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maple_tree: detect dead nodes in mas_start()

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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 <Liam.Howlett@oracle.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam Howlett 2023-02-27 09:36:01 -08:00 committed by Andrew Morton
parent 39d0bd86c4
commit a7b92d59c8
1 changed files with 4 additions and 0 deletions
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4
lib/maple_tree.c
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@ -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;
}