Received: by 2002:a05:6a10:22f:0:0:0:0 with SMTP id 15csp613670pxk; Wed, 2 Sep 2020 10:05:37 -0700 (PDT) X-Google-Smtp-Source: ABdhPJw1ApG8ihFyqtm8FrnN4HKUDbxp2Lvm8RVSARasG0UKIkzmNyLEXadGCLKjzcO4LiMOYCJi X-Received: by 2002:a50:fc83:: with SMTP id f3mr1008730edq.256.1599066337561; Wed, 02 Sep 2020 10:05:37 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1599066337; cv=none; d=google.com; s=arc-20160816; b=NTLH9EG1nsDftVvxYkGl69JHxgB414FilM4Xu/scZP5nwtkuis7XXVSvjm2csw5w/l NWZufhGqqJ3lUnE8tLDUL9UAu59EpEySINWs/wx5J5ar6+bcKsn7TwtylXxKae6ELI39 S7rpsHJQTFVRjWJilOo/1cepm85gYlB+9zLzOYlO0eAIONjmdH1R/fcLu8Oek/7ChIyJ YPc2bV6IV5oqbLTGKv6YS/mMeVuRhDZBboJSvuZISI/4NQ7bGDF/45soyqLj0ROzrUEh nZyaA8a/+gyc36Yf/Xvg7CEflSSVZB8PxbSaqHE2gC5f0S05kmDd9kLtzwlrkE7y4Prh N4SQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:dkim-signature:content-transfer-encoding :mime-version:references:in-reply-to:message-id:date:subject:cc:to :from; bh=rYznWX/3ek3S83R/7nq7shz57nrdV/4Q+HZHpdHukkI=; b=XZWGvxjCEIbgHrwBFC5MY54ZBc6PyRf/agDYwAeFGxsY0tQ8rwHFwmC6Ot9taojUmX bXBZEVDoJwuDCzqQLQv42Yhz5CaAqqUhzFUFAn5N58Fv17HKadJXI3G42S/1pvQr7FUy LkQH7J6HljgxkGC7SjlIBZ3hA6lUfJYrT+5J83+SgfeDUUV2eN8EWGyOlGqc9mBqOV25 DQjVm2gSjRJZPqhMyE06puzpwC/c/dqaF7Nss1H9v5+4jjP+uGuGypiquiHKyEkl4zCb npAs8X4de30lHQ6gPymTEqOCTLsNTaOKQA5tnK3TjdsVBsGqm7tZKo40n8IPqxxAnitm tmpw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=UuV7rEAu; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id s22si53886ejj.630.2020.09.02.10.05.13; Wed, 02 Sep 2020 10:05:37 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=UuV7rEAu; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728464AbgIBQ6p (ORCPT + 99 others); Wed, 2 Sep 2020 12:58:45 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:10769 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728418AbgIBQ6j (ORCPT ); Wed, 2 Sep 2020 12:58:39 -0400 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 02 Sep 2020 09:56:28 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Wed, 02 Sep 2020 09:58:36 -0700 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Wed, 02 Sep 2020 09:58:36 -0700 Received: from HQMAIL101.nvidia.com (172.20.187.10) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 2 Sep 2020 16:58:35 +0000 Received: from hqnvemgw03.nvidia.com (10.124.88.68) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Wed, 2 Sep 2020 16:58:35 +0000 Received: from rcampbell-dev.nvidia.com (Not Verified[10.110.48.66]) by hqnvemgw03.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Wed, 02 Sep 2020 09:58:35 -0700 From: Ralph Campbell To: , , , CC: Jerome Glisse , John Hubbard , Alistair Popple , Christoph Hellwig , Jason Gunthorpe , Bharata B Rao , Ben Skeggs , Shuah Khan , Andrew Morton , Ralph Campbell Subject: [PATCH v2 1/7] mm/thp: fix __split_huge_pmd_locked() for migration PMD Date: Wed, 2 Sep 2020 09:58:24 -0700 Message-ID: <20200902165830.5367-2-rcampbell@nvidia.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200902165830.5367-1-rcampbell@nvidia.com> References: <20200902165830.5367-1-rcampbell@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: quoted-printable Content-Type: text/plain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1599065788; bh=rYznWX/3ek3S83R/7nq7shz57nrdV/4Q+HZHpdHukkI=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=UuV7rEAutskEk3OCoCdPdBe6gOlmH/ZAhnWtJDfMYT0NTh+pvndsN15Tz3easb3Ns Rw1AZsD/UIX3dsS6tZs9MF8t4KZk4EkyC9a/zfDNF91ULaQYYwgWo+1lyQw6ghegAj 7b1+UKbB1rIZUMGwJ393qEydUIxuKq2enGDw3lxEdWnd1NFYlaT6NYd1/LshOIVCre MYHQqUrKh00QlOGM759IN1pT/I9LM68S4Ni6bn2k0IBRGJMzpJNNgg+Xcxhx/hf5+T 8sKcmGSNF+FNHsej6fZYSfrR6IaovFTJokeCvDqqWsD5w/zyYIX2JHUAmd9+v+d0hR E76dIGIbzcvMA== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A migrating transparent huge page has to already be unmapped. Otherwise, the page could be modified while it is being copied to a new page and data could be lost. The function __split_huge_pmd() checks for a PMD migration entry before calling __split_huge_pmd_locked() leading one to think that __split_huge_pmd_locked() can handle splitting a migrating PMD. However, the code always increments the page->_mapcount and adjusts the memory control group accounting assuming the page is mapped. Also, if the PMD entry is a migration PMD entry, the call to is_huge_zero_pmd(*pmd) is incorrect because it calls pmd_pfn(pmd) instead of migration_entry_to_pfn(pmd_to_swp_entry(pmd)). Fix these problems by checking for a PMD migration entry. Signed-off-by: Ralph Campbell --- mm/huge_memory.c | 42 +++++++++++++++++++++++------------------- 1 file changed, 23 insertions(+), 19 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2a468a4acb0a..606d712d9505 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2023,7 +2023,7 @@ static void __split_huge_pmd_locked(struct vm_area_st= ruct *vma, pmd_t *pmd, put_page(page); add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); return; - } else if (is_huge_zero_pmd(*pmd)) { + } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) { /* * FIXME: Do we want to invalidate secondary mmu by calling * mmu_notifier_invalidate_range() see comments below inside @@ -2117,30 +2117,34 @@ static void __split_huge_pmd_locked(struct vm_area_= struct *vma, pmd_t *pmd, pte =3D pte_offset_map(&_pmd, addr); BUG_ON(!pte_none(*pte)); set_pte_at(mm, addr, pte, entry); - atomic_inc(&page[i]._mapcount); - pte_unmap(pte); - } - - /* - * Set PG_double_map before dropping compound_mapcount to avoid - * false-negative page_mapped(). - */ - if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { - for (i =3D 0; i < HPAGE_PMD_NR; i++) + if (!pmd_migration) atomic_inc(&page[i]._mapcount); + pte_unmap(pte); } =20 - lock_page_memcg(page); - if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { - /* Last compound_mapcount is gone. */ - __dec_lruvec_page_state(page, NR_ANON_THPS); - if (TestClearPageDoubleMap(page)) { - /* No need in mapcount reference anymore */ + if (!pmd_migration) { + /* + * Set PG_double_map before dropping compound_mapcount to avoid + * false-negative page_mapped(). + */ + if (compound_mapcount(page) > 1 && + !TestSetPageDoubleMap(page)) { for (i =3D 0; i < HPAGE_PMD_NR; i++) - atomic_dec(&page[i]._mapcount); + atomic_inc(&page[i]._mapcount); + } + + lock_page_memcg(page); + if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { + /* Last compound_mapcount is gone. */ + __dec_lruvec_page_state(page, NR_ANON_THPS); + if (TestClearPageDoubleMap(page)) { + /* No need in mapcount reference anymore */ + for (i =3D 0; i < HPAGE_PMD_NR; i++) + atomic_dec(&page[i]._mapcount); + } } + unlock_page_memcg(page); } - unlock_page_memcg(page); =20 smp_wmb(); /* make pte visible before pmd */ pmd_populate(mm, pmd, pgtable); --=20 2.20.1