[EROFS] Add a check for erofs

Add an additional check to verify whether the host machine
truly supports the EROFS file system, and only mount it as
the EROFS file system if it is supported.

Signed-off-by: Hongzhen Luo <hongzhen@linux.alibaba.com>

Author: Hongzhen Luo

pkg/snapshot/overlay.go

@@ -17,6 +17,7 @@
 package snapshot
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"os"
@@ -1379,10 +1380,18 @@ func (o *snapshotter) blockPath(id string) string {
 	return filepath.Join(o.root, "snapshots", id, "block")
 }
 
+func IsErofsSupported() bool {
+	fs, err := os.ReadFile("/proc/filesystems")
+	if err != nil || !bytes.Contains(fs, []byte("\terofs\n")) {
+		return false
+	}
+	return true
+}
+
 func (o *snapshotter) turboOCIFsMeta(id string) (string, string) {
 	// TODO: make the priority order (multi-meta exists) configurable later if needed
 	erofsmeta := filepath.Join(o.root, "snapshots", id, "fs", "erofs.fs.meta")
-	if _, err := os.Stat(erofsmeta); err == nil {
+	if _, err := os.Stat(erofsmeta); err == nil && IsErofsSupported() {
 		return erofsmeta, "erofs"
 	}
 	return filepath.Join(o.root, "snapshots", id, "fs", "ext4.fs.meta"), "ext4"