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
  31 static unsigned char ext4_filetype_table[] = {
  32         DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
  33 };
  34
  35 static int ext4_readdir(struct file *, void *, filldir_t);
  36 static int ext4_dx_readdir(struct file *filp,
  37                            void *dirent, filldir_t filldir);
  38 static int ext4_release_dir(struct inode *inode,
  39                                 struct file *filp);
  40
  41 const struct file_operations ext4_dir_operations = {
  42         .llseek         = ext4_llseek,
  43         .read           = generic_read_dir,
  44         .readdir        = ext4_readdir,         /* we take BKL. needed?*/
  45         .unlocked_ioctl = ext4_ioctl,
  46 #ifdef CONFIG_COMPAT
  47         .compat_ioctl   = ext4_compat_ioctl,
  48 #endif
  49         .fsync          = ext4_sync_file,
  50         .release        = ext4_release_dir,
  51 };
  52
  53
  54 static unsigned char get_dtype(struct super_block *sb, int filetype)
  55 {
  56         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FILETYPE) ||
  57             (filetype >= EXT4_FT_MAX))
  58                 return DT_UNKNOWN;
  59
  60         return (ext4_filetype_table[filetype]);
  61 }
  62
  63 /*
  64  * Return 0 if the directory entry is OK, and 1 if there is a problem
  65  *
  66  * Note: this is the opposite of what ext2 and ext3 historically returned...
  67  */
  68 int __ext4_check_dir_entry(const char *function, unsigned int line,
  69                            struct inode *dir,
  70                            struct ext4_dir_entry_2 *de,
  71                            struct buffer_head *bh,
  72                            unsigned int offset)
  73 {
  74         const char *error_msg = NULL;
  75         const int rlen = ext4_rec_len_from_disk(de->rec_len,
  76                                                 dir->i_sb->s_blocksize);
  77
  78         if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
  79                 error_msg = "rec_len is smaller than minimal";
  80         else if (unlikely(rlen % 4 != 0))
  81                 error_msg = "rec_len % 4 != 0";
  82         else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
  83                 error_msg = "rec_len is too small for name_len";
  84         else if (unlikely(((char *) de - bh->b_data) + rlen >
  85                           dir->i_sb->s_blocksize))
  86                 error_msg = "directory entry across blocks";
  87         else if (unlikely(le32_to_cpu(de->inode) >
  88                         le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
  89                 error_msg = "inode out of bounds";
  90         else
  91                 return 0;
  92
  93         ext4_error_inode(dir, function, line, bh->b_blocknr,
  94                          "bad entry in directory: %s - "
  95                          "offset=%u(%u), inode=%u, rec_len=%d, name_len=%d",
  96                          error_msg, (unsigned) (offset%bh->b_size), offset,
  97                          le32_to_cpu(de->inode),
  98                          rlen, de->name_len);
  99         return 1;
 100 }
 101
 102 static int ext4_readdir(struct file *filp,
 103                          void *dirent, filldir_t filldir)
 104 {
 105         int error = 0;
 106         unsigned int offset;
 107         int i, stored;
 108         struct ext4_dir_entry_2 *de;
 109         struct super_block *sb;
 110         int err;
 111         struct inode *inode = filp->f_path.dentry->d_inode;
 112         int ret = 0;
 113         int dir_has_error = 0;
 114
 115         sb = inode->i_sb;
 116
 117         if (EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
 118                                     EXT4_FEATURE_COMPAT_DIR_INDEX) &&
 119             ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
 120              ((inode->i_size >> sb->s_blocksize_bits) == 1))) {
 121                 err = ext4_dx_readdir(filp, dirent, filldir);
 122                 if (err != ERR_BAD_DX_DIR) {
 123                         ret = err;
 124                         goto out;
 125                 }
 126                 /*
 127                  * We don't set the inode dirty flag since it's not
 128                  * critical that it get flushed back to the disk.
 129                  */
 130                 ext4_clear_inode_flag(filp->f_path.dentry->d_inode,
 131                                       EXT4_INODE_INDEX);
 132         }
 133         stored = 0;
 134         offset = filp->f_pos & (sb->s_blocksize - 1);
 135
 136         while (!error && !stored && filp->f_pos < inode->i_size) {
 137                 struct ext4_map_blocks map;
 138                 struct buffer_head *bh = NULL;
 139
 140                 map.m_lblk = filp->f_pos >> EXT4_BLOCK_SIZE_BITS(sb);
 141                 map.m_len = 1;
 142                 err = ext4_map_blocks(NULL, inode, &map, 0);
 143                 if (err > 0) {
 144                         pgoff_t index = map.m_pblk >>
 145                                         (PAGE_CACHE_SHIFT - inode->i_blkbits);
 146                         if (!ra_has_index(&filp->f_ra, index))
 147                                 page_cache_sync_readahead(
 148                                         sb->s_bdev->bd_inode->i_mapping,
 149                                         &filp->f_ra, filp,
 150                                         index, 1);
 151                         filp->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 152                         bh = ext4_bread(NULL, inode, map.m_lblk, 0, &err);
 153                 }
 154
 155                 /*
 156                  * We ignore I/O errors on directories so users have a chance
 157                  * of recovering data when there's a bad sector
 158                  */
 159                 if (!bh) {
 160                         if (!dir_has_error) {
 161                                 EXT4_ERROR_INODE(inode, "directory "
 162                                            "contains a hole at offset %Lu",
 163                                            (unsigned long long) filp->f_pos);
 164                                 dir_has_error = 1;
 165                         }
 166                         /* corrupt size?  Maybe no more blocks to read */
 167                         if (filp->f_pos > inode->i_blocks << 9)
 168                                 break;
 169                         filp->f_pos += sb->s_blocksize - offset;
 170                         continue;
 171                 }
 172
 173 revalidate:
 174                 /* If the dir block has changed since the last call to
 175                  * readdir(2), then we might be pointing to an invalid
 176                  * dirent right now.  Scan from the start of the block
 177                  * to make sure. */
 178                 if (filp->f_version != inode->i_version) {
 179                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
 180                                 de = (struct ext4_dir_entry_2 *)
 181                                         (bh->b_data + i);
 182                                 /* It's too expensive to do a full
 183                                  * dirent test each time round this
 184                                  * loop, but we do have to test at
 185                                  * least that it is non-zero.  A
 186                                  * failure will be detected in the
 187                                  * dirent test below. */
 188                                 if (ext4_rec_len_from_disk(de->rec_len,
 189                                         sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
 190                                         break;
 191                                 i += ext4_rec_len_from_disk(de->rec_len,
 192                                                             sb->s_blocksize);
 193                         }
 194                         offset = i;
 195                         filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
 196                                 | offset;
 197                         filp->f_version = inode->i_version;
 198                 }
 199
 200                 while (!error && filp->f_pos < inode->i_size
 201                        && offset < sb->s_blocksize) {
 202                         de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
 203                         if (ext4_check_dir_entry(inode, de,
 204                                                  bh, offset)) {
 205                                 /*
 206                                  * On error, skip the f_pos to the next block
 207                                  */
 208                                 filp->f_pos = (filp->f_pos |
 209                                                 (sb->s_blocksize - 1)) + 1;
 210                                 brelse(bh);
 211                                 ret = stored;
 212                                 goto out;
 213                         }
 214                         offset += ext4_rec_len_from_disk(de->rec_len,
 215                                         sb->s_blocksize);
 216                         if (le32_to_cpu(de->inode)) {
 217                                 /* We might block in the next section
 218                                  * if the data destination is
 219                                  * currently swapped out.  So, use a
 220                                  * version stamp to detect whether or
 221                                  * not the directory has been modified
 222                                  * during the copy operation.
 223                                  */
 224                                 u64 version = filp->f_version;
 225
 226                                 error = filldir(dirent, de->name,
 227                                                 de->name_len,
 228                                                 filp->f_pos,
 229                                                 le32_to_cpu(de->inode),
 230                                                 get_dtype(sb, de->file_type));
 231                                 if (error)
 232                                         break;
 233                                 if (version != filp->f_version)
 234                                         goto revalidate;
 235                                 stored++;
 236                         }
 237                         filp->f_pos += ext4_rec_len_from_disk(de->rec_len,
 238                                                 sb->s_blocksize);
 239                 }
 240                 offset = 0;
 241                 brelse(bh);
 242         }
 243 out:
 244         return ret;
 245 }
 246
 247 /*
 248  * These functions convert from the major/minor hash to an f_pos
 249  * value.
 250  *
 251  * Currently we only use major hash numer.  This is unfortunate, but
 252  * on 32-bit machines, the same VFS interface is used for lseek and
 253  * llseek, so if we use the 64 bit offset, then the 32-bit versions of
 254  * lseek/telldir/seekdir will blow out spectacularly, and from within
 255  * the ext2 low-level routine, we don't know if we're being called by
 256  * a 64-bit version of the system call or the 32-bit version of the
 257  * system call.  Worse yet, NFSv2 only allows for a 32-bit readdir
 258  * cookie.  Sigh.
 259  */
 260 #define hash2pos(major, minor)  (major >> 1)
 261 #define pos2maj_hash(pos)       ((pos << 1) & 0xffffffff)
 262 #define pos2min_hash(pos)       (0)
 263
 264 /*
 265  * This structure holds the nodes of the red-black tree used to store
 266  * the directory entry in hash order.
 267  */
 268 struct fname {
 269         __u32           hash;
 270         __u32           minor_hash;
 271         struct rb_node  rb_hash;
 272         struct fname    *next;
 273         __u32           inode;
 274         __u8            name_len;
 275         __u8            file_type;
 276         char            name[0];
 277 };
 278
 279 /*
 280  * This functoin implements a non-recursive way of freeing all of the
 281  * nodes in the red-black tree.
 282  */
 283 static void free_rb_tree_fname(struct rb_root *root)
 284 {
 285         struct rb_node  *n = root->rb_node;
 286         struct rb_node  *parent;
 287         struct fname    *fname;
 288
 289         while (n) {
 290                 /* Do the node's children first */
 291                 if (n->rb_left) {
 292                         n = n->rb_left;
 293                         continue;
 294                 }
 295                 if (n->rb_right) {
 296                         n = n->rb_right;
 297                         continue;
 298                 }
 299                 /*
 300                  * The node has no children; free it, and then zero
 301                  * out parent's link to it.  Finally go to the
 302                  * beginning of the loop and try to free the parent
 303                  * node.
 304                  */
 305                 parent = rb_parent(n);
 306                 fname = rb_entry(n, struct fname, rb_hash);
 307                 while (fname) {
 308                         struct fname *old = fname;
 309                         fname = fname->next;
 310                         kfree(old);
 311                 }
 312                 if (!parent)
 313                         *root = RB_ROOT;
 314                 else if (parent->rb_left == n)
 315                         parent->rb_left = NULL;
 316                 else if (parent->rb_right == n)
 317                         parent->rb_right = NULL;
 318                 n = parent;
 319         }
 320 }
 321
 322
 323 static struct dir_private_info *ext4_htree_create_dir_info(loff_t pos)
 324 {
 325         struct dir_private_info *p;
 326
 327         p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
 328         if (!p)
 329                 return NULL;
 330         p->curr_hash = pos2maj_hash(pos);
 331         p->curr_minor_hash = pos2min_hash(pos);
 332         return p;
 333 }
 334
 335 void ext4_htree_free_dir_info(struct dir_private_info *p)
 336 {
 337         free_rb_tree_fname(&p->root);
 338         kfree(p);
 339 }
 340
 341 /*
 342  * Given a directory entry, enter it into the fname rb tree.
 343  */
 344 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
 345                              __u32 minor_hash,
 346                              struct ext4_dir_entry_2 *dirent)
 347 {
 348         struct rb_node **p, *parent = NULL;
 349         struct fname *fname, *new_fn;
 350         struct dir_private_info *info;
 351         int len;
 352
 353         info = dir_file->private_data;
 354         p = &info->root.rb_node;
 355
 356         /* Create and allocate the fname structure */
 357         len = sizeof(struct fname) + dirent->name_len + 1;
 358         new_fn = kzalloc(len, GFP_KERNEL);
 359         if (!new_fn)
 360                 return -ENOMEM;
 361         new_fn->hash = hash;
 362         new_fn->minor_hash = minor_hash;
 363         new_fn->inode = le32_to_cpu(dirent->inode);
 364         new_fn->name_len = dirent->name_len;
 365         new_fn->file_type = dirent->file_type;
 366         memcpy(new_fn->name, dirent->name, dirent->name_len);
 367         new_fn->name[dirent->name_len] = 0;
 368
 369         while (*p) {
 370                 parent = *p;
 371                 fname = rb_entry(parent, struct fname, rb_hash);
 372
 373                 /*
 374                  * If the hash and minor hash match up, then we put
 375                  * them on a linked list.  This rarely happens...
 376                  */
 377                 if ((new_fn->hash == fname->hash) &&
 378                     (new_fn->minor_hash == fname->minor_hash)) {
 379                         new_fn->next = fname->next;
 380                         fname->next = new_fn;
 381                         return 0;
 382                 }
 383
 384                 if (new_fn->hash < fname->hash)
 385                         p = &(*p)->rb_left;
 386                 else if (new_fn->hash > fname->hash)
 387                         p = &(*p)->rb_right;
 388                 else if (new_fn->minor_hash < fname->minor_hash)
 389                         p = &(*p)->rb_left;
 390                 else /* if (new_fn->minor_hash > fname->minor_hash) */
 391                         p = &(*p)->rb_right;
 392         }
 393
 394         rb_link_node(&new_fn->rb_hash, parent, p);
 395         rb_insert_color(&new_fn->rb_hash, &info->root);
 396         return 0;
 397 }
 398
 399
 400
 401 /*
 402  * This is a helper function for ext4_dx_readdir.  It calls filldir
 403  * for all entres on the fname linked list.  (Normally there is only
 404  * one entry on the linked list, unless there are 62 bit hash collisions.)
 405  */
 406 static int call_filldir(struct file *filp, void *dirent,
 407                         filldir_t filldir, struct fname *fname)
 408 {
 409         struct dir_private_info *info = filp->private_data;
 410         loff_t  curr_pos;
 411         struct inode *inode = filp->f_path.dentry->d_inode;
 412         struct super_block *sb;
 413         int error;
 414
 415         sb = inode->i_sb;
 416
 417         if (!fname) {
 418                 printk(KERN_ERR "EXT4-fs: call_filldir: called with "
 419                        "null fname?!?\n");
 420                 return 0;
 421         }
 422         curr_pos = hash2pos(fname->hash, fname->minor_hash);
 423         while (fname) {
 424                 error = filldir(dirent, fname->name,
 425                                 fname->name_len, curr_pos,
 426                                 fname->inode,
 427                                 get_dtype(sb, fname->file_type));
 428                 if (error) {
 429                         filp->f_pos = curr_pos;
 430                         info->extra_fname = fname;
 431                         return error;
 432                 }
 433                 fname = fname->next;
 434         }
 435         return 0;
 436 }
 437
 438 static int ext4_dx_readdir(struct file *filp,
 439                          void *dirent, filldir_t filldir)
 440 {
 441         struct dir_private_info *info = filp->private_data;
 442         struct inode *inode = filp->f_path.dentry->d_inode;
 443         struct fname *fname;
 444         int     ret;
 445
 446         if (!info) {
 447                 info = ext4_htree_create_dir_info(filp->f_pos);
 448                 if (!info)
 449                         return -ENOMEM;
 450                 filp->private_data = info;
 451         }
 452
 453         if (filp->f_pos == EXT4_HTREE_EOF)
 454                 return 0;       /* EOF */
 455
 456         /* Some one has messed with f_pos; reset the world */
 457         if (info->last_pos != filp->f_pos) {
 458                 free_rb_tree_fname(&info->root);
 459                 info->curr_node = NULL;
 460                 info->extra_fname = NULL;
 461                 info->curr_hash = pos2maj_hash(filp->f_pos);
 462                 info->curr_minor_hash = pos2min_hash(filp->f_pos);
 463         }
 464
 465         /*
 466          * If there are any leftover names on the hash collision
 467          * chain, return them first.
 468          */
 469         if (info->extra_fname) {
 470                 if (call_filldir(filp, dirent, filldir, info->extra_fname))
 471                         goto finished;
 472                 info->extra_fname = NULL;
 473                 goto next_node;
 474         } else if (!info->curr_node)
 475                 info->curr_node = rb_first(&info->root);
 476
 477         while (1) {
 478                 /*
 479                  * Fill the rbtree if we have no more entries,
 480                  * or the inode has changed since we last read in the
 481                  * cached entries.
 482                  */
 483                 if ((!info->curr_node) ||
 484                     (filp->f_version != inode->i_version)) {
 485                         info->curr_node = NULL;
 486                         free_rb_tree_fname(&info->root);
 487                         filp->f_version = inode->i_version;
 488                         ret = ext4_htree_fill_tree(filp, info->curr_hash,
 489                                                    info->curr_minor_hash,
 490                                                    &info->next_hash);
 491                         if (ret < 0)
 492                                 return ret;
 493                         if (ret == 0) {
 494                                 filp->f_pos = EXT4_HTREE_EOF;
 495                                 break;
 496                         }
 497                         info->curr_node = rb_first(&info->root);
 498                 }
 499
 500                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
 501                 info->curr_hash = fname->hash;
 502                 info->curr_minor_hash = fname->minor_hash;
 503                 if (call_filldir(filp, dirent, filldir, fname))
 504                         break;
 505         next_node:
 506                 info->curr_node = rb_next(info->curr_node);
 507                 if (info->curr_node) {
 508                         fname = rb_entry(info->curr_node, struct fname,
 509                                          rb_hash);
 510                         info->curr_hash = fname->hash;
 511                         info->curr_minor_hash = fname->minor_hash;
 512                 } else {
 513                         if (info->next_hash == ~0) {
 514                                 filp->f_pos = EXT4_HTREE_EOF;
 515                                 break;
 516                         }
 517                         info->curr_hash = info->next_hash;
 518                         info->curr_minor_hash = 0;
 519                 }
 520         }
 521 finished:
 522         info->last_pos = filp->f_pos;
 523         return 0;
 524 }
 525
 526 static int ext4_release_dir(struct inode *inode, struct file *filp)
 527 {
 528         if (filp->private_data)
 529                 ext4_htree_free_dir_info(filp->private_data);
 530
 531         return 0;
 532 }