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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4362571776asm168383885e9.40.2024.12.17.03.55.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Dec 2024 03:55:33 -0800 (PST) Message-ID: Date: Tue, 17 Dec 2024 12:55:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: hugetlb: independent PMD page table shared count To: jane.chu@oracle.com, Liu Shixin , Andrew Morton , Muchun Song , Kenneth W Chen , Kefeng Wang , Nanyong Sun Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20241214104401.1052550-1-liushixin2@huawei.com> From: David Hildenbrand 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: hjwDOpedafrtEB-_GC5LNdZCfhdcMYd78UgWRiDPUvo_1734436535 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 1BF4440008 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 4zfm9gces8jog3ya8p3ygjch1eikrdnm X-HE-Tag: 1734436511-421500 X-HE-Meta: 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 fz838X5o 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000053, 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 16.12.24 19:33, jane.chu@oracle.com wrote: > On 12/14/2024 2:44 AM, Liu Shixin wrote: > >> The folio refcount may be increased unexpectly through try_get_folio() by >> caller such as split_huge_pages. In huge_pmd_unshare(), we use refcount to >> check whether a pmd page table is shared. The check is incorrect if the >> refcount is increased by the above caller, and this can cause the page >> table leaked: > > hugetlb and THP don't overlap, right?  how does split_huge_pages() end > up messing up huge_pmd_share() ? > > Am I missing something? > If first grabs a reference to then check if it's a THP. So we can end up grabbing anything temporarily. In general, we'll have to be smarter about what we try grabbing, but handling races for now is tricky. -- Cheers, David / dhildenb