fs: Allow overlays to revalidate files from the upper fs.

Previously, an overlay would panic if either the upper or lower fs required
revalidation for a given Dirent. Now, we allow revalidation from the upper
file, but not the lower.

If a cached overlay inode does need revalidation (because the upper needs
revalidation), then the entire overlay Inode will be discarded and a new
overlay Inode will be built with a fresh copy of the upper file.

As a side effect of this change, Revalidate must take an Inode instead of a
Dirent, since an overlay needs to revalidate individual Inodes.

PiperOrigin-RevId: 208293638
Change-Id: Ic8f8d1ffdc09114721745661a09522b54420c5f1

1 files changed, 1 insertions, 1 deletions

diff --git a/pkg/sentry/fs/tty/fs.go b/pkg/sentry/fs/tty/fs.go
index e28635607..fe7da05b5 100644
--- a/pkg/sentry/fs/tty/fs.go
+++ b/pkg/sentry/fs/tty/fs.go
@@ -82,7 +82,7 @@ type superOperations struct{}
 // Slave entries are dropped from dir when their master is closed, so an
 // existing slave Dirent in the tree is not sufficient to guarantee that it
 // still exists on the filesystem.
-func (superOperations) Revalidate(context.Context, *fs.Dirent) bool {
+func (superOperations) Revalidate(context.Context, *fs.Inode) bool {
 	return true
 }