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/jbd2.h>
  26 #include <linux/buffer_head.h>
  27 #include <linux/slab.h>
  28 #include <linux/rbtree.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_COMPAT_FEATURE(inode->i_sb,
  46                      EXT4_FEATURE_COMPAT_DIR_INDEX) &&
  47             ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
  48              ((inode->i_size >> sb->s_blocksize_bits) == 1) ||
  49              ext4_has_inline_data(inode)))
  50                 return 1;
  51
  52         return 0;
  53 }
  54
  55 /*
  56  * Return 0 if the directory entry is OK, and 1 if there is a problem
  57  *
  58  * Note: this is the opposite of what ext2 and ext3 historically returned...
  59  *
  60  * bh passed here can be an inode block or a dir data block, depending
  61  * on the inode inline data flag.
  62  */
  63 int __ext4_check_dir_entry(const char *function, unsigned int line,
  64                            struct inode *dir, struct file *filp,
  65                            struct ext4_dir_entry_2 *de,
  66                            struct buffer_head *bh, char *buf, int size,
  67                            unsigned int offset)
  68 {
  69         const char *error_msg = NULL;
  70         const int rlen = ext4_rec_len_from_disk(de->rec_len,
  71                                                 dir->i_sb->s_blocksize);
  72
  73         if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
  74                 error_msg = "rec_len is smaller than minimal";
  75         else if (unlikely(rlen % 4 != 0))
  76                 error_msg = "rec_len % 4 != 0";
  77         else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
  78                 error_msg = "rec_len is too small for name_len";
  79         else if (unlikely(((char *) de - buf) + rlen > size))
  80                 error_msg = "directory entry across range";
  81         else if (unlikely(le32_to_cpu(de->inode) >
  82                         le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
  83                 error_msg = "inode out of bounds";
  84         else
  85                 return 0;
  86
  87         if (filp)
  88                 ext4_error_file(filp, function, line, bh->b_blocknr,
  89                                 "bad entry in directory: %s - offset=%u(%u), "
  90                                 "inode=%u, rec_len=%d, name_len=%d",
  91                                 error_msg, (unsigned) (offset % size),
  92                                 offset, le32_to_cpu(de->inode),
  93                                 rlen, de->name_len);
  94         else
  95                 ext4_error_inode(dir, function, line, bh->b_blocknr,
  96                                 "bad entry in directory: %s - offset=%u(%u), "
  97                                 "inode=%u, rec_len=%d, name_len=%d",
  98                                 error_msg, (unsigned) (offset % size),
  99                                 offset, le32_to_cpu(de->inode),
 100                                 rlen, de->name_len);
 101
 102         return 1;
 103 }
 104
 105 static int ext4_readdir(struct file *file, struct dir_context *ctx)
 106 {
 107         unsigned int offset;
 108         int i;
 109         struct ext4_dir_entry_2 *de;
 110         int err;
 111         struct inode *inode = file_inode(file);
 112         struct super_block *sb = inode->i_sb;
 113         int dir_has_error = 0;
 114
 115         if (is_dx_dir(inode)) {
 116                 err = ext4_dx_readdir(file, ctx);
 117                 if (err != ERR_BAD_DX_DIR) {
 118                         return err;
 119                 }
 120                 /*
 121                  * We don't set the inode dirty flag since it's not
 122                  * critical that it get flushed back to the disk.
 123                  */
 124                 ext4_clear_inode_flag(file_inode(file),
 125                                       EXT4_INODE_INDEX);
 126         }
 127
 128         if (ext4_has_inline_data(inode)) {
 129                 int has_inline_data = 1;
 130                 int ret = ext4_read_inline_dir(file, ctx,
 131                                            &has_inline_data);
 132                 if (has_inline_data)
 133                         return ret;
 134         }
 135
 136         offset = ctx->pos & (sb->s_blocksize - 1);
 137
 138         while (ctx->pos < inode->i_size) {
 139                 struct ext4_map_blocks map;
 140                 struct buffer_head *bh = NULL;
 141
 142                 map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
 143                 map.m_len = 1;
 144                 err = ext4_map_blocks(NULL, inode, &map, 0);
 145                 if (err > 0) {
 146                         pgoff_t index = map.m_pblk >>
 147                                         (PAGE_CACHE_SHIFT - inode->i_blkbits);
 148                         if (!ra_has_index(&file->f_ra, index))
 149                                 page_cache_sync_readahead(
 150                                         sb->s_bdev->bd_inode->i_mapping,
 151                                         &file->f_ra, file,
 152                                         index, 1);
 153                         file->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 154                         bh = ext4_bread(NULL, inode, map.m_lblk, 0, &err);
 155                 }
 156
 157                 /*
 158                  * We ignore I/O errors on directories so users have a chance
 159                  * of recovering data when there's a bad sector
 160                  */
 161                 if (!bh) {
 162                         if (!dir_has_error) {
 163                                 EXT4_ERROR_FILE(file, 0,
 164                                                 "directory contains a "
 165                                                 "hole at offset %llu",
 166                                            (unsigned long long) ctx->pos);
 167                                 dir_has_error = 1;
 168                         }
 169                         /* corrupt size?  Maybe no more blocks to read */
 170                         if (ctx->pos > inode->i_blocks << 9)
 171                                 break;
 172                         ctx->pos += sb->s_blocksize - offset;
 173                         continue;
 174                 }
 175
 176                 /* Check the checksum */
 177                 if (!buffer_verified(bh) &&
 178                     !ext4_dirent_csum_verify(inode,
 179                                 (struct ext4_dir_entry *)bh->b_data)) {
 180                         EXT4_ERROR_FILE(file, 0, "directory fails checksum "
 181                                         "at offset %llu",
 182                                         (unsigned long long)ctx->pos);
 183                         ctx->pos += sb->s_blocksize - offset;
 184                         brelse(bh);
 185                         continue;
 186                 }
 187                 set_buffer_verified(bh);
 188
 189                 /* If the dir block has changed since the last call to
 190                  * readdir(2), then we might be pointing to an invalid
 191                  * dirent right now.  Scan from the start of the block
 192                  * to make sure. */
 193                 if (file->f_version != inode->i_version) {
 194                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 195                                 de = (struct ext4_dir_entry_2 *)
 196                                         (bh->b_data + i);
 197                                 /* It's too expensive to do a full
 198                                  * dirent test each time round this
 199                                  * loop, but we do have to test at
 200                                  * least that it is non-zero.  A
 201                                  * failure will be detected in the
 202                                  * dirent test below. */
 203                                 if (ext4_rec_len_from_disk(de->rec_len,
 204                                         sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
 205                                         break;
 206                                 i += ext4_rec_len_from_disk(de->rec_len,
 207                                                             sb->s_blocksize);
 208                         }
 209                         offset = i;
 210                         ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
 211                                 | offset;
 212                         file->f_version = inode->i_version;
 213                 }
 214
 215                 while (ctx->pos < inode->i_size
 216                        && offset < sb->s_blocksize) {
 217                         de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
 218                         if (ext4_check_dir_entry(inode, file, de, bh,
 219                                                  bh->b_data, bh->b_size,
 220                                                  offset)) {
 221                                 /*
 222                                  * On error, skip to the next block
 223                                  */
 224                                 ctx->pos = (ctx->pos |
 225                                                 (sb->s_blocksize - 1)) + 1;
 226                                 break;
 227                         }
 228                         offset += ext4_rec_len_from_disk(de->rec_len,
 229                                         sb->s_blocksize);
 230                         if (le32_to_cpu(de->inode)) {
 231                                 if (!dir_emit(ctx, de->name,
 232                                                 de->name_len,
 233                                                 le32_to_cpu(de->inode),
 234                                                 get_dtype(sb, de->file_type))) {
 235                                         brelse(bh);
 236                                         return 0;
 237                                 }
 238                         }
 239                         ctx->pos += ext4_rec_len_from_disk(de->rec_len,
 240                                                 sb->s_blocksize);
 241                 }
 242                 offset = 0;
 243                 brelse(bh);
 244                 if (ctx->pos < inode->i_size) {
 245                         if (!dir_relax(inode))
 246                                 return 0;
 247                 }
 248         }
 249         return 0;
 250 }
 251
 252 static inline int is_32bit_api(void)
 253 {
 254 #ifdef CONFIG_COMPAT
 255         return is_compat_task();
 256 #else
 257         return (BITS_PER_LONG == 32);
 258 #endif
 259 }
 260
 261 /*
 262  * These functions convert from the major/minor hash to an f_pos
 263  * value for dx directories
 264  *
 265  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
 266  * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
 267  * directly on both 32-bit and 64-bit nodes, under such case, neither
 268  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
 269  */
 270 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
 271 {
 272         if ((filp->f_mode & FMODE_32BITHASH) ||
 273             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 274                 return major >> 1;
 275         else
 276                 return ((__u64)(major >> 1) << 32) | (__u64)minor;
 277 }
 278
 279 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
 280 {
 281         if ((filp->f_mode & FMODE_32BITHASH) ||
 282             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 283                 return (pos << 1) & 0xffffffff;
 284         else
 285                 return ((pos >> 32) << 1) & 0xffffffff;
 286 }
 287
 288 static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
 289 {
 290         if ((filp->f_mode & FMODE_32BITHASH) ||
 291             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 292                 return 0;
 293         else
 294                 return pos & 0xffffffff;
 295 }
 296
 297 /*
 298  * Return 32- or 64-bit end-of-file for dx directories
 299  */
 300 static inline loff_t ext4_get_htree_eof(struct file *filp)
 301 {
 302         if ((filp->f_mode & FMODE_32BITHASH) ||
 303             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 304                 return EXT4_HTREE_EOF_32BIT;
 305         else
 306                 return EXT4_HTREE_EOF_64BIT;
 307 }
 308
 309
 310 /*
 311  * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
 312  * directories, where the "offset" is in terms of the filename hash
 313  * value instead of the byte offset.
 314  *
 315  * Because we may return a 64-bit hash that is well beyond offset limits,
 316  * we need to pass the max hash as the maximum allowable offset in
 317  * the htree directory case.
 318  *
 319  * For non-htree, ext4_llseek already chooses the proper max offset.
 320  */
 321 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
 322 {
 323         struct inode *inode = file->f_mapping->host;
 324         int dx_dir = is_dx_dir(inode);
 325         loff_t htree_max = ext4_get_htree_eof(file);
 326
 327         if (likely(dx_dir))
 328                 return generic_file_llseek_size(file, offset, whence,
 329                                                     htree_max, htree_max);
 330         else
 331                 return ext4_llseek(file, offset, whence);
 332 }
 333
 334 /*
 335  * This structure holds the nodes of the red-black tree used to store
 336  * the directory entry in hash order.
 337  */
 338 struct fname {
 339         __u32           hash;
 340         __u32           minor_hash;
 341         struct rb_node  rb_hash;
 342         struct fname    *next;
 343         __u32           inode;
 344         __u8            name_len;
 345         __u8            file_type;
 346         char            name[0];
 347 };
 348
 349 /*
 350  * This functoin implements a non-recursive way of freeing all of the
 351  * nodes in the red-black tree.
 352  */
 353 static void free_rb_tree_fname(struct rb_root *root)
 354 {
 355         struct fname *fname, *next;
 356
 357         rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
 358                 while (fname) {
 359                         struct fname *old = fname;
 360                         fname = fname->next;
 361                         kfree(old);
 362                 }
 363
 364         *root = RB_ROOT;
 365 }
 366
 367
 368 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
 369                                                            loff_t pos)
 370 {
 371         struct dir_private_info *p;
 372
 373         p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
 374         if (!p)
 375                 return NULL;
 376         p->curr_hash = pos2maj_hash(filp, pos);
 377         p->curr_minor_hash = pos2min_hash(filp, pos);
 378         return p;
 379 }
 380
 381 void ext4_htree_free_dir_info(struct dir_private_info *p)
 382 {
 383         free_rb_tree_fname(&p->root);
 384         kfree(p);
 385 }
 386
 387 /*
 388  * Given a directory entry, enter it into the fname rb tree.
 389  */
 390 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
 391                              __u32 minor_hash,
 392                              struct ext4_dir_entry_2 *dirent)
 393 {
 394         struct rb_node **p, *parent = NULL;
 395         struct fname *fname, *new_fn;
 396         struct dir_private_info *info;
 397         int len;
 398
 399         info = dir_file->private_data;
 400         p = &info->root.rb_node;
 401
 402         /* Create and allocate the fname structure */
 403         len = sizeof(struct fname) + dirent->name_len + 1;
 404         new_fn = kzalloc(len, GFP_KERNEL);
 405         if (!new_fn)
 406                 return -ENOMEM;
 407         new_fn->hash = hash;
 408         new_fn->minor_hash = minor_hash;
 409         new_fn->inode = le32_to_cpu(dirent->inode);
 410         new_fn->name_len = dirent->name_len;
 411         new_fn->file_type = dirent->file_type;
 412         memcpy(new_fn->name, dirent->name, dirent->name_len);
 413         new_fn->name[dirent->name_len] = 0;
 414
 415         while (*p) {
 416                 parent = *p;
 417                 fname = rb_entry(parent, struct fname, rb_hash);
 418
 419                 /*
 420                  * If the hash and minor hash match up, then we put
 421                  * them on a linked list.  This rarely happens...
 422                  */
 423                 if ((new_fn->hash == fname->hash) &&
 424                     (new_fn->minor_hash == fname->minor_hash)) {
 425                         new_fn->next = fname->next;
 426                         fname->next = new_fn;
 427                         return 0;
 428                 }
 429
 430                 if (new_fn->hash < fname->hash)
 431                         p = &(*p)->rb_left;
 432                 else if (new_fn->hash > fname->hash)
 433                         p = &(*p)->rb_right;
 434                 else if (new_fn->minor_hash < fname->minor_hash)
 435                         p = &(*p)->rb_left;
 436                 else /* if (new_fn->minor_hash > fname->minor_hash) */
 437                         p = &(*p)->rb_right;
 438         }
 439
 440         rb_link_node(&new_fn->rb_hash, parent, p);
 441         rb_insert_color(&new_fn->rb_hash, &info->root);
 442         return 0;
 443 }
 444
 445
 446
 447 /*
 448  * This is a helper function for ext4_dx_readdir.  It calls filldir
 449  * for all entres on the fname linked list.  (Normally there is only
 450  * one entry on the linked list, unless there are 62 bit hash collisions.)
 451  */
 452 static int call_filldir(struct file *file, struct dir_context *ctx,
 453                         struct fname *fname)
 454 {
 455         struct dir_private_info *info = file->private_data;
 456         struct inode *inode = file_inode(file);
 457         struct super_block *sb = inode->i_sb;
 458
 459         if (!fname) {
 460                 ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
 461                          "called with null fname?!?", __func__, __LINE__,
 462                          inode->i_ino, current->comm);
 463                 return 0;
 464         }
 465         ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
 466         while (fname) {
 467                 if (!dir_emit(ctx, fname->name,
 468                                 fname->name_len,
 469                                 fname->inode,
 470                                 get_dtype(sb, fname->file_type))) {
 471                         info->extra_fname = fname;
 472                         return 1;
 473                 }
 474                 fname = fname->next;
 475         }
 476         return 0;
 477 }
 478
 479 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
 480 {
 481         struct dir_private_info *info = file->private_data;
 482         struct inode *inode = file_inode(file);
 483         struct fname *fname;
 484         int     ret;
 485
 486         if (!info) {
 487                 info = ext4_htree_create_dir_info(file, ctx->pos);
 488                 if (!info)
 489                         return -ENOMEM;
 490                 file->private_data = info;
 491         }
 492
 493         if (ctx->pos == ext4_get_htree_eof(file))
 494                 return 0;       /* EOF */
 495
 496         /* Some one has messed with f_pos; reset the world */
 497         if (info->last_pos != ctx->pos) {
 498                 free_rb_tree_fname(&info->root);
 499                 info->curr_node = NULL;
 500                 info->extra_fname = NULL;
 501                 info->curr_hash = pos2maj_hash(file, ctx->pos);
 502                 info->curr_minor_hash = pos2min_hash(file, ctx->pos);
 503         }
 504
 505         /*
 506          * If there are any leftover names on the hash collision
 507          * chain, return them first.
 508          */
 509         if (info->extra_fname) {
 510                 if (call_filldir(file, ctx, info->extra_fname))
 511                         goto finished;
 512                 info->extra_fname = NULL;
 513                 goto next_node;
 514         } else if (!info->curr_node)
 515                 info->curr_node = rb_first(&info->root);
 516
 517         while (1) {
 518                 /*
 519                  * Fill the rbtree if we have no more entries,
 520                  * or the inode has changed since we last read in the
 521                  * cached entries.
 522                  */
 523                 if ((!info->curr_node) ||
 524                     (file->f_version != inode->i_version)) {
 525                         info->curr_node = NULL;
 526                         free_rb_tree_fname(&info->root);
 527                         file->f_version = inode->i_version;
 528                         ret = ext4_htree_fill_tree(file, info->curr_hash,
 529                                                    info->curr_minor_hash,
 530                                                    &info->next_hash);
 531                         if (ret < 0)
 532                                 return ret;
 533                         if (ret == 0) {
 534                                 ctx->pos = ext4_get_htree_eof(file);
 535                                 break;
 536                         }
 537                         info->curr_node = rb_first(&info->root);
 538                 }
 539
 540                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
 541                 info->curr_hash = fname->hash;
 542                 info->curr_minor_hash = fname->minor_hash;
 543                 if (call_filldir(file, ctx, fname))
 544                         break;
 545         next_node:
 546                 info->curr_node = rb_next(info->curr_node);
 547                 if (info->curr_node) {
 548                         fname = rb_entry(info->curr_node, struct fname,
 549                                          rb_hash);
 550                         info->curr_hash = fname->hash;
 551                         info->curr_minor_hash = fname->minor_hash;
 552                 } else {
 553                         if (info->next_hash == ~0) {
 554                                 ctx->pos = ext4_get_htree_eof(file);
 555                                 break;
 556                         }
 557                         info->curr_hash = info->next_hash;
 558                         info->curr_minor_hash = 0;
 559                 }
 560         }
 561 finished:
 562         info->last_pos = ctx->pos;
 563         return 0;
 564 }
 565
 566 static int ext4_release_dir(struct inode *inode, struct file *filp)
 567 {
 568         if (filp->private_data)
 569                 ext4_htree_free_dir_info(filp->private_data);
 570
 571         return 0;
 572 }
 573
 574 const struct file_operations ext4_dir_operations = {
 575         .llseek         = ext4_dir_llseek,
 576         .read           = generic_read_dir,
 577         .iterate        = ext4_readdir,
 578         .unlocked_ioctl = ext4_ioctl,
 579 #ifdef CONFIG_COMPAT
 580         .compat_ioctl   = ext4_compat_ioctl,
 581 #endif
 582         .fsync          = ext4_sync_file,
 583         .release        = ext4_release_dir,
 584 };