diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 1867 |
1 files changed, 1223 insertions, 644 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index ceee0c54c6a4..70776aec2562 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -26,6 +26,8 @@ * distribution for more details. */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + #include <linux/cgroup.h> #include <linux/cred.h> #include <linux/ctype.h> @@ -70,15 +72,6 @@ MAX_CFTYPE_NAME + 2) /* - * cgroup_tree_mutex nests above cgroup_mutex and protects cftypes, file - * creation/removal and hierarchy changing operations including cgroup - * creation, removal, css association and controller rebinding. This outer - * lock is needed mainly to resolve the circular dependency between kernfs - * active ref and cgroup_mutex. cgroup_tree_mutex nests above both. - */ -static DEFINE_MUTEX(cgroup_tree_mutex); - -/* * cgroup_mutex is the master lock. Any modification to cgroup or its * hierarchy must be performed while holding it. * @@ -99,16 +92,21 @@ static DECLARE_RWSEM(css_set_rwsem); #endif /* + * Protects cgroup_idr and css_idr so that IDs can be released without + * grabbing cgroup_mutex. + */ +static DEFINE_SPINLOCK(cgroup_idr_lock); + +/* * Protects cgroup_subsys->release_agent_path. Modifying it also requires * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock. */ static DEFINE_SPINLOCK(release_agent_path_lock); -#define cgroup_assert_mutexes_or_rcu_locked() \ +#define cgroup_assert_mutex_or_rcu_locked() \ rcu_lockdep_assert(rcu_read_lock_held() || \ - lockdep_is_held(&cgroup_tree_mutex) || \ lockdep_is_held(&cgroup_mutex), \ - "cgroup_[tree_]mutex or RCU read lock required"); + "cgroup_mutex or RCU read lock required"); /* * cgroup destruction makes heavy use of work items and there can be a lot @@ -151,6 +149,13 @@ struct cgroup_root cgrp_dfl_root; */ static bool cgrp_dfl_root_visible; +/* some controllers are not supported in the default hierarchy */ +static const unsigned int cgrp_dfl_root_inhibit_ss_mask = 0 +#ifdef CONFIG_CGROUP_DEBUG + | (1 << debug_cgrp_id) +#endif + ; + /* The list of hierarchy roots */ static LIST_HEAD(cgroup_roots); @@ -160,14 +165,13 @@ static int cgroup_root_count; static DEFINE_IDR(cgroup_hierarchy_idr); /* - * Assign a monotonically increasing serial number to cgroups. It - * guarantees cgroups with bigger numbers are newer than those with smaller - * numbers. Also, as cgroups are always appended to the parent's - * ->children list, it guarantees that sibling cgroups are always sorted in - * the ascending serial number order on the list. Protected by - * cgroup_mutex. + * Assign a monotonically increasing serial number to csses. It guarantees + * cgroups with bigger numbers are newer than those with smaller numbers. + * Also, as csses are always appended to the parent's ->children list, it + * guarantees that sibling csses are always sorted in the ascending serial + * number order on the list. Protected by cgroup_mutex. */ -static u64 cgroup_serial_nr_next = 1; +static u64 css_serial_nr_next = 1; /* This flag indicates whether tasks in the fork and exit paths should * check for fork/exit handlers to call. This avoids us having to do @@ -180,17 +184,59 @@ static struct cftype cgroup_base_files[]; static void cgroup_put(struct cgroup *cgrp); static int rebind_subsystems(struct cgroup_root *dst_root, - unsigned long ss_mask); -static void cgroup_destroy_css_killed(struct cgroup *cgrp); + unsigned int ss_mask); static int cgroup_destroy_locked(struct cgroup *cgrp); +static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss); +static void css_release(struct percpu_ref *ref); +static void kill_css(struct cgroup_subsys_state *css); static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], bool is_add); static void cgroup_pidlist_destroy_all(struct cgroup *cgrp); +/* IDR wrappers which synchronize using cgroup_idr_lock */ +static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end, + gfp_t gfp_mask) +{ + int ret; + + idr_preload(gfp_mask); + spin_lock_bh(&cgroup_idr_lock); + ret = idr_alloc(idr, ptr, start, end, gfp_mask); + spin_unlock_bh(&cgroup_idr_lock); + idr_preload_end(); + return ret; +} + +static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id) +{ + void *ret; + + spin_lock_bh(&cgroup_idr_lock); + ret = idr_replace(idr, ptr, id); + spin_unlock_bh(&cgroup_idr_lock); + return ret; +} + +static void cgroup_idr_remove(struct idr *idr, int id) +{ + spin_lock_bh(&cgroup_idr_lock); + idr_remove(idr, id); + spin_unlock_bh(&cgroup_idr_lock); +} + +static struct cgroup *cgroup_parent(struct cgroup *cgrp) +{ + struct cgroup_subsys_state *parent_css = cgrp->self.parent; + + if (parent_css) + return container_of(parent_css, struct cgroup, self); + return NULL; +} + /** * cgroup_css - obtain a cgroup's css for the specified subsystem * @cgrp: the cgroup of interest - * @ss: the subsystem of interest (%NULL returns the dummy_css) + * @ss: the subsystem of interest (%NULL returns @cgrp->self) * * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This * function must be called either under cgroup_mutex or rcu_read_lock() and @@ -203,23 +249,49 @@ static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp, { if (ss) return rcu_dereference_check(cgrp->subsys[ss->id], - lockdep_is_held(&cgroup_tree_mutex) || lockdep_is_held(&cgroup_mutex)); else - return &cgrp->dummy_css; + return &cgrp->self; +} + +/** + * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem + * @cgrp: the cgroup of interest + * @ss: the subsystem of interest (%NULL returns @cgrp->self) + * + * Similar to cgroup_css() but returns the effctive css, which is defined + * as the matching css of the nearest ancestor including self which has @ss + * enabled. If @ss is associated with the hierarchy @cgrp is on, this + * function is guaranteed to return non-NULL css. + */ +static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, + struct cgroup_subsys *ss) +{ + lockdep_assert_held(&cgroup_mutex); + + if (!ss) + return &cgrp->self; + + if (!(cgrp->root->subsys_mask & (1 << ss->id))) + return NULL; + + while (cgroup_parent(cgrp) && + !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id))) + cgrp = cgroup_parent(cgrp); + + return cgroup_css(cgrp, ss); } /* convenient tests for these bits */ static inline bool cgroup_is_dead(const struct cgroup *cgrp) { - return test_bit(CGRP_DEAD, &cgrp->flags); + return !(cgrp->self.flags & CSS_ONLINE); } -struct cgroup_subsys_state *seq_css(struct seq_file *seq) +struct cgroup_subsys_state *of_css(struct kernfs_open_file *of) { - struct kernfs_open_file *of = seq->private; struct cgroup *cgrp = of->kn->parent->priv; - struct cftype *cft = seq_cft(seq); + struct cftype *cft = of_cft(of); /* * This is open and unprotected implementation of cgroup_css(). @@ -232,9 +304,9 @@ struct cgroup_subsys_state *seq_css(struct seq_file *seq) if (cft->ss) return rcu_dereference_raw(cgrp->subsys[cft->ss->id]); else - return &cgrp->dummy_css; + return &cgrp->self; } -EXPORT_SYMBOL_GPL(seq_css); +EXPORT_SYMBOL_GPL(of_css); /** * cgroup_is_descendant - test ancestry @@ -250,7 +322,7 @@ bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor) while (cgrp) { if (cgrp == ancestor) return true; - cgrp = cgrp->parent; + cgrp = cgroup_parent(cgrp); } return false; } @@ -274,17 +346,30 @@ static int notify_on_release(const struct cgroup *cgrp) * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end * @cgrp: the target cgroup to iterate css's of * - * Should be called under cgroup_mutex. + * Should be called under cgroup_[tree_]mutex. */ #define for_each_css(css, ssid, cgrp) \ for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \ if (!((css) = rcu_dereference_check( \ (cgrp)->subsys[(ssid)], \ - lockdep_is_held(&cgroup_tree_mutex) || \ lockdep_is_held(&cgroup_mutex)))) { } \ else /** + * for_each_e_css - iterate all effective css's of a cgroup + * @css: the iteration cursor + * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end + * @cgrp: the target cgroup to iterate css's of + * + * Should be called under cgroup_[tree_]mutex. + */ +#define for_each_e_css(css, ssid, cgrp) \ + for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \ + if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \ + ; \ + else + +/** * for_each_subsys - iterate all enabled cgroup subsystems * @ss: the iteration cursor * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end @@ -297,22 +382,13 @@ static int notify_on_release(const struct cgroup *cgrp) #define for_each_root(root) \ list_for_each_entry((root), &cgroup_roots, root_list) -/** - * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive. - * @cgrp: the cgroup to be checked for liveness - * - * On success, returns true; the mutex should be later unlocked. On - * failure returns false with no lock held. - */ -static bool cgroup_lock_live_group(struct cgroup *cgrp) -{ - mutex_lock(&cgroup_mutex); - if (cgroup_is_dead(cgrp)) { - mutex_unlock(&cgroup_mutex); - return false; - } - return true; -} +/* iterate over child cgrps, lock should be held throughout iteration */ +#define cgroup_for_each_live_child(child, cgrp) \ + list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \ + if (({ lockdep_assert_held(&cgroup_mutex); \ + cgroup_is_dead(child); })) \ + ; \ + else /* the list of cgroups eligible for automatic release. Protected by * release_list_lock */ @@ -360,6 +436,43 @@ struct css_set init_css_set = { static int css_set_count = 1; /* 1 for init_css_set */ +/** + * cgroup_update_populated - updated populated count of a cgroup + * @cgrp: the target cgroup + * @populated: inc or dec populated count + * + * @cgrp is either getting the first task (css_set) or losing the last. + * Update @cgrp->populated_cnt accordingly. The count is propagated + * towards root so that a given cgroup's populated_cnt is zero iff the + * cgroup and all its descendants are empty. + * + * @cgrp's interface file "cgroup.populated" is zero if + * @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt + * changes from or to zero, userland is notified that the content of the + * interface file has changed. This can be used to detect when @cgrp and + * its descendants become populated or empty. + */ +static void cgroup_update_populated(struct cgroup *cgrp, bool populated) +{ + lockdep_assert_held(&css_set_rwsem); + + do { + bool trigger; + + if (populated) + trigger = !cgrp->populated_cnt++; + else + trigger = !--cgrp->populated_cnt; + + if (!trigger) + break; + + if (cgrp->populated_kn) + kernfs_notify(cgrp->populated_kn); + cgrp = cgroup_parent(cgrp); + } while (cgrp); +} + /* * hash table for cgroup groups. This improves the performance to find * an existing css_set. This hash doesn't (currently) take into @@ -384,6 +497,8 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[]) static void put_css_set_locked(struct css_set *cset, bool taskexit) { struct cgrp_cset_link *link, *tmp_link; + struct cgroup_subsys *ss; + int ssid; lockdep_assert_held(&css_set_rwsem); @@ -391,6 +506,8 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit) return; /* This css_set is dead. unlink it and release cgroup refcounts */ + for_each_subsys(ss, ssid) + list_del(&cset->e_cset_node[ssid]); hash_del(&cset->hlist); css_set_count--; @@ -401,10 +518,13 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit) list_del(&link->cgrp_link); /* @cgrp can't go away while we're holding css_set_rwsem */ - if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) { - if (taskexit) - set_bit(CGRP_RELEASABLE, &cgrp->flags); - check_for_release(cgrp); + if (list_empty(&cgrp->cset_links)) { + cgroup_update_populated(cgrp, false); + if (notify_on_release(cgrp)) { + if (taskexit) + set_bit(CGRP_RELEASABLE, &cgrp->flags); + check_for_release(cgrp); + } } kfree(link); @@ -453,20 +573,20 @@ static bool compare_css_sets(struct css_set *cset, { struct list_head *l1, *l2; - if (memcmp(template, cset->subsys, sizeof(cset->subsys))) { - /* Not all subsystems matched */ + /* + * On the default hierarchy, there can be csets which are + * associated with the same set of cgroups but different csses. + * Let's first ensure that csses match. + */ + if (memcmp(template, cset->subsys, sizeof(cset->subsys))) return false; - } /* * Compare cgroup pointers in order to distinguish between - * different cgroups in 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. + * different cgroups in hierarchies. As different cgroups may + * share the same effective css, this comparison is always + * necessary. */ - l1 = &cset->cgrp_links; l2 = &old_cset->cgrp_links; while (1) { @@ -530,14 +650,17 @@ static struct css_set *find_existing_css_set(struct css_set *old_cset, * won't change, so no need for locking. */ for_each_subsys(ss, i) { - if (root->cgrp.subsys_mask & (1UL << i)) { - /* Subsystem is in this hierarchy. So we want - * the subsystem state from the new - * cgroup */ - template[i] = cgroup_css(cgrp, ss); + if (root->subsys_mask & (1UL << i)) { + /* + * @ss is in this hierarchy, so we want the + * effective css from @cgrp. + */ + template[i] = cgroup_e_css(cgrp, ss); } else { - /* Subsystem is not in this hierarchy, so we - * don't want to change the subsystem state */ + /* + * @ss is not in this hierarchy, so we don't want + * to change the css. + */ template[i] = old_cset->subsys[i]; } } @@ -603,10 +726,18 @@ static void link_css_set(struct list_head *tmp_links, struct css_set *cset, struct cgrp_cset_link *link; BUG_ON(list_empty(tmp_links)); + + if (cgroup_on_dfl(cgrp)) + cset->dfl_cgrp = cgrp; + link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link); link->cset = cset; link->cgrp = cgrp; + + if (list_empty(&cgrp->cset_links)) + cgroup_update_populated(cgrp, true); list_move(&link->cset_link, &cgrp->cset_links); + /* * Always add links to the tail of the list so that the list * is sorted by order of hierarchy creation @@ -629,7 +760,9 @@ static struct css_set *find_css_set(struct css_set *old_cset, struct css_set *cset; struct list_head tmp_links; struct cgrp_cset_link *link; + struct cgroup_subsys *ss; unsigned long key; + int ssid; lockdep_assert_held(&cgroup_mutex); @@ -680,10 +813,14 @@ static struct css_set *find_css_set(struct css_set *old_cset, css_set_count++; - /* Add this cgroup group to the hash table */ + /* Add @cset to the hash table */ key = css_set_hash(cset->subsys); hash_add(css_set_table, &cset->hlist, key); + for_each_subsys(ss, ssid) + list_add_tail(&cset->e_cset_node[ssid], + &cset->subsys[ssid]->cgroup->e_csets[ssid]); + up_write(&css_set_rwsem); return cset; @@ -736,14 +873,13 @@ static void cgroup_destroy_root(struct cgroup_root *root) struct cgroup *cgrp = &root->cgrp; struct cgrp_cset_link *link, *tmp_link; - mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_mutex); BUG_ON(atomic_read(&root->nr_cgrps)); - BUG_ON(!list_empty(&cgrp->children)); + BUG_ON(!list_empty(&cgrp->self.children)); /* Rebind all subsystems back to the default hierarchy */ - rebind_subsystems(&cgrp_dfl_root, cgrp->subsys_mask); + rebind_subsystems(&cgrp_dfl_root, root->subsys_mask); /* * Release all the links from cset_links to this hierarchy's @@ -766,7 +902,6 @@ static void cgroup_destroy_root(struct cgroup_root *root) cgroup_exit_root_id(root); mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); kernfs_destroy_root(root->kf_root); cgroup_free_root(root); @@ -849,7 +984,7 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task, * update of a tasks cgroup pointer by cgroup_attach_task() */ -static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask); +static int cgroup_populate_dir(struct cgroup *cgrp, unsigned int subsys_mask); static struct kernfs_syscall_ops cgroup_kf_syscall_ops; static const struct file_operations proc_cgroupstats_operations; @@ -884,79 +1019,95 @@ static umode_t cgroup_file_mode(const struct cftype *cft) if (cft->read_u64 || cft->read_s64 || cft->seq_show) mode |= S_IRUGO; - if (cft->write_u64 || cft->write_s64 || cft->write_string || - cft->trigger) + if (cft->write_u64 || cft->write_s64 || cft->write) mode |= S_IWUSR; return mode; } -static void cgroup_free_fn(struct work_struct *work) +static void cgroup_get(struct cgroup *cgrp) { - struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work); - - atomic_dec(&cgrp->root->nr_cgrps); - cgroup_pidlist_destroy_all(cgrp); - - if (cgrp->parent) { - /* - * We get a ref to the parent, and put the ref when this - * cgroup is being freed, so it's guaranteed that the - * parent won't be destroyed before its children. - */ - cgroup_put(cgrp->parent); - kernfs_put(cgrp->kn); - kfree(cgrp); - } else { - /* - * This is root cgroup's refcnt reaching zero, which - * indicates that the root should be released. - */ - cgroup_destroy_root(cgrp->root); - } + WARN_ON_ONCE(cgroup_is_dead(cgrp)); + css_get(&cgrp->self); } -static void cgroup_free_rcu(struct rcu_head *head) +static void cgroup_put(struct cgroup *cgrp) { - struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head); - - INIT_WORK(&cgrp->destroy_work, cgroup_free_fn); - queue_work(cgroup_destroy_wq, &cgrp->destroy_work); + css_put(&cgrp->self); } -static void cgroup_get(struct cgroup *cgrp) +/** + * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods + * @kn: the kernfs_node being serviced + * + * This helper undoes cgroup_kn_lock_live() and should be invoked before + * the method finishes if locking succeeded. Note that once this function + * returns the cgroup returned by cgroup_kn_lock_live() may become + * inaccessible any time. If the caller intends to continue to access the + * cgroup, it should pin it before invoking this function. + */ +static void cgroup_kn_unlock(struct kernfs_node *kn) { - WARN_ON_ONCE(cgroup_is_dead(cgrp)); - WARN_ON_ONCE(atomic_read(&cgrp->refcnt) <= 0); - atomic_inc(&cgrp->refcnt); + struct cgroup *cgrp; + + if (kernfs_type(kn) == KERNFS_DIR) + cgrp = kn->priv; + else + cgrp = kn->parent->priv; + + mutex_unlock(&cgroup_mutex); + + kernfs_unbreak_active_protection(kn); + cgroup_put(cgrp); } -static void cgroup_put(struct cgroup *cgrp) +/** + * cgroup_kn_lock_live - locking helper for cgroup kernfs methods + * @kn: the kernfs_node being serviced + * + * This helper is to be used by a cgroup kernfs method currently servicing + * @kn. It breaks the active protection, performs cgroup locking and + * verifies that the associated cgroup is alive. Returns the cgroup if + * alive; otherwise, %NULL. A successful return should be undone by a + * matching cgroup_kn_unlock() invocation. + * + * Any cgroup kernfs method implementation which requires locking the + * associated cgroup should use this helper. It avoids nesting cgroup + * locking under kernfs active protection and allows all kernfs operations + * including self-removal. + */ +static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn) { - if (!atomic_dec_and_test(&cgrp->refcnt)) - return; - if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp))) - return; + struct cgroup *cgrp; + + if (kernfs_type(kn) == KERNFS_DIR) + cgrp = kn->priv; + else + cgrp = kn->parent->priv; /* - * XXX: cgrp->id is only used to look up css's. As cgroup and - * css's lifetimes will be decoupled, it should be made - * per-subsystem and moved to css->id so that lookups are - * successful until the target css is released. + * We're gonna grab cgroup_mutex which nests outside kernfs + * active_ref. cgroup liveliness check alone provides enough + * protection against removal. Ensure @cgrp stays accessible and + * break the active_ref protection. */ + cgroup_get(cgrp); + kernfs_break_active_protection(kn); + mutex_lock(&cgroup_mutex); - idr_remove(&cgrp->root->cgroup_idr, cgrp->id); - mutex_unlock(&cgroup_mutex); - cgrp->id = -1; - call_rcu(&cgrp->rcu_head, cgroup_free_rcu); + if (!cgroup_is_dead(cgrp)) + return cgrp; + + cgroup_kn_unlock(kn); + return NULL; } static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) { char name[CGROUP_FILE_NAME_MAX]; - lockdep_assert_held(&cgroup_tree_mutex); + lockdep_assert_held(&cgroup_mutex); kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name)); } @@ -965,7 +1116,7 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) * @cgrp: target cgroup * @subsys_mask: mask of the subsystem ids whose files should be removed */ -static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask) +static void cgroup_clear_dir(struct cgroup *cgrp, unsigned int subsys_mask) { struct cgroup_subsys *ss; int i; @@ -973,40 +1124,40 @@ static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask) for_each_subsys(ss, i) { struct cftype *cfts; - if (!test_bit(i, &subsys_mask)) + if (!(subsys_mask & (1 << i))) continue; list_for_each_entry(cfts, &ss->cfts, node) cgroup_addrm_files(cgrp, cfts, false); } } -static int rebind_subsystems(struct cgroup_root *dst_root, - unsigned long ss_mask) +static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask) { struct cgroup_subsys *ss; - int ssid, ret; + unsigned int tmp_ss_mask; + int ssid, i, ret; - lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); for_each_subsys(ss, ssid) { if (!(ss_mask & (1 << ssid))) continue; - /* if @ss is on the dummy_root, we can always move it */ - if (ss->root == &cgrp_dfl_root) - continue; - - /* if @ss has non-root cgroups attached to it, can't move */ - if (!list_empty(&ss->root->cgrp.children)) + /* if @ss has non-root csses attached to it, can't move */ + if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss))) return -EBUSY; /* can't move between two non-dummy roots either */ - if (dst_root != &cgrp_dfl_root) + if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root) return -EBUSY; } - ret = cgroup_populate_dir(&dst_root->cgrp, ss_mask); + /* skip creating root files on dfl_root for inhibited subsystems */ + tmp_ss_mask = ss_mask; + if (dst_root == &cgrp_dfl_root) + tmp_ss_mask &= ~cgrp_dfl_root_inhibit_ss_mask; + + ret = cgroup_populate_dir(&dst_root->cgrp, tmp_ss_mask); if (ret) { if (dst_root != &cgrp_dfl_root) return ret; @@ -1018,9 +1169,9 @@ static int rebind_subsystems(struct cgroup_root *dst_root, * Just warn about it and continue. */ if (cgrp_dfl_root_visible) { - pr_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n", - ret, ss_mask); - pr_warning("cgroup: you may retry by moving them to a different hierarchy and unbinding\n"); + pr_warn("failed to create files (%d) while rebinding 0x%x to default root\n", + ret, ss_mask); + pr_warn("you may retry by moving them to a different hierarchy and unbinding\n"); } } @@ -1028,15 +1179,14 @@ static int rebind_subsystems(struct cgroup_root *dst_root, * Nothing can fail from this point on. Remove files for the * removed subsystems and rebind each subsystem. */ - mutex_unlock(&cgroup_mutex); for_each_subsys(ss, ssid) if (ss_mask & (1 << ssid)) cgroup_clear_dir(&ss->root->cgrp, 1 << ssid); - mutex_lock(&cgroup_mutex); for_each_subsys(ss, ssid) { struct cgroup_root *src_root; struct cgroup_subsys_state *css; + struct css_set *cset; if (!(ss_mask & (1 << ssid))) continue; @@ -1051,8 +1201,19 @@ static int rebind_subsystems(struct cgroup_root *dst_root, ss->root = dst_root; css->cgroup = &dst_root->cgrp; - src_root->cgrp.subsys_mask &= ~(1 << ssid); - dst_root->cgrp.subsys_mask |= 1 << ssid; + down_write(&css_set_rwsem); + hash_for_each(css_set_table, i, cset, hlist) + list_move_tail(&cset->e_cset_node[ss->id], + &dst_root->cgrp.e_csets[ss->id]); + up_write(&css_set_rwsem); + + src_root->subsys_mask &= ~(1 << ssid); + src_root->cgrp.child_subsys_mask &= ~(1 << ssid); + + /* default hierarchy doesn't enable controllers by default */ + dst_root->subsys_mask |= 1 << ssid; + if (dst_root != &cgrp_dfl_root) + dst_root->cgrp.child_subsys_mask |= 1 << ssid; if (ss->bind) ss->bind(css); @@ -1070,7 +1231,7 @@ static int cgroup_show_options(struct seq_file *seq, int ssid; for_each_subsys(ss, ssid) - if (root->cgrp.subsys_mask & (1 << ssid)) + if (root->subsys_mask & (1 << ssid)) seq_printf(seq, ",%s", ss->name); if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) seq_puts(seq, ",sane_behavior"); @@ -1092,8 +1253,8 @@ static int cgroup_show_options(struct seq_file *seq, } struct cgroup_sb_opts { - unsigned long subsys_mask; - unsigned long flags; + unsigned int subsys_mask; + unsigned int flags; char *release_agent; bool cpuset_clone_children; char *name; @@ -1101,24 +1262,16 @@ struct cgroup_sb_opts { bool none; }; -/* - * Convert a hierarchy specifier into a bitmask of subsystems and - * flags. Call with cgroup_mutex held to protect the cgroup_subsys[] - * array. This function takes refcounts on subsystems to be used, unless it - * returns error, in which case no refcounts are taken. - */ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) { char *token, *o = data; bool all_ss = false, one_ss = false; - unsigned long mask = (unsigned long)-1; + unsigned int mask = -1U; struct cgroup_subsys *ss; int i; - BUG_ON(!mutex_is_locked(&cgroup_mutex)); - #ifdef CONFIG_CPUSETS - mask = ~(1UL << cpuset_cgrp_id); + mask = ~(1U << cpuset_cgrp_id); #endif memset(opts, 0, sizeof(*opts)); @@ -1199,7 +1352,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) /* Mutually exclusive option 'all' + subsystem name */ if (all_ss) return -EINVAL; - set_bit(i, &opts->subsys_mask); + opts->subsys_mask |= (1 << i); one_ss = true; break; @@ -1211,12 +1364,12 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) /* 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"); + pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n"); if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) || opts->cpuset_clone_children || opts->release_agent || opts->name) { - pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n"); + pr_err("sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n"); return -EINVAL; } } else { @@ -1228,7 +1381,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) if (all_ss || (!one_ss && !opts->none && !opts->name)) for_each_subsys(ss, i) if (!ss->disabled) - set_bit(i, &opts->subsys_mask); + opts->subsys_mask |= (1 << i); /* * We either have to specify by name or by subsystems. (So @@ -1259,14 +1412,13 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data) int ret = 0; struct cgroup_root *root = cgroup_root_from_kf(kf_root); struct cgroup_sb_opts opts; - unsigned long added_mask, removed_mask; + unsigned int added_mask, removed_mask; if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) { - pr_err("cgroup: sane_behavior: remount is not allowed\n"); + pr_err("sane_behavior: remount is not allowed\n"); return -EINVAL; } - mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_mutex); /* See what subsystems are wanted */ @@ -1274,17 +1426,17 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data) if (ret) goto out_unlock; - if (opts.subsys_mask != root->cgrp.subsys_mask || opts.release_agent) - pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n", - task_tgid_nr(current), current->comm); + if (opts.subsys_mask != root->subsys_mask || opts.release_agent) + pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n", + task_tgid_nr(current), current->comm); - added_mask = opts.subsys_mask & ~root->cgrp.subsys_mask; - removed_mask = root->cgrp.subsys_mask & ~opts.subsys_mask; + 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) & CGRP_ROOT_OPTION_MASK) || (opts.name && strcmp(opts.name, root->name))) { - pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n", + pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n", opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "", root->flags & CGRP_ROOT_OPTION_MASK, root->name); ret = -EINVAL; @@ -1292,7 +1444,7 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data) } /* remounting is not allowed for populated hierarchies */ - if (!list_empty(&root->cgrp.children)) { + if (!list_empty(&root->cgrp.self.children)) { ret = -EBUSY; goto out_unlock; } @@ -1312,7 +1464,6 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data) kfree(opts.release_agent); kfree(opts.name); mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); return ret; } @@ -1370,14 +1521,22 @@ out_unlock: static void init_cgroup_housekeeping(struct cgroup *cgrp) { - atomic_set(&cgrp->refcnt, 1); - INIT_LIST_HEAD(&cgrp->sibling); - INIT_LIST_HEAD(&cgrp->children); + struct cgroup_subsys *ss; + int ssid; + + INIT_LIST_HEAD(&cgrp->self.sibling); + INIT_LIST_HEAD(&cgrp->self.children); INIT_LIST_HEAD(&cgrp->cset_links); INIT_LIST_HEAD(&cgrp->release_list); INIT_LIST_HEAD(&cgrp->pidlists); mutex_init(&cgrp->pidlist_mutex); - cgrp->dummy_css.cgroup = cgrp; + cgrp->self.cgroup = cgrp; + cgrp->self.flags |= CSS_ONLINE; + + for_each_subsys(ss, ssid) + INIT_LIST_HEAD(&cgrp->e_csets[ssid]); + + init_waitqueue_head(&cgrp->offline_waitq); } static void init_cgroup_root(struct cgroup_root *root, @@ -1400,21 +1559,24 @@ static void init_cgroup_root(struct cgroup_root *root, set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags); } -static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask) +static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask) { LIST_HEAD(tmp_links); struct cgroup *root_cgrp = &root->cgrp; struct css_set *cset; int i, ret; - lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); - ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL); + ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_NOWAIT); if (ret < 0) goto out; root_cgrp->id = ret; + ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release); + if (ret) + goto out; + /* * We're accessing css_set_count without locking css_set_rwsem here, * but that's OK - it can only be increased by someone holding @@ -1423,11 +1585,11 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask) */ ret = allocate_cgrp_cset_links(css_set_count, &tmp_links); if (ret) - goto out; + goto cancel_ref; ret = cgroup_init_root_id(root); if (ret) - goto out; + goto cancel_ref; root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops, KERNFS_ROOT_CREATE_DEACTIVATED, @@ -1463,7 +1625,7 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask) link_css_set(&tmp_links, cset, root_cgrp); up_write(&css_set_rwsem); - BUG_ON(!list_empty(&root_cgrp->children)); + BUG_ON(!list_empty(&root_cgrp->self.children)); BUG_ON(atomic_read(&root->nr_cgrps) != 1); kernfs_activate(root_cgrp->kn); @@ -1475,6 +1637,8 @@ destroy_root: root->kf_root = NULL; exit_root_id: cgroup_exit_root_id(root); +cancel_ref: + percpu_ref_cancel_init(&root_cgrp->self.refcnt); out: free_cgrp_cset_links(&tmp_links); return ret; @@ -1484,10 +1648,13 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, int flags, const char *unused_dev_name, void *data) { + struct super_block *pinned_sb = NULL; + struct cgroup_subsys *ss; struct cgroup_root *root; struct cgroup_sb_opts opts; struct dentry *dentry; int ret; + int i; bool new_sb; /* @@ -1497,14 +1664,13 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, if (!use_task_css_set_links) cgroup_enable_task_cg_lists(); - mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_mutex); /* First find the desired set of subsystems */ ret = parse_cgroupfs_options(data, &opts); if (ret) goto out_unlock; -retry: + /* look for a matching existing root */ if (!opts.subsys_mask && !opts.none && !opts.name) { cgrp_dfl_root_visible = true; @@ -1514,6 +1680,27 @@ retry: goto out_unlock; } + /* + * Destruction of cgroup root is asynchronous, so subsystems may + * still be dying after the previous unmount. Let's drain the + * dying subsystems. We just need to ensure that the ones + * unmounted previously finish dying and don't care about new ones + * starting. Testing ref liveliness is good enough. + */ + for_each_subsys(ss, i) { + if (!(opts.subsys_mask & (1 << i)) || + ss->root == &cgrp_dfl_root) + continue; + + if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) { + mutex_unlock(&cgroup_mutex); + msleep(10); + ret = restart_syscall(); + goto out_free; + } + cgroup_put(&ss->root->cgrp); + } + for_each_root(root) { bool name_match = false; @@ -1536,7 +1723,7 @@ retry: * subsystems) then they must match. */ if ((opts.subsys_mask || opts.none) && - (opts.subsys_mask != root->cgrp.subsys_mask)) { + (opts.subsys_mask != root->subsys_mask)) { if (!name_match) continue; ret = -EBUSY; @@ -1545,28 +1732,35 @@ retry: if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) { if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) { - pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n"); + pr_err("sane_behavior: new mount options should match the existing superblock\n"); ret = -EINVAL; goto out_unlock; } else { - pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n"); + pr_warn("new mount options do not match the existing superblock, will be ignored\n"); } } /* - * A root's lifetime is governed by its root cgroup. Zero - * ref indicate that the root is being destroyed. Wait for - * destruction to complete so that the subsystems are free. - * We can use wait_queue for the wait but this path is - * super cold. Let's just sleep for a bit and retry. + * We want to reuse @root whose lifetime is governed by its + * ->cgrp. Let's check whether @root is alive and keep it + * that way. As cgroup_kill_sb() can happen anytime, we + * want to block it by pinning the sb so that @root doesn't + * get killed before mount is complete. + * + * With the sb pinned, tryget_live can reliably indicate + * whether @root can be reused. If it's being killed, + * drain it. We can use wait_queue for the wait but this + * path is super cold. Let's just sleep a bit and retry. */ - if (!atomic_inc_not_zero(&root->cgrp.refcnt)) { + pinned_sb = kernfs_pin_sb(root->kf_root, NULL); + if (IS_ERR(pinned_sb) || + !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) { mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); + if (!IS_ERR_OR_NULL(pinned_sb)) + deactivate_super(pinned_sb); msleep(10); - mutex_lock(&cgroup_tree_mutex); - mutex_lock(&cgroup_mutex); - goto retry; + ret = restart_syscall(); + goto out_free; } ret = 0; @@ -1597,8 +1791,7 @@ retry: out_unlock: mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); - +out_free: kfree(opts.release_agent); kfree(opts.name); @@ -1609,6 +1802,16 @@ out_unlock: CGROUP_SUPER_MAGIC, &new_sb); if (IS_ERR(dentry) || !new_sb) cgroup_put(&root->cgrp); + + /* + * If @pinned_sb, we're reusing an existing root and holding an + * extra ref on its sb. Mount is complete. Put the extra ref. + */ + if (pinned_sb) { + WARN_ON(new_sb); + deactivate_super(pinned_sb); + } + return dentry; } @@ -1617,7 +1820,19 @@ static void cgroup_kill_sb(struct super_block *sb) struct kernfs_root *kf_root = kernfs_root_from_sb(sb); struct cgroup_root *root = cgroup_root_from_kf(kf_root); - cgroup_put(&root->cgrp); + /* + * If @root doesn't have any mounts or children, start killing it. + * This prevents new mounts by disabling percpu_ref_tryget_live(). + * cgroup_mount() may wait for @root's release. + * + * And don't kill the default root. + */ + if (css_has_online_children(&root->cgrp.self) || + root == &cgrp_dfl_root) + cgroup_put(&root->cgrp); + else + percpu_ref_kill(&root->cgrp.self.refcnt); + kernfs_kill_sb(sb); } @@ -1739,7 +1954,7 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset) /** * cgroup_task_migrate - move a task from one cgroup to another. - * @old_cgrp; the cgroup @tsk is being migrated from + * @old_cgrp: the cgroup @tsk is being migrated from * @tsk: the task being migrated * @new_cset: the new css_set @tsk is being attached to * @@ -1831,10 +2046,6 @@ static void cgroup_migrate_add_src(struct css_set *src_cset, src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root); - /* nothing to do if this cset already belongs to the cgroup */ - if (src_cgrp == dst_cgrp) - return; - if (!list_empty(&src_cset->mg_preload_node)) return; @@ -1849,13 +2060,14 @@ static void cgroup_migrate_add_src(struct css_set *src_cset, /** * cgroup_migrate_prepare_dst - prepare destination css_sets for migration - * @dst_cgrp: the destination cgroup + * @dst_cgrp: the destination cgroup (may be %NULL) * @preloaded_csets: list of preloaded source css_sets * * Tasks are about to be moved to @dst_cgrp and all the source css_sets * have been preloaded to @preloaded_csets. This function looks up and - * pins all destination css_sets, links each to its source, and put them on - * @preloaded_csets. + * pins all destination css_sets, links each to its source, and append them + * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each + * source css_set is assumed to be its cgroup on the default hierarchy. * * This function must be called after cgroup_migrate_add_src() has been * called on each migration source css_set. After migration is performed @@ -1866,19 +2078,42 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, struct list_head *preloaded_csets) { LIST_HEAD(csets); - struct css_set *src_cset; + struct css_set *src_cset, *tmp_cset; lockdep_assert_held(&cgroup_mutex); + /* + * Except for the root, child_subsys_mask must be zero for a cgroup + * with tasks so that child cgroups don't compete against tasks. + */ + if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) && + dst_cgrp->child_subsys_mask) + return -EBUSY; + /* look up the dst cset for each src cset and link it to src */ - list_for_each_entry(src_cset, preloaded_csets, mg_preload_node) { + list_for_each_entry_safe(src_cset, tmp_cset, preloaded_csets, mg_preload_node) { struct css_set *dst_cset; - dst_cset = find_css_set(src_cset, dst_cgrp); + dst_cset = find_css_set(src_cset, + dst_cgrp ?: src_cset->dfl_cgrp); if (!dst_cset) goto err; WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset); + + /* + * If src cset equals dst, it's noop. Drop the src. + * cgroup_migrate() will skip the cset too. Note that we + * can't handle src == dst as some nodes are used by both. + */ + if (src_cset == dst_cset) { + src_cset->mg_src_cgrp = NULL; + list_del_init(&src_cset->mg_preload_node); + put_css_set(src_cset, false); + put_css_set(dst_cset, false); + continue; + } + src_cset->mg_dst_cset = dst_cset; if (list_empty(&dst_cset->mg_preload_node)) @@ -1887,7 +2122,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp, put_css_set(dst_cset, false); } - list_splice(&csets, preloaded_csets); + list_splice_tail(&csets, preloaded_csets); return 0; err: cgroup_migrate_finish(&csets); @@ -1968,7 +2203,7 @@ static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader, return 0; /* check that we can legitimately attach to the cgroup */ - for_each_css(css, i, cgrp) { + for_each_e_css(css, i, cgrp) { if (css->ss->can_attach) { ret = css->ss->can_attach(css, &tset); if (ret) { @@ -1998,7 +2233,7 @@ static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader, */ tset.csets = &tset.dst_csets; - for_each_css(css, i, cgrp) + for_each_e_css(css, i, cgrp) if (css->ss->attach) css->ss->attach(css, &tset); @@ -2006,7 +2241,7 @@ static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader, goto out_release_tset; out_cancel_attach: - for_each_css(css, i, cgrp) { + for_each_e_css(css, i, cgrp) { if (css == failed_css) break; if (css->ss->cancel_attach) @@ -2065,13 +2300,20 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp, * function to attach either it or all tasks in its threadgroup. Will lock * cgroup_mutex and threadgroup. */ -static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) +static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf, + size_t nbytes, loff_t off, bool threadgroup) { struct task_struct *tsk; const struct cred *cred = current_cred(), *tcred; + struct cgroup *cgrp; + pid_t pid; int ret; - if (!cgroup_lock_live_group(cgrp)) + if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0) + return -EINVAL; + + cgrp = cgroup_kn_lock_live(of->kn); + if (!cgrp) return -ENODEV; retry_find_task: @@ -2137,8 +2379,8 @@ retry_find_task: put_task_struct(tsk); out_unlock_cgroup: - mutex_unlock(&cgroup_mutex); - return ret; + cgroup_kn_unlock(of->kn); + return ret ?: nbytes; } /** @@ -2172,43 +2414,44 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) } EXPORT_SYMBOL_GPL(cgroup_attach_task_all); -static int cgroup_tasks_write(struct cgroup_subsys_state *css, - struct cftype *cft, u64 pid) +static ssize_t cgroup_tasks_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) { - return attach_task_by_pid(css->cgroup, pid, false); + return __cgroup_procs_write(of, buf, nbytes, off, false); } -static int cgroup_procs_write(struct cgroup_subsys_state *css, - struct cftype *cft, u64 tgid) +static ssize_t cgroup_procs_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) { - return attach_task_by_pid(css->cgroup, tgid, true); + return __cgroup_procs_write(of, buf, nbytes, off, true); } -static int cgroup_release_agent_write(struct cgroup_subsys_state *css, - struct cftype *cft, char *buffer) +static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) { - struct cgroup_root *root = css->cgroup->root; + struct cgroup *cgrp; + + BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX); - BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX); - if (!cgroup_lock_live_group(css->cgroup)) + cgrp = cgroup_kn_lock_live(of->kn); + if (!cgrp) return -ENODEV; spin_lock(&release_agent_path_lock); - strlcpy(root->release_agent_path, buffer, - sizeof(root->release_agent_path)); + strlcpy(cgrp->root->release_agent_path, strstrip(buf), + sizeof(cgrp->root->release_agent_path)); spin_unlock(&release_agent_path_lock); - mutex_unlock(&cgroup_mutex); - return 0; + cgroup_kn_unlock(of->kn); + return nbytes; } static int cgroup_release_agent_show(struct seq_file *seq, void *v) { struct cgroup *cgrp = seq_css(seq)->cgroup; - if (!cgroup_lock_live_group(cgrp)) - return -ENODEV; + spin_lock(&release_agent_path_lock); seq_puts(seq, cgrp->root->release_agent_path); + spin_unlock(&release_agent_path_lock); seq_putc(seq, '\n'); - mutex_unlock(&cgroup_mutex); return 0; } @@ -2220,6 +2463,320 @@ static int cgroup_sane_behavior_show(struct seq_file *seq, void *v) return 0; } +static void cgroup_print_ss_mask(struct seq_file *seq, unsigned int ss_mask) +{ + struct cgroup_subsys *ss; + bool printed = false; + int ssid; + + for_each_subsys(ss, ssid) { + if (ss_mask & (1 << ssid)) { + if (printed) + seq_putc(seq, ' '); + seq_printf(seq, "%s", ss->name); + printed = true; + } + } + if (printed) + seq_putc(seq, '\n'); +} + +/* show controllers which are currently attached to the default hierarchy */ +static int cgroup_root_controllers_show(struct seq_file *seq, void *v) +{ + struct cgroup *cgrp = seq_css(seq)->cgroup; + + cgroup_print_ss_mask(seq, cgrp->root->subsys_mask & + ~cgrp_dfl_root_inhibit_ss_mask); + return 0; +} + +/* show controllers which are enabled from the parent */ +static int cgroup_controllers_show(struct seq_file *seq, void *v) +{ + struct cgroup *cgrp = seq_css(seq)->cgroup; + + cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->child_subsys_mask); + return 0; +} + +/* show controllers which are enabled for a given cgroup's children */ +static int cgroup_subtree_control_show(struct seq_file *seq, void *v) +{ + struct cgroup *cgrp = seq_css(seq)->cgroup; + + cgroup_print_ss_mask(seq, cgrp->child_subsys_mask); + return 0; +} + +/** + * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy + * @cgrp: root of the subtree to update csses for + * + * @cgrp's child_subsys_mask has changed and its subtree's (self excluded) + * css associations need to be updated accordingly. This function looks up + * all css_sets which are attached to the subtree, creates the matching + * updated css_sets and migrates the tasks to the new ones. + */ +static int cgroup_update_dfl_csses(struct cgroup *cgrp) +{ + LIST_HEAD(preloaded_csets); + struct cgroup_subsys_state *css; + struct css_set *src_cset; + int ret; + + lockdep_assert_held(&cgroup_mutex); + + /* look up all csses currently attached to @cgrp's subtree */ + down_read(&css_set_rwsem); + css_for_each_descendant_pre(css, cgroup_css(cgrp, NULL)) { + struct cgrp_cset_link *link; + + /* self is not affected by child_subsys_mask change */ + if (css->cgroup == cgrp) + continue; + + list_for_each_entry(link, &css->cgroup->cset_links, cset_link) + cgroup_migrate_add_src(link->cset, cgrp, + &preloaded_csets); + } + up_read(&css_set_rwsem); + + /* NULL dst indicates self on default hierarchy */ + ret = cgroup_migrate_prepare_dst(NULL, &preloaded_csets); + if (ret) + goto out_finish; + + list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) { + struct task_struct *last_task = NULL, *task; + + /* src_csets precede dst_csets, break on the first dst_cset */ + if (!src_cset->mg_src_cgrp) + break; + + /* + * All tasks in src_cset need to be migrated to the + * matching dst_cset. Empty it process by process. We + * walk tasks but migrate processes. The leader might even + * belong to a different cset but such src_cset would also + * be among the target src_csets because the default + * hierarchy enforces per-process membership. + */ + while (true) { + down_read(&css_set_rwsem); + task = list_first_entry_or_null(&src_cset->tasks, + struct task_struct, cg_list); + if (task) { + task = task->group_leader; + WARN_ON_ONCE(!task_css_set(task)->mg_src_cgrp); + get_task_struct(task); + } + up_read(&css_set_rwsem); + + if (!task) + break; + + /* guard against possible infinite loop */ + if (WARN(last_task == task, + "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n")) + goto out_finish; + last_task = task; + + threadgroup_lock(task); + /* raced against de_thread() from another thread? */ + if (!thread_group_leader(task)) { + threadgroup_unlock(task); + put_task_struct(task); + continue; + } + + ret = cgroup_migrate(src_cset->dfl_cgrp, task, true); + + threadgroup_unlock(task); + put_task_struct(task); + + if (WARN(ret, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret)) + goto out_finish; + } + } + +out_finish: + cgroup_migrate_finish(&preloaded_csets); + return ret; +} + +/* change the enabled child controllers for a cgroup in the default hierarchy */ +static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, + loff_t off) +{ + unsigned int enable = 0, disable = 0; + struct cgroup *cgrp, *child; + struct cgroup_subsys *ss; + char *tok; + int ssid, ret; + + /* + * Parse input - space separated list of subsystem names prefixed + * with either + or -. + */ + buf = strstrip(buf); + while ((tok = strsep(&buf, " "))) { + if (tok[0] == '\0') + continue; + for_each_subsys(ss, ssid) { + if (ss->disabled || strcmp(tok + 1, ss->name) || + ((1 << ss->id) & cgrp_dfl_root_inhibit_ss_mask)) + continue; + + if (*tok == '+') { + enable |= 1 << ssid; + disable &= ~(1 << ssid); + } else if (*tok == '-') { + disable |= 1 << ssid; + enable &= ~(1 << ssid); + } else { + return -EINVAL; + } + break; + } + if (ssid == CGROUP_SUBSYS_COUNT) + return -EINVAL; + } + + cgrp = cgroup_kn_lock_live(of->kn); + if (!cgrp) + return -ENODEV; + + for_each_subsys(ss, ssid) { + if (enable & (1 << ssid)) { + if (cgrp->child_subsys_mask & (1 << ssid)) { + enable &= ~(1 << ssid); + continue; + } + + /* + * Because css offlining is asynchronous, userland + * might try to re-enable the same controller while + * the previous instance is still around. In such + * cases, wait till it's gone using offline_waitq. + */ + cgroup_for_each_live_child(child, cgrp) { + DEFINE_WAIT(wait); + + if (!cgroup_css(child, ss)) + continue; + + cgroup_get(child); + prepare_to_wait(&child->offline_waitq, &wait, + TASK_UNINTERRUPTIBLE); + cgroup_kn_unlock(of->kn); + schedule(); + finish_wait(&child->offline_waitq, &wait); + cgroup_put(child); + + return restart_syscall(); + } + + /* unavailable or not enabled on the parent? */ + if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) || + (cgroup_parent(cgrp) && + !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) { + ret = -ENOENT; + goto out_unlock; + } + } else if (disable & (1 << ssid)) { + if (!(cgrp->child_subsys_mask & (1 << ssid))) { + disable &= ~(1 << ssid); + continue; + } + + /* a child has it enabled? */ + cgroup_for_each_live_child(child, cgrp) { + if (child->child_subsys_mask & (1 << ssid)) { + ret = -EBUSY; + goto out_unlock; + } + } + } + } + + if (!enable && !disable) { + ret = 0; + goto out_unlock; + } + + /* + * Except for the root, child_subsys_mask must be zero for a cgroup + * with tasks so that child cgroups don't compete against tasks. + */ + if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) { + ret = -EBUSY; + goto out_unlock; + } + + /* + * Create csses for enables and update child_subsys_mask. This + * changes cgroup_e_css() results which in turn makes the + * subsequent cgroup_update_dfl_csses() associate all tasks in the + * subtree to the updated csses. + */ + for_each_subsys(ss, ssid) { + if (!(enable & (1 << ssid))) + continue; + + cgroup_for_each_live_child(child, cgrp) { + ret = create_css(child, ss); + if (ret) + goto err_undo_css; + } + } + + cgrp->child_subsys_mask |= enable; + cgrp->child_subsys_mask &= ~disable; + + ret = cgroup_update_dfl_csses(cgrp); + if (ret) + goto err_undo_css; + + /* all tasks are now migrated away from the old csses, kill them */ + for_each_subsys(ss, ssid) { + if (!(disable & (1 << ssid))) + continue; + + cgroup_for_each_live_child(child, cgrp) + kill_css(cgroup_css(child, ss)); + } + + kernfs_activate(cgrp->kn); + ret = 0; +out_unlock: + cgroup_kn_unlock(of->kn); + return ret ?: nbytes; + +err_undo_css: + cgrp->child_subsys_mask &= ~enable; + cgrp->child_subsys_mask |= disable; + + for_each_subsys(ss, ssid) { + if (!(enable & (1 << ssid))) + continue; + + cgroup_for_each_live_child(child, cgrp) { + struct cgroup_subsys_state *css = cgroup_css(child, ss); + if (css) + kill_css(css); + } + } + goto out_unlock; +} + +static int cgroup_populated_show(struct seq_file *seq, void *v) +{ + seq_printf(seq, "%d\n", (bool)seq_css(seq)->cgroup->populated_cnt); + return 0; +} + static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { @@ -2228,6 +2785,9 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, struct cgroup_subsys_state *css; int ret; + if (cft->write) + return cft->write(of, buf, nbytes, off); + /* * kernfs guarantees that a file isn't deleted with operations in * flight, which means that the matching css is and stays alive and @@ -2238,9 +2798,7 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, css = cgroup_css(cgrp, cft->ss); rcu_read_unlock(); - if (cft->write_string) { - ret = cft->write_string(css, cft, strstrip(buf)); - } else if (cft->write_u64) { + if (cft->write_u64) { unsigned long long v; ret = kstrtoull(buf, 0, &v); if (!ret) @@ -2250,8 +2808,6 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, ret = kstrtoll(buf, 0, &v); if (!ret) ret = cft->write_s64(css, cft, v); - } else if (cft->trigger) { - ret = cft->trigger(css, (unsigned int)cft->private); } else { ret = -EINVAL; } @@ -2328,20 +2884,18 @@ static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent, return -EPERM; /* - * We're gonna grab cgroup_tree_mutex which nests outside kernfs + * We're gonna grab cgroup_mutex which nests outside kernfs * active_ref. kernfs_rename() doesn't require active_ref - * protection. Break them before grabbing cgroup_tree_mutex. + * protection. Break them before grabbing cgroup_mutex. */ kernfs_break_active_protection(new_parent); kernfs_break_active_protection(kn); - mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_mutex); ret = kernfs_rename(kn, new_parent, new_name_str); mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); kernfs_unbreak_active_protection(kn); kernfs_unbreak_active_protection(new_parent); @@ -2379,9 +2933,14 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft) return PTR_ERR(kn); ret = cgroup_kn_set_ugid(kn); - if (ret) + if (ret) { kernfs_remove(kn); - return ret; + return ret; + } + + if (cft->seq_show == cgroup_populated_show) + cgrp->populated_kn = kn; + return 0; } /** @@ -2401,7 +2960,7 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], struct cftype *cft; int ret; - lockdep_assert_held(&cgroup_tree_mutex); + lockdep_assert_held(&cgroup_mutex); for (cft = cfts; cft->name[0] != '\0'; cft++) { /* does cft->flags tell us to skip this file on @cgrp? */ @@ -2409,16 +2968,16 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], continue; if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp)) continue; - if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent) + if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp)) continue; - if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent) + if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp)) continue; if (is_add) { ret = cgroup_add_file(cgrp, cft); if (ret) { - pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n", - cft->name, ret); + pr_warn("%s: failed to add %s, err=%d\n", + __func__, cft->name, ret); return ret; } } else { @@ -2436,11 +2995,7 @@ static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add) struct cgroup_subsys_state *css; int ret = 0; - lockdep_assert_held(&cgroup_tree_mutex); - - /* don't bother if @ss isn't attached */ - if (ss->root == &cgrp_dfl_root) - return 0; + lockdep_assert_held(&cgroup_mutex); /* add/rm files for all cgroups created before */ css_for_each_descendant_pre(css, cgroup_css(root, ss)) { @@ -2508,7 +3063,7 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) static int cgroup_rm_cftypes_locked(struct cftype *cfts) { - lockdep_assert_held(&cgroup_tree_mutex); + lockdep_assert_held(&cgroup_mutex); if (!cfts || !cfts[0].ss) return -ENOENT; @@ -2534,9 +3089,9 @@ int cgroup_rm_cftypes(struct cftype *cfts) { int ret; - mutex_lock(&cgroup_tree_mutex); + mutex_lock(&cgroup_mutex); ret = cgroup_rm_cftypes_locked(cfts); - mutex_unlock(&cgroup_tree_mutex); + mutex_unlock(&cgroup_mutex); return ret; } @@ -2558,6 +3113,9 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) { int ret; + if (ss->disabled) + return 0; + if (!cfts || cfts[0].name[0] == '\0') return 0; @@ -2565,14 +3123,14 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) if (ret) return ret; - mutex_lock(&cgroup_tree_mutex); + mutex_lock(&cgroup_mutex); list_add_tail(&cfts->node, &ss->cfts); ret = cgroup_apply_cftypes(cfts, true); if (ret) cgroup_rm_cftypes_locked(cfts); - mutex_unlock(&cgroup_tree_mutex); + mutex_unlock(&cgroup_mutex); return ret; } @@ -2596,57 +3154,65 @@ static int cgroup_task_count(const struct cgroup *cgrp) /** * css_next_child - find the next child of a given css - * @pos_css: the current position (%NULL to initiate traversal) - * @parent_css: css whose children to walk + * @pos: the current position (%NULL to initiate traversal) + * @parent: css whose children to walk * - * This function returns the next child of @parent_css and should be called + * This function returns the next child of @parent and should be called * under either cgroup_mutex or RCU read lock. The only requirement is - * that @parent_css and @pos_css are accessible. The next sibling is - * guaranteed to be returned regardless of their states. + * that @parent and @pos are accessible. The next sibling is guaranteed to + * be returned regardless of their states. + * + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. */ -struct cgroup_subsys_state * -css_next_child(struct cgroup_subsys_state *pos_css, - struct cgroup_subsys_state *parent_css) +struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos, + struct cgroup_subsys_state *parent) { - struct cgroup *pos = pos_css ? pos_css->cgroup : NULL; - struct cgroup *cgrp = parent_css->cgroup; - struct cgroup *next; + struct cgroup_subsys_state *next; - cgroup_assert_mutexes_or_rcu_locked(); + cgroup_assert_mutex_or_rcu_locked(); /* - * @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_DEAD assertion is serialized and happens - * before the cgroup is taken off the ->sibling list, 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_dead() is guaranteed - * to be visible as %true here. + * @pos could already have been unlinked from the sibling list. + * Once a cgroup is removed, its ->sibling.next is no longer + * updated when its next sibling changes. CSS_RELEASED is set when + * @pos is taken off list, at which time its next pointer is valid, + * and, as releases are serialized, the one pointed to by the next + * pointer is guaranteed to not have started release yet. This + * implies that if we observe !CSS_RELEASED on @pos in this RCU + * critical section, the one pointed to by its next pointer is + * guaranteed to not have finished its RCU grace period even if we + * have dropped rcu_read_lock() inbetween iterations. * - * If @pos is dead, its next pointer can't be dereferenced; - * however, as each cgroup is given a monotonically increasing - * unique serial number and always appended to the sibling list, - * the next one can be found by walking the parent's children until - * we see a cgroup with higher serial number than @pos's. While - * this path can be slower, it's taken only when either the current - * cgroup is removed or iteration and removal race. + * If @pos has CSS_RELEASED set, its next pointer can't be + * dereferenced; however, as each css is given a monotonically + * increasing unique serial number and always appended to the + * sibling list, the next one can be found by walking the parent's + * children until the first css with higher serial number than + * @pos's. While this path can be slower, it happens iff iteration + * races against release and the race window is very small. */ if (!pos) { - next = list_entry_rcu(cgrp->children.next, struct cgroup, sibling); - } else if (likely(!cgroup_is_dead(pos))) { - next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling); + next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling); + } else if (likely(!(pos->flags & CSS_RELEASED))) { + next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling); } else { - list_for_each_entry_rcu(next, &cgrp->children, sibling) + list_for_each_entry_rcu(next, &parent->children, sibling) if (next->serial_nr > pos->serial_nr) break; } - if (&next->sibling == &cgrp->children) - return NULL; - - return cgroup_css(next, parent_css->ss); + /* + * @next, if not pointing to the head, can be dereferenced and is + * the next sibling. + */ + if (&next->sibling != &parent->children) + return next; + return NULL; } /** @@ -2662,6 +3228,13 @@ css_next_child(struct cgroup_subsys_state *pos_css, * doesn't require the whole traversal to be contained in a single critical * section. This function will return the correct next descendant as long * as both @pos and @root are accessible and @pos is a descendant of @root. + * + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. */ struct cgroup_subsys_state * css_next_descendant_pre(struct cgroup_subsys_state *pos, @@ -2669,7 +3242,7 @@ css_next_descendant_pre(struct cgroup_subsys_state *pos, { struct cgroup_subsys_state *next; - cgroup_assert_mutexes_or_rcu_locked(); + cgroup_assert_mutex_or_rcu_locked(); /* if first iteration, visit @root */ if (!pos) @@ -2682,10 +3255,10 @@ css_next_descendant_pre(struct cgroup_subsys_state *pos, /* no child, visit my or the closest ancestor's next sibling */ while (pos != root) { - next = css_next_child(pos, css_parent(pos)); + next = css_next_child(pos, pos->parent); if (next) return next; - pos = css_parent(pos); + pos = pos->parent; } return NULL; @@ -2709,7 +3282,7 @@ css_rightmost_descendant(struct cgroup_subsys_state *pos) { struct cgroup_subsys_state *last, *tmp; - cgroup_assert_mutexes_or_rcu_locked(); + cgroup_assert_mutex_or_rcu_locked(); do { last = pos; @@ -2749,6 +3322,13 @@ css_leftmost_descendant(struct cgroup_subsys_state *pos) * section. This function will return the correct next descendant as long * as both @pos and @cgroup are accessible and @pos is a descendant of * @cgroup. + * + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. */ struct cgroup_subsys_state * css_next_descendant_post(struct cgroup_subsys_state *pos, @@ -2756,7 +3336,7 @@ css_next_descendant_post(struct cgroup_subsys_state *pos, { struct cgroup_subsys_state *next; - cgroup_assert_mutexes_or_rcu_locked(); + cgroup_assert_mutex_or_rcu_locked(); /* if first iteration, visit leftmost descendant which may be @root */ if (!pos) @@ -2767,12 +3347,36 @@ css_next_descendant_post(struct cgroup_subsys_state *pos, return NULL; /* if there's an unvisited sibling, visit its leftmost descendant */ - next = css_next_child(pos, css_parent(pos)); + next = css_next_child(pos, pos->parent); if (next) return css_leftmost_descendant(next); /* no sibling left, visit parent */ - return css_parent(pos); + return pos->parent; +} + +/** + * css_has_online_children - does a css have online children + * @css: the target css + * + * Returns %true if @css has any online children; otherwise, %false. This + * function can be called from any context but the caller is responsible + * for synchronizing against on/offlining as necessary. + */ +bool css_has_online_children(struct cgroup_subsys_state *css) +{ + struct cgroup_subsys_state *child; + bool ret = false; + + rcu_read_lock(); + css_for_each_child(child, css) { + if (child->flags & CSS_ONLINE) { + ret = true; + break; + } + } + rcu_read_unlock(); + return ret; } /** @@ -2783,27 +3387,36 @@ css_next_descendant_post(struct cgroup_subsys_state *pos, */ static void css_advance_task_iter(struct css_task_iter *it) { - struct list_head *l = it->cset_link; + struct list_head *l = it->cset_pos; struct cgrp_cset_link *link; struct css_set *cset; /* Advance to the next non-empty css_set */ do { l = l->next; - if (l == &it->origin_css->cgroup->cset_links) { - it->cset_link = NULL; + if (l == it->cset_head) { + it->cset_pos = NULL; return; } - link = list_entry(l, struct cgrp_cset_link, cset_link); - cset = link->cset; + + if (it->ss) { + cset = container_of(l, struct css_set, + e_cset_node[it->ss->id]); + } else { + link = list_entry(l, struct cgrp_cset_link, cset_link); + cset = link->cset; + } } while (list_empty(&cset->tasks) && list_empty(&cset->mg_tasks)); - it->cset_link = l; + it->cset_pos = l; if (!list_empty(&cset->tasks)) - it->task = cset->tasks.next; + it->task_pos = cset->tasks.next; else - it->task = cset->mg_tasks.next; + it->task_pos = cset->mg_tasks.next; + + it->tasks_head = &cset->tasks; + it->mg_tasks_head = &cset->mg_tasks; } /** @@ -2829,8 +3442,14 @@ void css_task_iter_start(struct cgroup_subsys_state *css, down_read(&css_set_rwsem); - it->origin_css = css; - it->cset_link = &css->cgroup->cset_links; + it->ss = css->ss; + + if (it->ss) + it->cset_pos = &css->cgroup->e_csets[css->ss->id]; + else + it->cset_pos = &css->cgroup->cset_links; + + it->cset_head = it->cset_pos; css_advance_task_iter(it); } @@ -2846,12 +3465,10 @@ void css_task_iter_start(struct cgroup_subsys_state *css, struct task_struct *css_task_iter_next(struct css_task_iter *it) { struct task_struct *res; - struct list_head *l = it->task; - struct cgrp_cset_link *link = list_entry(it->cset_link, - struct cgrp_cset_link, cset_link); + struct list_head *l = it->task_pos; /* If the iterator cg is NULL, we have no tasks */ - if (!it->cset_link) + if (!it->cset_pos) return NULL; res = list_entry(l, struct task_struct, cg_list); @@ -2862,13 +3479,13 @@ struct task_struct *css_task_iter_next(struct css_task_iter *it) */ l = l->next; - if (l == &link->cset->tasks) - l = link->cset->mg_tasks.next; + if (l == it->tasks_head) + l = it->mg_tasks_head->next; - if (l == &link->cset->mg_tasks) + if (l == it->mg_tasks_head) css_advance_task_iter(it); else - it->task = l; + it->task_pos = l; return res; } @@ -2921,7 +3538,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from) * ->can_attach() fails. */ do { - css_task_iter_start(&from->dummy_css, &it); + css_task_iter_start(&from->self, &it); task = css_task_iter_next(&it); if (task) get_task_struct(task); @@ -3186,7 +3803,7 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type, if (!array) return -ENOMEM; /* now, populate the array */ - css_task_iter_start(&cgrp->dummy_css, &it); + css_task_iter_start(&cgrp->self, &it); while ((tsk = css_task_iter_next(&it))) { if (unlikely(n == length)) break; @@ -3248,7 +3865,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) /* * We aren't being called from kernfs and there's no guarantee on - * @kn->priv's validity. For this and css_tryget_from_dir(), + * @kn->priv's validity. For this and css_tryget_online_from_dir(), * @kn->priv is RCU safe. Let's do the RCU dancing. */ rcu_read_lock(); @@ -3260,7 +3877,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) } rcu_read_unlock(); - css_task_iter_start(&cgrp->dummy_css, &it); + css_task_iter_start(&cgrp->self, &it); while ((tsk = css_task_iter_next(&it))) { switch (tsk->state) { case TASK_RUNNING: @@ -3390,17 +4007,6 @@ 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 u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css, struct cftype *cft) { @@ -3442,7 +4048,7 @@ static struct cftype cgroup_base_files[] = { .seq_stop = cgroup_pidlist_stop, .seq_show = cgroup_pidlist_show, .private = CGROUP_FILE_PROCS, - .write_u64 = cgroup_procs_write, + .write = cgroup_procs_write, .mode = S_IRUGO | S_IWUSR, }, { @@ -3456,6 +4062,27 @@ static struct cftype cgroup_base_files[] = { .flags = CFTYPE_ONLY_ON_ROOT, .seq_show = cgroup_sane_behavior_show, }, + { + .name = "cgroup.controllers", + .flags = CFTYPE_ONLY_ON_DFL | CFTYPE_ONLY_ON_ROOT, + .seq_show = cgroup_root_controllers_show, + }, + { + .name = "cgroup.controllers", + .flags = CFTYPE_ONLY_ON_DFL | CFTYPE_NOT_ON_ROOT, + .seq_show = cgroup_controllers_show, + }, + { + .name = "cgroup.subtree_control", + .flags = CFTYPE_ONLY_ON_DFL, + .seq_show = cgroup_subtree_control_show, + .write = cgroup_subtree_control_write, + }, + { + .name = "cgroup.populated", + .flags = CFTYPE_ONLY_ON_DFL | CFTYPE_NOT_ON_ROOT, + .seq_show = cgroup_populated_show, + }, /* * Historical crazy stuff. These don't have "cgroup." prefix and @@ -3470,7 +4097,7 @@ static struct cftype cgroup_base_files[] = { .seq_stop = cgroup_pidlist_stop, .seq_show = cgroup_pidlist_show, .private = CGROUP_FILE_TASKS, - .write_u64 = cgroup_tasks_write, + .write = cgroup_tasks_write, .mode = S_IRUGO | S_IWUSR, }, { @@ -3483,7 +4110,7 @@ static struct cftype cgroup_base_files[] = { .name = "release_agent", .flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT, .seq_show = cgroup_release_agent_show, - .write_string = cgroup_release_agent_write, + .write = cgroup_release_agent_write, .max_write_len = PATH_MAX - 1, }, { } /* terminate */ @@ -3496,7 +4123,7 @@ static struct cftype cgroup_base_files[] = { * * On failure, no file is added. */ -static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask) +static int cgroup_populate_dir(struct cgroup *cgrp, unsigned int subsys_mask) { struct cgroup_subsys *ss; int i, ret = 0; @@ -3505,7 +4132,7 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask) for_each_subsys(ss, i) { struct cftype *cfts; - if (!test_bit(i, &subsys_mask)) + if (!(subsys_mask & (1 << i))) continue; list_for_each_entry(cfts, &ss->cfts, node) { @@ -3527,9 +4154,9 @@ err: * Implemented in kill_css(). * * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs - * and thus css_tryget() is guaranteed to fail, the css can be offlined - * by invoking offline_css(). After offlining, the base ref is put. - * Implemented in css_killed_work_fn(). + * and thus css_tryget_online() is guaranteed to fail, the css can be + * offlined by invoking offline_css(). After offlining, the base ref is + * put. Implemented in css_killed_work_fn(). * * 3. When the percpu_ref reaches zero, the only possible remaining * accessors are inside RCU read sections. css_release() schedules the @@ -3548,11 +4175,37 @@ static void css_free_work_fn(struct work_struct *work) container_of(work, struct cgroup_subsys_state, destroy_work); struct cgroup *cgrp = css->cgroup; - if (css->parent) - css_put(css->parent); + if (css->ss) { + /* css free path */ + if (css->parent) + css_put(css->parent); - css->ss->css_free(css); - cgroup_put(cgrp); + css->ss->css_free(css); + cgroup_put(cgrp); + } else { + /* cgroup free path */ + atomic_dec(&cgrp->root->nr_cgrps); + cgroup_pidlist_destroy_all(cgrp); + + if (cgroup_parent(cgrp)) { + /* + * We get a ref to the parent, and put the ref when + * this cgroup is being freed, so it's guaranteed + * that the parent won't be destroyed before its + * children. + */ + cgroup_put(cgroup_parent(cgrp)); + kernfs_put(cgrp->kn); + kfree(cgrp); + } else { + /* + * This is root cgroup's refcnt reaching zero, + * which indicates that the root should be + * released. + */ + cgroup_destroy_root(cgrp->root); + } + } } static void css_free_rcu_fn(struct rcu_head *rcu_head) @@ -3564,26 +4217,59 @@ static void css_free_rcu_fn(struct rcu_head *rcu_head) queue_work(cgroup_destroy_wq, &css->destroy_work); } +static void css_release_work_fn(struct work_struct *work) +{ + struct cgroup_subsys_state *css = + container_of(work, struct cgroup_subsys_state, destroy_work); + struct cgroup_subsys *ss = css->ss; + struct cgroup *cgrp = css->cgroup; + + mutex_lock(&cgroup_mutex); + + css->flags |= CSS_RELEASED; + list_del_rcu(&css->sibling); + + if (ss) { + /* css release path */ + cgroup_idr_remove(&ss->css_idr, css->id); + } else { + /* cgroup release path */ + cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id); + cgrp->id = -1; + } + + mutex_unlock(&cgroup_mutex); + + call_rcu(&css->rcu_head, css_free_rcu_fn); +} + static void css_release(struct percpu_ref *ref) { struct cgroup_subsys_state *css = container_of(ref, struct cgroup_subsys_state, refcnt); - RCU_INIT_POINTER(css->cgroup->subsys[css->ss->id], NULL); - call_rcu(&css->rcu_head, css_free_rcu_fn); + INIT_WORK(&css->destroy_work, css_release_work_fn); + queue_work(cgroup_destroy_wq, &css->destroy_work); } -static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss, - struct cgroup *cgrp) +static void init_and_link_css(struct cgroup_subsys_state *css, + struct cgroup_subsys *ss, struct cgroup *cgrp) { + lockdep_assert_held(&cgroup_mutex); + + cgroup_get(cgrp); + + memset(css, 0, sizeof(*css)); css->cgroup = cgrp; css->ss = ss; - css->flags = 0; + INIT_LIST_HEAD(&css->sibling); + INIT_LIST_HEAD(&css->children); + css->serial_nr = css_serial_nr_next++; - if (cgrp->parent) - css->parent = cgroup_css(cgrp->parent, ss); - else - css->flags |= CSS_ROOT; + if (cgroup_parent(cgrp)) { + css->parent = cgroup_css(cgroup_parent(cgrp), ss); + css_get(css->parent); + } BUG_ON(cgroup_css(cgrp, ss)); } @@ -3594,14 +4280,12 @@ static int online_css(struct cgroup_subsys_state *css) struct cgroup_subsys *ss = css->ss; int ret = 0; - lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); if (ss->css_online) ret = ss->css_online(css); if (!ret) { css->flags |= CSS_ONLINE; - css->cgroup->nr_css++; rcu_assign_pointer(css->cgroup->subsys[ss->id], css); } return ret; @@ -3612,7 +4296,6 @@ static void offline_css(struct cgroup_subsys_state *css) { struct cgroup_subsys *ss = css->ss; - lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); if (!(css->flags & CSS_ONLINE)) @@ -3622,8 +4305,9 @@ static void offline_css(struct cgroup_subsys_state *css) ss->css_offline(css); css->flags &= ~CSS_ONLINE; - css->cgroup->nr_css--; - RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css); + RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL); + + wake_up_all(&css->cgroup->offline_waitq); } /** @@ -3637,111 +4321,102 @@ static void offline_css(struct cgroup_subsys_state *css) */ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) { - struct cgroup *parent = cgrp->parent; + struct cgroup *parent = cgroup_parent(cgrp); + struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss); struct cgroup_subsys_state *css; int err; lockdep_assert_held(&cgroup_mutex); - css = ss->css_alloc(cgroup_css(parent, ss)); + css = ss->css_alloc(parent_css); if (IS_ERR(css)) return PTR_ERR(css); + init_and_link_css(css, ss, cgrp); + err = percpu_ref_init(&css->refcnt, css_release); if (err) goto err_free_css; - init_css(css, ss, cgrp); + err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_NOWAIT); + if (err < 0) + goto err_free_percpu_ref; + css->id = err; err = cgroup_populate_dir(cgrp, 1 << ss->id); if (err) - goto err_free_percpu_ref; + goto err_free_id; + + /* @css is ready to be brought online now, make it visible */ + list_add_tail_rcu(&css->sibling, &parent_css->children); + cgroup_idr_replace(&ss->css_idr, css, css->id); err = online_css(css); if (err) - goto err_clear_dir; - - cgroup_get(cgrp); - css_get(css->parent); - - cgrp->subsys_mask |= 1 << ss->id; + goto err_list_del; 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); + cgroup_parent(parent)) { + pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n", + current->comm, current->pid, ss->name); if (!strcmp(ss->name, "memory")) - pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n"); + pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n"); ss->warned_broken_hierarchy = true; } return 0; -err_clear_dir: +err_list_del: + list_del_rcu(&css->sibling); cgroup_clear_dir(css->cgroup, 1 << css->ss->id); +err_free_id: + cgroup_idr_remove(&ss->css_idr, css->id); err_free_percpu_ref: percpu_ref_cancel_init(&css->refcnt); err_free_css: - ss->css_free(css); + call_rcu(&css->rcu_head, css_free_rcu_fn); return err; } -/** - * cgroup_create - create a cgroup - * @parent: cgroup that will be parent of the new cgroup - * @name: name of the new cgroup - * @mode: mode to set on new cgroup - */ -static long cgroup_create(struct cgroup *parent, const char *name, - umode_t mode) +static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, + umode_t mode) { - struct cgroup *cgrp; - struct cgroup_root *root = parent->root; - int ssid, err; + struct cgroup *parent, *cgrp; + struct cgroup_root *root; struct cgroup_subsys *ss; struct kernfs_node *kn; + int ssid, ret; - /* - * XXX: The default hierarchy isn't fully implemented yet. Block - * !root cgroup creation on it for now. - */ - if (root == &cgrp_dfl_root) - return -EINVAL; + parent = cgroup_kn_lock_live(parent_kn); + if (!parent) + return -ENODEV; + root = parent->root; /* allocate the cgroup and its ID, 0 is reserved for the root */ cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL); - if (!cgrp) - return -ENOMEM; - - mutex_lock(&cgroup_tree_mutex); - - /* - * 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_unlock_tree; + if (!cgrp) { + ret = -ENOMEM; + goto out_unlock; } + ret = percpu_ref_init(&cgrp->self.refcnt, css_release); + if (ret) + goto out_free_cgrp; + /* * Temporarily set the pointer to NULL, so idr_find() won't return * a half-baked cgroup. */ - cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL); + cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_NOWAIT); if (cgrp->id < 0) { - err = -ENOMEM; - goto err_unlock; + ret = -ENOMEM; + goto out_cancel_ref; } init_cgroup_housekeeping(cgrp); - cgrp->parent = parent; - cgrp->dummy_css.parent = &parent->dummy_css; - cgrp->root = parent->root; + cgrp->self.parent = &parent->self; + cgrp->root = root; if (notify_on_release(parent)) set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); @@ -3752,8 +4427,8 @@ static long cgroup_create(struct cgroup *parent, const char *name, /* create the directory */ kn = kernfs_create_dir(parent->kn, name, mode, cgrp); if (IS_ERR(kn)) { - err = PTR_ERR(kn); - goto err_free_id; + ret = PTR_ERR(kn); + goto out_free_id; } cgrp->kn = kn; @@ -3763,10 +4438,10 @@ static long cgroup_create(struct cgroup *parent, const char *name, */ kernfs_get(kn); - cgrp->serial_nr = cgroup_serial_nr_next++; + cgrp->self.serial_nr = css_serial_nr_next++; /* allocation complete, commit to creation */ - list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children); + list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children); atomic_inc(&root->nr_cgrps); cgroup_get(parent); @@ -3774,107 +4449,66 @@ static long cgroup_create(struct cgroup *parent, const char *name, * @cgrp is now fully operational. If something fails after this * point, it'll be released via the normal destruction path. */ - idr_replace(&root->cgroup_idr, cgrp, cgrp->id); + cgroup_idr_replace(&root->cgroup_idr, cgrp, cgrp->id); - err = cgroup_kn_set_ugid(kn); - if (err) - goto err_destroy; + ret = cgroup_kn_set_ugid(kn); + if (ret) + goto out_destroy; - err = cgroup_addrm_files(cgrp, cgroup_base_files, true); - if (err) - goto err_destroy; + ret = cgroup_addrm_files(cgrp, cgroup_base_files, true); + if (ret) + goto out_destroy; /* let's create and online css's */ for_each_subsys(ss, ssid) { - if (root->cgrp.subsys_mask & (1 << ssid)) { - err = create_css(cgrp, ss); - if (err) - goto err_destroy; + if (parent->child_subsys_mask & (1 << ssid)) { + ret = create_css(cgrp, ss); + if (ret) + goto out_destroy; } } - kernfs_activate(kn); + /* + * On the default hierarchy, a child doesn't automatically inherit + * child_subsys_mask from the parent. Each is configured manually. + */ + if (!cgroup_on_dfl(cgrp)) + cgrp->child_subsys_mask = parent->child_subsys_mask; - mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); + kernfs_activate(kn); - return 0; + ret = 0; + goto out_unlock; -err_free_id: - idr_remove(&root->cgroup_idr, cgrp->id); -err_unlock: - mutex_unlock(&cgroup_mutex); -err_unlock_tree: - mutex_unlock(&cgroup_tree_mutex); +out_free_id: + cgroup_idr_remove(&root->cgroup_idr, cgrp->id); +out_cancel_ref: + percpu_ref_cancel_init(&cgrp->self.refcnt); +out_free_cgrp: kfree(cgrp); - return err; +out_unlock: + cgroup_kn_unlock(parent_kn); + return ret; -err_destroy: +out_destroy: cgroup_destroy_locked(cgrp); - mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); - return err; -} - -static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, - umode_t mode) -{ - struct cgroup *parent = parent_kn->priv; - int ret; - - /* - * cgroup_create() grabs cgroup_tree_mutex which nests outside - * kernfs active_ref and cgroup_create() already synchronizes - * properly against removal through cgroup_lock_live_group(). - * Break it before calling cgroup_create(). - */ - cgroup_get(parent); - kernfs_break_active_protection(parent_kn); - - ret = cgroup_create(parent, name, mode); - - kernfs_unbreak_active_protection(parent_kn); - cgroup_put(parent); - return ret; + goto out_unlock; } /* * This is called when the refcnt of a css is confirmed to be killed. - * css_tryget() is now guaranteed to fail. + * css_tryget_online() is now guaranteed to fail. Tell the subsystem to + * initate destruction and put the css ref from kill_css(). */ static void css_killed_work_fn(struct work_struct *work) { struct cgroup_subsys_state *css = container_of(work, struct cgroup_subsys_state, destroy_work); - struct cgroup *cgrp = css->cgroup; - mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_mutex); - - /* - * css_tryget() is guaranteed to fail now. Tell subsystems to - * initate destruction. - */ offline_css(css); - - /* - * If @cgrp is marked dead, it's waiting for refs of all css's to - * be disabled before proceeding to the second phase of cgroup - * destruction. If we are the last one, kick it off. - */ - if (!cgrp->nr_css && cgroup_is_dead(cgrp)) - cgroup_destroy_css_killed(cgrp); - mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); - /* - * Put the css refs from kill_css(). 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. - */ css_put(css); } @@ -3888,9 +4522,18 @@ static void css_killed_ref_fn(struct percpu_ref *ref) queue_work(cgroup_destroy_wq, &css->destroy_work); } -static void __kill_css(struct cgroup_subsys_state *css) +/** + * kill_css - destroy a css + * @css: css to destroy + * + * This function initiates destruction of @css by removing cgroup interface + * files and putting its base reference. ->css_offline() will be invoked + * asynchronously once css_tryget_online() is guaranteed to fail and when + * the reference count reaches zero, @css will be released. + */ +static void kill_css(struct cgroup_subsys_state *css) { - lockdep_assert_held(&cgroup_tree_mutex); + lockdep_assert_held(&cgroup_mutex); /* * This must happen before css is disassociated with its cgroup. @@ -3907,7 +4550,7 @@ static void __kill_css(struct cgroup_subsys_state *css) /* * cgroup core guarantees that, by the time ->css_offline() is * invoked, no new css reference will be given out via - * css_tryget(). We can't simply call percpu_ref_kill() and + * css_tryget_online(). We can't simply call percpu_ref_kill() and * proceed to offlining css's because percpu_ref_kill() doesn't * guarantee that the ref is seen as killed on all CPUs on return. * @@ -3918,36 +4561,14 @@ static void __kill_css(struct cgroup_subsys_state *css) } /** - * kill_css - destroy a css - * @css: css to destroy - * - * This function initiates destruction of @css by removing cgroup interface - * files and putting its base reference. ->css_offline() will be invoked - * asynchronously once css_tryget() is guaranteed to fail and when the - * reference count reaches zero, @css will be released. - */ -static void kill_css(struct cgroup_subsys_state *css) -{ - struct cgroup *cgrp = css->cgroup; - - lockdep_assert_held(&cgroup_tree_mutex); - - /* if already killed, noop */ - if (cgrp->subsys_mask & (1 << css->ss->id)) { - cgrp->subsys_mask &= ~(1 << css->ss->id); - __kill_css(css); - } -} - -/** * cgroup_destroy_locked - the first stage of cgroup destruction * @cgrp: cgroup to be destroyed * * css's make use of percpu refcnts whose killing latency shouldn't be * exposed to userland and are RCU protected. Also, cgroup core needs to - * guarantee that css_tryget() won't succeed by the time ->css_offline() is - * invoked. To satisfy all the requirements, destruction is implemented in - * the following two steps. + * guarantee that css_tryget_online() won't succeed by the time + * ->css_offline() is invoked. To satisfy all the requirements, + * destruction is implemented in the following two steps. * * s1. Verify @cgrp can be destroyed and mark it dying. Remove all * userland visible parts and start killing the percpu refcnts of @@ -3966,12 +4587,10 @@ static void kill_css(struct cgroup_subsys_state *css) static int cgroup_destroy_locked(struct cgroup *cgrp) __releases(&cgroup_mutex) __acquires(&cgroup_mutex) { - struct cgroup *child; struct cgroup_subsys_state *css; bool empty; int ssid; - lockdep_assert_held(&cgroup_tree_mutex); lockdep_assert_held(&cgroup_mutex); /* @@ -3985,127 +4604,68 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) return -EBUSY; /* - * Make sure there's no live children. We can't test ->children - * emptiness as dead children linger on it while being destroyed; - * otherwise, "rmdir parent/child parent" may fail with -EBUSY. + * Make sure there's no live children. We can't test emptiness of + * ->self.children as dead children linger on it while being + * drained; otherwise, "rmdir parent/child parent" may fail. */ - empty = true; - rcu_read_lock(); - list_for_each_entry_rcu(child, &cgrp->children, sibling) { - empty = cgroup_is_dead(child); - if (!empty) - break; - } - rcu_read_unlock(); - if (!empty) + if (css_has_online_children(&cgrp->self)) return -EBUSY; /* * Mark @cgrp dead. This prevents further task migration and child - * creation by disabling cgroup_lock_live_group(). Note that - * CGRP_DEAD assertion is depended upon by css_next_child() to - * resume iteration after dropping RCU read lock. See - * css_next_child() for details. + * creation by disabling cgroup_lock_live_group(). */ - set_bit(CGRP_DEAD, &cgrp->flags); + cgrp->self.flags &= ~CSS_ONLINE; - /* - * Initiate massacre of all css's. cgroup_destroy_css_killed() - * will be invoked to perform the rest of destruction once the - * percpu refs of all css's are confirmed to be killed. This - * involves removing the subsystem's files, drop cgroup_mutex. - */ - mutex_unlock(&cgroup_mutex); + /* initiate massacre of all css's */ for_each_css(css, ssid, cgrp) kill_css(css); - mutex_lock(&cgroup_mutex); - /* CGRP_DEAD is set, remove from ->release_list for the last time */ + /* CSS_ONLINE is clear, remove from ->release_list for the last time */ raw_spin_lock(&release_list_lock); if (!list_empty(&cgrp->release_list)) list_del_init(&cgrp->release_list); raw_spin_unlock(&release_list_lock); /* - * If @cgrp has css's attached, the second stage of cgroup - * destruction is kicked off from css_killed_work_fn() after the - * refs of all attached css's are killed. If @cgrp doesn't have - * any css, we kick it off here. + * Remove @cgrp directory along with the base files. @cgrp has an + * extra ref on its kn. */ - if (!cgrp->nr_css) - cgroup_destroy_css_killed(cgrp); + kernfs_remove(cgrp->kn); - /* remove @cgrp directory along with the base files */ - mutex_unlock(&cgroup_mutex); - - /* - * There are two control paths which try to determine cgroup from - * dentry without going through kernfs - cgroupstats_build() and - * css_tryget_from_dir(). Those are supported by RCU protecting - * clearing of cgrp->kn->priv backpointer, which should happen - * after all files under it have been removed. - */ - kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */ - RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL); + set_bit(CGRP_RELEASABLE, &cgroup_parent(cgrp)->flags); + check_for_release(cgroup_parent(cgrp)); - mutex_lock(&cgroup_mutex); + /* put the base reference */ + percpu_ref_kill(&cgrp->self.refcnt); return 0; }; -/** - * cgroup_destroy_css_killed - the second step of cgroup destruction - * @work: cgroup->destroy_free_work - * - * This function is invoked from a work item for a cgroup which is being - * destroyed after all css's are offlined and performs the rest of - * destruction. This is the second step of destruction described in the - * comment above cgroup_destroy_locked(). - */ -static void cgroup_destroy_css_killed(struct cgroup *cgrp) -{ - struct cgroup *parent = cgrp->parent; - - lockdep_assert_held(&cgroup_tree_mutex); - lockdep_assert_held(&cgroup_mutex); - - /* delete this cgroup from parent->children */ - list_del_rcu(&cgrp->sibling); - - cgroup_put(cgrp); - - set_bit(CGRP_RELEASABLE, &parent->flags); - check_for_release(parent); -} - static int cgroup_rmdir(struct kernfs_node *kn) { - struct cgroup *cgrp = kn->priv; + struct cgroup *cgrp; int ret = 0; - /* - * This is self-destruction but @kn can't be removed while this - * callback is in progress. Let's break active protection. Once - * the protection is broken, @cgrp can be destroyed at any point. - * Pin it so that it stays accessible. - */ - cgroup_get(cgrp); - kernfs_break_active_protection(kn); + cgrp = cgroup_kn_lock_live(kn); + if (!cgrp) + return 0; + cgroup_get(cgrp); /* for @kn->priv clearing */ - mutex_lock(&cgroup_tree_mutex); - mutex_lock(&cgroup_mutex); + ret = cgroup_destroy_locked(cgrp); + + cgroup_kn_unlock(kn); /* - * @cgrp might already have been destroyed while we're trying to - * grab the mutexes. + * There are two control paths which try to determine cgroup from + * dentry without going through kernfs - cgroupstats_build() and + * css_tryget_online_from_dir(). Those are supported by RCU + * protecting clearing of cgrp->kn->priv backpointer, which should + * happen after all files under it have been removed. */ - if (!cgroup_is_dead(cgrp)) - ret = cgroup_destroy_locked(cgrp); - - mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); + if (!ret) + RCU_INIT_POINTER(*(void __rcu __force **)&kn->priv, NULL); - kernfs_unbreak_active_protection(kn); cgroup_put(cgrp); return ret; } @@ -4118,15 +4678,15 @@ static struct kernfs_syscall_ops cgroup_kf_syscall_ops = { .rename = cgroup_rename, }; -static void __init cgroup_init_subsys(struct cgroup_subsys *ss) +static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early) { struct cgroup_subsys_state *css; printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name); - mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_mutex); + idr_init(&ss->css_idr); INIT_LIST_HEAD(&ss->cfts); /* Create the root cgroup state for this subsystem */ @@ -4134,7 +4694,21 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss) css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss)); /* We don't handle early failures gracefully */ BUG_ON(IS_ERR(css)); - init_css(css, ss, &cgrp_dfl_root.cgrp); + init_and_link_css(css, ss, &cgrp_dfl_root.cgrp); + + /* + * Root csses are never destroyed and we can't initialize + * percpu_ref during early init. Disable refcnting. + */ + css->flags |= CSS_NO_REF; + + if (early) { + /* allocation can't be done safely during early init */ + css->id = 1; + } else { + css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL); + BUG_ON(css->id < 0); + } /* Update the init_css_set to contain a subsys * pointer to this state - since the subsystem is @@ -4151,10 +4725,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss) BUG_ON(online_css(css)); - cgrp_dfl_root.cgrp.subsys_mask |= 1 << ss->id; - mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); } /** @@ -4171,6 +4742,8 @@ int __init cgroup_init_early(void) int i; init_cgroup_root(&cgrp_dfl_root, &opts); + cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF; + RCU_INIT_POINTER(init_task.cgroups, &init_css_set); for_each_subsys(ss, i) { @@ -4185,7 +4758,7 @@ int __init cgroup_init_early(void) ss->name = cgroup_subsys_name[i]; if (ss->early_init) - cgroup_init_subsys(ss); + cgroup_init_subsys(ss, true); } return 0; } @@ -4204,7 +4777,6 @@ int __init cgroup_init(void) BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files)); - mutex_lock(&cgroup_tree_mutex); mutex_lock(&cgroup_mutex); /* Add init_css_set to the hash table */ @@ -4214,18 +4786,31 @@ int __init cgroup_init(void) BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0)); mutex_unlock(&cgroup_mutex); - mutex_unlock(&cgroup_tree_mutex); for_each_subsys(ss, ssid) { - if (!ss->early_init) - cgroup_init_subsys(ss); + if (ss->early_init) { + struct cgroup_subsys_state *css = + init_css_set.subsys[ss->id]; + + css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, + GFP_KERNEL); + BUG_ON(css->id < 0); + } else { + cgroup_init_subsys(ss, false); + } + + list_add_tail(&init_css_set.e_cset_node[ssid], + &cgrp_dfl_root.cgrp.e_csets[ssid]); /* - * cftype registration needs kmalloc and can't be done - * during early_init. Register base cftypes separately. + * Setting dfl_root subsys_mask needs to consider the + * disabled flag and cftype registration needs kmalloc, + * both of which aren't available during early_init. */ - if (ss->base_cftypes) + if (!ss->disabled) { + cgrp_dfl_root.subsys_mask |= 1 << ss->id; WARN_ON(cgroup_add_cftypes(ss, ss->base_cftypes)); + } } cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj); @@ -4308,7 +4893,7 @@ int proc_cgroup_show(struct seq_file *m, void *v) seq_printf(m, "%d:", root->hierarchy_id); for_each_subsys(ss, ssid) - if (root->cgrp.subsys_mask & (1 << ssid)) + if (root->subsys_mask & (1 << ssid)) seq_printf(m, "%s%s", count++ ? "," : "", ss->name); if (strlen(root->name)) seq_printf(m, "%sname=%s", count ? "," : "", @@ -4503,8 +5088,8 @@ void cgroup_exit(struct task_struct *tsk) static void check_for_release(struct cgroup *cgrp) { - if (cgroup_is_releasable(cgrp) && - list_empty(&cgrp->cset_links) && list_empty(&cgrp->children)) { + if (cgroup_is_releasable(cgrp) && list_empty(&cgrp->cset_links) && + !css_has_online_children(&cgrp->self)) { /* * Control Group is currently removeable. If it's not * already queued for a userspace notification, queue @@ -4621,7 +5206,7 @@ static int __init cgroup_disable(char *str) __setup("cgroup_disable=", cgroup_disable); /** - * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir + * css_tryget_online_from_dir - get corresponding css from a cgroup dentry * @dentry: directory dentry of interest * @ss: subsystem of interest * @@ -4629,8 +5214,8 @@ __setup("cgroup_disable=", cgroup_disable); * to get the corresponding css and return it. If such css doesn't exist * or can't be pinned, an ERR_PTR value is returned. */ -struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry, - struct cgroup_subsys *ss) +struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, + struct cgroup_subsys *ss) { struct kernfs_node *kn = kernfs_node_from_dentry(dentry); struct cgroup_subsys_state *css = NULL; @@ -4646,13 +5231,13 @@ struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry, /* * This path doesn't originate from kernfs and @kn could already * have been or be removed at any point. @kn->priv is RCU - * protected for this access. See destroy_locked() for details. + * protected for this access. See cgroup_rmdir() for details. */ cgrp = rcu_dereference(kn->priv); if (cgrp) css = cgroup_css(cgrp, ss); - if (!css || !css_tryget(css)) + if (!css || !css_tryget_online(css)) css = ERR_PTR(-ENOENT); rcu_read_unlock(); @@ -4669,14 +5254,8 @@ struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry, */ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss) { - struct cgroup *cgrp; - - cgroup_assert_mutexes_or_rcu_locked(); - - cgrp = idr_find(&ss->root->cgroup_idr, id); - if (cgrp) - return cgroup_css(cgrp, ss); - return NULL; + WARN_ON_ONCE(!rcu_read_lock_held()); + return idr_find(&ss->css_idr, id); } #ifdef CONFIG_CGROUP_DEBUG |