1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * dir.c - Operations for configfs directories.
4 *
5 * Based on sysfs:
6 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
7 *
8 * configfs Copyright (C) 2005 Oracle. All rights reserved.
9 */
10
11#undef DEBUG
12
13#include <linux/fs.h>
14#include <linux/fsnotify.h>
15#include <linux/mount.h>
16#include <linux/module.h>
17#include <linux/slab.h>
18#include <linux/err.h>
19
20#include <linux/configfs.h>
21#include "configfs_internal.h"
22
23/*
24 * Protects mutations of configfs_dirent linkage together with proper i_mutex
25 * Also protects mutations of symlinks linkage to target configfs_dirent
26 * Mutators of configfs_dirent linkage must *both* have the proper inode locked
27 * and configfs_dirent_lock locked, in that order.
28 * This allows one to safely traverse configfs_dirent trees and symlinks without
29 * having to lock inodes.
30 *
31 * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
32 * unlocked is not reliable unless in detach_groups() called from
33 * rmdir()/unregister() and from configfs_attach_group()
34 */
35DEFINE_SPINLOCK(configfs_dirent_lock);
36
37/*
38 * All of link_obj/unlink_obj/link_group/unlink_group require that
39 * subsys->su_mutex is held.
40 * But parent configfs_subsystem is NULL when config_item is root.
41 * Use this mutex when config_item is root.
42 */
43static DEFINE_MUTEX(configfs_subsystem_mutex);
44
45static void configfs_d_iput(struct dentry * dentry,
46 struct inode * inode)
47{
48 struct configfs_dirent *sd = dentry->d_fsdata;
49
50 if (sd) {
51 /* Coordinate with configfs_readdir */
52 spin_lock(lock: &configfs_dirent_lock);
53 /*
54 * Set sd->s_dentry to null only when this dentry is the one
55 * that is going to be killed. Otherwise configfs_d_iput may
56 * run just after configfs_lookup and set sd->s_dentry to
57 * NULL even it's still in use.
58 */
59 if (sd->s_dentry == dentry)
60 sd->s_dentry = NULL;
61
62 spin_unlock(lock: &configfs_dirent_lock);
63 configfs_put(sd);
64 }
65 iput(inode);
66}
67
68const struct dentry_operations configfs_dentry_ops = {
69 .d_iput = configfs_d_iput,
70 .d_delete = always_delete_dentry,
71};
72
73#ifdef CONFIG_LOCKDEP
74
75/*
76 * Helpers to make lockdep happy with our recursive locking of default groups'
77 * inodes (see configfs_attach_group() and configfs_detach_group()).
78 * We put default groups i_mutexes in separate classes according to their depth
79 * from the youngest non-default group ancestor.
80 *
81 * For a non-default group A having default groups A/B, A/C, and A/C/D, default
82 * groups A/B and A/C will have their inode's mutex in class
83 * default_group_class[0], and default group A/C/D will be in
84 * default_group_class[1].
85 *
86 * The lock classes are declared and assigned in inode.c, according to the
87 * s_depth value.
88 * The s_depth value is initialized to -1, adjusted to >= 0 when attaching
89 * default groups, and reset to -1 when all default groups are attached. During
90 * attachment, if configfs_create() sees s_depth > 0, the lock class of the new
91 * inode's mutex is set to default_group_class[s_depth - 1].
92 */
93
94static void configfs_init_dirent_depth(struct configfs_dirent *sd)
95{
96 sd->s_depth = -1;
97}
98
99static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
100 struct configfs_dirent *sd)
101{
102 int parent_depth = parent_sd->s_depth;
103
104 if (parent_depth >= 0)
105 sd->s_depth = parent_depth + 1;
106}
107
108static void
109configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
110{
111 /*
112 * item's i_mutex class is already setup, so s_depth is now only
113 * used to set new sub-directories s_depth, which is always done
114 * with item's i_mutex locked.
115 */
116 /*
117 * sd->s_depth == -1 iff we are a non default group.
118 * else (we are a default group) sd->s_depth > 0 (see
119 * create_dir()).
120 */
121 if (sd->s_depth == -1)
122 /*
123 * We are a non default group and we are going to create
124 * default groups.
125 */
126 sd->s_depth = 0;
127}
128
129static void
130configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
131{
132 /* We will not create default groups anymore. */
133 sd->s_depth = -1;
134}
135
136#else /* CONFIG_LOCKDEP */
137
138static void configfs_init_dirent_depth(struct configfs_dirent *sd)
139{
140}
141
142static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
143 struct configfs_dirent *sd)
144{
145}
146
147static void
148configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
149{
150}
151
152static void
153configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
154{
155}
156
157#endif /* CONFIG_LOCKDEP */
158
159static struct configfs_fragment *new_fragment(void)
160{
161 struct configfs_fragment *p;
162
163 p = kmalloc(size: sizeof(struct configfs_fragment), GFP_KERNEL);
164 if (p) {
165 atomic_set(v: &p->frag_count, i: 1);
166 init_rwsem(&p->frag_sem);
167 p->frag_dead = false;
168 }
169 return p;
170}
171
172void put_fragment(struct configfs_fragment *frag)
173{
174 if (frag && atomic_dec_and_test(v: &frag->frag_count))
175 kfree(objp: frag);
176}
177
178struct configfs_fragment *get_fragment(struct configfs_fragment *frag)
179{
180 if (likely(frag))
181 atomic_inc(v: &frag->frag_count);
182 return frag;
183}
184
185/*
186 * Allocates a new configfs_dirent and links it to the parent configfs_dirent
187 */
188static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd,
189 void *element, int type,
190 struct configfs_fragment *frag)
191{
192 struct configfs_dirent * sd;
193
194 sd = kmem_cache_zalloc(k: configfs_dir_cachep, GFP_KERNEL);
195 if (!sd)
196 return ERR_PTR(error: -ENOMEM);
197
198 atomic_set(v: &sd->s_count, i: 1);
199 INIT_LIST_HEAD(list: &sd->s_children);
200 sd->s_element = element;
201 sd->s_type = type;
202 configfs_init_dirent_depth(sd);
203 spin_lock(lock: &configfs_dirent_lock);
204 if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
205 spin_unlock(lock: &configfs_dirent_lock);
206 kmem_cache_free(s: configfs_dir_cachep, objp: sd);
207 return ERR_PTR(error: -ENOENT);
208 }
209 sd->s_frag = get_fragment(frag);
210 list_add(new: &sd->s_sibling, head: &parent_sd->s_children);
211 spin_unlock(lock: &configfs_dirent_lock);
212
213 return sd;
214}
215
216/*
217 *
218 * Return -EEXIST if there is already a configfs element with the same
219 * name for the same parent.
220 *
221 * called with parent inode's i_mutex held
222 */
223static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
224 const unsigned char *new)
225{
226 struct configfs_dirent * sd;
227
228 list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
229 if (sd->s_element) {
230 const unsigned char *existing = configfs_get_name(sd);
231 if (strcmp(existing, new))
232 continue;
233 else
234 return -EEXIST;
235 }
236 }
237
238 return 0;
239}
240
241
242int configfs_make_dirent(struct configfs_dirent * parent_sd,
243 struct dentry * dentry, void * element,
244 umode_t mode, int type, struct configfs_fragment *frag)
245{
246 struct configfs_dirent * sd;
247
248 sd = configfs_new_dirent(parent_sd, element, type, frag);
249 if (IS_ERR(ptr: sd))
250 return PTR_ERR(ptr: sd);
251
252 sd->s_mode = mode;
253 sd->s_dentry = dentry;
254 if (dentry)
255 dentry->d_fsdata = configfs_get(sd);
256
257 return 0;
258}
259
260static void configfs_remove_dirent(struct dentry *dentry)
261{
262 struct configfs_dirent *sd = dentry->d_fsdata;
263
264 if (!sd)
265 return;
266 spin_lock(lock: &configfs_dirent_lock);
267 list_del_init(entry: &sd->s_sibling);
268 spin_unlock(lock: &configfs_dirent_lock);
269 configfs_put(sd);
270}
271
272/**
273 * configfs_create_dir - create a directory for an config_item.
274 * @item: config_itemwe're creating directory for.
275 * @dentry: config_item's dentry.
276 * @frag: config_item's fragment.
277 *
278 * Note: user-created entries won't be allowed under this new directory
279 * until it is validated by configfs_dir_set_ready()
280 */
281
282static int configfs_create_dir(struct config_item *item, struct dentry *dentry,
283 struct configfs_fragment *frag)
284{
285 int error;
286 umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
287 struct dentry *p = dentry->d_parent;
288 struct inode *inode;
289
290 BUG_ON(!item);
291
292 error = configfs_dirent_exists(parent_sd: p->d_fsdata, new: dentry->d_name.name);
293 if (unlikely(error))
294 return error;
295
296 error = configfs_make_dirent(parent_sd: p->d_fsdata, dentry, element: item, mode,
297 CONFIGFS_DIR | CONFIGFS_USET_CREATING,
298 frag);
299 if (unlikely(error))
300 return error;
301
302 configfs_set_dir_dirent_depth(parent_sd: p->d_fsdata, sd: dentry->d_fsdata);
303 inode = configfs_create(dentry, mode);
304 if (IS_ERR(ptr: inode))
305 goto out_remove;
306
307 inode->i_op = &configfs_dir_inode_operations;
308 inode->i_fop = &configfs_dir_operations;
309 /* directory inodes start off with i_nlink == 2 (for "." entry) */
310 inc_nlink(inode);
311 d_instantiate(dentry, inode);
312 /* already hashed */
313 dget(dentry); /* pin directory dentries in core */
314 inc_nlink(inode: d_inode(dentry: p));
315 item->ci_dentry = dentry;
316 return 0;
317
318out_remove:
319 configfs_put(sd: dentry->d_fsdata);
320 configfs_remove_dirent(dentry);
321 return PTR_ERR(ptr: inode);
322}
323
324/*
325 * Allow userspace to create new entries under a new directory created with
326 * configfs_create_dir(), and under all of its chidlren directories recursively.
327 * @sd configfs_dirent of the new directory to validate
328 *
329 * Caller must hold configfs_dirent_lock.
330 */
331static void configfs_dir_set_ready(struct configfs_dirent *sd)
332{
333 struct configfs_dirent *child_sd;
334
335 sd->s_type &= ~CONFIGFS_USET_CREATING;
336 list_for_each_entry(child_sd, &sd->s_children, s_sibling)
337 if (child_sd->s_type & CONFIGFS_USET_CREATING)
338 configfs_dir_set_ready(sd: child_sd);
339}
340
341/*
342 * Check that a directory does not belong to a directory hierarchy being
343 * attached and not validated yet.
344 * @sd configfs_dirent of the directory to check
345 *
346 * @return non-zero iff the directory was validated
347 *
348 * Note: takes configfs_dirent_lock, so the result may change from false to true
349 * in two consecutive calls, but never from true to false.
350 */
351int configfs_dirent_is_ready(struct configfs_dirent *sd)
352{
353 int ret;
354
355 spin_lock(lock: &configfs_dirent_lock);
356 ret = !(sd->s_type & CONFIGFS_USET_CREATING);
357 spin_unlock(lock: &configfs_dirent_lock);
358
359 return ret;
360}
361
362int configfs_create_link(struct configfs_dirent *target, struct dentry *parent,
363 struct dentry *dentry, char *body)
364{
365 int err = 0;
366 umode_t mode = S_IFLNK | S_IRWXUGO;
367 struct configfs_dirent *p = parent->d_fsdata;
368 struct inode *inode;
369
370 err = configfs_make_dirent(parent_sd: p, dentry, element: target, mode, CONFIGFS_ITEM_LINK,
371 frag: p->s_frag);
372 if (err)
373 return err;
374
375 inode = configfs_create(dentry, mode);
376 if (IS_ERR(ptr: inode))
377 goto out_remove;
378
379 inode->i_link = body;
380 inode->i_op = &configfs_symlink_inode_operations;
381 d_instantiate(dentry, inode);
382 dget(dentry); /* pin link dentries in core */
383 return 0;
384
385out_remove:
386 configfs_put(sd: dentry->d_fsdata);
387 configfs_remove_dirent(dentry);
388 return PTR_ERR(ptr: inode);
389}
390
391static void remove_dir(struct dentry * d)
392{
393 struct dentry * parent = dget(dentry: d->d_parent);
394
395 configfs_remove_dirent(dentry: d);
396
397 if (d_really_is_positive(dentry: d))
398 simple_rmdir(d_inode(dentry: parent),d);
399
400 pr_debug(" o %pd removing done (%d)\n", d, d_count(d));
401
402 dput(parent);
403}
404
405/**
406 * configfs_remove_dir - remove an config_item's directory.
407 * @item: config_item we're removing.
408 *
409 * The only thing special about this is that we remove any files in
410 * the directory before we remove the directory, and we've inlined
411 * what used to be configfs_rmdir() below, instead of calling separately.
412 *
413 * Caller holds the mutex of the item's inode
414 */
415
416static void configfs_remove_dir(struct config_item * item)
417{
418 struct dentry * dentry = dget(dentry: item->ci_dentry);
419
420 if (!dentry)
421 return;
422
423 remove_dir(d: dentry);
424 /**
425 * Drop reference from dget() on entrance.
426 */
427 dput(dentry);
428}
429
430static struct dentry * configfs_lookup(struct inode *dir,
431 struct dentry *dentry,
432 unsigned int flags)
433{
434 struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
435 struct configfs_dirent * sd;
436 struct inode *inode = NULL;
437
438 if (dentry->d_name.len > NAME_MAX)
439 return ERR_PTR(error: -ENAMETOOLONG);
440
441 /*
442 * Fake invisibility if dir belongs to a group/default groups hierarchy
443 * being attached
444 *
445 * This forbids userspace to read/write attributes of items which may
446 * not complete their initialization, since the dentries of the
447 * attributes won't be instantiated.
448 */
449 if (!configfs_dirent_is_ready(sd: parent_sd))
450 return ERR_PTR(error: -ENOENT);
451
452 spin_lock(lock: &configfs_dirent_lock);
453 list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
454 if ((sd->s_type & CONFIGFS_NOT_PINNED) &&
455 !strcmp(configfs_get_name(sd), dentry->d_name.name)) {
456 struct configfs_attribute *attr = sd->s_element;
457 umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
458
459 dentry->d_fsdata = configfs_get(sd);
460 sd->s_dentry = dentry;
461 spin_unlock(lock: &configfs_dirent_lock);
462
463 inode = configfs_create(dentry, mode);
464 if (IS_ERR(ptr: inode)) {
465 configfs_put(sd);
466 return ERR_CAST(ptr: inode);
467 }
468 if (sd->s_type & CONFIGFS_ITEM_BIN_ATTR) {
469 inode->i_size = 0;
470 inode->i_fop = &configfs_bin_file_operations;
471 } else {
472 inode->i_size = PAGE_SIZE;
473 inode->i_fop = &configfs_file_operations;
474 }
475 goto done;
476 }
477 }
478 spin_unlock(lock: &configfs_dirent_lock);
479done:
480 d_add(dentry, inode);
481 return NULL;
482}
483
484/*
485 * Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are
486 * attributes and are removed by rmdir(). We recurse, setting
487 * CONFIGFS_USET_DROPPING on all children that are candidates for
488 * default detach.
489 * If there is an error, the caller will reset the flags via
490 * configfs_detach_rollback().
491 */
492static int configfs_detach_prep(struct dentry *dentry, struct dentry **wait)
493{
494 struct configfs_dirent *parent_sd = dentry->d_fsdata;
495 struct configfs_dirent *sd;
496 int ret;
497
498 /* Mark that we're trying to drop the group */
499 parent_sd->s_type |= CONFIGFS_USET_DROPPING;
500
501 ret = -EBUSY;
502 if (parent_sd->s_links)
503 goto out;
504
505 ret = 0;
506 list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
507 if (!sd->s_element ||
508 (sd->s_type & CONFIGFS_NOT_PINNED))
509 continue;
510 if (sd->s_type & CONFIGFS_USET_DEFAULT) {
511 /* Abort if racing with mkdir() */
512 if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
513 if (wait)
514 *wait= dget(dentry: sd->s_dentry);
515 return -EAGAIN;
516 }
517
518 /*
519 * Yup, recursive. If there's a problem, blame
520 * deep nesting of default_groups
521 */
522 ret = configfs_detach_prep(dentry: sd->s_dentry, wait);
523 if (!ret)
524 continue;
525 } else
526 ret = -ENOTEMPTY;
527
528 break;
529 }
530
531out:
532 return ret;
533}
534
535/*
536 * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
537 * set.
538 */
539static void configfs_detach_rollback(struct dentry *dentry)
540{
541 struct configfs_dirent *parent_sd = dentry->d_fsdata;
542 struct configfs_dirent *sd;
543
544 parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
545
546 list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
547 if (sd->s_type & CONFIGFS_USET_DEFAULT)
548 configfs_detach_rollback(dentry: sd->s_dentry);
549}
550
551static void detach_attrs(struct config_item * item)
552{
553 struct dentry * dentry = dget(dentry: item->ci_dentry);
554 struct configfs_dirent * parent_sd;
555 struct configfs_dirent * sd, * tmp;
556
557 if (!dentry)
558 return;
559
560 pr_debug("configfs %s: dropping attrs for dir\n",
561 dentry->d_name.name);
562
563 parent_sd = dentry->d_fsdata;
564 list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
565 if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED))
566 continue;
567 spin_lock(lock: &configfs_dirent_lock);
568 list_del_init(entry: &sd->s_sibling);
569 spin_unlock(lock: &configfs_dirent_lock);
570 configfs_drop_dentry(sd, parent: dentry);
571 configfs_put(sd);
572 }
573
574 /**
575 * Drop reference from dget() on entrance.
576 */
577 dput(dentry);
578}
579
580static int populate_attrs(struct config_item *item)
581{
582 const struct config_item_type *t = item->ci_type;
583 struct configfs_attribute *attr;
584 struct configfs_bin_attribute *bin_attr;
585 int error = 0;
586 int i;
587
588 if (!t)
589 return -EINVAL;
590 if (t->ct_attrs) {
591 for (i = 0; (attr = t->ct_attrs[i]) != NULL; i++) {
592 if ((error = configfs_create_file(item, attr)))
593 break;
594 }
595 }
596 if (t->ct_bin_attrs) {
597 for (i = 0; (bin_attr = t->ct_bin_attrs[i]) != NULL; i++) {
598 error = configfs_create_bin_file(item, bin_attr);
599 if (error)
600 break;
601 }
602 }
603
604 if (error)
605 detach_attrs(item);
606
607 return error;
608}
609
610static int configfs_attach_group(struct config_item *parent_item,
611 struct config_item *item,
612 struct dentry *dentry,
613 struct configfs_fragment *frag);
614static void configfs_detach_group(struct config_item *item);
615
616static void detach_groups(struct config_group *group)
617{
618 struct dentry * dentry = dget(dentry: group->cg_item.ci_dentry);
619 struct dentry *child;
620 struct configfs_dirent *parent_sd;
621 struct configfs_dirent *sd, *tmp;
622
623 if (!dentry)
624 return;
625
626 parent_sd = dentry->d_fsdata;
627 list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
628 if (!sd->s_element ||
629 !(sd->s_type & CONFIGFS_USET_DEFAULT))
630 continue;
631
632 child = sd->s_dentry;
633
634 inode_lock(inode: d_inode(dentry: child));
635
636 configfs_detach_group(item: sd->s_element);
637 d_inode(dentry: child)->i_flags |= S_DEAD;
638 dont_mount(dentry: child);
639
640 inode_unlock(inode: d_inode(dentry: child));
641
642 d_delete(child);
643 dput(child);
644 }
645
646 /**
647 * Drop reference from dget() on entrance.
648 */
649 dput(dentry);
650}
651
652/*
653 * This fakes mkdir(2) on a default_groups[] entry. It
654 * creates a dentry, attachs it, and then does fixup
655 * on the sd->s_type.
656 *
657 * We could, perhaps, tweak our parent's ->mkdir for a minute and
658 * try using vfs_mkdir. Just a thought.
659 */
660static int create_default_group(struct config_group *parent_group,
661 struct config_group *group,
662 struct configfs_fragment *frag)
663{
664 int ret;
665 struct configfs_dirent *sd;
666 /* We trust the caller holds a reference to parent */
667 struct dentry *child, *parent = parent_group->cg_item.ci_dentry;
668
669 if (!group->cg_item.ci_name)
670 group->cg_item.ci_name = group->cg_item.ci_namebuf;
671
672 ret = -ENOMEM;
673 child = d_alloc_name(parent, group->cg_item.ci_name);
674 if (child) {
675 d_add(child, NULL);
676
677 ret = configfs_attach_group(parent_item: &parent_group->cg_item,
678 item: &group->cg_item, dentry: child, frag);
679 if (!ret) {
680 sd = child->d_fsdata;
681 sd->s_type |= CONFIGFS_USET_DEFAULT;
682 } else {
683 BUG_ON(d_inode(child));
684 d_drop(dentry: child);
685 dput(child);
686 }
687 }
688
689 return ret;
690}
691
692static int populate_groups(struct config_group *group,
693 struct configfs_fragment *frag)
694{
695 struct config_group *new_group;
696 int ret = 0;
697
698 list_for_each_entry(new_group, &group->default_groups, group_entry) {
699 ret = create_default_group(parent_group: group, group: new_group, frag);
700 if (ret) {
701 detach_groups(group);
702 break;
703 }
704 }
705
706 return ret;
707}
708
709void configfs_remove_default_groups(struct config_group *group)
710{
711 struct config_group *g, *n;
712
713 list_for_each_entry_safe(g, n, &group->default_groups, group_entry) {
714 list_del(entry: &g->group_entry);
715 config_item_put(&g->cg_item);
716 }
717}
718EXPORT_SYMBOL(configfs_remove_default_groups);
719
720/*
721 * All of link_obj/unlink_obj/link_group/unlink_group require that
722 * subsys->su_mutex is held.
723 */
724
725static void unlink_obj(struct config_item *item)
726{
727 struct config_group *group;
728
729 group = item->ci_group;
730 if (group) {
731 list_del_init(entry: &item->ci_entry);
732
733 item->ci_group = NULL;
734 item->ci_parent = NULL;
735
736 /* Drop the reference for ci_entry */
737 config_item_put(item);
738
739 /* Drop the reference for ci_parent */
740 config_group_put(group);
741 }
742}
743
744static void link_obj(struct config_item *parent_item, struct config_item *item)
745{
746 /*
747 * Parent seems redundant with group, but it makes certain
748 * traversals much nicer.
749 */
750 item->ci_parent = parent_item;
751
752 /*
753 * We hold a reference on the parent for the child's ci_parent
754 * link.
755 */
756 item->ci_group = config_group_get(group: to_config_group(item: parent_item));
757 list_add_tail(new: &item->ci_entry, head: &item->ci_group->cg_children);
758
759 /*
760 * We hold a reference on the child for ci_entry on the parent's
761 * cg_children
762 */
763 config_item_get(item);
764}
765
766static void unlink_group(struct config_group *group)
767{
768 struct config_group *new_group;
769
770 list_for_each_entry(new_group, &group->default_groups, group_entry)
771 unlink_group(group: new_group);
772
773 group->cg_subsys = NULL;
774 unlink_obj(item: &group->cg_item);
775}
776
777static void link_group(struct config_group *parent_group, struct config_group *group)
778{
779 struct config_group *new_group;
780 struct configfs_subsystem *subsys = NULL; /* gcc is a turd */
781
782 link_obj(parent_item: &parent_group->cg_item, item: &group->cg_item);
783
784 if (parent_group->cg_subsys)
785 subsys = parent_group->cg_subsys;
786 else if (configfs_is_root(item: &parent_group->cg_item))
787 subsys = to_configfs_subsystem(group);
788 else
789 BUG();
790 group->cg_subsys = subsys;
791
792 list_for_each_entry(new_group, &group->default_groups, group_entry)
793 link_group(parent_group: group, group: new_group);
794}
795
796/*
797 * The goal is that configfs_attach_item() (and
798 * configfs_attach_group()) can be called from either the VFS or this
799 * module. That is, they assume that the items have been created,
800 * the dentry allocated, and the dcache is all ready to go.
801 *
802 * If they fail, they must clean up after themselves as if they
803 * had never been called. The caller (VFS or local function) will
804 * handle cleaning up the dcache bits.
805 *
806 * configfs_detach_group() and configfs_detach_item() behave similarly on
807 * the way out. They assume that the proper semaphores are held, they
808 * clean up the configfs items, and they expect their callers will
809 * handle the dcache bits.
810 */
811static int configfs_attach_item(struct config_item *parent_item,
812 struct config_item *item,
813 struct dentry *dentry,
814 struct configfs_fragment *frag)
815{
816 int ret;
817
818 ret = configfs_create_dir(item, dentry, frag);
819 if (!ret) {
820 ret = populate_attrs(item);
821 if (ret) {
822 /*
823 * We are going to remove an inode and its dentry but
824 * the VFS may already have hit and used them. Thus,
825 * we must lock them as rmdir() would.
826 */
827 inode_lock(inode: d_inode(dentry));
828 configfs_remove_dir(item);
829 d_inode(dentry)->i_flags |= S_DEAD;
830 dont_mount(dentry);
831 inode_unlock(inode: d_inode(dentry));
832 d_delete(dentry);
833 }
834 }
835
836 return ret;
837}
838
839/* Caller holds the mutex of the item's inode */
840static void configfs_detach_item(struct config_item *item)
841{
842 detach_attrs(item);
843 configfs_remove_dir(item);
844}
845
846static int configfs_attach_group(struct config_item *parent_item,
847 struct config_item *item,
848 struct dentry *dentry,
849 struct configfs_fragment *frag)
850{
851 int ret;
852 struct configfs_dirent *sd;
853
854 ret = configfs_attach_item(parent_item, item, dentry, frag);
855 if (!ret) {
856 sd = dentry->d_fsdata;
857 sd->s_type |= CONFIGFS_USET_DIR;
858
859 /*
860 * FYI, we're faking mkdir in populate_groups()
861 * We must lock the group's inode to avoid races with the VFS
862 * which can already hit the inode and try to add/remove entries
863 * under it.
864 *
865 * We must also lock the inode to remove it safely in case of
866 * error, as rmdir() would.
867 */
868 inode_lock_nested(inode: d_inode(dentry), subclass: I_MUTEX_CHILD);
869 configfs_adjust_dir_dirent_depth_before_populate(sd);
870 ret = populate_groups(group: to_config_group(item), frag);
871 if (ret) {
872 configfs_detach_item(item);
873 d_inode(dentry)->i_flags |= S_DEAD;
874 dont_mount(dentry);
875 }
876 configfs_adjust_dir_dirent_depth_after_populate(sd);
877 inode_unlock(inode: d_inode(dentry));
878 if (ret)
879 d_delete(dentry);
880 }
881
882 return ret;
883}
884
885/* Caller holds the mutex of the group's inode */
886static void configfs_detach_group(struct config_item *item)
887{
888 detach_groups(group: to_config_group(item));
889 configfs_detach_item(item);
890}
891
892/*
893 * After the item has been detached from the filesystem view, we are
894 * ready to tear it out of the hierarchy. Notify the client before
895 * we do that so they can perform any cleanup that requires
896 * navigating the hierarchy. A client does not need to provide this
897 * callback. The subsystem semaphore MUST be held by the caller, and
898 * references must be valid for both items. It also assumes the
899 * caller has validated ci_type.
900 */
901static void client_disconnect_notify(struct config_item *parent_item,
902 struct config_item *item)
903{
904 const struct config_item_type *type;
905
906 type = parent_item->ci_type;
907 BUG_ON(!type);
908
909 if (type->ct_group_ops && type->ct_group_ops->disconnect_notify)
910 type->ct_group_ops->disconnect_notify(to_config_group(item: parent_item),
911 item);
912}
913
914/*
915 * Drop the initial reference from make_item()/make_group()
916 * This function assumes that reference is held on item
917 * and that item holds a valid reference to the parent. Also, it
918 * assumes the caller has validated ci_type.
919 */
920static void client_drop_item(struct config_item *parent_item,
921 struct config_item *item)
922{
923 const struct config_item_type *type;
924
925 type = parent_item->ci_type;
926 BUG_ON(!type);
927
928 /*
929 * If ->drop_item() exists, it is responsible for the
930 * config_item_put().
931 */
932 if (type->ct_group_ops && type->ct_group_ops->drop_item)
933 type->ct_group_ops->drop_item(to_config_group(item: parent_item),
934 item);
935 else
936 config_item_put(item);
937}
938
939#ifdef DEBUG
940static void configfs_dump_one(struct configfs_dirent *sd, int level)
941{
942 pr_info("%*s\"%s\":\n", level, " ", configfs_get_name(sd));
943
944#define type_print(_type) if (sd->s_type & _type) pr_info("%*s %s\n", level, " ", #_type);
945 type_print(CONFIGFS_ROOT);
946 type_print(CONFIGFS_DIR);
947 type_print(CONFIGFS_ITEM_ATTR);
948 type_print(CONFIGFS_ITEM_LINK);
949 type_print(CONFIGFS_USET_DIR);
950 type_print(CONFIGFS_USET_DEFAULT);
951 type_print(CONFIGFS_USET_DROPPING);
952#undef type_print
953}
954
955static int configfs_dump(struct configfs_dirent *sd, int level)
956{
957 struct configfs_dirent *child_sd;
958 int ret = 0;
959
960 configfs_dump_one(sd, level);
961
962 if (!(sd->s_type & (CONFIGFS_DIR|CONFIGFS_ROOT)))
963 return 0;
964
965 list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
966 ret = configfs_dump(child_sd, level + 2);
967 if (ret)
968 break;
969 }
970
971 return ret;
972}
973#endif
974
975
976/*
977 * configfs_depend_item() and configfs_undepend_item()
978 *
979 * WARNING: Do not call these from a configfs callback!
980 *
981 * This describes these functions and their helpers.
982 *
983 * Allow another kernel system to depend on a config_item. If this
984 * happens, the item cannot go away until the dependent can live without
985 * it. The idea is to give client modules as simple an interface as
986 * possible. When a system asks them to depend on an item, they just
987 * call configfs_depend_item(). If the item is live and the client
988 * driver is in good shape, we'll happily do the work for them.
989 *
990 * Why is the locking complex? Because configfs uses the VFS to handle
991 * all locking, but this function is called outside the normal
992 * VFS->configfs path. So it must take VFS locks to prevent the
993 * VFS->configfs stuff (configfs_mkdir(), configfs_rmdir(), etc). This is
994 * why you can't call these functions underneath configfs callbacks.
995 *
996 * Note, btw, that this can be called at *any* time, even when a configfs
997 * subsystem isn't registered, or when configfs is loading or unloading.
998 * Just like configfs_register_subsystem(). So we take the same
999 * precautions. We pin the filesystem. We lock configfs_dirent_lock.
1000 * If we can find the target item in the
1001 * configfs tree, it must be part of the subsystem tree as well, so we
1002 * do not need the subsystem semaphore. Holding configfs_dirent_lock helps
1003 * locking out mkdir() and rmdir(), who might be racing us.
1004 */
1005
1006/*
1007 * configfs_depend_prep()
1008 *
1009 * Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are
1010 * attributes. This is similar but not the same to configfs_detach_prep().
1011 * Note that configfs_detach_prep() expects the parent to be locked when it
1012 * is called, but we lock the parent *inside* configfs_depend_prep(). We
1013 * do that so we can unlock it if we find nothing.
1014 *
1015 * Here we do a depth-first search of the dentry hierarchy looking for
1016 * our object.
1017 * We deliberately ignore items tagged as dropping since they are virtually
1018 * dead, as well as items in the middle of attachment since they virtually
1019 * do not exist yet. This completes the locking out of racing mkdir() and
1020 * rmdir().
1021 * Note: subdirectories in the middle of attachment start with s_type =
1022 * CONFIGFS_DIR|CONFIGFS_USET_CREATING set by create_dir(). When
1023 * CONFIGFS_USET_CREATING is set, we ignore the item. The actual set of
1024 * s_type is in configfs_new_dirent(), which has configfs_dirent_lock.
1025 *
1026 * If the target is not found, -ENOENT is bubbled up.
1027 *
1028 * This adds a requirement that all config_items be unique!
1029 *
1030 * This is recursive. There isn't
1031 * much on the stack, though, so folks that need this function - be careful
1032 * about your stack! Patches will be accepted to make it iterative.
1033 */
1034static int configfs_depend_prep(struct dentry *origin,
1035 struct config_item *target)
1036{
1037 struct configfs_dirent *child_sd, *sd;
1038 int ret = 0;
1039
1040 BUG_ON(!origin || !origin->d_fsdata);
1041 sd = origin->d_fsdata;
1042
1043 if (sd->s_element == target) /* Boo-yah */
1044 goto out;
1045
1046 list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
1047 if ((child_sd->s_type & CONFIGFS_DIR) &&
1048 !(child_sd->s_type & CONFIGFS_USET_DROPPING) &&
1049 !(child_sd->s_type & CONFIGFS_USET_CREATING)) {
1050 ret = configfs_depend_prep(origin: child_sd->s_dentry,
1051 target);
1052 if (!ret)
1053 goto out; /* Child path boo-yah */
1054 }
1055 }
1056
1057 /* We looped all our children and didn't find target */
1058 ret = -ENOENT;
1059
1060out:
1061 return ret;
1062}
1063
1064static int configfs_do_depend_item(struct dentry *subsys_dentry,
1065 struct config_item *target)
1066{
1067 struct configfs_dirent *p;
1068 int ret;
1069
1070 spin_lock(lock: &configfs_dirent_lock);
1071 /* Scan the tree, return 0 if found */
1072 ret = configfs_depend_prep(origin: subsys_dentry, target);
1073 if (ret)
1074 goto out_unlock_dirent_lock;
1075
1076 /*
1077 * We are sure that the item is not about to be removed by rmdir(), and
1078 * not in the middle of attachment by mkdir().
1079 */
1080 p = target->ci_dentry->d_fsdata;
1081 p->s_dependent_count += 1;
1082
1083out_unlock_dirent_lock:
1084 spin_unlock(lock: &configfs_dirent_lock);
1085
1086 return ret;
1087}
1088
1089static inline struct configfs_dirent *
1090configfs_find_subsys_dentry(struct configfs_dirent *root_sd,
1091 struct config_item *subsys_item)
1092{
1093 struct configfs_dirent *p;
1094 struct configfs_dirent *ret = NULL;
1095
1096 list_for_each_entry(p, &root_sd->s_children, s_sibling) {
1097 if (p->s_type & CONFIGFS_DIR &&
1098 p->s_element == subsys_item) {
1099 ret = p;
1100 break;
1101 }
1102 }
1103
1104 return ret;
1105}
1106
1107
1108int configfs_depend_item(struct configfs_subsystem *subsys,
1109 struct config_item *target)
1110{
1111 int ret;
1112 struct configfs_dirent *subsys_sd;
1113 struct config_item *s_item = &subsys->su_group.cg_item;
1114 struct dentry *root;
1115
1116 /*
1117 * Pin the configfs filesystem. This means we can safely access
1118 * the root of the configfs filesystem.
1119 */
1120 root = configfs_pin_fs();
1121 if (IS_ERR(ptr: root))
1122 return PTR_ERR(ptr: root);
1123
1124 /*
1125 * Next, lock the root directory. We're going to check that the
1126 * subsystem is really registered, and so we need to lock out
1127 * configfs_[un]register_subsystem().
1128 */
1129 inode_lock(inode: d_inode(dentry: root));
1130
1131 subsys_sd = configfs_find_subsys_dentry(root_sd: root->d_fsdata, subsys_item: s_item);
1132 if (!subsys_sd) {
1133 ret = -ENOENT;
1134 goto out_unlock_fs;
1135 }
1136
1137 /* Ok, now we can trust subsys/s_item */
1138 ret = configfs_do_depend_item(subsys_dentry: subsys_sd->s_dentry, target);
1139
1140out_unlock_fs:
1141 inode_unlock(inode: d_inode(dentry: root));
1142
1143 /*
1144 * If we succeeded, the fs is pinned via other methods. If not,
1145 * we're done with it anyway. So release_fs() is always right.
1146 */
1147 configfs_release_fs();
1148
1149 return ret;
1150}
1151EXPORT_SYMBOL(configfs_depend_item);
1152
1153/*
1154 * Release the dependent linkage. This is much simpler than
1155 * configfs_depend_item() because we know that the client driver is
1156 * pinned, thus the subsystem is pinned, and therefore configfs is pinned.
1157 */
1158void configfs_undepend_item(struct config_item *target)
1159{
1160 struct configfs_dirent *sd;
1161
1162 /*
1163 * Since we can trust everything is pinned, we just need
1164 * configfs_dirent_lock.
1165 */
1166 spin_lock(lock: &configfs_dirent_lock);
1167
1168 sd = target->ci_dentry->d_fsdata;
1169 BUG_ON(sd->s_dependent_count < 1);
1170
1171 sd->s_dependent_count -= 1;
1172
1173 /*
1174 * After this unlock, we cannot trust the item to stay alive!
1175 * DO NOT REFERENCE item after this unlock.
1176 */
1177 spin_unlock(lock: &configfs_dirent_lock);
1178}
1179EXPORT_SYMBOL(configfs_undepend_item);
1180
1181/*
1182 * caller_subsys is a caller's subsystem not target's. This is used to
1183 * determine if we should lock root and check subsys or not. When we are
1184 * in the same subsystem as our target there is no need to do locking as
1185 * we know that subsys is valid and is not unregistered during this function
1186 * as we are called from callback of one of his children and VFS holds a lock
1187 * on some inode. Otherwise we have to lock our root to ensure that target's
1188 * subsystem it is not unregistered during this function.
1189 */
1190int configfs_depend_item_unlocked(struct configfs_subsystem *caller_subsys,
1191 struct config_item *target)
1192{
1193 struct configfs_subsystem *target_subsys;
1194 struct config_group *root, *parent;
1195 struct configfs_dirent *subsys_sd;
1196 int ret = -ENOENT;
1197
1198 /* Disallow this function for configfs root */
1199 if (configfs_is_root(item: target))
1200 return -EINVAL;
1201
1202 parent = target->ci_group;
1203 /*
1204 * This may happen when someone is trying to depend root
1205 * directory of some subsystem
1206 */
1207 if (configfs_is_root(item: &parent->cg_item)) {
1208 target_subsys = to_configfs_subsystem(group: to_config_group(item: target));
1209 root = parent;
1210 } else {
1211 target_subsys = parent->cg_subsys;
1212 /* Find a cofnigfs root as we may need it for locking */
1213 for (root = parent; !configfs_is_root(item: &root->cg_item);
1214 root = root->cg_item.ci_group)
1215 ;
1216 }
1217
1218 if (target_subsys != caller_subsys) {
1219 /*
1220 * We are in other configfs subsystem, so we have to do
1221 * additional locking to prevent other subsystem from being
1222 * unregistered
1223 */
1224 inode_lock(inode: d_inode(dentry: root->cg_item.ci_dentry));
1225
1226 /*
1227 * As we are trying to depend item from other subsystem
1228 * we have to check if this subsystem is still registered
1229 */
1230 subsys_sd = configfs_find_subsys_dentry(
1231 root_sd: root->cg_item.ci_dentry->d_fsdata,
1232 subsys_item: &target_subsys->su_group.cg_item);
1233 if (!subsys_sd)
1234 goto out_root_unlock;
1235 } else {
1236 subsys_sd = target_subsys->su_group.cg_item.ci_dentry->d_fsdata;
1237 }
1238
1239 /* Now we can execute core of depend item */
1240 ret = configfs_do_depend_item(subsys_dentry: subsys_sd->s_dentry, target);
1241
1242 if (target_subsys != caller_subsys)
1243out_root_unlock:
1244 /*
1245 * We were called from subsystem other than our target so we
1246 * took some locks so now it's time to release them
1247 */
1248 inode_unlock(inode: d_inode(dentry: root->cg_item.ci_dentry));
1249
1250 return ret;
1251}
1252EXPORT_SYMBOL(configfs_depend_item_unlocked);
1253
1254static int configfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
1255 struct dentry *dentry, umode_t mode)
1256{
1257 int ret = 0;
1258 int module_got = 0;
1259 struct config_group *group = NULL;
1260 struct config_item *item = NULL;
1261 struct config_item *parent_item;
1262 struct configfs_subsystem *subsys;
1263 struct configfs_dirent *sd;
1264 const struct config_item_type *type;
1265 struct module *subsys_owner = NULL, *new_item_owner = NULL;
1266 struct configfs_fragment *frag;
1267 char *name;
1268
1269 sd = dentry->d_parent->d_fsdata;
1270
1271 /*
1272 * Fake invisibility if dir belongs to a group/default groups hierarchy
1273 * being attached
1274 */
1275 if (!configfs_dirent_is_ready(sd)) {
1276 ret = -ENOENT;
1277 goto out;
1278 }
1279
1280 if (!(sd->s_type & CONFIGFS_USET_DIR)) {
1281 ret = -EPERM;
1282 goto out;
1283 }
1284
1285 frag = new_fragment();
1286 if (!frag) {
1287 ret = -ENOMEM;
1288 goto out;
1289 }
1290
1291 /* Get a working ref for the duration of this function */
1292 parent_item = configfs_get_config_item(dentry: dentry->d_parent);
1293 type = parent_item->ci_type;
1294 subsys = to_config_group(item: parent_item)->cg_subsys;
1295 BUG_ON(!subsys);
1296
1297 if (!type || !type->ct_group_ops ||
1298 (!type->ct_group_ops->make_group &&
1299 !type->ct_group_ops->make_item)) {
1300 ret = -EPERM; /* Lack-of-mkdir returns -EPERM */
1301 goto out_put;
1302 }
1303
1304 /*
1305 * The subsystem may belong to a different module than the item
1306 * being created. We don't want to safely pin the new item but
1307 * fail to pin the subsystem it sits under.
1308 */
1309 if (!subsys->su_group.cg_item.ci_type) {
1310 ret = -EINVAL;
1311 goto out_put;
1312 }
1313 subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
1314 if (!try_module_get(module: subsys_owner)) {
1315 ret = -EINVAL;
1316 goto out_put;
1317 }
1318
1319 name = kmalloc(size: dentry->d_name.len + 1, GFP_KERNEL);
1320 if (!name) {
1321 ret = -ENOMEM;
1322 goto out_subsys_put;
1323 }
1324
1325 snprintf(buf: name, size: dentry->d_name.len + 1, fmt: "%s", dentry->d_name.name);
1326
1327 mutex_lock(&subsys->su_mutex);
1328 if (type->ct_group_ops->make_group) {
1329 group = type->ct_group_ops->make_group(to_config_group(item: parent_item), name);
1330 if (!group)
1331 group = ERR_PTR(error: -ENOMEM);
1332 if (!IS_ERR(ptr: group)) {
1333 link_group(parent_group: to_config_group(item: parent_item), group);
1334 item = &group->cg_item;
1335 } else
1336 ret = PTR_ERR(ptr: group);
1337 } else {
1338 item = type->ct_group_ops->make_item(to_config_group(item: parent_item), name);
1339 if (!item)
1340 item = ERR_PTR(error: -ENOMEM);
1341 if (!IS_ERR(ptr: item))
1342 link_obj(parent_item, item);
1343 else
1344 ret = PTR_ERR(ptr: item);
1345 }
1346 mutex_unlock(lock: &subsys->su_mutex);
1347
1348 kfree(objp: name);
1349 if (ret) {
1350 /*
1351 * If ret != 0, then link_obj() was never called.
1352 * There are no extra references to clean up.
1353 */
1354 goto out_subsys_put;
1355 }
1356
1357 /*
1358 * link_obj() has been called (via link_group() for groups).
1359 * From here on out, errors must clean that up.
1360 */
1361
1362 type = item->ci_type;
1363 if (!type) {
1364 ret = -EINVAL;
1365 goto out_unlink;
1366 }
1367
1368 new_item_owner = type->ct_owner;
1369 if (!try_module_get(module: new_item_owner)) {
1370 ret = -EINVAL;
1371 goto out_unlink;
1372 }
1373
1374 /*
1375 * I hate doing it this way, but if there is
1376 * an error, module_put() probably should
1377 * happen after any cleanup.
1378 */
1379 module_got = 1;
1380
1381 /*
1382 * Make racing rmdir() fail if it did not tag parent with
1383 * CONFIGFS_USET_DROPPING
1384 * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will
1385 * fail and let rmdir() terminate correctly
1386 */
1387 spin_lock(lock: &configfs_dirent_lock);
1388 /* This will make configfs_detach_prep() fail */
1389 sd->s_type |= CONFIGFS_USET_IN_MKDIR;
1390 spin_unlock(lock: &configfs_dirent_lock);
1391
1392 if (group)
1393 ret = configfs_attach_group(parent_item, item, dentry, frag);
1394 else
1395 ret = configfs_attach_item(parent_item, item, dentry, frag);
1396
1397 spin_lock(lock: &configfs_dirent_lock);
1398 sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
1399 if (!ret)
1400 configfs_dir_set_ready(sd: dentry->d_fsdata);
1401 spin_unlock(lock: &configfs_dirent_lock);
1402
1403out_unlink:
1404 if (ret) {
1405 /* Tear down everything we built up */
1406 mutex_lock(&subsys->su_mutex);
1407
1408 client_disconnect_notify(parent_item, item);
1409 if (group)
1410 unlink_group(group);
1411 else
1412 unlink_obj(item);
1413 client_drop_item(parent_item, item);
1414
1415 mutex_unlock(lock: &subsys->su_mutex);
1416
1417 if (module_got)
1418 module_put(module: new_item_owner);
1419 }
1420
1421out_subsys_put:
1422 if (ret)
1423 module_put(module: subsys_owner);
1424
1425out_put:
1426 /*
1427 * link_obj()/link_group() took a reference from child->parent,
1428 * so the parent is safely pinned. We can drop our working
1429 * reference.
1430 */
1431 config_item_put(parent_item);
1432 put_fragment(frag);
1433
1434out:
1435 return ret;
1436}
1437
1438static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
1439{
1440 struct config_item *parent_item;
1441 struct config_item *item;
1442 struct configfs_subsystem *subsys;
1443 struct configfs_dirent *sd;
1444 struct configfs_fragment *frag;
1445 struct module *subsys_owner = NULL, *dead_item_owner = NULL;
1446 int ret;
1447
1448 sd = dentry->d_fsdata;
1449 if (sd->s_type & CONFIGFS_USET_DEFAULT)
1450 return -EPERM;
1451
1452 /* Get a working ref until we have the child */
1453 parent_item = configfs_get_config_item(dentry: dentry->d_parent);
1454 subsys = to_config_group(item: parent_item)->cg_subsys;
1455 BUG_ON(!subsys);
1456
1457 if (!parent_item->ci_type) {
1458 config_item_put(parent_item);
1459 return -EINVAL;
1460 }
1461
1462 /* configfs_mkdir() shouldn't have allowed this */
1463 BUG_ON(!subsys->su_group.cg_item.ci_type);
1464 subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
1465
1466 /*
1467 * Ensure that no racing symlink() will make detach_prep() fail while
1468 * the new link is temporarily attached
1469 */
1470 do {
1471 struct dentry *wait;
1472
1473 mutex_lock(&configfs_symlink_mutex);
1474 spin_lock(lock: &configfs_dirent_lock);
1475 /*
1476 * Here's where we check for dependents. We're protected by
1477 * configfs_dirent_lock.
1478 * If no dependent, atomically tag the item as dropping.
1479 */
1480 ret = sd->s_dependent_count ? -EBUSY : 0;
1481 if (!ret) {
1482 ret = configfs_detach_prep(dentry, wait: &wait);
1483 if (ret)
1484 configfs_detach_rollback(dentry);
1485 }
1486 spin_unlock(lock: &configfs_dirent_lock);
1487 mutex_unlock(lock: &configfs_symlink_mutex);
1488
1489 if (ret) {
1490 if (ret != -EAGAIN) {
1491 config_item_put(parent_item);
1492 return ret;
1493 }
1494
1495 /* Wait until the racing operation terminates */
1496 inode_lock(inode: d_inode(dentry: wait));
1497 inode_unlock(inode: d_inode(dentry: wait));
1498 dput(wait);
1499 }
1500 } while (ret == -EAGAIN);
1501
1502 frag = sd->s_frag;
1503 if (down_write_killable(sem: &frag->frag_sem)) {
1504 spin_lock(lock: &configfs_dirent_lock);
1505 configfs_detach_rollback(dentry);
1506 spin_unlock(lock: &configfs_dirent_lock);
1507 config_item_put(parent_item);
1508 return -EINTR;
1509 }
1510 frag->frag_dead = true;
1511 up_write(sem: &frag->frag_sem);
1512
1513 /* Get a working ref for the duration of this function */
1514 item = configfs_get_config_item(dentry);
1515
1516 /* Drop reference from above, item already holds one. */
1517 config_item_put(parent_item);
1518
1519 if (item->ci_type)
1520 dead_item_owner = item->ci_type->ct_owner;
1521
1522 if (sd->s_type & CONFIGFS_USET_DIR) {
1523 configfs_detach_group(item);
1524
1525 mutex_lock(&subsys->su_mutex);
1526 client_disconnect_notify(parent_item, item);
1527 unlink_group(group: to_config_group(item));
1528 } else {
1529 configfs_detach_item(item);
1530
1531 mutex_lock(&subsys->su_mutex);
1532 client_disconnect_notify(parent_item, item);
1533 unlink_obj(item);
1534 }
1535
1536 client_drop_item(parent_item, item);
1537 mutex_unlock(lock: &subsys->su_mutex);
1538
1539 /* Drop our reference from above */
1540 config_item_put(item);
1541
1542 module_put(module: dead_item_owner);
1543 module_put(module: subsys_owner);
1544
1545 return 0;
1546}
1547
1548const struct inode_operations configfs_dir_inode_operations = {
1549 .mkdir = configfs_mkdir,
1550 .rmdir = configfs_rmdir,
1551 .symlink = configfs_symlink,
1552 .unlink = configfs_unlink,
1553 .lookup = configfs_lookup,
1554 .setattr = configfs_setattr,
1555};
1556
1557const struct inode_operations configfs_root_inode_operations = {
1558 .lookup = configfs_lookup,
1559 .setattr = configfs_setattr,
1560};
1561
1562static int configfs_dir_open(struct inode *inode, struct file *file)
1563{
1564 struct dentry * dentry = file->f_path.dentry;
1565 struct configfs_dirent * parent_sd = dentry->d_fsdata;
1566 int err;
1567
1568 inode_lock(inode: d_inode(dentry));
1569 /*
1570 * Fake invisibility if dir belongs to a group/default groups hierarchy
1571 * being attached
1572 */
1573 err = -ENOENT;
1574 if (configfs_dirent_is_ready(sd: parent_sd)) {
1575 file->private_data = configfs_new_dirent(parent_sd, NULL, type: 0, NULL);
1576 if (IS_ERR(ptr: file->private_data))
1577 err = PTR_ERR(ptr: file->private_data);
1578 else
1579 err = 0;
1580 }
1581 inode_unlock(inode: d_inode(dentry));
1582
1583 return err;
1584}
1585
1586static int configfs_dir_close(struct inode *inode, struct file *file)
1587{
1588 struct dentry * dentry = file->f_path.dentry;
1589 struct configfs_dirent * cursor = file->private_data;
1590
1591 inode_lock(inode: d_inode(dentry));
1592 spin_lock(lock: &configfs_dirent_lock);
1593 list_del_init(entry: &cursor->s_sibling);
1594 spin_unlock(lock: &configfs_dirent_lock);
1595 inode_unlock(inode: d_inode(dentry));
1596
1597 release_configfs_dirent(sd: cursor);
1598
1599 return 0;
1600}
1601
1602static int configfs_readdir(struct file *file, struct dir_context *ctx)
1603{
1604 struct dentry *dentry = file->f_path.dentry;
1605 struct super_block *sb = dentry->d_sb;
1606 struct configfs_dirent * parent_sd = dentry->d_fsdata;
1607 struct configfs_dirent *cursor = file->private_data;
1608 struct list_head *p, *q = &cursor->s_sibling;
1609 ino_t ino = 0;
1610
1611 if (!dir_emit_dots(file, ctx))
1612 return 0;
1613 spin_lock(lock: &configfs_dirent_lock);
1614 if (ctx->pos == 2)
1615 list_move(list: q, head: &parent_sd->s_children);
1616 for (p = q->next; p != &parent_sd->s_children; p = p->next) {
1617 struct configfs_dirent *next;
1618 const char *name;
1619 int len;
1620 struct inode *inode = NULL;
1621
1622 next = list_entry(p, struct configfs_dirent, s_sibling);
1623 if (!next->s_element)
1624 continue;
1625
1626 /*
1627 * We'll have a dentry and an inode for
1628 * PINNED items and for open attribute
1629 * files. We lock here to prevent a race
1630 * with configfs_d_iput() clearing
1631 * s_dentry before calling iput().
1632 *
1633 * Why do we go to the trouble? If
1634 * someone has an attribute file open,
1635 * the inode number should match until
1636 * they close it. Beyond that, we don't
1637 * care.
1638 */
1639 dentry = next->s_dentry;
1640 if (dentry)
1641 inode = d_inode(dentry);
1642 if (inode)
1643 ino = inode->i_ino;
1644 spin_unlock(lock: &configfs_dirent_lock);
1645 if (!inode)
1646 ino = iunique(sb, 2);
1647
1648 name = configfs_get_name(sd: next);
1649 len = strlen(name);
1650
1651 if (!dir_emit(ctx, name, namelen: len, ino,
1652 type: fs_umode_to_dtype(mode: next->s_mode)))
1653 return 0;
1654
1655 spin_lock(lock: &configfs_dirent_lock);
1656 list_move(list: q, head: p);
1657 p = q;
1658 ctx->pos++;
1659 }
1660 spin_unlock(lock: &configfs_dirent_lock);
1661 return 0;
1662}
1663
1664static loff_t configfs_dir_lseek(struct file *file, loff_t offset, int whence)
1665{
1666 struct dentry * dentry = file->f_path.dentry;
1667
1668 switch (whence) {
1669 case 1:
1670 offset += file->f_pos;
1671 fallthrough;
1672 case 0:
1673 if (offset >= 0)
1674 break;
1675 fallthrough;
1676 default:
1677 return -EINVAL;
1678 }
1679 if (offset != file->f_pos) {
1680 file->f_pos = offset;
1681 if (file->f_pos >= 2) {
1682 struct configfs_dirent *sd = dentry->d_fsdata;
1683 struct configfs_dirent *cursor = file->private_data;
1684 struct list_head *p;
1685 loff_t n = file->f_pos - 2;
1686
1687 spin_lock(lock: &configfs_dirent_lock);
1688 list_del(entry: &cursor->s_sibling);
1689 p = sd->s_children.next;
1690 while (n && p != &sd->s_children) {
1691 struct configfs_dirent *next;
1692 next = list_entry(p, struct configfs_dirent,
1693 s_sibling);
1694 if (next->s_element)
1695 n--;
1696 p = p->next;
1697 }
1698 list_add_tail(new: &cursor->s_sibling, head: p);
1699 spin_unlock(lock: &configfs_dirent_lock);
1700 }
1701 }
1702 return offset;
1703}
1704
1705const struct file_operations configfs_dir_operations = {
1706 .open = configfs_dir_open,
1707 .release = configfs_dir_close,
1708 .llseek = configfs_dir_lseek,
1709 .read = generic_read_dir,
1710 .iterate_shared = configfs_readdir,
1711};
1712
1713/**
1714 * configfs_register_group - creates a parent-child relation between two groups
1715 * @parent_group: parent group
1716 * @group: child group
1717 *
1718 * link groups, creates dentry for the child and attaches it to the
1719 * parent dentry.
1720 *
1721 * Return: 0 on success, negative errno code on error
1722 */
1723int configfs_register_group(struct config_group *parent_group,
1724 struct config_group *group)
1725{
1726 struct configfs_subsystem *subsys = parent_group->cg_subsys;
1727 struct dentry *parent;
1728 struct configfs_fragment *frag;
1729 int ret;
1730
1731 frag = new_fragment();
1732 if (!frag)
1733 return -ENOMEM;
1734
1735 mutex_lock(&subsys->su_mutex);
1736 link_group(parent_group, group);
1737 mutex_unlock(lock: &subsys->su_mutex);
1738
1739 parent = parent_group->cg_item.ci_dentry;
1740
1741 inode_lock_nested(inode: d_inode(dentry: parent), subclass: I_MUTEX_PARENT);
1742 ret = create_default_group(parent_group, group, frag);
1743 if (ret)
1744 goto err_out;
1745
1746 spin_lock(lock: &configfs_dirent_lock);
1747 configfs_dir_set_ready(sd: group->cg_item.ci_dentry->d_fsdata);
1748 spin_unlock(lock: &configfs_dirent_lock);
1749 inode_unlock(inode: d_inode(dentry: parent));
1750 put_fragment(frag);
1751 return 0;
1752err_out:
1753 inode_unlock(inode: d_inode(dentry: parent));
1754 mutex_lock(&subsys->su_mutex);
1755 unlink_group(group);
1756 mutex_unlock(lock: &subsys->su_mutex);
1757 put_fragment(frag);
1758 return ret;
1759}
1760EXPORT_SYMBOL(configfs_register_group);
1761
1762/**
1763 * configfs_unregister_group() - unregisters a child group from its parent
1764 * @group: parent group to be unregistered
1765 *
1766 * Undoes configfs_register_group()
1767 */
1768void configfs_unregister_group(struct config_group *group)
1769{
1770 struct configfs_subsystem *subsys = group->cg_subsys;
1771 struct dentry *dentry = group->cg_item.ci_dentry;
1772 struct dentry *parent = group->cg_item.ci_parent->ci_dentry;
1773 struct configfs_dirent *sd = dentry->d_fsdata;
1774 struct configfs_fragment *frag = sd->s_frag;
1775
1776 down_write(sem: &frag->frag_sem);
1777 frag->frag_dead = true;
1778 up_write(sem: &frag->frag_sem);
1779
1780 inode_lock_nested(inode: d_inode(dentry: parent), subclass: I_MUTEX_PARENT);
1781 spin_lock(lock: &configfs_dirent_lock);
1782 configfs_detach_prep(dentry, NULL);
1783 spin_unlock(lock: &configfs_dirent_lock);
1784
1785 configfs_detach_group(item: &group->cg_item);
1786 d_inode(dentry)->i_flags |= S_DEAD;
1787 dont_mount(dentry);
1788 d_drop(dentry);
1789 fsnotify_rmdir(dir: d_inode(dentry: parent), dentry);
1790 inode_unlock(inode: d_inode(dentry: parent));
1791
1792 dput(dentry);
1793
1794 mutex_lock(&subsys->su_mutex);
1795 unlink_group(group);
1796 mutex_unlock(lock: &subsys->su_mutex);
1797}
1798EXPORT_SYMBOL(configfs_unregister_group);
1799
1800/**
1801 * configfs_register_default_group() - allocates and registers a child group
1802 * @parent_group: parent group
1803 * @name: child group name
1804 * @item_type: child item type description
1805 *
1806 * boilerplate to allocate and register a child group with its parent. We need
1807 * kzalloc'ed memory because child's default_group is initially empty.
1808 *
1809 * Return: allocated config group or ERR_PTR() on error
1810 */
1811struct config_group *
1812configfs_register_default_group(struct config_group *parent_group,
1813 const char *name,
1814 const struct config_item_type *item_type)
1815{
1816 int ret;
1817 struct config_group *group;
1818
1819 group = kzalloc(size: sizeof(*group), GFP_KERNEL);
1820 if (!group)
1821 return ERR_PTR(error: -ENOMEM);
1822 config_group_init_type_name(group, name, type: item_type);
1823
1824 ret = configfs_register_group(parent_group, group);
1825 if (ret) {
1826 kfree(objp: group);
1827 return ERR_PTR(error: ret);
1828 }
1829 return group;
1830}
1831EXPORT_SYMBOL(configfs_register_default_group);
1832
1833/**
1834 * configfs_unregister_default_group() - unregisters and frees a child group
1835 * @group: the group to act on
1836 */
1837void configfs_unregister_default_group(struct config_group *group)
1838{
1839 configfs_unregister_group(group);
1840 kfree(objp: group);
1841}
1842EXPORT_SYMBOL(configfs_unregister_default_group);
1843
1844int configfs_register_subsystem(struct configfs_subsystem *subsys)
1845{
1846 int err;
1847 struct config_group *group = &subsys->su_group;
1848 struct dentry *dentry;
1849 struct dentry *root;
1850 struct configfs_dirent *sd;
1851 struct configfs_fragment *frag;
1852
1853 frag = new_fragment();
1854 if (!frag)
1855 return -ENOMEM;
1856
1857 root = configfs_pin_fs();
1858 if (IS_ERR(ptr: root)) {
1859 put_fragment(frag);
1860 return PTR_ERR(ptr: root);
1861 }
1862
1863 if (!group->cg_item.ci_name)
1864 group->cg_item.ci_name = group->cg_item.ci_namebuf;
1865
1866 sd = root->d_fsdata;
1867 mutex_lock(&configfs_subsystem_mutex);
1868 link_group(parent_group: to_config_group(item: sd->s_element), group);
1869 mutex_unlock(lock: &configfs_subsystem_mutex);
1870
1871 inode_lock_nested(inode: d_inode(dentry: root), subclass: I_MUTEX_PARENT);
1872
1873 err = -ENOMEM;
1874 dentry = d_alloc_name(root, group->cg_item.ci_name);
1875 if (dentry) {
1876 d_add(dentry, NULL);
1877
1878 err = configfs_attach_group(parent_item: sd->s_element, item: &group->cg_item,
1879 dentry, frag);
1880 if (err) {
1881 BUG_ON(d_inode(dentry));
1882 d_drop(dentry);
1883 dput(dentry);
1884 } else {
1885 spin_lock(lock: &configfs_dirent_lock);
1886 configfs_dir_set_ready(sd: dentry->d_fsdata);
1887 spin_unlock(lock: &configfs_dirent_lock);
1888 }
1889 }
1890
1891 inode_unlock(inode: d_inode(dentry: root));
1892
1893 if (err) {
1894 mutex_lock(&configfs_subsystem_mutex);
1895 unlink_group(group);
1896 mutex_unlock(lock: &configfs_subsystem_mutex);
1897 configfs_release_fs();
1898 }
1899 put_fragment(frag);
1900
1901 return err;
1902}
1903
1904void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
1905{
1906 struct config_group *group = &subsys->su_group;
1907 struct dentry *dentry = group->cg_item.ci_dentry;
1908 struct dentry *root = dentry->d_sb->s_root;
1909 struct configfs_dirent *sd = dentry->d_fsdata;
1910 struct configfs_fragment *frag = sd->s_frag;
1911
1912 if (dentry->d_parent != root) {
1913 pr_err("Tried to unregister non-subsystem!\n");
1914 return;
1915 }
1916
1917 down_write(sem: &frag->frag_sem);
1918 frag->frag_dead = true;
1919 up_write(sem: &frag->frag_sem);
1920
1921 inode_lock_nested(inode: d_inode(dentry: root),
1922 subclass: I_MUTEX_PARENT);
1923 inode_lock_nested(inode: d_inode(dentry), subclass: I_MUTEX_CHILD);
1924 mutex_lock(&configfs_symlink_mutex);
1925 spin_lock(lock: &configfs_dirent_lock);
1926 if (configfs_detach_prep(dentry, NULL)) {
1927 pr_err("Tried to unregister non-empty subsystem!\n");
1928 }
1929 spin_unlock(lock: &configfs_dirent_lock);
1930 mutex_unlock(lock: &configfs_symlink_mutex);
1931 configfs_detach_group(item: &group->cg_item);
1932 d_inode(dentry)->i_flags |= S_DEAD;
1933 dont_mount(dentry);
1934 inode_unlock(inode: d_inode(dentry));
1935
1936 d_drop(dentry);
1937 fsnotify_rmdir(dir: d_inode(dentry: root), dentry);
1938
1939 inode_unlock(inode: d_inode(dentry: root));
1940
1941 dput(dentry);
1942
1943 mutex_lock(&configfs_subsystem_mutex);
1944 unlink_group(group);
1945 mutex_unlock(lock: &configfs_subsystem_mutex);
1946 configfs_release_fs();
1947}
1948
1949EXPORT_SYMBOL(configfs_register_subsystem);
1950EXPORT_SYMBOL(configfs_unregister_subsystem);
1951

source code of linux/fs/configfs/dir.c