From mboxrd@z Thu Jan 1 00:00:00 1970 From: Toshiaki Makita Subject: Re: [PATCH 12/21] bridge: slight optimization of addr compare Date: Mon, 23 Dec 2013 17:33:47 +0900 Message-ID: <1387787627.1797.10.camel@localhost.localdomain> References: <52B7C5D5.2040202@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , "David S. Miller" , bridge@lists.linux-foundation.org, Netdev , "linux-kernel@vger.kernel.org" To: Ding Tianhong Return-path: In-Reply-To: <52B7C5D5.2040202@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Mon, 2013-12-23 at 13:10 +0800, Ding Tianhong wrote: > Use the recently added and possibly more efficient > ether_addr_equal_unaligned to instead of memcmp. > > Cc: Stephen Hemminger > Cc: David Miller > Cc: bridge@lists.linux-foundation.org > Cc: netdev@vger.kernel.org > Signed-off-by: Wang Weidong > Signed-off-by: Ding Tianhong > --- > net/bridge/br_stp_if.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c > index 656a6f3..04217d1 100644 > --- a/net/bridge/br_stp_if.c > +++ b/net/bridge/br_stp_if.c > @@ -229,7 +229,7 @@ bool br_stp_recalculate_bridge_id(struct net_bridge *br) > > list_for_each_entry(p, &br->port_list, list) { > if (addr == br_mac_zero || > - memcmp(p->dev->dev_addr, addr, ETH_ALEN) < 0) > + !ether_addr_equal_unaligned(p->dev->dev_addr, addr) < 0) > addr = p->dev->dev_addr; > > } We cannot do this change. !ether_addr_equal() isn't identical to memcmp(). memcmp() can return negative value but ether_addr_equal() cannot. br_stp_recalculate_bridge_id() is searching the smallest address among its ports. This change breaks it. Thanks, Toshiaki Makita