swapfile.c

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

	int i, j, prev;
	int error;
	static int least_priority = 0;
	union swap_header *swap_header = 0;
	int swap_header_version;
	int nr_good_pages = 0;
	unsigned long maxpages = 1;
	int swapfilesize;
	struct block_device *bdev = NULL;
	unsigned short *swap_map;
	
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	lock_kernel();
	swap_list_lock();
	p = swap_info;
	for (type = 0 ; type < nr_swapfiles ; type++,p++)
		if (!(p->flags & SWP_USED))
			break;
	error = -EPERM;
	if (type >= MAX_SWAPFILES) {
		swap_list_unlock();
		goto out;
	}
	if (type >= nr_swapfiles)
		nr_swapfiles = type+1;
	p->flags = SWP_USED;
	p->swap_file = NULL;
	p->swap_vfsmnt = NULL;
	p->swap_device = 0;
	p->swap_map = NULL;
	p->lowest_bit = 0;
	p->highest_bit = 0;
	p->cluster_nr = 0;
	p->sdev_lock = SPIN_LOCK_UNLOCKED;
	p->next = -1;
	if (swap_flags & SWAP_FLAG_PREFER) {
		p->prio =
		  (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
	} else {
		p->prio = --least_priority;
	}
	swap_list_unlock();
	error = user_path_walk(specialfile, &nd);
	if (error)
		goto bad_swap_2;

	p->swap_file = nd.dentry;
	p->swap_vfsmnt = nd.mnt;
	swap_inode = nd.dentry->d_inode;
	error = -EINVAL;

	if (S_ISBLK(swap_inode->i_mode)) {
		kdev_t dev = swap_inode->i_rdev;
		struct block_device_operations *bdops;
		devfs_handle_t de;

		p->swap_device = dev;
		set_blocksize(dev, PAGE_SIZE);
		
		bd_acquire(swap_inode);
		bdev = swap_inode->i_bdev;
		de = devfs_get_handle_from_inode(swap_inode);
		bdops = devfs_get_ops(de);  /*  Increments module use count  */
		if (bdops) bdev->bd_op = bdops;

		error = blkdev_get(bdev, FMODE_READ|FMODE_WRITE, 0, BDEV_SWAP);
		devfs_put_ops(de);/*Decrement module use count now we're safe*/
		if (error)
			goto bad_swap_2;
		set_blocksize(dev, PAGE_SIZE);
		error = -ENODEV;
		if (!dev || (blk_size[MAJOR(dev)] &&
		     !blk_size[MAJOR(dev)][MINOR(dev)]))
			goto bad_swap;
		swapfilesize = 0;
		if (blk_size[MAJOR(dev)])
			swapfilesize = blk_size[MAJOR(dev)][MINOR(dev)]
				>> (PAGE_SHIFT - 10);
	} else if (S_ISREG(swap_inode->i_mode))
		swapfilesize = swap_inode->i_size >> PAGE_SHIFT;
	else
		goto bad_swap;

	error = -EBUSY;
	for (i = 0 ; i < nr_swapfiles ; i++) {
		struct swap_info_struct *q = &swap_info[i];
		if (i == type || !q->swap_file)
			continue;
		if (swap_inode->i_mapping == q->swap_file->d_inode->i_mapping)
			goto bad_swap;
	}

	swap_header = (void *) __get_free_page(GFP_USER);
	if (!swap_header) {
		printk("Unable to start swapping: out of memory :-)\n");
		error = -ENOMEM;
		goto bad_swap;
	}

	lock_page(virt_to_page(swap_header));
	rw_swap_page_nolock(READ, SWP_ENTRY(type,0), (char *) swap_header);

	if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
		swap_header_version = 1;
	else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
		swap_header_version = 2;
	else {
		printk("Unable to find swap-space signature\n");
		error = -EINVAL;
		goto bad_swap;
	}
	
	switch (swap_header_version) {
	case 1:
		memset(((char *) swap_header)+PAGE_SIZE-10,0,10);
		j = 0;
		p->lowest_bit = 0;
		p->highest_bit = 0;
		for (i = 1 ; i < 8*PAGE_SIZE ; i++) {
			if (test_bit(i,(char *) swap_header)) {
				if (!p->lowest_bit)
					p->lowest_bit = i;
				p->highest_bit = i;
				maxpages = i+1;
				j++;
			}
		}
		nr_good_pages = j;
		p->swap_map = vmalloc(maxpages * sizeof(short));
		if (!p->swap_map) {
			error = -ENOMEM;		
			goto bad_swap;
		}
		for (i = 1 ; i < maxpages ; i++) {
			if (test_bit(i,(char *) swap_header))
				p->swap_map[i] = 0;
			else
				p->swap_map[i] = SWAP_MAP_BAD;
		}
		break;

	case 2:
		/* Check the swap header's sub-version and the size of
                   the swap file and bad block lists */
		if (swap_header->info.version != 1) {
			printk(KERN_WARNING
			       "Unable to handle swap header version %d\n",
			       swap_header->info.version);
			error = -EINVAL;
			goto bad_swap;
		}

		p->lowest_bit  = 1;
		maxpages = SWP_OFFSET(SWP_ENTRY(0,~0UL)) - 1;
		if (maxpages > swap_header->info.last_page)
			maxpages = swap_header->info.last_page;
		p->highest_bit = maxpages - 1;

		error = -EINVAL;
		if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
			goto bad_swap;
		
		/* OK, set up the swap map and apply the bad block list */
		if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
			error = -ENOMEM;
			goto bad_swap;
		}

		error = 0;
		memset(p->swap_map, 0, maxpages * sizeof(short));
		for (i=0; i<swap_header->info.nr_badpages; i++) {
			int page = swap_header->info.badpages[i];
			if (page <= 0 || page >= swap_header->info.last_page)
				error = -EINVAL;
			else
				p->swap_map[page] = SWAP_MAP_BAD;
		}
		nr_good_pages = swap_header->info.last_page -
				swap_header->info.nr_badpages -
				1 /* header page */;
		if (error) 
			goto bad_swap;
	}
	
	if (swapfilesize && maxpages > swapfilesize) {
		printk(KERN_WARNING
		       "Swap area shorter than signature indicates\n");
		error = -EINVAL;
		goto bad_swap;
	}
	if (!nr_good_pages) {
		printk(KERN_WARNING "Empty swap-file\n");
		error = -EINVAL;
		goto bad_swap;
	}
	p->swap_map[0] = SWAP_MAP_BAD;
	swap_list_lock();
	swap_device_lock(p);
	p->max = maxpages;
	p->flags = SWP_WRITEOK;
	p->pages = nr_good_pages;
	nr_swap_pages += nr_good_pages;
	total_swap_pages += nr_good_pages;
	printk(KERN_INFO "Adding Swap: %dk swap-space (priority %d)\n",
	       nr_good_pages<<(PAGE_SHIFT-10), p->prio);

	/* insert swap space into swap_list: */
	prev = -1;
	for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
		if (p->prio >= swap_info[i].prio) {
			break;
		}
		prev = i;
	}
	p->next = i;
	if (prev < 0) {
		swap_list.head = swap_list.next = p - swap_info;
	} else {
		swap_info[prev].next = p - swap_info;
	}
	swap_device_unlock(p);
	swap_list_unlock();
	error = 0;
	goto out;
bad_swap:
	if (bdev)
		blkdev_put(bdev, BDEV_SWAP);
bad_swap_2:
	swap_list_lock();
	swap_map = p->swap_map;
	nd.mnt = p->swap_vfsmnt;
	nd.dentry = p->swap_file;
	p->swap_device = 0;
	p->swap_file = NULL;
	p->swap_vfsmnt = NULL;
	p->swap_map = NULL;
	p->flags = 0;
	if (!(swap_flags & SWAP_FLAG_PREFER))
		++least_priority;
	swap_list_unlock();
	if (swap_map)
		vfree(swap_map);
	path_release(&nd);
out:
	if (swap_header)
		free_page((long) swap_header);
	unlock_kernel();
	return error;
}

void si_swapinfo(struct sysinfo *val)
{
	unsigned int i;
	unsigned long nr_to_be_unused = 0;

	swap_list_lock();
	for (i = 0; i < nr_swapfiles; i++) {
		unsigned int j;
		if (swap_info[i].flags != SWP_USED)
			continue;
		for (j = 0; j < swap_info[i].max; ++j) {
			switch (swap_info[i].swap_map[j]) {
				case 0:
				case SWAP_MAP_BAD:
					continue;
				default:
					nr_to_be_unused++;
			}
		}
	}
	val->freeswap = nr_swap_pages + nr_to_be_unused;
	val->totalswap = total_swap_pages + nr_to_be_unused;
	swap_list_unlock();
}

/*
 * Verify that a swap entry is valid and increment its swap map count.
 *
 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
 * "permanent", but will be reclaimed by the next swapoff.
 */
int swap_duplicate(swp_entry_t entry)
{
	struct swap_info_struct * p;
	unsigned long offset, type;
	int result = 0;

	type = SWP_TYPE(entry);
	if (type >= nr_swapfiles)
		goto bad_file;
	p = type + swap_info;
	offset = SWP_OFFSET(entry);

	swap_device_lock(p);
	if (offset < p->max && p->swap_map[offset]) {
		if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
			p->swap_map[offset]++;
			result = 1;
		} else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
			if (swap_overflow++ < 5)
				printk(KERN_WARNING "swap_dup: swap entry overflow\n");
			p->swap_map[offset] = SWAP_MAP_MAX;
			result = 1;
		}
	}
	swap_device_unlock(p);
out:
	return result;

bad_file:
	printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
	goto out;
}

/*
 * Page lock needs to be held in all cases to prevent races with
 * swap file deletion.
 */
int swap_count(struct page *page)
{
	struct swap_info_struct * p;
	unsigned long offset, type;
	swp_entry_t entry;
	int retval = 0;

	entry.val = page->index;
	if (!entry.val)
		goto bad_entry;
	type = SWP_TYPE(entry);
	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;
	retval = p->swap_map[offset];
out:
	return retval;

bad_entry:
	printk(KERN_ERR "swap_count: null entry!\n");
	goto out;
bad_file:
	printk(KERN_ERR "swap_count: %s%08lx\n", Bad_file, entry.val);
	goto out;
bad_offset:
	printk(KERN_ERR "swap_count: %s%08lx\n", Bad_offset, entry.val);
	goto out;
bad_unused:
	printk(KERN_ERR "swap_count: %s%08lx\n", Unused_offset, entry.val);
	goto out;
}

/*
 * Prior swap_duplicate protects against swap device deletion.
 */
void get_swaphandle_info(swp_entry_t entry, unsigned long *offset, 
			kdev_t *dev, struct inode **swapf)
{
	unsigned long type;
	struct swap_info_struct *p;

	type = SWP_TYPE(entry);
	if (type >= nr_swapfiles) {
		printk(KERN_ERR "rw_swap_page: %s%08lx\n", Bad_file, entry.val);
		return;
	}

	p = &swap_info[type];
	*offset = SWP_OFFSET(entry);
	if (*offset >= p->max && *offset != 0) {
		printk(KERN_ERR "rw_swap_page: %s%08lx\n", Bad_offset, entry.val);
		return;
	}
	if (p->swap_map && !p->swap_map[*offset]) {
		printk(KERN_ERR "rw_swap_page: %s%08lx\n", Unused_offset, entry.val);
		return;
	}
	if (!(p->flags & SWP_USED)) {
		printk(KERN_ERR "rw_swap_page: %s%08lx\n", Unused_file, entry.val);
		return;
	}

	if (p->swap_device) {
		*dev = p->swap_device;
	} else if (p->swap_file) {
		*swapf = p->swap_file->d_inode;
	} else {
		printk(KERN_ERR "rw_swap_page: no swap file or device\n");
	}
	return;
}

/*
 * swap_device_lock prevents swap_map being freed. Don't grab an extra
 * reference on the swaphandle, it doesn't matter if it becomes unused.
 */
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
{
	int ret = 0, i = 1 << page_cluster;
	unsigned long toff;
	struct swap_info_struct *swapdev = SWP_TYPE(entry) + swap_info;

	if (!page_cluster)	/* no readahead */
		return 0;
	toff = (SWP_OFFSET(entry) >> page_cluster) << page_cluster;
	if (!toff)		/* first page is swap header */
		toff++, i--;
	*offset = toff;

	swap_device_lock(swapdev);
	do {
		/* Don't read-ahead past the end of the swap area */
		if (toff >= swapdev->max)
			break;
		/* Don't read in free or bad pages */
		if (!swapdev->swap_map[toff])
			break;
		if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
			break;
		toff++;
		ret++;
	} while (--i);
	swap_device_unlock(swapdev);
	return ret;
}