From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Subject: mm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online() 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. Link: https://lkml.kernel.org/r/20220228122126.37293-10-songmuchun@xxxxxxxxxxxxx Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Acked-by: Roman Gushchin <roman.gushchin@xxxxxxxxx> Cc: Alex Shi <alexs@xxxxxxxxxx> Cc: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx> Cc: Chao Yu <chao@xxxxxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Cc: Fam Zheng <fam.zheng@xxxxxxxxxxxxx> Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Kari Argillander <kari.argillander@xxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Theodore Ts'o <tytso@xxxxxxx> Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Wei Yang <richard.weiyang@xxxxxxxxx> Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 37 ++++++++++++++++--------------------- 1 file changed, 16 insertions(+), 21 deletions(-) --- a/mm/memcontrol.c~mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online +++ a/mm/memcontrol.c @@ -3670,7 +3670,8 @@ static int memcg_online_kmem(struct mem_ 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) @@ -3696,7 +3697,10 @@ static void memcg_offline_kmem(struct me 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); @@ -3706,7 +3710,6 @@ static void memcg_offline_kmem(struct me 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 @@ -3717,7 +3720,6 @@ static void memcg_offline_kmem(struct me 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) @@ -5237,7 +5239,6 @@ mem_cgroup_css_alloc(struct cgroup_subsy { 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(); @@ -5266,34 +5267,26 @@ mem_cgroup_css_alloc(struct cgroup_subsy 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); @@ -5303,6 +5296,11 @@ static int mem_cgroup_css_online(struct 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) @@ -5360,9 +5358,6 @@ static void mem_cgroup_css_free(struct c 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); } _
