[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 <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/i386/mm/hugetlbpage.c

···
 	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;
 }