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Date: Wed, 09 Jul 2014 12:14:54 +0200
From: Nikolay Aleksandrov <nikolay@...hat.com>
To: Mahesh Bandewar <maheshb@...gle.com>,
Jay Vosburgh <fubar@...ibm.com>,
Veaceslav Falico <vfalico@...hat.com>,
Andy Gospodarek <andy@...yhouse.net>,
David Miller <davem@...emloft.net>
CC: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Maciej Zenczykowski <maze@...gle.com>
Subject: Re: [PATCH] bonding: Do not try to send packets over dead link in
TLB mode.
On 07/09/2014 03:09 AM, Mahesh Bandewar wrote:
> In TLB mode if tlb_dynamic_lb is NOT set, slaves from the bond
> group are selected based on the hash distribution. This does not
> exclude dead links which are part of the bond. Also if there is a
> temporary link event which brings down the interface, packets
> hashed on that interface would be dropped too.
>
> This patch fixes these issues and distributes flows across the
> UP links only. Also the array construction of links which are
> capable of sending packets happen in the control path leaving
> only link-selection duing the data-path.
>
> One possible side effect of this is - at a link event; all
> flows will be shuffled to get good distribution. But impact of
> this should be minimum with the assumption that a member or
> members of the bond group are not available is a very temporary
> situation.
>
> Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
> ---
Hi Mahesh,
I think this should be targeted at net-next (and it actually applies there). I
also think you may be able to drop the spinlock as the
bond_alb_handle_link_change() function and its callers are always run under
RTNL, now I'm not 100% sure about this, it would require a more thorough check
but an ASSERT_RTNL at the correct spot could be useful to make sure and convert
anything left, in any case I'm okay as it is now too, this is merely a suggestion.
A few small nitpicks below. I'll give it a spin and if anything pops up will get
back to you.
Thanks for doing this, I like it :-)
> drivers/net/bonding/bond_alb.c | 52 +++++++++++++++++++++++++++++++++++++-----
> drivers/net/bonding/bond_alb.h | 11 +++++++++
> drivers/net/bonding/bonding.h | 6 +++++
> 3 files changed, 63 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
> index 76c0dade233f..1f39d41fde4b 100644
> --- a/drivers/net/bonding/bond_alb.c
> +++ b/drivers/net/bonding/bond_alb.c
> @@ -195,6 +195,9 @@ static int tlb_initialize(struct bonding *bond)
>
> _unlock_tx_hashtbl_bh(bond);
>
> + /* Initialize the TLB array spin-lock */
> + spin_lock_init(&bond_info->slave_arr_lock);
> +
> return 0;
> }
>
> @@ -209,6 +212,9 @@ static void tlb_deinitialize(struct bonding *bond)
> bond_info->tx_hashtbl = NULL;
>
> _unlock_tx_hashtbl_bh(bond);
> +
> + if (bond_is_nondyn_tlb(bond) && bond_info->slave_arr)
> + kfree_rcu(bond_info->slave_arr, rcu);
> }
>
> static long long compute_gap(struct slave *slave)
> @@ -1406,9 +1412,37 @@ out:
> return NETDEV_TX_OK;
> }
>
> +static int bond_tlb_update_slave_arr(struct bonding *bond)
> +{
> + struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
> + struct slave *tx_slave;
> + struct list_head *iter;
> + struct tlb_up_slave *new_arr, *old_arr;
> +
> + new_arr = kzalloc(offsetof(struct tlb_up_slave, arr[bond->slave_cnt]),
> + GFP_KERNEL);
> + if (!new_arr)
> + return -ENOMEM;
> +
> + bond_for_each_slave(bond, tx_slave, iter) {
> + if (bond_slave_can_tx(tx_slave))
> + new_arr->arr[new_arr->count++] = tx_slave;
> + }
> +
> + spin_lock(&bond_info->slave_arr_lock);
> + old_arr = bond_info->slave_arr;
> + rcu_assign_pointer(bond_info->slave_arr, new_arr);
> + spin_unlock(&bond_info->slave_arr_lock);
> + if (old_arr)
> + kfree_rcu(old_arr, rcu);
> +
> + return 0;
> +}
> +
> int bond_tlb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
> {
> struct bonding *bond = netdev_priv(bond_dev);
> + struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
> struct ethhdr *eth_data;
> struct slave *tx_slave = NULL;
> u32 hash_index;
> @@ -1429,12 +1463,13 @@ int bond_tlb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
> hash_index & 0xFF,
> skb->len);
> } else {
> - struct list_head *iter;
> - int idx = hash_index % bond->slave_cnt;
> -
> - bond_for_each_slave_rcu(bond, tx_slave, iter)
> - if (--idx < 0)
> - break;
> + struct tlb_up_slave *slaves;
Please leave a blank line between local variable definition and the code.
> + rcu_read_lock();
All bonding xmit functions already run in rcu, so this is not really necessary.
> + slaves = rcu_dereference(bond_info->slave_arr);
> + if (slaves && slaves->count)
> + tx_slave = slaves->arr[hash_index %
> + slaves->count];
> + rcu_read_unlock();
> }
> break;
> }
> @@ -1721,6 +1756,11 @@ void bond_alb_handle_link_change(struct bonding *bond, struct slave *slave, char
> */
> }
> }
> +
> + if (bond_is_nondyn_tlb(bond)) {
> + if (bond_tlb_update_slave_arr(bond))
> + pr_err("Failed to build slave-array for TLB mode.\n");
> + }
> }
>
> /**
> diff --git a/drivers/net/bonding/bond_alb.h b/drivers/net/bonding/bond_alb.h
> index 5fc76c01636c..731a8e830639 100644
> --- a/drivers/net/bonding/bond_alb.h
> +++ b/drivers/net/bonding/bond_alb.h
> @@ -139,12 +139,23 @@ struct tlb_slave_info {
> */
> };
>
> +struct tlb_up_slave {
> + unsigned int count;
> + struct rcu_head rcu;
> + struct slave *arr[0];
> +};
> +
> struct alb_bond_info {
> struct tlb_client_info *tx_hashtbl; /* Dynamically allocated */
> spinlock_t tx_hashtbl_lock;
> u32 unbalanced_load;
> int tx_rebalance_counter;
> int lp_counter;
> + /* -------- non-dynamic tlb mode only ---------*/
> + struct tlb_up_slave __rcu *slave_arr; /* Up slaves */
> + spinlock_t slave_arr_lock; /* Lock to manage concurrent
> + * writers
> + */
> /* -------- rlb parameters -------- */
> int rlb_enabled;
> struct rlb_client_info *rx_hashtbl; /* Receive hash table */
> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
> index 0b4d9cde0b05..ad9b3dce07d8 100644
> --- a/drivers/net/bonding/bonding.h
> +++ b/drivers/net/bonding/bonding.h
> @@ -265,6 +265,12 @@ static inline bool bond_is_lb(const struct bonding *bond)
> BOND_MODE(bond) == BOND_MODE_ALB;
> }
>
> +static inline bool bond_is_nondyn_tlb(const struct bonding *bond)
> +{
> + return (BOND_MODE(bond) == BOND_MODE_TLB) &&
> + (bond->params.tlb_dynamic_lb == 0);
> +}
> +
> static inline bool bond_mode_uses_arp(int mode)
> {
> return mode != BOND_MODE_8023AD && mode != BOND_MODE_TLB &&
>
--
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