Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1669 insertions, 0 deletions

diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
new file mode 100644
index 00000000000..4d8b165bfa4
--- /dev/null
+++ b/arch/um/drivers/ubd_kern.c
@@ -0,0 +1,1669 @@
+/* 
+ * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+ * Licensed under the GPL
+ */
+
+/* 2001-09-28...2002-04-17
+ * Partition stuff by James_McMechan@hotmail.com
+ * old style ubd by setting UBD_SHIFT to 0
+ * 2002-09-27...2002-10-18 massive tinkering for 2.5
+ * partitions have changed in 2.5
+ * 2003-01-29 more tinkering for 2.5.59-1
+ * This should now address the sysfs problems and has
+ * the symlink for devfs to allow for booting with
+ * the common /dev/ubd/discX/... names rather than
+ * only /dev/ubdN/discN this version also has lots of
+ * clean ups preparing for ubd-many.
+ * James McMechan
+ */
+
+#define MAJOR_NR UBD_MAJOR
+#define UBD_SHIFT 4
+
+#include "linux/config.h"
+#include "linux/module.h"
+#include "linux/blkdev.h"
+#include "linux/hdreg.h"
+#include "linux/init.h"
+#include "linux/devfs_fs_kernel.h"
+#include "linux/cdrom.h"
+#include "linux/proc_fs.h"
+#include "linux/ctype.h"
+#include "linux/capability.h"
+#include "linux/mm.h"
+#include "linux/vmalloc.h"
+#include "linux/blkpg.h"
+#include "linux/genhd.h"
+#include "linux/spinlock.h"
+#include "asm/segment.h"
+#include "asm/uaccess.h"
+#include "asm/irq.h"
+#include "asm/types.h"
+#include "asm/tlbflush.h"
+#include "user_util.h"
+#include "mem_user.h"
+#include "kern_util.h"
+#include "kern.h"
+#include "mconsole_kern.h"
+#include "init.h"
+#include "irq_user.h"
+#include "irq_kern.h"
+#include "ubd_user.h"
+#include "2_5compat.h"
+#include "os.h"
+#include "mem.h"
+#include "mem_kern.h"
+#include "cow.h"
+
+enum ubd_req { UBD_READ, UBD_WRITE, UBD_MMAP };
+
+struct io_thread_req {
+	enum ubd_req op;
+	int fds[2];
+	unsigned long offsets[2];
+	unsigned long long offset;
+	unsigned long length;
+	char *buffer;
+	int sectorsize;
+	unsigned long sector_mask;
+	unsigned long long cow_offset;
+	unsigned long bitmap_words[2];
+	int map_fd;
+	unsigned long long map_offset;
+	int error;
+};
+
+extern int open_ubd_file(char *file, struct openflags *openflags,
+			 char **backing_file_out, int *bitmap_offset_out,
+			 unsigned long *bitmap_len_out, int *data_offset_out,
+			 int *create_cow_out);
+extern int create_cow_file(char *cow_file, char *backing_file,
+			   struct openflags flags, int sectorsize,
+			   int alignment, int *bitmap_offset_out,
+			   unsigned long *bitmap_len_out,
+			   int *data_offset_out);
+extern int read_cow_bitmap(int fd, void *buf, int offset, int len);
+extern void do_io(struct io_thread_req *req);
+
+static inline int ubd_test_bit(__u64 bit, unsigned char *data)
+{
+	__u64 n;
+	int bits, off;
+
+	bits = sizeof(data[0]) * 8;
+	n = bit / bits;
+	off = bit % bits;
+	return((data[n] & (1 << off)) != 0);
+}
+
+static inline void ubd_set_bit(__u64 bit, unsigned char *data)
+{
+	__u64 n;
+	int bits, off;
+
+	bits = sizeof(data[0]) * 8;
+	n = bit / bits;
+	off = bit % bits;
+	data[n] |= (1 << off);
+}
+/*End stuff from ubd_user.h*/
+
+#define DRIVER_NAME "uml-blkdev"
+
+static DEFINE_SPINLOCK(ubd_io_lock);
+static DEFINE_SPINLOCK(ubd_lock);
+
+static void (*do_ubd)(void);
+
+static int ubd_open(struct inode * inode, struct file * filp);
+static int ubd_release(struct inode * inode, struct file * file);
+static int ubd_ioctl(struct inode * inode, struct file * file,
+		     unsigned int cmd, unsigned long arg);
+
+#define MAX_DEV (8)
+
+/* Changed in early boot */
+static int ubd_do_mmap = 0;
+#define UBD_MMAP_BLOCK_SIZE PAGE_SIZE
+
+static struct block_device_operations ubd_blops = {
+        .owner		= THIS_MODULE,
+        .open		= ubd_open,
+        .release	= ubd_release,
+        .ioctl		= ubd_ioctl,
+};
+
+/* Protected by the queue_lock */
+static request_queue_t *ubd_queue;
+
+/* Protected by ubd_lock */
+static int fake_major = MAJOR_NR;
+
+static struct gendisk *ubd_gendisk[MAX_DEV];
+static struct gendisk *fake_gendisk[MAX_DEV];
+ 
+#ifdef CONFIG_BLK_DEV_UBD_SYNC
+#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
+					 .cl = 1 })
+#else
+#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
+					 .cl = 1 })
+#endif
+
+/* Not protected - changed only in ubd_setup_common and then only to
+ * to enable O_SYNC.
+ */
+static struct openflags global_openflags = OPEN_FLAGS;
+
+struct cow {
+	char *file;
+	int fd;
+	unsigned long *bitmap;
+	unsigned long bitmap_len;
+	int bitmap_offset;
+        int data_offset;
+};
+
+struct ubd {
+	char *file;
+	int count;
+	int fd;
+	__u64 size;
+	struct openflags boot_openflags;
+	struct openflags openflags;
+	int no_cow;
+	struct cow cow;
+	struct platform_device pdev;
+
+	int map_writes;
+	int map_reads;
+	int nomap_writes;
+	int nomap_reads;
+	int write_maps;
+};
+
+#define DEFAULT_COW { \
+	.file =			NULL, \
+        .fd =			-1, \
+        .bitmap =		NULL, \
+	.bitmap_offset =	0, \
+        .data_offset =		0, \
+}
+
+#define DEFAULT_UBD { \
+	.file = 		NULL, \
+	.count =		0, \
+	.fd =			-1, \
+	.size =			-1, \
+	.boot_openflags =	OPEN_FLAGS, \
+	.openflags =		OPEN_FLAGS, \
+        .no_cow =               0, \
+        .cow =			DEFAULT_COW, \
+	.map_writes		= 0, \
+	.map_reads		= 0, \
+	.nomap_writes		= 0, \
+	.nomap_reads		= 0, \
+	.write_maps		= 0, \
+}
+
+struct ubd ubd_dev[MAX_DEV] = { [ 0 ... MAX_DEV - 1 ] = DEFAULT_UBD };
+
+static int ubd0_init(void)
+{
+	struct ubd *dev = &ubd_dev[0];
+
+	if(dev->file == NULL)
+		dev->file = "root_fs";
+	return(0);
+}
+
+__initcall(ubd0_init);
+
+/* Only changed by fake_ide_setup which is a setup */
+static int fake_ide = 0;
+static struct proc_dir_entry *proc_ide_root = NULL;
+static struct proc_dir_entry *proc_ide = NULL;
+
+static void make_proc_ide(void)
+{
+	proc_ide_root = proc_mkdir("ide", NULL);
+	proc_ide = proc_mkdir("ide0", proc_ide_root);
+}
+
+static int proc_ide_read_media(char *page, char **start, off_t off, int count,
+			       int *eof, void *data)
+{
+	int len;
+
+	strcpy(page, "disk\n");
+	len = strlen("disk\n");
+	len -= off;
+	if (len < count){
+		*eof = 1;
+		if (len <= 0) return 0;
+	}
+	else len = count;
+	*start = page + off;
+	return len;
+}
+
+static void make_ide_entries(char *dev_name)
+{
+	struct proc_dir_entry *dir, *ent;
+	char name[64];
+
+	if(proc_ide_root == NULL) make_proc_ide();
+
+	dir = proc_mkdir(dev_name, proc_ide);
+	if(!dir) return;
+
+	ent = create_proc_entry("media", S_IFREG|S_IRUGO, dir);
+	if(!ent) return;
+	ent->nlink = 1;
+	ent->data = NULL;
+	ent->read_proc = proc_ide_read_media;
+	ent->write_proc = NULL;
+	sprintf(name,"ide0/%s", dev_name);
+	proc_symlink(dev_name, proc_ide_root, name);
+}
+
+static int fake_ide_setup(char *str)
+{
+	fake_ide = 1;
+	return(1);
+}
+
+__setup("fake_ide", fake_ide_setup);
+
+__uml_help(fake_ide_setup,
+"fake_ide\n"
+"    Create ide0 entries that map onto ubd devices.\n\n"
+);
+
+static int parse_unit(char **ptr)
+{
+	char *str = *ptr, *end;
+	int n = -1;
+
+	if(isdigit(*str)) {
+		n = simple_strtoul(str, &end, 0);
+		if(end == str)
+			return(-1);
+		*ptr = end;
+	}
+	else if (('a' <= *str) && (*str <= 'h')) {
+		n = *str - 'a';
+		str++;
+		*ptr = str;
+	}
+	return(n);
+}
+
+static int ubd_setup_common(char *str, int *index_out)
+{
+	struct ubd *dev;
+	struct openflags flags = global_openflags;
+	char *backing_file;
+	int n, err, i;
+
+	if(index_out) *index_out = -1;
+	n = *str;
+	if(n == '='){
+		char *end;
+		int major;
+
+		str++;
+		if(!strcmp(str, "mmap")){
+			CHOOSE_MODE(printk("mmap not supported by the ubd "
+					   "driver in tt mode\n"),
+				    ubd_do_mmap = 1);
+			return(0);
+		}
+
+		if(!strcmp(str, "sync")){
+			global_openflags = of_sync(global_openflags);
+			return(0);
+		}
+		major = simple_strtoul(str, &end, 0);
+		if((*end != '\0') || (end == str)){
+			printk(KERN_ERR 
+			       "ubd_setup : didn't parse major number\n");
+			return(1);
+		}
+
+		err = 1;
+ 		spin_lock(&ubd_lock);
+ 		if(fake_major != MAJOR_NR){
+ 			printk(KERN_ERR "Can't assign a fake major twice\n");
+ 			goto out1;
+ 		}
+ 
+ 		fake_major = major;
+
+		printk(KERN_INFO "Setting extra ubd major number to %d\n",
+		       major);
+ 		err = 0;
+ 	out1:
+ 		spin_unlock(&ubd_lock);
+		return(err);
+	}
+
+	n = parse_unit(&str);
+	if(n < 0){
+		printk(KERN_ERR "ubd_setup : couldn't parse unit number "
+		       "'%s'\n", str);
+		return(1);
+	}
+	if(n >= MAX_DEV){
+		printk(KERN_ERR "ubd_setup : index %d out of range "
+		       "(%d devices, from 0 to %d)\n", n, MAX_DEV, MAX_DEV - 1);
+		return(1);
+	}
+
+	err = 1;
+	spin_lock(&ubd_lock);
+
+	dev = &ubd_dev[n];
+	if(dev->file != NULL){
+		printk(KERN_ERR "ubd_setup : device already configured\n");
+		goto out;
+	}
+
+	if (index_out)
+		*index_out = n;
+
+	for (i = 0; i < 4; i++) {
+		switch (*str) {
+		case 'r':
+			flags.w = 0;
+			break;
+		case 's':
+			flags.s = 1;
+			break;
+		case 'd':
+			dev->no_cow = 1;
+			break;
+		case '=':
+			str++;
+			goto break_loop;
+		default:
+			printk(KERN_ERR "ubd_setup : Expected '=' or flag letter (r,s or d)\n");
+			goto out;
+		}
+		str++;
+	}
+
+        if (*str == '=')
+		printk(KERN_ERR "ubd_setup : Too many flags specified\n");
+        else
+		printk(KERN_ERR "ubd_setup : Expected '='\n");
+	goto out;
+
+break_loop:
+	err = 0;
+	backing_file = strchr(str, ',');
+
+	if (!backing_file) {
+		backing_file = strchr(str, ':');
+	}
+
+	if(backing_file){
+		if(dev->no_cow)
+			printk(KERN_ERR "Can't specify both 'd' and a "
+			       "cow file\n");
+		else {
+			*backing_file = '\0';
+			backing_file++;
+		}
+	}
+	dev->file = str;
+	dev->cow.file = backing_file;
+	dev->boot_openflags = flags;
+out:
+	spin_unlock(&ubd_lock);
+	return(err);
+}
+
+static int ubd_setup(char *str)
+{
+	ubd_setup_common(str, NULL);
+	return(1);
+}
+
+__setup("ubd", ubd_setup);
+__uml_help(ubd_setup,
+"ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
+"    This is used to associate a device with a file in the underlying\n"
+"    filesystem. When specifying two filenames, the first one is the\n"
+"    COW name and the second is the backing file name. As separator you can\n"
+"    use either a ':' or a ',': the first one allows writing things like;\n"
+"	ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
+"    while with a ',' the shell would not expand the 2nd '~'.\n"
+"    When using only one filename, UML will detect whether to thread it like\n"
+"    a COW file or a backing file. To override this detection, add the 'd'\n"
+"    flag:\n"
+"	ubd0d=BackingFile\n"
+"    Usually, there is a filesystem in the file, but \n"
+"    that's not required. Swap devices containing swap files can be\n"
+"    specified like this. Also, a file which doesn't contain a\n"
+"    filesystem can have its contents read in the virtual \n"
+"    machine by running 'dd' on the device. <n> must be in the range\n"
+"    0 to 7. Appending an 'r' to the number will cause that device\n"
+"    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
+"    an 's' will cause data to be written to disk on the host immediately.\n\n"
+);
+
+static int udb_setup(char *str)
+{
+	printk("udb%s specified on command line is almost certainly a ubd -> "
+	       "udb TYPO\n", str);
+	return(1);
+}
+
+__setup("udb", udb_setup);
+__uml_help(udb_setup,
+"udb\n"
+"    This option is here solely to catch ubd -> udb typos, which can be\n\n"
+"    to impossible to catch visually unless you specifically look for\n\n"
+"    them.  The only result of any option starting with 'udb' is an error\n\n"
+"    in the boot output.\n\n"
+);
+
+static int fakehd_set = 0;
+static int fakehd(char *str)
+{
+	printk(KERN_INFO "fakehd : Changing ubd name to \"hd\".\n");
+	fakehd_set = 1;
+	return 1;
+}
+
+__setup("fakehd", fakehd);
+__uml_help(fakehd,
+"fakehd\n"
+"    Change the ubd device name to \"hd\".\n\n"
+);
+
+static void do_ubd_request(request_queue_t * q);
+
+/* Only changed by ubd_init, which is an initcall. */
+int thread_fd = -1;
+
+/* Changed by ubd_handler, which is serialized because interrupts only
+ * happen on CPU 0.
+ */
+int intr_count = 0;
+
+/* call ubd_finish if you need to serialize */
+static void __ubd_finish(struct request *req, int error)
+{
+	int nsect;
+
+	if(error){
+		end_request(req, 0);
+		return;
+	}
+	nsect = req->current_nr_sectors;
+	req->sector += nsect;
+	req->buffer += nsect << 9;
+	req->errors = 0;
+	req->nr_sectors -= nsect;
+	req->current_nr_sectors = 0;
+	end_request(req, 1);
+}
+
+static inline void ubd_finish(struct request *req, int error)
+{
+ 	spin_lock(&ubd_io_lock);
+	__ubd_finish(req, error);
+	spin_unlock(&ubd_io_lock);
+}
+
+/* Called without ubd_io_lock held */
+static void ubd_handler(void)
+{
+	struct io_thread_req req;
+	struct request *rq = elv_next_request(ubd_queue);
+	int n, err;
+
+	do_ubd = NULL;
+	intr_count++;
+	n = os_read_file(thread_fd, &req, sizeof(req));
+	if(n != sizeof(req)){
+		printk(KERN_ERR "Pid %d - spurious interrupt in ubd_handler, "
+		       "err = %d\n", os_getpid(), -n);
+		spin_lock(&ubd_io_lock);
+		end_request(rq, 0);
+		spin_unlock(&ubd_io_lock);
+		return;
+	}
+        
+	if((req.op != UBD_MMAP) &&
+	   ((req.offset != ((__u64) (rq->sector)) << 9) ||
+	    (req.length != (rq->current_nr_sectors) << 9)))
+		panic("I/O op mismatch");
+	
+	if(req.map_fd != -1){
+		err = physmem_subst_mapping(req.buffer, req.map_fd,
+					    req.map_offset, 1);
+		if(err)
+			printk("ubd_handler - physmem_subst_mapping failed, "
+			       "err = %d\n", -err);
+	}
+
+	ubd_finish(rq, req.error);
+	reactivate_fd(thread_fd, UBD_IRQ);	
+	do_ubd_request(ubd_queue);
+}
+
+static irqreturn_t ubd_intr(int irq, void *dev, struct pt_regs *unused)
+{
+	ubd_handler();
+	return(IRQ_HANDLED);
+}
+
+/* Only changed by ubd_init, which is an initcall. */
+static int io_pid = -1;
+
+void kill_io_thread(void)
+{
+	if(io_pid != -1) 
+		os_kill_process(io_pid, 1);
+}
+
+__uml_exitcall(kill_io_thread);
+
+static int ubd_file_size(struct ubd *dev, __u64 *size_out)
+{
+	char *file;
+
+	file = dev->cow.file ? dev->cow.file : dev->file;
+	return(os_file_size(file, size_out));
+}
+
+static void ubd_close(struct ubd *dev)
+{
+	if(ubd_do_mmap)
+		physmem_forget_descriptor(dev->fd);
+	os_close_file(dev->fd);
+	if(dev->cow.file == NULL)
+		return;
+
+	if(ubd_do_mmap)
+		physmem_forget_descriptor(dev->cow.fd);
+	os_close_file(dev->cow.fd);
+	vfree(dev->cow.bitmap);
+	dev->cow.bitmap = NULL;
+}
+
+static int ubd_open_dev(struct ubd *dev)
+{
+	struct openflags flags;
+	char **back_ptr;
+	int err, create_cow, *create_ptr;
+
+	dev->openflags = dev->boot_openflags;
+	create_cow = 0;
+	create_ptr = (dev->cow.file != NULL) ? &create_cow : NULL;
+	back_ptr = dev->no_cow ? NULL : &dev->cow.file;
+	dev->fd = open_ubd_file(dev->file, &dev->openflags, back_ptr,
+				&dev->cow.bitmap_offset, &dev->cow.bitmap_len, 
+				&dev->cow.data_offset, create_ptr);
+
+	if((dev->fd == -ENOENT) && create_cow){
+		dev->fd = create_cow_file(dev->file, dev->cow.file, 
+					  dev->openflags, 1 << 9, PAGE_SIZE,
+					  &dev->cow.bitmap_offset, 
+					  &dev->cow.bitmap_len,
+					  &dev->cow.data_offset);
+		if(dev->fd >= 0){
+			printk(KERN_INFO "Creating \"%s\" as COW file for "
+			       "\"%s\"\n", dev->file, dev->cow.file);
+		}
+	}
+
+	if(dev->fd < 0){
+		printk("Failed to open '%s', errno = %d\n", dev->file,
+		       -dev->fd);
+		return(dev->fd);
+	}
+
+	if(dev->cow.file != NULL){
+		err = -ENOMEM;
+		dev->cow.bitmap = (void *) vmalloc(dev->cow.bitmap_len);
+		if(dev->cow.bitmap == NULL){
+			printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
+			goto error;
+		}
+		flush_tlb_kernel_vm();
+
+		err = read_cow_bitmap(dev->fd, dev->cow.bitmap, 
+				      dev->cow.bitmap_offset, 
+				      dev->cow.bitmap_len);
+		if(err < 0)
+			goto error;
+
+		flags = dev->openflags;
+		flags.w = 0;
+		err = open_ubd_file(dev->cow.file, &flags, NULL, NULL, NULL, 
+				    NULL, NULL);
+		if(err < 0) goto error;
+		dev->cow.fd = err;
+	}
+	return(0);
+ error:
+	os_close_file(dev->fd);
+	return(err);
+}
+
+static int ubd_new_disk(int major, u64 size, int unit,
+			struct gendisk **disk_out)
+			
+{
+	struct gendisk *disk;
+	char from[sizeof("ubd/nnnnn\0")], to[sizeof("discnnnnn/disc\0")];
+	int err;
+
+	disk = alloc_disk(1 << UBD_SHIFT);
+	if(disk == NULL)
+		return(-ENOMEM);
+
+	disk->major = major;
+	disk->first_minor = unit << UBD_SHIFT;
+	disk->fops = &ubd_blops;
+	set_capacity(disk, size / 512);
+	if(major == MAJOR_NR){
+		sprintf(disk->disk_name, "ubd%c", 'a' + unit);
+		sprintf(disk->devfs_name, "ubd/disc%d", unit);
+		sprintf(from, "ubd/%d", unit);
+		sprintf(to, "disc%d/disc", unit);
+		err = devfs_mk_symlink(from, to);
+		if(err)
+			printk("ubd_new_disk failed to make link from %s to "
+			       "%s, error = %d\n", from, to, err);
+	}
+	else {
+		sprintf(disk->disk_name, "ubd_fake%d", unit);
+		sprintf(disk->devfs_name, "ubd_fake/disc%d", unit);
+	}
+
+	/* sysfs register (not for ide fake devices) */
+	if (major == MAJOR_NR) {
+		ubd_dev[unit].pdev.id   = unit;
+		ubd_dev[unit].pdev.name = DRIVER_NAME;
+		platform_device_register(&ubd_dev[unit].pdev);
+		disk->driverfs_dev = &ubd_dev[unit].pdev.dev;
+	}
+
+	disk->private_data = &ubd_dev[unit];
+	disk->queue = ubd_queue;
+	add_disk(disk);
+
+	*disk_out = disk;
+	return 0;
+}
+
+#define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
+
+static int ubd_add(int n)
+{
+	struct ubd *dev = &ubd_dev[n];
+	int err;
+
+	if(dev->file == NULL)
+		return(-ENODEV);
+
+	if (ubd_open_dev(dev))
+		return(-ENODEV);
+
+	err = ubd_file_size(dev, &dev->size);
+	if(err < 0)
+		return(err);
+
+	dev->size = ROUND_BLOCK(dev->size);
+
+	err = ubd_new_disk(MAJOR_NR, dev->size, n, &ubd_gendisk[n]);
+	if(err) 
+		return(err);
+ 
+	if(fake_major != MAJOR_NR)
+		ubd_new_disk(fake_major, dev->size, n, 
+			     &fake_gendisk[n]);
+
+	/* perhaps this should also be under the "if (fake_major)" above */
+	/* using the fake_disk->disk_name and also the fakehd_set name */
+	if (fake_ide)
+		make_ide_entries(ubd_gendisk[n]->disk_name);
+
+	ubd_close(dev);
+	return 0;
+}
+
+static int ubd_config(char *str)
+{
+	int n, err;
+
+	str = uml_strdup(str);
+	if(str == NULL){
+		printk(KERN_ERR "ubd_config failed to strdup string\n");
+		return(1);
+	}
+	err = ubd_setup_common(str, &n);
+	if(err){
+		kfree(str);
+		return(-1);
+	}
+	if(n == -1) return(0);
+
+ 	spin_lock(&ubd_lock);
+	err = ubd_add(n);
+	if(err)
+		ubd_dev[n].file = NULL;
+ 	spin_unlock(&ubd_lock);
+
+	return(err);
+}
+
+static int ubd_get_config(char *name, char *str, int size, char **error_out)
+{
+	struct ubd *dev;
+	int n, len = 0;
+
+	n = parse_unit(&name);
+	if((n >= MAX_DEV) || (n < 0)){
+		*error_out = "ubd_get_config : device number out of range";
+		return(-1);
+	}
+
+	dev = &ubd_dev[n];
+	spin_lock(&ubd_lock);
+
+	if(dev->file == NULL){
+		CONFIG_CHUNK(str, size, len, "", 1);
+		goto out;
+	}
+
+	CONFIG_CHUNK(str, size, len, dev->file, 0);
+
+	if(dev->cow.file != NULL){
+		CONFIG_CHUNK(str, size, len, ",", 0);
+		CONFIG_CHUNK(str, size, len, dev->cow.file, 1);
+	}
+	else CONFIG_CHUNK(str, size, len, "", 1);
+
+ out:
+	spin_unlock(&ubd_lock);
+	return(len);
+}
+
+static int ubd_remove(char *str)
+{
+	struct ubd *dev;
+	int n, err = -ENODEV;
+
+	n = parse_unit(&str);
+
+	if((n < 0) || (n >= MAX_DEV))
+		return(err);
+
+	dev = &ubd_dev[n];
+	if(dev->count > 0)
+		return(-EBUSY);	/* you cannot remove a open disk */
+
+	err = 0;
+ 	spin_lock(&ubd_lock);
+
+	if(ubd_gendisk[n] == NULL)
+		goto out;
+
+	del_gendisk(ubd_gendisk[n]);
+	put_disk(ubd_gendisk[n]);
+	ubd_gendisk[n] = NULL;
+
+	if(fake_gendisk[n] != NULL){
+		del_gendisk(fake_gendisk[n]);
+		put_disk(fake_gendisk[n]);
+		fake_gendisk[n] = NULL;
+	}
+
+	platform_device_unregister(&dev->pdev);
+	*dev = ((struct ubd) DEFAULT_UBD);
+	err = 0;
+ out:
+ 	spin_unlock(&ubd_lock);
+	return(err);
+}
+
+static struct mc_device ubd_mc = {
+	.name		= "ubd",
+	.config		= ubd_config,
+ 	.get_config	= ubd_get_config,
+	.remove		= ubd_remove,
+};
+
+static int ubd_mc_init(void)
+{
+	mconsole_register_dev(&ubd_mc);
+	return 0;
+}
+
+__initcall(ubd_mc_init);
+
+static struct device_driver ubd_driver = {
+	.name  = DRIVER_NAME,
+	.bus   = &platform_bus_type,
+};
+
+int ubd_init(void)
+{
+        int i;
+
+	devfs_mk_dir("ubd");
+	if (register_blkdev(MAJOR_NR, "ubd"))
+		return -1;
+
+	ubd_queue = blk_init_queue(do_ubd_request, &ubd_io_lock);
+	if (!ubd_queue) {
+		unregister_blkdev(MAJOR_NR, "ubd");
+		return -1;
+	}
+		
+	if (fake_major != MAJOR_NR) {
+		char name[sizeof("ubd_nnn\0")];
+
+		snprintf(name, sizeof(name), "ubd_%d", fake_major);
+		devfs_mk_dir(name);
+		if (register_blkdev(fake_major, "ubd"))
+			return -1;
+	}
+	driver_register(&ubd_driver);
+	for (i = 0; i < MAX_DEV; i++) 
+		ubd_add(i);
+	return 0;
+}
+
+late_initcall(ubd_init);
+
+int ubd_driver_init(void){
+	unsigned long stack;
+	int err;
+
+	/* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
+	if(global_openflags.s){
+		printk(KERN_INFO "ubd: Synchronous mode\n");
+		/* Letting ubd=sync be like using ubd#s= instead of ubd#= is
+		 * enough. So use anyway the io thread. */
+	}
+	stack = alloc_stack(0, 0);
+	io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *), 
+				 &thread_fd);
+	if(io_pid < 0){
+		printk(KERN_ERR 
+		       "ubd : Failed to start I/O thread (errno = %d) - "
+		       "falling back to synchronous I/O\n", -io_pid);
+		io_pid = -1;
+		return(0);
+	}
+	err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr, 
+			     SA_INTERRUPT, "ubd", ubd_dev);
+	if(err != 0)
+		printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
+	return(err);
+}
+
+device_initcall(ubd_driver_init);
+
+static int ubd_open(struct inode *inode, struct file *filp)
+{
+	struct gendisk *disk = inode->i_bdev->bd_disk;
+	struct ubd *dev = disk->private_data;
+	int err = 0;
+
+	if(dev->count == 0){
+		err = ubd_open_dev(dev);
+		if(err){
+			printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
+			       disk->disk_name, dev->file, -err);
+			goto out;
+		}
+	}
+	dev->count++;
+	if((filp->f_mode & FMODE_WRITE) && !dev->openflags.w){
+	        if(--dev->count == 0) ubd_close(dev);
+	        err = -EROFS;
+	}
+ out:
+	return(err);
+}
+
+static int ubd_release(struct inode * inode, struct file * file)
+{
+	struct gendisk *disk = inode->i_bdev->bd_disk;
+	struct ubd *dev = disk->private_data;
+
+	if(--dev->count == 0)
+		ubd_close(dev);
+	return(0);
+}
+
+static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
+			  __u64 *cow_offset, unsigned long *bitmap,
+			  __u64 bitmap_offset, unsigned long *bitmap_words,
+			  __u64 bitmap_len)
+{
+	__u64 sector = io_offset >> 9;
+	int i, update_bitmap = 0;
+
+	for(i = 0; i < length >> 9; i++){
+		if(cow_mask != NULL)
+			ubd_set_bit(i, (unsigned char *) cow_mask);
+		if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
+			continue;
+
+		update_bitmap = 1;
+		ubd_set_bit(sector + i, (unsigned char *) bitmap);
+	}
+
+	if(!update_bitmap)
+		return;
+
+	*cow_offset = sector / (sizeof(unsigned long) * 8);
+
+	/* This takes care of the case where we're exactly at the end of the
+	 * device, and *cow_offset + 1 is off the end.  So, just back it up
+	 * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
+	 * for the original diagnosis.
+	 */
+	if(*cow_offset == ((bitmap_len + sizeof(unsigned long) - 1) /
+			   sizeof(unsigned long) - 1))
+		(*cow_offset)--;
+
+	bitmap_words[0] = bitmap[*cow_offset];
+	bitmap_words[1] = bitmap[*cow_offset + 1];
+
+	*cow_offset *= sizeof(unsigned long);
+	*cow_offset += bitmap_offset;
+}
+
+static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
+		       __u64 bitmap_offset, __u64 bitmap_len)
+{
+	__u64 sector = req->offset >> 9;
+	int i;
+
+	if(req->length > (sizeof(req->sector_mask) * 8) << 9)
+		panic("Operation too long");
+
+	if(req->op == UBD_READ) {
+		for(i = 0; i < req->length >> 9; i++){
+			if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
+				ubd_set_bit(i, (unsigned char *) 
+					    &req->sector_mask);
+                }
+	}
+	else cowify_bitmap(req->offset, req->length, &req->sector_mask,
+			   &req->cow_offset, bitmap, bitmap_offset,
+			   req->bitmap_words, bitmap_len);
+}
+
+static int mmap_fd(struct request *req, struct ubd *dev, __u64 offset)
+{
+	__u64 sector;
+	unsigned char *bitmap;
+	int bit, i;
+
+	/* mmap must have been requested on the command line */
+	if(!ubd_do_mmap)
+		return(-1);
+
+	/* The buffer must be page aligned */
+	if(((unsigned long) req->buffer % UBD_MMAP_BLOCK_SIZE) != 0)
+		return(-1);
+
+	/* The request must be a page long */
+	if((req->current_nr_sectors << 9) != PAGE_SIZE)
+		return(-1);
+
+	if(dev->cow.file == NULL)
+		return(dev->fd);
+
+	sector = offset >> 9;
+	bitmap = (unsigned char *) dev->cow.bitmap;
+	bit = ubd_test_bit(sector, bitmap);
+
+	for(i = 1; i < req->current_nr_sectors; i++){
+		if(ubd_test_bit(sector + i, bitmap) != bit)
+			return(-1);
+	}
+
+	if(bit || (rq_data_dir(req) == WRITE))
+		offset += dev->cow.data_offset;
+
+	/* The data on disk must be page aligned */
+	if((offset % UBD_MMAP_BLOCK_SIZE) != 0)
+		return(-1);
+
+	return(bit ? dev->fd : dev->cow.fd);
+}
+
+static int prepare_mmap_request(struct ubd *dev, int fd, __u64 offset,
+				struct request *req,
+				struct io_thread_req *io_req)
+{
+	int err;
+
+	if(rq_data_dir(req) == WRITE){
+		/* Writes are almost no-ops since the new data is already in the
+		 * host page cache
+		 */
+		dev->map_writes++;
+		if(dev->cow.file != NULL)
+			cowify_bitmap(io_req->offset, io_req->length,
+				      &io_req->sector_mask, &io_req->cow_offset,
+				      dev->cow.bitmap, dev->cow.bitmap_offset,
+				      io_req->bitmap_words,
+				      dev->cow.bitmap_len);
+	}
+	else {
+		int w;
+
+		if((dev->cow.file != NULL) && (fd == dev->cow.fd))
+			w = 0;
+		else w = dev->openflags.w;
+
+		if((dev->cow.file != NULL) && (fd == dev->fd))
+			offset += dev->cow.data_offset;
+
+		err = physmem_subst_mapping(req->buffer, fd, offset, w);
+		if(err){
+			printk("physmem_subst_mapping failed, err = %d\n",
+			       -err);
+			return(1);
+		}
+		dev->map_reads++;
+	}
+	io_req->op = UBD_MMAP;
+	io_req->buffer = req->buffer;
+	return(0);
+}
+
+/* Called with ubd_io_lock held */
+static int prepare_request(struct request *req, struct io_thread_req *io_req)
+{
+	struct gendisk *disk = req->rq_disk;
+	struct ubd *dev = disk->private_data;
+	__u64 offset;
+	int len, fd;
+
+	if(req->rq_status == RQ_INACTIVE) return(1);
+
+	if((rq_data_dir(req) == WRITE) && !dev->openflags.w){
+		printk("Write attempted on readonly ubd device %s\n", 
+		       disk->disk_name);
+		end_request(req, 0);
+		return(1);
+	}
+
+	offset = ((__u64) req->sector) << 9;
+	len = req->current_nr_sectors << 9;
+
+	io_req->fds[0] = (dev->cow.file != NULL) ? dev->cow.fd : dev->fd;
+	io_req->fds[1] = dev->fd;
+	io_req->map_fd = -1;
+	io_req->cow_offset = -1;
+	io_req->offset = offset;
+	io_req->length = len;
+	io_req->error = 0;
+	io_req->sector_mask = 0;
+
+	fd = mmap_fd(req, dev, io_req->offset);
+	if(fd > 0){
+		/* If mmapping is otherwise OK, but the first access to the
+		 * page is a write, then it's not mapped in yet.  So we have
+		 * to write the data to disk first, then we can map the disk
+		 * page in and continue normally from there.
+		 */
+		if((rq_data_dir(req) == WRITE) && !is_remapped(req->buffer)){
+			io_req->map_fd = dev->fd;
+			io_req->map_offset = io_req->offset +
+				dev->cow.data_offset;
+			dev->write_maps++;
+		}
+		else return(prepare_mmap_request(dev, fd, io_req->offset, req,
+						 io_req));
+	}
+
+	if(rq_data_dir(req) == READ)
+		dev->nomap_reads++;
+	else dev->nomap_writes++;
+
+	io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
+	io_req->offsets[0] = 0;
+	io_req->offsets[1] = dev->cow.data_offset;
+	io_req->buffer = req->buffer;
+	io_req->sectorsize = 1 << 9;
+
+	if(dev->cow.file != NULL)
+		cowify_req(io_req, dev->cow.bitmap, dev->cow.bitmap_offset,
+			   dev->cow.bitmap_len);
+
+	return(0);
+}
+
+/* Called with ubd_io_lock held */
+static void do_ubd_request(request_queue_t *q)
+{
+	struct io_thread_req io_req;
+	struct request *req;
+	int err, n;
+
+	if(thread_fd == -1){
+		while((req = elv_next_request(q)) != NULL){
+			err = prepare_request(req, &io_req);
+			if(!err){
+				do_io(&io_req);
+				__ubd_finish(req, io_req.error);
+			}
+		}
+	}
+	else {
+		if(do_ubd || (req = elv_next_request(q)) == NULL)
+			return;
+		err = prepare_request(req, &io_req);
+		if(!err){
+			do_ubd = ubd_handler;
+			n = os_write_file(thread_fd, (char *) &io_req,
+					 sizeof(io_req));
+			if(n != sizeof(io_req))
+				printk("write to io thread failed, "
+				       "errno = %d\n", -n);
+		}
+	}
+}
+
+static int ubd_ioctl(struct inode * inode, struct file * file,
+		     unsigned int cmd, unsigned long arg)
+{
+	struct hd_geometry __user *loc = (struct hd_geometry __user *) arg;
+	struct ubd *dev = inode->i_bdev->bd_disk->private_data;
+	struct hd_driveid ubd_id = {
+		.cyls		= 0,
+		.heads		= 128,
+		.sectors	= 32,
+	};
+
+	switch (cmd) {
+	        struct hd_geometry g;
+		struct cdrom_volctrl volume;
+	case HDIO_GETGEO:
+		if(!loc) return(-EINVAL);
+		g.heads = 128;
+		g.sectors = 32;
+		g.cylinders = dev->size / (128 * 32 * 512);
+		g.start = get_start_sect(inode->i_bdev);
+		return(copy_to_user(loc, &g, sizeof(g)) ? -EFAULT : 0);
+
+	case HDIO_GET_IDENTITY:
+		ubd_id.cyls = dev->size / (128 * 32 * 512);
+		if(copy_to_user((char __user *) arg, (char *) &ubd_id,
+				 sizeof(ubd_id)))
+			return(-EFAULT);
+		return(0);
+		
+	case CDROMVOLREAD:
+		if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
+			return(-EFAULT);
+		volume.channel0 = 255;
+		volume.channel1 = 255;
+		volume.channel2 = 255;
+		volume.channel3 = 255;
+		if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
+			return(-EFAULT);
+		return(0);
+	}
+	return(-EINVAL);
+}
+
+static int ubd_check_remapped(int fd, unsigned long address, int is_write,
+			      __u64 offset)
+{
+	__u64 bitmap_offset;
+	unsigned long new_bitmap[2];
+	int i, err, n;
+
+	/* If it's not a write access, we can't do anything about it */
+	if(!is_write)
+		return(0);
+
+	/* We have a write */
+	for(i = 0; i < sizeof(ubd_dev) / sizeof(ubd_dev[0]); i++){
+		struct ubd *dev = &ubd_dev[i];
+
+		if((dev->fd != fd) && (dev->cow.fd != fd))
+			continue;
+
+		/* It's a write to a ubd device */
+
+		if(!dev->openflags.w){
+			/* It's a write access on a read-only device - probably
+			 * shouldn't happen.  If the kernel is trying to change
+			 * something with no intention of writing it back out,
+			 * then this message will clue us in that this needs
+			 * fixing
+			 */
+			printk("Write access to mapped page from readonly ubd "
+			       "device %d\n", i);
+			return(0);
+		}
+
+		/* It's a write to a writeable ubd device - it must be COWed
+		 * because, otherwise, the page would have been mapped in
+		 * writeable
+		 */
+
+		if(!dev->cow.file)
+			panic("Write fault on writeable non-COW ubd device %d",
+			      i);
+
+		/* It should also be an access to the backing file since the
+		 * COW pages should be mapped in read-write
+		 */
+
+		if(fd == dev->fd)
+			panic("Write fault on a backing page of ubd "
+			      "device %d\n", i);
+
+		/* So, we do the write, copying the backing data to the COW
+		 * file...
+		 */
+
+		err = os_seek_file(dev->fd, offset + dev->cow.data_offset);
+		if(err < 0)
+			panic("Couldn't seek to %lld in COW file of ubd "
+			      "device %d, err = %d",
+			      offset + dev->cow.data_offset, i, -err);
+
+		n = os_write_file(dev->fd, (void *) address, PAGE_SIZE);
+		if(n != PAGE_SIZE)
+			panic("Couldn't copy data to COW file of ubd "
+			      "device %d, err = %d", i, -n);
+
+		/* ... updating the COW bitmap... */
+
+		cowify_bitmap(offset, PAGE_SIZE, NULL, &bitmap_offset,
+			      dev->cow.bitmap, dev->cow.bitmap_offset,
+			      new_bitmap, dev->cow.bitmap_len);
+
+		err = os_seek_file(dev->fd, bitmap_offset);
+		if(err < 0)
+			panic("Couldn't seek to %lld in COW file of ubd "
+			      "device %d, err = %d", bitmap_offset, i, -err);
+
+		n = os_write_file(dev->fd, new_bitmap, sizeof(new_bitmap));
+		if(n != sizeof(new_bitmap))
+			panic("Couldn't update bitmap  of ubd device %d, "
+			      "err = %d", i, -n);
+
+		/* Maybe we can map the COW page in, and maybe we can't.  If
+		 * it is a pre-V3 COW file, we can't, since the alignment will
+		 * be wrong.  If it is a V3 or later COW file which has been
+		 * moved to a system with a larger page size, then maybe we
+		 * can't, depending on the exact location of the page.
+		 */
+
+		offset += dev->cow.data_offset;
+
+		/* Remove the remapping, putting the original anonymous page
+		 * back.  If the COW file can be mapped in, that is done.
+		 * Otherwise, the COW page is read in.
+		 */
+
+		if(!physmem_remove_mapping((void *) address))
+			panic("Address 0x%lx not remapped by ubd device %d",
+			      address, i);
+		if((offset % UBD_MMAP_BLOCK_SIZE) == 0)
+			physmem_subst_mapping((void *) address, dev->fd,
+					      offset, 1);
+		else {
+			err = os_seek_file(dev->fd, offset);
+			if(err < 0)
+				panic("Couldn't seek to %lld in COW file of "
+				      "ubd device %d, err = %d", offset, i,
+				      -err);
+
+			n = os_read_file(dev->fd, (void *) address, PAGE_SIZE);
+			if(n != PAGE_SIZE)
+				panic("Failed to read page from offset %llx of "
+				      "COW file of ubd device %d, err = %d",
+				      offset, i, -n);
+		}
+
+		return(1);
+	}
+
+	/* It's not a write on a ubd device */
+	return(0);
+}
+
+static struct remapper ubd_remapper = {
+	.list	= LIST_HEAD_INIT(ubd_remapper.list),
+	.proc	= ubd_check_remapped,
+};
+
+static int ubd_remapper_setup(void)
+{
+	if(ubd_do_mmap)
+		register_remapper(&ubd_remapper);
+
+	return(0);
+}
+
+__initcall(ubd_remapper_setup);
+
+static int same_backing_files(char *from_cmdline, char *from_cow, char *cow)
+{
+	struct uml_stat buf1, buf2;
+	int err;
+
+	if(from_cmdline == NULL) return(1);
+	if(!strcmp(from_cmdline, from_cow)) return(1);
+
+	err = os_stat_file(from_cmdline, &buf1);
+	if(err < 0){
+		printk("Couldn't stat '%s', err = %d\n", from_cmdline, -err);
+		return(1);
+	}
+	err = os_stat_file(from_cow, &buf2);
+	if(err < 0){
+		printk("Couldn't stat '%s', err = %d\n", from_cow, -err);
+		return(1);
+	}
+	if((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
+		return(1);
+
+	printk("Backing file mismatch - \"%s\" requested,\n"
+	       "\"%s\" specified in COW header of \"%s\"\n",
+	       from_cmdline, from_cow, cow);
+	return(0);
+}
+
+static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
+{
+	unsigned long modtime;
+	long long actual;
+	int err;
+
+	err = os_file_modtime(file, &modtime);
+	if(err < 0){
+		printk("Failed to get modification time of backing file "
+		       "\"%s\", err = %d\n", file, -err);
+		return(err);
+	}
+
+	err = os_file_size(file, &actual);
+	if(err < 0){
+		printk("Failed to get size of backing file \"%s\", "
+		       "err = %d\n", file, -err);
+		return(err);
+	}
+
+  	if(actual != size){
+		/*__u64 can be a long on AMD64 and with %lu GCC complains; so
+		 * the typecast.*/
+		printk("Size mismatch (%llu vs %llu) of COW header vs backing "
+		       "file\n", (unsigned long long) size, actual);
+		return(-EINVAL);
+	}
+	if(modtime != mtime){
+		printk("mtime mismatch (%ld vs %ld) of COW header vs backing "
+		       "file\n", mtime, modtime);
+		return(-EINVAL);
+	}
+	return(0);
+}
+
+int read_cow_bitmap(int fd, void *buf, int offset, int len)
+{
+	int err;
+
+	err = os_seek_file(fd, offset);
+	if(err < 0)
+		return(err);
+
+	err = os_read_file(fd, buf, len);
+	if(err < 0)
+		return(err);
+
+	return(0);
+}
+
+int open_ubd_file(char *file, struct openflags *openflags,
+		  char **backing_file_out, int *bitmap_offset_out,
+		  unsigned long *bitmap_len_out, int *data_offset_out,
+		  int *create_cow_out)
+{
+	time_t mtime;
+	unsigned long long size;
+	__u32 version, align;
+	char *backing_file;
+	int fd, err, sectorsize, same, mode = 0644;
+
+	fd = os_open_file(file, *openflags, mode);
+	if(fd < 0){
+		if((fd == -ENOENT) && (create_cow_out != NULL))
+			*create_cow_out = 1;
+                if(!openflags->w ||
+                   ((fd != -EROFS) && (fd != -EACCES))) return(fd);
+		openflags->w = 0;
+		fd = os_open_file(file, *openflags, mode);
+		if(fd < 0)
+			return(fd);
+        }
+
+	err = os_lock_file(fd, openflags->w);
+	if(err < 0){
+		printk("Failed to lock '%s', err = %d\n", file, -err);
+		goto out_close;
+	}
+
+	if(backing_file_out == NULL) return(fd);
+
+	err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
+			      &size, &sectorsize, &align, bitmap_offset_out);
+	if(err && (*backing_file_out != NULL)){
+		printk("Failed to read COW header from COW file \"%s\", "
+		       "errno = %d\n", file, -err);
+		goto out_close;
+	}
+	if(err) return(fd);
+
+	if(backing_file_out == NULL) return(fd);
+
+	same = same_backing_files(*backing_file_out, backing_file, file);
+
+	if(!same && !backing_file_mismatch(*backing_file_out, size, mtime)){
+		printk("Switching backing file to '%s'\n", *backing_file_out);
+		err = write_cow_header(file, fd, *backing_file_out,
+				       sectorsize, align, &size);
+		if(err){
+			printk("Switch failed, errno = %d\n", -err);
+			return(err);
+		}
+	}
+	else {
+		*backing_file_out = backing_file;
+		err = backing_file_mismatch(*backing_file_out, size, mtime);
+		if(err) goto out_close;
+	}
+
+	cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
+		  bitmap_len_out, data_offset_out);
+
+        return(fd);
+ out_close:
+	os_close_file(fd);
+	return(err);
+}
+
+int create_cow_file(char *cow_file, char *backing_file, struct openflags flags,
+		    int sectorsize, int alignment, int *bitmap_offset_out,
+		    unsigned long *bitmap_len_out, int *data_offset_out)
+{
+	int err, fd;
+
+	flags.c = 1;
+	fd = open_ubd_file(cow_file, &flags, NULL, NULL, NULL, NULL, NULL);
+	if(fd < 0){
+		err = fd;
+		printk("Open of COW file '%s' failed, errno = %d\n", cow_file,
+		       -err);
+		goto out;
+	}
+
+	err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
+			    bitmap_offset_out, bitmap_len_out,
+			    data_offset_out);
+	if(!err)
+		return(fd);
+	os_close_file(fd);
+ out:
+	return(err);
+}
+
+static int update_bitmap(struct io_thread_req *req)
+{
+	int n;
+
+	if(req->cow_offset == -1)
+		return(0);
+
+	n = os_seek_file(req->fds[1], req->cow_offset);
+	if(n < 0){
+		printk("do_io - bitmap lseek failed : err = %d\n", -n);
+		return(1);
+	}
+
+	n = os_write_file(req->fds[1], &req->bitmap_words,
+		          sizeof(req->bitmap_words));
+	if(n != sizeof(req->bitmap_words)){
+		printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
+		       req->fds[1]);
+		return(1);
+	}
+
+	return(0);
+}
+
+void do_io(struct io_thread_req *req)
+{
+	char *buf;
+	unsigned long len;
+	int n, nsectors, start, end, bit;
+	int err;
+	__u64 off;
+
+	if(req->op == UBD_MMAP){
+		/* Touch the page to force the host to do any necessary IO to
+		 * get it into memory
+		 */
+		n = *((volatile int *) req->buffer);
+		req->error = update_bitmap(req);
+		return;
+	}
+
+	nsectors = req->length / req->sectorsize;
+	start = 0;
+	do {
+		bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
+		end = start;
+		while((end < nsectors) &&
+		      (ubd_test_bit(end, (unsigned char *)
+				    &req->sector_mask) == bit))
+			end++;
+
+		off = req->offset + req->offsets[bit] +
+			start * req->sectorsize;
+		len = (end - start) * req->sectorsize;
+		buf = &req->buffer[start * req->sectorsize];
+
+		err = os_seek_file(req->fds[bit], off);
+		if(err < 0){
+			printk("do_io - lseek failed : err = %d\n", -err);
+			req->error = 1;
+			return;
+		}
+		if(req->op == UBD_READ){
+			n = 0;
+			do {
+				buf = &buf[n];
+				len -= n;
+				n = os_read_file(req->fds[bit], buf, len);
+				if (n < 0) {
+					printk("do_io - read failed, err = %d "
+					       "fd = %d\n", -n, req->fds[bit]);
+					req->error = 1;
+					return;
+				}
+			} while((n < len) && (n != 0));
+			if (n < len) memset(&buf[n], 0, len - n);
+		}
+		else {
+			n = os_write_file(req->fds[bit], buf, len);
+			if(n != len){
+				printk("do_io - write failed err = %d "
+				       "fd = %d\n", -n, req->fds[bit]);
+				req->error = 1;
+				return;
+			}
+		}
+
+		start = end;
+	} while(start < nsectors);
+
+	req->error = update_bitmap(req);
+}
+
+/* Changed in start_io_thread, which is serialized by being called only
+ * from ubd_init, which is an initcall.
+ */
+int kernel_fd = -1;
+
+/* Only changed by the io thread */
+int io_count = 0;
+
+int io_thread(void *arg)
+{
+	struct io_thread_req req;
+	int n;
+
+	ignore_sigwinch_sig();
+	while(1){
+		n = os_read_file(kernel_fd, &req, sizeof(req));
+		if(n != sizeof(req)){
+			if(n < 0)
+				printk("io_thread - read failed, fd = %d, "
+				       "err = %d\n", kernel_fd, -n);
+			else {
+				printk("io_thread - short read, fd = %d, "
+				       "length = %d\n", kernel_fd, n);
+			}
+			continue;
+		}
+		io_count++;
+		do_io(&req);
+		n = os_write_file(kernel_fd, &req, sizeof(req));
+		if(n != sizeof(req))
+			printk("io_thread - write failed, fd = %d, err = %d\n",
+			       kernel_fd, -n);
+	}
+}
+
+/*
+ * Overrides for Emacs so that we follow Linus's tabbing style.
+ * Emacs will notice this stuff at the end of the file and automatically
+ * adjust the settings for this buffer only.  This must remain at the end
+ * of the file.
+ * ---------------------------------------------------------------------------
+ * Local variables:
+ * c-file-style: "linux"
+ * End:
+ */