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 000000000000..4d8b165bfa48
--- /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:
+ */