ovl: fix wrong detection of 32bit inode numbers

The implicit FILEID_INO32_GEN encoder was changed to be explicit,
so we need to fix the detection.

When mounting overlayfs with upperdir and lowerdir on different ext4
filesystems, the expected kmsg log is:

  overlayfs: "xino" feature enabled using 32 upper inode bits.

But instead, since the regressing commit, the kmsg log was:

  overlayfs: "xino" feature enabled using 2 upper inode bits.

Fixes: e21fc20 ("exportfs: make ->encode_fh() a mandatory method for NFS export")
Cc: stable@vger.kernel.org # v6.7+
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Author: amir73il

fs/overlayfs/util.c

@@ -85,7 +85,10 @@ int ovl_can_decode_fh(struct super_block *sb)
 	if (!exportfs_can_decode_fh(sb->s_export_op))
 		return 0;
 
-	return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN;
+	if (sb->s_export_op->encode_fh == generic_encode_ino32_fh)
+		return FILEID_INO32_GEN;
+
+	return -1;
 }
 
 struct dentry *ovl_indexdir(struct super_block *sb)