aboutsummaryrefslogblamecommitdiffstats
path: root/fs/afs/proc.c
blob: 101d21b6c03715b45ead510a2abccb706f23d209 (plain) (tree)
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






































                                                                              
                                                           














                                                                             
                                                              






















                                                                              
                                                                  






















                                                                            
                                                                    





















                                                                              
                                                                  

























































































































































































































































































































































































































































































































































































































































































































































                                                                                
/* proc.c: /proc interface for AFS
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program 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; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include "cell.h"
#include "volume.h"
#include <asm/uaccess.h>
#include "internal.h"

static struct proc_dir_entry *proc_afs;


static int afs_proc_cells_open(struct inode *inode, struct file *file);
static void *afs_proc_cells_start(struct seq_file *p, loff_t *pos);
static void *afs_proc_cells_next(struct seq_file *p, void *v, loff_t *pos);
static void afs_proc_cells_stop(struct seq_file *p, void *v);
static int afs_proc_cells_show(struct seq_file *m, void *v);
static ssize_t afs_proc_cells_write(struct file *file, const char __user *buf,
				    size_t size, loff_t *_pos);

static struct seq_operations afs_proc_cells_ops = {
	.start	= afs_proc_cells_start,
	.next	= afs_proc_cells_next,
	.stop	= afs_proc_cells_stop,
	.show	= afs_proc_cells_show,
};

static const struct file_operations afs_proc_cells_fops = {
	.open		= afs_proc_cells_open,
	.read		= seq_read,
	.write		= afs_proc_cells_write,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

static int afs_proc_rootcell_open(struct inode *inode, struct file *file);
static int afs_proc_rootcell_release(struct inode *inode, struct file *file);
static ssize_t afs_proc_rootcell_read(struct file *file, char __user *buf,
				      size_t size, loff_t *_pos);
static ssize_t afs_proc_rootcell_write(struct file *file,
				       const char __user *buf,
				       size_t size, loff_t *_pos);

static const struct file_operations afs_proc_rootcell_fops = {
	.open		= afs_proc_rootcell_open,
	.read		= afs_proc_rootcell_read,
	.write		= afs_proc_rootcell_write,
	.llseek		= no_llseek,
	.release	= afs_proc_rootcell_release
};

static int afs_proc_cell_volumes_open(struct inode *inode, struct file *file);
static int afs_proc_cell_volumes_release(struct inode *inode,
					 struct file *file);
static void *afs_proc_cell_volumes_start(struct seq_file *p, loff_t *pos);
static void *afs_proc_cell_volumes_next(struct seq_file *p, void *v,
					loff_t *pos);
static void afs_proc_cell_volumes_stop(struct seq_file *p, void *v);
static int afs_proc_cell_volumes_show(struct seq_file *m, void *v);

static struct seq_operations afs_proc_cell_volumes_ops = {
	.start	= afs_proc_cell_volumes_start,
	.next	= afs_proc_cell_volumes_next,
	.stop	= afs_proc_cell_volumes_stop,
	.show	= afs_proc_cell_volumes_show,
};

static const struct file_operations afs_proc_cell_volumes_fops = {
	.open		= afs_proc_cell_volumes_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= afs_proc_cell_volumes_release,
};

static int afs_proc_cell_vlservers_open(struct inode *inode,
					struct file *file);
static int afs_proc_cell_vlservers_release(struct inode *inode,
					   struct file *file);
static void *afs_proc_cell_vlservers_start(struct seq_file *p, loff_t *pos);
static void *afs_proc_cell_vlservers_next(struct seq_file *p, void *v,
					  loff_t *pos);
static void afs_proc_cell_vlservers_stop(struct seq_file *p, void *v);
static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v);

static struct seq_operations afs_proc_cell_vlservers_ops = {
	.start	= afs_proc_cell_vlservers_start,
	.next	= afs_proc_cell_vlservers_next,
	.stop	= afs_proc_cell_vlservers_stop,
	.show	= afs_proc_cell_vlservers_show,
};

static const struct file_operations afs_proc_cell_vlservers_fops = {
	.open		= afs_proc_cell_vlservers_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= afs_proc_cell_vlservers_release,
};

static int afs_proc_cell_servers_open(struct inode *inode, struct file *file);
static int afs_proc_cell_servers_release(struct inode *inode,
					 struct file *file);
static void *afs_proc_cell_servers_start(struct seq_file *p, loff_t *pos);
static void *afs_proc_cell_servers_next(struct seq_file *p, void *v,
					loff_t *pos);
static void afs_proc_cell_servers_stop(struct seq_file *p, void *v);
static int afs_proc_cell_servers_show(struct seq_file *m, void *v);

static struct seq_operations afs_proc_cell_servers_ops = {
	.start	= afs_proc_cell_servers_start,
	.next	= afs_proc_cell_servers_next,
	.stop	= afs_proc_cell_servers_stop,
	.show	= afs_proc_cell_servers_show,
};

static const struct file_operations afs_proc_cell_servers_fops = {
	.open		= afs_proc_cell_servers_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= afs_proc_cell_servers_release,
};

/*****************************************************************************/
/*
 * initialise the /proc/fs/afs/ directory
 */
int afs_proc_init(void)
{
	struct proc_dir_entry *p;

	_enter("");

	proc_afs = proc_mkdir("fs/afs", NULL);
	if (!proc_afs)
		goto error;
	proc_afs->owner = THIS_MODULE;

	p = create_proc_entry("cells", 0, proc_afs);
	if (!p)
		goto error_proc;
	p->proc_fops = &afs_proc_cells_fops;
	p->owner = THIS_MODULE;

	p = create_proc_entry("rootcell", 0, proc_afs);
	if (!p)
		goto error_cells;
	p->proc_fops = &afs_proc_rootcell_fops;
	p->owner = THIS_MODULE;

	_leave(" = 0");
	return 0;

 error_cells:
 	remove_proc_entry("cells", proc_afs);
 error_proc:
	remove_proc_entry("fs/afs", NULL);
 error:
	_leave(" = -ENOMEM");
	return -ENOMEM;

} /* end afs_proc_init() */

/*****************************************************************************/
/*
 * clean up the /proc/fs/afs/ directory
 */
void afs_proc_cleanup(void)
{
	remove_proc_entry("cells", proc_afs);

	remove_proc_entry("fs/afs", NULL);

} /* end afs_proc_cleanup() */

/*****************************************************************************/
/*
 * open "/proc/fs/afs/cells" which provides a summary of extant cells
 */
static int afs_proc_cells_open(struct inode *inode, struct file *file)
{
	struct seq_file *m;
	int ret;

	ret = seq_open(file, &afs_proc_cells_ops);
	if (ret < 0)
		return ret;

	m = file->private_data;
	m->private = PDE(inode)->data;

	return 0;
} /* end afs_proc_cells_open() */

/*****************************************************************************/
/*
 * set up the iterator to start reading from the cells list and return the
 * first item
 */
static void *afs_proc_cells_start(struct seq_file *m, loff_t *_pos)
{
	struct list_head *_p;
	loff_t pos = *_pos;

	/* lock the list against modification */
	down_read(&afs_proc_cells_sem);

	/* allow for the header line */
	if (!pos)
		return (void *) 1;
	pos--;

	/* find the n'th element in the list */
	list_for_each(_p, &afs_proc_cells)
		if (!pos--)
			break;

	return _p != &afs_proc_cells ? _p : NULL;
} /* end afs_proc_cells_start() */

/*****************************************************************************/
/*
 * move to next cell in cells list
 */
static void *afs_proc_cells_next(struct seq_file *p, void *v, loff_t *pos)
{
	struct list_head *_p;

	(*pos)++;

	_p = v;
	_p = v == (void *) 1 ? afs_proc_cells.next : _p->next;

	return _p != &afs_proc_cells ? _p : NULL;
} /* end afs_proc_cells_next() */

/*****************************************************************************/
/*
 * clean up after reading from the cells list
 */
static void afs_proc_cells_stop(struct seq_file *p, void *v)
{
	up_read(&afs_proc_cells_sem);

} /* end afs_proc_cells_stop() */

/*****************************************************************************/
/*
 * display a header line followed by a load of cell lines
 */
static int afs_proc_cells_show(struct seq_file *m, void *v)
{
	struct afs_cell *cell = list_entry(v, struct afs_cell, proc_link);

	/* display header on line 1 */
	if (v == (void *) 1) {
		seq_puts(m, "USE NAME\n");
		return 0;
	}

	/* display one cell per line on subsequent lines */
	seq_printf(m, "%3d %s\n", atomic_read(&cell->usage), cell->name);

	return 0;
} /* end afs_proc_cells_show() */

/*****************************************************************************/
/*
 * handle writes to /proc/fs/afs/cells
 * - to add cells: echo "add <cellname> <IP>[:<IP>][:<IP>]"
 */
static ssize_t afs_proc_cells_write(struct file *file, const char __user *buf,
				    size_t size, loff_t *_pos)
{
	char *kbuf, *name, *args;
	int ret;

	/* start by dragging the command into memory */
	if (size <= 1 || size >= PAGE_SIZE)
		return -EINVAL;

	kbuf = kmalloc(size + 1, GFP_KERNEL);
	if (!kbuf)
		return -ENOMEM;

	ret = -EFAULT;
	if (copy_from_user(kbuf, buf, size) != 0)
		goto done;
	kbuf[size] = 0;

	/* trim to first NL */
	name = memchr(kbuf, '\n', size);
	if (name)
		*name = 0;

	/* split into command, name and argslist */
	name = strchr(kbuf, ' ');
	if (!name)
		goto inval;
	do {
		*name++ = 0;
	} while(*name == ' ');
	if (!*name)
		goto inval;

	args = strchr(name, ' ');
	if (!args)
		goto inval;
	do {
		*args++ = 0;
	} while(*args == ' ');
	if (!*args)
		goto inval;

	/* determine command to perform */
	_debug("cmd=%s name=%s args=%s", kbuf, name, args);

	if (strcmp(kbuf, "add") == 0) {
		struct afs_cell *cell;
		ret = afs_cell_create(name, args, &cell);
		if (ret < 0)
			goto done;

		printk("kAFS: Added new cell '%s'\n", name);
	}
	else {
		goto inval;
	}

	ret = size;

 done:
	kfree(kbuf);
	_leave(" = %d", ret);
	return ret;

 inval:
	ret = -EINVAL;
	printk("kAFS: Invalid Command on /proc/fs/afs/cells file\n");
	goto done;
} /* end afs_proc_cells_write() */

/*****************************************************************************/
/*
 * Stubs for /proc/fs/afs/rootcell
 */
static int afs_proc_rootcell_open(struct inode *inode, struct file *file)
{
	return 0;
}

static int afs_proc_rootcell_release(struct inode *inode, struct file *file)
{
	return 0;
}

static ssize_t afs_proc_rootcell_read(struct file *file, char __user *buf,
				      size_t size, loff_t *_pos)
{
	return 0;
}

/*****************************************************************************/
/*
 * handle writes to /proc/fs/afs/rootcell
 * - to initialize rootcell: echo "cell.name:192.168.231.14"
 */
static ssize_t afs_proc_rootcell_write(struct file *file,
				       const char __user *buf,
				       size_t size, loff_t *_pos)
{
	char *kbuf, *s;
	int ret;

	/* start by dragging the command into memory */
	if (size <= 1 || size >= PAGE_SIZE)
		return -EINVAL;

	ret = -ENOMEM;
	kbuf = kmalloc(size + 1, GFP_KERNEL);
	if (!kbuf)
		goto nomem;

	ret = -EFAULT;
	if (copy_from_user(kbuf, buf, size) != 0)
		goto infault;
	kbuf[size] = 0;

	/* trim to first NL */
	s = memchr(kbuf, '\n', size);
	if (s)
		*s = 0;

	/* determine command to perform */
	_debug("rootcell=%s", kbuf);

	ret = afs_cell_init(kbuf);
	if (ret >= 0)
		ret = size;	/* consume everything, always */

 infault:
	kfree(kbuf);
 nomem:
	_leave(" = %d", ret);
	return ret;
} /* end afs_proc_rootcell_write() */

/*****************************************************************************/
/*
 * initialise /proc/fs/afs/<cell>/
 */
int afs_proc_cell_setup(struct afs_cell *cell)
{
	struct proc_dir_entry *p;

	_enter("%p{%s}", cell, cell->name);

	cell->proc_dir = proc_mkdir(cell->name, proc_afs);
	if (!cell->proc_dir)
		return -ENOMEM;

	p = create_proc_entry("servers", 0, cell->proc_dir);
	if (!p)
		goto error_proc;
	p->proc_fops = &afs_proc_cell_servers_fops;
	p->owner = THIS_MODULE;
	p->data = cell;

	p = create_proc_entry("vlservers", 0, cell->proc_dir);
	if (!p)
		goto error_servers;
	p->proc_fops = &afs_proc_cell_vlservers_fops;
	p->owner = THIS_MODULE;
	p->data = cell;

	p = create_proc_entry("volumes", 0, cell->proc_dir);
	if (!p)
		goto error_vlservers;
	p->proc_fops = &afs_proc_cell_volumes_fops;
	p->owner = THIS_MODULE;
	p->data = cell;

	_leave(" = 0");
	return 0;

 error_vlservers:
	remove_proc_entry("vlservers", cell->proc_dir);
 error_servers:
	remove_proc_entry("servers", cell->proc_dir);
 error_proc:
	remove_proc_entry(cell->name, proc_afs);
	_leave(" = -ENOMEM");
	return -ENOMEM;
} /* end afs_proc_cell_setup() */

/*****************************************************************************/
/*
 * remove /proc/fs/afs/<cell>/
 */
void afs_proc_cell_remove(struct afs_cell *cell)
{
	_enter("");

	remove_proc_entry("volumes", cell->proc_dir);
	remove_proc_entry("vlservers", cell->proc_dir);
	remove_proc_entry("servers", cell->proc_dir);
	remove_proc_entry(cell->name, proc_afs);

	_leave("");
} /* end afs_proc_cell_remove() */

/*****************************************************************************/
/*
 * open "/proc/fs/afs/<cell>/volumes" which provides a summary of extant cells
 */
static int afs_proc_cell_volumes_open(struct inode *inode, struct file *file)
{
	struct afs_cell *cell;
	struct seq_file *m;
	int ret;

	cell = afs_get_cell_maybe((struct afs_cell **) &PDE(inode)->data);
	if (!cell)
		return -ENOENT;

	ret = seq_open(file, &afs_proc_cell_volumes_ops);
	if (ret < 0)
		return ret;

	m = file->private_data;
	m->private = cell;

	return 0;
} /* end afs_proc_cell_volumes_open() */

/*****************************************************************************/
/*
 * close the file and release the ref to the cell
 */
static int afs_proc_cell_volumes_release(struct inode *inode, struct file *file)
{
	struct afs_cell *cell = PDE(inode)->data;
	int ret;

	ret = seq_release(inode,file);

	afs_put_cell(cell);

	return ret;
} /* end afs_proc_cell_volumes_release() */

/*****************************************************************************/
/*
 * set up the iterator to start reading from the cells list and return the
 * first item
 */
static void *afs_proc_cell_volumes_start(struct seq_file *m, loff_t *_pos)
{
	struct list_head *_p;
	struct afs_cell *cell = m->private;
	loff_t pos = *_pos;

	_enter("cell=%p pos=%Ld", cell, *_pos);

	/* lock the list against modification */
	down_read(&cell->vl_sem);

	/* allow for the header line */
	if (!pos)
		return (void *) 1;
	pos--;

	/* find the n'th element in the list */
	list_for_each(_p, &cell->vl_list)
		if (!pos--)
			break;

	return _p != &cell->vl_list ? _p : NULL;
} /* end afs_proc_cell_volumes_start() */

/*****************************************************************************/
/*
 * move to next cell in cells list
 */
static void *afs_proc_cell_volumes_next(struct seq_file *p, void *v,
					loff_t *_pos)
{
	struct list_head *_p;
	struct afs_cell *cell = p->private;

	_enter("cell=%p pos=%Ld", cell, *_pos);

	(*_pos)++;

	_p = v;
	_p = v == (void *) 1 ? cell->vl_list.next : _p->next;

	return _p != &cell->vl_list ? _p : NULL;
} /* end afs_proc_cell_volumes_next() */

/*****************************************************************************/
/*
 * clean up after reading from the cells list
 */
static void afs_proc_cell_volumes_stop(struct seq_file *p, void *v)
{
	struct afs_cell *cell = p->private;

	up_read(&cell->vl_sem);

} /* end afs_proc_cell_volumes_stop() */

/*****************************************************************************/
/*
 * display a header line followed by a load of volume lines
 */
static int afs_proc_cell_volumes_show(struct seq_file *m, void *v)
{
	struct afs_vlocation *vlocation =
		list_entry(v, struct afs_vlocation, link);

	/* display header on line 1 */
	if (v == (void *) 1) {
		seq_puts(m, "USE VLID[0]  VLID[1]  VLID[2]  NAME\n");
		return 0;
	}

	/* display one cell per line on subsequent lines */
	seq_printf(m, "%3d %08x %08x %08x %s\n",
		   atomic_read(&vlocation->usage),
		   vlocation->vldb.vid[0],
		   vlocation->vldb.vid[1],
		   vlocation->vldb.vid[2],
		   vlocation->vldb.name
		   );

	return 0;
} /* end afs_proc_cell_volumes_show() */

/*****************************************************************************/
/*
 * open "/proc/fs/afs/<cell>/vlservers" which provides a list of volume
 * location server
 */
static int afs_proc_cell_vlservers_open(struct inode *inode, struct file *file)
{
	struct afs_cell *cell;
	struct seq_file *m;
	int ret;

	cell = afs_get_cell_maybe((struct afs_cell**)&PDE(inode)->data);
	if (!cell)
		return -ENOENT;

	ret = seq_open(file,&afs_proc_cell_vlservers_ops);
	if (ret<0)
		return ret;

	m = file->private_data;
	m->private = cell;

	return 0;
} /* end afs_proc_cell_vlservers_open() */

/*****************************************************************************/
/*
 * close the file and release the ref to the cell
 */
static int afs_proc_cell_vlservers_release(struct inode *inode,
					   struct file *file)
{
	struct afs_cell *cell = PDE(inode)->data;
	int ret;

	ret = seq_release(inode,file);

	afs_put_cell(cell);

	return ret;
} /* end afs_proc_cell_vlservers_release() */

/*****************************************************************************/
/*
 * set up the iterator to start reading from the cells list and return the
 * first item
 */
static void *afs_proc_cell_vlservers_start(struct seq_file *m, loff_t *_pos)
{
	struct afs_cell *cell = m->private;
	loff_t pos = *_pos;

	_enter("cell=%p pos=%Ld", cell, *_pos);

	/* lock the list against modification */
	down_read(&cell->vl_sem);

	/* allow for the header line */
	if (!pos)
		return (void *) 1;
	pos--;

	if (pos >= cell->vl_naddrs)
		return NULL;

	return &cell->vl_addrs[pos];
} /* end afs_proc_cell_vlservers_start() */

/*****************************************************************************/
/*
 * move to next cell in cells list
 */
static void *afs_proc_cell_vlservers_next(struct seq_file *p, void *v,
					  loff_t *_pos)
{
	struct afs_cell *cell = p->private;
	loff_t pos;

	_enter("cell=%p{nad=%u} pos=%Ld", cell, cell->vl_naddrs, *_pos);

	pos = *_pos;
	(*_pos)++;
	if (pos >= cell->vl_naddrs)
		return NULL;

	return &cell->vl_addrs[pos];
} /* end afs_proc_cell_vlservers_next() */

/*****************************************************************************/
/*
 * clean up after reading from the cells list
 */
static void afs_proc_cell_vlservers_stop(struct seq_file *p, void *v)
{
	struct afs_cell *cell = p->private;

	up_read(&cell->vl_sem);

} /* end afs_proc_cell_vlservers_stop() */

/*****************************************************************************/
/*
 * display a header line followed by a load of volume lines
 */
static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v)
{
	struct in_addr *addr = v;

	/* display header on line 1 */
	if (v == (struct in_addr *) 1) {
		seq_puts(m, "ADDRESS\n");
		return 0;
	}

	/* display one cell per line on subsequent lines */
	seq_printf(m, "%u.%u.%u.%u\n", NIPQUAD(addr->s_addr));

	return 0;
} /* end afs_proc_cell_vlservers_show() */

/*****************************************************************************/
/*
 * open "/proc/fs/afs/<cell>/servers" which provides a summary of active
 * servers
 */
static int afs_proc_cell_servers_open(struct inode *inode, struct file *file)
{
	struct afs_cell *cell;
	struct seq_file *m;
	int ret;

	cell = afs_get_cell_maybe((struct afs_cell **) &PDE(inode)->data);
	if (!cell)
		return -ENOENT;

	ret = seq_open(file, &afs_proc_cell_servers_ops);
	if (ret < 0)
		return ret;

	m = file->private_data;
	m->private = cell;

	return 0;
} /* end afs_proc_cell_servers_open() */

/*****************************************************************************/
/*
 * close the file and release the ref to the cell
 */
static int afs_proc_cell_servers_release(struct inode *inode,
					 struct file *file)
{
	struct afs_cell *cell = PDE(inode)->data;
	int ret;

	ret = seq_release(inode, file);

	afs_put_cell(cell);

	return ret;
} /* end afs_proc_cell_servers_release() */

/*****************************************************************************/
/*
 * set up the iterator to start reading from the cells list and return the
 * first item
 */
static void *afs_proc_cell_servers_start(struct seq_file *m, loff_t *_pos)
{
	struct list_head *_p;
	struct afs_cell *cell = m->private;
	loff_t pos = *_pos;

	_enter("cell=%p pos=%Ld", cell, *_pos);

	/* lock the list against modification */
	read_lock(&cell->sv_lock);

	/* allow for the header line */
	if (!pos)
		return (void *) 1;
	pos--;

	/* find the n'th element in the list */
	list_for_each(_p, &cell->sv_list)
		if (!pos--)
			break;

	return _p != &cell->sv_list ? _p : NULL;
} /* end afs_proc_cell_servers_start() */

/*****************************************************************************/
/*
 * move to next cell in cells list
 */
static void *afs_proc_cell_servers_next(struct seq_file *p, void *v,
					loff_t *_pos)
{
	struct list_head *_p;
	struct afs_cell *cell = p->private;

	_enter("cell=%p pos=%Ld", cell, *_pos);

	(*_pos)++;

	_p = v;
	_p = v == (void *) 1 ? cell->sv_list.next : _p->next;

	return _p != &cell->sv_list ? _p : NULL;
} /* end afs_proc_cell_servers_next() */

/*****************************************************************************/
/*
 * clean up after reading from the cells list
 */
static void afs_proc_cell_servers_stop(struct seq_file *p, void *v)
{
	struct afs_cell *cell = p->private;

	read_unlock(&cell->sv_lock);

} /* end afs_proc_cell_servers_stop() */

/*****************************************************************************/
/*
 * display a header line followed by a load of volume lines
 */
static int afs_proc_cell_servers_show(struct seq_file *m, void *v)
{
	struct afs_server *server = list_entry(v, struct afs_server, link);
	char ipaddr[20];

	/* display header on line 1 */
	if (v == (void *) 1) {
		seq_puts(m, "USE ADDR            STATE\n");
		return 0;
	}

	/* display one cell per line on subsequent lines */
	sprintf(ipaddr, "%u.%u.%u.%u", NIPQUAD(server->addr));
	seq_printf(m, "%3d %-15.15s %5d\n",
		   atomic_read(&server->usage),
		   ipaddr,
		   server->fs_state
		   );

	return 0;
} /* end afs_proc_cell_servers_show() */