RDMA/restrack: Translate from ID to restrack object

Add new general helper to get restrack entry given by ID and their
respective type.

Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/restrack.c

@@ -256,6 +256,31 @@ int __must_check rdma_restrack_get(struct rdma_restrack_entry *res)
 }
 EXPORT_SYMBOL(rdma_restrack_get);
 
+/**
+ * rdma_restrack_get_byid() - translate from ID to restrack object
+ * @dev: IB device
+ * @type: resource track type
+ * @id: ID to take a look
+ *
+ * Return: Pointer to restrack entry or -ENOENT in case of error.
+ */
+struct rdma_restrack_entry *
+rdma_restrack_get_byid(struct ib_device *dev,
+		       enum rdma_restrack_type type, u32 id)
+{
+	struct rdma_restrack_root *rt = &dev->res;
+	struct rdma_restrack_entry *res;
+
+	down_read(&dev->res.rwsem);
+	res = xa_load(&rt->xa[type], id);
+	if (!res || !rdma_restrack_get(res))
+		res = ERR_PTR(-ENOENT);
+	up_read(&dev->res.rwsem);
+
+	return res;
+}
+EXPORT_SYMBOL(rdma_restrack_get_byid);
+
 static void restrack_release(struct kref *kref)
 {
 	struct rdma_restrack_entry *res;

include/rdma/restrack.h

@@ -179,4 +179,7 @@ int rdma_nl_put_driver_u32_hex(struct sk_buff *msg, const char *name,
 int rdma_nl_put_driver_u64(struct sk_buff *msg, const char *name, u64 value);
 int rdma_nl_put_driver_u64_hex(struct sk_buff *msg, const char *name,
 			       u64 value);
+struct rdma_restrack_entry *rdma_restrack_get_byid(struct ib_device *dev,
+						   enum rdma_restrack_type type,
+						   u32 id);
 #endif /* _RDMA_RESTRACK_H_ */