Re: [PATCH 18/24] mm/swap: introduce a helper non fault swapin

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

Hi Kairui,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on linus/master v6.7-rc2 next-20231117]
[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/Kairui-Song/mm-swap-fix-a-potential-undefined-behavior-issue/20231120-035926
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20231119194740.94101-19-ryncsn%40gmail.com
patch subject: [PATCH 18/24] mm/swap: introduce a helper non fault swapin
config: i386-buildonly-randconfig-002-20231120 (https://download.01.org/0day-ci/archive/20231120/202311200850.FrQj7bMD-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231120/202311200850.FrQj7bMD-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/202311200850.FrQj7bMD-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from mm/shmem.c:43:
   mm/swap.h:105:31: warning: declaration of 'enum swap_cache_result' will not be visible outside of this function [-Wvisibility]
                           struct vm_fault *vmf, enum swap_cache_result *result)
                                                      ^
   mm/swap.h:112:8: warning: declaration of 'enum swap_cache_result' will not be visible outside of this function [-Wvisibility]
                   enum swap_cache_result *result)
                        ^
>> mm/shmem.c:1841:25: error: variable has incomplete type 'enum swap_cache_result'
           enum swap_cache_result result;
                                  ^
   mm/shmem.c:1841:7: note: forward declaration of 'enum swap_cache_result'
           enum swap_cache_result result;
                ^
>> mm/shmem.c:1870:31: error: use of undeclared identifier 'SWAP_CACHE_HIT'
                   if (fault_type && result != SWAP_CACHE_HIT) {
                                               ^
>> mm/shmem.c:1879:17: error: use of undeclared identifier 'SWAP_CACHE_BYPASS'
           if ((result != SWAP_CACHE_BYPASS && !folio_test_swapcache(folio)) ||
                          ^
   2 warnings and 3 errors generated.


vim +1841 mm/shmem.c

  1827	
  1828	/*
  1829	 * Swap in the folio pointed to by *foliop.
  1830	 * Caller has to make sure that *foliop contains a valid swapped folio.
  1831	 * Returns 0 and the folio in foliop if success. On failure, returns the
  1832	 * error code and NULL in *foliop.
  1833	 */
  1834	static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
  1835				     struct folio **foliop, enum sgp_type sgp,
  1836				     gfp_t gfp, struct mm_struct *fault_mm,
  1837				     vm_fault_t *fault_type)
  1838	{
  1839		struct address_space *mapping = inode->i_mapping;
  1840		struct shmem_inode_info *info = SHMEM_I(inode);
> 1841		enum swap_cache_result result;
  1842		struct folio *folio = NULL;
  1843		struct mempolicy *mpol;
  1844		struct page *page;
  1845		swp_entry_t swap;
  1846		pgoff_t ilx;
  1847		int error;
  1848	
  1849		VM_BUG_ON(!*foliop || !xa_is_value(*foliop));
  1850		swap = radix_to_swp_entry(*foliop);
  1851		*foliop = NULL;
  1852	
  1853		if (is_poisoned_swp_entry(swap))
  1854			return -EIO;
  1855	
  1856		mpol = shmem_get_pgoff_policy(info, index, 0, &ilx);
  1857		page = swapin_page_non_fault(swap, gfp, mpol, ilx, fault_mm, &result);
  1858		mpol_cond_put(mpol);
  1859	
  1860		if (PTR_ERR(page) == -EBUSY) {
  1861			if (!shmem_confirm_swap(mapping, index, swap))
  1862				return -EEXIST;
  1863			else
  1864				return -EINVAL;
  1865		} else if (!page) {
  1866			error = -ENOMEM;
  1867			goto failed;
  1868		} else {
  1869			folio = page_folio(page);
> 1870			if (fault_type && result != SWAP_CACHE_HIT) {
  1871				*fault_type |= VM_FAULT_MAJOR;
  1872				count_vm_event(PGMAJFAULT);
  1873				count_memcg_event_mm(fault_mm, PGMAJFAULT);
  1874			}
  1875		}
  1876	
  1877		/* We have to do this with folio locked to prevent races */
  1878		folio_lock(folio);
> 1879		if ((result != SWAP_CACHE_BYPASS && !folio_test_swapcache(folio)) ||
  1880		    folio->swap.val != swap.val ||
  1881		    !shmem_confirm_swap(mapping, index, swap)) {
  1882			error = -EEXIST;
  1883			goto unlock;
  1884		}
  1885		if (!folio_test_uptodate(folio)) {
  1886			error = -EIO;
  1887			goto failed;
  1888		}
  1889		folio_wait_writeback(folio);
  1890	
  1891		/*
  1892		 * Some architectures may have to restore extra metadata to the
  1893		 * folio after reading from swap.
  1894		 */
  1895		arch_swap_restore(swap, folio);
  1896	
  1897		if (shmem_should_replace_folio(folio, gfp)) {
  1898			error = shmem_replace_folio(&folio, gfp, info, index);
  1899			if (error)
  1900				goto failed;
  1901		}
  1902	
  1903		error = shmem_add_to_page_cache(folio, mapping, index,
  1904						swp_to_radix_entry(swap), gfp);
  1905		if (error)
  1906			goto failed;
  1907	
  1908		shmem_recalc_inode(inode, 0, -1);
  1909	
  1910		if (sgp == SGP_WRITE)
  1911			folio_mark_accessed(folio);
  1912	
  1913		delete_from_swap_cache(folio);
  1914		folio_mark_dirty(folio);
  1915		swap_free(swap);
  1916	
  1917		*foliop = folio;
  1918		return 0;
  1919	failed:
  1920		if (!shmem_confirm_swap(mapping, index, swap))
  1921			error = -EEXIST;
  1922		if (error == -EIO)
  1923			shmem_set_folio_swapin_error(inode, index, folio, swap);
  1924	unlock:
  1925		if (folio) {
  1926			folio_unlock(folio);
  1927			folio_put(folio);
  1928		}
  1929	
  1930		return error;
  1931	}
  1932	

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