From: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Date: Thu, 9 Mar 2017 14:24:08 +0000 (+0300)
Subject: mm: introduce __p4d_alloc()
X-Git-Tag: v4.1.12-102.0.20170530_1700~9
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=f1826d5a552d1aa9e574d32d246b90300acb2bdf;p=users%2Fjedix%2Flinux-maple.git

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 31fb7571bdf9c..5c5a11380df19 100644
--- 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.