From 6e0c170522279ca72119b17c41e2e1dc93c49d6a Mon Sep 17 00:00:00 2001
From: Fabricio Voznika <fvoznika@google.com>
Date: Wed, 17 Jun 2020 21:21:08 -0700
Subject: Implement Sync() to directories

Updates #1035, #1199

PiperOrigin-RevId: 317028108
---
 pkg/sentry/fsimpl/overlay/directory.go | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

(limited to 'pkg/sentry/fsimpl/overlay')

diff --git a/pkg/sentry/fsimpl/overlay/directory.go b/pkg/sentry/fsimpl/overlay/directory.go
index 6f47167d3..f5c2462a5 100644
--- a/pkg/sentry/fsimpl/overlay/directory.go
+++ b/pkg/sentry/fsimpl/overlay/directory.go
@@ -263,3 +263,25 @@ func (fd *directoryFD) Seek(ctx context.Context, offset int64, whence int32) (in
 		return 0, syserror.EINVAL
 	}
 }
+
+// Sync implements vfs.FileDescriptionImpl.Sync. Forwards sync to the upper
+// layer, if there is one. The lower layer doesn't need to sync because it
+// never changes.
+func (fd *directoryFD) Sync(ctx context.Context) error {
+	d := fd.dentry()
+	if !d.isCopiedUp() {
+		return nil
+	}
+	vfsObj := d.fs.vfsfs.VirtualFilesystem()
+	pop := vfs.PathOperation{
+		Root:  d.upperVD,
+		Start: d.upperVD,
+	}
+	upperFD, err := vfsObj.OpenAt(ctx, d.fs.creds, &pop, &vfs.OpenOptions{Flags: linux.O_RDONLY | linux.O_DIRECTORY})
+	if err != nil {
+		return err
+	}
+	err = upperFD.Sync(ctx)
+	upperFD.DecRef()
+	return err
+}
-- 
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