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 <[email protected]>
Reviewed-by: Shakeel Butt <[email protected]>
Acked-by: Vladimir Davydov <[email protected]>
---
 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 be9344777b29..8eaf553b67f1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2812,6 +2812,22 @@ 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
@@ -2826,14 +2842,7 @@ 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 */
-- 
2.21.0

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