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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 598F4C4363D for ; Tue, 22 Sep 2020 14:37:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D312220739 for ; Tue, 22 Sep 2020 14:37:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D312220739 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E094F90009D; Tue, 22 Sep 2020 10:37:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D418B900097; Tue, 22 Sep 2020 10:37:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BE46990009B; Tue, 22 Sep 2020 10:37:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0081.hostedemail.com [216.40.44.81]) by kanga.kvack.org (Postfix) with ESMTP id 9F905900096 for ; Tue, 22 Sep 2020 10:37:23 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 611CD3628 for ; Tue, 22 Sep 2020 14:37:23 +0000 (UTC) X-FDA: 77290950366.29.glass51_09026162714e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin29.hostedemail.com (Postfix) with ESMTP id 30ECC18086CDA for ; Tue, 22 Sep 2020 14:37:23 +0000 (UTC) X-HE-Tag: glass51_09026162714e X-Filterd-Recvd-Size: 2801 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Tue, 22 Sep 2020 14:37:22 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 34205B11F; Tue, 22 Sep 2020 14:37:57 +0000 (UTC) From: Vlastimil Babka To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Michal Hocko , Pavel Tatashin , David Hildenbrand , Oscar Salvador , Joonsoo Kim , Vlastimil Babka Subject: [PATCH 5/9] mm, page_alloc: make per_cpu_pageset accessible only after init Date: Tue, 22 Sep 2020 16:37:08 +0200 Message-Id: <20200922143712.12048-6-vbabka@suse.cz> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200922143712.12048-1-vbabka@suse.cz> References: <20200922143712.12048-1-vbabka@suse.cz> MIME-Version: 1.0 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: setup_zone_pageset() replaces the boot_pageset by allocating and initiali= zing a proper percpu one. Currently it assigns zone->pageset with the newly allo= cated one before initializing it. That's currently not an issue, because the zo= ne should not be in any zonelist, thus not visible to allocators at this poi= nt. Memory ordering between the pcplist contents and its visibility is also n= ot guaranteed here, but that also shouldn't be an issue because online_pages= () does a spin_unlock(pgdat->node_size_lock) before building the zonelists. However it's best that we don't silently rely on operations that can be c= hanged in the future. Make sure only properly initialized pcplists are visible, = using smp_store_release(). The read side has a data dependency via the zone->pa= geset pointer instead of an explicit read barrier. Signed-off-by: Vlastimil Babka --- mm/page_alloc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 99b74c1c2b0a..de3b48bda45c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6246,15 +6246,17 @@ static void zone_set_pageset_high_and_batch(struc= t zone *zone) =20 void __meminit setup_zone_pageset(struct zone *zone) { + struct per_cpu_pageset __percpu * new_pageset; struct per_cpu_pageset *p; int cpu; =20 - zone->pageset =3D alloc_percpu(struct per_cpu_pageset); + new_pageset =3D alloc_percpu(struct per_cpu_pageset); for_each_possible_cpu(cpu) { - p =3D per_cpu_ptr(zone->pageset, cpu); + p =3D per_cpu_ptr(new_pageset, cpu); pageset_init(p); } =20 + smp_store_release(&zone->pageset, new_pageset); zone_set_pageset_high_and_batch(zone); } =20 --=20 2.28.0