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[2003:cb:c72a:9100:23d2:3800:cdcc:90f0]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3997f9a3428sm2692106f8f.26.2025.03.21.08.38.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Mar 2025 08:38:30 -0700 (PDT) Message-ID: <3e6040c1-81f4-4977-bbb7-70908104aa45@redhat.com> Date: Fri, 21 Mar 2025 16:38:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] mm/debug: Fix parameter passed to page_mapcount_is_type() To: Vlastimil Babka , Gavin Shan , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, willy@infradead.org, linmiaohe@huawei.com, gehao@kylinos.cn, shan.gavin@gmail.com References: <20250321120222.1456770-1-gshan@redhat.com> <20250321120222.1456770-3-gshan@redhat.com> <809792d8-8717-41d9-8dd8-ca91a5b54a28@suse.cz> 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: <809792d8-8717-41d9-8dd8-ca91a5b54a28@suse.cz> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: NU_fLL955PujVaVcUhfnom34nTzSqLTZm3HTYsrmZaY_1742571511 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8E61C140013 X-Stat-Signature: 6ewxab98mf3simg4n7pwfi6cwpmszmqq X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1742571514-798815 X-HE-Meta: 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 GCLxrpPt 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 21.03.25 16:19, Vlastimil Babka wrote: > On 3/21/25 13:02, Gavin Shan wrote: >> As the comments of page_mapcount_is_type() indicate, the parameter >> passed to the function should be one more than page->_mapcount. >> However, page->_mapcount is passed to the function by commit 4ffca5a96678 >> ("mm: support only one page_type per page") where page_type_has_type() >> is replaced by page_mapcount_is_type(), but the parameter isn't adjusted. >> >> Fix the parameter for page_mapcount_is_type() to be (page->__mapcount >> + 1). Note that the issue doesn't cause any visible impacts due to the >> safety gap introduced by PGTY_mapcount_underflow limit. >> >> Fixes: 4ffca5a96678 ("mm: support only one page_type per page") >> Signed-off-by: Gavin Shan >> Acked-by: David Hildenbrand > > Acked-by: Vlastimil Babka > >> --- >> mm/debug.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/mm/debug.c b/mm/debug.c >> index 8d2acf432385..b6bd9555ec7b 100644 >> --- a/mm/debug.c >> +++ b/mm/debug.c >> @@ -71,10 +71,10 @@ static void __dump_folio(struct folio *folio, struct page *page, >> unsigned long pfn, unsigned long idx) >> { >> struct address_space *mapping = folio_mapping(folio); >> - int mapcount = atomic_read(&page->_mapcount); >> + int mapcount = atomic_read(&page->_mapcount) + 1; >> char *type = ""; >> >> - mapcount = page_mapcount_is_type(mapcount) ? 0 : mapcount + 1; >> + mapcount = page_mapcount_is_type(mapcount) ? 0 : mapcount; > > At this point it would be perhaps more obvious: > > if (page_mapcount_is_type(mapcount)) > mapcount = 0; Agreed, maybe Andrew can fix that up. -- Cheers, David / dhildenb