include/linux/cgroup-defs.h

   1 /*
   2  * linux/cgroup-defs.h - basic definitions for cgroup
   3  *
   4  * This file provides basic type and interface.  Include this file directly
   5  * only if necessary to avoid cyclic dependencies.
   6  */
   7 #ifndef _LINUX_CGROUP_DEFS_H
   8 #define _LINUX_CGROUP_DEFS_H
   9
  10 #include <linux/limits.h>
  11 #include <linux/list.h>
  12 #include <linux/idr.h>
  13 #include <linux/wait.h>
  14 #include <linux/mutex.h>
  15 #include <linux/rcupdate.h>
  16 #include <linux/percpu-refcount.h>
  17 #include <linux/percpu-rwsem.h>
  18 #include <linux/workqueue.h>
  19
  20 #ifdef CONFIG_CGROUPS
  21
  22 struct cgroup;
  23 struct cgroup_root;
  24 struct cgroup_subsys;
  25 struct cgroup_taskset;
  26 struct kernfs_node;
  27 struct kernfs_ops;
  28 struct kernfs_open_file;
  29 struct seq_file;
  30
  31 #define MAX_CGROUP_TYPE_NAMELEN 32
  32 #define MAX_CGROUP_ROOT_NAMELEN 64
  33 #define MAX_CFTYPE_NAME         64
  34
  35 /* define the enumeration of all cgroup subsystems */
  36 #define SUBSYS(_x) _x ## _cgrp_id,
  37 #define SUBSYS_TAG(_t) CGROUP_ ## _t, \
  38         __unused_tag_ ## _t = CGROUP_ ## _t - 1,
  39 enum cgroup_subsys_id {
  40 #include <linux/cgroup_subsys.h>
  41         CGROUP_SUBSYS_COUNT,
  42 };
  43 #undef SUBSYS_TAG
  44 #undef SUBSYS
  45
  46 #define CGROUP_CANFORK_COUNT (CGROUP_CANFORK_END - CGROUP_CANFORK_START)
  47
  48 /* bits in struct cgroup_subsys_state flags field */
  49 enum {
  50         CSS_NO_REF      = (1 << 0), /* no reference counting for this css */
  51         CSS_ONLINE      = (1 << 1), /* between ->css_online() and ->css_offline() */
  52         CSS_RELEASED    = (1 << 2), /* refcnt reached zero, released */
  53 };
  54
  55 /* bits in struct cgroup flags field */
  56 enum {
  57         /* Control Group requires release notifications to userspace */
  58         CGRP_NOTIFY_ON_RELEASE,
  59         /*
  60          * Clone the parent's configuration when creating a new child
  61          * cpuset cgroup.  For historical reasons, this option can be
  62          * specified at mount time and thus is implemented here.
  63          */
  64         CGRP_CPUSET_CLONE_CHILDREN,
  65 };
  66
  67 /* cgroup_root->flags */
  68 enum {
  69         CGRP_ROOT_SANE_BEHAVIOR = (1 << 0), /* __DEVEL__sane_behavior specified */
  70         CGRP_ROOT_NOPREFIX      = (1 << 1), /* mounted subsystems have no named prefix */
  71         CGRP_ROOT_XATTR         = (1 << 2), /* supports extended attributes */
  72 };
  73
  74 /* cftype->flags */
  75 enum {
  76         CFTYPE_ONLY_ON_ROOT     = (1 << 0),     /* only create on root cgrp */
  77         CFTYPE_NOT_ON_ROOT      = (1 << 1),     /* don't create on root cgrp */
  78         CFTYPE_NO_PREFIX        = (1 << 3),     /* (DON'T USE FOR NEW FILES) no subsys prefix */
  79         CFTYPE_WORLD_WRITABLE   = (1 << 4),     /* (DON'T USE FOR NEW FILES) S_IWUGO */
  80
  81         /* internal flags, do not use outside cgroup core proper */
  82         __CFTYPE_ONLY_ON_DFL    = (1 << 16),    /* only on default hierarchy */
  83         __CFTYPE_NOT_ON_DFL     = (1 << 17),    /* not on default hierarchy */
  84 };
  85
  86 /*
  87  * cgroup_file is the handle for a file instance created in a cgroup which
  88  * is used, for example, to generate file changed notifications.  This can
  89  * be obtained by setting cftype->file_offset.
  90  */
  91 struct cgroup_file {
  92         /* do not access any fields from outside cgroup core */
  93         struct kernfs_node *kn;
  94 };
  95
  96 /*
  97  * Per-subsystem/per-cgroup state maintained by the system.  This is the
  98  * fundamental structural building block that controllers deal with.
  99  *
 100  * Fields marked with "PI:" are public and immutable and may be accessed
 101  * directly without synchronization.
 102  */
 103 struct cgroup_subsys_state {
 104         /* PI: the cgroup that this css is attached to */
 105         struct cgroup *cgroup;
 106
 107         /* PI: the cgroup subsystem that this css is attached to */
 108         struct cgroup_subsys *ss;
 109
 110         /* reference count - access via css_[try]get() and css_put() */
 111         struct percpu_ref refcnt;
 112
 113         /* PI: the parent css */
 114         struct cgroup_subsys_state *parent;
 115
 116         /* siblings list anchored at the parent's ->children */
 117         struct list_head sibling;
 118         struct list_head children;
 119
 120         /*
 121          * PI: Subsys-unique ID.  0 is unused and root is always 1.  The
 122          * matching css can be looked up using css_from_id().
 123          */
 124         int id;
 125
 126         unsigned int flags;
 127
 128         /*
 129          * Monotonically increasing unique serial number which defines a
 130          * uniform order among all csses.  It's guaranteed that all
 131          * ->children lists are in the ascending order of ->serial_nr and
 132          * used to allow interrupting and resuming iterations.
 133          */
 134         u64 serial_nr;
 135
 136         /* percpu_ref killing and RCU release */
 137         struct rcu_head rcu_head;
 138         struct work_struct destroy_work;
 139 };
 140
 141 /*
 142  * A css_set is a structure holding pointers to a set of
 143  * cgroup_subsys_state objects. This saves space in the task struct
 144  * object and speeds up fork()/exit(), since a single inc/dec and a
 145  * list_add()/del() can bump the reference count on the entire cgroup
 146  * set for a task.
 147  */
 148 struct css_set {
 149         /* Reference count */
 150         atomic_t refcount;
 151
 152         /*
 153          * List running through all cgroup groups in the same hash
 154          * slot. Protected by css_set_lock
 155          */
 156         struct hlist_node hlist;
 157
 158         /*
 159          * Lists running through all tasks using this cgroup group.
 160          * mg_tasks lists tasks which belong to this cset but are in the
 161          * process of being migrated out or in.  Protected by
 162          * css_set_rwsem, but, during migration, once tasks are moved to
 163          * mg_tasks, it can be read safely while holding cgroup_mutex.
 164          */
 165         struct list_head tasks;
 166         struct list_head mg_tasks;
 167
 168         /*
 169          * List of cgrp_cset_links pointing at cgroups referenced from this
 170          * css_set.  Protected by css_set_lock.
 171          */
 172         struct list_head cgrp_links;
 173
 174         /* the default cgroup associated with this css_set */
 175         struct cgroup *dfl_cgrp;
 176
 177         /*
 178          * Set of subsystem states, one for each subsystem. This array is
 179          * immutable after creation apart from the init_css_set during
 180          * subsystem registration (at boot time).
 181          */
 182         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 183
 184         /*
 185          * List of csets participating in the on-going migration either as
 186          * source or destination.  Protected by cgroup_mutex.
 187          */
 188         struct list_head mg_preload_node;
 189         struct list_head mg_node;
 190
 191         /*
 192          * If this cset is acting as the source of migration the following
 193          * two fields are set.  mg_src_cgrp is the source cgroup of the
 194          * on-going migration and mg_dst_cset is the destination cset the
 195          * target tasks on this cset should be migrated to.  Protected by
 196          * cgroup_mutex.
 197          */
 198         struct cgroup *mg_src_cgrp;
 199         struct css_set *mg_dst_cset;
 200
 201         /*
 202          * On the default hierarhcy, ->subsys[ssid] may point to a css
 203          * attached to an ancestor instead of the cgroup this css_set is
 204          * associated with.  The following node is anchored at
 205          * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
 206          * iterate through all css's attached to a given cgroup.
 207          */
 208         struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
 209
 210         /* all css_task_iters currently walking this cset */
 211         struct list_head task_iters;
 212
 213         /* For RCU-protected deletion */
 214         struct rcu_head rcu_head;
 215 };
 216
 217 struct cgroup {
 218         /* self css with NULL ->ss, points back to this cgroup */
 219         struct cgroup_subsys_state self;
 220
 221         unsigned long flags;            /* "unsigned long" so bitops work */
 222
 223         /*
 224          * idr allocated in-hierarchy ID.
 225          *
 226          * ID 0 is not used, the ID of the root cgroup is always 1, and a
 227          * new cgroup will be assigned with a smallest available ID.
 228          *
 229          * Allocating/Removing ID must be protected by cgroup_mutex.
 230          */
 231         int id;
 232
 233         /*
 234          * Each non-empty css_set associated with this cgroup contributes
 235          * one to populated_cnt.  All children with non-zero popuplated_cnt
 236          * of their own contribute one.  The count is zero iff there's no
 237          * task in this cgroup or its subtree.
 238          */
 239         int populated_cnt;
 240
 241         struct kernfs_node *kn;         /* cgroup kernfs entry */
 242         struct cgroup_file procs_file;  /* handle for "cgroup.procs" */
 243         struct cgroup_file events_file; /* handle for "cgroup.events" */
 244
 245         /*
 246          * The bitmask of subsystems enabled on the child cgroups.
 247          * ->subtree_control is the one configured through
 248          * "cgroup.subtree_control" while ->child_subsys_mask is the
 249          * effective one which may have more subsystems enabled.
 250          * Controller knobs are made available iff it's enabled in
 251          * ->subtree_control.
 252          */
 253         unsigned int subtree_control;
 254         unsigned int child_subsys_mask;
 255
 256         /* Private pointers for each registered subsystem */
 257         struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
 258
 259         struct cgroup_root *root;
 260
 261         /*
 262          * List of cgrp_cset_links pointing at css_sets with tasks in this
 263          * cgroup.  Protected by css_set_lock.
 264          */
 265         struct list_head cset_links;
 266
 267         /*
 268          * On the default hierarchy, a css_set for a cgroup with some
 269          * susbsys disabled will point to css's which are associated with
 270          * the closest ancestor which has the subsys enabled.  The
 271          * following lists all css_sets which point to this cgroup's css
 272          * for the given subsystem.
 273          */
 274         struct list_head e_csets[CGROUP_SUBSYS_COUNT];
 275
 276         /*
 277          * list of pidlists, up to two for each namespace (one for procs, one
 278          * for tasks); created on demand.
 279          */
 280         struct list_head pidlists;
 281         struct mutex pidlist_mutex;
 282
 283         /* used to wait for offlining of csses */
 284         wait_queue_head_t offline_waitq;
 285
 286         /* used to schedule release agent */
 287         struct work_struct release_agent_work;
 288 };
 289
 290 /*
 291  * A cgroup_root represents the root of a cgroup hierarchy, and may be
 292  * associated with a kernfs_root to form an active hierarchy.  This is
 293  * internal to cgroup core.  Don't access directly from controllers.
 294  */
 295 struct cgroup_root {
 296         struct kernfs_root *kf_root;
 297
 298         /* The bitmask of subsystems attached to this hierarchy */
 299         unsigned int subsys_mask;
 300
 301         /* Unique id for this hierarchy. */
 302         int hierarchy_id;
 303
 304         /* The root cgroup.  Root is destroyed on its release. */
 305         struct cgroup cgrp;
 306
 307         /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
 308         atomic_t nr_cgrps;
 309
 310         /* A list running through the active hierarchies */
 311         struct list_head root_list;
 312
 313         /* Hierarchy-specific flags */
 314         unsigned int flags;
 315
 316         /* IDs for cgroups in this hierarchy */
 317         struct idr cgroup_idr;
 318
 319         /* The path to use for release notifications. */
 320         char release_agent_path[PATH_MAX];
 321
 322         /* The name for this hierarchy - may be empty */
 323         char name[MAX_CGROUP_ROOT_NAMELEN];
 324 };
 325
 326 /*
 327  * struct cftype: handler definitions for cgroup control files
 328  *
 329  * When reading/writing to a file:
 330  *      - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
 331  *      - the 'cftype' of the file is file->f_path.dentry->d_fsdata
 332  */
 333 struct cftype {
 334         /*
 335          * By convention, the name should begin with the name of the
 336          * subsystem, followed by a period.  Zero length string indicates
 337          * end of cftype array.
 338          */
 339         char name[MAX_CFTYPE_NAME];
 340         unsigned long private;
 341
 342         /*
 343          * The maximum length of string, excluding trailing nul, that can
 344          * be passed to write.  If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
 345          */
 346         size_t max_write_len;
 347
 348         /* CFTYPE_* flags */
 349         unsigned int flags;
 350
 351         /*
 352          * If non-zero, should contain the offset from the start of css to
 353          * a struct cgroup_file field.  cgroup will record the handle of
 354          * the created file into it.  The recorded handle can be used as
 355          * long as the containing css remains accessible.
 356          */
 357         unsigned int file_offset;
 358
 359         /*
 360          * Fields used for internal bookkeeping.  Initialized automatically
 361          * during registration.
 362          */
 363         struct cgroup_subsys *ss;       /* NULL for cgroup core files */
 364         struct list_head node;          /* anchored at ss->cfts */
 365         struct kernfs_ops *kf_ops;
 366
 367         /*
 368          * read_u64() is a shortcut for the common case of returning a
 369          * single integer. Use it in place of read()
 370          */
 371         u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
 372         /*
 373          * read_s64() is a signed version of read_u64()
 374          */
 375         s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
 376
 377         /* generic seq_file read interface */
 378         int (*seq_show)(struct seq_file *sf, void *v);
 379
 380         /* optional ops, implement all or none */
 381         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 382         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 383         void (*seq_stop)(struct seq_file *sf, void *v);
 384
 385         /*
 386          * write_u64() is a shortcut for the common case of accepting
 387          * a single integer (as parsed by simple_strtoull) from
 388          * userspace. Use in place of write(); return 0 or error.
 389          */
 390         int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
 391                          u64 val);
 392         /*
 393          * write_s64() is a signed version of write_u64()
 394          */
 395         int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
 396                          s64 val);
 397
 398         /*
 399          * write() is the generic write callback which maps directly to
 400          * kernfs write operation and overrides all other operations.
 401          * Maximum write size is determined by ->max_write_len.  Use
 402          * of_css/cft() to access the associated css and cft.
 403          */
 404         ssize_t (*write)(struct kernfs_open_file *of,
 405                          char *buf, size_t nbytes, loff_t off);
 406
 407 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 408         struct lock_class_key   lockdep_key;
 409 #endif
 410 };
 411
 412 /*
 413  * Control Group subsystem type.
 414  * See Documentation/cgroups/cgroups.txt for details
 415  */
 416 struct cgroup_subsys {
 417         struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
 418         int (*css_online)(struct cgroup_subsys_state *css);
 419         void (*css_offline)(struct cgroup_subsys_state *css);
 420         void (*css_released)(struct cgroup_subsys_state *css);
 421         void (*css_free)(struct cgroup_subsys_state *css);
 422         void (*css_reset)(struct cgroup_subsys_state *css);
 423         void (*css_e_css_changed)(struct cgroup_subsys_state *css);
 424
 425         int (*can_attach)(struct cgroup_taskset *tset);
 426         void (*cancel_attach)(struct cgroup_taskset *tset);
 427         void (*attach)(struct cgroup_taskset *tset);
 428         int (*can_fork)(struct task_struct *task, void **priv_p);
 429         void (*cancel_fork)(struct task_struct *task, void *priv);
 430         void (*fork)(struct task_struct *task, void *priv);
 431         void (*exit)(struct task_struct *task);
 432         void (*free)(struct task_struct *task);
 433         void (*bind)(struct cgroup_subsys_state *root_css);
 434
 435         int early_init;
 436
 437         /*
 438          * If %false, this subsystem is properly hierarchical -
 439          * configuration, resource accounting and restriction on a parent
 440          * cgroup cover those of its children.  If %true, hierarchy support
 441          * is broken in some ways - some subsystems ignore hierarchy
 442          * completely while others are only implemented half-way.
 443          *
 444          * It's now disallowed to create nested cgroups if the subsystem is
 445          * broken and cgroup core will emit a warning message on such
 446          * cases.  Eventually, all subsystems will be made properly
 447          * hierarchical and this will go away.
 448          */
 449         bool broken_hierarchy;
 450         bool warned_broken_hierarchy;
 451
 452         /* the following two fields are initialized automtically during boot */
 453         int id;
 454         const char *name;
 455
 456         /* optional, initialized automatically during boot if not set */
 457         const char *legacy_name;
 458
 459         /* link to parent, protected by cgroup_lock() */
 460         struct cgroup_root *root;
 461
 462         /* idr for css->id */
 463         struct idr css_idr;
 464
 465         /*
 466          * List of cftypes.  Each entry is the first entry of an array
 467          * terminated by zero length name.
 468          */
 469         struct list_head cfts;
 470
 471         /*
 472          * Base cftypes which are automatically registered.  The two can
 473          * point to the same array.
 474          */
 475         struct cftype *dfl_cftypes;     /* for the default hierarchy */
 476         struct cftype *legacy_cftypes;  /* for the legacy hierarchies */
 477
 478         /*
 479          * A subsystem may depend on other subsystems.  When such subsystem
 480          * is enabled on a cgroup, the depended-upon subsystems are enabled
 481          * together if available.  Subsystems enabled due to dependency are
 482          * not visible to userland until explicitly enabled.  The following
 483          * specifies the mask of subsystems that this one depends on.
 484          */
 485         unsigned int depends_on;
 486 };
 487
 488 extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
 489
 490 /**
 491  * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
 492  * @tsk: target task
 493  *
 494  * Called from threadgroup_change_begin() and allows cgroup operations to
 495  * synchronize against threadgroup changes using a percpu_rw_semaphore.
 496  */
 497 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
 498 {
 499         percpu_down_read(&cgroup_threadgroup_rwsem);
 500 }
 501
 502 /**
 503  * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
 504  * @tsk: target task
 505  *
 506  * Called from threadgroup_change_end().  Counterpart of
 507  * cgroup_threadcgroup_change_begin().
 508  */
 509 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
 510 {
 511         percpu_up_read(&cgroup_threadgroup_rwsem);
 512 }
 513
 514 #else   /* CONFIG_CGROUPS */
 515
 516 #define CGROUP_CANFORK_COUNT 0
 517 #define CGROUP_SUBSYS_COUNT 0
 518
 519 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk) {}
 520 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
 521
 522 #endif  /* CONFIG_CGROUPS */
 523
 524 #endif  /* _LINUX_CGROUP_DEFS_H */