1 /* SPDX-License-Identifier: GPL-2.0 */
3 * linux/cgroup-defs.h - basic definitions for cgroup
5 * This file provides basic type and interface. Include this file directly
6 * only if necessary to avoid cyclic dependencies.
8 #ifndef _LINUX_CGROUP_DEFS_H
9 #define _LINUX_CGROUP_DEFS_H
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/u64_stats_sync.h>
21 #include <linux/workqueue.h>
22 #include <linux/bpf-cgroup.h>
23 #include <linux/psi_types.h>
30 struct cgroup_taskset
;
33 struct kernfs_open_file
;
35 struct poll_table_struct
;
37 #define MAX_CGROUP_TYPE_NAMELEN 32
38 #define MAX_CGROUP_ROOT_NAMELEN 64
39 #define MAX_CFTYPE_NAME 64
41 /* define the enumeration of all cgroup subsystems */
42 #define SUBSYS(_x) _x ## _cgrp_id,
43 enum cgroup_subsys_id
{
44 #include <linux/cgroup_subsys.h>
49 /* bits in struct cgroup_subsys_state flags field */
51 CSS_NO_REF
= (1 << 0), /* no reference counting for this css */
52 CSS_ONLINE
= (1 << 1), /* between ->css_online() and ->css_offline() */
53 CSS_RELEASED
= (1 << 2), /* refcnt reached zero, released */
54 CSS_VISIBLE
= (1 << 3), /* css is visible to userland */
55 CSS_DYING
= (1 << 4), /* css is dying */
58 /* bits in struct cgroup flags field */
60 /* Control Group requires release notifications to userspace */
61 CGRP_NOTIFY_ON_RELEASE
,
63 * Clone the parent's configuration when creating a new child
64 * cpuset cgroup. For historical reasons, this option can be
65 * specified at mount time and thus is implemented here.
67 CGRP_CPUSET_CLONE_CHILDREN
,
69 /* Control group has to be frozen. */
72 /* Cgroup is frozen. */
76 /* cgroup_root->flags */
78 CGRP_ROOT_NOPREFIX
= (1 << 1), /* mounted subsystems have no named prefix */
79 CGRP_ROOT_XATTR
= (1 << 2), /* supports extended attributes */
82 * Consider namespaces as delegation boundaries. If this flag is
83 * set, controller specific interface files in a namespace root
84 * aren't writeable from inside the namespace.
86 CGRP_ROOT_NS_DELEGATE
= (1 << 3),
89 * Enable cpuset controller in v1 cgroup to use v2 behavior.
91 CGRP_ROOT_CPUSET_V2_MODE
= (1 << 4),
94 * Enable legacy local memory.events.
96 CGRP_ROOT_MEMORY_LOCAL_EVENTS
= (1 << 5),
101 CFTYPE_ONLY_ON_ROOT
= (1 << 0), /* only create on root cgrp */
102 CFTYPE_NOT_ON_ROOT
= (1 << 1), /* don't create on root cgrp */
103 CFTYPE_NS_DELEGATABLE
= (1 << 2), /* writeable beyond delegation boundaries */
105 CFTYPE_NO_PREFIX
= (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
106 CFTYPE_WORLD_WRITABLE
= (1 << 4), /* (DON'T USE FOR NEW FILES) S_IWUGO */
107 CFTYPE_DEBUG
= (1 << 5), /* create when cgroup_debug */
109 /* internal flags, do not use outside cgroup core proper */
110 __CFTYPE_ONLY_ON_DFL
= (1 << 16), /* only on default hierarchy */
111 __CFTYPE_NOT_ON_DFL
= (1 << 17), /* not on default hierarchy */
115 * cgroup_file is the handle for a file instance created in a cgroup which
116 * is used, for example, to generate file changed notifications. This can
117 * be obtained by setting cftype->file_offset.
120 /* do not access any fields from outside cgroup core */
121 struct kernfs_node
*kn
;
122 unsigned long notified_at
;
123 struct timer_list notify_timer
;
127 * Per-subsystem/per-cgroup state maintained by the system. This is the
128 * fundamental structural building block that controllers deal with.
130 * Fields marked with "PI:" are public and immutable and may be accessed
131 * directly without synchronization.
133 struct cgroup_subsys_state
{
134 /* PI: the cgroup that this css is attached to */
135 struct cgroup
*cgroup
;
137 /* PI: the cgroup subsystem that this css is attached to */
138 struct cgroup_subsys
*ss
;
140 /* reference count - access via css_[try]get() and css_put() */
141 struct percpu_ref refcnt
;
143 /* siblings list anchored at the parent's ->children */
144 struct list_head sibling
;
145 struct list_head children
;
147 /* flush target list anchored at cgrp->rstat_css_list */
148 struct list_head rstat_css_node
;
151 * PI: Subsys-unique ID. 0 is unused and root is always 1. The
152 * matching css can be looked up using css_from_id().
159 * Monotonically increasing unique serial number which defines a
160 * uniform order among all csses. It's guaranteed that all
161 * ->children lists are in the ascending order of ->serial_nr and
162 * used to allow interrupting and resuming iterations.
167 * Incremented by online self and children. Used to guarantee that
168 * parents are not offlined before their children.
172 /* percpu_ref killing and RCU release */
173 struct work_struct destroy_work
;
174 struct rcu_work destroy_rwork
;
177 * PI: the parent css. Placed here for cache proximity to following
178 * fields of the containing structure.
180 struct cgroup_subsys_state
*parent
;
184 * A css_set is a structure holding pointers to a set of
185 * cgroup_subsys_state objects. This saves space in the task struct
186 * object and speeds up fork()/exit(), since a single inc/dec and a
187 * list_add()/del() can bump the reference count on the entire cgroup
192 * Set of subsystem states, one for each subsystem. This array is
193 * immutable after creation apart from the init_css_set during
194 * subsystem registration (at boot time).
196 struct cgroup_subsys_state
*subsys
[CGROUP_SUBSYS_COUNT
];
198 /* reference count */
202 * For a domain cgroup, the following points to self. If threaded,
203 * to the matching cset of the nearest domain ancestor. The
204 * dom_cset provides access to the domain cgroup and its csses to
205 * which domain level resource consumptions should be charged.
207 struct css_set
*dom_cset
;
209 /* the default cgroup associated with this css_set */
210 struct cgroup
*dfl_cgrp
;
212 /* internal task count, protected by css_set_lock */
216 * Lists running through all tasks using this cgroup group.
217 * mg_tasks lists tasks which belong to this cset but are in the
218 * process of being migrated out or in. Protected by
219 * css_set_rwsem, but, during migration, once tasks are moved to
220 * mg_tasks, it can be read safely while holding cgroup_mutex.
222 struct list_head tasks
;
223 struct list_head mg_tasks
;
224 struct list_head dying_tasks
;
226 /* all css_task_iters currently walking this cset */
227 struct list_head task_iters
;
230 * On the default hierarhcy, ->subsys[ssid] may point to a css
231 * attached to an ancestor instead of the cgroup this css_set is
232 * associated with. The following node is anchored at
233 * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
234 * iterate through all css's attached to a given cgroup.
236 struct list_head e_cset_node
[CGROUP_SUBSYS_COUNT
];
238 /* all threaded csets whose ->dom_cset points to this cset */
239 struct list_head threaded_csets
;
240 struct list_head threaded_csets_node
;
243 * List running through all cgroup groups in the same hash
244 * slot. Protected by css_set_lock
246 struct hlist_node hlist
;
249 * List of cgrp_cset_links pointing at cgroups referenced from this
250 * css_set. Protected by css_set_lock.
252 struct list_head cgrp_links
;
255 * List of csets participating in the on-going migration either as
256 * source or destination. Protected by cgroup_mutex.
258 struct list_head mg_preload_node
;
259 struct list_head mg_node
;
262 * If this cset is acting as the source of migration the following
263 * two fields are set. mg_src_cgrp and mg_dst_cgrp are
264 * respectively the source and destination cgroups of the on-going
265 * migration. mg_dst_cset is the destination cset the target tasks
266 * on this cset should be migrated to. Protected by cgroup_mutex.
268 struct cgroup
*mg_src_cgrp
;
269 struct cgroup
*mg_dst_cgrp
;
270 struct css_set
*mg_dst_cset
;
272 /* dead and being drained, ignore for migration */
275 /* For RCU-protected deletion */
276 struct rcu_head rcu_head
;
279 struct cgroup_base_stat
{
280 struct task_cputime cputime
;
284 * rstat - cgroup scalable recursive statistics. Accounting is done
285 * per-cpu in cgroup_rstat_cpu which is then lazily propagated up the
286 * hierarchy on reads.
288 * When a stat gets updated, the cgroup_rstat_cpu and its ancestors are
289 * linked into the updated tree. On the following read, propagation only
290 * considers and consumes the updated tree. This makes reading O(the
291 * number of descendants which have been active since last read) instead of
292 * O(the total number of descendants).
294 * This is important because there can be a lot of (draining) cgroups which
295 * aren't active and stat may be read frequently. The combination can
296 * become very expensive. By propagating selectively, increasing reading
297 * frequency decreases the cost of each read.
299 * This struct hosts both the fields which implement the above -
300 * updated_children and updated_next - and the fields which track basic
301 * resource statistics on top of it - bsync, bstat and last_bstat.
303 struct cgroup_rstat_cpu
{
305 * ->bsync protects ->bstat. These are the only fields which get
306 * updated in the hot path.
308 struct u64_stats_sync bsync
;
309 struct cgroup_base_stat bstat
;
312 * Snapshots at the last reading. These are used to calculate the
313 * deltas to propagate to the global counters.
315 struct cgroup_base_stat last_bstat
;
318 * Child cgroups with stat updates on this cpu since the last read
319 * are linked on the parent's ->updated_children through
322 * In addition to being more compact, singly-linked list pointing
323 * to the cgroup makes it unnecessary for each per-cpu struct to
324 * point back to the associated cgroup.
326 * Protected by per-cpu cgroup_rstat_cpu_lock.
328 struct cgroup
*updated_children
; /* terminated by self cgroup */
329 struct cgroup
*updated_next
; /* NULL iff not on the list */
332 struct cgroup_freezer_state
{
333 /* Should the cgroup and its descendants be frozen. */
336 /* Should the cgroup actually be frozen? */
339 /* Fields below are protected by css_set_lock */
341 /* Number of frozen descendant cgroups */
342 int nr_frozen_descendants
;
345 * Number of tasks, which are counted as frozen:
346 * frozen, SIGSTOPped, and PTRACEd.
352 /* self css with NULL ->ss, points back to this cgroup */
353 struct cgroup_subsys_state self
;
355 unsigned long flags
; /* "unsigned long" so bitops work */
358 * idr allocated in-hierarchy ID.
360 * ID 0 is not used, the ID of the root cgroup is always 1, and a
361 * new cgroup will be assigned with a smallest available ID.
363 * Allocating/Removing ID must be protected by cgroup_mutex.
368 * The depth this cgroup is at. The root is at depth zero and each
369 * step down the hierarchy increments the level. This along with
370 * ancestor_ids[] can determine whether a given cgroup is a
371 * descendant of another without traversing the hierarchy.
375 /* Maximum allowed descent tree depth */
379 * Keep track of total numbers of visible and dying descent cgroups.
380 * Dying cgroups are cgroups which were deleted by a user,
381 * but are still existing because someone else is holding a reference.
382 * max_descendants is a maximum allowed number of descent cgroups.
384 * nr_descendants and nr_dying_descendants are protected
385 * by cgroup_mutex and css_set_lock. It's fine to read them holding
386 * any of cgroup_mutex and css_set_lock; for writing both locks
390 int nr_dying_descendants
;
394 * Each non-empty css_set associated with this cgroup contributes
395 * one to nr_populated_csets. The counter is zero iff this cgroup
396 * doesn't have any tasks.
398 * All children which have non-zero nr_populated_csets and/or
399 * nr_populated_children of their own contribute one to either
400 * nr_populated_domain_children or nr_populated_threaded_children
401 * depending on their type. Each counter is zero iff all cgroups
402 * of the type in the subtree proper don't have any tasks.
404 int nr_populated_csets
;
405 int nr_populated_domain_children
;
406 int nr_populated_threaded_children
;
408 int nr_threaded_children
; /* # of live threaded child cgroups */
410 struct kernfs_node
*kn
; /* cgroup kernfs entry */
411 struct cgroup_file procs_file
; /* handle for "cgroup.procs" */
412 struct cgroup_file events_file
; /* handle for "cgroup.events" */
415 * The bitmask of subsystems enabled on the child cgroups.
416 * ->subtree_control is the one configured through
417 * "cgroup.subtree_control" while ->child_ss_mask is the effective
418 * one which may have more subsystems enabled. Controller knobs
419 * are made available iff it's enabled in ->subtree_control.
423 u16 old_subtree_control
;
424 u16 old_subtree_ss_mask
;
426 /* Private pointers for each registered subsystem */
427 struct cgroup_subsys_state __rcu
*subsys
[CGROUP_SUBSYS_COUNT
];
429 struct cgroup_root
*root
;
432 * List of cgrp_cset_links pointing at css_sets with tasks in this
433 * cgroup. Protected by css_set_lock.
435 struct list_head cset_links
;
438 * On the default hierarchy, a css_set for a cgroup with some
439 * susbsys disabled will point to css's which are associated with
440 * the closest ancestor which has the subsys enabled. The
441 * following lists all css_sets which point to this cgroup's css
442 * for the given subsystem.
444 struct list_head e_csets
[CGROUP_SUBSYS_COUNT
];
447 * If !threaded, self. If threaded, it points to the nearest
448 * domain ancestor. Inside a threaded subtree, cgroups are exempt
449 * from process granularity and no-internal-task constraint.
450 * Domain level resource consumptions which aren't tied to a
451 * specific task are charged to the dom_cgrp.
453 struct cgroup
*dom_cgrp
;
454 struct cgroup
*old_dom_cgrp
; /* used while enabling threaded */
456 /* per-cpu recursive resource statistics */
457 struct cgroup_rstat_cpu __percpu
*rstat_cpu
;
458 struct list_head rstat_css_list
;
460 /* cgroup basic resource statistics */
461 struct cgroup_base_stat pending_bstat
; /* pending from children */
462 struct cgroup_base_stat bstat
;
463 struct prev_cputime prev_cputime
; /* for printing out cputime */
466 * list of pidlists, up to two for each namespace (one for procs, one
467 * for tasks); created on demand.
469 struct list_head pidlists
;
470 struct mutex pidlist_mutex
;
472 /* used to wait for offlining of csses */
473 wait_queue_head_t offline_waitq
;
475 /* used to schedule release agent */
476 struct work_struct release_agent_work
;
478 /* used to track pressure stalls */
479 struct psi_group psi
;
481 /* used to store eBPF programs */
482 struct cgroup_bpf bpf
;
484 /* If there is block congestion on this cgroup. */
485 atomic_t congestion_count
;
487 /* Used to store internal freezer state */
488 struct cgroup_freezer_state freezer
;
490 /* ids of the ancestors at each level including self */
495 * A cgroup_root represents the root of a cgroup hierarchy, and may be
496 * associated with a kernfs_root to form an active hierarchy. This is
497 * internal to cgroup core. Don't access directly from controllers.
500 struct kernfs_root
*kf_root
;
502 /* The bitmask of subsystems attached to this hierarchy */
503 unsigned int subsys_mask
;
505 /* Unique id for this hierarchy. */
508 /* The root cgroup. Root is destroyed on its release. */
511 /* for cgrp->ancestor_ids[0] */
512 int cgrp_ancestor_id_storage
;
514 /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
517 /* A list running through the active hierarchies */
518 struct list_head root_list
;
520 /* Hierarchy-specific flags */
523 /* IDs for cgroups in this hierarchy */
524 struct idr cgroup_idr
;
526 /* The path to use for release notifications. */
527 char release_agent_path
[PATH_MAX
];
529 /* The name for this hierarchy - may be empty */
530 char name
[MAX_CGROUP_ROOT_NAMELEN
];
534 * struct cftype: handler definitions for cgroup control files
536 * When reading/writing to a file:
537 * - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
538 * - the 'cftype' of the file is file->f_path.dentry->d_fsdata
542 * By convention, the name should begin with the name of the
543 * subsystem, followed by a period. Zero length string indicates
544 * end of cftype array.
546 char name
[MAX_CFTYPE_NAME
];
547 unsigned long private;
550 * The maximum length of string, excluding trailing nul, that can
551 * be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
553 size_t max_write_len
;
559 * If non-zero, should contain the offset from the start of css to
560 * a struct cgroup_file field. cgroup will record the handle of
561 * the created file into it. The recorded handle can be used as
562 * long as the containing css remains accessible.
564 unsigned int file_offset
;
567 * Fields used for internal bookkeeping. Initialized automatically
568 * during registration.
570 struct cgroup_subsys
*ss
; /* NULL for cgroup core files */
571 struct list_head node
; /* anchored at ss->cfts */
572 struct kernfs_ops
*kf_ops
;
574 int (*open
)(struct kernfs_open_file
*of
);
575 void (*release
)(struct kernfs_open_file
*of
);
578 * read_u64() is a shortcut for the common case of returning a
579 * single integer. Use it in place of read()
581 u64 (*read_u64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
);
583 * read_s64() is a signed version of read_u64()
585 s64 (*read_s64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
);
587 /* generic seq_file read interface */
588 int (*seq_show
)(struct seq_file
*sf
, void *v
);
590 /* optional ops, implement all or none */
591 void *(*seq_start
)(struct seq_file
*sf
, loff_t
*ppos
);
592 void *(*seq_next
)(struct seq_file
*sf
, void *v
, loff_t
*ppos
);
593 void (*seq_stop
)(struct seq_file
*sf
, void *v
);
596 * write_u64() is a shortcut for the common case of accepting
597 * a single integer (as parsed by simple_strtoull) from
598 * userspace. Use in place of write(); return 0 or error.
600 int (*write_u64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
,
603 * write_s64() is a signed version of write_u64()
605 int (*write_s64
)(struct cgroup_subsys_state
*css
, struct cftype
*cft
,
609 * write() is the generic write callback which maps directly to
610 * kernfs write operation and overrides all other operations.
611 * Maximum write size is determined by ->max_write_len. Use
612 * of_css/cft() to access the associated css and cft.
614 ssize_t (*write
)(struct kernfs_open_file
*of
,
615 char *buf
, size_t nbytes
, loff_t off
);
617 __poll_t (*poll
)(struct kernfs_open_file
*of
,
618 struct poll_table_struct
*pt
);
620 #ifdef CONFIG_DEBUG_LOCK_ALLOC
621 struct lock_class_key lockdep_key
;
626 * Control Group subsystem type.
627 * See Documentation/cgroup-v1/cgroups.txt for details
629 struct cgroup_subsys
{
630 struct cgroup_subsys_state
*(*css_alloc
)(struct cgroup_subsys_state
*parent_css
);
631 int (*css_online
)(struct cgroup_subsys_state
*css
);
632 void (*css_offline
)(struct cgroup_subsys_state
*css
);
633 void (*css_released
)(struct cgroup_subsys_state
*css
);
634 void (*css_free
)(struct cgroup_subsys_state
*css
);
635 void (*css_reset
)(struct cgroup_subsys_state
*css
);
636 void (*css_rstat_flush
)(struct cgroup_subsys_state
*css
, int cpu
);
637 int (*css_extra_stat_show
)(struct seq_file
*seq
,
638 struct cgroup_subsys_state
*css
);
640 int (*can_attach
)(struct cgroup_taskset
*tset
);
641 void (*cancel_attach
)(struct cgroup_taskset
*tset
);
642 void (*attach
)(struct cgroup_taskset
*tset
);
643 void (*post_attach
)(void);
644 int (*can_fork
)(struct task_struct
*task
);
645 void (*cancel_fork
)(struct task_struct
*task
);
646 void (*fork
)(struct task_struct
*task
);
647 void (*exit
)(struct task_struct
*task
);
648 void (*release
)(struct task_struct
*task
);
649 void (*bind
)(struct cgroup_subsys_state
*root_css
);
654 * If %true, the controller, on the default hierarchy, doesn't show
655 * up in "cgroup.controllers" or "cgroup.subtree_control", is
656 * implicitly enabled on all cgroups on the default hierarchy, and
657 * bypasses the "no internal process" constraint. This is for
658 * utility type controllers which is transparent to userland.
660 * An implicit controller can be stolen from the default hierarchy
661 * anytime and thus must be okay with offline csses from previous
662 * hierarchies coexisting with csses for the current one.
664 bool implicit_on_dfl
:1;
667 * If %true, the controller, supports threaded mode on the default
668 * hierarchy. In a threaded subtree, both process granularity and
669 * no-internal-process constraint are ignored and a threaded
670 * controllers should be able to handle that.
672 * Note that as an implicit controller is automatically enabled on
673 * all cgroups on the default hierarchy, it should also be
674 * threaded. implicit && !threaded is not supported.
679 * If %false, this subsystem is properly hierarchical -
680 * configuration, resource accounting and restriction on a parent
681 * cgroup cover those of its children. If %true, hierarchy support
682 * is broken in some ways - some subsystems ignore hierarchy
683 * completely while others are only implemented half-way.
685 * It's now disallowed to create nested cgroups if the subsystem is
686 * broken and cgroup core will emit a warning message on such
687 * cases. Eventually, all subsystems will be made properly
688 * hierarchical and this will go away.
690 bool broken_hierarchy
:1;
691 bool warned_broken_hierarchy
:1;
693 /* the following two fields are initialized automtically during boot */
697 /* optional, initialized automatically during boot if not set */
698 const char *legacy_name
;
700 /* link to parent, protected by cgroup_lock() */
701 struct cgroup_root
*root
;
703 /* idr for css->id */
707 * List of cftypes. Each entry is the first entry of an array
708 * terminated by zero length name.
710 struct list_head cfts
;
713 * Base cftypes which are automatically registered. The two can
714 * point to the same array.
716 struct cftype
*dfl_cftypes
; /* for the default hierarchy */
717 struct cftype
*legacy_cftypes
; /* for the legacy hierarchies */
720 * A subsystem may depend on other subsystems. When such subsystem
721 * is enabled on a cgroup, the depended-upon subsystems are enabled
722 * together if available. Subsystems enabled due to dependency are
723 * not visible to userland until explicitly enabled. The following
724 * specifies the mask of subsystems that this one depends on.
726 unsigned int depends_on
;
729 extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem
;
732 * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
735 * Allows cgroup operations to synchronize against threadgroup changes
736 * using a percpu_rw_semaphore.
738 static inline void cgroup_threadgroup_change_begin(struct task_struct
*tsk
)
740 percpu_down_read(&cgroup_threadgroup_rwsem
);
744 * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
747 * Counterpart of cgroup_threadcgroup_change_begin().
749 static inline void cgroup_threadgroup_change_end(struct task_struct
*tsk
)
751 percpu_up_read(&cgroup_threadgroup_rwsem
);
754 #else /* CONFIG_CGROUPS */
756 #define CGROUP_SUBSYS_COUNT 0
758 static inline void cgroup_threadgroup_change_begin(struct task_struct
*tsk
)
763 static inline void cgroup_threadgroup_change_end(struct task_struct
*tsk
) {}
765 #endif /* CONFIG_CGROUPS */
767 #ifdef CONFIG_SOCK_CGROUP_DATA
770 * sock_cgroup_data is embedded at sock->sk_cgrp_data and contains
771 * per-socket cgroup information except for memcg association.
773 * On legacy hierarchies, net_prio and net_cls controllers directly set
774 * attributes on each sock which can then be tested by the network layer.
775 * On the default hierarchy, each sock is associated with the cgroup it was
776 * created in and the networking layer can match the cgroup directly.
778 * To avoid carrying all three cgroup related fields separately in sock,
779 * sock_cgroup_data overloads (prioidx, classid) and the cgroup pointer.
780 * On boot, sock_cgroup_data records the cgroup that the sock was created
781 * in so that cgroup2 matches can be made; however, once either net_prio or
782 * net_cls starts being used, the area is overriden to carry prioidx and/or
783 * classid. The two modes are distinguished by whether the lowest bit is
784 * set. Clear bit indicates cgroup pointer while set bit prioidx and
787 * While userland may start using net_prio or net_cls at any time, once
788 * either is used, cgroup2 matching no longer works. There is no reason to
789 * mix the two and this is in line with how legacy and v2 compatibility is
790 * handled. On mode switch, cgroup references which are already being
791 * pointed to by socks may be leaked. While this can be remedied by adding
792 * synchronization around sock_cgroup_data, given that the number of leaked
793 * cgroups is bound and highly unlikely to be high, this seems to be the
796 struct sock_cgroup_data
{
798 #ifdef __LITTLE_ENDIAN
818 * There's a theoretical window where the following accessors race with
819 * updaters and return part of the previous pointer as the prioidx or
820 * classid. Such races are short-lived and the result isn't critical.
822 static inline u16
sock_cgroup_prioidx(const struct sock_cgroup_data
*skcd
)
824 /* fallback to 1 which is always the ID of the root cgroup */
825 return (skcd
->is_data
& 1) ? skcd
->prioidx
: 1;
828 static inline u32
sock_cgroup_classid(const struct sock_cgroup_data
*skcd
)
830 /* fallback to 0 which is the unconfigured default classid */
831 return (skcd
->is_data
& 1) ? skcd
->classid
: 0;
835 * If invoked concurrently, the updaters may clobber each other. The
836 * caller is responsible for synchronization.
838 static inline void sock_cgroup_set_prioidx(struct sock_cgroup_data
*skcd
,
841 struct sock_cgroup_data skcd_buf
= {{ .val
= READ_ONCE(skcd
->val
) }};
843 if (sock_cgroup_prioidx(&skcd_buf
) == prioidx
)
846 if (!(skcd_buf
.is_data
& 1)) {
848 skcd_buf
.is_data
= 1;
851 skcd_buf
.prioidx
= prioidx
;
852 WRITE_ONCE(skcd
->val
, skcd_buf
.val
); /* see sock_cgroup_ptr() */
855 static inline void sock_cgroup_set_classid(struct sock_cgroup_data
*skcd
,
858 struct sock_cgroup_data skcd_buf
= {{ .val
= READ_ONCE(skcd
->val
) }};
860 if (sock_cgroup_classid(&skcd_buf
) == classid
)
863 if (!(skcd_buf
.is_data
& 1)) {
865 skcd_buf
.is_data
= 1;
868 skcd_buf
.classid
= classid
;
869 WRITE_ONCE(skcd
->val
, skcd_buf
.val
); /* see sock_cgroup_ptr() */
872 #else /* CONFIG_SOCK_CGROUP_DATA */
874 struct sock_cgroup_data
{
877 #endif /* CONFIG_SOCK_CGROUP_DATA */
879 #endif /* _LINUX_CGROUP_DEFS_H */