mm/list_lru.c: revert "mm/list_lru: optimize memcg_reparent_list_lru_node()"

Commit 405cc51fc104 ("mm/list_lru: optimize memcg_reparent_list_lru_node()") has subtle races which are proving ugly to fix. Revert the original optimization. If quantitative testing indicates that we have a significant problem here then other implementations can be looked at.

Andrew Morton committed 4 years ago

Commit b33e1041 parent 0347b2b1 file · +0 −6Browse files

Unified · Split

mm/list_lru.c+0−6

@@ -394,12 +394,6 @@ static void memcg_reparent_list_lru_node(struct list_lru *lru, int nid, · 393 unmodified lines
394	394	int dst_idx = dst_memcg->kmemcg_id;
395	395	struct list_lru_one src, dst;
396	396
397		− /*
398		− * If there is no lru entry in this nlru, we can skip it immediately.
399		− */
400		− if (!READ_ONCE(nlru->nr_items))
401		− return;
402		−
403	397	/*
404	398	* Since list_lru_{add,del} may be called under an IRQ-safe lock,
405	399	* we have to use IRQ-safe primitives here to avoid deadlock.