[Devel] [PATCH RHEL v22 13/14] ve/cgroup: cleanup per_cgroot_data at cgroup mount destruction

[Kirill Tkhai]

On 31.07.2020 15:54, Valeriy Vdovin wrote:
> Implemented function 've_cleanup_per_cgroot_data' that is called in two
> resource release cases.
> 
> 1. At container stop procedure, container' init process goes through
> exit process routines, and calls ve_exit_ns. ve_exit_ns knows about
> ve from it's agrument it and can call ve_cleanup_per_cgroot_data with
> ve argument.
> 2. At destruction of cgroup mount point, 'cgroup_drop_root' will be called
> from cgroup's unmount implementation code. Also same code will be executed
> during cgroup_mount function when error happens and cleanup is needed.
> In both cases cgroup_drop_root will call 've_cleanup_per_cgroot_data'.
> All those codepaths will know cgroup and pass it as an argument.
> 
> 've_cleaup_per_cgroot_data' releases per-cgroup-root resources stored in ve
> It expects any of two arguments (ve or cgroup) to be non-NULL to derive
> type of cleanup, that is needed. If cgroup is NULL, it cleans up values
> for all cgroup roots that it possesses.
> If cgroup is non-NULL it only cleans out values for this particular
> cgroup.
> 
> Signed-off-by: Valeriy Vdovin <valeriy.vdovin at virtuozzo.com>

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

> ---
>  include/linux/ve.h |  2 ++
>  kernel/cgroup.c    |  1 +
>  kernel/ve/ve.c     | 30 +++++++++++++++++++++---------
>  3 files changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/ve.h b/include/linux/ve.h
> index 5bf275f..2dcd7bb 100644
> --- a/include/linux/ve.h
> +++ b/include/linux/ve.h
> @@ -220,6 +220,8 @@ int ve_set_release_agent_path(struct cgroup *cgroot,
>  
>  const char *ve_get_release_agent_path(struct cgroup *cgrp_root);
>  
> +void ve_cleanup_per_cgroot_data(struct ve_struct *ve, struct cgroup *cgrp);
> +
>  extern struct ve_struct *get_ve(struct ve_struct *ve);
>  extern void put_ve(struct ve_struct *ve);
>  
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 989f73e..3305032 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1591,6 +1591,7 @@ static void cgroup_drop_root(struct cgroupfs_root *root)
>  {
>  	if (!root)
>  		return;
> +	ve_cleanup_per_cgroot_data(NULL, &root->top_cgroup);
>  
>  	BUG_ON(!root->hierarchy_id);
>  	spin_lock(&hierarchy_id_lock);
> diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
> index 8d78270..db26cbd4 100644
> --- a/kernel/ve/ve.c
> +++ b/kernel/ve/ve.c
> @@ -745,21 +745,33 @@ err_list:
>  	return err;
>  }
>  
> -static void ve_per_cgroot_free(struct ve_struct *ve)
> +static inline void per_cgroot_data_free(struct per_cgroot_data *data)
> +{
> +	struct cgroup_rcu_string *release_agent = data->release_agent_path;
> +
> +	RCU_INIT_POINTER(data->release_agent_path, NULL);
> +	if (release_agent)
> +		kfree_rcu(release_agent, rcu_head);
> +	kfree(data);
> +}
> +
> +void ve_cleanup_per_cgroot_data(struct ve_struct *ve, struct cgroup *cgrp)
>  {
>  	struct per_cgroot_data *data, *saved;
> -	struct cgroup_rcu_string *release_agent;
>  
> +	BUG_ON(!ve && !cgrp);
> +	rcu_read_lock();
> +	if (!ve)
> +		ve = cgroup_get_ve_owner(cgrp);
>  	raw_spin_lock(&ve->per_cgroot_list_lock);
>  	list_for_each_entry_safe(data, saved, &ve->per_cgroot_list, list) {
> -		release_agent = data->release_agent_path;
> -		RCU_INIT_POINTER(data->release_agent_path, NULL);
> -		if (release_agent)
> -			kfree_rcu(release_agent, rcu_head);
> -		list_del_init(&data->list);
> -		kfree(data);
> +		if (!cgrp || data->cgroot == cgrp) {
> +			list_del_init(&data->list);
> +			per_cgroot_data_free(data);
> +		}
>  	}
>  	raw_spin_unlock(&ve->per_cgroot_list_lock);
> +	rcu_read_unlock();
>  }
>  
>  void ve_stop_ns(struct pid_namespace *pid_ns)
> @@ -812,7 +824,7 @@ void ve_exit_ns(struct pid_namespace *pid_ns)
>  
>  	ve_workqueue_stop(ve);
>  
> -	ve_per_cgroot_free(ve);
> +	ve_cleanup_per_cgroot_data(ve, NULL);
>  
>  	/*
>  	 * At this point all userspace tasks in container are dead.
>