[PATCH net-next V7 07/14] devlink: Add parent dev to devlink API
From: Tariq Toukan <tariqt@nvidia.com>
Date: 2026-01-28 11:28:25
Also in:
linux-doc, linux-rdma, lkml
Subsystem:
devlink, networking [general], the rest, yaml netlink (ynl) · Maintainers:
Jiri Pirko, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Donald Hunter
From: Cosmin Ratiu <redacted> Upcoming changes to the rate commands need the parent devlink specified. This change adds a nested 'parent-dev' attribute to the API and helpers to obtain and put a reference to the parent devlink instance in info->user_ptr[1]. To avoid deadlocks, the parent devlink is unlocked before obtaining the main devlink instance that is the target of the request. A reference to the parent is kept until the end of the request to avoid it suddenly disappearing. This means that this reference is of limited use without additional protection. Signed-off-by: Cosmin Ratiu <redacted> Reviewed-by: Carolina Jubran <redacted> Reviewed-by: Jiri Pirko <redacted> Signed-off-by: Tariq Toukan <tariqt@nvidia.com> --- Documentation/netlink/specs/devlink.yaml | 12 ++++++ include/uapi/linux/devlink.h | 2 + net/devlink/devl_internal.h | 2 + net/devlink/netlink.c | 51 +++++++++++++++++++++--- 4 files changed, 62 insertions(+), 5 deletions(-)
diff --git a/Documentation/netlink/specs/devlink.yaml b/Documentation/netlink/specs/devlink.yaml
index 837112da6738..a8fd0a815c0d 100644
--- a/Documentation/netlink/specs/devlink.yaml
+++ b/Documentation/netlink/specs/devlink.yaml@@ -867,6 +867,10 @@ attribute-sets: type: flag doc: Request restoring parameter to its default value. value: 183 + + - name: parent-dev + type: nest + nested-attributes: dl-parent-dev - name: dl-dev-stats subset-of: devlink
@@ -1289,6 +1293,14 @@ attribute-sets: Specifies the bandwidth share assigned to the Traffic Class. The bandwidth for the traffic class is determined in proportion to the sum of the shares of all configured classes. + - + name: dl-parent-dev + subset-of: devlink + attributes: + - + name: bus-name + - + name: dev-name operations: enum-model: directional
diff --git a/include/uapi/linux/devlink.h b/include/uapi/linux/devlink.h
index e7d6b6d13470..94b8a4437bac 100644
--- a/include/uapi/linux/devlink.h
+++ b/include/uapi/linux/devlink.h@@ -642,6 +642,8 @@ enum devlink_attr { DEVLINK_ATTR_PARAM_VALUE_DEFAULT, /* dynamic */ DEVLINK_ATTR_PARAM_RESET_DEFAULT, /* flag */ + DEVLINK_ATTR_PARENT_DEV, /* nested */ + /* Add new attributes above here, update the spec in * Documentation/netlink/specs/devlink.yaml and re-generate * net/devlink/netlink_gen.c.
diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
index 8374c9cab6ce..3ca4cc8517cd 100644
--- a/net/devlink/devl_internal.h
+++ b/net/devlink/devl_internal.h@@ -162,6 +162,8 @@ typedef int devlink_nl_dump_one_func_t(struct sk_buff *msg, struct devlink * devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs, bool dev_lock); +struct devlink * +devlink_get_parent_from_attrs_lock(struct net *net, struct nlattr **attrs); int devlink_nl_dumpit(struct sk_buff *msg, struct netlink_callback *cb, devlink_nl_dump_one_func_t *dump_one);
diff --git a/net/devlink/netlink.c b/net/devlink/netlink.c
index 593605c1b1ef..72897b19c372 100644
--- a/net/devlink/netlink.c
+++ b/net/devlink/netlink.c@@ -12,6 +12,7 @@ #define DEVLINK_NL_FLAG_NEED_PORT BIT(0) #define DEVLINK_NL_FLAG_NEED_DEVLINK_OR_PORT BIT(1) #define DEVLINK_NL_FLAG_NEED_DEV_LOCK BIT(2) +#define DEVLINK_NL_FLAG_OPTIONAL_PARENT_DEV BIT(3) static const struct genl_multicast_group devlink_nl_mcgrps[] = { [DEVLINK_MCGRP_CONFIG] = { .name = DEVLINK_GENL_MCGRP_CONFIG_NAME },
@@ -206,19 +207,51 @@ devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs, return ERR_PTR(-ENODEV); } +struct devlink * +devlink_get_parent_from_attrs_lock(struct net *net, struct nlattr **attrs) +{ + struct nlattr *tb[DEVLINK_ATTR_DEV_NAME + 1]; + int err; + + if (!attrs[DEVLINK_ATTR_PARENT_DEV]) + return ERR_PTR(-EINVAL); + + err = nla_parse_nested(tb, DEVLINK_ATTR_DEV_NAME, + attrs[DEVLINK_ATTR_PARENT_DEV], + NULL, NULL); + if (err) + return ERR_PTR(err); + + return devlink_get_from_attrs_lock(net, tb, false); +} + static int __devlink_nl_pre_doit(struct sk_buff *skb, struct genl_info *info, u8 flags) { + bool parent_dev = flags & DEVLINK_NL_FLAG_OPTIONAL_PARENT_DEV; bool dev_lock = flags & DEVLINK_NL_FLAG_NEED_DEV_LOCK; + struct devlink *devlink, *parent_devlink = NULL; + struct net *net = genl_info_net(info); + struct nlattr **attrs = info->attrs; struct devlink_port *devlink_port; - struct devlink *devlink; int err; - devlink = devlink_get_from_attrs_lock(genl_info_net(info), info->attrs, - dev_lock); - if (IS_ERR(devlink)) - return PTR_ERR(devlink); + if (parent_dev && attrs[DEVLINK_ATTR_PARENT_DEV]) { + parent_devlink = devlink_get_parent_from_attrs_lock(net, attrs); + if (IS_ERR(parent_devlink)) + return PTR_ERR(parent_devlink); + info->user_ptr[1] = parent_devlink; + /* Drop the parent devlink lock but don't release the reference. + * This will keep it alive until the end of the request. + */ + devl_unlock(parent_devlink); + } + devlink = devlink_get_from_attrs_lock(net, attrs, dev_lock); + if (IS_ERR(devlink)) { + err = PTR_ERR(devlink); + goto parent_put; + } info->user_ptr[0] = devlink; if (flags & DEVLINK_NL_FLAG_NEED_PORT) { devlink_port = devlink_port_get_from_info(devlink, info);
@@ -237,6 +270,9 @@ static int __devlink_nl_pre_doit(struct sk_buff *skb, struct genl_info *info, unlock: devl_dev_unlock(devlink, dev_lock); devlink_put(devlink); +parent_put: + if (parent_dev && parent_devlink) + devlink_put(parent_devlink); return err; }
@@ -274,6 +310,11 @@ static void __devlink_nl_post_doit(struct sk_buff *skb, struct genl_info *info, devlink = info->user_ptr[0]; devl_dev_unlock(devlink, dev_lock); devlink_put(devlink); + if ((flags & DEVLINK_NL_FLAG_OPTIONAL_PARENT_DEV) && + info->user_ptr[1]) { + devlink = info->user_ptr[1]; + devlink_put(devlink); + } } void devlink_nl_post_doit(const struct genl_split_ops *ops,
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2.44.0