tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next
head:   413d9f332cbd16d951c22a41f2e5f53c1a75ae1c
commit: f7c3fb4fc476a8a7a3cfc78cffbf1de13c1899b7 [94/101] mm: Add kmem_last_alloc() to return last allocation for memory block
config: i386-randconfig-p001-20201204 (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/paulmck/linux-rcu.git/commit/?id=f7c3fb4fc476a8a7a3cfc78cffbf1de13c1899b7
        git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
        git fetch --no-tags rcu rcu/next
        git checkout f7c3fb4fc476a8a7a3cfc78cffbf1de13c1899b7
        # save the attached .config to linux build tree
        make W=1 ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   ld: mm/slab_common.o: in function `kmem_last_alloc':
>> mm/slab_common.c:555: undefined reference to `kmem_cache_last_alloc'

vim +555 mm/slab_common.c

   538	
   539	/*
   540	 * If the pointer references a slab-allocated object and if sufficient
   541	 * debugging is enabled, return the returrn address for the corresponding
   542	 * allocation.  Otherwise, return NULL.  Note that passing random pointers
   543	 * to this function (including addresses of on-stack variables) is likely
   544	 * to result in panics.
   545	 */
   546	void *kmem_last_alloc(void *object)
   547	{
   548		struct page *page;
   549	
   550		if (!virt_addr_valid(object))
   551			return NULL;
   552		page = virt_to_head_page(object);
   553		if (!PageSlab(page))
   554			return NULL;
 > 555		return kmem_cache_last_alloc(page->slab_cache, object);
   556	}
   557	EXPORT_SYMBOL_GPL(kmem_last_alloc);
   558	

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