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b=d3DJ1IlJr2PbIYtyPe1EHjVSNiEkQvbtkz8FxHghXcc6SkoMHCIXfC29zvDQaPl3X hReetQ7y365MhJ8ANoQfUjrbljdM68N/SRI4koZfgHfluUvrDiIDBiSL81YG0UoVmn 64z7dgqf/RLdsZjxusvqHbJXptKGLCMGGaRyHPMRTYJAlrBPO+0JahWsEZds5cM+ww FDOYCfOGW8H6YP6QcglJXrqom5no2/bOFbHUV8nRV9wUFC/nHnNk3k1U7ZV1UZdqVy MnruoDufrRoC0lHDNvS4NasYzSvDgMWO7l53s/skajOoE6KewFXRwLOMCk0WDjP5Cf 9r5gkzb0zl0xg== Message-ID: Date: Tue, 21 Apr 2026 16:49:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/sparse: remove unnecessary NULL check before allocating mem_section To: Sang-Heon Jeon , akpm@linux-foundation.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com Cc: linux-mm@kvack.org References: <20260419144225.2875654-1-ekffu200098@gmail.com> 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: <20260419144225.2875654-1-ekffu200098@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: sxx9oem9ho473kx3ckeknwsnpn7auith X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E8340140006 X-HE-Tag: 1776782952-995342 X-HE-Meta: U2FsdGVkX1////BvLqVApIo82OxWSUg0jl9wgbtk6Bpv9bz7AifKNUW9cw2SqJqIfTF6oPBOt4gZ77Er68GfdFFxpDv/M5GMXL9KNjiucEtz2PEr63F5kkblPwRE4z/j0g+v1/3Fhs3bVW7arp/E66z+zDYOjw4nj3gPlDSmfz+mIjJNQ5hoWV4iXZY8/s7OalJVMpQ0f4HfewbQKWXq/829XlOKL1MjNskjyjU6+P+SC79ecD8bBAUjyh3DHdni5dwEq/xY8lO5rkBlejSRRYVQZV33zlTTX3Fi5YJzm09JECHXEq4qt2Ta+3LjnbcC+DdO2sso/1VRSnLYzsh5mJ97Shg2prGR+osNNQQZndDY4h6xEH42yIM5kmV0WPnHoqrXqrPJ4d7DjA6Sc5zTeEPEQv4kXqfdRY5paP7v4VEQw7iVzZyu+sS50n9kGybmOrFk1ffUVftLz5WBQbOBzhwpQ5impEIcRXGvdUUn5iFY8D3c7/WvVuHYmR14ZxymksSZsLpYMkXLAFaOsh8i1aj9zU0v3GrAQT1CDxp3Ky7OqV2JNoRr/1uIgxcbVcrpeT0bCdwxZuWkEHyGMjqWBMNzzbM7++UEi1J6F1iOhYwiS7Ie4fic66ICeaLK6WDogVzhyR6WTRu+llPdh2r6qzl2OJhrFC0gPoT6Q+xlHQjbFG43Bmbz1mhYtdUl94k4MG2w7P3Tr5xlv57tMlhjmzCpAM77bCjTGqExa/xPuHZW52giDQBzXYY3d4OusXPiewkNYr4n/FTVIV3uZ4lvIbCK0xoo+H7UfiK62YFQOQNW+BCWSnEnS9NOseR4OENfAATILZ1U6pkxVwEWZVTNuaUunb/hgJ9TPtMAquCBQH9ti6MSZJkv6dyrTQnlSJYk9Djw/lE0LTNbG8wGvcl7pi9h4Rns0AOJSnZGI3lcnQscP76MucgKrauMaJ3UuOpbmC1mLwCVTuQPqfcxcff fa90jZTU ohoLpFL32YqlSWWqciqhgQUjRjrZHpKCI9tFr+dCY9dxom7ySBkhI5PhD/B23HapEhyg2liVR9Lb25gyUz8G4A6SK/mIwNAoeZpjJqMzK6PwX9j4TvLTVxsFGLlGbSSuNo53QMtGV48l0Jz/2soVzw+IoYTxpnsAOlvai87tZBe0c3Q9cC4Zee80iYfHS3zXhiwEiCbAy2qHGc5+VTawHrsLhoibYz+2lf6oyLybDUhopYYBDEFhGPyzTKy0omjyUrPiJ1iK7tTdMUApFtpsMRPjBOmqeRbTKV99AW3jffMAmvTpg4Lx3sFulHMlwvuSnscRUDgcT3ymWSniNp2sC50dNjqmfv6JKZUa5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/19/26 16:42, Sang-Heon Jeon wrote: > Commit 850ed20539a4 ("mm: move array mem_section init code out > of memory_present()") moved mem_section allocation logic > into memblocks_present(). > > Before that move, memory_present() could be called multiple times, so > unlikely() matched the common case, where most calls found mem_section > already allocated. > > After that move, memblocks_present() is called exactly once from > sparse_init(). Under CONFIG_SPARSEMEM_EXTREME, mem_section is always > NULL when it is called. > > So remove unnecessary NULL check before allocating mem_section. No > functional change. > > Signed-off-by: Sang-Heon Jeon > --- > Hello, > > While looking into boot information, I found a minor enhancement point. > If I misunderstood anything, please feel free to let me know. > > Thank you for taking valuable time to review this work. > > Best Regards, > Sang-Heon Jeon > --- > mm/sparse.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index effdac6b0ab1..e13f9f5fa090 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -201,13 +201,11 @@ static void __init memblocks_present(void) > int i, nid; > > #ifdef CONFIG_SPARSEMEM_EXTREME > - if (unlikely(!mem_section)) { > - unsigned long size, align; > + unsigned long size, align; > > - size = sizeof(struct mem_section *) * NR_SECTION_ROOTS; > - align = 1 << (INTERNODE_CACHE_SHIFT); > - mem_section = memblock_alloc_or_panic(size, align); > - } > + size = sizeof(struct mem_section *) * NR_SECTION_ROOTS; > + align = 1 << (INTERNODE_CACHE_SHIFT); > + mem_section = memblock_alloc_or_panic(size, align); Given that there is no other code that assigns mem_section Acked-by: David Hildenbrand (Arm) -- Cheers, David