rmap_walk_arg
struct rmap_walk_arg *rmap_walk_arg = arg;
DEFINE_FOLIO_VMA_WALK(pvmw, rmap_walk_arg->folio, vma, addr, PVMW_SYNC | PVMW_MIGRATION);
if (rmap_walk_arg->map_unused_to_zeropage &&
struct rmap_walk_arg rmap_walk_arg = {
.arg = &rmap_walk_arg,