[PATCH 02/41] maple_tree: Detect dead nodes in mas_start()

[Suren Baghdasaryan]

From: Liam Howlett <Liam.Howlett at oracle.com>

When initially starting a search, the root node may already be in the
process of being replaced in RCU mode.  Detect and restart the walk if
this is the case.  This is necessary for RCU mode of the maple tree.

Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam Howlett <Liam.Howlett at oracle.com>
Signed-off-by: Suren Baghdasaryan <surenb at google.com>
---
 lib/maple_tree.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index ff9f04e0150d..a748938ad2e9 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1359,11 +1359,15 @@ static inline struct maple_enode *mas_start(struct ma_state *mas)
 		mas->depth = 0;
 		mas->offset = 0;
 
+retry:
 		root = mas_root(mas);
 		/* Tree with nodes */
 		if (likely(xa_is_node(root))) {
 			mas->depth = 1;
 			mas->node = mte_safe_root(root);
+			if (mte_dead_node(mas->node))
+				goto retry;
+
 			return NULL;
 		}
 
-- 
2.39.0