add scoutfs move_blocks

scoutfs.go

@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"math"
 	"os"
@@ -716,3 +717,44 @@ func GetDF(f *os.File) (DiskUsage, error) {
 		FreeDataBlocks:  dataFree,
 	}, nil
 }
+
+// MoveData will move all of the extents in "from" file handle
+// and append to the end of "to" file handle.
+// The end of "to" must be 4KB aligned boundary.
+// errors this can return:
+// EINVAL: from_off, len, or to_off aren't a multiple of 4KB; the source
+//	   and destination files are the same inode; either the source or
+//	   destination is not a regular file; the destination file has
+//	   an existing overlapping extent.
+// EOVERFLOW: either from_off + len or to_off + len exceeded 64bits.
+// EBADF: from_fd isn't a valid open file descriptor.
+// EXDEV: the source and destination files are in different filesystems.
+// EISDIR: either the source or destination is a directory.
+// ENODATA: either the source or destination file have offline extents.
+func MoveData(from, to *os.File) error {
+	ffi, err := from.Stat()
+	if err != nil {
+		return fmt.Errorf("stat from: %v", err)
+	}
+	tfi, err := to.Stat()
+	if err != nil {
+		return fmt.Errorf("stat to: %v", err)
+	}
+
+	mb := moveBlocks{
+		From_fd:  uint64(from.Fd()),
+		From_off: 0,
+		Len:      uint64(ffi.Size()),
+		To_off:   uint64(tfi.Size()),
+	}
+
+	_, err = scoutfsctl(to, IOCMOVEBLOCKS, unsafe.Pointer(&mb))
+	if err != nil {
+		return err
+	}
+
+	from.Truncate(0)
+	from.Seek(0, io.SeekStart)
+
+	return nil
+}