fib: use __fls() on non null argument

__fls(x) is a bit faster than fls(x), granted we know x is non null.

As Ben Hutchings pointed out, fls(x) = __fls(x) + 1

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index f0cdb30921c0..f84a0e90d675 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1550,7 +1550,8 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp,
                  * state.directly.
                  */
                 if (pref_mismatch) {
-                        int mp = KEYLENGTH - fls(pref_mismatch);
+                        /* fls(x) = __fls(x) + 1 */
+                        int mp = KEYLENGTH - __fls(pref_mismatch) - 1;
 
                         if (tkey_extract_bits(cn->key, mp, cn->pos - mp) != 0)
                                 goto backtrace;