[PATCH v1 2/7] mm/memcontrol: add mem_cgroup_recharge

[Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>]

This function tries to move page into other cgroup.
Caller must lock page and isolate it from LRU.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
 include/linux/memcontrol.h |    9 +++++++++
 mm/memcontrol.c            |   40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 2cd4359cb38c..d94950584f60 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -352,6 +352,8 @@ void mem_cgroup_uncharge(struct page *page);
 void mem_cgroup_uncharge_list(struct list_head *page_list);
 
 void mem_cgroup_migrate(struct page *oldpage, struct page *newpage);
+int mem_cgroup_try_recharge(struct page *page, struct mm_struct *mm,
+			    gfp_t gfp_mask);
 
 static struct mem_cgroup_per_node *
 mem_cgroup_nodeinfo(struct mem_cgroup *memcg, int nid)
@@ -857,6 +859,13 @@ static inline void mem_cgroup_migrate(struct page *old, struct page *new)
 {
 }
 
+static inline int mem_cgroup_try_recharge(struct page *page,
+					  struct mm_struct *mm,
+					  gfp_t gfp_mask)
+{
+	return 0;
+}
+
 static inline struct lruvec *mem_cgroup_lruvec(struct pglist_data *pgdat,
 				struct mem_cgroup *memcg)
 {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 40ddc233e973..953a0bbb9f43 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6507,6 +6507,46 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 	local_irq_restore(flags);
 }
 
+/*
+ * mem_cgroup_try_recharge - try to recharge page to mm's memcg.
+ *
+ * Page must be locked and isolated.
+ */
+int mem_cgroup_try_recharge(struct page *page, struct mm_struct *mm,
+			    gfp_t gfp_mask)
+{
+	struct mem_cgroup *from, *to;
+	int nr_pages;
+	int err = 0;
+
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+	VM_BUG_ON_PAGE(PageLRU(page), page);
+
+	if (mem_cgroup_disabled())
+		return 0;
+
+	from = page->mem_cgroup;
+	to = get_mem_cgroup_from_mm(mm);
+
+	if (likely(from == to) || !from)
+		goto out;
+
+	nr_pages = hpage_nr_pages(page);
+	err = try_charge(to, gfp_mask, nr_pages);
+	if (err)
+		goto out;
+
+	err = mem_cgroup_move_account(page, nr_pages > 1, from, to);
+	if (err)
+		cancel_charge(to, nr_pages);
+	else
+		cancel_charge(from, nr_pages);
+out:
+	css_put(&to->css);
+
+	return err;
+}
+
 DEFINE_STATIC_KEY_FALSE(memcg_sockets_enabled_key);
 EXPORT_SYMBOL(memcg_sockets_enabled_key);