Fix image pull after a failure

content/helpers.go

@@ -77,7 +77,7 @@ func Copy(ctx context.Context, cw Writer, r io.Reader, size int64, expected dige
 		r, err = seekReader(r, ws.Offset, size)
 		if err != nil {
 			if !isUnseekable(err) {
-				return errors.Wrapf(err, "unabled to resume write to %v", ws.Ref)
+				return errors.Wrapf(err, "unable to resume write to %v", ws.Ref)
 			}
 
 			// reader is unseekable, try to move the writer back to the start.

content/local/store_test.go

@@ -22,6 +22,7 @@ import (
 	"github.com/containerd/containerd/content/testsuite"
 	"github.com/containerd/containerd/testutil"
 	"github.com/opencontainers/go-digest"
+	"github.com/stretchr/testify/require"
 )
 
 type memoryLabelStore struct {
@@ -335,3 +336,42 @@ func checkWrite(ctx context.Context, t checker, cs content.Store, dgst digest.Di
 
 	return dgst
 }
+
+func TestWriterTruncateRecoversFromIncompleteWrite(t *testing.T) {
+	tmpdir, err := ioutil.TempDir("", "test-local-content-store-recover")
+	require.NoError(t, err)
+	defer os.RemoveAll(tmpdir)
+
+	cs, err := NewStore(tmpdir)
+	require.NoError(t, err)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	ref := "ref"
+	content := []byte("this is the content")
+	total := int64(len(content))
+	setupIncompleteWrite(ctx, t, cs, ref, total)
+
+	writer, err := cs.Writer(ctx, ref, total, "")
+	require.NoError(t, err)
+
+	require.NoError(t, writer.Truncate(0))
+
+	_, err = writer.Write(content)
+	require.NoError(t, err)
+
+	dgst := digest.FromBytes(content)
+	err = writer.Commit(ctx, total, dgst)
+	require.NoError(t, err)
+}
+
+func setupIncompleteWrite(ctx context.Context, t *testing.T, cs content.Store, ref string, total int64) {
+	writer, err := cs.Writer(ctx, ref, total, "")
+	require.NoError(t, err)
+
+	_, err = writer.Write([]byte("bad data"))
+	require.NoError(t, err)
+
+	require.NoError(t, writer.Close())
+}

content/local/writer.go

@@ -2,6 +2,7 @@ package local
 
 import (
 	"context"
+	"io"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -167,5 +168,8 @@ func (w *writer) Truncate(size int64) error {
 	}
 	w.offset = 0
 	w.digester.Hash().Reset()
+	if _, err := w.fp.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
 	return w.fp.Truncate(0)
 }