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Wed, 2 Sep 2020 22:02:46 +0000 (UTC) X-HE-Tag: loaf05_0a17990270a4 X-Filterd-Recvd-Size: 4191 Received: from hqnvemgate25.nvidia.com (hqnvemgate25.nvidia.com [216.228.121.64]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Wed, 2 Sep 2020 22:02:45 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 02 Sep 2020 15:01:57 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 02 Sep 2020 15:02:44 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 02 Sep 2020 15:02:44 -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; Wed, 2 Sep 2020 22:02:43 +0000 Subject: Re: [PATCH v2 1/7] mm/thp: fix __split_huge_pmd_locked() for migration PMD To: Zi Yan CC: , , , , "Jerome Glisse" , John Hubbard , "Alistair Popple" , Christoph Hellwig , Jason Gunthorpe , Bharata B Rao , Ben Skeggs , Shuah Khan , Andrew Morton , References: <20200902165830.5367-1-rcampbell@nvidia.com> <20200902165830.5367-2-rcampbell@nvidia.com> <78B69571-13C6-4BF5-8478-6AAA4AB2C287@nvidia.com> From: Ralph Campbell X-Nvconfidentiality: public Message-ID: <171f31cd-91e5-5c74-a68a-ec7cbd9bb450@nvidia.com> Date: Wed, 2 Sep 2020 15:02:43 -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: <78B69571-13C6-4BF5-8478-6AAA4AB2C287@nvidia.com> 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=1599084117; bh=kkuRtxf1vezbhGt7LWXFhp9w3lxcVmX2TYTJjhJna0A=; 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=PYlXhRotiQZLfTXQ3wUKaNi2lAIqWGmhDdY0PnXG5Z+lN/QCMYFo0RG5cTDV6WwFH CnfNo7aO+sfSX2fI+lJwU6aarLglAM/a5KXmMrCwp2e1o9Baq4M81nd71iUwdUgx// uZ/a2+LKxSXP2G1SaaWWxXeK+62Cc8u3wUAa1bnCoMsdwDkTq4p9UjZ7iM9A35rRXq JIFyutr6uKQ66rQKeR1y+8M4g0+cnTjIYBu59SdC1oEOjQqwNU4m4C6gP6n5Hhq5ba bJJgl8MHVyNQvB3qHhrFcZXNGUdYAp0il6xrP4DrP96t1panNvmqFIm5/Wpc+h4Dk6 GwYzA74WFlDOQ== X-Rspamd-Queue-Id: 591E1180F8B81 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: On 9/2/20 2:47 PM, Zi Yan wrote: > On 2 Sep 2020, at 12:58, Ralph Campbell wrote: >=20 >> 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 PM= D. >> 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) instea= d >> 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 >=20 > Thanks for the fix. You can add Reviewed-by: Zi Yan >=20 > I think you also want to add the Fixes tag and cc stable. >=20 > Fixes 84c3fc4e9c56 (=E2=80=9Cmm: thp: check pmd migration entry in common= path=E2=80=9D) > cc: stable@vger.kernel.org # 4.14+ Thanks, I'll add these.