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234 lines
8.3 KiB
Go
234 lines
8.3 KiB
Go
package graphdriver
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import (
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"errors"
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"fmt"
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"os"
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"path/filepath"
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"strings"
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"github.com/Sirupsen/logrus"
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"github.com/vbatts/tar-split/tar/storage"
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"github.com/docker/docker/pkg/archive"
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"github.com/docker/docker/pkg/idtools"
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)
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// FsMagic unsigned id of the filesystem in use.
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type FsMagic uint32
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const (
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// FsMagicUnsupported is a predefined constant value other than a valid filesystem id.
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FsMagicUnsupported = FsMagic(0x00000000)
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)
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var (
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// All registered drivers
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drivers map[string]InitFunc
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// ErrNotSupported returned when driver is not supported.
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ErrNotSupported = errors.New("driver not supported")
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// ErrPrerequisites retuned when driver does not meet prerequisites.
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ErrPrerequisites = errors.New("prerequisites for driver not satisfied (wrong filesystem?)")
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// ErrIncompatibleFS returned when file system is not supported.
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ErrIncompatibleFS = fmt.Errorf("backing file system is unsupported for this graph driver")
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)
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// InitFunc initializes the storage driver.
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type InitFunc func(root string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error)
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// ProtoDriver defines the basic capabilities of a driver.
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// This interface exists solely to be a minimum set of methods
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// for client code which choose not to implement the entire Driver
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// interface and use the NaiveDiffDriver wrapper constructor.
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//
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// Use of ProtoDriver directly by client code is not recommended.
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type ProtoDriver interface {
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// String returns a string representation of this driver.
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String() string
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// Create creates a new, empty, filesystem layer with the
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// specified id and parent and mountLabel. Parent and mountLabel may be "".
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Create(id, parent, mountLabel string, storageOpt map[string]string) error
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// Remove attempts to remove the filesystem layer with this id.
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Remove(id string) error
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// Get returns the mountpoint for the layered filesystem referred
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// to by this id. You can optionally specify a mountLabel or "".
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// Returns the absolute path to the mounted layered filesystem.
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Get(id, mountLabel string) (dir string, err error)
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// Put releases the system resources for the specified id,
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// e.g, unmounting layered filesystem.
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Put(id string) error
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// Exists returns whether a filesystem layer with the specified
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// ID exists on this driver.
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Exists(id string) bool
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// Status returns a set of key-value pairs which give low
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// level diagnostic status about this driver.
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Status() [][2]string
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// Returns a set of key-value pairs which give low level information
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// about the image/container driver is managing.
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GetMetadata(id string) (map[string]string, error)
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// Cleanup performs necessary tasks to release resources
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// held by the driver, e.g., unmounting all layered filesystems
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// known to this driver.
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Cleanup() error
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}
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// Driver is the interface for layered/snapshot file system drivers.
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type Driver interface {
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ProtoDriver
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// Diff produces an archive of the changes between the specified
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// layer and its parent layer which may be "".
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Diff(id, parent string) (archive.Archive, error)
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// Changes produces a list of changes between the specified layer
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// and its parent layer. If parent is "", then all changes will be ADD changes.
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Changes(id, parent string) ([]archive.Change, error)
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// ApplyDiff extracts the changeset from the given diff into the
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// layer with the specified id and parent, returning the size of the
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// new layer in bytes.
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// The archive.Reader must be an uncompressed stream.
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ApplyDiff(id, parent string, diff archive.Reader) (size int64, err error)
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// DiffSize calculates the changes between the specified id
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// and its parent and returns the size in bytes of the changes
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// relative to its base filesystem directory.
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DiffSize(id, parent string) (size int64, err error)
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}
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// DiffGetterDriver is the interface for layered file system drivers that
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// provide a specialized function for getting file contents for tar-split.
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type DiffGetterDriver interface {
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Driver
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// DiffGetter returns an interface to efficiently retrieve the contents
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// of files in a layer.
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DiffGetter(id string) (FileGetCloser, error)
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}
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// FileGetCloser extends the storage.FileGetter interface with a Close method
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// for cleaning up.
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type FileGetCloser interface {
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storage.FileGetter
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// Close cleans up any resources associated with the FileGetCloser.
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Close() error
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}
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func init() {
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drivers = make(map[string]InitFunc)
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}
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// Register registers a InitFunc for the driver.
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func Register(name string, initFunc InitFunc) error {
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if _, exists := drivers[name]; exists {
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return fmt.Errorf("Name already registered %s", name)
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}
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drivers[name] = initFunc
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return nil
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}
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// GetDriver initializes and returns the registered driver
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func GetDriver(name, home string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error) {
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if initFunc, exists := drivers[name]; exists {
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return initFunc(filepath.Join(home, name), options, uidMaps, gidMaps)
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}
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if pluginDriver, err := lookupPlugin(name, home, options); err == nil {
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return pluginDriver, nil
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}
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logrus.Errorf("Failed to GetDriver graph %s %s", name, home)
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return nil, ErrNotSupported
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}
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// getBuiltinDriver initializes and returns the registered driver, but does not try to load from plugins
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func getBuiltinDriver(name, home string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error) {
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if initFunc, exists := drivers[name]; exists {
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return initFunc(filepath.Join(home, name), options, uidMaps, gidMaps)
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}
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logrus.Errorf("Failed to built-in GetDriver graph %s %s", name, home)
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return nil, ErrNotSupported
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}
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// New creates the driver and initializes it at the specified root.
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func New(root string, name string, options []string, uidMaps, gidMaps []idtools.IDMap) (Driver, error) {
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if name != "" {
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logrus.Debugf("[graphdriver] trying provided driver %q", name) // so the logs show specified driver
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return GetDriver(name, root, options, uidMaps, gidMaps)
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}
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// Guess for prior driver
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driversMap := scanPriorDrivers(root)
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for _, name := range priority {
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if name == "vfs" {
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// don't use vfs even if there is state present.
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continue
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}
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if _, prior := driversMap[name]; prior {
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// of the state found from prior drivers, check in order of our priority
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// which we would prefer
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driver, err := getBuiltinDriver(name, root, options, uidMaps, gidMaps)
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if err != nil {
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// unlike below, we will return error here, because there is prior
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// state, and now it is no longer supported/prereq/compatible, so
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// something changed and needs attention. Otherwise the daemon's
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// images would just "disappear".
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logrus.Errorf("[graphdriver] prior storage driver %q failed: %s", name, err)
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return nil, err
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}
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// abort starting when there are other prior configured drivers
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// to ensure the user explicitly selects the driver to load
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if len(driversMap)-1 > 0 {
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var driversSlice []string
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for name := range driversMap {
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driversSlice = append(driversSlice, name)
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}
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return nil, fmt.Errorf("%q contains several valid graphdrivers: %s; Please cleanup or explicitly choose storage driver (-s <DRIVER>)", root, strings.Join(driversSlice, ", "))
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}
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logrus.Infof("[graphdriver] using prior storage driver %q", name)
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return driver, nil
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}
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}
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// Check for priority drivers first
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for _, name := range priority {
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driver, err := getBuiltinDriver(name, root, options, uidMaps, gidMaps)
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if err != nil {
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if isDriverNotSupported(err) {
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continue
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}
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return nil, err
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}
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return driver, nil
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}
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// Check all registered drivers if no priority driver is found
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for name, initFunc := range drivers {
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driver, err := initFunc(filepath.Join(root, name), options, uidMaps, gidMaps)
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if err != nil {
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if isDriverNotSupported(err) {
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continue
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}
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return nil, err
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}
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return driver, nil
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}
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return nil, fmt.Errorf("No supported storage backend found")
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}
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// isDriverNotSupported returns true if the error initializing
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// the graph driver is a non-supported error.
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func isDriverNotSupported(err error) bool {
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return err == ErrNotSupported || err == ErrPrerequisites || err == ErrIncompatibleFS
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}
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// scanPriorDrivers returns an un-ordered scan of directories of prior storage drivers
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func scanPriorDrivers(root string) map[string]bool {
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driversMap := make(map[string]bool)
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for driver := range drivers {
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p := filepath.Join(root, driver)
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if _, err := os.Stat(p); err == nil && driver != "vfs" {
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driversMap[driver] = true
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}
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}
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return driversMap
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}
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