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b=omSocrIJOd3epz0Zk7VYPLQoIydgsSrM3HbIdITgEg2cP9aAb1iLkGFHr8jZYQSnP i5vi/LSCvP3i8G3+ek5Sg+V09jcgZapbOZDTRfYU8/yKJeBDOnsk6j7ZDnPFP/zvSC RmYrsaKV1q4gXOnZKIC16HAL7q/29+xnshekt9zISxhPHNnDA1cRNEHm2DiKQ1u8Fe 88QbqZv0r3FMliJc6al0BXavXHnMm4yp2FJFJwpY3H+28I9bA/aiQusDJ52zSlsLT9 1JN1cj5KC0jwSsMGb99xnoaa9CSNaLV4SKsylpbv+Uom/kls6pLEPTT8cCHXyLXBHg DSK5M/J3bPnrA== Message-ID: <699fc1b0-7af8-42ac-9882-c01225379586@kernel.org> Date: Thu, 6 Aug 2026 10:41:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/madvise: avoid skipping pages after splitting large folios To: Yunhui Cui , akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, jannh@google.com, 00moses.alexander00@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org References: <20260806055501.56761-1-cuiyunhui@bytedance.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: <20260806055501.56761-1-cuiyunhui@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 31C7716000D X-Stat-Signature: m64cq85hm1cxjuaffg8iza1g99pmxya1 X-Rspam-User: X-HE-Tag: 1786005672-968964 X-HE-Meta: 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 YBIEkSjV dPYzZddgeagZeKRX59UCKzGv5NshE8qu//ly/YaHn1V3zPjoX+VlWTEL4bm0+tiKPcKSXN87m5H7ne4EzYcI0BW+juxxQfif3R17yU5s1RDYB88ULwAtL0vKZQUnp0xINqDx+XQyWf/lfMxbII1c5tBP7xAbzhJ1Ugioy3CAOoDXMzE6BC/orYCS+qkoH9a6l+Dztw8N4xg9vrLyrYhupEM3v9Pc6uxPdhuzY5UhwvtAAKXVo9ivQuXEHg1rSxeNFZYwUwGlkFUx8smnts+JhJQseEt6hfUE9ka+ursVcMIj3HJ5eLcTMmo7/SRDYkKmRfKD3Qgt/ujhnZCHk1HsepGapihXnh7wMtdY3/0fPCf6LMXhBXBfRYB1nYa9+IBE4HusS Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/6/26 07:55, Yunhui Cui wrote: > madvise_inject_error() advances through the requested range using the > size of the page returned by get_user_pages_fast(). Saving the size > before error injection is required for hugetlb pages because successful > soft offlining can dissolve the source huge page. > > That stride is incorrect for non-hugetlb large folios in system memory. > The memory failure handlers split such a folio and handle only the base > page for the supplied PFN. Advancing by the pre-split folio size then > skips the remaining pages in the requested range while madvise() still > reports success. > > Advance by PAGE_SIZE for non-hugetlb folios in system memory. Retain > folio_size() for hugetlb and ZONE_DEVICE folios, as compound Device DAX > folios are handled as a whole. > > Fixes: 19bfbe22f59a ("mm, hugetlb, soft_offline: save compound page order before page migration") > Cc: stable@vger.kernel.org > Signed-off-by: Yunhui Cui > --- > mm/madvise.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 5a09cc24f04a0..e9d4c3bbc5290 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -1455,20 +1455,25 @@ static int madvise_inject_error(struct madvise_behavior *madv_behavior) > > for (; start < end; start += size) { > unsigned long pfn; > + struct folio *folio; > struct page *page; > int ret; > > ret = get_user_pages_fast(start, 1, 0, &page); > if (ret != 1) > return ret; > + folio = page_folio(page); > pfn = page_to_pfn(page); > > /* > - * When soft offlining hugepages, after migrating the page > - * we dissolve it, therefore in the second loop "page" will > - * no longer be a compound page. > + * Non-hugetlb large folios in system memory are split and only > + * the addressed base page is handled. Hugetlb folios may be > + * dissolved and ZONE_DEVICE folios may be handled as a whole, > + * so save their size before error injection. > */ > - size = page_size(compound_head(page)); > + size = PAGE_SIZE; > + if (folio_test_hugetlb(folio) || folio_is_zone_device(folio)) > + size = folio_size(folio); We should never ever try deferring "how much has been mapped" from a single PTE. While this currently works for hugetlb, it's just an anti-pattern to throw hugetlb checks and similar around. So this is not the way to fix it. -- Cheers, David