[PATCH net-next V10 02/14] devlink: Add a helper for getting a nested-in instance

[Tariq Toukan <tariqt@nvidia.com>]

From: Cosmin Ratiu <cratiu@nvidia.com>

Upcoming code will need to obtain references to locked nested-in
devlink instances. Add a helper to lock, reference and return the
nested-in instance.

Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 net/devlink/core.c          | 16 ++++++++++++++++
 net/devlink/devl_internal.h |  4 ++++
 2 files changed, 20 insertions(+)

diff --git a/net/devlink/core.c b/net/devlink/core.c
index fe9f6a0a67d5..ee26c50b4118 100644
--- a/net/devlink/core.c
+++ b/net/devlink/core.c
@@ -67,6 +67,22 @@ static void __devlink_rel_put(struct devlink_rel *rel)
 		devlink_rel_free(rel);
 }
 
+struct devlink *__must_check devlink_nested_in_get_lock(struct devlink *devlink)
+{
+	devl_assert_locked(devlink);
+	if (!devlink->rel)
+		return NULL;
+	devlink = devlinks_xa_get(devlink->rel->nested_in.devlink_index);
+	if (!devlink)
+		return NULL;
+	devl_lock(devlink);
+	if (devl_is_registered(devlink))
+		return devlink;
+	devl_unlock(devlink);
+	devlink_put(devlink);
+	return NULL;
+}
+
 static void devlink_rel_nested_in_notify_work(struct work_struct *work)
 {
 	struct devlink_rel *rel = container_of(work, struct devlink_rel,
diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
index e4e48ee2da5a..36dff282f9b0 100644
--- a/net/devlink/devl_internal.h
+++ b/net/devlink/devl_internal.h
@@ -136,6 +136,10 @@ typedef void devlink_rel_notify_cb_t(struct devlink *devlink, u32 obj_index);
 typedef void devlink_rel_cleanup_cb_t(struct devlink *devlink, u32 obj_index,
 				      u32 rel_index);
 
+/* Returns the locked+referenced nested-in instance or NULL. */
+struct devlink *__must_check
+devlink_nested_in_get_lock(struct devlink *devlink);
+
 void devlink_rel_nested_in_clear(u32 rel_index);
 int devlink_rel_nested_in_add(u32 *rel_index, u32 devlink_index,
 			      u32 obj_index, devlink_rel_notify_cb_t *notify_cb,
-- 
2.44.0