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[2003:d8:2f1b:b800:6fdb:1af2:4fbd:1fdf]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a5233b0723sm1074178f8f.86.2025.06.04.06.18.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Jun 2025 06:18:37 -0700 (PDT) Message-ID: <830b10df-f697-409d-9ec4-37bc0196cec7@redhat.com> Date: Wed, 4 Jun 2025 15:18:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: gup: fail migration when no migratable page to prevent CMA pinning To: Jason Gunthorpe Cc: Hyesoo Yu , janghyuck.kim@samsung.com, zhaoyang.huang@unisoc.com, jaewon31.kim@gmail.com, Andrew Morton , John Hubbard , Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250604095049.4052078-1-hyesoo.yu@samsung.com> <20250604131158.GA17991@ziepe.ca> 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: <20250604131158.GA17991@ziepe.ca> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: pl6KMG37cxdbOPXPy1qFMO4z0lbzO6lfgnIUynHaYVQ_1749043119 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: A2026A0007 X-Rspamd-Server: rspam09 X-Stat-Signature: nxetnjay77zrcmbhzmd19j3hoo3ayqwo X-HE-Tag: 1749043123-931747 X-HE-Meta: U2FsdGVkX1/EbPoosczlsUuywSiKFcGStLt4+vM1x95mDMpKTQuyr9ufMcICzOCEvF6An7gXOQPCKMElZhjcFq8V7kOI/3oMXyc778ByOHkcpm1qnCxaB1+xrM+4LeRlOs4fjMXgrvwPk3zr5GltZwQHj079DJLe4PeASxifWaigPvHIQwYadi+Q1BDnt80al8xPQNbRfP5oJr80T2XEuhia7quVvMNOTg6fS6o4M46SHkJsu+8ZlzyY9w6QR9YokvfjUCzvQKMxQF9LSsBPBIs4kuNH5KYwpboWnP8ALpsNEt2mAfmQw8KrP4FqNx3uSmYnEJKEyKwtzpFpk06LrMC082rLu7ZzbPfEYfxwVZBSbPJMkSqxE/z7+b/3c69a0JogsKXhvkrnN38+JDaZHN/v56i/sLGxSXNOKHyhN/r7rPXA519sIw2Ckg6Oxg+pbJnAZCf56a/bJOZwMyNQC4EixetymDTUirCmZjqQZBl7KpOwfX/WZhWeiG0g8NkRZ/f/rnXO6A5BHy0jVF20jN8CS0eoUBxEHIWVYSIZUkVCS5zzVAdQLgsfwWWrcPBJ+VunruQfRX7qyDRbpzZu3iDwu0UzoBEAaEzVN2lhqquInAUOXH8MpGOW8x+PcF7ALlN2SVX2RZiDNbDFbQ2BY99WaqLkVTfaAeCp31wAE09z/A902kvhbfb5P/AzF+OuUOcUMVS3Mf01XV/FCfjcbIPfAFZswVExSxyKHdh8NT1Fur+HGBBo6svo7L7lRQrER0ln9vsM+U6Ox6zSmQ48q5rSr8i6nL02lE3voneQ2egDAVnisc7hal1U4kg8AtK43DtJv5MtfobTQ+JNvlsnG6y+mZQboRvkXRVrZ0todZzFCODVsbein5+H+YNn+qy6c/of/S5Q5JU0iPSWSqzKnvbctvyicsJQhdSQyQjEcyXzIs9hFqOnhXiZs3GtX+5onYDq7Ek4k0OQ65SluHw C8poOkDL 4jDdh+plvzk1bcdBIhn5DZgSt/WAt4NGvIf5y2eKgmPOCDlXOlBi/B4EN59DnUMmsMcLf/7Br1rG6PvrZU2uI7nPTc1Ac6j+sipdmGOuUN4JDijcyki9FgIPJ5SIm9BnU4zA44hHN6mdIYaDNqZARzmdmXnUgryLouRmhwnuxu0W9PEa9Jx934Fdg2ReJQPsD7Kvj4yKERMXxyzYQKkuPenY7Z3aeg8VDVO/5QuUagl4UQStWyy1cpKz2okoy14AHsQEG5aTKcMuPZ2z3RzbbI0GSi3HwuNJsCH2sGhTCtTDOS8tOBPE91HZpBEjCnCIKLERb7UtEQ753JHCjY63sBTNTwsel160k7upMUGDn8OT/2Ta42KwZWsO5jgoDxyikFnsCcxvdVR+Q3icvLpZNoaauWFulTUxG7cEF 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 04.06.25 15:11, Jason Gunthorpe wrote: > On Wed, Jun 04, 2025 at 12:07:21PM +0200, David Hildenbrand wrote: > >>> Instead of retrying, this patch explicitly fails the migration attempt >>> (-EBUSY) if no movable pages are found and unpinnable pages remain. >>> This avoids infinite loops and gives user a clear signal to retry, >>> rather then spinning inside kernel. >> >> Hmmm, that means we will return EBUSY to the caller. Are all users actually >> prepared to deal with that? > > I don't think anyone is really prepared to deal with GUP temporarily > failing.. > > Kernel is expected to sort it out. We tolerated the existing temporary > failure due to its rarity and lack of a solution only. > > Either it can be gup'd or not. There should be no retry. Right, so -EAGAIN should be used for now such that GUP itself will retry and can be canceled on signal if required. -- Cheers, David / dhildenb