Fix LCOW layer ordering

kevpar · kevpar · commit 225d9b120c13 · 2019-02-07T17:27:01.000-08:00
Due to an error in the OCI specf for layerFolders, the runhcs shim was
passing the layers for LCOW in reverse order. This fixes the ordering
by simply removing the code which reversed the layers for LCOW.

Signed-off-by: Kevin Parsons &lt;kevpar@microsoft.com&gt;
diff --git a/runtime/v2/runhcs/service.go b/runtime/v2/runhcs/service.go
@@ -366,11 +366,11 @@ func writeMountsToConfig(bundle string, mounts []*containerd_types.Mount) error
 		return errors.Errorf("unsupported mount type '%s'", m.Type)
 	}
 
-	// parentLayerPaths are passed in layerN, layerN-1, ..., layer 0
+	// parentLayerPaths are passed in:
+	//   layerN, layerN-1, ..., layer0
 	//
 	// The OCI spec expects:
-	//   windows-layer order is layerN, layerN-1, ..., layer0, scratch
-	//   lcow-layer    order is layer0,   layer1, ..., layerN, scratch
+	//   layerN, layerN-1, ..., layer0, scratch
 	var parentLayerPaths []string
 	for _, option := range mounts[0].Options {
 		if strings.HasPrefix(option, mount.ParentLayerPathsFlag) {
@@ -382,12 +382,6 @@ func writeMountsToConfig(bundle string, mounts []*containerd_types.Mount) error
 	}
 
 	if m.Type == "lcow-layer" {
-		// Reverse the lcow-layer parents
-		for i := len(parentLayerPaths)/2 - 1; i >= 0; i-- {
-			opp := len(parentLayerPaths) - 1 - i
-			parentLayerPaths[i], parentLayerPaths[opp] = parentLayerPaths[opp], parentLayerPaths[i]
-		}
-
 		// If we are creating LCOW make sure that spec.Windows is filled out before
 		// appending layer folders.
 		if spec.Windows == nil {
