lib/model: More precise deletion detection (fixes #2571, fixes #4573) (#4765)

lib/model/model.go

@@ -2044,18 +2044,18 @@ func (m *Model) internalScanFolderSubdirs(ctx context.Context, folder string, su
 				batchSizeBytes += nf.ProtoSize()
 				changes++
 
+			case f.IsInvalid() && !ignores.Match(f.Name).IsIgnored():
+				// Successfully scanned items are already un-ignored during
+				// the scan, so check whether it is deleted.
+				fallthrough
 			case !f.IsInvalid() && !f.IsDeleted():
 				// The file is valid and not deleted. Lets check if it's
 				// still here.
-
-				if _, err := mtimefs.Lstat(f.Name); err != nil {
-					// We don't specifically verify that the error is
-					// fs.IsNotExist because there is a corner case when a
-					// directory is suddenly transformed into a file. When that
-					// happens, files that were in the directory (that is now a
-					// file) are deleted but will return a confusing error ("not a
-					// directory") when we try to Lstat() them.
-
+				// Simply stating it wont do as there are tons of corner
+				// cases (e.g. parent dir->simlink, missing permissions)
+				if !osutil.IsDeleted(mtimefs, f.Name) {
+					return true
+				}
 				nf := protocol.FileInfo{
 					Name:       f.Name,
 					Type:       f.Type,
@@ -2071,7 +2071,6 @@ func (m *Model) internalScanFolderSubdirs(ctx context.Context, folder string, su
 				batchSizeBytes += nf.ProtoSize()
 				changes++
 			}
-			}
 			return true
 		})
 

lib/model/model_test.go

@@ -2808,6 +2808,186 @@ func TestNoRequestsFromPausedDevices(t *testing.T) {
 	}
 }
 
+// TestIssue2571 tests replacing a directory with content with a symlink
+func TestIssue2571(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Scanning symlinks isn't supported on windows")
+	}
+
+	err := defaultFs.MkdirAll("replaceDir", 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		defaultFs.RemoveAll("replaceDir")
+	}()
+
+	testFs := fs.NewFilesystem(fs.FilesystemTypeBasic, filepath.Join(defaultFs.URI(), "replaceDir"))
+
+	for _, dir := range []string{"toLink", "linkTarget"} {
+		err := testFs.MkdirAll(dir, 0775)
+		if err != nil {
+			t.Fatal(err)
+		}
+		fd, err := testFs.Create(filepath.Join(dir, "a"))
+		if err != nil {
+			t.Fatal(err)
+		}
+		fd.Close()
+	}
+
+	dbi := db.OpenMemory()
+	m := NewModel(defaultConfig, protocol.LocalDeviceID, "syncthing", "dev", dbi, nil)
+	m.AddFolder(defaultFolderConfig)
+	m.StartFolder("default")
+	m.ServeBackground()
+	defer m.Stop()
+	m.ScanFolder("default")
+
+	if err = testFs.RemoveAll("toLink"); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := osutil.DebugSymlinkForTestsOnly(filepath.Join(testFs.URI(), "linkTarget"), filepath.Join(testFs.URI(), "toLink")); err != nil {
+		t.Fatal(err)
+	}
+
+	m.ScanFolder("default")
+
+	if dir, ok := m.CurrentFolderFile("default", filepath.Join("replaceDir", "toLink")); !ok {
+		t.Fatalf("Dir missing in db")
+	} else if !dir.IsSymlink() {
+		t.Errorf("Dir wasn't changed to symlink")
+	}
+	if file, ok := m.CurrentFolderFile("default", filepath.Join("replaceDir", "toLink", "a")); !ok {
+		t.Fatalf("File missing in db")
+	} else if !file.Deleted {
+		t.Errorf("File below symlink has not been marked as deleted")
+	}
+}
+
+// TestIssue4573 tests that contents of an unavailable dir aren't marked deleted
+func TestIssue4573(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Can't make the dir inaccessible on windows")
+	}
+
+	err := defaultFs.MkdirAll("inaccessible", 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		defaultFs.Chmod("inaccessible", 0777)
+		defaultFs.RemoveAll("inaccessible")
+	}()
+
+	file := filepath.Join("inaccessible", "a")
+	fd, err := defaultFs.Create(file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	fd.Close()
+
+	dbi := db.OpenMemory()
+	m := NewModel(defaultConfig, protocol.LocalDeviceID, "syncthing", "dev", dbi, nil)
+	m.AddFolder(defaultFolderConfig)
+	m.StartFolder("default")
+	m.ServeBackground()
+	defer m.Stop()
+	m.ScanFolder("default")
+
+	err = defaultFs.Chmod("inaccessible", 0000)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	m.ScanFolder("default")
+
+	if file, ok := m.CurrentFolderFile("default", file); !ok {
+		t.Fatalf("File missing in db")
+	} else if file.Deleted {
+		t.Errorf("Inaccessible file has been marked as deleted.")
+	}
+}
+
+// TestInternalScan checks whether various fs operations are correctly represented
+// in the db after scanning.
+func TestInternalScan(t *testing.T) {
+	err := defaultFs.MkdirAll("internalScan", 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		defaultFs.RemoveAll("internalScan")
+	}()
+
+	testFs := fs.NewFilesystem(fs.FilesystemTypeBasic, filepath.Join(defaultFs.URI(), "internalScan"))
+
+	testCases := map[string]func(protocol.FileInfo) bool{
+		"removeDir": func(f protocol.FileInfo) bool {
+			return !f.Deleted
+		},
+		"dirToFile": func(f protocol.FileInfo) bool {
+			return f.Deleted || f.IsDirectory()
+		},
+	}
+
+	baseDirs := []string{"dirToFile", "removeDir"}
+	for _, dir := range baseDirs {
+		sub := filepath.Join(dir, "subDir")
+		for _, dir := range []string{dir, sub} {
+			err := testFs.MkdirAll(dir, 0775)
+			if err != nil {
+				t.Fatalf("%v: %v", dir, err)
+			}
+		}
+		testCases[sub] = func(f protocol.FileInfo) bool {
+			return !f.Deleted
+		}
+		for _, dir := range []string{dir, sub} {
+			file := filepath.Join(dir, "a")
+			fd, err := testFs.Create(file)
+			if err != nil {
+				t.Fatal(err)
+			}
+			fd.Close()
+			testCases[file] = func(f protocol.FileInfo) bool {
+				return !f.Deleted
+			}
+		}
+	}
+
+	dbi := db.OpenMemory()
+	m := NewModel(defaultConfig, protocol.LocalDeviceID, "syncthing", "dev", dbi, nil)
+	m.AddFolder(defaultFolderConfig)
+	m.StartFolder("default")
+	m.ServeBackground()
+	defer m.Stop()
+	m.ScanFolder("default")
+
+	for _, dir := range baseDirs {
+		if err = testFs.RemoveAll(dir); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	fd, err := testFs.Create("dirToFile")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fd.Close()
+
+	m.ScanFolder("default")
+
+	for path, cond := range testCases {
+		if f, ok := m.CurrentFolderFile("default", filepath.Join("internalScan", path)); !ok {
+			t.Fatalf("%v missing in db", path)
+		} else if cond(f) {
+			t.Errorf("Incorrect db entry for %v", path)
+		}
+	}
+}
+
 func TestCustomMarkerName(t *testing.T) {
 	ldb := db.OpenMemory()
 	set := db.NewFileSet("default", defaultFs, ldb)

lib/osutil/osutil.go

@@ -153,3 +153,14 @@ func init() {
 func IsWindowsExecutable(path string) bool {
 	return execExts[strings.ToLower(filepath.Ext(path))]
 }
+
+func IsDeleted(ffs fs.Filesystem, name string) bool {
+	if _, err := ffs.Lstat(name); fs.IsNotExist(err) {
+		return true
+	}
+	switch TraversesSymlink(ffs, filepath.Dir(name)).(type) {
+	case *NotADirectoryError, *TraversesSymlinkError:
+		return true
+	}
+	return false
+}