Pull alexey-fixes into release branch
[linux-2.6] / 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/kernel.h"
24 #include "linux/module.h"
25 #include "linux/blkdev.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/ctype.h"
31 #include "linux/capability.h"
32 #include "linux/mm.h"
33 #include "linux/vmalloc.h"
34 #include "linux/blkpg.h"
35 #include "linux/genhd.h"
36 #include "linux/spinlock.h"
37 #include "linux/platform_device.h"
38 #include "linux/scatterlist.h"
39 #include "asm/segment.h"
40 #include "asm/uaccess.h"
41 #include "asm/irq.h"
42 #include "asm/types.h"
43 #include "asm/tlbflush.h"
44 #include "mem_user.h"
45 #include "kern_util.h"
46 #include "kern.h"
47 #include "mconsole_kern.h"
48 #include "init.h"
49 #include "irq_user.h"
50 #include "irq_kern.h"
51 #include "ubd_user.h"
52 #include "os.h"
53 #include "mem.h"
54 #include "mem_kern.h"
55 #include "cow.h"
56
57 enum ubd_req { UBD_READ, UBD_WRITE };
58
59 struct io_thread_req {
60         struct request *req;
61         enum ubd_req op;
62         int fds[2];
63         unsigned long offsets[2];
64         unsigned long long offset;
65         unsigned long length;
66         char *buffer;
67         int sectorsize;
68         unsigned long sector_mask;
69         unsigned long long cow_offset;
70         unsigned long bitmap_words[2];
71         int error;
72 };
73
74 extern int open_ubd_file(char *file, struct openflags *openflags, int shared,
75                          char **backing_file_out, int *bitmap_offset_out,
76                          unsigned long *bitmap_len_out, int *data_offset_out,
77                          int *create_cow_out);
78 extern int create_cow_file(char *cow_file, char *backing_file,
79                            struct openflags flags, int sectorsize,
80                            int alignment, int *bitmap_offset_out,
81                            unsigned long *bitmap_len_out,
82                            int *data_offset_out);
83 extern int read_cow_bitmap(int fd, void *buf, int offset, int len);
84 extern void do_io(struct io_thread_req *req);
85
86 static inline int ubd_test_bit(__u64 bit, unsigned char *data)
87 {
88         __u64 n;
89         int bits, off;
90
91         bits = sizeof(data[0]) * 8;
92         n = bit / bits;
93         off = bit % bits;
94         return (data[n] & (1 << off)) != 0;
95 }
96
97 static inline void ubd_set_bit(__u64 bit, unsigned char *data)
98 {
99         __u64 n;
100         int bits, off;
101
102         bits = sizeof(data[0]) * 8;
103         n = bit / bits;
104         off = bit % bits;
105         data[n] |= (1 << off);
106 }
107 /*End stuff from ubd_user.h*/
108
109 #define DRIVER_NAME "uml-blkdev"
110
111 static DEFINE_MUTEX(ubd_lock);
112
113 static int ubd_open(struct inode * inode, struct file * filp);
114 static int ubd_release(struct inode * inode, struct file * file);
115 static int ubd_ioctl(struct inode * inode, struct file * file,
116                      unsigned int cmd, unsigned long arg);
117 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
118
119 #define MAX_DEV (16)
120
121 static struct block_device_operations ubd_blops = {
122         .owner          = THIS_MODULE,
123         .open           = ubd_open,
124         .release        = ubd_release,
125         .ioctl          = ubd_ioctl,
126         .getgeo         = ubd_getgeo,
127 };
128
129 /* Protected by ubd_lock */
130 static int fake_major = MAJOR_NR;
131 static struct gendisk *ubd_gendisk[MAX_DEV];
132 static struct gendisk *fake_gendisk[MAX_DEV];
133
134 #ifdef CONFIG_BLK_DEV_UBD_SYNC
135 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
136                                          .cl = 1 })
137 #else
138 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
139                                          .cl = 1 })
140 #endif
141 static struct openflags global_openflags = OPEN_FLAGS;
142
143 struct cow {
144         /* backing file name */
145         char *file;
146         /* backing file fd */
147         int fd;
148         unsigned long *bitmap;
149         unsigned long bitmap_len;
150         int bitmap_offset;
151         int data_offset;
152 };
153
154 #define MAX_SG 64
155
156 struct ubd {
157         struct list_head restart;
158         /* name (and fd, below) of the file opened for writing, either the
159          * backing or the cow file. */
160         char *file;
161         int count;
162         int fd;
163         __u64 size;
164         struct openflags boot_openflags;
165         struct openflags openflags;
166         unsigned shared:1;
167         unsigned no_cow:1;
168         struct cow cow;
169         struct platform_device pdev;
170         struct request_queue *queue;
171         spinlock_t lock;
172         struct scatterlist sg[MAX_SG];
173         struct request *request;
174         int start_sg, end_sg;
175 };
176
177 #define DEFAULT_COW { \
178         .file =                 NULL, \
179         .fd =                   -1,     \
180         .bitmap =               NULL, \
181         .bitmap_offset =        0, \
182         .data_offset =          0, \
183 }
184
185 #define DEFAULT_UBD { \
186         .file =                 NULL, \
187         .count =                0, \
188         .fd =                   -1, \
189         .size =                 -1, \
190         .boot_openflags =       OPEN_FLAGS, \
191         .openflags =            OPEN_FLAGS, \
192         .no_cow =               0, \
193         .shared =               0, \
194         .cow =                  DEFAULT_COW, \
195         .lock =                 SPIN_LOCK_UNLOCKED,     \
196         .request =              NULL, \
197         .start_sg =             0, \
198         .end_sg =               0, \
199 }
200
201 /* Protected by ubd_lock */
202 struct ubd ubd_devs[MAX_DEV] = { [ 0 ... MAX_DEV - 1 ] = DEFAULT_UBD };
203
204 /* Only changed by fake_ide_setup which is a setup */
205 static int fake_ide = 0;
206 static struct proc_dir_entry *proc_ide_root = NULL;
207 static struct proc_dir_entry *proc_ide = NULL;
208
209 static void make_proc_ide(void)
210 {
211         proc_ide_root = proc_mkdir("ide", NULL);
212         proc_ide = proc_mkdir("ide0", proc_ide_root);
213 }
214
215 static int proc_ide_read_media(char *page, char **start, off_t off, int count,
216                                int *eof, void *data)
217 {
218         int len;
219
220         strcpy(page, "disk\n");
221         len = strlen("disk\n");
222         len -= off;
223         if (len < count){
224                 *eof = 1;
225                 if (len <= 0) return 0;
226         }
227         else len = count;
228         *start = page + off;
229         return len;
230 }
231
232 static void make_ide_entries(char *dev_name)
233 {
234         struct proc_dir_entry *dir, *ent;
235         char name[64];
236
237         if(proc_ide_root == NULL) make_proc_ide();
238
239         dir = proc_mkdir(dev_name, proc_ide);
240         if(!dir) return;
241
242         ent = create_proc_entry("media", S_IFREG|S_IRUGO, dir);
243         if(!ent) return;
244         ent->data = NULL;
245         ent->read_proc = proc_ide_read_media;
246         ent->write_proc = NULL;
247         sprintf(name,"ide0/%s", dev_name);
248         proc_symlink(dev_name, proc_ide_root, name);
249 }
250
251 static int fake_ide_setup(char *str)
252 {
253         fake_ide = 1;
254         return 1;
255 }
256
257 __setup("fake_ide", fake_ide_setup);
258
259 __uml_help(fake_ide_setup,
260 "fake_ide\n"
261 "    Create ide0 entries that map onto ubd devices.\n\n"
262 );
263
264 static int parse_unit(char **ptr)
265 {
266         char *str = *ptr, *end;
267         int n = -1;
268
269         if(isdigit(*str)) {
270                 n = simple_strtoul(str, &end, 0);
271                 if(end == str)
272                         return -1;
273                 *ptr = end;
274         }
275         else if (('a' <= *str) && (*str <= 'z')) {
276                 n = *str - 'a';
277                 str++;
278                 *ptr = str;
279         }
280         return n;
281 }
282
283 /* If *index_out == -1 at exit, the passed option was a general one;
284  * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
285  * should not be freed on exit.
286  */
287 static int ubd_setup_common(char *str, int *index_out, char **error_out)
288 {
289         struct ubd *ubd_dev;
290         struct openflags flags = global_openflags;
291         char *backing_file;
292         int n, err = 0, i;
293
294         if(index_out) *index_out = -1;
295         n = *str;
296         if(n == '='){
297                 char *end;
298                 int major;
299
300                 str++;
301                 if(!strcmp(str, "sync")){
302                         global_openflags = of_sync(global_openflags);
303                         goto out1;
304                 }
305
306                 err = -EINVAL;
307                 major = simple_strtoul(str, &end, 0);
308                 if((*end != '\0') || (end == str)){
309                         *error_out = "Didn't parse major number";
310                         goto out1;
311                 }
312
313                 mutex_lock(&ubd_lock);
314                 if(fake_major != MAJOR_NR){
315                         *error_out = "Can't assign a fake major twice";
316                         goto out1;
317                 }
318
319                 fake_major = major;
320
321                 printk(KERN_INFO "Setting extra ubd major number to %d\n",
322                        major);
323                 err = 0;
324         out1:
325                 mutex_unlock(&ubd_lock);
326                 return err;
327         }
328
329         n = parse_unit(&str);
330         if(n < 0){
331                 *error_out = "Couldn't parse device number";
332                 return -EINVAL;
333         }
334         if(n >= MAX_DEV){
335                 *error_out = "Device number out of range";
336                 return 1;
337         }
338
339         err = -EBUSY;
340         mutex_lock(&ubd_lock);
341
342         ubd_dev = &ubd_devs[n];
343         if(ubd_dev->file != NULL){
344                 *error_out = "Device is already configured";
345                 goto out;
346         }
347
348         if (index_out)
349                 *index_out = n;
350
351         err = -EINVAL;
352         for (i = 0; i < sizeof("rscd="); i++) {
353                 switch (*str) {
354                 case 'r':
355                         flags.w = 0;
356                         break;
357                 case 's':
358                         flags.s = 1;
359                         break;
360                 case 'd':
361                         ubd_dev->no_cow = 1;
362                         break;
363                 case 'c':
364                         ubd_dev->shared = 1;
365                         break;
366                 case '=':
367                         str++;
368                         goto break_loop;
369                 default:
370                         *error_out = "Expected '=' or flag letter "
371                                 "(r, s, c, or d)";
372                         goto out;
373                 }
374                 str++;
375         }
376
377         if (*str == '=')
378                 *error_out = "Too many flags specified";
379         else
380                 *error_out = "Missing '='";
381         goto out;
382
383 break_loop:
384         backing_file = strchr(str, ',');
385
386         if (backing_file == NULL)
387                 backing_file = strchr(str, ':');
388
389         if(backing_file != NULL){
390                 if(ubd_dev->no_cow){
391                         *error_out = "Can't specify both 'd' and a cow file";
392                         goto out;
393                 }
394                 else {
395                         *backing_file = '\0';
396                         backing_file++;
397                 }
398         }
399         err = 0;
400         ubd_dev->file = str;
401         ubd_dev->cow.file = backing_file;
402         ubd_dev->boot_openflags = flags;
403 out:
404         mutex_unlock(&ubd_lock);
405         return err;
406 }
407
408 static int ubd_setup(char *str)
409 {
410         char *error;
411         int err;
412
413         err = ubd_setup_common(str, NULL, &error);
414         if(err)
415                 printk(KERN_ERR "Failed to initialize device with \"%s\" : "
416                        "%s\n", str, error);
417         return 1;
418 }
419
420 __setup("ubd", ubd_setup);
421 __uml_help(ubd_setup,
422 "ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
423 "    This is used to associate a device with a file in the underlying\n"
424 "    filesystem. When specifying two filenames, the first one is the\n"
425 "    COW name and the second is the backing file name. As separator you can\n"
426 "    use either a ':' or a ',': the first one allows writing things like;\n"
427 "       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
428 "    while with a ',' the shell would not expand the 2nd '~'.\n"
429 "    When using only one filename, UML will detect whether to treat it like\n"
430 "    a COW file or a backing file. To override this detection, add the 'd'\n"
431 "    flag:\n"
432 "       ubd0d=BackingFile\n"
433 "    Usually, there is a filesystem in the file, but \n"
434 "    that's not required. Swap devices containing swap files can be\n"
435 "    specified like this. Also, a file which doesn't contain a\n"
436 "    filesystem can have its contents read in the virtual \n"
437 "    machine by running 'dd' on the device. <n> must be in the range\n"
438 "    0 to 7. Appending an 'r' to the number will cause that device\n"
439 "    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
440 "    an 's' will cause data to be written to disk on the host immediately.\n\n"
441 );
442
443 static int udb_setup(char *str)
444 {
445         printk("udb%s specified on command line is almost certainly a ubd -> "
446                "udb TYPO\n", str);
447         return 1;
448 }
449
450 __setup("udb", udb_setup);
451 __uml_help(udb_setup,
452 "udb\n"
453 "    This option is here solely to catch ubd -> udb typos, which can be\n"
454 "    to impossible to catch visually unless you specifically look for\n"
455 "    them.  The only result of any option starting with 'udb' is an error\n"
456 "    in the boot output.\n\n"
457 );
458
459 static int fakehd_set = 0;
460 static int fakehd(char *str)
461 {
462         printk(KERN_INFO "fakehd : Changing ubd name to \"hd\".\n");
463         fakehd_set = 1;
464         return 1;
465 }
466
467 __setup("fakehd", fakehd);
468 __uml_help(fakehd,
469 "fakehd\n"
470 "    Change the ubd device name to \"hd\".\n\n"
471 );
472
473 static void do_ubd_request(struct request_queue * q);
474
475 /* Only changed by ubd_init, which is an initcall. */
476 int thread_fd = -1;
477
478 static void ubd_end_request(struct request *req, int bytes, int uptodate)
479 {
480         if (!end_that_request_first(req, uptodate, bytes >> 9)) {
481                 struct ubd *dev = req->rq_disk->private_data;
482                 unsigned long flags;
483
484                 add_disk_randomness(req->rq_disk);
485                 spin_lock_irqsave(&dev->lock, flags);
486                 end_that_request_last(req, uptodate);
487                 spin_unlock_irqrestore(&dev->lock, flags);
488         }
489 }
490
491 /* Callable only from interrupt context - otherwise you need to do
492  * spin_lock_irq()/spin_lock_irqsave() */
493 static inline void ubd_finish(struct request *req, int bytes)
494 {
495         if(bytes < 0){
496                 ubd_end_request(req, 0, 0);
497                 return;
498         }
499         ubd_end_request(req, bytes, 1);
500 }
501
502 static LIST_HEAD(restart);
503
504 /* XXX - move this inside ubd_intr. */
505 /* Called without dev->lock held, and only in interrupt context. */
506 static void ubd_handler(void)
507 {
508         struct io_thread_req *req;
509         struct request *rq;
510         struct ubd *ubd;
511         struct list_head *list, *next_ele;
512         unsigned long flags;
513         int n;
514
515         while(1){
516                 n = os_read_file(thread_fd, &req,
517                                  sizeof(struct io_thread_req *));
518                 if(n != sizeof(req)){
519                         if(n == -EAGAIN)
520                                 break;
521                         printk(KERN_ERR "spurious interrupt in ubd_handler, "
522                                "err = %d\n", -n);
523                         return;
524                 }
525
526                 rq = req->req;
527                 rq->nr_sectors -= req->length >> 9;
528                 if(rq->nr_sectors == 0)
529                         ubd_finish(rq, rq->hard_nr_sectors << 9);
530                 kfree(req);
531         }
532         reactivate_fd(thread_fd, UBD_IRQ);
533
534         list_for_each_safe(list, next_ele, &restart){
535                 ubd = container_of(list, struct ubd, restart);
536                 list_del_init(&ubd->restart);
537                 spin_lock_irqsave(&ubd->lock, flags);
538                 do_ubd_request(ubd->queue);
539                 spin_unlock_irqrestore(&ubd->lock, flags);
540         }
541 }
542
543 static irqreturn_t ubd_intr(int irq, void *dev)
544 {
545         ubd_handler();
546         return IRQ_HANDLED;
547 }
548
549 /* Only changed by ubd_init, which is an initcall. */
550 static int io_pid = -1;
551
552 void kill_io_thread(void)
553 {
554         if(io_pid != -1)
555                 os_kill_process(io_pid, 1);
556 }
557
558 __uml_exitcall(kill_io_thread);
559
560 static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
561 {
562         char *file;
563
564         file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
565         return os_file_size(file, size_out);
566 }
567
568 static void ubd_close_dev(struct ubd *ubd_dev)
569 {
570         os_close_file(ubd_dev->fd);
571         if(ubd_dev->cow.file == NULL)
572                 return;
573
574         os_close_file(ubd_dev->cow.fd);
575         vfree(ubd_dev->cow.bitmap);
576         ubd_dev->cow.bitmap = NULL;
577 }
578
579 static int ubd_open_dev(struct ubd *ubd_dev)
580 {
581         struct openflags flags;
582         char **back_ptr;
583         int err, create_cow, *create_ptr;
584         int fd;
585
586         ubd_dev->openflags = ubd_dev->boot_openflags;
587         create_cow = 0;
588         create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
589         back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;
590
591         fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
592                                 back_ptr, &ubd_dev->cow.bitmap_offset,
593                                 &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
594                                 create_ptr);
595
596         if((fd == -ENOENT) && create_cow){
597                 fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
598                                           ubd_dev->openflags, 1 << 9, PAGE_SIZE,
599                                           &ubd_dev->cow.bitmap_offset,
600                                           &ubd_dev->cow.bitmap_len,
601                                           &ubd_dev->cow.data_offset);
602                 if(fd >= 0){
603                         printk(KERN_INFO "Creating \"%s\" as COW file for "
604                                "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
605                 }
606         }
607
608         if(fd < 0){
609                 printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
610                        -fd);
611                 return fd;
612         }
613         ubd_dev->fd = fd;
614
615         if(ubd_dev->cow.file != NULL){
616                 blk_queue_max_sectors(ubd_dev->queue, 8 * sizeof(long));
617
618                 err = -ENOMEM;
619                 ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
620                 if(ubd_dev->cow.bitmap == NULL){
621                         printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
622                         goto error;
623                 }
624                 flush_tlb_kernel_vm();
625
626                 err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
627                                       ubd_dev->cow.bitmap_offset,
628                                       ubd_dev->cow.bitmap_len);
629                 if(err < 0)
630                         goto error;
631
632                 flags = ubd_dev->openflags;
633                 flags.w = 0;
634                 err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
635                                     NULL, NULL, NULL, NULL);
636                 if(err < 0) goto error;
637                 ubd_dev->cow.fd = err;
638         }
639         return 0;
640  error:
641         os_close_file(ubd_dev->fd);
642         return err;
643 }
644
645 static void ubd_device_release(struct device *dev)
646 {
647         struct ubd *ubd_dev = dev->driver_data;
648
649         blk_cleanup_queue(ubd_dev->queue);
650         *ubd_dev = ((struct ubd) DEFAULT_UBD);
651 }
652
653 static int ubd_disk_register(int major, u64 size, int unit,
654                              struct gendisk **disk_out)
655 {
656         struct gendisk *disk;
657
658         disk = alloc_disk(1 << UBD_SHIFT);
659         if(disk == NULL)
660                 return -ENOMEM;
661
662         disk->major = major;
663         disk->first_minor = unit << UBD_SHIFT;
664         disk->fops = &ubd_blops;
665         set_capacity(disk, size / 512);
666         if(major == MAJOR_NR)
667                 sprintf(disk->disk_name, "ubd%c", 'a' + unit);
668         else
669                 sprintf(disk->disk_name, "ubd_fake%d", unit);
670
671         /* sysfs register (not for ide fake devices) */
672         if (major == MAJOR_NR) {
673                 ubd_devs[unit].pdev.id   = unit;
674                 ubd_devs[unit].pdev.name = DRIVER_NAME;
675                 ubd_devs[unit].pdev.dev.release = ubd_device_release;
676                 ubd_devs[unit].pdev.dev.driver_data = &ubd_devs[unit];
677                 platform_device_register(&ubd_devs[unit].pdev);
678                 disk->driverfs_dev = &ubd_devs[unit].pdev.dev;
679         }
680
681         disk->private_data = &ubd_devs[unit];
682         disk->queue = ubd_devs[unit].queue;
683         add_disk(disk);
684
685         *disk_out = disk;
686         return 0;
687 }
688
689 #define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
690
691 static int ubd_add(int n, char **error_out)
692 {
693         struct ubd *ubd_dev = &ubd_devs[n];
694         int err = 0;
695
696         if(ubd_dev->file == NULL)
697                 goto out;
698
699         err = ubd_file_size(ubd_dev, &ubd_dev->size);
700         if(err < 0){
701                 *error_out = "Couldn't determine size of device's file";
702                 goto out;
703         }
704
705         ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
706
707         INIT_LIST_HEAD(&ubd_dev->restart);
708         sg_init_table(&ubd_dev->sg, MAX_SG);
709
710         err = -ENOMEM;
711         ubd_dev->queue = blk_init_queue(do_ubd_request, &ubd_dev->lock);
712         if (ubd_dev->queue == NULL) {
713                 *error_out = "Failed to initialize device queue";
714                 goto out;
715         }
716         ubd_dev->queue->queuedata = ubd_dev;
717
718         blk_queue_max_hw_segments(ubd_dev->queue, MAX_SG);
719         err = ubd_disk_register(MAJOR_NR, ubd_dev->size, n, &ubd_gendisk[n]);
720         if(err){
721                 *error_out = "Failed to register device";
722                 goto out_cleanup;
723         }
724
725         if(fake_major != MAJOR_NR)
726                 ubd_disk_register(fake_major, ubd_dev->size, n,
727                                   &fake_gendisk[n]);
728
729         /* perhaps this should also be under the "if (fake_major)" above */
730         /* using the fake_disk->disk_name and also the fakehd_set name */
731         if (fake_ide)
732                 make_ide_entries(ubd_gendisk[n]->disk_name);
733
734         err = 0;
735 out:
736         return err;
737
738 out_cleanup:
739         blk_cleanup_queue(ubd_dev->queue);
740         goto out;
741 }
742
743 static int ubd_config(char *str, char **error_out)
744 {
745         int n, ret;
746
747         /* This string is possibly broken up and stored, so it's only
748          * freed if ubd_setup_common fails, or if only general options
749          * were set.
750          */
751         str = kstrdup(str, GFP_KERNEL);
752         if (str == NULL) {
753                 *error_out = "Failed to allocate memory";
754                 return -ENOMEM;
755         }
756
757         ret = ubd_setup_common(str, &n, error_out);
758         if (ret)
759                 goto err_free;
760
761         if (n == -1) {
762                 ret = 0;
763                 goto err_free;
764         }
765
766         mutex_lock(&ubd_lock);
767         ret = ubd_add(n, error_out);
768         if (ret)
769                 ubd_devs[n].file = NULL;
770         mutex_unlock(&ubd_lock);
771
772 out:
773         return ret;
774
775 err_free:
776         kfree(str);
777         goto out;
778 }
779
780 static int ubd_get_config(char *name, char *str, int size, char **error_out)
781 {
782         struct ubd *ubd_dev;
783         int n, len = 0;
784
785         n = parse_unit(&name);
786         if((n >= MAX_DEV) || (n < 0)){
787                 *error_out = "ubd_get_config : device number out of range";
788                 return -1;
789         }
790
791         ubd_dev = &ubd_devs[n];
792         mutex_lock(&ubd_lock);
793
794         if(ubd_dev->file == NULL){
795                 CONFIG_CHUNK(str, size, len, "", 1);
796                 goto out;
797         }
798
799         CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);
800
801         if(ubd_dev->cow.file != NULL){
802                 CONFIG_CHUNK(str, size, len, ",", 0);
803                 CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
804         }
805         else CONFIG_CHUNK(str, size, len, "", 1);
806
807  out:
808         mutex_unlock(&ubd_lock);
809         return len;
810 }
811
812 static int ubd_id(char **str, int *start_out, int *end_out)
813 {
814         int n;
815
816         n = parse_unit(str);
817         *start_out = 0;
818         *end_out = MAX_DEV - 1;
819         return n;
820 }
821
822 static int ubd_remove(int n, char **error_out)
823 {
824         struct gendisk *disk = ubd_gendisk[n];
825         struct ubd *ubd_dev;
826         int err = -ENODEV;
827
828         mutex_lock(&ubd_lock);
829
830         ubd_dev = &ubd_devs[n];
831
832         if(ubd_dev->file == NULL)
833                 goto out;
834
835         /* you cannot remove a open disk */
836         err = -EBUSY;
837         if(ubd_dev->count > 0)
838                 goto out;
839
840         ubd_gendisk[n] = NULL;
841         if(disk != NULL){
842                 del_gendisk(disk);
843                 put_disk(disk);
844         }
845
846         if(fake_gendisk[n] != NULL){
847                 del_gendisk(fake_gendisk[n]);
848                 put_disk(fake_gendisk[n]);
849                 fake_gendisk[n] = NULL;
850         }
851
852         err = 0;
853         platform_device_unregister(&ubd_dev->pdev);
854 out:
855         mutex_unlock(&ubd_lock);
856         return err;
857 }
858
859 /* All these are called by mconsole in process context and without
860  * ubd-specific locks.  The structure itself is const except for .list.
861  */
862 static struct mc_device ubd_mc = {
863         .list           = LIST_HEAD_INIT(ubd_mc.list),
864         .name           = "ubd",
865         .config         = ubd_config,
866         .get_config     = ubd_get_config,
867         .id             = ubd_id,
868         .remove         = ubd_remove,
869 };
870
871 static int __init ubd_mc_init(void)
872 {
873         mconsole_register_dev(&ubd_mc);
874         return 0;
875 }
876
877 __initcall(ubd_mc_init);
878
879 static int __init ubd0_init(void)
880 {
881         struct ubd *ubd_dev = &ubd_devs[0];
882
883         mutex_lock(&ubd_lock);
884         if(ubd_dev->file == NULL)
885                 ubd_dev->file = "root_fs";
886         mutex_unlock(&ubd_lock);
887
888         return 0;
889 }
890
891 __initcall(ubd0_init);
892
893 /* Used in ubd_init, which is an initcall */
894 static struct platform_driver ubd_driver = {
895         .driver = {
896                 .name  = DRIVER_NAME,
897         },
898 };
899
900 static int __init ubd_init(void)
901 {
902         char *error;
903         int i, err;
904
905         if (register_blkdev(MAJOR_NR, "ubd"))
906                 return -1;
907
908         if (fake_major != MAJOR_NR) {
909                 char name[sizeof("ubd_nnn\0")];
910
911                 snprintf(name, sizeof(name), "ubd_%d", fake_major);
912                 if (register_blkdev(fake_major, "ubd"))
913                         return -1;
914         }
915         platform_driver_register(&ubd_driver);
916         mutex_lock(&ubd_lock);
917         for (i = 0; i < MAX_DEV; i++){
918                 err = ubd_add(i, &error);
919                 if(err)
920                         printk(KERN_ERR "Failed to initialize ubd device %d :"
921                                "%s\n", i, error);
922         }
923         mutex_unlock(&ubd_lock);
924         return 0;
925 }
926
927 late_initcall(ubd_init);
928
929 static int __init ubd_driver_init(void){
930         unsigned long stack;
931         int err;
932
933         /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
934         if(global_openflags.s){
935                 printk(KERN_INFO "ubd: Synchronous mode\n");
936                 /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
937                  * enough. So use anyway the io thread. */
938         }
939         stack = alloc_stack(0, 0);
940         io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
941                                  &thread_fd);
942         if(io_pid < 0){
943                 printk(KERN_ERR
944                        "ubd : Failed to start I/O thread (errno = %d) - "
945                        "falling back to synchronous I/O\n", -io_pid);
946                 io_pid = -1;
947                 return 0;
948         }
949         err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
950                              IRQF_DISABLED, "ubd", ubd_devs);
951         if(err != 0)
952                 printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
953         return 0;
954 }
955
956 device_initcall(ubd_driver_init);
957
958 static int ubd_open(struct inode *inode, struct file *filp)
959 {
960         struct gendisk *disk = inode->i_bdev->bd_disk;
961         struct ubd *ubd_dev = disk->private_data;
962         int err = 0;
963
964         if(ubd_dev->count == 0){
965                 err = ubd_open_dev(ubd_dev);
966                 if(err){
967                         printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
968                                disk->disk_name, ubd_dev->file, -err);
969                         goto out;
970                 }
971         }
972         ubd_dev->count++;
973         set_disk_ro(disk, !ubd_dev->openflags.w);
974
975         /* This should no more be needed. And it didn't work anyway to exclude
976          * read-write remounting of filesystems.*/
977         /*if((filp->f_mode & FMODE_WRITE) && !ubd_dev->openflags.w){
978                 if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
979                 err = -EROFS;
980         }*/
981  out:
982         return err;
983 }
984
985 static int ubd_release(struct inode * inode, struct file * file)
986 {
987         struct gendisk *disk = inode->i_bdev->bd_disk;
988         struct ubd *ubd_dev = disk->private_data;
989
990         if(--ubd_dev->count == 0)
991                 ubd_close_dev(ubd_dev);
992         return 0;
993 }
994
995 static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
996                           __u64 *cow_offset, unsigned long *bitmap,
997                           __u64 bitmap_offset, unsigned long *bitmap_words,
998                           __u64 bitmap_len)
999 {
1000         __u64 sector = io_offset >> 9;
1001         int i, update_bitmap = 0;
1002
1003         for(i = 0; i < length >> 9; i++){
1004                 if(cow_mask != NULL)
1005                         ubd_set_bit(i, (unsigned char *) cow_mask);
1006                 if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1007                         continue;
1008
1009                 update_bitmap = 1;
1010                 ubd_set_bit(sector + i, (unsigned char *) bitmap);
1011         }
1012
1013         if(!update_bitmap)
1014                 return;
1015
1016         *cow_offset = sector / (sizeof(unsigned long) * 8);
1017
1018         /* This takes care of the case where we're exactly at the end of the
1019          * device, and *cow_offset + 1 is off the end.  So, just back it up
1020          * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
1021          * for the original diagnosis.
1022          */
1023         if(*cow_offset == ((bitmap_len + sizeof(unsigned long) - 1) /
1024                            sizeof(unsigned long) - 1))
1025                 (*cow_offset)--;
1026
1027         bitmap_words[0] = bitmap[*cow_offset];
1028         bitmap_words[1] = bitmap[*cow_offset + 1];
1029
1030         *cow_offset *= sizeof(unsigned long);
1031         *cow_offset += bitmap_offset;
1032 }
1033
1034 static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
1035                        __u64 bitmap_offset, __u64 bitmap_len)
1036 {
1037         __u64 sector = req->offset >> 9;
1038         int i;
1039
1040         if(req->length > (sizeof(req->sector_mask) * 8) << 9)
1041                 panic("Operation too long");
1042
1043         if(req->op == UBD_READ) {
1044                 for(i = 0; i < req->length >> 9; i++){
1045                         if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1046                                 ubd_set_bit(i, (unsigned char *)
1047                                             &req->sector_mask);
1048                 }
1049         }
1050         else cowify_bitmap(req->offset, req->length, &req->sector_mask,
1051                            &req->cow_offset, bitmap, bitmap_offset,
1052                            req->bitmap_words, bitmap_len);
1053 }
1054
1055 /* Called with dev->lock held */
1056 static void prepare_request(struct request *req, struct io_thread_req *io_req,
1057                             unsigned long long offset, int page_offset,
1058                             int len, struct page *page)
1059 {
1060         struct gendisk *disk = req->rq_disk;
1061         struct ubd *ubd_dev = disk->private_data;
1062
1063         io_req->req = req;
1064         io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
1065                 ubd_dev->fd;
1066         io_req->fds[1] = ubd_dev->fd;
1067         io_req->cow_offset = -1;
1068         io_req->offset = offset;
1069         io_req->length = len;
1070         io_req->error = 0;
1071         io_req->sector_mask = 0;
1072
1073         io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
1074         io_req->offsets[0] = 0;
1075         io_req->offsets[1] = ubd_dev->cow.data_offset;
1076         io_req->buffer = page_address(page) + page_offset;
1077         io_req->sectorsize = 1 << 9;
1078
1079         if(ubd_dev->cow.file != NULL)
1080                 cowify_req(io_req, ubd_dev->cow.bitmap,
1081                            ubd_dev->cow.bitmap_offset, ubd_dev->cow.bitmap_len);
1082
1083 }
1084
1085 /* Called with dev->lock held */
1086 static void do_ubd_request(struct request_queue *q)
1087 {
1088         struct io_thread_req *io_req;
1089         struct request *req;
1090         int n, last_sectors;
1091
1092         while(1){
1093                 struct ubd *dev = q->queuedata;
1094                 if(dev->end_sg == 0){
1095                         struct request *req = elv_next_request(q);
1096                         if(req == NULL)
1097                                 return;
1098
1099                         dev->request = req;
1100                         blkdev_dequeue_request(req);
1101                         dev->start_sg = 0;
1102                         dev->end_sg = blk_rq_map_sg(q, req, dev->sg);
1103                 }
1104
1105                 req = dev->request;
1106                 last_sectors = 0;
1107                 while(dev->start_sg < dev->end_sg){
1108                         struct scatterlist *sg = &dev->sg[dev->start_sg];
1109
1110                         req->sector += last_sectors;
1111                         io_req = kmalloc(sizeof(struct io_thread_req),
1112                                          GFP_ATOMIC);
1113                         if(io_req == NULL){
1114                                 if(list_empty(&dev->restart))
1115                                         list_add(&dev->restart, &restart);
1116                                 return;
1117                         }
1118                         prepare_request(req, io_req,
1119                                         (unsigned long long) req->sector << 9,
1120                                         sg->offset, sg->length, sg_page(sg));
1121
1122                         last_sectors = sg->length >> 9;
1123                         n = os_write_file(thread_fd, &io_req,
1124                                           sizeof(struct io_thread_req *));
1125                         if(n != sizeof(struct io_thread_req *)){
1126                                 if(n != -EAGAIN)
1127                                         printk("write to io thread failed, "
1128                                                "errno = %d\n", -n);
1129                                 else if(list_empty(&dev->restart))
1130                                         list_add(&dev->restart, &restart);
1131                                 return;
1132                         }
1133
1134                         dev->start_sg++;
1135                 }
1136                 dev->end_sg = 0;
1137                 dev->request = NULL;
1138         }
1139 }
1140
1141 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
1142 {
1143         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1144
1145         geo->heads = 128;
1146         geo->sectors = 32;
1147         geo->cylinders = ubd_dev->size / (128 * 32 * 512);
1148         return 0;
1149 }
1150
1151 static int ubd_ioctl(struct inode * inode, struct file * file,
1152                      unsigned int cmd, unsigned long arg)
1153 {
1154         struct ubd *ubd_dev = inode->i_bdev->bd_disk->private_data;
1155         struct hd_driveid ubd_id = {
1156                 .cyls           = 0,
1157                 .heads          = 128,
1158                 .sectors        = 32,
1159         };
1160
1161         switch (cmd) {
1162                 struct cdrom_volctrl volume;
1163         case HDIO_GET_IDENTITY:
1164                 ubd_id.cyls = ubd_dev->size / (128 * 32 * 512);
1165                 if(copy_to_user((char __user *) arg, (char *) &ubd_id,
1166                                  sizeof(ubd_id)))
1167                         return -EFAULT;
1168                 return 0;
1169
1170         case CDROMVOLREAD:
1171                 if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
1172                         return -EFAULT;
1173                 volume.channel0 = 255;
1174                 volume.channel1 = 255;
1175                 volume.channel2 = 255;
1176                 volume.channel3 = 255;
1177                 if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
1178                         return -EFAULT;
1179                 return 0;
1180         }
1181         return -EINVAL;
1182 }
1183
1184 static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
1185 {
1186         struct uml_stat buf1, buf2;
1187         int err;
1188
1189         if(from_cmdline == NULL)
1190                 return 0;
1191         if(!strcmp(from_cmdline, from_cow))
1192                 return 0;
1193
1194         err = os_stat_file(from_cmdline, &buf1);
1195         if(err < 0){
1196                 printk("Couldn't stat '%s', err = %d\n", from_cmdline, -err);
1197                 return 0;
1198         }
1199         err = os_stat_file(from_cow, &buf2);
1200         if(err < 0){
1201                 printk("Couldn't stat '%s', err = %d\n", from_cow, -err);
1202                 return 1;
1203         }
1204         if((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
1205                 return 0;
1206
1207         printk("Backing file mismatch - \"%s\" requested,\n"
1208                "\"%s\" specified in COW header of \"%s\"\n",
1209                from_cmdline, from_cow, cow);
1210         return 1;
1211 }
1212
1213 static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
1214 {
1215         unsigned long modtime;
1216         unsigned long long actual;
1217         int err;
1218
1219         err = os_file_modtime(file, &modtime);
1220         if(err < 0){
1221                 printk("Failed to get modification time of backing file "
1222                        "\"%s\", err = %d\n", file, -err);
1223                 return err;
1224         }
1225
1226         err = os_file_size(file, &actual);
1227         if(err < 0){
1228                 printk("Failed to get size of backing file \"%s\", "
1229                        "err = %d\n", file, -err);
1230                 return err;
1231         }
1232
1233         if(actual != size){
1234                 /*__u64 can be a long on AMD64 and with %lu GCC complains; so
1235                  * the typecast.*/
1236                 printk("Size mismatch (%llu vs %llu) of COW header vs backing "
1237                        "file\n", (unsigned long long) size, actual);
1238                 return -EINVAL;
1239         }
1240         if(modtime != mtime){
1241                 printk("mtime mismatch (%ld vs %ld) of COW header vs backing "
1242                        "file\n", mtime, modtime);
1243                 return -EINVAL;
1244         }
1245         return 0;
1246 }
1247
1248 int read_cow_bitmap(int fd, void *buf, int offset, int len)
1249 {
1250         int err;
1251
1252         err = os_seek_file(fd, offset);
1253         if(err < 0)
1254                 return err;
1255
1256         err = os_read_file(fd, buf, len);
1257         if(err < 0)
1258                 return err;
1259
1260         return 0;
1261 }
1262
1263 int open_ubd_file(char *file, struct openflags *openflags, int shared,
1264                   char **backing_file_out, int *bitmap_offset_out,
1265                   unsigned long *bitmap_len_out, int *data_offset_out,
1266                   int *create_cow_out)
1267 {
1268         time_t mtime;
1269         unsigned long long size;
1270         __u32 version, align;
1271         char *backing_file;
1272         int fd, err, sectorsize, asked_switch, mode = 0644;
1273
1274         fd = os_open_file(file, *openflags, mode);
1275         if (fd < 0) {
1276                 if ((fd == -ENOENT) && (create_cow_out != NULL))
1277                         *create_cow_out = 1;
1278                 if (!openflags->w ||
1279                     ((fd != -EROFS) && (fd != -EACCES)))
1280                         return fd;
1281                 openflags->w = 0;
1282                 fd = os_open_file(file, *openflags, mode);
1283                 if (fd < 0)
1284                         return fd;
1285         }
1286
1287         if(shared)
1288                 printk("Not locking \"%s\" on the host\n", file);
1289         else {
1290                 err = os_lock_file(fd, openflags->w);
1291                 if(err < 0){
1292                         printk("Failed to lock '%s', err = %d\n", file, -err);
1293                         goto out_close;
1294                 }
1295         }
1296
1297         /* Successful return case! */
1298         if(backing_file_out == NULL)
1299                 return fd;
1300
1301         err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
1302                               &size, &sectorsize, &align, bitmap_offset_out);
1303         if(err && (*backing_file_out != NULL)){
1304                 printk("Failed to read COW header from COW file \"%s\", "
1305                        "errno = %d\n", file, -err);
1306                 goto out_close;
1307         }
1308         if(err)
1309                 return fd;
1310
1311         asked_switch = path_requires_switch(*backing_file_out, backing_file, file);
1312
1313         /* Allow switching only if no mismatch. */
1314         if (asked_switch && !backing_file_mismatch(*backing_file_out, size, mtime)) {
1315                 printk("Switching backing file to '%s'\n", *backing_file_out);
1316                 err = write_cow_header(file, fd, *backing_file_out,
1317                                        sectorsize, align, &size);
1318                 if (err) {
1319                         printk("Switch failed, errno = %d\n", -err);
1320                         goto out_close;
1321                 }
1322         } else {
1323                 *backing_file_out = backing_file;
1324                 err = backing_file_mismatch(*backing_file_out, size, mtime);
1325                 if (err)
1326                         goto out_close;
1327         }
1328
1329         cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
1330                   bitmap_len_out, data_offset_out);
1331
1332         return fd;
1333  out_close:
1334         os_close_file(fd);
1335         return err;
1336 }
1337
1338 int create_cow_file(char *cow_file, char *backing_file, struct openflags flags,
1339                     int sectorsize, int alignment, int *bitmap_offset_out,
1340                     unsigned long *bitmap_len_out, int *data_offset_out)
1341 {
1342         int err, fd;
1343
1344         flags.c = 1;
1345         fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
1346         if(fd < 0){
1347                 err = fd;
1348                 printk("Open of COW file '%s' failed, errno = %d\n", cow_file,
1349                        -err);
1350                 goto out;
1351         }
1352
1353         err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
1354                             bitmap_offset_out, bitmap_len_out,
1355                             data_offset_out);
1356         if(!err)
1357                 return fd;
1358         os_close_file(fd);
1359  out:
1360         return err;
1361 }
1362
1363 static int update_bitmap(struct io_thread_req *req)
1364 {
1365         int n;
1366
1367         if(req->cow_offset == -1)
1368                 return 0;
1369
1370         n = os_seek_file(req->fds[1], req->cow_offset);
1371         if(n < 0){
1372                 printk("do_io - bitmap lseek failed : err = %d\n", -n);
1373                 return 1;
1374         }
1375
1376         n = os_write_file(req->fds[1], &req->bitmap_words,
1377                           sizeof(req->bitmap_words));
1378         if(n != sizeof(req->bitmap_words)){
1379                 printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
1380                        req->fds[1]);
1381                 return 1;
1382         }
1383
1384         return 0;
1385 }
1386
1387 void do_io(struct io_thread_req *req)
1388 {
1389         char *buf;
1390         unsigned long len;
1391         int n, nsectors, start, end, bit;
1392         int err;
1393         __u64 off;
1394
1395         nsectors = req->length / req->sectorsize;
1396         start = 0;
1397         do {
1398                 bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
1399                 end = start;
1400                 while((end < nsectors) &&
1401                       (ubd_test_bit(end, (unsigned char *)
1402                                     &req->sector_mask) == bit))
1403                         end++;
1404
1405                 off = req->offset + req->offsets[bit] +
1406                         start * req->sectorsize;
1407                 len = (end - start) * req->sectorsize;
1408                 buf = &req->buffer[start * req->sectorsize];
1409
1410                 err = os_seek_file(req->fds[bit], off);
1411                 if(err < 0){
1412                         printk("do_io - lseek failed : err = %d\n", -err);
1413                         req->error = 1;
1414                         return;
1415                 }
1416                 if(req->op == UBD_READ){
1417                         n = 0;
1418                         do {
1419                                 buf = &buf[n];
1420                                 len -= n;
1421                                 n = os_read_file(req->fds[bit], buf, len);
1422                                 if (n < 0) {
1423                                         printk("do_io - read failed, err = %d "
1424                                                "fd = %d\n", -n, req->fds[bit]);
1425                                         req->error = 1;
1426                                         return;
1427                                 }
1428                         } while((n < len) && (n != 0));
1429                         if (n < len) memset(&buf[n], 0, len - n);
1430                 } else {
1431                         n = os_write_file(req->fds[bit], buf, len);
1432                         if(n != len){
1433                                 printk("do_io - write failed err = %d "
1434                                        "fd = %d\n", -n, req->fds[bit]);
1435                                 req->error = 1;
1436                                 return;
1437                         }
1438                 }
1439
1440                 start = end;
1441         } while(start < nsectors);
1442
1443         req->error = update_bitmap(req);
1444 }
1445
1446 /* Changed in start_io_thread, which is serialized by being called only
1447  * from ubd_init, which is an initcall.
1448  */
1449 int kernel_fd = -1;
1450
1451 /* Only changed by the io thread. XXX: currently unused. */
1452 static int io_count = 0;
1453
1454 int io_thread(void *arg)
1455 {
1456         struct io_thread_req *req;
1457         int n;
1458
1459         ignore_sigwinch_sig();
1460         while(1){
1461                 n = os_read_file(kernel_fd, &req,
1462                                  sizeof(struct io_thread_req *));
1463                 if(n != sizeof(struct io_thread_req *)){
1464                         if(n < 0)
1465                                 printk("io_thread - read failed, fd = %d, "
1466                                        "err = %d\n", kernel_fd, -n);
1467                         else {
1468                                 printk("io_thread - short read, fd = %d, "
1469                                        "length = %d\n", kernel_fd, n);
1470                         }
1471                         continue;
1472                 }
1473                 io_count++;
1474                 do_io(req);
1475                 n = os_write_file(kernel_fd, &req,
1476                                   sizeof(struct io_thread_req *));
1477                 if(n != sizeof(struct io_thread_req *))
1478                         printk("io_thread - write failed, fd = %d, err = %d\n",
1479                                kernel_fd, -n);
1480         }
1481
1482         return 0;
1483 }