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[87.161.166.165]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-452730b9b27sm12529925e9.23.2025.06.06.00.56.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Jun 2025 00:56:18 -0700 (PDT) Message-ID: <02fd89c3-d0f9-412c-8f31-d343803c0982@redhat.com> Date: Fri, 6 Jun 2025 09:56:17 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] kernel BUG in try_to_unmap_one (2) To: Jinjiang Tu , syzbot , Liam.Howlett@oracle.com, akpm@linux-foundation.org, harry.yoo@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, riel@surriel.com, syzkaller-bugs@googlegroups.com, vbabka@suse.cz, Jens Axboe , Catalin Marinas References: <68412d57.050a0220.2461cf.000e.GAE@google.com> <4fc2c008-2384-4d94-b1bf-f0a076585a4a@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 05.06.25 09:18, Jinjiang Tu wrote: > > 在 2025/6/5 14:37, David Hildenbrand 写道: >> On 05.06.25 08:27, David Hildenbrand wrote: >>> On 05.06.25 08:11, David Hildenbrand wrote: >>>> On 05.06.25 07:38, syzbot wrote: >>>>> Hello, >>>>> >>>>> syzbot found the following issue on: >>>>> >>>>> HEAD commit:    d7fa1af5b33e Merge branch 'for-next/core' into >>>>> for-kernelci >>>> >>>> Hmmm, another very odd page-table mapping related problem on that tree >>>> found on arm64 only: >>> >>> In this particular reproducer we seem to be having MADV_HUGEPAGE and >>> io_uring_setup() be racing with MADV_HWPOISON, MADV_PAGEOUT and >>> io_uring_register(IORING_REGISTER_BUFFERS). >>> >>> I assume the issue is related to MADV_HWPOISON, MADV_PAGEOUT and >>> io_uring_register racing, only. I suspect MADV_HWPOISON is trying to >>> split a THP, while MADV_PAGEOUT tries paging it out. >>> >>> IORING_REGISTER_BUFFERS ends up in >>> io_sqe_buffers_register->io_sqe_buffer_register where we GUP-fast and >>> try coalescing buffers. >>> >>> And something about THPs is not particularly happy :) >>> >> >> Not sure if realted to io_uring. >> >> unmap_poisoned_folio() calls try_to_unmap() without TTU_SPLIT_HUGE_PMD. >> >> When called from memory_failure(), we make sure to never call it on a >> large folio: WARN_ON(folio_test_large(folio)); >> >> However, from shrink_folio_list() we might call unmap_poisoned_folio() >> on a large folio, which doesn't work if it is still PMD-mapped. Maybe >> passing TTU_SPLIT_HUGE_PMD would fix it. >> > TTU_SPLIT_HUGE_PMD only converts the PMD-mapped THP to PTE-mapped THP, and may trigger the below WARN_ON_ONCE in try_to_unmap_one. > > if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) { > ... > } else if (likely(pte_present(pteval)) && pte_unused(pteval) && > !userfaultfd_armed(vma)) { > .... > } else if (folio_test_anon(folio)) { > swp_entry_t entry = page_swap_entry(subpage); > pte_t swp_pte; > /* > * Store the swap location in the pte. > * See handle_pte_fault() ... > */ > if (unlikely(folio_test_swapbacked(folio) != > folio_test_swapcache(folio))) { > WARN_ON_ONCE(1);          // here. if the subpage isn't hwposioned, and we hasn't call add_to_swap() for the THP > goto walk_abort; > } This makes me wonder if we should start splitting up try_to_unmap(), to handle the individual cases more cleanly at some point ... Maybe for now something like: diff --git a/mm/memory-failure.c b/mm/memory-failure.c index b91a33fb6c694..995486a3ff4d2 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1566,6 +1566,14 @@ int unmap_poisoned_folio(struct folio *folio, unsigned long pfn, bool must_kill) enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC | TTU_HWPOISON; struct address_space *mapping; + /* + * try_to_unmap() cannot deal with some subpages of an anon folio + * not being hwpoisoned: we cannot unmap them without swap. + */ + if (folio_test_large(folio) && !folio_test_hugetlb(folio) && + folio_test_anon(folio) && !folio_test_swapcache(folio)) + return -EBUSY; + if (folio_test_swapcache(folio)) { pr_err("%#lx: keeping poisoned page in swap cache\n", pfn); ttu &= ~TTU_HWPOISON; > > If we want to unmap in shrink_folio_list, we have to try_to_split_thp_page() like memory_failure(). But it't too complicated, maybe just skip the > hwpoisoned folio is enough? If the folio is accessed again, memory_failure will be trigerred again and kill the accessing process since the folio > has be hwpoisoned. Maybe we should try splitting in there? But staring at shrink_folio_list(), not that easy. We could return -E2BIG and let the caller try splitting, to then retry. -- Cheers, David / dhildenb