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Date: Wed, 30 May 2012 21:19:54 -0400
From: Konrad Rzeszutek Wilk <konrad@...nok.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc: linux-mm@...ck.org, kamezawa.hiroyu@...fujitsu.com,
dhillf@...il.com, rientjes@...gle.com, mhocko@...e.cz,
akpm@...ux-foundation.org, hannes@...xchg.org,
linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH -V7 10/14] hugetlbfs: Add new HugeTLB cgroup
> +static inline bool hugetlb_cgroup_have_usage(struct cgroup *cg)
> +{
> + int idx;
> + struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cg);
> +
> + for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
> + if ((res_counter_read_u64(&h_cg->hugepage[idx], RES_USAGE)) > 0)
> + return 1;
return true;
> + }
> + return 0;
And return false here
> +}
> +
> +static struct cgroup_subsys_state *hugetlb_cgroup_create(struct cgroup *cgroup)
> +{
> + int idx;
> + struct cgroup *parent_cgroup;
> + struct hugetlb_cgroup *h_cgroup, *parent_h_cgroup;
> +
> + h_cgroup = kzalloc(sizeof(*h_cgroup), GFP_KERNEL);
> + if (!h_cgroup)
> + return ERR_PTR(-ENOMEM);
> +
No need to check cgroup for NULL?
> + parent_cgroup = cgroup->parent;
> + if (parent_cgroup) {
> + parent_h_cgroup = hugetlb_cgroup_from_cgroup(parent_cgroup);
> + for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
> + res_counter_init(&h_cgroup->hugepage[idx],
> + &parent_h_cgroup->hugepage[idx]);
> + } else {
> + root_h_cgroup = h_cgroup;
> + for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
> + res_counter_init(&h_cgroup->hugepage[idx], NULL);
> + }
> + return &h_cgroup->css;
> +}
> +
> +static int hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup,
> + struct page *page)
> +{
> + int csize, ret = 0;
> + struct page_cgroup *pc;
> + struct res_counter *counter;
> + struct res_counter *fail_res;
> + 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;
Hmm, so it goes to out, and does return ret. ret is zero. Is
that correct? Should ret be set to -EBUSY or such?
> +
> + pc = lookup_page_cgroup(page);
What if pc is NULL? Or is it guaranteed that it will
never happen so?
> + lock_page_cgroup(pc);
> + if (!PageCgroupUsed(pc) || pc->cgroup != cgroup)
> + goto err_out;
err is still set to zero. Is that OK? Should it be -EINVAL
or such?
> +
> + csize = PAGE_SIZE << compound_order(page);
> + /* If use_hierarchy == 0, we need to charge root */
> + 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);
> +
> + pc->cgroup = cgroup->parent;
> +err_out:
> + unlock_page_cgroup(pc);
> + put_page(page);
> +out:
> + return ret;
> +}
> +
> +/*
> + * 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)
> +{
> + 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;
> + }
> + /*
> + * If the task doing the cgroup_rmdir got a signal
> + * we don't really need to loop till the hugetlb resource
> + * usage become zero.
Why don't we need to loop? Is somebody else (and if so can you
say who) doing the deletion?
> + */
> + if (signal_pending(current)) {
> + ret = -EINTR;
> + goto out;
> + }
> + for_each_hstate(h) {
> + spin_lock(&hugetlb_lock);
> + list_for_each_entry(page, &h->hugepage_activelist, lru) {
> + ret = hugetlb_cgroup_move_parent(idx, cgroup, page);
> + if (ret) {
> + spin_unlock(&hugetlb_lock);
> + goto out;
> + }
> + }
> + spin_unlock(&hugetlb_lock);
> + idx++;
> + }
> + cond_resched();
> + } while (hugetlb_cgroup_have_usage(cgroup));
> +out:
> + return ret;
> +}
> +
> +static void hugetlb_cgroup_destroy(struct cgroup *cgroup)
> +{
> + struct hugetlb_cgroup *h_cgroup;
> +
> + h_cgroup = hugetlb_cgroup_from_cgroup(cgroup);
> + kfree(h_cgroup);
> +}
> +
> +int hugetlb_cgroup_charge_page(int idx, unsigned long nr_pages,
> + struct hugetlb_cgroup **ptr)
> +{
> + int ret = 0;
> + struct res_counter *fail_res;
> + struct hugetlb_cgroup *h_cg = NULL;
> + unsigned long csize = nr_pages * PAGE_SIZE;
> +
> + if (hugetlb_cgroup_disabled())
> + goto done;
> +again:
> + rcu_read_lock();
> + h_cg = hugetlb_cgroup_from_task(current);
> + if (!h_cg)
> + h_cg = root_h_cgroup;
> +
> + if (!css_tryget(&h_cg->css)) {
> + rcu_read_unlock();
> + goto again;
You don't want some form of limit on how many times you can
loop around?
> + }
> + rcu_read_unlock();
> +
> + ret = res_counter_charge(&h_cg->hugepage[idx], csize, &fail_res);
> + css_put(&h_cg->css);
> +done:
> + *ptr = h_cg;
> + return ret;
> +}
> +
--
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