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[2003:d8:2f4d:e00:298:59cc:2514:52]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45dd063fc8dsm34549275e9.7.2025.09.05.02.40.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Sep 2025 02:40:43 -0700 (PDT) Message-ID: <83f5643f-7a6f-4954-a989-4d76a206d0a9@redhat.com> Date: Fri, 5 Sep 2025 11:40:42 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: check the correct buddy if it is a starting block To: Wei Yang , akpm@linux-foundation.org Cc: linux-mm@kvack.org, Johannes Weiner , Zi Yan , Baolin Wang , Vlastimil Babka References: <20250904020654.28689-1-richard.weiyang@gmail.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: <20250904020654.28689-1-richard.weiyang@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: irkwZTENLDOFgwykWj2PyHS0Rd9Fk1BwCXHU76rveYk_1757065245 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: rspam07 X-Rspamd-Queue-Id: F040018000A X-Stat-Signature: qo58c3q353qz98a6s5d6wtnbfynwq5op X-Rspam-User: X-HE-Tag: 1757065247-5723 X-HE-Meta: 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 55DFbt3h 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 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 04.09.25 04:06, Wei Yang wrote: > find_large_buddy() search buddy based on start_pfn, which maybe > different from page's pfn, e.g. when page is not pageblock aligned, > because prep_move_freepages_block() always align start_pfn to pageblock. > > This means when we found a starting block at start_pfn, it may check > on the wrong page theoretically. > > The good news is the page passed to __move_freepages_block_isolate() has > only two possible cases: > > * page is pageblock aligned > * page is __first_valid_page() of this block > > So it is safe for the first case, and it won't get a buddy larger than > pageblock for the second case. > > To eliminate the ambiguity, unify the handling for starting/tail block. > > Signed-off-by: Wei Yang > Cc: Johannes Weiner > Cc: Zi Yan > Cc: David Hildenbrand > Cc: Baolin Wang > Cc: Vlastimil Babka > > --- > Tried memory online/offine, which looks good. > --- > mm/page_alloc.c | 17 ++++------------- > 1 file changed, 4 insertions(+), 13 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5183a646fa09..453cd361386c 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2093,6 +2093,7 @@ static bool __move_freepages_block_isolate(struct zone *zone, > unsigned long start_pfn, pfn; > int from_mt; > int to_mt; > + struct page *buddy; > > if (isolate == get_pageblock_isolate(page)) { > VM_WARN_ONCE(1, "%s a pageblock that is already in that state", > @@ -2107,10 +2108,10 @@ static bool __move_freepages_block_isolate(struct zone *zone, > if (pageblock_order == MAX_PAGE_ORDER) > goto move; > > - /* We're a tail block in a larger buddy */ > pfn = find_large_buddy(start_pfn); > - if (pfn != start_pfn) { > - struct page *buddy = pfn_to_page(pfn); > + buddy = pfn_to_page(pfn); While at it, can you please rename "pfn" to "buddy_pfn" ? > + /* We're a part of a larger buddy */ > + if (PageBuddy(buddy) && buddy_order(buddy) > pageblock_order) { > int order = buddy_order(buddy); Yes, I think this should work. -- Cheers David / dhildenb