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authorMel Gorman <mel@csn.ul.ie>2010-05-24 14:32:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-25 08:06:58 -0700
commit7f60c214fd3a360461f3286c6908084f7f8b1950 (patch)
treedba48cf988a22a40796187c7274f7903a288f7f4
parent3f6c82728f4e31a97c3a1b32abccb512fed0b573 (diff)
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mm: migration: share the anon_vma ref counts between KSM and page migration
For clarity of review, KSM and page migration have separate refcounts on the anon_vma. While clear, this is a waste of memory. This patch gets KSM and page migration to share their toys in a spirit of harmony. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Christoph Lameter <cl@linux-foundation.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/rmap.h50
-rw-r--r--mm/ksm.c4
-rw-r--r--mm/migrate.c4
-rw-r--r--mm/rmap.c6
4 files changed, 24 insertions, 40 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 567d43f29a1..77216742c17 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -26,11 +26,17 @@
*/
struct anon_vma {
spinlock_t lock; /* Serialize access to vma list */
-#ifdef CONFIG_KSM
- atomic_t ksm_refcount;
-#endif
-#ifdef CONFIG_MIGRATION
- atomic_t migrate_refcount;
+#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
+ * 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
/*
* NOTE: the LSB of the head.next is set by
@@ -64,46 +70,26 @@ struct anon_vma_chain {
};
#ifdef CONFIG_MMU
-#ifdef CONFIG_KSM
-static inline void ksm_refcount_init(struct anon_vma *anon_vma)
+#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
+static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
{
- atomic_set(&anon_vma->ksm_refcount, 0);
+ atomic_set(&anon_vma->external_refcount, 0);
}
-static inline int ksm_refcount(struct anon_vma *anon_vma)
+static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
{
- return atomic_read(&anon_vma->ksm_refcount);
+ return atomic_read(&anon_vma->external_refcount);
}
#else
-static inline void ksm_refcount_init(struct anon_vma *anon_vma)
+static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
{
}
-static inline int ksm_refcount(struct anon_vma *anon_vma)
+static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
{
return 0;
}
#endif /* CONFIG_KSM */
-#ifdef CONFIG_MIGRATION
-static inline void migrate_refcount_init(struct anon_vma *anon_vma)
-{
- atomic_set(&anon_vma->migrate_refcount, 0);
-}
-
-static inline int migrate_refcount(struct anon_vma *anon_vma)
-{
- return atomic_read(&anon_vma->migrate_refcount);
-}
-#else
-static inline void migrate_refcount_init(struct anon_vma *anon_vma)
-{
-}
-
-static inline int migrate_refcount(struct anon_vma *anon_vma)
-{
- return 0;
-}
-#endif /* CONFIG_MIGRATE */
static inline struct anon_vma *page_anon_vma(struct page *page)
{
diff --git a/mm/ksm.c b/mm/ksm.c
index 956880f2ff4..6c3e99b4ae7 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -318,14 +318,14 @@ static void hold_anon_vma(struct rmap_item *rmap_item,
struct anon_vma *anon_vma)
{
rmap_item->anon_vma = anon_vma;
- atomic_inc(&anon_vma->ksm_refcount);
+ atomic_inc(&anon_vma->external_refcount);
}
static void drop_anon_vma(struct rmap_item *rmap_item)
{
struct anon_vma *anon_vma = rmap_item->anon_vma;
- if (atomic_dec_and_lock(&anon_vma->ksm_refcount, &anon_vma->lock)) {
+ if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {
int empty = list_empty(&anon_vma->head);
spin_unlock(&anon_vma->lock);
if (empty)
diff --git a/mm/migrate.c b/mm/migrate.c
index b768a1d4fa4..42a3d24d110 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -601,7 +601,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
rcu_read_lock();
rcu_locked = 1;
anon_vma = page_anon_vma(page);
- atomic_inc(&anon_vma->migrate_refcount);
+ atomic_inc(&anon_vma->external_refcount);
}
/*
@@ -643,7 +643,7 @@ skip_unmap:
rcu_unlock:
/* Drop an anon_vma reference if we took one */
- if (anon_vma && atomic_dec_and_lock(&anon_vma->migrate_refcount, &anon_vma->lock)) {
+ if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {
int empty = list_empty(&anon_vma->head);
spin_unlock(&anon_vma->lock);
if (empty)
diff --git a/mm/rmap.c b/mm/rmap.c
index f522cb00864..b5c320f7d0a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -250,8 +250,7 @@ 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) && !ksm_refcount(anon_vma) &&
- !migrate_refcount(anon_vma);
+ empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);
spin_unlock(&anon_vma->lock);
if (empty)
@@ -275,8 +274,7 @@ static void anon_vma_ctor(void *data)
struct anon_vma *anon_vma = data;
spin_lock_init(&anon_vma->lock);
- ksm_refcount_init(anon_vma);
- migrate_refcount_init(anon_vma);
+ anonvma_external_refcount_init(anon_vma);
INIT_LIST_HEAD(&anon_vma->head);
}