linux-kernel - [PATCH RFC 1/4] mm: kmem: move memcg_kmem_bypass() calls to get_mem/obj_cgroup_from

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Message-ID: <20200827175215.319780-2-guro@fb.com>
Date:   Thu, 27 Aug 2020 10:52:12 -0700
From:   Roman Gushchin <guro@...com>
To:     <linux-mm@...ck.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        =Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>, <kernel-team@...com>,
        <linux-kernel@...r.kernel.org>, Roman Gushchin <guro@...com>
Subject: [PATCH RFC 1/4] mm: kmem: move memcg_kmem_bypass() calls to get_mem/obj_cgroup_from_current()

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 <guro@...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