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Date: Fri, 11 Jul 2014 14:15:08 -0700
From: Mahesh Bandewar <maheshb@...gle.com>
To: Jay Vosburgh <j.vosburgh@...il.com>,
Veaceslav Falico <vfalico@...hat.com>,
Andy Gospodarek <andy@...yhouse.net>,
David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Mahesh Bandewar <maheshb@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Maciej Zenczykowski <maze@...gle.com>
Subject: Re: [PATCHv2] bonding: Do not try to send packets over dead link in
TLB mode.
In my tests with added instrumentation (similar to __might_sleep()) in
the update_arr function; the calls were never in the automic context
so did not change the GFP flag to GFP_ATOMIC.
On Fri, Jul 11, 2014 at 2:10 PM, Mahesh Bandewar <maheshb@...gle.com> 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 during 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>
> ---
> drivers/net/bonding/bond_alb.c | 44 +++++++++++++++++++++++++++++++++++++-----
> drivers/net/bonding/bond_alb.h | 8 ++++++++
> drivers/net/bonding/bonding.h | 6 ++++++
> 3 files changed, 53 insertions(+), 5 deletions(-)
>
> [v1]
> * Initial patch
> [v2]
> * Removed spinlock protection
> * Removed explicit rcu_read_(un)lock() calls since Xmit fn run in RCU
> * Updated condition during bond-dismantle to check for only arrays' existance.
>
> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
> index 76c0dade233f..7fb2066432b1 100644
> --- a/drivers/net/bonding/bond_alb.c
> +++ b/drivers/net/bonding/bond_alb.c
> @@ -209,6 +209,9 @@ static void tlb_deinitialize(struct bonding *bond)
> bond_info->tx_hashtbl = NULL;
>
> _unlock_tx_hashtbl_bh(bond);
> +
> + if (bond_info->slave_arr)
> + kfree_rcu(bond_info->slave_arr, rcu);
> }
>
> static long long compute_gap(struct slave *slave)
> @@ -1406,9 +1409,35 @@ 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;
> + }
> +
> + old_arr = bond_info->slave_arr;
> + rcu_assign_pointer(bond_info->slave_arr, new_arr);
> + 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 +1458,12 @@ 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;
> + struct tlb_up_slave *slaves;
>
> - bond_for_each_slave_rcu(bond, tx_slave, iter)
> - if (--idx < 0)
> - break;
> + slaves = rcu_dereference(bond_info->slave_arr);
> + if (slaves && slaves->count)
> + tx_slave = slaves->arr[hash_index %
> + slaves->count];
> }
> break;
> }
> @@ -1721,6 +1750,11 @@ 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..aaeac61d03cf 100644
> --- a/drivers/net/bonding/bond_alb.h
> +++ b/drivers/net/bonding/bond_alb.h
> @@ -139,12 +139,20 @@ 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 */
> /* -------- 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 &&
> --
> 2.0.0.526.g5318336
>
--
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