[Devel] [PATCH v13 10/12] ve/cgroup: private per-cgroup-root data container

[Kirill Tkhai]

On 20.04.2020 15:13, Valeriy Vdovin wrote:
> As long as each ve is internally attached to a particular
> css_set via it's init_task, it's good to have container with parameters,
> which are common to each cgroup subsystem hierarchy, rooting from it's
> virtual root.
> 
> Signed-off-by: Valeriy Vdovin <valeriy.vdovin at virtuozzo.com>
> ---
>  include/linux/ve.h |  7 +++++
>  kernel/ve/ve.c     | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 84 insertions(+)
> 
> diff --git a/include/linux/ve.h b/include/linux/ve.h
> index 787a96f..94a07df 100644
> --- a/include/linux/ve.h
> +++ b/include/linux/ve.h
> @@ -137,6 +137,13 @@ struct ve_struct {
>  	struct work_struct	release_agent_work;
>  
>  	/*
> +	 * List of data, private for each root cgroup in
> +	 * ve's css_set.
> +	 */
> +	struct list_head	per_cgroot_list;
> +	struct raw_spinlock	per_cgroot_list_lock;
>
> +	/*
>  	 * All tasks, that belong to this ve, live
>  	 * in cgroups, that are children to cgroups
>  	 * that form this css_set.
> diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
> index eb266ae..a30343f 100644
> --- a/kernel/ve/ve.c
> +++ b/kernel/ve/ve.c
> @@ -45,6 +45,14 @@
>  #include <linux/vziptable_defs.h>
>  #include <net/rtnetlink.h>
>  
> +struct per_cgroot_data {
> +	struct list_head list;
> +	/*
> +	 * data is related to this cgroup
> +	 */
> +	struct cgroup *cgroot;
> +};
> +
>  extern struct kmapset_set sysfs_ve_perms_set;
>  
>  static struct kmem_cache *ve_cachep;
> @@ -92,6 +100,9 @@ struct ve_struct ve0 = {
>  	.release_list		= LIST_HEAD_INIT(ve0.release_list),
>  	.release_agent_work	= __WORK_INITIALIZER(ve0.release_agent_work,
>  					cgroup_release_agent),
> +	.per_cgroot_list	= LIST_HEAD_INIT(ve0.per_cgroot_list),
> +	.per_cgroot_list_lock	= __RAW_SPIN_LOCK_UNLOCKED(
> +					ve0.per_cgroot_list_lock),
>  };
>  EXPORT_SYMBOL(ve0);
>  
> @@ -118,6 +129,52 @@ void put_ve(struct ve_struct *ve)
>  }
>  EXPORT_SYMBOL(put_ve);
>  
> +static struct per_cgroot_data *per_cgroot_data_find_locked(
> +	struct list_head *per_cgroot_list, struct cgroup *cgroot)
> +{
> +	struct per_cgroot_data *data;
> +
> +	list_for_each_entry(data, per_cgroot_list, list) {
> +		if (data->cgroot == cgroot)
> +			return data;
> +	}
> +	return NULL;
> +}
> +
> +static inline struct per_cgroot_data *per_cgroot_get_or_create(
> +	struct ve_struct *ve, struct cgroup *cgroot)
> +{
> +	struct per_cgroot_data *data, *other_data;
> +
> +	raw_spin_lock(&ve->per_cgroot_list_lock);
> +	data = per_cgroot_data_find_locked(&ve->per_cgroot_list,
> +		cgroot);
> +	raw_spin_unlock(&ve->per_cgroot_list_lock);
> +
> +	if (data)
> +		return data;
> +
> +	data = kzalloc(sizeof(struct per_cgroot_data), GFP_KERNEL);
> +	if (!data)
> +		return ERR_PTR(-ENOMEM);
> +
> +	raw_spin_lock(&ve->per_cgroot_list_lock);
> +	other_data = per_cgroot_data_find_locked(&ve->per_cgroot_list,
> +		cgroot);
> +
> +	if (other_data) {
> +		raw_spin_unlock(&ve->per_cgroot_list_lock);
> +		kfree(data);
> +		return other_data;
> +	}
> +
> +	data->cgroot = cgroot;
> +	list_add(&data->list, &ve->per_cgroot_list);
> +
> +	raw_spin_unlock(&ve->per_cgroot_list_lock);
> +	return data;
> +}
> +
>  struct cgroup_subsys_state *ve_get_init_css(struct ve_struct *ve, int subsys_id)
>  {
>  	struct cgroup_subsys_state *css, *tmp;
> @@ -612,6 +669,22 @@ err_list:
>  	return err;
>  }
>  
> +static void per_cgroot_free_all_locked(struct list_head *per_cgroot_list)
> +{
> +	struct per_cgroot_data *data, *saved;
> +	list_for_each_entry_safe(data, saved, per_cgroot_list, list) {
> +		list_del_init(&data->list);
> +		kfree(data);
> +	}
> +}
> +
> +static void ve_per_cgroot_free(struct ve_struct *ve)
> +{
> +	raw_spin_lock(&ve->per_cgroot_list_lock);
> +	per_cgroot_free_all_locked(&ve->per_cgroot_list);
> +	raw_spin_unlock(&ve->per_cgroot_list_lock);
> +}
> +
>  void ve_stop_ns(struct pid_namespace *pid_ns)
>  {
>  	struct ve_struct *ve = current->task_ve;
> @@ -662,6 +735,8 @@ void ve_exit_ns(struct pid_namespace *pid_ns)
>  
>  	ve_workqueue_stop(ve);
>  
> +	ve_per_cgroot_free(ve);
> +
>  	/*
>  	 * At this point all userspace tasks in container are dead.
>  	 */
> @@ -735,6 +810,7 @@ static struct cgroup_subsys_state *ve_create(struct cgroup *cg)
>  
>  	INIT_WORK(&ve->release_agent_work, cgroup_release_agent);
>  	raw_spin_lock_init(&ve->release_list_lock);
> +	raw_spin_lock_init(&ve->per_cgroot_list_lock);
>  
>  	ve->_randomize_va_space = ve0._randomize_va_space;
>  
> @@ -771,6 +847,7 @@ do_init:
>  	INIT_LIST_HEAD(&ve->ve_list);
>  	INIT_LIST_HEAD(&ve->devmnt_list);
>  	INIT_LIST_HEAD(&ve->release_list);
> +	INIT_LIST_HEAD(&ve->per_cgroot_list);
>  	mutex_init(&ve->devmnt_mutex);
>  
>  #ifdef CONFIG_AIO
> 

What is this all for? Do you introduce per-cgroup-root data instead of cgroup::release_agent
to save memory (avoid distribution release agent pointer to every cgroup)?