From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f173.google.com (mail-qk0-f173.google.com [209.85.220.173]) by kanga.kvack.org (Postfix) with ESMTP id D119B6B0255 for ; Mon, 10 Aug 2015 05:21:58 -0400 (EDT) Received: by qkbm65 with SMTP id m65so56004025qkb.2 for ; Mon, 10 Aug 2015 02:21:58 -0700 (PDT) Received: from tyo201.gate.nec.co.jp (TYO201.gate.nec.co.jp. [210.143.35.51]) by mx.google.com with ESMTPS id h184si5985712qhc.21.2015.08.10.02.21.57 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 10 Aug 2015 02:21:58 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case Date: Mon, 10 Aug 2015 09:20:20 +0000 Message-ID: <20150810092020.GB28025@hori1.linux.bs1.fc.nec.co.jp> References: <1439188351-24292-1-git-send-email-wanpeng.li@hotmail.com> <20150810083529.GB21282@hori1.linux.bs1.fc.nec.co.jp> In-Reply-To: Content-Language: ja-JP Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <5A7E6C0848CAAB46B5D541334679DB88@gisp.nec.co.jp> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Wanpeng Li Cc: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" 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 !=3D 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 !=3D 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. = :) >=20 > How about something like this: >=20 > +void put_hwpoison_page(struct page *page) > +{ > + struct page *head =3D compound_head(page); > + > + if (PageHuge(head)) > + goto put_out; > + > + if (PageTransHuge(head)) > + if (page !=3D 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(). 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