Re: [PATCH] Corrections to Documentation/rbtree.txt

Ian Abbott
2008-03-25T11:02:41Z

On 20/03/08 18:39, Rob Landley wrote:
> On Thursday 20 March 2008 10:29:57 Ian Abbott wrote:
>> From: Ian Abbott <abbotti@mev.co.uk>
>>
>> The description of the rb_entry() macro in Documentation/rbtree.txt seems
>> incorrect. This patch improves it (hopefully). Also I changed the example
>> code to call the previous 'my_search()' example instead of an undefined
>> 'mysearch()'.
>
> I have no objection to the patch (and the my_search thing seems like an
> obvious typo), but is there a reason to prefer rb_entry() rather than
> container_of()? If so, the rationale might be a good thing to add to the
> documentation...

I don't know the rationale, but all the code I can see uses rb_entry()
and not container_of(). The only rationale I can think of is that it
abstracts away from the nodes being embedded in the data a little bit.
(But not by much - in particular, an implementation of rb trees that
stored data in the node explicitly would only need a single parameter in
its rb_entry() accessor. I like the approach taken in
include/linux/elevator.h that uses the rb_entry() macro to create a
specialized accessor macro (rb_entry_rq()) with a single parameter.