mm/page_alloc: fix and rework pfn handling in memmap_init_zone()

Let's update the pfn manually whenever we continue the loop.  This makes
the code easier to read but also less error prone (and we can directly fix
one issue).

When overlap_memmap_init() returns true, pfn is updated to
"memblock_region_memory_end_pfn(r)".  So it already points at the *next*
pfn to process.  Incrementing the pfn another time is wrong, we might
leave one uninitialized.  I spotted this by inspecting the code, so I have
no idea if this is relevant in practise (with kernelcore=mirror).

Link: http://lkml.kernel.org/r/[email protected]
Fixes: a9a9e77fbf27 ("mm: move mirrored memory specific code outside of memmap_init_zone")
Signed-off-by: David Hildenbrand <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Alexander Duyck <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: "Jin, Zhi" <[email protected]>
Cc: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 6 insertions, 3 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7d5b9dbf4087..461ed73bc30f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5905,18 +5905,20 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 	}
 #endif
 
-	for (pfn = start_pfn; pfn < end_pfn; pfn++) {
+	for (pfn = start_pfn; pfn < end_pfn; ) {
 		/*
 		 * There can be holes in boot-time mem_map[]s handed to this
 		 * function.  They do not exist on hotplugged memory.
 		 */
 		if (context == MEMMAP_EARLY) {
 			if (!early_pfn_valid(pfn)) {
-				pfn = next_pfn(pfn) - 1;
+				pfn = next_pfn(pfn);
 				continue;
 			}
-			if (!early_pfn_in_nid(pfn, nid))
+			if (!early_pfn_in_nid(pfn, nid)) {
+				pfn++;
 				continue;
+			}
 			if (overlap_memmap_init(zone, &pfn))
 				continue;
 			if (defer_init(nid, pfn, end_pfn))
@@ -5944,6 +5946,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
 			cond_resched();
 		}
+		pfn++;
 	}
 }