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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 93ADDC43441 for ; Tue, 13 Nov 2018 13:04:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 62D72223CB for ; Tue, 13 Nov 2018 13:04:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 62D72223CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733276AbeKMXCi (ORCPT ); Tue, 13 Nov 2018 18:02:38 -0500 Received: from mx2.suse.de ([195.135.220.15]:58044 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1733149AbeKMXCi (ORCPT ); Tue, 13 Nov 2018 18:02:38 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 17F2DB0F8; Tue, 13 Nov 2018 13:04:34 +0000 (UTC) Date: Tue, 13 Nov 2018 14:04:33 +0100 From: Michal Hocko To: Yongkai Wu Cc: mike.kravetz@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/hugetl.c: keep the page mapping info when free_huge_page() hit the VM_BUG_ON_PAGE Message-ID: <20181113130433.GB16182@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 13-11-18 20:38:16, Yongkai Wu wrote: > It is better to keep page mapping info when free_huge_page() hit the > VM_BUG_ON_PAGE, > so we can get more infomation from the coredump for further analysis. The patch seems to be whitespace damaged. Put that aside, have you actually seen a case where preservning the page state would help to nail down any bug. I am not objecting to the patch, it actually makes some sense to me, I am just curious about a background motivation. > Signed-off-by: Yongkai Wu > --- > mm/hugetlb.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index c007fb5..ba693bb 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1248,10 +1248,11 @@ void free_huge_page(struct page *page) > (struct hugepage_subpool *)page_private(page); > bool restore_reserve; > > + VM_BUG_ON_PAGE(page_count(page), page); > + VM_BUG_ON_PAGE(page_mapcount(page), page); > + > set_page_private(page, 0); > page->mapping = NULL; > - VM_BUG_ON_PAGE(page_count(page), page); > - VM_BUG_ON_PAGE(page_mapcount(page), page); > restore_reserve = PagePrivate(page); > ClearPagePrivate(page); > > -- > 1.8.3.1 -- Michal Hocko SUSE Labs