aboutsummaryrefslogtreecommitdiff
path: root/fs/seq_file.c
blob: ce9e39fd5dafc768c27b2ceaa4e69a02c3ed1e6e (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
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
/*
 * linux/fs/seq_file.c
 *
 * helper functions for making synthetic files from sequences of records.
 * initial implementation -- AV, Oct 2001.
 */

#include <linux/fs.h>
#include <linux/export.h>
#include <linux/seq_file.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/mm.h>

#include <asm/uaccess.h>
#include <asm/page.h>

static void seq_set_overflow(struct seq_file *m)
{
	m->count = m->size;
}

static void *seq_buf_alloc(unsigned long size)
{
	void *buf;

	/*
	 * __GFP_NORETRY to avoid oom-killings with high-order allocations -
	 * it's better to fall back to vmalloc() than to kill things.
	 */
	buf = kmalloc(size, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
	if (!buf && size > PAGE_SIZE)
		buf = vmalloc(size);
	return buf;
}

/**
 *	seq_open -	initialize sequential file
 *	@file: file we initialize
 *	@op: method table describing the sequence
 *
 *	seq_open() sets @file, associating it with a sequence described
 *	by @op.  @op->start() sets the iterator up and returns the first
 *	element of sequence. @op->stop() shuts it down.  @op->next()
 *	returns the next element of sequence.  @op->show() prints element
 *	into the buffer.  In case of error ->start() and ->next() return
 *	ERR_PTR(error).  In the end of sequence they return %NULL. ->show()
 *	returns 0 in case of success and negative number in case of error.
 *	Returning SEQ_SKIP means "discard this element and move on".
 *	Note: seq_open() will allocate a struct seq_file and store its
 *	pointer in @file->private_data. This pointer should not be modified.
 */
int seq_open(struct file *file, const struct seq_operations *op)
{
	struct seq_file *p;

	WARN_ON(file->private_data);

	p = kzalloc(sizeof(*p), GFP_KERNEL);
	if (!p)
		return -ENOMEM;

	file->private_data = p;

	mutex_init(&p->lock);
	p->op = op;
#ifdef CONFIG_USER_NS
	p->user_ns = file->f_cred->user_ns;
#endif

	/*
	 * Wrappers around seq_open(e.g. swaps_open) need to be
	 * aware of this. If they set f_version themselves, they
	 * should call seq_open first and then set f_version.
	 */
	file->f_version = 0;

	/*
	 * seq_files support lseek() and pread().  They do not implement
	 * write() at all, but we clear FMODE_PWRITE here for historical
	 * reasons.
	 *
	 * If a client of seq_files a) implements file.write() and b) wishes to
	 * support pwrite() then that client will need to implement its own
	 * file.open() which calls seq_open() and then sets FMODE_PWRITE.
	 */
	file->f_mode &= ~FMODE_PWRITE;
	return 0;
}
EXPORT_SYMBOL(seq_open);

static int traverse(struct seq_file *m, loff_t offset)
{
	loff_t pos = 0, index;
	int error = 0;
	void *p;

	m->version = 0;
	index = 0;
	m->count = m->from = 0;
	if (!offset) {
		m->index = index;
		return 0;
	}
	if (!m->buf) {
		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
		if (!m->buf)
			return -ENOMEM;
	}
	p = m->op->start(m, &index);
	while (p) {
		error = PTR_ERR(p);
		if (IS_ERR(p))
			break;
		error = m->op->show(m, p);
		if (error < 0)
			break;
		if (unlikely(error)) {
			error = 0;
			m->count = 0;
		}
		if (seq_has_overflowed(m))
			goto Eoverflow;
		if (pos + m->count > offset) {
			m->from = offset - pos;
			m->count -= m->from;
			m->index = index;
			break;
		}
		pos += m->count;
		m->count = 0;
		if (pos == offset) {
			index++;
			m->index = index;
			break;
		}
		p = m->op->next(m, p, &index);
	}
	m->op->stop(m, p);
	m->index = index;
	return error;

Eoverflow:
	m->op->stop(m, p);
	kvfree(m->buf);
	m->count = 0;
	m->buf = seq_buf_alloc(m->size <<= 1);
	return !m->buf ? -ENOMEM : -EAGAIN;
}

/**
 *	seq_read -	->read() method for sequential files.
 *	@file: the file to read from
 *	@buf: the buffer to read to
 *	@size: the maximum number of bytes to read
 *	@ppos: the current position in the file
 *
 *	Ready-made ->f_op->read()
 */
ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
	struct seq_file *m = file->private_data;
	size_t copied = 0;
	loff_t pos;
	size_t n;
	void *p;
	int err = 0;

	mutex_lock(&m->lock);

	/*
	 * seq_file->op->..m_start/m_stop/m_next may do special actions
	 * or optimisations based on the file->f_version, so we want to
	 * pass the file->f_version to those methods.
	 *
	 * seq_file->version is just copy of f_version, and seq_file
	 * methods can treat it simply as file version.
	 * It is copied in first and copied out after all operations.
	 * It is convenient to have it as  part of structure to avoid the
	 * need of passing another argument to all the seq_file methods.
	 */
	m->version = file->f_version;

	/* Don't assume *ppos is where we left it */
	if (unlikely(*ppos != m->read_pos)) {
		while ((err = traverse(m, *ppos)) == -EAGAIN)
			;
		if (err) {
			/* With prejudice... */
			m->read_pos = 0;
			m->version = 0;
			m->index = 0;
			m->count = 0;
			goto Done;
		} else {
			m->read_pos = *ppos;
		}
	}

	/* grab buffer if we didn't have one */
	if (!m->buf) {
		m->buf = seq_buf_alloc(m->size = PAGE_SIZE);
		if (!m->buf)
			goto Enomem;
	}
	/* if not empty - flush it first */
	if (m->count) {
		n = min(m->count, size);
		err = copy_to_user(buf, m->buf + m->from, n);
		if (err)
			goto Efault;
		m->count -= n;
		m->from += n;
		size -= n;
		buf += n;
		copied += n;
		if (!m->count)
			m->index++;
		if (!size)
			goto Done;
	}
	/* we need at least one record in buffer */
	pos = m->index;
	p = m->op->start(m, &pos);
	while (1) {
		err = PTR_ERR(p);
		if (!p || IS_ERR(p))
			break;
		err = m->op->show(m, p);
		if (err < 0)
			break;
		if (unlikely(err))
			m->count = 0;
		if (unlikely(!m->count)) {
			p = m->op->next(m, p, &pos);
			m->index = pos;
			continue;
		}
		if (m->count < m->size)
			goto Fill;
		m->op->stop(m, p);
		kvfree(m->buf);
		m->count = 0;
		m->buf = seq_buf_alloc(m->size <<= 1);
		if (!m->buf)
			goto Enomem;
		m->version = 0;
		pos = m->index;
		p = m->op->start(m, &pos);
	}
	m->op->stop(m, p);
	m->count = 0;
	goto Done;
Fill:
	/* they want more? let's try to get some more */
	while (m->count < size) {
		size_t offs = m->count;
		loff_t next = pos;
		p = m->op->next(m, p, &next);
		if (!p || IS_ERR(p)) {
			err = PTR_ERR(p);
			break;
		}
		err = m->op->show(m, p);
		if (seq_has_overflowed(m) || err) {
			m->count = offs;
			if (likely(err <= 0))
				break;
		}
		pos = next;
	}
	m->op->stop(m, p);
	n = min(m->count, size);
	err = copy_to_user(buf, m->buf, n);
	if (err)
		goto Efault;
	copied += n;
	m->count -= n;
	if (m->count)
		m->from = n;
	else
		pos++;
	m->index = pos;
Done:
	if (!copied)
		copied = err;
	else {
		*ppos += copied;
		m->read_pos += copied;
	}
	file->f_version = m->version;
	mutex_unlock(&m->lock);
	return copied;
Enomem:
	err = -ENOMEM;
	goto Done;
Efault:
	err = -EFAULT;
	goto Done;
}
EXPORT_SYMBOL(seq_read);

/**
 *	seq_lseek -	->llseek() method for sequential files.
 *	@file: the file in question
 *	@offset: new position
 *	@whence: 0 for absolute, 1 for relative position
 *
 *	Ready-made ->f_op->llseek()
 */
loff_t seq_lseek(struct file *file, loff_t offset, int whence)
{
	struct seq_file *m = file->private_data;
	loff_t retval = -EINVAL;

	mutex_lock(&m->lock);
	m->version = file->f_version;
	switch (whence) {
	case SEEK_CUR:
		offset += file->f_pos;
	case SEEK_SET:
		if (offset < 0)
			break;
		retval = offset;
		if (offset != m->read_pos) {
			while ((retval = traverse(m, offset)) == -EAGAIN)
				;
			if (retval) {
				/* with extreme prejudice... */
				file->f_pos = 0;
				m->read_pos = 0;
				m->version = 0;
				m->index = 0;
				m->count = 0;
			} else {
				m->read_pos = offset;
				retval = file->f_pos = offset;
			}
		} else {
			file->f_pos = offset;
		}
	}
	file->f_version = m->version;
	mutex_unlock(&m->lock);
	return retval;
}
EXPORT_SYMBOL(seq_lseek);

/**
 *	seq_release -	free the structures associated with sequential file.
 *	@file: file in question
 *	@inode: its inode
 *
 *	Frees the structures associated with sequential file; can be used
 *	as ->f_op->release() if you don't have private data to destroy.
 */
int seq_release(struct inode *inode, struct file *file)
{
	struct seq_file *m = file->private_data;
	kvfree(m->buf);
	kfree(m);
	return 0;
}
EXPORT_SYMBOL(seq_release);

/**
 *	seq_escape -	print string into buffer, escaping some characters
 *	@m:	target buffer
 *	@s:	string
 *	@esc:	set of characters that need escaping
 *
 *	Puts string into buffer, replacing each occurrence of character from
 *	@esc with usual octal escape.  Returns 0 in case of success, -1 - in
 *	case of overflow.
 */
int seq_escape(struct seq_file *m, const char *s, const char *esc)
{
	char *end = m->buf + m->size;
        char *p;
	char c;

        for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
		if (!strchr(esc, c)) {
			*p++ = c;
			continue;
		}
		if (p + 3 < end) {
			*p++ = '\\';
			*p++ = '0' + ((c & 0300) >> 6);
			*p++ = '0' + ((c & 070) >> 3);
			*p++ = '0' + (c & 07);
			continue;
		}
		seq_set_overflow(m);
		return -1;
        }
	m->count = p - m->buf;
        return 0;
}
EXPORT_SYMBOL(seq_escape);

int seq_vprintf(struct seq_file *m, const char *f, va_list args)
{
	int len;

	if (m->count < m->size) {
		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
		if (m->count + len < m->size) {
			m->count += len;
			return 0;
		}
	}
	seq_set_overflow(m);
	return -1;
}
EXPORT_SYMBOL(seq_vprintf);

int seq_printf(struct seq_file *m, const char *f, ...)
{
	int ret;
	va_list args;

	va_start(args, f);
	ret = seq_vprintf(m, f, args);
	va_end(args);

	return ret;
}
EXPORT_SYMBOL(seq_printf);

/**
 *	mangle_path -	mangle and copy path to buffer beginning
 *	@s: buffer start
 *	@p: beginning of path in above buffer
 *	@esc: set of characters that need escaping
 *
 *      Copy the path from @p to @s, replacing each occurrence of character from
 *      @esc with usual octal escape.
 *      Returns pointer past last written character in @s, or NULL in case of
 *      failure.
 */
char *mangle_path(char *s, const char *p, const char *esc)
{
	while (s <= p) {
		char c = *p++;
		if (!c) {
			return s;
		} else if (!strchr(esc, c)) {
			*s++ = c;
		} else if (s + 4 > p) {
			break;
		} else {
			*s++ = '\\';
			*s++ = '0' + ((c & 0300) >> 6);
			*s++ = '0' + ((c & 070) >> 3);
			*s++ = '0' + (c & 07);
		}
	}
	return NULL;
}
EXPORT_SYMBOL(mangle_path);

/**
 * seq_path - seq_file interface to print a pathname
 * @m: the seq_file handle
 * @path: the struct path to print
 * @esc: set of characters to escape in the output
 *
 * return the absolute path of 'path', as represented by the
 * dentry / mnt pair in the path parameter.
 */
int seq_path(struct seq_file *m, const struct path *path, const char *esc)
{
	char *buf;
	size_t size = seq_get_buf(m, &buf);
	int res = -1;

	if (size) {
		char *p = d_path(path, buf, size);
		if (!IS_ERR(p)) {
			char *end = mangle_path(buf, p, esc);
			if (end)
				res = end - buf;
		}
	}
	seq_commit(m, res);

	return res;
}
EXPORT_SYMBOL(seq_path);

/**
 * seq_file_path - seq_file interface to print a pathname of a file
 * @m: the seq_file handle
 * @file: the struct file to print
 * @esc: set of characters to escape in the output
 *
 * return the absolute path to the file.
 */
int seq_file_path(struct seq_file *m, struct file *file, const char *esc)
{
	return seq_path(m, &file->f_path, esc);
}
EXPORT_SYMBOL(seq_file_path);

/*
 * Same as seq_path, but relative to supplied root.
 */
int seq_path_root(struct seq_file *m, const struct path *path,
		  const struct path *root, const char *esc)
{
	char *buf;
	size_t size = seq_get_buf(m, &buf);
	int res = -ENAMETOOLONG;

	if (size) {
		char *p;

		p = __d_path(path, root, buf, size);
		if (!p)
			return SEQ_SKIP;
		res = PTR_ERR(p);
		if (!IS_ERR(p)) {
			char *end = mangle_path(buf, p, esc);
			if (end)
				res = end - buf;
			else
				res = -ENAMETOOLONG;
		}
	}
	seq_commit(m, res);

	return res < 0 && res != -ENAMETOOLONG ? res : 0;
}

/*
 * returns the path of the 'dentry' from the root of its filesystem.
 */
int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)
{
	char *buf;
	size_t size = seq_get_buf(m, &buf);
	int res = -1;

	if (size) {
		char *p = dentry_path(dentry, buf, size);
		if (!IS_ERR(p)) {
			char *end = mangle_path(buf, p, esc);
			if (end)
				res = end - buf;
		}
	}
	seq_commit(m, res);

	return res;
}
EXPORT_SYMBOL(seq_dentry);

static void *single_start(struct seq_file *p, loff_t *pos)
{
	return NULL + (*pos == 0);
}

static void *single_next(struct seq_file *p, void *v, loff_t *pos)
{
	++*pos;
	return NULL;
}

static void single_stop(struct seq_file *p, void *v)
{
}

int single_open(struct file *file, int (*show)(struct seq_file *, void *),
		void *data)
{
	struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
	int res = -ENOMEM;

	if (op) {
		op->start = single_start;
		op->next = single_next;
		op->stop = single_stop;
		op->show = show;
		res = seq_open(file, op);
		if (!res)
			((struct seq_file *)file->private_data)->private = data;
		else
			kfree(op);
	}
	return res;
}
EXPORT_SYMBOL(single_open);

int single_open_size(struct file *file, int (*show)(struct seq_file *, void *),
		void *data, size_t size)
{
	char *buf = seq_buf_alloc(size);
	int ret;
	if (!buf)
		return -ENOMEM;
	ret = single_open(file, show, data);
	if (ret) {
		kvfree(buf);
		return ret;
	}
	((struct seq_file *)file->private_data)->buf = buf;
	((struct seq_file *)file->private_data)->size = size;
	return 0;
}
EXPORT_SYMBOL(single_open_size);

int single_release(struct inode *inode, struct file *file)
{
	const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
	int res = seq_release(inode, file);
	kfree(op);
	return res;
}
EXPORT_SYMBOL(single_release);

int seq_release_private(struct inode *inode, struct file *file)
{
	struct seq_file *seq = file->private_data;

	kfree(seq->private);
	seq->private = NULL;
	return seq_release(inode, file);
}
EXPORT_SYMBOL(seq_release_private);

void *__seq_open_private(struct file *f, const struct seq_operations *ops,
		int psize)
{
	int rc;
	void *private;
	struct seq_file *seq;

	private = kzalloc(psize, GFP_KERNEL);
	if (private == NULL)
		goto out;

	rc = seq_open(f, ops);
	if (rc < 0)
		goto out_free;

	seq = f->private_data;
	seq->private = private;
	return private;

out_free:
	kfree(private);
out:
	return NULL;
}
EXPORT_SYMBOL(__seq_open_private);

int seq_open_private(struct file *filp, const struct seq_operations *ops,
		int psize)
{
	return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
}
EXPORT_SYMBOL(seq_open_private);

int seq_putc(struct seq_file *m, char c)
{
	if (m->count < m->size) {
		m->buf[m->count++] = c;
		return 0;
	}
	return -1;
}
EXPORT_SYMBOL(seq_putc);

int seq_puts(struct seq_file *m, const char *s)
{
	int len = strlen(s);
	if (m->count + len < m->size) {
		memcpy(m->buf + m->count, s, len);
		m->count += len;
		return 0;
	}
	seq_set_overflow(m);
	return -1;
}
EXPORT_SYMBOL(seq_puts);

/*
 * A helper routine for putting decimal numbers without rich format of printf().
 * only 'unsigned long long' is supported.
 * This routine will put one byte delimiter + number into seq_file.
 * This routine is very quick when you show lots of numbers.
 * In usual cases, it will be better to use seq_printf(). It's easier to read.
 */
int seq_put_decimal_ull(struct seq_file *m, char delimiter,
			unsigned long long num)
{
	int len;

	if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
		goto overflow;

	if (delimiter)
		m->buf[m->count++] = delimiter;

	if (num < 10) {
		m->buf[m->count++] = num + '0';
		return 0;
	}

	len = num_to_str(m->buf + m->count, m->size - m->count, num);
	if (!len)
		goto overflow;
	m->count += len;
	return 0;
overflow:
	seq_set_overflow(m);
	return -1;
}
EXPORT_SYMBOL(seq_put_decimal_ull);

int seq_put_decimal_ll(struct seq_file *m, char delimiter,
			long long num)
{
	if (num < 0) {
		if (m->count + 3 >= m->size) {
			seq_set_overflow(m);
			return -1;
		}
		if (delimiter)
			m->buf[m->count++] = delimiter;
		num = -num;
		delimiter = '-';
	}
	return seq_put_decimal_ull(m, delimiter, num);

}
EXPORT_SYMBOL(seq_put_decimal_ll);

/**
 * seq_write - write arbitrary data to buffer
 * @seq: seq_file identifying the buffer to which data should be written
 * @data: data address
 * @len: number of bytes
 *
 * Return 0 on success, non-zero otherwise.
 */
int seq_write(struct seq_file *seq, const void *data, size_t len)
{
	if (seq->count + len < seq->size) {
		memcpy(seq->buf + seq->count, data, len);
		seq->count += len;
		return 0;
	}
	seq_set_overflow(seq);
	return -1;
}
EXPORT_SYMBOL(seq_write);

/**
 * seq_pad - write padding spaces to buffer
 * @m: seq_file identifying the buffer to which data should be written
 * @c: the byte to append after padding if non-zero
 */
void seq_pad(struct seq_file *m, char c)
{
	int size = m->pad_until - m->count;
	if (size > 0)
		seq_printf(m, "%*s", size, "");
	if (c)
		seq_putc(m, c);
}
EXPORT_SYMBOL(seq_pad);

struct list_head *seq_list_start(struct list_head *head, loff_t pos)
{
	struct list_head *lh;

	list_for_each(lh, head)
		if (pos-- == 0)
			return lh;

	return NULL;
}
EXPORT_SYMBOL(seq_list_start);

struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
{
	if (!pos)
		return head;

	return seq_list_start(head, pos - 1);
}
EXPORT_SYMBOL(seq_list_start_head);

struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
{
	struct list_head *lh;

	lh = ((struct list_head *)v)->next;
	++*ppos;
	return lh == head ? NULL : lh;
}
EXPORT_SYMBOL(seq_list_next);

/**
 * seq_hlist_start - start an iteration of a hlist
 * @head: the head of the hlist
 * @pos:  the start position of the sequence
 *
 * Called at seq_file->op->start().
 */
struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
{
	struct hlist_node *node;

	hlist_for_each(node, head)
		if (pos-- == 0)
			return node;
	return NULL;
}
EXPORT_SYMBOL(seq_hlist_start);

/**
 * seq_hlist_start_head - start an iteration of a hlist
 * @head: the head of the hlist
 * @pos:  the start position of the sequence
 *
 * Called at seq_file->op->start(). Call this function if you want to
 * print a header at the top of the output.
 */
struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
{
	if (!pos)
		return SEQ_START_TOKEN;

	return seq_hlist_start(head, pos - 1);
}
EXPORT_SYMBOL(seq_hlist_start_head);

/**
 * seq_hlist_next - move to the next position of the hlist
 * @v:    the current iterator
 * @head: the head of the hlist
 * @ppos: the current position
 *
 * Called at seq_file->op->next().
 */
struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
				  loff_t *ppos)
{
	struct hlist_node *node = v;

	++*ppos;
	if (v == SEQ_START_TOKEN)
		return head->first;
	else
		return node->next;
}
EXPORT_SYMBOL(seq_hlist_next);

/**
 * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
 * @head: the head of the hlist
 * @pos:  the start position of the sequence
 *
 * Called at seq_file->op->start().
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
				       loff_t pos)
{
	struct hlist_node *node;

	__hlist_for_each_rcu(node, head)
		if (pos-- == 0)
			return node;
	return NULL;
}
EXPORT_SYMBOL(seq_hlist_start_rcu);

/**
 * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
 * @head: the head of the hlist
 * @pos:  the start position of the sequence
 *
 * Called at seq_file->op->start(). Call this function if you want to
 * print a header at the top of the output.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
					    loff_t pos)
{
	if (!pos)
		return SEQ_START_TOKEN;

	return seq_hlist_start_rcu(head, pos - 1);
}
EXPORT_SYMBOL(seq_hlist_start_head_rcu);

/**
 * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
 * @v:    the current iterator
 * @head: the head of the hlist
 * @ppos: the current position
 *
 * Called at seq_file->op->next().
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
struct hlist_node *seq_hlist_next_rcu(void *v,
				      struct hlist_head *head,
				      loff_t *ppos)
{
	struct hlist_node *node = v;

	++*ppos;
	if (v == SEQ_START_TOKEN)
		return rcu_dereference(head->first);
	else
		return rcu_dereference(node->next);
}
EXPORT_SYMBOL(seq_hlist_next_rcu);

/**
 * seq_hlist_start_precpu - start an iteration of a percpu hlist array
 * @head: pointer to percpu array of struct hlist_heads
 * @cpu:  pointer to cpu "cursor"
 * @pos:  start position of sequence
 *
 * Called at seq_file->op->start().
 */
struct hlist_node *
seq_hlist_start_percpu(struct hlist_head __percpu *head, int *cpu, loff_t pos)
{
	struct hlist_node *node;

	for_each_possible_cpu(*cpu) {
		hlist_for_each(node, per_cpu_ptr(head, *cpu)) {
			if (pos-- == 0)
				return node;
		}
	}
	return NULL;
}
EXPORT_SYMBOL(seq_hlist_start_percpu);

/**
 * seq_hlist_next_percpu - move to the next position of the percpu hlist array
 * @v:    pointer to current hlist_node
 * @head: pointer to percpu array of struct hlist_heads
 * @cpu:  pointer to cpu "cursor"
 * @pos:  start position of sequence
 *
 * Called at seq_file->op->next().
 */
struct hlist_node *
seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
			int *cpu, loff_t *pos)
{
	struct hlist_node *node = v;

	++*pos;

	if (node->next)
		return node->next;

	for (*cpu = cpumask_next(*cpu, cpu_possible_mask); *cpu < nr_cpu_ids;
	     *cpu = cpumask_next(*cpu, cpu_possible_mask)) {
		struct hlist_head *bucket = per_cpu_ptr(head, *cpu);

		if (!hlist_empty(bucket))
			return bucket->first;
	}
	return NULL;
}
EXPORT_SYMBOL(seq_hlist_next_percpu);