On Wed, Sep 20, 2017 at 12:51 PM, Daniel Mack <dan...@zonque.org> wrote:
> Hi Craig,
>
> Thanks, this looks much cleaner already :)
>
> On 09/20/2017 06:22 PM, Craig Gallek wrote:
>> diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
>> index 9d58a576b2ae..b5a7d70ec8b5 100644
>> --- a/kernel/bpf/lpm_trie.c
>> +++ b/kernel/bpf/lpm_trie.c
>> @@ -397,7 +397,7 @@ static int trie_delete_elem(struct bpf_map *map, void
>> *_key)
>> struct lpm_trie_node __rcu **trim;
>> struct lpm_trie_node *node;
>> unsigned long irq_flags;
>> - unsigned int next_bit;
>> + unsigned int next_bit = 0;
>
> This default assignment seems wrong, and I guess you only added it to
> squelch a compiler warning?
Yes, this variable is only initialized after the lookup iterations
below (meaning it will never be initialized the the root-removal
case).
> [...]
>
>> + /* If the node has one child, we may be able to collapse the tree
>> + * while removing this node if the node's child is in the same
>> + * 'next bit' slot as this node was in its parent or if the node
>> + * itself is the root.
>> + */
>> + if (trim == &trie->root) {
>> + next_bit = node->child[0] ? 0 : 1;
>> + rcu_assign_pointer(trie->root, node->child[next_bit]);
>> + kfree_rcu(node, rcu);
>
> I don't think you should treat this 'root' case special.
>
> Instead, move the 'next_bit' assignment outside of the condition ...
I'm not quite sure I follow. Are you saying do something like this:
if (trim == &trie->root) {
next_bit = node->child[0] ? 0 : 1;
}
if (rcu_access_pointer(node->child[next_bit])) {
...
This would save a couple lines of code, but I think the as-is
implementation is slightly easier to understand. I don't have a
strong opinion either way, though.
Thanks for the pointers,
Craig
