1 files changed, 105 insertions, 5 deletions

diff --git a/pkg/sentry/vfs/filesystem.go b/pkg/sentry/vfs/filesystem.go
index 7a074b718..b766614e7 100644
--- a/pkg/sentry/vfs/filesystem.go
+++ b/pkg/sentry/vfs/filesystem.go
@@ -18,6 +18,7 @@ import (
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/context"
 )
 
@@ -33,15 +34,28 @@ type Filesystem struct {
 	// operations.
 	refs int64
 
+	// vfs is the VirtualFilesystem that uses this Filesystem. vfs is
+	// immutable.
+	vfs *VirtualFilesystem
+
 	// impl is the FilesystemImpl associated with this Filesystem. impl is
 	// immutable. This should be the last field in Dentry.
 	impl FilesystemImpl
 }
 
 // Init must be called before first use of fs.
-func (fs *Filesystem) Init(impl FilesystemImpl) {
+func (fs *Filesystem) Init(vfsObj *VirtualFilesystem, impl FilesystemImpl) {
 	fs.refs = 1
+	fs.vfs = vfsObj
 	fs.impl = impl
+	vfsObj.filesystemsMu.Lock()
+	vfsObj.filesystems[fs] = struct{}{}
+	vfsObj.filesystemsMu.Unlock()
+}
+
+// VirtualFilesystem returns the containing VirtualFilesystem.
+func (fs *Filesystem) VirtualFilesystem() *VirtualFilesystem {
+	return fs.vfs
 }
 
 // Impl returns the FilesystemImpl associated with fs.
@@ -49,14 +63,35 @@ func (fs *Filesystem) Impl() FilesystemImpl {
 	return fs.impl
 }
 
-func (fs *Filesystem) incRef() {
+// IncRef increments fs' reference count.
+func (fs *Filesystem) IncRef() {
 	if atomic.AddInt64(&fs.refs, 1) <= 1 {
-		panic("Filesystem.incRef() called without holding a reference")
+		panic("Filesystem.IncRef() called without holding a reference")
+	}
+}
+
+// TryIncRef increments fs' reference count and returns true. If fs' reference
+// count is zero, TryIncRef does nothing and returns false.
+//
+// TryIncRef does not require that a reference is held on fs.
+func (fs *Filesystem) TryIncRef() bool {
+	for {
+		refs := atomic.LoadInt64(&fs.refs)
+		if refs <= 0 {
+			return false
+		}
+		if atomic.CompareAndSwapInt64(&fs.refs, refs, refs+1) {
+			return true
+		}
 	}
 }
 
-func (fs *Filesystem) decRef() {
+// DecRef decrements fs' reference count.
+func (fs *Filesystem) DecRef() {
 	if refs := atomic.AddInt64(&fs.refs, -1); refs == 0 {
+		fs.vfs.filesystemsMu.Lock()
+		delete(fs.vfs.filesystems, fs)
+		fs.vfs.filesystemsMu.Unlock()
 		fs.impl.Release()
 	} else if refs < 0 {
 		panic("Filesystem.decRef() called without holding a reference")
@@ -151,5 +186,70 @@ type FilesystemImpl interface {
 	// UnlinkAt removes the non-directory file at rp.
 	UnlinkAt(ctx context.Context, rp *ResolvingPath) error
 
-	// TODO: d_path(); extended attributes; inotify_add_watch(); bind()
+	// ListxattrAt returns all extended attribute names for the file at rp.
+	ListxattrAt(ctx context.Context, rp *ResolvingPath) ([]string, error)
+
+	// GetxattrAt returns the value associated with the given extended
+	// attribute for the file at rp.
+	GetxattrAt(ctx context.Context, rp *ResolvingPath, name string) (string, error)
+
+	// SetxattrAt changes the value associated with the given extended
+	// attribute for the file at rp.
+	SetxattrAt(ctx context.Context, rp *ResolvingPath, opts SetxattrOptions) error
+
+	// RemovexattrAt removes the given extended attribute from the file at rp.
+	RemovexattrAt(ctx context.Context, rp *ResolvingPath, name string) error
+
+	// PrependPath prepends a path from vd to vd.Mount().Root() to b.
+	//
+	// If vfsroot.Ok(), it is the contextual VFS root; if it is encountered
+	// before vd.Mount().Root(), PrependPath should stop prepending path
+	// components and return a PrependPathAtVFSRootError.
+	//
+	// If traversal of vd.Dentry()'s ancestors encounters an independent
+	// ("root") Dentry that is not vd.Mount().Root() (i.e. vd.Dentry() is not a
+	// descendant of vd.Mount().Root()), PrependPath should stop prepending
+	// path components and return a PrependPathAtNonMountRootError.
+	//
+	// Filesystems for which Dentries do not have meaningful paths may prepend
+	// an arbitrary descriptive string to b and then return a
+	// PrependPathSyntheticError.
+	//
+	// Most implementations can acquire the appropriate locks to ensure that
+	// Dentry.Name() and Dentry.Parent() are fixed for vd.Dentry() and all of
+	// its ancestors, then call GenericPrependPath.
+	//
+	// Preconditions: vd.Mount().Filesystem().Impl() == this FilesystemImpl.
+	PrependPath(ctx context.Context, vfsroot, vd VirtualDentry, b *fspath.Builder) error
+
+	// TODO: inotify_add_watch(); bind()
+}
+
+// PrependPathAtVFSRootError is returned by implementations of
+// FilesystemImpl.PrependPath() when they encounter the contextual VFS root.
+type PrependPathAtVFSRootError struct{}
+
+// Error implements error.Error.
+func (PrependPathAtVFSRootError) Error() string {
+	return "vfs.FilesystemImpl.PrependPath() reached VFS root"
+}
+
+// PrependPathAtNonMountRootError is returned by implementations of
+// FilesystemImpl.PrependPath() when they encounter an independent ancestor
+// Dentry that is not the Mount root.
+type PrependPathAtNonMountRootError struct{}
+
+// Error implements error.Error.
+func (PrependPathAtNonMountRootError) Error() string {
+	return "vfs.FilesystemImpl.PrependPath() reached root other than Mount root"
+}
+
+// PrependPathSyntheticError is returned by implementations of
+// FilesystemImpl.PrependPath() for which prepended names do not represent real
+// paths.
+type PrependPathSyntheticError struct{}
+
+// Error implements error.Error.
+func (PrependPathSyntheticError) Error() string {
+	return "vfs.FilesystemImpl.PrependPath() prepended synthetic name"
 }