Mark some kernfs inode as Anonymous.

These inodes can never be part of a filesystem tree. They are nameless and
never have a parent.

This allows us to avoid taking a lock in kernfs.InotifyWithParent for such
anonymous inodes.

PiperOrigin-RevId: 538823227

pkg/sentry/fsimpl/devpts/devpts.go

@@ -150,6 +150,7 @@ type rootInode struct {
 	kernfs.InodeAlwaysValid
 	kernfs.InodeAttrs
 	kernfs.InodeDirectoryNoNewChildren
+	kernfs.InodeNotAnonymous
 	kernfs.InodeNotSymlink
 	kernfs.InodeTemporary // This holds no meaning as this inode can't be Looked up and is always valid.
 	kernfs.InodeWatches

pkg/sentry/fsimpl/devpts/master.go

@@ -36,6 +36,7 @@ type masterInode struct {
 	implStatFS
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
+	kernfs.InodeNotAnonymous
 	kernfs.InodeNotDirectory
 	kernfs.InodeNotSymlink
 	kernfs.InodeWatches

pkg/sentry/fsimpl/devpts/replica.go

@@ -35,6 +35,7 @@ type replicaInode struct {
 	implStatFS
 	kernfs.InodeAttrs
 	kernfs.InodeNoopRefCount
+	kernfs.InodeNotAnonymous
 	kernfs.InodeNotDirectory
 	kernfs.InodeNotSymlink
 	kernfs.InodeWatches