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 spinlock_t kobj_sysfs_assoc_lock = SPIN_LOCK_UNLOCKED;
  19
  20 static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;
  21 static DEFINE_IDA(sysfs_ino_ida);
  22
  23 int sysfs_alloc_ino(ino_t *pino)
  24 {
  25         int ino, rc;
  26
  27  retry:
  28         spin_lock(&sysfs_ino_lock);
  29         rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
  30         spin_unlock(&sysfs_ino_lock);
  31
  32         if (rc == -EAGAIN) {
  33                 if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL))
  34                         goto retry;
  35                 rc = -ENOMEM;
  36         }
  37
  38         *pino = ino;
  39         return rc;
  40 }
  41
  42 static void sysfs_free_ino(ino_t ino)
  43 {
  44         spin_lock(&sysfs_ino_lock);
  45         ida_remove(&sysfs_ino_ida, ino);
  46         spin_unlock(&sysfs_ino_lock);
  47 }
  48
  49 void release_sysfs_dirent(struct sysfs_dirent * sd)
  50 {
  51         struct sysfs_dirent *parent_sd;
  52
  53  repeat:
  54         parent_sd = sd->s_parent;
  55
  56         if (sd->s_type & SYSFS_KOBJ_LINK)
  57                 sysfs_put(sd->s_elem.symlink.target_sd);
  58         if (sd->s_type & SYSFS_COPY_NAME)
  59                 kfree(sd->s_name);
  60         kfree(sd->s_iattr);
  61         sysfs_free_ino(sd->s_ino);
  62         kmem_cache_free(sysfs_dir_cachep, sd);
  63
  64         sd = parent_sd;
  65         if (sd && atomic_dec_and_test(&sd->s_count))
  66                 goto repeat;
  67 }
  68
  69 static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
  70 {
  71         struct sysfs_dirent * sd = dentry->d_fsdata;
  72
  73         if (sd) {
  74                 /* sd->s_dentry is protected with sysfs_lock.  This
  75                  * allows sysfs_drop_dentry() to dereference it.
  76                  */
  77                 spin_lock(&sysfs_lock);
  78
  79                 /* The dentry might have been deleted or another
  80                  * lookup could have happened updating sd->s_dentry to
  81                  * point the new dentry.  Ignore if it isn't pointing
  82                  * to this dentry.
  83                  */
  84                 if (sd->s_dentry == dentry)
  85                         sd->s_dentry = NULL;
  86                 spin_unlock(&sysfs_lock);
  87                 sysfs_put(sd);
  88         }
  89         iput(inode);
  90 }
  91
  92 static struct dentry_operations sysfs_dentry_ops = {
  93         .d_iput         = sysfs_d_iput,
  94 };
  95
  96 struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
  97 {
  98         char *dup_name = NULL;
  99         struct sysfs_dirent *sd = NULL;
 100
 101         if (type & SYSFS_COPY_NAME) {
 102                 name = dup_name = kstrdup(name, GFP_KERNEL);
 103                 if (!name)
 104                         goto err_out;
 105         }
 106
 107         sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
 108         if (!sd)
 109                 goto err_out;
 110
 111         if (sysfs_alloc_ino(&sd->s_ino))
 112                 goto err_out;
 113
 114         atomic_set(&sd->s_count, 1);
 115         atomic_set(&sd->s_event, 1);
 116         INIT_LIST_HEAD(&sd->s_children);
 117         INIT_LIST_HEAD(&sd->s_sibling);
 118
 119         sd->s_name = name;
 120         sd->s_mode = mode;
 121         sd->s_type = type;
 122
 123         return sd;
 124
 125  err_out:
 126         kfree(dup_name);
 127         kmem_cache_free(sysfs_dir_cachep, sd);
 128         return NULL;
 129 }
 130
 131 void sysfs_attach_dirent(struct sysfs_dirent *sd,
 132                          struct sysfs_dirent *parent_sd, struct dentry *dentry)
 133 {
 134         if (dentry) {
 135                 sd->s_dentry = dentry;
 136                 dentry->d_fsdata = sysfs_get(sd);
 137                 dentry->d_op = &sysfs_dentry_ops;
 138         }
 139
 140         if (parent_sd) {
 141                 sd->s_parent = sysfs_get(parent_sd);
 142                 list_add(&sd->s_sibling, &parent_sd->s_children);
 143         }
 144 }
 145
 146 /*
 147  *
 148  * Return -EEXIST if there is already a sysfs element with the same name for
 149  * the same parent.
 150  *
 151  * called with parent inode's i_mutex held
 152  */
 153 int sysfs_dirent_exist(struct sysfs_dirent *parent_sd,
 154                           const unsigned char *new)
 155 {
 156         struct sysfs_dirent * sd;
 157
 158         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 159                 if (sd->s_type) {
 160                         if (strcmp(sd->s_name, new))
 161                                 continue;
 162                         else
 163                                 return -EEXIST;
 164                 }
 165         }
 166
 167         return 0;
 168 }
 169
 170 static int init_dir(struct inode * inode)
 171 {
 172         inode->i_op = &sysfs_dir_inode_operations;
 173         inode->i_fop = &sysfs_dir_operations;
 174
 175         /* directory inodes start off with i_nlink == 2 (for "." entry) */
 176         inc_nlink(inode);
 177         return 0;
 178 }
 179
 180 static int init_file(struct inode * inode)
 181 {
 182         inode->i_size = PAGE_SIZE;
 183         inode->i_fop = &sysfs_file_operations;
 184         return 0;
 185 }
 186
 187 static int init_symlink(struct inode * inode)
 188 {
 189         inode->i_op = &sysfs_symlink_inode_operations;
 190         return 0;
 191 }
 192
 193 static int create_dir(struct kobject *kobj, struct dentry *parent,
 194                       const char *name, struct dentry **p_dentry)
 195 {
 196         int error;
 197         umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
 198         struct dentry *dentry;
 199         struct sysfs_dirent *sd;
 200
 201         mutex_lock(&parent->d_inode->i_mutex);
 202
 203         dentry = lookup_one_len(name, parent, strlen(name));
 204         if (IS_ERR(dentry)) {
 205                 error = PTR_ERR(dentry);
 206                 goto out_unlock;
 207         }
 208
 209         error = -EEXIST;
 210         if (sysfs_dirent_exist(parent->d_fsdata, name))
 211                 goto out_dput;
 212
 213         error = -ENOMEM;
 214         sd = sysfs_new_dirent(name, mode, SYSFS_DIR);
 215         if (!sd)
 216                 goto out_drop;
 217         sd->s_elem.dir.kobj = kobj;
 218         sysfs_attach_dirent(sd, parent->d_fsdata, dentry);
 219
 220         error = sysfs_create(dentry, mode, init_dir);
 221         if (error)
 222                 goto out_sput;
 223
 224         inc_nlink(parent->d_inode);
 225         dentry->d_op = &sysfs_dentry_ops;
 226         d_rehash(dentry);
 227
 228         *p_dentry = dentry;
 229         error = 0;
 230         goto out_dput;
 231
 232  out_sput:
 233         list_del_init(&sd->s_sibling);
 234         sysfs_put(sd);
 235  out_drop:
 236         d_drop(dentry);
 237  out_dput:
 238         dput(dentry);
 239  out_unlock:
 240         mutex_unlock(&parent->d_inode->i_mutex);
 241         return error;
 242 }
 243
 244
 245 int sysfs_create_subdir(struct kobject * k, const char * n, struct dentry ** d)
 246 {
 247         return create_dir(k,k->dentry,n,d);
 248 }
 249
 250 /**
 251  *      sysfs_create_dir - create a directory for an object.
 252  *      @kobj:          object we're creating directory for.
 253  *      @shadow_parent: parent parent object.
 254  */
 255
 256 int sysfs_create_dir(struct kobject * kobj, struct dentry *shadow_parent)
 257 {
 258         struct dentry * dentry = NULL;
 259         struct dentry * parent;
 260         int error = 0;
 261
 262         BUG_ON(!kobj);
 263
 264         if (shadow_parent)
 265                 parent = shadow_parent;
 266         else if (kobj->parent)
 267                 parent = kobj->parent->dentry;
 268         else if (sysfs_mount && sysfs_mount->mnt_sb)
 269                 parent = sysfs_mount->mnt_sb->s_root;
 270         else
 271                 return -EFAULT;
 272
 273         error = create_dir(kobj,parent,kobject_name(kobj),&dentry);
 274         if (!error)
 275                 kobj->dentry = dentry;
 276         return error;
 277 }
 278
 279 /* attaches attribute's sysfs_dirent to the dentry corresponding to the
 280  * attribute file
 281  */
 282 static int sysfs_attach_attr(struct sysfs_dirent * sd, struct dentry * dentry)
 283 {
 284         struct attribute * attr = NULL;
 285         struct bin_attribute * bin_attr = NULL;
 286         int (* init) (struct inode *) = NULL;
 287         int error = 0;
 288
 289         if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
 290                 bin_attr = sd->s_elem.bin_attr.bin_attr;
 291                 attr = &bin_attr->attr;
 292         } else {
 293                 attr = sd->s_elem.attr.attr;
 294                 init = init_file;
 295         }
 296
 297         dentry->d_fsdata = sysfs_get(sd);
 298         /* protect sd->s_dentry against sysfs_d_iput */
 299         spin_lock(&sysfs_lock);
 300         sd->s_dentry = dentry;
 301         spin_unlock(&sysfs_lock);
 302         error = sysfs_create(dentry, (attr->mode & S_IALLUGO) | S_IFREG, init);
 303         if (error) {
 304                 sysfs_put(sd);
 305                 return error;
 306         }
 307
 308         if (bin_attr) {
 309                 dentry->d_inode->i_size = bin_attr->size;
 310                 dentry->d_inode->i_fop = &bin_fops;
 311         }
 312         dentry->d_op = &sysfs_dentry_ops;
 313         d_rehash(dentry);
 314
 315         return 0;
 316 }
 317
 318 static int sysfs_attach_link(struct sysfs_dirent * sd, struct dentry * dentry)
 319 {
 320         int err = 0;
 321
 322         dentry->d_fsdata = sysfs_get(sd);
 323         /* protect sd->s_dentry against sysfs_d_iput */
 324         spin_lock(&sysfs_lock);
 325         sd->s_dentry = dentry;
 326         spin_unlock(&sysfs_lock);
 327         err = sysfs_create(dentry, S_IFLNK|S_IRWXUGO, init_symlink);
 328         if (!err) {
 329                 dentry->d_op = &sysfs_dentry_ops;
 330                 d_rehash(dentry);
 331         } else
 332                 sysfs_put(sd);
 333
 334         return err;
 335 }
 336
 337 static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
 338                                 struct nameidata *nd)
 339 {
 340         struct sysfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
 341         struct sysfs_dirent * sd;
 342         int err = 0;
 343
 344         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 345                 if (sd->s_type & SYSFS_NOT_PINNED) {
 346                         if (strcmp(sd->s_name, dentry->d_name.name))
 347                                 continue;
 348
 349                         if (sd->s_type & SYSFS_KOBJ_LINK)
 350                                 err = sysfs_attach_link(sd, dentry);
 351                         else
 352                                 err = sysfs_attach_attr(sd, dentry);
 353                         break;
 354                 }
 355         }
 356
 357         return ERR_PTR(err);
 358 }
 359
 360 const struct inode_operations sysfs_dir_inode_operations = {
 361         .lookup         = sysfs_lookup,
 362         .setattr        = sysfs_setattr,
 363 };
 364
 365 static void remove_dir(struct dentry * d)
 366 {
 367         struct dentry * parent = dget(d->d_parent);
 368         struct sysfs_dirent * sd;
 369
 370         mutex_lock(&parent->d_inode->i_mutex);
 371         d_delete(d);
 372         sd = d->d_fsdata;
 373         list_del_init(&sd->s_sibling);
 374         sysfs_put(sd);
 375         if (d->d_inode)
 376                 simple_rmdir(parent->d_inode,d);
 377
 378         pr_debug(" o %s removing done (%d)\n",d->d_name.name,
 379                  atomic_read(&d->d_count));
 380
 381         mutex_unlock(&parent->d_inode->i_mutex);
 382         dput(parent);
 383 }
 384
 385 void sysfs_remove_subdir(struct dentry * d)
 386 {
 387         remove_dir(d);
 388 }
 389
 390
 391 static void __sysfs_remove_dir(struct dentry *dentry)
 392 {
 393         struct sysfs_dirent * parent_sd;
 394         struct sysfs_dirent * sd, * tmp;
 395
 396         dget(dentry);
 397         if (!dentry)
 398                 return;
 399
 400         pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);
 401         mutex_lock(&dentry->d_inode->i_mutex);
 402         parent_sd = dentry->d_fsdata;
 403         list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
 404                 if (!sd->s_type || !(sd->s_type & SYSFS_NOT_PINNED))
 405                         continue;
 406                 list_del_init(&sd->s_sibling);
 407                 sysfs_drop_dentry(sd, dentry);
 408                 sysfs_put(sd);
 409         }
 410         mutex_unlock(&dentry->d_inode->i_mutex);
 411
 412         remove_dir(dentry);
 413         /**
 414          * Drop reference from dget() on entrance.
 415          */
 416         dput(dentry);
 417 }
 418
 419 /**
 420  *      sysfs_remove_dir - remove an object's directory.
 421  *      @kobj:  object.
 422  *
 423  *      The only thing special about this is that we remove any files in
 424  *      the directory before we remove the directory, and we've inlined
 425  *      what used to be sysfs_rmdir() below, instead of calling separately.
 426  */
 427
 428 void sysfs_remove_dir(struct kobject * kobj)
 429 {
 430         struct dentry *d = kobj->dentry;
 431
 432         spin_lock(&kobj_sysfs_assoc_lock);
 433         kobj->dentry = NULL;
 434         spin_unlock(&kobj_sysfs_assoc_lock);
 435
 436         __sysfs_remove_dir(d);
 437 }
 438
 439 int sysfs_rename_dir(struct kobject * kobj, struct dentry *new_parent,
 440                      const char *new_name)
 441 {
 442         struct sysfs_dirent *sd = kobj->dentry->d_fsdata;
 443         struct sysfs_dirent *parent_sd = new_parent->d_fsdata;
 444         struct dentry *new_dentry;
 445         char *dup_name;
 446         int error;
 447
 448         if (!new_parent)
 449                 return -EFAULT;
 450
 451         down_write(&sysfs_rename_sem);
 452         mutex_lock(&new_parent->d_inode->i_mutex);
 453
 454         new_dentry = lookup_one_len(new_name, new_parent, strlen(new_name));
 455         if (IS_ERR(new_dentry)) {
 456                 error = PTR_ERR(new_dentry);
 457                 goto out_unlock;
 458         }
 459
 460         /* By allowing two different directories with the same
 461          * d_parent we allow this routine to move between different
 462          * shadows of the same directory
 463          */
 464         error = -EINVAL;
 465         if (kobj->dentry->d_parent->d_inode != new_parent->d_inode ||
 466             new_dentry->d_parent->d_inode != new_parent->d_inode ||
 467             new_dentry == kobj->dentry)
 468                 goto out_dput;
 469
 470         error = -EEXIST;
 471         if (new_dentry->d_inode)
 472                 goto out_dput;
 473
 474         /* rename kobject and sysfs_dirent */
 475         error = -ENOMEM;
 476         new_name = dup_name = kstrdup(new_name, GFP_KERNEL);
 477         if (!new_name)
 478                 goto out_drop;
 479
 480         error = kobject_set_name(kobj, "%s", new_name);
 481         if (error)
 482                 goto out_free;
 483
 484         kfree(sd->s_name);
 485         sd->s_name = new_name;
 486
 487         /* move under the new parent */
 488         d_add(new_dentry, NULL);
 489         d_move(kobj->dentry, new_dentry);
 490
 491         list_del_init(&sd->s_sibling);
 492         list_add(&sd->s_sibling, &parent_sd->s_children);
 493
 494         error = 0;
 495         goto out_unlock;
 496
 497  out_free:
 498         kfree(dup_name);
 499  out_drop:
 500         d_drop(new_dentry);
 501  out_dput:
 502         dput(new_dentry);
 503  out_unlock:
 504         mutex_unlock(&new_parent->d_inode->i_mutex);
 505         up_write(&sysfs_rename_sem);
 506         return error;
 507 }
 508
 509 int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent)
 510 {
 511         struct dentry *old_parent_dentry, *new_parent_dentry, *new_dentry;
 512         struct sysfs_dirent *new_parent_sd, *sd;
 513         int error;
 514
 515         old_parent_dentry = kobj->parent ?
 516                 kobj->parent->dentry : sysfs_mount->mnt_sb->s_root;
 517         new_parent_dentry = new_parent ?
 518                 new_parent->dentry : sysfs_mount->mnt_sb->s_root;
 519
 520         if (old_parent_dentry->d_inode == new_parent_dentry->d_inode)
 521                 return 0;       /* nothing to move */
 522 again:
 523         mutex_lock(&old_parent_dentry->d_inode->i_mutex);
 524         if (!mutex_trylock(&new_parent_dentry->d_inode->i_mutex)) {
 525                 mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
 526                 goto again;
 527         }
 528
 529         new_parent_sd = new_parent_dentry->d_fsdata;
 530         sd = kobj->dentry->d_fsdata;
 531
 532         new_dentry = lookup_one_len(kobj->name, new_parent_dentry,
 533                                     strlen(kobj->name));
 534         if (IS_ERR(new_dentry)) {
 535                 error = PTR_ERR(new_dentry);
 536                 goto out;
 537         } else
 538                 error = 0;
 539         d_add(new_dentry, NULL);
 540         d_move(kobj->dentry, new_dentry);
 541         dput(new_dentry);
 542
 543         /* Remove from old parent's list and insert into new parent's list. */
 544         list_del_init(&sd->s_sibling);
 545         list_add(&sd->s_sibling, &new_parent_sd->s_children);
 546
 547 out:
 548         mutex_unlock(&new_parent_dentry->d_inode->i_mutex);
 549         mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
 550
 551         return error;
 552 }
 553
 554 static int sysfs_dir_open(struct inode *inode, struct file *file)
 555 {
 556         struct dentry * dentry = file->f_path.dentry;
 557         struct sysfs_dirent * parent_sd = dentry->d_fsdata;
 558         struct sysfs_dirent * sd;
 559
 560         mutex_lock(&dentry->d_inode->i_mutex);
 561         sd = sysfs_new_dirent("_DIR_", 0, 0);
 562         if (sd)
 563                 sysfs_attach_dirent(sd, parent_sd, NULL);
 564         mutex_unlock(&dentry->d_inode->i_mutex);
 565
 566         file->private_data = sd;
 567         return sd ? 0 : -ENOMEM;
 568 }
 569
 570 static int sysfs_dir_close(struct inode *inode, struct file *file)
 571 {
 572         struct dentry * dentry = file->f_path.dentry;
 573         struct sysfs_dirent * cursor = file->private_data;
 574
 575         mutex_lock(&dentry->d_inode->i_mutex);
 576         list_del_init(&cursor->s_sibling);
 577         mutex_unlock(&dentry->d_inode->i_mutex);
 578
 579         release_sysfs_dirent(cursor);
 580
 581         return 0;
 582 }
 583
 584 /* Relationship between s_mode and the DT_xxx types */
 585 static inline unsigned char dt_type(struct sysfs_dirent *sd)
 586 {
 587         return (sd->s_mode >> 12) & 15;
 588 }
 589
 590 static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 591 {
 592         struct dentry *dentry = filp->f_path.dentry;
 593         struct sysfs_dirent * parent_sd = dentry->d_fsdata;
 594         struct sysfs_dirent *cursor = filp->private_data;
 595         struct list_head *p, *q = &cursor->s_sibling;
 596         ino_t ino;
 597         int i = filp->f_pos;
 598
 599         switch (i) {
 600                 case 0:
 601                         ino = parent_sd->s_ino;
 602                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 603                                 break;
 604                         filp->f_pos++;
 605                         i++;
 606                         /* fallthrough */
 607                 case 1:
 608                         if (parent_sd->s_parent)
 609                                 ino = parent_sd->s_parent->s_ino;
 610                         else
 611                                 ino = parent_sd->s_ino;
 612                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 613                                 break;
 614                         filp->f_pos++;
 615                         i++;
 616                         /* fallthrough */
 617                 default:
 618                         if (filp->f_pos == 2)
 619                                 list_move(q, &parent_sd->s_children);
 620
 621                         for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
 622                                 struct sysfs_dirent *next;
 623                                 const char * name;
 624                                 int len;
 625
 626                                 next = list_entry(p, struct sysfs_dirent,
 627                                                    s_sibling);
 628                                 if (!next->s_type)
 629                                         continue;
 630
 631                                 name = next->s_name;
 632                                 len = strlen(name);
 633                                 ino = next->s_ino;
 634
 635                                 if (filldir(dirent, name, len, filp->f_pos, ino,
 636                                                  dt_type(next)) < 0)
 637                                         return 0;
 638
 639                                 list_move(q, p);
 640                                 p = q;
 641                                 filp->f_pos++;
 642                         }
 643         }
 644         return 0;
 645 }
 646
 647 static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
 648 {
 649         struct dentry * dentry = file->f_path.dentry;
 650
 651         mutex_lock(&dentry->d_inode->i_mutex);
 652         switch (origin) {
 653                 case 1:
 654                         offset += file->f_pos;
 655                 case 0:
 656                         if (offset >= 0)
 657                                 break;
 658                 default:
 659                         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 660                         return -EINVAL;
 661         }
 662         if (offset != file->f_pos) {
 663                 file->f_pos = offset;
 664                 if (file->f_pos >= 2) {
 665                         struct sysfs_dirent *sd = dentry->d_fsdata;
 666                         struct sysfs_dirent *cursor = file->private_data;
 667                         struct list_head *p;
 668                         loff_t n = file->f_pos - 2;
 669
 670                         list_del(&cursor->s_sibling);
 671                         p = sd->s_children.next;
 672                         while (n && p != &sd->s_children) {
 673                                 struct sysfs_dirent *next;
 674                                 next = list_entry(p, struct sysfs_dirent,
 675                                                    s_sibling);
 676                                 if (next->s_type)
 677                                         n--;
 678                                 p = p->next;
 679                         }
 680                         list_add_tail(&cursor->s_sibling, p);
 681                 }
 682         }
 683         mutex_unlock(&dentry->d_inode->i_mutex);
 684         return offset;
 685 }
 686
 687
 688 /**
 689  *      sysfs_make_shadowed_dir - Setup so a directory can be shadowed
 690  *      @kobj:  object we're creating shadow of.
 691  */
 692
 693 int sysfs_make_shadowed_dir(struct kobject *kobj,
 694         void * (*follow_link)(struct dentry *, struct nameidata *))
 695 {
 696         struct inode *inode;
 697         struct inode_operations *i_op;
 698
 699         inode = kobj->dentry->d_inode;
 700         if (inode->i_op != &sysfs_dir_inode_operations)
 701                 return -EINVAL;
 702
 703         i_op = kmalloc(sizeof(*i_op), GFP_KERNEL);
 704         if (!i_op)
 705                 return -ENOMEM;
 706
 707         memcpy(i_op, &sysfs_dir_inode_operations, sizeof(*i_op));
 708         i_op->follow_link = follow_link;
 709
 710         /* Locking of inode->i_op?
 711          * Since setting i_op is a single word write and they
 712          * are atomic we should be ok here.
 713          */
 714         inode->i_op = i_op;
 715         return 0;
 716 }
 717
 718 /**
 719  *      sysfs_create_shadow_dir - create a shadow directory for an object.
 720  *      @kobj:  object we're creating directory for.
 721  *
 722  *      sysfs_make_shadowed_dir must already have been called on this
 723  *      directory.
 724  */
 725
 726 struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)
 727 {
 728         struct dentry *dir = kobj->dentry;
 729         struct inode *inode = dir->d_inode;
 730         struct dentry *parent = dir->d_parent;
 731         struct sysfs_dirent *parent_sd = parent->d_fsdata;
 732         struct dentry *shadow;
 733         struct sysfs_dirent *sd;
 734
 735         shadow = ERR_PTR(-EINVAL);
 736         if (!sysfs_is_shadowed_inode(inode))
 737                 goto out;
 738
 739         shadow = d_alloc(parent, &dir->d_name);
 740         if (!shadow)
 741                 goto nomem;
 742
 743         sd = sysfs_new_dirent("_SHADOW_", inode->i_mode, SYSFS_DIR);
 744         if (!sd)
 745                 goto nomem;
 746         sd->s_elem.dir.kobj = kobj;
 747         /* point to parent_sd but don't attach to it */
 748         sd->s_parent = sysfs_get(parent_sd);
 749         sysfs_attach_dirent(sd, NULL, shadow);
 750
 751         d_instantiate(shadow, igrab(inode));
 752         inc_nlink(inode);
 753         inc_nlink(parent->d_inode);
 754         shadow->d_op = &sysfs_dentry_ops;
 755
 756         dget(shadow);           /* Extra count - pin the dentry in core */
 757
 758 out:
 759         return shadow;
 760 nomem:
 761         dput(shadow);
 762         shadow = ERR_PTR(-ENOMEM);
 763         goto out;
 764 }
 765
 766 /**
 767  *      sysfs_remove_shadow_dir - remove an object's directory.
 768  *      @shadow: dentry of shadow directory
 769  *
 770  *      The only thing special about this is that we remove any files in
 771  *      the directory before we remove the directory, and we've inlined
 772  *      what used to be sysfs_rmdir() below, instead of calling separately.
 773  */
 774
 775 void sysfs_remove_shadow_dir(struct dentry *shadow)
 776 {
 777         __sysfs_remove_dir(shadow);
 778 }
 779
 780 const struct file_operations sysfs_dir_operations = {
 781         .open           = sysfs_dir_open,
 782         .release        = sysfs_dir_close,
 783         .llseek         = sysfs_dir_lseek,
 784         .read           = generic_read_dir,
 785         .readdir        = sysfs_readdir,
 786 };