tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git mm/apply-to-page-range head: c7e0ff9c0e75727aca201140e679ffcfcc3155f0 commit: 6734b686b6bb06054ae6c380034b15b4dc3c86ac [4/6] mm: Introduce verify_page_range() config: x86_64-rhel (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?... git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git git fetch --no-tags peterz-queue mm/apply-to-page-range git checkout 6734b686b6bb06054ae6c380034b15b4dc3c86ac # save the attached .config to linux build tree make W=1 ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): mm/memory.c: In function 'verify_page_range': 2582 | return apply_to_page_range(mm, addr, size, vpr_fn, &vpr); | ^~~~~~ mm/memory.c:2578:18: warning: unused variable 'vpr' [-Wunused-variable] 2578 | struct vpr_data vpr = { | ^~~ mm/memory.c:2583:1: error: control reaches end of non-void function [-Werror=return-type] 2583 | } | ^ At top level: mm/memory.c:2567:12: warning: 'vpr_fn' defined but not used [-Wunused-function] 2567 | static int vpr_fn(pte_t *pte, unsigned long addr, void *data) | ^~~~~~ cc1: some warnings being treated as errors vim +2582 mm/memory.c 2572 2573 int verify_page_range(struct mm_struct *mm, 2574 unsigned long addr, unsigned long size, 2575 int (*fn)(pte_t pte, unsigned long addr, void *data), 2576 void *data) 2577 { 2578 struct vpr_data vpr = { 2579 .fn = fn, 2580 .data = data, 2581 } 2583 } 2584 EXPORT_SYMBOL_GPL(verify_page_range); 2585 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org