sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

alb_break_llc() decides whether to break LLC preference during active
load balance. It does so by testing that every runnable fair task on the
source rq prefers its LLC:

	env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable

But the two counters cover different sets. nr_pref_llc_running is updated
in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued,
so it follows queued tasks. h_nr_runnable is updated in set_delayed()/
clear_delayed() and drops delay-dequeued tasks.

So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted
in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks,
alb_break_llc() returns false, and active balance is free to pull a task
off its preferred LLC. Active balance only moves runnable tasks, and this
is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB
skips the per-task test in can_migrate_task(). The runnable set is the one
we want.

Fix it on the counter side. A task should be counted in
nr_pref_llc_running exactly while it is both queued on its preferred LLC
(pref_llc_queued) and runnable (!sched_delayed). Define that membership
once in task_pref_llc_runnable(), and adjust the counter only through
pref_llc_running_inc()/pref_llc_running_dec() from the four sites that
change either input: account_llc_enqueue(), account_llc_dequeue(),
set_delayed() and clear_delayed(). Gating every update on the same
predicate keeps the delay, wake and dequeue paths from double-counting
or underflowing; see the comments at those sites for the ordering.

nr_llc_running and sd->llc_counts are not touched and stay on queued
semantics.

Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC")
Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/
Reported-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 627 insertions, 0 deletions

diff --git a/net/devlink/linecard.c b/net/devlink/linecard.c
new file mode 100644
index 000000000..fd18f2759
--- /dev/null
+++ b/net/devlink/linecard.c
@@ -0,0 +1,627 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Jiri Pirko <jiri@mellanox.com>
+ */
+
+#include "devl_internal.h"
+
+struct devlink_linecard {
+	struct list_head list;
+	struct devlink *devlink;
+	unsigned int index;
+	const struct devlink_linecard_ops *ops;
+	void *priv;
+	enum devlink_linecard_state state;
+	struct mutex state_lock; /* Protects state */
+	const char *type;
+	struct devlink_linecard_type *types;
+	unsigned int types_count;
+	u32 rel_index;
+};
+
+unsigned int devlink_linecard_index(struct devlink_linecard *linecard)
+{
+	return linecard->index;
+}
+
+static struct devlink_linecard *
+devlink_linecard_get_by_index(struct devlink *devlink,
+			      unsigned int linecard_index)
+{
+	struct devlink_linecard *devlink_linecard;
+
+	list_for_each_entry(devlink_linecard, &devlink->linecard_list, list) {
+		if (devlink_linecard->index == linecard_index)
+			return devlink_linecard;
+	}
+	return NULL;
+}
+
+static bool devlink_linecard_index_exists(struct devlink *devlink,
+					  unsigned int linecard_index)
+{
+	return devlink_linecard_get_by_index(devlink, linecard_index);
+}
+
+static struct devlink_linecard *
+devlink_linecard_get_from_attrs(struct devlink *devlink, struct nlattr **attrs)
+{
+	if (attrs[DEVLINK_ATTR_LINECARD_INDEX]) {
+		u32 linecard_index = nla_get_u32(attrs[DEVLINK_ATTR_LINECARD_INDEX]);
+		struct devlink_linecard *linecard;
+
+		linecard = devlink_linecard_get_by_index(devlink, linecard_index);
+		if (!linecard)
+			return ERR_PTR(-ENODEV);
+		return linecard;
+	}
+	return ERR_PTR(-EINVAL);
+}
+
+static struct devlink_linecard *
+devlink_linecard_get_from_info(struct devlink *devlink, struct genl_info *info)
+{
+	return devlink_linecard_get_from_attrs(devlink, info->attrs);
+}
+
+struct devlink_linecard_type {
+	const char *type;
+	const void *priv;
+};
+
+static int devlink_nl_linecard_fill(struct sk_buff *msg,
+				    struct devlink *devlink,
+				    struct devlink_linecard *linecard,
+				    enum devlink_command cmd, u32 portid,
+				    u32 seq, int flags,
+				    struct netlink_ext_ack *extack)
+{
+	struct devlink_linecard_type *linecard_type;
+	struct nlattr *attr;
+	void *hdr;
+	int i;
+
+	hdr = genlmsg_put(msg, portid, seq, &devlink_nl_family, flags, cmd);
+	if (!hdr)
+		return -EMSGSIZE;
+
+	if (devlink_nl_put_handle(msg, devlink))
+		goto nla_put_failure;
+	if (nla_put_u32(msg, DEVLINK_ATTR_LINECARD_INDEX, linecard->index))
+		goto nla_put_failure;
+	if (nla_put_u8(msg, DEVLINK_ATTR_LINECARD_STATE, linecard->state))
+		goto nla_put_failure;
+	if (linecard->type &&
+	    nla_put_string(msg, DEVLINK_ATTR_LINECARD_TYPE, linecard->type))
+		goto nla_put_failure;
+
+	if (linecard->types_count) {
+		attr = nla_nest_start(msg,
+				      DEVLINK_ATTR_LINECARD_SUPPORTED_TYPES);
+		if (!attr)
+			goto nla_put_failure;
+		for (i = 0; i < linecard->types_count; i++) {
+			linecard_type = &linecard->types[i];
+			if (nla_put_string(msg, DEVLINK_ATTR_LINECARD_TYPE,
+					   linecard_type->type)) {
+				nla_nest_cancel(msg, attr);
+				goto nla_put_failure;
+			}
+		}
+		nla_nest_end(msg, attr);
+	}
+
+	if (devlink_rel_devlink_handle_put(msg, devlink,
+					   linecard->rel_index,
+					   DEVLINK_ATTR_NESTED_DEVLINK,
+					   NULL))
+		goto nla_put_failure;
+
+	genlmsg_end(msg, hdr);
+	return 0;
+
+nla_put_failure:
+	genlmsg_cancel(msg, hdr);
+	return -EMSGSIZE;
+}
+
+static void devlink_linecard_notify(struct devlink_linecard *linecard,
+				    enum devlink_command cmd)
+{
+	struct devlink *devlink = linecard->devlink;
+	struct sk_buff *msg;
+	int err;
+
+	WARN_ON(cmd != DEVLINK_CMD_LINECARD_NEW &&
+		cmd != DEVLINK_CMD_LINECARD_DEL);
+
+	if (!__devl_is_registered(devlink) || !devlink_nl_notify_need(devlink))
+		return;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return;
+
+	err = devlink_nl_linecard_fill(msg, devlink, linecard, cmd, 0, 0, 0,
+				       NULL);
+	if (err) {
+		nlmsg_free(msg);
+		return;
+	}
+
+	devlink_nl_notify_send(devlink, msg);
+}
+
+void devlink_linecards_notify_register(struct devlink *devlink)
+{
+	struct devlink_linecard *linecard;
+
+	list_for_each_entry(linecard, &devlink->linecard_list, list)
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+}
+
+void devlink_linecards_notify_unregister(struct devlink *devlink)
+{
+	struct devlink_linecard *linecard;
+
+	list_for_each_entry_reverse(linecard, &devlink->linecard_list, list)
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_DEL);
+}
+
+int devlink_nl_linecard_get_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct devlink *devlink = devlink_nl_ctx(info)->devlink;
+	struct devlink_linecard *linecard;
+	struct sk_buff *msg;
+	int err;
+
+	linecard = devlink_linecard_get_from_info(devlink, info);
+	if (IS_ERR(linecard))
+		return PTR_ERR(linecard);
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	mutex_lock(&linecard->state_lock);
+	err = devlink_nl_linecard_fill(msg, devlink, linecard,
+				       DEVLINK_CMD_LINECARD_NEW,
+				       info->snd_portid, info->snd_seq, 0,
+				       info->extack);
+	mutex_unlock(&linecard->state_lock);
+	if (err) {
+		nlmsg_free(msg);
+		return err;
+	}
+
+	return genlmsg_reply(msg, info);
+}
+
+static int devlink_nl_linecard_get_dump_one(struct sk_buff *msg,
+					    struct devlink *devlink,
+					    struct netlink_callback *cb,
+					    int flags)
+{
+	struct devlink_nl_dump_state *state = devlink_dump_state(cb);
+	struct devlink_linecard *linecard;
+	int idx = 0;
+	int err = 0;
+
+	list_for_each_entry(linecard, &devlink->linecard_list, list) {
+		if (idx < state->idx) {
+			idx++;
+			continue;
+		}
+		mutex_lock(&linecard->state_lock);
+		err = devlink_nl_linecard_fill(msg, devlink, linecard,
+					       DEVLINK_CMD_LINECARD_NEW,
+					       NETLINK_CB(cb->skb).portid,
+					       cb->nlh->nlmsg_seq, flags,
+					       cb->extack);
+		mutex_unlock(&linecard->state_lock);
+		if (err) {
+			state->idx = idx;
+			break;
+		}
+		idx++;
+	}
+
+	return err;
+}
+
+int devlink_nl_linecard_get_dumpit(struct sk_buff *skb,
+				   struct netlink_callback *cb)
+{
+	return devlink_nl_dumpit(skb, cb, devlink_nl_linecard_get_dump_one);
+}
+
+static struct devlink_linecard_type *
+devlink_linecard_type_lookup(struct devlink_linecard *linecard,
+			     const char *type)
+{
+	struct devlink_linecard_type *linecard_type;
+	int i;
+
+	for (i = 0; i < linecard->types_count; i++) {
+		linecard_type = &linecard->types[i];
+		if (!strcmp(type, linecard_type->type))
+			return linecard_type;
+	}
+	return NULL;
+}
+
+static int devlink_linecard_type_set(struct devlink_linecard *linecard,
+				     const char *type,
+				     struct netlink_ext_ack *extack)
+{
+	const struct devlink_linecard_ops *ops = linecard->ops;
+	struct devlink_linecard_type *linecard_type;
+	int err;
+
+	mutex_lock(&linecard->state_lock);
+	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being provisioned");
+		err = -EBUSY;
+		goto out;
+	}
+	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being unprovisioned");
+		err = -EBUSY;
+		goto out;
+	}
+
+	linecard_type = devlink_linecard_type_lookup(linecard, type);
+	if (!linecard_type) {
+		NL_SET_ERR_MSG(extack, "Unsupported line card type provided");
+		err = -EINVAL;
+		goto out;
+	}
+
+	if (linecard->state != DEVLINK_LINECARD_STATE_UNPROVISIONED &&
+	    linecard->state != DEVLINK_LINECARD_STATE_PROVISIONING_FAILED) {
+		NL_SET_ERR_MSG(extack, "Line card already provisioned");
+		err = -EBUSY;
+		/* Check if the line card is provisioned in the same
+		 * way the user asks. In case it is, make the operation
+		 * to return success.
+		 */
+		if (ops->same_provision &&
+		    ops->same_provision(linecard, linecard->priv,
+					linecard_type->type,
+					linecard_type->priv))
+			err = 0;
+		goto out;
+	}
+
+	linecard->state = DEVLINK_LINECARD_STATE_PROVISIONING;
+	linecard->type = linecard_type->type;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+	err = ops->provision(linecard, linecard->priv, linecard_type->type,
+			     linecard_type->priv, extack);
+	if (err) {
+		/* Provisioning failed. Assume the linecard is unprovisioned
+		 * for future operations.
+		 */
+		mutex_lock(&linecard->state_lock);
+		linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+		linecard->type = NULL;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		mutex_unlock(&linecard->state_lock);
+	}
+	return err;
+
+out:
+	mutex_unlock(&linecard->state_lock);
+	return err;
+}
+
+static int devlink_linecard_type_unset(struct devlink_linecard *linecard,
+				       struct netlink_ext_ack *extack)
+{
+	int err;
+
+	mutex_lock(&linecard->state_lock);
+	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being provisioned");
+		err = -EBUSY;
+		goto out;
+	}
+	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONING) {
+		NL_SET_ERR_MSG(extack, "Line card is currently being unprovisioned");
+		err = -EBUSY;
+		goto out;
+	}
+	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING_FAILED) {
+		linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+		linecard->type = NULL;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		err = 0;
+		goto out;
+	}
+
+	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONED) {
+		NL_SET_ERR_MSG(extack, "Line card is not provisioned");
+		err = 0;
+		goto out;
+	}
+	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONING;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+	err = linecard->ops->unprovision(linecard, linecard->priv,
+					 extack);
+	if (err) {
+		/* Unprovisioning failed. Assume the linecard is unprovisioned
+		 * for future operations.
+		 */
+		mutex_lock(&linecard->state_lock);
+		linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+		linecard->type = NULL;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		mutex_unlock(&linecard->state_lock);
+	}
+	return err;
+
+out:
+	mutex_unlock(&linecard->state_lock);
+	return err;
+}
+
+int devlink_nl_linecard_set_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct netlink_ext_ack *extack = info->extack;
+	struct devlink *devlink = devlink_nl_ctx(info)->devlink;
+	struct devlink_linecard *linecard;
+	int err;
+
+	linecard = devlink_linecard_get_from_info(devlink, info);
+	if (IS_ERR(linecard))
+		return PTR_ERR(linecard);
+
+	if (info->attrs[DEVLINK_ATTR_LINECARD_TYPE]) {
+		const char *type;
+
+		type = nla_data(info->attrs[DEVLINK_ATTR_LINECARD_TYPE]);
+		if (strcmp(type, "")) {
+			err = devlink_linecard_type_set(linecard, type, extack);
+			if (err)
+				return err;
+		} else {
+			err = devlink_linecard_type_unset(linecard, extack);
+			if (err)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
+static int devlink_linecard_types_init(struct devlink_linecard *linecard)
+{
+	struct devlink_linecard_type *linecard_type;
+	unsigned int count;
+	int i;
+
+	count = linecard->ops->types_count(linecard, linecard->priv);
+	linecard->types = kmalloc_objs(*linecard_type, count);
+	if (!linecard->types)
+		return -ENOMEM;
+	linecard->types_count = count;
+
+	for (i = 0; i < count; i++) {
+		linecard_type = &linecard->types[i];
+		linecard->ops->types_get(linecard, linecard->priv, i,
+					 &linecard_type->type,
+					 &linecard_type->priv);
+	}
+	return 0;
+}
+
+static void devlink_linecard_types_fini(struct devlink_linecard *linecard)
+{
+	kfree(linecard->types);
+}
+
+/**
+ *	devl_linecard_create - Create devlink linecard
+ *
+ *	@devlink: devlink
+ *	@linecard_index: driver-specific numerical identifier of the linecard
+ *	@ops: linecards ops
+ *	@priv: user priv pointer
+ *
+ *	Create devlink linecard instance with provided linecard index.
+ *	Caller can use any indexing, even hw-related one.
+ *
+ *	Return: Line card structure or an ERR_PTR() encoded error code.
+ */
+struct devlink_linecard *
+devl_linecard_create(struct devlink *devlink, unsigned int linecard_index,
+		     const struct devlink_linecard_ops *ops, void *priv)
+{
+	struct devlink_linecard *linecard;
+	int err;
+
+	if (WARN_ON(!ops || !ops->provision || !ops->unprovision ||
+		    !ops->types_count || !ops->types_get))
+		return ERR_PTR(-EINVAL);
+
+	if (devlink_linecard_index_exists(devlink, linecard_index))
+		return ERR_PTR(-EEXIST);
+
+	linecard = kzalloc_obj(*linecard);
+	if (!linecard)
+		return ERR_PTR(-ENOMEM);
+
+	linecard->devlink = devlink;
+	linecard->index = linecard_index;
+	linecard->ops = ops;
+	linecard->priv = priv;
+	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+	mutex_init(&linecard->state_lock);
+
+	err = devlink_linecard_types_init(linecard);
+	if (err) {
+		mutex_destroy(&linecard->state_lock);
+		kfree(linecard);
+		return ERR_PTR(err);
+	}
+
+	list_add_tail(&linecard->list, &devlink->linecard_list);
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	return linecard;
+}
+EXPORT_SYMBOL_GPL(devl_linecard_create);
+
+/**
+ *	devl_linecard_destroy - Destroy devlink linecard
+ *
+ *	@linecard: devlink linecard
+ */
+void devl_linecard_destroy(struct devlink_linecard *linecard)
+{
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_DEL);
+	list_del(&linecard->list);
+	devlink_linecard_types_fini(linecard);
+	mutex_destroy(&linecard->state_lock);
+	kfree(linecard);
+}
+EXPORT_SYMBOL_GPL(devl_linecard_destroy);
+
+/**
+ *	devlink_linecard_provision_set - Set provisioning on linecard
+ *
+ *	@linecard: devlink linecard
+ *	@type: linecard type
+ *
+ *	This is either called directly from the provision() op call or
+ *	as a result of the provision() op call asynchronously.
+ */
+void devlink_linecard_provision_set(struct devlink_linecard *linecard,
+				    const char *type)
+{
+	mutex_lock(&linecard->state_lock);
+	WARN_ON(linecard->type && strcmp(linecard->type, type));
+	linecard->state = DEVLINK_LINECARD_STATE_PROVISIONED;
+	linecard->type = type;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_provision_set);
+
+/**
+ *	devlink_linecard_provision_clear - Clear provisioning on linecard
+ *
+ *	@linecard: devlink linecard
+ *
+ *	This is either called directly from the unprovision() op call or
+ *	as a result of the unprovision() op call asynchronously.
+ */
+void devlink_linecard_provision_clear(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
+	linecard->type = NULL;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_provision_clear);
+
+/**
+ *	devlink_linecard_provision_fail - Fail provisioning on linecard
+ *
+ *	@linecard: devlink linecard
+ *
+ *	This is either called directly from the provision() op call or
+ *	as a result of the provision() op call asynchronously.
+ */
+void devlink_linecard_provision_fail(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	linecard->state = DEVLINK_LINECARD_STATE_PROVISIONING_FAILED;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_provision_fail);
+
+/**
+ *	devlink_linecard_activate - Set linecard active
+ *
+ *	@linecard: devlink linecard
+ */
+void devlink_linecard_activate(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	WARN_ON(linecard->state != DEVLINK_LINECARD_STATE_PROVISIONED);
+	linecard->state = DEVLINK_LINECARD_STATE_ACTIVE;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_activate);
+
+/**
+ *	devlink_linecard_deactivate - Set linecard inactive
+ *
+ *	@linecard: devlink linecard
+ */
+void devlink_linecard_deactivate(struct devlink_linecard *linecard)
+{
+	mutex_lock(&linecard->state_lock);
+	switch (linecard->state) {
+	case DEVLINK_LINECARD_STATE_ACTIVE:
+		linecard->state = DEVLINK_LINECARD_STATE_PROVISIONED;
+		devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+		break;
+	case DEVLINK_LINECARD_STATE_UNPROVISIONING:
+		/* Line card is being deactivated as part
+		 * of unprovisioning flow.
+		 */
+		break;
+	default:
+		WARN_ON(1);
+		break;
+	}
+	mutex_unlock(&linecard->state_lock);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_deactivate);
+
+static void devlink_linecard_rel_notify_cb(struct devlink *devlink,
+					   u32 linecard_index)
+{
+	struct devlink_linecard *linecard;
+
+	linecard = devlink_linecard_get_by_index(devlink, linecard_index);
+	if (!linecard)
+		return;
+	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
+}
+
+static void devlink_linecard_rel_cleanup_cb(struct devlink *devlink,
+					    u32 linecard_index, u32 rel_index)
+{
+	struct devlink_linecard *linecard;
+
+	linecard = devlink_linecard_get_by_index(devlink, linecard_index);
+	if (linecard && linecard->rel_index == rel_index)
+		linecard->rel_index = 0;
+}
+
+/**
+ *	devlink_linecard_nested_dl_set - Attach/detach nested devlink
+ *					 instance to linecard.
+ *
+ *	@linecard: devlink linecard
+ *	@nested_devlink: devlink instance to attach or NULL to detach
+ */
+int devlink_linecard_nested_dl_set(struct devlink_linecard *linecard,
+				   struct devlink *nested_devlink)
+{
+	return devlink_rel_nested_in_add(&linecard->rel_index,
+					 linecard->devlink->index,
+					 linecard->index,
+					 devlink_linecard_rel_notify_cb,
+					 devlink_linecard_rel_cleanup_cb,
+					 nested_devlink);
+}
+EXPORT_SYMBOL_GPL(devlink_linecard_nested_dl_set);