Re: [RFC 6/6] Swapless V1: Revise main migration logic

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Mon, 3 Apr 2006 23:58:10 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:

> New migration scheme
> 
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
> 
> Index: linux-2.6.17-rc1/mm/migrate.c
> ===================================================================
> --- linux-2.6.17-rc1.orig/mm/migrate.c	2006-04-03 23:44:31.000000000 -0700
> +++ linux-2.6.17-rc1/mm/migrate.c	2006-04-03 23:48:02.000000000 -0700
> @@ -151,27 +151,21 @@ int migrate_page_remove_references(struc
>  	 * indicates that the page is in use or truncate has removed
>  	 * the page.
>  	 */
> -	if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
> -		return -EAGAIN;
> +	if (!page->mapping ||
> +		page_mapcount(page) + nr_refs + !!mapping != page_count(page))
> +			return -EAGAIN;
>  
I think this hidden !!mapping refcnt is not easy to read.

How about modifying caller istead of callee ?

in migrate_page()
==
if (page->mapping) 
	rc = migrate_page_remove_reference(newpage, page, 2)
else
	rc = migrate_page_remove_reference(newpage, page, 1);
==

If you dislike this 'if', plz do as you like.

Thanks,
--Kame


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