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mm/list_lru: code clean up for reparenting

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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: Kairui Song <kasong@tencent.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Shakeel 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kairui Song 2024-11-05 01:52:54 +08:00 committed by Andrew Morton
parent 78c0ed0913
commit 8d42abbfa4
2 changed files with 17 additions and 29 deletions
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39
mm/list_lru.c
View File

@ -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);
}

7
mm/memcontrol.c
View File

@ -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);
}