summaryrefslogtreecommitdiffstats
path: root/lib/iov_iter.c
blob: ce463200261155cc9d3b73b8d7543676e049fc93 (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
#include <linux/export.h>
#include <linux/uio.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <net/checksum.h>

#define iterate_iovec(i, n, __v, __p, skip, STEP) {	\
	size_t left;					\
	size_t wanted = n;				\
	__p = i->iov;					\
	__v.iov_len = min(n, __p->iov_len - skip);	\
	if (likely(__v.iov_len)) {			\
		__v.iov_base = __p->iov_base + skip;	\
		left = (STEP);				\
		__v.iov_len -= left;			\
		skip += __v.iov_len;			\
		n -= __v.iov_len;			\
	} else {					\
		left = 0;				\
	}						\
	while (unlikely(!left && n)) {			\
		__p++;					\
		__v.iov_len = min(n, __p->iov_len);	\
		if (unlikely(!__v.iov_len))		\
			continue;			\
		__v.iov_base = __p->iov_base;		\
		left = (STEP);				\
		__v.iov_len -= left;			\
		skip = __v.iov_len;			\
		n -= __v.iov_len;			\
	}						\
	n = wanted - n;					\
}

#define iterate_kvec(i, n, __v, __p, skip, STEP) {	\
	size_t wanted = n;				\
	__p = i->kvec;					\
	__v.iov_len = min(n, __p->iov_len - skip);	\
	if (likely(__v.iov_len)) {			\
		__v.iov_base = __p->iov_base + skip;	\
		(void)(STEP);				\
		skip += __v.iov_len;			\
		n -= __v.iov_len;			\
	}						\
	while (unlikely(n)) {				\
		__p++;					\
		__v.iov_len = min(n, __p->iov_len);	\
		if (unlikely(!__v.iov_len))		\
			continue;			\
		__v.iov_base = __p->iov_base;		\
		(void)(STEP);				\
		skip = __v.iov_len;			\
		n -= __v.iov_len;			\
	}						\
	n = wanted;					\
}

#define iterate_bvec(i, n, __v, __bi, skip, STEP) {	\
	struct bvec_iter __start;			\
	__start.bi_size = n;				\
	__start.bi_bvec_done = skip;			\
	__start.bi_idx = 0;				\
	for_each_bvec(__v, i->bvec, __bi, __start) {	\
		if (!__v.bv_len)			\
			continue;			\
		(void)(STEP);				\
	}						\
}

#define iterate_all_kinds(i, n, v, I, B, K) {			\
	size_t skip = i->iov_offset;				\
	if (unlikely(i->type & ITER_BVEC)) {			\
		struct bio_vec v;				\
		struct bvec_iter __bi;				\
		iterate_bvec(i, n, v, __bi, skip, (B))		\
	} else if (unlikely(i->type & ITER_KVEC)) {		\
		const struct kvec *kvec;			\
		struct kvec v;					\
		iterate_kvec(i, n, v, kvec, skip, (K))		\
	} else {						\
		const struct iovec *iov;			\
		struct iovec v;					\
		iterate_iovec(i, n, v, iov, skip, (I))		\
	}							\
}

#define iterate_and_advance(i, n, v, I, B, K) {			\
	if (unlikely(i->count < n))				\
		n = i->count;					\
	if (i->count) {						\
		size_t skip = i->iov_offset;			\
		if (unlikely(i->type & ITER_BVEC)) {		\
			const struct bio_vec *bvec = i->bvec;	\
			struct bio_vec v;			\
			struct bvec_iter __bi;			\
			iterate_bvec(i, n, v, __bi, skip, (B))	\
			i->bvec = __bvec_iter_bvec(i->bvec, __bi);	\
			i->nr_segs -= i->bvec - bvec;		\
			skip = __bi.bi_bvec_done;		\
		} else if (unlikely(i->type & ITER_KVEC)) {	\
			const struct kvec *kvec;		\
			struct kvec v;				\
			iterate_kvec(i, n, v, kvec, skip, (K))	\
			if (skip == kvec->iov_len) {		\
				kvec++;				\
				skip = 0;			\
			}					\
			i->nr_segs -= kvec - i->kvec;		\
			i->kvec = kvec;				\
		} else {					\
			const struct iovec *iov;		\
			struct iovec v;				\
			iterate_iovec(i, n, v, iov, skip, (I))	\
			if (skip == iov->iov_len) {		\
				iov++;				\
				skip = 0;			\
			}					\
			i->nr_segs -= iov - i->iov;		\
			i->iov = iov;				\
		}						\
		i->count -= n;					\
		i->iov_offset = skip;				\
	}							\
}

static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
			 struct iov_iter *i)
{
	size_t skip, copy, left, wanted;
	const struct iovec *iov;
	char __user *buf;
	void *kaddr, *from;

	if (unlikely(bytes > i->count))
		bytes = i->count;

	if (unlikely(!bytes))
		return 0;

	wanted = bytes;
	iov = i->iov;
	skip = i->iov_offset;
	buf = iov->iov_base + skip;
	copy = min(bytes, iov->iov_len - skip);

	if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_writeable(buf, copy)) {
		kaddr = kmap_atomic(page);
		from = kaddr + offset;

		/* first chunk, usually the only one */
		left = __copy_to_user_inatomic(buf, from, copy);
		copy -= left;
		skip += copy;
		from += copy;
		bytes -= copy;

		while (unlikely(!left && bytes)) {
			iov++;
			buf = iov->iov_base;
			copy = min(bytes, iov->iov_len);
			left = __copy_to_user_inatomic(buf, from, copy);
			copy -= left;
			skip = copy;
			from += copy;
			bytes -= copy;
		}
		if (likely(!bytes)) {
			kunmap_atomic(kaddr);
			goto done;
		}
		offset = from - kaddr;
		buf += copy;
		kunmap_atomic(kaddr);
		copy = min(bytes, iov->iov_len - skip);
	}
	/* Too bad - revert to non-atomic kmap */

	kaddr = kmap(page);
	from = kaddr + offset;
	left = __copy_to_user(buf, from, copy);
	copy -= left;
	skip += copy;
	from += copy;
	bytes -= copy;
	while (unlikely(!left && bytes)) {
		iov++;
		buf = iov->iov_base;
		copy = min(bytes, iov->iov_len);
		left = __copy_to_user(buf, from, copy);
		copy -= left;
		skip = copy;
		from += copy;
		bytes -= copy;
	}
	kunmap(page);

done:
	if (skip == iov->iov_len) {
		iov++;
		skip = 0;
	}
	i->count -= wanted - bytes;
	i->nr_segs -= iov - i->iov;
	i->iov = iov;
	i->iov_offset = skip;
	return wanted - bytes;
}

static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
			 struct iov_iter *i)
{
	size_t skip, copy, left, wanted;
	const struct iovec *iov;
	char __user *buf;
	void *kaddr, *to;

	if (unlikely(bytes > i->count))
		bytes = i->count;

	if (unlikely(!bytes))
		return 0;

	wanted = bytes;
	iov = i->iov;
	skip = i->iov_offset;
	buf = iov->iov_base + skip;
	copy = min(bytes, iov->iov_len - skip);

	if (IS_ENABLED(CONFIG_HIGHMEM) && !fault_in_pages_readable(buf, copy)) {
		kaddr = kmap_atomic(page);
		to = kaddr + offset;

		/* first chunk, usually the only one */
		left = __copy_from_user_inatomic(to, buf, copy);
		copy -= left;
		skip += copy;
		to += copy;
		bytes -= copy;

		while (unlikely(!left && bytes)) {
			iov++;
			buf = iov->iov_base;
			copy = min(bytes, iov->iov_len);
			left = __copy_from_user_inatomic(to, buf, copy);
			copy -= left;
			skip = copy;
			to += copy;
			bytes -= copy;
		}
		if (likely(!bytes)) {
			kunmap_atomic(kaddr);
			goto done;
		}
		offset = to - kaddr;
		buf += copy;
		kunmap_atomic(kaddr);
		copy = min(bytes, iov->iov_len - skip);
	}
	/* Too bad - revert to non-atomic kmap */

	kaddr = kmap(page);
	to = kaddr + offset;
	left = __copy_from_user(to, buf, copy);
	copy -= left;
	skip += copy;
	to += copy;
	bytes -= copy;
	while (unlikely(!left && bytes)) {
		iov++;
		buf = iov->iov_base;
		copy = min(bytes, iov->iov_len);
		left = __copy_from_user(to, buf, copy);
		copy -= left;
		skip = copy;
		to += copy;
		bytes -= copy;
	}
	kunmap(page);

done:
	if (skip == iov->iov_len) {
		iov++;
		skip = 0;
	}
	i->count -= wanted - bytes;
	i->nr_segs -= iov - i->iov;
	i->iov = iov;
	i->iov_offset = skip;
	return wanted - bytes;
}

/*
 * Fault in one or more iovecs of the given iov_iter, to a maximum length of
 * bytes.  For each iovec, fault in each page that constitutes the iovec.
 *
 * Return 0 on success, or non-zero if the memory could not be accessed (i.e.
 * because it is an invalid address).
 */
int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
{
	size_t skip = i->iov_offset;
	const struct iovec *iov;
	int err;
	struct iovec v;

	if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
		iterate_iovec(i, bytes, v, iov, skip, ({
			err = fault_in_pages_readable(v.iov_base, v.iov_len);
			if (unlikely(err))
			return err;
		0;}))
	}
	return 0;
}
EXPORT_SYMBOL(iov_iter_fault_in_readable);

void iov_iter_init(struct iov_iter *i, int direction,
			const struct iovec *iov, unsigned long nr_segs,
			size_t count)
{
	/* It will get better.  Eventually... */
	if (segment_eq(get_fs(), KERNEL_DS)) {
		direction |= ITER_KVEC;
		i->type = direction;
		i->kvec = (struct kvec *)iov;
	} else {
		i->type = direction;
		i->iov = iov;
	}
	i->nr_segs = nr_segs;
	i->iov_offset = 0;
	i->count = count;
}
EXPORT_SYMBOL(iov_iter_init);

static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
{
	char *from = kmap_atomic(page);
	memcpy(to, from + offset, len);
	kunmap_atomic(from);
}

static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
{
	char *to = kmap_atomic(page);
	memcpy(to + offset, from, len);
	kunmap_atomic(to);
}

static void memzero_page(struct page *page, size_t offset, size_t len)
{
	char *addr = kmap_atomic(page);
	memset(addr + offset, 0, len);
	kunmap_atomic(addr);
}

size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
	const char *from = addr;
	iterate_and_advance(i, bytes, v,
		__copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
			       v.iov_len),
		memcpy_to_page(v.bv_page, v.bv_offset,
			       (from += v.bv_len) - v.bv_len, v.bv_len),
		memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
	)

	return bytes;
}
EXPORT_SYMBOL(copy_to_iter);

size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
	char *to = addr;
	iterate_and_advance(i, bytes, v,
		__copy_from_user((to += v.iov_len) - v.iov_len, v.iov_base,
				 v.iov_len),
		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
				 v.bv_offset, v.bv_len),
		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
	)

	return bytes;
}
EXPORT_SYMBOL(copy_from_iter);

size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
{
	char *to = addr;
	iterate_and_advance(i, bytes, v,
		__copy_from_user_nocache((to += v.iov_len) - v.iov_len,
					 v.iov_base, v.iov_len),
		memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
				 v.bv_offset, v.bv_len),
		memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
	)

	return bytes;
}
EXPORT_SYMBOL(copy_from_iter_nocache);

size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
			 struct iov_iter *i)
{
	if (i->type & (ITER_BVEC|ITER_KVEC)) {
		void *kaddr = kmap_atomic(page);
		size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
		kunmap_atomic(kaddr);
		return wanted;
	} else
		return copy_page_to_iter_iovec(page, offset, bytes, i);
}
EXPORT_SYMBOL(copy_page_to_iter);

size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
			 struct iov_iter *i)
{
	if (i->type & (ITER_BVEC|ITER_KVEC)) {
		void *kaddr = kmap_atomic(page);
		size_t wanted = copy_from_iter(kaddr + offset, bytes, i);
		kunmap_atomic(kaddr);
		return wanted;
	} else
		return copy_page_from_iter_iovec(page, offset, bytes, i);
}
EXPORT_SYMBOL(copy_page_from_iter);

size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
{
	iterate_and_advance(i, bytes, v,
		__clear_user(v.iov_base, v.iov_len),
		memzero_page(v.bv_page, v.bv_offset, v.bv_len),
		memset(v.iov_base, 0, v.iov_len)
	)

	return bytes;
}
EXPORT_SYMBOL(iov_iter_zero);

size_t iov_iter_copy_from_user_atomic(struct page *page,
		struct iov_iter *i, unsigned long offset, size_t bytes)
{
	char *kaddr = kmap_atomic(page), *p = kaddr + offset;
	iterate_all_kinds(i, bytes, v,
		__copy_from_user_inatomic((p += v.iov_len) - v.iov_len,
					  v.iov_base, v.iov_len),
		memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
				 v.bv_offset, v.bv_len),
		memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
	)
	kunmap_atomic(kaddr);
	return bytes;
}
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);

void iov_iter_advance(struct iov_iter *i, size_t size)
{
	iterate_and_advance(i, size, v, 0, 0, 0)
}
EXPORT_SYMBOL(iov_iter_advance);

/*
 * Return the count of just the current iov_iter segment.
 */
size_t iov_iter_single_seg_count(const struct iov_iter *i)
{
	if (i->nr_segs == 1)
		return i->count;
	else if (i->type & ITER_BVEC)
		return min(i->count, i->bvec->bv_len - i->iov_offset);
	else
		return min(i->count, i->iov->iov_len - i->iov_offset);
}
EXPORT_SYMBOL(iov_iter_single_seg_count);

void iov_iter_kvec(struct iov_iter *i, int direction,
			const struct kvec *kvec, unsigned long nr_segs,
			size_t count)
{
	BUG_ON(!(direction & ITER_KVEC));
	i->type = direction;
	i->kvec = kvec;
	i->nr_segs = nr_segs;
	i->iov_offset = 0;
	i->count = count;
}
EXPORT_SYMBOL(iov_iter_kvec);

void iov_iter_bvec(struct iov_iter *i, int direction,
			const struct bio_vec *bvec, unsigned long nr_segs,
			size_t count)
{
	BUG_ON(!(direction & ITER_BVEC));
	i->type = direction;
	i->bvec = bvec;
	i->nr_segs = nr_segs;
	i->iov_offset = 0;
	i->count = count;
}
EXPORT_SYMBOL(iov_iter_bvec);

unsigned long iov_iter_alignment(const struct iov_iter *i)
{
	unsigned long res = 0;
	size_t size = i->count;

	if (!size)
		return 0;

	iterate_all_kinds(i, size, v,
		(res |= (unsigned long)v.iov_base | v.iov_len, 0),
		res |= v.bv_offset | v.bv_len,
		res |= (unsigned long)v.iov_base | v.iov_len
	)
	return res;
}
EXPORT_SYMBOL(iov_iter_alignment);

unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
{
        unsigned long res = 0;
	size_t size = i->count;
	if (!size)
		return 0;

	iterate_all_kinds(i, size, v,
		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
			(size != v.iov_len ? size : 0), 0),
		(res |= (!res ? 0 : (unsigned long)v.bv_offset) |
			(size != v.bv_len ? size : 0)),
		(res |= (!res ? 0 : (unsigned long)v.iov_base) |
			(size != v.iov_len ? size : 0))
		);
		return res;
}
EXPORT_SYMBOL(iov_iter_gap_alignment);

ssize_t iov_iter_get_pages(struct iov_iter *i,
		   struct page **pages, size_t maxsize, unsigned maxpages,
		   size_t *start)
{
	if (maxsize > i->count)
		maxsize = i->count;

	if (!maxsize)
		return 0;

	iterate_all_kinds(i, maxsize, v, ({
		unsigned long addr = (unsigned long)v.iov_base;
		size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
		int n;
		int res;

		if (len > maxpages * PAGE_SIZE)
			len = maxpages * PAGE_SIZE;
		addr &= ~(PAGE_SIZE - 1);
		n = DIV_ROUND_UP(len, PAGE_SIZE);
		res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, pages);
		if (unlikely(res < 0))
			return res;
		return (res == n ? len : res * PAGE_SIZE) - *start;
	0;}),({
		/* can't be more than PAGE_SIZE */
		*start = v.bv_offset;
		get_page(*pages = v.bv_page);
		return v.bv_len;
	}),({
		return -EFAULT;
	})
	)
	return 0;
}
EXPORT_SYMBOL(iov_iter_get_pages);

static struct page **get_pages_array(size_t n)
{
	struct page **p = kmalloc(n * sizeof(struct page *), GFP_KERNEL);
	if (!p)
		p = vmalloc(n * sizeof(struct page *));
	return p;
}

ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
		   struct page ***pages, size_t maxsize,
		   size_t *start)
{
	struct page **p;

	if (maxsize > i->count)
		maxsize = i->count;

	if (!maxsize)
		return 0;

	iterate_all_kinds(i, maxsize, v, ({
		unsigned long addr = (unsigned long)v.iov_base;
		size_t len = v.iov_len + (*start = addr & (PAGE_SIZE - 1));
		int n;
		int res;

		addr &= ~(PAGE_SIZE - 1);
		n = DIV_ROUND_UP(len, PAGE_SIZE);
		p = get_pages_array(n);
		if (!p)
			return -ENOMEM;
		res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
		if (unlikely(res < 0)) {
			kvfree(p);
			return res;
		}
		*pages = p;
		return (res == n ? len : res * PAGE_SIZE) - *start;
	0;}),({
		/* can't be more than PAGE_SIZE */
		*start = v.bv_offset;
		*pages = p = get_pages_array(1);
		if (!p)
			return -ENOMEM;
		get_page(*p = v.bv_page);
		return v.bv_len;
	}),({
		return -EFAULT;
	})
	)
	return 0;
}
EXPORT_SYMBOL(iov_iter_get_pages_alloc);

size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
			       struct iov_iter *i)
{
	char *to = addr;
	__wsum sum, next;
	size_t off = 0;
	sum = *csum;
	iterate_and_advance(i, bytes, v, ({
		int err = 0;
		next = csum_and_copy_from_user(v.iov_base, 
					       (to += v.iov_len) - v.iov_len,
					       v.iov_len, 0, &err);
		if (!err) {
			sum = csum_block_add(sum, next, off);
			off += v.iov_len;
		}
		err ? v.iov_len : 0;
	}), ({
		char *p = kmap_atomic(v.bv_page);
		next = csum_partial_copy_nocheck(p + v.bv_offset,
						 (to += v.bv_len) - v.bv_len,
						 v.bv_len, 0);
		kunmap_atomic(p);
		sum = csum_block_add(sum, next, off);
		off += v.bv_len;
	}),({
		next = csum_partial_copy_nocheck(v.iov_base,
						 (to += v.iov_len) - v.iov_len,
						 v.iov_len, 0);
		sum = csum_block_add(sum, next, off);
		off += v.iov_len;
	})
	)
	*csum = sum;
	return bytes;
}
EXPORT_SYMBOL(csum_and_copy_from_iter);

size_t csum_and_copy_to_iter(const void *addr, size_t bytes, __wsum *csum,
			     struct iov_iter *i)
{
	const char *from = addr;
	__wsum sum, next;
	size_t off = 0;
	sum = *csum;
	iterate_and_advance(i, bytes, v, ({
		int err = 0;
		next = csum_and_copy_to_user((from += v.iov_len) - v.iov_len,
					     v.iov_base, 
					     v.iov_len, 0, &err);
		if (!err) {
			sum = csum_block_add(sum, next, off);
			off += v.iov_len;
		}
		err ? v.iov_len : 0;
	}), ({
		char *p = kmap_atomic(v.bv_page);
		next = csum_partial_copy_nocheck((from += v.bv_len) - v.bv_len,
						 p + v.bv_offset,
						 v.bv_len, 0);
		kunmap_atomic(p);
		sum = csum_block_add(sum, next, off);
		off += v.bv_len;
	}),({
		next = csum_partial_copy_nocheck((from += v.iov_len) - v.iov_len,
						 v.iov_base,
						 v.iov_len, 0);
		sum = csum_block_add(sum, next, off);
		off += v.iov_len;
	})
	)
	*csum = sum;
	return bytes;
}
EXPORT_SYMBOL(csum_and_copy_to_iter);

int iov_iter_npages(const struct iov_iter *i, int maxpages)
{
	size_t size = i->count;
	int npages = 0;

	if (!size)
		return 0;

	iterate_all_kinds(i, size, v, ({
		unsigned long p = (unsigned long)v.iov_base;
		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
			- p / PAGE_SIZE;
		if (npages >= maxpages)
			return maxpages;
	0;}),({
		npages++;
		if (npages >= maxpages)
			return maxpages;
	}),({
		unsigned long p = (unsigned long)v.iov_base;
		npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
			- p / PAGE_SIZE;
		if (npages >= maxpages)
			return maxpages;
	})
	)
	return npages;
}
EXPORT_SYMBOL(iov_iter_npages);

const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
{
	*new = *old;
	if (new->type & ITER_BVEC)
		return new->bvec = kmemdup(new->bvec,
				    new->nr_segs * sizeof(struct bio_vec),
				    flags);
	else
		/* iovec and kvec have identical layout */
		return new->iov = kmemdup(new->iov,
				   new->nr_segs * sizeof(struct iovec),
				   flags);
}
EXPORT_SYMBOL(dup_iter);

int import_iovec(int type, const struct iovec __user * uvector,
		 unsigned nr_segs, unsigned fast_segs,
		 struct iovec **iov, struct iov_iter *i)
{
	ssize_t n;
	struct iovec *p;
	n = rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
				  *iov, &p);
	if (n < 0) {
		if (p != *iov)
			kfree(p);
		*iov = NULL;
		return n;
	}
	iov_iter_init(i, type, p, nr_segs, n);
	*iov = p == *iov ? NULL : p;
	return 0;
}
EXPORT_SYMBOL(import_iovec);

#ifdef CONFIG_COMPAT
#include <linux/compat.h>

int compat_import_iovec(int type, const struct compat_iovec __user * uvector,
		 unsigned nr_segs, unsigned fast_segs,
		 struct iovec **iov, struct iov_iter *i)
{
	ssize_t n;
	struct iovec *p;
	n = compat_rw_copy_check_uvector(type, uvector, nr_segs, fast_segs,
				  *iov, &p);
	if (n < 0) {
		if (p != *iov)
			kfree(p);
		*iov = NULL;
		return n;
	}
	iov_iter_init(i, type, p, nr_segs, n);
	*iov = p == *iov ? NULL : p;
	return 0;
}
#endif

int import_single_range(int rw, void __user *buf, size_t len,
		 struct iovec *iov, struct iov_iter *i)
{
	if (len > MAX_RW_COUNT)
		len = MAX_RW_COUNT;
	if (unlikely(!access_ok(!rw, buf, len)))
		return -EFAULT;

	iov->iov_base = buf;
	iov->iov_len = len;
	iov_iter_init(i, rw, iov, 1, len);
	return 0;
}
EXPORT_SYMBOL(import_single_range);