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[2003:d8:2f20:da00:b70a:d502:3b51:1f2d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e7607e2fd7sm5942242f8f.63.2025.09.12.02.36.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Sep 2025 02:36:18 -0700 (PDT) Message-ID: <37816bb5-97f8-4c05-84ed-9a81cfc5c755@redhat.com> Date: Fri, 12 Sep 2025 11:36:17 +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] resource: Improve child resource handling in release_mem_region_adjustable() To: Sumanth Korikkar Cc: Andrew Morton , linux-mm , linux-s390@vger.kernel.org, LKML , Dan Williams , Andy Shevchenko , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Alexander Gordeev References: <20250911140004.2241566-1-sumanthk@linux.ibm.com> <0ab2cb14-ba8e-4436-b03d-9457137f492a@redhat.com> 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: 7bit > > Hi David, Hi! > > I am working on the item related to the last discussion - dynamic > runtime (de)configuration of memory on s390: > https://lore.kernel.org/all/aCx-SJdHd-3Z12af@li-2b55cdcc-350b-11b2-a85c-a78bff51fc11.ibm.com/ > > I came across the problem when I tried to offline and remove the memory > via /sys/firmware/memory interface. Ah, that makes sense. Sorry that I didn't immediately connect the dots when seeing your name. > > I have also modified lsmem (not yet upstream) to list deconfigured > memory, which currently appears as offline. An additional "configured" > column is also introduced to show the configuration state, but it is not > displayed here yet (without --output-all). Worth mentioning in the patch description, otherwise it's confusing. > >>> 0x0000000150000000-0x0000000157ffffff 128M offline 42 > > True, this will not be shown with the master lsmem, since the sysfs > entry is removed after deconfiguration. > >> Do we need a Fixes: and CC stable? > > It will reference commit 825f787bb496 ("resource: add > release_mem_region_adjustable()"). Since the commit already states > "enhance this logic when necessary," I did not add a Fixes tag. So if this cannot be triggered yet, all good and no need for Fixes:. I was assuming that maybe this can be triggered with ppc dlpar, so I was concerned. > >>> Signed-off-by: Sumanth Korikkar >>> --- >>> kernel/resource.c | 44 +++++++++++++++++++++++++++++++++++++++----- >>> 1 file changed, 39 insertions(+), 5 deletions(-) >>> >>> diff --git a/kernel/resource.c b/kernel/resource.c >>> index f9bb5481501a..c329b8a4aa2f 100644 >>> --- a/kernel/resource.c >>> +++ b/kernel/resource.c >>> @@ -1388,6 +1388,41 @@ void __release_region(struct resource *parent, resource_size_t start, >>> EXPORT_SYMBOL(__release_region); >>> #ifdef CONFIG_MEMORY_HOTREMOVE >>> +static void append_child_to_parent(struct resource *new_parent, struct resource *new_child) >>> +{ >>> + struct resource *child; >>> + >>> + child = new_parent->child; >>> + if (child) { >>> + while (child->sibling) >>> + child = child->sibling; >>> + child->sibling = new_child; >> >> Shouldn't we take care of the address ordering here? I guess this works >> because we process them in left-to-right (lowest-to-highest) address. > > __request_resource() adds the child resources in the increasing order. > With that, we dont need to check the ordering again here. True, here we > process the child resources from lowest to highest address. > >>> + } else { >>> + new_parent->child = new_child; >>> + } >>> + new_child->parent = new_parent; >>> + new_child->sibling = NULL; >>> +} >>> + >>> +static void move_children_to_parent(struct resource *old_parent, >>> + struct resource *new_parent, >>> + resource_size_t split_addr) >> >> I'd call this "reparent_child_resources". But actually the function is >> weird. Because you only reparents some resources from old to now. >> >> Two questions: >> >> a) Is split_addr really required. Couldn't we derive that from "old_parent" > > old_parent->end points to old end range before the split, so I think it > doesnt tell where the split boundary is, until __adjust_resource() is > called. Hence, split_addr was added. Makes sense, that's also where the sanity checks happen. Worth throwing in a comment for the function telling that lower was not adjusted yet. -- Cheers David / dhildenb