chunked: do not use a temporary file

and use directly the stream to create the temporary zstd:chunked file.

Signed-off-by: Giuseppe Scrivano <[email protected]>

pkg/chunked/storage_linux.go

@@ -26,6 +26,7 @@ import (
 	"github.com/containers/storage/pkg/chunked/toc"
 	"github.com/containers/storage/pkg/fsverity"
 	"github.com/containers/storage/pkg/idtools"
+	"github.com/containers/storage/pkg/ioutils"
 	"github.com/containers/storage/pkg/system"
 	jsoniter "github.com/json-iterator/go"
 	"github.com/klauspost/compress/zstd"
@@ -107,7 +108,7 @@ type chunkedLayerData struct {
 	Format graphdriver.DifferOutputFormat `json:"format"`
 }
 
-func (c *chunkedDiffer) convertTarToZstdChunked(destDirectory string, payload *os.File) (int64, *seekableFile, digest.Digest, map[string]string, error) {
+func (c *chunkedDiffer) convertTarToZstdChunked(destDirectory string, payload io.Reader) (int64, *seekableFile, digest.Digest, map[string]string, error) {
 	diff, err := archive.DecompressStream(payload)
 	if err != nil {
 		return 0, nil, "", nil, err
@@ -1076,7 +1077,7 @@ func makeEntriesFlat(mergedEntries []fileMetadata) ([]fileMetadata, error) {
 	return new, nil
 }
 
-func (c *chunkedDiffer) copyAllBlobToFile(destination *os.File) (digest.Digest, error) {
+func (c *chunkedDiffer) requestWholeBlob() (io.ReadCloser, digest.Digester, error) {
 	var payload io.ReadCloser
 	var streams chan io.ReadCloser
 	var errs chan error
@@ -1091,26 +1092,27 @@ func (c *chunkedDiffer) copyAllBlobToFile(destination *os.File) (digest.Digest,
 
 	streams, errs, err = c.stream.GetBlobAt(chunksToRequest)
 	if err != nil {
-		return "", err
+		return nil, nil, err
 	}
 	select {
 	case p := <-streams:
 		payload = p
 	case err := <-errs:
-		return "", err
+		return nil, nil, err
 	}
 	if payload == nil {
-		return "", errors.New("invalid stream returned")
+		return nil, nil, errors.New("invalid stream returned")
 	}
 
-	originalRawDigester := digest.Canonical.Digester()
+	digester := digest.Canonical.Digester()
 
-	r := io.TeeReader(payload, originalRawDigester.Hash())
+	r := io.TeeReader(payload, digester.Hash())
 
-	// copy the entire tarball and compute its digest
-	_, err = io.CopyBuffer(destination, r, c.copyBuffer)
+	rc := ioutils.NewReadCloserWrapper(r, func() error {
+		return payload.Close()
+	})
 
-	return originalRawDigester.Digest(), err
+	return rc, digester, nil
 }
 
 func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, differOpts *graphdriver.DifferOptions) (graphdriver.DriverWithDifferOutput, error) {
@@ -1131,32 +1133,17 @@ func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, diff
 	var convertedBlobSize int64
 
 	if c.convertToZstdChunked {
-		fd, err := unix.Open(dest, unix.O_TMPFILE|unix.O_RDWR|unix.O_CLOEXEC, 0o600)
+		payload, digester, err := c.requestWholeBlob()
 		if err != nil {
-			return graphdriver.DriverWithDifferOutput{}, &fs.PathError{Op: "open", Path: dest, Err: err}
+			return graphdriver.DriverWithDifferOutput{}, err
 		}
-		blobFile := os.NewFile(uintptr(fd), "blob-file")
 		defer func() {
-			if blobFile != nil {
-				blobFile.Close()
+			if payload != nil {
+				payload.Close()
 			}
 		}()
 
-		// calculate the checksum before accessing the file.
-		compressedDigest, err = c.copyAllBlobToFile(blobFile)
-		if err != nil {
-			return graphdriver.DriverWithDifferOutput{}, err
-		}
-
-		if compressedDigest != c.blobDigest {
-			return graphdriver.DriverWithDifferOutput{}, fmt.Errorf("invalid digest to convert: expected %q, got %q", c.blobDigest, compressedDigest)
-		}
-
-		if _, err := blobFile.Seek(0, io.SeekStart); err != nil {
-			return graphdriver.DriverWithDifferOutput{}, err
-		}
-
-		tarSize, fileSource, diffID, annotations, err := c.convertTarToZstdChunked(dest, blobFile)
+		tarSize, fileSource, diffID, annotations, err := c.convertTarToZstdChunked(dest, payload)
 		if err != nil {
 			return graphdriver.DriverWithDifferOutput{}, err
 		}
@@ -1165,9 +1152,15 @@ func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, diff
 		// need to keep it open until the entire file is processed.
 		defer fileSource.Close()
 
-		// Close the file so that the file descriptor is released and the file is deleted.
-		blobFile.Close()
-		blobFile = nil
+		// Make sure the entire payload is consumed.
+		_, _ = io.Copy(io.Discard, payload)
+		payload.Close()
+		payload = nil
+
+		compressedDigest = digester.Digest()
+		if compressedDigest != c.blobDigest {
+			return graphdriver.DriverWithDifferOutput{}, fmt.Errorf("invalid digest to convert: expected %q, got %q", c.blobDigest, compressedDigest)
+		}
 
 		tocDigest, err := toc.GetTOCDigest(annotations)
 		if err != nil {