mm: memcontrol: rein in the CONFIG space madness

What CONFIG_INET and CONFIG_LEGACY_KMEM guard inside the memory
controller code is insignificant, having these conditionals is not
worth the complication and fragility that comes with them.

[akpm@linux-foundation.org: rework mem_cgroup_css_free() statement ordering]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 12 insertions, 78 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 2bb14d021cd0..47995b499429 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -233,9 +233,11 @@ struct mem_cgroup {
          */
         struct mem_cgroup_stat_cpu __percpu *stat;
 
-#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
+        unsigned long           socket_pressure;
+
+        /* Legacy tcp memory accounting */
         struct cg_proto tcp_mem;
-#endif
+
 #ifndef CONFIG_SLOB
         /* Index in the kmem_cache->memcg_params.memcg_caches array */
         int kmemcg_id;
@@ -254,10 +256,6 @@ struct mem_cgroup {
         struct wb_domain cgwb_domain;
 #endif
 
-#ifdef CONFIG_INET
-        unsigned long           socket_pressure;
-#endif
-
         /* List of events which userspace want to receive */
         struct list_head event_list;
         spinlock_t event_list_lock;
@@ -712,15 +710,13 @@ void sock_update_memcg(struct sock *sk);
 void sock_release_memcg(struct sock *sk);
 bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
 void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
-#if defined(CONFIG_MEMCG) && defined(CONFIG_INET)
+#ifdef CONFIG_MEMCG
 extern struct static_key_false memcg_sockets_enabled_key;
 #define mem_cgroup_sockets_enabled static_branch_unlikely(&memcg_sockets_enabled_key)
 static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
 {
-#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (memcg->tcp_mem.memory_pressure)
                 return true;
-#endif
         do {
                 if (time_before(jiffies, memcg->socket_pressure))
                         return true;
diff --git a/init/Kconfig b/init/Kconfig
index a0a15cec8daf..22320804fbaf 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -964,20 +964,6 @@ config MEMCG_SWAP_ENABLED
           For those who want to have the feature enabled by default should
           select this option (if, for some reason, they need to disable it
           then swapaccount=0 does the trick).
-config MEMCG_LEGACY_KMEM
-       bool
-config MEMCG_KMEM
-        bool "Legacy Memory Resource Controller Kernel Memory accounting"
-        depends on MEMCG
-        depends on SLUB || SLAB
-        select MEMCG_LEGACY_KMEM
-        help
-          The Kernel Memory extension for Memory Resource Controller can limit
-          the amount of memory used by kernel objects in the system. Those are
-          fundamentally different from the entities handled by the standard
-          Memory Controller, which are page-based, and can be swapped. Users of
-          the kmem extension can use it to guarantee that no group of processes
-          will ever exhaust kernel resources alone.
 
 config BLK_CGROUP
         bool "IO controller"
@@ -1190,10 +1176,9 @@ config USER_NS
           to provide different user info for different servers.
 
           When user namespaces are enabled in the kernel it is
-          recommended that the MEMCG and MEMCG_KMEM options also be
-          enabled and that user-space use the memory control groups to
-          limit the amount of memory a memory unprivileged users can
-          use.
+          recommended that the MEMCG option also be enabled and that
+          user-space use the memory control groups to limit the amount
+          of memory a memory unprivileged users can use.
 
           If unsure, say N.
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 15896708429b..379f9911b87b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2842,11 +2842,9 @@ static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
         case _KMEM:
                 counter = &memcg->kmem;
                 break;
-#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
         case _TCP:
                 counter = &memcg->tcp_mem.memory_allocated;
                 break;
-#endif
         default:
                 BUG();
         }
@@ -3006,7 +3004,6 @@ static void memcg_free_kmem(struct mem_cgroup *memcg)
 }
 #endif /* !CONFIG_SLOB */
 
-#ifdef CONFIG_MEMCG_LEGACY_KMEM
 static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
                                    unsigned long limit)
 {
@@ -3024,16 +3021,7 @@ out:
         mutex_unlock(&memcg_limit_mutex);
         return ret;
 }
-#else
-static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
-                                   unsigned long limit)
-{
-        return -EINVAL;
-}
-#endif /* CONFIG_MEMCG_LEGACY_KMEM */
 
-
-#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
 static int memcg_update_tcp_limit(struct mem_cgroup *memcg, unsigned long limit)
 {
         int ret;
@@ -3068,12 +3056,6 @@ out:
         mutex_unlock(&memcg_limit_mutex);
         return ret;
 }
-#else
-static int memcg_update_tcp_limit(struct mem_cgroup *memcg, unsigned long limit)
-{
-        return -EINVAL;
-}
-#endif /* CONFIG_MEMCG_LEGACY_KMEM && CONFIG_INET */
 
 /*
  * The user of this function is...
@@ -3136,11 +3118,9 @@ static ssize_t mem_cgroup_reset(struct kernfs_open_file *of, char *buf,
         case _KMEM:
                 counter = &memcg->kmem;
                 break;
-#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
         case _TCP:
                 counter = &memcg->tcp_mem.memory_allocated;
                 break;
-#endif
         default:
                 BUG();
         }
@@ -4094,7 +4074,6 @@ static struct cftype mem_cgroup_legacy_files[] = {
                 .seq_show = memcg_numa_stat_show,
         },
 #endif
-#ifdef CONFIG_MEMCG_LEGACY_KMEM
         {
                 .name = "kmem.limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
@@ -4127,7 +4106,6 @@ static struct cftype mem_cgroup_legacy_files[] = {
                 .seq_show = memcg_slab_show,
         },
 #endif
-#ifdef CONFIG_INET
         {
                 .name = "kmem.tcp.limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_TCP, RES_LIMIT),
@@ -4151,8 +4129,6 @@ static struct cftype mem_cgroup_legacy_files[] = {
                 .write = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read_u64,
         },
-#endif
-#endif
         { },    /* terminate */
 };
 
@@ -4280,15 +4256,13 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
         vmpressure_init(&memcg->vmpressure);
         INIT_LIST_HEAD(&memcg->event_list);
         spin_lock_init(&memcg->event_list_lock);
+        memcg->socket_pressure = jiffies;
 #ifndef CONFIG_SLOB
         memcg->kmemcg_id = -1;
 #endif
 #ifdef CONFIG_CGROUP_WRITEBACK
         INIT_LIST_HEAD(&memcg->cgwb_list);
 #endif
-#ifdef CONFIG_INET
-        memcg->socket_pressure = jiffies;
-#endif
         return &memcg->css;
 
 free_out:
@@ -4321,10 +4295,8 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
                 memcg->soft_limit = PAGE_COUNTER_MAX;
                 page_counter_init(&memcg->memsw, &parent->memsw);
                 page_counter_init(&memcg->kmem, &parent->kmem);
-#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
                 page_counter_init(&memcg->tcp_mem.memory_allocated,
                                   &parent->tcp_mem.memory_allocated);
-#endif
 
                 /*
                  * No need to take a reference to the parent because cgroup
@@ -4336,9 +4308,7 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
                 memcg->soft_limit = PAGE_COUNTER_MAX;
                 page_counter_init(&memcg->memsw, NULL);
                 page_counter_init(&memcg->kmem, NULL);
-#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
                 page_counter_init(&memcg->tcp_mem.memory_allocated, NULL);
-#endif
                 /*
                  * Deeper hierachy with use_hierarchy == false doesn't make
                  * much sense so let cgroup subsystem know about this
@@ -4353,10 +4323,8 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
         if (ret)
                 return ret;
 
-#ifdef CONFIG_INET
         if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
                 static_branch_inc(&memcg_sockets_enabled_key);
-#endif
 
         /*
          * Make sure the memcg is initialized: mem_cgroup_iter()
@@ -4403,18 +4371,13 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
-#ifdef CONFIG_INET
         if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
                 static_branch_dec(&memcg_sockets_enabled_key);
-#endif
-
-        memcg_free_kmem(memcg);
 
-#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
         if (memcg->tcp_mem.active)
                 static_branch_dec(&memcg_sockets_enabled_key);
-#endif
 
+        memcg_free_kmem(memcg);
         __mem_cgroup_free(memcg);
 }
 
@@ -5613,8 +5576,6 @@ void mem_cgroup_replace_page(struct page *oldpage, struct page *newpage)
         commit_charge(newpage, memcg, true);
 }
 
-#ifdef CONFIG_INET
-
 DEFINE_STATIC_KEY_FALSE(memcg_sockets_enabled_key);
 EXPORT_SYMBOL(memcg_sockets_enabled_key);
 
@@ -5640,10 +5601,8 @@ void sock_update_memcg(struct sock *sk)
         memcg = mem_cgroup_from_task(current);
         if (memcg == root_mem_cgroup)
                 goto out;
-#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !memcg->tcp_mem.active)
                 goto out;
-#endif
         if (css_tryget_online(&memcg->css))
                 sk->sk_memcg = memcg;
 out:
@@ -5669,7 +5628,6 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
         gfp_t gfp_mask = GFP_KERNEL;
 
-#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
                 struct page_counter *counter;
 
@@ -5682,7 +5640,7 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
                 memcg->tcp_mem.memory_pressure = 1;
                 return false;
         }
-#endif
+
         /* Don't block in the packet receive path */
         if (in_softirq())
                 gfp_mask = GFP_NOWAIT;
@@ -5701,19 +5659,16 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
  */
 void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
-#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
                 page_counter_uncharge(&memcg->tcp_mem.memory_allocated,
                                       nr_pages);
                 return;
         }
-#endif
+
         page_counter_uncharge(&memcg->memory, nr_pages);
         css_put_many(&memcg->css, nr_pages);
 }
 
-#endif /* CONFIG_INET */
-
 static int __init cgroup_memory(char *s)
 {
         char *token;
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 89b1d441af4b..9a6c0704211c 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -275,7 +275,6 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
 
                 level = vmpressure_calc_level(scanned, reclaimed);
 
-#ifdef CONFIG_INET
                 if (level > VMPRESSURE_LOW) {
                         /*
                          * Let the socket buffer allocator know that
@@ -287,7 +286,6 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
                          */
                         memcg->socket_pressure = jiffies + HZ;
                 }
-#endif
         }
 }