist_free(l->list);
4032 0 : l->list = array;
4033 0 : l->length = length;
4034 0 : *lp = l;
4035 0 : return 0;
4036 : }
4037 :
4038 : /**
4039 : * cgroupstats_build - build and fill cgroupstats
4040 : * @stats: cgroupstats to fill information into
4041 : * @dentry: A dentry entry belonging to the cgroup for which stats have
4042 : * been requested.
4043 : *
4044 : * Build and fill cgroupstats so that taskstats can export it to user
4045 : * space.
4046 : */
4047 0 : int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
4048 : {
4049 0 : struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
4050 0 : struct cgroup *cgrp;
4051 : struct css_task_iter it;
4052 : struct task_struct *tsk;
4053 :
4054 : /* it should be kernfs_node belonging to cgroupfs and is a directory */
4055 0 : if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
4056 : kernfs_type(kn) != KERNFS_DIR)
4057 : return -EINVAL;
4058 :
4059 0 : mutex_lock(&cgroup_mutex);
4060 :
4061 : /*
4062 : * We aren't being called from kernfs and there's no guarantee on
4063 : * @kn->priv's validity. For this and css_tryget_online_from_dir(),
4064 : * @kn->priv is RCU safe. Let's do the RCU dancing.
4065 : */
4066 : rcu_read_lock();
4067 0 : cgrp = rcu_dereference(kn->priv);
4068 0 : if (!cgrp || cgroup_is_dead(cgrp)) {
4069 : rcu_read_unlock();
4070 0 : mutex_unlock(&cgroup_mutex);
4071 0 : return -ENOENT;
4072 : }
4073 : rcu_read_unlock();
4074 :
4075 0 : css_task_iter_start(&cgrp->self, &it);
4076 0 : while ((tsk = css_task_iter_next(&it))) {
4077 0 : switch (tsk->state) {
4078 : case TASK_RUNNING:
4079 0 : stats->nr_running++;
4080 0 : break;
4081 : case TASK_INTERRUPTIBLE:
4082 0 : stats->nr_sleeping++;
4083 0 : break;
4084 : case TASK_UNINTERRUPTIBLE:
4085 0 : stats->nr_uninterruptible++;
4086 0 : break;
4087 : case TASK_STOPPED:
4088 0 : stats->nr_stopped++;
4089 0 : break;
4090 : default:
4091 0 : if (delayacct_is_task_waiting_on_io(tsk))
4092 0 : stats->nr_io_wait++;
4093 : break;
4094 : }
4095 : }
4096 : css_task_iter_end(&it);
4097 :
4098 0 : mutex_unlock(&cgroup_mutex);
4099 0 : return 0;
4100 : }
4101 :
4102 :
4103 : /*
4104 : * seq_file methods for the tasks/procs files. The seq_file position is the
4105 : * next pid to display; the seq_file iterator is a pointer to the pid
4106 : * in the cgroup->l->list array.
4107 : */
4108 :
4109 0 : static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
4110 : {
4111 : /*
4112 : * Initially we receive a position value that corresponds to
4113 : * one more than the last pid shown (or 0 on the first call or
4114 : * after a seek to the start). Use a binary-search to find the
4115 : * next pid to display, if any
4116 : */
4117 0 : struct kernfs_open_file *of = s->private;
4118 0 : struct cgroup *cgrp = seq_css(s)->cgroup;
4119 : struct cgroup_pidlist *l;
4120 0 : enum cgroup_filetype type = seq_cft(s)->private;
4121 0 : int index = 0, pid = *pos;
4122 : int *iter, ret;
4123 :
4124 0 : mutex_lock(&cgrp->pidlist_mutex);
4125 :
4126 : /*
4127 : * !NULL @of->priv indicates that this isn't the first start()
4128 : * after open. If the matching pidlist is around, we can use that.
4129 : * Look for it. Note that @of->priv can't be used directly. It
4130 : * could already have been destroyed.
4131 : */
4132 0 : if (of->priv)
4133 0 : of->priv = cgroup_pidlist_find(cgrp, type);
4134 :
4135 : /*
4136 : * Either this is the first start() after open or the matching
4137 : * pidlist has been destroyed inbetween. Create a new one.
4138 : */
4139 0 : if (!of->priv) {
4140 0 : ret = pidlist_array_load(cgrp, type,
4141 0 : (struct cgroup_pidlist **)&of->priv);
4142 0 : if (ret)
4143 0 : return ERR_PTR(ret);
4144 : }
4145 0 : l = of->priv;
4146 :
4147 0 : if (pid) {
4148 0 : int end = l->length;
4149 :
4150 0 : while (index < end) {
4151 0 : int mid = (index + end) / 2;
4152 0 : if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
4153 : index = mid;
4154 : break;
4155 0 : } else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid)
4156 0 : index = mid + 1;
4157 : else
4158 : end = mid;
4159 : }
4160 : }
4161 : /* If we're off the end of the array, we're done */
4162 0 : if (index >= l->length)
4163 : return NULL;
4164 : /* Update the abstract position to be the actual pid that we found */
4165 0 : iter = l->list + index;
4166 0 : *pos = cgroup_pid_fry(cgrp, *iter);
4167 0 : return iter;
4168 : }
4169 :
4170 0 : static void cgroup_pidlist_stop(struct seq_file *s, void *v)
4171 : {
4172 0 : struct kernfs_open_file *of = s->private;
4173 0 : struct cgroup_pidlist *l = of->priv;
4174 :
4175 0 : if (l)
4176 0 : mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
4177 : CGROUP_PIDLIST_DESTROY_DELAY);
4178 0 : mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
4179 0 : }
4180 :
4181 0 : static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
4182 : {
4183 0 : struct kernfs_open_file *of = s->private;
4184 0 : struct cgroup_pidlist *l = of->priv;
4185 : pid_t *p = v;
4186 0 : pid_t *end = l->list + l->length;
4187 : /*
4188 : * Advance to the next pid in the array. If this goes off the
4189 : * end, we're done
4190 : */
4191 0 : p++;
4192 0 : if (p >= end) {
4193 : return NULL;
4194 : } else {
4195 0 : *pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
4196 0 : return p;
4197 : }
4198 : }
4199 :
4200 0 : static int cgroup_pidlist_show(struct seq_file *s, void *v)
4201 : {
4202 0 : return seq_printf(s, "%d\n", *(int *)v);
4203 : }
4204 :
4205 0 : static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
4206 : struct cftype *cft)
4207 : {
4208 0 : return notify_on_release(css->cgroup);
4209 : }
4210 :
4211 0 : static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
4212 : struct cftype *cft, u64 val)
4213 : {
4214 0 : if (val)
4215 0 : set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
4216 : else
4217 0 : clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
4218 0 : return 0;
4219 : }
4220 :
4221 0 : static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
4222 : struct cftype *cft)
4223 : {
4224 0 : return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
4225 : }
4226 :
4227 0 : static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
4228 : struct cftype *cft, u64 val)
4229 : {
4230 0 : if (val)
4231 0 : set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
4232 : else
4233 0 : clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
4234 0 : return 0;
4235 : }
4236 :
4237 : /* cgroup core interface files for the default hierarchy */
4238 : static struct cftype cgroup_dfl_base_files[] = {
4239 : {
4240 : .name = "cgroup.procs",
4241 : .seq_start = cgroup_pidlist_start,
4242 : .seq_next = cgroup_pidlist_next,
4243 : .seq_stop = cgroup_pidlist_stop,
4244 : .seq_show = cgroup_pidlist_show,
4245 : .private = CGROUP_FILE_PROCS,
4246 : .write = cgroup_procs_write,
4247 : .mode = S_IRUGO | S_IWUSR,
4248 : },
4249 : {
4250 : .name = "cgroup.controllers",
4251 : .flags = CFTYPE_ONLY_ON_ROOT,
4252 : .seq_show = cgroup_root_controllers_show,
4253 : },
4254 : {
4255 : .name = "cgroup.controllers",
4256 : .flags = CFTYPE_NOT_ON_ROOT,
4257 : .seq_show = cgroup_controllers_show,
4258 : },
4259 : {
4260 : .name = "cgroup.subtree_control",
4261 : .seq_show = cgroup_subtree_control_show,
4262 : .write = cgroup_subtree_control_write,
4263 : },
4264 : {
4265 : .name = "cgroup.populated",
4266 : .flags = CFTYPE_NOT_ON_ROOT,
4267 : .seq_show = cgroup_populated_show,
4268 : },
4269 : { } /* terminate */
4270 : };
4271 :
4272 : /* cgroup core interface files for the legacy hierarchies */
4273 : static struct cftype cgroup_legacy_base_files[] = {
4274 : {
4275 : .name = "cgroup.procs",
4276 : .seq_start = cgroup_pidlist_start,
4277 : .seq_next = cgroup_pidlist_next,
4278 : .seq_stop = cgroup_pidlist_stop,
4279 : .seq_show = cgroup_pidlist_show,
4280 : .private = CGROUP_FILE_PROCS,
4281 : .write = cgroup_procs_write,
4282 : .mode = S_IRUGO | S_IWUSR,
4283 : },
4284 : {
4285 : .name = "cgroup.clone_children",
4286 : .read_u64 = cgroup_clone_children_read,
4287 : .write_u64 = cgroup_clone_children_write,
4288 : },
4289 : {
4290 : .name = "cgroup.sane_behavior",
4291 : .flags = CFTYPE_ONLY_ON_ROOT,
4292 : .seq_show = cgroup_sane_behavior_show,
4293 : },
4294 : {
4295 : .name = "tasks",
4296 : .seq_start = cgroup_pidlist_start,
4297 : .seq_next = cgroup_pidlist_next,
4298 : .seq_stop = cgroup_pidlist_stop,
4299 : .seq_show = cgroup_pidlist_show,
4300 : .private = CGROUP_FILE_TASKS,
4301 : .write = cgroup_tasks_write,
4302 : .mode = S_IRUGO | S_IWUSR,
4303 : },
4304 : {
4305 : .name = "notify_on_release",
4306 : .read_u64 = cgroup_read_notify_on_release,
4307 : .write_u64 = cgroup_write_notify_on_release,
4308 : },
4309 : {
4310 : .name = "release_agent",
4311 : .flags = CFTYPE_ONLY_ON_ROOT,
4312 : .seq_show = cgroup_release_agent_show,
4313 : .write = cgroup_release_agent_write,
4314 : .max_write_len = PATH_MAX - 1,
4315 : },
4316 : { } /* terminate */
4317 : };
4318 :
4319 : /**
4320 : * cgroup_populate_dir - create subsys files in a cgroup directory
4321 : * @cgrp: target cgroup
4322 : * @subsys_mask: mask of the subsystem ids whose files should be added
4323 : *
4324 : * On failure, no file is added.
4325 : */
4326 1 : static int cgroup_populate_dir(struct cgroup *cgrp, unsigned int subsys_mask)
4327 : {
4328 : struct cgroup_subsys *ss;
4329 : int i, ret = 0;
4330 :
4331 : /* process cftsets of each subsystem */
4332 8 : for_each_subsys(ss, i) {
4333 : struct cftype *cfts;
4334 :
4335 7 : if (!(subsys_mask & (1 << i)))
4336 7 : continue;
4337 :
4338 0 : list_for_each_entry(cfts, &ss->cfts, node) {
4339 0 : ret = cgroup_addrm_files(cgrp, cfts, true);
4340 0 : if (ret < 0)
4341 : goto err;
4342 : }
4343 : }
4344 : return 0;
4345 : err:
4346 0 : cgroup_clear_dir(cgrp, subsys_mask);
4347 0 : return ret;
4348 : }
4349 :
4350 : /*
4351 : * css destruction is four-stage process.
4352 : *
4353 : * 1. Destruction starts. Killing of the percpu_ref is initiated.
4354 : * Implemented in kill_css().
4355 : *
4356 : * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4357 : * and thus css_tryget_online() is guaranteed to fail, the css can be
4358 : * offlined by invoking offline_css(). After offlining, the base ref is
4359 : * put. Implemented in css_killed_work_fn().
4360 : *
4361 : * 3. When the percpu_ref reaches zero, the only possible remaining
4362 : * accessors are inside RCU read sections. css_release() schedules the
4363 : * RCU callback.
4364 : *
4365 : * 4. After the grace period, the css can be freed. Implemented in
4366 : * css_free_work_fn().
4367 : *
4368 : * It is actually hairier because both step 2 and 4 require process context
4369 : * and thus involve punting to css->destroy_work adding two additional
4370 : * steps to the already complex sequence.
4371 : */
4372 0 : static void css_free_work_fn(struct work_struct *work)
4373 : {
4374 0 : struct cgroup_subsys_state *css =
4375 : container_of(work, struct cgroup_subsys_state, destroy_work);
4376 0 : struct cgroup *cgrp = css->cgroup;
4377 :
4378 0 : percpu_ref_exit(&css->refcnt);
4379 :
4380 0 : if (css->ss) {
4381 : /* css free path */
4382 0 : if (css->parent)
4383 : css_put(css->parent);
4384 :
4385 0 : css->ss->css_free(css);
4386 0 : cgroup_put(cgrp);
4387 : } else {
4388 : /* cgroup free path */
4389 0 : atomic_dec(&cgrp->root->nr_cgrps);
4390 0 : cgroup_pidlist_destroy_all(cgrp);
4391 0 : cancel_work_sync(&cgrp->release_agent_work);
4392 :
4393 0 : if (cgroup_parent(cgrp)) {
4394 : /*
4395 : * We get a ref to the parent, and put the ref when
4396 : * this cgroup is being freed, so it's guaranteed
4397 : * that the parent won't be destroyed before its
4398 : * children.
4399 : */
4400 0 : cgroup_put(cgroup_parent(cgrp));
4401 0 : kernfs_put(cgrp->kn);
4402 0 : kfree(cgrp);
4403 : } else {
4404 : /*
4405 : * This is root cgroup's refcnt reaching zero,
4406 : * which indicates that the root should be
4407 : * released.
4408 : */
4409 0 : cgroup_destroy_root(cgrp->root);
4410 : }
4411 : }
4412 0 : }
4413 :
4414 0 : static void css_free_rcu_fn(struct rcu_head *rcu_head)
4415 : {
4416 : struct cgroup_subsys_state *css =
4417 : container_of(rcu_head, struct cgroup_subsys_state, rcu_head);
4418 :
4419 0 : INIT_WORK(&css->destroy_work, css_free_work_fn);
4420 0 : queue_work(cgroup_destroy_wq, &css->destroy_work);
4421 0 : }
4422 :
4423 0 : static void css_release_work_fn(struct work_struct *work)
4424 : {
4425 0 : struct cgroup_subsys_state *css =
4426 : container_of(work, struct cgroup_subsys_state, destroy_work);
4427 0 : struct cgroup_subsys *ss = css->ss;
4428 0 : struct cgroup *cgrp = css->cgroup;
4429 :
4430 0 : mutex_lock(&cgroup_mutex);
4431 :
4432 0 : css->flags |= CSS_RELEASED;
4433 : list_del_rcu(&css->sibling);
4434 :
4435 0 : if (ss) {
4436 : /* css release path */
4437 0 : cgroup_idr_remove(&ss->css_idr, css->id);
4438 0 : if (ss->css_released)
4439 0 : ss->css_released(css);
4440 : } else {
4441 : /* cgroup release path */
4442 0 : cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
4443 0 : cgrp->id = -1;
4444 :
4445 : /*
4446 : * There are two control paths which try to determine
4447 : * cgroup from dentry without going through kernfs -
4448 : * cgroupstats_build() and css_tryget_online_from_dir().
4449 : * Those are supported by RCU protecting clearing of
4450 : * cgrp->kn->priv backpointer.
4451 : */
4452 0 : RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
4453 : }
4454 :
4455 0 : mutex_unlock(&cgroup_mutex);
4456 :
4457 0 : call_rcu(&css->rcu_head, css_free_rcu_fn);
4458 0 : }
4459 :
4460 0 : static void css_release(struct percpu_ref *ref)
4461 : {
4462 : struct cgroup_subsys_state *css =
4463 : container_of(ref, struct cgroup_subsys_state, refcnt);
4464 :
4465 0 : INIT_WORK(&css->destroy_work, css_release_work_fn);
4466 0 : queue_work(cgroup_destroy_wq, &css->destroy_work);
4467 0 : }
4468 :
4469 7 : static void init_and_link_css(struct cgroup_subsys_state *css,
4470 7 : struct cgroup_subsys *ss, struct cgroup *cgrp)
4471 : {
4472 : lockdep_assert_held(&cgroup_mutex);
4473 :
4474 7 : cgroup_get(cgrp);
4475 :
4476 7 : memset(css, 0, sizeof(*css));
4477 7 : css->cgroup = cgrp;
4478 7 : css->ss = ss;
4479 7 : INIT_LIST_HEAD(&css->sibling);
4480 7 : INIT_LIST_HEAD(&css->children);
4481 7 : css->serial_nr = css_serial_nr_next++;
4482 :
4483 7 : if (cgroup_parent(cgrp)) {
4484 0 : css->parent = cgroup_css(cgroup_parent(cgrp), ss);
4485 : css_get(css->parent);
4486 : }
4487 :
4488 : BUG_ON(cgroup_css(cgrp, ss));
4489 7 : }
4490 :
4491 : /* invoke ->css_online() on a new CSS and mark it online if successful */
4492 7 : static int online_css(struct cgroup_subsys_state *css)
4493 : {
4494 7 : struct cgroup_subsys *ss = css->ss;
4495 : int ret = 0;
4496 :
4497 : lockdep_assert_held(&cgroup_mutex);
4498 :
4499 7 : if (ss->css_online)
4500 5 : ret = ss->css_online(css);
4501 7 : if (!ret) {
4502 7 : css->flags |= CSS_ONLINE;
4503 7 : rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
4504 : }
4505 7 : return ret;
4506 : }
4507 :
4508 : /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4509 0 : static void offline_css(struct cgroup_subsys_state *css)
4510 : {
4511 0 : struct cgroup_subsys *ss = css->ss;
4512 :
4513 : lockdep_assert_held(&cgroup_mutex);
4514 :
4515 0 : if (!(css->flags & CSS_ONLINE))
4516 0 : return;
4517 :
4518 0 : if (ss->css_offline)
4519 0 : ss->css_offline(css);
4520 :
4521 0 : css->flags &= ~CSS_ONLINE;
4522 0 : RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
4523 :
4524 0 : wake_up_all(&css->cgroup->offline_waitq);
4525 : }
4526 :
4527 : /**
4528 : * create_css - create a cgroup_subsys_state
4529 : * @cgrp: the cgroup new css will be associated with
4530 : * @ss: the subsys of new css
4531 : * @visible: whether to create control knobs for the new css or not
4532 : *
4533 : * Create a new css associated with @cgrp - @ss pair. On success, the new
4534 : * css is online and installed in @cgrp with all interface files created if
4535 : * @visible. Returns 0 on success, -errno on failure.
4536 : */
4537 0 : static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
4538 : bool visible)
4539 : {
4540 0 : struct cgroup *parent = cgroup_parent(cgrp);
4541 : struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
4542 : struct cgroup_subsys_state *css;
4543 : int err;
4544 :
4545 : lockdep_assert_held(&cgroup_mutex);
4546 :
4547 0 : css = ss->css_alloc(parent_css);
4548 0 : if (IS_ERR(css))
4549 0 : return PTR_ERR(css);
4550 :
4551 0 : init_and_link_css(css, ss, cgrp);
4552 :
4553 0 : err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
4554 0 : if (err)
4555 : goto err_free_css;
4556 :
4557 0 : err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_NOWAIT);
4558 0 : if (err < 0)
4559 : goto err_free_percpu_ref;
4560 0 : css->id = err;
4561 :
4562 0 : if (visible) {
4563 0 : err = cgroup_populate_dir(cgrp, 1 << ss->id);
4564 0 : if (err)
4565 : goto err_free_id;
4566 : }
4567 :
4568 : /* @css is ready to be brought online now, make it visible */
4569 0 : list_add_tail_rcu(&css->sibling, &parent_css->children);
4570 0 : cgroup_idr_replace(&ss->css_idr, css, css->id);
4571 :
4572 0 : err = online_css(css);
4573 0 : if (err)
4574 : goto err_list_del;
4575 :
4576 0 : if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
4577 : cgroup_parent(parent)) {
4578 0 : pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4579 : current->comm, current->pid, ss->name);
4580 0 : if (!strcmp(ss->name, "memory"))
4581 0 : pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
4582 0 : ss->warned_broken_hierarchy = true;
4583 : }
4584 :
4585 : return 0;
4586 :
4587 : err_list_del:
4588 : list_del_rcu(&css->sibling);
4589 0 : cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
4590 : err_free_id:
4591 0 : cgroup_idr_remove(&ss->css_idr, css->id);
4592 : err_free_percpu_ref:
4593 0 : percpu_ref_exit(&css->refcnt);
4594 : err_free_css:
4595 0 : call_rcu(&css->rcu_head, css_free_rcu_fn);
4596 0 : return err;
4597 : }
4598 :
4599 0 : static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
4600 : umode_t mode)
4601 : {
4602 0 : struct cgroup *parent, *cgrp;
4603 : struct cgroup_root *root;
4604 : struct cgroup_subsys *ss;
4605 : struct kernfs_node *kn;
4606 : struct cftype *base_files;
4607 : int ssid, ret;
4608 :
4609 : /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
4610 : */
4611 0 : if (strchr(name, '\n'))
4612 : return -EINVAL;
4613 :
4614 0 : parent = cgroup_kn_lock_live(parent_kn);
4615 0 : if (!parent)
4616 : return -ENODEV;
4617 0 : root = parent->root;
4618 :
4619 : /* allocate the cgroup and its ID, 0 is reserved for the root */
4620 : cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
4621 0 : if (!cgrp) {
4622 : ret = -ENOMEM;
4623 : goto out_unlock;
4624 : }
4625 :
4626 0 : ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
4627 0 : if (ret)
4628 : goto out_free_cgrp;
4629 :
4630 : /*
4631 : * Temporarily set the pointer to NULL, so idr_find() won't return
4632 : * a half-baked cgroup.
4633 : */
4634 0 : cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_NOWAIT);
4635 0 : if (cgrp->id < 0) {
4636 : ret = -ENOMEM;
4637 : goto out_cancel_ref;
4638 : }
4639 :
4640 0 : init_cgroup_housekeeping(cgrp);
4641 :
4642 0 : cgrp->self.parent = &parent->self;
4643 0 : cgrp->root = root;
4644 :
4645 0 : if (notify_on_release(parent))
4646 : set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
4647 :
4648 0 : if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
4649 : set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4650 :
4651 : /* create the directory */
4652 0 : kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
4653 0 : if (IS_ERR(kn)) {
4654 : ret = PTR_ERR(kn);
4655 : goto out_free_id;
4656 : }
4657 0 : cgrp->kn = kn;
4658 :
4659 : /*
4660 : * This extra ref will be put in cgroup_free_fn() and guarantees
4661 : * that @cgrp->kn is always accessible.
4662 : */
4663 0 : kernfs_get(kn);
4664 :
4665 0 : cgrp->self.serial_nr = css_serial_nr_next++;
4666 :
4667 : /* allocation complete, commit to creation */
4668 0 : list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
4669 0 : atomic_inc(&root->nr_cgrps);
4670 0 : cgroup_get(parent);
4671 :
4672 : /*
4673 : * @cgrp is now fully operational. If something fails after this
4674 : * point, it'll be released via the normal destruction path.
4675 : */
4676 0 : cgroup_idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
4677 :
4678 0 : ret = cgroup_kn_set_ugid(kn);
4679 0 : if (ret)
4680 : goto out_destroy;
4681 :
4682 0 : if (cgroup_on_dfl(cgrp))
4683 : base_files = cgroup_dfl_base_files;
4684 : else
4685 : base_files = cgroup_legacy_base_files;
4686 :
4687 0 : ret = cgroup_addrm_files(cgrp, base_files, true);
4688 0 : if (ret)
4689 : goto out_destroy;
4690 :
4691 : /* let's create and online css's */
4692 0 : for_each_subsys(ss, ssid) {
4693 0 : if (parent->child_subsys_mask & (1 << ssid)) {
4694 0 : ret = create_css(cgrp, ss,
4695 0 : parent->subtree_control & (1 << ssid));
4696 0 : if (ret)
4697 : goto out_destroy;
4698 : }
4699 : }
4700 :
4701 : /*
4702 : * On the default hierarchy, a child doesn't automatically inherit
4703 : * subtree_control from the parent. Each is configured manually.
4704 : */
4705 0 : if (!cgroup_on_dfl(cgrp)) {
4706 0 : cgrp->subtree_control = parent->subtree_control;
4707 : cgroup_refresh_child_subsys_mask(cgrp);
4708 : }
4709 :
4710 0 : kernfs_activate(kn);
4711 :
4712 : ret = 0;
4713 0 : goto out_unlock;
4714 :
4715 : out_free_id:
4716 0 : cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
4717 : out_cancel_ref:
4718 0 : percpu_ref_exit(&cgrp->self.refcnt);
4719 : out_free_cgrp:
4720 0 : kfree(cgrp);
4721 : out_unlock:
4722 0 : cgroup_kn_unlock(parent_kn);
4723 0 : return ret;
4724 :
4725 : out_destroy:
4726 0 : cgroup_destroy_locked(cgrp);
4727 0 : goto out_unlock;
4728 : }
4729 :
4730 : /*
4731 : * This is called when the refcnt of a css is confirmed to be killed.
4732 : * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
4733 : * initate destruction and put the css ref from kill_css().
4734 : */
4735 0 : static void css_killed_work_fn(struct work_struct *work)
4736 : {
4737 0 : struct cgroup_subsys_state *css =
4738 : container_of(work, struct cgroup_subsys_state, destroy_work);
4739 :
4740 0 : mutex_lock(&cgroup_mutex);
4741 0 : offline_css(css);
4742 0 : mutex_unlock(&cgroup_mutex);
4743 :
4744 : css_put(css);
4745 0 : }
4746 :
4747 : /* css kill confirmation processing requires process context, bounce */
4748 0 : static void css_killed_ref_fn(struct percpu_ref *ref)
4749 : {
4750 : struct cgroup_subsys_state *css =
4751 : container_of(ref, struct cgroup_subsys_state, refcnt);
4752 :
4753 0 : INIT_WORK(&css->destroy_work, css_killed_work_fn);
4754 0 : queue_work(cgroup_destroy_wq, &css->destroy_work);
4755 0 : }
4756 :
4757 : /**
4758 : * kill_css - destroy a css
4759 : * @css: css to destroy
4760 : *
4761 : * This function initiates destruction of @css by removing cgroup interface
4762 : * files and putting its base reference. ->css_offline() will be invoked
4763 : * asynchronously once css_tryget_online() is guaranteed to fail and when
4764 : * the reference count reaches zero, @css will be released.
4765 : */
4766 0 : static void kill_css(struct cgroup_subsys_state *css)
4767 : {
4768 : lockdep_assert_held(&cgroup_mutex);
4769 :
4770 : /*
4771 : * This must happen before css is disassociated with its cgroup.
4772 : * See seq_css() for details.
4773 : */
4774 0 : cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
4775 :
4776 : /*
4777 : * Killing would put the base ref, but we need to keep it alive
4778 : * until after ->css_offline().
4779 : */
4780 : css_get(css);
4781 :
4782 : /*
4783 : * cgroup core guarantees that, by the time ->css_offline() is
4784 : * invoked, no new css reference will be given out via
4785 : * css_tryget_online(). We can't simply call percpu_ref_kill() and
4786 : * proceed to offlining css's because percpu_ref_kill() doesn't
4787 : * guarantee that the ref is seen as killed on all CPUs on return.
4788 : *
4789 : * Use percpu_ref_kill_and_confirm() to get notifications as each
4790 : * css is confirmed to be seen as killed on all CPUs.
4791 : */
4792 0 : percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
4793 0 : }
4794 :
4795 : /**
4796 : * cgroup_destroy_locked - the first stage of cgroup destruction
4797 : * @cgrp: cgroup to be destroyed
4798 : *
4799 : * css's make use of percpu refcnts whose killing latency shouldn't be
4800 : * exposed to userland and are RCU protected. Also, cgroup core needs to
4801 : * guarantee that css_tryget_online() won't succeed by the time
4802 : * ->css_offline() is invoked. To satisfy all the requirements,
4803 : * destruction is implemented in the following two steps.
4804 : *
4805 : * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4806 : * userland visible parts and start killing the percpu refcnts of
4807 : * css's. Set up so that the next stage will be kicked off once all
4808 : * the percpu refcnts are confirmed to be killed.
4809 : *
4810 : * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4811 : * rest of destruction. Once all cgroup references are gone, the
4812 : * cgroup is RCU-freed.
4813 : *
4814 : * This function implements s1. After this step, @cgrp is gone as far as
4815 : * the userland is concerned and a new cgroup with the same name may be
4816 : * created. As cgroup doesn't care about the names internally, this
4817 : * doesn't cause any problem.
4818 : */
4819 0 : static int cgroup_destroy_locked(struct cgroup *cgrp)
4820 : __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4821 : {
4822 : struct cgroup_subsys_state *css;
4823 : bool empty;
4824 : int ssid;
4825 :
4826 : lockdep_assert_held(&cgroup_mutex);
4827 :
4828 : /*
4829 : * css_set_rwsem synchronizes access to ->cset_links and prevents
4830 : * @cgrp from being removed while put_css_set() is in progress.
4831 : */
4832 0 : down_read(&css_set_rwsem);
4833 0 : empty = list_empty(&cgrp->cset_links);
4834 0 : up_read(&css_set_rwsem);
4835 0 : if (!empty)
4836 : return -EBUSY;
4837 :
4838 : /*
4839 : * Make sure there's no live children. We can't test emptiness of
4840 : * ->self.children as dead children linger on it while being
4841 : * drained; otherwise, "rmdir parent/child parent" may fail.
4842 : */
4843 0 : if (css_has_online_children(&cgrp->self))
4844 : return -EBUSY;
4845 :
4846 : /*
4847 : * Mark @cgrp dead. This prevents further task migration and child
4848 : * creation by disabling cgroup_lock_live_group().
4849 : */
4850 0 : cgrp->self.flags &= ~CSS_ONLINE;
4851 :
4852 : /* initiate massacre of all css's */
4853 0 : for_each_css(css, ssid, cgrp)
4854 0 : kill_css(css);
4855 :
4856 : /*
4857 : * Remove @cgrp directory along with the base files. @cgrp has an
4858 : * extra ref on its kn.
4859 : */
4860 0 : kernfs_remove(cgrp->kn);
4861 :
4862 0 : check_for_release(cgroup_parent(cgrp));
4863 :
4864 : /* put the base reference */
4865 0 : percpu_ref_kill(&cgrp->self.refcnt);
4866 :
4867 0 : return 0;
4868 : };
4869 :
4870 0 : static int cgroup_rmdir(struct kernfs_node *kn)
4871 : {
4872 : struct cgroup *cgrp;
4873 : int ret = 0;
4874 :
4875 0 : cgrp = cgroup_kn_lock_live(kn);
4876 0 : if (!cgrp)
4877 : return 0;
4878 :
4879 0 : ret = cgroup_destroy_locked(cgrp);
4880 :
4881 0 : cgroup_kn_unlock(kn);
4882 0 : return ret;
4883 : }
4884 :
4885 : static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
4886 : .remount_fs = cgroup_remount,
4887 : .show_options = cgroup_show_options,
4888 : .mkdir = cgroup_mkdir,
4889 : .rmdir = cgroup_rmdir,
4890 : .rename = cgroup_rename,
4891 : };
4892 :
4893 7 : static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
4894 : {
4895 : struct cgroup_subsys_state *css;
4896 :
4897 7 : printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4898 :
4899 7 : mutex_lock(&cgroup_mutex);
4900 :
4901 7 : idr_init(&ss->css_idr);
4902 7 : INIT_LIST_HEAD(&ss->cfts);
4903 :
4904 : /* Create the root cgroup state for this subsystem */
4905 7 : ss->root = &cgrp_dfl_root;
4906 14 : css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
4907 : /* We don't handle early failures gracefully */
4908 : BUG_ON(IS_ERR(css));
4909 7 : init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
4910 :
4911 : /*
4912 : * Root csses are never destroyed and we can't initialize
4913 : * percpu_ref during early init. Disable refcnting.
4914 : */
4915 7 : css->flags |= CSS_NO_REF;
4916 :
4917 7 : if (early) {
4918 : /* allocation can't be done safely during early init */
4919 2 : css->id = 1;
4920 : } else {
4921 5 : css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
4922 : BUG_ON(css->id < 0);
4923 : }
4924 :
4925 : /* Update the init_css_set to contain a subsys
4926 : * pointer to this state - since the subsystem is
4927 : * newly registered, all tasks and hence the
4928 : * init_css_set is in the subsystem's root cgroup. */
4929 7 : init_css_set.subsys[ss->id] = css;
4930 :
4931 7 : need_forkexit_callback |= ss->fork || ss->exit;
4932 :
4933 : /* At system boot, before all subsystems have been
4934 : * registered, no tasks have been forked, so we don't
4935 : * need to invoke fork callbacks here. */
4936 : BUG_ON(!list_empty(&init_task.tasks));
4937 :
4938 7 : BUG_ON(online_css(css));
4939 :
4940 7 : mutex_unlock(&cgroup_mutex);
4941 7 : }
4942 :
4943 : /**
4944 : * cgroup_init_early - cgroup initialization at system boot
4945 : *
4946 : * Initialize cgroups at system boot, and initialize any
4947 : * subsystems that request early init.
4948 : */
4949 1 : int __init cgroup_init_early(void)
4950 : {
4951 : static struct cgroup_sb_opts __initdata opts;
4952 : struct cgroup_subsys *ss;
4953 : int i;
4954 :
4955 1 : init_cgroup_root(&cgrp_dfl_root, &opts);
4956 1 : cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
4957 :
4958 1 : RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
4959 :
4960 8 : for_each_subsys(ss, i) {
4961 : WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
4962 : "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4963 : i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
4964 : ss->id, ss->name);
4965 : WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
4966 : "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
4967 :
4968 7 : ss->id = i;
4969 7 : ss->name = cgroup_subsys_name[i];
4970 :
4971 7 : if (ss->early_init)
4972 2 : cgroup_init_subsys(ss, true);
4973 : }
4974 1 : return 0;
4975 : }
4976 :
4977 : /**
4978 : * cgroup_init - cgroup initialization
4979 : *
4980 : * Register cgroup filesystem and /proc file, and initialize
4981 : * any subsystems that didn't request early init.
4982 : */
4983 1 : int __init cgroup_init(void)
4984 : {
4985 : struct cgroup_subsys *ss;
4986 : unsigned long key;
4987 : int ssid, err;
4988 :
4989 1 : BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
4990 1 : BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));
4991 :
4992 1 : mutex_lock(&cgroup_mutex);
4993 :
4994 : /* Add init_css_set to the hash table */
4995 : key = css_set_hash(init_css_set.subsys);
4996 1 : hash_add(css_set_table, &init_css_set.hlist, key);
4997 :
4998 1 : BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
4999 :
5000 1 : mutex_unlock(&cgroup_mutex);
5001 :
5002 8 : for_each_subsys(ss, ssid) {
5003 7 : if (ss->early_init) {
5004 2 : struct cgroup_subsys_state *css =
5005 2 : init_css_set.subsys[ss->id];
5006 :
5007 2 : css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
5008 : GFP_KERNEL);
5009 : BUG_ON(css->id < 0);
5010 : } else {
5011 5 : cgroup_init_subsys(ss, false);
5012 : }
5013 :
5014 7 : list_add_tail(&init_css_set.e_cset_node[ssid],
5015 : &cgrp_dfl_root.cgrp.e_csets[ssid]);
5016 :
5017 : /*
5018 : * Setting dfl_root subsys_mask needs to consider the
5019 : * disabled flag and cftype registration needs kmalloc,
5020 : * both of which aren't available during early_init.
5021 : */
5022 7 : if (ss->disabled)
5023 1 : continue;
5024 :
5025 6 : cgrp_dfl_root.subsys_mask |= 1 << ss->id;
5026 :
5027 6 : if (cgroup_legacy_files_on_dfl && !ss->dfl_cftypes)
5028 0 : ss->dfl_cftypes = ss->legacy_cftypes;
5029 :
5030 6 : if (!ss->dfl_cftypes)
5031 6 : cgrp_dfl_root_inhibit_ss_mask |= 1 << ss->id;
5032 :
5033 6 : if (ss->dfl_cftypes == ss->legacy_cftypes) {
5034 0 : WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
5035 : } else {
5036 6 : WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
5037 6 : WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
5038 : }
5039 : }
5040 :
5041 1 : cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
5042 1 : if (!cgroup_kobj)
5043 : return -ENOMEM;
5044 :
5045 1 : err = register_filesystem(&cgroup_fs_type);
5046 1 : if (err < 0) {
5047 0 : kobject_put(cgroup_kobj);
5048 0 : return err;
5049 : }
5050 :
5051 : proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
5052 1 : return 0;
5053 : }
5054 :
5055 1 : static int __init cgroup_wq_init(void)
5056 : {
5057 : /*
5058 : * There isn't much point in executing destruction path in
5059 : * parallel. Good chunk is serialized with cgroup_mutex anyway.
5060 : * Use 1 for @max_active.
5061 : *
5062 : * We would prefer to do this in cgroup_init() above, but that
5063 : * is called before init_workqueues(): so leave this until after.
5064 : */
5065 1 : cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
5066 : BUG_ON(!cgroup_destroy_wq);
5067 :
5068 : /*
5069 : * Used to destroy pidlists and separate to serve as flush domain.
5070 : * Cap @max_active to 1 too.
5071 : */
5072 1 : cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
5073 : 0, 1);
5074 : BUG_ON(!cgroup_pidlist_destroy_wq);
5075 :
5076 1 : return 0;
5077 : }
5078 : core_initcall(cgroup_wq_init);
5079 :
5080 : /*
5081 : * proc_cgroup_show()
5082 : * - Print task's cgroup paths into seq_file, one line for each hierarchy
5083 : * - Used for /proc/<pid>/cgroup.
5084 : */
5085 0 : int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
5086 : struct pid *pid, struct task_struct *tsk)
5087 : {
5088 : char *buf, *path;
5089 : int retval;
5090 : struct cgroup_root *root;
5091 :
5092 : retval = -ENOMEM;
5093 : buf = kmalloc(PATH_MAX, GFP_KERNEL);
5094 0 : if (!buf)
5095 : goto out;
5096 :
5097 0 : mutex_lock(&cgroup_mutex);
5098 0 : down_read(&css_set_rwsem);
5099 :
5100 0 : for_each_root(root) {
5101 : struct cgroup_subsys *ss;
5102 : struct cgroup *cgrp;
5103 : int ssid, count = 0;
5104 :
5105 0 : if (root == &cgrp_dfl_root && !cgrp_dfl_root_visible)
5106 0 : continue;
5107 :
5108 0 : seq_printf(m, "%d:", root->hierarchy_id);
5109 0 : for_each_subsys(ss, ssid)
5110 0 : if (root->subsys_mask & (1 << ssid))
5111 0 : seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
5112 0 : if (strlen(root->name))
5113 0 : seq_printf(m, "%sname=%s", count ? "," : "",
5114 0 : root->name);
5115 0 : seq_putc(m, ':');
5116 : cgrp = task_cgroup_from_root(tsk, root);
5117 : path = cgroup_path(cgrp, buf, PATH_MAX);
5118 0 : if (!path) {
5119 : retval = -ENAMETOOLONG;
5120 : goto out_unlock;
5121 : }
5122 0 : seq_puts(m, path);
5123 0 : seq_putc(m, '\n');
5124 : }
5125 :
5126 : retval = 0;
5127 : out_unlock:
5128 0 : up_read(&css_set_rwsem);
5129 0 : mutex_unlock(&cgroup_mutex);
5130 0 : kfree(buf);
5131 : out:
5132 0 : return retval;
5133 : }
5134 :
5135 : /* Display information about each subsystem and each hierarchy */
5136 0 : static int proc_cgroupstats_show(struct seq_file *m, void *v)
5137 : {
5138 : struct cgroup_subsys *ss;
5139 : int i;
5140 :
5141 0 : seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
5142 : /*
5143 : * ideally we don't want subsystems moving around while we do this.
5144 : * cgroup_mutex is also necessary to guarantee an atomic snapshot of
5145 : * subsys/hierarchy state.
5146 : */
5147 0 : mutex_lock(&cgroup_mutex);
5148 :
5149 0 : for_each_subsys(ss, i)
5150 0 : seq_printf(m, "%s\t%d\t%d\t%d\n",
5151 0 : ss->name, ss->root->hierarchy_id,
5152 0 : atomic_read(&ss->root->nr_cgrps), !ss->disabled);
5153 :
5154 0 : mutex_unlock(&cgroup_mutex);
5155 0 : return 0;
5156 : }
5157 :
5158 0 : static int cgroupstats_open(struct inode *inode, struct file *file)
5159 : {
5160 0 : return single_open(file, proc_cgroupstats_show, NULL);
5161 : }
5162 :
5163 : static const struct file_operations proc_cgroupstats_operations = {
5164 : .open = cgroupstats_open,
5165 : .read = seq_read,
5166 : .llseek = seq_lseek,
5167 : .release = single_release,
5168 : };
5169 :
5170 : /**
5171 : * cgroup_fork - initialize cgroup related fields during copy_process()
5172 : * @child: pointer to task_struct of forking parent process.
5173 : *
5174 : * A task is associated with the init_css_set until cgroup_post_fork()
5175 : * attaches it to the parent's css_set. Empty cg_list indicates that
5176 : * @child isn't holding reference to its css_set.
5177 : */
5178 2993 : void cgroup_fork(struct task_struct *child)
5179 : {
5180 2993 : RCU_INIT_POINTER(child->cgroups, &init_css_set);
5181 2993 : INIT_LIST_HEAD(&child->cg_list);
5182 2993 : }
5183 :
5184 : /**
5185 : * cgroup_post_fork - called on a new task after adding it to the task list
5186 : * @child: the task in question
5187 : *
5188 : * Adds the task to the list running through its css_set if necessary and
5189 : * call the subsystem fork() callbacks. Has to be after the task is
5190 : * visible on the task list in case we race with the first call to
5191 : * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5192 : * list.
5193 : */
5194 2992 : void cgroup_post_fork(struct task_struct *child)
5195 : {
5196 : struct cgroup_subsys *ss;
5197 : int i;
5198 :
5199 : /*
5200 : * This may race against cgroup_enable_task_cg_lists(). As that
5201 : * function sets use_task_css_set_links before grabbing
5202 : * tasklist_lock and we just went through tasklist_lock to add
5203 : * @child, it's guaranteed that either we see the set
5204 : * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5205 : * @child during its iteration.
5206 : *
5207 : * If we won the race, @child is associated with %current's
5208 : * css_set. Grabbing css_set_rwsem guarantees both that the
5209 : * association is stable, and, on completion of the parent's
5210 : * migration, @child is visible in the source of migration or
5211 : * already in the destination cgroup. This guarantee is necessary
5212 : * when implementing operations which need to migrate all tasks of
5213 : * a cgroup to another.
5214 : *
5215 : * Note that if we lose to cgroup_enable_task_cg_lists(), @child
5216 : * will remain in init_css_set. This is safe because all tasks are
5217 : * in the init_css_set before cg_links is enabled and there's no
5218 : * operation which transfers all tasks out of init_css_set.
5219 : */
5220 2992 : if (use_task_css_set_links) {
5221 : struct css_set *cset;
5222 :
5223 909 : down_write(&css_set_rwsem);
5224 909 : cset = task_css_set(current);
5225 1818 : if (list_empty(&child->cg_list)) {
5226 909 : rcu_assign_pointer(child->cgroups, cset);
5227 909 : list_add(&child->cg_list, &cset->tasks);
5228 : get_css_set(cset);
5229 : }
5230 909 : up_write(&css_set_rwsem);
5231 : }
5232 :
5233 : /*
5234 : * Call ss->fork(). This must happen after @child is linked on
5235 : * css_set; otherwise, @child might change state between ->fork()
5236 : * and addition to css_set.
5237 : */
5238 2992 : if (need_forkexit_callback) {
5239 20944 : for_each_subsys(ss, i)
5240 20944 : if (ss->fork)
5241 5984 : ss->fork(child);
5242 : }
5243 2992 : }
5244 :
5245 : /**
5246 : * cgroup_exit - detach cgroup from exiting task
5247 : * @tsk: pointer to task_struct of exiting process
5248 : *
5249 : * Description: Detach cgroup from @tsk and release it.
5250 : *
5251 : * Note that cgroups marked notify_on_release force every task in
5252 : * them to take the global cgroup_mutex mutex when exiting.
5253 : * This could impact scaling on very large systems. Be reluctant to
5254 : * use notify_on_release cgroups where very high task exit scaling
5255 : * is required on large systems.
5256 : *
5257 : * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
5258 : * call cgroup_exit() while the task is still competent to handle
5259 : * notify_on_release(), then leave the task attached to the root cgroup in
5260 : * each hierarchy for the remainder of its exit. No need to bother with
5261 : * init_css_set refcnting. init_css_set never goes away and we can't race
5262 : * with migration path - PF_EXITING is visible to migration path.
5263 : */
5264 2914 : void cgroup_exit(struct task_struct *tsk)
5265 : {
5266 : struct cgroup_subsys *ss;
5267 : struct css_set *cset;
5268 : bool put_cset = false;
5269 : int i;
5270 :
5271 : /*
5272 : * Unlink from @tsk from its css_set. As migration path can't race
5273 : * with us, we can check cg_list without grabbing css_set_rwsem.
5274 : */
5275 5828 : if (!list_empty(&tsk->cg_list)) {
5276 887 : down_write(&css_set_rwsem);
5277 : list_del_init(&tsk->cg_list);
5278 887 : up_write(&css_set_rwsem);
5279 : put_cset = true;
5280 : }
5281 :
5282 : /* Reassign the task to the init_css_set. */
5283 : cset = task_css_set(tsk);
5284 2914 : RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
5285 :
5286 2914 : if (need_forkexit_callback) {
5287 : /* see cgroup_post_fork() for details */
5288 20398 : for_each_subsys(ss, i) {
5289 20398 : if (ss->exit) {
5290 2914 : struct cgroup_subsys_state *old_css = cset->subsys[i];
5291 : struct cgroup_subsys_state *css = task_css(tsk, i);
5292 :
5293 2914 : ss->exit(css, old_css, tsk);
5294 : }
5295 : }
5296 : }
5297 :
5298 2914 : if (put_cset)
5299 887 : put_css_set(cset);
5300 2914 : }
5301 :
5302 0 : static void check_for_release(struct cgroup *cgrp)
5303 : {
5304 0 : if (notify_on_release(cgrp) && !cgroup_has_tasks(cgrp) &&
5305 0 : !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
5306 0 : schedule_work(&cgrp->release_agent_work);
5307 0 : }
5308 :
5309 : /*
5310 : * Notify userspace when a cgroup is released, by running the
5311 : * configured release agent with the name of the cgroup (path
5312 : * relative to the root of cgroup file system) as the argument.
5313 : *
5314 : * Most likely, this user command will try to rmdir this cgroup.
5315 : *
5316 : * This races with the possibility that some other task will be
5317 : * attached to this cgroup before it is removed, or that some other
5318 : * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5319 : * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5320 : * unused, and this cgroup will be reprieved from its death sentence,
5321 : * to continue to serve a useful existence. Next time it's released,
5322 : * we will get notified again, if it still has 'notify_on_release' set.
5323 : *
5324 : * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5325 : * means only wait until the task is successfully execve()'d. The
5326 : * separate release agent task is forked by call_usermodehelper(),
5327 : * then control in this thread returns here, without waiting for the
5328 : * release agent task. We don't bother to wait because the caller of
5329 : * this routine has no use for the exit status of the release agent
5330 : * task, so no sense holding our caller up for that.
5331 : */
5332 0 : static void cgroup_release_agent(struct work_struct *work)
5333 : {
5334 : struct cgroup *cgrp =
5335 : container_of(work, struct cgroup, release_agent_work);
5336 : char *pathbuf = NULL, *agentbuf = NULL, *path;
5337 : char *argv[3], *envp[3];
5338 :
5339 0 : mutex_lock(&cgroup_mutex);
5340 :
5341 : pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
5342 0 : agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
5343 0 : if (!pathbuf || !agentbuf)
5344 : goto out;
5345 :
5346 : path = cgroup_path(cgrp, pathbuf, PATH_MAX);
5347 0 : if (!path)
5348 : goto out;
5349 :
5350 0 : argv[0] = agentbuf;
5351 0 : argv[1] = path;
5352 0 : argv[2] = NULL;
5353 :
5354 : /* minimal command environment */
5355 0 : envp[0] = "HOME=/";
5356 0 : envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5357 0 : envp[2] = NULL;
5358 :
5359 0 : mutex_unlock(&cgroup_mutex);
5360 0 : call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
5361 0 : goto out_free;
5362 : out:
5363 0 : mutex_unlock(&cgroup_mutex);
5364 : out_free:
5365 0 : kfree(agentbuf);
5366 0 : kfree(pathbuf);
5367 0 : }
5368 :
5369 0 : static int __init cgroup_disable(char *str)
5370 : {
5371 : struct cgroup_subsys *ss;
5372 : char *token;
5373 : int i;
5374 :
5375 0 : while ((token = strsep(&str, ",")) != NULL) {
5376 0 : if (!*token)
5377 0 : continue;
5378 :
5379 0 : for_each_subsys(ss, i) {
5380 0 : if (!strcmp(token, ss->name)) {
5381 0 : ss->disabled = 1;
5382 0 : printk(KERN_INFO "Disabling %s control group"
5383 : " subsystem\n", ss->name);
5384 0 : break;
5385 : }
5386 : }
5387 : }
5388 0 : return 1;
5389 : }
5390 : __setup("cgroup_disable=", cgroup_disable);
5391 :
5392 0 : static int __init cgroup_enable(char *str)
5393 : {
5394 : struct cgroup_subsys *ss;
5395 : char *token;
5396 : int i;
5397 :
5398 0 : while ((token = strsep(&str, ",")) != NULL) {
5399 0 : if (!*token)
5400 0 : continue;
5401 :
5402 0 : for_each_subsys(ss, i) {
5403 0 : if (!strcmp(token, ss->name)) {
5404 0 : ss->disabled = 0;
5405 0 : printk(KERN_INFO "Enabling %s control group"
5406 : " subsystem\n", ss->name);
5407 0 : break;
5408 : }
5409 : }
5410 : }
5411 0 : return 1;
5412 : }
5413 : __setup("cgroup_enable=", cgroup_enable);
5414 :
5415 0 : static int __init cgroup_set_legacy_files_on_dfl(char *str)
5416 : {
5417 0 : printk("cgroup: using legacy files on the default hierarchy\n");
5418 0 : cgroup_legacy_files_on_dfl = true;
5419 0 : return 0;
5420 : }
5421 : __setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl);
5422 :
5423 : /**
5424 : * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
5425 : * @dentry: directory dentry of interest
5426 : * @ss: subsystem of interest
5427 : *
5428 : * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5429 : * to get the corresponding css and return it. If such css doesn't exist
5430 : * or can't be pinned, an ERR_PTR value is returned.
5431 : */
5432 0 : struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
5433 : struct cgroup_subsys *ss)
5434 : {
5435 0 : struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
5436 : struct cgroup_subsys_state *css = NULL;
5437 : struct cgroup *cgrp;
5438 :
5439 : /* is @dentry a cgroup dir? */
5440 0 : if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
5441 : kernfs_type(kn) != KERNFS_DIR)
5442 : return ERR_PTR(-EBADF);
5443 :
5444 : rcu_read_lock();
5445 :
5446 : /*
5447 : * This path doesn't originate from kernfs and @kn could already
5448 : * have been or be removed at any point. @kn->priv is RCU
5449 : * protected for this access. See css_release_work_fn() for details.
5450 : */
5451 0 : cgrp = rcu_dereference(kn->priv);
5452 0 : if (cgrp)
5453 : css = cgroup_css(cgrp, ss);
5454 :
5455 0 : if (!css || !css_tryget_online(css))
5456 : css = ERR_PTR(-ENOENT);
5457 :
5458 : rcu_read_unlock();
5459 0 : return css;
5460 : }
5461 :
5462 : /**
5463 : * css_from_id - lookup css by id
5464 : * @id: the cgroup id
5465 : * @ss: cgroup subsys to be looked into
5466 : *
5467 : * Returns the css if there's valid one with @id, otherwise returns NULL.
5468 : * Should be called under rcu_read_lock().
5469 : */
5470 0 : struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
5471 : {
5472 : WARN_ON_ONCE(!rcu_read_lock_held());
5473 0 : return idr_find(&ss->css_idr, id);
5474 : }
5475 :
5476 : #ifdef CONFIG_CGROUP_DEBUG
5477 : static struct cgroup_subsys_state *
5478 : debug_css_alloc(struct cgroup_subsys_state *parent_css)
5479 : {
5480 : struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5481 :
5482 : if (!css)
5483 : return ERR_PTR(-ENOMEM);
5484 :
5485 : return css;
5486 : }
5487 :
5488 : static void debug_css_free(struct cgroup_subsys_state *css)
5489 : {
5490 : kfree(css);
5491 : }
5492 :
5493 : static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
5494 : struct cftype *cft)
5495 : {
5496 : return cgroup_task_count(css->cgroup);
5497 : }
5498 :
5499 : static u64 current_css_set_read(struct cgroup_subsys_state *css,
5500 : struct cftype *cft)
5501 : {
5502 : return (u64)(unsigned long)current->cgroups;
5503 : }
5504 :
5505 : static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
5506 : struct cftype *cft)
5507 : {
5508 : u64 count;
5509 :
5510 : rcu_read_lock();
5511 : count = atomic_read(&task_css_set(current)->refcount);
5512 : rcu_read_unlock();
5513 : return count;
5514 : }
5515 :
5516 : static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
5517 : {
5518 : struct cgrp_cset_link *link;
5519 : struct css_set *cset;
5520 : char *name_buf;
5521 :
5522 : name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
5523 : if (!name_buf)
5524 : return -ENOMEM;
5525 :
5526 : down_read(&css_set_rwsem);
5527 : rcu_read_lock();
5528 : cset = rcu_dereference(current->cgroups);
5529 : list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
5530 : struct cgroup *c = link->cgrp;
5531 :
5532 : cgroup_name(c, name_buf, NAME_MAX + 1);
5533 : seq_printf(seq, "Root %d group %s\n",
5534 : c->root->hierarchy_id, name_buf);
5535 : }
5536 : rcu_read_unlock();
5537 : up_read(&css_set_rwsem);
5538 : kfree(name_buf);
5539 : return 0;
5540 : }
5541 :
5542 : #define MAX_TASKS_SHOWN_PER_CSS 25
5543 : static int cgroup_css_links_read(struct seq_file *seq, void *v)
5544 : {
5545 : struct cgroup_subsys_state *css = seq_css(seq);
5546 : struct cgrp_cset_link *link;
5547 :
5548 : down_read(&css_set_rwsem);
5549 : list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
5550 : struct css_set *cset = link->cset;
5551 : struct task_struct *task;
5552 : int count = 0;
5553 :
5554 : seq_printf(seq, "css_set %p\n", cset);
5555 :
5556 : list_for_each_entry(task, &cset->tasks, cg_list) {
5557 : if (count++ > MAX_TASKS_SHOWN_PER_CSS)
5558 : goto overflow;
5559 : seq_printf(seq, " task %d\n", task_pid_vnr(task));
5560 : }
5561 :
5562 : list_for_each_entry(task, &cset->mg_tasks, cg_list) {
5563 : if (count++ > MAX_TASKS_SHOWN_PER_CSS)
5564 : goto overflow;
5565 : seq_printf(seq, " task %d\n", task_pid_vnr(task));
5566 : }
5567 : continue;
5568 : overflow:
5569 : seq_puts(seq, " ...\n");
5570 : }
5571 : up_read(&css_set_rwsem);
5572 : return 0;
5573 : }
5574 :
5575 : static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
5576 : {
5577 : return (!cgroup_has_tasks(css->cgroup) &&
5578 : !css_has_online_children(&css->cgroup->self));
5579 : }
5580 :
5581 : static struct cftype debug_files[] = {
5582 : {
5583 : .name = "taskcount",
5584 : .read_u64 = debug_taskcount_read,
5585 : },
5586 :
5587 : {
5588 : .name = "current_css_set",
5589 : .read_u64 = current_css_set_read,
5590 : },
5591 :
5592 : {
5593 : .name = "current_css_set_refcount",
5594 : .read_u64 = current_css_set_refcount_read,
5595 : },
5596 :
5597 : {
5598 : .name = "current_css_set_cg_links",
5599 : .seq_show = current_css_set_cg_links_read,
5600 : },
5601 :
5602 : {
5603 : .name = "cgroup_css_links",
5604 : .seq_show = cgroup_css_links_read,
5605 : },
5606 :
5607 : {
5608 : .name = "releasable",
5609 : .read_u64 = releasable_read,
5610 : },
5611 :
5612 : { } /* terminate */
5613 : };
5614 :
5615 : struct cgroup_subsys debug_cgrp_subsys = {
5616 : .css_alloc = debug_css_alloc,
5617 : .css_free = debug_css_free,
5618 : .legacy_cftypes = debug_files,
5619 : };
5620 : #endif /* CONFIG_CGROUP_DEBUG */
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