[PATCH 2/2] maple_tree: Add testing for restoring maple state to active

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

Restoring maple status to ma_active on overflow/underflow when mas->node
was NULL could have happened in the past, but was masked by a bug in
mas_walk().  Add test cases that triggered the bug when the node was
mas->node prior to fixing the maple state setup.

Add a few extra tests around restoring the active maple status.

Link: https://lore.kernel.org/all/202506191556.6bfc7b93-lkp@intel.com/
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
 lib/test_maple_tree.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/lib/test_maple_tree.c b/lib/test_maple_tree.c
index 13e2a10d7554d..cb3936595b0d5 100644
--- a/lib/test_maple_tree.c
+++ b/lib/test_maple_tree.c
@@ -3177,6 +3177,7 @@ static noinline void __init check_state_handling(struct maple_tree *mt)
 	void *entry, *ptr = (void *) 0x1234500;
 	void *ptr2 = &ptr;
 	void *ptr3 = &ptr2;
+	unsigned long index;
 
 	/* Check MAS_ROOT First */
 	mtree_store_range(mt, 0, 0, ptr, GFP_KERNEL);
@@ -3706,6 +3707,37 @@ static noinline void __init check_state_handling(struct maple_tree *mt)
 	MT_BUG_ON(mt, mas.last != 0x1fff);
 	MT_BUG_ON(mt, !mas_is_active(&mas));
 
+	mas_unlock(&mas);
+	mtree_destroy(mt);
+
+	mt_init_flags(mt, MT_FLAGS_ALLOC_RANGE);
+	mas_lock(&mas);
+	for (int count = 0; count < 30; count++) {
+		mas_set(&mas, count);
+		mas_store_gfp(&mas, xa_mk_value(count), GFP_KERNEL);
+	}
+
+	/* Ensure mas_find works with MA_UNDERFLOW */
+	mas_set(&mas, 0);
+	entry = mas_walk(&mas);
+	mas_set(&mas, 0);
+	mas_prev(&mas, 0);
+	MT_BUG_ON(mt, mas.status != ma_underflow);
+	MT_BUG_ON(mt, mas_find(&mas, ULONG_MAX) != entry);
+
+	/* Restore active on mas_next */
+	entry = mas_next(&mas, ULONG_MAX);
+	index = mas.index;
+	mas_prev(&mas, index);
+	MT_BUG_ON(mt, mas.status != ma_underflow);
+	MT_BUG_ON(mt, mas_next(&mas, ULONG_MAX) != entry);
+
+	/* Ensure overflow -> active works */
+	mas_prev(&mas, 0);
+	mas_next(&mas, index - 1);
+	MT_BUG_ON(mt, mas.status != ma_overflow);
+	MT_BUG_ON(mt, mas_next(&mas, ULONG_MAX) != entry);
+
 	mas_unlock(&mas);
 }
 
-- 
2.47.2