Re: [PATCH v4] mm: assert exclusive nid/zonenum bits at the page/folio access sites

Re: [PATCH v4] mm: assert exclusive nid/zonenum bits at the page/folio access sites

[kernel test robot]

Hi Hui,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Hui-Zhu/mm-assert-exclusive-nid-zonenum-bits-at-the-page-folio-access-sites/20260625-134106
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260625053958.918738-1-hui.zhu%40linux.dev
patch subject: [PATCH v4] mm: assert exclusive nid/zonenum bits at the page/folio access sites
config: s390-allnoconfig (https://download.01.org/0day-ci/archive/20260625/202606251454.M74ab4Rw-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 6cc609bb250b21b47fc7d394b4019101e9983597)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260625/202606251454.M74ab4Rw-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202606251454.M74ab4Rw-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/fork.c:258:18: warning: unused variable 'page' [-Wunused-variable]
     258 |                                 struct page *page = vm_area->pages[i];
         |                                              ^~~~
   1 warning generated.


vim +/page +258 kernel/fork.c

262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  240  
449e0b4ed5a16c7 Pasha Tatashin            2025-05-09  241  static bool try_release_thread_stack_to_cache(struct vm_struct *vm_area)
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  242  {
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  243  	unsigned int i;
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  244  	int nid;
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  245  
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  246  	/*
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  247  	 * Don't cache stacks if any of the pages don't match the local domain, unless
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  248  	 * there is no local memory to begin with.
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  249  	 *
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  250  	 * Note that lack of local memory does not automatically mean it makes no difference
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  251  	 * performance-wise which other domain backs the stack. In this case we are merely
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  252  	 * trying to avoid constantly going to vmalloc.
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  253  	 */
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  254  	scoped_guard(preempt) {
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  255  		nid = numa_node_id();
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  256  		if (node_state(nid, N_MEMORY)) {
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  257  			for (i = 0; i < vm_area->nr_pages; i++) {
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20 @258  				struct page *page = vm_area->pages[i];
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  259  				if (page_to_nid(page) != nid)
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  260  					return false;
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  261  			}
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  262  		}
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  263  
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  264  		for (i = 0; i < NR_CACHED_STACKS; i++) {
47e39c793367600 Uros Bizjak               2024-05-23  265  			struct vm_struct *tmp = NULL;
47e39c793367600 Uros Bizjak               2024-05-23  266  
449e0b4ed5a16c7 Pasha Tatashin            2025-05-09  267  			if (this_cpu_try_cmpxchg(cached_stacks[i], &tmp, vm_area))
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  268  				return true;
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  269  		}
262ef8e55b7ccd4 Mateusz Guzik             2025-11-20  270  	}
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  271  	return false;
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  272  }
e540bf3162e822d Sebastian Andrzej Siewior 2022-02-17  273  

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