Currently we have three times the same few lines repeated in the
code. Deduplicate them by newly introduced pmd_install() helper.

Signed-off-by: Qi Zheng <redacted>
Reviewed-by: David Hildenbrand <redacted>
Reviewed-by: Muchun Song <redacted>
---
 include/linux/mm.h |  1 +
 mm/filemap.c       | 11 ++---------
 mm/memory.c        | 34 ++++++++++++++++------------------
 3 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a3cc83d64564..0af420a7e382 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -2463,6 +2463,7 @@ static inline spinlock_t *pud_lock(struct mm_struct *mm, pud_t *pud)
 	return ptl;
 }
 
+extern void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte);
 extern void __init pagecache_init(void);
 extern void __init free_area_init_memoryless_node(int nid);
 extern void free_initmem(void);