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, stored;
 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         stored = 0;
 137         offset = ctx->pos & (sb->s_blocksize - 1);
 138
 139         while (ctx->pos < inode->i_size) {
 140                 struct ext4_map_blocks map;
 141                 struct buffer_head *bh = NULL;
 142
 143                 map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
 144                 map.m_len = 1;
 145                 err = ext4_map_blocks(NULL, inode, &map, 0);
 146                 if (err > 0) {
 147                         pgoff_t index = map.m_pblk >>
 148                                         (PAGE_CACHE_SHIFT - inode->i_blkbits);
 149                         if (!ra_has_index(&file->f_ra, index))
 150                                 page_cache_sync_readahead(
 151                                         sb->s_bdev->bd_inode->i_mapping,
 152                                         &file->f_ra, file,
 153                                         index, 1);
 154                         file->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 155                         bh = ext4_bread(NULL, inode, map.m_lblk, 0, &err);
 156                 }
 157
 158                 /*
 159                  * We ignore I/O errors on directories so users have a chance
 160                  * of recovering data when there's a bad sector
 161                  */
 162                 if (!bh) {
 163                         if (!dir_has_error) {
 164                                 EXT4_ERROR_FILE(file, 0,
 165                                                 "directory contains a "
 166                                                 "hole at offset %llu",
 167                                            (unsigned long long) ctx->pos);
 168                                 dir_has_error = 1;
 169                         }
 170                         /* corrupt size?  Maybe no more blocks to read */
 171                         if (ctx->pos > inode->i_blocks << 9)
 172                                 break;
 173                         ctx->pos += sb->s_blocksize - offset;
 174                         continue;
 175                 }
 176
 177                 /* Check the checksum */
 178                 if (!buffer_verified(bh) &&
 179                     !ext4_dirent_csum_verify(inode,
 180                                 (struct ext4_dir_entry *)bh->b_data)) {
 181                         EXT4_ERROR_FILE(file, 0, "directory fails checksum "
 182                                         "at offset %llu",
 183                                         (unsigned long long)ctx->pos);
 184                         ctx->pos += sb->s_blocksize - offset;
 185                         brelse(bh);
 186                         continue;
 187                 }
 188                 set_buffer_verified(bh);
 189
 190                 /* If the dir block has changed since the last call to
 191                  * readdir(2), then we might be pointing to an invalid
 192                  * dirent right now.  Scan from the start of the block
 193                  * to make sure. */
 194                 if (file->f_version != inode->i_version) {
 195                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 196                                 de = (struct ext4_dir_entry_2 *)
 197                                         (bh->b_data + i);
 198                                 /* It's too expensive to do a full
 199                                  * dirent test each time round this
 200                                  * loop, but we do have to test at
 201                                  * least that it is non-zero.  A
 202                                  * failure will be detected in the
 203                                  * dirent test below. */
 204                                 if (ext4_rec_len_from_disk(de->rec_len,
 205                                         sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
 206                                         break;
 207                                 i += ext4_rec_len_from_disk(de->rec_len,
 208                                                             sb->s_blocksize);
 209                         }
 210                         offset = i;
 211                         ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
 212                                 | offset;
 213                         file->f_version = inode->i_version;
 214                 }
 215
 216                 while (ctx->pos < inode->i_size
 217                        && offset < sb->s_blocksize) {
 218                         de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
 219                         if (ext4_check_dir_entry(inode, file, de, bh,
 220                                                  bh->b_data, bh->b_size,
 221                                                  offset)) {
 222                                 /*
 223                                  * On error, skip to the next block
 224                                  */
 225                                 ctx->pos = (ctx->pos |
 226                                                 (sb->s_blocksize - 1)) + 1;
 227                                 break;
 228                         }
 229                         offset += ext4_rec_len_from_disk(de->rec_len,
 230                                         sb->s_blocksize);
 231                         if (le32_to_cpu(de->inode)) {
 232                                 if (!dir_emit(ctx, de->name,
 233                                                 de->name_len,
 234                                                 le32_to_cpu(de->inode),
 235                                                 get_dtype(sb, de->file_type))) {
 236                                         brelse(bh);
 237                                         return 0;
 238                                 }
 239                         }
 240                         ctx->pos += ext4_rec_len_from_disk(de->rec_len,
 241                                                 sb->s_blocksize);
 242                 }
 243                 offset = 0;
 244                 brelse(bh);
 245                 if (ctx->pos < inode->i_size) {
 246                         if (!dir_relax(inode))
 247                                 return 0;
 248                 }
 249         }
 250         return 0;
 251 }
 252
 253 static inline int is_32bit_api(void)
 254 {
 255 #ifdef CONFIG_COMPAT
 256         return is_compat_task();
 257 #else
 258         return (BITS_PER_LONG == 32);
 259 #endif
 260 }
 261
 262 /*
 263  * These functions convert from the major/minor hash to an f_pos
 264  * value for dx directories
 265  *
 266  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
 267  * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
 268  * directly on both 32-bit and 64-bit nodes, under such case, neither
 269  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
 270  */
 271 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
 272 {
 273         if ((filp->f_mode & FMODE_32BITHASH) ||
 274             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 275                 return major >> 1;
 276         else
 277                 return ((__u64)(major >> 1) << 32) | (__u64)minor;
 278 }
 279
 280 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
 281 {
 282         if ((filp->f_mode & FMODE_32BITHASH) ||
 283             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 284                 return (pos << 1) & 0xffffffff;
 285         else
 286                 return ((pos >> 32) << 1) & 0xffffffff;
 287 }
 288
 289 static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
 290 {
 291         if ((filp->f_mode & FMODE_32BITHASH) ||
 292             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 293                 return 0;
 294         else
 295                 return pos & 0xffffffff;
 296 }
 297
 298 /*
 299  * Return 32- or 64-bit end-of-file for dx directories
 300  */
 301 static inline loff_t ext4_get_htree_eof(struct file *filp)
 302 {
 303         if ((filp->f_mode & FMODE_32BITHASH) ||
 304             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 305                 return EXT4_HTREE_EOF_32BIT;
 306         else
 307                 return EXT4_HTREE_EOF_64BIT;
 308 }
 309
 310
 311 /*
 312  * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
 313  * directories, where the "offset" is in terms of the filename hash
 314  * value instead of the byte offset.
 315  *
 316  * Because we may return a 64-bit hash that is well beyond offset limits,
 317  * we need to pass the max hash as the maximum allowable offset in
 318  * the htree directory case.
 319  *
 320  * For non-htree, ext4_llseek already chooses the proper max offset.
 321  */
 322 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
 323 {
 324         struct inode *inode = file->f_mapping->host;
 325         int dx_dir = is_dx_dir(inode);
 326         loff_t htree_max = ext4_get_htree_eof(file);
 327
 328         if (likely(dx_dir))
 329                 return generic_file_llseek_size(file, offset, whence,
 330                                                     htree_max, htree_max);
 331         else
 332                 return ext4_llseek(file, offset, whence);
 333 }
 334
 335 /*
 336  * This structure holds the nodes of the red-black tree used to store
 337  * the directory entry in hash order.
 338  */
 339 struct fname {
 340         __u32           hash;
 341         __u32           minor_hash;
 342         struct rb_node  rb_hash;
 343         struct fname    *next;
 344         __u32           inode;
 345         __u8            name_len;
 346         __u8            file_type;
 347         char            name[0];
 348 };
 349
 350 /*
 351  * This functoin implements a non-recursive way of freeing all of the
 352  * nodes in the red-black tree.
 353  */
 354 static void free_rb_tree_fname(struct rb_root *root)
 355 {
 356         struct rb_node  *n = root->rb_node;
 357         struct rb_node  *parent;
 358         struct fname    *fname;
 359
 360         while (n) {
 361                 /* Do the node's children first */
 362                 if (n->rb_left) {
 363                         n = n->rb_left;
 364                         continue;
 365                 }
 366                 if (n->rb_right) {
 367                         n = n->rb_right;
 368                         continue;
 369                 }
 370                 /*
 371                  * The node has no children; free it, and then zero
 372                  * out parent's link to it.  Finally go to the
 373                  * beginning of the loop and try to free the parent
 374                  * node.
 375                  */
 376                 parent = rb_parent(n);
 377                 fname = rb_entry(n, struct fname, rb_hash);
 378                 while (fname) {
 379                         struct fname *old = fname;
 380                         fname = fname->next;
 381                         kfree(old);
 382                 }
 383                 if (!parent)
 384                         *root = RB_ROOT;
 385                 else if (parent->rb_left == n)
 386                         parent->rb_left = NULL;
 387                 else if (parent->rb_right == n)
 388                         parent->rb_right = NULL;
 389                 n = parent;
 390         }
 391 }
 392
 393
 394 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
 395                                                            loff_t pos)
 396 {
 397         struct dir_private_info *p;
 398
 399         p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
 400         if (!p)
 401                 return NULL;
 402         p->curr_hash = pos2maj_hash(filp, pos);
 403         p->curr_minor_hash = pos2min_hash(filp, pos);
 404         return p;
 405 }
 406
 407 void ext4_htree_free_dir_info(struct dir_private_info *p)
 408 {
 409         free_rb_tree_fname(&p->root);
 410         kfree(p);
 411 }
 412
 413 /*
 414  * Given a directory entry, enter it into the fname rb tree.
 415  */
 416 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
 417                              __u32 minor_hash,
 418                              struct ext4_dir_entry_2 *dirent)
 419 {
 420         struct rb_node **p, *parent = NULL;
 421         struct fname *fname, *new_fn;
 422         struct dir_private_info *info;
 423         int len;
 424
 425         info = dir_file->private_data;
 426         p = &info->root.rb_node;
 427
 428         /* Create and allocate the fname structure */
 429         len = sizeof(struct fname) + dirent->name_len + 1;
 430         new_fn = kzalloc(len, GFP_KERNEL);
 431         if (!new_fn)
 432                 return -ENOMEM;
 433         new_fn->hash = hash;
 434         new_fn->minor_hash = minor_hash;
 435         new_fn->inode = le32_to_cpu(dirent->inode);
 436         new_fn->name_len = dirent->name_len;
 437         new_fn->file_type = dirent->file_type;
 438         memcpy(new_fn->name, dirent->name, dirent->name_len);
 439         new_fn->name[dirent->name_len] = 0;
 440
 441         while (*p) {
 442                 parent = *p;
 443                 fname = rb_entry(parent, struct fname, rb_hash);
 444
 445                 /*
 446                  * If the hash and minor hash match up, then we put
 447                  * them on a linked list.  This rarely happens...
 448                  */
 449                 if ((new_fn->hash == fname->hash) &&
 450                     (new_fn->minor_hash == fname->minor_hash)) {
 451                         new_fn->next = fname->next;
 452                         fname->next = new_fn;
 453                         return 0;
 454                 }
 455
 456                 if (new_fn->hash < fname->hash)
 457                         p = &(*p)->rb_left;
 458                 else if (new_fn->hash > fname->hash)
 459                         p = &(*p)->rb_right;
 460                 else if (new_fn->minor_hash < fname->minor_hash)
 461                         p = &(*p)->rb_left;
 462                 else /* if (new_fn->minor_hash > fname->minor_hash) */
 463                         p = &(*p)->rb_right;
 464         }
 465
 466         rb_link_node(&new_fn->rb_hash, parent, p);
 467         rb_insert_color(&new_fn->rb_hash, &info->root);
 468         return 0;
 469 }
 470
 471
 472
 473 /*
 474  * This is a helper function for ext4_dx_readdir.  It calls filldir
 475  * for all entres on the fname linked list.  (Normally there is only
 476  * one entry on the linked list, unless there are 62 bit hash collisions.)
 477  */
 478 static int call_filldir(struct file *file, struct dir_context *ctx,
 479                         struct fname *fname)
 480 {
 481         struct dir_private_info *info = file->private_data;
 482         struct inode *inode = file_inode(file);
 483         struct super_block *sb = inode->i_sb;
 484
 485         if (!fname) {
 486                 ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
 487                          "called with null fname?!?", __func__, __LINE__,
 488                          inode->i_ino, current->comm);
 489                 return 0;
 490         }
 491         ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
 492         while (fname) {
 493                 if (!dir_emit(ctx, fname->name,
 494                                 fname->name_len,
 495                                 fname->inode,
 496                                 get_dtype(sb, fname->file_type))) {
 497                         info->extra_fname = fname;
 498                         return 1;
 499                 }
 500                 fname = fname->next;
 501         }
 502         return 0;
 503 }
 504
 505 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
 506 {
 507         struct dir_private_info *info = file->private_data;
 508         struct inode *inode = file_inode(file);
 509         struct fname *fname;
 510         int     ret;
 511
 512         if (!info) {
 513                 info = ext4_htree_create_dir_info(file, ctx->pos);
 514                 if (!info)
 515                         return -ENOMEM;
 516                 file->private_data = info;
 517         }
 518
 519         if (ctx->pos == ext4_get_htree_eof(file))
 520                 return 0;       /* EOF */
 521
 522         /* Some one has messed with f_pos; reset the world */
 523         if (info->last_pos != ctx->pos) {
 524                 free_rb_tree_fname(&info->root);
 525                 info->curr_node = NULL;
 526                 info->extra_fname = NULL;
 527                 info->curr_hash = pos2maj_hash(file, ctx->pos);
 528                 info->curr_minor_hash = pos2min_hash(file, ctx->pos);
 529         }
 530
 531         /*
 532          * If there are any leftover names on the hash collision
 533          * chain, return them first.
 534          */
 535         if (info->extra_fname) {
 536                 if (call_filldir(file, ctx, info->extra_fname))
 537                         goto finished;
 538                 info->extra_fname = NULL;
 539                 goto next_node;
 540         } else if (!info->curr_node)
 541                 info->curr_node = rb_first(&info->root);
 542
 543         while (1) {
 544                 /*
 545                  * Fill the rbtree if we have no more entries,
 546                  * or the inode has changed since we last read in the
 547                  * cached entries.
 548                  */
 549                 if ((!info->curr_node) ||
 550                     (file->f_version != inode->i_version)) {
 551                         info->curr_node = NULL;
 552                         free_rb_tree_fname(&info->root);
 553                         file->f_version = inode->i_version;
 554                         ret = ext4_htree_fill_tree(file, info->curr_hash,
 555                                                    info->curr_minor_hash,
 556                                                    &info->next_hash);
 557                         if (ret < 0)
 558                                 return ret;
 559                         if (ret == 0) {
 560                                 ctx->pos = ext4_get_htree_eof(file);
 561                                 break;
 562                         }
 563                         info->curr_node = rb_first(&info->root);
 564                 }
 565
 566                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
 567                 info->curr_hash = fname->hash;
 568                 info->curr_minor_hash = fname->minor_hash;
 569                 if (call_filldir(file, ctx, fname))
 570                         break;
 571         next_node:
 572                 info->curr_node = rb_next(info->curr_node);
 573                 if (info->curr_node) {
 574                         fname = rb_entry(info->curr_node, struct fname,
 575                                          rb_hash);
 576                         info->curr_hash = fname->hash;
 577                         info->curr_minor_hash = fname->minor_hash;
 578                 } else {
 579                         if (info->next_hash == ~0) {
 580                                 ctx->pos = ext4_get_htree_eof(file);
 581                                 break;
 582                         }
 583                         info->curr_hash = info->next_hash;
 584                         info->curr_minor_hash = 0;
 585                 }
 586         }
 587 finished:
 588         info->last_pos = ctx->pos;
 589         return 0;
 590 }
 591
 592 static int ext4_release_dir(struct inode *inode, struct file *filp)
 593 {
 594         if (filp->private_data)
 595                 ext4_htree_free_dir_info(filp->private_data);
 596
 597         return 0;
 598 }
 599
 600 const struct file_operations ext4_dir_operations = {
 601         .llseek         = ext4_dir_llseek,
 602         .read           = generic_read_dir,
 603         .iterate        = ext4_readdir,
 604         .unlocked_ioctl = ext4_ioctl,
 605 #ifdef CONFIG_COMPAT
 606         .compat_ioctl   = ext4_compat_ioctl,
 607 #endif
 608         .fsync          = ext4_sync_file,
 609         .release        = ext4_release_dir,
 610 };