Try to resize data and metadata loopback file when initiating devicemapper

Signed-off-by: Chun Chen <ramichen@tencent.com>
Upstream-commit: 2458452a3b96d0e6f6dfa44d7c30585db83c2fd1
Component: engine

components/engine/daemon/graphdriver/devmapper/deviceset.go

@@ -232,7 +232,7 @@ func (devices *DeviceSet) hasImage(name string) bool {
 
 // ensureImage creates a sparse file of <size> bytes at the path
 // <root>/devicemapper/<name>.
-// If the file already exists, it does nothing.
+// If the file already exists and new size is larger than its current size, it grows to the new size.
 // Either way it returns the full path.
 func (devices *DeviceSet) ensureImage(name string, size int64) (string, error) {
 	dirname := devices.loopbackDir()
@@ -242,7 +242,7 @@ func (devices *DeviceSet) ensureImage(name string, size int64) (string, error) {
 		return "", err
 	}
 
-	if _, err := os.Stat(filename); err != nil {
+	if fi, err := os.Stat(filename); err != nil {
 		if !os.IsNotExist(err) {
 			return "", err
 		}
@@ -256,6 +256,19 @@ func (devices *DeviceSet) ensureImage(name string, size int64) (string, error) {
 		if err := file.Truncate(size); err != nil {
 			return "", err
 		}
+	} else {
+		if fi.Size() < size {
+			file, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE, 0600)
+			if err != nil {
+				return "", err
+			}
+			defer file.Close()
+			if err := file.Truncate(size); err != nil {
+				return "", fmt.Errorf("Unable to grow loopback file %s: %v", filename, err)
+			}
+		} else if fi.Size() > size {
+			logrus.Warnf("Can't shrink loopback file %s", filename)
+		}
 	}
 	return filename, nil
 }

components/engine/daemon/graphdriver/devmapper/devmapper_test.go

@@ -3,8 +3,10 @@
 package devmapper
 
 import (
+	"fmt"
 	"testing"
 
+	"github.com/docker/docker/daemon/graphdriver"
 	"github.com/docker/docker/daemon/graphdriver/graphtest"
 )
 
@@ -40,3 +42,40 @@ func TestDevmapperCreateSnap(t *testing.T) {
 func TestDevmapperTeardown(t *testing.T) {
 	graphtest.PutDriver(t)
 }
+
+func TestDevmapperReduceLoopBackSize(t *testing.T) {
+	tenMB := int64(10 * 1024 * 1024)
+	testChangeLoopBackSize(t, -tenMB, defaultDataLoopbackSize, defaultMetaDataLoopbackSize)
+}
+
+func TestDevmapperIncreaseLoopBackSize(t *testing.T) {
+	tenMB := int64(10 * 1024 * 1024)
+	testChangeLoopBackSize(t, tenMB, defaultDataLoopbackSize+tenMB, defaultMetaDataLoopbackSize+tenMB)
+}
+
+func testChangeLoopBackSize(t *testing.T, delta, expectDataSize, expectMetaDataSize int64) {
+	driver := graphtest.GetDriver(t, "devicemapper").(*graphtest.Driver).Driver.(*graphdriver.NaiveDiffDriver).ProtoDriver.(*Driver)
+	defer graphtest.PutDriver(t)
+	// make sure data or metadata loopback size are the default size
+	if s := driver.DeviceSet.Status(); s.Data.Total != uint64(defaultDataLoopbackSize) || s.Metadata.Total != uint64(defaultMetaDataLoopbackSize) {
+		t.Fatalf("data or metadata loop back size is incorrect")
+	}
+	if err := driver.Cleanup(); err != nil {
+		t.Fatal(err)
+	}
+	//Reload
+	d, err := Init(driver.home, []string{
+		fmt.Sprintf("dm.loopdatasize=%d", defaultDataLoopbackSize+delta),
+		fmt.Sprintf("dm.loopmetadatasize=%d", defaultMetaDataLoopbackSize+delta),
+	})
+	if err != nil {
+		t.Fatalf("error creating devicemapper driver: %v", err)
+	}
+	driver = d.(*graphdriver.NaiveDiffDriver).ProtoDriver.(*Driver)
+	if s := driver.DeviceSet.Status(); s.Data.Total != uint64(expectDataSize) || s.Metadata.Total != uint64(expectMetaDataSize) {
+		t.Fatalf("data or metadata loop back size is incorrect")
+	}
+	if err := driver.Cleanup(); err != nil {
+		t.Fatal(err)
+	}
+}

components/engine/daemon/graphdriver/devmapper/driver.go

@@ -57,7 +57,7 @@ func Init(home string, options []string) (graphdriver.Driver, error) {
 		home:      home,
 	}
 
-	return graphdriver.NaiveDiffDriver(d), nil
+	return graphdriver.NewNaiveDiffDriver(d), nil
 }
 
 func (d *Driver) String() string {