Change linux.FileMode from uint to uint16, and update VFS to use FileMode.

In Linux (include/linux/types.h), mode_t is an unsigned short.

PiperOrigin-RevId: 272956350

pkg/abi/linux/file.go

@@ -271,7 +271,7 @@ type Statx struct {
 }
 
 // FileMode represents a mode_t.
-type FileMode uint
+type FileMode uint16
 
 // Permissions returns just the permission bits.
 func (m FileMode) Permissions() FileMode {

pkg/sentry/fsimpl/memfs/directory.go

@@ -32,7 +32,7 @@ type directory struct {
 	childList dentryList
 }
 
-func (fs *filesystem) newDirectory(creds *auth.Credentials, mode uint16) *inode {
+func (fs *filesystem) newDirectory(creds *auth.Credentials, mode linux.FileMode) *inode {
 	dir := &directory{}
 	dir.inode.init(dir, fs, creds, mode)
 	dir.inode.nlink = 2 // from "." and parent directory or ".." for root

pkg/sentry/fsimpl/memfs/memfs.go

@@ -137,7 +137,7 @@ type inode struct {
 	impl interface{} // immutable
 }
 
-func (i *inode) init(impl interface{}, fs *filesystem, creds *auth.Credentials, mode uint16) {
+func (i *inode) init(impl interface{}, fs *filesystem, creds *auth.Credentials, mode linux.FileMode) {
 	i.refs = 1
 	i.mode = uint32(mode)
 	i.uid = uint32(creds.EffectiveKUID)

pkg/sentry/fsimpl/memfs/regular_file.go

@@ -37,7 +37,7 @@ type regularFile struct {
 	dataLen int64
 }
 
-func (fs *filesystem) newRegularFile(creds *auth.Credentials, mode uint16) *inode {
+func (fs *filesystem) newRegularFile(creds *auth.Credentials, mode linux.FileMode) *inode {
 	file := &regularFile{}
 	file.inode.init(file, fs, creds, mode)
 	file.inode.nlink = 1 // from parent directory

pkg/sentry/vfs/options.go

@@ -31,14 +31,14 @@ type GetDentryOptions struct {
 // FilesystemImpl.MkdirAt().
 type MkdirOptions struct {
 	// Mode is the file mode bits for the created directory.
-	Mode uint16
+	Mode linux.FileMode
 }
 
 // MknodOptions contains options to VirtualFilesystem.MknodAt() and
 // FilesystemImpl.MknodAt().
 type MknodOptions struct {
 	// Mode is the file type and mode bits for the created file.
-	Mode uint16
+	Mode linux.FileMode
 
 	// If Mode specifies a character or block device special file, DevMajor and
 	// DevMinor are the major and minor device numbers for the created device.
@@ -61,7 +61,7 @@ type OpenOptions struct {
 
 	// If FilesystemImpl.OpenAt() creates a file, Mode is the file mode for the
 	// created file.
-	Mode uint16
+	Mode linux.FileMode
 }
 
 // ReadOptions contains options to FileDescription.PRead(),