Re: [PATCH v1 1/2] mm: migrate: add vm event counters thp_migrate_(success|fail)

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

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Hi Naoya,

I love your patch! Perhaps something to improve:

[auto build test WARNING on mmotm/master]
[also build test WARNING on next-20180411]
[cannot apply to v4.16]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Naoya-Horiguchi/mm-migrate-add-vm-event-counters-thp_migrate_-success-fail/20180412-011244
base:   git://git.cmpxchg.org/linux-mmotm.git master
config: i386-randconfig-a1-201814 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   mm/migrate.c: In function 'migrate_pages':
>> mm/migrate.c:1426:2: warning: missing braces around initializer [-Wmissing-braces]
     int counts[MIGRATE_RESULT_TYPES][MIGRATE_PAGE_TYPES] = {0};
     ^
   mm/migrate.c:1426:2: warning: (near initialization for 'counts[0]') [-Wmissing-braces]

vim +1426 mm/migrate.c

  1400	
  1401	/*
  1402	 * migrate_pages - migrate the pages specified in a list, to the free pages
  1403	 *		   supplied as the target for the page migration
  1404	 *
  1405	 * @from:		The list of pages to be migrated.
  1406	 * @get_new_page:	The function used to allocate free pages to be used
  1407	 *			as the target of the page migration.
  1408	 * @put_new_page:	The function used to free target pages if migration
  1409	 *			fails, or NULL if no special handling is necessary.
  1410	 * @private:		Private data to be passed on to get_new_page()
  1411	 * @mode:		The migration mode that specifies the constraints for
  1412	 *			page migration, if any.
  1413	 * @reason:		The reason for page migration.
  1414	 *
  1415	 * The function returns after 10 attempts or if no pages are movable any more
  1416	 * because the list has become empty or no retryable pages exist any more.
  1417	 * The caller should call putback_movable_pages() to return pages to the LRU
  1418	 * or free list only if ret != 0.
  1419	 *
  1420	 * Returns the number of pages that were not migrated, or an error code.
  1421	 */
  1422	int migrate_pages(struct list_head *from, new_page_t get_new_page,
  1423			free_page_t put_new_page, unsigned long private,
  1424			enum migrate_mode mode, int reason)
  1425	{
> 1426		int counts[MIGRATE_RESULT_TYPES][MIGRATE_PAGE_TYPES] = {0};
  1427		int pass = 0;
  1428		struct page *page;
  1429		struct page *page2;
  1430		int swapwrite = current->flags & PF_SWAPWRITE;
  1431		int rc;
  1432	
  1433		if (!swapwrite)
  1434			current->flags |= PF_SWAPWRITE;
  1435	
  1436		for (pass = 0; !pass || (pass < 10 && get_count(counts, MIGRATE_RETRY));
  1437		     pass++) {
  1438			reset_nr_retry(counts);
  1439	
  1440			list_for_each_entry_safe(page, page2, from, lru) {
  1441				enum migrate_page_type mpt;
  1442	retry:
  1443				cond_resched();
  1444	
  1445				mpt = get_type(page);
  1446				if (PageHuge(page))
  1447					rc = unmap_and_move_huge_page(get_new_page,
  1448							put_new_page, private, page,
  1449							pass > 2, mode, reason);
  1450				else
  1451					rc = unmap_and_move(get_new_page, put_new_page,
  1452							private, page, pass > 2, mode,
  1453							reason);
  1454	
  1455				switch(rc) {
  1456				case -ENOMEM:
  1457					/*
  1458					 * THP migration might be unsupported or the
  1459					 * allocation could've failed so we should
  1460					 * retry on the same page with the THP split
  1461					 * to base pages.
  1462					 *
  1463					 * Head page is retried immediately and tail
  1464					 * pages are added to the tail of the list so
  1465					 * we encounter them after the rest of the list
  1466					 * is processed.
  1467					 */
  1468					if (PageTransHuge(page)) {
  1469						lock_page(page);
  1470						rc = split_huge_page_to_list(page, from);
  1471						unlock_page(page);
  1472						if (!rc) {
  1473							list_safe_reset_next(page, page2, lru);
  1474							goto retry;
  1475						}
  1476					}
  1477					counts[MIGRATE_FAIL][mpt]++;
  1478					goto out;
  1479				case -EAGAIN:
  1480					counts[MIGRATE_RETRY][mpt]++;
  1481					break;
  1482				case MIGRATEPAGE_SUCCESS:
  1483					counts[MIGRATE_SUCCEED][mpt]++;
  1484					break;
  1485				default:
  1486					/*
  1487					 * Permanent failure (-EBUSY, -ENOSYS, etc.):
  1488					 * unlike -EAGAIN case, the failed page is
  1489					 * removed from migration page list and not
  1490					 * retried in the next outer loop.
  1491					 */
  1492					counts[MIGRATE_FAIL][mpt]++;
  1493					break;
  1494				}
  1495			}
  1496		}
  1497		rc = get_count(counts, MIGRATE_FAIL) + get_count(counts, MIGRATE_RETRY);
  1498	out:
  1499		update_vm_migrate_events(counts);
  1500		trace_mm_migrate_pages(get_count(counts, MIGRATE_SUCCEED), rc,
  1501				       mode, reason);
  1502	
  1503		if (!swapwrite)
  1504			current->flags &= ~PF_SWAPWRITE;
  1505	
  1506		return rc;
  1507	}
  1508	

---
0-DAY kernel test infrastructure                Open Source Technology Center
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