linux-kernel - Re: [PATCH Fix] maple_tree: Use metadata for mas_dead

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Message-ID: <20220712153818.mtgozcaqngsyjl4q@revolver>
Date:   Tue, 12 Jul 2022 15:38:28 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH Fix] maple_tree: Use metadata for mas_dead_leaves() walk

Please do not apply this patch.  More testing is needed.  Again, sorry
for the noise.

* Liam R. Howlett <Liam.Howlett@...cle.com> [220712 10:53]:
> When walking the dead leaves, use the nodes metadata for the end of the
> node.  This avoids needing to use tricks for BE/LE unions.
> 
> Fixes: d0aac5e48048 (Maple Tree: add new data structure)
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>  lib/maple_tree.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 14e9ab14c1da..c661fda37665 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -5390,15 +5390,12 @@ unsigned char mas_dead_leaves(struct ma_state *mas, void __rcu **slots)
>  	enum maple_type type;
>  	void *entry;
>  	int offset;
> +	unsigned end = mas_data_end(mas);
>  
> -	for (offset = 0; offset < mt_slot_count(mas->node); offset++) {
> +	for (offset = 0; offset <= end; offset++) {
>  		entry = mas_slot_locked(mas, slots, offset);
>  		type = mte_node_type(entry);
>  		node = mte_to_node(entry);
> -		/* Use both node and type to catch LE & BE metadata */
> -		if (!node || !type)
> -			break;
> -
>  		mte_set_node_dead(entry);
>  		smp_wmb(); /* Needed for RCU */
>  		node->type = type;
> -- 
> 2.35.1