--- /dev/null
+/*
+ * 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 <linux/cgroup.h>
+#include <linux/cred.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/init_task.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/magic.h>
+#include <linux/mm.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/rwsem.h>
+#include <linux/string.h>
+#include <linux/sort.h>
+#include <linux/kmod.h>
+#include <linux/delayacct.h>
+#include <linux/cgroupstats.h>
+#include <linux/hashtable.h>
+#include <linux/pid_namespace.h>
+#include <linux/idr.h>
+#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
+#include <linux/kthread.h>
+#include <linux/delay.h>
+
+#include <linux/atomic.h>
+
+/*
+ * pidlists linger the following amount before being destroyed. The goal
+ * is avoiding frequent destruction in the middle of consecutive read calls
+ * Expiring in the middle is a performance problem not a correctness one.
+ * 1 sec should be enough.
+ */
+#define CGROUP_PIDLIST_DESTROY_DELAY HZ
+
+#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_rwsem 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.
+ */
+#ifdef CONFIG_PROVE_RCU
+DEFINE_MUTEX(cgroup_mutex);
+DECLARE_RWSEM(css_set_rwsem);
+EXPORT_SYMBOL_GPL(cgroup_mutex);
+EXPORT_SYMBOL_GPL(css_set_rwsem);
+#else
+static DEFINE_MUTEX(cgroup_mutex);
+static DECLARE_RWSEM(css_set_rwsem);
+#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_subsys->release_agent_path. Modifying it also requires
+ * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
+ */
+static DEFINE_SPINLOCK(release_agent_path_lock);
+
+#define cgroup_assert_mutex_or_rcu_locked() \
+ rcu_lockdep_assert(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;
+
+/*
+ * pidlist destructions need to be flushed on cgroup destruction. Use a
+ * separate workqueue as flush domain.
+ */
+static struct workqueue_struct *cgroup_pidlist_destroy_wq;
+
+/* generate an array of cgroup subsystem pointers */
+#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
+static 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
+
+/*
+ * 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;
+
+/*
+ * The default hierarchy always exists but is hidden until mounted for the
+ * first time. This is for backward compatibility.
+ */
+static bool cgrp_dfl_root_visible;
+
+/*
+ * Set by the boot param of the same name and makes subsystems with NULL
+ * ->dfl_files to use ->legacy_files on the default hierarchy.
+ */
+static bool cgroup_legacy_files_on_dfl;
+
+/* some controllers are not supported in the default hierarchy */
+static unsigned int cgrp_dfl_root_inhibit_ss_mask;
+
+/* The list of hierarchy roots */
+
+static 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;
+
+/* This flag indicates whether tasks in the fork and exit paths should
+ * check for fork/exit handlers to call. This avoids us having to do
+ * extra work in the fork/exit path if none of the subsystems need to
+ * be called.
+ */
+static int need_forkexit_callback __read_mostly;
+
+static struct cftype cgroup_dfl_base_files[];
+static struct cftype cgroup_legacy_base_files[];
+
+static int rebind_subsystems(struct cgroup_root *dst_root,
+ unsigned int ss_mask);
+static int cgroup_destroy_locked(struct cgroup *cgrp);
+static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
+ bool visible);
+static void css_release(struct percpu_ref *ref);
+static void kill_css(struct cgroup_subsys_state *css);
+static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
+ bool is_add);
+
+/* 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);
+ 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;
+}
+
+/**
+ * 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 effctive 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;
+
+ if (!(cgrp->root->subsys_mask & (1 << ss->id)))
+ return NULL;
+
+ /*
+ * This function is used while updating css associations and thus
+ * can't test the csses directly. Use ->child_subsys_mask.
+ */
+ while (cgroup_parent(cgrp) &&
+ !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id)))
+ cgrp = cgroup_parent(cgrp);
+
+ 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;
+}
+
+/* convenient tests for these bits */
+static inline bool cgroup_is_dead(const struct cgroup *cgrp)
+{
+ return !(cgrp->self.flags & CSS_ONLINE);
+}
+
+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);
+
+/**
+ * cgroup_is_descendant - test ancestry
+ * @cgrp: the cgroup to be tested
+ * @ancestor: possible ancestor of @cgrp
+ *
+ * Test whether @cgrp is a descendant of @ancestor. It also returns %true
+ * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
+ * and @ancestor are accessible.
+ */
+bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
+{
+ while (cgrp) {
+ if (cgrp == ancestor)
+ return true;
+ cgrp = cgroup_parent(cgrp);
+ }
+ return false;
+}
+
+static int notify_on_release(const struct cgroup *cgrp)
+{
+ return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
+}
+
+/**
+ * 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
+
+/**
+ * for_each_subsys - iterate all enabled cgroup subsystems
+ * @ss: the iteration cursor
+ * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
+ */
+#define for_each_subsys(ss, ssid) \
+ for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
+ (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
+
+/* iterate across the hierarchies */
+#define for_each_root(root) \
+ list_for_each_entry((root), &cgroup_roots, root_list)
+
+/* 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
+
+static void cgroup_release_agent(struct work_struct *work);
+static void check_for_release(struct cgroup *cgrp);
+
+/*
+ * A cgroup can be associated with multiple css_sets as different tasks may
+ * belong to different cgroups on different hierarchies. In the other
+ * direction, a css_set is naturally associated with multiple cgroups.
+ * This M:N relationship is represented by the following link structure
+ * which exists for each association and allows traversing the associations
+ * from both sides.
+ */
+struct cgrp_cset_link {
+ /* the cgroup and css_set this link associates */
+ struct cgroup *cgrp;
+ struct css_set *cset;
+
+ /* list of cgrp_cset_links anchored at cgrp->cset_links */
+ struct list_head cset_link;
+
+ /* list of cgrp_cset_links anchored at css_set->cgrp_links */
+ struct list_head cgrp_link;
+};
+
+/*
+ * 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),
+ .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
+ .tasks = LIST_HEAD_INIT(init_css_set.tasks),
+ .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
+ .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 */
+
+/**
+ * cgroup_update_populated - updated populated count of a cgroup
+ * @cgrp: the target cgroup
+ * @populated: inc or dec populated count
+ *
+ * @cgrp is either getting the first task (css_set) 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 are empty.
+ *
+ * @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_rwsem);
+
+ do {
+ bool trigger;
+
+ if (populated)
+ trigger = !cgrp->populated_cnt++;
+ else
+ trigger = !--cgrp->populated_cnt;
+
+ if (!trigger)
+ break;
+
+ if (cgrp->populated_kn)
+ kernfs_notify(cgrp->populated_kn);
+ cgrp = cgroup_parent(cgrp);
+ } while (cgrp);
+}
+
+/*
+ * 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;
+}
+
+static 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_rwsem);
+
+ if (!atomic_dec_and_test(&cset->refcount))
+ return;
+
+ /* This css_set is dead. unlink it and release cgroup refcounts */
+ for_each_subsys(ss, ssid)
+ list_del(&cset->e_cset_node[ssid]);
+ hash_del(&cset->hlist);
+ css_set_count--;
+
+ list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
+ struct cgroup *cgrp = link->cgrp;
+
+ list_del(&link->cset_link);
+ list_del(&link->cgrp_link);
+
+ /* @cgrp can't go away while we're holding css_set_rwsem */
+ if (list_empty(&cgrp->cset_links)) {
+ cgroup_update_populated(cgrp, false);
+ check_for_release(cgrp);
+ }
+
+ kfree(link);
+ }
+
+ kfree_rcu(cset, rcu_head);
+}
+
+static void put_css_set(struct css_set *cset)
+{
+ /*
+ * Ensure that the refcount doesn't hit zero while any readers
+ * can see it. Similar to atomic_dec_and_lock(), but for an
+ * rwlock
+ */
+ if (atomic_add_unless(&cset->refcount, -1, 1))
+ return;
+
+ down_write(&css_set_rwsem);
+ put_css_set_locked(cset);
+ up_write(&css_set_rwsem);
+}
+
+/*
+ * refcounted get/put for css_set objects
+ */
+static inline void get_css_set(struct css_set *cset)
+{
+ atomic_inc(&cset->refcount);
+}
+
+/**
+ * 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;
+
+ if (list_empty(&cgrp->cset_links))
+ cgroup_update_populated(cgrp, true);
+ list_move(&link->cset_link, &cgrp->cset_links);
+
+ /*
+ * Always add links to the tail of the list so that the list
+ * is sorted by order of hierarchy creation
+ */
+ list_add_tail(&link->cgrp_link, &cset->cgrp_links);
+}
+
+/**
+ * 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 */
+ down_read(&css_set_rwsem);
+ cset = find_existing_css_set(old_cset, cgrp, template);
+ if (cset)
+ get_css_set(cset);
+ up_read(&css_set_rwsem);
+
+ 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->cgrp_links);
+ INIT_LIST_HEAD(&cset->tasks);
+ INIT_LIST_HEAD(&cset->mg_tasks);
+ INIT_LIST_HEAD(&cset->mg_preload_node);
+ INIT_LIST_HEAD(&cset->mg_node);
+ INIT_HLIST_NODE(&cset->hlist);
+
+ /* Copy the set of subsystem state objects generated in
+ * find_existing_css_set() */
+ memcpy(cset->subsys, template, sizeof(cset->subsys));
+
+ down_write(&css_set_rwsem);
+ /* 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)
+ list_add_tail(&cset->e_cset_node[ssid],
+ &cset->subsys[ssid]->cgroup->e_csets[ssid]);
+
+ up_write(&css_set_rwsem);
+
+ return cset;
+}
+
+static 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);
+
+ if (root->hierarchy_id) {
+ idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
+ root->hierarchy_id = 0;
+ }
+}
+
+static void cgroup_free_root(struct cgroup_root *root)
+{
+ if (root) {
+ /* hierarhcy ID shoulid already have been released */
+ WARN_ON_ONCE(root->hierarchy_id);
+
+ 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;
+
+ mutex_lock(&cgroup_mutex);
+
+ BUG_ON(atomic_read(&root->nr_cgrps));
+ BUG_ON(!list_empty(&cgrp->self.children));
+
+ /* Rebind all subsystems back to the default hierarchy */
+ rebind_subsystems(&cgrp_dfl_root, root->subsys_mask);
+
+ /*
+ * Release all the links from cset_links to this hierarchy's
+ * root cgroup
+ */
+ down_write(&css_set_rwsem);
+
+ 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);
+ }
+ up_write(&css_set_rwsem);
+
+ 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 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_rwsem);
+
+ 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_rwsem held.
+ */
+static 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 int cgroup_populate_dir(struct cgroup *cgrp, unsigned int subsys_mask);
+static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
+static const struct file_operations proc_cgroupstats_operations;
+
+static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
+ char *buf)
+{
+ if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
+ !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
+ snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
+ cft->ss->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
+ *
+ * returns cft->mode if ->mode is not 0
+ * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
+ * returns S_IRUGO if it has only a read handler
+ * returns S_IWUSR if it has only a write hander
+ */
+static umode_t cgroup_file_mode(const struct cftype *cft)
+{
+ umode_t mode = 0;
+
+ if (cft->mode)
+ return cft->mode;
+
+ if (cft->read_u64 || cft->read_s64 || cft->seq_show)
+ mode |= S_IRUGO;
+
+ if (cft->write_u64 || cft->write_s64 || cft->write)
+ mode |= S_IWUSR;
+
+ return mode;
+}
+
+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);
+}
+
+static void cgroup_put(struct cgroup *cgrp)
+{
+ css_put(&cgrp->self);
+}
+
+/**
+ * cgroup_calc_child_subsys_mask - calculate child_subsys_mask
+ * @cgrp: the target cgroup
+ * @subtree_control: the new subtree_control mask to consider
+ *
+ * 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 to @cgrp. The returned mask is always
+ * a superset of @subtree_control and follows the usual hierarchy rules.
+ */
+static unsigned int cgroup_calc_child_subsys_mask(struct cgroup *cgrp,
+ unsigned int subtree_control)
+{
+ struct cgroup *parent = cgroup_parent(cgrp);
+ unsigned int cur_ss_mask = subtree_control;
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ if (!cgroup_on_dfl(cgrp))
+ return cur_ss_mask;
+
+ while (true) {
+ unsigned int new_ss_mask = cur_ss_mask;
+
+ for_each_subsys(ss, ssid)
+ if (cur_ss_mask & (1 << ssid))
+ new_ss_mask |= ss->depends_on;
+
+ /*
+ * Mask out subsystems which aren't available. This can
+ * happen only if some depended-upon subsystems were bound
+ * to non-default hierarchies.
+ */
+ if (parent)
+ new_ss_mask &= parent->child_subsys_mask;
+ else
+ new_ss_mask &= cgrp->root->subsys_mask;
+
+ if (new_ss_mask == cur_ss_mask)
+ break;
+ cur_ss_mask = new_ss_mask;
+ }
+
+ return cur_ss_mask;
+}
+
+/**
+ * cgroup_refresh_child_subsys_mask - update child_subsys_mask
+ * @cgrp: the target cgroup
+ *
+ * Update @cgrp->child_subsys_mask according to the current
+ * @cgrp->subtree_control using cgroup_calc_child_subsys_mask().
+ */
+static void cgroup_refresh_child_subsys_mask(struct cgroup *cgrp)
+{
+ cgrp->child_subsys_mask =
+ cgroup_calc_child_subsys_mask(cgrp, cgrp->subtree_control);
+}
+
+/**
+ * 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.
+ */
+static 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
+ *
+ * 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.
+ *
+ * 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.
+ */
+static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
+{
+ 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);
+
+ 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);
+ kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
+}
+
+/**
+ * cgroup_clear_dir - remove subsys files in a cgroup directory
+ * @cgrp: target cgroup
+ * @subsys_mask: mask of the subsystem ids whose files should be removed
+ */
+static void cgroup_clear_dir(struct cgroup *cgrp, unsigned int subsys_mask)
+{
+ struct cgroup_subsys *ss;
+ int i;
+
+ for_each_subsys(ss, i) {
+ struct cftype *cfts;
+
+ if (!(subsys_mask & (1 << i)))
+ continue;
+ list_for_each_entry(cfts, &ss->cfts, node)
+ cgroup_addrm_files(cgrp, cfts, false);
+ }
+}
+
+static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask)
+{
+ struct cgroup_subsys *ss;
+ unsigned int tmp_ss_mask;
+ int ssid, i, ret;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ for_each_subsys(ss, ssid) {
+ if (!(ss_mask & (1 << ssid)))
+ continue;
+
+ /* if @ss has non-root csses attached to it, can't move */
+ if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)))
+ return -EBUSY;
+
+ /* can't move between two non-dummy roots either */
+ if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
+ return -EBUSY;
+ }
+
+ /* skip creating root files on dfl_root for inhibited subsystems */
+ tmp_ss_mask = ss_mask;
+ if (dst_root == &cgrp_dfl_root)
+ tmp_ss_mask &= ~cgrp_dfl_root_inhibit_ss_mask;
+
+ ret = cgroup_populate_dir(&dst_root->cgrp, tmp_ss_mask);
+ if (ret) {
+ if (dst_root != &cgrp_dfl_root)
+ return ret;
+
+ /*
+ * Rebinding back to the default root is not allowed to
+ * fail. Using both default and non-default roots should
+ * be rare. Moving subsystems back and forth even more so.
+ * Just warn about it and continue.
+ */
+ if (cgrp_dfl_root_visible) {
+ pr_warn("failed to create files (%d) while rebinding 0x%x to default root\n",
+ ret, ss_mask);
+ pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
+ }
+ }
+
+ /*
+ * Nothing can fail from this point on. Remove files for the
+ * removed subsystems and rebind each subsystem.
+ */
+ for_each_subsys(ss, ssid)
+ if (ss_mask & (1 << ssid))
+ cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
+
+ for_each_subsys(ss, ssid) {
+ struct cgroup_root *src_root;
+ struct cgroup_subsys_state *css;
+ struct css_set *cset;
+
+ if (!(ss_mask & (1 << ssid)))
+ continue;
+
+ src_root = ss->root;
+ css = cgroup_css(&src_root->cgrp, ss);
+
+ WARN_ON(!css || cgroup_css(&dst_root->cgrp, ss));
+
+ RCU_INIT_POINTER(src_root->cgrp.subsys[ssid], NULL);
+ rcu_assign_pointer(dst_root->cgrp.subsys[ssid], css);
+ ss->root = dst_root;
+ css->cgroup = &dst_root->cgrp;
+
+ down_write(&css_set_rwsem);
+ hash_for_each(css_set_table, i, cset, hlist)
+ list_move_tail(&cset->e_cset_node[ss->id],
+ &dst_root->cgrp.e_csets[ss->id]);
+ up_write(&css_set_rwsem);
+
+ src_root->subsys_mask &= ~(1 << ssid);
+ src_root->cgrp.subtree_control &= ~(1 << ssid);
+ cgroup_refresh_child_subsys_mask(&src_root->cgrp);
+
+ /* default hierarchy doesn't enable controllers by default */
+ dst_root->subsys_mask |= 1 << ssid;
+ if (dst_root != &cgrp_dfl_root) {
+ dst_root->cgrp.subtree_control |= 1 << ssid;
+ cgroup_refresh_child_subsys_mask(&dst_root->cgrp);
+ }
+
+ if (ss->bind)
+ ss->bind(css);
+ }
+
+ kernfs_activate(dst_root->cgrp.kn);
+ return 0;
+}
+
+static int cgroup_show_options(struct seq_file *seq,
+ struct kernfs_root *kf_root)
+{
+ struct cgroup_root *root = cgroup_root_from_kf(kf_root);
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ for_each_subsys(ss, ssid)
+ if (root->subsys_mask & (1 << ssid))
+ seq_printf(seq, ",%s", ss->name);
+ if (root->flags & CGRP_ROOT_NOPREFIX)
+ seq_puts(seq, ",noprefix");
+ if (root->flags & CGRP_ROOT_XATTR)
+ seq_puts(seq, ",xattr");
+
+ spin_lock(&release_agent_path_lock);
+ if (strlen(root->release_agent_path))
+ seq_printf(seq, ",release_agent=%s", root->release_agent_path);
+ spin_unlock(&release_agent_path_lock);
+
+ if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
+ seq_puts(seq, ",clone_children");
+ if (strlen(root->name))
+ seq_printf(seq, ",name=%s", root->name);
+ return 0;
+}
+
+struct cgroup_sb_opts {
+ unsigned int subsys_mask;
+ unsigned int flags;
+ char *release_agent;
+ bool cpuset_clone_children;
+ char *name;
+ /* User explicitly requested empty subsystem */
+ bool none;
+};
+
+static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
+{
+ char *token, *o = data;
+ bool all_ss = false, one_ss = false;
+ unsigned int mask = -1U;
+ struct cgroup_subsys *ss;
+ int nr_opts = 0;
+ int i;
+
+#ifdef CONFIG_CPUSETS
+ mask = ~(1U << cpuset_cgrp_id);
+#endif
+
+ memset(opts, 0, sizeof(*opts));
+
+ while ((token = strsep(&o, ",")) != NULL) {
+ nr_opts++;
+
+ if (!*token)
+ return -EINVAL;
+ if (!strcmp(token, "none")) {
+ /* Explicitly have no subsystems */
+ opts->none = true;
+ continue;
+ }
+ if (!strcmp(token, "all")) {
+ /* Mutually exclusive option 'all' + subsystem name */
+ if (one_ss)
+ return -EINVAL;
+ all_ss = true;
+ continue;
+ }
+ if (!strcmp(token, "__DEVEL__sane_behavior")) {
+ opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
+ continue;
+ }
+ if (!strcmp(token, "noprefix")) {
+ opts->flags |= CGRP_ROOT_NOPREFIX;
+ continue;
+ }
+ if (!strcmp(token, "clone_children")) {
+ opts->cpuset_clone_children = true;
+ continue;
+ }
+ if (!strcmp(token, "xattr")) {
+ opts->flags |= CGRP_ROOT_XATTR;
+ continue;
+ }
+ if (!strncmp(token, "release_agent=", 14)) {
+ /* Specifying two release agents is forbidden */
+ if (opts->release_agent)
+ return -EINVAL;
+ opts->release_agent =
+ kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
+ if (!opts->release_agent)
+ return -ENOMEM;
+ continue;
+ }
+ if (!strncmp(token, "name=", 5)) {
+ const char *name = token + 5;
+ /* Can't specify an empty name */
+ if (!strlen(name))
+ return -EINVAL;
+ /* Must match [\w.-]+ */
+ for (i = 0; i < strlen(name); i++) {
+ char c = name[i];
+ if (isalnum(c))
+ continue;
+ if ((c == '.') || (c == '-') || (c == '_'))
+ continue;
+ return -EINVAL;
+ }
+ /* Specifying two names is forbidden */
+ if (opts->name)
+ return -EINVAL;
+ opts->name = kstrndup(name,
+ MAX_CGROUP_ROOT_NAMELEN - 1,
+ GFP_KERNEL);
+ if (!opts->name)
+ return -ENOMEM;
+
+ continue;
+ }
+
+ for_each_subsys(ss, i) {
+ if (strcmp(token, ss->name))
+ continue;
+ if (ss->disabled)
+ continue;
+
+ /* Mutually exclusive option 'all' + subsystem name */
+ if (all_ss)
+ return -EINVAL;
+ opts->subsys_mask |= (1 << i);
+ one_ss = true;
+
+ break;
+ }
+ if (i == CGROUP_SUBSYS_COUNT)
+ return -ENOENT;
+ }
+
+ if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
+ pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
+ if (nr_opts != 1) {
+ pr_err("sane_behavior: no other mount options allowed\n");
+ return -EINVAL;
+ }
+ return 0;
+ }
+
+ /*
+ * If the 'all' option was specified select all the subsystems,
+ * otherwise if 'none', 'name=' and a subsystem name options were
+ * not specified, let's default to 'all'
+ */
+ if (all_ss || (!one_ss && !opts->none && !opts->name))
+ for_each_subsys(ss, i)
+ if (!ss->disabled)
+ opts->subsys_mask |= (1 << i);
+
+ /*
+ * We either have to specify by name or by subsystems. (So all
+ * empty hierarchies must have a name).
+ */
+ if (!opts->subsys_mask && !opts->name)
+ return -EINVAL;
+
+ /*
+ * Option noprefix was introduced just for backward compatibility
+ * with the old cpuset, so we allow noprefix only if mounting just
+ * the cpuset subsystem.
+ */
+ if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
+ return -EINVAL;
+
+ /* Can't specify "none" and some subsystems */
+ if (opts->subsys_mask && opts->none)
+ return -EINVAL;
+
+ return 0;
+}
+
+static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
+{
+ int ret = 0;
+ struct cgroup_root *root = cgroup_root_from_kf(kf_root);
+ struct cgroup_sb_opts opts;
+ unsigned int added_mask, removed_mask;
+
+ if (root == &cgrp_dfl_root) {
+ pr_err("remount is not allowed\n");
+ return -EINVAL;
+ }
+
+ mutex_lock(&cgroup_mutex);
+
+ /* See what subsystems are wanted */
+ ret = parse_cgroupfs_options(data, &opts);
+ if (ret)
+ goto out_unlock;
+
+ if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
+ pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
+ task_tgid_nr(current), current->comm);
+
+ added_mask = opts.subsys_mask & ~root->subsys_mask;
+ removed_mask = root->subsys_mask & ~opts.subsys_mask;
+
+ /* Don't allow flags or name to change at remount */
+ if ((opts.flags ^ root->flags) ||
+ (opts.name && strcmp(opts.name, root->name))) {
+ pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
+ opts.flags, opts.name ?: "", root->flags, root->name);
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ /* remounting is not allowed for populated hierarchies */
+ if (!list_empty(&root->cgrp.self.children)) {
+ ret = -EBUSY;
+ goto out_unlock;
+ }
+
+ ret = rebind_subsystems(root, added_mask);
+ if (ret)
+ goto out_unlock;
+
+ rebind_subsystems(&cgrp_dfl_root, removed_mask);
+
+ if (opts.release_agent) {
+ spin_lock(&release_agent_path_lock);
+ strcpy(root->release_agent_path, opts.release_agent);
+ spin_unlock(&release_agent_path_lock);
+ }
+ out_unlock:
+ kfree(opts.release_agent);
+ kfree(opts.name);
+ mutex_unlock(&cgroup_mutex);
+ return ret;
+}
+
+/*
+ * 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;
+
+ down_write(&css_set_rwsem);
+
+ 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().
+ */
+ spin_lock_irq(&p->sighand->siglock);
+ if (!(p->flags & PF_EXITING)) {
+ struct css_set *cset = task_css_set(p);
+
+ list_add(&p->cg_list, &cset->tasks);
+ get_css_set(cset);
+ }
+ spin_unlock_irq(&p->sighand->siglock);
+ } while_each_thread(g, p);
+ read_unlock(&tasklist_lock);
+out_unlock:
+ up_write(&css_set_rwsem);
+}
+
+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, cgroup_release_agent);
+}
+
+static 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);
+}
+
+static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask)
+{
+ LIST_HEAD(tmp_links);
+ struct cgroup *root_cgrp = &root->cgrp;
+ struct cftype *base_files;
+ struct css_set *cset;
+ int i, ret;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_NOWAIT);
+ if (ret < 0)
+ goto out;
+ root_cgrp->id = 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_rwsem here,
+ * but that's OK - it can only be increased by someone holding
+ * cgroup_lock, and that's us. The worst that can happen is that we
+ * have some link structures left over
+ */
+ ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
+ if (ret)
+ goto cancel_ref;
+
+ ret = cgroup_init_root_id(root);
+ if (ret)
+ goto cancel_ref;
+
+ root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
+ 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;
+
+ if (root == &cgrp_dfl_root)
+ base_files = cgroup_dfl_base_files;
+ else
+ base_files = cgroup_legacy_base_files;
+
+ ret = cgroup_addrm_files(root_cgrp, base_files, true);
+ if (ret)
+ goto destroy_root;
+
+ ret = rebind_subsystems(root, ss_mask);
+ if (ret)
+ goto destroy_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.
+ */
+ down_write(&css_set_rwsem);
+ hash_for_each(css_set_table, i, cset, hlist)
+ link_css_set(&tmp_links, cset, root_cgrp);
+ up_write(&css_set_rwsem);
+
+ 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;
+}
+
+static struct dentry *cgroup_mount(struct file_system_type *fs_type,
+ int flags, const char *unused_dev_name,
+ void *data)
+{
+ struct super_block *pinned_sb = NULL;
+ struct cgroup_subsys *ss;
+ struct cgroup_root *root;
+ struct cgroup_sb_opts opts;
+ struct dentry *dentry;
+ int ret;
+ int i;
+ bool new_sb;
+
+ /*
+ * 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();
+
+ mutex_lock(&cgroup_mutex);
+
+ /* First find the desired set of subsystems */
+ ret = parse_cgroupfs_options(data, &opts);
+ if (ret)
+ goto out_unlock;
+
+ /* look for a matching existing root */
+ if (opts.flags & CGRP_ROOT_SANE_BEHAVIOR) {
+ cgrp_dfl_root_visible = true;
+ root = &cgrp_dfl_root;
+ cgroup_get(&root->cgrp);
+ ret = 0;
+ goto out_unlock;
+ }
+
+ /*
+ * Destruction of cgroup root is asynchronous, so subsystems may
+ * still be dying after the previous unmount. Let's drain the
+ * dying subsystems. We just need to ensure that the ones
+ * unmounted previously finish dying and don't care about new ones
+ * starting. Testing ref liveliness is good enough.
+ */
+ for_each_subsys(ss, i) {
+ if (!(opts.subsys_mask & (1 << i)) ||
+ ss->root == &cgrp_dfl_root)
+ continue;
+
+ if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
+ mutex_unlock(&cgroup_mutex);
+ msleep(10);
+ ret = restart_syscall();
+ goto out_free;
+ }
+ cgroup_put(&ss->root->cgrp);
+ }
+
+ for_each_root(root) {
+ bool name_match = false;
+
+ if (root == &cgrp_dfl_root)
+ continue;
+
+ /*
+ * If we asked for a name then it must match. Also, if
+ * name matches but sybsys_mask doesn't, we should fail.
+ * Remember whether name matched.
+ */
+ if (opts.name) {
+ if (strcmp(opts.name, root->name))
+ continue;
+ name_match = true;
+ }
+
+ /*
+ * If we asked for subsystems (or explicitly for no
+ * subsystems) then they must match.
+ */
+ if ((opts.subsys_mask || opts.none) &&
+ (opts.subsys_mask != root->subsys_mask)) {
+ if (!name_match)
+ continue;
+ ret = -EBUSY;
+ goto out_unlock;
+ }
+
+ if (root->flags ^ opts.flags)
+ pr_warn("new mount options do not match the existing superblock, will be ignored\n");
+
+ /*
+ * We want to reuse @root whose lifetime is governed by its
+ * ->cgrp. Let's check whether @root is alive and keep it
+ * that way. As cgroup_kill_sb() can happen anytime, we
+ * want to block it by pinning the sb so that @root doesn't
+ * get killed before mount is complete.
+ *
+ * With the sb pinned, tryget_live can reliably indicate
+ * whether @root can be reused. If it's being killed,
+ * drain it. We can use wait_queue for the wait but this
+ * path is super cold. Let's just sleep a bit and retry.
+ */
+ pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
+ if (IS_ERR(pinned_sb) ||
+ !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
+ mutex_unlock(&cgroup_mutex);
+ if (!IS_ERR_OR_NULL(pinned_sb))
+ deactivate_super(pinned_sb);
+ msleep(10);
+ ret = restart_syscall();
+ goto out_free;
+ }
+
+ ret = 0;
+ goto out_unlock;
+ }
+
+ /*
+ * No such thing, create a new one. name= matching without subsys
+ * specification is allowed for already existing hierarchies but we
+ * can't create new one without subsys specification.
+ */
+ if (!opts.subsys_mask && !opts.none) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ root = kzalloc(sizeof(*root), GFP_KERNEL);
+ if (!root) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ init_cgroup_root(root, &opts);
+
+ ret = cgroup_setup_root(root, opts.subsys_mask);
+ if (ret)
+ cgroup_free_root(root);
+
+out_unlock:
+ mutex_unlock(&cgroup_mutex);
+out_free:
+ kfree(opts.release_agent);
+ kfree(opts.name);
+
+ if (ret)
+ return ERR_PTR(ret);
+
+ dentry = kernfs_mount(fs_type, flags, root->kf_root,
+ CGROUP_SUPER_MAGIC, &new_sb);
+ if (IS_ERR(dentry) || !new_sb)
+ cgroup_put(&root->cgrp);
+
+ /*
+ * If @pinned_sb, we're reusing an existing root and holding an
+ * extra ref on its sb. Mount is complete. Put the extra ref.
+ */
+ if (pinned_sb) {
+ WARN_ON(new_sb);
+ deactivate_super(pinned_sb);
+ }
+
+ 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);
+}
+
+static struct file_system_type cgroup_fs_type = {
+ .name = "cgroup",
+ .mount = cgroup_mount,
+ .kill_sb = cgroup_kill_sb,
+};
+
+/**
+ * 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().
+ */
+char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
+{
+ struct cgroup_root *root;
+ struct cgroup *cgrp;
+ int hierarchy_id = 1;
+ char *path = NULL;
+
+ mutex_lock(&cgroup_mutex);
+ down_read(&css_set_rwsem);
+
+ root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
+
+ if (root) {
+ cgrp = task_cgroup_from_root(task, root);
+ path = cgroup_path(cgrp, buf, buflen);
+ } else {
+ /* if no hierarchy exists, everyone is in "/" */
+ if (strlcpy(buf, "/", buflen) < buflen)
+ path = buf;
+ }
+
+ up_read(&css_set_rwsem);
+ mutex_unlock(&cgroup_mutex);
+ return path;
+}
+EXPORT_SYMBOL_GPL(task_cgroup_path);
+
+/* used to track tasks and other necessary states during migration */
+struct cgroup_taskset {
+ /* the src and dst cset list running through cset->mg_node */
+ struct list_head src_csets;
+ struct list_head dst_csets;
+
+ /*
+ * Fields for cgroup_taskset_*() iteration.
+ *
+ * Before migration is committed, the target migration tasks are on
+ * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
+ * the csets on ->dst_csets. ->csets point to either ->src_csets
+ * or ->dst_csets depending on whether migration is committed.
+ *
+ * ->cur_csets and ->cur_task point to the current task position
+ * during iteration.
+ */
+ struct list_head *csets;
+ struct css_set *cur_cset;
+ struct task_struct *cur_task;
+};
+
+/**
+ * cgroup_taskset_first - reset taskset and return the first task
+ * @tset: taskset of interest
+ *
+ * @tset iteration is initialized and the first task is returned.
+ */
+struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
+{
+ tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
+ tset->cur_task = NULL;
+
+ return cgroup_taskset_next(tset);
+}
+
+/**
+ * cgroup_taskset_next - iterate to the next task in taskset
+ * @tset: taskset of interest
+ *
+ * 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 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;
+ return task;
+ }
+
+ cset = list_next_entry(cset, mg_node);
+ task = NULL;
+ }
+
+ return NULL;
+}
+
+/**
+ * cgroup_task_migrate - move a task from one cgroup to another.
+ * @old_cgrp: the cgroup @tsk is being migrated from
+ * @tsk: the task being migrated
+ * @new_cset: the new css_set @tsk is being attached to
+ *
+ * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
+ */
+static void cgroup_task_migrate(struct cgroup *old_cgrp,
+ struct task_struct *tsk,
+ struct css_set *new_cset)
+{
+ struct css_set *old_cset;
+
+ lockdep_assert_held(&cgroup_mutex);
+ lockdep_assert_held(&css_set_rwsem);
+
+ /*
+ * We are synchronized through threadgroup_lock() 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(tsk->flags & PF_EXITING);
+ old_cset = task_css_set(tsk);
+
+ get_css_set(new_cset);
+ rcu_assign_pointer(tsk->cgroups, new_cset);
+
+ /*
+ * Use move_tail so that cgroup_taskset_first() still returns the
+ * leader after migration. This works because cgroup_migrate()
+ * ensures that the dst_cset of the leader is the first on the
+ * tset's dst_csets list.
+ */
+ list_move_tail(&tsk->cg_list, &new_cset->mg_tasks);
+
+ /*
+ * We just gained a reference on old_cset by taking it from the
+ * task. As trading it for new_cset is protected by cgroup_mutex,
+ * we're safe to drop it here; it will be freed under RCU.
+ */
+ put_css_set_locked(old_cset);
+}
+
+/**
+ * cgroup_migrate_finish - cleanup after attach
+ * @preloaded_csets: list of preloaded css_sets
+ *
+ * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
+ * those functions for details.
+ */
+static void cgroup_migrate_finish(struct list_head *preloaded_csets)
+{
+ struct css_set *cset, *tmp_cset;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ down_write(&css_set_rwsem);
+ list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
+ cset->mg_src_cgrp = NULL;
+ cset->mg_dst_cset = NULL;
+ list_del_init(&cset->mg_preload_node);
+ put_css_set_locked(cset);
+ }
+ up_write(&css_set_rwsem);
+}
+
+/**
+ * cgroup_migrate_add_src - add a migration source css_set
+ * @src_cset: the source css_set to add
+ * @dst_cgrp: the destination cgroup
+ * @preloaded_csets: list of preloaded css_sets
+ *
+ * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
+ * @src_cset and add it to @preloaded_csets, which should later be cleaned
+ * up by cgroup_migrate_finish().
+ *
+ * This function may be called without holding threadgroup_lock 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.
+ */
+static void cgroup_migrate_add_src(struct css_set *src_cset,
+ struct cgroup *dst_cgrp,
+ struct list_head *preloaded_csets)
+{
+ struct cgroup *src_cgrp;
+
+ lockdep_assert_held(&cgroup_mutex);
+ lockdep_assert_held(&css_set_rwsem);
+
+ 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(!list_empty(&src_cset->mg_tasks));
+ WARN_ON(!list_empty(&src_cset->mg_node));
+
+ src_cset->mg_src_cgrp = src_cgrp;
+ get_css_set(src_cset);
+ list_add(&src_cset->mg_preload_node, preloaded_csets);
+}
+
+/**
+ * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
+ * @dst_cgrp: the destination cgroup (may be %NULL)
+ * @preloaded_csets: list of preloaded source css_sets
+ *
+ * Tasks are about to be moved to @dst_cgrp and all the source css_sets
+ * have been preloaded to @preloaded_csets. This function looks up and
+ * pins all destination css_sets, links each to its source, and append them
+ * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
+ * source css_set is assumed to be its cgroup on the default hierarchy.
+ *
+ * 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
+ * @preloaded_csets.
+ */
+static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
+ struct list_head *preloaded_csets)
+{
+ LIST_HEAD(csets);
+ struct css_set *src_cset, *tmp_cset;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ /*
+ * Except for the root, child_subsys_mask must be zero for a cgroup
+ * with tasks so that child cgroups don't compete against tasks.
+ */
+ if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
+ dst_cgrp->child_subsys_mask)
+ return -EBUSY;
+
+ /* look up the dst cset for each src cset and link it to src */
+ list_for_each_entry_safe(src_cset, tmp_cset, preloaded_csets, mg_preload_node) {
+ struct css_set *dst_cset;
+
+ dst_cset = find_css_set(src_cset,
+ dst_cgrp ?: src_cset->dfl_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;
+ 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(&dst_cset->mg_preload_node, &csets);
+ else
+ put_css_set(dst_cset);
+ }
+
+ list_splice_tail(&csets, preloaded_csets);
+ return 0;
+err:
+ cgroup_migrate_finish(&csets);
+ return -ENOMEM;
+}
+
+/**
+ * cgroup_migrate - migrate a process or task to a cgroup
+ * @cgrp: the destination cgroup
+ * @leader: the leader of the process or the task to migrate
+ * @threadgroup: whether @leader points to the whole process or a single task
+ *
+ * Migrate a process or task denoted by @leader to @cgrp. If migrating a
+ * process, the caller must be holding threadgroup_lock of @leader. 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.
+ */
+static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader,
+ bool threadgroup)
+{
+ struct cgroup_taskset tset = {
+ .src_csets = LIST_HEAD_INIT(tset.src_csets),
+ .dst_csets = LIST_HEAD_INIT(tset.dst_csets),
+ .csets = &tset.src_csets,
+ };
+ struct cgroup_subsys_state *css, *failed_css = NULL;
+ struct css_set *cset, *tmp_cset;
+ struct task_struct *task, *tmp_task;
+ int i, ret;
+
+ /*
+ * 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.
+ */
+ down_write(&css_set_rwsem);
+ rcu_read_lock();
+ task = leader;
+ do {
+ /* @task either already exited or can't exit until the end */
+ if (task->flags & PF_EXITING)
+ goto next;
+
+ /* leave @task alone if post_fork() hasn't linked it yet */
+ if (list_empty(&task->cg_list))
+ goto next;
+
+ cset = task_css_set(task);
+ if (!cset->mg_src_cgrp)
+ goto next;
+
+ /*
+ * cgroup_taskset_first() must always return the leader.
+ * Take care to avoid disturbing the ordering.
+ */
+ list_move_tail(&task->cg_list, &cset->mg_tasks);
+ if (list_empty(&cset->mg_node))
+ list_add_tail(&cset->mg_node, &tset.src_csets);
+ if (list_empty(&cset->mg_dst_cset->mg_node))
+ list_move_tail(&cset->mg_dst_cset->mg_node,
+ &tset.dst_csets);
+ next:
+ if (!threadgroup)
+ break;
+ } while_each_thread(leader, task);
+ rcu_read_unlock();
+ up_write(&css_set_rwsem);
+
+ /* 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 */
+ for_each_e_css(css, i, cgrp) {
+ if (css->ss->can_attach) {
+ ret = css->ss->can_attach(css, &tset);
+ if (ret) {
+ failed_css = css;
+ goto out_cancel_attach;
+ }
+ }
+ }
+
+ /*
+ * 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.
+ */
+ down_write(&css_set_rwsem);
+ list_for_each_entry(cset, &tset.src_csets, mg_node) {
+ list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list)
+ cgroup_task_migrate(cset->mg_src_cgrp, task,
+ cset->mg_dst_cset);
+ }
+ up_write(&css_set_rwsem);
+
+ /*
+ * 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;
+
+ for_each_e_css(css, i, cgrp)
+ if (css->ss->attach)
+ css->ss->attach(css, &tset);
+
+ ret = 0;
+ goto out_release_tset;
+
+out_cancel_attach:
+ for_each_e_css(css, i, cgrp) {
+ if (css == failed_css)
+ break;
+ if (css->ss->cancel_attach)
+ css->ss->cancel_attach(css, &tset);
+ }
+out_release_tset:
+ down_write(&css_set_rwsem);
+ 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);
+ }
+ up_write(&css_set_rwsem);
+ return ret;
+}
+
+/**
+ * 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 threadgroup_lock of @leader.
+ */
+static int cgroup_attach_task(struct cgroup *dst_cgrp,
+ struct task_struct *leader, bool threadgroup)
+{
+ LIST_HEAD(preloaded_csets);
+ struct task_struct *task;
+ int ret;
+
+ /* look up all src csets */
+ down_read(&css_set_rwsem);
+ rcu_read_lock();
+ task = leader;
+ do {
+ cgroup_migrate_add_src(task_css_set(task), dst_cgrp,
+ &preloaded_csets);
+ if (!threadgroup)
+ break;
+ } while_each_thread(leader, task);
+ rcu_read_unlock();
+ up_read(&css_set_rwsem);
+
+ /* prepare dst csets and commit */
+ ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets);
+ if (!ret)
+ ret = cgroup_migrate(dst_cgrp, leader, threadgroup);
+
+ cgroup_migrate_finish(&preloaded_csets);
+ 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.
+ */
+static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off, bool threadgroup)
+{
+ struct task_struct *tsk;
+ const struct cred *cred = current_cred(), *tcred;
+ struct cgroup *cgrp;
+ pid_t pid;
+ int ret;
+
+ if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
+ return -EINVAL;
+
+ cgrp = cgroup_kn_lock_live(of->kn);
+ if (!cgrp)
+ return -ENODEV;
+
+retry_find_task:
+ rcu_read_lock();
+ if (pid) {
+ tsk = find_task_by_vpid(pid);
+ if (!tsk) {
+ rcu_read_unlock();
+ ret = -ESRCH;
+ goto out_unlock_cgroup;
+ }
+ /*
+ * even if we're attaching all tasks in the thread group, we
+ * only need to check permissions on one of them.
+ */
+ tcred = __task_cred(tsk);
+ if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
+ !uid_eq(cred->euid, tcred->uid) &&
+ !uid_eq(cred->euid, tcred->suid)) {
+ rcu_read_unlock();
+ ret = -EACCES;
+ goto out_unlock_cgroup;
+ }
+ } 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;
+ rcu_read_unlock();
+ goto out_unlock_cgroup;
+ }
+
+ get_task_struct(tsk);
+ rcu_read_unlock();
+
+ threadgroup_lock(tsk);
+ if (threadgroup) {
+ if (!thread_group_leader(tsk)) {
+ /*
+ * a race with de_thread from another thread's exec()
+ * may strip us of our leadership, if this happens,
+ * there is no choice but to throw this task away and
+ * try again; this is
+ * "double-double-toil-and-trouble-check locking".
+ */
+ threadgroup_unlock(tsk);
+ put_task_struct(tsk);
+ goto retry_find_task;
+ }
+ }
+
+ ret = cgroup_attach_task(cgrp, tsk, threadgroup);
+
+ threadgroup_unlock(tsk);
+
+ put_task_struct(tsk);
+out_unlock_cgroup:
+ cgroup_kn_unlock(of->kn);
+ return ret ?: nbytes;
+}
+
+/**
+ * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
+ * @from: attach to all cgroups of a given task
+ * @tsk: the task to be attached
+ */
+int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
+{
+ struct cgroup_root *root;
+ int retval = 0;
+
+ mutex_lock(&cgroup_mutex);
+ for_each_root(root) {
+ struct cgroup *from_cgrp;
+
+ if (root == &cgrp_dfl_root)
+ continue;
+
+ down_read(&css_set_rwsem);
+ from_cgrp = task_cgroup_from_root(from, root);
+ up_read(&css_set_rwsem);
+
+ retval = cgroup_attach_task(from_cgrp, tsk, false);
+ if (retval)
+ break;
+ }
+ mutex_unlock(&cgroup_mutex);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
+
+static ssize_t cgroup_tasks_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ return __cgroup_procs_write(of, buf, nbytes, off, false);
+}
+
+static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ return __cgroup_procs_write(of, buf, nbytes, off, true);
+}
+
+static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct cgroup *cgrp;
+
+ BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
+
+ cgrp = cgroup_kn_lock_live(of->kn);
+ if (!cgrp)
+ return -ENODEV;
+ spin_lock(&release_agent_path_lock);
+ strlcpy(cgrp->root->release_agent_path, strstrip(buf),
+ sizeof(cgrp->root->release_agent_path));
+ spin_unlock(&release_agent_path_lock);
+ cgroup_kn_unlock(of->kn);
+ return nbytes;
+}
+
+static int cgroup_release_agent_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+
+ spin_lock(&release_agent_path_lock);
+ seq_puts(seq, cgrp->root->release_agent_path);
+ spin_unlock(&release_agent_path_lock);
+ seq_putc(seq, '\n');
+ return 0;
+}
+
+static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
+{
+ seq_puts(seq, "0\n");
+ return 0;
+}
+
+static void cgroup_print_ss_mask(struct seq_file *seq, unsigned int ss_mask)
+{
+ struct cgroup_subsys *ss;
+ bool printed = false;
+ int ssid;
+
+ for_each_subsys(ss, ssid) {
+ if (ss_mask & (1 << ssid)) {
+ if (printed)
+ seq_putc(seq, ' ');
+ seq_printf(seq, "%s", ss->name);
+ printed = true;
+ }
+ }
+ if (printed)
+ seq_putc(seq, '\n');
+}
+
+/* show controllers which are currently attached to the default hierarchy */
+static int cgroup_root_controllers_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+
+ cgroup_print_ss_mask(seq, cgrp->root->subsys_mask &
+ ~cgrp_dfl_root_inhibit_ss_mask);
+ return 0;
+}
+
+/* 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_parent(cgrp)->subtree_control);
+ 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 child_subsys_mask has changed and its subtree's (self excluded)
+ * 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)
+{
+ LIST_HEAD(preloaded_csets);
+ struct cgroup_subsys_state *css;
+ struct css_set *src_cset;
+ int ret;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ /* look up all csses currently attached to @cgrp's subtree */
+ down_read(&css_set_rwsem);
+ css_for_each_descendant_pre(css, cgroup_css(cgrp, NULL)) {
+ struct cgrp_cset_link *link;
+
+ /* self is not affected by child_subsys_mask change */
+ if (css->cgroup == cgrp)
+ continue;
+
+ list_for_each_entry(link, &css->cgroup->cset_links, cset_link)
+ cgroup_migrate_add_src(link->cset, cgrp,
+ &preloaded_csets);
+ }
+ up_read(&css_set_rwsem);
+
+ /* NULL dst indicates self on default hierarchy */
+ ret = cgroup_migrate_prepare_dst(NULL, &preloaded_csets);
+ if (ret)
+ goto out_finish;
+
+ list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) {
+ struct task_struct *last_task = NULL, *task;
+
+ /* src_csets precede dst_csets, break on the first dst_cset */
+ if (!src_cset->mg_src_cgrp)
+ break;
+
+ /*
+ * All tasks in src_cset need to be migrated to the
+ * matching dst_cset. Empty it process by process. We
+ * walk tasks but migrate processes. The leader might even
+ * belong to a different cset but such src_cset would also
+ * be among the target src_csets because the default
+ * hierarchy enforces per-process membership.
+ */
+ while (true) {
+ down_read(&css_set_rwsem);
+ task = list_first_entry_or_null(&src_cset->tasks,
+ struct task_struct, cg_list);
+ if (task) {
+ task = task->group_leader;
+ WARN_ON_ONCE(!task_css_set(task)->mg_src_cgrp);
+ get_task_struct(task);
+ }
+ up_read(&css_set_rwsem);
+
+ if (!task)
+ break;
+
+ /* guard against possible infinite loop */
+ if (WARN(last_task == task,
+ "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
+ goto out_finish;
+ last_task = task;
+
+ threadgroup_lock(task);
+ /* raced against de_thread() from another thread? */
+ if (!thread_group_leader(task)) {
+ threadgroup_unlock(task);
+ put_task_struct(task);
+ continue;
+ }
+
+ ret = cgroup_migrate(src_cset->dfl_cgrp, task, true);
+
+ threadgroup_unlock(task);
+ put_task_struct(task);
+
+ if (WARN(ret, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret))
+ goto out_finish;
+ }
+ }
+
+out_finish:
+ cgroup_migrate_finish(&preloaded_csets);
+ return ret;
+}
+
+/* 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)
+{
+ unsigned int enable = 0, disable = 0;
+ unsigned int css_enable, css_disable, old_sc, new_sc, old_ss, new_ss;
+ 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;
+ for_each_subsys(ss, ssid) {
+ if (ss->disabled || strcmp(tok + 1, ss->name) ||
+ ((1 << ss->id) & cgrp_dfl_root_inhibit_ss_mask))
+ continue;
+
+ if (*tok == '+') {
+ enable |= 1 << ssid;
+ disable &= ~(1 << ssid);
+ } else if (*tok == '-') {
+ disable |= 1 << ssid;
+ enable &= ~(1 << ssid);
+ } else {
+ return -EINVAL;
+ }
+ break;
+ }
+ if (ssid == CGROUP_SUBSYS_COUNT)
+ return -EINVAL;
+ }
+
+ cgrp = cgroup_kn_lock_live(of->kn);
+ if (!cgrp)
+ return -ENODEV;
+
+ for_each_subsys(ss, ssid) {
+ if (enable & (1 << ssid)) {
+ if (cgrp->subtree_control & (1 << ssid)) {
+ enable &= ~(1 << ssid);
+ continue;
+ }
+
+ /* unavailable or not enabled on the parent? */
+ if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
+ (cgroup_parent(cgrp) &&
+ !(cgroup_parent(cgrp)->subtree_control & (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) && !list_empty(&cgrp->cset_links)) {
+ ret = -EBUSY;
+ goto out_unlock;
+ }
+
+ /*
+ * Update subsys masks and calculate what needs to be done. More
+ * subsystems than specified may need to be enabled or disabled
+ * depending on subsystem dependencies.
+ */
+ old_sc = cgrp->subtree_control;
+ old_ss = cgrp->child_subsys_mask;
+ new_sc = (old_sc | enable) & ~disable;
+ new_ss = cgroup_calc_child_subsys_mask(cgrp, new_sc);
+
+ css_enable = ~old_ss & new_ss;
+ css_disable = old_ss & ~new_ss;
+ enable |= css_enable;
+ disable |= css_disable;
+
+ /*
+ * Because css offlining is asynchronous, userland might try to
+ * re-enable the same controller while the previous instance is
+ * still around. In such cases, wait till it's gone using
+ * offline_waitq.
+ */
+ for_each_subsys(ss, ssid) {
+ if (!(css_enable & (1 << ssid)))
+ continue;
+
+ cgroup_for_each_live_child(child, cgrp) {
+ DEFINE_WAIT(wait);
+
+ if (!cgroup_css(child, ss))
+ continue;
+
+ cgroup_get(child);
+ prepare_to_wait(&child->offline_waitq, &wait,
+ TASK_UNINTERRUPTIBLE);
+ cgroup_kn_unlock(of->kn);
+ schedule();
+ finish_wait(&child->offline_waitq, &wait);
+ cgroup_put(child);
+
+ return restart_syscall();
+ }
+ }
+
+ cgrp->subtree_control = new_sc;
+ cgrp->child_subsys_mask = new_ss;
+
+ /*
+ * 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.
+ */
+ for_each_subsys(ss, ssid) {
+ if (!(enable & (1 << ssid)))
+ continue;
+
+ cgroup_for_each_live_child(child, cgrp) {
+ if (css_enable & (1 << ssid))
+ ret = create_css(child, ss,
+ cgrp->subtree_control & (1 << ssid));
+ else
+ ret = cgroup_populate_dir(child, 1 << ssid);
+ if (ret)
+ goto err_undo_css;
+ }
+ }
+
+ /*
+ * 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)
+ goto err_undo_css;
+
+ /*
+ * All tasks are migrated out of disabled csses. Kill or hide
+ * them. 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.
+ */
+ for_each_subsys(ss, ssid) {
+ if (!(disable & (1 << ssid)))
+ continue;
+
+ cgroup_for_each_live_child(child, cgrp) {
+ struct cgroup_subsys_state *css = cgroup_css(child, ss);
+
+ if (css_disable & (1 << ssid)) {
+ kill_css(css);
+ } else {
+ cgroup_clear_dir(child, 1 << ssid);
+ if (ss->css_reset)
+ ss->css_reset(css);
+ }
+ }
+ }
+
+ /*
+ * The effective csses of all the descendants (excluding @cgrp) may
+ * have changed. Subsystems can optionally subscribe to this event
+ * by implementing ->css_e_css_changed() which is invoked if any of
+ * the effective csses seen from the css's cgroup may have changed.
+ */
+ for_each_subsys(ss, ssid) {
+ struct cgroup_subsys_state *this_css = cgroup_css(cgrp, ss);
+ struct cgroup_subsys_state *css;
+
+ if (!ss->css_e_css_changed || !this_css)
+ continue;
+
+ css_for_each_descendant_pre(css, this_css)
+ if (css != this_css)
+ ss->css_e_css_changed(css);
+ }
+
+ kernfs_activate(cgrp->kn);
+ ret = 0;
+out_unlock:
+ cgroup_kn_unlock(of->kn);
+ return ret ?: nbytes;
+
+err_undo_css:
+ cgrp->subtree_control = old_sc;
+ cgrp->child_subsys_mask = old_ss;
+
+ for_each_subsys(ss, ssid) {
+ if (!(enable & (1 << ssid)))
+ continue;
+
+ cgroup_for_each_live_child(child, cgrp) {
+ struct cgroup_subsys_state *css = cgroup_css(child, ss);
+
+ if (!css)
+ continue;
+
+ if (css_enable & (1 << ssid))
+ kill_css(css);
+ else
+ cgroup_clear_dir(child, 1 << ssid);
+ }
+ }
+ goto out_unlock;
+}
+
+static int cgroup_populated_show(struct seq_file *seq, void *v)
+{
+ seq_printf(seq, "%d\n", (bool)seq_css(seq)->cgroup->populated_cnt);
+ return 0;
+}
+
+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)
+{
+ 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,
+ .write = cgroup_file_write,
+ .seq_show = cgroup_seqfile_show,
+};
+
+static struct kernfs_ops cgroup_kf_ops = {
+ .atomic_write_len = PAGE_SIZE,
+ .write = cgroup_file_write,
+ .seq_start = cgroup_seqfile_start,
+ .seq_next = cgroup_seqfile_next,
+ .seq_stop = cgroup_seqfile_stop,
+ .seq_show = cgroup_seqfile_show,
+};
+
+/*
+ * cgroup_rename - Only allow simple rename of directories in place.
+ */
+static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
+ const char *new_name_str)
+{
+ struct cgroup *cgrp = kn->priv;
+ int ret;
+
+ if (kernfs_type(kn) != KERNFS_DIR)
+ return -ENOTDIR;
+ if (kn->parent != new_parent)
+ return -EIO;
+
+ /*
+ * This isn't a proper migration and its usefulness is very
+ * limited. Disallow on the default hierarchy.
+ */
+ if (cgroup_on_dfl(cgrp))
+ return -EPERM;
+
+ /*
+ * We're gonna grab cgroup_mutex which nests outside kernfs
+ * active_ref. kernfs_rename() doesn't require active_ref
+ * protection. Break them before grabbing cgroup_mutex.
+ */
+ kernfs_break_active_protection(new_parent);
+ kernfs_break_active_protection(kn);
+
+ mutex_lock(&cgroup_mutex);
+
+ ret = kernfs_rename(kn, new_parent, new_name_str);
+
+ mutex_unlock(&cgroup_mutex);
+
+ kernfs_unbreak_active_protection(kn);
+ kernfs_unbreak_active_protection(new_parent);
+ return ret;
+}
+
+/* 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 *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->seq_show == cgroup_populated_show)
+ cgrp->populated_kn = kn;
+ return 0;
+}
+
+/**
+ * cgroup_addrm_files - add or remove files to a cgroup directory
+ * @cgrp: the target 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. If addition fails, this
+ * function doesn't remove files already added. The caller is responsible
+ * for cleaning up.
+ */
+static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
+ bool is_add)
+{
+ struct cftype *cft;
+ int ret;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ for (cft = cfts; 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(cgrp, cft);
+ if (ret) {
+ pr_warn("%s: failed to add %s, err=%d\n",
+ __func__, cft->name, ret);
+ return ret;
+ }
+ } else {
+ cgroup_rm_file(cgrp, cft);
+ }
+ }
+ return 0;
+}
+
+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 (cgroup_is_dead(cgrp))
+ continue;
+
+ ret = cgroup_addrm_files(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 (ss->disabled)
+ 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;
+
+ /*
+ * If legacy_flies_on_dfl, we want to show the legacy files on the
+ * dfl hierarchy but iff the target subsystem hasn't been updated
+ * for the dfl hierarchy yet.
+ */
+ if (!cgroup_legacy_files_on_dfl ||
+ ss->dfl_cftypes != ss->legacy_cftypes) {
+ for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
+ cft->flags |= __CFTYPE_NOT_ON_DFL;
+ }
+
+ return cgroup_add_cftypes(ss, cfts);
+}
+
+/**
+ * cgroup_task_count - count the number of tasks in a cgroup.
+ * @cgrp: the cgroup in question
+ *
+ * Return the number of tasks in the cgroup.
+ */
+static int cgroup_task_count(const struct cgroup *cgrp)
+{
+ int count = 0;
+ struct cgrp_cset_link *link;
+
+ down_read(&css_set_rwsem);
+ list_for_each_entry(link, &cgrp->cset_links, cset_link)
+ count += atomic_read(&link->cset->refcount);
+ up_read(&css_set_rwsem);
+ return count;
+}
+
+/**
+ * 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_advance_task_iter - 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_advance_task_iter(struct css_task_iter *it)
+{
+ struct list_head *l = it->cset_pos;
+ struct cgrp_cset_link *link;
+ struct css_set *cset;
+
+ /* Advance to the next non-empty css_set */
+ do {
+ l = l->next;
+ if (l == it->cset_head) {
+ it->cset_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 (list_empty(&cset->tasks) && list_empty(&cset->mg_tasks));
+
+ 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;
+}
+
+/**
+ * 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.
+ *
+ * Note that this function acquires a lock which is released when the
+ * iteration finishes. The caller can't sleep while iteration is in
+ * progress.
+ */
+void css_task_iter_start(struct cgroup_subsys_state *css,
+ struct css_task_iter *it)
+ __acquires(css_set_rwsem)
+{
+ /* no one should try to iterate before mounting cgroups */
+ WARN_ON_ONCE(!use_task_css_set_links);
+
+ down_read(&css_set_rwsem);
+
+ 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_advance_task_iter(it);
+}
+
+/**
+ * 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)
+{
+ struct task_struct *res;
+ struct list_head *l = it->task_pos;
+
+ /* If the iterator cg is NULL, we have no tasks */
+ if (!it->cset_pos)
+ return NULL;
+ res = list_entry(l, struct task_struct, cg_list);
+
+ /*
+ * 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_advance_task_iter(it);
+ else
+ it->task_pos = l;
+
+ return res;
+}
+
+/**
+ * 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)
+ __releases(css_set_rwsem)
+{
+ up_read(&css_set_rwsem);
+}
+
+/**
+ * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
+ * @to: cgroup to which the tasks will be moved
+ * @from: cgroup in which the tasks currently reside
+ *
+ * Locking rules between cgroup_post_fork() and the migration path
+ * guarantee that, if a task is forking while being migrated, the new child
+ * is guaranteed to be either visible in the source cgroup after the
+ * parent's migration is complete or put into the target cgroup. No task
+ * can slip out of migration through forking.
+ */
+int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
+{
+ LIST_HEAD(preloaded_csets);
+ struct cgrp_cset_link *link;
+ struct css_task_iter it;
+ struct task_struct *task;
+ int ret;
+
+ mutex_lock(&cgroup_mutex);
+
+ /* all tasks in @from are being moved, all csets are source */
+ down_read(&css_set_rwsem);
+ list_for_each_entry(link, &from->cset_links, cset_link)
+ cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
+ up_read(&css_set_rwsem);
+
+ ret = cgroup_migrate_prepare_dst(to, &preloaded_csets);
+ if (ret)
+ goto out_err;
+
+ /*
+ * Migrate tasks one-by-one until @form is empty. This fails iff
+ * ->can_attach() fails.
+ */
+ do {
+ css_task_iter_start(&from->self, &it);
+ task = css_task_iter_next(&it);
+ if (task)
+ get_task_struct(task);
+ css_task_iter_end(&it);
+
+ if (task) {
+ ret = cgroup_migrate(to, task, false);
+ put_task_struct(task);
+ }
+ } while (task && !ret);
+out_err:
+ cgroup_migrate_finish(&preloaded_csets);
+ mutex_unlock(&cgroup_mutex);
+ return ret;
+}
+
+/*
+ * Stuff for reading the 'tasks'/'procs' files.
+ *
+ * Reading this file can return large amounts of data if a cgroup has
+ * *lots* of attached tasks. So it may need several calls to read(),
+ * but we cannot guarantee that the information we produce is correct
+ * unless we produce it entirely atomically.
+ *
+ */
+
+/* which pidlist file are we talking about? */
+enum cgroup_filetype {
+ CGROUP_FILE_PROCS,
+ CGROUP_FILE_TASKS,
+};
+
+/*
+ * A pidlist is a list of pids that virtually represents the contents of one
+ * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
+ * a pair (one each for procs, tasks) for each pid namespace that's relevant
+ * to the cgroup.
+ */
+struct cgroup_pidlist {
+ /*
+ * used to find which pidlist is wanted. doesn't change as long as
+ * this particular list stays in the list.
+ */
+ struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
+ /* array of xids */
+ pid_t *list;
+ /* how many elements the above list has */
+ int length;
+ /* each of these stored in a list by its cgroup */
+ struct list_head links;
+ /* pointer to the cgroup we belong to, for list removal purposes */
+ struct cgroup *owner;
+ /* for delayed destruction */
+ struct delayed_work destroy_dwork;
+};
+
+/*
+ * The following two functions "fix" the issue where there are more pids
+ * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
+ * TODO: replace with a kernel-wide solution to this problem
+ */
+#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
+static void *pidlist_allocate(int count)
+{
+ if (PIDLIST_TOO_LARGE(count))
+ return vmalloc(count * sizeof(pid_t));
+ else
+ return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
+}
+
+static void pidlist_free(void *p)
+{
+ kvfree(p);
+}
+
+/*
+ * Used to destroy all pidlists lingering waiting for destroy timer. None
+ * should be left afterwards.
+ */
+static void cgroup_pidlist_destroy_all(struct cgroup *cgrp)
+{
+ struct cgroup_pidlist *l, *tmp_l;
+
+ mutex_lock(&cgrp->pidlist_mutex);
+ list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
+ mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
+ mutex_unlock(&cgrp->pidlist_mutex);
+
+ flush_workqueue(cgroup_pidlist_destroy_wq);
+ BUG_ON(!list_empty(&cgrp->pidlists));
+}
+
+static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
+{
+ struct delayed_work *dwork = to_delayed_work(work);
+ struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
+ destroy_dwork);
+ struct cgroup_pidlist *tofree = NULL;
+
+ mutex_lock(&l->owner->pidlist_mutex);
+
+ /*
+ * Destroy iff we didn't get queued again. The state won't change
+ * as destroy_dwork can only be queued while locked.
+ */
+ if (!delayed_work_pending(dwork)) {
+ list_del(&l->links);
+ pidlist_free(l->list);
+ put_pid_ns(l->key.ns);
+ tofree = l;
+ }
+
+ mutex_unlock(&l->owner->pidlist_mutex);
+ kfree(tofree);
+}
+
+/*
+ * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
+ * Returns the number of unique elements.
+ */
+static int pidlist_uniq(pid_t *list, int length)
+{
+ int src, dest = 1;
+
+ /*
+ * we presume the 0th element is unique, so i starts at 1. trivial
+ * edge cases first; no work needs to be done for either
+ */
+ if (length == 0 || length == 1)
+ return length;
+ /* src and dest walk down the list; dest counts unique elements */
+ for (src = 1; src < length; src++) {
+ /* find next unique element */
+ while (list[src] == list[src-1]) {
+ src++;
+ if (src == length)
+ goto after;
+ }
+ /* dest always points to where the next unique element goes */
+ list[dest] = list[src];
+ dest++;
+ }
+after:
+ return dest;
+}
+
+/*
+ * The two pid files - task and cgroup.procs - guaranteed that the result
+ * is sorted, which forced this whole pidlist fiasco. As pid order is
+ * different per namespace, each namespace needs differently sorted list,
+ * making it impossible to use, for example, single rbtree of member tasks
+ * sorted by task pointer. As pidlists can be fairly large, allocating one
+ * per open file is dangerous, so cgroup had to implement shared pool of
+ * pidlists keyed by cgroup and namespace.
+ *
+ * All this extra complexity was caused by the original implementation
+ * committing to an entirely unnecessary property. In the long term, we
+ * want to do away with it. Explicitly scramble sort order if on the
+ * default hierarchy so that no such expectation exists in the new
+ * interface.
+ *
+ * Scrambling is done by swapping every two consecutive bits, which is
+ * non-identity one-to-one mapping which disturbs sort order sufficiently.
+ */
+static pid_t pid_fry(pid_t pid)
+{
+ unsigned a = pid & 0x55555555;
+ unsigned b = pid & 0xAAAAAAAA;
+
+ return (a << 1) | (b >> 1);
+}
+
+static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
+{
+ if (cgroup_on_dfl(cgrp))
+ return pid_fry(pid);
+ else
+ return pid;
+}
+
+static int cmppid(const void *a, const void *b)
+{
+ return *(pid_t *)a - *(pid_t *)b;
+}
+
+static int fried_cmppid(const void *a, const void *b)
+{
+ return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
+}
+
+static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
+ enum cgroup_filetype type)
+{
+ struct cgroup_pidlist *l;
+ /* don't need task_nsproxy() if we're looking at ourself */
+ struct pid_namespace *ns = task_active_pid_ns(current);
+
+ lockdep_assert_held(&cgrp->pidlist_mutex);
+
+ list_for_each_entry(l, &cgrp->pidlists, links)
+ if (l->key.type == type && l->key.ns == ns)
+ return l;
+ return NULL;
+}
+
+/*
+ * find the appropriate pidlist for our purpose (given procs vs tasks)
+ * returns with the lock on that pidlist already held, and takes care
+ * of the use count, or returns NULL with no locks held if we're out of
+ * memory.
+ */
+static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
+ enum cgroup_filetype type)
+{
+ struct cgroup_pidlist *l;
+
+ lockdep_assert_held(&cgrp->pidlist_mutex);
+
+ l = cgroup_pidlist_find(cgrp, type);
+ if (l)
+ return l;
+
+ /* entry not found; create a new one */
+ l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
+ if (!l)
+ return l;
+
+ INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
+ l->key.type = type;
+ /* don't need task_nsproxy() if we're looking at ourself */
+ l->key.ns = get_pid_ns(task_active_pid_ns(current));
+ l->owner = cgrp;
+ list_add(&l->links, &cgrp->pidlists);
+ return l;
+}
+
+/*
+ * Load a cgroup's pidarray with either procs' tgids or tasks' pids
+ */
+static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
+ struct cgroup_pidlist **lp)
+{
+ pid_t *array;
+ int length;
+ int pid, n = 0; /* used for populating the array */
+ struct css_task_iter it;
+ struct task_struct *tsk;
+ struct cgroup_pidlist *l;
+
+ lockdep_assert_held(&cgrp->pidlist_mutex);
+
+ /*
+ * If cgroup gets more users after we read count, we won't have
+ * enough space - tough. This race is indistinguishable to the
+ * caller from the case that the additional cgroup users didn't
+ * show up until sometime later on.
+ */
+ length = cgroup_task_count(cgrp);
+ array = pidlist_allocate(length);
+ if (!array)
+ return -ENOMEM;
+ /* now, populate the array */
+ css_task_iter_start(&cgrp->self, &it);
+ while ((tsk = css_task_iter_next(&it))) {
+ if (unlikely(n == length))
+ break;
+ /* get tgid or pid for procs or tasks file respectively */
+ if (type == CGROUP_FILE_PROCS)
+ pid = task_tgid_vnr(tsk);
+ else
+ pid = task_pid_vnr(tsk);
+ if (pid > 0) /* make sure to only use valid results */
+ array[n++] = pid;
+ }
+ css_task_iter_end(&it);
+ length = n;
+ /* now sort & (if procs) strip out duplicates */
+ if (cgroup_on_dfl(cgrp))
+ sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
+ else
+ sort(array, length, sizeof(pid_t), cmppid, NULL);
+ if (type == CGROUP_FILE_PROCS)
+ length = pidlist_uniq(array, length);
+
+ l = cgroup_pidlist_find_create(cgrp, type);
+ if (!l) {
+ pidlist_free(array);
+ return -ENOMEM;
+ }
+
+ /* store array, freeing old if necessary */
+ pidlist_free(l->list);
+ l->list = array;
+ l->length = length;
+ *lp = l;
+ return 0;
+}
+
+/**
+ * cgroupstats_build - build and fill cgroupstats
+ * @stats: cgroupstats to fill information into
+ * @dentry: A dentry entry belonging to the cgroup for which stats have
+ * been requested.
+ *
+ * Build and fill cgroupstats so that taskstats can export it to user
+ * space.
+ */
+int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
+{
+ struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
+ struct cgroup *cgrp;
+ struct css_task_iter it;
+ struct task_struct *tsk;
+
+ /* it should be kernfs_node belonging to cgroupfs and is a directory */
+ if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
+ kernfs_type(kn) != KERNFS_DIR)
+ return -EINVAL;
+
+ mutex_lock(&cgroup_mutex);
+
+ /*
+ * We aren't being called from kernfs and there's no guarantee on
+ * @kn->priv's validity. For this and css_tryget_online_from_dir(),
+ * @kn->priv is RCU safe. Let's do the RCU dancing.
+ */
+ rcu_read_lock();
+ cgrp = rcu_dereference(kn->priv);
+ if (!cgrp || cgroup_is_dead(cgrp)) {
+ rcu_read_unlock();
+ mutex_unlock(&cgroup_mutex);
+ return -ENOENT;
+ }
+ rcu_read_unlock();
+
+ css_task_iter_start(&cgrp->self, &it);
+ while ((tsk = css_task_iter_next(&it))) {
+ switch (tsk->state) {
+ case TASK_RUNNING:
+ stats->nr_running++;
+ break;
+ case TASK_INTERRUPTIBLE:
+ stats->nr_sleeping++;
+ break;
+ case TASK_UNINTERRUPTIBLE:
+ stats->nr_uninterruptible++;
+ break;
+ case TASK_STOPPED:
+ stats->nr_stopped++;
+ break;
+ default:
+ if (delayacct_is_task_waiting_on_io(tsk))
+ stats->nr_io_wait++;
+ break;
+ }
+ }
+ css_task_iter_end(&it);
+
+ mutex_unlock(&cgroup_mutex);
+ return 0;
+}
+
+
+/*
+ * seq_file methods for the tasks/procs files. The seq_file position is the
+ * next pid to display; the seq_file iterator is a pointer to the pid
+ * in the cgroup->l->list array.
+ */
+
+static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
+{
+ /*
+ * Initially we receive a position value that corresponds to
+ * one more than the last pid shown (or 0 on the first call or
+ * after a seek to the start). Use a binary-search to find the
+ * next pid to display, if any
+ */
+ struct kernfs_open_file *of = s->private;
+ struct cgroup *cgrp = seq_css(s)->cgroup;
+ struct cgroup_pidlist *l;
+ enum cgroup_filetype type = seq_cft(s)->private;
+ int index = 0, pid = *pos;
+ int *iter, ret;
+
+ mutex_lock(&cgrp->pidlist_mutex);
+
+ /*
+ * !NULL @of->priv indicates that this isn't the first start()
+ * after open. If the matching pidlist is around, we can use that.
+ * Look for it. Note that @of->priv can't be used directly. It
+ * could already have been destroyed.
+ */
+ if (of->priv)
+ of->priv = cgroup_pidlist_find(cgrp, type);
+
+ /*
+ * Either this is the first start() after open or the matching
+ * pidlist has been destroyed inbetween. Create a new one.
+ */
+ if (!of->priv) {
+ ret = pidlist_array_load(cgrp, type,
+ (struct cgroup_pidlist **)&of->priv);
+ if (ret)
+ return ERR_PTR(ret);
+ }
+ l = of->priv;
+
+ if (pid) {
+ int end = l->length;
+
+ while (index < end) {
+ int mid = (index + end) / 2;
+ if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
+ index = mid;
+ break;
+ } else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid)
+ index = mid + 1;
+ else
+ end = mid;
+ }
+ }
+ /* If we're off the end of the array, we're done */
+ if (index >= l->length)
+ return NULL;
+ /* Update the abstract position to be the actual pid that we found */
+ iter = l->list + index;
+ *pos = cgroup_pid_fry(cgrp, *iter);
+ return iter;
+}
+
+static void cgroup_pidlist_stop(struct seq_file *s, void *v)
+{
+ struct kernfs_open_file *of = s->private;
+ struct cgroup_pidlist *l = of->priv;
+
+ if (l)
+ mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
+ CGROUP_PIDLIST_DESTROY_DELAY);
+ mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
+}
+
+static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
+{
+ struct kernfs_open_file *of = s->private;
+ struct cgroup_pidlist *l = of->priv;
+ pid_t *p = v;
+ pid_t *end = l->list + l->length;
+ /*
+ * Advance to the next pid in the array. If this goes off the
+ * end, we're done
+ */
+ p++;
+ if (p >= end) {
+ return NULL;
+ } else {
+ *pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
+ return p;
+ }
+}
+
+static int cgroup_pidlist_show(struct seq_file *s, void *v)
+{
+ seq_printf(s, "%d\n", *(int *)v);
+
+ return 0;
+}
+
+static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return notify_on_release(css->cgroup);
+}
+
+static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
+ struct cftype *cft, u64 val)
+{
+ if (val)
+ set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
+ else
+ clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
+ return 0;
+}
+
+static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
+}
+
+static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
+ struct cftype *cft, u64 val)
+{
+ if (val)
+ set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
+ else
+ clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
+ return 0;
+}
+
+/* cgroup core interface files for the default hierarchy */
+static struct cftype cgroup_dfl_base_files[] = {
+ {
+ .name = "cgroup.procs",
+ .seq_start = cgroup_pidlist_start,
+ .seq_next = cgroup_pidlist_next,
+ .seq_stop = cgroup_pidlist_stop,
+ .seq_show = cgroup_pidlist_show,
+ .private = CGROUP_FILE_PROCS,
+ .write = cgroup_procs_write,
+ .mode = S_IRUGO | S_IWUSR,
+ },
+ {
+ .name = "cgroup.controllers",
+ .flags = CFTYPE_ONLY_ON_ROOT,
+ .seq_show = cgroup_root_controllers_show,
+ },
+ {
+ .name = "cgroup.controllers",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cgroup_controllers_show,
+ },
+ {
+ .name = "cgroup.subtree_control",
+ .seq_show = cgroup_subtree_control_show,
+ .write = cgroup_subtree_control_write,
+ },
+ {
+ .name = "cgroup.populated",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cgroup_populated_show,
+ },
+ { } /* terminate */
+};
+
+/* cgroup core interface files for the legacy hierarchies */
+static struct cftype cgroup_legacy_base_files[] = {
+ {
+ .name = "cgroup.procs",
+ .seq_start = cgroup_pidlist_start,
+ .seq_next = cgroup_pidlist_next,
+ .seq_stop = cgroup_pidlist_stop,
+ .seq_show = cgroup_pidlist_show,
+ .private = CGROUP_FILE_PROCS,
+ .write = cgroup_procs_write,
+ .mode = S_IRUGO | S_IWUSR,
+ },
+ {
+ .name = "cgroup.clone_children",
+ .read_u64 = cgroup_clone_children_read,
+ .write_u64 = cgroup_clone_children_write,
+ },
+ {
+ .name = "cgroup.sane_behavior",
+ .flags = CFTYPE_ONLY_ON_ROOT,
+ .seq_show = cgroup_sane_behavior_show,
+ },
+ {
+ .name = "tasks",
+ .seq_start = cgroup_pidlist_start,
+ .seq_next = cgroup_pidlist_next,
+ .seq_stop = cgroup_pidlist_stop,
+ .seq_show = cgroup_pidlist_show,
+ .private = CGROUP_FILE_TASKS,
+ .write = cgroup_tasks_write,
+ .mode = S_IRUGO | S_IWUSR,
+ },
+ {
+ .name = "notify_on_release",
+ .read_u64 = cgroup_read_notify_on_release,
+ .write_u64 = cgroup_write_notify_on_release,
+ },
+ {
+ .name = "release_agent",
+ .flags = CFTYPE_ONLY_ON_ROOT,
+ .seq_show = cgroup_release_agent_show,
+ .write = cgroup_release_agent_write,
+ .max_write_len = PATH_MAX - 1,
+ },
+ { } /* terminate */
+};
+
+/**
+ * cgroup_populate_dir - create subsys files in a cgroup directory
+ * @cgrp: target cgroup
+ * @subsys_mask: mask of the subsystem ids whose files should be added
+ *
+ * On failure, no file is added.
+ */
+static int cgroup_populate_dir(struct cgroup *cgrp, unsigned int subsys_mask)
+{
+ struct cgroup_subsys *ss;
+ int i, ret = 0;
+
+ /* process cftsets of each subsystem */
+ for_each_subsys(ss, i) {
+ struct cftype *cfts;
+
+ if (!(subsys_mask & (1 << i)))
+ continue;
+
+ list_for_each_entry(cfts, &ss->cfts, node) {
+ ret = cgroup_addrm_files(cgrp, cfts, true);
+ if (ret < 0)
+ goto err;
+ }
+ }
+ return 0;
+err:
+ cgroup_clear_dir(cgrp, subsys_mask);
+ return ret;
+}
+
+/*
+ * 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 */
+ int id = css->id;
+
+ if (css->parent)
+ css_put(css->parent);
+
+ ss->css_free(css);
+ cgroup_idr_remove(&ss->css_idr, id);
+ cgroup_put(cgrp);
+ } else {
+ /* cgroup free path */
+ atomic_dec(&cgrp->root->nr_cgrps);
+ cgroup_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 swork_event *sev)
+{
+ struct cgroup_subsys_state *css =
+ container_of(sev, struct cgroup_subsys_state, destroy_swork);
+ 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 */
+ 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.
+ */
+ RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
+ }
+
+ 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_SWORK(&css->destroy_swork, css_release_work_fn);
+ swork_queue(&css->destroy_swork);
+}
+
+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;
+ INIT_LIST_HEAD(&css->sibling);
+ INIT_LIST_HEAD(&css->children);
+ css->serial_nr = css_serial_nr_next++;
+
+ 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);
+ }
+ return ret;
+}
+
+/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
+static void offline_css(struct cgroup_subsys_state *css)
+{
+ struct cgroup_subsys *ss = css->ss;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ if (!(css->flags & CSS_ONLINE))
+ return;
+
+ if (ss->css_offline)
+ ss->css_offline(css);
+
+ css->flags &= ~CSS_ONLINE;
+ RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
+
+ wake_up_all(&css->cgroup->offline_waitq);
+}
+
+/**
+ * create_css - create a cgroup_subsys_state
+ * @cgrp: the cgroup new css will be associated with
+ * @ss: the subsys of new css
+ * @visible: whether to create control knobs for the new css or not
+ *
+ * Create a new css associated with @cgrp - @ss pair. On success, the new
+ * css is online and installed in @cgrp with all interface files created if
+ * @visible. Returns 0 on success, -errno on failure.
+ */
+static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
+ bool visible)
+{
+ 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 (IS_ERR(css))
+ return PTR_ERR(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_NOWAIT);
+ if (err < 0)
+ goto err_free_percpu_ref;
+ css->id = err;
+
+ if (visible) {
+ err = cgroup_populate_dir(cgrp, 1 << ss->id);
+ if (err)
+ goto err_free_id;
+ }
+
+ /* @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 0;
+
+err_list_del:
+ list_del_rcu(&css->sibling);
+ cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
+err_free_id:
+ cgroup_idr_remove(&ss->css_idr, css->id);
+err_free_percpu_ref:
+ percpu_ref_exit(&css->refcnt);
+err_free_css:
+ call_rcu(&css->rcu_head, css_free_rcu_fn);
+ return err;
+}
+
+static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
+ umode_t mode)
+{
+ struct cgroup *parent, *cgrp;
+ struct cgroup_root *root;
+ struct cgroup_subsys *ss;
+ struct kernfs_node *kn;
+ struct cftype *base_files;
+ int ssid, 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);
+ if (!parent)
+ return -ENODEV;
+ root = parent->root;
+
+ /* allocate the cgroup and its ID, 0 is reserved for the root */
+ cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
+ if (!cgrp) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ 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_NOWAIT);
+ if (cgrp->id < 0) {
+ ret = -ENOMEM;
+ goto out_cancel_ref;
+ }
+
+ init_cgroup_housekeeping(cgrp);
+
+ cgrp->self.parent = &parent->self;
+ cgrp->root = root;
+
+ 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);
+
+ /* create the directory */
+ kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
+ if (IS_ERR(kn)) {
+ ret = PTR_ERR(kn);
+ goto out_free_id;
+ }
+ cgrp->kn = kn;
+
+ /*
+ * This extra ref will be put in cgroup_free_fn() and guarantees
+ * that @cgrp->kn is always accessible.
+ */
+ kernfs_get(kn);
+
+ 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);
+
+ ret = cgroup_kn_set_ugid(kn);
+ if (ret)
+ goto out_destroy;
+
+ if (cgroup_on_dfl(cgrp))
+ base_files = cgroup_dfl_base_files;
+ else
+ base_files = cgroup_legacy_base_files;
+
+ ret = cgroup_addrm_files(cgrp, base_files, true);
+ if (ret)
+ goto out_destroy;
+
+ /* let's create and online css's */
+ for_each_subsys(ss, ssid) {
+ if (parent->child_subsys_mask & (1 << ssid)) {
+ ret = create_css(cgrp, ss,
+ parent->subtree_control & (1 << ssid));
+ if (ret)
+ goto out_destroy;
+ }
+ }
+
+ /*
+ * 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 = parent->subtree_control;
+ cgroup_refresh_child_subsys_mask(cgrp);
+ }
+
+ kernfs_activate(kn);
+
+ ret = 0;
+ goto out_unlock;
+
+out_free_id:
+ cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
+out_cancel_ref:
+ percpu_ref_exit(&cgrp->self.refcnt);
+out_free_cgrp:
+ kfree(cgrp);
+out_unlock:
+ cgroup_kn_unlock(parent_kn);
+ return ret;
+
+out_destroy:
+ cgroup_destroy_locked(cgrp);
+ goto out_unlock;
+}
+
+/*
+ * 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);
+ offline_css(css);
+ mutex_unlock(&cgroup_mutex);
+
+ css_put(css);
+}
+
+/* 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);
+
+ 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.
+ */
+ cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
+
+ /*
+ * 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;
+ bool empty;
+ int ssid;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ /*
+ * css_set_rwsem synchronizes access to ->cset_links and prevents
+ * @cgrp from being removed while put_css_set() is in progress.
+ */
+ down_read(&css_set_rwsem);
+ empty = list_empty(&cgrp->cset_links);
+ up_read(&css_set_rwsem);
+ if (!empty)
+ 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 dead. This prevents further task migration and child
+ * creation by disabling cgroup_lock_live_group().
+ */
+ cgrp->self.flags &= ~CSS_ONLINE;
+
+ /* 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);
+
+ check_for_release(cgroup_parent(cgrp));
+
+ /* put the base reference */
+ percpu_ref_kill(&cgrp->self.refcnt);
+
+ return 0;
+};
+
+static int cgroup_rmdir(struct kernfs_node *kn)
+{
+ struct cgroup *cgrp;
+ int ret = 0;
+
+ cgrp = cgroup_kn_lock_live(kn);
+ if (!cgrp)
+ return 0;
+
+ ret = cgroup_destroy_locked(cgrp);
+
+ cgroup_kn_unlock(kn);
+ return ret;
+}
+
+static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
+ .remount_fs = cgroup_remount,
+ .show_options = cgroup_show_options,
+ .mkdir = cgroup_mkdir,
+ .rmdir = cgroup_rmdir,
+ .rename = cgroup_rename,
+};
+
+static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
+{
+ struct cgroup_subsys_state *css;
+
+ printk(KERN_INFO "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;
+
+ need_forkexit_callback |= ss->fork || ss->exit;
+
+ /* 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 name:id=%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->early_init)
+ cgroup_init_subsys(ss, true);
+ }
+ return 0;
+}
+
+/**
+ * cgroup_init - cgroup initialization
+ *
+ * Register cgroup filesystem and /proc file, and initialize
+ * any subsystems that didn't request early init.
+ */
+int __init cgroup_init(void)
+{
+ struct cgroup_subsys *ss;
+ unsigned long key;
+ int ssid, err;
+
+ BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
+ BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));
+
+ mutex_lock(&cgroup_mutex);
+
+ /* Add init_css_set to the hash table */
+ key = css_set_hash(init_css_set.subsys);
+ hash_add(css_set_table, &init_css_set.hlist, key);
+
+ 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 (ss->disabled)
+ continue;
+
+ cgrp_dfl_root.subsys_mask |= 1 << ss->id;
+
+ if (cgroup_legacy_files_on_dfl && !ss->dfl_cftypes)
+ ss->dfl_cftypes = ss->legacy_cftypes;
+
+ if (!ss->dfl_cftypes)
+ cgrp_dfl_root_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]);
+ }
+
+ err = sysfs_create_mount_point(fs_kobj, "cgroup");
+ if (err)
+ return err;
+
+ err = register_filesystem(&cgroup_fs_type);
+ if (err < 0) {
+ sysfs_remove_mount_point(fs_kobj, "cgroup");
+ return err;
+ }
+
+ 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);
+ BUG_ON(swork_get());
+
+ /*
+ * Used to destroy pidlists and separate to serve as flush domain.
+ * Cap @max_active to 1 too.
+ */
+ cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
+ 0, 1);
+ BUG_ON(!cgroup_pidlist_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, *path;
+ int retval;
+ struct cgroup_root *root;
+
+ retval = -ENOMEM;
+ buf = kmalloc(PATH_MAX, GFP_KERNEL);
+ if (!buf)
+ goto out;
+
+ mutex_lock(&cgroup_mutex);
+ down_read(&css_set_rwsem);
+
+ for_each_root(root) {
+ struct cgroup_subsys *ss;
+ struct cgroup *cgrp;
+ int ssid, count = 0;
+
+ if (root == &cgrp_dfl_root && !cgrp_dfl_root_visible)
+ continue;
+
+ seq_printf(m, "%d:", root->hierarchy_id);
+ for_each_subsys(ss, ssid)
+ if (root->subsys_mask & (1 << ssid))
+ seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
+ if (strlen(root->name))
+ seq_printf(m, "%sname=%s", count ? "," : "",
+ root->name);
+ seq_putc(m, ':');
+ cgrp = task_cgroup_from_root(tsk, root);
+ path = cgroup_path(cgrp, buf, PATH_MAX);
+ if (!path) {
+ retval = -ENAMETOOLONG;
+ goto out_unlock;
+ }
+ seq_puts(m, path);
+ seq_putc(m, '\n');
+ }
+
+ retval = 0;
+out_unlock:
+ up_read(&css_set_rwsem);
+ mutex_unlock(&cgroup_mutex);
+ kfree(buf);
+out:
+ return retval;
+}
+
+/* Display information about each subsystem and each hierarchy */
+static int proc_cgroupstats_show(struct seq_file *m, void *v)
+{
+ struct cgroup_subsys *ss;
+ int i;
+
+ seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
+ /*
+ * ideally we don't want subsystems moving around while we do this.
+ * cgroup_mutex is also necessary to guarantee an atomic snapshot of
+ * subsys/hierarchy state.
+ */
+ mutex_lock(&cgroup_mutex);
+
+ for_each_subsys(ss, i)
+ seq_printf(m, "%s\t%d\t%d\t%d\n",
+ ss->name, ss->root->hierarchy_id,
+ atomic_read(&ss->root->nr_cgrps), !ss->disabled);
+
+ mutex_unlock(&cgroup_mutex);
+ return 0;
+}
+
+static int cgroupstats_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, proc_cgroupstats_show, NULL);
+}
+
+static const struct file_operations proc_cgroupstats_operations = {
+ .open = cgroupstats_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+/**
+ * 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_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_rwsem 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;
+
+ down_write(&css_set_rwsem);
+ cset = task_css_set(current);
+ if (list_empty(&child->cg_list)) {
+ rcu_assign_pointer(child->cgroups, cset);
+ list_add(&child->cg_list, &cset->tasks);
+ get_css_set(cset);
+ }
+ up_write(&css_set_rwsem);
+ }
+
+ /*
+ * 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.
+ */
+ if (need_forkexit_callback) {
+ for_each_subsys(ss, i)
+ if (ss->fork)
+ ss->fork(child);
+ }
+}
+
+/**
+ * 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;
+ bool put_cset = false;
+ int i;
+
+ /*
+ * Unlink from @tsk from its css_set. As migration path can't race
+ * with us, we can check cg_list without grabbing css_set_rwsem.
+ */
+ if (!list_empty(&tsk->cg_list)) {
+ down_write(&css_set_rwsem);
+ list_del_init(&tsk->cg_list);
+ up_write(&css_set_rwsem);
+ put_cset = true;
+ }
+
+ /* Reassign the task to the init_css_set. */
+ cset = task_css_set(tsk);
+ RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
+
+ if (need_forkexit_callback) {
+ /* see cgroup_post_fork() for details */
+ for_each_subsys(ss, i) {
+ if (ss->exit) {
+ struct cgroup_subsys_state *old_css = cset->subsys[i];
+ struct cgroup_subsys_state *css = task_css(tsk, i);
+
+ ss->exit(css, old_css, tsk);
+ }
+ }
+ }
+
+ if (put_cset)
+ put_css_set(cset);
+}
+
+static void check_for_release(struct cgroup *cgrp)
+{
+ if (notify_on_release(cgrp) && !cgroup_has_tasks(cgrp) &&
+ !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
+ schedule_work(&cgrp->release_agent_work);
+}
+
+/*
+ * Notify userspace when a cgroup is released, by running the
+ * configured release agent with the name of the cgroup (path
+ * relative to the root of cgroup file system) as the argument.
+ *
+ * Most likely, this user command will try to rmdir this cgroup.
+ *
+ * This races with the possibility that some other task will be
+ * attached to this cgroup before it is removed, or that some other
+ * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
+ * The presumed 'rmdir' will fail quietly if this cgroup is no longer
+ * unused, and this cgroup will be reprieved from its death sentence,
+ * to continue to serve a useful existence. Next time it's released,
+ * we will get notified again, if it still has 'notify_on_release' set.
+ *
+ * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
+ * means only wait until the task is successfully execve()'d. The
+ * separate release agent task is forked by call_usermodehelper(),
+ * then control in this thread returns here, without waiting for the
+ * release agent task. We don't bother to wait because the caller of
+ * this routine has no use for the exit status of the release agent
+ * task, so no sense holding our caller up for that.
+ */
+static void cgroup_release_agent(struct work_struct *work)
+{
+ struct cgroup *cgrp =
+ container_of(work, struct cgroup, release_agent_work);
+ char *pathbuf = NULL, *agentbuf = NULL, *path;
+ char *argv[3], *envp[3];
+
+ mutex_lock(&cgroup_mutex);
+
+ pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
+ agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
+ if (!pathbuf || !agentbuf)
+ goto out;
+
+ path = cgroup_path(cgrp, pathbuf, PATH_MAX);
+ if (!path)
+ goto out;
+
+ argv[0] = agentbuf;
+ argv[1] = path;
+ argv[2] = NULL;
+
+ /* minimal command environment */
+ envp[0] = "HOME=/";
+ envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+ envp[2] = NULL;
+
+ mutex_unlock(&cgroup_mutex);
+ call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
+ goto out_free;
+out:
+ mutex_unlock(&cgroup_mutex);
+out_free:
+ kfree(agentbuf);
+ kfree(pathbuf);
+}
+
+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)) {
+ ss->disabled = 1;
+ printk(KERN_INFO "Disabling %s control group"
+ " subsystem\n", ss->name);
+ break;
+ }
+ }
+ }
+ return 1;
+}
+__setup("cgroup_disable=", cgroup_disable);
+
+static int __init cgroup_set_legacy_files_on_dfl(char *str)
+{
+ printk("cgroup: using legacy files on the default hierarchy\n");
+ cgroup_legacy_files_on_dfl = true;
+ return 0;
+}
+__setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl);
+
+/**
+ * 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 cgroup_subsys_state *css = NULL;
+ struct cgroup *cgrp;
+
+ /* is @dentry a cgroup dir? */
+ if (dentry->d_sb->s_type != &cgroup_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(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 id > 0 ? idr_find(&ss->css_idr, id) : NULL;
+}
+
+#ifdef CONFIG_CGROUP_DEBUG
+static struct cgroup_subsys_state *
+debug_css_alloc(struct cgroup_subsys_state *parent_css)
+{
+ struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
+
+ if (!css)
+ return ERR_PTR(-ENOMEM);
+
+ return css;
+}
+
+static void debug_css_free(struct cgroup_subsys_state *css)
+{
+ kfree(css);
+}
+
+static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return cgroup_task_count(css->cgroup);
+}
+
+static u64 current_css_set_read(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ return (u64)(unsigned long)current->cgroups;
+}
+
+static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
+ struct cftype *cft)
+{
+ u64 count;
+
+ rcu_read_lock();
+ count = atomic_read(&task_css_set(current)->refcount);
+ rcu_read_unlock();
+ return count;
+}
+
+static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
+{
+ struct cgrp_cset_link *link;
+ struct css_set *cset;
+ char *name_buf;
+
+ name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+ if (!name_buf)
+ return -ENOMEM;
+
+ down_read(&css_set_rwsem);
+ rcu_read_lock();
+ cset = rcu_dereference(current->cgroups);
+ list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
+ struct cgroup *c = link->cgrp;
+
+ cgroup_name(c, name_buf, NAME_MAX + 1);
+ seq_printf(seq, "Root %d group %s\n",
+ c->root->hierarchy_id, name_buf);
+ }
+ rcu_read_unlock();
+ up_read(&css_set_rwsem);
+ kfree(name_buf);
+ return 0;
+}
+
+#define MAX_TASKS_SHOWN_PER_CSS 25
+static int cgroup_css_links_read(struct seq_file *seq, void *v)
+{
+ struct cgroup_subsys_state *css = seq_css(seq);
+ struct cgrp_cset_link *link;
+
+ down_read(&css_set_rwsem);
+ list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
+ struct css_set *cset = link->cset;
+ struct task_struct *task;
+ int count = 0;
+
+ seq_printf(seq, "css_set %p\n", cset);
+
+ list_for_each_entry(task, &cset->tasks, cg_list) {
+ if (count++ > MAX_TASKS_SHOWN_PER_CSS)
+ goto overflow;
+ seq_printf(seq, " task %d\n", task_pid_vnr(task));
+ }
+
+ list_for_each_entry(task, &cset->mg_tasks, cg_list) {
+ if (count++ > MAX_TASKS_SHOWN_PER_CSS)
+ goto overflow;
+ seq_printf(seq, " task %d\n", task_pid_vnr(task));
+ }
+ continue;
+ overflow:
+ seq_puts(seq, " ...\n");
+ }
+ up_read(&css_set_rwsem);
+ return 0;
+}
+
+static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
+{
+ return (!cgroup_has_tasks(css->cgroup) &&
+ !css_has_online_children(&css->cgroup->self));
+}
+
+static struct cftype debug_files[] = {
+ {
+ .name = "taskcount",
+ .read_u64 = debug_taskcount_read,
+ },
+
+ {
+ .name = "current_css_set",
+ .read_u64 = current_css_set_read,
+ },
+
+ {
+ .name = "current_css_set_refcount",
+ .read_u64 = current_css_set_refcount_read,
+ },
+
+ {
+ .name = "current_css_set_cg_links",
+ .seq_show = current_css_set_cg_links_read,
+ },
+
+ {
+ .name = "cgroup_css_links",
+ .seq_show = cgroup_css_links_read,
+ },
+
+ {
+ .name = "releasable",
+ .read_u64 = releasable_read,
+ },
+
+ { } /* terminate */
+};
+
+struct cgroup_subsys debug_cgrp_subsys = {
+ .css_alloc = debug_css_alloc,
+ .css_free = debug_css_free,
+ .legacy_cftypes = debug_files,
+};
+#endif /* CONFIG_CGROUP_DEBUG */
Code Review / kvmfornfv.git / blobdiff