cmd_migrate_db: use lnd package for disk size check

The previous disk space check only supported Linux/Unix. But we also
want to build binaries for Windows.
Luckily, we already have this functionality for all our supported
platforms in the healthcheck package of lnd.

Author: guggero

cmd_migrate_db.go

@@ -9,14 +9,14 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"syscall"
 	"time"
 
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/btcsuite/btclog/v2"
 	"github.com/jessevdk/go-flags"
 	"github.com/lightninglabs/lndinit/migratekvdb"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/healthcheck"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/kvdb/postgres"
 	"github.com/lightningnetwork/lnd/kvdb/sqlbase"
@@ -590,7 +590,7 @@ func openSourceDb(cfg *SourceDB, prefix, network string,
 	// Because the destination can also just be a postgres dsn, we just
 	// check if the source dir has enough free space to hold a copy of the
 	// db.
-	freeSpace, err := availableDiskSpace(cfg.Bolt.DataDir)
+	freeSpace, err := healthcheck.AvailableDiskSpace(cfg.Bolt.DataDir)
 	if err != nil {
 		return nil, fmt.Errorf("error determining source directory "+
 			"free space: %v", err)
@@ -922,20 +922,6 @@ func createMigrationCompletedFile(sourceDB *SourceDB, prefix,
 	return nil
 }
 
-// availableDiskSpace returns the available disk space in bytes of the given
-// file system.
-func availableDiskSpace(path string) (uint64, error) {
-	s := syscall.Statfs_t{}
-	err := syscall.Statfs(path, &s)
-	if err != nil {
-		return 0, err
-	}
-
-	// Some OSes have s.Bavail defined as int64, others as uint64, so we
-	// need the explicit type conversion here.
-	return uint64(s.Bavail) * uint64(s.Bsize), nil // nolint:unconvert
-}
-
 // checkPathExists verifies that the directory exists.
 func checkPathExists(path string) error {
 	dir := filepath.Dir(path)