linux-kernel - Re: [RESEND Patch v2 3/3] maple_tree: assert retrieving new value on a tree containing just a leaf node

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Message-ID: <vgiarjjxk2hy2m5nm6vuotizgndofyb6436eaulhamt56ytra3@cjswiccpnrii>
Date: Mon, 7 Apr 2025 21:45:55 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Wei Yang <richard.weiyang@...il.com>
Cc: akpm@...ux-foundation.org, willy@...radead.org,
        linux-kernel@...r.kernel.org, maple-tree@...ts.infradead.org,
        linux-mm@...ck.org
Subject: Re: [RESEND Patch v2 3/3] maple_tree: assert retrieving new value on
 a tree containing just a leaf node

* Wei Yang <richard.weiyang@...il.com> [250407 19:14]:
> Original code may not get the new value after overwriting the whole
> range on a maple tree containing just a leaf node. The reason is we didn't
> set the only root node dead during destroy.
> 
> Add a test case to ensure the new value is returned when overwriting a
> tree containing just a leaf node.
> 
> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> CC: Liam R. Howlett <Liam.Howlett@...cle.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>

> 
> ---
> v2: adjust the changelog according to Liam's suggestion
> ---
>  tools/testing/radix-tree/maple.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/tools/testing/radix-tree/maple.c b/tools/testing/radix-tree/maple.c
> index bc30050227fd..1e293e4d856d 100644
> --- a/tools/testing/radix-tree/maple.c
> +++ b/tools/testing/radix-tree/maple.c
> @@ -35256,6 +35256,30 @@ static noinline void __init check_rcu_simulated(struct maple_tree *mt)
>  	MT_BUG_ON(mt, mas_prev(&mas_reader, 0) != xa_mk_value(val));
>  	rcu_read_unlock();
>  
> +	/* Clear out tree & create one with only root node */
> +	mas_lock(&mas_writer);
> +	mas_set_range(&mas_writer, 0, ULONG_MAX);
> +	mas_store_gfp(&mas_writer, NULL, GFP_KERNEL);
> +	mas_set_range(&mas_writer, 0, 0);
> +	for (i = 0; i <= 5; i++) {
> +		mas_writer.index = i * 10;
> +		mas_writer.last = i * 10 + 5;
> +		mas_store_gfp(&mas_writer, xa_mk_value(i), GFP_KERNEL);
> +	}
> +	mas_unlock(&mas_writer);
> +	target = 10;
> +	mas_set_range(&mas_reader, target, target);
> +	rcu_read_lock();
> +	MT_BUG_ON(mt, mas_walk(&mas_reader) != xa_mk_value(target/10));
> +
> +	/* Overwrite the whole range */
> +	mas_lock(&mas_writer);
> +	mas_set_range(&mas_writer, 0, ULONG_MAX);
> +	mas_store_gfp(&mas_writer, xa_mk_value(val), GFP_KERNEL);
> +	mas_unlock(&mas_writer);
> +	MT_BUG_ON(mt, mas_walk(&mas_reader) != xa_mk_value(val));
> +	rcu_read_unlock();
> +
>  	rcu_unregister_thread();
>  }
>  
> -- 
> 2.34.1
>