From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f179.google.com (mail-ob0-f179.google.com [209.85.214.179]) by kanga.kvack.org (Postfix) with ESMTP id 8C9826B0255 for ; Mon, 10 Aug 2015 05:25:20 -0400 (EDT) Received: by obbop1 with SMTP id op1so119729550obb.2 for ; Mon, 10 Aug 2015 02:25:20 -0700 (PDT) Received: from BLU004-OMC1S24.hotmail.com (blu004-omc1s24.hotmail.com. [65.55.116.35]) by mx.google.com with ESMTPS id k7si13934810oes.103.2015.08.10.02.25.19 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 10 Aug 2015 02:25:20 -0700 (PDT) Message-ID: Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case 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> From: Wanpeng Li Date: Mon, 10 Aug 2015 17:24:36 +0800 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 Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" 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, 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