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bpf: Implement map_delete_elem for BPF_MAP_TYPE_LPM_TRIE 

This is a simple non-recursive delete operation.  It prunes paths
of empty nodes in the tree, but it does not try to further compress
the tree as nodes are removed.

Signed-off-by: Craig Gallek <kraig@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Craig Gallek 2017-09-18 15:30:55 -04:00 committed by David S. Miller
parent 173f4c5ebb
commit e454cf5958
1 changed files with 77 additions and 3 deletions
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80
kernel/bpf/lpm_trie.c
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@ -389,10 +389,84 @@ out:
return ret;
}
static int trie_delete_elem(struct bpf_map *map, void *key)
/* Called from syscall or from eBPF program */
static int trie_delete_elem(struct bpf_map *map, void *_key)
{
/* TODO */
return -ENOSYS;
struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
struct bpf_lpm_trie_key *key = _key;
struct lpm_trie_node __rcu **trim;
struct lpm_trie_node *node;
unsigned long irq_flags;
unsigned int next_bit;
size_t matchlen = 0;
int ret = 0;
if (key->prefixlen > trie->max_prefixlen)
return -EINVAL;
raw_spin_lock_irqsave(&trie->lock, irq_flags);
/* Walk the tree looking for an exact key/length match and keeping
* track of where we could begin trimming the tree. The trim-point
* is the sub-tree along the walk consisting of only single-child
* intermediate nodes and ending at a leaf node that we want to
* remove.
*/
trim = &trie->root;
node = rcu_dereference_protected(
trie->root, lockdep_is_held(&trie->lock));
while (node) {
matchlen = longest_prefix_match(trie, node, key);
if (node->prefixlen != matchlen ||
node->prefixlen == key->prefixlen)
break;
next_bit = extract_bit(key->data, node->prefixlen);
/* If we hit a node that has more than one child or is a valid
* prefix itself, do not remove it. Reset the root of the trim
* path to its descendant on our path.
*/
if (!(node->flags & LPM_TREE_NODE_FLAG_IM) ||
(node->child[0] && node->child[1]))
trim = &node->child[next_bit];
node = rcu_dereference_protected(
node->child[next_bit], lockdep_is_held(&trie->lock));
}
if (!node || node->prefixlen != key->prefixlen ||
(node->flags & LPM_TREE_NODE_FLAG_IM)) {
ret = -ENOENT;
goto out;
}
trie->n_entries--;
/* If the node we are removing is not a leaf node, simply mark it
* as intermediate and we are done.
*/
if (rcu_access_pointer(node->child[0]) ||
rcu_access_pointer(node->child[1])) {
node->flags |= LPM_TREE_NODE_FLAG_IM;
goto out;
}
/* trim should now point to the slot holding the start of a path from
* zero or more intermediate nodes to our leaf node for deletion.
*/
while ((node = rcu_dereference_protected(
*trim, lockdep_is_held(&trie->lock)))) {
RCU_INIT_POINTER(*trim, NULL);
trim = rcu_access_pointer(node->child[0]) ?
&node->child[0] :
&node->child[1];
kfree_rcu(node, rcu);
}
out:
raw_spin_unlock_irqrestore(&trie->lock, irq_flags);
return ret;
}
#define LPM_DATA_SIZE_MAX 256