diff --git a/mm/bootmem.c b/mm/bootmem.c
index 1324cd74faec..b93376c39b61 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -185,10 +185,23 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 
 	while (start < end) {
 		unsigned long *map, idx, vec;
+		unsigned shift;
 
 		map = bdata->node_bootmem_map;
 		idx = start - bdata->node_min_pfn;
+		shift = idx & (BITS_PER_LONG - 1);
+		/*
+		 * vec holds at most BITS_PER_LONG map bits,
+		 * bit 0 corresponds to start.
+		 */
 		vec = ~map[idx / BITS_PER_LONG];
+
+		if (shift) {
+			vec >>= shift;
+			if (end - start >= BITS_PER_LONG)
+				vec |= ~map[idx / BITS_PER_LONG + 1] <<
+					(BITS_PER_LONG - shift);
+		}
 		/*
 		 * If we have a properly aligned and fully unreserved
 		 * BITS_PER_LONG block of pages in front of us, free
@@ -201,19 +214,18 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 			count += BITS_PER_LONG;
 			start += BITS_PER_LONG;
 		} else {
-			unsigned long off = 0;
+			unsigned long cur = start;
 
-			vec >>= start & (BITS_PER_LONG - 1);
-			while (vec) {
+			start = ALIGN(start + 1, BITS_PER_LONG);
+			while (vec && cur != start) {
 				if (vec & 1) {
-					page = pfn_to_page(start + off);
+					page = pfn_to_page(cur);
 					__free_pages_bootmem(page, 0);
 					count++;
 				}
 				vec >>= 1;
-				off++;
+				++cur;
 			}
-			start = ALIGN(start + 1, BITS_PER_LONG);
 		}
 	}