Re: [PATCH] page_cgroup: add helper function to get swap_cgroup

[Michal Hocko <mhocko@suse.cz>]

On Fri 02-12-11 17:42:11, Bob Liu wrote:
> There are multi places need to get swap_cgroup, so add a helper
> function:
> static struct swap_cgroup *swap_cgroup_getsc(swp_entry_t ent);
> to simple the code.

I like the cleanup but I guess we can do a little bit better ;)

[...]
> +static struct swap_cgroup *swap_cgroup_getsc(swp_entry_t ent)

Add struct swap_cgroup_ctrl ** ctrl parameter

> +{
> +	int type = swp_type(ent);
> +	unsigned long offset = swp_offset(ent);
> +	unsigned long idx = offset / SC_PER_PAGE;
> +	unsigned long pos = offset & SC_POS_MASK;
> +	struct swap_cgroup_ctrl *ctrl;
> +	struct page *mappage;
> +	struct swap_cgroup *sc;
> +
> +	ctrl = &swap_cgroup_ctrl[type];

	if (ctrl)
		*ctrl = &swap_cgroup_ctrl[type]

[...]
> @@ -375,20 +393,14 @@ unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
>  					unsigned short old, unsigned short new)
>  {
>  	int type = swp_type(ent);
> -	unsigned long offset = swp_offset(ent);
> -	unsigned long idx = offset / SC_PER_PAGE;
> -	unsigned long pos = offset & SC_POS_MASK;
>  	struct swap_cgroup_ctrl *ctrl;
> -	struct page *mappage;
>  	struct swap_cgroup *sc;
>  	unsigned long flags;
>  	unsigned short retval;
>  
>  	ctrl = &swap_cgroup_ctrl[type];
> +	sc = swap_cgroup_getsc(ent);

	sc = swap_cgroup_getsc(ent, &ctrl);
[...]
> @@ -410,20 +422,14 @@ unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
>  unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
>  {
>  	int type = swp_type(ent);
> -	unsigned long offset = swp_offset(ent);
> -	unsigned long idx = offset / SC_PER_PAGE;
> -	unsigned long pos = offset & SC_POS_MASK;
>  	struct swap_cgroup_ctrl *ctrl;
> -	struct page *mappage;
>  	struct swap_cgroup *sc;
>  	unsigned short old;
>  	unsigned long flags;
>  
>  	ctrl = &swap_cgroup_ctrl[type];
> +	sc = swap_cgroup_getsc(ent);

Same here

[...]
> @@ -440,21 +446,10 @@ unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
>   */
>  unsigned short lookup_swap_cgroup(swp_entry_t ent)
>  {
> -	int type = swp_type(ent);
> -	unsigned long offset = swp_offset(ent);
> -	unsigned long idx = offset / SC_PER_PAGE;
> -	unsigned long pos = offset & SC_POS_MASK;
> -	struct swap_cgroup_ctrl *ctrl;
> -	struct page *mappage;
>  	struct swap_cgroup *sc;
> -	unsigned short ret;
>  
> -	ctrl = &swap_cgroup_ctrl[type];
> -	mappage = ctrl->map[idx];
> -	sc = page_address(mappage);
> -	sc += pos;
> -	ret = sc->id;
> -	return ret;
> +	sc = swap_cgroup_getsc(ent);
> +	return sc->id;

	return swap_cgroup_getsc(ent, NULL)->id;

What do you think?
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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