[Devel] [PATCH RH8 v2 2/4] kernel/ve: simplify ve_get_init_css

[Kirill Tkhai]

On 09.07.2021 02:23, Andrey Zhadchenko wrote:
> Reuse css_local_root to ascend to marked css.
> 
> https://jira.sw.ru/browse/PSBM-131253
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
> ---
>  kernel/ve/ve.c | 16 +++-------------
>  1 file changed, 3 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
> index 9667f90..0f42971 100644
> --- a/kernel/ve/ve.c
> +++ b/kernel/ve/ve.c
> @@ -392,8 +392,7 @@ const char *ve_get_release_agent_path(struct ve_struct *ve,
>  
>  struct cgroup_subsys_state *ve_get_init_css(struct ve_struct *ve, int subsys_id)
>  {
> -	struct cgroup_subsys_state *css, *tmp;
> -	struct cgroup *cgroup;
> +	struct cgroup_subsys_state *css;
>  	struct css_set *root_cset;
>  	struct nsproxy *nsproxy;
>  
> @@ -403,18 +402,9 @@ struct cgroup_subsys_state *ve_get_init_css(struct ve_struct *ve, int subsys_id)
>  	root_cset = nsproxy->cgroup_ns->root_cset;
>  	css = root_cset->subsys[subsys_id];
>  	/* nsproxy->cgroup_ns must hold root_cset refcnt */
> -	BUG_ON(!css_tryget(css));
> -
> -	cgroup = css->cgroup;
> -	while (!test_bit(CGRP_VE_ROOT, &cgroup->flags) && cgroup_parent(cgroup))
> -		cgroup = cgroup_parent(cgroup);
>  
> -	if (cgroup != css->cgroup) {
> -		tmp = cgroup->subsys[subsys_id];
> -		css_get(tmp);
> -		css_put(css);
> -		css = tmp;
> -	}
> +	css = css_local_root(css);
> +	BUG_ON(!css_tryget(css));
>  
>  	rcu_read_unlock();
>  	return css;

Looks OK. Since child is definitely alive (BUG_ON() even says this),
parent is also alive. So, we may simplify this.

Reviewed-by: Kirill Tkhai <ktkhai at virtuozzo.com>