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SubjectRe: [PATCH 5.4 1/5] memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER
On Mon, Dec 13, 2021 at 04:57:06PM +0800, Mark-PK Tsai wrote:

> Subject: [PATCH 5.4 1/5] memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER

I'd replace memblock: with arm: in the subject. I believe it's clearer this
way.

The same applies for the second patch in the series and for 5.10 posting.

> 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>
> ---
> arch/arm/mm/init.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index 7ea4d3b43444..6905dd8bc03f 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -381,11 +381,11 @@ 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
> @@ -395,12 +395,12 @@ 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
> --
> 2.18.0
>

--
Sincerely yours,
Mike.

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