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c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2r/6wM2urus7RuK+nJNOIaHAlYFuE3iJoIvxfk3Ke04=; b=siwAM2hmDi3nYsZ+FeQprU0Se9gdXMyqbYh6vOCUQAXHnWTEtNVjuYi/9DznBH7Mo/ YgL7qEhc0bfsjyPObJVgGQLJKEoesdm3aR8v1vmNQiqLj0LZxsZOL6i5VR6K3M4j/7av cHJO4yM8l3yUiy4dRqlgveLc/DAg8P9W9VLOs2vLfo+lyVllaTXc1XNhapP9uBZ/fpNH rlFZyhjWoEH3dGvMek7PJq9Lj/OobQ0yRCxpCRgdNBi7i3idvUnKv4CHUmbkBwLTtv44 zDYmRag3ClPA/D/KSkWOBCgNHFYPHnOfM7ogyZCBeU8CElw5fxxjBnAPIqkANbpn+GBI Gc3Q== X-Gm-Message-State: AOAM530YSW+Oor2am94sfWELZkF+mwk95tCo39do0VqBIpvhq6oHNVCF XsN6jGcEj5Xjl6/2ViN64vI6eozHZTWljE2B2cy1MA== X-Google-Smtp-Source: ABdhPJyWYIE4OTNvD1Li2UgYskyIXudRuzoDpQ5mbVNn2nBDoaVGbFjNKzwuIOmIbtQ3Tu3mU4VqlNbMc44uum/3l/c= X-Received: by 2002:a65:5383:: with SMTP id x3mr15962pgq.341.1603767552671; Mon, 26 Oct 2020 19:59:12 -0700 (PDT) MIME-Version: 1.0 References: <20201026145114.59424-1-songmuchun@bytedance.com> <20201026145114.59424-8-songmuchun@bytedance.com> <20201026160142.GT20115@casper.infradead.org> In-Reply-To: <20201026160142.GT20115@casper.infradead.org> From: Muchun Song Date: Tue, 27 Oct 2020 10:58:36 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v2 07/19] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page To: Matthew Wilcox Cc: Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" 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 Tue, Oct 27, 2020 at 12:01 AM Matthew Wilcox wrote: > > On Mon, Oct 26, 2020 at 10:51:02PM +0800, Muchun Song wrote: > > +static void split_vmemmap_pmd(pmd_t *pmd, pte_t *pte_p, unsigned long addr) > > +{ > > + struct mm_struct *mm = &init_mm; > > + struct page *page; > > + pmd_t old_pmd, _pmd; > > + int i; > > + > > + old_pmd = READ_ONCE(*pmd); > > + page = pmd_page(old_pmd); > > + pmd_populate_kernel(mm, &_pmd, pte_p); > > + > > + for (i = 0; i < VMEMMAP_HPAGE_NR; i++, addr += PAGE_SIZE) { > > + pte_t entry, *pte; > > + > > + entry = mk_pte(page + i, PAGE_KERNEL); > > I'd be happier if that were: > > pgprot_t pgprot = PAGE_KERNEL; > ... > for (i = 0; i < VMEMMAP_HPAGE_NR; i++, addr += PAGE_SIZE) { > pte_t entry, *pte; > > entry = mk_pte(page + i, pgprot); > pgprot = PAGE_KERNEL_RO; > > so that all subsequent tail pages are mapped read-only. > Good idea, do this can catch some illegal operations. Thanks. -- Yours, Muchun