Re: [PATCH v4 6/9] rbtree: Implement generic latch_tree

[Lai Jiangshan <laijs@cn.fujitsu.com>]

On 04/09/2015 04:14 PM, Peter Zijlstra wrote:
> On Thu, Apr 09, 2015 at 04:09:07PM +0800, Lai Jiangshan wrote:
>> On 04/09/2015 12:48 AM, Peter Zijlstra wrote:
>>
>>> +
>>> +struct latch_tree_node {
>>> +	/*
>>> +	 * Because we have an array of two entries in struct latch_tree_nodes
>>> +	 * it's not possible to use container_of() to get back to the
>>> +	 * encapsulating structure; therefore we have to put in a back pointer.
>>> +	 */
>>> +	void		*priv;
>>> +	struct rb_node	node;
>>> +};
>>
>> I don't think @priv is strictly needed. It is possible to use container_of()
>> to go back. @priv is even not used in this file (except the initialization).
>>
>> First, we can use container_of() to find encapsulating structure from the
>> struct latch_tree_nodeS.
>>
>> Second, we can add a @idx to __lt_insert() and __lt_find(), 
> 
> insert yes, find no. Remember that both nodes are in the _same_ tree.
> 
> There is no way of knowing if a tree node is an init or core node while
> iterating.
> .
> 

This sentence is talking about module.c not latch_tree.h. So I guess
it is user(module.c)'s problem, not latch_tree.h's problem.

The user(module.c) can wrap the struct latch_tree_nodes and add @priv.