memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER

commit e2a86800d58639b3acde7eaeb9eb393dca066e08 upstream.

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>
Link: https://lore.kernel.org/lkml/20210630071211.21011-1-rppt@kernel.org/
[backport upstream modification in mm/memblock.c to arch/arm/mm/init.c]
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 5a3641b5ec2cd09e5638dfbcd07c7ae8823e769c..72e4bb97f6c48b546e6c1abcb2c8165c023cb6cc 100644 (file)
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -373,11 +373,11 @@ static void __init free_unused_memmap(void)
                                 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
                /*
                 * If we had a previous bank, and there is a space
@@ -387,12 +387,12 @@ 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(memblock_region_memory_end_pfn(reg),
-                                MAX_ORDER_NR_PAGES);
+                                pageblock_nr_pages);
        }
 
 #ifdef CONFIG_SPARSEMEM