libs/sys-util: add function to detect and update K8s emptyDir volume

Add function to detect and update K8s emptyDir volume.

Signed-off-by: Liu Jiang <gerry@linux.alibaba.com>
Signed-off-by: Qingyuan Hou <qingyuan.hou@linux.alibaba.com>

src/libs/kata-sys-util/Cargo.toml

@@ -24,6 +24,7 @@ slog-scope = "4.4.0"
 thiserror = "1.0.30"
 
 kata-types = { path = "../kata-types" }
+oci = { path = "../../agent/oci" }
 
 [dev-dependencies]
 num_cpus = "1.13.1"

src/libs/kata-sys-util/src/k8s.rs

@@ -0,0 +1,69 @@
+// Copyright (c) 2019-2021 Alibaba Cloud
+// Copyright (c) 2019-2021 Ant Group
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+//! Utilities to support Kubernetes (K8s).
+//!
+//! This module depends on kubelet internal implementation details, a better way is needed
+//! to detect K8S EmptyDir medium type from `oci::spec::Mount` objects.
+
+use kata_types::mount;
+use oci::Spec;
+
+use crate::mount::get_linux_mount_info;
+
+pub use kata_types::k8s::is_empty_dir;
+
+/// Check whether the given path is a kubernetes ephemeral volume.
+///
+/// This method depends on a specific path used by k8s to detect if it's type of ephemeral.
+/// As of now, this is a very k8s specific solution that works but in future there should be a
+/// better way for this method to determine if the path is for ephemeral volume type.
+pub fn is_ephemeral_volume(path: &str) -> bool {
+    if is_empty_dir(path) {
+        if let Ok(info) = get_linux_mount_info(path) {
+            if info.fs_type == "tmpfs" {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+/// Check whether the given path is a kubernetes empty-dir volume of medium "default".
+///
+/// K8s `EmptyDir` volumes are directories on the host. If the fs type is tmpfs, it's a ephemeral
+/// volume instead of a `EmptyDir` volume.
+pub fn is_host_empty_dir(path: &str) -> bool {
+    if is_empty_dir(path) {
+        if let Ok(info) = get_linux_mount_info(path) {
+            if info.fs_type != "tmpfs" {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+// set_ephemeral_storage_type sets the mount type to 'ephemeral'
+// if the mount source path is provisioned by k8s for ephemeral storage.
+// For the given pod ephemeral volume is created only once
+// backed by tmpfs inside the VM. For successive containers
+// of the same pod the already existing volume is reused.
+pub fn update_ephemeral_storage_type(oci_spec: &mut Spec) {
+    for m in oci_spec.mounts.iter_mut() {
+        if mount::is_kata_guest_mount_volume(&m.r#type) {
+            continue;
+        }
+
+        if is_ephemeral_volume(&m.source) {
+            m.r#type = String::from(mount::KATA_EPHEMERAL_VOLUME_TYPE);
+        } else if is_host_empty_dir(&m.source) {
+            m.r#type = String::from(mount::KATA_HOST_DIR_VOLUME_TYPE);
+        }
+    }
+}

src/libs/kata-sys-util/src/lib.rs

@@ -9,6 +9,7 @@ extern crate slog;
 pub mod cgroup;
 pub mod device;
 pub mod fs;
+pub mod k8s;
 pub mod mount;
 pub mod numa;