summaryrefslogtreecommitdiffstats
path: root/fs/exofs/ios.c
blob: f9d5c5a823fbdf454bef08277a837db892b3194f (plain)
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
806
807
808
809
810
/*
 * Copyright (C) 2005, 2006
 * Avishay Traeger (avishay@gmail.com)
 * Copyright (C) 2008, 2009
 * Boaz Harrosh <bharrosh@panasas.com>
 *
 * This file is part of exofs.
 *
 * exofs is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation.  Since it is based on ext2, and the only
 * valid version of GPL for the Linux kernel is version 2, the only valid
 * version of GPL for exofs is version 2.
 *
 * exofs is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with exofs; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <linux/slab.h>
#include <scsi/scsi_device.h>
#include <asm/div64.h>

#include "exofs.h"

#define EXOFS_DBGMSG2(M...) do {} while (0)
/* #define EXOFS_DBGMSG2 EXOFS_DBGMSG */

static u8 *_ios_cred(struct exofs_io_state *ios, unsigned index)
{
	return ios->comps->comps[index & ios->comps->single_comp].cred;
}

static struct osd_obj_id *_ios_obj(struct exofs_io_state *ios, unsigned index)
{
	return &ios->comps->comps[index & ios->comps->single_comp].obj;
}

static struct osd_dev *_ios_od(struct exofs_io_state *ios, unsigned index)
{
	return ios->comps->ods[index];
}

int exofs_get_rw_state(struct exofs_layout *layout,
			struct exofs_components *comps,
			bool is_reading, u64 offset, u64 length,
			struct exofs_io_state **pios)
{
	struct exofs_io_state *ios;

	/*TODO: Maybe use kmem_cach per sbi of size
	 * exofs_io_state_size(layout->s_numdevs)
	 */
	ios = kzalloc(exofs_io_state_size(comps->numdevs), GFP_KERNEL);
	if (unlikely(!ios)) {
		EXOFS_DBGMSG("Failed kzalloc bytes=%d\n",
			     exofs_io_state_size(comps->numdevs));
		*pios = NULL;
		return -ENOMEM;
	}

	ios->layout = layout;
	ios->comps = comps;
	ios->offset = offset;
	ios->length = length;
	ios->reading = is_reading;

	*pios = ios;
	return 0;
}

int  exofs_get_io_state(struct exofs_layout *layout,
			struct exofs_components *comps,
			struct exofs_io_state **ios)
{
	return exofs_get_rw_state(layout, comps, true, 0, 0, ios);
}

void exofs_put_io_state(struct exofs_io_state *ios)
{
	if (ios) {
		unsigned i;

		for (i = 0; i < ios->numdevs; i++) {
			struct exofs_per_dev_state *per_dev = &ios->per_dev[i];

			if (per_dev->or)
				osd_end_request(per_dev->or);
			if (per_dev->bio)
				bio_put(per_dev->bio);
		}

		kfree(ios);
	}
}

static void _sync_done(struct exofs_io_state *ios, void *p)
{
	struct completion *waiting = p;

	complete(waiting);
}

static void _last_io(struct kref *kref)
{
	struct exofs_io_state *ios = container_of(
					kref, struct exofs_io_state, kref);

	ios->done(ios, ios->private);
}

static void _done_io(struct osd_request *or, void *p)
{
	struct exofs_io_state *ios = p;

	kref_put(&ios->kref, _last_io);
}

static int exofs_io_execute(struct exofs_io_state *ios)
{
	DECLARE_COMPLETION_ONSTACK(wait);
	bool sync = (ios->done == NULL);
	int i, ret;

	if (sync) {
		ios->done = _sync_done;
		ios->private = &wait;
	}

	for (i = 0; i < ios->numdevs; i++) {
		struct osd_request *or = ios->per_dev[i].or;
		if (unlikely(!or))
			continue;

		ret = osd_finalize_request(or, 0, _ios_cred(ios, i), NULL);
		if (unlikely(ret)) {
			EXOFS_DBGMSG("Failed to osd_finalize_request() => %d\n",
				     ret);
			return ret;
		}
	}

	kref_init(&ios->kref);

	for (i = 0; i < ios->numdevs; i++) {
		struct osd_request *or = ios->per_dev[i].or;
		if (unlikely(!or))
			continue;

		kref_get(&ios->kref);
		osd_execute_request_async(or, _done_io, ios);
	}

	kref_put(&ios->kref, _last_io);
	ret = 0;

	if (sync) {
		wait_for_completion(&wait);
		ret = exofs_check_io(ios, NULL);
	}
	return ret;
}

static void _clear_bio(struct bio *bio)
{
	struct bio_vec *bv;
	unsigned i;

	__bio_for_each_segment(bv, bio, i, 0) {
		unsigned this_count = bv->bv_len;

		if (likely(PAGE_SIZE == this_count))
			clear_highpage(bv->bv_page);
		else
			zero_user(bv->bv_page, bv->bv_offset, this_count);
	}
}

int exofs_check_io(struct exofs_io_state *ios, u64 *resid)
{
	enum osd_err_priority acumulated_osd_err = 0;
	int acumulated_lin_err = 0;
	int i;

	for (i = 0; i < ios->numdevs; i++) {
		struct osd_sense_info osi;
		struct osd_request *or = ios->per_dev[i].or;
		int ret;

		if (unlikely(!or))
			continue;

		ret = osd_req_decode_sense(or, &osi);
		if (likely(!ret))
			continue;

		if (OSD_ERR_PRI_CLEAR_PAGES == osi.osd_err_pri) {
			/* start read offset passed endof file */
			_clear_bio(ios->per_dev[i].bio);
			EXOFS_DBGMSG("start read offset passed end of file "
				"offset=0x%llx, length=0x%llx\n",
				_LLU(ios->per_dev[i].offset),
				_LLU(ios->per_dev[i].length));

			continue; /* we recovered */
		}

		if (osi.osd_err_pri >= acumulated_osd_err) {
			acumulated_osd_err = osi.osd_err_pri;
			acumulated_lin_err = ret;
		}
	}

	/* TODO: raid specific residual calculations */
	if (resid) {
		if (likely(!acumulated_lin_err))
			*resid = 0;
		else
			*resid = ios->length;
	}

	return acumulated_lin_err;
}

/*
 * L - logical offset into the file
 *
 * U - The number of bytes in a stripe within a group
 *
 *	U = stripe_unit * group_width
 *
 * T - The number of bytes striped within a group of component objects
 *     (before advancing to the next group)
 *
 *	T = stripe_unit * group_width * group_depth
 *
 * S - The number of bytes striped across all component objects
 *     before the pattern repeats
 *
 *	S = stripe_unit * group_width * group_depth * group_count
 *
 * M - The "major" (i.e., across all components) stripe number
 *
 *	M = L / S
 *
 * G - Counts the groups from the beginning of the major stripe
 *
 *	G = (L - (M * S)) / T	[or (L % S) / T]
 *
 * H - The byte offset within the group
 *
 *	H = (L - (M * S)) % T	[or (L % S) % T]
 *
 * N - The "minor" (i.e., across the group) stripe number
 *
 *	N = H / U
 *
 * C - The component index coresponding to L
 *
 *	C = (H - (N * U)) / stripe_unit + G * group_width
 *	[or (L % U) / stripe_unit + G * group_width]
 *
 * O - The component offset coresponding to L
 *
 *	O = L % stripe_unit + N * stripe_unit + M * group_depth * stripe_unit
 */
struct _striping_info {
	u64 obj_offset;
	u64 group_length;
	u64 M; /* for truncate */
	unsigned dev;
	unsigned unit_off;
};

static void _calc_stripe_info(struct exofs_layout *layout, u64 file_offset,
			      struct _striping_info *si)
{
	u32	stripe_unit = layout->stripe_unit;
	u32	group_width = layout->group_width;
	u64	group_depth = layout->group_depth;

	u32	U = stripe_unit * group_width;
	u64	T = U * group_depth;
	u64	S = T * layout->group_count;
	u64	M = div64_u64(file_offset, S);

	/*
	G = (L - (M * S)) / T
	H = (L - (M * S)) % T
	*/
	u64	LmodS = file_offset - M * S;
	u32	G = div64_u64(LmodS, T);
	u64	H = LmodS - G * T;

	u32	N = div_u64(H, U);

	/* "H - (N * U)" is just "H % U" so it's bound to u32 */
	si->dev = (u32)(H - (N * U)) / stripe_unit + G * group_width;
	si->dev *= layout->mirrors_p1;

	div_u64_rem(file_offset, stripe_unit, &si->unit_off);

	si->obj_offset = si->unit_off + (N * stripe_unit) +
				  (M * group_depth * stripe_unit);

	si->group_length = T - H;
	si->M = M;
}

static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_pg,
		unsigned pgbase, struct exofs_per_dev_state *per_dev,
		int cur_len)
{
	unsigned pg = *cur_pg;
	struct request_queue *q =
			osd_request_queue(_ios_od(ios, per_dev->dev));

	per_dev->length += cur_len;

	if (per_dev->bio == NULL) {
		unsigned pages_in_stripe = ios->layout->group_width *
					(ios->layout->stripe_unit / PAGE_SIZE);
		unsigned bio_size = (ios->nr_pages + pages_in_stripe) /
						ios->layout->group_width;

		per_dev->bio = bio_kmalloc(GFP_KERNEL, bio_size);
		if (unlikely(!per_dev->bio)) {
			EXOFS_DBGMSG("Failed to allocate BIO size=%u\n",
				     bio_size);
			return -ENOMEM;
		}
	}

	while (cur_len > 0) {
		unsigned pglen = min_t(unsigned, PAGE_SIZE - pgbase, cur_len);
		unsigned added_len;

		BUG_ON(ios->nr_pages <= pg);
		cur_len -= pglen;

		added_len = bio_add_pc_page(q, per_dev->bio, ios->pages[pg],
					    pglen, pgbase);
		if (unlikely(pglen != added_len))
			return -ENOMEM;
		pgbase = 0;
		++pg;
	}
	BUG_ON(cur_len);

	*cur_pg = pg;
	return 0;
}

static int _prepare_one_group(struct exofs_io_state *ios, u64 length,
			      struct _striping_info *si)
{
	unsigned stripe_unit = ios->layout->stripe_unit;
	unsigned mirrors_p1 = ios->layout->mirrors_p1;
	unsigned devs_in_group = ios->layout->group_width * mirrors_p1;
	unsigned dev = si->dev;
	unsigned first_dev = dev - (dev % devs_in_group);
	unsigned max_comp = ios->numdevs ? ios->numdevs - mirrors_p1 : 0;
	unsigned cur_pg = ios->pages_consumed;
	int ret = 0;

	while (length) {
		struct exofs_per_dev_state *per_dev = &ios->per_dev[dev];
		unsigned cur_len, page_off = 0;

		if (!per_dev->length) {
			per_dev->dev = dev;
			if (dev < si->dev) {
				per_dev->offset = si->obj_offset + stripe_unit -
								   si->unit_off;
				cur_len = stripe_unit;
			} else if (dev == si->dev) {
				per_dev->offset = si->obj_offset;
				cur_len = stripe_unit - si->unit_off;
				page_off = si->unit_off & ~PAGE_MASK;
				BUG_ON(page_off && (page_off != ios->pgbase));
			} else { /* dev > si->dev */
				per_dev->offset = si->obj_offset - si->unit_off;
				cur_len = stripe_unit;
			}

			if (max_comp < dev)
				max_comp = dev;
		} else {
			cur_len = stripe_unit;
		}
		if (cur_len >= length)
			cur_len = length;

		ret = _add_stripe_unit(ios, &cur_pg, page_off , per_dev,
				       cur_len);
		if (unlikely(ret))
			goto out;

		dev += mirrors_p1;
		dev = (dev % devs_in_group) + first_dev;

		length -= cur_len;
	}
out:
	ios->numdevs = max_comp + mirrors_p1;
	ios->pages_consumed = cur_pg;
	return ret;
}

static int _prepare_for_striping(struct exofs_io_state *ios)
{
	u64 length = ios->length;
	u64 offset = ios->offset;
	struct _striping_info si;
	int ret = 0;

	if (!ios->pages) {
		if (ios->kern_buff) {
			struct exofs_per_dev_state *per_dev = &ios->per_dev[0];

			_calc_stripe_info(ios->layout, ios->offset, &si);
			per_dev->offset = si.obj_offset;
			per_dev->dev = si.dev;

			/* no cross device without page array */
			BUG_ON((ios->layout->group_width > 1) &&
			       (si.unit_off + ios->length >
				ios->layout->stripe_unit));
		}
		ios->numdevs = ios->layout->mirrors_p1;
		return 0;
	}

	while (length) {
		_calc_stripe_info(ios->layout, offset, &si);

		if (length < si.group_length)
			si.group_length = length;

		ret = _prepare_one_group(ios, si.group_length, &si);
		if (unlikely(ret))
			goto out;

		offset += si.group_length;
		length -= si.group_length;
	}

out:
	return ret;
}

int exofs_sbi_create(struct exofs_io_state *ios)
{
	int i, ret;

	for (i = 0; i < ios->comps->numdevs; i++) {
		struct osd_request *or;

		or = osd_start_request(_ios_od(ios, i), GFP_KERNEL);
		if (unlikely(!or)) {
			EXOFS_ERR("%s: osd_start_request failed\n", __func__);
			ret = -ENOMEM;
			goto out;
		}
		ios->per_dev[i].or = or;
		ios->numdevs++;

		osd_req_create_object(or, _ios_obj(ios, i));
	}
	ret = exofs_io_execute(ios);

out:
	return ret;
}

int exofs_sbi_remove(struct exofs_io_state *ios)
{
	int i, ret;

	for (i = 0; i < ios->comps->numdevs; i++) {
		struct osd_request *or;

		or = osd_start_request(_ios_od(ios, i), GFP_KERNEL);
		if (unlikely(!or)) {
			EXOFS_ERR("%s: osd_start_request failed\n", __func__);
			ret = -ENOMEM;
			goto out;
		}
		ios->per_dev[i].or = or;
		ios->numdevs++;

		osd_req_remove_object(or, _ios_obj(ios, i));
	}
	ret = exofs_io_execute(ios);

out:
	return ret;
}

static int _sbi_write_mirror(struct exofs_io_state *ios, int cur_comp)
{
	struct exofs_per_dev_state *master_dev = &ios->per_dev[cur_comp];
	unsigned dev = ios->per_dev[cur_comp].dev;
	unsigned last_comp = cur_comp + ios->layout->mirrors_p1;
	int ret = 0;

	if (ios->pages && !master_dev->length)
		return 0; /* Just an empty slot */

	for (; cur_comp < last_comp; ++cur_comp, ++dev) {
		struct exofs_per_dev_state *per_dev = &ios->per_dev[cur_comp];
		struct osd_request *or;

		or = osd_start_request(_ios_od(ios, dev), GFP_KERNEL);
		if (unlikely(!or)) {
			EXOFS_ERR("%s: osd_start_request failed\n", __func__);
			ret = -ENOMEM;
			goto out;
		}
		per_dev->or = or;
		per_dev->offset = master_dev->offset;

		if (ios->pages) {
			struct bio *bio;

			if (per_dev != master_dev) {
				bio = bio_kmalloc(GFP_KERNEL,
						  master_dev->bio->bi_max_vecs);
				if (unlikely(!bio)) {
					EXOFS_DBGMSG(
					      "Failed to allocate BIO size=%u\n",
					      master_dev->bio->bi_max_vecs);
					ret = -ENOMEM;
					goto out;
				}

				__bio_clone(bio, master_dev->bio);
				bio->bi_bdev = NULL;
				bio->bi_next = NULL;
				per_dev->length = master_dev->length;
				per_dev->bio =  bio;
				per_dev->dev = dev;
			} else {
				bio = master_dev->bio;
				/* FIXME: bio_set_dir() */
				bio->bi_rw |= REQ_WRITE;
			}

			osd_req_write(or, _ios_obj(ios, dev), per_dev->offset,
				      bio, per_dev->length);
			EXOFS_DBGMSG("write(0x%llx) offset=0x%llx "
				      "length=0x%llx dev=%d\n",
				     _LLU(_ios_obj(ios, dev)->id),
				     _LLU(per_dev->offset),
				     _LLU(per_dev->length), dev);
		} else if (ios->kern_buff) {
			ret = osd_req_write_kern(or, _ios_obj(ios, dev),
						 per_dev->offset,
						 ios->kern_buff, ios->length);
			if (unlikely(ret))
				goto out;
			EXOFS_DBGMSG2("write_kern(0x%llx) offset=0x%llx "
				      "length=0x%llx dev=%d\n",
				     _LLU(_ios_obj(ios, dev)->id),
				     _LLU(per_dev->offset),
				     _LLU(ios->length), dev);
		} else {
			osd_req_set_attributes(or, _ios_obj(ios, dev));
			EXOFS_DBGMSG2("obj(0x%llx) set_attributes=%d dev=%d\n",
				     _LLU(_ios_obj(ios, dev)->id),
				     ios->out_attr_len, dev);
		}

		if (ios->out_attr)
			osd_req_add_set_attr_list(or, ios->out_attr,
						  ios->out_attr_len);

		if (ios->in_attr)
			osd_req_add_get_attr_list(or, ios->in_attr,
						  ios->in_attr_len);
	}

out:
	return ret;
}

int exofs_sbi_write(struct exofs_io_state *ios)
{
	int i;
	int ret;

	ret = _prepare_for_striping(ios);
	if (unlikely(ret))
		return ret;

	for (i = 0; i < ios->numdevs; i += ios->layout->mirrors_p1) {
		ret = _sbi_write_mirror(ios, i);
		if (unlikely(ret))
			return ret;
	}

	ret = exofs_io_execute(ios);
	return ret;
}

static int _sbi_read_mirror(struct exofs_io_state *ios, unsigned cur_comp)
{
	struct osd_request *or;
	struct exofs_per_dev_state *per_dev = &ios->per_dev[cur_comp];
	struct osd_obj_id *obj = _ios_obj(ios, cur_comp);
	unsigned first_dev = (unsigned)obj->id;

	if (ios->pages && !per_dev->length)
		return 0; /* Just an empty slot */

	first_dev = per_dev->dev + first_dev % ios->layout->mirrors_p1;
	or = osd_start_request(_ios_od(ios, first_dev), GFP_KERNEL);
	if (unlikely(!or)) {
		EXOFS_ERR("%s: osd_start_request failed\n", __func__);
		return -ENOMEM;
	}
	per_dev->or = or;

	if (ios->pages) {
		osd_req_read(or, obj, per_dev->offset,
				per_dev->bio, per_dev->length);
		EXOFS_DBGMSG("read(0x%llx) offset=0x%llx length=0x%llx"
			     " dev=%d\n", _LLU(obj->id),
			     _LLU(per_dev->offset), _LLU(per_dev->length),
			     first_dev);
	} else if (ios->kern_buff) {
		int ret = osd_req_read_kern(or, obj, per_dev->offset,
					    ios->kern_buff, ios->length);
		EXOFS_DBGMSG2("read_kern(0x%llx) offset=0x%llx "
			      "length=0x%llx dev=%d ret=>%d\n",
			      _LLU(obj->id), _LLU(per_dev->offset),
			      _LLU(ios->length), first_dev, ret);
		if (unlikely(ret))
			return ret;
	} else {
		osd_req_get_attributes(or, obj);
		EXOFS_DBGMSG2("obj(0x%llx) get_attributes=%d dev=%d\n",
			      _LLU(obj->id),
			      ios->in_attr_len, first_dev);
	}
	if (ios->out_attr)
		osd_req_add_set_attr_list(or, ios->out_attr, ios->out_attr_len);

	if (ios->in_attr)
		osd_req_add_get_attr_list(or, ios->in_attr, ios->in_attr_len);

	return 0;
}

int exofs_sbi_read(struct exofs_io_state *ios)
{
	int i;
	int ret;

	ret = _prepare_for_striping(ios);
	if (unlikely(ret))
		return ret;

	for (i = 0; i < ios->numdevs; i += ios->layout->mirrors_p1) {
		ret = _sbi_read_mirror(ios, i);
		if (unlikely(ret))
			return ret;
	}

	ret = exofs_io_execute(ios);
	return ret;
}

int extract_attr_from_ios(struct exofs_io_state *ios, struct osd_attr *attr)
{
	struct osd_attr cur_attr = {.attr_page = 0}; /* start with zeros */
	void *iter = NULL;
	int nelem;

	do {
		nelem = 1;
		osd_req_decode_get_attr_list(ios->per_dev[0].or,
					     &cur_attr, &nelem, &iter);
		if ((cur_attr.attr_page == attr->attr_page) &&
		    (cur_attr.attr_id == attr->attr_id)) {
			attr->len = cur_attr.len;
			attr->val_ptr = cur_attr.val_ptr;
			return 0;
		}
	} while (iter);

	return -EIO;
}

static int _truncate_mirrors(struct exofs_io_state *ios, unsigned cur_comp,
			     struct osd_attr *attr)
{
	int last_comp = cur_comp + ios->layout->mirrors_p1;

	for (; cur_comp < last_comp; ++cur_comp) {
		struct exofs_per_dev_state *per_dev = &ios->per_dev[cur_comp];
		struct osd_request *or;

		or = osd_start_request(_ios_od(ios, cur_comp), GFP_KERNEL);
		if (unlikely(!or)) {
			EXOFS_ERR("%s: osd_start_request failed\n", __func__);
			return -ENOMEM;
		}
		per_dev->or = or;

		osd_req_set_attributes(or, _ios_obj(ios, cur_comp));
		osd_req_add_set_attr_list(or, attr, 1);
	}

	return 0;
}

struct _trunc_info {
	struct _striping_info si;
	u64 prev_group_obj_off;
	u64 next_group_obj_off;

	unsigned first_group_dev;
	unsigned nex_group_dev;
	unsigned max_devs;
};

void _calc_trunk_info(struct exofs_layout *layout, u64 file_offset,
		       struct _trunc_info *ti)
{
	unsigned stripe_unit = layout->stripe_unit;

	_calc_stripe_info(layout, file_offset, &ti->si);

	ti->prev_group_obj_off = ti->si.M * stripe_unit;
	ti->next_group_obj_off = ti->si.M ? (ti->si.M - 1) * stripe_unit : 0;

	ti->first_group_dev = ti->si.dev - (ti->si.dev % layout->group_width);
	ti->nex_group_dev = ti->first_group_dev + layout->group_width;
	ti->max_devs = layout->group_width * layout->group_count;
}

int exofs_truncate(struct exofs_layout *layout, struct exofs_components *comps,
		   u64 size)
{
	struct exofs_io_state *ios;
	struct exofs_trunc_attr {
		struct osd_attr attr;
		__be64 newsize;
	} *size_attrs;
	struct _trunc_info ti;
	int i, ret;

	ret = exofs_get_io_state(layout, comps, &ios);
	if (unlikely(ret))
		return ret;

	_calc_trunk_info(ios->layout, size, &ti);

	size_attrs = kcalloc(ti.max_devs, sizeof(*size_attrs),
			     GFP_KERNEL);
	if (unlikely(!size_attrs)) {
		ret = -ENOMEM;
		goto out;
	}

	ios->numdevs = ios->comps->numdevs;

	for (i = 0; i < ti.max_devs; ++i) {
		struct exofs_trunc_attr *size_attr = &size_attrs[i];
		u64 obj_size;

		if (i < ti.first_group_dev)
			obj_size = ti.prev_group_obj_off;
		else if (i >= ti.nex_group_dev)
			obj_size = ti.next_group_obj_off;
		else if (i < ti.si.dev) /* dev within this group */
			obj_size = ti.si.obj_offset +
				      ios->layout->stripe_unit - ti.si.unit_off;
		else if (i == ti.si.dev)
			obj_size = ti.si.obj_offset;
		else /* i > ti.dev */
			obj_size = ti.si.obj_offset - ti.si.unit_off;

		size_attr->newsize = cpu_to_be64(obj_size);
		size_attr->attr = g_attr_logical_length;
		size_attr->attr.val_ptr = &size_attr->newsize;

		EXOFS_DBGMSG("trunc(0x%llx) obj_offset=0x%llx dev=%d\n",
			     _LLU(comps->comps->obj.id), _LLU(obj_size), i);
		ret = _truncate_mirrors(ios, i * ios->layout->mirrors_p1,
					&size_attr->attr);
		if (unlikely(ret))
			goto out;
	}
	ret = exofs_io_execute(ios);

out:
	kfree(size_attrs);
	exofs_put_io_state(ios);
	return ret;
}

const struct osd_attr g_attr_logical_length = ATTR_DEF(
	OSD_APAGE_OBJECT_INFORMATION, OSD_ATTR_OI_LOGICAL_LENGTH, 8);