avoid data race read volume.IsEmpty (#4574)

* avoid data race read volume.IsEmpty

-   avoid phantom read isEmpty for onlyEmpty
-   use `v.DataBackend.GetStat()` in v.dataFileAccessLock scope

* add Destroy(onlyEmpty: true) test

* add Destroy(onlyEmpty: false) test

* remove unused `IsEmpty()`

* change literal `8` to `SuperBlockSize`

weed/storage/volume_write_test.go

@@ -1,7 +1,10 @@
 package storage
 
 import (
+	"errors"
 	"fmt"
+	"github.com/stretchr/testify/assert"
+	"os"
 	"testing"
 	"time"
 
@@ -53,3 +56,111 @@ func TestSearchVolumesWithDeletedNeedles(t *testing.T) {
 	fmt.Printf("offset: %v, isLast: %v\n", offset.ToActualOffset(), isLast)
 
 }
+
+func isFileExist(path string) (bool, error) {
+	if _, err := os.Stat(path); err == nil {
+		return true, nil
+	} else if errors.Is(err, os.ErrNotExist) {
+		return false, nil
+	} else {
+		return false, err
+	}
+}
+
+func assertFileExist(t *testing.T, expected bool, path string) {
+	exist, err := isFileExist(path)
+	if err != nil {
+		t.Fatalf("isFileExist: %v", err)
+	}
+	assert.Equal(t, expected, exist)
+}
+
+func TestDestroyEmptyVolumeWithOnlyEmpty(t *testing.T) {
+	dir := t.TempDir()
+
+	v, err := NewVolume(dir, dir, "", 1, NeedleMapInMemory, &super_block.ReplicaPlacement{}, &needle.TTL{}, 0, 0, 0)
+	if err != nil {
+		t.Fatalf("volume creation: %v", err)
+	}
+	path := v.DataBackend.Name()
+
+	// should can Destroy empty volume with onlyEmpty
+	assertFileExist(t, true, path)
+	err = v.Destroy(true)
+	if err != nil {
+		t.Fatalf("destroy volume: %v", err)
+	}
+	assertFileExist(t, false, path)
+}
+
+func TestDestroyEmptyVolumeWithoutOnlyEmpty(t *testing.T) {
+	dir := t.TempDir()
+
+	v, err := NewVolume(dir, dir, "", 1, NeedleMapInMemory, &super_block.ReplicaPlacement{}, &needle.TTL{}, 0, 0, 0)
+	if err != nil {
+		t.Fatalf("volume creation: %v", err)
+	}
+	path := v.DataBackend.Name()
+
+	// should can Destroy empty volume without onlyEmpty
+	assertFileExist(t, true, path)
+	err = v.Destroy(false)
+	if err != nil {
+		t.Fatalf("destroy volume: %v", err)
+	}
+	assertFileExist(t, false, path)
+}
+
+func TestDestroyNonemptyVolumeWithOnlyEmpty(t *testing.T) {
+	dir := t.TempDir()
+
+	v, err := NewVolume(dir, dir, "", 1, NeedleMapInMemory, &super_block.ReplicaPlacement{}, &needle.TTL{}, 0, 0, 0)
+	if err != nil {
+		t.Fatalf("volume creation: %v", err)
+	}
+	path := v.DataBackend.Name()
+
+	// should return "volume not empty" error and do not delete file when Destroy non-empty volume
+	_, _, _, err = v.writeNeedle2(newRandomNeedle(1), true, false)
+	if err != nil {
+		t.Fatalf("write needle: %v", err)
+	}
+	assert.Equal(t, uint64(1), v.FileCount())
+
+	assertFileExist(t, true, path)
+	err = v.Destroy(true)
+	assert.EqualError(t, err, "volume not empty")
+	assertFileExist(t, true, path)
+
+	// should keep working after "volume not empty"
+	_, _, _, err = v.writeNeedle2(newRandomNeedle(2), true, false)
+	if err != nil {
+		t.Fatalf("write needle: %v", err)
+	}
+
+	assert.Equal(t, uint64(2), v.FileCount())
+}
+
+func TestDestroyNonemptyVolumeWithoutOnlyEmpty(t *testing.T) {
+	dir := t.TempDir()
+
+	v, err := NewVolume(dir, dir, "", 1, NeedleMapInMemory, &super_block.ReplicaPlacement{}, &needle.TTL{}, 0, 0, 0)
+	if err != nil {
+		t.Fatalf("volume creation: %v", err)
+	}
+	path := v.DataBackend.Name()
+
+	// should can Destroy non-empty volume without onlyEmpty
+	_, _, _, err = v.writeNeedle2(newRandomNeedle(1), true, false)
+	if err != nil {
+		t.Fatalf("write needle: %v", err)
+	}
+	assert.Equal(t, uint64(1), v.FileCount())
+
+	assertFileExist(t, true, path)
+	err = v.Destroy(false)
+	if err != nil {
+		t.Fatalf("destroy volume: %v", err)
+	}
+	assertFileExist(t, false, path)
+}