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 D02EB3D0BFB; Tue, 9 Jun 2026 07:09:34 +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=1780988975; cv=none; b=uEckzRRoTrjn8lktbhXfEUR63wQz1tE1BEyLKlIk7HruKmJAEsCXBhPpmVYjyC897HCGC6ILlCiVHANj4L2/WJH+XpLWRPPspwktUqqNXg7HmxwhWMu2kBLKUHtHtnoyOhm2MKdW9/Ejj/g7Fw8B9UaJkkHch1NTIjrYKyVc8Hk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780988975; c=relaxed/simple; bh=+p+VbsF4pxTO7J94NH8S734p7MiCRWzL+B4AuaBouPM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hePWzOu6LgItHktJWMfo5hHE1TgG21QM7HEegA6NovAoS6PBB7+EgXLLS6SgL9eIfugvX/eAop4AD5s1T4w3keVIIsnBr8/1Y8hmG7T9xVmukrsjQF7oxiwptXPLAiPHWH1ZNLV6JEwkEWT/Its3Fpbz0E047mK7l4Dz7Pc9Rx0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NY1mGYm4; 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="NY1mGYm4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D1661F00893; Tue, 9 Jun 2026 07:09:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780988974; bh=139iQQq4xBncPJiuXIb4sR0v5L2oZgj0QjKCDvmp8NE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NY1mGYm4C+vT98RYZN6oqOfXouBddRRCeQIlOLsXTuf42zmsBzIb3wlrK311N6tyc eKLm4M1smhZ7tnWnZtiOWuOiTCN5Vy66LVwjXRsJhqycdSndJLiH3nXX9enxFgUxyF 1n1SMz4An3LfJ1YEv7E0w/Hhw82ofcIKwFa69CoLA/nj/cPw2Zp9PqGnb6B6oL4On0 tyQ8TcflwrX4Xa2W+sj84SA89JQLACXHdV+SQRzCCiWHaEVesd7K6Wpe+ROh0qrU6m Hm5a/1pQulWI3CPK+UDJgAUHiOPYdfdfNQXYcLn5vIin4Ci9WzO6xVsNCzhaCng2NM WNcxmhrv36J6A== Message-ID: Date: Tue, 9 Jun 2026 09:09:27 +0200 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 2/6] mm/memory-failure: surface unhandlable kernel pages as -ENOTRECOVERABLE To: Miaohe Lin , Breno Leitao Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com, Lance Yang , Andrew Morton , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Naoya Horiguchi , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , "Liam R. Howlett" References: <20260527-ecc_panic-v8-0-9ea0cfa16bb0@debian.org> <20260527-ecc_panic-v8-2-9ea0cfa16bb0@debian.org> <19f968f5-1289-f573-4406-e5c91dcd8923@huawei.com> <33ef8821-c809-b7d1-ea77-6e8a07a6e784@huawei.com> <21732071-14a1-486a-951c-34de97b7c757@kernel.org> <4b27467e-935f-5587-2f48-5a794c30a592@huawei.com> <4953bcee-5a0f-2bc5-7295-63e5e7513e8b@huawei.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: <4953bcee-5a0f-2bc5-7295-63e5e7513e8b@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/9/26 04:39, Miaohe Lin wrote: > On 2026/6/8 22:15, Breno Leitao wrote: >> On Fri, Jun 05, 2026 at 11:42:53AM +0200, David Hildenbrand (Arm) wrote: >>> >>> I mean, any such races can currently already happen one way or the other? >>> >>> Really, the only way to not get races is to tryget the (compound)page, >>> revalidate that the page is still part of the compound page. >>> >>> I'm not sure if that's really a good idea. >>> >>> But my memory is a bit vague in which scenarios we already hold a page reference >>> here to prevent any concurrent freeing? >> >> No, we don't hold one here in the case that matters. >> >> HWPoisonKernelOwned() runs at the very top of get_any_page(), before >> try_again: and before __get_hwpoison_page(). The first refcount taken in >> the whole path is the folio_try_get() inside __get_hwpoison_page(), which >> runs *after* the short-circuit. >> >> So get_any_page() itself never holds a reference at the check -- the only way >> one exists is if the caller passed MF_COUNT_INCREASED (count_increased == >> true). >> >> So on the MCE/GHES path -- the one this panic option exists for -- no >> reference is held when HWPoisonKernelOwned() does its compound_head() + >> PageSlab()/PageTable()/PageLargeKmalloc() checks. >> >> Given that, I'd rather keep it racy and take no refcount than add a >> tryget + revalidate purely for this check. As I've said earleir, an operator > > Would it be acceptable to add a simple recheck? Something like below: > > retry: > head = compound_head(page); > PageSlab()/PageTable()/PageLargeKmalloc() checks > if (head != compound_head(page)) > goto retry Sure. I guess it could still be racy in some weird scenarios where we free+allocate+free in-between. -- Cheers, David