linux-kernel - [RESEND Patch v2 3/3] maple_tree: assert retrieving new value on a tree containing just a leaf node

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Message-Id: <20250407231354.11771-4-richard.weiyang@gmail.com>
Date: Mon,  7 Apr 2025 23:13:54 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Liam.Howlett@...cle.com,
	akpm@...ux-foundation.org,
	willy@...radead.org
Cc: linux-kernel@...r.kernel.org,
	maple-tree@...ts.infradead.org,
	linux-mm@...ck.org,
	Wei Yang <richard.weiyang@...il.com>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>
Subject: [RESEND Patch v2 3/3] maple_tree: assert retrieving new value on a tree containing just a leaf node

Original code may not get the new value after overwriting the whole
range on a maple tree containing just a leaf node. The reason is we didn't
set the only root node dead during destroy.

Add a test case to ensure the new value is returned when overwriting a
tree containing just a leaf node.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
CC: Liam R. Howlett <Liam.Howlett@...cle.com>

---
v2: adjust the changelog according to Liam's suggestion
---
 tools/testing/radix-tree/maple.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
index bc30050227fd..1e293e4d856d 100644
--- a/tools/testing/radix-tree/maple.c
+++ b/tools/testing/radix-tree/maple.c
@@ -35256,6 +35256,30 @@ static noinline void __init check_rcu_simulated(struct maple_tree *mt)
 	MT_BUG_ON(mt, mas_prev(&mas_reader, 0) != xa_mk_value(val));
 	rcu_read_unlock();
 
+	/* Clear out tree & create one with only root node */
+	mas_lock(&mas_writer);
+	mas_set_range(&mas_writer, 0, ULONG_MAX);
+	mas_store_gfp(&mas_writer, NULL, GFP_KERNEL);
+	mas_set_range(&mas_writer, 0, 0);
+	for (i = 0; i <= 5; i++) {
+		mas_writer.index = i * 10;
+		mas_writer.last = i * 10 + 5;
+		mas_store_gfp(&mas_writer, xa_mk_value(i), GFP_KERNEL);
+	}
+	mas_unlock(&mas_writer);
+	target = 10;
+	mas_set_range(&mas_reader, target, target);
+	rcu_read_lock();
+	MT_BUG_ON(mt, mas_walk(&mas_reader) != xa_mk_value(target/10));
+
+	/* Overwrite the whole range */
+	mas_lock(&mas_writer);
+	mas_set_range(&mas_writer, 0, ULONG_MAX);
+	mas_store_gfp(&mas_writer, xa_mk_value(val), GFP_KERNEL);
+	mas_unlock(&mas_writer);
+	MT_BUG_ON(mt, mas_walk(&mas_reader) != xa_mk_value(val));
+	rcu_read_unlock();
+
 	rcu_unregister_thread();
 }
 
-- 
2.34.1