/* * Generic process-grouping system. * * Based originally on the cpuset system, extracted by Paul Menage * Copyright (C) 2006 Google, Inc * * Notifications support * Copyright (C) 2009 Nokia Corporation * Author: Kirill A. Shutemov * * Copyright notices from the original cpuset code: * -------------------------------------------------- * Copyright (C) 2003 BULL SA. * Copyright (C) 2004-2006 Silicon Graphics, Inc. * * Portions derived from Patrick Mochel's sysfs code. * sysfs is Copyright (c) 2001-3 Patrick Mochel * * 2003-10-10 Written by Simon Derr. * 2003-10-22 Updates by Stephen Hemminger. * 2004 May-July Rework by Paul Jackson. * --------------------------------------------------- * * This file is subject to the terms and conditions of the GNU General Public * License. See the file COPYING in the main directory of the Linux * distribution for more details. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* TODO: replace with more sophisticated array */ #include #include #include /* used in cgroup_attach_task */ #include #include /* 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); /* * 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 }; /* * 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; /* * Hierarchy ID allocation and mapping. It follows the same exclusion * rules as other root ops - both cgroup_mutex and cgroup_root_mutex for * writes, either for reads. */ static DEFINE_IDR(cgroup_hierarchy_idr); /* 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 */ static inline bool 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); schedule_work(&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 int cgroup_init_root_id(struct cgroupfs_root *root) { int id; lockdep_assert_held(&cgroup_mutex); lockdep_assert_held(&cgroup_root_mutex); id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 2, 0, GFP_KERNEL); if (id < 0) return id; root->hierarchy_id = id; return 0; } static void cgroup_exit_root_id(struct cgroupfs_root *root) { lockdep_assert_held(&cgroup_mutex); lockdep_assert_held(&cgroup_root_mutex); if (root->hierarchy_id) { idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id); root->hierarchy_id = 0; } } 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); 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_free_root(struct cgroupfs_root *root) { if (root) { /* hierarhcy ID shoulid already have been released */ WARN_ON_ONCE(root->hierarchy_id); 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_free_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 = cgroup_init_root_id(root); 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_free_root(opts.new_root); if (((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) && root->flags != opts.flags) { pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n"); ret = -EINVAL; goto drop_new_super; } /* 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: cgroup_exit_root_id(root); 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--; } cgroup_exit_root_id(root); mutex_unlock(&cgroup_root_mutex); mutex_unlock(&cgroup_mutex); simple_xattrs_free(&cgrp->xattrs); kill_litter_super(sb); cgroup_free_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); /** * task_cgroup_path_from_hierarchy - cgroup path of a task on a hierarchy * @task: target task * @hierarchy_id: the hierarchy to look up @task's cgroup from * @buf: the buffer to write the path into * @buflen: the length of the buffer * * Determine @task's cgroup on the hierarchy specified by @hierarchy_id and * copy its path into @buf. This function grabs cgroup_mutex and shouldn't * be used inside locks used by cgroup controller callbacks. */ int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id, char *buf, size_t buflen) { struct cgroupfs_root *root; struct cgroup *cgrp = NULL; int ret = -ENOENT; mutex_lock(&cgroup_mutex); root = idr_find(&cgroup_hierarchy_idr, hierarchy_id); if (root) { cgrp = task_cgroup_from_root(task, root); ret = cgroup_path(cgrp, buf, buflen); } mutex_unlock(&cgroup_mutex); return ret; } EXPORT_SYMBOL_GPL(task_cgroup_path_from_hierarchy); /* * 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) continue; /* 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) continue; /* * 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++; 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; } /* * 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)) { rcu_read_unlock(); ret = -EACCES; goto out_unlock_cgroup; } } else tsk = current; if (threadgroup) tsk = tsk->group_leader; /* * Workqueue threads may acquire PF_NO_SETAFFINITY and become * trapped in a cpuset, or RT worker may be born in a cgroup * with no rt_runtime allocated. Just say no. */ if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) { ret = -EINVAL; rcu_read_unlock(); goto out_unlock_cgroup; } get_task_struct(tsk); rcu_read_unlock(); threadgroup_lock(tsk); if (threadgroup) { if (!thread_group_leader(tsk)) { /* * a race with de_thread from another thread's exec() * may strip us of our leadership, if this happens, * there is no choice but to throw this task away and * try again; this is * "double-double-toil-and-trouble-check locking". */ threadgroup_unlock(tsk); put_task_struct(tsk); goto retry_find_task; } } ret = cgroup_attach_task(cgrp, tsk, threadgroup); threadgroup_unlock(tsk); put_task_struct(tsk); out_unlock_cgroup: mutex_unlock(&cgroup_mutex); return ret; } /** * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from' * @from: attach to all cgroups of a given task * @tsk: the task to be attached */ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) { struct 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; /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */ if (cfts && ss->root != &rootnode) { list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) { dget(cgrp->dentry); list_add_tail(&cgrp->cft_q_node, &pending); } } 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); } 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_sibling - find the next sibling of a given cgroup * @pos: the current cgroup * * This function returns the next sibling of @pos and should be called * under RCU read lock. The only requirement is that @pos is accessible. * The next sibling is guaranteed to be returned regardless of @pos's * state. */ struct cgroup *cgroup_next_sibling(struct cgroup *pos) { struct cgroup *next; WARN_ON_ONCE(!rcu_read_lock_held()); /* * @pos could already have been removed. Once a cgroup is removed, * its ->sibling.next is no longer updated when its next sibling * changes. As CGRP_REMOVED is set on removal which is fully * serialized, if we see it unasserted, it's guaranteed that the * next sibling hasn't finished its grace period even if it's * already removed, and thus safe to dereference from this RCU * critical section. If ->sibling.next is inaccessible, * cgroup_is_removed() is guaranteed to be visible as %true here. */ if (likely(!cgroup_is_removed(pos))) { next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling); if (&next->sibling != &pos->parent->children) return next; return NULL; } /* * Can't dereference the next pointer. Each cgroup is given a * monotonically increasing unique serial number and always * appended to the sibling list, so the next one can be found by * walking the parent's children until we see a cgroup with higher * serial number than @pos's. * * While this path can be slow, it's taken only when either the * current cgroup is removed or iteration and removal race. */ list_for_each_entry_rcu(next, &pos->parent->children, sibling) if (next->serial_nr > pos->serial_nr) return next; return NULL; } EXPORT_SYMBOL_GPL(cgroup_next_sibling); /** * 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; } /* * 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); dput(cgrp->dentry); } /* * 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 ' '. * 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); struct dentry *dentry = css->cgroup->dentry; struct super_block *sb = dentry->d_sb; atomic_inc(&sb->s_active); dput(dentry); deactivate_super(sb); } 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) { static atomic64_t serial_nr_cursor = ATOMIC64_INIT(0); 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); /* * Assign a monotonically increasing serial number. With the list * appending below, it guarantees that sibling cgroups are always * sorted in the ascending serial number order on the parent's * ->children. */ cgrp->serial_nr = atomic64_inc_return(&serial_nr_cursor); /* 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. * * Note that CGRP_REMVOED clearing is depended upon by * cgroup_next_sibling() to resume iteration after dropping RCU * read lock. See cgroup_next_sibling() for details. */ 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); /* allocate id for the dummy hierarchy */ mutex_lock(&cgroup_mutex); mutex_lock(&cgroup_root_mutex); BUG_ON(cgroup_init_root_id(&rootnode)); mutex_unlock(&cgroup_root_mutex); mutex_unlock(&cgroup_mutex); 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; } /* * proc_cgroup_show() * - Print task's cgroup paths into seq_file, one line for each hierarchy * - Used for /proc//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) schedule_work(&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 */