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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 18275C56201 for ; Tue, 10 Nov 2020 05:43:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4D19207BC for ; Tue, 10 Nov 2020 05:43:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731924AbgKJFm4 (ORCPT ); Tue, 10 Nov 2020 00:42:56 -0500 Received: from mx2.suse.de ([195.135.220.15]:41040 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729801AbgKJFm4 (ORCPT ); Tue, 10 Nov 2020 00:42:56 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B02C6ABDE; Tue, 10 Nov 2020 05:42:54 +0000 (UTC) Date: Tue, 10 Nov 2020 06:42:50 +0100 From: Oscar Salvador To: Muchun Song 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 , Matthew Wilcox , Michal Hocko , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Subject: Re: [External] Re: [PATCH v3 05/21] mm/hugetlb: Introduce pgtable allocation/freeing helpers Message-ID: <20201110054250.GA2906@localhost.localdomain> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Nov 10, 2020 at 11:49:27AM +0800, Muchun Song wrote: > On Tue, Nov 10, 2020 at 1:21 AM Oscar Salvador wrote: > > > > On Sun, Nov 08, 2020 at 10:10:57PM +0800, Muchun Song wrote: > > > +static inline unsigned int pgtable_pages_to_prealloc_per_hpage(struct hstate *h) > > > +{ > > > + unsigned long vmemmap_size = vmemmap_pages_size_per_hpage(h); > > > + > > > + /* > > > + * No need pre-allocate page tabels when there is no vmemmap pages > > > + * to free. > > s /tabels/tables/ > > Thanks. > > > > > > +static int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page) > > > +{ > > > + int i; > > > + pgtable_t pgtable; > > > + unsigned int nr = pgtable_pages_to_prealloc_per_hpage(h); > > > + > > > + if (!nr) > > > + return 0; > > > + > > > + vmemmap_pgtable_init(page); > > > + > > > + for (i = 0; i < nr; i++) { > > > + pte_t *pte_p; > > > + > > > + pte_p = pte_alloc_one_kernel(&init_mm); > > > + if (!pte_p) > > > + goto out; > > > + vmemmap_pgtable_deposit(page, virt_to_page(pte_p)); > > > + } > > > + > > > + return 0; > > > +out: > > > + while (i-- && (pgtable = vmemmap_pgtable_withdraw(page))) > > > + pte_free_kernel(&init_mm, page_to_virt(pgtable)); > > > > would not be enough to: > > > > while (pgtable = vmemmap_pgtable_withdrag(page)) > > pte_free_kernel(&init_mm, page_to_virt(pgtable)); > > The vmemmap_pgtable_withdraw can not return NULL. So we can not > drop the "i--". Yeah, you are right, I managed to confuse myself. But why not make it return null, something like: static pgtable_t vmemmap_pgtable_withdraw(struct page *page) { pgtable_t pgtable; /* FIFO */ pgtable = page_huge_pte(page); page_huge_pte(page) = list_first_entry_or_null(&pgtable->lru, struct page, lru); if (page_huge_pte(page)) list_del(&pgtable->lru); return page_huge_pte(page) ? pgtable : NULL; } What do you think? -- Oscar Salvador SUSE L3