[josef-btrfs:master 3/11] mm/vmstat.c:1445:4: warning: iteration 28 invokes undefined behavior

[josef-btrfs:master 3/11] mm/vmstat.c:1445:4: warning: iteration 28 invokes undefined behavior

[kbuild test robot]

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/josef/btrfs-next.git master
head:   570b2b152bf32db746eb6de1a144491b5f7ca34f
commit: 3bfb81930e877c80af87a9954ca5714aa6ae60ee [3/11] writeback: allow for dirty metadata accounting
config: i386-randconfig-s0-201642 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        git checkout 3bfb81930e877c80af87a9954ca5714aa6ae60ee
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   mm/vmstat.c: In function 'zoneinfo_show_print':
>> mm/vmstat.c:1445:4: warning: iteration 28 invokes undefined behavior [-Waggressive-loop-optimizations]
       seq_printf(m, "\n      %-12s %lu",
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        node_page_state(pgdat, i));
        ~~~~~~~~~~~~~~~~~~~~~~~~~~
   mm/vmstat.c:1444:3: note: within this loop
      for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
      ^~~

vim +1445 mm/vmstat.c

e2ecc8a7 Mel Gorman        2016-07-28  1429  			return zone == compare;
e2ecc8a7 Mel Gorman        2016-07-28  1430  	}
e2ecc8a7 Mel Gorman        2016-07-28  1431  
e2ecc8a7 Mel Gorman        2016-07-28  1432  	/* The zone must be somewhere! */
e2ecc8a7 Mel Gorman        2016-07-28  1433  	WARN_ON_ONCE(1);
e2ecc8a7 Mel Gorman        2016-07-28  1434  	return false;
e2ecc8a7 Mel Gorman        2016-07-28  1435  }
e2ecc8a7 Mel Gorman        2016-07-28  1436  
467c996c Mel Gorman        2007-10-16  1437  static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
467c996c Mel Gorman        2007-10-16  1438  							struct zone *zone)
f6ac2354 Christoph Lameter 2006-06-30  1439  {
f6ac2354 Christoph Lameter 2006-06-30  1440  	int i;
f6ac2354 Christoph Lameter 2006-06-30  1441  	seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
e2ecc8a7 Mel Gorman        2016-07-28  1442  	if (is_zone_first_populated(pgdat, zone)) {
e2ecc8a7 Mel Gorman        2016-07-28  1443  		seq_printf(m, "\n  per-node stats");
e2ecc8a7 Mel Gorman        2016-07-28  1444  		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
e2ecc8a7 Mel Gorman        2016-07-28 @1445  			seq_printf(m, "\n      %-12s %lu",
e2ecc8a7 Mel Gorman        2016-07-28  1446  				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
e2ecc8a7 Mel Gorman        2016-07-28  1447  				node_page_state(pgdat, i));
e2ecc8a7 Mel Gorman        2016-07-28  1448  		}
e2ecc8a7 Mel Gorman        2016-07-28  1449  	}
f6ac2354 Christoph Lameter 2006-06-30  1450  	seq_printf(m,
f6ac2354 Christoph Lameter 2006-06-30  1451  		   "\n  pages free     %lu"
f6ac2354 Christoph Lameter 2006-06-30  1452  		   "\n        min      %lu"
f6ac2354 Christoph Lameter 2006-06-30  1453  		   "\n        low      %lu"

:::::: The code at line 1445 was first introduced by commit
:::::: e2ecc8a79ed49f7838b4fdf352c4c48cec9424ac mm, vmstat: print node-based stats in zoneinfo file

:::::: TO: Mel Gorman <mgorman@techsingularity.net>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>

---
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