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[2003:cb:c717:a000:d4df:4b8f:37d4:59e4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-35dd04da29csm2382073f8f.55.2024.05.31.11.24.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 31 May 2024 11:24:31 -0700 (PDT) Message-ID: Date: Fri, 31 May 2024 20:24:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [linus:master] [mm] efa7df3e3b: kernel_BUG_at_include/linux/page_ref.h To: Yang Shi Cc: kernel test robot , Peter Xu , Jason Gunthorpe , Vivek Kasireddy , Rik van Riel , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Andrew Morton , Matthew Wilcox , Christopher Lameter , linux-mm@kvack.org References: <202405311534.86cd4043-lkp@intel.com> <890e5a79-8574-4a24-90ab-b9888968d5e5@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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 40BB018001C X-Stat-Signature: mtn5tk9ajq1yqi89d1rxbpb6gwdfgfe6 X-HE-Tag: 1717179878-678059 X-HE-Meta: U2FsdGVkX18ZAaTlKCjl6PHV1Iqgyfi/fFrTZHuwrbVbhefFqiAS2ZRBJDxyDvdULmaD8GcApaWeZX78KZg/F1RZpoWOwx+jujxpw56YLlLgQOcbRsZYEixZmcdHMhRTiHbCgpQ/jDMsDUGoWK6Gu36Oa31PW+TocTVlkJNjz+XfiHpsQE62S3EXmFUbbeDVpggWBadvsT8QbHw/XsKu2emvMRmgSjuQiCGQya4lGGJ3OpIvLbzySmVgGRhXQ3qWsw+ZyRRQIp5yHqrOZ57cZJ7rtd59MA070Xyzi/vsq9lnFeA9soDHQex+n2mScj5krJa1Filo0ZwuImLhGznIEjk+GX2NJs6LdCZnfXURzZDw9Tp0QY1xZuMEDKes+lF2pDydIrXg2shVaAlz8EEGA5Izy0RXlM/6N0aFCwgKThAeRhOHtZgiALI4zd8VdJEcW87iAdl4LB+fsbrZ7YrWaVNIGVYcKkRjLNhsSHsx3SVgZF4LyoZGiX7rKzX6Bo6rpV5pm4jU9JkFqjmtvRPI8c/2QhysmwPMd5ncUs0toVvDyav5uGjgSvFKdHmXmkCgSSHrufybW8PFUk1fz3/Ebt0Cgc0iGfRv5wI5+BmkLM3Rq5C+pVme/8w+I6tWbO2olqhJ8A9qfUsISE/eNRFmF9B16ExjEBbtZbT//gnEpZAw5AiBnJB09nvq3NJ73FTo4xUEcdXlv/GDsSYUihp6bzJELDH680CtE3Zxuv1N/+oHpFICMkgZNUmcR24hjfgZW1mRAWAZzgXXlQ66E3tivPyKTMS7YCrk4lhfdE1DCMjHmVE0bBQvC4/tkt1mGjriKdJfJExG16gR6/ZLpCp5VJo93vYcw8pgiG5A8i2eNWAdvflAkC+LneuAq/wXjxL+cCsIyD1E6u6VfOFs8FdO59mZXuss6cjltPYShCkz2Xq9e+eiGCDpNtb1UkqDdqSnD1jfYYxBbQsa6VtRPK4 ENx2z7Nm 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 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 31.05.24 20:13, Yang Shi wrote: > On Fri, May 31, 2024 at 11:07 AM Yang Shi wrote: >> >> On Fri, May 31, 2024 at 10:46 AM David Hildenbrand wrote: >>> >>> On 31.05.24 18:50, Yang Shi wrote: >>>> On Fri, May 31, 2024 at 1:24 AM kernel test robot wrote: >>>>> >>>>> >>>>> >>>>> Hello, >>>>> >>>>> kernel test robot noticed "kernel_BUG_at_include/linux/page_ref.h" on: >>>>> >>>>> commit: efa7df3e3bb5da8e6abbe37727417f32a37fba47 ("mm: align larger anonymous mappings on THP boundaries") >>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master >>>>> >>>>> [test failed on linus/master e0cce98fe279b64f4a7d81b7f5c3a23d80b92fbc] >>>>> [test failed on linux-next/master 6dc544b66971c7f9909ff038b62149105272d26a] >>>>> >>>>> in testcase: trinity >>>>> version: trinity-x86_64-6a17c218-1_20240527 >>>>> with following parameters: >>>>> >>>>> runtime: 300s >>>>> group: group-00 >>>>> nr_groups: 5 >>>>> >>>>> >>>>> >>>>> compiler: gcc-13 >>>>> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G >>>>> >>>>> (please refer to attached dmesg/kmsg for entire log/backtrace) >>>>> >>>>> >>>>> we noticed the issue does not always happen. 34 times out of 50 runs as below. >>>>> the parent is clean. >>>>> >>>>> 1803d0c5ee1a3bbe efa7df3e3bb5da8e6abbe377274 >>>>> ---------------- --------------------------- >>>>> fail:runs %reproduction fail:runs >>>>> | | | >>>>> :50 68% 34:50 dmesg.Kernel_panic-not_syncing:Fatal_exception >>>>> :50 68% 34:50 dmesg.RIP:try_get_folio >>>>> :50 68% 34:50 dmesg.invalid_opcode:#[##] >>>>> :50 68% 34:50 dmesg.kernel_BUG_at_include/linux/page_ref.h >>>>> >>>>> >>>>> >>>>> If you fix the issue in a separate patch/commit (i.e. not just a new version of >>>>> the same patch/commit), kindly add following tags >>>>> | Reported-by: kernel test robot >>>>> | Closes: https://lore.kernel.org/oe-lkp/202405311534.86cd4043-lkp@intel.com >>>>> >>>>> >>>>> [ 275.267158][ T4335] ------------[ cut here ]------------ >>>>> [ 275.267949][ T4335] kernel BUG at include/linux/page_ref.h:275! >>>>> [ 275.268526][ T4335] invalid opcode: 0000 [#1] KASAN PTI >>>>> [ 275.269001][ T4335] CPU: 0 PID: 4335 Comm: trinity-c3 Not tainted 6.7.0-rc4-00061-gefa7df3e3bb5 #1 >>>>> [ 275.269787][ T4335] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 >>>>> [ 275.270679][ T4335] RIP: 0010:try_get_folio (include/linux/page_ref.h:275 (discriminator 3) mm/gup.c:79 (discriminator 3)) >>>>> [ 275.271159][ T4335] Code: c3 cc cc cc cc 44 89 e6 48 89 df e8 e4 54 11 00 eb ae 90 0f 0b 90 31 db eb d5 9c 58 0f 1f 40 00 f6 c4 02 0f 84 46 ff ff ff 90 <0f> 0b 48 c7 c6 a0 54 d2 87 48 89 df e8 a9 e9 ff ff 90 0f 0b be 04 >>>> >>>> If I read this BUG correctly, it is: >>>> >>>> VM_BUG_ON(!in_atomic() && !irqs_disabled()); >>>> >>> >>> Yes, that seems to be the one. >>> >>>> try_grab_folio() actually assumes it is in an atomic context (irq >>>> disabled or preempt disabled) for this call path. This is achieved by >>>> disabling irq in gup fast or calling it in rcu critical section in >>>> page cache lookup path >>> >>> try_grab_folio()->try_get_folio()->folio_ref_try_add_rcu() >>> >>> Is called (mm-unstable) from: >>> >>> (1) gup_fast function, here IRQs are disable >>> (2) gup_hugepte(), possibly problematic >>> (3) memfd_pin_folios(), possibly problematic >>> (4) __get_user_pages(), likely problematic >>> >>> (1) should be fine. >>> >>> (2) is possibly problematic on the !fast path. If so, due to commit >>> a12083d721d7 ("mm/gup: handle hugepd for follow_page()") ? CCing Peter. >>> >>> (3) is possibly wrong. CCing Vivek. >>> >>> (4) is what we hit here >>> >>>> >>>> And try_grab_folio() is used when the folio is a large folio. The >>> >>> >>> We come via process_vm_rw()->pin_user_pages_remote()->__get_user_pages()->try_grab_folio() >>> >>> That code was added in >>> >>> commit 57edfcfd3419b4799353d8cbd6ce49da075cfdbd >>> Author: Peter Xu >>> Date: Wed Jun 28 17:53:07 2023 -0400 >>> >>> mm/gup: accelerate thp gup even for "pages != NULL" >>> >>> The acceleration of THP was done with ctx.page_mask, however it'll be >>> ignored if **pages is non-NULL. >>> >>> >>> Likely the try_grab_folio() in __get_user_pages() is wrong? >>> >>> As documented, we already hold a refcount. Likely we should better do a >>> folio_ref_add() and sanity check the refcount. >> >> Yes, a plain folio_ref_add() seems ok for these cases. >> >> In addition, the comment of folio_try_get_rcu() says, which is just a >> wrapper of folio_ref_try_add_rcu(): >> >> You can also use this function if you're holding a lock that prevents >> pages being frozen & removed; eg the i_pages lock for the page cache >> or the mmap_lock or page table lock for page tables. In this case, it >> will always succeed, and you could have used a plain folio_get(), but >> it's sometimes more convenient to have a common function called from >> both locked and RCU-protected contexts. >> >> So IIUC we can use the plain folio_get() at least for >> process_vm_readv/writev since mmap_lock is held in this path. >> >>> >>> >>> In essence, I think: try_grab_folio() should only be called from GUP-fast where >>> IRQs are disabled. >> >> Yes, I agree. Just the fast path should need to call try_grab_folio(). > > try_grab_folio() also handles FOLL_PIN and FOLL_GET, so we may just > keep calling it and add a flag to try_grab_folio, just like: > > if flag is true > folio_ref_add() > else > try_get_folio() try_grab_page() is what we use on the GUP-slow path. We'd likely want a folio variant of that. We might want to call that gup_try_grab_folio() and rename the other one to gup_fast_try_grab_folio(). Or something like that :) -- Cheers, David / dhildenb