linux-kernel - Re: [PATCH 1/2] mm: introduce page reference manipulation functions

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Date:	Mon, 9 Nov 2015 16:53:37 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Joonsoo Kim <js1304@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Nazarewicz <mina86@...a86.com>,
	Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>,
	Vlastimil Babka <vbabka@...e.cz>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org, Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 1/2] mm: introduce page reference manipulation functions

Hi,

On (11/09/15 16:23), Joonsoo Kim wrote:
[..]
> +static inline int page_count(struct page *page)
> +{
> +	return atomic_read(&compound_head(page)->_count);
> +}
> +
> +static inline void set_page_count(struct page *page, int v)
> +{
> +	atomic_set(&page->_count, v);
> +}
> +
> +/*
> + * Setup the page count before being freed into the page allocator for
> + * the first time (boot or memory hotplug)
> + */
> +static inline void init_page_count(struct page *page)
> +{
> +	set_page_count(page, 1);
> +}
> +
> +static inline void page_ref_add(struct page *page, int nr)
> +{
> +	atomic_add(nr, &page->_count);
> +}

Since page_ref_FOO wrappers operate with page->_count and there
are already page_count()/set_page_count()/etc. may be name new
wrappers in page_count_FOO() manner?


> +static inline void page_ref_sub(struct page *page, int nr)

for example, page_count_sub(), etc.

	-ss

> +{
> +	atomic_sub(nr, &page->_count);
> +}
> +
> +static inline void page_ref_inc(struct page *page)
> +{
> +	atomic_inc(&page->_count);
> +}
> +
> +static inline void page_ref_dec(struct page *page)
> +{
> +	atomic_dec(&page->_count);
> +}
> +
> +static inline int page_ref_sub_and_test(struct page *page, int nr)
> +{
> +	return atomic_sub_and_test(nr, &page->_count);
> +}
> +
> +static inline int page_ref_dec_and_test(struct page *page)
> +{
> +	return atomic_dec_and_test(&page->_count);
> +}
> +
> +static inline int page_ref_dec_return(struct page *page)
> +{
> +	return atomic_dec_return(&page->_count);
> +}
> +
> +static inline int page_ref_add_unless(struct page *page, int nr, int u)
> +{
> +	return atomic_add_unless(&page->_count, nr, u);
> +}
> +
> +static inline int page_ref_freeze(struct page *page, int count)
> +{
> +	return likely(atomic_cmpxchg(&page->_count, count, 0) == count);
> +}
> +
> +static inline void page_ref_unfreeze(struct page *page, int count)
> +{
> +	VM_BUG_ON_PAGE(page_count(page) != 0, page);
> +	VM_BUG_ON(count == 0);
> +
> +	atomic_set(&page->_count, count);
> +}
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