We need the anon_vma refcount unconditionally to simplify the anon_vma
lifetime rules.
Acked-by: Mel Gorman <mel@xxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
include/linux/rmap.h | 40 ++++------------------------------------
mm/rmap.c | 14 ++++++--------
2 files changed, 10 insertions(+), 44 deletions(-)
Index: linux-2.6/include/linux/rmap.h
===================================================================
--- linux-2.6.orig/include/linux/rmap.h
+++ linux-2.6/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)
{
Index: linux-2.6/mm/rmap.c
===================================================================
--- linux-2.6.orig/mm/rmap.c
+++ linux-2.6/mm/rmap.c
@@ -272,7 +272,7 @@ static void anon_vma_unlink(struct anon_
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);
}
@@ -1482,7 +1482,6 @@ 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
@@ -1491,8 +1490,8 @@ 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;
@@ -1503,8 +1502,8 @@ void put_anon_vma(struct anon_vma *anon_
* 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);
@@ -1516,7 +1515,6 @@ void put_anon_vma(struct anon_vma *anon_
}
}
}
-#endif
#ifdef CONFIG_MIGRATION
/*
--
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