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>

include/linux/hugetlb_cgroup.h

@@ -63,6 +63,8 @@ extern void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
 extern void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
 					   struct hugetlb_cgroup *h_cg);
 extern int hugetlb_cgroup_file_init(int idx) __init;
+extern void hugetlb_cgroup_migrate(struct page *oldhpage,
+				   struct page *newhpage);
 
 #else
 static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
@@ -114,5 +116,11 @@ static inline int __init hugetlb_cgroup_file_init(int idx)
 	return 0;
 }
 
+static inline void hugetlb_cgroup_migrate(struct page *oldhpage,
+					  struct page *newhpage)
+{
+	return;
+}
+
 #endif  /* CONFIG_MEM_RES_CTLR_HUGETLB */
 #endif

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,

mm/migrate.c

@@ -33,6 +33,7 @@
 #include <linux/memcontrol.h>
 #include <linux/syscalls.h>
 #include <linux/hugetlb.h>
+#include <linux/hugetlb_cgroup.h>
 #include <linux/gfp.h>
 
 #include <asm/tlbflush.h>
@@ -931,6 +932,10 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 
 	if (anon_vma)
 		put_anon_vma(anon_vma);
+
+	if (!rc)
+		hugetlb_cgroup_migrate(hpage, new_hpage);
+
 	unlock_page(hpage);
 out:
 	put_page(new_hpage);