mm/hugetlb_cgroup.c - kernel/msm-4.19 - Gitiles

 /*
  *
  * Copyright IBM Corporation, 2012
  * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of version 2.1 of the GNU Lesser General Public License
  * as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it would be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  *
  */

 #include <linux/cgroup.h>
 #include <linux/page_counter.h>
 #include <linux/slab.h>
 #include <linux/hugetlb.h>
 #include <linux/hugetlb_cgroup.h>

 struct hugetlb_cgroup {
 	struct cgroup_subsys_state css;
 	/*
 	 * the counter to account for hugepages from hugetlb.
 	 */
 	struct page_counter hugepage[HUGE_MAX_HSTATE];
 };

 #define MEMFILE_PRIVATE(x, val)	(((x) << 16) | (val))
 #define MEMFILE_IDX(val)	(((val) >> 16) & 0xffff)
 #define MEMFILE_ATTR(val)	((val) & 0xffff)

 static struct hugetlb_cgroup *root_h_cgroup __read_mostly;

 static inline
 struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s)
 {
 	return s ? container_of(s, struct hugetlb_cgroup, css) : NULL;
 }

 static inline
 struct hugetlb_cgroup *hugetlb_cgroup_from_task(struct task_struct *task)
 {
 	return hugetlb_cgroup_from_css(task_css(task, hugetlb_cgrp_id));
 }

 static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup *h_cg)
 {
 	return (h_cg == root_h_cgroup);
 }

 static inline struct hugetlb_cgroup *
 parent_hugetlb_cgroup(struct hugetlb_cgroup *h_cg)
 {
 	return hugetlb_cgroup_from_css(h_cg->css.parent);
 }

 static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
 {
 	int idx;

 	for (idx = 0; idx < hugetlb_max_hstate; idx++) {
 		if (page_counter_read(&h_cg->hugepage[idx]))
 			return true;
 	}
 	return false;
 }

 static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
 				struct hugetlb_cgroup *parent_h_cgroup)
 {
 	int idx;

 	for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
 		struct page_counter *counter = &h_cgroup->hugepage[idx];
 		struct page_counter *parent = NULL;
 		unsigned long limit;
 		int ret;

 		if (parent_h_cgroup)
 			parent = &parent_h_cgroup->hugepage[idx];
 		page_counter_init(counter, parent);

 		limit = round_down(PAGE_COUNTER_MAX,
 				   1 << huge_page_order(&hstates[idx]));
 		ret = page_counter_set_max(counter, limit);
 		VM_BUG_ON(ret);
 	}
 }

 static struct cgroup_subsys_state *
 hugetlb_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 {
 	struct hugetlb_cgroup *parent_h_cgroup = hugetlb_cgroup_from_css(parent_css);
 	struct hugetlb_cgroup *h_cgroup;

 	h_cgroup = kzalloc(sizeof(*h_cgroup), GFP_KERNEL);
 	if (!h_cgroup)
 		return ERR_PTR(-ENOMEM);

 	if (!parent_h_cgroup)
 		root_h_cgroup = h_cgroup;

 	hugetlb_cgroup_init(h_cgroup, parent_h_cgroup);
 	return &h_cgroup->css;
 }

 static void hugetlb_cgroup_css_free(struct cgroup_subsys_state *css)
 {
 	struct hugetlb_cgroup *h_cgroup;

 	h_cgroup = hugetlb_cgroup_from_css(css);
 	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 hugetlb_cgroup *h_cg,
 				       struct page *page)
 {
 	unsigned int nr_pages;
 	struct page_counter *counter;
 	struct hugetlb_cgroup *page_hcg;
 	struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(h_cg);

 	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;

 	nr_pages = 1 << compound_order(page);
 	if (!parent) {
 		parent = root_h_cgroup;
 		/* root has no limit */
 		page_counter_charge(&parent->hugepage[idx], nr_pages);
 	}
 	counter = &h_cg->hugepage[idx];
 	/* Take the pages off the local counter */
 	page_counter_cancel(counter, nr_pages);

 	set_hugetlb_cgroup(page, parent);
 out:
 	return;
 }

 /*
  * Force the hugetlb cgroup to empty the hugetlb resources by moving them to
  * the parent cgroup.
  */
 static void hugetlb_cgroup_css_offline(struct cgroup_subsys_state *css)
 {
 	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
 	struct hstate *h;
 	struct page *page;
 	int idx = 0;

 	do {
 		for_each_hstate(h) {
 			spin_lock(&hugetlb_lock);
 			list_for_each_entry(page, &h->hugepage_activelist, lru)
 				hugetlb_cgroup_move_parent(idx, h_cg, page);

 			spin_unlock(&hugetlb_lock);
 			idx++;
 		}
 		cond_resched();
 	} while (hugetlb_cgroup_have_usage(h_cg));
 }

 int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
 				 struct hugetlb_cgroup **ptr)
 {
 	int ret = 0;
 	struct page_counter *counter;
 	struct hugetlb_cgroup *h_cg = NULL;

 	if (hugetlb_cgroup_disabled())
 		goto done;
 	/*
 	 * We don't charge any cgroup if the compound page have less
 	 * than 3 pages.
 	 */
 	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
 		goto done;
 again:
 	rcu_read_lock();
 	h_cg = hugetlb_cgroup_from_task(current);
 	if (!css_tryget_online(&h_cg->css)) {
 		rcu_read_unlock();
 		goto again;
 	}
 	rcu_read_unlock();

 	if (!page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter))
 		ret = -ENOMEM;
 	css_put(&h_cg->css);
 done:
 	*ptr = h_cg;
 	return ret;
 }

 /* Should be called with hugetlb_lock held */
 void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
 				  struct hugetlb_cgroup *h_cg,
 				  struct page *page)
 {
 	if (hugetlb_cgroup_disabled() || !h_cg)
 		return;

 	set_hugetlb_cgroup(page, h_cg);
 	return;
 }

 /*
  * Should be called with hugetlb_lock held
  */
 void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
 				  struct page *page)
 {
 	struct hugetlb_cgroup *h_cg;

 	if (hugetlb_cgroup_disabled())
 		return;
 	lockdep_assert_held(&hugetlb_lock);
 	h_cg = hugetlb_cgroup_from_page(page);
 	if (unlikely(!h_cg))
 		return;
 	set_hugetlb_cgroup(page, NULL);
 	page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
 	return;
 }

 void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
 				    struct hugetlb_cgroup *h_cg)
 {
 	if (hugetlb_cgroup_disabled() || !h_cg)
 		return;

 	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
 		return;

 	page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
 	return;
 }

 enum {
 	RES_USAGE,
 	RES_LIMIT,
 	RES_MAX_USAGE,
 	RES_FAILCNT,
 };

 static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
 				   struct cftype *cft)
 {
 	struct page_counter *counter;
 	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);

 	counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)];

 	switch (MEMFILE_ATTR(cft->private)) {
 	case RES_USAGE:
 		return (u64)page_counter_read(counter) * PAGE_SIZE;
 	case RES_LIMIT:
 		return (u64)counter->max * PAGE_SIZE;
 	case RES_MAX_USAGE:
 		return (u64)counter->watermark * PAGE_SIZE;
 	case RES_FAILCNT:
 		return counter->failcnt;
 	default:
 		BUG();
 	}
 }

 static DEFINE_MUTEX(hugetlb_limit_mutex);

 static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
 				    char *buf, size_t nbytes, loff_t off)
 {
 	int ret, idx;
 	unsigned long nr_pages;
 	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

 	if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */
 		return -EINVAL;

 	buf = strstrip(buf);
 	ret = page_counter_memparse(buf, "-1", &nr_pages);
 	if (ret)
 		return ret;

 	idx = MEMFILE_IDX(of_cft(of)->private);
 	nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));

 	switch (MEMFILE_ATTR(of_cft(of)->private)) {
 	case RES_LIMIT:
 		mutex_lock(&hugetlb_limit_mutex);
 		ret = page_counter_set_max(&h_cg->hugepage[idx], nr_pages);
 		mutex_unlock(&hugetlb_limit_mutex);
 		break;
 	default:
 		ret = -EINVAL;
 		break;
 	}
 	return ret ?: nbytes;
 }

 static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
 				    char *buf, size_t nbytes, loff_t off)
 {
 	int ret = 0;
 	struct page_counter *counter;
 	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

 	counter = &h_cg->hugepage[MEMFILE_IDX(of_cft(of)->private)];

 	switch (MEMFILE_ATTR(of_cft(of)->private)) {
 	case RES_MAX_USAGE:
 		page_counter_reset_watermark(counter);
 		break;
 	case RES_FAILCNT:
 		counter->failcnt = 0;
 		break;
 	default:
 		ret = -EINVAL;
 		break;
 	}
 	return ret ?: nbytes;
 }

 static char *mem_fmt(char *buf, int size, unsigned long hsize)
 {
 	if (hsize >= (1UL << 30))
 		snprintf(buf, size, "%luGB", hsize >> 30);
 	else if (hsize >= (1UL << 20))
 		snprintf(buf, size, "%luMB", hsize >> 20);
 	else
 		snprintf(buf, size, "%luKB", hsize >> 10);
 	return buf;
 }

 static void __init __hugetlb_cgroup_file_init(int idx)
 {
 	char buf[32];
 	struct cftype *cft;
 	struct hstate *h = &hstates[idx];

 	/* format the size */
 	mem_fmt(buf, 32, huge_page_size(h));

 	/* Add the limit file */
 	cft = &h->cgroup_files[0];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf);
 	cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
 	cft->read_u64 = hugetlb_cgroup_read_u64;
 	cft->write = hugetlb_cgroup_write;

 	/* Add the usage file */
 	cft = &h->cgroup_files[1];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf);
 	cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
 	cft->read_u64 = hugetlb_cgroup_read_u64;

 	/* Add the MAX usage file */
 	cft = &h->cgroup_files[2];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
 	cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
 	cft->write = hugetlb_cgroup_reset;
 	cft->read_u64 = hugetlb_cgroup_read_u64;

 	/* Add the failcntfile */
 	cft = &h->cgroup_files[3];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
 	cft->private  = MEMFILE_PRIVATE(idx, RES_FAILCNT);
 	cft->write = hugetlb_cgroup_reset;
 	cft->read_u64 = hugetlb_cgroup_read_u64;

 	/* NULL terminate the last cft */
 	cft = &h->cgroup_files[4];
 	memset(cft, 0, sizeof(*cft));

 	WARN_ON(cgroup_add_legacy_cftypes(&hugetlb_cgrp_subsys,
 					  h->cgroup_files));
 }

 void __init hugetlb_cgroup_file_init(void)
 {
 	struct hstate *h;

 	for_each_hstate(h) {
 		/*
 		 * Add cgroup control files only if the huge page consists
 		 * of more than two normal pages. This is because we use
 		 * page[2].private for storing cgroup details.
 		 */
 		if (huge_page_order(h) >= HUGETLB_CGROUP_MIN_ORDER)
 			__hugetlb_cgroup_file_init(hstate_index(h));
 	}
 }

 /*
  * hugetlb_lock will make sure a parallel cgroup rmdir won't happen
  * when we migrate hugepages
  */
 void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
 {
 	struct hugetlb_cgroup *h_cg;
 	struct hstate *h = page_hstate(oldhpage);

 	if (hugetlb_cgroup_disabled())
 		return;

 	VM_BUG_ON_PAGE(!PageHuge(oldhpage), oldhpage);
 	spin_lock(&hugetlb_lock);
 	h_cg = hugetlb_cgroup_from_page(oldhpage);
 	set_hugetlb_cgroup(oldhpage, NULL);

 	/* move the h_cg details to new cgroup */
 	set_hugetlb_cgroup(newhpage, h_cg);
 	list_move(&newhpage->lru, &h->hugepage_activelist);
 	spin_unlock(&hugetlb_lock);
 	return;
 }

 struct cgroup_subsys hugetlb_cgrp_subsys = {
 	.css_alloc	= hugetlb_cgroup_css_alloc,
 	.css_offline	= hugetlb_cgroup_css_offline,
 	.css_free	= hugetlb_cgroup_css_free,
 };
	/*
	*
	* Copyright IBM Corporation, 2012
	* Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
	*
	* This program is free software; you can redistribute it and/or modify it
	* under the terms of version 2.1 of the GNU Lesser General Public License
	* as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it would be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
	*
	*/

	#include <linux/cgroup.h>
	#include <linux/page_counter.h>
	#include <linux/slab.h>
	#include <linux/hugetlb.h>
	#include <linux/hugetlb_cgroup.h>

	struct hugetlb_cgroup {
	struct cgroup_subsys_state css;
	/*
	* the counter to account for hugepages from hugetlb.
	*/
	struct page_counter hugepage[HUGE_MAX_HSTATE];
	};

	#define MEMFILE_PRIVATE(x, val) (((x) << 16) \| (val))
	#define MEMFILE_IDX(val) (((val) >> 16) & 0xffff)
	#define MEMFILE_ATTR(val) ((val) & 0xffff)

	static struct hugetlb_cgroup *root_h_cgroup __read_mostly;

	static inline
	struct hugetlb_cgroup hugetlb_cgroup_from_css(struct cgroup_subsys_state s)
	{
	return s ? container_of(s, struct hugetlb_cgroup, css) : NULL;
	}

	static inline
	struct hugetlb_cgroup hugetlb_cgroup_from_task(struct task_struct task)
	{
	return hugetlb_cgroup_from_css(task_css(task, hugetlb_cgrp_id));
	}

	static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup *h_cg)
	{
	return (h_cg == root_h_cgroup);
	}

	static inline struct hugetlb_cgroup *
	parent_hugetlb_cgroup(struct hugetlb_cgroup *h_cg)
	{
	return hugetlb_cgroup_from_css(h_cg->css.parent);
	}

	static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
	{
	int idx;

	for (idx = 0; idx < hugetlb_max_hstate; idx++) {
	if (page_counter_read(&h_cg->hugepage[idx]))
	return true;
	}
	return false;
	}

	static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
	struct hugetlb_cgroup *parent_h_cgroup)
	{
	int idx;

	for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
	struct page_counter *counter = &h_cgroup->hugepage[idx];
	struct page_counter *parent = NULL;
	unsigned long limit;
	int ret;

	if (parent_h_cgroup)
	parent = &parent_h_cgroup->hugepage[idx];
	page_counter_init(counter, parent);

	limit = round_down(PAGE_COUNTER_MAX,
	1 << huge_page_order(&hstates[idx]));
	ret = page_counter_set_max(counter, limit);
	VM_BUG_ON(ret);
	}
	}

	static struct cgroup_subsys_state *
	hugetlb_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
	{
	struct hugetlb_cgroup *parent_h_cgroup = hugetlb_cgroup_from_css(parent_css);
	struct hugetlb_cgroup *h_cgroup;

	h_cgroup = kzalloc(sizeof(*h_cgroup), GFP_KERNEL);
	if (!h_cgroup)
	return ERR_PTR(-ENOMEM);

	if (!parent_h_cgroup)
	root_h_cgroup = h_cgroup;

	hugetlb_cgroup_init(h_cgroup, parent_h_cgroup);
	return &h_cgroup->css;
	}

	static void hugetlb_cgroup_css_free(struct cgroup_subsys_state *css)
	{
	struct hugetlb_cgroup *h_cgroup;

	h_cgroup = hugetlb_cgroup_from_css(css);
	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 hugetlb_cgroup *h_cg,
	struct page *page)
	{
	unsigned int nr_pages;
	struct page_counter *counter;
	struct hugetlb_cgroup *page_hcg;
	struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(h_cg);

	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;

	nr_pages = 1 << compound_order(page);
	if (!parent) {
	parent = root_h_cgroup;
	/* root has no limit */
	page_counter_charge(&parent->hugepage[idx], nr_pages);
	}
	counter = &h_cg->hugepage[idx];
	/* Take the pages off the local counter */
	page_counter_cancel(counter, nr_pages);

	set_hugetlb_cgroup(page, parent);
	out:
	return;
	}

	/*
	* Force the hugetlb cgroup to empty the hugetlb resources by moving them to
	* the parent cgroup.
	*/
	static void hugetlb_cgroup_css_offline(struct cgroup_subsys_state *css)
	{
	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
	struct hstate *h;
	struct page *page;
	int idx = 0;

	do {
	for_each_hstate(h) {
	spin_lock(&hugetlb_lock);
	list_for_each_entry(page, &h->hugepage_activelist, lru)
	hugetlb_cgroup_move_parent(idx, h_cg, page);

	spin_unlock(&hugetlb_lock);
	idx++;
	}
	cond_resched();
	} while (hugetlb_cgroup_have_usage(h_cg));
	}

	int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
	struct hugetlb_cgroup **ptr)
	{
	int ret = 0;
	struct page_counter *counter;
	struct hugetlb_cgroup *h_cg = NULL;

	if (hugetlb_cgroup_disabled())
	goto done;
	/*
	* We don't charge any cgroup if the compound page have less
	* than 3 pages.
	*/
	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
	goto done;
	again:
	rcu_read_lock();
	h_cg = hugetlb_cgroup_from_task(current);
	if (!css_tryget_online(&h_cg->css)) {
	rcu_read_unlock();
	goto again;
	}
	rcu_read_unlock();

	if (!page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter))
	ret = -ENOMEM;
	css_put(&h_cg->css);
	done:
	*ptr = h_cg;
	return ret;
	}

	/* Should be called with hugetlb_lock held */
	void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
	struct hugetlb_cgroup *h_cg,
	struct page *page)
	{
	if (hugetlb_cgroup_disabled() \|\| !h_cg)
	return;

	set_hugetlb_cgroup(page, h_cg);
	return;
	}

	/*
	* Should be called with hugetlb_lock held
	*/
	void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
	struct page *page)
	{
	struct hugetlb_cgroup *h_cg;

	if (hugetlb_cgroup_disabled())
	return;
	lockdep_assert_held(&hugetlb_lock);
	h_cg = hugetlb_cgroup_from_page(page);
	if (unlikely(!h_cg))
	return;
	set_hugetlb_cgroup(page, NULL);
	page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
	return;
	}

	void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
	struct hugetlb_cgroup *h_cg)
	{
	if (hugetlb_cgroup_disabled() \|\| !h_cg)
	return;

	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
	return;

	page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
	return;
	}

	enum {
	RES_USAGE,
	RES_LIMIT,
	RES_MAX_USAGE,
	RES_FAILCNT,
	};

	static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
	struct cftype *cft)
	{
	struct page_counter *counter;
	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);

	counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)];

	switch (MEMFILE_ATTR(cft->private)) {
	case RES_USAGE:
	return (u64)page_counter_read(counter) * PAGE_SIZE;
	case RES_LIMIT:
	return (u64)counter->max * PAGE_SIZE;
	case RES_MAX_USAGE:
	return (u64)counter->watermark * PAGE_SIZE;
	case RES_FAILCNT:
	return counter->failcnt;
	default:
	BUG();
	}
	}

	static DEFINE_MUTEX(hugetlb_limit_mutex);

	static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
	char *buf, size_t nbytes, loff_t off)
	{
	int ret, idx;
	unsigned long nr_pages;
	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

	if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */
	return -EINVAL;

	buf = strstrip(buf);
	ret = page_counter_memparse(buf, "-1", &nr_pages);
	if (ret)
	return ret;

	idx = MEMFILE_IDX(of_cft(of)->private);
	nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));

	switch (MEMFILE_ATTR(of_cft(of)->private)) {
	case RES_LIMIT:
	mutex_lock(&hugetlb_limit_mutex);
	ret = page_counter_set_max(&h_cg->hugepage[idx], nr_pages);
	mutex_unlock(&hugetlb_limit_mutex);
	break;
	default:
	ret = -EINVAL;
	break;
	}
	return ret ?: nbytes;
	}

	static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
	char *buf, size_t nbytes, loff_t off)
	{
	int ret = 0;
	struct page_counter *counter;
	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

	counter = &h_cg->hugepage[MEMFILE_IDX(of_cft(of)->private)];

	switch (MEMFILE_ATTR(of_cft(of)->private)) {
	case RES_MAX_USAGE:
	page_counter_reset_watermark(counter);
	break;
	case RES_FAILCNT:
	counter->failcnt = 0;
	break;
	default:
	ret = -EINVAL;
	break;
	}
	return ret ?: nbytes;
	}

	static char mem_fmt(char buf, int size, unsigned long hsize)
	{
	if (hsize >= (1UL << 30))
	snprintf(buf, size, "%luGB", hsize >> 30);
	else if (hsize >= (1UL << 20))
	snprintf(buf, size, "%luMB", hsize >> 20);
	else
	snprintf(buf, size, "%luKB", hsize >> 10);
	return buf;
	}

	static void __init __hugetlb_cgroup_file_init(int idx)
	{
	char buf[32];
	struct cftype *cft;
	struct hstate *h = &hstates[idx];

	/* format the size */
	mem_fmt(buf, 32, huge_page_size(h));

	/* Add the limit file */
	cft = &h->cgroup_files[0];
	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf);
	cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
	cft->read_u64 = hugetlb_cgroup_read_u64;
	cft->write = hugetlb_cgroup_write;

	/* Add the usage file */
	cft = &h->cgroup_files[1];
	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf);
	cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
	cft->read_u64 = hugetlb_cgroup_read_u64;

	/* Add the MAX usage file */
	cft = &h->cgroup_files[2];
	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
	cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
	cft->write = hugetlb_cgroup_reset;
	cft->read_u64 = hugetlb_cgroup_read_u64;

	/* Add the failcntfile */
	cft = &h->cgroup_files[3];
	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
	cft->private = MEMFILE_PRIVATE(idx, RES_FAILCNT);
	cft->write = hugetlb_cgroup_reset;
	cft->read_u64 = hugetlb_cgroup_read_u64;

	/* NULL terminate the last cft */
	cft = &h->cgroup_files[4];
	memset(cft, 0, sizeof(*cft));

	WARN_ON(cgroup_add_legacy_cftypes(&hugetlb_cgrp_subsys,
	h->cgroup_files));
	}

	void __init hugetlb_cgroup_file_init(void)
	{
	struct hstate *h;

	for_each_hstate(h) {
	/*
	* Add cgroup control files only if the huge page consists
	* of more than two normal pages. This is because we use
	* page[2].private for storing cgroup details.
	*/
	if (huge_page_order(h) >= HUGETLB_CGROUP_MIN_ORDER)
	__hugetlb_cgroup_file_init(hstate_index(h));
	}
	}

	/*
	* hugetlb_lock will make sure a parallel cgroup rmdir won't happen
	* when we migrate hugepages
	*/
	void hugetlb_cgroup_migrate(struct page oldhpage, struct page newhpage)
	{
	struct hugetlb_cgroup *h_cg;
	struct hstate *h = page_hstate(oldhpage);

	if (hugetlb_cgroup_disabled())
	return;

	VM_BUG_ON_PAGE(!PageHuge(oldhpage), oldhpage);
	spin_lock(&hugetlb_lock);
	h_cg = hugetlb_cgroup_from_page(oldhpage);
	set_hugetlb_cgroup(oldhpage, NULL);

	/* move the h_cg details to new cgroup */
	set_hugetlb_cgroup(newhpage, h_cg);
	list_move(&newhpage->lru, &h->hugepage_activelist);
	spin_unlock(&hugetlb_lock);
	return;
	}

	struct cgroup_subsys hugetlb_cgrp_subsys = {
	.css_alloc = hugetlb_cgroup_css_alloc,
	.css_offline = hugetlb_cgroup_css_offline,
	.css_free = hugetlb_cgroup_css_free,
	};