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[2003:d8:2f2c:1e00:1e1e:7a32:e798:6457]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e2449f1sm19945735e9.23.2025.06.12.05.44.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Jun 2025 05:44:44 -0700 (PDT) Message-ID: <65505f1f-90e7-4cf5-9e81-0036892a505a@redhat.com> Date: Thu, 12 Jun 2025 14:44:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: fix folio_test_{anon,ksm}() false positive on slabs To: Harry Yoo , Vlastimil Babka Cc: rientjes@google.com, cl@gentwo.org, akpm@linux-foundation.org, roman.gushchin@linux.dev, willy@infradead.org, linux-mm@kvack.org References: <20250609132723.13118-1-harry.yoo@oracle.com> <83e262c2-419d-42cf-84db-b4ea2befbb72@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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 0aOuUq0LhjZAhSJQMYmQiJRVLWgGSzBliGswbFuoF3k_1749732286 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: 66F4A1C0008 X-Rspamd-Server: rspam03 X-Rspam-User: X-Stat-Signature: zj5e3zr5uwrfmnfaurzt8s6nzihxbeco X-HE-Tag: 1749732289-457579 X-HE-Meta: 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 +Z15NlWY 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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 10.06.25 15:17, Harry Yoo wrote: > On Tue, Jun 10, 2025 at 03:03:12PM +0200, Vlastimil Babka wrote: >> On 6/10/25 14:38, Harry Yoo wrote: >>> On Mon, Jun 09, 2025 at 04:22:01PM +0200, Vlastimil Babka wrote: >>>>> With the change, the nonsense slab pages disappear: >>>>> >>>>> $ sudo ./page-types | grep slab >>>>> _______S___________________________________ slab >>>>> >>>>> Fixes: 130d4df57390 ("mm/sl[au]b: rearrange struct slab fields to allow larger rcu_head") >>>>> Signed-off-by: Harry Yoo >>>>> --- >>>>> >>>>> No Cc: stable because we don't usually check folio_test_anon() on slabs. >>>> >>>> Hmm maybe we could just make the code generating /proc/kpageflags stop >>>> testing/reporting those "flags" for slab pages? >>>> >>>> It could be even more future proof code for when struct slab is separated. >>> >>> Not sure if I follow. When struct slab is separated, checking if a memdesc >>> refers to slab or not will not have false positives, and thus no need for >>> "must check folio_test_slab() before checking folio_test_anon()" rule? >> >> Not sure I follow either. I mean today we can add code testing >> folio_test_slab() and only evaluating the mapping flags (ksm, anon) if it's >> not slab. Once we convert to memdescs, that code will stay logically the >> same even the testing functions will be named differently, no? > > Ah, I thought you were saying it is unnecessary to fix folio_test_slab() > false positives as long as we always check folio_test_slab() before > folio_test_anon(). Yes, relevant code should do that. And we already do it at a couple of places (e.g., folio_expected_ref_count()). -- Cheers, David / dhildenb