v4.19.13 snapshot.
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
new file mode 100644
index 0000000..22254c1
--- /dev/null
+++ b/include/linux/cgroup-defs.h
@@ -0,0 +1,831 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * linux/cgroup-defs.h - basic definitions for cgroup
+ *
+ * This file provides basic type and interface. Include this file directly
+ * only if necessary to avoid cyclic dependencies.
+ */
+#ifndef _LINUX_CGROUP_DEFS_H
+#define _LINUX_CGROUP_DEFS_H
+
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/idr.h>
+#include <linux/wait.h>
+#include <linux/mutex.h>
+#include <linux/rcupdate.h>
+#include <linux/refcount.h>
+#include <linux/percpu-refcount.h>
+#include <linux/percpu-rwsem.h>
+#include <linux/u64_stats_sync.h>
+#include <linux/workqueue.h>
+#include <linux/bpf-cgroup.h>
+
+#ifdef CONFIG_CGROUPS
+
+struct cgroup;
+struct cgroup_root;
+struct cgroup_subsys;
+struct cgroup_taskset;
+struct kernfs_node;
+struct kernfs_ops;
+struct kernfs_open_file;
+struct seq_file;
+
+#define MAX_CGROUP_TYPE_NAMELEN 32
+#define MAX_CGROUP_ROOT_NAMELEN 64
+#define MAX_CFTYPE_NAME 64
+
+/* define the enumeration of all cgroup subsystems */
+#define SUBSYS(_x) _x ## _cgrp_id,
+enum cgroup_subsys_id {
+#include <linux/cgroup_subsys.h>
+ CGROUP_SUBSYS_COUNT,
+};
+#undef SUBSYS
+
+/* bits in struct cgroup_subsys_state flags field */
+enum {
+ CSS_NO_REF = (1 << 0), /* no reference counting for this css */
+ CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
+ CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */
+ CSS_VISIBLE = (1 << 3), /* css is visible to userland */
+ CSS_DYING = (1 << 4), /* css is dying */
+};
+
+/* bits in struct cgroup flags field */
+enum {
+ /* Control Group requires release notifications to userspace */
+ CGRP_NOTIFY_ON_RELEASE,
+ /*
+ * Clone the parent's configuration when creating a new child
+ * cpuset cgroup. For historical reasons, this option can be
+ * specified at mount time and thus is implemented here.
+ */
+ CGRP_CPUSET_CLONE_CHILDREN,
+};
+
+/* cgroup_root->flags */
+enum {
+ CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
+ CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
+
+ /*
+ * Consider namespaces as delegation boundaries. If this flag is
+ * set, controller specific interface files in a namespace root
+ * aren't writeable from inside the namespace.
+ */
+ CGRP_ROOT_NS_DELEGATE = (1 << 3),
+
+ /*
+ * Enable cpuset controller in v1 cgroup to use v2 behavior.
+ */
+ CGRP_ROOT_CPUSET_V2_MODE = (1 << 4),
+};
+
+/* cftype->flags */
+enum {
+ CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
+ CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
+ CFTYPE_NS_DELEGATABLE = (1 << 2), /* writeable beyond delegation boundaries */
+
+ CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
+ CFTYPE_WORLD_WRITABLE = (1 << 4), /* (DON'T USE FOR NEW FILES) S_IWUGO */
+
+ /* internal flags, do not use outside cgroup core proper */
+ __CFTYPE_ONLY_ON_DFL = (1 << 16), /* only on default hierarchy */
+ __CFTYPE_NOT_ON_DFL = (1 << 17), /* not on default hierarchy */
+};
+
+/*
+ * cgroup_file is the handle for a file instance created in a cgroup which
+ * is used, for example, to generate file changed notifications. This can
+ * be obtained by setting cftype->file_offset.
+ */
+struct cgroup_file {
+ /* do not access any fields from outside cgroup core */
+ struct kernfs_node *kn;
+ unsigned long notified_at;
+ struct timer_list notify_timer;
+};
+
+/*
+ * Per-subsystem/per-cgroup state maintained by the system. This is the
+ * fundamental structural building block that controllers deal with.
+ *
+ * Fields marked with "PI:" are public and immutable and may be accessed
+ * directly without synchronization.
+ */
+struct cgroup_subsys_state {
+ /* PI: the cgroup that this css is attached to */
+ struct cgroup *cgroup;
+
+ /* PI: the cgroup subsystem that this css is attached to */
+ struct cgroup_subsys *ss;
+
+ /* reference count - access via css_[try]get() and css_put() */
+ struct percpu_ref refcnt;
+
+ /* siblings list anchored at the parent's ->children */
+ struct list_head sibling;
+ struct list_head children;
+
+ /* flush target list anchored at cgrp->rstat_css_list */
+ struct list_head rstat_css_node;
+
+ /*
+ * PI: Subsys-unique ID. 0 is unused and root is always 1. The
+ * matching css can be looked up using css_from_id().
+ */
+ int id;
+
+ unsigned int flags;
+
+ /*
+ * Monotonically increasing unique serial number which defines a
+ * uniform order among all csses. It's guaranteed that all
+ * ->children lists are in the ascending order of ->serial_nr and
+ * used to allow interrupting and resuming iterations.
+ */
+ u64 serial_nr;
+
+ /*
+ * Incremented by online self and children. Used to guarantee that
+ * parents are not offlined before their children.
+ */
+ atomic_t online_cnt;
+
+ /* percpu_ref killing and RCU release */
+ struct work_struct destroy_work;
+ struct rcu_work destroy_rwork;
+
+ /*
+ * PI: the parent css. Placed here for cache proximity to following
+ * fields of the containing structure.
+ */
+ struct cgroup_subsys_state *parent;
+};
+
+/*
+ * A css_set is a structure holding pointers to a set of
+ * cgroup_subsys_state objects. This saves space in the task struct
+ * object and speeds up fork()/exit(), since a single inc/dec and a
+ * list_add()/del() can bump the reference count on the entire cgroup
+ * set for a task.
+ */
+struct css_set {
+ /*
+ * Set of subsystem states, one for each subsystem. This array is
+ * immutable after creation apart from the init_css_set during
+ * subsystem registration (at boot time).
+ */
+ struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
+
+ /* reference count */
+ refcount_t refcount;
+
+ /*
+ * For a domain cgroup, the following points to self. If threaded,
+ * to the matching cset of the nearest domain ancestor. The
+ * dom_cset provides access to the domain cgroup and its csses to
+ * which domain level resource consumptions should be charged.
+ */
+ struct css_set *dom_cset;
+
+ /* the default cgroup associated with this css_set */
+ struct cgroup *dfl_cgrp;
+
+ /* internal task count, protected by css_set_lock */
+ int nr_tasks;
+
+ /*
+ * Lists running through all tasks using this cgroup group.
+ * mg_tasks lists tasks which belong to this cset but are in the
+ * process of being migrated out or in. Protected by
+ * css_set_rwsem, but, during migration, once tasks are moved to
+ * mg_tasks, it can be read safely while holding cgroup_mutex.
+ */
+ struct list_head tasks;
+ struct list_head mg_tasks;
+
+ /* all css_task_iters currently walking this cset */
+ struct list_head task_iters;
+
+ /*
+ * On the default hierarhcy, ->subsys[ssid] may point to a css
+ * attached to an ancestor instead of the cgroup this css_set is
+ * associated with. The following node is anchored at
+ * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
+ * iterate through all css's attached to a given cgroup.
+ */
+ struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
+
+ /* all threaded csets whose ->dom_cset points to this cset */
+ struct list_head threaded_csets;
+ struct list_head threaded_csets_node;
+
+ /*
+ * List running through all cgroup groups in the same hash
+ * slot. Protected by css_set_lock
+ */
+ struct hlist_node hlist;
+
+ /*
+ * List of cgrp_cset_links pointing at cgroups referenced from this
+ * css_set. Protected by css_set_lock.
+ */
+ struct list_head cgrp_links;
+
+ /*
+ * List of csets participating in the on-going migration either as
+ * source or destination. Protected by cgroup_mutex.
+ */
+ struct list_head mg_preload_node;
+ struct list_head mg_node;
+
+ /*
+ * If this cset is acting as the source of migration the following
+ * two fields are set. mg_src_cgrp and mg_dst_cgrp are
+ * respectively the source and destination cgroups of the on-going
+ * migration. mg_dst_cset is the destination cset the target tasks
+ * on this cset should be migrated to. Protected by cgroup_mutex.
+ */
+ struct cgroup *mg_src_cgrp;
+ struct cgroup *mg_dst_cgrp;
+ struct css_set *mg_dst_cset;
+
+ /* dead and being drained, ignore for migration */
+ bool dead;
+
+ /* For RCU-protected deletion */
+ struct rcu_head rcu_head;
+};
+
+struct cgroup_base_stat {
+ struct task_cputime cputime;
+};
+
+/*
+ * rstat - cgroup scalable recursive statistics. Accounting is done
+ * per-cpu in cgroup_rstat_cpu which is then lazily propagated up the
+ * hierarchy on reads.
+ *
+ * When a stat gets updated, the cgroup_rstat_cpu and its ancestors are
+ * linked into the updated tree. On the following read, propagation only
+ * considers and consumes the updated tree. This makes reading O(the
+ * number of descendants which have been active since last read) instead of
+ * O(the total number of descendants).
+ *
+ * This is important because there can be a lot of (draining) cgroups which
+ * aren't active and stat may be read frequently. The combination can
+ * become very expensive. By propagating selectively, increasing reading
+ * frequency decreases the cost of each read.
+ *
+ * This struct hosts both the fields which implement the above -
+ * updated_children and updated_next - and the fields which track basic
+ * resource statistics on top of it - bsync, bstat and last_bstat.
+ */
+struct cgroup_rstat_cpu {
+ /*
+ * ->bsync protects ->bstat. These are the only fields which get
+ * updated in the hot path.
+ */
+ struct u64_stats_sync bsync;
+ struct cgroup_base_stat bstat;
+
+ /*
+ * Snapshots at the last reading. These are used to calculate the
+ * deltas to propagate to the global counters.
+ */
+ struct cgroup_base_stat last_bstat;
+
+ /*
+ * Child cgroups with stat updates on this cpu since the last read
+ * are linked on the parent's ->updated_children through
+ * ->updated_next.
+ *
+ * In addition to being more compact, singly-linked list pointing
+ * to the cgroup makes it unnecessary for each per-cpu struct to
+ * point back to the associated cgroup.
+ *
+ * Protected by per-cpu cgroup_rstat_cpu_lock.
+ */
+ struct cgroup *updated_children; /* terminated by self cgroup */
+ struct cgroup *updated_next; /* NULL iff not on the list */
+};
+
+struct cgroup {
+ /* self css with NULL ->ss, points back to this cgroup */
+ struct cgroup_subsys_state self;
+
+ unsigned long flags; /* "unsigned long" so bitops work */
+
+ /*
+ * idr allocated in-hierarchy ID.
+ *
+ * ID 0 is not used, the ID of the root cgroup is always 1, and a
+ * new cgroup will be assigned with a smallest available ID.
+ *
+ * Allocating/Removing ID must be protected by cgroup_mutex.
+ */
+ int id;
+
+ /*
+ * The depth this cgroup is at. The root is at depth zero and each
+ * step down the hierarchy increments the level. This along with
+ * ancestor_ids[] can determine whether a given cgroup is a
+ * descendant of another without traversing the hierarchy.
+ */
+ int level;
+
+ /* Maximum allowed descent tree depth */
+ int max_depth;
+
+ /*
+ * Keep track of total numbers of visible and dying descent cgroups.
+ * Dying cgroups are cgroups which were deleted by a user,
+ * but are still existing because someone else is holding a reference.
+ * max_descendants is a maximum allowed number of descent cgroups.
+ */
+ int nr_descendants;
+ int nr_dying_descendants;
+ int max_descendants;
+
+ /*
+ * Each non-empty css_set associated with this cgroup contributes
+ * one to nr_populated_csets. The counter is zero iff this cgroup
+ * doesn't have any tasks.
+ *
+ * All children which have non-zero nr_populated_csets and/or
+ * nr_populated_children of their own contribute one to either
+ * nr_populated_domain_children or nr_populated_threaded_children
+ * depending on their type. Each counter is zero iff all cgroups
+ * of the type in the subtree proper don't have any tasks.
+ */
+ int nr_populated_csets;
+ int nr_populated_domain_children;
+ int nr_populated_threaded_children;
+
+ int nr_threaded_children; /* # of live threaded child cgroups */
+
+ struct kernfs_node *kn; /* cgroup kernfs entry */
+ struct cgroup_file procs_file; /* handle for "cgroup.procs" */
+ struct cgroup_file events_file; /* handle for "cgroup.events" */
+
+ /*
+ * The bitmask of subsystems enabled on the child cgroups.
+ * ->subtree_control is the one configured through
+ * "cgroup.subtree_control" while ->child_ss_mask is the effective
+ * one which may have more subsystems enabled. Controller knobs
+ * are made available iff it's enabled in ->subtree_control.
+ */
+ u16 subtree_control;
+ u16 subtree_ss_mask;
+ u16 old_subtree_control;
+ u16 old_subtree_ss_mask;
+
+ /* Private pointers for each registered subsystem */
+ struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
+
+ struct cgroup_root *root;
+
+ /*
+ * List of cgrp_cset_links pointing at css_sets with tasks in this
+ * cgroup. Protected by css_set_lock.
+ */
+ struct list_head cset_links;
+
+ /*
+ * On the default hierarchy, a css_set for a cgroup with some
+ * susbsys disabled will point to css's which are associated with
+ * the closest ancestor which has the subsys enabled. The
+ * following lists all css_sets which point to this cgroup's css
+ * for the given subsystem.
+ */
+ struct list_head e_csets[CGROUP_SUBSYS_COUNT];
+
+ /*
+ * If !threaded, self. If threaded, it points to the nearest
+ * domain ancestor. Inside a threaded subtree, cgroups are exempt
+ * from process granularity and no-internal-task constraint.
+ * Domain level resource consumptions which aren't tied to a
+ * specific task are charged to the dom_cgrp.
+ */
+ struct cgroup *dom_cgrp;
+ struct cgroup *old_dom_cgrp; /* used while enabling threaded */
+
+ /* per-cpu recursive resource statistics */
+ struct cgroup_rstat_cpu __percpu *rstat_cpu;
+ struct list_head rstat_css_list;
+
+ /* cgroup basic resource statistics */
+ struct cgroup_base_stat pending_bstat; /* pending from children */
+ struct cgroup_base_stat bstat;
+ struct prev_cputime prev_cputime; /* for printing out cputime */
+
+ /*
+ * list of pidlists, up to two for each namespace (one for procs, one
+ * for tasks); created on demand.
+ */
+ struct list_head pidlists;
+ struct mutex pidlist_mutex;
+
+ /* used to wait for offlining of csses */
+ wait_queue_head_t offline_waitq;
+
+ /* used to schedule release agent */
+ struct work_struct release_agent_work;
+
+ /* used to store eBPF programs */
+ struct cgroup_bpf bpf;
+
+ /* If there is block congestion on this cgroup. */
+ atomic_t congestion_count;
+
+ /* ids of the ancestors at each level including self */
+ int ancestor_ids[];
+};
+
+/*
+ * A cgroup_root represents the root of a cgroup hierarchy, and may be
+ * associated with a kernfs_root to form an active hierarchy. This is
+ * internal to cgroup core. Don't access directly from controllers.
+ */
+struct cgroup_root {
+ struct kernfs_root *kf_root;
+
+ /* The bitmask of subsystems attached to this hierarchy */
+ unsigned int subsys_mask;
+
+ /* Unique id for this hierarchy. */
+ int hierarchy_id;
+
+ /* The root cgroup. Root is destroyed on its release. */
+ struct cgroup cgrp;
+
+ /* for cgrp->ancestor_ids[0] */
+ int cgrp_ancestor_id_storage;
+
+ /* Number of cgroups in the hierarchy, used only for /proc/cgroups */
+ atomic_t nr_cgrps;
+
+ /* A list running through the active hierarchies */
+ struct list_head root_list;
+
+ /* Hierarchy-specific flags */
+ unsigned int flags;
+
+ /* IDs for cgroups in this hierarchy */
+ struct idr cgroup_idr;
+
+ /* The path to use for release notifications. */
+ char release_agent_path[PATH_MAX];
+
+ /* The name for this hierarchy - may be empty */
+ char name[MAX_CGROUP_ROOT_NAMELEN];
+};
+
+/*
+ * struct cftype: handler definitions for cgroup control files
+ *
+ * When reading/writing to a file:
+ * - the cgroup to use is file->f_path.dentry->d_parent->d_fsdata
+ * - the 'cftype' of the file is file->f_path.dentry->d_fsdata
+ */
+struct cftype {
+ /*
+ * By convention, the name should begin with the name of the
+ * subsystem, followed by a period. Zero length string indicates
+ * end of cftype array.
+ */
+ char name[MAX_CFTYPE_NAME];
+ unsigned long private;
+
+ /*
+ * The maximum length of string, excluding trailing nul, that can
+ * be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
+ */
+ size_t max_write_len;
+
+ /* CFTYPE_* flags */
+ unsigned int flags;
+
+ /*
+ * If non-zero, should contain the offset from the start of css to
+ * a struct cgroup_file field. cgroup will record the handle of
+ * the created file into it. The recorded handle can be used as
+ * long as the containing css remains accessible.
+ */
+ unsigned int file_offset;
+
+ /*
+ * Fields used for internal bookkeeping. Initialized automatically
+ * during registration.
+ */
+ struct cgroup_subsys *ss; /* NULL for cgroup core files */
+ struct list_head node; /* anchored at ss->cfts */
+ struct kernfs_ops *kf_ops;
+
+ int (*open)(struct kernfs_open_file *of);
+ void (*release)(struct kernfs_open_file *of);
+
+ /*
+ * read_u64() is a shortcut for the common case of returning a
+ * single integer. Use it in place of read()
+ */
+ u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
+ /*
+ * read_s64() is a signed version of read_u64()
+ */
+ s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
+
+ /* generic seq_file read interface */
+ int (*seq_show)(struct seq_file *sf, void *v);
+
+ /* optional ops, implement all or none */
+ void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
+ void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
+ void (*seq_stop)(struct seq_file *sf, void *v);
+
+ /*
+ * write_u64() is a shortcut for the common case of accepting
+ * a single integer (as parsed by simple_strtoull) from
+ * userspace. Use in place of write(); return 0 or error.
+ */
+ int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
+ u64 val);
+ /*
+ * write_s64() is a signed version of write_u64()
+ */
+ int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
+ s64 val);
+
+ /*
+ * write() is the generic write callback which maps directly to
+ * kernfs write operation and overrides all other operations.
+ * Maximum write size is determined by ->max_write_len. Use
+ * of_css/cft() to access the associated css and cft.
+ */
+ ssize_t (*write)(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lock_class_key lockdep_key;
+#endif
+};
+
+/*
+ * Control Group subsystem type.
+ * See Documentation/cgroup-v1/cgroups.txt for details
+ */
+struct cgroup_subsys {
+ struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
+ int (*css_online)(struct cgroup_subsys_state *css);
+ void (*css_offline)(struct cgroup_subsys_state *css);
+ void (*css_released)(struct cgroup_subsys_state *css);
+ void (*css_free)(struct cgroup_subsys_state *css);
+ void (*css_reset)(struct cgroup_subsys_state *css);
+ void (*css_rstat_flush)(struct cgroup_subsys_state *css, int cpu);
+ int (*css_extra_stat_show)(struct seq_file *seq,
+ struct cgroup_subsys_state *css);
+
+ int (*can_attach)(struct cgroup_taskset *tset);
+ void (*cancel_attach)(struct cgroup_taskset *tset);
+ void (*attach)(struct cgroup_taskset *tset);
+ void (*post_attach)(void);
+ int (*can_fork)(struct task_struct *task);
+ void (*cancel_fork)(struct task_struct *task);
+ void (*fork)(struct task_struct *task);
+ void (*exit)(struct task_struct *task);
+ void (*free)(struct task_struct *task);
+ void (*bind)(struct cgroup_subsys_state *root_css);
+
+ bool early_init:1;
+
+ /*
+ * If %true, the controller, on the default hierarchy, doesn't show
+ * up in "cgroup.controllers" or "cgroup.subtree_control", is
+ * implicitly enabled on all cgroups on the default hierarchy, and
+ * bypasses the "no internal process" constraint. This is for
+ * utility type controllers which is transparent to userland.
+ *
+ * An implicit controller can be stolen from the default hierarchy
+ * anytime and thus must be okay with offline csses from previous
+ * hierarchies coexisting with csses for the current one.
+ */
+ bool implicit_on_dfl:1;
+
+ /*
+ * If %true, the controller, supports threaded mode on the default
+ * hierarchy. In a threaded subtree, both process granularity and
+ * no-internal-process constraint are ignored and a threaded
+ * controllers should be able to handle that.
+ *
+ * Note that as an implicit controller is automatically enabled on
+ * all cgroups on the default hierarchy, it should also be
+ * threaded. implicit && !threaded is not supported.
+ */
+ bool threaded:1;
+
+ /*
+ * If %false, this subsystem is properly hierarchical -
+ * configuration, resource accounting and restriction on a parent
+ * cgroup cover those of its children. If %true, hierarchy support
+ * is broken in some ways - some subsystems ignore hierarchy
+ * completely while others are only implemented half-way.
+ *
+ * It's now disallowed to create nested cgroups if the subsystem is
+ * broken and cgroup core will emit a warning message on such
+ * cases. Eventually, all subsystems will be made properly
+ * hierarchical and this will go away.
+ */
+ bool broken_hierarchy:1;
+ bool warned_broken_hierarchy:1;
+
+ /* the following two fields are initialized automtically during boot */
+ int id;
+ const char *name;
+
+ /* optional, initialized automatically during boot if not set */
+ const char *legacy_name;
+
+ /* link to parent, protected by cgroup_lock() */
+ struct cgroup_root *root;
+
+ /* idr for css->id */
+ struct idr css_idr;
+
+ /*
+ * List of cftypes. Each entry is the first entry of an array
+ * terminated by zero length name.
+ */
+ struct list_head cfts;
+
+ /*
+ * Base cftypes which are automatically registered. The two can
+ * point to the same array.
+ */
+ struct cftype *dfl_cftypes; /* for the default hierarchy */
+ struct cftype *legacy_cftypes; /* for the legacy hierarchies */
+
+ /*
+ * A subsystem may depend on other subsystems. When such subsystem
+ * is enabled on a cgroup, the depended-upon subsystems are enabled
+ * together if available. Subsystems enabled due to dependency are
+ * not visible to userland until explicitly enabled. The following
+ * specifies the mask of subsystems that this one depends on.
+ */
+ unsigned int depends_on;
+};
+
+extern struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
+
+/**
+ * cgroup_threadgroup_change_begin - threadgroup exclusion for cgroups
+ * @tsk: target task
+ *
+ * Allows cgroup operations to synchronize against threadgroup changes
+ * using a percpu_rw_semaphore.
+ */
+static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
+{
+ percpu_down_read(&cgroup_threadgroup_rwsem);
+}
+
+/**
+ * cgroup_threadgroup_change_end - threadgroup exclusion for cgroups
+ * @tsk: target task
+ *
+ * Counterpart of cgroup_threadcgroup_change_begin().
+ */
+static inline void cgroup_threadgroup_change_end(struct task_struct *tsk)
+{
+ percpu_up_read(&cgroup_threadgroup_rwsem);
+}
+
+#else /* CONFIG_CGROUPS */
+
+#define CGROUP_SUBSYS_COUNT 0
+
+static inline void cgroup_threadgroup_change_begin(struct task_struct *tsk)
+{
+ might_sleep();
+}
+
+static inline void cgroup_threadgroup_change_end(struct task_struct *tsk) {}
+
+#endif /* CONFIG_CGROUPS */
+
+#ifdef CONFIG_SOCK_CGROUP_DATA
+
+/*
+ * sock_cgroup_data is embedded at sock->sk_cgrp_data and contains
+ * per-socket cgroup information except for memcg association.
+ *
+ * On legacy hierarchies, net_prio and net_cls controllers directly set
+ * attributes on each sock which can then be tested by the network layer.
+ * On the default hierarchy, each sock is associated with the cgroup it was
+ * created in and the networking layer can match the cgroup directly.
+ *
+ * To avoid carrying all three cgroup related fields separately in sock,
+ * sock_cgroup_data overloads (prioidx, classid) and the cgroup pointer.
+ * On boot, sock_cgroup_data records the cgroup that the sock was created
+ * in so that cgroup2 matches can be made; however, once either net_prio or
+ * net_cls starts being used, the area is overriden to carry prioidx and/or
+ * classid. The two modes are distinguished by whether the lowest bit is
+ * set. Clear bit indicates cgroup pointer while set bit prioidx and
+ * classid.
+ *
+ * While userland may start using net_prio or net_cls at any time, once
+ * either is used, cgroup2 matching no longer works. There is no reason to
+ * mix the two and this is in line with how legacy and v2 compatibility is
+ * handled. On mode switch, cgroup references which are already being
+ * pointed to by socks may be leaked. While this can be remedied by adding
+ * synchronization around sock_cgroup_data, given that the number of leaked
+ * cgroups is bound and highly unlikely to be high, this seems to be the
+ * better trade-off.
+ */
+struct sock_cgroup_data {
+ union {
+#ifdef __LITTLE_ENDIAN
+ struct {
+ u8 is_data;
+ u8 padding;
+ u16 prioidx;
+ u32 classid;
+ } __packed;
+#else
+ struct {
+ u32 classid;
+ u16 prioidx;
+ u8 padding;
+ u8 is_data;
+ } __packed;
+#endif
+ u64 val;
+ };
+};
+
+/*
+ * There's a theoretical window where the following accessors race with
+ * updaters and return part of the previous pointer as the prioidx or
+ * classid. Such races are short-lived and the result isn't critical.
+ */
+static inline u16 sock_cgroup_prioidx(const struct sock_cgroup_data *skcd)
+{
+ /* fallback to 1 which is always the ID of the root cgroup */
+ return (skcd->is_data & 1) ? skcd->prioidx : 1;
+}
+
+static inline u32 sock_cgroup_classid(const struct sock_cgroup_data *skcd)
+{
+ /* fallback to 0 which is the unconfigured default classid */
+ return (skcd->is_data & 1) ? skcd->classid : 0;
+}
+
+/*
+ * If invoked concurrently, the updaters may clobber each other. The
+ * caller is responsible for synchronization.
+ */
+static inline void sock_cgroup_set_prioidx(struct sock_cgroup_data *skcd,
+ u16 prioidx)
+{
+ struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
+
+ if (sock_cgroup_prioidx(&skcd_buf) == prioidx)
+ return;
+
+ if (!(skcd_buf.is_data & 1)) {
+ skcd_buf.val = 0;
+ skcd_buf.is_data = 1;
+ }
+
+ skcd_buf.prioidx = prioidx;
+ WRITE_ONCE(skcd->val, skcd_buf.val); /* see sock_cgroup_ptr() */
+}
+
+static inline void sock_cgroup_set_classid(struct sock_cgroup_data *skcd,
+ u32 classid)
+{
+ struct sock_cgroup_data skcd_buf = {{ .val = READ_ONCE(skcd->val) }};
+
+ if (sock_cgroup_classid(&skcd_buf) == classid)
+ return;
+
+ if (!(skcd_buf.is_data & 1)) {
+ skcd_buf.val = 0;
+ skcd_buf.is_data = 1;
+ }
+
+ skcd_buf.classid = classid;
+ WRITE_ONCE(skcd->val, skcd_buf.val); /* see sock_cgroup_ptr() */
+}
+
+#else /* CONFIG_SOCK_CGROUP_DATA */
+
+struct sock_cgroup_data {
+};
+
+#endif /* CONFIG_SOCK_CGROUP_DATA */
+
+#endif /* _LINUX_CGROUP_DEFS_H */