xref: /openbmc/linux/fs/afs/proc.c (revision 64c70b1c)
1 /* /proc interface for AFS
2  *
3  * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/slab.h>
13 #include <linux/module.h>
14 #include <linux/proc_fs.h>
15 #include <linux/seq_file.h>
16 #include <linux/sched.h>
17 #include <asm/uaccess.h>
18 #include "internal.h"
19 
20 static struct proc_dir_entry *proc_afs;
21 
22 
23 static int afs_proc_cells_open(struct inode *inode, struct file *file);
24 static void *afs_proc_cells_start(struct seq_file *p, loff_t *pos);
25 static void *afs_proc_cells_next(struct seq_file *p, void *v, loff_t *pos);
26 static void afs_proc_cells_stop(struct seq_file *p, void *v);
27 static int afs_proc_cells_show(struct seq_file *m, void *v);
28 static ssize_t afs_proc_cells_write(struct file *file, const char __user *buf,
29 				    size_t size, loff_t *_pos);
30 
31 static struct seq_operations afs_proc_cells_ops = {
32 	.start	= afs_proc_cells_start,
33 	.next	= afs_proc_cells_next,
34 	.stop	= afs_proc_cells_stop,
35 	.show	= afs_proc_cells_show,
36 };
37 
38 static const struct file_operations afs_proc_cells_fops = {
39 	.open		= afs_proc_cells_open,
40 	.read		= seq_read,
41 	.write		= afs_proc_cells_write,
42 	.llseek		= seq_lseek,
43 	.release	= seq_release,
44 };
45 
46 static int afs_proc_rootcell_open(struct inode *inode, struct file *file);
47 static int afs_proc_rootcell_release(struct inode *inode, struct file *file);
48 static ssize_t afs_proc_rootcell_read(struct file *file, char __user *buf,
49 				      size_t size, loff_t *_pos);
50 static ssize_t afs_proc_rootcell_write(struct file *file,
51 				       const char __user *buf,
52 				       size_t size, loff_t *_pos);
53 
54 static const struct file_operations afs_proc_rootcell_fops = {
55 	.open		= afs_proc_rootcell_open,
56 	.read		= afs_proc_rootcell_read,
57 	.write		= afs_proc_rootcell_write,
58 	.llseek		= no_llseek,
59 	.release	= afs_proc_rootcell_release
60 };
61 
62 static int afs_proc_cell_volumes_open(struct inode *inode, struct file *file);
63 static int afs_proc_cell_volumes_release(struct inode *inode,
64 					 struct file *file);
65 static void *afs_proc_cell_volumes_start(struct seq_file *p, loff_t *pos);
66 static void *afs_proc_cell_volumes_next(struct seq_file *p, void *v,
67 					loff_t *pos);
68 static void afs_proc_cell_volumes_stop(struct seq_file *p, void *v);
69 static int afs_proc_cell_volumes_show(struct seq_file *m, void *v);
70 
71 static struct seq_operations afs_proc_cell_volumes_ops = {
72 	.start	= afs_proc_cell_volumes_start,
73 	.next	= afs_proc_cell_volumes_next,
74 	.stop	= afs_proc_cell_volumes_stop,
75 	.show	= afs_proc_cell_volumes_show,
76 };
77 
78 static const struct file_operations afs_proc_cell_volumes_fops = {
79 	.open		= afs_proc_cell_volumes_open,
80 	.read		= seq_read,
81 	.llseek		= seq_lseek,
82 	.release	= afs_proc_cell_volumes_release,
83 };
84 
85 static int afs_proc_cell_vlservers_open(struct inode *inode,
86 					struct file *file);
87 static int afs_proc_cell_vlservers_release(struct inode *inode,
88 					   struct file *file);
89 static void *afs_proc_cell_vlservers_start(struct seq_file *p, loff_t *pos);
90 static void *afs_proc_cell_vlservers_next(struct seq_file *p, void *v,
91 					  loff_t *pos);
92 static void afs_proc_cell_vlservers_stop(struct seq_file *p, void *v);
93 static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v);
94 
95 static struct seq_operations afs_proc_cell_vlservers_ops = {
96 	.start	= afs_proc_cell_vlservers_start,
97 	.next	= afs_proc_cell_vlservers_next,
98 	.stop	= afs_proc_cell_vlservers_stop,
99 	.show	= afs_proc_cell_vlservers_show,
100 };
101 
102 static const struct file_operations afs_proc_cell_vlservers_fops = {
103 	.open		= afs_proc_cell_vlservers_open,
104 	.read		= seq_read,
105 	.llseek		= seq_lseek,
106 	.release	= afs_proc_cell_vlservers_release,
107 };
108 
109 static int afs_proc_cell_servers_open(struct inode *inode, struct file *file);
110 static int afs_proc_cell_servers_release(struct inode *inode,
111 					 struct file *file);
112 static void *afs_proc_cell_servers_start(struct seq_file *p, loff_t *pos);
113 static void *afs_proc_cell_servers_next(struct seq_file *p, void *v,
114 					loff_t *pos);
115 static void afs_proc_cell_servers_stop(struct seq_file *p, void *v);
116 static int afs_proc_cell_servers_show(struct seq_file *m, void *v);
117 
118 static struct seq_operations afs_proc_cell_servers_ops = {
119 	.start	= afs_proc_cell_servers_start,
120 	.next	= afs_proc_cell_servers_next,
121 	.stop	= afs_proc_cell_servers_stop,
122 	.show	= afs_proc_cell_servers_show,
123 };
124 
125 static const struct file_operations afs_proc_cell_servers_fops = {
126 	.open		= afs_proc_cell_servers_open,
127 	.read		= seq_read,
128 	.llseek		= seq_lseek,
129 	.release	= afs_proc_cell_servers_release,
130 };
131 
132 /*
133  * initialise the /proc/fs/afs/ directory
134  */
135 int afs_proc_init(void)
136 {
137 	struct proc_dir_entry *p;
138 
139 	_enter("");
140 
141 	proc_afs = proc_mkdir("fs/afs", NULL);
142 	if (!proc_afs)
143 		goto error_dir;
144 	proc_afs->owner = THIS_MODULE;
145 
146 	p = create_proc_entry("cells", 0, proc_afs);
147 	if (!p)
148 		goto error_cells;
149 	p->proc_fops = &afs_proc_cells_fops;
150 	p->owner = THIS_MODULE;
151 
152 	p = create_proc_entry("rootcell", 0, proc_afs);
153 	if (!p)
154 		goto error_rootcell;
155 	p->proc_fops = &afs_proc_rootcell_fops;
156 	p->owner = THIS_MODULE;
157 
158 	_leave(" = 0");
159 	return 0;
160 
161 error_rootcell:
162  	remove_proc_entry("cells", proc_afs);
163 error_cells:
164 	remove_proc_entry("fs/afs", NULL);
165 error_dir:
166 	_leave(" = -ENOMEM");
167 	return -ENOMEM;
168 }
169 
170 /*
171  * clean up the /proc/fs/afs/ directory
172  */
173 void afs_proc_cleanup(void)
174 {
175 	remove_proc_entry("rootcell", proc_afs);
176 	remove_proc_entry("cells", proc_afs);
177 	remove_proc_entry("fs/afs", NULL);
178 }
179 
180 /*
181  * open "/proc/fs/afs/cells" which provides a summary of extant cells
182  */
183 static int afs_proc_cells_open(struct inode *inode, struct file *file)
184 {
185 	struct seq_file *m;
186 	int ret;
187 
188 	ret = seq_open(file, &afs_proc_cells_ops);
189 	if (ret < 0)
190 		return ret;
191 
192 	m = file->private_data;
193 	m->private = PDE(inode)->data;
194 
195 	return 0;
196 }
197 
198 /*
199  * set up the iterator to start reading from the cells list and return the
200  * first item
201  */
202 static void *afs_proc_cells_start(struct seq_file *m, loff_t *_pos)
203 {
204 	struct list_head *_p;
205 	loff_t pos = *_pos;
206 
207 	/* lock the list against modification */
208 	down_read(&afs_proc_cells_sem);
209 
210 	/* allow for the header line */
211 	if (!pos)
212 		return (void *) 1;
213 	pos--;
214 
215 	/* find the n'th element in the list */
216 	list_for_each(_p, &afs_proc_cells)
217 		if (!pos--)
218 			break;
219 
220 	return _p != &afs_proc_cells ? _p : NULL;
221 }
222 
223 /*
224  * move to next cell in cells list
225  */
226 static void *afs_proc_cells_next(struct seq_file *p, void *v, loff_t *pos)
227 {
228 	struct list_head *_p;
229 
230 	(*pos)++;
231 
232 	_p = v;
233 	_p = v == (void *) 1 ? afs_proc_cells.next : _p->next;
234 
235 	return _p != &afs_proc_cells ? _p : NULL;
236 }
237 
238 /*
239  * clean up after reading from the cells list
240  */
241 static void afs_proc_cells_stop(struct seq_file *p, void *v)
242 {
243 	up_read(&afs_proc_cells_sem);
244 }
245 
246 /*
247  * display a header line followed by a load of cell lines
248  */
249 static int afs_proc_cells_show(struct seq_file *m, void *v)
250 {
251 	struct afs_cell *cell = list_entry(v, struct afs_cell, proc_link);
252 
253 	if (v == (void *) 1) {
254 		/* display header on line 1 */
255 		seq_puts(m, "USE NAME\n");
256 		return 0;
257 	}
258 
259 	/* display one cell per line on subsequent lines */
260 	seq_printf(m, "%3d %s\n",
261 		   atomic_read(&cell->usage), cell->name);
262 	return 0;
263 }
264 
265 /*
266  * handle writes to /proc/fs/afs/cells
267  * - to add cells: echo "add <cellname> <IP>[:<IP>][:<IP>]"
268  */
269 static ssize_t afs_proc_cells_write(struct file *file, const char __user *buf,
270 				    size_t size, loff_t *_pos)
271 {
272 	char *kbuf, *name, *args;
273 	int ret;
274 
275 	/* start by dragging the command into memory */
276 	if (size <= 1 || size >= PAGE_SIZE)
277 		return -EINVAL;
278 
279 	kbuf = kmalloc(size + 1, GFP_KERNEL);
280 	if (!kbuf)
281 		return -ENOMEM;
282 
283 	ret = -EFAULT;
284 	if (copy_from_user(kbuf, buf, size) != 0)
285 		goto done;
286 	kbuf[size] = 0;
287 
288 	/* trim to first NL */
289 	name = memchr(kbuf, '\n', size);
290 	if (name)
291 		*name = 0;
292 
293 	/* split into command, name and argslist */
294 	name = strchr(kbuf, ' ');
295 	if (!name)
296 		goto inval;
297 	do {
298 		*name++ = 0;
299 	} while(*name == ' ');
300 	if (!*name)
301 		goto inval;
302 
303 	args = strchr(name, ' ');
304 	if (!args)
305 		goto inval;
306 	do {
307 		*args++ = 0;
308 	} while(*args == ' ');
309 	if (!*args)
310 		goto inval;
311 
312 	/* determine command to perform */
313 	_debug("cmd=%s name=%s args=%s", kbuf, name, args);
314 
315 	if (strcmp(kbuf, "add") == 0) {
316 		struct afs_cell *cell;
317 
318 		cell = afs_cell_create(name, args);
319 		if (IS_ERR(cell)) {
320 			ret = PTR_ERR(cell);
321 			goto done;
322 		}
323 
324 		afs_put_cell(cell);
325 		printk("kAFS: Added new cell '%s'\n", name);
326 	} else {
327 		goto inval;
328 	}
329 
330 	ret = size;
331 
332 done:
333 	kfree(kbuf);
334 	_leave(" = %d", ret);
335 	return ret;
336 
337 inval:
338 	ret = -EINVAL;
339 	printk("kAFS: Invalid Command on /proc/fs/afs/cells file\n");
340 	goto done;
341 }
342 
343 /*
344  * Stubs for /proc/fs/afs/rootcell
345  */
346 static int afs_proc_rootcell_open(struct inode *inode, struct file *file)
347 {
348 	return 0;
349 }
350 
351 static int afs_proc_rootcell_release(struct inode *inode, struct file *file)
352 {
353 	return 0;
354 }
355 
356 static ssize_t afs_proc_rootcell_read(struct file *file, char __user *buf,
357 				      size_t size, loff_t *_pos)
358 {
359 	return 0;
360 }
361 
362 /*
363  * handle writes to /proc/fs/afs/rootcell
364  * - to initialize rootcell: echo "cell.name:192.168.231.14"
365  */
366 static ssize_t afs_proc_rootcell_write(struct file *file,
367 				       const char __user *buf,
368 				       size_t size, loff_t *_pos)
369 {
370 	char *kbuf, *s;
371 	int ret;
372 
373 	/* start by dragging the command into memory */
374 	if (size <= 1 || size >= PAGE_SIZE)
375 		return -EINVAL;
376 
377 	ret = -ENOMEM;
378 	kbuf = kmalloc(size + 1, GFP_KERNEL);
379 	if (!kbuf)
380 		goto nomem;
381 
382 	ret = -EFAULT;
383 	if (copy_from_user(kbuf, buf, size) != 0)
384 		goto infault;
385 	kbuf[size] = 0;
386 
387 	/* trim to first NL */
388 	s = memchr(kbuf, '\n', size);
389 	if (s)
390 		*s = 0;
391 
392 	/* determine command to perform */
393 	_debug("rootcell=%s", kbuf);
394 
395 	ret = afs_cell_init(kbuf);
396 	if (ret >= 0)
397 		ret = size;	/* consume everything, always */
398 
399 infault:
400 	kfree(kbuf);
401 nomem:
402 	_leave(" = %d", ret);
403 	return ret;
404 }
405 
406 /*
407  * initialise /proc/fs/afs/<cell>/
408  */
409 int afs_proc_cell_setup(struct afs_cell *cell)
410 {
411 	struct proc_dir_entry *p;
412 
413 	_enter("%p{%s}", cell, cell->name);
414 
415 	cell->proc_dir = proc_mkdir(cell->name, proc_afs);
416 	if (!cell->proc_dir)
417 		goto error_dir;
418 
419 	p = create_proc_entry("servers", 0, cell->proc_dir);
420 	if (!p)
421 		goto error_servers;
422 	p->proc_fops = &afs_proc_cell_servers_fops;
423 	p->owner = THIS_MODULE;
424 	p->data = cell;
425 
426 	p = create_proc_entry("vlservers", 0, cell->proc_dir);
427 	if (!p)
428 		goto error_vlservers;
429 	p->proc_fops = &afs_proc_cell_vlservers_fops;
430 	p->owner = THIS_MODULE;
431 	p->data = cell;
432 
433 	p = create_proc_entry("volumes", 0, cell->proc_dir);
434 	if (!p)
435 		goto error_volumes;
436 	p->proc_fops = &afs_proc_cell_volumes_fops;
437 	p->owner = THIS_MODULE;
438 	p->data = cell;
439 
440 	_leave(" = 0");
441 	return 0;
442 
443 error_volumes:
444 	remove_proc_entry("vlservers", cell->proc_dir);
445 error_vlservers:
446 	remove_proc_entry("servers", cell->proc_dir);
447 error_servers:
448 	remove_proc_entry(cell->name, proc_afs);
449 error_dir:
450 	_leave(" = -ENOMEM");
451 	return -ENOMEM;
452 }
453 
454 /*
455  * remove /proc/fs/afs/<cell>/
456  */
457 void afs_proc_cell_remove(struct afs_cell *cell)
458 {
459 	_enter("");
460 
461 	remove_proc_entry("volumes", cell->proc_dir);
462 	remove_proc_entry("vlservers", cell->proc_dir);
463 	remove_proc_entry("servers", cell->proc_dir);
464 	remove_proc_entry(cell->name, proc_afs);
465 
466 	_leave("");
467 }
468 
469 /*
470  * open "/proc/fs/afs/<cell>/volumes" which provides a summary of extant cells
471  */
472 static int afs_proc_cell_volumes_open(struct inode *inode, struct file *file)
473 {
474 	struct afs_cell *cell;
475 	struct seq_file *m;
476 	int ret;
477 
478 	cell = PDE(inode)->data;
479 	if (!cell)
480 		return -ENOENT;
481 
482 	ret = seq_open(file, &afs_proc_cell_volumes_ops);
483 	if (ret < 0)
484 		return ret;
485 
486 	m = file->private_data;
487 	m->private = cell;
488 
489 	return 0;
490 }
491 
492 /*
493  * close the file and release the ref to the cell
494  */
495 static int afs_proc_cell_volumes_release(struct inode *inode, struct file *file)
496 {
497 	return seq_release(inode, file);
498 }
499 
500 /*
501  * set up the iterator to start reading from the cells list and return the
502  * first item
503  */
504 static void *afs_proc_cell_volumes_start(struct seq_file *m, loff_t *_pos)
505 {
506 	struct list_head *_p;
507 	struct afs_cell *cell = m->private;
508 	loff_t pos = *_pos;
509 
510 	_enter("cell=%p pos=%Ld", cell, *_pos);
511 
512 	/* lock the list against modification */
513 	down_read(&cell->vl_sem);
514 
515 	/* allow for the header line */
516 	if (!pos)
517 		return (void *) 1;
518 	pos--;
519 
520 	/* find the n'th element in the list */
521 	list_for_each(_p, &cell->vl_list)
522 		if (!pos--)
523 			break;
524 
525 	return _p != &cell->vl_list ? _p : NULL;
526 }
527 
528 /*
529  * move to next cell in cells list
530  */
531 static void *afs_proc_cell_volumes_next(struct seq_file *p, void *v,
532 					loff_t *_pos)
533 {
534 	struct list_head *_p;
535 	struct afs_cell *cell = p->private;
536 
537 	_enter("cell=%p pos=%Ld", cell, *_pos);
538 
539 	(*_pos)++;
540 
541 	_p = v;
542 	_p = (v == (void *) 1) ? cell->vl_list.next : _p->next;
543 
544 	return (_p != &cell->vl_list) ? _p : NULL;
545 }
546 
547 /*
548  * clean up after reading from the cells list
549  */
550 static void afs_proc_cell_volumes_stop(struct seq_file *p, void *v)
551 {
552 	struct afs_cell *cell = p->private;
553 
554 	up_read(&cell->vl_sem);
555 }
556 
557 const char afs_vlocation_states[][4] = {
558 	[AFS_VL_NEW]			= "New",
559 	[AFS_VL_CREATING]		= "Crt",
560 	[AFS_VL_VALID]			= "Val",
561 	[AFS_VL_NO_VOLUME]		= "NoV",
562 	[AFS_VL_UPDATING]		= "Upd",
563 	[AFS_VL_VOLUME_DELETED]		= "Del",
564 	[AFS_VL_UNCERTAIN]		= "Unc",
565 };
566 
567 /*
568  * display a header line followed by a load of volume lines
569  */
570 static int afs_proc_cell_volumes_show(struct seq_file *m, void *v)
571 {
572 	struct afs_vlocation *vlocation =
573 		list_entry(v, struct afs_vlocation, link);
574 
575 	/* display header on line 1 */
576 	if (v == (void *) 1) {
577 		seq_puts(m, "USE STT VLID[0]  VLID[1]  VLID[2]  NAME\n");
578 		return 0;
579 	}
580 
581 	/* display one cell per line on subsequent lines */
582 	seq_printf(m, "%3d %s %08x %08x %08x %s\n",
583 		   atomic_read(&vlocation->usage),
584 		   afs_vlocation_states[vlocation->state],
585 		   vlocation->vldb.vid[0],
586 		   vlocation->vldb.vid[1],
587 		   vlocation->vldb.vid[2],
588 		   vlocation->vldb.name);
589 
590 	return 0;
591 }
592 
593 /*
594  * open "/proc/fs/afs/<cell>/vlservers" which provides a list of volume
595  * location server
596  */
597 static int afs_proc_cell_vlservers_open(struct inode *inode, struct file *file)
598 {
599 	struct afs_cell *cell;
600 	struct seq_file *m;
601 	int ret;
602 
603 	cell = PDE(inode)->data;
604 	if (!cell)
605 		return -ENOENT;
606 
607 	ret = seq_open(file, &afs_proc_cell_vlservers_ops);
608 	if (ret<0)
609 		return ret;
610 
611 	m = file->private_data;
612 	m->private = cell;
613 
614 	return 0;
615 }
616 
617 /*
618  * close the file and release the ref to the cell
619  */
620 static int afs_proc_cell_vlservers_release(struct inode *inode,
621 					   struct file *file)
622 {
623 	return seq_release(inode, file);
624 }
625 
626 /*
627  * set up the iterator to start reading from the cells list and return the
628  * first item
629  */
630 static void *afs_proc_cell_vlservers_start(struct seq_file *m, loff_t *_pos)
631 {
632 	struct afs_cell *cell = m->private;
633 	loff_t pos = *_pos;
634 
635 	_enter("cell=%p pos=%Ld", cell, *_pos);
636 
637 	/* lock the list against modification */
638 	down_read(&cell->vl_sem);
639 
640 	/* allow for the header line */
641 	if (!pos)
642 		return (void *) 1;
643 	pos--;
644 
645 	if (pos >= cell->vl_naddrs)
646 		return NULL;
647 
648 	return &cell->vl_addrs[pos];
649 }
650 
651 /*
652  * move to next cell in cells list
653  */
654 static void *afs_proc_cell_vlservers_next(struct seq_file *p, void *v,
655 					  loff_t *_pos)
656 {
657 	struct afs_cell *cell = p->private;
658 	loff_t pos;
659 
660 	_enter("cell=%p{nad=%u} pos=%Ld", cell, cell->vl_naddrs, *_pos);
661 
662 	pos = *_pos;
663 	(*_pos)++;
664 	if (pos >= cell->vl_naddrs)
665 		return NULL;
666 
667 	return &cell->vl_addrs[pos];
668 }
669 
670 /*
671  * clean up after reading from the cells list
672  */
673 static void afs_proc_cell_vlservers_stop(struct seq_file *p, void *v)
674 {
675 	struct afs_cell *cell = p->private;
676 
677 	up_read(&cell->vl_sem);
678 }
679 
680 /*
681  * display a header line followed by a load of volume lines
682  */
683 static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v)
684 {
685 	struct in_addr *addr = v;
686 
687 	/* display header on line 1 */
688 	if (v == (struct in_addr *) 1) {
689 		seq_puts(m, "ADDRESS\n");
690 		return 0;
691 	}
692 
693 	/* display one cell per line on subsequent lines */
694 	seq_printf(m, "%u.%u.%u.%u\n", NIPQUAD(addr->s_addr));
695 	return 0;
696 }
697 
698 /*
699  * open "/proc/fs/afs/<cell>/servers" which provides a summary of active
700  * servers
701  */
702 static int afs_proc_cell_servers_open(struct inode *inode, struct file *file)
703 {
704 	struct afs_cell *cell;
705 	struct seq_file *m;
706 	int ret;
707 
708 	cell = PDE(inode)->data;
709 	if (!cell)
710 		return -ENOENT;
711 
712 	ret = seq_open(file, &afs_proc_cell_servers_ops);
713 	if (ret < 0)
714 		return ret;
715 
716 	m = file->private_data;
717 	m->private = cell;
718 	return 0;
719 }
720 
721 /*
722  * close the file and release the ref to the cell
723  */
724 static int afs_proc_cell_servers_release(struct inode *inode,
725 					 struct file *file)
726 {
727 	return seq_release(inode, file);
728 }
729 
730 /*
731  * set up the iterator to start reading from the cells list and return the
732  * first item
733  */
734 static void *afs_proc_cell_servers_start(struct seq_file *m, loff_t *_pos)
735 	__acquires(m->private->servers_lock)
736 {
737 	struct list_head *_p;
738 	struct afs_cell *cell = m->private;
739 	loff_t pos = *_pos;
740 
741 	_enter("cell=%p pos=%Ld", cell, *_pos);
742 
743 	/* lock the list against modification */
744 	read_lock(&cell->servers_lock);
745 
746 	/* allow for the header line */
747 	if (!pos)
748 		return (void *) 1;
749 	pos--;
750 
751 	/* find the n'th element in the list */
752 	list_for_each(_p, &cell->servers)
753 		if (!pos--)
754 			break;
755 
756 	return _p != &cell->servers ? _p : NULL;
757 }
758 
759 /*
760  * move to next cell in cells list
761  */
762 static void *afs_proc_cell_servers_next(struct seq_file *p, void *v,
763 					loff_t *_pos)
764 {
765 	struct list_head *_p;
766 	struct afs_cell *cell = p->private;
767 
768 	_enter("cell=%p pos=%Ld", cell, *_pos);
769 
770 	(*_pos)++;
771 
772 	_p = v;
773 	_p = v == (void *) 1 ? cell->servers.next : _p->next;
774 
775 	return _p != &cell->servers ? _p : NULL;
776 }
777 
778 /*
779  * clean up after reading from the cells list
780  */
781 static void afs_proc_cell_servers_stop(struct seq_file *p, void *v)
782 	__releases(p->private->servers_lock)
783 {
784 	struct afs_cell *cell = p->private;
785 
786 	read_unlock(&cell->servers_lock);
787 }
788 
789 /*
790  * display a header line followed by a load of volume lines
791  */
792 static int afs_proc_cell_servers_show(struct seq_file *m, void *v)
793 {
794 	struct afs_server *server = list_entry(v, struct afs_server, link);
795 	char ipaddr[20];
796 
797 	/* display header on line 1 */
798 	if (v == (void *) 1) {
799 		seq_puts(m, "USE ADDR            STATE\n");
800 		return 0;
801 	}
802 
803 	/* display one cell per line on subsequent lines */
804 	sprintf(ipaddr, "%u.%u.%u.%u", NIPQUAD(server->addr));
805 	seq_printf(m, "%3d %-15.15s %5d\n",
806 		   atomic_read(&server->usage), ipaddr, server->fs_state);
807 
808 	return 0;
809 }
810