| Message ID | 73f674075ae5279e3d2fa07d61a0a75bc50790f3.1644659879.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | Rejected |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: bridge: Slightly optimize br_stp_change_bridge_id() | expand |
On 12/02/2022 11:58, Christophe JAILLET wrote: > ether_addr_equal_64bits() can easy be used in place of ether_addr_equal() > here. > Padding in the 'net_bridge_port' structure is already there because it is a > huge structure and the required fields are not at the end. > 'oldaddr' is local to the function. So add the required padding > explicitly and simplify its definition. > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> > --- > This patch is more a POC for me. > > I'm unsure that using ether_addr_equal_64bits() is really useful. The > speedup should be mostly un-noticeable. > > To make sure that we have the required padding, we either need to waste > some space or rely on the fact that the address is embedded in a large > enough structure. (which is the case here) > > So, it looks fragile to me and not future-proof. > > Feed-back highly appreciated to see if such patches are welcome and if I > should spend some time on it. > --- This is slow path, more so as you've noted above the change is fragile and someone can easily miss it, I appreciate the comments but for this case I'd prefer to leave the code as-is to keep it obviously correct and avoid future problems. Thanks, Nik > net/bridge/br_private.h | 5 +++++ > net/bridge/br_stp_if.c | 12 +++++++----- > 2 files changed, 12 insertions(+), 5 deletions(-) > > diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h > index 2661dda1a92b..2f78090574c9 100644 > --- a/net/bridge/br_private.h > +++ b/net/bridge/br_private.h > @@ -363,6 +363,11 @@ struct net_bridge_port { > unsigned char config_pending; > port_id port_id; > port_id designated_port; > + /* > + * designated_root and designated_bridge must NOT be at the end of the > + * structure because ether_addr_equal_64bits() requires 2 bytes of > + * padding. > + */ > bridge_id designated_root; > bridge_id designated_bridge; > u32 path_cost; > diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c > index 75204d36d7f9..1bf0aaf29e5e 100644 > --- a/net/bridge/br_stp_if.c > +++ b/net/bridge/br_stp_if.c > @@ -221,9 +221,11 @@ int br_stp_set_enabled(struct net_bridge *br, unsigned long val, > /* called under bridge lock */ > void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr) > { > - /* should be aligned on 2 bytes for ether_addr_equal() */ > - unsigned short oldaddr_aligned[ETH_ALEN >> 1]; > - unsigned char *oldaddr = (unsigned char *)oldaddr_aligned; > + /* > + * should be aligned on 2 bytes and have 2 bytes of padding for > + * ether_addr_equal_64bits() > + */ > + unsigned char oldaddr[ETH_ALEN + 2] __aligned(2); > struct net_bridge_port *p; > int wasroot; > > @@ -236,10 +238,10 @@ void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr) > eth_hw_addr_set(br->dev, addr); > > list_for_each_entry(p, &br->port_list, list) { > - if (ether_addr_equal(p->designated_bridge.addr, oldaddr)) > + if (ether_addr_equal_64bits(p->designated_bridge.addr, oldaddr)) > memcpy(p->designated_bridge.addr, addr, ETH_ALEN); > > - if (ether_addr_equal(p->designated_root.addr, oldaddr)) > + if (ether_addr_equal_64bits(p->designated_root.addr, oldaddr)) > memcpy(p->designated_root.addr, addr, ETH_ALEN); > } >
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index 2661dda1a92b..2f78090574c9 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -363,6 +363,11 @@ struct net_bridge_port { unsigned char config_pending; port_id port_id; port_id designated_port; + /* + * designated_root and designated_bridge must NOT be at the end of the + * structure because ether_addr_equal_64bits() requires 2 bytes of + * padding. + */ bridge_id designated_root; bridge_id designated_bridge; u32 path_cost; diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c index 75204d36d7f9..1bf0aaf29e5e 100644 --- a/net/bridge/br_stp_if.c +++ b/net/bridge/br_stp_if.c @@ -221,9 +221,11 @@ int br_stp_set_enabled(struct net_bridge *br, unsigned long val, /* called under bridge lock */ void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr) { - /* should be aligned on 2 bytes for ether_addr_equal() */ - unsigned short oldaddr_aligned[ETH_ALEN >> 1]; - unsigned char *oldaddr = (unsigned char *)oldaddr_aligned; + /* + * should be aligned on 2 bytes and have 2 bytes of padding for + * ether_addr_equal_64bits() + */ + unsigned char oldaddr[ETH_ALEN + 2] __aligned(2); struct net_bridge_port *p; int wasroot; @@ -236,10 +238,10 @@ void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr) eth_hw_addr_set(br->dev, addr); list_for_each_entry(p, &br->port_list, list) { - if (ether_addr_equal(p->designated_bridge.addr, oldaddr)) + if (ether_addr_equal_64bits(p->designated_bridge.addr, oldaddr)) memcpy(p->designated_bridge.addr, addr, ETH_ALEN); - if (ether_addr_equal(p->designated_root.addr, oldaddr)) + if (ether_addr_equal_64bits(p->designated_root.addr, oldaddr)) memcpy(p->designated_root.addr, addr, ETH_ALEN); }
ether_addr_equal_64bits() can easy be used in place of ether_addr_equal() here. Padding in the 'net_bridge_port' structure is already there because it is a huge structure and the required fields are not at the end. 'oldaddr' is local to the function. So add the required padding explicitly and simplify its definition. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- This patch is more a POC for me. I'm unsure that using ether_addr_equal_64bits() is really useful. The speedup should be mostly un-noticeable. To make sure that we have the required padding, we either need to waste some space or rely on the fact that the address is embedded in a large enough structure. (which is the case here) So, it looks fragile to me and not future-proof. Feed-back highly appreciated to see if such patches are welcome and if I should spend some time on it. --- net/bridge/br_private.h | 5 +++++ net/bridge/br_stp_if.c | 12 +++++++----- 2 files changed, 12 insertions(+), 5 deletions(-)