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(p200300cbc72237006501892506f9fcdc.dip0.t-ipconnect.de. [2003:cb:c722:3700:6501:8925:6f9:fcdc]) by smtp.gmail.com with ESMTPSA id fs16-20020a05600c3f9000b0040b48690c49sm15576505wmb.6.2023.12.04.08.51.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Dec 2023 08:51:30 -0800 (PST) Message-ID: <1db10afb-9088-4b9a-a46f-646c33bd932a@redhat.com> Date: Mon, 4 Dec 2023 17:51:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Issue with 8K folio size in __filemap_get_folio() From: David Hildenbrand To: Matthew Wilcox , Viacheslav Dubeyko Cc: Linux FS Devel , linux-mm@kvack.org, Hugh Dickins , "Kirill A. Shutemov" References: <22d5bd19-c1a7-4a6c-9be4-e4cb1213e439@redhat.com> 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: <22d5bd19-c1a7-4a6c-9be4-e4cb1213e439@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-Rspamd-Queue-Id: DE20720023 X-Rspam-User: X-Stat-Signature: 1srzk459uiupprtx9z8az68qhjs8spfy X-Rspamd-Server: rspam03 X-HE-Tag: 1701708694-533376 X-HE-Meta: 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 GWtypEdn fWNstJhw1KTESVc0FO6Yc12w91GYKlEdFt+KtOi3yIcWX8+CGCWjdfGk3ni42NanxS7cE31Iv4KypCPdWuA7j6Ks1J9/yEkYGTN/4zFqOMJ6YcpSyzwh6mxm1/IeHI9xShJ7X0xvU1LU7WWvvhsJjr3QKZZiheTjDg84hDYpDsGBlP/nfpTzZhyYPtvTXodMItIxuUT3v6YDFVcME1kE3fUpFi0Azw8mt1vTmtiKtGz1+DFRlUr+EK3tNin01U5Up0OTZ04WK6GOwAKyMvUEG71Q0PmVBjJSD9Ee+IRzTvGYvYnJ6rx+oHL7m39MRLYrGI2p9ZD/2VWC/tK3Pvx2G4S1H0DPDZlp5d2NhGykIl5y1Q0ZXGWnRWgKT0AONRowtARom1wk/4Kd+i3LPhhk7YUbYy0eJMUfGatrXjuiLF0CzP0IzZs/+gaq3zERBQnX++sDs57qekbm+mEseqSHu9Te1jA== 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 04.12.23 16:09, David Hildenbrand wrote: > On 04.12.23 00:12, Matthew Wilcox wrote: >> On Sun, Dec 03, 2023 at 09:27:57PM +0000, Matthew Wilcox wrote: >>> I was talking with Darrick on Friday and he convinced me that this is >>> something we're going to need to fix sooner rather than later for the >>> benefit of devices with block size 8kB. So it's definitely on my todo >>> list, but I haven't investigated in any detail yet. >> >> OK, here's my initial analysis of just not putting order-1 folios >> on the deferred split list. folio->_deferred_list is only used in >> mm/huge_memory.c, which makes this a nice simple analysis. >> >> - folio_prep_large_rmappable() initialises the list_head. No problem, >> just don't do that for order-1 folios. >> - split_huge_page_to_list() will remove the folio from the split queue. >> No problem, just don't do that. >> - folio_undo_large_rmappable() removes it from the list if it's >> on the list. Again, no problem, don't do that for order-1 folios. >> - deferred_split_scan() walks the list, it won't find any order-1 >> folios. >> >> - deferred_split_folio() will add the folio to the list. Returning >> here will avoid adding the folio to the list. But what consequences >> will that have? Ah. There's only one caller of >> deferred_split_folio() and it's in page_remove_rmap() ... and it's >> only called for anon folios anyway. >> >> So it looks like we can support order-1 folios in the page cache without >> any change in behaviour since file-backed folios were never added to >> the deferred split list. > > I think for the pagecache it should work. In the context of [1], a total > mapcount would likely still be possible. Anything beyond that likely > not, if we ever care. Thinking about it, maybe 64bit could be made working. Anyhow, just something to keep in mind once we want to support folio-1 orders: memmap space can start getting a problem again. -- Cheers, David / dhildenb