vfs: fix SIGHUP killing serve instead of flushing directory caches

Before, rclone serve would crash when sent a SIGHUP which contradicts
the documentation - saying it should flush the directory caches.

Moved signal handling from the mount into the vfs layer, which now
handles SIGHUP on all uses of the VFS including mount and serve.

Fixes #8607

cmd/mountlib/mount.go

@@ -403,27 +403,7 @@ func (m *MountPoint) Wait() error {
 	fnHandle := atexit.Register(finalise)
 	defer atexit.Unregister(fnHandle)
 
-	// Reload VFS cache on SIGHUP
+	err := <-m.ErrChan
-	sigHup := make(chan os.Signal, 1)
-	NotifyOnSigHup(sigHup)
-	var err error
-
-	waiting := true
-	for waiting {
-		select {
-		// umount triggered outside the app
-		case err = <-m.ErrChan:
-			waiting = false
-		// user sent SIGHUP to clear the cache
-		case <-sigHup:
-			root, err := m.VFS.Root()
-			if err != nil {
-				fs.Errorf(m.VFS.Fs(), "Error reading root: %v", err)
-			} else {
-				root.ForgetAll()
-			}
-		}
-	}
 
 	finalise()
 

cmd/serve/docker/driver.go

@@ -76,7 +76,6 @@ func NewDriver(ctx context.Context, root string, mntOpt *mountlib.Options, vfsOp
 	// start mount monitoring
 	drv.hupChan = make(chan os.Signal, 1)
 	drv.monChan = make(chan bool, 1)
-	mountlib.NotifyOnSigHup(drv.hupChan)
 	go drv.monitor()
 
 	// unmount all volumes on exit

vfs/sighup.go

@@ -1,6 +1,6 @@
 //go:build !plan9 && !js
 
-package mountlib
+package vfs
 
 import (
 	"os"

vfs/sighup_unsupported.go

@@ -1,6 +1,6 @@
 //go:build plan9 || js
 
-package mountlib
+package vfs
 
 import (
 	"os"

vfs/vfs.go

@@ -179,6 +179,7 @@ type VFS struct {
 	root        *Dir
 	Opt         vfscommon.Options
 	cache       *vfscache.Cache
+	cancel      context.CancelFunc
 	cancelCache context.CancelFunc
 	usageMu     sync.Mutex
 	usageTime   time.Time
@@ -197,8 +198,10 @@ var (
 // DefaultOpt will be used
 func New(f fs.Fs, opt *vfscommon.Options) *VFS {
 	fsDir := fs.NewDir("", time.Now())
+	ctx, cancel := context.WithCancel(context.Background())
 	vfs := &VFS{
-		f: f,
+		f:      f,
+		cancel: cancel,
 	}
 	vfs.inUse.Store(1)
 
@@ -259,6 +262,9 @@ func New(f fs.Fs, opt *vfscommon.Options) *VFS {
 		go vfs.refresh()
 	}
 
+	// Handle supported signals
+	go vfs.signalHandler(ctx)
+
 	// This can take some time so do it after the Pin
 	vfs.SetCacheMode(vfs.Opt.CacheMode)
 
@@ -274,6 +280,27 @@ func (vfs *VFS) refresh() {
 	}
 }
 
+// Reload VFS cache on SIGHUP
+func (vfs *VFS) signalHandler(ctx context.Context) {
+	sigHup := make(chan os.Signal, 1)
+	NotifyOnSigHup(sigHup)
+
+	waiting := true
+	for waiting {
+		select {
+		case <-ctx.Done():
+			waiting = false
+		case <-sigHup:
+			root, err := vfs.Root()
+			if err != nil {
+				fs.Errorf(vfs.Fs(), "Error reading root: %v", err)
+			} else {
+				root.ForgetAll()
+			}
+		}
+	}
+}
+
 // Stats returns info about the VFS
 func (vfs *VFS) Stats() (out rc.Params) {
 	out = make(rc.Params)
@@ -372,6 +399,9 @@ func (vfs *VFS) Shutdown() {
 		close(vfs.pollChan)
 		vfs.pollChan = nil
 	}
+
+	// Cancel any background go routines
+	vfs.cancel()
 }
 
 // CleanUp deletes the contents of the on disk cache