Merge pull request #2718 from nirs/convert-to-raw

Fix nativeimgutil.ConvertToRaw()

pkg/nativeimgutil/nativeimgutil.go

@@ -68,6 +68,13 @@ func ConvertToRaw(source, dest string, size *int64, allowSourceWithBackingFile b
  defer os.RemoveAll(destTmp)
  defer destTmpF.Close()
 
+ // Truncating before copy eliminates the seeks during copy and provide a
+ // hint to the file system that may minimize allocations and fragmanation
+ // of the file.
+ if err := MakeSparse(destTmpF, srcImg.Size()); err != nil {
+ return err
+ }
+
  // Copy
  srcImgR := io.NewSectionReader(srcImg, 0, srcImg.Size())
  bar, err := progressbar.New(srcImg.Size())
@@ -124,8 +131,8 @@ func convertRawToRaw(source, dest string, size *int64) error {
 
 func copySparse(w *os.File, r io.Reader, bufSize int64) (int64, error) {
  var (
- n  int64
- eof, hasWrites bool
+ n int64
+ eof bool
  )
 
  zeroBuf := make([]byte, bufSize)
@@ -139,31 +146,22 @@ func copySparse(w *os.File, r io.Reader, bufSize int64) (int64, error) {
  }
  }
  // TODO: qcow2reader should have a method to notify whether buf is zero
- if bytes.Equal(buf, zeroBuf) {
- if _, sErr := w.Seek(int64(rN), io.SeekCurrent); sErr != nil {
- return n, fmt.Errorf("failed seek: %w", sErr)
- }
- // no need to ftruncate here
+ if bytes.Equal(buf[:rN], zeroBuf[:rN]) {
  n += int64(rN)
  } else {
- hasWrites = true
- wN, wErr := w.Write(buf)
+ wN, wErr := w.WriteAt(buf[:rN], n)
  if wN > 0 {
  n += int64(wN)
  }
  if wErr != nil {
- return n, fmt.Errorf("failed to read: %w", wErr)
+ return n, fmt.Errorf("failed to write: %w", wErr)
  }
  if wN != rN {
  return n, fmt.Errorf("read %d, but wrote %d bytes", rN, wN)
  }
  }
  }
 
- // Ftruncate must be run if the file contains only zeros
- if !hasWrites {
- return n, MakeSparse(w, n)
- }
  return n, nil
 }