Began fixing Connection.

connection.go

@@ -80,6 +80,7 @@ type Connection struct {
 
 	// Freelists, serviced by freelists.go.
 	inMessages  freelist.Freelist // GUARDED_BY(mu)
+	outMessages freelist.Freelist // GUARDED_BY(mu)
 }
 
 // State that is maintained for each in-flight op. This is stuffed into the

conversions.go

@@ -387,35 +387,31 @@ func convertInMessage(
 // Outgoing messages
 ////////////////////////////////////////////////////////////////////////
 
-// Return the response that should be sent to the kernel. If the op requires no
-// response, return a nil response.
-func kernelResponse(
+// Return the response that should be sent to the kernel, or nil if the op
+// requires no response.
+func (c *Connection) kernelResponse(
 	fuseID uint64,
 	op interface{},
-	opErr error,
-	protocol fusekernel.Protocol) (msg []byte) {
-	// If the user replied with an error, create room enough just for the result
-	// header and fill it in with an error. Otherwise create an appropriate
+	opErr error) (m *buffer.OutMessage) {
+	// If the user replied with an error, create a response containing just the
+	// result header with the error filled in. Otherwise create an appropriate
 	// response.
-	var b buffer.OutMessage
 	if opErr != nil {
-		b = buffer.NewOutMessage(0)
+		m = c.getOutMessage()
 		if errno, ok := opErr.(syscall.Errno); ok {
-			b.OutHeader().Error = -int32(errno)
+			m.OutHeader().Error = -int32(errno)
 		} else {
-			b.OutHeader().Error = -int32(syscall.EIO)
+			m.OutHeader().Error = -int32(syscall.EIO)
 		}
 	} else {
-		b = kernelResponseForOp(op, protocol)
+		m = c.kernelResponseForOp(op)
 	}
 
-	msg = b.Bytes()
-
 	// Fill in the rest of the header, if a response is required.
-	if msg != nil {
-		h := b.OutHeader()
+	if m != nil {
+		h := m.OutHeader()
 		h.Unique = fuseID
-		h.Len = uint32(len(msg))
+		h.Len = uint32(m.Len())
 	}
 
 	return

freelists.go

@@ -20,14 +20,20 @@ import (
 	"github.com/jacobsa/fuse/internal/buffer"
 )
 
+////////////////////////////////////////////////////////////////////////
+// buffer.InMessage
+////////////////////////////////////////////////////////////////////////
+
 // LOCKS_EXCLUDED(c.mu)
-func (c *Connection) getInMessage() (m *buffer.InMessage) {
+func (c *Connection) getInMessage() (x *buffer.InMessage) {
 	c.mu.Lock()
-	m = (*buffer.InMessage)(c.inMessages.Get())
-	if m == nil {
-		m = new(buffer.InMessage)
-	}
+	x = (*buffer.InMessage)(c.inMessages.Get())
 	c.mu.Unlock()
+
+	if x == nil {
+		x = new(buffer.InMessage)
+	}
+
 	return
 }
 
@@ -37,3 +43,28 @@ func (c *Connection) putInMessage(x *buffer.InMessage) {
 	c.inMessages.Put(unsafe.Pointer(x))
 	c.mu.Unlock()
 }
+
+////////////////////////////////////////////////////////////////////////
+// buffer.OutMessage
+////////////////////////////////////////////////////////////////////////
+
+// LOCKS_EXCLUDED(c.mu)
+func (c *Connection) getOutMessage() (x *buffer.OutMessage) {
+	c.mu.Lock()
+	x = (*buffer.OutMessage)(c.outMessages.Get())
+	c.mu.Unlock()
+
+	if x == nil {
+		x = new(buffer.OutMessage)
+	}
+	x.Reset()
+
+	return
+}
+
+// LOCKS_EXCLUDED(c.mu)
+func (c *Connection) putOutMessage(x *buffer.OutMessage) {
+	c.mu.Lock()
+	c.outMessages.Put(unsafe.Pointer(x))
+	c.mu.Unlock()
+}