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 "cgroup-internal.h" 32 33 #include <linux/cred.h> 34 #include <linux/errno.h> 35 #include <linux/init_task.h> 36 #include <linux/kernel.h> 37 #include <linux/magic.h> 38 #include <linux/mutex.h> 39 #include <linux/mount.h> 40 #include <linux/pagemap.h> 41 #include <linux/proc_fs.h> 42 #include <linux/rcupdate.h> 43 #include <linux/sched.h> 44 #include <linux/sched/task.h> 45 #include <linux/slab.h> 46 #include <linux/spinlock.h> 47 #include <linux/percpu-rwsem.h> 48 #include <linux/string.h> 49 #include <linux/hashtable.h> 50 #include <linux/idr.h> 51 #include <linux/kthread.h> 52 #include <linux/atomic.h> 53 #include <linux/cpuset.h> 54 #include <linux/proc_ns.h> 55 #include <linux/nsproxy.h> 56 #include <linux/file.h> 57 #include <linux/fs_parser.h> 58 #include <linux/sched/cputime.h> 59 #include <linux/psi.h> 60 #include <net/sock.h> 61 62 #define CREATE_TRACE_POINTS 63 #include <trace/events/cgroup.h> 64 65 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \ 66 MAX_CFTYPE_NAME + 2) 67 /* let's not notify more than 100 times per second */ 68 #define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100) 69 70 /* 71 * cgroup_mutex is the master lock. Any modification to cgroup or its 72 * hierarchy must be performed while holding it. 73 * 74 * css_set_lock protects task->cgroups pointer, the list of css_set 75 * objects, and the chain of tasks off each css_set. 76 * 77 * These locks are exported if CONFIG_PROVE_RCU so that accessors in 78 * cgroup.h can use them for lockdep annotations. 79 */ 80 DEFINE_MUTEX(cgroup_mutex); 81 DEFINE_SPINLOCK(css_set_lock); 82 83 #ifdef CONFIG_PROVE_RCU 84 EXPORT_SYMBOL_GPL(cgroup_mutex); 85 EXPORT_SYMBOL_GPL(css_set_lock); 86 #endif 87 88 DEFINE_SPINLOCK(trace_cgroup_path_lock); 89 char trace_cgroup_path[TRACE_CGROUP_PATH_LEN]; 90 bool cgroup_debug __read_mostly; 91 92 /* 93 * Protects cgroup_idr and css_idr so that IDs can be released without 94 * grabbing cgroup_mutex. 95 */ 96 static DEFINE_SPINLOCK(cgroup_idr_lock); 97 98 /* 99 * Protects cgroup_file->kn for !self csses. It synchronizes notifications 100 * against file removal/re-creation across css hiding. 101 */ 102 static DEFINE_SPINLOCK(cgroup_file_kn_lock); 103 104 DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem); 105 106 #define cgroup_assert_mutex_or_rcu_locked() \ 107 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \ 108 !lockdep_is_held(&cgroup_mutex), \ 109 "cgroup_mutex or RCU read lock required"); 110 111 /* 112 * cgroup destruction makes heavy use of work items and there can be a lot 113 * of concurrent destructions. Use a separate workqueue so that cgroup 114 * destruction work items don't end up filling up max_active of system_wq 115 * which may lead to deadlock. 116 */ 117 static struct workqueue_struct *cgroup_destroy_wq; 118 119 /* generate an array of cgroup subsystem pointers */ 120 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys, 121 struct cgroup_subsys *cgroup_subsys[] = { 122 #include <linux/cgroup_subsys.h> 123 }; 124 #undef SUBSYS 125 126 /* array of cgroup subsystem names */ 127 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x, 128 static const char *cgroup_subsys_name[] = { 129 #include <linux/cgroup_subsys.h> 130 }; 131 #undef SUBSYS 132 133 /* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */ 134 #define SUBSYS(_x) \ 135 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \ 136 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \ 137 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \ 138 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key); 139 #include <linux/cgroup_subsys.h> 140 #undef SUBSYS 141 142 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key, 143 static struct static_key_true *cgroup_subsys_enabled_key[] = { 144 #include <linux/cgroup_subsys.h> 145 }; 146 #undef SUBSYS 147 148 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key, 149 static struct static_key_true *cgroup_subsys_on_dfl_key[] = { 150 #include <linux/cgroup_subsys.h> 151 }; 152 #undef SUBSYS 153 154 static DEFINE_PER_CPU(struct cgroup_rstat_cpu, cgrp_dfl_root_rstat_cpu); 155 156 /* the default hierarchy */ 157 struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu }; 158 EXPORT_SYMBOL_GPL(cgrp_dfl_root); 159 160 /* 161 * The default hierarchy always exists but is hidden until mounted for the 162 * first time. This is for backward compatibility. 163 */ 164 static bool cgrp_dfl_visible; 165 166 /* some controllers are not supported in the default hierarchy */ 167 static u16 cgrp_dfl_inhibit_ss_mask; 168 169 /* some controllers are implicitly enabled on the default hierarchy */ 170 static u16 cgrp_dfl_implicit_ss_mask; 171 172 /* some controllers can be threaded on the default hierarchy */ 173 static u16 cgrp_dfl_threaded_ss_mask; 174 175 /* The list of hierarchy roots */ 176 LIST_HEAD(cgroup_roots); 177 static int cgroup_root_count; 178 179 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */ 180 static DEFINE_IDR(cgroup_hierarchy_idr); 181 182 /* 183 * Assign a monotonically increasing serial number to csses. It guarantees 184 * cgroups with bigger numbers are newer than those with smaller numbers. 185 * Also, as csses are always appended to the parent's ->children list, it 186 * guarantees that sibling csses are always sorted in the ascending serial 187 * number order on the list. Protected by cgroup_mutex. 188 */ 189 static u64 css_serial_nr_next = 1; 190 191 /* 192 * These bitmasks identify subsystems with specific features to avoid 193 * having to do iterative checks repeatedly. 194 */ 195 static u16 have_fork_callback __read_mostly; 196 static u16 have_exit_callback __read_mostly; 197 static u16 have_release_callback __read_mostly; 198 static u16 have_canfork_callback __read_mostly; 199 200 /* cgroup namespace for init task */ 201 struct cgroup_namespace init_cgroup_ns = { 202 .ns.count = REFCOUNT_INIT(2), 203 .user_ns = &init_user_ns, 204 .ns.ops = &cgroupns_operations, 205 .ns.inum = PROC_CGROUP_INIT_INO, 206 .root_cset = &init_css_set, 207 }; 208 209 static struct file_system_type cgroup2_fs_type; 210 static struct cftype cgroup_base_files[]; 211 212 static int cgroup_apply_control(struct cgroup *cgrp); 213 static void cgroup_finalize_control(struct cgroup *cgrp, int ret); 214 static void css_task_iter_skip(struct css_task_iter *it, 215 struct task_struct *task); 216 static int cgroup_destroy_locked(struct cgroup *cgrp); 217 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp, 218 struct cgroup_subsys *ss); 219 static void css_release(struct percpu_ref *ref); 220 static void kill_css(struct cgroup_subsys_state *css); 221 static int cgroup_addrm_files(struct cgroup_subsys_state *css, 222 struct cgroup *cgrp, struct cftype cfts[], 223 bool is_add); 224 225 /** 226 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID 227 * @ssid: subsys ID of interest 228 * 229 * cgroup_subsys_enabled() can only be used with literal subsys names which 230 * is fine for individual subsystems but unsuitable for cgroup core. This 231 * is slower static_key_enabled() based test indexed by @ssid. 232 */ 233 bool cgroup_ssid_enabled(int ssid) 234 { 235 if (CGROUP_SUBSYS_COUNT == 0) 236 return false; 237 238 return static_key_enabled(cgroup_subsys_enabled_key[ssid]); 239 } 240 241 /** 242 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy 243 * @cgrp: the cgroup of interest 244 * 245 * The default hierarchy is the v2 interface of cgroup and this function 246 * can be used to test whether a cgroup is on the default hierarchy for 247 * cases where a subsystem should behave differently depending on the 248 * interface version. 249 * 250 * List of changed behaviors: 251 * 252 * - Mount options "noprefix", "xattr", "clone_children", "release_agent" 253 * and "name" are disallowed. 254 * 255 * - When mounting an existing superblock, mount options should match. 256 * 257 * - Remount is disallowed. 258 * 259 * - rename(2) is disallowed. 260 * 261 * - "tasks" is removed. Everything should be at process granularity. Use 262 * "cgroup.procs" instead. 263 * 264 * - "cgroup.procs" is not sorted. pids will be unique unless they got 265 * recycled in-between reads. 266 * 267 * - "release_agent" and "notify_on_release" are removed. Replacement 268 * notification mechanism will be implemented. 269 * 270 * - "cgroup.clone_children" is removed. 271 * 272 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup 273 * and its descendants contain no task; otherwise, 1. The file also 274 * generates kernfs notification which can be monitored through poll and 275 * [di]notify when the value of the file changes. 276 * 277 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and 278 * take masks of ancestors with non-empty cpus/mems, instead of being 279 * moved to an ancestor. 280 * 281 * - cpuset: a task can be moved into an empty cpuset, and again it takes 282 * masks of ancestors. 283 * 284 * - blkcg: blk-throttle becomes properly hierarchical. 285 * 286 * - debug: disallowed on the default hierarchy. 287 */ 288 bool cgroup_on_dfl(const struct cgroup *cgrp) 289 { 290 return cgrp->root == &cgrp_dfl_root; 291 } 292 293 /* IDR wrappers which synchronize using cgroup_idr_lock */ 294 static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end, 295 gfp_t gfp_mask) 296 { 297 int ret; 298 299 idr_preload(gfp_mask); 300 spin_lock_bh(&cgroup_idr_lock); 301 ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM); 302 spin_unlock_bh(&cgroup_idr_lock); 303 idr_preload_end(); 304 return ret; 305 } 306 307 static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id) 308 { 309 void *ret; 310 311 spin_lock_bh(&cgroup_idr_lock); 312 ret = idr_replace(idr, ptr, id); 313 spin_unlock_bh(&cgroup_idr_lock); 314 return ret; 315 } 316 317 static void cgroup_idr_remove(struct idr *idr, int id) 318 { 319 spin_lock_bh(&cgroup_idr_lock); 320 idr_remove(idr, id); 321 spin_unlock_bh(&cgroup_idr_lock); 322 } 323 324 static bool cgroup_has_tasks(struct cgroup *cgrp) 325 { 326 return cgrp->nr_populated_csets; 327 } 328 329 bool cgroup_is_threaded(struct cgroup *cgrp) 330 { 331 return cgrp->dom_cgrp != cgrp; 332 } 333 334 /* can @cgrp host both domain and threaded children? */ 335 static bool cgroup_is_mixable(struct cgroup *cgrp) 336 { 337 /* 338 * Root isn't under domain level resource control exempting it from 339 * the no-internal-process constraint, so it can serve as a thread 340 * root and a parent of resource domains at the same time. 341 */ 342 return !cgroup_parent(cgrp); 343 } 344 345 /* can @cgrp become a thread root? Should always be true for a thread root */ 346 static bool cgroup_can_be_thread_root(struct cgroup *cgrp) 347 { 348 /* mixables don't care */ 349 if (cgroup_is_mixable(cgrp)) 350 return true; 351 352 /* domain roots can't be nested under threaded */ 353 if (cgroup_is_threaded(cgrp)) 354 return false; 355 356 /* can only have either domain or threaded children */ 357 if (cgrp->nr_populated_domain_children) 358 return false; 359 360 /* and no domain controllers can be enabled */ 361 if (cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask) 362 return false; 363 364 return true; 365 } 366 367 /* is @cgrp root of a threaded subtree? */ 368 bool cgroup_is_thread_root(struct cgroup *cgrp) 369 { 370 /* thread root should be a domain */ 371 if (cgroup_is_threaded(cgrp)) 372 return false; 373 374 /* a domain w/ threaded children is a thread root */ 375 if (cgrp->nr_threaded_children) 376 return true; 377 378 /* 379 * A domain which has tasks and explicit threaded controllers 380 * enabled is a thread root. 381 */ 382 if (cgroup_has_tasks(cgrp) && 383 (cgrp->subtree_control & cgrp_dfl_threaded_ss_mask)) 384 return true; 385 386 return false; 387 } 388 389 /* a domain which isn't connected to the root w/o brekage can't be used */ 390 static bool cgroup_is_valid_domain(struct cgroup *cgrp) 391 { 392 /* the cgroup itself can be a thread root */ 393 if (cgroup_is_threaded(cgrp)) 394 return false; 395 396 /* but the ancestors can't be unless mixable */ 397 while ((cgrp = cgroup_parent(cgrp))) { 398 if (!cgroup_is_mixable(cgrp) && cgroup_is_thread_root(cgrp)) 399 return false; 400 if (cgroup_is_threaded(cgrp)) 401 return false; 402 } 403 404 return true; 405 } 406 407 /* subsystems visibly enabled on a cgroup */ 408 static u16 cgroup_control(struct cgroup *cgrp) 409 { 410 struct cgroup *parent = cgroup_parent(cgrp); 411 u16 root_ss_mask = cgrp->root->subsys_mask; 412 413 if (parent) { 414 u16 ss_mask = parent->subtree_control; 415 416 /* threaded cgroups can only have threaded controllers */ 417 if (cgroup_is_threaded(cgrp)) 418 ss_mask &= cgrp_dfl_threaded_ss_mask; 419 return ss_mask; 420 } 421 422 if (cgroup_on_dfl(cgrp)) 423 root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask | 424 cgrp_dfl_implicit_ss_mask); 425 return root_ss_mask; 426 } 427 428 /* subsystems enabled on a cgroup */ 429 static u16 cgroup_ss_mask(struct cgroup *cgrp) 430 { 431 struct cgroup *parent = cgroup_parent(cgrp); 432 433 if (parent) { 434 u16 ss_mask = parent->subtree_ss_mask; 435 436 /* threaded cgroups can only have threaded controllers */ 437 if (cgroup_is_threaded(cgrp)) 438 ss_mask &= cgrp_dfl_threaded_ss_mask; 439 return ss_mask; 440 } 441 442 return cgrp->root->subsys_mask; 443 } 444 445 /** 446 * cgroup_css - obtain a cgroup's css for the specified subsystem 447 * @cgrp: the cgroup of interest 448 * @ss: the subsystem of interest (%NULL returns @cgrp->self) 449 * 450 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This 451 * function must be called either under cgroup_mutex or rcu_read_lock() and 452 * the caller is responsible for pinning the returned css if it wants to 453 * keep accessing it outside the said locks. This function may return 454 * %NULL if @cgrp doesn't have @subsys_id enabled. 455 */ 456 static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp, 457 struct cgroup_subsys *ss) 458 { 459 if (ss) 460 return rcu_dereference_check(cgrp->subsys[ss->id], 461 lockdep_is_held(&cgroup_mutex)); 462 else 463 return &cgrp->self; 464 } 465 466 /** 467 * cgroup_tryget_css - try to get a cgroup's css for the specified subsystem 468 * @cgrp: the cgroup of interest 469 * @ss: the subsystem of interest 470 * 471 * Find and get @cgrp's css associated with @ss. If the css doesn't exist 472 * or is offline, %NULL is returned. 473 */ 474 static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp, 475 struct cgroup_subsys *ss) 476 { 477 struct cgroup_subsys_state *css; 478 479 rcu_read_lock(); 480 css = cgroup_css(cgrp, ss); 481 if (css && !css_tryget_online(css)) 482 css = NULL; 483 rcu_read_unlock(); 484 485 return css; 486 } 487 488 /** 489 * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss 490 * @cgrp: the cgroup of interest 491 * @ss: the subsystem of interest (%NULL returns @cgrp->self) 492 * 493 * Similar to cgroup_css() but returns the effective css, which is defined 494 * as the matching css of the nearest ancestor including self which has @ss 495 * enabled. If @ss is associated with the hierarchy @cgrp is on, this 496 * function is guaranteed to return non-NULL css. 497 */ 498 static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp, 499 struct cgroup_subsys *ss) 500 { 501 lockdep_assert_held(&cgroup_mutex); 502 503 if (!ss) 504 return &cgrp->self; 505 506 /* 507 * This function is used while updating css associations and thus 508 * can't test the csses directly. Test ss_mask. 509 */ 510 while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) { 511 cgrp = cgroup_parent(cgrp); 512 if (!cgrp) 513 return NULL; 514 } 515 516 return cgroup_css(cgrp, ss); 517 } 518 519 /** 520 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem 521 * @cgrp: the cgroup of interest 522 * @ss: the subsystem of interest 523 * 524 * Find and get the effective css of @cgrp for @ss. The effective css is 525 * defined as the matching css of the nearest ancestor including self which 526 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on, 527 * the root css is returned, so this function always returns a valid css. 528 * 529 * The returned css is not guaranteed to be online, and therefore it is the 530 * callers responsibility to try get a reference for it. 531 */ 532 struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, 533 struct cgroup_subsys *ss) 534 { 535 struct cgroup_subsys_state *css; 536 537 do { 538 css = cgroup_css(cgrp, ss); 539 540 if (css) 541 return css; 542 cgrp = cgroup_parent(cgrp); 543 } while (cgrp); 544 545 return init_css_set.subsys[ss->id]; 546 } 547 548 /** 549 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem 550 * @cgrp: the cgroup of interest 551 * @ss: the subsystem of interest 552 * 553 * Find and get the effective css of @cgrp for @ss. The effective css is 554 * defined as the matching css of the nearest ancestor including self which 555 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on, 556 * the root css is returned, so this function always returns a valid css. 557 * The returned css must be put using css_put(). 558 */ 559 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp, 560 struct cgroup_subsys *ss) 561 { 562 struct cgroup_subsys_state *css; 563 564 rcu_read_lock(); 565 566 do { 567 css = cgroup_css(cgrp, ss); 568 569 if (css && css_tryget_online(css)) 570 goto out_unlock; 571 cgrp = cgroup_parent(cgrp); 572 } while (cgrp); 573 574 css = init_css_set.subsys[ss->id]; 575 css_get(css); 576 out_unlock: 577 rcu_read_unlock(); 578 return css; 579 } 580 EXPORT_SYMBOL_GPL(cgroup_get_e_css); 581 582 static void cgroup_get_live(struct cgroup *cgrp) 583 { 584 WARN_ON_ONCE(cgroup_is_dead(cgrp)); 585 css_get(&cgrp->self); 586 } 587 588 /** 589 * __cgroup_task_count - count the number of tasks in a cgroup. The caller 590 * is responsible for taking the css_set_lock. 591 * @cgrp: the cgroup in question 592 */ 593 int __cgroup_task_count(const struct cgroup *cgrp) 594 { 595 int count = 0; 596 struct cgrp_cset_link *link; 597 598 lockdep_assert_held(&css_set_lock); 599 600 list_for_each_entry(link, &cgrp->cset_links, cset_link) 601 count += link->cset->nr_tasks; 602 603 return count; 604 } 605 606 /** 607 * cgroup_task_count - count the number of tasks in a cgroup. 608 * @cgrp: the cgroup in question 609 */ 610 int cgroup_task_count(const struct cgroup *cgrp) 611 { 612 int count; 613 614 spin_lock_irq(&css_set_lock); 615 count = __cgroup_task_count(cgrp); 616 spin_unlock_irq(&css_set_lock); 617 618 return count; 619 } 620 621 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of) 622 { 623 struct cgroup *cgrp = of->kn->parent->priv; 624 struct cftype *cft = of_cft(of); 625 626 /* 627 * This is open and unprotected implementation of cgroup_css(). 628 * seq_css() is only called from a kernfs file operation which has 629 * an active reference on the file. Because all the subsystem 630 * files are drained before a css is disassociated with a cgroup, 631 * the matching css from the cgroup's subsys table is guaranteed to 632 * be and stay valid until the enclosing operation is complete. 633 */ 634 if (cft->ss) 635 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]); 636 else 637 return &cgrp->self; 638 } 639 EXPORT_SYMBOL_GPL(of_css); 640 641 /** 642 * for_each_css - iterate all css's of a cgroup 643 * @css: the iteration cursor 644 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end 645 * @cgrp: the target cgroup to iterate css's of 646 * 647 * Should be called under cgroup_[tree_]mutex. 648 */ 649 #define for_each_css(css, ssid, cgrp) \ 650 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \ 651 if (!((css) = rcu_dereference_check( \ 652 (cgrp)->subsys[(ssid)], \ 653 lockdep_is_held(&cgroup_mutex)))) { } \ 654 else 655 656 /** 657 * for_each_e_css - iterate all effective css's of a cgroup 658 * @css: the iteration cursor 659 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end 660 * @cgrp: the target cgroup to iterate css's of 661 * 662 * Should be called under cgroup_[tree_]mutex. 663 */ 664 #define for_each_e_css(css, ssid, cgrp) \ 665 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \ 666 if (!((css) = cgroup_e_css_by_mask(cgrp, \ 667 cgroup_subsys[(ssid)]))) \ 668 ; \ 669 else 670 671 /** 672 * do_each_subsys_mask - filter for_each_subsys with a bitmask 673 * @ss: the iteration cursor 674 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end 675 * @ss_mask: the bitmask 676 * 677 * The block will only run for cases where the ssid-th bit (1 << ssid) of 678 * @ss_mask is set. 679 */ 680 #define do_each_subsys_mask(ss, ssid, ss_mask) do { \ 681 unsigned long __ss_mask = (ss_mask); \ 682 if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */ \ 683 (ssid) = 0; \ 684 break; \ 685 } \ 686 for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \ 687 (ss) = cgroup_subsys[ssid]; \ 688 { 689 690 #define while_each_subsys_mask() \ 691 } \ 692 } \ 693 } while (false) 694 695 /* iterate over child cgrps, lock should be held throughout iteration */ 696 #define cgroup_for_each_live_child(child, cgrp) \ 697 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \ 698 if (({ lockdep_assert_held(&cgroup_mutex); \ 699 cgroup_is_dead(child); })) \ 700 ; \ 701 else 702 703 /* walk live descendants in pre order */ 704 #define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \ 705 css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \ 706 if (({ lockdep_assert_held(&cgroup_mutex); \ 707 (dsct) = (d_css)->cgroup; \ 708 cgroup_is_dead(dsct); })) \ 709 ; \ 710 else 711 712 /* walk live descendants in postorder */ 713 #define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \ 714 css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \ 715 if (({ lockdep_assert_held(&cgroup_mutex); \ 716 (dsct) = (d_css)->cgroup; \ 717 cgroup_is_dead(dsct); })) \ 718 ; \ 719 else 720 721 /* 722 * The default css_set - used by init and its children prior to any 723 * hierarchies being mounted. It contains a pointer to the root state 724 * for each subsystem. Also used to anchor the list of css_sets. Not 725 * reference-counted, to improve performance when child cgroups 726 * haven't been created. 727 */ 728 struct css_set init_css_set = { 729 .refcount = REFCOUNT_INIT(1), 730 .dom_cset = &init_css_set, 731 .tasks = LIST_HEAD_INIT(init_css_set.tasks), 732 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks), 733 .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks), 734 .task_iters = LIST_HEAD_INIT(init_css_set.task_iters), 735 .threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets), 736 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links), 737 .mg_preload_node = LIST_HEAD_INIT(init_css_set.mg_preload_node), 738 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node), 739 740 /* 741 * The following field is re-initialized when this cset gets linked 742 * in cgroup_init(). However, let's initialize the field 743 * statically too so that the default cgroup can be accessed safely 744 * early during boot. 745 */ 746 .dfl_cgrp = &cgrp_dfl_root.cgrp, 747 }; 748 749 static int css_set_count = 1; /* 1 for init_css_set */ 750 751 static bool css_set_threaded(struct css_set *cset) 752 { 753 return cset->dom_cset != cset; 754 } 755 756 /** 757 * css_set_populated - does a css_set contain any tasks? 758 * @cset: target css_set 759 * 760 * css_set_populated() should be the same as !!cset->nr_tasks at steady 761 * state. However, css_set_populated() can be called while a task is being 762 * added to or removed from the linked list before the nr_tasks is 763 * properly updated. Hence, we can't just look at ->nr_tasks here. 764 */ 765 static bool css_set_populated(struct css_set *cset) 766 { 767 lockdep_assert_held(&css_set_lock); 768 769 return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks); 770 } 771 772 /** 773 * cgroup_update_populated - update the populated count of a cgroup 774 * @cgrp: the target cgroup 775 * @populated: inc or dec populated count 776 * 777 * One of the css_sets associated with @cgrp is either getting its first 778 * task or losing the last. Update @cgrp->nr_populated_* accordingly. The 779 * count is propagated towards root so that a given cgroup's 780 * nr_populated_children is zero iff none of its descendants contain any 781 * tasks. 782 * 783 * @cgrp's interface file "cgroup.populated" is zero if both 784 * @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and 785 * 1 otherwise. When the sum changes from or to zero, userland is notified 786 * that the content of the interface file has changed. This can be used to 787 * detect when @cgrp and its descendants become populated or empty. 788 */ 789 static void cgroup_update_populated(struct cgroup *cgrp, bool populated) 790 { 791 struct cgroup *child = NULL; 792 int adj = populated ? 1 : -1; 793 794 lockdep_assert_held(&css_set_lock); 795 796 do { 797 bool was_populated = cgroup_is_populated(cgrp); 798 799 if (!child) { 800 cgrp->nr_populated_csets += adj; 801 } else { 802 if (cgroup_is_threaded(child)) 803 cgrp->nr_populated_threaded_children += adj; 804 else 805 cgrp->nr_populated_domain_children += adj; 806 } 807 808 if (was_populated == cgroup_is_populated(cgrp)) 809 break; 810 811 cgroup1_check_for_release(cgrp); 812 TRACE_CGROUP_PATH(notify_populated, cgrp, 813 cgroup_is_populated(cgrp)); 814 cgroup_file_notify(&cgrp->events_file); 815 816 child = cgrp; 817 cgrp = cgroup_parent(cgrp); 818 } while (cgrp); 819 } 820 821 /** 822 * css_set_update_populated - update populated state of a css_set 823 * @cset: target css_set 824 * @populated: whether @cset is populated or depopulated 825 * 826 * @cset is either getting the first task or losing the last. Update the 827 * populated counters of all associated cgroups accordingly. 828 */ 829 static void css_set_update_populated(struct css_set *cset, bool populated) 830 { 831 struct cgrp_cset_link *link; 832 833 lockdep_assert_held(&css_set_lock); 834 835 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) 836 cgroup_update_populated(link->cgrp, populated); 837 } 838 839 /* 840 * @task is leaving, advance task iterators which are pointing to it so 841 * that they can resume at the next position. Advancing an iterator might 842 * remove it from the list, use safe walk. See css_task_iter_skip() for 843 * details. 844 */ 845 static void css_set_skip_task_iters(struct css_set *cset, 846 struct task_struct *task) 847 { 848 struct css_task_iter *it, *pos; 849 850 list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node) 851 css_task_iter_skip(it, task); 852 } 853 854 /** 855 * css_set_move_task - move a task from one css_set to another 856 * @task: task being moved 857 * @from_cset: css_set @task currently belongs to (may be NULL) 858 * @to_cset: new css_set @task is being moved to (may be NULL) 859 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks 860 * 861 * Move @task from @from_cset to @to_cset. If @task didn't belong to any 862 * css_set, @from_cset can be NULL. If @task is being disassociated 863 * instead of moved, @to_cset can be NULL. 864 * 865 * This function automatically handles populated counter updates and 866 * css_task_iter adjustments but the caller is responsible for managing 867 * @from_cset and @to_cset's reference counts. 868 */ 869 static void css_set_move_task(struct task_struct *task, 870 struct css_set *from_cset, struct css_set *to_cset, 871 bool use_mg_tasks) 872 { 873 lockdep_assert_held(&css_set_lock); 874 875 if (to_cset && !css_set_populated(to_cset)) 876 css_set_update_populated(to_cset, true); 877 878 if (from_cset) { 879 WARN_ON_ONCE(list_empty(&task->cg_list)); 880 881 css_set_skip_task_iters(from_cset, task); 882 list_del_init(&task->cg_list); 883 if (!css_set_populated(from_cset)) 884 css_set_update_populated(from_cset, false); 885 } else { 886 WARN_ON_ONCE(!list_empty(&task->cg_list)); 887 } 888 889 if (to_cset) { 890 /* 891 * We are synchronized through cgroup_threadgroup_rwsem 892 * against PF_EXITING setting such that we can't race 893 * against cgroup_exit()/cgroup_free() dropping the css_set. 894 */ 895 WARN_ON_ONCE(task->flags & PF_EXITING); 896 897 cgroup_move_task(task, to_cset); 898 list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks : 899 &to_cset->tasks); 900 } 901 } 902 903 /* 904 * hash table for cgroup groups. This improves the performance to find 905 * an existing css_set. This hash doesn't (currently) take into 906 * account cgroups in empty hierarchies. 907 */ 908 #define CSS_SET_HASH_BITS 7 909 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS); 910 911 static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) 912 { 913 unsigned long key = 0UL; 914 struct cgroup_subsys *ss; 915 int i; 916 917 for_each_subsys(ss, i) 918 key += (unsigned long)css[i]; 919 key = (key >> 16) ^ key; 920 921 return key; 922 } 923 924 void put_css_set_locked(struct css_set *cset) 925 { 926 struct cgrp_cset_link *link, *tmp_link; 927 struct cgroup_subsys *ss; 928 int ssid; 929 930 lockdep_assert_held(&css_set_lock); 931 932 if (!refcount_dec_and_test(&cset->refcount)) 933 return; 934 935 WARN_ON_ONCE(!list_empty(&cset->threaded_csets)); 936 937 /* This css_set is dead. Unlink it and release cgroup and css refs */ 938 for_each_subsys(ss, ssid) { 939 list_del(&cset->e_cset_node[ssid]); 940 css_put(cset->subsys[ssid]); 941 } 942 hash_del(&cset->hlist); 943 css_set_count--; 944 945 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) { 946 list_del(&link->cset_link); 947 list_del(&link->cgrp_link); 948 if (cgroup_parent(link->cgrp)) 949 cgroup_put(link->cgrp); 950 kfree(link); 951 } 952 953 if (css_set_threaded(cset)) { 954 list_del(&cset->threaded_csets_node); 955 put_css_set_locked(cset->dom_cset); 956 } 957 958 kfree_rcu(cset, rcu_head); 959 } 960 961 /** 962 * compare_css_sets - helper function for find_existing_css_set(). 963 * @cset: candidate css_set being tested 964 * @old_cset: existing css_set for a task 965 * @new_cgrp: cgroup that's being entered by the task 966 * @template: desired set of css pointers in css_set (pre-calculated) 967 * 968 * Returns true if "cset" matches "old_cset" except for the hierarchy 969 * which "new_cgrp" belongs to, for which it should match "new_cgrp". 970 */ 971 static bool compare_css_sets(struct css_set *cset, 972 struct css_set *old_cset, 973 struct cgroup *new_cgrp, 974 struct cgroup_subsys_state *template[]) 975 { 976 struct cgroup *new_dfl_cgrp; 977 struct list_head *l1, *l2; 978 979 /* 980 * On the default hierarchy, there can be csets which are 981 * associated with the same set of cgroups but different csses. 982 * Let's first ensure that csses match. 983 */ 984 if (memcmp(template, cset->subsys, sizeof(cset->subsys))) 985 return false; 986 987 988 /* @cset's domain should match the default cgroup's */ 989 if (cgroup_on_dfl(new_cgrp)) 990 new_dfl_cgrp = new_cgrp; 991 else 992 new_dfl_cgrp = old_cset->dfl_cgrp; 993 994 if (new_dfl_cgrp->dom_cgrp != cset->dom_cset->dfl_cgrp) 995 return false; 996 997 /* 998 * Compare cgroup pointers in order to distinguish between 999 * different cgroups in hierarchies. As different cgroups may 1000 * share the same effective css, this comparison is always 1001 * necessary. 1002 */ 1003 l1 = &cset->cgrp_links; 1004 l2 = &old_cset->cgrp_links; 1005 while (1) { 1006 struct cgrp_cset_link *link1, *link2; 1007 struct cgroup *cgrp1, *cgrp2; 1008 1009 l1 = l1->next; 1010 l2 = l2->next; 1011 /* See if we reached the end - both lists are equal length. */ 1012 if (l1 == &cset->cgrp_links) { 1013 BUG_ON(l2 != &old_cset->cgrp_links); 1014 break; 1015 } else { 1016 BUG_ON(l2 == &old_cset->cgrp_links); 1017 } 1018 /* Locate the cgroups associated with these links. */ 1019 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link); 1020 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link); 1021 cgrp1 = link1->cgrp; 1022 cgrp2 = link2->cgrp; 1023 /* Hierarchies should be linked in the same order. */ 1024 BUG_ON(cgrp1->root != cgrp2->root); 1025 1026 /* 1027 * If this hierarchy is the hierarchy of the cgroup 1028 * that's changing, then we need to check that this 1029 * css_set points to the new cgroup; if it's any other 1030 * hierarchy, then this css_set should point to the 1031 * same cgroup as the old css_set. 1032 */ 1033 if (cgrp1->root == new_cgrp->root) { 1034 if (cgrp1 != new_cgrp) 1035 return false; 1036 } else { 1037 if (cgrp1 != cgrp2) 1038 return false; 1039 } 1040 } 1041 return true; 1042 } 1043 1044 /** 1045 * find_existing_css_set - init css array and find the matching css_set 1046 * @old_cset: the css_set that we're using before the cgroup transition 1047 * @cgrp: the cgroup that we're moving into 1048 * @template: out param for the new set of csses, should be clear on entry 1049 */ 1050 static struct css_set *find_existing_css_set(struct css_set *old_cset, 1051 struct cgroup *cgrp, 1052 struct cgroup_subsys_state *template[]) 1053 { 1054 struct cgroup_root *root = cgrp->root; 1055 struct cgroup_subsys *ss; 1056 struct css_set *cset; 1057 unsigned long key; 1058 int i; 1059 1060 /* 1061 * Build the set of subsystem state objects that we want to see in the 1062 * new css_set. While subsystems can change globally, the entries here 1063 * won't change, so no need for locking. 1064 */ 1065 for_each_subsys(ss, i) { 1066 if (root->subsys_mask & (1UL << i)) { 1067 /* 1068 * @ss is in this hierarchy, so we want the 1069 * effective css from @cgrp. 1070 */ 1071 template[i] = cgroup_e_css_by_mask(cgrp, ss); 1072 } else { 1073 /* 1074 * @ss is not in this hierarchy, so we don't want 1075 * to change the css. 1076 */ 1077 template[i] = old_cset->subsys[i]; 1078 } 1079 } 1080 1081 key = css_set_hash(template); 1082 hash_for_each_possible(css_set_table, cset, hlist, key) { 1083 if (!compare_css_sets(cset, old_cset, cgrp, template)) 1084 continue; 1085 1086 /* This css_set matches what we need */ 1087 return cset; 1088 } 1089 1090 /* No existing cgroup group matched */ 1091 return NULL; 1092 } 1093 1094 static void free_cgrp_cset_links(struct list_head *links_to_free) 1095 { 1096 struct cgrp_cset_link *link, *tmp_link; 1097 1098 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) { 1099 list_del(&link->cset_link); 1100 kfree(link); 1101 } 1102 } 1103 1104 /** 1105 * allocate_cgrp_cset_links - allocate cgrp_cset_links 1106 * @count: the number of links to allocate 1107 * @tmp_links: list_head the allocated links are put on 1108 * 1109 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links 1110 * through ->cset_link. Returns 0 on success or -errno. 1111 */ 1112 static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links) 1113 { 1114 struct cgrp_cset_link *link; 1115 int i; 1116 1117 INIT_LIST_HEAD(tmp_links); 1118 1119 for (i = 0; i < count; i++) { 1120 link = kzalloc(sizeof(*link), GFP_KERNEL); 1121 if (!link) { 1122 free_cgrp_cset_links(tmp_links); 1123 return -ENOMEM; 1124 } 1125 list_add(&link->cset_link, tmp_links); 1126 } 1127 return 0; 1128 } 1129 1130 /** 1131 * link_css_set - a helper function to link a css_set to a cgroup 1132 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links() 1133 * @cset: the css_set to be linked 1134 * @cgrp: the destination cgroup 1135 */ 1136 static void link_css_set(struct list_head *tmp_links, struct css_set *cset, 1137 struct cgroup *cgrp) 1138 { 1139 struct cgrp_cset_link *link; 1140 1141 BUG_ON(list_empty(tmp_links)); 1142 1143 if (cgroup_on_dfl(cgrp)) 1144 cset->dfl_cgrp = cgrp; 1145 1146 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link); 1147 link->cset = cset; 1148 link->cgrp = cgrp; 1149 1150 /* 1151 * Always add links to the tail of the lists so that the lists are 1152 * in chronological order. 1153 */ 1154 list_move_tail(&link->cset_link, &cgrp->cset_links); 1155 list_add_tail(&link->cgrp_link, &cset->cgrp_links); 1156 1157 if (cgroup_parent(cgrp)) 1158 cgroup_get_live(cgrp); 1159 } 1160 1161 /** 1162 * find_css_set - return a new css_set with one cgroup updated 1163 * @old_cset: the baseline css_set 1164 * @cgrp: the cgroup to be updated 1165 * 1166 * Return a new css_set that's equivalent to @old_cset, but with @cgrp 1167 * substituted into the appropriate hierarchy. 1168 */ 1169 static struct css_set *find_css_set(struct css_set *old_cset, 1170 struct cgroup *cgrp) 1171 { 1172 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { }; 1173 struct css_set *cset; 1174 struct list_head tmp_links; 1175 struct cgrp_cset_link *link; 1176 struct cgroup_subsys *ss; 1177 unsigned long key; 1178 int ssid; 1179 1180 lockdep_assert_held(&cgroup_mutex); 1181 1182 /* First see if we already have a cgroup group that matches 1183 * the desired set */ 1184 spin_lock_irq(&css_set_lock); 1185 cset = find_existing_css_set(old_cset, cgrp, template); 1186 if (cset) 1187 get_css_set(cset); 1188 spin_unlock_irq(&css_set_lock); 1189 1190 if (cset) 1191 return cset; 1192 1193 cset = kzalloc(sizeof(*cset), GFP_KERNEL); 1194 if (!cset) 1195 return NULL; 1196 1197 /* Allocate all the cgrp_cset_link objects that we'll need */ 1198 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) { 1199 kfree(cset); 1200 return NULL; 1201 } 1202 1203 refcount_set(&cset->refcount, 1); 1204 cset->dom_cset = cset; 1205 INIT_LIST_HEAD(&cset->tasks); 1206 INIT_LIST_HEAD(&cset->mg_tasks); 1207 INIT_LIST_HEAD(&cset->dying_tasks); 1208 INIT_LIST_HEAD(&cset->task_iters); 1209 INIT_LIST_HEAD(&cset->threaded_csets); 1210 INIT_HLIST_NODE(&cset->hlist); 1211 INIT_LIST_HEAD(&cset->cgrp_links); 1212 INIT_LIST_HEAD(&cset->mg_preload_node); 1213 INIT_LIST_HEAD(&cset->mg_node); 1214 1215 /* Copy the set of subsystem state objects generated in 1216 * find_existing_css_set() */ 1217 memcpy(cset->subsys, template, sizeof(cset->subsys)); 1218 1219 spin_lock_irq(&css_set_lock); 1220 /* Add reference counts and links from the new css_set. */ 1221 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) { 1222 struct cgroup *c = link->cgrp; 1223 1224 if (c->root == cgrp->root) 1225 c = cgrp; 1226 link_css_set(&tmp_links, cset, c); 1227 } 1228 1229 BUG_ON(!list_empty(&tmp_links)); 1230 1231 css_set_count++; 1232 1233 /* Add @cset to the hash table */ 1234 key = css_set_hash(cset->subsys); 1235 hash_add(css_set_table, &cset->hlist, key); 1236 1237 for_each_subsys(ss, ssid) { 1238 struct cgroup_subsys_state *css = cset->subsys[ssid]; 1239 1240 list_add_tail(&cset->e_cset_node[ssid], 1241 &css->cgroup->e_csets[ssid]); 1242 css_get(css); 1243 } 1244 1245 spin_unlock_irq(&css_set_lock); 1246 1247 /* 1248 * If @cset should be threaded, look up the matching dom_cset and 1249 * link them up. We first fully initialize @cset then look for the 1250 * dom_cset. It's simpler this way and safe as @cset is guaranteed 1251 * to stay empty until we return. 1252 */ 1253 if (cgroup_is_threaded(cset->dfl_cgrp)) { 1254 struct css_set *dcset; 1255 1256 dcset = find_css_set(cset, cset->dfl_cgrp->dom_cgrp); 1257 if (!dcset) { 1258 put_css_set(cset); 1259 return NULL; 1260 } 1261 1262 spin_lock_irq(&css_set_lock); 1263 cset->dom_cset = dcset; 1264 list_add_tail(&cset->threaded_csets_node, 1265 &dcset->threaded_csets); 1266 spin_unlock_irq(&css_set_lock); 1267 } 1268 1269 return cset; 1270 } 1271 1272 struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root) 1273 { 1274 struct cgroup *root_cgrp = kf_root->kn->priv; 1275 1276 return root_cgrp->root; 1277 } 1278 1279 static int cgroup_init_root_id(struct cgroup_root *root) 1280 { 1281 int id; 1282 1283 lockdep_assert_held(&cgroup_mutex); 1284 1285 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL); 1286 if (id < 0) 1287 return id; 1288 1289 root->hierarchy_id = id; 1290 return 0; 1291 } 1292 1293 static void cgroup_exit_root_id(struct cgroup_root *root) 1294 { 1295 lockdep_assert_held(&cgroup_mutex); 1296 1297 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id); 1298 } 1299 1300 void cgroup_free_root(struct cgroup_root *root) 1301 { 1302 kfree(root); 1303 } 1304 1305 static void cgroup_destroy_root(struct cgroup_root *root) 1306 { 1307 struct cgroup *cgrp = &root->cgrp; 1308 struct cgrp_cset_link *link, *tmp_link; 1309 1310 trace_cgroup_destroy_root(root); 1311 1312 cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp); 1313 1314 BUG_ON(atomic_read(&root->nr_cgrps)); 1315 BUG_ON(!list_empty(&cgrp->self.children)); 1316 1317 /* Rebind all subsystems back to the default hierarchy */ 1318 WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask)); 1319 1320 /* 1321 * Release all the links from cset_links to this hierarchy's 1322 * root cgroup 1323 */ 1324 spin_lock_irq(&css_set_lock); 1325 1326 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) { 1327 list_del(&link->cset_link); 1328 list_del(&link->cgrp_link); 1329 kfree(link); 1330 } 1331 1332 spin_unlock_irq(&css_set_lock); 1333 1334 if (!list_empty(&root->root_list)) { 1335 list_del(&root->root_list); 1336 cgroup_root_count--; 1337 } 1338 1339 cgroup_exit_root_id(root); 1340 1341 mutex_unlock(&cgroup_mutex); 1342 1343 cgroup_rstat_exit(cgrp); 1344 kernfs_destroy_root(root->kf_root); 1345 cgroup_free_root(root); 1346 } 1347 1348 /* 1349 * look up cgroup associated with current task's cgroup namespace on the 1350 * specified hierarchy 1351 */ 1352 static struct cgroup * 1353 current_cgns_cgroup_from_root(struct cgroup_root *root) 1354 { 1355 struct cgroup *res = NULL; 1356 struct css_set *cset; 1357 1358 lockdep_assert_held(&css_set_lock); 1359 1360 rcu_read_lock(); 1361 1362 cset = current->nsproxy->cgroup_ns->root_cset; 1363 if (cset == &init_css_set) { 1364 res = &root->cgrp; 1365 } else if (root == &cgrp_dfl_root) { 1366 res = cset->dfl_cgrp; 1367 } else { 1368 struct cgrp_cset_link *link; 1369 1370 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { 1371 struct cgroup *c = link->cgrp; 1372 1373 if (c->root == root) { 1374 res = c; 1375 break; 1376 } 1377 } 1378 } 1379 rcu_read_unlock(); 1380 1381 BUG_ON(!res); 1382 return res; 1383 } 1384 1385 /* look up cgroup associated with given css_set on the specified hierarchy */ 1386 static struct cgroup *cset_cgroup_from_root(struct css_set *cset, 1387 struct cgroup_root *root) 1388 { 1389 struct cgroup *res = NULL; 1390 1391 lockdep_assert_held(&cgroup_mutex); 1392 lockdep_assert_held(&css_set_lock); 1393 1394 if (cset == &init_css_set) { 1395 res = &root->cgrp; 1396 } else if (root == &cgrp_dfl_root) { 1397 res = cset->dfl_cgrp; 1398 } else { 1399 struct cgrp_cset_link *link; 1400 1401 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { 1402 struct cgroup *c = link->cgrp; 1403 1404 if (c->root == root) { 1405 res = c; 1406 break; 1407 } 1408 } 1409 } 1410 1411 BUG_ON(!res); 1412 return res; 1413 } 1414 1415 /* 1416 * Return the cgroup for "task" from the given hierarchy. Must be 1417 * called with cgroup_mutex and css_set_lock held. 1418 */ 1419 struct cgroup *task_cgroup_from_root(struct task_struct *task, 1420 struct cgroup_root *root) 1421 { 1422 /* 1423 * No need to lock the task - since we hold css_set_lock the 1424 * task can't change groups. 1425 */ 1426 return cset_cgroup_from_root(task_css_set(task), root); 1427 } 1428 1429 /* 1430 * A task must hold cgroup_mutex to modify cgroups. 1431 * 1432 * Any task can increment and decrement the count field without lock. 1433 * So in general, code holding cgroup_mutex can't rely on the count 1434 * field not changing. However, if the count goes to zero, then only 1435 * cgroup_attach_task() can increment it again. Because a count of zero 1436 * means that no tasks are currently attached, therefore there is no 1437 * way a task attached to that cgroup can fork (the other way to 1438 * increment the count). So code holding cgroup_mutex can safely 1439 * assume that if the count is zero, it will stay zero. Similarly, if 1440 * a task holds cgroup_mutex on a cgroup with zero count, it 1441 * knows that the cgroup won't be removed, as cgroup_rmdir() 1442 * needs that mutex. 1443 * 1444 * A cgroup can only be deleted if both its 'count' of using tasks 1445 * is zero, and its list of 'children' cgroups is empty. Since all 1446 * tasks in the system use _some_ cgroup, and since there is always at 1447 * least one task in the system (init, pid == 1), therefore, root cgroup 1448 * always has either children cgroups and/or using tasks. So we don't 1449 * need a special hack to ensure that root cgroup cannot be deleted. 1450 * 1451 * P.S. One more locking exception. RCU is used to guard the 1452 * update of a tasks cgroup pointer by cgroup_attach_task() 1453 */ 1454 1455 static struct kernfs_syscall_ops cgroup_kf_syscall_ops; 1456 1457 static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft, 1458 char *buf) 1459 { 1460 struct cgroup_subsys *ss = cft->ss; 1461 1462 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) && 1463 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) { 1464 const char *dbg = (cft->flags & CFTYPE_DEBUG) ? ".__DEBUG__." : ""; 1465 1466 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s", 1467 dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name, 1468 cft->name); 1469 } else { 1470 strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX); 1471 } 1472 return buf; 1473 } 1474 1475 /** 1476 * cgroup_file_mode - deduce file mode of a control file 1477 * @cft: the control file in question 1478 * 1479 * S_IRUGO for read, S_IWUSR for write. 1480 */ 1481 static umode_t cgroup_file_mode(const struct cftype *cft) 1482 { 1483 umode_t mode = 0; 1484 1485 if (cft->read_u64 || cft->read_s64 || cft->seq_show) 1486 mode |= S_IRUGO; 1487 1488 if (cft->write_u64 || cft->write_s64 || cft->write) { 1489 if (cft->flags & CFTYPE_WORLD_WRITABLE) 1490 mode |= S_IWUGO; 1491 else 1492 mode |= S_IWUSR; 1493 } 1494 1495 return mode; 1496 } 1497 1498 /** 1499 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask 1500 * @subtree_control: the new subtree_control mask to consider 1501 * @this_ss_mask: available subsystems 1502 * 1503 * On the default hierarchy, a subsystem may request other subsystems to be 1504 * enabled together through its ->depends_on mask. In such cases, more 1505 * subsystems than specified in "cgroup.subtree_control" may be enabled. 1506 * 1507 * This function calculates which subsystems need to be enabled if 1508 * @subtree_control is to be applied while restricted to @this_ss_mask. 1509 */ 1510 static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask) 1511 { 1512 u16 cur_ss_mask = subtree_control; 1513 struct cgroup_subsys *ss; 1514 int ssid; 1515 1516 lockdep_assert_held(&cgroup_mutex); 1517 1518 cur_ss_mask |= cgrp_dfl_implicit_ss_mask; 1519 1520 while (true) { 1521 u16 new_ss_mask = cur_ss_mask; 1522 1523 do_each_subsys_mask(ss, ssid, cur_ss_mask) { 1524 new_ss_mask |= ss->depends_on; 1525 } while_each_subsys_mask(); 1526 1527 /* 1528 * Mask out subsystems which aren't available. This can 1529 * happen only if some depended-upon subsystems were bound 1530 * to non-default hierarchies. 1531 */ 1532 new_ss_mask &= this_ss_mask; 1533 1534 if (new_ss_mask == cur_ss_mask) 1535 break; 1536 cur_ss_mask = new_ss_mask; 1537 } 1538 1539 return cur_ss_mask; 1540 } 1541 1542 /** 1543 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods 1544 * @kn: the kernfs_node being serviced 1545 * 1546 * This helper undoes cgroup_kn_lock_live() and should be invoked before 1547 * the method finishes if locking succeeded. Note that once this function 1548 * returns the cgroup returned by cgroup_kn_lock_live() may become 1549 * inaccessible any time. If the caller intends to continue to access the 1550 * cgroup, it should pin it before invoking this function. 1551 */ 1552 void cgroup_kn_unlock(struct kernfs_node *kn) 1553 { 1554 struct cgroup *cgrp; 1555 1556 if (kernfs_type(kn) == KERNFS_DIR) 1557 cgrp = kn->priv; 1558 else 1559 cgrp = kn->parent->priv; 1560 1561 mutex_unlock(&cgroup_mutex); 1562 1563 kernfs_unbreak_active_protection(kn); 1564 cgroup_put(cgrp); 1565 } 1566 1567 /** 1568 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods 1569 * @kn: the kernfs_node being serviced 1570 * @drain_offline: perform offline draining on the cgroup 1571 * 1572 * This helper is to be used by a cgroup kernfs method currently servicing 1573 * @kn. It breaks the active protection, performs cgroup locking and 1574 * verifies that the associated cgroup is alive. Returns the cgroup if 1575 * alive; otherwise, %NULL. A successful return should be undone by a 1576 * matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the 1577 * cgroup is drained of offlining csses before return. 1578 * 1579 * Any cgroup kernfs method implementation which requires locking the 1580 * associated cgroup should use this helper. It avoids nesting cgroup 1581 * locking under kernfs active protection and allows all kernfs operations 1582 * including self-removal. 1583 */ 1584 struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline) 1585 { 1586 struct cgroup *cgrp; 1587 1588 if (kernfs_type(kn) == KERNFS_DIR) 1589 cgrp = kn->priv; 1590 else 1591 cgrp = kn->parent->priv; 1592 1593 /* 1594 * We're gonna grab cgroup_mutex which nests outside kernfs 1595 * active_ref. cgroup liveliness check alone provides enough 1596 * protection against removal. Ensure @cgrp stays accessible and 1597 * break the active_ref protection. 1598 */ 1599 if (!cgroup_tryget(cgrp)) 1600 return NULL; 1601 kernfs_break_active_protection(kn); 1602 1603 if (drain_offline) 1604 cgroup_lock_and_drain_offline(cgrp); 1605 else 1606 mutex_lock(&cgroup_mutex); 1607 1608 if (!cgroup_is_dead(cgrp)) 1609 return cgrp; 1610 1611 cgroup_kn_unlock(kn); 1612 return NULL; 1613 } 1614 1615 static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) 1616 { 1617 char name[CGROUP_FILE_NAME_MAX]; 1618 1619 lockdep_assert_held(&cgroup_mutex); 1620 1621 if (cft->file_offset) { 1622 struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss); 1623 struct cgroup_file *cfile = (void *)css + cft->file_offset; 1624 1625 spin_lock_irq(&cgroup_file_kn_lock); 1626 cfile->kn = NULL; 1627 spin_unlock_irq(&cgroup_file_kn_lock); 1628 1629 del_timer_sync(&cfile->notify_timer); 1630 } 1631 1632 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name)); 1633 } 1634 1635 /** 1636 * css_clear_dir - remove subsys files in a cgroup directory 1637 * @css: target css 1638 */ 1639 static void css_clear_dir(struct cgroup_subsys_state *css) 1640 { 1641 struct cgroup *cgrp = css->cgroup; 1642 struct cftype *cfts; 1643 1644 if (!(css->flags & CSS_VISIBLE)) 1645 return; 1646 1647 css->flags &= ~CSS_VISIBLE; 1648 1649 if (!css->ss) { 1650 if (cgroup_on_dfl(cgrp)) 1651 cfts = cgroup_base_files; 1652 else 1653 cfts = cgroup1_base_files; 1654 1655 cgroup_addrm_files(css, cgrp, cfts, false); 1656 } else { 1657 list_for_each_entry(cfts, &css->ss->cfts, node) 1658 cgroup_addrm_files(css, cgrp, cfts, false); 1659 } 1660 } 1661 1662 /** 1663 * css_populate_dir - create subsys files in a cgroup directory 1664 * @css: target css 1665 * 1666 * On failure, no file is added. 1667 */ 1668 static int css_populate_dir(struct cgroup_subsys_state *css) 1669 { 1670 struct cgroup *cgrp = css->cgroup; 1671 struct cftype *cfts, *failed_cfts; 1672 int ret; 1673 1674 if ((css->flags & CSS_VISIBLE) || !cgrp->kn) 1675 return 0; 1676 1677 if (!css->ss) { 1678 if (cgroup_on_dfl(cgrp)) 1679 cfts = cgroup_base_files; 1680 else 1681 cfts = cgroup1_base_files; 1682 1683 ret = cgroup_addrm_files(&cgrp->self, cgrp, cfts, true); 1684 if (ret < 0) 1685 return ret; 1686 } else { 1687 list_for_each_entry(cfts, &css->ss->cfts, node) { 1688 ret = cgroup_addrm_files(css, cgrp, cfts, true); 1689 if (ret < 0) { 1690 failed_cfts = cfts; 1691 goto err; 1692 } 1693 } 1694 } 1695 1696 css->flags |= CSS_VISIBLE; 1697 1698 return 0; 1699 err: 1700 list_for_each_entry(cfts, &css->ss->cfts, node) { 1701 if (cfts == failed_cfts) 1702 break; 1703 cgroup_addrm_files(css, cgrp, cfts, false); 1704 } 1705 return ret; 1706 } 1707 1708 int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask) 1709 { 1710 struct cgroup *dcgrp = &dst_root->cgrp; 1711 struct cgroup_subsys *ss; 1712 int ssid, i, ret; 1713 1714 lockdep_assert_held(&cgroup_mutex); 1715 1716 do_each_subsys_mask(ss, ssid, ss_mask) { 1717 /* 1718 * If @ss has non-root csses attached to it, can't move. 1719 * If @ss is an implicit controller, it is exempt from this 1720 * rule and can be stolen. 1721 */ 1722 if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) && 1723 !ss->implicit_on_dfl) 1724 return -EBUSY; 1725 1726 /* can't move between two non-dummy roots either */ 1727 if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root) 1728 return -EBUSY; 1729 } while_each_subsys_mask(); 1730 1731 do_each_subsys_mask(ss, ssid, ss_mask) { 1732 struct cgroup_root *src_root = ss->root; 1733 struct cgroup *scgrp = &src_root->cgrp; 1734 struct cgroup_subsys_state *css = cgroup_css(scgrp, ss); 1735 struct css_set *cset; 1736 1737 WARN_ON(!css || cgroup_css(dcgrp, ss)); 1738 1739 /* disable from the source */ 1740 src_root->subsys_mask &= ~(1 << ssid); 1741 WARN_ON(cgroup_apply_control(scgrp)); 1742 cgroup_finalize_control(scgrp, 0); 1743 1744 /* rebind */ 1745 RCU_INIT_POINTER(scgrp->subsys[ssid], NULL); 1746 rcu_assign_pointer(dcgrp->subsys[ssid], css); 1747 ss->root = dst_root; 1748 css->cgroup = dcgrp; 1749 1750 spin_lock_irq(&css_set_lock); 1751 hash_for_each(css_set_table, i, cset, hlist) 1752 list_move_tail(&cset->e_cset_node[ss->id], 1753 &dcgrp->e_csets[ss->id]); 1754 spin_unlock_irq(&css_set_lock); 1755 1756 if (ss->css_rstat_flush) { 1757 list_del_rcu(&css->rstat_css_node); 1758 list_add_rcu(&css->rstat_css_node, 1759 &dcgrp->rstat_css_list); 1760 } 1761 1762 /* default hierarchy doesn't enable controllers by default */ 1763 dst_root->subsys_mask |= 1 << ssid; 1764 if (dst_root == &cgrp_dfl_root) { 1765 static_branch_enable(cgroup_subsys_on_dfl_key[ssid]); 1766 } else { 1767 dcgrp->subtree_control |= 1 << ssid; 1768 static_branch_disable(cgroup_subsys_on_dfl_key[ssid]); 1769 } 1770 1771 ret = cgroup_apply_control(dcgrp); 1772 if (ret) 1773 pr_warn("partial failure to rebind %s controller (err=%d)\n", 1774 ss->name, ret); 1775 1776 if (ss->bind) 1777 ss->bind(css); 1778 } while_each_subsys_mask(); 1779 1780 kernfs_activate(dcgrp->kn); 1781 return 0; 1782 } 1783 1784 int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node, 1785 struct kernfs_root *kf_root) 1786 { 1787 int len = 0; 1788 char *buf = NULL; 1789 struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root); 1790 struct cgroup *ns_cgroup; 1791 1792 buf = kmalloc(PATH_MAX, GFP_KERNEL); 1793 if (!buf) 1794 return -ENOMEM; 1795 1796 spin_lock_irq(&css_set_lock); 1797 ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot); 1798 len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX); 1799 spin_unlock_irq(&css_set_lock); 1800 1801 if (len >= PATH_MAX) 1802 len = -ERANGE; 1803 else if (len > 0) { 1804 seq_escape(sf, buf, " \t\n\\"); 1805 len = 0; 1806 } 1807 kfree(buf); 1808 return len; 1809 } 1810 1811 enum cgroup2_param { 1812 Opt_nsdelegate, 1813 Opt_memory_localevents, 1814 Opt_memory_recursiveprot, 1815 nr__cgroup2_params 1816 }; 1817 1818 static const struct fs_parameter_spec cgroup2_fs_parameters[] = { 1819 fsparam_flag("nsdelegate", Opt_nsdelegate), 1820 fsparam_flag("memory_localevents", Opt_memory_localevents), 1821 fsparam_flag("memory_recursiveprot", Opt_memory_recursiveprot), 1822 {} 1823 }; 1824 1825 static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param) 1826 { 1827 struct cgroup_fs_context *ctx = cgroup_fc2context(fc); 1828 struct fs_parse_result result; 1829 int opt; 1830 1831 opt = fs_parse(fc, cgroup2_fs_parameters, param, &result); 1832 if (opt < 0) 1833 return opt; 1834 1835 switch (opt) { 1836 case Opt_nsdelegate: 1837 ctx->flags |= CGRP_ROOT_NS_DELEGATE; 1838 return 0; 1839 case Opt_memory_localevents: 1840 ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS; 1841 return 0; 1842 case Opt_memory_recursiveprot: 1843 ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT; 1844 return 0; 1845 } 1846 return -EINVAL; 1847 } 1848 1849 static void apply_cgroup_root_flags(unsigned int root_flags) 1850 { 1851 if (current->nsproxy->cgroup_ns == &init_cgroup_ns) { 1852 if (root_flags & CGRP_ROOT_NS_DELEGATE) 1853 cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE; 1854 else 1855 cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE; 1856 1857 if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS) 1858 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS; 1859 else 1860 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS; 1861 1862 if (root_flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT) 1863 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT; 1864 else 1865 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT; 1866 } 1867 } 1868 1869 static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root) 1870 { 1871 if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) 1872 seq_puts(seq, ",nsdelegate"); 1873 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS) 1874 seq_puts(seq, ",memory_localevents"); 1875 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT) 1876 seq_puts(seq, ",memory_recursiveprot"); 1877 return 0; 1878 } 1879 1880 static int cgroup_reconfigure(struct fs_context *fc) 1881 { 1882 struct cgroup_fs_context *ctx = cgroup_fc2context(fc); 1883 1884 apply_cgroup_root_flags(ctx->flags); 1885 return 0; 1886 } 1887 1888 static void init_cgroup_housekeeping(struct cgroup *cgrp) 1889 { 1890 struct cgroup_subsys *ss; 1891 int ssid; 1892 1893 INIT_LIST_HEAD(&cgrp->self.sibling); 1894 INIT_LIST_HEAD(&cgrp->self.children); 1895 INIT_LIST_HEAD(&cgrp->cset_links); 1896 INIT_LIST_HEAD(&cgrp->pidlists); 1897 mutex_init(&cgrp->pidlist_mutex); 1898 cgrp->self.cgroup = cgrp; 1899 cgrp->self.flags |= CSS_ONLINE; 1900 cgrp->dom_cgrp = cgrp; 1901 cgrp->max_descendants = INT_MAX; 1902 cgrp->max_depth = INT_MAX; 1903 INIT_LIST_HEAD(&cgrp->rstat_css_list); 1904 prev_cputime_init(&cgrp->prev_cputime); 1905 1906 for_each_subsys(ss, ssid) 1907 INIT_LIST_HEAD(&cgrp->e_csets[ssid]); 1908 1909 init_waitqueue_head(&cgrp->offline_waitq); 1910 INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent); 1911 } 1912 1913 void init_cgroup_root(struct cgroup_fs_context *ctx) 1914 { 1915 struct cgroup_root *root = ctx->root; 1916 struct cgroup *cgrp = &root->cgrp; 1917 1918 INIT_LIST_HEAD(&root->root_list); 1919 atomic_set(&root->nr_cgrps, 1); 1920 cgrp->root = root; 1921 init_cgroup_housekeeping(cgrp); 1922 1923 root->flags = ctx->flags; 1924 if (ctx->release_agent) 1925 strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX); 1926 if (ctx->name) 1927 strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN); 1928 if (ctx->cpuset_clone_children) 1929 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags); 1930 } 1931 1932 int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask) 1933 { 1934 LIST_HEAD(tmp_links); 1935 struct cgroup *root_cgrp = &root->cgrp; 1936 struct kernfs_syscall_ops *kf_sops; 1937 struct css_set *cset; 1938 int i, ret; 1939 1940 lockdep_assert_held(&cgroup_mutex); 1941 1942 ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release, 1943 0, GFP_KERNEL); 1944 if (ret) 1945 goto out; 1946 1947 /* 1948 * We're accessing css_set_count without locking css_set_lock here, 1949 * but that's OK - it can only be increased by someone holding 1950 * cgroup_lock, and that's us. Later rebinding may disable 1951 * controllers on the default hierarchy and thus create new csets, 1952 * which can't be more than the existing ones. Allocate 2x. 1953 */ 1954 ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links); 1955 if (ret) 1956 goto cancel_ref; 1957 1958 ret = cgroup_init_root_id(root); 1959 if (ret) 1960 goto cancel_ref; 1961 1962 kf_sops = root == &cgrp_dfl_root ? 1963 &cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops; 1964 1965 root->kf_root = kernfs_create_root(kf_sops, 1966 KERNFS_ROOT_CREATE_DEACTIVATED | 1967 KERNFS_ROOT_SUPPORT_EXPORTOP | 1968 KERNFS_ROOT_SUPPORT_USER_XATTR, 1969 root_cgrp); 1970 if (IS_ERR(root->kf_root)) { 1971 ret = PTR_ERR(root->kf_root); 1972 goto exit_root_id; 1973 } 1974 root_cgrp->kn = root->kf_root->kn; 1975 WARN_ON_ONCE(cgroup_ino(root_cgrp) != 1); 1976 root_cgrp->ancestor_ids[0] = cgroup_id(root_cgrp); 1977 1978 ret = css_populate_dir(&root_cgrp->self); 1979 if (ret) 1980 goto destroy_root; 1981 1982 ret = cgroup_rstat_init(root_cgrp); 1983 if (ret) 1984 goto destroy_root; 1985 1986 ret = rebind_subsystems(root, ss_mask); 1987 if (ret) 1988 goto exit_stats; 1989 1990 ret = cgroup_bpf_inherit(root_cgrp); 1991 WARN_ON_ONCE(ret); 1992 1993 trace_cgroup_setup_root(root); 1994 1995 /* 1996 * There must be no failure case after here, since rebinding takes 1997 * care of subsystems' refcounts, which are explicitly dropped in 1998 * the failure exit path. 1999 */ 2000 list_add(&root->root_list, &cgroup_roots); 2001 cgroup_root_count++; 2002 2003 /* 2004 * Link the root cgroup in this hierarchy into all the css_set 2005 * objects. 2006 */ 2007 spin_lock_irq(&css_set_lock); 2008 hash_for_each(css_set_table, i, cset, hlist) { 2009 link_css_set(&tmp_links, cset, root_cgrp); 2010 if (css_set_populated(cset)) 2011 cgroup_update_populated(root_cgrp, true); 2012 } 2013 spin_unlock_irq(&css_set_lock); 2014 2015 BUG_ON(!list_empty(&root_cgrp->self.children)); 2016 BUG_ON(atomic_read(&root->nr_cgrps) != 1); 2017 2018 ret = 0; 2019 goto out; 2020 2021 exit_stats: 2022 cgroup_rstat_exit(root_cgrp); 2023 destroy_root: 2024 kernfs_destroy_root(root->kf_root); 2025 root->kf_root = NULL; 2026 exit_root_id: 2027 cgroup_exit_root_id(root); 2028 cancel_ref: 2029 percpu_ref_exit(&root_cgrp->self.refcnt); 2030 out: 2031 free_cgrp_cset_links(&tmp_links); 2032 return ret; 2033 } 2034 2035 int cgroup_do_get_tree(struct fs_context *fc) 2036 { 2037 struct cgroup_fs_context *ctx = cgroup_fc2context(fc); 2038 int ret; 2039 2040 ctx->kfc.root = ctx->root->kf_root; 2041 if (fc->fs_type == &cgroup2_fs_type) 2042 ctx->kfc.magic = CGROUP2_SUPER_MAGIC; 2043 else 2044 ctx->kfc.magic = CGROUP_SUPER_MAGIC; 2045 ret = kernfs_get_tree(fc); 2046 2047 /* 2048 * In non-init cgroup namespace, instead of root cgroup's dentry, 2049 * we return the dentry corresponding to the cgroupns->root_cgrp. 2050 */ 2051 if (!ret && ctx->ns != &init_cgroup_ns) { 2052 struct dentry *nsdentry; 2053 struct super_block *sb = fc->root->d_sb; 2054 struct cgroup *cgrp; 2055 2056 mutex_lock(&cgroup_mutex); 2057 spin_lock_irq(&css_set_lock); 2058 2059 cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root); 2060 2061 spin_unlock_irq(&css_set_lock); 2062 mutex_unlock(&cgroup_mutex); 2063 2064 nsdentry = kernfs_node_dentry(cgrp->kn, sb); 2065 dput(fc->root); 2066 if (IS_ERR(nsdentry)) { 2067 deactivate_locked_super(sb); 2068 ret = PTR_ERR(nsdentry); 2069 nsdentry = NULL; 2070 } 2071 fc->root = nsdentry; 2072 } 2073 2074 if (!ctx->kfc.new_sb_created) 2075 cgroup_put(&ctx->root->cgrp); 2076 2077 return ret; 2078 } 2079 2080 /* 2081 * Destroy a cgroup filesystem context. 2082 */ 2083 static void cgroup_fs_context_free(struct fs_context *fc) 2084 { 2085 struct cgroup_fs_context *ctx = cgroup_fc2context(fc); 2086 2087 kfree(ctx->name); 2088 kfree(ctx->release_agent); 2089 put_cgroup_ns(ctx->ns); 2090 kernfs_free_fs_context(fc); 2091 kfree(ctx); 2092 } 2093 2094 static int cgroup_get_tree(struct fs_context *fc) 2095 { 2096 struct cgroup_fs_context *ctx = cgroup_fc2context(fc); 2097 int ret; 2098 2099 cgrp_dfl_visible = true; 2100 cgroup_get_live(&cgrp_dfl_root.cgrp); 2101 ctx->root = &cgrp_dfl_root; 2102 2103 ret = cgroup_do_get_tree(fc); 2104 if (!ret) 2105 apply_cgroup_root_flags(ctx->flags); 2106 return ret; 2107 } 2108 2109 static const struct fs_context_operations cgroup_fs_context_ops = { 2110 .free = cgroup_fs_context_free, 2111 .parse_param = cgroup2_parse_param, 2112 .get_tree = cgroup_get_tree, 2113 .reconfigure = cgroup_reconfigure, 2114 }; 2115 2116 static const struct fs_context_operations cgroup1_fs_context_ops = { 2117 .free = cgroup_fs_context_free, 2118 .parse_param = cgroup1_parse_param, 2119 .get_tree = cgroup1_get_tree, 2120 .reconfigure = cgroup1_reconfigure, 2121 }; 2122 2123 /* 2124 * Initialise the cgroup filesystem creation/reconfiguration context. Notably, 2125 * we select the namespace we're going to use. 2126 */ 2127 static int cgroup_init_fs_context(struct fs_context *fc) 2128 { 2129 struct cgroup_fs_context *ctx; 2130 2131 ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL); 2132 if (!ctx) 2133 return -ENOMEM; 2134 2135 ctx->ns = current->nsproxy->cgroup_ns; 2136 get_cgroup_ns(ctx->ns); 2137 fc->fs_private = &ctx->kfc; 2138 if (fc->fs_type == &cgroup2_fs_type) 2139 fc->ops = &cgroup_fs_context_ops; 2140 else 2141 fc->ops = &cgroup1_fs_context_ops; 2142 put_user_ns(fc->user_ns); 2143 fc->user_ns = get_user_ns(ctx->ns->user_ns); 2144 fc->global = true; 2145 return 0; 2146 } 2147 2148 static void cgroup_kill_sb(struct super_block *sb) 2149 { 2150 struct kernfs_root *kf_root = kernfs_root_from_sb(sb); 2151 struct cgroup_root *root = cgroup_root_from_kf(kf_root); 2152 2153 /* 2154 * If @root doesn't have any children, start killing it. 2155 * This prevents new mounts by disabling percpu_ref_tryget_live(). 2156 * cgroup_mount() may wait for @root's release. 2157 * 2158 * And don't kill the default root. 2159 */ 2160 if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root && 2161 !percpu_ref_is_dying(&root->cgrp.self.refcnt)) 2162 percpu_ref_kill(&root->cgrp.self.refcnt); 2163 cgroup_put(&root->cgrp); 2164 kernfs_kill_sb(sb); 2165 } 2166 2167 struct file_system_type cgroup_fs_type = { 2168 .name = "cgroup", 2169 .init_fs_context = cgroup_init_fs_context, 2170 .parameters = cgroup1_fs_parameters, 2171 .kill_sb = cgroup_kill_sb, 2172 .fs_flags = FS_USERNS_MOUNT, 2173 }; 2174 2175 static struct file_system_type cgroup2_fs_type = { 2176 .name = "cgroup2", 2177 .init_fs_context = cgroup_init_fs_context, 2178 .parameters = cgroup2_fs_parameters, 2179 .kill_sb = cgroup_kill_sb, 2180 .fs_flags = FS_USERNS_MOUNT, 2181 }; 2182 2183 #ifdef CONFIG_CPUSETS 2184 static const struct fs_context_operations cpuset_fs_context_ops = { 2185 .get_tree = cgroup1_get_tree, 2186 .free = cgroup_fs_context_free, 2187 }; 2188 2189 /* 2190 * This is ugly, but preserves the userspace API for existing cpuset 2191 * users. If someone tries to mount the "cpuset" filesystem, we 2192 * silently switch it to mount "cgroup" instead 2193 */ 2194 static int cpuset_init_fs_context(struct fs_context *fc) 2195 { 2196 char *agent = kstrdup("/sbin/cpuset_release_agent", GFP_USER); 2197 struct cgroup_fs_context *ctx; 2198 int err; 2199 2200 err = cgroup_init_fs_context(fc); 2201 if (err) { 2202 kfree(agent); 2203 return err; 2204 } 2205 2206 fc->ops = &cpuset_fs_context_ops; 2207 2208 ctx = cgroup_fc2context(fc); 2209 ctx->subsys_mask = 1 << cpuset_cgrp_id; 2210 ctx->flags |= CGRP_ROOT_NOPREFIX; 2211 ctx->release_agent = agent; 2212 2213 get_filesystem(&cgroup_fs_type); 2214 put_filesystem(fc->fs_type); 2215 fc->fs_type = &cgroup_fs_type; 2216 2217 return 0; 2218 } 2219 2220 static struct file_system_type cpuset_fs_type = { 2221 .name = "cpuset", 2222 .init_fs_context = cpuset_init_fs_context, 2223 .fs_flags = FS_USERNS_MOUNT, 2224 }; 2225 #endif 2226 2227 int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen, 2228 struct cgroup_namespace *ns) 2229 { 2230 struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root); 2231 2232 return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen); 2233 } 2234 2235 int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen, 2236 struct cgroup_namespace *ns) 2237 { 2238 int ret; 2239 2240 mutex_lock(&cgroup_mutex); 2241 spin_lock_irq(&css_set_lock); 2242 2243 ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns); 2244 2245 spin_unlock_irq(&css_set_lock); 2246 mutex_unlock(&cgroup_mutex); 2247 2248 return ret; 2249 } 2250 EXPORT_SYMBOL_GPL(cgroup_path_ns); 2251 2252 /** 2253 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy 2254 * @task: target task 2255 * @buf: the buffer to write the path into 2256 * @buflen: the length of the buffer 2257 * 2258 * Determine @task's cgroup on the first (the one with the lowest non-zero 2259 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This 2260 * function grabs cgroup_mutex and shouldn't be used inside locks used by 2261 * cgroup controller callbacks. 2262 * 2263 * Return value is the same as kernfs_path(). 2264 */ 2265 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen) 2266 { 2267 struct cgroup_root *root; 2268 struct cgroup *cgrp; 2269 int hierarchy_id = 1; 2270 int ret; 2271 2272 mutex_lock(&cgroup_mutex); 2273 spin_lock_irq(&css_set_lock); 2274 2275 root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id); 2276 2277 if (root) { 2278 cgrp = task_cgroup_from_root(task, root); 2279 ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns); 2280 } else { 2281 /* if no hierarchy exists, everyone is in "/" */ 2282 ret = strlcpy(buf, "/", buflen); 2283 } 2284 2285 spin_unlock_irq(&css_set_lock); 2286 mutex_unlock(&cgroup_mutex); 2287 return ret; 2288 } 2289 EXPORT_SYMBOL_GPL(task_cgroup_path); 2290 2291 /** 2292 * cgroup_migrate_add_task - add a migration target task to a migration context 2293 * @task: target task 2294 * @mgctx: target migration context 2295 * 2296 * Add @task, which is a migration target, to @mgctx->tset. This function 2297 * becomes noop if @task doesn't need to be migrated. @task's css_set 2298 * should have been added as a migration source and @task->cg_list will be 2299 * moved from the css_set's tasks list to mg_tasks one. 2300 */ 2301 static void cgroup_migrate_add_task(struct task_struct *task, 2302 struct cgroup_mgctx *mgctx) 2303 { 2304 struct css_set *cset; 2305 2306 lockdep_assert_held(&css_set_lock); 2307 2308 /* @task either already exited or can't exit until the end */ 2309 if (task->flags & PF_EXITING) 2310 return; 2311 2312 /* cgroup_threadgroup_rwsem protects racing against forks */ 2313 WARN_ON_ONCE(list_empty(&task->cg_list)); 2314 2315 cset = task_css_set(task); 2316 if (!cset->mg_src_cgrp) 2317 return; 2318 2319 mgctx->tset.nr_tasks++; 2320 2321 list_move_tail(&task->cg_list, &cset->mg_tasks); 2322 if (list_empty(&cset->mg_node)) 2323 list_add_tail(&cset->mg_node, 2324 &mgctx->tset.src_csets); 2325 if (list_empty(&cset->mg_dst_cset->mg_node)) 2326 list_add_tail(&cset->mg_dst_cset->mg_node, 2327 &mgctx->tset.dst_csets); 2328 } 2329 2330 /** 2331 * cgroup_taskset_first - reset taskset and return the first task 2332 * @tset: taskset of interest 2333 * @dst_cssp: output variable for the destination css 2334 * 2335 * @tset iteration is initialized and the first task is returned. 2336 */ 2337 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset, 2338 struct cgroup_subsys_state **dst_cssp) 2339 { 2340 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node); 2341 tset->cur_task = NULL; 2342 2343 return cgroup_taskset_next(tset, dst_cssp); 2344 } 2345 2346 /** 2347 * cgroup_taskset_next - iterate to the next task in taskset 2348 * @tset: taskset of interest 2349 * @dst_cssp: output variable for the destination css 2350 * 2351 * Return the next task in @tset. Iteration must have been initialized 2352 * with cgroup_taskset_first(). 2353 */ 2354 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset, 2355 struct cgroup_subsys_state **dst_cssp) 2356 { 2357 struct css_set *cset = tset->cur_cset; 2358 struct task_struct *task = tset->cur_task; 2359 2360 while (&cset->mg_node != tset->csets) { 2361 if (!task) 2362 task = list_first_entry(&cset->mg_tasks, 2363 struct task_struct, cg_list); 2364 else 2365 task = list_next_entry(task, cg_list); 2366 2367 if (&task->cg_list != &cset->mg_tasks) { 2368 tset->cur_cset = cset; 2369 tset->cur_task = task; 2370 2371 /* 2372 * This function may be called both before and 2373 * after cgroup_taskset_migrate(). The two cases 2374 * can be distinguished by looking at whether @cset 2375 * has its ->mg_dst_cset set. 2376 */ 2377 if (cset->mg_dst_cset) 2378 *dst_cssp = cset->mg_dst_cset->subsys[tset->ssid]; 2379 else 2380 *dst_cssp = cset->subsys[tset->ssid]; 2381 2382 return task; 2383 } 2384 2385 cset = list_next_entry(cset, mg_node); 2386 task = NULL; 2387 } 2388 2389 return NULL; 2390 } 2391 2392 /** 2393 * cgroup_taskset_migrate - migrate a taskset 2394 * @mgctx: migration context 2395 * 2396 * Migrate tasks in @mgctx as setup by migration preparation functions. 2397 * This function fails iff one of the ->can_attach callbacks fails and 2398 * guarantees that either all or none of the tasks in @mgctx are migrated. 2399 * @mgctx is consumed regardless of success. 2400 */ 2401 static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx) 2402 { 2403 struct cgroup_taskset *tset = &mgctx->tset; 2404 struct cgroup_subsys *ss; 2405 struct task_struct *task, *tmp_task; 2406 struct css_set *cset, *tmp_cset; 2407 int ssid, failed_ssid, ret; 2408 2409 /* check that we can legitimately attach to the cgroup */ 2410 if (tset->nr_tasks) { 2411 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { 2412 if (ss->can_attach) { 2413 tset->ssid = ssid; 2414 ret = ss->can_attach(tset); 2415 if (ret) { 2416 failed_ssid = ssid; 2417 goto out_cancel_attach; 2418 } 2419 } 2420 } while_each_subsys_mask(); 2421 } 2422 2423 /* 2424 * Now that we're guaranteed success, proceed to move all tasks to 2425 * the new cgroup. There are no failure cases after here, so this 2426 * is the commit point. 2427 */ 2428 spin_lock_irq(&css_set_lock); 2429 list_for_each_entry(cset, &tset->src_csets, mg_node) { 2430 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) { 2431 struct css_set *from_cset = task_css_set(task); 2432 struct css_set *to_cset = cset->mg_dst_cset; 2433 2434 get_css_set(to_cset); 2435 to_cset->nr_tasks++; 2436 css_set_move_task(task, from_cset, to_cset, true); 2437 from_cset->nr_tasks--; 2438 /* 2439 * If the source or destination cgroup is frozen, 2440 * the task might require to change its state. 2441 */ 2442 cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp, 2443 to_cset->dfl_cgrp); 2444 put_css_set_locked(from_cset); 2445 2446 } 2447 } 2448 spin_unlock_irq(&css_set_lock); 2449 2450 /* 2451 * Migration is committed, all target tasks are now on dst_csets. 2452 * Nothing is sensitive to fork() after this point. Notify 2453 * controllers that migration is complete. 2454 */ 2455 tset->csets = &tset->dst_csets; 2456 2457 if (tset->nr_tasks) { 2458 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { 2459 if (ss->attach) { 2460 tset->ssid = ssid; 2461 ss->attach(tset); 2462 } 2463 } while_each_subsys_mask(); 2464 } 2465 2466 ret = 0; 2467 goto out_release_tset; 2468 2469 out_cancel_attach: 2470 if (tset->nr_tasks) { 2471 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { 2472 if (ssid == failed_ssid) 2473 break; 2474 if (ss->cancel_attach) { 2475 tset->ssid = ssid; 2476 ss->cancel_attach(tset); 2477 } 2478 } while_each_subsys_mask(); 2479 } 2480 out_release_tset: 2481 spin_lock_irq(&css_set_lock); 2482 list_splice_init(&tset->dst_csets, &tset->src_csets); 2483 list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) { 2484 list_splice_tail_init(&cset->mg_tasks, &cset->tasks); 2485 list_del_init(&cset->mg_node); 2486 } 2487 spin_unlock_irq(&css_set_lock); 2488 2489 /* 2490 * Re-initialize the cgroup_taskset structure in case it is reused 2491 * again in another cgroup_migrate_add_task()/cgroup_migrate_execute() 2492 * iteration. 2493 */ 2494 tset->nr_tasks = 0; 2495 tset->csets = &tset->src_csets; 2496 return ret; 2497 } 2498 2499 /** 2500 * cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination 2501 * @dst_cgrp: destination cgroup to test 2502 * 2503 * On the default hierarchy, except for the mixable, (possible) thread root 2504 * and threaded cgroups, subtree_control must be zero for migration 2505 * destination cgroups with tasks so that child cgroups don't compete 2506 * against tasks. 2507 */ 2508 int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp) 2509 { 2510 /* v1 doesn't have any restriction */ 2511 if (!cgroup_on_dfl(dst_cgrp)) 2512 return 0; 2513 2514 /* verify @dst_cgrp can host resources */ 2515 if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp)) 2516 return -EOPNOTSUPP; 2517 2518 /* mixables don't care */ 2519 if (cgroup_is_mixable(dst_cgrp)) 2520 return 0; 2521 2522 /* 2523 * If @dst_cgrp is already or can become a thread root or is 2524 * threaded, it doesn't matter. 2525 */ 2526 if (cgroup_can_be_thread_root(dst_cgrp) || cgroup_is_threaded(dst_cgrp)) 2527 return 0; 2528 2529 /* apply no-internal-process constraint */ 2530 if (dst_cgrp->subtree_control) 2531 return -EBUSY; 2532 2533 return 0; 2534 } 2535 2536 /** 2537 * cgroup_migrate_finish - cleanup after attach 2538 * @mgctx: migration context 2539 * 2540 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See 2541 * those functions for details. 2542 */ 2543 void cgroup_migrate_finish(struct cgroup_mgctx *mgctx) 2544 { 2545 LIST_HEAD(preloaded); 2546 struct css_set *cset, *tmp_cset; 2547 2548 lockdep_assert_held(&cgroup_mutex); 2549 2550 spin_lock_irq(&css_set_lock); 2551 2552 list_splice_tail_init(&mgctx->preloaded_src_csets, &preloaded); 2553 list_splice_tail_init(&mgctx->preloaded_dst_csets, &preloaded); 2554 2555 list_for_each_entry_safe(cset, tmp_cset, &preloaded, mg_preload_node) { 2556 cset->mg_src_cgrp = NULL; 2557 cset->mg_dst_cgrp = NULL; 2558 cset->mg_dst_cset = NULL; 2559 list_del_init(&cset->mg_preload_node); 2560 put_css_set_locked(cset); 2561 } 2562 2563 spin_unlock_irq(&css_set_lock); 2564 } 2565 2566 /** 2567 * cgroup_migrate_add_src - add a migration source css_set 2568 * @src_cset: the source css_set to add 2569 * @dst_cgrp: the destination cgroup 2570 * @mgctx: migration context 2571 * 2572 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin 2573 * @src_cset and add it to @mgctx->src_csets, which should later be cleaned 2574 * up by cgroup_migrate_finish(). 2575 * 2576 * This function may be called without holding cgroup_threadgroup_rwsem 2577 * even if the target is a process. Threads may be created and destroyed 2578 * but as long as cgroup_mutex is not dropped, no new css_set can be put 2579 * into play and the preloaded css_sets are guaranteed to cover all 2580 * migrations. 2581 */ 2582 void cgroup_migrate_add_src(struct css_set *src_cset, 2583 struct cgroup *dst_cgrp, 2584 struct cgroup_mgctx *mgctx) 2585 { 2586 struct cgroup *src_cgrp; 2587 2588 lockdep_assert_held(&cgroup_mutex); 2589 lockdep_assert_held(&css_set_lock); 2590 2591 /* 2592 * If ->dead, @src_set is associated with one or more dead cgroups 2593 * and doesn't contain any migratable tasks. Ignore it early so 2594 * that the rest of migration path doesn't get confused by it. 2595 */ 2596 if (src_cset->dead) 2597 return; 2598 2599 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root); 2600 2601 if (!list_empty(&src_cset->mg_preload_node)) 2602 return; 2603 2604 WARN_ON(src_cset->mg_src_cgrp); 2605 WARN_ON(src_cset->mg_dst_cgrp); 2606 WARN_ON(!list_empty(&src_cset->mg_tasks)); 2607 WARN_ON(!list_empty(&src_cset->mg_node)); 2608 2609 src_cset->mg_src_cgrp = src_cgrp; 2610 src_cset->mg_dst_cgrp = dst_cgrp; 2611 get_css_set(src_cset); 2612 list_add_tail(&src_cset->mg_preload_node, &mgctx->preloaded_src_csets); 2613 } 2614 2615 /** 2616 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration 2617 * @mgctx: migration context 2618 * 2619 * Tasks are about to be moved and all the source css_sets have been 2620 * preloaded to @mgctx->preloaded_src_csets. This function looks up and 2621 * pins all destination css_sets, links each to its source, and append them 2622 * to @mgctx->preloaded_dst_csets. 2623 * 2624 * This function must be called after cgroup_migrate_add_src() has been 2625 * called on each migration source css_set. After migration is performed 2626 * using cgroup_migrate(), cgroup_migrate_finish() must be called on 2627 * @mgctx. 2628 */ 2629 int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx) 2630 { 2631 struct css_set *src_cset, *tmp_cset; 2632 2633 lockdep_assert_held(&cgroup_mutex); 2634 2635 /* look up the dst cset for each src cset and link it to src */ 2636 list_for_each_entry_safe(src_cset, tmp_cset, &mgctx->preloaded_src_csets, 2637 mg_preload_node) { 2638 struct css_set *dst_cset; 2639 struct cgroup_subsys *ss; 2640 int ssid; 2641 2642 dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp); 2643 if (!dst_cset) 2644 return -ENOMEM; 2645 2646 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset); 2647 2648 /* 2649 * If src cset equals dst, it's noop. Drop the src. 2650 * cgroup_migrate() will skip the cset too. Note that we 2651 * can't handle src == dst as some nodes are used by both. 2652 */ 2653 if (src_cset == dst_cset) { 2654 src_cset->mg_src_cgrp = NULL; 2655 src_cset->mg_dst_cgrp = NULL; 2656 list_del_init(&src_cset->mg_preload_node); 2657 put_css_set(src_cset); 2658 put_css_set(dst_cset); 2659 continue; 2660 } 2661 2662 src_cset->mg_dst_cset = dst_cset; 2663 2664 if (list_empty(&dst_cset->mg_preload_node)) 2665 list_add_tail(&dst_cset->mg_preload_node, 2666 &mgctx->preloaded_dst_csets); 2667 else 2668 put_css_set(dst_cset); 2669 2670 for_each_subsys(ss, ssid) 2671 if (src_cset->subsys[ssid] != dst_cset->subsys[ssid]) 2672 mgctx->ss_mask |= 1 << ssid; 2673 } 2674 2675 return 0; 2676 } 2677 2678 /** 2679 * cgroup_migrate - migrate a process or task to a cgroup 2680 * @leader: the leader of the process or the task to migrate 2681 * @threadgroup: whether @leader points to the whole process or a single task 2682 * @mgctx: migration context 2683 * 2684 * Migrate a process or task denoted by @leader. If migrating a process, 2685 * the caller must be holding cgroup_threadgroup_rwsem. The caller is also 2686 * responsible for invoking cgroup_migrate_add_src() and 2687 * cgroup_migrate_prepare_dst() on the targets before invoking this 2688 * function and following up with cgroup_migrate_finish(). 2689 * 2690 * As long as a controller's ->can_attach() doesn't fail, this function is 2691 * guaranteed to succeed. This means that, excluding ->can_attach() 2692 * failure, when migrating multiple targets, the success or failure can be 2693 * decided for all targets by invoking group_migrate_prepare_dst() before 2694 * actually starting migrating. 2695 */ 2696 int cgroup_migrate(struct task_struct *leader, bool threadgroup, 2697 struct cgroup_mgctx *mgctx) 2698 { 2699 struct task_struct *task; 2700 2701 /* 2702 * Prevent freeing of tasks while we take a snapshot. Tasks that are 2703 * already PF_EXITING could be freed from underneath us unless we 2704 * take an rcu_read_lock. 2705 */ 2706 spin_lock_irq(&css_set_lock); 2707 rcu_read_lock(); 2708 task = leader; 2709 do { 2710 cgroup_migrate_add_task(task, mgctx); 2711 if (!threadgroup) 2712 break; 2713 } while_each_thread(leader, task); 2714 rcu_read_unlock(); 2715 spin_unlock_irq(&css_set_lock); 2716 2717 return cgroup_migrate_execute(mgctx); 2718 } 2719 2720 /** 2721 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup 2722 * @dst_cgrp: the cgroup to attach to 2723 * @leader: the task or the leader of the threadgroup to be attached 2724 * @threadgroup: attach the whole threadgroup? 2725 * 2726 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem. 2727 */ 2728 int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader, 2729 bool threadgroup) 2730 { 2731 DEFINE_CGROUP_MGCTX(mgctx); 2732 struct task_struct *task; 2733 int ret = 0; 2734 2735 /* look up all src csets */ 2736 spin_lock_irq(&css_set_lock); 2737 rcu_read_lock(); 2738 task = leader; 2739 do { 2740 cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx); 2741 if (!threadgroup) 2742 break; 2743 } while_each_thread(leader, task); 2744 rcu_read_unlock(); 2745 spin_unlock_irq(&css_set_lock); 2746 2747 /* prepare dst csets and commit */ 2748 ret = cgroup_migrate_prepare_dst(&mgctx); 2749 if (!ret) 2750 ret = cgroup_migrate(leader, threadgroup, &mgctx); 2751 2752 cgroup_migrate_finish(&mgctx); 2753 2754 if (!ret) 2755 TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup); 2756 2757 return ret; 2758 } 2759 2760 struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup, 2761 bool *locked) 2762 __acquires(&cgroup_threadgroup_rwsem) 2763 { 2764 struct task_struct *tsk; 2765 pid_t pid; 2766 2767 if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0) 2768 return ERR_PTR(-EINVAL); 2769 2770 /* 2771 * If we migrate a single thread, we don't care about threadgroup 2772 * stability. If the thread is `current`, it won't exit(2) under our 2773 * hands or change PID through exec(2). We exclude 2774 * cgroup_update_dfl_csses and other cgroup_{proc,thread}s_write 2775 * callers by cgroup_mutex. 2776 * Therefore, we can skip the global lock. 2777 */ 2778 lockdep_assert_held(&cgroup_mutex); 2779 if (pid || threadgroup) { 2780 percpu_down_write(&cgroup_threadgroup_rwsem); 2781 *locked = true; 2782 } else { 2783 *locked = false; 2784 } 2785 2786 rcu_read_lock(); 2787 if (pid) { 2788 tsk = find_task_by_vpid(pid); 2789 if (!tsk) { 2790 tsk = ERR_PTR(-ESRCH); 2791 goto out_unlock_threadgroup; 2792 } 2793 } else { 2794 tsk = current; 2795 } 2796 2797 if (threadgroup) 2798 tsk = tsk->group_leader; 2799 2800 /* 2801 * kthreads may acquire PF_NO_SETAFFINITY during initialization. 2802 * If userland migrates such a kthread to a non-root cgroup, it can 2803 * become trapped in a cpuset, or RT kthread may be born in a 2804 * cgroup with no rt_runtime allocated. Just say no. 2805 */ 2806 if (tsk->no_cgroup_migration || (tsk->flags & PF_NO_SETAFFINITY)) { 2807 tsk = ERR_PTR(-EINVAL); 2808 goto out_unlock_threadgroup; 2809 } 2810 2811 get_task_struct(tsk); 2812 goto out_unlock_rcu; 2813 2814 out_unlock_threadgroup: 2815 if (*locked) { 2816 percpu_up_write(&cgroup_threadgroup_rwsem); 2817 *locked = false; 2818 } 2819 out_unlock_rcu: 2820 rcu_read_unlock(); 2821 return tsk; 2822 } 2823 2824 void cgroup_procs_write_finish(struct task_struct *task, bool locked) 2825 __releases(&cgroup_threadgroup_rwsem) 2826 { 2827 struct cgroup_subsys *ss; 2828 int ssid; 2829 2830 /* release reference from cgroup_procs_write_start() */ 2831 put_task_struct(task); 2832 2833 if (locked) 2834 percpu_up_write(&cgroup_threadgroup_rwsem); 2835 for_each_subsys(ss, ssid) 2836 if (ss->post_attach) 2837 ss->post_attach(); 2838 } 2839 2840 static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask) 2841 { 2842 struct cgroup_subsys *ss; 2843 bool printed = false; 2844 int ssid; 2845 2846 do_each_subsys_mask(ss, ssid, ss_mask) { 2847 if (printed) 2848 seq_putc(seq, ' '); 2849 seq_puts(seq, ss->name); 2850 printed = true; 2851 } while_each_subsys_mask(); 2852 if (printed) 2853 seq_putc(seq, '\n'); 2854 } 2855 2856 /* show controllers which are enabled from the parent */ 2857 static int cgroup_controllers_show(struct seq_file *seq, void *v) 2858 { 2859 struct cgroup *cgrp = seq_css(seq)->cgroup; 2860 2861 cgroup_print_ss_mask(seq, cgroup_control(cgrp)); 2862 return 0; 2863 } 2864 2865 /* show controllers which are enabled for a given cgroup's children */ 2866 static int cgroup_subtree_control_show(struct seq_file *seq, void *v) 2867 { 2868 struct cgroup *cgrp = seq_css(seq)->cgroup; 2869 2870 cgroup_print_ss_mask(seq, cgrp->subtree_control); 2871 return 0; 2872 } 2873 2874 /** 2875 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy 2876 * @cgrp: root of the subtree to update csses for 2877 * 2878 * @cgrp's control masks have changed and its subtree's css associations 2879 * need to be updated accordingly. This function looks up all css_sets 2880 * which are attached to the subtree, creates the matching updated css_sets 2881 * and migrates the tasks to the new ones. 2882 */ 2883 static int cgroup_update_dfl_csses(struct cgroup *cgrp) 2884 { 2885 DEFINE_CGROUP_MGCTX(mgctx); 2886 struct cgroup_subsys_state *d_css; 2887 struct cgroup *dsct; 2888 struct css_set *src_cset; 2889 int ret; 2890 2891 lockdep_assert_held(&cgroup_mutex); 2892 2893 percpu_down_write(&cgroup_threadgroup_rwsem); 2894 2895 /* look up all csses currently attached to @cgrp's subtree */ 2896 spin_lock_irq(&css_set_lock); 2897 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) { 2898 struct cgrp_cset_link *link; 2899 2900 list_for_each_entry(link, &dsct->cset_links, cset_link) 2901 cgroup_migrate_add_src(link->cset, dsct, &mgctx); 2902 } 2903 spin_unlock_irq(&css_set_lock); 2904 2905 /* NULL dst indicates self on default hierarchy */ 2906 ret = cgroup_migrate_prepare_dst(&mgctx); 2907 if (ret) 2908 goto out_finish; 2909 2910 spin_lock_irq(&css_set_lock); 2911 list_for_each_entry(src_cset, &mgctx.preloaded_src_csets, mg_preload_node) { 2912 struct task_struct *task, *ntask; 2913 2914 /* all tasks in src_csets need to be migrated */ 2915 list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list) 2916 cgroup_migrate_add_task(task, &mgctx); 2917 } 2918 spin_unlock_irq(&css_set_lock); 2919 2920 ret = cgroup_migrate_execute(&mgctx); 2921 out_finish: 2922 cgroup_migrate_finish(&mgctx); 2923 percpu_up_write(&cgroup_threadgroup_rwsem); 2924 return ret; 2925 } 2926 2927 /** 2928 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses 2929 * @cgrp: root of the target subtree 2930 * 2931 * Because css offlining is asynchronous, userland may try to re-enable a 2932 * controller while the previous css is still around. This function grabs 2933 * cgroup_mutex and drains the previous css instances of @cgrp's subtree. 2934 */ 2935 void cgroup_lock_and_drain_offline(struct cgroup *cgrp) 2936 __acquires(&cgroup_mutex) 2937 { 2938 struct cgroup *dsct; 2939 struct cgroup_subsys_state *d_css; 2940 struct cgroup_subsys *ss; 2941 int ssid; 2942 2943 restart: 2944 mutex_lock(&cgroup_mutex); 2945 2946 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) { 2947 for_each_subsys(ss, ssid) { 2948 struct cgroup_subsys_state *css = cgroup_css(dsct, ss); 2949 DEFINE_WAIT(wait); 2950 2951 if (!css || !percpu_ref_is_dying(&css->refcnt)) 2952 continue; 2953 2954 cgroup_get_live(dsct); 2955 prepare_to_wait(&dsct->offline_waitq, &wait, 2956 TASK_UNINTERRUPTIBLE); 2957 2958 mutex_unlock(&cgroup_mutex); 2959 schedule(); 2960 finish_wait(&dsct->offline_waitq, &wait); 2961 2962 cgroup_put(dsct); 2963 goto restart; 2964 } 2965 } 2966 } 2967 2968 /** 2969 * cgroup_save_control - save control masks and dom_cgrp of a subtree 2970 * @cgrp: root of the target subtree 2971 * 2972 * Save ->subtree_control, ->subtree_ss_mask and ->dom_cgrp to the 2973 * respective old_ prefixed fields for @cgrp's subtree including @cgrp 2974 * itself. 2975 */ 2976 static void cgroup_save_control(struct cgroup *cgrp) 2977 { 2978 struct cgroup *dsct; 2979 struct cgroup_subsys_state *d_css; 2980 2981 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) { 2982 dsct->old_subtree_control = dsct->subtree_control; 2983 dsct->old_subtree_ss_mask = dsct->subtree_ss_mask; 2984 dsct->old_dom_cgrp = dsct->dom_cgrp; 2985 } 2986 } 2987 2988 /** 2989 * cgroup_propagate_control - refresh control masks of a subtree 2990 * @cgrp: root of the target subtree 2991 * 2992 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches 2993 * ->subtree_control and propagate controller availability through the 2994 * subtree so that descendants don't have unavailable controllers enabled. 2995 */ 2996 static void cgroup_propagate_control(struct cgroup *cgrp) 2997 { 2998 struct cgroup *dsct; 2999 struct cgroup_subsys_state *d_css; 3000 3001 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) { 3002 dsct->subtree_control &= cgroup_control(dsct); 3003 dsct->subtree_ss_mask = 3004 cgroup_calc_subtree_ss_mask(dsct->subtree_control, 3005 cgroup_ss_mask(dsct)); 3006 } 3007 } 3008 3009 /** 3010 * cgroup_restore_control - restore control masks and dom_cgrp of a subtree 3011 * @cgrp: root of the target subtree 3012 * 3013 * Restore ->subtree_control, ->subtree_ss_mask and ->dom_cgrp from the 3014 * respective old_ prefixed fields for @cgrp's subtree including @cgrp 3015 * itself. 3016 */ 3017 static void cgroup_restore_control(struct cgroup *cgrp) 3018 { 3019 struct cgroup *dsct; 3020 struct cgroup_subsys_state *d_css; 3021 3022 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) { 3023 dsct->subtree_control = dsct->old_subtree_control; 3024 dsct->subtree_ss_mask = dsct->old_subtree_ss_mask; 3025 dsct->dom_cgrp = dsct->old_dom_cgrp; 3026 } 3027 } 3028 3029 static bool css_visible(struct cgroup_subsys_state *css) 3030 { 3031 struct cgroup_subsys *ss = css->ss; 3032 struct cgroup *cgrp = css->cgroup; 3033 3034 if (cgroup_control(cgrp) & (1 << ss->id)) 3035 return true; 3036 if (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) 3037 return false; 3038 return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl; 3039 } 3040 3041 /** 3042 * cgroup_apply_control_enable - enable or show csses according to control 3043 * @cgrp: root of the target subtree 3044 * 3045 * Walk @cgrp's subtree and create new csses or make the existing ones 3046 * visible. A css is created invisible if it's being implicitly enabled 3047 * through dependency. An invisible css is made visible when the userland 3048 * explicitly enables it. 3049 * 3050 * Returns 0 on success, -errno on failure. On failure, csses which have 3051 * been processed already aren't cleaned up. The caller is responsible for 3052 * cleaning up with cgroup_apply_control_disable(). 3053 */ 3054 static int cgroup_apply_control_enable(struct cgroup *cgrp) 3055 { 3056 struct cgroup *dsct; 3057 struct cgroup_subsys_state *d_css; 3058 struct cgroup_subsys *ss; 3059 int ssid, ret; 3060 3061 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) { 3062 for_each_subsys(ss, ssid) { 3063 struct cgroup_subsys_state *css = cgroup_css(dsct, ss); 3064 3065 if (!(cgroup_ss_mask(dsct) & (1 << ss->id))) 3066 continue; 3067 3068 if (!css) { 3069 css = css_create(dsct, ss); 3070 if (IS_ERR(css)) 3071 return PTR_ERR(css); 3072 } 3073 3074 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt)); 3075 3076 if (css_visible(css)) { 3077 ret = css_populate_dir(css); 3078 if (ret) 3079 return ret; 3080 } 3081 } 3082 } 3083 3084 return 0; 3085 } 3086 3087 /** 3088 * cgroup_apply_control_disable - kill or hide csses according to control 3089 * @cgrp: root of the target subtree 3090 * 3091 * Walk @cgrp's subtree and kill and hide csses so that they match 3092 * cgroup_ss_mask() and cgroup_visible_mask(). 3093 * 3094 * A css is hidden when the userland requests it to be disabled while other 3095 * subsystems are still depending on it. The css must not actively control 3096 * resources and be in the vanilla state if it's made visible again later. 3097 * Controllers which may be depended upon should provide ->css_reset() for 3098 * this purpose. 3099 */ 3100 static void cgroup_apply_control_disable(struct cgroup *cgrp) 3101 { 3102 struct cgroup *dsct; 3103 struct cgroup_subsys_state *d_css; 3104 struct cgroup_subsys *ss; 3105 int ssid; 3106 3107 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) { 3108 for_each_subsys(ss, ssid) { 3109 struct cgroup_subsys_state *css = cgroup_css(dsct, ss); 3110 3111 if (!css) 3112 continue; 3113 3114 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt)); 3115 3116 if (css->parent && 3117 !(cgroup_ss_mask(dsct) & (1 << ss->id))) { 3118 kill_css(css); 3119 } else if (!css_visible(css)) { 3120 css_clear_dir(css); 3121 if (ss->css_reset) 3122 ss->css_reset(css); 3123 } 3124 } 3125 } 3126 } 3127 3128 /** 3129 * cgroup_apply_control - apply control mask updates to the subtree 3130 * @cgrp: root of the target subtree 3131 * 3132 * subsystems can be enabled and disabled in a subtree using the following 3133 * steps. 3134 * 3135 * 1. Call cgroup_save_control() to stash the current state. 3136 * 2. Update ->subtree_control masks in the subtree as desired. 3137 * 3. Call cgroup_apply_control() to apply the changes. 3138 * 4. Optionally perform other related operations. 3139 * 5. Call cgroup_finalize_control() to finish up. 3140 * 3141 * This function implements step 3 and propagates the mask changes 3142 * throughout @cgrp's subtree, updates csses accordingly and perform 3143 * process migrations. 3144 */ 3145 static int cgroup_apply_control(struct cgroup *cgrp) 3146 { 3147 int ret; 3148 3149 cgroup_propagate_control(cgrp); 3150 3151 ret = cgroup_apply_control_enable(cgrp); 3152 if (ret) 3153 return ret; 3154 3155 /* 3156 * At this point, cgroup_e_css_by_mask() results reflect the new csses 3157 * making the following cgroup_update_dfl_csses() properly update 3158 * css associations of all tasks in the subtree. 3159 */ 3160 ret = cgroup_update_dfl_csses(cgrp); 3161 if (ret) 3162 return ret; 3163 3164 return 0; 3165 } 3166 3167 /** 3168 * cgroup_finalize_control - finalize control mask update 3169 * @cgrp: root of the target subtree 3170 * @ret: the result of the update 3171 * 3172 * Finalize control mask update. See cgroup_apply_control() for more info. 3173 */ 3174 static void cgroup_finalize_control(struct cgroup *cgrp, int ret) 3175 { 3176 if (ret) { 3177 cgroup_restore_control(cgrp); 3178 cgroup_propagate_control(cgrp); 3179 } 3180 3181 cgroup_apply_control_disable(cgrp); 3182 } 3183 3184 static int cgroup_vet_subtree_control_enable(struct cgroup *cgrp, u16 enable) 3185 { 3186 u16 domain_enable = enable & ~cgrp_dfl_threaded_ss_mask; 3187 3188 /* if nothing is getting enabled, nothing to worry about */ 3189 if (!enable) 3190 return 0; 3191 3192 /* can @cgrp host any resources? */ 3193 if (!cgroup_is_valid_domain(cgrp->dom_cgrp)) 3194 return -EOPNOTSUPP; 3195 3196 /* mixables don't care */ 3197 if (cgroup_is_mixable(cgrp)) 3198 return 0; 3199 3200 if (domain_enable) { 3201 /* can't enable domain controllers inside a thread subtree */ 3202 if (cgroup_is_thread_root(cgrp) || cgroup_is_threaded(cgrp)) 3203 return -EOPNOTSUPP; 3204 } else { 3205 /* 3206 * Threaded controllers can handle internal competitions 3207 * and are always allowed inside a (prospective) thread 3208 * subtree. 3209 */ 3210 if (cgroup_can_be_thread_root(cgrp) || cgroup_is_threaded(cgrp)) 3211 return 0; 3212 } 3213 3214 /* 3215 * Controllers can't be enabled for a cgroup with tasks to avoid 3216 * child cgroups competing against tasks. 3217 */ 3218 if (cgroup_has_tasks(cgrp)) 3219 return -EBUSY; 3220 3221 return 0; 3222 } 3223 3224 /* change the enabled child controllers for a cgroup in the default hierarchy */ 3225 static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 3226 char *buf, size_t nbytes, 3227 loff_t off) 3228 { 3229 u16 enable = 0, disable = 0; 3230 struct cgroup *cgrp, *child; 3231 struct cgroup_subsys *ss; 3232 char *tok; 3233 int ssid, ret; 3234 3235 /* 3236 * Parse input - space separated list of subsystem names prefixed 3237 * with either + or -. 3238 */ 3239 buf = strstrip(buf); 3240 while ((tok = strsep(&buf, " "))) { 3241 if (tok[0] == '\0') 3242 continue; 3243 do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) { 3244 if (!cgroup_ssid_enabled(ssid) || 3245 strcmp(tok + 1, ss->name)) 3246 continue; 3247 3248 if (*tok == '+') { 3249 enable |= 1 << ssid; 3250 disable &= ~(1 << ssid); 3251 } else if (*tok == '-') { 3252 disable |= 1 << ssid; 3253 enable &= ~(1 << ssid); 3254 } else { 3255 return -EINVAL; 3256 } 3257 break; 3258 } while_each_subsys_mask(); 3259 if (ssid == CGROUP_SUBSYS_COUNT) 3260 return -EINVAL; 3261 } 3262 3263 cgrp = cgroup_kn_lock_live(of->kn, true); 3264 if (!cgrp) 3265 return -ENODEV; 3266 3267 for_each_subsys(ss, ssid) { 3268 if (enable & (1 << ssid)) { 3269 if (cgrp->subtree_control & (1 << ssid)) { 3270 enable &= ~(1 << ssid); 3271 continue; 3272 } 3273 3274 if (!(cgroup_control(cgrp) & (1 << ssid))) { 3275 ret = -ENOENT; 3276 goto out_unlock; 3277 } 3278 } else if (disable & (1 << ssid)) { 3279 if (!(cgrp->subtree_control & (1 << ssid))) { 3280 disable &= ~(1 << ssid); 3281 continue; 3282 } 3283 3284 /* a child has it enabled? */ 3285 cgroup_for_each_live_child(child, cgrp) { 3286 if (child->subtree_control & (1 << ssid)) { 3287 ret = -EBUSY; 3288 goto out_unlock; 3289 } 3290 } 3291 } 3292 } 3293 3294 if (!enable && !disable) { 3295 ret = 0; 3296 goto out_unlock; 3297 } 3298 3299 ret = cgroup_vet_subtree_control_enable(cgrp, enable); 3300 if (ret) 3301 goto out_unlock; 3302 3303 /* save and update control masks and prepare csses */ 3304 cgroup_save_control(cgrp); 3305 3306 cgrp->subtree_control |= enable; 3307 cgrp->subtree_control &= ~disable; 3308 3309 ret = cgroup_apply_control(cgrp); 3310 cgroup_finalize_control(cgrp, ret); 3311 if (ret) 3312 goto out_unlock; 3313 3314 kernfs_activate(cgrp->kn); 3315 out_unlock: 3316 cgroup_kn_unlock(of->kn); 3317 return ret ?: nbytes; 3318 } 3319 3320 /** 3321 * cgroup_enable_threaded - make @cgrp threaded 3322 * @cgrp: the target cgroup 3323 * 3324 * Called when "threaded" is written to the cgroup.type interface file and 3325 * tries to make @cgrp threaded and join the parent's resource domain. 3326 * This function is never called on the root cgroup as cgroup.type doesn't 3327 * exist on it. 3328 */ 3329 static int cgroup_enable_threaded(struct cgroup *cgrp) 3330 { 3331 struct cgroup *parent = cgroup_parent(cgrp); 3332 struct cgroup *dom_cgrp = parent->dom_cgrp; 3333 struct cgroup *dsct; 3334 struct cgroup_subsys_state *d_css; 3335 int ret; 3336 3337 lockdep_assert_held(&cgroup_mutex); 3338 3339 /* noop if already threaded */ 3340 if (cgroup_is_threaded(cgrp)) 3341 return 0; 3342 3343 /* 3344 * If @cgroup is populated or has domain controllers enabled, it 3345 * can't be switched. While the below cgroup_can_be_thread_root() 3346 * test can catch the same conditions, that's only when @parent is 3347 * not mixable, so let's check it explicitly. 3348 */ 3349 if (cgroup_is_populated(cgrp) || 3350 cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask) 3351 return -EOPNOTSUPP; 3352 3353 /* we're joining the parent's domain, ensure its validity */ 3354 if (!cgroup_is_valid_domain(dom_cgrp) || 3355 !cgroup_can_be_thread_root(dom_cgrp)) 3356 return -EOPNOTSUPP; 3357 3358 /* 3359 * The following shouldn't cause actual migrations and should 3360 * always succeed. 3361 */ 3362 cgroup_save_control(cgrp); 3363 3364 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) 3365 if (dsct == cgrp || cgroup_is_threaded(dsct)) 3366 dsct->dom_cgrp = dom_cgrp; 3367 3368 ret = cgroup_apply_control(cgrp); 3369 if (!ret) 3370 parent->nr_threaded_children++; 3371 3372 cgroup_finalize_control(cgrp, ret); 3373 return ret; 3374 } 3375 3376 static int cgroup_type_show(struct seq_file *seq, void *v) 3377 { 3378 struct cgroup *cgrp = seq_css(seq)->cgroup; 3379 3380 if (cgroup_is_threaded(cgrp)) 3381 seq_puts(seq, "threaded\n"); 3382 else if (!cgroup_is_valid_domain(cgrp)) 3383 seq_puts(seq, "domain invalid\n"); 3384 else if (cgroup_is_thread_root(cgrp)) 3385 seq_puts(seq, "domain threaded\n"); 3386 else 3387 seq_puts(seq, "domain\n"); 3388 3389 return 0; 3390 } 3391 3392 static ssize_t cgroup_type_write(struct kernfs_open_file *of, char *buf, 3393 size_t nbytes, loff_t off) 3394 { 3395 struct cgroup *cgrp; 3396 int ret; 3397 3398 /* only switching to threaded mode is supported */ 3399 if (strcmp(strstrip(buf), "threaded")) 3400 return -EINVAL; 3401 3402 /* drain dying csses before we re-apply (threaded) subtree control */ 3403 cgrp = cgroup_kn_lock_live(of->kn, true); 3404 if (!cgrp) 3405 return -ENOENT; 3406 3407 /* threaded can only be enabled */ 3408 ret = cgroup_enable_threaded(cgrp); 3409 3410 cgroup_kn_unlock(of->kn); 3411 return ret ?: nbytes; 3412 } 3413 3414 static int cgroup_max_descendants_show(struct seq_file *seq, void *v) 3415 { 3416 struct cgroup *cgrp = seq_css(seq)->cgroup; 3417 int descendants = READ_ONCE(cgrp->max_descendants); 3418 3419 if (descendants == INT_MAX) 3420 seq_puts(seq, "max\n"); 3421 else 3422 seq_printf(seq, "%d\n", descendants); 3423 3424 return 0; 3425 } 3426 3427 static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of, 3428 char *buf, size_t nbytes, loff_t off) 3429 { 3430 struct cgroup *cgrp; 3431 int descendants; 3432 ssize_t ret; 3433 3434 buf = strstrip(buf); 3435 if (!strcmp(buf, "max")) { 3436 descendants = INT_MAX; 3437 } else { 3438 ret = kstrtoint(buf, 0, &descendants); 3439 if (ret) 3440 return ret; 3441 } 3442 3443 if (descendants < 0) 3444 return -ERANGE; 3445 3446 cgrp = cgroup_kn_lock_live(of->kn, false); 3447 if (!cgrp) 3448 return -ENOENT; 3449 3450 cgrp->max_descendants = descendants; 3451 3452 cgroup_kn_unlock(of->kn); 3453 3454 return nbytes; 3455 } 3456 3457 static int cgroup_max_depth_show(struct seq_file *seq, void *v) 3458 { 3459 struct cgroup *cgrp = seq_css(seq)->cgroup; 3460 int depth = READ_ONCE(cgrp->max_depth); 3461 3462 if (depth == INT_MAX) 3463 seq_puts(seq, "max\n"); 3464 else 3465 seq_printf(seq, "%d\n", depth); 3466 3467 return 0; 3468 } 3469 3470 static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of, 3471 char *buf, size_t nbytes, loff_t off) 3472 { 3473 struct cgroup *cgrp; 3474 ssize_t ret; 3475 int depth; 3476 3477 buf = strstrip(buf); 3478 if (!strcmp(buf, "max")) { 3479 depth = INT_MAX; 3480 } else { 3481 ret = kstrtoint(buf, 0, &depth); 3482 if (ret) 3483 return ret; 3484 } 3485 3486 if (depth < 0) 3487 return -ERANGE; 3488 3489 cgrp = cgroup_kn_lock_live(of->kn, false); 3490 if (!cgrp) 3491 return -ENOENT; 3492 3493 cgrp->max_depth = depth; 3494 3495 cgroup_kn_unlock(of->kn); 3496 3497 return nbytes; 3498 } 3499 3500 static int cgroup_events_show(struct seq_file *seq, void *v) 3501 { 3502 struct cgroup *cgrp = seq_css(seq)->cgroup; 3503 3504 seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp)); 3505 seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags)); 3506 3507 return 0; 3508 } 3509 3510 static int cgroup_stat_show(struct seq_file *seq, void *v) 3511 { 3512 struct cgroup *cgroup = seq_css(seq)->cgroup; 3513 3514 seq_printf(seq, "nr_descendants %d\n", 3515 cgroup->nr_descendants); 3516 seq_printf(seq, "nr_dying_descendants %d\n", 3517 cgroup->nr_dying_descendants); 3518 3519 return 0; 3520 } 3521 3522 static int __maybe_unused cgroup_extra_stat_show(struct seq_file *seq, 3523 struct cgroup *cgrp, int ssid) 3524 { 3525 struct cgroup_subsys *ss = cgroup_subsys[ssid]; 3526 struct cgroup_subsys_state *css; 3527 int ret; 3528 3529 if (!ss->css_extra_stat_show) 3530 return 0; 3531 3532 css = cgroup_tryget_css(cgrp, ss); 3533 if (!css) 3534 return 0; 3535 3536 ret = ss->css_extra_stat_show(seq, css); 3537 css_put(css); 3538 return ret; 3539 } 3540 3541 static int cpu_stat_show(struct seq_file *seq, void *v) 3542 { 3543 struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup; 3544 int ret = 0; 3545 3546 cgroup_base_stat_cputime_show(seq); 3547 #ifdef CONFIG_CGROUP_SCHED 3548 ret = cgroup_extra_stat_show(seq, cgrp, cpu_cgrp_id); 3549 #endif 3550 return ret; 3551 } 3552 3553 #ifdef CONFIG_PSI 3554 static int cgroup_io_pressure_show(struct seq_file *seq, void *v) 3555 { 3556 struct cgroup *cgrp = seq_css(seq)->cgroup; 3557 struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; 3558 3559 return psi_show(seq, psi, PSI_IO); 3560 } 3561 static int cgroup_memory_pressure_show(struct seq_file *seq, void *v) 3562 { 3563 struct cgroup *cgrp = seq_css(seq)->cgroup; 3564 struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; 3565 3566 return psi_show(seq, psi, PSI_MEM); 3567 } 3568 static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v) 3569 { 3570 struct cgroup *cgrp = seq_css(seq)->cgroup; 3571 struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; 3572 3573 return psi_show(seq, psi, PSI_CPU); 3574 } 3575 3576 static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf, 3577 size_t nbytes, enum psi_res res) 3578 { 3579 struct psi_trigger *new; 3580 struct cgroup *cgrp; 3581 struct psi_group *psi; 3582 3583 cgrp = cgroup_kn_lock_live(of->kn, false); 3584 if (!cgrp) 3585 return -ENODEV; 3586 3587 cgroup_get(cgrp); 3588 cgroup_kn_unlock(of->kn); 3589 3590 psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi; 3591 new = psi_trigger_create(psi, buf, nbytes, res); 3592 if (IS_ERR(new)) { 3593 cgroup_put(cgrp); 3594 return PTR_ERR(new); 3595 } 3596 3597 psi_trigger_replace(&of->priv, new); 3598 3599 cgroup_put(cgrp); 3600 3601 return nbytes; 3602 } 3603 3604 static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of, 3605 char *buf, size_t nbytes, 3606 loff_t off) 3607 { 3608 return cgroup_pressure_write(of, buf, nbytes, PSI_IO); 3609 } 3610 3611 static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of, 3612 char *buf, size_t nbytes, 3613 loff_t off) 3614 { 3615 return cgroup_pressure_write(of, buf, nbytes, PSI_MEM); 3616 } 3617 3618 static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of, 3619 char *buf, size_t nbytes, 3620 loff_t off) 3621 { 3622 return cgroup_pressure_write(of, buf, nbytes, PSI_CPU); 3623 } 3624 3625 static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of, 3626 poll_table *pt) 3627 { 3628 return psi_trigger_poll(&of->priv, of->file, pt); 3629 } 3630 3631 static void cgroup_pressure_release(struct kernfs_open_file *of) 3632 { 3633 psi_trigger_replace(&of->priv, NULL); 3634 } 3635 #endif /* CONFIG_PSI */ 3636 3637 static int cgroup_freeze_show(struct seq_file *seq, void *v) 3638 { 3639 struct cgroup *cgrp = seq_css(seq)->cgroup; 3640 3641 seq_printf(seq, "%d\n", cgrp->freezer.freeze); 3642 3643 return 0; 3644 } 3645 3646 static ssize_t cgroup_freeze_write(struct kernfs_open_file *of, 3647 char *buf, size_t nbytes, loff_t off) 3648 { 3649 struct cgroup *cgrp; 3650 ssize_t ret; 3651 int freeze; 3652 3653 ret = kstrtoint(strstrip(buf), 0, &freeze); 3654 if (ret) 3655 return ret; 3656 3657 if (freeze < 0 || freeze > 1) 3658 return -ERANGE; 3659 3660 cgrp = cgroup_kn_lock_live(of->kn, false); 3661 if (!cgrp) 3662 return -ENOENT; 3663 3664 cgroup_freeze(cgrp, freeze); 3665 3666 cgroup_kn_unlock(of->kn); 3667 3668 return nbytes; 3669 } 3670 3671 static int cgroup_file_open(struct kernfs_open_file *of) 3672 { 3673 struct cftype *cft = of_cft(of); 3674 3675 if (cft->open) 3676 return cft->open(of); 3677 return 0; 3678 } 3679 3680 static void cgroup_file_release(struct kernfs_open_file *of) 3681 { 3682 struct cftype *cft = of_cft(of); 3683 3684 if (cft->release) 3685 cft->release(of); 3686 } 3687 3688 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, 3689 size_t nbytes, loff_t off) 3690 { 3691 struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; 3692 struct cgroup *cgrp = of->kn->parent->priv; 3693 struct cftype *cft = of_cft(of); 3694 struct cgroup_subsys_state *css; 3695 int ret; 3696 3697 if (!nbytes) 3698 return 0; 3699 3700 /* 3701 * If namespaces are delegation boundaries, disallow writes to 3702 * files in an non-init namespace root from inside the namespace 3703 * except for the files explicitly marked delegatable - 3704 * cgroup.procs and cgroup.subtree_control. 3705 */ 3706 if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) && 3707 !(cft->flags & CFTYPE_NS_DELEGATABLE) && 3708 ns != &init_cgroup_ns && ns->root_cset->dfl_cgrp == cgrp) 3709 return -EPERM; 3710 3711 if (cft->write) 3712 return cft->write(of, buf, nbytes, off); 3713 3714 /* 3715 * kernfs guarantees that a file isn't deleted with operations in 3716 * flight, which means that the matching css is and stays alive and 3717 * doesn't need to be pinned. The RCU locking is not necessary 3718 * either. It's just for the convenience of using cgroup_css(). 3719 */ 3720 rcu_read_lock(); 3721 css = cgroup_css(cgrp, cft->ss); 3722 rcu_read_unlock(); 3723 3724 if (cft->write_u64) { 3725 unsigned long long v; 3726 ret = kstrtoull(buf, 0, &v); 3727 if (!ret) 3728 ret = cft->write_u64(css, cft, v); 3729 } else if (cft->write_s64) { 3730 long long v; 3731 ret = kstrtoll(buf, 0, &v); 3732 if (!ret) 3733 ret = cft->write_s64(css, cft, v); 3734 } else { 3735 ret = -EINVAL; 3736 } 3737 3738 return ret ?: nbytes; 3739 } 3740 3741 static __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt) 3742 { 3743 struct cftype *cft = of_cft(of); 3744 3745 if (cft->poll) 3746 return cft->poll(of, pt); 3747 3748 return kernfs_generic_poll(of, pt); 3749 } 3750 3751 static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos) 3752 { 3753 return seq_cft(seq)->seq_start(seq, ppos); 3754 } 3755 3756 static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos) 3757 { 3758 return seq_cft(seq)->seq_next(seq, v, ppos); 3759 } 3760 3761 static void cgroup_seqfile_stop(struct seq_file *seq, void *v) 3762 { 3763 if (seq_cft(seq)->seq_stop) 3764 seq_cft(seq)->seq_stop(seq, v); 3765 } 3766 3767 static int cgroup_seqfile_show(struct seq_file *m, void *arg) 3768 { 3769 struct cftype *cft = seq_cft(m); 3770 struct cgroup_subsys_state *css = seq_css(m); 3771 3772 if (cft->seq_show) 3773 return cft->seq_show(m, arg); 3774 3775 if (cft->read_u64) 3776 seq_printf(m, "%llu\n", cft->read_u64(css, cft)); 3777 else if (cft->read_s64) 3778 seq_printf(m, "%lld\n", cft->read_s64(css, cft)); 3779 else 3780 return -EINVAL; 3781 return 0; 3782 } 3783 3784 static struct kernfs_ops cgroup_kf_single_ops = { 3785 .atomic_write_len = PAGE_SIZE, 3786 .open = cgroup_file_open, 3787 .release = cgroup_file_release, 3788 .write = cgroup_file_write, 3789 .poll = cgroup_file_poll, 3790 .seq_show = cgroup_seqfile_show, 3791 }; 3792 3793 static struct kernfs_ops cgroup_kf_ops = { 3794 .atomic_write_len = PAGE_SIZE, 3795 .open = cgroup_file_open, 3796 .release = cgroup_file_release, 3797 .write = cgroup_file_write, 3798 .poll = cgroup_file_poll, 3799 .seq_start = cgroup_seqfile_start, 3800 .seq_next = cgroup_seqfile_next, 3801 .seq_stop = cgroup_seqfile_stop, 3802 .seq_show = cgroup_seqfile_show, 3803 }; 3804 3805 /* set uid and gid of cgroup dirs and files to that of the creator */ 3806 static int cgroup_kn_set_ugid(struct kernfs_node *kn) 3807 { 3808 struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID, 3809 .ia_uid = current_fsuid(), 3810 .ia_gid = current_fsgid(), }; 3811 3812 if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) && 3813 gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID)) 3814 return 0; 3815 3816 return kernfs_setattr(kn, &iattr); 3817 } 3818 3819 static void cgroup_file_notify_timer(struct timer_list *timer) 3820 { 3821 cgroup_file_notify(container_of(timer, struct cgroup_file, 3822 notify_timer)); 3823 } 3824 3825 static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp, 3826 struct cftype *cft) 3827 { 3828 char name[CGROUP_FILE_NAME_MAX]; 3829 struct kernfs_node *kn; 3830 struct lock_class_key *key = NULL; 3831 int ret; 3832 3833 #ifdef CONFIG_DEBUG_LOCK_ALLOC 3834 key = &cft->lockdep_key; 3835 #endif 3836 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name), 3837 cgroup_file_mode(cft), 3838 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, 3839 0, cft->kf_ops, cft, 3840 NULL, key); 3841 if (IS_ERR(kn)) 3842 return PTR_ERR(kn); 3843 3844 ret = cgroup_kn_set_ugid(kn); 3845 if (ret) { 3846 kernfs_remove(kn); 3847 return ret; 3848 } 3849 3850 if (cft->file_offset) { 3851 struct cgroup_file *cfile = (void *)css + cft->file_offset; 3852 3853 timer_setup(&cfile->notify_timer, cgroup_file_notify_timer, 0); 3854 3855 spin_lock_irq(&cgroup_file_kn_lock); 3856 cfile->kn = kn; 3857 spin_unlock_irq(&cgroup_file_kn_lock); 3858 } 3859 3860 return 0; 3861 } 3862 3863 /** 3864 * cgroup_addrm_files - add or remove files to a cgroup directory 3865 * @css: the target css 3866 * @cgrp: the target cgroup (usually css->cgroup) 3867 * @cfts: array of cftypes to be added 3868 * @is_add: whether to add or remove 3869 * 3870 * Depending on @is_add, add or remove files defined by @cfts on @cgrp. 3871 * For removals, this function never fails. 3872 */ 3873 static int cgroup_addrm_files(struct cgroup_subsys_state *css, 3874 struct cgroup *cgrp, struct cftype cfts[], 3875 bool is_add) 3876 { 3877 struct cftype *cft, *cft_end = NULL; 3878 int ret = 0; 3879 3880 lockdep_assert_held(&cgroup_mutex); 3881 3882 restart: 3883 for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) { 3884 /* does cft->flags tell us to skip this file on @cgrp? */ 3885 if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp)) 3886 continue; 3887 if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp)) 3888 continue; 3889 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp)) 3890 continue; 3891 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp)) 3892 continue; 3893 if ((cft->flags & CFTYPE_DEBUG) && !cgroup_debug) 3894 continue; 3895 if (is_add) { 3896 ret = cgroup_add_file(css, cgrp, cft); 3897 if (ret) { 3898 pr_warn("%s: failed to add %s, err=%d\n", 3899 __func__, cft->name, ret); 3900 cft_end = cft; 3901 is_add = false; 3902 goto restart; 3903 } 3904 } else { 3905 cgroup_rm_file(cgrp, cft); 3906 } 3907 } 3908 return ret; 3909 } 3910 3911 static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add) 3912 { 3913 struct cgroup_subsys *ss = cfts[0].ss; 3914 struct cgroup *root = &ss->root->cgrp; 3915 struct cgroup_subsys_state *css; 3916 int ret = 0; 3917 3918 lockdep_assert_held(&cgroup_mutex); 3919 3920 /* add/rm files for all cgroups created before */ 3921 css_for_each_descendant_pre(css, cgroup_css(root, ss)) { 3922 struct cgroup *cgrp = css->cgroup; 3923 3924 if (!(css->flags & CSS_VISIBLE)) 3925 continue; 3926 3927 ret = cgroup_addrm_files(css, cgrp, cfts, is_add); 3928 if (ret) 3929 break; 3930 } 3931 3932 if (is_add && !ret) 3933 kernfs_activate(root->kn); 3934 return ret; 3935 } 3936 3937 static void cgroup_exit_cftypes(struct cftype *cfts) 3938 { 3939 struct cftype *cft; 3940 3941 for (cft = cfts; cft->name[0] != '\0'; cft++) { 3942 /* free copy for custom atomic_write_len, see init_cftypes() */ 3943 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) 3944 kfree(cft->kf_ops); 3945 cft->kf_ops = NULL; 3946 cft->ss = NULL; 3947 3948 /* revert flags set by cgroup core while adding @cfts */ 3949 cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL); 3950 } 3951 } 3952 3953 static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) 3954 { 3955 struct cftype *cft; 3956 3957 for (cft = cfts; cft->name[0] != '\0'; cft++) { 3958 struct kernfs_ops *kf_ops; 3959 3960 WARN_ON(cft->ss || cft->kf_ops); 3961 3962 if (cft->seq_start) 3963 kf_ops = &cgroup_kf_ops; 3964 else 3965 kf_ops = &cgroup_kf_single_ops; 3966 3967 /* 3968 * Ugh... if @cft wants a custom max_write_len, we need to 3969 * make a copy of kf_ops to set its atomic_write_len. 3970 */ 3971 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) { 3972 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL); 3973 if (!kf_ops) { 3974 cgroup_exit_cftypes(cfts); 3975 return -ENOMEM; 3976 } 3977 kf_ops->atomic_write_len = cft->max_write_len; 3978 } 3979 3980 cft->kf_ops = kf_ops; 3981 cft->ss = ss; 3982 } 3983 3984 return 0; 3985 } 3986 3987 static int cgroup_rm_cftypes_locked(struct cftype *cfts) 3988 { 3989 lockdep_assert_held(&cgroup_mutex); 3990 3991 if (!cfts || !cfts[0].ss) 3992 return -ENOENT; 3993 3994 list_del(&cfts->node); 3995 cgroup_apply_cftypes(cfts, false); 3996 cgroup_exit_cftypes(cfts); 3997 return 0; 3998 } 3999 4000 /** 4001 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem 4002 * @cfts: zero-length name terminated array of cftypes 4003 * 4004 * Unregister @cfts. Files described by @cfts are removed from all 4005 * existing cgroups and all future cgroups won't have them either. This 4006 * function can be called anytime whether @cfts' subsys is attached or not. 4007 * 4008 * Returns 0 on successful unregistration, -ENOENT if @cfts is not 4009 * registered. 4010 */ 4011 int cgroup_rm_cftypes(struct cftype *cfts) 4012 { 4013 int ret; 4014 4015 mutex_lock(&cgroup_mutex); 4016 ret = cgroup_rm_cftypes_locked(cfts); 4017 mutex_unlock(&cgroup_mutex); 4018 return ret; 4019 } 4020 4021 /** 4022 * cgroup_add_cftypes - add an array of cftypes to a subsystem 4023 * @ss: target cgroup subsystem 4024 * @cfts: zero-length name terminated array of cftypes 4025 * 4026 * Register @cfts to @ss. Files described by @cfts are created for all 4027 * existing cgroups to which @ss is attached and all future cgroups will 4028 * have them too. This function can be called anytime whether @ss is 4029 * attached or not. 4030 * 4031 * Returns 0 on successful registration, -errno on failure. Note that this 4032 * function currently returns 0 as long as @cfts registration is successful 4033 * even if some file creation attempts on existing cgroups fail. 4034 */ 4035 static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) 4036 { 4037 int ret; 4038 4039 if (!cgroup_ssid_enabled(ss->id)) 4040 return 0; 4041 4042 if (!cfts || cfts[0].name[0] == '\0') 4043 return 0; 4044 4045 ret = cgroup_init_cftypes(ss, cfts); 4046 if (ret) 4047 return ret; 4048 4049 mutex_lock(&cgroup_mutex); 4050 4051 list_add_tail(&cfts->node, &ss->cfts); 4052 ret = cgroup_apply_cftypes(cfts, true); 4053 if (ret) 4054 cgroup_rm_cftypes_locked(cfts); 4055 4056 mutex_unlock(&cgroup_mutex); 4057 return ret; 4058 } 4059 4060 /** 4061 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy 4062 * @ss: target cgroup subsystem 4063 * @cfts: zero-length name terminated array of cftypes 4064 * 4065 * Similar to cgroup_add_cftypes() but the added files are only used for 4066 * the default hierarchy. 4067 */ 4068 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) 4069 { 4070 struct cftype *cft; 4071 4072 for (cft = cfts; cft && cft->name[0] != '\0'; cft++) 4073 cft->flags |= __CFTYPE_ONLY_ON_DFL; 4074 return cgroup_add_cftypes(ss, cfts); 4075 } 4076 4077 /** 4078 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies 4079 * @ss: target cgroup subsystem 4080 * @cfts: zero-length name terminated array of cftypes 4081 * 4082 * Similar to cgroup_add_cftypes() but the added files are only used for 4083 * the legacy hierarchies. 4084 */ 4085 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) 4086 { 4087 struct cftype *cft; 4088 4089 for (cft = cfts; cft && cft->name[0] != '\0'; cft++) 4090 cft->flags |= __CFTYPE_NOT_ON_DFL; 4091 return cgroup_add_cftypes(ss, cfts); 4092 } 4093 4094 /** 4095 * cgroup_file_notify - generate a file modified event for a cgroup_file 4096 * @cfile: target cgroup_file 4097 * 4098 * @cfile must have been obtained by setting cftype->file_offset. 4099 */ 4100 void cgroup_file_notify(struct cgroup_file *cfile) 4101 { 4102 unsigned long flags; 4103 4104 spin_lock_irqsave(&cgroup_file_kn_lock, flags); 4105 if (cfile->kn) { 4106 unsigned long last = cfile->notified_at; 4107 unsigned long next = last + CGROUP_FILE_NOTIFY_MIN_INTV; 4108 4109 if (time_in_range(jiffies, last, next)) { 4110 timer_reduce(&cfile->notify_timer, next); 4111 } else { 4112 kernfs_notify(cfile->kn); 4113 cfile->notified_at = jiffies; 4114 } 4115 } 4116 spin_unlock_irqrestore(&cgroup_file_kn_lock, flags); 4117 } 4118 4119 /** 4120 * css_next_child - find the next child of a given css 4121 * @pos: the current position (%NULL to initiate traversal) 4122 * @parent: css whose children to walk 4123 * 4124 * This function returns the next child of @parent and should be called 4125 * under either cgroup_mutex or RCU read lock. The only requirement is 4126 * that @parent and @pos are accessible. The next sibling is guaranteed to 4127 * be returned regardless of their states. 4128 * 4129 * If a subsystem synchronizes ->css_online() and the start of iteration, a 4130 * css which finished ->css_online() is guaranteed to be visible in the 4131 * future iterations and will stay visible until the last reference is put. 4132 * A css which hasn't finished ->css_online() or already finished 4133 * ->css_offline() may show up during traversal. It's each subsystem's 4134 * responsibility to synchronize against on/offlining. 4135 */ 4136 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos, 4137 struct cgroup_subsys_state *parent) 4138 { 4139 struct cgroup_subsys_state *next; 4140 4141 cgroup_assert_mutex_or_rcu_locked(); 4142 4143 /* 4144 * @pos could already have been unlinked from the sibling list. 4145 * Once a cgroup is removed, its ->sibling.next is no longer 4146 * updated when its next sibling changes. CSS_RELEASED is set when 4147 * @pos is taken off list, at which time its next pointer is valid, 4148 * and, as releases are serialized, the one pointed to by the next 4149 * pointer is guaranteed to not have started release yet. This 4150 * implies that if we observe !CSS_RELEASED on @pos in this RCU 4151 * critical section, the one pointed to by its next pointer is 4152 * guaranteed to not have finished its RCU grace period even if we 4153 * have dropped rcu_read_lock() in-between iterations. 4154 * 4155 * If @pos has CSS_RELEASED set, its next pointer can't be 4156 * dereferenced; however, as each css is given a monotonically 4157 * increasing unique serial number and always appended to the 4158 * sibling list, the next one can be found by walking the parent's 4159 * children until the first css with higher serial number than 4160 * @pos's. While this path can be slower, it happens iff iteration 4161 * races against release and the race window is very small. 4162 */ 4163 if (!pos) { 4164 next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling); 4165 } else if (likely(!(pos->flags & CSS_RELEASED))) { 4166 next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling); 4167 } else { 4168 list_for_each_entry_rcu(next, &parent->children, sibling, 4169 lockdep_is_held(&cgroup_mutex)) 4170 if (next->serial_nr > pos->serial_nr) 4171 break; 4172 } 4173 4174 /* 4175 * @next, if not pointing to the head, can be dereferenced and is 4176 * the next sibling. 4177 */ 4178 if (&next->sibling != &parent->children) 4179 return next; 4180 return NULL; 4181 } 4182 4183 /** 4184 * css_next_descendant_pre - find the next descendant for pre-order walk 4185 * @pos: the current position (%NULL to initiate traversal) 4186 * @root: css whose descendants to walk 4187 * 4188 * To be used by css_for_each_descendant_pre(). Find the next descendant 4189 * to visit for pre-order traversal of @root's descendants. @root is 4190 * included in the iteration and the first node to be visited. 4191 * 4192 * While this function requires cgroup_mutex or RCU read locking, it 4193 * doesn't require the whole traversal to be contained in a single critical 4194 * section. This function will return the correct next descendant as long 4195 * as both @pos and @root are accessible and @pos is a descendant of @root. 4196 * 4197 * If a subsystem synchronizes ->css_online() and the start of iteration, a 4198 * css which finished ->css_online() is guaranteed to be visible in the 4199 * future iterations and will stay visible until the last reference is put. 4200 * A css which hasn't finished ->css_online() or already finished 4201 * ->css_offline() may show up during traversal. It's each subsystem's 4202 * responsibility to synchronize against on/offlining. 4203 */ 4204 struct cgroup_subsys_state * 4205 css_next_descendant_pre(struct cgroup_subsys_state *pos, 4206 struct cgroup_subsys_state *root) 4207 { 4208 struct cgroup_subsys_state *next; 4209 4210 cgroup_assert_mutex_or_rcu_locked(); 4211 4212 /* if first iteration, visit @root */ 4213 if (!pos) 4214 return root; 4215 4216 /* visit the first child if exists */ 4217 next = css_next_child(NULL, pos); 4218 if (next) 4219 return next; 4220 4221 /* no child, visit my or the closest ancestor's next sibling */ 4222 while (pos != root) { 4223 next = css_next_child(pos, pos->parent); 4224 if (next) 4225 return next; 4226 pos = pos->parent; 4227 } 4228 4229 return NULL; 4230 } 4231 EXPORT_SYMBOL_GPL(css_next_descendant_pre); 4232 4233 /** 4234 * css_rightmost_descendant - return the rightmost descendant of a css 4235 * @pos: css of interest 4236 * 4237 * Return the rightmost descendant of @pos. If there's no descendant, @pos 4238 * is returned. This can be used during pre-order traversal to skip 4239 * subtree of @pos. 4240 * 4241 * While this function requires cgroup_mutex or RCU read locking, it 4242 * doesn't require the whole traversal to be contained in a single critical 4243 * section. This function will return the correct rightmost descendant as 4244 * long as @pos is accessible. 4245 */ 4246 struct cgroup_subsys_state * 4247 css_rightmost_descendant(struct cgroup_subsys_state *pos) 4248 { 4249 struct cgroup_subsys_state *last, *tmp; 4250 4251 cgroup_assert_mutex_or_rcu_locked(); 4252 4253 do { 4254 last = pos; 4255 /* ->prev isn't RCU safe, walk ->next till the end */ 4256 pos = NULL; 4257 css_for_each_child(tmp, last) 4258 pos = tmp; 4259 } while (pos); 4260 4261 return last; 4262 } 4263 4264 static struct cgroup_subsys_state * 4265 css_leftmost_descendant(struct cgroup_subsys_state *pos) 4266 { 4267 struct cgroup_subsys_state *last; 4268 4269 do { 4270 last = pos; 4271 pos = css_next_child(NULL, pos); 4272 } while (pos); 4273 4274 return last; 4275 } 4276 4277 /** 4278 * css_next_descendant_post - find the next descendant for post-order walk 4279 * @pos: the current position (%NULL to initiate traversal) 4280 * @root: css whose descendants to walk 4281 * 4282 * To be used by css_for_each_descendant_post(). Find the next descendant 4283 * to visit for post-order traversal of @root's descendants. @root is 4284 * included in the iteration and the last node to be visited. 4285 * 4286 * While this function requires cgroup_mutex or RCU read locking, it 4287 * doesn't require the whole traversal to be contained in a single critical 4288 * section. This function will return the correct next descendant as long 4289 * as both @pos and @cgroup are accessible and @pos is a descendant of 4290 * @cgroup. 4291 * 4292 * If a subsystem synchronizes ->css_online() and the start of iteration, a 4293 * css which finished ->css_online() is guaranteed to be visible in the 4294 * future iterations and will stay visible until the last reference is put. 4295 * A css which hasn't finished ->css_online() or already finished 4296 * ->css_offline() may show up during traversal. It's each subsystem's 4297 * responsibility to synchronize against on/offlining. 4298 */ 4299 struct cgroup_subsys_state * 4300 css_next_descendant_post(struct cgroup_subsys_state *pos, 4301 struct cgroup_subsys_state *root) 4302 { 4303 struct cgroup_subsys_state *next; 4304 4305 cgroup_assert_mutex_or_rcu_locked(); 4306 4307 /* if first iteration, visit leftmost descendant which may be @root */ 4308 if (!pos) 4309 return css_leftmost_descendant(root); 4310 4311 /* if we visited @root, we're done */ 4312 if (pos == root) 4313 return NULL; 4314 4315 /* if there's an unvisited sibling, visit its leftmost descendant */ 4316 next = css_next_child(pos, pos->parent); 4317 if (next) 4318 return css_leftmost_descendant(next); 4319 4320 /* no sibling left, visit parent */ 4321 return pos->parent; 4322 } 4323 4324 /** 4325 * css_has_online_children - does a css have online children 4326 * @css: the target css 4327 * 4328 * Returns %true if @css has any online children; otherwise, %false. This 4329 * function can be called from any context but the caller is responsible 4330 * for synchronizing against on/offlining as necessary. 4331 */ 4332 bool css_has_online_children(struct cgroup_subsys_state *css) 4333 { 4334 struct cgroup_subsys_state *child; 4335 bool ret = false; 4336 4337 rcu_read_lock(); 4338 css_for_each_child(child, css) { 4339 if (child->flags & CSS_ONLINE) { 4340 ret = true; 4341 break; 4342 } 4343 } 4344 rcu_read_unlock(); 4345 return ret; 4346 } 4347 4348 static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it) 4349 { 4350 struct list_head *l; 4351 struct cgrp_cset_link *link; 4352 struct css_set *cset; 4353 4354 lockdep_assert_held(&css_set_lock); 4355 4356 /* find the next threaded cset */ 4357 if (it->tcset_pos) { 4358 l = it->tcset_pos->next; 4359 4360 if (l != it->tcset_head) { 4361 it->tcset_pos = l; 4362 return container_of(l, struct css_set, 4363 threaded_csets_node); 4364 } 4365 4366 it->tcset_pos = NULL; 4367 } 4368 4369 /* find the next cset */ 4370 l = it->cset_pos; 4371 l = l->next; 4372 if (l == it->cset_head) { 4373 it->cset_pos = NULL; 4374 return NULL; 4375 } 4376 4377 if (it->ss) { 4378 cset = container_of(l, struct css_set, e_cset_node[it->ss->id]); 4379 } else { 4380 link = list_entry(l, struct cgrp_cset_link, cset_link); 4381 cset = link->cset; 4382 } 4383 4384 it->cset_pos = l; 4385 4386 /* initialize threaded css_set walking */ 4387 if (it->flags & CSS_TASK_ITER_THREADED) { 4388 if (it->cur_dcset) 4389 put_css_set_locked(it->cur_dcset); 4390 it->cur_dcset = cset; 4391 get_css_set(cset); 4392 4393 it->tcset_head = &cset->threaded_csets; 4394 it->tcset_pos = &cset->threaded_csets; 4395 } 4396 4397 return cset; 4398 } 4399 4400 /** 4401 * css_task_iter_advance_css_set - advance a task iterator to the next css_set 4402 * @it: the iterator to advance 4403 * 4404 * Advance @it to the next css_set to walk. 4405 */ 4406 static void css_task_iter_advance_css_set(struct css_task_iter *it) 4407 { 4408 struct css_set *cset; 4409 4410 lockdep_assert_held(&css_set_lock); 4411 4412 /* Advance to the next non-empty css_set and find first non-empty tasks list*/ 4413 while ((cset = css_task_iter_next_css_set(it))) { 4414 if (!list_empty(&cset->tasks)) { 4415 it->cur_tasks_head = &cset->tasks; 4416 break; 4417 } else if (!list_empty(&cset->mg_tasks)) { 4418 it->cur_tasks_head = &cset->mg_tasks; 4419 break; 4420 } else if (!list_empty(&cset->dying_tasks)) { 4421 it->cur_tasks_head = &cset->dying_tasks; 4422 break; 4423 } 4424 } 4425 if (!cset) { 4426 it->task_pos = NULL; 4427 return; 4428 } 4429 it->task_pos = it->cur_tasks_head->next; 4430 4431 /* 4432 * We don't keep css_sets locked across iteration steps and thus 4433 * need to take steps to ensure that iteration can be resumed after 4434 * the lock is re-acquired. Iteration is performed at two levels - 4435 * css_sets and tasks in them. 4436 * 4437 * Once created, a css_set never leaves its cgroup lists, so a 4438 * pinned css_set is guaranteed to stay put and we can resume 4439 * iteration afterwards. 4440 * 4441 * Tasks may leave @cset across iteration steps. This is resolved 4442 * by registering each iterator with the css_set currently being 4443 * walked and making css_set_move_task() advance iterators whose 4444 * next task is leaving. 4445 */ 4446 if (it->cur_cset) { 4447 list_del(&it->iters_node); 4448 put_css_set_locked(it->cur_cset); 4449 } 4450 get_css_set(cset); 4451 it->cur_cset = cset; 4452 list_add(&it->iters_node, &cset->task_iters); 4453 } 4454 4455 static void css_task_iter_skip(struct css_task_iter *it, 4456 struct task_struct *task) 4457 { 4458 lockdep_assert_held(&css_set_lock); 4459 4460 if (it->task_pos == &task->cg_list) { 4461 it->task_pos = it->task_pos->next; 4462 it->flags |= CSS_TASK_ITER_SKIPPED; 4463 } 4464 } 4465 4466 static void css_task_iter_advance(struct css_task_iter *it) 4467 { 4468 struct task_struct *task; 4469 4470 lockdep_assert_held(&css_set_lock); 4471 repeat: 4472 if (it->task_pos) { 4473 /* 4474 * Advance iterator to find next entry. We go through cset 4475 * tasks, mg_tasks and dying_tasks, when consumed we move onto 4476 * the next cset. 4477 */ 4478 if (it->flags & CSS_TASK_ITER_SKIPPED) 4479 it->flags &= ~CSS_TASK_ITER_SKIPPED; 4480 else 4481 it->task_pos = it->task_pos->next; 4482 4483 if (it->task_pos == &it->cur_cset->tasks) { 4484 it->cur_tasks_head = &it->cur_cset->mg_tasks; 4485 it->task_pos = it->cur_tasks_head->next; 4486 } 4487 if (it->task_pos == &it->cur_cset->mg_tasks) { 4488 it->cur_tasks_head = &it->cur_cset->dying_tasks; 4489 it->task_pos = it->cur_tasks_head->next; 4490 } 4491 if (it->task_pos == &it->cur_cset->dying_tasks) 4492 css_task_iter_advance_css_set(it); 4493 } else { 4494 /* called from start, proceed to the first cset */ 4495 css_task_iter_advance_css_set(it); 4496 } 4497 4498 if (!it->task_pos) 4499 return; 4500 4501 task = list_entry(it->task_pos, struct task_struct, cg_list); 4502 4503 if (it->flags & CSS_TASK_ITER_PROCS) { 4504 /* if PROCS, skip over tasks which aren't group leaders */ 4505 if (!thread_group_leader(task)) 4506 goto repeat; 4507 4508 /* and dying leaders w/o live member threads */ 4509 if (it->cur_tasks_head == &it->cur_cset->dying_tasks && 4510 !atomic_read(&task->signal->live)) 4511 goto repeat; 4512 } else { 4513 /* skip all dying ones */ 4514 if (it->cur_tasks_head == &it->cur_cset->dying_tasks) 4515 goto repeat; 4516 } 4517 } 4518 4519 /** 4520 * css_task_iter_start - initiate task iteration 4521 * @css: the css to walk tasks of 4522 * @flags: CSS_TASK_ITER_* flags 4523 * @it: the task iterator to use 4524 * 4525 * Initiate iteration through the tasks of @css. The caller can call 4526 * css_task_iter_next() to walk through the tasks until the function 4527 * returns NULL. On completion of iteration, css_task_iter_end() must be 4528 * called. 4529 */ 4530 void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags, 4531 struct css_task_iter *it) 4532 { 4533 memset(it, 0, sizeof(*it)); 4534 4535 spin_lock_irq(&css_set_lock); 4536 4537 it->ss = css->ss; 4538 it->flags = flags; 4539 4540 if (it->ss) 4541 it->cset_pos = &css->cgroup->e_csets[css->ss->id]; 4542 else 4543 it->cset_pos = &css->cgroup->cset_links; 4544 4545 it->cset_head = it->cset_pos; 4546 4547 css_task_iter_advance(it); 4548 4549 spin_unlock_irq(&css_set_lock); 4550 } 4551 4552 /** 4553 * css_task_iter_next - return the next task for the iterator 4554 * @it: the task iterator being iterated 4555 * 4556 * The "next" function for task iteration. @it should have been 4557 * initialized via css_task_iter_start(). Returns NULL when the iteration 4558 * reaches the end. 4559 */ 4560 struct task_struct *css_task_iter_next(struct css_task_iter *it) 4561 { 4562 if (it->cur_task) { 4563 put_task_struct(it->cur_task); 4564 it->cur_task = NULL; 4565 } 4566 4567 spin_lock_irq(&css_set_lock); 4568 4569 /* @it may be half-advanced by skips, finish advancing */ 4570 if (it->flags & CSS_TASK_ITER_SKIPPED) 4571 css_task_iter_advance(it); 4572 4573 if (it->task_pos) { 4574 it->cur_task = list_entry(it->task_pos, struct task_struct, 4575 cg_list); 4576 get_task_struct(it->cur_task); 4577 css_task_iter_advance(it); 4578 } 4579 4580 spin_unlock_irq(&css_set_lock); 4581 4582 return it->cur_task; 4583 } 4584 4585 /** 4586 * css_task_iter_end - finish task iteration 4587 * @it: the task iterator to finish 4588 * 4589 * Finish task iteration started by css_task_iter_start(). 4590 */ 4591 void css_task_iter_end(struct css_task_iter *it) 4592 { 4593 if (it->cur_cset) { 4594 spin_lock_irq(&css_set_lock); 4595 list_del(&it->iters_node); 4596 put_css_set_locked(it->cur_cset); 4597 spin_unlock_irq(&css_set_lock); 4598 } 4599 4600 if (it->cur_dcset) 4601 put_css_set(it->cur_dcset); 4602 4603 if (it->cur_task) 4604 put_task_struct(it->cur_task); 4605 } 4606 4607 static void cgroup_procs_release(struct kernfs_open_file *of) 4608 { 4609 if (of->priv) { 4610 css_task_iter_end(of->priv); 4611 kfree(of->priv); 4612 } 4613 } 4614 4615 static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos) 4616 { 4617 struct kernfs_open_file *of = s->private; 4618 struct css_task_iter *it = of->priv; 4619 4620 if (pos) 4621 (*pos)++; 4622 4623 return css_task_iter_next(it); 4624 } 4625 4626 static void *__cgroup_procs_start(struct seq_file *s, loff_t *pos, 4627 unsigned int iter_flags) 4628 { 4629 struct kernfs_open_file *of = s->private; 4630 struct cgroup *cgrp = seq_css(s)->cgroup; 4631 struct css_task_iter *it = of->priv; 4632 4633 /* 4634 * When a seq_file is seeked, it's always traversed sequentially 4635 * from position 0, so we can simply keep iterating on !0 *pos. 4636 */ 4637 if (!it) { 4638 if (WARN_ON_ONCE((*pos))) 4639 return ERR_PTR(-EINVAL); 4640 4641 it = kzalloc(sizeof(*it), GFP_KERNEL); 4642 if (!it) 4643 return ERR_PTR(-ENOMEM); 4644 of->priv = it; 4645 css_task_iter_start(&cgrp->self, iter_flags, it); 4646 } else if (!(*pos)) { 4647 css_task_iter_end(it); 4648 css_task_iter_start(&cgrp->self, iter_flags, it); 4649 } else 4650 return it->cur_task; 4651 4652 return cgroup_procs_next(s, NULL, NULL); 4653 } 4654 4655 static void *cgroup_procs_start(struct seq_file *s, loff_t *pos) 4656 { 4657 struct cgroup *cgrp = seq_css(s)->cgroup; 4658 4659 /* 4660 * All processes of a threaded subtree belong to the domain cgroup 4661 * of the subtree. Only threads can be distributed across the 4662 * subtree. Reject reads on cgroup.procs in the subtree proper. 4663 * They're always empty anyway. 4664 */ 4665 if (cgroup_is_threaded(cgrp)) 4666 return ERR_PTR(-EOPNOTSUPP); 4667 4668 return __cgroup_procs_start(s, pos, CSS_TASK_ITER_PROCS | 4669 CSS_TASK_ITER_THREADED); 4670 } 4671 4672 static int cgroup_procs_show(struct seq_file *s, void *v) 4673 { 4674 seq_printf(s, "%d\n", task_pid_vnr(v)); 4675 return 0; 4676 } 4677 4678 static int cgroup_may_write(const struct cgroup *cgrp, struct super_block *sb) 4679 { 4680 int ret; 4681 struct inode *inode; 4682 4683 lockdep_assert_held(&cgroup_mutex); 4684 4685 inode = kernfs_get_inode(sb, cgrp->procs_file.kn); 4686 if (!inode) 4687 return -ENOMEM; 4688 4689 ret = inode_permission(&init_user_ns, inode, MAY_WRITE); 4690 iput(inode); 4691 return ret; 4692 } 4693 4694 static int cgroup_procs_write_permission(struct cgroup *src_cgrp, 4695 struct cgroup *dst_cgrp, 4696 struct super_block *sb) 4697 { 4698 struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; 4699 struct cgroup *com_cgrp = src_cgrp; 4700 int ret; 4701 4702 lockdep_assert_held(&cgroup_mutex); 4703 4704 /* find the common ancestor */ 4705 while (!cgroup_is_descendant(dst_cgrp, com_cgrp)) 4706 com_cgrp = cgroup_parent(com_cgrp); 4707 4708 /* %current should be authorized to migrate to the common ancestor */ 4709 ret = cgroup_may_write(com_cgrp, sb); 4710 if (ret) 4711 return ret; 4712 4713 /* 4714 * If namespaces are delegation boundaries, %current must be able 4715 * to see both source and destination cgroups from its namespace. 4716 */ 4717 if ((cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) && 4718 (!cgroup_is_descendant(src_cgrp, ns->root_cset->dfl_cgrp) || 4719 !cgroup_is_descendant(dst_cgrp, ns->root_cset->dfl_cgrp))) 4720 return -ENOENT; 4721 4722 return 0; 4723 } 4724 4725 static int cgroup_attach_permissions(struct cgroup *src_cgrp, 4726 struct cgroup *dst_cgrp, 4727 struct super_block *sb, bool threadgroup) 4728 { 4729 int ret = 0; 4730 4731 ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb); 4732 if (ret) 4733 return ret; 4734 4735 ret = cgroup_migrate_vet_dst(dst_cgrp); 4736 if (ret) 4737 return ret; 4738 4739 if (!threadgroup && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp)) 4740 ret = -EOPNOTSUPP; 4741 4742 return ret; 4743 } 4744 4745 static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf, 4746 bool threadgroup) 4747 { 4748 struct cgroup *src_cgrp, *dst_cgrp; 4749 struct task_struct *task; 4750 ssize_t ret; 4751 bool locked; 4752 4753 dst_cgrp = cgroup_kn_lock_live(of->kn, false); 4754 if (!dst_cgrp) 4755 return -ENODEV; 4756 4757 task = cgroup_procs_write_start(buf, threadgroup, &locked); 4758 ret = PTR_ERR_OR_ZERO(task); 4759 if (ret) 4760 goto out_unlock; 4761 4762 /* find the source cgroup */ 4763 spin_lock_irq(&css_set_lock); 4764 src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root); 4765 spin_unlock_irq(&css_set_lock); 4766 4767 /* process and thread migrations follow same delegation rule */ 4768 ret = cgroup_attach_permissions(src_cgrp, dst_cgrp, 4769 of->file->f_path.dentry->d_sb, threadgroup); 4770 if (ret) 4771 goto out_finish; 4772 4773 ret = cgroup_attach_task(dst_cgrp, task, threadgroup); 4774 4775 out_finish: 4776 cgroup_procs_write_finish(task, locked); 4777 out_unlock: 4778 cgroup_kn_unlock(of->kn); 4779 4780 return ret; 4781 } 4782 4783 static ssize_t cgroup_procs_write(struct kernfs_open_file *of, 4784 char *buf, size_t nbytes, loff_t off) 4785 { 4786 return __cgroup_procs_write(of, buf, true) ?: nbytes; 4787 } 4788 4789 static void *cgroup_threads_start(struct seq_file *s, loff_t *pos) 4790 { 4791 return __cgroup_procs_start(s, pos, 0); 4792 } 4793 4794 static ssize_t cgroup_threads_write(struct kernfs_open_file *of, 4795 char *buf, size_t nbytes, loff_t off) 4796 { 4797 return __cgroup_procs_write(of, buf, false) ?: nbytes; 4798 } 4799 4800 /* cgroup core interface files for the default hierarchy */ 4801 static struct cftype cgroup_base_files[] = { 4802 { 4803 .name = "cgroup.type", 4804 .flags = CFTYPE_NOT_ON_ROOT, 4805 .seq_show = cgroup_type_show, 4806 .write = cgroup_type_write, 4807 }, 4808 { 4809 .name = "cgroup.procs", 4810 .flags = CFTYPE_NS_DELEGATABLE, 4811 .file_offset = offsetof(struct cgroup, procs_file), 4812 .release = cgroup_procs_release, 4813 .seq_start = cgroup_procs_start, 4814 .seq_next = cgroup_procs_next, 4815 .seq_show = cgroup_procs_show, 4816 .write = cgroup_procs_write, 4817 }, 4818 { 4819 .name = "cgroup.threads", 4820 .flags = CFTYPE_NS_DELEGATABLE, 4821 .release = cgroup_procs_release, 4822 .seq_start = cgroup_threads_start, 4823 .seq_next = cgroup_procs_next, 4824 .seq_show = cgroup_procs_show, 4825 .write = cgroup_threads_write, 4826 }, 4827 { 4828 .name = "cgroup.controllers", 4829 .seq_show = cgroup_controllers_show, 4830 }, 4831 { 4832 .name = "cgroup.subtree_control", 4833 .flags = CFTYPE_NS_DELEGATABLE, 4834 .seq_show = cgroup_subtree_control_show, 4835 .write = cgroup_subtree_control_write, 4836 }, 4837 { 4838 .name = "cgroup.events", 4839 .flags = CFTYPE_NOT_ON_ROOT, 4840 .file_offset = offsetof(struct cgroup, events_file), 4841 .seq_show = cgroup_events_show, 4842 }, 4843 { 4844 .name = "cgroup.max.descendants", 4845 .seq_show = cgroup_max_descendants_show, 4846 .write = cgroup_max_descendants_write, 4847 }, 4848 { 4849 .name = "cgroup.max.depth", 4850 .seq_show = cgroup_max_depth_show, 4851 .write = cgroup_max_depth_write, 4852 }, 4853 { 4854 .name = "cgroup.stat", 4855 .seq_show = cgroup_stat_show, 4856 }, 4857 { 4858 .name = "cgroup.freeze", 4859 .flags = CFTYPE_NOT_ON_ROOT, 4860 .seq_show = cgroup_freeze_show, 4861 .write = cgroup_freeze_write, 4862 }, 4863 { 4864 .name = "cpu.stat", 4865 .seq_show = cpu_stat_show, 4866 }, 4867 #ifdef CONFIG_PSI 4868 { 4869 .name = "io.pressure", 4870 .seq_show = cgroup_io_pressure_show, 4871 .write = cgroup_io_pressure_write, 4872 .poll = cgroup_pressure_poll, 4873 .release = cgroup_pressure_release, 4874 }, 4875 { 4876 .name = "memory.pressure", 4877 .seq_show = cgroup_memory_pressure_show, 4878 .write = cgroup_memory_pressure_write, 4879 .poll = cgroup_pressure_poll, 4880 .release = cgroup_pressure_release, 4881 }, 4882 { 4883 .name = "cpu.pressure", 4884 .seq_show = cgroup_cpu_pressure_show, 4885 .write = cgroup_cpu_pressure_write, 4886 .poll = cgroup_pressure_poll, 4887 .release = cgroup_pressure_release, 4888 }, 4889 #endif /* CONFIG_PSI */ 4890 { } /* terminate */ 4891 }; 4892 4893 /* 4894 * css destruction is four-stage process. 4895 * 4896 * 1. Destruction starts. Killing of the percpu_ref is initiated. 4897 * Implemented in kill_css(). 4898 * 4899 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs 4900 * and thus css_tryget_online() is guaranteed to fail, the css can be 4901 * offlined by invoking offline_css(). After offlining, the base ref is 4902 * put. Implemented in css_killed_work_fn(). 4903 * 4904 * 3. When the percpu_ref reaches zero, the only possible remaining 4905 * accessors are inside RCU read sections. css_release() schedules the 4906 * RCU callback. 4907 * 4908 * 4. After the grace period, the css can be freed. Implemented in 4909 * css_free_work_fn(). 4910 * 4911 * It is actually hairier because both step 2 and 4 require process context 4912 * and thus involve punting to css->destroy_work adding two additional 4913 * steps to the already complex sequence. 4914 */ 4915 static void css_free_rwork_fn(struct work_struct *work) 4916 { 4917 struct cgroup_subsys_state *css = container_of(to_rcu_work(work), 4918 struct cgroup_subsys_state, destroy_rwork); 4919 struct cgroup_subsys *ss = css->ss; 4920 struct cgroup *cgrp = css->cgroup; 4921 4922 percpu_ref_exit(&css->refcnt); 4923 4924 if (ss) { 4925 /* css free path */ 4926 struct cgroup_subsys_state *parent = css->parent; 4927 int id = css->id; 4928 4929 ss->css_free(css); 4930 cgroup_idr_remove(&ss->css_idr, id); 4931 cgroup_put(cgrp); 4932 4933 if (parent) 4934 css_put(parent); 4935 } else { 4936 /* cgroup free path */ 4937 atomic_dec(&cgrp->root->nr_cgrps); 4938 cgroup1_pidlist_destroy_all(cgrp); 4939 cancel_work_sync(&cgrp->release_agent_work); 4940 4941 if (cgroup_parent(cgrp)) { 4942 /* 4943 * We get a ref to the parent, and put the ref when 4944 * this cgroup is being freed, so it's guaranteed 4945 * that the parent won't be destroyed before its 4946 * children. 4947 */ 4948 cgroup_put(cgroup_parent(cgrp)); 4949 kernfs_put(cgrp->kn); 4950 psi_cgroup_free(cgrp); 4951 cgroup_rstat_exit(cgrp); 4952 kfree(cgrp); 4953 } else { 4954 /* 4955 * This is root cgroup's refcnt reaching zero, 4956 * which indicates that the root should be 4957 * released. 4958 */ 4959 cgroup_destroy_root(cgrp->root); 4960 } 4961 } 4962 } 4963 4964 static void css_release_work_fn(struct work_struct *work) 4965 { 4966 struct cgroup_subsys_state *css = 4967 container_of(work, struct cgroup_subsys_state, destroy_work); 4968 struct cgroup_subsys *ss = css->ss; 4969 struct cgroup *cgrp = css->cgroup; 4970 4971 mutex_lock(&cgroup_mutex); 4972 4973 css->flags |= CSS_RELEASED; 4974 list_del_rcu(&css->sibling); 4975 4976 if (ss) { 4977 /* css release path */ 4978 if (!list_empty(&css->rstat_css_node)) { 4979 cgroup_rstat_flush(cgrp); 4980 list_del_rcu(&css->rstat_css_node); 4981 } 4982 4983 cgroup_idr_replace(&ss->css_idr, NULL, css->id); 4984 if (ss->css_released) 4985 ss->css_released(css); 4986 } else { 4987 struct cgroup *tcgrp; 4988 4989 /* cgroup release path */ 4990 TRACE_CGROUP_PATH(release, cgrp); 4991 4992 cgroup_rstat_flush(cgrp); 4993 4994 spin_lock_irq(&css_set_lock); 4995 for (tcgrp = cgroup_parent(cgrp); tcgrp; 4996 tcgrp = cgroup_parent(tcgrp)) 4997 tcgrp->nr_dying_descendants--; 4998 spin_unlock_irq(&css_set_lock); 4999 5000 /* 5001 * There are two control paths which try to determine 5002 * cgroup from dentry without going through kernfs - 5003 * cgroupstats_build() and css_tryget_online_from_dir(). 5004 * Those are supported by RCU protecting clearing of 5005 * cgrp->kn->priv backpointer. 5006 */ 5007 if (cgrp->kn) 5008 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, 5009 NULL); 5010 } 5011 5012 mutex_unlock(&cgroup_mutex); 5013 5014 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn); 5015 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork); 5016 } 5017 5018 static void css_release(struct percpu_ref *ref) 5019 { 5020 struct cgroup_subsys_state *css = 5021 container_of(ref, struct cgroup_subsys_state, refcnt); 5022 5023 INIT_WORK(&css->destroy_work, css_release_work_fn); 5024 queue_work(cgroup_destroy_wq, &css->destroy_work); 5025 } 5026 5027 static void init_and_link_css(struct cgroup_subsys_state *css, 5028 struct cgroup_subsys *ss, struct cgroup *cgrp) 5029 { 5030 lockdep_assert_held(&cgroup_mutex); 5031 5032 cgroup_get_live(cgrp); 5033 5034 memset(css, 0, sizeof(*css)); 5035 css->cgroup = cgrp; 5036 css->ss = ss; 5037 css->id = -1; 5038 INIT_LIST_HEAD(&css->sibling); 5039 INIT_LIST_HEAD(&css->children); 5040 INIT_LIST_HEAD(&css->rstat_css_node); 5041 css->serial_nr = css_serial_nr_next++; 5042 atomic_set(&css->online_cnt, 0); 5043 5044 if (cgroup_parent(cgrp)) { 5045 css->parent = cgroup_css(cgroup_parent(cgrp), ss); 5046 css_get(css->parent); 5047 } 5048 5049 if (ss->css_rstat_flush) 5050 list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list); 5051 5052 BUG_ON(cgroup_css(cgrp, ss)); 5053 } 5054 5055 /* invoke ->css_online() on a new CSS and mark it online if successful */ 5056 static int online_css(struct cgroup_subsys_state *css) 5057 { 5058 struct cgroup_subsys *ss = css->ss; 5059 int ret = 0; 5060 5061 lockdep_assert_held(&cgroup_mutex); 5062 5063 if (ss->css_online) 5064 ret = ss->css_online(css); 5065 if (!ret) { 5066 css->flags |= CSS_ONLINE; 5067 rcu_assign_pointer(css->cgroup->subsys[ss->id], css); 5068 5069 atomic_inc(&css->online_cnt); 5070 if (css->parent) 5071 atomic_inc(&css->parent->online_cnt); 5072 } 5073 return ret; 5074 } 5075 5076 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */ 5077 static void offline_css(struct cgroup_subsys_state *css) 5078 { 5079 struct cgroup_subsys *ss = css->ss; 5080 5081 lockdep_assert_held(&cgroup_mutex); 5082 5083 if (!(css->flags & CSS_ONLINE)) 5084 return; 5085 5086 if (ss->css_offline) 5087 ss->css_offline(css); 5088 5089 css->flags &= ~CSS_ONLINE; 5090 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL); 5091 5092 wake_up_all(&css->cgroup->offline_waitq); 5093 } 5094 5095 /** 5096 * css_create - create a cgroup_subsys_state 5097 * @cgrp: the cgroup new css will be associated with 5098 * @ss: the subsys of new css 5099 * 5100 * Create a new css associated with @cgrp - @ss pair. On success, the new 5101 * css is online and installed in @cgrp. This function doesn't create the 5102 * interface files. Returns 0 on success, -errno on failure. 5103 */ 5104 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp, 5105 struct cgroup_subsys *ss) 5106 { 5107 struct cgroup *parent = cgroup_parent(cgrp); 5108 struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss); 5109 struct cgroup_subsys_state *css; 5110 int err; 5111 5112 lockdep_assert_held(&cgroup_mutex); 5113 5114 css = ss->css_alloc(parent_css); 5115 if (!css) 5116 css = ERR_PTR(-ENOMEM); 5117 if (IS_ERR(css)) 5118 return css; 5119 5120 init_and_link_css(css, ss, cgrp); 5121 5122 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL); 5123 if (err) 5124 goto err_free_css; 5125 5126 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL); 5127 if (err < 0) 5128 goto err_free_css; 5129 css->id = err; 5130 5131 /* @css is ready to be brought online now, make it visible */ 5132 list_add_tail_rcu(&css->sibling, &parent_css->children); 5133 cgroup_idr_replace(&ss->css_idr, css, css->id); 5134 5135 err = online_css(css); 5136 if (err) 5137 goto err_list_del; 5138 5139 return css; 5140 5141 err_list_del: 5142 list_del_rcu(&css->sibling); 5143 err_free_css: 5144 list_del_rcu(&css->rstat_css_node); 5145 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn); 5146 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork); 5147 return ERR_PTR(err); 5148 } 5149 5150 /* 5151 * The returned cgroup is fully initialized including its control mask, but 5152 * it isn't associated with its kernfs_node and doesn't have the control 5153 * mask applied. 5154 */ 5155 static struct cgroup *cgroup_create(struct cgroup *parent, const char *name, 5156 umode_t mode) 5157 { 5158 struct cgroup_root *root = parent->root; 5159 struct cgroup *cgrp, *tcgrp; 5160 struct kernfs_node *kn; 5161 int level = parent->level + 1; 5162 int ret; 5163 5164 /* allocate the cgroup and its ID, 0 is reserved for the root */ 5165 cgrp = kzalloc(struct_size(cgrp, ancestor_ids, (level + 1)), 5166 GFP_KERNEL); 5167 if (!cgrp) 5168 return ERR_PTR(-ENOMEM); 5169 5170 ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL); 5171 if (ret) 5172 goto out_free_cgrp; 5173 5174 ret = cgroup_rstat_init(cgrp); 5175 if (ret) 5176 goto out_cancel_ref; 5177 5178 /* create the directory */ 5179 kn = kernfs_create_dir(parent->kn, name, mode, cgrp); 5180 if (IS_ERR(kn)) { 5181 ret = PTR_ERR(kn); 5182 goto out_stat_exit; 5183 } 5184 cgrp->kn = kn; 5185 5186 init_cgroup_housekeeping(cgrp); 5187 5188 cgrp->self.parent = &parent->self; 5189 cgrp->root = root; 5190 cgrp->level = level; 5191 5192 ret = psi_cgroup_alloc(cgrp); 5193 if (ret) 5194 goto out_kernfs_remove; 5195 5196 ret = cgroup_bpf_inherit(cgrp); 5197 if (ret) 5198 goto out_psi_free; 5199 5200 /* 5201 * New cgroup inherits effective freeze counter, and 5202 * if the parent has to be frozen, the child has too. 5203 */ 5204 cgrp->freezer.e_freeze = parent->freezer.e_freeze; 5205 if (cgrp->freezer.e_freeze) { 5206 /* 5207 * Set the CGRP_FREEZE flag, so when a process will be 5208 * attached to the child cgroup, it will become frozen. 5209 * At this point the new cgroup is unpopulated, so we can 5210 * consider it frozen immediately. 5211 */ 5212 set_bit(CGRP_FREEZE, &cgrp->flags); 5213 set_bit(CGRP_FROZEN, &cgrp->flags); 5214 } 5215 5216 spin_lock_irq(&css_set_lock); 5217 for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) { 5218 cgrp->ancestor_ids[tcgrp->level] = cgroup_id(tcgrp); 5219 5220 if (tcgrp != cgrp) { 5221 tcgrp->nr_descendants++; 5222 5223 /* 5224 * If the new cgroup is frozen, all ancestor cgroups 5225 * get a new frozen descendant, but their state can't 5226 * change because of this. 5227 */ 5228 if (cgrp->freezer.e_freeze) 5229 tcgrp->freezer.nr_frozen_descendants++; 5230 } 5231 } 5232 spin_unlock_irq(&css_set_lock); 5233 5234 if (notify_on_release(parent)) 5235 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); 5236 5237 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags)) 5238 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags); 5239 5240 cgrp->self.serial_nr = css_serial_nr_next++; 5241 5242 /* allocation complete, commit to creation */ 5243 list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children); 5244 atomic_inc(&root->nr_cgrps); 5245 cgroup_get_live(parent); 5246 5247 /* 5248 * On the default hierarchy, a child doesn't automatically inherit 5249 * subtree_control from the parent. Each is configured manually. 5250 */ 5251 if (!cgroup_on_dfl(cgrp)) 5252 cgrp->subtree_control = cgroup_control(cgrp); 5253 5254 cgroup_propagate_control(cgrp); 5255 5256 return cgrp; 5257 5258 out_psi_free: 5259 psi_cgroup_free(cgrp); 5260 out_kernfs_remove: 5261 kernfs_remove(cgrp->kn); 5262 out_stat_exit: 5263 cgroup_rstat_exit(cgrp); 5264 out_cancel_ref: 5265 percpu_ref_exit(&cgrp->self.refcnt); 5266 out_free_cgrp: 5267 kfree(cgrp); 5268 return ERR_PTR(ret); 5269 } 5270 5271 static bool cgroup_check_hierarchy_limits(struct cgroup *parent) 5272 { 5273 struct cgroup *cgroup; 5274 int ret = false; 5275 int level = 1; 5276 5277 lockdep_assert_held(&cgroup_mutex); 5278 5279 for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) { 5280 if (cgroup->nr_descendants >= cgroup->max_descendants) 5281 goto fail; 5282 5283 if (level > cgroup->max_depth) 5284 goto fail; 5285 5286 level++; 5287 } 5288 5289 ret = true; 5290 fail: 5291 return ret; 5292 } 5293 5294 int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode) 5295 { 5296 struct cgroup *parent, *cgrp; 5297 int ret; 5298 5299 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */ 5300 if (strchr(name, '\n')) 5301 return -EINVAL; 5302 5303 parent = cgroup_kn_lock_live(parent_kn, false); 5304 if (!parent) 5305 return -ENODEV; 5306 5307 if (!cgroup_check_hierarchy_limits(parent)) { 5308 ret = -EAGAIN; 5309 goto out_unlock; 5310 } 5311 5312 cgrp = cgroup_create(parent, name, mode); 5313 if (IS_ERR(cgrp)) { 5314 ret = PTR_ERR(cgrp); 5315 goto out_unlock; 5316 } 5317 5318 /* 5319 * This extra ref will be put in cgroup_free_fn() and guarantees 5320 * that @cgrp->kn is always accessible. 5321 */ 5322 kernfs_get(cgrp->kn); 5323 5324 ret = cgroup_kn_set_ugid(cgrp->kn); 5325 if (ret) 5326 goto out_destroy; 5327 5328 ret = css_populate_dir(&cgrp->self); 5329 if (ret) 5330 goto out_destroy; 5331 5332 ret = cgroup_apply_control_enable(cgrp); 5333 if (ret) 5334 goto out_destroy; 5335 5336 TRACE_CGROUP_PATH(mkdir, cgrp); 5337 5338 /* let's create and online css's */ 5339 kernfs_activate(cgrp->kn); 5340 5341 ret = 0; 5342 goto out_unlock; 5343 5344 out_destroy: 5345 cgroup_destroy_locked(cgrp); 5346 out_unlock: 5347 cgroup_kn_unlock(parent_kn); 5348 return ret; 5349 } 5350 5351 /* 5352 * This is called when the refcnt of a css is confirmed to be killed. 5353 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to 5354 * initiate destruction and put the css ref from kill_css(). 5355 */ 5356 static void css_killed_work_fn(struct work_struct *work) 5357 { 5358 struct cgroup_subsys_state *css = 5359 container_of(work, struct cgroup_subsys_state, destroy_work); 5360 5361 mutex_lock(&cgroup_mutex); 5362 5363 do { 5364 offline_css(css); 5365 css_put(css); 5366 /* @css can't go away while we're holding cgroup_mutex */ 5367 css = css->parent; 5368 } while (css && atomic_dec_and_test(&css->online_cnt)); 5369 5370 mutex_unlock(&cgroup_mutex); 5371 } 5372 5373 /* css kill confirmation processing requires process context, bounce */ 5374 static void css_killed_ref_fn(struct percpu_ref *ref) 5375 { 5376 struct cgroup_subsys_state *css = 5377 container_of(ref, struct cgroup_subsys_state, refcnt); 5378 5379 if (atomic_dec_and_test(&css->online_cnt)) { 5380 INIT_WORK(&css->destroy_work, css_killed_work_fn); 5381 queue_work(cgroup_destroy_wq, &css->destroy_work); 5382 } 5383 } 5384 5385 /** 5386 * kill_css - destroy a css 5387 * @css: css to destroy 5388 * 5389 * This function initiates destruction of @css by removing cgroup interface 5390 * files and putting its base reference. ->css_offline() will be invoked 5391 * asynchronously once css_tryget_online() is guaranteed to fail and when 5392 * the reference count reaches zero, @css will be released. 5393 */ 5394 static void kill_css(struct cgroup_subsys_state *css) 5395 { 5396 lockdep_assert_held(&cgroup_mutex); 5397 5398 if (css->flags & CSS_DYING) 5399 return; 5400 5401 css->flags |= CSS_DYING; 5402 5403 /* 5404 * This must happen before css is disassociated with its cgroup. 5405 * See seq_css() for details. 5406 */ 5407 css_clear_dir(css); 5408 5409 /* 5410 * Killing would put the base ref, but we need to keep it alive 5411 * until after ->css_offline(). 5412 */ 5413 css_get(css); 5414 5415 /* 5416 * cgroup core guarantees that, by the time ->css_offline() is 5417 * invoked, no new css reference will be given out via 5418 * css_tryget_online(). We can't simply call percpu_ref_kill() and 5419 * proceed to offlining css's because percpu_ref_kill() doesn't 5420 * guarantee that the ref is seen as killed on all CPUs on return. 5421 * 5422 * Use percpu_ref_kill_and_confirm() to get notifications as each 5423 * css is confirmed to be seen as killed on all CPUs. 5424 */ 5425 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn); 5426 } 5427 5428 /** 5429 * cgroup_destroy_locked - the first stage of cgroup destruction 5430 * @cgrp: cgroup to be destroyed 5431 * 5432 * css's make use of percpu refcnts whose killing latency shouldn't be 5433 * exposed to userland and are RCU protected. Also, cgroup core needs to 5434 * guarantee that css_tryget_online() won't succeed by the time 5435 * ->css_offline() is invoked. To satisfy all the requirements, 5436 * destruction is implemented in the following two steps. 5437 * 5438 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all 5439 * userland visible parts and start killing the percpu refcnts of 5440 * css's. Set up so that the next stage will be kicked off once all 5441 * the percpu refcnts are confirmed to be killed. 5442 * 5443 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the 5444 * rest of destruction. Once all cgroup references are gone, the 5445 * cgroup is RCU-freed. 5446 * 5447 * This function implements s1. After this step, @cgrp is gone as far as 5448 * the userland is concerned and a new cgroup with the same name may be 5449 * created. As cgroup doesn't care about the names internally, this 5450 * doesn't cause any problem. 5451 */ 5452 static int cgroup_destroy_locked(struct cgroup *cgrp) 5453 __releases(&cgroup_mutex) __acquires(&cgroup_mutex) 5454 { 5455 struct cgroup *tcgrp, *parent = cgroup_parent(cgrp); 5456 struct cgroup_subsys_state *css; 5457 struct cgrp_cset_link *link; 5458 int ssid; 5459 5460 lockdep_assert_held(&cgroup_mutex); 5461 5462 /* 5463 * Only migration can raise populated from zero and we're already 5464 * holding cgroup_mutex. 5465 */ 5466 if (cgroup_is_populated(cgrp)) 5467 return -EBUSY; 5468 5469 /* 5470 * Make sure there's no live children. We can't test emptiness of 5471 * ->self.children as dead children linger on it while being 5472 * drained; otherwise, "rmdir parent/child parent" may fail. 5473 */ 5474 if (css_has_online_children(&cgrp->self)) 5475 return -EBUSY; 5476 5477 /* 5478 * Mark @cgrp and the associated csets dead. The former prevents 5479 * further task migration and child creation by disabling 5480 * cgroup_lock_live_group(). The latter makes the csets ignored by 5481 * the migration path. 5482 */ 5483 cgrp->self.flags &= ~CSS_ONLINE; 5484 5485 spin_lock_irq(&css_set_lock); 5486 list_for_each_entry(link, &cgrp->cset_links, cset_link) 5487 link->cset->dead = true; 5488 spin_unlock_irq(&css_set_lock); 5489 5490 /* initiate massacre of all css's */ 5491 for_each_css(css, ssid, cgrp) 5492 kill_css(css); 5493 5494 /* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */ 5495 css_clear_dir(&cgrp->self); 5496 kernfs_remove(cgrp->kn); 5497 5498 if (parent && cgroup_is_threaded(cgrp)) 5499 parent->nr_threaded_children--; 5500 5501 spin_lock_irq(&css_set_lock); 5502 for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) { 5503 tcgrp->nr_descendants--; 5504 tcgrp->nr_dying_descendants++; 5505 /* 5506 * If the dying cgroup is frozen, decrease frozen descendants 5507 * counters of ancestor cgroups. 5508 */ 5509 if (test_bit(CGRP_FROZEN, &cgrp->flags)) 5510 tcgrp->freezer.nr_frozen_descendants--; 5511 } 5512 spin_unlock_irq(&css_set_lock); 5513 5514 cgroup1_check_for_release(parent); 5515 5516 cgroup_bpf_offline(cgrp); 5517 5518 /* put the base reference */ 5519 percpu_ref_kill(&cgrp->self.refcnt); 5520 5521 return 0; 5522 }; 5523 5524 int cgroup_rmdir(struct kernfs_node *kn) 5525 { 5526 struct cgroup *cgrp; 5527 int ret = 0; 5528 5529 cgrp = cgroup_kn_lock_live(kn, false); 5530 if (!cgrp) 5531 return 0; 5532 5533 ret = cgroup_destroy_locked(cgrp); 5534 if (!ret) 5535 TRACE_CGROUP_PATH(rmdir, cgrp); 5536 5537 cgroup_kn_unlock(kn); 5538 return ret; 5539 } 5540 5541 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = { 5542 .show_options = cgroup_show_options, 5543 .mkdir = cgroup_mkdir, 5544 .rmdir = cgroup_rmdir, 5545 .show_path = cgroup_show_path, 5546 }; 5547 5548 static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early) 5549 { 5550 struct cgroup_subsys_state *css; 5551 5552 pr_debug("Initializing cgroup subsys %s\n", ss->name); 5553 5554 mutex_lock(&cgroup_mutex); 5555 5556 idr_init(&ss->css_idr); 5557 INIT_LIST_HEAD(&ss->cfts); 5558 5559 /* Create the root cgroup state for this subsystem */ 5560 ss->root = &cgrp_dfl_root; 5561 css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss)); 5562 /* We don't handle early failures gracefully */ 5563 BUG_ON(IS_ERR(css)); 5564 init_and_link_css(css, ss, &cgrp_dfl_root.cgrp); 5565 5566 /* 5567 * Root csses are never destroyed and we can't initialize 5568 * percpu_ref during early init. Disable refcnting. 5569 */ 5570 css->flags |= CSS_NO_REF; 5571 5572 if (early) { 5573 /* allocation can't be done safely during early init */ 5574 css->id = 1; 5575 } else { 5576 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL); 5577 BUG_ON(css->id < 0); 5578 } 5579 5580 /* Update the init_css_set to contain a subsys 5581 * pointer to this state - since the subsystem is 5582 * newly registered, all tasks and hence the 5583 * init_css_set is in the subsystem's root cgroup. */ 5584 init_css_set.subsys[ss->id] = css; 5585 5586 have_fork_callback |= (bool)ss->fork << ss->id; 5587 have_exit_callback |= (bool)ss->exit << ss->id; 5588 have_release_callback |= (bool)ss->release << ss->id; 5589 have_canfork_callback |= (bool)ss->can_fork << ss->id; 5590 5591 /* At system boot, before all subsystems have been 5592 * registered, no tasks have been forked, so we don't 5593 * need to invoke fork callbacks here. */ 5594 BUG_ON(!list_empty(&init_task.tasks)); 5595 5596 BUG_ON(online_css(css)); 5597 5598 mutex_unlock(&cgroup_mutex); 5599 } 5600 5601 /** 5602 * cgroup_init_early - cgroup initialization at system boot 5603 * 5604 * Initialize cgroups at system boot, and initialize any 5605 * subsystems that request early init. 5606 */ 5607 int __init cgroup_init_early(void) 5608 { 5609 static struct cgroup_fs_context __initdata ctx; 5610 struct cgroup_subsys *ss; 5611 int i; 5612 5613 ctx.root = &cgrp_dfl_root; 5614 init_cgroup_root(&ctx); 5615 cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF; 5616 5617 RCU_INIT_POINTER(init_task.cgroups, &init_css_set); 5618 5619 for_each_subsys(ss, i) { 5620 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id, 5621 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n", 5622 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free, 5623 ss->id, ss->name); 5624 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN, 5625 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]); 5626 5627 ss->id = i; 5628 ss->name = cgroup_subsys_name[i]; 5629 if (!ss->legacy_name) 5630 ss->legacy_name = cgroup_subsys_name[i]; 5631 5632 if (ss->early_init) 5633 cgroup_init_subsys(ss, true); 5634 } 5635 return 0; 5636 } 5637 5638 /** 5639 * cgroup_init - cgroup initialization 5640 * 5641 * Register cgroup filesystem and /proc file, and initialize 5642 * any subsystems that didn't request early init. 5643 */ 5644 int __init cgroup_init(void) 5645 { 5646 struct cgroup_subsys *ss; 5647 int ssid; 5648 5649 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16); 5650 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files)); 5651 BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files)); 5652 5653 cgroup_rstat_boot(); 5654 5655 /* 5656 * The latency of the synchronize_rcu() is too high for cgroups, 5657 * avoid it at the cost of forcing all readers into the slow path. 5658 */ 5659 rcu_sync_enter_start(&cgroup_threadgroup_rwsem.rss); 5660 5661 get_user_ns(init_cgroup_ns.user_ns); 5662 5663 mutex_lock(&cgroup_mutex); 5664 5665 /* 5666 * Add init_css_set to the hash table so that dfl_root can link to 5667 * it during init. 5668 */ 5669 hash_add(css_set_table, &init_css_set.hlist, 5670 css_set_hash(init_css_set.subsys)); 5671 5672 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0)); 5673 5674 mutex_unlock(&cgroup_mutex); 5675 5676 for_each_subsys(ss, ssid) { 5677 if (ss->early_init) { 5678 struct cgroup_subsys_state *css = 5679 init_css_set.subsys[ss->id]; 5680 5681 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, 5682 GFP_KERNEL); 5683 BUG_ON(css->id < 0); 5684 } else { 5685 cgroup_init_subsys(ss, false); 5686 } 5687 5688 list_add_tail(&init_css_set.e_cset_node[ssid], 5689 &cgrp_dfl_root.cgrp.e_csets[ssid]); 5690 5691 /* 5692 * Setting dfl_root subsys_mask needs to consider the 5693 * disabled flag and cftype registration needs kmalloc, 5694 * both of which aren't available during early_init. 5695 */ 5696 if (!cgroup_ssid_enabled(ssid)) 5697 continue; 5698 5699 if (cgroup1_ssid_disabled(ssid)) 5700 printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n", 5701 ss->name); 5702 5703 cgrp_dfl_root.subsys_mask |= 1 << ss->id; 5704 5705 /* implicit controllers must be threaded too */ 5706 WARN_ON(ss->implicit_on_dfl && !ss->threaded); 5707 5708 if (ss->implicit_on_dfl) 5709 cgrp_dfl_implicit_ss_mask |= 1 << ss->id; 5710 else if (!ss->dfl_cftypes) 5711 cgrp_dfl_inhibit_ss_mask |= 1 << ss->id; 5712 5713 if (ss->threaded) 5714 cgrp_dfl_threaded_ss_mask |= 1 << ss->id; 5715 5716 if (ss->dfl_cftypes == ss->legacy_cftypes) { 5717 WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes)); 5718 } else { 5719 WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes)); 5720 WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes)); 5721 } 5722 5723 if (ss->bind) 5724 ss->bind(init_css_set.subsys[ssid]); 5725 5726 mutex_lock(&cgroup_mutex); 5727 css_populate_dir(init_css_set.subsys[ssid]); 5728 mutex_unlock(&cgroup_mutex); 5729 } 5730 5731 /* init_css_set.subsys[] has been updated, re-hash */ 5732 hash_del(&init_css_set.hlist); 5733 hash_add(css_set_table, &init_css_set.hlist, 5734 css_set_hash(init_css_set.subsys)); 5735 5736 WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup")); 5737 WARN_ON(register_filesystem(&cgroup_fs_type)); 5738 WARN_ON(register_filesystem(&cgroup2_fs_type)); 5739 WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show)); 5740 #ifdef CONFIG_CPUSETS 5741 WARN_ON(register_filesystem(&cpuset_fs_type)); 5742 #endif 5743 5744 return 0; 5745 } 5746 5747 static int __init cgroup_wq_init(void) 5748 { 5749 /* 5750 * There isn't much point in executing destruction path in 5751 * parallel. Good chunk is serialized with cgroup_mutex anyway. 5752 * Use 1 for @max_active. 5753 * 5754 * We would prefer to do this in cgroup_init() above, but that 5755 * is called before init_workqueues(): so leave this until after. 5756 */ 5757 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1); 5758 BUG_ON(!cgroup_destroy_wq); 5759 return 0; 5760 } 5761 core_initcall(cgroup_wq_init); 5762 5763 void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen) 5764 { 5765 struct kernfs_node *kn; 5766 5767 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id); 5768 if (!kn) 5769 return; 5770 kernfs_path(kn, buf, buflen); 5771 kernfs_put(kn); 5772 } 5773 5774 /* 5775 * proc_cgroup_show() 5776 * - Print task's cgroup paths into seq_file, one line for each hierarchy 5777 * - Used for /proc/<pid>/cgroup. 5778 */ 5779 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns, 5780 struct pid *pid, struct task_struct *tsk) 5781 { 5782 char *buf; 5783 int retval; 5784 struct cgroup_root *root; 5785 5786 retval = -ENOMEM; 5787 buf = kmalloc(PATH_MAX, GFP_KERNEL); 5788 if (!buf) 5789 goto out; 5790 5791 mutex_lock(&cgroup_mutex); 5792 spin_lock_irq(&css_set_lock); 5793 5794 for_each_root(root) { 5795 struct cgroup_subsys *ss; 5796 struct cgroup *cgrp; 5797 int ssid, count = 0; 5798 5799 if (root == &cgrp_dfl_root && !cgrp_dfl_visible) 5800 continue; 5801 5802 seq_printf(m, "%d:", root->hierarchy_id); 5803 if (root != &cgrp_dfl_root) 5804 for_each_subsys(ss, ssid) 5805 if (root->subsys_mask & (1 << ssid)) 5806 seq_printf(m, "%s%s", count++ ? "," : "", 5807 ss->legacy_name); 5808 if (strlen(root->name)) 5809 seq_printf(m, "%sname=%s", count ? "," : "", 5810 root->name); 5811 seq_putc(m, ':'); 5812 5813 cgrp = task_cgroup_from_root(tsk, root); 5814 5815 /* 5816 * On traditional hierarchies, all zombie tasks show up as 5817 * belonging to the root cgroup. On the default hierarchy, 5818 * while a zombie doesn't show up in "cgroup.procs" and 5819 * thus can't be migrated, its /proc/PID/cgroup keeps 5820 * reporting the cgroup it belonged to before exiting. If 5821 * the cgroup is removed before the zombie is reaped, 5822 * " (deleted)" is appended to the cgroup path. 5823 */ 5824 if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) { 5825 retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX, 5826 current->nsproxy->cgroup_ns); 5827 if (retval >= PATH_MAX) 5828 retval = -ENAMETOOLONG; 5829 if (retval < 0) 5830 goto out_unlock; 5831 5832 seq_puts(m, buf); 5833 } else { 5834 seq_puts(m, "/"); 5835 } 5836 5837 if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp)) 5838 seq_puts(m, " (deleted)\n"); 5839 else 5840 seq_putc(m, '\n'); 5841 } 5842 5843 retval = 0; 5844 out_unlock: 5845 spin_unlock_irq(&css_set_lock); 5846 mutex_unlock(&cgroup_mutex); 5847 kfree(buf); 5848 out: 5849 return retval; 5850 } 5851 5852 /** 5853 * cgroup_fork - initialize cgroup related fields during copy_process() 5854 * @child: pointer to task_struct of forking parent process. 5855 * 5856 * A task is associated with the init_css_set until cgroup_post_fork() 5857 * attaches it to the target css_set. 5858 */ 5859 void cgroup_fork(struct task_struct *child) 5860 { 5861 RCU_INIT_POINTER(child->cgroups, &init_css_set); 5862 INIT_LIST_HEAD(&child->cg_list); 5863 } 5864 5865 static struct cgroup *cgroup_get_from_file(struct file *f) 5866 { 5867 struct cgroup_subsys_state *css; 5868 struct cgroup *cgrp; 5869 5870 css = css_tryget_online_from_dir(f->f_path.dentry, NULL); 5871 if (IS_ERR(css)) 5872 return ERR_CAST(css); 5873 5874 cgrp = css->cgroup; 5875 if (!cgroup_on_dfl(cgrp)) { 5876 cgroup_put(cgrp); 5877 return ERR_PTR(-EBADF); 5878 } 5879 5880 return cgrp; 5881 } 5882 5883 /** 5884 * cgroup_css_set_fork - find or create a css_set for a child process 5885 * @kargs: the arguments passed to create the child process 5886 * 5887 * This functions finds or creates a new css_set which the child 5888 * process will be attached to in cgroup_post_fork(). By default, 5889 * the child process will be given the same css_set as its parent. 5890 * 5891 * If CLONE_INTO_CGROUP is specified this function will try to find an 5892 * existing css_set which includes the requested cgroup and if not create 5893 * a new css_set that the child will be attached to later. If this function 5894 * succeeds it will hold cgroup_threadgroup_rwsem on return. If 5895 * CLONE_INTO_CGROUP is requested this function will grab cgroup mutex 5896 * before grabbing cgroup_threadgroup_rwsem and will hold a reference 5897 * to the target cgroup. 5898 */ 5899 static int cgroup_css_set_fork(struct kernel_clone_args *kargs) 5900 __acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem) 5901 { 5902 int ret; 5903 struct cgroup *dst_cgrp = NULL; 5904 struct css_set *cset; 5905 struct super_block *sb; 5906 struct file *f; 5907 5908 if (kargs->flags & CLONE_INTO_CGROUP) 5909 mutex_lock(&cgroup_mutex); 5910 5911 cgroup_threadgroup_change_begin(current); 5912 5913 spin_lock_irq(&css_set_lock); 5914 cset = task_css_set(current); 5915 get_css_set(cset); 5916 spin_unlock_irq(&css_set_lock); 5917 5918 if (!(kargs->flags & CLONE_INTO_CGROUP)) { 5919 kargs->cset = cset; 5920 return 0; 5921 } 5922 5923 f = fget_raw(kargs->cgroup); 5924 if (!f) { 5925 ret = -EBADF; 5926 goto err; 5927 } 5928 sb = f->f_path.dentry->d_sb; 5929 5930 dst_cgrp = cgroup_get_from_file(f); 5931 if (IS_ERR(dst_cgrp)) { 5932 ret = PTR_ERR(dst_cgrp); 5933 dst_cgrp = NULL; 5934 goto err; 5935 } 5936 5937 if (cgroup_is_dead(dst_cgrp)) { 5938 ret = -ENODEV; 5939 goto err; 5940 } 5941 5942 /* 5943 * Verify that we the target cgroup is writable for us. This is 5944 * usually done by the vfs layer but since we're not going through 5945 * the vfs layer here we need to do it "manually". 5946 */ 5947 ret = cgroup_may_write(dst_cgrp, sb); 5948 if (ret) 5949 goto err; 5950 5951 ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb, 5952 !(kargs->flags & CLONE_THREAD)); 5953 if (ret) 5954 goto err; 5955 5956 kargs->cset = find_css_set(cset, dst_cgrp); 5957 if (!kargs->cset) { 5958 ret = -ENOMEM; 5959 goto err; 5960 } 5961 5962 put_css_set(cset); 5963 fput(f); 5964 kargs->cgrp = dst_cgrp; 5965 return ret; 5966 5967 err: 5968 cgroup_threadgroup_change_end(current); 5969 mutex_unlock(&cgroup_mutex); 5970 if (f) 5971 fput(f); 5972 if (dst_cgrp) 5973 cgroup_put(dst_cgrp); 5974 put_css_set(cset); 5975 if (kargs->cset) 5976 put_css_set(kargs->cset); 5977 return ret; 5978 } 5979 5980 /** 5981 * cgroup_css_set_put_fork - drop references we took during fork 5982 * @kargs: the arguments passed to create the child process 5983 * 5984 * Drop references to the prepared css_set and target cgroup if 5985 * CLONE_INTO_CGROUP was requested. 5986 */ 5987 static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs) 5988 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex) 5989 { 5990 cgroup_threadgroup_change_end(current); 5991 5992 if (kargs->flags & CLONE_INTO_CGROUP) { 5993 struct cgroup *cgrp = kargs->cgrp; 5994 struct css_set *cset = kargs->cset; 5995 5996 mutex_unlock(&cgroup_mutex); 5997 5998 if (cset) { 5999 put_css_set(cset); 6000 kargs->cset = NULL; 6001 } 6002 6003 if (cgrp) { 6004 cgroup_put(cgrp); 6005 kargs->cgrp = NULL; 6006 } 6007 } 6008 } 6009 6010 /** 6011 * cgroup_can_fork - called on a new task before the process is exposed 6012 * @child: the child process 6013 * 6014 * This prepares a new css_set for the child process which the child will 6015 * be attached to in cgroup_post_fork(). 6016 * This calls the subsystem can_fork() callbacks. If the cgroup_can_fork() 6017 * callback returns an error, the fork aborts with that error code. This 6018 * allows for a cgroup subsystem to conditionally allow or deny new forks. 6019 */ 6020 int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs) 6021 { 6022 struct cgroup_subsys *ss; 6023 int i, j, ret; 6024 6025 ret = cgroup_css_set_fork(kargs); 6026 if (ret) 6027 return ret; 6028 6029 do_each_subsys_mask(ss, i, have_canfork_callback) { 6030 ret = ss->can_fork(child, kargs->cset); 6031 if (ret) 6032 goto out_revert; 6033 } while_each_subsys_mask(); 6034 6035 return 0; 6036 6037 out_revert: 6038 for_each_subsys(ss, j) { 6039 if (j >= i) 6040 break; 6041 if (ss->cancel_fork) 6042 ss->cancel_fork(child, kargs->cset); 6043 } 6044 6045 cgroup_css_set_put_fork(kargs); 6046 6047 return ret; 6048 } 6049 6050 /** 6051 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork() 6052 * @child: the child process 6053 * @kargs: the arguments passed to create the child process 6054 * 6055 * This calls the cancel_fork() callbacks if a fork failed *after* 6056 * cgroup_can_fork() succeeded and cleans up references we took to 6057 * prepare a new css_set for the child process in cgroup_can_fork(). 6058 */ 6059 void cgroup_cancel_fork(struct task_struct *child, 6060 struct kernel_clone_args *kargs) 6061 { 6062 struct cgroup_subsys *ss; 6063 int i; 6064 6065 for_each_subsys(ss, i) 6066 if (ss->cancel_fork) 6067 ss->cancel_fork(child, kargs->cset); 6068 6069 cgroup_css_set_put_fork(kargs); 6070 } 6071 6072 /** 6073 * cgroup_post_fork - finalize cgroup setup for the child process 6074 * @child: the child process 6075 * 6076 * Attach the child process to its css_set calling the subsystem fork() 6077 * callbacks. 6078 */ 6079 void cgroup_post_fork(struct task_struct *child, 6080 struct kernel_clone_args *kargs) 6081 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex) 6082 { 6083 struct cgroup_subsys *ss; 6084 struct css_set *cset; 6085 int i; 6086 6087 cset = kargs->cset; 6088 kargs->cset = NULL; 6089 6090 spin_lock_irq(&css_set_lock); 6091 6092 /* init tasks are special, only link regular threads */ 6093 if (likely(child->pid)) { 6094 WARN_ON_ONCE(!list_empty(&child->cg_list)); 6095 cset->nr_tasks++; 6096 css_set_move_task(child, NULL, cset, false); 6097 } else { 6098 put_css_set(cset); 6099 cset = NULL; 6100 } 6101 6102 /* 6103 * If the cgroup has to be frozen, the new task has too. Let's set 6104 * the JOBCTL_TRAP_FREEZE jobctl bit to get the task into the 6105 * frozen state. 6106 */ 6107 if (unlikely(cgroup_task_freeze(child))) { 6108 spin_lock(&child->sighand->siglock); 6109 WARN_ON_ONCE(child->frozen); 6110 child->jobctl |= JOBCTL_TRAP_FREEZE; 6111 spin_unlock(&child->sighand->siglock); 6112 6113 /* 6114 * Calling cgroup_update_frozen() isn't required here, 6115 * because it will be called anyway a bit later from 6116 * do_freezer_trap(). So we avoid cgroup's transient switch 6117 * from the frozen state and back. 6118 */ 6119 } 6120 6121 spin_unlock_irq(&css_set_lock); 6122 6123 /* 6124 * Call ss->fork(). This must happen after @child is linked on 6125 * css_set; otherwise, @child might change state between ->fork() 6126 * and addition to css_set. 6127 */ 6128 do_each_subsys_mask(ss, i, have_fork_callback) { 6129 ss->fork(child); 6130 } while_each_subsys_mask(); 6131 6132 /* Make the new cset the root_cset of the new cgroup namespace. */ 6133 if (kargs->flags & CLONE_NEWCGROUP) { 6134 struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset; 6135 6136 get_css_set(cset); 6137 child->nsproxy->cgroup_ns->root_cset = cset; 6138 put_css_set(rcset); 6139 } 6140 6141 cgroup_css_set_put_fork(kargs); 6142 } 6143 6144 /** 6145 * cgroup_exit - detach cgroup from exiting task 6146 * @tsk: pointer to task_struct of exiting process 6147 * 6148 * Description: Detach cgroup from @tsk. 6149 * 6150 */ 6151 void cgroup_exit(struct task_struct *tsk) 6152 { 6153 struct cgroup_subsys *ss; 6154 struct css_set *cset; 6155 int i; 6156 6157 spin_lock_irq(&css_set_lock); 6158 6159 WARN_ON_ONCE(list_empty(&tsk->cg_list)); 6160 cset = task_css_set(tsk); 6161 css_set_move_task(tsk, cset, NULL, false); 6162 list_add_tail(&tsk->cg_list, &cset->dying_tasks); 6163 cset->nr_tasks--; 6164 6165 WARN_ON_ONCE(cgroup_task_frozen(tsk)); 6166 if (unlikely(cgroup_task_freeze(tsk))) 6167 cgroup_update_frozen(task_dfl_cgroup(tsk)); 6168 6169 spin_unlock_irq(&css_set_lock); 6170 6171 /* see cgroup_post_fork() for details */ 6172 do_each_subsys_mask(ss, i, have_exit_callback) { 6173 ss->exit(tsk); 6174 } while_each_subsys_mask(); 6175 } 6176 6177 void cgroup_release(struct task_struct *task) 6178 { 6179 struct cgroup_subsys *ss; 6180 int ssid; 6181 6182 do_each_subsys_mask(ss, ssid, have_release_callback) { 6183 ss->release(task); 6184 } while_each_subsys_mask(); 6185 6186 spin_lock_irq(&css_set_lock); 6187 css_set_skip_task_iters(task_css_set(task), task); 6188 list_del_init(&task->cg_list); 6189 spin_unlock_irq(&css_set_lock); 6190 } 6191 6192 void cgroup_free(struct task_struct *task) 6193 { 6194 struct css_set *cset = task_css_set(task); 6195 put_css_set(cset); 6196 } 6197 6198 static int __init cgroup_disable(char *str) 6199 { 6200 struct cgroup_subsys *ss; 6201 char *token; 6202 int i; 6203 6204 while ((token = strsep(&str, ",")) != NULL) { 6205 if (!*token) 6206 continue; 6207 6208 for_each_subsys(ss, i) { 6209 if (strcmp(token, ss->name) && 6210 strcmp(token, ss->legacy_name)) 6211 continue; 6212 6213 static_branch_disable(cgroup_subsys_enabled_key[i]); 6214 pr_info("Disabling %s control group subsystem\n", 6215 ss->name); 6216 } 6217 } 6218 return 1; 6219 } 6220 __setup("cgroup_disable=", cgroup_disable); 6221 6222 void __init __weak enable_debug_cgroup(void) { } 6223 6224 static int __init enable_cgroup_debug(char *str) 6225 { 6226 cgroup_debug = true; 6227 enable_debug_cgroup(); 6228 return 1; 6229 } 6230 __setup("cgroup_debug", enable_cgroup_debug); 6231 6232 /** 6233 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry 6234 * @dentry: directory dentry of interest 6235 * @ss: subsystem of interest 6236 * 6237 * If @dentry is a directory for a cgroup which has @ss enabled on it, try 6238 * to get the corresponding css and return it. If such css doesn't exist 6239 * or can't be pinned, an ERR_PTR value is returned. 6240 */ 6241 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, 6242 struct cgroup_subsys *ss) 6243 { 6244 struct kernfs_node *kn = kernfs_node_from_dentry(dentry); 6245 struct file_system_type *s_type = dentry->d_sb->s_type; 6246 struct cgroup_subsys_state *css = NULL; 6247 struct cgroup *cgrp; 6248 6249 /* is @dentry a cgroup dir? */ 6250 if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) || 6251 !kn || kernfs_type(kn) != KERNFS_DIR) 6252 return ERR_PTR(-EBADF); 6253 6254 rcu_read_lock(); 6255 6256 /* 6257 * This path doesn't originate from kernfs and @kn could already 6258 * have been or be removed at any point. @kn->priv is RCU 6259 * protected for this access. See css_release_work_fn() for details. 6260 */ 6261 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv); 6262 if (cgrp) 6263 css = cgroup_css(cgrp, ss); 6264 6265 if (!css || !css_tryget_online(css)) 6266 css = ERR_PTR(-ENOENT); 6267 6268 rcu_read_unlock(); 6269 return css; 6270 } 6271 6272 /** 6273 * css_from_id - lookup css by id 6274 * @id: the cgroup id 6275 * @ss: cgroup subsys to be looked into 6276 * 6277 * Returns the css if there's valid one with @id, otherwise returns NULL. 6278 * Should be called under rcu_read_lock(). 6279 */ 6280 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss) 6281 { 6282 WARN_ON_ONCE(!rcu_read_lock_held()); 6283 return idr_find(&ss->css_idr, id); 6284 } 6285 6286 /** 6287 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path 6288 * @path: path on the default hierarchy 6289 * 6290 * Find the cgroup at @path on the default hierarchy, increment its 6291 * reference count and return it. Returns pointer to the found cgroup on 6292 * success, ERR_PTR(-ENOENT) if @path doesn't exist and ERR_PTR(-ENOTDIR) 6293 * if @path points to a non-directory. 6294 */ 6295 struct cgroup *cgroup_get_from_path(const char *path) 6296 { 6297 struct kernfs_node *kn; 6298 struct cgroup *cgrp; 6299 6300 mutex_lock(&cgroup_mutex); 6301 6302 kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path); 6303 if (kn) { 6304 if (kernfs_type(kn) == KERNFS_DIR) { 6305 cgrp = kn->priv; 6306 cgroup_get_live(cgrp); 6307 } else { 6308 cgrp = ERR_PTR(-ENOTDIR); 6309 } 6310 kernfs_put(kn); 6311 } else { 6312 cgrp = ERR_PTR(-ENOENT); 6313 } 6314 6315 mutex_unlock(&cgroup_mutex); 6316 return cgrp; 6317 } 6318 EXPORT_SYMBOL_GPL(cgroup_get_from_path); 6319 6320 /** 6321 * cgroup_get_from_fd - get a cgroup pointer from a fd 6322 * @fd: fd obtained by open(cgroup2_dir) 6323 * 6324 * Find the cgroup from a fd which should be obtained 6325 * by opening a cgroup directory. Returns a pointer to the 6326 * cgroup on success. ERR_PTR is returned if the cgroup 6327 * cannot be found. 6328 */ 6329 struct cgroup *cgroup_get_from_fd(int fd) 6330 { 6331 struct cgroup *cgrp; 6332 struct file *f; 6333 6334 f = fget_raw(fd); 6335 if (!f) 6336 return ERR_PTR(-EBADF); 6337 6338 cgrp = cgroup_get_from_file(f); 6339 fput(f); 6340 return cgrp; 6341 } 6342 EXPORT_SYMBOL_GPL(cgroup_get_from_fd); 6343 6344 static u64 power_of_ten(int power) 6345 { 6346 u64 v = 1; 6347 while (power--) 6348 v *= 10; 6349 return v; 6350 } 6351 6352 /** 6353 * cgroup_parse_float - parse a floating number 6354 * @input: input string 6355 * @dec_shift: number of decimal digits to shift 6356 * @v: output 6357 * 6358 * Parse a decimal floating point number in @input and store the result in 6359 * @v with decimal point right shifted @dec_shift times. For example, if 6360 * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345. 6361 * Returns 0 on success, -errno otherwise. 6362 * 6363 * There's nothing cgroup specific about this function except that it's 6364 * currently the only user. 6365 */ 6366 int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v) 6367 { 6368 s64 whole, frac = 0; 6369 int fstart = 0, fend = 0, flen; 6370 6371 if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend)) 6372 return -EINVAL; 6373 if (frac < 0) 6374 return -EINVAL; 6375 6376 flen = fend > fstart ? fend - fstart : 0; 6377 if (flen < dec_shift) 6378 frac *= power_of_ten(dec_shift - flen); 6379 else 6380 frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift)); 6381 6382 *v = whole * power_of_ten(dec_shift) + frac; 6383 return 0; 6384 } 6385 6386 /* 6387 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data 6388 * definition in cgroup-defs.h. 6389 */ 6390 #ifdef CONFIG_SOCK_CGROUP_DATA 6391 6392 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID) 6393 6394 DEFINE_SPINLOCK(cgroup_sk_update_lock); 6395 static bool cgroup_sk_alloc_disabled __read_mostly; 6396 6397 void cgroup_sk_alloc_disable(void) 6398 { 6399 if (cgroup_sk_alloc_disabled) 6400 return; 6401 pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n"); 6402 cgroup_sk_alloc_disabled = true; 6403 } 6404 6405 #else 6406 6407 #define cgroup_sk_alloc_disabled false 6408 6409 #endif 6410 6411 void cgroup_sk_alloc(struct sock_cgroup_data *skcd) 6412 { 6413 if (cgroup_sk_alloc_disabled) { 6414 skcd->no_refcnt = 1; 6415 return; 6416 } 6417 6418 /* Don't associate the sock with unrelated interrupted task's cgroup. */ 6419 if (in_interrupt()) 6420 return; 6421 6422 rcu_read_lock(); 6423 6424 while (true) { 6425 struct css_set *cset; 6426 6427 cset = task_css_set(current); 6428 if (likely(cgroup_tryget(cset->dfl_cgrp))) { 6429 skcd->val = (unsigned long)cset->dfl_cgrp; 6430 cgroup_bpf_get(cset->dfl_cgrp); 6431 break; 6432 } 6433 cpu_relax(); 6434 } 6435 6436 rcu_read_unlock(); 6437 } 6438 6439 void cgroup_sk_clone(struct sock_cgroup_data *skcd) 6440 { 6441 if (skcd->val) { 6442 if (skcd->no_refcnt) 6443 return; 6444 /* 6445 * We might be cloning a socket which is left in an empty 6446 * cgroup and the cgroup might have already been rmdir'd. 6447 * Don't use cgroup_get_live(). 6448 */ 6449 cgroup_get(sock_cgroup_ptr(skcd)); 6450 cgroup_bpf_get(sock_cgroup_ptr(skcd)); 6451 } 6452 } 6453 6454 void cgroup_sk_free(struct sock_cgroup_data *skcd) 6455 { 6456 struct cgroup *cgrp = sock_cgroup_ptr(skcd); 6457 6458 if (skcd->no_refcnt) 6459 return; 6460 cgroup_bpf_put(cgrp); 6461 cgroup_put(cgrp); 6462 } 6463 6464 #endif /* CONFIG_SOCK_CGROUP_DATA */ 6465 6466 #ifdef CONFIG_CGROUP_BPF 6467 int cgroup_bpf_attach(struct cgroup *cgrp, 6468 struct bpf_prog *prog, struct bpf_prog *replace_prog, 6469 struct bpf_cgroup_link *link, 6470 enum bpf_attach_type type, 6471 u32 flags) 6472 { 6473 int ret; 6474 6475 mutex_lock(&cgroup_mutex); 6476 ret = __cgroup_bpf_attach(cgrp, prog, replace_prog, link, type, flags); 6477 mutex_unlock(&cgroup_mutex); 6478 return ret; 6479 } 6480 6481 int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog, 6482 enum bpf_attach_type type) 6483 { 6484 int ret; 6485 6486 mutex_lock(&cgroup_mutex); 6487 ret = __cgroup_bpf_detach(cgrp, prog, NULL, type); 6488 mutex_unlock(&cgroup_mutex); 6489 return ret; 6490 } 6491 6492 int cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr, 6493 union bpf_attr __user *uattr) 6494 { 6495 int ret; 6496 6497 mutex_lock(&cgroup_mutex); 6498 ret = __cgroup_bpf_query(cgrp, attr, uattr); 6499 mutex_unlock(&cgroup_mutex); 6500 return ret; 6501 } 6502 #endif /* CONFIG_CGROUP_BPF */ 6503 6504 #ifdef CONFIG_SYSFS 6505 static ssize_t show_delegatable_files(struct cftype *files, char *buf, 6506 ssize_t size, const char *prefix) 6507 { 6508 struct cftype *cft; 6509 ssize_t ret = 0; 6510 6511 for (cft = files; cft && cft->name[0] != '\0'; cft++) { 6512 if (!(cft->flags & CFTYPE_NS_DELEGATABLE)) 6513 continue; 6514 6515 if (prefix) 6516 ret += snprintf(buf + ret, size - ret, "%s.", prefix); 6517 6518 ret += snprintf(buf + ret, size - ret, "%s\n", cft->name); 6519 6520 if (WARN_ON(ret >= size)) 6521 break; 6522 } 6523 6524 return ret; 6525 } 6526 6527 static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr, 6528 char *buf) 6529 { 6530 struct cgroup_subsys *ss; 6531 int ssid; 6532 ssize_t ret = 0; 6533 6534 ret = show_delegatable_files(cgroup_base_files, buf, PAGE_SIZE - ret, 6535 NULL); 6536 6537 for_each_subsys(ss, ssid) 6538 ret += show_delegatable_files(ss->dfl_cftypes, buf + ret, 6539 PAGE_SIZE - ret, 6540 cgroup_subsys_name[ssid]); 6541 6542 return ret; 6543 } 6544 static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate); 6545 6546 static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr, 6547 char *buf) 6548 { 6549 return snprintf(buf, PAGE_SIZE, 6550 "nsdelegate\n" 6551 "memory_localevents\n" 6552 "memory_recursiveprot\n"); 6553 } 6554 static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features); 6555 6556 static struct attribute *cgroup_sysfs_attrs[] = { 6557 &cgroup_delegate_attr.attr, 6558 &cgroup_features_attr.attr, 6559 NULL, 6560 }; 6561 6562 static const struct attribute_group cgroup_sysfs_attr_group = { 6563 .attrs = cgroup_sysfs_attrs, 6564 .name = "cgroup", 6565 }; 6566 6567 static int __init cgroup_sysfs_init(void) 6568 { 6569 return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group); 6570 } 6571 subsys_initcall(cgroup_sysfs_init); 6572 6573 #endif /* CONFIG_SYSFS */ 6574