add directory kernel
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gohigh
253
kernel/0.1x/linux-0.12/mm/swap.c
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253
kernel/0.1x/linux-0.12/mm/swap.c
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/*
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* linux/mm/swap.c
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*
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* (C) 1991 Linus Torvalds
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*/
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/*
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* This file should contain most things doing the swapping from/to disk.
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* Started 18.12.91
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*/
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#include <string.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/head.h>
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#include <linux/kernel.h>
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#define SWAP_BITS (4096<<3)
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#define bitop(name,op) \
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static inline int name(char * addr,unsigned int nr) \
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{ \
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int __res; \
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__asm__ __volatile__("bt" op " %1,%2; adcl $0,%0" \
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:"=g" (__res) \
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:"r" (nr),"m" (*(addr)),"0" (0)); \
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return __res; \
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}
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bitop(bit,"")
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bitop(setbit,"s")
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bitop(clrbit,"r")
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static char * swap_bitmap = NULL;
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int SWAP_DEV = 0;
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/*
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* We never page the pages in task[0] - kernel memory.
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* We page all other pages.
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*/
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#define FIRST_VM_PAGE (TASK_SIZE>>12)
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#define LAST_VM_PAGE (1024*1024)
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#define VM_PAGES (LAST_VM_PAGE - FIRST_VM_PAGE)
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static int get_swap_page(void)
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{
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int nr;
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if (!swap_bitmap)
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return 0;
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for (nr = 1; nr < 32768 ; nr++)
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if (clrbit(swap_bitmap,nr))
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return nr;
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return 0;
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}
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void swap_free(int swap_nr)
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{
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if (!swap_nr)
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return;
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if (swap_bitmap && swap_nr < SWAP_BITS)
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if (!setbit(swap_bitmap,swap_nr))
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return;
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printk("Swap-space bad (swap_free())\n\r");
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return;
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}
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void swap_in(unsigned long *table_ptr)
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{
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int swap_nr;
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unsigned long page;
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if (!swap_bitmap) {
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printk("Trying to swap in without swap bit-map");
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return;
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}
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if (1 & *table_ptr) {
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printk("trying to swap in present page\n\r");
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return;
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}
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swap_nr = *table_ptr >> 1;
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if (!swap_nr) {
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printk("No swap page in swap_in\n\r");
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return;
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}
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if (!(page = get_free_page()))
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oom();
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read_swap_page(swap_nr, (char *) page);
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if (setbit(swap_bitmap,swap_nr))
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printk("swapping in multiply from same page\n\r");
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*table_ptr = page | (PAGE_DIRTY | 7);
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}
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int try_to_swap_out(unsigned long * table_ptr)
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{
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unsigned long page;
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unsigned long swap_nr;
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page = *table_ptr;
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if (!(PAGE_PRESENT & page))
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return 0;
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if (page - LOW_MEM > PAGING_MEMORY)
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return 0;
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if (PAGE_DIRTY & page) {
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page &= 0xfffff000;
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if (mem_map[MAP_NR(page)] != 1)
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return 0;
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if (!(swap_nr = get_swap_page()))
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return 0;
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*table_ptr = swap_nr<<1;
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invalidate();
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write_swap_page(swap_nr, (char *) page);
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free_page(page);
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return 1;
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}
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*table_ptr = 0;
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invalidate();
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free_page(page);
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return 1;
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}
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/*
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* Ok, this has a rather intricate logic - the idea is to make good
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* and fast machine code. If we didn't worry about that, things would
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* be easier.
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*/
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int swap_out(void)
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{
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static int dir_entry = FIRST_VM_PAGE>>10;
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static int page_entry = -1;
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int counter = VM_PAGES;
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int pg_table;
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while (counter>0) {
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pg_table = pg_dir[dir_entry];
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if (pg_table & 1)
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break;
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counter -= 1024;
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dir_entry++;
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if (dir_entry >= 1024)
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dir_entry = FIRST_VM_PAGE>>10;
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}
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pg_table &= 0xfffff000;
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while (counter-- > 0) {
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page_entry++;
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if (page_entry >= 1024) {
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page_entry = 0;
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repeat:
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dir_entry++;
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if (dir_entry >= 1024)
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dir_entry = FIRST_VM_PAGE>>10;
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pg_table = pg_dir[dir_entry];
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if (!(pg_table&1))
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if ((counter -= 1024) > 0)
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goto repeat;
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else
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break;
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pg_table &= 0xfffff000;
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}
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if (try_to_swap_out(page_entry + (unsigned long *) pg_table))
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return 1;
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}
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printk("Out of swap-memory\n\r");
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return 0;
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}
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/*
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* Get physical address of first (actually last :-) free page, and mark it
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* used. If no free pages left, return 0.
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*/
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unsigned long get_free_page(void)
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{
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register unsigned long __res asm("ax");
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repeat:
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__asm__("std ; repne ; scasb\n\t"
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"jne 1f\n\t"
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"movb $1,1(%%edi)\n\t"
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"sall $12,%%ecx\n\t"
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"addl %2,%%ecx\n\t"
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"movl %%ecx,%%edx\n\t"
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"movl $1024,%%ecx\n\t"
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"leal 4092(%%edx),%%edi\n\t"
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"rep ; stosl\n\t"
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"movl %%edx,%%eax\n"
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"1:"
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:"=a" (__res)
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:"0" (0),"i" (LOW_MEM),"c" (PAGING_PAGES),
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"D" (mem_map+PAGING_PAGES-1)
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:"di","cx","dx");
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if (__res >= HIGH_MEMORY)
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goto repeat;
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if (!__res && swap_out())
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goto repeat;
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return __res;
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}
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void init_swapping(void)
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{
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extern int *blk_size[];
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int swap_size,i,j;
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if (!SWAP_DEV)
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return;
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if (!blk_size[MAJOR(SWAP_DEV)]) {
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printk("Unable to get size of swap device\n\r");
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return;
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}
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swap_size = blk_size[MAJOR(SWAP_DEV)][MINOR(SWAP_DEV)];
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if (!swap_size)
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return;
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if (swap_size < 100) {
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printk("Swap device too small (%d blocks)\n\r",swap_size);
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return;
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}
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swap_size >>= 2;
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if (swap_size > SWAP_BITS)
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swap_size = SWAP_BITS;
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swap_bitmap = (char *) get_free_page();
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if (!swap_bitmap) {
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printk("Unable to start swapping: out of memory :-)\n\r");
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return;
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}
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read_swap_page(0,swap_bitmap);
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if (strncmp("SWAP-SPACE",swap_bitmap+4086,10)) {
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printk("Unable to find swap-space signature\n\r");
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free_page((long) swap_bitmap);
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swap_bitmap = NULL;
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return;
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}
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memset(swap_bitmap+4086,0,10);
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for (i = 0 ; i < SWAP_BITS ; i++) {
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if (i == 1)
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i = swap_size;
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if (bit(swap_bitmap,i)) {
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printk("Bad swap-space bit-map\n\r");
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free_page((long) swap_bitmap);
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swap_bitmap = NULL;
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return;
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}
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}
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j = 0;
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for (i = 1 ; i < swap_size ; i++)
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if (bit(swap_bitmap,i))
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j++;
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if (!j) {
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free_page((long) swap_bitmap);
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swap_bitmap = NULL;
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return;
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}
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printk("Swap device ok: %d pages (%d bytes) swap-space\n\r",j,j*4096);
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}
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