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Subject[PATCH -V9 12/15] hugetlb/cgroup: Add support for cgroup removal
Date
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

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 <aneesh.kumar@linux.vnet.ibm.com>
---
mm/hugetlb_cgroup.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 68 insertions(+), 2 deletions(-)
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 0f2f6ac..a3a68a4 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -107,10 +107,76 @@ static void hugetlb_cgroup_destroy(struct cgroup *cgroup)
kfree(h_cgroup);
}

+
+/*
+ * Should be called with hugetlb_lock held.
+ * Since we are holding hugetlb_lock, pages cannot get moved from
+ * active list or uncharged from the cgroup, So no need to get
+ * page reference and test for page active here. This function
+ * cannot fail.
+ */
+static void hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup,
+ struct page *page)
+{
+ 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);
+
+ 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 out;
+
+ csize = PAGE_SIZE << compound_order(page);
+ if (!parent) {
+ parent = root_h_cgroup;
+ /* root has no limit */
+ res_counter_charge_nofail(&parent->hugepage[idx],
+ csize, &fail_res);
+ }
+ counter = &h_cg->hugepage[idx];
+ res_counter_uncharge_until(counter, counter->parent, csize);
+
+ set_hugetlb_cgroup(page, parent);
+out:
+ return;
+}
+
+/*
+ * Force the hugetlb cgroup to empty the hugetlb resources by moving them to
+ * the parent cgroup.
+ */
static int hugetlb_cgroup_pre_destroy(struct cgroup *cgroup)
{
- /* We will add the cgroup removal support in later patches */
- return -EBUSY;
+ struct hstate *h;
+ struct page *page;
+ int ret = 0, idx = 0;
+
+ do {
+ if (cgroup_task_count(cgroup) ||
+ !list_empty(&cgroup->children)) {
+ ret = -EBUSY;
+ goto out;
+ }
+ for_each_hstate(h) {
+ spin_lock(&hugetlb_lock);
+ list_for_each_entry(page, &h->hugepage_activelist, lru)
+ hugetlb_cgroup_move_parent(idx, cgroup, page);
+
+ spin_unlock(&hugetlb_lock);
+ idx++;
+ }
+ cond_resched();
+ } while (hugetlb_cgroup_have_usage(cgroup));
+out:
+ return ret;
}

int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
--
1.7.10


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