/*
   *
   * 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/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 res_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)

  struct cgroup_subsys hugetlb_subsys __read_mostly;
  static struct hugetlb_cgroup *root_h_cgroup __read_mostly;
  
  static inline
  struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s)
  {
  	return container_of(s, struct hugetlb_cgroup, css);
  }
  
  static inline
  struct hugetlb_cgroup *hugetlb_cgroup_from_cgroup(struct cgroup *cgroup)
  {
  	return hugetlb_cgroup_from_css(cgroup_subsys_state(cgroup,
  							   hugetlb_subsys_id));
  }
  
  static inline
  struct hugetlb_cgroup *hugetlb_cgroup_from_task(struct task_struct *task)
  {
  	return hugetlb_cgroup_from_css(task_subsys_state(task,
  							 hugetlb_subsys_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 cgroup *cg)
  {
  	if (!cg->parent)
  		return NULL;
  	return hugetlb_cgroup_from_cgroup(cg->parent);
  }
  
  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 < hugetlb_max_hstate; idx++) {
  		if ((res_counter_read_u64(&h_cg->hugepage[idx], RES_USAGE)) > 0)
  			return true;
  	}
  	return false;
  }

  static struct cgroup_subsys_state *hugetlb_cgroup_css_alloc(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);
  
  	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 void hugetlb_cgroup_css_free(struct cgroup *cgroup)

  {
  	struct hugetlb_cgroup *h_cgroup;
  
  	h_cgroup = hugetlb_cgroup_from_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 void hugetlb_cgroup_css_offline(struct cgroup *cgroup)

  {

  	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, cgroup, page);
  
  			spin_unlock(&hugetlb_lock);
  			idx++;
  		}
  		cond_resched();
  	} while (hugetlb_cgroup_have_usage(cgroup));

  }

  int hugetlb_cgroup_charge_cgroup(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;
  	/*
  	 * 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(&h_cg->css)) {
  		rcu_read_unlock();
  		goto again;
  	}
  	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;
  }

  /* 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;
  	unsigned long csize = nr_pages * PAGE_SIZE;
  
  	if (hugetlb_cgroup_disabled())
  		return;
  	VM_BUG_ON(!spin_is_locked(&hugetlb_lock));
  	h_cg = hugetlb_cgroup_from_page(page);
  	if (unlikely(!h_cg))
  		return;
  	set_hugetlb_cgroup(page, NULL);
  	res_counter_uncharge(&h_cg->hugepage[idx], csize);
  	return;
  }
  
  void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
  				    struct hugetlb_cgroup *h_cg)
  {
  	unsigned long csize = nr_pages * PAGE_SIZE;
  
  	if (hugetlb_cgroup_disabled() || !h_cg)
  		return;
  
  	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
  		return;
  
  	res_counter_uncharge(&h_cg->hugepage[idx], csize);
  	return;
  }

  static ssize_t hugetlb_cgroup_read(struct cgroup *cgroup, struct cftype *cft,
  				   struct file *file, char __user *buf,
  				   size_t nbytes, loff_t *ppos)
  {
  	u64 val;
  	char str[64];
  	int idx, name, len;
  	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup);
  
  	idx = MEMFILE_IDX(cft->private);
  	name = MEMFILE_ATTR(cft->private);
  
  	val = res_counter_read_u64(&h_cg->hugepage[idx], name);
  	len = scnprintf(str, sizeof(str), "%llu
  ", (unsigned long long)val);
  	return simple_read_from_buffer(buf, nbytes, ppos, str, len);
  }
  
  static int hugetlb_cgroup_write(struct cgroup *cgroup, struct cftype *cft,
  				const char *buffer)
  {
  	int idx, name, ret;
  	unsigned long long val;
  	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup);
  
  	idx = MEMFILE_IDX(cft->private);
  	name = MEMFILE_ATTR(cft->private);
  
  	switch (name) {
  	case RES_LIMIT:
  		if (hugetlb_cgroup_is_root(h_cg)) {
  			/* Can't set limit on root */
  			ret = -EINVAL;
  			break;
  		}
  		/* This function does all necessary parse...reuse it */
  		ret = res_counter_memparse_write_strategy(buffer, &val);
  		if (ret)
  			break;
  		ret = res_counter_set_limit(&h_cg->hugepage[idx], val);
  		break;
  	default:
  		ret = -EINVAL;
  		break;
  	}
  	return ret;
  }
  
  static int hugetlb_cgroup_reset(struct cgroup *cgroup, unsigned int event)
  {
  	int idx, name, ret = 0;
  	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup);
  
  	idx = MEMFILE_IDX(event);
  	name = MEMFILE_ATTR(event);
  
  	switch (name) {
  	case RES_MAX_USAGE:
  		res_counter_reset_max(&h_cg->hugepage[idx]);
  		break;
  	case RES_FAILCNT:
  		res_counter_reset_failcnt(&h_cg->hugepage[idx]);
  		break;
  	default:
  		ret = -EINVAL;
  		break;
  	}
  	return ret;
  }
  
  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;
  }
  
  int __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 = hugetlb_cgroup_read;
  	cft->write_string = 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 = hugetlb_cgroup_read;
  
  	/* 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->trigger = hugetlb_cgroup_reset;
  	cft->read = hugetlb_cgroup_read;
  
  	/* 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->trigger  = hugetlb_cgroup_reset;
  	cft->read = hugetlb_cgroup_read;
  
  	/* NULL terminate the last cft */
  	cft = &h->cgroup_files[4];
  	memset(cft, 0, sizeof(*cft));
  
  	WARN_ON(cgroup_add_cftypes(&hugetlb_subsys, h->cgroup_files));
  
  	return 0;
  }

  /*
   * 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(!PageHuge(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_subsys = {
  	.name = "hugetlb",

  	.css_alloc	= hugetlb_cgroup_css_alloc,
  	.css_offline	= hugetlb_cgroup_css_offline,
  	.css_free	= hugetlb_cgroup_css_free,
  	.subsys_id	= hugetlb_subsys_id,

  };