Plug memory leak in bufferpool code: reused buffers should also be in

the handed-out table.

fuse/bufferpool.go

@@ -4,8 +4,11 @@ import (
 	"sync"
 	"fmt"
 	"unsafe"
+	"log"
 )
 
+var _ = log.Println
+
 // This implements a pool of buffers that returns slices with capacity
 // (2^e * PAGESIZE) for e=0,1,...  which have possibly been used, and
 // may contain random contents.
@@ -17,6 +20,10 @@ type BufferPool struct {
 
 	// start of slice -> exponent.
 	outstandingBuffers map[uintptr]uint
+
+	// Total count of created buffers.  Handy for finding memory
+	// leaks.
+	createdBuffers int
 }
 
 // Returns the smallest E such that 2^E >= Z.
@@ -71,6 +78,13 @@ func (me *BufferPool) addBuffer(slice []byte, exp uint) {
 }
 
 
+func (me *BufferPool) AllocCount() int {
+	me.lock.Lock()
+	defer me.lock.Unlock()
+
+	return me.createdBuffers
+}
+
 func (me *BufferPool) AllocBuffer(size uint32) []byte {
 	sz := int(size)
 	if sz < PAGESIZE {
@@ -87,12 +101,13 @@ func (me *BufferPool) AllocBuffer(size uint32) []byte {
 
 	b := me.getBuffer(exp)
 
-	if b != nil {
+	if b == nil {
+		me.createdBuffers++
+		b = make([]byte, size, rounded)
+	} else {
 		b = b[:size]
-		return b
 	}
 
-	b = make([]byte, size, rounded)
 	me.outstandingBuffers[uintptr(unsafe.Pointer(&b[0]))] = exp
 	return b
 }
@@ -103,9 +118,9 @@ func (me *BufferPool) FreeBuffer(slice []byte) {
 	if cap(slice) < PAGESIZE {
 		return
 	}
-	slice = slice[:cap(slice)] 
+	slice = slice[:cap(slice)]
 	key := uintptr(unsafe.Pointer(&slice[0]))
-	
+
 	me.lock.Lock()
 	defer me.lock.Unlock()
 	exp, ok := me.outstandingBuffers[key]

fuse/fuse.go

@@ -3,7 +3,6 @@ package fuse
 import (
 	"bytes"
 	"encoding/binary"
-	"expvar"
 	"fmt"
 	"log"
 	"os"
@@ -240,18 +239,8 @@ func (me *MountState) OperationCounts() map[string]int64 {
 }
 
 func (me *MountState) Stats() string {
-	var lines []string
-
-	// TODO - bufferpool should use expvar.
-	lines = append(lines,
-		fmt.Sprintf("buffers: %v", me.buffers.String()))
-
-	for v := range expvar.Iter() {
-		if strings.HasPrefix(v.Key, "mount") {
-			lines = append(lines, fmt.Sprintf("%v: %v\n", v.Key, v.Value))
-		}
-	}
-	return strings.Join(lines, "\n")
+	return fmt.Sprintf("buffer alloc count %d\nbuffers %v",
+		me.buffers.AllocCount(), me.buffers.String())
 }
 
 ////////////////////////////////////////////////////////////////