Hi Waiman,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[cannot apply to v5.3-rc6 next-20190823]
[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/Waiman-Long/fs-proc-page-Skip-uninitialized-page-when-iterating-page-structures/20190826-105836
config: x86_64-lkp (attached as .config)
compiler: gcc-7 (Debian 7.4.0-10) 7.4.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   fs/proc/page.c: In function 'find_next_zone_range':
>> fs/proc/page.c:58:2: error: expected ';' before 'for'
     for (pgdat = first_online_pgdat(); pgdat;
     ^~~
   fs/proc/page.c:52:6: warning: unused variable 'i' [-Wunused-variable]
     int i;
         ^
   fs/proc/page.c:51:15: warning: unused variable 'zone' [-Wunused-variable]
     struct zone *zone;
                  ^~~~
   fs/proc/page.c:50:13: warning: unused variable 'pgdat' [-Wunused-variable]
     pg_data_t *pgdat;
                ^~~~~
   fs/proc/page.c: In function 'pfn_in_zone':
>> fs/proc/page.c:79:23: error: 'struct zone_range' has no member named 'start'; did you mean 'pfn_start'?
     return pfn >= range->start && pfn < range->end;
                          ^~~~~
                          pfn_start
>> fs/proc/page.c:79:43: error: 'struct zone_range' has no member named 'end'
     return pfn >= range->start && pfn < range->end;
                                              ^~
   fs/proc/page.c:80:1: warning: control reaches end of non-void function [-Wreturn-type]
    }
    ^

vim +58 fs/proc/page.c

    46	
    47	static void find_next_zone_range(struct zone_range *range)
    48	{
    49		unsigned long start, end;
  > 50		pg_data_t *pgdat;
  > 51		struct zone *zone;
    52		int i;
    53	
    54		/*
    55		 * Scan all the zone structures to find the next closest one.
    56		 */
    57		start = end = -1UL
  > 58		for (pgdat = first_online_pgdat(); pgdat;
    59		     pgdat = next_online_pgdat(pgdat)) {
    60			for (zone = pgdat->node_zones, i = 0; i < MAX_NR_ZONES;
    61			     zone++, i++) {
    62				if (!zone->spanned_pages)
    63					continue;
    64				if ((zone->zone_start_pfn >= range->pfn_end) &&
    65				    (zone->zone_start_pfn < start)) {
    66					start = zone->zone_start_pfn;
    67					end   = start + zone->spanned_pages;
    68				}
    69			}
    70		}
    71		range->pfn_start = start;
    72		range->pfn_end   = end;
    73	}
    74	
    75	static inline bool pfn_in_zone(unsigned long pfn, struct zone_range *range)
    76	{
    77		if (pfn >= range->pfn_end)
    78			find_next_zone_range(range);
  > 79		return pfn >= range->start && pfn < range->end;
    80	}
    81	

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