mm: move anon_vma ref out from under CONFIG_foo

We need the anon_vma refcount unconditionally to simplify the anon_vma
lifetime rules.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 36 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b9b23ddca63a..fd56111a52c1 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -27,18 +27,15 @@
 struct anon_vma {
         struct anon_vma *root;  /* Root of this anon_vma tree */
         spinlock_t lock;        /* Serialize access to vma list */
-#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
-
         /*
-         * The external_refcount is taken by either KSM or page migration
-         * to take a reference to an anon_vma when there is no
+         * The refcount is taken on an anon_vma when there is no
          * guarantee that the vma of page tables will exist for
          * the duration of the operation. A caller that takes
          * the reference is responsible for clearing up the
          * anon_vma if they are the last user on release
          */
-        atomic_t external_refcount;
-#endif
+        atomic_t refcount;
+
         /*
          * NOTE: the LSB of the head.next is set by
          * mm_take_all_locks() _after_ taking the above lock. So the
@@ -71,41 +68,12 @@ struct anon_vma_chain {
 };
 
 #ifdef CONFIG_MMU
-#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
-static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
-{
-        atomic_set(&anon_vma->external_refcount, 0);
-}
-
-static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
-{
-        return atomic_read(&anon_vma->external_refcount);
-}
-
 static inline void get_anon_vma(struct anon_vma *anon_vma)
 {
-        atomic_inc(&anon_vma->external_refcount);
+        atomic_inc(&anon_vma->refcount);
 }
 
 void put_anon_vma(struct anon_vma *);
-#else
-static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
-{
-}
-
-static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
-{
-        return 0;
-}
-
-static inline void get_anon_vma(struct anon_vma *anon_vma)
-{
-}
-
-static inline void put_anon_vma(struct anon_vma *anon_vma)
-{
-}
-#endif /* CONFIG_KSM */
 
 static inline struct anon_vma *page_anon_vma(struct page *page)
 {