linux-kernel - Re: [PATCH 2/4] [RFC] Range tree implementation

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Date:	Thu, 31 May 2012 14:04:23 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Jan Kara <jack@...e.cz>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>,
	Hugh Dickins <hughd@...gle.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>,
	Andrea Righi <andrea@...terlinux.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Taras Glek <tgek@...illa.com>, Mike Hommey <mh@...ndium.org>
Subject: Re: [PATCH 2/4] [RFC] Range tree implementation

On 05/31/2012 01:48 PM, Jan Kara wrote:
> On Fri 25-05-12 12:17:34, John Stultz wrote:
>> I suspect range-tree isn't a totally accurate name, but I
>> couldn't quite make out the difference between range trees
>> and interval trees, so I just picked one to call it. Do
>> let me know if you have a better name.
>    Well, interval tree is a data structure for tracking a set of
> possibly overlapping intervals. Range tree is a data structure tracking
> points allowing for fast queries on a set of points contained in a given
> range (gets useful and interesting when dimension>  1). Your data structure
> is neither so it would be good to have a different name. OTOH there are so
> many data structures that it's hard to find a reasonable unused name ;)

Although I'm not sure your interval tree description doesn't match what 
I'm trying to provide. Could you clarify why that doesn't match?

>> +/**
>> + * range_tree_next_in_range - Return the next range in a range_tree still
>> + *                            contained within a specified range.
>    'within' isn't really correct, right? It should rather be 'intersecting'.

That is more clear, thanks for the suggestion!

>
>> + * @root: range_tree root
>> + * @start: range start
>> + * @end: range end
>> + *
>> + */
>> +struct range_tree_node *range_tree_next_in_range(struct range_tree_node *node,
>> +							u64 start, u64 end)
>> +{
>> +	struct rb_node *next;
>> +	struct range_tree_node *candidate;
>> +	if (!node)
>> +		return NULL;
>> +	next = rb_next(&node->rb);
>> +	if (!next)
>> +		return NULL;
>> +
>> +	candidate = container_of(next, struct range_tree_node, rb);
>> +
>> +	if ((candidate->start>  end) || (candidate->end<  start))
>> +		return NULL;
>> +
>> +	return candidate;
>> +}
>> +
>> +/**
>> + * range_tree_add - Add a node to a range tree
>> + * @root: range tree to be added to
>> + * @node: range_tree_node to be added
>> + *
>> + * Adds a node to the range tree.
>    I think you should document here that the added range must not intersect
> with any other range in the tree.

So for my usage in the volatile range code, I don't want intersecting or 
overlapping ranges added, but I didn't feel it was necessary to add this 
restriction to my rangetree code as well, since someone might want to 
store overlapping ranges.

thanks for the review!
-john


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