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