Add FilesystemType.Name method, and FilesystemType field to Filesystem struct.

Both have analogues in Linux:
* struct file_system_type has a char *name field.
* struct super_block keeps a pointer to the file_system_type.

These fields are necessary to support the `filesystem type` field in
/proc/[pid]/mountinfo.

PiperOrigin-RevId: 303434063

2 files changed, 8 insertions, 7 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index 794e38908..2cefef020 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -63,9 +63,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sync"
 )
 
-// FilesystemType implements vfs.FilesystemType.
-type FilesystemType struct{}
-
 // Filesystem mostly implements vfs.FilesystemImpl for a generic in-memory
 // filesystem. Concrete implementations are expected to embed this in their own
 // Filesystem type.
@@ -138,8 +135,8 @@ func (fs *Filesystem) processDeferredDecRefsLocked() {
 // Init initializes a kernfs filesystem. This should be called from during
 // vfs.FilesystemType.NewFilesystem for the concrete filesystem embedding
 // kernfs.
-func (fs *Filesystem) Init(vfsObj *vfs.VirtualFilesystem) {
-	fs.vfsfs.Init(vfsObj, fs)
+func (fs *Filesystem) Init(vfsObj *vfs.VirtualFilesystem, fsType vfs.FilesystemType) {
+	fs.vfsfs.Init(vfsObj, fsType, fs)
 }
 
 // VFSFilesystem returns the generic vfs filesystem object.
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs_test.go b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
index fb0d25ad7..465451f35 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs_test.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
@@ -187,9 +187,13 @@ func (*dir) NewNode(context.Context, string, vfs.MknodOptions) (*vfs.Dentry, err
 	return nil, syserror.EPERM
 }
 
-func (fst *fsType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opt vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
+func (fsType) Name() string {
+	return "kernfs"
+}
+
+func (fst fsType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opt vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
 	fs := &filesystem{}
-	fs.Init(vfsObj)
+	fs.Init(vfsObj, &fst)
 	root := fst.rootFn(creds, fs)
 	return fs.VFSFilesystem(), root.VFSDentry(), nil
 }