From 2f67681e3b6113710343c396cb24c43930062f43 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Thu, 28 Jan 2021 18:17:47 +0000
Subject: [PATCH] cmount: don't attempt to unmount if fs has been destroyed
 already #4957

---
 cmd/cmount/fs.go    | 13 ++++++++-----
 cmd/cmount/mount.go |  6 +++++-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/cmd/cmount/fs.go b/cmd/cmount/fs.go
index 34b5b7f66..32a6b8c21 100644
--- a/cmd/cmount/fs.go
+++ b/cmd/cmount/fs.go
@@ -9,6 +9,7 @@ import (
 	"os"
 	"path"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/billziss-gh/cgofuse/fuse"
@@ -23,11 +24,12 @@ const fhUnset = ^uint64(0)
 
 // FS represents the top level filing system
 type FS struct {
-	VFS     *vfs.VFS
-	f       fs.Fs
-	ready   chan (struct{})
-	mu      sync.Mutex // to protect the below
-	handles []vfs.Handle
+	VFS       *vfs.VFS
+	f         fs.Fs
+	ready     chan (struct{})
+	mu        sync.Mutex // to protect the below
+	handles   []vfs.Handle
+	destroyed int32 // read/write with sync/atomic
 }
 
 // NewFS makes a new FS
@@ -187,6 +189,7 @@ func (fsys *FS) Init() {
 // Destroy call).
 func (fsys *FS) Destroy() {
 	defer log.Trace(fsys.f, "")("")
+	atomic.StoreInt32(&fsys.destroyed, 1)
 }
 
 // Getattr reads the attributes for path
diff --git a/cmd/cmount/mount.go b/cmd/cmount/mount.go
index ecfabe3f4..de5691399 100644
--- a/cmd/cmount/mount.go
+++ b/cmd/cmount/mount.go
@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"os"
 	"runtime"
+	"sync/atomic"
 	"time"
 
 	"github.com/billziss-gh/cgofuse/fuse"
@@ -168,7 +169,10 @@ func mount(VFS *vfs.VFS, mountPath string, opt *mountlib.Options) (<-chan error,
 		// Shutdown the VFS
 		fsys.VFS.Shutdown()
 		var umountOK bool
-		if atexit.Signalled() {
+		if atomic.LoadInt32(&fsys.destroyed) != 0 {
+			fs.Debugf(nil, "Not calling host.Unmount as mount already Destroyed")
+			umountOK = true
+		} else if atexit.Signalled() {
 			// If we have received a signal then FUSE will be shutting down already
 			fs.Debugf(nil, "Not calling host.Unmount as signal received")
 			umountOK = true