Message-Id: <6CFF2375-252B-4228-A5D2-1144ABB8FDBF@bamaicloud.com>
Date: Tue, 17 Jun 2025 20:01:07 +0800
From: Tonghao Zhang <tonghao@...aicloud.com>
To: Jay Vosburgh <jv@...sburgh.net>
Cc: netdev@...r.kernel.org,
 "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>,
 Jonathan Corbet <corbet@....net>,
 Andrew Lunn <andrew+netdev@...n.ch>,
 Stanislav Fomichev <sdf@...ichev.me>,
 Hangbin Liu <liuhangbin@...il.com>,
 linux-doc@...r.kernel.org
Subject: Re: [PATCH net-next] bonding: Remove support for use_carrier = 0



> 2025年6月17日 05:28，Jay Vosburgh <jv@...sburgh.net> 写道：
> 
> Remove the ability to disable use_carrier in bonding, and remove
> all code related to the old link state check that utilizes ethtool or
> ioctl to determine the link state of an interface in a bond.
> 
> To avoid acquiring RTNL many times per second, bonding's miimon
> link monitor inspects link state under RCU, but not under RTNL.  However,
> ethtool implementations in drivers may sleep, and therefore the ethtool or
> ioctl strategy is unsuitable for use with calls into driver ethtool
> functions.
> 
> The use_carrier option was introduced in 2003, to provide
> backwards compatibility for network device drivers that did not support
> the then-new netif_carrier_ok/on/off system.  Today, device drivers are
> expected to support netif_carrier_*, and the use_carrier backwards
> compatibility logic is no longer necessary.
> 
> Bonding now always behaves as if use_carrier=1, which relies on
> netif_carrier_ok() to determine the link state of interfaces.  This has
> been the default setting for use_carrier since its introduction.  For
> backwards compatibility, the option itself remains, but may only be set to
> 1, and queries will always return 1.
> 
> Reported-by: syzbot+b8c48ea38ca27d150063@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=b8c48ea38ca27d150063
> Link: https://lore.kernel.org/lkml/000000000000eb54bf061cfd666a@google.com/
> Link: https://lore.kernel.org/netdev/20240718122017.d2e33aaac43a.I10ab9c9ded97163aef4e4de10985cd8f7de60d28@changeid/
> Link: http://lore.kernel.org/netdev/aEt6LvBMwUMxmUyx@mini-arch
> Signed-off-by: Jay Vosburgh <jv@...sburgh.net>
> 
> ---
> Documentation/networking/bonding.rst |  79 +++----------------
> drivers/net/bonding/bond_main.c      | 113 ++-------------------------
> drivers/net/bonding/bond_netlink.c   |  11 +--
> drivers/net/bonding/bond_options.c   |   7 +-
> drivers/net/bonding/bond_sysfs.c     |   6 +-
> include/net/bonding.h                |   1 -
> 6 files changed, 25 insertions(+), 192 deletions(-)
> 
> diff --git a/Documentation/networking/bonding.rst b/Documentation/networking/bonding.rst
> index a4c1291d2561..4ee20f6ab733 100644
> --- a/Documentation/networking/bonding.rst
> +++ b/Documentation/networking/bonding.rst
> @@ -576,10 +576,8 @@ miimon
> This determines how often the link state of each slave is
> inspected for link failures.  A value of zero disables MII
> link monitoring.  A value of 100 is a good starting point.
> - The use_carrier option, below, affects how the link state is
> - determined.  See the High Availability section for additional
> - information.  The default value is 100 if arp_interval is not
> - set.
> +
> + The default value is 100 if arp_interval is not set.
> 
> min_links
> 
> @@ -889,25 +887,14 @@ updelay
> 
> use_carrier
> 
> - Specifies whether or not miimon should use MII or ETHTOOL
> - ioctls vs. netif_carrier_ok() to determine the link
> - status. The MII or ETHTOOL ioctls are less efficient and
> - utilize a deprecated calling sequence within the kernel.  The
> - netif_carrier_ok() relies on the device driver to maintain its
> - state with netif_carrier_on/off; at this writing, most, but
> - not all, device drivers support this facility.
> -
> - If bonding insists that the link is up when it should not be,
> - it may be that your network device driver does not support
> - netif_carrier_on/off.  The default state for netif_carrier is
> - "carrier on," so if a driver does not support netif_carrier,
> - it will appear as if the link is always up.  In this case,
> - setting use_carrier to 0 will cause bonding to revert to the
> - MII / ETHTOOL ioctl method to determine the link state.
> -
> - A value of 1 enables the use of netif_carrier_ok(), a value of
> - 0 will use the deprecated MII / ETHTOOL ioctls.  The default
> - value is 1.
> + Obsolete option that previously selected between MII /
> + ETHTOOL ioctls and netif_carrier_ok() to determine link
> + state.
> +
> + All link state checks are now done with netif_carrier_ok().
> +
> + For backwards compatibility, this option's value may be inspected
> + or set.  The only valid setting is 1.
> 
> xmit_hash_policy
> 
> @@ -2029,22 +2016,8 @@ depending upon the device driver to maintain its carrier state, by
> querying the device's MII registers, or by making an ethtool query to
> the device.
> 
> -If the use_carrier module parameter is 1 (the default value),
> -then the MII monitor will rely on the driver for carrier state
> -information (via the netif_carrier subsystem).  As explained in the
> -use_carrier parameter information, above, if the MII monitor fails to
> -detect carrier loss on the device (e.g., when the cable is physically
> -disconnected), it may be that the driver does not support
> -netif_carrier.
> -
> -If use_carrier is 0, then the MII monitor will first query the
> -device's (via ioctl) MII registers and check the link state.  If that
> -request fails (not just that it returns carrier down), then the MII
> -monitor will make an ethtool ETHTOOL_GLINK request to attempt to obtain
> -the same information.  If both methods fail (i.e., the driver either
> -does not support or had some error in processing both the MII register
> -and ethtool requests), then the MII monitor will assume the link is
> -up.
> +The MII monitor relies on the driver for carrier state information (via
> +the netif_carrier subsystem).
> 
> 8. Potential Sources of Trouble
> ===============================
> @@ -2128,34 +2101,6 @@ This will load tg3 and e1000 modules before loading the bonding one.
> Full documentation on this can be found in the modprobe.d and modprobe
> manual pages.
> 
> -8.3. Painfully Slow Or No Failed Link Detection By Miimon
> ----------------------------------------------------------
> -
> -By default, bonding enables the use_carrier option, which
> -instructs bonding to trust the driver to maintain carrier state.
> -
> -As discussed in the options section, above, some drivers do
> -not support the netif_carrier_on/_off link state tracking system.
> -With use_carrier enabled, bonding will always see these links as up,
> -regardless of their actual state.
> -
> -Additionally, other drivers do support netif_carrier, but do
> -not maintain it in real time, e.g., only polling the link state at
> -some fixed interval.  In this case, miimon will detect failures, but
> -only after some long period of time has expired.  If it appears that
> -miimon is very slow in detecting link failures, try specifying
> -use_carrier=0 to see if that improves the failure detection time.  If
> -it does, then it may be that the driver checks the carrier state at a
> -fixed interval, but does not cache the MII register values (so the
> -use_carrier=0 method of querying the registers directly works).  If
> -use_carrier=0 does not improve the failover, then the driver may cache
> -the registers, or the problem may be elsewhere.
> -
> -Also, remember that miimon only checks for the device's
> -carrier state.  It has no way to determine the state of devices on or
> -beyond other ports of a switch, or if a switch is refusing to pass
> -traffic while still maintaining carrier on.
> -
> 9. SNMP agents
> ===============
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index c4d53e8e7c15..3534561fd932 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -142,8 +142,7 @@ module_param(downdelay, int, 0);
> MODULE_PARM_DESC(downdelay, "Delay before considering link down, "
>    "in milliseconds");
> module_param(use_carrier, int, 0);
> -MODULE_PARM_DESC(use_carrier, "Use netif_carrier_ok (vs MII ioctls) in miimon; "
> -      "0 for off, 1 for on (default)");
> +MODULE_PARM_DESC(use_carrier, "Obsolete, has no effect");
> module_param(mode, charp, 0);
> MODULE_PARM_DESC(mode, "Mode of operation; 0 for balance-rr, "
>       "1 for active-backup, 2 for balance-xor, "
> @@ -828,77 +827,6 @@ const char *bond_slave_link_status(s8 link)
> }
> }
> 
> -/* if <dev> supports MII link status reporting, check its link status.
> - *
> - * We either do MII/ETHTOOL ioctls, or check netif_carrier_ok(),
> - * depending upon the setting of the use_carrier parameter.
> - *
> - * Return either BMSR_LSTATUS, meaning that the link is up (or we
> - * can't tell and just pretend it is), or 0, meaning that the link is
> - * down.
> - *
> - * If reporting is non-zero, instead of faking link up, return -1 if
> - * both ETHTOOL and MII ioctls fail (meaning the device does not
> - * support them).  If use_carrier is set, return whatever it says.
> - * It'd be nice if there was a good way to tell if a driver supports
> - * netif_carrier, but there really isn't.
> - */
> -static int bond_check_dev_link(struct bonding *bond,
> -       struct net_device *slave_dev, int reporting)
> -{
> - const struct net_device_ops *slave_ops = slave_dev->netdev_ops;
> - struct mii_ioctl_data *mii;
> - struct ifreq ifr;
> - int ret;
> -
> - if (!reporting && !netif_running(slave_dev))
> - return 0;
> -
> - if (bond->params.use_carrier)
> - return netif_carrier_ok(slave_dev) ? BMSR_LSTATUS : 0;
> -
> - /* Try to get link status using Ethtool first. */
> - if (slave_dev->ethtool_ops->get_link) {
> - netdev_lock_ops(slave_dev);
> - ret = slave_dev->ethtool_ops->get_link(slave_dev);
> - netdev_unlock_ops(slave_dev);
> -
> - return ret ? BMSR_LSTATUS : 0;
> - }
> -
> - /* Ethtool can't be used, fallback to MII ioctls. */
> - if (slave_ops->ndo_eth_ioctl) {
> - /* TODO: set pointer to correct ioctl on a per team member
> - *       bases to make this more efficient. that is, once
> - *       we determine the correct ioctl, we will always
> - *       call it and not the others for that team
> - *       member.
> - */
> -
> - /* We cannot assume that SIOCGMIIPHY will also read a
> - * register; not all network drivers (e.g., e100)
> - * support that.
> - */
> -
> - /* Yes, the mii is overlaid on the ifreq.ifr_ifru */
> - strscpy_pad(ifr.ifr_name, slave_dev->name, IFNAMSIZ);
> - mii = if_mii(&ifr);
> -
> - if (dev_eth_ioctl(slave_dev, &ifr, SIOCGMIIPHY) == 0) {
> - mii->reg_num = MII_BMSR;
> - if (dev_eth_ioctl(slave_dev, &ifr, SIOCGMIIREG) == 0)
> - return mii->val_out & BMSR_LSTATUS;
> - }
> - }
> -
> - /* If reporting, report that either there's no ndo_eth_ioctl,
> - * or both SIOCGMIIREG and get_link failed (meaning that we
> - * cannot report link status).  If not reporting, pretend
> - * we're ok.
> - */
> - return reporting ? -1 : BMSR_LSTATUS;
> -}
> -
> /*----------------------------- Multicast list ------------------------------*/
> 
> /* Push the promiscuity flag down to appropriate slaves */
> @@ -1949,7 +1877,6 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
> const struct net_device_ops *slave_ops = slave_dev->netdev_ops;
> struct slave *new_slave = NULL, *prev_slave;
> struct sockaddr_storage ss;
> - int link_reporting;
> int res = 0, i;
> 
> if (slave_dev->flags & IFF_MASTER &&
> @@ -1959,12 +1886,6 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
> return -EPERM;
> }
> 
> - if (!bond->params.use_carrier &&
> -    slave_dev->ethtool_ops->get_link == NULL &&
> -    slave_ops->ndo_eth_ioctl == NULL) {
> - slave_warn(bond_dev, slave_dev, "no link monitoring support\n");
> - }
> -
> /* already in-use? */
> if (netdev_is_rx_handler_busy(slave_dev)) {
> SLAVE_NL_ERR(bond_dev, slave_dev, extack,
> @@ -2178,29 +2099,10 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
> 
> new_slave->last_tx = new_slave->last_rx;
> 
> - if (bond->params.miimon && !bond->params.use_carrier) {
> - link_reporting = bond_check_dev_link(bond, slave_dev, 1);
> -
> - if ((link_reporting == -1) && !bond->params.arp_interval) {
> - /* miimon is set but a bonded network driver
> - * does not support ETHTOOL/MII and
> - * arp_interval is not set.  Note: if
> - * use_carrier is enabled, we will never go
> - * here (because netif_carrier is always
> - * supported); thus, we don't need to change
> - * the messages for netif_carrier.
> - */
> - slave_warn(bond_dev, slave_dev, "MII and ETHTOOL support not available for slave, and arp_interval/arp_ip_target module parameters not specified, thus bonding will not detect link failures! see bonding.txt for details\n");
> - } else if (link_reporting == -1) {
> - /* unable get link status using mii/ethtool */
> - slave_warn(bond_dev, slave_dev, "can't get link status from slave; the network driver associated with this interface does not support MII or ETHTOOL link status reporting, thus miimon has no effect on this interface\n");
> - }
> - }
> -
> /* check for initial state */
> new_slave->link = BOND_LINK_NOCHANGE;
> if (bond->params.miimon) {
> - if (bond_check_dev_link(bond, slave_dev, 0) == BMSR_LSTATUS) {
> + if (netif_carrier_ok(slave_dev)) {
> if (bond->params.updelay) {
> bond_set_slave_link_state(new_slave,
>  BOND_LINK_BACK,
> @@ -2742,7 +2644,7 @@ static int bond_miimon_inspect(struct bonding *bond)
> bond_for_each_slave_rcu(bond, slave, iter) {
> bond_propose_link_state(slave, BOND_LINK_NOCHANGE);
> 
> - link_state = bond_check_dev_link(bond, slave->dev, 0);
> + link_state = netif_carrier_ok(slave->dev);
> 
> switch (slave->link) {
> case BOND_LINK_UP:
> @@ -6189,10 +6091,10 @@ static int __init bond_check_params(struct bond_params *params)
> downdelay = 0;
> }
> 
> - if ((use_carrier != 0) && (use_carrier != 1)) {
> - pr_warn("Warning: use_carrier module parameter (%d), not of valid value (0/1), so it was set to 1\n",
> - use_carrier);
> - use_carrier = 1;
> + if (use_carrier != 1) {
> + pr_err("Error: invalid use_carrier parameter (%d)\n",
> +       use_carrier);
> + return -EINVAL;
> }
> 
> if (num_peer_notif < 0 || num_peer_notif > 255) {
> @@ -6439,7 +6341,6 @@ static int __init bond_check_params(struct bond_params *params)
> params->updelay = updelay;
> params->downdelay = downdelay;
> params->peer_notif_delay = 0;
> - params->use_carrier = use_carrier;
> params->lacp_active = 1;
> params->lacp_fast = lacp_fast;
> params->primary[0] = 0;
> diff --git a/drivers/net/bonding/bond_netlink.c b/drivers/net/bonding/bond_netlink.c
> index ac5e402c34bc..98f9bef61474 100644
> --- a/drivers/net/bonding/bond_netlink.c
> +++ b/drivers/net/bonding/bond_netlink.c
> @@ -258,13 +258,8 @@ static int bond_changelink(struct net_device *bond_dev, struct nlattr *tb[],
> return err;
> }
> if (data[IFLA_BOND_USE_CARRIER]) {
> - int use_carrier = nla_get_u8(data[IFLA_BOND_USE_CARRIER]);
> -
> - bond_opt_initval(&newval, use_carrier);
> - err = __bond_opt_set(bond, BOND_OPT_USE_CARRIER, &newval,
> -     data[IFLA_BOND_USE_CARRIER], extack);
> - if (err)
> - return err;
> + if (nla_get_u8(data[IFLA_BOND_USE_CARRIER]) != 1)
> + return -EINVAL;
> }
> if (data[IFLA_BOND_ARP_INTERVAL]) {
> int arp_interval = nla_get_u32(data[IFLA_BOND_ARP_INTERVAL]);
> @@ -676,7 +671,7 @@ static int bond_fill_info(struct sk_buff *skb,
> bond->params.peer_notif_delay * bond->params.miimon))
> goto nla_put_failure;
> 
> - if (nla_put_u8(skb, IFLA_BOND_USE_CARRIER, bond->params.use_carrier))
> + if (nla_put_u8(skb, IFLA_BOND_USE_CARRIER, 1))
> goto nla_put_failure;
> 
> if (nla_put_u32(skb, IFLA_BOND_ARP_INTERVAL, bond->params.arp_interval))
> diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
> index 91893c29b899..98dbee2b6aba 100644
> --- a/drivers/net/bonding/bond_options.c
> +++ b/drivers/net/bonding/bond_options.c
> @@ -185,7 +185,6 @@ static const struct bond_opt_value bond_primary_reselect_tbl[] = {
> };
> 
> static const struct bond_opt_value bond_use_carrier_tbl[] = {
> - { "off", 0,  0},
> { "on",  1,  BOND_VALFLAG_DEFAULT},
> { NULL,  -1, 0}
> };
Your other patch deletes these lines.
> @@ -411,7 +410,7 @@ static const struct bond_option bond_opts[BOND_OPT_LAST] = {
> [BOND_OPT_USE_CARRIER] = {
> .id = BOND_OPT_USE_CARRIER,
> .name = "use_carrier",
> - .desc = "Use netif_carrier_ok (vs MII ioctls) in miimon",
> + .desc = "Obsolete, has no effect”,
Add more information? "Obsolete, option has no effect, netif_carrier_ok used as default"
> 
> .values = bond_use_carrier_tbl,
> .set = bond_option_use_carrier_set
> },
> @@ -1068,10 +1067,6 @@ static int bond_option_peer_notif_delay_set(struct bonding *bond,
> static int bond_option_use_carrier_set(struct bonding *bond,
>       const struct bond_opt_value *newval)
> {
> - netdev_dbg(bond->dev, "Setting use_carrier to %llu\n",
> -   newval->value);
> - bond->params.use_carrier = newval->value;
> -
> return 0;
> }
> 
> diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
> index 1e13bb170515..9a75ad3181ab 100644
> --- a/drivers/net/bonding/bond_sysfs.c
> +++ b/drivers/net/bonding/bond_sysfs.c
> @@ -467,14 +467,12 @@ static ssize_t bonding_show_primary_reselect(struct device *d,
> static DEVICE_ATTR(primary_reselect, 0644,
>   bonding_show_primary_reselect, bonding_sysfs_store_option);
> 
> -/* Show the use_carrier flag. */
> +/* use_carrier is obsolete, but print value for compatibility */
> static ssize_t bonding_show_carrier(struct device *d,
>    struct device_attribute *attr,
>    char *buf)
> {
> - struct bonding *bond = to_bond(d);
> -
> - return sysfs_emit(buf, "%d\n", bond->params.use_carrier);
> + return sysfs_emit(buf, "1\n");
> }
> static DEVICE_ATTR(use_carrier, 0644,
>   bonding_show_carrier, bonding_sysfs_store_option);
> diff --git a/include/net/bonding.h b/include/net/bonding.h
> index 95f67b308c19..6fdf4d1e5256 100644
> --- a/include/net/bonding.h
> +++ b/include/net/bonding.h
> @@ -124,7 +124,6 @@ struct bond_params {
> int arp_interval;
> int arp_validate;
> int arp_all_targets;
> - int use_carrier;
> int fail_over_mac;
> int updelay;
> int downdelay;
> -- 
> 2.25.1
> 
> 
> 

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