loop.c-2.2.original

Fast and transparent file system and swap encryption package for linux. No source code changes to li

/*
 *  linux/drivers/block/loop.c
 *
 *  Written by Theodore Ts'o, 3/29/93
 * 
 * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
 * permitted under the GNU Public License.
 *
 * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
 * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
 *
 * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
 * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
 *
 * Fixed do_loop_request() re-entrancy - [e-mail] Mar 20, 1997
 *
 * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
 *
 * Loadable modules and other fixes by AK, 1998
 *
 * Make real block number available to downstream transfer functions, enables
 * CBC (and relatives) mode encryption requiring unique IVs per data block. 
 * Reed H. Petty, [e-mail]
 * 
 * Still To Fix:
 * - Advisory locking is ignored here. 
 * - Should use an own CAP_* category instead of CAP_SYS_ADMIN 
 * - Should use the underlying filesystems/devices read function if possible
 *   to support read ahead (and for write)
 *
 * WARNING/FIXME:
 * - The block number as IV passing to low level transfer functions is broken:
 *   it passes the underlying device's block number instead of the
 *   offset. This makes it change for a given block when the file is 
 *   moved/restored/copied and also doesn't work over NFS. 
 */ 

#include <linux/module.h>

#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/major.h>

#include <linux/init.h>

#include <asm/uaccess.h>

#include <linux/loop.h>		

#define MAJOR_NR LOOP_MAJOR

#define DEVICE_NAME "loop"
#define DEVICE_REQUEST do_lo_request
#define DEVICE_NR(device) (MINOR(device))
#define DEVICE_ON(device)
#define DEVICE_OFF(device)
#define DEVICE_NO_RANDOM
#define TIMEOUT_VALUE (6 * HZ)
#include <linux/blk.h>

#define MAX_LOOP 8
static struct loop_device loop_dev[MAX_LOOP];
static int loop_sizes[MAX_LOOP];
static int loop_blksizes[MAX_LOOP];

#define FALSE 0
#define TRUE (!FALSE)

/* Forward declaration of function to create missing blocks in the 
   backing file (can happen if the backing file is sparse) */
static int create_missing_block(struct loop_device *lo, int block, int blksize);

/*
 * Transfer functions
 */
static int transfer_none(struct loop_device *lo, int cmd, char *raw_buf,
		  char *loop_buf, int size, int real_block)
{
	if (cmd == READ)
		memcpy(loop_buf, raw_buf, size);
	else
		memcpy(raw_buf, loop_buf, size);
	return 0;
}

static int transfer_xor(struct loop_device *lo, int cmd, char *raw_buf,
		 char *loop_buf, int size, int real_block)
{
	char	*in, *out, *key;
	int	i, keysize;

	if (cmd == READ) {
		in = raw_buf;
		out = loop_buf;
	} else {
		in = loop_buf;
		out = raw_buf;
	}
	key = lo->lo_encrypt_key;
	keysize = lo->lo_encrypt_key_size;
	for (i=0; i < size; i++)
		*out++ = *in++ ^ key[(i & 511) % keysize];
	return 0;
}

static int none_status(struct loop_device *lo, struct loop_info *info)
{
	return 0; 
} 

static int xor_status(struct loop_device *lo, struct loop_info *info)
{
	if (info->lo_encrypt_key_size <= 0)
		return -EINVAL;
	return 0;
}

struct loop_func_table none_funcs = { 
	number: LO_CRYPT_NONE,
	transfer: transfer_none,
	init: none_status
}; 	

struct loop_func_table xor_funcs = { 
	number: LO_CRYPT_XOR,
	transfer: transfer_xor,
	init: xor_status
}; 	

/* xfer_funcs[0] is special - its release function is never called */ 
struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
	&none_funcs,
	&xor_funcs  
};

#define MAX_DISK_SIZE 1024*1024*1024

static void figure_loop_size(struct loop_device *lo)
{
	int	size;

	if (S_ISREG(lo->lo_dentry->d_inode->i_mode))
		size = (lo->lo_dentry->d_inode->i_size - lo->lo_offset) / BLOCK_SIZE;
	else {
		kdev_t lodev = lo->lo_device;
		if (blk_size[MAJOR(lodev)])
			size = blk_size[MAJOR(lodev)][MINOR(lodev)] -
                                lo->lo_offset / BLOCK_SIZE;
		else
			size = MAX_DISK_SIZE;
	}

	loop_sizes[lo->lo_number] = size;
}

static void do_lo_request(void)
{
	int	real_block, block, offset, len, blksize, size;
	char	*dest_addr;
	struct loop_device *lo;
	struct buffer_head *bh;
	struct request *current_request;
	int	block_present;

repeat:
	INIT_REQUEST;
	current_request=CURRENT;
	CURRENT=current_request->next;
	if (MINOR(current_request->rq_dev) >= MAX_LOOP)
		goto error_out;
	lo = &loop_dev[MINOR(current_request->rq_dev)];
	if (!lo->lo_dentry || !lo->transfer)
		goto error_out;

	blksize = BLOCK_SIZE;
	if (blksize_size[MAJOR(lo->lo_device)]) {
	    blksize = blksize_size[MAJOR(lo->lo_device)][MINOR(lo->lo_device)];
	    if (!blksize)
	      blksize = BLOCK_SIZE;
	}

	dest_addr = current_request->buffer;
	
	if (blksize < 512) {
		block = current_request->sector * (512/blksize);
		offset = 0;
	} else {
		block = current_request->sector / (blksize >> 9);
		offset = (current_request->sector % (blksize >> 9)) << 9;
	}
	block += lo->lo_offset / blksize;
	offset += lo->lo_offset % blksize;
	if (offset > blksize) {
		block++;
		offset -= blksize;
	}
	len = current_request->current_nr_sectors << 9;

	if (current_request->cmd == WRITE) {
		if (lo->lo_flags & LO_FLAGS_READ_ONLY)
			goto error_out;
	} else if (current_request->cmd != READ) {
		printk(KERN_ERR "unknown loop device command (%d)?!?", current_request->cmd);
		goto error_out;
	}
	spin_unlock_irq(&io_request_lock);
	while (len > 0) {

		size = blksize - offset;
		if (size > len)
			size = len;

		real_block = block;
		block_present = TRUE;

		if (lo->lo_flags & LO_FLAGS_DO_BMAP) {
			real_block = bmap(lo->lo_dentry->d_inode, block);
			if (!real_block) {

				/* The backing file is a sparse file and this block
				   doesn't exist.  If reading, return zeros.  If
				   writing, force the underlying FS to create
				   the block */
				if (current_request->cmd == READ) {
					memset(dest_addr, 0, size);
					block_present = FALSE;
				} else {
					if (!create_missing_block(lo, block, blksize)) {
						goto error_out_lock;
					}
					real_block = bmap(lo->lo_dentry->d_inode, block);
				}

			}
		}

		if (block_present) {
			bh = getblk(lo->lo_device, real_block, blksize);
			if (!bh) {
				printk(KERN_ERR "loop: device %s: getblk(-, %d, %d) returned NULL",
					kdevname(lo->lo_device),
					block, blksize);
				goto error_out_lock;
			}
			if (!buffer_uptodate(bh) && ((current_request->cmd == READ) ||
						(offset || (len < blksize)))) {
				ll_rw_block(READ, 1, &bh);
				wait_on_buffer(bh);
				if (!buffer_uptodate(bh)) {
					brelse(bh);
					goto error_out_lock;
				}
			}

			if ((lo->transfer)(lo, current_request->cmd, bh->b_data + offset,
					dest_addr, size, real_block)) {
				printk(KERN_ERR "loop: transfer error block %d\n", block);
				brelse(bh);
				goto error_out_lock;
			}

			if (current_request->cmd == WRITE) {
				mark_buffer_uptodate(bh, 1);
				mark_buffer_dirty(bh, 1);
			}
			brelse(bh);
		}
		dest_addr += size;
		len -= size;
		offset = 0;
		block++;
	}
	spin_lock_irq(&io_request_lock);
	current_request->next=CURRENT;
	CURRENT=current_request;
	end_request(1);
	goto repeat;
error_out_lock:
	spin_lock_irq(&io_request_lock);
error_out:
	current_request->next=CURRENT;
	CURRENT=current_request;
	end_request(0);
	goto repeat;
}

static int create_missing_block(struct loop_device *lo, int block, int blksize)
{
	struct file     *file;
	loff_t          new_offset;
	char            zero_buf[1] = { 0 };
	ssize_t         retval;
	mm_segment_t	old_fs;
	struct inode	*inode;

	file = lo->lo_backing_file;
	if (file == NULL) {
		printk(KERN_WARNING "loop: cannot create block - no backing file\n");
		return FALSE;
	}

	if (file->f_op == NULL) {
		printk(KERN_WARNING "loop: cannot create block - no file ops\n");
		return FALSE;
	}

	new_offset = block * blksize;

	if (file->f_op->llseek != NULL) {
		file->f_op->llseek(file, new_offset, 0);
	} else {
		/* Do what the default llseek() code would have done */
		file->f_pos = new_offset;
		file->f_reada = 0;
		file->f_version = ++global_event;
	}

	if (file->f_op->write == NULL) {
		printk(KERN_WARNING "loop: cannot create block - file not writeable\n");
		return FALSE;
	}

	old_fs = get_fs();
	set_fs(get_ds());

	inode = file->f_dentry->d_inode;
	down(&inode->i_sem); 
	retval = file->f_op->write(file, zero_buf, 1, &file->f_pos);
	up(&inode->i_sem);
	
	set_fs(old_fs);

	if (retval < 0) {
		printk(KERN_WARNING
		    "loop: cannot create block - FS write failed: code %d\n",
		    (int)retval);
		return FALSE;
	} else {
		return TRUE;
	}
}

static int loop_set_fd(struct loop_device *lo, kdev_t dev, unsigned int arg)
{
	struct file	*file;
	struct inode	*inode;
	int error;

	MOD_INC_USE_COUNT;

	error = -EBUSY;
	if (lo->lo_dentry)
		goto out;

	error = -EBADF;
	file = fget(arg);
	if (!file)
		goto out;

	error = -EINVAL;
	inode = file->f_dentry->d_inode;
	if (!inode) {
		printk(KERN_ERR "loop_set_fd: NULL inode?!?\n");
		goto out_putf;
	}

	if (S_ISBLK(inode->i_mode)) {
		error = blkdev_open(inode, file);