CacheFiles: A cache that backs onto a mounted filesystem
[linux-2.6.git] / fs / cachefiles / namei.c
1 /* CacheFiles path walking and related routines
2  *
3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public Licence
8  * as published by the Free Software Foundation; either version
9  * 2 of the Licence, or (at your option) any later version.
10  */
11
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/file.h>
15 #include <linux/fs.h>
16 #include <linux/fsnotify.h>
17 #include <linux/quotaops.h>
18 #include <linux/xattr.h>
19 #include <linux/mount.h>
20 #include <linux/namei.h>
21 #include <linux/security.h>
22 #include "internal.h"
23
24 static int cachefiles_wait_bit(void *flags)
25 {
26         schedule();
27         return 0;
28 }
29
30 /*
31  * record the fact that an object is now active
32  */
33 static void cachefiles_mark_object_active(struct cachefiles_cache *cache,
34                                           struct cachefiles_object *object)
35 {
36         struct cachefiles_object *xobject;
37         struct rb_node **_p, *_parent = NULL;
38         struct dentry *dentry;
39
40         _enter(",%p", object);
41
42 try_again:
43         write_lock(&cache->active_lock);
44
45         if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags))
46                 BUG();
47
48         dentry = object->dentry;
49         _p = &cache->active_nodes.rb_node;
50         while (*_p) {
51                 _parent = *_p;
52                 xobject = rb_entry(_parent,
53                                    struct cachefiles_object, active_node);
54
55                 ASSERT(xobject != object);
56
57                 if (xobject->dentry > dentry)
58                         _p = &(*_p)->rb_left;
59                 else if (xobject->dentry < dentry)
60                         _p = &(*_p)->rb_right;
61                 else
62                         goto wait_for_old_object;
63         }
64
65         rb_link_node(&object->active_node, _parent, _p);
66         rb_insert_color(&object->active_node, &cache->active_nodes);
67
68         write_unlock(&cache->active_lock);
69         _leave("");
70         return;
71
72         /* an old object from a previous incarnation is hogging the slot - we
73          * need to wait for it to be destroyed */
74 wait_for_old_object:
75         if (xobject->fscache.state < FSCACHE_OBJECT_DYING) {
76                 printk(KERN_ERR "\n");
77                 printk(KERN_ERR "CacheFiles: Error:"
78                        " Unexpected object collision\n");
79                 printk(KERN_ERR "xobject: OBJ%x\n",
80                        xobject->fscache.debug_id);
81                 printk(KERN_ERR "xobjstate=%s\n",
82                        fscache_object_states[xobject->fscache.state]);
83                 printk(KERN_ERR "xobjflags=%lx\n", xobject->fscache.flags);
84                 printk(KERN_ERR "xobjevent=%lx [%lx]\n",
85                        xobject->fscache.events, xobject->fscache.event_mask);
86                 printk(KERN_ERR "xops=%u inp=%u exc=%u\n",
87                        xobject->fscache.n_ops, xobject->fscache.n_in_progress,
88                        xobject->fscache.n_exclusive);
89                 printk(KERN_ERR "xcookie=%p [pr=%p nd=%p fl=%lx]\n",
90                        xobject->fscache.cookie,
91                        xobject->fscache.cookie->parent,
92                        xobject->fscache.cookie->netfs_data,
93                        xobject->fscache.cookie->flags);
94                 printk(KERN_ERR "xparent=%p\n",
95                        xobject->fscache.parent);
96                 printk(KERN_ERR "object: OBJ%x\n",
97                        object->fscache.debug_id);
98                 printk(KERN_ERR "cookie=%p [pr=%p nd=%p fl=%lx]\n",
99                        object->fscache.cookie,
100                        object->fscache.cookie->parent,
101                        object->fscache.cookie->netfs_data,
102                        object->fscache.cookie->flags);
103                 printk(KERN_ERR "parent=%p\n",
104                        object->fscache.parent);
105                 BUG();
106         }
107         atomic_inc(&xobject->usage);
108         write_unlock(&cache->active_lock);
109
110         _debug(">>> wait");
111         wait_on_bit(&xobject->flags, CACHEFILES_OBJECT_ACTIVE,
112                     cachefiles_wait_bit, TASK_UNINTERRUPTIBLE);
113         _debug("<<< waited");
114
115         cache->cache.ops->put_object(&xobject->fscache);
116         goto try_again;
117 }
118
119 /*
120  * delete an object representation from the cache
121  * - file backed objects are unlinked
122  * - directory backed objects are stuffed into the graveyard for userspace to
123  *   delete
124  * - unlocks the directory mutex
125  */
126 static int cachefiles_bury_object(struct cachefiles_cache *cache,
127                                   struct dentry *dir,
128                                   struct dentry *rep)
129 {
130         struct dentry *grave, *trap;
131         char nbuffer[8 + 8 + 1];
132         int ret;
133
134         _enter(",'%*.*s','%*.*s'",
135                dir->d_name.len, dir->d_name.len, dir->d_name.name,
136                rep->d_name.len, rep->d_name.len, rep->d_name.name);
137
138         /* non-directories can just be unlinked */
139         if (!S_ISDIR(rep->d_inode->i_mode)) {
140                 _debug("unlink stale object");
141                 ret = vfs_unlink(dir->d_inode, rep);
142
143                 mutex_unlock(&dir->d_inode->i_mutex);
144
145                 if (ret == -EIO)
146                         cachefiles_io_error(cache, "Unlink failed");
147
148                 _leave(" = %d", ret);
149                 return ret;
150         }
151
152         /* directories have to be moved to the graveyard */
153         _debug("move stale object to graveyard");
154         mutex_unlock(&dir->d_inode->i_mutex);
155
156 try_again:
157         /* first step is to make up a grave dentry in the graveyard */
158         sprintf(nbuffer, "%08x%08x",
159                 (uint32_t) get_seconds(),
160                 (uint32_t) atomic_inc_return(&cache->gravecounter));
161
162         /* do the multiway lock magic */
163         trap = lock_rename(cache->graveyard, dir);
164
165         /* do some checks before getting the grave dentry */
166         if (rep->d_parent != dir) {
167                 /* the entry was probably culled when we dropped the parent dir
168                  * lock */
169                 unlock_rename(cache->graveyard, dir);
170                 _leave(" = 0 [culled?]");
171                 return 0;
172         }
173
174         if (!S_ISDIR(cache->graveyard->d_inode->i_mode)) {
175                 unlock_rename(cache->graveyard, dir);
176                 cachefiles_io_error(cache, "Graveyard no longer a directory");
177                 return -EIO;
178         }
179
180         if (trap == rep) {
181                 unlock_rename(cache->graveyard, dir);
182                 cachefiles_io_error(cache, "May not make directory loop");
183                 return -EIO;
184         }
185
186         if (d_mountpoint(rep)) {
187                 unlock_rename(cache->graveyard, dir);
188                 cachefiles_io_error(cache, "Mountpoint in cache");
189                 return -EIO;
190         }
191
192         grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
193         if (IS_ERR(grave)) {
194                 unlock_rename(cache->graveyard, dir);
195
196                 if (PTR_ERR(grave) == -ENOMEM) {
197                         _leave(" = -ENOMEM");
198                         return -ENOMEM;
199                 }
200
201                 cachefiles_io_error(cache, "Lookup error %ld",
202                                     PTR_ERR(grave));
203                 return -EIO;
204         }
205
206         if (grave->d_inode) {
207                 unlock_rename(cache->graveyard, dir);
208                 dput(grave);
209                 grave = NULL;
210                 cond_resched();
211                 goto try_again;
212         }
213
214         if (d_mountpoint(grave)) {
215                 unlock_rename(cache->graveyard, dir);
216                 dput(grave);
217                 cachefiles_io_error(cache, "Mountpoint in graveyard");
218                 return -EIO;
219         }
220
221         /* target should not be an ancestor of source */
222         if (trap == grave) {
223                 unlock_rename(cache->graveyard, dir);
224                 dput(grave);
225                 cachefiles_io_error(cache, "May not make directory loop");
226                 return -EIO;
227         }
228
229         /* attempt the rename */
230         ret = vfs_rename(dir->d_inode, rep, cache->graveyard->d_inode, grave);
231         if (ret != 0 && ret != -ENOMEM)
232                 cachefiles_io_error(cache, "Rename failed with error %d", ret);
233
234         unlock_rename(cache->graveyard, dir);
235         dput(grave);
236         _leave(" = 0");
237         return 0;
238 }
239
240 /*
241  * delete an object representation from the cache
242  */
243 int cachefiles_delete_object(struct cachefiles_cache *cache,
244                              struct cachefiles_object *object)
245 {
246         struct dentry *dir;
247         int ret;
248
249         _enter(",{%p}", object->dentry);
250
251         ASSERT(object->dentry);
252         ASSERT(object->dentry->d_inode);
253         ASSERT(object->dentry->d_parent);
254
255         dir = dget_parent(object->dentry);
256
257         mutex_lock(&dir->d_inode->i_mutex);
258         ret = cachefiles_bury_object(cache, dir, object->dentry);
259
260         dput(dir);
261         _leave(" = %d", ret);
262         return ret;
263 }
264
265 /*
266  * walk from the parent object to the child object through the backing
267  * filesystem, creating directories as we go
268  */
269 int cachefiles_walk_to_object(struct cachefiles_object *parent,
270                               struct cachefiles_object *object,
271                               const char *key,
272                               struct cachefiles_xattr *auxdata)
273 {
274         struct cachefiles_cache *cache;
275         struct dentry *dir, *next = NULL;
276         unsigned long start;
277         const char *name;
278         int ret, nlen;
279
280         _enter("{%p},,%s,", parent->dentry, key);
281
282         cache = container_of(parent->fscache.cache,
283                              struct cachefiles_cache, cache);
284
285         ASSERT(parent->dentry);
286         ASSERT(parent->dentry->d_inode);
287
288         if (!(S_ISDIR(parent->dentry->d_inode->i_mode))) {
289                 // TODO: convert file to dir
290                 _leave("looking up in none directory");
291                 return -ENOBUFS;
292         }
293
294         dir = dget(parent->dentry);
295
296 advance:
297         /* attempt to transit the first directory component */
298         name = key;
299         nlen = strlen(key);
300
301         /* key ends in a double NUL */
302         key = key + nlen + 1;
303         if (!*key)
304                 key = NULL;
305
306 lookup_again:
307         /* search the current directory for the element name */
308         _debug("lookup '%s'", name);
309
310         mutex_lock(&dir->d_inode->i_mutex);
311
312         start = jiffies;
313         next = lookup_one_len(name, dir, nlen);
314         cachefiles_hist(cachefiles_lookup_histogram, start);
315         if (IS_ERR(next))
316                 goto lookup_error;
317
318         _debug("next -> %p %s", next, next->d_inode ? "positive" : "negative");
319
320         if (!key)
321                 object->new = !next->d_inode;
322
323         /* if this element of the path doesn't exist, then the lookup phase
324          * failed, and we can release any readers in the certain knowledge that
325          * there's nothing for them to actually read */
326         if (!next->d_inode)
327                 fscache_object_lookup_negative(&object->fscache);
328
329         /* we need to create the object if it's negative */
330         if (key || object->type == FSCACHE_COOKIE_TYPE_INDEX) {
331                 /* index objects and intervening tree levels must be subdirs */
332                 if (!next->d_inode) {
333                         ret = cachefiles_has_space(cache, 1, 0);
334                         if (ret < 0)
335                                 goto create_error;
336
337                         start = jiffies;
338                         ret = vfs_mkdir(dir->d_inode, next, 0);
339                         cachefiles_hist(cachefiles_mkdir_histogram, start);
340                         if (ret < 0)
341                                 goto create_error;
342
343                         ASSERT(next->d_inode);
344
345                         _debug("mkdir -> %p{%p{ino=%lu}}",
346                                next, next->d_inode, next->d_inode->i_ino);
347
348                 } else if (!S_ISDIR(next->d_inode->i_mode)) {
349                         kerror("inode %lu is not a directory",
350                                next->d_inode->i_ino);
351                         ret = -ENOBUFS;
352                         goto error;
353                 }
354
355         } else {
356                 /* non-index objects start out life as files */
357                 if (!next->d_inode) {
358                         ret = cachefiles_has_space(cache, 1, 0);
359                         if (ret < 0)
360                                 goto create_error;
361
362                         start = jiffies;
363                         ret = vfs_create(dir->d_inode, next, S_IFREG, NULL);
364                         cachefiles_hist(cachefiles_create_histogram, start);
365                         if (ret < 0)
366                                 goto create_error;
367
368                         ASSERT(next->d_inode);
369
370                         _debug("create -> %p{%p{ino=%lu}}",
371                                next, next->d_inode, next->d_inode->i_ino);
372
373                 } else if (!S_ISDIR(next->d_inode->i_mode) &&
374                            !S_ISREG(next->d_inode->i_mode)
375                            ) {
376                         kerror("inode %lu is not a file or directory",
377                                next->d_inode->i_ino);
378                         ret = -ENOBUFS;
379                         goto error;
380                 }
381         }
382
383         /* process the next component */
384         if (key) {
385                 _debug("advance");
386                 mutex_unlock(&dir->d_inode->i_mutex);
387                 dput(dir);
388                 dir = next;
389                 next = NULL;
390                 goto advance;
391         }
392
393         /* we've found the object we were looking for */
394         object->dentry = next;
395
396         /* if we've found that the terminal object exists, then we need to
397          * check its attributes and delete it if it's out of date */
398         if (!object->new) {
399                 _debug("validate '%*.*s'",
400                        next->d_name.len, next->d_name.len, next->d_name.name);
401
402                 ret = cachefiles_check_object_xattr(object, auxdata);
403                 if (ret == -ESTALE) {
404                         /* delete the object (the deleter drops the directory
405                          * mutex) */
406                         object->dentry = NULL;
407
408                         ret = cachefiles_bury_object(cache, dir, next);
409                         dput(next);
410                         next = NULL;
411
412                         if (ret < 0)
413                                 goto delete_error;
414
415                         _debug("redo lookup");
416                         goto lookup_again;
417                 }
418         }
419
420         /* note that we're now using this object */
421         cachefiles_mark_object_active(cache, object);
422
423         mutex_unlock(&dir->d_inode->i_mutex);
424         dput(dir);
425         dir = NULL;
426
427         _debug("=== OBTAINED_OBJECT ===");
428
429         if (object->new) {
430                 /* attach data to a newly constructed terminal object */
431                 ret = cachefiles_set_object_xattr(object, auxdata);
432                 if (ret < 0)
433                         goto check_error;
434         } else {
435                 /* always update the atime on an object we've just looked up
436                  * (this is used to keep track of culling, and atimes are only
437                  * updated by read, write and readdir but not lookup or
438                  * open) */
439                 touch_atime(cache->mnt, next);
440         }
441
442         /* open a file interface onto a data file */
443         if (object->type != FSCACHE_COOKIE_TYPE_INDEX) {
444                 if (S_ISREG(object->dentry->d_inode->i_mode)) {
445                         const struct address_space_operations *aops;
446
447                         ret = -EPERM;
448                         aops = object->dentry->d_inode->i_mapping->a_ops;
449                         if (!aops->bmap)
450                                 goto check_error;
451
452                         object->backer = object->dentry;
453                 } else {
454                         BUG(); // TODO: open file in data-class subdir
455                 }
456         }
457
458         object->new = 0;
459         fscache_obtained_object(&object->fscache);
460
461         _leave(" = 0 [%lu]", object->dentry->d_inode->i_ino);
462         return 0;
463
464 create_error:
465         _debug("create error %d", ret);
466         if (ret == -EIO)
467                 cachefiles_io_error(cache, "Create/mkdir failed");
468         goto error;
469
470 check_error:
471         _debug("check error %d", ret);
472         write_lock(&cache->active_lock);
473         rb_erase(&object->active_node, &cache->active_nodes);
474         clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
475         wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
476         write_unlock(&cache->active_lock);
477
478         dput(object->dentry);
479         object->dentry = NULL;
480         goto error_out;
481
482 delete_error:
483         _debug("delete error %d", ret);
484         goto error_out2;
485
486 lookup_error:
487         _debug("lookup error %ld", PTR_ERR(next));
488         ret = PTR_ERR(next);
489         if (ret == -EIO)
490                 cachefiles_io_error(cache, "Lookup failed");
491         next = NULL;
492 error:
493         mutex_unlock(&dir->d_inode->i_mutex);
494         dput(next);
495 error_out2:
496         dput(dir);
497 error_out:
498         if (ret == -ENOSPC)
499                 ret = -ENOBUFS;
500
501         _leave(" = error %d", -ret);
502         return ret;
503 }
504
505 /*
506  * get a subdirectory
507  */
508 struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
509                                         struct dentry *dir,
510                                         const char *dirname)
511 {
512         struct dentry *subdir;
513         unsigned long start;
514         int ret;
515
516         _enter(",,%s", dirname);
517
518         /* search the current directory for the element name */
519         mutex_lock(&dir->d_inode->i_mutex);
520
521         start = jiffies;
522         subdir = lookup_one_len(dirname, dir, strlen(dirname));
523         cachefiles_hist(cachefiles_lookup_histogram, start);
524         if (IS_ERR(subdir)) {
525                 if (PTR_ERR(subdir) == -ENOMEM)
526                         goto nomem_d_alloc;
527                 goto lookup_error;
528         }
529
530         _debug("subdir -> %p %s",
531                subdir, subdir->d_inode ? "positive" : "negative");
532
533         /* we need to create the subdir if it doesn't exist yet */
534         if (!subdir->d_inode) {
535                 ret = cachefiles_has_space(cache, 1, 0);
536                 if (ret < 0)
537                         goto mkdir_error;
538
539                 _debug("attempt mkdir");
540
541                 ret = vfs_mkdir(dir->d_inode, subdir, 0700);
542                 if (ret < 0)
543                         goto mkdir_error;
544
545                 ASSERT(subdir->d_inode);
546
547                 _debug("mkdir -> %p{%p{ino=%lu}}",
548                        subdir,
549                        subdir->d_inode,
550                        subdir->d_inode->i_ino);
551         }
552
553         mutex_unlock(&dir->d_inode->i_mutex);
554
555         /* we need to make sure the subdir is a directory */
556         ASSERT(subdir->d_inode);
557
558         if (!S_ISDIR(subdir->d_inode->i_mode)) {
559                 kerror("%s is not a directory", dirname);
560                 ret = -EIO;
561                 goto check_error;
562         }
563
564         ret = -EPERM;
565         if (!subdir->d_inode->i_op ||
566             !subdir->d_inode->i_op->setxattr ||
567             !subdir->d_inode->i_op->getxattr ||
568             !subdir->d_inode->i_op->lookup ||
569             !subdir->d_inode->i_op->mkdir ||
570             !subdir->d_inode->i_op->create ||
571             !subdir->d_inode->i_op->rename ||
572             !subdir->d_inode->i_op->rmdir ||
573             !subdir->d_inode->i_op->unlink)
574                 goto check_error;
575
576         _leave(" = [%lu]", subdir->d_inode->i_ino);
577         return subdir;
578
579 check_error:
580         dput(subdir);
581         _leave(" = %d [check]", ret);
582         return ERR_PTR(ret);
583
584 mkdir_error:
585         mutex_unlock(&dir->d_inode->i_mutex);
586         dput(subdir);
587         kerror("mkdir %s failed with error %d", dirname, ret);
588         return ERR_PTR(ret);
589
590 lookup_error:
591         mutex_unlock(&dir->d_inode->i_mutex);
592         ret = PTR_ERR(subdir);
593         kerror("Lookup %s failed with error %d", dirname, ret);
594         return ERR_PTR(ret);
595
596 nomem_d_alloc:
597         mutex_unlock(&dir->d_inode->i_mutex);
598         _leave(" = -ENOMEM");
599         return ERR_PTR(-ENOMEM);
600 }
601
602 /*
603  * find out if an object is in use or not
604  * - if finds object and it's not in use:
605  *   - returns a pointer to the object and a reference on it
606  *   - returns with the directory locked
607  */
608 static struct dentry *cachefiles_check_active(struct cachefiles_cache *cache,
609                                               struct dentry *dir,
610                                               char *filename)
611 {
612         struct cachefiles_object *object;
613         struct rb_node *_n;
614         struct dentry *victim;
615         unsigned long start;
616         int ret;
617
618         //_enter(",%*.*s/,%s",
619         //       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);
620
621         /* look up the victim */
622         mutex_lock_nested(&dir->d_inode->i_mutex, 1);
623
624         start = jiffies;
625         victim = lookup_one_len(filename, dir, strlen(filename));
626         cachefiles_hist(cachefiles_lookup_histogram, start);
627         if (IS_ERR(victim))
628                 goto lookup_error;
629
630         //_debug("victim -> %p %s",
631         //       victim, victim->d_inode ? "positive" : "negative");
632
633         /* if the object is no longer there then we probably retired the object
634          * at the netfs's request whilst the cull was in progress
635          */
636         if (!victim->d_inode) {
637                 mutex_unlock(&dir->d_inode->i_mutex);
638                 dput(victim);
639                 _leave(" = -ENOENT [absent]");
640                 return ERR_PTR(-ENOENT);
641         }
642
643         /* check to see if we're using this object */
644         read_lock(&cache->active_lock);
645
646         _n = cache->active_nodes.rb_node;
647
648         while (_n) {
649                 object = rb_entry(_n, struct cachefiles_object, active_node);
650
651                 if (object->dentry > victim)
652                         _n = _n->rb_left;
653                 else if (object->dentry < victim)
654                         _n = _n->rb_right;
655                 else
656                         goto object_in_use;
657         }
658
659         read_unlock(&cache->active_lock);
660
661         //_leave(" = %p", victim);
662         return victim;
663
664 object_in_use:
665         read_unlock(&cache->active_lock);
666         mutex_unlock(&dir->d_inode->i_mutex);
667         dput(victim);
668         //_leave(" = -EBUSY [in use]");
669         return ERR_PTR(-EBUSY);
670
671 lookup_error:
672         mutex_unlock(&dir->d_inode->i_mutex);
673         ret = PTR_ERR(victim);
674         if (ret == -ENOENT) {
675                 /* file or dir now absent - probably retired by netfs */
676                 _leave(" = -ESTALE [absent]");
677                 return ERR_PTR(-ESTALE);
678         }
679
680         if (ret == -EIO) {
681                 cachefiles_io_error(cache, "Lookup failed");
682         } else if (ret != -ENOMEM) {
683                 kerror("Internal error: %d", ret);
684                 ret = -EIO;
685         }
686
687         _leave(" = %d", ret);
688         return ERR_PTR(ret);
689 }
690
691 /*
692  * cull an object if it's not in use
693  * - called only by cache manager daemon
694  */
695 int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
696                     char *filename)
697 {
698         struct dentry *victim;
699         int ret;
700
701         _enter(",%*.*s/,%s",
702                dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);
703
704         victim = cachefiles_check_active(cache, dir, filename);
705         if (IS_ERR(victim))
706                 return PTR_ERR(victim);
707
708         _debug("victim -> %p %s",
709                victim, victim->d_inode ? "positive" : "negative");
710
711         /* okay... the victim is not being used so we can cull it
712          * - start by marking it as stale
713          */
714         _debug("victim is cullable");
715
716         ret = cachefiles_remove_object_xattr(cache, victim);
717         if (ret < 0)
718                 goto error_unlock;
719
720         /*  actually remove the victim (drops the dir mutex) */
721         _debug("bury");
722
723         ret = cachefiles_bury_object(cache, dir, victim);
724         if (ret < 0)
725                 goto error;
726
727         dput(victim);
728         _leave(" = 0");
729         return 0;
730
731 error_unlock:
732         mutex_unlock(&dir->d_inode->i_mutex);
733 error:
734         dput(victim);
735         if (ret == -ENOENT) {
736                 /* file or dir now absent - probably retired by netfs */
737                 _leave(" = -ESTALE [absent]");
738                 return -ESTALE;
739         }
740
741         if (ret != -ENOMEM) {
742                 kerror("Internal error: %d", ret);
743                 ret = -EIO;
744         }
745
746         _leave(" = %d", ret);
747         return ret;
748 }
749
750 /*
751  * find out if an object is in use or not
752  * - called only by cache manager daemon
753  * - returns -EBUSY or 0 to indicate whether an object is in use or not
754  */
755 int cachefiles_check_in_use(struct cachefiles_cache *cache, struct dentry *dir,
756                             char *filename)
757 {
758         struct dentry *victim;
759
760         //_enter(",%*.*s/,%s",
761         //       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);
762
763         victim = cachefiles_check_active(cache, dir, filename);
764         if (IS_ERR(victim))
765                 return PTR_ERR(victim);
766
767         mutex_unlock(&dir->d_inode->i_mutex);
768         dput(victim);
769         //_leave(" = 0");
770         return 0;
771 }