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Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 5536 |
1 files changed, 5536 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c new file mode 100644 index 000000000..e646e870e --- /dev/null +++ b/kernel/cgroup.c @@ -0,0 +1,5536 @@ +/* + * 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 <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/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/backing-dev.h> +#include <linux/seq_file.h> +#include <linux/slab.h> +#include <linux/magic.h> +#include <linux/spinlock.h> +#include <linux/string.h> +#include <linux/sort.h> +#include <linux/kmod.h> +#include <linux/module.h> +#include <linux/delayacct.h> +#include <linux/cgroupstats.h> +#include <linux/hashtable.h> +#include <linux/namei.h> +#include <linux/pid_namespace.h> +#include <linux/idr.h> +#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */ +#include <linux/eventfd.h> +#include <linux/poll.h> +#include <linux/flex_array.h> /* used in cgroup_attach_task */ +#include <linux/kthread.h> + +#include <linux/atomic.h> + +/* css deactivation bias, makes css->refcnt negative to deny new trygets */ +#define CSS_DEACT_BIAS INT_MIN + +/* + * cgroup_mutex is the master lock. Any modification to cgroup or its + * hierarchy must be performed while holding it. + * + * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify + * cgroupfs_root of any cgroup hierarchy - subsys list, flags, + * release_agent_path and so on. Modifying requires both cgroup_mutex and + * cgroup_root_mutex. Readers can acquire either of the two. This is to + * break the following locking order cycle. + * + * A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem + * B. namespace_sem -> cgroup_mutex + * + * B happens only through cgroup_show_options() and using cgroup_root_mutex + * breaks it. + */ +#ifdef CONFIG_PROVE_RCU +DEFINE_MUTEX(cgroup_mutex); +EXPORT_SYMBOL_GPL(cgroup_mutex); /* only for task_subsys_state_check() */ +#else +static DEFINE_MUTEX(cgroup_mutex); +#endif + +static DEFINE_MUTEX(cgroup_root_mutex); + +/* + * cgroup destruction makes heavy use of work items and there can be a lot + * of concurrent destructions. Use a separate workqueue so that cgroup + * destruction work items don't end up filling up max_active of system_wq + * which may lead to deadlock. + */ +static struct workqueue_struct *cgroup_destroy_wq; + +/* + * Generate an array of cgroup subsystem pointers. At boot time, this is + * populated with the built in subsystems, and modular subsystems are + * registered after that. The mutable section of this array is protected by + * cgroup_mutex. + */ +#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys, +#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option) +static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = { +#include <linux/cgroup_subsys.h> +}; + +/* + * The "rootnode" hierarchy is the "dummy 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. + */ +static struct cgroupfs_root rootnode; + +/* + * cgroupfs file entry, pointed to from leaf dentry->d_fsdata. + */ +struct cfent { + struct list_head node; + struct dentry *dentry; + struct cftype *type; + + /* file xattrs */ + struct simple_xattrs xattrs; +}; + +/* + * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when + * cgroup_subsys->use_id != 0. + */ +#define CSS_ID_MAX (65535) +struct css_id { + /* + * The css to which this ID points. This pointer is set to valid value + * after cgroup is populated. If cgroup is removed, this will be NULL. + * This pointer is expected to be RCU-safe because destroy() + * is called after synchronize_rcu(). But for safe use, css_tryget() + * should be used for avoiding race. + */ + struct cgroup_subsys_state __rcu *css; + /* + * ID of this css. + */ + unsigned short id; + /* + * Depth in hierarchy which this ID belongs to. + */ + unsigned short depth; + /* + * ID is freed by RCU. (and lookup routine is RCU safe.) + */ + struct rcu_head rcu_head; + /* + * Hierarchy of CSS ID belongs to. + */ + unsigned short stack[0]; /* Array of Length (depth+1) */ +}; + +/* + * cgroup_event represents events which userspace want to receive. + */ +struct cgroup_event { + /* + * Cgroup which the event belongs to. + */ + struct cgroup *cgrp; + /* + * Control file which the event associated. + */ + struct cftype *cft; + /* + * eventfd to signal userspace about the event. + */ + struct eventfd_ctx *eventfd; + /* + * Each of these stored in a list by the cgroup. + */ + struct list_head list; + /* + * All fields below needed to unregister event when + * userspace closes eventfd. + */ + poll_table pt; + wait_queue_head_t *wqh; + wait_queue_t wait; + struct work_struct remove; +}; + +/* The list of hierarchy roots */ + +static LIST_HEAD(roots); +static int root_count; + +static DEFINE_IDA(hierarchy_ida); +static int next_hierarchy_id; +static DEFINE_SPINLOCK(hierarchy_id_lock); + +/* dummytop is a shorthand for the dummy hierarchy's top cgroup */ +#define dummytop (&rootnode.top_cgroup) + +static struct cgroup_name root_cgroup_name = { .name = "/" }; + +/* 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 int cgroup_destroy_locked(struct cgroup *cgrp); +static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys, + struct cftype cfts[], bool is_add); + +static int css_unbias_refcnt(int refcnt) +{ + return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS; +} + +/* the current nr of refs, always >= 0 whether @css is deactivated or not */ +static int css_refcnt(struct cgroup_subsys_state *css) +{ + int v = atomic_read(&css->refcnt); + + return css_unbias_refcnt(v); +} + +/* convenient tests for these bits */ +inline int cgroup_is_removed(const struct cgroup *cgrp) +{ + return test_bit(CGRP_REMOVED, &cgrp->flags); +} + +/** + * 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; +} +EXPORT_SYMBOL_GPL(cgroup_is_descendant); + +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_subsys() allows you to iterate on each subsystem attached to + * an active hierarchy + */ +#define for_each_subsys(_root, _ss) \ +list_for_each_entry(_ss, &_root->subsys_list, sibling) + +/* for_each_active_root() allows you to iterate across the active hierarchies */ +#define for_each_active_root(_root) \ +list_for_each_entry(_root, &roots, root_list) + +static inline struct cgroup *__d_cgrp(struct dentry *dentry) +{ + return dentry->d_fsdata; +} + +static inline struct cfent *__d_cfe(struct dentry *dentry) +{ + return dentry->d_fsdata; +} + +static inline struct cftype *__d_cft(struct dentry *dentry) +{ + return __d_cfe(dentry)->type; +} + +/** + * 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_removed(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); + +/* Link structure for associating css_set objects with cgroups */ +struct cg_cgroup_link { + /* + * List running through cg_cgroup_links associated with a + * cgroup, anchored on cgroup->css_sets + */ + struct list_head cgrp_link_list; + struct cgroup *cgrp; + /* + * List running through cg_cgroup_links pointing at a + * single css_set object, anchored on css_set->cg_links + */ + struct list_head cg_link_list; + struct css_set *cg; +}; + +/* 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; +static struct cg_cgroup_link init_css_set_link; + +static int cgroup_init_idr(struct cgroup_subsys *ss, + struct cgroup_subsys_state *css); + +/* css_set_lock protects the list of css_set objects, and the + * chain of tasks off each css_set. Nests outside task->alloc_lock + * due to cgroup_iter_start() */ +static DEFINE_RWLOCK(css_set_lock); +static int css_set_count; + +/* + * 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[]) +{ + int i; + unsigned long key = 0UL; + + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) + key += (unsigned long)css[i]; + key = (key >> 16) ^ key; + + return key; +} + +/* We don't maintain the lists running through each css_set to its + * task until after the first call to cgroup_iter_start(). This + * reduces the fork()/exit() overhead for people who have cgroups + * compiled into their kernel but not actually in use */ +static int use_task_css_set_links __read_mostly; + +static void __put_css_set(struct css_set *cg, int taskexit) +{ + struct cg_cgroup_link *link; + struct cg_cgroup_link *saved_link; + /* + * 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(&cg->refcount, -1, 1)) + return; + write_lock(&css_set_lock); + if (!atomic_dec_and_test(&cg->refcount)) { + write_unlock(&css_set_lock); + return; + } + + /* This css_set is dead. unlink it and release cgroup refcounts */ + hash_del(&cg->hlist); + css_set_count--; + + list_for_each_entry_safe(link, saved_link, &cg->cg_links, + cg_link_list) { + struct cgroup *cgrp = link->cgrp; + list_del(&link->cg_link_list); + list_del(&link->cgrp_link_list); + + /* + * We may not be holding cgroup_mutex, and if cgrp->count is + * dropped to 0 the cgroup can be destroyed at any time, hence + * rcu_read_lock is used to keep it alive. + */ + rcu_read_lock(); + if (atomic_dec_and_test(&cgrp->count) && + notify_on_release(cgrp)) { + if (taskexit) + set_bit(CGRP_RELEASABLE, &cgrp->flags); + check_for_release(cgrp); + } + rcu_read_unlock(); + + kfree(link); + } + + write_unlock(&css_set_lock); + kfree_rcu(cg, rcu_head); +} + +/* + * refcounted get/put for css_set objects + */ +static inline void get_css_set(struct css_set *cg) +{ + atomic_inc(&cg->refcount); +} + +static inline void put_css_set(struct css_set *cg) +{ + __put_css_set(cg, 0); +} + +static inline void put_css_set_taskexit(struct css_set *cg) +{ + __put_css_set(cg, 1); +} + +/* + * compare_css_sets - helper function for find_existing_css_set(). + * @cg: candidate css_set being tested + * @old_cg: 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 "cg" matches "old_cg" except for the hierarchy + * which "new_cgrp" belongs to, for which it should match "new_cgrp". + */ +static bool compare_css_sets(struct css_set *cg, + struct css_set *old_cg, + struct cgroup *new_cgrp, + struct cgroup_subsys_state *template[]) +{ + struct list_head *l1, *l2; + + if (memcmp(template, cg->subsys, sizeof(cg->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 = &cg->cg_links; + l2 = &old_cg->cg_links; + while (1) { + struct cg_cgroup_link *cgl1, *cgl2; + struct cgroup *cg1, *cg2; + + l1 = l1->next; + l2 = l2->next; + /* See if we reached the end - both lists are equal length. */ + if (l1 == &cg->cg_links) { + BUG_ON(l2 != &old_cg->cg_links); + break; + } else { + BUG_ON(l2 == &old_cg->cg_links); + } + /* Locate the cgroups associated with these links. */ + cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list); + cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list); + cg1 = cgl1->cgrp; + cg2 = cgl2->cgrp; + /* Hierarchies should be linked in the same order. */ + BUG_ON(cg1->root != cg2->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 (cg1->root == new_cgrp->root) { + if (cg1 != new_cgrp) + return false; + } else { + if (cg1 != cg2) + return false; + } + } + return true; +} + +/* + * find_existing_css_set() is a helper for + * find_css_set(), and checks to see whether an existing + * css_set is suitable. + * + * oldcg: the cgroup group that we're using before the cgroup + * transition + * + * cgrp: the cgroup that we're moving into + * + * template: location in which to build the desired set of subsystem + * state objects for the new cgroup group + */ +static struct css_set *find_existing_css_set( + struct css_set *oldcg, + struct cgroup *cgrp, + struct cgroup_subsys_state *template[]) +{ + int i; + struct cgroupfs_root *root = cgrp->root; + struct css_set *cg; + unsigned long key; + + /* + * 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 (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + if (root->subsys_mask & (1UL << i)) { + /* Subsystem is in this hierarchy. So we want + * the subsystem state from the new + * cgroup */ + template[i] = cgrp->subsys[i]; + } else { + /* Subsystem is not in this hierarchy, so we + * don't want to change the subsystem state */ + template[i] = oldcg->subsys[i]; + } + } + + key = css_set_hash(template); + hash_for_each_possible(css_set_table, cg, hlist, key) { + if (!compare_css_sets(cg, oldcg, cgrp, template)) + continue; + + /* This css_set matches what we need */ + return cg; + } + + /* No existing cgroup group matched */ + return NULL; +} + +static void free_cg_links(struct list_head *tmp) +{ + struct cg_cgroup_link *link; + struct cg_cgroup_link *saved_link; + + list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) { + list_del(&link->cgrp_link_list); + kfree(link); + } +} + +/* + * allocate_cg_links() allocates "count" cg_cgroup_link structures + * and chains them on tmp through their cgrp_link_list fields. Returns 0 on + * success or a negative error + */ +static int allocate_cg_links(int count, struct list_head *tmp) +{ + struct cg_cgroup_link *link; + int i; + INIT_LIST_HEAD(tmp); + for (i = 0; i < count; i++) { + link = kmalloc(sizeof(*link), GFP_KERNEL); + if (!link) { + free_cg_links(tmp); + return -ENOMEM; + } + list_add(&link->cgrp_link_list, tmp); + } + return 0; +} + +/** + * link_css_set - a helper function to link a css_set to a cgroup + * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links() + * @cg: the css_set to be linked + * @cgrp: the destination cgroup + */ +static void link_css_set(struct list_head *tmp_cg_links, + struct css_set *cg, struct cgroup *cgrp) +{ + struct cg_cgroup_link *link; + + BUG_ON(list_empty(tmp_cg_links)); + link = list_first_entry(tmp_cg_links, struct cg_cgroup_link, + cgrp_link_list); + link->cg = cg; + link->cgrp = cgrp; + atomic_inc(&cgrp->count); + list_move(&link->cgrp_link_list, &cgrp->css_sets); + /* + * Always add links to the tail of the list so that the list + * is sorted by order of hierarchy creation + */ + list_add_tail(&link->cg_link_list, &cg->cg_links); +} + +/* + * find_css_set() takes an existing cgroup group and a + * cgroup object, and returns a css_set object that's + * equivalent to the old group, but with the given cgroup + * substituted into the appropriate hierarchy. Must be called with + * cgroup_mutex held + */ +static struct css_set *find_css_set( + struct css_set *oldcg, struct cgroup *cgrp) +{ + struct css_set *res; + struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT]; + + struct list_head tmp_cg_links; + + struct cg_cgroup_link *link; + unsigned long key; + + /* First see if we already have a cgroup group that matches + * the desired set */ + read_lock(&css_set_lock); + res = find_existing_css_set(oldcg, cgrp, template); + if (res) + get_css_set(res); + read_unlock(&css_set_lock); + + if (res) + return res; + + res = kmalloc(sizeof(*res), GFP_KERNEL); + if (!res) + return NULL; + + /* Allocate all the cg_cgroup_link objects that we'll need */ + if (allocate_cg_links(root_count, &tmp_cg_links) < 0) { + kfree(res); + return NULL; + } + + atomic_set(&res->refcount, 1); + INIT_LIST_HEAD(&res->cg_links); + INIT_LIST_HEAD(&res->tasks); + INIT_HLIST_NODE(&res->hlist); + + /* Copy the set of subsystem state objects generated in + * find_existing_css_set() */ + memcpy(res->subsys, template, sizeof(res->subsys)); + + write_lock(&css_set_lock); + /* Add reference counts and links from the new css_set. */ + list_for_each_entry(link, &oldcg->cg_links, cg_link_list) { + struct cgroup *c = link->cgrp; + if (c->root == cgrp->root) + c = cgrp; + link_css_set(&tmp_cg_links, res, c); + } + + BUG_ON(!list_empty(&tmp_cg_links)); + + css_set_count++; + + /* Add this cgroup group to the hash table */ + key = css_set_hash(res->subsys); + hash_add(css_set_table, &res->hlist, key); + + write_unlock(&css_set_lock); + + return res; +} + +/* + * Return the cgroup for "task" from the given hierarchy. Must be + * called with cgroup_mutex held. + */ +static struct cgroup *task_cgroup_from_root(struct task_struct *task, + struct cgroupfs_root *root) +{ + struct css_set *css; + struct cgroup *res = NULL; + + BUG_ON(!mutex_is_locked(&cgroup_mutex)); + read_lock(&css_set_lock); + /* + * 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. + */ + css = task->cgroups; + if (css == &init_css_set) { + res = &root->top_cgroup; + } else { + struct cg_cgroup_link *link; + list_for_each_entry(link, &css->cg_links, cg_link_list) { + struct cgroup *c = link->cgrp; + if (c->root == root) { + res = c; + break; + } + } + } + read_unlock(&css_set_lock); + BUG_ON(!res); + return res; +} + +/* + * There is one global cgroup mutex. We also require taking + * task_lock() when dereferencing a task's cgroup subsys pointers. + * See "The task_lock() exception", at the end of this comment. + * + * 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, top_cgroup + * always has either children cgroups and/or using tasks. So we don't + * need a special hack to ensure that top_cgroup cannot be deleted. + * + * The task_lock() exception + * + * The need for this exception arises from the action of + * cgroup_attach_task(), which overwrites one task's cgroup pointer with + * another. It does so using cgroup_mutex, however there are + * several performance critical places that need to reference + * task->cgroup without the expense of grabbing a system global + * mutex. Therefore except as noted below, when dereferencing or, as + * in cgroup_attach_task(), modifying a task's cgroup pointer we use + * task_lock(), which acts on a spinlock (task->alloc_lock) already in + * the task_struct routinely used for such matters. + * + * P.S. One more locking exception. RCU is used to guard the + * update of a tasks cgroup pointer by cgroup_attach_task() + */ + +/* + * A couple of forward declarations required, due to cyclic reference loop: + * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir -> + * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations + * -> cgroup_mkdir. + */ + +static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode); +static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int); +static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry); +static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files, + unsigned long subsys_mask); +static const struct inode_operations cgroup_dir_inode_operations; +static const struct file_operations proc_cgroupstats_operations; + +static struct backing_dev_info cgroup_backing_dev_info = { + .name = "cgroup", + .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK, +}; + +static int alloc_css_id(struct cgroup_subsys *ss, + struct cgroup *parent, struct cgroup *child); + +static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb) +{ + struct inode *inode = new_inode(sb); + + if (inode) { + inode->i_ino = get_next_ino(); + inode->i_mode = mode; + inode->i_uid = current_fsuid(); + inode->i_gid = current_fsgid(); + inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; + inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info; + } + return inode; +} + +static struct cgroup_name *cgroup_alloc_name(struct dentry *dentry) +{ + struct cgroup_name *name; + + name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL); + if (!name) + return NULL; + strcpy(name->name, dentry->d_name.name); + return name; +} + +static void cgroup_free_fn(struct work_struct *work) +{ + struct cgroup *cgrp = container_of(work, struct cgroup, free_work); + struct cgroup_subsys *ss; + + mutex_lock(&cgroup_mutex); + /* + * Release the subsystem state objects. + */ + for_each_subsys(cgrp->root, ss) + ss->css_free(cgrp); + + cgrp->root->number_of_cgroups--; + mutex_unlock(&cgroup_mutex); + + /* + * We get a ref to the parent's dentry, and put the ref when + * this cgroup is being freed, so it's guaranteed that the + * parent won't be destroyed before its children. + */ + dput(cgrp->parent->dentry); + + ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id); + + /* + * Drop the active superblock reference that we took when we + * created the cgroup. This will free cgrp->root, if we are + * holding the last reference to @sb. + */ + deactivate_super(cgrp->root->sb); + + /* + * if we're getting rid of the cgroup, refcount should ensure + * that there are no pidlists left. + */ + BUG_ON(!list_empty(&cgrp->pidlists)); + + simple_xattrs_free(&cgrp->xattrs); + + kfree(rcu_dereference_raw(cgrp->name)); + kfree(cgrp); +} + +static void cgroup_free_rcu(struct rcu_head *head) +{ + struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head); + + queue_work(cgroup_destroy_wq, &cgrp->free_work); +} + +static void cgroup_diput(struct dentry *dentry, struct inode *inode) +{ + /* is dentry a directory ? if so, kfree() associated cgroup */ + if (S_ISDIR(inode->i_mode)) { + struct cgroup *cgrp = dentry->d_fsdata; + + BUG_ON(!(cgroup_is_removed(cgrp))); + call_rcu(&cgrp->rcu_head, cgroup_free_rcu); + } else { + struct cfent *cfe = __d_cfe(dentry); + struct cgroup *cgrp = dentry->d_parent->d_fsdata; + + WARN_ONCE(!list_empty(&cfe->node) && + cgrp != &cgrp->root->top_cgroup, + "cfe still linked for %s\n", cfe->type->name); + simple_xattrs_free(&cfe->xattrs); + kfree(cfe); + } + iput(inode); +} + +static int cgroup_delete(const struct dentry *d) +{ + return 1; +} + +static void remove_dir(struct dentry *d) +{ + struct dentry *parent = dget(d->d_parent); + + d_delete(d); + simple_rmdir(parent->d_inode, d); + dput(parent); +} + +static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) +{ + struct cfent *cfe; + + lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex); + lockdep_assert_held(&cgroup_mutex); + + /* + * If we're doing cleanup due to failure of cgroup_create(), + * the corresponding @cfe may not exist. + */ + list_for_each_entry(cfe, &cgrp->files, node) { + struct dentry *d = cfe->dentry; + + if (cft && cfe->type != cft) + continue; + + dget(d); + d_delete(d); + simple_unlink(cgrp->dentry->d_inode, d); + list_del_init(&cfe->node); + dput(d); + + break; + } +} + +/** + * cgroup_clear_directory - selective removal of base and subsystem files + * @dir: directory containing the files + * @base_files: true if the base files should be removed + * @subsys_mask: mask of the subsystem ids whose files should be removed + */ +static void cgroup_clear_directory(struct dentry *dir, bool base_files, + unsigned long subsys_mask) +{ + struct cgroup *cgrp = __d_cgrp(dir); + struct cgroup_subsys *ss; + + for_each_subsys(cgrp->root, ss) { + struct cftype_set *set; + if (!test_bit(ss->subsys_id, &subsys_mask)) + continue; + list_for_each_entry(set, &ss->cftsets, node) + cgroup_addrm_files(cgrp, NULL, set->cfts, false); + } + if (base_files) { + while (!list_empty(&cgrp->files)) + cgroup_rm_file(cgrp, NULL); + } +} + +/* + * NOTE : the dentry must have been dget()'ed + */ +static void cgroup_d_remove_dir(struct dentry *dentry) +{ + struct dentry *parent; + struct cgroupfs_root *root = dentry->d_sb->s_fs_info; + + cgroup_clear_directory(dentry, true, root->subsys_mask); + + parent = dentry->d_parent; + spin_lock(&parent->d_lock); + spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); + list_del_init(&dentry->d_u.d_child); + spin_unlock(&dentry->d_lock); + spin_unlock(&parent->d_lock); + remove_dir(dentry); +} + +/* + * Call with cgroup_mutex held. Drops reference counts on modules, including + * any duplicate ones that parse_cgroupfs_options took. If this function + * returns an error, no reference counts are touched. + */ +static int rebind_subsystems(struct cgroupfs_root *root, + unsigned long final_subsys_mask) +{ + unsigned long added_mask, removed_mask; + struct cgroup *cgrp = &root->top_cgroup; + int i; + + BUG_ON(!mutex_is_locked(&cgroup_mutex)); + BUG_ON(!mutex_is_locked(&cgroup_root_mutex)); + + removed_mask = root->actual_subsys_mask & ~final_subsys_mask; + added_mask = final_subsys_mask & ~root->actual_subsys_mask; + /* Check that any added subsystems are currently free */ + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + unsigned long bit = 1UL << i; + struct cgroup_subsys *ss = subsys[i]; + if (!(bit & added_mask)) + continue; + /* + * Nobody should tell us to do a subsys that doesn't exist: + * parse_cgroupfs_options should catch that case and refcounts + * ensure that subsystems won't disappear once selected. + */ + BUG_ON(ss == NULL); + if (ss->root != &rootnode) { + /* Subsystem isn't free */ + return -EBUSY; + } + } + + /* Currently we don't handle adding/removing subsystems when + * any child cgroups exist. This is theoretically supportable + * but involves complex error handling, so it's being left until + * later */ + if (root->number_of_cgroups > 1) + return -EBUSY; + + /* Process each subsystem */ + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + unsigned long bit = 1UL << i; + if (bit & added_mask) { + /* We're binding this subsystem to this hierarchy */ + BUG_ON(ss == NULL); + BUG_ON(cgrp->subsys[i]); + BUG_ON(!dummytop->subsys[i]); + BUG_ON(dummytop->subsys[i]->cgroup != dummytop); + cgrp->subsys[i] = dummytop->subsys[i]; + cgrp->subsys[i]->cgroup = cgrp; + list_move(&ss->sibling, &root->subsys_list); + ss->root = root; + if (ss->bind) + ss->bind(cgrp); + /* refcount was already taken, and we're keeping it */ + } else if (bit & removed_mask) { + /* We're removing this subsystem */ + BUG_ON(ss == NULL); + BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]); + BUG_ON(cgrp->subsys[i]->cgroup != cgrp); + if (ss->bind) + ss->bind(dummytop); + dummytop->subsys[i]->cgroup = dummytop; + cgrp->subsys[i] = NULL; + subsys[i]->root = &rootnode; + list_move(&ss->sibling, &rootnode.subsys_list); + /* subsystem is now free - drop reference on module */ + module_put(ss->module); + } else if (bit & final_subsys_mask) { + /* Subsystem state should already exist */ + BUG_ON(ss == NULL); + BUG_ON(!cgrp->subsys[i]); + /* + * a refcount was taken, but we already had one, so + * drop the extra reference. + */ + module_put(ss->module); +#ifdef CONFIG_MODULE_UNLOAD + BUG_ON(ss->module && !module_refcount(ss->module)); +#endif + } else { + /* Subsystem state shouldn't exist */ + BUG_ON(cgrp->subsys[i]); + } + } + root->subsys_mask = root->actual_subsys_mask = final_subsys_mask; + + return 0; +} + +static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry) +{ + struct cgroupfs_root *root = dentry->d_sb->s_fs_info; + struct cgroup_subsys *ss; + + mutex_lock(&cgroup_root_mutex); + for_each_subsys(root, ss) + 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"); + if (strlen(root->release_agent_path)) + seq_printf(seq, ",release_agent=%s", root->release_agent_path); + if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags)) + seq_puts(seq, ",clone_children"); + if (strlen(root->name)) + seq_printf(seq, ",name=%s", root->name); + mutex_unlock(&cgroup_root_mutex); + 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; + + struct cgroupfs_root *new_root; + +}; + +/* + * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call + * with cgroup_mutex held to protect the 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; + int i; + bool module_pin_failed = false; + + BUG_ON(!mutex_is_locked(&cgroup_mutex)); + +#ifdef CONFIG_CPUSETS + mask = ~(1UL << cpuset_subsys_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 (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + if (ss == NULL) + continue; + 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; + } + + /* + * 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 (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + if (ss == NULL) + continue; + if (ss->disabled) + continue; + set_bit(i, &opts->subsys_mask); + } + } + + /* 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) { + pr_err("cgroup: sane_behavior: noprefix is not allowed\n"); + return -EINVAL; + } + + if (opts->cpuset_clone_children) { + pr_err("cgroup: sane_behavior: clone_children is not allowed\n"); + 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; + + /* + * 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; + + /* + * Grab references on all the modules we'll need, so the subsystems + * don't dance around before rebind_subsystems attaches them. This may + * take duplicate reference counts on a subsystem that's already used, + * but rebind_subsystems handles this case. + */ + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + unsigned long bit = 1UL << i; + + if (!(bit & opts->subsys_mask)) + continue; + if (!try_module_get(subsys[i]->module)) { + module_pin_failed = true; + break; + } + } + if (module_pin_failed) { + /* + * oops, one of the modules was going away. this means that we + * raced with a module_delete call, and to the user this is + * essentially a "subsystem doesn't exist" case. + */ + for (i--; i >= 0; i--) { + /* drop refcounts only on the ones we took */ + unsigned long bit = 1UL << i; + + if (!(bit & opts->subsys_mask)) + continue; + module_put(subsys[i]->module); + } + return -ENOENT; + } + + return 0; +} + +static void drop_parsed_module_refcounts(unsigned long subsys_mask) +{ + int i; + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + unsigned long bit = 1UL << i; + + if (!(bit & subsys_mask)) + continue; + module_put(subsys[i]->module); + } +} + +static int cgroup_remount(struct super_block *sb, int *flags, char *data) +{ + int ret = 0; + struct cgroupfs_root *root = sb->s_fs_info; + struct cgroup *cgrp = &root->top_cgroup; + 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(&cgrp->dentry->d_inode->i_mutex); + mutex_lock(&cgroup_mutex); + mutex_lock(&cgroup_root_mutex); + + /* See what subsystems are wanted */ + ret = parse_cgroupfs_options(data, &opts); + if (ret) + goto out_unlock; + + if (opts.subsys_mask != root->actual_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->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))) { + ret = -EINVAL; + drop_parsed_module_refcounts(opts.subsys_mask); + goto out_unlock; + } + + /* + * Clear out the files of subsystems that should be removed, do + * this before rebind_subsystems, since rebind_subsystems may + * change this hierarchy's subsys_list. + */ + cgroup_clear_directory(cgrp->dentry, false, removed_mask); + + ret = rebind_subsystems(root, opts.subsys_mask); + if (ret) { + /* rebind_subsystems failed, re-populate the removed files */ + cgroup_populate_dir(cgrp, false, removed_mask); + drop_parsed_module_refcounts(opts.subsys_mask); + goto out_unlock; + } + + /* re-populate subsystem files */ + cgroup_populate_dir(cgrp, false, added_mask); + + if (opts.release_agent) + strcpy(root->release_agent_path, opts.release_agent); + out_unlock: + kfree(opts.release_agent); + kfree(opts.name); + mutex_unlock(&cgroup_root_mutex); + mutex_unlock(&cgroup_mutex); + mutex_unlock(&cgrp->dentry->d_inode->i_mutex); + return ret; +} + +static const struct super_operations cgroup_ops = { + .statfs = simple_statfs, + .drop_inode = generic_delete_inode, + .show_options = cgroup_show_options, + .remount_fs = cgroup_remount, +}; + +static void init_cgroup_housekeeping(struct cgroup *cgrp) +{ + INIT_LIST_HEAD(&cgrp->sibling); + INIT_LIST_HEAD(&cgrp->children); + INIT_LIST_HEAD(&cgrp->files); + INIT_LIST_HEAD(&cgrp->css_sets); + INIT_LIST_HEAD(&cgrp->allcg_node); + INIT_LIST_HEAD(&cgrp->release_list); + INIT_LIST_HEAD(&cgrp->pidlists); + INIT_WORK(&cgrp->free_work, cgroup_free_fn); + mutex_init(&cgrp->pidlist_mutex); + INIT_LIST_HEAD(&cgrp->event_list); + spin_lock_init(&cgrp->event_list_lock); + simple_xattrs_init(&cgrp->xattrs); +} + +static void init_cgroup_root(struct cgroupfs_root *root) +{ + struct cgroup *cgrp = &root->top_cgroup; + + INIT_LIST_HEAD(&root->subsys_list); + INIT_LIST_HEAD(&root->root_list); + INIT_LIST_HEAD(&root->allcg_list); + root->number_of_cgroups = 1; + cgrp->root = root; + cgrp->name = &root_cgroup_name; + init_cgroup_housekeeping(cgrp); + list_add_tail(&cgrp->allcg_node, &root->allcg_list); +} + +static bool init_root_id(struct cgroupfs_root *root) +{ + int ret = 0; + + do { + if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL)) + return false; + spin_lock(&hierarchy_id_lock); + /* Try to allocate the next unused ID */ + ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id, + &root->hierarchy_id); + if (ret == -ENOSPC) + /* Try again starting from 0 */ + ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id); + if (!ret) { + next_hierarchy_id = root->hierarchy_id + 1; + } else if (ret != -EAGAIN) { + /* Can only get here if the 31-bit IDR is full ... */ + BUG_ON(ret); + } + spin_unlock(&hierarchy_id_lock); + } while (ret); + return true; +} + +static int cgroup_test_super(struct super_block *sb, void *data) +{ + struct cgroup_sb_opts *opts = data; + struct cgroupfs_root *root = sb->s_fs_info; + + /* If we asked for a name then it must match */ + if (opts->name && strcmp(opts->name, root->name)) + return 0; + + /* + * 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)) + return 0; + + return 1; +} + +static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts) +{ + struct cgroupfs_root *root; + + if (!opts->subsys_mask && !opts->none) + return NULL; + + root = kzalloc(sizeof(*root), GFP_KERNEL); + if (!root) + return ERR_PTR(-ENOMEM); + + if (!init_root_id(root)) { + kfree(root); + return ERR_PTR(-ENOMEM); + } + init_cgroup_root(root); + + root->subsys_mask = opts->subsys_mask; + root->flags = opts->flags; + ida_init(&root->cgroup_ida); + 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->top_cgroup.flags); + return root; +} + +static void cgroup_drop_root(struct cgroupfs_root *root) +{ + if (!root) + return; + + BUG_ON(!root->hierarchy_id); + spin_lock(&hierarchy_id_lock); + ida_remove(&hierarchy_ida, root->hierarchy_id); + spin_unlock(&hierarchy_id_lock); + ida_destroy(&root->cgroup_ida); + kfree(root); +} + +static int cgroup_set_super(struct super_block *sb, void *data) +{ + int ret; + struct cgroup_sb_opts *opts = data; + + /* If we don't have a new root, we can't set up a new sb */ + if (!opts->new_root) + return -EINVAL; + + BUG_ON(!opts->subsys_mask && !opts->none); + + ret = set_anon_super(sb, NULL); + if (ret) + return ret; + + sb->s_fs_info = opts->new_root; + opts->new_root->sb = sb; + + sb->s_blocksize = PAGE_CACHE_SIZE; + sb->s_blocksize_bits = PAGE_CACHE_SHIFT; + sb->s_magic = CGROUP_SUPER_MAGIC; + sb->s_op = &cgroup_ops; + + return 0; +} + +static int cgroup_get_rootdir(struct super_block *sb) +{ + static const struct dentry_operations cgroup_dops = { + .d_iput = cgroup_diput, + .d_delete = cgroup_delete, + }; + + struct inode *inode = + cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb); + + if (!inode) + return -ENOMEM; + + inode->i_fop = &simple_dir_operations; + inode->i_op = &cgroup_dir_inode_operations; + /* directories start off with i_nlink == 2 (for "." entry) */ + inc_nlink(inode); + sb->s_root = d_make_root(inode); + if (!sb->s_root) + return -ENOMEM; + /* for everything else we want ->d_op set */ + sb->s_d_op = &cgroup_dops; + return 0; +} + +static struct dentry *cgroup_mount(struct file_system_type *fs_type, + int flags, const char *unused_dev_name, + void *data) +{ + struct cgroup_sb_opts opts; + struct cgroupfs_root *root; + int ret = 0; + struct super_block *sb; + struct cgroupfs_root *new_root; + struct inode *inode; + + /* First find the desired set of subsystems */ + mutex_lock(&cgroup_mutex); + ret = parse_cgroupfs_options(data, &opts); + mutex_unlock(&cgroup_mutex); + if (ret) + goto out_err; + + /* + * Allocate a new cgroup root. We may not need it if we're + * reusing an existing hierarchy. + */ + new_root = cgroup_root_from_opts(&opts); + if (IS_ERR(new_root)) { + ret = PTR_ERR(new_root); + goto drop_modules; + } + opts.new_root = new_root; + + /* Locate an existing or new sb for this hierarchy */ + sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts); + if (IS_ERR(sb)) { + ret = PTR_ERR(sb); + cgroup_drop_root(opts.new_root); + goto drop_modules; + } + + root = sb->s_fs_info; + BUG_ON(!root); + if (root == opts.new_root) { + /* We used the new root structure, so this is a new hierarchy */ + struct list_head tmp_cg_links; + struct cgroup *root_cgrp = &root->top_cgroup; + struct cgroupfs_root *existing_root; + const struct cred *cred; + int i; + struct css_set *cg; + + BUG_ON(sb->s_root != NULL); + + ret = cgroup_get_rootdir(sb); + if (ret) + goto drop_new_super; + inode = sb->s_root->d_inode; + + mutex_lock(&inode->i_mutex); + mutex_lock(&cgroup_mutex); + mutex_lock(&cgroup_root_mutex); + + /* Check for name clashes with existing mounts */ + ret = -EBUSY; + if (strlen(root->name)) + for_each_active_root(existing_root) + if (!strcmp(existing_root->name, root->name)) + goto unlock_drop; + + /* + * We're accessing css_set_count without locking + * css_set_lock here, but that's OK - it can only be + * increased by someone holding cgroup_lock, and + * that's us. The worst that can happen is that we + * have some link structures left over + */ + ret = allocate_cg_links(css_set_count, &tmp_cg_links); + if (ret) + goto unlock_drop; + + ret = rebind_subsystems(root, root->subsys_mask); + if (ret == -EBUSY) { + free_cg_links(&tmp_cg_links); + goto unlock_drop; + } + /* + * There must be no failure case after here, since rebinding + * takes care of subsystems' refcounts, which are explicitly + * dropped in the failure exit path. + */ + + /* EBUSY should be the only error here */ + BUG_ON(ret); + + list_add(&root->root_list, &roots); + root_count++; + + sb->s_root->d_fsdata = root_cgrp; + root->top_cgroup.dentry = sb->s_root; + + /* Link the top cgroup in this hierarchy into all + * the css_set objects */ + write_lock(&css_set_lock); + hash_for_each(css_set_table, i, cg, hlist) + link_css_set(&tmp_cg_links, cg, root_cgrp); + write_unlock(&css_set_lock); + + free_cg_links(&tmp_cg_links); + + BUG_ON(!list_empty(&root_cgrp->children)); + BUG_ON(root->number_of_cgroups != 1); + + cred = override_creds(&init_cred); + cgroup_populate_dir(root_cgrp, true, root->subsys_mask); + revert_creds(cred); + mutex_unlock(&cgroup_root_mutex); + mutex_unlock(&cgroup_mutex); + mutex_unlock(&inode->i_mutex); + } else { + /* + * We re-used an existing hierarchy - the new root (if + * any) is not needed + */ + cgroup_drop_root(opts.new_root); + + if (root->flags != opts.flags) { + 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 drop_new_super; + } else { + pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n"); + } + } + + /* no subsys rebinding, so refcounts don't change */ + drop_parsed_module_refcounts(opts.subsys_mask); + } + + kfree(opts.release_agent); + kfree(opts.name); + return dget(sb->s_root); + + unlock_drop: + mutex_unlock(&cgroup_root_mutex); + mutex_unlock(&cgroup_mutex); + mutex_unlock(&inode->i_mutex); + drop_new_super: + deactivate_locked_super(sb); + drop_modules: + drop_parsed_module_refcounts(opts.subsys_mask); + out_err: + kfree(opts.release_agent); + kfree(opts.name); + return ERR_PTR(ret); +} + +static void cgroup_kill_sb(struct super_block *sb) { + struct cgroupfs_root *root = sb->s_fs_info; + struct cgroup *cgrp = &root->top_cgroup; + int ret; + struct cg_cgroup_link *link; + struct cg_cgroup_link *saved_link; + + BUG_ON(!root); + + BUG_ON(root->number_of_cgroups != 1); + BUG_ON(!list_empty(&cgrp->children)); + + mutex_lock(&cgroup_mutex); + mutex_lock(&cgroup_root_mutex); + + /* Rebind all subsystems back to the default hierarchy */ + ret = rebind_subsystems(root, 0); + /* Shouldn't be able to fail ... */ + BUG_ON(ret); + + /* + * Release all the links from css_sets to this hierarchy's + * root cgroup + */ + write_lock(&css_set_lock); + + list_for_each_entry_safe(link, saved_link, &cgrp->css_sets, + cgrp_link_list) { + list_del(&link->cg_link_list); + list_del(&link->cgrp_link_list); + kfree(link); + } + write_unlock(&css_set_lock); + + if (!list_empty(&root->root_list)) { + list_del(&root->root_list); + root_count--; + } + + mutex_unlock(&cgroup_root_mutex); + mutex_unlock(&cgroup_mutex); + + simple_xattrs_free(&cgrp->xattrs); + + kill_litter_super(sb); + cgroup_drop_root(root); +} + +static struct file_system_type cgroup_fs_type = { + .name = "cgroup", + .mount = cgroup_mount, + .kill_sb = cgroup_kill_sb, +}; + +static struct kobject *cgroup_kobj; + +/** + * cgroup_path - generate the path of a cgroup + * @cgrp: the cgroup in question + * @buf: the buffer to write the path into + * @buflen: the length of the buffer + * + * Writes path of cgroup into buf. Returns 0 on success, -errno on error. + * + * We can't generate cgroup path using dentry->d_name, as accessing + * dentry->name must be protected by irq-unsafe dentry->d_lock or parent + * inode's i_mutex, while on the other hand cgroup_path() can be called + * with some irq-safe spinlocks held. + */ +int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen) +{ + int ret = -ENAMETOOLONG; + char *start; + + if (!cgrp->parent) { + if (strlcpy(buf, "/", buflen) >= buflen) + return -ENAMETOOLONG; + return 0; + } + + start = buf + buflen - 1; + *start = '\0'; + + rcu_read_lock(); + do { + const char *name = cgroup_name(cgrp); + int len; + + len = strlen(name); + if ((start -= len) < buf) + goto out; + memcpy(start, name, len); + + if (--start < buf) + goto out; + *start = '/'; + + cgrp = cgrp->parent; + } while (cgrp->parent); + ret = 0; + memmove(buf, start, buf + buflen - start); +out: + rcu_read_unlock(); + return ret; +} +EXPORT_SYMBOL_GPL(cgroup_path); + +/* + * Control Group taskset + */ +struct task_and_cgroup { + struct task_struct *task; + struct cgroup *cgrp; + struct css_set *cg; +}; + +struct cgroup_taskset { + struct task_and_cgroup single; + struct flex_array *tc_array; + int tc_array_len; + int idx; + struct cgroup *cur_cgrp; +}; + +/** + * 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) +{ + if (tset->tc_array) { + tset->idx = 0; + return cgroup_taskset_next(tset); + } else { + tset->cur_cgrp = tset->single.cgrp; + return tset->single.task; + } +} +EXPORT_SYMBOL_GPL(cgroup_taskset_first); + +/** + * 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 task_and_cgroup *tc; + + if (!tset->tc_array || tset->idx >= tset->tc_array_len) + return NULL; + + tc = flex_array_get(tset->tc_array, tset->idx++); + tset->cur_cgrp = tc->cgrp; + return tc->task; +} +EXPORT_SYMBOL_GPL(cgroup_taskset_next); + +/** + * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task + * @tset: taskset of interest + * + * Return the cgroup for the current (last returned) task of @tset. This + * function must be preceded by either cgroup_taskset_first() or + * cgroup_taskset_next(). + */ +struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset) +{ + return tset->cur_cgrp; +} +EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup); + +/** + * cgroup_taskset_size - return the number of tasks in taskset + * @tset: taskset of interest + */ +int cgroup_taskset_size(struct cgroup_taskset *tset) +{ + return tset->tc_array ? tset->tc_array_len : 1; +} +EXPORT_SYMBOL_GPL(cgroup_taskset_size); + + +/* + * cgroup_task_migrate - move a task from one cgroup to another. + * + * Must be called with cgroup_mutex and threadgroup locked. + */ +static void cgroup_task_migrate(struct cgroup *oldcgrp, + struct task_struct *tsk, struct css_set *newcg) +{ + struct css_set *oldcg; + + /* + * 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); + oldcg = tsk->cgroups; + + task_lock(tsk); + rcu_assign_pointer(tsk->cgroups, newcg); + task_unlock(tsk); + + /* Update the css_set linked lists if we're using them */ + write_lock(&css_set_lock); + if (!list_empty(&tsk->cg_list)) + list_move(&tsk->cg_list, &newcg->tasks); + write_unlock(&css_set_lock); + + /* + * We just gained a reference on oldcg by taking it from the task. As + * trading it for newcg is protected by cgroup_mutex, we're safe to drop + * it here; it will be freed under RCU. + */ + set_bit(CGRP_RELEASABLE, &oldcgrp->flags); + put_css_set(oldcg); +} + +/** + * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup + * @cgrp: the cgroup to attach to + * @tsk: the task or the leader of the threadgroup to be attached + * @threadgroup: attach the whole threadgroup? + * + * Call holding cgroup_mutex and the group_rwsem of the leader. Will take + * task_lock of @tsk or each thread in the threadgroup individually in turn. + */ +static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, + bool threadgroup) +{ + int retval, i, group_size; + struct cgroup_subsys *ss, *failed_ss = NULL; + struct cgroupfs_root *root = cgrp->root; + /* threadgroup list cursor and array */ + struct task_struct *leader = tsk; + struct task_and_cgroup *tc; + struct flex_array *group; + struct cgroup_taskset tset = { }; + + /* + * step 0: in order to do expensive, possibly blocking operations for + * every thread, we cannot iterate the thread group list, since it needs + * rcu or tasklist locked. instead, build an array of all threads in the + * group - group_rwsem prevents new threads from appearing, and if + * threads exit, this will just be an over-estimate. + */ + if (threadgroup) + group_size = get_nr_threads(tsk); + else + group_size = 1; + /* flex_array supports very large thread-groups better than kmalloc. */ + group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL); + if (!group) + return -ENOMEM; + /* pre-allocate to guarantee space while iterating in rcu read-side. */ + retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL); + if (retval) + goto out_free_group_list; + + i = 0; + /* + * 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. + */ + rcu_read_lock(); + do { + struct task_and_cgroup ent; + + /* @tsk either already exited or can't exit until the end */ + if (tsk->flags & PF_EXITING) + goto next; + + /* as per above, nr_threads may decrease, but not increase. */ + BUG_ON(i >= group_size); + ent.task = tsk; + ent.cgrp = task_cgroup_from_root(tsk, root); + /* nothing to do if this task is already in the cgroup */ + if (ent.cgrp == cgrp) + goto next; + /* + * saying GFP_ATOMIC has no effect here because we did prealloc + * earlier, but it's good form to communicate our expectations. + */ + retval = flex_array_put(group, i, &ent, GFP_ATOMIC); + BUG_ON(retval != 0); + i++; + next: + if (!threadgroup) + break; + } while_each_thread(leader, tsk); + rcu_read_unlock(); + /* remember the number of threads in the array for later. */ + group_size = i; + tset.tc_array = group; + tset.tc_array_len = group_size; + + /* methods shouldn't be called if no task is actually migrating */ + retval = 0; + if (!group_size) + goto out_free_group_list; + + /* + * step 1: check that we can legitimately attach to the cgroup. + */ + for_each_subsys(root, ss) { + if (ss->can_attach) { + retval = ss->can_attach(cgrp, &tset); + if (retval) { + failed_ss = ss; + goto out_cancel_attach; + } + } + } + + /* + * step 2: make sure css_sets exist for all threads to be migrated. + * we use find_css_set, which allocates a new one if necessary. + */ + for (i = 0; i < group_size; i++) { + tc = flex_array_get(group, i); + tc->cg = find_css_set(tc->task->cgroups, cgrp); + if (!tc->cg) { + retval = -ENOMEM; + goto out_put_css_set_refs; + } + } + + /* + * step 3: now that we're guaranteed success wrt the css_sets, + * proceed to move all tasks to the new cgroup. There are no + * failure cases after here, so this is the commit point. + */ + for (i = 0; i < group_size; i++) { + tc = flex_array_get(group, i); + cgroup_task_migrate(tc->cgrp, tc->task, tc->cg); + } + /* nothing is sensitive to fork() after this point. */ + + /* + * step 4: do subsystem attach callbacks. + */ + for_each_subsys(root, ss) { + if (ss->attach) + ss->attach(cgrp, &tset); + } + + /* + * step 5: success! and cleanup + */ + retval = 0; +out_put_css_set_refs: + if (retval) { + for (i = 0; i < group_size; i++) { + tc = flex_array_get(group, i); + if (!tc->cg) + break; + put_css_set(tc->cg); + } + } +out_cancel_attach: + if (retval) { + for_each_subsys(root, ss) { + if (ss == failed_ss) + break; + if (ss->cancel_attach) + ss->cancel_attach(cgrp, &tset); + } + } +out_free_group_list: + flex_array_free(group); + return retval; +} + +static int cgroup_allow_attach(struct cgroup *cgrp, struct cgroup_taskset *tset) +{ + struct cgroup_subsys *ss; + int ret; + + for_each_subsys(cgrp->root, ss) { + if (ss->allow_attach) { + ret = ss->allow_attach(cgrp, tset); + if (ret) + return ret; + } else { + return -EACCES; + } + } + + return 0; +} + +int subsys_cgroup_allow_attach(struct cgroup *cgrp, struct cgroup_taskset *tset) +{ + const struct cred *cred = current_cred(), *tcred; + struct task_struct *task; + + if (capable(CAP_SYS_NICE)) + return 0; + + cgroup_taskset_for_each(task, cgrp, tset) { + tcred = __task_cred(task); + + if (current != task && cred->euid != tcred->uid && + cred->euid != tcred->suid) + return -EACCES; + } + + return 0; +} + +/* + * 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; may take task_lock of task. + */ +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)) { + /* + * if the default permission check fails, give each + * cgroup a chance to extend the permission check + */ + struct cgroup_taskset tset = { }; + tset.single.task = tsk; + tset.single.cgrp = cgrp; + ret = cgroup_allow_attach(cgrp, &tset); + if (ret) { + rcu_read_unlock(); + 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 cgroupfs_root *root; + int retval = 0; + + mutex_lock(&cgroup_mutex); + for_each_active_root(root) { + struct cgroup *from_cg = task_cgroup_from_root(from, root); + + retval = cgroup_attach_task(from_cg, 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 *cgrp, struct cftype *cft, u64 pid) +{ + return attach_task_by_pid(cgrp, pid, false); +} + +static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid) +{ + return attach_task_by_pid(cgrp, tgid, true); +} + +static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft, + const char *buffer) +{ + BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX); + if (strlen(buffer) >= PATH_MAX) + return -EINVAL; + if (!cgroup_lock_live_group(cgrp)) + return -ENODEV; + mutex_lock(&cgroup_root_mutex); + strcpy(cgrp->root->release_agent_path, buffer); + mutex_unlock(&cgroup_root_mutex); + mutex_unlock(&cgroup_mutex); + return 0; +} + +static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft, + struct seq_file *seq) +{ + 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 cgroup *cgrp, struct cftype *cft, + struct seq_file *seq) +{ + seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp)); + return 0; +} + +/* A buffer size big enough for numbers or short strings */ +#define CGROUP_LOCAL_BUFFER_SIZE 64 + +static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + const char __user *userbuf, + size_t nbytes, loff_t *unused_ppos) +{ + char buffer[CGROUP_LOCAL_BUFFER_SIZE]; + int retval = 0; + char *end; + + if (!nbytes) + return -EINVAL; + if (nbytes >= sizeof(buffer)) + return -E2BIG; + if (copy_from_user(buffer, userbuf, nbytes)) + return -EFAULT; + + buffer[nbytes] = 0; /* nul-terminate */ + if (cft->write_u64) { + u64 val = simple_strtoull(strstrip(buffer), &end, 0); + if (*end) + return -EINVAL; + retval = cft->write_u64(cgrp, cft, val); + } else { + s64 val = simple_strtoll(strstrip(buffer), &end, 0); + if (*end) + return -EINVAL; + retval = cft->write_s64(cgrp, cft, val); + } + if (!retval) + retval = nbytes; + return retval; +} + +static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + const char __user *userbuf, + size_t nbytes, loff_t *unused_ppos) +{ + char local_buffer[CGROUP_LOCAL_BUFFER_SIZE]; + int retval = 0; + size_t max_bytes = cft->max_write_len; + char *buffer = local_buffer; + + if (!max_bytes) + max_bytes = sizeof(local_buffer) - 1; + if (nbytes >= max_bytes) + return -E2BIG; + /* Allocate a dynamic buffer if we need one */ + if (nbytes >= sizeof(local_buffer)) { + buffer = kmalloc(nbytes + 1, GFP_KERNEL); + if (buffer == NULL) + return -ENOMEM; + } + if (nbytes && copy_from_user(buffer, userbuf, nbytes)) { + retval = -EFAULT; + goto out; + } + + buffer[nbytes] = 0; /* nul-terminate */ + retval = cft->write_string(cgrp, cft, strstrip(buffer)); + if (!retval) + retval = nbytes; +out: + if (buffer != local_buffer) + kfree(buffer); + return retval; +} + +static ssize_t cgroup_file_write(struct file *file, const char __user *buf, + size_t nbytes, loff_t *ppos) +{ + struct cftype *cft = __d_cft(file->f_dentry); + struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent); + + if (cgroup_is_removed(cgrp)) + return -ENODEV; + if (cft->write) + return cft->write(cgrp, cft, file, buf, nbytes, ppos); + if (cft->write_u64 || cft->write_s64) + return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos); + if (cft->write_string) + return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos); + if (cft->trigger) { + int ret = cft->trigger(cgrp, (unsigned int)cft->private); + return ret ? ret : nbytes; + } + return -EINVAL; +} + +static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + char __user *buf, size_t nbytes, + loff_t *ppos) +{ + char tmp[CGROUP_LOCAL_BUFFER_SIZE]; + u64 val = cft->read_u64(cgrp, cft); + int len = sprintf(tmp, "%llu\n", (unsigned long long) val); + + return simple_read_from_buffer(buf, nbytes, ppos, tmp, len); +} + +static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + char __user *buf, size_t nbytes, + loff_t *ppos) +{ + char tmp[CGROUP_LOCAL_BUFFER_SIZE]; + s64 val = cft->read_s64(cgrp, cft); + int len = sprintf(tmp, "%lld\n", (long long) val); + + return simple_read_from_buffer(buf, nbytes, ppos, tmp, len); +} + +static ssize_t cgroup_file_read(struct file *file, char __user *buf, + size_t nbytes, loff_t *ppos) +{ + struct cftype *cft = __d_cft(file->f_dentry); + struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent); + + if (cgroup_is_removed(cgrp)) + return -ENODEV; + + if (cft->read) + return cft->read(cgrp, cft, file, buf, nbytes, ppos); + if (cft->read_u64) + return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos); + if (cft->read_s64) + return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos); + return -EINVAL; +} + +/* + * seqfile ops/methods for returning structured data. Currently just + * supports string->u64 maps, but can be extended in future. + */ + +struct cgroup_seqfile_state { + struct cftype *cft; + struct cgroup *cgroup; +}; + +static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value) +{ + struct seq_file *sf = cb->state; + return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value); +} + +static int cgroup_seqfile_show(struct seq_file *m, void *arg) +{ + struct cgroup_seqfile_state *state = m->private; + struct cftype *cft = state->cft; + if (cft->read_map) { + struct cgroup_map_cb cb = { + .fill = cgroup_map_add, + .state = m, + }; + return cft->read_map(state->cgroup, cft, &cb); + } + return cft->read_seq_string(state->cgroup, cft, m); +} + +static int cgroup_seqfile_release(struct inode *inode, struct file *file) +{ + struct seq_file *seq = file->private_data; + kfree(seq->private); + return single_release(inode, file); +} + +static const struct file_operations cgroup_seqfile_operations = { + .read = seq_read, + .write = cgroup_file_write, + .llseek = seq_lseek, + .release = cgroup_seqfile_release, +}; + +static int cgroup_file_open(struct inode *inode, struct file *file) +{ + int err; + struct cftype *cft; + + err = generic_file_open(inode, file); + if (err) + return err; + cft = __d_cft(file->f_dentry); + + if (cft->read_map || cft->read_seq_string) { + struct cgroup_seqfile_state *state = + kzalloc(sizeof(*state), GFP_USER); + if (!state) + return -ENOMEM; + state->cft = cft; + state->cgroup = __d_cgrp(file->f_dentry->d_parent); + file->f_op = &cgroup_seqfile_operations; + err = single_open(file, cgroup_seqfile_show, state); + if (err < 0) + kfree(state); + } else if (cft->open) + err = cft->open(inode, file); + else + err = 0; + + return err; +} + +static int cgroup_file_release(struct inode *inode, struct file *file) +{ + struct cftype *cft = __d_cft(file->f_dentry); + if (cft->release) + return cft->release(inode, file); + return 0; +} + +/* + * cgroup_rename - Only allow simple rename of directories in place. + */ +static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry) +{ + int ret; + struct cgroup_name *name, *old_name; + struct cgroup *cgrp; + + /* + * It's convinient to use parent dir's i_mutex to protected + * cgrp->name. + */ + lockdep_assert_held(&old_dir->i_mutex); + + if (!S_ISDIR(old_dentry->d_inode->i_mode)) + return -ENOTDIR; + if (new_dentry->d_inode) + return -EEXIST; + if (old_dir != new_dir) + return -EIO; + + cgrp = __d_cgrp(old_dentry); + + name = cgroup_alloc_name(new_dentry); + if (!name) + return -ENOMEM; + + ret = simple_rename(old_dir, old_dentry, new_dir, new_dentry); + if (ret) { + kfree(name); + return ret; + } + + old_name = cgrp->name; + rcu_assign_pointer(cgrp->name, name); + + kfree_rcu(old_name, rcu_head); + return 0; +} + +static struct simple_xattrs *__d_xattrs(struct dentry *dentry) +{ + if (S_ISDIR(dentry->d_inode->i_mode)) + return &__d_cgrp(dentry)->xattrs; + else + return &__d_cfe(dentry)->xattrs; +} + +static inline int xattr_enabled(struct dentry *dentry) +{ + struct cgroupfs_root *root = dentry->d_sb->s_fs_info; + return root->flags & CGRP_ROOT_XATTR; +} + +static bool is_valid_xattr(const char *name) +{ + if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) || + !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) + return true; + return false; +} + +static int cgroup_setxattr(struct dentry *dentry, const char *name, + const void *val, size_t size, int flags) +{ + if (!xattr_enabled(dentry)) + return -EOPNOTSUPP; + if (!is_valid_xattr(name)) + return -EINVAL; + return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags); +} + +static int cgroup_removexattr(struct dentry *dentry, const char *name) +{ + if (!xattr_enabled(dentry)) + return -EOPNOTSUPP; + if (!is_valid_xattr(name)) + return -EINVAL; + return simple_xattr_remove(__d_xattrs(dentry), name); +} + +static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name, + void *buf, size_t size) +{ + if (!xattr_enabled(dentry)) + return -EOPNOTSUPP; + if (!is_valid_xattr(name)) + return -EINVAL; + return simple_xattr_get(__d_xattrs(dentry), name, buf, size); +} + +static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size) +{ + if (!xattr_enabled(dentry)) + return -EOPNOTSUPP; + return simple_xattr_list(__d_xattrs(dentry), buf, size); +} + +static const struct file_operations cgroup_file_operations = { + .read = cgroup_file_read, + .write = cgroup_file_write, + .llseek = generic_file_llseek, + .open = cgroup_file_open, + .release = cgroup_file_release, +}; + +static const struct inode_operations cgroup_file_inode_operations = { + .setxattr = cgroup_setxattr, + .getxattr = cgroup_getxattr, + .listxattr = cgroup_listxattr, + .removexattr = cgroup_removexattr, +}; + +static const struct inode_operations cgroup_dir_inode_operations = { + .lookup = cgroup_lookup, + .mkdir = cgroup_mkdir, + .rmdir = cgroup_rmdir, + .rename = cgroup_rename, + .setxattr = cgroup_setxattr, + .getxattr = cgroup_getxattr, + .listxattr = cgroup_listxattr, + .removexattr = cgroup_removexattr, +}; + +static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) +{ + if (dentry->d_name.len > NAME_MAX) + return ERR_PTR(-ENAMETOOLONG); + d_add(dentry, NULL); + return NULL; +} + +/* + * Check if a file is a control file + */ +static inline struct cftype *__file_cft(struct file *file) +{ + if (file_inode(file)->i_fop != &cgroup_file_operations) + return ERR_PTR(-EINVAL); + return __d_cft(file->f_dentry); +} + +static int cgroup_create_file(struct dentry *dentry, umode_t mode, + struct super_block *sb) +{ + struct inode *inode; + + if (!dentry) + return -ENOENT; + if (dentry->d_inode) + return -EEXIST; + + inode = cgroup_new_inode(mode, sb); + if (!inode) + return -ENOMEM; + + if (S_ISDIR(mode)) { + inode->i_op = &cgroup_dir_inode_operations; + inode->i_fop = &simple_dir_operations; + + /* start off with i_nlink == 2 (for "." entry) */ + inc_nlink(inode); + inc_nlink(dentry->d_parent->d_inode); + + /* + * Control reaches here with cgroup_mutex held. + * @inode->i_mutex should nest outside cgroup_mutex but we + * want to populate it immediately without releasing + * cgroup_mutex. As @inode isn't visible to anyone else + * yet, trylock will always succeed without affecting + * lockdep checks. + */ + WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex)); + } else if (S_ISREG(mode)) { + inode->i_size = 0; + inode->i_fop = &cgroup_file_operations; + inode->i_op = &cgroup_file_inode_operations; + } + d_instantiate(dentry, inode); + dget(dentry); /* Extra count - pin the dentry in core */ + return 0; +} + +/** + * 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 || cft->read_u64 || cft->read_s64 || + cft->read_map || cft->read_seq_string) + mode |= S_IRUGO; + + if (cft->write || cft->write_u64 || cft->write_s64 || + cft->write_string || cft->trigger) + mode |= S_IWUSR; + + return mode; +} + +static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys, + struct cftype *cft) +{ + struct dentry *dir = cgrp->dentry; + struct cgroup *parent = __d_cgrp(dir); + struct dentry *dentry; + struct cfent *cfe; + int error; + umode_t mode; + char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 }; + + if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) { + strcpy(name, subsys->name); + strcat(name, "."); + } + strcat(name, cft->name); + + BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex)); + + cfe = kzalloc(sizeof(*cfe), GFP_KERNEL); + if (!cfe) + return -ENOMEM; + + dentry = lookup_one_len(name, dir, strlen(name)); + if (IS_ERR(dentry)) { + error = PTR_ERR(dentry); + goto out; + } + + cfe->type = (void *)cft; + cfe->dentry = dentry; + dentry->d_fsdata = cfe; + simple_xattrs_init(&cfe->xattrs); + + mode = cgroup_file_mode(cft); + error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb); + if (!error) { + list_add_tail(&cfe->node, &parent->files); + cfe = NULL; + } + dput(dentry); +out: + kfree(cfe); + return error; +} + +static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys, + struct cftype cfts[], bool is_add) +{ + struct cftype *cft; + int err, ret = 0; + + for (cft = cfts; cft->name[0] != '\0'; cft++) { + /* does cft->flags tell us to skip this file on @cgrp? */ + if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp)) + continue; + if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent) + continue; + if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent) + continue; + + if (is_add) { + err = cgroup_add_file(cgrp, subsys, cft); + if (err) + pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n", + cft->name, err); + ret = err; + } else { + cgroup_rm_file(cgrp, cft); + } + } + return ret; +} + +static DEFINE_MUTEX(cgroup_cft_mutex); + +static void cgroup_cfts_prepare(void) + __acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex) +{ + /* + * Thanks to the entanglement with vfs inode locking, we can't walk + * the existing cgroups under cgroup_mutex and create files. + * Instead, we increment reference on all cgroups and build list of + * them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure + * exclusive access to the field. + */ + mutex_lock(&cgroup_cft_mutex); + mutex_lock(&cgroup_mutex); +} + +static void cgroup_cfts_commit(struct cgroup_subsys *ss, + struct cftype *cfts, bool is_add) + __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex) +{ + LIST_HEAD(pending); + struct cgroup *cgrp, *n; + struct super_block *sb = ss->root->sb; + + /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */ + if (cfts && ss->root != &rootnode && + atomic_inc_not_zero(&sb->s_active)) { + list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) { + dget(cgrp->dentry); + list_add_tail(&cgrp->cft_q_node, &pending); + } + } else { + sb = NULL; + } + + mutex_unlock(&cgroup_mutex); + + /* + * All new cgroups will see @cfts update on @ss->cftsets. Add/rm + * files for all cgroups which were created before. + */ + list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) { + struct inode *inode = cgrp->dentry->d_inode; + + mutex_lock(&inode->i_mutex); + mutex_lock(&cgroup_mutex); + if (!cgroup_is_removed(cgrp)) + cgroup_addrm_files(cgrp, ss, cfts, is_add); + mutex_unlock(&cgroup_mutex); + mutex_unlock(&inode->i_mutex); + + list_del_init(&cgrp->cft_q_node); + dput(cgrp->dentry); + } + + if (sb) + deactivate_super(sb); + + mutex_unlock(&cgroup_cft_mutex); +} + +/** + * 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. + */ +int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) +{ + struct cftype_set *set; + + set = kzalloc(sizeof(*set), GFP_KERNEL); + if (!set) + return -ENOMEM; + + cgroup_cfts_prepare(); + set->cfts = cfts; + list_add_tail(&set->node, &ss->cftsets); + cgroup_cfts_commit(ss, cfts, true); + + return 0; +} +EXPORT_SYMBOL_GPL(cgroup_add_cftypes); + +/** + * cgroup_rm_cftypes - remove an array of cftypes from a subsystem + * @ss: target cgroup subsystem + * @cfts: zero-length name terminated array of cftypes + * + * Unregister @cfts from @ss. Files described by @cfts are removed from + * all existing cgroups to which @ss is attached and all future cgroups + * won't have them either. This function can be called anytime whether @ss + * is attached or not. + * + * Returns 0 on successful unregistration, -ENOENT if @cfts is not + * registered with @ss. + */ +int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) +{ + struct cftype_set *set; + + cgroup_cfts_prepare(); + + list_for_each_entry(set, &ss->cftsets, node) { + if (set->cfts == cfts) { + list_del_init(&set->node); + cgroup_cfts_commit(ss, cfts, false); + return 0; + } + } + + cgroup_cfts_commit(ss, NULL, false); + return -ENOENT; +} + +/** + * cgroup_task_count - count the number of tasks in a cgroup. + * @cgrp: the cgroup in question + * + * Return the number of tasks in the cgroup. + */ +int cgroup_task_count(const struct cgroup *cgrp) +{ + int count = 0; + struct cg_cgroup_link *link; + + read_lock(&css_set_lock); + list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) { + count += atomic_read(&link->cg->refcount); + } + read_unlock(&css_set_lock); + return count; +} + +/* + * Advance a list_head iterator. The iterator should be positioned at + * the start of a css_set + */ +static void cgroup_advance_iter(struct cgroup *cgrp, + struct cgroup_iter *it) +{ + struct list_head *l = it->cg_link; + struct cg_cgroup_link *link; + struct css_set *cg; + + /* Advance to the next non-empty css_set */ + do { + l = l->next; + if (l == &cgrp->css_sets) { + it->cg_link = NULL; + return; + } + link = list_entry(l, struct cg_cgroup_link, cgrp_link_list); + cg = link->cg; + } while (list_empty(&cg->tasks)); + it->cg_link = l; + it->task = cg->tasks.next; +} + +/* + * 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 call to cgroup_iter_start(). + */ +static void cgroup_enable_task_cg_lists(void) +{ + struct task_struct *p, *g; + write_lock(&css_set_lock); + use_task_css_set_links = 1; + /* + * 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) { + task_lock(p); + /* + * 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. + */ + if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list)) + list_add(&p->cg_list, &p->cgroups->tasks); + task_unlock(p); + } while_each_thread(g, p); + read_unlock(&tasklist_lock); + write_unlock(&css_set_lock); +} + +/** + * cgroup_next_descendant_pre - find the next descendant for pre-order walk + * @pos: the current position (%NULL to initiate traversal) + * @cgroup: cgroup whose descendants to walk + * + * To be used by cgroup_for_each_descendant_pre(). Find the next + * descendant to visit for pre-order traversal of @cgroup's descendants. + */ +struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos, + struct cgroup *cgroup) +{ + struct cgroup *next; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + /* if first iteration, pretend we just visited @cgroup */ + if (!pos) + pos = cgroup; + + /* visit the first child if exists */ + next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling); + if (next) + return next; + + /* no child, visit my or the closest ancestor's next sibling */ + while (pos != cgroup) { + next = list_entry_rcu(pos->sibling.next, struct cgroup, + sibling); + if (&next->sibling != &pos->parent->children) + return next; + + pos = pos->parent; + } + + return NULL; +} +EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre); + +/** + * cgroup_rightmost_descendant - return the rightmost descendant of a cgroup + * @pos: cgroup 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. + */ +struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos) +{ + struct cgroup *last, *tmp; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + do { + last = pos; + /* ->prev isn't RCU safe, walk ->next till the end */ + pos = NULL; + list_for_each_entry_rcu(tmp, &last->children, sibling) + pos = tmp; + } while (pos); + + return last; +} +EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant); + +static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos) +{ + struct cgroup *last; + + do { + last = pos; + pos = list_first_or_null_rcu(&pos->children, struct cgroup, + sibling); + } while (pos); + + return last; +} + +/** + * cgroup_next_descendant_post - find the next descendant for post-order walk + * @pos: the current position (%NULL to initiate traversal) + * @cgroup: cgroup whose descendants to walk + * + * To be used by cgroup_for_each_descendant_post(). Find the next + * descendant to visit for post-order traversal of @cgroup's descendants. + */ +struct cgroup *cgroup_next_descendant_post(struct cgroup *pos, + struct cgroup *cgroup) +{ + struct cgroup *next; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + /* if first iteration, visit the leftmost descendant */ + if (!pos) { + next = cgroup_leftmost_descendant(cgroup); + return next != cgroup ? next : NULL; + } + + /* if there's an unvisited sibling, visit its leftmost descendant */ + next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling); + if (&next->sibling != &pos->parent->children) + return cgroup_leftmost_descendant(next); + + /* no sibling left, visit parent */ + next = pos->parent; + return next != cgroup ? next : NULL; +} +EXPORT_SYMBOL_GPL(cgroup_next_descendant_post); + +void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it) + __acquires(css_set_lock) +{ + /* + * The first time anyone tries to iterate across a cgroup, + * we need to 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(); + + read_lock(&css_set_lock); + it->cg_link = &cgrp->css_sets; + cgroup_advance_iter(cgrp, it); +} + +struct task_struct *cgroup_iter_next(struct cgroup *cgrp, + struct cgroup_iter *it) +{ + struct task_struct *res; + struct list_head *l = it->task; + struct cg_cgroup_link *link; + + /* If the iterator cg is NULL, we have no tasks */ + if (!it->cg_link) + return NULL; + res = list_entry(l, struct task_struct, cg_list); + /* Advance iterator to find next entry */ + l = l->next; + link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list); + if (l == &link->cg->tasks) { + /* We reached the end of this task list - move on to + * the next cg_cgroup_link */ + cgroup_advance_iter(cgrp, it); + } else { + it->task = l; + } + return res; +} + +void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it) + __releases(css_set_lock) +{ + read_unlock(&css_set_lock); +} + +static inline int started_after_time(struct task_struct *t1, + struct timespec *time, + struct task_struct *t2) +{ + int start_diff = timespec_compare(&t1->start_time, time); + if (start_diff > 0) { + return 1; + } else if (start_diff < 0) { + return 0; + } else { + /* + * Arbitrarily, if two processes started at the same + * time, we'll say that the lower pointer value + * started first. Note that t2 may have exited by now + * so this may not be a valid pointer any longer, but + * that's fine - it still serves to distinguish + * between two tasks started (effectively) simultaneously. + */ + return t1 > t2; + } +} + +/* + * This function is a callback from heap_insert() and is used to order + * the heap. + * In this case we order the heap in descending task start time. + */ +static inline int started_after(void *p1, void *p2) +{ + struct task_struct *t1 = p1; + struct task_struct *t2 = p2; + return started_after_time(t1, &t2->start_time, t2); +} + +/** + * cgroup_scan_tasks - iterate though all the tasks in a cgroup + * @scan: struct cgroup_scanner containing arguments for the scan + * + * Arguments include pointers to callback functions test_task() and + * process_task(). + * Iterate through all the tasks in a cgroup, calling test_task() for each, + * and if it returns true, call process_task() for it also. + * The test_task pointer may be NULL, meaning always true (select all tasks). + * Effectively duplicates cgroup_iter_{start,next,end}() + * but does not lock css_set_lock for the call to process_task(). + * The struct cgroup_scanner may be embedded in any structure of the caller's + * creation. + * It is guaranteed that process_task() will act on every task that + * is a member of the cgroup for the duration of this call. This + * function may or may not call process_task() for tasks that exit + * or move to a different cgroup during the call, or are forked or + * move into the cgroup during the call. + * + * Note that test_task() may be called with locks held, and may in some + * situations be called multiple times for the same task, so it should + * be cheap. + * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been + * pre-allocated and will be used for heap operations (and its "gt" member will + * be overwritten), else a temporary heap will be used (allocation of which + * may cause this function to fail). + */ +int cgroup_scan_tasks(struct cgroup_scanner *scan) +{ + int retval, i; + struct cgroup_iter it; + struct task_struct *p, *dropped; + /* Never dereference latest_task, since it's not refcounted */ + struct task_struct *latest_task = NULL; + struct ptr_heap tmp_heap; + struct ptr_heap *heap; + struct timespec latest_time = { 0, 0 }; + + if (scan->heap) { + /* The caller supplied our heap and pre-allocated its memory */ + heap = scan->heap; + heap->gt = &started_after; + } else { + /* We need to allocate our own heap memory */ + heap = &tmp_heap; + retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after); + if (retval) + /* cannot allocate the heap */ + return retval; + } + + again: + /* + * Scan tasks in the cgroup, using the scanner's "test_task" callback + * to determine which are of interest, and using the scanner's + * "process_task" callback to process any of them that need an update. + * Since we don't want to hold any locks during the task updates, + * gather tasks to be processed in a heap structure. + * The heap is sorted by descending task start time. + * If the statically-sized heap fills up, we overflow tasks that + * started later, and in future iterations only consider tasks that + * started after the latest task in the previous pass. This + * guarantees forward progress and that we don't miss any tasks. + */ + heap->size = 0; + cgroup_iter_start(scan->cg, &it); + while ((p = cgroup_iter_next(scan->cg, &it))) { + /* + * Only affect tasks that qualify per the caller's callback, + * if he provided one + */ + if (scan->test_task && !scan->test_task(p, scan)) + continue; + /* + * Only process tasks that started after the last task + * we processed + */ + if (!started_after_time(p, &latest_time, latest_task)) + continue; + dropped = heap_insert(heap, p); + if (dropped == NULL) { + /* + * The new task was inserted; the heap wasn't + * previously full + */ + get_task_struct(p); + } else if (dropped != p) { + /* + * The new task was inserted, and pushed out a + * different task + */ + get_task_struct(p); + put_task_struct(dropped); + } + /* + * Else the new task was newer than anything already in + * the heap and wasn't inserted + */ + } + cgroup_iter_end(scan->cg, &it); + + if (heap->size) { + for (i = 0; i < heap->size; i++) { + struct task_struct *q = heap->ptrs[i]; + if (i == 0) { + latest_time = q->start_time; + latest_task = q; + } + /* Process the task per the caller's callback */ + scan->process_task(q, scan); + put_task_struct(q); + } + /* + * If we had to process any tasks at all, scan again + * in case some of them were in the middle of forking + * children that didn't get processed. + * Not the most efficient way to do it, but it avoids + * having to take callback_mutex in the fork path + */ + goto again; + } + if (heap == &tmp_heap) + heap_free(&tmp_heap); + return 0; +} + +static void cgroup_transfer_one_task(struct task_struct *task, + struct cgroup_scanner *scan) +{ + struct cgroup *new_cgroup = scan->data; + + mutex_lock(&cgroup_mutex); + cgroup_attach_task(new_cgroup, task, false); + mutex_unlock(&cgroup_mutex); +} + +/** + * 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 + */ +int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from) +{ + struct cgroup_scanner scan; + + scan.cg = from; + scan.test_task = NULL; /* select all tasks in cgroup */ + scan.process_task = cgroup_transfer_one_task; + scan.heap = NULL; + scan.data = to; + + return cgroup_scan_tasks(&scan); +} + +/* + * 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; + /* how many files are using the current array */ + int use_count; + /* 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; + /* protects the other fields */ + struct rw_semaphore mutex; +}; + +/* + * 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) +{ + if (is_vmalloc_addr(p)) + vfree(p); + else + kfree(p); +} + +/* + * 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; +} + +static int cmppid(const void *a, const void *b) +{ + return *(pid_t *)a - *(pid_t *)b; +} + +/* + * 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(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); + + /* + * We can't drop the pidlist_mutex before taking the l->mutex in case + * the last ref-holder is trying to remove l from the list at the same + * time. Holding the pidlist_mutex precludes somebody taking whichever + * list we find out from under us - compare release_pid_array(). + */ + mutex_lock(&cgrp->pidlist_mutex); + list_for_each_entry(l, &cgrp->pidlists, links) { + if (l->key.type == type && l->key.ns == ns) { + /* make sure l doesn't vanish out from under us */ + down_write(&l->mutex); + mutex_unlock(&cgrp->pidlist_mutex); + return l; + } + } + /* entry not found; create a new one */ + l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL); + if (!l) { + mutex_unlock(&cgrp->pidlist_mutex); + return l; + } + init_rwsem(&l->mutex); + down_write(&l->mutex); + l->key.type = type; + l->key.ns = get_pid_ns(ns); + l->use_count = 0; /* don't increment here */ + l->list = NULL; + l->owner = cgrp; + list_add(&l->links, &cgrp->pidlists); + mutex_unlock(&cgrp->pidlist_mutex); + 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 cgroup_iter it; + struct task_struct *tsk; + struct cgroup_pidlist *l; + + /* + * 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 */ + cgroup_iter_start(cgrp, &it); + while ((tsk = cgroup_iter_next(cgrp, &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; + } + cgroup_iter_end(cgrp, &it); + length = n; + /* now sort & (if procs) strip out duplicates */ + sort(array, length, sizeof(pid_t), cmppid, NULL); + if (type == CGROUP_FILE_PROCS) + length = pidlist_uniq(array, length); + l = cgroup_pidlist_find(cgrp, type); + if (!l) { + pidlist_free(array); + return -ENOMEM; + } + /* store array, freeing old if necessary - lock already held */ + pidlist_free(l->list); + l->list = array; + l->length = length; + l->use_count++; + up_write(&l->mutex); + *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) +{ + int ret = -EINVAL; + struct cgroup *cgrp; + struct cgroup_iter it; + struct task_struct *tsk; + + /* + * Validate dentry by checking the superblock operations, + * and make sure it's a directory. + */ + if (dentry->d_sb->s_op != &cgroup_ops || + !S_ISDIR(dentry->d_inode->i_mode)) + goto err; + + ret = 0; + cgrp = dentry->d_fsdata; + + cgroup_iter_start(cgrp, &it); + while ((tsk = cgroup_iter_next(cgrp, &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; + } + } + cgroup_iter_end(cgrp, &it); + +err: + return ret; +} + + +/* + * 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 cgroup_pidlist *l = s->private; + int index = 0, pid = *pos; + int *iter; + + down_read(&l->mutex); + if (pid) { + int end = l->length; + + while (index < end) { + int mid = (index + end) / 2; + if (l->list[mid] == pid) { + index = mid; + break; + } else if (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 = *iter; + return iter; +} + +static void cgroup_pidlist_stop(struct seq_file *s, void *v) +{ + struct cgroup_pidlist *l = s->private; + up_read(&l->mutex); +} + +static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos) +{ + struct cgroup_pidlist *l = s->private; + 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 = *p; + return p; + } +} + +static int cgroup_pidlist_show(struct seq_file *s, void *v) +{ + return seq_printf(s, "%d\n", *(int *)v); +} + +/* + * seq_operations functions for iterating on pidlists through seq_file - + * independent of whether it's tasks or procs + */ +static const struct seq_operations cgroup_pidlist_seq_operations = { + .start = cgroup_pidlist_start, + .stop = cgroup_pidlist_stop, + .next = cgroup_pidlist_next, + .show = cgroup_pidlist_show, +}; + +static void cgroup_release_pid_array(struct cgroup_pidlist *l) +{ + /* + * the case where we're the last user of this particular pidlist will + * have us remove it from the cgroup's list, which entails taking the + * mutex. since in pidlist_find the pidlist->lock depends on cgroup-> + * pidlist_mutex, we have to take pidlist_mutex first. + */ + mutex_lock(&l->owner->pidlist_mutex); + down_write(&l->mutex); + BUG_ON(!l->use_count); + if (!--l->use_count) { + /* we're the last user if refcount is 0; remove and free */ + list_del(&l->links); + mutex_unlock(&l->owner->pidlist_mutex); + pidlist_free(l->list); + put_pid_ns(l->key.ns); + up_write(&l->mutex); + kfree(l); + return; + } + mutex_unlock(&l->owner->pidlist_mutex); + up_write(&l->mutex); +} + +static int cgroup_pidlist_release(struct inode *inode, struct file *file) +{ + struct cgroup_pidlist *l; + if (!(file->f_mode & FMODE_READ)) + return 0; + /* + * the seq_file will only be initialized if the file was opened for + * reading; hence we check if it's not null only in that case. + */ + l = ((struct seq_file *)file->private_data)->private; + cgroup_release_pid_array(l); + return seq_release(inode, file); +} + +static const struct file_operations cgroup_pidlist_operations = { + .read = seq_read, + .llseek = seq_lseek, + .write = cgroup_file_write, + .release = cgroup_pidlist_release, +}; + +/* + * The following functions handle opens on a file that displays a pidlist + * (tasks or procs). Prepare an array of the process/thread IDs of whoever's + * in the cgroup. + */ +/* helper function for the two below it */ +static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type) +{ + struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent); + struct cgroup_pidlist *l; + int retval; + + /* Nothing to do for write-only files */ + if (!(file->f_mode & FMODE_READ)) + return 0; + + /* have the array populated */ + retval = pidlist_array_load(cgrp, type, &l); + if (retval) + return retval; + /* configure file information */ + file->f_op = &cgroup_pidlist_operations; + + retval = seq_open(file, &cgroup_pidlist_seq_operations); + if (retval) { + cgroup_release_pid_array(l); + return retval; + } + ((struct seq_file *)file->private_data)->private = l; + return 0; +} +static int cgroup_tasks_open(struct inode *unused, struct file *file) +{ + return cgroup_pidlist_open(file, CGROUP_FILE_TASKS); +} +static int cgroup_procs_open(struct inode *unused, struct file *file) +{ + return cgroup_pidlist_open(file, CGROUP_FILE_PROCS); +} + +static u64 cgroup_read_notify_on_release(struct cgroup *cgrp, + struct cftype *cft) +{ + return notify_on_release(cgrp); +} + +static int cgroup_write_notify_on_release(struct cgroup *cgrp, + struct cftype *cft, + u64 val) +{ + clear_bit(CGRP_RELEASABLE, &cgrp->flags); + if (val) + set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); + else + clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); + return 0; +} + +/* + * When dput() is called asynchronously, if umount has been done and + * then deactivate_super() in cgroup_free_fn() kills the superblock, + * there's a small window that vfs will see the root dentry with non-zero + * refcnt and trigger BUG(). + * + * That's why we hold a reference before dput() and drop it right after. + */ +static void cgroup_dput(struct cgroup *cgrp) +{ + struct super_block *sb = cgrp->root->sb; + + atomic_inc(&sb->s_active); + dput(cgrp->dentry); + deactivate_super(sb); +} + +/* + * Unregister event and free resources. + * + * Gets called from workqueue. + */ +static void cgroup_event_remove(struct work_struct *work) +{ + struct cgroup_event *event = container_of(work, struct cgroup_event, + remove); + struct cgroup *cgrp = event->cgrp; + + remove_wait_queue(event->wqh, &event->wait); + + event->cft->unregister_event(cgrp, event->cft, event->eventfd); + + /* Notify userspace the event is going away. */ + eventfd_signal(event->eventfd, 1); + + eventfd_ctx_put(event->eventfd); + kfree(event); + cgroup_dput(cgrp); +} + +/* + * Gets called on POLLHUP on eventfd when user closes it. + * + * Called with wqh->lock held and interrupts disabled. + */ +static int cgroup_event_wake(wait_queue_t *wait, unsigned mode, + int sync, void *key) +{ + struct cgroup_event *event = container_of(wait, + struct cgroup_event, wait); + struct cgroup *cgrp = event->cgrp; + unsigned long flags = (unsigned long)key; + + if (flags & POLLHUP) { + /* + * If the event has been detached at cgroup removal, we + * can simply return knowing the other side will cleanup + * for us. + * + * We can't race against event freeing since the other + * side will require wqh->lock via remove_wait_queue(), + * which we hold. + */ + spin_lock(&cgrp->event_list_lock); + if (!list_empty(&event->list)) { + list_del_init(&event->list); + /* + * We are in atomic context, but cgroup_event_remove() + * may sleep, so we have to call it in workqueue. + */ + schedule_work(&event->remove); + } + spin_unlock(&cgrp->event_list_lock); + } + + return 0; +} + +static void cgroup_event_ptable_queue_proc(struct file *file, + wait_queue_head_t *wqh, poll_table *pt) +{ + struct cgroup_event *event = container_of(pt, + struct cgroup_event, pt); + + event->wqh = wqh; + add_wait_queue(wqh, &event->wait); +} + +/* + * Parse input and register new cgroup event handler. + * + * Input must be in format '<event_fd> <control_fd> <args>'. + * Interpretation of args is defined by control file implementation. + */ +static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft, + const char *buffer) +{ + struct cgroup_event *event = NULL; + struct cgroup *cgrp_cfile; + unsigned int efd, cfd; + struct file *efile = NULL; + struct file *cfile = NULL; + char *endp; + int ret; + + efd = simple_strtoul(buffer, &endp, 10); + if (*endp != ' ') + return -EINVAL; + buffer = endp + 1; + + cfd = simple_strtoul(buffer, &endp, 10); + if ((*endp != ' ') && (*endp != '\0')) + return -EINVAL; + buffer = endp + 1; + + event = kzalloc(sizeof(*event), GFP_KERNEL); + if (!event) + return -ENOMEM; + event->cgrp = cgrp; + INIT_LIST_HEAD(&event->list); + init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc); + init_waitqueue_func_entry(&event->wait, cgroup_event_wake); + INIT_WORK(&event->remove, cgroup_event_remove); + + efile = eventfd_fget(efd); + if (IS_ERR(efile)) { + ret = PTR_ERR(efile); + goto fail; + } + + event->eventfd = eventfd_ctx_fileget(efile); + if (IS_ERR(event->eventfd)) { + ret = PTR_ERR(event->eventfd); + goto fail; + } + + cfile = fget(cfd); + if (!cfile) { + ret = -EBADF; + goto fail; + } + + /* the process need read permission on control file */ + /* AV: shouldn't we check that it's been opened for read instead? */ + ret = inode_permission(file_inode(cfile), MAY_READ); + if (ret < 0) + goto fail; + + event->cft = __file_cft(cfile); + if (IS_ERR(event->cft)) { + ret = PTR_ERR(event->cft); + goto fail; + } + + /* + * The file to be monitored must be in the same cgroup as + * cgroup.event_control is. + */ + cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent); + if (cgrp_cfile != cgrp) { + ret = -EINVAL; + goto fail; + } + + if (!event->cft->register_event || !event->cft->unregister_event) { + ret = -EINVAL; + goto fail; + } + + ret = event->cft->register_event(cgrp, event->cft, + event->eventfd, buffer); + if (ret) + goto fail; + + efile->f_op->poll(efile, &event->pt); + + /* + * Events should be removed after rmdir of cgroup directory, but before + * destroying subsystem state objects. Let's take reference to cgroup + * directory dentry to do that. + */ + dget(cgrp->dentry); + + spin_lock(&cgrp->event_list_lock); + list_add(&event->list, &cgrp->event_list); + spin_unlock(&cgrp->event_list_lock); + + fput(cfile); + fput(efile); + + return 0; + +fail: + if (cfile) + fput(cfile); + + if (event && event->eventfd && !IS_ERR(event->eventfd)) + eventfd_ctx_put(event->eventfd); + + if (!IS_ERR_OR_NULL(efile)) + fput(efile); + + kfree(event); + + return ret; +} + +static u64 cgroup_clone_children_read(struct cgroup *cgrp, + struct cftype *cft) +{ + return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags); +} + +static int cgroup_clone_children_write(struct cgroup *cgrp, + struct cftype *cft, + u64 val) +{ + if (val) + set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags); + else + clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags); + return 0; +} + +/* + * for the common functions, 'private' gives the type of file + */ +/* for hysterical raisins, we can't put this on the older files */ +#define CGROUP_FILE_GENERIC_PREFIX "cgroup." +static struct cftype files[] = { + { + .name = "tasks", + .open = cgroup_tasks_open, + .write_u64 = cgroup_tasks_write, + .release = cgroup_pidlist_release, + .mode = S_IRUGO | S_IWUSR, + }, + { + .name = CGROUP_FILE_GENERIC_PREFIX "procs", + .open = cgroup_procs_open, + .write_u64 = cgroup_procs_write, + .release = cgroup_pidlist_release, + .mode = S_IRUGO | S_IWUSR, + }, + { + .name = "notify_on_release", + .read_u64 = cgroup_read_notify_on_release, + .write_u64 = cgroup_write_notify_on_release, + }, + { + .name = CGROUP_FILE_GENERIC_PREFIX "event_control", + .write_string = cgroup_write_event_control, + .mode = S_IWUGO, + }, + { + .name = "cgroup.clone_children", + .flags = CFTYPE_INSANE, + .read_u64 = cgroup_clone_children_read, + .write_u64 = cgroup_clone_children_write, + }, + { + .name = "cgroup.sane_behavior", + .flags = CFTYPE_ONLY_ON_ROOT, + .read_seq_string = cgroup_sane_behavior_show, + }, + { + .name = "release_agent", + .flags = CFTYPE_ONLY_ON_ROOT, + .read_seq_string = cgroup_release_agent_show, + .write_string = cgroup_release_agent_write, + .max_write_len = PATH_MAX, + }, + { } /* terminate */ +}; + +/** + * cgroup_populate_dir - selectively creation of files in a directory + * @cgrp: target cgroup + * @base_files: true if the base files should be added + * @subsys_mask: mask of the subsystem ids whose files should be added + */ +static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files, + unsigned long subsys_mask) +{ + int err; + struct cgroup_subsys *ss; + + if (base_files) { + err = cgroup_addrm_files(cgrp, NULL, files, true); + if (err < 0) + return err; + } + + /* process cftsets of each subsystem */ + for_each_subsys(cgrp->root, ss) { + struct cftype_set *set; + if (!test_bit(ss->subsys_id, &subsys_mask)) + continue; + + list_for_each_entry(set, &ss->cftsets, node) + cgroup_addrm_files(cgrp, ss, set->cfts, true); + } + + /* This cgroup is ready now */ + for_each_subsys(cgrp->root, ss) { + struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id]; + /* + * Update id->css pointer and make this css visible from + * CSS ID functions. This pointer will be dereferened + * from RCU-read-side without locks. + */ + if (css->id) + rcu_assign_pointer(css->id->css, css); + } + + return 0; +} + +static void css_dput_fn(struct work_struct *work) +{ + struct cgroup_subsys_state *css = + container_of(work, struct cgroup_subsys_state, dput_work); + + cgroup_dput(css->cgroup); +} + +static void init_cgroup_css(struct cgroup_subsys_state *css, + struct cgroup_subsys *ss, + struct cgroup *cgrp) +{ + css->cgroup = cgrp; + atomic_set(&css->refcnt, 1); + css->flags = 0; + css->id = NULL; + if (cgrp == dummytop) + css->flags |= CSS_ROOT; + BUG_ON(cgrp->subsys[ss->subsys_id]); + cgrp->subsys[ss->subsys_id] = css; + + /* + * css holds an extra ref to @cgrp->dentry which is put on the last + * css_put(). dput() requires process context, which css_put() may + * be called without. @css->dput_work will be used to invoke + * dput() asynchronously from css_put(). + */ + INIT_WORK(&css->dput_work, css_dput_fn); +} + +/* invoke ->post_create() on a new CSS and mark it online if successful */ +static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp) +{ + int ret = 0; + + lockdep_assert_held(&cgroup_mutex); + + if (ss->css_online) + ret = ss->css_online(cgrp); + if (!ret) + cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE; + return ret; +} + +/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */ +static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp) + __releases(&cgroup_mutex) __acquires(&cgroup_mutex) +{ + struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id]; + + lockdep_assert_held(&cgroup_mutex); + + if (!(css->flags & CSS_ONLINE)) + return; + + if (ss->css_offline) + ss->css_offline(cgrp); + + cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE; +} + +/* + * cgroup_create - create a cgroup + * @parent: cgroup that will be parent of the new cgroup + * @dentry: dentry of the new cgroup + * @mode: mode to set on new inode + * + * Must be called with the mutex on the parent inode held + */ +static long cgroup_create(struct cgroup *parent, struct dentry *dentry, + umode_t mode) +{ + struct cgroup *cgrp; + struct cgroup_name *name; + struct cgroupfs_root *root = parent->root; + int err = 0; + struct cgroup_subsys *ss; + struct super_block *sb = root->sb; + + /* allocate the cgroup and its ID, 0 is reserved for the root */ + cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL); + if (!cgrp) + return -ENOMEM; + + name = cgroup_alloc_name(dentry); + if (!name) + goto err_free_cgrp; + rcu_assign_pointer(cgrp->name, name); + + cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL); + if (cgrp->id < 0) + goto err_free_name; + + /* + * Only live parents can have children. Note that the liveliness + * check isn't strictly necessary because cgroup_mkdir() and + * cgroup_rmdir() are fully synchronized by i_mutex; however, do it + * anyway so that locking is contained inside cgroup proper and we + * don't get nasty surprises if we ever grow another caller. + */ + if (!cgroup_lock_live_group(parent)) { + err = -ENODEV; + goto err_free_id; + } + + /* Grab a reference on the superblock so the hierarchy doesn't + * get deleted on unmount if there are child cgroups. This + * can be done outside cgroup_mutex, since the sb can't + * disappear while someone has an open control file on the + * fs */ + atomic_inc(&sb->s_active); + + init_cgroup_housekeeping(cgrp); + + dentry->d_fsdata = cgrp; + cgrp->dentry = dentry; + + cgrp->parent = parent; + cgrp->root = parent->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); + + for_each_subsys(root, ss) { + struct cgroup_subsys_state *css; + + css = ss->css_alloc(cgrp); + if (IS_ERR(css)) { + err = PTR_ERR(css); + goto err_free_all; + } + init_cgroup_css(css, ss, cgrp); + if (ss->use_id) { + err = alloc_css_id(ss, parent, cgrp); + if (err) + goto err_free_all; + } + } + + /* + * Create directory. cgroup_create_file() returns with the new + * directory locked on success so that it can be populated without + * dropping cgroup_mutex. + */ + err = cgroup_create_file(dentry, S_IFDIR | mode, sb); + if (err < 0) + goto err_free_all; + lockdep_assert_held(&dentry->d_inode->i_mutex); + + /* allocation complete, commit to creation */ + list_add_tail(&cgrp->allcg_node, &root->allcg_list); + list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children); + root->number_of_cgroups++; + + /* each css holds a ref to the cgroup's dentry */ + for_each_subsys(root, ss) + dget(dentry); + + /* hold a ref to the parent's dentry */ + dget(parent->dentry); + + /* creation succeeded, notify subsystems */ + for_each_subsys(root, ss) { + err = online_css(ss, cgrp); + if (err) + goto err_destroy; + + if (ss->broken_hierarchy && !ss->warned_broken_hierarchy && + parent->parent) { + pr_warning("cgroup: %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_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n"); + ss->warned_broken_hierarchy = true; + } + } + + err = cgroup_populate_dir(cgrp, true, root->subsys_mask); + if (err) + goto err_destroy; + + mutex_unlock(&cgroup_mutex); + mutex_unlock(&cgrp->dentry->d_inode->i_mutex); + + return 0; + +err_free_all: + for_each_subsys(root, ss) { + if (cgrp->subsys[ss->subsys_id]) + ss->css_free(cgrp); + } + mutex_unlock(&cgroup_mutex); + /* Release the reference count that we took on the superblock */ + deactivate_super(sb); +err_free_id: + ida_simple_remove(&root->cgroup_ida, cgrp->id); +err_free_name: + kfree(rcu_dereference_raw(cgrp->name)); +err_free_cgrp: + kfree(cgrp); + return err; + +err_destroy: + cgroup_destroy_locked(cgrp); + mutex_unlock(&cgroup_mutex); + mutex_unlock(&dentry->d_inode->i_mutex); + return err; +} + +static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) +{ + struct cgroup *c_parent = dentry->d_parent->d_fsdata; + + /* the vfs holds inode->i_mutex already */ + return cgroup_create(c_parent, dentry, mode | S_IFDIR); +} + +static int cgroup_destroy_locked(struct cgroup *cgrp) + __releases(&cgroup_mutex) __acquires(&cgroup_mutex) +{ + struct dentry *d = cgrp->dentry; + struct cgroup *parent = cgrp->parent; + struct cgroup_event *event, *tmp; + struct cgroup_subsys *ss; + + lockdep_assert_held(&d->d_inode->i_mutex); + lockdep_assert_held(&cgroup_mutex); + + if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) + return -EBUSY; + + /* + * Block new css_tryget() by deactivating refcnt and mark @cgrp + * removed. This makes future css_tryget() and child creation + * attempts fail thus maintaining the removal conditions verified + * above. + */ + for_each_subsys(cgrp->root, ss) { + struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id]; + + WARN_ON(atomic_read(&css->refcnt) < 0); + atomic_add(CSS_DEACT_BIAS, &css->refcnt); + } + set_bit(CGRP_REMOVED, &cgrp->flags); + + /* tell subsystems to initate destruction */ + for_each_subsys(cgrp->root, ss) + offline_css(ss, cgrp); + + /* + * Put all the base refs. Each css holds an extra reference to the + * cgroup's dentry and cgroup removal proceeds regardless of css + * refs. On the last put of each css, whenever that may be, the + * extra dentry ref is put so that dentry destruction happens only + * after all css's are released. + */ + for_each_subsys(cgrp->root, ss) + css_put(cgrp->subsys[ss->subsys_id]); + + raw_spin_lock(&release_list_lock); + if (!list_empty(&cgrp->release_list)) + list_del_init(&cgrp->release_list); + raw_spin_unlock(&release_list_lock); + + /* delete this cgroup from parent->children */ + list_del_rcu(&cgrp->sibling); + list_del_init(&cgrp->allcg_node); + + dget(d); + cgroup_d_remove_dir(d); + dput(d); + + set_bit(CGRP_RELEASABLE, &parent->flags); + check_for_release(parent); + + /* + * Unregister events and notify userspace. + * Notify userspace about cgroup removing only after rmdir of cgroup + * directory to avoid race between userspace and kernelspace. + */ + spin_lock(&cgrp->event_list_lock); + list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) { + list_del_init(&event->list); + schedule_work(&event->remove); + } + spin_unlock(&cgrp->event_list_lock); + + return 0; +} + +static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry) +{ + int ret; + + mutex_lock(&cgroup_mutex); + ret = cgroup_destroy_locked(dentry->d_fsdata); + mutex_unlock(&cgroup_mutex); + + return ret; +} + +static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss) +{ + INIT_LIST_HEAD(&ss->cftsets); + + /* + * base_cftset is embedded in subsys itself, no need to worry about + * deregistration. + */ + if (ss->base_cftypes) { + ss->base_cftset.cfts = ss->base_cftypes; + list_add_tail(&ss->base_cftset.node, &ss->cftsets); + } +} + +static void __init cgroup_init_subsys(struct cgroup_subsys *ss) +{ + struct cgroup_subsys_state *css; + + printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name); + + mutex_lock(&cgroup_mutex); + + /* init base cftset */ + cgroup_init_cftsets(ss); + + /* Create the top cgroup state for this subsystem */ + list_add(&ss->sibling, &rootnode.subsys_list); + ss->root = &rootnode; + css = ss->css_alloc(dummytop); + /* We don't handle early failures gracefully */ + BUG_ON(IS_ERR(css)); + init_cgroup_css(css, ss, dummytop); + + /* 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 top cgroup. */ + init_css_set.subsys[ss->subsys_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(ss, dummytop)); + + mutex_unlock(&cgroup_mutex); + + /* this function shouldn't be used with modular subsystems, since they + * need to register a subsys_id, among other things */ + BUG_ON(ss->module); +} + +/** + * cgroup_load_subsys: load and register a modular subsystem at runtime + * @ss: the subsystem to load + * + * This function should be called in a modular subsystem's initcall. If the + * subsystem is built as a module, it will be assigned a new subsys_id and set + * up for use. If the subsystem is built-in anyway, work is delegated to the + * simpler cgroup_init_subsys. + */ +int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss) +{ + struct cgroup_subsys_state *css; + int i, ret; + struct hlist_node *tmp; + struct css_set *cg; + unsigned long key; + + /* check name and function validity */ + if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN || + ss->css_alloc == NULL || ss->css_free == NULL) + return -EINVAL; + + /* + * we don't support callbacks in modular subsystems. this check is + * before the ss->module check for consistency; a subsystem that could + * be a module should still have no callbacks even if the user isn't + * compiling it as one. + */ + if (ss->fork || ss->exit) + return -EINVAL; + + /* + * an optionally modular subsystem is built-in: we want to do nothing, + * since cgroup_init_subsys will have already taken care of it. + */ + if (ss->module == NULL) { + /* a sanity check */ + BUG_ON(subsys[ss->subsys_id] != ss); + return 0; + } + + /* init base cftset */ + cgroup_init_cftsets(ss); + + mutex_lock(&cgroup_mutex); + subsys[ss->subsys_id] = ss; + + /* + * no ss->css_alloc seems to need anything important in the ss + * struct, so this can happen first (i.e. before the rootnode + * attachment). + */ + css = ss->css_alloc(dummytop); + if (IS_ERR(css)) { + /* failure case - need to deassign the subsys[] slot. */ + subsys[ss->subsys_id] = NULL; + mutex_unlock(&cgroup_mutex); + return PTR_ERR(css); + } + + list_add(&ss->sibling, &rootnode.subsys_list); + ss->root = &rootnode; + + /* our new subsystem will be attached to the dummy hierarchy. */ + init_cgroup_css(css, ss, dummytop); + /* init_idr must be after init_cgroup_css because it sets css->id. */ + if (ss->use_id) { + ret = cgroup_init_idr(ss, css); + if (ret) + goto err_unload; + } + + /* + * Now we need to entangle the css into the existing css_sets. unlike + * in cgroup_init_subsys, there are now multiple css_sets, so each one + * will need a new pointer to it; done by iterating the css_set_table. + * furthermore, modifying the existing css_sets will corrupt the hash + * table state, so each changed css_set will need its hash recomputed. + * this is all done under the css_set_lock. + */ + write_lock(&css_set_lock); + hash_for_each_safe(css_set_table, i, tmp, cg, hlist) { + /* skip entries that we already rehashed */ + if (cg->subsys[ss->subsys_id]) + continue; + /* remove existing entry */ + hash_del(&cg->hlist); + /* set new value */ + cg->subsys[ss->subsys_id] = css; + /* recompute hash and restore entry */ + key = css_set_hash(cg->subsys); + hash_add(css_set_table, &cg->hlist, key); + } + write_unlock(&css_set_lock); + + ret = online_css(ss, dummytop); + if (ret) + goto err_unload; + + /* success! */ + mutex_unlock(&cgroup_mutex); + return 0; + +err_unload: + mutex_unlock(&cgroup_mutex); + /* @ss can't be mounted here as try_module_get() would fail */ + cgroup_unload_subsys(ss); + return ret; +} +EXPORT_SYMBOL_GPL(cgroup_load_subsys); + +/** + * cgroup_unload_subsys: unload a modular subsystem + * @ss: the subsystem to unload + * + * This function should be called in a modular subsystem's exitcall. When this + * function is invoked, the refcount on the subsystem's module will be 0, so + * the subsystem will not be attached to any hierarchy. + */ +void cgroup_unload_subsys(struct cgroup_subsys *ss) +{ + struct cg_cgroup_link *link; + + BUG_ON(ss->module == NULL); + + /* + * we shouldn't be called if the subsystem is in use, and the use of + * try_module_get in parse_cgroupfs_options should ensure that it + * doesn't start being used while we're killing it off. + */ + BUG_ON(ss->root != &rootnode); + + mutex_lock(&cgroup_mutex); + + offline_css(ss, dummytop); + + if (ss->use_id) + idr_destroy(&ss->idr); + + /* deassign the subsys_id */ + subsys[ss->subsys_id] = NULL; + + /* remove subsystem from rootnode's list of subsystems */ + list_del_init(&ss->sibling); + + /* + * disentangle the css from all css_sets attached to the dummytop. as + * in loading, we need to pay our respects to the hashtable gods. + */ + write_lock(&css_set_lock); + list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) { + struct css_set *cg = link->cg; + unsigned long key; + + hash_del(&cg->hlist); + cg->subsys[ss->subsys_id] = NULL; + key = css_set_hash(cg->subsys); + hash_add(css_set_table, &cg->hlist, key); + } + write_unlock(&css_set_lock); + + /* + * remove subsystem's css from the dummytop and free it - need to + * free before marking as null because ss->css_free needs the + * cgrp->subsys pointer to find their state. note that this also + * takes care of freeing the css_id. + */ + ss->css_free(dummytop); + dummytop->subsys[ss->subsys_id] = NULL; + + mutex_unlock(&cgroup_mutex); +} +EXPORT_SYMBOL_GPL(cgroup_unload_subsys); + +/** + * 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) +{ + int i; + atomic_set(&init_css_set.refcount, 1); + INIT_LIST_HEAD(&init_css_set.cg_links); + INIT_LIST_HEAD(&init_css_set.tasks); + INIT_HLIST_NODE(&init_css_set.hlist); + css_set_count = 1; + init_cgroup_root(&rootnode); + root_count = 1; + init_task.cgroups = &init_css_set; + + init_css_set_link.cg = &init_css_set; + init_css_set_link.cgrp = dummytop; + list_add(&init_css_set_link.cgrp_link_list, + &rootnode.top_cgroup.css_sets); + list_add(&init_css_set_link.cg_link_list, + &init_css_set.cg_links); + + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + + /* at bootup time, we don't worry about modular subsystems */ + if (!ss || ss->module) + continue; + + BUG_ON(!ss->name); + BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN); + BUG_ON(!ss->css_alloc); + BUG_ON(!ss->css_free); + if (ss->subsys_id != i) { + printk(KERN_ERR "cgroup: Subsys %s id == %d\n", + ss->name, ss->subsys_id); + BUG(); + } + + if (ss->early_init) + cgroup_init_subsys(ss); + } + 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) +{ + int err; + int i; + unsigned long key; + + err = bdi_init(&cgroup_backing_dev_info); + if (err) + return err; + + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + + /* at bootup time, we don't worry about modular subsystems */ + if (!ss || ss->module) + continue; + if (!ss->early_init) + cgroup_init_subsys(ss); + if (ss->use_id) + cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]); + } + + /* 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(!init_root_id(&rootnode)); + + cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj); + if (!cgroup_kobj) { + err = -ENOMEM; + goto out; + } + + err = register_filesystem(&cgroup_fs_type); + if (err < 0) { + kobject_put(cgroup_kobj); + goto out; + } + + proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations); + +out: + if (err) + bdi_destroy(&cgroup_backing_dev_info); + + return err; +} + +static int __init cgroup_wq_init(void) +{ + /* + * There isn't much point in executing destruction path in + * parallel. Good chunk is serialized with cgroup_mutex anyway. + * Use 1 for @max_active. + * + * We would prefer to do this in cgroup_init() above, but that + * is called before init_workqueues(): so leave this until after. + */ + cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1); + BUG_ON(!cgroup_destroy_wq); + return 0; +} +core_initcall(cgroup_wq_init); + +/* + * proc_cgroup_show() + * - Print task's cgroup paths into seq_file, one line for each hierarchy + * - Used for /proc/<pid>/cgroup. + * - No need to task_lock(tsk) on this tsk->cgroup reference, as it + * doesn't really matter if tsk->cgroup changes after we read it, + * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it + * anyway. No need to check that tsk->cgroup != NULL, thanks to + * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks + * cgroup to top_cgroup. + */ + +/* TODO: Use a proper seq_file iterator */ +int proc_cgroup_show(struct seq_file *m, void *v) +{ + struct pid *pid; + struct task_struct *tsk; + char *buf; + int retval; + struct cgroupfs_root *root; + + retval = -ENOMEM; + buf = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!buf) + goto out; + + retval = -ESRCH; + pid = m->private; + tsk = get_pid_task(pid, PIDTYPE_PID); + if (!tsk) + goto out_free; + + retval = 0; + + mutex_lock(&cgroup_mutex); + + for_each_active_root(root) { + struct cgroup_subsys *ss; + struct cgroup *cgrp; + int count = 0; + + seq_printf(m, "%d:", root->hierarchy_id); + for_each_subsys(root, ss) + 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); + retval = cgroup_path(cgrp, buf, PAGE_SIZE); + if (retval < 0) + goto out_unlock; + seq_puts(m, buf); + seq_putc(m, '\n'); + } + +out_unlock: + mutex_unlock(&cgroup_mutex); + put_task_struct(tsk); +out_free: + kfree(buf); +out: + return retval; +} + +/* Display information about each subsystem and each hierarchy */ +static int proc_cgroupstats_show(struct seq_file *m, void *v) +{ + 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 (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + if (ss == NULL) + continue; + seq_printf(m, "%s\t%d\t%d\t%d\n", + ss->name, ss->root->hierarchy_id, + ss->root->number_of_cgroups, !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 - attach newly forked task to its parents cgroup. + * @child: pointer to task_struct of forking parent process. + * + * Description: A task inherits its parent's cgroup at fork(). + * + * A pointer to the shared css_set was automatically copied in + * fork.c by dup_task_struct(). However, we ignore that copy, since + * it was not made under the protection of RCU or cgroup_mutex, so + * might no longer be a valid cgroup pointer. cgroup_attach_task() might + * have already changed current->cgroups, allowing the previously + * referenced cgroup group to be removed and freed. + * + * At the point that cgroup_fork() is called, 'current' is the parent + * task, and the passed argument 'child' points to the child task. + */ +void cgroup_fork(struct task_struct *child) +{ + task_lock(current); + child->cgroups = current->cgroups; + get_css_set(child->cgroups); + task_unlock(current); + 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_iter_start() - to guarantee that the new task ends up on its + * list. + */ +void cgroup_post_fork(struct task_struct *child) +{ + int i; + + /* + * use_task_css_set_links is set to 1 before we walk the tasklist + * under the tasklist_lock and we read it here after we added the child + * to the tasklist under the tasklist_lock as well. If the child wasn't + * yet in the tasklist when we walked through it from + * cgroup_enable_task_cg_lists(), then use_task_css_set_links value + * should be visible now due to the paired locking and barriers implied + * by LOCK/UNLOCK: it is written before the tasklist_lock unlock + * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock + * lock on fork. + */ + if (use_task_css_set_links) { + write_lock(&css_set_lock); + task_lock(child); + if (list_empty(&child->cg_list)) + list_add(&child->cg_list, &child->cgroups->tasks); + task_unlock(child); + write_unlock(&css_set_lock); + } + + /* + * Call ss->fork(). This must happen after @child is linked on + * css_set; otherwise, @child might change state between ->fork() + * and addition to css_set. + */ + if (need_forkexit_callback) { + /* + * fork/exit callbacks are supported only for builtin + * subsystems, and the builtin section of the subsys + * array is immutable, so we don't need to lock the + * subsys array here. On the other hand, modular section + * of the array can be freed at module unload, so we + * can't touch that. + */ + for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + + if (ss->fork) + ss->fork(child); + } + } +} + +/** + * cgroup_exit - detach cgroup from exiting task + * @tsk: pointer to task_struct of exiting process + * @run_callback: run exit callbacks? + * + * 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. + * + * the_top_cgroup_hack: + * + * 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. + * + * To do this properly, we would increment the reference count on + * top_cgroup, and near the very end of the kernel/exit.c do_exit() + * code we would add a second cgroup function call, to drop that + * reference. This would just create an unnecessary hot spot on + * the top_cgroup reference count, to no avail. + * + * Normally, holding a reference to a cgroup without bumping its + * count is unsafe. The cgroup could go away, or someone could + * attach us to a different cgroup, decrementing the count on + * the first cgroup that we never incremented. But in this case, + * top_cgroup isn't going away, and either task has PF_EXITING set, + * which wards off any cgroup_attach_task() attempts, or task is a failed + * fork, never visible to cgroup_attach_task. + */ +void cgroup_exit(struct task_struct *tsk, int run_callbacks) +{ + struct css_set *cg; + int i; + + /* + * Unlink from the css_set task list if necessary. + * Optimistically check cg_list before taking + * css_set_lock + */ + if (!list_empty(&tsk->cg_list)) { + write_lock(&css_set_lock); + if (!list_empty(&tsk->cg_list)) + list_del_init(&tsk->cg_list); + write_unlock(&css_set_lock); + } + + /* Reassign the task to the init_css_set. */ + task_lock(tsk); + cg = tsk->cgroups; + tsk->cgroups = &init_css_set; + + if (run_callbacks && need_forkexit_callback) { + /* + * fork/exit callbacks are supported only for builtin + * subsystems, see cgroup_post_fork() for details. + */ + for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + + if (ss->exit) { + struct cgroup *old_cgrp = + rcu_dereference_raw(cg->subsys[i])->cgroup; + struct cgroup *cgrp = task_cgroup(tsk, i); + ss->exit(cgrp, old_cgrp, tsk); + } + } + } + task_unlock(tsk); + + put_css_set_taskexit(cg); +} + +static void check_for_release(struct cgroup *cgrp) +{ + /* All of these checks rely on RCU to keep the cgroup + * structure alive */ + if (cgroup_is_releasable(cgrp) && + !atomic_read(&cgrp->count) && list_empty(&cgrp->children)) { + /* + * Control Group is currently removeable. If it's not + * already queued for a userspace notification, queue + * it now + */ + int need_schedule_work = 0; + + raw_spin_lock(&release_list_lock); + if (!cgroup_is_removed(cgrp) && + list_empty(&cgrp->release_list)) { + list_add(&cgrp->release_list, &release_list); + need_schedule_work = 1; + } + raw_spin_unlock(&release_list_lock); + if (need_schedule_work) + schedule_work(&release_agent_work); + } +} + +/* Caller must verify that the css is not for root cgroup */ +bool __css_tryget(struct cgroup_subsys_state *css) +{ + while (true) { + int t, v; + + v = css_refcnt(css); + t = atomic_cmpxchg(&css->refcnt, v, v + 1); + if (likely(t == v)) + return true; + else if (t < 0) + return false; + cpu_relax(); + } +} +EXPORT_SYMBOL_GPL(__css_tryget); + +/* Caller must verify that the css is not for root cgroup */ +void __css_put(struct cgroup_subsys_state *css) +{ + int v; + + v = css_unbias_refcnt(atomic_dec_return(&css->refcnt)); + if (v == 0) + queue_work(cgroup_destroy_wq, &css->dput_work); +} +EXPORT_SYMBOL_GPL(__css_put); + +/* + * 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) +{ + BUG_ON(work != &release_agent_work); + mutex_lock(&cgroup_mutex); + raw_spin_lock(&release_list_lock); + while (!list_empty(&release_list)) { + char *argv[3], *envp[3]; + int i; + char *pathbuf = NULL, *agentbuf = NULL; + struct cgroup *cgrp = list_entry(release_list.next, + struct cgroup, + release_list); + list_del_init(&cgrp->release_list); + raw_spin_unlock(&release_list_lock); + pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!pathbuf) + goto continue_free; + if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0) + goto continue_free; + agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL); + if (!agentbuf) + goto continue_free; + + i = 0; + argv[i++] = agentbuf; + argv[i++] = pathbuf; + argv[i] = NULL; + + i = 0; + /* minimal command environment */ + envp[i++] = "HOME=/"; + envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin"; + envp[i] = NULL; + + /* Drop the lock while we invoke the usermode helper, + * since the exec could involve hitting disk and hence + * be a slow process */ + mutex_unlock(&cgroup_mutex); + call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC); + mutex_lock(&cgroup_mutex); + continue_free: + kfree(pathbuf); + kfree(agentbuf); + raw_spin_lock(&release_list_lock); + } + raw_spin_unlock(&release_list_lock); + mutex_unlock(&cgroup_mutex); +} + +static int __init cgroup_disable(char *str) +{ + int i; + char *token; + + while ((token = strsep(&str, ",")) != NULL) { + if (!*token) + continue; + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + + /* + * cgroup_disable, being at boot time, can't + * know about module subsystems, so we don't + * worry about them. + */ + if (!ss || ss->module) + continue; + + 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); + +/* + * Functons for CSS ID. + */ + +/* + *To get ID other than 0, this should be called when !cgroup_is_removed(). + */ +unsigned short css_id(struct cgroup_subsys_state *css) +{ + struct css_id *cssid; + + /* + * This css_id() can return correct value when somone has refcnt + * on this or this is under rcu_read_lock(). Once css->id is allocated, + * it's unchanged until freed. + */ + cssid = rcu_dereference_check(css->id, css_refcnt(css)); + + if (cssid) + return cssid->id; + return 0; +} +EXPORT_SYMBOL_GPL(css_id); + +unsigned short css_depth(struct cgroup_subsys_state *css) +{ + struct css_id *cssid; + + cssid = rcu_dereference_check(css->id, css_refcnt(css)); + + if (cssid) + return cssid->depth; + return 0; +} +EXPORT_SYMBOL_GPL(css_depth); + +/** + * css_is_ancestor - test "root" css is an ancestor of "child" + * @child: the css to be tested. + * @root: the css supporsed to be an ancestor of the child. + * + * Returns true if "root" is an ancestor of "child" in its hierarchy. Because + * this function reads css->id, the caller must hold rcu_read_lock(). + * But, considering usual usage, the csses should be valid objects after test. + * Assuming that the caller will do some action to the child if this returns + * returns true, the caller must take "child";s reference count. + * If "child" is valid object and this returns true, "root" is valid, too. + */ + +bool css_is_ancestor(struct cgroup_subsys_state *child, + const struct cgroup_subsys_state *root) +{ + struct css_id *child_id; + struct css_id *root_id; + + child_id = rcu_dereference(child->id); + if (!child_id) + return false; + root_id = rcu_dereference(root->id); + if (!root_id) + return false; + if (child_id->depth < root_id->depth) + return false; + if (child_id->stack[root_id->depth] != root_id->id) + return false; + return true; +} + +void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css) +{ + struct css_id *id = css->id; + /* When this is called before css_id initialization, id can be NULL */ + if (!id) + return; + + BUG_ON(!ss->use_id); + + rcu_assign_pointer(id->css, NULL); + rcu_assign_pointer(css->id, NULL); + spin_lock(&ss->id_lock); + idr_remove(&ss->idr, id->id); + spin_unlock(&ss->id_lock); + kfree_rcu(id, rcu_head); +} +EXPORT_SYMBOL_GPL(free_css_id); + +/* + * This is called by init or create(). Then, calls to this function are + * always serialized (By cgroup_mutex() at create()). + */ + +static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth) +{ + struct css_id *newid; + int ret, size; + + BUG_ON(!ss->use_id); + + size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1); + newid = kzalloc(size, GFP_KERNEL); + if (!newid) + return ERR_PTR(-ENOMEM); + + idr_preload(GFP_KERNEL); + spin_lock(&ss->id_lock); + /* Don't use 0. allocates an ID of 1-65535 */ + ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT); + spin_unlock(&ss->id_lock); + idr_preload_end(); + + /* Returns error when there are no free spaces for new ID.*/ + if (ret < 0) + goto err_out; + + newid->id = ret; + newid->depth = depth; + return newid; +err_out: + kfree(newid); + return ERR_PTR(ret); + +} + +static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss, + struct cgroup_subsys_state *rootcss) +{ + struct css_id *newid; + + spin_lock_init(&ss->id_lock); + idr_init(&ss->idr); + + newid = get_new_cssid(ss, 0); + if (IS_ERR(newid)) + return PTR_ERR(newid); + + newid->stack[0] = newid->id; + newid->css = rootcss; + rootcss->id = newid; + return 0; +} + +static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent, + struct cgroup *child) +{ + int subsys_id, i, depth = 0; + struct cgroup_subsys_state *parent_css, *child_css; + struct css_id *child_id, *parent_id; + + subsys_id = ss->subsys_id; + parent_css = parent->subsys[subsys_id]; + child_css = child->subsys[subsys_id]; + parent_id = parent_css->id; + depth = parent_id->depth + 1; + + child_id = get_new_cssid(ss, depth); + if (IS_ERR(child_id)) + return PTR_ERR(child_id); + + for (i = 0; i < depth; i++) + child_id->stack[i] = parent_id->stack[i]; + child_id->stack[depth] = child_id->id; + /* + * child_id->css pointer will be set after this cgroup is available + * see cgroup_populate_dir() + */ + rcu_assign_pointer(child_css->id, child_id); + + return 0; +} + +/** + * css_lookup - lookup css by id + * @ss: cgroup subsys to be looked into. + * @id: the id + * + * Returns pointer to cgroup_subsys_state if there is valid one with id. + * NULL if not. Should be called under rcu_read_lock() + */ +struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id) +{ + struct css_id *cssid = NULL; + + BUG_ON(!ss->use_id); + cssid = idr_find(&ss->idr, id); + + if (unlikely(!cssid)) + return NULL; + + return rcu_dereference(cssid->css); +} +EXPORT_SYMBOL_GPL(css_lookup); + +/* + * get corresponding css from file open on cgroupfs directory + */ +struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id) +{ + struct cgroup *cgrp; + struct inode *inode; + struct cgroup_subsys_state *css; + + inode = file_inode(f); + /* check in cgroup filesystem dir */ + if (inode->i_op != &cgroup_dir_inode_operations) + return ERR_PTR(-EBADF); + + if (id < 0 || id >= CGROUP_SUBSYS_COUNT) + return ERR_PTR(-EINVAL); + + /* get cgroup */ + cgrp = __d_cgrp(f->f_dentry); + css = cgrp->subsys[id]; + return css ? css : ERR_PTR(-ENOENT); +} + +#ifdef CONFIG_CGROUP_DEBUG +static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont) +{ + 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 *cont) +{ + kfree(cont->subsys[debug_subsys_id]); +} + +static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft) +{ + return atomic_read(&cont->count); +} + +static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft) +{ + return cgroup_task_count(cont); +} + +static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft) +{ + return (u64)(unsigned long)current->cgroups; +} + +static u64 current_css_set_refcount_read(struct cgroup *cont, + struct cftype *cft) +{ + u64 count; + + rcu_read_lock(); + count = atomic_read(¤t->cgroups->refcount); + rcu_read_unlock(); + return count; +} + +static int current_css_set_cg_links_read(struct cgroup *cont, + struct cftype *cft, + struct seq_file *seq) +{ + struct cg_cgroup_link *link; + struct css_set *cg; + + read_lock(&css_set_lock); + rcu_read_lock(); + cg = rcu_dereference(current->cgroups); + list_for_each_entry(link, &cg->cg_links, cg_link_list) { + struct cgroup *c = link->cgrp; + const char *name; + + if (c->dentry) + name = c->dentry->d_name.name; + else + name = "?"; + seq_printf(seq, "Root %d group %s\n", + c->root->hierarchy_id, name); + } + rcu_read_unlock(); + read_unlock(&css_set_lock); + return 0; +} + +#define MAX_TASKS_SHOWN_PER_CSS 25 +static int cgroup_css_links_read(struct cgroup *cont, + struct cftype *cft, + struct seq_file *seq) +{ + struct cg_cgroup_link *link; + + read_lock(&css_set_lock); + list_for_each_entry(link, &cont->css_sets, cgrp_link_list) { + struct css_set *cg = link->cg; + struct task_struct *task; + int count = 0; + seq_printf(seq, "css_set %p\n", cg); + list_for_each_entry(task, &cg->tasks, cg_list) { + if (count++ > MAX_TASKS_SHOWN_PER_CSS) { + seq_puts(seq, " ...\n"); + break; + } else { + seq_printf(seq, " task %d\n", + task_pid_vnr(task)); + } + } + } + read_unlock(&css_set_lock); + return 0; +} + +static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft) +{ + return test_bit(CGRP_RELEASABLE, &cgrp->flags); +} + +static struct cftype debug_files[] = { + { + .name = "cgroup_refcount", + .read_u64 = cgroup_refcount_read, + }, + { + .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", + .read_seq_string = current_css_set_cg_links_read, + }, + + { + .name = "cgroup_css_links", + .read_seq_string = cgroup_css_links_read, + }, + + { + .name = "releasable", + .read_u64 = releasable_read, + }, + + { } /* terminate */ +}; + +struct cgroup_subsys debug_subsys = { + .name = "debug", + .css_alloc = debug_css_alloc, + .css_free = debug_css_free, + .subsys_id = debug_subsys_id, + .base_cftypes = debug_files, +}; +#endif /* CONFIG_CGROUP_DEBUG */ |