include/linux/cgroup-defs.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * linux/cgroup-defs.h - basic definitions for cgroup
   4  *
   5  * This file provides basic type and interface.  Include this file directly
   6  * only if necessary to avoid cyclic dependencies.
   7  */
   8 #ifndef _LINUX_CGROUP_DEFS_H
   9 #define _LINUX_CGROUP_DEFS_H
  10
  11 #include <linux/limits.h>
  12 #include <linux/list.h>
  13 #include <linux/idr.h>
  14 #include <linux/wait.h>
  15 #include <linux/mutex.h>
  16 #include <linux/rcupdate.h>
  17 #include <linux/refcount.h>
  18 #include <linux/percpu-refcount.h>
  19 #include <linux/percpu-rwsem.h>
  20 #include <linux/workqueue.h>
  21 #include <linux/bpf-cgroup.h>
  22 #include <linux/psi_types.h>
  23
  24 #ifdef CONFIG_CGROUPS
  25
  26 struct cgroup;
  27 struct cgroup_root;
  28 struct cgroup_subsys;
  29 struct cgroup_taskset;
  30 struct kernfs_node;
  31 struct kernfs_ops;
  32 struct kernfs_open_file;
  33 struct seq_file;
  34 struct poll_table_struct;
  35
  36 #define MAX_CGROUP_TYPE_NAMELEN 32
  37 #define MAX_CGROUP_ROOT_NAMELEN 64
  38 #define MAX_CFTYPE_NAME         64
  39
  40 /* define the enumeration of all cgroup subsystems */
  41 #define SUBSYS(_x) _x ## _cgrp_id,
  42 enum cgroup_subsys_id {
  43 #include <linux/cgroup_subsys.h>
  44         CGROUP_SUBSYS_COUNT,
  45 };
  46 #undef SUBSYS
  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         CSS_VISIBLE     = (1 << 3), /* css is visible to userland */
  54         CSS_DYING       = (1 << 4), /* css is dying */
  55 };
  56
  57 /* bits in struct cgroup flags field */
  58 enum {
  59         /* Control Group requires release notifications to userspace */
  60         CGRP_NOTIFY_ON_RELEASE,
  61         /*
  62          * Clone the parent's configuration when creating a new child
  63          * cpuset cgroup.  For historical reasons, this option can be
  64          * specified at mount time and thus is implemented here.
  65          */
  66         CGRP_CPUSET_CLONE_CHILDREN,
  67 };
  68
  69 /* cgroup_root->flags */
  70 enum {
  71         CGRP_ROOT_NOPREFIX      = (1 << 1), /* mounted subsystems have no named prefix */
  72         CGRP_ROOT_XATTR         = (1 << 2), /* supports extended attributes */
  73
  74         /*
  75          * Consider namespaces as delegation boundaries.  If this flag is
  76          * set, controller specific interface files in a namespace root
  77          * aren't writeable from inside the namespace.
  78          */
  79         CGRP_ROOT_NS_DELEGATE   = (1 << 3),
  80
  81         /*
  82          * Enable cpuset controller in v1 cgroup to use v2 behavior.
  83          */
  84         CGRP_ROOT_CPUSET_V2_MODE = (1 << 4),
  85 };
  86
  87 /* cftype->flags */
  88 enum {
  89         CFTYPE_ONLY_ON_ROOT     = (1 << 0),     /* only create on root cgrp */
  90         CFTYPE_NOT_ON_ROOT      = (1 << 1),     /* don't create on root cgrp */
  91         CFTYPE_NS_DELEGATABLE   = (1 << 2),     /* writeable beyond delegation boundaries */
  92
  93         CFTYPE_NO_PREFIX        = (1 << 3),     /* (DON'T USE FOR NEW FILES) no subsys prefix */
  94         CFTYPE_WORLD_WRITABLE   = (1 << 4),     /* (DON'T USE FOR NEW FILES) S_IWUGO */
  95
  96         /* internal flags, do not use outside cgroup core proper */
  97         __CFTYPE_ONLY_ON_DFL    = (1 << 16),    /* only on default hierarchy */
  98         __CFTYPE_NOT_ON_DFL     = (1 << 17),    /* not on default hierarchy */
  99 };
 100
 101 /*
 102  * cgroup_file is the handle for a file instance created in a cgroup which
 103  * is used, for example, to generate file changed notifications.  This can
 104  * be obtained by setting cftype->file_offset.
 105  */
 106 struct cgroup_file {
 107         /* do not access any fields from outside cgroup core */
 108         struct kernfs_node *kn;
 109 };
 110
 111 /*
 112  * Per-subsystem/per-cgroup state maintained by the system.  This is the
 113  * fundamental structural building block that controllers deal with.
 114  *
 115  * Fields marked with "PI:" are public and immutable and may be accessed
 116  * directly without synchronization.
 117  */
 118 struct cgroup_subsys_state {
 119         /* PI: the cgroup that this css is attached to */
 120         struct cgroup *cgroup;
 121
 122         /* PI: the cgroup subsystem that this css is attached to */
 123         struct cgroup_subsys *ss;
 124
 125         /* reference count - access via css_[try]get() and css_put() */
 126         struct percpu_ref refcnt;
 127
 128         /* siblings list anchored at the parent's ->children */
 129         struct list_head sibling;
 130         struct list_head children;
 131
 132         /*
 133          * PI: Subsys-unique ID.  0 is unused and root is always 1.  The
 134          * matching css can be looked up using css_from_id().
 135          */
 136         int id;
 137
 138         unsigned int flags;
 139
 140         /*
 141          * Monotonically increasing unique serial number which defines a
 142          * uniform order among all csses.  It's guaranteed that all
 143          * ->children lists are in the ascending order of ->serial_nr and
 144          * used to allow interrupting and resuming iterations.
 145          */
 146         u64 serial_nr;
 147
 148         /*
 149          * Incremented by online self and children.  Used to guarantee that
 150          * parents are not offlined before their children.
 151          */
 152         atomic_t online_cnt;
 153
 154         /* percpu_ref killing and RCU release */
 155         struct rcu_head rcu_head;
 156         struct work_struct destroy_work;
 157
 158         /*
 159          * PI: the parent css.  Placed here for cache proximity to following
 160          * fields of the containing structure.
 161          */
 162         struct cgroup_subsys_state *parent;
 163 };
 164
 165 /*
 166  * A css_set is a structure holding pointers to a set of
 167  * cgroup_subsys_state objects. This saves space in the task struct
 168  * object and speeds up fork()/exit(), since a single inc/dec and a
 169  * list_add()/del() can bump the reference count on the entire cgroup
 170  * set for a task.
 171  */
 172 struct css_set {
 173         /*
 174          * Set of subsystem states, one for each subsystem. This array is
 175          * immutable after creation apart from the init_css_set during
 176          * subsystem registration (at boot time).
 177          */
 178         struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
 179
 180         /* reference count */
 181         refcount_t refcount;
 182
 183         /*
 184          * For a domain cgroup, the following points to self.  If threaded,
 185          * to the matching cset of the nearest domain ancestor.  The
 186          * dom_cset provides access to the domain cgroup and its csses to
 187          * which domain level resource consumptions should be charged.
 188          */
 189         struct css_set *dom_cset;
 190
 191         /* the default cgroup associated with this css_set */
 192         struct cgroup *dfl_cgrp;
 193
 194         /* internal task count, protected by css_set_lock */
 195         int nr_tasks;
 196
 197         /*
 198          * Lists running through all tasks using this cgroup group.
 199          * mg_tasks lists tasks which belong to this cset but are in the
 200          * process of being migrated out or in.  Protected by
 201          * css_set_rwsem, but, during migration, once tasks are moved to
 202          * mg_tasks, it can be read safely while holding cgroup_mutex.
 203          */
 204         struct list_head tasks;
 205         struct list_head mg_tasks;
 206
 207         /* all css_task_iters currently walking this cset */
 208         struct list_head task_iters;
 209
 210         /*
 211          * On the default hierarhcy, ->subsys[ssid] may point to a css
 212          * attached to an ancestor instead of the cgroup this css_set is
 213          * associated with.  The following node is anchored at
 214          * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
 215          * iterate through all css's attached to a given cgroup.
 216          */
 217         struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
 218
 219         /* all threaded csets whose ->dom_cset points to this cset */
 220         struct list_head threaded_csets;
 221         struct list_head threaded_csets_node;
 222
 223         /*
 224          * List running through all cgroup groups in the same hash
 225          * slot. Protected by css_set_lock
 226          */
 227         struct hlist_node hlist;
 228
 229         /*
 230          * List of cgrp_cset_links pointing at cgroups referenced from this
 231          * css_set.  Protected by css_set_lock.
 232          */
 233         struct list_head cgrp_links;
 234
 235         /*
 236          * List of csets participating in the on-going migration either as
 237          * source or destination.  Protected by cgroup_mutex.
 238          */
 239         struct list_head mg_preload_node;
 240         struct list_head mg_node;
 241
 242         /*
 243          * If this cset is acting as the source of migration the following
 244          * two fields are set.  mg_src_cgrp and mg_dst_cgrp are
 245          * respectively the source and destination cgroups of the on-going
 246          * migration.  mg_dst_cset is the destination cset the target tasks
 247          * on this cset should be migrated to.  Protected by cgroup_mutex.
 248          */
 249         struct cgroup *mg_src_cgrp;
 250         struct cgroup *mg_dst_cgrp;
 251         struct css_set *mg_dst_cset;
 252
 253         /* dead and being drained, ignore for migration */
 254         bool dead;
 255
 256         /* For RCU-protected deletion */
 257         struct rcu_head rcu_head;
 258 };
 259
 260 struct cgroup {
 261         /* self css with NULL ->ss, points back to this cgroup */
 262         struct cgroup_subsys_state self;
 263
 264         unsigned long flags;            /* "unsigned long" so bitops work */
 265
 266         /*
 267          * idr allocated in-hierarchy ID.
 268          *
 269          * ID 0 is not used, the ID of the root cgroup is always 1, and a
 270          * new cgroup will be assigned with a smallest available ID.
 271          *
 272          * Allocating/Removing ID must be protected by cgroup_mutex.
 273          */
 274         int id;
 275
 276         /*
 277          * The depth this cgroup is at.  The root is at depth zero and each
 278          * step down the hierarchy increments the level.  This along with
 279          * ancestor_ids[] can determine whether a given cgroup is a
 280          * descendant of another without traversing the hierarchy.
 281          */
 282         int level;
 283
 284         /* Maximum allowed descent tree depth */
 285         int max_depth;
 286
 287         /*
 288          * Keep track of total numbers of visible and dying descent cgroups.
 289          * Dying cgroups are cgroups which were deleted by a user,
 290          * but are still existing because someone else is holding a reference.
 291          * max_descendants is a maximum allowed number of descent cgroups.
 292          */
 293         int nr_descendants;
 294         int nr_dying_descendants;
 295         int max_descendants;
 296
 297         /*
 298          * Each non-empty css_set associated with this cgroup contributes
 299          * one to nr_populated_csets.  The counter is zero iff this cgroup
 300          * doesn't have any tasks.
 301          *
 302          * All children which have non-zero nr_populated_csets and/or
 303          * nr_populated_children of their own contribute one to either
 304          * nr_populated_domain_children or nr_populated_threaded_children
 305          * depending on their type.  Each counter is zero iff all cgroups
 306          * of the type in the subtree proper don't have any tasks.
 307          */
 308         int nr_populated_csets;
 309         int nr_populated_domain_children;
 310         int nr_populated_threaded_children;
 311
 312         int nr_threaded_children;       /* # of live threaded child cgroups */
 313
 314         struct kernfs_node *kn;         /* cgroup kernfs entry */
 315         struct cgroup_file procs_file;  /* handle for "cgroup.procs" */
 316         struct cgroup_file events_file; /* handle for "cgroup.events" */
 317
 318         /*
 319          * The bitmask of subsystems enabled on the child cgroups.
 320          * ->subtree_control is the one configured through
 321          * "cgroup.subtree_control" while ->child_ss_mask is the effective
 322          * one which may have more subsystems enabled.  Controller knobs
 323          * are made available iff it's enabled in ->subtree_control.
 324          */
 325         u16 subtree_control;
 326         u16 subtree_ss_mask;
 327         u16 old_subtree_control;
 328         u16 old_subtree_ss_mask;
 329
 330         /* Private pointers for each registered subsystem */
 331         struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
 332
 333         struct cgroup_root *root;
 334
 335         /*
 336          * List of cgrp_cset_links pointing at css_sets with tasks in this
 337          * cgroup.  Protected by css_set_lock.
 338          */
 339         struct list_head cset_links;
 340
 341         /*
 342          * On the default hierarchy, a css_set for a cgroup with some
 343          * susbsys disabled will point to css's which are associated with
 344          * the closest ancestor which has the subsys enabled.  The
 345          * following lists all css_sets which point to this cgroup's css
 346          * for the given subsystem.
 347          */
 348         struct list_head e_csets[CGROUP_SUBSYS_COUNT];
 349
 350         /*
 351          * If !threaded, self.  If threaded, it points to the nearest
 352          * domain ancestor.  Inside a threaded subtree, cgroups are exempt
 353          * from process granularity and no-internal-task constraint.
 354          * Domain level resource consumptions which aren't tied to a
 355          * specific task are charged to the dom_cgrp.
 356          */
 357         struct cgroup *dom_cgrp;
 358         struct cgroup *old_dom_cgrp;            /* used while enabling threaded */
 359
 360         /*
 361          * list of pidlists, up to two for each namespace (one for procs, one
 362          * for tasks); created on demand.
 363          */
 364         struct list_head pidlists;
 365         struct mutex pidlist_mutex;
 366
 367         /* used to wait for offlining of csses */
 368         wait_queue_head_t offline_waitq;
 369
 370         /* used to schedule release agent */
 371         struct work_struct release_agent_work;
 372
 373         /* used to track pressure stalls */
 374         struct psi_group psi;
 375
 376         /* used to store eBPF programs */
 377         struct cgroup_bpf bpf;
 378
 379         /* ids of the ancestors at each level including self */
 380         int ancestor_ids[];
 381 };
 382
 383 /*
 384  * A cgroup_root represents the root of a cgroup hierarchy, and may be
 385  * associated with a kernfs_root to form an active hierarchy.  This is
 386  * internal to cgroup core.  Don't access directly from controllers.
 387  */
 388 struct cgroup_root {
 389         struct kernfs_root *kf_root;
 390
 391         /* The bitmask of subsystems attached to this hierarchy */
 392         unsigned int subsys_mask;
 393
 394         /* Unique id for this hierarchy. */
 395         int hierarchy_id;
 396
 397         /* The root cgroup.  Root is destroyed on its release. */
 398         struct cgroup cgrp;
 399
 400         /* for cgrp->ancestor_ids[0] */
 401         int cgrp_ancestor_id_storage;
 402
 403         /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
 404         atomic_t nr_cgrps;
 405
 406         /* A list running through the active hierarchies */
 407         struct list_head root_list;
 408
 409         /* Hierarchy-specific flags */
 410         unsigned int flags;
 411
 412         /* IDs for cgroups in this hierarchy */
 413         struct idr cgroup_idr;
 414
 415         /* The path to use for release notifications. */
 416         char release_agent_path[PATH_MAX];
 417
 418         /* The name for this hierarchy - may be empty */
 419         char name[MAX_CGROUP_ROOT_NAMELEN];
 420 };
 421
 422 /*
 423  * struct cftype: handler definitions for cgroup control files
 424  *
 425  * When reading/writing to a file:
 426  *      - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
 427  *      - the 'cftype' of the file is file->f_path.dentry->d_fsdata
 428  */
 429 struct cftype {
 430         /*
 431          * By convention, the name should begin with the name of the
 432          * subsystem, followed by a period.  Zero length string indicates
 433          * end of cftype array.
 434          */
 435         char name[MAX_CFTYPE_NAME];
 436         unsigned long private;
 437
 438         /*
 439          * The maximum length of string, excluding trailing nul, that can
 440          * be passed to write.  If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
 441          */
 442         size_t max_write_len;
 443
 444         /* CFTYPE_* flags */
 445         unsigned int flags;
 446
 447         /*
 448          * If non-zero, should contain the offset from the start of css to
 449          * a struct cgroup_file field.  cgroup will record the handle of
 450          * the created file into it.  The recorded handle can be used as
 451          * long as the containing css remains accessible.
 452          */
 453         unsigned int file_offset;
 454
 455         /*
 456          * Fields used for internal bookkeeping.  Initialized automatically
 457          * during registration.
 458          */
 459         struct cgroup_subsys *ss;       /* NULL for cgroup core files */
 460         struct list_head node;          /* anchored at ss->cfts */
 461         struct kernfs_ops *kf_ops;
 462
 463         int (*open)(struct kernfs_open_file *of);
 464         void (*release)(struct kernfs_open_file *of);
 465
 466         /*
 467          * read_u64() is a shortcut for the common case of returning a
 468          * single integer. Use it in place of read()
 469          */
 470         u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
 471         /*
 472          * read_s64() is a signed version of read_u64()
 473          */
 474         s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
 475
 476         /* generic seq_file read interface */
 477         int (*seq_show)(struct seq_file *sf, void *v);
 478
 479         /* optional ops, implement all or none */
 480         void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
 481         void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
 482         void (*seq_stop)(struct seq_file *sf, void *v);
 483
 484         /*
 485          * write_u64() is a shortcut for the common case of accepting
 486          * a single integer (as parsed by simple_strtoull) from
 487          * userspace. Use in place of write(); return 0 or error.
 488          */
 489         int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
 490                          u64 val);
 491         /*
 492          * write_s64() is a signed version of write_u64()
 493          */
 494         int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
 495                          s64 val);
 496
 497         /*
 498          * write() is the generic write callback which maps directly to
 499          * kernfs write operation and overrides all other operations.
 500          * Maximum write size is determined by ->max_write_len.  Use
 501          * of_css/cft() to access the associated css and cft.
 502          */
 503         ssize_t (*write)(struct kernfs_open_file *of,
 504                          char *buf, size_t nbytes, loff_t off);
 505
 506         unsigned int (*poll)(struct kernfs_open_file *of,
 507                              struct poll_table_struct *pt);
 508
 509 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 510         struct lock_class_key   lockdep_key;
 511 #endif
 512 };
 513
 514 /*
 515  * Control Group subsystem type.
 516  * See Documentation/cgroups/cgroups.txt for details
 517  */
 518 struct cgroup_subsys {
 519         struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
 520         int (*css_online)(struct cgroup_subsys_state *css);
 521         void (*css_offline)(struct cgroup_subsys_state *css);
 522         void (*css_released)(struct cgroup_subsys_state *css);
 523         void (*css_free)(struct cgroup_subsys_state *css);
 524         void (*css_reset)(struct cgroup_subsys_state *css);
 525
 526         int (*can_attach)(struct cgroup_taskset *tset);
 527         void (*cancel_attach)(struct cgroup_taskset *tset);
 528         void (*attach)(struct cgroup_taskset *tset);
 529         void (*post_attach)(void);
 530         int (*can_fork)(struct task_struct *task);
 531         void (*cancel_fork)(struct task_struct *task);
 532         void (*fork)(struct task_struct *task);
 533         void (*exit)(struct task_struct *task);
 534         void (*release)(struct task_struct *task);
 535         void (*bind)(struct cgroup_subsys_state *root_css);
 536
 537         bool early_init:1;
 538
 539         /*
 540          * If %true, the controller, on the default hierarchy, doesn't show
 541          * up in "cgroup.controllers" or "cgroup.subtree_control", is
 542          * implicitly enabled on all cgroups on the default hierarchy, and
 543          * bypasses the "no internal process" constraint.  This is for
 544          * utility type controllers which is transparent to userland.
 545          *
 546          * An implicit controller can be stolen from the default hierarchy
 547          * anytime and thus must be okay with offline csses from previous
 548          * hierarchies coexisting with csses for the current one.
 549          */
 550         bool implicit_on_dfl:1;
 551
 552         /*
 553          * If %true, the controller, supports threaded mode on the default
 554          * hierarchy.  In a threaded subtree, both process granularity and
 555          * no-internal-process constraint are ignored and a threaded
 556          * controllers should be able to handle that.
 557          *
 558          * Note that as an implicit controller is automatically enabled on
 559          * all cgroups on the default hierarchy, it should also be
 560          * threaded.  implicit && !threaded is not supported.
 561          */
 562         bool threaded:1;
 563
 564         /*
 565          * If %false, this subsystem is properly hierarchical -
 566          * configuration, resource accounting and restriction on a parent
 567          * cgroup cover those of its children.  If %true, hierarchy support
 568          * is broken in some ways - some subsystems ignore hierarchy
 569          * completely while others are only implemented half-way.
 570          *
 571          * It's now disallowed to create nested cgroups if the subsystem is
 572          * broken and cgroup core will emit a warning message on such
 573          * cases.  Eventually, all subsystems will be made properly
 574          * hierarchical and this will go away.
 575          */
 576         bool broken_hierarchy:1;
 577         bool warned_broken_hierarchy:1;
 578
 579         /* the following two fields are initialized automtically during boot */
 580         int id;
 581         const char *name;
 582
 583         /* optional, initialized automatically during boot if not set */
 584         const char *legacy_name;
 585
 586         /* link to parent, protected by cgroup_lock() */
 587         struct cgroup_root *root;
 588
 589         /* idr for css->id */
 590         struct idr css_idr;
 591
 592         /*
 593          * List of cftypes.  Each entry is the first entry of an array
 594          * terminated by zero length name.
 595          */
 596         struct list_head cfts;
 597
 598         /*
 599          * Base cftypes which are automatically registered.  The two can
 600          * point to the same array.
 601          */
 602         struct cftype *dfl_cftypes;     /* for the default hierarchy */
 603         struct cftype *legacy_cftypes;  /* for the legacy hierarchies */
 604
 605         /*
 606          * A subsystem may depend on other subsystems.  When such subsystem
 607          * is enabled on a cgroup, the depended-upon subsystems are enabled
 608          * together if available.  Subsystems enabled due to dependency are
 609          * not visible to userland until explicitly enabled.  The following
 610          * specifies the mask of subsystems that this one depends on.
 611          */
 612         unsigned int depends_on;
 613 };
 614
 615 extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
 616
 617 /**
 618  * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
 619  * @tsk: target task
 620  *
 621  * Allows cgroup operations to synchronize against threadgroup changes
 622  * using a percpu_rw_semaphore.
 623  */
 624 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
 625 {
 626         percpu_down_read(&cgroup_threadgroup_rwsem);
 627 }
 628
 629 /**
 630  * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
 631  * @tsk: target task
 632  *
 633  * Counterpart of cgroup_threadcgroup_change_begin().
 634  */
 635 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
 636 {
 637         percpu_up_read(&cgroup_threadgroup_rwsem);
 638 }
 639
 640 #else   /* CONFIG_CGROUPS */
 641
 642 #define CGROUP_SUBSYS_COUNT 0
 643
 644 static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
 645 {
 646         might_sleep();
 647 }
 648
 649 static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
 650
 651 #endif  /* CONFIG_CGROUPS */
 652
 653 #ifdef CONFIG_SOCK_CGROUP_DATA
 654
 655 /*
 656  * sock_cgroup_data is embedded at sock->sk_cgrp_data and contains
 657  * per-socket cgroup information except for memcg association.
 658  *
 659  * On legacy hierarchies, net_prio and net_cls controllers directly set
 660  * attributes on each sock which can then be tested by the network layer.
 661  * On the default hierarchy, each sock is associated with the cgroup it was
 662  * created in and the networking layer can match the cgroup directly.
 663  *
 664  * To avoid carrying all three cgroup related fields separately in sock,
 665  * sock_cgroup_data overloads (prioidx, classid) and the cgroup pointer.
 666  * On boot, sock_cgroup_data records the cgroup that the sock was created
 667  * in so that cgroup2 matches can be made; however, once either net_prio or
 668  * net_cls starts being used, the area is overriden to carry prioidx and/or
 669  * classid.  The two modes are distinguished by whether the lowest bit is
 670  * set.  Clear bit indicates cgroup pointer while set bit prioidx and
 671  * classid.
 672  *
 673  * While userland may start using net_prio or net_cls at any time, once
 674  * either is used, cgroup2 matching no longer works.  There is no reason to
 675  * mix the two and this is in line with how legacy and v2 compatibility is
 676  * handled.  On mode switch, cgroup references which are already being
 677  * pointed to by socks may be leaked.  While this can be remedied by adding
 678  * synchronization around sock_cgroup_data, given that the number of leaked
 679  * cgroups is bound and highly unlikely to be high, this seems to be the
 680  * better trade-off.
 681  */
 682 struct sock_cgroup_data {
 683         union {
 684 #ifdef __LITTLE_ENDIAN
 685                 struct {
 686                         u8      is_data;
 687                         u8      padding;
 688                         u16     prioidx;
 689                         u32     classid;
 690                 } __packed;
 691 #else
 692                 struct {
 693                         u32     classid;
 694                         u16     prioidx;
 695                         u8      padding;
 696                         u8      is_data;
 697                 } __packed;
 698 #endif
 699                 u64             val;
 700         };
 701 };
 702
 703 /*
 704  * There's a theoretical window where the following accessors race with
 705  * updaters and return part of the previous pointer as the prioidx or
 706  * classid.  Such races are short-lived and the result isn't critical.
 707  */
 708 static inline u16 sock_cgroup_prioidx(const struct sock_cgroup_data *skcd)
 709 {
 710         /* fallback to 1 which is always the ID of the root cgroup */
 711         return (skcd->is_data & 1) ? skcd->prioidx : 1;
 712 }
 713
 714 static inline u32 sock_cgroup_classid(const struct sock_cgroup_data *skcd)
 715 {
 716         /* fallback to 0 which is the unconfigured default classid */
 717         return (skcd->is_data & 1) ? skcd->classid : 0;
 718 }
 719
 720 /*
 721  * If invoked concurrently, the updaters may clobber each other.  The
 722  * caller is responsible for synchronization.
 723  */
 724 static inline void sock_cgroup_set_prioidx(struct sock_cgroup_data *skcd,
 725                                            u16 prioidx)
 726 {
 727         struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
 728
 729         if (sock_cgroup_prioidx(&skcd_buf) == prioidx)
 730                 return;
 731
 732         if (!(skcd_buf.is_data & 1)) {
 733                 skcd_buf.val = 0;
 734                 skcd_buf.is_data = 1;
 735         }
 736
 737         skcd_buf.prioidx = prioidx;
 738         WRITE_ONCE(skcd->val, skcd_buf.val);    /* see sock_cgroup_ptr() */
 739 }
 740
 741 static inline void sock_cgroup_set_classid(struct sock_cgroup_data *skcd,
 742                                            u32 classid)
 743 {
 744         struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
 745
 746         if (sock_cgroup_classid(&skcd_buf) == classid)
 747                 return;
 748
 749         if (!(skcd_buf.is_data & 1)) {
 750                 skcd_buf.val = 0;
 751                 skcd_buf.is_data = 1;
 752         }
 753
 754         skcd_buf.classid = classid;
 755         WRITE_ONCE(skcd->val, skcd_buf.val);    /* see sock_cgroup_ptr() */
 756 }
 757
 758 #else   /* CONFIG_SOCK_CGROUP_DATA */
 759
 760 struct sock_cgroup_data {
 761 };
 762
 763 #endif  /* CONFIG_SOCK_CGROUP_DATA */
 764
 765 #endif  /* _LINUX_CGROUP_DEFS_H */