[PATCH v6 2/4] mm: Introduce mem_cgroup_swapin_uncharge_swap_nr() helper for large folios swap-in

[Barry Song <v-songbaohua@xxxxxxxx>]

With large folios swap-in, we might need to uncharge multiple entries
all together, it is better to introduce a helper for that.

Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
 include/linux/memcontrol.h | 10 ++++++++--
 mm/memcontrol.c            |  7 ++++---
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 1b79760af685..f5dd1e34654a 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -682,7 +682,8 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
 
 int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
 				  gfp_t gfp, swp_entry_t entry);
-void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry);
+
+void mem_cgroup_swapin_uncharge_swap_nr(swp_entry_t entry, unsigned int nr_pages);
 
 void __mem_cgroup_uncharge(struct folio *folio);
 
@@ -1181,7 +1182,7 @@ static inline int mem_cgroup_swapin_charge_folio(struct folio *folio,
 	return 0;
 }
 
-static inline void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
+static inline void mem_cgroup_swapin_uncharge_swap_nr(swp_entry_t entry, int nr)
 {
 }
 
@@ -1796,6 +1797,11 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 
 #endif /* CONFIG_MEMCG */
 
+static inline void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
+{
+	mem_cgroup_swapin_uncharge_swap_nr(entry, 1);
+}
+
 #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP)
 bool obj_cgroup_may_zswap(struct obj_cgroup *objcg);
 void obj_cgroup_charge_zswap(struct obj_cgroup *objcg, size_t size);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index eb92c21615eb..25657d6a133f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4573,14 +4573,15 @@ int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
 
 /*
  * mem_cgroup_swapin_uncharge_swap - uncharge swap slot
- * @entry: swap entry for which the page is charged
+ * @entry: the first swap entry for which the pages are charged
+ * @nr_pages: number of pages which will be uncharged
  *
  * Call this function after successfully adding the charged page to swapcache.
  *
  * Note: This function assumes the page for which swap slot is being uncharged
  * is order 0 page.
  */
-void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
+void mem_cgroup_swapin_uncharge_swap_nr(swp_entry_t entry, unsigned int nr_pages)
 {
 	/*
 	 * Cgroup1's unified memory+swap counter has been charged with the
@@ -4600,7 +4601,7 @@ void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
 		 * let's not wait for it.  The page already received a
 		 * memory+swap charge, drop the swap entry duplicate.
 		 */
-		mem_cgroup_uncharge_swap(entry, 1);
+		mem_cgroup_uncharge_swap(entry, nr_pages);
 	}
 }
 
-- 
2.34.1

>
> > +}
> > +
> >  void __mem_cgroup_uncharge(struct folio *folio);
> >
> >  /**
> > @@ -1185,6 +1193,10 @@ static inline void mem_cgroup_swapin_uncharge_swap(swp_entry_t entry)
> >  {
> >  }
> >
> > +static inline void mem_cgroup_swapin_uncharge_swap_nr(swp_entry_t entry, int nr)
> > +{
> > +}
> > +
> >  static inline void mem_cgroup_uncharge(struct folio *folio)
> >  {
> >  }
> > --
> > 2.34.1
> >