memblock: Reimplement memblock_enforce_memory_limit() using __memblock_remove()

With recent updates, the basic memblock operations are robust enough
that there's no reason for memblock_enfore_memory_limit() to directly
manipulate memblock region arrays.  Reimplement it using
__memblock_remove().
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Yinghai Lu <yinghai@kernel.org>

mm/memblock.c

@@ -804,44 +804,28 @@ phys_addr_t __init_memblock memblock_end_of_DRAM(void)
 }
 
 /* You must call memblock_analyze() after this. */
-void __init memblock_enforce_memory_limit(phys_addr_t memory_limit)
+void __init memblock_enforce_memory_limit(phys_addr_t limit)
 {
 	unsigned long i;
-	phys_addr_t limit;
-	struct memblock_region *p;
+	phys_addr_t max_addr = (phys_addr_t)ULLONG_MAX;
 
-	if (!memory_limit)
+	if (!limit)
 		return;
 
-	/* Truncate the memblock regions to satisfy the memory limit. */
-	limit = memory_limit;
+	/* find out max address */
 	for (i = 0; i < memblock.memory.cnt; i++) {
-		if (limit > memblock.memory.regions[i].size) {
-			limit -= memblock.memory.regions[i].size;
-			continue;
-		}
-
-		memblock.memory.regions[i].size = limit;
-		memblock.memory.cnt = i + 1;
-		break;
-	}
-
-	memory_limit = memblock_end_of_DRAM();
+		struct memblock_region *r = &memblock.memory.regions[i];
 
-	/* And truncate any reserves above the limit also. */
-	for (i = 0; i < memblock.reserved.cnt; i++) {
-		p = &memblock.reserved.regions[i];
-
-		if (p->base > memory_limit)
-			p->size = 0;
-		else if ((p->base + p->size) > memory_limit)
-			p->size = memory_limit - p->base;
-
-		if (p->size == 0) {
-			memblock_remove_region(&memblock.reserved, i);
-			i--;
+		if (limit <= r->size) {
+			max_addr = r->base + limit;
+			break;
 		}
+		limit -= r->size;
 	}
+
+	/* truncate both memory and reserved regions */
+	__memblock_remove(&memblock.memory, max_addr, (phys_addr_t)ULLONG_MAX);
+	__memblock_remove(&memblock.reserved, max_addr, (phys_addr_t)ULLONG_MAX);
 }
 
 static int __init_memblock memblock_search(struct memblock_type *type, phys_addr_t addr)