From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by an-out-0708.google.com with SMTP id d17so96764and.105 for ; Fri, 27 Jun 2008 03:13:06 -0700 (PDT) Message-ID: <28c262360806270313o7a22e46cy8a482489cd35332@mail.gmail.com> Date: Fri, 27 Jun 2008 19:13:06 +0900 From: "MinChan Kim" Subject: Re: [-mm][PATCH 8/10] fix shmem page migration incorrectness on memcgroup In-Reply-To: <20080627175201.cbe86a06.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080625190750.D864.KOSAKI.MOTOHIRO@jp.fujitsu.com> <28c262360806262208i6791d67at446f7323ded16206@mail.gmail.com> <20080627142950.7A83.KOSAKI.MOTOHIRO@jp.fujitsu.com> <28c262360806270057w2b2d3e56ob4dde9aacf42327b@mail.gmail.com> <20080627175201.cbe86a06.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org Return-Path: To: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro , LKML , linux-mm , Andrew Morton , Lee Schermerhorn , Rik van Riel , Daisuke Nishimura List-ID: On Fri, Jun 27, 2008 at 5:52 PM, KAMEZAWA Hiroyuki wrote: > On Fri, 27 Jun 2008 16:57:56 +0900 > "MinChan Kim" wrote: > >> On Fri, Jun 27, 2008 at 2:41 PM, KOSAKI Motohiro >> wrote: >> >> > mem_cgroup_uncharge() against old page is done after radix-tree-replacement. >> >> > And there were special handling to ingore swap-cache page. But, shmem can >> >> > be swap-cache and file-cache at the same time. Chekcing PageSwapCache() is >> >> > not correct here. Check PageAnon() instead. >> >> >> >> When/How shmem can be both swap-cache and file-cache ? >> >> I can't understand that situation. >> > >> > Hi >> > >> > see, >> > >> > shmem_writepage() >> > -> add_to_swap_cache() >> > -> SetPageSwapCache() >> > >> > >> > BTW: his file-cache mean !Anon, not mean !SwapBacked. >> >> Hi KOSAKI-san. >> Thanks for explaining. >> >> In the migrate_page_move_mapping, the page was already locked in unmap_and_move. >> Also, we have a lock for that page for calling shmem_writepage. >> >> So I think race problem between shmem_writepage and >> migrate_page_move_mapping don't occur. >> But I am not sure I am right. >> >> If I am wrong, could you tell me when race problem happen ? :) >> > You are right. I misundestood the swap/shmem code. there is no race. > Hmm... > > But situation is a bit complicated. > - shmem's page is charged as file-cache. > - shmem's swap cache is still charged by mem_cgroup_cache_charge() because > it's implicitly (to memcg) converted to swap cache. > - anon's swap cache is charged by mem_cgroup_uncharge_cache_page() > > So, uncharging swap-cache of shmem by mem_cgroup_uncharge_cache_page() is valid. > Checking PageSwapCache() was bad and Cheking PageAnon() is good. > (From maintainance view) I agree. I also thought your patch is no problem. It is just description problem. > I think the patch is valid but my patch description contains wrong information. > Andrew, could you drop this ? I'll rewrite the patch description. > > Sorry, > -Kame > > -- Kinds regards, MinChan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org