linux-kernel - [PATCH v6 14/19] mm: memcg/slab: remove memcg_kmem_get

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Date:   Mon, 8 Jun 2020 16:06:49 -0700
From:   Roman Gushchin <guro@...com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>
CC:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>, <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>, <kernel-team@...com>,
        <linux-kernel@...r.kernel.org>, Roman Gushchin <guro@...com>
Subject: [PATCH v6 14/19] mm: memcg/slab: remove memcg_kmem_get_cache()

The memcg_kmem_get_cache() function became really trivial,
so let's just inline it into the single call point:
memcg_slab_pre_alloc_hook().

It will make the code less bulky and can also help the compiler
to generate a better code.

Signed-off-by: Roman Gushchin <guro@...com>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
---
 include/linux/memcontrol.h |  2 --
 mm/memcontrol.c            | 25 +------------------------
 mm/slab.h                  | 11 +++++++++--
 mm/slab_common.c           |  2 +-
 4 files changed, 11 insertions(+), 29 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ed0d2ac6a5d2..eede46c43573 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1403,8 +1403,6 @@ static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
 }
 #endif
 
-struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
-
 #ifdef CONFIG_MEMCG_KMEM
 int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp,
 			unsigned int nr_pages);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2695cdc15baa..09a84326ead1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -393,7 +393,7 @@ void memcg_put_cache_ids(void)
 
 /*
  * A lot of the calls to the cache allocation functions are expected to be
- * inlined by the compiler. Since the calls to memcg_kmem_get_cache are
+ * inlined by the compiler. Since the calls to memcg_slab_pre_alloc_hook() are
  * conditional to this static branch, we'll have to allow modules that does
  * kmem_cache_alloc and the such to see this symbol as well
  */
@@ -2900,29 +2900,6 @@ static void memcg_free_cache_id(int id)
 	ida_simple_remove(&memcg_cache_ida, id);
 }
 
-/**
- * memcg_kmem_get_cache: select memcg or root cache for allocation
- * @cachep: the original global kmem cache
- *
- * Return the kmem_cache we're supposed to use for a slab allocation.
- *
- * If the cache does not exist yet, if we are the first user of it, we
- * create it asynchronously in a workqueue and let the current allocation
- * go through with the original cache.
- */
-struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
-{
-	struct kmem_cache *memcg_cachep;
-
-	memcg_cachep = READ_ONCE(cachep->memcg_params.memcg_cache);
-	if (unlikely(!memcg_cachep)) {
-		queue_work(system_wq, &cachep->memcg_params.work);
-		return cachep;
-	}
-
-	return memcg_cachep;
-}
-
 /**
  * __memcg_kmem_charge: charge a number of kernel pages to a memcg
  * @memcg: memory cgroup to charge
diff --git a/mm/slab.h b/mm/slab.h
index c6c7987dfd85..f4033298a776 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -333,9 +333,16 @@ static inline struct kmem_cache *memcg_slab_pre_alloc_hook(struct kmem_cache *s,
 	if (memcg_kmem_bypass())
 		return s;
 
-	cachep = memcg_kmem_get_cache(s);
-	if (is_root_cache(cachep))
+	cachep = READ_ONCE(s->memcg_params.memcg_cache);
+	if (unlikely(!cachep)) {
+		/*
+		 * If memcg cache does not exist yet, we schedule it's
+		 * asynchronous creation and let the current allocation
+		 * go through with the root cache.
+		 */
+		queue_work(system_wq, &s->memcg_params.work);
 		return s;
+	}
 
 	objcg = get_obj_cgroup_from_current();
 	if (!objcg)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 10aa2acb84ca..f8874a159637 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -568,7 +568,7 @@ void memcg_create_kmem_cache(struct kmem_cache *root_cache)
 	}
 
 	/*
-	 * Since readers won't lock (see memcg_kmem_get_cache()), we need a
+	 * Since readers won't lock (see memcg_slab_pre_alloc_hook()), we need a
 	 * barrier here to ensure nobody will see the kmem_cache partially
 	 * initialized.
 	 */
-- 
2.25.4