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SubjectRe: [PATCH v3 2/3] augmented rbtree: add new RB_DECLARE_CALLBACKS_MAX macro
Hello, Michel.

>
> Hmmm, I had not thought about that. Agree that this can be useful -
> there is already similar test code in rbtree_test.c and also
> vma_compute_subtree_gap() in mmap.c, ...
>
> With patch 3/3 of this series, the RBCOMPUTE function (typically
> generated through the RB_DECLARE_CALLBACKS_MAX macro) will return a
> bool indicating if the node's augmented value was already correctly
> set. Maybe this can be used for test code, through in the false case,
> the node's augmented value is already overwritten with the correct
> value. Not sure if that is a problem though - the files I mentioned
> above have test code that will dump the values if there is a mismatch,
> but really I think in every realistic case just noting that there was
> one would be just as helpful as being able to dump the old (incorrect)
> value....
>
> What do you think - is the RBCOMPUTE(node, true) function sufficient
> for such debugging ?
>
I think so, at least i do not see any issues with that. If it returns
"false" then it will indicate that the node was not correctly augmented.

Also, i see in many places across your patches there is below code:

<snip>
RBSTRUCT *child; \
RBTYPE max = RBCOMPUTE(node); \
if (node->RBFIELD.rb_left) { \
child = rb_entry(node->RBFIELD.rb_left, RBSTRUCT, RBFIELD); \
if (child->RBAUGMENTED > max) \
max = child->RBAUGMENTED; \
} \
if (node->RBFIELD.rb_right) { \
child = rb_entry(node->RBFIELD.rb_right, RBSTRUCT, RBFIELD); \
if (child->RBAUGMENTED > max) \
max = child->RBAUGMENTED; \
} \
if (exit && node->RBAUGMENTED == max) \
return true; \
node->RBAUGMENTED = max; \
return false;
<snip>

i think it can be simplified by using max3 macro. For example:

<snip>
get_subtree_max(struct rb_node *node)
{
struct something *foo;

va = rb_entry_safe(node, struct something, rb_node);
return foo ? foo->subtree_max : 0;
}

compute_subtree_max_size(struct vmap_area *va)
{
return max3(va_size(va),
get_subtree_max_size(va->rb_node.rb_left),
get_subtree_max_size(va->rb_node.rb_right));
}
<snip>

What do you think about that?

Thank you.

--
Vlad Rezki

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