From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 B98952F0C66 for ; Wed, 27 Aug 2025 11:56:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756295779; cv=none; b=aEima4k7ORhRk+okfku+qYHswY9sM9g1eV0vMmnzjLxomG3W1Rwst6mF9N7k1OFRfBdQj46vM0iZBygDYp0gPTZTD04y428jSJnRn4arc5gX+vBUTQBwe7fgHbWdPDtrczOhg4e4bx+kbb12vmEF/qEtoGXVUxxTSYlN2jRLT44= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756295779; c=relaxed/simple; bh=qWNuJq1pI1gUfa8dF93j+5XqoglzDjHXlUFmD/BAW/g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Rv07fp878IguGgnL5DY7WyEd1BsM0cZOgg5l7m9Nh0SG7LZRjmJQ948k74sJd/mVky/QwlQiETv0Q0iV1ePobYDTZuLLMObHDuWbyV+Yd/jgmnHpedrVQsH+hTiEoQZTFnH8SFUJ4H6iJ4j+ihif+tcxPEuWkv9vducrpsyT65o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=Wx5o7ttt; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="Wx5o7ttt" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1756295776; 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=UcP+MKIMKTIXme29nP4iQa3HplkH4GbIfVhPmf/w8b4=; b=Wx5o7ttt0tnBE5qCgHCWUMS3bD3hOqWmkbUcayrQlqqcsFHXB/3l/wNT8rUELLpbEXSank NnOEikjS2mJ8HML4mPJfzMV4WE4+yAJYw56tacBL8cx9CXmKJWs/cbrE44H3w2J2EltnkJ snn4+gwogqdUxi5WAzqMn7gq6xTz/lo= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-533-BMnZbrdSPJynBh2Q9leoCg-1; Wed, 27 Aug 2025 07:56:15 -0400 X-MC-Unique: BMnZbrdSPJynBh2Q9leoCg-1 X-Mimecast-MFC-AGG-ID: BMnZbrdSPJynBh2Q9leoCg_1756295774 Received: by mail-qv1-f71.google.com with SMTP id 6a1803df08f44-70ddd80d02fso9987586d6.1 for ; Wed, 27 Aug 2025 04:56:14 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756295774; x=1756900574; h=content-transfer-encoding:in-reply-to: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=UcP+MKIMKTIXme29nP4iQa3HplkH4GbIfVhPmf/w8b4=; b=RPt/MJNBh353ZgJqe3CiKUf3I0mlvlJQ28s7twFQDQxkWCv3IGNFvqMhCThgVPyeJX 7BVQA2kC5UaqZN6ZQql2x3o1F+I1NcbnYt2OW0d1ijob4q/4227yw45X6j6PijYtobOi IkPE9/siZ0/4CkLPCBAZaZkKl1BGvl3WV+mdd++O4qB1O2OC9uddAmy6ZvQACKRzxW1p 4V9ZLP2Dsg3NvjpRVxWW9XClpIyu0LunWAxHz8zFUPSjYjPDwURWyrXLJAEIdUtMf1hB /ukvWwztvR33oGjNhbg8CmQ0VunCNVCd2c1mQuJlWyLKvA56ISRDXu1RBEgOOKkv6ZeH QEUA== X-Forwarded-Encrypted: i=1; AJvYcCU1v7aBTN3NcTN7RehEY3W/dRPI49v1HsRVW6IYDA1PvUiWRW/hlcun+vvoHLj0557NxlVQt9w3ozjCXvc=@vger.kernel.org X-Gm-Message-State: AOJu0YxbkQ+XSkkNQYFd764E6S4OTirw/suche1215kjPHN/PBmWEdyV kpi00lT9SSc0/mZ1n+i3ykMWI/N36McuCjRgOMMjG1rog31Pmdkk101+mfak759Dpcm8afzUR1s jYfLmL8EMwX32M4WM7cfvAB6co7yRuEG94H7ElXM4vvEHrHwzGhBEJRPxuwfQ3LRQFg== X-Gm-Gg: ASbGncsLexyPfYyDiAt5b634ym3bY82WxCM6WqRXmsmjZrLVNq0Egbu40gCcXqStFHr h3nWkd9VSma9TaOAKwA7R3r0RRcwIKwjWod9CAIqX0yGxn+IgkVR4pif1rzedBkhyojavC+z75E rVcpk5PPo0w3K9AiZCKB+eIWRTb0vMYH+H3i5iDhReDDutXeCl1xgLMGZGRu6g34lIGcw9GRQRd 8JtCA4UobImO5T3Du749O7te0f6/AyLalU0GHhOwh9Wdnlq/jIZDg/yC3Y76kCs8PKVPLJ1OMbs +CgFSrlbsi1XJQlsR0/FFZsP2VnOzuoW9a7kWcTRcDXoKSRqtCje0CiIKtMKnQ== X-Received: by 2002:a05:6214:1d09:b0:70d:b0d3:e50c with SMTP id 6a1803df08f44-70db0d3f0b8mr164309576d6.3.1756295773992; Wed, 27 Aug 2025 04:56:13 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGP+7/f9Dza6Dboh0+crUGjlYh2k6wyTyltwaqvnIJ5dLoNHOMhcL4Qv2lqiKTxRR93kuSh9A== X-Received: by 2002:a05:6214:1d09:b0:70d:b0d3:e50c with SMTP id 6a1803df08f44-70db0d3f0b8mr164309146d6.3.1756295773424; Wed, 27 Aug 2025 04:56:13 -0700 (PDT) Received: from [10.32.64.156] (nat-pool-muc-t.redhat.com. [149.14.88.26]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-70da717df65sm81671596d6.30.2025.08.27.04.56.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Aug 2025 04:56:12 -0700 (PDT) Message-ID: <11a5d391-3a13-4376-98f1-34b529d3c583@redhat.com> Date: Wed, 27 Aug 2025 13:56:09 +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 1/2] huge_mm.h: is_huge_zero_folio(NULL) should return false To: Max Kellermann Cc: Andrew Morton , lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, shikemeng@huaweicloud.com, kasong@tencent.com, nphamcs@gmail.com, bhe@redhat.com, chrisl@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250826231626.218675-1-max.kellermann@ionos.com> <20250826185515.7fbe1821713195b170ac1b31@linux-foundation.org> From: David Hildenbrand 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 27.08.25 12:13, Max Kellermann wrote: > On Wed, Aug 27, 2025 at 11:36 AM David Hildenbrand wrote: >> Why should it be allowed to pass in garbage (folio == NULL) into a >> function that operates on valid folios? > > This patch isn't about the function parameter but about the global > variable being NULL. > (Don't mix up with my other patch.) Huh? "Calling is_huge_zero_folio(NULL) should not be legal - it makes no sense, and a different (theoretical) implementation may dereference the pointer." And then "But currently, lacking any explicit documentation, this call is legal." No. It isn't. It never was. -- Cheers David / dhildenb