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=1793438949; b=GOe/ilxXnaBJhUUWCijxVlJe2Wmg77zWYFBu7iDEgbjjWJpGihOTnK/fcJA10Q/QGkZB KA+vX0BDXtODwR8Ry07ZIXtrPL+U2qswDwEB2fCssGPxGjkQVoskFVDCxdnshdQJsl9ty wXM/Qwk6nReRZSwkm4oBqP5hYzTLtMTDpsNMEWuf7pYvS/pNZGNzTTFzl6MPzAED8M00l xIOy8La5+u62mdPTl2kR1+Q76Uarv0881iv+np/OcBx/Gs11yJEqNoMnGMvrYU2nRDWwe 5iXZ6Os8PKop+3IHkjD3Nc1eGSuzA5AH+pumB4ZMwD40AmIfDfeZGp4x7WZKCyDXkMA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793438949; 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=ll2fis6PW3e6O4+ywq8trqmNgeraIhRzhSrv/X2z4g0=; b=ZI0a6FlO1GNJoJRe6+LEw4YyOGSgs9hUT2w6mEukaGUqpACoGutbiANiaUKEgOUx44GS PXGkyrZckTSgjsshrX1jZzP42yaOKkVm9GIKzu3Z5Y4mfQNWaZmufdJSUCnu35vnfQjRI MxV1ybfCX2XR2sKWBC+I+4kXYlf1TLbHdt6pdonZgDWyIzt6ul1OxKxmsbKX8g5fGdKQc bzXKWIkmSw8psSmnBbGHD/UjK52jg0W30GMeUB8Xp77AIXhuWkLzzqCAKtdLraNXtuil2 mFXcoy/LhbCn4P0bwHd3+FyOu2KT5wwH/olhRDbh2FfPfuL9QaoA/68jc1pUQFQvvlQ== 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=gHRZmNCY; 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 25907606A31A; Sat, 31 Oct 2026 09:29:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=gHRZmNCY Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACA2A1F00919; Sat, 31 Oct 2026 09:29:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793438948; bh=ll2fis6PW3e6O4+ywq8trqmNgeraIhRzhSrv/X2z4g0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=gHRZmNCYSYLpZ9UHoD4zM/HC7SGTVM0A+qag4isL8bPqhVyIKmMKxBwYQT/kurhLU YX4Im7ICJiVFbQdXjxUm1jGIpb9SOovzJ75QNt/SEGA901F1JcUW6APRiOnIjH/HCC +ttOQJloaaFWtPSM+g+SqBPso2zMPiqyjSHtv7cqV9Ikyax6g7vDG7OSYEatKBpZmA 1ZgClYcVbjTGH7ODF7ZiS7gVXb3tAV3KrkVcje7xbDH6dlhP5xEeUe9mkFlAR614yM cnOW377XQtEtbpWyRBM4/9L3pb7HUxd0TF+eAaVJCD/wx+3adlIO7y5POMyH/klW2s VEt7XUYwKd4VQ== Message-ID: <895a3483-c773-4d5d-9760-c526c6cfb922@kernel.org> Date: Sat, 31 Oct 2026 10:28:59 +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 v2] mm/memory-failure: fix folio refcount leak and min_order_for_split() locking To: Andrew Morton Cc: Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Miaohe Lin , Naoya Horiguchi , Wei Yang , Nico Pache , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Luis Chamberlain , Tal Zussman , Li Youhong , stable@vger.kernel.org References: <20261030-try_to_split_thp_page-v2-1-c957c9b42eab@kernel.org> <20261030163553.c5dec200dd39cec4695e545c@linux-foundation.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: <20261030163553.c5dec200dd39cec4695e545c@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/31/26 00:35, Andrew Morton wrote: > On Fri, 30 Oct 2026 23:29:13 +0100 "David Hildenbrand (Arm)" wrote: > >> hwpoison code can end up calling min_order_for_split() without holding >> the folio lock. There isn't really something that would prevent >> concurrent folio split. Consequently folio->mapping can get set to >> NULL after checking for "!folio->mapping", and if the compiler >> reloads folio->mapping, mapping_min_folio_order() would try to >> dereference NULL. > > Bit confused here. Is it referring to folios which end up outside EOF > which split effectively truncates, or did it mean to say "truncate"? I think above should say "There isn't really something that would prevent concurrent truncation." > > If the former, how is split able to folio_ref_freeze() a folio which > hwpoison has grabbed a ref on? > > IOW, is the race against split, or against truncate? It's splitting (min_order_for_split() reading ->mapping) racing with truncate (changing ->mapping). Want to fix up the s/folio split/truncate/ when applying or want me to resend? Thanks¡ -- Cheers, David