thp: share get_huge_page_tail()

This avoids duplicating the function in every arch gup_fast.
Signed-off-by: NAndrea Arcangeli <aarcange@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/mm/hugetlbpage.c

@@ -385,17 +385,6 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 	return NULL;
 }
 
-static inline void get_huge_page_tail(struct page *page)
-{
-	/*
-	 * __split_huge_page_refcount() cannot run
-	 * from under us.
-	 */
-	VM_BUG_ON(page_mapcount(page) < 0);
-	VM_BUG_ON(atomic_read(&page->_count) != 0);
-	atomic_inc(&page->_mapcount);
-}
-
 static noinline int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 		       unsigned long end, int write, struct page **pages, int *nr)
 {

arch/s390/mm/gup.c

@@ -48,17 +48,6 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 	return 1;
 }
 
-static inline void get_huge_page_tail(struct page *page)
-{
-	/*
-	 * __split_huge_page_refcount() cannot run
-	 * from under us.
-	 */
-	VM_BUG_ON(page_mapcount(page) < 0);
-	VM_BUG_ON(atomic_read(&page->_count) != 0);
-	atomic_inc(&page->_mapcount);
-}
-
 static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		unsigned long end, int write, struct page **pages, int *nr)
 {

arch/sparc/mm/gup.c

@@ -12,17 +12,6 @@
 #include <linux/rwsem.h>
 #include <asm/pgtable.h>
 
-static inline void get_huge_page_tail(struct page *page)
-{
-	/*
-	 * __split_huge_page_refcount() cannot run
-	 * from under us.
-	 */
-	VM_BUG_ON(page_mapcount(page) < 0);
-	VM_BUG_ON(atomic_read(&page->_count) != 0);
-	atomic_inc(&page->_mapcount);
-}
-
 /*
  * The performance critical leaf functions are made noinline otherwise gcc
  * inlines everything into a single function which results in too much

arch/x86/mm/gup.c

@@ -108,17 +108,6 @@ static inline void get_head_page_multiple(struct page *page, int nr)
 	SetPageReferenced(page);
 }
 
-static inline void get_huge_page_tail(struct page *page)
-{
-	/*
-	 * __split_huge_page_refcount() cannot run
-	 * from under us.
-	 */
-	VM_BUG_ON(page_mapcount(page) < 0);
-	VM_BUG_ON(atomic_read(&page->_count) != 0);
-	atomic_inc(&page->_mapcount);
-}
-
 static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
 		unsigned long end, int write, struct page **pages, int *nr)
 {

include/linux/mm.h

@@ -376,6 +376,17 @@ static inline int page_count(struct page *page)
 	return atomic_read(&compound_head(page)->_count);
 }
 
+static inline void get_huge_page_tail(struct page *page)
+{
+	/*
+	 * __split_huge_page_refcount() cannot run
+	 * from under us.
+	 */
+	VM_BUG_ON(page_mapcount(page) < 0);
+	VM_BUG_ON(atomic_read(&page->_count) != 0);
+	atomic_inc(&page->_mapcount);
+}
+
 extern bool __get_page_tail(struct page *page);
 
 static inline void get_page(struct page *page)