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[2003:cb:c73d:3300:9bad:96b:3e57:65bc]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a28f17315sm36058478f8f.108.2025.01.03.12.31.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Jan 2025 12:31:15 -0800 (PST) Message-ID: Date: Fri, 3 Jan 2025 21:31:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/5] mm/migrate: skip migrating folios under writeback with AS_WRITEBACK_INDETERMINATE mappings To: Joanne Koong , Shakeel Butt Cc: Bernd Schubert , Zi Yan , miklos@szeredi.hu, linux-fsdevel@vger.kernel.org, jefflexu@linux.alibaba.com, josef@toxicpanda.com, linux-mm@kvack.org, kernel-team@meta.com, Matthew Wilcox , Oscar Salvador , Michal Hocko References: <9404aaa2-4fc2-4b8b-8f95-5604c54c162a@redhat.com> <3f3c7254-7171-4987-bb1b-24c323e22a0f@redhat.com> <0ed5241e-10af-43ee-baaf-87a5b4dc9694@redhat.com> <446704ab-434e-45ac-a062-45fef78815e4@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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: UC0nPdNHlqaQQ1RzY13uRvYtD6zLLrodSSGvLS33poc_1735936277 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: A5145140006 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: w51xgqdy61bqiws9sdh3mmt1hz7miotx X-HE-Tag: 1735936280-50887 X-HE-Meta: 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 Q7GZMmg9 mZxKOCejcisdVCzv13441gNgDyfyqHNSRptCQ267rew1Okru5EZSWJ8diVNey9jU9AM7FDfXbdiuWRj2KF3y1WX8udLFjJ98Q80ulKpLdYV6LuS/Mqr9uG3bT2Axi3fvbzzliATy2x4HWirbZe+hYtkl9qDsJ/YXCU1T9+26Z7/y9OHn3xd5t7TXG7PTFT3ZY5FrG2zYU3ZVbYfQxes6P02zGNGJKlZOTl+PzXW2TUpi/BJaRCLybNOxoSCCpMyUmz43bHyVdX52XQ9ilBTs65b5IXN7r83UABVT5WiAZwBDd3cqSLnRihI53bwpGuXXthUwtNHoW3SK3Ve6hytU291pcpOiXzUaP8qiskGRzhxtKDLiJ+O7FUA4gUKZrq/AYp3VKkLys8J+sW2inDt1fUrCXSZvx3xpgO2J+ooDRmS3jDlgjeNMU/CvA0VePTaxfkIUVtH38S2FVmTxbgaxyLl/Lgw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000272, 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 02.01.25 19:54, Joanne Koong wrote: > On Mon, Dec 30, 2024 at 12:11 PM Shakeel Butt wrote: >> >> On Mon, Dec 30, 2024 at 08:52:04PM +0100, David Hildenbrand wrote: >>> >> [...] >>>> I'm looking back at some of the discussions in v2 [1] and I'm still >>>> not clear on how memory fragmentation for non-movable pages differs >>>> from memory fragmentation from movable pages and whether one is worse >>>> than the other. Currently fuse uses movable temp pages (allocated with >>>> gfp flags GFP_NOFS | __GFP_HIGHMEM), and these can run into the same >>> >>> Why are they movable? Do you also specify __GFP_MOVABLE? >>> >>> If not, they are unmovable and are never allocated from >>> ZONE_MOVABLE/MIGRATE_CMA -- and usually only from MIGRATE_UNMOVBALE, to >>> group these unmovable pages. >>> >> >> Yes, these temp pages are non-movable. (Must be a typo in Joanne's >> email). > > Sorry for the confusion, that should have been "non-movable temp pages". > >> >> [...] >>> >>> I assume not regarding fragmentation. >>> >>> >>> In general, I see two main issues: >>> >>> A) We are no longer waiting on writeback, even though we expect in sane >>> environments that writeback will happen and we it might be worthwhile to >>> just wait for writeback so we can migrate these folios. >>> >>> B) We allow turning movable pages to be unmovable, possibly forever/long >>> time, and there is no way to make them movable again (e.g., cancel >>> writeback). >>> >>> >>> I'm wondering if A) is actually a new issue introduced by this change. Can >>> folios with busy temp pages (writeback cleared on folio, but temp pages are >>> still around) be migrated? I will look into some details once I'm back from >>> vacation. >>> > > Folios with busy temp pages can be migrated since fuse will clear > writeback on the folio immediately once it's copied to the temp page. I was rather wondering if there is something else that prevents migrating these folios: for example, if there is a raised refcount on the folio while the temp pages exist. If that is not the case, then it should indeed just work. > > To me, these two issues seem like one and the same. No longer waiting > on writeback renders it unmovable, which prevents > compaction/migration. > >> >> My suggestion is to just drop the patch related to A as it is not >> required for deadlock avoidance. For B, I think we need a long term >> solution which is usable by other filesystems as well. > > Sounds good. With that, we need to take this patchset out of > mm-unstable or this could lead to migration infinitely waiting on > folio writeback without the migrate patch there. I want to try triggering it with NFS next week when I am back from PTO, to see if it is indeed a problem there as well on connection loss. In any case, having movable pages be turned unmovable due to persistent writaback is something that must be fixed, not worked around. Likely a good topic for LSF/MM. -- Cheers, David / dhildenb