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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E2F1C433F5 for ; Wed, 27 Oct 2021 07:47:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 175FE61039 for ; Wed, 27 Oct 2021 07:47:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 175FE61039 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id ADE1D80008; Wed, 27 Oct 2021 03:47:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A8DBA940007; Wed, 27 Oct 2021 03:47:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9A41C80008; Wed, 27 Oct 2021 03:47:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0078.hostedemail.com [216.40.44.78]) by kanga.kvack.org (Postfix) with ESMTP id 8D35B940007 for ; Wed, 27 Oct 2021 03:47:22 -0400 (EDT) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 4A6CF8249980 for ; Wed, 27 Oct 2021 07:47:22 +0000 (UTC) X-FDA: 78741437124.20.E16EE07 Received: from mail-yb1-f173.google.com (mail-yb1-f173.google.com [209.85.219.173]) by imf13.hostedemail.com (Postfix) with ESMTP id B2ED41047F59 for ; Wed, 27 Oct 2021 07:47:15 +0000 (UTC) Received: by mail-yb1-f173.google.com with SMTP id t127so4028767ybf.13 for ; Wed, 27 Oct 2021 00:47:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=loo6J+IxIj4clOI8hbAYwr44QCVgT2WqP23IkmlyE90=; b=ejNHgkTEI3rvzEqVdyGTwC4ZsTd3PDCtXvqQq6h7xYm339qXrcU/LTl4td5IJ9K80l PDNmBPPXvQvVaBiiZy7PN77C7Czz+NStfGWc39W0PiK9prM9AT9f9ivIUH3nZFIriI5F DqBL6YR/3Pd9WTECoGr0FNUp0mAdSqAJ7x9IvKOjAF4Eei+IrsiX3gCMIpSS8lnvQcfO tPV9rmIQvzqweHp9j7FRlN2Aj2U94P3ECNMGnwpExpWsaG1pcGzR7r6cwjmGGRlxZ+mv ldbrKEaIAHjOHVr8Oia34oebIlHlXXUlIpNgUsWRdXVA3jtrqvR+tD1bkjSJLRjLJwUp 2Ykw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=loo6J+IxIj4clOI8hbAYwr44QCVgT2WqP23IkmlyE90=; b=5rSLT+5GSPe+be0nUOS6fClZlfrS4arIVxTv2iI0XL5XPN+nez2FwpRFc+0zpStCjk YXY8RwkqCgTkRXKIg5hUGQazYG0hdfXfZyp55QYqtgCuCo8GLxvR26loJTBeYEMoVvFV S93c3/fJqzhIO+/OOP7J4yHOJdkB+WemKbX0I7h571Cz79T2nHdp6a39//XWIoDozD6x 3Aqkq1ZS+QwPJjO0xDIx94mQGZcCcx27IlLCZeXfLqlPX3h03Xgu3WVH6gzbYid0Znyg iDf3H46xeoYZt5h/JVgXSEzwM8KhOz9VTIbUHXFSy0Ogq1+z1wRPvREyvSHDNFHtTVat cfKw== X-Gm-Message-State: AOAM5337+XqEsisQRXbQNzGBXqlf0t07G3m6y13x6hv2EEEWteY46pJz gSTkqwZqsI9er9mfqJgoNi0cwKnIonMpkd0jvBHByg== X-Google-Smtp-Source: ABdhPJz+XebE2bOjEj4+R9On6uOHRAEk9nRXfXlxTPyeWvga0rJ1rMsvtN+tWifQabRIRggo5SvYAy4Nno4c280mUp4= X-Received: by 2002:a25:3b50:: with SMTP id i77mr1035222yba.404.1635320840664; Wed, 27 Oct 2021 00:47:20 -0700 (PDT) MIME-Version: 1.0 References: <20211026173822.502506-1-pasha.tatashin@soleen.com> <20211026173822.502506-2-pasha.tatashin@soleen.com> In-Reply-To: <20211026173822.502506-2-pasha.tatashin@soleen.com> From: Muchun Song Date: Wed, 27 Oct 2021 15:46:42 +0800 Message-ID: Subject: Re: [RFC 1/8] mm: add overflow and underflow checks for page->_refcount To: Pasha Tatashin Cc: LKML , Linux Memory Management List , linux-m68k@lists.linux-m68k.org, Anshuman Khandual , Matthew Wilcox , Andrew Morton , william.kucharski@oracle.com, Mike Kravetz , Vlastimil Babka , geert@linux-m68k.org, schmitzmic@gmail.com, Steven Rostedt , Ingo Molnar , Johannes Weiner , Roman Gushchin , weixugc@google.com, Greg Thelen Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: B2ED41047F59 X-Stat-Signature: 3bza3rhfpgmwfhwhwiyytyjfh9u1iswp Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=ejNHgkTE; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf13.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.219.173 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-HE-Tag: 1635320835-575341 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 Wed, Oct 27, 2021 at 1:38 AM Pasha Tatashin wrote: > > The problems with page->_refcount are hard to debug, because usually > when they are detected, the damage has occurred a long time ago. Yet, > the problems with invalid page refcount may be catastrophic and lead to > memory corruptions. > > Reduce the scope of when the _refcount problems manifest themselves by > adding checks for underflows and overflows into functions that modify > _refcount. > > Signed-off-by: Pasha Tatashin I found some atomic_add/dec are replaced with atomic_add/dec_return, those helpers with return value imply a full memory barrier around it, but others without return value do not. Do you have any numbers to show the impact? Maybe atomic_add/dec_return_relaxed can help this. Thanks.