fs: support renameExchange in loopback for darwin

Tested on MacOS 14.2 (macfuse 4.5.0) and Ubuntu 20.04.2 (Linux 5.15.0)

Change-Id: I3f4f92c2d2aa3f4fc3696b661fa3cb0e3b43282b

fs/loopback.go

@@ -11,6 +11,7 @@ import (
 	"syscall"
 
 	"github.com/hanwen/go-fuse/v2/fuse"
+	"github.com/hanwen/go-fuse/v2/internal/renameat"
 )
 
 // LoopbackRoot holds the parameters for creating a new loopback
@@ -218,6 +219,41 @@ func (n *LoopbackNode) Create(ctx context.Context, name string, flags uint32, mo
 	return ch, lf, 0, 0
 }
 
+func (n *LoopbackNode) renameExchange(name string, newparent InodeEmbedder, newName string) syscall.Errno {
+	fd1, err := syscall.Open(n.path(), syscall.O_DIRECTORY, 0)
+	if err != nil {
+		return ToErrno(err)
+	}
+	defer syscall.Close(fd1)
+	p2 := filepath.Join(n.RootData.Path, newparent.EmbeddedInode().Path(nil))
+	fd2, err := syscall.Open(p2, syscall.O_DIRECTORY, 0)
+	defer syscall.Close(fd2)
+	if err != nil {
+		return ToErrno(err)
+	}
+
+	var st syscall.Stat_t
+	if err := syscall.Fstat(fd1, &st); err != nil {
+		return ToErrno(err)
+	}
+
+	// Double check that nodes didn't change from under us.
+	inode := &n.Inode
+	if inode.Root() != inode && inode.StableAttr().Ino != n.RootData.idFromStat(&st).Ino {
+		return syscall.EBUSY
+	}
+	if err := syscall.Fstat(fd2, &st); err != nil {
+		return ToErrno(err)
+	}
+
+	newinode := newparent.EmbeddedInode()
+	if newinode.Root() != newinode && newinode.StableAttr().Ino != n.RootData.idFromStat(&st).Ino {
+		return syscall.EBUSY
+	}
+
+	return ToErrno(renameat.Renameat(fd1, name, fd2, newName, renameat.RENAME_EXCHANGE))
+}
+
 var _ = (NodeSymlinker)((*LoopbackNode)(nil))
 
 func (n *LoopbackNode) Symlink(ctx context.Context, target, name string, out *fuse.EntryOut) (*Inode, syscall.Errno) {

fs/loopback_darwin.go

@@ -41,10 +41,6 @@ func (n *LoopbackNode) Listxattr(ctx context.Context, dest []byte) (uint32, sysc
 	return 0, syscall.ENOSYS
 }
 
-func (n *LoopbackNode) renameExchange(name string, newparent InodeEmbedder, newName string) syscall.Errno {
-	return syscall.ENOSYS
-}
-
 func (f *loopbackFile) Allocate(ctx context.Context, off uint64, sz uint64, mode uint32) syscall.Errno {
 	// TODO: Handle `mode` parameter.
 

fs/loopback_linux.go

@@ -9,7 +9,6 @@ package fs
 
 import (
 	"context"
-	"path/filepath"
 	"syscall"
 
 	"golang.org/x/sys/unix"
@@ -43,41 +42,6 @@ func (n *LoopbackNode) Listxattr(ctx context.Context, dest []byte) (uint32, sysc
 	return uint32(sz), ToErrno(err)
 }
 
-func (n *LoopbackNode) renameExchange(name string, newparent InodeEmbedder, newName string) syscall.Errno {
-	fd1, err := syscall.Open(n.path(), syscall.O_DIRECTORY, 0)
-	if err != nil {
-		return ToErrno(err)
-	}
-	defer syscall.Close(fd1)
-	p2 := filepath.Join(n.RootData.Path, newparent.EmbeddedInode().Path(nil))
-	fd2, err := syscall.Open(p2, syscall.O_DIRECTORY, 0)
-	defer syscall.Close(fd2)
-	if err != nil {
-		return ToErrno(err)
-	}
-
-	var st syscall.Stat_t
-	if err := syscall.Fstat(fd1, &st); err != nil {
-		return ToErrno(err)
-	}
-
-	// Double check that nodes didn't change from under us.
-	inode := &n.Inode
-	if inode.Root() != inode && inode.StableAttr().Ino != n.RootData.idFromStat(&st).Ino {
-		return syscall.EBUSY
-	}
-	if err := syscall.Fstat(fd2, &st); err != nil {
-		return ToErrno(err)
-	}
-
-	newinode := newparent.EmbeddedInode()
-	if newinode.Root() != newinode && newinode.StableAttr().Ino != n.RootData.idFromStat(&st).Ino {
-		return syscall.EBUSY
-	}
-
-	return ToErrno(unix.Renameat2(fd1, name, fd2, newName, unix.RENAME_EXCHANGE))
-}
-
 var _ = (NodeCopyFileRanger)((*LoopbackNode)(nil))
 
 func (n *LoopbackNode) CopyFileRange(ctx context.Context, fhIn FileHandle,

fs/loopback_linux_test.go

@@ -8,7 +8,6 @@ import (
 	"bytes"
 	"io/ioutil"
 	"os"
-	"reflect"
 	"sync"
 	"syscall"
 	"testing"
@@ -16,82 +15,9 @@ import (
 
 	"github.com/hanwen/go-fuse/v2/fuse"
 	"github.com/hanwen/go-fuse/v2/internal/testutil"
-	"github.com/kylelemons/godebug/pretty"
 	"golang.org/x/sys/unix"
 )
 
-func TestRenameExchange(t *testing.T) {
-	tc := newTestCase(t, &testOptions{attrCache: true, entryCache: true})
-
-	if err := os.Mkdir(tc.origDir+"/dir", 0755); err != nil {
-		t.Fatalf("Mkdir: %v", err)
-	}
-	tc.writeOrig("file", "hello", 0644)
-	tc.writeOrig("dir/file", "x", 0644)
-
-	f1, err := syscall.Open(tc.mntDir+"/", syscall.O_DIRECTORY, 0)
-	if err != nil {
-		t.Fatalf("open 1: %v", err)
-	}
-	defer syscall.Close(f1)
-	f2, err := syscall.Open(tc.mntDir+"/dir", syscall.O_DIRECTORY, 0)
-	if err != nil {
-		t.Fatalf("open 2: %v", err)
-	}
-	defer syscall.Close(f2)
-
-	var before1, before2 unix.Stat_t
-	if err := unix.Fstatat(f1, "file", &before1, 0); err != nil {
-		t.Fatalf("Fstatat: %v", err)
-	}
-	if err := unix.Fstatat(f2, "file", &before2, 0); err != nil {
-		t.Fatalf("Fstatat: %v", err)
-	}
-
-	if err := unix.Renameat2(f1, "file", f2, "file", unix.RENAME_EXCHANGE); err != nil {
-		t.Errorf("rename EXCHANGE: %v", err)
-	}
-
-	var after1, after2 unix.Stat_t
-	if err := unix.Fstatat(f1, "file", &after1, 0); err != nil {
-		t.Fatalf("Fstatat: %v", err)
-	}
-	if err := unix.Fstatat(f2, "file", &after2, 0); err != nil {
-		t.Fatalf("Fstatat: %v", err)
-	}
-	clearCtime := func(s *unix.Stat_t) {
-		s.Ctim.Sec = 0
-		s.Ctim.Nsec = 0
-	}
-
-	clearCtime(&after1)
-	clearCtime(&after2)
-	clearCtime(&before2)
-	clearCtime(&before1)
-	if diff := pretty.Compare(after1, before2); diff != "" {
-		t.Errorf("after1, before2: %s", diff)
-	}
-	if !reflect.DeepEqual(after2, before1) {
-		t.Errorf("after2, before1: %#v, %#v", after2, before1)
-	}
-
-	root := tc.loopback.EmbeddedInode().Root()
-	ino1 := root.GetChild("file")
-	if ino1 == nil {
-		t.Fatalf("root.GetChild(%q): null inode", "file")
-	}
-	ino2 := root.GetChild("dir").GetChild("file")
-	if ino2 == nil {
-		t.Fatalf("dir.GetChild(%q): null inode", "file")
-	}
-	if ino1.StableAttr().Ino != after1.Ino {
-		t.Errorf("got inode %d for %q, want %d", ino1.StableAttr().Ino, "file", after1.Ino)
-	}
-	if ino2.StableAttr().Ino != after2.Ino {
-		t.Errorf("got inode %d for %q want %d", ino2.StableAttr().Ino, "dir/file", after2.Ino)
-	}
-}
-
 func TestRenameNoOverwrite(t *testing.T) {
 	tc := newTestCase(t, &testOptions{attrCache: true, entryCache: true})
 

fs/loopback_test.go

+package fs
+
+import (
+	"os"
+	"reflect"
+	"syscall"
+	"testing"
+
+	"github.com/kylelemons/godebug/pretty"
+	"golang.org/x/sys/unix"
+)
+
+func TestRenameExchange(t *testing.T) {
+	tc := newTestCase(t, &testOptions{attrCache: true, entryCache: true})
+
+	if err := os.Mkdir(tc.origDir+"/dir", 0755); err != nil {
+		t.Fatalf("Mkdir: %v", err)
+	}
+	tc.writeOrig("file", "hello", 0644)
+	tc.writeOrig("dir/file", "x", 0644)
+
+	f1, err := syscall.Open(tc.mntDir+"/", syscall.O_DIRECTORY, 0)
+	if err != nil {
+		t.Fatalf("open 1: %v", err)
+	}
+	defer syscall.Close(f1)
+	f2, err := syscall.Open(tc.mntDir+"/dir", syscall.O_DIRECTORY, 0)
+	if err != nil {
+		t.Fatalf("open 2: %v", err)
+	}
+	defer syscall.Close(f2)
+
+	var before1, before2 unix.Stat_t
+	if err := unix.Fstatat(f1, "file", &before1, 0); err != nil {
+		t.Fatalf("Fstatat: %v", err)
+	}
+	if err := unix.Fstatat(f2, "file", &before2, 0); err != nil {
+		t.Fatalf("Fstatat: %v", err)
+	}
+
+	if err := unix.Renameat2(f1, "file", f2, "file", unix.RENAME_EXCHANGE); err != nil {
+		t.Errorf("rename EXCHANGE: %v", err)
+	}
+
+	var after1, after2 unix.Stat_t
+	if err := unix.Fstatat(f1, "file", &after1, 0); err != nil {
+		t.Fatalf("Fstatat: %v", err)
+	}
+	if err := unix.Fstatat(f2, "file", &after2, 0); err != nil {
+		t.Fatalf("Fstatat: %v", err)
+	}
+	clearCtime := func(s *unix.Stat_t) {
+		s.Ctim.Sec = 0
+		s.Ctim.Nsec = 0
+	}
+
+	clearCtime(&after1)
+	clearCtime(&after2)
+	clearCtime(&before2)
+	clearCtime(&before1)
+	if diff := pretty.Compare(after1, before2); diff != "" {
+		t.Errorf("after1, before2: %s", diff)
+	}
+	if !reflect.DeepEqual(after2, before1) {
+		t.Errorf("after2, before1: %#v, %#v", after2, before1)
+	}
+
+	root := tc.loopback.EmbeddedInode().Root()
+	ino1 := root.GetChild("file")
+	if ino1 == nil {
+		t.Fatalf("root.GetChild(%q): null inode", "file")
+	}
+	ino2 := root.GetChild("dir").GetChild("file")
+	if ino2 == nil {
+		t.Fatalf("dir.GetChild(%q): null inode", "file")
+	}
+	if ino1.StableAttr().Ino != after1.Ino {
+		t.Errorf("got inode %d for %q, want %d", ino1.StableAttr().Ino, "file", after1.Ino)
+	}
+	if ino2.StableAttr().Ino != after2.Ino {
+		t.Errorf("got inode %d for %q want %d", ino2.StableAttr().Ino, "dir/file", after2.Ino)
+	}
+}

fuse/opcode.go

@@ -102,7 +102,7 @@ func doInit(server *Server, req *request) {
 	server.reqMu.Lock()
 	server.kernelSettings = *input
 	server.kernelSettings.Flags = input.Flags & (CAP_ASYNC_READ | CAP_BIG_WRITES | CAP_FILE_OPS |
-		CAP_READDIRPLUS | CAP_NO_OPEN_SUPPORT | CAP_PARALLEL_DIROPS | CAP_MAX_PAGES)
+		CAP_READDIRPLUS | CAP_NO_OPEN_SUPPORT | CAP_PARALLEL_DIROPS | CAP_MAX_PAGES | CAP_RENAME_SWAP)
 
 	if server.opts.EnableLocks {
 		server.kernelSettings.Flags |= CAP_FLOCK_LOCKS | CAP_POSIX_LOCKS
@@ -443,6 +443,10 @@ func doSymlink(server *Server, req *request) {
 }
 
 func doRename(server *Server, req *request) {
+	if server.kernelSettings.supportsRenameSwap() {
+		doRename2(server, req)
+		return
+	}
 	in1 := (*Rename1In)(req.inData)
 	in := RenameIn{
 		InHeader: in1.InHeader,

fuse/request.go

@@ -172,7 +172,7 @@ func (r *request) parseHeader() Status {
 	return OK
 }
 
-func (r *request) parse() {
+func (r *request) parse(kernelSettings InitIn) {
 	r.arg = r.inputBuf[:]
 	r.handler = getHandler(r.inHeader.Opcode)
 	if r.handler == nil {
@@ -182,6 +182,9 @@ func (r *request) parse() {
 	}
 
 	inSz := int(r.handler.InputSize)
+	if r.inHeader.Opcode == _OP_RENAME && kernelSettings.supportsRenameSwap() {
+		inSz = int(unsafe.Sizeof(RenameIn{}))
+	}
 	if r.inHeader.Opcode == _OP_INIT && inSz > len(r.arg) {
 		// Minor version 36 extended the size of InitIn struct
 		inSz = len(r.arg)

fuse/request_darwin.go

@@ -9,5 +9,5 @@ const outputHeaderSize = 200
 const (
 	_FUSE_KERNEL_VERSION   = 7
 	_MINIMUM_MINOR_VERSION = 12
-	_OUR_MINOR_VERSION     = 12
+	_OUR_MINOR_VERSION     = 19
 )

fuse/server.go

@@ -508,7 +508,7 @@ func (ms *Server) handleRequest(req *request) Status {
 		defer ms.requestProcessingMu.Unlock()
 	}
 
-	req.parse()
+	req.parse(ms.kernelSettings)
 	if req.handler == nil {
 		req.status = ENOSYS
 	}
@@ -906,6 +906,12 @@ func (in *InitIn) SupportsNotify(notifyType int) bool {
 	return false
 }
 
+// supportsRenameSwap returns whether the kernel supports the
+// renamex_np(2) syscall. This is only supported on OS X.
+func (in *InitIn) supportsRenameSwap() bool {
+	return in.Flags&CAP_RENAME_SWAP != 0
+}
+
 // WaitMount waits for the first request to be served. Use this to
 // avoid racing between accessing the (empty or not yet mounted)
 // mountpoint, and the OS trying to setup the user-space mount.

fuse/types_linux.go

@@ -28,6 +28,9 @@ const (
 	CAP_SETXATTR_EXT        = (1 << 29)
 	CAP_INIT_EXT            = (1 << 30)
 	CAP_INIT_RESERVED       = (1 << 31)
+
+	// CAP_RENAME_SWAP only exists on OSX.
+	CAP_RENAME_SWAP = 0x0
 )
 
 type Attr struct {

internal/renameat/renameat.go

+package renameat
+
+// Renameat is a wrapper around renameat syscall.
+// On Linux, it is a wrapper around renameat2(2).
+// On Darwin, it is a wrapper around renameatx_np(2).
+func Renameat(olddirfd int, oldpath string, newdirfd int, newpath string, flags uint) (err error) {
+	return renameat(olddirfd, oldpath, newdirfd, newpath, flags)
+}

internal/renameat/renameat_darwin.go

+package renameat
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const (
+	SYS_RENAMEATX_NP = 488
+	RENAME_SWAP      = 0x2
+	RENAME_EXCHANGE  = RENAME_SWAP
+)
+
+func renameat(olddirfd int, oldpath string, newdirfd int, newpath string, flags uint) error {
+	oldpathCString, err := syscall.BytePtrFromString(oldpath)
+	if err != nil {
+		return err
+	}
+	newpathCString, err := syscall.BytePtrFromString(newpath)
+	if err != nil {
+		return err
+	}
+
+	_, _, errno := syscall.Syscall6(
+		SYS_RENAMEATX_NP,
+		uintptr(olddirfd),
+		uintptr(unsafe.Pointer(oldpathCString)),
+		uintptr(newdirfd),
+		uintptr(unsafe.Pointer(newpathCString)),
+		uintptr(flags),
+		0,
+	)
+
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

internal/renameat/renameat_linux.go

+package renameat
+
+import "golang.org/x/sys/unix"
+
+const (
+	RENAME_EXCHANGE = unix.RENAME_EXCHANGE
+)
+
+func renameat(olddirfd int, oldpath string, newdirfd int, newpath string, flags uint) (err error) {
+	return unix.Renameat2(olddirfd, oldpath, newdirfd, newpath, flags)
+}