diff --git a/mm/percpu.c b/mm/percpu.c
index e2ac58a..287f59c 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1235,7 +1235,7 @@
  * pcpu_setup_first_chunk - initialize the first percpu chunk
  * @static_size: the size of static percpu area in bytes
  * @reserved_size: the size of reserved percpu area in bytes, 0 for none
- * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
+ * @dyn_size: free size for dynamic allocation in bytes
  * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE
  * @base_addr: mapped address
  * @unit_map: cpu -> unit map, NULL for sequential mapping
@@ -1252,10 +1252,9 @@
  * limited offset range for symbol relocations to guarantee module
  * percpu symbols fall inside the relocatable range.
  *
- * @dyn_size, if non-negative, determines the number of bytes
- * available for dynamic allocation in the first chunk.  Specifying
- * non-negative value makes percpu leave alone the area beyond
- * @static_size + @reserved_size + @dyn_size.
+ * @dyn_size determines the number of bytes available for dynamic
+ * allocation in the first chunk.  The area between @static_size +
+ * @reserved_size + @dyn_size and @unit_size is unused.
  *
  * @unit_size specifies unit size and must be aligned to PAGE_SIZE and
  * equal to or larger than @static_size + @reserved_size + if
@@ -1276,13 +1275,12 @@
  * percpu access.
  */
 size_t __init pcpu_setup_first_chunk(size_t static_size, size_t reserved_size,
-				     ssize_t dyn_size, size_t unit_size,
+				     size_t dyn_size, size_t unit_size,
 				     void *base_addr, const int *unit_map)
 {
 	static struct vm_struct first_vm;
 	static int smap[2], dmap[2];
-	size_t size_sum = static_size + reserved_size +
-			  (dyn_size >= 0 ? dyn_size : 0);
+	size_t size_sum = static_size + reserved_size + dyn_size;
 	struct pcpu_chunk *schunk, *dchunk = NULL;
 	unsigned int cpu, tcpu;
 	int i;
@@ -1345,9 +1343,6 @@
 	pcpu_chunk_struct_size = sizeof(struct pcpu_chunk) +
 		BITS_TO_LONGS(pcpu_unit_pages) * sizeof(unsigned long);
 
-	if (dyn_size < 0)
-		dyn_size = pcpu_unit_size - static_size - reserved_size;
-
 	first_vm.flags = VM_ALLOC;
 	first_vm.size = pcpu_chunk_size;
 	first_vm.addr = base_addr;
@@ -1557,6 +1552,8 @@
 {
 	static struct vm_struct vm;
 	const size_t static_size = __per_cpu_end - __per_cpu_start;
+	ssize_t dyn_size = -1;
+	size_t size_sum, unit_size;
 	char psize_str[16];
 	int unit_pages;
 	size_t pages_size;
@@ -1567,8 +1564,9 @@
 
 	snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
 
-	unit_pages = PFN_UP(max_t(size_t, static_size + reserved_size,
-				  PCPU_MIN_UNIT_SIZE));
+	size_sum = pcpu_calc_fc_sizes(static_size, reserved_size, &dyn_size);
+	unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
+	unit_pages = unit_size >> PAGE_SHIFT;
 
 	/* unaligned allocations can't be freed, round up to page size */
 	pages_size = PFN_ALIGN(unit_pages * nr_cpu_ids * sizeof(pages[0]));
@@ -1591,12 +1589,12 @@
 
 	/* allocate vm area, map the pages and copy static data */
 	vm.flags = VM_ALLOC;
-	vm.size = nr_cpu_ids * unit_pages << PAGE_SHIFT;
+	vm.size = nr_cpu_ids * unit_size;
 	vm_area_register_early(&vm, PAGE_SIZE);
 
 	for_each_possible_cpu(cpu) {
-		unsigned long unit_addr = (unsigned long)vm.addr +
-			(cpu * unit_pages << PAGE_SHIFT);
+		unsigned long unit_addr =
+			(unsigned long)vm.addr + cpu * unit_size;
 
 		for (i = 0; i < unit_pages; i++)
 			populate_pte_fn(unit_addr + (i << PAGE_SHIFT));
@@ -1620,11 +1618,12 @@
 	}
 
 	/* we're ready, commit */
-	pr_info("PERCPU: %d %s pages/cpu @%p s%zu r%zu\n",
-		unit_pages, psize_str, vm.addr, static_size, reserved_size);
+	pr_info("PERCPU: %d %s pages/cpu @%p s%zu r%zu d%zu\n",
+		unit_pages, psize_str, vm.addr, static_size, reserved_size,
+		dyn_size);
 
-	ret = pcpu_setup_first_chunk(static_size, reserved_size, -1,
-				     unit_pages << PAGE_SHIFT, vm.addr, NULL);
+	ret = pcpu_setup_first_chunk(static_size, reserved_size, dyn_size,
+				     unit_size, vm.addr, NULL);
 	goto out_free_ar;
 
 enomem: