From: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Thu, 24 Nov 2022 15:48:23 +0000 (-0500)
Subject: maple_tree: Detect dead nodes in mas_start()
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=10baabda8ba5a01ca81e095a1097f633838ab351;p=users%2Fjedix%2Flinux-maple.git

maple_tree: Detect dead nodes in mas_start()

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.

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

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 6bf865c72041..c5bbd2a07228 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1365,11 +1365,15 @@ 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;
 		}