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Linux/include/linux/cgroup.h

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  2 #ifndef _LINUX_CGROUP_H
  3 #define _LINUX_CGROUP_H
  4 /*
  5  *  cgroup interface
  6  *
  7  *  Copyright (C) 2003 BULL SA
  8  *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
  9  *
 10  */
 11 
 12 #include <linux/sched.h>
 13 #include <linux/cpumask.h>
 14 #include <linux/nodemask.h>
 15 #include <linux/rculist.h>
 16 #include <linux/cgroupstats.h>
 17 #include <linux/fs.h>
 18 #include <linux/seq_file.h>
 19 #include <linux/kernfs.h>
 20 #include <linux/jump_label.h>
 21 #include <linux/types.h>
 22 #include <linux/ns_common.h>
 23 #include <linux/nsproxy.h>
 24 #include <linux/user_namespace.h>
 25 #include <linux/refcount.h>
 26 #include <linux/kernel_stat.h>
 27 
 28 #include <linux/cgroup-defs.h>
 29 
 30 #ifdef CONFIG_CGROUPS
 31 
 32 /*
 33  * All weight knobs on the default hierarhcy should use the following min,
 34  * default and max values.  The default value is the logarithmic center of
 35  * MIN and MAX and allows 100x to be expressed in both directions.
 36  */
 37 #define CGROUP_WEIGHT_MIN               1
 38 #define CGROUP_WEIGHT_DFL               100
 39 #define CGROUP_WEIGHT_MAX               10000
 40 
 41 /* walk only threadgroup leaders */
 42 #define CSS_TASK_ITER_PROCS             (1U << 0)
 43 /* walk all threaded css_sets in the domain */
 44 #define CSS_TASK_ITER_THREADED          (1U << 1)
 45 
 46 /* a css_task_iter should be treated as an opaque object */
 47 struct css_task_iter {
 48         struct cgroup_subsys            *ss;
 49         unsigned int                    flags;
 50 
 51         struct list_head                *cset_pos;
 52         struct list_head                *cset_head;
 53 
 54         struct list_head                *tcset_pos;
 55         struct list_head                *tcset_head;
 56 
 57         struct list_head                *task_pos;
 58         struct list_head                *tasks_head;
 59         struct list_head                *mg_tasks_head;
 60 
 61         struct css_set                  *cur_cset;
 62         struct css_set                  *cur_dcset;
 63         struct task_struct              *cur_task;
 64         struct list_head                iters_node;     /* css_set->task_iters */
 65 };
 66 
 67 extern struct cgroup_root cgrp_dfl_root;
 68 extern struct css_set init_css_set;
 69 
 70 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
 71 #include <linux/cgroup_subsys.h>
 72 #undef SUBSYS
 73 
 74 #define SUBSYS(_x)                                                              \
 75         extern struct static_key_true _x ## _cgrp_subsys_enabled_key;           \
 76         extern struct static_key_true _x ## _cgrp_subsys_on_dfl_key;
 77 #include <linux/cgroup_subsys.h>
 78 #undef SUBSYS
 79 
 80 /**
 81  * cgroup_subsys_enabled - fast test on whether a subsys is enabled
 82  * @ss: subsystem in question
 83  */
 84 #define cgroup_subsys_enabled(ss)                                               \
 85         static_branch_likely(&ss ## _enabled_key)
 86 
 87 /**
 88  * cgroup_subsys_on_dfl - fast test on whether a subsys is on default hierarchy
 89  * @ss: subsystem in question
 90  */
 91 #define cgroup_subsys_on_dfl(ss)                                                \
 92         static_branch_likely(&ss ## _on_dfl_key)
 93 
 94 bool css_has_online_children(struct cgroup_subsys_state *css);
 95 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
 96 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
 97                                              struct cgroup_subsys *ss);
 98 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
 99                                                        struct cgroup_subsys *ss);
100 
101 struct cgroup *cgroup_get_from_path(const char *path);
102 struct cgroup *cgroup_get_from_fd(int fd);
103 
104 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
105 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
106 
107 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
108 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
109 int cgroup_rm_cftypes(struct cftype *cfts);
110 void cgroup_file_notify(struct cgroup_file *cfile);
111 
112 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
113 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
114 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
115                      struct pid *pid, struct task_struct *tsk);
116 
117 void cgroup_fork(struct task_struct *p);
118 extern int cgroup_can_fork(struct task_struct *p);
119 extern void cgroup_cancel_fork(struct task_struct *p);
120 extern void cgroup_post_fork(struct task_struct *p);
121 void cgroup_exit(struct task_struct *p);
122 void cgroup_free(struct task_struct *p);
123 
124 int cgroup_init_early(void);
125 int cgroup_init(void);
126 
127 /*
128  * Iteration helpers and macros.
129  */
130 
131 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
132                                            struct cgroup_subsys_state *parent);
133 struct cgroup_subsys_state *css_next_descendant_pre(struct cgroup_subsys_state *pos,
134                                                     struct cgroup_subsys_state *css);
135 struct cgroup_subsys_state *css_rightmost_descendant(struct cgroup_subsys_state *pos);
136 struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos,
137                                                      struct cgroup_subsys_state *css);
138 
139 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
140                                          struct cgroup_subsys_state **dst_cssp);
141 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
142                                         struct cgroup_subsys_state **dst_cssp);
143 
144 void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
145                          struct css_task_iter *it);
146 struct task_struct *css_task_iter_next(struct css_task_iter *it);
147 void css_task_iter_end(struct css_task_iter *it);
148 
149 /**
150  * css_for_each_child - iterate through children of a css
151  * @pos: the css * to use as the loop cursor
152  * @parent: css whose children to walk
153  *
154  * Walk @parent's children.  Must be called under rcu_read_lock().
155  *
156  * If a subsystem synchronizes ->css_online() and the start of iteration, a
157  * css which finished ->css_online() is guaranteed to be visible in the
158  * future iterations and will stay visible until the last reference is put.
159  * A css which hasn't finished ->css_online() or already finished
160  * ->css_offline() may show up during traversal.  It's each subsystem's
161  * responsibility to synchronize against on/offlining.
162  *
163  * It is allowed to temporarily drop RCU read lock during iteration.  The
164  * caller is responsible for ensuring that @pos remains accessible until
165  * the start of the next iteration by, for example, bumping the css refcnt.
166  */
167 #define css_for_each_child(pos, parent)                                 \
168         for ((pos) = css_next_child(NULL, (parent)); (pos);             \
169              (pos) = css_next_child((pos), (parent)))
170 
171 /**
172  * css_for_each_descendant_pre - pre-order walk of a css's descendants
173  * @pos: the css * to use as the loop cursor
174  * @root: css whose descendants to walk
175  *
176  * Walk @root's descendants.  @root is included in the iteration and the
177  * first node to be visited.  Must be called under rcu_read_lock().
178  *
179  * If a subsystem synchronizes ->css_online() and the start of iteration, a
180  * css which finished ->css_online() is guaranteed to be visible in the
181  * future iterations and will stay visible until the last reference is put.
182  * A css which hasn't finished ->css_online() or already finished
183  * ->css_offline() may show up during traversal.  It's each subsystem's
184  * responsibility to synchronize against on/offlining.
185  *
186  * For example, the following guarantees that a descendant can't escape
187  * state updates of its ancestors.
188  *
189  * my_online(@css)
190  * {
191  *      Lock @css's parent and @css;
192  *      Inherit state from the parent;
193  *      Unlock both.
194  * }
195  *
196  * my_update_state(@css)
197  * {
198  *      css_for_each_descendant_pre(@pos, @css) {
199  *              Lock @pos;
200  *              if (@pos == @css)
201  *                      Update @css's state;
202  *              else
203  *                      Verify @pos is alive and inherit state from its parent;
204  *              Unlock @pos;
205  *      }
206  * }
207  *
208  * As long as the inheriting step, including checking the parent state, is
209  * enclosed inside @pos locking, double-locking the parent isn't necessary
210  * while inheriting.  The state update to the parent is guaranteed to be
211  * visible by walking order and, as long as inheriting operations to the
212  * same @pos are atomic to each other, multiple updates racing each other
213  * still result in the correct state.  It's guaranateed that at least one
214  * inheritance happens for any css after the latest update to its parent.
215  *
216  * If checking parent's state requires locking the parent, each inheriting
217  * iteration should lock and unlock both @pos->parent and @pos.
218  *
219  * Alternatively, a subsystem may choose to use a single global lock to
220  * synchronize ->css_online() and ->css_offline() against tree-walking
221  * operations.
222  *
223  * It is allowed to temporarily drop RCU read lock during iteration.  The
224  * caller is responsible for ensuring that @pos remains accessible until
225  * the start of the next iteration by, for example, bumping the css refcnt.
226  */
227 #define css_for_each_descendant_pre(pos, css)                           \
228         for ((pos) = css_next_descendant_pre(NULL, (css)); (pos);       \
229              (pos) = css_next_descendant_pre((pos), (css)))
230 
231 /**
232  * css_for_each_descendant_post - post-order walk of a css's descendants
233  * @pos: the css * to use as the loop cursor
234  * @css: css whose descendants to walk
235  *
236  * Similar to css_for_each_descendant_pre() but performs post-order
237  * traversal instead.  @root is included in the iteration and the last
238  * node to be visited.
239  *
240  * If a subsystem synchronizes ->css_online() and the start of iteration, a
241  * css which finished ->css_online() is guaranteed to be visible in the
242  * future iterations and will stay visible until the last reference is put.
243  * A css which hasn't finished ->css_online() or already finished
244  * ->css_offline() may show up during traversal.  It's each subsystem's
245  * responsibility to synchronize against on/offlining.
246  *
247  * Note that the walk visibility guarantee example described in pre-order
248  * walk doesn't apply the same to post-order walks.
249  */
250 #define css_for_each_descendant_post(pos, css)                          \
251         for ((pos) = css_next_descendant_post(NULL, (css)); (pos);      \
252              (pos) = css_next_descendant_post((pos), (css)))
253 
254 /**
255  * cgroup_taskset_for_each - iterate cgroup_taskset
256  * @task: the loop cursor
257  * @dst_css: the destination css
258  * @tset: taskset to iterate
259  *
260  * @tset may contain multiple tasks and they may belong to multiple
261  * processes.
262  *
263  * On the v2 hierarchy, there may be tasks from multiple processes and they
264  * may not share the source or destination csses.
265  *
266  * On traditional hierarchies, when there are multiple tasks in @tset, if a
267  * task of a process is in @tset, all tasks of the process are in @tset.
268  * Also, all are guaranteed to share the same source and destination csses.
269  *
270  * Iteration is not in any specific order.
271  */
272 #define cgroup_taskset_for_each(task, dst_css, tset)                    \
273         for ((task) = cgroup_taskset_first((tset), &(dst_css));         \
274              (task);                                                    \
275              (task) = cgroup_taskset_next((tset), &(dst_css)))
276 
277 /**
278  * cgroup_taskset_for_each_leader - iterate group leaders in a cgroup_taskset
279  * @leader: the loop cursor
280  * @dst_css: the destination css
281  * @tset: taskset to iterate
282  *
283  * Iterate threadgroup leaders of @tset.  For single-task migrations, @tset
284  * may not contain any.
285  */
286 #define cgroup_taskset_for_each_leader(leader, dst_css, tset)           \
287         for ((leader) = cgroup_taskset_first((tset), &(dst_css));       \
288              (leader);                                                  \
289              (leader) = cgroup_taskset_next((tset), &(dst_css)))        \
290                 if ((leader) != (leader)->group_leader)                 \
291                         ;                                               \
292                 else
293 
294 /*
295  * Inline functions.
296  */
297 
298 /**
299  * css_get - obtain a reference on the specified css
300  * @css: target css
301  *
302  * The caller must already have a reference.
303  */
304 static inline void css_get(struct cgroup_subsys_state *css)
305 {
306         if (!(css->flags & CSS_NO_REF))
307                 percpu_ref_get(&css->refcnt);
308 }
309 
310 /**
311  * css_get_many - obtain references on the specified css
312  * @css: target css
313  * @n: number of references to get
314  *
315  * The caller must already have a reference.
316  */
317 static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n)
318 {
319         if (!(css->flags & CSS_NO_REF))
320                 percpu_ref_get_many(&css->refcnt, n);
321 }
322 
323 /**
324  * css_tryget - try to obtain a reference on the specified css
325  * @css: target css
326  *
327  * Obtain a reference on @css unless it already has reached zero and is
328  * being released.  This function doesn't care whether @css is on or
329  * offline.  The caller naturally needs to ensure that @css is accessible
330  * but doesn't have to be holding a reference on it - IOW, RCU protected
331  * access is good enough for this function.  Returns %true if a reference
332  * count was successfully obtained; %false otherwise.
333  */
334 static inline bool css_tryget(struct cgroup_subsys_state *css)
335 {
336         if (!(css->flags & CSS_NO_REF))
337                 return percpu_ref_tryget(&css->refcnt);
338         return true;
339 }
340 
341 /**
342  * css_tryget_online - try to obtain a reference on the specified css if online
343  * @css: target css
344  *
345  * Obtain a reference on @css if it's online.  The caller naturally needs
346  * to ensure that @css is accessible but doesn't have to be holding a
347  * reference on it - IOW, RCU protected access is good enough for this
348  * function.  Returns %true if a reference count was successfully obtained;
349  * %false otherwise.
350  */
351 static inline bool css_tryget_online(struct cgroup_subsys_state *css)
352 {
353         if (!(css->flags & CSS_NO_REF))
354                 return percpu_ref_tryget_live(&css->refcnt);
355         return true;
356 }
357 
358 /**
359  * css_is_dying - test whether the specified css is dying
360  * @css: target css
361  *
362  * Test whether @css is in the process of offlining or already offline.  In
363  * most cases, ->css_online() and ->css_offline() callbacks should be
364  * enough; however, the actual offline operations are RCU delayed and this
365  * test returns %true also when @css is scheduled to be offlined.
366  *
367  * This is useful, for example, when the use case requires synchronous
368  * behavior with respect to cgroup removal.  cgroup removal schedules css
369  * offlining but the css can seem alive while the operation is being
370  * delayed.  If the delay affects user visible semantics, this test can be
371  * used to resolve the situation.
372  */
373 static inline bool css_is_dying(struct cgroup_subsys_state *css)
374 {
375         return !(css->flags & CSS_NO_REF) && percpu_ref_is_dying(&css->refcnt);
376 }
377 
378 /**
379  * css_put - put a css reference
380  * @css: target css
381  *
382  * Put a reference obtained via css_get() and css_tryget_online().
383  */
384 static inline void css_put(struct cgroup_subsys_state *css)
385 {
386         if (!(css->flags & CSS_NO_REF))
387                 percpu_ref_put(&css->refcnt);
388 }
389 
390 /**
391  * css_put_many - put css references
392  * @css: target css
393  * @n: number of references to put
394  *
395  * Put references obtained via css_get() and css_tryget_online().
396  */
397 static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
398 {
399         if (!(css->flags & CSS_NO_REF))
400                 percpu_ref_put_many(&css->refcnt, n);
401 }
402 
403 static inline void cgroup_get(struct cgroup *cgrp)
404 {
405         css_get(&cgrp->self);
406 }
407 
408 static inline bool cgroup_tryget(struct cgroup *cgrp)
409 {
410         return css_tryget(&cgrp->self);
411 }
412 
413 static inline void cgroup_put(struct cgroup *cgrp)
414 {
415         css_put(&cgrp->self);
416 }
417 
418 /**
419  * task_css_set_check - obtain a task's css_set with extra access conditions
420  * @task: the task to obtain css_set for
421  * @__c: extra condition expression to be passed to rcu_dereference_check()
422  *
423  * A task's css_set is RCU protected, initialized and exited while holding
424  * task_lock(), and can only be modified while holding both cgroup_mutex
425  * and task_lock() while the task is alive.  This macro verifies that the
426  * caller is inside proper critical section and returns @task's css_set.
427  *
428  * The caller can also specify additional allowed conditions via @__c, such
429  * as locks used during the cgroup_subsys::attach() methods.
430  */
431 #ifdef CONFIG_PROVE_RCU
432 extern struct mutex cgroup_mutex;
433 extern spinlock_t css_set_lock;
434 #define task_css_set_check(task, __c)                                   \
435         rcu_dereference_check((task)->cgroups,                          \
436                 lockdep_is_held(&cgroup_mutex) ||                       \
437                 lockdep_is_held(&css_set_lock) ||                       \
438                 ((task)->flags & PF_EXITING) || (__c))
439 #else
440 #define task_css_set_check(task, __c)                                   \
441         rcu_dereference((task)->cgroups)
442 #endif
443 
444 /**
445  * task_css_check - obtain css for (task, subsys) w/ extra access conds
446  * @task: the target task
447  * @subsys_id: the target subsystem ID
448  * @__c: extra condition expression to be passed to rcu_dereference_check()
449  *
450  * Return the cgroup_subsys_state for the (@task, @subsys_id) pair.  The
451  * synchronization rules are the same as task_css_set_check().
452  */
453 #define task_css_check(task, subsys_id, __c)                            \
454         task_css_set_check((task), (__c))->subsys[(subsys_id)]
455 
456 /**
457  * task_css_set - obtain a task's css_set
458  * @task: the task to obtain css_set for
459  *
460  * See task_css_set_check().
461  */
462 static inline struct css_set *task_css_set(struct task_struct *task)
463 {
464         return task_css_set_check(task, false);
465 }
466 
467 /**
468  * task_css - obtain css for (task, subsys)
469  * @task: the target task
470  * @subsys_id: the target subsystem ID
471  *
472  * See task_css_check().
473  */
474 static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
475                                                    int subsys_id)
476 {
477         return task_css_check(task, subsys_id, false);
478 }
479 
480 /**
481  * task_get_css - find and get the css for (task, subsys)
482  * @task: the target task
483  * @subsys_id: the target subsystem ID
484  *
485  * Find the css for the (@task, @subsys_id) combination, increment a
486  * reference on and return it.  This function is guaranteed to return a
487  * valid css.
488  */
489 static inline struct cgroup_subsys_state *
490 task_get_css(struct task_struct *task, int subsys_id)
491 {
492         struct cgroup_subsys_state *css;
493 
494         rcu_read_lock();
495         while (true) {
496                 css = task_css(task, subsys_id);
497                 if (likely(css_tryget_online(css)))
498                         break;
499                 cpu_relax();
500         }
501         rcu_read_unlock();
502         return css;
503 }
504 
505 /**
506  * task_css_is_root - test whether a task belongs to the root css
507  * @task: the target task
508  * @subsys_id: the target subsystem ID
509  *
510  * Test whether @task belongs to the root css on the specified subsystem.
511  * May be invoked in any context.
512  */
513 static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
514 {
515         return task_css_check(task, subsys_id, true) ==
516                 init_css_set.subsys[subsys_id];
517 }
518 
519 static inline struct cgroup *task_cgroup(struct task_struct *task,
520                                          int subsys_id)
521 {
522         return task_css(task, subsys_id)->cgroup;
523 }
524 
525 static inline struct cgroup *task_dfl_cgroup(struct task_struct *task)
526 {
527         return task_css_set(task)->dfl_cgrp;
528 }
529 
530 static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
531 {
532         struct cgroup_subsys_state *parent_css = cgrp->self.parent;
533 
534         if (parent_css)
535                 return container_of(parent_css, struct cgroup, self);
536         return NULL;
537 }
538 
539 /**
540  * cgroup_is_descendant - test ancestry
541  * @cgrp: the cgroup to be tested
542  * @ancestor: possible ancestor of @cgrp
543  *
544  * Test whether @cgrp is a descendant of @ancestor.  It also returns %true
545  * if @cgrp == @ancestor.  This function is safe to call as long as @cgrp
546  * and @ancestor are accessible.
547  */
548 static inline bool cgroup_is_descendant(struct cgroup *cgrp,
549                                         struct cgroup *ancestor)
550 {
551         if (cgrp->root != ancestor->root || cgrp->level < ancestor->level)
552                 return false;
553         return cgrp->ancestor_ids[ancestor->level] == ancestor->id;
554 }
555 
556 /**
557  * task_under_cgroup_hierarchy - test task's membership of cgroup ancestry
558  * @task: the task to be tested
559  * @ancestor: possible ancestor of @task's cgroup
560  *
561  * Tests whether @task's default cgroup hierarchy is a descendant of @ancestor.
562  * It follows all the same rules as cgroup_is_descendant, and only applies
563  * to the default hierarchy.
564  */
565 static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
566                                                struct cgroup *ancestor)
567 {
568         struct css_set *cset = task_css_set(task);
569 
570         return cgroup_is_descendant(cset->dfl_cgrp, ancestor);
571 }
572 
573 /* no synchronization, the result can only be used as a hint */
574 static inline bool cgroup_is_populated(struct cgroup *cgrp)
575 {
576         return cgrp->nr_populated_csets + cgrp->nr_populated_domain_children +
577                 cgrp->nr_populated_threaded_children;
578 }
579 
580 /* returns ino associated with a cgroup */
581 static inline ino_t cgroup_ino(struct cgroup *cgrp)
582 {
583         return cgrp->kn->id.ino;
584 }
585 
586 /* cft/css accessors for cftype->write() operation */
587 static inline struct cftype *of_cft(struct kernfs_open_file *of)
588 {
589         return of->kn->priv;
590 }
591 
592 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of);
593 
594 /* cft/css accessors for cftype->seq_*() operations */
595 static inline struct cftype *seq_cft(struct seq_file *seq)
596 {
597         return of_cft(seq->private);
598 }
599 
600 static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
601 {
602         return of_css(seq->private);
603 }
604 
605 /*
606  * Name / path handling functions.  All are thin wrappers around the kernfs
607  * counterparts and can be called under any context.
608  */
609 
610 static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
611 {
612         return kernfs_name(cgrp->kn, buf, buflen);
613 }
614 
615 static inline int cgroup_path(struct cgroup *cgrp, char *buf, size_t buflen)
616 {
617         return kernfs_path(cgrp->kn, buf, buflen);
618 }
619 
620 static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
621 {
622         pr_cont_kernfs_name(cgrp->kn);
623 }
624 
625 static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
626 {
627         pr_cont_kernfs_path(cgrp->kn);
628 }
629 
630 static inline void cgroup_init_kthreadd(void)
631 {
632         /*
633          * kthreadd is inherited by all kthreads, keep it in the root so
634          * that the new kthreads are guaranteed to stay in the root until
635          * initialization is finished.
636          */
637         current->no_cgroup_migration = 1;
638 }
639 
640 static inline void cgroup_kthread_ready(void)
641 {
642         /*
643          * This kthread finished initialization.  The creator should have
644          * set PF_NO_SETAFFINITY if this kthread should stay in the root.
645          */
646         current->no_cgroup_migration = 0;
647 }
648 
649 static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp)
650 {
651         return &cgrp->kn->id;
652 }
653 
654 void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
655                                         char *buf, size_t buflen);
656 #else /* !CONFIG_CGROUPS */
657 
658 struct cgroup_subsys_state;
659 struct cgroup;
660 
661 static inline void css_put(struct cgroup_subsys_state *css) {}
662 static inline int cgroup_attach_task_all(struct task_struct *from,
663                                          struct task_struct *t) { return 0; }
664 static inline int cgroupstats_build(struct cgroupstats *stats,
665                                     struct dentry *dentry) { return -EINVAL; }
666 
667 static inline void cgroup_fork(struct task_struct *p) {}
668 static inline int cgroup_can_fork(struct task_struct *p) { return 0; }
669 static inline void cgroup_cancel_fork(struct task_struct *p) {}
670 static inline void cgroup_post_fork(struct task_struct *p) {}
671 static inline void cgroup_exit(struct task_struct *p) {}
672 static inline void cgroup_free(struct task_struct *p) {}
673 
674 static inline int cgroup_init_early(void) { return 0; }
675 static inline int cgroup_init(void) { return 0; }
676 static inline void cgroup_init_kthreadd(void) {}
677 static inline void cgroup_kthread_ready(void) {}
678 static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp)
679 {
680         return NULL;
681 }
682 
683 static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
684                                                struct cgroup *ancestor)
685 {
686         return true;
687 }
688 
689 static inline void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
690         char *buf, size_t buflen) {}
691 #endif /* !CONFIG_CGROUPS */
692 
693 #ifdef CONFIG_CGROUPS
694 /*
695  * cgroup scalable recursive statistics.
696  */
697 void cgroup_rstat_updated(struct cgroup *cgrp, int cpu);
698 void cgroup_rstat_flush(struct cgroup *cgrp);
699 void cgroup_rstat_flush_irqsafe(struct cgroup *cgrp);
700 void cgroup_rstat_flush_hold(struct cgroup *cgrp);
701 void cgroup_rstat_flush_release(void);
702 
703 /*
704  * Basic resource stats.
705  */
706 #ifdef CONFIG_CGROUP_CPUACCT
707 void cpuacct_charge(struct task_struct *tsk, u64 cputime);
708 void cpuacct_account_field(struct task_struct *tsk, int index, u64 val);
709 #else
710 static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime) {}
711 static inline void cpuacct_account_field(struct task_struct *tsk, int index,
712                                          u64 val) {}
713 #endif
714 
715 void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec);
716 void __cgroup_account_cputime_field(struct cgroup *cgrp,
717                                     enum cpu_usage_stat index, u64 delta_exec);
718 
719 static inline void cgroup_account_cputime(struct task_struct *task,
720                                           u64 delta_exec)
721 {
722         struct cgroup *cgrp;
723 
724         cpuacct_charge(task, delta_exec);
725 
726         rcu_read_lock();
727         cgrp = task_dfl_cgroup(task);
728         if (cgroup_parent(cgrp))
729                 __cgroup_account_cputime(cgrp, delta_exec);
730         rcu_read_unlock();
731 }
732 
733 static inline void cgroup_account_cputime_field(struct task_struct *task,
734                                                 enum cpu_usage_stat index,
735                                                 u64 delta_exec)
736 {
737         struct cgroup *cgrp;
738 
739         cpuacct_account_field(task, index, delta_exec);
740 
741         rcu_read_lock();
742         cgrp = task_dfl_cgroup(task);
743         if (cgroup_parent(cgrp))
744                 __cgroup_account_cputime_field(cgrp, index, delta_exec);
745         rcu_read_unlock();
746 }
747 
748 #else   /* CONFIG_CGROUPS */
749 
750 static inline void cgroup_account_cputime(struct task_struct *task,
751                                           u64 delta_exec) {}
752 static inline void cgroup_account_cputime_field(struct task_struct *task,
753                                                 enum cpu_usage_stat index,
754                                                 u64 delta_exec) {}
755 
756 #endif  /* CONFIG_CGROUPS */
757 
758 /*
759  * sock->sk_cgrp_data handling.  For more info, see sock_cgroup_data
760  * definition in cgroup-defs.h.
761  */
762 #ifdef CONFIG_SOCK_CGROUP_DATA
763 
764 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
765 extern spinlock_t cgroup_sk_update_lock;
766 #endif
767 
768 void cgroup_sk_alloc_disable(void);
769 void cgroup_sk_alloc(struct sock_cgroup_data *skcd);
770 void cgroup_sk_free(struct sock_cgroup_data *skcd);
771 
772 static inline struct cgroup *sock_cgroup_ptr(struct sock_cgroup_data *skcd)
773 {
774 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
775         unsigned long v;
776 
777         /*
778          * @skcd->val is 64bit but the following is safe on 32bit too as we
779          * just need the lower ulong to be written and read atomically.
780          */
781         v = READ_ONCE(skcd->val);
782 
783         if (v & 1)
784                 return &cgrp_dfl_root.cgrp;
785 
786         return (struct cgroup *)(unsigned long)v ?: &cgrp_dfl_root.cgrp;
787 #else
788         return (struct cgroup *)(unsigned long)skcd->val;
789 #endif
790 }
791 
792 #else   /* CONFIG_CGROUP_DATA */
793 
794 static inline void cgroup_sk_alloc(struct sock_cgroup_data *skcd) {}
795 static inline void cgroup_sk_free(struct sock_cgroup_data *skcd) {}
796 
797 #endif  /* CONFIG_CGROUP_DATA */
798 
799 struct cgroup_namespace {
800         refcount_t              count;
801         struct ns_common        ns;
802         struct user_namespace   *user_ns;
803         struct ucounts          *ucounts;
804         struct css_set          *root_cset;
805 };
806 
807 extern struct cgroup_namespace init_cgroup_ns;
808 
809 #ifdef CONFIG_CGROUPS
810 
811 void free_cgroup_ns(struct cgroup_namespace *ns);
812 
813 struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
814                                         struct user_namespace *user_ns,
815                                         struct cgroup_namespace *old_ns);
816 
817 int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
818                    struct cgroup_namespace *ns);
819 
820 #else /* !CONFIG_CGROUPS */
821 
822 static inline void free_cgroup_ns(struct cgroup_namespace *ns) { }
823 static inline struct cgroup_namespace *
824 copy_cgroup_ns(unsigned long flags, struct user_namespace *user_ns,
825                struct cgroup_namespace *old_ns)
826 {
827         return old_ns;
828 }
829 
830 #endif /* !CONFIG_CGROUPS */
831 
832 static inline void get_cgroup_ns(struct cgroup_namespace *ns)
833 {
834         if (ns)
835                 refcount_inc(&ns->count);
836 }
837 
838 static inline void put_cgroup_ns(struct cgroup_namespace *ns)
839 {
840         if (ns && refcount_dec_and_test(&ns->count))
841                 free_cgroup_ns(ns);
842 }
843 
844 #endif /* _LINUX_CGROUP_H */
845 

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