fs/sysfs/dir.c

   1 /*
   2  * dir.c - Operations for sysfs directories.
   3  */
   4
   5 #undef DEBUG
   6
   7 #include <linux/fs.h>
   8 #include <linux/mount.h>
   9 #include <linux/module.h>
  10 #include <linux/kobject.h>
  11 #include <linux/namei.h>
  12 #include <linux/idr.h>
  13 #include <asm/semaphore.h>
  14 #include "sysfs.h"
  15
  16 DECLARE_RWSEM(sysfs_rename_sem);
  17 spinlock_t sysfs_lock = SPIN_LOCK_UNLOCKED;
  18
  19 static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;
  20 static DEFINE_IDA(sysfs_ino_ida);
  21
  22 int sysfs_alloc_ino(ino_t *pino)
  23 {
  24         int ino, rc;
  25
  26  retry:
  27         spin_lock(&sysfs_ino_lock);
  28         rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
  29         spin_unlock(&sysfs_ino_lock);
  30
  31         if (rc == -EAGAIN) {
  32                 if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL))
  33                         goto retry;
  34                 rc = -ENOMEM;
  35         }
  36
  37         *pino = ino;
  38         return rc;
  39 }
  40
  41 static void sysfs_free_ino(ino_t ino)
  42 {
  43         spin_lock(&sysfs_ino_lock);
  44         ida_remove(&sysfs_ino_ida, ino);
  45         spin_unlock(&sysfs_ino_lock);
  46 }
  47
  48 void release_sysfs_dirent(struct sysfs_dirent * sd)
  49 {
  50         struct sysfs_dirent *parent_sd;
  51
  52  repeat:
  53         parent_sd = sd->s_parent;
  54
  55         if (sd->s_type & SYSFS_KOBJ_LINK) {
  56                 struct sysfs_symlink * sl = sd->s_element;
  57                 kobject_put(sl->target_kobj);
  58                 kfree(sl);
  59         }
  60         if (sd->s_type & SYSFS_COPY_NAME)
  61                 kfree(sd->s_name);
  62         kfree(sd->s_iattr);
  63         sysfs_free_ino(sd->s_ino);
  64         kmem_cache_free(sysfs_dir_cachep, sd);
  65
  66         sd = parent_sd;
  67         if (sd && atomic_dec_and_test(&sd->s_count))
  68                 goto repeat;
  69 }
  70
  71 static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
  72 {
  73         struct sysfs_dirent * sd = dentry->d_fsdata;
  74
  75         if (sd) {
  76                 /* sd->s_dentry is protected with sysfs_lock.  This
  77                  * allows sysfs_drop_dentry() to dereference it.
  78                  */
  79                 spin_lock(&sysfs_lock);
  80
  81                 /* The dentry might have been deleted or another
  82                  * lookup could have happened updating sd->s_dentry to
  83                  * point the new dentry.  Ignore if it isn't pointing
  84                  * to this dentry.
  85                  */
  86                 if (sd->s_dentry == dentry)
  87                         sd->s_dentry = NULL;
  88                 spin_unlock(&sysfs_lock);
  89                 sysfs_put(sd);
  90         }
  91         iput(inode);
  92 }
  93
  94 static struct dentry_operations sysfs_dentry_ops = {
  95         .d_iput         = sysfs_d_iput,
  96 };
  97
  98 struct sysfs_dirent *sysfs_new_dirent(const char *name, void *element,
  99                                       umode_t mode, int type)
 100 {
 101         char *dup_name = NULL;
 102         struct sysfs_dirent *sd = NULL;
 103
 104         if (type & SYSFS_COPY_NAME) {
 105                 name = dup_name = kstrdup(name, GFP_KERNEL);
 106                 if (!name)
 107                         goto err_out;
 108         }
 109
 110         sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
 111         if (!sd)
 112                 goto err_out;
 113
 114         if (sysfs_alloc_ino(&sd->s_ino))
 115                 goto err_out;
 116
 117         atomic_set(&sd->s_count, 1);
 118         atomic_set(&sd->s_event, 1);
 119         INIT_LIST_HEAD(&sd->s_children);
 120         INIT_LIST_HEAD(&sd->s_sibling);
 121
 122         sd->s_name = name;
 123         sd->s_element = element;
 124         sd->s_mode = mode;
 125         sd->s_type = type;
 126
 127         return sd;
 128
 129  err_out:
 130         kfree(dup_name);
 131         kmem_cache_free(sysfs_dir_cachep, sd);
 132         return NULL;
 133 }
 134
 135 void sysfs_attach_dirent(struct sysfs_dirent *sd,
 136                          struct sysfs_dirent *parent_sd, struct dentry *dentry)
 137 {
 138         if (dentry) {
 139                 sd->s_dentry = dentry;
 140                 dentry->d_fsdata = sysfs_get(sd);
 141                 dentry->d_op = &sysfs_dentry_ops;
 142         }
 143
 144         if (parent_sd) {
 145                 sd->s_parent = sysfs_get(parent_sd);
 146                 list_add(&sd->s_sibling, &parent_sd->s_children);
 147         }
 148 }
 149
 150 /*
 151  *
 152  * Return -EEXIST if there is already a sysfs element with the same name for
 153  * the same parent.
 154  *
 155  * called with parent inode's i_mutex held
 156  */
 157 int sysfs_dirent_exist(struct sysfs_dirent *parent_sd,
 158                           const unsigned char *new)
 159 {
 160         struct sysfs_dirent * sd;
 161
 162         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 163                 if (sd->s_element) {
 164                         if (strcmp(sd->s_name, new))
 165                                 continue;
 166                         else
 167                                 return -EEXIST;
 168                 }
 169         }
 170
 171         return 0;
 172 }
 173
 174 static int init_dir(struct inode * inode)
 175 {
 176         inode->i_op = &sysfs_dir_inode_operations;
 177         inode->i_fop = &sysfs_dir_operations;
 178
 179         /* directory inodes start off with i_nlink == 2 (for "." entry) */
 180         inc_nlink(inode);
 181         return 0;
 182 }
 183
 184 static int init_file(struct inode * inode)
 185 {
 186         inode->i_size = PAGE_SIZE;
 187         inode->i_fop = &sysfs_file_operations;
 188         return 0;
 189 }
 190
 191 static int init_symlink(struct inode * inode)
 192 {
 193         inode->i_op = &sysfs_symlink_inode_operations;
 194         return 0;
 195 }
 196
 197 static int create_dir(struct kobject *kobj, struct dentry *parent,
 198                       const char *name, struct dentry **p_dentry)
 199 {
 200         int error;
 201         umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
 202         struct dentry *dentry;
 203         struct sysfs_dirent *sd;
 204
 205         mutex_lock(&parent->d_inode->i_mutex);
 206
 207         dentry = lookup_one_len(name, parent, strlen(name));
 208         if (IS_ERR(dentry)) {
 209                 error = PTR_ERR(dentry);
 210                 goto out_unlock;
 211         }
 212
 213         error = -EEXIST;
 214         if (sysfs_dirent_exist(parent->d_fsdata, name))
 215                 goto out_dput;
 216
 217         error = -ENOMEM;
 218         sd = sysfs_new_dirent(name, kobj, mode, SYSFS_DIR);
 219         if (!sd)
 220                 goto out_drop;
 221         sysfs_attach_dirent(sd, parent->d_fsdata, dentry);
 222
 223         error = sysfs_create(dentry, mode, init_dir);
 224         if (error)
 225                 goto out_sput;
 226
 227         inc_nlink(parent->d_inode);
 228         dentry->d_op = &sysfs_dentry_ops;
 229         d_rehash(dentry);
 230
 231         *p_dentry = dentry;
 232         error = 0;
 233         goto out_dput;
 234
 235  out_sput:
 236         list_del_init(&sd->s_sibling);
 237         sysfs_put(sd);
 238  out_drop:
 239         d_drop(dentry);
 240  out_dput:
 241         dput(dentry);
 242  out_unlock:
 243         mutex_unlock(&parent->d_inode->i_mutex);
 244         return error;
 245 }
 246
 247
 248 int sysfs_create_subdir(struct kobject * k, const char * n, struct dentry ** d)
 249 {
 250         return create_dir(k,k->dentry,n,d);
 251 }
 252
 253 /**
 254  *      sysfs_create_dir - create a directory for an object.
 255  *      @kobj:          object we're creating directory for.
 256  *      @shadow_parent: parent parent object.
 257  */
 258
 259 int sysfs_create_dir(struct kobject * kobj, struct dentry *shadow_parent)
 260 {
 261         struct dentry * dentry = NULL;
 262         struct dentry * parent;
 263         int error = 0;
 264
 265         BUG_ON(!kobj);
 266
 267         if (shadow_parent)
 268                 parent = shadow_parent;
 269         else if (kobj->parent)
 270                 parent = kobj->parent->dentry;
 271         else if (sysfs_mount && sysfs_mount->mnt_sb)
 272                 parent = sysfs_mount->mnt_sb->s_root;
 273         else
 274                 return -EFAULT;
 275
 276         error = create_dir(kobj,parent,kobject_name(kobj),&dentry);
 277         if (!error)
 278                 kobj->dentry = dentry;
 279         return error;
 280 }
 281
 282 /* attaches attribute's sysfs_dirent to the dentry corresponding to the
 283  * attribute file
 284  */
 285 static int sysfs_attach_attr(struct sysfs_dirent * sd, struct dentry * dentry)
 286 {
 287         struct attribute * attr = NULL;
 288         struct bin_attribute * bin_attr = NULL;
 289         int (* init) (struct inode *) = NULL;
 290         int error = 0;
 291
 292         if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
 293                 bin_attr = sd->s_element;
 294                 attr = &bin_attr->attr;
 295         } else {
 296                 attr = sd->s_element;
 297                 init = init_file;
 298         }
 299
 300         dentry->d_fsdata = sysfs_get(sd);
 301         /* protect sd->s_dentry against sysfs_d_iput */
 302         spin_lock(&sysfs_lock);
 303         sd->s_dentry = dentry;
 304         spin_unlock(&sysfs_lock);
 305         error = sysfs_create(dentry, (attr->mode & S_IALLUGO) | S_IFREG, init);
 306         if (error) {
 307                 sysfs_put(sd);
 308                 return error;
 309         }
 310
 311         if (bin_attr) {
 312                 dentry->d_inode->i_size = bin_attr->size;
 313                 dentry->d_inode->i_fop = &bin_fops;
 314         }
 315         dentry->d_op = &sysfs_dentry_ops;
 316         d_rehash(dentry);
 317
 318         return 0;
 319 }
 320
 321 static int sysfs_attach_link(struct sysfs_dirent * sd, struct dentry * dentry)
 322 {
 323         int err = 0;
 324
 325         dentry->d_fsdata = sysfs_get(sd);
 326         /* protect sd->s_dentry against sysfs_d_iput */
 327         spin_lock(&sysfs_lock);
 328         sd->s_dentry = dentry;
 329         spin_unlock(&sysfs_lock);
 330         err = sysfs_create(dentry, S_IFLNK|S_IRWXUGO, init_symlink);
 331         if (!err) {
 332                 dentry->d_op = &sysfs_dentry_ops;
 333                 d_rehash(dentry);
 334         } else
 335                 sysfs_put(sd);
 336
 337         return err;
 338 }
 339
 340 static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
 341                                 struct nameidata *nd)
 342 {
 343         struct sysfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
 344         struct sysfs_dirent * sd;
 345         int err = 0;
 346
 347         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 348                 if (sd->s_type & SYSFS_NOT_PINNED) {
 349                         if (strcmp(sd->s_name, dentry->d_name.name))
 350                                 continue;
 351
 352                         if (sd->s_type & SYSFS_KOBJ_LINK)
 353                                 err = sysfs_attach_link(sd, dentry);
 354                         else
 355                                 err = sysfs_attach_attr(sd, dentry);
 356                         break;
 357                 }
 358         }
 359
 360         return ERR_PTR(err);
 361 }
 362
 363 const struct inode_operations sysfs_dir_inode_operations = {
 364         .lookup         = sysfs_lookup,
 365         .setattr        = sysfs_setattr,
 366 };
 367
 368 static void remove_dir(struct dentry * d)
 369 {
 370         struct dentry * parent = dget(d->d_parent);
 371         struct sysfs_dirent * sd;
 372
 373         mutex_lock(&parent->d_inode->i_mutex);
 374         d_delete(d);
 375         sd = d->d_fsdata;
 376         list_del_init(&sd->s_sibling);
 377         sysfs_put(sd);
 378         if (d->d_inode)
 379                 simple_rmdir(parent->d_inode,d);
 380
 381         pr_debug(" o %s removing done (%d)\n",d->d_name.name,
 382                  atomic_read(&d->d_count));
 383
 384         mutex_unlock(&parent->d_inode->i_mutex);
 385         dput(parent);
 386 }
 387
 388 void sysfs_remove_subdir(struct dentry * d)
 389 {
 390         remove_dir(d);
 391 }
 392
 393
 394 static void __sysfs_remove_dir(struct dentry *dentry)
 395 {
 396         struct sysfs_dirent * parent_sd;
 397         struct sysfs_dirent * sd, * tmp;
 398
 399         dget(dentry);
 400         if (!dentry)
 401                 return;
 402
 403         pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);
 404         mutex_lock(&dentry->d_inode->i_mutex);
 405         parent_sd = dentry->d_fsdata;
 406         list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
 407                 if (!sd->s_element || !(sd->s_type & SYSFS_NOT_PINNED))
 408                         continue;
 409                 list_del_init(&sd->s_sibling);
 410                 sysfs_drop_dentry(sd, dentry);
 411                 sysfs_put(sd);
 412         }
 413         mutex_unlock(&dentry->d_inode->i_mutex);
 414
 415         remove_dir(dentry);
 416         /**
 417          * Drop reference from dget() on entrance.
 418          */
 419         dput(dentry);
 420 }
 421
 422 /**
 423  *      sysfs_remove_dir - remove an object's directory.
 424  *      @kobj:  object.
 425  *
 426  *      The only thing special about this is that we remove any files in
 427  *      the directory before we remove the directory, and we've inlined
 428  *      what used to be sysfs_rmdir() below, instead of calling separately.
 429  */
 430
 431 void sysfs_remove_dir(struct kobject * kobj)
 432 {
 433         __sysfs_remove_dir(kobj->dentry);
 434         kobj->dentry = NULL;
 435 }
 436
 437 int sysfs_rename_dir(struct kobject * kobj, struct dentry *new_parent,
 438                      const char *new_name)
 439 {
 440         struct sysfs_dirent *sd = kobj->dentry->d_fsdata;
 441         struct sysfs_dirent *parent_sd = new_parent->d_fsdata;
 442         struct dentry *new_dentry;
 443         char *dup_name;
 444         int error;
 445
 446         if (!new_parent)
 447                 return -EFAULT;
 448
 449         down_write(&sysfs_rename_sem);
 450         mutex_lock(&new_parent->d_inode->i_mutex);
 451
 452         new_dentry = lookup_one_len(new_name, new_parent, strlen(new_name));
 453         if (IS_ERR(new_dentry)) {
 454                 error = PTR_ERR(new_dentry);
 455                 goto out_unlock;
 456         }
 457
 458         /* By allowing two different directories with the same
 459          * d_parent we allow this routine to move between different
 460          * shadows of the same directory
 461          */
 462         error = -EINVAL;
 463         if (kobj->dentry->d_parent->d_inode != new_parent->d_inode ||
 464             new_dentry->d_parent->d_inode != new_parent->d_inode ||
 465             new_dentry == kobj->dentry)
 466                 goto out_dput;
 467
 468         error = -EEXIST;
 469         if (new_dentry->d_inode)
 470                 goto out_dput;
 471
 472         /* rename kobject and sysfs_dirent */
 473         error = -ENOMEM;
 474         new_name = dup_name = kstrdup(new_name, GFP_KERNEL);
 475         if (!new_name)
 476                 goto out_drop;
 477
 478         error = kobject_set_name(kobj, "%s", new_name);
 479         if (error)
 480                 goto out_free;
 481
 482         kfree(sd->s_name);
 483         sd->s_name = new_name;
 484
 485         /* move under the new parent */
 486         d_add(new_dentry, NULL);
 487         d_move(kobj->dentry, new_dentry);
 488
 489         list_del_init(&sd->s_sibling);
 490         list_add(&sd->s_sibling, &parent_sd->s_children);
 491
 492         error = 0;
 493         goto out_unlock;
 494
 495  out_free:
 496         kfree(dup_name);
 497  out_drop:
 498         d_drop(new_dentry);
 499  out_dput:
 500         dput(new_dentry);
 501  out_unlock:
 502         mutex_unlock(&new_parent->d_inode->i_mutex);
 503         up_write(&sysfs_rename_sem);
 504         return error;
 505 }
 506
 507 int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent)
 508 {
 509         struct dentry *old_parent_dentry, *new_parent_dentry, *new_dentry;
 510         struct sysfs_dirent *new_parent_sd, *sd;
 511         int error;
 512
 513         old_parent_dentry = kobj->parent ?
 514                 kobj->parent->dentry : sysfs_mount->mnt_sb->s_root;
 515         new_parent_dentry = new_parent ?
 516                 new_parent->dentry : sysfs_mount->mnt_sb->s_root;
 517
 518         if (old_parent_dentry->d_inode == new_parent_dentry->d_inode)
 519                 return 0;       /* nothing to move */
 520 again:
 521         mutex_lock(&old_parent_dentry->d_inode->i_mutex);
 522         if (!mutex_trylock(&new_parent_dentry->d_inode->i_mutex)) {
 523                 mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
 524                 goto again;
 525         }
 526
 527         new_parent_sd = new_parent_dentry->d_fsdata;
 528         sd = kobj->dentry->d_fsdata;
 529
 530         new_dentry = lookup_one_len(kobj->name, new_parent_dentry,
 531                                     strlen(kobj->name));
 532         if (IS_ERR(new_dentry)) {
 533                 error = PTR_ERR(new_dentry);
 534                 goto out;
 535         } else
 536                 error = 0;
 537         d_add(new_dentry, NULL);
 538         d_move(kobj->dentry, new_dentry);
 539         dput(new_dentry);
 540
 541         /* Remove from old parent's list and insert into new parent's list. */
 542         list_del_init(&sd->s_sibling);
 543         list_add(&sd->s_sibling, &new_parent_sd->s_children);
 544
 545 out:
 546         mutex_unlock(&new_parent_dentry->d_inode->i_mutex);
 547         mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
 548
 549         return error;
 550 }
 551
 552 static int sysfs_dir_open(struct inode *inode, struct file *file)
 553 {
 554         struct dentry * dentry = file->f_path.dentry;
 555         struct sysfs_dirent * parent_sd = dentry->d_fsdata;
 556         struct sysfs_dirent * sd;
 557
 558         mutex_lock(&dentry->d_inode->i_mutex);
 559         sd = sysfs_new_dirent("_DIR_", NULL, 0, 0);
 560         if (sd)
 561                 sysfs_attach_dirent(sd, parent_sd, NULL);
 562         mutex_unlock(&dentry->d_inode->i_mutex);
 563
 564         file->private_data = sd;
 565         return sd ? 0 : -ENOMEM;
 566 }
 567
 568 static int sysfs_dir_close(struct inode *inode, struct file *file)
 569 {
 570         struct dentry * dentry = file->f_path.dentry;
 571         struct sysfs_dirent * cursor = file->private_data;
 572
 573         mutex_lock(&dentry->d_inode->i_mutex);
 574         list_del_init(&cursor->s_sibling);
 575         mutex_unlock(&dentry->d_inode->i_mutex);
 576
 577         release_sysfs_dirent(cursor);
 578
 579         return 0;
 580 }
 581
 582 /* Relationship between s_mode and the DT_xxx types */
 583 static inline unsigned char dt_type(struct sysfs_dirent *sd)
 584 {
 585         return (sd->s_mode >> 12) & 15;
 586 }
 587
 588 static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 589 {
 590         struct dentry *dentry = filp->f_path.dentry;
 591         struct sysfs_dirent * parent_sd = dentry->d_fsdata;
 592         struct sysfs_dirent *cursor = filp->private_data;
 593         struct list_head *p, *q = &cursor->s_sibling;
 594         ino_t ino;
 595         int i = filp->f_pos;
 596
 597         switch (i) {
 598                 case 0:
 599                         ino = parent_sd->s_ino;
 600                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 601                                 break;
 602                         filp->f_pos++;
 603                         i++;
 604                         /* fallthrough */
 605                 case 1:
 606                         if (parent_sd->s_parent)
 607                                 ino = parent_sd->s_parent->s_ino;
 608                         else
 609                                 ino = parent_sd->s_ino;
 610                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 611                                 break;
 612                         filp->f_pos++;
 613                         i++;
 614                         /* fallthrough */
 615                 default:
 616                         if (filp->f_pos == 2)
 617                                 list_move(q, &parent_sd->s_children);
 618
 619                         for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
 620                                 struct sysfs_dirent *next;
 621                                 const char * name;
 622                                 int len;
 623
 624                                 next = list_entry(p, struct sysfs_dirent,
 625                                                    s_sibling);
 626                                 if (!next->s_element)
 627                                         continue;
 628
 629                                 name = next->s_name;
 630                                 len = strlen(name);
 631                                 ino = next->s_ino;
 632
 633                                 if (filldir(dirent, name, len, filp->f_pos, ino,
 634                                                  dt_type(next)) < 0)
 635                                         return 0;
 636
 637                                 list_move(q, p);
 638                                 p = q;
 639                                 filp->f_pos++;
 640                         }
 641         }
 642         return 0;
 643 }
 644
 645 static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
 646 {
 647         struct dentry * dentry = file->f_path.dentry;
 648
 649         mutex_lock(&dentry->d_inode->i_mutex);
 650         switch (origin) {
 651                 case 1:
 652                         offset += file->f_pos;
 653                 case 0:
 654                         if (offset >= 0)
 655                                 break;
 656                 default:
 657                         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 658                         return -EINVAL;
 659         }
 660         if (offset != file->f_pos) {
 661                 file->f_pos = offset;
 662                 if (file->f_pos >= 2) {
 663                         struct sysfs_dirent *sd = dentry->d_fsdata;
 664                         struct sysfs_dirent *cursor = file->private_data;
 665                         struct list_head *p;
 666                         loff_t n = file->f_pos - 2;
 667
 668                         list_del(&cursor->s_sibling);
 669                         p = sd->s_children.next;
 670                         while (n && p != &sd->s_children) {
 671                                 struct sysfs_dirent *next;
 672                                 next = list_entry(p, struct sysfs_dirent,
 673                                                    s_sibling);
 674                                 if (next->s_element)
 675                                         n--;
 676                                 p = p->next;
 677                         }
 678                         list_add_tail(&cursor->s_sibling, p);
 679                 }
 680         }
 681         mutex_unlock(&dentry->d_inode->i_mutex);
 682         return offset;
 683 }
 684
 685
 686 /**
 687  *      sysfs_make_shadowed_dir - Setup so a directory can be shadowed
 688  *      @kobj:  object we're creating shadow of.
 689  */
 690
 691 int sysfs_make_shadowed_dir(struct kobject *kobj,
 692         void * (*follow_link)(struct dentry *, struct nameidata *))
 693 {
 694         struct inode *inode;
 695         struct inode_operations *i_op;
 696
 697         inode = kobj->dentry->d_inode;
 698         if (inode->i_op != &sysfs_dir_inode_operations)
 699                 return -EINVAL;
 700
 701         i_op = kmalloc(sizeof(*i_op), GFP_KERNEL);
 702         if (!i_op)
 703                 return -ENOMEM;
 704
 705         memcpy(i_op, &sysfs_dir_inode_operations, sizeof(*i_op));
 706         i_op->follow_link = follow_link;
 707
 708         /* Locking of inode->i_op?
 709          * Since setting i_op is a single word write and they
 710          * are atomic we should be ok here.
 711          */
 712         inode->i_op = i_op;
 713         return 0;
 714 }
 715
 716 /**
 717  *      sysfs_create_shadow_dir - create a shadow directory for an object.
 718  *      @kobj:  object we're creating directory for.
 719  *
 720  *      sysfs_make_shadowed_dir must already have been called on this
 721  *      directory.
 722  */
 723
 724 struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)
 725 {
 726         struct dentry *dir = kobj->dentry;
 727         struct inode *inode = dir->d_inode;
 728         struct dentry *parent = dir->d_parent;
 729         struct sysfs_dirent *parent_sd = parent->d_fsdata;
 730         struct dentry *shadow;
 731         struct sysfs_dirent *sd;
 732
 733         shadow = ERR_PTR(-EINVAL);
 734         if (!sysfs_is_shadowed_inode(inode))
 735                 goto out;
 736
 737         shadow = d_alloc(parent, &dir->d_name);
 738         if (!shadow)
 739                 goto nomem;
 740
 741         sd = sysfs_new_dirent("_SHADOW_", kobj, inode->i_mode, SYSFS_DIR);
 742         if (!sd)
 743                 goto nomem;
 744         /* point to parent_sd but don't attach to it */
 745         sd->s_parent = sysfs_get(parent_sd);
 746         sysfs_attach_dirent(sd, NULL, shadow);
 747
 748         d_instantiate(shadow, igrab(inode));
 749         inc_nlink(inode);
 750         inc_nlink(parent->d_inode);
 751         shadow->d_op = &sysfs_dentry_ops;
 752
 753         dget(shadow);           /* Extra count - pin the dentry in core */
 754
 755 out:
 756         return shadow;
 757 nomem:
 758         dput(shadow);
 759         shadow = ERR_PTR(-ENOMEM);
 760         goto out;
 761 }
 762
 763 /**
 764  *      sysfs_remove_shadow_dir - remove an object's directory.
 765  *      @shadow: dentry of shadow directory
 766  *
 767  *      The only thing special about this is that we remove any files in
 768  *      the directory before we remove the directory, and we've inlined
 769  *      what used to be sysfs_rmdir() below, instead of calling separately.
 770  */
 771
 772 void sysfs_remove_shadow_dir(struct dentry *shadow)
 773 {
 774         __sysfs_remove_dir(shadow);
 775 }
 776
 777 const struct file_operations sysfs_dir_operations = {
 778         .open           = sysfs_dir_open,
 779         .release        = sysfs_dir_close,
 780         .llseek         = sysfs_dir_lseek,
 781         .read           = generic_read_dir,
 782         .readdir        = sysfs_readdir,
 783 };