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b=cbpZZvN1V4yJhr0654j0pNRf6FbcuIx6mTMvt1ROw6G9X1SImEmMDOJ8lH1jBsd7o PCYd8QZSQxPI3rWir6g0spJlEVytWn5Aj0Z9YDz+Zs0RjPHXjxWwZPO+Gh+7AoQRT2 2Pazx6lAvyFTAezAxSfnddj4eTjun3C5nXk3/h/unfXMMJA1HapLsKbUObn0MyoMX+ ZyyEwpScnoo3K1x1ZcyOlP+WsdL9Bmall51adOCKtDYfcGY+wrBESCcFjoj3xY1Gok CCMlpYOTN8a6Iy3/fVzKtd3gBDKV426pk/v88DTkF1VbsHtNukMjCw3fGlvxjCtPbz vKUfzJ2aNbdOg== Message-ID: Date: Wed, 30 Sep 2026 18:46:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/memory_hotplug: fix missing rollback in __add_pages() To: Lance Yang , osalvador@suse.de Cc: akpm@linux-foundation.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260930160432.5564-1-lance.yang@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: <20260930160432.5564-1-lance.yang@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 555wcyfqzmraq5ui3u4e7frab37zs89o X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0867C180013 X-HE-Tag: 1790786787-373397 X-HE-Meta: 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 B8l+WGXk 4xa51SJCh2qChb8Teg85XFecFwgDM6MtsyeCAisRUHFPMpkiv13JMQSQZGvesVTujq5MYklWNvP/b6f1sHF8JZ3IoLZn4Z592u6IJb2tdC1SM8d6BGqhE1+q0nZw84kJ1wUPRhpMjmTzM4rBXkSSWJ6SQNwVRyNGbgrT7/ewU4/yUw0HmUpAl81wjzCk7Sli3nnMNaW1n9rqcxrn3u9ZfotP/r5ra9qtrdcuwVqZqIch0OpFI/A0rk2RbEyLkhopxAcyr5MRqYi58OJu7k95+m/J2Z1wC8Co1BlbcfYb/izmJ9Huq17y1dZ/iW5NNJsrPRxvjYnVierkvJDI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/30/26 18:04, Lance Yang wrote: > __add_pages() returns on a sparse_add_section() failure without removing > the sections already added in the same request. > > For memremap_pages(), the failed range is not counted in pgmap->nr_range, > so memunmap_pages() skips it. The sections already added in that range > retain their vmemmap mappings and subsection bits. Retrying a > section-aligned range can then fail with -EEXIST. > > Save the initial PFN and remove [start_pfn, pfn) on failure. For a vmemmap > population failure, section_activate() already cleans up the current > section, so the rollback excludes it. If the first section fails, > __remove_pages() receives an empty range and does nothing. > > Link: https://lore.kernel.org/all/BAD58999-1EDD-4A37-ABA0-DB1BD8AB3453@linux.dev/ > Suggested-by: Muchun Song > Signed-off-by: Lance Yang > --- > No Fixes tag, as I couldn't identify the commit that introduced this issue. > > mm/memory_hotplug.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 796af1028ee2..ca4656698148 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -380,6 +380,7 @@ EXPORT_SYMBOL_GPL(pfn_to_online_page); > int __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, > struct mhp_params *params) > { > + const unsigned long start_pfn = pfn; > const unsigned long end_pfn = pfn + nr_pages; > unsigned long cur_nr_pages; > int err; > @@ -413,8 +414,11 @@ int __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, > SECTION_ALIGN_UP(pfn + 1) - pfn); > err = sparse_add_section(nid, pfn, cur_nr_pages, altmap, > params->pgmap); > - if (err) > + if (err) { > + __remove_pages(start_pfn, pfn - start_pfn, altmap, > + params->pgmap); > break; > + } > cond_resched(); > } > vmemmap_populate_print_last(); Makes sense and LGTM. Do we have a Fixes: tag? It probably dates back quite a while ... not sure about stable, we never saw this in practice. But if it's easy, we should just do it? (not sure if we ever had __remove_pages be limited to hotunplug support) I'm planning on picking this up and sending it for the next merge window (so not as a hotfix). Looking at this ... x86 does not really expect add_pages to fail: ret = __add_pages(nid, start_pfn, nr_pages, params); WARN_ON_ONCE(ret); That's probably something to clean up as well? -- Cheers, David