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=1794426037; b=REKfKNFk8EMTkcx6C/TcrRSpsmXRPwZ47HzUtIeIgO0FVFKHicOX5HYDKpDPulUDyIGi tnALOjMPAa62KEL6hF7b9vlVzuKkwM2d6Ytea7LYF/HuQY/BELec/ZILpu7w1vTQwby6x BhLQ2izwzgWau4s3cRUtLw+eV2Yh5JaFK4aYla23PJPMNd8yCgWNhsihAMdTtazrq/nIQ MitGQLT6SWKpYO77q3QcCLzE+AsEiUsUbYPfhe0q0jJmH1iY65+BIzTwWY0BmuDN0zC1v LKX0hjGAW6TycQkfkct9LAQKnPaWuCPnXwutjcMwrRrcaGqWiOQImINBendCvefcxCQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794426037; 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=QlMNLrjFCKMvbIv5BxgSsbHdwfPDXIwUE7VZtJM3UGU=; b=yxdS9ZxC6ymgvpDBNpGlJVKl3AMNKUmdopeyOZH/QHwRbGCz7CSSb9W+6wvT5+OA9l1v Os3Cru6ChZTnjzEURRXHPMHk1Zb7pxpHPRl1tWf9MTxTB4ZbfI7jXQfsjPiuwJs6J/mph z/hE6RRD8VJ7ZXfNB5ERp9RDyDxgpUgIDuHe+jS5jWdxbVvghpwDvFdHgAu2URQLt+XVW kaZgi633ixpFL2C9hCN1Utxoymfh9U4C+jKGYP5yhgfaprIPllNm5j8nJOPg71KxW7keW Bpz8ZNhETOSkvU/SIUDAMX/18wCk8YAd96YDA+vjO3wsqjyfIIyhXVYDssJGPkKBSNQ== 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="Xgh/iYq3"; 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 61DB860A6F48; Wed, 11 Nov 2026 19:40:37 +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=Xgh/iYq3 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D89F1F00A0E; Wed, 11 Nov 2026 19:40:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794426037; bh=QlMNLrjFCKMvbIv5BxgSsbHdwfPDXIwUE7VZtJM3UGU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Xgh/iYq3vd67L6NTqm8caRRgqD3doSELAM90BwjbiVe2TuOfg5HU/nGnVnxM5ZViT xKFD0jmWf9ybwTYZReajidXaZZDdSRcocRYyTsFQaP+J1fTlYvExJ2byegLxqTg3Ob B+oiXrUeResJs9rVN/oF5nd17NJiD/wjpWH1qYpB6sgmWHtdr2ke7nHMRda46oPHPQ 9kD3l9BYsuA8DIGTKGDv5q1jvOfzpsbdZVPPa5txyY/Q4DaN5TDhfIaSJbiLYAo6Rm Fb2PKqEN/CWk12hkxW8BDE0VwyAzozMeIqXzxgaEYJNEamhYXt3XiipU7S9ZQAyGbh ZlqWr9sTlgtXQ== Message-ID: <95682ddd-d200-4827-a009-77ee59d14f86@kernel.org> Date: Wed, 11 Nov 2026 20:40:17 +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 04/13] mm/migrate_device: allocate THP deferred split heads To: Kiryl Shutsemau , "Lorenzo Stoakes (ARM)" Cc: "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , David Rientjes , Shakeel Butt , Andrew Morton , Jann Horn , Pedro Falcato , "Matthew Wilcox (Oracle)" , Jan Kara , Nhat Pham , Johannes Weiner , Zi Yan , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Usama Arif , Kairui Song , Balbir Singh , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Yu-cheng Yu , Dave Hansen , Dennis Zhou , Tejun Heo , Christoph Lameter , Peng Fan , Josef Bacik , Chris Mason , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Borislav Petkov (AMD)" , Mark Brown , "Dennis Zhou (Facebook)" , Rick Edgecombe , Josef Bacik , stable@vger.kernel.org References: <20261111-mason-migrate-et-al-fixes-v1-0-3d2454362e8d@kernel.org> <20261111-mason-migrate-et-al-fixes-v1-4-3d2454362e8d@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 11/11/26 20:30, Kiryl Shutsemau wrote: > On Wed, Nov 11, 2026 at 06:13:18PM +0000, Lorenzo Stoakes (ARM) wrote: >> From: Josef Bacik >> >> A THP that device migration maps into an empty PMD can end up on the wrong >> deferred split list when it is later queued for a deferred split. >> >> This occurs if the memcg has no heads yet (resulting in a warning if >> CONFIG_DEBUG_VM is set), where deferred_split_folio() will then queue the >> folio on the parent's list. >> >> Once a later THP fault in the same memcg allocates the heads, >> __folio_unqueue_deferred_split() and the split path resolve folio_memcg() >> to the memcg's own, now existing, list and take its lock. They then >> list_del_init() a folio that is linked on the parent's list, racing with >> anything holding the parent's lock, and both lists' nr_items counts go >> wrong. >> >> Resolve the issue by calling folio_memcg_alloc_deferred() after the charge >> in migrate_vma_insert_huge_pmd_page() and falling back like a failed charge >> if that fails, as __do_huge_pmd_anonymous_page() does. >> >> This was originally discovered by code inspection. >> >> Fixes: fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") >> Cc: >> Signed-off-by: Josef Bacik >> [ ljs: tweak commit message, remove unnecessary comment ] >> Signed-off-by: Lorenzo Stoakes (ARM) > > mm-new already has this: "mm/migrate_device: allocate deferred split > sublists for new huge folios", same Fixes: tag. > > Hm? I assume that's one from Andrew that he created after a security report (where I was CCed and the reporter didn't follow up), but he never sent it out officially. So let's review this one here. It's supposed to go through my tree either way :) -- Cheers, David