From: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Tue, 25 Feb 2020 16:18:51 +0000 (-0500)
Subject: maple_tree: Fix off by one on mas_prev when going to previous node.
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=467a6b52a4459e99fe22490eeef67ad99ee4622e;p=users%2Fjedix%2Flinux-maple.git

maple_tree: Fix off by one on mas_prev when going to previous node.

mas_prev_nentry decrements the slot prior to checking for an entry, so
don't decrement the slot in mas_prev loop on new nodes.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index a58caac4defa4..12838071355a6 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3207,7 +3207,7 @@ static inline void* _mas_prev(struct ma_state *mas, unsigned long limit)
 			break;
 
 		mas_prev_node(mas, limit);
-		mas_set_slot(mas, mt_slot_count(mas->node) - 1);
+		mas_set_slot(mas, mt_slot_count(mas->node));
 	}
 
 	if (mas_is_none(mas))
diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index 0477191b93c57..7e86303c403f3 100644
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -11671,10 +11671,18 @@ static noinline void check_next_entry(struct maple_tree *mt)
 
 static noinline void check_prev_entry(struct maple_tree *mt)
 {
-	MT_BUG_ON(mt, !mtree_empty(mt));
+	unsigned long index = 16;
+	void *value;
+	MA_STATE(mas, mt, index, index);
 
+	MT_BUG_ON(mt, !mtree_empty(mt));
 	check_seq(mt, 30, false);
+
 	rcu_read_lock();
+	value = mas_find(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, value != xa_mk_value(index));
+	value = mas_prev(&mas, 0);
+	MT_BUG_ON(mt, value != xa_mk_value(index - 1));
 	rcu_read_unlock();
 	mtree_destroy(mt);
 
@@ -11834,7 +11842,7 @@ static int maple_tree_seed(void)
 	mtree_destroy(&tree);
 
 
-	mtree_init(&tree, 0);
+	mtree_init(&tree, MAPLE_ALLOC_RANGE);
 	check_prev_entry(&tree);
 
 	mtree_init(&tree, 0);