linux/fs/ext4/dir.c
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   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
  31static unsigned char ext4_filetype_table[] = {
  32        DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
  33};
  34
  35static int ext4_dx_readdir(struct file *filp,
  36                           void *dirent, filldir_t filldir);
  37
  38static unsigned char get_dtype(struct super_block *sb, int filetype)
  39{
  40        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FILETYPE) ||
  41            (filetype >= EXT4_FT_MAX))
  42                return DT_UNKNOWN;
  43
  44        return (ext4_filetype_table[filetype]);
  45}
  46
  47/**
  48 * Check if the given dir-inode refers to an htree-indexed directory
  49 * (or a directory which chould potentially get coverted to use htree
  50 * indexing).
  51 *
  52 * Return 1 if it is a dx dir, 0 if not
  53 */
  54static int is_dx_dir(struct inode *inode)
  55{
  56        struct super_block *sb = inode->i_sb;
  57
  58        if (EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
  59                     EXT4_FEATURE_COMPAT_DIR_INDEX) &&
  60            ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
  61             ((inode->i_size >> sb->s_blocksize_bits) == 1)))
  62                return 1;
  63
  64        return 0;
  65}
  66
  67/*
  68 * Return 0 if the directory entry is OK, and 1 if there is a problem
  69 *
  70 * Note: this is the opposite of what ext2 and ext3 historically returned...
  71 */
  72int __ext4_check_dir_entry(const char *function, unsigned int line,
  73                           struct inode *dir, struct file *filp,
  74                           struct ext4_dir_entry_2 *de,
  75                           struct buffer_head *bh,
  76                           unsigned int offset)
  77{
  78        const char *error_msg = NULL;
  79        const int rlen = ext4_rec_len_from_disk(de->rec_len,
  80                                                dir->i_sb->s_blocksize);
  81
  82        if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
  83                error_msg = "rec_len is smaller than minimal";
  84        else if (unlikely(rlen % 4 != 0))
  85                error_msg = "rec_len % 4 != 0";
  86        else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
  87                error_msg = "rec_len is too small for name_len";
  88        else if (unlikely(((char *) de - bh->b_data) + rlen >
  89                          dir->i_sb->s_blocksize))
  90                error_msg = "directory entry across blocks";
  91        else if (unlikely(le32_to_cpu(de->inode) >
  92                        le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
  93                error_msg = "inode out of bounds";
  94        else
  95                return 0;
  96
  97        if (filp)
  98                ext4_error_file(filp, function, line, bh->b_blocknr,
  99                                "bad entry in directory: %s - offset=%u(%u), "
 100                                "inode=%u, rec_len=%d, name_len=%d",
 101                                error_msg, (unsigned) (offset % bh->b_size),
 102                                offset, le32_to_cpu(de->inode),
 103                                rlen, de->name_len);
 104        else
 105                ext4_error_inode(dir, function, line, bh->b_blocknr,
 106                                "bad entry in directory: %s - offset=%u(%u), "
 107                                "inode=%u, rec_len=%d, name_len=%d",
 108                                error_msg, (unsigned) (offset % bh->b_size),
 109                                offset, le32_to_cpu(de->inode),
 110                                rlen, de->name_len);
 111
 112        return 1;
 113}
 114
 115static int ext4_readdir(struct file *filp,
 116                         void *dirent, filldir_t filldir)
 117{
 118        int error = 0;
 119        unsigned int offset;
 120        int i, stored;
 121        struct ext4_dir_entry_2 *de;
 122        int err;
 123        struct inode *inode = filp->f_path.dentry->d_inode;
 124        struct super_block *sb = inode->i_sb;
 125        int ret = 0;
 126        int dir_has_error = 0;
 127
 128        if (is_dx_dir(inode)) {
 129                err = ext4_dx_readdir(filp, dirent, filldir);
 130                if (err != ERR_BAD_DX_DIR) {
 131                        ret = err;
 132                        goto out;
 133                }
 134                /*
 135                 * We don't set the inode dirty flag since it's not
 136                 * critical that it get flushed back to the disk.
 137                 */
 138                ext4_clear_inode_flag(filp->f_path.dentry->d_inode,
 139                                      EXT4_INODE_INDEX);
 140        }
 141        stored = 0;
 142        offset = filp->f_pos & (sb->s_blocksize - 1);
 143
 144        while (!error && !stored && filp->f_pos < inode->i_size) {
 145                struct ext4_map_blocks map;
 146                struct buffer_head *bh = NULL;
 147
 148                map.m_lblk = filp->f_pos >> EXT4_BLOCK_SIZE_BITS(sb);
 149                map.m_len = 1;
 150                err = ext4_map_blocks(NULL, inode, &map, 0);
 151                if (err > 0) {
 152                        pgoff_t index = map.m_pblk >>
 153                                        (PAGE_CACHE_SHIFT - inode->i_blkbits);
 154                        if (!ra_has_index(&filp->f_ra, index))
 155                                page_cache_sync_readahead(
 156                                        sb->s_bdev->bd_inode->i_mapping,
 157                                        &filp->f_ra, filp,
 158                                        index, 1);
 159                        filp->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 160                        bh = ext4_bread(NULL, inode, map.m_lblk, 0, &err);
 161                }
 162
 163                /*
 164                 * We ignore I/O errors on directories so users have a chance
 165                 * of recovering data when there's a bad sector
 166                 */
 167                if (!bh) {
 168                        if (!dir_has_error) {
 169                                EXT4_ERROR_FILE(filp, 0,
 170                                                "directory contains a "
 171                                                "hole at offset %llu",
 172                                           (unsigned long long) filp->f_pos);
 173                                dir_has_error = 1;
 174                        }
 175                        /* corrupt size?  Maybe no more blocks to read */
 176                        if (filp->f_pos > inode->i_blocks << 9)
 177                                break;
 178                        filp->f_pos += sb->s_blocksize - offset;
 179                        continue;
 180                }
 181
 182                /* Check the checksum */
 183                if (!buffer_verified(bh) &&
 184                    !ext4_dirent_csum_verify(inode,
 185                                (struct ext4_dir_entry *)bh->b_data)) {
 186                        EXT4_ERROR_FILE(filp, 0, "directory fails checksum "
 187                                        "at offset %llu",
 188                                        (unsigned long long)filp->f_pos);
 189                        filp->f_pos += sb->s_blocksize - offset;
 190                        continue;
 191                }
 192                set_buffer_verified(bh);
 193
 194revalidate:
 195                /* If the dir block has changed since the last call to
 196                 * readdir(2), then we might be pointing to an invalid
 197                 * dirent right now.  Scan from the start of the block
 198                 * to make sure. */
 199                if (filp->f_version != inode->i_version) {
 200                        for (i = 0; i < sb->s_blocksize && i < offset; ) {
 201                                de = (struct ext4_dir_entry_2 *)
 202                                        (bh->b_data + i);
 203                                /* It's too expensive to do a full
 204                                 * dirent test each time round this
 205                                 * loop, but we do have to test at
 206                                 * least that it is non-zero.  A
 207                                 * failure will be detected in the
 208                                 * dirent test below. */
 209                                if (ext4_rec_len_from_disk(de->rec_len,
 210                                        sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
 211                                        break;
 212                                i += ext4_rec_len_from_disk(de->rec_len,
 213                                                            sb->s_blocksize);
 214                        }
 215                        offset = i;
 216                        filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
 217                                | offset;
 218                        filp->f_version = inode->i_version;
 219                }
 220
 221                while (!error && filp->f_pos < inode->i_size
 222                       && offset < sb->s_blocksize) {
 223                        de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
 224                        if (ext4_check_dir_entry(inode, filp, de,
 225                                                 bh, offset)) {
 226                                /*
 227                                 * On error, skip the f_pos to the next block
 228                                 */
 229                                filp->f_pos = (filp->f_pos |
 230                                                (sb->s_blocksize - 1)) + 1;
 231                                brelse(bh);
 232                                ret = stored;
 233                                goto out;
 234                        }
 235                        offset += ext4_rec_len_from_disk(de->rec_len,
 236                                        sb->s_blocksize);
 237                        if (le32_to_cpu(de->inode)) {
 238                                /* We might block in the next section
 239                                 * if the data destination is
 240                                 * currently swapped out.  So, use a
 241                                 * version stamp to detect whether or
 242                                 * not the directory has been modified
 243                                 * during the copy operation.
 244                                 */
 245                                u64 version = filp->f_version;
 246
 247                                error = filldir(dirent, de->name,
 248                                                de->name_len,
 249                                                filp->f_pos,
 250                                                le32_to_cpu(de->inode),
 251                                                get_dtype(sb, de->file_type));
 252                                if (error)
 253                                        break;
 254                                if (version != filp->f_version)
 255                                        goto revalidate;
 256                                stored++;
 257                        }
 258                        filp->f_pos += ext4_rec_len_from_disk(de->rec_len,
 259                                                sb->s_blocksize);
 260                }
 261                offset = 0;
 262                brelse(bh);
 263        }
 264out:
 265        return ret;
 266}
 267
 268static inline int is_32bit_api(void)
 269{
 270#ifdef CONFIG_COMPAT
 271        return is_compat_task();
 272#else
 273        return (BITS_PER_LONG == 32);
 274#endif
 275}
 276
 277/*
 278 * These functions convert from the major/minor hash to an f_pos
 279 * value for dx directories
 280 *
 281 * Upper layer (for example NFS) should specify FMODE_32BITHASH or
 282 * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
 283 * directly on both 32-bit and 64-bit nodes, under such case, neither
 284 * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
 285 */
 286static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
 287{
 288        if ((filp->f_mode & FMODE_32BITHASH) ||
 289            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 290                return major >> 1;
 291        else
 292                return ((__u64)(major >> 1) << 32) | (__u64)minor;
 293}
 294
 295static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
 296{
 297        if ((filp->f_mode & FMODE_32BITHASH) ||
 298            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 299                return (pos << 1) & 0xffffffff;
 300        else
 301                return ((pos >> 32) << 1) & 0xffffffff;
 302}
 303
 304static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
 305{
 306        if ((filp->f_mode & FMODE_32BITHASH) ||
 307            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 308                return 0;
 309        else
 310                return pos & 0xffffffff;
 311}
 312
 313/*
 314 * Return 32- or 64-bit end-of-file for dx directories
 315 */
 316static inline loff_t ext4_get_htree_eof(struct file *filp)
 317{
 318        if ((filp->f_mode & FMODE_32BITHASH) ||
 319            (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
 320                return EXT4_HTREE_EOF_32BIT;
 321        else
 322                return EXT4_HTREE_EOF_64BIT;
 323}
 324
 325
 326/*
 327 * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
 328 * directories, where the "offset" is in terms of the filename hash
 329 * value instead of the byte offset.
 330 *
 331 * Because we may return a 64-bit hash that is well beyond offset limits,
 332 * we need to pass the max hash as the maximum allowable offset in
 333 * the htree directory case.
 334 *
 335 * For non-htree, ext4_llseek already chooses the proper max offset.
 336 */
 337loff_t ext4_dir_llseek(struct file *file, loff_t offset, int origin)
 338{
 339        struct inode *inode = file->f_mapping->host;
 340        int dx_dir = is_dx_dir(inode);
 341        loff_t htree_max = ext4_get_htree_eof(file);
 342
 343        if (likely(dx_dir))
 344                return generic_file_llseek_size(file, offset, origin,
 345                                                    htree_max, htree_max);
 346        else
 347                return ext4_llseek(file, offset, origin);
 348}
 349
 350/*
 351 * This structure holds the nodes of the red-black tree used to store
 352 * the directory entry in hash order.
 353 */
 354struct fname {
 355        __u32           hash;
 356        __u32           minor_hash;
 357        struct rb_node  rb_hash;
 358        struct fname    *next;
 359        __u32           inode;
 360        __u8            name_len;
 361        __u8            file_type;
 362        char            name[0];
 363};
 364
 365/*
 366 * This functoin implements a non-recursive way of freeing all of the
 367 * nodes in the red-black tree.
 368 */
 369static void free_rb_tree_fname(struct rb_root *root)
 370{
 371        struct rb_node  *n = root->rb_node;
 372        struct rb_node  *parent;
 373        struct fname    *fname;
 374
 375        while (n) {
 376                /* Do the node's children first */
 377                if (n->rb_left) {
 378                        n = n->rb_left;
 379                        continue;
 380                }
 381                if (n->rb_right) {
 382                        n = n->rb_right;
 383                        continue;
 384                }
 385                /*
 386                 * The node has no children; free it, and then zero
 387                 * out parent's link to it.  Finally go to the
 388                 * beginning of the loop and try to free the parent
 389                 * node.
 390                 */
 391                parent = rb_parent(n);
 392                fname = rb_entry(n, struct fname, rb_hash);
 393                while (fname) {
 394                        struct fname *old = fname;
 395                        fname = fname->next;
 396                        kfree(old);
 397                }
 398                if (!parent)
 399                        *root = RB_ROOT;
 400                else if (parent->rb_left == n)
 401                        parent->rb_left = NULL;
 402                else if (parent->rb_right == n)
 403                        parent->rb_right = NULL;
 404                n = parent;
 405        }
 406}
 407
 408
 409static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
 410                                                           loff_t pos)
 411{
 412        struct dir_private_info *p;
 413
 414        p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
 415        if (!p)
 416                return NULL;
 417        p->curr_hash = pos2maj_hash(filp, pos);
 418        p->curr_minor_hash = pos2min_hash(filp, pos);
 419        return p;
 420}
 421
 422void ext4_htree_free_dir_info(struct dir_private_info *p)
 423{
 424        free_rb_tree_fname(&p->root);
 425        kfree(p);
 426}
 427
 428/*
 429 * Given a directory entry, enter it into the fname rb tree.
 430 */
 431int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
 432                             __u32 minor_hash,
 433                             struct ext4_dir_entry_2 *dirent)
 434{
 435        struct rb_node **p, *parent = NULL;
 436        struct fname *fname, *new_fn;
 437        struct dir_private_info *info;
 438        int len;
 439
 440        info = dir_file->private_data;
 441        p = &info->root.rb_node;
 442
 443        /* Create and allocate the fname structure */
 444        len = sizeof(struct fname) + dirent->name_len + 1;
 445        new_fn = kzalloc(len, GFP_KERNEL);
 446        if (!new_fn)
 447                return -ENOMEM;
 448        new_fn->hash = hash;
 449        new_fn->minor_hash = minor_hash;
 450        new_fn->inode = le32_to_cpu(dirent->inode);
 451        new_fn->name_len = dirent->name_len;
 452        new_fn->file_type = dirent->file_type;
 453        memcpy(new_fn->name, dirent->name, dirent->name_len);
 454        new_fn->name[dirent->name_len] = 0;
 455
 456        while (*p) {
 457                parent = *p;
 458                fname = rb_entry(parent, struct fname, rb_hash);
 459
 460                /*
 461                 * If the hash and minor hash match up, then we put
 462                 * them on a linked list.  This rarely happens...
 463                 */
 464                if ((new_fn->hash == fname->hash) &&
 465                    (new_fn->minor_hash == fname->minor_hash)) {
 466                        new_fn->next = fname->next;
 467                        fname->next = new_fn;
 468                        return 0;
 469                }
 470
 471                if (new_fn->hash < fname->hash)
 472                        p = &(*p)->rb_left;
 473                else if (new_fn->hash > fname->hash)
 474                        p = &(*p)->rb_right;
 475                else if (new_fn->minor_hash < fname->minor_hash)
 476                        p = &(*p)->rb_left;
 477                else /* if (new_fn->minor_hash > fname->minor_hash) */
 478                        p = &(*p)->rb_right;
 479        }
 480
 481        rb_link_node(&new_fn->rb_hash, parent, p);
 482        rb_insert_color(&new_fn->rb_hash, &info->root);
 483        return 0;
 484}
 485
 486
 487
 488/*
 489 * This is a helper function for ext4_dx_readdir.  It calls filldir
 490 * for all entres on the fname linked list.  (Normally there is only
 491 * one entry on the linked list, unless there are 62 bit hash collisions.)
 492 */
 493static int call_filldir(struct file *filp, void *dirent,
 494                        filldir_t filldir, struct fname *fname)
 495{
 496        struct dir_private_info *info = filp->private_data;
 497        loff_t  curr_pos;
 498        struct inode *inode = filp->f_path.dentry->d_inode;
 499        struct super_block *sb;
 500        int error;
 501
 502        sb = inode->i_sb;
 503
 504        if (!fname) {
 505                ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
 506                         "called with null fname?!?", __func__, __LINE__,
 507                         inode->i_ino, current->comm);
 508                return 0;
 509        }
 510        curr_pos = hash2pos(filp, fname->hash, fname->minor_hash);
 511        while (fname) {
 512                error = filldir(dirent, fname->name,
 513                                fname->name_len, curr_pos,
 514                                fname->inode,
 515                                get_dtype(sb, fname->file_type));
 516                if (error) {
 517                        filp->f_pos = curr_pos;
 518                        info->extra_fname = fname;
 519                        return error;
 520                }
 521                fname = fname->next;
 522        }
 523        return 0;
 524}
 525
 526static int ext4_dx_readdir(struct file *filp,
 527                         void *dirent, filldir_t filldir)
 528{
 529        struct dir_private_info *info = filp->private_data;
 530        struct inode *inode = filp->f_path.dentry->d_inode;
 531        struct fname *fname;
 532        int     ret;
 533
 534        if (!info) {
 535                info = ext4_htree_create_dir_info(filp, filp->f_pos);
 536                if (!info)
 537                        return -ENOMEM;
 538                filp->private_data = info;
 539        }
 540
 541        if (filp->f_pos == ext4_get_htree_eof(filp))
 542                return 0;       /* EOF */
 543
 544        /* Some one has messed with f_pos; reset the world */
 545        if (info->last_pos != filp->f_pos) {
 546                free_rb_tree_fname(&info->root);
 547                info->curr_node = NULL;
 548                info->extra_fname = NULL;
 549                info->curr_hash = pos2maj_hash(filp, filp->f_pos);
 550                info->curr_minor_hash = pos2min_hash(filp, filp->f_pos);
 551        }
 552
 553        /*
 554         * If there are any leftover names on the hash collision
 555         * chain, return them first.
 556         */
 557        if (info->extra_fname) {
 558                if (call_filldir(filp, dirent, filldir, info->extra_fname))
 559                        goto finished;
 560                info->extra_fname = NULL;
 561                goto next_node;
 562        } else if (!info->curr_node)
 563                info->curr_node = rb_first(&info->root);
 564
 565        while (1) {
 566                /*
 567                 * Fill the rbtree if we have no more entries,
 568                 * or the inode has changed since we last read in the
 569                 * cached entries.
 570                 */
 571                if ((!info->curr_node) ||
 572                    (filp->f_version != inode->i_version)) {
 573                        info->curr_node = NULL;
 574                        free_rb_tree_fname(&info->root);
 575                        filp->f_version = inode->i_version;
 576                        ret = ext4_htree_fill_tree(filp, info->curr_hash,
 577                                                   info->curr_minor_hash,
 578                                                   &info->next_hash);
 579                        if (ret < 0)
 580                                return ret;
 581                        if (ret == 0) {
 582                                filp->f_pos = ext4_get_htree_eof(filp);
 583                                break;
 584                        }
 585                        info->curr_node = rb_first(&info->root);
 586                }
 587
 588                fname = rb_entry(info->curr_node, struct fname, rb_hash);
 589                info->curr_hash = fname->hash;
 590                info->curr_minor_hash = fname->minor_hash;
 591                if (call_filldir(filp, dirent, filldir, fname))
 592                        break;
 593        next_node:
 594                info->curr_node = rb_next(info->curr_node);
 595                if (info->curr_node) {
 596                        fname = rb_entry(info->curr_node, struct fname,
 597                                         rb_hash);
 598                        info->curr_hash = fname->hash;
 599                        info->curr_minor_hash = fname->minor_hash;
 600                } else {
 601                        if (info->next_hash == ~0) {
 602                                filp->f_pos = ext4_get_htree_eof(filp);
 603                                break;
 604                        }
 605                        info->curr_hash = info->next_hash;
 606                        info->curr_minor_hash = 0;
 607                }
 608        }
 609finished:
 610        info->last_pos = filp->f_pos;
 611        return 0;
 612}
 613
 614static int ext4_release_dir(struct inode *inode, struct file *filp)
 615{
 616        if (filp->private_data)
 617                ext4_htree_free_dir_info(filp->private_data);
 618
 619        return 0;
 620}
 621
 622const struct file_operations ext4_dir_operations = {
 623        .llseek         = ext4_dir_llseek,
 624        .read           = generic_read_dir,
 625        .readdir        = ext4_readdir,
 626        .unlocked_ioctl = ext4_ioctl,
 627#ifdef CONFIG_COMPAT
 628        .compat_ioctl   = ext4_compat_ioctl,
 629#endif
 630        .fsync          = ext4_sync_file,
 631        .release        = ext4_release_dir,
 632};
 633
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