/* * 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. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* TODO: replace with more sophisticated array */ #include #include #include /* * 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_tree_mutex nests above cgroup_mutex and protects cftypes, file * creation/removal and hierarchy changing operations including cgroup * creation, removal, css association and controller rebinding. This outer * lock is needed mainly to resolve the circular dependency between kernfs * active ref and cgroup_mutex. cgroup_tree_mutex nests above both. */ static DEFINE_MUTEX(cgroup_tree_mutex); /* * 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_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_mutexes_or_rcu_locked() \ rcu_lockdep_assert(rcu_read_lock_held() || \ lockdep_is_held(&cgroup_tree_mutex) || \ lockdep_is_held(&cgroup_mutex), \ "cgroup_[tree_]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 }; #undef SUBSYS /* array of cgroup subsystem names */ #define SUBSYS(_x) [_x ## _cgrp_id] = #_x, static const char *cgroup_subsys_name[] = { #include }; #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; /* 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 cgroups. It * guarantees cgroups with bigger numbers are newer than those with smaller * numbers. Also, as cgroups are always appended to the parent's * ->children list, it guarantees that sibling cgroups are always sorted in * the ascending serial number order on the list. Protected by * cgroup_mutex. */ static u64 cgroup_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_base_files[]; static void cgroup_put(struct cgroup *cgrp); static int rebind_subsystems(struct cgroup_root *dst_root, unsigned long ss_mask); static void cgroup_destroy_css_killed(struct cgroup *cgrp); static int cgroup_destroy_locked(struct cgroup *cgrp); static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], bool is_add); static void cgroup_pidlist_destroy_all(struct cgroup *cgrp); /** * cgroup_css - obtain a cgroup's css for the specified subsystem * @cgrp: the cgroup of interest * @ss: the subsystem of interest (%NULL returns the dummy_css) * * 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_tree_mutex) || lockdep_is_held(&cgroup_mutex)); else return &cgrp->dummy_css; } /* convenient tests for these bits */ static inline bool cgroup_is_dead(const struct cgroup *cgrp) { return test_bit(CGRP_DEAD, &cgrp->flags); } struct cgroup_subsys_state *seq_css(struct seq_file *seq) { struct kernfs_open_file *of = seq->private; struct cgroup *cgrp = of->kn->parent->priv; struct cftype *cft = seq_cft(seq); /* * 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->dummy_css; } EXPORT_SYMBOL_GPL(seq_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 = cgrp->parent; } return false; } static int cgroup_is_releasable(const struct cgroup *cgrp) { const int bits = (1 << CGRP_RELEASABLE) | (1 << CGRP_NOTIFY_ON_RELEASE); return (cgrp->flags & bits) == bits; } 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_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_tree_mutex) || \ lockdep_is_held(&cgroup_mutex)))) { } \ 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) /** * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive. * @cgrp: the cgroup to be checked for liveness * * On success, returns true; the mutex should be later unlocked. On * failure returns false with no lock held. */ static bool cgroup_lock_live_group(struct cgroup *cgrp) { mutex_lock(&cgroup_mutex); if (cgroup_is_dead(cgrp)) { mutex_unlock(&cgroup_mutex); return false; } return true; } /* the list of cgroups eligible for automatic release. Protected by * release_list_lock */ static LIST_HEAD(release_list); static DEFINE_RAW_SPINLOCK(release_list_lock); static void cgroup_release_agent(struct work_struct *work); static DECLARE_WORK(release_agent_work, cgroup_release_agent); 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. */ static 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 */ /* * 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, bool taskexit) { struct cgrp_cset_link *link, *tmp_link; 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 */ 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) && notify_on_release(cgrp)) { if (taskexit) set_bit(CGRP_RELEASABLE, &cgrp->flags); check_for_release(cgrp); } kfree(link); } kfree_rcu(cset, rcu_head); } static void put_css_set(struct css_set *cset, bool taskexit) { /* * 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, taskexit); 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; if (memcmp(template, cset->subsys, sizeof(cset->subsys))) { /* Not all subsystems matched */ return false; } /* * Compare cgroup pointers in order to distinguish between * different cgroups in heirarchies with no subsystems. We * could get by with just this check alone (and skip the * memcmp above) but on most setups the memcmp check will * avoid the need for this more expensive check on almost all * candidates. */ 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->cgrp.subsys_mask & (1UL << i)) { /* Subsystem is in this hierarchy. So we want * the subsystem state from the new * cgroup */ template[i] = cgroup_css(cgrp, ss); } else { /* Subsystem is not in this hierarchy, so we * don't want to change the subsystem state */ 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)); link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link); link->cset = cset; link->cgrp = cgrp; 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; unsigned long key; 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 this cgroup group to the hash table */ key = css_set_hash(cset->subsys); hash_add(css_set_table, &cset->hlist, key); 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_tree_mutex); mutex_lock(&cgroup_mutex); BUG_ON(atomic_read(&root->nr_cgrps)); BUG_ON(!list_empty(&cgrp->children)); /* Rebind all subsystems back to the default hierarchy */ rebind_subsystems(&cgrp_dfl_root, cgrp->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); mutex_unlock(&cgroup_tree_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. * * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't * (usually) take cgroup_mutex. These are the two most performance * critical pieces of code here. The exception occurs on cgroup_exit(), * when a task in a notify_on_release cgroup exits. Then cgroup_mutex * is taken, and if the cgroup count is zero, a usermode call made * to the release agent with the name of the cgroup (path relative to * the root of cgroup file system) as the argument. * * 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 long 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_string || cft->trigger) mode |= S_IWUSR; return mode; } static void cgroup_free_fn(struct work_struct *work) { struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work); atomic_dec(&cgrp->root->nr_cgrps); cgroup_pidlist_destroy_all(cgrp); if (cgrp->parent) { /* * 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(cgrp->parent); 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 cgroup_free_rcu(struct rcu_head *head) { struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head); INIT_WORK(&cgrp->destroy_work, cgroup_free_fn); queue_work(cgroup_destroy_wq, &cgrp->destroy_work); } static void cgroup_get(struct cgroup *cgrp) { WARN_ON_ONCE(cgroup_is_dead(cgrp)); WARN_ON_ONCE(atomic_read(&cgrp->refcnt) <= 0); atomic_inc(&cgrp->refcnt); } static void cgroup_put(struct cgroup *cgrp) { if (!atomic_dec_and_test(&cgrp->refcnt)) return; if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp))) return; /* * XXX: cgrp->id is only used to look up css's. As cgroup and * css's lifetimes will be decoupled, it should be made * per-subsystem and moved to css->id so that lookups are * successful until the target css is released. */ mutex_lock(&cgroup_mutex); idr_remove(&cgrp->root->cgroup_idr, cgrp->id); mutex_unlock(&cgroup_mutex); cgrp->id = -1; call_rcu(&cgrp->rcu_head, cgroup_free_rcu); } static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) { char name[CGROUP_FILE_NAME_MAX]; lockdep_assert_held(&cgroup_tree_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 long subsys_mask) { struct cgroup_subsys *ss; int i; for_each_subsys(ss, i) { struct cftype *cfts; if (!test_bit(i, &subsys_mask)) 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 long ss_mask) { struct cgroup_subsys *ss; int ssid, ret; lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); for_each_subsys(ss, ssid) { if (!(ss_mask & (1 << ssid))) continue; /* if @ss is on the dummy_root, we can always move it */ if (ss->root == &cgrp_dfl_root) continue; /* if @ss has non-root cgroups attached to it, can't move */ if (!list_empty(&ss->root->cgrp.children)) return -EBUSY; /* can't move between two non-dummy roots either */ if (dst_root != &cgrp_dfl_root) return -EBUSY; } ret = cgroup_populate_dir(&dst_root->cgrp, 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_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n", ret, ss_mask); pr_warning("cgroup: 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. */ mutex_unlock(&cgroup_mutex); for_each_subsys(ss, ssid) if (ss_mask & (1 << ssid)) cgroup_clear_dir(&ss->root->cgrp, 1 << ssid); mutex_lock(&cgroup_mutex); for_each_subsys(ss, ssid) { struct cgroup_root *src_root; struct cgroup_subsys_state *css; 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; src_root->cgrp.subsys_mask &= ~(1 << ssid); dst_root->cgrp.subsys_mask |= 1 << ssid; 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->cgrp.subsys_mask & (1 << ssid)) seq_printf(seq, ",%s", ss->name); if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) seq_puts(seq, ",sane_behavior"); 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 long subsys_mask; unsigned long flags; char *release_agent; bool cpuset_clone_children; char *name; /* User explicitly requested empty subsystem */ bool none; }; /* * Convert a hierarchy specifier into a bitmask of subsystems and * flags. Call with cgroup_mutex held to protect the cgroup_subsys[] * array. This function takes refcounts on subsystems to be used, unless it * returns error, in which case no refcounts are taken. */ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) { char *token, *o = data; bool all_ss = false, one_ss = false; unsigned long mask = (unsigned long)-1; struct cgroup_subsys *ss; int i; BUG_ON(!mutex_is_locked(&cgroup_mutex)); #ifdef CONFIG_CPUSETS mask = ~(1UL << cpuset_cgrp_id); #endif memset(opts, 0, sizeof(*opts)); while ((token = strsep(&o, ",")) != NULL) { 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; set_bit(i, &opts->subsys_mask); one_ss = true; break; } if (i == CGROUP_SUBSYS_COUNT) return -ENOENT; } /* Consistency checks */ if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) { pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n"); if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) || opts->cpuset_clone_children || opts->release_agent || opts->name) { pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n"); return -EINVAL; } } else { /* * 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) set_bit(i, &opts->subsys_mask); /* * 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 long added_mask, removed_mask; if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) { pr_err("cgroup: sane_behavior: remount is not allowed\n"); return -EINVAL; } mutex_lock(&cgroup_tree_mutex); 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->cgrp.subsys_mask || opts.release_agent) pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n", task_tgid_nr(current), current->comm); added_mask = opts.subsys_mask & ~root->cgrp.subsys_mask; removed_mask = root->cgrp.subsys_mask & ~opts.subsys_mask; /* Don't allow flags or name to change at remount */ if (((opts.flags ^ root->flags) & CGRP_ROOT_OPTION_MASK) || (opts.name && strcmp(opts.name, root->name))) { pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n", opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "", root->flags & CGRP_ROOT_OPTION_MASK, root->name); ret = -EINVAL; goto out_unlock; } /* remounting is not allowed for populated hierarchies */ if (!list_empty(&root->cgrp.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); mutex_unlock(&cgroup_tree_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) { atomic_set(&cgrp->refcnt, 1); INIT_LIST_HEAD(&cgrp->sibling); INIT_LIST_HEAD(&cgrp->children); INIT_LIST_HEAD(&cgrp->cset_links); INIT_LIST_HEAD(&cgrp->release_list); INIT_LIST_HEAD(&cgrp->pidlists); mutex_init(&cgrp->pidlist_mutex); cgrp->dummy_css.cgroup = cgrp; } 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 long ss_mask) { LIST_HEAD(tmp_links); struct cgroup *root_cgrp = &root->cgrp; struct css_set *cset; int i, ret; lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL); if (ret < 0) goto out; root_cgrp->id = ret; /* * 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 out; ret = cgroup_init_root_id(root); if (ret) goto out; 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; ret = cgroup_addrm_files(root_cgrp, cgroup_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->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); 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 cgroup_root *root; struct cgroup_sb_opts opts; struct dentry *dentry; int ret; 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(); retry: mutex_lock(&cgroup_tree_mutex); 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.subsys_mask && !opts.none && !opts.name) { cgrp_dfl_root_visible = true; root = &cgrp_dfl_root; cgroup_get(&root->cgrp); ret = 0; goto out_unlock; } 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->cgrp.subsys_mask)) { if (!name_match) continue; ret = -EBUSY; goto out_unlock; } if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) { if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) { pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n"); ret = -EINVAL; goto out_unlock; } else { pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n"); } } /* * A root's lifetime is governed by its root cgroup. Zero * ref indicate that the root is being destroyed. Wait for * destruction to complete so that the subsystems are free. * We can use wait_queue for the wait but this path is * super cold. Let's just sleep for a bit and retry. */ if (!atomic_inc_not_zero(&root->cgrp.refcnt)) { mutex_unlock(&cgroup_mutex); mutex_unlock(&cgroup_tree_mutex); kfree(opts.release_agent); kfree(opts.name); msleep(10); goto retry; } 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); mutex_unlock(&cgroup_tree_mutex); kfree(opts.release_agent); kfree(opts.name); if (ret) return ERR_PTR(ret); dentry = kernfs_mount(fs_type, flags, root->kf_root, &new_sb); if (IS_ERR(dentry) || !new_sb) cgroup_put(&root->cgrp); 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); cgroup_put(&root->cgrp); kernfs_kill_sb(sb); } static struct file_system_type cgroup_fs_type = { .name = "cgroup", .mount = cgroup_mount, .kill_sb = cgroup_kill_sb, }; static struct kobject *cgroup_kobj; /** * 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. */ set_bit(CGRP_RELEASABLE, &old_cgrp->flags); put_css_set_locked(old_cset, false); } /** * 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, false); } 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); /* nothing to do if this cset already belongs to the cgroup */ if (src_cgrp == dst_cgrp) return; 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 * @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 put them on * @preloaded_csets. * * This function must be called after cgroup_migrate_add_src() has been * called on each migration source css_set. After migration is performed * using cgroup_migrate(), cgroup_migrate_finish() must be called on * @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; lockdep_assert_held(&cgroup_mutex); /* look up the dst cset for each src cset and link it to src */ list_for_each_entry(src_cset, preloaded_csets, mg_preload_node) { struct css_set *dst_cset; dst_cset = find_css_set(src_cset, dst_cgrp); if (!dst_cset) goto err; WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset); 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, false); } list_splice(&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_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_css(css, i, cgrp) if (css->ss->attach) css->ss->attach(css, &tset); ret = 0; goto out_release_tset; out_cancel_attach: for_each_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 int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) { struct task_struct *tsk; const struct cred *cred = current_cred(), *tcred; int ret; if (!cgroup_lock_live_group(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: mutex_unlock(&cgroup_mutex); return ret; } /** * 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 int cgroup_tasks_write(struct cgroup_subsys_state *css, struct cftype *cft, u64 pid) { return attach_task_by_pid(css->cgroup, pid, false); } static int cgroup_procs_write(struct cgroup_subsys_state *css, struct cftype *cft, u64 tgid) { return attach_task_by_pid(css->cgroup, tgid, true); } static int cgroup_release_agent_write(struct cgroup_subsys_state *css, struct cftype *cft, char *buffer) { struct cgroup_root *root = css->cgroup->root; BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX); if (!cgroup_lock_live_group(css->cgroup)) return -ENODEV; spin_lock(&release_agent_path_lock); strlcpy(root->release_agent_path, buffer, sizeof(root->release_agent_path)); spin_unlock(&release_agent_path_lock); mutex_unlock(&cgroup_mutex); return 0; } static int cgroup_release_agent_show(struct seq_file *seq, void *v) { struct cgroup *cgrp = seq_css(seq)->cgroup; if (!cgroup_lock_live_group(cgrp)) return -ENODEV; seq_puts(seq, cgrp->root->release_agent_path); seq_putc(seq, '\n'); mutex_unlock(&cgroup_mutex); return 0; } static int cgroup_sane_behavior_show(struct seq_file *seq, void *v) { struct cgroup *cgrp = seq_css(seq)->cgroup; seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp)); 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; /* * 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_string) { ret = cft->write_string(css, cft, strstrip(buf)); } else 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 if (cft->trigger) { ret = cft->trigger(css, (unsigned int)cft->private); } 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 if sane_behavior. */ if (cgroup_sane_behavior(cgrp)) return -EPERM; /* * We're gonna gra