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=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 ADE3DC33CAF for ; Thu, 16 Jan 2020 03:18:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 718B3222C3 for ; Thu, 16 Jan 2020 03:18:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="P1GmzIqD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 718B3222C3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 06A588E002D; Wed, 15 Jan 2020 22:18:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 01ACD8E0026; Wed, 15 Jan 2020 22:18:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E9A6F8E002D; Wed, 15 Jan 2020 22:18:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0099.hostedemail.com [216.40.44.99]) by kanga.kvack.org (Postfix) with ESMTP id D185E8E0026 for ; Wed, 15 Jan 2020 22:18:04 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 83C3D180AD815 for ; Thu, 16 Jan 2020 03:18:04 +0000 (UTC) X-FDA: 76382038488.30.alarm38_638c996d04754 X-HE-Tag: alarm38_638c996d04754 X-Filterd-Recvd-Size: 4940 Received: from mail-qk1-f193.google.com (mail-qk1-f193.google.com [209.85.222.193]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Thu, 16 Jan 2020 03:18:03 +0000 (UTC) Received: by mail-qk1-f193.google.com with SMTP id x1so17832359qkl.12 for ; Wed, 15 Jan 2020 19:18:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=IEKlpc0uHkxg7ftyD2BWL9CXaM9Q/Pz80DDkjKwvweo=; b=P1GmzIqD8b1H52UsZBO6vLhfyQKw+5XhCQbyXBUP4lyrqOCdDn7gXUexGFXO1hPbIk ExvfzVLMduOxLvBgW5ThlxPceHlOVWxJWiyiGzL9yHi8U4SEEPaXhwp23CEkPMz9dUhd fZJzIEqr5Cwu7hWygq+yqwuBQpct1iENDjInmuhSOSDKdvU+u4pN1/D5K9tfuqc/vtFg JKI9sXpRp68dsjmttJkG0rJ3JHZvi5zHf/+Pr15LrnnP7cvCBBzMINzqykIOZeVusKlR kgJ35OUPIM2rZl57p1BQNGAi/B18+C1CkDZLyWBqsNbmV7cYg/uBXiVtNF0YqoQ1ZfKi QAew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=IEKlpc0uHkxg7ftyD2BWL9CXaM9Q/Pz80DDkjKwvweo=; b=D5cdfu4ccVxUygoF4ui8LKTVw8mxATi5ak5KcVJ9KWow10BK0mRCqrciNocbsVEU+4 ShXZKQj/SxPMpHzNr+JjUQUcFcLNIaCjp3He8QGijaf+fzAkrfE2Sj22RZJIGleSe7rE uiRn7nFITwvHh7Q9ZrbCwho8O05YXwvZPigjCYeIpOe3FWBMrFTOS7YKzxSFpA8HpxlN 29r9PtflGuSNq623/yp8rNp9X7kTHHTBF6KTEP3junNL0zJhJcDKnJVGDSVGk780RUWz mYzTHmElxMCT9bzZMmKREPAAX2eR7GU2Q2IPRwBGiIgG2k8I6+GIAQMj7h4lxfRS6pnW r87w== X-Gm-Message-State: APjAAAX8TfChBI/1CeSX7o9kMVQDftfpLWkYi0uCzNvj7UusA9/K8KEF fDFuTu0wAN0oiO5AT93zfA/TsQ== X-Google-Smtp-Source: APXvYqxEnOvPFqZnGHvzL6aowMsEqAo82LUHWuX7Ai9OEhP3xCOYIxAfgsg1apL6OGGjt7eetKxwYw== X-Received: by 2002:ae9:e714:: with SMTP id m20mr30779300qka.403.1579144683349; Wed, 15 Jan 2020 19:18:03 -0800 (PST) Received: from [192.168.1.153] (pool-71-184-117-43.bstnma.fios.verizon.net. [71.184.117.43]) by smtp.gmail.com with ESMTPSA id h1sm10724866qte.42.2020.01.15.19.18.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 15 Jan 2020 19:18:02 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3608.40.2.2.4\)) Subject: Re: [PATCH] mm/sparse: reset section's mem_map when fully deactivated From: Qian Cai In-Reply-To: <1579143668-27941-1-git-send-email-kernelfans@gmail.com> Date: Wed, 15 Jan 2020 22:18:01 -0500 Cc: Linux-MM , Andrew Morton , David Hildenbrand , Dan Williams , Oscar Salvador , Michal Hocko , kexec@lists.infradead.org, Kazuhito Hagio Content-Transfer-Encoding: quoted-printable Message-Id: References: <1579143668-27941-1-git-send-email-kernelfans@gmail.com> To: Pingfan Liu X-Mailer: Apple Mail (2.3608.40.2.2.4) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > On Jan 15, 2020, at 10:01 PM, Pingfan Liu = wrote: >=20 > 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. >=20 > Beside this, it breaks the user space tool "makedumpfile", which makes > assumption that a hot-removed section having mem_map as NULL. Well, tools like makedumpfile and the crash utility always has to copy = with low kernel implementation details changes like this. Why is it different = this time? >=20 > The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" , > trigger a crash, and save vmcore by makedumpfile >=20 > Signed-off-by: Pingfan Liu > To: linux-mm@kvack.org > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Dan Williams > Cc: Oscar Salvador > Cc: Michal Hocko > Cc: kexec@lists.infradead.org > Cc: Kazuhito Hagio > --- > mm/sparse.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/mm/sparse.c b/mm/sparse.c > index 3822ecb..fddac80 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -789,7 +789,7 @@ static void section_deactivate(unsigned long pfn, = unsigned long nr_pages, > ms->usage =3D NULL; > } > memmap =3D sparse_decode_mem_map(ms->section_mem_map, = section_nr); > - ms->section_mem_map =3D sparse_encode_mem_map(NULL, = section_nr); > + ms->section_mem_map =3D NULL; > } >=20 > if (section_is_early && memmap) > --=20 > 2.7.5 >=20 >=20