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@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Alex Shi <alexs@kernel.org>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Fam Zheng <fam.zheng@bytedance.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kari Argillander <kari.argillander@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5283552..f08a0dc 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3670,7 +3670,8 @@ 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)
@@ -3696,7 +3697,10 @@ 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);
@@ -3706,7 +3710,6 @@ 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
@@ -3717,7 +3720,6 @@ 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)
@@ -5237,7 +5239,6 @@ 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();
@@ -5266,34 +5267,26 @@ 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);
@@ -5303,6 +5296,11 @@ 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)
@@ -5360,9 +5358,6 @@ 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);
 }