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bpf: map_get_next_key to return first key on NULL

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When iterating through a map, we need to find a key that does not exist
in the map so map_get_next_key will give us the first key of the map.
This often requires a lot of guessing in production systems.

This patch makes map_get_next_key return the first key when the key
pointer in the parameter is NULL.

Signed-off-by: Teng Qin <qinteng@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Teng Qin
2017-04-24 19:00:37 -07:00
committed by David S. Miller
parent 472ecf084a
commit 8fe4592438
5 changed files with 49 additions and 19 deletions
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9
kernel/bpf/hashtab.c
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@@ -540,12 +540,15 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
struct hlist_nulls_head *head;
struct htab_elem *l, *next_l;
u32 hash, key_size;
int i;
int i = 0;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
if (!key)
goto find_first_elem;
hash = htab_map_hash(key, key_size);
head = select_bucket(htab, hash);
@@ -553,10 +556,8 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
/* lookup the key */
l = lookup_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
if (!l) {
i = 0;
if (!l)
goto find_first_elem;
}
/* key was found, get next key in the same bucket */
next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_next_rcu(&l->hash_node)),