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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 3A77BC433E0 for ; Sat, 26 Dec 2020 22:40:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C4385207AB for ; Sat, 26 Dec 2020 22:40:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4385207AB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B3AA98D0095; Sat, 26 Dec 2020 17:40:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AE9EB8D0080; Sat, 26 Dec 2020 17:40:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 964E48D0095; Sat, 26 Dec 2020 17:40:20 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0083.hostedemail.com [216.40.44.83]) by kanga.kvack.org (Postfix) with ESMTP id 7DD218D0080 for ; Sat, 26 Dec 2020 17:40:20 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 38A24362C for ; Sat, 26 Dec 2020 22:40:20 +0000 (UTC) X-FDA: 77636903400.08.loss73_5b0014127486 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id 1A0AC1819E76F for ; Sat, 26 Dec 2020 22:40:20 +0000 (UTC) X-HE-Tag: loss73_5b0014127486 X-Filterd-Recvd-Size: 7613 Received: from mail-lf1-f42.google.com (mail-lf1-f42.google.com [209.85.167.42]) by imf14.hostedemail.com (Postfix) with ESMTP for ; Sat, 26 Dec 2020 22:40:19 +0000 (UTC) Received: by mail-lf1-f42.google.com with SMTP id 23so16131678lfg.10 for ; Sat, 26 Dec 2020 14:40:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=5xV1Uwr5QvPwGAEEhmKQuNt1ecyJlCF/DYUO0nnGbJA=; b=SSDOvkJaPZLQbLl1/R2yfC0vD8pNo/R7kwvwiR0BP96LI5plYaxX1qyeGTF5DDBAle Mo8kLCOdwcA3MLI3xds9N6DR0mR8YcPh8435LV12lTkVb7z8s/jFxu8aCFrWAzzJUUAx g/GK5Fi4t9MRDLYmUWaK9rgbfXgMXKSeAXeUa+bfRcHPK8APDNC8EGbShpG7KAI36SdC atxEb/OH8TBUcAyQcr1NCjzL/tS0AG1dM0/L+sQKDNLwl6XDx36uavQQdFqhRjWxZVXd E2OjzaZCA2OX8/82QsmFQLLMRPEVEBZN1TaKU3eQST1GmGun+pNtH/lyfbsbsWIW0YOH Nrnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=5xV1Uwr5QvPwGAEEhmKQuNt1ecyJlCF/DYUO0nnGbJA=; b=tPu9YZ1fXZLkMjA2r+LFVTzujK8U+2Nubk8cftXRt+2GXl4AWL3xRcuijLnDw9vp8v 7az1bZXL+BLzbcGjmcbN9DEkqxeS1pg4guiFxzHTw4hXWbRzdpUHJQugkfy9IsbAtrZ/ ZzToYU9irUJ/5uiiJlAiRr2AtrJ1Ju9UwYQKGRVNopTQT/3aX1D9z3hEnKUHrwbFjQM1 kLwN3brAuGdABMI4Yx3bvzqDIWBhPI+JHyWZKvUQdTcPvWImTzWySkZSk5XzsEhSrQLo 8PPIKd+HV7y3bwduz/hZCPEJ0OxBT4y/Hy+4ba1uqFKA8kif+tqjHeWERtQkI01nYHgx AapA== X-Gm-Message-State: AOAM5323gA/2jvku4sTp0Yn8PTHceYWeaCBZNaHEztpaIDLXpmHrYoeF 585PDFLQUUXUwZmhGxoELqZ16w== X-Google-Smtp-Source: ABdhPJy9c7fz+61qQ39Hm9FQ6OMVPp5gAk3EtmrlxqSIgqfg7pTj+frNOUo4gc5k5Hr9EwE043FbPA== X-Received: by 2002:a05:651c:1063:: with SMTP id y3mr17737679ljm.431.1609022417964; Sat, 26 Dec 2020 14:40:17 -0800 (PST) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id y26sm5596811ljh.63.2020.12.26.14.40.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Dec 2020 14:40:17 -0800 (PST) Received: by box.localdomain (Postfix, from userid 1000) id 9EEEC1026FB; Sun, 27 Dec 2020 01:40:16 +0300 (+03) Date: Sun, 27 Dec 2020 01:40:16 +0300 From: "Kirill A. Shutemov" To: Linus Torvalds Cc: Hugh Dickins , Matthew Wilcox , "Kirill A. Shutemov" , Will Deacon , Linux Kernel Mailing List , Linux-MM , Linux ARM , Catalin Marinas , Jan Kara , Minchan Kim , Andrew Morton , Vinayak Menon , Android Kernel Team Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting Message-ID: <20201226224016.dxjmordcfj75xgte@box> References: <20201219124103.w6isern3ywc7xbur@box> <20201222100047.p5zdb4ghagncq2oe@box> <20201225113157.e7hmluffh56fszfc@box> <20201226204335.dikqkrkezqet6oqf@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Sat, Dec 26, 2020 at 01:16:09PM -0800, Linus Torvalds wrote: > On Sat, Dec 26, 2020 at 1:04 PM Hugh Dickins wrote: > > > > > > Hold on. I guess this one will suffer from the same bug as the previous. > > I was about to report back, after satisfactory overnight testing of that > > version - provided that one big little bug is fixed: > > > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -2919,7 +2919,7 @@ static bool filemap_map_pmd(struct vm_fa > > > > if (pmd_none(*vmf->pmd) && > > PageTransHuge(page) && > > - do_set_pmd(vmf, page)) { > > + do_set_pmd(vmf, page) == 0) { > > unlock_page(page); > > return true; > > } > > I missed that entirely, because when just reading the patch it looks > fine and I didn't look at what do_set_pmd() function returns outside > the patch. > > And maybe it would be better to write it as > > if (pmd_none(*vmf->pmd) && PageTransHuge(page)) { > vm_fault_t ret = do_set_pmd(vmf, page); > if (!ret) { > ... > > instead to make it a bit more explicit about how that return value is > a vm_fault_t there... > > And see my other email about how I suspect there is still a leak in > that patch for the previous test-case. Ughh... Here's the fixup I have so far. It doesn't blow up immediately, but please take a closer look. Who knows what stupid mistake I did this time. :/ diff --git a/mm/filemap.c b/mm/filemap.c index 3a92aaa59b9b..c4b374678e7d 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2837,16 +2837,21 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page) struct mm_struct *mm = vmf->vma->vm_mm; /* Huge page is mapped? No need to proceed. */ - if (pmd_trans_huge(*vmf->pmd)) - return true; - - if (pmd_none(*vmf->pmd) && - PageTransHuge(page) && - do_set_pmd(vmf, page)) { + if (pmd_trans_huge(*vmf->pmd)) { unlock_page(page); + put_page(page); return true; } + if (pmd_none(*vmf->pmd) && PageTransHuge(page)) { + vm_fault_t ret = do_set_pmd(vmf, page); + if (!ret) { + /* The page is mapped successfully, reference consumed. */ + unlock_page(page); + return true; + } + } + if (pmd_none(*vmf->pmd)) { vmf->ptl = pmd_lock(mm, vmf->pmd); if (likely(pmd_none(*vmf->pmd))) { @@ -2867,7 +2872,7 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page) return false; } -static struct page *next_stable_page(struct page *page, struct vm_fault *vmf, +static struct page *next_uptodate_page(struct page *page, struct vm_fault *vmf, struct xa_state *xas, pgoff_t end_pgoff) { struct address_space *mapping = vmf->vma->vm_file->f_mapping; @@ -2914,15 +2919,16 @@ static inline struct page *first_map_page(struct vm_fault *vmf, struct xa_state *xas, pgoff_t end_pgoff) { - return next_stable_page(xas_find(xas, end_pgoff), vmf, xas, end_pgoff); + return next_uptodate_page(xas_find(xas, end_pgoff), + vmf, xas, end_pgoff); } static inline struct page *next_map_page(struct vm_fault *vmf, struct xa_state *xas, pgoff_t end_pgoff) { - return next_stable_page(xas_next_entry(xas, end_pgoff), - vmf, xas, end_pgoff); + return next_uptodate_page(xas_next_entry(xas, end_pgoff), + vmf, xas, end_pgoff); } void filemap_map_pages(struct vm_fault *vmf, -- Kirill A. Shutemov