Commit 8d42abbf authored by Kairui Song's avatar Kairui Song Committed by Andrew Morton
Browse files

mm/list_lru: code clean up for reparenting 

No feature change, just change of code structure and fix comment.

The list lrus are not empty until memcg_reparent_list_lru_node() calls are
all done, so the comments in memcg_offline_kmem were slightly inaccurate.

Link: https://lkml.kernel.org/r/20241104175257.60853-4-ryncsn@gmail.com


Signed-off-by: default avatarKairui Song <kasong@tencent.com>
Reviewed-by: default avatarMuchun Song <muchun.song@linux.dev>
Acked-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 78c0ed09

mm/list_lru.c

+17 −22
Original line number Diff line number Diff line
@@ -421,35 +421,16 @@ static void memcg_reparent_list_lru_node(struct list_lru *lru, int nid, 
	spin_unlock_irq(&nlru->lock);

}



static void memcg_reparent_list_lru(struct list_lru *lru,

				    int src_idx, struct mem_cgroup *dst_memcg)

{

	int i;



	for_each_node(i)

		memcg_reparent_list_lru_node(lru, i, src_idx, dst_memcg);



	memcg_list_lru_free(lru, src_idx);

}



void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent)

{

	struct cgroup_subsys_state *css;

	struct list_lru *lru;

	int src_idx = memcg->kmemcg_id;

	int src_idx = memcg->kmemcg_id, i;



	/*

	 * Change kmemcg_id of this cgroup and all its descendants to the

	 * parent's id, and then move all entries from this cgroup's list_lrus

	 * to ones of the parent.

	 *

	 * After we have finished, all list_lrus corresponding to this cgroup

	 * are guaranteed to remain empty. So we can safely free this cgroup's

	 * list lrus in memcg_list_lru_free().

	 *

	 * Changing ->kmemcg_id to the parent can prevent memcg_list_lru_alloc()

	 * from allocating list lrus for this cgroup after memcg_list_lru_free()

	 * call.

	 */

	rcu_read_lock();

	css_for_each_descendant_pre(css, &memcg->css) {
@@ -460,9 +441,23 @@ void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *paren 
	}

	rcu_read_unlock();



	/*

	 * With kmemcg_id set to parent, holding the lock of each list_lru_node

	 * below can prevent list_lru_{add,del,isolate} from touching the lru,

	 * safe to reparent.

	 */

	mutex_lock(&list_lrus_mutex);

	list_for_each_entry(lru, &memcg_list_lrus, list)

		memcg_reparent_list_lru(lru, src_idx, parent);

	list_for_each_entry(lru, &memcg_list_lrus, list) {

		for_each_node(i)

			memcg_reparent_list_lru_node(lru, i, src_idx, parent);



		/*

		 * Here all list_lrus corresponding to the cgroup are guaranteed

		 * to remain empty, we can safely free this lru, any further

		 * memcg_list_lru_alloc() call will simply bail out.

		 */

		memcg_list_lru_free(lru, src_idx);

	}

	mutex_unlock(&list_lrus_mutex);

}

mm/memcontrol.c

+0 −7
Original line number Diff line number Diff line
@@ -3111,13 +3111,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg) 
		parent = root_mem_cgroup;



	memcg_reparent_objcgs(memcg, parent);



	/*

	 * After we have finished memcg_reparent_objcgs(), all list_lrus

	 * corresponding to this cgroup are guaranteed to remain empty.

	 * The ordering is imposed by list_lru_node->lock taken by

	 * memcg_reparent_list_lrus().

	 */

	memcg_reparent_list_lrus(memcg, parent);

}