[PATCH v4 13/16] mm: Add pt_mm to struct page

[Matthew Wilcox <willy@infradead.org>]

From: Matthew Wilcox <mawilcox@microsoft.com>

x86 overloads the page->index field to store a pointer to the mm_struct.
Rename this to pt_mm so it's visible to other users.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 arch/x86/mm/pgtable.c    | 5 ++---
 include/linux/mm_types.h | 2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index ffc8c13c50e4..938dbcd46b97 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -114,13 +114,12 @@ static inline void pgd_list_del(pgd_t *pgd)
 
 static void pgd_set_mm(pgd_t *pgd, struct mm_struct *mm)
 {
-	BUILD_BUG_ON(sizeof(virt_to_page(pgd)->index) < sizeof(mm));
-	virt_to_page(pgd)->index = (pgoff_t)mm;
+	virt_to_page(pgd)->pt_mm = mm;
 }
 
 struct mm_struct *pgd_page_get_mm(struct page *page)
 {
-	return (struct mm_struct *)page->index;
+	return page->pt_mm;
 }
 
 static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index e0e74e91f3e8..0e6117123737 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -134,7 +134,7 @@ struct page {
 			unsigned long _pt_pad_1;	/* compound_head */
 			pgtable_t pmd_huge_pte; /* protected by page->ptl */
 			unsigned long _pt_pad_2;	/* mapping */
-			unsigned long _pt_pad_3;
+			struct mm_struct *pt_mm;
 #if ALLOC_SPLIT_PTLOCKS
 			spinlock_t *ptl;
 #else
-- 
2.17.0