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(p200300d82f23c700d8ae41bf492a9e4c.dip0.t-ipconnect.de. [2003:d8:2f23:c700:d8ae:41bf:492a:9e4c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3bb5d089e07sm5007536f8f.0.2025.08.16.02.01.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 16 Aug 2025 02:01:48 -0700 (PDT) Message-ID: <66ebc632-6704-4637-b62d-1cb11e5a4782@redhat.com> Date: Sat, 16 Aug 2025 11:01:47 +0200 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] mm/migrate: Fix NULL movable_ops if CONFIG_ZSMALLOC=m To: Huacai Chen Cc: Huacai Chen , Andrew Morton , linux-mm@kvack.org, Zi Yan , Lorenzo Stoakes , Harry Yoo , linux-kernel@vger.kernel.org, Minchan Kim , Sergey Senozhatsky , "Michael S. Tsirkin" References: <20250815090539.1578484-1-chenhuacai@loongson.cn> 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 16.08.25 10:57, Huacai Chen wrote: > Hi, David, > > On Sat, Aug 16, 2025 at 3:22 PM David Hildenbrand wrote: >> >> On 15.08.25 11:05, Huacai Chen wrote: >> >> Hi, >> >> please CC the appropriate maintainers next time. You missed (some) >> balloon and zsmalloc maintainers. > OK, thanks. > >> >>> After commit 84caf98838a3e5f4bdb34 ("mm: stop storing migration_ops in >>> page->mapping") we get such an error message if CONFIG_ZSMALLOC=m: >>> >>> WARNING: CPU: 3 PID: 42 at mm/migrate.c:142 isolate_movable_ops_page+0xa8/0x1c0 >>> CPU: 3 UID: 0 PID: 42 Comm: kcompactd0 Not tainted 6.16.0-rc5+ #2133 PREEMPT >>> pc 9000000000540bd8 ra 9000000000540b84 tp 9000000100420000 sp 9000000100423a60 >>> a0 9000000100193a80 a1 000000000000000c a2 000000000000001b a3 ffffffffffffffff >>> a4 ffffffffffffffff a5 0000000000000267 a6 0000000000000000 a7 9000000100423ae0 >>> t0 00000000000000f1 t1 00000000000000f6 t2 0000000000000000 t3 0000000000000001 >>> t4 ffffff00010eb834 t5 0000000000000040 t6 900000010c89d380 t7 90000000023fcc70 >>> t8 0000000000000018 u0 0000000000000000 s9 ffffff00010eb800 s0 ffffff00010eb800 >>> s1 000000000000000c s2 0000000000043ae0 s3 0000800000000000 s4 900000000219cc40 >>> s5 0000000000000000 s6 ffffff00010eb800 s7 0000000000000001 s8 90000000025b4000 >>> ra: 9000000000540b84 isolate_movable_ops_page+0x54/0x1c0 >>> ERA: 9000000000540bd8 isolate_movable_ops_page+0xa8/0x1c0 >>> CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) >>> PRMD: 00000004 (PPLV0 +PIE -PWE) >>> EUEN: 00000000 (-FPE -SXE -ASXE -BTE) >>> ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7) >>> ESTAT: 000c0000 [BRK] (IS= ECode=12 EsubCode=0) >>> PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) >>> CPU: 3 UID: 0 PID: 42 Comm: kcompactd0 Not tainted 6.16.0-rc5+ #2133 PREEMPT >>> Stack : 90000000021fd000 0000000000000000 9000000000247720 9000000100420000 >>> 90000001004236a0 90000001004236a8 0000000000000000 90000001004237e8 >>> 90000001004237e0 90000001004237e0 9000000100423550 0000000000000001 >>> 0000000000000001 90000001004236a8 725a84864a19e2d9 90000000023fcc58 >>> 9000000100420000 90000000024c6848 9000000002416848 0000000000000001 >>> 0000000000000000 000000000000000a 0000000007fe0000 ffffff00010eb800 >>> 0000000000000000 90000000021fd000 0000000000000000 900000000205cf30 >>> 000000000000008e 0000000000000009 ffffff00010eb800 0000000000000001 >>> 90000000025b4000 0000000000000000 900000000024773c 00007ffff103d748 >>> 00000000000000b0 0000000000000004 0000000000000000 0000000000071c1d >>> ... >>> Call Trace: >>> [<900000000024773c>] show_stack+0x5c/0x190 >>> [<90000000002415e0>] dump_stack_lvl+0x70/0x9c >>> [<90000000004abe6c>] isolate_migratepages_block+0x3bc/0x16e0 >>> [<90000000004af408>] compact_zone+0x558/0x1000 >>> [<90000000004b0068>] compact_node+0xa8/0x1e0 >>> [<90000000004b0aa4>] kcompactd+0x394/0x410 >>> [<90000000002b3c98>] kthread+0x128/0x140 >>> [<9000000001779148>] ret_from_kernel_thread+0x28/0xc0 >>> [<9000000000245528>] ret_from_kernel_thread_asm+0x10/0x88 >>> >>> The reason is that defined(CONFIG_ZSMALLOC) evaluates to 1 only when >>> CONFIG_ZSMALLOC=y, we should use IS_ENABLED(CONFIG_ZSMALLOC) instead. >> >> Ouch, I missed that CONFIG_ZSMALLOC can be configured like that. I >> thought it would always be builtin. > Make CONFIG_ZSMALLOC be bool can solve this, if you think it is reasonable. > >> >>> But when I use IS_ENABLED(CONFIG_ZSMALLOC), page_movable_ops() cannot >>> access zsmalloc_mops because zsmalloc_mops is in a module. >>> >>> To solve this problem, we define a movable_ops[] array in mm/migrate.c, >>> initialise its elements at mm/balloon_compaction.c & mm/zsmalloc.c, and >>> let the page_movable_ops() function return elements from movable_ops[]. >> >> Before I took that easy route to just get it working quickly, I >> envisioned a proper registration interface. See below. > When I found I cannot access zsmalloc_mops in a module I considered > the registration interface. But in this case I think that is an > over-design and not straight forward. > > Moreover, a registration interface looks like a redesign and not > suitable for hot-fix. I think you misread my message: This is not debatable. If you don't want to fix it properly, I can send a fix. -- Cheers David / dhildenb