[PATCH v6 1/2] mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios

[Barry Song <21cnbao@xxxxxxxxx>]

From: Barry Song <v-songbaohua@xxxxxxxx>

With large folios swap-in, we might need to uncharge multiple entries
all together, add nr argument in mem_cgroup_swapin_uncharge_swap().

For the existing two users, just pass nr=1.

Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
 include/linux/memcontrol.h | 5 +++--
 mm/memcontrol.c            | 7 ++++---
 mm/memory.c                | 2 +-
 mm/swap_state.c            | 2 +-
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 1b79760af685..44f7fb7dc0c8 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(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(swp_entry_t entry, unsigned int nr)
 {
 }
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b889a7fbf382..5d763c234c44 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4572,14 +4572,15 @@ 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(swp_entry_t entry, unsigned int nr_pages)
 {
 	/*
 	 * Cgroup1's unified memory+swap counter has been charged with the
@@ -4599,7 +4600,7 @@ 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);
 	}
 }
 
diff --git a/mm/memory.c b/mm/memory.c
index 4c8716cb306c..4cf4902db1ec 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4102,7 +4102,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 					ret = VM_FAULT_OOM;
 					goto out_page;
 				}
-				mem_cgroup_swapin_uncharge_swap(entry);
+				mem_cgroup_swapin_uncharge_swap(entry, 1);
 
 				shadow = get_shadow_from_swap_cache(entry);
 				if (shadow)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 293ff1afdca4..1159e3225754 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -522,7 +522,7 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 	if (add_to_swap_cache(new_folio, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
 		goto fail_unlock;
 
-	mem_cgroup_swapin_uncharge_swap(entry);
+	mem_cgroup_swapin_uncharge_swap(entry, 1);
 
 	if (shadow)
 		workingset_refault(new_folio, shadow);
-- 
2.34.1