Subject: Re: [PATCH net-next 3/3] bonding: fix bond_release_all inconsistencies

From: Jay Vosburgh <[email-masked]>
Date: Mon, 18 Feb 2013 13:56:48 -0800

Nikolay Aleksandrov <[email-masked]> wrote:

>This patch fixes the following inconsistencies in bond_release_all:
>- IFF_BONDING flag is not stripped from slaves
>- MTU is not restored
>- no netdev notifiers are sent
>Instead of trying to keep bond_release and bond_release_all in sync
>I think we can re-use bond_release as the environment for calling it
>is correct (RTNL is held). I have been running tests for the past
>week and they came out successful. The only way for bond_release to fail
>is for the slave to be attached in a different bond or to not be a slave
>but that cannot happen as RTNL is held and no slave manipulations can be
>achieved.

	It might be worthwhile to add an "all" argument to bond_release
that skips some things that don't make sense if all slaves are being
released.  I'm thinking in particular of this block:

	if (oldcurrent == slave) {
		/*
		 * Note that we hold RTNL over this sequence, so there
		 * is no concern that another slave add/remove event
		 * will interfere.
		 */
		write_unlock_bh(&bond->lock);
		read_lock(&bond->lock);
		write_lock_bh(&bond->curr_slave_lock);

		bond_select_active_slave(bond);

		write_unlock_bh(&bond->curr_slave_lock);
		read_unlock(&bond->lock);
		write_lock_bh(&bond->lock);
	}

	as it's written now, for the release all case, the code may go
to the trouble of assigning a new active slave each time one slave is
removed (including various log messages, maybe sending IGMPs, etc).  If
all slaves are being removed, that's pointless.  This could be something
like:

	if (release_all) {
		bond->curr_active_slave = NULL;
	} else if (oldcurrent == slave) {
		[ the current block of stuff ]
	}

	it's safe here to unconditionally set curr_active_slave to NULL
because we hold bond->lock for write.  The lock dance stuff for the
bond_select_active_slave() call is to satisfy its locking requirements.

	-J

>Signed-off-by: Nikolay Aleksandrov <[email-masked]>
>---
> drivers/net/bonding/bond_main.c | 106 ++--------------------------------------
> 1 file changed, 5 insertions(+), 101 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 94c1534..fcfc880 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -2140,113 +2140,17 @@ static int  bond_release_and_destroy(struct net_device *bond_dev,
> /*
>  * This function releases all slaves.
>  */
>-static int bond_release_all(struct net_device *bond_dev)
>+static void bond_release_all(struct net_device *bond_dev)
> {
> 	struct bonding *bond = netdev_priv(bond_dev);
>-	struct slave *slave;
>-	struct net_device *slave_dev;
>-	struct sockaddr addr;
>-
>-	write_lock_bh(&bond->lock);
>-
>-	netif_carrier_off(bond_dev);
>
> 	if (bond->slave_cnt == 0)
>-		goto out;
>-
>-	bond->current_arp_slave = NULL;
>-	bond->primary_slave = NULL;
>-	bond_change_active_slave(bond, NULL);
>-
>-	while ((slave = bond->first_slave) != NULL) {
>-		/* Inform AD package of unbinding of slave
>-		 * before slave is detached from the list.
>-		 */
>-		if (bond->params.mode == BOND_MODE_8023AD)
>-			bond_3ad_unbind_slave(slave);
>-
>-		slave_dev = slave->dev;
>-		bond_detach_slave(bond, slave);
>-
>-		/* now that the slave is detached, unlock and perform
>-		 * all the undo steps that should not be called from
>-		 * within a lock.
>-		 */
>-		write_unlock_bh(&bond->lock);
>-
>-		/* unregister rx_handler early so bond_handle_frame wouldn't
>-		 * be called for this slave anymore.
>-		 */
>-		netdev_rx_handler_unregister(slave_dev);
>-		synchronize_net();
>-
>-		if (bond_is_lb(bond)) {
>-			/* must be called only after the slave
>-			 * has been detached from the list
>-			 */
>-			bond_alb_deinit_slave(bond, slave);
>-		}
>-
>-		bond_destroy_slave_symlinks(bond_dev, slave_dev);
>-		bond_del_vlans_from_slave(bond, slave_dev);
>-
>-		/* If the mode USES_PRIMARY, then we should only remove its
>-		 * promisc and mc settings if it was the curr_active_slave, but that was
>-		 * already taken care of above when we detached the slave
>-		 */
>-		if (!USES_PRIMARY(bond->params.mode)) {
>-			/* unset promiscuity level from slave */
>-			if (bond_dev->flags & IFF_PROMISC)
>-				dev_set_promiscuity(slave_dev, -1);
>-
>-			/* unset allmulti level from slave */
>-			if (bond_dev->flags & IFF_ALLMULTI)
>-				dev_set_allmulti(slave_dev, -1);
>-
>-			/* flush master's mc_list from slave */
>-			netif_addr_lock_bh(bond_dev);
>-			bond_mc_list_flush(bond_dev, slave_dev);
>-			netif_addr_unlock_bh(bond_dev);
>-		}
>-
>-		bond_upper_dev_unlink(bond_dev, slave_dev);
>-
>-		slave_disable_netpoll(slave);
>-
>-		/* close slave before restoring its mac address */
>-		dev_close(slave_dev);
>-
>-		if (!bond->params.fail_over_mac) {
>-			/* restore original ("permanent") mac address*/
>-			memcpy(addr.sa_data, slave->perm_hwaddr, ETH_ALEN);
>-			addr.sa_family = slave_dev->type;
>-			dev_set_mac_address(slave_dev, &addr);
>-		}
>-
>-		kfree(slave);
>-
>-		/* re-acquire the lock before getting the next slave */
>-		write_lock_bh(&bond->lock);
>-	}
>-
>-	eth_hw_addr_random(bond_dev);
>-	bond->dev_addr_from_first = true;
>-
>-	if (bond_vlan_used(bond)) {
>-		pr_warning("%s: Warning: clearing HW address of %s while it still has VLANs.\n",
>-			   bond_dev->name, bond_dev->name);
>-		pr_warning("%s: When re-adding slaves, make sure the bond's HW address matches its VLANs'.\n",
>-			   bond_dev->name);
>-	}
>-
>+		return;
>+	while (bond->first_slave != NULL)
>+		bond_release(bond_dev, bond->first_slave->dev);
> 	pr_info("%s: released all slaves\n", bond_dev->name);
>
>-out:
>-	write_unlock_bh(&bond->lock);
>-
>-	bond_compute_features(bond);
>-
>-	return 0;
>+	return;
> }
>
> /*
>-- 
>1.7.11.7

---
	-Jay Vosburgh, IBM Linux Technology Center, [email-masked]