[PATCH] hugetlb: check p?d_present in huge_pte_offset()

For demand faulting, we cannot assume that the page tables will be
populated.  Do what the rest of the architectures do and test p?d_present()
while walking down the page table.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/i386/mm/hugetlbpage.c b/arch/i386/mm/hugetlbpage.c
index 57c486f0e896..24c8a536b588 100644
--- a/arch/i386/mm/hugetlbpage.c
+++ b/arch/i386/mm/hugetlbpage.c
@@ -46,8 +46,11 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
         pmd_t *pmd = NULL;
 
         pgd = pgd_offset(mm, addr);
-        pud = pud_offset(pgd, addr);
-        pmd = pmd_offset(pud, addr);
+        if (pgd_present(*pgd)) {
+                pud = pud_offset(pgd, addr);
+                if (pud_present(*pud))
+                        pmd = pmd_offset(pud, addr);
+        }
         return (pte_t *) pmd;
 }