mm: introduce __p4d_alloc()

For full 5-level paging we need a helper to allocate p4d page table.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 90eceff1a375f6ffa78caf8654e787c0a8a591ef)

Orabug: 25808647

Signed-off-by: Vijay Kumar <vijay.ac.kumar@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>

diff --git a/mm/memory.c b/mm/memory.c
index 31fb7571bdf9c2ba534bfc9839d96d3fa151622f..5c5a11380df196ab26cc8a651edcbe7633b8e198 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3590,6 +3590,29 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL_GPL(handle_mm_fault);
 
+#ifndef __PAGETABLE_P4D_FOLDED
+/*
+ * Allocate p4d page table.
+ * We've already handled the fast-path in-line.
+ */
+int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
+{
+       p4d_t *new = p4d_alloc_one(mm, address);
+       if (!new)
+               return -ENOMEM;
+
+       smp_wmb(); /* See comment in __pte_alloc */
+
+       spin_lock(&mm->page_table_lock);
+       if (pgd_present(*pgd))          /* Another has populated it */
+               p4d_free(mm, new);
+       else
+               pgd_populate(mm, pgd, new);
+       spin_unlock(&mm->page_table_lock);
+       return 0;
+}
+#endif /* __PAGETABLE_P4D_FOLDED */
+
 #ifndef __PAGETABLE_PUD_FOLDED
 /*
  * Allocate page upper directory.