Added an Nlink field and updated tests and samples to use it.

For #2.

file_system.go

@@ -265,6 +265,9 @@ func init() {
 type InodeAttributes struct {
 	Size uint64
 
+	// The number of incoming hard links to this inode.
+	Nlink uint64
+
 	// The mode of the inode. This is exposed to the user in e.g. the result of
 	// fstat(2).
 	//

samples/cachingfs/caching_fs.go

@@ -164,6 +164,7 @@ func (fs *cachingFS) rootAttrs() fuse.InodeAttributes {
 // LOCKS_REQUIRED(fs.mu)
 func (fs *cachingFS) fooAttrs() fuse.InodeAttributes {
 	return fuse.InodeAttributes{
+		Nlink: 1,
 		Size:  FooSize,
 		Mode:  0777,
 		Mtime: fs.mtime,
@@ -173,6 +174,7 @@ func (fs *cachingFS) fooAttrs() fuse.InodeAttributes {
 // LOCKS_REQUIRED(fs.mu)
 func (fs *cachingFS) dirAttrs() fuse.InodeAttributes {
 	return fuse.InodeAttributes{
+		Nlink: 1,
 		Mode:  os.ModeDir | 0777,
 		Mtime: fs.mtime,
 	}
@@ -181,6 +183,7 @@ func (fs *cachingFS) dirAttrs() fuse.InodeAttributes {
 // LOCKS_REQUIRED(fs.mu)
 func (fs *cachingFS) barAttrs() fuse.InodeAttributes {
 	return fuse.InodeAttributes{
+		Nlink: 1,
 		Size:  BarSize,
 		Mode:  0777,
 		Mtime: fs.mtime,

samples/cachingfs/caching_fs_test.go

@@ -201,6 +201,7 @@ func (t *BasicsTest) StatFoo() {
 	ExpectThat(fi.ModTime(), timeutil.TimeEq(t.initialMtime))
 	ExpectFalse(fi.IsDir())
 	ExpectEq(t.fs.FooID(), getInodeID(fi))
+	ExpectEq(1, fi.Sys().(*syscall.Stat_t).Nlink)
 }
 
 func (t *BasicsTest) StatDir() {
@@ -212,6 +213,7 @@ func (t *BasicsTest) StatDir() {
 	ExpectThat(fi.ModTime(), timeutil.TimeEq(t.initialMtime))
 	ExpectTrue(fi.IsDir())
 	ExpectEq(t.fs.DirID(), getInodeID(fi))
+	ExpectEq(1, fi.Sys().(*syscall.Stat_t).Nlink)
 }
 
 func (t *BasicsTest) StatBar() {
@@ -224,6 +226,7 @@ func (t *BasicsTest) StatBar() {
 	ExpectThat(fi.ModTime(), timeutil.TimeEq(t.initialMtime))
 	ExpectFalse(fi.IsDir())
 	ExpectEq(t.fs.BarID(), getInodeID(fi))
+	ExpectEq(1, fi.Sys().(*syscall.Stat_t).Nlink)
 }
 
 ////////////////////////////////////////////////////////////////////////

samples/hellofs/hello_fs.go

@@ -61,6 +61,7 @@ var gInodeInfo = map[fuse.InodeID]inodeInfo{
 	// root
 	rootInode: inodeInfo{
 		attributes: fuse.InodeAttributes{
+			Nlink: 1,
 			Mode:  0555 | os.ModeDir,
 		},
 		dir: true,
@@ -83,6 +84,7 @@ var gInodeInfo = map[fuse.InodeID]inodeInfo{
 	// hello
 	helloInode: inodeInfo{
 		attributes: fuse.InodeAttributes{
+			Nlink: 1,
 			Mode:  0444,
 			Size:  uint64(len("Hello, world!")),
 		},
@@ -91,6 +93,7 @@ var gInodeInfo = map[fuse.InodeID]inodeInfo{
 	// dir
 	dirInode: inodeInfo{
 		attributes: fuse.InodeAttributes{
+			Nlink: 1,
 			Mode:  0555 | os.ModeDir,
 		},
 		dir: true,
@@ -107,6 +110,7 @@ var gInodeInfo = map[fuse.InodeID]inodeInfo{
 	// world
 	worldInode: inodeInfo{
 		attributes: fuse.InodeAttributes{
+			Nlink: 1,
 			Mode:  0444,
 			Size:  uint64(len("Hello, world!")),
 		},

samples/hellofs/hello_fs_test.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"path"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -158,6 +159,7 @@ func (t *HelloFSTest) Stat_Hello() {
 	ExpectEq(0444, fi.Mode())
 	ExpectEq(0, t.clock.Now().Sub(fi.ModTime()), "ModTime: %v", fi.ModTime())
 	ExpectFalse(fi.IsDir())
+	ExpectEq(1, fi.Sys().(*syscall.Stat_t).Nlink)
 }
 
 func (t *HelloFSTest) Stat_Dir() {
@@ -169,6 +171,7 @@ func (t *HelloFSTest) Stat_Dir() {
 	ExpectEq(0555|os.ModeDir, fi.Mode())
 	ExpectEq(0, t.clock.Now().Sub(fi.ModTime()), "ModTime: %v", fi.ModTime())
 	ExpectTrue(fi.IsDir())
+	ExpectEq(1, fi.Sys().(*syscall.Stat_t).Nlink)
 }
 
 func (t *HelloFSTest) Stat_World() {
@@ -180,6 +183,7 @@ func (t *HelloFSTest) Stat_World() {
 	ExpectEq(0444, fi.Mode())
 	ExpectEq(0, t.clock.Now().Sub(fi.ModTime()), "ModTime: %v", fi.ModTime())
 	ExpectFalse(fi.IsDir())
+	ExpectEq(1, fi.Sys().(*syscall.Stat_t).Nlink)
 }
 
 func (t *HelloFSTest) Stat_NonExistent() {

samples/memfs/fs.go

@@ -305,6 +305,7 @@ func (fs *memFS) MkDir(
 	// Set up attributes from the child, using the credentials of the calling
 	// process as owner (matching inode_init_owner, cf. http://goo.gl/5qavg8).
 	childAttrs := fuse.InodeAttributes{
+		Nlink: 1,
 		Mode:  req.Mode,
 		Uid:   req.Header.Uid,
 		Gid:   req.Header.Gid,
@@ -345,6 +346,7 @@ func (fs *memFS) CreateFile(
 	// process as owner (matching inode_init_owner, cf. http://goo.gl/5qavg8).
 	now := fs.clock.Now()
 	childAttrs := fuse.InodeAttributes{
+		Nlink:  1,
 		Mode:   req.Mode,
 		Atime:  now,
 		Mtime:  now,
@@ -408,7 +410,7 @@ func (fs *memFS) RmDir(
 	parent.RemoveChild(req.Name)
 
 	// Mark the child as unlinked.
-	child.linkCount--
+	child.attributes.Nlink--
 
 	return
 }
@@ -440,7 +442,7 @@ func (fs *memFS) Unlink(
 	parent.RemoveChild(req.Name)
 
 	// Mark the child as unlinked.
-	child.linkCount--
+	child.attributes.Nlink--
 
 	return
 }

samples/memfs/inode.go

@@ -47,13 +47,6 @@ type inode struct {
 
 	mu syncutil.InvariantMutex
 
-	// The number of times this inode is linked into a parent directory. This may
-	// be zero if the inode has been unlinked but not yet forgotten, because some
-	// process still has an  open file handle.
-	//
-	// INVARIANT: linkCount >= 0
-	linkCount int // GUARDED_BY(mu)
-
 	// The current attributes of this inode.
 	//
 	// INVARIANT: No non-permission mode bits are set besides os.ModeDir
@@ -87,7 +80,6 @@ type inode struct {
 
 // Create a new inode with the supplied attributes, which need not contain
 // time-related information (the inode object will take care of that).
-// Initially the link count is one.
 func newInode(
 	clock timeutil.Clock,
 	attrs fuse.InodeAttributes) (in *inode) {
@@ -99,7 +91,6 @@ func newInode(
 	// Create the object.
 	in = &inode{
 		clock:      clock,
-		linkCount:  1,
 		dir:        (attrs.Mode&os.ModeDir != 0),
 		attributes: attrs,
 	}
@@ -109,11 +100,6 @@ func newInode(
 }
 
 func (inode *inode) checkInvariants() {
-	// Check the link count.
-	if inode.linkCount < 0 {
-		panic(fmt.Sprintf("Negative link count: %v", inode.linkCount))
-	}
-
 	// No non-permission mode bits should be set besides os.ModeDir.
 	if inode.attributes.Mode & ^(os.ModePerm|os.ModeDir) != 0 {
 		panic(fmt.Sprintf("Unexpected mode: %v", inode.attributes.Mode))

samples/memfs/memfs_test.go

@@ -602,9 +602,7 @@ func (t *MemFSTest) UnlinkFile_StillOpen() {
 
 	AssertEq(nil, err)
 	ExpectEq(4, fi.Size())
-	// TODO(jacobsa): Re-enable this assertion if the following issue is fixed:
-	//     https://github.com/bazillion/fuse/issues/66
-	// ExpectEq(0, fi.Sys().(*syscall.Stat_t).Nlink)
+	ExpectEq(0, fi.Sys().(*syscall.Stat_t).Nlink)
 
 	// The contents should still be available.
 	buf := make([]byte, 1024)
@@ -724,10 +722,7 @@ func (t *MemFSTest) Rmdir_OpenedForReading() {
 
 	ExpectEq("dir", fi.Name())
 	ExpectEq(0, fi.ModTime().Sub(createTime))
-
-	// TODO(jacobsa): Re-enable this assertion if the following issue is fixed:
-	//     https://github.com/bazillion/fuse/issues/66
-	// ExpectEq(0, fi.Sys().(*syscall.Stat_t).Nlink)
+	ExpectEq(0, fi.Sys().(*syscall.Stat_t).Nlink)
 
 	// Attempt to read from the directory. This shouldn't see any junk from the
 	// new directory. It should either succeed with an empty result or should

server.go

@@ -504,6 +504,7 @@ func convertAttributes(inode InodeID, attr InodeAttributes) bazilfuse.Attr {
 		Inode:  uint64(inode),
 		Size:   attr.Size,
 		Mode:   attr.Mode,
+		Nlink:  uint32(attr.Nlink),
 		Atime:  attr.Atime,
 		Mtime:  attr.Mtime,
 		Ctime:  attr.Ctime,