hugetlb/cgroup: migrate hugetlb cgroup info from oldpage to new page during migration

With HugeTLB pages, hugetlb cgroup is uncharged in compound page
destructor.  Since we are holding a hugepage reference, we can be sure
that old page won't get uncharged till the last put_page().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index d1ca1196e62f..680e4819e077 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -386,6 +386,26 @@ int __init hugetlb_cgroup_file_init(int idx)
         return 0;
 }
 
+void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
+{
+        struct hugetlb_cgroup *h_cg;
+
+        if (hugetlb_cgroup_disabled())
+                return;
+
+        VM_BUG_ON(!PageHuge(oldhpage));
+        spin_lock(&hugetlb_lock);
+        h_cg = hugetlb_cgroup_from_page(oldhpage);
+        set_hugetlb_cgroup(oldhpage, NULL);
+        cgroup_exclude_rmdir(&h_cg->css);
+
+        /* move the h_cg details to new cgroup */
+        set_hugetlb_cgroup(newhpage, h_cg);
+        spin_unlock(&hugetlb_lock);
+        cgroup_release_and_wakeup_rmdir(&h_cg->css);
+        return;
+}
+
 struct cgroup_subsys hugetlb_subsys = {
         .name = "hugetlb",
         .create     = hugetlb_cgroup_create,