aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/s390/block/dcssblk.c
blob: 4d8798bacf9717a256b20f02bb933b72ec4ca3f9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
/*
 * dcssblk.c -- the S/390 block driver for dcss memory
 *
 * Authors: Carsten Otte, Stefan Weinhuber, Gerald Schaefer
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <asm/extmem.h>
#include <asm/io.h>
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <asm/s390_rdev.h>

//#define DCSSBLK_DEBUG		/* Debug messages on/off */
#define DCSSBLK_NAME "dcssblk"
#define DCSSBLK_MINORS_PER_DISK 1
#define DCSSBLK_PARM_LEN 400

#ifdef DCSSBLK_DEBUG
#define PRINT_DEBUG(x...) printk(KERN_DEBUG DCSSBLK_NAME " debug: " x)
#else
#define PRINT_DEBUG(x...) do {} while (0)
#endif
#define PRINT_INFO(x...)  printk(KERN_INFO DCSSBLK_NAME " info: " x)
#define PRINT_WARN(x...)  printk(KERN_WARNING DCSSBLK_NAME " warning: " x)
#define PRINT_ERR(x...)	  printk(KERN_ERR DCSSBLK_NAME " error: " x)


static int dcssblk_open(struct inode *inode, struct file *filp);
static int dcssblk_release(struct inode *inode, struct file *filp);
static int dcssblk_make_request(struct request_queue *q, struct bio *bio);
static int dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
				 unsigned long *data);

static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";

static int dcssblk_major;
static struct block_device_operations dcssblk_devops = {
	.owner   	= THIS_MODULE,
	.open    	= dcssblk_open,
	.release 	= dcssblk_release,
	.direct_access 	= dcssblk_direct_access,
};

static ssize_t dcssblk_add_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_remove_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_save_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_save_show(struct device *dev, struct device_attribute *attr, char *buf);
static ssize_t dcssblk_shared_store(struct device * dev, struct device_attribute *attr, const char * buf,
				  size_t count);
static ssize_t dcssblk_shared_show(struct device *dev, struct device_attribute *attr, char *buf);

static DEVICE_ATTR(add, S_IWUSR, NULL, dcssblk_add_store);
static DEVICE_ATTR(remove, S_IWUSR, NULL, dcssblk_remove_store);
static DEVICE_ATTR(save, S_IWUSR | S_IRUGO, dcssblk_save_show,
		   dcssblk_save_store);
static DEVICE_ATTR(shared, S_IWUSR | S_IRUGO, dcssblk_shared_show,
		   dcssblk_shared_store);

static struct device *dcssblk_root_dev;

struct dcssblk_dev_info {
	struct list_head lh;
	struct device dev;
	char segment_name[BUS_ID_SIZE];
	atomic_t use_count;
	struct gendisk *gd;
	unsigned long start;
	unsigned long end;
	int segment_type;
	unsigned char save_pending;
	unsigned char is_shared;
	struct request_queue *dcssblk_queue;
};

static struct list_head dcssblk_devices = LIST_HEAD_INIT(dcssblk_devices);
static struct rw_semaphore dcssblk_devices_sem;

/*
 * release function for segment device.
 */
static void
dcssblk_release_segment(struct device *dev)
{
	PRINT_DEBUG("segment release fn called for %s\n", dev->bus_id);
	kfree(container_of(dev, struct dcssblk_dev_info, dev));
	module_put(THIS_MODULE);
}

/*
 * get a minor number. needs to be called with
 * down_write(&dcssblk_devices_sem) and the
 * device needs to be enqueued before the semaphore is
 * freed.
 */
static int
dcssblk_assign_free_minor(struct dcssblk_dev_info *dev_info)
{
	int minor, found;
	struct dcssblk_dev_info *entry;

	if (dev_info == NULL)
		return -EINVAL;
	for (minor = 0; minor < (1<<MINORBITS); minor++) {
		found = 0;
		// test if minor available
		list_for_each_entry(entry, &dcssblk_devices, lh)
			if (minor == entry->gd->first_minor)
				found++;
		if (!found) break; // got unused minor
	}
	if (found)
		return -EBUSY;
	dev_info->gd->first_minor = minor;
	return 0;
}

/*
 * get the struct dcssblk_dev_info from dcssblk_devices
 * for the given name.
 * down_read(&dcssblk_devices_sem) must be held.
 */
static struct dcssblk_dev_info *
dcssblk_get_device_by_name(char *name)
{
	struct dcssblk_dev_info *entry;

	list_for_each_entry(entry, &dcssblk_devices, lh) {
		if (!strcmp(name, entry->segment_name)) {
			return entry;
		}
	}
	return NULL;
}

/*
 * print appropriate error message for segment_load()/segment_type()
 * return code
 */
static void
dcssblk_segment_warn(int rc, char* seg_name)
{
	switch (rc) {
	case -ENOENT:
		PRINT_WARN("cannot load/query segment %s, does not exist\n",
			   seg_name);
		break;
	case -ENOSYS:
		PRINT_WARN("cannot load/query segment %s, not running on VM\n",
			   seg_name);
		break;
	case -EIO:
		PRINT_WARN("cannot load/query segment %s, hardware error\n",
			   seg_name);
		break;
	case -ENOTSUPP:
		PRINT_WARN("cannot load/query segment %s, is a multi-part "
			   "segment\n", seg_name);
		break;
	case -ENOSPC:
		PRINT_WARN("cannot load/query segment %s, overlaps with "
			   "storage\n", seg_name);
		break;
	case -EBUSY:
		PRINT_WARN("cannot load/query segment %s, overlaps with "
			   "already loaded dcss\n", seg_name);
		break;
	case -EPERM:
		PRINT_WARN("cannot load/query segment %s, already loaded in "
			   "incompatible mode\n", seg_name);
		break;
	case -ENOMEM:
		PRINT_WARN("cannot load/query segment %s, out of memory\n",
			   seg_name);
		break;
	case -ERANGE:
		PRINT_WARN("cannot load/query segment %s, exceeds kernel "
			   "mapping range\n", seg_name);
		break;
	default:
		PRINT_WARN("cannot load/query segment %s, return value %i\n",
			   seg_name, rc);
		break;
	}
}

/*
 * device attribute for switching shared/nonshared (exclusive)
 * operation (show + store)
 */
static ssize_t
dcssblk_shared_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct dcssblk_dev_info *dev_info;

	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
	return sprintf(buf, dev_info->is_shared ? "1\n" : "0\n");
}

static ssize_t
dcssblk_shared_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
{
	struct dcssblk_dev_info *dev_info;
	int rc;

	if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0')) {
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		return -EINVAL;
	}
	down_write(&dcssblk_devices_sem);
	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
	if (atomic_read(&dev_info->use_count)) {
		PRINT_ERR("share: segment %s is busy!\n",
			  dev_info->segment_name);
		rc = -EBUSY;
		goto out;
	}
	if (inbuf[0] == '1') {
		// reload segment in shared mode
		rc = segment_modify_shared(dev_info->segment_name,
					   SEGMENT_SHARED);
		if (rc < 0) {
			BUG_ON(rc == -EINVAL);
			if (rc != -EAGAIN)
				goto removeseg;
		} else {
			dev_info->is_shared = 1;
			switch (dev_info->segment_type) {
				case SEG_TYPE_SR:
				case SEG_TYPE_ER:
				case SEG_TYPE_SC:
					set_disk_ro(dev_info->gd,1);
			}
		}
	} else if (inbuf[0] == '0') {
		// reload segment in exclusive mode
		if (dev_info->segment_type == SEG_TYPE_SC) {
			PRINT_ERR("Segment type SC (%s) cannot be loaded in "
				  "non-shared mode\n", dev_info->segment_name);
			rc = -EINVAL;
			goto out;
		}
		rc = segment_modify_shared(dev_info->segment_name,
					   SEGMENT_EXCLUSIVE);
		if (rc < 0) {
			BUG_ON(rc == -EINVAL);
			if (rc != -EAGAIN)
				goto removeseg;
		} else {
			dev_info->is_shared = 0;
			set_disk_ro(dev_info->gd, 0);
		}
	} else {
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		rc = -EINVAL;
		goto out;
	}
	rc = count;
	goto out;

removeseg:
	PRINT_ERR("Could not reload segment %s, removing it now!\n",
			dev_info->segment_name);
	list_del(&dev_info->lh);

	del_gendisk(dev_info->gd);
	blk_cleanup_queue(dev_info->dcssblk_queue);
	dev_info->gd->queue = NULL;
	put_disk(dev_info->gd);
	device_unregister(dev);
	put_device(dev);
out:
	up_write(&dcssblk_devices_sem);
	return rc;
}

/*
 * device attribute for save operation on current copy
 * of the segment. If the segment is busy, saving will
 * become pending until it gets released, which can be
 * undone by storing a non-true value to this entry.
 * (show + store)
 */
static ssize_t
dcssblk_save_show(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct dcssblk_dev_info *dev_info;

	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
	return sprintf(buf, dev_info->save_pending ? "1\n" : "0\n");
}

static ssize_t
dcssblk_save_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
{
	struct dcssblk_dev_info *dev_info;

	if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0')) {
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		return -EINVAL;
	}
	dev_info = container_of(dev, struct dcssblk_dev_info, dev);

	down_write(&dcssblk_devices_sem);
	if (inbuf[0] == '1') {
		if (atomic_read(&dev_info->use_count) == 0) {
			// device is idle => we save immediately
			PRINT_INFO("Saving segment %s\n",
				   dev_info->segment_name);
			segment_save(dev_info->segment_name);
		}  else {
			// device is busy => we save it when it becomes
			// idle in dcssblk_release
			PRINT_INFO("Segment %s is currently busy, it will "
				   "be saved when it becomes idle...\n",
				   dev_info->segment_name);
			dev_info->save_pending = 1;
		}
	} else if (inbuf[0] == '0') {
		if (dev_info->save_pending) {
			// device is busy & the user wants to undo his save
			// request
			dev_info->save_pending = 0;
			PRINT_INFO("Pending save for segment %s deactivated\n",
					dev_info->segment_name);
		}
	} else {
		up_write(&dcssblk_devices_sem);
		PRINT_WARN("Invalid value, must be 0 or 1\n");
		return -EINVAL;
	}
	up_write(&dcssblk_devices_sem);
	return count;
}

/*
 * device attribute for adding devices
 */
static ssize_t
dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	int rc, i;
	struct dcssblk_dev_info *dev_info;
	char *local_buf;
	unsigned long seg_byte_size;

	dev_info = NULL;
	if (dev != dcssblk_root_dev) {
		rc = -EINVAL;
		goto out_nobuf;
	}
	local_buf = kmalloc(count + 1, GFP_KERNEL);
	if (local_buf == NULL) {
		rc = -ENOMEM;
		goto out_nobuf;
	}
	/*
	 * parse input
	 */
	for (i = 0; ((buf[i] != '\0') && (buf[i] != '\n') && i < count); i++) {
		local_buf[i] = toupper(buf[i]);
	}
	local_buf[i] = '\0';
	if ((i == 0) || (i > 8)) {
		rc = -ENAMETOOLONG;
		goto out;
	}
	/*
	 * already loaded?
	 */
	down_read(&dcssblk_devices_sem);
	dev_info = dcssblk_get_device_by_name(local_buf);
	up_read(&dcssblk_devices_sem);
	if (dev_info != NULL) {
		PRINT_WARN("Segment %s already loaded!\n", local_buf);
		rc = -EEXIST;
		goto out;
	}
	/*
	 * get a struct dcssblk_dev_info
	 */
	dev_info = kzalloc(sizeof(struct dcssblk_dev_info), GFP_KERNEL);
	if (dev_info == NULL) {
		rc = -ENOMEM;
		goto out;
	}

	strcpy(dev_info->segment_name, local_buf);
	strlcpy(dev_info->dev.bus_id, local_buf, BUS_ID_SIZE);
	dev_info->dev.release = dcssblk_release_segment;
	INIT_LIST_HEAD(&dev_info->lh);

	dev_info->gd = alloc_disk(DCSSBLK_MINORS_PER_DISK);
	if (dev_info->gd == NULL) {
		rc = -ENOMEM;
		goto free_dev_info;
	}
	dev_info->gd->major = dcssblk_major;
	dev_info->gd->fops = &dcssblk_devops;
	dev_info->dcssblk_queue = blk_alloc_queue(GFP_KERNEL);
	dev_info->gd->queue = dev_info->dcssblk_queue;
	dev_info->gd->private_data = dev_info;
	dev_info->gd->driverfs_dev = &dev_info->dev;
	/*
	 * load the segment
	 */
	rc = segment_load(local_buf, SEGMENT_SHARED,
				&dev_info->start, &dev_info->end);
	if (rc < 0) {
		dcssblk_segment_warn(rc, dev_info->segment_name);
		goto dealloc_gendisk;
	}
	seg_byte_size = (dev_info->end - dev_info->start + 1);
	set_capacity(dev_info->gd, seg_byte_size >> 9); // size in sectors
	PRINT_INFO("Loaded segment %s, size = %lu Byte, "
		   "capacity = %lu (512 Byte) sectors\n", local_buf,
		   seg_byte_size, seg_byte_size >> 9);

	dev_info->segment_type = rc;
	dev_info->save_pending = 0;
	dev_info->is_shared = 1;
	dev_info->dev.parent = dcssblk_root_dev;

	/*
	 * get minor, add to list
	 */
	down_write(&dcssblk_devices_sem);
	rc = dcssblk_assign_free_minor(dev_info);
	if (rc) {
		up_write(&dcssblk_devices_sem);
		PRINT_ERR("No free minor number available! "
			  "Unloading segment...\n");
		goto unload_seg;
	}
	sprintf(dev_info->gd->disk_name, "dcssblk%d",
		dev_info->gd->first_minor);
	list_add_tail(&dev_info->lh, &dcssblk_devices);

	if (!try_module_get(THIS_MODULE)) {
		rc = -ENODEV;
		goto list_del;
	}
	/*
	 * register the device
	 */
	rc = device_register(&dev_info->dev);
	if (rc) {
		PRINT_ERR("Segment %s could not be registered RC=%d\n",
				local_buf, rc);
		module_put(THIS_MODULE);
		goto list_del;
	}
	get_device(&dev_info->dev);
	rc = device_create_file(&dev_info->dev, &dev_attr_shared);
	if (rc)
		goto unregister_dev;
	rc = device_create_file(&dev_info->dev, &dev_attr_save);
	if (rc)
		goto unregister_dev;

	add_disk(dev_info->gd);

	blk_queue_make_request(dev_info->dcssblk_queue, dcssblk_make_request);
	blk_queue_hardsect_size(dev_info->dcssblk_queue, 4096);

	switch (dev_info->segment_type) {
		case SEG_TYPE_SR:
		case SEG_TYPE_ER:
		case SEG_TYPE_SC:
			set_disk_ro(dev_info->gd,1);
			break;
		default:
			set_disk_ro(dev_info->gd,0);
			break;
	}
	PRINT_DEBUG("Segment %s loaded successfully\n", local_buf);
	up_write(&dcssblk_devices_sem);
	rc = count;
	goto out;

unregister_dev:
	PRINT_ERR("device_create_file() failed!\n");
	list_del(&dev_info->lh);
	blk_cleanup_queue(dev_info->dcssblk_queue);
	dev_info->gd->queue = NULL;
	put_disk(dev_info->gd);
	device_unregister(&dev_info->dev);
	segment_unload(dev_info->segment_name);
	put_device(&dev_info->dev);
	up_write(&dcssblk_devices_sem);
	goto out;
list_del:
	list_del(&dev_info->lh);
	up_write(&dcssblk_devices_sem);
unload_seg:
	segment_unload(local_buf);
dealloc_gendisk:
	blk_cleanup_queue(dev_info->dcssblk_queue);
	dev_info->gd->queue = NULL;
	put_disk(dev_info->gd);
free_dev_info:
	kfree(dev_info);
out:
	kfree(local_buf);
out_nobuf:
	return rc;
}

/*
 * device attribute for removing devices
 */
static ssize_t
dcssblk_remove_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	struct dcssblk_dev_info *dev_info;
	int rc, i;
	char *local_buf;

	if (dev != dcssblk_root_dev) {
		return -EINVAL;
	}
	local_buf = kmalloc(count + 1, GFP_KERNEL);
	if (local_buf == NULL) {
		return -ENOMEM;
	}
	/*
	 * parse input
	 */
	for (i = 0; ((*(buf+i)!='\0') && (*(buf+i)!='\n') && i < count); i++) {
		local_buf[i] = toupper(buf[i]);
	}
	local_buf[i] = '\0';
	if ((i == 0) || (i > 8)) {
		rc = -ENAMETOOLONG;
		goto out_buf;
	}

	down_write(&dcssblk_devices_sem);
	dev_info = dcssblk_get_device_by_name(local_buf);
	if (dev_info == NULL) {
		up_write(&dcssblk_devices_sem);
		PRINT_WARN("Segment %s is not loaded!\n", local_buf);
		rc = -ENODEV;
		goto out_buf;
	}
	if (atomic_read(&dev_info->use_count) != 0) {
		up_write(&dcssblk_devices_sem);
		PRINT_WARN("Segment %s is in use!\n", local_buf);
		rc = -EBUSY;
		goto out_buf;
	}
	list_del(&dev_info->lh);

	del_gendisk(dev_info->gd);
	blk_cleanup_queue(dev_info->dcssblk_queue);
	dev_info->gd->queue = NULL;
	put_disk(dev_info->gd);
	device_unregister(&dev_info->dev);
	segment_unload(dev_info->segment_name);
	PRINT_DEBUG("Segment %s unloaded successfully\n",
			dev_info->segment_name);
	put_device(&dev_info->dev);
	up_write(&dcssblk_devices_sem);

	rc = count;
out_buf:
	kfree(local_buf);
	return rc;
}

static int
dcssblk_open(struct inode *inode, struct file *filp)
{
	struct dcssblk_dev_info *dev_info;
	int rc;

	dev_info = inode->i_bdev->bd_disk->private_data;
	if (NULL == dev_info) {
		rc = -ENODEV;
		goto out;
	}
	atomic_inc(&dev_info->use_count);
	inode->i_bdev->bd_block_size = 4096;
	rc = 0;
out:
	return rc;
}

static int
dcssblk_release(struct inode *inode, struct file *filp)
{
	struct dcssblk_dev_info *dev_info;
	int rc;

	dev_info = inode->i_bdev->bd_disk->private_data;
	if (NULL == dev_info) {
		rc = -ENODEV;
		goto out;
	}
	down_write(&dcssblk_devices_sem);
	if (atomic_dec_and_test(&dev_info->use_count)
	    && (dev_info->save_pending)) {
		PRINT_INFO("Segment %s became idle and is being saved now\n",
			    dev_info->segment_name);
		segment_save(dev_info->segment_name);
		dev_info->save_pending = 0;
	}
	up_write(&dcssblk_devices_sem);
	rc = 0;
out:
	return rc;
}

static int
dcssblk_make_request(struct request_queue *q, struct bio *bio)
{
	struct dcssblk_dev_info *dev_info;
	struct bio_vec *bvec;
	unsigned long index;
	unsigned long page_addr;
	unsigned long source_addr;
	unsigned long bytes_done;
	int i;

	bytes_done = 0;
	dev_info = bio->bi_bdev->bd_disk->private_data;
	if (dev_info == NULL)
		goto fail;
	if ((bio->bi_sector & 7) != 0 || (bio->bi_size & 4095) != 0)
		/* Request is not page-aligned. */
		goto fail;
	if (((bio->bi_size >> 9) + bio->bi_sector)
			> get_capacity(bio->bi_bdev->bd_disk)) {
		/* Request beyond end of DCSS segment. */
		goto fail;
	}
	/* verify data transfer direction */
	if (dev_info->is_shared) {
		switch (dev_info->segment_type) {
		case SEG_TYPE_SR:
		case SEG_TYPE_ER:
		case SEG_TYPE_SC:
			/* cannot write to these segments */
			if (bio_data_dir(bio) == WRITE) {
				PRINT_WARN("rejecting write to ro segment %s\n", dev_info->dev.bus_id);
				goto fail;
			}
		}
	}

	index = (bio->bi_sector >> 3);
	bio_for_each_segment(bvec, bio, i) {
		page_addr = (unsigned long)
			page_address(bvec->bv_page) + bvec->bv_offset;
		source_addr = dev_info->start + (index<<12) + bytes_done;
		if (unlikely(page_addr & 4095) != 0 || (bvec->bv_len & 4095) != 0)
			// More paranoia.
			goto fail;
		if (bio_data_dir(bio) == READ) {
			memcpy((void*)page_addr, (void*)source_addr,
				bvec->bv_len);
		} else {
			memcpy((void*)source_addr, (void*)page_addr,
				bvec->bv_len);
		}
		bytes_done += bvec->bv_len;
	}
	bio_endio(bio, bytes_done, 0);
	return 0;
fail:
	bio_io_error(bio, bio->bi_size);
	return 0;
}

static int
dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
			unsigned long *data)
{
	struct dcssblk_dev_info *dev_info;
	unsigned long pgoff;

	dev_info = bdev->bd_disk->private_data;
	if (!dev_info)
		return -ENODEV;
	if (secnum % (PAGE_SIZE/512))
		return -EINVAL;
	pgoff = secnum / (PAGE_SIZE / 512);
	if ((pgoff+1)*PAGE_SIZE-1 > dev_info->end - dev_info->start)
		return -ERANGE;
	*data = (unsigned long) (dev_info->start+pgoff*PAGE_SIZE);
	return 0;
}

static void
dcssblk_check_params(void)
{
	int rc, i, j, k;
	char buf[9];
	struct dcssblk_dev_info *dev_info;

	for (i = 0; (i < DCSSBLK_PARM_LEN) && (dcssblk_segments[i] != '\0');
	     i++) {
		for (j = i; (dcssblk_segments[j] != ',')  &&
			    (dcssblk_segments[j] != '\0') &&
			    (dcssblk_segments[j] != '(')  &&
			    (j - i) < 8; j++)
		{
			buf[j-i] = dcssblk_segments[j];
		}
		buf[j-i] = '\0';
		rc = dcssblk_add_store(dcssblk_root_dev, NULL, buf, j-i);
		if ((rc >= 0) && (dcssblk_segments[j] == '(')) {
			for (k = 0; buf[k] != '\0'; k++)
				buf[k] = toupper(buf[k]);
			if (!strncmp(&dcssblk_segments[j], "(local)", 7)) {
				down_read(&dcssblk_devices_sem);
				dev_info = dcssblk_get_device_by_name(buf);
				up_read(&dcssblk_devices_sem);
				if (dev_info)
					dcssblk_shared_store(&dev_info->dev,
							     NULL, "0\n", 2);
			}
		}
		while ((dcssblk_segments[j] != ',') &&
		       (dcssblk_segments[j] != '\0'))
		{
			j++;
		}
		if (dcssblk_segments[j] == '\0')
			break;
		i = j;
	}
}

/*
 * The init/exit functions.
 */
static void __exit
dcssblk_exit(void)
{
	PRINT_DEBUG("DCSSBLOCK EXIT...\n");
	s390_root_dev_unregister(dcssblk_root_dev);
	unregister_blkdev(dcssblk_major, DCSSBLK_NAME);
	PRINT_DEBUG("...finished!\n");
}

static int __init
dcssblk_init(void)
{
	int rc;

	PRINT_DEBUG("DCSSBLOCK INIT...\n");
	dcssblk_root_dev = s390_root_dev_register("dcssblk");
	if (IS_ERR(dcssblk_root_dev)) {
		PRINT_ERR("device_register() failed!\n");
		return PTR_ERR(dcssblk_root_dev);
	}
	rc = device_create_file(dcssblk_root_dev, &dev_attr_add);
	if (rc) {
		PRINT_ERR("device_create_file(add) failed!\n");
		s390_root_dev_unregister(dcssblk_root_dev);
		return rc;
	}
	rc = device_create_file(dcssblk_root_dev, &dev_attr_remove);
	if (rc) {
		PRINT_ERR("device_create_file(remove) failed!\n");
		s390_root_dev_unregister(dcssblk_root_dev);
		return rc;
	}
	rc = register_blkdev(0, DCSSBLK_NAME);
	if (rc < 0) {
		PRINT_ERR("Can't get dynamic major!\n");
		s390_root_dev_unregister(dcssblk_root_dev);
		return rc;
	}
	dcssblk_major = rc;
	init_rwsem(&dcssblk_devices_sem);

	dcssblk_check_params();

	PRINT_DEBUG("...finished!\n");
	return 0;
}

module_init(dcssblk_init);
module_exit(dcssblk_exit);

module_param_string(segments, dcssblk_segments, DCSSBLK_PARM_LEN, 0444);
MODULE_PARM_DESC(segments, "Name of DCSS segment(s) to be loaded, "
		 "comma-separated list, each name max. 8 chars.\n"
		 "Adding \"(local)\" to segment name equals echoing 0 to "
		 "/sys/devices/dcssblk/<segment name>/shared after loading "
		 "the segment - \n"
		 "e.g. segments=\"mydcss1,mydcss2,mydcss3(local)\"");

MODULE_LICENSE("GPL");