From 62e4130b5f56d415a30f1a6717622939b8428fdb Mon Sep 17 00:00:00 2001
From: Tonis Tiigi <tonistiigi@gmail.com>
Date: Thu, 24 Oct 2024 17:38:26 -0700
Subject: [PATCH] ociindex: allow readonly access

If file lock can't be taken because of a permission or readonly
error then assume that the index is immutable and locks are not needed.

Writer side is unchanged as if lock would be skipped then the write
is assumed to fail anyway.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
---
 client/ociindex/ociindex.go | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/client/ociindex/ociindex.go b/client/ociindex/ociindex.go
index 5321f773d70e..e427f6550806 100644
--- a/client/ociindex/ociindex.go
+++ b/client/ociindex/ociindex.go
@@ -5,6 +5,7 @@ import (
 	"io"
 	"os"
 	"path"
+	"syscall"
 
 	"github.com/gofrs/flock"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
@@ -36,15 +37,18 @@ func (s StoreIndex) Read() (*ocispecs.Index, error) {
 	lock := flock.New(s.lockPath)
 	locked, err := lock.TryRLock()
 	if err != nil {
-		return nil, errors.Wrapf(err, "could not lock %s", s.lockPath)
-	}
-	if !locked {
-		return nil, errors.Errorf("could not lock %s", s.lockPath)
+		if !errors.Is(err, syscall.EPERM) && !errors.Is(err, syscall.EROFS) {
+			return nil, errors.Wrapf(err, "could not lock %s", s.lockPath)
+		}
+	} else {
+		if !locked {
+			return nil, errors.Errorf("could not lock %s", s.lockPath)
+		}
+		defer func() {
+			lock.Unlock()
+			os.RemoveAll(s.lockPath)
+		}()
 	}
-	defer func() {
-		lock.Unlock()
-		os.RemoveAll(s.lockPath)
-	}()
 
 	b, err := os.ReadFile(s.indexPath)
 	if err != nil {