fuse: support RENAME2 in RawFileSystem

In practice, this only triggers for RENAME_EXCHANGE, as the kernel
issues the RENAME opcode in case of a normal rename or a
RENAME_NOREPLACE.

We have always advertised rename2 support (protocol v23), but it returned
ENOSYS always. Instead, rename RenameIn => Rename1In, and add Flags to
RenameIn.

For raw filesystems that want to support rename2 should examine
RenameIn.Flags and check for syscall.RENAME_XXX.

For fuse/nodefs, we return ENOSYS in case of Rename2, since we lack
API surface to propagate the flags.

fuse/nodefs/fsops.go

@@ -305,6 +305,9 @@ func (c *rawBridge) Symlink(header *fuse.InHeader, pointedTo string, linkName st
 }
 
 func (c *rawBridge) Rename(input *fuse.RenameIn, oldName string, newName string) (code fuse.Status) {
+	if input.Flags != 0 {
+		return fuse.ENOSYS
+	}
 	oldParent := c.toInode(input.NodeId)
 
 	child := oldParent.GetChild(oldName)

fuse/opcode.go

@@ -56,7 +56,7 @@ const (
 	_OP_BATCH_FORGET = int32(42)
 	_OP_FALLOCATE    = int32(43) // protocol version 19.
 	_OP_READDIRPLUS  = int32(44) // protocol version 21.
-	_OP_FUSE_RENAME2 = int32(45) // protocol version 23.
+	_OP_RENAME2      = int32(45) // protocol version 23.
 
 	// The following entries don't have to be compatible across Go-FUSE versions.
 	_OP_NOTIFY_INVAL_ENTRY    = int32(100)
@@ -410,6 +410,15 @@ func doSymlink(server *Server, req *request) {
 }
 
 func doRename(server *Server, req *request) {
+	in1 := (*Rename1In)(req.inData)
+	in := RenameIn{
+		InHeader: in1.InHeader,
+		Newdir:   in1.Newdir,
+	}
+	req.status = server.fileSystem.Rename(&in, req.filenames[0], req.filenames[1])
+}
+
+func doRename2(server *Server, req *request) {
 	req.status = server.fileSystem.Rename((*RenameIn)(req.inData), req.filenames[0], req.filenames[1])
 }
 
@@ -499,7 +508,7 @@ func init() {
 		_OP_SETATTR:      unsafe.Sizeof(SetAttrIn{}),
 		_OP_MKNOD:        unsafe.Sizeof(MknodIn{}),
 		_OP_MKDIR:        unsafe.Sizeof(MkdirIn{}),
-		_OP_RENAME:       unsafe.Sizeof(RenameIn{}),
+		_OP_RENAME:       unsafe.Sizeof(Rename1In{}),
 		_OP_LINK:         unsafe.Sizeof(LinkIn{}),
 		_OP_OPEN:         unsafe.Sizeof(OpenIn{}),
 		_OP_READ:         unsafe.Sizeof(ReadIn{}),
@@ -527,6 +536,7 @@ func init() {
 		_OP_NOTIFY_REPLY: unsafe.Sizeof(NotifyRetrieveIn{}),
 		_OP_FALLOCATE:    unsafe.Sizeof(FallocateIn{}),
 		_OP_READDIRPLUS:  unsafe.Sizeof(ReadIn{}),
+		_OP_RENAME2:      unsafe.Sizeof(RenameIn{}),
 	} {
 		operationHandlers[op].InputSize = sz
 	}
@@ -608,6 +618,7 @@ func init() {
 		_OP_NOTIFY_DELETE:         "NOTIFY_DELETE",
 		_OP_FALLOCATE:             "FALLOCATE",
 		_OP_READDIRPLUS:           "READDIRPLUS",
+		_OP_RENAME2:               "RENAME2",
 	} {
 		operationHandlers[op].Name = v
 	}
@@ -652,6 +663,7 @@ func init() {
 		_OP_NOTIFY_REPLY: doNotifyReply,
 		_OP_FALLOCATE:    doFallocate,
 		_OP_READDIRPLUS:  doReadDirPlus,
+		_OP_RENAME2:      doRename2,
 	} {
 		operationHandlers[op].Func = v
 	}
@@ -704,10 +716,11 @@ func init() {
 		_OP_FALLOCATE:    func(ptr unsafe.Pointer) interface{} { return (*FallocateIn)(ptr) },
 		_OP_NOTIFY_REPLY: func(ptr unsafe.Pointer) interface{} { return (*NotifyRetrieveIn)(ptr) },
 		_OP_READDIRPLUS:  func(ptr unsafe.Pointer) interface{} { return (*ReadIn)(ptr) },
-		_OP_RENAME:       func(ptr unsafe.Pointer) interface{} { return (*RenameIn)(ptr) },
+		_OP_RENAME:       func(ptr unsafe.Pointer) interface{} { return (*Rename1In)(ptr) },
 		_OP_GETLK:        func(ptr unsafe.Pointer) interface{} { return (*LkIn)(ptr) },
 		_OP_SETLK:        func(ptr unsafe.Pointer) interface{} { return (*LkIn)(ptr) },
 		_OP_SETLKW:       func(ptr unsafe.Pointer) interface{} { return (*LkIn)(ptr) },
+		_OP_RENAME2:      func(ptr unsafe.Pointer) interface{} { return (*RenameIn)(ptr) },
 	} {
 		operationHandlers[op].DecodeIn = f
 	}
@@ -723,6 +736,7 @@ func init() {
 		_OP_MKNOD:       1,
 		_OP_REMOVEXATTR: 1,
 		_OP_RENAME:      2,
+		_OP_RENAME2:     2,
 		_OP_RMDIR:       1,
 		_OP_SYMLINK:     2,
 		_OP_UNLINK:      1,

fuse/print.go

@@ -115,8 +115,12 @@ func (me *MkdirIn) string() string {
 	return fmt.Sprintf("{0%o (0%o)}", me.Mode, me.Umask)
 }
 
+func (me *Rename1In) string() string {
+	return fmt.Sprintf("{i%d}", me.Newdir)
+}
+
 func (me *RenameIn) string() string {
-	return fmt.Sprintf("{%d}", me.Newdir)
+	return fmt.Sprintf("{i%d %x}", me.Newdir, me.Flags)
 }
 
 func (me *SetAttrIn) string() string {

fuse/types.go

@@ -97,12 +97,12 @@ type MkdirIn struct {
 	Umask uint32
 }
 
-type RenameIn struct {
+type Rename1In struct {
 	InHeader
 	Newdir uint64
 }
 
-type Rename2In struct {
+type RenameIn struct {
 	InHeader
 	Newdir  uint64
 	Flags   uint32