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(p200300cbc72237006501892506f9fcdc.dip0.t-ipconnect.de. [2003:cb:c722:3700:6501:8925:6f9:fcdc]) by smtp.gmail.com with ESMTPSA id m16-20020a05600c4f5000b0040b349c91acsm18891644wmq.16.2023.12.04.07.09.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Dec 2023 07:09:37 -0800 (PST) Message-ID: <22d5bd19-c1a7-4a6c-9be4-e4cb1213e439@redhat.com> Date: Mon, 4 Dec 2023 16:09:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Issue with 8K folio size in __filemap_get_folio() To: Matthew Wilcox , Viacheslav Dubeyko Cc: Linux FS Devel , linux-mm@kvack.org, Hugh Dickins , "Kirill A. Shutemov" References: 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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B88E01A0033 X-Stat-Signature: 7gx3u8xqtf3dozzxfoqwg5joewrc7eme X-Rspam-User: X-HE-Tag: 1701702581-751348 X-HE-Meta: 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 zh39Iwj/ G4jJydHmhbaEJP3Dc5OnE7EvII1rTn2r5cdxwgbKgXoCcdJugs/ElQX5VuBUzTssL1dTtDGyxSLhFBp60CLm5BvC7aXstdgMsh+65+rT0Ta2LbS6+OnBkKHkVjhghiasPWPUNJp5nMZS0V9T0FKJ2C41hDjOw8MaK9w5KanW3po98jbu9bGLdyJgZ4FLXR+GXrkLYgNPykzj63umK1FG1r2J6uz8FE3qiYLXLF2oDehZCBz4VXZLECFFVX9BGPTPwlHw9gFYgbspBWL1SnPTnXOB454bbngfB1FU7GFlox/7muucvMrsQGA0+mEeZN0hFMiqbTyl37FqxupEoXkwNG3rQQFWEZaraqT9qwJUniY20ejyWTJSWb8YArtdGJhXotYQ/CUP6mSNADuRKDVZOvUZAI4fT9hcIbuE7WHGg01sxeike0OPwbs9xp0T85/NUXgMSQMRwyytAWPWEQbCTgzDcCqTRkQR40sCXmLfyxW/jAUgMmcrV7Tfba5FceBQUNGWphMjrUS0ZmfcFyXM3cwa6gGTLP05sy/i97olN3au/X7Q= 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 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. [1] https://lkml.kernel.org/r/20231124132626.235350-1-david@redhat.com -- Cheers, David / dhildenb