linux-kernel - Re: [PATCH 5/9] mmzone: add pgdat_{end_pfn,is

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Date:	Fri, 1 Feb 2013 16:23:59 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Cody P Schafer <cody@...ux.vnet.ibm.com>
Cc:	Linux MM <linux-mm@...ck.org>,
	David Hansen <dave@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Cody P Schafer <jmesmon@...il.com>
Subject: Re: [PATCH 5/9] mmzone: add pgdat_{end_pfn,is_empty}() helpers &
 consolidate.

On Thu, 17 Jan 2013 14:52:57 -0800
Cody P Schafer <cody@...ux.vnet.ibm.com> wrote:

> From: Cody P Schafer <jmesmon@...il.com>
> 
> Add pgdat_end_pfn() and pgdat_is_empty() helpers which match the similar
> zone_*() functions.
> 
> Change node_end_pfn() to be a wrapper of pgdat_end_pfn().
> 
> ...
>
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -772,11 +772,17 @@ typedef struct pglist_data {
>  #define nid_page_nr(nid, pagenr) 	pgdat_page_nr(NODE_DATA(nid),(pagenr))
>  
>  #define node_start_pfn(nid)	(NODE_DATA(nid)->node_start_pfn)
> +#define node_end_pfn(nid) pgdat_end_pfn(NODE_DATA(nid))

I wonder if these could be implemented in nice C code rather than nasty
cpp code.

> -#define node_end_pfn(nid) ({\
> -	pg_data_t *__pgdat = NODE_DATA(nid);\
> -	__pgdat->node_start_pfn + __pgdat->node_spanned_pages;\
> -})
> +static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)
> +{
> +	return pgdat->node_start_pfn + pgdat->node_spanned_pages;
> +}

It wouldn't hurt to add a little comment pointing out that this returns
"end pfn plus one", or similar.  ie, it is exclusive, not inclusive. 
Ditto the "zone_*() functions", if needed.

> +static inline bool pgdat_is_empty(pg_data_t *pgdat)
> +{
> +	return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
> +}

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