[rppt:direct-map/v0 5/7] mm/vmalloc.h:41:26: error: call to undeclared function 'get_vm_area_page_order'; ISO C99 and later do not support implicit function declarations

[kernel test robot <lkp@intel.com>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git direct-map/v0
head:   21effbca0418e549e468c2141da5ba1ef83f06fb
commit: 741e3d404d2d11569c68f713ebd9345e283f8455 [5/7] mm/vmalloc: pull out set_direct_map into mm/vmalloc.h ...
config: arm-allnoconfig (https://download.01.org/0day-ci/archive/20260706/202607062104.DeqKFZxf-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260706/202607062104.DeqKFZxf-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/202607062104.DeqKFZxf-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from mm/mm_init.c:38:
>> mm/vmalloc.h:41:26: error: call to undeclared function 'get_vm_area_page_order'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      41 |         unsigned int nr = (1 << get_vm_area_page_order(vm));
         |                                 ^
   mm/vmalloc.h:41:26: note: did you mean 'get_vm_area_caller'?
   include/linux/vmalloc.h:247:26: note: 'get_vm_area_caller' declared here
     247 | extern struct vm_struct *get_vm_area_caller(unsigned long size,
         |                          ^
   1 error generated.


vim +/get_vm_area_page_order +41 mm/vmalloc.h

    37	
    38	static inline void vm_area_set_direct_map(struct vm_struct *vm,
    39			int (*set_direct_map)(const void *addr, unsigned long numpages))
    40	{
  > 41		unsigned int nr = (1 << get_vm_area_page_order(vm));
    42		int err = 0;
    43	
    44		for (int i = 0; i < vm->nr_pages; i += nr) {
    45			err = set_direct_map(page_address(vm->pages[i]), nr);
    46			WARN_ON_ONCE(err);
    47		}
    48	}
    49	

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