On Fri, 17 Oct 2014 10:08:06 +0530 "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote:
> Update generic gup implementation with powerpc specific details.
> On powerpc at pmd level we can have hugepte, normal pmd pointer
> or a pointer to the hugepage directory.
>
> ...
>
> --- a/arch/arm/include/asm/pgtable.h
> +++ b/arch/arm/include/asm/pgtable.h
> @@ -181,6 +181,8 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
> /* to find an entry in a kernel page-table-directory */
> #define pgd_offset_k(addr) pgd_offset(&init_mm, addr)
>
> +#define pgd_huge(pgd) (0)
> +
> #define pmd_none(pmd) (!pmd_val(pmd))
> #define pmd_present(pmd) (pmd_val(pmd))
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index cefd3e825612..ed8f42497ac4 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -464,6 +464,8 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
> extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
> extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
>
> +#define pgd_huge(pgd) (0)
> +
So only arm, arm64 and powerpc implement CONFIG_HAVE_GENERIC_RCU_GUP
and only powerpc impements pgd_huge().
Could we get a bit of documentation in place for pgd_huge() so that
people who aren't familiar with powerpc can understand what's going on?
> /*
> * Encode and decode a swap entry:
> * bits 0-1: present (must be zero)
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 02d11ee7f19d..f97732412cb4 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1219,6 +1219,32 @@ long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> struct vm_area_struct **vmas);
> int get_user_pages_fast(unsigned long start, int nr_pages, int write,
> struct page **pages);
> +
> +#ifdef CONFIG_HAVE_GENERIC_RCU_GUP
> +#ifndef is_hugepd
And is_hugepd is a bit of a mystery. Let's get some description in
place for this as well? Why it exists, what its role is. Also,
specifically which arch header file is responsible for defining it.
It takes a hugepd_t argument, but hugepd_t is defined later in this
header file. This is weird because any preceding implementation of
is_hugepd() can't actually be implemented because it hasn't seen the
hugepd_t definition yet! So any is_hugepd() implementation is forced
to be a simple macro which punts to a C function which *has* seen the
hugepd_t definition. What a twisty maze.
It all seems messy, confusing and poorly documented. Can we clean this
up?
> +/*
> + * Some architectures support hugepage directory format that is
> + * required to support different hugetlbfs sizes.
> + */
> +typedef struct { unsigned long pd; } hugepd_t;
> +#define is_hugepd(hugepd) (0)
> +#define __hugepd(x) ((hugepd_t) { (x) })
What's this.
> +static inline int gup_hugepd(hugepd_t hugepd, unsigned long addr,
> + unsigned pdshift, unsigned long end,
> + int write, struct page **pages, int *nr)
> +{
> + return 0;
> +}
> +#else
> +extern int gup_hugepd(hugepd_t hugepd, unsigned long addr,
> + unsigned pdshift, unsigned long end,
> + int write, struct page **pages, int *nr);
> +#endif
> +extern int gup_huge_pte(pte_t orig, pte_t *ptep, unsigned long addr,
> + unsigned long sz, unsigned long end, int write,
> + struct page **pages, int *nr);
> +#endif
> +
>
> ...
>
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