ovl: whiteout orphan index entries on mount

Orphan index entries are non-dir index entries whose union nlink count
dropped to zero. With index=on, orphan index entries are removed on
mount. With NFS export feature enabled, orphan index entries are replaced
with white out index entries to block future open by handle from opening
the lower file.

When dir index has a stale 'upper' xattr, we assume that the upper dir
was removed and we treat the dir index as orphan entry that needs to be
whited out or removed.

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

1 files changed, 23 insertions, 2 deletions

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 4c660c7085b7..c11f5c0906c3 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -1067,12 +1067,33 @@ int ovl_indexdir_cleanup(struct ovl_fs *ofs)
 			break;
 		}
 		err = ovl_verify_index(ofs, index);
-		/* Cleanup stale and orphan index entries */
-		if (err && (err == -ESTALE || err == -ENOENT))
+		if (!err) {
+			goto next;
+		} else if (err == -ESTALE) {
+			/* Cleanup stale index entries */
 			err = ovl_cleanup(dir, index);
+		} else if (err != -ENOENT) {
+			/*
+			 * Abort mount to avoid corrupting the index if
+			 * an incompatible index entry was found or on out
+			 * of memory.
+			 */
+			break;
+		} else if (ofs->config.nfs_export) {
+			/*
+			 * Whiteout orphan index to block future open by
+			 * handle after overlay nlink dropped to zero.
+			 */
+			err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+		} else {
+			/* Cleanup orphan index entries */
+			err = ovl_cleanup(dir, index);
+		}
+
 		if (err)
 			break;
 
+next:
 		dput(index);
 		index = NULL;
 	}