b2: fix server side copies greater than 4GB

After the multipart chunker refactor the multipart chunked server side
copy was accidentally sending one part too many. The last part was 0
length which was rejected by b2.

This was caused by a simple off by one error in the refactoring where
we went from 1 based part number counting to 0 based part number
counting.

Fixing this revealed that the metadata wasn't being re-read for the
copied object either.

This fixes both of those issues and adds an integration tests so it
won't happen again.

See: https://forum.rclone.org/t/large-server-side-copy-in-b2-fails-due-to-bad-byte-range/42294

backend/b2/b2.go

@@ -1332,7 +1332,11 @@ func (f *Fs) copy(ctx context.Context, dstObj *Object, srcObj *Object, newInfo *
 		if err != nil {
 			return err
 		}
-		return up.Copy(ctx)
+		err = up.Copy(ctx)
+		if err != nil {
+			return err
+		}
+		return dstObj.decodeMetaDataFileInfo(up.info)
 	}
 
 	dstBucket, dstPath := dstObj.split()

backend/b2/b2_internal_test.go

@@ -1,10 +1,15 @@
 package b2
 
 import (
+	"context"
 	"testing"
 	"time"
 
 	"github.com/rclone/rclone/fstest"
+	"github.com/rclone/rclone/fstest/fstests"
+	"github.com/rclone/rclone/lib/random"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 // Test b2 string encoding
@@ -168,3 +173,52 @@ func TestParseTimeString(t *testing.T) {
 	}
 
 }
+
+// The integration tests do a reasonable job of testing the normal
+// copy but don't test the chunked copy.
+func (f *Fs) InternalTestChunkedCopy(t *testing.T) {
+	ctx := context.Background()
+
+	contents := random.String(8 * 1024 * 1024)
+	item := fstest.NewItem("chunked-copy", contents, fstest.Time("2001-05-06T04:05:06.499999999Z"))
+	src := fstests.PutTestContents(ctx, t, f, &item, contents, true)
+	defer func() {
+		assert.NoError(t, src.Remove(ctx))
+	}()
+
+	var itemCopy = item
+	itemCopy.Path += ".copy"
+
+	// Set copy cutoff to mininum value so we make chunks
+	origCutoff := f.opt.CopyCutoff
+	f.opt.CopyCutoff = 5 * 1024 * 1024
+	defer func() {
+		f.opt.CopyCutoff = origCutoff
+	}()
+
+	// Do the copy
+	dst, err := f.Copy(ctx, src, itemCopy.Path)
+	require.NoError(t, err)
+	defer func() {
+		assert.NoError(t, dst.Remove(ctx))
+	}()
+
+	// Check size
+	assert.Equal(t, src.Size(), dst.Size())
+
+	// Check modtime
+	srcModTime := src.ModTime(ctx)
+	dstModTime := dst.ModTime(ctx)
+	assert.True(t, srcModTime.Equal(dstModTime))
+
+	// Make sure contents are correct
+	gotContents := fstests.ReadObject(ctx, t, dst, -1)
+	assert.Equal(t, contents, gotContents)
+}
+
+// -run TestIntegration/FsMkdir/FsPutFiles/Internal
+func (f *Fs) InternalTest(t *testing.T) {
+	t.Run("ChunkedCopy", f.InternalTestChunkedCopy)
+}
+
+var _ fstests.InternalTester = (*Fs)(nil)

backend/b2/upload.go

@@ -456,7 +456,7 @@ func (up *largeUpload) Copy(ctx context.Context) (err error) {
 		remaining = up.size
 	)
 	g.SetLimit(up.f.opt.UploadConcurrency)
-	for part := 0; part <= up.parts; part++ {
+	for part := 0; part < up.parts; part++ {
 		// Fail fast, in case an errgroup managed function returns an error
 		// gCtx is cancelled. There is no point in copying all the other parts.
 		if gCtx.Err() != nil {