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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 67350C46CD2 for ; Tue, 30 Jan 2024 08:21:05 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4TPJ5r0xXjz3bvy for ; Tue, 30 Jan 2024 19:21:04 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=ryan.roberts@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4TPJ5M3Zg1z2yVT for ; Tue, 30 Jan 2024 19:20:38 +1100 (AEDT) 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 923B3DA7; Tue, 30 Jan 2024 00:20:50 -0800 (PST) Received: from [10.57.79.54] (unknown [10.57.79.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D4FD33F738; Tue, 30 Jan 2024 00:20:03 -0800 (PST) Message-ID: <7d25f28f-67fe-4bb8-b686-61f4f96471e5@arm.com> Date: Tue, 30 Jan 2024 08:20:02 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/9] mm/memory: handle !page case in zap_present_pte() separately Content-Language: en-GB To: David Hildenbrand , linux-kernel@vger.kernel.org References: <20240129143221.263763-1-david@redhat.com> <20240129143221.263763-3-david@redhat.com> From: Ryan Roberts In-Reply-To: <20240129143221.263763-3-david@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Alexander Gordeev , Christian Borntraeger , Arnd Bergmann , Vasily Gorbik , Peter Zijlstra , "Aneesh Kumar K.V" , linuxppc-dev@lists.ozlabs.org, Matthew Wilcox , linux-mm@kvack.org, Nick Piggin , Catalin Marinas , "Naveen N. Rao" , Andrew Morton , Will Deacon , Heiko Carstens , Sven Schnelle Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 29/01/2024 14:32, David Hildenbrand wrote: > We don't need uptodate accessed/dirty bits, so in theory we could > replace ptep_get_and_clear_full() by an optimized ptep_clear_full() > function. Let's rely on the provided pte. > > Further, there is no scenario where we would have to insert uffd-wp > markers when zapping something that is not a normal page (i.e., zeropage). > Add a sanity check to make sure this remains true. > > should_zap_folio() no longer has to handle NULL pointers. This change > replaces 2/3 "!page/!folio" checks by a single "!page" one. > > Signed-off-by: David Hildenbrand Reviewed-by: Ryan Roberts > --- > mm/memory.c | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 50a6c79c78fc..69502cdc0a7d 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1497,10 +1497,6 @@ static inline bool should_zap_folio(struct zap_details *details, > if (should_zap_cows(details)) > return true; > > - /* E.g. the caller passes NULL for the case of a zero folio */ > - if (!folio) > - return true; > - > /* Otherwise we should only zap non-anon folios */ > return !folio_test_anon(folio); > } > @@ -1543,19 +1539,23 @@ static inline void zap_present_pte(struct mmu_gather *tlb, > struct page *page; > > page = vm_normal_page(vma, addr, ptent); > - if (page) > - folio = page_folio(page); > + if (!page) { > + /* We don't need up-to-date accessed/dirty bits. */ > + ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); > + arch_check_zapped_pte(vma, ptent); > + tlb_remove_tlb_entry(tlb, pte, addr); > + VM_WARN_ON_ONCE(userfaultfd_wp(vma)); > + ksm_might_unmap_zero_page(mm, ptent); > + return; > + } > > + folio = page_folio(page); > if (unlikely(!should_zap_folio(details, folio))) > return; > ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); > arch_check_zapped_pte(vma, ptent); > tlb_remove_tlb_entry(tlb, pte, addr); > zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent); > - if (unlikely(!page)) { > - ksm_might_unmap_zero_page(mm, ptent); > - return; > - } > > if (!folio_test_anon(folio)) { > if (pte_dirty(ptent)) {