include/linux/cgroup.h

   1 #ifndef _LINUX_CGROUP_H
   2 #define _LINUX_CGROUP_H
   3 /*
   4  *  cgroup interface
   5  *
   6  *  Copyright (C) 2003 BULL SA
   7  *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
   8  *
   9  */
  10
  11 #include <linux/sched.h>
  12 #include <linux/cpumask.h>
  13 #include <linux/nodemask.h>
  14 #include <linux/rculist.h>
  15 #include <linux/cgroupstats.h>
  16 #include <linux/fs.h>
  17 #include <linux/seq_file.h>
  18 #include <linux/kernfs.h>
  19 #include <linux/jump_label.h>
  20 #include <linux/types.h>
  21 #include <linux/ns_common.h>
  22 #include <linux/nsproxy.h>
  23 #include <linux/user_namespace.h>
  24 #include <linux/refcount.h>
  25
  26 #include <linux/cgroup-defs.h>
  27
  28 #ifdef CONFIG_CGROUPS
  29
  30 /*
  31  * All weight knobs on the default hierarhcy should use the following min,
  32  * default and max values.  The default value is the logarithmic center of
  33  * MIN and MAX and allows 100x to be expressed in both directions.
  34  */
  35 #define CGROUP_WEIGHT_MIN               1
  36 #define CGROUP_WEIGHT_DFL               100
  37 #define CGROUP_WEIGHT_MAX               10000
  38
  39 /* a css_task_iter should be treated as an opaque object */
  40 struct css_task_iter {
  41         struct cgroup_subsys            *ss;
  42
  43         struct list_head                *cset_pos;
  44         struct list_head                *cset_head;
  45
  46         struct list_head                *task_pos;
  47         struct list_head                *tasks_head;
  48         struct list_head                *mg_tasks_head;
  49
  50         struct css_set                  *cur_cset;
  51         struct task_struct              *cur_task;
  52         struct list_head                iters_node;     /* css_set->task_iters */
  53 };
  54
  55 extern struct cgroup_root cgrp_dfl_root;
  56 extern struct css_set init_css_set;
  57
  58 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
  59 #include <linux/cgroup_subsys.h>
  60 #undef SUBSYS
  61
  62 #define SUBSYS(_x)                                                              \
  63         extern struct static_key_true _x ## _cgrp_subsys_enabled_key;           \
  64         extern struct static_key_true _x ## _cgrp_subsys_on_dfl_key;
  65 #include <linux/cgroup_subsys.h>
  66 #undef SUBSYS
  67
  68 /**
  69  * cgroup_subsys_enabled - fast test on whether a subsys is enabled
  70  * @ss: subsystem in question
  71  */
  72 #define cgroup_subsys_enabled(ss)                                               \
  73         static_branch_likely(&ss ## _enabled_key)
  74
  75 /**
  76  * cgroup_subsys_on_dfl - fast test on whether a subsys is on default hierarchy
  77  * @ss: subsystem in question
  78  */
  79 #define cgroup_subsys_on_dfl(ss)                                                \
  80         static_branch_likely(&ss ## _on_dfl_key)
  81
  82 bool css_has_online_children(struct cgroup_subsys_state *css);
  83 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
  84 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
  85                                              struct cgroup_subsys *ss);
  86 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
  87                                                        struct cgroup_subsys *ss);
  88
  89 struct cgroup *cgroup_get_from_path(const char *path);
  90 struct cgroup *cgroup_get_from_fd(int fd);
  91
  92 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
  93 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
  94
  95 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
  96 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
  97 int cgroup_rm_cftypes(struct cftype *cfts);
  98 void cgroup_file_notify(struct cgroup_file *cfile);
  99
 100 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
 101 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
 102 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
 103                      struct pid *pid, struct task_struct *tsk);
 104
 105 void cgroup_fork(struct task_struct *p);
 106 extern int cgroup_can_fork(struct task_struct *p);
 107 extern void cgroup_cancel_fork(struct task_struct *p);
 108 extern void cgroup_post_fork(struct task_struct *p);
 109 void cgroup_exit(struct task_struct *p);
 110 void cgroup_free(struct task_struct *p);
 111
 112 int cgroup_init_early(void);
 113 int cgroup_init(void);
 114
 115 /*
 116  * Iteration helpers and macros.
 117  */
 118
 119 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
 120                                            struct cgroup_subsys_state *parent);
 121 struct cgroup_subsys_state *css_next_descendant_pre(struct cgroup_subsys_state *pos,
 122                                                     struct cgroup_subsys_state *css);
 123 struct cgroup_subsys_state *css_rightmost_descendant(struct cgroup_subsys_state *pos);
 124 struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos,
 125                                                      struct cgroup_subsys_state *css);
 126
 127 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
 128                                          struct cgroup_subsys_state **dst_cssp);
 129 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
 130                                         struct cgroup_subsys_state **dst_cssp);
 131
 132 void css_task_iter_start(struct cgroup_subsys_state *css,
 133                          struct css_task_iter *it);
 134 struct task_struct *css_task_iter_next(struct css_task_iter *it);
 135 void css_task_iter_end(struct css_task_iter *it);
 136
 137 /**
 138  * css_for_each_child - iterate through children of a css
 139  * @pos: the css * to use as the loop cursor
 140  * @parent: css whose children to walk
 141  *
 142  * Walk @parent's children.  Must be called under rcu_read_lock().
 143  *
 144  * If a subsystem synchronizes ->css_online() and the start of iteration, a
 145  * css which finished ->css_online() is guaranteed to be visible in the
 146  * future iterations and will stay visible until the last reference is put.
 147  * A css which hasn't finished ->css_online() or already finished
 148  * ->css_offline() may show up during traversal.  It's each subsystem's
 149  * responsibility to synchronize against on/offlining.
 150  *
 151  * It is allowed to temporarily drop RCU read lock during iteration.  The
 152  * caller is responsible for ensuring that @pos remains accessible until
 153  * the start of the next iteration by, for example, bumping the css refcnt.
 154  */
 155 #define css_for_each_child(pos, parent)                                 \
 156         for ((pos) = css_next_child(NULL, (parent)); (pos);             \
 157              (pos) = css_next_child((pos), (parent)))
 158
 159 /**
 160  * css_for_each_descendant_pre - pre-order walk of a css's descendants
 161  * @pos: the css * to use as the loop cursor
 162  * @root: css whose descendants to walk
 163  *
 164  * Walk @root's descendants.  @root is included in the iteration and the
 165  * first node to be visited.  Must be called under rcu_read_lock().
 166  *
 167  * If a subsystem synchronizes ->css_online() and the start of iteration, a
 168  * css which finished ->css_online() is guaranteed to be visible in the
 169  * future iterations and will stay visible until the last reference is put.
 170  * A css which hasn't finished ->css_online() or already finished
 171  * ->css_offline() may show up during traversal.  It's each subsystem's
 172  * responsibility to synchronize against on/offlining.
 173  *
 174  * For example, the following guarantees that a descendant can't escape
 175  * state updates of its ancestors.
 176  *
 177  * my_online(@css)
 178  * {
 179  *      Lock @css's parent and @css;
 180  *      Inherit state from the parent;
 181  *      Unlock both.
 182  * }
 183  *
 184  * my_update_state(@css)
 185  * {
 186  *      css_for_each_descendant_pre(@pos, @css) {
 187  *              Lock @pos;
 188  *              if (@pos == @css)
 189  *                      Update @css's state;
 190  *              else
 191  *                      Verify @pos is alive and inherit state from its parent;
 192  *              Unlock @pos;
 193  *      }
 194  * }
 195  *
 196  * As long as the inheriting step, including checking the parent state, is
 197  * enclosed inside @pos locking, double-locking the parent isn't necessary
 198  * while inheriting.  The state update to the parent is guaranteed to be
 199  * visible by walking order and, as long as inheriting operations to the
 200  * same @pos are atomic to each other, multiple updates racing each other
 201  * still result in the correct state.  It's guaranateed that at least one
 202  * inheritance happens for any css after the latest update to its parent.
 203  *
 204  * If checking parent's state requires locking the parent, each inheriting
 205  * iteration should lock and unlock both @pos->parent and @pos.
 206  *
 207  * Alternatively, a subsystem may choose to use a single global lock to
 208  * synchronize ->css_online() and ->css_offline() against tree-walking
 209  * operations.
 210  *
 211  * It is allowed to temporarily drop RCU read lock during iteration.  The
 212  * caller is responsible for ensuring that @pos remains accessible until
 213  * the start of the next iteration by, for example, bumping the css refcnt.
 214  */
 215 #define css_for_each_descendant_pre(pos, css)                           \
 216         for ((pos) = css_next_descendant_pre(NULL, (css)); (pos);       \
 217              (pos) = css_next_descendant_pre((pos), (css)))
 218
 219 /**
 220  * css_for_each_descendant_post - post-order walk of a css's descendants
 221  * @pos: the css * to use as the loop cursor
 222  * @css: css whose descendants to walk
 223  *
 224  * Similar to css_for_each_descendant_pre() but performs post-order
 225  * traversal instead.  @root is included in the iteration and the last
 226  * node to be visited.
 227  *
 228  * If a subsystem synchronizes ->css_online() and the start of iteration, a
 229  * css which finished ->css_online() is guaranteed to be visible in the
 230  * future iterations and will stay visible until the last reference is put.
 231  * A css which hasn't finished ->css_online() or already finished
 232  * ->css_offline() may show up during traversal.  It's each subsystem's
 233  * responsibility to synchronize against on/offlining.
 234  *
 235  * Note that the walk visibility guarantee example described in pre-order
 236  * walk doesn't apply the same to post-order walks.
 237  */
 238 #define css_for_each_descendant_post(pos, css)                          \
 239         for ((pos) = css_next_descendant_post(NULL, (css)); (pos);      \
 240              (pos) = css_next_descendant_post((pos), (css)))
 241
 242 /**
 243  * cgroup_taskset_for_each - iterate cgroup_taskset
 244  * @task: the loop cursor
 245  * @dst_css: the destination css
 246  * @tset: taskset to iterate
 247  *
 248  * @tset may contain multiple tasks and they may belong to multiple
 249  * processes.
 250  *
 251  * On the v2 hierarchy, there may be tasks from multiple processes and they
 252  * may not share the source or destination csses.
 253  *
 254  * On traditional hierarchies, when there are multiple tasks in @tset, if a
 255  * task of a process is in @tset, all tasks of the process are in @tset.
 256  * Also, all are guaranteed to share the same source and destination csses.
 257  *
 258  * Iteration is not in any specific order.
 259  */
 260 #define cgroup_taskset_for_each(task, dst_css, tset)                    \
 261         for ((task) = cgroup_taskset_first((tset), &(dst_css));         \
 262              (task);                                                    \
 263              (task) = cgroup_taskset_next((tset), &(dst_css)))
 264
 265 /**
 266  * cgroup_taskset_for_each_leader - iterate group leaders in a cgroup_taskset
 267  * @leader: the loop cursor
 268  * @dst_css: the destination css
 269  * @tset: taskset to iterate
 270  *
 271  * Iterate threadgroup leaders of @tset.  For single-task migrations, @tset
 272  * may not contain any.
 273  */
 274 #define cgroup_taskset_for_each_leader(leader, dst_css, tset)           \
 275         for ((leader) = cgroup_taskset_first((tset), &(dst_css));       \
 276              (leader);                                                  \
 277              (leader) = cgroup_taskset_next((tset), &(dst_css)))        \
 278                 if ((leader) != (leader)->group_leader)                 \
 279                         ;                                               \
 280                 else
 281
 282 /*
 283  * Inline functions.
 284  */
 285
 286 /**
 287  * css_get - obtain a reference on the specified css
 288  * @css: target css
 289  *
 290  * The caller must already have a reference.
 291  */
 292 static inline void css_get(struct cgroup_subsys_state *css)
 293 {
 294         if (!(css->flags & CSS_NO_REF))
 295                 percpu_ref_get(&css->refcnt);
 296 }
 297
 298 /**
 299  * css_get_many - obtain references on the specified css
 300  * @css: target css
 301  * @n: number of references to get
 302  *
 303  * The caller must already have a reference.
 304  */
 305 static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n)
 306 {
 307         if (!(css->flags & CSS_NO_REF))
 308                 percpu_ref_get_many(&css->refcnt, n);
 309 }
 310
 311 /**
 312  * css_tryget - try to obtain a reference on the specified css
 313  * @css: target css
 314  *
 315  * Obtain a reference on @css unless it already has reached zero and is
 316  * being released.  This function doesn't care whether @css is on or
 317  * offline.  The caller naturally needs to ensure that @css is accessible
 318  * but doesn't have to be holding a reference on it - IOW, RCU protected
 319  * access is good enough for this function.  Returns %true if a reference
 320  * count was successfully obtained; %false otherwise.
 321  */
 322 static inline bool css_tryget(struct cgroup_subsys_state *css)
 323 {
 324         if (!(css->flags & CSS_NO_REF))
 325                 return percpu_ref_tryget(&css->refcnt);
 326         return true;
 327 }
 328
 329 /**
 330  * css_tryget_online - try to obtain a reference on the specified css if online
 331  * @css: target css
 332  *
 333  * Obtain a reference on @css if it's online.  The caller naturally needs
 334  * to ensure that @css is accessible but doesn't have to be holding a
 335  * reference on it - IOW, RCU protected access is good enough for this
 336  * function.  Returns %true if a reference count was successfully obtained;
 337  * %false otherwise.
 338  */
 339 static inline bool css_tryget_online(struct cgroup_subsys_state *css)
 340 {
 341         if (!(css->flags & CSS_NO_REF))
 342                 return percpu_ref_tryget_live(&css->refcnt);
 343         return true;
 344 }
 345
 346 /**
 347  * css_is_dying - test whether the specified css is dying
 348  * @css: target css
 349  *
 350  * Test whether @css is in the process of offlining or already offline.  In
 351  * most cases, ->css_online() and ->css_offline() callbacks should be
 352  * enough; however, the actual offline operations are RCU delayed and this
 353  * test returns %true also when @css is scheduled to be offlined.
 354  *
 355  * This is useful, for example, when the use case requires synchronous
 356  * behavior with respect to cgroup removal.  cgroup removal schedules css
 357  * offlining but the css can seem alive while the operation is being
 358  * delayed.  If the delay affects user visible semantics, this test can be
 359  * used to resolve the situation.
 360  */
 361 static inline bool css_is_dying(struct cgroup_subsys_state *css)
 362 {
 363         return !(css->flags & CSS_NO_REF) && percpu_ref_is_dying(&css->refcnt);
 364 }
 365
 366 /**
 367  * css_put - put a css reference
 368  * @css: target css
 369  *
 370  * Put a reference obtained via css_get() and css_tryget_online().
 371  */
 372 static inline void css_put(struct cgroup_subsys_state *css)
 373 {
 374         if (!(css->flags & CSS_NO_REF))
 375                 percpu_ref_put(&css->refcnt);
 376 }
 377
 378 /**
 379  * css_put_many - put css references
 380  * @css: target css
 381  * @n: number of references to put
 382  *
 383  * Put references obtained via css_get() and css_tryget_online().
 384  */
 385 static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
 386 {
 387         if (!(css->flags & CSS_NO_REF))
 388                 percpu_ref_put_many(&css->refcnt, n);
 389 }
 390
 391 static inline void cgroup_put(struct cgroup *cgrp)
 392 {
 393         css_put(&cgrp->self);
 394 }
 395
 396 /**
 397  * task_css_set_check - obtain a task's css_set with extra access conditions
 398  * @task: the task to obtain css_set for
 399  * @__c: extra condition expression to be passed to rcu_dereference_check()
 400  *
 401  * A task's css_set is RCU protected, initialized and exited while holding
 402  * task_lock(), and can only be modified while holding both cgroup_mutex
 403  * and task_lock() while the task is alive.  This macro verifies that the
 404  * caller is inside proper critical section and returns @task's css_set.
 405  *
 406  * The caller can also specify additional allowed conditions via @__c, such
 407  * as locks used during the cgroup_subsys::attach() methods.
 408  */
 409 #ifdef CONFIG_PROVE_RCU
 410 extern struct mutex cgroup_mutex;
 411 extern spinlock_t css_set_lock;
 412 #define task_css_set_check(task, __c)                                   \
 413         rcu_dereference_check((task)->cgroups,                          \
 414                 lockdep_is_held(&cgroup_mutex) ||                       \
 415                 lockdep_is_held(&css_set_lock) ||                       \
 416                 ((task)->flags & PF_EXITING) || (__c))
 417 #else
 418 #define task_css_set_check(task, __c)                                   \
 419         rcu_dereference((task)->cgroups)
 420 #endif
 421
 422 /**
 423  * task_css_check - obtain css for (task, subsys) w/ extra access conds
 424  * @task: the target task
 425  * @subsys_id: the target subsystem ID
 426  * @__c: extra condition expression to be passed to rcu_dereference_check()
 427  *
 428  * Return the cgroup_subsys_state for the (@task, @subsys_id) pair.  The
 429  * synchronization rules are the same as task_css_set_check().
 430  */
 431 #define task_css_check(task, subsys_id, __c)                            \
 432         task_css_set_check((task), (__c))->subsys[(subsys_id)]
 433
 434 /**
 435  * task_css_set - obtain a task's css_set
 436  * @task: the task to obtain css_set for
 437  *
 438  * See task_css_set_check().
 439  */
 440 static inline struct css_set *task_css_set(struct task_struct *task)
 441 {
 442         return task_css_set_check(task, false);
 443 }
 444
 445 /**
 446  * task_css - obtain css for (task, subsys)
 447  * @task: the target task
 448  * @subsys_id: the target subsystem ID
 449  *
 450  * See task_css_check().
 451  */
 452 static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
 453                                                    int subsys_id)
 454 {
 455         return task_css_check(task, subsys_id, false);
 456 }
 457
 458 /**
 459  * task_get_css - find and get the css for (task, subsys)
 460  * @task: the target task
 461  * @subsys_id: the target subsystem ID
 462  *
 463  * Find the css for the (@task, @subsys_id) combination, increment a
 464  * reference on and return it.  This function is guaranteed to return a
 465  * valid css.
 466  */
 467 static inline struct cgroup_subsys_state *
 468 task_get_css(struct task_struct *task, int subsys_id)
 469 {
 470         struct cgroup_subsys_state *css;
 471
 472         rcu_read_lock();
 473         while (true) {
 474                 css = task_css(task, subsys_id);
 475                 if (likely(css_tryget_online(css)))
 476                         break;
 477                 cpu_relax();
 478         }
 479         rcu_read_unlock();
 480         return css;
 481 }
 482
 483 /**
 484  * task_css_is_root - test whether a task belongs to the root css
 485  * @task: the target task
 486  * @subsys_id: the target subsystem ID
 487  *
 488  * Test whether @task belongs to the root css on the specified subsystem.
 489  * May be invoked in any context.
 490  */
 491 static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
 492 {
 493         return task_css_check(task, subsys_id, true) ==
 494                 init_css_set.subsys[subsys_id];
 495 }
 496
 497 static inline struct cgroup *task_cgroup(struct task_struct *task,
 498                                          int subsys_id)
 499 {
 500         return task_css(task, subsys_id)->cgroup;
 501 }
 502
 503 /**
 504  * cgroup_is_descendant - test ancestry
 505  * @cgrp: the cgroup to be tested
 506  * @ancestor: possible ancestor of @cgrp
 507  *
 508  * Test whether @cgrp is a descendant of @ancestor.  It also returns %true
 509  * if @cgrp == @ancestor.  This function is safe to call as long as @cgrp
 510  * and @ancestor are accessible.
 511  */
 512 static inline bool cgroup_is_descendant(struct cgroup *cgrp,
 513                                         struct cgroup *ancestor)
 514 {
 515         if (cgrp->root != ancestor->root || cgrp->level < ancestor->level)
 516                 return false;
 517         return cgrp->ancestor_ids[ancestor->level] == ancestor->id;
 518 }
 519
 520 /**
 521  * task_under_cgroup_hierarchy - test task's membership of cgroup ancestry
 522  * @task: the task to be tested
 523  * @ancestor: possible ancestor of @task's cgroup
 524  *
 525  * Tests whether @task's default cgroup hierarchy is a descendant of @ancestor.
 526  * It follows all the same rules as cgroup_is_descendant, and only applies
 527  * to the default hierarchy.
 528  */
 529 static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
 530                                                struct cgroup *ancestor)
 531 {
 532         struct css_set *cset = task_css_set(task);
 533
 534         return cgroup_is_descendant(cset->dfl_cgrp, ancestor);
 535 }
 536
 537 /* no synchronization, the result can only be used as a hint */
 538 static inline bool cgroup_is_populated(struct cgroup *cgrp)
 539 {
 540         return cgrp->populated_cnt;
 541 }
 542
 543 /* returns ino associated with a cgroup */
 544 static inline ino_t cgroup_ino(struct cgroup *cgrp)
 545 {
 546         return cgrp->kn->ino;
 547 }
 548
 549 /* cft/css accessors for cftype->write() operation */
 550 static inline struct cftype *of_cft(struct kernfs_open_file *of)
 551 {
 552         return of->kn->priv;
 553 }
 554
 555 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of);
 556
 557 /* cft/css accessors for cftype->seq_*() operations */
 558 static inline struct cftype *seq_cft(struct seq_file *seq)
 559 {
 560         return of_cft(seq->private);
 561 }
 562
 563 static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
 564 {
 565         return of_css(seq->private);
 566 }
 567
 568 /*
 569  * Name / path handling functions.  All are thin wrappers around the kernfs
 570  * counterparts and can be called under any context.
 571  */
 572
 573 static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
 574 {
 575         return kernfs_name(cgrp->kn, buf, buflen);
 576 }
 577
 578 static inline int cgroup_path(struct cgroup *cgrp, char *buf, size_t buflen)
 579 {
 580         return kernfs_path(cgrp->kn, buf, buflen);
 581 }
 582
 583 static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
 584 {
 585         pr_cont_kernfs_name(cgrp->kn);
 586 }
 587
 588 static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
 589 {
 590         pr_cont_kernfs_path(cgrp->kn);
 591 }
 592
 593 static inline void cgroup_init_kthreadd(void)
 594 {
 595         /*
 596          * kthreadd is inherited by all kthreads, keep it in the root so
 597          * that the new kthreads are guaranteed to stay in the root until
 598          * initialization is finished.
 599          */
 600         current->no_cgroup_migration = 1;
 601 }
 602
 603 static inline void cgroup_kthread_ready(void)
 604 {
 605         /*
 606          * This kthread finished initialization.  The creator should have
 607          * set PF_NO_SETAFFINITY if this kthread should stay in the root.
 608          */
 609         current->no_cgroup_migration = 0;
 610 }
 611
 612 #else /* !CONFIG_CGROUPS */
 613
 614 struct cgroup_subsys_state;
 615 struct cgroup;
 616
 617 static inline void css_put(struct cgroup_subsys_state *css) {}
 618 static inline int cgroup_attach_task_all(struct task_struct *from,
 619                                          struct task_struct *t) { return 0; }
 620 static inline int cgroupstats_build(struct cgroupstats *stats,
 621                                     struct dentry *dentry) { return -EINVAL; }
 622
 623 static inline void cgroup_fork(struct task_struct *p) {}
 624 static inline int cgroup_can_fork(struct task_struct *p) { return 0; }
 625 static inline void cgroup_cancel_fork(struct task_struct *p) {}
 626 static inline void cgroup_post_fork(struct task_struct *p) {}
 627 static inline void cgroup_exit(struct task_struct *p) {}
 628 static inline void cgroup_free(struct task_struct *p) {}
 629
 630 static inline int cgroup_init_early(void) { return 0; }
 631 static inline int cgroup_init(void) { return 0; }
 632 static inline void cgroup_init_kthreadd(void) {}
 633 static inline void cgroup_kthread_ready(void) {}
 634
 635 static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
 636                                                struct cgroup *ancestor)
 637 {
 638         return true;
 639 }
 640 #endif /* !CONFIG_CGROUPS */
 641
 642 /*
 643  * sock->sk_cgrp_data handling.  For more info, see sock_cgroup_data
 644  * definition in cgroup-defs.h.
 645  */
 646 #ifdef CONFIG_SOCK_CGROUP_DATA
 647
 648 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
 649 extern spinlock_t cgroup_sk_update_lock;
 650 #endif
 651
 652 void cgroup_sk_alloc_disable(void);
 653 void cgroup_sk_alloc(struct sock_cgroup_data *skcd);
 654 void cgroup_sk_free(struct sock_cgroup_data *skcd);
 655
 656 static inline struct cgroup *sock_cgroup_ptr(struct sock_cgroup_data *skcd)
 657 {
 658 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
 659         unsigned long v;
 660
 661         /*
 662          * @skcd->val is 64bit but the following is safe on 32bit too as we
 663          * just need the lower ulong to be written and read atomically.
 664          */
 665         v = READ_ONCE(skcd->val);
 666
 667         if (v & 1)
 668                 return &cgrp_dfl_root.cgrp;
 669
 670         return (struct cgroup *)(unsigned long)v ?: &cgrp_dfl_root.cgrp;
 671 #else
 672         return (struct cgroup *)(unsigned long)skcd->val;
 673 #endif
 674 }
 675
 676 #else   /* CONFIG_CGROUP_DATA */
 677
 678 static inline void cgroup_sk_alloc(struct sock_cgroup_data *skcd) {}
 679 static inline void cgroup_sk_free(struct sock_cgroup_data *skcd) {}
 680
 681 #endif  /* CONFIG_CGROUP_DATA */
 682
 683 struct cgroup_namespace {
 684         refcount_t              count;
 685         struct ns_common        ns;
 686         struct user_namespace   *user_ns;
 687         struct ucounts          *ucounts;
 688         struct css_set          *root_cset;
 689 };
 690
 691 extern struct cgroup_namespace init_cgroup_ns;
 692
 693 #ifdef CONFIG_CGROUPS
 694
 695 void free_cgroup_ns(struct cgroup_namespace *ns);
 696
 697 struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
 698                                         struct user_namespace *user_ns,
 699                                         struct cgroup_namespace *old_ns);
 700
 701 int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
 702                    struct cgroup_namespace *ns);
 703
 704 #else /* !CONFIG_CGROUPS */
 705
 706 static inline void free_cgroup_ns(struct cgroup_namespace *ns) { }
 707 static inline struct cgroup_namespace *
 708 copy_cgroup_ns(unsigned long flags, struct user_namespace *user_ns,
 709                struct cgroup_namespace *old_ns)
 710 {
 711         return old_ns;
 712 }
 713
 714 #endif /* !CONFIG_CGROUPS */
 715
 716 static inline void get_cgroup_ns(struct cgroup_namespace *ns)
 717 {
 718         if (ns)
 719                 refcount_inc(&ns->count);
 720 }
 721
 722 static inline void put_cgroup_ns(struct cgroup_namespace *ns)
 723 {
 724         if (ns && refcount_dec_and_test(&ns->count))
 725                 free_cgroup_ns(ns);
 726 }
 727
 728 #endif /* _LINUX_CGROUP_H */