Fix empty inode paths caused by stack movement

The inode path request stored the result buffer address as an integer,
which could become stale if the Go stack moved before the syscall.
Pin the buffer while the ioctl runs so ScoutFS writes to the address
that Go later reads.

go.mod

@@ -1,3 +1,3 @@
 module github.com/versity/scoutfs-go
 
-go 1.16
+go 1.26

scoutfs.go

@@ -16,6 +16,7 @@ import (
 	"math"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strconv"
 	"strings"
 	"syscall"
@@ -230,6 +231,10 @@ type inoPathResult struct {
 // (usually just the base mount point directory)
 func InoToPath(dirfd *os.File, ino uint64) (string, error) {
 	var res inoPathResult
+	// Result_ptr is an integer, so keep its target at a stable address.
+	var pin runtime.Pinner
+	pin.Pin(&res)
+	defer pin.Unpin()
 	ip := inoPath{
 		Ino:          ino,
 		Result_ptr:   uint64(uintptr(unsafe.Pointer(&res))),
@@ -251,6 +256,10 @@ func InoToPath(dirfd *os.File, ino uint64) (string, error) {
 // (usually just the base mount point directory)
 func InoToPaths(dirfd *os.File, ino uint64) ([]string, error) {
 	var res inoPathResult
+	// Result_ptr is an integer, so keep its target at a stable address.
+	var pin runtime.Pinner
+	pin.Pin(&res)
+	defer pin.Unpin()
 	ip := inoPath{
 		Ino:          ino,
 		Result_ptr:   uint64(uintptr(unsafe.Pointer(&res))),