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=-13.1 required=3.0 tests=BAYES_00,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_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 5192BC2BD11 for ; Wed, 2 Sep 2020 16:58:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0F61D207EA for ; Wed, 2 Sep 2020 16:58:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="UuV7rEAu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0F61D207EA 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 34BD86B0071; Wed, 2 Sep 2020 12:58:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2D6736B0095; Wed, 2 Sep 2020 12:58:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F1A886B0099; Wed, 2 Sep 2020 12:58:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0066.hostedemail.com [216.40.44.66]) by kanga.kvack.org (Postfix) with ESMTP id CBD766B0073 for ; Wed, 2 Sep 2020 12:58:38 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 798EA3634 for ; Wed, 2 Sep 2020 16:58:38 +0000 (UTC) X-FDA: 77218730316.22.fan60_1b008ae270a2 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin22.hostedemail.com (Postfix) with ESMTP id 2F13218038E6A for ; Wed, 2 Sep 2020 16:58:38 +0000 (UTC) X-HE-Tag: fan60_1b008ae270a2 X-Filterd-Recvd-Size: 6137 Received: from hqnvemgate24.nvidia.com (hqnvemgate24.nvidia.com [216.228.121.143]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Wed, 2 Sep 2020 16:58:37 +0000 (UTC) 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== X-Rspamd-Queue-Id: 2F13218038E6A X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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: 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