[PATCH] mm: memcg/slab: don't create kmalloc-cg caches with cgroup.memory=nokmem

[Vlastimil Babka]

The caches should not be created when kmemcg is disabled on boot, otherwise
they are also filled by kmalloc(__GFP_ACCOUNT) allocations. When booted with
cgroup.memory=nokmem, link the kmalloc_caches[KMALLOC_CGROUP] entries to
KMALLOC_NORMAL entries instead.

Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 mm/internal.h    | 5 +++++
 mm/memcontrol.c  | 2 +-
 mm/slab_common.c | 9 +++++++--
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index ef5f336f59bd..b2d60b3403c7 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -135,6 +135,11 @@ extern void putback_lru_page(struct page *page);
  */
 extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
 
+/*
+ * in mm/memcontrol.c:
+ */
+extern bool cgroup_memory_nokmem;
+
 /*
  * in mm/page_alloc.c
  */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5e3b4f23b830..b9ec01f2b4f6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -83,7 +83,7 @@ DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
 static bool cgroup_memory_nosocket;
 
 /* Kernel memory accounting disabled? */
-static bool cgroup_memory_nokmem;
+bool cgroup_memory_nokmem;
 
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
diff --git a/mm/slab_common.c b/mm/slab_common.c
index bbaf41a7c77e..363f90215401 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -832,10 +832,15 @@ void __init setup_kmalloc_cache_index_table(void)
 static void __init
 new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
 {
-	if (type == KMALLOC_RECLAIM)
+	if (type == KMALLOC_RECLAIM) {
 		flags |= SLAB_RECLAIM_ACCOUNT;
-	else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP))
+	} else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP)) {
+		if (cgroup_memory_nokmem) {
+			kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
+			return;
+		}
 		flags |= SLAB_ACCOUNT;
+	}
 
 	kmalloc_caches[type][idx] = create_kmalloc_cache(
 					kmalloc_info[idx].name[type],
-- 
2.31.1