From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70806145A18 for ; Tue, 30 Jul 2024 15:49:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722354558; cv=none; b=WC5+Xt04AgZewog9P6uS4GX7WizqaBoKiPo7Csjcbe9c6Q4EzO+uAYsr9RJXUQ+m0WcXFmRF29MGd+iy2v/W6ns+z0Q9nd1iQh3FYl729ei0jpS9KA7VAB0i2ERdOL42zFSqAzTggmmsy7jLHFy54+HkMJIVTL9qIKIPVyxbqM4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722354558; c=relaxed/simple; bh=3VNOrrTG7GfKdUncVfrkg1AqRAJShRz9sEI61Jm2lv0=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=ko083bxVbESP5FFNIzY5z7q/sfhwLzECw5YJ5H8Oh7Ni5Eaqx4CijWmyHRi1KWtkweNIoSzff7Lkegx+8MglWcbdDS2AnAPihtpzZXe52TTwUWQeg7Szibs75E4OPDodIEOhWmY0bakcZP2gE5QE3gLeO677vHUzchfCf+EwKio= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Yapr8ZdA; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Yapr8ZdA" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722354555; 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=Xi8KbBbM4q6iVh9OwAGJirNn1W3JeV89B3/oDQFc+xU=; b=Yapr8ZdAryjIWy+uOM7sNgssVvmmSzNLjYAwHprEFU4ebrsqDkdPXLjfDqRwCe0t3zQHOq D2yHzk6lcEiwR894jsSEwqJzad0LN88Fc5dQkKZZlfgchJqY+ISXunALaYHz8gkfqpYcyv BE2JSLaqR2sBih1Vn2/BUDJ3dU+fQTU= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-352-h10chnNbMTWkXhKbxY7FPw-1; Tue, 30 Jul 2024 11:49:13 -0400 X-MC-Unique: h10chnNbMTWkXhKbxY7FPw-1 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-4281b7196bbso21057765e9.0 for ; Tue, 30 Jul 2024 08:49:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722354552; x=1722959352; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:references:cc:to:from:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=Xi8KbBbM4q6iVh9OwAGJirNn1W3JeV89B3/oDQFc+xU=; b=wZUrjH+pgVCPyZYvQZgmx2A+LDbqCYjRhN6KTSNZmVMrJ9oqAo1e999ythoiY93hCP ttN4l9lhWaG1sIbnEKKWqsliZXqbO+MpO9EbPI76TTONtUUNuvbBO9J7Tx8m49SUvOtv dFButsiL90LP6Yuj4CdN+fXa52JMdKQxL23drQAmdlYjWi/L+AW62HxeXtbSWn7curAO j+ACq/hkGTUtq1jUrxkvcI8SVPFSnsFJcvi+kkv0fOOzl3kPeklY9q5vj6ytZzUdsa3z hIxl1dN/IQecxW9836TZIBcVRGTJwJ0QvQTgT6to1FSbO2W4Msnxl+w2rSLf26Ba6plU bO6w== X-Forwarded-Encrypted: i=1; AJvYcCVA+bRAhQq35LilOidG4hZM86JEjDy9m2gQ7te6m/vsy5SRhFpiEl8v+uYdaqImtiC23v/4m1cIDNbduHtX7yS6htgo5ttmUCyRJ0TB X-Gm-Message-State: AOJu0YyPirGIuzNKoeH4zdhsdJ/MYAtDjnRBEuOtwr7naP30ohXOFrvp hzTHo0GPxxTtUaDorpZ2fMwFVKSerefMIh7KVu71gQV60ClDX7o9KgfFUTt9BWGo4eLEIvT1uqM rlWLQFPgywtNxKI9BsxXAnAnT7eWw3CYMuhz0g8JGL2FVZDang32mEzM65HlQsg== X-Received: by 2002:a05:600c:3112:b0:426:61e8:fb35 with SMTP id 5b1f17b1804b1-42811d82e26mr77457315e9.4.1722354552514; Tue, 30 Jul 2024 08:49:12 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEr0B0yPEx0e3k4hDKqbbpw4/6BdLrwMzEeOuOS/C1/U1jdQ2i0XfyJ0Kx7vQD0jbmjhCp3Kw== X-Received: by 2002:a05:600c:3112:b0:426:61e8:fb35 with SMTP id 5b1f17b1804b1-42811d82e26mr77457225e9.4.1722354552068; Tue, 30 Jul 2024 08:49:12 -0700 (PDT) Received: from ?IPV6:2003:cb:c706:4e00:31ad:5274:e21c:b59? (p200300cbc7064e0031ad5274e21c0b59.dip0.t-ipconnect.de. [2003:cb:c706:4e00:31ad:5274:e21c:b59]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4281c3cc71fsm88211015e9.39.2024.07.30.08.49.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Jul 2024 08:49:11 -0700 (PDT) Message-ID: <82e77547-5116-4ef2-a232-f5ab1fca7e02@redhat.com> Date: Tue, 30 Jul 2024 17:49:10 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/2] mm: let pte_lockptr() consume a pte_t pointer From: David Hildenbrand To: Marek Szyprowski , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Muchun Song , Peter Xu , Oscar Salvador References: <20240725183955.2268884-1-david@redhat.com> <20240725183955.2268884-2-david@redhat.com> <97d87df8-6076-4df0-90a9-a8f5ddea42e9@samsung.com> Content-Language: en-US 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 30.07.24 17:45, David Hildenbrand wrote: > On 30.07.24 17:30, Marek Szyprowski wrote: >> On 25.07.2024 20:39, David Hildenbrand wrote: >>> pte_lockptr() is the only *_lockptr() function that doesn't consume >>> what would be expected: it consumes a pmd_t pointer instead of a pte_t >>> pointer. >>> >>> Let's change that. The two callers in pgtable-generic.c are easily >>> adjusted. Adjust khugepaged.c:retract_page_tables() to simply do a >>> pte_offset_map_nolock() to obtain the lock, even though we won't actually >>> be traversing the page table. >>> >>> This makes the code more similar to the other variants and avoids other >>> hacks to make the new pte_lockptr() version happy. pte_lockptr() users >>> reside now only in pgtable-generic.c. >>> >>> Maybe, using pte_offset_map_nolock() is the right thing to do because >>> the PTE table could have been removed in the meantime? At least it sounds >>> more future proof if we ever have other means of page table reclaim. >>> >>> It's not quite clear if holding the PTE table lock is really required: >>> what if someone else obtains the lock just after we unlock it? But we'll >>> leave that as is for now, maybe there are good reasons. >>> >>> This is a preparation for adapting hugetlb page table locking logic to >>> take the same locks as core-mm page table walkers would. >>> >>> Signed-off-by: David Hildenbrand >> >> This patch landed in today's linux-next as commit e98970a1d2d4 ("mm: let >> pte_lockptr() consume a pte_t pointer"). Unfortunately it causes the >> following issue on most of my ARM 32bit based test boards: >> > > That is ... rather surprising. > > The issue below seems to point at __pte_offset_map_lock(), where we > essentially convert from > > ptlock_ptr(page_ptdesc(pmd_page(*pmd))); > > to > > ptlock_ptr(virt_to_ptdesc(pte)); I'm wondering, is highmem involved here such that the PTE would be kmap'ed and virt_to_page() would not do what we would expect it to do? -- Cheers, David / dhildenb