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/rcupdate.h>
  15 #include <linux/cgroupstats.h>
  16 #include <linux/prio_heap.h>
  17 #include <linux/rwsem.h>
  18 #include <linux/idr.h>
  19
  20 #ifdef CONFIG_CGROUPS
  21
  22 struct cgroupfs_root;
  23 struct cgroup_subsys;
  24 struct inode;
  25 struct cgroup;
  26 struct css_id;
  27
  28 extern int cgroup_init_early(void);
  29 extern int cgroup_init(void);
  30 extern void cgroup_lock(void);
  31 extern bool cgroup_lock_live_group(struct cgroup *cgrp);
  32 extern void cgroup_unlock(void);
  33 extern void cgroup_fork(struct task_struct *p);
  34 extern void cgroup_fork_callbacks(struct task_struct *p);
  35 extern void cgroup_post_fork(struct task_struct *p);
  36 extern void cgroup_exit(struct task_struct *p, int run_callbacks);
  37 extern int cgroupstats_build(struct cgroupstats *stats,
  38                                 struct dentry *dentry);
  39
  40 extern struct file_operations proc_cgroup_operations;
  41
  42 /* Define the enumeration of all cgroup subsystems */
  43 #define SUBSYS(_x) _x ## _subsys_id,
  44 enum cgroup_subsys_id {
  45 #include <linux/cgroup_subsys.h>
  46         CGROUP_SUBSYS_COUNT
  47 };
  48 #undef SUBSYS
  49
  50 /* Per-subsystem/per-cgroup state maintained by the system. */
  51 struct cgroup_subsys_state {
  52         /*
  53          * The cgroup that this subsystem is attached to. Useful
  54          * for subsystems that want to know about the cgroup
  55          * hierarchy structure
  56          */
  57         struct cgroup *cgroup;
  58
  59         /*
  60          * State maintained by the cgroup system to allow subsystems
  61          * to be "busy". Should be accessed via css_get(),
  62          * css_tryget() and and css_put().
  63          */
  64
  65         atomic_t refcnt;
  66
  67         unsigned long flags;
  68         /* ID for this css, if possible */
  69         struct css_id *id;
  70 };
  71
  72 /* bits in struct cgroup_subsys_state flags field */
  73 enum {
  74         CSS_ROOT, /* This CSS is the root of the subsystem */
  75         CSS_REMOVED, /* This CSS is dead */
  76 };
  77
  78 /*
  79  * Call css_get() to hold a reference on the css; it can be used
  80  * for a reference obtained via:
  81  * - an existing ref-counted reference to the css
  82  * - task->cgroups for a locked task
  83  */
  84
  85 static inline void css_get(struct cgroup_subsys_state *css)
  86 {
  87         /* We don't need to reference count the root state */
  88         if (!test_bit(CSS_ROOT, &css->flags))
  89                 atomic_inc(&css->refcnt);
  90 }
  91
  92 static inline bool css_is_removed(struct cgroup_subsys_state *css)
  93 {
  94         return test_bit(CSS_REMOVED, &css->flags);
  95 }
  96
  97 /*
  98  * Call css_tryget() to take a reference on a css if your existing
  99  * (known-valid) reference isn't already ref-counted. Returns false if
 100  * the css has been destroyed.
 101  */
 102
 103 static inline bool css_tryget(struct cgroup_subsys_state *css)
 104 {
 105         if (test_bit(CSS_ROOT, &css->flags))
 106                 return true;
 107         while (!atomic_inc_not_zero(&css->refcnt)) {
 108                 if (test_bit(CSS_REMOVED, &css->flags))
 109                         return false;
 110                 cpu_relax();
 111         }
 112         return true;
 113 }
 114
 115 /*
 116  * css_put() should be called to release a reference taken by
 117  * css_get() or css_tryget()
 118  */
 119
 120 extern void __css_put(struct cgroup_subsys_state *css);
 121 static inline void css_put(struct cgroup_subsys_state *css)
 122 {
 123         if (!test_bit(CSS_ROOT, &css->flags))
 124                 __css_put(css);
 125 }
 126
 127 /* bits in struct cgroup flags field */
 128 enum {
 129         /* Control Group is dead */
 130         CGRP_REMOVED,
 131         /*
 132          * Control Group has previously had a child cgroup or a task,
 133          * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
 134          */
 135         CGRP_RELEASABLE,
 136         /* Control Group requires release notifications to userspace */
 137         CGRP_NOTIFY_ON_RELEASE,
 138         /*
 139          * A thread in rmdir() is wating for this cgroup.
 140          */
 141         CGRP_WAIT_ON_RMDIR,
 142 };
 143
 144 struct cgroup {
 145         unsigned long flags;            /* "unsigned long" so bitops work */
 146
 147         /*
 148          * count users of this cgroup. >0 means busy, but doesn't
 149          * necessarily indicate the number of tasks in the cgroup
 150          */
 151         atomic_t count;
 152
 153         /*
 154          * We link our 'sibling' struct into our parent's 'children'.
 155          * Our children link their 'sibling' into our 'children'.
 156          */
 157         struct list_head sibling;       /* my parent's children */
 158         struct list_head children;      /* my children */
 159
 160         struct cgroup *parent;          /* my parent */
 161         struct dentry *dentry;          /* cgroup fs entry, RCU protected */
 162
 163         /* Private pointers for each registered subsystem */
 164         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 165
 166         struct cgroupfs_root *root;
 167         struct cgroup *top_cgroup;
 168
 169         /*
 170          * List of cg_cgroup_links pointing at css_sets with
 171          * tasks in this cgroup. Protected by css_set_lock
 172          */
 173         struct list_head css_sets;
 174
 175         /*
 176          * Linked list running through all cgroups that can
 177          * potentially be reaped by the release agent. Protected by
 178          * release_list_lock
 179          */
 180         struct list_head release_list;
 181
 182         /* pids_mutex protects pids_list and cached pid arrays. */
 183         struct rw_semaphore pids_mutex;
 184
 185         /* Linked list of struct cgroup_pids */
 186         struct list_head pids_list;
 187
 188         /* For RCU-protected deletion */
 189         struct rcu_head rcu_head;
 190 };
 191
 192 /*
 193  * A css_set is a structure holding pointers to a set of
 194  * cgroup_subsys_state objects. This saves space in the task struct
 195  * object and speeds up fork()/exit(), since a single inc/dec and a
 196  * list_add()/del() can bump the reference count on the entire cgroup
 197  * set for a task.
 198  */
 199
 200 struct css_set {
 201
 202         /* Reference count */
 203         atomic_t refcount;
 204
 205         /*
 206          * List running through all cgroup groups in the same hash
 207          * slot. Protected by css_set_lock
 208          */
 209         struct hlist_node hlist;
 210
 211         /*
 212          * List running through all tasks using this cgroup
 213          * group. Protected by css_set_lock
 214          */
 215         struct list_head tasks;
 216
 217         /*
 218          * List of cg_cgroup_link objects on link chains from
 219          * cgroups referenced from this css_set. Protected by
 220          * css_set_lock
 221          */
 222         struct list_head cg_links;
 223
 224         /*
 225          * Set of subsystem states, one for each subsystem. This array
 226          * is immutable after creation apart from the init_css_set
 227          * during subsystem registration (at boot time).
 228          */
 229         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 230 };
 231
 232 /*
 233  * cgroup_map_cb is an abstract callback API for reporting map-valued
 234  * control files
 235  */
 236
 237 struct cgroup_map_cb {
 238         int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
 239         void *state;
 240 };
 241
 242 /*
 243  * struct cftype: handler definitions for cgroup control files
 244  *
 245  * When reading/writing to a file:
 246  *      - the cgroup to use is file->f_dentry->d_parent->d_fsdata
 247  *      - the 'cftype' of the file is file->f_dentry->d_fsdata
 248  */
 249
 250 #define MAX_CFTYPE_NAME 64
 251 struct cftype {
 252         /*
 253          * By convention, the name should begin with the name of the
 254          * subsystem, followed by a period
 255          */
 256         char name[MAX_CFTYPE_NAME];
 257         int private;
 258         /*
 259          * If not 0, file mode is set to this value, otherwise it will
 260          * be figured out automatically
 261          */
 262         mode_t mode;
 263
 264         /*
 265          * If non-zero, defines the maximum length of string that can
 266          * be passed to write_string; defaults to 64
 267          */
 268         size_t max_write_len;
 269
 270         int (*open)(struct inode *inode, struct file *file);
 271         ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
 272                         struct file *file,
 273                         char __user *buf, size_t nbytes, loff_t *ppos);
 274         /*
 275          * read_u64() is a shortcut for the common case of returning a
 276          * single integer. Use it in place of read()
 277          */
 278         u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
 279         /*
 280          * read_s64() is a signed version of read_u64()
 281          */
 282         s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
 283         /*
 284          * read_map() is used for defining a map of key/value
 285          * pairs. It should call cb->fill(cb, key, value) for each
 286          * entry. The key/value pairs (and their ordering) should not
 287          * change between reboots.
 288          */
 289         int (*read_map)(struct cgroup *cont, struct cftype *cft,
 290                         struct cgroup_map_cb *cb);
 291         /*
 292          * read_seq_string() is used for outputting a simple sequence
 293          * using seqfile.
 294          */
 295         int (*read_seq_string)(struct cgroup *cont, struct cftype *cft,
 296                                struct seq_file *m);
 297
 298         ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
 299                          struct file *file,
 300                          const char __user *buf, size_t nbytes, loff_t *ppos);
 301
 302         /*
 303          * write_u64() is a shortcut for the common case of accepting
 304          * a single integer (as parsed by simple_strtoull) from
 305          * userspace. Use in place of write(); return 0 or error.
 306          */
 307         int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
 308         /*
 309          * write_s64() is a signed version of write_u64()
 310          */
 311         int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
 312
 313         /*
 314          * write_string() is passed a nul-terminated kernelspace
 315          * buffer of maximum length determined by max_write_len.
 316          * Returns 0 or -ve error code.
 317          */
 318         int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
 319                             const char *buffer);
 320         /*
 321          * trigger() callback can be used to get some kick from the
 322          * userspace, when the actual string written is not important
 323          * at all. The private field can be used to determine the
 324          * kick type for multiplexing.
 325          */
 326         int (*trigger)(struct cgroup *cgrp, unsigned int event);
 327
 328         int (*release)(struct inode *inode, struct file *file);
 329 };
 330
 331 struct cgroup_scanner {
 332         struct cgroup *cg;
 333         int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
 334         void (*process_task)(struct task_struct *p,
 335                         struct cgroup_scanner *scan);
 336         struct ptr_heap *heap;
 337         void *data;
 338 };
 339
 340 /*
 341  * Add a new file to the given cgroup directory. Should only be
 342  * called by subsystems from within a populate() method
 343  */
 344 int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
 345                        const struct cftype *cft);
 346
 347 /*
 348  * Add a set of new files to the given cgroup directory. Should
 349  * only be called by subsystems from within a populate() method
 350  */
 351 int cgroup_add_files(struct cgroup *cgrp,
 352                         struct cgroup_subsys *subsys,
 353                         const struct cftype cft[],
 354                         int count);
 355
 356 int cgroup_is_removed(const struct cgroup *cgrp);
 357
 358 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
 359
 360 int cgroup_task_count(const struct cgroup *cgrp);
 361
 362 /* Return true if cgrp is a descendant of the task's cgroup */
 363 int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
 364
 365 /*
 366  * When the subsys has to access css and may add permanent refcnt to css,
 367  * it should take care of racy conditions with rmdir(). Following set of
 368  * functions, is for stop/restart rmdir if necessary.
 369  * Because these will call css_get/put, "css" should be alive css.
 370  *
 371  *  cgroup_exclude_rmdir();
 372  *  ...do some jobs which may access arbitrary empty cgroup
 373  *  cgroup_release_and_wakeup_rmdir();
 374  *
 375  *  When someone removes a cgroup while cgroup_exclude_rmdir() holds it,
 376  *  it sleeps and cgroup_release_and_wakeup_rmdir() will wake him up.
 377  */
 378
 379 void cgroup_exclude_rmdir(struct cgroup_subsys_state *css);
 380 void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css);
 381
 382 /*
 383  * Control Group subsystem type.
 384  * See Documentation/cgroups/cgroups.txt for details
 385  */
 386
 387 struct cgroup_subsys {
 388         struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
 389                                                   struct cgroup *cgrp);
 390         int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 391         void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 392         int (*can_attach)(struct cgroup_subsys *ss,
 393                           struct cgroup *cgrp, struct task_struct *tsk);
 394         void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
 395                         struct cgroup *old_cgrp, struct task_struct *tsk);
 396         void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
 397         void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
 398         int (*populate)(struct cgroup_subsys *ss,
 399                         struct cgroup *cgrp);
 400         void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 401         void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
 402
 403         int subsys_id;
 404         int active;
 405         int disabled;
 406         int early_init;
 407         /*
 408          * True if this subsys uses ID. ID is not available before cgroup_init()
 409          * (not available in early_init time.)
 410          */
 411         bool use_id;
 412 #define MAX_CGROUP_TYPE_NAMELEN 32
 413         const char *name;
 414
 415         /*
 416          * Protects sibling/children links of cgroups in this
 417          * hierarchy, plus protects which hierarchy (or none) the
 418          * subsystem is a part of (i.e. root/sibling).  To avoid
 419          * potential deadlocks, the following operations should not be
 420          * undertaken while holding any hierarchy_mutex:
 421          *
 422          * - allocating memory
 423          * - initiating hotplug events
 424          */
 425         struct mutex hierarchy_mutex;
 426         struct lock_class_key subsys_key;
 427
 428         /*
 429          * Link to parent, and list entry in parent's children.
 430          * Protected by this->hierarchy_mutex and cgroup_lock()
 431          */
 432         struct cgroupfs_root *root;
 433         struct list_head sibling;
 434         /* used when use_id == true */
 435         struct idr idr;
 436         spinlock_t id_lock;
 437 };
 438
 439 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
 440 #include <linux/cgroup_subsys.h>
 441 #undef SUBSYS
 442
 443 static inline struct cgroup_subsys_state *cgroup_subsys_state(
 444         struct cgroup *cgrp, int subsys_id)
 445 {
 446         return cgrp->subsys[subsys_id];
 447 }
 448
 449 static inline struct cgroup_subsys_state *task_subsys_state(
 450         struct task_struct *task, int subsys_id)
 451 {
 452         return rcu_dereference(task->cgroups->subsys[subsys_id]);
 453 }
 454
 455 static inline struct cgroup* task_cgroup(struct task_struct *task,
 456                                                int subsys_id)
 457 {
 458         return task_subsys_state(task, subsys_id)->cgroup;
 459 }
 460
 461 int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss,
 462                                                         char *nodename);
 463
 464 /* A cgroup_iter should be treated as an opaque object */
 465 struct cgroup_iter {
 466         struct list_head *cg_link;
 467         struct list_head *task;
 468 };
 469
 470 /*
 471  * To iterate across the tasks in a cgroup:
 472  *
 473  * 1) call cgroup_iter_start to intialize an iterator
 474  *
 475  * 2) call cgroup_iter_next() to retrieve member tasks until it
 476  *    returns NULL or until you want to end the iteration
 477  *
 478  * 3) call cgroup_iter_end() to destroy the iterator.
 479  *
 480  * Or, call cgroup_scan_tasks() to iterate through every task in a
 481  * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
 482  * the test_task() callback, but not while calling the process_task()
 483  * callback.
 484  */
 485 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
 486 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
 487                                         struct cgroup_iter *it);
 488 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
 489 int cgroup_scan_tasks(struct cgroup_scanner *scan);
 490 int cgroup_attach_task(struct cgroup *, struct task_struct *);
 491
 492 /*
 493  * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
 494  * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
 495  * CSS ID is assigned at cgroup allocation (create) automatically
 496  * and removed when subsys calls free_css_id() function. This is because
 497  * the lifetime of cgroup_subsys_state is subsys's matter.
 498  *
 499  * Looking up and scanning function should be called under rcu_read_lock().
 500  * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
 501  * But the css returned by this routine can be "not populated yet" or "being
 502  * destroyed". The caller should check css and cgroup's status.
 503  */
 504
 505 /*
 506  * Typically Called at ->destroy(), or somewhere the subsys frees
 507  * cgroup_subsys_state.
 508  */
 509 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
 510
 511 /* Find a cgroup_subsys_state which has given ID */
 512
 513 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
 514
 515 /*
 516  * Get a cgroup whose id is greater than or equal to id under tree of root.
 517  * Returning a cgroup_subsys_state or NULL.
 518  */
 519 struct cgroup_subsys_state *css_get_next(struct cgroup_subsys *ss, int id,
 520                 struct cgroup_subsys_state *root, int *foundid);
 521
 522 /* Returns true if root is ancestor of cg */
 523 bool css_is_ancestor(struct cgroup_subsys_state *cg,
 524                      const struct cgroup_subsys_state *root);
 525
 526 /* Get id and depth of css */
 527 unsigned short css_id(struct cgroup_subsys_state *css);
 528 unsigned short css_depth(struct cgroup_subsys_state *css);
 529
 530 #else /* !CONFIG_CGROUPS */
 531
 532 static inline int cgroup_init_early(void) { return 0; }
 533 static inline int cgroup_init(void) { return 0; }
 534 static inline void cgroup_fork(struct task_struct *p) {}
 535 static inline void cgroup_fork_callbacks(struct task_struct *p) {}
 536 static inline void cgroup_post_fork(struct task_struct *p) {}
 537 static inline void cgroup_exit(struct task_struct *p, int callbacks) {}
 538
 539 static inline void cgroup_lock(void) {}
 540 static inline void cgroup_unlock(void) {}
 541 static inline int cgroupstats_build(struct cgroupstats *stats,
 542                                         struct dentry *dentry)
 543 {
 544         return -EINVAL;
 545 }
 546
 547 #endif /* !CONFIG_CGROUPS */
 548
 549 #endif /* _LINUX_CGROUP_H */