Re: [PATCH v2 6/6] mm/truncate: use folio_split() for truncate operation.

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

Hi Zi,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on next-20241101]
[cannot apply to linus/master v6.12-rc5]
[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-huge_memory-add-two-new-yet-used-functions-for-folio_split/20241101-230623
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20241101150357.1752726-7-ziy%40nvidia.com
patch subject: [PATCH v2 6/6] mm/truncate: use folio_split() for truncate operation.
config: arc-tb10x_defconfig (https://download.01.org/0day-ci/archive/20241103/202411030124.ZWzXWxPU-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241103/202411030124.ZWzXWxPU-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/202411030124.ZWzXWxPU-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/truncate.c: In function 'truncate_inode_partial_folio':
>> mm/truncate.c:214:13: error: implicit declaration of function 'split_folio_at'; did you mean 'split_folio'? [-Werror=implicit-function-declaration]
     214 |         if (split_folio_at(folio, folio_page(folio, in_folio_offset), NULL) == 0)
         |             ^~~~~~~~~~~~~~
         |             split_folio
   cc1: some warnings being treated as errors


vim +214 mm/truncate.c

   166	
   167	/*
   168	 * Handle partial folios.  The folio may be entirely within the
   169	 * range if a split has raced with us.  If not, we zero the part of the
   170	 * folio that's within the [start, end] range, and then split the folio if
   171	 * it's large.  split_page_range() will discard pages which now lie beyond
   172	 * i_size, and we rely on the caller to discard pages which lie within a
   173	 * newly created hole.
   174	 *
   175	 * Returns false if splitting failed so the caller can avoid
   176	 * discarding the entire folio which is stubbornly unsplit.
   177	 */
   178	bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
   179	{
   180		loff_t pos = folio_pos(folio);
   181		unsigned int offset, length;
   182		long in_folio_offset;
   183	
   184		if (pos < start)
   185			offset = start - pos;
   186		else
   187			offset = 0;
   188		length = folio_size(folio);
   189		if (pos + length <= (u64)end)
   190			length = length - offset;
   191		else
   192			length = end + 1 - pos - offset;
   193	
   194		folio_wait_writeback(folio);
   195		if (length == folio_size(folio)) {
   196			truncate_inode_folio(folio->mapping, folio);
   197			return true;
   198		}
   199	
   200		/*
   201		 * We may be zeroing pages we're about to discard, but it avoids
   202		 * doing a complex calculation here, and then doing the zeroing
   203		 * anyway if the page split fails.
   204		 */
   205		if (!mapping_inaccessible(folio->mapping))
   206			folio_zero_range(folio, offset, length);
   207	
   208		if (folio_needs_release(folio))
   209			folio_invalidate(folio, offset, length);
   210		if (!folio_test_large(folio))
   211			return true;
   212	
   213		in_folio_offset = PAGE_ALIGN_DOWN(offset) / PAGE_SIZE;
 > 214		if (split_folio_at(folio, folio_page(folio, in_folio_offset), NULL) == 0)
   215			return true;
   216		if (folio_test_dirty(folio))
   217			return false;
   218		truncate_inode_folio(folio->mapping, folio);
   219		return true;
   220	}
   221	

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