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 5BCF0C433F5 for ; Thu, 5 May 2022 06:48:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B548E6B0071; Thu, 5 May 2022 02:48:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B03A56B0073; Thu, 5 May 2022 02:48:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9A4E16B0074; Thu, 5 May 2022 02:48:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 8B75E6B0071 for ; Thu, 5 May 2022 02:48:34 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 5FE652CE34 for ; Thu, 5 May 2022 06:48:34 +0000 (UTC) X-FDA: 79430760948.23.1B657FD Received: from mail-pf1-f180.google.com (mail-pf1-f180.google.com [209.85.210.180]) by imf10.hostedemail.com (Postfix) with ESMTP id 40D10C0081 for ; Thu, 5 May 2022 06:48:17 +0000 (UTC) Received: by mail-pf1-f180.google.com with SMTP id c14so2938155pfn.2 for ; Wed, 04 May 2022 23:48:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=ZV+Ja+Gjo1y5MTQG69wFb+r8JKmUtK4HnaqQsncUWMs=; b=cB22BeNOddpZtIMXGrGVUQYuBQHcTiJ5jPRZYmkVRrgGhzOUBdnTVM4YaoCihZlfKU ZrV8m04VQQwxbTyGChLW4qaRTAWAQaRSA0Su5gBCSoIwSXUp5WILWppOOfe56MY4bx0S LbOl87PzKF86xD+WPfZ9Dmf+9niWbsXoQZhNJtQ01RPVgwIyjvjkKV8+7hbDlnWoKRws Xs0LmWOM1twaDaHwORg9NcseG9dymMwivmgYBx6kC3bluPlvDJodhAdGHpTaP0IEqjTB qhq7Puhnt/Yi/PxpQXU6h2ay1f29YLr7ogvKPIp//P/CDN2FT4AuyLMU1MQHCKG9sthA 6oGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=ZV+Ja+Gjo1y5MTQG69wFb+r8JKmUtK4HnaqQsncUWMs=; b=xZgTxtPpGGO9oIAQo0C3KJnf7Z7+F3bMLc+ppGvIF7Q5MSzKX4mHc3J4vX+i40ln8E Jnss1rnO7cv8cGu1SKX/e4RQBjhy4kR/+sRaJfvMZKpa3gpk6U9Y4osy/yZO9mttr9tX EaX/bk2na5gjRqNN0gfEKpB68iwk3aQughubbKLseMkMtG27FeeoxQus2Z3fK/ymhEZz 1vqv+uBHyZORsPk2EkzAplhiQlYljDoibBKXSw+mjQBVs+2zUMqYb2ggYdyoztD6YEMY hrMAumimV4qSY+qmrcMo7cHnzA+crR8/ZwhJJQ+QDS8Lbv4X5jwzVJ0224HcG2FZjOsP sGFw== X-Gm-Message-State: AOAM533L4cDz8mz/y2W3pfzx/CenyWNE/67SBWkvE0W0wukGO52cg2bn myXpkRhbRgW0w3Pc7US2hrU= X-Google-Smtp-Source: ABdhPJxuBZXn592UMcBRFN/HRz1xjjWTl7dGVUaEYcIUVZQfLN3z206B2OpmliYgpIZP4Y2t2rnhjg== X-Received: by 2002:a05:6a00:1590:b0:50d:f473:c346 with SMTP id u16-20020a056a00159000b0050df473c346mr16017357pfk.27.1651733312876; Wed, 04 May 2022 23:48:32 -0700 (PDT) Received: from google.com ([2620:15c:211:201:8435:b3e7:62fc:4dfa]) by smtp.gmail.com with ESMTPSA id u2-20020a170902e80200b0015e8d4eb1casm693010plg.20.2022.05.04.23.48.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 May 2022 23:48:32 -0700 (PDT) Date: Wed, 4 May 2022 23:48:30 -0700 From: Minchan Kim To: David Hildenbrand Cc: Andrew Morton , linux-mm , LKML , John Hubbard , John Dias Subject: Re: [PATCH] mm: fix is_pinnable_page against on cma page Message-ID: References: <20220502173558.2510641-1-minchan@kernel.org> <29d0c1c3-a44e-4573-7e7e-32be07544dbe@redhat.com> <08e9855c-395d-f40c-de3d-1ec8b644bfe8@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 40D10C0081 X-Stat-Signature: phhggoredf1sja4yskfpnxf6owzk8dhe X-Rspam-User: Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=cB22BeNO; spf=pass (imf10.hostedemail.com: domain of minchan.kim@gmail.com designates 209.85.210.180 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) X-HE-Tag: 1651733297-606108 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, May 04, 2022 at 03:48:54PM -0700, Minchan Kim wrote: > On Tue, May 03, 2022 at 06:02:33PM +0200, David Hildenbrand wrote: > > On 03.05.22 17:26, Minchan Kim wrote: > > > On Tue, May 03, 2022 at 03:15:24AM +0200, David Hildenbrand wrote: > > >> > > >>>>>> However, I assume we have the same issue right now already with > > >>>> ZONE_MOVABLE and MIGRATE_CMA when trying to pin a page residing on these > > >>> > > >>> ZONE_MOVALBE is also changed dynamically? > > >>> > > >> > > >> Sorry, with "same issue" I meant failing to pin if having to migrate and > > >> the page is temporarily unmovable. > > >> > > >>>> there are temporarily unmovable and we fail to migrate. But it would now > > >>>> apply even without ZONE_MOVABLE or MIGRATE_CMA. Hm... > > >>> > > >>> Didn't parse your last mention. > > >> > > >> On a system that neither uses ZONE_MOVABLE nor MIGRATE_CMA we might have > > >> to migrate now when pinning. > > > > > > I don't understand your point. My problem is pin_user_pages with > > > FOLL_LONGTERM. It shouldn't pin a page from ZONE_MOVABLE and cma area > > > without migrating page out of movable zone or CMA area. > > > That's why try_grab_folio checks whether target page stays in those > > > movable areas. However, to check CMA area, is_migrate_cma_page is > > > racy so the FOLL_LONGTERM flag semantic is broken right now. > > > > > > Do you see any problem of the fix? > > > > My point is that you might decide to migrate a page because you stumble > > over MIGRATE_ISOLATE, although there is no need to reject long-term > > pinning and to trigger page migration. > > > > Assume a system without ZONE_MOVABLE and without MIGRATE_CMA. Assume > > someone reserves gigantic pages (alloc_contig_range()) and you have > > concurrent long-term pinning on a page that is no MIGRATE_ISOLATE. > > > > GUP would see MIGRATE_ISOLATE and would reject pinning. The page has to > > be migrated, which can fail if the page is temporarily unmovable. > > A dump question since I'm not familiar with hugetlb. > > Is above reasonable scenario? > > The gigantic page is about to be created using alloc_contig_range so > they has MIGRATE_ISOLATE as temporal state. It means no one uses the > page yet so I guess the page is not mapped at userspace but other is > trying to access the page using pin_user_pages? > Too dump question. Never mind. Posted v2 - https://lore.kernel.org/all/20220505064429.2818496-1-minchan@kernel.org/T/#u Thanks.