Re: [RFC PATCH 06/11] mm/truncate: use folio_split() in truncate_inode_partial_folio()

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

Hi Zi,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[cannot apply to brauner-vfs/vfs.all kdave/for-next linus/master v7.0-rc5 next-20260323]
[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/Zi-Yan/mm-remove-READ_ONLY_THP_FOR_FS-Kconfig-option/20260324-043510
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260323190644.1714379-7-ziy%40nvidia.com
patch subject: [RFC PATCH 06/11] mm/truncate: use folio_split() in truncate_inode_partial_folio()
config: x86_64-allnoconfig (https://download.01.org/0day-ci/archive/20260325/202603250033.ifbSFRek-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260325/202603250033.ifbSFRek-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/202603250033.ifbSFRek-lkp@intel.com/

All errors (new ones prefixed by >>):

>> mm/truncate.c:189:8: error: call to undeclared function 'folio_split'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     189 |         ret = folio_split(folio, min_order, split_at, NULL);
         |               ^
   1 error generated.


vim +/folio_split +189 mm/truncate.c

   179	
   180	static int folio_split_or_unmap(struct folio *folio, struct page *split_at,
   181					    unsigned long min_order)
   182	{
   183		enum ttu_flags ttu_flags =
   184			TTU_SYNC |
   185			TTU_SPLIT_HUGE_PMD |
   186			TTU_IGNORE_MLOCK;
   187		int ret;
   188	
 > 189		ret = folio_split(folio, min_order, split_at, NULL);
   190	
   191		/*
   192		 * If the split fails, unmap the folio, so it will be refaulted
   193		 * with PTEs to respect SIGBUS semantics.
   194		 *
   195		 * Make an exception for shmem/tmpfs that for long time
   196		 * intentionally mapped with PMDs across i_size.
   197		 */
   198		if (ret && !shmem_mapping(folio->mapping)) {
   199			try_to_unmap(folio, ttu_flags);
   200			WARN_ON(folio_mapped(folio));
   201		}
   202	
   203		return ret;
   204	}
   205	

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