[RFC PATCH 4/7] mm/follow_page_mask: Add support for hugepage directory entry

[Aneesh Kumar K.V]

The defaul implementation prints warning and returns NULL. We will add ppc64
support in later patches

Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
---
 include/linux/hugetlb.h |  3 +++
 mm/gup.c                | 33 +++++++++++++++++++++++++++++++++
 mm/hugetlb.c            |  8 ++++++++
 3 files changed, 44 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index fddf6cf403d5..d3a4be0022d8 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -117,6 +117,9 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long 
addr);
 int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep);
 struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
                              int write);
+struct page *follow_huge_pd(struct vm_area_struct *vma,
+                           unsigned long address, hugepd_t hpd,
+                           int flags, int pdshift);
 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,
diff --git a/mm/gup.c b/mm/gup.c
index 73d46f9f7b81..0e18fd5f65b4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -226,6 +226,14 @@ static struct page *follow_pmd_mask(struct vm_area_struct 
*vma,
                        return page;
                return no_page_table(vma, flags);
        }
+       if (is_hugepd(__hugepd(pmd_val(*pmd)))) {
+               page = follow_huge_pd(vma, address,
+                                     __hugepd(pmd_val(*pmd)), flags,
+                                     PMD_SHIFT);
+               if (page)
+                       return page;
+               return no_page_table(vma, flags);
+       }
        if (pmd_devmap(*pmd)) {
                ptl = pmd_lock(mm, pmd);
                page = follow_devmap_pmd(vma, address, pmd, flags);
@@ -292,6 +300,14 @@ static struct page *follow_pud_mask(struct vm_area_struct 
*vma,
                        return page;
                return no_page_table(vma, flags);
        }
+       if (is_hugepd(__hugepd(pud_val(*pud)))) {
+               page = follow_huge_pd(vma, address,
+                                     __hugepd(pud_val(*pud)), flags,
+                                     PUD_SHIFT);
+               if (page)
+                       return page;
+               return no_page_table(vma, flags);
+       }
        if (pud_devmap(*pud)) {
                ptl = pud_lock(mm, pud);
                page = follow_devmap_pud(vma, address, pud, flags);
@@ -311,6 +327,7 @@ static struct page *follow_p4d_mask(struct vm_area_struct 
*vma,
                                    unsigned int flags, unsigned int *page_mask)
 {
        p4d_t *p4d;
+       struct page *page;
 
        p4d = p4d_offset(pgdp, address);
        if (p4d_none(*p4d))
@@ -319,6 +336,14 @@ static struct page *follow_p4d_mask(struct vm_area_struct 
*vma,
        if (unlikely(p4d_bad(*p4d)))
                return no_page_table(vma, flags);
 
+       if (is_hugepd(__hugepd(p4d_val(*p4d)))) {
+               page = follow_huge_pd(vma, address,
+                                     __hugepd(p4d_val(*p4d)), flags,
+                                     P4D_SHIFT);
+               if (page)
+                       return page;
+               return no_page_table(vma, flags);
+       }
        return follow_pud_mask(vma, address, p4d, flags, page_mask);
 }
 
@@ -357,6 +382,14 @@ 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 (is_hugepd(__hugepd(pgd_val(*pgd)))) {
+               page = follow_huge_pd(vma, address,
+                                     __hugepd(pgd_val(*pgd)), flags,
+                                     PGDIR_SHIFT);
+               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 34ec2ab62215..b02faa1079bd 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4650,6 +4650,14 @@ follow_huge_addr(struct mm_struct *mm, unsigned long 
address,
 }
 
 struct page * __weak
+follow_huge_pd(struct vm_area_struct *vma,
+              unsigned long address, hugepd_t hpd, int flags, int pdshift)
+{
+       WARN(1, "hugepd follow called with no support for hugepage directory 
format\n");
+       return NULL;
+}
+
+struct page * __weak
 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
                pmd_t *pmd, int flags)
 {
-- 
2.7.4