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[2003:cb:c709:6200:16ba:af70:999d:6a1a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38bf3214fbdsm12908147f8f.19.2025.01.21.00.13.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jan 2025 00:13:27 -0800 (PST) Message-ID: <56fe9ae8-e9bf-4627-a10a-ba1d3e84e8c8@redhat.com> Date: Tue, 21 Jan 2025 09:13:26 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: gup: fix infinite loop within __get_longterm_locked To: "zhaoyang.huang" , Andrew Morton , Alistair Popple , John Hubbard , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zhaoyang Huang , steve.kang@unisoc.com, aijun.sun@unisoc.com References: <20250121020159.3636477-1-zhaoyang.huang@unisoc.com> From: David Hildenbrand Content-Language: en-US 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: <20250121020159.3636477-1-zhaoyang.huang@unisoc.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 21.01.25 03:01, zhaoyang.huang wrote: > From: Zhaoyang Huang > > We can run into an infinite loop in __get_longterm_locked() when > collect_longterm_unpinnable_folios() finds only folios that are isolated > from the LRU or were never added to the LRU. This can happen when all > folios to be pinned are never added to the LRU, for example when > vm_ops->fault allocated pages using cma_alloc() and never added them to > the LRU. > > We incorrectly update the "collected" variable even if nothing was > collected. Fix it by incrementing "collected" only when we isolated a > folio and added it to the list of folios to migrate. Last sentence now has to be "Fix it by simply taking a look at the list in the single caller, to see if anything was added.". > > Fixes: 67e139b02d99 ("mm/gup.c: refactor check_and_migrate_movable_pages()") > > Reviewed-by: John Hubbard > Suggested-by: David Hildenbrand > Signed-off-by: Zhaoyang Huang > --- > v2: judge if there are unpinnable pages via list_empty and update commit > message > --- > --- > mm/gup.c | 14 ++++---------- > 1 file changed, 4 insertions(+), 10 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 3b75e631f369..37951fba929a 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2323,11 +2323,11 @@ static void pofs_unpin(struct pages_or_folios *pofs) > /* > * Returns the number of collected folios. Return value is always >= 0. > */ > -static unsigned long collect_longterm_unpinnable_folios( > +static void collect_longterm_unpinnable_folios( > struct list_head *movable_folio_list, > struct pages_or_folios *pofs) > { > - unsigned long i, collected = 0; > + unsigned long i; Nit: "reverse christmas tree" parameter format wants this to come after the "drain_allow" variable now. > struct folio *prev_folio = NULL; > bool drain_allow = true; > > @@ -2341,8 +2341,6 @@ static unsigned long collect_longterm_unpinnable_folios( > if (folio_is_longterm_pinnable(folio)) > continue; > > - collected++; > - > if (folio_is_device_coherent(folio)) > continue; > > @@ -2364,8 +2362,6 @@ static unsigned long collect_longterm_unpinnable_folios( > NR_ISOLATED_ANON + folio_is_file_lru(folio), > folio_nr_pages(folio)); > } > - > - return collected; > } > > /* > @@ -2442,11 +2438,9 @@ static long > check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs) > { > LIST_HEAD(movable_folio_list); > - unsigned long collected; > > - collected = collect_longterm_unpinnable_folios(&movable_folio_list, > - pofs); > - if (!collected) > + collect_longterm_unpinnable_folios(&movable_folio_list, pofs); > + if (list_empty(&movable_folio_list)) > return 0; > > return migrate_longterm_unpinnable_folios(&movable_folio_list, pofs); Nice, exactly what I just recommended as reply to #1 after waking up :) Reviewed-by: David Hildenbrand -- Cheers, David / dhildenb