repository: cancel streampack context after error

internal/repository/repository.go

@@ -11,7 +11,7 @@ import (
 	"sort"
 	"sync"
 
-	"github.com/cenkalti/backoff"
+	"github.com/cenkalti/backoff/v4"
 	"github.com/restic/chunker"
 	"github.com/restic/restic/internal/backend/dryrun"
 	"github.com/restic/restic/internal/cache"
@@ -746,6 +746,10 @@ type Loader interface {
 
 type BackendLoadFn func(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error
 
+// StreamPack loads the listed blobs from the specified pack file. The plaintext blob is passed to
+// the handleBlobFn callback or an error if decryption failed or the blob hash does not match. In
+// case of download errors handleBlobFn might be called multiple times for the same blob. If the
+// callback returns an error, then StreamPack will abort and not retry it.
 func StreamPack(ctx context.Context, beLoad BackendLoadFn, key *crypto.Key, packID restic.ID, blobs []restic.Blob, handleBlobFn func(blob restic.BlobHandle, buf []byte, err error) error) error {
 	if len(blobs) == 0 {
 		// nothing to do
@@ -762,8 +766,13 @@ func StreamPack(ctx context.Context, beLoad BackendLoadFn, key *crypto.Key, pack
 
 	debug.Log("streaming pack %v (%d to %d bytes), blobs: %v", packID, dataStart, dataEnd, len(blobs))
 
+	ctx, cancel := context.WithCancel(ctx)
 	// stream blobs in pack
 	err := beLoad(ctx, h, int(dataEnd-dataStart), int64(dataStart), func(rd io.Reader) error {
+		// prevent callbacks after cancelation
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
 		bufferSize := int(dataEnd - dataStart)
 		if bufferSize > MaxStreamBufferSize {
 			bufferSize = MaxStreamBufferSize
@@ -823,6 +832,7 @@ func StreamPack(ctx context.Context, beLoad BackendLoadFn, key *crypto.Key, pack
 
 			err = handleBlobFn(entry.BlobHandle, plaintext, err)
 			if err != nil {
+				cancel()
 				return backoff.Permanent(err)
 			}
 		}