Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754689AbbHJJZV (ORCPT ); Mon, 10 Aug 2015 05:25:21 -0400 Received: from blu004-omc1s24.hotmail.com ([65.55.116.35]:64112 "EHLO BLU004-OMC1S24.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753421AbbHJJZU (ORCPT ); Mon, 10 Aug 2015 05:25:20 -0400 X-TMN: [fStPEnwypW9IHGiN92sYkBjOifFccvuM] X-Originating-Email: [wanpeng.li@hotmail.com] Message-ID: Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case To: Naoya Horiguchi References: <1439188351-24292-1-git-send-email-wanpeng.li@hotmail.com> <20150810083529.GB21282@hori1.linux.bs1.fc.nec.co.jp> <20150810092020.GB28025@hori1.linux.bs1.fc.nec.co.jp> CC: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" From: Wanpeng Li Date: Mon, 10 Aug 2015 17:24:36 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 MIME-Version: 1.0 In-Reply-To: <20150810092020.GB28025@hori1.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 10 Aug 2015 09:25:18.0334 (UTC) FILETIME=[78EB49E0:01D0D34E] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2226 Lines: 73 On 8/10/15 5:20 PM, Naoya Horiguchi wrote: > On Mon, Aug 10, 2015 at 05:06:25PM +0800, Wanpeng Li wrote: > ... >>>>> diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c >>>>> index 5015679..c343a45 100644 >>>>> --- a/mm/hwpoison-inject.c >>>>> +++ b/mm/hwpoison-inject.c >>>>> @@ -56,6 +56,8 @@ inject: >>>>> return memory_failure(pfn, 18, MF_COUNT_INCREASED); >>>>> put_out: >>>>> put_page(p); >>>>> + if (p != hpage) >>>>> + put_page(hpage); >>>> Yes, we need this when we inject to a thp tail page and "goto put_out" >>>> is >>>> called. But it seems that this code can be called also when injecting >>>> error >>>> to a hugetlb tail page and hwpoison_filter() returns non-zero, which is >>>> not >>>> expected. Unfortunately simply doing like below >>>> >>>> + if (!PageHuge(p) && p != hpage) >>>> + put_page(hpage); >>>> >>>> doesn't work, because exisiting put_page(p) can release refcount of >>>> hugetlb >>>> tail page, while get_hwpoison_page() takes refcount of hugetlb head >>>> page. >>>> >>>> So I feel that we need put_hwpoison_page() to properly release the >>>> refcount >>>> taken by memory error handlers. >>> Good point. I think I will continue to do it and will post it out soon. :) >> How about something like this: >> >> +void put_hwpoison_page(struct page *page) >> +{ >> + struct page *head = compound_head(page); >> + >> + if (PageHuge(head)) >> + goto put_out; >> + >> + if (PageTransHuge(head)) >> + if (page != head) >> + put_page(head); >> + >> +put_out: >> + put_page(page); >> + return; >> +} >> + > Looks good. > >> Any comments are welcome, I can update the patch by myself. :) > Most of callsites of put_page() in memory_failure(), soft_offline_page(), > and unpoison_page() can be replaced with put_hwpoison_page(). Cool, thanks for your pointing out. I will do it soon. :) Regards, Wanpeng Li > > Thanks, > Naoya Horiguchi -- 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/