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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 7DF86C10F0B for ; Tue, 26 Feb 2019 20:10:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4861921850 for ; Tue, 26 Feb 2019 20:10:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="szj5Pezo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729041AbfBZUKm (ORCPT ); Tue, 26 Feb 2019 15:10:42 -0500 Received: from mail-qt1-f196.google.com ([209.85.160.196]:38558 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727196AbfBZUKm (ORCPT ); Tue, 26 Feb 2019 15:10:42 -0500 Received: by mail-qt1-f196.google.com with SMTP id s1so16495029qte.5 for ; Tue, 26 Feb 2019 12:10:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=PVAJQc7zm0/UuJ2/28R2Kg+xhez7CklWKF4FR40pHt4=; b=szj5PezodOf6fy3TTJDCb6FuY6gx5NlIo+SgoBO/yoy5OIf2REWokCmVLNRLNJfxTM 1YEvAwiY0UrzkPyP4CJyioVjKN/ZSwAVg3cZuyD655dSus84GhS4wib5eYKNvoI1LOVf U1cVfPgANCdKx7TlRkWvLhHC1fzhIBb3l4o8TnB8ys1FFGF96iZPXNYOvzBDcNO3boOd GB1I8yhCfwx9cI9K+wugOHBVzlVsEb2B2FfaPTDulHoDK6uI+ExJ3ynEtzqo3AnTAtGn H4s+cZu4VkBVNsBB400YQmvV3uBH1COFj6aBNxOB/Z+zPnRcsjWJkc/nk+PLDE6ceNPB qJpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=PVAJQc7zm0/UuJ2/28R2Kg+xhez7CklWKF4FR40pHt4=; b=IEBPX4g5lXk87gAJT3geiEPirot7WFgCwWKTOetJEM3/Na99BvcZPUAKkydSNMhl3c 6tJw0j+qQVuhi5mAlP3EJfcAZ1ysR9U4UASk8gHi0xlZuV0fyeypfNdR5HsKxTqM3cll 4t8VZqXR3wBlFdzPzPFZ7Yw2IVkznuH8uRs+Z0azVo54r+ypfXjDpM1PzAwp8WatJGyP Yxxg+2eeqb+nXTBppbheqDBpPNy9M0b92OERv1ccpXFUs9XO+fF0lmTGDm716YkugeRo pZ/CfzeYUZDwR40hDf05aGZt9uUM8MPbR976ZEd2z8W7zNuOkcF4DIhT7rzr3IkQud2Y iTEA== X-Gm-Message-State: AHQUAuZXRglKSqGAtbAL2gim/DL9UxaRfN3v+KxkkA5KMYCmdmLOZiix JMOK/84Rz/BE/icFj/Zcby15IUKxHjg= X-Google-Smtp-Source: AHgI3IbwIASi1Yl1POT27rifla4p+mkrU+55VCWmojDk/BpmEDuBF3muTAszov9c9OLMp6LXHLjHzA== X-Received: by 2002:ac8:1b6b:: with SMTP id p40mr18870589qtk.155.1551211841157; Tue, 26 Feb 2019 12:10:41 -0800 (PST) Received: from dhcp-41-57.bos.redhat.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id m128sm7927982qkf.53.2019.02.26.12.10.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Feb 2019 12:10:40 -0800 (PST) Message-ID: <1551211839.6911.54.camel@lca.pw> Subject: Re: [PATCH] mm/hotplug: fix an imbalance with DEBUG_PAGEALLOC From: Qian Cai To: Michal Hocko Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Tue, 26 Feb 2019 15:10:39 -0500 In-Reply-To: <20190226194024.GI10588@dhcp22.suse.cz> References: <20190225191710.48131-1-cai@lca.pw> <20190226123521.GZ10588@dhcp22.suse.cz> <4d4d3140-6d83-6d22-efdb-370351023aea@lca.pw> <20190226142352.GC10588@dhcp22.suse.cz> <1551203585.6911.47.camel@lca.pw> <20190226181648.GG10588@dhcp22.suse.cz> <20190226182007.GH10588@dhcp22.suse.cz> <1551208782.6911.51.camel@lca.pw> <20190226194024.GI10588@dhcp22.suse.cz> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2019-02-26 at 20:40 +0100, Michal Hocko wrote: > It seems you have missed the point of my question. It simply doesn't > make much sense to have offline memory mapped. That memory is not > accessible in general. So mapping it at the offline time is dubious at > best. Well, kernel_map_pages() is like other debug features which could look "unusual". > Also you do not get through the offlining phase on a newly > hotplugged (and not yet onlined) memory. So the patch doesn't look > correct to me and it all smells like the bug you are seeing is a wrong > reporting. > That (physical memory hotadd) is a special case like during the boot. The patch is strictly to deal with offline/online memory, i.e., logical/soft memory hotplug.