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Mon, 26 Oct 2020 16:01:43 +0000 Date: Mon, 26 Oct 2020 16:01:42 +0000 From: Matthew Wilcox To: Muchun Song Cc: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v2 07/19] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page Message-ID: <20201026160142.GT20115@casper.infradead.org> References: <20201026145114.59424-1-songmuchun@bytedance.com> <20201026145114.59424-8-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201026145114.59424-8-songmuchun@bytedance.com> 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 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.