[PATCH 4/7] mm/follow_page_mask: Add support for hugetlb pgd entries.

[Aneesh Kumar K.V]

From: Anshuman Khandual <khand...@linux.vnet.ibm.com>

ppc64 supports pgd hugetlb entries. Add code to handle hugetlb pgd entries to
follow_page_mask so that ppc64 can switch to it to handle hugetlbe entries.

Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
---
 include/linux/hugetlb.h | 4 ++++
 mm/gup.c                | 7 +++++++
 mm/hugetlb.c            | 9 +++++++++
 3 files changed, 20 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index fddf6cf403d5..edab98f0a7b8 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -121,6 +121,9 @@ struct page *follow_huge_pmd(struct mm_struct *mm, unsigned 
long address,
                                pmd_t *pmd, int flags);
 struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
                                pud_t *pud, int flags);
+struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address,
+                            pgd_t *pgd, int flags);
+
 int pmd_huge(pmd_t pmd);
 int pud_huge(pud_t pud);
 unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
@@ -150,6 +153,7 @@ static inline void hugetlb_show_meminfo(void)
 }
 #define follow_huge_pmd(mm, addr, pmd, flags)  NULL
 #define follow_huge_pud(mm, addr, pud, flags)  NULL
+#define follow_huge_pgd(mm, addr, pgd, flags)  NULL
 #define prepare_hugepage_range(file, addr, len)        (-EINVAL)
 #define pmd_huge(x)    0
 #define pud_huge(x)    0
diff --git a/mm/gup.c b/mm/gup.c
index 73d46f9f7b81..65255389620a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -357,6 +357,13 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
        if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
                return no_page_table(vma, flags);
 
+       if (pgd_huge(*pgd)) {
+               page = follow_huge_pgd(mm, address, pgd, flags);
+               if (page)
+                       return page;
+               return no_page_table(vma, flags);
+       }
+
        return follow_p4d_mask(vma, address, pgd, flags, page_mask);
 }
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9b630e2195d5..83f39cf5162a 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4694,6 +4694,15 @@ follow_huge_pud(struct mm_struct *mm, unsigned long 
address,
        return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
 }
 
+struct page * __weak
+follow_huge_pgd(struct mm_struct *mm, unsigned long address, pgd_t *pgd, int 
flags)
+{
+       if (flags & FOLL_GET)
+               return NULL;
+
+       return pte_page(*(pte_t *)pgd) + ((address & ~PGDIR_MASK) >> 
PAGE_SHIFT);
+}
+
 #ifdef CONFIG_MEMORY_FAILURE
 
 /*
-- 
2.7.4