/*
   *
   * 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 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;

  	int idx;

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

  	if (parent_h_cgroup) {

  		for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)

  			page_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++)

  			page_counter_init(&h_cgroup->hugepage[idx], NULL);

  	}
  	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();

  	ret = page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter);

  	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->limit * 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);

  	switch (MEMFILE_ATTR(of_cft(of)->private)) {

  	case RES_LIMIT:

  		mutex_lock(&hugetlb_limit_mutex);
  		ret = page_counter_limit(&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].lru.next 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,

  };