memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER

The code that frees unused memory map uses rounds start and end of the
holes that are freed to MAX_ORDER_NR_PAGES to preserve continuity of the
memory map for MAX_ORDER regions.

Lots of core memory management functionality relies on homogeneity of the
memory map within each pageblock which size may differ from MAX_ORDER in
certain configurations.

Although currently, for the architectures that use free_unused_memmap(),
pageblock_order and MAX_ORDER are equivalent, it is cleaner to have common
notation thought mm code.

Replace MAX_ORDER_NR_PAGES with pageblock_nr_pages and update the comments
to make it more clear why the alignment to pageblock boundaries is
required.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Tested-by: Tony Lindgren <tony@atomide.com>

diff --git a/mm/memblock.c b/mm/memblock.c
index afaefa8..97fa875 100644 (file)
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1943,11 +1943,11 @@ static void __init free_unused_memmap(void)
                start = min(start, ALIGN(prev_end, PAGES_PER_SECTION));
 #else
                /*
-                * Align down here since the VM subsystem insists that the
-                * memmap entries are valid from the bank start aligned to
-                * MAX_ORDER_NR_PAGES.
+                * Align down here since many operations in VM subsystem
+                * presume that there are no holes in the memory map inside
+                * a pageblock
                 */
-               start = round_down(start, MAX_ORDER_NR_PAGES);
+               start = round_down(start, pageblock_nr_pages);
 #endif
 
                /*
@@ -1958,11 +1958,11 @@ static void __init free_unused_memmap(void)
                        free_memmap(prev_end, start);
 
                /*
-                * Align up here since the VM subsystem insists that the
-                * memmap entries are valid from the bank end aligned to
-                * MAX_ORDER_NR_PAGES.
+                * Align up here since many operations in VM subsystem
+                * presume that there are no holes in the memory map inside
+                * a pageblock
                 */
-               prev_end = ALIGN(end, MAX_ORDER_NR_PAGES);
+               prev_end = ALIGN(end, pageblock_nr_pages);
        }
 
 #ifdef CONFIG_SPARSEMEM