/*
 *  linux/mm/swap_state.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 */

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/head.h>
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/swap.h>
#include <linux/fs.h>
#include <linux/swapctl.h>
#include <linux/init.h>

#include <asm/bitops.h>
#include <asm/pgtable.h>

#ifdef SWAP_CACHE_INFO
unsigned long swap_cache_add_total = 0;
unsigned long swap_cache_add_success = 0;
unsigned long swap_cache_del_total = 0;
unsigned long swap_cache_del_success = 0;
unsigned long swap_cache_find_total = 0;
unsigned long swap_cache_find_success = 0;

void show_swap_cache_info(void)
{
	printk("Swap cache: add %ld/%ld, delete %ld/%ld, find %ld/%ld\n",
		swap_cache_add_total, swap_cache_add_success, 
		swap_cache_del_total, swap_cache_del_success,
		swap_cache_find_total, swap_cache_find_success);
}
#endif

int add_to_swap_cache(struct page *page, unsigned long entry)
{
	struct swap_info_struct * p = &swap_info[SWP_TYPE(entry)];

#ifdef SWAP_CACHE_INFO
	swap_cache_add_total++;
#endif
	if ((p->flags & SWP_WRITEOK) == SWP_WRITEOK) {
		page->pg_swap_entry = entry;
		if (PageTestandSetSwapCache(page))
			printk("swap_cache: replacing non-empty entry\n");
#ifdef SWAP_CACHE_INFO
		swap_cache_add_success++;
#endif
		return 1;
	}
	return 0;
}

/*
 * If swap_map[] reaches 127, the entries are treated as "permanent".
 */
void swap_duplicate(unsigned long entry)
{
	struct swap_info_struct * p;
	unsigned long offset, type;

	if (!entry)
		goto out;
	type = SWP_TYPE(entry);
	if (type & SHM_SWP_TYPE)
		goto out;
	if (type >= nr_swapfiles)
		goto bad_file;
	p = type + swap_info;
	offset = SWP_OFFSET(entry);
	if (offset >= p->max)
		goto bad_offset;
	if (!p->swap_map[offset])
		goto bad_unused;
	if (p->swap_map[offset] < 126)
		p->swap_map[offset]++;
	else {
		static int overflow = 0;
		if (overflow++ < 5)
			printk("swap_duplicate: entry %08lx map count=%d\n",
				entry, p->swap_map[offset]);
		p->swap_map[offset] = 127;
	}
out:
	return;

bad_file:
	printk("swap_duplicate: Trying to duplicate nonexistent swap-page\n");
	goto out;
bad_offset:
	printk("swap_duplicate: offset exceeds max\n");
	goto out;
bad_unused:
	printk("swap_duplicate: unused page\n");
	goto out;
}