linux-kernel - Re: [RESEND PATCH 5/8] maple_tree: make mas_validate_limits() check root node and node limit

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Message-ID: <42945254-beb8-8a04-8689-1419595b0b85@bytedance.com>
Date:   Mon, 10 Jul 2023 17:11:47 +0800
From:   Peng Zhang <zhangpeng.00@...edance.com>
To:     "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc:     Peng Zhang <zhangpeng.00@...edance.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        maple-tree@...ts.infradead.org
Subject: Re: [RESEND PATCH 5/8] maple_tree: make mas_validate_limits() check
 root node and node limit


在 2023/7/7 22:58, Liam R. Howlett 写道:
> * Peng Zhang <zhangpeng.00@...edance.com> [230707 06:11]:
>> 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().
>>
> 
> The comments for this function say:
>   * Validate all pivots are within mas->min and mas->max.
> 
> This needs adjusting since we are doing a whole lot more now..
Thanks, I will update it in v2.
> 
> Validate limits is now checking metadata ends where the maximum ends,
> checks the pivots are within the limits of the node, and ensures
> there is no slots or pivots set outside of the end of the data.
> 
> Did I miss anything?
You're right, that's exactly all the checks it does.
> 
>> Signed-off-by: Peng Zhang <zhangpeng.00@...edance.com>
>> ---
>>   lib/maple_tree.c | 26 +++++++++++---------------
>>   1 file changed, 11 insertions(+), 15 deletions(-)
>>
>> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
>> index 88d6373f37b0..e84a042b6d84 100644
>> --- a/lib/maple_tree.c
>> +++ b/lib/maple_tree.c
>> @@ -7148,26 +7148,15 @@ 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) {
>> @@ -7190,6 +7179,13 @@ 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
>>
>>
>> -- 
>> maple-tree mailing list
>> maple-tree@...ts.infradead.org
>> https://lists.infradead.org/mailman/listinfo/maple-tree

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