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TOMOYO Linux Cross Reference
Linux/fs/configfs/dir.c

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  1 /* -*- mode: c; c-basic-offset: 8; -*-
  2  * vim: noexpandtab sw=8 ts=8 sts=0:
  3  *
  4  * dir.c - Operations for configfs directories.
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public
  8  * License as published by the Free Software Foundation; either
  9  * version 2 of the License, or (at your option) any later version.
 10  *
 11  * This program is distributed in the hope that it will be useful,
 12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 14  * General Public License for more details.
 15  *
 16  * You should have received a copy of the GNU General Public
 17  * License along with this program; if not, write to the
 18  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 19  * Boston, MA 021110-1307, USA.
 20  *
 21  * Based on sysfs:
 22  *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
 23  *
 24  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
 25  */
 26 
 27 #undef DEBUG
 28 
 29 #include <linux/fs.h>
 30 #include <linux/mount.h>
 31 #include <linux/module.h>
 32 #include <linux/slab.h>
 33 #include <linux/err.h>
 34 
 35 #include <linux/configfs.h>
 36 #include "configfs_internal.h"
 37 
 38 DECLARE_RWSEM(configfs_rename_sem);
 39 /*
 40  * Protects mutations of configfs_dirent linkage together with proper i_mutex
 41  * Also protects mutations of symlinks linkage to target configfs_dirent
 42  * Mutators of configfs_dirent linkage must *both* have the proper inode locked
 43  * and configfs_dirent_lock locked, in that order.
 44  * This allows one to safely traverse configfs_dirent trees and symlinks without
 45  * having to lock inodes.
 46  *
 47  * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
 48  * unlocked is not reliable unless in detach_groups() called from
 49  * rmdir()/unregister() and from configfs_attach_group()
 50  */
 51 DEFINE_SPINLOCK(configfs_dirent_lock);
 52 
 53 static void configfs_d_iput(struct dentry * dentry,
 54                             struct inode * inode)
 55 {
 56         struct configfs_dirent *sd = dentry->d_fsdata;
 57 
 58         if (sd) {
 59                 /* Coordinate with configfs_readdir */
 60                 spin_lock(&configfs_dirent_lock);
 61                 /* Coordinate with configfs_attach_attr where will increase
 62                  * sd->s_count and update sd->s_dentry to new allocated one.
 63                  * Only set sd->dentry to null when this dentry is the only
 64                  * sd owner.
 65                  * If not do so, configfs_d_iput may run just after
 66                  * configfs_attach_attr and set sd->s_dentry to null
 67                  * even it's still in use.
 68                  */
 69                 if (atomic_read(&sd->s_count) <= 2)
 70                         sd->s_dentry = NULL;
 71 
 72                 spin_unlock(&configfs_dirent_lock);
 73                 configfs_put(sd);
 74         }
 75         iput(inode);
 76 }
 77 
 78 const struct dentry_operations configfs_dentry_ops = {
 79         .d_iput         = configfs_d_iput,
 80         .d_delete       = always_delete_dentry,
 81 };
 82 
 83 #ifdef CONFIG_LOCKDEP
 84 
 85 /*
 86  * Helpers to make lockdep happy with our recursive locking of default groups'
 87  * inodes (see configfs_attach_group() and configfs_detach_group()).
 88  * We put default groups i_mutexes in separate classes according to their depth
 89  * from the youngest non-default group ancestor.
 90  *
 91  * For a non-default group A having default groups A/B, A/C, and A/C/D, default
 92  * groups A/B and A/C will have their inode's mutex in class
 93  * default_group_class[0], and default group A/C/D will be in
 94  * default_group_class[1].
 95  *
 96  * The lock classes are declared and assigned in inode.c, according to the
 97  * s_depth value.
 98  * The s_depth value is initialized to -1, adjusted to >= 0 when attaching
 99  * default groups, and reset to -1 when all default groups are attached. During
100  * attachment, if configfs_create() sees s_depth > 0, the lock class of the new
101  * inode's mutex is set to default_group_class[s_depth - 1].
102  */
103 
104 static void configfs_init_dirent_depth(struct configfs_dirent *sd)
105 {
106         sd->s_depth = -1;
107 }
108 
109 static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
110                                           struct configfs_dirent *sd)
111 {
112         int parent_depth = parent_sd->s_depth;
113 
114         if (parent_depth >= 0)
115                 sd->s_depth = parent_depth + 1;
116 }
117 
118 static void
119 configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
120 {
121         /*
122          * item's i_mutex class is already setup, so s_depth is now only
123          * used to set new sub-directories s_depth, which is always done
124          * with item's i_mutex locked.
125          */
126         /*
127          *  sd->s_depth == -1 iff we are a non default group.
128          *  else (we are a default group) sd->s_depth > 0 (see
129          *  create_dir()).
130          */
131         if (sd->s_depth == -1)
132                 /*
133                  * We are a non default group and we are going to create
134                  * default groups.
135                  */
136                 sd->s_depth = 0;
137 }
138 
139 static void
140 configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
141 {
142         /* We will not create default groups anymore. */
143         sd->s_depth = -1;
144 }
145 
146 #else /* CONFIG_LOCKDEP */
147 
148 static void configfs_init_dirent_depth(struct configfs_dirent *sd)
149 {
150 }
151 
152 static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
153                                           struct configfs_dirent *sd)
154 {
155 }
156 
157 static void
158 configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
159 {
160 }
161 
162 static void
163 configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
164 {
165 }
166 
167 #endif /* CONFIG_LOCKDEP */
168 
169 /*
170  * Allocates a new configfs_dirent and links it to the parent configfs_dirent
171  */
172 static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd,
173                                                    void *element, int type)
174 {
175         struct configfs_dirent * sd;
176 
177         sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
178         if (!sd)
179                 return ERR_PTR(-ENOMEM);
180 
181         atomic_set(&sd->s_count, 1);
182         INIT_LIST_HEAD(&sd->s_links);
183         INIT_LIST_HEAD(&sd->s_children);
184         sd->s_element = element;
185         sd->s_type = type;
186         configfs_init_dirent_depth(sd);
187         spin_lock(&configfs_dirent_lock);
188         if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
189                 spin_unlock(&configfs_dirent_lock);
190                 kmem_cache_free(configfs_dir_cachep, sd);
191                 return ERR_PTR(-ENOENT);
192         }
193         list_add(&sd->s_sibling, &parent_sd->s_children);
194         spin_unlock(&configfs_dirent_lock);
195 
196         return sd;
197 }
198 
199 /*
200  *
201  * Return -EEXIST if there is already a configfs element with the same
202  * name for the same parent.
203  *
204  * called with parent inode's i_mutex held
205  */
206 static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
207                                   const unsigned char *new)
208 {
209         struct configfs_dirent * sd;
210 
211         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
212                 if (sd->s_element) {
213                         const unsigned char *existing = configfs_get_name(sd);
214                         if (strcmp(existing, new))
215                                 continue;
216                         else
217                                 return -EEXIST;
218                 }
219         }
220 
221         return 0;
222 }
223 
224 
225 int configfs_make_dirent(struct configfs_dirent * parent_sd,
226                          struct dentry * dentry, void * element,
227                          umode_t mode, int type)
228 {
229         struct configfs_dirent * sd;
230 
231         sd = configfs_new_dirent(parent_sd, element, type);
232         if (IS_ERR(sd))
233                 return PTR_ERR(sd);
234 
235         sd->s_mode = mode;
236         sd->s_dentry = dentry;
237         if (dentry)
238                 dentry->d_fsdata = configfs_get(sd);
239 
240         return 0;
241 }
242 
243 static void init_dir(struct inode * inode)
244 {
245         inode->i_op = &configfs_dir_inode_operations;
246         inode->i_fop = &configfs_dir_operations;
247 
248         /* directory inodes start off with i_nlink == 2 (for "." entry) */
249         inc_nlink(inode);
250 }
251 
252 static void configfs_init_file(struct inode * inode)
253 {
254         inode->i_size = PAGE_SIZE;
255         inode->i_fop = &configfs_file_operations;
256 }
257 
258 static void configfs_init_bin_file(struct inode *inode)
259 {
260         inode->i_size = 0;
261         inode->i_fop = &configfs_bin_file_operations;
262 }
263 
264 static void init_symlink(struct inode * inode)
265 {
266         inode->i_op = &configfs_symlink_inode_operations;
267 }
268 
269 /**
270  *      configfs_create_dir - create a directory for an config_item.
271  *      @item:          config_itemwe're creating directory for.
272  *      @dentry:        config_item's dentry.
273  *
274  *      Note: user-created entries won't be allowed under this new directory
275  *      until it is validated by configfs_dir_set_ready()
276  */
277 
278 static int configfs_create_dir(struct config_item *item, struct dentry *dentry)
279 {
280         int error;
281         umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
282         struct dentry *p = dentry->d_parent;
283 
284         BUG_ON(!item);
285 
286         error = configfs_dirent_exists(p->d_fsdata, dentry->d_name.name);
287         if (unlikely(error))
288                 return error;
289 
290         error = configfs_make_dirent(p->d_fsdata, dentry, item, mode,
291                                      CONFIGFS_DIR | CONFIGFS_USET_CREATING);
292         if (unlikely(error))
293                 return error;
294 
295         configfs_set_dir_dirent_depth(p->d_fsdata, dentry->d_fsdata);
296         error = configfs_create(dentry, mode, init_dir);
297         if (!error) {
298                 inc_nlink(d_inode(p));
299                 item->ci_dentry = dentry;
300         } else {
301                 struct configfs_dirent *sd = dentry->d_fsdata;
302                 if (sd) {
303                         spin_lock(&configfs_dirent_lock);
304                         list_del_init(&sd->s_sibling);
305                         spin_unlock(&configfs_dirent_lock);
306                         configfs_put(sd);
307                 }
308         }
309         return error;
310 }
311 
312 /*
313  * Allow userspace to create new entries under a new directory created with
314  * configfs_create_dir(), and under all of its chidlren directories recursively.
315  * @sd          configfs_dirent of the new directory to validate
316  *
317  * Caller must hold configfs_dirent_lock.
318  */
319 static void configfs_dir_set_ready(struct configfs_dirent *sd)
320 {
321         struct configfs_dirent *child_sd;
322 
323         sd->s_type &= ~CONFIGFS_USET_CREATING;
324         list_for_each_entry(child_sd, &sd->s_children, s_sibling)
325                 if (child_sd->s_type & CONFIGFS_USET_CREATING)
326                         configfs_dir_set_ready(child_sd);
327 }
328 
329 /*
330  * Check that a directory does not belong to a directory hierarchy being
331  * attached and not validated yet.
332  * @sd          configfs_dirent of the directory to check
333  *
334  * @return      non-zero iff the directory was validated
335  *
336  * Note: takes configfs_dirent_lock, so the result may change from false to true
337  * in two consecutive calls, but never from true to false.
338  */
339 int configfs_dirent_is_ready(struct configfs_dirent *sd)
340 {
341         int ret;
342 
343         spin_lock(&configfs_dirent_lock);
344         ret = !(sd->s_type & CONFIGFS_USET_CREATING);
345         spin_unlock(&configfs_dirent_lock);
346 
347         return ret;
348 }
349 
350 int configfs_create_link(struct configfs_symlink *sl,
351                          struct dentry *parent,
352                          struct dentry *dentry)
353 {
354         int err = 0;
355         umode_t mode = S_IFLNK | S_IRWXUGO;
356 
357         err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
358                                    CONFIGFS_ITEM_LINK);
359         if (!err) {
360                 err = configfs_create(dentry, mode, init_symlink);
361                 if (err) {
362                         struct configfs_dirent *sd = dentry->d_fsdata;
363                         if (sd) {
364                                 spin_lock(&configfs_dirent_lock);
365                                 list_del_init(&sd->s_sibling);
366                                 spin_unlock(&configfs_dirent_lock);
367                                 configfs_put(sd);
368                         }
369                 }
370         }
371         return err;
372 }
373 
374 static void remove_dir(struct dentry * d)
375 {
376         struct dentry * parent = dget(d->d_parent);
377         struct configfs_dirent * sd;
378 
379         sd = d->d_fsdata;
380         spin_lock(&configfs_dirent_lock);
381         list_del_init(&sd->s_sibling);
382         spin_unlock(&configfs_dirent_lock);
383         configfs_put(sd);
384         if (d_really_is_positive(d))
385                 simple_rmdir(d_inode(parent),d);
386 
387         pr_debug(" o %pd removing done (%d)\n", d, d_count(d));
388 
389         dput(parent);
390 }
391 
392 /**
393  * configfs_remove_dir - remove an config_item's directory.
394  * @item:       config_item we're removing.
395  *
396  * The only thing special about this is that we remove any files in
397  * the directory before we remove the directory, and we've inlined
398  * what used to be configfs_rmdir() below, instead of calling separately.
399  *
400  * Caller holds the mutex of the item's inode
401  */
402 
403 static void configfs_remove_dir(struct config_item * item)
404 {
405         struct dentry * dentry = dget(item->ci_dentry);
406 
407         if (!dentry)
408                 return;
409 
410         remove_dir(dentry);
411         /**
412          * Drop reference from dget() on entrance.
413          */
414         dput(dentry);
415 }
416 
417 
418 /* attaches attribute's configfs_dirent to the dentry corresponding to the
419  * attribute file
420  */
421 static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * dentry)
422 {
423         struct configfs_attribute * attr = sd->s_element;
424         int error;
425 
426         spin_lock(&configfs_dirent_lock);
427         dentry->d_fsdata = configfs_get(sd);
428         sd->s_dentry = dentry;
429         spin_unlock(&configfs_dirent_lock);
430 
431         error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
432                                 (sd->s_type & CONFIGFS_ITEM_BIN_ATTR) ?
433                                         configfs_init_bin_file :
434                                         configfs_init_file);
435         if (error)
436                 configfs_put(sd);
437         return error;
438 }
439 
440 static struct dentry * configfs_lookup(struct inode *dir,
441                                        struct dentry *dentry,
442                                        unsigned int flags)
443 {
444         struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
445         struct configfs_dirent * sd;
446         int found = 0;
447         int err;
448 
449         /*
450          * Fake invisibility if dir belongs to a group/default groups hierarchy
451          * being attached
452          *
453          * This forbids userspace to read/write attributes of items which may
454          * not complete their initialization, since the dentries of the
455          * attributes won't be instantiated.
456          */
457         err = -ENOENT;
458         if (!configfs_dirent_is_ready(parent_sd))
459                 goto out;
460 
461         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
462                 if (sd->s_type & CONFIGFS_NOT_PINNED) {
463                         const unsigned char * name = configfs_get_name(sd);
464 
465                         if (strcmp(name, dentry->d_name.name))
466                                 continue;
467 
468                         found = 1;
469                         err = configfs_attach_attr(sd, dentry);
470                         break;
471                 }
472         }
473 
474         if (!found) {
475                 /*
476                  * If it doesn't exist and it isn't a NOT_PINNED item,
477                  * it must be negative.
478                  */
479                 if (dentry->d_name.len > NAME_MAX)
480                         return ERR_PTR(-ENAMETOOLONG);
481                 d_add(dentry, NULL);
482                 return NULL;
483         }
484 
485 out:
486         return ERR_PTR(err);
487 }
488 
489 /*
490  * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
491  * attributes and are removed by rmdir().  We recurse, setting
492  * CONFIGFS_USET_DROPPING on all children that are candidates for
493  * default detach.
494  * If there is an error, the caller will reset the flags via
495  * configfs_detach_rollback().
496  */
497 static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex)
498 {
499         struct configfs_dirent *parent_sd = dentry->d_fsdata;
500         struct configfs_dirent *sd;
501         int ret;
502 
503         /* Mark that we're trying to drop the group */
504         parent_sd->s_type |= CONFIGFS_USET_DROPPING;
505 
506         ret = -EBUSY;
507         if (!list_empty(&parent_sd->s_links))
508                 goto out;
509 
510         ret = 0;
511         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
512                 if (!sd->s_element ||
513                     (sd->s_type & CONFIGFS_NOT_PINNED))
514                         continue;
515                 if (sd->s_type & CONFIGFS_USET_DEFAULT) {
516                         /* Abort if racing with mkdir() */
517                         if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
518                                 if (wait_mutex)
519                                         *wait_mutex = &d_inode(sd->s_dentry)->i_mutex;
520                                 return -EAGAIN;
521                         }
522 
523                         /*
524                          * Yup, recursive.  If there's a problem, blame
525                          * deep nesting of default_groups
526                          */
527                         ret = configfs_detach_prep(sd->s_dentry, wait_mutex);
528                         if (!ret)
529                                 continue;
530                 } else
531                         ret = -ENOTEMPTY;
532 
533                 break;
534         }
535 
536 out:
537         return ret;
538 }
539 
540 /*
541  * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
542  * set.
543  */
544 static void configfs_detach_rollback(struct dentry *dentry)
545 {
546         struct configfs_dirent *parent_sd = dentry->d_fsdata;
547         struct configfs_dirent *sd;
548 
549         parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
550 
551         list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
552                 if (sd->s_type & CONFIGFS_USET_DEFAULT)
553                         configfs_detach_rollback(sd->s_dentry);
554 }
555 
556 static void detach_attrs(struct config_item * item)
557 {
558         struct dentry * dentry = dget(item->ci_dentry);
559         struct configfs_dirent * parent_sd;
560         struct configfs_dirent * sd, * tmp;
561 
562         if (!dentry)
563                 return;
564 
565         pr_debug("configfs %s: dropping attrs for  dir\n",
566                  dentry->d_name.name);
567 
568         parent_sd = dentry->d_fsdata;
569         list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
570                 if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED))
571                         continue;
572                 spin_lock(&configfs_dirent_lock);
573                 list_del_init(&sd->s_sibling);
574                 spin_unlock(&configfs_dirent_lock);
575                 configfs_drop_dentry(sd, dentry);
576                 configfs_put(sd);
577         }
578 
579         /**
580          * Drop reference from dget() on entrance.
581          */
582         dput(dentry);
583 }
584 
585 static int populate_attrs(struct config_item *item)
586 {
587         struct config_item_type *t = item->ci_type;
588         struct configfs_attribute *attr;
589         struct configfs_bin_attribute *bin_attr;
590         int error = 0;
591         int i;
592 
593         if (!t)
594                 return -EINVAL;
595         if (t->ct_attrs) {
596                 for (i = 0; (attr = t->ct_attrs[i]) != NULL; i++) {
597                         if ((error = configfs_create_file(item, attr)))
598                                 break;
599                 }
600         }
601         if (t->ct_bin_attrs) {
602                 for (i = 0; (bin_attr = t->ct_bin_attrs[i]) != NULL; i++) {
603                         error = configfs_create_bin_file(item, bin_attr);
604                         if (error)
605                                 break;
606                 }
607         }
608 
609         if (error)
610                 detach_attrs(item);
611 
612         return error;
613 }
614 
615 static int configfs_attach_group(struct config_item *parent_item,
616                                  struct config_item *item,
617                                  struct dentry *dentry);
618 static void configfs_detach_group(struct config_item *item);
619 
620 static void detach_groups(struct config_group *group)
621 {
622         struct dentry * dentry = dget(group->cg_item.ci_dentry);
623         struct dentry *child;
624         struct configfs_dirent *parent_sd;
625         struct configfs_dirent *sd, *tmp;
626 
627         if (!dentry)
628                 return;
629 
630         parent_sd = dentry->d_fsdata;
631         list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
632                 if (!sd->s_element ||
633                     !(sd->s_type & CONFIGFS_USET_DEFAULT))
634                         continue;
635 
636                 child = sd->s_dentry;
637 
638                 inode_lock(d_inode(child));
639 
640                 configfs_detach_group(sd->s_element);
641                 d_inode(child)->i_flags |= S_DEAD;
642                 dont_mount(child);
643 
644                 inode_unlock(d_inode(child));
645 
646                 d_delete(child);
647                 dput(child);
648         }
649 
650         /**
651          * Drop reference from dget() on entrance.
652          */
653         dput(dentry);
654 }
655 
656 /*
657  * This fakes mkdir(2) on a default_groups[] entry.  It
658  * creates a dentry, attachs it, and then does fixup
659  * on the sd->s_type.
660  *
661  * We could, perhaps, tweak our parent's ->mkdir for a minute and
662  * try using vfs_mkdir.  Just a thought.
663  */
664 static int create_default_group(struct config_group *parent_group,
665                                 struct config_group *group)
666 {
667         int ret;
668         struct configfs_dirent *sd;
669         /* We trust the caller holds a reference to parent */
670         struct dentry *child, *parent = parent_group->cg_item.ci_dentry;
671 
672         if (!group->cg_item.ci_name)
673                 group->cg_item.ci_name = group->cg_item.ci_namebuf;
674 
675         ret = -ENOMEM;
676         child = d_alloc_name(parent, group->cg_item.ci_name);
677         if (child) {
678                 d_add(child, NULL);
679 
680                 ret = configfs_attach_group(&parent_group->cg_item,
681                                             &group->cg_item, child);
682                 if (!ret) {
683                         sd = child->d_fsdata;
684                         sd->s_type |= CONFIGFS_USET_DEFAULT;
685                 } else {
686                         BUG_ON(d_inode(child));
687                         d_drop(child);
688                         dput(child);
689                 }
690         }
691 
692         return ret;
693 }
694 
695 static int populate_groups(struct config_group *group)
696 {
697         struct config_group *new_group;
698         int ret = 0;
699 
700         list_for_each_entry(new_group, &group->default_groups, group_entry) {
701                 ret = create_default_group(group, new_group);
702                 if (ret) {
703                         detach_groups(group);
704                         break;
705                 }
706         }
707 
708         return ret;
709 }
710 
711 void configfs_remove_default_groups(struct config_group *group)
712 {
713         struct config_group *g, *n;
714 
715         list_for_each_entry_safe(g, n, &group->default_groups, group_entry) {
716                 list_del(&g->group_entry);
717                 config_item_put(&g->cg_item);
718         }
719 }
720 EXPORT_SYMBOL(configfs_remove_default_groups);
721 
722 /*
723  * All of link_obj/unlink_obj/link_group/unlink_group require that
724  * subsys->su_mutex is held.
725  */
726 
727 static void unlink_obj(struct config_item *item)
728 {
729         struct config_group *group;
730 
731         group = item->ci_group;
732         if (group) {
733                 list_del_init(&item->ci_entry);
734 
735                 item->ci_group = NULL;
736                 item->ci_parent = NULL;
737 
738                 /* Drop the reference for ci_entry */
739                 config_item_put(item);
740 
741                 /* Drop the reference for ci_parent */
742                 config_group_put(group);
743         }
744 }
745 
746 static void link_obj(struct config_item *parent_item, struct config_item *item)
747 {
748         /*
749          * Parent seems redundant with group, but it makes certain
750          * traversals much nicer.
751          */
752         item->ci_parent = parent_item;
753 
754         /*
755          * We hold a reference on the parent for the child's ci_parent
756          * link.
757          */
758         item->ci_group = config_group_get(to_config_group(parent_item));
759         list_add_tail(&item->ci_entry, &item->ci_group->cg_children);
760 
761         /*
762          * We hold a reference on the child for ci_entry on the parent's
763          * cg_children
764          */
765         config_item_get(item);
766 }
767 
768 static void unlink_group(struct config_group *group)
769 {
770         struct config_group *new_group;
771 
772         list_for_each_entry(new_group, &group->default_groups, group_entry)
773                 unlink_group(new_group);
774 
775         group->cg_subsys = NULL;
776         unlink_obj(&group->cg_item);
777 }
778 
779 static void link_group(struct config_group *parent_group, struct config_group *group)
780 {
781         struct config_group *new_group;
782         struct configfs_subsystem *subsys = NULL; /* gcc is a turd */
783 
784         link_obj(&parent_group->cg_item, &group->cg_item);
785 
786         if (parent_group->cg_subsys)
787                 subsys = parent_group->cg_subsys;
788         else if (configfs_is_root(&parent_group->cg_item))
789                 subsys = to_configfs_subsystem(group);
790         else
791                 BUG();
792         group->cg_subsys = subsys;
793 
794         list_for_each_entry(new_group, &group->default_groups, group_entry)
795                 link_group(group, new_group);
796 }
797 
798 /*
799  * The goal is that configfs_attach_item() (and
800  * configfs_attach_group()) can be called from either the VFS or this
801  * module.  That is, they assume that the items have been created,
802  * the dentry allocated, and the dcache is all ready to go.
803  *
804  * If they fail, they must clean up after themselves as if they
805  * had never been called.  The caller (VFS or local function) will
806  * handle cleaning up the dcache bits.
807  *
808  * configfs_detach_group() and configfs_detach_item() behave similarly on
809  * the way out.  They assume that the proper semaphores are held, they
810  * clean up the configfs items, and they expect their callers will
811  * handle the dcache bits.
812  */
813 static int configfs_attach_item(struct config_item *parent_item,
814                                 struct config_item *item,
815                                 struct dentry *dentry)
816 {
817         int ret;
818 
819         ret = configfs_create_dir(item, dentry);
820         if (!ret) {
821                 ret = populate_attrs(item);
822                 if (ret) {
823                         /*
824                          * We are going to remove an inode and its dentry but
825                          * the VFS may already have hit and used them. Thus,
826                          * we must lock them as rmdir() would.
827                          */
828                         inode_lock(d_inode(dentry));
829                         configfs_remove_dir(item);
830                         d_inode(dentry)->i_flags |= S_DEAD;
831                         dont_mount(dentry);
832                         inode_unlock(d_inode(dentry));
833                         d_delete(dentry);
834                 }
835         }
836 
837         return ret;
838 }
839 
840 /* Caller holds the mutex of the item's inode */
841 static void configfs_detach_item(struct config_item *item)
842 {
843         detach_attrs(item);
844         configfs_remove_dir(item);
845 }
846 
847 static int configfs_attach_group(struct config_item *parent_item,
848                                  struct config_item *item,
849                                  struct dentry *dentry)
850 {
851         int ret;
852         struct configfs_dirent *sd;
853 
854         ret = configfs_attach_item(parent_item, item, dentry);
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(d_inode(dentry), I_MUTEX_CHILD);
869                 configfs_adjust_dir_dirent_depth_before_populate(sd);
870                 ret = populate_groups(to_config_group(item));
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(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 */
886 static void configfs_detach_group(struct config_item *item)
887 {
888         detach_groups(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  */
901 static void client_disconnect_notify(struct config_item *parent_item,
902                                      struct config_item *item)
903 {
904         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(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  */
920 static void client_drop_item(struct config_item *parent_item,
921                              struct config_item *item)
922 {
923         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(parent_item),
934                                               item);
935         else
936                 config_item_put(item);
937 }
938 
939 #ifdef DEBUG
940 static 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 
955 static 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  */
1034 static 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(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 
1060 out:
1061         return ret;
1062 }
1063 
1064 static 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(&configfs_dirent_lock);
1071         /* Scan the tree, return 0 if found */
1072         ret = configfs_depend_prep(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 
1083 out_unlock_dirent_lock:
1084         spin_unlock(&configfs_dirent_lock);
1085 
1086         return ret;
1087 }
1088 
1089 static inline struct configfs_dirent *
1090 configfs_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 
1108 int 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(root))
1122                 return PTR_ERR(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(d_inode(root));
1130 
1131         subsys_sd = configfs_find_subsys_dentry(root->d_fsdata, 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_sd->s_dentry, target);
1139 
1140 out_unlock_fs:
1141         inode_unlock(d_inode(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 }
1151 EXPORT_SYMBOL(configfs_depend_item);
1152 
1153 /*
1154  * Release the dependent linkage.  This is much simpler than
1155  * configfs_depend_item() because we know that that the client driver is
1156  * pinned, thus the subsystem is pinned, and therefore configfs is pinned.
1157  */
1158 void 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(&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(&configfs_dirent_lock);
1178 }
1179 EXPORT_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  */
1190 int 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(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(&parent->cg_item)) {
1208                 target_subsys = to_configfs_subsystem(to_config_group(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(&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(d_inode(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->cg_item.ci_dentry->d_fsdata,
1232                                 &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_sd->s_dentry, target);
1241 
1242         if (target_subsys != caller_subsys)
1243 out_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(d_inode(root->cg_item.ci_dentry));
1249 
1250         return ret;
1251 }
1252 EXPORT_SYMBOL(configfs_depend_item_unlocked);
1253 
1254 static int configfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1255 {
1256         int ret = 0;
1257         int module_got = 0;
1258         struct config_group *group = NULL;
1259         struct config_item *item = NULL;
1260         struct config_item *parent_item;
1261         struct configfs_subsystem *subsys;
1262         struct configfs_dirent *sd;
1263         struct config_item_type *type;
1264         struct module *subsys_owner = NULL, *new_item_owner = NULL;
1265         char *name;
1266 
1267         sd = dentry->d_parent->d_fsdata;
1268 
1269         /*
1270          * Fake invisibility if dir belongs to a group/default groups hierarchy
1271          * being attached
1272          */
1273         if (!configfs_dirent_is_ready(sd)) {
1274                 ret = -ENOENT;
1275                 goto out;
1276         }
1277 
1278         if (!(sd->s_type & CONFIGFS_USET_DIR)) {
1279                 ret = -EPERM;
1280                 goto out;
1281         }
1282 
1283         /* Get a working ref for the duration of this function */
1284         parent_item = configfs_get_config_item(dentry->d_parent);
1285         type = parent_item->ci_type;
1286         subsys = to_config_group(parent_item)->cg_subsys;
1287         BUG_ON(!subsys);
1288 
1289         if (!type || !type->ct_group_ops ||
1290             (!type->ct_group_ops->make_group &&
1291              !type->ct_group_ops->make_item)) {
1292                 ret = -EPERM;  /* Lack-of-mkdir returns -EPERM */
1293                 goto out_put;
1294         }
1295 
1296         /*
1297          * The subsystem may belong to a different module than the item
1298          * being created.  We don't want to safely pin the new item but
1299          * fail to pin the subsystem it sits under.
1300          */
1301         if (!subsys->su_group.cg_item.ci_type) {
1302                 ret = -EINVAL;
1303                 goto out_put;
1304         }
1305         subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
1306         if (!try_module_get(subsys_owner)) {
1307                 ret = -EINVAL;
1308                 goto out_put;
1309         }
1310 
1311         name = kmalloc(dentry->d_name.len + 1, GFP_KERNEL);
1312         if (!name) {
1313                 ret = -ENOMEM;
1314                 goto out_subsys_put;
1315         }
1316 
1317         snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);
1318 
1319         mutex_lock(&subsys->su_mutex);
1320         if (type->ct_group_ops->make_group) {
1321                 group = type->ct_group_ops->make_group(to_config_group(parent_item), name);
1322                 if (!group)
1323                         group = ERR_PTR(-ENOMEM);
1324                 if (!IS_ERR(group)) {
1325                         link_group(to_config_group(parent_item), group);
1326                         item = &group->cg_item;
1327                 } else
1328                         ret = PTR_ERR(group);
1329         } else {
1330                 item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
1331                 if (!item)
1332                         item = ERR_PTR(-ENOMEM);
1333                 if (!IS_ERR(item))
1334                         link_obj(parent_item, item);
1335                 else
1336                         ret = PTR_ERR(item);
1337         }
1338         mutex_unlock(&subsys->su_mutex);
1339 
1340         kfree(name);
1341         if (ret) {
1342                 /*
1343                  * If ret != 0, then link_obj() was never called.
1344                  * There are no extra references to clean up.
1345                  */
1346                 goto out_subsys_put;
1347         }
1348 
1349         /*
1350          * link_obj() has been called (via link_group() for groups).
1351          * From here on out, errors must clean that up.
1352          */
1353 
1354         type = item->ci_type;
1355         if (!type) {
1356                 ret = -EINVAL;
1357                 goto out_unlink;
1358         }
1359 
1360         new_item_owner = type->ct_owner;
1361         if (!try_module_get(new_item_owner)) {
1362                 ret = -EINVAL;
1363                 goto out_unlink;
1364         }
1365 
1366         /*
1367          * I hate doing it this way, but if there is
1368          * an error,  module_put() probably should
1369          * happen after any cleanup.
1370          */
1371         module_got = 1;
1372 
1373         /*
1374          * Make racing rmdir() fail if it did not tag parent with
1375          * CONFIGFS_USET_DROPPING
1376          * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will
1377          * fail and let rmdir() terminate correctly
1378          */
1379         spin_lock(&configfs_dirent_lock);
1380         /* This will make configfs_detach_prep() fail */
1381         sd->s_type |= CONFIGFS_USET_IN_MKDIR;
1382         spin_unlock(&configfs_dirent_lock);
1383 
1384         if (group)
1385                 ret = configfs_attach_group(parent_item, item, dentry);
1386         else
1387                 ret = configfs_attach_item(parent_item, item, dentry);
1388 
1389         spin_lock(&configfs_dirent_lock);
1390         sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
1391         if (!ret)
1392                 configfs_dir_set_ready(dentry->d_fsdata);
1393         spin_unlock(&configfs_dirent_lock);
1394 
1395 out_unlink:
1396         if (ret) {
1397                 /* Tear down everything we built up */
1398                 mutex_lock(&subsys->su_mutex);
1399 
1400                 client_disconnect_notify(parent_item, item);
1401                 if (group)
1402                         unlink_group(group);
1403                 else
1404                         unlink_obj(item);
1405                 client_drop_item(parent_item, item);
1406 
1407                 mutex_unlock(&subsys->su_mutex);
1408 
1409                 if (module_got)
1410                         module_put(new_item_owner);
1411         }
1412 
1413 out_subsys_put:
1414         if (ret)
1415                 module_put(subsys_owner);
1416 
1417 out_put:
1418         /*
1419          * link_obj()/link_group() took a reference from child->parent,
1420          * so the parent is safely pinned.  We can drop our working
1421          * reference.
1422          */
1423         config_item_put(parent_item);
1424 
1425 out:
1426         return ret;
1427 }
1428 
1429 static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
1430 {
1431         struct config_item *parent_item;
1432         struct config_item *item;
1433         struct configfs_subsystem *subsys;
1434         struct configfs_dirent *sd;
1435         struct module *subsys_owner = NULL, *dead_item_owner = NULL;
1436         int ret;
1437 
1438         sd = dentry->d_fsdata;
1439         if (sd->s_type & CONFIGFS_USET_DEFAULT)
1440                 return -EPERM;
1441 
1442         /* Get a working ref until we have the child */
1443         parent_item = configfs_get_config_item(dentry->d_parent);
1444         subsys = to_config_group(parent_item)->cg_subsys;
1445         BUG_ON(!subsys);
1446 
1447         if (!parent_item->ci_type) {
1448                 config_item_put(parent_item);
1449                 return -EINVAL;
1450         }
1451 
1452         /* configfs_mkdir() shouldn't have allowed this */
1453         BUG_ON(!subsys->su_group.cg_item.ci_type);
1454         subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
1455 
1456         /*
1457          * Ensure that no racing symlink() will make detach_prep() fail while
1458          * the new link is temporarily attached
1459          */
1460         do {
1461                 struct mutex *wait_mutex;
1462 
1463                 mutex_lock(&configfs_symlink_mutex);
1464                 spin_lock(&configfs_dirent_lock);
1465                 /*
1466                  * Here's where we check for dependents.  We're protected by
1467                  * configfs_dirent_lock.
1468                  * If no dependent, atomically tag the item as dropping.
1469                  */
1470                 ret = sd->s_dependent_count ? -EBUSY : 0;
1471                 if (!ret) {
1472                         ret = configfs_detach_prep(dentry, &wait_mutex);
1473                         if (ret)
1474                                 configfs_detach_rollback(dentry);
1475                 }
1476                 spin_unlock(&configfs_dirent_lock);
1477                 mutex_unlock(&configfs_symlink_mutex);
1478 
1479                 if (ret) {
1480                         if (ret != -EAGAIN) {
1481                                 config_item_put(parent_item);
1482                                 return ret;
1483                         }
1484 
1485                         /* Wait until the racing operation terminates */
1486                         mutex_lock(wait_mutex);
1487                         mutex_unlock(wait_mutex);
1488                 }
1489         } while (ret == -EAGAIN);
1490 
1491         /* Get a working ref for the duration of this function */
1492         item = configfs_get_config_item(dentry);
1493 
1494         /* Drop reference from above, item already holds one. */
1495         config_item_put(parent_item);
1496 
1497         if (item->ci_type)
1498                 dead_item_owner = item->ci_type->ct_owner;
1499 
1500         if (sd->s_type & CONFIGFS_USET_DIR) {
1501                 configfs_detach_group(item);
1502 
1503                 mutex_lock(&subsys->su_mutex);
1504                 client_disconnect_notify(parent_item, item);
1505                 unlink_group(to_config_group(item));
1506         } else {
1507                 configfs_detach_item(item);
1508 
1509                 mutex_lock(&subsys->su_mutex);
1510                 client_disconnect_notify(parent_item, item);
1511                 unlink_obj(item);
1512         }
1513 
1514         client_drop_item(parent_item, item);
1515         mutex_unlock(&subsys->su_mutex);
1516 
1517         /* Drop our reference from above */
1518         config_item_put(item);
1519 
1520         module_put(dead_item_owner);
1521         module_put(subsys_owner);
1522 
1523         return 0;
1524 }
1525 
1526 const struct inode_operations configfs_dir_inode_operations = {
1527         .mkdir          = configfs_mkdir,
1528         .rmdir          = configfs_rmdir,
1529         .symlink        = configfs_symlink,
1530         .unlink         = configfs_unlink,
1531         .lookup         = configfs_lookup,
1532         .setattr        = configfs_setattr,
1533 };
1534 
1535 const struct inode_operations configfs_root_inode_operations = {
1536         .lookup         = configfs_lookup,
1537         .setattr        = configfs_setattr,
1538 };
1539 
1540 #if 0
1541 int configfs_rename_dir(struct config_item * item, const char *new_name)
1542 {
1543         int error = 0;
1544         struct dentry * new_dentry, * parent;
1545 
1546         if (!strcmp(config_item_name(item), new_name))
1547                 return -EINVAL;
1548 
1549         if (!item->parent)
1550                 return -EINVAL;
1551 
1552         down_write(&configfs_rename_sem);
1553         parent = item->parent->dentry;
1554 
1555         inode_lock(d_inode(parent));
1556 
1557         new_dentry = lookup_one_len(new_name, parent, strlen(new_name));
1558         if (!IS_ERR(new_dentry)) {
1559                 if (d_really_is_negative(new_dentry)) {
1560                         error = config_item_set_name(item, "%s", new_name);
1561                         if (!error) {
1562                                 d_add(new_dentry, NULL);
1563                                 d_move(item->dentry, new_dentry);
1564                         }
1565                         else
1566                                 d_delete(new_dentry);
1567                 } else
1568                         error = -EEXIST;
1569                 dput(new_dentry);
1570         }
1571         inode_unlock(d_inode(parent));
1572         up_write(&configfs_rename_sem);
1573 
1574         return error;
1575 }
1576 #endif
1577 
1578 static int configfs_dir_open(struct inode *inode, struct file *file)
1579 {
1580         struct dentry * dentry = file->f_path.dentry;
1581         struct configfs_dirent * parent_sd = dentry->d_fsdata;
1582         int err;
1583 
1584         inode_lock(d_inode(dentry));
1585         /*
1586          * Fake invisibility if dir belongs to a group/default groups hierarchy
1587          * being attached
1588          */
1589         err = -ENOENT;
1590         if (configfs_dirent_is_ready(parent_sd)) {
1591                 file->private_data = configfs_new_dirent(parent_sd, NULL, 0);
1592                 if (IS_ERR(file->private_data))
1593                         err = PTR_ERR(file->private_data);
1594                 else
1595                         err = 0;
1596         }
1597         inode_unlock(d_inode(dentry));
1598 
1599         return err;
1600 }
1601 
1602 static int configfs_dir_close(struct inode *inode, struct file *file)
1603 {
1604         struct dentry * dentry = file->f_path.dentry;
1605         struct configfs_dirent * cursor = file->private_data;
1606 
1607         inode_lock(d_inode(dentry));
1608         spin_lock(&configfs_dirent_lock);
1609         list_del_init(&cursor->s_sibling);
1610         spin_unlock(&configfs_dirent_lock);
1611         inode_unlock(d_inode(dentry));
1612 
1613         release_configfs_dirent(cursor);
1614 
1615         return 0;
1616 }
1617 
1618 /* Relationship between s_mode and the DT_xxx types */
1619 static inline unsigned char dt_type(struct configfs_dirent *sd)
1620 {
1621         return (sd->s_mode >> 12) & 15;
1622 }
1623 
1624 static int configfs_readdir(struct file *file, struct dir_context *ctx)
1625 {
1626         struct dentry *dentry = file->f_path.dentry;
1627         struct super_block *sb = dentry->d_sb;
1628         struct configfs_dirent * parent_sd = dentry->d_fsdata;
1629         struct configfs_dirent *cursor = file->private_data;
1630         struct list_head *p, *q = &cursor->s_sibling;
1631         ino_t ino = 0;
1632 
1633         if (!dir_emit_dots(file, ctx))
1634                 return 0;
1635         if (ctx->pos == 2) {
1636                 spin_lock(&configfs_dirent_lock);
1637                 list_move(q, &parent_sd->s_children);
1638                 spin_unlock(&configfs_dirent_lock);
1639         }
1640         for (p = q->next; p != &parent_sd->s_children; p = p->next) {
1641                 struct configfs_dirent *next;
1642                 const char *name;
1643                 int len;
1644                 struct inode *inode = NULL;
1645 
1646                 next = list_entry(p, struct configfs_dirent, s_sibling);
1647                 if (!next->s_element)
1648                         continue;
1649 
1650                 name = configfs_get_name(next);
1651                 len = strlen(name);
1652 
1653                 /*
1654                  * We'll have a dentry and an inode for
1655                  * PINNED items and for open attribute
1656                  * files.  We lock here to prevent a race
1657                  * with configfs_d_iput() clearing
1658                  * s_dentry before calling iput().
1659                  *
1660                  * Why do we go to the trouble?  If
1661                  * someone has an attribute file open,
1662                  * the inode number should match until
1663                  * they close it.  Beyond that, we don't
1664                  * care.
1665                  */
1666                 spin_lock(&configfs_dirent_lock);
1667                 dentry = next->s_dentry;
1668                 if (dentry)
1669                         inode = d_inode(dentry);
1670                 if (inode)
1671                         ino = inode->i_ino;
1672                 spin_unlock(&configfs_dirent_lock);
1673                 if (!inode)
1674                         ino = iunique(sb, 2);
1675 
1676                 if (!dir_emit(ctx, name, len, ino, dt_type(next)))
1677                         return 0;
1678 
1679                 spin_lock(&configfs_dirent_lock);
1680                 list_move(q, p);
1681                 spin_unlock(&configfs_dirent_lock);
1682                 p = q;
1683                 ctx->pos++;
1684         }
1685         return 0;
1686 }
1687 
1688 static loff_t configfs_dir_lseek(struct file *file, loff_t offset, int whence)
1689 {
1690         struct dentry * dentry = file->f_path.dentry;
1691 
1692         inode_lock(d_inode(dentry));
1693         switch (whence) {
1694                 case 1:
1695                         offset += file->f_pos;
1696                 case 0:
1697                         if (offset >= 0)
1698                                 break;
1699                 default:
1700                         inode_unlock(d_inode(dentry));
1701                         return -EINVAL;
1702         }
1703         if (offset != file->f_pos) {
1704                 file->f_pos = offset;
1705                 if (file->f_pos >= 2) {
1706                         struct configfs_dirent *sd = dentry->d_fsdata;
1707                         struct configfs_dirent *cursor = file->private_data;
1708                         struct list_head *p;
1709                         loff_t n = file->f_pos - 2;
1710 
1711                         spin_lock(&configfs_dirent_lock);
1712                         list_del(&cursor->s_sibling);
1713                         p = sd->s_children.next;
1714                         while (n && p != &sd->s_children) {
1715                                 struct configfs_dirent *next;
1716                                 next = list_entry(p, struct configfs_dirent,
1717                                                    s_sibling);
1718                                 if (next->s_element)
1719                                         n--;
1720                                 p = p->next;
1721                         }
1722                         list_add_tail(&cursor->s_sibling, p);
1723                         spin_unlock(&configfs_dirent_lock);
1724                 }
1725         }
1726         inode_unlock(d_inode(dentry));
1727         return offset;
1728 }
1729 
1730 const struct file_operations configfs_dir_operations = {
1731         .open           = configfs_dir_open,
1732         .release        = configfs_dir_close,
1733         .llseek         = configfs_dir_lseek,
1734         .read           = generic_read_dir,
1735         .iterate        = configfs_readdir,
1736 };
1737 
1738 /**
1739  * configfs_register_group - creates a parent-child relation between two groups
1740  * @parent_group:       parent group
1741  * @group:              child group
1742  *
1743  * link groups, creates dentry for the child and attaches it to the
1744  * parent dentry.
1745  *
1746  * Return: 0 on success, negative errno code on error
1747  */
1748 int configfs_register_group(struct config_group *parent_group,
1749                             struct config_group *group)
1750 {
1751         struct configfs_subsystem *subsys = parent_group->cg_subsys;
1752         struct dentry *parent;
1753         int ret;
1754 
1755         mutex_lock(&subsys->su_mutex);
1756         link_group(parent_group, group);
1757         mutex_unlock(&subsys->su_mutex);
1758 
1759         parent = parent_group->cg_item.ci_dentry;
1760 
1761         inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
1762         ret = create_default_group(parent_group, group);
1763         if (!ret) {
1764                 spin_lock(&configfs_dirent_lock);
1765                 configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
1766                 spin_unlock(&configfs_dirent_lock);
1767         }
1768         inode_unlock(d_inode(parent));
1769         return ret;
1770 }
1771 EXPORT_SYMBOL(configfs_register_group);
1772 
1773 /**
1774  * configfs_unregister_group() - unregisters a child group from its parent
1775  * @group: parent group to be unregistered
1776  *
1777  * Undoes configfs_register_group()
1778  */
1779 void configfs_unregister_group(struct config_group *group)
1780 {
1781         struct configfs_subsystem *subsys = group->cg_subsys;
1782         struct dentry *dentry = group->cg_item.ci_dentry;
1783         struct dentry *parent = group->cg_item.ci_parent->ci_dentry;
1784 
1785         inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
1786         spin_lock(&configfs_dirent_lock);
1787         configfs_detach_prep(dentry, NULL);
1788         spin_unlock(&configfs_dirent_lock);
1789 
1790         configfs_detach_group(&group->cg_item);
1791         d_inode(dentry)->i_flags |= S_DEAD;
1792         dont_mount(dentry);
1793         d_delete(dentry);
1794         inode_unlock(d_inode(parent));
1795 
1796         dput(dentry);
1797 
1798         mutex_lock(&subsys->su_mutex);
1799         unlink_group(group);
1800         mutex_unlock(&subsys->su_mutex);
1801 }
1802 EXPORT_SYMBOL(configfs_unregister_group);
1803 
1804 /**
1805  * configfs_register_default_group() - allocates and registers a child group
1806  * @parent_group:       parent group
1807  * @name:               child group name
1808  * @item_type:          child item type description
1809  *
1810  * boilerplate to allocate and register a child group with its parent. We need
1811  * kzalloc'ed memory because child's default_group is initially empty.
1812  *
1813  * Return: allocated config group or ERR_PTR() on error
1814  */
1815 struct config_group *
1816 configfs_register_default_group(struct config_group *parent_group,
1817                                 const char *name,
1818                                 struct config_item_type *item_type)
1819 {
1820         int ret;
1821         struct config_group *group;
1822 
1823         group = kzalloc(sizeof(*group), GFP_KERNEL);
1824         if (!group)
1825                 return ERR_PTR(-ENOMEM);
1826         config_group_init_type_name(group, name, item_type);
1827 
1828         ret = configfs_register_group(parent_group, group);
1829         if (ret) {
1830                 kfree(group);
1831                 return ERR_PTR(ret);
1832         }
1833         return group;
1834 }
1835 EXPORT_SYMBOL(configfs_register_default_group);
1836 
1837 /**
1838  * configfs_unregister_default_group() - unregisters and frees a child group
1839  * @group:      the group to act on
1840  */
1841 void configfs_unregister_default_group(struct config_group *group)
1842 {
1843         configfs_unregister_group(group);
1844         kfree(group);
1845 }
1846 EXPORT_SYMBOL(configfs_unregister_default_group);
1847 
1848 int configfs_register_subsystem(struct configfs_subsystem *subsys)
1849 {
1850         int err;
1851         struct config_group *group = &subsys->su_group;
1852         struct dentry *dentry;
1853         struct dentry *root;
1854         struct configfs_dirent *sd;
1855 
1856         root = configfs_pin_fs();
1857         if (IS_ERR(root))
1858                 return PTR_ERR(root);
1859 
1860         if (!group->cg_item.ci_name)
1861                 group->cg_item.ci_name = group->cg_item.ci_namebuf;
1862 
1863         sd = root->d_fsdata;
1864         link_group(to_config_group(sd->s_element), group);
1865 
1866         inode_lock_nested(d_inode(root), I_MUTEX_PARENT);
1867 
1868         err = -ENOMEM;
1869         dentry = d_alloc_name(root, group->cg_item.ci_name);
1870         if (dentry) {
1871                 d_add(dentry, NULL);
1872 
1873                 err = configfs_attach_group(sd->s_element, &group->cg_item,
1874                                             dentry);
1875                 if (err) {
1876                         BUG_ON(d_inode(dentry));
1877                         d_drop(dentry);
1878                         dput(dentry);
1879                 } else {
1880                         spin_lock(&configfs_dirent_lock);
1881                         configfs_dir_set_ready(dentry->d_fsdata);
1882                         spin_unlock(&configfs_dirent_lock);
1883                 }
1884         }
1885 
1886         inode_unlock(d_inode(root));
1887 
1888         if (err) {
1889                 unlink_group(group);
1890                 configfs_release_fs();
1891         }
1892 
1893         return err;
1894 }
1895 
1896 void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
1897 {
1898         struct config_group *group = &subsys->su_group;
1899         struct dentry *dentry = group->cg_item.ci_dentry;
1900         struct dentry *root = dentry->d_sb->s_root;
1901 
1902         if (dentry->d_parent != root) {
1903                 pr_err("Tried to unregister non-subsystem!\n");
1904                 return;
1905         }
1906 
1907         inode_lock_nested(d_inode(root),
1908                           I_MUTEX_PARENT);
1909         inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);
1910         mutex_lock(&configfs_symlink_mutex);
1911         spin_lock(&configfs_dirent_lock);
1912         if (configfs_detach_prep(dentry, NULL)) {
1913                 pr_err("Tried to unregister non-empty subsystem!\n");
1914         }
1915         spin_unlock(&configfs_dirent_lock);
1916         mutex_unlock(&configfs_symlink_mutex);
1917         configfs_detach_group(&group->cg_item);
1918         d_inode(dentry)->i_flags |= S_DEAD;
1919         dont_mount(dentry);
1920         inode_unlock(d_inode(dentry));
1921 
1922         d_delete(dentry);
1923 
1924         inode_unlock(d_inode(root));
1925 
1926         dput(dentry);
1927 
1928         unlink_group(group);
1929         configfs_release_fs();
1930 }
1931 
1932 EXPORT_SYMBOL(configfs_register_subsystem);
1933 EXPORT_SYMBOL(configfs_unregister_subsystem);
1934 

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