Cleanup handling of default driver name, when storage.conf has drivername=""

drivers/aufs/aufs.go

@@ -93,7 +93,7 @@ func Init(home string, options graphdriver.Options) (graphdriver.Driver, error)
 
 	fsMagic, err := graphdriver.GetFSMagic(home)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrapf(err, "aufs: failed to getfsmagic %s", home)
 	}
 	if fsName, ok := graphdriver.FsNames[fsMagic]; ok {
 		backingFs = fsName
@@ -109,7 +109,7 @@ func Init(home string, options graphdriver.Options) (graphdriver.Driver, error)
 	for _, option := range options.DriverOptions {
 		key, val, err := parsers.ParseKeyValueOpt(option)
 		if err != nil {
-			return nil, err
+			return nil, errors.Wrapf(err, "aufs: ParseKeyValueOpt %s", option)
 		}
 		key = strings.ToLower(key)
 		switch key {
@@ -137,7 +137,7 @@ func Init(home string, options graphdriver.Options) (graphdriver.Driver, error)
 
 	rootUID, rootGID, err := idtools.GetRootUIDGID(options.UIDMaps, options.GIDMaps)
 	if err != nil {
-		return nil, err
+		return nil, errors.Wrapf(err, "aufs: failed to GetRootUIDGID")
 	}
 	// Create the root aufs driver dir and return
 	// if it already exists
@@ -146,17 +146,17 @@ func Init(home string, options graphdriver.Options) (graphdriver.Driver, error)
 		if os.IsExist(err) {
 			return a, nil
 		}
-		return nil, err
+		return nil, errors.Wrapf(err, "aufs: failed to mkdirallas: %s", home)
 	}
 
 	if err := mountpk.MakePrivate(home); err != nil {
-		return nil, err
+		return nil, errors.Wrapf(err, "aufs: failed to MakePrivate: %s", home)
 	}
 
 	// Populate the dir structure
 	for _, p := range paths {
 		if err := idtools.MkdirAllAs(path.Join(home, p), 0700, rootUID, rootGID); err != nil {
-			return nil, err
+			return nil, errors.Wrapf(err, "aufs: failed to MakePrivate: %s", path.Join(home, p))
 		}
 	}
 	logger := logrus.WithFields(logrus.Fields{
@@ -326,7 +326,7 @@ func (a *Driver) createDirsFor(id, parent string) error {
 			rootPair.GID = int(st.GID())
 		}
 		if err := idtools.MkdirAllAndChownNew(path.Join(a.rootPath(), p, id), os.FileMode(0755), rootPair); err != nil {
-			return err
+			return errors.Wrapf(err, "aufs: failed to makedir %s", path.Join(a.rootPath(), p))
 		}
 	}
 	return nil

drivers/driver.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -24,6 +25,9 @@ const (
 )
 
 var (
+	once                 sync.Once
+	defaultDriverName    string
+	defaultDriverNameErr error
 	// All registered drivers
 	drivers map[string]InitFunc
 
@@ -209,6 +213,46 @@ func Register(name string, initFunc InitFunc) error {
 	return nil
 }
 
+// GetDefaultDriverName returns the driver name
+func GetDefaultDriverName(config Options) (string, error) {
+	once.Do(func() {
+		driver, err := getDefaultDriver(config)
+		if err != nil {
+			defaultDriverNameErr = err
+		} else {
+			defaultDriverName = driver.String()
+		}
+	})
+	return defaultDriverName, defaultDriverNameErr
+}
+
+// GetDefaultDriver initializes and returns the registered driver
+func getDefaultDriver(config Options) (Driver, error) {
+	// Check for priority drivers first
+	for _, name := range priority {
+		driver, err := getBuiltinDriver(name, config.Root, config)
+		if err != nil {
+			if isDriverNotSupported(err) {
+				continue
+			}
+			return nil, err
+		}
+		return driver, nil
+	}
+	// Check all registered drivers if no priority driver is found
+	for name, initFunc := range drivers {
+		driver, err := initFunc(filepath.Join(config.Root, name), config)
+		if err != nil {
+			if isDriverNotSupported(err) {
+				continue
+			}
+			return nil, err
+		}
+		return driver, nil
+	}
+	return nil, fmt.Errorf("No supported storage backend found")
+}
+
 // GetDriver initializes and returns the registered driver
 func GetDriver(name string, config Options) (Driver, error) {
 	if initFunc, exists := drivers[name]; exists {
@@ -281,30 +325,7 @@ func New(name string, config Options) (Driver, error) {
 		}
 	}
 
-	// Check for priority drivers first
-	for _, name := range priority {
-		driver, err := getBuiltinDriver(name, config.Root, config)
-		if err != nil {
-			if isDriverNotSupported(err) {
-				continue
-			}
-			return nil, err
-		}
-		return driver, nil
-	}
-
-	// Check all registered drivers if no priority driver is found
-	for name, initFunc := range drivers {
-		driver, err := initFunc(filepath.Join(config.Root, name), config)
-		if err != nil {
-			if isDriverNotSupported(err) {
-				continue
-			}
-			return nil, err
-		}
-		return driver, nil
-	}
-	return nil, fmt.Errorf("No supported storage backend found")
+	return getDefaultDriver(config)
 }
 
 // isDriverNotSupported returns true if the error initializing

store.go

@@ -3278,15 +3278,15 @@ func ReloadConfigurationFile(configFile string, storeOptions *StoreOptions) {
 	data, err := ioutil.ReadFile(configFile)
 	if err != nil {
 		if !os.IsNotExist(err) {
-			fmt.Printf("Failed to read %s %v\n", configFile, err.Error())
+			fmt.Fprintf(os.Stderr, "Failed to read %s %v\n", configFile, err.Error())
 			return
 		}
 	}
 
 	config := new(tomlConfig)
 
 	if _, err := toml.Decode(string(data), config); err != nil {
-		fmt.Printf("Failed to parse %s %v\n", configFile, err.Error())
+		fmt.Fprintf(os.Stderr, "Failed to parse %s %v\n", configFile, err.Error())
 		return
 	}
 	if config.Storage.Driver != "" {
@@ -3322,7 +3322,7 @@ func ReloadConfigurationFile(configFile string, storeOptions *StoreOptions) {
 	if config.Storage.Options.RemapUser != "" && config.Storage.Options.RemapGroup != "" {
 		mappings, err := idtools.NewIDMappings(config.Storage.Options.RemapUser, config.Storage.Options.RemapGroup)
 		if err != nil {
-			fmt.Printf("Error initializing ID mappings for %s:%s %v\n", config.Storage.Options.RemapUser, config.Storage.Options.RemapGroup, err)
+			fmt.Fprintf(os.Stderr, "Error initializing ID mappings for %s:%s %v\n", config.Storage.Options.RemapUser, config.Storage.Options.RemapGroup, err)
 			return
 		}
 		storeOptions.UIDMap = mappings.UIDs()
@@ -3331,20 +3331,34 @@ func ReloadConfigurationFile(configFile string, storeOptions *StoreOptions) {
 
 	uidmap, err := idtools.ParseIDMap([]string{config.Storage.Options.RemapUIDs}, "remap-uids")
 	if err != nil {
-		fmt.Print(err)
+		fmt.Fprint(os.Stderr, err)
 	} else {
 		storeOptions.UIDMap = append(storeOptions.UIDMap, uidmap...)
 	}
 	gidmap, err := idtools.ParseIDMap([]string{config.Storage.Options.RemapGIDs}, "remap-gids")
 	if err != nil {
-		fmt.Print(err)
+		fmt.Fprint(os.Stderr, err)
 	} else {
 		storeOptions.GIDMap = append(storeOptions.GIDMap, gidmap...)
 	}
 	if os.Getenv("STORAGE_DRIVER") != "" {
 		storeOptions.GraphDriverName = os.Getenv("STORAGE_DRIVER")
 	}
 
+	if storeOptions.GraphDriverName == "" {
+		options := drivers.Options{
+			Root:    storeOptions.GraphRoot,
+			RunRoot: storeOptions.RunRoot,
+			UIDMaps: storeOptions.UIDMap,
+			GIDMaps: storeOptions.GIDMap,
+		}
+		name, err := drivers.GetDefaultDriverName(options)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error getting default driver name: %v\n", err)
+		} else {
+			storeOptions.GraphDriverName = name
+		}
+	}
 	storeOptions.GraphDriverOptions = cfg.GetGraphDriverOptions(storeOptions.GraphDriverName, config.Storage.Options)
 
 	if os.Getenv("STORAGE_OPTS") != "" {

tests/helpers.bash

@@ -54,6 +54,7 @@ populate() {
 	lowerlayer="$output"
 	# Mount the layer.
 	run storage --debug=false mount $lowerlayer
+	echo $output
 	[ "$status" -eq 0 ]
 	[ "$output" != "" ]
 	local lowermount="$output"
@@ -81,11 +82,13 @@ populate() {
 
 	# Create a second layer based on the first.
 	run storage --debug=false create-layer "$lowerlayer"
+	echo $output
 	[ "$status" -eq 0 ]
 	[ "$output" != "" ]
 	midlayer="$output"
 	# Mount the second layer.
 	run storage --debug=false mount $midlayer
+	echo $output
 	[ "$status" -eq 0 ]
 	[ "$output" != "" ]
 	local midmount="$output"
@@ -133,11 +136,13 @@ populate() {
 
 	# Create a third layer based on the second.
 	run storage --debug=false create-layer "$midlayer"
+	echo $output
 	[ "$status" -eq 0 ]
 	[ "$output" != "" ]
 	upperlayer="$output"
 	# Mount the third layer.
 	run storage --debug=false mount $upperlayer
+	echo $output
 	[ "$status" -eq 0 ]
 	[ "$output" != "" ]
 	local uppermount="$output"