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b=VSAluQ55HJaUtEG1IsJ5NWIOkQbWebceW3r1y0lVAN1ze5DOwc8hy9yROLrEGLdBM 2MSALqdm602Mb3a36SCUcQFeoMJ/f25tFxICxTaPLU6hMm07C/PQgyV1K/2Gj8OyvP eESt4Wuc6GXc1se05GfxyikSydHlpXChUNz9igLQ5mI69KB5t6AFBJdt32dazC5bQ5 wS+F5hmlJcryXi1DyHdAyLrNSPLLo4gdbtvh9+QL/RQ98nFvRor5L3Hnpedglld0L0 VdptgsNVO5Tb/Qz/qbGf+sbGhIVr37CKmT3sLitwCEJEthI0nKSSp1a70gIj/xTKqo NbNqGef5zVqBw== Message-ID: Date: Thu, 19 Mar 2026 09:49:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/huge_memory: fix folio isn't locked in softleaf_to_folio() To: Jinjiang Tu , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, baohua@kernel.org, ryan.roberts@arm.com, linux-mm@kvack.org Cc: wangkefeng.wang@huawei.com, sunnanyong@huawei.com References: <20260319012541.4158561-1-tujinjiang@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: <20260319012541.4158561-1-tujinjiang@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4011DC0005 X-Stat-Signature: efnhzjmmmtfjnbig3g3y53ech56qhe64 X-Rspam-User: X-HE-Tag: 1773910180-798343 X-HE-Meta: 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 oNxpwMFD vcY9KZNySdf2bDONcPJP2Pcsd/nPvQ3HxUD0Pk/eVn/WFNhCVg6oc5nPb4n19abUq/zlilk3kw6NYVwPp3KDK0IePzLcId6LmRu2tjxmhunPhq9rgxJW7iLC+RjAeZiJE/kVDmTyNW5/57qjYY9vomYE0F/OoZ4tpgT9fs9yqi8wB4itUS0eZkb6v4zF3XIp70M1njb1fM7c3YW0sl7QSyolSSO/6NIyTVdR/D8hSaTlcT5RHJADZrsCOa1075Kj0GnF6+AiZ0rmgtK0mEWbgR0AUu/rLy3cLAMRVKBCJwHwlb+XMK+gMHA69FxgCg2AW9Atv404RhhlfSJB3Tl8fFL4/xN7xdNZGhLqH Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/19/26 02:25, Jinjiang Tu wrote: > On arm64 server, we found folio that get from migration entry isn't locked > in softleaf_to_folio(). This issue triggers when mTHP splitting and > zap_nonpresent_ptes() races, and the root cause is lack of memory barrier > in softleaf_to_folio(). The race is as follows: > > CPU0 CPU1 > > deferred_split_scan() zap_nonpresent_ptes() > lock folio > split_folio() > unmap_folio() > change ptes to migration entries > __split_folio_to_order() softleaf_to_folio() > set flags(including PG_locked) for tail pages folio = pfn_folio(softleaf_to_pfn(entry)) > smp_wmb() VM_WARN_ON_ONCE(!folio_test_locked(folio)) > prep_compound_page() for tail pages > > In __split_folio_to_order(), smp_wmb() guarantees page flags of tail pages > are visible before the tail page becomes non-compound. smp_wmb() should > be paired with smp_rmb() in softleaf_to_folio(), which is missed. As a > result, if zap_nonpresent_ptes() accesses migration entry that stores > tail pfn, softleaf_to_folio() may see the updated compound_head of tail > page before page->flags. > > To fix it, add missing smp_rmb() if the softleaf entry is migration entry > in softleaf_to_folio() and softleaf_to_page(). > > Fixes: e9b61f19858a ("thp: reintroduce split_huge_page()") > Signed-off-by: Jinjiang Tu > --- > > Change in v3: > * move softleaf_is_migration() check out of softleaf_migration_entry_check() > > include/linux/leafops.h | 28 +++++++++++++++++----------- > 1 file changed, 17 insertions(+), 11 deletions(-) > > diff --git a/include/linux/leafops.h b/include/linux/leafops.h > index a9ff94b744f2..dd4130b7cb7f 100644 > --- a/include/linux/leafops.h > +++ b/include/linux/leafops.h > @@ -363,6 +363,19 @@ static inline unsigned long softleaf_to_pfn(softleaf_t entry) > return swp_offset(entry) & SWP_PFN_MASK; > } > > +static inline void softleaf_migration_entry_check(softleaf_t entry, > + struct folio *folio) Nit: ^ should be two tabs. Likely no need to resend because of that. Acked-by: David Hildenbrand (Arm) -- Cheers, David