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