quoted

+     if (err)
+             goto  err_files_mem;

 Nit:                ^^ two spaces here.

Removed.

quoted

+
+     if (file_set->count == LUO_FILE_MAX) {
+             err = -ENOSPC;
+             goto err_files_mem;
+     }
+
+     err = -ENOENT;
+     luo_list_for_each_private(fh, &luo_file_handler_list, list) {
+             if (fh->ops->can_preserve(fh, file)) {
+                     err = 0;
+                     break;
+             }
+     }
+

[...]

quoted

+int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
+{
+     struct liveupdate_file_handler *fh_iter;
+     int err;
+
+     if (!liveupdate_enabled())
+             return -EOPNOTSUPP;
+
+     /* Sanity check that all required callbacks are set */
+     if (!fh->ops->preserve || !fh->ops->unpreserve ||
+         !fh->ops->retrieve || !fh->ops->finish) {

 You are still missing a check for can_preserve() here. It is a mandatory
 callback and luo_preserve_file() calls it without checking for NULL.

Added.

 With these and Mike's comments addressed,

 Reviewed-by: Pratyush Yadav [off-list ref]

Thanks.

quoted

+             return -EINVAL;
+     }
+

[...]

--
Regards,
Pratyush Yadav