[PATCH 2/4] maple_tree: Test emptying tree while RCU reading

[Liam R. Howlett (Google)]

Add a test case for the rcu reader being restarted by emptying the tree.

Signed-off-by: Liam R. Howlett (Google) <liam@xxxxxxxxxxxxx>
---
 lib/test_maple_tree.c | 129 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)

diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index fb40e193a3cb7..894f5893e1be2 100644
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -3740,6 +3740,134 @@ static noinline void __init check_range64_in_rcu(struct maple_tree *mt)
 	rcu_barrier();
 }
 
+/*
+ * A reader that restarts after its leaf died may find a tree without nodes:
+ * emptied, or emptied and then given a single entry at 0.  Each case starts
+ * from a tree with nodes, built by check_seq().  The stores run while the
+ * reader holds rcu_read_lock, so they use GFP_ATOMIC.
+ */
+static noinline void __init check_restart_no_node(struct maple_tree *mt)
+{
+	void *ptr = xa_mk_value(1234);
+	void *entry;
+	MA_STATE(mas, mt, 0, 0);
+
+	MT_BUG_ON(mt, !mtree_empty(mt));
+	mt_set_non_kernel(99999);
+
+	/* find: the tree is emptied */
+	mt_init_flags(mt, MT_FLAGS_USE_RCU);
+	check_seq(mt, 100, false);
+	rcu_read_lock();
+	mas_set(&mas, 0);
+	entry = mas_find(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, entry != xa_mk_value(0));
+	MT_BUG_ON(mt, mtree_store_range(mt, 0, ULONG_MAX, NULL, GFP_ATOMIC));
+	entry = mas_find(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, entry != NULL);
+	MT_BUG_ON(mt, mas.status != ma_none);
+	MT_BUG_ON(mt, mas.index != 0);
+	MT_BUG_ON(mt, mas.last != ULONG_MAX);
+	entry = mas_find(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, entry != NULL);
+	MT_BUG_ON(mt, mas.status != ma_none);
+	rcu_read_unlock();
+	mtree_destroy(mt);
+	rcu_barrier();
+
+	/* next: the tree is emptied */
+	mt_init_flags(mt, MT_FLAGS_USE_RCU);
+	check_seq(mt, 100, false);
+	rcu_read_lock();
+	mas_set(&mas, 0);
+	entry = mas_find(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, entry != xa_mk_value(0));
+	MT_BUG_ON(mt, mtree_store_range(mt, 0, ULONG_MAX, NULL, GFP_ATOMIC));
+	entry = mas_next(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, entry != NULL);
+	MT_BUG_ON(mt, mas.status != ma_none);
+	MT_BUG_ON(mt, mas.index != 0);
+	MT_BUG_ON(mt, mas.last != ULONG_MAX);
+	rcu_read_unlock();
+	mtree_destroy(mt);
+	rcu_barrier();
+
+	/* find: the tree is emptied, then holds one entry at 0 */
+	mt_init_flags(mt, MT_FLAGS_USE_RCU);
+	check_seq(mt, 100, false);
+	rcu_read_lock();
+	mas_set(&mas, 0);
+	entry = mas_find(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, entry != xa_mk_value(0));
+	MT_BUG_ON(mt, mtree_store_range(mt, 0, ULONG_MAX, NULL, GFP_ATOMIC));
+	MT_BUG_ON(mt, mtree_store(mt, 0, ptr, GFP_ATOMIC));
+	entry = mas_find(&mas, ULONG_MAX);
+	MT_BUG_ON(mt, entry != NULL);
+	MT_BUG_ON(mt, mas.status != ma_none);
+	MT_BUG_ON(mt, mas.index != 1);
+	MT_BUG_ON(mt, mas.last != ULONG_MAX);
+	rcu_read_unlock();
+	mtree_destroy(mt);
+	rcu_barrier();
+
+	/* find_rev: the tree is emptied */
+	mt_init_flags(mt, MT_FLAGS_USE_RCU);
+	check_seq(mt, 100, false);
+	rcu_read_lock();
+	mas_set(&mas, ULONG_MAX);
+	entry = mas_find_rev(&mas, 0);
+	MT_BUG_ON(mt, entry != xa_mk_value(100));
+	MT_BUG_ON(mt, mtree_store_range(mt, 0, ULONG_MAX, NULL, GFP_ATOMIC));
+	entry = mas_find_rev(&mas, 0);
+	MT_BUG_ON(mt, entry != NULL);
+	MT_BUG_ON(mt, mas.status != ma_none);
+	MT_BUG_ON(mt, mas.index != 0);
+	MT_BUG_ON(mt, mas.last != ULONG_MAX);
+	entry = mas_find_rev(&mas, 0);
+	MT_BUG_ON(mt, entry != NULL);
+	MT_BUG_ON(mt, mas.status != ma_none);
+	rcu_read_unlock();
+	mtree_destroy(mt);
+	rcu_barrier();
+
+	/* prev: the tree is emptied, then holds one entry at 0 */
+	mt_init_flags(mt, MT_FLAGS_USE_RCU);
+	check_seq(mt, 100, false);
+	rcu_read_lock();
+	mas_set(&mas, ULONG_MAX);
+	entry = mas_find_rev(&mas, 0);
+	MT_BUG_ON(mt, entry != xa_mk_value(100));
+	MT_BUG_ON(mt, mtree_store_range(mt, 0, ULONG_MAX, NULL, GFP_ATOMIC));
+	MT_BUG_ON(mt, mtree_store(mt, 0, ptr, GFP_ATOMIC));
+	entry = mas_prev(&mas, 0);
+	MT_BUG_ON(mt, entry != ptr);
+	MT_BUG_ON(mt, mas.status != ma_root);
+	MT_BUG_ON(mt, mas.index != 0);
+	MT_BUG_ON(mt, mas.last != 0);
+	rcu_read_unlock();
+	mtree_destroy(mt);
+	rcu_barrier();
+
+	/* find_rev: the entry at 0 is below the minimum */
+	mt_init_flags(mt, MT_FLAGS_USE_RCU);
+	check_seq(mt, 100, false);
+	rcu_read_lock();
+	mas_set(&mas, ULONG_MAX);
+	entry = mas_find_rev(&mas, 1);
+	MT_BUG_ON(mt, entry != xa_mk_value(100));
+	MT_BUG_ON(mt, mtree_store_range(mt, 0, ULONG_MAX, NULL, GFP_ATOMIC));
+	MT_BUG_ON(mt, mtree_store(mt, 0, ptr, GFP_ATOMIC));
+	entry = mas_find_rev(&mas, 1);
+	MT_BUG_ON(mt, entry != NULL);
+	MT_BUG_ON(mt, mas.status != ma_root);
+	MT_BUG_ON(mt, mas.index != 0);
+	MT_BUG_ON(mt, mas.last != 0);
+	rcu_read_unlock();
+	mtree_destroy(mt);
+	rcu_barrier();
+	mt_set_non_kernel(0);
+}
+
 static DEFINE_MTREE(tree);
 static int __init maple_tree_seed(void)
 {
@@ -4031,6 +4159,7 @@ static int __init maple_tree_seed(void)
 
 	check_range64_in_rcu(&tree);
 
+	check_restart_no_node(&tree);
 
 #if defined(BENCH)
 skip:
-- 
2.47.3