fs/ext4/dir.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/ext4/dir.c
   4  *
   5  * Copyright (C) 1992, 1993, 1994, 1995
   6  * Remy Card (card@masi.ibp.fr)
   7  * Laboratoire MASI - Institut Blaise Pascal
   8  * Universite Pierre et Marie Curie (Paris VI)
   9  *
  10  *  from
  11  *
  12  *  linux/fs/minix/dir.c
  13  *
  14  *  Copyright (C) 1991, 1992  Linus Torvalds
  15  *
  16  *  ext4 directory handling functions
  17  *
  18  *  Big-endian to little-endian byte-swapping/bitmaps by
  19  *        David S. Miller (davem@caip.rutgers.edu), 1995
  20  *
  21  * Hash Tree Directory indexing (c) 2001  Daniel Phillips
  22  *
  23  */
  24
  25 #include <linux/fs.h>
  26 #include <linux/buffer_head.h>
  27 #include <linux/slab.h>
  28 #include <linux/iversion.h>
  29 #include "ext4.h"
  30 #include "xattr.h"
  31
  32 static int ext4_dx_readdir(struct file *, struct dir_context *);
  33
  34 /**
  35  * Check if the given dir-inode refers to an htree-indexed directory
  36  * (or a directory which could potentially get converted to use htree
  37  * indexing).
  38  *
  39  * Return 1 if it is a dx dir, 0 if not
  40  */
  41 static int is_dx_dir(struct inode *inode)
  42 {
  43         struct super_block *sb = inode->i_sb;
  44
  45         if (ext4_has_feature_dir_index(inode->i_sb) &&
  46             ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
  47              ((inode->i_size >> sb->s_blocksize_bits) == 1) ||
  48              ext4_has_inline_data(inode)))
  49                 return 1;
  50
  51         return 0;
  52 }
  53
  54 /*
  55  * Return 0 if the directory entry is OK, and 1 if there is a problem
  56  *
  57  * Note: this is the opposite of what ext2 and ext3 historically returned...
  58  *
  59  * bh passed here can be an inode block or a dir data block, depending
  60  * on the inode inline data flag.
  61  */
  62 int __ext4_check_dir_entry(const char *function, unsigned int line,
  63                            struct inode *dir, struct file *filp,
  64                            struct ext4_dir_entry_2 *de,
  65                            struct buffer_head *bh, char *buf, int size,
  66                            unsigned int offset)
  67 {
  68         const char *error_msg = NULL;
  69         const int rlen = ext4_rec_len_from_disk(de->rec_len,
  70                                                 dir->i_sb->s_blocksize);
  71
  72         if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
  73                 error_msg = "rec_len is smaller than minimal";
  74         else if (unlikely(rlen % 4 != 0))
  75                 error_msg = "rec_len % 4 != 0";
  76         else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
  77                 error_msg = "rec_len is too small for name_len";
  78         else if (unlikely(((char *) de - buf) + rlen > size))
  79                 error_msg = "directory entry overrun";
  80         else if (unlikely(((char *) de - buf) + rlen >
  81                           size - EXT4_DIR_REC_LEN(1) &&
  82                           ((char *) de - buf) + rlen != size)) {
  83                 error_msg = "directory entry too close to block end";
  84         }
  85         else if (unlikely(le32_to_cpu(de->inode) >
  86                         le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
  87                 error_msg = "inode out of bounds";
  88         else
  89                 return 0;
  90
  91         if (filp)
  92                 ext4_error_file(filp, function, line, bh->b_blocknr,
  93                                 "bad entry in directory: %s - offset=%u, "
  94                                 "inode=%u, rec_len=%d, name_len=%d, size=%d",
  95                                 error_msg, offset, le32_to_cpu(de->inode),
  96                                 rlen, de->name_len, size);
  97         else
  98                 ext4_error_inode(dir, function, line, bh->b_blocknr,
  99                                 "bad entry in directory: %s - offset=%u, "
 100                                 "inode=%u, rec_len=%d, name_len=%d, size=%d",
 101                                  error_msg, offset, le32_to_cpu(de->inode),
 102                                  rlen, de->name_len, size);
 103
 104         return 1;
 105 }
 106
 107 static int ext4_readdir(struct file *file, struct dir_context *ctx)
 108 {
 109         unsigned int offset;
 110         int i;
 111         struct ext4_dir_entry_2 *de;
 112         int err;
 113         struct inode *inode = file_inode(file);
 114         struct super_block *sb = inode->i_sb;
 115         struct buffer_head *bh = NULL;
 116         struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
 117
 118         if (ext4_encrypted_inode(inode)) {
 119                 err = fscrypt_get_encryption_info(inode);
 120                 if (err && err != -ENOKEY)
 121                         return err;
 122         }
 123
 124         if (is_dx_dir(inode)) {
 125                 err = ext4_dx_readdir(file, ctx);
 126                 if (err != ERR_BAD_DX_DIR) {
 127                         return err;
 128                 }
 129                 /* Can we just clear INDEX flag to ignore htree information? */
 130                 if (!ext4_has_metadata_csum(sb)) {
 131                         /*
 132                          * We don't set the inode dirty flag since it's not
 133                          * critical that it gets flushed back to the disk.
 134                          */
 135                         ext4_clear_inode_flag(inode, EXT4_INODE_INDEX);
 136                 }
 137         }
 138
 139         if (ext4_has_inline_data(inode)) {
 140                 int has_inline_data = 1;
 141                 err = ext4_read_inline_dir(file, ctx,
 142                                            &has_inline_data);
 143                 if (has_inline_data)
 144                         return err;
 145         }
 146
 147         if (ext4_encrypted_inode(inode)) {
 148                 err = fscrypt_fname_alloc_buffer(inode, EXT4_NAME_LEN, &fstr);
 149                 if (err < 0)
 150                         return err;
 151         }
 152
 153         while (ctx->pos < inode->i_size) {
 154                 struct ext4_map_blocks map;
 155
 156                 if (fatal_signal_pending(current)) {
 157                         err = -ERESTARTSYS;
 158                         goto errout;
 159                 }
 160                 cond_resched();
 161                 offset = ctx->pos & (sb->s_blocksize - 1);
 162                 map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
 163                 map.m_len = 1;
 164                 err = ext4_map_blocks(NULL, inode, &map, 0);
 165                 if (err == 0) {
 166                         /* m_len should never be zero but let's avoid
 167                          * an infinite loop if it somehow is */
 168                         if (map.m_len == 0)
 169                                 map.m_len = 1;
 170                         ctx->pos += map.m_len * sb->s_blocksize;
 171                         continue;
 172                 }
 173                 if (err > 0) {
 174                         pgoff_t index = map.m_pblk >>
 175                                         (PAGE_SHIFT - inode->i_blkbits);
 176                         if (!ra_has_index(&file->f_ra, index))
 177                                 page_cache_sync_readahead(
 178                                         sb->s_bdev->bd_inode->i_mapping,
 179                                         &file->f_ra, file,
 180                                         index, 1);
 181                         file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
 182                         bh = ext4_bread(NULL, inode, map.m_lblk, 0);
 183                         if (IS_ERR(bh)) {
 184                                 err = PTR_ERR(bh);
 185                                 bh = NULL;
 186                                 goto errout;
 187                         }
 188                 }
 189
 190                 if (!bh) {
 191                         /* corrupt size?  Maybe no more blocks to read */
 192                         if (ctx->pos > inode->i_blocks << 9)
 193                                 break;
 194                         ctx->pos += sb->s_blocksize - offset;
 195                         continue;
 196                 }
 197
 198                 /* Check the checksum */
 199                 if (!buffer_verified(bh) &&
 200                     !ext4_dirent_csum_verify(inode,
 201                                 (struct ext4_dir_entry *)bh->b_data)) {
 202                         EXT4_ERROR_FILE(file, 0, "directory fails checksum "
 203                                         "at offset %llu",
 204                                         (unsigned long long)ctx->pos);
 205                         ctx->pos += sb->s_blocksize - offset;
 206                         brelse(bh);
 207                         bh = NULL;
 208                         continue;
 209                 }
 210                 set_buffer_verified(bh);
 211
 212                 /* If the dir block has changed since the last call to
 213                  * readdir(2), then we might be pointing to an invalid
 214                  * dirent right now.  Scan from the start of the block
 215                  * to make sure. */
 216                 if (!inode_eq_iversion(inode, file->f_version)) {
 217                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 218                                 de = (struct ext4_dir_entry_2 *)
 219                                         (bh->b_data + i);
 220                                 /* It's too expensive to do a full
 221                                  * dirent test each time round this
 222                                  * loop, but we do have to test at
 223                                  * least that it is non-zero.  A
 224                                  * failure will be detected in the
 225                                  * dirent test below. */
 226                                 if (ext4_rec_len_from_disk(de->rec_len,
 227                                         sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
 228                                         break;
 229                                 i += ext4_rec_len_from_disk(de->rec_len,
 230                                                             sb->s_blocksize);
 231                         }
 232                         offset = i;
 233                         ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
 234                                 | offset;
 235                         file->f_version = inode_query_iversion(inode);
 236                 }
 237
 238                 while (ctx->pos < inode->i_size
 239                        && offset < sb->s_blocksize) {
 240                         de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
 241                         if (ext4_check_dir_entry(inode, file, de, bh,
 242                                                  bh->b_data, bh->b_size,
 243                                                  offset)) {
 244                                 /*
 245                                  * On error, skip to the next block
 246                                  */
 247                                 ctx->pos = (ctx->pos |
 248                                                 (sb->s_blocksize - 1)) + 1;
 249                                 break;
 250                         }
 251                         offset += ext4_rec_len_from_disk(de->rec_len,
 252                                         sb->s_blocksize);
 253                         if (le32_to_cpu(de->inode)) {
 254                                 if (!ext4_encrypted_inode(inode)) {
 255                                         if (!dir_emit(ctx, de->name,
 256                                             de->name_len,
 257                                             le32_to_cpu(de->inode),
 258                                             get_dtype(sb, de->file_type)))
 259                                                 goto done;
 260                                 } else {
 261                                         int save_len = fstr.len;
 262                                         struct fscrypt_str de_name =
 263                                                         FSTR_INIT(de->name,
 264                                                                 de->name_len);
 265
 266                                         /* Directory is encrypted */
 267                                         err = fscrypt_fname_disk_to_usr(inode,
 268                                                 0, 0, &de_name, &fstr);
 269                                         de_name = fstr;
 270                                         fstr.len = save_len;
 271                                         if (err)
 272                                                 goto errout;
 273                                         if (!dir_emit(ctx,
 274                                             de_name.name, de_name.len,
 275                                             le32_to_cpu(de->inode),
 276                                             get_dtype(sb, de->file_type)))
 277                                                 goto done;
 278                                 }
 279                         }
 280                         ctx->pos += ext4_rec_len_from_disk(de->rec_len,
 281                                                 sb->s_blocksize);
 282                 }
 283                 if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
 284                         goto done;
 285                 brelse(bh);
 286                 bh = NULL;
 287                 offset = 0;
 288         }
 289 done:
 290         err = 0;
 291 errout:
 292 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 293         fscrypt_fname_free_buffer(&fstr);
 294 #endif
 295         brelse(bh);
 296         return err;
 297 }
 298
 299 static inline int is_32bit_api(void)
 300 {
 301 #ifdef CONFIG_COMPAT
 302         return in_compat_syscall();
 303 #else
 304         return (BITS_PER_LONG == 32);
 305 #endif
 306 }
 307
 308 /*
 309  * These functions convert from the major/minor hash to an f_pos
 310  * value for dx directories
 311  *
 312  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
 313  * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
 314  * directly on both 32-bit and 64-bit nodes, under such case, neither
 315  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
 316  */
 317 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
 318 {
 319         if ((filp->f_mode & FMODE_32BITHASH) ||
 320             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 321                 return major >> 1;
 322         else
 323                 return ((__u64)(major >> 1) << 32) | (__u64)minor;
 324 }
 325
 326 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
 327 {
 328         if ((filp->f_mode & FMODE_32BITHASH) ||
 329             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 330                 return (pos << 1) & 0xffffffff;
 331         else
 332                 return ((pos >> 32) << 1) & 0xffffffff;
 333 }
 334
 335 static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
 336 {
 337         if ((filp->f_mode & FMODE_32BITHASH) ||
 338             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 339                 return 0;
 340         else
 341                 return pos & 0xffffffff;
 342 }
 343
 344 /*
 345  * Return 32- or 64-bit end-of-file for dx directories
 346  */
 347 static inline loff_t ext4_get_htree_eof(struct file *filp)
 348 {
 349         if ((filp->f_mode & FMODE_32BITHASH) ||
 350             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 351                 return EXT4_HTREE_EOF_32BIT;
 352         else
 353                 return EXT4_HTREE_EOF_64BIT;
 354 }
 355
 356
 357 /*
 358  * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
 359  * directories, where the "offset" is in terms of the filename hash
 360  * value instead of the byte offset.
 361  *
 362  * Because we may return a 64-bit hash that is well beyond offset limits,
 363  * we need to pass the max hash as the maximum allowable offset in
 364  * the htree directory case.
 365  *
 366  * For non-htree, ext4_llseek already chooses the proper max offset.
 367  */
 368 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
 369 {
 370         struct inode *inode = file->f_mapping->host;
 371         int dx_dir = is_dx_dir(inode);
 372         loff_t ret, htree_max = ext4_get_htree_eof(file);
 373
 374         if (likely(dx_dir))
 375                 ret = generic_file_llseek_size(file, offset, whence,
 376                                                     htree_max, htree_max);
 377         else
 378                 ret = ext4_llseek(file, offset, whence);
 379         file->f_version = inode_peek_iversion(inode) - 1;
 380         return ret;
 381 }
 382
 383 /*
 384  * This structure holds the nodes of the red-black tree used to store
 385  * the directory entry in hash order.
 386  */
 387 struct fname {
 388         __u32           hash;
 389         __u32           minor_hash;
 390         struct rb_node  rb_hash;
 391         struct fname    *next;
 392         __u32           inode;
 393         __u8            name_len;
 394         __u8            file_type;
 395         char            name[0];
 396 };
 397
 398 /*
 399  * This functoin implements a non-recursive way of freeing all of the
 400  * nodes in the red-black tree.
 401  */
 402 static void free_rb_tree_fname(struct rb_root *root)
 403 {
 404         struct fname *fname, *next;
 405
 406         rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
 407                 while (fname) {
 408                         struct fname *old = fname;
 409                         fname = fname->next;
 410                         kfree(old);
 411                 }
 412
 413         *root = RB_ROOT;
 414 }
 415
 416
 417 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
 418                                                            loff_t pos)
 419 {
 420         struct dir_private_info *p;
 421
 422         p = kzalloc(sizeof(*p), GFP_KERNEL);
 423         if (!p)
 424                 return NULL;
 425         p->curr_hash = pos2maj_hash(filp, pos);
 426         p->curr_minor_hash = pos2min_hash(filp, pos);
 427         return p;
 428 }
 429
 430 void ext4_htree_free_dir_info(struct dir_private_info *p)
 431 {
 432         free_rb_tree_fname(&p->root);
 433         kfree(p);
 434 }
 435
 436 /*
 437  * Given a directory entry, enter it into the fname rb tree.
 438  *
 439  * When filename encryption is enabled, the dirent will hold the
 440  * encrypted filename, while the htree will hold decrypted filename.
 441  * The decrypted filename is passed in via ent_name.  parameter.
 442  */
 443 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
 444                              __u32 minor_hash,
 445                             struct ext4_dir_entry_2 *dirent,
 446                             struct fscrypt_str *ent_name)
 447 {
 448         struct rb_node **p, *parent = NULL;
 449         struct fname *fname, *new_fn;
 450         struct dir_private_info *info;
 451         int len;
 452
 453         info = dir_file->private_data;
 454         p = &info->root.rb_node;
 455
 456         /* Create and allocate the fname structure */
 457         len = sizeof(struct fname) + ent_name->len + 1;
 458         new_fn = kzalloc(len, GFP_KERNEL);
 459         if (!new_fn)
 460                 return -ENOMEM;
 461         new_fn->hash = hash;
 462         new_fn->minor_hash = minor_hash;
 463         new_fn->inode = le32_to_cpu(dirent->inode);
 464         new_fn->name_len = ent_name->len;
 465         new_fn->file_type = dirent->file_type;
 466         memcpy(new_fn->name, ent_name->name, ent_name->len);
 467         new_fn->name[ent_name->len] = 0;
 468
 469         while (*p) {
 470                 parent = *p;
 471                 fname = rb_entry(parent, struct fname, rb_hash);
 472
 473                 /*
 474                  * If the hash and minor hash match up, then we put
 475                  * them on a linked list.  This rarely happens...
 476                  */
 477                 if ((new_fn->hash == fname->hash) &&
 478                     (new_fn->minor_hash == fname->minor_hash)) {
 479                         new_fn->next = fname->next;
 480                         fname->next = new_fn;
 481                         return 0;
 482                 }
 483
 484                 if (new_fn->hash < fname->hash)
 485                         p = &(*p)->rb_left;
 486                 else if (new_fn->hash > fname->hash)
 487                         p = &(*p)->rb_right;
 488                 else if (new_fn->minor_hash < fname->minor_hash)
 489                         p = &(*p)->rb_left;
 490                 else /* if (new_fn->minor_hash > fname->minor_hash) */
 491                         p = &(*p)->rb_right;
 492         }
 493
 494         rb_link_node(&new_fn->rb_hash, parent, p);
 495         rb_insert_color(&new_fn->rb_hash, &info->root);
 496         return 0;
 497 }
 498
 499
 500
 501 /*
 502  * This is a helper function for ext4_dx_readdir.  It calls filldir
 503  * for all entres on the fname linked list.  (Normally there is only
 504  * one entry on the linked list, unless there are 62 bit hash collisions.)
 505  */
 506 static int call_filldir(struct file *file, struct dir_context *ctx,
 507                         struct fname *fname)
 508 {
 509         struct dir_private_info *info = file->private_data;
 510         struct inode *inode = file_inode(file);
 511         struct super_block *sb = inode->i_sb;
 512
 513         if (!fname) {
 514                 ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
 515                          "called with null fname?!?", __func__, __LINE__,
 516                          inode->i_ino, current->comm);
 517                 return 0;
 518         }
 519         ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
 520         while (fname) {
 521                 if (!dir_emit(ctx, fname->name,
 522                                 fname->name_len,
 523                                 fname->inode,
 524                                 get_dtype(sb, fname->file_type))) {
 525                         info->extra_fname = fname;
 526                         return 1;
 527                 }
 528                 fname = fname->next;
 529         }
 530         return 0;
 531 }
 532
 533 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
 534 {
 535         struct dir_private_info *info = file->private_data;
 536         struct inode *inode = file_inode(file);
 537         struct fname *fname;
 538         int ret = 0;
 539
 540         if (!info) {
 541                 info = ext4_htree_create_dir_info(file, ctx->pos);
 542                 if (!info)
 543                         return -ENOMEM;
 544                 file->private_data = info;
 545         }
 546
 547         if (ctx->pos == ext4_get_htree_eof(file))
 548                 return 0;       /* EOF */
 549
 550         /* Some one has messed with f_pos; reset the world */
 551         if (info->last_pos != ctx->pos) {
 552                 free_rb_tree_fname(&info->root);
 553                 info->curr_node = NULL;
 554                 info->extra_fname = NULL;
 555                 info->curr_hash = pos2maj_hash(file, ctx->pos);
 556                 info->curr_minor_hash = pos2min_hash(file, ctx->pos);
 557         }
 558
 559         /*
 560          * If there are any leftover names on the hash collision
 561          * chain, return them first.
 562          */
 563         if (info->extra_fname) {
 564                 if (call_filldir(file, ctx, info->extra_fname))
 565                         goto finished;
 566                 info->extra_fname = NULL;
 567                 goto next_node;
 568         } else if (!info->curr_node)
 569                 info->curr_node = rb_first(&info->root);
 570
 571         while (1) {
 572                 /*
 573                  * Fill the rbtree if we have no more entries,
 574                  * or the inode has changed since we last read in the
 575                  * cached entries.
 576                  */
 577                 if ((!info->curr_node) ||
 578                     !inode_eq_iversion(inode, file->f_version)) {
 579                         info->curr_node = NULL;
 580                         free_rb_tree_fname(&info->root);
 581                         file->f_version = inode_query_iversion(inode);
 582                         ret = ext4_htree_fill_tree(file, info->curr_hash,
 583                                                    info->curr_minor_hash,
 584                                                    &info->next_hash);
 585                         if (ret < 0)
 586                                 goto finished;
 587                         if (ret == 0) {
 588                                 ctx->pos = ext4_get_htree_eof(file);
 589                                 break;
 590                         }
 591                         info->curr_node = rb_first(&info->root);
 592                 }
 593
 594                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
 595                 info->curr_hash = fname->hash;
 596                 info->curr_minor_hash = fname->minor_hash;
 597                 if (call_filldir(file, ctx, fname))
 598                         break;
 599         next_node:
 600                 info->curr_node = rb_next(info->curr_node);
 601                 if (info->curr_node) {
 602                         fname = rb_entry(info->curr_node, struct fname,
 603                                          rb_hash);
 604                         info->curr_hash = fname->hash;
 605                         info->curr_minor_hash = fname->minor_hash;
 606                 } else {
 607                         if (info->next_hash == ~0) {
 608                                 ctx->pos = ext4_get_htree_eof(file);
 609                                 break;
 610                         }
 611                         info->curr_hash = info->next_hash;
 612                         info->curr_minor_hash = 0;
 613                 }
 614         }
 615 finished:
 616         info->last_pos = ctx->pos;
 617         return ret < 0 ? ret : 0;
 618 }
 619
 620 static int ext4_dir_open(struct inode * inode, struct file * filp)
 621 {
 622         if (ext4_encrypted_inode(inode))
 623                 return fscrypt_get_encryption_info(inode) ? -EACCES : 0;
 624         return 0;
 625 }
 626
 627 static int ext4_release_dir(struct inode *inode, struct file *filp)
 628 {
 629         if (filp->private_data)
 630                 ext4_htree_free_dir_info(filp->private_data);
 631
 632         return 0;
 633 }
 634
 635 int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
 636                       int buf_size)
 637 {
 638         struct ext4_dir_entry_2 *de;
 639         int rlen;
 640         unsigned int offset = 0;
 641         char *top;
 642
 643         de = (struct ext4_dir_entry_2 *)buf;
 644         top = buf + buf_size;
 645         while ((char *) de < top) {
 646                 if (ext4_check_dir_entry(dir, NULL, de, bh,
 647                                          buf, buf_size, offset))
 648                         return -EFSCORRUPTED;
 649                 rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
 650                 de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
 651                 offset += rlen;
 652         }
 653         if ((char *) de > top)
 654                 return -EFSCORRUPTED;
 655
 656         return 0;
 657 }
 658
 659 const struct file_operations ext4_dir_operations = {
 660         .llseek         = ext4_dir_llseek,
 661         .read           = generic_read_dir,
 662         .iterate_shared = ext4_readdir,
 663         .unlocked_ioctl = ext4_ioctl,
 664 #ifdef CONFIG_COMPAT
 665         .compat_ioctl   = ext4_compat_ioctl,
 666 #endif
 667         .fsync          = ext4_sync_file,
 668         .open           = ext4_dir_open,
 669         .release        = ext4_release_dir,
 670 };