From: Liam 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=0d6ead6d985507fafac61abaa3c5ef20a76f1add;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.  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@oracle.com>
---

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 4c7b1bcdd24c..548fed5212bc 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1354,11 +1354,15 @@ 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;
 		}