Hi Daniel,
Thanks for your feedback! I agree on all points. Two questions below.
On 01/05/2017 05:25 PM, Daniel Borkmann wrote:
> On 12/29/2016 06:28 PM, Daniel Mack wrote:
>> diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
>> new file mode 100644
>> index 0000000..8b6a61d
>> --- /dev/null
>> +++ b/kernel/bpf/lpm_trie.c
[..]
>> +static struct bpf_map *trie_alloc(union bpf_attr *attr)
>> +{
>> + struct lpm_trie *trie;
>> +
>> + /* check sanity of attributes */
>> + if (attr->max_entries == 0 || attr->map_flags ||
>> + attr->key_size < sizeof(struct bpf_lpm_trie_key) + 1 ||
>> + attr->key_size > sizeof(struct bpf_lpm_trie_key) + 256 ||
>> + attr->value_size != sizeof(u64))
>> + return ERR_PTR(-EINVAL);
>
> The correct attr->map_flags test here would need to be ...
>
> attr->map_flags != BPF_F_NO_PREALLOC
>
> ... since in this case we don't have any prealloc pool, and
> should that come one day that test could be relaxed again.
>
>> + trie = kzalloc(sizeof(*trie), GFP_USER | __GFP_NOWARN);
>> + if (!trie)
>> + return NULL;
>> +
>> + /* copy mandatory map attributes */
>> + trie->map.map_type = attr->map_type;
>> + trie->map.key_size = attr->key_size;
>> + trie->map.value_size = attr->value_size;
>> + trie->map.max_entries = attr->max_entries;
>
> You also need to fill in trie->map.pages as that is eventually
> used to charge memory against in bpf_map_charge_memlock(), right
> now that would remain as 0 meaning the map is not accounted for.
Hmm, okay. The nodes are, however, allocated dynamically at runtime in
this case. That means that we have trie->map.pages on each allocation,
right?
>> +static void trie_free(struct bpf_map *map)
>> +{
>> + struct lpm_trie_node __rcu **slot;
>> + struct lpm_trie_node *node;
>> + struct lpm_trie *trie =
>> + container_of(map, struct lpm_trie, map);
>> +
>> + spin_lock(&trie->lock);
>> +
>> + /*
>> + * Always start at the root and walk down to a node that has no
>> + * children. Then free that node, nullify its pointer in the parent,
>> + * then start over.
>> + */
>> +
>> + for (;;) {
>> + slot = &trie->root;
>> +
>> + for (;;) {
>> + node = rcu_dereference_protected(*slot,
>> + lockdep_is_held(&trie->lock));
>> + if (!node)
>> + goto out;
>> +
>> + if (node->child[0]) {
>
> rcu_access_pointer(node->child[0]) (at least to keep sparse happy?)
Done, but sparse does not actually complain here.
Thanks,
Daniel
