[PATCH 2/2] mm/mm_init.c: do not calculate memmap and reserved pages for empty zone

[Haifeng Xu <haifeng.xu@shopee.com>]

For empty zone, it's unnecessary to account for pages used by memmap.
Also, the pages reserved in dma zone can be ignored.

Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
---
 mm/mm_init.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 232efac9a929..b82718d596c3 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1543,6 +1543,13 @@ static void __init free_area_init_core(struct pglist_data *pgdat)
 		size = zone->spanned_pages;
 		freesize = zone->present_pages;
 
+		if (!size) {
+			nr_kernel_pages += 0;
+			nr_all_pages += 0;
+			zone_init_internals(zone, j, nid, 0);
+			continue;
+		}
+
 		/*
 		 * Adjust freesize so that it accounts for how much memory
 		 * is used by this zone for memmap. This affects the watermark
@@ -1579,10 +1586,6 @@ static void __init free_area_init_core(struct pglist_data *pgdat)
 		 * And all highmem pages will be managed by the buddy system.
 		 */
 		zone_init_internals(zone, j, nid, freesize);
-
-		if (!size)
-			continue;
-
 		setup_usemap(zone);
 		init_currently_empty_zone(zone, zone->zone_start_pfn, size);
 	}
-- 
2.25.1