Michal Hocko [off-list ref] writes:

On Sat 09-06-12 14:29:57, Aneesh Kumar K.V wrote:

quoted

From: "Aneesh Kumar K.V" <redacted>

This patch add support for cgroup removal. If we don't have parent
cgroup, the charges are moved to root cgroup.

Signed-off-by: Aneesh Kumar K.V <redacted>
---
 mm/hugetlb_cgroup.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 79 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 48efd5a..9458fe3 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c

@@ -99,10 +99,87 @@ static void hugetlb_cgroup_destroy(struct cgroup *cgroup)
 	kfree(h_cgroup);
 }
 
+
+static int hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup,
+				      struct page *page)

deserves a comment about the locking (needs to be called with
hugetlb_lock).

will do

quoted

+{
+	int csize;
+	struct res_counter *counter;
+	struct res_counter *fail_res;
+	struct hugetlb_cgroup *page_hcg;
+	struct hugetlb_cgroup *h_cg   = hugetlb_cgroup_from_cgroup(cgroup);
+	struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(cgroup);
+
+	if (!get_page_unless_zero(page))
+		goto out;
+
+	page_hcg = hugetlb_cgroup_from_page(page);
+	/*
+	 * We can have pages in active list without any cgroup
+	 * ie, hugepage with less than 3 pages. We can safely
+	 * ignore those pages.
+	 */
+	if (!page_hcg || page_hcg != h_cg)
+		goto err_out;

How can we have page_hcg != NULL && page_hcg != h_cg?

pages belonging to other cgroup ?

-aneesh