fs/ext4/dir.c

   1 /*
   2  *  linux/fs/ext4/dir.c
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  *
   9  *  from
  10  *
  11  *  linux/fs/minix/dir.c
  12  *
  13  *  Copyright (C) 1991, 1992  Linus Torvalds
  14  *
  15  *  ext4 directory handling functions
  16  *
  17  *  Big-endian to little-endian byte-swapping/bitmaps by
  18  *        David S. Miller (davem@caip.rutgers.edu), 1995
  19  *
  20  * Hash Tree Directory indexing (c) 2001  Daniel Phillips
  21  *
  22  */
  23
  24 #include <linux/fs.h>
  25 #include <linux/buffer_head.h>
  26 #include <linux/slab.h>
  27 #include "ext4.h"
  28 #include "xattr.h"
  29
  30 static int ext4_dx_readdir(struct file *, struct dir_context *);
  31
  32 /**
  33  * Check if the given dir-inode refers to an htree-indexed directory
  34  * (or a directory which could potentially get converted to use htree
  35  * indexing).
  36  *
  37  * Return 1 if it is a dx dir, 0 if not
  38  */
  39 static int is_dx_dir(struct inode *inode)
  40 {
  41         struct super_block *sb = inode->i_sb;
  42
  43         if (ext4_has_feature_dir_index(inode->i_sb) &&
  44             ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
  45              ((inode->i_size >> sb->s_blocksize_bits) == 1) ||
  46              ext4_has_inline_data(inode)))
  47                 return 1;
  48
  49         return 0;
  50 }
  51
  52 /*
  53  * Return 0 if the directory entry is OK, and 1 if there is a problem
  54  *
  55  * Note: this is the opposite of what ext2 and ext3 historically returned...
  56  *
  57  * bh passed here can be an inode block or a dir data block, depending
  58  * on the inode inline data flag.
  59  */
  60 int __ext4_check_dir_entry(const char *function, unsigned int line,
  61                            struct inode *dir, struct file *filp,
  62                            struct ext4_dir_entry_2 *de,
  63                            struct buffer_head *bh, char *buf, int size,
  64                            unsigned int offset)
  65 {
  66         const char *error_msg = NULL;
  67         const int rlen = ext4_rec_len_from_disk(de->rec_len,
  68                                                 dir->i_sb->s_blocksize);
  69
  70         if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
  71                 error_msg = "rec_len is smaller than minimal";
  72         else if (unlikely(rlen % 4 != 0))
  73                 error_msg = "rec_len % 4 != 0";
  74         else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
  75                 error_msg = "rec_len is too small for name_len";
  76         else if (unlikely(((char *) de - buf) + rlen > size))
  77                 error_msg = "directory entry across range";
  78         else if (unlikely(le32_to_cpu(de->inode) >
  79                         le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
  80                 error_msg = "inode out of bounds";
  81         else
  82                 return 0;
  83
  84         if (filp)
  85                 ext4_error_file(filp, function, line, bh->b_blocknr,
  86                                 "bad entry in directory: %s - offset=%u(%u), "
  87                                 "inode=%u, rec_len=%d, name_len=%d",
  88                                 error_msg, (unsigned) (offset % size),
  89                                 offset, le32_to_cpu(de->inode),
  90                                 rlen, de->name_len);
  91         else
  92                 ext4_error_inode(dir, function, line, bh->b_blocknr,
  93                                 "bad entry in directory: %s - offset=%u(%u), "
  94                                 "inode=%u, rec_len=%d, name_len=%d",
  95                                 error_msg, (unsigned) (offset % size),
  96                                 offset, le32_to_cpu(de->inode),
  97                                 rlen, de->name_len);
  98
  99         return 1;
 100 }
 101
 102 static int ext4_readdir(struct file *file, struct dir_context *ctx)
 103 {
 104         unsigned int offset;
 105         int i;
 106         struct ext4_dir_entry_2 *de;
 107         int err;
 108         struct inode *inode = file_inode(file);
 109         struct super_block *sb = inode->i_sb;
 110         struct buffer_head *bh = NULL;
 111         int dir_has_error = 0;
 112         struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
 113
 114         if (ext4_encrypted_inode(inode)) {
 115                 err = fscrypt_get_encryption_info(inode);
 116                 if (err && err != -ENOKEY)
 117                         return err;
 118         }
 119
 120         if (is_dx_dir(inode)) {
 121                 err = ext4_dx_readdir(file, ctx);
 122                 if (err != ERR_BAD_DX_DIR) {
 123                         return err;
 124                 }
 125                 /*
 126                  * We don't set the inode dirty flag since it's not
 127                  * critical that it get flushed back to the disk.
 128                  */
 129                 ext4_clear_inode_flag(file_inode(file),
 130                                       EXT4_INODE_INDEX);
 131         }
 132
 133         if (ext4_has_inline_data(inode)) {
 134                 int has_inline_data = 1;
 135                 err = ext4_read_inline_dir(file, ctx,
 136                                            &has_inline_data);
 137                 if (has_inline_data)
 138                         return err;
 139         }
 140
 141         if (ext4_encrypted_inode(inode)) {
 142                 err = fscrypt_fname_alloc_buffer(inode, EXT4_NAME_LEN, &fstr);
 143                 if (err < 0)
 144                         return err;
 145         }
 146
 147         offset = ctx->pos & (sb->s_blocksize - 1);
 148
 149         while (ctx->pos < inode->i_size) {
 150                 struct ext4_map_blocks map;
 151
 152                 if (fatal_signal_pending(current)) {
 153                         err = -ERESTARTSYS;
 154                         goto errout;
 155                 }
 156                 cond_resched();
 157                 map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
 158                 map.m_len = 1;
 159                 err = ext4_map_blocks(NULL, inode, &map, 0);
 160                 if (err > 0) {
 161                         pgoff_t index = map.m_pblk >>
 162                                         (PAGE_SHIFT - inode->i_blkbits);
 163                         if (!ra_has_index(&file->f_ra, index))
 164                                 page_cache_sync_readahead(
 165                                         sb->s_bdev->bd_inode->i_mapping,
 166                                         &file->f_ra, file,
 167                                         index, 1);
 168                         file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
 169                         bh = ext4_bread(NULL, inode, map.m_lblk, 0);
 170                         if (IS_ERR(bh)) {
 171                                 err = PTR_ERR(bh);
 172                                 bh = NULL;
 173                                 goto errout;
 174                         }
 175                 }
 176
 177                 if (!bh) {
 178                         if (!dir_has_error) {
 179                                 EXT4_ERROR_FILE(file, 0,
 180                                                 "directory contains a "
 181                                                 "hole at offset %llu",
 182                                            (unsigned long long) ctx->pos);
 183                                 dir_has_error = 1;
 184                         }
 185                         /* corrupt size?  Maybe no more blocks to read */
 186                         if (ctx->pos > inode->i_blocks << 9)
 187                                 break;
 188                         ctx->pos += sb->s_blocksize - offset;
 189                         continue;
 190                 }
 191
 192                 /* Check the checksum */
 193                 if (!buffer_verified(bh) &&
 194                     !ext4_dirent_csum_verify(inode,
 195                                 (struct ext4_dir_entry *)bh->b_data)) {
 196                         EXT4_ERROR_FILE(file, 0, "directory fails checksum "
 197                                         "at offset %llu",
 198                                         (unsigned long long)ctx->pos);
 199                         ctx->pos += sb->s_blocksize - offset;
 200                         brelse(bh);
 201                         bh = NULL;
 202                         continue;
 203                 }
 204                 set_buffer_verified(bh);
 205
 206                 /* If the dir block has changed since the last call to
 207                  * readdir(2), then we might be pointing to an invalid
 208                  * dirent right now.  Scan from the start of the block
 209                  * to make sure. */
 210                 if (file->f_version != inode->i_version) {
 211                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 212                                 de = (struct ext4_dir_entry_2 *)
 213                                         (bh->b_data + i);
 214                                 /* It's too expensive to do a full
 215                                  * dirent test each time round this
 216                                  * loop, but we do have to test at
 217                                  * least that it is non-zero.  A
 218                                  * failure will be detected in the
 219                                  * dirent test below. */
 220                                 if (ext4_rec_len_from_disk(de->rec_len,
 221                                         sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
 222                                         break;
 223                                 i += ext4_rec_len_from_disk(de->rec_len,
 224                                                             sb->s_blocksize);
 225                         }
 226                         offset = i;
 227                         ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
 228                                 | offset;
 229                         file->f_version = inode->i_version;
 230                 }
 231
 232                 while (ctx->pos < inode->i_size
 233                        && offset < sb->s_blocksize) {
 234                         de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
 235                         if (ext4_check_dir_entry(inode, file, de, bh,
 236                                                  bh->b_data, bh->b_size,
 237                                                  offset)) {
 238                                 /*
 239                                  * On error, skip to the next block
 240                                  */
 241                                 ctx->pos = (ctx->pos |
 242                                                 (sb->s_blocksize - 1)) + 1;
 243                                 break;
 244                         }
 245                         offset += ext4_rec_len_from_disk(de->rec_len,
 246                                         sb->s_blocksize);
 247                         if (le32_to_cpu(de->inode)) {
 248                                 if (!ext4_encrypted_inode(inode)) {
 249                                         if (!dir_emit(ctx, de->name,
 250                                             de->name_len,
 251                                             le32_to_cpu(de->inode),
 252                                             get_dtype(sb, de->file_type)))
 253                                                 goto done;
 254                                 } else {
 255                                         int save_len = fstr.len;
 256                                         struct fscrypt_str de_name =
 257                                                         FSTR_INIT(de->name,
 258                                                                 de->name_len);
 259
 260                                         /* Directory is encrypted */
 261                                         err = fscrypt_fname_disk_to_usr(inode,
 262                                                 0, 0, &de_name, &fstr);
 263                                         de_name = fstr;
 264                                         fstr.len = save_len;
 265                                         if (err)
 266                                                 goto errout;
 267                                         if (!dir_emit(ctx,
 268                                             de_name.name, de_name.len,
 269                                             le32_to_cpu(de->inode),
 270                                             get_dtype(sb, de->file_type)))
 271                                                 goto done;
 272                                 }
 273                         }
 274                         ctx->pos += ext4_rec_len_from_disk(de->rec_len,
 275                                                 sb->s_blocksize);
 276                 }
 277                 if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
 278                         goto done;
 279                 brelse(bh);
 280                 bh = NULL;
 281                 offset = 0;
 282         }
 283 done:
 284         err = 0;
 285 errout:
 286 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 287         fscrypt_fname_free_buffer(&fstr);
 288 #endif
 289         brelse(bh);
 290         return err;
 291 }
 292
 293 static inline int is_32bit_api(void)
 294 {
 295 #ifdef CONFIG_COMPAT
 296         return in_compat_syscall();
 297 #else
 298         return (BITS_PER_LONG == 32);
 299 #endif
 300 }
 301
 302 /*
 303  * These functions convert from the major/minor hash to an f_pos
 304  * value for dx directories
 305  *
 306  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
 307  * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
 308  * directly on both 32-bit and 64-bit nodes, under such case, neither
 309  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
 310  */
 311 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
 312 {
 313         if ((filp->f_mode & FMODE_32BITHASH) ||
 314             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 315                 return major >> 1;
 316         else
 317                 return ((__u64)(major >> 1) << 32) | (__u64)minor;
 318 }
 319
 320 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
 321 {
 322         if ((filp->f_mode & FMODE_32BITHASH) ||
 323             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 324                 return (pos << 1) & 0xffffffff;
 325         else
 326                 return ((pos >> 32) << 1) & 0xffffffff;
 327 }
 328
 329 static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
 330 {
 331         if ((filp->f_mode & FMODE_32BITHASH) ||
 332             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 333                 return 0;
 334         else
 335                 return pos & 0xffffffff;
 336 }
 337
 338 /*
 339  * Return 32- or 64-bit end-of-file for dx directories
 340  */
 341 static inline loff_t ext4_get_htree_eof(struct file *filp)
 342 {
 343         if ((filp->f_mode & FMODE_32BITHASH) ||
 344             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 345                 return EXT4_HTREE_EOF_32BIT;
 346         else
 347                 return EXT4_HTREE_EOF_64BIT;
 348 }
 349
 350
 351 /*
 352  * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
 353  * directories, where the "offset" is in terms of the filename hash
 354  * value instead of the byte offset.
 355  *
 356  * Because we may return a 64-bit hash that is well beyond offset limits,
 357  * we need to pass the max hash as the maximum allowable offset in
 358  * the htree directory case.
 359  *
 360  * For non-htree, ext4_llseek already chooses the proper max offset.
 361  */
 362 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
 363 {
 364         struct inode *inode = file->f_mapping->host;
 365         int dx_dir = is_dx_dir(inode);
 366         loff_t htree_max = ext4_get_htree_eof(file);
 367
 368         if (likely(dx_dir))
 369                 return generic_file_llseek_size(file, offset, whence,
 370                                                     htree_max, htree_max);
 371         else
 372                 return ext4_llseek(file, offset, whence);
 373 }
 374
 375 /*
 376  * This structure holds the nodes of the red-black tree used to store
 377  * the directory entry in hash order.
 378  */
 379 struct fname {
 380         __u32           hash;
 381         __u32           minor_hash;
 382         struct rb_node  rb_hash;
 383         struct fname    *next;
 384         __u32           inode;
 385         __u8            name_len;
 386         __u8            file_type;
 387         char            name[0];
 388 };
 389
 390 /*
 391  * This functoin implements a non-recursive way of freeing all of the
 392  * nodes in the red-black tree.
 393  */
 394 static void free_rb_tree_fname(struct rb_root *root)
 395 {
 396         struct fname *fname, *next;
 397
 398         rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
 399                 while (fname) {
 400                         struct fname *old = fname;
 401                         fname = fname->next;
 402                         kfree(old);
 403                 }
 404
 405         *root = RB_ROOT;
 406 }
 407
 408
 409 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
 410                                                            loff_t pos)
 411 {
 412         struct dir_private_info *p;
 413
 414         p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
 415         if (!p)
 416                 return NULL;
 417         p->curr_hash = pos2maj_hash(filp, pos);
 418         p->curr_minor_hash = pos2min_hash(filp, pos);
 419         return p;
 420 }
 421
 422 void ext4_htree_free_dir_info(struct dir_private_info *p)
 423 {
 424         free_rb_tree_fname(&p->root);
 425         kfree(p);
 426 }
 427
 428 /*
 429  * Given a directory entry, enter it into the fname rb tree.
 430  *
 431  * When filename encryption is enabled, the dirent will hold the
 432  * encrypted filename, while the htree will hold decrypted filename.
 433  * The decrypted filename is passed in via ent_name.  parameter.
 434  */
 435 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
 436                              __u32 minor_hash,
 437                             struct ext4_dir_entry_2 *dirent,
 438                             struct fscrypt_str *ent_name)
 439 {
 440         struct rb_node **p, *parent = NULL;
 441         struct fname *fname, *new_fn;
 442         struct dir_private_info *info;
 443         int len;
 444
 445         info = dir_file->private_data;
 446         p = &info->root.rb_node;
 447
 448         /* Create and allocate the fname structure */
 449         len = sizeof(struct fname) + ent_name->len + 1;
 450         new_fn = kzalloc(len, GFP_KERNEL);
 451         if (!new_fn)
 452                 return -ENOMEM;
 453         new_fn->hash = hash;
 454         new_fn->minor_hash = minor_hash;
 455         new_fn->inode = le32_to_cpu(dirent->inode);
 456         new_fn->name_len = ent_name->len;
 457         new_fn->file_type = dirent->file_type;
 458         memcpy(new_fn->name, ent_name->name, ent_name->len);
 459         new_fn->name[ent_name->len] = 0;
 460
 461         while (*p) {
 462                 parent = *p;
 463                 fname = rb_entry(parent, struct fname, rb_hash);
 464
 465                 /*
 466                  * If the hash and minor hash match up, then we put
 467                  * them on a linked list.  This rarely happens...
 468                  */
 469                 if ((new_fn->hash == fname->hash) &&
 470                     (new_fn->minor_hash == fname->minor_hash)) {
 471                         new_fn->next = fname->next;
 472                         fname->next = new_fn;
 473                         return 0;
 474                 }
 475
 476                 if (new_fn->hash < fname->hash)
 477                         p = &(*p)->rb_left;
 478                 else if (new_fn->hash > fname->hash)
 479                         p = &(*p)->rb_right;
 480                 else if (new_fn->minor_hash < fname->minor_hash)
 481                         p = &(*p)->rb_left;
 482                 else /* if (new_fn->minor_hash > fname->minor_hash) */
 483                         p = &(*p)->rb_right;
 484         }
 485
 486         rb_link_node(&new_fn->rb_hash, parent, p);
 487         rb_insert_color(&new_fn->rb_hash, &info->root);
 488         return 0;
 489 }
 490
 491
 492
 493 /*
 494  * This is a helper function for ext4_dx_readdir.  It calls filldir
 495  * for all entres on the fname linked list.  (Normally there is only
 496  * one entry on the linked list, unless there are 62 bit hash collisions.)
 497  */
 498 static int call_filldir(struct file *file, struct dir_context *ctx,
 499                         struct fname *fname)
 500 {
 501         struct dir_private_info *info = file->private_data;
 502         struct inode *inode = file_inode(file);
 503         struct super_block *sb = inode->i_sb;
 504
 505         if (!fname) {
 506                 ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
 507                          "called with null fname?!?", __func__, __LINE__,
 508                          inode->i_ino, current->comm);
 509                 return 0;
 510         }
 511         ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
 512         while (fname) {
 513                 if (!dir_emit(ctx, fname->name,
 514                                 fname->name_len,
 515                                 fname->inode,
 516                                 get_dtype(sb, fname->file_type))) {
 517                         info->extra_fname = fname;
 518                         return 1;
 519                 }
 520                 fname = fname->next;
 521         }
 522         return 0;
 523 }
 524
 525 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
 526 {
 527         struct dir_private_info *info = file->private_data;
 528         struct inode *inode = file_inode(file);
 529         struct fname *fname;
 530         int     ret;
 531
 532         if (!info) {
 533                 info = ext4_htree_create_dir_info(file, ctx->pos);
 534                 if (!info)
 535                         return -ENOMEM;
 536                 file->private_data = info;
 537         }
 538
 539         if (ctx->pos == ext4_get_htree_eof(file))
 540                 return 0;       /* EOF */
 541
 542         /* Some one has messed with f_pos; reset the world */
 543         if (info->last_pos != ctx->pos) {
 544                 free_rb_tree_fname(&info->root);
 545                 info->curr_node = NULL;
 546                 info->extra_fname = NULL;
 547                 info->curr_hash = pos2maj_hash(file, ctx->pos);
 548                 info->curr_minor_hash = pos2min_hash(file, ctx->pos);
 549         }
 550
 551         /*
 552          * If there are any leftover names on the hash collision
 553          * chain, return them first.
 554          */
 555         if (info->extra_fname) {
 556                 if (call_filldir(file, ctx, info->extra_fname))
 557                         goto finished;
 558                 info->extra_fname = NULL;
 559                 goto next_node;
 560         } else if (!info->curr_node)
 561                 info->curr_node = rb_first(&info->root);
 562
 563         while (1) {
 564                 /*
 565                  * Fill the rbtree if we have no more entries,
 566                  * or the inode has changed since we last read in the
 567                  * cached entries.
 568                  */
 569                 if ((!info->curr_node) ||
 570                     (file->f_version != inode->i_version)) {
 571                         info->curr_node = NULL;
 572                         free_rb_tree_fname(&info->root);
 573                         file->f_version = inode->i_version;
 574                         ret = ext4_htree_fill_tree(file, info->curr_hash,
 575                                                    info->curr_minor_hash,
 576                                                    &info->next_hash);
 577                         if (ret < 0)
 578                                 return ret;
 579                         if (ret == 0) {
 580                                 ctx->pos = ext4_get_htree_eof(file);
 581                                 break;
 582                         }
 583                         info->curr_node = rb_first(&info->root);
 584                 }
 585
 586                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
 587                 info->curr_hash = fname->hash;
 588                 info->curr_minor_hash = fname->minor_hash;
 589                 if (call_filldir(file, ctx, fname))
 590                         break;
 591         next_node:
 592                 info->curr_node = rb_next(info->curr_node);
 593                 if (info->curr_node) {
 594                         fname = rb_entry(info->curr_node, struct fname,
 595                                          rb_hash);
 596                         info->curr_hash = fname->hash;
 597                         info->curr_minor_hash = fname->minor_hash;
 598                 } else {
 599                         if (info->next_hash == ~0) {
 600                                 ctx->pos = ext4_get_htree_eof(file);
 601                                 break;
 602                         }
 603                         info->curr_hash = info->next_hash;
 604                         info->curr_minor_hash = 0;
 605                 }
 606         }
 607 finished:
 608         info->last_pos = ctx->pos;
 609         return 0;
 610 }
 611
 612 static int ext4_dir_open(struct inode * inode, struct file * filp)
 613 {
 614         if (ext4_encrypted_inode(inode))
 615                 return fscrypt_get_encryption_info(inode) ? -EACCES : 0;
 616         return 0;
 617 }
 618
 619 static int ext4_release_dir(struct inode *inode, struct file *filp)
 620 {
 621         if (filp->private_data)
 622                 ext4_htree_free_dir_info(filp->private_data);
 623
 624         return 0;
 625 }
 626
 627 int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
 628                       int buf_size)
 629 {
 630         struct ext4_dir_entry_2 *de;
 631         int rlen;
 632         unsigned int offset = 0;
 633         char *top;
 634
 635         de = (struct ext4_dir_entry_2 *)buf;
 636         top = buf + buf_size;
 637         while ((char *) de < top) {
 638                 if (ext4_check_dir_entry(dir, NULL, de, bh,
 639                                          buf, buf_size, offset))
 640                         return -EFSCORRUPTED;
 641                 rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
 642                 de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
 643                 offset += rlen;
 644         }
 645         if ((char *) de > top)
 646                 return -EFSCORRUPTED;
 647
 648         return 0;
 649 }
 650
 651 const struct file_operations ext4_dir_operations = {
 652         .llseek         = ext4_dir_llseek,
 653         .read           = generic_read_dir,
 654         .iterate_shared = ext4_readdir,
 655         .unlocked_ioctl = ext4_ioctl,
 656 #ifdef CONFIG_COMPAT
 657         .compat_ioctl   = ext4_compat_ioctl,
 658 #endif
 659         .fsync          = ext4_sync_file,
 660         .open           = ext4_dir_open,
 661         .release        = ext4_release_dir,
 662 };