vfs: add read write files and caching #711

This adds new flags to mount, cmount, serve * --cache-max-age duration Max age of objects in the cache. (default 1h0m0s) --cache-mode string Cache mode off|minimal|writes|full (default "off") --cache-poll-interval duration Interval to poll the cache for stale objects. (default 1m0s)
2024-11-07 09:04:52 +01:00 · 2017-11-06 21:38:52 +00:00 · 2017-11-06 21:38:52 +00:00 · 7f20e1d7f3
commit 7f20e1d7f3
parent bb0ce0cb5f
10 changed files with 1438 additions and 55 deletions
--- a/vfs/cache.go
+++ b/vfs/cache.go
@ -0,0 +1,276 @@
+// This deals with caching of files locally
+
+package vfs
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/djherbis/times"
+	"github.com/ncw/rclone/fs"
+	"github.com/pkg/errors"
+	"golang.org/x/net/context"
+)
+
+// CacheMode controls the functionality of the cache
+type CacheMode byte
+
+// CacheMode options
+const (
+	CacheModeOff     CacheMode = iota // cache nothing - return errors for writes which can't be satisfied
+	CacheModeMinimal                  // cache only the minimum, eg read/write opens
+	CacheModeWrites                   // cache all files opened with write intent
+	CacheModeFull                     // cache all files opened in any mode
+)
+
+var cacheModeToString = []string{
+	CacheModeOff:     "off",
+	CacheModeMinimal: "minimal",
+	CacheModeWrites:  "writes",
+	CacheModeFull:    "full",
+}
+
+// String turns a CacheMode into a string
+func (l CacheMode) String() string {
+	if l >= CacheMode(len(cacheModeToString)) {
+		return fmt.Sprintf("CacheMode(%d)", l)
+	}
+	return cacheModeToString[l]
+}
+
+// Set a CacheMode
+func (l *CacheMode) Set(s string) error {
+	for n, name := range cacheModeToString {
+		if s != "" && name == s {
+			*l = CacheMode(n)
+			return nil
+		}
+	}
+	return errors.Errorf("Unknown cache mode level %q", s)
+}
+
+// Type of the value
+func (l *CacheMode) Type() string {
+	return "string"
+}
+
+// cache opened files
+type cache struct {
+	f      fs.Fs                 // fs for the cache directory
+	opt    *Options              // vfs Options
+	root   string                // root of the cache directory
+	itemMu sync.Mutex            // protects the next two maps
+	item   map[string]*cacheItem // files in the cache
+}
+
+// cacheItem is stored in the item map
+type cacheItem struct {
+	opens int       // number of times file is open
+	atime time.Time // last time file was accessed
+}
+
+// newCacheItem returns an item for the cache
+func newCacheItem() *cacheItem {
+	return &cacheItem{atime: time.Now()}
+}
+
+// newCache creates a new cache heirachy for f
+//
+// This starts background goroutines which can be cancelled with the
+// context passed in.
+func newCache(ctx context.Context, f fs.Fs, opt *Options) (*cache, error) {
+	fRoot := filepath.FromSlash(f.Root())
+	if runtime.GOOS == "windows" {
+		if strings.HasPrefix(fRoot, `\\?`) {
+			fRoot = fRoot[3:]
+		}
+		fRoot = strings.Replace(fRoot, ":", "", -1)
+	}
+	root := filepath.Join(fs.CacheDir, "vfs", f.Name(), fRoot)
+	fs.Debugf(nil, "vfs cache root is %q", root)
+
+	f, err := fs.NewFs(root)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to create cache remote")
+	}
+
+	c := &cache{
+		f:    f,
+		opt:  opt,
+		root: root,
+		item: make(map[string]*cacheItem),
+	}
+
+	go c.cleaner(ctx)
+
+	return c, nil
+}
+
+// mkdir makes the directory for name in the cache and returns an os
+// path for the file
+func (c *cache) mkdir(name string) (string, error) {
+	parent := path.Dir(name)
+	if parent == "." {
+		parent = ""
+	}
+	leaf := path.Base(name)
+	parentPath := filepath.Join(c.root, filepath.FromSlash(parent))
+	err := os.MkdirAll(parentPath, 0700)
+	if err != nil {
+		return "", errors.Wrap(err, "make cache directory failed")
+	}
+	return filepath.Join(parentPath, leaf), nil
+}
+
+// _get gets name from the cache or creates a new one
+//
+// must be called with itemMu held
+func (c *cache) _get(name string) *cacheItem {
+	item := c.item[name]
+	if item == nil {
+		item = newCacheItem()
+		c.item[name] = item
+	}
+	return item
+}
+
+// get gets name from the cache or creates a new one
+func (c *cache) get(name string) *cacheItem {
+	c.itemMu.Lock()
+	item := c._get(name)
+	c.itemMu.Unlock()
+	return item
+}
+
+// updateTime sets the atime of the name to that passed in if it is
+// newer than the existing or there isn't an existing time.
+func (c *cache) updateTime(name string, when time.Time) {
+	c.itemMu.Lock()
+	item := c._get(name)
+	if when.Sub(item.atime) > 0 {
+		fs.Debugf(name, "updateTime: setting atime to %v", when)
+		item.atime = when
+	}
+	c.itemMu.Unlock()
+}
+
+// open marks name as open
+func (c *cache) open(name string) {
+	c.itemMu.Lock()
+	item := c._get(name)
+	item.opens++
+	item.atime = time.Now()
+	c.itemMu.Unlock()
+}
+
+// close marks name as closed
+func (c *cache) close(name string) {
+	c.itemMu.Lock()
+	item := c._get(name)
+	item.opens--
+	item.atime = time.Now()
+	if item.opens < 0 {
+		fs.Errorf(name, "cache: double close")
+	}
+	c.itemMu.Unlock()
+}
+
+// cleanUp empties the cache of everything
+func (c *cache) cleanUp() error {
+	return os.RemoveAll(c.root)
+}
+
+// updateAtimes walks the cache updating any atimes it finds
+func (c *cache) updateAtimes() error {
+	return filepath.Walk(c.root, func(osPath string, fi os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if !fi.IsDir() {
+			// Find path relative to the cache root
+			name, err := filepath.Rel(c.root, osPath)
+			if err != nil {
+				return errors.Wrap(err, "filepath.Rel failed in updatAtimes")
+			}
+			// And convert into slashes
+			name = filepath.ToSlash(name)
+
+			// Update the atime with that of the file
+			atime := times.Get(fi).AccessTime()
+			c.updateTime(name, atime)
+		}
+		return nil
+	})
+}
+
+// purgeOld gets rid of any files that are over age
+func (c *cache) purgeOld(maxAge time.Duration) {
+	c.itemMu.Lock()
+	defer c.itemMu.Unlock()
+	cutoff := time.Now().Add(-maxAge)
+	for name, item := range c.item {
+		// If not locked and access time too long ago - delete the file
+		dt := item.atime.Sub(cutoff)
+		// fs.Debugf(name, "atime=%v cutoff=%v, dt=%v", item.atime, cutoff, dt)
+		if item.opens == 0 && dt < 0 {
+			osPath := filepath.Join(c.root, filepath.FromSlash(name))
+			err := os.Remove(osPath)
+			if err != nil {
+				fs.Errorf(name, "Failed to remove from cache: %v", err)
+			} else {
+				fs.Debugf(name, "Removed from cache")
+			}
+			// Remove the entry
+			delete(c.item, name)
+		}
+	}
+}
+
+// clean empties the cache of stuff if it can
+func (c *cache) clean() {
+	// Cache may be empty so end
+	_, err := os.Stat(c.root)
+	if os.IsNotExist(err) {
+		return
+	}
+
+	fs.Debugf(nil, "Cleaning the cache")
+
+	// first walk the FS to update the atimes
+	err = c.updateAtimes()
+	if err != nil {
+		fs.Errorf(nil, "Error traversing cache %q: %v", c.root, err)
+	}
+
+	// Now remove any files that are over age
+	c.purgeOld(c.opt.CacheMaxAge)
+
+	// Now tidy up any empty directories
+	err = fs.Rmdirs(c.f, "")
+	if err != nil {
+		fs.Errorf(c.f, "Failed to remove empty directories from cache: %v", err)
+	}
+}
+
+// cleaner calls clean at regular intervals
+//
+// doesn't return until context is cancelled
+func (c *cache) cleaner(ctx context.Context) {
+	timer := time.NewTicker(c.opt.CachePollInterval)
+	defer timer.Stop()
+	for {
+		select {
+		case <-timer.C:
+			c.clean()
+		case <-ctx.Done():
+			fs.Debugf(nil, "cache cleaner exiting")
+			return
+		}
+	}
+}
--- a/vfs/cache_test.go
+++ b/vfs/cache_test.go
@ -0,0 +1,144 @@
+package vfs
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/djherbis/times"
+	"github.com/ncw/rclone/fstest"
+	"github.com/spf13/pflag"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/net/context" // switch to "context" when we stop supporting go1.6
+)
+
+// Check CacheMode it satisfies the pflag interface
+var _ pflag.Value = (*CacheMode)(nil)
+
+func TestCacheModeString(t *testing.T) {
+	assert.Equal(t, "off", CacheModeOff.String())
+	assert.Equal(t, "full", CacheModeFull.String())
+	assert.Equal(t, "CacheMode(17)", CacheMode(17).String())
+}
+
+func TestCacheModeSet(t *testing.T) {
+	var m CacheMode
+
+	err := m.Set("full")
+	assert.NoError(t, err)
+	assert.Equal(t, CacheModeFull, m)
+
+	err = m.Set("potato")
+	assert.Error(t, err, "Unknown cache mode level")
+
+	err = m.Set("")
+	assert.Error(t, err, "Unknown cache mode level")
+}
+
+func TestCacheModeType(t *testing.T) {
+	var m CacheMode
+	assert.Equal(t, "string", m.Type())
+}
+
+func TestCacheNew(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	c, err := newCache(ctx, r.Fremote, &DefaultOpt)
+	require.NoError(t, err)
+
+	assert.Contains(t, c.root, "vfs")
+	assert.Contains(t, c.f.Root(), filepath.Base(r.Fremote.Root()))
+
+	// mkdir
+	p, err := c.mkdir("potato")
+	require.NoError(t, err)
+	assert.Equal(t, "potato", filepath.Base(p))
+
+	fi, err := os.Stat(filepath.Dir(p))
+	require.NoError(t, err)
+	assert.True(t, fi.IsDir())
+
+	// get
+	item := c.get("potato")
+	item2 := c.get("potato")
+	assert.Equal(t, item, item2)
+	assert.WithinDuration(t, time.Now(), item.atime, time.Second)
+
+	// updateTime
+	//.. before
+	t1 := time.Now().Add(-60 * time.Minute)
+	c.updateTime("potato", t1)
+	item = c.get("potato")
+	assert.NotEqual(t, t1, item.atime)
+	assert.Equal(t, 0, item.opens)
+	//..after
+	t2 := time.Now().Add(60 * time.Minute)
+	c.updateTime("potato", t2)
+	item = c.get("potato")
+	assert.Equal(t, t2, item.atime)
+	assert.Equal(t, 0, item.opens)
+
+	// open
+	c.open("potato")
+	item = c.get("potato")
+	assert.WithinDuration(t, time.Now(), item.atime, time.Second)
+	assert.Equal(t, 1, item.opens)
+
+	// write the file
+	err = ioutil.WriteFile(p, []byte("hello"), 0600)
+	require.NoError(t, err)
+
+	// read its atime
+	fi, err = os.Stat(p)
+	assert.NoError(t, err)
+	atime := times.Get(fi).AccessTime()
+
+	// updateAtimes
+	log.Printf("updateAtimes")
+	item = c.get("potato")
+	item.atime = time.Now().Add(-24 * time.Hour)
+	err = c.updateAtimes()
+	require.NoError(t, err)
+	item = c.get("potato")
+	assert.Equal(t, atime, item.atime)
+
+	// try purging with file open
+	c.purgeOld(10 * time.Second)
+	_, err = os.Stat(p)
+	assert.NoError(t, err)
+
+	// close
+	c.updateTime("potato", t2)
+	c.close("potato")
+	item = c.get("potato")
+	assert.WithinDuration(t, time.Now(), item.atime, time.Second)
+	assert.Equal(t, 0, item.opens)
+
+	// try purging with file closed
+	c.purgeOld(10 * time.Second)
+	// ...nothing should happend
+	_, err = os.Stat(p)
+	assert.NoError(t, err)
+
+	//.. purge again with -ve age
+	c.purgeOld(-10 * time.Second)
+	_, err = os.Stat(p)
+	assert.True(t, os.IsNotExist(err))
+
+	// clean - have tested the internals already
+	c.clean()
+
+	// cleanup
+	err = c.cleanUp()
+	require.NoError(t, err)
+	_, err = os.Stat(c.root)
+	assert.True(t, os.IsNotExist(err))
+}
--- a/vfs/dir.go
+++ b/vfs/dir.go
@ -306,9 +306,12 @@ func (d *Dir) ReadDirAll() (items Nodes, err error) {
 	return items, nil
 }

+// accessModeMask masks off the read modes from the flags
+const accessModeMask = (os.O_RDONLY | os.O_WRONLY | os.O_RDWR)
+
 // Open the directory according to the flags provided
 func (d *Dir) Open(flags int) (fd Handle, err error) {
-	rdwrMode := flags & (os.O_RDONLY | os.O_WRONLY | os.O_RDWR)
+	rdwrMode := flags & accessModeMask
 	if rdwrMode != os.O_RDONLY {
 		fs.Errorf(d, "Can only open directories read only")
 		return nil, EPERM
@ -498,3 +501,8 @@ func (d *Dir) Fsync() error {
 func (d *Dir) VFS() *VFS {
 	return d.vfs
 }
+
+// Truncate changes the size of the named file.
+func (d *Dir) Truncate(size int64) error {
+	return ENOSYS
+}
--- a/vfs/dir_test.go
+++ b/vfs/dir_test.go
@ -282,7 +282,7 @@ func TestDirCreate(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, int64(0), file.Size())

-	fd, err := file.Open(os.O_WRONLY)
+	fd, err := file.Open(os.O_WRONLY | os.O_CREATE)
 	require.NoError(t, err)

 	// FIXME Note that this fails with the current implementation
--- a/vfs/file.go
+++ b/vfs/file.go
@ -189,7 +189,7 @@ func (f *File) setObject(o fs.Object) {
 }

 // Wait for f.o to become non nil for a short time returning it or an
-// error
+// error.  Use when opening a read handle.
 //
 // Call without the mutex held
 func (f *File) waitForValidObject() (o fs.Object, err error) {
@ -219,9 +219,8 @@ func (f *File) OpenRead() (fh *ReadFileHandle, err error) {
 	// fs.Debugf(o, "File.OpenRead")

 	fh, err = newReadFileHandle(f, o)
-	err = errors.Wrap(err, "open for read")
-
 	if err != nil {
+		err = errors.Wrap(err, "open for read")
 		fs.Errorf(f, "File.OpenRead failed: %v", err)
 		return nil, err
 	}
@ -236,15 +235,32 @@ func (f *File) OpenWrite() (fh *WriteFileHandle, err error) {
 	// fs.Debugf(o, "File.OpenWrite")

 	fh, err = newWriteFileHandle(f.d, f, f.path())
-	err = errors.Wrap(err, "open for write")
-
 	if err != nil {
+		err = errors.Wrap(err, "open for write")
 		fs.Errorf(f, "File.OpenWrite failed: %v", err)
 		return nil, err
 	}
 	return fh, nil
 }

+// OpenRW open the file for read and write using a temporay file
+//
+// It uses the open flags passed in.
+func (f *File) OpenRW(flags int) (fh *RWFileHandle, err error) {
+	if flags&accessModeMask != os.O_RDONLY && f.d.vfs.Opt.ReadOnly {
+		return nil, EROFS
+	}
+	// fs.Debugf(o, "File.OpenRW")
+
+	fh, err = newRWFileHandle(f.d, f, f.path(), flags)
+	if err != nil {
+		err = errors.Wrap(err, "open for read write")
+		fs.Errorf(f, "File.OpenRW failed: %v", err)
+		return nil, err
+	}
+	return fh, nil
+}
+
 // Fsync the file
 //
 // Note that we don't do anything except return OK
@ -290,25 +306,85 @@ func (f *File) VFS() *VFS {
 }

 // Open a file according to the flags provided
+//
+//   O_RDONLY open the file read-only.
+//   O_WRONLY open the file write-only.
+//   O_RDWR   open the file read-write.
+//
+//   O_APPEND append data to the file when writing.
+//   O_CREATE create a new file if none exists.
+//   O_EXCL   used with O_CREATE, file must not exist
+//   O_SYNC   open for synchronous I/O.
+//   O_TRUNC  if possible, truncate file when opene
+//
+// We ignore O_SYNC and O_EXCL
 func (f *File) Open(flags int) (fd Handle, err error) {
-	rdwrMode := flags & (os.O_RDONLY | os.O_WRONLY | os.O_RDWR)
-	var read bool
+	var (
+		write    bool // if set need write support
+		read     bool // if set need read support
+		rdwrMode = flags & (os.O_RDONLY | os.O_WRONLY | os.O_RDWR)
+	)
+
+	// Figure out the read/write intents
 	switch {
 	case rdwrMode == os.O_RDONLY:
 		read = true
-	case rdwrMode == os.O_WRONLY || (rdwrMode == os.O_RDWR && (flags&os.O_TRUNC) != 0):
-		read = false
+	case rdwrMode == os.O_WRONLY:
+		write = true
 	case rdwrMode == os.O_RDWR:
-		fs.Errorf(f, "Can't open for Read and Write")
-		return nil, EPERM
+		read = true
+		write = true
 	default:
 		fs.Errorf(f, "Can't figure out how to open with flags: 0x%X", flags)
 		return nil, EPERM
 	}
-	if read {
-		fd, err = f.OpenRead()
+
+	// If append is set then set read to force OpenRW
+	if flags&os.O_APPEND != 0 {
+		read = true
+	}
+
+	// If truncate is set then set write to force OpenRW
+	if flags&os.O_TRUNC != 0 {
+		write = true
+	}
+
+	// FIXME discover if file is in cache or not?
+
+	// Open the correct sort of handle
+	CacheMode := f.d.vfs.Opt.CacheMode
+	if read && write {
+		if CacheMode >= CacheModeMinimal {
+			fd, err = f.OpenRW(flags)
+		} else if flags&os.O_TRUNC != 0 {
+			fd, err = f.OpenWrite()
+		} else {
+			fs.Errorf(f, "Can't open for read and write without cache")
+			return nil, EPERM
+		}
+	} else if write {
+		if CacheMode >= CacheModeWrites {
+			fd, err = f.OpenRW(flags)
+		} else {
+			fd, err = f.OpenWrite()
+		}
+	} else if read {
+		if CacheMode >= CacheModeFull {
+			fd, err = f.OpenRW(flags)
+		} else {
+			fd, err = f.OpenRead()
+		}
 	} else {
-		fd, err = f.OpenWrite()
+		fs.Errorf(f, "Can't figure out how to open with flags: 0x%X", flags)
+		return nil, EPERM
 	}
 	return fd, err
 }
+
+// Truncate changes the size of the named file.
+func (f *File) Truncate(size int64) error {
+	if f.d.vfs.Opt.CacheMode >= CacheModeWrites {
+	}
+	// FIXME
+	return ENOSYS
+}
--- a/vfs/file_test.go
+++ b/vfs/file_test.go
@ -160,7 +160,7 @@ func TestFileOpen(t *testing.T) {
 	_, file, _ := fileCreate(t, r)

 	fd, err := file.Open(os.O_RDONLY)
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	_, ok := fd.(*ReadFileHandle)
 	assert.True(t, ok)
 	require.NoError(t, fd.Close())
@ -171,12 +171,6 @@ func TestFileOpen(t *testing.T) {
 	assert.True(t, ok)
 	require.NoError(t, fd.Close())

-	fd, err = file.Open(os.O_RDWR | os.O_TRUNC)
-	assert.NoError(t, err)
-	_, ok = fd.(*WriteFileHandle)
-	assert.True(t, ok)
-	require.NoError(t, fd.Close())
-
 	fd, err = file.Open(os.O_RDWR)
 	assert.Equal(t, EPERM, err)

--- a/vfs/read_write.go
+++ b/vfs/read_write.go
@ -0,0 +1,406 @@
+package vfs
+
+import (
+	"io"
+	"os"
+	"sync"
+
+	"github.com/ncw/rclone/fs"
+	"github.com/pkg/errors"
+)
+
+// RWFileHandle is a handle that can be open for read and write.
+//
+// It will be open to a temporary file which, when closed, will be
+// transferred to the remote.
+type RWFileHandle struct {
+	*os.File
+	mu          sync.Mutex
+	closed      bool      // set if handle has been closed
+	o           fs.Object // may be nil
+	remote      string
+	file        *File
+	d           *Dir
+	opened      bool
+	flags       int    // open flags
+	osPath      string // path to the file in the cache
+	writeCalled bool   // if any Write() methods have been called
+}
+
+// Check interfaces
+var (
+	_ io.Reader   = (*RWFileHandle)(nil)
+	_ io.ReaderAt = (*RWFileHandle)(nil)
+	_ io.Writer   = (*RWFileHandle)(nil)
+	_ io.WriterAt = (*RWFileHandle)(nil)
+	_ io.Seeker   = (*RWFileHandle)(nil)
+	_ io.Closer   = (*RWFileHandle)(nil)
+)
+
+func newRWFileHandle(d *Dir, f *File, remote string, flags int) (fh *RWFileHandle, err error) {
+	// Make a place for the file
+	osPath, err := d.vfs.cache.mkdir(remote)
+	if err != nil {
+		return nil, errors.Wrap(err, "open RW handle failed to make cache directory")
+	}
+
+	fh = &RWFileHandle{
+		o:      f.o,
+		file:   f,
+		d:      d,
+		remote: remote,
+		flags:  flags,
+		osPath: osPath,
+	}
+	return fh, nil
+}
+
+// openPending opens the file if there is a pending open
+//
+// call with the lock held
+func (fh *RWFileHandle) openPending(truncate bool) (err error) {
+	if fh.opened {
+		return nil
+	}
+
+	rdwrMode := fh.flags & accessModeMask
+
+	// if not truncating the file, need to read it first
+	if fh.flags&os.O_TRUNC == 0 && !truncate {
+		// Fetch the file if it hasn't changed
+		// FIXME retries
+		err = fs.CopyFile(fh.d.vfs.cache.f, fh.d.vfs.f, fh.remote, fh.remote)
+		if err != nil {
+			// if the object wasn't found AND O_CREATE is set then...
+			cause := errors.Cause(err)
+			notFound := cause == fs.ErrorObjectNotFound || cause == fs.ErrorDirNotFound
+			if notFound {
+				// Remove cached item if there is one
+				err = os.Remove(fh.osPath)
+				if err != nil && !os.IsNotExist(err) {
+					return errors.Wrap(err, "open RW handle failed to delete stale cache file")
+				}
+			}
+			if notFound && fh.flags&os.O_CREATE != 0 {
+				// ...ignore error as we are about to create the file
+			} else {
+				return errors.Wrap(err, "open RW handle failed to cache file")
+			}
+		}
+	} else {
+		// Set the size to 0 since we are truncating
+		fh.file.setSize(0)
+	}
+
+	if rdwrMode != os.O_RDONLY {
+		fh.file.addWriters(1)
+	}
+
+	fs.Debugf(fh.remote, "Opening cached copy with flags=0x%02X", fh.flags)
+	fd, err := os.OpenFile(fh.osPath, fh.flags|os.O_CREATE, 0600)
+	if err != nil {
+		return errors.Wrap(err, "cache open file failed")
+	}
+	fh.File = fd
+	fh.opened = true
+	fh.d.vfs.cache.open(fh.osPath)
+	return nil
+}
+
+// String converts it to printable
+func (fh *RWFileHandle) String() string {
+	if fh == nil {
+		return "<nil *RWFileHandle>"
+	}
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if fh.file == nil {
+		return "<nil *RWFileHandle.file>"
+	}
+	return fh.file.String() + " (rw)"
+}
+
+// Node returns the Node assocuated with this - satisfies Noder interface
+func (fh *RWFileHandle) Node() Node {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	return fh.file
+}
+
+// close the file handle returning EBADF if it has been
+// closed already.
+//
+// Must be called with fh.mu held
+//
+// Note that we leave the file around in the cache on error conditions
+// to give the user a chance to recover it.
+func (fh *RWFileHandle) close() (err error) {
+	defer fs.Trace(fh.remote, "")("err=%v", &err)
+	if fh.closed {
+		return ECLOSED
+	}
+	fh.closed = true
+	rdwrMode := fh.flags & accessModeMask
+	if !fh.opened {
+		// If read only then return
+		if rdwrMode == os.O_RDONLY {
+			return nil
+		}
+		// If we aren't creating or truncating the file then
+		// we haven't modified it so don't need to transfer it
+		if fh.flags&(os.O_CREATE|os.O_TRUNC) == 0 {
+			return nil
+		}
+		// Otherwise open the file
+		// FIXME this could be more efficient
+		if err := fh.openPending(false); err != nil {
+			return err
+		}
+	}
+	if rdwrMode != os.O_RDONLY {
+		fh.file.addWriters(-1)
+		fi, err := fh.File.Stat()
+		if err != nil {
+			fs.Errorf(fh.remote, "Failed to stat cache file: %v", err)
+		} else {
+			fh.file.setSize(fi.Size())
+		}
+	}
+	fh.d.vfs.cache.close(fh.osPath)
+
+	// Close the underlying file
+	err = fh.File.Close()
+	if err != nil {
+		return err
+	}
+
+	// FIXME measure whether we actually did any writes or not -
+	// no writes means no transfer?
+	if rdwrMode == os.O_RDONLY {
+		fs.Debugf(fh.remote, "read only so not transferring")
+		return nil
+	}
+
+	// If write hasn't been called and we aren't creating or
+	// truncating the file then we haven't modified it so don't
+	// need to transfer it
+	if !fh.writeCalled && fh.flags&(os.O_CREATE|os.O_TRUNC) == 0 {
+		fs.Debugf(fh.remote, "not modified so not transferring")
+		return nil
+	}
+
+	// Transfer the temp file to the remote
+	// FIXME retries
+	if fh.d.vfs.Opt.CacheMode < CacheModeFull {
+		err = fs.MoveFile(fh.d.vfs.f, fh.d.vfs.cache.f, fh.remote, fh.remote)
+	} else {
+		err = fs.CopyFile(fh.d.vfs.f, fh.d.vfs.cache.f, fh.remote, fh.remote)
+	}
+	if err != nil {
+		err = errors.Wrap(err, "failed to transfer file from cache to remote")
+		fs.Errorf(fh.remote, "%v", err)
+		return err
+	}
+
+	// FIXME get MoveFile to return this object
+	o, err := fh.d.vfs.f.NewObject(fh.remote)
+	if err != nil {
+		err = errors.Wrap(err, "failed to find object after transfer to remote")
+		fs.Errorf(fh.remote, "%v", err)
+		return err
+	}
+	fh.file.setObject(o)
+	fs.Debugf(o, "transferred to remote")
+
+	return nil
+}
+
+// Close closes the file
+func (fh *RWFileHandle) Close() error {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	return fh.close()
+}
+
+// Flush is called each time the file or directory is closed.
+// Because there can be multiple file descriptors referring to a
+// single opened file, Flush can be called multiple times.
+func (fh *RWFileHandle) Flush() error {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if !fh.opened {
+		return nil
+	}
+	if fh.closed {
+		fs.Debugf(fh.remote, "RWFileHandle.Flush nothing to do")
+		return nil
+	}
+	// fs.Debugf(fh.remote, "RWFileHandle.Flush")
+	if !fh.opened {
+		fs.Debugf(fh.remote, "RWFileHandle.Flush ignoring flush on unopened handle")
+		return nil
+	}
+
+	// If Write hasn't been called then ignore the Flush - Release
+	// will pick it up
+	if !fh.writeCalled {
+		fs.Debugf(fh.remote, "RWFileHandle.Flush ignoring flush on unwritten handle")
+		return nil
+	}
+	err := fh.close()
+	if err != nil {
+		fs.Errorf(fh.remote, "RWFileHandle.Flush error: %v", err)
+	} else {
+		// fs.Debugf(fh.remote, "RWFileHandle.Flush OK")
+	}
+	return err
+}
+
+// Release is called when we are finished with the file handle
+//
+// It isn't called directly from userspace so the error is ignored by
+// the kernel
+func (fh *RWFileHandle) Release() error {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if fh.closed {
+		fs.Debugf(fh.remote, "RWFileHandle.Release nothing to do")
+		return nil
+	}
+	fs.Debugf(fh.remote, "RWFileHandle.Release closing")
+	err := fh.close()
+	if err != nil {
+		fs.Errorf(fh.remote, "RWFileHandle.Release error: %v", err)
+	} else {
+		// fs.Debugf(fh.remote, "RWFileHandle.Release OK")
+	}
+	return err
+}
+
+// Size returns the size of the underlying file
+func (fh *RWFileHandle) Size() int64 {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if !fh.opened {
+		return fh.file.Size()
+	}
+	fi, err := fh.File.Stat()
+	if err != nil {
+		return 0
+	}
+	return fi.Size()
+}
+
+// Stat returns info about the file
+func (fh *RWFileHandle) Stat() (os.FileInfo, error) {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	return fh.file, nil
+}
+
+// Read bytes from the file
+func (fh *RWFileHandle) Read(b []byte) (n int, err error) {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if fh.closed {
+		return 0, ECLOSED
+	}
+	if err = fh.openPending(false); err != nil {
+		return n, err
+	}
+	return fh.File.Read(b)
+}
+
+// ReadAt bytes from the file at off
+func (fh *RWFileHandle) ReadAt(b []byte, off int64) (n int, err error) {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if fh.closed {
+		return 0, ECLOSED
+	}
+	if err = fh.openPending(false); err != nil {
+		return n, err
+	}
+	return fh.File.ReadAt(b, off)
+}
+
+// Seek to new file position
+func (fh *RWFileHandle) Seek(offset int64, whence int) (ret int64, err error) {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if fh.closed {
+		return 0, ECLOSED
+	}
+	if err = fh.openPending(false); err != nil {
+		return ret, err
+	}
+	return fh.File.Seek(offset, whence)
+}
+
+// writeFn general purpose write call
+//
+// Pass a closure to do the actual write
+func (fh *RWFileHandle) writeFn(write func() error) (err error) {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if fh.closed {
+		return ECLOSED
+	}
+	if err = fh.openPending(false); err != nil {
+		return err
+	}
+	fh.writeCalled = true
+	err = write()
+	if err != nil {
+		return err
+	}
+	fi, err := fh.File.Stat()
+	if err != nil {
+		return errors.Wrap(err, "failed to stat cache file")
+	}
+	fh.file.setSize(fi.Size())
+	return nil
+}
+
+// Write bytes to the file
+func (fh *RWFileHandle) Write(b []byte) (n int, err error) {
+	err = fh.writeFn(func() error {
+		n, err = fh.File.Write(b)
+		return err
+	})
+	return n, err
+}
+
+// WriteAt bytes to the file at off
+func (fh *RWFileHandle) WriteAt(b []byte, off int64) (n int, err error) {
+	err = fh.writeFn(func() error {
+		n, err = fh.File.WriteAt(b, off)
+		return err
+	})
+	return n, err
+}
+
+// WriteString a string to the file
+func (fh *RWFileHandle) WriteString(s string) (n int, err error) {
+	err = fh.writeFn(func() error {
+		n, err = fh.File.WriteString(s)
+		return err
+	})
+	return n, err
+
+}
+
+// Truncate file to given size
+func (fh *RWFileHandle) Truncate(size int64) (err error) {
+	fh.mu.Lock()
+	defer fh.mu.Unlock()
+	if fh.closed {
+		return ECLOSED
+	}
+	if err = fh.openPending(size == 0); err != nil {
+		return err
+	}
+	fh.writeCalled = true
+	fh.file.setSize(size)
+	return fh.File.Truncate(size)
+}
--- a/vfs/read_write_test.go
+++ b/vfs/read_write_test.go
@ -0,0 +1,432 @@
+package vfs
+
+import (
+	"io"
+	"os"
+	"testing"
+
+	"github.com/ncw/rclone/fs"
+	"github.com/ncw/rclone/fstest"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// Open a file for write
+func rwHandleCreateReadOnly(t *testing.T, r *fstest.Run) (*VFS, *RWFileHandle) {
+	vfs := New(r.Fremote, nil)
+	vfs.Opt.CacheMode = CacheModeFull
+
+	file1 := r.WriteObject("dir/file1", "0123456789abcdef", t1)
+	fstest.CheckItems(t, r.Fremote, file1)
+
+	h, err := vfs.OpenFile("dir/file1", os.O_RDONLY, 0777)
+	require.NoError(t, err)
+	fh, ok := h.(*RWFileHandle)
+	require.True(t, ok)
+
+	return vfs, fh
+}
+
+// Open a file for write
+func rwHandleCreateWriteOnly(t *testing.T, r *fstest.Run) (*VFS, *RWFileHandle) {
+	vfs := New(r.Fremote, nil)
+	vfs.Opt.CacheMode = CacheModeFull
+
+	h, err := vfs.OpenFile("file1", os.O_WRONLY|os.O_CREATE, 0777)
+	require.NoError(t, err)
+	fh, ok := h.(*RWFileHandle)
+	require.True(t, ok)
+
+	return vfs, fh
+}
+
+// read data from the string
+func rwReadString(t *testing.T, fh *RWFileHandle, n int) string {
+	buf := make([]byte, n)
+	n, err := fh.Read(buf)
+	if err != io.EOF {
+		assert.NoError(t, err)
+	}
+	return string(buf[:n])
+}
+
+func TestRWFileHandleMethodsRead(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	_, fh := rwHandleCreateReadOnly(t, r)
+
+	// String
+	assert.Equal(t, "dir/file1 (rw)", fh.String())
+	assert.Equal(t, "<nil *RWFileHandle>", (*RWFileHandle)(nil).String())
+	assert.Equal(t, "<nil *RWFileHandle.file>", new(RWFileHandle).String())
+
+	// Node
+	node := fh.Node()
+	assert.Equal(t, "file1", node.Name())
+
+	// Size
+	assert.Equal(t, int64(16), fh.Size())
+
+	// Read 1
+	assert.Equal(t, "0", rwReadString(t, fh, 1))
+
+	// Read remainder
+	assert.Equal(t, "123456789abcdef", rwReadString(t, fh, 256))
+
+	// Read EOF
+	buf := make([]byte, 16)
+	_, err := fh.Read(buf)
+	assert.Equal(t, io.EOF, err)
+
+	// Stat
+	var fi os.FileInfo
+	fi, err = fh.Stat()
+	assert.NoError(t, err)
+	assert.Equal(t, int64(16), fi.Size())
+	assert.Equal(t, "file1", fi.Name())
+
+	// Close
+	assert.False(t, fh.closed)
+	assert.Equal(t, nil, fh.Close())
+	assert.True(t, fh.closed)
+
+	// Close again
+	assert.Equal(t, ECLOSED, fh.Close())
+}
+
+func TestRWFileHandleSeek(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	_, fh := rwHandleCreateReadOnly(t, r)
+
+	assert.Equal(t, "0", rwReadString(t, fh, 1))
+
+	// 0 means relative to the origin of the file,
+	n, err := fh.Seek(5, 0)
+	assert.NoError(t, err)
+	assert.Equal(t, int64(5), n)
+	assert.Equal(t, "5", rwReadString(t, fh, 1))
+
+	// 1 means relative to the current offset
+	n, err = fh.Seek(-3, 1)
+	assert.NoError(t, err)
+	assert.Equal(t, int64(3), n)
+	assert.Equal(t, "3", rwReadString(t, fh, 1))
+
+	// 2 means relative to the end.
+	n, err = fh.Seek(-3, 2)
+	assert.NoError(t, err)
+	assert.Equal(t, int64(13), n)
+	assert.Equal(t, "d", rwReadString(t, fh, 1))
+
+	// Seek off the end
+	n, err = fh.Seek(100, 0)
+	assert.NoError(t, err)
+
+	// Get the error on read
+	buf := make([]byte, 16)
+	l, err := fh.Read(buf)
+	assert.Equal(t, io.EOF, err)
+	assert.Equal(t, 0, l)
+
+	// Close
+	assert.Equal(t, nil, fh.Close())
+}
+
+func TestRWFileHandleReadAt(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	_, fh := rwHandleCreateReadOnly(t, r)
+
+	// read from start
+	buf := make([]byte, 1)
+	n, err := fh.ReadAt(buf, 0)
+	require.NoError(t, err)
+	assert.Equal(t, 1, n)
+	assert.Equal(t, "0", string(buf[:n]))
+
+	// seek forwards
+	n, err = fh.ReadAt(buf, 5)
+	require.NoError(t, err)
+	assert.Equal(t, 1, n)
+	assert.Equal(t, "5", string(buf[:n]))
+
+	// seek backwards
+	n, err = fh.ReadAt(buf, 1)
+	require.NoError(t, err)
+	assert.Equal(t, 1, n)
+	assert.Equal(t, "1", string(buf[:n]))
+
+	// read exactly to the end
+	buf = make([]byte, 6)
+	n, err = fh.ReadAt(buf, 10)
+	require.NoError(t, err)
+	assert.Equal(t, 6, n)
+	assert.Equal(t, "abcdef", string(buf[:n]))
+
+	// read off the end
+	buf = make([]byte, 256)
+	n, err = fh.ReadAt(buf, 10)
+	assert.Equal(t, io.EOF, err)
+	assert.Equal(t, 6, n)
+	assert.Equal(t, "abcdef", string(buf[:n]))
+
+	// read starting off the end
+	n, err = fh.ReadAt(buf, 100)
+	assert.Equal(t, io.EOF, err)
+	assert.Equal(t, 0, n)
+
+	// Properly close the file
+	assert.NoError(t, fh.Close())
+
+	// check reading on closed file
+	n, err = fh.ReadAt(buf, 100)
+	assert.Equal(t, ECLOSED, err)
+}
+
+func TestRWFileHandleFlushRead(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	_, fh := rwHandleCreateReadOnly(t, r)
+
+	// Check Flush does nothing if read not called
+	err := fh.Flush()
+	assert.NoError(t, err)
+	assert.False(t, fh.closed)
+
+	// Read data
+	buf := make([]byte, 256)
+	n, err := fh.Read(buf)
+	assert.True(t, err == io.EOF || err == nil)
+	assert.Equal(t, 16, n)
+
+	// Check Flush does nothing if read called
+	err = fh.Flush()
+	assert.NoError(t, err)
+	assert.False(t, fh.closed)
+
+	// Check flush does nothing if called again
+	err = fh.Flush()
+	assert.NoError(t, err)
+	assert.False(t, fh.closed)
+
+	// Properly close the file
+	assert.NoError(t, fh.Close())
+}
+
+func TestRWFileHandleReleaseRead(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	_, fh := rwHandleCreateReadOnly(t, r)
+
+	// Read data
+	buf := make([]byte, 256)
+	n, err := fh.Read(buf)
+	assert.True(t, err == io.EOF || err == nil)
+	assert.Equal(t, 16, n)
+
+	// Check Release closes file
+	err = fh.Release()
+	assert.NoError(t, err)
+	assert.True(t, fh.closed)
+
+	// Check Release does nothing if called again
+	err = fh.Release()
+	assert.NoError(t, err)
+	assert.True(t, fh.closed)
+}
+
+/// ------------------------------------------------------------
+
+func TestRWFileHandleMethodsWrite(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	vfs, fh := rwHandleCreateWriteOnly(t, r)
+
+	// String
+	assert.Equal(t, "file1 (rw)", fh.String())
+	assert.Equal(t, "<nil *RWFileHandle>", (*RWFileHandle)(nil).String())
+	assert.Equal(t, "<nil *RWFileHandle.file>", new(RWFileHandle).String())
+
+	// Node
+	node := fh.Node()
+	assert.Equal(t, "file1", node.Name())
+
+	offset := func() int64 {
+		n, err := fh.Seek(0, 1)
+		require.NoError(t, err)
+		return n
+	}
+
+	// Offset #1
+	assert.Equal(t, int64(0), offset())
+	assert.Equal(t, int64(0), node.Size())
+
+	// Size #1
+	assert.Equal(t, int64(0), fh.Size())
+
+	// Write
+	n, err := fh.Write([]byte("hello"))
+	assert.NoError(t, err)
+	assert.Equal(t, 5, n)
+
+	// Offset #2
+	assert.Equal(t, int64(5), offset())
+	assert.Equal(t, int64(5), node.Size())
+
+	// Size #2
+	assert.Equal(t, int64(5), fh.Size())
+
+	// WriteString
+	n, err = fh.WriteString(" world!")
+	assert.NoError(t, err)
+	assert.Equal(t, 7, n)
+
+	// Stat
+	var fi os.FileInfo
+	fi, err = fh.Stat()
+	assert.NoError(t, err)
+	assert.Equal(t, int64(12), fi.Size())
+	assert.Equal(t, "file1", fi.Name())
+
+	// Truncate
+	err = fh.Truncate(11)
+	assert.NoError(t, err)
+
+	// Close
+	assert.NoError(t, fh.Close())
+
+	// Check double close
+	err = fh.Close()
+	assert.Equal(t, ECLOSED, err)
+
+	// check vfs
+	root, err := vfs.Root()
+	checkListing(t, root, []string{"file1,11,false"})
+
+	// check the underlying r.Fremote but not the modtime
+	file1 := fstest.NewItem("file1", "hello world", t1)
+	fstest.CheckListingWithPrecision(t, r.Fremote, []fstest.Item{file1}, []string{}, fs.ModTimeNotSupported)
+}
+
+func TestRWFileHandleWriteAt(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	vfs, fh := rwHandleCreateWriteOnly(t, r)
+
+	offset := func() int64 {
+		n, err := fh.Seek(0, 1)
+		require.NoError(t, err)
+		return n
+	}
+
+	// Preconditions
+	assert.Equal(t, int64(0), offset())
+	assert.False(t, fh.writeCalled)
+
+	// Write the data
+	n, err := fh.WriteAt([]byte("hello**"), 0)
+	assert.NoError(t, err)
+	assert.Equal(t, 7, n)
+
+	// After write
+	assert.Equal(t, int64(0), offset())
+	assert.True(t, fh.writeCalled)
+
+	// Write more data
+	n, err = fh.WriteAt([]byte(" world"), 5)
+	assert.NoError(t, err)
+	assert.Equal(t, 6, n)
+
+	// Close
+	assert.NoError(t, fh.Close())
+
+	// Check can't write on closed handle
+	n, err = fh.WriteAt([]byte("hello"), 0)
+	assert.Equal(t, ECLOSED, err)
+	assert.Equal(t, 0, n)
+
+	// check vfs
+	root, err := vfs.Root()
+	checkListing(t, root, []string{"file1,11,false"})
+
+	// check the underlying r.Fremote but not the modtime
+	file1 := fstest.NewItem("file1", "hello world", t1)
+	fstest.CheckListingWithPrecision(t, r.Fremote, []fstest.Item{file1}, []string{}, fs.ModTimeNotSupported)
+}
+
+func TestRWFileHandleWriteNoWrite(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	vfs, fh := rwHandleCreateWriteOnly(t, r)
+
+	// Close the file without writing to it
+	err := fh.Close()
+	assert.NoError(t, err)
+
+	// Create a different file (not in the cache)
+	h, err := vfs.OpenFile("file2", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0777)
+	require.NoError(t, err)
+
+	// Close it with Flush and Release
+	err = h.Flush()
+	assert.NoError(t, err)
+	err = h.Release()
+	assert.NoError(t, err)
+
+	// check vfs
+	root, err := vfs.Root()
+	checkListing(t, root, []string{"file1,0,false", "file2,0,false"})
+
+	// check the underlying r.Fremote but not the modtime
+	file1 := fstest.NewItem("file1", "", t1)
+	file2 := fstest.NewItem("file2", "", t1)
+	fstest.CheckListingWithPrecision(t, r.Fremote, []fstest.Item{file1, file2}, []string{}, fs.ModTimeNotSupported)
+}
+
+func TestRWFileHandleFlushWrite(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	_, fh := rwHandleCreateWriteOnly(t, r)
+
+	// Check Flush does nothing if write not called
+	err := fh.Flush()
+	assert.NoError(t, err)
+	assert.False(t, fh.closed)
+
+	// Write some data
+	n, err := fh.Write([]byte("hello"))
+	assert.NoError(t, err)
+	assert.Equal(t, 5, n)
+
+	// Check Flush closes file if write called
+	err = fh.Flush()
+	assert.NoError(t, err)
+	assert.True(t, fh.closed)
+
+	// Check flush does nothing if called again
+	err = fh.Flush()
+	assert.NoError(t, err)
+	assert.True(t, fh.closed)
+}
+
+func TestRWFileHandleReleaseWrite(t *testing.T) {
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	_, fh := rwHandleCreateWriteOnly(t, r)
+
+	// Write some data
+	n, err := fh.Write([]byte("hello"))
+	assert.NoError(t, err)
+	assert.Equal(t, 5, n)
+
+	// Check Release closes file
+	err = fh.Release()
+	assert.NoError(t, err)
+	assert.True(t, fh.closed)
+
+	// Check Release does nothing if called again
+	err = fh.Release()
+	assert.NoError(t, err)
+	assert.True(t, fh.closed)
+}
--- a/vfs/vfs.go
+++ b/vfs/vfs.go
@ -27,21 +27,25 @@ import (
 	"time"

 	"github.com/ncw/rclone/fs"
+	"golang.org/x/net/context" // switch to "context" when we stop supporting go1.6
 )

 // DefaultOpt is the default values uses for Opt
 var DefaultOpt = Options{
-	NoModTime:    false,
-	NoChecksum:   false,
-	NoSeek:       false,
-	DirCacheTime: 5 * 60 * time.Second,
-	PollInterval: time.Minute,
-	ReadOnly:     false,
-	Umask:        0,
-	UID:          ^uint32(0), // these values instruct WinFSP-FUSE to use the current user
-	GID:          ^uint32(0), // overriden for non windows in mount_unix.go
-	DirPerms:     os.FileMode(0777) | os.ModeDir,
-	FilePerms:    os.FileMode(0666),
+	NoModTime:         false,
+	NoChecksum:        false,
+	NoSeek:            false,
+	DirCacheTime:      5 * 60 * time.Second,
+	PollInterval:      time.Minute,
+	ReadOnly:          false,
+	Umask:             0,
+	UID:               ^uint32(0), // these values instruct WinFSP-FUSE to use the current user
+	GID:               ^uint32(0), // overriden for non windows in mount_unix.go
+	DirPerms:          os.FileMode(0777) | os.ModeDir,
+	FilePerms:         os.FileMode(0666),
+	CacheMode:         CacheModeOff,
+	CacheMaxAge:       3600 * time.Second,
+	CachePollInterval: 60 * time.Second,
 }

 // Node represents either a directory (*Dir) or a file (*File)
@ -56,6 +60,7 @@ type Node interface {
 	DirEntry() fs.DirEntry
 	VFS() *VFS
 	Open(flags int) (Handle, error)
+	Truncate(size int64) error
 }

 // Check interfaces
@ -84,12 +89,12 @@ var (
 	_ Noder = (*Dir)(nil)
 	_ Noder = (*ReadFileHandle)(nil)
 	_ Noder = (*WriteFileHandle)(nil)
+	_ Noder = (*RWFileHandle)(nil)
 	_ Noder = (*DirHandle)(nil)
 )

-// Handle is the interface statisified by open files or directories.
-// It is the methods on *os.File.  Not all of them are supported.
-type Handle interface {
+// OsFiler is the methods on *os.File
+type OsFiler interface {
 	Chdir() error
 	Chmod(mode os.FileMode) error
 	Chown(uid, gid int) error
@ -107,10 +112,18 @@ type Handle interface {
 	Write(b []byte) (n int, err error)
 	WriteAt(b []byte, off int64) (n int, err error)
 	WriteString(s string) (n int, err error)
+}
+
+// Handle is the interface statisified by open files or directories.
+// It is the methods on *os.File, plus a few more useful for FUSE
+// filingsystems.  Not all of them are supported.
+type Handle interface {
+	OsFiler
 	// Additional methods useful for FUSE filesystems
 	Flush() error
 	Release() error
 	Node() Node
+	//	Size() int64
 }

 // baseHandle implements all the missing methods
@ -137,34 +150,42 @@ func (h baseHandle) Flush() (err error)                                   { retu
 func (h baseHandle) Release() (err error)                                 { return ENOSYS }
 func (h baseHandle) Node() Node                                           { return nil }

+//func (h baseHandle) Size() int64                                          { return 0 }
+
 // Check interfaces
 var (
-	_ Handle = (*baseHandle)(nil)
-	_ Handle = (*ReadFileHandle)(nil)
-	_ Handle = (*WriteFileHandle)(nil)
-	_ Handle = (*DirHandle)(nil)
+	_ OsFiler = (*os.File)(nil)
+	_ Handle  = (*baseHandle)(nil)
+	_ Handle  = (*ReadFileHandle)(nil)
+	_ Handle  = (*WriteFileHandle)(nil)
+	_ Handle  = (*DirHandle)(nil)
 )

 // VFS represents the top level filing system
 type VFS struct {
-	f    fs.Fs
-	root *Dir
-	Opt  Options
+	f      fs.Fs
+	root   *Dir
+	Opt    Options
+	cache  *cache
+	cancel context.CancelFunc
 }

 // Options is options for creating the vfs
 type Options struct {
-	NoSeek       bool          // don't allow seeking if set
-	NoChecksum   bool          // don't check checksums if set
-	ReadOnly     bool          // if set VFS is read only
-	NoModTime    bool          // don't read mod times for files
-	DirCacheTime time.Duration // how long to consider directory listing cache valid
-	PollInterval time.Duration
-	Umask        int
-	UID          uint32
-	GID          uint32
-	DirPerms     os.FileMode
-	FilePerms    os.FileMode
+	NoSeek            bool          // don't allow seeking if set
+	NoChecksum        bool          // don't check checksums if set
+	ReadOnly          bool          // if set VFS is read only
+	NoModTime         bool          // don't read mod times for files
+	DirCacheTime      time.Duration // how long to consider directory listing cache valid
+	PollInterval      time.Duration
+	Umask             int
+	UID               uint32
+	GID               uint32
+	DirPerms          os.FileMode
+	FilePerms         os.FileMode
+	CacheMode         CacheMode
+	CacheMaxAge       time.Duration
+	CachePollInterval time.Duration
 }

 // New creates a new VFS and root directory.  If opt is nil, then
@ -200,9 +221,32 @@ func New(f fs.Fs, opt *Options) *VFS {
 			fs.Logf(f, "poll-interval is not supported by this remote")
 		}
 	}
+
+	// Create the cache
+	ctx, cancel := context.WithCancel(context.Background())
+	vfs.cancel = cancel
+	cache, err := newCache(ctx, f, &vfs.Opt) // FIXME pass on context or get from Opt?
+	if err != nil {
+		// FIXME
+		panic(fmt.Sprintf("failed to create local cache: %v", err))
+	}
+	vfs.cache = cache
 	return vfs
 }

+// Shutdown stops any background go-routines
+func (vfs *VFS) Shutdown() {
+	if vfs.cancel != nil {
+		vfs.cancel()
+		vfs.cancel = nil
+	}
+}
+
+// CleanUp deletes the contents of the cache
+func (vfs *VFS) CleanUp() error {
+	return vfs.cache.cleanUp()
+}
+
 // Root returns the root node
 func (vfs *VFS) Root() (*Dir, error) {
 	// fs.Debugf(vfs.f, "Root()")
--- a/vfs/vfsflags/vfsflags.go
+++ b/vfs/vfsflags/vfsflags.go
@ -19,5 +19,8 @@ func AddFlags(flags *pflag.FlagSet) {
 	flags.DurationVarP(&Opt.DirCacheTime, "dir-cache-time", "", Opt.DirCacheTime, "Time to cache directory entries for.")
 	flags.DurationVarP(&Opt.PollInterval, "poll-interval", "", Opt.PollInterval, "Time to wait between polling for changes. Must be smaller than dir-cache-time. Only on supported remotes. Set to 0 to disable.")
 	flags.BoolVarP(&Opt.ReadOnly, "read-only", "", Opt.ReadOnly, "Mount read-only.")
+	flags.VarP(&Opt.CacheMode, "cache-mode", "", "Cache mode off|minimal|writes|full")
+	flags.DurationVarP(&Opt.CachePollInterval, "cache-poll-interval", "", Opt.CachePollInterval, "Interval to poll the cache for stale objects.")
+	flags.DurationVarP(&Opt.CacheMaxAge, "cache-max-age", "", Opt.CacheMaxAge, "Max age of objects in the cache.")
 	platformFlags(flags)
 }