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=-17.4 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 6D71BC433EF for ; Tue, 7 Sep 2021 09:52:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E56A56105A for ; Tue, 7 Sep 2021 09:52:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E56A56105A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 0F0F66B0071; Tue, 7 Sep 2021 05:52:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 07AF6900002; Tue, 7 Sep 2021 05:52:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E368D6B0073; Tue, 7 Sep 2021 05:52:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0107.hostedemail.com [216.40.44.107]) by kanga.kvack.org (Postfix) with ESMTP id D16436B0071 for ; Tue, 7 Sep 2021 05:52:56 -0400 (EDT) Received: from smtpin36.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 891B48249980 for ; Tue, 7 Sep 2021 09:52:56 +0000 (UTC) X-FDA: 78560313552.36.BE1B15E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf18.hostedemail.com (Postfix) with ESMTP id 22DE64002085 for ; Tue, 7 Sep 2021 09:52:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631008375; 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=ec0XhsGsDLFUF6H9oW55TW4umdjrK/glnKsmv1QEvRs=; b=htn5Cqe7ROgudBd46POeeek71Wj9gNAyGDrpFaKTb7i7ivHbNuHORosU4o25VaVE+fYD6N bDWa58X5lyoCFECPL6akDESvIH/i3OshNEjL0qcpEcU4Zkq+HAZkH1kyrCDBqGAqh4FKZq Cw6oHhIJ/58hbY+A4xpo7bL0CxCRD3g= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-230-YFScJ312N7y-Jpmajamheg-1; Tue, 07 Sep 2021 05:52:54 -0400 X-MC-Unique: YFScJ312N7y-Jpmajamheg-1 Received: by mail-wm1-f70.google.com with SMTP id u14-20020a7bcb0e0000b0290248831d46e4so904445wmj.6 for ; Tue, 07 Sep 2021 02:52:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:organization :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=ec0XhsGsDLFUF6H9oW55TW4umdjrK/glnKsmv1QEvRs=; b=XUHb98FOFwOMjMFtr+s4w1u6aH9VRJ4bJ8tlLUBsOO9C5/9uhSaxgJDYJXXisHQ8qG brLbQXSm33sTjQCRnrgLUPxbv0KrDG1tTa6UC3JwmgQD7p/GN9WhHnatBoBXYMakdNy/ GMkUzGv2IegUSZ+0JpnES7+qoRVpGxvgYJeNVvZedRD+hzDXXQcohdpKtGYgvPH+QzA2 pdj4Z7p/vagRvFOjSp7+y4Bft8G9YKLtDuYEE0eEEOJW53UhmuAE8JwJiMKj9AVrgq01 bD75ChUT/a5ET12+LxDZzeaP/htej3mZBgq9mT6R44YjbL1XtoCjHBNHnVCVx+3YfhpS vmkQ== X-Gm-Message-State: AOAM533UudCbuZ/7mqsOtbUS1/JLQGj5xRKUDBy6ZPnuOo7/POl1UF4i L3++Is18GrE4BQ6BijOP54bYEvkTlLT6q3kUaKEEP1Ooq27yJ/6JSuONpPpEjME5mJCChqKXELg w0+tfw4+rwHI= X-Received: by 2002:adf:9e05:: with SMTP id u5mr17347357wre.352.1631008373192; Tue, 07 Sep 2021 02:52:53 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzEsD0WB8/viCKGE71XpFE4F5eN/VdHrPSfxW7jC2HliVmfsQMFZ8e3q2V3pyZY4uuUPkmIhA== X-Received: by 2002:adf:9e05:: with SMTP id u5mr17347337wre.352.1631008372931; Tue, 07 Sep 2021 02:52:52 -0700 (PDT) Received: from [192.168.3.132] (p4ff23fca.dip0.t-ipconnect.de. [79.242.63.202]) by smtp.gmail.com with ESMTPSA id w1sm1894852wmc.19.2021.09.07.02.52.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Sep 2021 02:52:52 -0700 (PDT) Subject: Re: [PATCH] mm/page_isolation: don't putback unisolated page To: Miaohe Lin , akpm@linux-foundation.org Cc: vbabka@suse.cz, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210904091839.20270-1-linmiaohe@huawei.com> <3b36529f-ab97-ddfe-0407-66f0cd1fd38d@redhat.com> <2d06db75-5c26-8fe2-6883-ac99056a9894@redhat.com> <57392d12-9a6c-dbb5-3c3e-39ed9ab7c31c@huawei.com> From: David Hildenbrand Organization: Red Hat Message-ID: <96b7c46d-8af1-4841-c97e-694abcf3b28b@redhat.com> Date: Tue, 7 Sep 2021 11:52:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <57392d12-9a6c-dbb5-3c3e-39ed9ab7c31c@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=htn5Cqe7; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf18.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=david@redhat.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 22DE64002085 X-Stat-Signature: cztoutwgxp6zxftyec76yek3o65whmom X-HE-Tag: 1631008375-450285 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: On 07.09.21 03:46, Miaohe Lin wrote: > On 2021/9/6 20:49, David Hildenbrand wrote: >> On 06.09.21 14:45, Miaohe Lin wrote: >>> On 2021/9/6 20:11, David Hildenbrand wrote: >>>> On 06.09.21 14:02, David Hildenbrand wrote: >>>>> On 04.09.21 11:18, Miaohe Lin wrote: >>>>>> If __isolate_free_page() failed, due to zone watermark check, the = page is >>>>>> still on the free list. But this page will be put back to free lis= t again >>>>>> via __putback_isolated_page() now. This may trigger page->flags ch= ecks in >>>>>> __free_one_page() if PageReported is set. Or we will corrupt the f= ree list >>>>>> because list_add() will be called for pages already on another lis= t. >>>>>> >>>>>> Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging= on isolated pageblock") >>>>>> Signed-off-by: Miaohe Lin >>>>>> --- >>>>>> =C2=A0=C2=A0=C2=A0 mm/page_isolation.c | 6 ++---- >>>>>> =C2=A0=C2=A0=C2=A0 1 file changed, 2 insertions(+), 4 deletions(-= ) >>>>>> >>>>>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >>>>>> index 9bb562d5d194..7d70d772525c 100644 >>>>>> --- a/mm/page_isolation.c >>>>>> +++ b/mm/page_isolation.c >>>>>> @@ -93,10 +93,8 @@ static void unset_migratetype_isolate(struct pa= ge *page, unsigned migratetype) >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 buddy_pfn =3D __find_buddy_pfn(pfn, order); >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 buddy =3D page + (buddy_pfn - pfn); >>>>>> =C2=A0=C2=A0=C2=A0 -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 if (!is_migrate_isolate_page(buddy)) { >>>>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 __isolate_free_page(page, order); >>>>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 isolated_page =3D true; >>>>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= } >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= if (!is_migrate_isolate_page(buddy)) >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 isolated_page =3D !!__isolate_free_page(page, or= der); >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= } >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >>>>>> =20 >>>>> >>>>> Thanks! >>>>> >>>>> Reviewed-by: David Hildenbrand >>>>> >>>> >>>> To make the confusion perfect (sorry) :D I tripple-checked: >>>> >>>> In unset_migratetype_isolate() we check that is_migrate_isolate_page= (page) holds, otherwise we return. >>>> >>>> We call __isolate_free_page() only for such pages. >>>> >>>> __isolate_free_page() won't perform watermark checks on is_migrate_i= solate(). >>>> >>>> Consequently, __isolate_free_page() should never fail when called fr= om unset_migratetype_isolate() >>>> >>>> If that's correct then we=C2=A0 could instead maybe add a VM_BUG_ON(= ) and a comment why this can't fail. >>>> >>>> >>>> Makes sense or am I missing something? >>> >>> I think you're right. __isolate_free_page() should never fail when ca= lled from unset_migratetype_isolate() >>> as explained by you. But it might be too fragile to reply on the fail= ure conditions of __isolate_free_page(). >>> If that changes, VM_BUG_ON() here might trigger unexpectedly. Or am I= just over-worried as failure conditions >>> of __isolate_free_page() can hardly change? >> >> Maybe >> >> isolated_page =3D !!__isolate_free_page(page, order); >> /* >> =C2=A0* Isolating a free page in an isolated pageblock is expected to= always >> =C2=A0* work as watermarks don't apply here. >> =C2=A0*/ >> VM_BUG_ON(isolated_page); >=20 > Should this be VM_BUG_ON(!isolated_page) ? >=20 Ehm, yes :) --=20 Thanks, David / dhildenb