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Tsirkin" References: <20250815090539.1578484-1-chenhuacai@loongson.cn> <66ebc632-6704-4637-b62d-1cb11e5a4782@redhat.com> <9db98f7f-b90f-464b-ae7f-e94ac523bc28@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 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 5DLAWQk9EmyNNUxpfcebIy7Lf43UCoc85SpJOQPDwuE_1755417898 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: BF6F2140008 X-Rspam-User: X-Stat-Signature: 16jxwgofqrnqswphsth1q8h4mynnedz4 X-Rspamd-Server: rspam09 X-HE-Tag: 1755417903-950401 X-HE-Meta: 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 yENkKUge 3xjwIgGvBvWO5vY5Y5vcoZbMBmGpjimzyE6E2+bC2PKXGTg02WOxsheefQ0f4IDV/rY1OykU5P1H71ZbmttcaiEHyOCCaGR2qy9sVZLI1LjMMJQL7zBItp5e4UyqlyXzXDQDF5PYogtGxvHz3Pz91kduFuPcQCvsEdLnwbjyd9cQbtBiiypF4pop14A0cFrHwLx0DCtL/quue2tUSLwo3BFIBLRWy2J8pHEk7pCE49h28yC3GTVUHa6SWmmq807/5lQk3Z399MPMl2Yz84HQZJZ5plkmUCr66rFFYI1+dveeGQQTCUiVkAn9eteDJC+MY3VlK05G5twS6wmoaLKGiR6YmZe7HhMofKng/+Li77EsaL3j2ueVzJYa/724+M+NPgLaHoGd7i23XQghyiwNGoEzZuO37MR0023pD22LXTcPQmZIGRWVVASsv0BJ0MjseGLNYb9PFD7O/3hLrfLaa6H+fhM3WM4H5ngGnBP6Sutf5jcc= 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 17.08.25 03:37, Huacai Chen wrote: > On Sun, Aug 17, 2025 at 1:02 AM David Hildenbrand wrote: >> >> On 16.08.25 18:23, Matthew Wilcox wrote: >>> On Sat, Aug 16, 2025 at 12:54:52PM +0200, David Hildenbrand wrote: >>>> +++ b/mm/balloon_compaction.c >>>> @@ -256,8 +256,10 @@ const struct movable_operations balloon_mops = { >>>> static int __init balloon_init(void) >>>> { >>>> - movable_ops[MOVABLE_BALLOON] = &balloon_mops; >>>> - return 0; >>>> + int rc; >>>> + >>>> + rc = register_movable_ops(&balloon_mops, PGTY_offline); >>>> + return rc; >>> >>> Using 'rc' as the name of this variable is an anti-pattern. All it >>> tells you is "this is the return value". Calling it 'err' is far >>> better because now we know it's an error number (or zero for success, >>> of course). >> >> I know, we all have our things to complain about. Some about Cc: above >> --, others about the name of error variables :P >> >> $ git grep "int rc" | wc -l >> 12730 >> $ git grep "int ret" | wc -l >> 80386 >> $ git grep "int error" | wc -l >> 4349 >> $ git grep "int err " | wc -l >> 6117 >> >>> >>> It seems to be a particularly IBM derived antipattern ;-) >> >> Careful miser :D >> >>> Some internal style guide, perhaps? >> >> Kernel-internal style guide maybe ;) >> >>> >>>> +void unregister_movable_ops(const struct movable_operations *ops, enum pagetype type) >>>> +{ >>>> + switch (type) { >>>> + case PGTY_offline: >>>> + WARN_ON_ONCE(offline_movable_ops != ops); >>>> + offline_movable_ops = NULL; >>>> + break; >>>> + case PGTY_zsmalloc: >>>> + WARN_ON_ONCE(zsmalloc_movable_ops != ops); >>>> + zsmalloc_movable_ops = NULL; >>>> + break; >>> >>> This might be a bit excessive ... just passing the pagetype and not >>> having the sanity checks should be enough for the tiny number of users >>> this interface will have. >> >> Yeah, no strong opinion, this was a 3 minute hack. > I have tested your code, everything works well. But if the checking is > too excessive, can I use a set_movalbe_ops() to replace both > register_movable_ops() and unregister_movable_ops()? Makes sense, given that I don't expect us to have multiple handlers for the same type in the near future. Please do keep a sanity check for replacing valid pointers if (old_ops && new_ops) return -EBUSY; Thanks! -- Cheers David / dhildenb