[PATCH] arm64: mm: Add pgd_page to support RCU fast_gup
catalin.marinas at arm.com
Tue Dec 23 08:01:13 PST 2014
On Tue, Dec 23, 2014 at 03:37:14PM +0000, Jungseok Lee wrote:
> It looks like that pmd_page cannot be written using pmd_pfn unless pmd_pfn is
> changed since pmd_pfn masks an input value with PMD_MASK, but pmd_page does not.
> Additionally, I'm not sure about whether pmd_pfn with PMD_MASK works well for an
> user process page table.
> So, my change on pmd_pfn and pmd_page is as follows. Please correct me if I am wrong.
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -294,11 +294,11 @@ void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
> #define pmd_mkhuge(pmd) (__pmd(pmd_val(pmd) & ~PMD_TABLE_BIT))
> -#define pmd_pfn(pmd) (((pmd_val(pmd) & PMD_MASK) & PHYS_MASK) >> PAGE_SHIFT)
> +#define pmd_pfn(pmd) ((pmd_val(pmd) & PHYS_MASK) >> PAGE_SHIFT)
> #define pfn_pmd(pfn,prot) (__pmd(((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot)))
> #define mk_pmd(page,prot) pfn_pmd(page_to_pfn(page),prot)
> -#define pmd_page(pmd) pfn_to_page(__phys_to_pfn(pmd_val(pmd) & PHYS_MASK))
> +#define pmd_page(pmd) pfn_to_page(pmd_pfn(pmd))
> #define pud_write(pud) pte_write(pud_pte(pud))
> #define pud_pfn(pud) (((pud_val(pud) & PUD_MASK) & PHYS_MASK) >> PAGE_SHIFT)
It looks like pmd_pfn() is only used for huge pages, so the original
code was safe. As I said, I won't do further changes here, at least not
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