1 files changed, 43 insertions, 0 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3270ce7375db..128f45c16fa6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -492,6 +492,49 @@ void mem_cgroup_uncharge(struct page_cgroup *pc)
                 }
         }
 }
+/*
+ * Returns non-zero if a page (under migration) has valid page_cgroup member.
+ * Refcnt of page_cgroup is incremented.
+ */
+
+int mem_cgroup_prepare_migration(struct page *page)
+{
+        struct page_cgroup *pc;
+        int ret = 0;
+        lock_page_cgroup(page);
+        pc = page_get_page_cgroup(page);
+        if (pc && atomic_inc_not_zero(&pc->ref_cnt))
+                ret = 1;
+        unlock_page_cgroup(page);
+        return ret;
+}
+
+void mem_cgroup_end_migration(struct page *page)
+{
+        struct page_cgroup *pc = page_get_page_cgroup(page);
+        mem_cgroup_uncharge(pc);
+}
+/*
+ * We know both *page* and *newpage* are now not-on-LRU and Pg_locked.
+ * And no race with uncharge() routines because page_cgroup for *page*
+ * has extra one reference by mem_cgroup_prepare_migration.
+ */
+
+void mem_cgroup_page_migration(struct page *page, struct page *newpage)
+{
+        struct page_cgroup *pc;
+retry:
+        pc = page_get_page_cgroup(page);
+        if (!pc)
+                return;
+        if (clear_page_cgroup(page, pc) != pc)
+                goto retry;
+        pc->page = newpage;
+        lock_page_cgroup(newpage);
+        page_assign_page_cgroup(newpage, pc);
+        unlock_page_cgroup(newpage);
+        return;
+}
 
 int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
 {