mm: memcontrol: introduce CONFIG_MEMCG_LEGACY_KMEM

Let the user know that CONFIG_MEMCG_KMEM does not apply to the cgroup2
interface. This also makes legacy-only code sections stand out better.

[arnd@arndb.de: mm: memcontrol: only manage socket pressure for CONFIG_INET]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 23 insertions, 13 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a87704e3668e..2bb14d021cd0 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -233,7 +233,7 @@ struct mem_cgroup {
          */
         struct mem_cgroup_stat_cpu __percpu *stat;
 
-#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_INET)
+#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
         struct cg_proto tcp_mem;
 #endif
 #ifndef CONFIG_SLOB
@@ -717,7 +717,7 @@ 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_KMEM
+#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (memcg->tcp_mem.memory_pressure)
                 return true;
 #endif
diff --git a/init/Kconfig b/init/Kconfig
index 5b86082fa238..a0a15cec8daf 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -964,10 +964,13 @@ 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 "Memory Resource Controller Kernel Memory accounting"
+        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
@@ -1071,6 +1074,11 @@ config CGROUP_FREEZER
           Provides a way to freeze and unfreeze all tasks in a
           cgroup.
 
+          This option affects the ORIGINAL cgroup interface. The cgroup2 memory
+          controller includes important in-kernel memory consumers per default.
+
+          If you're using cgroup2, say N.
+
 config CGROUP_HUGETLB
         bool "HugeTLB controller"
         depends on HUGETLB_PAGE
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2239e6dd4d4c..92e8ab67b6df 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3001,7 +3001,7 @@ static void memcg_free_kmem(struct mem_cgroup *memcg)
 }
 #endif /* !CONFIG_SLOB */
 
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG_LEGACY_KMEM
 static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
                                    unsigned long limit)
 {
@@ -3025,7 +3025,7 @@ static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
 {
         return -EINVAL;
 }
-#endif /* CONFIG_MEMCG_KMEM */
+#endif /* CONFIG_MEMCG_LEGACY_KMEM */
 
 
 /*
@@ -4039,7 +4039,7 @@ static struct cftype mem_cgroup_legacy_files[] = {
                 .seq_show = memcg_numa_stat_show,
         },
 #endif
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG_LEGACY_KMEM
         {
                 .name = "kmem.limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
@@ -4266,13 +4266,13 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
         if (ret)
                 return ret;
 
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_INET
+#ifdef CONFIG_MEMCG_LEGACY_KMEM
         ret = tcp_init_cgroup(memcg);
         if (ret)
                 return ret;
 #endif
 
-#ifdef CONFIG_INET
         if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
                 static_branch_inc(&memcg_sockets_enabled_key);
 #endif
@@ -4329,7 +4329,7 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
 
         memcg_free_kmem(memcg);
 
-#ifdef CONFIG_MEMCG_KMEM
+#if defined(CONFIG_MEMCG_LEGACY_KMEM) && defined(CONFIG_INET)
         tcp_destroy_cgroup(memcg);
 #endif
 
@@ -5558,7 +5558,7 @@ void sock_update_memcg(struct sock *sk)
         memcg = mem_cgroup_from_task(current);
         if (memcg == root_mem_cgroup)
                 goto out;
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !memcg->tcp_mem.active)
                 goto out;
 #endif
@@ -5587,7 +5587,7 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
         gfp_t gfp_mask = GFP_KERNEL;
 
-#ifdef CONFIG_MEMCG_KMEM
+#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
                 struct page_counter *counter;
 
@@ -5619,7 +5619,7 @@ 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_KMEM
+#ifdef CONFIG_MEMCG_LEGACY_KMEM
         if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
                 page_counter_uncharge(&memcg->tcp_mem.memory_allocated,
                                       nr_pages);
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 9a6c0704211c..89b1d441af4b 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -275,6 +275,7 @@ 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
@@ -286,6 +287,7 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
                          */
                         memcg->socket_pressure = jiffies + HZ;
                 }
+#endif
         }
 }
 
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index c29809f765dc..bee5055832a1 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -56,7 +56,7 @@ obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
 obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
 obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.o
 obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
-obj-$(CONFIG_MEMCG_KMEM) += tcp_memcontrol.o
+obj-$(CONFIG_MEMCG_LEGACY_KMEM) += tcp_memcontrol.o
 obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \