diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 146 |
1 files changed, 80 insertions, 66 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index cb5864e36f99..c01e8e8dfad0 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -176,10 +176,12 @@ static int need_forkexit_callback __read_mostly; static struct cftype cgroup_base_files[]; static void cgroup_put(struct cgroup *cgrp); +static bool cgroup_has_live_children(struct cgroup *cgrp); static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask); static int cgroup_destroy_locked(struct cgroup *cgrp); static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss); +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); @@ -1008,62 +1010,15 @@ static umode_t cgroup_file_mode(const struct cftype *cft) return mode; } -static void cgroup_free_fn(struct work_struct *work) -{ - struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work); - - atomic_dec(&cgrp->root->nr_cgrps); - cgroup_pidlist_destroy_all(cgrp); - - if (cgrp->parent) { - /* - * We get a ref to the parent, and put the ref when this - * cgroup is being freed, so it's guaranteed that the - * parent won't be destroyed before its children. - */ - cgroup_put(cgrp->parent); - kernfs_put(cgrp->kn); - kfree(cgrp); - } else { - /* - * This is root cgroup's refcnt reaching zero, which - * indicates that the root should be released. - */ - cgroup_destroy_root(cgrp->root); - } -} - -static void cgroup_free_rcu(struct rcu_head *head) -{ - struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head); - - INIT_WORK(&cgrp->destroy_work, cgroup_free_fn); - queue_work(cgroup_destroy_wq, &cgrp->destroy_work); -} - static void cgroup_get(struct cgroup *cgrp) { WARN_ON_ONCE(cgroup_is_dead(cgrp)); - WARN_ON_ONCE(atomic_read(&cgrp->refcnt) <= 0); - atomic_inc(&cgrp->refcnt); + css_get(&cgrp->self); } static void cgroup_put(struct cgroup *cgrp) { - if (!atomic_dec_and_test(&cgrp->refcnt)) - return; - if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp))) - return; - - /* delete this cgroup from parent->children */ - mutex_lock(&cgroup_mutex); - list_del_rcu(&cgrp->sibling); - mutex_unlock(&cgroup_mutex); - - cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id); - cgrp->id = -1; - - call_rcu(&cgrp->rcu_head, cgroup_free_rcu); + css_put(&cgrp->self); } /** @@ -1548,7 +1503,6 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp) struct cgroup_subsys *ss; int ssid; - atomic_set(&cgrp->refcnt, 1); INIT_LIST_HEAD(&cgrp->sibling); INIT_LIST_HEAD(&cgrp->children); INIT_LIST_HEAD(&cgrp->cset_links); @@ -1597,6 +1551,10 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask) 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 @@ -1605,11 +1563,11 @@ static int cgroup_setup_root(struct cgroup_root *root, unsigned int 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, @@ -1657,6 +1615,8 @@ 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; @@ -1735,13 +1695,14 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, } /* - * 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. + * A root's lifetime is governed by its root cgroup. + * tryget_live failure indicate that the root is being + * destroyed. Wait for destruction to complete so that the + * subsystems are free. We can use wait_queue for the wait + * but this path is super cold. Let's just sleep for a bit + * and retry. */ - if (!atomic_inc_not_zero(&root->cgrp.refcnt)) { + if (!percpu_ref_tryget_live(&root->cgrp.self.refcnt)) { mutex_unlock(&cgroup_mutex); msleep(10); ret = restart_syscall(); @@ -1794,7 +1755,16 @@ 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. + */ + if (cgroup_has_live_children(&root->cgrp)) + cgroup_put(&root->cgrp); + else + percpu_ref_kill(&root->cgrp.self.refcnt); + kernfs_kill_sb(sb); } @@ -4110,11 +4080,37 @@ 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 (cgrp->parent) { + /* + * We get a ref to the parent, and put the ref when + * this cgroup is being freed, so it's guaranteed + * that the parent won't be destroyed before its + * children. + */ + cgroup_put(cgrp->parent); + kernfs_put(cgrp->kn); + kfree(cgrp); + } else { + /* + * This is root cgroup's refcnt reaching zero, + * which indicates that the root should be + * released. + */ + cgroup_destroy_root(cgrp->root); + } + } } static void css_free_rcu_fn(struct rcu_head *rcu_head) @@ -4131,8 +4127,20 @@ 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; - cgroup_idr_remove(&ss->css_idr, css->id); + if (ss) { + /* css release path */ + cgroup_idr_remove(&ss->css_idr, css->id); + } else { + /* cgroup release path */ + mutex_lock(&cgroup_mutex); + list_del_rcu(&cgrp->sibling); + mutex_unlock(&cgroup_mutex); + + cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id); + cgrp->id = -1; + } call_rcu(&css->rcu_head, css_free_rcu_fn); } @@ -4285,6 +4293,10 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, 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. @@ -4292,7 +4304,7 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_NOWAIT); if (cgrp->id < 0) { ret = -ENOMEM; - goto out_free_cgrp; + goto out_cancel_ref; } init_cgroup_housekeeping(cgrp); @@ -4365,6 +4377,8 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, 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); out_unlock: @@ -4521,7 +4535,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) check_for_release(cgrp->parent); /* put the base reference */ - cgroup_put(cgrp); + percpu_ref_kill(&cgrp->self.refcnt); return 0; }; |