[PATCH RFC 1/4] mm: kmem: move memcg_kmem_bypass() calls to get_mem/obj_cgroup_from_current()

[Roman Gushchin]

Currently memcg_kmem_bypass() is called before obtaining the current
memory/obj cgroup using get_mem/obj_cgroup_from_current(). Moving
memcg_kmem_bypass() into get_mem/obj_cgroup_from_current() reduces
the number of call sites and allows further code simplifications.

Signed-off-by: Roman Gushchin <g...@fb.com>
---
 mm/memcontrol.c | 13 ++++++++-----
 mm/percpu.c     |  3 +--
 mm/slab.h       |  3 ---
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dc892a3c4b17..9c08d8d14bc0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1074,6 +1074,9 @@ EXPORT_SYMBOL(get_mem_cgroup_from_page);
  */
 static __always_inline struct mem_cgroup *get_mem_cgroup_from_current(void)
 {
+       if (memcg_kmem_bypass())
+               return NULL;
+
        if (unlikely(current->active_memcg)) {
                struct mem_cgroup *memcg;
 
@@ -2913,6 +2916,9 @@ __always_inline struct obj_cgroup 
*get_obj_cgroup_from_current(void)
        struct obj_cgroup *objcg = NULL;
        struct mem_cgroup *memcg;
 
+       if (memcg_kmem_bypass())
+               return NULL;
+
        if (unlikely(!current->mm && !current->active_memcg))
                return NULL;
 
@@ -3039,19 +3045,16 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t 
gfp, int order)
        struct mem_cgroup *memcg;
        int ret = 0;
 
-       if (memcg_kmem_bypass())
-               return 0;
-
        memcg = get_mem_cgroup_from_current();
-       if (!mem_cgroup_is_root(memcg)) {
+       if (memcg && !mem_cgroup_is_root(memcg)) {
                ret = __memcg_kmem_charge(memcg, gfp, 1 << order);
                if (!ret) {
                        page->mem_cgroup = memcg;
                        __SetPageKmemcg(page);
                        return 0;
                }
+               css_put(&memcg->css);
        }
-       css_put(&memcg->css);
        return ret;
 }
 
diff --git a/mm/percpu.c b/mm/percpu.c
index f4709629e6de..9b07bd5bc45f 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1584,8 +1584,7 @@ static enum pcpu_chunk_type 
pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp,
 {
        struct obj_cgroup *objcg;
 
-       if (!memcg_kmem_enabled() || !(gfp & __GFP_ACCOUNT) ||
-           memcg_kmem_bypass())
+       if (!memcg_kmem_enabled() || !(gfp & __GFP_ACCOUNT))
                return PCPU_CHUNK_ROOT;
 
        objcg = get_obj_cgroup_from_current();
diff --git a/mm/slab.h b/mm/slab.h
index 95e5cc1bb2a3..4a24e1702923 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -280,9 +280,6 @@ static inline struct obj_cgroup 
*memcg_slab_pre_alloc_hook(struct kmem_cache *s,
 {
        struct obj_cgroup *objcg;
 
-       if (memcg_kmem_bypass())
-               return NULL;
-
        objcg = get_obj_cgroup_from_current();
        if (!objcg)
                return NULL;
-- 
2.26.2