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>

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b9b23dd..fd56111 100644 (file)
--- 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)
 {

diff --git a/mm/rmap.c b/mm/rmap.c
index ad416af..873cd9e 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -272,7 +272,7 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
        list_del(&anon_vma_chain->same_anon_vma);
 
        /* We must garbage collect the anon_vma if it's empty */
-       empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);
+       empty = list_empty(&anon_vma->head) && !atomic_read(&anon_vma->refcount);
        anon_vma_unlock(anon_vma);
 
        if (empty) {
@@ -303,7 +303,7 @@ static void anon_vma_ctor(void *data)
        struct anon_vma *anon_vma = data;
 
        spin_lock_init(&anon_vma->lock);
-       anonvma_external_refcount_init(anon_vma);
+       atomic_set(&anon_vma->refcount, 0);
        INIT_LIST_HEAD(&anon_vma->head);
 }
 
@@ -1486,7 +1486,6 @@ int try_to_munlock(struct page *page)
                return try_to_unmap_file(page, TTU_MUNLOCK);
 }
 
-#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
 /*
  * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root
  * if necessary.  Be careful to do all the tests under the lock.  Once
@@ -1495,8 +1494,8 @@ int try_to_munlock(struct page *page)
  */
 void put_anon_vma(struct anon_vma *anon_vma)
 {
-       BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0);
-       if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
+       BUG_ON(atomic_read(&anon_vma->refcount) <= 0);
+       if (atomic_dec_and_lock(&anon_vma->refcount, &anon_vma->root->lock)) {
                struct anon_vma *root = anon_vma->root;
                int empty = list_empty(&anon_vma->head);
                int last_root_user = 0;
@@ -1507,8 +1506,8 @@ void put_anon_vma(struct anon_vma *anon_vma)
                 * the refcount on the root and check if we need to free it.
                 */
                if (empty && anon_vma != root) {
-                       BUG_ON(atomic_read(&root->external_refcount) <= 0);
-                       last_root_user = atomic_dec_and_test(&root->external_refcount);
+                       BUG_ON(atomic_read(&root->refcount) <= 0);
+                       last_root_user = atomic_dec_and_test(&root->refcount);
                        root_empty = list_empty(&root->head);
                }
                anon_vma_unlock(anon_vma);
@@ -1520,7 +1519,6 @@ void put_anon_vma(struct anon_vma *anon_vma)
                }
        }
 }
-#endif
 
 #ifdef CONFIG_MIGRATION
 /*