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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CEBFC624B4 for ; Thu, 23 Nov 2023 12:12:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6A0AA6B0636; Thu, 23 Nov 2023 07:12:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 64FF96B0638; Thu, 23 Nov 2023 07:12:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4CA416B063A; Thu, 23 Nov 2023 07:12:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 3B56A6B0636 for ; Thu, 23 Nov 2023 07:12:45 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id A2B8A1CBE92 for ; Thu, 23 Nov 2023 12:12:44 +0000 (UTC) X-FDA: 81489107448.08.CFB21E5 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf02.hostedemail.com (Postfix) with ESMTP id 7004380025 for ; Thu, 23 Nov 2023 12:12:41 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=YWxdwKti; spf=pass (imf02.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1700741561; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=br8PZpiDxHycNKjGY2IqHlXCn3cwGOqUyLD1EtqcwYk=; b=x9FCcGrVbi+VLO8KAH9R6RY7UQi+fLXRhUTj3hy7MqJUjAo7bsJQe1oYdrAz8zthnaLZsY NAWjrnKFFDzwQqaNGGRUe7i+IFNWi5OHX6kHBLHqYd9RztcHMB9j5L7OOFEBzdQAJ6J0o8 MUmMHHhq0J7+B2fT5beZBnch7k8BcKQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1700741561; a=rsa-sha256; cv=none; b=KKuYEzZDKPPesrNCtrMqnLN8KOTgDNWUsqKGzRDgjkzaK/WOSGftMp5WDgRXL1ET5Gamsi nsI7NokDo5uh32eriz21+Bg0JF8G+F/SrsyuSUqSJLuvWjww06Q6s+DZj/8sbaixaoacWL Q1xkzslm2UaTnNlZWTddePWPXfsXuu8= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=YWxdwKti; spf=pass (imf02.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700741560; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=br8PZpiDxHycNKjGY2IqHlXCn3cwGOqUyLD1EtqcwYk=; b=YWxdwKtiSzSvD0j/26cD5iffbtWtS+5vPvQhXMPd7F0r62ZesPHItwdAqQAkgLS0BGc6Ec /3NTizhjwLNVTL43DElTClNluoD6pU76sXYYz1ni5phNy+evoJHp5AHc80Fu3BF1ZiN/1R CLIYvBDoz+aQC016pgkCez4YIIqmOeg= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-627-8iu5lZ_ZNkSp3vhCd9vVsg-1; Thu, 23 Nov 2023 07:12:37 -0500 X-MC-Unique: 8iu5lZ_ZNkSp3vhCd9vVsg-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-408524e2368so4031445e9.0 for ; Thu, 23 Nov 2023 04:12:37 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1700741556; x=1701346356; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :references:cc:to:content-language:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=br8PZpiDxHycNKjGY2IqHlXCn3cwGOqUyLD1EtqcwYk=; b=RHg3LC8IZyvX2nsQ0ubfteQ181ym0QpPd5MqwfvMPM3cZsTvuXn0hDc3P51VgDaGNn kNxueduiCQXdqS/WKZO/2+itrPE/F5SoGCDc4A8hpGUZHg7b6Eq0C6x6Ug9Huk2G3iWm jrKCsmCXeuwa9t9TCIIhHcStB+U+c/ecOw23VKfPPcyOEIDw3DBjIFiHjz2jUAl4kHph pzQVKSklJBp3WXgUVd17Cq9Cq4lZUNRMQRhLZppJOOwddUzyyc5st8Oxl2oTjnzrtcCK aOkS8F0KBngEN2Zj6QU/8QTFLqHKKX/xJUkYuc1xthuTALTit/bOHTLFS5U3PG6G2X1x bpBQ== X-Gm-Message-State: AOJu0YynnDTWpi3VzP/vCH48i9X8Sfj3yGVyPFtmXh0LpHF09VVb9iZZ HHl8dP7/Ypcch/pYpq899RMwQ7so0eP4UkUIdR1ZJXRHue3u50gbgUoQdQzjna2296kwfn+3YGT 4UgDf8wUBsKg= X-Received: by 2002:a05:600c:3516:b0:40b:2a06:be27 with SMTP id h22-20020a05600c351600b0040b2a06be27mr3684772wmq.35.1700741556070; Thu, 23 Nov 2023 04:12:36 -0800 (PST) X-Google-Smtp-Source: AGHT+IFoLy3xdIe8KATXYjVxuk+/JNXP7Zo6WlFJRDLs7tki2lDO8ExLqeBirh/uSGwKYADLJgr7Kw== X-Received: by 2002:a05:600c:3516:b0:40b:2a06:be27 with SMTP id h22-20020a05600c351600b0040b2a06be27mr3684752wmq.35.1700741555519; Thu, 23 Nov 2023 04:12:35 -0800 (PST) Received: from ?IPV6:2003:cb:c716:c800:ed2f:91bf:8c46:7078? (p200300cbc716c800ed2f91bf8c467078.dip0.t-ipconnect.de. [2003:cb:c716:c800:ed2f:91bf:8c46:7078]) by smtp.gmail.com with ESMTPSA id m23-20020a056000025700b00332ce0d7300sm1501635wrz.92.2023.11.23.04.12.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Nov 2023 04:12:35 -0800 (PST) Message-ID: <15e2c6cb-e86d-417b-b83d-7c7459d5be8f@redhat.com> Date: Thu, 23 Nov 2023 13:12:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 01/14] mm: Batch-copy PTE ranges during fork() To: Ryan Roberts , Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Zenghui Yu , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Anshuman Khandual , Matthew Wilcox , Yu Zhao , Mark Rutland , Kefeng Wang , John Hubbard , Zi Yan Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20231115163018.1303287-1-ryan.roberts@arm.com> <20231115163018.1303287-2-ryan.roberts@arm.com> <89a9fe07-a5c5-4a99-b588-e6145053c58f@redhat.com> <1459f78b-e80c-4f21-bc65-f0ab259d348a@arm.com> <08ef2c36-2b9c-4b96-9d1d-68cca0f68ba5@redhat.com> <2d027a8d-adfb-481d-89ea-c99139e669aa@arm.com> <2618b024-6a95-4bfc-a08d-59d86e9931e5@redhat.com> <118eb2d3-d504-49f0-b7f2-f29b64a8f404@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <118eb2d3-d504-49f0-b7f2-f29b64a8f404@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: c555kw9i1t5ue9nwhrpkceeid8853tos X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7004380025 X-Rspam-User: X-HE-Tag: 1700741561-425066 X-HE-Meta: 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 Ul0HgLif 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 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: List-Subscribe: List-Unsubscribe: On 23.11.23 11:26, Ryan Roberts wrote: > On 16/11/2023 14:15, David Hildenbrand wrote: >> On 16.11.23 15:13, David Hildenbrand wrote: >>> On 16.11.23 14:49, Ryan Roberts wrote: >>>> On 16/11/2023 13:20, David Hildenbrand wrote: >>>>> On 16.11.23 12:20, Ryan Roberts wrote: >>>>>> On 16/11/2023 11:03, David Hildenbrand wrote: >>>>>>> On 15.11.23 17:30, Ryan Roberts wrote: >>>>>>>> Convert copy_pte_range() to copy a set of ptes in a batch. A given batch >>>>>>>> maps a physically contiguous block of memory, all belonging to the same >>>>>>>> folio, with the same permissions, and for shared mappings, the same >>>>>>>> dirty state. This will likely improve performance by a tiny amount due >>>>>>>> to batching the folio reference count management and calling set_ptes() >>>>>>>> rather than making individual calls to set_pte_at(). >>>>>>>> >>>>>>>> However, the primary motivation for this change is to reduce the number >>>>>>>> of tlb maintenance operations that the arm64 backend has to perform >>>>>>>> during fork, as it is about to add transparent support for the >>>>>>>> "contiguous bit" in its ptes. By write-protecting the parent using the >>>>>>>> new ptep_set_wrprotects() (note the 's' at the end) function, the >>>>>>>> backend can avoid having to unfold contig ranges of PTEs, which is >>>>>>>> expensive, when all ptes in the range are being write-protected. >>>>>>>> Similarly, by using set_ptes() rather than set_pte_at() to set up ptes >>>>>>>> in the child, the backend does not need to fold a contiguous range once >>>>>>>> they are all populated - they can be initially populated as a contiguous >>>>>>>> range in the first place. >>>>>>>> >>>>>>>> This change addresses the core-mm refactoring only, and introduces >>>>>>>> ptep_set_wrprotects() with a default implementation that calls >>>>>>>> ptep_set_wrprotect() for each pte in the range. A separate change will >>>>>>>> implement ptep_set_wrprotects() in the arm64 backend to realize the >>>>>>>> performance improvement as part of the work to enable contpte mappings. >>>>>>>> >>>>>>>> Signed-off-by: Ryan Roberts >>>>>>>> --- >>>>>>>>      include/linux/pgtable.h |  13 +++ >>>>>>>>      mm/memory.c             | 175 +++++++++++++++++++++++++++++++--------- >>>>>>>>      2 files changed, 150 insertions(+), 38 deletions(-) >>>>>>>> >>>>>>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>>>>>>> index af7639c3b0a3..1c50f8a0fdde 100644 >>>>>>>> --- a/include/linux/pgtable.h >>>>>>>> +++ b/include/linux/pgtable.h >>>>>>>> @@ -622,6 +622,19 @@ static inline void ptep_set_wrprotect(struct mm_struct >>>>>>>> *mm, unsigned long addres >>>>>>>>      } >>>>>>>>      #endif >>>>>>>>      +#ifndef ptep_set_wrprotects >>>>>>>> +struct mm_struct; >>>>>>>> +static inline void ptep_set_wrprotects(struct mm_struct *mm, >>>>>>>> +                unsigned long address, pte_t *ptep, >>>>>>>> +                unsigned int nr) >>>>>>>> +{ >>>>>>>> +    unsigned int i; >>>>>>>> + >>>>>>>> +    for (i = 0; i < nr; i++, address += PAGE_SIZE, ptep++) >>>>>>>> +        ptep_set_wrprotect(mm, address, ptep); >>>>>>>> +} >>>>>>>> +#endif >>>>>>>> + >>>>>>>>      /* >>>>>>>>       * On some architectures hardware does not set page access bit when >>>>>>>> accessing >>>>>>>>       * memory page, it is responsibility of software setting this bit. >>>>>>>> It brings >>>>>>>> diff --git a/mm/memory.c b/mm/memory.c >>>>>>>> index 1f18ed4a5497..b7c8228883cf 100644 >>>>>>>> --- a/mm/memory.c >>>>>>>> +++ b/mm/memory.c >>>>>>>> @@ -921,46 +921,129 @@ copy_present_page(struct vm_area_struct *dst_vma, >>>>>>>> struct vm_area_struct *src_vma >>>>>>>>              /* Uffd-wp needs to be delivered to dest pte as well */ >>>>>>>>              pte = pte_mkuffd_wp(pte); >>>>>>>>          set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte); >>>>>>>> -    return 0; >>>>>>>> +    return 1; >>>>>>>> +} >>>>>>>> + >>>>>>>> +static inline unsigned long page_cont_mapped_vaddr(struct page *page, >>>>>>>> +                struct page *anchor, unsigned long anchor_vaddr) >>>>>>>> +{ >>>>>>>> +    unsigned long offset; >>>>>>>> +    unsigned long vaddr; >>>>>>>> + >>>>>>>> +    offset = (page_to_pfn(page) - page_to_pfn(anchor)) << PAGE_SHIFT; >>>>>>>> +    vaddr = anchor_vaddr + offset; >>>>>>>> + >>>>>>>> +    if (anchor > page) { >>>>>>>> +        if (vaddr > anchor_vaddr) >>>>>>>> +            return 0; >>>>>>>> +    } else { >>>>>>>> +        if (vaddr < anchor_vaddr) >>>>>>>> +            return ULONG_MAX; >>>>>>>> +    } >>>>>>>> + >>>>>>>> +    return vaddr; >>>>>>>> +} >>>>>>>> + >>>>>>>> +static int folio_nr_pages_cont_mapped(struct folio *folio, >>>>>>>> +                      struct page *page, pte_t *pte, >>>>>>>> +                      unsigned long addr, unsigned long end, >>>>>>>> +                      pte_t ptent, bool *any_dirty) >>>>>>>> +{ >>>>>>>> +    int floops; >>>>>>>> +    int i; >>>>>>>> +    unsigned long pfn; >>>>>>>> +    pgprot_t prot; >>>>>>>> +    struct page *folio_end; >>>>>>>> + >>>>>>>> +    if (!folio_test_large(folio)) >>>>>>>> +        return 1; >>>>>>>> + >>>>>>>> +    folio_end = &folio->page + folio_nr_pages(folio); >>>>>>>> +    end = min(page_cont_mapped_vaddr(folio_end, page, addr), end); >>>>>>>> +    floops = (end - addr) >> PAGE_SHIFT; >>>>>>>> +    pfn = page_to_pfn(page); >>>>>>>> +    prot = pte_pgprot(pte_mkold(pte_mkclean(ptent))); >>>>>>>> + >>>>>>>> +    *any_dirty = pte_dirty(ptent); >>>>>>>> + >>>>>>>> +    pfn++; >>>>>>>> +    pte++; >>>>>>>> + >>>>>>>> +    for (i = 1; i < floops; i++) { >>>>>>>> +        ptent = ptep_get(pte); >>>>>>>> +        ptent = pte_mkold(pte_mkclean(ptent)); >>>>>>>> + >>>>>>>> +        if (!pte_present(ptent) || pte_pfn(ptent) != pfn || >>>>>>>> +            pgprot_val(pte_pgprot(ptent)) != pgprot_val(prot)) >>>>>>>> +            break; >>>>>>>> + >>>>>>>> +        if (pte_dirty(ptent)) >>>>>>>> +            *any_dirty = true; >>>>>>>> + >>>>>>>> +        pfn++; >>>>>>>> +        pte++; >>>>>>>> +    } >>>>>>>> + >>>>>>>> +    return i; >>>>>>>>      } >>>>>>>>        /* >>>>>>>> - * Copy one pte.  Returns 0 if succeeded, or -EAGAIN if one preallocated >>>>>>>> page >>>>>>>> - * is required to copy this pte. >>>>>>>> + * Copy set of contiguous ptes.  Returns number of ptes copied if succeeded >>>>>>>> + * (always gte 1), or -EAGAIN if one preallocated page is required to >>>>>>>> copy the >>>>>>>> + * first pte. >>>>>>>>       */ >>>>>>>>      static inline int >>>>>>>> -copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct >>>>>>>> *src_vma, >>>>>>>> -         pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss, >>>>>>>> -         struct folio **prealloc) >>>>>>>> +copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct >>>>>>>> *src_vma, >>>>>>>> +          pte_t *dst_pte, pte_t *src_pte, >>>>>>>> +          unsigned long addr, unsigned long end, >>>>>>>> +          int *rss, struct folio **prealloc) >>>>>>>>      { >>>>>>>>          struct mm_struct *src_mm = src_vma->vm_mm; >>>>>>>>          unsigned long vm_flags = src_vma->vm_flags; >>>>>>>>          pte_t pte = ptep_get(src_pte); >>>>>>>>          struct page *page; >>>>>>>>          struct folio *folio; >>>>>>>> +    int nr = 1; >>>>>>>> +    bool anon; >>>>>>>> +    bool any_dirty = pte_dirty(pte); >>>>>>>> +    int i; >>>>>>>>            page = vm_normal_page(src_vma, addr, pte); >>>>>>>> -    if (page) >>>>>>>> +    if (page) { >>>>>>>>              folio = page_folio(page); >>>>>>>> -    if (page && folio_test_anon(folio)) { >>>>>>>> -        /* >>>>>>>> -         * If this page may have been pinned by the parent process, >>>>>>>> -         * copy the page immediately for the child so that we'll always >>>>>>>> -         * guarantee the pinned page won't be randomly replaced in the >>>>>>>> -         * future. >>>>>>>> -         */ >>>>>>>> -        folio_get(folio); >>>>>>>> -        if (unlikely(page_try_dup_anon_rmap(page, false, src_vma))) { >>>>>>>> -            /* Page may be pinned, we have to copy. */ >>>>>>>> -            folio_put(folio); >>>>>>>> -            return copy_present_page(dst_vma, src_vma, dst_pte, src_pte, >>>>>>>> -                         addr, rss, prealloc, page); >>>>>>>> +        anon = folio_test_anon(folio); >>>>>>>> +        nr = folio_nr_pages_cont_mapped(folio, page, src_pte, addr, >>>>>>>> +                        end, pte, &any_dirty); >>>>>>>> + >>>>>>>> +        for (i = 0; i < nr; i++, page++) { >>>>>>>> +            if (anon) { >>>>>>>> +                /* >>>>>>>> +                 * If this page may have been pinned by the >>>>>>>> +                 * parent process, copy the page immediately for >>>>>>>> +                 * the child so that we'll always guarantee the >>>>>>>> +                 * pinned page won't be randomly replaced in the >>>>>>>> +                 * future. >>>>>>>> +                 */ >>>>>>>> +                if (unlikely(page_try_dup_anon_rmap( >>>>>>>> +                        page, false, src_vma))) { >>>>>>>> +                    if (i != 0) >>>>>>>> +                        break; >>>>>>>> +                    /* Page may be pinned, we have to copy. */ >>>>>>>> +                    return copy_present_page( >>>>>>>> +                        dst_vma, src_vma, dst_pte, >>>>>>>> +                        src_pte, addr, rss, prealloc, >>>>>>>> +                        page); >>>>>>>> +                } >>>>>>>> +                rss[MM_ANONPAGES]++; >>>>>>>> +                VM_BUG_ON(PageAnonExclusive(page)); >>>>>>>> +            } else { >>>>>>>> +                page_dup_file_rmap(page, false); >>>>>>>> +                rss[mm_counter_file(page)]++; >>>>>>>> +            } >>>>>>>>              } >>>>>>>> -        rss[MM_ANONPAGES]++; >>>>>>>> -    } else if (page) { >>>>>>>> -        folio_get(folio); >>>>>>>> -        page_dup_file_rmap(page, false); >>>>>>>> -        rss[mm_counter_file(page)]++; >>>>>>>> + >>>>>>>> +        nr = i; >>>>>>>> +        folio_ref_add(folio, nr); >>>>>>>>          } >>>>>>>>            /* >>>>>>>> @@ -968,24 +1051,28 @@ copy_present_pte(struct vm_area_struct *dst_vma, >>>>>>>> struct >>>>>>>> vm_area_struct *src_vma, >>>>>>>>           * in the parent and the child >>>>>>>>           */ >>>>>>>>          if (is_cow_mapping(vm_flags) && pte_write(pte)) { >>>>>>>> -        ptep_set_wrprotect(src_mm, addr, src_pte); >>>>>>>> +        ptep_set_wrprotects(src_mm, addr, src_pte, nr); >>>>>>>>              pte = pte_wrprotect(pte); >>>>>>> >>>>>>> You likely want an "any_pte_writable" check here instead, no? >>>>>>> >>>>>>> Any operations that target a single indiividual PTE while multiple PTEs are >>>>>>> adjusted are suspicious :) >>>>>> >>>>>> The idea is that I've already constrained the batch of pages such that the >>>>>> permissions are all the same (see folio_nr_pages_cont_mapped()). So if the >>>>>> first >>>>>> pte is writable, then they all are - something has gone badly wrong if some >>>>>> are >>>>>> writable and others are not. >>>>> >>>>> I wonder if it would be cleaner and easier to not do that, though. >>>>> >>>>> Simply record if any pte is writable. Afterwards they will *all* be R/O and you >>>>> can set the cont bit, correct? >>>> >>>> Oh I see what you mean - that only works for cow mappings though. If you have a >>>> shared mapping, you won't be making it read-only at fork. So if we ignore >>>> pte_write() state when demarking the batches, we will end up with a batch of >>>> pages with a mix of RO and RW in the parent, but then we set_ptes() for the >>>> child and those pages will all have the permissions of the first page of the >>>> batch. >>> >>> I see what you mean. >>> >>> After fork(), all anon pages will be R/O in the parent and the child. >>> Easy. If any PTE is writable, wrprotect all in the parent and the child. >>> >>> After fork(), all shared pages can be R/O or R/W in the parent. For >>> simplicity, I think you can simply set them all R/O in the child. So if >>> any PTE is writable, wrprotect all in the child. >> >> Or better: if any is R/O, set them all R/O. Otherwise just leave them as is. > > I've just come back to this to code it up, and want to clarify this last > comment; I'm already going to have to collect any_writable for the anon case, so > I will already have that info for the shared case too. I think you are > suggesting I *additionally* collect any_readonly, then in the shared case, I > only apply wrprotect if (any_writable && any_readonly). i.e. only apply > wrprotect if there is a mix of permissions for the batch, otherwise all the > permissions are the same (either all RW or all RO) and I can elide the wrprotet. > Is that what you meant? Yes. I suspect you might somehow be able to derive "any_readonly = nr - !any_writable". Within a VMA, we really should only see: * writable VMA: some might be R/O, some might be R/W * VMA applicable to NUMA hinting: some might be PROT_NONE, others R/O or R/W One could simply skip batching for now on pte_protnone() and focus on the "writable" vs. "not-writable". -- Cheers, David / dhildenb