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b=N8Uy5/ZVcNg7GQc6ga/4f6riaFB2eScs0ehWn5RE0IjCUBhMRPovH4J9/kEHOsn+o FC8wQz85M7asIudcCmh02IH3sM0yyaf+IVUrt97Nh20o+5CZpelqEFvZnY03ZX/LGc YypFEGGg/HSTCedKzw1tj3+jsKOYM/GYVfMryS4UWKSsjxU0k1kFIfFJFs8tSlnvmb Z/NTZ3HWrx5VllywgUjeJKHx043/MuxtXEngUhuQTAf02O2PeSPzdbUBO7hqCGfDpu Louob+P8g+WmXew3qqychIFWyjZ97XrLnbWT8T5daucZ4TUfz6MV3ZxJNkcp8gy8Ow H99WIGmnAw+FQ== Message-ID: <1e4580ab-75dd-4092-8afd-69180d064942@kernel.org> Date: Thu, 24 Sep 2026 09:12:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [BUG] shmem: FALLOC_FL_PUNCH_HOLE vs fault-around race corrupts page cache / rss counters To: Ayush Ranjan , Hugh Dickins , Matthew Wilcox , Andrew Morton , Jan Kara Cc: Baolin Wang , Gregory Price , Pedro Falcato , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260924061708.1645968-1-ayushr@modal.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: <20260924061708.1645968-1-ayushr@modal.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4064020003 X-Stat-Signature: abmdesyxejaazmwyox4zhz967skjc8rs X-Rspam-User: X-HE-Tag: 1790233962-146813 X-HE-Meta: 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 6CMUH/Qw 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/24/26 08:16, Ayush Ranjan wrote: > Hi, > > We are seeing shmem/tmpfs page cache corruption on production hosts > running a workload that punches holes in a memfd (hole-punch based > memory reclaim) while other threads and forked children fault the > same MAP_SHARED mapping. The kernel taints but does not oops: > > BUG: Bad page cache in process ... pfn:... > page dumped because: still mapped when deleted > ... > dentry name(?): "memfd:..." > > and, more frequently, a paired rss-counter imbalance when the mm is > torn down, always exactly one PMD-order folio (512 pages): > > BUG: Bad rss-counter state mm:... type:MM_FILEPAGES val:-512 > BUG: Bad rss-counter state mm:... type:MM_SHMEMPAGES val:512 > > Seen on 6.12 and 6.18, x86_64, bare metal and VM, with > /sys/kernel/mm/transparent_hugepage/shmem_enabled = always. > > This looks like the same corruption Gregory reported in March, which > as far as I can tell stalled without a fix; that report needed ~100 > ballooning VMs to reproduce: > > https://patchew.org/linux/20260326162611.693539-1-gourry@gourry.net/ Indeed, it looks like what was reported in https://lore.kernel.org/all/20260326162611.693539-1-gourry@gourry.net/ -- Cheers, David