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 0C8F7C33CB1 for ; Fri, 17 Jan 2020 09:49:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C1ACF20730 for ; Fri, 17 Jan 2020 09:49:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="VP/IqiZb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C1ACF20730 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 630A76B034A; Fri, 17 Jan 2020 04:49:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5E22C6B034B; Fri, 17 Jan 2020 04:49:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4A8F96B034C; Fri, 17 Jan 2020 04:49:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0041.hostedemail.com [216.40.44.41]) by kanga.kvack.org (Postfix) with ESMTP id 32DAC6B034A for ; Fri, 17 Jan 2020 04:49:51 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id D68F5181AC9B6 for ; Fri, 17 Jan 2020 09:49:50 +0000 (UTC) X-FDA: 76386654540.22.push71_55ed8f881ed11 X-HE-Tag: push71_55ed8f881ed11 X-Filterd-Recvd-Size: 4370 Received: from mail-io1-f65.google.com (mail-io1-f65.google.com [209.85.166.65]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Fri, 17 Jan 2020 09:49:50 +0000 (UTC) Received: by mail-io1-f65.google.com with SMTP id x1so25289471iop.7 for ; Fri, 17 Jan 2020 01:49:50 -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=m/iZn/9BSQqGd5e2yeTJ7gLwUn2LDa69ozHI95trysQ=; b=VP/IqiZbaCttiLBOghjGul8sqaQROlZhSqsHV6evcPJ1Qd56nXV5mKY4wAqRzkZUcZ xPxoggJUFq68LEHgcg2qWS84+8wdtNUuMPnNWte71tcs2jxapLOpsPuXP1tVrN0xe5SL 5mBcqCvZBf7vjGHHJpc4AWBrh23UFxs66T8ppsotn/LpQ+XBZBAiChFZQ68q/ImXP2xh fT7Sk8COj+fv9iT7whzDIwrbQm32sxKiJF9Sm5Ep3xg4av1MCTMZdAFZzXUOJTnlLS/R yu76ndm+e34CVYsLI7UQHK/epa0Snr66xOrkn+sImRa4A0csMNYPNIh19clnLCqO9GRQ mf9A== 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=m/iZn/9BSQqGd5e2yeTJ7gLwUn2LDa69ozHI95trysQ=; b=TL86PXkjVUbz20jUlAAcfW24gOMWbnKok8HGT/9/3qY+r2wgOBiN2nDBys5jsRCwKw dyKJLUp4a1T4EEvixNqtaCMo4oH20mFRWadaM6nyYge+O67kMGBKqqkDNL78jWTzJFTw X6YR3kB3PE/+dBNbdQC2ZoWIxRNYCipve+IWG5cNWveI6KRsn3xTQTn62QwueSqK6+5y AEWUHheuvefOMVC2729CYl45mKRkrb3QCEmfT+xeq38fFTQiWAU1XeV+4nbaGmZ3WAcx SHx6bogobtcKYxXBmlVIZPwIs0e7IuCWV0PZffBIdE7sYCB1/Sho0WWb82jM7UTmgBv6 CA2g== X-Gm-Message-State: APjAAAV2quPYqiIWdfDFWejBoIPSsHZDUS+gr1tlyJ9be03Riy5CKHMW BmVJjK5B7Er2DXgTaZfBbI4UU/dXqyUmqcu1iA== X-Google-Smtp-Source: APXvYqzQmAWw5bbh8bzvzgn4lRJGoXpwUQyoQO7yEDZzAyBu9XPyrTuO9JIG2Z3uBh79Tj4kj3mqumbnFCOxo4p4tlI= X-Received: by 2002:a5e:c244:: with SMTP id w4mr26067771iop.161.1579254589678; Fri, 17 Jan 2020 01:49:49 -0800 (PST) MIME-Version: 1.0 References: <1579143668-27941-1-git-send-email-kernelfans@gmail.com> <20200116075000.GM19428@dhcp22.suse.cz> <20200117074746.GF19428@dhcp22.suse.cz> In-Reply-To: <20200117074746.GF19428@dhcp22.suse.cz> From: Pingfan Liu Date: Fri, 17 Jan 2020 17:49:38 +0800 Message-ID: Subject: Re: [PATCH] mm/sparse: reset section's mem_map when fully deactivated To: Michal Hocko Cc: Dan Williams , Linux-MM , Andrew Morton , David Hildenbrand , Oscar Salvador , Kexec Mailing List , Kazuhito Hagio Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.007028, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jan 17, 2020 at 3:47 PM Michal Hocko wrote: > > On Thu 16-01-20 23:14:02, Dan Williams wrote: > > On Thu, Jan 16, 2020 at 10:23 PM Pingfan Liu wrote: > > > > > > On Thu, Jan 16, 2020 at 3:50 PM Michal Hocko wrote: > > > > > > > > On Thu 16-01-20 11:01:08, 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. > > > > > > > > We used to do that before ba72b4c8cf60 ("mm/sparsemem: support > > > > sub-section hotplug"). Dan was this an intentional change? > > > I do not know the purpose of this. But the change just leave section > > > start pfn in fully deactivated section_mem_map, and not used any more. > > > > Not intentional, IIRC at the time I had convinced myself that the > > value would always be translated by sparse_decode_mem_map(), so I > > thought it could be hiding NULL de-references. I don't see any harm > > in the patch. > > Thanks for the confirmation. It would be great to have this in the > changelog. Should I post V2 with this commit log? Thanks, Pingfan