/* SPDX-License-Identifier: GPL-2.0 */

  #ifndef _LINUX_PAGE_COUNTER_H
  #define _LINUX_PAGE_COUNTER_H
  
  #include <linux/atomic.h>
  #include <linux/kernel.h>
  #include <asm/page.h>
  
  struct page_counter {

  	atomic_long_t usage;

  	unsigned long min;

  	unsigned long low;

  	unsigned long high;

  	unsigned long max;

  	struct page_counter *parent;

  	/* effective memory.min and memory.min usage tracking */
  	unsigned long emin;
  	atomic_long_t min_usage;
  	atomic_long_t children_min_usage;

  	/* effective memory.low and memory.low usage tracking */
  	unsigned long elow;
  	atomic_long_t low_usage;
  	atomic_long_t children_low_usage;

  	/* legacy */
  	unsigned long watermark;
  	unsigned long failcnt;
  };
  
  #if BITS_PER_LONG == 32
  #define PAGE_COUNTER_MAX LONG_MAX
  #else
  #define PAGE_COUNTER_MAX (LONG_MAX / PAGE_SIZE)
  #endif
  
  static inline void page_counter_init(struct page_counter *counter,
  				     struct page_counter *parent)
  {

  	atomic_long_set(&counter->usage, 0);
  	counter->max = PAGE_COUNTER_MAX;

  	counter->parent = parent;
  }
  
  static inline unsigned long page_counter_read(struct page_counter *counter)
  {

  	return atomic_long_read(&counter->usage);

  }

  void page_counter_cancel(struct page_counter *counter, unsigned long nr_pages);

  void page_counter_charge(struct page_counter *counter, unsigned long nr_pages);

  bool page_counter_try_charge(struct page_counter *counter,
  			     unsigned long nr_pages,
  			     struct page_counter **fail);

  void page_counter_uncharge(struct page_counter *counter, unsigned long nr_pages);

  void page_counter_set_min(struct page_counter *counter, unsigned long nr_pages);

  void page_counter_set_low(struct page_counter *counter, unsigned long nr_pages);

  
  static inline void page_counter_set_high(struct page_counter *counter,
  					 unsigned long nr_pages)
  {
  	WRITE_ONCE(counter->high, nr_pages);
  }

  int page_counter_set_max(struct page_counter *counter, unsigned long nr_pages);

  int page_counter_memparse(const char *buf, const char *max,
  			  unsigned long *nr_pages);

  
  static inline void page_counter_reset_watermark(struct page_counter *counter)
  {
  	counter->watermark = page_counter_read(counter);
  }
  
  #endif /* _LINUX_PAGE_COUNTER_H */