/* Swap in a page on disk or on swap space, or initilize a zero page*/
bool swap_in (struct frame_struct *pframe)
{
struct block *device;
size_t length = pframe->length;
block_sector_t sector_no = pframe->sector_no;
uint32_t pos = pframe->flag & POSBITS;
uint32_t is_all_zero = pframe->flag & FS_ZERO;
/* Get a frame, from memory or by evict another frame */
uint8_t *kpage = palloc_get_page (PAL_USER | PAL_ZERO);
if (kpage == NULL)
{
/* Evict to get a frame */
kpage = sup_pt_evict_frame ();
if (kpage == NULL)
{
return false;
}
}
/* If zero page, just write a page of 0's */
if (is_all_zero)
{
memset (kpage, 0, PGSIZE);
sup_pt_set_swap_in (pframe, kpage);
return true;
}
/* On disk */
if (pos == POS_DISK)
{
/* Register filesys as block device */
device = fs_device;
/* Whether a newly loaded exec file page
or a swapped out mem-mapped file page
they are not dirty */
pframe->flag &= ~FS_DIRTY;
}
/* On swap */
else if (pos == POS_SWAP)
{
/* Register swap as block device */
device = sp_device;
}
else
{
/* Already in memeory, other processes race to swap_in the frame */
palloc_free_page (kpage);
return false;
}
if (device == fs_device)
lock_acquire (&glb_lock_filesys);
else
lock_acquire (&glb_lock_swapsys);
/* Read from disk or swap */
block_sector_t i;
for (i = 0; i < PGSIZE / BLOCK_SECTOR_SIZE; i++)
{
block_read (device, sector_no + i, kpage + BLOCK_SECTOR_SIZE * i);
}
if (device == fs_device)
lock_release (&glb_lock_filesys);
else
lock_release (&glb_lock_swapsys);
/* Set remaining of the page to 0, only necessary for disk */
if ((length < PGSIZE) && (device == fs_device))
memset (kpage + length, 0, PGSIZE - length);
/* Free swap table entries */
if (device == sp_device)
{
lock_acquire (&swap_set_lock);
bitmap_set_multiple (swap_free_map, sector_no,
PGSIZE / BLOCK_SECTOR_SIZE, false);
lock_release (&swap_set_lock);
}
/* Update sup_pt entry information */
sup_pt_set_swap_in (pframe, kpage);
return true;
}
/* Makes CNT sectors starting at SECTOR available for use. */
void free_map_release (disk_sector_t sector, size_t cnt)
{
ASSERT (bitmap_all (free_map, sector, cnt));
bitmap_set_multiple (free_map, sector, cnt, false);
bitmap_write (free_map, free_map_file);
}
