Add VFS2 support for device special files.

- Add FileDescriptionOptions.UseDentryMetadata, which reduces the amount of
  boilerplate needed for device FDs and the like between filesystems.

- Switch back to having FileDescription.Init() take references on the Mount and
  Dentry; otherwise managing refcounts around failed calls to
  OpenDeviceSpecialFile() / Device.Open() is tricky.

PiperOrigin-RevId: 287575574

2 files changed, 0 insertions, 4 deletions

diff --git a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
index c5fe65722..606ca692d 100644
--- a/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
+++ b/pkg/sentry/fsimpl/kernfs/dynamic_bytes_file.go
@@ -81,8 +81,6 @@ type DynamicBytesFD struct {
 
 // Init initializes a DynamicBytesFD.
 func (fd *DynamicBytesFD) Init(m *vfs.Mount, d *vfs.Dentry, data vfs.DynamicBytesSource, flags uint32) {
-	m.IncRef() // DecRef in vfs.FileDescription.vd.DecRef on final ref.
-	d.IncRef() // DecRef in vfs.FileDescription.vd.DecRef on final ref.
 	fd.inode = d.Impl().(*Dentry).inode
 	fd.SetDataSource(data)
 	fd.vfsfd.Init(fd, flags, m, d, &vfs.FileDescriptionOptions{})
diff --git a/pkg/sentry/fsimpl/kernfs/fd_impl_util.go b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
index 77975583b..bcf069b5f 100644
--- a/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/fd_impl_util.go
@@ -44,8 +44,6 @@ type GenericDirectoryFD struct {
 
 // Init initializes a GenericDirectoryFD.
 func (fd *GenericDirectoryFD) Init(m *vfs.Mount, d *vfs.Dentry, children *OrderedChildren, flags uint32) {
-	m.IncRef() // DecRef in vfs.FileDescription.vd.DecRef on final ref.
-	d.IncRef() // DecRef in vfs.FileDescription.vd.DecRef on final ref.
 	fd.children = children
 	fd.vfsfd.Init(fd, flags, m, d, &vfs.FileDescriptionOptions{})
 }