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[2003:d8:2f2c:5500:988:23f9:faa0:7232]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454b1890626sm23472705e9.40.2025.07.04.03.45.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Jul 2025 03:45:30 -0700 (PDT) Message-ID: <91213616-1e7c-4e75-aee7-862b68c23ab6@redhat.com> Date: Fri, 4 Jul 2025 12:45:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/5] mm,hugetlb: sort out folio locking in the faulting path To: Oscar Salvador , Andrew Morton Cc: Muchun Song , Peter Xu , Gavin Guo , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250630144212.156938-1-osalvador@suse.de> <20250630144212.156938-3-osalvador@suse.de> 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: <20250630144212.156938-3-osalvador@suse.de> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: DS3s0mh5GY23jI4mp0OSEJPCbwF9Og_YVgL4OongdS4_1751625931 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: D21C0A0002 X-Stat-Signature: prxchfo9fg3ze9d84jaisxhu57e3cqy3 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1751625934-468116 X-HE-Meta: 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 R/F11YZS 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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 30.06.25 16:42, Oscar Salvador wrote: > Recent conversations showed that there was a misunderstanding about why we > were locking the folio prior to call in hugetlb_wp(). In fact, as soon as > we have the folio mapped into the pagetables, we no longer need to hold it > locked, because we know that no concurrent truncation could have happened. > > There is only one case where the folio needs to be locked, and that is > when we are handling an anonymous folio, because hugetlb_wp() will check > whether it can re-use it exclusively for the process that is faulting it > in. > > So, pass the folio locked to hugetlb_wp() when that is the case. > > Link: https://lkml.kernel.org/r/20250627102904.107202-3-osalvador@suse.de > Signed-off-by: Oscar Salvador > Suggested-by: David Hildenbrand > Cc: Gavin Guo > Cc: Muchun Song > Cc: Peter Xu > Signed-off-by: Andrew Morton > --- Acked-by: David Hildenbrand -- Cheers, David / dhildenb