runtime-rs: load the cgroup path correctly

When the sandbox api was enabled, the pause container would
be removed and sandbox start api only pass an empty bundle
directory, which means there's no oci spec file under it, thus
the cgroup config couldn't get the cgroup path from pause container's
oci spec. So we should set a default cgroup path for sandbox api
case.

In the future, we can promote containerd to pass the cgroup path during
the sandbox start phase.

Signed-off-by: Fupan Li <fupan.lfp@antgroup.com>

src/runtime-rs/crates/resource/src/cgroups/mod.rs

@@ -29,6 +29,7 @@ use tokio::sync::RwLock;
 use crate::ResourceUpdateOp;
 
 const OS_ERROR_NO_SUCH_PROCESS: i32 = 3;
+const SANDBOXED_CGROUP_PATH: &str = "kata_sandboxed_pod";
 
 pub struct CgroupArgs {
     pub sid: String,
@@ -44,9 +45,8 @@ pub struct CgroupConfig {
 impl CgroupConfig {
     fn new(sid: &str, toml_config: &TomlConfig) -> Result<Self> {
         let overhead_path = utils::gen_overhead_path(sid);
-        let spec = load_oci_spec()?;
-        let path = spec
-            .linux()
+        let path = if let Ok(spec) = load_oci_spec() {
+            spec.linux()
                 .clone()
                 .and_then(|linux| linux.cgroups_path().clone())
                 .map(|path| {
@@ -56,8 +56,10 @@ impl CgroupConfig {
                         .trim_start_matches('/')
                         .to_string()
                 })
-            .unwrap_or_default();
-
+                .unwrap_or_default()
+        } else {
+            format!("{}/{}", SANDBOXED_CGROUP_PATH, sid)
+        };
         Ok(Self {
             path,
             overhead_path,