Re: [RFC][PATCH 1/4] cgroup: support per cgroup subsys state ID (CSS ID)

[Li Zefan <lizf@cn.fujitsu.com>]

>  static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
>  {
>  	struct inode *inode = new_inode(sb);
> @@ -2335,6 +2339,7 @@ static void init_cgroup_css(struct cgrou
>  	css->cgroup = cgrp;
>  	atomic_set(&css->refcnt, 1);
>  	css->flags = 0;
> +	css->id = NULL;
>  	if (cgrp == dummytop)
>  		set_bit(CSS_ROOT, &css->flags);
>  	BUG_ON(cgrp->subsys[ss->subsys_id]);
> @@ -2410,6 +2415,10 @@ static long cgroup_create(struct cgroup 
>  			goto err_destroy;
>  		}
>  		init_cgroup_css(css, ss, cgrp);
> +		if (ss->use_id)
> +			if (alloc_css_id(ss, parent, cgrp))
> +				goto err_destroy;
> +		/* At error, ->destroy() callback has to free assigned ID. */

A bug here:

if alloc_css_id(ss, parent, cgrp) failed, then ss->destroy() called free_css_id(),
then panic.

maybe check if (css->id == NULL) in free_css_id() ?

>  	}
>  
>  	cgroup_lock_hierarchy(root);
> @@ -2699,6 +2708,8 @@ int __init cgroup_init(void)
>  		struct cgroup_subsys *ss = subsys[i];
>  		if (!ss->early_init)
>  			cgroup_init_subsys(ss);
> +		if (ss->use_id)
> +			cgroup_subsys_init_idr(ss);
>  	}
>  
>  	/* Add init_css_set to the hash table */
> @@ -3231,3 +3242,260 @@ static int __init cgroup_disable(char *s
>  	return 1;
>  }
>  __setup("cgroup_disable=", cgroup_disable);