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