On Mon, Aug 18, 2025 at 05:36:53PM -0700, Boris Burkov wrote:
> +++ b/mm/filemap.c
> @@ -960,15 +960,19 @@ int filemap_add_folio(struct address_space *mapping, struct folio *folio,
> {
> void *shadow = NULL;
> int ret;
> + bool charge_mem_cgroup = !test_bit(AS_UNCHARGED, &mapping->flags);
>
> - ret = mem_cgroup_charge(folio, NULL, gfp);
> - if (ret)
> - return ret;
> + if (charge_mem_cgroup) {
> + ret = mem_cgroup_charge(folio, NULL, gfp);
> + if (ret)
> + return ret;
> + }
>
> __folio_set_locked(folio);
> ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow);
> if (unlikely(ret)) {
> - mem_cgroup_uncharge(folio);
> + if (charge_mem_cgroup)
> + mem_cgroup_uncharge(folio);
> __folio_clear_locked(folio);
This is unnecessarily complex; mem_cgroup_uncharge() is a no-op if
the folio is not charged. Sure, it's a wasted function call, but
this is a rare error path, so minimising size is more important than
minimising time.
So you can drop the 'bool' as well:
+ if (!test_bit(AS_UNCHARGED, &mapping->flags)) {
