[PATCH 1/3] memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER

Mike Rapoport
2021-05-18T09:06:39Z

From: Mike Rapoport <rppt@linux.ibm.com>

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>
---
mm/memblock.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index afaefa8fc6ab..97fa87541b5f 100644
--- 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
--
2.28.0