Hi Yu,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.14-rc3]
[cannot apply to hnaz-linux-mm/master linux/master next-20210730]
[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]

url:    https://github.com/0day-ci/linux/commits/Yu-Zhao/mm-optimize-thp-for-reclaim-and-migration/20210731-144129
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c7d102232649226a69dddd58a4942cf13cff4f7c
config: i386-randconfig-a003-20210730 (attached as .config)
compiler: gcc-10 (Ubuntu 10.3.0-1ubuntu1~20.04) 10.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/e4e76c4915b364558aacae2cf320a43306a20fa1
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Yu-Zhao/mm-optimize-thp-for-reclaim-and-migration/20210731-144129
        git checkout e4e76c4915b364558aacae2cf320a43306a20fa1
        # save the attached .config to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

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 >>):

   mm/migrate.c: In function 'try_to_unmap_clean':
>> mm/migrate.c:199:17: error: 'THP_SPLIT_UNMAP' undeclared (first use in this function)
     199 |  count_vm_event(THP_SPLIT_UNMAP);
         |                 ^~~~~~~~~~~~~~~
   mm/migrate.c:199:17: note: each undeclared identifier is reported only once for each function it appears in


vim +/THP_SPLIT_UNMAP +199 mm/migrate.c

   170	
   171	static bool try_to_unmap_clean(struct page_vma_mapped_walk *pvmw, struct page *page)
   172	{
   173		void *addr;
   174		bool dirty;
   175	
   176		VM_BUG_ON_PAGE(PageLRU(page), page);
   177		VM_BUG_ON_PAGE(PageCompound(page), page);
   178		VM_BUG_ON_PAGE(!PageAnon(page), page);
   179		VM_BUG_ON_PAGE(!PageLocked(page), page);
   180		VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page);
   181	
   182		if (PageMlocked(page) || (pvmw->vma->vm_flags & VM_LOCKED))
   183			return false;
   184	
   185		/*
   186		 * The pmd entry mapping the old thp was flushed and the pte mapping
   187		 * this subpage has been non present. Therefore, this subpage is
   188		 * inaccessible. We don't need to remap it if it contains only zeros.
   189		 */
   190		addr = kmap_atomic(page);
   191		dirty = !!memchr_inv(addr, 0, PAGE_SIZE);
   192		kunmap_atomic(addr);
   193	
   194		if (dirty)
   195			return false;
   196	
   197		pte_clear_not_present_full(pvmw->vma->vm_mm, pvmw->address, pvmw->pte, false);
   198		dec_mm_counter(pvmw->vma->vm_mm, mm_counter(page));
 > 199		count_vm_event(THP_SPLIT_UNMAP);
   200	
   201		return true;
   202	}
   203	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org