From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 05F72563FCB; Wed, 14 Oct 2026 18:30:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792002603; cv=none; b=oOreQRkVlN4s9dMgVHTR2HI+3TMuJHDHJC0O96EsXGCVnzVzTFt7GhGDJ7lL+oJprfzS2qX+v8f5RoyJeLB2BPDJr5cHkmXJSsEjEyFkxWFXdQqWTeW7U+hWeRJ8H8JJlBMUmtViXHiZmY7kbUKhMHMMF6y4VWOYosH9jIUu1Eo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792002603; c=relaxed/simple; bh=CvDZexJzjI7RxCUbV640at39KGkOo5+6t5uM91VSujc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HRujGbQBHinX4eJVYOZmKQz3hb8s3/w4xf4X+yMxBQrx5VEdisPwMJcp3j/HeCKv55iBLrLSmPdRjs8su9kZFCNwjY/OWpYws25D8lnlDjBKawf7pAVYPAnAB5ZPKdZZnB9FJsZO+NBTEbnGBqwYfz0dq/CTl/Bp60B0J3WHcO4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=h9/hPajC; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="h9/hPajC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0CEAD1F000C4; Wed, 14 Oct 2026 18:29:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792002601; bh=goPUvnwsBIJ7nqx5a1aYL/GrCgKsovn5VsOtQmOka0M=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=h9/hPajC0Azg9CvJ98mqMqpfTxxP3tEL0tJENRXOXOdPpN21/xwJANzF0XJT20uEB 8ELin1BYHvgD0N0NTjGV2SS7QTiVClPuKdy9qndWJLXyLmgxGK4y3mG8CdYKUqT/vF DyqP9JEHo7TMKboBIPuoQ8M7v9UQGhKIP4Qk9LOX6lTw5aMFzensHD/vWJS7osZ14+ lg0plopzf6p8DARJDysGNTpNSR8qvtJEcL9eMu+tb67MVL2m81S5bCWOth8AInlMpO 10+niaPkGe77yTgorT+xOIyc+8m6DbJOK17DYw3/z2S4+GG8xN36u7lttN4Evx/Yox khSNkfCi3qmtA== Message-ID: Date: Wed, 14 Oct 2026 20:29:55 +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] mm/userfaultfd: only allocate anon_vma in CoW mappings To: Kyle Zeng , "Lorenzo Stoakes (ARM)" Cc: Muchun Song , Oscar Salvador , Andrew Morton , Mike Rapoport , Peter Xu , Miaohe Lin , Lokesh Gidra , "Liam R. Howlett" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261014-copy_hugetlb_page_range-v1-1-5b68e03fe7fe@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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 Content-Transfer-Encoding: 7bit On 10/14/26 20:04, Kyle Zeng wrote: > On Wed, Oct 14, 2026 at 03:51:22PM +0100, Lorenzo Stoakes (ARM) wrote: >> On Wed, Oct 14, 2026 at 01:53:11PM +0200, David Hildenbrand (Arm) wrote: >>> As uffd_lock_vma() is part of the same lookup machinery and >>> also contains a misleading VM_SHARED check, change that one as well >>> directly for consistency. >> >> OK, I think that one isn't _strictly necessary_, but while we're there, >> worth doing too, clearly. >> >> We should also go through and convert the remaining !VM_SHARED checks -> >> vma_is_cow_mapping() too if possible, but that's a follow up, obviously! >> >>> >>> A follow-up cleanup will stop taking the hugetlb_vma_lock_read(src_vma) >>> lock in copy_hugetlb_page_range() entirely. Further, the usage of >> >> Hmm really? Is it possible to do that without the hugetlb lock? >> >> It'd be good in general if we could get rid of that lock as a whole :) but maybe >> dreaming. >> >>> VM_SHARED in userfaultfd code should be cleaned up later to focus on >>> CoW vs. non-CoW mappings. >> >> I think also anywhere else in the kernel where this is done. An audit on that in >> general would be useful! >> >>> >>> Reported-by: Kyle Zeng >>> Fixes: 867a43a34ff8a ("userfaultfd: use per-vma locks in userfaultfd operations") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: David Hildenbrand (Arm) >> >> This LGTM, thanks for handling this! >> >> Reviewed-by: Lorenzo Stoakes (ARM) >> >> -- >> Cheers, Lorenzo > > I ran the patch through my system and did not find any issues with this > patch. Thanks for addressing this! > > Reviewed-by: Kyle Zeng Thanks a bunch, and thanks for reporting all these issues! -- Cheers, David