nodefs: provide Inode.Root rather than Inode.IsRoot

Use this to simplify loopbackNode.

nodefs/inode.go

@@ -13,8 +13,6 @@ import (
 	"sync"
 	"syscall"
 	"unsafe"
-
-	"github.com/hanwen/go-fuse/fuse"
 )
 
 type parentData struct {
@@ -76,8 +74,9 @@ type Inode struct {
 	// by calling removeRef.
 	persistent bool
 
-	// changeCounter increments every time the below mutable state
-	// (lookupCount, nodeAttr, children, parents) is modified.
+	// changeCounter increments every time the mutable state
+	// (lookupCount, persistent, children, parents) protected by
+	// mu is modified.
 	//
 	// This is used in places where we have to relock inode into inode
 	// group lock, and after locking the group we have to check if inode
@@ -113,9 +112,9 @@ func (n *Inode) Mode() uint32 {
 	return n.nodeAttr.Mode
 }
 
-// IsRoot returns true if this is the root of the FUSE mount.
-func (n *Inode) IsRoot() bool {
-	return n.nodeAttr.Ino == fuse.FUSE_ROOT_ID
+// Returns the root of the tree
+func (n *Inode) Root() *Inode {
+	return n.bridge.root
 }
 
 // debugString is used for debugging. Racy.

nodefs/loopback.go

@@ -16,14 +16,8 @@ import (
 type loopbackRoot struct {
 	loopbackNode
 
-	root    string
-	rootDev uint64
-}
-
-func (n *loopbackRoot) newLoopbackNode() *loopbackNode {
-	return &loopbackNode{
-		rootNode: n,
-	}
+	rootPath string
+	rootDev  uint64
 }
 
 func (n *loopbackNode) StatFs(ctx context.Context, out *fuse.StatfsOut) syscall.Errno {
@@ -37,9 +31,8 @@ func (n *loopbackNode) StatFs(ctx context.Context, out *fuse.StatfsOut) syscall.
 }
 
 func (n *loopbackRoot) GetAttr(ctx context.Context, out *fuse.AttrOut) syscall.Errno {
-	var err error = nil
 	st := syscall.Stat_t{}
-	err = syscall.Stat(n.root, &st)
+	err := syscall.Stat(n.rootPath, &st)
 	if err != nil {
 		return ToErrno(err)
 	}
@@ -49,13 +42,15 @@ func (n *loopbackRoot) GetAttr(ctx context.Context, out *fuse.AttrOut) syscall.E
 
 type loopbackNode struct {
 	DefaultOperations
+}
 
-	rootNode *loopbackRoot
+func (n *loopbackNode) root() *loopbackRoot {
+	return n.Inode().Root().Operations().(*loopbackRoot)
 }
 
 func (n *loopbackNode) path() string {
 	path := n.Inode().Path(nil)
-	return filepath.Join(n.rootNode.root, path)
+	return filepath.Join(n.root().rootPath, path)
 }
 
 func (n *loopbackNode) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (*Inode, syscall.Errno) {
@@ -68,8 +63,8 @@ func (n *loopbackNode) Lookup(ctx context.Context, name string, out *fuse.EntryO
 	}
 
 	out.Attr.FromStat(&st)
-	node := n.rootNode.newLoopbackNode()
-	ch := n.inode().NewInode(ctx, node, n.rootNode.idFromStat(&st))
+	node := &loopbackNode{}
+	ch := n.inode().NewInode(ctx, node, n.root().idFromStat(&st))
 	return ch, 0
 }
 
@@ -87,8 +82,8 @@ func (n *loopbackNode) Mknod(ctx context.Context, name string, mode, rdev uint32
 
 	out.Attr.FromStat(&st)
 
-	node := n.rootNode.newLoopbackNode()
-	ch := n.inode().NewInode(ctx, node, n.rootNode.idFromStat(&st))
+	node := &loopbackNode{}
+	ch := n.inode().NewInode(ctx, node, n.root().idFromStat(&st))
 
 	return ch, 0
 }
@@ -107,8 +102,8 @@ func (n *loopbackNode) Mkdir(ctx context.Context, name string, mode uint32, out
 
 	out.Attr.FromStat(&st)
 
-	node := n.rootNode.newLoopbackNode()
-	ch := n.inode().NewInode(ctx, node, n.rootNode.idFromStat(&st))
+	node := &loopbackNode{}
+	ch := n.inode().NewInode(ctx, node, n.root().idFromStat(&st))
 
 	return ch, 0
 }
@@ -178,8 +173,8 @@ func (n *loopbackNode) Create(ctx context.Context, name string, flags uint32, mo
 		return nil, nil, 0, ToErrno(err)
 	}
 
-	node := n.rootNode.newLoopbackNode()
-	ch := n.inode().NewInode(ctx, node, n.rootNode.idFromStat(&st))
+	node := &loopbackNode{}
+	ch := n.inode().NewInode(ctx, node, n.root().idFromStat(&st))
 	lf := NewLoopbackFile(fd)
 	return ch, lf, 0, 0
 }
@@ -195,8 +190,8 @@ func (n *loopbackNode) Symlink(ctx context.Context, target, name string, out *fu
 		syscall.Unlink(p)
 		return nil, ToErrno(err)
 	}
-	node := n.rootNode.newLoopbackNode()
-	ch := n.inode().NewInode(ctx, node, n.rootNode.idFromStat(&st))
+	node := &loopbackNode{}
+	ch := n.inode().NewInode(ctx, node, n.root().idFromStat(&st))
 
 	out.Attr.FromStat(&st)
 	return ch, 0
@@ -215,8 +210,8 @@ func (n *loopbackNode) Link(ctx context.Context, target Operations, name string,
 		syscall.Unlink(p)
 		return nil, ToErrno(err)
 	}
-	node := n.rootNode.newLoopbackNode()
-	ch := n.inode().NewInode(ctx, node, n.rootNode.idFromStat(&st))
+	node := &loopbackNode{}
+	ch := n.inode().NewInode(ctx, node, n.root().idFromStat(&st))
 
 	out.Attr.FromStat(&st)
 	return ch, 0
@@ -288,9 +283,8 @@ func NewLoopbackRoot(root string) (DirOperations, error) {
 	}
 
 	n := &loopbackRoot{
-		root:    root,
-		rootDev: uint64(st.Dev),
+		rootPath: root,
+		rootDev:  uint64(st.Dev),
 	}
-	n.rootNode = n
 	return n, nil
 }

nodefs/loopback_linux.go

@@ -47,13 +47,18 @@ func (n *loopbackNode) renameExchange(name string, newparent *loopbackNode, newN
 	if err := syscall.Fstat(fd1, &st); err != nil {
 		return ToErrno(err)
 	}
-	if !n.Inode().IsRoot() && n.Inode().NodeAttr().Ino != n.rootNode.idFromStat(&st).Ino {
+
+	// Double check that nodes didn't change from under us.
+	inode := n.Inode()
+	if inode.Root() != inode && inode.NodeAttr().Ino != n.root().idFromStat(&st).Ino {
 		return syscall.EBUSY
 	}
 	if err := syscall.Fstat(fd2, &st); err != nil {
 		return ToErrno(err)
 	}
-	if !newparent.Inode().IsRoot() && newparent.Inode().NodeAttr().Ino != n.rootNode.idFromStat(&st).Ino {
+
+	newinode := newparent.Inode()
+	if newinode.Root() != newinode && newinode.NodeAttr().Ino != n.root().idFromStat(&st).Ino {
 		return syscall.EBUSY
 	}