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b=A5VgBRLS7qUh1f6Qaraszl8V6QgyyoxDbei3NIueJsMmBz4zIqzr2NbtjILNVXAcK op55rvHk1zDId3WrK/OycvLnQd4xMvqXRslpvTvUclOSAkugt+CXGm3ESoujjSQlUQ PbPcGKMrVOwHjg/5yTzLCV8Z0ync3NlrprhQb9e6vpDjGAP3pBgBSufSk3MSJzgdys 3kxyQ81UJSyoBlzt5FhMnK8GYmyZ0hGghII6KB8Spi2Yg+jdk3MRCC70MWCCy/GLfK w+f7A/BUF9bdbNLTjjniFeNJjgWhiBx1cplt338VkESX8FyhmAyCkQxbbySxx2ZN3m pfK1j9MTbuB5A== Message-ID: Date: Wed, 18 Feb 2026 08:53:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm/huge_memory: Mark moved huge zero page PMD as special To: Chris Down , Andrew Morton Cc: Matthew Wilcox , kernel-team@fb.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: 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; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: s5e5c4bpdptq13sxcyzr9nd8mxokwiw5 X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: 83B1040010 X-HE-Tag: 1771401199-474236 X-HE-Meta: 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 YDOKVv2f HJM7dtGKzXH8MnL1ZzEmGfYX6mB1jDUaULuU9x+74MhFXoONMoSHG0Sc99xwBrJKXrybTtuHRZTRTHPoKvQ1odDWDRG8rMs/Ixr5ZwF0qeMO4pO8E6UQbpl33DbATEerSAZ+7hz0p3e9MZKyiYQ6P1RLhJSKA1kmyt4/P6+ycY3CN/4ZC2ztB28TGUr0xswzfibZkSLtk8M12WhDLQwdS4HFlhk+IaOyelEKAG2Lhy9aHij8FPyn/JD/6HEkTT257ek02M1H4pB/bHIqGrYRBdXbeY9DUEUe8VaDB X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/18/26 04:45, Chris Down wrote: > Without pmd_mkspecial(), vm_normal_page_pmd() on architectures with > CONFIG_ARCH_HAS_PTE_SPECIAL does not recognise the moved huge zero page > as special, incorrectly treating it as a normal page and corrupting its > refcount. > > Fixes: d82d09e48219 ("mm/huge_memory: mark PMD mappings of the huge zero folio special") > Cc: stable@vger.kernel.org > Signed-off-by: Chris Down > --- > mm/huge_memory.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index fed57951a7cd..5f908cdb11f1 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2795,6 +2795,7 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm > } else { > src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); > _dst_pmd = folio_mk_pmd(page_folio(src_page), dst_vma->vm_page_prot); > + _dst_pmd = pmd_mkspecial(_dst_pmd); > } > set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd); > In theory that's correct, but we should look into just moving the PMD instead of reconstructing things. See my reply to patch #1. -- Cheers, David