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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67895C433F5 for ; Thu, 17 Feb 2022 06:08:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F0FEB6B007B; Thu, 17 Feb 2022 01:08:14 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E985A6B007D; Thu, 17 Feb 2022 01:08:14 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D12E96B007E; Thu, 17 Feb 2022 01:08:14 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0222.hostedemail.com [216.40.44.222]) by kanga.kvack.org (Postfix) with ESMTP id C09046B007B for ; Thu, 17 Feb 2022 01:08:14 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 83409181AC9C6 for ; Thu, 17 Feb 2022 06:08:14 +0000 (UTC) X-FDA: 79151241708.12.BE42C86 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf26.hostedemail.com (Postfix) with ESMTP id 0608F140003 for ; Thu, 17 Feb 2022 06:08:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645078093; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=A1vbZxsyzMifaaJqgkhHlizU7SHJnrILT5bLrmNnzMQ=; b=UF3otFFdlgED7oMXBGZHUacxQsvcyU15vFgTclZxvD8KhqpovrLqxowtUkt3LjzOvtcTMe WaA+oE035x+VA79LDH5E02m8Pkf7h2UwAzpnY1hqsvjf1t9OIpnJpvccqmS5E1y0iOGz2V Lj/jomIXCARDsErcL02s3/aQGIoPj0E= Received: from mail-pj1-f72.google.com (mail-pj1-f72.google.com [209.85.216.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-448-hB8rWLKKPlum9-3xlzb0RA-1; Thu, 17 Feb 2022 01:08:12 -0500 X-MC-Unique: hB8rWLKKPlum9-3xlzb0RA-1 Received: by mail-pj1-f72.google.com with SMTP id c6-20020a17090a020600b001b9b44c18aaso5840959pjc.4 for ; Wed, 16 Feb 2022 22:08:12 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=A1vbZxsyzMifaaJqgkhHlizU7SHJnrILT5bLrmNnzMQ=; b=pbbGxiv+w7Edae5lzWApha/SHC2wcEnIfBdozWmGjY5cceq/fiVfpWpLHwgQqV6oWo s6QWnhJgBloCxwOkXgsKcy1Ss39Ph4Sx27yEiDDiuE/QR5Mdikh+ncNIxetUc5VVR/pb wJsWz15eRl+249u7p36fghudS63n1PMdFX+rS4v4MkyjuEoY3QnKINQGn3jsIkyJ0+yc EtyviMYnppV/uX/7AUFJmw3PQKyhDO3+Sm8rFRJrN5DqFFvyrVQy/bc1dRVjIfwZ4nVM qsALbe5hzs0RZHMUKyzo2O1gYaX3NeR5Tv+4rXVbwjelSEy5sj90BIy0RyzIgPuqTFld jnvg== X-Gm-Message-State: AOAM531VvNKEWTDk9p3TEiU0+zXX4WzlM5hygqg8UR8sAvz95qvSzcI5 h+opV5V6EPoKSM6WtLAdgv81vYFb0oKmFRsLHgBv/0/zyJPp9dCdOCnCddhV/hS/qUOWMeDShsx Rmh9ksKyLbl7fRtfR7NPlOhkFBn+cmP91oUWWJ18hqcQK65MpyFZbEWK9nn2z X-Received: by 2002:a17:90a:ec10:b0:1b8:9da7:3d13 with SMTP id l16-20020a17090aec1000b001b89da73d13mr1531885pjy.194.1645078091273; Wed, 16 Feb 2022 22:08:11 -0800 (PST) X-Google-Smtp-Source: ABdhPJxJ+MRoSejjpjSfq3CLN/Ow3BCwyndgoRTeQRVbvX65z98rR9y1roji3xMcenHn/prKAwWNxg== X-Received: by 2002:a17:90a:ec10:b0:1b8:9da7:3d13 with SMTP id l16-20020a17090aec1000b001b89da73d13mr1531852pjy.194.1645078090846; Wed, 16 Feb 2022 22:08:10 -0800 (PST) Received: from localhost.localdomain ([94.177.118.126]) by smtp.gmail.com with ESMTPSA id j8sm224230pjc.11.2022.02.16.22.08.06 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 16 Feb 2022 22:08:10 -0800 (PST) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Alistair Popple , Matthew Wilcox , peterx@redhat.com, David Hildenbrand , Andrea Arcangeli , Hugh Dickins , Yang Shi , Vlastimil Babka , John Hubbard , Andrew Morton , "Kirill A . Shutemov" Subject: [PATCH v5 3/4] mm: Change zap_details.zap_mapping into even_cows Date: Thu, 17 Feb 2022 14:07:45 +0800 Message-Id: <20220217060746.71256-4-peterx@redhat.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220217060746.71256-1-peterx@redhat.com> References: <20220217060746.71256-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="US-ASCII" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0608F140003 X-Rspam-User: Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=UF3otFFd; spf=none (imf26.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Stat-Signature: wzatub9u8bedu6i3rpxffrgu3e39eyzz X-HE-Tag: 1645078093-658189 Content-Transfer-Encoding: quoted-printable 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: Currently we have a zap_mapping pointer maintained in zap_details, when i= t is specified we only want to zap the pages that has the same mapping with what the caller has specified. But what we want to do is actually simpler: we want to skip zapping private (COW-ed) pages in some cases. It comes from unmap_mapping_pages(= ) where we could have passed in different even_cows values. The other user is unmap_mapping_folio() where we always want to skip private pages. According to Hugh, we used a mapping pointer for historical reason, as explained here: https://lore.kernel.org/lkml/391aa58d-ce84-9d4-d68d-d98a9c533255@google= .com/ Quoting partly from Hugh: Which raises the question again of why I did not just use a boolean fla= g there originally: aah, I think I've found why. In those days there was= a horrible "optimization", for better performance on some benchmark I guess, which when you read from /dev/zero into a private mapping, would map the zero page there (look up read_zero_pagealigned() and zeromap_page_range() if you dare). So there was another category of pa= ge to be skipped along with the anon COWs, and I didn't want multiple test= s in the zap loop, so checking check_mapping against page->mapping did both. I think nowadays you could do it by checking for PageAnon page (= or genuine swap entry) instead. This patch replaced the zap_details.zap_mapping pointer into the even_cow= s boolean, then we check it against PageAnon. Suggested-by: Hugh Dickins Reviewed-by: John Hubbard Signed-off-by: Peter Xu --- mm/memory.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 3728632ea993..c2defe8a1472 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1309,8 +1309,8 @@ copy_page_range(struct vm_area_struct *dst_vma, str= uct vm_area_struct *src_vma) * Parameter block passed down to zap_pte_range in exceptional cases. */ struct zap_details { - struct address_space *zap_mapping; /* Check page->mapping if set */ struct folio *single_folio; /* Locked folio to be unmapped */ + bool even_cows; /* Zap COWed private pages too? */ }; =20 /* Whether we should zap all COWed (private) pages too */ @@ -1321,13 +1321,10 @@ static inline bool should_zap_cows(struct zap_det= ails *details) return true; =20 /* Or, we zap COWed pages only if the caller wants to */ - return !details->zap_mapping; + return details->even_cows; } =20 -/* - * We set details->zap_mapping when we want to unmap shared but keep pri= vate - * pages. Return true if we should zap this page, false otherwise. - */ +/* Decides whether we should zap this page with the page pointer specifi= ed */ static inline bool should_zap_page(struct zap_details *details, struct p= age *page) { /* If we can make a decision without *page.. */ @@ -1338,7 +1335,8 @@ static inline bool should_zap_page(struct zap_detai= ls *details, struct page *pag if (!page) return true; =20 - return details->zap_mapping =3D=3D page_rmapping(page); + /* Otherwise we should only zap non-anon pages */ + return !PageAnon(page); } =20 static unsigned long zap_pte_range(struct mmu_gather *tlb, @@ -3398,7 +3396,7 @@ void unmap_mapping_folio(struct folio *folio) first_index =3D folio->index; last_index =3D folio->index + folio_nr_pages(folio) - 1; =20 - details.zap_mapping =3D mapping; + details.even_cows =3D false; details.single_folio =3D folio; =20 i_mmap_lock_write(mapping); @@ -3427,7 +3425,7 @@ void unmap_mapping_pages(struct address_space *mapp= ing, pgoff_t start, pgoff_t first_index =3D start; pgoff_t last_index =3D start + nr - 1; =20 - details.zap_mapping =3D even_cows ? NULL : mapping; + details.even_cows =3D even_cows; if (last_index < first_index) last_index =3D ULONG_MAX; =20 --=20 2.32.0