1 files changed, 17 insertions, 13 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 87a1779..d8caff0 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2142,12 +2142,14 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
  *
  * Remember policies even when nobody has shared memory mapped.
  * The policies are kept in Red-Black tree linked from the inode.
- * They are protected by the sp->lock spinlock, which should be held
+ * They are protected by the sp->lock rwlock, which should be held
  * for any accesses to the tree.
  */
 
-/* lookup first element intersecting start-end */
-/* Caller holds sp->lock */
+/*
+ * lookup first element intersecting start-end.  Caller holds sp->lock for
+ * reading or for writing
+ */
 static struct sp_node *
 sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
 {
@@ -2178,8 +2180,10 @@ sp_lookup(struct shared_policy *sp, unsigned long start, unsigned long end)
 	return rb_entry(n, struct sp_node, nd);
 }
 
-/* Insert a new shared policy into the list. */
-/* Caller holds sp->lock */
+/*
+ * Insert a new shared policy into the list.  Caller holds sp->lock for
+ * writing.
+ */
 static void sp_insert(struct shared_policy *sp, struct sp_node *new)
 {
 	struct rb_node **p = &sp->root.rb_node;
@@ -2211,13 +2215,13 @@ mpol_shared_policy_lookup(struct shared_policy *sp, unsigned long idx)
 
 	if (!sp->root.rb_node)
 		return NULL;
-	spin_lock(&sp->lock);
+	read_lock(&sp->lock);
 	sn = sp_lookup(sp, idx, idx+1);
 	if (sn) {
 		mpol_get(sn->policy);
 		pol = sn->policy;
 	}
-	spin_unlock(&sp->lock);
+	read_unlock(&sp->lock);
 	return pol;
 }
 
@@ -2360,7 +2364,7 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
 	int ret = 0;
 
 restart:
-	spin_lock(&sp->lock);
+	write_lock(&sp->lock);
 	n = sp_lookup(sp, start, end);
 	/* Take care of old policies in the same range. */
 	while (n && n->start < end) {
@@ -2393,7 +2397,7 @@ restart:
 	}
 	if (new)
 		sp_insert(sp, new);
-	spin_unlock(&sp->lock);
+	write_unlock(&sp->lock);
 	ret = 0;
 
 err_out:
@@ -2405,7 +2409,7 @@ err_out:
 	return ret;
 
 alloc_new:
-	spin_unlock(&sp->lock);
+	write_unlock(&sp->lock);
 	ret = -ENOMEM;
 	n_new = kmem_cache_alloc(sn_cache, GFP_KERNEL);
 	if (!n_new)
@@ -2431,7 +2435,7 @@ void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
 	int ret;
 
 	sp->root = RB_ROOT;		/* empty tree == default mempolicy */
-	spin_lock_init(&sp->lock);
+	rwlock_init(&sp->lock);
 
 	if (mpol) {
 		struct vm_area_struct pvma;
@@ -2497,14 +2501,14 @@ void mpol_free_shared_policy(struct shared_policy *p)
 
 	if (!p->root.rb_node)
 		return;
-	spin_lock(&p->lock);
+	write_lock(&p->lock);
 	next = rb_first(&p->root);
 	while (next) {
 		n = rb_entry(next, struct sp_node, nd);
 		next = rb_next(&n->nd);
 		sp_delete(p, n);
 	}
-	spin_unlock(&p->lock);
+	write_unlock(&p->lock);
 }
 
 #ifdef CONFIG_NUMA_BALANCING