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 14401C433EF for ; Thu, 3 Mar 2022 20:12:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 744738D0002; Thu, 3 Mar 2022 15:12:34 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6F3BD8D0001; Thu, 3 Mar 2022 15:12:34 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5BB5E8D0002; Thu, 3 Mar 2022 15:12:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0030.hostedemail.com [216.40.44.30]) by kanga.kvack.org (Postfix) with ESMTP id 4DD8D8D0001 for ; Thu, 3 Mar 2022 15:12:34 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 09A2D820AC66 for ; Thu, 3 Mar 2022 20:12:34 +0000 (UTC) X-FDA: 79204172628.21.73589A5 Received: from mail-ed1-f48.google.com (mail-ed1-f48.google.com [209.85.208.48]) by imf28.hostedemail.com (Postfix) with ESMTP id 8E380C0007 for ; Thu, 3 Mar 2022 20:12:33 +0000 (UTC) Received: by mail-ed1-f48.google.com with SMTP id x5so8058153edd.11 for ; Thu, 03 Mar 2022 12:12:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jcjhnNvk1HWEeyW9eNcGg5KkoFIvCyZIDJD6HTvONRQ=; b=YOylv/btveKLuQVvZ1kmA2nj40j6cCDUvggt8BbMmKeBkTyAOHyLgNsJRu6ROaXisM V2vtj7I8AOYH9YOIPGbro3VPAlBm9udiUwtqMIkRhaeYKYT5AhxzZKFLkKxBuvJFXi00 3I81CH3usIWzaSVeByuzTMz0WYLmKdFjccG8fXNEb7wYhdtZjXOjcQBLgzRYeOTDJ9jy QEuEE4IGsDgZ2kLgRNL6XRzVRRCCxF4qfejNyTHUQmeD2AzIeHZIbCTB+5bJovY3yCSY 33wVXwk9953GUG+W/cpCjMAXiwSTZ8tJ4MBfJyPVZygoa0yX2BtNMa4+zPIwinbkJX1g r6qw== 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=jcjhnNvk1HWEeyW9eNcGg5KkoFIvCyZIDJD6HTvONRQ=; b=FjjCxU+yHX5LU4TefGLFlPWc2U4/i+Kp1/EQoA6loFbFXpIVU4A7eG7weeyuO9z82c +IYtaGZXpv5yDpW4Bq0LXJDNzJHuOYHSulAWlUKUOdVUiXxyuahDGSc7D3LxOF6/I4v1 vGI6CP7P+4QAFy1rHAvHPHJ+uiBHvISD/W/KqL8my2B/8roNzfIC5t0wkVXoPXqVspbu +DVB09S4OZ8A/mjn99OIh8MX6xWkwWGAmL+4XgdeX/hxSBbiV+GdjVPWaNnTo8UskvAO bnUB3gtvesuW7pIVtQHpUDh6JDxCjn5B3MwcUHwWIns8QhL41NMFe7TL3m/uuZx2sMMk 5Sag== X-Gm-Message-State: AOAM5324EBirJv7EYM/jG2QgAUxVf3YhY1UjSP0MnV6eIbdVmqSASv1v GuU8rsHxTyCE/Da3IJIn2jxdgkQ+bmqbcQxXa/k= X-Google-Smtp-Source: ABdhPJwGtbxb4HK/7M1I5Bs0jN/kCcFZ97zNwP/45VWZGjZwIcedLJ6e3lYx0rKQWOemFOH50WkV7oRnSEupZ1rX0t8= X-Received: by 2002:a05:6402:2987:b0:414:39b0:7fc1 with SMTP id eq7-20020a056402298700b0041439b07fc1mr15149857edb.214.1646338352492; Thu, 03 Mar 2022 12:12:32 -0800 (PST) MIME-Version: 1.0 References: <61c5cf99-a962-9a25-597a-53ab1bd8fbc0@google.com> In-Reply-To: <61c5cf99-a962-9a25-597a-53ab1bd8fbc0@google.com> From: Yang Shi Date: Thu, 3 Mar 2022 12:12:20 -0800 Message-ID: Subject: Re: [PATCH mmotm] mm/thp: ClearPageDoubleMap in first page_add_file_rmap() To: Hugh Dickins Cc: Andrew Morton , "Kirill A. Shutemov" , Linux Kernel Mailing List , Linux MM Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 8E380C0007 X-Stat-Signature: m3qfnmhfhc3qc7ek57jxcswrx77qupry Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="YOylv/bt"; spf=pass (imf28.hostedemail.com: domain of shy828301@gmail.com designates 209.85.208.48 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1646338353-511423 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, Mar 2, 2022 at 5:50 PM Hugh Dickins wrote: > > PageDoubleMap is maintained differently for anon and for shmem+file: > the shmem+file one was never cleared, because a safe place to do so > could not be found; so it would blight future use of the cached > hugepage until evicted. > > See https://lore.kernel.org/lkml/1571938066-29031-1-git-send-email-yang.shi@linux.alibaba.com/ > > But page_add_file_rmap() does provide a safe place to do so (though > later than one might wish): allowing testing to return to an initial > state without a damaging drop_caches. > > Fixes: 9a73f61bdb8a ("thp, mlock: do not mlock PTE-mapped file huge pages") > Signed-off-by: Hugh Dickins > --- > > mm/rmap.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1251,6 +1251,17 @@ void page_add_file_rmap(struct page *page, > } > if (!atomic_inc_and_test(compound_mapcount_ptr(page))) > goto out; > + > + /* > + * It is racy to ClearPageDoubleMap in page_remove_file_rmap(); > + * but page lock is held by all page_add_file_rmap() compound > + * callers, and SetPageDoubleMap below warns if !PageLocked: > + * so here is a place that DoubleMap can be safely cleared. > + */ > + VM_WARN_ON_ONCE(!PageLocked(page)); > + if (nr == nr_pages && PageDoubleMap(page)) > + ClearPageDoubleMap(page); Nice idea! Reviewed-by: Yang Shi > + > if (PageSwapBacked(page)) > __mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED, > nr_pages);