bugfix for memory cgroup controller: migration under memory controller fix

[linux-block.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3270ce7375dbf03d5837c74f5aa74f3a32d9bf67..128f45c16fa6626ac33813fdaefc239c18e9967f 100644 (file)
--- 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)
 {