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=-10.1 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, URIBL_BLOCKED autolearn=unavailable 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 41628C43461 for ; Wed, 2 Sep 2020 21:47:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 048D920758 for ; Wed, 2 Sep 2020 21:47:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="Sxs0HfRX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 048D920758 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 93704900022; Wed, 2 Sep 2020 17:47:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8E6C890000C; Wed, 2 Sep 2020 17:47:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7FC64900022; Wed, 2 Sep 2020 17:47:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0140.hostedemail.com [216.40.44.140]) by kanga.kvack.org (Postfix) with ESMTP id 6A25090000C for ; Wed, 2 Sep 2020 17:47:18 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id EF0551F06 for ; Wed, 2 Sep 2020 21:47:17 +0000 (UTC) X-FDA: 77219457714.28.debt17_2b10f2a270a4 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin28.hostedemail.com (Postfix) with ESMTP id C05C46C04 for ; Wed, 2 Sep 2020 21:47:17 +0000 (UTC) X-HE-Tag: debt17_2b10f2a270a4 X-Filterd-Recvd-Size: 7817 Received: from hqnvemgate24.nvidia.com (hqnvemgate24.nvidia.com [216.228.121.143]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Wed, 2 Sep 2020 21:47:16 +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 14:45:07 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Wed, 02 Sep 2020 14:47:15 -0700 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Wed, 02 Sep 2020 14:47:15 -0700 Received: from [10.2.161.253] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 2 Sep 2020 21:47:13 +0000 From: Zi Yan To: Ralph Campbell CC: , , , , "Jerome Glisse" , John Hubbard , "Alistair Popple" , Christoph Hellwig , Jason Gunthorpe , Bharata B Rao , Ben Skeggs , Shuah Khan , Andrew Morton , Subject: Re: [PATCH v2 1/7] mm/thp: fix __split_huge_pmd_locked() for migration PMD Date: Wed, 2 Sep 2020 17:47:10 -0400 X-Mailer: MailMate (1.13.1r5705) Message-ID: <78B69571-13C6-4BF5-8478-6AAA4AB2C287@nvidia.com> In-Reply-To: <20200902165830.5367-2-rcampbell@nvidia.com> References: <20200902165830.5367-1-rcampbell@nvidia.com> <20200902165830.5367-2-rcampbell@nvidia.com> MIME-Version: 1.0 X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: multipart/signed; boundary="=_MailMate_73631622-91D5-4F7B-9B08-2022739FCA8C_="; micalg=pgp-sha512; protocol="application/pgp-signature" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1599083107; bh=SZek1ZYQANXJT4VXlmp7MHjIQWueJPTMM8g01GnOGfQ=; h=X-PGP-Universal:From:To:CC:Subject:Date:X-Mailer:Message-ID: In-Reply-To:References:MIME-Version:X-Originating-IP: X-ClientProxiedBy:Content-Type; b=Sxs0HfRXu2g3r8QL5KmEF7wT2mHFg/ypmWRuBkArGct5jJkkS5WzYJrumWzk7nc4c b55YSPGbQhBBwE/77G9wVGG7YNr8dGfe6PdFMrcDIyb4yK7o/TZ2Xlc93rXbKFhg9r EQRO9BhOZgZCtMaf5rXnzP2C2j6gOJeElK4waNbd19aGTpfRLgSAOHSUhJJ/EitGZ5 LZVRadQNUj6VLmDXM1g5DCHaeMgTEYFjq9Wm1PaDeGB42HfvH3goVfzlyFOQHmf6JQ 28ncSFI/lCOE/B47LXbsfq//gd4rP0Hs3PZUkmofJhtMJ0cBOF72amG6cZUYwQ4l0l Mb1+X4w/lDC5Q== X-Rspamd-Queue-Id: C05C46C04 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: --=_MailMate_73631622-91D5-4F7B-9B08-2022739FCA8C_= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On 2 Sep 2020, at 12:58, Ralph Campbell wrote: > 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 P= MD. > 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) inste= ad > 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 Thanks for the fix. You can add Reviewed-by: Zi Yan I think you also want to add the Fixes tag and cc stable. Fixes 84c3fc4e9c56 (=E2=80=9Cmm: thp: check pmd migration entry in common= path=E2=80=9D) cc: stable@vger.kernel.org # 4.14+ > --- > 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_are= a_struct *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_a= rea_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); > } > > - 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); > > smp_wmb(); /* make pte visible before pmd */ > pmd_populate(mm, pmd, pgtable); > -- = > 2.20.1 =E2=80=94 Best Regards, Yan Zi --=_MailMate_73631622-91D5-4F7B-9B08-2022739FCA8C_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQJDBAEBCgAtFiEEh7yFAW3gwjwQ4C9anbJR82th+ooFAl9QEt4PHHppeUBudmlk aWEuY29tAAoJEJ2yUfNrYfqK2RAP/jZpNOlzIVAWu/HetcUk0JekLJU2qVRUKD7w +vSoB3QfAzbbHrEr44ZKzWHGYIADV2eun8GOlaY4U9I+V9d8VTJ7X6rPF4/P3Mj9 quvN3yVi9/GJnqYpBDD15L+p90SylE5lGwe+4zje5AYbq6BIj5l3fB6m3rNR0D9G 0Wx9BdnmPs6cMPkCz4Aj9nXX6LOVu7zlKb3FJPBO2NUoZnkQpda3wRzpd/0DVrj8 rGVNw+QtnjAcKZtH2St005dB/qb0Z1ng83dgmN3KNJRZWYRYetN3lF79vUU59iGn Kwcc+T4vDX8ZkzldCILIYi4qsWH7oqqTkoOT8oqHFzj4u3ZXttnvdeiE+cavZrUr QbgubSF9I7Sm4zheJ+LJEC53Wn8up8jbfdsbyzPXEFJbfozmTr8hK4gODmtAUNz9 KevDlttqqrf/BBGHoV94RnLt2wMMt9RyUwlpu6t1ETzRhO+vPKknji0h4DyX3o2v T7n3dbRN8uPNOEBabzrXeGDwlsqXbnzYdVEZTojuD5Umer3+36832TAOndjj4Zep pJEM3YCeoG4INtDDv0HlzNugZ9bwEaz1Hm4zicAlxqeiw7g19auPlNBvt3bsBALE LwW82R2jQGTNn7OtuMz5d7WVNAjtCnmGndupISnL1VI1lPcS+g933m4KRGGgDytN zdwgbnGP =A3iO -----END PGP SIGNATURE----- --=_MailMate_73631622-91D5-4F7B-9B08-2022739FCA8C_=--