vfs: fix deadlock on concurrent operations on a directory - fixes #2811

Before this fix there were two paths where concurrent use of a
directory could take the file lock then directory lock and the other
would take the locks in the reverse order.

Fix this by narrowing the locking windows so the file lock and
directory lock don't overlap.

vfs/file.go

@@ -331,9 +331,10 @@ func (f *File) setSize(n int64) {
 // Update the object when written and add it to the directory
 func (f *File) setObject(o fs.Object) {
 	f.mu.Lock()
-	defer f.mu.Unlock()
 	f.o = o
 	_ = f.applyPendingModTime()
+	f.mu.Unlock()
+
 	f.d.addObject(f)
 }
 
@@ -440,20 +441,23 @@ func (f *File) Sync() error {
 
 // Remove the file
 func (f *File) Remove() error {
-	f.mu.Lock()
-	defer f.mu.Unlock()
-	f.muRW.Lock()
-	defer f.muRW.Unlock()
 	if f.d.vfs.Opt.ReadOnly {
 		return EROFS
 	}
+	f.mu.Lock()
+	f.muRW.Lock()
 	if f.o != nil {
 		err := f.o.Remove()
 		if err != nil {
 			fs.Errorf(f, "File.Remove file error: %v", err)
+			f.muRW.Unlock()
+			f.mu.Unlock()
 			return err
 		}
 	}
+	f.muRW.Unlock()
+	f.mu.Unlock()
+
 	// Remove the item from the directory listing
 	f.d.delObject(f.Name())
 	// Remove the object from the cache