linux-kernel - Re: [PATCH 1/2] maple_tree: Fix mt_destroy

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Message-ID: <c63e9e0d-5f63-4e33-a1a5-426970370514@arm.com>
Date: Wed, 25 Jun 2025 10:45:10 +0530
From: Dev Jain <dev.jain@....com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: maple-tree@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Wei Yang <richard.weiyang@...il.com>,
 stable@...r.kernel.org
Subject: Re: [PATCH 1/2] maple_tree: Fix mt_destroy_walk() on root leaf node


On 25/06/25 12:48 am, Liam R. Howlett wrote:
> From: Wei Yang <richard.weiyang@...il.com>
>
> On destroy, we should set each node dead. But current code miss this
> when the maple tree has only the root node.
>
> The reason is mt_destroy_walk() leverage mte_destroy_descend() to set
> node dead, but this is skipped since the only root node is a leaf.
>
> Fixes this by setting the node dead if it is a leaf.
>
> Link: https://lore.kernel.org/all/20250407231354.11771-1-richard.weiyang@gmail.com/
> Fixes: 54a611b60590 ("Maple Tree: add new data structure")
> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> CC: Liam R. Howlett <Liam.Howlett@...cle.com>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>   lib/maple_tree.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 6b0fc6ebbe363..85d17d943753d 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -5319,6 +5319,7 @@ static void mt_destroy_walk(struct maple_enode *enode, struct maple_tree *mt,
>   	struct maple_enode *start;
>   
>   	if (mte_is_leaf(enode)) {
> +		mte_set_node_dead(enode);
>   		node->type = mte_node_type(enode);
>   		goto free_leaf;
>   	}

FWIW I have been reading the maple tree code and this looks good to me.

Reviewed-by: Dev Jain <dev.jain@....com>