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/rwsem.h>
  17 #include <linux/fs.h>
  18 #include <linux/seq_file.h>
  19 #include <linux/kernfs.h>
  20
  21 #include <linux/cgroup-defs.h>
  22
  23 #ifdef CONFIG_CGROUPS
  24
  25 /* a css_task_iter should be treated as an opaque object */
  26 struct css_task_iter {
  27         struct cgroup_subsys            *ss;
  28
  29         struct list_head                *cset_pos;
  30         struct list_head                *cset_head;
  31
  32         struct list_head                *task_pos;
  33         struct list_head                *tasks_head;
  34         struct list_head                *mg_tasks_head;
  35 };
  36
  37 extern struct cgroup_root cgrp_dfl_root;
  38 extern struct css_set init_css_set;
  39
  40 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
  41 #include <linux/cgroup_subsys.h>
  42 #undef SUBSYS
  43
  44 bool css_has_online_children(struct cgroup_subsys_state *css);
  45 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
  46 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
  47                                              struct cgroup_subsys *ss);
  48 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
  49                                                        struct cgroup_subsys *ss);
  50
  51 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
  52 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
  53 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
  54
  55 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
  56 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
  57 int cgroup_rm_cftypes(struct cftype *cfts);
  58
  59 char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
  60 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
  61 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
  62                      struct pid *pid, struct task_struct *tsk);
  63
  64 void cgroup_fork(struct task_struct *p);
  65 void cgroup_post_fork(struct task_struct *p);
  66 void cgroup_exit(struct task_struct *p);
  67
  68 int cgroup_init_early(void);
  69 int cgroup_init(void);
  70
  71 /*
  72  * Iteration helpers and macros.
  73  */
  74
  75 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
  76                                            struct cgroup_subsys_state *parent);
  77 struct cgroup_subsys_state *css_next_descendant_pre(struct cgroup_subsys_state *pos,
  78                                                     struct cgroup_subsys_state *css);
  79 struct cgroup_subsys_state *css_rightmost_descendant(struct cgroup_subsys_state *pos);
  80 struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos,
  81                                                      struct cgroup_subsys_state *css);
  82
  83 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
  84 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
  85
  86 void css_task_iter_start(struct cgroup_subsys_state *css,
  87                          struct css_task_iter *it);
  88 struct task_struct *css_task_iter_next(struct css_task_iter *it);
  89 void css_task_iter_end(struct css_task_iter *it);
  90
  91 /**
  92  * css_for_each_child - iterate through children of a css
  93  * @pos: the css * to use as the loop cursor
  94  * @parent: css whose children to walk
  95  *
  96  * Walk @parent's children.  Must be called under rcu_read_lock().
  97  *
  98  * If a subsystem synchronizes ->css_online() and the start of iteration, a
  99  * css which finished ->css_online() is guaranteed to be visible in the
 100  * future iterations and will stay visible until the last reference is put.
 101  * A css which hasn't finished ->css_online() or already finished
 102  * ->css_offline() may show up during traversal.  It's each subsystem's
 103  * responsibility to synchronize against on/offlining.
 104  *
 105  * It is allowed to temporarily drop RCU read lock during iteration.  The
 106  * caller is responsible for ensuring that @pos remains accessible until
 107  * the start of the next iteration by, for example, bumping the css refcnt.
 108  */
 109 #define css_for_each_child(pos, parent)                                 \
 110         for ((pos) = css_next_child(NULL, (parent)); (pos);             \
 111              (pos) = css_next_child((pos), (parent)))
 112
 113 /**
 114  * css_for_each_descendant_pre - pre-order walk of a css's descendants
 115  * @pos: the css * to use as the loop cursor
 116  * @root: css whose descendants to walk
 117  *
 118  * Walk @root's descendants.  @root is included in the iteration and the
 119  * first node to be visited.  Must be called under rcu_read_lock().
 120  *
 121  * If a subsystem synchronizes ->css_online() and the start of iteration, a
 122  * css which finished ->css_online() is guaranteed to be visible in the
 123  * future iterations and will stay visible until the last reference is put.
 124  * A css which hasn't finished ->css_online() or already finished
 125  * ->css_offline() may show up during traversal.  It's each subsystem's
 126  * responsibility to synchronize against on/offlining.
 127  *
 128  * For example, the following guarantees that a descendant can't escape
 129  * state updates of its ancestors.
 130  *
 131  * my_online(@css)
 132  * {
 133  *      Lock @css's parent and @css;
 134  *      Inherit state from the parent;
 135  *      Unlock both.
 136  * }
 137  *
 138  * my_update_state(@css)
 139  * {
 140  *      css_for_each_descendant_pre(@pos, @css) {
 141  *              Lock @pos;
 142  *              if (@pos == @css)
 143  *                      Update @css's state;
 144  *              else
 145  *                      Verify @pos is alive and inherit state from its parent;
 146  *              Unlock @pos;
 147  *      }
 148  * }
 149  *
 150  * As long as the inheriting step, including checking the parent state, is
 151  * enclosed inside @pos locking, double-locking the parent isn't necessary
 152  * while inheriting.  The state update to the parent is guaranteed to be
 153  * visible by walking order and, as long as inheriting operations to the
 154  * same @pos are atomic to each other, multiple updates racing each other
 155  * still result in the correct state.  It's guaranateed that at least one
 156  * inheritance happens for any css after the latest update to its parent.
 157  *
 158  * If checking parent's state requires locking the parent, each inheriting
 159  * iteration should lock and unlock both @pos->parent and @pos.
 160  *
 161  * Alternatively, a subsystem may choose to use a single global lock to
 162  * synchronize ->css_online() and ->css_offline() against tree-walking
 163  * operations.
 164  *
 165  * It is allowed to temporarily drop RCU read lock during iteration.  The
 166  * caller is responsible for ensuring that @pos remains accessible until
 167  * the start of the next iteration by, for example, bumping the css refcnt.
 168  */
 169 #define css_for_each_descendant_pre(pos, css)                           \
 170         for ((pos) = css_next_descendant_pre(NULL, (css)); (pos);       \
 171              (pos) = css_next_descendant_pre((pos), (css)))
 172
 173 /**
 174  * css_for_each_descendant_post - post-order walk of a css's descendants
 175  * @pos: the css * to use as the loop cursor
 176  * @css: css whose descendants to walk
 177  *
 178  * Similar to css_for_each_descendant_pre() but performs post-order
 179  * traversal instead.  @root is included in the iteration and the last
 180  * node to be visited.
 181  *
 182  * If a subsystem synchronizes ->css_online() and the start of iteration, a
 183  * css which finished ->css_online() is guaranteed to be visible in the
 184  * future iterations and will stay visible until the last reference is put.
 185  * A css which hasn't finished ->css_online() or already finished
 186  * ->css_offline() may show up during traversal.  It's each subsystem's
 187  * responsibility to synchronize against on/offlining.
 188  *
 189  * Note that the walk visibility guarantee example described in pre-order
 190  * walk doesn't apply the same to post-order walks.
 191  */
 192 #define css_for_each_descendant_post(pos, css)                          \
 193         for ((pos) = css_next_descendant_post(NULL, (css)); (pos);      \
 194              (pos) = css_next_descendant_post((pos), (css)))
 195
 196 /**
 197  * cgroup_taskset_for_each - iterate cgroup_taskset
 198  * @task: the loop cursor
 199  * @tset: taskset to iterate
 200  */
 201 #define cgroup_taskset_for_each(task, tset)                             \
 202         for ((task) = cgroup_taskset_first((tset)); (task);             \
 203              (task) = cgroup_taskset_next((tset)))
 204
 205 /*
 206  * Inline functions.
 207  */
 208
 209 /**
 210  * css_get - obtain a reference on the specified css
 211  * @css: target css
 212  *
 213  * The caller must already have a reference.
 214  */
 215 static inline void css_get(struct cgroup_subsys_state *css)
 216 {
 217         if (!(css->flags & CSS_NO_REF))
 218                 percpu_ref_get(&css->refcnt);
 219 }
 220
 221 /**
 222  * css_get_many - obtain references on the specified css
 223  * @css: target css
 224  * @n: number of references to get
 225  *
 226  * The caller must already have a reference.
 227  */
 228 static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n)
 229 {
 230         if (!(css->flags & CSS_NO_REF))
 231                 percpu_ref_get_many(&css->refcnt, n);
 232 }
 233
 234 /**
 235  * css_tryget - try to obtain a reference on the specified css
 236  * @css: target css
 237  *
 238  * Obtain a reference on @css unless it already has reached zero and is
 239  * being released.  This function doesn't care whether @css is on or
 240  * offline.  The caller naturally needs to ensure that @css is accessible
 241  * but doesn't have to be holding a reference on it - IOW, RCU protected
 242  * access is good enough for this function.  Returns %true if a reference
 243  * count was successfully obtained; %false otherwise.
 244  */
 245 static inline bool css_tryget(struct cgroup_subsys_state *css)
 246 {
 247         if (!(css->flags & CSS_NO_REF))
 248                 return percpu_ref_tryget(&css->refcnt);
 249         return true;
 250 }
 251
 252 /**
 253  * css_tryget_online - try to obtain a reference on the specified css if online
 254  * @css: target css
 255  *
 256  * Obtain a reference on @css if it's online.  The caller naturally needs
 257  * to ensure that @css is accessible but doesn't have to be holding a
 258  * reference on it - IOW, RCU protected access is good enough for this
 259  * function.  Returns %true if a reference count was successfully obtained;
 260  * %false otherwise.
 261  */
 262 static inline bool css_tryget_online(struct cgroup_subsys_state *css)
 263 {
 264         if (!(css->flags & CSS_NO_REF))
 265                 return percpu_ref_tryget_live(&css->refcnt);
 266         return true;
 267 }
 268
 269 /**
 270  * css_put - put a css reference
 271  * @css: target css
 272  *
 273  * Put a reference obtained via css_get() and css_tryget_online().
 274  */
 275 static inline void css_put(struct cgroup_subsys_state *css)
 276 {
 277         if (!(css->flags & CSS_NO_REF))
 278                 percpu_ref_put(&css->refcnt);
 279 }
 280
 281 /**
 282  * css_put_many - put css references
 283  * @css: target css
 284  * @n: number of references to put
 285  *
 286  * Put references obtained via css_get() and css_tryget_online().
 287  */
 288 static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
 289 {
 290         if (!(css->flags & CSS_NO_REF))
 291                 percpu_ref_put_many(&css->refcnt, n);
 292 }
 293
 294 /**
 295  * task_css_set_check - obtain a task's css_set with extra access conditions
 296  * @task: the task to obtain css_set for
 297  * @__c: extra condition expression to be passed to rcu_dereference_check()
 298  *
 299  * A task's css_set is RCU protected, initialized and exited while holding
 300  * task_lock(), and can only be modified while holding both cgroup_mutex
 301  * and task_lock() while the task is alive.  This macro verifies that the
 302  * caller is inside proper critical section and returns @task's css_set.
 303  *
 304  * The caller can also specify additional allowed conditions via @__c, such
 305  * as locks used during the cgroup_subsys::attach() methods.
 306  */
 307 #ifdef CONFIG_PROVE_RCU
 308 extern struct mutex cgroup_mutex;
 309 extern struct rw_semaphore css_set_rwsem;
 310 #define task_css_set_check(task, __c)                                   \
 311         rcu_dereference_check((task)->cgroups,                          \
 312                 lockdep_is_held(&cgroup_mutex) ||                       \
 313                 lockdep_is_held(&css_set_rwsem) ||                      \
 314                 ((task)->flags & PF_EXITING) || (__c))
 315 #else
 316 #define task_css_set_check(task, __c)                                   \
 317         rcu_dereference((task)->cgroups)
 318 #endif
 319
 320 /**
 321  * task_css_check - obtain css for (task, subsys) w/ extra access conds
 322  * @task: the target task
 323  * @subsys_id: the target subsystem ID
 324  * @__c: extra condition expression to be passed to rcu_dereference_check()
 325  *
 326  * Return the cgroup_subsys_state for the (@task, @subsys_id) pair.  The
 327  * synchronization rules are the same as task_css_set_check().
 328  */
 329 #define task_css_check(task, subsys_id, __c)                            \
 330         task_css_set_check((task), (__c))->subsys[(subsys_id)]
 331
 332 /**
 333  * task_css_set - obtain a task's css_set
 334  * @task: the task to obtain css_set for
 335  *
 336  * See task_css_set_check().
 337  */
 338 static inline struct css_set *task_css_set(struct task_struct *task)
 339 {
 340         return task_css_set_check(task, false);
 341 }
 342
 343 /**
 344  * task_css - obtain css for (task, subsys)
 345  * @task: the target task
 346  * @subsys_id: the target subsystem ID
 347  *
 348  * See task_css_check().
 349  */
 350 static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
 351                                                    int subsys_id)
 352 {
 353         return task_css_check(task, subsys_id, false);
 354 }
 355
 356 /**
 357  * task_get_css - find and get the css for (task, subsys)
 358  * @task: the target task
 359  * @subsys_id: the target subsystem ID
 360  *
 361  * Find the css for the (@task, @subsys_id) combination, increment a
 362  * reference on and return it.  This function is guaranteed to return a
 363  * valid css.
 364  */
 365 static inline struct cgroup_subsys_state *
 366 task_get_css(struct task_struct *task, int subsys_id)
 367 {
 368         struct cgroup_subsys_state *css;
 369
 370         rcu_read_lock();
 371         while (true) {
 372                 css = task_css(task, subsys_id);
 373                 if (likely(css_tryget_online(css)))
 374                         break;
 375                 cpu_relax();
 376         }
 377         rcu_read_unlock();
 378         return css;
 379 }
 380
 381 /**
 382  * task_css_is_root - test whether a task belongs to the root css
 383  * @task: the target task
 384  * @subsys_id: the target subsystem ID
 385  *
 386  * Test whether @task belongs to the root css on the specified subsystem.
 387  * May be invoked in any context.
 388  */
 389 static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
 390 {
 391         return task_css_check(task, subsys_id, true) ==
 392                 init_css_set.subsys[subsys_id];
 393 }
 394
 395 static inline struct cgroup *task_cgroup(struct task_struct *task,
 396                                          int subsys_id)
 397 {
 398         return task_css(task, subsys_id)->cgroup;
 399 }
 400
 401 /**
 402  * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
 403  * @cgrp: the cgroup of interest
 404  *
 405  * The default hierarchy is the v2 interface of cgroup and this function
 406  * can be used to test whether a cgroup is on the default hierarchy for
 407  * cases where a subsystem should behave differnetly depending on the
 408  * interface version.
 409  *
 410  * The set of behaviors which change on the default hierarchy are still
 411  * being determined and the mount option is prefixed with __DEVEL__.
 412  *
 413  * List of changed behaviors:
 414  *
 415  * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
 416  *   and "name" are disallowed.
 417  *
 418  * - When mounting an existing superblock, mount options should match.
 419  *
 420  * - Remount is disallowed.
 421  *
 422  * - rename(2) is disallowed.
 423  *
 424  * - "tasks" is removed.  Everything should be at process granularity.  Use
 425  *   "cgroup.procs" instead.
 426  *
 427  * - "cgroup.procs" is not sorted.  pids will be unique unless they got
 428  *   recycled inbetween reads.
 429  *
 430  * - "release_agent" and "notify_on_release" are removed.  Replacement
 431  *   notification mechanism will be implemented.
 432  *
 433  * - "cgroup.clone_children" is removed.
 434  *
 435  * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup
 436  *   and its descendants contain no task; otherwise, 1.  The file also
 437  *   generates kernfs notification which can be monitored through poll and
 438  *   [di]notify when the value of the file changes.
 439  *
 440  * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
 441  *   take masks of ancestors with non-empty cpus/mems, instead of being
 442  *   moved to an ancestor.
 443  *
 444  * - cpuset: a task can be moved into an empty cpuset, and again it takes
 445  *   masks of ancestors.
 446  *
 447  * - memcg: use_hierarchy is on by default and the cgroup file for the flag
 448  *   is not created.
 449  *
 450  * - blkcg: blk-throttle becomes properly hierarchical.
 451  *
 452  * - debug: disallowed on the default hierarchy.
 453  */
 454 static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
 455 {
 456         return cgrp->root == &cgrp_dfl_root;
 457 }
 458
 459 /* no synchronization, the result can only be used as a hint */
 460 static inline bool cgroup_has_tasks(struct cgroup *cgrp)
 461 {
 462         return !list_empty(&cgrp->cset_links);
 463 }
 464
 465 /* returns ino associated with a cgroup */
 466 static inline ino_t cgroup_ino(struct cgroup *cgrp)
 467 {
 468         return cgrp->kn->ino;
 469 }
 470
 471 /* cft/css accessors for cftype->write() operation */
 472 static inline struct cftype *of_cft(struct kernfs_open_file *of)
 473 {
 474         return of->kn->priv;
 475 }
 476
 477 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of);
 478
 479 /* cft/css accessors for cftype->seq_*() operations */
 480 static inline struct cftype *seq_cft(struct seq_file *seq)
 481 {
 482         return of_cft(seq->private);
 483 }
 484
 485 static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
 486 {
 487         return of_css(seq->private);
 488 }
 489
 490 /*
 491  * Name / path handling functions.  All are thin wrappers around the kernfs
 492  * counterparts and can be called under any context.
 493  */
 494
 495 static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
 496 {
 497         return kernfs_name(cgrp->kn, buf, buflen);
 498 }
 499
 500 static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
 501                                               size_t buflen)
 502 {
 503         return kernfs_path(cgrp->kn, buf, buflen);
 504 }
 505
 506 static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
 507 {
 508         pr_cont_kernfs_name(cgrp->kn);
 509 }
 510
 511 static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
 512 {
 513         pr_cont_kernfs_path(cgrp->kn);
 514 }
 515
 516 #else /* !CONFIG_CGROUPS */
 517
 518 struct cgroup_subsys_state;
 519
 520 static inline void css_put(struct cgroup_subsys_state *css) {}
 521 static inline int cgroup_attach_task_all(struct task_struct *from,
 522                                          struct task_struct *t) { return 0; }
 523 static inline int cgroupstats_build(struct cgroupstats *stats,
 524                                     struct dentry *dentry) { return -EINVAL; }
 525
 526 static inline void cgroup_fork(struct task_struct *p) {}
 527 static inline void cgroup_post_fork(struct task_struct *p) {}
 528 static inline void cgroup_exit(struct task_struct *p) {}
 529
 530 static inline int cgroup_init_early(void) { return 0; }
 531 static inline int cgroup_init(void) { return 0; }
 532
 533 #endif /* !CONFIG_CGROUPS */
 534
 535 #endif /* _LINUX_CGROUP_H */