nydus_rootfs/prefetch_files: add prefetch_files for RAFS

A sandbox annotation used to specify prefetch_files.list
path the container image being used, and runtime will pass
it to Hypervisor to search for corresponding prefetch file:
format looks like:
"io.katacontainers.config.hypervisor.prefetch_files.list"
      = /path/to/<uid>/xyz.com/fedora:36/prefetch_file.list

Fixes: #6582

Signed-off-by: alex.lyn <alex.lyn@antgroup.com>

src/runtime-rs/crates/resource/src/rootfs/nydus_rootfs.rs

@@ -3,7 +3,7 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 //
-use std::{fs, sync::Arc};
+use std::{fs, path::Path, sync::Arc};
 
 use super::{Rootfs, TYPE_OVERLAY_FS};
 use crate::{
@@ -28,6 +28,8 @@ const NYDUS_ROOTFS_V6: &str = "v6";
 
 const SNAPSHOT_DIR: &str = "snapshotdir";
 const KATA_OVERLAY_DEV_TYPE: &str = "overlayfs";
+// nydus prefetch file list name
+const NYDUS_PREFETCH_FILE_LIST: &str = "prefetch_file.list";
 
 pub(crate) struct NydusRootfs {
     guest_path: String,
@@ -42,6 +44,9 @@ impl NydusRootfs {
         cid: &str,
         rootfs: &Mount,
     ) -> Result<Self> {
+        let prefetch_list_path =
+            get_nydus_prefetch_files(h.hypervisor_config().await.prefetch_list_path).await;
+
         let share_fs_mount = share_fs.get_share_fs_mount();
         let extra_options =
             NydusExtraOptions::new(rootfs).context("failed to parse nydus extra options")?;
@@ -59,7 +64,7 @@ impl NydusRootfs {
                     rafs_meta.to_string(),
                     rafs_mnt,
                     extra_options.config.clone(),
-                    None,
+                    prefetch_list_path,
                 )
                 .await
                 .context("failed to do rafs mount")?;
@@ -151,3 +156,67 @@ impl Rootfs for NydusRootfs {
         Ok(())
     }
 }
+
+// Check prefetch files list path, and if invalid, discard it directly.
+// As the result of caller `rafs_mount`, it returns `Option<String>`.
+async fn get_nydus_prefetch_files(nydus_prefetch_path: String) -> Option<String> {
+    // nydus_prefetch_path is an annotation and pod with it will indicate
+    // that prefetch_files will be included.
+    if nydus_prefetch_path.is_empty() {
+        info!(sl!(), "nydus prefetch files path not set, just skip it.");
+
+        return None;
+    }
+
+    // Ensure the string ends with "/prefetch_files.list"
+    if !nydus_prefetch_path.ends_with(format!("/{}", NYDUS_PREFETCH_FILE_LIST).as_str()) {
+        info!(
+            sl!(),
+            "nydus prefetch file path no {:?} file exist.", NYDUS_PREFETCH_FILE_LIST
+        );
+
+        return None;
+    }
+
+    // ensure the prefetch_list_path is a regular file.
+    let prefetch_list_path = Path::new(nydus_prefetch_path.as_str());
+    if !prefetch_list_path.is_file() {
+        info!(
+            sl!(),
+            "nydus prefetch list file {:?} not a regular file", &prefetch_list_path
+        );
+
+        return None;
+    }
+
+    return Some(prefetch_list_path.display().to_string());
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::{fs::File, path::PathBuf};
+    use tempfile::tempdir;
+
+    #[tokio::test]
+    async fn test_get_nydus_prefetch_files() {
+        let temp_dir = tempdir().unwrap();
+        let prefetch_list_path01 = temp_dir.path().join("nydus_prefetch_files");
+        // /tmp_dir/nydus_prefetch_files/
+        std::fs::create_dir_all(prefetch_list_path01.clone()).unwrap();
+        // /tmp_dir/nydus_prefetch_files/prefetch_file.list
+        let prefetch_list_path02 = prefetch_list_path01
+            .as_path()
+            .join(NYDUS_PREFETCH_FILE_LIST);
+        let file = File::create(prefetch_list_path02.clone());
+        assert!(file.is_ok());
+
+        let prefetch_file =
+            get_nydus_prefetch_files(prefetch_list_path02.as_path().display().to_string()).await;
+        assert!(prefetch_file.is_some());
+        assert_eq!(PathBuf::from(prefetch_file.unwrap()), prefetch_list_path02);
+
+        drop(file);
+        temp_dir.close().unwrap_or_default();
+    }
+}