diff -Nur linux-2.5.1-orig/drivers/block/loop.c linux-2.5.1/drivers/block/loop.c
--- linux-2.5.1-orig/drivers/block/loop.c	Fri Nov 30 17:33:50 2001
+++ linux-2.5.1/drivers/block/loop.c	Sun Dec 30 14:41:18 2001
@@ -85,7 +85,7 @@
  * Transfer functions
  */
 static int transfer_none(struct loop_device *lo, int cmd, char *raw_buf,
-			 char *loop_buf, int size, int real_block)
+			 char *loop_buf, int size, loop_iv_t IV)
 {
 	if (raw_buf != loop_buf) {
 		if (cmd == READ)
@@ -98,7 +98,7 @@
 }
 
 static int transfer_xor(struct loop_device *lo, int cmd, char *raw_buf,
-			char *loop_buf, int size, int real_block)
+			char *loop_buf, int size, loop_iv_t IV)
 {
 	char	*in, *out, *key;
 	int	i, keysize;
@@ -185,7 +185,7 @@
 	len = bio->bi_size;
 	data = bio_data(bio);
 	while (len > 0) {
-		int IV = index * (PAGE_CACHE_SIZE/bsize) + offset/bsize;
+		const loop_iv_t IV = (index << (PAGE_CACHE_SHIFT - LOOP_IV_SECTOR_BITS)) + (offset >> LOOP_IV_SECTOR_BITS);
 		int transfer_result;
 
 		size = PAGE_CACHE_SIZE - offset;
@@ -243,7 +243,7 @@
 	unsigned long count = desc->count;
 	struct lo_read_data *p = (struct lo_read_data*)desc->buf;
 	struct loop_device *lo = p->lo;
-	int IV = page->index * (PAGE_CACHE_SIZE/p->bsize) + offset/p->bsize;
+	const loop_iv_t IV = (page->index << (PAGE_CACHE_SHIFT - LOOP_IV_SECTOR_BITS)) + (offset >> LOOP_IV_SECTOR_BITS);
 
 	if (size > count)
 		size = count;
@@ -294,20 +294,6 @@
 	return bs;
 }
 
-static inline unsigned long loop_get_iv(struct loop_device *lo,
-					unsigned long sector)
-{
-	int bs = loop_get_bs(lo);
-	unsigned long offset, IV;
-
-	IV = sector / (bs >> 9) + lo->lo_offset / bs;
-	offset = ((sector % (bs >> 9)) << 9) + lo->lo_offset % bs;
-	if (offset >= bs)
-		IV++;
-
-	return IV;
-}
-
 static int do_bio_filebacked(struct loop_device *lo, struct bio *bio)
 {
 	loff_t pos;
@@ -433,7 +419,7 @@
 {
 	struct bio *bh = NULL;
 	struct loop_device *lo;
-	unsigned long IV;
+	loop_iv_t IV;
 	int rw = bio_rw(rbh);
 
 	if (MINOR(rbh->bi_dev) >= max_loop)
@@ -470,7 +456,7 @@
 	 * piggy old buffer on original, and submit for I/O
 	 */
 	bh = loop_get_buffer(lo, rbh);
-	IV = loop_get_iv(lo, rbh->bi_sector);
+	IV = rbh->bi_sector + (lo->lo_offset >> LOOP_IV_SECTOR_BITS);
 	if (rw == WRITE) {
 		if (lo_do_transfer(lo, WRITE, bio_data(bh), bio_data(rbh),
 				   bh->bi_size, IV))
@@ -495,7 +481,7 @@
 static int do_bio_blockbacked(struct loop_device *lo, struct bio *bio,
 			      struct bio *rbh)
 {
-	unsigned long IV = loop_get_iv(lo, rbh->bi_sector);
+	const loop_iv_t IV = rbh->bi_sector + (lo->lo_offset >> LOOP_IV_SECTOR_BITS);
 	struct bio_vec *to;
 	char *vto, *vfrom;
 	int ret = 0, i;
diff -Nur linux-2.5.1-orig/include/linux/loop.h linux-2.5.1/include/linux/loop.h
--- linux-2.5.1-orig/include/linux/loop.h	Tue Nov 27 18:23:27 2001
+++ linux-2.5.1/include/linux/loop.h	Sun Dec 30 14:35:53 2001
@@ -17,6 +17,12 @@
 
 #ifdef __KERNEL__
 
+/* definitions for IV metric */
+#define LOOP_IV_SECTOR_BITS 9
+#define LOOP_IV_SECTOR_SIZE (1 << LOOP_IV_SECTOR_BITS)
+
+typedef int loop_iv_t;
+
 /* Possible states of device */
 enum {
 	Lo_unbound,
@@ -24,6 +30,12 @@
 	Lo_rundown,
 };
 
+struct loop_device;
+
+typedef	int (* transfer_proc_t)(struct loop_device *, int cmd,
+				char *raw_buf, char *loop_buf, int size,
+				loop_iv_t IV);
+
 struct loop_device {
 	int		lo_number;
 	int		lo_refcnt;
@@ -32,9 +44,7 @@
 	int		lo_encrypt_type;
 	int		lo_encrypt_key_size;
 	int		lo_flags;
-	int		(*transfer)(struct loop_device *, int cmd,
-				    char *raw_buf, char *loop_buf, int size,
-				    int real_block);
+	transfer_proc_t transfer;
 	char		lo_name[LO_NAME_SIZE];
 	char		lo_encrypt_key[LO_KEY_SIZE];
 	__u32           lo_init[2];
@@ -58,17 +68,13 @@
 	atomic_t		lo_pending;
 };
 
-typedef	int (* transfer_proc_t)(struct loop_device *, int cmd,
-				char *raw_buf, char *loop_buf, int size,
-				int real_block);
-
 static inline int lo_do_transfer(struct loop_device *lo, int cmd, char *rbuf,
-				 char *lbuf, int size, int rblock)
+				 char *lbuf, int size, loop_iv_t IV)
 {
 	if (!lo->transfer)
 		return 0;
 
-	return lo->transfer(lo, cmd, rbuf, lbuf, size, rblock);
+	return lo->transfer(lo, cmd, rbuf, lbuf, size, IV);
 }
 #endif /* __KERNEL__ */
 
@@ -122,6 +128,8 @@
 #define LO_CRYPT_IDEA     6
 #define LO_CRYPT_DUMMY    9
 #define LO_CRYPT_SKIPJACK 10
+#define LO_CRYPT_AES      16   /* loop-AES */
+#define LO_CRYPT_CRYPTOAPI 18  /* international crypto patch */
 #define MAX_LO_CRYPT	20
 
 #ifdef __KERNEL__
@@ -129,7 +137,7 @@
 struct loop_func_table {
 	int number; 	/* filter type */ 
 	int (*transfer)(struct loop_device *lo, int cmd, char *raw_buf,
-			char *loop_buf, int size, int real_block);
+			char *loop_buf, int size, loop_iv_t IV);
 	int (*init)(struct loop_device *, struct loop_info *); 
 	/* release is called from loop_unregister_transfer or clr_fd */
 	int (*release)(struct loop_device *);