summaryrefslogtreecommitdiffstats
path: root/kernel/cgroup/cgroup.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--kernel/cgroup/cgroup.c7062
1 files changed, 7062 insertions, 0 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
new file mode 100644
index 0000000000..518725b572
--- /dev/null
+++ b/kernel/cgroup/cgroup.c
@@ -0,0 +1,7062 @@
+/*
+ * 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/bpf-cgroup.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 <linux/fs_parser.h>
+#include <linux/sched/cputime.h>
+#include <linux/sched/deadline.h>
+#include <linux/psi.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)
+/* let's not notify more than 100 times per second */
+#define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100)
+
+/*
+ * To avoid confusing the compiler (and generating warnings) with code
+ * that attempts to access what would be a 0-element array (i.e. sized
+ * to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this
+ * constant expression can be added.
+ */
+#define CGROUP_HAS_SUBSYS_CONFIG (CGROUP_SUBSYS_COUNT > 0)
+
+/*
+ * 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
+
+DEFINE_SPINLOCK(trace_cgroup_path_lock);
+char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
+static bool cgroup_debug __read_mostly;
+
+/*
+ * 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);
+
+DEFINE_PERCPU_RWSEM(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_rstat_cpu, cgrp_dfl_root_rstat_cpu);
+
+/* the default hierarchy */
+struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu };
+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_release_callback __read_mostly;
+static u16 have_canfork_callback __read_mostly;
+
+/* cgroup namespace for init task */
+struct cgroup_namespace init_cgroup_ns = {
+ .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 struct cftype cgroup_psi_files[];
+
+/* cgroup optional features */
+enum cgroup_opt_features {
+#ifdef CONFIG_PSI
+ OPT_FEATURE_PRESSURE,
+#endif
+ OPT_FEATURE_COUNT
+};
+
+static const char *cgroup_opt_feature_names[OPT_FEATURE_COUNT] = {
+#ifdef CONFIG_PSI
+ "pressure",
+#endif
+};
+
+static u16 cgroup_feature_disable_mask __read_mostly;
+
+static int cgroup_apply_control(struct cgroup *cgrp);
+static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
+static void css_task_iter_skip(struct css_task_iter *it,
+ struct task_struct *task);
+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);
+
+#ifdef CONFIG_DEBUG_CGROUP_REF
+#define CGROUP_REF_FN_ATTRS noinline
+#define CGROUP_REF_EXPORT(fn) EXPORT_SYMBOL_GPL(fn);
+#include <linux/cgroup_refcnt.h>
+#endif
+
+/**
+ * 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_HAS_SUBSYS_CONFIG)
+ 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 differently depending on the
+ * interface version.
+ *
+ * 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.
+ *
+ * - 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 in-between 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.
+ *
+ * - blkcg: blk-throttle becomes properly hierarchical.
+ */
+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;
+}
+
+static 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? */
+static 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 (CGROUP_HAS_SUBSYS_CONFIG && ss)
+ return rcu_dereference_check(cgrp->subsys[ss->id],
+ lockdep_is_held(&cgroup_mutex));
+ else
+ return &cgrp->self;
+}
+
+/**
+ * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss
+ * @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_by_mask(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_e_css - obtain 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 is not guaranteed to be online, and therefore it is the
+ * callers responsibility to try get a reference for it.
+ */
+struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
+ struct cgroup_subsys *ss)
+{
+ struct cgroup_subsys_state *css;
+
+ if (!CGROUP_HAS_SUBSYS_CONFIG)
+ return NULL;
+
+ do {
+ css = cgroup_css(cgrp, ss);
+
+ if (css)
+ return css;
+ cgrp = cgroup_parent(cgrp);
+ } while (cgrp);
+
+ return init_css_set.subsys[ss->id];
+}
+
+/**
+ * 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;
+
+ if (!CGROUP_HAS_SUBSYS_CONFIG)
+ return NULL;
+
+ 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;
+}
+EXPORT_SYMBOL_GPL(cgroup_get_e_css);
+
+static void cgroup_get_live(struct cgroup *cgrp)
+{
+ WARN_ON_ONCE(cgroup_is_dead(cgrp));
+ cgroup_get(cgrp);
+}
+
+/**
+ * __cgroup_task_count - count the number of tasks in a cgroup. The caller
+ * is responsible for taking the css_set_lock.
+ * @cgrp: the cgroup in question
+ */
+int __cgroup_task_count(const struct cgroup *cgrp)
+{
+ int count = 0;
+ struct cgrp_cset_link *link;
+
+ lockdep_assert_held(&css_set_lock);
+
+ list_for_each_entry(link, &cgrp->cset_links, cset_link)
+ count += link->cset->nr_tasks;
+
+ return count;
+}
+
+/**
+ * cgroup_task_count - count the number of tasks in a cgroup.
+ * @cgrp: the cgroup in question
+ */
+int cgroup_task_count(const struct cgroup *cgrp)
+{
+ int count;
+
+ spin_lock_irq(&css_set_lock);
+ count = __cgroup_task_count(cgrp);
+ spin_unlock_irq(&css_set_lock);
+
+ return count;
+}
+
+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 (CGROUP_HAS_SUBSYS_CONFIG && 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_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
+
+/**
+ * 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_HAS_SUBSYS_CONFIG) { \
+ (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 pre order */
+#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),
+ .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_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_src_preload_node = LIST_HEAD_INIT(init_css_set.mg_src_preload_node),
+ .mg_dst_preload_node = LIST_HEAD_INIT(init_css_set.mg_dst_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);
+ TRACE_CGROUP_PATH(notify_populated, cgrp,
+ cgroup_is_populated(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);
+}
+
+/*
+ * @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_skip() for
+ * details.
+ */
+static void css_set_skip_task_iters(struct css_set *cset,
+ struct task_struct *task)
+{
+ struct css_task_iter *it, *pos;
+
+ list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node)
+ css_task_iter_skip(it, task);
+}
+
+/**
+ * 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) {
+ WARN_ON_ONCE(list_empty(&task->cg_list));
+
+ css_set_skip_task_iters(from_cset, task);
+ 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()/cgroup_free() dropping the css_set.
+ */
+ WARN_ON_ONCE(task->flags & PF_EXITING);
+
+ cgroup_move_task(task, 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_by_mask(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 chronological 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->dying_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_src_preload_node);
+ INIT_LIST_HEAD(&cset->mg_dst_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 = kernfs_root_to_node(kf_root)->priv;
+
+ return root_cgrp->root;
+}
+
+void cgroup_favor_dynmods(struct cgroup_root *root, bool favor)
+{
+ bool favoring = root->flags & CGRP_ROOT_FAVOR_DYNMODS;
+
+ /* see the comment above CGRP_ROOT_FAVOR_DYNMODS definition */
+ if (favor && !favoring) {
+ rcu_sync_enter(&cgroup_threadgroup_rwsem.rss);
+ root->flags |= CGRP_ROOT_FAVOR_DYNMODS;
+ } else if (!favor && favoring) {
+ rcu_sync_exit(&cgroup_threadgroup_rwsem.rss);
+ root->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
+ }
+}
+
+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)
+{
+ 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_favor_dynmods(root, false);
+ cgroup_exit_root_id(root);
+
+ cgroup_unlock();
+
+ cgroup_rstat_exit(cgrp);
+ kernfs_destroy_root(root->kf_root);
+ cgroup_free_root(root);
+}
+
+/*
+ * Returned cgroup is without refcount but it's valid as long as cset pins it.
+ */
+static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset,
+ struct cgroup_root *root)
+{
+ struct cgroup *res_cgroup = NULL;
+
+ if (cset == &init_css_set) {
+ res_cgroup = &root->cgrp;
+ } else if (root == &cgrp_dfl_root) {
+ res_cgroup = cset->dfl_cgrp;
+ } else {
+ struct cgrp_cset_link *link;
+ lockdep_assert_held(&css_set_lock);
+
+ list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
+ struct cgroup *c = link->cgrp;
+
+ if (c->root == root) {
+ res_cgroup = c;
+ break;
+ }
+ }
+ }
+
+ BUG_ON(!res_cgroup);
+ return res_cgroup;
+}
+
+/*
+ * 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;
+ res = __cset_cgroup_from_root(cset, root);
+
+ rcu_read_unlock();
+
+ return res;
+}
+
+/*
+ * Look up cgroup associated with current task's cgroup namespace on the default
+ * hierarchy.
+ *
+ * Unlike current_cgns_cgroup_from_root(), this doesn't need locks:
+ * - Internal rcu_read_lock is unnecessary because we don't dereference any rcu
+ * pointers.
+ * - css_set_lock is not needed because we just read cset->dfl_cgrp.
+ * - As a bonus returned cgrp is pinned with the current because it cannot
+ * switch cgroup_ns asynchronously.
+ */
+static struct cgroup *current_cgns_cgroup_dfl(void)
+{
+ struct css_set *cset;
+
+ if (current->nsproxy) {
+ cset = current->nsproxy->cgroup_ns->root_cset;
+ return __cset_cgroup_from_root(cset, &cgrp_dfl_root);
+ } else {
+ /*
+ * NOTE: This function may be called from bpf_cgroup_from_id()
+ * on a task which has already passed exit_task_namespaces() and
+ * nsproxy == NULL. Fall back to cgrp_dfl_root which will make all
+ * cgroups visible for lookups.
+ */
+ return &cgrp_dfl_root.cgrp;
+ }
+}
+
+/* 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)
+{
+ lockdep_assert_held(&cgroup_mutex);
+ lockdep_assert_held(&css_set_lock);
+
+ return __cset_cgroup_from_root(cset, root);
+}
+
+/*
+ * 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 css_set_lock the
+ * task can't change groups.
+ */
+ 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)) {
+ const char *dbg = (cft->flags & CFTYPE_DEBUG) ? ".__DEBUG__." : "";
+
+ snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
+ dbg, 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;
+
+ cgroup_unlock();
+
+ 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
+ cgroup_lock();
+
+ 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);
+
+ del_timer_sync(&cfile->notify_timer);
+ }
+
+ kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
+}
+
+/**
+ * css_clear_dir - remove subsys files in a cgroup directory
+ * @css: target 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)) {
+ cgroup_addrm_files(css, cgrp,
+ cgroup_base_files, false);
+ if (cgroup_psi_enabled())
+ cgroup_addrm_files(css, cgrp,
+ cgroup_psi_files, false);
+ } else {
+ cgroup_addrm_files(css, cgrp,
+ cgroup1_base_files, 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)
+ return 0;
+
+ if (!css->ss) {
+ if (cgroup_on_dfl(cgrp)) {
+ ret = cgroup_addrm_files(&cgrp->self, cgrp,
+ cgroup_base_files, true);
+ if (ret < 0)
+ return ret;
+
+ if (cgroup_psi_enabled()) {
+ ret = cgroup_addrm_files(&cgrp->self, cgrp,
+ cgroup_psi_files, true);
+ if (ret < 0)
+ return ret;
+ }
+ } else {
+ cgroup_addrm_files(css, cgrp,
+ cgroup1_base_files, true);
+ }
+ } 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, ret;
+ u16 dfl_disable_ss_mask = 0;
+
+ 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;
+
+ /*
+ * Collect ssid's that need to be disabled from default
+ * hierarchy.
+ */
+ if (ss->root == &cgrp_dfl_root)
+ dfl_disable_ss_mask |= 1 << ssid;
+
+ } while_each_subsys_mask();
+
+ if (dfl_disable_ss_mask) {
+ struct cgroup *scgrp = &cgrp_dfl_root.cgrp;
+
+ /*
+ * Controllers from default hierarchy that need to be rebound
+ * are all disabled together in one go.
+ */
+ cgrp_dfl_root.subsys_mask &= ~dfl_disable_ss_mask;
+ WARN_ON(cgroup_apply_control(scgrp));
+ cgroup_finalize_control(scgrp, 0);
+ }
+
+ 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, *cset_pos;
+ struct css_task_iter *it;
+
+ WARN_ON(!css || cgroup_css(dcgrp, ss));
+
+ if (src_root != &cgrp_dfl_root) {
+ /* 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);
+ WARN_ON(!list_empty(&dcgrp->e_csets[ss->id]));
+ list_for_each_entry_safe(cset, cset_pos, &scgrp->e_csets[ss->id],
+ e_cset_node[ss->id]) {
+ list_move_tail(&cset->e_cset_node[ss->id],
+ &dcgrp->e_csets[ss->id]);
+ /*
+ * all css_sets of scgrp together in same order to dcgrp,
+ * patch in-flight iterators to preserve correct iteration.
+ * since the iterator is always advanced right away and
+ * finished when it->cset_pos meets it->cset_head, so only
+ * update it->cset_head is enough here.
+ */
+ list_for_each_entry(it, &cset->task_iters, iters_node)
+ if (it->cset_head == &scgrp->e_csets[ss->id])
+ it->cset_head = &dcgrp->e_csets[ss->id];
+ }
+ spin_unlock_irq(&css_set_lock);
+
+ if (ss->css_rstat_flush) {
+ list_del_rcu(&css->rstat_css_node);
+ synchronize_rcu();
+ list_add_rcu(&css->rstat_css_node,
+ &dcgrp->rstat_css_list);
+ }
+
+ /* 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;
+}
+
+enum cgroup2_param {
+ Opt_nsdelegate,
+ Opt_favordynmods,
+ Opt_memory_localevents,
+ Opt_memory_recursiveprot,
+ nr__cgroup2_params
+};
+
+static const struct fs_parameter_spec cgroup2_fs_parameters[] = {
+ fsparam_flag("nsdelegate", Opt_nsdelegate),
+ fsparam_flag("favordynmods", Opt_favordynmods),
+ fsparam_flag("memory_localevents", Opt_memory_localevents),
+ fsparam_flag("memory_recursiveprot", Opt_memory_recursiveprot),
+ {}
+};
+
+static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+ struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+ struct fs_parse_result result;
+ int opt;
+
+ opt = fs_parse(fc, cgroup2_fs_parameters, param, &result);
+ if (opt < 0)
+ return opt;
+
+ switch (opt) {
+ case Opt_nsdelegate:
+ ctx->flags |= CGRP_ROOT_NS_DELEGATE;
+ return 0;
+ case Opt_favordynmods:
+ ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
+ return 0;
+ case Opt_memory_localevents:
+ ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
+ return 0;
+ case Opt_memory_recursiveprot:
+ ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
+ return 0;
+ }
+ return -EINVAL;
+}
+
+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;
+
+ cgroup_favor_dynmods(&cgrp_dfl_root,
+ root_flags & CGRP_ROOT_FAVOR_DYNMODS);
+
+ if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
+ cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
+ else
+ cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
+
+ if (root_flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
+ cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
+ else
+ cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;
+ }
+}
+
+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");
+ if (cgrp_dfl_root.flags & CGRP_ROOT_FAVOR_DYNMODS)
+ seq_puts(seq, ",favordynmods");
+ if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
+ seq_puts(seq, ",memory_localevents");
+ if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
+ seq_puts(seq, ",memory_recursiveprot");
+ return 0;
+}
+
+static int cgroup_reconfigure(struct fs_context *fc)
+{
+ struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+
+ apply_cgroup_root_flags(ctx->flags);
+ return 0;
+}
+
+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;
+ INIT_LIST_HEAD(&cgrp->rstat_css_list);
+ prev_cputime_init(&cgrp->prev_cputime);
+
+ 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_fs_context *ctx)
+{
+ struct cgroup_root *root = ctx->root;
+ struct cgroup *cgrp = &root->cgrp;
+
+ INIT_LIST_HEAD(&root->root_list);
+ atomic_set(&root->nr_cgrps, 1);
+ cgrp->root = root;
+ init_cgroup_housekeeping(cgrp);
+
+ /* DYNMODS must be modified through cgroup_favor_dynmods() */
+ root->flags = ctx->flags & ~CGRP_ROOT_FAVOR_DYNMODS;
+ if (ctx->release_agent)
+ strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX);
+ if (ctx->name)
+ strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN);
+ if (ctx->cpuset_clone_children)
+ set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
+}
+
+int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
+{
+ 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 = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
+ 0, 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 |
+ KERNFS_ROOT_SUPPORT_USER_XATTR,
+ root_cgrp);
+ if (IS_ERR(root->kf_root)) {
+ ret = PTR_ERR(root->kf_root);
+ goto exit_root_id;
+ }
+ root_cgrp->kn = kernfs_root_to_node(root->kf_root);
+ WARN_ON_ONCE(cgroup_ino(root_cgrp) != 1);
+ root_cgrp->ancestors[0] = root_cgrp;
+
+ ret = css_populate_dir(&root_cgrp->self);
+ if (ret)
+ goto destroy_root;
+
+ ret = cgroup_rstat_init(root_cgrp);
+ if (ret)
+ goto destroy_root;
+
+ ret = rebind_subsystems(root, ss_mask);
+ if (ret)
+ goto exit_stats;
+
+ 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);
+
+ ret = 0;
+ goto out;
+
+exit_stats:
+ cgroup_rstat_exit(root_cgrp);
+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;
+}
+
+int cgroup_do_get_tree(struct fs_context *fc)
+{
+ struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+ int ret;
+
+ ctx->kfc.root = ctx->root->kf_root;
+ if (fc->fs_type == &cgroup2_fs_type)
+ ctx->kfc.magic = CGROUP2_SUPER_MAGIC;
+ else
+ ctx->kfc.magic = CGROUP_SUPER_MAGIC;
+ ret = kernfs_get_tree(fc);
+
+ /*
+ * In non-init cgroup namespace, instead of root cgroup's dentry,
+ * we return the dentry corresponding to the cgroupns->root_cgrp.
+ */
+ if (!ret && ctx->ns != &init_cgroup_ns) {
+ struct dentry *nsdentry;
+ struct super_block *sb = fc->root->d_sb;
+ struct cgroup *cgrp;
+
+ cgroup_lock();
+ spin_lock_irq(&css_set_lock);
+
+ cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root);
+
+ spin_unlock_irq(&css_set_lock);
+ cgroup_unlock();
+
+ nsdentry = kernfs_node_dentry(cgrp->kn, sb);
+ dput(fc->root);
+ if (IS_ERR(nsdentry)) {
+ deactivate_locked_super(sb);
+ ret = PTR_ERR(nsdentry);
+ nsdentry = NULL;
+ }
+ fc->root = nsdentry;
+ }
+
+ if (!ctx->kfc.new_sb_created)
+ cgroup_put(&ctx->root->cgrp);
+
+ return ret;
+}
+
+/*
+ * Destroy a cgroup filesystem context.
+ */
+static void cgroup_fs_context_free(struct fs_context *fc)
+{
+ struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+
+ kfree(ctx->name);
+ kfree(ctx->release_agent);
+ put_cgroup_ns(ctx->ns);
+ kernfs_free_fs_context(fc);
+ kfree(ctx);
+}
+
+static int cgroup_get_tree(struct fs_context *fc)
+{
+ struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+ int ret;
+
+ WRITE_ONCE(cgrp_dfl_visible, true);
+ cgroup_get_live(&cgrp_dfl_root.cgrp);
+ ctx->root = &cgrp_dfl_root;
+
+ ret = cgroup_do_get_tree(fc);
+ if (!ret)
+ apply_cgroup_root_flags(ctx->flags);
+ return ret;
+}
+
+static const struct fs_context_operations cgroup_fs_context_ops = {
+ .free = cgroup_fs_context_free,
+ .parse_param = cgroup2_parse_param,
+ .get_tree = cgroup_get_tree,
+ .reconfigure = cgroup_reconfigure,
+};
+
+static const struct fs_context_operations cgroup1_fs_context_ops = {
+ .free = cgroup_fs_context_free,
+ .parse_param = cgroup1_parse_param,
+ .get_tree = cgroup1_get_tree,
+ .reconfigure = cgroup1_reconfigure,
+};
+
+/*
+ * Initialise the cgroup filesystem creation/reconfiguration context. Notably,
+ * we select the namespace we're going to use.
+ */
+static int cgroup_init_fs_context(struct fs_context *fc)
+{
+ struct cgroup_fs_context *ctx;
+
+ ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+
+ ctx->ns = current->nsproxy->cgroup_ns;
+ get_cgroup_ns(ctx->ns);
+ fc->fs_private = &ctx->kfc;
+ if (fc->fs_type == &cgroup2_fs_type)
+ fc->ops = &cgroup_fs_context_ops;
+ else
+ fc->ops = &cgroup1_fs_context_ops;
+ put_user_ns(fc->user_ns);
+ fc->user_ns = get_user_ns(ctx->ns->user_ns);
+ fc->global = true;
+
+#ifdef CONFIG_CGROUP_FAVOR_DYNMODS
+ ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
+#endif
+ return 0;
+}
+
+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 children, start killing it.
+ * This prevents new mounts by disabling percpu_ref_tryget_live().
+ *
+ * And don't kill the default root.
+ */
+ if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root &&
+ !percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
+ cgroup_bpf_offline(&root->cgrp);
+ percpu_ref_kill(&root->cgrp.self.refcnt);
+ }
+ cgroup_put(&root->cgrp);
+ kernfs_kill_sb(sb);
+}
+
+struct file_system_type cgroup_fs_type = {
+ .name = "cgroup",
+ .init_fs_context = cgroup_init_fs_context,
+ .parameters = cgroup1_fs_parameters,
+ .kill_sb = cgroup_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+
+static struct file_system_type cgroup2_fs_type = {
+ .name = "cgroup2",
+ .init_fs_context = cgroup_init_fs_context,
+ .parameters = cgroup2_fs_parameters,
+ .kill_sb = cgroup_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+
+#ifdef CONFIG_CPUSETS
+static const struct fs_context_operations cpuset_fs_context_ops = {
+ .get_tree = cgroup1_get_tree,
+ .free = cgroup_fs_context_free,
+};
+
+/*
+ * This is ugly, but preserves the userspace API for existing cpuset
+ * users. If someone tries to mount the "cpuset" filesystem, we
+ * silently switch it to mount "cgroup" instead
+ */
+static int cpuset_init_fs_context(struct fs_context *fc)
+{
+ char *agent = kstrdup("/sbin/cpuset_release_agent", GFP_USER);
+ struct cgroup_fs_context *ctx;
+ int err;
+
+ err = cgroup_init_fs_context(fc);
+ if (err) {
+ kfree(agent);
+ return err;
+ }
+
+ fc->ops = &cpuset_fs_context_ops;
+
+ ctx = cgroup_fc2context(fc);
+ ctx->subsys_mask = 1 << cpuset_cgrp_id;
+ ctx->flags |= CGRP_ROOT_NOPREFIX;
+ ctx->release_agent = agent;
+
+ get_filesystem(&cgroup_fs_type);
+ put_filesystem(fc->fs_type);
+ fc->fs_type = &cgroup_fs_type;
+
+ return 0;
+}
+
+static struct file_system_type cpuset_fs_type = {
+ .name = "cpuset",
+ .init_fs_context = cpuset_init_fs_context,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+#endif
+
+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;
+
+ cgroup_lock();
+ spin_lock_irq(&css_set_lock);
+
+ ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
+
+ spin_unlock_irq(&css_set_lock);
+ cgroup_unlock();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(cgroup_path_ns);
+
+/**
+ * cgroup_attach_lock - Lock for ->attach()
+ * @lock_threadgroup: whether to down_write cgroup_threadgroup_rwsem
+ *
+ * cgroup migration sometimes needs to stabilize threadgroups against forks and
+ * exits by write-locking cgroup_threadgroup_rwsem. However, some ->attach()
+ * implementations (e.g. cpuset), also need to disable CPU hotplug.
+ * Unfortunately, letting ->attach() operations acquire cpus_read_lock() can
+ * lead to deadlocks.
+ *
+ * Bringing up a CPU may involve creating and destroying tasks which requires
+ * read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
+ * cpus_read_lock(). If we call an ->attach() which acquires the cpus lock while
+ * write-locking threadgroup_rwsem, the locking order is reversed and we end up
+ * waiting for an on-going CPU hotplug operation which in turn is waiting for
+ * the threadgroup_rwsem to be released to create new tasks. For more details:
+ *
+ * http://lkml.kernel.org/r/20220711174629.uehfmqegcwn2lqzu@wubuntu
+ *
+ * Resolve the situation by always acquiring cpus_read_lock() before optionally
+ * write-locking cgroup_threadgroup_rwsem. This allows ->attach() to assume that
+ * CPU hotplug is disabled on entry.
+ */
+void cgroup_attach_lock(bool lock_threadgroup)
+{
+ cpus_read_lock();
+ if (lock_threadgroup)
+ percpu_down_write(&cgroup_threadgroup_rwsem);
+}
+
+/**
+ * cgroup_attach_unlock - Undo cgroup_attach_lock()
+ * @lock_threadgroup: whether to up_write cgroup_threadgroup_rwsem
+ */
+void cgroup_attach_unlock(bool lock_threadgroup)
+{
+ if (lock_threadgroup)
+ percpu_up_write(&cgroup_threadgroup_rwsem);
+ cpus_read_unlock();
+}
+
+/**
+ * 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;
+
+ /* cgroup_threadgroup_rwsem protects racing against forks */
+ WARN_ON_ONCE(list_empty(&task->cg_list));
+
+ 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 (CGROUP_HAS_SUBSYS_CONFIG && &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_migrate_execute(). 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_migrate_execute - 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);
+ from_cset->nr_tasks--;
+ /*
+ * If the source or destination cgroup is frozen,
+ * the task might require to change its state.
+ */
+ cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp,
+ to_cset->dfl_cgrp);
+ put_css_set_locked(from_cset);
+
+ }
+ }
+ 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;
+
+ /*
+ * 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)
+{
+ struct css_set *cset, *tmp_cset;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ spin_lock_irq(&css_set_lock);
+
+ list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_src_csets,
+ mg_src_preload_node) {
+ cset->mg_src_cgrp = NULL;
+ cset->mg_dst_cgrp = NULL;
+ cset->mg_dst_cset = NULL;
+ list_del_init(&cset->mg_src_preload_node);
+ put_css_set_locked(cset);
+ }
+
+ list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_dst_csets,
+ mg_dst_preload_node) {
+ cset->mg_src_cgrp = NULL;
+ cset->mg_dst_cgrp = NULL;
+ cset->mg_dst_cset = NULL;
+ list_del_init(&cset->mg_dst_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;
+
+ if (!list_empty(&src_cset->mg_src_preload_node))
+ return;
+
+ src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
+
+ 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_src_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_src_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)
+ return -ENOMEM;
+
+ 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_src_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_dst_preload_node))
+ list_add_tail(&dst_cset->mg_dst_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;
+}
+
+/**
+ * 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;
+
+ /*
+ * The following thread iteration should be inside an RCU critical
+ * section to prevent tasks from being freed while taking the snapshot.
+ * spin_lock_irq() implies RCU critical section here.
+ */
+ spin_lock_irq(&css_set_lock);
+ task = leader;
+ do {
+ cgroup_migrate_add_task(task, mgctx);
+ if (!threadgroup)
+ break;
+ } while_each_thread(leader, task);
+ 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 = 0;
+
+ /* 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_PATH(attach_task, dst_cgrp, leader, threadgroup);
+
+ return ret;
+}
+
+struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
+ bool *threadgroup_locked)
+{
+ struct task_struct *tsk;
+ pid_t pid;
+
+ if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
+ return ERR_PTR(-EINVAL);
+
+ /*
+ * If we migrate a single thread, we don't care about threadgroup
+ * stability. If the thread is `current`, it won't exit(2) under our
+ * hands or change PID through exec(2). We exclude
+ * cgroup_update_dfl_csses and other cgroup_{proc,thread}s_write
+ * callers by cgroup_mutex.
+ * Therefore, we can skip the global lock.
+ */
+ lockdep_assert_held(&cgroup_mutex);
+ *threadgroup_locked = pid || threadgroup;
+ cgroup_attach_lock(*threadgroup_locked);
+
+ 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:
+ cgroup_attach_unlock(*threadgroup_locked);
+ *threadgroup_locked = false;
+out_unlock_rcu:
+ rcu_read_unlock();
+ return tsk;
+}
+
+void cgroup_procs_write_finish(struct task_struct *task, bool threadgroup_locked)
+{
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ /* release reference from cgroup_procs_write_start() */
+ put_task_struct(task);
+
+ cgroup_attach_unlock(threadgroup_locked);
+
+ 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_puts(seq, 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;
+ bool has_tasks;
+ int ret;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ /* 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;
+
+ /*
+ * As cgroup_update_dfl_csses() is only called by
+ * cgroup_apply_control(). The csses associated with the
+ * given cgrp will not be affected by changes made to
+ * its subtree_control file. We can skip them.
+ */
+ if (dsct == cgrp)
+ continue;
+
+ list_for_each_entry(link, &dsct->cset_links, cset_link)
+ cgroup_migrate_add_src(link->cset, dsct, &mgctx);
+ }
+ spin_unlock_irq(&css_set_lock);
+
+ /*
+ * We need to write-lock threadgroup_rwsem while migrating tasks.
+ * However, if there are no source csets for @cgrp, changing its
+ * controllers isn't gonna produce any task migrations and the
+ * write-locking can be skipped safely.
+ */
+ has_tasks = !list_empty(&mgctx.preloaded_src_csets);
+ cgroup_attach_lock(has_tasks);
+
+ /* 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_src_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);
+ cgroup_attach_unlock(has_tasks);
+ 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:
+ cgroup_lock();
+
+ 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);
+
+ cgroup_unlock();
+ schedule();
+ finish_wait(&dsct->offline_waitq, &wait);
+
+ cgroup_put(dsct);
+ goto restart;
+ }
+ }
+}
+
+/**
+ * cgroup_save_control - save control masks and dom_cgrp of a subtree
+ * @cgrp: root of the target subtree
+ *
+ * Save ->subtree_control, ->subtree_ss_mask and ->dom_cgrp 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;
+ dsct->old_dom_cgrp = dsct->dom_cgrp;
+ }
+}
+
+/**
+ * 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 and dom_cgrp of a subtree
+ * @cgrp: root of the target subtree
+ *
+ * Restore ->subtree_control, ->subtree_ss_mask and ->dom_cgrp 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;
+ dsct->dom_cgrp = dsct->old_dom_cgrp;
+ }
+}
+
+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);
+
+ if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
+ continue;
+
+ if (!css) {
+ css = css_create(dsct, ss);
+ if (IS_ERR(css))
+ return PTR_ERR(css);
+ }
+
+ WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
+
+ 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);
+
+ if (!css)
+ continue;
+
+ WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
+
+ 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_by_mask() results reflect the new csses
+ * making the following cgroup_update_dfl_csses() properly update
+ * css associations of all tasks in the subtree.
+ */
+ return cgroup_update_dfl_csses(cgrp);
+}
+
+/**
+ * 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;
+ struct cgroup *dsct;
+ struct cgroup_subsys_state *d_css;
+ 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);
+
+ cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)
+ if (dsct == cgrp || cgroup_is_threaded(dsct))
+ dsct->dom_cgrp = dom_cgrp;
+
+ ret = cgroup_apply_control(cgrp);
+ if (!ret)
+ parent->nr_threaded_children++;
+
+ 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;
+
+ /* drain dying csses before we re-apply (threaded) subtree control */
+ cgrp = cgroup_kn_lock_live(of->kn, true);
+ 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)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+
+ seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp));
+ seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags));
+
+ 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;
+}
+
+#ifdef CONFIG_CGROUP_SCHED
+/**
+ * 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 associated 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;
+}
+
+static int cgroup_extra_stat_show(struct seq_file *seq, int ssid)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+ 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 cgroup_local_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_local_stat_show)
+ return 0;
+
+ css = cgroup_tryget_css(cgrp, ss);
+ if (!css)
+ return 0;
+
+ ret = ss->css_local_stat_show(seq, css);
+ css_put(css);
+ return ret;
+}
+#endif
+
+static int cpu_stat_show(struct seq_file *seq, void *v)
+{
+ int ret = 0;
+
+ cgroup_base_stat_cputime_show(seq);
+#ifdef CONFIG_CGROUP_SCHED
+ ret = cgroup_extra_stat_show(seq, cpu_cgrp_id);
+#endif
+ return ret;
+}
+
+static int cpu_local_stat_show(struct seq_file *seq, void *v)
+{
+ struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup;
+ int ret = 0;
+
+#ifdef CONFIG_CGROUP_SCHED
+ ret = cgroup_local_stat_show(seq, cgrp, cpu_cgrp_id);
+#endif
+ return ret;
+}
+
+#ifdef CONFIG_PSI
+static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+ struct psi_group *psi = cgroup_psi(cgrp);
+
+ return psi_show(seq, psi, PSI_IO);
+}
+static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+ struct psi_group *psi = cgroup_psi(cgrp);
+
+ return psi_show(seq, psi, PSI_MEM);
+}
+static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+ struct psi_group *psi = cgroup_psi(cgrp);
+
+ return psi_show(seq, psi, PSI_CPU);
+}
+
+static ssize_t pressure_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, enum psi_res res)
+{
+ struct cgroup_file_ctx *ctx = of->priv;
+ struct psi_trigger *new;
+ struct cgroup *cgrp;
+ struct psi_group *psi;
+
+ cgrp = cgroup_kn_lock_live(of->kn, false);
+ if (!cgrp)
+ return -ENODEV;
+
+ cgroup_get(cgrp);
+ cgroup_kn_unlock(of->kn);
+
+ /* Allow only one trigger per file descriptor */
+ if (ctx->psi.trigger) {
+ cgroup_put(cgrp);
+ return -EBUSY;
+ }
+
+ psi = cgroup_psi(cgrp);
+ new = psi_trigger_create(psi, buf, res, of->file, of);
+ if (IS_ERR(new)) {
+ cgroup_put(cgrp);
+ return PTR_ERR(new);
+ }
+
+ smp_store_release(&ctx->psi.trigger, new);
+ cgroup_put(cgrp);
+
+ return nbytes;
+}
+
+static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ return pressure_write(of, buf, nbytes, PSI_IO);
+}
+
+static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ return pressure_write(of, buf, nbytes, PSI_MEM);
+}
+
+static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ return pressure_write(of, buf, nbytes, PSI_CPU);
+}
+
+#ifdef CONFIG_IRQ_TIME_ACCOUNTING
+static int cgroup_irq_pressure_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+ struct psi_group *psi = cgroup_psi(cgrp);
+
+ return psi_show(seq, psi, PSI_IRQ);
+}
+
+static ssize_t cgroup_irq_pressure_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ return pressure_write(of, buf, nbytes, PSI_IRQ);
+}
+#endif
+
+static int cgroup_pressure_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+ struct psi_group *psi = cgroup_psi(cgrp);
+
+ seq_printf(seq, "%d\n", psi->enabled);
+
+ return 0;
+}
+
+static ssize_t cgroup_pressure_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ ssize_t ret;
+ int enable;
+ struct cgroup *cgrp;
+ struct psi_group *psi;
+
+ ret = kstrtoint(strstrip(buf), 0, &enable);
+ if (ret)
+ return ret;
+
+ if (enable < 0 || enable > 1)
+ return -ERANGE;
+
+ cgrp = cgroup_kn_lock_live(of->kn, false);
+ if (!cgrp)
+ return -ENOENT;
+
+ psi = cgroup_psi(cgrp);
+ if (psi->enabled != enable) {
+ int i;
+
+ /* show or hide {cpu,memory,io,irq}.pressure files */
+ for (i = 0; i < NR_PSI_RESOURCES; i++)
+ cgroup_file_show(&cgrp->psi_files[i], enable);
+
+ psi->enabled = enable;
+ if (enable)
+ psi_cgroup_restart(psi);
+ }
+
+ cgroup_kn_unlock(of->kn);
+
+ return nbytes;
+}
+
+static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of,
+ poll_table *pt)
+{
+ struct cgroup_file_ctx *ctx = of->priv;
+
+ return psi_trigger_poll(&ctx->psi.trigger, of->file, pt);
+}
+
+static void cgroup_pressure_release(struct kernfs_open_file *of)
+{
+ struct cgroup_file_ctx *ctx = of->priv;
+
+ psi_trigger_destroy(ctx->psi.trigger);
+}
+
+bool cgroup_psi_enabled(void)
+{
+ if (static_branch_likely(&psi_disabled))
+ return false;
+
+ return (cgroup_feature_disable_mask & (1 << OPT_FEATURE_PRESSURE)) == 0;
+}
+
+#else /* CONFIG_PSI */
+bool cgroup_psi_enabled(void)
+{
+ return false;
+}
+
+#endif /* CONFIG_PSI */
+
+static int cgroup_freeze_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+
+ seq_printf(seq, "%d\n", cgrp->freezer.freeze);
+
+ return 0;
+}
+
+static ssize_t cgroup_freeze_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct cgroup *cgrp;
+ ssize_t ret;
+ int freeze;
+
+ ret = kstrtoint(strstrip(buf), 0, &freeze);
+ if (ret)
+ return ret;
+
+ if (freeze < 0 || freeze > 1)
+ return -ERANGE;
+
+ cgrp = cgroup_kn_lock_live(of->kn, false);
+ if (!cgrp)
+ return -ENOENT;
+
+ cgroup_freeze(cgrp, freeze);
+
+ cgroup_kn_unlock(of->kn);
+
+ return nbytes;
+}
+
+static void __cgroup_kill(struct cgroup *cgrp)
+{
+ struct css_task_iter it;
+ struct task_struct *task;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ spin_lock_irq(&css_set_lock);
+ set_bit(CGRP_KILL, &cgrp->flags);
+ spin_unlock_irq(&css_set_lock);
+
+ css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED, &it);
+ while ((task = css_task_iter_next(&it))) {
+ /* Ignore kernel threads here. */
+ if (task->flags & PF_KTHREAD)
+ continue;
+
+ /* Skip tasks that are already dying. */
+ if (__fatal_signal_pending(task))
+ continue;
+
+ send_sig(SIGKILL, task, 0);
+ }
+ css_task_iter_end(&it);
+
+ spin_lock_irq(&css_set_lock);
+ clear_bit(CGRP_KILL, &cgrp->flags);
+ spin_unlock_irq(&css_set_lock);
+}
+
+static void cgroup_kill(struct cgroup *cgrp)
+{
+ struct cgroup_subsys_state *css;
+ struct cgroup *dsct;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ cgroup_for_each_live_descendant_pre(dsct, css, cgrp)
+ __cgroup_kill(dsct);
+}
+
+static ssize_t cgroup_kill_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off)
+{
+ ssize_t ret = 0;
+ int kill;
+ struct cgroup *cgrp;
+
+ ret = kstrtoint(strstrip(buf), 0, &kill);
+ if (ret)
+ return ret;
+
+ if (kill != 1)
+ return -ERANGE;
+
+ cgrp = cgroup_kn_lock_live(of->kn, false);
+ if (!cgrp)
+ return -ENOENT;
+
+ /*
+ * Killing is a process directed operation, i.e. the whole thread-group
+ * is taken down so act like we do for cgroup.procs and only make this
+ * writable in non-threaded cgroups.
+ */
+ if (cgroup_is_threaded(cgrp))
+ ret = -EOPNOTSUPP;
+ else
+ cgroup_kill(cgrp);
+
+ cgroup_kn_unlock(of->kn);
+
+ return ret ?: nbytes;
+}
+
+static int cgroup_file_open(struct kernfs_open_file *of)
+{
+ struct cftype *cft = of_cft(of);
+ struct cgroup_file_ctx *ctx;
+ int ret;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+
+ ctx->ns = current->nsproxy->cgroup_ns;
+ get_cgroup_ns(ctx->ns);
+ of->priv = ctx;
+
+ if (!cft->open)
+ return 0;
+
+ ret = cft->open(of);
+ if (ret) {
+ put_cgroup_ns(ctx->ns);
+ kfree(ctx);
+ }
+ return ret;
+}
+
+static void cgroup_file_release(struct kernfs_open_file *of)
+{
+ struct cftype *cft = of_cft(of);
+ struct cgroup_file_ctx *ctx = of->priv;
+
+ if (cft->release)
+ cft->release(of);
+ put_cgroup_ns(ctx->ns);
+ kfree(ctx);
+}
+
+static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off)
+{
+ struct cgroup_file_ctx *ctx = of->priv;
+ struct cgroup *cgrp = of->kn->parent->priv;
+ struct cftype *cft = of_cft(of);
+ struct cgroup_subsys_state *css;
+ int ret;
+
+ if (!nbytes)
+ return 0;
+
+ /*
+ * 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) &&
+ ctx->ns != &init_cgroup_ns && ctx->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 __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt)
+{
+ struct cftype *cft = of_cft(of);
+
+ if (cft->poll)
+ return cft->poll(of, pt);
+
+ return kernfs_generic_poll(of, pt);
+}
+
+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,
+ .poll = cgroup_file_poll,
+ .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,
+ .poll = cgroup_file_poll,
+ .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 void cgroup_file_notify_timer(struct timer_list *timer)
+{
+ cgroup_file_notify(container_of(timer, struct cgroup_file,
+ notify_timer));
+}
+
+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),
+ GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+ 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;
+
+ timer_setup(&cfile->notify_timer, cgroup_file_notify_timer, 0);
+
+ 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 ((cft->flags & CFTYPE_DEBUG) && !cgroup_debug)
+ 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 |
+ __CFTYPE_ADDED);
+ }
+}
+
+static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
+{
+ struct cftype *cft;
+ int ret = 0;
+
+ for (cft = cfts; cft->name[0] != '\0'; cft++) {
+ struct kernfs_ops *kf_ops;
+
+ WARN_ON(cft->ss || cft->kf_ops);
+
+ if (cft->flags & __CFTYPE_ADDED) {
+ ret = -EBUSY;
+ break;
+ }
+
+ 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) {
+ ret = -ENOMEM;
+ break;
+ }
+ kf_ops->atomic_write_len = cft->max_write_len;
+ }
+
+ cft->kf_ops = kf_ops;
+ cft->ss = ss;
+ cft->flags |= __CFTYPE_ADDED;
+ }
+
+ if (ret)
+ cgroup_exit_cftypes(cfts);
+ return ret;
+}
+
+static void cgroup_rm_cftypes_locked(struct cftype *cfts)
+{
+ lockdep_assert_held(&cgroup_mutex);
+
+ list_del(&cfts->node);
+ cgroup_apply_cftypes(cfts, false);
+ cgroup_exit_cftypes(cfts);
+}
+
+/**
+ * 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)
+{
+ if (!cfts || cfts[0].name[0] == '\0')
+ return 0;
+
+ if (!(cfts[0].flags & __CFTYPE_ADDED))
+ return -ENOENT;
+
+ cgroup_lock();
+ cgroup_rm_cftypes_locked(cfts);
+ cgroup_unlock();
+ return 0;
+}
+
+/**
+ * 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;
+
+ cgroup_lock();
+
+ list_add_tail(&cfts->node, &ss->cfts);
+ ret = cgroup_apply_cftypes(cfts, true);
+ if (ret)
+ cgroup_rm_cftypes_locked(cfts);
+
+ cgroup_unlock();
+ 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) {
+ unsigned long last = cfile->notified_at;
+ unsigned long next = last + CGROUP_FILE_NOTIFY_MIN_INTV;
+
+ if (time_in_range(jiffies, last, next)) {
+ timer_reduce(&cfile->notify_timer, next);
+ } else {
+ kernfs_notify(cfile->kn);
+ cfile->notified_at = jiffies;
+ }
+ }
+ spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
+}
+
+/**
+ * cgroup_file_show - show or hide a hidden cgroup file
+ * @cfile: target cgroup_file obtained by setting cftype->file_offset
+ * @show: whether to show or hide
+ */
+void cgroup_file_show(struct cgroup_file *cfile, bool show)
+{
+ struct kernfs_node *kn;
+
+ spin_lock_irq(&cgroup_file_kn_lock);
+ kn = cfile->kn;
+ kernfs_get(kn);
+ spin_unlock_irq(&cgroup_file_kn_lock);
+
+ if (kn)
+ kernfs_show(kn, show);
+
+ kernfs_put(kn);
+}
+
+/**
+ * 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() in-between 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,
+ lockdep_is_held(&cgroup_mutex))
+ 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;
+}
+EXPORT_SYMBOL_GPL(css_next_descendant_pre);
+
+/**
+ * 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 iterator 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 and find first non-empty tasks list*/
+ while ((cset = css_task_iter_next_css_set(it))) {
+ if (!list_empty(&cset->tasks)) {
+ it->cur_tasks_head = &cset->tasks;
+ break;
+ } else if (!list_empty(&cset->mg_tasks)) {
+ it->cur_tasks_head = &cset->mg_tasks;
+ break;
+ } else if (!list_empty(&cset->dying_tasks)) {
+ it->cur_tasks_head = &cset->dying_tasks;
+ break;
+ }
+ }
+ if (!cset) {
+ it->task_pos = NULL;
+ return;
+ }
+ it->task_pos = it->cur_tasks_head->next;
+
+ /*
+ * 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_skip(struct css_task_iter *it,
+ struct task_struct *task)
+{
+ lockdep_assert_held(&css_set_lock);
+
+ if (it->task_pos == &task->cg_list) {
+ it->task_pos = it->task_pos->next;
+ it->flags |= CSS_TASK_ITER_SKIPPED;
+ }
+}
+
+static void css_task_iter_advance(struct css_task_iter *it)
+{
+ struct task_struct *task;
+
+ lockdep_assert_held(&css_set_lock);
+repeat:
+ if (it->task_pos) {
+ /*
+ * Advance iterator to find next entry. We go through cset
+ * tasks, mg_tasks and dying_tasks, when consumed we move onto
+ * the next cset.
+ */
+ if (it->flags & CSS_TASK_ITER_SKIPPED)
+ it->flags &= ~CSS_TASK_ITER_SKIPPED;
+ else
+ it->task_pos = it->task_pos->next;
+
+ if (it->task_pos == &it->cur_cset->tasks) {
+ it->cur_tasks_head = &it->cur_cset->mg_tasks;
+ it->task_pos = it->cur_tasks_head->next;
+ }
+ if (it->task_pos == &it->cur_cset->mg_tasks) {
+ it->cur_tasks_head = &it->cur_cset->dying_tasks;
+ it->task_pos = it->cur_tasks_head->next;
+ }
+ if (it->task_pos == &it->cur_cset->dying_tasks)
+ css_task_iter_advance_css_set(it);
+ } else {
+ /* called from start, proceed to the first cset */
+ css_task_iter_advance_css_set(it);
+ }
+
+ if (!it->task_pos)
+ return;
+
+ task = list_entry(it->task_pos, struct task_struct, cg_list);
+
+ if (it->flags & CSS_TASK_ITER_PROCS) {
+ /* if PROCS, skip over tasks which aren't group leaders */
+ if (!thread_group_leader(task))
+ goto repeat;
+
+ /* and dying leaders w/o live member threads */
+ if (it->cur_tasks_head == &it->cur_cset->dying_tasks &&
+ !atomic_read(&task->signal->live))
+ goto repeat;
+ } else {
+ /* skip all dying ones */
+ if (it->cur_tasks_head == &it->cur_cset->dying_tasks)
+ 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)
+{
+ memset(it, 0, sizeof(*it));
+
+ spin_lock_irq(&css_set_lock);
+
+ it->ss = css->ss;
+ it->flags = flags;
+
+ if (CGROUP_HAS_SUBSYS_CONFIG && 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(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);
+
+ /* @it may be half-advanced by skips, finish advancing */
+ if (it->flags & CSS_TASK_ITER_SKIPPED)
+ css_task_iter_advance(it);
+
+ 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)
+{
+ struct cgroup_file_ctx *ctx = of->priv;
+
+ if (ctx->procs.started)
+ css_task_iter_end(&ctx->procs.iter);
+}
+
+static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
+{
+ struct kernfs_open_file *of = s->private;
+ struct cgroup_file_ctx *ctx = of->priv;
+
+ if (pos)
+ (*pos)++;
+
+ return css_task_iter_next(&ctx->procs.iter);
+}
+
+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 cgroup_file_ctx *ctx = of->priv;
+ struct css_task_iter *it = &ctx->procs.iter;
+
+ /*
+ * When a seq_file is seeked, it's always traversed sequentially
+ * from position 0, so we can simply keep iterating on !0 *pos.
+ */
+ if (!ctx->procs.started) {
+ if (WARN_ON_ONCE((*pos)))
+ return ERR_PTR(-EINVAL);
+ css_task_iter_start(&cgrp->self, iter_flags, it);
+ ctx->procs.started = true;
+ } else if (!(*pos)) {
+ css_task_iter_end(it);
+ css_task_iter_start(&cgrp->self, iter_flags, it);
+ } else
+ return it->cur_task;
+
+ 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_may_write(const struct cgroup *cgrp, struct super_block *sb)
+{
+ int ret;
+ struct inode *inode;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
+ if (!inode)
+ return -ENOMEM;
+
+ ret = inode_permission(&nop_mnt_idmap, inode, MAY_WRITE);
+ iput(inode);
+ return ret;
+}
+
+static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
+ struct cgroup *dst_cgrp,
+ struct super_block *sb,
+ struct cgroup_namespace *ns)
+{
+ struct cgroup *com_cgrp = src_cgrp;
+ 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 */
+ ret = cgroup_may_write(com_cgrp, sb);
+ 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 int cgroup_attach_permissions(struct cgroup *src_cgrp,
+ struct cgroup *dst_cgrp,
+ struct super_block *sb, bool threadgroup,
+ struct cgroup_namespace *ns)
+{
+ int ret = 0;
+
+ ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb, ns);
+ if (ret)
+ return ret;
+
+ ret = cgroup_migrate_vet_dst(dst_cgrp);
+ if (ret)
+ return ret;
+
+ if (!threadgroup && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp))
+ ret = -EOPNOTSUPP;
+
+ return ret;
+}
+
+static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
+ bool threadgroup)
+{
+ struct cgroup_file_ctx *ctx = of->priv;
+ struct cgroup *src_cgrp, *dst_cgrp;
+ struct task_struct *task;
+ const struct cred *saved_cred;
+ ssize_t ret;
+ bool threadgroup_locked;
+
+ dst_cgrp = cgroup_kn_lock_live(of->kn, false);
+ if (!dst_cgrp)
+ return -ENODEV;
+
+ task = cgroup_procs_write_start(buf, threadgroup, &threadgroup_locked);
+ 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);
+
+ /*
+ * Process and thread migrations follow same delegation rule. Check
+ * permissions using the credentials from file open to protect against
+ * inherited fd attacks.
+ */
+ saved_cred = override_creds(of->file->f_cred);
+ ret = cgroup_attach_permissions(src_cgrp, dst_cgrp,
+ of->file->f_path.dentry->d_sb,
+ threadgroup, ctx->ns);
+ revert_creds(saved_cred);
+ if (ret)
+ goto out_finish;
+
+ ret = cgroup_attach_task(dst_cgrp, task, threadgroup);
+
+out_finish:
+ cgroup_procs_write_finish(task, threadgroup_locked);
+out_unlock:
+ cgroup_kn_unlock(of->kn);
+
+ return ret;
+}
+
+static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ return __cgroup_procs_write(of, buf, true) ?: 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)
+{
+ return __cgroup_procs_write(of, buf, false) ?: 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 = "cgroup.freeze",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cgroup_freeze_show,
+ .write = cgroup_freeze_write,
+ },
+ {
+ .name = "cgroup.kill",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .write = cgroup_kill_write,
+ },
+ {
+ .name = "cpu.stat",
+ .seq_show = cpu_stat_show,
+ },
+ {
+ .name = "cpu.stat.local",
+ .seq_show = cpu_local_stat_show,
+ },
+ { } /* terminate */
+};
+
+static struct cftype cgroup_psi_files[] = {
+#ifdef CONFIG_PSI
+ {
+ .name = "io.pressure",
+ .file_offset = offsetof(struct cgroup, psi_files[PSI_IO]),
+ .seq_show = cgroup_io_pressure_show,
+ .write = cgroup_io_pressure_write,
+ .poll = cgroup_pressure_poll,
+ .release = cgroup_pressure_release,
+ },
+ {
+ .name = "memory.pressure",
+ .file_offset = offsetof(struct cgroup, psi_files[PSI_MEM]),
+ .seq_show = cgroup_memory_pressure_show,
+ .write = cgroup_memory_pressure_write,
+ .poll = cgroup_pressure_poll,
+ .release = cgroup_pressure_release,
+ },
+ {
+ .name = "cpu.pressure",
+ .file_offset = offsetof(struct cgroup, psi_files[PSI_CPU]),
+ .seq_show = cgroup_cpu_pressure_show,
+ .write = cgroup_cpu_pressure_write,
+ .poll = cgroup_pressure_poll,
+ .release = cgroup_pressure_release,
+ },
+#ifdef CONFIG_IRQ_TIME_ACCOUNTING
+ {
+ .name = "irq.pressure",
+ .file_offset = offsetof(struct cgroup, psi_files[PSI_IRQ]),
+ .seq_show = cgroup_irq_pressure_show,
+ .write = cgroup_irq_pressure_write,
+ .poll = cgroup_pressure_poll,
+ .release = cgroup_pressure_release,
+ },
+#endif
+ {
+ .name = "cgroup.pressure",
+ .seq_show = cgroup_pressure_show,
+ .write = cgroup_pressure_write,
+ },
+#endif /* CONFIG_PSI */
+ { } /* 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_rwork_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);
+ bpf_cgrp_storage_free(cgrp);
+
+ 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);
+ psi_cgroup_free(cgrp);
+ cgroup_rstat_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;
+
+ cgroup_lock();
+
+ css->flags |= CSS_RELEASED;
+ list_del_rcu(&css->sibling);
+
+ if (ss) {
+ /* css release path */
+ if (!list_empty(&css->rstat_css_node)) {
+ cgroup_rstat_flush(cgrp);
+ list_del_rcu(&css->rstat_css_node);
+ }
+
+ 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_PATH(release, cgrp);
+
+ cgroup_rstat_flush(cgrp);
+
+ spin_lock_irq(&css_set_lock);
+ for (tcgrp = cgroup_parent(cgrp); tcgrp;
+ tcgrp = cgroup_parent(tcgrp))
+ tcgrp->nr_dying_descendants--;
+ spin_unlock_irq(&css_set_lock);
+
+ /*
+ * 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_unlock();
+
+ 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);
+ INIT_LIST_HEAD(&css->rstat_css_node);
+ 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);
+ }
+
+ if (ss->css_rstat_flush)
+ list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list);
+
+ 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;
+
+ return css;
+
+err_list_del:
+ list_del_rcu(&css->sibling);
+err_free_css:
+ list_del_rcu(&css->rstat_css_node);
+ 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 doesn't have the control mask applied.
+ */
+static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
+ umode_t mode)
+{
+ struct cgroup_root *root = parent->root;
+ struct cgroup *cgrp, *tcgrp;
+ struct kernfs_node *kn;
+ int level = parent->level + 1;
+ int ret;
+
+ /* allocate the cgroup and its ID, 0 is reserved for the root */
+ cgrp = kzalloc(struct_size(cgrp, ancestors, (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;
+
+ ret = cgroup_rstat_init(cgrp);
+ if (ret)
+ goto out_cancel_ref;
+
+ /* create the directory */
+ kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
+ if (IS_ERR(kn)) {
+ ret = PTR_ERR(kn);
+ goto out_stat_exit;
+ }
+ cgrp->kn = kn;
+
+ init_cgroup_housekeeping(cgrp);
+
+ cgrp->self.parent = &parent->self;
+ cgrp->root = root;
+ cgrp->level = level;
+
+ ret = psi_cgroup_alloc(cgrp);
+ if (ret)
+ goto out_kernfs_remove;
+
+ ret = cgroup_bpf_inherit(cgrp);
+ if (ret)
+ goto out_psi_free;
+
+ /*
+ * New cgroup inherits effective freeze counter, and
+ * if the parent has to be frozen, the child has too.
+ */
+ cgrp->freezer.e_freeze = parent->freezer.e_freeze;
+ if (cgrp->freezer.e_freeze) {
+ /*
+ * Set the CGRP_FREEZE flag, so when a process will be
+ * attached to the child cgroup, it will become frozen.
+ * At this point the new cgroup is unpopulated, so we can
+ * consider it frozen immediately.
+ */
+ set_bit(CGRP_FREEZE, &cgrp->flags);
+ set_bit(CGRP_FROZEN, &cgrp->flags);
+ }
+
+ spin_lock_irq(&css_set_lock);
+ for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
+ cgrp->ancestors[tcgrp->level] = tcgrp;
+
+ if (tcgrp != cgrp) {
+ tcgrp->nr_descendants++;
+
+ /*
+ * If the new cgroup is frozen, all ancestor cgroups
+ * get a new frozen descendant, but their state can't
+ * change because of this.
+ */
+ if (cgrp->freezer.e_freeze)
+ tcgrp->freezer.nr_frozen_descendants++;
+ }
+ }
+ spin_unlock_irq(&css_set_lock);
+
+ 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);
+
+ /*
+ * 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_psi_free:
+ psi_cgroup_free(cgrp);
+out_kernfs_remove:
+ kernfs_remove(cgrp->kn);
+out_stat_exit:
+ cgroup_rstat_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;
+ 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, name, mode);
+ if (IS_ERR(cgrp)) {
+ ret = PTR_ERR(cgrp);
+ goto out_unlock;
+ }
+
+ /*
+ * This extra ref will be put in cgroup_free_fn() and guarantees
+ * that @cgrp->kn is always accessible.
+ */
+ kernfs_get(cgrp->kn);
+
+ ret = cgroup_kn_set_ugid(cgrp->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_PATH(mkdir, cgrp);
+
+ /* let's create and online css's */
+ kernfs_activate(cgrp->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
+ * initiate 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);
+
+ cgroup_lock();
+
+ 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));
+
+ cgroup_unlock();
+}
+
+/* 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_kn_lock_live(). 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 (cgroup_is_threaded(cgrp))
+ parent->nr_threaded_children--;
+
+ spin_lock_irq(&css_set_lock);
+ for (tcgrp = parent; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
+ tcgrp->nr_descendants--;
+ tcgrp->nr_dying_descendants++;
+ /*
+ * If the dying cgroup is frozen, decrease frozen descendants
+ * counters of ancestor cgroups.
+ */
+ if (test_bit(CGRP_FROZEN, &cgrp->flags))
+ tcgrp->freezer.nr_frozen_descendants--;
+ }
+ spin_unlock_irq(&css_set_lock);
+
+ cgroup1_check_for_release(parent);
+
+ cgroup_bpf_offline(cgrp);
+
+ /* 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_PATH(rmdir, cgrp);
+
+ cgroup_kn_unlock(kn);
+ return ret;
+}
+
+static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
+ .show_options = cgroup_show_options,
+ .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);
+
+ cgroup_lock();
+
+ 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(NULL);
+ /* 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_release_callback |= (bool)ss->release << 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));
+
+ cgroup_unlock();
+}
+
+/**
+ * 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_fs_context __initdata ctx;
+ struct cgroup_subsys *ss;
+ int i;
+
+ ctx.root = &cgrp_dfl_root;
+ init_cgroup_root(&ctx);
+ 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;
+}
+
+/**
+ * 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(cgroup_init_cftypes(NULL, cgroup_base_files));
+ BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));
+ BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
+
+ cgroup_rstat_boot();
+
+ get_user_ns(init_cgroup_ns.user_ns);
+
+ cgroup_lock();
+
+ /*
+ * 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));
+
+ cgroup_unlock();
+
+ 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_ssid_enabled(ssid))
+ continue;
+
+ if (cgroup1_ssid_disabled(ssid))
+ pr_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]);
+
+ cgroup_lock();
+ css_populate_dir(init_css_set.subsys[ssid]);
+ cgroup_unlock();
+ }
+
+ /* 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_single("cgroups", 0, NULL, proc_cgroupstats_show));
+#ifdef CONFIG_CPUSETS
+ WARN_ON(register_filesystem(&cpuset_fs_type));
+#endif
+
+ 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(u64 id, char *buf, size_t buflen)
+{
+ struct kernfs_node *kn;
+
+ kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
+ if (!kn)
+ return;
+ kernfs_path(kn, buf, buflen);
+ kernfs_put(kn);
+}
+
+/*
+ * cgroup_get_from_id : get the cgroup associated with cgroup id
+ * @id: cgroup id
+ * On success return the cgrp or ERR_PTR on failure
+ * Only cgroups within current task's cgroup NS are valid.
+ */
+struct cgroup *cgroup_get_from_id(u64 id)
+{
+ struct kernfs_node *kn;
+ struct cgroup *cgrp, *root_cgrp;
+
+ kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
+ if (!kn)
+ return ERR_PTR(-ENOENT);
+
+ if (kernfs_type(kn) != KERNFS_DIR) {
+ kernfs_put(kn);
+ return ERR_PTR(-ENOENT);
+ }
+
+ rcu_read_lock();
+
+ cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
+ if (cgrp && !cgroup_tryget(cgrp))
+ cgrp = NULL;
+
+ rcu_read_unlock();
+ kernfs_put(kn);
+
+ if (!cgrp)
+ return ERR_PTR(-ENOENT);
+
+ root_cgrp = current_cgns_cgroup_dfl();
+ if (!cgroup_is_descendant(cgrp, root_cgrp)) {
+ cgroup_put(cgrp);
+ return ERR_PTR(-ENOENT);
+ }
+
+ return cgrp;
+}
+EXPORT_SYMBOL_GPL(cgroup_get_from_id);
+
+/*
+ * 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;
+
+ cgroup_lock();
+ 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 && !READ_ONCE(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);
+ cgroup_unlock();
+ 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 target css_set.
+ */
+void cgroup_fork(struct task_struct *child)
+{
+ RCU_INIT_POINTER(child->cgroups, &init_css_set);
+ INIT_LIST_HEAD(&child->cg_list);
+}
+
+/**
+ * cgroup_v1v2_get_from_file - get a cgroup pointer from a file pointer
+ * @f: file corresponding to cgroup_dir
+ *
+ * Find the cgroup from a file pointer associated with a cgroup directory.
+ * Returns a pointer to the cgroup on success. ERR_PTR is returned if the
+ * cgroup cannot be found.
+ */
+static struct cgroup *cgroup_v1v2_get_from_file(struct file *f)
+{
+ struct cgroup_subsys_state *css;
+
+ css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
+ if (IS_ERR(css))
+ return ERR_CAST(css);
+
+ return css->cgroup;
+}
+
+/**
+ * cgroup_get_from_file - same as cgroup_v1v2_get_from_file, but only supports
+ * cgroup2.
+ * @f: file corresponding to cgroup2_dir
+ */
+static struct cgroup *cgroup_get_from_file(struct file *f)
+{
+ struct cgroup *cgrp = cgroup_v1v2_get_from_file(f);
+
+ if (IS_ERR(cgrp))
+ return ERR_CAST(cgrp);
+
+ if (!cgroup_on_dfl(cgrp)) {
+ cgroup_put(cgrp);
+ return ERR_PTR(-EBADF);
+ }
+
+ return cgrp;
+}
+
+/**
+ * cgroup_css_set_fork - find or create a css_set for a child process
+ * @kargs: the arguments passed to create the child process
+ *
+ * This functions finds or creates a new css_set which the child
+ * process will be attached to in cgroup_post_fork(). By default,
+ * the child process will be given the same css_set as its parent.
+ *
+ * If CLONE_INTO_CGROUP is specified this function will try to find an
+ * existing css_set which includes the requested cgroup and if not create
+ * a new css_set that the child will be attached to later. If this function
+ * succeeds it will hold cgroup_threadgroup_rwsem on return. If
+ * CLONE_INTO_CGROUP is requested this function will grab cgroup mutex
+ * before grabbing cgroup_threadgroup_rwsem and will hold a reference
+ * to the target cgroup.
+ */
+static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
+ __acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
+{
+ int ret;
+ struct cgroup *dst_cgrp = NULL;
+ struct css_set *cset;
+ struct super_block *sb;
+ struct file *f;
+
+ if (kargs->flags & CLONE_INTO_CGROUP)
+ cgroup_lock();
+
+ cgroup_threadgroup_change_begin(current);
+
+ spin_lock_irq(&css_set_lock);
+ cset = task_css_set(current);
+ get_css_set(cset);
+ spin_unlock_irq(&css_set_lock);
+
+ if (!(kargs->flags & CLONE_INTO_CGROUP)) {
+ kargs->cset = cset;
+ return 0;
+ }
+
+ f = fget_raw(kargs->cgroup);
+ if (!f) {
+ ret = -EBADF;
+ goto err;
+ }
+ sb = f->f_path.dentry->d_sb;
+
+ dst_cgrp = cgroup_get_from_file(f);
+ if (IS_ERR(dst_cgrp)) {
+ ret = PTR_ERR(dst_cgrp);
+ dst_cgrp = NULL;
+ goto err;
+ }
+
+ if (cgroup_is_dead(dst_cgrp)) {
+ ret = -ENODEV;
+ goto err;
+ }
+
+ /*
+ * Verify that we the target cgroup is writable for us. This is
+ * usually done by the vfs layer but since we're not going through
+ * the vfs layer here we need to do it "manually".
+ */
+ ret = cgroup_may_write(dst_cgrp, sb);
+ if (ret)
+ goto err;
+
+ /*
+ * Spawning a task directly into a cgroup works by passing a file
+ * descriptor to the target cgroup directory. This can even be an O_PATH
+ * file descriptor. But it can never be a cgroup.procs file descriptor.
+ * This was done on purpose so spawning into a cgroup could be
+ * conceptualized as an atomic
+ *
+ * fd = openat(dfd_cgroup, "cgroup.procs", ...);
+ * write(fd, <child-pid>, ...);
+ *
+ * sequence, i.e. it's a shorthand for the caller opening and writing
+ * cgroup.procs of the cgroup indicated by @dfd_cgroup. This allows us
+ * to always use the caller's credentials.
+ */
+ ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
+ !(kargs->flags & CLONE_THREAD),
+ current->nsproxy->cgroup_ns);
+ if (ret)
+ goto err;
+
+ kargs->cset = find_css_set(cset, dst_cgrp);
+ if (!kargs->cset) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ put_css_set(cset);
+ fput(f);
+ kargs->cgrp = dst_cgrp;
+ return ret;
+
+err:
+ cgroup_threadgroup_change_end(current);
+ cgroup_unlock();
+ if (f)
+ fput(f);
+ if (dst_cgrp)
+ cgroup_put(dst_cgrp);
+ put_css_set(cset);
+ if (kargs->cset)
+ put_css_set(kargs->cset);
+ return ret;
+}
+
+/**
+ * cgroup_css_set_put_fork - drop references we took during fork
+ * @kargs: the arguments passed to create the child process
+ *
+ * Drop references to the prepared css_set and target cgroup if
+ * CLONE_INTO_CGROUP was requested.
+ */
+static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
+ __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
+{
+ struct cgroup *cgrp = kargs->cgrp;
+ struct css_set *cset = kargs->cset;
+
+ cgroup_threadgroup_change_end(current);
+
+ if (cset) {
+ put_css_set(cset);
+ kargs->cset = NULL;
+ }
+
+ if (kargs->flags & CLONE_INTO_CGROUP) {
+ cgroup_unlock();
+ if (cgrp) {
+ cgroup_put(cgrp);
+ kargs->cgrp = NULL;
+ }
+ }
+}
+
+/**
+ * cgroup_can_fork - called on a new task before the process is exposed
+ * @child: the child process
+ * @kargs: the arguments passed to create the child process
+ *
+ * This prepares a new css_set for the child process which the child will
+ * be attached to in cgroup_post_fork().
+ * This calls the subsystem can_fork() callbacks. If the cgroup_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 kernel_clone_args *kargs)
+{
+ struct cgroup_subsys *ss;
+ int i, j, ret;
+
+ ret = cgroup_css_set_fork(kargs);
+ if (ret)
+ return ret;
+
+ do_each_subsys_mask(ss, i, have_canfork_callback) {
+ ret = ss->can_fork(child, kargs->cset);
+ 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, kargs->cset);
+ }
+
+ cgroup_css_set_put_fork(kargs);
+
+ return ret;
+}
+
+/**
+ * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
+ * @child: the child process
+ * @kargs: the arguments passed to create the child process
+ *
+ * This calls the cancel_fork() callbacks if a fork failed *after*
+ * cgroup_can_fork() succeeded and cleans up references we took to
+ * prepare a new css_set for the child process in cgroup_can_fork().
+ */
+void cgroup_cancel_fork(struct task_struct *child,
+ struct kernel_clone_args *kargs)
+{
+ struct cgroup_subsys *ss;
+ int i;
+
+ for_each_subsys(ss, i)
+ if (ss->cancel_fork)
+ ss->cancel_fork(child, kargs->cset);
+
+ cgroup_css_set_put_fork(kargs);
+}
+
+/**
+ * cgroup_post_fork - finalize cgroup setup for the child process
+ * @child: the child process
+ * @kargs: the arguments passed to create the child process
+ *
+ * Attach the child process to its css_set calling the subsystem fork()
+ * callbacks.
+ */
+void cgroup_post_fork(struct task_struct *child,
+ struct kernel_clone_args *kargs)
+ __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
+{
+ unsigned long cgrp_flags = 0;
+ bool kill = false;
+ struct cgroup_subsys *ss;
+ struct css_set *cset;
+ int i;
+
+ cset = kargs->cset;
+ kargs->cset = NULL;
+
+ spin_lock_irq(&css_set_lock);
+
+ /* init tasks are special, only link regular threads */
+ if (likely(child->pid)) {
+ if (kargs->cgrp)
+ cgrp_flags = kargs->cgrp->flags;
+ else
+ cgrp_flags = cset->dfl_cgrp->flags;
+
+ WARN_ON_ONCE(!list_empty(&child->cg_list));
+ cset->nr_tasks++;
+ css_set_move_task(child, NULL, cset, false);
+ } else {
+ put_css_set(cset);
+ cset = NULL;
+ }
+
+ if (!(child->flags & PF_KTHREAD)) {
+ if (unlikely(test_bit(CGRP_FREEZE, &cgrp_flags))) {
+ /*
+ * If the cgroup has to be frozen, the new task has
+ * too. Let's set the JOBCTL_TRAP_FREEZE jobctl bit to
+ * get the task into the frozen state.
+ */
+ spin_lock(&child->sighand->siglock);
+ WARN_ON_ONCE(child->frozen);
+ child->jobctl |= JOBCTL_TRAP_FREEZE;
+ spin_unlock(&child->sighand->siglock);
+
+ /*
+ * Calling cgroup_update_frozen() isn't required here,
+ * because it will be called anyway a bit later from
+ * do_freezer_trap(). So we avoid cgroup's transient
+ * switch from the frozen state and back.
+ */
+ }
+
+ /*
+ * If the cgroup is to be killed notice it now and take the
+ * child down right after we finished preparing it for
+ * userspace.
+ */
+ kill = test_bit(CGRP_KILL, &cgrp_flags);
+ }
+
+ 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();
+
+ /* Make the new cset the root_cset of the new cgroup namespace. */
+ if (kargs->flags & CLONE_NEWCGROUP) {
+ struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset;
+
+ get_css_set(cset);
+ child->nsproxy->cgroup_ns->root_cset = cset;
+ put_css_set(rcset);
+ }
+
+ /* Cgroup has to be killed so take down child immediately. */
+ if (unlikely(kill))
+ do_send_sig_info(SIGKILL, SEND_SIG_NOINFO, child, PIDTYPE_TGID);
+
+ cgroup_css_set_put_fork(kargs);
+}
+
+/**
+ * cgroup_exit - detach cgroup from exiting task
+ * @tsk: pointer to task_struct of exiting process
+ *
+ * Description: Detach cgroup from @tsk.
+ *
+ */
+void cgroup_exit(struct task_struct *tsk)
+{
+ struct cgroup_subsys *ss;
+ struct css_set *cset;
+ int i;
+
+ spin_lock_irq(&css_set_lock);
+
+ WARN_ON_ONCE(list_empty(&tsk->cg_list));
+ cset = task_css_set(tsk);
+ css_set_move_task(tsk, cset, NULL, false);
+ list_add_tail(&tsk->cg_list, &cset->dying_tasks);
+ cset->nr_tasks--;
+
+ if (dl_task(tsk))
+ dec_dl_tasks_cs(tsk);
+
+ WARN_ON_ONCE(cgroup_task_frozen(tsk));
+ if (unlikely(!(tsk->flags & PF_KTHREAD) &&
+ test_bit(CGRP_FREEZE, &task_dfl_cgroup(tsk)->flags)))
+ cgroup_update_frozen(task_dfl_cgroup(tsk));
+
+ spin_unlock_irq(&css_set_lock);
+
+ /* see cgroup_post_fork() for details */
+ do_each_subsys_mask(ss, i, have_exit_callback) {
+ ss->exit(tsk);
+ } while_each_subsys_mask();
+}
+
+void cgroup_release(struct task_struct *task)
+{
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ do_each_subsys_mask(ss, ssid, have_release_callback) {
+ ss->release(task);
+ } while_each_subsys_mask();
+
+ spin_lock_irq(&css_set_lock);
+ css_set_skip_task_iters(task_css_set(task), task);
+ list_del_init(&task->cg_list);
+ spin_unlock_irq(&css_set_lock);
+}
+
+void cgroup_free(struct task_struct *task)
+{
+ struct css_set *cset = task_css_set(task);
+ 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;
+
+ static_branch_disable(cgroup_subsys_enabled_key[i]);
+ pr_info("Disabling %s control group subsystem\n",
+ ss->name);
+ }
+
+ for (i = 0; i < OPT_FEATURE_COUNT; i++) {
+ if (strcmp(token, cgroup_opt_feature_names[i]))
+ continue;
+ cgroup_feature_disable_mask |= 1 << i;
+ pr_info("Disabling %s control group feature\n",
+ cgroup_opt_feature_names[i]);
+ break;
+ }
+ }
+ return 1;
+}
+__setup("cgroup_disable=", cgroup_disable);
+
+void __init __weak enable_debug_cgroup(void) { }
+
+static int __init enable_cgroup_debug(char *str)
+{
+ cgroup_debug = true;
+ enable_debug_cgroup();
+ return 1;
+}
+__setup("cgroup_debug", enable_cgroup_debug);
+
+/**
+ * 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 doesn't exist or if the cgroup has already
+ * been released 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 = ERR_PTR(-ENOENT);
+ struct cgroup *root_cgrp;
+
+ root_cgrp = current_cgns_cgroup_dfl();
+ kn = kernfs_walk_and_get(root_cgrp->kn, path);
+ if (!kn)
+ goto out;
+
+ if (kernfs_type(kn) != KERNFS_DIR) {
+ cgrp = ERR_PTR(-ENOTDIR);
+ goto out_kernfs;
+ }
+
+ rcu_read_lock();
+
+ cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
+ if (!cgrp || !cgroup_tryget(cgrp))
+ cgrp = ERR_PTR(-ENOENT);
+
+ rcu_read_unlock();
+
+out_kernfs:
+ kernfs_put(kn);
+out:
+ return cgrp;
+}
+EXPORT_SYMBOL_GPL(cgroup_get_from_path);
+
+/**
+ * cgroup_v1v2_get_from_fd - get a cgroup pointer from a fd
+ * @fd: fd obtained by open(cgroup_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_v1v2_get_from_fd(int fd)
+{
+ struct cgroup *cgrp;
+ struct fd f = fdget_raw(fd);
+ if (!f.file)
+ return ERR_PTR(-EBADF);
+
+ cgrp = cgroup_v1v2_get_from_file(f.file);
+ fdput(f);
+ return cgrp;
+}
+
+/**
+ * cgroup_get_from_fd - same as cgroup_v1v2_get_from_fd, but only supports
+ * cgroup2.
+ * @fd: fd obtained by open(cgroup2_dir)
+ */
+struct cgroup *cgroup_get_from_fd(int fd)
+{
+ struct cgroup *cgrp = cgroup_v1v2_get_from_fd(fd);
+
+ if (IS_ERR(cgrp))
+ return ERR_CAST(cgrp);
+
+ if (!cgroup_on_dfl(cgrp)) {
+ cgroup_put(cgrp);
+ return ERR_PTR(-EBADF);
+ }
+ return cgrp;
+}
+EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
+
+static u64 power_of_ten(int power)
+{
+ u64 v = 1;
+ while (power--)
+ v *= 10;
+ return v;
+}
+
+/**
+ * cgroup_parse_float - parse a floating number
+ * @input: input string
+ * @dec_shift: number of decimal digits to shift
+ * @v: output
+ *
+ * Parse a decimal floating point number in @input and store the result in
+ * @v with decimal point right shifted @dec_shift times. For example, if
+ * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345.
+ * Returns 0 on success, -errno otherwise.
+ *
+ * There's nothing cgroup specific about this function except that it's
+ * currently the only user.
+ */
+int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v)
+{
+ s64 whole, frac = 0;
+ int fstart = 0, fend = 0, flen;
+
+ if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend))
+ return -EINVAL;
+ if (frac < 0)
+ return -EINVAL;
+
+ flen = fend > fstart ? fend - fstart : 0;
+ if (flen < dec_shift)
+ frac *= power_of_ten(dec_shift - flen);
+ else
+ frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift));
+
+ *v = whole * power_of_ten(dec_shift) + frac;
+ return 0;
+}
+
+/*
+ * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
+ * definition in cgroup-defs.h.
+ */
+#ifdef CONFIG_SOCK_CGROUP_DATA
+
+void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
+{
+ struct cgroup *cgroup;
+
+ rcu_read_lock();
+ /* Don't associate the sock with unrelated interrupted task's cgroup. */
+ if (in_interrupt()) {
+ cgroup = &cgrp_dfl_root.cgrp;
+ cgroup_get(cgroup);
+ goto out;
+ }
+
+ while (true) {
+ struct css_set *cset;
+
+ cset = task_css_set(current);
+ if (likely(cgroup_tryget(cset->dfl_cgrp))) {
+ cgroup = cset->dfl_cgrp;
+ break;
+ }
+ cpu_relax();
+ }
+out:
+ skcd->cgroup = cgroup;
+ cgroup_bpf_get(cgroup);
+ rcu_read_unlock();
+}
+
+void cgroup_sk_clone(struct sock_cgroup_data *skcd)
+{
+ struct cgroup *cgrp = sock_cgroup_ptr(skcd);
+
+ /*
+ * 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(cgrp);
+ cgroup_bpf_get(cgrp);
+}
+
+void cgroup_sk_free(struct sock_cgroup_data *skcd)
+{
+ struct cgroup *cgrp = sock_cgroup_ptr(skcd);
+
+ cgroup_bpf_put(cgrp);
+ cgroup_put(cgrp);
+}
+
+#endif /* CONFIG_SOCK_CGROUP_DATA */
+
+#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 (WARN_ON(ret >= size))
+ 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 + ret,
+ PAGE_SIZE - ret, NULL);
+ if (cgroup_psi_enabled())
+ ret += show_delegatable_files(cgroup_psi_files, buf + ret,
+ 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"
+ "favordynmods\n"
+ "memory_localevents\n"
+ "memory_recursiveprot\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 */