[Crash-utility] Adding a new command rbtree

[qiaonuohan]

At 2012-5-23 22:06, Dave Anderson wrote:
>
>
> ----- Original Message -----
>> At 2012-5-22 23:15, Dave Anderson wrote:
>>> Doing it that way really confuses two different "offset" issues that are associated
>>> with this command:
>>>
>>>    (1) the offset of an rb_root or radix_tree_node within a containing
>>>        data structure, and
>>>    (2) the offset of an rb_node within a containing data structure.
>>>
>>> And in both cases, forget trying to implement the "the -o is not necessary" and
>>> "the -o is only necessary..." optimizations, because it would be almost impossible
>>> to do.
>>
>> Hello Dave,
>>
>> I will list all the situations I was concerning.
>>
>> First red-black tree:
>> 1. rb_node is embedded in a structure. Address is the address of the
>> structure, and -o shows the offset of rb_node to the structure.
>>
>> 2. same as 1., but the address is the address of rb_node when using -N
>> in command line.
>>
>> rb_root was not concering. I will recall the reason. I can get the root
>> node from rb_root. And then the offspring of the root node. Then I still
>> need a offset that shows the offset of the offspring node to its related
>> structure to get the structure's information.
>>
>> Then radix tree:
>> 3. radix_tree_root's address is specified.
>>
>> 4. radix_tree_node's address is specified.
>>
>> According to your reply, "-r offset" indicates rb_root and radix_tree_root,
>
> Correct, but only if the rb_root or radix_tree_root are embedded in a
> data structure, and the address argument points to the data stucture.
>
>> and "-n offset" indicates rb_node and radix_tree_node.
>
> No -- the "-n offset" would only applicable to rb_nodes.
>
> radix_tree_node structures data are standalone entities that are allocated
> from the "radix_tree_node" slab cache, correct?  When would a radix_tree_node
> ever be embedded in a containing data structure?
>
>> And if I use "-r offset", then I need another option to show the offset
>> of rb_node. And when using "-n offset" together with an address, which
>> can only be one of rb_node's address and address of the structure
>> rb_node embedded in, I may need another option to indicate the address's
>> type.
>
> The address is either that of an rb_root or radix_tree_root, or the
> address of the containing data structure, in which case it would
> require the "-r offset" option.
>
>>
>> So I think "tree -t type -r offset -n offset -m addr..." is a good
>> choice. "-r offset" indicates the rb_root or radix_tree_root's offset,
>> and "-n offset" indicates the rb_node or radix_tree_node's offset.
>
> Again, what is a "radix_tree_node offset"?
>
>> only using "-n offset" indicates the addr is related to rb_node or
>> radix_tree_node, but if "-r offset" is also specified, the addr is
>> related to rb_root or radix_tree_root. When "-m" is specified, the addr
>> is the address of the root(when specified "-r offset") or the node.  If
>> "-m" is not specified, the addr is the address of the structure that
>> containing the root(when specified "-r offset") or the node.
>>
>> Do you think it's OK?
>
> No, that confuses the hell out me...
>
> I really don't understand the need for the additional "-m" option?
>
> To me it's simple -- but I may be missing something.  The address argument
> can be either:
>
>   (1) A pointer to an rb_root or radix_tree_root.
>       The "-r offset" is not required.
>
>   (2) A pointer to a data structure containing an rb_root or radix_tree_root.
>       The "-r offset" option is required if the member offset is non-zero.
>
> That being the case, this should work:
>
>   red-black tree:  tree -t type [-r offset] [-n offset] address
>       radix tree:  tree -t type [-r offset] address
>
> In the case of a red-black tree, it seems that you are also trying to
> support the bypassing of the rb_root entirely, and point to an rb_node
> directly?  That would seem to be an odd-ball case, because the list
> would be truncated if you don't point to the topmost rb_node.  Is that
> what you have in mind?  If so, I suppose that you could also have a
> additional "-N" option or something like that to signal that the address
> argument is a pointer to an rb_node (and not applicable to radix trees).

I still add "-N" option to make it possible to start from node.

>
> Dave
>
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>
>


-- 
--
Regards
Qiao Nuohan


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