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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 BA311C352A4 for ; Sun, 9 Feb 2020 13:50:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9003F20715 for ; Sun, 9 Feb 2020 13:50:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EMbIWCTn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727752AbgBINu2 (ORCPT ); Sun, 9 Feb 2020 08:50:28 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:39824 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727631AbgBINu2 (ORCPT ); Sun, 9 Feb 2020 08:50:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581256227; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Udi2H1EwM2qQoiqz9yVbyKVFlwCemua0aBE5Wupm5+Q=; b=EMbIWCTnk9zCyYSb/iZhY7FEfxT3spkdKRggd2JFyBgqU2Cy/Ylsgq0WQxKO4BkmGrYxTz AtM4C0YxIbjzaQlNTVvYPRfoaacGg6LOoRQXvAm1vjZLOIK9Fl+L7slQMw4G/TYh6OYSiE bzzWZ3v/F7ip1FJ0V7IZaJxhWRXYv+E= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-219-AHWhzolrOT27cMUr1QaVmg-1; Sun, 09 Feb 2020 08:50:23 -0500 X-MC-Unique: AHWhzolrOT27cMUr1QaVmg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CFB3F18B6382; Sun, 9 Feb 2020 13:50:21 +0000 (UTC) Received: from localhost (ovpn-12-31.pek2.redhat.com [10.72.12.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9444187B0A; Sun, 9 Feb 2020 13:50:18 +0000 (UTC) Date: Sun, 9 Feb 2020 21:50:15 +0800 From: Baoquan He To: Wei Yang Cc: Dan Williams , Wei Yang , Andrew Morton , Oscar Salvador , Linux MM , Linux Kernel Mailing List , David Hildenbrand Subject: Re: [PATCH 2/3] mm/sparsemem: get physical address to page struct instead of virtual address to pfn Message-ID: <20200209135015.GX8965@MiWiFi-R3L-srv> References: <20200206231629.14151-1-richardw.yang@linux.intel.com> <20200206231629.14151-3-richardw.yang@linux.intel.com> <20200207112632.5inklkwyiewhrd75@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200207112632.5inklkwyiewhrd75@master> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/07/20 at 11:26am, Wei Yang wrote: > On Thu, Feb 06, 2020 at 06:19:46PM -0800, Dan Williams wrote: > >On Thu, Feb 6, 2020 at 3:17 PM Wei Yang wrote: > >> > >> memmap should be the physical address to page struct instead of virtual > >> address to pfn. > >> > >> Since we call this only for SPARSEMEM_VMEMMAP, pfn_to_page() is valid at > >> this point. > >> > >> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") > >> Signed-off-by: Wei Yang > >> CC: Dan Williams > >> --- > >> mm/sparse.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/mm/sparse.c b/mm/sparse.c > >> index b5da121bdd6e..56816f653588 100644 > >> --- a/mm/sparse.c > >> +++ b/mm/sparse.c > >> @@ -888,7 +888,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, > >> /* Align memmap to section boundary in the subsection case */ > >> if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && > >> section_nr_to_pfn(section_nr) != start_pfn) > >> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr)); > >> + memmap = pfn_to_page(section_nr_to_pfn(section_nr)); > > > >Yes, this looks obviously correct. This might be tripping up > >makedumpfile. Do you see any practical effects of this bug? The kernel > >mostly avoids ->section_mem_map in the vmemmap case and in the > >!vmemmap case section_nr_to_pfn(section_nr) should always equal > >start_pfn. > > I took another look into the code. Looks there is no practical effect after > this. Because in the vmemmap case, we don't need ->section_mem_map to retrieve > the real memmap. > > But leave a inconsistent data in section_mem_map is not a good practice. Yeah, it does has no pratical effect. I tried to create sub-section alighed namespace, then trigger crash, makedumpfile isn't impacted. Because pmem memory is only added, but not onlined. We don't report it to kdump, makedumpfile will ignore it. I think it's worth fixing it to encode a correct memmap address. We don't know if in the future this will break anything. Thanks Baoquan