From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id 41C1C6B0253 for ; Mon, 10 Aug 2015 04:59:27 -0400 (EDT) Received: by pacgr6 with SMTP id gr6so22677621pac.2 for ; Mon, 10 Aug 2015 01:59:27 -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 gc5si32006332pbd.186.2015.08.10.01.59.25 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 10 Aug 2015 01:59:26 -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 08:58:38 +0000 Message-ID: <20150810085837.GA28025@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: <78BFF436DADF6D419A22B400E83FBB24@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 04:54:39PM +0800, Wanpeng Li wrote: > On 8/10/15 4:35 PM, Naoya Horiguchi wrote: > >On Mon, Aug 10, 2015 at 02:32:31PM +0800, Wanpeng Li wrote: > >>Hwpoison injection takes a refcount of target page and another refcount > >>of head page of THP if the target page is the tail page of a THP. Howev= er, > >>current code doesn't release the refcount of head page if the THP is no= t > >>supported to be injected wrt hwpoison filter. > >> > >>Fix it by reducing the refcount of head page if the target page is the = tail > >>page of a THP and it is not supported to be injected. > >> > >>Signed-off-by: Wanpeng Li > >>--- > >> mm/hwpoison-inject.c | 2 ++ > >> 1 files changed, 2 insertions(+), 0 deletions(-) > >> > >>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" i= s > >called. But it seems that this code can be called also when injecting er= ror > >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 huge= tlb > >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 refco= unt > >taken by memory error handlers. >=20 > Good point. I think I will continue to do it and will post it out soon. := ) Great, thank you :) Naoya= -- 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