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|
/*
* Generic process-grouping system.
*
* Based originally on the cpuset system, extracted by Paul Menage
* Copyright (C) 2006 Google, Inc
*
* Notifications support
* Copyright (C) 2009 Nokia Corporation
* Author: Kirill A. Shutemov
*
* Copyright notices from the original cpuset code:
* --------------------------------------------------
* Copyright (C) 2003 BULL SA.
* Copyright (C) 2004-2006 Silicon Graphics, Inc.
*
* Portions derived from Patrick Mochel's sysfs code.
* sysfs is Copyright (c) 2001-3 Patrick Mochel
*
* 2003-10-10 Written by Simon Derr.
* 2003-10-22 Updates by Stephen Hemminger.
* 2004 May-July Rework by Paul Jackson.
* ---------------------------------------------------
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of the Linux
* distribution for more details.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include "cgroup-internal.h"
#include <linux/cred.h>
#include <linux/errno.h>
#include <linux/init_task.h>
#include <linux/kernel.h>
#include <linux/magic.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/proc_fs.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/percpu-rwsem.h>
#include <linux/string.h>
#include <linux/hashtable.h>
#include <linux/idr.h>
#include <linux/kthread.h>
#include <linux/atomic.h>
#include <linux/cpuset.h>
#include <linux/proc_ns.h>
#include <linux/nsproxy.h>
#include <linux/file.h>
#include <net/sock.h>
#define CREATE_TRACE_POINTS
#include <trace/events/cgroup.h>
#define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
MAX_CFTYPE_NAME + 2)
/*
* cgroup_mutex is the master lock. Any modification to cgroup or its
* hierarchy must be performed while holding it.
*
* css_set_lock protects task->cgroups pointer, the list of css_set
* objects, and the chain of tasks off each css_set.
*
* These locks are exported if CONFIG_PROVE_RCU so that accessors in
* cgroup.h can use them for lockdep annotations.
*/
DEFINE_MUTEX(cgroup_mutex);
DEFINE_SPINLOCK(css_set_lock);
#ifdef CONFIG_PROVE_RCU
EXPORT_SYMBOL_GPL(cgroup_mutex);
EXPORT_SYMBOL_GPL(css_set_lock);
#endif
/*
* Protects cgroup_idr and css_idr so that IDs can be released without
* grabbing cgroup_mutex.
*/
static DEFINE_SPINLOCK(cgroup_idr_lock);
/*
* Protects cgroup_file->kn for !self csses. It synchronizes notifications
* against file removal/re-creation across css hiding.
*/
static DEFINE_SPINLOCK(cgroup_file_kn_lock);
struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
#define cgroup_assert_mutex_or_rcu_locked() \
RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
!lockdep_is_held(&cgroup_mutex), \
"cgroup_mutex or RCU read lock required");
/*
* cgroup destruction makes heavy use of work items and there can be a lot
* of concurrent destructions. Use a separate workqueue so that cgroup
* destruction work items don't end up filling up max_active of system_wq
* which may lead to deadlock.
*/
static struct workqueue_struct *cgroup_destroy_wq;
/* generate an array of cgroup subsystem pointers */
#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
struct cgroup_subsys *cgroup_subsys[] = {
#include <linux/cgroup_subsys.h>
};
#undef SUBSYS
/* array of cgroup subsystem names */
#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
static const char *cgroup_subsys_name[] = {
#include <linux/cgroup_subsys.h>
};
#undef SUBSYS
/* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
#define SUBSYS(_x) \
DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
#include <linux/cgroup_subsys.h>
#undef SUBSYS
#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
static struct static_key_true *cgroup_subsys_enabled_key[] = {
#include <linux/cgroup_subsys.h>
};
#undef SUBSYS
#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
#include <linux/cgroup_subsys.h>
};
#undef SUBSYS
static DEFINE_PER_CPU(struct cgroup_cpu_stat, cgrp_dfl_root_cpu_stat);
/*
* The default hierarchy, reserved for the subsystems that are otherwise
* unattached - it never has more than a single cgroup, and all tasks are
* part of that cgroup.
*/
struct cgroup_root cgrp_dfl_root = { .cgrp.cpu_stat = &cgrp_dfl_root_cpu_stat };
EXPORT_SYMBOL_GPL(cgrp_dfl_root);
/*
* The default hierarchy always exists but is hidden until mounted for the
* first time. This is for backward compatibility.
*/
static bool cgrp_dfl_visible;
/* some controllers are not supported in the default hierarchy */
static u16 cgrp_dfl_inhibit_ss_mask;
/* some controllers are implicitly enabled on the default hierarchy */
static u16 cgrp_dfl_implicit_ss_mask;
/* some controllers can be threaded on the default hierarchy */
static u16 cgrp_dfl_threaded_ss_mask;
/* The list of hierarchy roots */
LIST_HEAD(cgroup_roots);
static int cgroup_root_count;
/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
static DEFINE_IDR(cgroup_hierarchy_idr);
/*
* Assign a monotonically increasing serial number to csses. It guarantees
* cgroups with bigger numbers are newer than those with smaller numbers.
* Also, as csses are always appended to the parent's ->children list, it
* guarantees that sibling csses are always sorted in the ascending serial
* number order on the list. Protected by cgroup_mutex.
*/
static u64 css_serial_nr_next = 1;
/*
* These bitmasks identify subsystems with specific features to avoid
* having to do iterative checks repeatedly.
*/
static u16 have_fork_callback __read_mostly;
static u16 have_exit_callback __read_mostly;
static u16 have_free_callback __read_mostly;
static u16 have_canfork_callback __read_mostly;
/* cgroup namespace for init task */
struct cgroup_namespace init_cgroup_ns = {
.count = REFCOUNT_INIT(2),
.user_ns = &init_user_ns,
.ns.ops = &cgroupns_operations,
.ns.inum = PROC_CGROUP_INIT_INO,
.root_cset = &init_css_set,
};
static struct file_system_type cgroup2_fs_type;
static struct cftype cgroup_base_files[];
static int cgroup_apply_control(struct cgroup *cgrp);
static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
static void css_task_iter_advance(struct css_task_iter *it);
static int cgroup_destroy_locked(struct cgroup *cgrp);
static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
struct cgroup_subsys *ss);
static void css_release(struct percpu_ref *ref);
static void kill_css(struct cgroup_subsys_state *css);
static int cgroup_addrm_files(struct cgroup_subsys_state *css,
struct cgroup *cgrp, struct cftype cfts[],
bool is_add);
/**
* cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
* @ssid: subsys ID of interest
*
* cgroup_subsys_enabled() can only be used with literal subsys names which
* is fine for individual subsystems but unsuitable for cgroup core. This
* is slower static_key_enabled() based test indexed by @ssid.
*/
bool cgroup_ssid_enabled(int ssid)
{
if (CGROUP_SUBSYS_COUNT == 0)
return false;
return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
}
/**
* cgroup_on_dfl - test whether a cgroup is on the default hierarchy
* @cgrp: the cgroup of interest
*
* The default hierarchy is the v2 interface of cgroup and this function
* can be used to test whether a cgroup is on the default hierarchy for
* cases where a subsystem should behave differnetly depending on the
* interface version.
*
* The set of behaviors which change on the default hierarchy are still
* being determined and the mount option is prefixed with __DEVEL__.
*
* List of changed behaviors:
*
* - Mount options "noprefix", "xattr", "clone_children", "release_agent"
* and "name" are disallowed.
*
* - When mounting an existing superblock, mount options should match.
*
* - Remount is disallowed.
*
* - rename(2) is disallowed.
*
* - "tasks" is removed. Everything should be at process granularity. Use
* "cgroup.procs" instead.
*
* - "cgroup.procs" is not sorted. pids will be unique unless they got
* recycled inbetween reads.
*
* - "release_agent" and "notify_on_release" are removed. Replacement
* notification mechanism will be implemented.
*
* - "cgroup.clone_children" is removed.
*
* - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
* and its descendants contain no task; otherwise, 1. The file also
* generates kernfs notification which can be monitored through poll and
* [di]notify when the value of the file changes.
*
* - cpuset: tasks will be kept in empty cpusets when hotplug happens and
* take masks of ancestors with non-empty cpus/mems, instead of being
* moved to an ancestor.
*
* - cpuset: a task can be moved into an empty cpuset, and again it takes
* masks of ancestors.
*
* - memcg: use_hierarchy is on by default and the cgroup file for the flag
* is not created.
*
* - blkcg: blk-throttle becomes properly hierarchical.
*
* - debug: disallowed on the default hierarchy.
*/
bool cgroup_on_dfl(const struct cgroup *cgrp)
{
return cgrp->root == &cgrp_dfl_root;
}
/* IDR wrappers which synchronize using cgroup_idr_lock */
static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
gfp_t gfp_mask)
{
int ret;
idr_preload(gfp_mask);
spin_lock_bh(&cgroup_idr_lock);
ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
spin_unlock_bh(&cgroup_idr_lock);
idr_preload_end();
return ret;
}
static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
{
void *ret;
spin_lock_bh(&cgroup_idr_lock);
ret = idr_replace(idr, ptr, id);
spin_unlock_bh(&cgroup_idr_lock);
return ret;
}
static void cgroup_idr_remove(struct idr *idr, int id)
{
spin_lock_bh(&cgroup_idr_lock);
idr_remove(idr, id);
spin_unlock_bh(&cgroup_idr_lock);
}
static bool cgroup_has_tasks(struct cgroup *cgrp)
{
return cgrp->nr_populated_csets;
}
bool cgroup_is_threaded(struct cgroup *cgrp)
{
return cgrp->dom_cgrp != cgrp;
}
/* can @cgrp host both domain and threaded children? */
static bool cgroup_is_mixable(struct cgroup *cgrp)
{
/*
* Root isn't under domain level resource control exempting it from
* the no-internal-process constraint, so it can serve as a thread
* root and a parent of resource domains at the same time.
*/
return !cgroup_parent(cgrp);
}
/* can @cgrp become a thread root? should always be true for a thread root */
static bool cgroup_can_be_thread_root(struct cgroup *cgrp)
{
/* mixables don't care */
if (cgroup_is_mixable(cgrp))
return true;
/* domain roots can't be nested under threaded */
if (cgroup_is_threaded(cgrp))
return false;
/* can only have either domain or threaded children */
if (cgrp->nr_populated_domain_children)
return false;
/* and no domain controllers can be enabled */
if (cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
return false;
return true;
}
/* is @cgrp root of a threaded subtree? */
bool cgroup_is_thread_root(struct cgroup *cgrp)
{
/* thread root should be a domain */
if (cgroup_is_threaded(cgrp))
return false;
/* a domain w/ threaded children is a thread root */
if (cgrp->nr_threaded_children)
return true;
/*
* A domain which has tasks and explicit threaded controllers
* enabled is a thread root.
*/
if (cgroup_has_tasks(cgrp) &&
(cgrp->subtree_control & cgrp_dfl_threaded_ss_mask))
return true;
return false;
}
/* a domain which isn't connected to the root w/o brekage can't be used */
static bool cgroup_is_valid_domain(struct cgroup *cgrp)
{
/* the cgroup itself can be a thread root */
if (cgroup_is_threaded(cgrp))
return false;
/* but the ancestors can't be unless mixable */
while ((cgrp = cgroup_parent(cgrp))) {
if (!cgroup_is_mixable(cgrp) && cgroup_is_thread_root(cgrp))
return false;
if (cgroup_is_threaded(cgrp))
return false;
}
return true;
}
/* subsystems visibly enabled on a cgroup */
static u16 cgroup_control(struct cgroup *cgrp)
{
struct cgroup *parent = cgroup_parent(cgrp);
u16 root_ss_mask = cgrp->root->subsys_mask;
if (parent) {
u16 ss_mask = parent->subtree_control;
/* threaded cgroups can only have threaded controllers */
if (cgroup_is_threaded(cgrp))
ss_mask &= cgrp_dfl_threaded_ss_mask;
return ss_mask;
}
if (cgroup_on_dfl(cgrp))
root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
cgrp_dfl_implicit_ss_mask);
return root_ss_mask;
}
/* subsystems enabled on a cgroup */
static u16 cgroup_ss_mask(struct cgroup *cgrp)
{
struct cgroup *parent = cgroup_parent(cgrp);
if (parent) {
u16 ss_mask = parent->subtree_ss_mask;
/* threaded cgroups can only have threaded controllers */
if (cgroup_is_threaded(cgrp))
ss_mask &= cgrp_dfl_threaded_ss_mask;
return ss_mask;
}
return cgrp->root->subsys_mask;
}
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
* @cgrp: the cgroup of interest
* @ss: the subsystem of interest (%NULL returns @cgrp->self)
*
* Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
* function must be called either under cgroup_mutex or rcu_read_lock() and
* the caller is responsible for pinning the returned css if it wants to
* keep accessing it outside the said locks. This function may return
* %NULL if @cgrp doesn't have @subsys_id enabled.
*/
static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
if (ss)
return rcu_dereference_check(cgrp->subsys[ss->id],
lockdep_is_held(&cgroup_mutex));
else
return &cgrp->self;
}
/**
* cgroup_tryget_css - try to get a cgroup's css for the specified subsystem
* @cgrp: the cgroup of interest
* @ss: the subsystem of interest
*
* Find and get @cgrp's css assocaited with @ss. If the css doesn't exist
* or is offline, %NULL is returned.
*/
static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
struct cgroup_subsys_state *css;
rcu_read_lock();
css = cgroup_css(cgrp, ss);
if (!css || !css_tryget_online(css))
css = NULL;
rcu_read_unlock();
return css;
}
/**
* cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
* @cgrp: the cgroup of interest
* @ss: the subsystem of interest (%NULL returns @cgrp->self)
*
* Similar to cgroup_css() but returns the effective css, which is defined
* as the matching css of the nearest ancestor including self which has @ss
* enabled. If @ss is associated with the hierarchy @cgrp is on, this
* function is guaranteed to return non-NULL css.
*/
static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
lockdep_assert_held(&cgroup_mutex);
if (!ss)
return &cgrp->self;
/*
* This function is used while updating css associations and thus
* can't test the csses directly. Test ss_mask.
*/
while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
cgrp = cgroup_parent(cgrp);
if (!cgrp)
return NULL;
}
return cgroup_css(cgrp, ss);
}
/**
* cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
* @cgrp: the cgroup of interest
* @ss: the subsystem of interest
*
* Find and get the effective css of @cgrp for @ss. The effective css is
* defined as the matching css of the nearest ancestor including self which
* has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
* the root css is returned, so this function always returns a valid css.
* The returned css must be put using css_put().
*/
struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
struct cgroup_subsys_state *css;
rcu_read_lock();
do {
css = cgroup_css(cgrp, ss);
if (css && css_tryget_online(css))
goto out_unlock;
cgrp = cgroup_parent(cgrp);
} while (cgrp);
css = init_css_set.subsys[ss->id];
css_get(css);
out_unlock:
rcu_read_unlock();
return css;
}
static void cgroup_get_live(struct cgroup *cgrp)
{
WARN_ON_ONCE(cgroup_is_dead(cgrp));
css_get(&cgrp->self);
}
struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
{
struct cgroup *cgrp = of->kn->parent->priv;
struct cftype *cft = of_cft(of);
/*
* This is open and unprotected implementation of cgroup_css().
* seq_css() is only called from a kernfs file operation which has
* an active reference on the file. Because all the subsystem
* files are drained before a css is disassociated with a cgroup,
* the matching css from the cgroup's subsys table is guaranteed to
* be and stay valid until the enclosing operation is complete.
*/
if (cft->ss)
return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
else
return &cgrp->self;
}
EXPORT_SYMBOL_GPL(of_css);
/**
* for_each_css - iterate all css's of a cgroup
* @css: the iteration cursor
* @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
* @cgrp: the target cgroup to iterate css's of
*
* Should be called under cgroup_[tree_]mutex.
*/
#define for_each_css(css, ssid, cgrp) \
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
if (!((css) = rcu_dereference_check( \
(cgrp)->subsys[(ssid)], \
lockdep_is_held(&cgroup_mutex)))) { } \
else
/**
* for_each_e_css - iterate all effective css's of a cgroup
* @css: the iteration cursor
* @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
* @cgrp: the target cgroup to iterate css's of
*
* Should be called under cgroup_[tree_]mutex.
*/
#define for_each_e_css(css, ssid, cgrp) \
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
; \
else
/**
* do_each_subsys_mask - filter for_each_subsys with a bitmask
* @ss: the iteration cursor
* @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
* @ss_mask: the bitmask
*
* The block will only run for cases where the ssid-th bit (1 << ssid) of
* @ss_mask is set.
*/
#define do_each_subsys_mask(ss, ssid, ss_mask) do { \
unsigned long __ss_mask = (ss_mask); \
if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */ \
(ssid) = 0; \
break; \
} \
for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
(ss) = cgroup_subsys[ssid]; \
{
#define while_each_subsys_mask() \
} \
} \
} while (false)
/* iterate over child cgrps, lock should be held throughout iteration */
#define cgroup_for_each_live_child(child, cgrp) \
list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
if (({ lockdep_assert_held(&cgroup_mutex); \
cgroup_is_dead(child); })) \
; \
else
/* walk live descendants in preorder */
#define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \
css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \
if (({ lockdep_assert_held(&cgroup_mutex); \
(dsct) = (d_css)->cgroup; \
cgroup_is_dead(dsct); })) \
; \
else
/* walk live descendants in postorder */
#define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \
css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \
if (({ lockdep_assert_held(&cgroup_mutex); \
(dsct) = (d_css)->cgroup; \
cgroup_is_dead(dsct); })) \
; \
else
/*
* The default css_set - used by init and its children prior to any
* hierarchies being mounted. It contains a pointer to the root state
* for each subsystem. Also used to anchor the list of css_sets. Not
* reference-counted, to improve performance when child cgroups
* haven't been created.
*/
struct css_set init_css_set = {
.refcount = REFCOUNT_INIT(1),
.dom_cset = &init_css_set,
.tasks = LIST_HEAD_INIT(init_css_set.tasks),
.mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
.task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
.threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
.cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
.mg_preload_node = LIST_HEAD_INIT(init_css_set.mg_preload_node),
.mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
/*
* The following field is re-initialized when this cset gets linked
* in cgroup_init(). However, let's initialize the field
* statically too so that the default cgroup can be accessed safely
* early during boot.
*/
.dfl_cgrp = &cgrp_dfl_root.cgrp,
};
static int css_set_count = 1; /* 1 for init_css_set */
static bool css_set_threaded(struct css_set *cset)
{
return cset->dom_cset != cset;
}
/**
* css_set_populated - does a css_set contain any tasks?
* @cset: target css_set
*
* css_set_populated() should be the same as !!cset->nr_tasks at steady
* state. However, css_set_populated() can be called while a task is being
* added to or removed from the linked list before the nr_tasks is
* properly updated. Hence, we can't just look at ->nr_tasks here.
*/
static bool css_set_populated(struct css_set *cset)
{
lockdep_assert_held(&css_set_lock);
return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
}
/**
* cgroup_update_populated - update the populated count of a cgroup
* @cgrp: the target cgroup
* @populated: inc or dec populated count
*
* One of the css_sets associated with @cgrp is either getting its first
* task or losing the last. Update @cgrp->nr_populated_* accordingly. The
* count is propagated towards root so that a given cgroup's
* nr_populated_children is zero iff none of its descendants contain any
* tasks.
*
* @cgrp's interface file "cgroup.populated" is zero if both
* @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and
* 1 otherwise. When the sum changes from or to zero, userland is notified
* that the content of the interface file has changed. This can be used to
* detect when @cgrp and its descendants become populated or empty.
*/
static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
{
struct cgroup *child = NULL;
int adj = populated ? 1 : -1;
lockdep_assert_held(&css_set_lock);
do {
bool was_populated = cgroup_is_populated(cgrp);
if (!child) {
cgrp->nr_populated_csets += adj;
} else {
if (cgroup_is_threaded(child))
cgrp->nr_populated_threaded_children += adj;
else
cgrp->nr_populated_domain_children += adj;
}
if (was_populated == cgroup_is_populated(cgrp))
break;
cgroup1_check_for_release(cgrp);
cgroup_file_notify(&cgrp->events_file);
child = cgrp;
cgrp = cgroup_parent(cgrp);
} while (cgrp);
}
/**
* css_set_update_populated - update populated state of a css_set
* @cset: target css_set
* @populated: whether @cset is populated or depopulated
*
* @cset is either getting the first task or losing the last. Update the
* populated counters of all associated cgroups accordingly.
*/
static void css_set_update_populated(struct css_set *cset, bool populated)
{
struct cgrp_cset_link *link;
lockdep_assert_held(&css_set_lock);
list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
cgroup_update_populated(link->cgrp, populated);
}
/**
* css_set_move_task - move a task from one css_set to another
* @task: task being moved
* @from_cset: css_set @task currently belongs to (may be NULL)
* @to_cset: new css_set @task is being moved to (may be NULL)
* @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
*
* Move @task from @from_cset to @to_cset. If @task didn't belong to any
* css_set, @from_cset can be NULL. If @task is being disassociated
* instead of moved, @to_cset can be NULL.
*
* This function automatically handles populated counter updates and
* css_task_iter adjustments but the caller is responsible for managing
* @from_cset and @to_cset's reference counts.
*/
static void css_set_move_task(struct task_struct *task,
struct css_set *from_cset, struct css_set *to_cset,
bool use_mg_tasks)
{
lockdep_assert_held(&css_set_lock);
if (to_cset && !css_set_populated(to_cset))
css_set_update_populated(to_cset, true);
if (from_cset) {
struct css_task_iter *it, *pos;
WARN_ON_ONCE(list_empty(&task->cg_list));
/*
* @task is leaving, advance task iterators which are
* pointing to it so that they can resume at the next
* position. Advancing an iterator might remove it from
* the list, use safe walk. See css_task_iter_advance*()
* for details.
*/
list_for_each_entry_safe(it, pos, &from_cset->task_iters,
iters_node)
if (it->task_pos == &task->cg_list)
css_task_iter_advance(it);
list_del_init(&task->cg_list);
if (!css_set_populated(from_cset))
css_set_update_populated(from_cset, false);
} else {
WARN_ON_ONCE(!list_empty(&task->cg_list));
}
if (to_cset) {
/*
* We are synchronized through cgroup_threadgroup_rwsem
* against PF_EXITING setting such that we can't race
* against cgroup_exit() changing the css_set to
* init_css_set and dropping the old one.
*/
WARN_ON_ONCE(task->flags & PF_EXITING);
rcu_assign_pointer(task->cgroups, to_cset);
list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
&to_cset->tasks);
}
}
/*
* hash table for cgroup groups. This improves the performance to find
* an existing css_set. This hash doesn't (currently) take into
* account cgroups in empty hierarchies.
*/
#define CSS_SET_HASH_BITS 7
static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
{
unsigned long key = 0UL;
struct cgroup_subsys *ss;
int i;
for_each_subsys(ss, i)
key += (unsigned long)css[i];
key = (key >> 16) ^ key;
return key;
}
void put_css_set_locked(struct css_set *cset)
{
struct cgrp_cset_link *link, *tmp_link;
struct cgroup_subsys *ss;
int ssid;
lockdep_assert_held(&css_set_lock);
if (!refcount_dec_and_test(&cset->refcount))
return;
WARN_ON_ONCE(!list_empty(&cset->threaded_csets));
/* This css_set is dead. unlink it and release cgroup and css refs */
for_each_subsys(ss, ssid) {
list_del(&cset->e_cset_node[ssid]);
css_put(cset->subsys[ssid]);
}
hash_del(&cset->hlist);
css_set_count--;
list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
list_del(&link->cset_link);
list_del(&link->cgrp_link);
if (cgroup_parent(link->cgrp))
cgroup_put(link->cgrp);
kfree(link);
}
if (css_set_threaded(cset)) {
list_del(&cset->threaded_csets_node);
put_css_set_locked(cset->dom_cset);
}
kfree_rcu(cset, rcu_head);
}
/**
* compare_css_sets - helper function for find_existing_css_set().
* @cset: candidate css_set being tested
* @old_cset: existing css_set for a task
* @new_cgrp: cgroup that's being entered by the task
* @template: desired set of css pointers in css_set (pre-calculated)
*
* Returns true if "cset" matches "old_cset" except for the hierarchy
* which "new_cgrp" belongs to, for which it should match "new_cgrp".
*/
static bool compare_css_sets(struct css_set *cset,
struct css_set *old_cset,
struct cgroup *new_cgrp,
struct cgroup_subsys_state *template[])
{
struct cgroup *new_dfl_cgrp;
struct list_head *l1, *l2;
/*
* On the default hierarchy, there can be csets which are
* associated with the same set of cgroups but different csses.
* Let's first ensure that csses match.
*/
if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
return false;
/* @cset's domain should match the default cgroup's */
if (cgroup_on_dfl(new_cgrp))
new_dfl_cgrp = new_cgrp;
else
new_dfl_cgrp = old_cset->dfl_cgrp;
if (new_dfl_cgrp->dom_cgrp != cset->dom_cset->dfl_cgrp)
return false;
/*
* Compare cgroup pointers in order to distinguish between
* different cgroups in hierarchies. As different cgroups may
* share the same effective css, this comparison is always
* necessary.
*/
l1 = &cset->cgrp_links;
l2 = &old_cset->cgrp_links;
while (1) {
struct cgrp_cset_link *link1, *link2;
struct cgroup *cgrp1, *cgrp2;
l1 = l1->next;
l2 = l2->next;
/* See if we reached the end - both lists are equal length. */
if (l1 == &cset->cgrp_links) {
BUG_ON(l2 != &old_cset->cgrp_links);
break;
} else {
BUG_ON(l2 == &old_cset->cgrp_links);
}
/* Locate the cgroups associated with these links. */
link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
cgrp1 = link1->cgrp;
cgrp2 = link2->cgrp;
/* Hierarchies should be linked in the same order. */
BUG_ON(cgrp1->root != cgrp2->root);
/*
* If this hierarchy is the hierarchy of the cgroup
* that's changing, then we need to check that this
* css_set points to the new cgroup; if it's any other
* hierarchy, then this css_set should point to the
* same cgroup as the old css_set.
*/
if (cgrp1->root == new_cgrp->root) {
if (cgrp1 != new_cgrp)
return false;
} else {
if (cgrp1 != cgrp2)
return false;
}
}
return true;
}
/**
* find_existing_css_set - init css array and find the matching css_set
* @old_cset: the css_set that we're using before the cgroup transition
* @cgrp: the cgroup that we're moving into
* @template: out param for the new set of csses, should be clear on entry
*/
static struct css_set *find_existing_css_set(struct css_set *old_cset,
struct cgroup *cgrp,
struct cgroup_subsys_state *template[])
{
struct cgroup_root *root = cgrp->root;
struct cgroup_subsys *ss;
struct css_set *cset;
unsigned long key;
int i;
/*
* Build the set of subsystem state objects that we want to see in the
* new css_set. while subsystems can change globally, the entries here
* won't change, so no need for locking.
*/
for_each_subsys(ss, i) {
if (root->subsys_mask & (1UL << i)) {
/*
* @ss is in this hierarchy, so we want the
* effective css from @cgrp.
*/
template[i] = cgroup_e_css(cgrp, ss);
} else {
/*
* @ss is not in this hierarchy, so we don't want
* to change the css.
*/
template[i] = old_cset->subsys[i];
}
}
key = css_set_hash(template);
hash_for_each_possible(css_set_table, cset, hlist, key) {
if (!compare_css_sets(cset, old_cset, cgrp, template))
continue;
/* This css_set matches what we need */
return cset;
}
/* No existing cgroup group matched */
return NULL;
}
static void free_cgrp_cset_links(struct list_head *links_to_free)
{
struct cgrp_cset_link *link, *tmp_link;
list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
list_del(&link->cset_link);
kfree(link);
}
}
/**
* allocate_cgrp_cset_links - allocate cgrp_cset_links
* @count: the number of links to allocate
* @tmp_links: list_head the allocated links are put on
*
* Allocate @count cgrp_cset_link structures and chain them on @tmp_links
* through ->cset_link. Returns 0 on success or -errno.
*/
static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
{
struct cgrp_cset_link *link;
int i;
INIT_LIST_HEAD(tmp_links);
for (i = 0; i < count; i++) {
link = kzalloc(sizeof(*link), GFP_KERNEL);
if (!link) {
free_cgrp_cset_links(tmp_links);
return -ENOMEM;
}
list_add(&link->cset_link, tmp_links);
}
return 0;
}
/**
* link_css_set - a helper function to link a css_set to a cgroup
* @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
* @cset: the css_set to be linked
* @cgrp: the destination cgroup
*/
static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
struct cgroup *cgrp)
{
struct cgrp_cset_link *link;
BUG_ON(list_empty(tmp_links));
if (cgroup_on_dfl(cgrp))
cset->dfl_cgrp = cgrp;
link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
link->cset = cset;
link->cgrp = cgrp;
/*
* Always add links to the tail of the lists so that the lists are
* in choronological order.
*/
list_move_tail(&link->cset_link, &cgrp->cset_links);
list_add_tail(&link->cgrp_link, &cset->cgrp_links);
if (cgroup_parent(cgrp))
cgroup_get_live(cgrp);
}
/**
* find_css_set - return a new css_set with one cgroup updated
* @old_cset: the baseline css_set
* @cgrp: the cgroup to be updated
*
* Return a new css_set that's equivalent to @old_cset, but with @cgrp
* substituted into the appropriate hierarchy.
*/
static struct css_set *find_css_set(struct css_set *old_cset,
struct cgroup *cgrp)
{
struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
struct css_set *cset;
struct list_head tmp_links;
struct cgrp_cset_link *link;
struct cgroup_subsys *ss;
unsigned long key;
int ssid;
lockdep_assert_held(&cgroup_mutex);
/* First see if we already have a cgroup group that matches
* the desired set */
spin_lock_irq(&css_set_lock);
cset = find_existing_css_set(old_cset, cgrp, template);
if (cset)
get_css_set(cset);
spin_unlock_irq(&css_set_lock);
if (cset)
return cset;
cset = kzalloc(sizeof(*cset), GFP_KERNEL);
if (!cset)
return NULL;
/* Allocate all the cgrp_cset_link objects that we'll need */
if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
kfree(cset);
return NULL;
}
refcount_set(&cset->refcount, 1);
cset->dom_cset = cset;
INIT_LIST_HEAD(&cset->tasks);
INIT_LIST_HEAD(&cset->mg_tasks);
INIT_LIST_HEAD(&cset->task_iters);
INIT_LIST_HEAD(&cset->threaded_csets);
INIT_HLIST_NODE(&cset->hlist);
INIT_LIST_HEAD(&cset->cgrp_links);
INIT_LIST_HEAD(&cset->mg_preload_node);
INIT_LIST_HEAD(&cset->mg_node);
/* Copy the set of subsystem state objects generated in
* find_existing_css_set() */
memcpy(cset->subsys, template, sizeof(cset->subsys));
spin_lock_irq(&css_set_lock);
/* Add reference counts and links from the new css_set. */
list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
if (c->root == cgrp->root)
c = cgrp;
link_css_set(&tmp_links, cset, c);
}
BUG_ON(!list_empty(&tmp_links));
css_set_count++;
/* Add @cset to the hash table */
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
for_each_subsys(ss, ssid) {
struct cgroup_subsys_state *css = cset->subsys[ssid];
list_add_tail(&cset->e_cset_node[ssid],
&css->cgroup->e_csets[ssid]);
css_get(css);
}
spin_unlock_irq(&css_set_lock);
/*
* If @cset should be threaded, look up the matching dom_cset and
* link them up. We first fully initialize @cset then look for the
* dom_cset. It's simpler this way and safe as @cset is guaranteed
* to stay empty until we return.
*/
if (cgroup_is_threaded(cset->dfl_cgrp)) {
struct css_set *dcset;
dcset = find_css_set(cset, cset->dfl_cgrp->dom_cgrp);
if (!dcset) {
put_css_set(cset);
return NULL;
}
spin_lock_irq(&css_set_lock);
cset->dom_cset = dcset;
list_add_tail(&cset->threaded_csets_node,
&dcset->threaded_csets);
spin_unlock_irq(&css_set_lock);
}
return cset;
}
struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
{
struct cgroup *root_cgrp = kf_root->kn->priv;
return root_cgrp->root;
}
static int cgroup_init_root_id(struct cgroup_root *root)
{
int id;
lockdep_assert_held(&cgroup_mutex);
id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
if (id < 0)
return id;
root->hierarchy_id = id;
return 0;
}
static void cgroup_exit_root_id(struct cgroup_root *root)
{
lockdep_assert_held(&cgroup_mutex);
idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
}
void cgroup_free_root(struct cgroup_root *root)
{
if (root) {
idr_destroy(&root->cgroup_idr);
kfree(root);
}
}
static void cgroup_destroy_root(struct cgroup_root *root)
{
struct cgroup *cgrp = &root->cgrp;
struct cgrp_cset_link *link, *tmp_link;
trace_cgroup_destroy_root(root);
cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
BUG_ON(atomic_read(&root->nr_cgrps));
BUG_ON(!list_empty(&cgrp->self.children));
/* Rebind all subsystems back to the default hierarchy */
WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
/*
* Release all the links from cset_links to this hierarchy's
* root cgroup
*/
spin_lock_irq(&css_set_lock);
list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
list_del(&link->cset_link);
list_del(&link->cgrp_link);
kfree(link);
}
spin_unlock_irq(&css_set_lock);
if (!list_empty(&root->root_list)) {
list_del(&root->root_list);
cgroup_root_count--;
}
cgroup_exit_root_id(root);
mutex_unlock(&cgroup_mutex);
kernfs_destroy_root(root->kf_root);
cgroup_free_root(root);
}
/*
* look up cgroup associated with current task's cgroup namespace on the
* specified hierarchy
*/
static struct cgroup *
current_cgns_cgroup_from_root(struct cgroup_root *root)
{
struct cgroup *res = NULL;
struct css_set *cset;
lockdep_assert_held(&css_set_lock);
rcu_read_lock();
cset = current->nsproxy->cgroup_ns->root_cset;
if (cset == &init_css_set) {
res = &root->cgrp;
} else {
struct cgrp_cset_link *link;
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
if (c->root == root) {
res = c;
break;
}
}
}
rcu_read_unlock();
BUG_ON(!res);
return res;
}
/* look up cgroup associated with given css_set on the specified hierarchy */
static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
struct cgroup_root *root)
{
struct cgroup *res = NULL;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&css_set_lock);
if (cset == &init_css_set) {
res = &root->cgrp;
} else if (root == &cgrp_dfl_root) {
res = cset->dfl_cgrp;
} else {
struct cgrp_cset_link *link;
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
if (c->root == root) {
res = c;
break;
}
}
}
BUG_ON(!res);
return res;
}
/*
* Return the cgroup for "task" from the given hierarchy. Must be
* called with cgroup_mutex and css_set_lock held.
*/
struct cgroup *task_cgroup_from_root(struct task_struct *task,
struct cgroup_root *root)
{
/*
* No need to lock the task - since we hold cgroup_mutex the
* task can't change groups, so the only thing that can happen
* is that it exits and its css is set back to init_css_set.
*/
return cset_cgroup_from_root(task_css_set(task), root);
}
/*
* A task must hold cgroup_mutex to modify cgroups.
*
* Any task can increment and decrement the count field without lock.
* So in general, code holding cgroup_mutex can't rely on the count
* field not changing. However, if the count goes to zero, then only
* cgroup_attach_task() can increment it again. Because a count of zero
* means that no tasks are currently attached, therefore there is no
* way a task attached to that cgroup can fork (the other way to
* increment the count). So code holding cgroup_mutex can safely
* assume that if the count is zero, it will stay zero. Similarly, if
* a task holds cgroup_mutex on a cgroup with zero count, it
* knows that the cgroup won't be removed, as cgroup_rmdir()
* needs that mutex.
*
* A cgroup can only be deleted if both its 'count' of using tasks
* is zero, and its list of 'children' cgroups is empty. Since all
* tasks in the system use _some_ cgroup, and since there is always at
* least one task in the system (init, pid == 1), therefore, root cgroup
* always has either children cgroups and/or using tasks. So we don't
* need a special hack to ensure that root cgroup cannot be deleted.
*
* P.S. One more locking exception. RCU is used to guard the
* update of a tasks cgroup pointer by cgroup_attach_task()
*/
static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
char *buf)
{
struct cgroup_subsys *ss = cft->ss;
if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
!(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
cft->name);
else
strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
return buf;
}
/**
* cgroup_file_mode - deduce file mode of a control file
* @cft: the control file in question
*
* S_IRUGO for read, S_IWUSR for write.
*/
static umode_t cgroup_file_mode(const struct cftype *cft)
{
umode_t mode = 0;
if (cft->read_u64 || cft->read_s64 || cft->seq_show)
mode |= S_IRUGO;
if (cft->write_u64 || cft->write_s64 || cft->write) {
if (cft->flags & CFTYPE_WORLD_WRITABLE)
mode |= S_IWUGO;
else
mode |= S_IWUSR;
}
return mode;
}
/**
* cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
* @subtree_control: the new subtree_control mask to consider
* @this_ss_mask: available subsystems
*
* On the default hierarchy, a subsystem may request other subsystems to be
* enabled together through its ->depends_on mask. In such cases, more
* subsystems than specified in "cgroup.subtree_control" may be enabled.
*
* This function calculates which subsystems need to be enabled if
* @subtree_control is to be applied while restricted to @this_ss_mask.
*/
static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
{
u16 cur_ss_mask = subtree_control;
struct cgroup_subsys *ss;
int ssid;
lockdep_assert_held(&cgroup_mutex);
cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
while (true) {
u16 new_ss_mask = cur_ss_mask;
do_each_subsys_mask(ss, ssid, cur_ss_mask) {
new_ss_mask |= ss->depends_on;
} while_each_subsys_mask();
/*
* Mask out subsystems which aren't available. This can
* happen only if some depended-upon subsystems were bound
* to non-default hierarchies.
*/
new_ss_mask &= this_ss_mask;
if (new_ss_mask == cur_ss_mask)
break;
cur_ss_mask = new_ss_mask;
}
return cur_ss_mask;
}
/**
* cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
* @kn: the kernfs_node being serviced
*
* This helper undoes cgroup_kn_lock_live() and should be invoked before
* the method finishes if locking succeeded. Note that once this function
* returns the cgroup returned by cgroup_kn_lock_live() may become
* inaccessible any time. If the caller intends to continue to access the
* cgroup, it should pin it before invoking this function.
*/
void cgroup_kn_unlock(struct kernfs_node *kn)
{
struct cgroup *cgrp;
if (kernfs_type(kn) == KERNFS_DIR)
cgrp = kn->priv;
else
cgrp = kn->parent->priv;
mutex_unlock(&cgroup_mutex);
kernfs_unbreak_active_protection(kn);
cgroup_put(cgrp);
}
/**
* cgroup_kn_lock_live - locking helper for cgroup kernfs methods
* @kn: the kernfs_node being serviced
* @drain_offline: perform offline draining on the cgroup
*
* This helper is to be used by a cgroup kernfs method currently servicing
* @kn. It breaks the active protection, performs cgroup locking and
* verifies that the associated cgroup is alive. Returns the cgroup if
* alive; otherwise, %NULL. A successful return should be undone by a
* matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the
* cgroup is drained of offlining csses before return.
*
* Any cgroup kernfs method implementation which requires locking the
* associated cgroup should use this helper. It avoids nesting cgroup
* locking under kernfs active protection and allows all kernfs operations
* including self-removal.
*/
struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
{
struct cgroup *cgrp;
if (kernfs_type(kn) == KERNFS_DIR)
cgrp = kn->priv;
else
cgrp = kn->parent->priv;
/*
* We're gonna grab cgroup_mutex which nests outside kernfs
* active_ref. cgroup liveliness check alone provides enough
* protection against removal. Ensure @cgrp stays accessible and
* break the active_ref protection.
*/
if (!cgroup_tryget(cgrp))
return NULL;
kernfs_break_active_protection(kn);
if (drain_offline)
cgroup_lock_and_drain_offline(cgrp);
else
mutex_lock(&cgroup_mutex);
if (!cgroup_is_dead(cgrp))
return cgrp;
cgroup_kn_unlock(kn);
return NULL;
}
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
{
char name[CGROUP_FILE_NAME_MAX];
lockdep_assert_held(&cgroup_mutex);
if (cft->file_offset) {
struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
struct cgroup_file *cfile = (void *)css + cft->file_offset;
spin_lock_irq(&cgroup_file_kn_lock);
cfile->kn = NULL;
spin_unlock_irq(&cgroup_file_kn_lock);
}
kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
}
/**
* css_clear_dir - remove subsys files in a cgroup directory
* @css: taget css
*/
static void css_clear_dir(struct cgroup_subsys_state *css)
{
struct cgroup *cgrp = css->cgroup;
struct cftype *cfts;
if (!(css->flags & CSS_VISIBLE))
return;
css->flags &= ~CSS_VISIBLE;
if (!css->ss) {
if (cgroup_on_dfl(cgrp))
cfts = cgroup_base_files;
else
cfts = cgroup1_base_files;
cgroup_addrm_files(css, cgrp, cfts, false);
} else {
list_for_each_entry(cfts, &css->ss->cfts, node)
cgroup_addrm_files(css, cgrp, cfts, false);
}
}
/**
* css_populate_dir - create subsys files in a cgroup directory
* @css: target css
*
* On failure, no file is added.
*/
static int css_populate_dir(struct cgroup_subsys_state *css)
{
struct cgroup *cgrp = css->cgroup;
struct cftype *cfts, *failed_cfts;
int ret;
if ((css->flags & CSS_VISIBLE) || !cgrp->kn)
return 0;
if (!css->ss) {
if (cgroup_on_dfl(cgrp))
cfts = cgroup_base_files;
else
cfts = cgroup1_base_files;
ret = cgroup_addrm_files(&cgrp->self, cgrp, cfts, true);
if (ret < 0)
return ret;
} else {
list_for_each_entry(cfts, &css->ss->cfts, node) {
ret = cgroup_addrm_files(css, cgrp, cfts, true);
if (ret < 0) {
failed_cfts = cfts;
goto err;
}
}
}
css->flags |= CSS_VISIBLE;
return 0;
err:
list_for_each_entry(cfts, &css->ss->cfts, node) {
if (cfts == failed_cfts)
break;
cgroup_addrm_files(css, cgrp, cfts, false);
}
return ret;
}
int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
{
struct cgroup *dcgrp = &dst_root->cgrp;
struct cgroup_subsys *ss;
int ssid, i, ret;
lockdep_assert_held(&cgroup_mutex);
do_each_subsys_mask(ss, ssid, ss_mask) {
/*
* If @ss has non-root csses attached to it, can't move.
* If @ss is an implicit controller, it is exempt from this
* rule and can be stolen.
*/
if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
!ss->implicit_on_dfl)
return -EBUSY;
/* can't move between two non-dummy roots either */
if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
return -EBUSY;
} while_each_subsys_mask();
do_each_subsys_mask(ss, ssid, ss_mask) {
struct cgroup_root *src_root = ss->root;
struct cgroup *scgrp = &src_root->cgrp;
struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
struct css_set *cset;
WARN_ON(!css || cgroup_css(dcgrp, ss));
/* disable from the source */
src_root->subsys_mask &= ~(1 << ssid);
WARN_ON(cgroup_apply_control(scgrp));
cgroup_finalize_control(scgrp, 0);
/* rebind */
RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
rcu_assign_pointer(dcgrp->subsys[ssid], css);
ss->root = dst_root;
css->cgroup = dcgrp;
spin_lock_irq(&css_set_lock);
hash_for_each(css_set_table, i, cset, hlist)
list_move_tail(&cset->e_cset_node[ss->id],
&dcgrp->e_csets[ss->id]);
spin_unlock_irq(&css_set_lock);
/* default hierarchy doesn't enable controllers by default */
dst_root->subsys_mask |= 1 << ssid;
if (dst_root == &cgrp_dfl_root) {
static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
} else {
dcgrp->subtree_control |= 1 << ssid;
static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
}
ret = cgroup_apply_control(dcgrp);
if (ret)
pr_warn("partial failure to rebind %s controller (err=%d)\n",
ss->name, ret);
if (ss->bind)
ss->bind(css);
} while_each_subsys_mask();
kernfs_activate(dcgrp->kn);
return 0;
}
int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
struct kernfs_root *kf_root)
{
int len = 0;
char *buf = NULL;
struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
struct cgroup *ns_cgroup;
buf = kmalloc(PATH_MAX, GFP_KERNEL);
if (!buf)
return -ENOMEM;
spin_lock_irq(&css_set_lock);
ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
spin_unlock_irq(&css_set_lock);
if (len >= PATH_MAX)
len = -ERANGE;
else if (len > 0) {
seq_escape(sf, buf, " \t\n\\");
len = 0;
}
kfree(buf);
return len;
}
static int parse_cgroup_root_flags(char *data, unsigned int *root_flags)
{
char *token;
*root_flags = 0;
if (!data)
return 0;
while ((token = strsep(&data, ",")) != NULL) {
if (!strcmp(token, "nsdelegate")) {
*root_flags |= CGRP_ROOT_NS_DELEGATE;
continue;
}
pr_err("cgroup2: unknown option \"%s\"\n", token);
return -EINVAL;
}
return 0;
}
static void apply_cgroup_root_flags(unsigned int root_flags)
{
if (current->nsproxy->cgroup_ns == &init_cgroup_ns) {
if (root_flags & CGRP_ROOT_NS_DELEGATE)
cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
else
cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
}
}
static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
{
if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
seq_puts(seq, ",nsdelegate");
return 0;
}
static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
{
unsigned int root_flags;
int ret;
ret = parse_cgroup_root_flags(data, &root_flags);
if (ret)
return ret;
apply_cgroup_root_flags(root_flags);
return 0;
}
/*
* To reduce the fork() overhead for systems that are not actually using
* their cgroups capability, we don't maintain the lists running through
* each css_set to its tasks until we see the list actually used - in other
* words after the first mount.
*/
static bool use_task_css_set_links __read_mostly;
static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
spin_lock_irq(&css_set_lock);
if (use_task_css_set_links)
goto out_unlock;
use_task_css_set_links = true;
/*
* We need tasklist_lock because RCU is not safe against
* while_each_thread(). Besides, a forking task that has passed
* cgroup_post_fork() without seeing use_task_css_set_links = 1
* is not guaranteed to have its child immediately visible in the
* tasklist if we walk through it with RCU.
*/
read_lock(&tasklist_lock);
do_each_thread(g, p) {
WARN_ON_ONCE(!list_empty(&p->cg_list) ||
task_css_set(p) != &init_css_set);
/*
* We should check if the process is exiting, otherwise
* it will race with cgroup_exit() in that the list
* entry won't be deleted though the process has exited.
* Do it while holding siglock so that we don't end up
* racing against cgroup_exit().
*
* Interrupts were already disabled while acquiring
* the css_set_lock, so we do not need to disable it
* again when acquiring the sighand->siglock here.
*/
spin_lock(&p->sighand->siglock);
if (!(p->flags & PF_EXITING)) {
struct css_set *cset = task_css_set(p);
if (!css_set_populated(cset))
css_set_update_populated(cset, true);
list_add_tail(&p->cg_list, &cset->tasks);
get_css_set(cset);
cset->nr_tasks++;
}
spin_unlock(&p->sighand->siglock);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
out_unlock:
spin_unlock_irq(&css_set_lock);
}
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
int ssid;
INIT_LIST_HEAD(&cgrp->self.sibling);
INIT_LIST_HEAD(&cgrp->self.children);
INIT_LIST_HEAD(&cgrp->cset_links);
INIT_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
cgrp->self.cgroup = cgrp;
cgrp->self.flags |= CSS_ONLINE;
cgrp->dom_cgrp = cgrp;
cgrp->max_descendants = INT_MAX;
cgrp->max_depth = INT_MAX;
for_each_subsys(ss, ssid)
INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
init_waitqueue_head(&cgrp->offline_waitq);
INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent);
}
void init_cgroup_root(struct cgroup_root *root, struct cgroup_sb_opts *opts)
{
struct cgroup *cgrp = &root->cgrp;
INIT_LIST_HEAD(&root->root_list);
atomic_set(&root->nr_cgrps, 1);
cgrp->root = root;
init_cgroup_housekeeping(cgrp);
idr_init(&root->cgroup_idr);
root->flags = opts->flags;
if (opts->release_agent)
strscpy(root->release_agent_path, opts->release_agent, PATH_MAX);
if (opts->name)
strscpy(root->name, opts->name, MAX_CGROUP_ROOT_NAMELEN);
if (opts->cpuset_clone_children)
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
}
int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask, int ref_flags)
{
LIST_HEAD(tmp_links);
struct cgroup *root_cgrp = &root->cgrp;
struct kernfs_syscall_ops *kf_sops;
struct css_set *cset;
int i, ret;
lockdep_assert_held(&cgroup_mutex);
ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_KERNEL);
if (ret < 0)
goto out;
root_cgrp->id = ret;
root_cgrp->ancestor_ids[0] = ret;
ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
ref_flags, GFP_KERNEL);
if (ret)
goto out;
/*
* We're accessing css_set_count without locking css_set_lock here,
* but that's OK - it can only be increased by someone holding
* cgroup_lock, and that's us. Later rebinding may disable
* controllers on the default hierarchy and thus create new csets,
* which can't be more than the existing ones. Allocate 2x.
*/
ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
if (ret)
goto cancel_ref;
ret = cgroup_init_root_id(root);
if (ret)
goto cancel_ref;
kf_sops = root == &cgrp_dfl_root ?
&cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops;
root->kf_root = kernfs_create_root(kf_sops,
KERNFS_ROOT_CREATE_DEACTIVATED |
KERNFS_ROOT_SUPPORT_EXPORTOP,
root_cgrp);
if (IS_ERR(root->kf_root)) {
ret = PTR_ERR(root->kf_root);
goto exit_root_id;
}
root_cgrp->kn = root->kf_root->kn;
ret = css_populate_dir(&root_cgrp->self);
if (ret)
goto destroy_root;
ret = rebind_subsystems(root, ss_mask);
if (ret)
goto destroy_root;
ret = cgroup_bpf_inherit(root_cgrp);
WARN_ON_ONCE(ret);
trace_cgroup_setup_root(root);
/*
* There must be no failure case after here, since rebinding takes
* care of subsystems' refcounts, which are explicitly dropped in
* the failure exit path.
*/
list_add(&root->root_list, &cgroup_roots);
cgroup_root_count++;
/*
* Link the root cgroup in this hierarchy into all the css_set
* objects.
*/
spin_lock_irq(&css_set_lock);
hash_for_each(css_set_table, i, cset, hlist) {
link_css_set(&tmp_links, cset, root_cgrp);
if (css_set_populated(cset))
cgroup_update_populated(root_cgrp, true);
}
spin_unlock_irq(&css_set_lock);
BUG_ON(!list_empty(&root_cgrp->self.children));
BUG_ON(atomic_read(&root->nr_cgrps) != 1);
kernfs_activate(root_cgrp->kn);
ret = 0;
goto out;
destroy_root:
kernfs_destroy_root(root->kf_root);
root->kf_root = NULL;
exit_root_id:
cgroup_exit_root_id(root);
cancel_ref:
percpu_ref_exit(&root_cgrp->self.refcnt);
out:
free_cgrp_cset_links(&tmp_links);
return ret;
}
struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags,
struct cgroup_root *root, unsigned long magic,
struct cgroup_namespace *ns)
{
struct dentry *dentry;
bool new_sb;
dentry = kernfs_mount(fs_type, flags, root->kf_root, magic, &new_sb);
/*
* In non-init cgroup namespace, instead of root cgroup's dentry,
* we return the dentry corresponding to the cgroupns->root_cgrp.
*/
if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
struct dentry *nsdentry;
struct cgroup *cgrp;
mutex_lock(&cgroup_mutex);
spin_lock_irq(&css_set_lock);
cgrp = cset_cgroup_from_root(ns->root_cset, root);
spin_unlock_irq(&css_set_lock);
mutex_unlock(&cgroup_mutex);
nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
dput(dentry);
dentry = nsdentry;
}
if (IS_ERR(dentry) || !new_sb)
cgroup_put(&root->cgrp);
return dentry;
}
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data)
{
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct dentry *dentry;
int ret;
get_cgroup_ns(ns);
/* Check if the caller has permission to mount. */
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
put_cgroup_ns(ns);
return ERR_PTR(-EPERM);
}
/*
* The first time anyone tries to mount a cgroup, enable the list
* linking each css_set to its tasks and fix up all existing tasks.
*/
if (!use_task_css_set_links)
cgroup_enable_task_cg_lists();
if (fs_type == &cgroup2_fs_type) {
unsigned int root_flags;
ret = parse_cgroup_root_flags(data, &root_flags);
if (ret) {
put_cgroup_ns(ns);
return ERR_PTR(ret);
}
cgrp_dfl_visible = true;
cgroup_get_live(&cgrp_dfl_root.cgrp);
dentry = cgroup_do_mount(&cgroup2_fs_type, flags, &cgrp_dfl_root,
CGROUP2_SUPER_MAGIC, ns);
if (!IS_ERR(dentry))
apply_cgroup_root_flags(root_flags);
} else {
dentry = cgroup1_mount(&cgroup_fs_type, flags, data,
CGROUP_SUPER_MAGIC, ns);
}
put_cgroup_ns(ns);
return dentry;
}
static void cgroup_kill_sb(struct super_block *sb)
{
struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
struct cgroup_root *root = cgroup_root_from_kf(kf_root);
/*
* If @root doesn't have any mounts or children, start killing it.
* This prevents new mounts by disabling percpu_ref_tryget_live().
* cgroup_mount() may wait for @root's release.
*
* And don't kill the default root.
*/
if (!list_empty(&root->cgrp.self.children) ||
root == &cgrp_dfl_root)
cgroup_put(&root->cgrp);
else
percpu_ref_kill(&root->cgrp.self.refcnt);
kernfs_kill_sb(sb);
}
struct file_system_type cgroup_fs_type = {
.name = "cgroup",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
.fs_flags = FS_USERNS_MOUNT,
};
static struct file_system_type cgroup2_fs_type = {
.name = "cgroup2",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
.fs_flags = FS_USERNS_MOUNT,
};
int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
struct cgroup_namespace *ns)
{
struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
}
int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
struct cgroup_namespace *ns)
{
int ret;
mutex_lock(&cgroup_mutex);
spin_lock_irq(&css_set_lock);
ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
spin_unlock_irq(&css_set_lock);
mutex_unlock(&cgroup_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(cgroup_path_ns);
/**
* task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
* @task: target task
* @buf: the buffer to write the path into
* @buflen: the length of the buffer
*
* Determine @task's cgroup on the first (the one with the lowest non-zero
* hierarchy_id) cgroup hierarchy and copy its path into @buf. This
* function grabs cgroup_mutex and shouldn't be used inside locks used by
* cgroup controller callbacks.
*
* Return value is the same as kernfs_path().
*/
int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
{
struct cgroup_root *root;
struct cgroup *cgrp;
int hierarchy_id = 1;
int ret;
mutex_lock(&cgroup_mutex);
spin_lock_irq(&css_set_lock);
root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
if (root) {
cgrp = task_cgroup_from_root(task, root);
ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
} else {
/* if no hierarchy exists, everyone is in "/" */
ret = strlcpy(buf, "/", buflen);
}
spin_unlock_irq(&css_set_lock);
mutex_unlock(&cgroup_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(task_cgroup_path);
/**
* cgroup_migrate_add_task - add a migration target task to a migration context
* @task: target task
* @mgctx: target migration context
*
* Add @task, which is a migration target, to @mgctx->tset. This function
* becomes noop if @task doesn't need to be migrated. @task's css_set
* should have been added as a migration source and @task->cg_list will be
* moved from the css_set's tasks list to mg_tasks one.
*/
static void cgroup_migrate_add_task(struct task_struct *task,
struct cgroup_mgctx *mgctx)
{
struct css_set *cset;
lockdep_assert_held(&css_set_lock);
/* @task either already exited or can't exit until the end */
if (task->flags & PF_EXITING)
return;
/* leave @task alone if post_fork() hasn't linked it yet */
if (list_empty(&task->cg_list))
return;
cset = task_css_set(task);
if (!cset->mg_src_cgrp)
return;
mgctx->tset.nr_tasks++;
list_move_tail(&task->cg_list, &cset->mg_tasks);
if (list_empty(&cset->mg_node))
list_add_tail(&cset->mg_node,
&mgctx->tset.src_csets);
if (list_empty(&cset->mg_dst_cset->mg_node))
list_add_tail(&cset->mg_dst_cset->mg_node,
&mgctx->tset.dst_csets);
}
/**
* cgroup_taskset_first - reset taskset and return the first task
* @tset: taskset of interest
* @dst_cssp: output variable for the destination css
*
* @tset iteration is initialized and the first task is returned.
*/
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
struct cgroup_subsys_state **dst_cssp)
{
tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
tset->cur_task = NULL;
return cgroup_taskset_next(tset, dst_cssp);
}
/**
* cgroup_taskset_next - iterate to the next task in taskset
* @tset: taskset of interest
* @dst_cssp: output variable for the destination css
*
* Return the next task in @tset. Iteration must have been initialized
* with cgroup_taskset_first().
*/
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
struct cgroup_subsys_state **dst_cssp)
{
struct css_set *cset = tset->cur_cset;
struct task_struct *task = tset->cur_task;
while (&cset->mg_node != tset->csets) {
if (!task)
task = list_first_entry(&cset->mg_tasks,
struct task_struct, cg_list);
else
task = list_next_entry(task, cg_list);
if (&task->cg_list != &cset->mg_tasks) {
tset->cur_cset = cset;
tset->cur_task = task;
/*
* This function may be called both before and
* after cgroup_taskset_migrate(). The two cases
* can be distinguished by looking at whether @cset
* has its ->mg_dst_cset set.
*/
if (cset->mg_dst_cset)
*dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
else
*dst_cssp = cset->subsys[tset->ssid];
return task;
}
cset = list_next_entry(cset, mg_node);
task = NULL;
}
return NULL;
}
/**
* cgroup_taskset_migrate - migrate a taskset
* @mgctx: migration context
*
* Migrate tasks in @mgctx as setup by migration preparation functions.
* This function fails iff one of the ->can_attach callbacks fails and
* guarantees that either all or none of the tasks in @mgctx are migrated.
* @mgctx is consumed regardless of success.
*/
static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
{
struct cgroup_taskset *tset = &mgctx->tset;
struct cgroup_subsys *ss;
struct task_struct *task, *tmp_task;
struct css_set *cset, *tmp_cset;
int ssid, failed_ssid, ret;
/* check that we can legitimately attach to the cgroup */
if (tset->nr_tasks) {
do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
if (ss->can_attach) {
tset->ssid = ssid;
ret = ss->can_attach(tset);
if (ret) {
failed_ssid = ssid;
goto out_cancel_attach;
}
}
} while_each_subsys_mask();
}
/*
* Now that we're guaranteed success, proceed to move all tasks to
* the new cgroup. There are no failure cases after here, so this
* is the commit point.
*/
spin_lock_irq(&css_set_lock);
list_for_each_entry(cset, &tset->src_csets, mg_node) {
list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
struct css_set *from_cset = task_css_set(task);
struct css_set *to_cset = cset->mg_dst_cset;
get_css_set(to_cset);
to_cset->nr_tasks++;
css_set_move_task(task, from_cset, to_cset, true);
put_css_set_locked(from_cset);
from_cset->nr_tasks--;
}
}
spin_unlock_irq(&css_set_lock);
/*
* Migration is committed, all target tasks are now on dst_csets.
* Nothing is sensitive to fork() after this point. Notify
* controllers that migration is complete.
*/
tset->csets = &tset->dst_csets;
if (tset->nr_tasks) {
do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
if (ss->attach) {
tset->ssid = ssid;
ss->attach(tset);
}
} while_each_subsys_mask();
}
ret = 0;
goto out_release_tset;
out_cancel_attach:
if (tset->nr_tasks) {
do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
if (ssid == failed_ssid)
break;
if (ss->cancel_attach) {
tset->ssid = ssid;
ss->cancel_attach(tset);
}
} while_each_subsys_mask();
}
out_release_tset:
spin_lock_irq(&css_set_lock);
list_splice_init(&tset->dst_csets, &tset->src_csets);
list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
list_del_init(&cset->mg_node);
}
spin_unlock_irq(&css_set_lock);
/*
* Re-initialize the cgroup_taskset structure in case it is reused
* again in another cgroup_migrate_add_task()/cgroup_migrate_execute()
* iteration.
*/
tset->nr_tasks = 0;
tset->csets = &tset->src_csets;
return ret;
}
/**
* cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination
* @dst_cgrp: destination cgroup to test
*
* On the default hierarchy, except for the mixable, (possible) thread root
* and threaded cgroups, subtree_control must be zero for migration
* destination cgroups with tasks so that child cgroups don't compete
* against tasks.
*/
int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp)
{
/* v1 doesn't have any restriction */
if (!cgroup_on_dfl(dst_cgrp))
return 0;
/* verify @dst_cgrp can host resources */
if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp))
return -EOPNOTSUPP;
/* mixables don't care */
if (cgroup_is_mixable(dst_cgrp))
return 0;
/*
* If @dst_cgrp is already or can become a thread root or is
* threaded, it doesn't matter.
*/
if (cgroup_can_be_thread_root(dst_cgrp) || cgroup_is_threaded(dst_cgrp))
return 0;
/* apply no-internal-process constraint */
if (dst_cgrp->subtree_control)
return -EBUSY;
return 0;
}
/**
* cgroup_migrate_finish - cleanup after attach
* @mgctx: migration context
*
* Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
* those functions for details.
*/
void cgroup_migrate_finish(struct cgroup_mgctx *mgctx)
{
LIST_HEAD(preloaded);
struct css_set *cset, *tmp_cset;
lockdep_assert_held(&cgroup_mutex);
spin_lock_irq(&css_set_lock);
list_splice_tail_init(&mgctx->preloaded_src_csets, &preloaded);
list_splice_tail_init(&mgctx->preloaded_dst_csets, &preloaded);
list_for_each_entry_safe(cset, tmp_cset, &preloaded, mg_preload_node) {
cset->mg_src_cgrp = NULL;
cset->mg_dst_cgrp = NULL;
cset->mg_dst_cset = NULL;
list_del_init(&cset->mg_preload_node);
put_css_set_locked(cset);
}
spin_unlock_irq(&css_set_lock);
}
/**
* cgroup_migrate_add_src - add a migration source css_set
* @src_cset: the source css_set to add
* @dst_cgrp: the destination cgroup
* @mgctx: migration context
*
* Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
* @src_cset and add it to @mgctx->src_csets, which should later be cleaned
* up by cgroup_migrate_finish().
*
* This function may be called without holding cgroup_threadgroup_rwsem
* even if the target is a process. Threads may be created and destroyed
* but as long as cgroup_mutex is not dropped, no new css_set can be put
* into play and the preloaded css_sets are guaranteed to cover all
* migrations.
*/
void cgroup_migrate_add_src(struct css_set *src_cset,
struct cgroup *dst_cgrp,
struct cgroup_mgctx *mgctx)
{
struct cgroup *src_cgrp;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&css_set_lock);
/*
* If ->dead, @src_set is associated with one or more dead cgroups
* and doesn't contain any migratable tasks. Ignore it early so
* that the rest of migration path doesn't get confused by it.
*/
if (src_cset->dead)
return;
src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
if (!list_empty(&src_cset->mg_preload_node))
return;
WARN_ON(src_cset->mg_src_cgrp);
WARN_ON(src_cset->mg_dst_cgrp);
WARN_ON(!list_empty(&src_cset->mg_tasks));
WARN_ON(!list_empty(&src_cset->mg_node));
src_cset->mg_src_cgrp = src_cgrp;
src_cset->mg_dst_cgrp = dst_cgrp;
get_css_set(src_cset);
list_add_tail(&src_cset->mg_preload_node, &mgctx->preloaded_src_csets);
}
/**
* cgroup_migrate_prepare_dst - prepare destination css_sets for migration
* @mgctx: migration context
*
* Tasks are about to be moved and all the source css_sets have been
* preloaded to @mgctx->preloaded_src_csets. This function looks up and
* pins all destination css_sets, links each to its source, and append them
* to @mgctx->preloaded_dst_csets.
*
* This function must be called after cgroup_migrate_add_src() has been
* called on each migration source css_set. After migration is performed
* using cgroup_migrate(), cgroup_migrate_finish() must be called on
* @mgctx.
*/
int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
{
struct css_set *src_cset, *tmp_cset;
lockdep_assert_held(&cgroup_mutex);
/* look up the dst cset for each src cset and link it to src */
list_for_each_entry_safe(src_cset, tmp_cset, &mgctx->preloaded_src_csets,
mg_preload_node) {
struct css_set *dst_cset;
struct cgroup_subsys *ss;
int ssid;
dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
if (!dst_cset)
goto err;
WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
/*
* If src cset equals dst, it's noop. Drop the src.
* cgroup_migrate() will skip the cset too. Note that we
* can't handle src == dst as some nodes are used by both.
*/
if (src_cset == dst_cset) {
src_cset->mg_src_cgrp = NULL;
src_cset->mg_dst_cgrp = NULL;
list_del_init(&src_cset->mg_preload_node);
put_css_set(src_cset);
put_css_set(dst_cset);
continue;
}
src_cset->mg_dst_cset = dst_cset;
if (list_empty(&dst_cset->mg_preload_node))
list_add_tail(&dst_cset->mg_preload_node,
&mgctx->preloaded_dst_csets);
else
put_css_set(dst_cset);
for_each_subsys(ss, ssid)
if (src_cset->subsys[ssid] != dst_cset->subsys[ssid])
mgctx->ss_mask |= 1 << ssid;
}
return 0;
err:
cgroup_migrate_finish(mgctx);
return -ENOMEM;
}
/**
* cgroup_migrate - migrate a process or task to a cgroup
* @leader: the leader of the process or the task to migrate
* @threadgroup: whether @leader points to the whole process or a single task
* @mgctx: migration context
*
* Migrate a process or task denoted by @leader. If migrating a process,
* the caller must be holding cgroup_threadgroup_rwsem. The caller is also
* responsible for invoking cgroup_migrate_add_src() and
* cgroup_migrate_prepare_dst() on the targets before invoking this
* function and following up with cgroup_migrate_finish().
*
* As long as a controller's ->can_attach() doesn't fail, this function is
* guaranteed to succeed. This means that, excluding ->can_attach()
* failure, when migrating multiple targets, the success or failure can be
* decided for all targets by invoking group_migrate_prepare_dst() before
* actually starting migrating.
*/
int cgroup_migrate(struct task_struct *leader, bool threadgroup,
struct cgroup_mgctx *mgctx)
{
struct task_struct *task;
/*
* Prevent freeing of tasks while we take a snapshot. Tasks that are
* already PF_EXITING could be freed from underneath us unless we
* take an rcu_read_lock.
*/
spin_lock_irq(&css_set_lock);
rcu_read_lock();
task = leader;
do {
cgroup_migrate_add_task(task, mgctx);
if (!threadgroup)
break;
} while_each_thread(leader, task);
rcu_read_unlock();
spin_unlock_irq(&css_set_lock);
return cgroup_migrate_execute(mgctx);
}
/**
* cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
* @dst_cgrp: the cgroup to attach to
* @leader: the task or the leader of the threadgroup to be attached
* @threadgroup: attach the whole threadgroup?
*
* Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
*/
int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
bool threadgroup)
{
DEFINE_CGROUP_MGCTX(mgctx);
struct task_struct *task;
int ret;
ret = cgroup_migrate_vet_dst(dst_cgrp);
if (ret)
return ret;
/* look up all src csets */
spin_lock_irq(&css_set_lock);
rcu_read_lock();
task = leader;
do {
cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);
if (!threadgroup)
break;
} while_each_thread(leader, task);
rcu_read_unlock();
spin_unlock_irq(&css_set_lock);
/* prepare dst csets and commit */
ret = cgroup_migrate_prepare_dst(&mgctx);
if (!ret)
ret = cgroup_migrate(leader, threadgroup, &mgctx);
cgroup_migrate_finish(&mgctx);
if (!ret)
trace_cgroup_attach_task(dst_cgrp, leader, threadgroup);
return ret;
}
struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup)
__acquires(&cgroup_threadgroup_rwsem)
{
struct task_struct *tsk;
pid_t pid;
if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
return ERR_PTR(-EINVAL);
percpu_down_write(&cgroup_threadgroup_rwsem);
rcu_read_lock();
if (pid) {
tsk = find_task_by_vpid(pid);
if (!tsk) {
tsk = ERR_PTR(-ESRCH);
goto out_unlock_threadgroup;
}
} else {
tsk = current;
}
if (threadgroup)
tsk = tsk->group_leader;
/*
* kthreads may acquire PF_NO_SETAFFINITY during initialization.
* If userland migrates such a kthread to a non-root cgroup, it can
* become trapped in a cpuset, or RT kthread may be born in a
* cgroup with no rt_runtime allocated. Just say no.
*/
if (tsk->no_cgroup_migration || (tsk->flags & PF_NO_SETAFFINITY)) {
tsk = ERR_PTR(-EINVAL);
goto out_unlock_threadgroup;
}
get_task_struct(tsk);
goto out_unlock_rcu;
out_unlock_threadgroup:
percpu_up_write(&cgroup_threadgroup_rwsem);
out_unlock_rcu:
rcu_read_unlock();
return tsk;
}
void cgroup_procs_write_finish(struct task_struct *task)
__releases(&cgroup_threadgroup_rwsem)
{
struct cgroup_subsys *ss;
int ssid;
/* release reference from cgroup_procs_write_start() */
put_task_struct(task);
percpu_up_write(&cgroup_threadgroup_rwsem);
for_each_subsys(ss, ssid)
if (ss->post_attach)
ss->post_attach();
}
static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
{
struct cgroup_subsys *ss;
bool printed = false;
int ssid;
do_each_subsys_mask(ss, ssid, ss_mask) {
if (printed)
seq_putc(seq, ' ');
seq_printf(seq, "%s", ss->name);
printed = true;
} while_each_subsys_mask();
if (printed)
seq_putc(seq, '\n');
}
/* show controllers which are enabled from the parent */
static int cgroup_controllers_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
cgroup_print_ss_mask(seq, cgroup_control(cgrp));
return 0;
}
/* show controllers which are enabled for a given cgroup's children */
static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
cgroup_print_ss_mask(seq, cgrp->subtree_control);
return 0;
}
/**
* cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
* @cgrp: root of the subtree to update csses for
*
* @cgrp's control masks have changed and its subtree's css associations
* need to be updated accordingly. This function looks up all css_sets
* which are attached to the subtree, creates the matching updated css_sets
* and migrates the tasks to the new ones.
*/
static int cgroup_update_dfl_csses(struct cgroup *cgrp)
{
DEFINE_CGROUP_MGCTX(mgctx);
struct cgroup_subsys_state *d_css;
struct cgroup *dsct;
struct css_set *src_cset;
int ret;
lockdep_assert_held(&cgroup_mutex);
percpu_down_write(&cgroup_threadgroup_rwsem);
/* look up all csses currently attached to @cgrp's subtree */
spin_lock_irq(&css_set_lock);
cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
struct cgrp_cset_link *link;
list_for_each_entry(link, &dsct->cset_links, cset_link)
cgroup_migrate_add_src(link->cset, dsct, &mgctx);
}
spin_unlock_irq(&css_set_lock);
/* NULL dst indicates self on default hierarchy */
ret = cgroup_migrate_prepare_dst(&mgctx);
if (ret)
goto out_finish;
spin_lock_irq(&css_set_lock);
list_for_each_entry(src_cset, &mgctx.preloaded_src_csets, mg_preload_node) {
struct task_struct *task, *ntask;
/* all tasks in src_csets need to be migrated */
list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
cgroup_migrate_add_task(task, &mgctx);
}
spin_unlock_irq(&css_set_lock);
ret = cgroup_migrate_execute(&mgctx);
out_finish:
cgroup_migrate_finish(&mgctx);
percpu_up_write(&cgroup_threadgroup_rwsem);
return ret;
}
/**
* cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
* @cgrp: root of the target subtree
*
* Because css offlining is asynchronous, userland may try to re-enable a
* controller while the previous css is still around. This function grabs
* cgroup_mutex and drains the previous css instances of @cgrp's subtree.
*/
void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
__acquires(&cgroup_mutex)
{
struct cgroup *dsct;
struct cgroup_subsys_state *d_css;
struct cgroup_subsys *ss;
int ssid;
restart:
mutex_lock(&cgroup_mutex);
cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
for_each_subsys(ss, ssid) {
struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
DEFINE_WAIT(wait);
if (!css || !percpu_ref_is_dying(&css->refcnt))
continue;
cgroup_get_live(dsct);
prepare_to_wait(&dsct->offline_waitq, &wait,
TASK_UNINTERRUPTIBLE);
mutex_unlock(&cgroup_mutex);
schedule();
finish_wait(&dsct->offline_waitq, &wait);
cgroup_put(dsct);
goto restart;
}
}
}
/**
* cgroup_save_control - save control masks of a subtree
* @cgrp: root of the target subtree
*
* Save ->subtree_control and ->subtree_ss_mask to the respective old_
* prefixed fields for @cgrp's subtree including @cgrp itself.
*/
static void cgroup_save_control(struct cgroup *cgrp)
{
struct cgroup *dsct;
struct cgroup_subsys_state *d_css;
cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
dsct->old_subtree_control = dsct->subtree_control;
dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
}
}
/**
* cgroup_propagate_control - refresh control masks of a subtree
* @cgrp: root of the target subtree
*
* For @cgrp and its subtree, ensure ->subtree_ss_mask matches
* ->subtree_control and propagate controller availability through the
* subtree so that descendants don't have unavailable controllers enabled.
*/
static void cgroup_propagate_control(struct cgroup *cgrp)
{
struct cgroup *dsct;
struct cgroup_subsys_state *d_css;
cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
dsct->subtree_control &= cgroup_control(dsct);
dsct->subtree_ss_mask =
cgroup_calc_subtree_ss_mask(dsct->subtree_control,
cgroup_ss_mask(dsct));
}
}
/**
* cgroup_restore_control - restore control masks of a subtree
* @cgrp: root of the target subtree
*
* Restore ->subtree_control and ->subtree_ss_mask from the respective old_
* prefixed fields for @cgrp's subtree including @cgrp itself.
*/
static void cgroup_restore_control(struct cgroup *cgrp)
{
struct cgroup *dsct;
struct cgroup_subsys_state *d_css;
cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
dsct->subtree_control = dsct->old_subtree_control;
dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
}
}
static bool css_visible(struct cgroup_subsys_state *css)
{
struct cgroup_subsys *ss = css->ss;
struct cgroup *cgrp = css->cgroup;
if (cgroup_control(cgrp) & (1 << ss->id))
return true;
if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
return false;
return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
}
/**
* cgroup_apply_control_enable - enable or show csses according to control
* @cgrp: root of the target subtree
*
* Walk @cgrp's subtree and create new csses or make the existing ones
* visible. A css is created invisible if it's being implicitly enabled
* through dependency. An invisible css is made visible when the userland
* explicitly enables it.
*
* Returns 0 on success, -errno on failure. On failure, csses which have
* been processed already aren't cleaned up. The caller is responsible for
* cleaning up with cgroup_apply_control_disable().
*/
static int cgroup_apply_control_enable(struct cgroup *cgrp)
{
struct cgroup *dsct;
struct cgroup_subsys_state *d_css;
struct cgroup_subsys *ss;
int ssid, ret;
cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
for_each_subsys(ss, ssid) {
struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
continue;
if (!css) {
css = css_create(dsct, ss);
if (IS_ERR(css))
return PTR_ERR(css);
}
if (css_visible(css)) {
ret = css_populate_dir(css);
if (ret)
return ret;
}
}
}
return 0;
}
/**
* cgroup_apply_control_disable - kill or hide csses according to control
* @cgrp: root of the target subtree
*
* Walk @cgrp's subtree and kill and hide csses so that they match
* cgroup_ss_mask() and cgroup_visible_mask().
*
* A css is hidden when the userland requests it to be disabled while other
* subsystems are still depending on it. The css must not actively control
* resources and be in the vanilla state if it's made visible again later.
* Controllers which may be depended upon should provide ->css_reset() for
* this purpose.
*/
static void cgroup_apply_control_disable(struct cgroup *cgrp)
{
struct cgroup *dsct;
struct cgroup_subsys_state *d_css;
struct cgroup_subsys *ss;
int ssid;
cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
for_each_subsys(ss, ssid) {
struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
if (!css)
continue;
if (css->parent &&
!(cgroup_ss_mask(dsct) & (1 << ss->id))) {
kill_css(css);
} else if (!css_visible(css)) {
css_clear_dir(css);
if (ss->css_reset)
ss->css_reset(css);
}
}
}
}
/**
* cgroup_apply_control - apply control mask updates to the subtree
* @cgrp: root of the target subtree
*
* subsystems can be enabled and disabled in a subtree using the following
* steps.
*
* 1. Call cgroup_save_control() to stash the current state.
* 2. Update ->subtree_control masks in the subtree as desired.
* 3. Call cgroup_apply_control() to apply the changes.
* 4. Optionally perform other related operations.
* 5. Call cgroup_finalize_control() to finish up.
*
* This function implements step 3 and propagates the mask changes
* throughout @cgrp's subtree, updates csses accordingly and perform
* process migrations.
*/
static int cgroup_apply_control(struct cgroup *cgrp)
{
int ret;
cgroup_propagate_control(cgrp);
ret = cgroup_apply_control_enable(cgrp);
if (ret)
return ret;
/*
* At this point, cgroup_e_css() results reflect the new csses
* making the following cgroup_update_dfl_csses() properly update
* css associations of all tasks in the subtree.
*/
ret = cgroup_update_dfl_csses(cgrp);
if (ret)
return ret;
return 0;
}
/**
* cgroup_finalize_control - finalize control mask update
* @cgrp: root of the target subtree
* @ret: the result of the update
*
* Finalize control mask update. See cgroup_apply_control() for more info.
*/
static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
{
if (ret) {
cgroup_restore_control(cgrp);
cgroup_propagate_control(cgrp);
}
cgroup_apply_control_disable(cgrp);
}
static int cgroup_vet_subtree_control_enable(struct cgroup *cgrp, u16 enable)
{
u16 domain_enable = enable & ~cgrp_dfl_threaded_ss_mask;
/* if nothing is getting enabled, nothing to worry about */
if (!enable)
return 0;
/* can @cgrp host any resources? */
if (!cgroup_is_valid_domain(cgrp->dom_cgrp))
return -EOPNOTSUPP;
/* mixables don't care */
if (cgroup_is_mixable(cgrp))
return 0;
if (domain_enable) {
/* can't enable domain controllers inside a thread subtree */
if (cgroup_is_thread_root(cgrp) || cgroup_is_threaded(cgrp))
return -EOPNOTSUPP;
} else {
/*
* Threaded controllers can handle internal competitions
* and are always allowed inside a (prospective) thread
* subtree.
*/
if (cgroup_can_be_thread_root(cgrp) || cgroup_is_threaded(cgrp))
return 0;
}
/*
* Controllers can't be enabled for a cgroup with tasks to avoid
* child cgroups competing against tasks.
*/
if (cgroup_has_tasks(cgrp))
return -EBUSY;
return 0;
}
/* change the enabled child controllers for a cgroup in the default hierarchy */
static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
char *buf, size_t nbytes,
loff_t off)
{
u16 enable = 0, disable = 0;
struct cgroup *cgrp, *child;
struct cgroup_subsys *ss;
char *tok;
int ssid, ret;
/*
* Parse input - space separated list of subsystem names prefixed
* with either + or -.
*/
buf = strstrip(buf);
while ((tok = strsep(&buf, " "))) {
if (tok[0] == '\0')
continue;
do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
if (!cgroup_ssid_enabled(ssid) ||
strcmp(tok + 1, ss->name))
continue;
if (*tok == '+') {
enable |= 1 << ssid;
disable &= ~(1 << ssid);
} else if (*tok == '-') {
disable |= 1 << ssid;
enable &= ~(1 << ssid);
} else {
return -EINVAL;
}
break;
} while_each_subsys_mask();
if (ssid == CGROUP_SUBSYS_COUNT)
return -EINVAL;
}
cgrp = cgroup_kn_lock_live(of->kn, true);
if (!cgrp)
return -ENODEV;
for_each_subsys(ss, ssid) {
if (enable & (1 << ssid)) {
if (cgrp->subtree_control & (1 << ssid)) {
enable &= ~(1 << ssid);
continue;
}
if (!(cgroup_control(cgrp) & (1 << ssid))) {
ret = -ENOENT;
goto out_unlock;
}
} else if (disable & (1 << ssid)) {
if (!(cgrp->subtree_control & (1 << ssid))) {
disable &= ~(1 << ssid);
continue;
}
/* a child has it enabled? */
cgroup_for_each_live_child(child, cgrp) {
if (child->subtree_control & (1 << ssid)) {
ret = -EBUSY;
goto out_unlock;
}
}
}
}
if (!enable && !disable) {
ret = 0;
goto out_unlock;
}
ret = cgroup_vet_subtree_control_enable(cgrp, enable);
if (ret)
goto out_unlock;
/* save and update control masks and prepare csses */
cgroup_save_control(cgrp);
cgrp->subtree_control |= enable;
cgrp->subtree_control &= ~disable;
ret = cgroup_apply_control(cgrp);
cgroup_finalize_control(cgrp, ret);
if (ret)
goto out_unlock;
kernfs_activate(cgrp->kn);
out_unlock:
cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
}
/**
* cgroup_enable_threaded - make @cgrp threaded
* @cgrp: the target cgroup
*
* Called when "threaded" is written to the cgroup.type interface file and
* tries to make @cgrp threaded and join the parent's resource domain.
* This function is never called on the root cgroup as cgroup.type doesn't
* exist on it.
*/
static int cgroup_enable_threaded(struct cgroup *cgrp)
{
struct cgroup *parent = cgroup_parent(cgrp);
struct cgroup *dom_cgrp = parent->dom_cgrp;
int ret;
lockdep_assert_held(&cgroup_mutex);
/* noop if already threaded */
if (cgroup_is_threaded(cgrp))
return 0;
/*
* If @cgroup is populated or has domain controllers enabled, it
* can't be switched. While the below cgroup_can_be_thread_root()
* test can catch the same conditions, that's only when @parent is
* not mixable, so let's check it explicitly.
*/
if (cgroup_is_populated(cgrp) ||
cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
return -EOPNOTSUPP;
/* we're joining the parent's domain, ensure its validity */
if (!cgroup_is_valid_domain(dom_cgrp) ||
!cgroup_can_be_thread_root(dom_cgrp))
return -EOPNOTSUPP;
/*
* The following shouldn't cause actual migrations and should
* always succeed.
*/
cgroup_save_control(cgrp);
cgrp->dom_cgrp = dom_cgrp;
ret = cgroup_apply_control(cgrp);
if (!ret)
parent->nr_threaded_children++;
else
cgrp->dom_cgrp = cgrp;
cgroup_finalize_control(cgrp, ret);
return ret;
}
static int cgroup_type_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
if (cgroup_is_threaded(cgrp))
seq_puts(seq, "threaded\n");
else if (!cgroup_is_valid_domain(cgrp))
seq_puts(seq, "domain invalid\n");
else if (cgroup_is_thread_root(cgrp))
seq_puts(seq, "domain threaded\n");
else
seq_puts(seq, "domain\n");
return 0;
}
static ssize_t cgroup_type_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off)
{
struct cgroup *cgrp;
int ret;
/* only switching to threaded mode is supported */
if (strcmp(strstrip(buf), "threaded"))
return -EINVAL;
cgrp = cgroup_kn_lock_live(of->kn, false);
if (!cgrp)
return -ENOENT;
/* threaded can only be enabled */
ret = cgroup_enable_threaded(cgrp);
cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
}
static int cgroup_max_descendants_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
int descendants = READ_ONCE(cgrp->max_descendants);
if (descendants == INT_MAX)
seq_puts(seq, "max\n");
else
seq_printf(seq, "%d\n", descendants);
return 0;
}
static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct cgroup *cgrp;
int descendants;
ssize_t ret;
buf = strstrip(buf);
if (!strcmp(buf, "max")) {
descendants = INT_MAX;
} else {
ret = kstrtoint(buf, 0, &descendants);
if (ret)
return ret;
}
if (descendants < 0)
return -ERANGE;
cgrp = cgroup_kn_lock_live(of->kn, false);
if (!cgrp)
return -ENOENT;
cgrp->max_descendants = descendants;
cgroup_kn_unlock(of->kn);
return nbytes;
}
static int cgroup_max_depth_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
int depth = READ_ONCE(cgrp->max_depth);
if (depth == INT_MAX)
seq_puts(seq, "max\n");
else
seq_printf(seq, "%d\n", depth);
return 0;
}
static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct cgroup *cgrp;
ssize_t ret;
int depth;
buf = strstrip(buf);
if (!strcmp(buf, "max")) {
depth = INT_MAX;
} else {
ret = kstrtoint(buf, 0, &depth);
if (ret)
return ret;
}
if (depth < 0)
return -ERANGE;
cgrp = cgroup_kn_lock_live(of->kn, false);
if (!cgrp)
return -ENOENT;
cgrp->max_depth = depth;
cgroup_kn_unlock(of->kn);
return nbytes;
}
static int cgroup_events_show(struct seq_file *seq, void *v)
{
seq_printf(seq, "populated %d\n",
cgroup_is_populated(seq_css(seq)->cgroup));
return 0;
}
static int cgroup_stat_show(struct seq_file *seq, void *v)
{
struct cgroup *cgroup = seq_css(seq)->cgroup;
seq_printf(seq, "nr_descendants %d\n",
cgroup->nr_descendants);
seq_printf(seq, "nr_dying_descendants %d\n",
cgroup->nr_dying_descendants);
return 0;
}
static int __maybe_unused cgroup_extra_stat_show(struct seq_file *seq,
struct cgroup *cgrp, int ssid)
{
struct cgroup_subsys *ss = cgroup_subsys[ssid];
struct cgroup_subsys_state *css;
int ret;
if (!ss->css_extra_stat_show)
return 0;
css = cgroup_tryget_css(cgrp, ss);
if (!css)
return 0;
ret = ss->css_extra_stat_show(seq, css);
css_put(css);
return ret;
}
static int cpu_stat_show(struct seq_file *seq, void *v)
{
struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup;
int ret = 0;
cgroup_stat_show_cputime(seq);
#ifdef CONFIG_CGROUP_SCHED
ret = cgroup_extra_stat_show(seq, cgrp, cpu_cgrp_id);
#endif
return ret;
}
static int cgroup_file_open(struct kernfs_open_file *of)
{
struct cftype *cft = of->kn->priv;
if (cft->open)
return cft->open(of);
return 0;
}
static void cgroup_file_release(struct kernfs_open_file *of)
{
struct cftype *cft = of->kn->priv;
if (cft->release)
cft->release(of);
}
static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off)
{
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct cgroup *cgrp = of->kn->parent->priv;
struct cftype *cft = of->kn->priv;
struct cgroup_subsys_state *css;
int ret;
/*
* If namespaces are delegation boundaries, disallow writes to
* files in an non-init namespace root from inside the namespace
* except for the files explicitly marked delegatable -
* cgroup.procs and cgroup.subtree_control.
*/
if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) &&
!(cft->flags & CFTYPE_NS_DELEGATABLE) &&
ns != &init_cgroup_ns && ns->root_cset->dfl_cgrp == cgrp)
return -EPERM;
if (cft->write)
return cft->write(of, buf, nbytes, off);
/*
* kernfs guarantees that a file isn't deleted with operations in
* flight, which means that the matching css is and stays alive and
* doesn't need to be pinned. The RCU locking is not necessary
* either. It's just for the convenience of using cgroup_css().
*/
rcu_read_lock();
css = cgroup_css(cgrp, cft->ss);
rcu_read_unlock();
if (cft->write_u64) {
unsigned long long v;
ret = kstrtoull(buf, 0, &v);
if (!ret)
ret = cft->write_u64(css, cft, v);
} else if (cft->write_s64) {
long long v;
ret = kstrtoll(buf, 0, &v);
if (!ret)
ret = cft->write_s64(css, cft, v);
} else {
ret = -EINVAL;
}
return ret ?: nbytes;
}
static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
{
return seq_cft(seq)->seq_start(seq, ppos);
}
static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
{
return seq_cft(seq)->seq_next(seq, v, ppos);
}
static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
{
if (seq_cft(seq)->seq_stop)
seq_cft(seq)->seq_stop(seq, v);
}
static int cgroup_seqfile_show(struct seq_file *m, void *arg)
{
struct cftype *cft = seq_cft(m);
struct cgroup_subsys_state *css = seq_css(m);
if (cft->seq_show)
return cft->seq_show(m, arg);
if (cft->read_u64)
seq_printf(m, "%llu\n", cft->read_u64(css, cft));
else if (cft->read_s64)
seq_printf(m, "%lld\n", cft->read_s64(css, cft));
else
return -EINVAL;
return 0;
}
static struct kernfs_ops cgroup_kf_single_ops = {
.atomic_write_len = PAGE_SIZE,
.open = cgroup_file_open,
.release = cgroup_file_release,
.write = cgroup_file_write,
.seq_show = cgroup_seqfile_show,
};
static struct kernfs_ops cgroup_kf_ops = {
.atomic_write_len = PAGE_SIZE,
.open = cgroup_file_open,
.release = cgroup_file_release,
.write = cgroup_file_write,
.seq_start = cgroup_seqfile_start,
.seq_next = cgroup_seqfile_next,
.seq_stop = cgroup_seqfile_stop,
.seq_show = cgroup_seqfile_show,
};
/* set uid and gid of cgroup dirs and files to that of the creator */
static int cgroup_kn_set_ugid(struct kernfs_node *kn)
{
struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
.ia_uid = current_fsuid(),
.ia_gid = current_fsgid(), };
if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
return 0;
return kernfs_setattr(kn, &iattr);
}
static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
struct cftype *cft)
{
char name[CGROUP_FILE_NAME_MAX];
struct kernfs_node *kn;
struct lock_class_key *key = NULL;
int ret;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
key = &cft->lockdep_key;
#endif
kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
cgroup_file_mode(cft), 0, cft->kf_ops, cft,
NULL, key);
if (IS_ERR(kn))
return PTR_ERR(kn);
ret = cgroup_kn_set_ugid(kn);
if (ret) {
kernfs_remove(kn);
return ret;
}
if (cft->file_offset) {
struct cgroup_file *cfile = (void *)css + cft->file_offset;
spin_lock_irq(&cgroup_file_kn_lock);
cfile->kn = kn;
spin_unlock_irq(&cgroup_file_kn_lock);
}
return 0;
}
/**
* cgroup_addrm_files - add or remove files to a cgroup directory
* @css: the target css
* @cgrp: the target cgroup (usually css->cgroup)
* @cfts: array of cftypes to be added
* @is_add: whether to add or remove
*
* Depending on @is_add, add or remove files defined by @cfts on @cgrp.
* For removals, this function never fails.
*/
static int cgroup_addrm_files(struct cgroup_subsys_state *css,
struct cgroup *cgrp, struct cftype cfts[],
bool is_add)
{
struct cftype *cft, *cft_end = NULL;
int ret = 0;
lockdep_assert_held(&cgroup_mutex);
restart:
for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) {
/* does cft->flags tell us to skip this file on @cgrp? */
if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
continue;
if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
continue;
if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
continue;
if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
continue;
if (is_add) {
ret = cgroup_add_file(css, cgrp, cft);
if (ret) {
pr_warn("%s: failed to add %s, err=%d\n",
__func__, cft->name, ret);
cft_end = cft;
is_add = false;
goto restart;
}
} else {
cgroup_rm_file(cgrp, cft);
}
}
return ret;
}
static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
{
struct cgroup_subsys *ss = cfts[0].ss;
struct cgroup *root = &ss->root->cgrp;
struct cgroup_subsys_state *css;
int ret = 0;
lockdep_assert_held(&cgroup_mutex);
/* add/rm files for all cgroups created before */
css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
struct cgroup *cgrp = css->cgroup;
if (!(css->flags & CSS_VISIBLE))
continue;
ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
if (ret)
break;
}
if (is_add && !ret)
kernfs_activate(root->kn);
return ret;
}
static void cgroup_exit_cftypes(struct cftype *cfts)
{
struct cftype *cft;
for (cft = cfts; cft->name[0] != '\0'; cft++) {
/* free copy for custom atomic_write_len, see init_cftypes() */
if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
kfree(cft->kf_ops);
cft->kf_ops = NULL;
cft->ss = NULL;
/* revert flags set by cgroup core while adding @cfts */
cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
}
}
static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype *cft;
for (cft = cfts; cft->name[0] != '\0'; cft++) {
struct kernfs_ops *kf_ops;
WARN_ON(cft->ss || cft->kf_ops);
if (cft->seq_start)
kf_ops = &cgroup_kf_ops;
else
kf_ops = &cgroup_kf_single_ops;
/*
* Ugh... if @cft wants a custom max_write_len, we need to
* make a copy of kf_ops to set its atomic_write_len.
*/
if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
if (!kf_ops) {
cgroup_exit_cftypes(cfts);
return -ENOMEM;
}
kf_ops->atomic_write_len = cft->max_write_len;
}
cft->kf_ops = kf_ops;
cft->ss = ss;
}
return 0;
}
static int cgroup_rm_cftypes_locked(struct cftype *cfts)
{
lockdep_assert_held(&cgroup_mutex);
if (!cfts || !cfts[0].ss)
return -ENOENT;
list_del(&cfts->node);
cgroup_apply_cftypes(cfts, false);
cgroup_exit_cftypes(cfts);
return 0;
}
/**
* cgroup_rm_cftypes - remove an array of cftypes from a subsystem
* @cfts: zero-length name terminated array of cftypes
*
* Unregister @cfts. Files described by @cfts are removed from all
* existing cgroups and all future cgroups won't have them either. This
* function can be called anytime whether @cfts' subsys is attached or not.
*
* Returns 0 on successful unregistration, -ENOENT if @cfts is not
* registered.
*/
int cgroup_rm_cftypes(struct cftype *cfts)
{
int ret;
mutex_lock(&cgroup_mutex);
ret = cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
return ret;
}
/**
* cgroup_add_cftypes - add an array of cftypes to a subsystem
* @ss: target cgroup subsystem
* @cfts: zero-length name terminated array of cftypes
*
* Register @cfts to @ss. Files described by @cfts are created for all
* existing cgroups to which @ss is attached and all future cgroups will
* have them too. This function can be called anytime whether @ss is
* attached or not.
*
* Returns 0 on successful registration, -errno on failure. Note that this
* function currently returns 0 as long as @cfts registration is successful
* even if some file creation attempts on existing cgroups fail.
*/
static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
int ret;
if (!cgroup_ssid_enabled(ss->id))
return 0;
if (!cfts || cfts[0].name[0] == '\0')
return 0;
ret = cgroup_init_cftypes(ss, cfts);
if (ret)
return ret;
mutex_lock(&cgroup_mutex);
list_add_tail(&cfts->node, &ss->cfts);
ret = cgroup_apply_cftypes(cfts, true);
if (ret)
cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
return ret;
}
/**
* cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
* @ss: target cgroup subsystem
* @cfts: zero-length name terminated array of cftypes
*
* Similar to cgroup_add_cftypes() but the added files are only used for
* the default hierarchy.
*/
int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype *cft;
for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
cft->flags |= __CFTYPE_ONLY_ON_DFL;
return cgroup_add_cftypes(ss, cfts);
}
/**
* cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
* @ss: target cgroup subsystem
* @cfts: zero-length name terminated array of cftypes
*
* Similar to cgroup_add_cftypes() but the added files are only used for
* the legacy hierarchies.
*/
int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype *cft;
for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
cft->flags |= __CFTYPE_NOT_ON_DFL;
return cgroup_add_cftypes(ss, cfts);
}
/**
* cgroup_file_notify - generate a file modified event for a cgroup_file
* @cfile: target cgroup_file
*
* @cfile must have been obtained by setting cftype->file_offset.
*/
void cgroup_file_notify(struct cgroup_file *cfile)
{
unsigned long flags;
spin_lock_irqsave(&cgroup_file_kn_lock, flags);
if (cfile->kn)
kernfs_notify(cfile->kn);
spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
}
/**
* css_next_child - find the next child of a given css
* @pos: the current position (%NULL to initiate traversal)
* @parent: css whose children to walk
*
* This function returns the next child of @parent and should be called
* under either cgroup_mutex or RCU read lock. The only requirement is
* that @parent and @pos are accessible. The next sibling is guaranteed to
* be returned regardless of their states.
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*/
struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *parent)
{
struct cgroup_subsys_state *next;
cgroup_assert_mutex_or_rcu_locked();
/*
* @pos could already have been unlinked from the sibling list.
* Once a cgroup is removed, its ->sibling.next is no longer
* updated when its next sibling changes. CSS_RELEASED is set when
* @pos is taken off list, at which time its next pointer is valid,
* and, as releases are serialized, the one pointed to by the next
* pointer is guaranteed to not have started release yet. This
* implies that if we observe !CSS_RELEASED on @pos in this RCU
* critical section, the one pointed to by its next pointer is
* guaranteed to not have finished its RCU grace period even if we
* have dropped rcu_read_lock() inbetween iterations.
*
* If @pos has CSS_RELEASED set, its next pointer can't be
* dereferenced; however, as each css is given a monotonically
* increasing unique serial number and always appended to the
* sibling list, the next one can be found by walking the parent's
* children until the first css with higher serial number than
* @pos's. While this path can be slower, it happens iff iteration
* races against release and the race window is very small.
*/
if (!pos) {
next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
} else if (likely(!(pos->flags & CSS_RELEASED))) {
next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
} else {
list_for_each_entry_rcu(next, &parent->children, sibling)
if (next->serial_nr > pos->serial_nr)
break;
}
/*
* @next, if not pointing to the head, can be dereferenced and is
* the next sibling.
*/
if (&next->sibling != &parent->children)
return next;
return NULL;
}
/**
* css_next_descendant_pre - find the next descendant for pre-order walk
* @pos: the current position (%NULL to initiate traversal)
* @root: css whose descendants to walk
*
* To be used by css_for_each_descendant_pre(). Find the next descendant
* to visit for pre-order traversal of @root's descendants. @root is
* included in the iteration and the first node to be visited.
*
* While this function requires cgroup_mutex or RCU read locking, it
* doesn't require the whole traversal to be contained in a single critical
* section. This function will return the correct next descendant as long
* as both @pos and @root are accessible and @pos is a descendant of @root.
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*/
struct cgroup_subsys_state *
css_next_descendant_pre(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *root)
{
struct cgroup_subsys_state *next;
cgroup_assert_mutex_or_rcu_locked();
/* if first iteration, visit @root */
if (!pos)
return root;
/* visit the first child if exists */
next = css_next_child(NULL, pos);
if (next)
return next;
/* no child, visit my or the closest ancestor's next sibling */
while (pos != root) {
next = css_next_child(pos, pos->parent);
if (next)
return next;
pos = pos->parent;
}
return NULL;
}
/**
* css_rightmost_descendant - return the rightmost descendant of a css
* @pos: css of interest
*
* Return the rightmost descendant of @pos. If there's no descendant, @pos
* is returned. This can be used during pre-order traversal to skip
* subtree of @pos.
*
* While this function requires cgroup_mutex or RCU read locking, it
* doesn't require the whole traversal to be contained in a single critical
* section. This function will return the correct rightmost descendant as
* long as @pos is accessible.
*/
struct cgroup_subsys_state *
css_rightmost_descendant(struct cgroup_subsys_state *pos)
{
struct cgroup_subsys_state *last, *tmp;
cgroup_assert_mutex_or_rcu_locked();
do {
last = pos;
/* ->prev isn't RCU safe, walk ->next till the end */
pos = NULL;
css_for_each_child(tmp, last)
pos = tmp;
} while (pos);
return last;
}
static struct cgroup_subsys_state *
css_leftmost_descendant(struct cgroup_subsys_state *pos)
{
struct cgroup_subsys_state *last;
do {
last = pos;
pos = css_next_child(NULL, pos);
} while (pos);
return last;
}
/**
* css_next_descendant_post - find the next descendant for post-order walk
* @pos: the current position (%NULL to initiate traversal)
* @root: css whose descendants to walk
*
* To be used by css_for_each_descendant_post(). Find the next descendant
* to visit for post-order traversal of @root's descendants. @root is
* included in the iteration and the last node to be visited.
*
* While this function requires cgroup_mutex or RCU read locking, it
* doesn't require the whole traversal to be contained in a single critical
* section. This function will return the correct next descendant as long
* as both @pos and @cgroup are accessible and @pos is a descendant of
* @cgroup.
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*/
struct cgroup_subsys_state *
css_next_descendant_post(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *root)
{
struct cgroup_subsys_state *next;
cgroup_assert_mutex_or_rcu_locked();
/* if first iteration, visit leftmost descendant which may be @root */
if (!pos)
return css_leftmost_descendant(root);
/* if we visited @root, we're done */
if (pos == root)
return NULL;
/* if there's an unvisited sibling, visit its leftmost descendant */
next = css_next_child(pos, pos->parent);
if (next)
return css_leftmost_descendant(next);
/* no sibling left, visit parent */
return pos->parent;
}
/**
* css_has_online_children - does a css have online children
* @css: the target css
*
* Returns %true if @css has any online children; otherwise, %false. This
* function can be called from any context but the caller is responsible
* for synchronizing against on/offlining as necessary.
*/
bool css_has_online_children(struct cgroup_subsys_state *css)
{
struct cgroup_subsys_state *child;
bool ret = false;
rcu_read_lock();
css_for_each_child(child, css) {
if (child->flags & CSS_ONLINE) {
ret = true;
break;
}
}
rcu_read_unlock();
return ret;
}
static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it)
{
struct list_head *l;
struct cgrp_cset_link *link;
struct css_set *cset;
lockdep_assert_held(&css_set_lock);
/* find the next threaded cset */
if (it->tcset_pos) {
l = it->tcset_pos->next;
if (l != it->tcset_head) {
it->tcset_pos = l;
return container_of(l, struct css_set,
threaded_csets_node);
}
it->tcset_pos = NULL;
}
/* find the next cset */
l = it->cset_pos;
l = l->next;
if (l == it->cset_head) {
it->cset_pos = NULL;
return NULL;
}
if (it->ss) {
cset = container_of(l, struct css_set, e_cset_node[it->ss->id]);
} else {
link = list_entry(l, struct cgrp_cset_link, cset_link);
cset = link->cset;
}
it->cset_pos = l;
/* initialize threaded css_set walking */
if (it->flags & CSS_TASK_ITER_THREADED) {
if (it->cur_dcset)
put_css_set_locked(it->cur_dcset);
it->cur_dcset = cset;
get_css_set(cset);
it->tcset_head = &cset->threaded_csets;
it->tcset_pos = &cset->threaded_csets;
}
return cset;
}
/**
* css_task_iter_advance_css_set - advance a task itererator to the next css_set
* @it: the iterator to advance
*
* Advance @it to the next css_set to walk.
*/
static void css_task_iter_advance_css_set(struct css_task_iter *it)
{
struct css_set *cset;
lockdep_assert_held(&css_set_lock);
/* Advance to the next non-empty css_set */
do {
cset = css_task_iter_next_css_set(it);
if (!cset) {
it->task_pos = NULL;
return;
}
} while (!css_set_populated(cset));
if (!list_empty(&cset->tasks))
it->task_pos = cset->tasks.next;
else
it->task_pos = cset->mg_tasks.next;
it->tasks_head = &cset->tasks;
it->mg_tasks_head = &cset->mg_tasks;
/*
* We don't keep css_sets locked across iteration steps and thus
* need to take steps to ensure that iteration can be resumed after
* the lock is re-acquired. Iteration is performed at two levels -
* css_sets and tasks in them.
*
* Once created, a css_set never leaves its cgroup lists, so a
* pinned css_set is guaranteed to stay put and we can resume
* iteration afterwards.
*
* Tasks may leave @cset across iteration steps. This is resolved
* by registering each iterator with the css_set currently being
* walked and making css_set_move_task() advance iterators whose
* next task is leaving.
*/
if (it->cur_cset) {
list_del(&it->iters_node);
put_css_set_locked(it->cur_cset);
}
get_css_set(cset);
it->cur_cset = cset;
list_add(&it->iters_node, &cset->task_iters);
}
static void css_task_iter_advance(struct css_task_iter *it)
{
struct list_head *next;
lockdep_assert_held(&css_set_lock);
repeat:
/*
* Advance iterator to find next entry. cset->tasks is consumed
* first and then ->mg_tasks. After ->mg_tasks, we move onto the
* next cset.
*/
next = it->task_pos->next;
if (next == it->tasks_head)
next = it->mg_tasks_head->next;
if (next == it->mg_tasks_head)
css_task_iter_advance_css_set(it);
else
it->task_pos = next;
/* if PROCS, skip over tasks which aren't group leaders */
if ((it->flags & CSS_TASK_ITER_PROCS) && it->task_pos &&
!thread_group_leader(list_entry(it->task_pos, struct task_struct,
cg_list)))
goto repeat;
}
/**
* css_task_iter_start - initiate task iteration
* @css: the css to walk tasks of
* @flags: CSS_TASK_ITER_* flags
* @it: the task iterator to use
*
* Initiate iteration through the tasks of @css. The caller can call
* css_task_iter_next() to walk through the tasks until the function
* returns NULL. On completion of iteration, css_task_iter_end() must be
* called.
*/
void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
struct css_task_iter *it)
{
/* no one should try to iterate before mounting cgroups */
WARN_ON_ONCE(!use_task_css_set_links);
memset(it, 0, sizeof(*it));
spin_lock_irq(&css_set_lock);
it->ss = css->ss;
it->flags = flags;
if (it->ss)
it->cset_pos = &css->cgroup->e_csets[css->ss->id];
else
it->cset_pos = &css->cgroup->cset_links;
it->cset_head = it->cset_pos;
css_task_iter_advance_css_set(it);
spin_unlock_irq(&css_set_lock);
}
/**
* css_task_iter_next - return the next task for the iterator
* @it: the task iterator being iterated
*
* The "next" function for task iteration. @it should have been
* initialized via css_task_iter_start(). Returns NULL when the iteration
* reaches the end.
*/
struct task_struct *css_task_iter_next(struct css_task_iter *it)
{
if (it->cur_task) {
put_task_struct(it->cur_task);
it->cur_task = NULL;
}
spin_lock_irq(&css_set_lock);
if (it->task_pos) {
it->cur_task = list_entry(it->task_pos, struct task_struct,
cg_list);
get_task_struct(it->cur_task);
css_task_iter_advance(it);
}
spin_unlock_irq(&css_set_lock);
return it->cur_task;
}
/**
* css_task_iter_end - finish task iteration
* @it: the task iterator to finish
*
* Finish task iteration started by css_task_iter_start().
*/
void css_task_iter_end(struct css_task_iter *it)
{
if (it->cur_cset) {
spin_lock_irq(&css_set_lock);
list_del(&it->iters_node);
put_css_set_locked(it->cur_cset);
spin_unlock_irq(&css_set_lock);
}
if (it->cur_dcset)
put_css_set(it->cur_dcset);
if (it->cur_task)
put_task_struct(it->cur_task);
}
static void cgroup_procs_release(struct kernfs_open_file *of)
{
if (of->priv) {
css_task_iter_end(of->priv);
kfree(of->priv);
}
}
static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
{
struct kernfs_open_file *of = s->private;
struct css_task_iter *it = of->priv;
return css_task_iter_next(it);
}
static void *__cgroup_procs_start(struct seq_file *s, loff_t *pos,
unsigned int iter_flags)
{
struct kernfs_open_file *of = s->private;
struct cgroup *cgrp = seq_css(s)->cgroup;
struct css_task_iter *it = of->priv;
/*
* When a seq_file is seeked, it's always traversed sequentially
* from position 0, so we can simply keep iterating on !0 *pos.
*/
if (!it) {
if (WARN_ON_ONCE((*pos)++))
return ERR_PTR(-EINVAL);
it = kzalloc(sizeof(*it), GFP_KERNEL);
if (!it)
return ERR_PTR(-ENOMEM);
of->priv = it;
css_task_iter_start(&cgrp->self, iter_flags, it);
} else if (!(*pos)++) {
css_task_iter_end(it);
css_task_iter_start(&cgrp->self, iter_flags, it);
}
return cgroup_procs_next(s, NULL, NULL);
}
static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
{
struct cgroup *cgrp = seq_css(s)->cgroup;
/*
* All processes of a threaded subtree belong to the domain cgroup
* of the subtree. Only threads can be distributed across the
* subtree. Reject reads on cgroup.procs in the subtree proper.
* They're always empty anyway.
*/
if (cgroup_is_threaded(cgrp))
return ERR_PTR(-EOPNOTSUPP);
return __cgroup_procs_start(s, pos, CSS_TASK_ITER_PROCS |
CSS_TASK_ITER_THREADED);
}
static int cgroup_procs_show(struct seq_file *s, void *v)
{
seq_printf(s, "%d\n", task_pid_vnr(v));
return 0;
}
static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
struct cgroup *dst_cgrp,
struct super_block *sb)
{
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct cgroup *com_cgrp = src_cgrp;
struct inode *inode;
int ret;
lockdep_assert_held(&cgroup_mutex);
/* find the common ancestor */
while (!cgroup_is_descendant(dst_cgrp, com_cgrp))
com_cgrp = cgroup_parent(com_cgrp);
/* %current should be authorized to migrate to the common ancestor */
inode = kernfs_get_inode(sb, com_cgrp->procs_file.kn);
if (!inode)
return -ENOMEM;
ret = inode_permission(inode, MAY_WRITE);
iput(inode);
if (ret)
return ret;
/*
* If namespaces are delegation boundaries, %current must be able
* to see both source and destination cgroups from its namespace.
*/
if ((cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) &&
(!cgroup_is_descendant(src_cgrp, ns->root_cset->dfl_cgrp) ||
!cgroup_is_descendant(dst_cgrp, ns->root_cset->dfl_cgrp)))
return -ENOENT;
return 0;
}
static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct cgroup *src_cgrp, *dst_cgrp;
struct task_struct *task;
ssize_t ret;
dst_cgrp = cgroup_kn_lock_live(of->kn, false);
if (!dst_cgrp)
return -ENODEV;
task = cgroup_procs_write_start(buf, true);
ret = PTR_ERR_OR_ZERO(task);
if (ret)
goto out_unlock;
/* find the source cgroup */
spin_lock_irq(&css_set_lock);
src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
spin_unlock_irq(&css_set_lock);
ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp,
of->file->f_path.dentry->d_sb);
if (ret)
goto out_finish;
ret = cgroup_attach_task(dst_cgrp, task, true);
out_finish:
cgroup_procs_write_finish(task);
out_unlock:
cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
}
static void *cgroup_threads_start(struct seq_file *s, loff_t *pos)
{
return __cgroup_procs_start(s, pos, 0);
}
static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct cgroup *src_cgrp, *dst_cgrp;
struct task_struct *task;
ssize_t ret;
buf = strstrip(buf);
dst_cgrp = cgroup_kn_lock_live(of->kn, false);
if (!dst_cgrp)
return -ENODEV;
task = cgroup_procs_write_start(buf, false);
ret = PTR_ERR_OR_ZERO(task);
if (ret)
goto out_unlock;
/* find the source cgroup */
spin_lock_irq(&css_set_lock);
src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
spin_unlock_irq(&css_set_lock);
/* thread migrations follow the cgroup.procs delegation rule */
ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp,
of->file->f_path.dentry->d_sb);
if (ret)
goto out_finish;
/* and must be contained in the same domain */
ret = -EOPNOTSUPP;
if (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp)
goto out_finish;
ret = cgroup_attach_task(dst_cgrp, task, false);
out_finish:
cgroup_procs_write_finish(task);
out_unlock:
cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
}
/* cgroup core interface files for the default hierarchy */
static struct cftype cgroup_base_files[] = {
{
.name = "cgroup.type",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = cgroup_type_show,
.write = cgroup_type_write,
},
{
.name = "cgroup.procs",
.flags = CFTYPE_NS_DELEGATABLE,
.file_offset = offsetof(struct cgroup, procs_file),
.release = cgroup_procs_release,
.seq_start = cgroup_procs_start,
.seq_next = cgroup_procs_next,
.seq_show = cgroup_procs_show,
.write = cgroup_procs_write,
},
{
.name = "cgroup.threads",
.flags = CFTYPE_NS_DELEGATABLE,
.release = cgroup_procs_release,
.seq_start = cgroup_threads_start,
.seq_next = cgroup_procs_next,
.seq_show = cgroup_procs_show,
.write = cgroup_threads_write,
},
{
.name = "cgroup.controllers",
.seq_show = cgroup_controllers_show,
},
{
.name = "cgroup.subtree_control",
.flags = CFTYPE_NS_DELEGATABLE,
.seq_show = cgroup_subtree_control_show,
.write = cgroup_subtree_control_write,
},
{
.name = "cgroup.events",
.flags = CFTYPE_NOT_ON_ROOT,
.file_offset = offsetof(struct cgroup, events_file),
.seq_show = cgroup_events_show,
},
{
.name = "cgroup.max.descendants",
.seq_show = cgroup_max_descendants_show,
.write = cgroup_max_descendants_write,
},
{
.name = "cgroup.max.depth",
.seq_show = cgroup_max_depth_show,
.write = cgroup_max_depth_write,
},
{
.name = "cgroup.stat",
.seq_show = cgroup_stat_show,
},
{
.name = "cpu.stat",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = cpu_stat_show,
},
{ } /* terminate */
};
/*
* css destruction is four-stage process.
*
* 1. Destruction starts. Killing of the percpu_ref is initiated.
* Implemented in kill_css().
*
* 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
* and thus css_tryget_online() is guaranteed to fail, the css can be
* offlined by invoking offline_css(). After offlining, the base ref is
* put. Implemented in css_killed_work_fn().
*
* 3. When the percpu_ref reaches zero, the only possible remaining
* accessors are inside RCU read sections. css_release() schedules the
* RCU callback.
*
* 4. After the grace period, the css can be freed. Implemented in
* css_free_work_fn().
*
* It is actually hairier because both step 2 and 4 require process context
* and thus involve punting to css->destroy_work adding two additional
* steps to the already complex sequence.
*/
static void css_free_rwork_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css = container_of(to_rcu_work(work),
struct cgroup_subsys_state, destroy_rwork);
struct cgroup_subsys *ss = css->ss;
struct cgroup *cgrp = css->cgroup;
percpu_ref_exit(&css->refcnt);
if (ss) {
/* css free path */
struct cgroup_subsys_state *parent = css->parent;
int id = css->id;
ss->css_free(css);
cgroup_idr_remove(&ss->css_idr, id);
cgroup_put(cgrp);
if (parent)
css_put(parent);
} else {
/* cgroup free path */
atomic_dec(&cgrp->root->nr_cgrps);
cgroup1_pidlist_destroy_all(cgrp);
cancel_work_sync(&cgrp->release_agent_work);
if (cgroup_parent(cgrp)) {
/*
* We get a ref to the parent, and put the ref when
* this cgroup is being freed, so it's guaranteed
* that the parent won't be destroyed before its
* children.
*/
cgroup_put(cgroup_parent(cgrp));
kernfs_put(cgrp->kn);
if (cgroup_on_dfl(cgrp))
cgroup_stat_exit(cgrp);
kfree(cgrp);
} else {
/*
* This is root cgroup's refcnt reaching zero,
* which indicates that the root should be
* released.
*/
cgroup_destroy_root(cgrp->root);
}
}
}
static void css_release_work_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);
struct cgroup_subsys *ss = css->ss;
struct cgroup *cgrp = css->cgroup;
mutex_lock(&cgroup_mutex);
css->flags |= CSS_RELEASED;
list_del_rcu(&css->sibling);
if (ss) {
/* css release path */
cgroup_idr_replace(&ss->css_idr, NULL, css->id);
if (ss->css_released)
ss->css_released(css);
} else {
struct cgroup *tcgrp;
/* cgroup release path */
trace_cgroup_release(cgrp);
if (cgroup_on_dfl(cgrp))
cgroup_stat_flush(cgrp);
for (tcgrp = cgroup_parent(cgrp); tcgrp;
tcgrp = cgroup_parent(tcgrp))
tcgrp->nr_dying_descendants--;
cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
cgrp->id = -1;
/*
* There are two control paths which try to determine
* cgroup from dentry without going through kernfs -
* cgroupstats_build() and css_tryget_online_from_dir().
* Those are supported by RCU protecting clearing of
* cgrp->kn->priv backpointer.
*/
if (cgrp->kn)
RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
NULL);
cgroup_bpf_put(cgrp);
}
mutex_unlock(&cgroup_mutex);
INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
}
static void css_release(struct percpu_ref *ref)
{
struct cgroup_subsys_state *css =
container_of(ref, struct cgroup_subsys_state, refcnt);
INIT_WORK(&css->destroy_work, css_release_work_fn);
queue_work(cgroup_destroy_wq, &css->destroy_work);
}
static void init_and_link_css(struct cgroup_subsys_state *css,
struct cgroup_subsys *ss, struct cgroup *cgrp)
{
lockdep_assert_held(&cgroup_mutex);
cgroup_get_live(cgrp);
memset(css, 0, sizeof(*css));
css->cgroup = cgrp;
css->ss = ss;
css->id = -1;
INIT_LIST_HEAD(&css->sibling);
INIT_LIST_HEAD(&css->children);
css->serial_nr = css_serial_nr_next++;
atomic_set(&css->online_cnt, 0);
if (cgroup_parent(cgrp)) {
css->parent = cgroup_css(cgroup_parent(cgrp), ss);
css_get(css->parent);
}
BUG_ON(cgroup_css(cgrp, ss));
}
/* invoke ->css_online() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys_state *css)
{
struct cgroup_subsys *ss = css->ss;
int ret = 0;
lockdep_assert_held(&cgroup_mutex);
if (ss->css_online)
ret = ss->css_online(css);
if (!ret) {
css->flags |= CSS_ONLINE;
rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
atomic_inc(&css->online_cnt);
if (css->parent)
atomic_inc(&css->parent->online_cnt);
}
return ret;
}
/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
static void offline_css(struct cgroup_subsys_state *css)
{
struct cgroup_subsys *ss = css->ss;
lockdep_assert_held(&cgroup_mutex);
if (!(css->flags & CSS_ONLINE))
return;
if (ss->css_offline)
ss->css_offline(css);
css->flags &= ~CSS_ONLINE;
RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
wake_up_all(&css->cgroup->offline_waitq);
}
/**
* css_create - create a cgroup_subsys_state
* @cgrp: the cgroup new css will be associated with
* @ss: the subsys of new css
*
* Create a new css associated with @cgrp - @ss pair. On success, the new
* css is online and installed in @cgrp. This function doesn't create the
* interface files. Returns 0 on success, -errno on failure.
*/
static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
struct cgroup *parent = cgroup_parent(cgrp);
struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
struct cgroup_subsys_state *css;
int err;
lockdep_assert_held(&cgroup_mutex);
css = ss->css_alloc(parent_css);
if (!css)
css = ERR_PTR(-ENOMEM);
if (IS_ERR(css))
return css;
init_and_link_css(css, ss, cgrp);
err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
if (err)
goto err_free_css;
err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
if (err < 0)
goto err_free_css;
css->id = err;
/* @css is ready to be brought online now, make it visible */
list_add_tail_rcu(&css->sibling, &parent_css->children);
cgroup_idr_replace(&ss->css_idr, css, css->id);
err = online_css(css);
if (err)
goto err_list_del;
if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
cgroup_parent(parent)) {
pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
current->comm, current->pid, ss->name);
if (!strcmp(ss->name, "memory"))
pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
ss->warned_broken_hierarchy = true;
}
return css;
err_list_del:
list_del_rcu(&css->sibling);
err_free_css:
INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
return ERR_PTR(err);
}
/*
* The returned cgroup is fully initialized including its control mask, but
* it isn't associated with its kernfs_node and doesn't have the control
* mask applied.
*/
static struct cgroup *cgroup_create(struct cgroup *parent)
{
struct cgroup_root *root = parent->root;
struct cgroup *cgrp, *tcgrp;
int level = parent->level + 1;
int ret;
/* allocate the cgroup and its ID, 0 is reserved for the root */
cgrp = kzalloc(sizeof(*cgrp) +
sizeof(cgrp->ancestor_ids[0]) * (level + 1), GFP_KERNEL);
if (!cgrp)
return ERR_PTR(-ENOMEM);
ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
if (ret)
goto out_free_cgrp;
if (cgroup_on_dfl(parent)) {
ret = cgroup_stat_init(cgrp);
if (ret)
goto out_cancel_ref;
}
/*
* Temporarily set the pointer to NULL, so idr_find() won't return
* a half-baked cgroup.
*/
cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_KERNEL);
if (cgrp->id < 0) {
ret = -ENOMEM;
goto out_stat_exit;
}
init_cgroup_housekeeping(cgrp);
cgrp->self.parent = &parent->self;
cgrp->root = root;
cgrp->level = level;
ret = cgroup_bpf_inherit(cgrp);
if (ret)
goto out_idr_free;
for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
if (tcgrp != cgrp)
tcgrp->nr_descendants++;
}
if (notify_on_release(parent))
set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
cgrp->self.serial_nr = css_serial_nr_next++;
/* allocation complete, commit to creation */
list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
atomic_inc(&root->nr_cgrps);
cgroup_get_live(parent);
/*
* @cgrp is now fully operational. If something fails after this
* point, it'll be released via the normal destruction path.
*/
cgroup_idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
/*
* On the default hierarchy, a child doesn't automatically inherit
* subtree_control from the parent. Each is configured manually.
*/
if (!cgroup_on_dfl(cgrp))
cgrp->subtree_control = cgroup_control(cgrp);
cgroup_propagate_control(cgrp);
return cgrp;
out_idr_free:
cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
out_stat_exit:
if (cgroup_on_dfl(parent))
cgroup_stat_exit(cgrp);
out_cancel_ref:
percpu_ref_exit(&cgrp->self.refcnt);
out_free_cgrp:
kfree(cgrp);
return ERR_PTR(ret);
}
static bool cgroup_check_hierarchy_limits(struct cgroup *parent)
{
struct cgroup *cgroup;
int ret = false;
int level = 1;
lockdep_assert_held(&cgroup_mutex);
for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) {
if (cgroup->nr_descendants >= cgroup->max_descendants)
goto fail;
if (level > cgroup->max_depth)
goto fail;
level++;
}
ret = true;
fail:
return ret;
}
int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
{
struct cgroup *parent, *cgrp;
struct kernfs_node *kn;
int ret;
/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
if (strchr(name, '\n'))
return -EINVAL;
parent = cgroup_kn_lock_live(parent_kn, false);
if (!parent)
return -ENODEV;
if (!cgroup_check_hierarchy_limits(parent)) {
ret = -EAGAIN;
goto out_unlock;
}
cgrp = cgroup_create(parent);
if (IS_ERR(cgrp)) {
ret = PTR_ERR(cgrp);
goto out_unlock;
}
/* create the directory */
kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
if (IS_ERR(kn)) {
ret = PTR_ERR(kn);
goto out_destroy;
}
cgrp->kn = kn;
/*
* This extra ref will be put in cgroup_free_fn() and guarantees
* that @cgrp->kn is always accessible.
*/
kernfs_get(kn);
ret = cgroup_kn_set_ugid(kn);
if (ret)
goto out_destroy;
ret = css_populate_dir(&cgrp->self);
if (ret)
goto out_destroy;
ret = cgroup_apply_control_enable(cgrp);
if (ret)
goto out_destroy;
trace_cgroup_mkdir(cgrp);
/* let's create and online css's */
kernfs_activate(kn);
ret = 0;
goto out_unlock;
out_destroy:
cgroup_destroy_locked(cgrp);
out_unlock:
cgroup_kn_unlock(parent_kn);
return ret;
}
/*
* This is called when the refcnt of a css is confirmed to be killed.
* css_tryget_online() is now guaranteed to fail. Tell the subsystem to
* initate destruction and put the css ref from kill_css().
*/
static void css_killed_work_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);
mutex_lock(&cgroup_mutex);
do {
offline_css(css);
css_put(css);
/* @css can't go away while we're holding cgroup_mutex */
css = css->parent;
} while (css && atomic_dec_and_test(&css->online_cnt));
mutex_unlock(&cgroup_mutex);
}
/* css kill confirmation processing requires process context, bounce */
static void css_killed_ref_fn(struct percpu_ref *ref)
{
struct cgroup_subsys_state *css =
container_of(ref, struct cgroup_subsys_state, refcnt);
if (atomic_dec_and_test(&css->online_cnt)) {
INIT_WORK(&css->destroy_work, css_killed_work_fn);
queue_work(cgroup_destroy_wq, &css->destroy_work);
}
}
/**
* kill_css - destroy a css
* @css: css to destroy
*
* This function initiates destruction of @css by removing cgroup interface
* files and putting its base reference. ->css_offline() will be invoked
* asynchronously once css_tryget_online() is guaranteed to fail and when
* the reference count reaches zero, @css will be released.
*/
static void kill_css(struct cgroup_subsys_state *css)
{
lockdep_assert_held(&cgroup_mutex);
if (css->flags & CSS_DYING)
return;
css->flags |= CSS_DYING;
/*
* This must happen before css is disassociated with its cgroup.
* See seq_css() for details.
*/
css_clear_dir(css);
/*
* Killing would put the base ref, but we need to keep it alive
* until after ->css_offline().
*/
css_get(css);
/*
* cgroup core guarantees that, by the time ->css_offline() is
* invoked, no new css reference will be given out via
* css_tryget_online(). We can't simply call percpu_ref_kill() and
* proceed to offlining css's because percpu_ref_kill() doesn't
* guarantee that the ref is seen as killed on all CPUs on return.
*
* Use percpu_ref_kill_and_confirm() to get notifications as each
* css is confirmed to be seen as killed on all CPUs.
*/
percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
}
/**
* cgroup_destroy_locked - the first stage of cgroup destruction
* @cgrp: cgroup to be destroyed
*
* css's make use of percpu refcnts whose killing latency shouldn't be
* exposed to userland and are RCU protected. Also, cgroup core needs to
* guarantee that css_tryget_online() won't succeed by the time
* ->css_offline() is invoked. To satisfy all the requirements,
* destruction is implemented in the following two steps.
*
* s1. Verify @cgrp can be destroyed and mark it dying. Remove all
* userland visible parts and start killing the percpu refcnts of
* css's. Set up so that the next stage will be kicked off once all
* the percpu refcnts are confirmed to be killed.
*
* s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
* rest of destruction. Once all cgroup references are gone, the
* cgroup is RCU-freed.
*
* This function implements s1. After this step, @cgrp is gone as far as
* the userland is concerned and a new cgroup with the same name may be
* created. As cgroup doesn't care about the names internally, this
* doesn't cause any problem.
*/
static int cgroup_destroy_locked(struct cgroup *cgrp)
__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
struct cgroup_subsys_state *css;
struct cgrp_cset_link *link;
int ssid;
lockdep_assert_held(&cgroup_mutex);
/*
* Only migration can raise populated from zero and we're already
* holding cgroup_mutex.
*/
if (cgroup_is_populated(cgrp))
return -EBUSY;
/*
* Make sure there's no live children. We can't test emptiness of
* ->self.children as dead children linger on it while being
* drained; otherwise, "rmdir parent/child parent" may fail.
*/
if (css_has_online_children(&cgrp->self))
return -EBUSY;
/*
* Mark @cgrp and the associated csets dead. The former prevents
* further task migration and child creation by disabling
* cgroup_lock_live_group(). The latter makes the csets ignored by
* the migration path.
*/
cgrp->self.flags &= ~CSS_ONLINE;
spin_lock_irq(&css_set_lock);
list_for_each_entry(link, &cgrp->cset_links, cset_link)
link->cset->dead = true;
spin_unlock_irq(&css_set_lock);
/* initiate massacre of all css's */
for_each_css(css, ssid, cgrp)
kill_css(css);
/* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */
css_clear_dir(&cgrp->self);
kernfs_remove(cgrp->kn);
if (parent && cgroup_is_threaded(cgrp))
parent->nr_threaded_children--;
for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) {
tcgrp->nr_descendants--;
tcgrp->nr_dying_descendants++;
}
cgroup1_check_for_release(parent);
/* put the base reference */
percpu_ref_kill(&cgrp->self.refcnt);
return 0;
};
int cgroup_rmdir(struct kernfs_node *kn)
{
struct cgroup *cgrp;
int ret = 0;
cgrp = cgroup_kn_lock_live(kn, false);
if (!cgrp)
return 0;
ret = cgroup_destroy_locked(cgrp);
if (!ret)
trace_cgroup_rmdir(cgrp);
cgroup_kn_unlock(kn);
return ret;
}
static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
.show_options = cgroup_show_options,
.remount_fs = cgroup_remount,
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.show_path = cgroup_show_path,
};
static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
{
struct cgroup_subsys_state *css;
pr_debug("Initializing cgroup subsys %s\n", ss->name);
mutex_lock(&cgroup_mutex);
idr_init(&ss->css_idr);
INIT_LIST_HEAD(&ss->cfts);
/* Create the root cgroup state for this subsystem */
ss->root = &cgrp_dfl_root;
css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
/* We don't handle early failures gracefully */
BUG_ON(IS_ERR(css));
init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
/*
* Root csses are never destroyed and we can't initialize
* percpu_ref during early init. Disable refcnting.
*/
css->flags |= CSS_NO_REF;
if (early) {
/* allocation can't be done safely during early init */
css->id = 1;
} else {
css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
BUG_ON(css->id < 0);
}
/* Update the init_css_set to contain a subsys
* pointer to this state - since the subsystem is
* newly registered, all tasks and hence the
* init_css_set is in the subsystem's root cgroup. */
init_css_set.subsys[ss->id] = css;
have_fork_callback |= (bool)ss->fork << ss->id;
have_exit_callback |= (bool)ss->exit << ss->id;
have_free_callback |= (bool)ss->free << ss->id;
have_canfork_callback |= (bool)ss->can_fork << ss->id;
/* At system boot, before all subsystems have been
* registered, no tasks have been forked, so we don't
* need to invoke fork callbacks here. */
BUG_ON(!list_empty(&init_task.tasks));
BUG_ON(online_css(css));
mutex_unlock(&cgroup_mutex);
}
/**
* cgroup_init_early - cgroup initialization at system boot
*
* Initialize cgroups at system boot, and initialize any
* subsystems that request early init.
*/
int __init cgroup_init_early(void)
{
static struct cgroup_sb_opts __initdata opts;
struct cgroup_subsys *ss;
int i;
init_cgroup_root(&cgrp_dfl_root, &opts);
cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
for_each_subsys(ss, i) {
WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
"invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
ss->id, ss->name);
WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
"cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
ss->id = i;
ss->name = cgroup_subsys_name[i];
if (!ss->legacy_name)
ss->legacy_name = cgroup_subsys_name[i];
if (ss->early_init)
cgroup_init_subsys(ss, true);
}
return 0;
}
static u16 cgroup_disable_mask __initdata;
/**
* cgroup_init - cgroup initialization
*
* Register cgroup filesystem and /proc file, and initialize
* any subsystems that didn't request early init.
*/
int __init cgroup_init(void)
{
struct cgroup_subsys *ss;
int ssid;
BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem));
BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
cgroup_stat_boot();
/*
* The latency of the synchronize_sched() is too high for cgroups,
* avoid it at the cost of forcing all readers into the slow path.
*/
rcu_sync_enter_start(&cgroup_threadgroup_rwsem.rss);
get_user_ns(init_cgroup_ns.user_ns);
mutex_lock(&cgroup_mutex);
/*
* Add init_css_set to the hash table so that dfl_root can link to
* it during init.
*/
hash_add(css_set_table, &init_css_set.hlist,
css_set_hash(init_css_set.subsys));
BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0, 0));
mutex_unlock(&cgroup_mutex);
for_each_subsys(ss, ssid) {
if (ss->early_init) {
struct cgroup_subsys_state *css =
init_css_set.subsys[ss->id];
css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
GFP_KERNEL);
BUG_ON(css->id < 0);
} else {
cgroup_init_subsys(ss, false);
}
list_add_tail(&init_css_set.e_cset_node[ssid],
&cgrp_dfl_root.cgrp.e_csets[ssid]);
/*
* Setting dfl_root subsys_mask needs to consider the
* disabled flag and cftype registration needs kmalloc,
* both of which aren't available during early_init.
*/
if (cgroup_disable_mask & (1 << ssid)) {
static_branch_disable(cgroup_subsys_enabled_key[ssid]);
printk(KERN_INFO "Disabling %s control group subsystem\n",
ss->name);
continue;
}
if (cgroup1_ssid_disabled(ssid))
printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n",
ss->name);
cgrp_dfl_root.subsys_mask |= 1 << ss->id;
/* implicit controllers must be threaded too */
WARN_ON(ss->implicit_on_dfl && !ss->threaded);
if (ss->implicit_on_dfl)
cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
else if (!ss->dfl_cftypes)
cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
if (ss->threaded)
cgrp_dfl_threaded_ss_mask |= 1 << ss->id;
if (ss->dfl_cftypes == ss->legacy_cftypes) {
WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
} else {
WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
}
if (ss->bind)
ss->bind(init_css_set.subsys[ssid]);
mutex_lock(&cgroup_mutex);
css_populate_dir(init_css_set.subsys[ssid]);
mutex_unlock(&cgroup_mutex);
}
/* init_css_set.subsys[] has been updated, re-hash */
hash_del(&init_css_set.hlist);
hash_add(css_set_table, &init_css_set.hlist,
css_set_hash(init_css_set.subsys));
WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
WARN_ON(register_filesystem(&cgroup_fs_type));
WARN_ON(register_filesystem(&cgroup2_fs_type));
WARN_ON(!proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations));
return 0;
}
static int __init cgroup_wq_init(void)
{
/*
* There isn't much point in executing destruction path in
* parallel. Good chunk is serialized with cgroup_mutex anyway.
* Use 1 for @max_active.
*
* We would prefer to do this in cgroup_init() above, but that
* is called before init_workqueues(): so leave this until after.
*/
cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
BUG_ON(!cgroup_destroy_wq);
return 0;
}
core_initcall(cgroup_wq_init);
void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
char *buf, size_t buflen)
{
struct kernfs_node *kn;
kn = kernfs_get_node_by_id(cgrp_dfl_root.kf_root, id);
if (!kn)
return;
kernfs_path(kn, buf, buflen);
kernfs_put(kn);
}
/*
* proc_cgroup_show()
* - Print task's cgroup paths into seq_file, one line for each hierarchy
* - Used for /proc/<pid>/cgroup.
*/
int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *tsk)
{
char *buf;
int retval;
struct cgroup_root *root;
retval = -ENOMEM;
buf = kmalloc(PATH_MAX, GFP_KERNEL);
if (!buf)
goto out;
mutex_lock(&cgroup_mutex);
spin_lock_irq(&css_set_lock);
for_each_root(root) {
struct cgroup_subsys *ss;
struct cgroup *cgrp;
int ssid, count = 0;
if (root == &cgrp_dfl_root && !cgrp_dfl_visible)
continue;
seq_printf(m, "%d:", root->hierarchy_id);
if (root != &cgrp_dfl_root)
for_each_subsys(ss, ssid)
if (root->subsys_mask & (1 << ssid))
seq_printf(m, "%s%s", count++ ? "," : "",
ss->legacy_name);
if (strlen(root->name))
seq_printf(m, "%sname=%s", count ? "," : "",
root->name);
seq_putc(m, ':');
cgrp = task_cgroup_from_root(tsk, root);
/*
* On traditional hierarchies, all zombie tasks show up as
* belonging to the root cgroup. On the default hierarchy,
* while a zombie doesn't show up in "cgroup.procs" and
* thus can't be migrated, its /proc/PID/cgroup keeps
* reporting the cgroup it belonged to before exiting. If
* the cgroup is removed before the zombie is reaped,
* " (deleted)" is appended to the cgroup path.
*/
if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
current->nsproxy->cgroup_ns);
if (retval >= PATH_MAX)
retval = -ENAMETOOLONG;
if (retval < 0)
goto out_unlock;
seq_puts(m, buf);
} else {
seq_puts(m, "/");
}
if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
seq_puts(m, " (deleted)\n");
else
seq_putc(m, '\n');
}
retval = 0;
out_unlock:
spin_unlock_irq(&css_set_lock);
mutex_unlock(&cgroup_mutex);
kfree(buf);
out:
return retval;
}
/**
* cgroup_fork - initialize cgroup related fields during copy_process()
* @child: pointer to task_struct of forking parent process.
*
* A task is associated with the init_css_set until cgroup_post_fork()
* attaches it to the parent's css_set. Empty cg_list indicates that
* @child isn't holding reference to its css_set.
*/
void cgroup_fork(struct task_struct *child)
{
RCU_INIT_POINTER(child->cgroups, &init_css_set);
INIT_LIST_HEAD(&child->cg_list);
}
/**
* cgroup_can_fork - called on a new task before the process is exposed
* @child: the task in question.
*
* This calls the subsystem can_fork() callbacks. If the can_fork() callback
* returns an error, the fork aborts with that error code. This allows for
* a cgroup subsystem to conditionally allow or deny new forks.
*/
int cgroup_can_fork(struct task_struct *child)
{
struct cgroup_subsys *ss;
int i, j, ret;
do_each_subsys_mask(ss, i, have_canfork_callback) {
ret = ss->can_fork(child);
if (ret)
goto out_revert;
} while_each_subsys_mask();
return 0;
out_revert:
for_each_subsys(ss, j) {
if (j >= i)
break;
if (ss->cancel_fork)
ss->cancel_fork(child);
}
return ret;
}
/**
* cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
* @child: the task in question
*
* This calls the cancel_fork() callbacks if a fork failed *after*
* cgroup_can_fork() succeded.
*/
void cgroup_cancel_fork(struct task_struct *child)
{
struct cgroup_subsys *ss;
int i;
for_each_subsys(ss, i)
if (ss->cancel_fork)
ss->cancel_fork(child);
}
/**
* cgroup_post_fork - called on a new task after adding it to the task list
* @child: the task in question
*
* Adds the task to the list running through its css_set if necessary and
* call the subsystem fork() callbacks. Has to be after the task is
* visible on the task list in case we race with the first call to
* cgroup_task_iter_start() - to guarantee that the new task ends up on its
* list.
*/
void cgroup_post_fork(struct task_struct *child)
{
struct cgroup_subsys *ss;
int i;
/*
* This may race against cgroup_enable_task_cg_lists(). As that
* function sets use_task_css_set_links before grabbing
* tasklist_lock and we just went through tasklist_lock to add
* @child, it's guaranteed that either we see the set
* use_task_css_set_links or cgroup_enable_task_cg_lists() sees
* @child during its iteration.
*
* If we won the race, @child is associated with %current's
* css_set. Grabbing css_set_lock guarantees both that the
* association is stable, and, on completion of the parent's
* migration, @child is visible in the source of migration or
* already in the destination cgroup. This guarantee is necessary
* when implementing operations which need to migrate all tasks of
* a cgroup to another.
*
* Note that if we lose to cgroup_enable_task_cg_lists(), @child
* will remain in init_css_set. This is safe because all tasks are
* in the init_css_set before cg_links is enabled and there's no
* operation which transfers all tasks out of init_css_set.
*/
if (use_task_css_set_links) {
struct css_set *cset;
spin_lock_irq(&css_set_lock);
cset = task_css_set(current);
if (list_empty(&child->cg_list)) {
get_css_set(cset);
cset->nr_tasks++;
css_set_move_task(child, NULL, cset, false);
}
spin_unlock_irq(&css_set_lock);
}
/*
* Call ss->fork(). This must happen after @child is linked on
* css_set; otherwise, @child might change state between ->fork()
* and addition to css_set.
*/
do_each_subsys_mask(ss, i, have_fork_callback) {
ss->fork(child);
} while_each_subsys_mask();
}
/**
* cgroup_exit - detach cgroup from exiting task
* @tsk: pointer to task_struct of exiting process
*
* Description: Detach cgroup from @tsk and release it.
*
* Note that cgroups marked notify_on_release force every task in
* them to take the global cgroup_mutex mutex when exiting.
* This could impact scaling on very large systems. Be reluctant to
* use notify_on_release cgroups where very high task exit scaling
* is required on large systems.
*
* We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
* call cgroup_exit() while the task is still competent to handle
* notify_on_release(), then leave the task attached to the root cgroup in
* each hierarchy for the remainder of its exit. No need to bother with
* init_css_set refcnting. init_css_set never goes away and we can't race
* with migration path - PF_EXITING is visible to migration path.
*/
void cgroup_exit(struct task_struct *tsk)
{
struct cgroup_subsys *ss;
struct css_set *cset;
int i;
/*
* Unlink from @tsk from its css_set. As migration path can't race
* with us, we can check css_set and cg_list without synchronization.
*/
cset = task_css_set(tsk);
if (!list_empty(&tsk->cg_list)) {
spin_lock_irq(&css_set_lock);
css_set_move_task(tsk, cset, NULL, false);
cset->nr_tasks--;
spin_unlock_irq(&css_set_lock);
} else {
get_css_set(cset);
}
/* see cgroup_post_fork() for details */
do_each_subsys_mask(ss, i, have_exit_callback) {
ss->exit(tsk);
} while_each_subsys_mask();
}
void cgroup_free(struct task_struct *task)
{
struct css_set *cset = task_css_set(task);
struct cgroup_subsys *ss;
int ssid;
do_each_subsys_mask(ss, ssid, have_free_callback) {
ss->free(task);
} while_each_subsys_mask();
put_css_set(cset);
}
static int __init cgroup_disable(char *str)
{
struct cgroup_subsys *ss;
char *token;
int i;
while ((token = strsep(&str, ",")) != NULL) {
if (!*token)
continue;
for_each_subsys(ss, i) {
if (strcmp(token, ss->name) &&
strcmp(token, ss->legacy_name))
continue;
cgroup_disable_mask |= 1 << i;
}
}
return 1;
}
__setup("cgroup_disable=", cgroup_disable);
/**
* css_tryget_online_from_dir - get corresponding css from a cgroup dentry
* @dentry: directory dentry of interest
* @ss: subsystem of interest
*
* If @dentry is a directory for a cgroup which has @ss enabled on it, try
* to get the corresponding css and return it. If such css doesn't exist
* or can't be pinned, an ERR_PTR value is returned.
*/
struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
struct cgroup_subsys *ss)
{
struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
struct file_system_type *s_type = dentry->d_sb->s_type;
struct cgroup_subsys_state *css = NULL;
struct cgroup *cgrp;
/* is @dentry a cgroup dir? */
if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
!kn || kernfs_type(kn) != KERNFS_DIR)
return ERR_PTR(-EBADF);
rcu_read_lock();
/*
* This path doesn't originate from kernfs and @kn could already
* have been or be removed at any point. @kn->priv is RCU
* protected for this access. See css_release_work_fn() for details.
*/
cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
if (cgrp)
css = cgroup_css(cgrp, ss);
if (!css || !css_tryget_online(css))
css = ERR_PTR(-ENOENT);
rcu_read_unlock();
return css;
}
/**
* css_from_id - lookup css by id
* @id: the cgroup id
* @ss: cgroup subsys to be looked into
*
* Returns the css if there's valid one with @id, otherwise returns NULL.
* Should be called under rcu_read_lock().
*/
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
{
WARN_ON_ONCE(!rcu_read_lock_held());
return idr_find(&ss->css_idr, id);
}
/**
* cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
* @path: path on the default hierarchy
*
* Find the cgroup at @path on the default hierarchy, increment its
* reference count and return it. Returns pointer to the found cgroup on
* success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
* if @path points to a non-directory.
*/
struct cgroup *cgroup_get_from_path(const char *path)
{
struct kernfs_node *kn;
struct cgroup *cgrp;
mutex_lock(&cgroup_mutex);
kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
if (kn) {
if (kernfs_type(kn) == KERNFS_DIR) {
cgrp = kn->priv;
cgroup_get_live(cgrp);
} else {
cgrp = ERR_PTR(-ENOTDIR);
}
kernfs_put(kn);
} else {
cgrp = ERR_PTR(-ENOENT);
}
mutex_unlock(&cgroup_mutex);
return cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_get_from_path);
/**
* cgroup_get_from_fd - get a cgroup pointer from a fd
* @fd: fd obtained by open(cgroup2_dir)
*
* Find the cgroup from a fd which should be obtained
* by opening a cgroup directory. Returns a pointer to the
* cgroup on success. ERR_PTR is returned if the cgroup
* cannot be found.
*/
struct cgroup *cgroup_get_from_fd(int fd)
{
struct cgroup_subsys_state *css;
struct cgroup *cgrp;
struct file *f;
f = fget_raw(fd);
if (!f)
return ERR_PTR(-EBADF);
css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
fput(f);
if (IS_ERR(css))
return ERR_CAST(css);
cgrp = css->cgroup;
if (!cgroup_on_dfl(cgrp)) {
cgroup_put(cgrp);
return ERR_PTR(-EBADF);
}
return cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
/*
* sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
* definition in cgroup-defs.h.
*/
#ifdef CONFIG_SOCK_CGROUP_DATA
#if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
DEFINE_SPINLOCK(cgroup_sk_update_lock);
static bool cgroup_sk_alloc_disabled __read_mostly;
void cgroup_sk_alloc_disable(void)
{
if (cgroup_sk_alloc_disabled)
return;
pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n");
cgroup_sk_alloc_disabled = true;
}
#else
#define cgroup_sk_alloc_disabled false
#endif
void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
{
if (cgroup_sk_alloc_disabled)
return;
/* Socket clone path */
if (skcd->val) {
/*
* We might be cloning a socket which is left in an empty
* cgroup and the cgroup might have already been rmdir'd.
* Don't use cgroup_get_live().
*/
cgroup_get(sock_cgroup_ptr(skcd));
return;
}
rcu_read_lock();
while (true) {
struct css_set *cset;
cset = task_css_set(current);
if (likely(cgroup_tryget(cset->dfl_cgrp))) {
skcd->val = (unsigned long)cset->dfl_cgrp;
break;
}
cpu_relax();
}
rcu_read_unlock();
}
void cgroup_sk_free(struct sock_cgroup_data *skcd)
{
cgroup_put(sock_cgroup_ptr(skcd));
}
#endif /* CONFIG_SOCK_CGROUP_DATA */
#ifdef CONFIG_CGROUP_BPF
int cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
enum bpf_attach_type type, u32 flags)
{
int ret;
mutex_lock(&cgroup_mutex);
ret = __cgroup_bpf_attach(cgrp, prog, type, flags);
mutex_unlock(&cgroup_mutex);
return ret;
}
int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
enum bpf_attach_type type, u32 flags)
{
int ret;
mutex_lock(&cgroup_mutex);
ret = __cgroup_bpf_detach(cgrp, prog, type, flags);
mutex_unlock(&cgroup_mutex);
return ret;
}
int cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
union bpf_attr __user *uattr)
{
int ret;
mutex_lock(&cgroup_mutex);
ret = __cgroup_bpf_query(cgrp, attr, uattr);
mutex_unlock(&cgroup_mutex);
return ret;
}
#endif /* CONFIG_CGROUP_BPF */
#ifdef CONFIG_SYSFS
static ssize_t show_delegatable_files(struct cftype *files, char *buf,
ssize_t size, const char *prefix)
{
struct cftype *cft;
ssize_t ret = 0;
for (cft = files; cft && cft->name[0] != '\0'; cft++) {
if (!(cft->flags & CFTYPE_NS_DELEGATABLE))
continue;
if (prefix)
ret += snprintf(buf + ret, size - ret, "%s.", prefix);
ret += snprintf(buf + ret, size - ret, "%s\n", cft->name);
if (unlikely(ret >= size)) {
WARN_ON(1);
break;
}
}
return ret;
}
static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
struct cgroup_subsys *ss;
int ssid;
ssize_t ret = 0;
ret = show_delegatable_files(cgroup_base_files, buf, PAGE_SIZE - ret,
NULL);
for_each_subsys(ss, ssid)
ret += show_delegatable_files(ss->dfl_cftypes, buf + ret,
PAGE_SIZE - ret,
cgroup_subsys_name[ssid]);
return ret;
}
static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
return snprintf(buf, PAGE_SIZE, "nsdelegate\n");
}
static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
static struct attribute *cgroup_sysfs_attrs[] = {
&cgroup_delegate_attr.attr,
&cgroup_features_attr.attr,
NULL,
};
static const struct attribute_group cgroup_sysfs_attr_group = {
.attrs = cgroup_sysfs_attrs,
.name = "cgroup",
};
static int __init cgroup_sysfs_init(void)
{
return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group);
}
subsys_initcall(cgroup_sysfs_init);
#endif /* CONFIG_SYSFS */
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