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Subject[PATCH 5.4 14/18] memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER
Date
From: Mike Rapoport <rppt@linux.ibm.com>

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

--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -373,11 +373,11 @@ static void __init free_unused_memmap(vo
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(vo
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

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