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[2003:d8:2f25:bd00:949:b5a9:e02a:f265]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e24155bsm135891305e9.17.2025.06.16.01.39.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Jun 2025 01:39:25 -0700 (PDT) Message-ID: <10c87a0e-c9fe-48fe-9bbd-16afd244b4ec@redhat.com> Date: Mon, 16 Jun 2025 10:39:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 03/10] mm,memory_hotplug: Implement numa node notifier To: Oscar Salvador Cc: Andrew Morton , Vlastimil Babka , Jonathan Cameron , Harry Yoo , Rakie Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Joshua Hahn , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250609092149.312114-1-osalvador@suse.de> <20250609092149.312114-4-osalvador@suse.de> <2bec8b53-f788-493e-a76e-1f804ed3aa0c@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-MFC-PROC-ID: DGK7snd24zAwmkU2_9CBj1W7t-XmJORk1QQm7Bvt_Lo_1750063167 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 988E980006 X-Stat-Signature: k9gym4uwjos54mdw1uuq1nzoejmpd6xu X-Rspam-User: X-HE-Tag: 1750063171-705041 X-HE-Meta: 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 3asxg+P1 nhNWPR9jrgZoVQbJxGRv6bj/PR2CIqgJBlcdIKwddveBwfxGK+oZDS6MhzXwsxzpA4IuSDctuU0sC3GLmDo5knzBdcBd7b0ZXnUgz45d/ZiIN2GVN1tXz84CwQR72mKoXN4g1Df6YE64Jng0rvBEOOm14cstg3hcZtF0eNCej24LqGvwoZwBMzZSyjgTJY47uehZIDgCa17b0K0NwBKBARdWOXyaJpelm/JQBT3IBt2WRajX3wXxH1EfwQOSN6i/IS+f74c2l9xbSYTV2oSpteDHC1T1Ik1zPnkcp5kEpy+yDI4hNm2sOO6JULAvtfg0C5V1KzI2CPCnAl6GLb4cWBGh5zwWPLCbt2sPREttsa9Iyl3yUpE8WVe60ie/uRZCZ543wn1+n/xD80K7ucCUbJCprO2YqM2LaMXRRVqZeMUr9eE1rywquYTOaKNn6UjI+1OevW3iD9tFBtf2KS5Rkbi5gJVvi8vCIad1tuchz4elJuwmSHbkgm2cutOBMlKJ8tTCiPQQ/84X++lI= 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 16.06.25 10:30, Oscar Salvador wrote: > On Tue, Jun 10, 2025 at 10:10:21AM +0200, David Hildenbrand wrote: >> On 09.06.25 11:21, Oscar Salvador wrote: >>> +The first argument of the callback function (self) is a pointer to the block >>> +of the notifier chain that points to the callback function itself. >>> +The second argument (action) is one of the event types described above. >>> +The third argument (arg) passes a pointer of struct node_notify:: >>> + >>> + struct node_notify { >>> + int nid; >>> + } >>> + >>> +- nid is the node we are adding or removing memory to. >>> + >>> + If nid >= 0, callback should create/discard structures for the >>> + node if necessary. >> >> Likely that should be removed? > > Yes, indeed. > >> >> It' probably worth mentioning that one might get notified about >> NODE_CANCEL_ADDING_FIRST_MEMORY even though never notified for >> NODE_ADDING_FIRST_MEMORY. (same for removing) >> >> I recall this can happen if one of the NODE_ADDING_FIRST_MEMORY notifiers >> fails. >> >> (same applies to MEM_CANCEL_*) >> >> Consequently, we might simplify the cancel_mem_notifier_on_err etc stuff, >> simply unconditionally calling the cancel counterparts. > > So, I managed to do another respin with all feedback included, but I > left this one for the end, and here I'm. > > It's true, currently users can get notified about e.g: MEM_CANCE_ONLINE without > going through MEM_GOING_ONLINE if another user fails for the latter, but I'm > trying to workaround the fact why that's not a problem. > > Because assume you have a user of MEM_CANCEL_ONLINE, who thinks it got called > for MEM_GOING_ONLINE, while in fact it didn't because some other user fail on > it, and it tries to free some memory it thinks it initialized during MEM_GOING_ONLINE. > > Isn't this a bit shaky? It's suboptimal yes, But to get it right, you'd have to remmeber for exactly which notofiers you performed the calls ... > I mean, yes, I guess we can put the burden on the users of > the notifiers to not assume anything, but then yes, I think we should document this > as it can lead to potential misbeliefs. The burden is already on the users I think. E.g., virio-mem maintains a "hotplug_active" variable, to detect whether MEM_ONLINE was actually called. -- Cheers, David / dhildenb