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 <linux/completion.h>
  14 #include <asm/semaphore.h>
  15 #include "sysfs.h"
  16
  17 DECLARE_RWSEM(sysfs_rename_sem);
  18 spinlock_t sysfs_lock = SPIN_LOCK_UNLOCKED;
  19 spinlock_t kobj_sysfs_assoc_lock = SPIN_LOCK_UNLOCKED;
  20
  21 static spinlock_t sysfs_ino_lock = SPIN_LOCK_UNLOCKED;
  22 static DEFINE_IDA(sysfs_ino_ida);
  23
  24 /**
  25  *      sysfs_get_active - get an active reference to sysfs_dirent
  26  *      @sd: sysfs_dirent to get an active reference to
  27  *
  28  *      Get an active reference of @sd.  This function is noop if @sd
  29  *      is NULL.
  30  *
  31  *      RETURNS:
  32  *      Pointer to @sd on success, NULL on failure.
  33  */
  34 struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd)
  35 {
  36         if (unlikely(!sd))
  37                 return NULL;
  38
  39         while (1) {
  40                 int v, t;
  41
  42                 v = atomic_read(&sd->s_active);
  43                 if (unlikely(v < 0))
  44                         return NULL;
  45
  46                 t = atomic_cmpxchg(&sd->s_active, v, v + 1);
  47                 if (likely(t == v))
  48                         return sd;
  49                 if (t < 0)
  50                         return NULL;
  51
  52                 cpu_relax();
  53         }
  54 }
  55
  56 /**
  57  *      sysfs_put_active - put an active reference to sysfs_dirent
  58  *      @sd: sysfs_dirent to put an active reference to
  59  *
  60  *      Put an active reference to @sd.  This function is noop if @sd
  61  *      is NULL.
  62  */
  63 void sysfs_put_active(struct sysfs_dirent *sd)
  64 {
  65         struct completion *cmpl;
  66         int v;
  67
  68         if (unlikely(!sd))
  69                 return;
  70
  71         v = atomic_dec_return(&sd->s_active);
  72         if (likely(v != SD_DEACTIVATED_BIAS))
  73                 return;
  74
  75         /* atomic_dec_return() is a mb(), we'll always see the updated
  76          * sd->s_sibling.next.
  77          */
  78         cmpl = (void *)sd->s_sibling.next;
  79         complete(cmpl);
  80 }
  81
  82 /**
  83  *      sysfs_get_active_two - get active references to sysfs_dirent and parent
  84  *      @sd: sysfs_dirent of interest
  85  *
  86  *      Get active reference to @sd and its parent.  Parent's active
  87  *      reference is grabbed first.  This function is noop if @sd is
  88  *      NULL.
  89  *
  90  *      RETURNS:
  91  *      Pointer to @sd on success, NULL on failure.
  92  */
  93 struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd)
  94 {
  95         if (sd) {
  96                 if (sd->s_parent && unlikely(!sysfs_get_active(sd->s_parent)))
  97                         return NULL;
  98                 if (unlikely(!sysfs_get_active(sd))) {
  99                         sysfs_put_active(sd->s_parent);
 100                         return NULL;
 101                 }
 102         }
 103         return sd;
 104 }
 105
 106 /**
 107  *      sysfs_put_active_two - put active references to sysfs_dirent and parent
 108  *      @sd: sysfs_dirent of interest
 109  *
 110  *      Put active references to @sd and its parent.  This function is
 111  *      noop if @sd is NULL.
 112  */
 113 void sysfs_put_active_two(struct sysfs_dirent *sd)
 114 {
 115         if (sd) {
 116                 sysfs_put_active(sd);
 117                 sysfs_put_active(sd->s_parent);
 118         }
 119 }
 120
 121 /**
 122  *      sysfs_deactivate - deactivate sysfs_dirent
 123  *      @sd: sysfs_dirent to deactivate
 124  *
 125  *      Deny new active references and drain existing ones.
 126  */
 127 void sysfs_deactivate(struct sysfs_dirent *sd)
 128 {
 129         DECLARE_COMPLETION_ONSTACK(wait);
 130         int v;
 131
 132         BUG_ON(!list_empty(&sd->s_sibling));
 133         sd->s_sibling.next = (void *)&wait;
 134
 135         /* atomic_add_return() is a mb(), put_active() will always see
 136          * the updated sd->s_sibling.next.
 137          */
 138         v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active);
 139
 140         if (v != SD_DEACTIVATED_BIAS)
 141                 wait_for_completion(&wait);
 142
 143         INIT_LIST_HEAD(&sd->s_sibling);
 144 }
 145
 146 static int sysfs_alloc_ino(ino_t *pino)
 147 {
 148         int ino, rc;
 149
 150  retry:
 151         spin_lock(&sysfs_ino_lock);
 152         rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
 153         spin_unlock(&sysfs_ino_lock);
 154
 155         if (rc == -EAGAIN) {
 156                 if (ida_pre_get(&sysfs_ino_ida, GFP_KERNEL))
 157                         goto retry;
 158                 rc = -ENOMEM;
 159         }
 160
 161         *pino = ino;
 162         return rc;
 163 }
 164
 165 static void sysfs_free_ino(ino_t ino)
 166 {
 167         spin_lock(&sysfs_ino_lock);
 168         ida_remove(&sysfs_ino_ida, ino);
 169         spin_unlock(&sysfs_ino_lock);
 170 }
 171
 172 void release_sysfs_dirent(struct sysfs_dirent * sd)
 173 {
 174         struct sysfs_dirent *parent_sd;
 175
 176  repeat:
 177         parent_sd = sd->s_parent;
 178
 179         if (sd->s_type & SYSFS_KOBJ_LINK)
 180                 sysfs_put(sd->s_elem.symlink.target_sd);
 181         if (sd->s_type & SYSFS_COPY_NAME)
 182                 kfree(sd->s_name);
 183         kfree(sd->s_iattr);
 184         sysfs_free_ino(sd->s_ino);
 185         kmem_cache_free(sysfs_dir_cachep, sd);
 186
 187         sd = parent_sd;
 188         if (sd && atomic_dec_and_test(&sd->s_count))
 189                 goto repeat;
 190 }
 191
 192 static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
 193 {
 194         struct sysfs_dirent * sd = dentry->d_fsdata;
 195
 196         if (sd) {
 197                 /* sd->s_dentry is protected with sysfs_lock.  This
 198                  * allows sysfs_drop_dentry() to dereference it.
 199                  */
 200                 spin_lock(&sysfs_lock);
 201
 202                 /* The dentry might have been deleted or another
 203                  * lookup could have happened updating sd->s_dentry to
 204                  * point the new dentry.  Ignore if it isn't pointing
 205                  * to this dentry.
 206                  */
 207                 if (sd->s_dentry == dentry)
 208                         sd->s_dentry = NULL;
 209                 spin_unlock(&sysfs_lock);
 210                 sysfs_put(sd);
 211         }
 212         iput(inode);
 213 }
 214
 215 static struct dentry_operations sysfs_dentry_ops = {
 216         .d_iput         = sysfs_d_iput,
 217 };
 218
 219 struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
 220 {
 221         char *dup_name = NULL;
 222         struct sysfs_dirent *sd = NULL;
 223
 224         if (type & SYSFS_COPY_NAME) {
 225                 name = dup_name = kstrdup(name, GFP_KERNEL);
 226                 if (!name)
 227                         goto err_out;
 228         }
 229
 230         sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
 231         if (!sd)
 232                 goto err_out;
 233
 234         if (sysfs_alloc_ino(&sd->s_ino))
 235                 goto err_out;
 236
 237         atomic_set(&sd->s_count, 1);
 238         atomic_set(&sd->s_active, 0);
 239         atomic_set(&sd->s_event, 1);
 240         INIT_LIST_HEAD(&sd->s_children);
 241         INIT_LIST_HEAD(&sd->s_sibling);
 242
 243         sd->s_name = name;
 244         sd->s_mode = mode;
 245         sd->s_type = type;
 246
 247         return sd;
 248
 249  err_out:
 250         kfree(dup_name);
 251         kmem_cache_free(sysfs_dir_cachep, sd);
 252         return NULL;
 253 }
 254
 255 static void sysfs_attach_dentry(struct sysfs_dirent *sd, struct dentry *dentry)
 256 {
 257         dentry->d_op = &sysfs_dentry_ops;
 258         dentry->d_fsdata = sysfs_get(sd);
 259
 260         /* protect sd->s_dentry against sysfs_d_iput */
 261         spin_lock(&sysfs_lock);
 262         sd->s_dentry = dentry;
 263         spin_unlock(&sysfs_lock);
 264
 265         d_rehash(dentry);
 266 }
 267
 268 void sysfs_attach_dirent(struct sysfs_dirent *sd,
 269                          struct sysfs_dirent *parent_sd, struct dentry *dentry)
 270 {
 271         if (dentry)
 272                 sysfs_attach_dentry(sd, dentry);
 273
 274         if (parent_sd) {
 275                 sd->s_parent = sysfs_get(parent_sd);
 276                 list_add(&sd->s_sibling, &parent_sd->s_children);
 277         }
 278 }
 279
 280 /*
 281  *
 282  * Return -EEXIST if there is already a sysfs element with the same name for
 283  * the same parent.
 284  *
 285  * called with parent inode's i_mutex held
 286  */
 287 int sysfs_dirent_exist(struct sysfs_dirent *parent_sd,
 288                           const unsigned char *new)
 289 {
 290         struct sysfs_dirent * sd;
 291
 292         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 293                 if (sd->s_type) {
 294                         if (strcmp(sd->s_name, new))
 295                                 continue;
 296                         else
 297                                 return -EEXIST;
 298                 }
 299         }
 300
 301         return 0;
 302 }
 303
 304 static int create_dir(struct kobject *kobj, struct dentry *parent,
 305                       const char *name, struct dentry **p_dentry)
 306 {
 307         int error;
 308         umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
 309         struct dentry *dentry;
 310         struct inode *inode;
 311         struct sysfs_dirent *sd;
 312
 313         mutex_lock(&parent->d_inode->i_mutex);
 314
 315         /* allocate */
 316         dentry = lookup_one_len(name, parent, strlen(name));
 317         if (IS_ERR(dentry)) {
 318                 error = PTR_ERR(dentry);
 319                 goto out_unlock;
 320         }
 321
 322         error = -EEXIST;
 323         if (dentry->d_inode)
 324                 goto out_dput;
 325
 326         error = -ENOMEM;
 327         sd = sysfs_new_dirent(name, mode, SYSFS_DIR);
 328         if (!sd)
 329                 goto out_drop;
 330         sd->s_elem.dir.kobj = kobj;
 331
 332         inode = sysfs_get_inode(sd);
 333         if (!inode)
 334                 goto out_sput;
 335
 336         if (inode->i_state & I_NEW) {
 337                 inode->i_op = &sysfs_dir_inode_operations;
 338                 inode->i_fop = &sysfs_dir_operations;
 339                 /* directory inodes start off with i_nlink == 2 (for ".") */
 340                 inc_nlink(inode);
 341         }
 342
 343         /* link in */
 344         error = -EEXIST;
 345         if (sysfs_dirent_exist(parent->d_fsdata, name))
 346                 goto out_iput;
 347
 348         sysfs_instantiate(dentry, inode);
 349         inc_nlink(parent->d_inode);
 350         sysfs_attach_dirent(sd, parent->d_fsdata, dentry);
 351
 352         *p_dentry = dentry;
 353         error = 0;
 354         goto out_unlock;        /* pin directory dentry in core */
 355
 356  out_iput:
 357         iput(inode);
 358  out_sput:
 359         sysfs_put(sd);
 360  out_drop:
 361         d_drop(dentry);
 362  out_dput:
 363         dput(dentry);
 364  out_unlock:
 365         mutex_unlock(&parent->d_inode->i_mutex);
 366         return error;
 367 }
 368
 369
 370 int sysfs_create_subdir(struct kobject * k, const char * n, struct dentry ** d)
 371 {
 372         return create_dir(k,k->dentry,n,d);
 373 }
 374
 375 /**
 376  *      sysfs_create_dir - create a directory for an object.
 377  *      @kobj:          object we're creating directory for.
 378  *      @shadow_parent: parent parent object.
 379  */
 380
 381 int sysfs_create_dir(struct kobject * kobj, struct dentry *shadow_parent)
 382 {
 383         struct dentry * dentry = NULL;
 384         struct dentry * parent;
 385         int error = 0;
 386
 387         BUG_ON(!kobj);
 388
 389         if (shadow_parent)
 390                 parent = shadow_parent;
 391         else if (kobj->parent)
 392                 parent = kobj->parent->dentry;
 393         else if (sysfs_mount && sysfs_mount->mnt_sb)
 394                 parent = sysfs_mount->mnt_sb->s_root;
 395         else
 396                 return -EFAULT;
 397
 398         error = create_dir(kobj,parent,kobject_name(kobj),&dentry);
 399         if (!error)
 400                 kobj->dentry = dentry;
 401         return error;
 402 }
 403
 404 static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
 405                                 struct nameidata *nd)
 406 {
 407         struct sysfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
 408         struct sysfs_dirent * sd;
 409         struct inode *inode;
 410         int found = 0;
 411
 412         list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 413                 if ((sd->s_type & SYSFS_NOT_PINNED) &&
 414                     !strcmp(sd->s_name, dentry->d_name.name)) {
 415                         found = 1;
 416                         break;
 417                 }
 418         }
 419
 420         /* no such entry */
 421         if (!found)
 422                 return NULL;
 423
 424         /* attach dentry and inode */
 425         inode = sysfs_get_inode(sd);
 426         if (!inode)
 427                 return ERR_PTR(-ENOMEM);
 428
 429         if (inode->i_state & I_NEW) {
 430                 /* initialize inode according to type */
 431                 if (sd->s_type & SYSFS_KOBJ_ATTR) {
 432                         inode->i_size = PAGE_SIZE;
 433                         inode->i_fop = &sysfs_file_operations;
 434                 } else if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
 435                         struct bin_attribute *bin_attr =
 436                                 sd->s_elem.bin_attr.bin_attr;
 437                         inode->i_size = bin_attr->size;
 438                         inode->i_fop = &bin_fops;
 439                 } else if (sd->s_type & SYSFS_KOBJ_LINK)
 440                         inode->i_op = &sysfs_symlink_inode_operations;
 441         }
 442
 443         sysfs_instantiate(dentry, inode);
 444         sysfs_attach_dentry(sd, dentry);
 445
 446         return NULL;
 447 }
 448
 449 const struct inode_operations sysfs_dir_inode_operations = {
 450         .lookup         = sysfs_lookup,
 451         .setattr        = sysfs_setattr,
 452 };
 453
 454 static void remove_dir(struct dentry * d)
 455 {
 456         struct dentry *parent = d->d_parent;
 457         struct sysfs_dirent *sd = d->d_fsdata;
 458
 459         mutex_lock(&parent->d_inode->i_mutex);
 460
 461         list_del_init(&sd->s_sibling);
 462
 463         pr_debug(" o %s removing done (%d)\n",d->d_name.name,
 464                  atomic_read(&d->d_count));
 465
 466         mutex_unlock(&parent->d_inode->i_mutex);
 467
 468         sysfs_drop_dentry(sd);
 469         sysfs_deactivate(sd);
 470         sysfs_put(sd);
 471 }
 472
 473 void sysfs_remove_subdir(struct dentry * d)
 474 {
 475         remove_dir(d);
 476 }
 477
 478
 479 static void __sysfs_remove_dir(struct dentry *dentry)
 480 {
 481         LIST_HEAD(removed);
 482         struct sysfs_dirent * parent_sd;
 483         struct sysfs_dirent * sd, * tmp;
 484
 485         if (!dentry)
 486                 return;
 487
 488         pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);
 489         mutex_lock(&dentry->d_inode->i_mutex);
 490         parent_sd = dentry->d_fsdata;
 491         list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
 492                 if (!sd->s_type || !(sd->s_type & SYSFS_NOT_PINNED))
 493                         continue;
 494                 list_move(&sd->s_sibling, &removed);
 495         }
 496         mutex_unlock(&dentry->d_inode->i_mutex);
 497
 498         list_for_each_entry_safe(sd, tmp, &removed, s_sibling) {
 499                 list_del_init(&sd->s_sibling);
 500                 sysfs_drop_dentry(sd);
 501                 sysfs_deactivate(sd);
 502                 sysfs_put(sd);
 503         }
 504
 505         remove_dir(dentry);
 506 }
 507
 508 /**
 509  *      sysfs_remove_dir - remove an object's directory.
 510  *      @kobj:  object.
 511  *
 512  *      The only thing special about this is that we remove any files in
 513  *      the directory before we remove the directory, and we've inlined
 514  *      what used to be sysfs_rmdir() below, instead of calling separately.
 515  */
 516
 517 void sysfs_remove_dir(struct kobject * kobj)
 518 {
 519         struct dentry *d = kobj->dentry;
 520
 521         spin_lock(&kobj_sysfs_assoc_lock);
 522         kobj->dentry = NULL;
 523         spin_unlock(&kobj_sysfs_assoc_lock);
 524
 525         __sysfs_remove_dir(d);
 526 }
 527
 528 int sysfs_rename_dir(struct kobject * kobj, struct dentry *new_parent,
 529                      const char *new_name)
 530 {
 531         struct sysfs_dirent *sd = kobj->dentry->d_fsdata;
 532         struct sysfs_dirent *parent_sd = new_parent->d_fsdata;
 533         struct dentry *new_dentry;
 534         char *dup_name;
 535         int error;
 536
 537         if (!new_parent)
 538                 return -EFAULT;
 539
 540         down_write(&sysfs_rename_sem);
 541         mutex_lock(&new_parent->d_inode->i_mutex);
 542
 543         new_dentry = lookup_one_len(new_name, new_parent, strlen(new_name));
 544         if (IS_ERR(new_dentry)) {
 545                 error = PTR_ERR(new_dentry);
 546                 goto out_unlock;
 547         }
 548
 549         /* By allowing two different directories with the same
 550          * d_parent we allow this routine to move between different
 551          * shadows of the same directory
 552          */
 553         error = -EINVAL;
 554         if (kobj->dentry->d_parent->d_inode != new_parent->d_inode ||
 555             new_dentry->d_parent->d_inode != new_parent->d_inode ||
 556             new_dentry == kobj->dentry)
 557                 goto out_dput;
 558
 559         error = -EEXIST;
 560         if (new_dentry->d_inode)
 561                 goto out_dput;
 562
 563         /* rename kobject and sysfs_dirent */
 564         error = -ENOMEM;
 565         new_name = dup_name = kstrdup(new_name, GFP_KERNEL);
 566         if (!new_name)
 567                 goto out_drop;
 568
 569         error = kobject_set_name(kobj, "%s", new_name);
 570         if (error)
 571                 goto out_free;
 572
 573         kfree(sd->s_name);
 574         sd->s_name = new_name;
 575
 576         /* move under the new parent */
 577         d_add(new_dentry, NULL);
 578         d_move(kobj->dentry, new_dentry);
 579
 580         list_del_init(&sd->s_sibling);
 581         sysfs_get(parent_sd);
 582         sysfs_put(sd->s_parent);
 583         sd->s_parent = parent_sd;
 584         list_add(&sd->s_sibling, &parent_sd->s_children);
 585
 586         error = 0;
 587         goto out_unlock;
 588
 589  out_free:
 590         kfree(dup_name);
 591  out_drop:
 592         d_drop(new_dentry);
 593  out_dput:
 594         dput(new_dentry);
 595  out_unlock:
 596         mutex_unlock(&new_parent->d_inode->i_mutex);
 597         up_write(&sysfs_rename_sem);
 598         return error;
 599 }
 600
 601 int sysfs_move_dir(struct kobject *kobj, struct kobject *new_parent)
 602 {
 603         struct dentry *old_parent_dentry, *new_parent_dentry, *new_dentry;
 604         struct sysfs_dirent *new_parent_sd, *sd;
 605         int error;
 606
 607         old_parent_dentry = kobj->parent ?
 608                 kobj->parent->dentry : sysfs_mount->mnt_sb->s_root;
 609         new_parent_dentry = new_parent ?
 610                 new_parent->dentry : sysfs_mount->mnt_sb->s_root;
 611
 612         if (old_parent_dentry->d_inode == new_parent_dentry->d_inode)
 613                 return 0;       /* nothing to move */
 614 again:
 615         mutex_lock(&old_parent_dentry->d_inode->i_mutex);
 616         if (!mutex_trylock(&new_parent_dentry->d_inode->i_mutex)) {
 617                 mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
 618                 goto again;
 619         }
 620
 621         new_parent_sd = new_parent_dentry->d_fsdata;
 622         sd = kobj->dentry->d_fsdata;
 623
 624         new_dentry = lookup_one_len(kobj->name, new_parent_dentry,
 625                                     strlen(kobj->name));
 626         if (IS_ERR(new_dentry)) {
 627                 error = PTR_ERR(new_dentry);
 628                 goto out;
 629         } else
 630                 error = 0;
 631         d_add(new_dentry, NULL);
 632         d_move(kobj->dentry, new_dentry);
 633         dput(new_dentry);
 634
 635         /* Remove from old parent's list and insert into new parent's list. */
 636         list_del_init(&sd->s_sibling);
 637         sysfs_get(new_parent_sd);
 638         sysfs_put(sd->s_parent);
 639         sd->s_parent = new_parent_sd;
 640         list_add(&sd->s_sibling, &new_parent_sd->s_children);
 641
 642 out:
 643         mutex_unlock(&new_parent_dentry->d_inode->i_mutex);
 644         mutex_unlock(&old_parent_dentry->d_inode->i_mutex);
 645
 646         return error;
 647 }
 648
 649 static int sysfs_dir_open(struct inode *inode, struct file *file)
 650 {
 651         struct dentry * dentry = file->f_path.dentry;
 652         struct sysfs_dirent * parent_sd = dentry->d_fsdata;
 653         struct sysfs_dirent * sd;
 654
 655         mutex_lock(&dentry->d_inode->i_mutex);
 656         sd = sysfs_new_dirent("_DIR_", 0, 0);
 657         if (sd)
 658                 sysfs_attach_dirent(sd, parent_sd, NULL);
 659         mutex_unlock(&dentry->d_inode->i_mutex);
 660
 661         file->private_data = sd;
 662         return sd ? 0 : -ENOMEM;
 663 }
 664
 665 static int sysfs_dir_close(struct inode *inode, struct file *file)
 666 {
 667         struct dentry * dentry = file->f_path.dentry;
 668         struct sysfs_dirent * cursor = file->private_data;
 669
 670         mutex_lock(&dentry->d_inode->i_mutex);
 671         list_del_init(&cursor->s_sibling);
 672         mutex_unlock(&dentry->d_inode->i_mutex);
 673
 674         release_sysfs_dirent(cursor);
 675
 676         return 0;
 677 }
 678
 679 /* Relationship between s_mode and the DT_xxx types */
 680 static inline unsigned char dt_type(struct sysfs_dirent *sd)
 681 {
 682         return (sd->s_mode >> 12) & 15;
 683 }
 684
 685 static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 686 {
 687         struct dentry *dentry = filp->f_path.dentry;
 688         struct sysfs_dirent * parent_sd = dentry->d_fsdata;
 689         struct sysfs_dirent *cursor = filp->private_data;
 690         struct list_head *p, *q = &cursor->s_sibling;
 691         ino_t ino;
 692         int i = filp->f_pos;
 693
 694         switch (i) {
 695                 case 0:
 696                         ino = parent_sd->s_ino;
 697                         if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
 698                                 break;
 699                         filp->f_pos++;
 700                         i++;
 701                         /* fallthrough */
 702                 case 1:
 703                         if (parent_sd->s_parent)
 704                                 ino = parent_sd->s_parent->s_ino;
 705                         else
 706                                 ino = parent_sd->s_ino;
 707                         if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
 708                                 break;
 709                         filp->f_pos++;
 710                         i++;
 711                         /* fallthrough */
 712                 default:
 713                         if (filp->f_pos == 2)
 714                                 list_move(q, &parent_sd->s_children);
 715
 716                         for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
 717                                 struct sysfs_dirent *next;
 718                                 const char * name;
 719                                 int len;
 720
 721                                 next = list_entry(p, struct sysfs_dirent,
 722                                                    s_sibling);
 723                                 if (!next->s_type)
 724                                         continue;
 725
 726                                 name = next->s_name;
 727                                 len = strlen(name);
 728                                 ino = next->s_ino;
 729
 730                                 if (filldir(dirent, name, len, filp->f_pos, ino,
 731                                                  dt_type(next)) < 0)
 732                                         return 0;
 733
 734                                 list_move(q, p);
 735                                 p = q;
 736                                 filp->f_pos++;
 737                         }
 738         }
 739         return 0;
 740 }
 741
 742 static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
 743 {
 744         struct dentry * dentry = file->f_path.dentry;
 745
 746         mutex_lock(&dentry->d_inode->i_mutex);
 747         switch (origin) {
 748                 case 1:
 749                         offset += file->f_pos;
 750                 case 0:
 751                         if (offset >= 0)
 752                                 break;
 753                 default:
 754                         mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
 755                         return -EINVAL;
 756         }
 757         if (offset != file->f_pos) {
 758                 file->f_pos = offset;
 759                 if (file->f_pos >= 2) {
 760                         struct sysfs_dirent *sd = dentry->d_fsdata;
 761                         struct sysfs_dirent *cursor = file->private_data;
 762                         struct list_head *p;
 763                         loff_t n = file->f_pos - 2;
 764
 765                         list_del(&cursor->s_sibling);
 766                         p = sd->s_children.next;
 767                         while (n && p != &sd->s_children) {
 768                                 struct sysfs_dirent *next;
 769                                 next = list_entry(p, struct sysfs_dirent,
 770                                                    s_sibling);
 771                                 if (next->s_type)
 772                                         n--;
 773                                 p = p->next;
 774                         }
 775                         list_add_tail(&cursor->s_sibling, p);
 776                 }
 777         }
 778         mutex_unlock(&dentry->d_inode->i_mutex);
 779         return offset;
 780 }
 781
 782
 783 /**
 784  *      sysfs_make_shadowed_dir - Setup so a directory can be shadowed
 785  *      @kobj:  object we're creating shadow of.
 786  */
 787
 788 int sysfs_make_shadowed_dir(struct kobject *kobj,
 789         void * (*follow_link)(struct dentry *, struct nameidata *))
 790 {
 791         struct inode *inode;
 792         struct inode_operations *i_op;
 793
 794         inode = kobj->dentry->d_inode;
 795         if (inode->i_op != &sysfs_dir_inode_operations)
 796                 return -EINVAL;
 797
 798         i_op = kmalloc(sizeof(*i_op), GFP_KERNEL);
 799         if (!i_op)
 800                 return -ENOMEM;
 801
 802         memcpy(i_op, &sysfs_dir_inode_operations, sizeof(*i_op));
 803         i_op->follow_link = follow_link;
 804
 805         /* Locking of inode->i_op?
 806          * Since setting i_op is a single word write and they
 807          * are atomic we should be ok here.
 808          */
 809         inode->i_op = i_op;
 810         return 0;
 811 }
 812
 813 /**
 814  *      sysfs_create_shadow_dir - create a shadow directory for an object.
 815  *      @kobj:  object we're creating directory for.
 816  *
 817  *      sysfs_make_shadowed_dir must already have been called on this
 818  *      directory.
 819  */
 820
 821 struct dentry *sysfs_create_shadow_dir(struct kobject *kobj)
 822 {
 823         struct dentry *dir = kobj->dentry;
 824         struct inode *inode = dir->d_inode;
 825         struct dentry *parent = dir->d_parent;
 826         struct sysfs_dirent *parent_sd = parent->d_fsdata;
 827         struct dentry *shadow;
 828         struct sysfs_dirent *sd;
 829
 830         shadow = ERR_PTR(-EINVAL);
 831         if (!sysfs_is_shadowed_inode(inode))
 832                 goto out;
 833
 834         shadow = d_alloc(parent, &dir->d_name);
 835         if (!shadow)
 836                 goto nomem;
 837
 838         sd = sysfs_new_dirent("_SHADOW_", inode->i_mode, SYSFS_DIR);
 839         if (!sd)
 840                 goto nomem;
 841         sd->s_elem.dir.kobj = kobj;
 842         /* point to parent_sd but don't attach to it */
 843         sd->s_parent = sysfs_get(parent_sd);
 844         sysfs_attach_dirent(sd, NULL, shadow);
 845
 846         d_instantiate(shadow, igrab(inode));
 847         inc_nlink(inode);
 848         inc_nlink(parent->d_inode);
 849
 850         dget(shadow);           /* Extra count - pin the dentry in core */
 851
 852 out:
 853         return shadow;
 854 nomem:
 855         dput(shadow);
 856         shadow = ERR_PTR(-ENOMEM);
 857         goto out;
 858 }
 859
 860 /**
 861  *      sysfs_remove_shadow_dir - remove an object's directory.
 862  *      @shadow: dentry of shadow directory
 863  *
 864  *      The only thing special about this is that we remove any files in
 865  *      the directory before we remove the directory, and we've inlined
 866  *      what used to be sysfs_rmdir() below, instead of calling separately.
 867  */
 868
 869 void sysfs_remove_shadow_dir(struct dentry *shadow)
 870 {
 871         __sysfs_remove_dir(shadow);
 872 }
 873
 874 const struct file_operations sysfs_dir_operations = {
 875         .open           = sysfs_dir_open,
 876         .release        = sysfs_dir_close,
 877         .llseek         = sysfs_dir_lseek,
 878         .read           = generic_read_dir,
 879         .readdir        = sysfs_readdir,
 880 };