Thread (19 messages) 19 messages, 3 authors, 2026-01-28

Re: [PATCH net-next V6 07/14] devlink: Add parent dev to devlink API

From: Cosmin Ratiu <hidden>
Date: 2026-01-27 14:25:54
Also in: linux-doc, linux-rdma, lkml

On Tue, 2026-01-27 at 13:49 +0000, Simon Horman wrote:
quoted hunk ↗ jump to hunk
On Sun, Jan 25, 2026 at 01:31:56PM +0200, Tariq Toukan wrote:
quoted
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>
...

Hi Cosmin, all,

The netlink_gen.[ch] and spec changes in this patch do not seem
consistent.

$ tools/net/ynl/ynl-regen.sh -f
$ git diff
diff --git a/net/devlink/netlink_gen.c b/net/devlink/netlink_gen.c
index 6b691bdbf037..f4c61c2b4f22 100644
--- a/net/devlink/netlink_gen.c
+++ b/net/devlink/netlink_gen.c
@@ -39,11 +39,6 @@ devlink_attr_param_type_validate(const struct
nlattr *attr,
 }

 /* Common nested types */
-const struct nla_policy
devlink_dl_parent_dev_nl_policy[DEVLINK_ATTR_DEV_NAME + 1] = {
-       [DEVLINK_ATTR_BUS_NAME] = { .type = NLA_NUL_STRING, },
-       [DEVLINK_ATTR_DEV_NAME] = { .type = NLA_NUL_STRING, },
-};
-
 const struct nla_policy
devlink_dl_port_function_nl_policy[DEVLINK_PORT_FN_ATTR_CAPS + 1] = {
        [DEVLINK_PORT_FUNCTION_ATTR_HW_ADDR] = { .type = NLA_BINARY,
},
        [DEVLINK_PORT_FN_ATTR_STATE] = NLA_POLICY_MAX(NLA_U8, 1),
diff --git a/net/devlink/netlink_gen.h b/net/devlink/netlink_gen.h
index d4db82a00522..2817d53a0eba 100644
--- a/net/devlink/netlink_gen.h
+++ b/net/devlink/netlink_gen.h
@@ -13,7 +13,6 @@
 #include <uapi/linux/devlink.h>

 /* Common nested types */
-extern const struct nla_policy
devlink_dl_parent_dev_nl_policy[DEVLINK_ATTR_DEV_NAME + 1];
 extern const struct nla_policy
devlink_dl_port_function_nl_policy[DEVLINK_PORT_FN_ATTR_CAPS + 1];
 extern const struct nla_policy
devlink_dl_rate_tc_bws_nl_policy[DEVLINK_RATE_TC_ATTR_BW + 1];
 extern const struct nla_policy
devlink_dl_selftest_id_nl_policy[DEVLINK_ATTR_SELFTEST_ID_FLASH + 1];
@@ -30,19 +29,12 @@ int devlink_nl_pre_doit_dev_lock(const struct
genl_split_ops *ops,
 int devlink_nl_pre_doit_port_optional(const struct genl_split_ops
*ops,
                                      struct sk_buff *skb,
                                      struct genl_info *info);
-int devlink_nl_pre_doit_parent_dev_optional(const struct
genl_split_ops *ops,
-                                           struct sk_buff *skb,
-                                           struct genl_info *info);
 void
 devlink_nl_post_doit(const struct genl_split_ops *ops, struct
sk_buff *skb,
                     struct genl_info *info);
 void
 devlink_nl_post_doit_dev_lock(const struct genl_split_ops *ops,
                              struct sk_buff *skb, struct genl_info
*info);
-void
-devlink_nl_post_doit_parent_dev_optional(const struct genl_split_ops
*ops,
-                                        struct sk_buff *skb,
-                                        struct genl_info *info);

 int devlink_nl_get_doit(struct sk_buff *skb, struct genl_info
*info);
 int devlink_nl_get_dumpit(struct sk_buff *skb, struct
netlink_callback *cb);
;
Hi Simon,

We had this conversation during v4, I replied then [1].
But thinking about it a bit more, I think it's indeed slightly cleaner
to move the policy and the new pre/post doit handlers to the next
patch, where they are actually used. The only bit is that the policy is
used from devlink_get_parent_from_attrs_lock from this function, but it
appears safe to use NULL there until next patch (the underlying parse
functions tolerate NULL policies).

So I'll do that in the next submission.

[1]
https://lore.kernel.org/netdev/3ec956ea1d0a1c6e56865b2ded6d83ed773ccd4d.camel@nvidia.com/ (local)
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