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 E6437C71136 for ; Mon, 16 Jun 2025 16:13:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5E6616B00A5; Mon, 16 Jun 2025 12:13:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5BDB26B00A6; Mon, 16 Jun 2025 12:13:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4ACFB6B00A7; Mon, 16 Jun 2025 12:13:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 3A7426B00A5 for ; Mon, 16 Jun 2025 12:13:13 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 0BAE3BBCD1 for ; Mon, 16 Jun 2025 16:13:13 +0000 (UTC) X-FDA: 83561758266.29.A4EFED6 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf03.hostedemail.com (Postfix) with ESMTP id 8AE7C20003 for ; Mon, 16 Jun 2025 16:13:10 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=KwU9lGZC; spf=pass (imf03.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1750090390; 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=C/ZrxZaPZVNPwZIrMln0mxQuZIriBwZ6wz5MhRzlmy4=; b=j7zKjRum5TStLKGhj4b3UUvqWyHIjO9stGIHRXD6I1wFvT3IPW8cOA8iUMjbqJzOfiNwrV 1flzvx4VN1ecV5K7YiLo560VISNJJF5kqE3cl8FMrpGNG2B5jZXMGqeJJFJLZWzSv5Soz3 GmckySrQxuBwOnGrJa7EkgnN+iZMp1c= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1750090390; a=rsa-sha256; cv=none; b=Lz0qN6N4jTvFVmczA8XKkpPW98KuURe8WP8dKN/bwRbSfPhy83g/FVioD2KRmmxa1SpvG7 nAAKbBG3FQO0cgPDp7ak4iPB3ieKJYV3Xp6IE5NsNHCNh1lSjIi+V8xPaOMGWS4eYOVI2X i8UwK9BTp3AgIeDOsHu5iQf2LKlQlgc= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=KwU9lGZC; spf=pass (imf03.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1750090389; 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=C/ZrxZaPZVNPwZIrMln0mxQuZIriBwZ6wz5MhRzlmy4=; b=KwU9lGZC48a2X3A5Dp7QbYNx3o2v4j7FrB3/EzWzddc3uQDJo7Zx7RftMbtMET6lUVykot cm+QHKzV7CF6M5hIYLlcU5tkitwvQjnz8zvfjpxKYWUnw60hom1eGRWhz1Oko8uuH+yNuS VWxWtiQfS2D2IlDpNnikz1sP2DZsHKE= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-375-UFw_hToxPTGxoPqfUovUgw-1; Mon, 16 Jun 2025 12:13:08 -0400 X-MC-Unique: UFw_hToxPTGxoPqfUovUgw-1 X-Mimecast-MFC-AGG-ID: UFw_hToxPTGxoPqfUovUgw_1750090388 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-450d6768d4dso30733975e9.2 for ; Mon, 16 Jun 2025 09:13:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750090387; x=1750695187; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=C/ZrxZaPZVNPwZIrMln0mxQuZIriBwZ6wz5MhRzlmy4=; b=HTrXIM15CIrypaVMQQm9XOThintAglGf4wnH/062+oibBtdvxTPE1bjFTqI1m5l4KY 96NUH1C6mRnqI7aA1sw1/CRsIWiOSjqLdyHLK32SJS5wj7mSJnRWwTiSX93DndPD0tN5 qSRDJws73lqtI/fuB89OTxM8SF+Vzck6sNplSJLsj7H6/wbb7XUAupqYZtOucjg9g1g9 4aVNA2836PTCueN9s+P2gSTxM0AN0Mj1mEILStf8TRaBM/sGciPDPiWSe1wVnAFJMLGs FqFS43j4fMzHK9fd0mrfuIqxTE1cQ60C+kTCMer2WSzCRRftpu2GeZVMk+a4zpNejXho 0EBw== X-Forwarded-Encrypted: i=1; AJvYcCWNQGRFDWcOQhRl6trmyv2qhhAnabJ+sljPMhKwV3ExbQP5SCVK4e6eFBKhLTutos/pJyULCAKH+A==@kvack.org X-Gm-Message-State: AOJu0YwfwqGso2gFdtck0ZqM6EAU4qGsKB+VAnmy4pEcpEoq/lfid3FJ XMFhAFIDrb8vZiGR/dKCJA7mZsB9eFxSZFi0Rhyp367PmPQvwjj3DPZ4M6HO11zhO4GCIvhloYM TZkYEZPm6uKop/hjvfsycd/pA3y8GwyOG8dBNaTRorl/TUIHpx5Jp X-Gm-Gg: ASbGncveaOq/xkjDcmR33bl72tJNV8qXAg/ldPHXx9c9N/4FKNdJBX1hKs4+wtNUz71 IfaWV96jri+n9hQzJbzRE7O/J8Se5RDD4zYzaimjRt4tmssXchvzvyZvD7XIvFQMP6xvoJa7K0u nbBh2ztIFee8Y8oI0hLEvnBctHUgxwQAMGlfkbxWWaHVpr19A9w/cV6W7x5VaDcSM5AliTkfhIe hSkYRgkJA9zScE8nDEIApe7PkJG0FHJofVZqhkT5UpJncqMZmmWugy+4QLKTtYWd+btduZZa+tw KiAmOy73Cy7SWyemPRK9c6X43SbxUwf/HypT8NBa9tCbyN2WWXDH1LknZ5d+udRKxGZPGrmoF+Z uJk2rToDBrN23hZDY0T5UiumY0NQg/98FMT262Z4QcsUHWmM= X-Received: by 2002:a5d:64ca:0:b0:3a3:6a9a:5ebf with SMTP id ffacd0b85a97d-3a5723a352dmr9392051f8f.20.1750090387594; Mon, 16 Jun 2025 09:13:07 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHLTGh3YT8u9DxTJL0pbpY5buLKzRYbIG3/oyV4xEIsnWDco5W5TIdegHqyAXMbHJ4AR4gvMw== X-Received: by 2002:a5d:64ca:0:b0:3a3:6a9a:5ebf with SMTP id ffacd0b85a97d-3a5723a352dmr9392006f8f.20.1750090387113; Mon, 16 Jun 2025 09:13:07 -0700 (PDT) Received: from ?IPV6:2003:d8:2f25:bd00:949:b5a9:e02a:f265? (p200300d82f25bd000949b5a9e02af265.dip0.t-ipconnect.de. [2003:d8:2f25:bd00:949:b5a9:e02a:f265]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e244392sm148792785e9.22.2025.06.16.09.13.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Jun 2025 09:13:06 -0700 (PDT) Message-ID: Date: Mon, 16 Jun 2025 18:13:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/2] mm: Optimize mremap() by PTE batching To: Lorenzo Stoakes Cc: Dev Jain , akpm@linux-foundation.org, Liam.Howlett@oracle.com, vbabka@suse.cz, jannh@google.com, pfalcato@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, peterx@redhat.com, ryan.roberts@arm.com, mingo@kernel.org, libang.li@antgroup.com, maobibo@loongson.cn, zhengqi.arch@bytedance.com, baohua@kernel.org, anshuman.khandual@arm.com, willy@infradead.org, ioworker0@gmail.com, yang@os.amperecomputing.com, baolin.wang@linux.alibaba.com, ziy@nvidia.com, hughd@google.com References: <20250610035043.75448-1-dev.jain@arm.com> <20250610035043.75448-3-dev.jain@arm.com> <43d9cb6e-1b8f-47b9-8c19-58fc7c74a71e@redhat.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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: QJSbQEap3ONKGwue1BARqRmmwEYlURx9faecHCcHA98_1750090388 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 8AE7C20003 X-Stat-Signature: dnocoyidtjz5gs9y6w5cyezyjygq9gos X-HE-Tag: 1750090390-539554 X-HE-Meta: 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 4iNYvsm2 qzsN2JOIEbq80cZxOse6LY28IUIaoOYRy3Y79EUGlVHmZTXZ80szO+zgCDPvH0FtWC07phpWCbeklmCbS8vx2TzsfBY0zzn/EgP3AI9ki1HJhFGnp3nxv9RA8MdXMPUCFgUXezTNKUdUX5PcoHHBCDTWEdX4EwfsCcbeOvP0Y0HZTlpvaApLaWD7u/aZkj+PDbGQOPge4NqxOUozwc/RnyddYFJXmJr5LxfJlobwcJKJoIzpnt3o2U+rIUFGNLThHQLWBsSMw7iTaM7Psi42xxRgP6PpbYnKvDQgMikX4C/UmtkRtiwyyBeGAzrOGXO730hWhLlVJBa/GZUfTyugFVBhY6Gs/QcJomIGw0oHevvx3aboxFPW5OPluvXNQclUz3EB8KcC8l+nUORnhy8hE9HcPaQ== 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: [...] >>> } >>> - set_pte_at(mm, new_addr, new_ptep, pte); >>> + set_ptes(mm, new_addr, new_ptep, pte, nr_ptes); >> >> >> What I dislike is that some paths work on a single PTE, and we implicitly have to know >> that they don't apply for !pte_present. > > I hate any kind of implicit knowledge like this. > >> >> Like >> if (need_clear_uffd_wp && pte_marker_uffd_wp(pte)) > > I also despise [with words I cannot use on-list] how uffd is implemented. > > It's _nothing but_ ad-hoc stuff like this spawned all around the place. > > It's hateful. > >> >> Will not get batched yet. And that is hidden inside the pte_marker_uffd_wp check ... >> >> Should we properly separate both paths (present vs. !present), and while at it, do >> some more cleanups? I'm thinking of the following on top (only compile-tested) > > I'd like to see that, but I think maybe better as a follow up series? I'd do the split as a cleanup patch upfront. Then add the batching for the pte_present() case. > > On the other hand, this does improve this quite a bit. Could also be another > patch in the series. > >> >> >> diff --git a/mm/mremap.c b/mm/mremap.c >> index 18b215521adae..b88abf02b34e0 100644 >> --- a/mm/mremap.c >> +++ b/mm/mremap.c >> @@ -155,21 +155,6 @@ static void drop_rmap_locks(struct vm_area_struct *vma) >> i_mmap_unlock_write(vma->vm_file->f_mapping); >> } >> -static pte_t move_soft_dirty_pte(pte_t pte) >> -{ >> - /* >> - * Set soft dirty bit so we can notice >> - * in userspace the ptes were moved. >> - */ >> -#ifdef CONFIG_MEM_SOFT_DIRTY >> - if (pte_present(pte)) >> - pte = pte_mksoft_dirty(pte); >> - else if (is_swap_pte(pte)) >> - pte = pte_swp_mksoft_dirty(pte); >> -#endif >> - return pte; >> -} >> - >> static int mremap_folio_pte_batch(struct vm_area_struct *vma, unsigned long addr, >> pte_t *ptep, pte_t pte, int max_nr) >> { >> @@ -260,7 +245,6 @@ static int move_ptes(struct pagetable_move_control *pmc, >> VM_WARN_ON_ONCE(!pte_none(*new_ptep)); >> nr_ptes = 1; >> - max_nr_ptes = (old_end - old_addr) >> PAGE_SHIFT; >> old_pte = ptep_get(old_ptep); >> if (pte_none(old_pte)) >> continue; >> @@ -277,24 +261,34 @@ static int move_ptes(struct pagetable_move_control *pmc, >> * flushed. >> */ >> if (pte_present(old_pte)) { >> + max_nr_ptes = (old_end - old_addr) >> PAGE_SHIFT; >> nr_ptes = mremap_folio_pte_batch(vma, old_addr, old_ptep, >> old_pte, max_nr_ptes); >> force_flush = true; >> - } >> - pte = get_and_clear_full_ptes(mm, old_addr, old_ptep, nr_ptes, 0); >> - pte = move_pte(pte, old_addr, new_addr); >> - pte = move_soft_dirty_pte(pte); >> - >> - if (need_clear_uffd_wp && pte_marker_uffd_wp(pte)) >> - pte_clear(mm, new_addr, new_ptep); >> - else { >> - if (need_clear_uffd_wp) { >> - if (pte_present(pte)) >> - pte = pte_clear_uffd_wp(pte); >> - else if (is_swap_pte(pte)) >> + >> + pte = get_and_clear_full_ptes(mm, old_addr, old_ptep, >> + nr_ptes, 0); >> + /* >> + * Moving present PTEs requires special care on some >> + * archs. >> + */ >> + pte = move_pte(pte, old_addr, new_addr); > > I guess we're good with only doing this in pte_present() case because the only > arch that implements this, sparc, does a present check anyway. Yes, we could then remove the call from pte_present(), see below. > >> + /* make userspace aware that this pte moved. */ >> + pte = pte_mksoft_dirty(pte); >> + if (need_clear_uffd_wp) >> + pte = pte_clear_uffd_wp(pte); >> + set_ptes(mm, new_addr, new_ptep, pte, nr_ptes); >> + } else if (need_clear_uffd_wp && pte_marker_uffd_wp(pte)) { >> + pte_clear(mm, old_addr, old_ptep); > > Same comment as below re: pte_clear(). > > I see you've dropped pte_clear(mm, new_addr, new_ptep) which I guess is > purposefully? > > I do think that it is pointless yes. Yeah, that's what I raised below. > >> + } else { >> + pte_clear(mm, old_addr, old_ptep); > > I guess this is intended to replace ptep_get_and_clear_full_ptes() above in the > single PTE case... no? Is this sufficient? > > In the original code we'd always do ptep_get_and_clear(). > > I think the key difference is page_table_check_pte_clear(). > > I notice, hilariously, that there is a ptep_clear() that _does_ call this. What > a mess. ptep_get_and_clear() is only relevant when something is present and could change concurrently (especially A/D bits managed by HW). We already obtained the pte, it's not present, and now just want to clear it. > > >> + if (is_swap_pte(pte)) { >> + if (need_clear_uffd_wp) >> pte = pte_swp_clear_uffd_wp(pte); >> + /* make userspace aware that this pte moved. */ >> + pte = pte_swp_mksoft_dirty(pte); >> } >> - set_ptes(mm, new_addr, new_ptep, pte, nr_ptes); >> + set_pte_at(mm, new_addr, new_ptep, pte); >> } >> } >> >> >> Note that I don't know why we had the existing >> >> - if (need_clear_uffd_wp && pte_marker_uffd_wp(pte)) >> - pte_clear(mm, new_addr, new_ptep); >> >> >> I thought we would always expect that the destination pte is already pte_none() ? > > I think this is because we already did the move_pte() call in the original code > before checking this: Oh, maybe that's why. > > pte = get_and_clear_full_ptes(mm, old_addr, old_ptep, nr_ptes, 0); > pte = move_pte(pte, old_addr, new_addr); > pte = move_soft_dirty_pte(pte); > > if (need_clear_uffd_wp && pte_marker_uffd_wp(pte)) > pte_clear(mm, new_addr, new_ptep); > > But maybe it's because there was a presumption move_pte() would like you know, > move a PTE entry? Which it doesn't, it - only on SPARC - does a hook to flush > the dcache. I wish we could remove move_pte() completely. Or just notify about the move of a present pte ... because it doesn't ever modify the pte val. So renaming it to "arch_notify_move_pte()" or sth. like that that is a void function might even be better. ... I think we could go one step further if we already have the folio: we could call it arch_notify_move_folio_pte(), and simplify the sparc implementation ... Anyhow, the move_pte() cleanup can be done separately. Splitting the present from !present case here should probably be done as a cleanup upfront. -- Cheers, David / dhildenb