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[216.228.121.65]) by mx.google.com with ESMTPS id a65si20794631ywh.462.2019.07.29.16.42.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Jul 2019 16:42:08 -0700 (PDT) Received-SPF: pass (google.com: domain of rcampbell@nvidia.com designates 216.228.121.65 as permitted sender) client-ip=216.228.121.65; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b="dkCF/sqU"; spf=pass (google.com: domain of rcampbell@nvidia.com designates 216.228.121.65 as permitted sender) smtp.mailfrom=rcampbell@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate16.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 29 Jul 2019 16:42:07 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 29 Jul 2019 16:42:07 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 29 Jul 2019 16:42:07 -0700 Received: from rcampbell-dev.nvidia.com (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 29 Jul 2019 23:42:02 +0000 Subject: Re: [PATCH 9/9] mm: remove the MIGRATE_PFN_WRITE flag To: Christoph Hellwig , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jason Gunthorpe , Ben Skeggs CC: Bharata B Rao , Andrew Morton , , , , References: <20190729142843.22320-1-hch@lst.de> <20190729142843.22320-10-hch@lst.de> X-Nvconfidentiality: public From: Ralph Campbell Message-ID: <1f0ef337-6ca5-54fa-e627-41a46be73f2b@nvidia.com> Date: Mon, 29 Jul 2019 16:42:01 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190729142843.22320-10-hch@lst.de> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1564443727; bh=mEZj3q5EnGdFR96z4O+Iz+WRmNblkDEHHCZr6fLsRoI=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=dkCF/sqUubSJ16D0gzxWuIiRNyylExBkjSHrf+wBYiOEClAdNIcs4OLHo2fvbGIoX 1HoTvy5tiILWD6dBrPFwdRF2JWe6qCogaekLOh7Q9mzfJygH45h8qJ5PLN8swqY07T H1AJG4slDbp8zFXaoA4gVYQpxo9dk3Ja5/reP1N0iQzGM2uEGVxa5oPVE2ahLha6XU XU7vinMQxUun59ktKiGlAoPT5x2NslQA58ySa1FgSzuEL5AR9P4hKjpvOH9Ww28B4H /6XKbzh2v/KF3c26Bvn4BAaIQuv9vhITJ4xA1s6tfjdxhUZXgaQvU2ZRaV1RuodxD0 NRxR0aABTDx7Q== 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 7/29/19 7:28 AM, Christoph Hellwig wrote: > The MIGRATE_PFN_WRITE is only used locally in migrate_vma_collect_pmd, > where it can be replaced with a simple boolean local variable. > > Signed-off-by: Christoph Hellwig Reviewed-by: Ralph Campbell > --- > include/linux/migrate.h | 1 - > mm/migrate.c | 9 +++++---- > 2 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index 8b46cfdb1a0e..ba74ef5a7702 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -165,7 +165,6 @@ static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm, > #define MIGRATE_PFN_VALID (1UL << 0) > #define MIGRATE_PFN_MIGRATE (1UL << 1) > #define MIGRATE_PFN_LOCKED (1UL << 2) > -#define MIGRATE_PFN_WRITE (1UL << 3) > #define MIGRATE_PFN_SHIFT 6 > > static inline struct page *migrate_pfn_to_page(unsigned long mpfn) > diff --git a/mm/migrate.c b/mm/migrate.c > index 74735256e260..724f92dcc31b 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2212,6 +2212,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > unsigned long mpfn, pfn; > struct page *page; > swp_entry_t entry; > + bool writable = false; > pte_t pte; > > pte = *ptep; > @@ -2240,7 +2241,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > mpfn = migrate_pfn(page_to_pfn(page)) | > MIGRATE_PFN_MIGRATE; > if (is_write_device_private_entry(entry)) > - mpfn |= MIGRATE_PFN_WRITE; > + writable = true; > } else { > if (is_zero_pfn(pfn)) { > mpfn = MIGRATE_PFN_MIGRATE; > @@ -2250,7 +2251,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > } > page = vm_normal_page(migrate->vma, addr, pte); > mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE; > - mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0; > + if (pte_write(pte)) > + writable = true; > } > > /* FIXME support THP */ > @@ -2284,8 +2286,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > ptep_get_and_clear(mm, addr, ptep); > > /* Setup special migration page table entry */ > - entry = make_migration_entry(page, mpfn & > - MIGRATE_PFN_WRITE); > + entry = make_migration_entry(page, writable); > swp_pte = swp_entry_to_pte(entry); > if (pte_soft_dirty(pte)) > swp_pte = pte_swp_mksoft_dirty(swp_pte); > MIGRATE_PFN_WRITE may mot being used but that seems like a bug to me. If a page is migrated to device memory, it could be mapped at the same time to avoid a device page fault but it would need the flag to know whether to map it RW or RO. But I suppose that could be inferred from the vma->vm_flags.