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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 B42A9C33CB1 for ; Fri, 17 Jan 2020 06:20:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 729072072B for ; Fri, 17 Jan 2020 06:20:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="YvXQjdwC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 729072072B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 14E0C6B031B; Fri, 17 Jan 2020 01:20:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 126C26B031C; Fri, 17 Jan 2020 01:20:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 063166B031D; Fri, 17 Jan 2020 01:20:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0102.hostedemail.com [216.40.44.102]) by kanga.kvack.org (Postfix) with ESMTP id E204E6B031B for ; Fri, 17 Jan 2020 01:20:29 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id A86F933C4 for ; Fri, 17 Jan 2020 06:20:29 +0000 (UTC) X-FDA: 76386126978.09.paint85_446e78ff513f X-HE-Tag: paint85_446e78ff513f X-Filterd-Recvd-Size: 4565 Received: from mail-io1-f67.google.com (mail-io1-f67.google.com [209.85.166.67]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Fri, 17 Jan 2020 06:20:29 +0000 (UTC) Received: by mail-io1-f67.google.com with SMTP id z193so24783812iof.1 for ; Thu, 16 Jan 2020 22:20:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sQWiLTE2DvXDXh9g6uQSeddAz6FsHc5UfztEn88LPo8=; b=YvXQjdwCH/CiaIheF8sV0fCvQuZ3pg1pESnfw9J/g5zJEaA/Bzq790dVANG+9EtB0l X2+VxwVpBRkTi7hJz9RkaV6OQk8pio1U7MSj79RaK0lvyHq3CCzxI4qxIcndOAW97lG4 Xbb1bXx6d6/pciwaGfj+SCYRics2/b+lz9cwV1EGQdVVlz58yTdPz9ezVtfU1QshHblK v71qNlszYAj+BowZ3uqTIJn/782jbLmFDPaC8w64zlJwCtvPLfW9HZyESK01Q1lr70yQ gjXLSSC/mRFx2CL0elpV71+WUI2LBov/0O5D8ZB25SesbWeF4DxZl3jq/MPwMZu2R4mp VVfA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sQWiLTE2DvXDXh9g6uQSeddAz6FsHc5UfztEn88LPo8=; b=oLZ95Em8w8pvtzQ5V8dRO8tL3M5G2Qb4YfrCm1vWaEaIuU/stUwMxzPf92ua2pbKyt uEFsXRG5tZhjXca27LhWBBgtEg4rw/LF9PH6d0y7VJkCARLWy5kj1STcA5US+2KDTmvf 7g9z81NsUqxC5YZlybexoAgwE3vCUWaX0WX4lgNDB8umTZZ7Nuq+O7GEIEMMEQil5H0d CdWs3owUx8MK0i9AfolApdnjeovwskLIZjVvdhIvJWvT5RZjBvyqGZf09LjX+q8xHgWn gVUyMUOd1kbVGXHOYz68Ponnte9Lz/ajiO/zNB+3gQhVFyoXdY/z2VMVwY5AR1kLpo+m rZIw== X-Gm-Message-State: APjAAAWilTHHuTaL3bLW3tjAlwGXOgT28lWuxzf5rDpxTz1lae/qiPEY 0M55qYB7Vltt9Zxk9NXx3iq4W06lAHXku56HJg== X-Google-Smtp-Source: APXvYqxM9ebn9rRNIE6/F7ya6utOSblLaOkfUBOLv4AbaQSaavkDJBfBLVPEhfeJ/yqOLLhxcKnSszLkBsIVF1Q7yBk= X-Received: by 2002:a5d:9d4d:: with SMTP id k13mr27266285iok.15.1579242028627; Thu, 16 Jan 2020 22:20:28 -0800 (PST) MIME-Version: 1.0 References: <1579143668-27941-1-git-send-email-kernelfans@gmail.com> <97ab281f-d038-d40c-648a-e0085a906dcf@redhat.com> <6cfd834a-72cc-656a-3954-40b37db5a66f@redhat.com> <20200116082451.GC26758@MiWiFi-R3L-srv> In-Reply-To: <20200116082451.GC26758@MiWiFi-R3L-srv> From: Pingfan Liu Date: Fri, 17 Jan 2020 14:20:17 +0800 Message-ID: Subject: Re: [PATCH] mm/sparse: reset section's mem_map when fully deactivated To: Baoquan He Cc: David Hildenbrand , Linux-MM , Andrew Morton , Dan Williams , Oscar Salvador , Michal Hocko , kexec@lists.infradead.org, Kazuhito Hagio Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.065123, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 16, 2020 at 4:25 PM Baoquan He wrote: > > On 01/16/20 at 09:14am, David Hildenbrand wrote: > > On 16.01.20 09:06, David Hildenbrand wrote: > > > On 16.01.20 04:01, Pingfan Liu wrote: > > >> When fully deactivated, it is meaningless to keep the value of a section's > > >> mem_map. And its mem_map will be reassigned during re-added. > > >> > > >> Beside this, it breaks the user space tool "makedumpfile", which makes > > >> assumption that a hot-removed section having mem_map as NULL. > > >> > > >> The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" , > > >> trigger a crash, and save vmcore by makedumpfile > > > > > > Are you using an up-to-date makedumfile and did kdump.service properly > > > get reloaded on the udev events? I remember that this works. > > > > > > makedumpfile will not dump memory sections that a) are not marked > > > offline (SECTION_IS_ONLINE) - after offlining b) are not part of an > > > iomem resource - after memory unplug. > > Makedumpfile seems to only check SECTION_MARKED_PRESENT. Then the NULL > memmap will fail vmcore dumping, I guess. makedumpfile.c / validate_mem_section() has some trick, so it will not fail. > > > > > > > > > > The current code makes sure that sparse_decode_mem_map() will return NULL. > > > > > > > ... but it's only used at this very place. I think we should add a > > Fixes: tag, although this might be fixed as well in makedumpfile (so > > people are aware that patch broke something) > > Agree, it's worth fixing it too in makedumpfile side to enhance. > Yeah, I also agree :)