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?
I ended up moving that to include/linux/hugetlb.h with the below
comments added. Let me know if the below is ok
/*
* hugepages at page global directory. If arch support
* hugepages at pgd level, they need to define this.
*/
#ifndef pgd_huge
#define pgd_huge(x) 0
#endif
#ifndef is_hugepd
/*
* Some architectures requires a hugepage directory format that is
* required to support multiple hugepage sizes. For example
* a4fe3ce7699bfe1bd88f816b55d42d8fe1dac655 introduced the same
* on powerpc. This allows for a more flexible hugepage pagetable
* layout.
*/
typedef struct { unsigned long pd; } hugepd_t;
#define is_hugepd(hugepd) (0)
#define __hugepd(x) ((hugepd_t) { (x) })
static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
unsigned pdshift, unsigned long end,
int write, struct page **pages, int *nr)
{
return 0;
}
#else
extern int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
unsigned pdshift, unsigned long end,
int write, struct page **pages, int *nr);
#endif
-aneesh
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