[PATCH RFC 1/2] mm/memcontrol: add page-level charge/uncharge functions

[Eric Chanudet <echanude@redhat.com>]

Expose functions to charge/uncharge memcg with a number of pages instead
of a folio.

Signed-off-by: Eric Chanudet <echanude@redhat.com>
---
 include/linux/memcontrol.h |  4 ++++
 mm/memcontrol.c            | 24 ++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 70b685a85bf4cd0e830c9c0253e4d48f75957fe4..32f03890f13e06551fc910515eb478597c1235d8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -642,6 +642,8 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup *target,
 
 int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp);
 
+int mem_cgroup_try_charge_pages(struct mem_cgroup *memcg, gfp_t gfp_mask,
+				unsigned int nr_pages);
 /**
  * mem_cgroup_charge - Charge a newly allocated folio to a cgroup.
  * @folio: Folio to charge.
@@ -692,6 +694,8 @@ static inline void mem_cgroup_uncharge_folios(struct folio_batch *folios)
 	__mem_cgroup_uncharge_folios(folios);
 }
 
+void mem_cgroup_uncharge_pages(struct mem_cgroup *memcg, unsigned int nr_pages);
+
 void mem_cgroup_replace_folio(struct folio *old, struct folio *new);
 void mem_cgroup_migrate(struct folio *old, struct folio *new);
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 772bac21d15584ce495cba6ad2eebfa7f693677f..49ed069a2dafd5d26d77e6737dffe7e64ba5118c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4764,6 +4764,24 @@ int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
 	return ret;
 }
 
+/**
+ * mem_cgroup_try_charge_pages - charge pages to a memory cgroup
+ * @memcg: memory cgroup to charge
+ * @gfp_mask: reclaim mode
+ * @nr_pages: number of pages to charge
+ *
+ * Try to charge @nr_pages to @memcg through try_charge_memcg.
+ *
+ * Returns 0 on success, an error code on failure.
+ */
+int mem_cgroup_try_charge_pages(struct mem_cgroup *memcg, gfp_t gfp_mask,
+				unsigned int nr_pages)
+{
+	return try_charge(memcg, gfp_mask, nr_pages);
+}
+EXPORT_SYMBOL_GPL(mem_cgroup_try_charge_pages);
+
+
 /**
  * mem_cgroup_charge_hugetlb - charge the memcg for a hugetlb folio
  * @folio: folio being charged
@@ -4948,6 +4966,12 @@ void __mem_cgroup_uncharge_folios(struct folio_batch *folios)
 		uncharge_batch(&ug);
 }
 
+void mem_cgroup_uncharge_pages(struct mem_cgroup *memcg, unsigned int nr_pages)
+{
+	memcg_uncharge(memcg, nr_pages);
+}
+EXPORT_SYMBOL_GPL(mem_cgroup_uncharge_pages);
+
 /**
  * mem_cgroup_replace_folio - Charge a folio's replacement.
  * @old: Currently circulating folio.

-- 
2.52.0