fs/nilfs2/dir.c

   1 /*
   2  * dir.c - NILFS directory entry operations
   3  *
   4  * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  19  *
  20  * Modified for NILFS by Amagai Yoshiji <amagai@osrg.net>
  21  */
  22 /*
  23  *  linux/fs/ext2/dir.c
  24  *
  25  * Copyright (C) 1992, 1993, 1994, 1995
  26  * Remy Card (card@masi.ibp.fr)
  27  * Laboratoire MASI - Institut Blaise Pascal
  28  * Universite Pierre et Marie Curie (Paris VI)
  29  *
  30  *  from
  31  *
  32  *  linux/fs/minix/dir.c
  33  *
  34  *  Copyright (C) 1991, 1992  Linus Torvalds
  35  *
  36  *  ext2 directory handling functions
  37  *
  38  *  Big-endian to little-endian byte-swapping/bitmaps by
  39  *        David S. Miller (davem@caip.rutgers.edu), 1995
  40  *
  41  * All code that works with directory layout had been switched to pagecache
  42  * and moved here. AV
  43  */
  44
  45 #include <linux/pagemap.h>
  46 #include <linux/smp_lock.h>
  47 #include "nilfs.h"
  48 #include "page.h"
  49
  50 /*
  51  * nilfs uses block-sized chunks. Arguably, sector-sized ones would be
  52  * more robust, but we have what we have
  53  */
  54 static inline unsigned nilfs_chunk_size(struct inode *inode)
  55 {
  56         return inode->i_sb->s_blocksize;
  57 }
  58
  59 static inline void nilfs_put_page(struct page *page)
  60 {
  61         kunmap(page);
  62         page_cache_release(page);
  63 }
  64
  65 static inline unsigned long dir_pages(struct inode *inode)
  66 {
  67         return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
  68 }
  69
  70 /*
  71  * Return the offset into page `page_nr' of the last valid
  72  * byte in that page, plus one.
  73  */
  74 static unsigned nilfs_last_byte(struct inode *inode, unsigned long page_nr)
  75 {
  76         unsigned last_byte = inode->i_size;
  77
  78         last_byte -= page_nr << PAGE_CACHE_SHIFT;
  79         if (last_byte > PAGE_CACHE_SIZE)
  80                 last_byte = PAGE_CACHE_SIZE;
  81         return last_byte;
  82 }
  83
  84 static int nilfs_prepare_chunk_uninterruptible(struct page *page,
  85                                                struct address_space *mapping,
  86                                                unsigned from, unsigned to)
  87 {
  88         loff_t pos = page_offset(page) + from;
  89         return block_write_begin(NULL, mapping, pos, to - from,
  90                                  AOP_FLAG_UNINTERRUPTIBLE, &page,
  91                                  NULL, nilfs_get_block);
  92 }
  93
  94 static int nilfs_prepare_chunk(struct page *page,
  95                                struct address_space *mapping,
  96                                unsigned from, unsigned to)
  97 {
  98         loff_t pos = page_offset(page) + from;
  99         return block_write_begin(NULL, mapping, pos, to - from, 0, &page,
 100                                  NULL, nilfs_get_block);
 101 }
 102
 103 static int nilfs_commit_chunk(struct page *page,
 104                               struct address_space *mapping,
 105                               unsigned from, unsigned to)
 106 {
 107         struct inode *dir = mapping->host;
 108         struct nilfs_sb_info *sbi = NILFS_SB(dir->i_sb);
 109         loff_t pos = page_offset(page) + from;
 110         unsigned len = to - from;
 111         unsigned nr_dirty, copied;
 112         int err;
 113
 114         nr_dirty = nilfs_page_count_clean_buffers(page, from, to);
 115         copied = block_write_end(NULL, mapping, pos, len, len, page, NULL);
 116         if (pos + copied > dir->i_size) {
 117                 i_size_write(dir, pos + copied);
 118                 mark_inode_dirty(dir);
 119         }
 120         if (IS_DIRSYNC(dir))
 121                 nilfs_set_transaction_flag(NILFS_TI_SYNC);
 122         err = nilfs_set_file_dirty(sbi, dir, nr_dirty);
 123         unlock_page(page);
 124         return err;
 125 }
 126
 127 static void nilfs_check_page(struct page *page)
 128 {
 129         struct inode *dir = page->mapping->host;
 130         struct super_block *sb = dir->i_sb;
 131         unsigned chunk_size = nilfs_chunk_size(dir);
 132         char *kaddr = page_address(page);
 133         unsigned offs, rec_len;
 134         unsigned limit = PAGE_CACHE_SIZE;
 135         struct nilfs_dir_entry *p;
 136         char *error;
 137
 138         if ((dir->i_size >> PAGE_CACHE_SHIFT) == page->index) {
 139                 limit = dir->i_size & ~PAGE_CACHE_MASK;
 140                 if (limit & (chunk_size - 1))
 141                         goto Ebadsize;
 142                 if (!limit)
 143                         goto out;
 144         }
 145         for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
 146                 p = (struct nilfs_dir_entry *)(kaddr + offs);
 147                 rec_len = le16_to_cpu(p->rec_len);
 148
 149                 if (rec_len < NILFS_DIR_REC_LEN(1))
 150                         goto Eshort;
 151                 if (rec_len & 3)
 152                         goto Ealign;
 153                 if (rec_len < NILFS_DIR_REC_LEN(p->name_len))
 154                         goto Enamelen;
 155                 if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
 156                         goto Espan;
 157         }
 158         if (offs != limit)
 159                 goto Eend;
 160 out:
 161         SetPageChecked(page);
 162         return;
 163
 164         /* Too bad, we had an error */
 165
 166 Ebadsize:
 167         nilfs_error(sb, "nilfs_check_page",
 168                     "size of directory #%lu is not a multiple of chunk size",
 169                     dir->i_ino
 170         );
 171         goto fail;
 172 Eshort:
 173         error = "rec_len is smaller than minimal";
 174         goto bad_entry;
 175 Ealign:
 176         error = "unaligned directory entry";
 177         goto bad_entry;
 178 Enamelen:
 179         error = "rec_len is too small for name_len";
 180         goto bad_entry;
 181 Espan:
 182         error = "directory entry across blocks";
 183 bad_entry:
 184         nilfs_error(sb, "nilfs_check_page", "bad entry in directory #%lu: %s - "
 185                     "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
 186                     dir->i_ino, error, (page->index<<PAGE_CACHE_SHIFT)+offs,
 187                     (unsigned long) le64_to_cpu(p->inode),
 188                     rec_len, p->name_len);
 189         goto fail;
 190 Eend:
 191         p = (struct nilfs_dir_entry *)(kaddr + offs);
 192         nilfs_error(sb, "nilfs_check_page",
 193                     "entry in directory #%lu spans the page boundary"
 194                     "offset=%lu, inode=%lu",
 195                     dir->i_ino, (page->index<<PAGE_CACHE_SHIFT)+offs,
 196                     (unsigned long) le64_to_cpu(p->inode));
 197 fail:
 198         SetPageChecked(page);
 199         SetPageError(page);
 200 }
 201
 202 static struct page *nilfs_get_page(struct inode *dir, unsigned long n)
 203 {
 204         struct address_space *mapping = dir->i_mapping;
 205         struct page *page = read_cache_page(mapping, n,
 206                                 (filler_t *)mapping->a_ops->readpage, NULL);
 207         if (!IS_ERR(page)) {
 208                 wait_on_page_locked(page);
 209                 kmap(page);
 210                 if (!PageUptodate(page))
 211                         goto fail;
 212                 if (!PageChecked(page))
 213                         nilfs_check_page(page);
 214                 if (PageError(page))
 215                         goto fail;
 216         }
 217         return page;
 218
 219 fail:
 220         nilfs_put_page(page);
 221         return ERR_PTR(-EIO);
 222 }
 223
 224 /*
 225  * NOTE! unlike strncmp, nilfs_match returns 1 for success, 0 for failure.
 226  *
 227  * len <= NILFS_NAME_LEN and de != NULL are guaranteed by caller.
 228  */
 229 static int
 230 nilfs_match(int len, const char * const name, struct nilfs_dir_entry *de)
 231 {
 232         if (len != de->name_len)
 233                 return 0;
 234         if (!de->inode)
 235                 return 0;
 236         return !memcmp(name, de->name, len);
 237 }
 238
 239 /*
 240  * p is at least 6 bytes before the end of page
 241  */
 242 static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
 243 {
 244         return (struct nilfs_dir_entry *)((char *)p + le16_to_cpu(p->rec_len));
 245 }
 246
 247 static unsigned char
 248 nilfs_filetype_table[NILFS_FT_MAX] = {
 249         [NILFS_FT_UNKNOWN]      = DT_UNKNOWN,
 250         [NILFS_FT_REG_FILE]     = DT_REG,
 251         [NILFS_FT_DIR]          = DT_DIR,
 252         [NILFS_FT_CHRDEV]       = DT_CHR,
 253         [NILFS_FT_BLKDEV]       = DT_BLK,
 254         [NILFS_FT_FIFO]         = DT_FIFO,
 255         [NILFS_FT_SOCK]         = DT_SOCK,
 256         [NILFS_FT_SYMLINK]      = DT_LNK,
 257 };
 258
 259 #define S_SHIFT 12
 260 static unsigned char
 261 nilfs_type_by_mode[S_IFMT >> S_SHIFT] = {
 262         [S_IFREG >> S_SHIFT]    = NILFS_FT_REG_FILE,
 263         [S_IFDIR >> S_SHIFT]    = NILFS_FT_DIR,
 264         [S_IFCHR >> S_SHIFT]    = NILFS_FT_CHRDEV,
 265         [S_IFBLK >> S_SHIFT]    = NILFS_FT_BLKDEV,
 266         [S_IFIFO >> S_SHIFT]    = NILFS_FT_FIFO,
 267         [S_IFSOCK >> S_SHIFT]   = NILFS_FT_SOCK,
 268         [S_IFLNK >> S_SHIFT]    = NILFS_FT_SYMLINK,
 269 };
 270
 271 static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *inode)
 272 {
 273         mode_t mode = inode->i_mode;
 274
 275         de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
 276 }
 277
 278 static int nilfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 279 {
 280         loff_t pos = filp->f_pos;
 281         struct inode *inode = filp->f_dentry->d_inode;
 282         struct super_block *sb = inode->i_sb;
 283         unsigned int offset = pos & ~PAGE_CACHE_MASK;
 284         unsigned long n = pos >> PAGE_CACHE_SHIFT;
 285         unsigned long npages = dir_pages(inode);
 286 /*      unsigned chunk_mask = ~(nilfs_chunk_size(inode)-1); */
 287         unsigned char *types = NULL;
 288         int ret;
 289
 290         if (pos > inode->i_size - NILFS_DIR_REC_LEN(1))
 291                 goto success;
 292
 293         types = nilfs_filetype_table;
 294
 295         for ( ; n < npages; n++, offset = 0) {
 296                 char *kaddr, *limit;
 297                 struct nilfs_dir_entry *de;
 298                 struct page *page = nilfs_get_page(inode, n);
 299
 300                 if (IS_ERR(page)) {
 301                         nilfs_error(sb, __func__, "bad page in #%lu",
 302                                     inode->i_ino);
 303                         filp->f_pos += PAGE_CACHE_SIZE - offset;
 304                         ret = -EIO;
 305                         goto done;
 306                 }
 307                 kaddr = page_address(page);
 308                 de = (struct nilfs_dir_entry *)(kaddr + offset);
 309                 limit = kaddr + nilfs_last_byte(inode, n) -
 310                         NILFS_DIR_REC_LEN(1);
 311                 for ( ; (char *)de <= limit; de = nilfs_next_entry(de)) {
 312                         if (de->rec_len == 0) {
 313                                 nilfs_error(sb, __func__,
 314                                             "zero-length directory entry");
 315                                 ret = -EIO;
 316                                 nilfs_put_page(page);
 317                                 goto done;
 318                         }
 319                         if (de->inode) {
 320                                 int over;
 321                                 unsigned char d_type = DT_UNKNOWN;
 322
 323                                 if (types && de->file_type < NILFS_FT_MAX)
 324                                         d_type = types[de->file_type];
 325
 326                                 offset = (char *)de - kaddr;
 327                                 over = filldir(dirent, de->name, de->name_len,
 328                                                 (n<<PAGE_CACHE_SHIFT) | offset,
 329                                                 le64_to_cpu(de->inode), d_type);
 330                                 if (over) {
 331                                         nilfs_put_page(page);
 332                                         goto success;
 333                                 }
 334                         }
 335                         filp->f_pos += le16_to_cpu(de->rec_len);
 336                 }
 337                 nilfs_put_page(page);
 338         }
 339
 340 success:
 341         ret = 0;
 342 done:
 343         return ret;
 344 }
 345
 346 /*
 347  *      nilfs_find_entry()
 348  *
 349  * finds an entry in the specified directory with the wanted name. It
 350  * returns the page in which the entry was found, and the entry itself
 351  * (as a parameter - res_dir). Page is returned mapped and unlocked.
 352  * Entry is guaranteed to be valid.
 353  */
 354 struct nilfs_dir_entry *
 355 nilfs_find_entry(struct inode *dir, struct dentry *dentry,
 356                  struct page **res_page)
 357 {
 358         const char *name = dentry->d_name.name;
 359         int namelen = dentry->d_name.len;
 360         unsigned reclen = NILFS_DIR_REC_LEN(namelen);
 361         unsigned long start, n;
 362         unsigned long npages = dir_pages(dir);
 363         struct page *page = NULL;
 364         struct nilfs_inode_info *ei = NILFS_I(dir);
 365         struct nilfs_dir_entry *de;
 366
 367         if (npages == 0)
 368                 goto out;
 369
 370         /* OFFSET_CACHE */
 371         *res_page = NULL;
 372
 373         start = ei->i_dir_start_lookup;
 374         if (start >= npages)
 375                 start = 0;
 376         n = start;
 377         do {
 378                 char *kaddr;
 379                 page = nilfs_get_page(dir, n);
 380                 if (!IS_ERR(page)) {
 381                         kaddr = page_address(page);
 382                         de = (struct nilfs_dir_entry *)kaddr;
 383                         kaddr += nilfs_last_byte(dir, n) - reclen;
 384                         while ((char *) de <= kaddr) {
 385                                 if (de->rec_len == 0) {
 386                                         nilfs_error(dir->i_sb, __func__,
 387                                                 "zero-length directory entry");
 388                                         nilfs_put_page(page);
 389                                         goto out;
 390                                 }
 391                                 if (nilfs_match(namelen, name, de))
 392                                         goto found;
 393                                 de = nilfs_next_entry(de);
 394                         }
 395                         nilfs_put_page(page);
 396                 }
 397                 if (++n >= npages)
 398                         n = 0;
 399                 /* next page is past the blocks we've got */
 400                 if (unlikely(n > (dir->i_blocks >> (PAGE_CACHE_SHIFT - 9)))) {
 401                         nilfs_error(dir->i_sb, __func__,
 402                                "dir %lu size %lld exceeds block cout %llu",
 403                                dir->i_ino, dir->i_size,
 404                                (unsigned long long)dir->i_blocks);
 405                         goto out;
 406                 }
 407         } while (n != start);
 408 out:
 409         return NULL;
 410
 411 found:
 412         *res_page = page;
 413         ei->i_dir_start_lookup = n;
 414         return de;
 415 }
 416
 417 struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
 418 {
 419         struct page *page = nilfs_get_page(dir, 0);
 420         struct nilfs_dir_entry *de = NULL;
 421
 422         if (!IS_ERR(page)) {
 423                 de = nilfs_next_entry(
 424                         (struct nilfs_dir_entry *)page_address(page));
 425                 *p = page;
 426         }
 427         return de;
 428 }
 429
 430 ino_t nilfs_inode_by_name(struct inode *dir, struct dentry *dentry)
 431 {
 432         ino_t res = 0;
 433         struct nilfs_dir_entry *de;
 434         struct page *page;
 435
 436         de = nilfs_find_entry(dir, dentry, &page);
 437         if (de) {
 438                 res = le64_to_cpu(de->inode);
 439                 kunmap(page);
 440                 page_cache_release(page);
 441         }
 442         return res;
 443 }
 444
 445 /* Releases the page */
 446 void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
 447                     struct page *page, struct inode *inode)
 448 {
 449         unsigned from = (char *) de - (char *) page_address(page);
 450         unsigned to = from + le16_to_cpu(de->rec_len);
 451         struct address_space *mapping = page->mapping;
 452         int err;
 453
 454         lock_page(page);
 455         err = nilfs_prepare_chunk_uninterruptible(page, mapping, from, to);
 456         BUG_ON(err);
 457         de->inode = cpu_to_le64(inode->i_ino);
 458         nilfs_set_de_type(de, inode);
 459         err = nilfs_commit_chunk(page, mapping, from, to);
 460         nilfs_put_page(page);
 461         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 462 /*      NILFS_I(dir)->i_flags &= ~NILFS_BTREE_FL; */
 463         mark_inode_dirty(dir);
 464 }
 465
 466 /*
 467  *      Parent is locked.
 468  */
 469 int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 470 {
 471         struct inode *dir = dentry->d_parent->d_inode;
 472         const char *name = dentry->d_name.name;
 473         int namelen = dentry->d_name.len;
 474         unsigned chunk_size = nilfs_chunk_size(dir);
 475         unsigned reclen = NILFS_DIR_REC_LEN(namelen);
 476         unsigned short rec_len, name_len;
 477         struct page *page = NULL;
 478         struct nilfs_dir_entry *de;
 479         unsigned long npages = dir_pages(dir);
 480         unsigned long n;
 481         char *kaddr;
 482         unsigned from, to;
 483         int err;
 484
 485         /*
 486          * We take care of directory expansion in the same loop.
 487          * This code plays outside i_size, so it locks the page
 488          * to protect that region.
 489          */
 490         for (n = 0; n <= npages; n++) {
 491                 char *dir_end;
 492
 493                 page = nilfs_get_page(dir, n);
 494                 err = PTR_ERR(page);
 495                 if (IS_ERR(page))
 496                         goto out;
 497                 lock_page(page);
 498                 kaddr = page_address(page);
 499                 dir_end = kaddr + nilfs_last_byte(dir, n);
 500                 de = (struct nilfs_dir_entry *)kaddr;
 501                 kaddr += PAGE_CACHE_SIZE - reclen;
 502                 while ((char *)de <= kaddr) {
 503                         if ((char *)de == dir_end) {
 504                                 /* We hit i_size */
 505                                 name_len = 0;
 506                                 rec_len = chunk_size;
 507                                 de->rec_len = cpu_to_le16(chunk_size);
 508                                 de->inode = 0;
 509                                 goto got_it;
 510                         }
 511                         if (de->rec_len == 0) {
 512                                 nilfs_error(dir->i_sb, __func__,
 513                                             "zero-length directory entry");
 514                                 err = -EIO;
 515                                 goto out_unlock;
 516                         }
 517                         err = -EEXIST;
 518                         if (nilfs_match(namelen, name, de))
 519                                 goto out_unlock;
 520                         name_len = NILFS_DIR_REC_LEN(de->name_len);
 521                         rec_len = le16_to_cpu(de->rec_len);
 522                         if (!de->inode && rec_len >= reclen)
 523                                 goto got_it;
 524                         if (rec_len >= name_len + reclen)
 525                                 goto got_it;
 526                         de = (struct nilfs_dir_entry *)((char *)de + rec_len);
 527                 }
 528                 unlock_page(page);
 529                 nilfs_put_page(page);
 530         }
 531         BUG();
 532         return -EINVAL;
 533
 534 got_it:
 535         from = (char *)de - (char *)page_address(page);
 536         to = from + rec_len;
 537         err = nilfs_prepare_chunk(page, page->mapping, from, to);
 538         if (err)
 539                 goto out_unlock;
 540         if (de->inode) {
 541                 struct nilfs_dir_entry *de1;
 542
 543                 de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
 544                 de1->rec_len = cpu_to_le16(rec_len - name_len);
 545                 de->rec_len = cpu_to_le16(name_len);
 546                 de = de1;
 547         }
 548         de->name_len = namelen;
 549         memcpy(de->name, name, namelen);
 550         de->inode = cpu_to_le64(inode->i_ino);
 551         nilfs_set_de_type(de, inode);
 552         err = nilfs_commit_chunk(page, page->mapping, from, to);
 553         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 554 /*      NILFS_I(dir)->i_flags &= ~NILFS_BTREE_FL; */
 555         mark_inode_dirty(dir);
 556         /* OFFSET_CACHE */
 557 out_put:
 558         nilfs_put_page(page);
 559 out:
 560         return err;
 561 out_unlock:
 562         unlock_page(page);
 563         goto out_put;
 564 }
 565
 566 /*
 567  * nilfs_delete_entry deletes a directory entry by merging it with the
 568  * previous entry. Page is up-to-date. Releases the page.
 569  */
 570 int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
 571 {
 572         struct address_space *mapping = page->mapping;
 573         struct inode *inode = mapping->host;
 574         char *kaddr = page_address(page);
 575         unsigned from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
 576         unsigned to = ((char *)dir - kaddr) + le16_to_cpu(dir->rec_len);
 577         struct nilfs_dir_entry *pde = NULL;
 578         struct nilfs_dir_entry *de = (struct nilfs_dir_entry *)(kaddr + from);
 579         int err;
 580
 581         while ((char *)de < (char *)dir) {
 582                 if (de->rec_len == 0) {
 583                         nilfs_error(inode->i_sb, __func__,
 584                                     "zero-length directory entry");
 585                         err = -EIO;
 586                         goto out;
 587                 }
 588                 pde = de;
 589                 de = nilfs_next_entry(de);
 590         }
 591         if (pde)
 592                 from = (char *)pde - (char *)page_address(page);
 593         lock_page(page);
 594         err = nilfs_prepare_chunk(page, mapping, from, to);
 595         BUG_ON(err);
 596         if (pde)
 597                 pde->rec_len = cpu_to_le16(to - from);
 598         dir->inode = 0;
 599         err = nilfs_commit_chunk(page, mapping, from, to);
 600         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 601 /*      NILFS_I(inode)->i_flags &= ~NILFS_BTREE_FL; */
 602         mark_inode_dirty(inode);
 603 out:
 604         nilfs_put_page(page);
 605         return err;
 606 }
 607
 608 /*
 609  * Set the first fragment of directory.
 610  */
 611 int nilfs_make_empty(struct inode *inode, struct inode *parent)
 612 {
 613         struct address_space *mapping = inode->i_mapping;
 614         struct page *page = grab_cache_page(mapping, 0);
 615         unsigned chunk_size = nilfs_chunk_size(inode);
 616         struct nilfs_dir_entry *de;
 617         int err;
 618         void *kaddr;
 619
 620         if (!page)
 621                 return -ENOMEM;
 622
 623         err = nilfs_prepare_chunk(page, mapping, 0, chunk_size);
 624         if (unlikely(err)) {
 625                 unlock_page(page);
 626                 goto fail;
 627         }
 628         kaddr = kmap_atomic(page, KM_USER0);
 629         memset(kaddr, 0, chunk_size);
 630         de = (struct nilfs_dir_entry *)kaddr;
 631         de->name_len = 1;
 632         de->rec_len = cpu_to_le16(NILFS_DIR_REC_LEN(1));
 633         memcpy(de->name, ".\0\0", 4);
 634         de->inode = cpu_to_le64(inode->i_ino);
 635         nilfs_set_de_type(de, inode);
 636
 637         de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
 638         de->name_len = 2;
 639         de->rec_len = cpu_to_le16(chunk_size - NILFS_DIR_REC_LEN(1));
 640         de->inode = cpu_to_le64(parent->i_ino);
 641         memcpy(de->name, "..\0", 4);
 642         nilfs_set_de_type(de, inode);
 643         kunmap_atomic(kaddr, KM_USER0);
 644         err = nilfs_commit_chunk(page, mapping, 0, chunk_size);
 645 fail:
 646         page_cache_release(page);
 647         return err;
 648 }
 649
 650 /*
 651  * routine to check that the specified directory is empty (for rmdir)
 652  */
 653 int nilfs_empty_dir(struct inode *inode)
 654 {
 655         struct page *page = NULL;
 656         unsigned long i, npages = dir_pages(inode);
 657
 658         for (i = 0; i < npages; i++) {
 659                 char *kaddr;
 660                 struct nilfs_dir_entry *de;
 661
 662                 page = nilfs_get_page(inode, i);
 663                 if (IS_ERR(page))
 664                         continue;
 665
 666                 kaddr = page_address(page);
 667                 de = (struct nilfs_dir_entry *)kaddr;
 668                 kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);
 669
 670                 while ((char *)de <= kaddr) {
 671                         if (de->rec_len == 0) {
 672                                 nilfs_error(inode->i_sb, __func__,
 673                                             "zero-length directory entry "
 674                                             "(kaddr=%p, de=%p)\n", kaddr, de);
 675                                 goto not_empty;
 676                         }
 677                         if (de->inode != 0) {
 678                                 /* check for . and .. */
 679                                 if (de->name[0] != '.')
 680                                         goto not_empty;
 681                                 if (de->name_len > 2)
 682                                         goto not_empty;
 683                                 if (de->name_len < 2) {
 684                                         if (de->inode !=
 685                                             cpu_to_le64(inode->i_ino))
 686                                                 goto not_empty;
 687                                 } else if (de->name[1] != '.')
 688                                         goto not_empty;
 689                         }
 690                         de = nilfs_next_entry(de);
 691                 }
 692                 nilfs_put_page(page);
 693         }
 694         return 1;
 695
 696 not_empty:
 697         nilfs_put_page(page);
 698         return 0;
 699 }
 700
 701 struct file_operations nilfs_dir_operations = {
 702         .llseek         = generic_file_llseek,
 703         .read           = generic_read_dir,
 704         .readdir        = nilfs_readdir,
 705         .unlocked_ioctl = nilfs_ioctl,
 706 #ifdef CONFIG_COMPAT
 707         .compat_ioctl   = nilfs_ioctl,
 708 #endif  /* CONFIG_COMPAT */
 709         .fsync          = nilfs_sync_file,
 710
 711 };