summaryrefslogtreecommitdiff
path: root/kernel/cgroup.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c146
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;
};
generated by cgit (git 2.34.1) at 2024-06-02 23:49:59 +0000