From 5a6f2f9fa059fea1b7de697f2dcb88781d80f23e Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Sun, 1 May 2022 14:52:00 +0200
Subject: [PATCH] Fix S3 legacy layout migration

---
 internal/migrations/s3_layout.go | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/internal/migrations/s3_layout.go b/internal/migrations/s3_layout.go
index 0cfd40e60..afb14b848 100644
--- a/internal/migrations/s3_layout.go
+++ b/internal/migrations/s3_layout.go
@@ -8,6 +8,7 @@ import (
 
 	"github.com/restic/restic/internal/backend"
 	"github.com/restic/restic/internal/backend/s3"
+	"github.com/restic/restic/internal/cache"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/restic"
@@ -21,10 +22,25 @@ func init() {
 // "default" layout.
 type S3Layout struct{}
 
+func toS3Backend(repo restic.Repository) *s3.Backend {
+	b := repo.Backend()
+	// unwrap cache
+	if be, ok := b.(*cache.Backend); ok {
+		b = be.Backend
+	}
+
+	be, ok := b.(*s3.Backend)
+	if !ok {
+		debug.Log("backend is not s3")
+		return nil
+	}
+	return be
+}
+
 // Check tests whether the migration can be applied.
 func (m *S3Layout) Check(ctx context.Context, repo restic.Repository) (bool, error) {
-	be, ok := repo.Backend().(*s3.Backend)
-	if !ok {
+	be := toS3Backend(repo)
+	if be == nil {
 		debug.Log("backend is not s3")
 		return false, nil
 	}
@@ -75,8 +91,8 @@ func (m *S3Layout) moveFiles(ctx context.Context, be *s3.Backend, l backend.Layo
 
 // Apply runs the migration.
 func (m *S3Layout) Apply(ctx context.Context, repo restic.Repository) error {
-	be, ok := repo.Backend().(*s3.Backend)
-	if !ok {
+	be := toS3Backend(repo)
+	if be == nil {
 		debug.Log("backend is not s3")
 		return errors.New("backend is not s3")
 	}