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maple_tree: detect dead nodes in mas_start()

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commit a7b92d59c885018cb7bb88539892278e4fd64b29 upstream.

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
Cc: <Stable@vger.kernel.org>
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Liam R. Howlett 2023-04-11 11:10:50 -04:00 committed by Greg Kroah-Hartman
parent 3825e4495b
commit 5f7c591264
1 changed files with 4 additions and 0 deletions
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4
lib/maple_tree.c
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@ -1352,12 +1352,16 @@ 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;
}