Hi,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.1-rc3]
[cannot apply to shuah-kselftest/next next-20221103]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/alexlzhu-fb-com/THP-Shrinker/20221103-140549
patch link:    https://lore.kernel.org/r/ddc216d41ff8cf2953488a2e041856c6e8dbd51e.1667454613.git.alexlzhu%40fb.com
patch subject: [PATCH v6 3/5] mm: do not remap clean subpages when splitting isolated thp
config: i386-randconfig-a004
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/4048042cde24d1c71ae7ce0770af3098195cc45c
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review alexlzhu-fb-com/THP-Shrinker/20221103-140549
        git checkout 4048042cde24d1c71ae7ce0770af3098195cc45c
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

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

All errors (new ones prefixed by >>):

>> mm/migrate.c:206:18: error: use of undeclared identifier 'THP_SPLIT_REMAP_READONLY_ZERO_PAGE'
                   count_vm_event(THP_SPLIT_REMAP_READONLY_ZERO_PAGE);
                                  ^
>> mm/migrate.c:211:17: error: use of undeclared identifier 'THP_SPLIT_UNMAP'
           count_vm_event(THP_SPLIT_UNMAP);
                          ^
   2 errors generated.


vim +/THP_SPLIT_REMAP_READONLY_ZERO_PAGE +206 mm/migrate.c

   171	
   172	static bool try_to_unmap_clean(struct page_vma_mapped_walk *pvmw, struct page *page)
   173	{
   174		void *addr;
   175		bool dirty;
   176		pte_t newpte;
   177	
   178		VM_BUG_ON_PAGE(PageCompound(page), page);
   179		VM_BUG_ON_PAGE(!PageAnon(page), page);
   180		VM_BUG_ON_PAGE(!PageLocked(page), page);
   181		VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page);
   182	
   183		if (PageMlocked(page) || (pvmw->vma->vm_flags & VM_LOCKED))
   184			return false;
   185	
   186		/*
   187		 * The pmd entry mapping the old thp was flushed and the pte mapping
   188		 * this subpage has been non present. Therefore, this subpage is
   189		 * inaccessible. We don't need to remap it if it contains only zeros.
   190		 */
   191		addr = kmap_local_page(page);
   192		dirty = memchr_inv(addr, 0, PAGE_SIZE);
   193		kunmap_local(addr);
   194	
   195		if (dirty)
   196			return false;
   197	
   198		pte_clear_not_present_full(pvmw->vma->vm_mm, pvmw->address, pvmw->pte, false);
   199	
   200		if (userfaultfd_armed(pvmw->vma)) {
   201			newpte = pte_mkspecial(pfn_pte(page_to_pfn(ZERO_PAGE(pvmw->address)),
   202						       pvmw->vma->vm_page_prot));
   203			ptep_clear_flush(pvmw->vma, pvmw->address, pvmw->pte);
   204			set_pte_at(pvmw->vma->vm_mm, pvmw->address, pvmw->pte, newpte);
   205			dec_mm_counter(pvmw->vma->vm_mm, MM_ANONPAGES);
 > 206			count_vm_event(THP_SPLIT_REMAP_READONLY_ZERO_PAGE);
   207			return true;
   208		}
   209	
   210		dec_mm_counter(pvmw->vma->vm_mm, mm_counter(page));
 > 211		count_vm_event(THP_SPLIT_UNMAP);
   212		return true;
   213	}
   214	

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