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(p200300d82f26e700f1c5285b72a5d8c8.dip0.t-ipconnect.de. [2003:d8:2f26:e700:f1c5:285b:72a5:d8c8]) by smtp.gmail.com with ESMTPSA id o12-20020a05600c4fcc00b00418a6d62ad0sm44285199wmq.34.2024.04.29.00.17.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Apr 2024 00:17:45 -0700 (PDT) Message-ID: <19c5b260-fddf-478e-abc5-1c645957b562@redhat.com> Date: Mon, 29 Apr 2024 09:17:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm/gup: Fix hugepd handling in hugetlb rework To: Peter Xu , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Christophe Leroy , Andrew Morton , "Aneesh Kumar K . V" , Lorenzo Stoakes , John Hubbard , linuxppc-dev@lists.ozlabs.org, Muchun Song , Jason Gunthorpe References: <20240428190151.201002-1-peterx@redhat.com> <20240428190151.201002-2-peterx@redhat.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: <20240428190151.201002-2-peterx@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 57CE118000C X-Rspamd-Server: rspam06 X-Stat-Signature: txm7hbfpp4f1sdbfm9mc3gqogpbd46bi X-HE-Tag: 1714375069-354541 X-HE-Meta: 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 HWDktEmT Phhev0UX51q54ntfr0VKz0Guwiwp8+6xlyTKhxQbx9mdcx7Eew/SnS+T3xvpERjG/rmMzstdnFWLDXNqWSljvymW95alyUgQvvU3rh/N24yiNAR5TtVOJm1CepniApYkD1IffYbO++34XTP4j3ftXJfJgGMKuBaOHu3VDBuvUzED0iUAhE31HCmsETx65wC/UJ+OIsrAV7fwTc2FrSP43CH5zys0nIo2FPjg3c0Ivqrs1e/UirU3O5xUml3inIS5c2xTBrLRtezFd9OqDmSkL03GoLg/ox1eCBTdtRFlZ/aAZfcOCXSgNXK59tLfXljcsUUJjJg/ALfW4ct8m6v9cQeL71jW0IGXzWQbfgRuga9eq6j9fXRgoY0k7RihSDkO9hYLGSjCWS0VT/IbDckhvBH6sl8VGr0Ir5nHnwkL5YfMYCT2i81yMs/zZThY1pnvVQKPm 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 28.04.24 21:01, Peter Xu wrote: > Commit a12083d721d7 added hugepd handling for gup-slow, reusing gup-fast > functions. follow_hugepd() correctly took the vma pointer in, however > didn't pass it over into the lower functions, which was overlooked. > > The issue is gup_fast_hugepte() uses the vma pointer to make the correct > decision on whether an unshare is needed for a FOLL_PIN|FOLL_LONGTERM. Now > without vma ponter it will constantly return "true" (needs an unshare) for > a page cache, even though in the SHARED case it will be wrong to unshare. > > The other problem is, even if an unshare is needed, it now returns 0 rather > than -EMLINK, which will not trigger a follow up FAULT_FLAG_UNSHARE fault. > That will need to be fixed too when the unshare is wanted. > > gup_longterm test didn't expose this issue in the past because it didn't > yet test R/O unshare in this case, another separate patch will enable that > in future tests. > > Fix it by passing vma correctly to the bottom, rename gup_fast_hugepte() > back to gup_hugepte() as it is shared between the fast/slow paths, and also > allow -EMLINK to be returned properly by gup_hugepte() even though gup-fast > will take it the same as zero. > > Reported-by: David Hildenbrand > Fixes: a12083d721d7 ("mm/gup: handle hugepd for follow_page()") > Signed-off-by: Peter Xu > --- LGTM Reviewed-by: David Hildenbrand -- Cheers, David / dhildenb