net: dynamically allocate fqdir structures

Following patch will add rcu grace period before fqdir
rhashtable destruction, so we need to dynamically allocate
fqdir structures to not force expensive synchronize_rcu() calls
in netns dismantle path.

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

net/ipv4/inet_fragment.c

@@ -150,6 +150,7 @@ void fqdir_exit(struct fqdir *fqdir)
 	fqdir->high_thresh = 0; /* prevent creation of new frags */
 
 	rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL);
+	kfree(fqdir);
 }
 EXPORT_SYMBOL(fqdir_exit);