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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4265C001B3 for ; Tue, 27 Jun 2023 07:29:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231332AbjF0H3j (ORCPT ); Tue, 27 Jun 2023 03:29:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229828AbjF0H3W (ORCPT ); Tue, 27 Jun 2023 03:29:22 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 40761F5; Tue, 27 Jun 2023 00:29:06 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A0B162F4; Tue, 27 Jun 2023 00:22:11 -0700 (PDT) Received: from [10.57.76.16] (unknown [10.57.76.16]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 26E843F663; Tue, 27 Jun 2023 00:21:24 -0700 (PDT) Message-ID: <2ff8ccf6-bf36-48b2-7dc2-e6c0d962f8b7@arm.com> Date: Tue, 27 Jun 2023 08:21:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v1 01/10] mm: Expose clear_huge_page() unconditionally To: Yu Zhao Cc: Andrew Morton , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , Yin Fengwei , David Hildenbrand , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-s390@vger.kernel.org References: <20230626171430.3167004-1-ryan.roberts@arm.com> <20230626171430.3167004-2-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/06/2023 02:55, Yu Zhao wrote: > On Mon, Jun 26, 2023 at 11:14 AM Ryan Roberts wrote: >> >> In preparation for extending vma_alloc_zeroed_movable_folio() to >> allocate a arbitrary order folio, expose clear_huge_page() >> unconditionally, so that it can be used to zero the allocated folio in >> the generic implementation of vma_alloc_zeroed_movable_folio(). >> >> Signed-off-by: Ryan Roberts >> --- >> include/linux/mm.h | 3 ++- >> mm/memory.c | 2 +- >> 2 files changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index 7f1741bd870a..7e3bf45e6491 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -3684,10 +3684,11 @@ enum mf_action_page_type { >> */ >> extern const struct attribute_group memory_failure_attr_group; >> >> -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS) >> extern void clear_huge_page(struct page *page, >> unsigned long addr_hint, >> unsigned int pages_per_huge_page); >> + >> +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS) > > We might not want to depend on THP eventually. Right now, we still > have to, unless splitting is optional, which seems to contradict > 06/10. (deferred_split_folio() is a nop without THP.) Yes, I agree - for large anon folios to work, we depend on THP. But I don't think that helps us here. In the next patch, I give vma_alloc_zeroed_movable_folio() an extra `order` parameter. So the generic/default version of the function now needs a way to clear a compound page. I guess I could do something like: static inline struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma, unsigned long vaddr, gfp_t gfp, int order) { struct folio *folio; folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE | gfp, order, vma, vaddr, false); if (folio) { #ifdef CONFIG_LARGE_FOLIO clear_huge_page(&folio->page, vaddr, 1U << order); #else BUG_ON(order != 0); clear_user_highpage(&folio->page, vaddr); #endif } return folio; } But that's pretty messy and there's no reason why other users might come along that pass order != 0 and will be surprised by the BUG_ON.