Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755367AbYKDJFc (ORCPT ); Tue, 4 Nov 2008 04:05:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755258AbYKDJFK (ORCPT ); Tue, 4 Nov 2008 04:05:10 -0500 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:38926 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755246AbYKDJFG (ORCPT ); Tue, 4 Nov 2008 04:05:06 -0500 Date: Tue, 4 Nov 2008 18:04:29 +0900 From: KAMEZAWA Hiroyuki To: Daisuke Nishimura Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "balbir@linux.vnet.ibm.com" , hugh@veritas.com, taka@valinux.co.jp Subject: Re: [RFC][PATCH 2/5] memcg : handle swap cache Message-Id: <20081104180429.4e47875e.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20081104174201.9e2dc44c.nishimura@mxp.nes.nec.co.jp> References: <20081031115057.6da3dafd.kamezawa.hiroyu@jp.fujitsu.com> <20081031115411.25478878.kamezawa.hiroyu@jp.fujitsu.com> <20081104174201.9e2dc44c.nishimura@mxp.nes.nec.co.jp> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1585 Lines: 46 On Tue, 4 Nov 2008 17:42:01 +0900 Daisuke Nishimura wrote: > > +#ifdef CONFIG_SWAP > > +int mem_cgroup_cache_charge_swapin(struct page *page, > > + struct mm_struct *mm, gfp_t mask) > > +{ > > + int ret = 0; > > + > > + if (mem_cgroup_subsys.disabled) > > + return 0; > > + if (unlikely(!mm)) > > + mm = &init_mm; > > + > > + ret = mem_cgroup_charge_common(page, mm, mask, > > + MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL); > > + /* > > + * The page may be dropped from SwapCache because we don't have > > + * lock_page().This may cause charge-after-uncharge trouble. > > + * Fix it up here. (the caller have refcnt to this page and > > + * page itself is guaranteed not to be freed.) > > + */ > > + if (ret && !PageSwapCache(page)) > > + mem_cgroup_uncharge_swapcache(page); > > + > Hmm.. after [5/5], mem_cgroup_cache_charge_swapin has 'locked' parameter, > calls lock_page(if !locked), and checks PageSwapCache under page lock. > > Why not doing it in this patch? > My intention is to guard swap_cgroup by lock_page() against SwapCache. In Mem+Swap controller. we get "memcg" from information in page->private. I think we need lock_page(), there. But here, we don't refer page->private information. I think we don't need lock_page() because there is no inofrmation we depends on. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/