vfs: Only make the VFS cache if --vfs-cache-mode > Off

This stops the cache cleaner running unnecessarily and saves
resources.

This also helps with issue #2227 which was caused by a second mount
deleting objects in the first mounts cache.

cmd/mountlib/mounttest/fs.go

@@ -215,7 +215,7 @@ func (r *Run) cacheMode(cacheMode vfs.CacheMode) {
 		log.Printf("Failed to cleanup the VFS cache: %v", err)
 	}
 	// Reset the cache mode
-	r.vfs.Opt.CacheMode = cacheMode
+	r.vfs.SetCacheMode(cacheMode)
 	// Flush the directory cache
 	r.vfs.FlushDirCache()
 

vfs/file.go

@@ -481,8 +481,7 @@ func (f *File) Open(flags int) (fd Handle, err error) {
 
 	// Open the correct sort of handle
 	CacheMode := f.d.vfs.Opt.CacheMode
-	opens := f.d.vfs.cache.opens(f.Path())
-	if CacheMode >= CacheModeMinimal && opens > 0 {
+	if CacheMode >= CacheModeMinimal && f.d.vfs.cache.opens(f.Path()) > 0 {
 		fd, err = f.openRW(flags)
 	} else if read && write {
 		if CacheMode >= CacheModeMinimal {

vfs/read_write_test.go

@@ -21,8 +21,9 @@ func cleanup(t *testing.T, r *fstest.Run, vfs *VFS) {
 
 // Open a file for write
 func rwHandleCreateReadOnly(t *testing.T, r *fstest.Run) (*VFS, *RWFileHandle) {
-	vfs := New(r.Fremote, nil)
-	vfs.Opt.CacheMode = CacheModeFull
+	opt := DefaultOpt
+	opt.CacheMode = CacheModeFull
+	vfs := New(r.Fremote, &opt)
 
 	file1 := r.WriteObject("dir/file1", "0123456789abcdef", t1)
 	fstest.CheckItems(t, r.Fremote, file1)
@@ -37,8 +38,9 @@ func rwHandleCreateReadOnly(t *testing.T, r *fstest.Run) (*VFS, *RWFileHandle) {
 
 // Open a file for write
 func rwHandleCreateWriteOnly(t *testing.T, r *fstest.Run) (*VFS, *RWFileHandle) {
-	vfs := New(r.Fremote, nil)
-	vfs.Opt.CacheMode = CacheModeFull
+	opt := DefaultOpt
+	opt.CacheMode = CacheModeFull
+	vfs := New(r.Fremote, &opt)
 
 	h, err := vfs.OpenFile("file1", os.O_WRONLY|os.O_CREATE, 0777)
 	require.NoError(t, err)
@@ -555,10 +557,11 @@ func testRWFileHandleOpenTest(t *testing.T, vfs *VFS, test *openTest) {
 
 func TestRWFileHandleOpenTests(t *testing.T) {
 	r := fstest.NewRun(t)
-	vfs := New(r.Fremote, nil)
+	opt := DefaultOpt
+	opt.CacheMode = CacheModeFull
+	vfs := New(r.Fremote, &opt)
 	defer cleanup(t, r, vfs)
 
-	vfs.Opt.CacheMode = CacheModeFull
 	for _, test := range openTests {
 		testRWFileHandleOpenTest(t, vfs, &test)
 	}

vfs/vfs.go

@@ -224,21 +224,31 @@ func New(f fs.Fs, opt *Options) *VFS {
 		}
 	}
 
-	// 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
+	vfs.SetCacheMode(vfs.Opt.CacheMode)
 
 	// add the remote control
 	vfs.addRC()
 	return vfs
 }
 
+// SetCacheMode change the cache mode
+func (vfs *VFS) SetCacheMode(cacheMode CacheMode) {
+	vfs.Shutdown()
+	vfs.cache = nil
+	if vfs.Opt.CacheMode > CacheModeOff {
+		ctx, cancel := context.WithCancel(context.Background())
+		cache, err := newCache(ctx, vfs.f, &vfs.Opt) // FIXME pass on context or get from Opt?
+		if err != nil {
+			fs.Errorf(nil, "Failed to create vfs cache - disabling: %v", err)
+			vfs.Opt.CacheMode = CacheModeOff
+			cancel()
+			return
+		}
+		vfs.cancel = cancel
+		vfs.cache = cache
+	}
+}
+
 // Shutdown stops any background go-routines
 func (vfs *VFS) Shutdown() {
 	if vfs.cancel != nil {
@@ -249,6 +259,9 @@ func (vfs *VFS) Shutdown() {
 
 // CleanUp deletes the contents of the on disk cache
 func (vfs *VFS) CleanUp() error {
+	if vfs.Opt.CacheMode == CacheModeOff {
+		return nil
+	}
 	return vfs.cache.cleanUp()
 }