From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794393032; b=5fMjj4ynqRO0CPmG8Zr3GMOL+D1S5pXwCX4D+yQHAB26NlG+w8qsLFghQZATMCHGPUx0 vmNNwMmzTimi/BqudLqKZiap9A3IvpWdf964M15+EickuMw58SXIvaZKG5bQOZ7Uyv+Ed e944V2MPcj/HKMtAS6U3c6QlM6/W3Zg+iDjIABI96pXP4L6hwPhIXqaY4nSpFg+Sm+Fxm 0UmvMbqU1AtSNSW1pFKv3Cpp42cZbVidGHyzK4GRy2qJfxy2pVqNftBcPHql8KZZSob5R KyRXarKqKjdHF6fnlLkym2McQqknnk8mYKUfbOGaZ9hECzgk8IUQ8ORZ500Qm/p/e3A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794393032; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=3saJzizEnMz5wH7u54dhoxxqETLwZ4xBqMdsXbVIbJg=; b=C8CCmODxfUTj//bI4zqWAUhUfiV/3EOcP3irfw+pHNA/rEKoMms0nxfsecMTgw1PdBAc QXaVM834OU3hN0o+6UMzpQk7oz9qDjfpGGaccH8MjXQuCDq1mesMW3oc5w63H3R4hIpiZ sU2ZRendiwoFvdCdTlSyatvCJYEy8WL6bCZfW3Bb82+cH3aZkrta7ofkbyvJAHF4Udfas sch9SHwuzJa8S8tAdu8fJmsYy4z5Qrjfm1H7HZEluS7Py4eNaDgLdpm5IuyZZhQpLOIQF TRPXduQv05SYbXjorOVrUNiivmkQcorKQyFwfixS7f9CYUbOBELBHml/96ERaoqEMsQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Blqa9Gyl; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BDFD8606A31C for ; Wed, 11 Nov 2026 10:30:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Blqa9Gyl Received: by smtp.kernel.org (Postfix) with ESMTPSA id C39161F00A06; Wed, 11 Nov 2026 10:30:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794393032; bh=3saJzizEnMz5wH7u54dhoxxqETLwZ4xBqMdsXbVIbJg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Blqa9GylRCpbtJozK/p/Zo193IJINi2WaRazttyjHzqBDPNoJRNAG1Vziv7InKfMm xoXOB2cKk/bUFZNRGvTrkPsch1q1hPHaStFBLVqxTtF6c12RMhuX7/RgHp3U54HKX9 W9TgRSqiQlPDbwe6Ct2C52W2zAH8kFVJspSa8lQ1mdo5XYiv1ZsHudg21foSJpwhiw PHquU0fbT4mFR6HmLFnHvH64e+t8ouqsuUuH/UT0BefrKwlHJI+iEMZt0h6tBz7UjC cEdzy3mMcK7KGZB+oNBWbJ19n0lVdM1IdHxPvHTuZFM5XJSUBTwx1cKrbXnYRx+beS ID87t6aBRiSNQ== Message-ID: <45f16b1d-d53b-4bd4-80af-292880622edc@kernel.org> Date: Tue, 10 Nov 2026 14:01:41 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/6] mm: gup: clarify a reason to check pte/pmd in gup_fast_pte_range() To: Rik van Riel , Yeoreum Yun , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Jason Gunthorpe , John Hubbard , Peter Xu , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Andrew Morton , Yuan-Hao Hsu References: <20261109-refactor_gup_fast-v3-0-2aaef02df0e1@arm.com> <20261109-refactor_gup_fast-v3-2-2aaef02df0e1@arm.com> 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: 8bit On 11/10/26 04:50, Rik van Riel wrote: > On Mon, 2026-11-09 at 12:32 +0000, Yeoreum Yun wrote: >> Clarify a reason to check pte/pmd in gup_fast_pte_range(). >> >> Signed-off-by: Yeoreum Yun >> --- >>  mm/gup.c | 8 ++++++++ >>  1 file changed, 8 insertions(+) >> >> diff --git a/mm/gup.c b/mm/gup.c >> index 7d43ce717b246..7f9348c633d58 100644 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -2881,6 +2881,14 @@ static unsigned long gup_fast_pte_range(pmd_t >> pmd, pmd_t *pmdp, >>   if (!folio) >>   goto pte_unmap; >>   >> + /* >> + * Recheck the PTE after grabbing the folio to >> detect concurrent >> + * unmapping or protection changes such as by KSM. >> + * >> + * Also, recheck the PMD: THP collpase can detach >> the PTE table > > collapse > >> + * while its entries remain unchaged. Checking the >> PTE alone > > unchanged > >> + * would not dtect that we are walking a detached >> page table. > > detect > > Other than that, Reviewed-by: Rik van Riel yes, thanks! Reviewed-by: David Hildenbrand (Arm) A respin please (maybe tomorrow?) -- Cheers, David