---
 include/linux/rmap.h |    2 +-
 mm/rmap.c            |   38 ++++++++++++++++++++++----------------
 2 files changed, 23 insertions(+), 17 deletions(-)

Index: linux-2.6/include/linux/rmap.h
===================================================================
--- linux-2.6.orig/include/linux/rmap.h	2008-02-27 20:06:44.000000000 -0800
+++ linux-2.6/include/linux/rmap.h	2008-02-27 20:07:05.000000000 -0800
@@ -25,7 +25,7 @@
  * pointing to this anon_vma once its vma list is empty.
  */
 struct anon_vma {
-	spinlock_t lock;	/* Serialize access to vma list */
+	struct rw_semaphore sem;/* Serialize access to vma list */
 	struct list_head head;	/* List of private "related" vmas */
 };
 
Index: linux-2.6/mm/rmap.c
===================================================================
--- linux-2.6.orig/mm/rmap.c	2008-02-27 20:06:21.000000000 -0800
+++ linux-2.6/mm/rmap.c	2008-02-27 20:13:04.000000000 -0800
@@ -25,7 +25,7 @@
  *   mm->mmap_sem
  *     page->flags PG_locked (lock_page)
  *       mapping->i_mmap_sem
- *         anon_vma->lock
+ *         anon_vma->sem
  *           mm->page_table_lock or pte_lock
  *             zone->lru_lock (in mark_page_accessed, isolate_lru_page)
  *             swap_lock (in swap_duplicate, swap_info_get)
@@ -68,7 +68,7 @@ int anon_vma_prepare(struct vm_area_stru
 		if (anon_vma) {
 			allocated = NULL;
 			locked = anon_vma;
-			spin_lock(&locked->lock);
+			down_write(&locked->sem);
 		} else {
 			anon_vma = anon_vma_alloc();
 			if (unlikely(!anon_vma))
@@ -87,7 +87,7 @@ int anon_vma_prepare(struct vm_area_stru
 		spin_unlock(&mm->page_table_lock);
 
 		if (locked)
-			spin_unlock(&locked->lock);
+			up_write(&locked->sem);
 		if (unlikely(allocated))
 			anon_vma_free(allocated);
 	}
@@ -113,9 +113,9 @@ void anon_vma_link(struct vm_area_struct
 	struct anon_vma *anon_vma = vma->anon_vma;
 
 	if (anon_vma) {
-		spin_lock(&anon_vma->lock);
+		down_write(&anon_vma->sem);
 		list_add_tail(&vma->anon_vma_node, &anon_vma->head);
-		spin_unlock(&anon_vma->lock);
+		up_write(&anon_vma->sem);
 	}
 }
 
@@ -127,12 +127,12 @@ void anon_vma_unlink(struct vm_area_stru
 	if (!anon_vma)
 		return;
 
-	spin_lock(&anon_vma->lock);
+	down_write(&anon_vma->sem);
 	list_del(&vma->anon_vma_node);
 
 	/* We must garbage collect the anon_vma if it's empty */
 	empty = list_empty(&anon_vma->head);
-	spin_unlock(&anon_vma->lock);
+	up_write(&anon_vma->lock);
 
 	if (empty)
 		anon_vma_free(anon_vma);
@@ -142,7 +142,7 @@ static void anon_vma_ctor(struct kmem_ca
 {
 	struct anon_vma *anon_vma = data;
 
-	spin_lock_init(&anon_vma->lock);
+	init_rwsem(&anon_vma->sem);
 	INIT_LIST_HEAD(&anon_vma->head);
 }
 
@@ -156,7 +156,7 @@ void __init anon_vma_init(void)
  * Getting a lock on a stable anon_vma from a page off the LRU is
  * tricky: page_lock_anon_vma rely on RCU to guard against the races.
  */
-static struct anon_vma *page_lock_anon_vma(struct page *page)
+static struct anon_vma *page_lock_anon_vma(struct page *page, int write)
 {
 	struct anon_vma *anon_vma;
 	unsigned long anon_mapping;
@@ -169,16 +169,22 @@ static struct anon_vma *page_lock_anon_v
 		goto out;
 
 	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
-	spin_lock(&anon_vma->lock);
+	if (write)
+		down_write(&anon_vma->sem);
+	else
+		down_read(&anon_vma->sem);
 	return anon_vma;
 out:
 	rcu_read_unlock();
 	return NULL;
 }
 
-static void page_unlock_anon_vma(struct anon_vma *anon_vma)
+static void page_unlock_anon_vma(struct anon_vma *anon_vma, int write)
 {
-	spin_unlock(&anon_vma->lock);
+	if (write)
+		up_write(&anon_vma->sem);
+	else
+		up_read(&anon_vma->sem);
 	rcu_read_unlock();
 }
 
@@ -310,7 +316,7 @@ static int page_referenced_anon(struct p
 	struct vm_area_struct *vma;
 	int referenced = 0;
 
-	anon_vma = page_lock_anon_vma(page);
+	anon_vma = page_lock_anon_vma(page, 0);
 	if (!anon_vma)
 		return referenced;
 
@@ -328,7 +334,7 @@ static int page_referenced_anon(struct p
 			break;
 	}
 
-	page_unlock_anon_vma(anon_vma);
+	page_unlock_anon_vma(anon_vma, 0);
 	return referenced;
 }
 
@@ -873,7 +879,7 @@ static int try_to_unmap_anon(struct page
 	struct vm_area_struct *vma;
 	int ret = SWAP_AGAIN;
 
-	anon_vma = page_lock_anon_vma(page);
+	anon_vma = page_lock_anon_vma(page, 0);
 	if (!anon_vma)
 		return ret;
 
@@ -883,7 +889,7 @@ static int try_to_unmap_anon(struct page
 			break;
 	}
 
-	page_unlock_anon_vma(anon_vma);
+	page_unlock_anon_vma(anon_vma, 0);
 	return ret;
 }