linux-kernel - Re: [PATCH v2 5/8] maple_tree: make mas_validate

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Date:   Tue, 11 Jul 2023 21:24:41 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Peng Zhang <zhangpeng.00@...edance.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, maple-tree@...ts.infradead.org
Subject: Re: [PATCH v2 5/8] maple_tree: make mas_validate_limits() check root
 node and node limit

* Peng Zhang <zhangpeng.00@...edance.com> [230710 23:55]:
> Update mas_validate_limits() to check root node, check node limit pivot
> if there is enough room for it to exist and check data_end. Remove the
> check for child existence as it is done in mas_validate_child_slot().
> 
> Signed-off-by: Peng Zhang <zhangpeng.00@...edance.com>

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

> ---
>  lib/maple_tree.c | 30 ++++++++++++++----------------
>  1 file changed, 14 insertions(+), 16 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index f750ebef595f..072532fa18ee 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -7146,7 +7146,9 @@ static void mas_validate_child_slot(struct ma_state *mas)
>  }
>  
>  /*
> - * Validate all pivots are within mas->min and mas->max.
> + * Validate all pivots are within mas->min and mas->max, check metadata ends
> + * where the maximum ends and ensure there is no slots or pivots set outside of
> + * the end of the data.
>   */
>  static void mas_validate_limits(struct ma_state *mas)
>  {
> @@ -7156,26 +7158,15 @@ static void mas_validate_limits(struct ma_state *mas)
>  	void __rcu **slots = ma_slots(mte_to_node(mas->node), type);
>  	unsigned long *pivots = ma_pivots(mas_mn(mas), type);
>  
> -	/* all limits are fine here. */
> -	if (mte_is_root(mas->node))
> -		return;
> -
>  	for (i = 0; i < mt_slots[type]; i++) {
>  		unsigned long piv;
>  
>  		piv = mas_safe_pivot(mas, pivots, i, type);
>  
> -		if (!piv && (i != 0))
> -			break;
> -
> -		if (!mte_is_leaf(mas->node)) {
> -			void *entry = mas_slot(mas, slots, i);
> -
> -			if (!entry)
> -				pr_err("%p[%u] cannot be null\n",
> -				       mas_mn(mas), i);
> -
> -			MT_BUG_ON(mas->tree, !entry);
> +		if (!piv && (i != 0)) {
> +			pr_err("Missing node limit pivot at %p[%u]",
> +			       mas_mn(mas), i);
> +			MAS_WARN_ON(mas, 1);
>  		}
>  
>  		if (prev_piv > piv) {
> @@ -7198,6 +7189,13 @@ static void mas_validate_limits(struct ma_state *mas)
>  		if (piv == mas->max)
>  			break;
>  	}
> +
> +	if (mas_data_end(mas) != i) {
> +		pr_err("node%p: data_end %u != the last slot offset %u\n",
> +		       mas_mn(mas), mas_data_end(mas), i);
> +		MT_BUG_ON(mas->tree, 1);
> +	}
> +
>  	for (i += 1; i < mt_slots[type]; i++) {
>  		void *entry = mas_slot(mas, slots, i);
>  
> -- 
> 2.20.1
> 
>