SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 MAJOR_NR UBD_MAJOR
  21 #define UBD_SHIFT 4
  22
  23 #include "linux/module.h"
  24 #include "linux/blkdev.h"
  25 #include "linux/hdreg.h"
  26 #include "linux/init.h"
  27 #include "linux/cdrom.h"
  28 #include "linux/proc_fs.h"
  29 #include "linux/ctype.h"
  30 #include "linux/capability.h"
  31 #include "linux/mm.h"
  32 #include "linux/vmalloc.h"
  33 #include "linux/blkpg.h"
  34 #include "linux/genhd.h"
  35 #include "linux/spinlock.h"
  36 #include "linux/platform_device.h"
  37 #include "asm/segment.h"
  38 #include "asm/uaccess.h"
  39 #include "asm/irq.h"
  40 #include "asm/types.h"
  41 #include "asm/tlbflush.h"
  42 #include "user_util.h"
  43 #include "mem_user.h"
  44 #include "kern_util.h"
  45 #include "kern.h"
  46 #include "mconsole_kern.h"
  47 #include "init.h"
  48 #include "irq_user.h"
  49 #include "irq_kern.h"
  50 #include "ubd_user.h"
  51 #include "os.h"
  52 #include "mem.h"
  53 #include "mem_kern.h"
  54 #include "cow.h"
  55
  56 enum ubd_req { UBD_READ, UBD_WRITE };
  57
  58 struct io_thread_req {
  59         enum ubd_req op;
  60         int fds[2];
  61         unsigned long offsets[2];
  62         unsigned long long offset;
  63         unsigned long length;
  64         char *buffer;
  65         int sectorsize;
  66         unsigned long sector_mask;
  67         unsigned long long cow_offset;
  68         unsigned long bitmap_words[2];
  69         int error;
  70 };
  71
  72 extern int open_ubd_file(char *file, struct openflags *openflags, int shared,
  73                          char **backing_file_out, int *bitmap_offset_out,
  74                          unsigned long *bitmap_len_out, int *data_offset_out,
  75                          int *create_cow_out);
  76 extern int create_cow_file(char *cow_file, char *backing_file,
  77                            struct openflags flags, int sectorsize,
  78                            int alignment, int *bitmap_offset_out,
  79                            unsigned long *bitmap_len_out,
  80                            int *data_offset_out);
  81 extern int read_cow_bitmap(int fd, void *buf, int offset, int len);
  82 extern void do_io(struct io_thread_req *req);
  83
  84 static inline int ubd_test_bit(__u64 bit, unsigned char *data)
  85 {
  86         __u64 n;
  87         int bits, off;
  88
  89         bits = sizeof(data[0]) * 8;
  90         n = bit / bits;
  91         off = bit % bits;
  92         return((data[n] & (1 << off)) != 0);
  93 }
  94
  95 static inline void ubd_set_bit(__u64 bit, unsigned char *data)
  96 {
  97         __u64 n;
  98         int bits, off;
  99
 100         bits = sizeof(data[0]) * 8;
 101         n = bit / bits;
 102         off = bit % bits;
 103         data[n] |= (1 << off);
 104 }
 105 /*End stuff from ubd_user.h*/
 106
 107 #define DRIVER_NAME "uml-blkdev"
 108
 109 /* Can be taken in interrupt context, and is passed to the block layer to lock
 110  * the request queue. Kernel side code knows that. */
 111 static DEFINE_SPINLOCK(ubd_io_lock);
 112
 113 static DEFINE_MUTEX(ubd_lock);
 114
 115 /* XXX - this made sense in 2.4 days, now it's only used as a boolean, and
 116  * probably it doesn't make sense even for that. */
 117 static int do_ubd;
 118
 119 static int ubd_open(struct inode * inode, struct file * filp);
 120 static int ubd_release(struct inode * inode, struct file * file);
 121 static int ubd_ioctl(struct inode * inode, struct file * file,
 122                      unsigned int cmd, unsigned long arg);
 123 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
 124
 125 #define MAX_DEV (16)
 126
 127 static struct block_device_operations ubd_blops = {
 128         .owner          = THIS_MODULE,
 129         .open           = ubd_open,
 130         .release        = ubd_release,
 131         .ioctl          = ubd_ioctl,
 132         .getgeo         = ubd_getgeo,
 133 };
 134
 135 /* Protected by the queue_lock */
 136 static request_queue_t *ubd_queue;
 137
 138 /* Protected by ubd_lock */
 139 static int fake_major = MAJOR_NR;
 140
 141 static struct gendisk *ubd_gendisk[MAX_DEV];
 142 static struct gendisk *fake_gendisk[MAX_DEV];
 143
 144 #ifdef CONFIG_BLK_DEV_UBD_SYNC
 145 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
 146                                          .cl = 1 })
 147 #else
 148 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
 149                                          .cl = 1 })
 150 #endif
 151
 152 /* Not protected - changed only in ubd_setup_common and then only to
 153  * to enable O_SYNC.
 154  */
 155 static struct openflags global_openflags = OPEN_FLAGS;
 156
 157 struct cow {
 158         /* backing file name */
 159         char *file;
 160         /* backing file fd */
 161         int fd;
 162         unsigned long *bitmap;
 163         unsigned long bitmap_len;
 164         int bitmap_offset;
 165         int data_offset;
 166 };
 167
 168 struct ubd {
 169         /* name (and fd, below) of the file opened for writing, either the
 170          * backing or the cow file. */
 171         char *file;
 172         int count;
 173         int fd;
 174         __u64 size;
 175         struct openflags boot_openflags;
 176         struct openflags openflags;
 177         int shared;
 178         int no_cow;
 179         struct cow cow;
 180         struct platform_device pdev;
 181 };
 182
 183 #define DEFAULT_COW { \
 184         .file =                 NULL, \
 185         .fd =                   -1, \
 186         .bitmap =               NULL, \
 187         .bitmap_offset =        0, \
 188         .data_offset =          0, \
 189 }
 190
 191 #define DEFAULT_UBD { \
 192         .file =                 NULL, \
 193         .count =                0, \
 194         .fd =                   -1, \
 195         .size =                 -1, \
 196         .boot_openflags =       OPEN_FLAGS, \
 197         .openflags =            OPEN_FLAGS, \
 198         .no_cow =               0, \
 199         .shared =               0, \
 200         .cow =                  DEFAULT_COW, \
 201 }
 202
 203 struct ubd ubd_devs[MAX_DEV] = { [ 0 ... MAX_DEV - 1 ] = DEFAULT_UBD };
 204
 205 static int ubd0_init(void)
 206 {
 207         struct ubd *ubd_dev = &ubd_devs[0];
 208
 209         if(ubd_dev->file == NULL)
 210                 ubd_dev->file = "root_fs";
 211         return(0);
 212 }
 213
 214 __initcall(ubd0_init);
 215
 216 /* Only changed by fake_ide_setup which is a setup */
 217 static int fake_ide = 0;
 218 static struct proc_dir_entry *proc_ide_root = NULL;
 219 static struct proc_dir_entry *proc_ide = NULL;
 220
 221 static void make_proc_ide(void)
 222 {
 223         proc_ide_root = proc_mkdir("ide", NULL);
 224         proc_ide = proc_mkdir("ide0", proc_ide_root);
 225 }
 226
 227 static int proc_ide_read_media(char *page, char **start, off_t off, int count,
 228                                int *eof, void *data)
 229 {
 230         int len;
 231
 232         strcpy(page, "disk\n");
 233         len = strlen("disk\n");
 234         len -= off;
 235         if (len < count){
 236                 *eof = 1;
 237                 if (len <= 0) return 0;
 238         }
 239         else len = count;
 240         *start = page + off;
 241         return len;
 242 }
 243
 244 static void make_ide_entries(char *dev_name)
 245 {
 246         struct proc_dir_entry *dir, *ent;
 247         char name[64];
 248
 249         if(proc_ide_root == NULL) make_proc_ide();
 250
 251         dir = proc_mkdir(dev_name, proc_ide);
 252         if(!dir) return;
 253
 254         ent = create_proc_entry("media", S_IFREG|S_IRUGO, dir);
 255         if(!ent) return;
 256         ent->nlink = 1;
 257         ent->data = NULL;
 258         ent->read_proc = proc_ide_read_media;
 259         ent->write_proc = NULL;
 260         sprintf(name,"ide0/%s", dev_name);
 261         proc_symlink(dev_name, proc_ide_root, name);
 262 }
 263
 264 static int fake_ide_setup(char *str)
 265 {
 266         fake_ide = 1;
 267         return(1);
 268 }
 269
 270 __setup("fake_ide", fake_ide_setup);
 271
 272 __uml_help(fake_ide_setup,
 273 "fake_ide\n"
 274 "    Create ide0 entries that map onto ubd devices.\n\n"
 275 );
 276
 277 static int parse_unit(char **ptr)
 278 {
 279         char *str = *ptr, *end;
 280         int n = -1;
 281
 282         if(isdigit(*str)) {
 283                 n = simple_strtoul(str, &end, 0);
 284                 if(end == str)
 285                         return(-1);
 286                 *ptr = end;
 287         }
 288         else if (('a' <= *str) && (*str <= 'z')) {
 289                 n = *str - 'a';
 290                 str++;
 291                 *ptr = str;
 292         }
 293         return(n);
 294 }
 295
 296 static int ubd_setup_common(char *str, int *index_out)
 297 {
 298         struct ubd *ubd_dev;
 299         struct openflags flags = global_openflags;
 300         char *backing_file;
 301         int n, err, i;
 302
 303         if(index_out) *index_out = -1;
 304         n = *str;
 305         if(n == '='){
 306                 char *end;
 307                 int major;
 308
 309                 str++;
 310                 if(!strcmp(str, "sync")){
 311                         global_openflags = of_sync(global_openflags);
 312                         return(0);
 313                 }
 314                 major = simple_strtoul(str, &end, 0);
 315                 if((*end != '\0') || (end == str)){
 316                         printk(KERN_ERR
 317                                "ubd_setup : didn't parse major number\n");
 318                         return(1);
 319                 }
 320
 321                 err = 1;
 322                 mutex_lock(&ubd_lock);
 323                 if(fake_major != MAJOR_NR){
 324                         printk(KERN_ERR "Can't assign a fake major twice\n");
 325                         goto out1;
 326                 }
 327
 328                 fake_major = major;
 329
 330                 printk(KERN_INFO "Setting extra ubd major number to %d\n",
 331                        major);
 332                 err = 0;
 333         out1:
 334                 mutex_unlock(&ubd_lock);
 335                 return(err);
 336         }
 337
 338         n = parse_unit(&str);
 339         if(n < 0){
 340                 printk(KERN_ERR "ubd_setup : couldn't parse unit number "
 341                        "'%s'\n", str);
 342                 return(1);
 343         }
 344         if(n >= MAX_DEV){
 345                 printk(KERN_ERR "ubd_setup : index %d out of range "
 346                        "(%d devices, from 0 to %d)\n", n, MAX_DEV, MAX_DEV - 1);
 347                 return(1);
 348         }
 349
 350         err = 1;
 351         mutex_lock(&ubd_lock);
 352
 353         ubd_dev = &ubd_devs[n];
 354         if(ubd_dev->file != NULL){
 355                 printk(KERN_ERR "ubd_setup : device already configured\n");
 356                 goto out;
 357         }
 358
 359         if (index_out)
 360                 *index_out = n;
 361
 362         for (i = 0; i < sizeof("rscd="); i++) {
 363                 switch (*str) {
 364                 case 'r':
 365                         flags.w = 0;
 366                         break;
 367                 case 's':
 368                         flags.s = 1;
 369                         break;
 370                 case 'd':
 371                         ubd_dev->no_cow = 1;
 372                         break;
 373                 case 'c':
 374                         ubd_dev->shared = 1;
 375                         break;
 376                 case '=':
 377                         str++;
 378                         goto break_loop;
 379                 default:
 380                         printk(KERN_ERR "ubd_setup : Expected '=' or flag letter (r, s, c, or d)\n");
 381                         goto out;
 382                 }
 383                 str++;
 384         }
 385
 386         if (*str == '=')
 387                 printk(KERN_ERR "ubd_setup : Too many flags specified\n");
 388         else
 389                 printk(KERN_ERR "ubd_setup : Expected '='\n");
 390         goto out;
 391
 392 break_loop:
 393         err = 0;
 394         backing_file = strchr(str, ',');
 395
 396         if (!backing_file) {
 397                 backing_file = strchr(str, ':');
 398         }
 399
 400         if(backing_file){
 401                 if(ubd_dev->no_cow)
 402                         printk(KERN_ERR "Can't specify both 'd' and a "
 403                                "cow file\n");
 404                 else {
 405                         *backing_file = '\0';
 406                         backing_file++;
 407                 }
 408         }
 409         ubd_dev->file = str;
 410         ubd_dev->cow.file = backing_file;
 411         ubd_dev->boot_openflags = flags;
 412 out:
 413         mutex_unlock(&ubd_lock);
 414         return(err);
 415 }
 416
 417 static int ubd_setup(char *str)
 418 {
 419         ubd_setup_common(str, NULL);
 420         return(1);
 421 }
 422
 423 __setup("ubd", ubd_setup);
 424 __uml_help(ubd_setup,
 425 "ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
 426 "    This is used to associate a device with a file in the underlying\n"
 427 "    filesystem. When specifying two filenames, the first one is the\n"
 428 "    COW name and the second is the backing file name. As separator you can\n"
 429 "    use either a ':' or a ',': the first one allows writing things like;\n"
 430 "       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
 431 "    while with a ',' the shell would not expand the 2nd '~'.\n"
 432 "    When using only one filename, UML will detect whether to thread it like\n"
 433 "    a COW file or a backing file. To override this detection, add the 'd'\n"
 434 "    flag:\n"
 435 "       ubd0d=BackingFile\n"
 436 "    Usually, there is a filesystem in the file, but \n"
 437 "    that's not required. Swap devices containing swap files can be\n"
 438 "    specified like this. Also, a file which doesn't contain a\n"
 439 "    filesystem can have its contents read in the virtual \n"
 440 "    machine by running 'dd' on the device. <n> must be in the range\n"
 441 "    0 to 7. Appending an 'r' to the number will cause that device\n"
 442 "    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
 443 "    an 's' will cause data to be written to disk on the host immediately.\n\n"
 444 );
 445
 446 static int udb_setup(char *str)
 447 {
 448         printk("udb%s specified on command line is almost certainly a ubd -> "
 449                "udb TYPO\n", str);
 450         return(1);
 451 }
 452
 453 __setup("udb", udb_setup);
 454 __uml_help(udb_setup,
 455 "udb\n"
 456 "    This option is here solely to catch ubd -> udb typos, which can be\n"
 457 "    to impossible to catch visually unless you specifically look for\n"
 458 "    them.  The only result of any option starting with 'udb' is an error\n"
 459 "    in the boot output.\n\n"
 460 );
 461
 462 static int fakehd_set = 0;
 463 static int fakehd(char *str)
 464 {
 465         printk(KERN_INFO "fakehd : Changing ubd name to \"hd\".\n");
 466         fakehd_set = 1;
 467         return 1;
 468 }
 469
 470 __setup("fakehd", fakehd);
 471 __uml_help(fakehd,
 472 "fakehd\n"
 473 "    Change the ubd device name to \"hd\".\n\n"
 474 );
 475
 476 static void do_ubd_request(request_queue_t * q);
 477
 478 /* Only changed by ubd_init, which is an initcall. */
 479 int thread_fd = -1;
 480
 481 /* Changed by ubd_handler, which is serialized because interrupts only
 482  * happen on CPU 0.
 483  */
 484 int intr_count = 0;
 485
 486 /* call ubd_finish if you need to serialize */
 487 static void __ubd_finish(struct request *req, int error)
 488 {
 489         int nsect;
 490
 491         if(error){
 492                 end_request(req, 0);
 493                 return;
 494         }
 495         nsect = req->current_nr_sectors;
 496         req->sector += nsect;
 497         req->buffer += nsect << 9;
 498         req->errors = 0;
 499         req->nr_sectors -= nsect;
 500         req->current_nr_sectors = 0;
 501         end_request(req, 1);
 502 }
 503
 504 /* Callable only from interrupt context - otherwise you need to do
 505  * spin_lock_irq()/spin_lock_irqsave() */
 506 static inline void ubd_finish(struct request *req, int error)
 507 {
 508         spin_lock(&ubd_io_lock);
 509         __ubd_finish(req, error);
 510         spin_unlock(&ubd_io_lock);
 511 }
 512
 513 /* XXX - move this inside ubd_intr. */
 514 /* Called without ubd_io_lock held, and only in interrupt context. */
 515 static void ubd_handler(void)
 516 {
 517         struct io_thread_req req;
 518         struct request *rq = elv_next_request(ubd_queue);
 519         int n;
 520
 521         do_ubd = 0;
 522         intr_count++;
 523         n = os_read_file(thread_fd, &req, sizeof(req));
 524         if(n != sizeof(req)){
 525                 printk(KERN_ERR "Pid %d - spurious interrupt in ubd_handler, "
 526                        "err = %d\n", os_getpid(), -n);
 527                 spin_lock(&ubd_io_lock);
 528                 end_request(rq, 0);
 529                 spin_unlock(&ubd_io_lock);
 530                 return;
 531         }
 532
 533         ubd_finish(rq, req.error);
 534         reactivate_fd(thread_fd, UBD_IRQ);
 535         spin_lock(&ubd_io_lock);
 536         do_ubd_request(ubd_queue);
 537         spin_unlock(&ubd_io_lock);
 538 }
 539
 540 static irqreturn_t ubd_intr(int irq, void *dev)
 541 {
 542         ubd_handler();
 543         return(IRQ_HANDLED);
 544 }
 545
 546 /* Only changed by ubd_init, which is an initcall. */
 547 static int io_pid = -1;
 548
 549 void kill_io_thread(void)
 550 {
 551         if(io_pid != -1)
 552                 os_kill_process(io_pid, 1);
 553 }
 554
 555 __uml_exitcall(kill_io_thread);
 556
 557 static int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
 558 {
 559         char *file;
 560
 561         file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
 562         return(os_file_size(file, size_out));
 563 }
 564
 565 static void ubd_close_dev(struct ubd *ubd_dev)
 566 {
 567         os_close_file(ubd_dev->fd);
 568         if(ubd_dev->cow.file == NULL)
 569                 return;
 570
 571         os_close_file(ubd_dev->cow.fd);
 572         vfree(ubd_dev->cow.bitmap);
 573         ubd_dev->cow.bitmap = NULL;
 574 }
 575
 576 static int ubd_open_dev(struct ubd *ubd_dev)
 577 {
 578         struct openflags flags;
 579         char **back_ptr;
 580         int err, create_cow, *create_ptr;
 581
 582         ubd_dev->openflags = ubd_dev->boot_openflags;
 583         create_cow = 0;
 584         create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
 585         back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;
 586         ubd_dev->fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
 587                                 back_ptr, &ubd_dev->cow.bitmap_offset,
 588                                 &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
 589                                 create_ptr);
 590
 591         if((ubd_dev->fd == -ENOENT) && create_cow){
 592                 ubd_dev->fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
 593                                           ubd_dev->openflags, 1 << 9, PAGE_SIZE,
 594                                           &ubd_dev->cow.bitmap_offset,
 595                                           &ubd_dev->cow.bitmap_len,
 596                                           &ubd_dev->cow.data_offset);
 597                 if(ubd_dev->fd >= 0){
 598                         printk(KERN_INFO "Creating \"%s\" as COW file for "
 599                                "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
 600                 }
 601         }
 602
 603         if(ubd_dev->fd < 0){
 604                 printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
 605                        -ubd_dev->fd);
 606                 return(ubd_dev->fd);
 607         }
 608
 609         if(ubd_dev->cow.file != NULL){
 610                 err = -ENOMEM;
 611                 ubd_dev->cow.bitmap = (void *) vmalloc(ubd_dev->cow.bitmap_len);
 612                 if(ubd_dev->cow.bitmap == NULL){
 613                         printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
 614                         goto error;
 615                 }
 616                 flush_tlb_kernel_vm();
 617
 618                 err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
 619                                       ubd_dev->cow.bitmap_offset,
 620                                       ubd_dev->cow.bitmap_len);
 621                 if(err < 0)
 622                         goto error;
 623
 624                 flags = ubd_dev->openflags;
 625                 flags.w = 0;
 626                 err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
 627                                     NULL, NULL, NULL, NULL);
 628                 if(err < 0) goto error;
 629                 ubd_dev->cow.fd = err;
 630         }
 631         return(0);
 632  error:
 633         os_close_file(ubd_dev->fd);
 634         return(err);
 635 }
 636
 637 static int ubd_disk_register(int major, u64 size, int unit,
 638                         struct gendisk **disk_out)
 639
 640 {
 641         struct gendisk *disk;
 642
 643         disk = alloc_disk(1 << UBD_SHIFT);
 644         if(disk == NULL)
 645                 return(-ENOMEM);
 646
 647         disk->major = major;
 648         disk->first_minor = unit << UBD_SHIFT;
 649         disk->fops = &ubd_blops;
 650         set_capacity(disk, size / 512);
 651         if(major == MAJOR_NR)
 652                 sprintf(disk->disk_name, "ubd%c", 'a' + unit);
 653         else
 654                 sprintf(disk->disk_name, "ubd_fake%d", unit);
 655
 656         /* sysfs register (not for ide fake devices) */
 657         if (major == MAJOR_NR) {
 658                 ubd_devs[unit].pdev.id   = unit;
 659                 ubd_devs[unit].pdev.name = DRIVER_NAME;
 660                 platform_device_register(&ubd_devs[unit].pdev);
 661                 disk->driverfs_dev = &ubd_devs[unit].pdev.dev;
 662         }
 663
 664         disk->private_data = &ubd_devs[unit];
 665         disk->queue = ubd_queue;
 666         add_disk(disk);
 667
 668         *disk_out = disk;
 669         return 0;
 670 }
 671
 672 #define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
 673
 674 static int ubd_add(int n)
 675 {
 676         struct ubd *ubd_dev = &ubd_devs[n];
 677         int err;
 678
 679         err = -ENODEV;
 680         if(ubd_dev->file == NULL)
 681                 goto out;
 682
 683         err = ubd_file_size(ubd_dev, &ubd_dev->size);
 684         if(err < 0)
 685                 goto out;
 686
 687         ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
 688
 689         err = ubd_disk_register(MAJOR_NR, ubd_dev->size, n, &ubd_gendisk[n]);
 690         if(err)
 691                 goto out;
 692
 693         if(fake_major != MAJOR_NR)
 694                 ubd_disk_register(fake_major, ubd_dev->size, n,
 695                              &fake_gendisk[n]);
 696
 697         /* perhaps this should also be under the "if (fake_major)" above */
 698         /* using the fake_disk->disk_name and also the fakehd_set name */
 699         if (fake_ide)
 700                 make_ide_entries(ubd_gendisk[n]->disk_name);
 701
 702         err = 0;
 703 out:
 704         return err;
 705 }
 706
 707 static int ubd_config(char *str)
 708 {
 709         int n, err;
 710
 711         str = kstrdup(str, GFP_KERNEL);
 712         if(str == NULL){
 713                 printk(KERN_ERR "ubd_config failed to strdup string\n");
 714                 return(1);
 715         }
 716         err = ubd_setup_common(str, &n);
 717         if(err){
 718                 kfree(str);
 719                 return(-1);
 720         }
 721         if(n == -1) return(0);
 722
 723         mutex_lock(&ubd_lock);
 724         err = ubd_add(n);
 725         if(err)
 726                 ubd_devs[n].file = NULL;
 727         mutex_unlock(&ubd_lock);
 728
 729         return(err);
 730 }
 731
 732 static int ubd_get_config(char *name, char *str, int size, char **error_out)
 733 {
 734         struct ubd *ubd_dev;
 735         int n, len = 0;
 736
 737         n = parse_unit(&name);
 738         if((n >= MAX_DEV) || (n < 0)){
 739                 *error_out = "ubd_get_config : device number out of range";
 740                 return(-1);
 741         }
 742
 743         ubd_dev = &ubd_devs[n];
 744         mutex_lock(&ubd_lock);
 745
 746         if(ubd_dev->file == NULL){
 747                 CONFIG_CHUNK(str, size, len, "", 1);
 748                 goto out;
 749         }
 750
 751         CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);
 752
 753         if(ubd_dev->cow.file != NULL){
 754                 CONFIG_CHUNK(str, size, len, ",", 0);
 755                 CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
 756         }
 757         else CONFIG_CHUNK(str, size, len, "", 1);
 758
 759  out:
 760         mutex_unlock(&ubd_lock);
 761         return(len);
 762 }
 763
 764 static int ubd_id(char **str, int *start_out, int *end_out)
 765 {
 766         int n;
 767
 768         n = parse_unit(str);
 769         *start_out = 0;
 770         *end_out = MAX_DEV - 1;
 771         return n;
 772 }
 773
 774 static int ubd_remove(int n)
 775 {
 776         struct ubd *ubd_dev;
 777         int err = -ENODEV;
 778
 779         mutex_lock(&ubd_lock);
 780
 781         if(ubd_gendisk[n] == NULL)
 782                 goto out;
 783
 784         ubd_dev = &ubd_devs[n];
 785
 786         if(ubd_dev->file == NULL)
 787                 goto out;
 788
 789         /* you cannot remove a open disk */
 790         err = -EBUSY;
 791         if(ubd_dev->count > 0)
 792                 goto out;
 793
 794         del_gendisk(ubd_gendisk[n]);
 795         put_disk(ubd_gendisk[n]);
 796         ubd_gendisk[n] = NULL;
 797
 798         if(fake_gendisk[n] != NULL){
 799                 del_gendisk(fake_gendisk[n]);
 800                 put_disk(fake_gendisk[n]);
 801                 fake_gendisk[n] = NULL;
 802         }
 803
 804         platform_device_unregister(&ubd_dev->pdev);
 805         *ubd_dev = ((struct ubd) DEFAULT_UBD);
 806         err = 0;
 807 out:
 808         mutex_unlock(&ubd_lock);
 809         return err;
 810 }
 811
 812 static struct mc_device ubd_mc = {
 813         .name           = "ubd",
 814         .config         = ubd_config,
 815         .get_config     = ubd_get_config,
 816         .id             = ubd_id,
 817         .remove         = ubd_remove,
 818 };
 819
 820 static int ubd_mc_init(void)
 821 {
 822         mconsole_register_dev(&ubd_mc);
 823         return 0;
 824 }
 825
 826 __initcall(ubd_mc_init);
 827
 828 static struct platform_driver ubd_driver = {
 829         .driver = {
 830                 .name  = DRIVER_NAME,
 831         },
 832 };
 833
 834 int ubd_init(void)
 835 {
 836         int i;
 837
 838         if (register_blkdev(MAJOR_NR, "ubd"))
 839                 return -1;
 840
 841         ubd_queue = blk_init_queue(do_ubd_request, &ubd_io_lock);
 842         if (!ubd_queue) {
 843                 unregister_blkdev(MAJOR_NR, "ubd");
 844                 return -1;
 845         }
 846
 847         if (fake_major != MAJOR_NR) {
 848                 char name[sizeof("ubd_nnn\0")];
 849
 850                 snprintf(name, sizeof(name), "ubd_%d", fake_major);
 851                 if (register_blkdev(fake_major, "ubd"))
 852                         return -1;
 853         }
 854         platform_driver_register(&ubd_driver);
 855         for (i = 0; i < MAX_DEV; i++)
 856                 ubd_add(i);
 857         return 0;
 858 }
 859
 860 late_initcall(ubd_init);
 861
 862 int ubd_driver_init(void){
 863         unsigned long stack;
 864         int err;
 865
 866         /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
 867         if(global_openflags.s){
 868                 printk(KERN_INFO "ubd: Synchronous mode\n");
 869                 /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
 870                  * enough. So use anyway the io thread. */
 871         }
 872         stack = alloc_stack(0, 0);
 873         io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
 874                                  &thread_fd);
 875         if(io_pid < 0){
 876                 printk(KERN_ERR
 877                        "ubd : Failed to start I/O thread (errno = %d) - "
 878                        "falling back to synchronous I/O\n", -io_pid);
 879                 io_pid = -1;
 880                 return(0);
 881         }
 882         err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
 883                              IRQF_DISABLED, "ubd", ubd_devs);
 884         if(err != 0)
 885                 printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
 886         return 0;
 887 }
 888
 889 device_initcall(ubd_driver_init);
 890
 891 static int ubd_open(struct inode *inode, struct file *filp)
 892 {
 893         struct gendisk *disk = inode->i_bdev->bd_disk;
 894         struct ubd *ubd_dev = disk->private_data;
 895         int err = 0;
 896
 897         if(ubd_dev->count == 0){
 898                 err = ubd_open_dev(ubd_dev);
 899                 if(err){
 900                         printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
 901                                disk->disk_name, ubd_dev->file, -err);
 902                         goto out;
 903                 }
 904         }
 905         ubd_dev->count++;
 906         set_disk_ro(disk, !ubd_dev->openflags.w);
 907
 908         /* This should no more be needed. And it didn't work anyway to exclude
 909          * read-write remounting of filesystems.*/
 910         /*if((filp->f_mode & FMODE_WRITE) && !ubd_dev->openflags.w){
 911                 if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
 912                 err = -EROFS;
 913         }*/
 914  out:
 915         return(err);
 916 }
 917
 918 static int ubd_release(struct inode * inode, struct file * file)
 919 {
 920         struct gendisk *disk = inode->i_bdev->bd_disk;
 921         struct ubd *ubd_dev = disk->private_data;
 922
 923         if(--ubd_dev->count == 0)
 924                 ubd_close_dev(ubd_dev);
 925         return(0);
 926 }
 927
 928 static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
 929                           __u64 *cow_offset, unsigned long *bitmap,
 930                           __u64 bitmap_offset, unsigned long *bitmap_words,
 931                           __u64 bitmap_len)
 932 {
 933         __u64 sector = io_offset >> 9;
 934         int i, update_bitmap = 0;
 935
 936         for(i = 0; i < length >> 9; i++){
 937                 if(cow_mask != NULL)
 938                         ubd_set_bit(i, (unsigned char *) cow_mask);
 939                 if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
 940                         continue;
 941
 942                 update_bitmap = 1;
 943                 ubd_set_bit(sector + i, (unsigned char *) bitmap);
 944         }
 945
 946         if(!update_bitmap)
 947                 return;
 948
 949         *cow_offset = sector / (sizeof(unsigned long) * 8);
 950
 951         /* This takes care of the case where we're exactly at the end of the
 952          * device, and *cow_offset + 1 is off the end.  So, just back it up
 953          * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
 954          * for the original diagnosis.
 955          */
 956         if(*cow_offset == ((bitmap_len + sizeof(unsigned long) - 1) /
 957                            sizeof(unsigned long) - 1))
 958                 (*cow_offset)--;
 959
 960         bitmap_words[0] = bitmap[*cow_offset];
 961         bitmap_words[1] = bitmap[*cow_offset + 1];
 962
 963         *cow_offset *= sizeof(unsigned long);
 964         *cow_offset += bitmap_offset;
 965 }
 966
 967 static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
 968                        __u64 bitmap_offset, __u64 bitmap_len)
 969 {
 970         __u64 sector = req->offset >> 9;
 971         int i;
 972
 973         if(req->length > (sizeof(req->sector_mask) * 8) << 9)
 974                 panic("Operation too long");
 975
 976         if(req->op == UBD_READ) {
 977                 for(i = 0; i < req->length >> 9; i++){
 978                         if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
 979                                 ubd_set_bit(i, (unsigned char *)
 980                                             &req->sector_mask);
 981                 }
 982         }
 983         else cowify_bitmap(req->offset, req->length, &req->sector_mask,
 984                            &req->cow_offset, bitmap, bitmap_offset,
 985                            req->bitmap_words, bitmap_len);
 986 }
 987
 988 /* Called with ubd_io_lock held */
 989 static int prepare_request(struct request *req, struct io_thread_req *io_req)
 990 {
 991         struct gendisk *disk = req->rq_disk;
 992         struct ubd *ubd_dev = disk->private_data;
 993         __u64 offset;
 994         int len;
 995
 996         /* This should be impossible now */
 997         if((rq_data_dir(req) == WRITE) && !ubd_dev->openflags.w){
 998                 printk("Write attempted on readonly ubd device %s\n",
 999                        disk->disk_name);
1000                 end_request(req, 0);
1001                 return(1);
1002         }
1003
1004         offset = ((__u64) req->sector) << 9;
1005         len = req->current_nr_sectors << 9;
1006
1007         io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd : ubd_dev->fd;
1008         io_req->fds[1] = ubd_dev->fd;
1009         io_req->cow_offset = -1;
1010         io_req->offset = offset;
1011         io_req->length = len;
1012         io_req->error = 0;
1013         io_req->sector_mask = 0;
1014
1015         io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
1016         io_req->offsets[0] = 0;
1017         io_req->offsets[1] = ubd_dev->cow.data_offset;
1018         io_req->buffer = req->buffer;
1019         io_req->sectorsize = 1 << 9;
1020
1021         if(ubd_dev->cow.file != NULL)
1022                 cowify_req(io_req, ubd_dev->cow.bitmap, ubd_dev->cow.bitmap_offset,
1023                            ubd_dev->cow.bitmap_len);
1024
1025         return(0);
1026 }
1027
1028 /* Called with ubd_io_lock held */
1029 static void do_ubd_request(request_queue_t *q)
1030 {
1031         struct io_thread_req io_req;
1032         struct request *req;
1033         int err, n;
1034
1035         if(thread_fd == -1){
1036                 while((req = elv_next_request(q)) != NULL){
1037                         err = prepare_request(req, &io_req);
1038                         if(!err){
1039                                 do_io(&io_req);
1040                                 __ubd_finish(req, io_req.error);
1041                         }
1042                 }
1043         }
1044         else {
1045                 if(do_ubd || (req = elv_next_request(q)) == NULL)
1046                         return;
1047                 err = prepare_request(req, &io_req);
1048                 if(!err){
1049                         do_ubd = 1;
1050                         n = os_write_file(thread_fd, (char *) &io_req,
1051                                          sizeof(io_req));
1052                         if(n != sizeof(io_req))
1053                                 printk("write to io thread failed, "
1054                                        "errno = %d\n", -n);
1055                 }
1056         }
1057 }
1058
1059 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
1060 {
1061         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1062
1063         geo->heads = 128;
1064         geo->sectors = 32;
1065         geo->cylinders = ubd_dev->size / (128 * 32 * 512);
1066         return 0;
1067 }
1068
1069 static int ubd_ioctl(struct inode * inode, struct file * file,
1070                      unsigned int cmd, unsigned long arg)
1071 {
1072         struct ubd *ubd_dev = inode->i_bdev->bd_disk->private_data;
1073         struct hd_driveid ubd_id = {
1074                 .cyls           = 0,
1075                 .heads          = 128,
1076                 .sectors        = 32,
1077         };
1078
1079         switch (cmd) {
1080                 struct cdrom_volctrl volume;
1081         case HDIO_GET_IDENTITY:
1082                 ubd_id.cyls = ubd_dev->size / (128 * 32 * 512);
1083                 if(copy_to_user((char __user *) arg, (char *) &ubd_id,
1084                                  sizeof(ubd_id)))
1085                         return(-EFAULT);
1086                 return(0);
1087
1088         case CDROMVOLREAD:
1089                 if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
1090                         return(-EFAULT);
1091                 volume.channel0 = 255;
1092                 volume.channel1 = 255;
1093                 volume.channel2 = 255;
1094                 volume.channel3 = 255;
1095                 if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
1096                         return(-EFAULT);
1097                 return(0);
1098         }
1099         return(-EINVAL);
1100 }
1101
1102 static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
1103 {
1104         struct uml_stat buf1, buf2;
1105         int err;
1106
1107         if(from_cmdline == NULL)
1108                 return 0;
1109         if(!strcmp(from_cmdline, from_cow))
1110                 return 0;
1111
1112         err = os_stat_file(from_cmdline, &buf1);
1113         if(err < 0){
1114                 printk("Couldn't stat '%s', err = %d\n", from_cmdline, -err);
1115                 return 0;
1116         }
1117         err = os_stat_file(from_cow, &buf2);
1118         if(err < 0){
1119                 printk("Couldn't stat '%s', err = %d\n", from_cow, -err);
1120                 return 1;
1121         }
1122         if((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
1123                 return 0;
1124
1125         printk("Backing file mismatch - \"%s\" requested,\n"
1126                "\"%s\" specified in COW header of \"%s\"\n",
1127                from_cmdline, from_cow, cow);
1128         return 1;
1129 }
1130
1131 static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
1132 {
1133         unsigned long modtime;
1134         unsigned long long actual;
1135         int err;
1136
1137         err = os_file_modtime(file, &modtime);
1138         if(err < 0){
1139                 printk("Failed to get modification time of backing file "
1140                        "\"%s\", err = %d\n", file, -err);
1141                 return(err);
1142         }
1143
1144         err = os_file_size(file, &actual);
1145         if(err < 0){
1146                 printk("Failed to get size of backing file \"%s\", "
1147                        "err = %d\n", file, -err);
1148                 return(err);
1149         }
1150
1151         if(actual != size){
1152                 /*__u64 can be a long on AMD64 and with %lu GCC complains; so
1153                  * the typecast.*/
1154                 printk("Size mismatch (%llu vs %llu) of COW header vs backing "
1155                        "file\n", (unsigned long long) size, actual);
1156                 return(-EINVAL);
1157         }
1158         if(modtime != mtime){
1159                 printk("mtime mismatch (%ld vs %ld) of COW header vs backing "
1160                        "file\n", mtime, modtime);
1161                 return(-EINVAL);
1162         }
1163         return(0);
1164 }
1165
1166 int read_cow_bitmap(int fd, void *buf, int offset, int len)
1167 {
1168         int err;
1169
1170         err = os_seek_file(fd, offset);
1171         if(err < 0)
1172                 return(err);
1173
1174         err = os_read_file(fd, buf, len);
1175         if(err < 0)
1176                 return(err);
1177
1178         return(0);
1179 }
1180
1181 int open_ubd_file(char *file, struct openflags *openflags, int shared,
1182                   char **backing_file_out, int *bitmap_offset_out,
1183                   unsigned long *bitmap_len_out, int *data_offset_out,
1184                   int *create_cow_out)
1185 {
1186         time_t mtime;
1187         unsigned long long size;
1188         __u32 version, align;
1189         char *backing_file;
1190         int fd, err, sectorsize, asked_switch, mode = 0644;
1191
1192         fd = os_open_file(file, *openflags, mode);
1193         if (fd < 0) {
1194                 if ((fd == -ENOENT) && (create_cow_out != NULL))
1195                         *create_cow_out = 1;
1196                 if (!openflags->w ||
1197                    ((fd != -EROFS) && (fd != -EACCES)))
1198                         return fd;
1199                 openflags->w = 0;
1200                 fd = os_open_file(file, *openflags, mode);
1201                 if (fd < 0)
1202                         return fd;
1203         }
1204
1205         if(shared)
1206                 printk("Not locking \"%s\" on the host\n", file);
1207         else {
1208                 err = os_lock_file(fd, openflags->w);
1209                 if(err < 0){
1210                         printk("Failed to lock '%s', err = %d\n", file, -err);
1211                         goto out_close;
1212                 }
1213         }
1214
1215         /* Successful return case! */
1216         if(backing_file_out == NULL)
1217                 return(fd);
1218
1219         err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
1220                               &size, &sectorsize, &align, bitmap_offset_out);
1221         if(err && (*backing_file_out != NULL)){
1222                 printk("Failed to read COW header from COW file \"%s\", "
1223                        "errno = %d\n", file, -err);
1224                 goto out_close;
1225         }
1226         if(err)
1227                 return(fd);
1228
1229         asked_switch = path_requires_switch(*backing_file_out, backing_file, file);
1230
1231         /* Allow switching only if no mismatch. */
1232         if (asked_switch && !backing_file_mismatch(*backing_file_out, size, mtime)) {
1233                 printk("Switching backing file to '%s'\n", *backing_file_out);
1234                 err = write_cow_header(file, fd, *backing_file_out,
1235                                        sectorsize, align, &size);
1236                 if (err) {
1237                         printk("Switch failed, errno = %d\n", -err);
1238                         goto out_close;
1239                 }
1240         } else {
1241                 *backing_file_out = backing_file;
1242                 err = backing_file_mismatch(*backing_file_out, size, mtime);
1243                 if (err)
1244                         goto out_close;
1245         }
1246
1247         cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
1248                   bitmap_len_out, data_offset_out);
1249
1250         return fd;
1251  out_close:
1252         os_close_file(fd);
1253         return err;
1254 }
1255
1256 int create_cow_file(char *cow_file, char *backing_file, struct openflags flags,
1257                     int sectorsize, int alignment, int *bitmap_offset_out,
1258                     unsigned long *bitmap_len_out, int *data_offset_out)
1259 {
1260         int err, fd;
1261
1262         flags.c = 1;
1263         fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
1264         if(fd < 0){
1265                 err = fd;
1266                 printk("Open of COW file '%s' failed, errno = %d\n", cow_file,
1267                        -err);
1268                 goto out;
1269         }
1270
1271         err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
1272                             bitmap_offset_out, bitmap_len_out,
1273                             data_offset_out);
1274         if(!err)
1275                 return(fd);
1276         os_close_file(fd);
1277  out:
1278         return(err);
1279 }
1280
1281 static int update_bitmap(struct io_thread_req *req)
1282 {
1283         int n;
1284
1285         if(req->cow_offset == -1)
1286                 return(0);
1287
1288         n = os_seek_file(req->fds[1], req->cow_offset);
1289         if(n < 0){
1290                 printk("do_io - bitmap lseek failed : err = %d\n", -n);
1291                 return(1);
1292         }
1293
1294         n = os_write_file(req->fds[1], &req->bitmap_words,
1295                           sizeof(req->bitmap_words));
1296         if(n != sizeof(req->bitmap_words)){
1297                 printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
1298                        req->fds[1]);
1299                 return(1);
1300         }
1301
1302         return(0);
1303 }
1304
1305 void do_io(struct io_thread_req *req)
1306 {
1307         char *buf;
1308         unsigned long len;
1309         int n, nsectors, start, end, bit;
1310         int err;
1311         __u64 off;
1312
1313         nsectors = req->length / req->sectorsize;
1314         start = 0;
1315         do {
1316                 bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
1317                 end = start;
1318                 while((end < nsectors) &&
1319                       (ubd_test_bit(end, (unsigned char *)
1320                                     &req->sector_mask) == bit))
1321                         end++;
1322
1323                 off = req->offset + req->offsets[bit] +
1324                         start * req->sectorsize;
1325                 len = (end - start) * req->sectorsize;
1326                 buf = &req->buffer[start * req->sectorsize];
1327
1328                 err = os_seek_file(req->fds[bit], off);
1329                 if(err < 0){
1330                         printk("do_io - lseek failed : err = %d\n", -err);
1331                         req->error = 1;
1332                         return;
1333                 }
1334                 if(req->op == UBD_READ){
1335                         n = 0;
1336                         do {
1337                                 buf = &buf[n];
1338                                 len -= n;
1339                                 n = os_read_file(req->fds[bit], buf, len);
1340                                 if (n < 0) {
1341                                         printk("do_io - read failed, err = %d "
1342                                                "fd = %d\n", -n, req->fds[bit]);
1343                                         req->error = 1;
1344                                         return;
1345                                 }
1346                         } while((n < len) && (n != 0));
1347                         if (n < len) memset(&buf[n], 0, len - n);
1348                 } else {
1349                         n = os_write_file(req->fds[bit], buf, len);
1350                         if(n != len){
1351                                 printk("do_io - write failed err = %d "
1352                                        "fd = %d\n", -n, req->fds[bit]);
1353                                 req->error = 1;
1354                                 return;
1355                         }
1356                 }
1357
1358                 start = end;
1359         } while(start < nsectors);
1360
1361         req->error = update_bitmap(req);
1362 }
1363
1364 /* Changed in start_io_thread, which is serialized by being called only
1365  * from ubd_init, which is an initcall.
1366  */
1367 int kernel_fd = -1;
1368
1369 /* Only changed by the io thread */
1370 int io_count = 0;
1371
1372 int io_thread(void *arg)
1373 {
1374         struct io_thread_req req;
1375         int n;
1376
1377         ignore_sigwinch_sig();
1378         while(1){
1379                 n = os_read_file(kernel_fd, &req, sizeof(req));
1380                 if(n != sizeof(req)){
1381                         if(n < 0)
1382                                 printk("io_thread - read failed, fd = %d, "
1383                                        "err = %d\n", kernel_fd, -n);
1384                         else {
1385                                 printk("io_thread - short read, fd = %d, "
1386                                        "length = %d\n", kernel_fd, n);
1387                         }
1388                         continue;
1389                 }
1390                 io_count++;
1391                 do_io(&req);
1392                 n = os_write_file(kernel_fd, &req, sizeof(req));
1393                 if(n != sizeof(req))
1394                         printk("io_thread - write failed, fd = %d, err = %d\n",
1395                                kernel_fd, -n);
1396         }
1397
1398         return 0;
1399 }