bonding: Fix jiffies overflow problems (again)

From: Jiri Bohac <jbohac@suse.cz>

The time_before_eq()/time_after_eq() functions operate on unsigned
long and only work if the difference between the two compared values
is smaller than half the range of unsigned long (31 bits on i386).

Some of the variables (slave->jiffies, dev->trans_start, dev->last_rx)
used by bonding store a copy of jiffies and may not be updated for a
long time. With HZ=1000, time_before_eq()/time_after_eq() will start
giving bad results after ~25 days.

jiffies will never be before slave->jiffies, dev->trans_start,
dev->last_rx by more than possibly a couple ticks caused by preemption
of this code. This allows us to detect/prevent these overflows by
replacing time_before_eq()/time_after_eq() with time_in_range().

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: Jean Delvare <jdelvare@suse.de>
---
 drivers/net/bonding/bond_main.c |   48 +++++++++++++++++++++++++++-------------
 1 file changed, 33 insertions(+), 15 deletions(-)

Le jeudi 02 septembre 2010 à 16:19 +0200, Jean Delvare a écrit :
> From: Jiri Bohac <jbohac@suse.cz>
> 
> The time_before_eq()/time_after_eq() functions operate on unsigned
> long and only work if the difference between the two compared values
> is smaller than half the range of unsigned long (31 bits on i386).
> 
> Some of the variables (slave->jiffies, dev->trans_start, dev->last_rx)
> used by bonding store a copy of jiffies and may not be updated for a
> long time. With HZ=1000, time_before_eq()/time_after_eq() will start
> giving bad results after ~25 days.
> 
> jiffies will never be before slave->jiffies, dev->trans_start,
> dev->last_rx by more than possibly a couple ticks caused by preemption
> of this code. This allows us to detect/prevent these overflows by
> replacing time_before_eq()/time_after_eq() with time_in_range().
> 
> Signed-off-by: Jiri Bohac <jbohac@suse.cz>
> Signed-off-by: Jean Delvare <jdelvare@suse.de>
> ---
>  drivers/net/bonding/bond_main.c |   48 +++++++++++++++++++++++++++-------------
>  1 file changed, 33 insertions(+), 15 deletions(-)
> 
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -2798,8 +2798,12 @@ void bond_loadbalance_arp_mon(struct wor
>  	 */
>  	bond_for_each_slave(bond, slave, i) {
>  		if (slave->link != BOND_LINK_UP) {
> -			if (time_before_eq(jiffies, dev_trans_start(slave->dev) + delta_in_ticks) &&
> -			    time_before_eq(jiffies, slave->dev->last_rx + delta_in_ticks)) {
> +			if (time_in_range(jiffies,
> +				dev_trans_start(slave->dev) - delta_in_ticks,
> +				dev_trans_start(slave->dev) + delta_in_ticks) &&

since dev_trans_start() might be expensive, you probably should cache
its result.


> +			    time_in_range(jiffies,
> +				slave->dev->last_rx - delta_in_ticks,
> +				slave->dev->last_rx + delta_in_ticks)) {
>  
>  				slave->link  = BOND_LINK_UP;
>  				slave->state = BOND_STATE_ACTIVE;
> @@ -2827,8 +2831,12 @@ void bond_loadbalance_arp_mon(struct wor
>  			 * when the source ip is 0, so don't take the link down
>  			 * if we don't know our ip yet
>  			 */
> -			if (time_after_eq(jiffies, dev_trans_start(slave->dev) + 2*delta_in_ticks) ||
> -			    (time_after_eq(jiffies, slave->dev->last_rx + 2*delta_in_ticks))) {
> +			if (!time_in_range(jiffies,
> +				dev_trans_start(slave->dev) - delta_in_ticks,
> +				dev_trans_start(slave->dev) + 2*delta_in_ticks) ||
> +			    (!time_in_range(jiffies,
> +				slave->dev->last_rx - delta_in_ticks,
> +				slave->dev->last_rx + 2*delta_in_ticks))) {
>  
>  				slave->link  = BOND_LINK_DOWN;
>  				slave->state = BOND_STATE_BACKUP;
> @@ -2888,8 +2896,10 @@ static int bond_ab_arp_inspect(struct bo
>  		slave->new_link = BOND_LINK_NOCHANGE;
>  
>  		if (slave->link != BOND_LINK_UP) {
> -			if (time_before_eq(jiffies, slave_last_rx(bond, slave) +
> -					   delta_in_ticks)) {
> +			if (time_in_range(jiffies,
> +				slave_last_rx(bond, slave) - delta_in_ticks,
> +				slave_last_rx(bond, slave) + delta_in_ticks)) {
> +
>  				slave->new_link = BOND_LINK_UP;
>  				commit++;
>  			}
> @@ -2902,8 +2912,9 @@ static int bond_ab_arp_inspect(struct bo
>  		 * active.  This avoids bouncing, as the last receive
>  		 * times need a full ARP monitor cycle to be updated.
>  		 */
> -		if (!time_after_eq(jiffies, slave->jiffies +
> -				   2 * delta_in_ticks))
> +		if (time_in_range(jiffies,
> +				  slave->jiffies - delta_in_ticks,
> +				  slave->jiffies + 2 * delta_in_ticks))
>  			continue;
>  
>  		/*
> @@ -2921,8 +2932,10 @@ static int bond_ab_arp_inspect(struct bo
>  		 */
>  		if (slave->state == BOND_STATE_BACKUP &&
>  		    !bond->current_arp_slave &&
> -		    time_after(jiffies, slave_last_rx(bond, slave) +
> -			       3 * delta_in_ticks)) {
> +		    !time_in_range(jiffies,
> +			slave_last_rx(bond, slave) - delta_in_ticks,
> +			slave_last_rx(bond, slave) + 3 * delta_in_ticks)) {
> +
>  			slave->new_link = BOND_LINK_DOWN;
>  			commit++;
>  		}
> @@ -2934,10 +2947,13 @@ static int bond_ab_arp_inspect(struct bo
>  		 *    the bond has an IP address)
>  		 */
>  		if ((slave->state == BOND_STATE_ACTIVE) &&
> -		    (time_after_eq(jiffies, dev_trans_start(slave->dev) +
> -				    2 * delta_in_ticks) ||
> -		      (time_after_eq(jiffies, slave_last_rx(bond, slave)
> -				     + 2 * delta_in_ticks)))) {
> +		    (!time_in_range(jiffies,
> +			dev_trans_start(slave->dev) - delta_in_ticks,
> +			dev_trans_start(slave->dev) + 2 * delta_in_ticks) ||
> +		     (!time_in_range(jiffies,
> +			slave_last_rx(bond, slave) - delta_in_ticks,
> +			slave_last_rx(bond, slave) + 2 * delta_in_ticks)))) {
> +
>  			slave->new_link = BOND_LINK_DOWN;
>  			commit++;
>  		}
> @@ -2964,7 +2980,9 @@ static void bond_ab_arp_commit(struct bo
>  
>  		case BOND_LINK_UP:
>  			if ((!bond->curr_active_slave &&
> -			     time_before_eq(jiffies,
> +			     time_in_range(jiffies,
> +					    dev_trans_start(slave->dev) -
> +					    delta_in_ticks,
>  					    dev_trans_start(slave->dev) +
>  					    delta_in_ticks)) ||
>  			    bond->curr_active_slave != slave) {
> 


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