[Devel] [PATCH rh7 v3 2/2] ve/fs/sync: fix CT's mountpoints traversal

[Vladimir Davydov]

On Thu, Feb 25, 2016 at 07:19:38PM +0300, Andrey Ryabinin wrote:
...
> @@ -2673,7 +2676,10 @@ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
>  		struct mount *mnt = real_mount(m);
>  		mnt->mnt_ns = new_ns;
>  		new_ns->root = mnt;
> +		down_write(&namespace_sem);
>  		list_add(&mnt->mnt_list, &new_ns->list);
> +		list_add(&new_ns->mntns_list, &get_exec_env()->mntns_list);

Do we really need to link such mnt_ns?

> +		up_write(&namespace_sem);
>  	} else {
>  		mntput(m);
>  	}
> @@ -2954,6 +2960,7 @@ void put_mnt_ns(struct mnt_namespace *ns)
>  	namespace_lock();
>  	br_write_lock(&vfsmount_lock);
>  	umount_tree(ns->root, 0);
> +	list_del(&ns->mntns_list);

Why under br_write_lock? namespace_lock should be enough.

>  	br_write_unlock(&vfsmount_lock);
>  	namespace_unlock();
>  	free_mnt_ns(ns);
...
> @@ -80,6 +80,7 @@ struct ve_struct ve0 = {
>  	.sched_lat_ve.cur	= &ve0_lat_stats,
>  	.init_cred		= &init_cred,
>  	.mnt_nr			= 0,
> +	.mntns_list		= LIST_HEAD_INIT(ve0.mntns_list),

It is initialized in ve_create below. Why is it not enough?

>  };
>  EXPORT_SYMBOL(ve0);
>  
> @@ -652,6 +653,7 @@ do_init:
>  	INIT_LIST_HEAD(&ve->devices);
>  	INIT_LIST_HEAD(&ve->ve_list);
>  	INIT_LIST_HEAD(&ve->devmnt_list);
> +	INIT_LIST_HEAD(&ve->mntns_list);
>  	mutex_init(&ve->devmnt_mutex);
>  	kmapset_init_key(&ve->ve_sysfs_perms);
>  
> @@ -706,6 +708,8 @@ static void ve_destroy(struct cgroup *cg)
>  	kmapset_unlink(&ve->ve_sysfs_perms, &ve_sysfs_perms);
>  	free_ve_devmnts(ve);
>  
> +	WARN_ON(!list_empty(&ve->mntns_list));
> +
>  	ve_log_destroy(ve);
>  #if IS_ENABLED(CONFIG_BINFMT_MISC)
>  	kfree(ve->binfmt_misc);