also ignore errors from readdirnames (#15947)

* also ignore errors from readdirnames

* test case for empty blobs dir

---------

Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>

changelog/kasey_ignore-readdir-errors.md

@@ -0,0 +1,2 @@
+### Ignored
+- Fix bug with layout detection when readdirnames returns io.EOF.

cmd/beacon-chain/storage/options.go

@@ -2,6 +2,7 @@ package storage
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"path"
 	"slices"
@@ -139,6 +140,10 @@ func detectLayout(dir string, c stringFlagGetter) (string, error) {
 	// amount of wiggle room to be confident that we'll likely see a by-root director if one exists.
 	entries, err := base.Readdirnames(16)
 	if err != nil {
+		// We can get this error if the directory exists and is empty
+		if errors.Is(err, io.EOF) {
+			return filesystem.LayoutNameByEpoch, nil
+		}
 		return "", errors.Wrap(err, "reading blob storage directory")
 	}
 	for _, entry := range entries {

cmd/beacon-chain/storage/options_test.go

@@ -192,6 +192,13 @@ func TestDetectLayout(t *testing.T) {
 			},
 			expectedErr: syscall.ENOTDIR,
 		},
+		{
+			name: "empty blobs dir",
+			setup: func(t *testing.T, dir string) {
+				require.NoError(t, os.MkdirAll(dir, 0o755))
+			},
+			expected: filesystem.LayoutNameByEpoch,
+		},
 	}
 
 	for _, tc := range cases {