In Raw API, make separate calls for XAttr size and data.

fuse/api.go

@@ -260,7 +260,8 @@ type RawFileSystem interface {
 	Access(header *InHeader, input *AccessIn) (code Status)
 
 	// Extended attributes.
-	GetXAttr(header *InHeader, attr string) (data []byte, code Status)
+	GetXAttrSize(header *InHeader, attr string) (sz int, code Status)
+	GetXAttrData(header *InHeader, attr string) (data []byte, code Status)
 	ListXAttr(header *InHeader) (attributes []byte, code Status)
 	SetXAttr(header *InHeader, input *SetXAttrIn, attr string, data []byte) Status
 	RemoveXAttr(header *InHeader, attr string) (code Status)

fuse/defaultraw.go

@@ -58,7 +58,11 @@ func (me *DefaultRawFileSystem) Link(header *InHeader, input *LinkIn, name strin
 	return nil, ENOSYS
 }
 
-func (me *DefaultRawFileSystem) GetXAttr(header *InHeader, attr string) (data []byte, code Status) {
+func (me *DefaultRawFileSystem) GetXAttrSize(header *InHeader, attr string) (size int, code Status) {
+	return 0, ENOSYS
+}
+
+func (me *DefaultRawFileSystem) GetXAttrData(header *InHeader, attr string) (data []byte, code Status) {
 	return nil, ENOSYS
 }
 

fuse/fsops.go

@@ -289,7 +289,13 @@ func (me *FileSystemConnector) ReleaseDir(header *InHeader, input *ReleaseIn) {
 	me.considerDropInode(node)
 }
 
-func (me *FileSystemConnector) GetXAttr(header *InHeader, attribute string) (data []byte, code Status) {
+func (me *FileSystemConnector) GetXAttrSize(header *InHeader, attribute string) (sz int, code Status) {
+	node := me.toInode(header.NodeId)
+	data, c := node.fsInode.GetXAttr(attribute, &header.Context)
+	return len(data), c
+}
+
+func (me *FileSystemConnector) GetXAttrData(header *InHeader, attribute string) (data []byte, code Status) {
 	node := me.toInode(header.NodeId)
 	return node.fsInode.GetXAttr(attribute, &header.Context)
 }

fuse/lockingfs.go

@@ -228,9 +228,14 @@ func (me *LockingRawFileSystem) SetXAttr(header *InHeader, input *SetXAttrIn, at
 	return me.RawFileSystem.SetXAttr(header, input, attr, data)
 }
 
-func (me *LockingRawFileSystem) GetXAttr(header *InHeader, attr string) (data []byte, code Status) {
+func (me *LockingRawFileSystem) GetXAttrData(header *InHeader, attr string) (data []byte, code Status) {
 	defer me.locked()()
-	return me.RawFileSystem.GetXAttr(header, attr)
+	return me.RawFileSystem.GetXAttrData(header, attr)
+}
+
+func (me *LockingRawFileSystem) GetXAttrSize(header *InHeader, attr string) (sz int, code Status) {
+	defer me.locked()()
+	return me.RawFileSystem.GetXAttrSize(header, attr)
 }
 
 func (me *LockingRawFileSystem) ListXAttr(header *InHeader) (data []byte, code Status) {

fuse/loopback.go

@@ -157,8 +157,9 @@ func (me *LoopbackFileSystem) Create(path string, flags uint32, mode uint32, con
 }
 
 func (me *LoopbackFileSystem) GetXAttr(name string, attr string, context *Context) ([]byte, Status) {
-	data, errNo := GetXAttr(me.GetPath(name), attr)
-
+	data := make([]byte, 1024)
+	data, errNo := GetXAttr(me.GetPath(name), attr, data)
+	
 	return data, Status(errNo)
 }
 

fuse/opcode.go

@@ -161,27 +161,31 @@ func doWrite(state *MountState, req *request) {
 func doGetXAttr(state *MountState, req *request) {
 	input := (*GetXAttrIn)(req.inData)
 	var data []byte
-	if req.inHeader.opcode == _OP_GETXATTR {
-		data, req.status = state.fileSystem.GetXAttr(req.inHeader, req.filenames[0])
-	} else {
-		data, req.status = state.fileSystem.ListXAttr(req.inHeader)
-	}
-
-	if req.status != OK {
-		return
-	}
-
-	size := uint32(len(data))
-	if input.Size == 0 {
-		out := &GetXAttrOut{
-			Size: size,
+	switch {
+	case req.inHeader.opcode == _OP_GETXATTR && input.Size == 0:
+		sz, code := state.fileSystem.GetXAttrSize(req.inHeader, req.filenames[0])
+		if code.Ok() {
+			out := &GetXAttrOut{
+			Size: uint32(sz),
+			}
+			req.outData = unsafe.Pointer(out)
+			req.status = ERANGE
+			return
 		}
-		req.outData = unsafe.Pointer(out)
+		req.status = code
+	case req.inHeader.opcode == _OP_GETXATTR:
+		data, req.status = state.fileSystem.GetXAttrData(req.inHeader, req.filenames[0])
+	default:
+		data, req.status = state.fileSystem.ListXAttr(req.inHeader)
 	}
 
-	if size > input.Size {
+	if len(data) > int(input.Size) {
 		req.status = ERANGE
 	}
+	
+	if !req.status.Ok() {
+		return
+	}
 
 	req.flatData = data
 }

fuse/syscall.go

@@ -50,8 +50,7 @@ func getxattr(path string, attr string, dest []byte) (sz int, errno int) {
 	return int(size), int(errNo)
 }
 
-func GetXAttr(path string, attr string) (value []byte, errno int) {
-	dest := make([]byte, 1024)
+func GetXAttr(path string, attr string, dest []byte) (value []byte, errno int) {
 	sz, errno := getxattr(path, attr, dest)
 
 	for sz > cap(dest) && errno == 0 {

fuse/xattr_test.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"syscall"
 	"testing"
 )
 
@@ -86,6 +87,11 @@ func (me *XAttrTestFs) RemoveXAttr(name string, attr string, context *Context) S
 	return OK
 }
 
+func readXAttr(p, a string) (val []byte, errno int) {
+	val = make([]byte, 1024)
+	return GetXAttr(p, a, val)
+}
+
 func TestXAttrRead(t *testing.T) {
 	nm := "filename"
 
@@ -112,21 +118,20 @@ func TestXAttrRead(t *testing.T) {
 		t.Error("Unexpected stat error", err)
 	}
 
-	val, errno := GetXAttr(mounted, "noexist")
+	val, errno := readXAttr(mounted, "noexist")
 	if errno == 0 {
 		t.Error("Expected GetXAttr error", val)
 	}
 
 	attrs, errno := ListXAttr(mounted)
-
 	readback := make(map[string][]byte)
 	if errno != 0 {
 		t.Error("Unexpected ListXAttr error", errno)
 	} else {
 		for _, a := range attrs {
-			val, errno = GetXAttr(mounted, a)
+			val, errno = readXAttr(mounted, a)
 			if errno != 0 {
-				t.Error("Unexpected GetXAttr error", errno)
+				t.Error("Unexpected GetXAttr error", syscall.Errno(errno))
 			}
 			readback[a] = val
 		}
@@ -146,13 +151,13 @@ func TestXAttrRead(t *testing.T) {
 	if errno != 0 {
 		t.Error("Setxattr error", errno)
 	}
-	val, errno = GetXAttr(mounted, "third")
+	val, errno = readXAttr(mounted, "third")
 	if errno != 0 || string(val) != "value" {
 		t.Error("Read back set xattr:", errno, string(val))
 	}
 
 	Removexattr(mounted, "third")
-	val, errno = GetXAttr(mounted, "third")
+	val, errno = readXAttr(mounted, "third")
 	if errno != int(ENODATA) {
 		t.Error("Data not removed?", errno, val)
 	}