2019-11-03 12:39:32

by Masahiro Yamada

Subject: [PATCH] arm64: mm: simplify the page end calculation in __create_pgd_mapping()

Calculate the page-aligned end address more simply.

The local variable, "length" is unneeded.

Signed-off-by: Masahiro Yamada <[email protected]>
---

arch/arm64/mm/mmu.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 60c929f3683b..a9f541912289 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -338,7 +338,7 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
phys_addr_t (*pgtable_alloc)(int),
int flags)
{
- unsigned long addr, length, end, next;
+ unsigned long addr, end, next;
pgd_t *pgdp = pgd_offset_raw(pgdir, virt);

/*
@@ -350,9 +350,8 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,

phys &= PAGE_MASK;
addr = virt & PAGE_MASK;
- length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));
+ end = PAGE_ALIGN(virt + size);

- end = addr + length;
do {
next = pgd_addr_end(addr, end);
alloc_init_pud(pgdp, addr, next, phys, prot, pgtable_alloc,
--
2.17.1

2019-11-05 20:16:26

by Mark Rutland

Subject: Re: [PATCH] arm64: mm: simplify the page end calculation in __create_pgd_mapping()

On Sun, Nov 03, 2019 at 09:35:58PM +0900, Masahiro Yamada wrote:
> Calculate the page-aligned end address more simply.
>
> The local variable, "length" is unneeded.
>
> Signed-off-by: Masahiro Yamada <[email protected]>
> ---
>
> arch/arm64/mm/mmu.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 60c929f3683b..a9f541912289 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -338,7 +338,7 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
> phys_addr_t (*pgtable_alloc)(int),
> int flags)
> {
> - unsigned long addr, length, end, next;
> + unsigned long addr, end, next;
> pgd_t *pgdp = pgd_offset_raw(pgdir, virt);
>
> /*
> @@ -350,9 +350,8 @@ static void __create_pgd_mapping(pgd_t *pgdir, phys_addr_t phys,
>
> phys &= PAGE_MASK;
> addr = virt & PAGE_MASK;
> - length = PAGE_ALIGN(size + (virt & ~PAGE_MASK));
> + end = PAGE_ALIGN(virt + size);
>
> - end = addr + length;

While looking at this, I got confused by the old code and thought that
there was an existing bug, but I now see that's not the case, and the
old and new code are equivalent.

The new code looks cleaner, and leaves less room for confusion, so I
think that's preferable:

Reviewed-by: Mark Rutland <[email protected]>

Mark.

> do {
> next = pgd_addr_end(addr, end);
> alloc_init_pud(pgdp, addr, next, phys, prot, pgtable_alloc,
> --
> 2.17.1
>

2019-11-06 11:19:23

by Catalin Marinas

Subject: Re: [PATCH] arm64: mm: simplify the page end calculation in __create_pgd_mapping()

On Sun, Nov 03, 2019 at 09:35:58PM +0900, Masahiro Yamada wrote:
> Calculate the page-aligned end address more simply.
>
> The local variable, "length" is unneeded.
>
> Signed-off-by: Masahiro Yamada <[email protected]>

Queued for 5.5. Thanks.

--
Catalin