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[2003:cb:c74b:bf00:182c:d606:87cf:6fea]) by smtp.gmail.com with ESMTPSA id p9-20020a05600c1d8900b0041563096e15sm19424980wms.5.2024.05.06.02.54.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 May 2024 02:54:50 -0700 (PDT) Message-ID: <96439935-ce2a-4714-be5d-cdeb8ea0eb41@redhat.com> Date: Mon, 6 May 2024 11:54:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: get_pageblock_bitmap() sometimes returns a NULL pointer which needs to be properly handled To: Baolin Wang , Markus Gothe , "linux-mm@kvack.org" Cc: "akpm@linux-foundation.org" , Zi Yan 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-Stat-Signature: jsng3idktw7j4jp6xtwjb4mgd4n5km6g X-Rspam-User: X-Rspamd-Queue-Id: 2CA19A0005 X-Rspamd-Server: rspam05 X-HE-Tag: 1714989296-281606 X-HE-Meta: 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 ksPoqlh1 qI0x+ckHTdLP16BwoYeYZ2XLVDTpArbjT9I4dW2eS4m3B1fHB58R0230NNmQixrGYDCejeLok4GXK36q17oqICszNsc0Cq1rXl5JoKawrIow0lbYbixrg7J4fjFfTtOWWsYw2zJ7WBOEUjXfc/HJYVOzvBpxGbw1kQXuNtu9oNN0O8pjE32Y7AI2db3WnogCmqVz01Z8GuR84YzesDzV0DKLMK/48JgjQlFvOyxB2Na8n6KX6cDzBXIXN6dy/S58Yv1zWqQz55+2i1STXU94d8NlSxwXSZNWouQh0czPgW5Z5hKsxsgxQIQ9Y57uAtOaxJwyi33kZ75kou4YnqDe4EOdY7jAxuDltfgB/XnNfkqVJ11I66ZWEYuc47wNrsKVMxjIf5pGOqz/nHIYni1iqbL43TPlfPHVREUpaOSLIp7ywZVcS4A33ZbwohIzShXqOJN+zkx1mjeZZR7Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.005148, 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 06.05.24 11:39, Baolin Wang wrote: > Ccing David. > > On 2024/5/3 00:02, Markus Gothe wrote: >> Hi, >> under some rare occasion I run into the following crash: >> >> [ 41.417606] pstate: 80400005 (Nzcv daif +PAN -UAO) >> [ 41.422406] pc : set_pfnblock_flags_mask+0x50/0x94 >> [ 41.427193] lr : compaction_alloc+0x220/0x804 >> [ 41.431544] sp : ffffffc01104bb10 >> [ 41.434852] x29: ffffffc01104bb10 x28: ffffffc010e5b500 >> [ 41.440165] x27: 0000000000098000 x26: ffffffc010e5b500 >> [ 41.445477] x25: 0000000000000066 x24: 0000000000090800 >> [ 41.450789] x23: 0000000000000200 x22: 0000000000084000 >> [ 41.456093] x21: ffffffc010e82000 x20: ffffffc010b88000 >> [ 41.461396] x19: ffffffc01104bd70 x18: 0000000000000000 >> [ 41.466700] x17: f1f24e35df34dda4 x16: 6b3f63a0e1157268 >> [ 41.472004] x15: 4b3990ec2568ada0 x14: 757ebc126939cb5f >> [ 41.477308] x13: 9df9488aba179ccb x12: 0000000000000000 >> [ 41.482612] x11: 0000000000000000 x10: ffffffc010c5fc30 >> [ 41.487916] x9 : ffffff801eea7c00 x8 : 000000001bf00000 >> [ 41.493219] x7 : 0000000000000000 x6 : 000000000000003f >> [ 41.498525] x5 : 0000000000000108 x4 : 1000000000000000 >> [ 41.503835] x3 : 0000000000000021 x2 : 000000000000003c >> [ 41.509139] x1 : 0000000000000001 x0 : 0000000000000003 >> [ 41.514443] Call trace: >> [ 41.516887] set_pfnblock_flags_mask+0x50/0x94 >> [ 41.521330] migrate_pages+0x90/0x7f0 >> [ 41.524992] compact_zone+0x854/0x9f0 >> [ 41.528647] kcompactd_do_work+0x168/0x230 >> [ 41.532734] kcompactd+0x58/0x140 >> [ 41.536043] kthread+0x120/0x124 >> [ 41.539263] ret_from_fork+0x10/0x24 >> [ 41.542835] Code: d346fc43 4b0000c2 8b030ce5 9ac22084 (f86378e0) >> [ 41.548925] ---[ end trace 731400a587304db3 ]--- >> >> >> I've pin-pointed it down to pageblock_flags pointer being initialized to NULL under certain conditions. I don't know why this happens. >> Maybe it is some obscure race condition which only shows up on my system. > > Is there memory hotplug in your test? It seems to be caused by the race > between memory hotplug and PFN walkers (such as compaction), which is > already a known issue. I think I've never seen races with access to pageblocks but only with access to the memmap. Further, I'd not expect races during migrate_pages()? We're holding a reference do all folios when calling migrate_pages(). So memory offlining+removal would not be able to succeed until we drop these references. But, could it be that we failing during compaction_alloc() [lr : compaction_alloc+0x220/0x804] and have an issue during set_pfnblock_flags_mask() on a page that sits on the isolated freelist? Similarly, memory hotunplug should not be able to mess up here. [again, racing with memory hotunplug is unlikely] On which kernel did we start seeing this issue? -- Cheers, David / dhildenb