From a7b92d59c885018cb7bb88539892278e4fd64b29 Mon Sep 17 00:00:00 2001 From: Liam Howlett Date: Mon, 27 Feb 2023 09:36:01 -0800 Subject: [PATCH] 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. Link: https://lkml.kernel.org/r/20230227173632.3292573-3-surenb@google.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam Howlett Signed-off-by: Suren Baghdasaryan Cc: Signed-off-by: Andrew Morton --- lib/maple_tree.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/lib/maple_tree.c b/lib/maple_tree.c index 095b9cb1f4f1..3d53339656e1 100644 --- a/lib/maple_tree.c +++ b/lib/maple_tree.c @@ -1360,12 +1360,16 @@ static inline struct maple_enode *mas_start(struct ma_state *mas) mas->max = ULONG_MAX; mas->depth = 0; +retry: root = mas_root(mas); /* Tree with nodes */ if (likely(xa_is_node(root))) { mas->depth = 1; mas->node = mte_safe_root(root); mas->offset = 0; + if (mte_dead_node(mas->node)) + goto retry; + return NULL; }