On Mon, Feb 28, 2022 at 08:21:22PM +0800, Muchun Song wrote:
> @@ -586,27 +508,48 @@ int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
> }
> }
>
> + xas_lock_irqsave(&xas, flags);
> while (i--) {
> + int index = READ_ONCE(table[i].memcg->kmemcg_id);
> struct list_lru_per_memcg *mlru = table[i].mlru;
>
> + xas_set(&xas, index);
> +retry:
> + if (unlikely(index < 0 || xas_error(&xas) || xas_load(&xas))) {
> kfree(mlru);
> + } else {
> + xas_store(&xas, mlru);
> + if (xas_error(&xas) == -ENOMEM) {
> + xas_unlock_irqrestore(&xas, flags);
> + if (xas_nomem(&xas, gfp))
> + xas_set_err(&xas, 0);
> + xas_lock_irqsave(&xas, flags);
> + /*
> + * The xas lock has been released, this memcg
> + * can be reparented before us. So reload
> + * memcg id. More details see the comments
> + * in memcg_reparent_list_lrus().
> + */
> + index = READ_ONCE(table[i].memcg->kmemcg_id);
> + if (index < 0)
> + xas_set_err(&xas, 0);
> + else if (!xas_error(&xas) && index != xas.xa_index)
> + xas_set(&xas, index);
> + goto retry;
> + }
> + }
> }
> + /* xas_nomem() is used to free memory instead of memory allocation. */
> + if (xas.xa_alloc)
> + xas_nomem(&xas, gfp);
> + xas_unlock_irqrestore(&xas, flags);
> kfree(table);
>
> + return xas_error(&xas);
> }
This is really unidiomatic. And so much more complicated than it needs
to be.
while (i--) {
do {
int index = READ_ONCE(table[i].memcg->kmemcg_id);
struct list_lru_per_memcg *mlru = table[i].mlru;
xas_set(&xas, index);
xas_lock_irqsave(&xas, flags);
if (index < 0 || xas_load(&xas))
xas_set_err(&xas, -EBUSY);
xas_store(&xas, mlru);
if (!xas_error(&xas))
break;
xas_unlock_irqrestore(&xas, flags);
} while (xas_nomem(&xas, gfp));
if (xas_error(&xas))
kfree(mlru);
}
kfree(table);
return xas_error(&xas);
(you might want to mask out the EBUSY error here)
