linux-kernel - Re: [PATCH v2 2/2] kfence: allow change number of object by early parameter

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Message-ID: <202512202213.aA8qY41g-lkp@intel.com>
Date: Sat, 20 Dec 2025 22:59:31 +0800
From: kernel test robot <lkp@...el.com>
To: yuan linyu <yuanlinyu@...or.com>,
	Alexander Potapenko <glider@...gle.com>,
	Marco Elver <elver@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Huacai Chen <chenhuacai@...nel.org>,
	WANG Xuerui <kernel@...0n.name>, kasan-dev@...glegroups.com,
	loongarch@...ts.linux.dev
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
	Linux Memory Management List <linux-mm@...ck.org>,
	linux-kernel@...r.kernel.org, yuan linyu <yuanlinyu@...or.com>
Subject: Re: [PATCH v2 2/2] kfence: allow change number of object by early
 parameter

Hi yuan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on drm-misc/drm-misc-next linus/master v6.19-rc1 next-20251219]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/yuan-linyu/LoongArch-kfence-avoid-use-CONFIG_KFENCE_NUM_OBJECTS/20251218-144322
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20251218063916.1433615-3-yuanlinyu%40honor.com
patch subject: [PATCH v2 2/2] kfence: allow change number of object by early parameter
config: i386-buildonly-randconfig-001-20251219 (https://download.01.org/0day-ci/archive/20251220/202512202213.aA8qY41g-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251220/202512202213.aA8qY41g-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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512202213.aA8qY41g-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/kfence/core.c:997:16: warning: variable 'nr_pages_covered' set but not used [-Wunused-but-set-variable]
     997 |         unsigned long nr_pages_covered, covered_size;
         |                       ^
   1 warning generated.


vim +/nr_pages_covered +997 mm/kfence/core.c

   991	
   992	static int kfence_init_late(void)
   993	{
   994		unsigned long nr_pages_meta = KFENCE_METADATA_SIZE / PAGE_SIZE;
   995		unsigned long addr = (unsigned long)__kfence_pool;
   996		unsigned long free_size = __kfence_pool_size;
 > 997		unsigned long nr_pages_covered, covered_size;
   998		int err = -ENOMEM;
   999	
  1000		kfence_alloc_covered_order = ilog2(__kfence_num_objects) + 2;
  1001		kfence_alloc_covered_mask = (1 << kfence_alloc_covered_order) - 1;
  1002		covered_size =  PAGE_ALIGN(KFENCE_COVERED_SIZE);
  1003		nr_pages_covered = (covered_size / PAGE_SIZE);
  1004	#ifdef CONFIG_CONTIG_ALLOC
  1005		struct page *pages;
  1006	
  1007		pages = alloc_contig_pages(__kfence_pool_pages, GFP_KERNEL, first_online_node,
  1008					   NULL);
  1009		if (!pages)
  1010			return -ENOMEM;
  1011	
  1012		__kfence_pool = page_to_virt(pages);
  1013		pages = alloc_contig_pages(nr_pages_covered, GFP_KERNEL, first_online_node,
  1014					   NULL);
  1015		if (!pages)
  1016			goto free_pool;
  1017		alloc_covered = page_to_virt(pages);
  1018		pages = alloc_contig_pages(nr_pages_meta, GFP_KERNEL, first_online_node,
  1019					   NULL);
  1020		if (pages)
  1021			kfence_metadata_init = page_to_virt(pages);
  1022	#else
  1023		if (__kfence_pool_pages > MAX_ORDER_NR_PAGES ||
  1024		    nr_pages_meta > MAX_ORDER_NR_PAGES) {
  1025			pr_warn("KFENCE_NUM_OBJECTS too large for buddy allocator\n");
  1026			return -EINVAL;
  1027		}
  1028	
  1029		__kfence_pool = alloc_pages_exact(__kfence_pool_size, GFP_KERNEL);
  1030		if (!__kfence_pool)
  1031			return -ENOMEM;
  1032	
  1033		alloc_covered = alloc_pages_exact(covered_size, GFP_KERNEL);
  1034		if (!alloc_covered)
  1035			goto free_pool;
  1036		kfence_metadata_init = alloc_pages_exact(KFENCE_METADATA_SIZE, GFP_KERNEL);
  1037	#endif
  1038	
  1039		if (!kfence_metadata_init)
  1040			goto free_cover;
  1041	
  1042		memzero_explicit(kfence_metadata_init, KFENCE_METADATA_SIZE);
  1043		addr = kfence_init_pool();
  1044		if (!addr) {
  1045			kfence_init_enable();
  1046			kfence_debugfs_init();
  1047			return 0;
  1048		}
  1049	
  1050		pr_err("%s failed\n", __func__);
  1051		free_size = __kfence_pool_size - (addr - (unsigned long)__kfence_pool);
  1052		err = -EBUSY;
  1053	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki