[net-next-2.6,v2] bonding: introduce primary_passive option

(updated 2)

In some cases there is not desirable to switch back to primary interface when
it's link recovers and rather stay with currently active one. We need to avoid
packetloss as much as we can in some cases. This is solved by introducing
primary_passive option. Note that enslaved primary slave is set as current
active no matter what.

This patch depends on the following one:
[net-next-2.6] bonding: make ab_arp select active slaves as other modes
http://patchwork.ozlabs.org/patch/32684/

Signed-off-by: Jiri Pirko <jpirko@redhat.com>

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Jiri Pirko wrote:
> (updated 2)
> 
> In some cases there is not desirable to switch back to primary interface when
> it's link recovers and rather stay with currently active one. We need to avoid
> packetloss as much as we can in some cases. This is solved by introducing
> primary_passive option. Note that enslaved primary slave is set as current
> active no matter what.
> 
> This patch depends on the following one:
> [net-next-2.6] bonding: make ab_arp select active slaves as other modes
> http://patchwork.ozlabs.org/patch/32684/
> 
> Signed-off-by: Jiri Pirko <jpirko@redhat.com>
> 
> diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
> index d5181ce..e5f2c31 100644
> --- a/Documentation/networking/bonding.txt
> +++ b/Documentation/networking/bonding.txt
> @@ -614,6 +614,32 @@ primary
>  
>  	The primary option is only valid for active-backup mode.
>  
> +primary_passive
> +
> +	Specifies the behavior of the current active slave when the primary was
> +	down and comes back up.  This option is designed to prevent
> +	flip-flopping between the primary slave and other slaves.  The possible
> +	values and their respective effects are:
> +
> +	disabled or 0 (default)
> +
> +		The primary slave becomes the active slave whenever it comes
> +		back up.
> +
> +	better or 1
> +
> +		The primary slave becomes the active slave when it comes back
> +		up, if the speed and duplex of the primary slave is better
> +		than the speed and duplex of the current active slave.
> +
> +	always or 2
> +
> +		The primary slave becomes the active slave only if the current
> +		active slave fails and the primary slave is up.
> +
> +	When no slave are active, if the primary comes back up, it becomes the
> +	active slave, regardless of the value of primary_return
> +
>  updelay

My feeling is that using primary_passive=disabled/better/always is far less 
clear than primary_return=always/better/failure_only.

The normal (current) behavior is to always return to primay if it is up. You 
want to add the ability to return to it only on failure of the current active 
slave and I suggested to add the ability the return to it if it is "better" than 
the current active slave.

Hence the suggested name for the option and option values.

>  
>  	Specifies the time, in milliseconds, to wait before enabling a
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index a7e731f..193eca4 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -94,6 +94,7 @@ static int downdelay;
>  static int use_carrier	= 1;
>  static char *mode;
>  static char *primary;
> +static char *primary_passive;
>  static char *lacp_rate;
>  static char *ad_select;
>  static char *xmit_hash_policy;
> @@ -126,6 +127,13 @@ MODULE_PARM_DESC(mode, "Mode of operation : 0 for balance-rr, "
>  		       "6 for balance-alb");
>  module_param(primary, charp, 0);
>  MODULE_PARM_DESC(primary, "Primary network device to use");
> +module_param(primary_passive, charp, 0);
> +MODULE_PARM_DESC(primary_passive, "Do not set primary slave active "
> +				  "once it comes up; "
> +				  "0 for disabled (default), "
> +				  "1 for on only if speed of primary is not "
> +				  "better, "
> +				  "2 for always on");

You have a double negative assertion here : a "do not" option whose value is 
"disabled". For clarity, I suggest to have a "do" option whose value is "enabled".

This is probably the reason why I suggested primary_return instead of 
primary_passive. primary_passive means "refuse to return to primary" and when 
disabled, it becomes "don't refuse to return to primary", which should be 
"accept to return to primary" instead :-)

It might be seen as not being that important, but having an option whose name 
and values are easy to understand leads to an easy to use option... :-)

>  module_param(lacp_rate, charp, 0);
>  MODULE_PARM_DESC(lacp_rate, "LACPDU tx rate to request from 802.3ad partner "
>  			    "(slow/fast)");
> @@ -200,6 +208,13 @@ const struct bond_parm_tbl fail_over_mac_tbl[] = {
>  {	NULL,			-1},
>  };
>  
> +const struct bond_parm_tbl pri_passive_tbl[] = {
> +{	"disabled",		BOND_PRI_PASSIVE_DISABLED},
> +{	"better",		BOND_PRI_PASSIVE_BETTER},
> +{	"always",		BOND_PRI_PASSIVE_ALWAYS},
> +{	NULL,			-1},
> +};
> +
>  struct bond_parm_tbl ad_select_tbl[] = {
>  {	"stable",	BOND_AD_STABLE},
>  {	"bandwidth",	BOND_AD_BANDWIDTH},
> @@ -1070,6 +1085,25 @@ out:
>  
>  }
>  
> +static bool bond_should_loose_active(struct bonding *bond)
> +{
> +	struct slave *prim = bond->primary_slave;
> +	struct slave *curr = bond->curr_active_slave;
> +
> +	if (!prim || !curr || curr->link != BOND_LINK_UP)
> +		return true;
> +	if (bond->force_primary) {
> +		bond->force_primary = false;
> +		return true;
> +	}
> +	if (bond->params.primary_passive == 1 &&

You should use the constants you defined in bonding.h and used in pri_passive_tbl :

if (bond->params.primary_passive == BOND_PRI_PASSIVE_BETTER &&

> +	    (prim->speed < curr->speed ||
> +	     (prim->speed == curr->speed && prim->duplex <= curr->duplex)))
> +		return false;
> +	if (bond->params.primary_passive == 2)

You should use the constants you defined in bonding.h and used in pri_passive_tbl :

if (bond->params.primary_passive == BOND_PRI_PASSIVE_ALWAYS)

> +		return false;
> +	return true;
> +}
>  
>  /**
>   * find_best_interface - select the best available slave to be the active one
> @@ -1093,15 +1127,9 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
>  			return NULL; /* still no slave, return NULL */
>  	}
>  
> -	/*
> -	 * first try the primary link; if arping, a link must tx/rx
> -	 * traffic before it can be considered the curr_active_slave.
> -	 * also, we would skip slaves between the curr_active_slave
> -	 * and primary_slave that may be up and able to arp
> -	 */
>  	if ((bond->primary_slave) &&
> -	    (!bond->params.arp_interval) &&
> -	    (IS_UP(bond->primary_slave->dev))) {
> +	    bond->primary_slave->link == BOND_LINK_UP &&
> +	    bond_should_loose_active(bond)) {
>  		new_active = bond->primary_slave;
>  	}
>  
> @@ -1109,15 +1137,14 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
>  	old_active = new_active;
>  
>  	bond_for_each_slave_from(bond, new_active, i, old_active) {
> -		if (IS_UP(new_active->dev)) {
> -			if (new_active->link == BOND_LINK_UP) {
> -				return new_active;
> -			} else if (new_active->link == BOND_LINK_BACK) {
> -				/* link up, but waiting for stabilization */
> -				if (new_active->delay < mintime) {
> -					mintime = new_active->delay;
> -					bestslave = new_active;
> -				}
> +		if (new_active->link == BOND_LINK_UP) {
> +			return new_active;
> +		} else if (new_active->link == BOND_LINK_BACK &&
> +			   IS_UP(new_active->dev)) {
> +			/* link up, but waiting for stabilization */
> +			if (new_active->delay < mintime) {
> +				mintime = new_active->delay;
> +				bestslave = new_active;
>  			}
>  		}
>  	}
> @@ -1683,8 +1710,10 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>  
>  	if (USES_PRIMARY(bond->params.mode) && bond->params.primary[0]) {
>  		/* if there is a primary slave, remember it */
> -		if (strcmp(bond->params.primary, new_slave->dev->name) == 0)
> +		if (strcmp(bond->params.primary, new_slave->dev->name) == 0) {
>  			bond->primary_slave = new_slave;
> +			bond->force_primary = true;
> +		}
>  	}
>  
>  	write_lock_bh(&bond->curr_slave_lock);
> @@ -2929,18 +2958,6 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
>  		}
>  	}
>  
> -	read_lock(&bond->curr_slave_lock);
> -
> -	/*
> -	 * Trigger a commit if the primary option setting has changed.
> -	 */
> -	if (bond->primary_slave &&
> -	    (bond->primary_slave != bond->curr_active_slave) &&
> -	    (bond->primary_slave->link == BOND_LINK_UP))
> -		commit++;
> -
> -	read_unlock(&bond->curr_slave_lock);
> -
>  	return commit;
>  }
>  
> @@ -2961,90 +2978,58 @@ static void bond_ab_arp_commit(struct bonding *bond, int delta_in_ticks)
>  			continue;
>  
>  		case BOND_LINK_UP:
> -			write_lock_bh(&bond->curr_slave_lock);
> -
> -			if (!bond->curr_active_slave &&
> -			    time_before_eq(jiffies, dev_trans_start(slave->dev) +
> -					   delta_in_ticks)) {
> +			if ((!bond->curr_active_slave &&
> +			     time_before_eq(jiffies,
> +					    dev_trans_start(slave->dev) +
> +					    delta_in_ticks)) ||
> +			    bond->curr_active_slave != slave) {
>  				slave->link = BOND_LINK_UP;
> -				bond_change_active_slave(bond, slave);
>  				bond->current_arp_slave = NULL;
>  
>  				pr_info(DRV_NAME
> -				       ": %s: %s is up and now the "
> -				       "active interface\n",
> -				       bond->dev->name, slave->dev->name);
> -
> -			} else if (bond->curr_active_slave != slave) {
> -				/* this slave has just come up but we
> -				 * already have a current slave; this can
> -				 * also happen if bond_enslave adds a new
> -				 * slave that is up while we are searching
> -				 * for a new slave
> -				 */
> -				slave->link = BOND_LINK_UP;
> -				bond_set_slave_inactive_flags(slave);
> -				bond->current_arp_slave = NULL;
> +					": %s: link status definitely "
> +					"up for interface %s.\n",
> +					bond->dev->name, slave->dev->name);
>  
> -				pr_info(DRV_NAME
> -				       ": %s: backup interface %s is now up\n",
> -				       bond->dev->name, slave->dev->name);
> -			}
> +				if (!bond->curr_active_slave ||
> +				    (slave == bond->primary_slave))
> +					goto do_failover;
>  
> -			write_unlock_bh(&bond->curr_slave_lock);
> +			}
>  
> -			break;
> +			continue;
>  
>  		case BOND_LINK_DOWN:
>  			if (slave->link_failure_count < UINT_MAX)
>  				slave->link_failure_count++;
>  
>  			slave->link = BOND_LINK_DOWN;
> +			bond_set_slave_inactive_flags(slave);
>  
> -			if (slave == bond->curr_active_slave) {
> -				pr_info(DRV_NAME
> -				       ": %s: link status down for active "
> -				       "interface %s, disabling it\n",
> -				       bond->dev->name, slave->dev->name);
> -
> -				bond_set_slave_inactive_flags(slave);
> -
> -				write_lock_bh(&bond->curr_slave_lock);
> -
> -				bond_select_active_slave(bond);
> -				if (bond->curr_active_slave)
> -					bond->curr_active_slave->jiffies =
> -						jiffies;
> -
> -				write_unlock_bh(&bond->curr_slave_lock);
> +			pr_info(DRV_NAME
> +				": %s: link status definitely down for "
> +				"interface %s, disabling it\n",
> +				bond->dev->name, slave->dev->name);
>  
> +			if (slave == bond->curr_active_slave) {
>  				bond->current_arp_slave = NULL;
> -
> -			} else if (slave->state == BOND_STATE_BACKUP) {
> -				pr_info(DRV_NAME
> -				       ": %s: backup interface %s is now down\n",
> -				       bond->dev->name, slave->dev->name);
> -
> -				bond_set_slave_inactive_flags(slave);
> +				goto do_failover;
>  			}
> -			break;
> +
> +			continue;
>  
>  		default:
>  			pr_err(DRV_NAME
>  			       ": %s: impossible: new_link %d on slave %s\n",
>  			       bond->dev->name, slave->new_link,
>  			       slave->dev->name);
> +			continue;
>  		}
> -	}
>  
> -	/*
> -	 * No race with changes to primary via sysfs, as we hold rtnl.
> -	 */
> -	if (bond->primary_slave &&
> -	    (bond->primary_slave != bond->curr_active_slave) &&
> -	    (bond->primary_slave->link == BOND_LINK_UP)) {
> +do_failover:
> +		ASSERT_RTNL();
>  		write_lock_bh(&bond->curr_slave_lock);
> -		bond_change_active_slave(bond, bond->primary_slave);
> +		bond_select_active_slave(bond);
>  		write_unlock_bh(&bond->curr_slave_lock);
>  	}
>  
> @@ -4695,7 +4680,7 @@ int bond_parse_parm(const char *buf, const struct bond_parm_tbl *tbl)
>  
>  static int bond_check_params(struct bond_params *params)
>  {
> -	int arp_validate_value, fail_over_mac_value;
> +	int arp_validate_value, fail_over_mac_value, primary_passive_value;
>  
>  	/*
>  	 * Convert string parameters.
> @@ -4994,6 +4979,20 @@ static int bond_check_params(struct bond_params *params)
>  		primary = NULL;
>  	}
>  
> +	if (primary && primary_passive) {
> +		primary_passive_value = bond_parse_parm(primary_passive,
> +							pri_passive_tbl);
> +		if (primary_passive_value == -1) {
> +			pr_err(DRV_NAME
> +			       ": Error: Invalid primary_passive \"%s\"\n",
> +			       primary_passive ==
> +					NULL ? "NULL" : primary_passive);
> +			return -EINVAL;
> +		}
> +	} else {
> +		primary_passive_value = BOND_PRI_PASSIVE_DISABLED;
> +	}
> +
>  	if (fail_over_mac) {
>  		fail_over_mac_value = bond_parse_parm(fail_over_mac,
>  						      fail_over_mac_tbl);
> @@ -5025,6 +5024,7 @@ static int bond_check_params(struct bond_params *params)
>  	params->use_carrier = use_carrier;
>  	params->lacp_fast = lacp_fast;
>  	params->primary[0] = 0;
> +	params->primary_passive = primary_passive_value;
>  	params->fail_over_mac = fail_over_mac_value;
>  
>  	if (primary) {
> diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
> index 6044e12..84ce933 100644
> --- a/drivers/net/bonding/bond_sysfs.c
> +++ b/drivers/net/bonding/bond_sysfs.c
> @@ -1212,6 +1212,59 @@ static DEVICE_ATTR(primary, S_IRUGO | S_IWUSR,
>  		   bonding_show_primary, bonding_store_primary);
>  
>  /*
> + * Show and set the primary_passive flag.
> + */
> +static ssize_t bonding_show_primary_passive(struct device *d,
> +					    struct device_attribute *attr,
> +					    char *buf)
> +{
> +	struct bonding *bond = to_bond(d);
> +
> +	return sprintf(buf, "%s %d\n",
> +		       pri_passive_tbl[bond->params.primary_passive].modename,
> +		       bond->params.primary_passive);
> +}
> +
> +static ssize_t bonding_store_primary_passive(struct device *d,
> +					     struct device_attribute *attr,
> +					     const char *buf, size_t count)
> +{
> +	int new_value, ret = count;
> +	struct bonding *bond = to_bond(d);
> +
> +	if (!rtnl_trylock())
> +		return restart_syscall();
> +
> +	new_value = bond_parse_parm(buf, pri_passive_tbl);
> +	if (new_value < 0)  {
> +		pr_err(DRV_NAME
> +		       ": %s: Ignoring invalid primary_passive value %.*s.\n",
> +		       bond->dev->name,
> +		       (int) strlen(buf) - 1, buf);
> +		ret = -EINVAL;
> +		goto out;
> +	} else {
> +		bond->params.primary_passive = new_value;
> +		pr_info(DRV_NAME ": %s: setting primary_passive to %s (%d).\n",
> +		       bond->dev->name, pri_passive_tbl[new_value].modename,
> +		       new_value);
> +		if (new_value == 0 || new_value == 1) {
> +			bond->force_primary = true;
> +			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);
> +		}
> +	}
> +out:
> +	rtnl_unlock();
> +	return ret;
> +}
> +static DEVICE_ATTR(primary_passive, S_IRUGO | S_IWUSR,
> +		   bonding_show_primary_passive, bonding_store_primary_passive);
> +
> +/*
>   * Show and set the use_carrier flag.
>   */
>  static ssize_t bonding_show_carrier(struct device *d,
> @@ -1500,6 +1553,7 @@ static struct attribute *per_bond_attrs[] = {
>  	&dev_attr_num_unsol_na.attr,
>  	&dev_attr_miimon.attr,
>  	&dev_attr_primary.attr,
> +	&dev_attr_primary_passive.attr,
>  	&dev_attr_use_carrier.attr,
>  	&dev_attr_active_slave.attr,
>  	&dev_attr_mii_status.attr,
> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
> index 6824771..9a9e0c7 100644
> --- a/drivers/net/bonding/bonding.h
> +++ b/drivers/net/bonding/bonding.h
> @@ -131,6 +131,7 @@ struct bond_params {
>  	int lacp_fast;
>  	int ad_select;
>  	char primary[IFNAMSIZ];
> +	int primary_passive;
>  	__be32 arp_targets[BOND_MAX_ARP_TARGETS];
>  };
>  
> @@ -190,6 +191,7 @@ struct bonding {
>  	struct   slave *curr_active_slave;
>  	struct   slave *current_arp_slave;
>  	struct   slave *primary_slave;
> +	bool     force_primary;
>  	s32      slave_cnt; /* never change this value outside the attach/detach wrappers */
>  	rwlock_t lock;
>  	rwlock_t curr_slave_lock;
> @@ -258,6 +260,10 @@ static inline bool bond_is_lb(const struct bonding *bond)
>  		|| bond->params.mode == BOND_MODE_ALB;
>  }
>  
> +#define BOND_PRI_PASSIVE_DISABLED	0
> +#define BOND_PRI_PASSIVE_BETTER		1
> +#define BOND_PRI_PASSIVE_ALWAYS		2
> +
>  #define BOND_FOM_NONE			0
>  #define BOND_FOM_ACTIVE			1
>  #define BOND_FOM_FOLLOW			2
> @@ -348,6 +354,7 @@ extern const struct bond_parm_tbl bond_mode_tbl[];
>  extern const struct bond_parm_tbl xmit_hashtype_tbl[];
>  extern const struct bond_parm_tbl arp_validate_tbl[];
>  extern const struct bond_parm_tbl fail_over_mac_tbl[];
> +extern const struct bond_parm_tbl pri_passive_tbl[];
>  extern struct bond_parm_tbl ad_select_tbl[];
>  
>  #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
> 

	Nicolas.
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Nicolas de Pesloüan <nicolas.2p.debian@free.fr> wrote:

>Jiri Pirko wrote:
>> (updated 2)
>>
>> In some cases there is not desirable to switch back to primary interface when
>> it's link recovers and rather stay with currently active one. We need to avoid
>> packetloss as much as we can in some cases. This is solved by introducing
>> primary_passive option. Note that enslaved primary slave is set as current
>> active no matter what.
>>
>> This patch depends on the following one:
>> [net-next-2.6] bonding: make ab_arp select active slaves as other modes
>> http://patchwork.ozlabs.org/patch/32684/
>>
>> Signed-off-by: Jiri Pirko <jpirko@redhat.com>
>>
>> diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
>> index d5181ce..e5f2c31 100644
>> --- a/Documentation/networking/bonding.txt
>> +++ b/Documentation/networking/bonding.txt
>> @@ -614,6 +614,32 @@ primary
>>   	The primary option is only valid for active-backup mode.
>>  +primary_passive
>> +
>> +	Specifies the behavior of the current active slave when the primary was
>> +	down and comes back up.  This option is designed to prevent
>> +	flip-flopping between the primary slave and other slaves.  The possible
>> +	values and their respective effects are:
>> +
>> +	disabled or 0 (default)
>> +
>> +		The primary slave becomes the active slave whenever it comes
>> +		back up.
>> +
>> +	better or 1
>> +
>> +		The primary slave becomes the active slave when it comes back
>> +		up, if the speed and duplex of the primary slave is better
>> +		than the speed and duplex of the current active slave.
>> +
>> +	always or 2
>> +
>> +		The primary slave becomes the active slave only if the current
>> +		active slave fails and the primary slave is up.
>> +
>> +	When no slave are active, if the primary comes back up, it becomes the
>> +	active slave, regardless of the value of primary_return
>> +
>>  updelay
>
>My feeling is that using primary_passive=disabled/better/always is far
>less clear than primary_return=always/better/failure_only.
>
>The normal (current) behavior is to always return to primay if it is
>up. You want to add the ability to return to it only on failure of the
>current active slave and I suggested to add the ability the return to it
>if it is "better" than the current active slave.

	Since this has changed from a real option to a "modify behavior
of another option" option, I'd call it something along the lines of
"primary_reselect" with the "always / better / failure" set of choices.

	Also, if "better" isn't implemented, leave it out entirely
(don't define the label or option stuff).  In the future, then, it can
be added in a complete patch, rather than splitting it across two
patches.

>Hence the suggested name for the option and option values.
>
>>   	Specifies the time, in milliseconds, to wait before enabling a
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index a7e731f..193eca4 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -94,6 +94,7 @@ static int downdelay;
>>  static int use_carrier	= 1;
>>  static char *mode;
>>  static char *primary;
>> +static char *primary_passive;
>>  static char *lacp_rate;
>>  static char *ad_select;
>>  static char *xmit_hash_policy;
>> @@ -126,6 +127,13 @@ MODULE_PARM_DESC(mode, "Mode of operation : 0 for balance-rr, "
>>  		       "6 for balance-alb");
>>  module_param(primary, charp, 0);
>>  MODULE_PARM_DESC(primary, "Primary network device to use");
>> +module_param(primary_passive, charp, 0);
>> +MODULE_PARM_DESC(primary_passive, "Do not set primary slave active "
>> +				  "once it comes up; "
>> +				  "0 for disabled (default), "
>> +				  "1 for on only if speed of primary is not "
>> +				  "better, "
>> +				  "2 for always on");
>
>You have a double negative assertion here : a "do not" option whose value
>is "disabled". For clarity, I suggest to have a "do" option whose value is
>"enabled".
>
>This is probably the reason why I suggested primary_return instead of
>primary_passive. primary_passive means "refuse to return to primary" and
>when disabled, it becomes "don't refuse to return to primary", which
>should be "accept to return to primary" instead :-)
>
>It might be seen as not being that important, but having an option whose
>name and values are easy to understand leads to an easy to use
>option... :-)
>
>>  module_param(lacp_rate, charp, 0);
>>  MODULE_PARM_DESC(lacp_rate, "LACPDU tx rate to request from 802.3ad partner "
>>  			    "(slow/fast)");
>> @@ -200,6 +208,13 @@ const struct bond_parm_tbl fail_over_mac_tbl[] = {
>>  {	NULL,			-1},
>>  };
>>  +const struct bond_parm_tbl pri_passive_tbl[] = {
>> +{	"disabled",		BOND_PRI_PASSIVE_DISABLED},
>> +{	"better",		BOND_PRI_PASSIVE_BETTER},
>> +{	"always",		BOND_PRI_PASSIVE_ALWAYS},
>> +{	NULL,			-1},
>> +};
>> +
>>  struct bond_parm_tbl ad_select_tbl[] = {
>>  {	"stable",	BOND_AD_STABLE},
>>  {	"bandwidth",	BOND_AD_BANDWIDTH},
>> @@ -1070,6 +1085,25 @@ out:
>>   }
>>  +static bool bond_should_loose_active(struct bonding *bond)

	I'm not sure what this function name means (beyond the
misspelling of "lose"); it's really "bond_should_change_active" as a
question, correct?

>> +{
>> +	struct slave *prim = bond->primary_slave;
>> +	struct slave *curr = bond->curr_active_slave;
>> +
>> +	if (!prim || !curr || curr->link != BOND_LINK_UP)
>> +		return true;
>> +	if (bond->force_primary) {
>> +		bond->force_primary = false;
>> +		return true;
>> +	}
>> +	if (bond->params.primary_passive == 1 &&
>
>You should use the constants you defined in bonding.h and used in pri_passive_tbl :
>
>if (bond->params.primary_passive == BOND_PRI_PASSIVE_BETTER &&
>
>> +	    (prim->speed < curr->speed ||
>> +	     (prim->speed == curr->speed && prim->duplex <= curr->duplex)))
>> +		return false;
>> +	if (bond->params.primary_passive == 2)

	Ah, ok, passive really is implemented; I just hunted for the
BETTER label.  So, yes, use the defined labels.

>You should use the constants you defined in bonding.h and used in pri_passive_tbl :
>
>if (bond->params.primary_passive == BOND_PRI_PASSIVE_ALWAYS)
>
>> +		return false;
>> +	return true;
>> +}
>>   /**
>>   * find_best_interface - select the best available slave to be the active one
>> @@ -1093,15 +1127,9 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
>>  			return NULL; /* still no slave, return NULL */
>>  	}
>>  -	/*
>> -	 * first try the primary link; if arping, a link must tx/rx
>> -	 * traffic before it can be considered the curr_active_slave.
>> -	 * also, we would skip slaves between the curr_active_slave
>> -	 * and primary_slave that may be up and able to arp
>> -	 */
>>  	if ((bond->primary_slave) &&
>> -	    (!bond->params.arp_interval) &&
>> -	    (IS_UP(bond->primary_slave->dev))) {
>> +	    bond->primary_slave->link == BOND_LINK_UP &&
>> +	    bond_should_loose_active(bond)) {
>>  		new_active = bond->primary_slave;
>>  	}
>>  @@ -1109,15 +1137,14 @@ static struct slave
>> *bond_find_best_slave(struct bonding *bond)
>>  	old_active = new_active;
>>   	bond_for_each_slave_from(bond, new_active, i, old_active) {
>> -		if (IS_UP(new_active->dev)) {
>> -			if (new_active->link == BOND_LINK_UP) {
>> -				return new_active;
>> -			} else if (new_active->link == BOND_LINK_BACK) {
>> -				/* link up, but waiting for stabilization */
>> -				if (new_active->delay < mintime) {
>> -					mintime = new_active->delay;
>> -					bestslave = new_active;
>> -				}
>> +		if (new_active->link == BOND_LINK_UP) {
>> +			return new_active;
>> +		} else if (new_active->link == BOND_LINK_BACK &&
>> +			   IS_UP(new_active->dev)) {
>> +			/* link up, but waiting for stabilization */
>> +			if (new_active->delay < mintime) {
>> +				mintime = new_active->delay;
>> +				bestslave = new_active;
>>  			}
>>  		}
>>  	}
>> @@ -1683,8 +1710,10 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>>   	if (USES_PRIMARY(bond->params.mode) && bond->params.primary[0]) {
>>  		/* if there is a primary slave, remember it */
>> -		if (strcmp(bond->params.primary, new_slave->dev->name) == 0)
>> +		if (strcmp(bond->params.primary, new_slave->dev->name) == 0) {
>>  			bond->primary_slave = new_slave;
>> +			bond->force_primary = true;
>> +		}
>>  	}
>>   	write_lock_bh(&bond->curr_slave_lock);
>> @@ -2929,18 +2958,6 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
>>  		}
>>  	}
>>  -	read_lock(&bond->curr_slave_lock);
>> -
>> -	/*
>> -	 * Trigger a commit if the primary option setting has changed.
>> -	 */
>> -	if (bond->primary_slave &&
>> -	    (bond->primary_slave != bond->curr_active_slave) &&
>> -	    (bond->primary_slave->link == BOND_LINK_UP))
>> -		commit++;
>> -
>> -	read_unlock(&bond->curr_slave_lock);
>> -
>>  	return commit;
>>  }
>>  @@ -2961,90 +2978,58 @@ static void bond_ab_arp_commit(struct bonding
>> *bond, int delta_in_ticks)
>>  			continue;
>>   		case BOND_LINK_UP:
>> -			write_lock_bh(&bond->curr_slave_lock);
>> -
>> -			if (!bond->curr_active_slave &&
>> -			    time_before_eq(jiffies, dev_trans_start(slave->dev) +
>> -					   delta_in_ticks)) {
>> +			if ((!bond->curr_active_slave &&
>> +			     time_before_eq(jiffies,
>> +					    dev_trans_start(slave->dev) +
>> +					    delta_in_ticks)) ||
>> +			    bond->curr_active_slave != slave) {
>>  				slave->link = BOND_LINK_UP;
>> -				bond_change_active_slave(bond, slave);
>>  				bond->current_arp_slave = NULL;
>>   				pr_info(DRV_NAME
>> -				       ": %s: %s is up and now the "
>> -				       "active interface\n",
>> -				       bond->dev->name, slave->dev->name);
>> -
>> -			} else if (bond->curr_active_slave != slave) {
>> -				/* this slave has just come up but we
>> -				 * already have a current slave; this can
>> -				 * also happen if bond_enslave adds a new
>> -				 * slave that is up while we are searching
>> -				 * for a new slave
>> -				 */
>> -				slave->link = BOND_LINK_UP;
>> -				bond_set_slave_inactive_flags(slave);
>> -				bond->current_arp_slave = NULL;
>> +					": %s: link status definitely "
>> +					"up for interface %s.\n",
>> +					bond->dev->name, slave->dev->name);
>>  -				pr_info(DRV_NAME
>> -				       ": %s: backup interface %s is now up\n",
>> -				       bond->dev->name, slave->dev->name);
>> -			}
>> +				if (!bond->curr_active_slave ||
>> +				    (slave == bond->primary_slave))
>> +					goto do_failover;
>>  -			write_unlock_bh(&bond->curr_slave_lock);
>> +			}
>>  -			break;
>> +			continue;
>>   		case BOND_LINK_DOWN:
>>  			if (slave->link_failure_count < UINT_MAX)
>>  				slave->link_failure_count++;
>>   			slave->link = BOND_LINK_DOWN;
>> +			bond_set_slave_inactive_flags(slave);
>>  -			if (slave == bond->curr_active_slave) {
>> -				pr_info(DRV_NAME
>> -				       ": %s: link status down for active "
>> -				       "interface %s, disabling it\n",
>> -				       bond->dev->name, slave->dev->name);
>> -
>> -				bond_set_slave_inactive_flags(slave);
>> -
>> -				write_lock_bh(&bond->curr_slave_lock);
>> -
>> -				bond_select_active_slave(bond);
>> -				if (bond->curr_active_slave)
>> -					bond->curr_active_slave->jiffies =
>> -						jiffies;
>> -
>> -				write_unlock_bh(&bond->curr_slave_lock);
>> +			pr_info(DRV_NAME
>> +				": %s: link status definitely down for "
>> +				"interface %s, disabling it\n",
>> +				bond->dev->name, slave->dev->name);
>>  +			if (slave == bond->curr_active_slave) {
>>  				bond->current_arp_slave = NULL;
>> -
>> -			} else if (slave->state == BOND_STATE_BACKUP) {
>> -				pr_info(DRV_NAME
>> -				       ": %s: backup interface %s is now down\n",
>> -				       bond->dev->name, slave->dev->name);
>> -
>> -				bond_set_slave_inactive_flags(slave);
>> +				goto do_failover;
>>  			}
>> -			break;
>> +
>> +			continue;
>>   		default:
>>  			pr_err(DRV_NAME
>>  			       ": %s: impossible: new_link %d on slave %s\n",
>>  			       bond->dev->name, slave->new_link,
>>  			       slave->dev->name);
>> +			continue;
>>  		}
>> -	}
>>  -	/*
>> -	 * No race with changes to primary via sysfs, as we hold rtnl.
>> -	 */
>> -	if (bond->primary_slave &&
>> -	    (bond->primary_slave != bond->curr_active_slave) &&
>> -	    (bond->primary_slave->link == BOND_LINK_UP)) {
>> +do_failover:
>> +		ASSERT_RTNL();
>>  		write_lock_bh(&bond->curr_slave_lock);
>> -		bond_change_active_slave(bond, bond->primary_slave);
>> +		bond_select_active_slave(bond);
>>  		write_unlock_bh(&bond->curr_slave_lock);
>>  	}
>>  @@ -4695,7 +4680,7 @@ int bond_parse_parm(const char *buf, const struct
>> bond_parm_tbl *tbl)
>>   static int bond_check_params(struct bond_params *params)
>>  {
>> -	int arp_validate_value, fail_over_mac_value;
>> +	int arp_validate_value, fail_over_mac_value, primary_passive_value;
>>   	/*
>>  	 * Convert string parameters.
>> @@ -4994,6 +4979,20 @@ static int bond_check_params(struct bond_params *params)
>>  		primary = NULL;
>>  	}
>>  +	if (primary && primary_passive) {
>> +		primary_passive_value = bond_parse_parm(primary_passive,
>> +							pri_passive_tbl);
>> +		if (primary_passive_value == -1) {
>> +			pr_err(DRV_NAME
>> +			       ": Error: Invalid primary_passive \"%s\"\n",
>> +			       primary_passive ==
>> +					NULL ? "NULL" : primary_passive);
>> +			return -EINVAL;
>> +		}
>> +	} else {
>> +		primary_passive_value = BOND_PRI_PASSIVE_DISABLED;
>> +	}
>> +
>>  	if (fail_over_mac) {
>>  		fail_over_mac_value = bond_parse_parm(fail_over_mac,
>>  						      fail_over_mac_tbl);
>> @@ -5025,6 +5024,7 @@ static int bond_check_params(struct bond_params *params)
>>  	params->use_carrier = use_carrier;
>>  	params->lacp_fast = lacp_fast;
>>  	params->primary[0] = 0;
>> +	params->primary_passive = primary_passive_value;
>>  	params->fail_over_mac = fail_over_mac_value;
>>   	if (primary) {
>> diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
>> index 6044e12..84ce933 100644
>> --- a/drivers/net/bonding/bond_sysfs.c
>> +++ b/drivers/net/bonding/bond_sysfs.c
>> @@ -1212,6 +1212,59 @@ static DEVICE_ATTR(primary, S_IRUGO | S_IWUSR,
>>  		   bonding_show_primary, bonding_store_primary);
>>   /*
>> + * Show and set the primary_passive flag.
>> + */
>> +static ssize_t bonding_show_primary_passive(struct device *d,
>> +					    struct device_attribute *attr,
>> +					    char *buf)
>> +{
>> +	struct bonding *bond = to_bond(d);
>> +
>> +	return sprintf(buf, "%s %d\n",
>> +		       pri_passive_tbl[bond->params.primary_passive].modename,
>> +		       bond->params.primary_passive);
>> +}
>> +
>> +static ssize_t bonding_store_primary_passive(struct device *d,
>> +					     struct device_attribute *attr,
>> +					     const char *buf, size_t count)
>> +{
>> +	int new_value, ret = count;
>> +	struct bonding *bond = to_bond(d);
>> +
>> +	if (!rtnl_trylock())
>> +		return restart_syscall();
>> +
>> +	new_value = bond_parse_parm(buf, pri_passive_tbl);
>> +	if (new_value < 0)  {
>> +		pr_err(DRV_NAME
>> +		       ": %s: Ignoring invalid primary_passive value %.*s.\n",
>> +		       bond->dev->name,
>> +		       (int) strlen(buf) - 1, buf);
>> +		ret = -EINVAL;
>> +		goto out;
>> +	} else {
>> +		bond->params.primary_passive = new_value;
>> +		pr_info(DRV_NAME ": %s: setting primary_passive to %s (%d).\n",
>> +		       bond->dev->name, pri_passive_tbl[new_value].modename,
>> +		       new_value);
>> +		if (new_value == 0 || new_value == 1) {

	Magic numbers again, but this test shouldn't be necessary.  The
new_value is known to be valid if bond_parse_parm didn't return failure.

>> +			bond->force_primary = true;
>> +			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);
>> +		}
>> +	}
>> +out:
>> +	rtnl_unlock();
>> +	return ret;
>> +}
>> +static DEVICE_ATTR(primary_passive, S_IRUGO | S_IWUSR,
>> +		   bonding_show_primary_passive, bonding_store_primary_passive);
>> +
>> +/*
>>   * Show and set the use_carrier flag.
>>   */
>>  static ssize_t bonding_show_carrier(struct device *d,
>> @@ -1500,6 +1553,7 @@ static struct attribute *per_bond_attrs[] = {
>>  	&dev_attr_num_unsol_na.attr,
>>  	&dev_attr_miimon.attr,
>>  	&dev_attr_primary.attr,
>> +	&dev_attr_primary_passive.attr,
>>  	&dev_attr_use_carrier.attr,
>>  	&dev_attr_active_slave.attr,
>>  	&dev_attr_mii_status.attr,
>> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
>> index 6824771..9a9e0c7 100644
>> --- a/drivers/net/bonding/bonding.h
>> +++ b/drivers/net/bonding/bonding.h
>> @@ -131,6 +131,7 @@ struct bond_params {
>>  	int lacp_fast;
>>  	int ad_select;
>>  	char primary[IFNAMSIZ];
>> +	int primary_passive;
>>  	__be32 arp_targets[BOND_MAX_ARP_TARGETS];
>>  };
>>  @@ -190,6 +191,7 @@ struct bonding {
>>  	struct   slave *curr_active_slave;
>>  	struct   slave *current_arp_slave;
>>  	struct   slave *primary_slave;
>> +	bool     force_primary;
>>  	s32      slave_cnt; /* never change this value outside the attach/detach wrappers */
>>  	rwlock_t lock;
>>  	rwlock_t curr_slave_lock;
>> @@ -258,6 +260,10 @@ static inline bool bond_is_lb(const struct bonding *bond)
>>  		|| bond->params.mode == BOND_MODE_ALB;
>>  }
>>  +#define BOND_PRI_PASSIVE_DISABLED	0
>> +#define BOND_PRI_PASSIVE_BETTER		1
>> +#define BOND_PRI_PASSIVE_ALWAYS		2
>> +
>>  #define BOND_FOM_NONE			0
>>  #define BOND_FOM_ACTIVE			1
>>  #define BOND_FOM_FOLLOW			2
>> @@ -348,6 +354,7 @@ extern const struct bond_parm_tbl bond_mode_tbl[];
>>  extern const struct bond_parm_tbl xmit_hashtype_tbl[];
>>  extern const struct bond_parm_tbl arp_validate_tbl[];
>>  extern const struct bond_parm_tbl fail_over_mac_tbl[];
>> +extern const struct bond_parm_tbl pri_passive_tbl[];
>>  extern struct bond_parm_tbl ad_select_tbl[];
>>   #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
>>
>
>	Nicolas.

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com
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Jay Vosburgh wrote:
> Nicolas de Pesloüan <nicolas.2p.debian@free.fr> wrote:
> 
>> Jiri Pirko wrote:
>>> (updated 2)
>>>
>>> In some cases there is not desirable to switch back to primary interface when
>>> it's link recovers and rather stay with currently active one. We need to avoid
>>> packetloss as much as we can in some cases. This is solved by introducing
>>> primary_passive option. Note that enslaved primary slave is set as current
>>> active no matter what.
>>>
>>> This patch depends on the following one:
>>> [net-next-2.6] bonding: make ab_arp select active slaves as other modes
>>> http://patchwork.ozlabs.org/patch/32684/
>>>
>>> Signed-off-by: Jiri Pirko <jpirko@redhat.com>
>>>
>>> diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
>>> index d5181ce..e5f2c31 100644
>>> --- a/Documentation/networking/bonding.txt
>>> +++ b/Documentation/networking/bonding.txt
>>> @@ -614,6 +614,32 @@ primary
>>>   	The primary option is only valid for active-backup mode.
>>>  +primary_passive
>>> +
>>> +	Specifies the behavior of the current active slave when the primary was
>>> +	down and comes back up.  This option is designed to prevent
>>> +	flip-flopping between the primary slave and other slaves.  The possible
>>> +	values and their respective effects are:
>>> +
>>> +	disabled or 0 (default)
>>> +
>>> +		The primary slave becomes the active slave whenever it comes
>>> +		back up.
>>> +
>>> +	better or 1
>>> +
>>> +		The primary slave becomes the active slave when it comes back
>>> +		up, if the speed and duplex of the primary slave is better
>>> +		than the speed and duplex of the current active slave.
>>> +
>>> +	always or 2
>>> +
>>> +		The primary slave becomes the active slave only if the current
>>> +		active slave fails and the primary slave is up.
>>> +
>>> +	When no slave are active, if the primary comes back up, it becomes the
>>> +	active slave, regardless of the value of primary_return
>>> +
>>>  updelay
>> My feeling is that using primary_passive=disabled/better/always is far
>> less clear than primary_return=always/better/failure_only.
>>
>> The normal (current) behavior is to always return to primay if it is
>> up. You want to add the ability to return to it only on failure of the
>> current active slave and I suggested to add the ability the return to it
>> if it is "better" than the current active slave.
> 
> 	Since this has changed from a real option to a "modify behavior
> of another option" option, I'd call it something along the lines of
> "primary_reselect" with the "always / better / failure" set of choices.

primary_reselect with always/better/failure sounds perfect for me.

> 	Also, if "better" isn't implemented, leave it out entirely
> (don't define the label or option stuff).  In the future, then, it can
> be added in a complete patch, rather than splitting it across two
> patches.
> 
>> Hence the suggested name for the option and option values.
>>
>>>   	Specifies the time, in milliseconds, to wait before enabling a
>>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>>> index a7e731f..193eca4 100644
>>> --- a/drivers/net/bonding/bond_main.c
>>> +++ b/drivers/net/bonding/bond_main.c
>>> @@ -94,6 +94,7 @@ static int downdelay;
>>>  static int use_carrier	= 1;
>>>  static char *mode;
>>>  static char *primary;
>>> +static char *primary_passive;
>>>  static char *lacp_rate;
>>>  static char *ad_select;
>>>  static char *xmit_hash_policy;
>>> @@ -126,6 +127,13 @@ MODULE_PARM_DESC(mode, "Mode of operation : 0 for balance-rr, "
>>>  		       "6 for balance-alb");
>>>  module_param(primary, charp, 0);
>>>  MODULE_PARM_DESC(primary, "Primary network device to use");
>>> +module_param(primary_passive, charp, 0);
>>> +MODULE_PARM_DESC(primary_passive, "Do not set primary slave active "
>>> +				  "once it comes up; "
>>> +				  "0 for disabled (default), "
>>> +				  "1 for on only if speed of primary is not "
>>> +				  "better, "
>>> +				  "2 for always on");
>> You have a double negative assertion here : a "do not" option whose value
>> is "disabled". For clarity, I suggest to have a "do" option whose value is
>> "enabled".
>>
>> This is probably the reason why I suggested primary_return instead of
>> primary_passive. primary_passive means "refuse to return to primary" and
>> when disabled, it becomes "don't refuse to return to primary", which
>> should be "accept to return to primary" instead :-)
>>
>> It might be seen as not being that important, but having an option whose
>> name and values are easy to understand leads to an easy to use
>> option... :-)
>>
>>>  module_param(lacp_rate, charp, 0);
>>>  MODULE_PARM_DESC(lacp_rate, "LACPDU tx rate to request from 802.3ad partner "
>>>  			    "(slow/fast)");
>>> @@ -200,6 +208,13 @@ const struct bond_parm_tbl fail_over_mac_tbl[] = {
>>>  {	NULL,			-1},
>>>  };
>>>  +const struct bond_parm_tbl pri_passive_tbl[] = {
>>> +{	"disabled",		BOND_PRI_PASSIVE_DISABLED},
>>> +{	"better",		BOND_PRI_PASSIVE_BETTER},
>>> +{	"always",		BOND_PRI_PASSIVE_ALWAYS},
>>> +{	NULL,			-1},
>>> +};
>>> +
>>>  struct bond_parm_tbl ad_select_tbl[] = {
>>>  {	"stable",	BOND_AD_STABLE},
>>>  {	"bandwidth",	BOND_AD_BANDWIDTH},
>>> @@ -1070,6 +1085,25 @@ out:
>>>   }
>>>  +static bool bond_should_loose_active(struct bonding *bond)
> 
> 	I'm not sure what this function name means (beyond the
> misspelling of "lose"); it's really "bond_should_change_active" as a
> question, correct?
> 
>>> +{
>>> +	struct slave *prim = bond->primary_slave;
>>> +	struct slave *curr = bond->curr_active_slave;
>>> +
>>> +	if (!prim || !curr || curr->link != BOND_LINK_UP)
>>> +		return true;
>>> +	if (bond->force_primary) {
>>> +		bond->force_primary = false;
>>> +		return true;
>>> +	}
>>> +	if (bond->params.primary_passive == 1 &&
>> You should use the constants you defined in bonding.h and used in pri_passive_tbl :
>>
>> if (bond->params.primary_passive == BOND_PRI_PASSIVE_BETTER &&
>>
>>> +	    (prim->speed < curr->speed ||
>>> +	     (prim->speed == curr->speed && prim->duplex <= curr->duplex)))
>>> +		return false;
>>> +	if (bond->params.primary_passive == 2)
> 
> 	Ah, ok, passive really is implemented; I just hunted for the
> BETTER label.  So, yes, use the defined labels.
> 
>> You should use the constants you defined in bonding.h and used in pri_passive_tbl :
>>
>> if (bond->params.primary_passive == BOND_PRI_PASSIVE_ALWAYS)
>>
>>> +		return false;
>>> +	return true;
>>> +}
>>>   /**
>>>   * find_best_interface - select the best available slave to be the active one
>>> @@ -1093,15 +1127,9 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
>>>  			return NULL; /* still no slave, return NULL */
>>>  	}
>>>  -	/*
>>> -	 * first try the primary link; if arping, a link must tx/rx
>>> -	 * traffic before it can be considered the curr_active_slave.
>>> -	 * also, we would skip slaves between the curr_active_slave
>>> -	 * and primary_slave that may be up and able to arp
>>> -	 */
>>>  	if ((bond->primary_slave) &&
>>> -	    (!bond->params.arp_interval) &&
>>> -	    (IS_UP(bond->primary_slave->dev))) {
>>> +	    bond->primary_slave->link == BOND_LINK_UP &&
>>> +	    bond_should_loose_active(bond)) {
>>>  		new_active = bond->primary_slave;
>>>  	}
>>>  @@ -1109,15 +1137,14 @@ static struct slave
>>> *bond_find_best_slave(struct bonding *bond)
>>>  	old_active = new_active;
>>>   	bond_for_each_slave_from(bond, new_active, i, old_active) {
>>> -		if (IS_UP(new_active->dev)) {
>>> -			if (new_active->link == BOND_LINK_UP) {
>>> -				return new_active;
>>> -			} else if (new_active->link == BOND_LINK_BACK) {
>>> -				/* link up, but waiting for stabilization */
>>> -				if (new_active->delay < mintime) {
>>> -					mintime = new_active->delay;
>>> -					bestslave = new_active;
>>> -				}
>>> +		if (new_active->link == BOND_LINK_UP) {
>>> +			return new_active;
>>> +		} else if (new_active->link == BOND_LINK_BACK &&
>>> +			   IS_UP(new_active->dev)) {
>>> +			/* link up, but waiting for stabilization */
>>> +			if (new_active->delay < mintime) {
>>> +				mintime = new_active->delay;
>>> +				bestslave = new_active;
>>>  			}
>>>  		}
>>>  	}
>>> @@ -1683,8 +1710,10 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>>>   	if (USES_PRIMARY(bond->params.mode) && bond->params.primary[0]) {
>>>  		/* if there is a primary slave, remember it */
>>> -		if (strcmp(bond->params.primary, new_slave->dev->name) == 0)
>>> +		if (strcmp(bond->params.primary, new_slave->dev->name) == 0) {
>>>  			bond->primary_slave = new_slave;
>>> +			bond->force_primary = true;
>>> +		}
>>>  	}
>>>   	write_lock_bh(&bond->curr_slave_lock);
>>> @@ -2929,18 +2958,6 @@ static int bond_ab_arp_inspect(struct bonding *bond, int delta_in_ticks)
>>>  		}
>>>  	}
>>>  -	read_lock(&bond->curr_slave_lock);
>>> -
>>> -	/*
>>> -	 * Trigger a commit if the primary option setting has changed.
>>> -	 */
>>> -	if (bond->primary_slave &&
>>> -	    (bond->primary_slave != bond->curr_active_slave) &&
>>> -	    (bond->primary_slave->link == BOND_LINK_UP))
>>> -		commit++;
>>> -
>>> -	read_unlock(&bond->curr_slave_lock);
>>> -
>>>  	return commit;
>>>  }
>>>  @@ -2961,90 +2978,58 @@ static void bond_ab_arp_commit(struct bonding
>>> *bond, int delta_in_ticks)
>>>  			continue;
>>>   		case BOND_LINK_UP:
>>> -			write_lock_bh(&bond->curr_slave_lock);
>>> -
>>> -			if (!bond->curr_active_slave &&
>>> -			    time_before_eq(jiffies, dev_trans_start(slave->dev) +
>>> -					   delta_in_ticks)) {
>>> +			if ((!bond->curr_active_slave &&
>>> +			     time_before_eq(jiffies,
>>> +					    dev_trans_start(slave->dev) +
>>> +					    delta_in_ticks)) ||
>>> +			    bond->curr_active_slave != slave) {
>>>  				slave->link = BOND_LINK_UP;
>>> -				bond_change_active_slave(bond, slave);
>>>  				bond->current_arp_slave = NULL;
>>>   				pr_info(DRV_NAME
>>> -				       ": %s: %s is up and now the "
>>> -				       "active interface\n",
>>> -				       bond->dev->name, slave->dev->name);
>>> -
>>> -			} else if (bond->curr_active_slave != slave) {
>>> -				/* this slave has just come up but we
>>> -				 * already have a current slave; this can
>>> -				 * also happen if bond_enslave adds a new
>>> -				 * slave that is up while we are searching
>>> -				 * for a new slave
>>> -				 */
>>> -				slave->link = BOND_LINK_UP;
>>> -				bond_set_slave_inactive_flags(slave);
>>> -				bond->current_arp_slave = NULL;
>>> +					": %s: link status definitely "
>>> +					"up for interface %s.\n",
>>> +					bond->dev->name, slave->dev->name);
>>>  -				pr_info(DRV_NAME
>>> -				       ": %s: backup interface %s is now up\n",
>>> -				       bond->dev->name, slave->dev->name);
>>> -			}
>>> +				if (!bond->curr_active_slave ||
>>> +				    (slave == bond->primary_slave))
>>> +					goto do_failover;
>>>  -			write_unlock_bh(&bond->curr_slave_lock);
>>> +			}
>>>  -			break;
>>> +			continue;
>>>   		case BOND_LINK_DOWN:
>>>  			if (slave->link_failure_count < UINT_MAX)
>>>  				slave->link_failure_count++;
>>>   			slave->link = BOND_LINK_DOWN;
>>> +			bond_set_slave_inactive_flags(slave);
>>>  -			if (slave == bond->curr_active_slave) {
>>> -				pr_info(DRV_NAME
>>> -				       ": %s: link status down for active "
>>> -				       "interface %s, disabling it\n",
>>> -				       bond->dev->name, slave->dev->name);
>>> -
>>> -				bond_set_slave_inactive_flags(slave);
>>> -
>>> -				write_lock_bh(&bond->curr_slave_lock);
>>> -
>>> -				bond_select_active_slave(bond);
>>> -				if (bond->curr_active_slave)
>>> -					bond->curr_active_slave->jiffies =
>>> -						jiffies;
>>> -
>>> -				write_unlock_bh(&bond->curr_slave_lock);
>>> +			pr_info(DRV_NAME
>>> +				": %s: link status definitely down for "
>>> +				"interface %s, disabling it\n",
>>> +				bond->dev->name, slave->dev->name);
>>>  +			if (slave == bond->curr_active_slave) {
>>>  				bond->current_arp_slave = NULL;
>>> -
>>> -			} else if (slave->state == BOND_STATE_BACKUP) {
>>> -				pr_info(DRV_NAME
>>> -				       ": %s: backup interface %s is now down\n",
>>> -				       bond->dev->name, slave->dev->name);
>>> -
>>> -				bond_set_slave_inactive_flags(slave);
>>> +				goto do_failover;
>>>  			}
>>> -			break;
>>> +
>>> +			continue;
>>>   		default:
>>>  			pr_err(DRV_NAME
>>>  			       ": %s: impossible: new_link %d on slave %s\n",
>>>  			       bond->dev->name, slave->new_link,
>>>  			       slave->dev->name);
>>> +			continue;
>>>  		}
>>> -	}
>>>  -	/*
>>> -	 * No race with changes to primary via sysfs, as we hold rtnl.
>>> -	 */
>>> -	if (bond->primary_slave &&
>>> -	    (bond->primary_slave != bond->curr_active_slave) &&
>>> -	    (bond->primary_slave->link == BOND_LINK_UP)) {
>>> +do_failover:
>>> +		ASSERT_RTNL();
>>>  		write_lock_bh(&bond->curr_slave_lock);
>>> -		bond_change_active_slave(bond, bond->primary_slave);
>>> +		bond_select_active_slave(bond);
>>>  		write_unlock_bh(&bond->curr_slave_lock);
>>>  	}
>>>  @@ -4695,7 +4680,7 @@ int bond_parse_parm(const char *buf, const struct
>>> bond_parm_tbl *tbl)
>>>   static int bond_check_params(struct bond_params *params)
>>>  {
>>> -	int arp_validate_value, fail_over_mac_value;
>>> +	int arp_validate_value, fail_over_mac_value, primary_passive_value;
>>>   	/*
>>>  	 * Convert string parameters.
>>> @@ -4994,6 +4979,20 @@ static int bond_check_params(struct bond_params *params)
>>>  		primary = NULL;
>>>  	}
>>>  +	if (primary && primary_passive) {
>>> +		primary_passive_value = bond_parse_parm(primary_passive,
>>> +							pri_passive_tbl);
>>> +		if (primary_passive_value == -1) {
>>> +			pr_err(DRV_NAME
>>> +			       ": Error: Invalid primary_passive \"%s\"\n",
>>> +			       primary_passive ==
>>> +					NULL ? "NULL" : primary_passive);
>>> +			return -EINVAL;
>>> +		}
>>> +	} else {
>>> +		primary_passive_value = BOND_PRI_PASSIVE_DISABLED;
>>> +	}
>>> +
>>>  	if (fail_over_mac) {
>>>  		fail_over_mac_value = bond_parse_parm(fail_over_mac,
>>>  						      fail_over_mac_tbl);
>>> @@ -5025,6 +5024,7 @@ static int bond_check_params(struct bond_params *params)
>>>  	params->use_carrier = use_carrier;
>>>  	params->lacp_fast = lacp_fast;
>>>  	params->primary[0] = 0;
>>> +	params->primary_passive = primary_passive_value;
>>>  	params->fail_over_mac = fail_over_mac_value;
>>>   	if (primary) {
>>> diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
>>> index 6044e12..84ce933 100644
>>> --- a/drivers/net/bonding/bond_sysfs.c
>>> +++ b/drivers/net/bonding/bond_sysfs.c
>>> @@ -1212,6 +1212,59 @@ static DEVICE_ATTR(primary, S_IRUGO | S_IWUSR,
>>>  		   bonding_show_primary, bonding_store_primary);
>>>   /*
>>> + * Show and set the primary_passive flag.
>>> + */
>>> +static ssize_t bonding_show_primary_passive(struct device *d,
>>> +					    struct device_attribute *attr,
>>> +					    char *buf)
>>> +{
>>> +	struct bonding *bond = to_bond(d);
>>> +
>>> +	return sprintf(buf, "%s %d\n",
>>> +		       pri_passive_tbl[bond->params.primary_passive].modename,
>>> +		       bond->params.primary_passive);
>>> +}
>>> +
>>> +static ssize_t bonding_store_primary_passive(struct device *d,
>>> +					     struct device_attribute *attr,
>>> +					     const char *buf, size_t count)
>>> +{
>>> +	int new_value, ret = count;
>>> +	struct bonding *bond = to_bond(d);
>>> +
>>> +	if (!rtnl_trylock())
>>> +		return restart_syscall();
>>> +
>>> +	new_value = bond_parse_parm(buf, pri_passive_tbl);
>>> +	if (new_value < 0)  {
>>> +		pr_err(DRV_NAME
>>> +		       ": %s: Ignoring invalid primary_passive value %.*s.\n",
>>> +		       bond->dev->name,
>>> +		       (int) strlen(buf) - 1, buf);
>>> +		ret = -EINVAL;
>>> +		goto out;
>>> +	} else {
>>> +		bond->params.primary_passive = new_value;
>>> +		pr_info(DRV_NAME ": %s: setting primary_passive to %s (%d).\n",
>>> +		       bond->dev->name, pri_passive_tbl[new_value].modename,
>>> +		       new_value);
>>> +		if (new_value == 0 || new_value == 1) {
> 
> 	Magic numbers again, but this test shouldn't be necessary.  The
> new_value is known to be valid if bond_parse_parm didn't return failure.
> 

The test is necessary, because it purpose is not to ensure that the given value 
is good, but to decide whether to trigger a possible active slave change.

/*
  * Only trigger a possible active slave change if new_value is
  * ALWAYS or BETTER. If new value is FAILURE, then only a later
  * failure of the active slave should trigger an active slave change.
  */

if (new_value == BOND_PRI_RESELECT_BETTER ||
	new_value == BOND_PRI_RESELECT_ALWAYS) {
...
}

>>> +			bond->force_primary = true;
>>> +			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);
>>> +		}
>>> +	}
>>> +out:
>>> +	rtnl_unlock();
>>> +	return ret;
>>> +}
>>> +static DEVICE_ATTR(primary_passive, S_IRUGO | S_IWUSR,
>>> +		   bonding_show_primary_passive, bonding_store_primary_passive);
>>> +
>>> +/*
>>>   * Show and set the use_carrier flag.
>>>   */
>>>  static ssize_t bonding_show_carrier(struct device *d,
>>> @@ -1500,6 +1553,7 @@ static struct attribute *per_bond_attrs[] = {
>>>  	&dev_attr_num_unsol_na.attr,
>>>  	&dev_attr_miimon.attr,
>>>  	&dev_attr_primary.attr,
>>> +	&dev_attr_primary_passive.attr,
>>>  	&dev_attr_use_carrier.attr,
>>>  	&dev_attr_active_slave.attr,
>>>  	&dev_attr_mii_status.attr,
>>> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
>>> index 6824771..9a9e0c7 100644
>>> --- a/drivers/net/bonding/bonding.h
>>> +++ b/drivers/net/bonding/bonding.h
>>> @@ -131,6 +131,7 @@ struct bond_params {
>>>  	int lacp_fast;
>>>  	int ad_select;
>>>  	char primary[IFNAMSIZ];
>>> +	int primary_passive;
>>>  	__be32 arp_targets[BOND_MAX_ARP_TARGETS];
>>>  };
>>>  @@ -190,6 +191,7 @@ struct bonding {
>>>  	struct   slave *curr_active_slave;
>>>  	struct   slave *current_arp_slave;
>>>  	struct   slave *primary_slave;
>>> +	bool     force_primary;
>>>  	s32      slave_cnt; /* never change this value outside the attach/detach wrappers */
>>>  	rwlock_t lock;
>>>  	rwlock_t curr_slave_lock;
>>> @@ -258,6 +260,10 @@ static inline bool bond_is_lb(const struct bonding *bond)
>>>  		|| bond->params.mode == BOND_MODE_ALB;
>>>  }
>>>  +#define BOND_PRI_PASSIVE_DISABLED	0
>>> +#define BOND_PRI_PASSIVE_BETTER		1
>>> +#define BOND_PRI_PASSIVE_ALWAYS		2
>>> +
>>>  #define BOND_FOM_NONE			0
>>>  #define BOND_FOM_ACTIVE			1
>>>  #define BOND_FOM_FOLLOW			2
>>> @@ -348,6 +354,7 @@ extern const struct bond_parm_tbl bond_mode_tbl[];
>>>  extern const struct bond_parm_tbl xmit_hashtype_tbl[];
>>>  extern const struct bond_parm_tbl arp_validate_tbl[];
>>>  extern const struct bond_parm_tbl fail_over_mac_tbl[];
>>> +extern const struct bond_parm_tbl pri_passive_tbl[];
>>>  extern struct bond_parm_tbl ad_select_tbl[];
>>>   #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
> 
> 	-J
> 
> ---
> 	-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com
> 

	Nicolas.
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