Remove argument from vfs.MountNamespace.DecRef()

Updates #1035

PiperOrigin-RevId: 293194631

pkg/sentry/fsimpl/devtmpfs/devtmpfs.go

@@ -86,7 +86,7 @@ func NewAccessor(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth
 // Release must be called when a is no longer in use.
 func (a *Accessor) Release() {
 	a.root.DecRef()
-	a.mntns.DecRef(a.vfsObj)
+	a.mntns.DecRef()
 }
 
 // accessorContext implements context.Context by extending an existing

pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go

@@ -45,7 +45,7 @@ func TestDevtmpfs(t *testing.T) {
 	if err != nil {
 		t.Fatalf("failed to create tmpfs root mount: %v", err)
 	}
-	defer mntns.DecRef(vfsObj)
+	defer mntns.DecRef()
 	root := mntns.Root()
 	defer root.DecRef()
 	devpop := vfs.PathOperation{

pkg/sentry/fsimpl/testutil/testutil.go

@@ -98,7 +98,7 @@ func (s *System) WithTemporaryContext(ctx context.Context) *System {
 // Destroy release resources associated with a test system.
 func (s *System) Destroy() {
 	s.Root.DecRef()
-	s.mns.DecRef(s.VFS) // Reference on mns passed to NewSystem.
+	s.mns.DecRef() // Reference on mns passed to NewSystem.
 }
 
 // ReadToEnd reads the contents of fd until EOF to a string.

pkg/sentry/fsimpl/tmpfs/benchmark_test.go

@@ -183,7 +183,7 @@ func BenchmarkVFS2MemfsStat(b *testing.B) {
 			if err != nil {
 				b.Fatalf("failed to create tmpfs root mount: %v", err)
 			}
-			defer mntns.DecRef(vfsObj)
+			defer mntns.DecRef()
 
 			var filePathBuilder strings.Builder
 			filePathBuilder.WriteByte('/')
@@ -374,7 +374,7 @@ func BenchmarkVFS2MemfsMountStat(b *testing.B) {
 			if err != nil {
 				b.Fatalf("failed to create tmpfs root mount: %v", err)
 			}
-			defer mntns.DecRef(vfsObj)
+			defer mntns.DecRef()
 
 			var filePathBuilder strings.Builder
 			filePathBuilder.WriteByte('/')

pkg/sentry/fsimpl/tmpfs/regular_file_test.go

@@ -51,7 +51,7 @@ func newTmpfsRoot(ctx context.Context) (*vfs.VirtualFilesystem, vfs.VirtualDentr
 	root := mntns.Root()
 	return vfsObj, root, func() {
 		root.DecRef()
-		mntns.DecRef(vfsObj)
+		mntns.DecRef()
 	}, nil
 }
 

pkg/sentry/vfs/mount.go

@@ -423,7 +423,8 @@ func (mntns *MountNamespace) IncRef() {
 }
 
 // DecRef decrements mntns' reference count.
-func (mntns *MountNamespace) DecRef(vfs *VirtualFilesystem) {
+func (mntns *MountNamespace) DecRef() {
+	vfs := mntns.root.fs.VirtualFilesystem()
 	if refs := atomic.AddInt64(&mntns.refs, -1); refs == 0 {
 		vfs.mountMu.Lock()
 		vfs.mounts.seq.BeginWrite()