arch/um/drivers/ubd_kern.c

   1 /*
   2  * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 /* 2001-09-28...2002-04-17
   7  * Partition stuff by James_McMechan@hotmail.com
   8  * old style ubd by setting UBD_SHIFT to 0
   9  * 2002-09-27...2002-10-18 massive tinkering for 2.5
  10  * partitions have changed in 2.5
  11  * 2003-01-29 more tinkering for 2.5.59-1
  12  * This should now address the sysfs problems and has
  13  * the symlink for devfs to allow for booting with
  14  * the common /dev/ubd/discX/... names rather than
  15  * only /dev/ubdN/discN this version also has lots of
  16  * clean ups preparing for ubd-many.
  17  * James McMechan
  18  */
  19
  20 #define UBD_SHIFT 4
  21
  22 #include "linux/kernel.h"
  23 #include "linux/module.h"
  24 #include "linux/blkdev.h"
  25 #include "linux/ata.h"
  26 #include "linux/hdreg.h"
  27 #include "linux/init.h"
  28 #include "linux/cdrom.h"
  29 #include "linux/proc_fs.h"
  30 #include "linux/seq_file.h"
  31 #include "linux/ctype.h"
  32 #include "linux/capability.h"
  33 #include "linux/mm.h"
  34 #include "linux/slab.h"
  35 #include "linux/vmalloc.h"
  36 #include "linux/blkpg.h"
  37 #include "linux/genhd.h"
  38 #include "linux/spinlock.h"
  39 #include "linux/platform_device.h"
  40 #include "linux/scatterlist.h"
  41 #include "asm/segment.h"
  42 #include "asm/uaccess.h"
  43 #include "asm/irq.h"
  44 #include "asm/types.h"
  45 #include "asm/tlbflush.h"
  46 #include "mem_user.h"
  47 #include "kern_util.h"
  48 #include "kern.h"
  49 #include "mconsole_kern.h"
  50 #include "init.h"
  51 #include "irq_user.h"
  52 #include "irq_kern.h"
  53 #include "ubd_user.h"
  54 #include "os.h"
  55 #include "mem.h"
  56 #include "mem_kern.h"
  57 #include "cow.h"
  58
  59 enum ubd_req { UBD_READ, UBD_WRITE };
  60
  61 struct io_thread_req {
  62         struct request *req;
  63         enum ubd_req op;
  64         int fds[2];
  65         unsigned long offsets[2];
  66         unsigned long long offset;
  67         unsigned long length;
  68         char *buffer;
  69         int sectorsize;
  70         unsigned long sector_mask;
  71         unsigned long long cow_offset;
  72         unsigned long bitmap_words[2];
  73         int error;
  74 };
  75
  76 static inline int ubd_test_bit(__u64 bit, unsigned char *data)
  77 {
  78         __u64 n;
  79         int bits, off;
  80
  81         bits = sizeof(data[0]) * 8;
  82         n = bit / bits;
  83         off = bit % bits;
  84         return (data[n] & (1 << off)) != 0;
  85 }
  86
  87 static inline void ubd_set_bit(__u64 bit, unsigned char *data)
  88 {
  89         __u64 n;
  90         int bits, off;
  91
  92         bits = sizeof(data[0]) * 8;
  93         n = bit / bits;
  94         off = bit % bits;
  95         data[n] |= (1 << off);
  96 }
  97 /*End stuff from ubd_user.h*/
  98
  99 #define DRIVER_NAME "uml-blkdev"
 100
 101 static DEFINE_MUTEX(ubd_lock);
 102
 103 static int ubd_open(struct block_device *bdev, fmode_t mode);
 104 static int ubd_release(struct gendisk *disk, fmode_t mode);
 105 static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
 106                      unsigned int cmd, unsigned long arg);
 107 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
 108
 109 #define MAX_DEV (16)
 110
 111 static const struct block_device_operations ubd_blops = {
 112         .owner          = THIS_MODULE,
 113         .open           = ubd_open,
 114         .release        = ubd_release,
 115         .ioctl          = ubd_ioctl,
 116         .getgeo         = ubd_getgeo,
 117 };
 118
 119 /* Protected by ubd_lock */
 120 static int fake_major = UBD_MAJOR;
 121 static struct gendisk *ubd_gendisk[MAX_DEV];
 122 static struct gendisk *fake_gendisk[MAX_DEV];
 123
 124 #ifdef CONFIG_BLK_DEV_UBD_SYNC
 125 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
 126                                          .cl = 1 })
 127 #else
 128 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
 129                                          .cl = 1 })
 130 #endif
 131 static struct openflags global_openflags = OPEN_FLAGS;
 132
 133 struct cow {
 134         /* backing file name */
 135         char *file;
 136         /* backing file fd */
 137         int fd;
 138         unsigned long *bitmap;
 139         unsigned long bitmap_len;
 140         int bitmap_offset;
 141         int data_offset;
 142 };
 143
 144 #define MAX_SG 64
 145
 146 struct ubd {
 147         struct list_head restart;
 148         /* name (and fd, below) of the file opened for writing, either the
 149          * backing or the cow file. */
 150         char *file;
 151         int count;
 152         int fd;
 153         __u64 size;
 154         struct openflags boot_openflags;
 155         struct openflags openflags;
 156         unsigned shared:1;
 157         unsigned no_cow:1;
 158         struct cow cow;
 159         struct platform_device pdev;
 160         struct request_queue *queue;
 161         spinlock_t lock;
 162         struct scatterlist sg[MAX_SG];
 163         struct request *request;
 164         int start_sg, end_sg;
 165 };
 166
 167 #define DEFAULT_COW { \
 168         .file =                 NULL, \
 169         .fd =                   -1,     \
 170         .bitmap =               NULL, \
 171         .bitmap_offset =        0, \
 172         .data_offset =          0, \
 173 }
 174
 175 #define DEFAULT_UBD { \
 176         .file =                 NULL, \
 177         .count =                0, \
 178         .fd =                   -1, \
 179         .size =                 -1, \
 180         .boot_openflags =       OPEN_FLAGS, \
 181         .openflags =            OPEN_FLAGS, \
 182         .no_cow =               0, \
 183         .shared =               0, \
 184         .cow =                  DEFAULT_COW, \
 185         .lock =                 SPIN_LOCK_UNLOCKED,     \
 186         .request =              NULL, \
 187         .start_sg =             0, \
 188         .end_sg =               0, \
 189 }
 190
 191 /* Protected by ubd_lock */
 192 static struct ubd ubd_devs[MAX_DEV] = { [0 ... MAX_DEV - 1] = DEFAULT_UBD };
 193
 194 /* Only changed by fake_ide_setup which is a setup */
 195 static int fake_ide = 0;
 196 static struct proc_dir_entry *proc_ide_root = NULL;
 197 static struct proc_dir_entry *proc_ide = NULL;
 198
 199 static void make_proc_ide(void)
 200 {
 201         proc_ide_root = proc_mkdir("ide", NULL);
 202         proc_ide = proc_mkdir("ide0", proc_ide_root);
 203 }
 204
 205 static int fake_ide_media_proc_show(struct seq_file *m, void *v)
 206 {
 207         seq_puts(m, "disk\n");
 208         return 0;
 209 }
 210
 211 static int fake_ide_media_proc_open(struct inode *inode, struct file *file)
 212 {
 213         return single_open(file, fake_ide_media_proc_show, NULL);
 214 }
 215
 216 static const struct file_operations fake_ide_media_proc_fops = {
 217         .owner          = THIS_MODULE,
 218         .open           = fake_ide_media_proc_open,
 219         .read           = seq_read,
 220         .llseek         = seq_lseek,
 221         .release        = single_release,
 222 };
 223
 224 static void make_ide_entries(const char *dev_name)
 225 {
 226         struct proc_dir_entry *dir, *ent;
 227         char name[64];
 228
 229         if(proc_ide_root == NULL) make_proc_ide();
 230
 231         dir = proc_mkdir(dev_name, proc_ide);
 232         if(!dir) return;
 233
 234         ent = proc_create("media", S_IRUGO, dir, &fake_ide_media_proc_fops);
 235         if(!ent) return;
 236         snprintf(name, sizeof(name), "ide0/%s", dev_name);
 237         proc_symlink(dev_name, proc_ide_root, name);
 238 }
 239
 240 static int fake_ide_setup(char *str)
 241 {
 242         fake_ide = 1;
 243         return 1;
 244 }
 245
 246 __setup("fake_ide", fake_ide_setup);
 247
 248 __uml_help(fake_ide_setup,
 249 "fake_ide\n"
 250 "    Create ide0 entries that map onto ubd devices.\n\n"
 251 );
 252
 253 static int parse_unit(char **ptr)
 254 {
 255         char *str = *ptr, *end;
 256         int n = -1;
 257
 258         if(isdigit(*str)) {
 259                 n = simple_strtoul(str, &end, 0);
 260                 if(end == str)
 261                         return -1;
 262                 *ptr = end;
 263         }
 264         else if (('a' <= *str) && (*str <= 'z')) {
 265                 n = *str - 'a';
 266                 str++;
 267                 *ptr = str;
 268         }
 269         return n;
 270 }
 271
 272 /* If *index_out == -1 at exit, the passed option was a general one;
 273  * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
 274  * should not be freed on exit.
 275  */
 276 static int ubd_setup_common(char *str, int *index_out, char **error_out)
 277 {
 278         struct ubd *ubd_dev;
 279         struct openflags flags = global_openflags;
 280         char *backing_file;
 281         int n, err = 0, i;
 282
 283         if(index_out) *index_out = -1;
 284         n = *str;
 285         if(n == '='){
 286                 char *end;
 287                 int major;
 288
 289                 str++;
 290                 if(!strcmp(str, "sync")){
 291                         global_openflags = of_sync(global_openflags);
 292                         goto out1;
 293                 }
 294
 295                 err = -EINVAL;
 296                 major = simple_strtoul(str, &end, 0);
 297                 if((*end != '\0') || (end == str)){
 298                         *error_out = "Didn't parse major number";
 299                         goto out1;
 300                 }
 301
 302                 mutex_lock(&ubd_lock);
 303                 if (fake_major != UBD_MAJOR) {
 304                         *error_out = "Can't assign a fake major twice";
 305                         goto out1;
 306                 }
 307
 308                 fake_major = major;
 309
 310                 printk(KERN_INFO "Setting extra ubd major number to %d\n",
 311                        major);
 312                 err = 0;
 313         out1:
 314                 mutex_unlock(&ubd_lock);
 315                 return err;
 316         }
 317
 318         n = parse_unit(&str);
 319         if(n < 0){
 320                 *error_out = "Couldn't parse device number";
 321                 return -EINVAL;
 322         }
 323         if(n >= MAX_DEV){
 324                 *error_out = "Device number out of range";
 325                 return 1;
 326         }
 327
 328         err = -EBUSY;
 329         mutex_lock(&ubd_lock);
 330
 331         ubd_dev = &ubd_devs[n];
 332         if(ubd_dev->file != NULL){
 333                 *error_out = "Device is already configured";
 334                 goto out;
 335         }
 336
 337         if (index_out)
 338                 *index_out = n;
 339
 340         err = -EINVAL;
 341         for (i = 0; i < sizeof("rscd="); i++) {
 342                 switch (*str) {
 343                 case 'r':
 344                         flags.w = 0;
 345                         break;
 346                 case 's':
 347                         flags.s = 1;
 348                         break;
 349                 case 'd':
 350                         ubd_dev->no_cow = 1;
 351                         break;
 352                 case 'c':
 353                         ubd_dev->shared = 1;
 354                         break;
 355                 case '=':
 356                         str++;
 357                         goto break_loop;
 358                 default:
 359                         *error_out = "Expected '=' or flag letter "
 360                                 "(r, s, c, or d)";
 361                         goto out;
 362                 }
 363                 str++;
 364         }
 365
 366         if (*str == '=')
 367                 *error_out = "Too many flags specified";
 368         else
 369                 *error_out = "Missing '='";
 370         goto out;
 371
 372 break_loop:
 373         backing_file = strchr(str, ',');
 374
 375         if (backing_file == NULL)
 376                 backing_file = strchr(str, ':');
 377
 378         if(backing_file != NULL){
 379                 if(ubd_dev->no_cow){
 380                         *error_out = "Can't specify both 'd' and a cow file";
 381                         goto out;
 382                 }
 383                 else {
 384                         *backing_file = '\0';
 385                         backing_file++;
 386                 }
 387         }
 388         err = 0;
 389         ubd_dev->file = str;
 390         ubd_dev->cow.file = backing_file;
 391         ubd_dev->boot_openflags = flags;
 392 out:
 393         mutex_unlock(&ubd_lock);
 394         return err;
 395 }
 396
 397 static int ubd_setup(char *str)
 398 {
 399         char *error;
 400         int err;
 401
 402         err = ubd_setup_common(str, NULL, &error);
 403         if(err)
 404                 printk(KERN_ERR "Failed to initialize device with \"%s\" : "
 405                        "%s\n", str, error);
 406         return 1;
 407 }
 408
 409 __setup("ubd", ubd_setup);
 410 __uml_help(ubd_setup,
 411 "ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
 412 "    This is used to associate a device with a file in the underlying\n"
 413 "    filesystem. When specifying two filenames, the first one is the\n"
 414 "    COW name and the second is the backing file name. As separator you can\n"
 415 "    use either a ':' or a ',': the first one allows writing things like;\n"
 416 "       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
 417 "    while with a ',' the shell would not expand the 2nd '~'.\n"
 418 "    When using only one filename, UML will detect whether to treat it like\n"
 419 "    a COW file or a backing file. To override this detection, add the 'd'\n"
 420 "    flag:\n"
 421 "       ubd0d=BackingFile\n"
 422 "    Usually, there is a filesystem in the file, but \n"
 423 "    that's not required. Swap devices containing swap files can be\n"
 424 "    specified like this. Also, a file which doesn't contain a\n"
 425 "    filesystem can have its contents read in the virtual \n"
 426 "    machine by running 'dd' on the device. <n> must be in the range\n"
 427 "    0 to 7. Appending an 'r' to the number will cause that device\n"
 428 "    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
 429 "    an 's' will cause data to be written to disk on the host immediately.\n"
 430 "    'c' will cause the device to be treated as being shared between multiple\n"
 431 "    UMLs and file locking will be turned off - this is appropriate for a\n"
 432 "    cluster filesystem and inappropriate at almost all other times.\n\n"
 433 );
 434
 435 static int udb_setup(char *str)
 436 {
 437         printk("udb%s specified on command line is almost certainly a ubd -> "
 438                "udb TYPO\n", str);
 439         return 1;
 440 }
 441
 442 __setup("udb", udb_setup);
 443 __uml_help(udb_setup,
 444 "udb\n"
 445 "    This option is here solely to catch ubd -> udb typos, which can be\n"
 446 "    to impossible to catch visually unless you specifically look for\n"
 447 "    them.  The only result of any option starting with 'udb' is an error\n"
 448 "    in the boot output.\n\n"
 449 );
 450
 451 static void do_ubd_request(struct request_queue * q);
 452
 453 /* Only changed by ubd_init, which is an initcall. */
 454 static int thread_fd = -1;
 455 static LIST_HEAD(restart);
 456
 457 /* XXX - move this inside ubd_intr. */
 458 /* Called without dev->lock held, and only in interrupt context. */
 459 static void ubd_handler(void)
 460 {
 461         struct io_thread_req *req;
 462         struct ubd *ubd;
 463         struct list_head *list, *next_ele;
 464         unsigned long flags;
 465         int n;
 466
 467         while(1){
 468                 n = os_read_file(thread_fd, &req,
 469                                  sizeof(struct io_thread_req *));
 470                 if(n != sizeof(req)){
 471                         if(n == -EAGAIN)
 472                                 break;
 473                         printk(KERN_ERR "spurious interrupt in ubd_handler, "
 474                                "err = %d\n", -n);
 475                         return;
 476                 }
 477
 478                 blk_end_request(req->req, 0, req->length);
 479                 kfree(req);
 480         }
 481         reactivate_fd(thread_fd, UBD_IRQ);
 482
 483         list_for_each_safe(list, next_ele, &restart){
 484                 ubd = container_of(list, struct ubd, restart);
 485                 list_del_init(&ubd->restart);
 486                 spin_lock_irqsave(&ubd->lock, flags);
 487                 do_ubd_request(ubd->queue);
 488                 spin_unlock_irqrestore(&ubd->lock, flags);
 489         }
 490 }
 491
 492 static irqreturn_t ubd_intr(int irq, void *dev)
 493 {
 494         ubd_handler();
 495         return IRQ_HANDLED;
 496 }
 497
 498 /* Only changed by ubd_init, which is an initcall. */
 499 static int io_pid = -1;
 500
 501 static void kill_io_thread(void)
 502 {
 503         if(io_pid != -1)
 504                 os_kill_process(io_pid, 1);
 505 }
 506
 507 __uml_exitcall(kill_io_thread);
 508
 509 static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
 510 {
 511         char *file;
 512
 513         file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
 514         return os_file_size(file, size_out);
 515 }
 516
 517 static int read_cow_bitmap(int fd, void *buf, int offset, int len)
 518 {
 519         int err;
 520
 521         err = os_seek_file(fd, offset);
 522         if (err < 0)
 523                 return err;
 524
 525         err = os_read_file(fd, buf, len);
 526         if (err < 0)
 527                 return err;
 528
 529         return 0;
 530 }
 531
 532 static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
 533 {
 534         unsigned long modtime;
 535         unsigned long long actual;
 536         int err;
 537
 538         err = os_file_modtime(file, &modtime);
 539         if (err < 0) {
 540                 printk(KERN_ERR "Failed to get modification time of backing "
 541                        "file \"%s\", err = %d\n", file, -err);
 542                 return err;
 543         }
 544
 545         err = os_file_size(file, &actual);
 546         if (err < 0) {
 547                 printk(KERN_ERR "Failed to get size of backing file \"%s\", "
 548                        "err = %d\n", file, -err);
 549                 return err;
 550         }
 551
 552         if (actual != size) {
 553                 /*__u64 can be a long on AMD64 and with %lu GCC complains; so
 554                  * the typecast.*/
 555                 printk(KERN_ERR "Size mismatch (%llu vs %llu) of COW header "
 556                        "vs backing file\n", (unsigned long long) size, actual);
 557                 return -EINVAL;
 558         }
 559         if (modtime != mtime) {
 560                 printk(KERN_ERR "mtime mismatch (%ld vs %ld) of COW header vs "
 561                        "backing file\n", mtime, modtime);
 562                 return -EINVAL;
 563         }
 564         return 0;
 565 }
 566
 567 static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
 568 {
 569         struct uml_stat buf1, buf2;
 570         int err;
 571
 572         if (from_cmdline == NULL)
 573                 return 0;
 574         if (!strcmp(from_cmdline, from_cow))
 575                 return 0;
 576
 577         err = os_stat_file(from_cmdline, &buf1);
 578         if (err < 0) {
 579                 printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cmdline,
 580                        -err);
 581                 return 0;
 582         }
 583         err = os_stat_file(from_cow, &buf2);
 584         if (err < 0) {
 585                 printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cow,
 586                        -err);
 587                 return 1;
 588         }
 589         if ((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
 590                 return 0;
 591
 592         printk(KERN_ERR "Backing file mismatch - \"%s\" requested, "
 593                "\"%s\" specified in COW header of \"%s\"\n",
 594                from_cmdline, from_cow, cow);
 595         return 1;
 596 }
 597
 598 static int open_ubd_file(char *file, struct openflags *openflags, int shared,
 599                   char **backing_file_out, int *bitmap_offset_out,
 600                   unsigned long *bitmap_len_out, int *data_offset_out,
 601                   int *create_cow_out)
 602 {
 603         time_t mtime;
 604         unsigned long long size;
 605         __u32 version, align;
 606         char *backing_file;
 607         int fd, err, sectorsize, asked_switch, mode = 0644;
 608
 609         fd = os_open_file(file, *openflags, mode);
 610         if (fd < 0) {
 611                 if ((fd == -ENOENT) && (create_cow_out != NULL))
 612                         *create_cow_out = 1;
 613                 if (!openflags->w ||
 614                     ((fd != -EROFS) && (fd != -EACCES)))
 615                         return fd;
 616                 openflags->w = 0;
 617                 fd = os_open_file(file, *openflags, mode);
 618                 if (fd < 0)
 619                         return fd;
 620         }
 621
 622         if (shared)
 623                 printk(KERN_INFO "Not locking \"%s\" on the host\n", file);
 624         else {
 625                 err = os_lock_file(fd, openflags->w);
 626                 if (err < 0) {
 627                         printk(KERN_ERR "Failed to lock '%s', err = %d\n",
 628                                file, -err);
 629                         goto out_close;
 630                 }
 631         }
 632
 633         /* Successful return case! */
 634         if (backing_file_out == NULL)
 635                 return fd;
 636
 637         err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
 638                               &size, &sectorsize, &align, bitmap_offset_out);
 639         if (err && (*backing_file_out != NULL)) {
 640                 printk(KERN_ERR "Failed to read COW header from COW file "
 641                        "\"%s\", errno = %d\n", file, -err);
 642                 goto out_close;
 643         }
 644         if (err)
 645                 return fd;
 646
 647         asked_switch = path_requires_switch(*backing_file_out, backing_file,
 648                                             file);
 649
 650         /* Allow switching only if no mismatch. */
 651         if (asked_switch && !backing_file_mismatch(*backing_file_out, size,
 652                                                    mtime)) {
 653                 printk(KERN_ERR "Switching backing file to '%s'\n",
 654                        *backing_file_out);
 655                 err = write_cow_header(file, fd, *backing_file_out,
 656                                        sectorsize, align, &size);
 657                 if (err) {
 658                         printk(KERN_ERR "Switch failed, errno = %d\n", -err);
 659                         goto out_close;
 660                 }
 661         } else {
 662                 *backing_file_out = backing_file;
 663                 err = backing_file_mismatch(*backing_file_out, size, mtime);
 664                 if (err)
 665                         goto out_close;
 666         }
 667
 668         cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
 669                   bitmap_len_out, data_offset_out);
 670
 671         return fd;
 672  out_close:
 673         os_close_file(fd);
 674         return err;
 675 }
 676
 677 static int create_cow_file(char *cow_file, char *backing_file,
 678                     struct openflags flags,
 679                     int sectorsize, int alignment, int *bitmap_offset_out,
 680                     unsigned long *bitmap_len_out, int *data_offset_out)
 681 {
 682         int err, fd;
 683
 684         flags.c = 1;
 685         fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
 686         if (fd < 0) {
 687                 err = fd;
 688                 printk(KERN_ERR "Open of COW file '%s' failed, errno = %d\n",
 689                        cow_file, -err);
 690                 goto out;
 691         }
 692
 693         err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
 694                             bitmap_offset_out, bitmap_len_out,
 695                             data_offset_out);
 696         if (!err)
 697                 return fd;
 698         os_close_file(fd);
 699  out:
 700         return err;
 701 }
 702
 703 static void ubd_close_dev(struct ubd *ubd_dev)
 704 {
 705         os_close_file(ubd_dev->fd);
 706         if(ubd_dev->cow.file == NULL)
 707                 return;
 708
 709         os_close_file(ubd_dev->cow.fd);
 710         vfree(ubd_dev->cow.bitmap);
 711         ubd_dev->cow.bitmap = NULL;
 712 }
 713
 714 static int ubd_open_dev(struct ubd *ubd_dev)
 715 {
 716         struct openflags flags;
 717         char **back_ptr;
 718         int err, create_cow, *create_ptr;
 719         int fd;
 720
 721         ubd_dev->openflags = ubd_dev->boot_openflags;
 722         create_cow = 0;
 723         create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
 724         back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;
 725
 726         fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
 727                                 back_ptr, &ubd_dev->cow.bitmap_offset,
 728                                 &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
 729                                 create_ptr);
 730
 731         if((fd == -ENOENT) && create_cow){
 732                 fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
 733                                           ubd_dev->openflags, 1 << 9, PAGE_SIZE,
 734                                           &ubd_dev->cow.bitmap_offset,
 735                                           &ubd_dev->cow.bitmap_len,
 736                                           &ubd_dev->cow.data_offset);
 737                 if(fd >= 0){
 738                         printk(KERN_INFO "Creating \"%s\" as COW file for "
 739                                "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
 740                 }
 741         }
 742
 743         if(fd < 0){
 744                 printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
 745                        -fd);
 746                 return fd;
 747         }
 748         ubd_dev->fd = fd;
 749
 750         if(ubd_dev->cow.file != NULL){
 751                 blk_queue_max_hw_sectors(ubd_dev->queue, 8 * sizeof(long));
 752
 753                 err = -ENOMEM;
 754                 ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
 755                 if(ubd_dev->cow.bitmap == NULL){
 756                         printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
 757                         goto error;
 758                 }
 759                 flush_tlb_kernel_vm();
 760
 761                 err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
 762                                       ubd_dev->cow.bitmap_offset,
 763                                       ubd_dev->cow.bitmap_len);
 764                 if(err < 0)
 765                         goto error;
 766
 767                 flags = ubd_dev->openflags;
 768                 flags.w = 0;
 769                 err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
 770                                     NULL, NULL, NULL, NULL);
 771                 if(err < 0) goto error;
 772                 ubd_dev->cow.fd = err;
 773         }
 774         return 0;
 775  error:
 776         os_close_file(ubd_dev->fd);
 777         return err;
 778 }
 779
 780 static void ubd_device_release(struct device *dev)
 781 {
 782         struct ubd *ubd_dev = dev_get_drvdata(dev);
 783
 784         blk_cleanup_queue(ubd_dev->queue);
 785         *ubd_dev = ((struct ubd) DEFAULT_UBD);
 786 }
 787
 788 static int ubd_disk_register(int major, u64 size, int unit,
 789                              struct gendisk **disk_out)
 790 {
 791         struct gendisk *disk;
 792
 793         disk = alloc_disk(1 << UBD_SHIFT);
 794         if(disk == NULL)
 795                 return -ENOMEM;
 796
 797         disk->major = major;
 798         disk->first_minor = unit << UBD_SHIFT;
 799         disk->fops = &ubd_blops;
 800         set_capacity(disk, size / 512);
 801         if (major == UBD_MAJOR)
 802                 sprintf(disk->disk_name, "ubd%c", 'a' + unit);
 803         else
 804                 sprintf(disk->disk_name, "ubd_fake%d", unit);
 805
 806         /* sysfs register (not for ide fake devices) */
 807         if (major == UBD_MAJOR) {
 808                 ubd_devs[unit].pdev.id   = unit;
 809                 ubd_devs[unit].pdev.name = DRIVER_NAME;
 810                 ubd_devs[unit].pdev.dev.release = ubd_device_release;
 811                 dev_set_drvdata(&ubd_devs[unit].pdev.dev, &ubd_devs[unit]);
 812                 platform_device_register(&ubd_devs[unit].pdev);
 813                 disk->driverfs_dev = &ubd_devs[unit].pdev.dev;
 814         }
 815
 816         disk->private_data = &ubd_devs[unit];
 817         disk->queue = ubd_devs[unit].queue;
 818         add_disk(disk);
 819
 820         *disk_out = disk;
 821         return 0;
 822 }
 823
 824 #define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
 825
 826 static int ubd_add(int n, char **error_out)
 827 {
 828         struct ubd *ubd_dev = &ubd_devs[n];
 829         int err = 0;
 830
 831         if(ubd_dev->file == NULL)
 832                 goto out;
 833
 834         err = ubd_file_size(ubd_dev, &ubd_dev->size);
 835         if(err < 0){
 836                 *error_out = "Couldn't determine size of device's file";
 837                 goto out;
 838         }
 839
 840         ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
 841
 842         INIT_LIST_HEAD(&ubd_dev->restart);
 843         sg_init_table(ubd_dev->sg, MAX_SG);
 844
 845         err = -ENOMEM;
 846         ubd_dev->queue = blk_init_queue(do_ubd_request, &ubd_dev->lock);
 847         if (ubd_dev->queue == NULL) {
 848                 *error_out = "Failed to initialize device queue";
 849                 goto out;
 850         }
 851         ubd_dev->queue->queuedata = ubd_dev;
 852
 853         blk_queue_max_segments(ubd_dev->queue, MAX_SG);
 854         err = ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, &ubd_gendisk[n]);
 855         if(err){
 856                 *error_out = "Failed to register device";
 857                 goto out_cleanup;
 858         }
 859
 860         if (fake_major != UBD_MAJOR)
 861                 ubd_disk_register(fake_major, ubd_dev->size, n,
 862                                   &fake_gendisk[n]);
 863
 864         /*
 865          * Perhaps this should also be under the "if (fake_major)" above
 866          * using the fake_disk->disk_name
 867          */
 868         if (fake_ide)
 869                 make_ide_entries(ubd_gendisk[n]->disk_name);
 870
 871         err = 0;
 872 out:
 873         return err;
 874
 875 out_cleanup:
 876         blk_cleanup_queue(ubd_dev->queue);
 877         goto out;
 878 }
 879
 880 static int ubd_config(char *str, char **error_out)
 881 {
 882         int n, ret;
 883
 884         /* This string is possibly broken up and stored, so it's only
 885          * freed if ubd_setup_common fails, or if only general options
 886          * were set.
 887          */
 888         str = kstrdup(str, GFP_KERNEL);
 889         if (str == NULL) {
 890                 *error_out = "Failed to allocate memory";
 891                 return -ENOMEM;
 892         }
 893
 894         ret = ubd_setup_common(str, &n, error_out);
 895         if (ret)
 896                 goto err_free;
 897
 898         if (n == -1) {
 899                 ret = 0;
 900                 goto err_free;
 901         }
 902
 903         mutex_lock(&ubd_lock);
 904         ret = ubd_add(n, error_out);
 905         if (ret)
 906                 ubd_devs[n].file = NULL;
 907         mutex_unlock(&ubd_lock);
 908
 909 out:
 910         return ret;
 911
 912 err_free:
 913         kfree(str);
 914         goto out;
 915 }
 916
 917 static int ubd_get_config(char *name, char *str, int size, char **error_out)
 918 {
 919         struct ubd *ubd_dev;
 920         int n, len = 0;
 921
 922         n = parse_unit(&name);
 923         if((n >= MAX_DEV) || (n < 0)){
 924                 *error_out = "ubd_get_config : device number out of range";
 925                 return -1;
 926         }
 927
 928         ubd_dev = &ubd_devs[n];
 929         mutex_lock(&ubd_lock);
 930
 931         if(ubd_dev->file == NULL){
 932                 CONFIG_CHUNK(str, size, len, "", 1);
 933                 goto out;
 934         }
 935
 936         CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);
 937
 938         if(ubd_dev->cow.file != NULL){
 939                 CONFIG_CHUNK(str, size, len, ",", 0);
 940                 CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
 941         }
 942         else CONFIG_CHUNK(str, size, len, "", 1);
 943
 944  out:
 945         mutex_unlock(&ubd_lock);
 946         return len;
 947 }
 948
 949 static int ubd_id(char **str, int *start_out, int *end_out)
 950 {
 951         int n;
 952
 953         n = parse_unit(str);
 954         *start_out = 0;
 955         *end_out = MAX_DEV - 1;
 956         return n;
 957 }
 958
 959 static int ubd_remove(int n, char **error_out)
 960 {
 961         struct gendisk *disk = ubd_gendisk[n];
 962         struct ubd *ubd_dev;
 963         int err = -ENODEV;
 964
 965         mutex_lock(&ubd_lock);
 966
 967         ubd_dev = &ubd_devs[n];
 968
 969         if(ubd_dev->file == NULL)
 970                 goto out;
 971
 972         /* you cannot remove a open disk */
 973         err = -EBUSY;
 974         if(ubd_dev->count > 0)
 975                 goto out;
 976
 977         ubd_gendisk[n] = NULL;
 978         if(disk != NULL){
 979                 del_gendisk(disk);
 980                 put_disk(disk);
 981         }
 982
 983         if(fake_gendisk[n] != NULL){
 984                 del_gendisk(fake_gendisk[n]);
 985                 put_disk(fake_gendisk[n]);
 986                 fake_gendisk[n] = NULL;
 987         }
 988
 989         err = 0;
 990         platform_device_unregister(&ubd_dev->pdev);
 991 out:
 992         mutex_unlock(&ubd_lock);
 993         return err;
 994 }
 995
 996 /* All these are called by mconsole in process context and without
 997  * ubd-specific locks.  The structure itself is const except for .list.
 998  */
 999 static struct mc_device ubd_mc = {
1000         .list           = LIST_HEAD_INIT(ubd_mc.list),
1001         .name           = "ubd",
1002         .config         = ubd_config,
1003         .get_config     = ubd_get_config,
1004         .id             = ubd_id,
1005         .remove         = ubd_remove,
1006 };
1007
1008 static int __init ubd_mc_init(void)
1009 {
1010         mconsole_register_dev(&ubd_mc);
1011         return 0;
1012 }
1013
1014 __initcall(ubd_mc_init);
1015
1016 static int __init ubd0_init(void)
1017 {
1018         struct ubd *ubd_dev = &ubd_devs[0];
1019
1020         mutex_lock(&ubd_lock);
1021         if(ubd_dev->file == NULL)
1022                 ubd_dev->file = "root_fs";
1023         mutex_unlock(&ubd_lock);
1024
1025         return 0;
1026 }
1027
1028 __initcall(ubd0_init);
1029
1030 /* Used in ubd_init, which is an initcall */
1031 static struct platform_driver ubd_driver = {
1032         .driver = {
1033                 .name  = DRIVER_NAME,
1034         },
1035 };
1036
1037 static int __init ubd_init(void)
1038 {
1039         char *error;
1040         int i, err;
1041
1042         if (register_blkdev(UBD_MAJOR, "ubd"))
1043                 return -1;
1044
1045         if (fake_major != UBD_MAJOR) {
1046                 char name[sizeof("ubd_nnn\0")];
1047
1048                 snprintf(name, sizeof(name), "ubd_%d", fake_major);
1049                 if (register_blkdev(fake_major, "ubd"))
1050                         return -1;
1051         }
1052         platform_driver_register(&ubd_driver);
1053         mutex_lock(&ubd_lock);
1054         for (i = 0; i < MAX_DEV; i++){
1055                 err = ubd_add(i, &error);
1056                 if(err)
1057                         printk(KERN_ERR "Failed to initialize ubd device %d :"
1058                                "%s\n", i, error);
1059         }
1060         mutex_unlock(&ubd_lock);
1061         return 0;
1062 }
1063
1064 late_initcall(ubd_init);
1065
1066 static int __init ubd_driver_init(void){
1067         unsigned long stack;
1068         int err;
1069
1070         /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
1071         if(global_openflags.s){
1072                 printk(KERN_INFO "ubd: Synchronous mode\n");
1073                 /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
1074                  * enough. So use anyway the io thread. */
1075         }
1076         stack = alloc_stack(0, 0);
1077         io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
1078                                  &thread_fd);
1079         if(io_pid < 0){
1080                 printk(KERN_ERR
1081                        "ubd : Failed to start I/O thread (errno = %d) - "
1082                        "falling back to synchronous I/O\n", -io_pid);
1083                 io_pid = -1;
1084                 return 0;
1085         }
1086         err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
1087                              IRQF_DISABLED, "ubd", ubd_devs);
1088         if(err != 0)
1089                 printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
1090         return 0;
1091 }
1092
1093 device_initcall(ubd_driver_init);
1094
1095 static int ubd_open(struct block_device *bdev, fmode_t mode)
1096 {
1097         struct gendisk *disk = bdev->bd_disk;
1098         struct ubd *ubd_dev = disk->private_data;
1099         int err = 0;
1100
1101         if(ubd_dev->count == 0){
1102                 err = ubd_open_dev(ubd_dev);
1103                 if(err){
1104                         printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
1105                                disk->disk_name, ubd_dev->file, -err);
1106                         goto out;
1107                 }
1108         }
1109         ubd_dev->count++;
1110         set_disk_ro(disk, !ubd_dev->openflags.w);
1111
1112         /* This should no more be needed. And it didn't work anyway to exclude
1113          * read-write remounting of filesystems.*/
1114         /*if((mode & FMODE_WRITE) && !ubd_dev->openflags.w){
1115                 if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
1116                 err = -EROFS;
1117         }*/
1118  out:
1119         return err;
1120 }
1121
1122 static int ubd_release(struct gendisk *disk, fmode_t mode)
1123 {
1124         struct ubd *ubd_dev = disk->private_data;
1125
1126         if(--ubd_dev->count == 0)
1127                 ubd_close_dev(ubd_dev);
1128         return 0;
1129 }
1130
1131 static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
1132                           __u64 *cow_offset, unsigned long *bitmap,
1133                           __u64 bitmap_offset, unsigned long *bitmap_words,
1134                           __u64 bitmap_len)
1135 {
1136         __u64 sector = io_offset >> 9;
1137         int i, update_bitmap = 0;
1138
1139         for(i = 0; i < length >> 9; i++){
1140                 if(cow_mask != NULL)
1141                         ubd_set_bit(i, (unsigned char *) cow_mask);
1142                 if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1143                         continue;
1144
1145                 update_bitmap = 1;
1146                 ubd_set_bit(sector + i, (unsigned char *) bitmap);
1147         }
1148
1149         if(!update_bitmap)
1150                 return;
1151
1152         *cow_offset = sector / (sizeof(unsigned long) * 8);
1153
1154         /* This takes care of the case where we're exactly at the end of the
1155          * device, and *cow_offset + 1 is off the end.  So, just back it up
1156          * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
1157          * for the original diagnosis.
1158          */
1159         if (*cow_offset == (DIV_ROUND_UP(bitmap_len,
1160                                          sizeof(unsigned long)) - 1))
1161                 (*cow_offset)--;
1162
1163         bitmap_words[0] = bitmap[*cow_offset];
1164         bitmap_words[1] = bitmap[*cow_offset + 1];
1165
1166         *cow_offset *= sizeof(unsigned long);
1167         *cow_offset += bitmap_offset;
1168 }
1169
1170 static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
1171                        __u64 bitmap_offset, __u64 bitmap_len)
1172 {
1173         __u64 sector = req->offset >> 9;
1174         int i;
1175
1176         if(req->length > (sizeof(req->sector_mask) * 8) << 9)
1177                 panic("Operation too long");
1178
1179         if(req->op == UBD_READ) {
1180                 for(i = 0; i < req->length >> 9; i++){
1181                         if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1182                                 ubd_set_bit(i, (unsigned char *)
1183                                             &req->sector_mask);
1184                 }
1185         }
1186         else cowify_bitmap(req->offset, req->length, &req->sector_mask,
1187                            &req->cow_offset, bitmap, bitmap_offset,
1188                            req->bitmap_words, bitmap_len);
1189 }
1190
1191 /* Called with dev->lock held */
1192 static void prepare_request(struct request *req, struct io_thread_req *io_req,
1193                             unsigned long long offset, int page_offset,
1194                             int len, struct page *page)
1195 {
1196         struct gendisk *disk = req->rq_disk;
1197         struct ubd *ubd_dev = disk->private_data;
1198
1199         io_req->req = req;
1200         io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
1201                 ubd_dev->fd;
1202         io_req->fds[1] = ubd_dev->fd;
1203         io_req->cow_offset = -1;
1204         io_req->offset = offset;
1205         io_req->length = len;
1206         io_req->error = 0;
1207         io_req->sector_mask = 0;
1208
1209         io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
1210         io_req->offsets[0] = 0;
1211         io_req->offsets[1] = ubd_dev->cow.data_offset;
1212         io_req->buffer = page_address(page) + page_offset;
1213         io_req->sectorsize = 1 << 9;
1214
1215         if(ubd_dev->cow.file != NULL)
1216                 cowify_req(io_req, ubd_dev->cow.bitmap,
1217                            ubd_dev->cow.bitmap_offset, ubd_dev->cow.bitmap_len);
1218
1219 }
1220
1221 /* Called with dev->lock held */
1222 static void do_ubd_request(struct request_queue *q)
1223 {
1224         struct io_thread_req *io_req;
1225         struct request *req;
1226         sector_t sector;
1227         int n;
1228
1229         while(1){
1230                 struct ubd *dev = q->queuedata;
1231                 if(dev->end_sg == 0){
1232                         struct request *req = blk_fetch_request(q);
1233                         if(req == NULL)
1234                                 return;
1235
1236                         dev->request = req;
1237                         dev->start_sg = 0;
1238                         dev->end_sg = blk_rq_map_sg(q, req, dev->sg);
1239                 }
1240
1241                 req = dev->request;
1242                 sector = blk_rq_pos(req);
1243                 while(dev->start_sg < dev->end_sg){
1244                         struct scatterlist *sg = &dev->sg[dev->start_sg];
1245
1246                         io_req = kmalloc(sizeof(struct io_thread_req),
1247                                          GFP_ATOMIC);
1248                         if(io_req == NULL){
1249                                 if(list_empty(&dev->restart))
1250                                         list_add(&dev->restart, &restart);
1251                                 return;
1252                         }
1253                         prepare_request(req, io_req,
1254                                         (unsigned long long)sector << 9,
1255                                         sg->offset, sg->length, sg_page(sg));
1256
1257                         sector += sg->length >> 9;
1258                         n = os_write_file(thread_fd, &io_req,
1259                                           sizeof(struct io_thread_req *));
1260                         if(n != sizeof(struct io_thread_req *)){
1261                                 if(n != -EAGAIN)
1262                                         printk("write to io thread failed, "
1263                                                "errno = %d\n", -n);
1264                                 else if(list_empty(&dev->restart))
1265                                         list_add(&dev->restart, &restart);
1266                                 kfree(io_req);
1267                                 return;
1268                         }
1269
1270                         dev->start_sg++;
1271                 }
1272                 dev->end_sg = 0;
1273                 dev->request = NULL;
1274         }
1275 }
1276
1277 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
1278 {
1279         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1280
1281         geo->heads = 128;
1282         geo->sectors = 32;
1283         geo->cylinders = ubd_dev->size / (128 * 32 * 512);
1284         return 0;
1285 }
1286
1287 static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
1288                      unsigned int cmd, unsigned long arg)
1289 {
1290         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1291         u16 ubd_id[ATA_ID_WORDS];
1292
1293         switch (cmd) {
1294                 struct cdrom_volctrl volume;
1295         case HDIO_GET_IDENTITY:
1296                 memset(&ubd_id, 0, ATA_ID_WORDS * 2);
1297                 ubd_id[ATA_ID_CYLS]     = ubd_dev->size / (128 * 32 * 512);
1298                 ubd_id[ATA_ID_HEADS]    = 128;
1299                 ubd_id[ATA_ID_SECTORS]  = 32;
1300                 if(copy_to_user((char __user *) arg, (char *) &ubd_id,
1301                                  sizeof(ubd_id)))
1302                         return -EFAULT;
1303                 return 0;
1304
1305         case CDROMVOLREAD:
1306                 if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
1307                         return -EFAULT;
1308                 volume.channel0 = 255;
1309                 volume.channel1 = 255;
1310                 volume.channel2 = 255;
1311                 volume.channel3 = 255;
1312                 if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
1313                         return -EFAULT;
1314                 return 0;
1315         }
1316         return -EINVAL;
1317 }
1318
1319 static int update_bitmap(struct io_thread_req *req)
1320 {
1321         int n;
1322
1323         if(req->cow_offset == -1)
1324                 return 0;
1325
1326         n = os_seek_file(req->fds[1], req->cow_offset);
1327         if(n < 0){
1328                 printk("do_io - bitmap lseek failed : err = %d\n", -n);
1329                 return 1;
1330         }
1331
1332         n = os_write_file(req->fds[1], &req->bitmap_words,
1333                           sizeof(req->bitmap_words));
1334         if(n != sizeof(req->bitmap_words)){
1335                 printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
1336                        req->fds[1]);
1337                 return 1;
1338         }
1339
1340         return 0;
1341 }
1342
1343 static void do_io(struct io_thread_req *req)
1344 {
1345         char *buf;
1346         unsigned long len;
1347         int n, nsectors, start, end, bit;
1348         int err;
1349         __u64 off;
1350
1351         nsectors = req->length / req->sectorsize;
1352         start = 0;
1353         do {
1354                 bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
1355                 end = start;
1356                 while((end < nsectors) &&
1357                       (ubd_test_bit(end, (unsigned char *)
1358                                     &req->sector_mask) == bit))
1359                         end++;
1360
1361                 off = req->offset + req->offsets[bit] +
1362                         start * req->sectorsize;
1363                 len = (end - start) * req->sectorsize;
1364                 buf = &req->buffer[start * req->sectorsize];
1365
1366                 err = os_seek_file(req->fds[bit], off);
1367                 if(err < 0){
1368                         printk("do_io - lseek failed : err = %d\n", -err);
1369                         req->error = 1;
1370                         return;
1371                 }
1372                 if(req->op == UBD_READ){
1373                         n = 0;
1374                         do {
1375                                 buf = &buf[n];
1376                                 len -= n;
1377                                 n = os_read_file(req->fds[bit], buf, len);
1378                                 if (n < 0) {
1379                                         printk("do_io - read failed, err = %d "
1380                                                "fd = %d\n", -n, req->fds[bit]);
1381                                         req->error = 1;
1382                                         return;
1383                                 }
1384                         } while((n < len) && (n != 0));
1385                         if (n < len) memset(&buf[n], 0, len - n);
1386                 } else {
1387                         n = os_write_file(req->fds[bit], buf, len);
1388                         if(n != len){
1389                                 printk("do_io - write failed err = %d "
1390                                        "fd = %d\n", -n, req->fds[bit]);
1391                                 req->error = 1;
1392                                 return;
1393                         }
1394                 }
1395
1396                 start = end;
1397         } while(start < nsectors);
1398
1399         req->error = update_bitmap(req);
1400 }
1401
1402 /* Changed in start_io_thread, which is serialized by being called only
1403  * from ubd_init, which is an initcall.
1404  */
1405 int kernel_fd = -1;
1406
1407 /* Only changed by the io thread. XXX: currently unused. */
1408 static int io_count = 0;
1409
1410 int io_thread(void *arg)
1411 {
1412         struct io_thread_req *req;
1413         int n;
1414
1415         ignore_sigwinch_sig();
1416         while(1){
1417                 n = os_read_file(kernel_fd, &req,
1418                                  sizeof(struct io_thread_req *));
1419                 if(n != sizeof(struct io_thread_req *)){
1420                         if(n < 0)
1421                                 printk("io_thread - read failed, fd = %d, "
1422                                        "err = %d\n", kernel_fd, -n);
1423                         else {
1424                                 printk("io_thread - short read, fd = %d, "
1425                                        "length = %d\n", kernel_fd, n);
1426                         }
1427                         continue;
1428                 }
1429                 io_count++;
1430                 do_io(req);
1431                 n = os_write_file(kernel_fd, &req,
1432                                   sizeof(struct io_thread_req *));
1433                 if(n != sizeof(struct io_thread_req *))
1434                         printk("io_thread - write failed, fd = %d, err = %d\n",
1435                                kernel_fd, -n);
1436         }
1437
1438         return 0;
1439 }