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SubjectRe: [PATCH] mm: define pte_add_end for consistency
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On 30.06.20 05:18, Wei Yang wrote:
> When walking page tables, we define several helpers to get the address of
> the next boundary. But we don't have one for pte level.
>
> Let's define it and consolidate the code in several places.
>
> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
> ---
> arch/x86/mm/init_64.c | 6 ++----
> include/linux/pgtable.h | 7 +++++++
> mm/kasan/init.c | 4 +---
> 3 files changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index dbae185511cd..f902fbd17f27 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -973,9 +973,7 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end,
>
> pte = pte_start + pte_index(addr);
> for (; addr < end; addr = next, pte++) {
> - next = (addr + PAGE_SIZE) & PAGE_MASK;
> - if (next > end)
> - next = end;
> + next = pte_addr_end(addr, end);
>
> if (!pte_present(*pte))
> continue;
> @@ -1558,7 +1556,7 @@ void register_page_bootmem_memmap(unsigned long section_nr,
> get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO);
>
> if (!boot_cpu_has(X86_FEATURE_PSE)) {
> - next = (addr + PAGE_SIZE) & PAGE_MASK;
> + next = pte_addr_end(addr, end);
> pmd = pmd_offset(pud, addr);
> if (pmd_none(*pmd))
> continue;
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 32b6c52d41b9..0de09c6c89d2 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -706,6 +706,13 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
> })
> #endif
>
> +#ifndef pte_addr_end
> +#define pte_addr_end(addr, end) \
> +({ unsigned long __boundary = ((addr) + PAGE_SIZE) & PAGE_MASK; \
> + (__boundary - 1 < (end) - 1) ? __boundary : (end); \
> +})
> +#endif
> +
> /*
> * When walking page tables, we usually want to skip any p?d_none entries;
> * and any p?d_bad entries - reporting the error before resetting to none.
> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> index fe6be0be1f76..89f748601f74 100644
> --- a/mm/kasan/init.c
> +++ b/mm/kasan/init.c
> @@ -349,9 +349,7 @@ static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
> unsigned long next;
>
> for (; addr < end; addr = next, pte++) {
> - next = (addr + PAGE_SIZE) & PAGE_MASK;
> - if (next > end)
> - next = end;
> + next = pte_addr_end(addr, end);
>
> if (!pte_present(*pte))
> continue;
>

I'm not really a friend of this I have to say. We're simply iterating
over single pages, not much magic ....

What would definitely make sense is replacing (addr + PAGE_SIZE) &
PAGE_MASK; by PAGE_ALIGN() ...

--
Thanks,

David / dhildenb

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