ovl: encode pure upper file handles

Encode overlay file handles as struct ovl_fh containing the file handle
encoding of the real upper inode.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 2dddcd257eb3..f2baa2ccaacd 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -68,6 +68,9 @@ enum ovl_entry_flag {
 #error Endianness not defined
 #endif
 
+/* The type returned by overlay exportfs ops when encoding an ovl_fh handle */
+#define OVL_FILEID      0xfb
+
 /* On-disk and in-memeory format for redirect by file handle */
 struct ovl_fh {
         u8 version;     /* 0 */
@@ -351,3 +354,6 @@ int ovl_set_attr(struct dentry *upper, struct kstat *stat);
 struct ovl_fh *ovl_encode_fh(struct dentry *real, bool is_upper);
 int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
                    struct dentry *upper);
+
+/* export.c */
+extern const struct export_operations ovl_export_operations;