Re: [RFC 3/6] mm: support madvise(MADV_FREE)

[Kirill A. Shutemov]

On Fri, Mar 14, 2014 at 03:37:47PM +0900, Minchan Kim wrote:
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index c1b7414c7bef..9b048cabce27 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -933,10 +933,16 @@ void page_address_init(void);
>   * Please note that, confusingly, "page_mapping" refers to the inode
>   * address_space which maps the page from disk; whereas "page_mapped"
>   * refers to user virtual address space into which the page is mapped.
> + *
> + * PAGE_MAPPING_LZFREE bit is set along with PAGE_MAPPING_ANON bit
> + * and then page->mapping points to an anon_vma. This flag is used
> + * for lazy freeing the page instead of swap.
>   */
>  #define PAGE_MAPPING_ANON	1
>  #define PAGE_MAPPING_KSM	2
> -#define PAGE_MAPPING_FLAGS	(PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
> +#define PAGE_MAPPING_LZFREE	4
> +#define PAGE_MAPPING_FLAGS	(PAGE_MAPPING_ANON | PAGE_MAPPING_KSM | \
> +				 PAGE_MAPPING_LZFREE)

Is it safe to use third bit in pointer everywhere?

-- 
 Kirill A. Shutemov
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