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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 BEEF5C4332B for ; Tue, 24 Mar 2020 00:20:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 763B5206F9 for ; Tue, 24 Mar 2020 00:20:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="rhkRdjMI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 763B5206F9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1AF156B0093; Mon, 23 Mar 2020 20:20:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1603A6B0096; Mon, 23 Mar 2020 20:20:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 04F466B0098; Mon, 23 Mar 2020 20:20:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0134.hostedemail.com [216.40.44.134]) by kanga.kvack.org (Postfix) with ESMTP id E156C6B0093 for ; Mon, 23 Mar 2020 20:20:58 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B1ECE186A549C for ; Tue, 24 Mar 2020 00:20:58 +0000 (UTC) X-FDA: 76628350596.26.gun24_2590b228f3420 X-HE-Tag: gun24_2590b228f3420 X-Filterd-Recvd-Size: 4977 Received: from hqnvemgate24.nvidia.com (hqnvemgate24.nvidia.com [216.228.121.143]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Tue, 24 Mar 2020 00:20:57 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 23 Mar 2020 17:19:26 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 23 Mar 2020 17:20:56 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 23 Mar 2020 17:20:56 -0700 Received: from rcampbell-dev.nvidia.com (172.20.13.39) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 24 Mar 2020 00:20:56 +0000 Subject: Re: [PATCH] mm/rmap: fix the handling of device private page in try_to_unmap_one() To: Michal Hocko , Pingfan Liu CC: , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , John Hubbard , "Kirill A . Shutemov" , Aneesh Kumar , Andrew Morton References: <1584885427-4952-1-git-send-email-kernelfans@gmail.com> <20200323073408.GA7524@dhcp22.suse.cz> From: Ralph Campbell X-Nvconfidentiality: public Message-ID: Date: Mon, 23 Mar 2020 17:20:53 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20200323073408.GA7524@dhcp22.suse.cz> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1585009166; bh=MIOBnor2K4n2cRYC7CDg50BPfwYEaWVk+tAoPnhmILE=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=rhkRdjMI5ogWeJOk6/UX5T4Py72SyzGK37FLpJpvljrxVpb168gbr7z9bKOZh9ORr n436DnOr44Gy/5aF3rigNGPeDLb30UVjhiMxWXjLi6GA5wV0PsUbtor/+PFImyq6W2 HTflhqxj05tPlVm+UYTCiTZfP4QLSZ3LX2+rUrxLb1o/5okKohTCqb0QjPK/slSJtX YEPRAHoKefvokWLms/IMa5dtWV+ycB7Ld7NGKgP7Lo81Q2Fzx9QRkRCj556g5eq5Zc 3nZIoe5Pch4uJNHqUWhWV/P67dn6o2Y+0Y28HLdFdiC+/vLUzgrxLa72LUWG0HKobV /Pet8wtRf+OoA== 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 3/23/20 12:34 AM, Michal Hocko wrote: > On Sun 22-03-20 21:57:07, Pingfan Liu wrote: >> For zone_device, migration can only happen on is_device_private_page(pag= e). >> Correct the logic in try_to_unmap_one(). >=20 > Maybe it is just me lacking knowledge in the zone_device ZOO. But > this really deserves a much more detailed explanation IMHO. It seems > a5430dda8a3a ("mm/migrate: support un-addressable ZONE_DEVICE page in > migration") deliberately made the decision to allow unmapping these > pages? Is the check just wrong, inncomplete? Why? >=20 > What is the real user visible problem here? > =20 >> Signed-off-by: Pingfan Liu >> Cc: J=C3=A9r=C3=B4me Glisse >> Cc: Michal Hocko >> Cc: John Hubbard >> Cc: Kirill A. Shutemov >> Cc: Aneesh Kumar >> Cc: Andrew Morton >> To: linux-mm@kvack.org >> --- >> mm/rmap.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index b838647..ffadf3e 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1380,7 +1380,7 @@ static bool try_to_unmap_one(struct page *page, st= ruct vm_area_struct *vma, >> >> if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) && >> is_zone_device_page(page) && !is_device_private_page(page)) >> - return true; >> + return false; Pages can be mapped in multiple vmas. Returning false here will only break = out of the loop and skip any other vmas mapping this page which is a minor opti= mization but shouldn't really affect what try_to_unmap_one() does. >> if (flags & TTU_SPLIT_HUGE_PMD) { >> split_huge_pmd_address(vma, address, >> @@ -1487,7 +1487,7 @@ static bool try_to_unmap_one(struct page *page, st= ruct vm_area_struct *vma, >> >> if (IS_ENABLED(CONFIG_MIGRATION) && >> (flags & TTU_MIGRATION) && >> - is_zone_device_page(page)) { >> + is_device_private_page(page)) { >> swp_entry_t entry; >> pte_t swp_pte; Since the page was checked for !device private, this is more clear but shou= ldn't change anything.