mm/page_owner.c: clean up init_pages_in_zone()

Remove two redundant assignments in init_pages_in_zone().

[osalvador@techadventures.net: v3]
  Link: http://lkml.kernel.org/r/20180117124513.GA876@techadventures.net
[akpm@linux-foundation.org: coding style tweaks]
Link: http://lkml.kernel.org/r/20180110084355.GA22822@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@techadventures.net>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_owner.c

@@ -528,21 +528,18 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 
 static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 {
-	struct page *page;
-	struct page_ext *page_ext;
-	unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
-	unsigned long end_pfn = pfn + zone->spanned_pages;
+	unsigned long pfn = zone->zone_start_pfn;
+	unsigned long end_pfn = zone_end_pfn(zone);
 	unsigned long count = 0;
 
-	/* Scan block by block. First and last block may be incomplete */
-	pfn = zone->zone_start_pfn;
-
 	/*
 	 * Walk the zone in pageblock_nr_pages steps. If a page block spans
 	 * a zone boundary, it will be double counted between zones. This does
 	 * not matter as the mixed block count will still be correct
 	 */
 	for (; pfn < end_pfn; ) {
+		unsigned long block_end_pfn;
+
 		if (!pfn_valid(pfn)) {
 			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
 			continue;
@@ -551,9 +548,10 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 		block_end_pfn = min(block_end_pfn, end_pfn);
 
-		page = pfn_to_page(pfn);
-
 		for (; pfn < block_end_pfn; pfn++) {
+			struct page *page;
+			struct page_ext *page_ext;
+
 			if (!pfn_valid_within(pfn))
 				continue;