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/*
* linux/arch/arm26/mm/small_page.c
*
* Copyright (C) 1996 Russell King
* Copyright (C) 2003 Ian Molton
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Changelog:
* 26/01/1996 RMK Cleaned up various areas to make little more generic
* 07/02/1999 RMK Support added for 16K and 32K page sizes
* containing 8K blocks
* 23/05/2004 IM Fixed to use struct page->lru (thanks wli)
*
*/
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/bitops.h>
#include <asm/pgtable.h>
#define PEDANTIC
/*
* Requirement:
* We need to be able to allocate naturally aligned memory of finer
* granularity than the page size. This is typically used for the
* second level page tables on 32-bit ARMs.
*
* FIXME - this comment is *out of date*
* Theory:
* We "misuse" the Linux memory management system. We use alloc_page
* to allocate a page and then mark it as reserved. The Linux memory
* management system will then ignore the "offset", "next_hash" and
* "pprev_hash" entries in the mem_map for this page.
*
* We then use a bitstring in the "offset" field to mark which segments
* of the page are in use, and manipulate this as required during the
* allocation and freeing of these small pages.
*
* We also maintain a queue of pages being used for this purpose using
* the "next_hash" and "pprev_hash" entries of mem_map;
*/
struct order {
struct list_head queue;
unsigned int mask; /* (1 << shift) - 1 */
unsigned int shift; /* (1 << shift) size of page */
unsigned int block_mask; /* nr_blocks - 1 */
unsigned int all_used; /* (1 << nr_blocks) - 1 */
};
static struct order orders[] = {
#if PAGE_SIZE == 32768
{ LIST_HEAD_INIT(orders[0].queue), 2047, 11, 15, 0x0000ffff },
{ LIST_HEAD_INIT(orders[1].queue), 8191, 13, 3, 0x0000000f }
#else
#error unsupported page size (ARGH!)
#endif
};
#define USED_MAP(pg) ((pg)->index)
#define TEST_AND_CLEAR_USED(pg,off) (test_and_clear_bit(off, &USED_MAP(pg)))
#define SET_USED(pg,off) (set_bit(off, &USED_MAP(pg)))
static DEFINE_SPINLOCK(small_page_lock);
static unsigned long __get_small_page(int priority, struct order *order)
{
unsigned long flags;
struct page *page;
int offset;
do {
spin_lock_irqsave(&small_page_lock, flags);
if (list_empty(&order->queue))
goto need_new_page;
page = list_entry(order->queue.next, struct page, lru);
again:
#ifdef PEDANTIC
BUG_ON(USED_MAP(page) & ~order->all_used);
#endif
offset = ffz(USED_MAP(page));
SET_USED(page, offset);
if (USED_MAP(page) == order->all_used)
list_del_init(&page->lru);
spin_unlock_irqrestore(&small_page_lock, flags);
return (unsigned long) page_address(page) + (offset << order->shift);
need_new_page:
spin_unlock_irqrestore(&small_page_lock, flags);
page = alloc_page(priority);
spin_lock_irqsave(&small_page_lock, flags);
if (list_empty(&order->queue)) {
if (!page)
goto no_page;
SetPageReserved(page);
USED_MAP(page) = 0;
list_add(&page->lru, &order->queue);
goto again;
}
spin_unlock_irqrestore(&small_page_lock, flags);
__free_page(page);
} while (1);
no_page:
spin_unlock_irqrestore(&small_page_lock, flags);
return 0;
}
static void __free_small_page(unsigned long spage, struct order *order)
{
unsigned long flags;
struct page *page;
if (virt_addr_valid(spage)) {
page = virt_to_page(spage);
/*
* The container-page must be marked Reserved
*/
if (!PageReserved(page) || spage & order->mask)
goto non_small;
#ifdef PEDANTIC
BUG_ON(USED_MAP(page) & ~order->all_used);
#endif
spage = spage >> order->shift;
spage &= order->block_mask;
/*
* the following must be atomic wrt get_page
*/
spin_lock_irqsave(&small_page_lock, flags);
if (USED_MAP(page) == order->all_used)
list_add(&page->lru, &order->queue);
if (!TEST_AND_CLEAR_USED(page, spage))
goto already_free;
if (USED_MAP(page) == 0)
goto free_page;
spin_unlock_irqrestore(&small_page_lock, flags);
}
return;
free_page:
/*
* unlink the page from the small page queue and free it
*/
list_del_init(&page->lru);
spin_unlock_irqrestore(&small_page_lock, flags);
ClearPageReserved(page);
__free_page(page);
return;
non_small:
printk("Trying to free non-small page from %p\n", __builtin_return_address(0));
return;
already_free:
printk("Trying to free free small page from %p\n", __builtin_return_address(0));
}
unsigned long get_page_8k(int priority)
{
return __get_small_page(priority, orders+1);
}
void free_page_8k(unsigned long spage)
{
__free_small_page(spage, orders+1);
}
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