xref: /linux/fs/afs/super.c (revision 37744feebc086908fd89760650f458ab19071750) 
1 /* AFS superblock handling
2  *
3  * Copyright (c) 2002, 2007, 2018 Red Hat, Inc. All rights reserved.
4  *
5  * This software may be freely redistributed under the terms of the
6  * GNU General Public License.
7  *
8  * You should have received a copy of the GNU General Public License
9  * along with this program; if not, write to the Free Software
10  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
11  *
12  * Authors: David Howells <dhowells@redhat.com>
13  *          David Woodhouse <dwmw2@infradead.org>
14  *
15  */
16 
17 #include <linux/kernel.h>
18 #include <linux/module.h>
19 #include <linux/mount.h>
20 #include <linux/init.h>
21 #include <linux/slab.h>
22 #include <linux/fs.h>
23 #include <linux/pagemap.h>
24 #include <linux/fs_parser.h>
25 #include <linux/statfs.h>
26 #include <linux/sched.h>
27 #include <linux/nsproxy.h>
28 #include <linux/magic.h>
29 #include <net/net_namespace.h>
30 #include "internal.h"
31 
32 static void afs_i_init_once(void *foo);
33 static void afs_kill_super(struct super_block *sb);
34 static struct inode *afs_alloc_inode(struct super_block *sb);
35 static void afs_destroy_inode(struct inode *inode);
36 static void afs_free_inode(struct inode *inode);
37 static int afs_statfs(struct dentry *dentry, struct kstatfs *buf);
38 static int afs_show_devname(struct seq_file *m, struct dentry *root);
39 static int afs_show_options(struct seq_file *m, struct dentry *root);
40 static int afs_init_fs_context(struct fs_context *fc);
41 static const struct fs_parameter_spec afs_fs_parameters[];
42 
43 struct file_system_type afs_fs_type = {
44 	.owner			= THIS_MODULE,
45 	.name			= "afs",
46 	.init_fs_context	= afs_init_fs_context,
47 	.parameters		= afs_fs_parameters,
48 	.kill_sb		= afs_kill_super,
49 	.fs_flags		= FS_RENAME_DOES_D_MOVE,
50 };
51 MODULE_ALIAS_FS("afs");
52 
53 int afs_net_id;
54 
55 static const struct super_operations afs_super_ops = {
56 	.statfs		= afs_statfs,
57 	.alloc_inode	= afs_alloc_inode,
58 	.drop_inode	= afs_drop_inode,
59 	.destroy_inode	= afs_destroy_inode,
60 	.free_inode	= afs_free_inode,
61 	.evict_inode	= afs_evict_inode,
62 	.show_devname	= afs_show_devname,
63 	.show_options	= afs_show_options,
64 };
65 
66 static struct kmem_cache *afs_inode_cachep;
67 static atomic_t afs_count_active_inodes;
68 
69 enum afs_param {
70 	Opt_autocell,
71 	Opt_dyn,
72 	Opt_flock,
73 	Opt_source,
74 };
75 
76 static const struct constant_table afs_param_flock[] = {
77 	{"local",	afs_flock_mode_local },
78 	{"openafs",	afs_flock_mode_openafs },
79 	{"strict",	afs_flock_mode_strict },
80 	{"write",	afs_flock_mode_write },
81 	{}
82 };
83 
84 static const struct fs_parameter_spec afs_fs_parameters[] = {
85 	fsparam_flag  ("autocell",	Opt_autocell),
86 	fsparam_flag  ("dyn",		Opt_dyn),
87 	fsparam_enum  ("flock",		Opt_flock, afs_param_flock),
88 	fsparam_string("source",	Opt_source),
89 	{}
90 };
91 
92 /*
93  * initialise the filesystem
94  */
95 int __init afs_fs_init(void)
96 {
97 	int ret;
98 
99 	_enter("");
100 
101 	/* create ourselves an inode cache */
102 	atomic_set(&afs_count_active_inodes, 0);
103 
104 	ret = -ENOMEM;
105 	afs_inode_cachep = kmem_cache_create("afs_inode_cache",
106 					     sizeof(struct afs_vnode),
107 					     0,
108 					     SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT,
109 					     afs_i_init_once);
110 	if (!afs_inode_cachep) {
111 		printk(KERN_NOTICE "kAFS: Failed to allocate inode cache\n");
112 		return ret;
113 	}
114 
115 	/* now export our filesystem to lesser mortals */
116 	ret = register_filesystem(&afs_fs_type);
117 	if (ret < 0) {
118 		kmem_cache_destroy(afs_inode_cachep);
119 		_leave(" = %d", ret);
120 		return ret;
121 	}
122 
123 	_leave(" = 0");
124 	return 0;
125 }
126 
127 /*
128  * clean up the filesystem
129  */
130 void afs_fs_exit(void)
131 {
132 	_enter("");
133 
134 	afs_mntpt_kill_timer();
135 	unregister_filesystem(&afs_fs_type);
136 
137 	if (atomic_read(&afs_count_active_inodes) != 0) {
138 		printk("kAFS: %d active inode objects still present\n",
139 		       atomic_read(&afs_count_active_inodes));
140 		BUG();
141 	}
142 
143 	/*
144 	 * Make sure all delayed rcu free inodes are flushed before we
145 	 * destroy cache.
146 	 */
147 	rcu_barrier();
148 	kmem_cache_destroy(afs_inode_cachep);
149 	_leave("");
150 }
151 
152 /*
153  * Display the mount device name in /proc/mounts.
154  */
155 static int afs_show_devname(struct seq_file *m, struct dentry *root)
156 {
157 	struct afs_super_info *as = AFS_FS_S(root->d_sb);
158 	struct afs_volume *volume = as->volume;
159 	struct afs_cell *cell = as->cell;
160 	const char *suf = "";
161 	char pref = '%';
162 
163 	if (as->dyn_root) {
164 		seq_puts(m, "none");
165 		return 0;
166 	}
167 
168 	switch (volume->type) {
169 	case AFSVL_RWVOL:
170 		break;
171 	case AFSVL_ROVOL:
172 		pref = '#';
173 		if (volume->type_force)
174 			suf = ".readonly";
175 		break;
176 	case AFSVL_BACKVOL:
177 		pref = '#';
178 		suf = ".backup";
179 		break;
180 	}
181 
182 	seq_printf(m, "%c%s:%s%s", pref, cell->name, volume->name, suf);
183 	return 0;
184 }
185 
186 /*
187  * Display the mount options in /proc/mounts.
188  */
189 static int afs_show_options(struct seq_file *m, struct dentry *root)
190 {
191 	struct afs_super_info *as = AFS_FS_S(root->d_sb);
192 	const char *p = NULL;
193 
194 	if (as->dyn_root)
195 		seq_puts(m, ",dyn");
196 	if (test_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(d_inode(root))->flags))
197 		seq_puts(m, ",autocell");
198 	switch (as->flock_mode) {
199 	case afs_flock_mode_unset:	break;
200 	case afs_flock_mode_local:	p = "local";	break;
201 	case afs_flock_mode_openafs:	p = "openafs";	break;
202 	case afs_flock_mode_strict:	p = "strict";	break;
203 	case afs_flock_mode_write:	p = "write";	break;
204 	}
205 	if (p)
206 		seq_printf(m, ",flock=%s", p);
207 
208 	return 0;
209 }
210 
211 /*
212  * Parse the source name to get cell name, volume name, volume type and R/W
213  * selector.
214  *
215  * This can be one of the following:
216  *	"%[cell:]volume[.]"		R/W volume
217  *	"#[cell:]volume[.]"		R/O or R/W volume (R/O parent),
218  *					 or R/W (R/W parent) volume
219  *	"%[cell:]volume.readonly"	R/O volume
220  *	"#[cell:]volume.readonly"	R/O volume
221  *	"%[cell:]volume.backup"		Backup volume
222  *	"#[cell:]volume.backup"		Backup volume
223  */
224 static int afs_parse_source(struct fs_context *fc, struct fs_parameter *param)
225 {
226 	struct afs_fs_context *ctx = fc->fs_private;
227 	struct afs_cell *cell;
228 	const char *cellname, *suffix, *name = param->string;
229 	int cellnamesz;
230 
231 	_enter(",%s", name);
232 
233 	if (!name) {
234 		printk(KERN_ERR "kAFS: no volume name specified\n");
235 		return -EINVAL;
236 	}
237 
238 	if ((name[0] != '%' && name[0] != '#') || !name[1]) {
239 		/* To use dynroot, we don't want to have to provide a source */
240 		if (strcmp(name, "none") == 0) {
241 			ctx->no_cell = true;
242 			return 0;
243 		}
244 		printk(KERN_ERR "kAFS: unparsable volume name\n");
245 		return -EINVAL;
246 	}
247 
248 	/* determine the type of volume we're looking for */
249 	if (name[0] == '%') {
250 		ctx->type = AFSVL_RWVOL;
251 		ctx->force = true;
252 	}
253 	name++;
254 
255 	/* split the cell name out if there is one */
256 	ctx->volname = strchr(name, ':');
257 	if (ctx->volname) {
258 		cellname = name;
259 		cellnamesz = ctx->volname - name;
260 		ctx->volname++;
261 	} else {
262 		ctx->volname = name;
263 		cellname = NULL;
264 		cellnamesz = 0;
265 	}
266 
267 	/* the volume type is further affected by a possible suffix */
268 	suffix = strrchr(ctx->volname, '.');
269 	if (suffix) {
270 		if (strcmp(suffix, ".readonly") == 0) {
271 			ctx->type = AFSVL_ROVOL;
272 			ctx->force = true;
273 		} else if (strcmp(suffix, ".backup") == 0) {
274 			ctx->type = AFSVL_BACKVOL;
275 			ctx->force = true;
276 		} else if (suffix[1] == 0) {
277 		} else {
278 			suffix = NULL;
279 		}
280 	}
281 
282 	ctx->volnamesz = suffix ?
283 		suffix - ctx->volname : strlen(ctx->volname);
284 
285 	_debug("cell %*.*s [%p]",
286 	       cellnamesz, cellnamesz, cellname ?: "", ctx->cell);
287 
288 	/* lookup the cell record */
289 	if (cellname) {
290 		cell = afs_lookup_cell(ctx->net, cellname, cellnamesz,
291 				       NULL, false);
292 		if (IS_ERR(cell)) {
293 			pr_err("kAFS: unable to lookup cell '%*.*s'\n",
294 			       cellnamesz, cellnamesz, cellname ?: "");
295 			return PTR_ERR(cell);
296 		}
297 		afs_put_cell(ctx->net, ctx->cell);
298 		ctx->cell = cell;
299 	}
300 
301 	_debug("CELL:%s [%p] VOLUME:%*.*s SUFFIX:%s TYPE:%d%s",
302 	       ctx->cell->name, ctx->cell,
303 	       ctx->volnamesz, ctx->volnamesz, ctx->volname,
304 	       suffix ?: "-", ctx->type, ctx->force ? " FORCE" : "");
305 
306 	fc->source = param->string;
307 	param->string = NULL;
308 	return 0;
309 }
310 
311 /*
312  * Parse a single mount parameter.
313  */
314 static int afs_parse_param(struct fs_context *fc, struct fs_parameter *param)
315 {
316 	struct fs_parse_result result;
317 	struct afs_fs_context *ctx = fc->fs_private;
318 	int opt;
319 
320 	opt = fs_parse(fc, afs_fs_parameters, param, &result);
321 	if (opt < 0)
322 		return opt;
323 
324 	switch (opt) {
325 	case Opt_source:
326 		return afs_parse_source(fc, param);
327 
328 	case Opt_autocell:
329 		ctx->autocell = true;
330 		break;
331 
332 	case Opt_dyn:
333 		ctx->dyn_root = true;
334 		break;
335 
336 	case Opt_flock:
337 		ctx->flock_mode = result.uint_32;
338 		break;
339 
340 	default:
341 		return -EINVAL;
342 	}
343 
344 	_leave(" = 0");
345 	return 0;
346 }
347 
348 /*
349  * Validate the options, get the cell key and look up the volume.
350  */
351 static int afs_validate_fc(struct fs_context *fc)
352 {
353 	struct afs_fs_context *ctx = fc->fs_private;
354 	struct afs_volume *volume;
355 	struct key *key;
356 
357 	if (!ctx->dyn_root) {
358 		if (ctx->no_cell) {
359 			pr_warn("kAFS: Can only specify source 'none' with -o dyn\n");
360 			return -EINVAL;
361 		}
362 
363 		if (!ctx->cell) {
364 			pr_warn("kAFS: No cell specified\n");
365 			return -EDESTADDRREQ;
366 		}
367 
368 		/* We try to do the mount securely. */
369 		key = afs_request_key(ctx->cell);
370 		if (IS_ERR(key))
371 			return PTR_ERR(key);
372 
373 		ctx->key = key;
374 
375 		if (ctx->volume) {
376 			afs_put_volume(ctx->cell, ctx->volume);
377 			ctx->volume = NULL;
378 		}
379 
380 		volume = afs_create_volume(ctx);
381 		if (IS_ERR(volume))
382 			return PTR_ERR(volume);
383 
384 		ctx->volume = volume;
385 	}
386 
387 	return 0;
388 }
389 
390 /*
391  * check a superblock to see if it's the one we're looking for
392  */
393 static int afs_test_super(struct super_block *sb, struct fs_context *fc)
394 {
395 	struct afs_fs_context *ctx = fc->fs_private;
396 	struct afs_super_info *as = AFS_FS_S(sb);
397 
398 	return (as->net_ns == fc->net_ns &&
399 		as->volume &&
400 		as->volume->vid == ctx->volume->vid &&
401 		as->cell == ctx->cell &&
402 		!as->dyn_root);
403 }
404 
405 static int afs_dynroot_test_super(struct super_block *sb, struct fs_context *fc)
406 {
407 	struct afs_super_info *as = AFS_FS_S(sb);
408 
409 	return (as->net_ns == fc->net_ns &&
410 		as->dyn_root);
411 }
412 
413 static int afs_set_super(struct super_block *sb, struct fs_context *fc)
414 {
415 	return set_anon_super(sb, NULL);
416 }
417 
418 /*
419  * fill in the superblock
420  */
421 static int afs_fill_super(struct super_block *sb, struct afs_fs_context *ctx)
422 {
423 	struct afs_super_info *as = AFS_FS_S(sb);
424 	struct afs_iget_data iget_data;
425 	struct inode *inode = NULL;
426 	int ret;
427 
428 	_enter("");
429 
430 	/* fill in the superblock */
431 	sb->s_blocksize		= PAGE_SIZE;
432 	sb->s_blocksize_bits	= PAGE_SHIFT;
433 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
434 	sb->s_magic		= AFS_FS_MAGIC;
435 	sb->s_op		= &afs_super_ops;
436 	if (!as->dyn_root)
437 		sb->s_xattr	= afs_xattr_handlers;
438 	ret = super_setup_bdi(sb);
439 	if (ret)
440 		return ret;
441 	sb->s_bdi->ra_pages	= VM_READAHEAD_PAGES;
442 
443 	/* allocate the root inode and dentry */
444 	if (as->dyn_root) {
445 		inode = afs_iget_pseudo_dir(sb, true);
446 	} else {
447 		sprintf(sb->s_id, "%llu", as->volume->vid);
448 		afs_activate_volume(as->volume);
449 		iget_data.fid.vid	= as->volume->vid;
450 		iget_data.fid.vnode	= 1;
451 		iget_data.fid.vnode_hi	= 0;
452 		iget_data.fid.unique	= 1;
453 		iget_data.cb_v_break	= as->volume->cb_v_break;
454 		iget_data.cb_s_break	= 0;
455 		inode = afs_iget(sb, ctx->key, &iget_data, NULL, NULL, NULL);
456 	}
457 
458 	if (IS_ERR(inode))
459 		return PTR_ERR(inode);
460 
461 	if (ctx->autocell || as->dyn_root)
462 		set_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(inode)->flags);
463 
464 	ret = -ENOMEM;
465 	sb->s_root = d_make_root(inode);
466 	if (!sb->s_root)
467 		goto error;
468 
469 	if (as->dyn_root) {
470 		sb->s_d_op = &afs_dynroot_dentry_operations;
471 		ret = afs_dynroot_populate(sb);
472 		if (ret < 0)
473 			goto error;
474 	} else {
475 		sb->s_d_op = &afs_fs_dentry_operations;
476 	}
477 
478 	_leave(" = 0");
479 	return 0;
480 
481 error:
482 	_leave(" = %d", ret);
483 	return ret;
484 }
485 
486 static struct afs_super_info *afs_alloc_sbi(struct fs_context *fc)
487 {
488 	struct afs_fs_context *ctx = fc->fs_private;
489 	struct afs_super_info *as;
490 
491 	as = kzalloc(sizeof(struct afs_super_info), GFP_KERNEL);
492 	if (as) {
493 		as->net_ns = get_net(fc->net_ns);
494 		as->flock_mode = ctx->flock_mode;
495 		if (ctx->dyn_root) {
496 			as->dyn_root = true;
497 		} else {
498 			as->cell = afs_get_cell(ctx->cell);
499 			as->volume = __afs_get_volume(ctx->volume);
500 		}
501 	}
502 	return as;
503 }
504 
505 static void afs_destroy_sbi(struct afs_super_info *as)
506 {
507 	if (as) {
508 		afs_put_volume(as->cell, as->volume);
509 		afs_put_cell(afs_net(as->net_ns), as->cell);
510 		put_net(as->net_ns);
511 		kfree(as);
512 	}
513 }
514 
515 static void afs_kill_super(struct super_block *sb)
516 {
517 	struct afs_super_info *as = AFS_FS_S(sb);
518 	struct afs_net *net = afs_net(as->net_ns);
519 
520 	if (as->dyn_root)
521 		afs_dynroot_depopulate(sb);
522 
523 	/* Clear the callback interests (which will do ilookup5) before
524 	 * deactivating the superblock.
525 	 */
526 	if (as->volume)
527 		afs_clear_callback_interests(net, as->volume->servers);
528 	kill_anon_super(sb);
529 	if (as->volume)
530 		afs_deactivate_volume(as->volume);
531 	afs_destroy_sbi(as);
532 }
533 
534 /*
535  * Get an AFS superblock and root directory.
536  */
537 static int afs_get_tree(struct fs_context *fc)
538 {
539 	struct afs_fs_context *ctx = fc->fs_private;
540 	struct super_block *sb;
541 	struct afs_super_info *as;
542 	int ret;
543 
544 	ret = afs_validate_fc(fc);
545 	if (ret)
546 		goto error;
547 
548 	_enter("");
549 
550 	/* allocate a superblock info record */
551 	ret = -ENOMEM;
552 	as = afs_alloc_sbi(fc);
553 	if (!as)
554 		goto error;
555 	fc->s_fs_info = as;
556 
557 	/* allocate a deviceless superblock */
558 	sb = sget_fc(fc,
559 		     as->dyn_root ? afs_dynroot_test_super : afs_test_super,
560 		     afs_set_super);
561 	if (IS_ERR(sb)) {
562 		ret = PTR_ERR(sb);
563 		goto error;
564 	}
565 
566 	if (!sb->s_root) {
567 		/* initial superblock/root creation */
568 		_debug("create");
569 		ret = afs_fill_super(sb, ctx);
570 		if (ret < 0)
571 			goto error_sb;
572 		sb->s_flags |= SB_ACTIVE;
573 	} else {
574 		_debug("reuse");
575 		ASSERTCMP(sb->s_flags, &, SB_ACTIVE);
576 	}
577 
578 	fc->root = dget(sb->s_root);
579 	trace_afs_get_tree(as->cell, as->volume);
580 	_leave(" = 0 [%p]", sb);
581 	return 0;
582 
583 error_sb:
584 	deactivate_locked_super(sb);
585 error:
586 	_leave(" = %d", ret);
587 	return ret;
588 }
589 
590 static void afs_free_fc(struct fs_context *fc)
591 {
592 	struct afs_fs_context *ctx = fc->fs_private;
593 
594 	afs_destroy_sbi(fc->s_fs_info);
595 	afs_put_volume(ctx->cell, ctx->volume);
596 	afs_put_cell(ctx->net, ctx->cell);
597 	key_put(ctx->key);
598 	kfree(ctx);
599 }
600 
601 static const struct fs_context_operations afs_context_ops = {
602 	.free		= afs_free_fc,
603 	.parse_param	= afs_parse_param,
604 	.get_tree	= afs_get_tree,
605 };
606 
607 /*
608  * Set up the filesystem mount context.
609  */
610 static int afs_init_fs_context(struct fs_context *fc)
611 {
612 	struct afs_fs_context *ctx;
613 	struct afs_cell *cell;
614 
615 	ctx = kzalloc(sizeof(struct afs_fs_context), GFP_KERNEL);
616 	if (!ctx)
617 		return -ENOMEM;
618 
619 	ctx->type = AFSVL_ROVOL;
620 	ctx->net = afs_net(fc->net_ns);
621 
622 	/* Default to the workstation cell. */
623 	rcu_read_lock();
624 	cell = afs_lookup_cell_rcu(ctx->net, NULL, 0);
625 	rcu_read_unlock();
626 	if (IS_ERR(cell))
627 		cell = NULL;
628 	ctx->cell = cell;
629 
630 	fc->fs_private = ctx;
631 	fc->ops = &afs_context_ops;
632 	return 0;
633 }
634 
635 /*
636  * Initialise an inode cache slab element prior to any use.  Note that
637  * afs_alloc_inode() *must* reset anything that could incorrectly leak from one
638  * inode to another.
639  */
640 static void afs_i_init_once(void *_vnode)
641 {
642 	struct afs_vnode *vnode = _vnode;
643 
644 	memset(vnode, 0, sizeof(*vnode));
645 	inode_init_once(&vnode->vfs_inode);
646 	mutex_init(&vnode->io_lock);
647 	init_rwsem(&vnode->validate_lock);
648 	spin_lock_init(&vnode->wb_lock);
649 	spin_lock_init(&vnode->lock);
650 	INIT_LIST_HEAD(&vnode->wb_keys);
651 	INIT_LIST_HEAD(&vnode->pending_locks);
652 	INIT_LIST_HEAD(&vnode->granted_locks);
653 	INIT_DELAYED_WORK(&vnode->lock_work, afs_lock_work);
654 	seqlock_init(&vnode->cb_lock);
655 }
656 
657 /*
658  * allocate an AFS inode struct from our slab cache
659  */
660 static struct inode *afs_alloc_inode(struct super_block *sb)
661 {
662 	struct afs_vnode *vnode;
663 
664 	vnode = kmem_cache_alloc(afs_inode_cachep, GFP_KERNEL);
665 	if (!vnode)
666 		return NULL;
667 
668 	atomic_inc(&afs_count_active_inodes);
669 
670 	/* Reset anything that shouldn't leak from one inode to the next. */
671 	memset(&vnode->fid, 0, sizeof(vnode->fid));
672 	memset(&vnode->status, 0, sizeof(vnode->status));
673 
674 	vnode->volume		= NULL;
675 	vnode->lock_key		= NULL;
676 	vnode->permit_cache	= NULL;
677 	RCU_INIT_POINTER(vnode->cb_interest, NULL);
678 #ifdef CONFIG_AFS_FSCACHE
679 	vnode->cache		= NULL;
680 #endif
681 
682 	vnode->flags		= 1 << AFS_VNODE_UNSET;
683 	vnode->lock_state	= AFS_VNODE_LOCK_NONE;
684 
685 	init_rwsem(&vnode->rmdir_lock);
686 
687 	_leave(" = %p", &vnode->vfs_inode);
688 	return &vnode->vfs_inode;
689 }
690 
691 static void afs_free_inode(struct inode *inode)
692 {
693 	kmem_cache_free(afs_inode_cachep, AFS_FS_I(inode));
694 }
695 
696 /*
697  * destroy an AFS inode struct
698  */
699 static void afs_destroy_inode(struct inode *inode)
700 {
701 	struct afs_vnode *vnode = AFS_FS_I(inode);
702 
703 	_enter("%p{%llx:%llu}", inode, vnode->fid.vid, vnode->fid.vnode);
704 
705 	_debug("DESTROY INODE %p", inode);
706 
707 	ASSERTCMP(rcu_access_pointer(vnode->cb_interest), ==, NULL);
708 
709 	atomic_dec(&afs_count_active_inodes);
710 }
711 
712 /*
713  * return information about an AFS volume
714  */
715 static int afs_statfs(struct dentry *dentry, struct kstatfs *buf)
716 {
717 	struct afs_super_info *as = AFS_FS_S(dentry->d_sb);
718 	struct afs_fs_cursor fc;
719 	struct afs_volume_status vs;
720 	struct afs_vnode *vnode = AFS_FS_I(d_inode(dentry));
721 	struct key *key;
722 	int ret;
723 
724 	buf->f_type	= dentry->d_sb->s_magic;
725 	buf->f_bsize	= AFS_BLOCK_SIZE;
726 	buf->f_namelen	= AFSNAMEMAX - 1;
727 
728 	if (as->dyn_root) {
729 		buf->f_blocks	= 1;
730 		buf->f_bavail	= 0;
731 		buf->f_bfree	= 0;
732 		return 0;
733 	}
734 
735 	key = afs_request_key(vnode->volume->cell);
736 	if (IS_ERR(key))
737 		return PTR_ERR(key);
738 
739 	ret = -ERESTARTSYS;
740 	if (afs_begin_vnode_operation(&fc, vnode, key, true)) {
741 		fc.flags |= AFS_FS_CURSOR_NO_VSLEEP;
742 		while (afs_select_fileserver(&fc)) {
743 			fc.cb_break = afs_calc_vnode_cb_break(vnode);
744 			afs_fs_get_volume_status(&fc, &vs);
745 		}
746 
747 		afs_check_for_remote_deletion(&fc, fc.vnode);
748 		ret = afs_end_vnode_operation(&fc);
749 	}
750 
751 	key_put(key);
752 
753 	if (ret == 0) {
754 		if (vs.max_quota == 0)
755 			buf->f_blocks = vs.part_max_blocks;
756 		else
757 			buf->f_blocks = vs.max_quota;
758 		buf->f_bavail = buf->f_bfree = buf->f_blocks - vs.blocks_in_use;
759 	}
760 
761 	return ret;
762 }
763