linux-kernel - Re: [PATCH 4/12] memcg make page->mapping NULL before calling uncharge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 26 Sep 2008 15:17:48 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"xemul@...nvz.org" <xemul@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Hansen <haveblue@...ibm.com>, ryov@...inux.co.jp
Subject: Re: [PATCH 4/12] memcg make page->mapping NULL before calling uncharge

KAMEZAWA Hiroyuki wrote:
> This patch tries to make page->mapping to be NULL before
> mem_cgroup_uncharge_cache_page() is called.
> 
> "page->mapping == NULL" is a good check for "whether the page is still
> radix-tree or not".
> This patch also adds BUG_ON() to mem_cgroup_uncharge_cache_page();
> 
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Looks good, small nit-pick below

>  #endif
>  	ClearPagePrivate(page);
>  	set_page_private(page, 0);
> -	page->mapping = NULL;
> +	/* page->mapping contains a flag for PageAnon() */
> +	if (PageAnon(page)) {
> +		/* This page is uncharged at try_to_unmap(). */
> +		page->mapping = NULL;
> +	} else {
> +		/* Obsolete file cache should be uncharged */
> +		page->mapping = NULL;
> +		mem_cgroup_uncharge_cache_page(page);
> +	}
> 

Isn't it better and correct coding style to do

	/*
	 * Uncharge obsolete file cache
	 */
	if (!PageAnon(page))
		mem_cgroup_uncharge_cache_page(page);
	/* else - uncharged at try_to_unmap() */
	page->mapping = NULL;


-- 
	Balbir
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/