Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:
> 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?
Will update
>
>> /*
>> * 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.
arch can definitely do
#defne is_hugepd is_hugepd
typedef struct { unsigned long pd; } hugepd_t;
static inline int is_hugepd(hugepd_t hpd)
{
}
I wanted to make sure arch can have their own definition of hugepd_t .
>
> 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.
macro that is used to convert value to type hugepd_t. We use that style
already for __pte() etc.
>
>> +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
-aneesh
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