From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6485C432C0 for ; Wed, 20 Nov 2019 00:46:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 89B732245F for ; Wed, 20 Nov 2019 00:46:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727428AbfKTAqb (ORCPT ); Tue, 19 Nov 2019 19:46:31 -0500 Received: from mga07.intel.com ([134.134.136.100]:37641 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727222AbfKTAqb (ORCPT ); Tue, 19 Nov 2019 19:46:31 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Nov 2019 16:46:30 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,220,1571727600"; d="scan'208";a="237537741" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 19 Nov 2019 16:46:29 -0800 Date: Wed, 20 Nov 2019 08:46:20 +0800 From: Wei Yang To: David Hildenbrand Cc: Wei Yang , n-horiguchi@ah.jp.nec.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/memory-failure.c: PageHuge is handled at the beginning of memory_failure Message-ID: <20191120004620.GB11061@richard> Reply-To: Wei Yang References: <20191118082003.26240-1-richardw.yang@linux.intel.com> <1e61c115-5787-9ef4-a449-2e490c53fca7@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1e61c115-5787-9ef4-a449-2e490c53fca7@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 19, 2019 at 01:23:54PM +0100, David Hildenbrand wrote: >On 18.11.19 09:20, Wei Yang wrote: >> PageHuge is handled by memory_failure_hugetlb(), so this case could be >> removed. >> >> Signed-off-by: Wei Yang >> --- >> mm/memory-failure.c | 5 +---- >> 1 file changed, 1 insertion(+), 4 deletions(-) >> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index 3151c87dff73..392ac277b17d 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -1359,10 +1359,7 @@ int memory_failure(unsigned long pfn, int flags) >> * page_remove_rmap() in try_to_unmap_one(). So to determine page status >> * correctly, we save a copy of the page flags at this time. >> */ >> - if (PageHuge(p)) >> - page_flags = hpage->flags; >> - else >> - page_flags = p->flags; >> + page_flags = p->flags; >> /* >> * unpoison always clear PG_hwpoison inside page lock >> > >I somewhat miss a proper explanation why this is safe to do. We access page >flags here, so why is it safe to refer to the ones of the sub-page? > Hi, David I think your comment is on this line: page_flags = p->flags; Maybe we need to use this: page_flags = hpage->flags; And use hpage in the following or even the whole function? While one thing interesting is not all "compound page" is PageCompound. For some sub-page, we can't get the correct head. This means we may just check on the sub-page. >-- > >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me