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From:   Roman Gushchin <guro@fb.com>
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To:     Andrew Morton <akpm@linux-foundation.org>
CC:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        <kernel-team@fb.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Shakeel Butt <shakeelb@google.com>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Waiman Long <longman@redhat.com>, Roman Gushchin <guro@fb.com>
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Subject: [PATCH v6 05/10] mm: introduce __memcg_kmem_uncharge_memcg()
Date:   Tue, 4 Jun 2019 19:44:49 -0700
Message-ID: <20190605024454.1393507-6-guro@fb.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Let's separate the page counter modification code out of
__memcg_kmem_uncharge() in a way similar to what
__memcg_kmem_charge() and __memcg_kmem_charge_memcg() work.

This will allow to reuse this code later using a new
memcg_kmem_uncharge_memcg() wrapper, which calls
__memcg_kmem_uncharge_memcg() if memcg_kmem_enabled()
check is passed.

Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
---
 include/linux/memcontrol.h | 10 ++++++++++
 mm/memcontrol.c            | 25 +++++++++++++++++--------
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3ca57bacfdd2..9abf31bbe53a 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1304,6 +1304,8 @@ int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order);
 void __memcg_kmem_uncharge(struct page *page, int order);
 int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
 			      struct mem_cgroup *memcg);
+void __memcg_kmem_uncharge_memcg(struct mem_cgroup *memcg,
+				 unsigned int nr_pages);
 
 extern struct static_key_false memcg_kmem_enabled_key;
 extern struct workqueue_struct *memcg_kmem_cache_wq;
@@ -1345,6 +1347,14 @@ static inline int memcg_kmem_charge_memcg(struct page *page, gfp_t gfp,
 		return __memcg_kmem_charge_memcg(page, gfp, order, memcg);
 	return 0;
 }
+
+static inline void memcg_kmem_uncharge_memcg(struct page *page, int order,
+					     struct mem_cgroup *memcg)
+{
+	if (memcg_kmem_enabled())
+		__memcg_kmem_uncharge_memcg(memcg, 1 << order);
+}
+
 /*
  * helper for accessing a memcg's index. It will be used as an index in the
  * child cache array in kmem_cache, and also to derive its name. This function
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bdb66871cdec..3427396da612 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2731,6 +2731,22 @@ int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
 	css_put(&memcg->css);
 	return ret;
 }
+
+/**
+ * __memcg_kmem_uncharge_memcg: uncharge a kmem page
+ * @memcg: memcg to uncharge
+ * @nr_pages: number of pages to uncharge
+ */
+void __memcg_kmem_uncharge_memcg(struct mem_cgroup *memcg,
+				 unsigned int nr_pages)
+{
+	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
+		page_counter_uncharge(&memcg->kmem, nr_pages);
+
+	page_counter_uncharge(&memcg->memory, nr_pages);
+	if (do_memsw_account())
+		page_counter_uncharge(&memcg->memsw, nr_pages);
+}
 /**
  * __memcg_kmem_uncharge: uncharge a kmem page
  * @page: page to uncharge
@@ -2745,14 +2761,7 @@ void __memcg_kmem_uncharge(struct page *page, int order)
 		return;
 
 	VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page);
-
-	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
-		page_counter_uncharge(&memcg->kmem, nr_pages);
-
-	page_counter_uncharge(&memcg->memory, nr_pages);
-	if (do_memsw_account())
-		page_counter_uncharge(&memcg->memsw, nr_pages);
-
+	__memcg_kmem_uncharge_memcg(memcg, nr_pages);
 	page->mem_cgroup = NULL;
 
 	/* slab pages do not have PageKmemcg flag set */
-- 
2.20.1