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/*
* linux/arch/arm/mm/small_page.c
*
* Copyright (C) 1996 Russell King
*
* 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
*/
#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>
#if PAGE_SIZE == 4096
/* 2K blocks */
#define SMALL_ALLOC_SHIFT (11)
#define NAME(x) x##_2k
#elif PAGE_SIZE == 32768 || PAGE_SIZE == 16384
/* 8K blocks */
#define SMALL_ALLOC_SHIFT (13)
#define NAME(x) x##_8k
#endif
#define SMALL_ALLOC_SIZE (1 << SMALL_ALLOC_SHIFT)
#define NR_BLOCKS (PAGE_SIZE / SMALL_ALLOC_SIZE)
#define BLOCK_MASK ((1 << NR_BLOCKS) - 1)
#define USED(pg) ((atomic_read(&(pg)->count) >> 8) & BLOCK_MASK)
#define SET_USED(pg,off) (atomic_read(&(pg)->count) |= 256 << off)
#define CLEAR_USED(pg,off) (atomic_read(&(pg)->count) &= ~(256 << off))
#define ALL_USED BLOCK_MASK
#define IS_FREE(pg,off) (!(atomic_read(&(pg)->count) & (256 << off)))
#define SM_PAGE_PTR(page,block) ((struct free_small_page *)((page) + \
((block) << SMALL_ALLOC_SHIFT)))
#if NR_BLOCKS != 2 && NR_BLOCKS != 4
#error I only support 2 or 4 blocks per page
#endif
struct free_small_page {
unsigned long next;
unsigned long prev;
};
/*
* To handle allocating small pages, we use the main get_free_page routine,
* and split the page up into 4. The page is marked in mem_map as reserved,
* so it can't be free'd by free_page. The count field is used to keep track
* of which sections of this page are allocated.
*/
static unsigned long small_page_ptr;
static unsigned char offsets[1<<NR_BLOCKS] = {
0, /* 0000 */
1, /* 0001 */
0, /* 0010 */
2, /* 0011 */
#if NR_BLOCKS == 4
0, /* 0100 */
1, /* 0101 */
0, /* 0110 */
3, /* 0111 */
0, /* 1000 */
1, /* 1001 */
0, /* 1010 */
2, /* 1011 */
0, /* 1100 */
1, /* 1101 */
0, /* 1110 */
4 /* 1111 */
#endif
};
static inline void clear_page_links(unsigned long page)
{
struct free_small_page *fsp;
int i;
for (i = 0; i < NR_BLOCKS; i++) {
fsp = SM_PAGE_PTR(page, i);
fsp->next = fsp->prev = 0;
}
}
static inline void set_page_links_prev(unsigned long page, unsigned long prev)
{
struct free_small_page *fsp;
unsigned int mask;
int i;
if (!page)
return;
mask = USED(&mem_map[MAP_NR(page)]);
for (i = 0; i < NR_BLOCKS; i++) {
if (mask & (1 << i))
continue;
fsp = SM_PAGE_PTR(page, i);
fsp->prev = prev;
}
}
static inline void set_page_links_next(unsigned long page, unsigned long next)
{
struct free_small_page *fsp;
unsigned int mask;
int i;
if (!page)
return;
mask = USED(&mem_map[MAP_NR(page)]);
for (i = 0; i < NR_BLOCKS; i++) {
if (mask & (1 << i))
continue;
fsp = SM_PAGE_PTR(page, i);
fsp->next = next;
}
}
unsigned long NAME(get_page)(int priority)
{
struct free_small_page *fsp;
unsigned long new_page;
unsigned long flags;
struct page *page;
int offset;
save_flags(flags);
if (!small_page_ptr)
goto need_new_page;
cli();
again:
page = mem_map + MAP_NR(small_page_ptr);
offset = offsets[USED(page)];
SET_USED(page, offset);
new_page = (unsigned long)SM_PAGE_PTR(small_page_ptr, offset);
if (USED(page) == ALL_USED) {
fsp = (struct free_small_page *)new_page;
set_page_links_prev (fsp->next, 0);
small_page_ptr = fsp->next;
}
restore_flags(flags);
return new_page;
need_new_page:
new_page = __get_free_page(priority);
if (!small_page_ptr) {
if (new_page) {
set_bit (PG_reserved, &mem_map[MAP_NR(new_page)].flags);
clear_page_links (new_page);
cli();
small_page_ptr = new_page;
goto again;
}
restore_flags(flags);
return 0;
}
free_page(new_page);
cli();
goto again;
}
void NAME(free_page)(unsigned long spage)
{
struct free_small_page *ofsp, *cfsp;
unsigned long flags;
struct page *page;
int offset, oldoffset;
if (!spage)
goto none;
offset = (spage >> SMALL_ALLOC_SHIFT) & (NR_BLOCKS - 1);
spage -= offset << SMALL_ALLOC_SHIFT;
page = mem_map + MAP_NR(spage);
if (!PageReserved(page) || !USED(page))
goto non_small;
if (IS_FREE(page, offset))
goto free;
save_flags_cli (flags);
oldoffset = offsets[USED(page)];
CLEAR_USED(page, offset);
ofsp = SM_PAGE_PTR(spage, oldoffset);
cfsp = SM_PAGE_PTR(spage, offset);
if (oldoffset == NR_BLOCKS) { /* going from totally used to mostly used */
cfsp->prev = 0;
cfsp->next = small_page_ptr;
set_page_links_prev (small_page_ptr, spage);
small_page_ptr = spage;
} else if (!USED(page)) {
set_page_links_prev (ofsp->next, ofsp->prev);
set_page_links_next (ofsp->prev, ofsp->next);
if (spage == small_page_ptr)
small_page_ptr = ofsp->next;
clear_bit (PG_reserved, &page->flags);
restore_flags(flags);
free_page (spage);
} else
*cfsp = *ofsp;
restore_flags(flags);
return;
non_small:
printk ("Trying to free non-small page from %p\n", __builtin_return_address(0));
return;
free:
printk ("Trying to free free small page from %p\n", __builtin_return_address(0));
none:
return;
}
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