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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 42A19C433DB for ; Sat, 30 Jan 2021 00:13:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7D30D64DE4 for ; Sat, 30 Jan 2021 00:13:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D30D64DE4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B57548D0002; Fri, 29 Jan 2021 19:13:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B07C48D0001; Fri, 29 Jan 2021 19:13:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A1E948D0002; Fri, 29 Jan 2021 19:13:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0045.hostedemail.com [216.40.44.45]) by kanga.kvack.org (Postfix) with ESMTP id 8CD238D0001 for ; Fri, 29 Jan 2021 19:13:12 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 55F41180AD837 for ; Sat, 30 Jan 2021 00:13:12 +0000 (UTC) X-FDA: 77760516624.08.legs71_010be18275ac Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id 36DD31819E769 for ; Sat, 30 Jan 2021 00:13:12 +0000 (UTC) X-HE-Tag: legs71_010be18275ac X-Filterd-Recvd-Size: 3469 Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Sat, 30 Jan 2021 00:13:11 +0000 (UTC) Received: by mail-pl1-f176.google.com with SMTP id q2so6261890plk.4 for ; Fri, 29 Jan 2021 16:13:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:mime-version :content-disposition; bh=Bdme9a9aanpUVpcYq5JbsEJ7euEwzJX6ZOal2gUnr2k=; b=Re7zJWVhjEdudsgVVkbSIrx/6220Yo5vkkLSSK8sQSr3LO/3IDBSj2aRQiIyFTf21H IUZiOYN6rv7aWQ1noYRsV6+eIEayR/P8b6sa4eYeQd/Qlb+mXffe7CDx4aq+aowRTYsz cmFofVu9P5b6BnYx5ce7k297Gt0lrv7D8Q2ZkbdAU4MUdXK4x1OHo+EKZQV6XQicl2v0 B2xiw14br84lSpv84BzXGq41bb3bQHYYDPLuQ2mk7KDh7/THLfjHpeZeC9Mpj0WWWwwU DUj3FmFfuDL0Oph6tvCyc5tZgkyhQkXf3rMCjqlzF+xqMMFQOK9TM6rSck2NH7D6hU8j tN4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :mime-version:content-disposition; bh=Bdme9a9aanpUVpcYq5JbsEJ7euEwzJX6ZOal2gUnr2k=; b=Z2/DpLI6rKDq3jELDVJ3c7mU5wpavfetDVnHdFvNaDcPLI7ZjRcsSbxrakS+9O5nD8 Nigc72KJYncytFZygqOm72unicfKl3YyaIrjuxLbkCcggpQe9UJxXNYJf3LfMIW01Ona x2m3n/Cuo+Fvh5Q/rxM2LVEaWaCldWbRduP66db/FYLCr6b3Jlm73+IE7seiD4YCLofx 0ru0Pn3DIWkp9jiUcLJWu03jJoN8pEqMe4I8qD80tDagx+6I2CisAT0rn0VDlkHV7f7B 8TP1ZNXvO3vIy+D18i44nNNI0eKyexBZKXoUIayjJMczOTHaLnbMPPLXyKJbKzwM2zJI uhqg== X-Gm-Message-State: AOAM532BNOUAYAOkVUhgi2xUnepXvaFZizlwyE1vFILfaMqIubHSAaFp pQVg3Dddn+mWsLzEKIi2hlE= X-Google-Smtp-Source: ABdhPJzTmhy7n7O5NpkFDhtn4A1hErCNdZvoWk+iaPQg/ML2bz90YNTrPmQ19OU9+FP5RH3X84vHag== X-Received: by 2002:a17:90a:9414:: with SMTP id r20mr7092902pjo.158.1611965590893; Fri, 29 Jan 2021 16:13:10 -0800 (PST) Received: from google.com ([2620:15c:211:201:b81c:be0c:d615:b5bb]) by smtp.gmail.com with ESMTPSA id n1sm8374239pjv.47.2021.01.29.16.13.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 Jan 2021 16:13:09 -0800 (PST) Date: Fri, 29 Jan 2021 16:13:07 -0800 From: Minchan Kim To: willy@infradead.org, hughd@google.com, kirill@shutemov.name Cc: linux-mm Subject: THP handling with driver compound page on fault Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Bogosity: Ham, tests=bogofilter, spamicity=0.000096, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Folks, A custom driver overrides (vm_operations_struct.fault) and map their compound page(__GFP_COMP) to page table on userprocess on demand. Here problem is page fault occur: __do_fault vma->vm_ops->fault <- driver returns their compould page finish_fault alloc_set_pte PageTransCompound(page) do_set_pmd map the page as THP page Since it's not a THP page, system goes random crash after a while due to conflict of VM THP handling with the driver compound page handling. Even though it happens in old kernel with backporting THP pagecache, I think it's still valid on recent kernel. What's the best way to fix it? Driver don't do that or VM need to deal with it? Thank you.