[linux-next:master 11986/12208] fs/proc/task_mmu.c:457:40: error: implicit declaration of function 'is_ksm_zero_pte'

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   e3f80d3eae76c3557b3c9b5938ad01c0e6cf25ec
commit: 5233d9beb1a81c08d8155b62df5e9635ee99ee27 [11986/12208] proc/ksm: add ksm stats to /proc/pid/smaps
config: powerpc-allnoconfig (https://download.01.org/0day-ci/archive/20230823/202308232003.eoFc7Z2h-lkp@intel.com/config)
compiler: powerpc-linux-gcc (GCC) 13.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230823/202308232003.eoFc7Z2h-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/202308232003.eoFc7Z2h-lkp@intel.com/

Note: the linux-next/master HEAD e3f80d3eae76c3557b3c9b5938ad01c0e6cf25ec builds fine.
      It may have been fixed somewhere.

All errors (new ones prefixed by >>):

   fs/proc/task_mmu.c: In function 'smaps_account':
>> fs/proc/task_mmu.c:457:40: error: implicit declaration of function 'is_ksm_zero_pte' [-Werror=implicit-function-declaration]
     457 |         if (PageKsm(page) && (!pte || !is_ksm_zero_pte(*pte)))
         |                                        ^~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/is_ksm_zero_pte +457 fs/proc/task_mmu.c

   439	
   440	static void smaps_account(struct mem_size_stats *mss, pte_t *pte,
   441			struct page *page, bool compound, bool young, bool dirty,
   442			bool locked, bool migration)
   443	{
   444		int i, nr = compound ? compound_nr(page) : 1;
   445		unsigned long size = nr * PAGE_SIZE;
   446	
   447		/*
   448		 * First accumulate quantities that depend only on |size| and the type
   449		 * of the compound page.
   450		 */
   451		if (PageAnon(page)) {
   452			mss->anonymous += size;
   453			if (!PageSwapBacked(page) && !dirty && !PageDirty(page))
   454				mss->lazyfree += size;
   455		}
   456	
 > 457		if (PageKsm(page) && (!pte || !is_ksm_zero_pte(*pte)))
   458			mss->ksm += size;
   459	
   460		mss->resident += size;
   461		/* Accumulate the size in pages that have been accessed. */
   462		if (young || page_is_young(page) || PageReferenced(page))
   463			mss->referenced += size;
   464	
   465		/*
   466		 * Then accumulate quantities that may depend on sharing, or that may
   467		 * differ page-by-page.
   468		 *
   469		 * page_count(page) == 1 guarantees the page is mapped exactly once.
   470		 * If any subpage of the compound page mapped with PTE it would elevate
   471		 * page_count().
   472		 *
   473		 * The page_mapcount() is called to get a snapshot of the mapcount.
   474		 * Without holding the page lock this snapshot can be slightly wrong as
   475		 * we cannot always read the mapcount atomically.  It is not safe to
   476		 * call page_mapcount() even with PTL held if the page is not mapped,
   477		 * especially for migration entries.  Treat regular migration entries
   478		 * as mapcount == 1.
   479		 */
   480		if ((page_count(page) == 1) || migration) {
   481			smaps_page_accumulate(mss, page, size, size << PSS_SHIFT, dirty,
   482				locked, true);
   483			return;
   484		}
   485		for (i = 0; i < nr; i++, page++) {
   486			int mapcount = page_mapcount(page);
   487			unsigned long pss = PAGE_SIZE << PSS_SHIFT;
   488			if (mapcount >= 2)
   489				pss /= mapcount;
   490			smaps_page_accumulate(mss, page, PAGE_SIZE, pss, dirty, locked,
   491					      mapcount < 2);
   492		}
   493	}
   494	

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