mm/zsmalloc.c: fix the migrated zspage statistics.

When zspage is migrated to the other zone, the zone page state should be
updated as well, otherwise the NR_ZSPAGE for each zone shows wrong
counts including proc/zoneinfo in practice.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 91537fe ("mm: add NR_ZSMALLOC to vmstat")
Signed-off-by: Chanho Min <[email protected]>
Signed-off-by: Jinsuk Choi <[email protected]>
Reviewed-by: Sergey Senozhatsky <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Cc: <[email protected]>        [4.9+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Chanho Min

mm/zsmalloc.c

@@ -2069,6 +2069,11 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage,
 		zs_pool_dec_isolated(pool);
 	}
 
+	if (page_zone(newpage) != page_zone(page)) {
+		dec_zone_page_state(page, NR_ZSPAGES);
+		inc_zone_page_state(newpage, NR_ZSPAGES);
+	}
+
 	reset_page(page);
 	put_page(page);
 	page = newpage;