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Subject[PATCH v4 10/17] mm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online()
Date
It will simplify the code if moving memcg_online_kmem() to
mem_cgroup_css_online() and do not need to set ->kmemcg_id
to -1 to indicate the memcg is offline. In the next patch,
->kmemcg_id will be used to sync list lru reparenting which
requires not to change ->kmemcg_id.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
mm/memcontrol.c | 37 ++++++++++++++++---------------------
1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d505b43d5f3b..ec7a62f39326 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3604,7 +3604,8 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
if (cgroup_memory_nokmem)
return 0;

- BUG_ON(memcg->kmemcg_id >= 0);
+ if (unlikely(mem_cgroup_is_root(memcg)))
+ return 0;

memcg_id = memcg_alloc_cache_id();
if (memcg_id < 0)
@@ -3630,7 +3631,10 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
struct mem_cgroup *parent;
int kmemcg_id;

- if (memcg->kmemcg_id == -1)
+ if (cgroup_memory_nokmem)
+ return;
+
+ if (unlikely(mem_cgroup_is_root(memcg)))
return;

parent = parent_mem_cgroup(memcg);
@@ -3640,7 +3644,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
memcg_reparent_objcgs(memcg, parent);

kmemcg_id = memcg->kmemcg_id;
- BUG_ON(kmemcg_id < 0);

/*
* After we have finished memcg_reparent_objcgs(), all list_lrus
@@ -3651,7 +3654,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
memcg_drain_all_list_lrus(kmemcg_id, parent);

memcg_free_cache_id(kmemcg_id);
- memcg->kmemcg_id = -1;
}
#else
static int memcg_online_kmem(struct mem_cgroup *memcg)
@@ -5159,7 +5161,6 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
{
struct mem_cgroup *parent = mem_cgroup_from_css(parent_css);
struct mem_cgroup *memcg, *old_memcg;
- long error = -ENOMEM;

old_memcg = set_active_memcg(parent);
memcg = mem_cgroup_alloc();
@@ -5188,34 +5189,26 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
return &memcg->css;
}

- /* The following stuff does not apply to the root */
- error = memcg_online_kmem(memcg);
- if (error)
- goto fail;
-
if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
static_branch_inc(&memcg_sockets_enabled_key);

return &memcg->css;
-fail:
- mem_cgroup_id_remove(memcg);
- mem_cgroup_free(memcg);
- return ERR_PTR(error);
}

static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);

+ if (memcg_online_kmem(memcg))
+ goto remove_id;
+
/*
* A memcg must be visible for expand_shrinker_info()
* by the time the maps are allocated. So, we allocate maps
* here, when for_each_mem_cgroup() can't skip it.
*/
- if (alloc_shrinker_info(memcg)) {
- mem_cgroup_id_remove(memcg);
- return -ENOMEM;
- }
+ if (alloc_shrinker_info(memcg))
+ goto offline_kmem;

/* Online state pins memcg ID, memcg ID pins CSS */
refcount_set(&memcg->id.ref, 1);
@@ -5225,6 +5218,11 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
queue_delayed_work(system_unbound_wq, &stats_flush_dwork,
2UL*HZ);
return 0;
+offline_kmem:
+ memcg_offline_kmem(memcg);
+remove_id:
+ mem_cgroup_id_remove(memcg);
+ return -ENOMEM;
}

static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
@@ -5282,9 +5280,6 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
cancel_work_sync(&memcg->high_work);
mem_cgroup_remove_from_trees(memcg);
free_shrinker_info(memcg);
-
- /* Need to offline kmem if online_css() fails */
- memcg_offline_kmem(memcg);
mem_cgroup_free(memcg);
}

--
2.11.0
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