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![Roman Gushchin](/assets/img/avatar_default.png)
An exiting task might belong to an offline cgroup. In this case an
attempt to grab a cgroup reference from the task can end up with an
infinite loop in hugetlb_cgroup_charge_cgroup(), because neither the
cgroup will become online, neither the task will be migrated to a live
cgroup.
Fix this by switching over to css_tryget(). As css_tryget_online()
can't guarantee that the cgroup won't go offline, in most cases the
check doesn't make sense. In this particular case users of
hugetlb_cgroup_charge_cgroup() are not affected by this change.
A similar problem is described by commit 18fa84a2db
("cgroup: Use
css_tryget() instead of css_tryget_online() in task_get_css()").
Link: http://lkml.kernel.org/r/20191106225131.3543616-2-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
440 lines
11 KiB
C
440 lines
11 KiB
C
/*
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*
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* Copyright IBM Corporation, 2012
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* Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of version 2.1 of the GNU Lesser General Public License
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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*
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*/
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#include <linux/cgroup.h>
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#include <linux/page_counter.h>
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#include <linux/slab.h>
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#include <linux/hugetlb.h>
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#include <linux/hugetlb_cgroup.h>
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struct hugetlb_cgroup {
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struct cgroup_subsys_state css;
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/*
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* the counter to account for hugepages from hugetlb.
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*/
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struct page_counter hugepage[HUGE_MAX_HSTATE];
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};
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#define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
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#define MEMFILE_IDX(val) (((val) >> 16) & 0xffff)
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#define MEMFILE_ATTR(val) ((val) & 0xffff)
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static struct hugetlb_cgroup *root_h_cgroup __read_mostly;
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static inline
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struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s)
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{
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return s ? container_of(s, struct hugetlb_cgroup, css) : NULL;
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}
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static inline
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struct hugetlb_cgroup *hugetlb_cgroup_from_task(struct task_struct *task)
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{
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return hugetlb_cgroup_from_css(task_css(task, hugetlb_cgrp_id));
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}
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static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup *h_cg)
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{
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return (h_cg == root_h_cgroup);
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}
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static inline struct hugetlb_cgroup *
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parent_hugetlb_cgroup(struct hugetlb_cgroup *h_cg)
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{
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return hugetlb_cgroup_from_css(h_cg->css.parent);
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}
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static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
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{
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int idx;
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for (idx = 0; idx < hugetlb_max_hstate; idx++) {
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if (page_counter_read(&h_cg->hugepage[idx]))
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return true;
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}
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return false;
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}
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static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
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struct hugetlb_cgroup *parent_h_cgroup)
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{
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int idx;
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for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
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struct page_counter *counter = &h_cgroup->hugepage[idx];
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struct page_counter *parent = NULL;
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unsigned long limit;
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int ret;
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if (parent_h_cgroup)
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parent = &parent_h_cgroup->hugepage[idx];
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page_counter_init(counter, parent);
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limit = round_down(PAGE_COUNTER_MAX,
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1 << huge_page_order(&hstates[idx]));
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ret = page_counter_set_max(counter, limit);
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VM_BUG_ON(ret);
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}
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}
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static struct cgroup_subsys_state *
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hugetlb_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
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{
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struct hugetlb_cgroup *parent_h_cgroup = hugetlb_cgroup_from_css(parent_css);
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struct hugetlb_cgroup *h_cgroup;
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h_cgroup = kzalloc(sizeof(*h_cgroup), GFP_KERNEL);
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if (!h_cgroup)
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return ERR_PTR(-ENOMEM);
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if (!parent_h_cgroup)
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root_h_cgroup = h_cgroup;
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hugetlb_cgroup_init(h_cgroup, parent_h_cgroup);
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return &h_cgroup->css;
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}
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static void hugetlb_cgroup_css_free(struct cgroup_subsys_state *css)
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{
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struct hugetlb_cgroup *h_cgroup;
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h_cgroup = hugetlb_cgroup_from_css(css);
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kfree(h_cgroup);
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}
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/*
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* Should be called with hugetlb_lock held.
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* Since we are holding hugetlb_lock, pages cannot get moved from
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* active list or uncharged from the cgroup, So no need to get
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* page reference and test for page active here. This function
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* cannot fail.
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*/
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static void hugetlb_cgroup_move_parent(int idx, struct hugetlb_cgroup *h_cg,
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struct page *page)
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{
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unsigned int nr_pages;
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struct page_counter *counter;
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struct hugetlb_cgroup *page_hcg;
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struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(h_cg);
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page_hcg = hugetlb_cgroup_from_page(page);
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/*
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* We can have pages in active list without any cgroup
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* ie, hugepage with less than 3 pages. We can safely
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* ignore those pages.
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*/
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if (!page_hcg || page_hcg != h_cg)
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goto out;
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nr_pages = compound_nr(page);
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if (!parent) {
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parent = root_h_cgroup;
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/* root has no limit */
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page_counter_charge(&parent->hugepage[idx], nr_pages);
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}
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counter = &h_cg->hugepage[idx];
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/* Take the pages off the local counter */
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page_counter_cancel(counter, nr_pages);
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set_hugetlb_cgroup(page, parent);
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out:
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return;
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}
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/*
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* Force the hugetlb cgroup to empty the hugetlb resources by moving them to
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* the parent cgroup.
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*/
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static void hugetlb_cgroup_css_offline(struct cgroup_subsys_state *css)
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{
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struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
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struct hstate *h;
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struct page *page;
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int idx = 0;
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do {
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for_each_hstate(h) {
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spin_lock(&hugetlb_lock);
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list_for_each_entry(page, &h->hugepage_activelist, lru)
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hugetlb_cgroup_move_parent(idx, h_cg, page);
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spin_unlock(&hugetlb_lock);
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idx++;
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}
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cond_resched();
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} while (hugetlb_cgroup_have_usage(h_cg));
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}
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int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
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struct hugetlb_cgroup **ptr)
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{
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int ret = 0;
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struct page_counter *counter;
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struct hugetlb_cgroup *h_cg = NULL;
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if (hugetlb_cgroup_disabled())
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goto done;
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/*
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* We don't charge any cgroup if the compound page have less
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* than 3 pages.
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*/
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if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
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goto done;
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again:
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rcu_read_lock();
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h_cg = hugetlb_cgroup_from_task(current);
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if (!css_tryget(&h_cg->css)) {
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rcu_read_unlock();
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goto again;
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}
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rcu_read_unlock();
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if (!page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter))
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ret = -ENOMEM;
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css_put(&h_cg->css);
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done:
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*ptr = h_cg;
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return ret;
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}
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/* Should be called with hugetlb_lock held */
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void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
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struct hugetlb_cgroup *h_cg,
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struct page *page)
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{
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if (hugetlb_cgroup_disabled() || !h_cg)
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return;
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set_hugetlb_cgroup(page, h_cg);
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return;
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}
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/*
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* Should be called with hugetlb_lock held
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*/
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void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
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struct page *page)
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{
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struct hugetlb_cgroup *h_cg;
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if (hugetlb_cgroup_disabled())
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return;
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lockdep_assert_held(&hugetlb_lock);
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h_cg = hugetlb_cgroup_from_page(page);
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if (unlikely(!h_cg))
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return;
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set_hugetlb_cgroup(page, NULL);
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page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
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return;
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}
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void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
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struct hugetlb_cgroup *h_cg)
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{
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if (hugetlb_cgroup_disabled() || !h_cg)
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return;
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if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
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return;
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page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
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return;
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}
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enum {
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RES_USAGE,
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RES_LIMIT,
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RES_MAX_USAGE,
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RES_FAILCNT,
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};
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static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
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struct cftype *cft)
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{
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struct page_counter *counter;
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struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
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counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)];
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switch (MEMFILE_ATTR(cft->private)) {
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case RES_USAGE:
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return (u64)page_counter_read(counter) * PAGE_SIZE;
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case RES_LIMIT:
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return (u64)counter->max * PAGE_SIZE;
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case RES_MAX_USAGE:
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return (u64)counter->watermark * PAGE_SIZE;
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case RES_FAILCNT:
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return counter->failcnt;
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default:
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BUG();
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}
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}
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static DEFINE_MUTEX(hugetlb_limit_mutex);
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static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
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char *buf, size_t nbytes, loff_t off)
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{
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int ret, idx;
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unsigned long nr_pages;
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struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));
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if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */
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return -EINVAL;
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buf = strstrip(buf);
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ret = page_counter_memparse(buf, "-1", &nr_pages);
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if (ret)
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return ret;
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idx = MEMFILE_IDX(of_cft(of)->private);
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nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));
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switch (MEMFILE_ATTR(of_cft(of)->private)) {
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case RES_LIMIT:
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mutex_lock(&hugetlb_limit_mutex);
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ret = page_counter_set_max(&h_cg->hugepage[idx], nr_pages);
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mutex_unlock(&hugetlb_limit_mutex);
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break;
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default:
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ret = -EINVAL;
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break;
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}
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return ret ?: nbytes;
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}
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static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
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char *buf, size_t nbytes, loff_t off)
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{
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int ret = 0;
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struct page_counter *counter;
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struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));
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counter = &h_cg->hugepage[MEMFILE_IDX(of_cft(of)->private)];
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switch (MEMFILE_ATTR(of_cft(of)->private)) {
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case RES_MAX_USAGE:
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page_counter_reset_watermark(counter);
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break;
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case RES_FAILCNT:
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counter->failcnt = 0;
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break;
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default:
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ret = -EINVAL;
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break;
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}
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return ret ?: nbytes;
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}
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static char *mem_fmt(char *buf, int size, unsigned long hsize)
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{
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if (hsize >= (1UL << 30))
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snprintf(buf, size, "%luGB", hsize >> 30);
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else if (hsize >= (1UL << 20))
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snprintf(buf, size, "%luMB", hsize >> 20);
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else
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snprintf(buf, size, "%luKB", hsize >> 10);
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return buf;
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}
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static void __init __hugetlb_cgroup_file_init(int idx)
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{
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char buf[32];
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struct cftype *cft;
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struct hstate *h = &hstates[idx];
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/* format the size */
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mem_fmt(buf, 32, huge_page_size(h));
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/* Add the limit file */
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cft = &h->cgroup_files[0];
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snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf);
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cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
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cft->read_u64 = hugetlb_cgroup_read_u64;
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cft->write = hugetlb_cgroup_write;
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/* Add the usage file */
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cft = &h->cgroup_files[1];
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snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf);
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cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
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cft->read_u64 = hugetlb_cgroup_read_u64;
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/* Add the MAX usage file */
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cft = &h->cgroup_files[2];
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snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
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cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
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cft->write = hugetlb_cgroup_reset;
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cft->read_u64 = hugetlb_cgroup_read_u64;
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/* Add the failcntfile */
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cft = &h->cgroup_files[3];
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snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
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cft->private = MEMFILE_PRIVATE(idx, RES_FAILCNT);
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cft->write = hugetlb_cgroup_reset;
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cft->read_u64 = hugetlb_cgroup_read_u64;
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/* NULL terminate the last cft */
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cft = &h->cgroup_files[4];
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memset(cft, 0, sizeof(*cft));
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WARN_ON(cgroup_add_legacy_cftypes(&hugetlb_cgrp_subsys,
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h->cgroup_files));
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}
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void __init hugetlb_cgroup_file_init(void)
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{
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struct hstate *h;
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for_each_hstate(h) {
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/*
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* Add cgroup control files only if the huge page consists
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* of more than two normal pages. This is because we use
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* page[2].private for storing cgroup details.
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*/
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if (huge_page_order(h) >= HUGETLB_CGROUP_MIN_ORDER)
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__hugetlb_cgroup_file_init(hstate_index(h));
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}
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}
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/*
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* hugetlb_lock will make sure a parallel cgroup rmdir won't happen
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* when we migrate hugepages
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*/
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void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
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{
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struct hugetlb_cgroup *h_cg;
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struct hstate *h = page_hstate(oldhpage);
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if (hugetlb_cgroup_disabled())
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return;
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VM_BUG_ON_PAGE(!PageHuge(oldhpage), oldhpage);
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spin_lock(&hugetlb_lock);
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h_cg = hugetlb_cgroup_from_page(oldhpage);
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set_hugetlb_cgroup(oldhpage, NULL);
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/* move the h_cg details to new cgroup */
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set_hugetlb_cgroup(newhpage, h_cg);
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list_move(&newhpage->lru, &h->hugepage_activelist);
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spin_unlock(&hugetlb_lock);
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return;
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}
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struct cgroup_subsys hugetlb_cgrp_subsys = {
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.css_alloc = hugetlb_cgroup_css_alloc,
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.css_offline = hugetlb_cgroup_css_offline,
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.css_free = hugetlb_cgroup_css_free,
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};
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