vfs: fix virtual entries causing deleted files to still appear

Before this change, if a file was created on a remote but deleted
externally from that remote then there was potential for the delete to
never be noticed.

The sequence of events was:

- Create file on VFS - creates virtual directory entry
- File deleted externally to remote before the directory refreshed
- Now the file has a virtual add but is not in the listings so will never disappear

This patch fixes it by removing all virtual directory entries except
the following when the directory is re-read.

- On remotes which can't have empty directories: virtual directory
  adds are not flushed. These will remain virtual as long as the
  directory is empty.

- For virtual file add: files that are in the process of being
  uploaded are not flushed

This patch also adds the distinction between virtually added files and
directories.

It also refactors the virtual directory logic to make it easier to follow.

Fixes #4446

vfs/dir.go

@@ -45,9 +45,10 @@ type Dir struct {
 type vState byte
 
 const (
-	vOK  vState = iota // Not virtual
-	vAdd               // added file or directory
-	vDel               // removed file or directory
+	vOK      vState = iota // Not virtual
+	vAddFile               // added file
+	vAddDir                // added directory
+	vDel                   // removed file or directory
 )
 
 func newDir(vfs *VFS, f fs.Fs, parent *Dir, fsDir fs.Directory) *Dir {
@@ -144,6 +145,9 @@ func (d *Dir) ForgetAll() (hasVirtual bool) {
 			}
 		}
 	}
+	// Purge any unecessary virtual entries
+	d._purgeVirtual()
+
 	d.read = time.Time{}
 	// Check if this dir has virtual entries
 	if len(d.virtual) != 0 {
@@ -296,6 +300,10 @@ func (d *Dir) addObject(node Node) {
 	if d.virtual == nil {
 		d.virtual = make(map[string]vState)
 	}
+	vAdd := vAddFile
+	if node.IsDir() {
+		vAdd = vAddDir
+	}
 	d.virtual[leaf] = vAdd
 	fs.Debugf(d.path, "Added virtual directory entry %v: %q", vAdd, leaf)
 	d.mu.Unlock()
@@ -348,7 +356,7 @@ func (d *Dir) delObject(leaf string) {
 // DelVirtual removes an object from the directory listing
 //
 // It marks it as removed until it has confirmed the object is missing when the
-// directory entries are re-read in which case the virtual mark is removed.
+// directory entries are re-read in.
 //
 // This is used to remove directory entries after things have been deleted or
 // renamed but before we've had confirmation from the backend.
@@ -389,33 +397,153 @@ func (d *Dir) _readDirFromDirTree(dirTree dirtree.DirTree, when time.Time) error
 	return d._readDirFromEntries(dirTree[d.path], dirTree, when)
 }
 
+// Remove the virtual directory entry leaf
+func (d *Dir) _deleteVirtual(name string) {
+	virtualState, ok := d.virtual[name]
+	if !ok {
+		return
+	}
+	delete(d.virtual, name)
+	if len(d.virtual) == 0 {
+		d.virtual = nil
+	}
+	fs.Debugf(d.path, "Removed virtual directory entry %v: %q", virtualState, name)
+}
+
+// Purge virtual entries assuming the directory has just been re-read
+//
+// Remove all the entries except:
+//
+// 1) vDirAdd on remotes which can't have empty directories. These will remain
+// virtual as long as the directory is empty. When the directory becomes real
+// (ie files are added) the virtual directory will be removed. This means that
+// directories will disappear when the last file is deleted which is probably
+// OK.
+//
+// 2) vFileAdd that are being written or uploaded
+func (d *Dir) _purgeVirtual() {
+	canHaveEmptyDirectories := d.f.Features().CanHaveEmptyDirectories
+	for name, virtualState := range d.virtual {
+		switch virtualState {
+		case vAddDir:
+			if canHaveEmptyDirectories {
+				// if remote can have empty directories then a
+				// new dir will be read in the listing
+				d._deleteVirtual(name)
+			} else {
+				// leave the empty directory marker
+			}
+		case vAddFile:
+			// Delete all virtual file adds that have finished uploading
+			node, ok := d.items[name]
+			if !ok {
+				// if the object has disappeared somehow then remove the virtual
+				d._deleteVirtual(name)
+				continue
+			}
+			f, ok := node.(*File)
+			if !ok {
+				// if the object isn't a file then remove the virtual as it is wrong
+				d._deleteVirtual(name)
+				continue
+			}
+			if f.writingInProgress() {
+				// if writing in progress then leave virtual
+				continue
+			}
+			if d.vfs.Opt.CacheMode >= vfscommon.CacheModeMinimal && d.vfs.cache.InUse(f.Path()) {
+				// if object in use or dirty then leave virtual
+				continue
+			}
+			d._deleteVirtual(name)
+		default:
+			d._deleteVirtual(name)
+		}
+	}
+}
+
+// Manage the virtuals in a listing
+//
+// This keeps a record of the names listed in this directory so far
+type manageVirtuals map[string]struct{}
+
+// Create a new manageVirtuals and purge the d.virtuals of any entries which can
+// be removed.
+//
+// must be called with the Dir lock held
+func (d *Dir) _newManageVirtuals() manageVirtuals {
+	tv := make(manageVirtuals)
+	d._purgeVirtual()
+	return tv
+}
+
+// This should be called for every entry added to the directory
+//
+// It returns true if this entry should be skipped
+//
+// must be called with the Dir lock held
+func (mv manageVirtuals) add(d *Dir, name string) bool {
+	// Keep a record of all names listed
+	mv[name] = struct{}{}
+	// Remove virtuals if possible
+	switch d.virtual[name] {
+	case vAddFile, vAddDir:
+		// item was added to the dir but since it is found in a
+		// listing is no longer virtual
+		d._deleteVirtual(name)
+	case vDel:
+		// item is deleted from the dir so skip it
+		return true
+	case vOK:
+	}
+	return false
+}
+
+// This should be called after the directory entry is read to update d.items
+// with virtual entries
+//
+// must be called with the Dir lock held
+func (mv manageVirtuals) end(d *Dir) {
+	// delete unused d.items
+	for name := range d.items {
+		if _, ok := mv[name]; !ok {
+			// name was previously in the directory but wasn't found
+			// in the current listing
+			switch d.virtual[name] {
+			case vAddFile, vAddDir:
+				// virtually added so leave virtual item
+			default:
+				// otherwise delete it
+				delete(d.items, name)
+			}
+		}
+	}
+	// delete unused d.virtual~s
+	for name, virtualState := range d.virtual {
+		if _, ok := mv[name]; !ok {
+			// name exists as a virtual but isn't in the current
+			// listing so if it is a virtual delete we can remove it
+			// as it is no longer needed.
+			if virtualState == vDel {
+				d._deleteVirtual(name)
+			}
+		}
+	}
+}
+
 // update d.items and if dirTree is not nil update each dir in the DirTree below this one and
 // set the last read time - must be called with the lock held
 func (d *Dir) _readDirFromEntries(entries fs.DirEntries, dirTree dirtree.DirTree, when time.Time) error {
 	var err error
-	// Cache the items by name
-	found := make(map[string]struct{})
+	mv := d._newManageVirtuals()
 	for _, entry := range entries {
 		name := path.Base(entry.Remote())
 		if name == "." || name == ".." {
 			continue
 		}
 		node := d.items[name]
-		found[name] = struct{}{}
-		virtualState := d.virtual[name]
-		switch virtualState {
-		case vAdd:
-			// item was added to the dir but since it is found in a
-			// listing is no longer virtual
-			delete(d.virtual, name)
-			if len(d.virtual) == 0 {
-				d.virtual = nil
-			}
-			fs.Debugf(d.path, "Removed virtual directory entry %v: %q", virtualState, name)
-		case vDel:
-			// item is deleted from the dir so skip it
+		if mv.add(d, name) {
 			continue
-		case vOK:
 		}
 		switch item := entry.(type) {
 		case fs.Object:
@@ -452,26 +580,7 @@ func (d *Dir) _readDirFromEntries(entries fs.DirEntries, dirTree dirtree.DirTree
 		}
 		d.items[name] = node
 	}
-	// delete unused entries
-	for name := range d.items {
-		if _, ok := found[name]; !ok && d.virtual[name] != vAdd {
-			// item was added to the dir but wasn't found in the
-			// listing - remove it unless it was virtually added
-			delete(d.items, name)
-		}
-	}
-	// delete unused virtuals
-	for name, virtualState := range d.virtual {
-		if _, ok := found[name]; !ok && virtualState == vDel {
-			// We have a virtual delete but the item wasn't found in
-			// the listing so no longer needs a virtual delete.
-			delete(d.virtual, name)
-			fs.Debugf(d.path, "Removed virtual directory entry %v: %q", virtualState, name)
-		}
-	}
-	if len(d.virtual) == 0 {
-		d.virtual = nil
-	}
+	mv.end(d)
 	return nil
 }
 

vfs/dir_test.go

@@ -289,16 +289,6 @@ func TestDirReadDirAll(t *testing.T) {
 
 		checkListing(t, dir, []string{"file1,14,false", "virtualDir,0,true", "virtualFile,17,false"})
 
-		// Force a directory reload...
-		dir.invalidateDir("dir")
-
-		checkListing(t, dir, []string{"file1,14,false", "virtualDir,0,true", "virtualFile,17,false"})
-
-		// Check that forgetting the root doesn't invalidate the virtual entries
-		root.ForgetAll()
-
-		checkListing(t, dir, []string{"file1,14,false", "virtualDir,0,true", "virtualFile,17,false"})
-
 		// Now action the deletes and uploads
 		_ = r.WriteObject(context.Background(), "dir/virtualFile", "virtualFile contents", t1)
 		_ = r.WriteObject(context.Background(), "dir/virtualDir/testFile", "testFile contents", t1)
@@ -317,6 +307,29 @@ func TestDirReadDirAll(t *testing.T) {
 		assert.Nil(t, dir.virtual)
 		dir.mu.Unlock()
 
+		// Add some virtual entries and check what happens
+		dir.AddVirtual("virtualFile2", 100, false)
+		dir.AddVirtual("virtualDir2", 0, true)
+		// Remove some existing entries
+		dir.DelVirtual("file1")
+
+		checkListing(t, dir, []string{"virtualDir,0,true", "virtualDir2,0,true", "virtualFile,20,false", "virtualFile2,100,false"})
+
+		// Force a directory reload...
+		dir.invalidateDir("dir")
+
+		want := []string{"file1,14,false", "virtualDir,0,true", "virtualDir2,0,true", "virtualFile,20,false", "virtualFile2,100,false"}
+		features := r.Fremote.Features()
+		if features.CanHaveEmptyDirectories {
+			// snip out virtualDir2 which will only be present if can't have empty dirs
+			want = append(want[:2], want[3:]...)
+		}
+		checkListing(t, dir, want)
+
+		// Check that forgetting the root doesn't invalidate the virtual entries
+		root.ForgetAll()
+
+		checkListing(t, dir, want)
 	})
 }
 

vfs/file.go

@@ -403,6 +403,13 @@ func (f *File) _writingInProgress() bool {
 	return f.o == nil || len(f.writers) != 0
 }
 
+// writingInProgress returns true of there are any open writers
+func (f *File) writingInProgress() bool {
+	f.mu.RLock()
+	defer f.mu.RUnlock()
+	return f.o == nil || len(f.writers) != 0
+}
+
 // Update the size while writing
 func (f *File) setSize(n int64) {
 	atomic.StoreInt64(&f.size, n)

vfs/vstate_string.go

@@ -9,13 +9,14 @@ func _() {
 	// Re-run the stringer command to generate them again.
 	var x [1]struct{}
 	_ = x[vOK-0]
-	_ = x[vAdd-1]
-	_ = x[vDel-2]
+	_ = x[vAddFile-1]
+	_ = x[vAddDir-2]
+	_ = x[vDel-3]
 }
 
-const _vState_name = "vOKvAddvDel"
+const _vState_name = "vOKvAddFilevAddDirvDel"
 
-var _vState_index = [...]uint8{0, 3, 7, 11}
+var _vState_index = [...]uint8{0, 3, 11, 18, 22}
 
 func (i vState) String() string {
 	if i >= vState(len(_vState_index)-1) {