fs/logfs/super.c

   1 /*
   2  * fs/logfs/super.c
   3  *
   4  * As should be obvious for Linux kernel code, license is GPLv2
   5  *
   6  * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
   7  *
   8  * Generally contains mount/umount code and also serves as a dump area for
   9  * any functions that don't fit elsewhere and neither justify a file of their
  10  * own.
  11  */
  12 #include "logfs.h"
  13 #include <linux/bio.h>
  14 #include <linux/slab.h>
  15 #include <linux/blkdev.h>
  16 #include <linux/module.h>
  17 #include <linux/mtd/mtd.h>
  18 #include <linux/statfs.h>
  19 #include <linux/buffer_head.h>
  20
  21 static DEFINE_MUTEX(emergency_mutex);
  22 static struct page *emergency_page;
  23
  24 struct page *emergency_read_begin(struct address_space *mapping, pgoff_t index)
  25 {
  26         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
  27         struct page *page;
  28         int err;
  29
  30         page = read_cache_page(mapping, index, filler, NULL);
  31         if (page)
  32                 return page;
  33
  34         /* No more pages available, switch to emergency page */
  35         printk(KERN_INFO"Logfs: Using emergency page\n");
  36         mutex_lock(&emergency_mutex);
  37         err = filler(NULL, emergency_page);
  38         if (err) {
  39                 mutex_unlock(&emergency_mutex);
  40                 printk(KERN_EMERG"Logfs: Error reading emergency page\n");
  41                 return ERR_PTR(err);
  42         }
  43         return emergency_page;
  44 }
  45
  46 void emergency_read_end(struct page *page)
  47 {
  48         if (page == emergency_page)
  49                 mutex_unlock(&emergency_mutex);
  50         else
  51                 put_page(page);
  52 }
  53
  54 static void dump_segfile(struct super_block *sb)
  55 {
  56         struct logfs_super *super = logfs_super(sb);
  57         struct logfs_segment_entry se;
  58         u32 segno;
  59
  60         for (segno = 0; segno < super->s_no_segs; segno++) {
  61                 logfs_get_segment_entry(sb, segno, &se);
  62                 printk("%3x: %6x %8x", segno, be32_to_cpu(se.ec_level),
  63                                 be32_to_cpu(se.valid));
  64                 if (++segno < super->s_no_segs) {
  65                         logfs_get_segment_entry(sb, segno, &se);
  66                         printk(" %6x %8x", be32_to_cpu(se.ec_level),
  67                                         be32_to_cpu(se.valid));
  68                 }
  69                 if (++segno < super->s_no_segs) {
  70                         logfs_get_segment_entry(sb, segno, &se);
  71                         printk(" %6x %8x", be32_to_cpu(se.ec_level),
  72                                         be32_to_cpu(se.valid));
  73                 }
  74                 if (++segno < super->s_no_segs) {
  75                         logfs_get_segment_entry(sb, segno, &se);
  76                         printk(" %6x %8x", be32_to_cpu(se.ec_level),
  77                                         be32_to_cpu(se.valid));
  78                 }
  79                 printk("\n");
  80         }
  81 }
  82
  83 /*
  84  * logfs_crash_dump - dump debug information to device
  85  *
  86  * The LogFS superblock only occupies part of a segment.  This function will
  87  * write as much debug information as it can gather into the spare space.
  88  */
  89 void logfs_crash_dump(struct super_block *sb)
  90 {
  91         dump_segfile(sb);
  92 }
  93
  94 /*
  95  * FIXME: There should be a reserve for root, similar to ext2.
  96  */
  97 int logfs_statfs(struct dentry *dentry, struct kstatfs *stats)
  98 {
  99         struct super_block *sb = dentry->d_sb;
 100         struct logfs_super *super = logfs_super(sb);
 101
 102         stats->f_type           = LOGFS_MAGIC_U32;
 103         stats->f_bsize          = sb->s_blocksize;
 104         stats->f_blocks         = super->s_size >> LOGFS_BLOCK_BITS >> 3;
 105         stats->f_bfree          = super->s_free_bytes >> sb->s_blocksize_bits;
 106         stats->f_bavail         = super->s_free_bytes >> sb->s_blocksize_bits;
 107         stats->f_files          = 0;
 108         stats->f_ffree          = 0;
 109         stats->f_namelen        = LOGFS_MAX_NAMELEN;
 110         return 0;
 111 }
 112
 113 static int logfs_sb_set(struct super_block *sb, void *_super)
 114 {
 115         struct logfs_super *super = _super;
 116
 117         sb->s_fs_info = super;
 118         sb->s_mtd = super->s_mtd;
 119         sb->s_bdev = super->s_bdev;
 120 #ifdef CONFIG_BLOCK
 121         if (sb->s_bdev)
 122                 sb->s_bdi = &bdev_get_queue(sb->s_bdev)->backing_dev_info;
 123 #endif
 124 #ifdef CONFIG_MTD
 125         if (sb->s_mtd)
 126                 sb->s_bdi = sb->s_mtd->backing_dev_info;
 127 #endif
 128         return 0;
 129 }
 130
 131 static int logfs_sb_test(struct super_block *sb, void *_super)
 132 {
 133         struct logfs_super *super = _super;
 134         struct mtd_info *mtd = super->s_mtd;
 135
 136         if (mtd && sb->s_mtd == mtd)
 137                 return 1;
 138         if (super->s_bdev && sb->s_bdev == super->s_bdev)
 139                 return 1;
 140         return 0;
 141 }
 142
 143 static void set_segment_header(struct logfs_segment_header *sh, u8 type,
 144                 u8 level, u32 segno, u32 ec)
 145 {
 146         sh->pad = 0;
 147         sh->type = type;
 148         sh->level = level;
 149         sh->segno = cpu_to_be32(segno);
 150         sh->ec = cpu_to_be32(ec);
 151         sh->gec = cpu_to_be64(segno);
 152         sh->crc = logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4);
 153 }
 154
 155 static void logfs_write_ds(struct super_block *sb, struct logfs_disk_super *ds,
 156                 u32 segno, u32 ec)
 157 {
 158         struct logfs_super *super = logfs_super(sb);
 159         struct logfs_segment_header *sh = &ds->ds_sh;
 160         int i;
 161
 162         memset(ds, 0, sizeof(*ds));
 163         set_segment_header(sh, SEG_SUPER, 0, segno, ec);
 164
 165         ds->ds_ifile_levels     = super->s_ifile_levels;
 166         ds->ds_iblock_levels    = super->s_iblock_levels;
 167         ds->ds_data_levels      = super->s_data_levels; /* XXX: Remove */
 168         ds->ds_segment_shift    = super->s_segshift;
 169         ds->ds_block_shift      = sb->s_blocksize_bits;
 170         ds->ds_write_shift      = super->s_writeshift;
 171         ds->ds_filesystem_size  = cpu_to_be64(super->s_size);
 172         ds->ds_segment_size     = cpu_to_be32(super->s_segsize);
 173         ds->ds_bad_seg_reserve  = cpu_to_be32(super->s_bad_seg_reserve);
 174         ds->ds_feature_incompat = cpu_to_be64(super->s_feature_incompat);
 175         ds->ds_feature_ro_compat= cpu_to_be64(super->s_feature_ro_compat);
 176         ds->ds_feature_compat   = cpu_to_be64(super->s_feature_compat);
 177         ds->ds_feature_flags    = cpu_to_be64(super->s_feature_flags);
 178         ds->ds_root_reserve     = cpu_to_be64(super->s_root_reserve);
 179         ds->ds_speed_reserve    = cpu_to_be64(super->s_speed_reserve);
 180         journal_for_each(i)
 181                 ds->ds_journal_seg[i] = cpu_to_be32(super->s_journal_seg[i]);
 182         ds->ds_magic            = cpu_to_be64(LOGFS_MAGIC);
 183         ds->ds_crc = logfs_crc32(ds, sizeof(*ds),
 184                         LOGFS_SEGMENT_HEADERSIZE + 12);
 185 }
 186
 187 static int write_one_sb(struct super_block *sb,
 188                 struct page *(*find_sb)(struct super_block *sb, u64 *ofs))
 189 {
 190         struct logfs_super *super = logfs_super(sb);
 191         struct logfs_disk_super *ds;
 192         struct logfs_segment_entry se;
 193         struct page *page;
 194         u64 ofs;
 195         u32 ec, segno;
 196         int err;
 197
 198         page = find_sb(sb, &ofs);
 199         if (!page)
 200                 return -EIO;
 201         ds = page_address(page);
 202         segno = seg_no(sb, ofs);
 203         logfs_get_segment_entry(sb, segno, &se);
 204         ec = be32_to_cpu(se.ec_level) >> 4;
 205         ec++;
 206         logfs_set_segment_erased(sb, segno, ec, 0);
 207         logfs_write_ds(sb, ds, segno, ec);
 208         err = super->s_devops->write_sb(sb, page);
 209         put_page(page);
 210         return err;
 211 }
 212
 213 int logfs_write_sb(struct super_block *sb)
 214 {
 215         struct logfs_super *super = logfs_super(sb);
 216         int err;
 217
 218         /* First superblock */
 219         err = write_one_sb(sb, super->s_devops->find_first_sb);
 220         if (err)
 221                 return err;
 222
 223         /* Last superblock */
 224         err = write_one_sb(sb, super->s_devops->find_last_sb);
 225         if (err)
 226                 return err;
 227         return 0;
 228 }
 229
 230 static int ds_cmp(const void *ds0, const void *ds1)
 231 {
 232         size_t len = sizeof(struct logfs_disk_super);
 233
 234         /* We know the segment headers differ, so ignore them */
 235         len -= LOGFS_SEGMENT_HEADERSIZE;
 236         ds0 += LOGFS_SEGMENT_HEADERSIZE;
 237         ds1 += LOGFS_SEGMENT_HEADERSIZE;
 238         return memcmp(ds0, ds1, len);
 239 }
 240
 241 static int logfs_recover_sb(struct super_block *sb)
 242 {
 243         struct logfs_super *super = logfs_super(sb);
 244         struct logfs_disk_super _ds0, *ds0 = &_ds0;
 245         struct logfs_disk_super _ds1, *ds1 = &_ds1;
 246         int err, valid0, valid1;
 247
 248         /* read first superblock */
 249         err = wbuf_read(sb, super->s_sb_ofs[0], sizeof(*ds0), ds0);
 250         if (err)
 251                 return err;
 252         /* read last superblock */
 253         err = wbuf_read(sb, super->s_sb_ofs[1], sizeof(*ds1), ds1);
 254         if (err)
 255                 return err;
 256         valid0 = logfs_check_ds(ds0) == 0;
 257         valid1 = logfs_check_ds(ds1) == 0;
 258
 259         if (!valid0 && valid1) {
 260                 printk(KERN_INFO"First superblock is invalid - fixing.\n");
 261                 return write_one_sb(sb, super->s_devops->find_first_sb);
 262         }
 263         if (valid0 && !valid1) {
 264                 printk(KERN_INFO"Last superblock is invalid - fixing.\n");
 265                 return write_one_sb(sb, super->s_devops->find_last_sb);
 266         }
 267         if (valid0 && valid1 && ds_cmp(ds0, ds1)) {
 268                 printk(KERN_INFO"Superblocks don't match - fixing.\n");
 269                 return logfs_write_sb(sb);
 270         }
 271         /* If neither is valid now, something's wrong.  Didn't we properly
 272          * check them before?!? */
 273         BUG_ON(!valid0 && !valid1);
 274         return 0;
 275 }
 276
 277 static int logfs_make_writeable(struct super_block *sb)
 278 {
 279         int err;
 280
 281         err = logfs_open_segfile(sb);
 282         if (err)
 283                 return err;
 284
 285         /* Repair any broken superblock copies */
 286         err = logfs_recover_sb(sb);
 287         if (err)
 288                 return err;
 289
 290         /* Check areas for trailing unaccounted data */
 291         err = logfs_check_areas(sb);
 292         if (err)
 293                 return err;
 294
 295         /* Do one GC pass before any data gets dirtied */
 296         logfs_gc_pass(sb);
 297
 298         /* after all initializations are done, replay the journal
 299          * for rw-mounts, if necessary */
 300         err = logfs_replay_journal(sb);
 301         if (err)
 302                 return err;
 303
 304         return 0;
 305 }
 306
 307 static int logfs_get_sb_final(struct super_block *sb)
 308 {
 309         struct logfs_super *super = logfs_super(sb);
 310         struct inode *rootdir;
 311         int err;
 312
 313         /* root dir */
 314         rootdir = logfs_iget(sb, LOGFS_INO_ROOT);
 315         if (IS_ERR(rootdir))
 316                 goto fail;
 317
 318         sb->s_root = d_make_root(rootdir);
 319         if (!sb->s_root)
 320                 goto fail;
 321
 322         /* at that point we know that ->put_super() will be called */
 323         super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
 324         if (!super->s_erase_page)
 325                 return -ENOMEM;
 326         memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);
 327
 328         /* FIXME: check for read-only mounts */
 329         err = logfs_make_writeable(sb);
 330         if (err) {
 331                 __free_page(super->s_erase_page);
 332                 return err;
 333         }
 334
 335         log_super("LogFS: Finished mounting\n");
 336         return 0;
 337
 338 fail:
 339         iput(super->s_master_inode);
 340         iput(super->s_segfile_inode);
 341         iput(super->s_mapping_inode);
 342         return -EIO;
 343 }
 344
 345 int logfs_check_ds(struct logfs_disk_super *ds)
 346 {
 347         struct logfs_segment_header *sh = &ds->ds_sh;
 348
 349         if (ds->ds_magic != cpu_to_be64(LOGFS_MAGIC))
 350                 return -EINVAL;
 351         if (sh->crc != logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4))
 352                 return -EINVAL;
 353         if (ds->ds_crc != logfs_crc32(ds, sizeof(*ds),
 354                                 LOGFS_SEGMENT_HEADERSIZE + 12))
 355                 return -EINVAL;
 356         return 0;
 357 }
 358
 359 static struct page *find_super_block(struct super_block *sb)
 360 {
 361         struct logfs_super *super = logfs_super(sb);
 362         struct page *first, *last;
 363
 364         first = super->s_devops->find_first_sb(sb, &super->s_sb_ofs[0]);
 365         if (!first || IS_ERR(first))
 366                 return NULL;
 367         last = super->s_devops->find_last_sb(sb, &super->s_sb_ofs[1]);
 368         if (!last || IS_ERR(last)) {
 369                 put_page(first);
 370                 return NULL;
 371         }
 372
 373         if (!logfs_check_ds(page_address(first))) {
 374                 put_page(last);
 375                 return first;
 376         }
 377
 378         /* First one didn't work, try the second superblock */
 379         if (!logfs_check_ds(page_address(last))) {
 380                 put_page(first);
 381                 return last;
 382         }
 383
 384         /* Neither worked, sorry folks */
 385         put_page(first);
 386         put_page(last);
 387         return NULL;
 388 }
 389
 390 static int __logfs_read_sb(struct super_block *sb)
 391 {
 392         struct logfs_super *super = logfs_super(sb);
 393         struct page *page;
 394         struct logfs_disk_super *ds;
 395         int i;
 396
 397         page = find_super_block(sb);
 398         if (!page)
 399                 return -EINVAL;
 400
 401         ds = page_address(page);
 402         super->s_size = be64_to_cpu(ds->ds_filesystem_size);
 403         super->s_root_reserve = be64_to_cpu(ds->ds_root_reserve);
 404         super->s_speed_reserve = be64_to_cpu(ds->ds_speed_reserve);
 405         super->s_bad_seg_reserve = be32_to_cpu(ds->ds_bad_seg_reserve);
 406         super->s_segsize = 1 << ds->ds_segment_shift;
 407         super->s_segmask = (1 << ds->ds_segment_shift) - 1;
 408         super->s_segshift = ds->ds_segment_shift;
 409         sb->s_blocksize = 1 << ds->ds_block_shift;
 410         sb->s_blocksize_bits = ds->ds_block_shift;
 411         super->s_writesize = 1 << ds->ds_write_shift;
 412         super->s_writeshift = ds->ds_write_shift;
 413         super->s_no_segs = super->s_size >> super->s_segshift;
 414         super->s_no_blocks = super->s_segsize >> sb->s_blocksize_bits;
 415         super->s_feature_incompat = be64_to_cpu(ds->ds_feature_incompat);
 416         super->s_feature_ro_compat = be64_to_cpu(ds->ds_feature_ro_compat);
 417         super->s_feature_compat = be64_to_cpu(ds->ds_feature_compat);
 418         super->s_feature_flags = be64_to_cpu(ds->ds_feature_flags);
 419
 420         journal_for_each(i)
 421                 super->s_journal_seg[i] = be32_to_cpu(ds->ds_journal_seg[i]);
 422
 423         super->s_ifile_levels = ds->ds_ifile_levels;
 424         super->s_iblock_levels = ds->ds_iblock_levels;
 425         super->s_data_levels = ds->ds_data_levels;
 426         super->s_total_levels = super->s_ifile_levels + super->s_iblock_levels
 427                 + super->s_data_levels;
 428         put_page(page);
 429         return 0;
 430 }
 431
 432 static int logfs_read_sb(struct super_block *sb, int read_only)
 433 {
 434         struct logfs_super *super = logfs_super(sb);
 435         int ret;
 436
 437         super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
 438         if (!super->s_btree_pool)
 439                 return -ENOMEM;
 440
 441         btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
 442         btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
 443         btree_init_mempool32(&super->s_shadow_tree.segment_map,
 444                         super->s_btree_pool);
 445
 446         ret = logfs_init_mapping(sb);
 447         if (ret)
 448                 return ret;
 449
 450         ret = __logfs_read_sb(sb);
 451         if (ret)
 452                 return ret;
 453
 454         if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
 455                 return -EIO;
 456         if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
 457                         !read_only)
 458                 return -EIO;
 459
 460         ret = logfs_init_rw(sb);
 461         if (ret)
 462                 return ret;
 463
 464         ret = logfs_init_areas(sb);
 465         if (ret)
 466                 return ret;
 467
 468         ret = logfs_init_gc(sb);
 469         if (ret)
 470                 return ret;
 471
 472         ret = logfs_init_journal(sb);
 473         if (ret)
 474                 return ret;
 475
 476         return 0;
 477 }
 478
 479 static void logfs_kill_sb(struct super_block *sb)
 480 {
 481         struct logfs_super *super = logfs_super(sb);
 482
 483         log_super("LogFS: Start unmounting\n");
 484         /* Alias entries slow down mount, so evict as many as possible */
 485         sync_filesystem(sb);
 486         logfs_write_anchor(sb);
 487         free_areas(sb);
 488
 489         /*
 490          * From this point on alias entries are simply dropped - and any
 491          * writes to the object store are considered bugs.
 492          */
 493         log_super("LogFS: Now in shutdown\n");
 494         generic_shutdown_super(sb);
 495         super->s_flags |= LOGFS_SB_FLAG_SHUTDOWN;
 496
 497         BUG_ON(super->s_dirty_used_bytes || super->s_dirty_free_bytes);
 498
 499         logfs_cleanup_gc(sb);
 500         logfs_cleanup_journal(sb);
 501         logfs_cleanup_areas(sb);
 502         logfs_cleanup_rw(sb);
 503         if (super->s_erase_page)
 504                 __free_page(super->s_erase_page);
 505         super->s_devops->put_device(super);
 506         logfs_mempool_destroy(super->s_btree_pool);
 507         logfs_mempool_destroy(super->s_alias_pool);
 508         kfree(super);
 509         log_super("LogFS: Finished unmounting\n");
 510 }
 511
 512 static struct dentry *logfs_get_sb_device(struct logfs_super *super,
 513                 struct file_system_type *type, int flags)
 514 {
 515         struct super_block *sb;
 516         int err = -ENOMEM;
 517         static int mount_count;
 518
 519         log_super("LogFS: Start mount %x\n", mount_count++);
 520
 521         err = -EINVAL;
 522         sb = sget(type, logfs_sb_test, logfs_sb_set, flags | MS_NOATIME, super);
 523         if (IS_ERR(sb)) {
 524                 super->s_devops->put_device(super);
 525                 kfree(super);
 526                 return ERR_CAST(sb);
 527         }
 528
 529         if (sb->s_root) {
 530                 /* Device is already in use */
 531                 super->s_devops->put_device(super);
 532                 kfree(super);
 533                 return dget(sb->s_root);
 534         }
 535
 536         /*
 537          * sb->s_maxbytes is limited to 8TB.  On 32bit systems, the page cache
 538          * only covers 16TB and the upper 8TB are used for indirect blocks.
 539          * On 64bit system we could bump up the limit, but that would make
 540          * the filesystem incompatible with 32bit systems.
 541          */
 542         sb->s_maxbytes  = (1ull << 43) - 1;
 543         sb->s_max_links = LOGFS_LINK_MAX;
 544         sb->s_op        = &logfs_super_operations;
 545
 546         err = logfs_read_sb(sb, sb->s_flags & MS_RDONLY);
 547         if (err)
 548                 goto err1;
 549
 550         sb->s_flags |= MS_ACTIVE;
 551         err = logfs_get_sb_final(sb);
 552         if (err) {
 553                 deactivate_locked_super(sb);
 554                 return ERR_PTR(err);
 555         }
 556         return dget(sb->s_root);
 557
 558 err1:
 559         /* no ->s_root, no ->put_super() */
 560         iput(super->s_master_inode);
 561         iput(super->s_segfile_inode);
 562         iput(super->s_mapping_inode);
 563         deactivate_locked_super(sb);
 564         return ERR_PTR(err);
 565 }
 566
 567 static struct dentry *logfs_mount(struct file_system_type *type, int flags,
 568                 const char *devname, void *data)
 569 {
 570         ulong mtdnr;
 571         struct logfs_super *super;
 572         int err;
 573
 574         super = kzalloc(sizeof(*super), GFP_KERNEL);
 575         if (!super)
 576                 return ERR_PTR(-ENOMEM);
 577
 578         mutex_init(&super->s_dirop_mutex);
 579         mutex_init(&super->s_object_alias_mutex);
 580         INIT_LIST_HEAD(&super->s_freeing_list);
 581
 582         if (!devname)
 583                 err = logfs_get_sb_bdev(super, type, devname);
 584         else if (strncmp(devname, "mtd", 3))
 585                 err = logfs_get_sb_bdev(super, type, devname);
 586         else {
 587                 char *garbage;
 588                 mtdnr = simple_strtoul(devname+3, &garbage, 0);
 589                 if (*garbage)
 590                         err = -EINVAL;
 591                 else
 592                         err = logfs_get_sb_mtd(super, mtdnr);
 593         }
 594
 595         if (err) {
 596                 kfree(super);
 597                 return ERR_PTR(err);
 598         }
 599
 600         return logfs_get_sb_device(super, type, flags);
 601 }
 602
 603 static struct file_system_type logfs_fs_type = {
 604         .owner          = THIS_MODULE,
 605         .name           = "logfs",
 606         .mount          = logfs_mount,
 607         .kill_sb        = logfs_kill_sb,
 608         .fs_flags       = FS_REQUIRES_DEV,
 609
 610 };
 611 MODULE_ALIAS_FS("logfs");
 612
 613 static int __init logfs_init(void)
 614 {
 615         int ret;
 616
 617         emergency_page = alloc_pages(GFP_KERNEL, 0);
 618         if (!emergency_page)
 619                 return -ENOMEM;
 620
 621         ret = logfs_compr_init();
 622         if (ret)
 623                 goto out1;
 624
 625         ret = logfs_init_inode_cache();
 626         if (ret)
 627                 goto out2;
 628
 629         ret = register_filesystem(&logfs_fs_type);
 630         if (!ret)
 631                 return 0;
 632         logfs_destroy_inode_cache();
 633 out2:
 634         logfs_compr_exit();
 635 out1:
 636         __free_pages(emergency_page, 0);
 637         return ret;
 638 }
 639
 640 static void __exit logfs_exit(void)
 641 {
 642         unregister_filesystem(&logfs_fs_type);
 643         logfs_destroy_inode_cache();
 644         logfs_compr_exit();
 645         __free_pages(emergency_page, 0);
 646 }
 647
 648 module_init(logfs_init);
 649 module_exit(logfs_exit);
 650
 651 MODULE_LICENSE("GPL v2");
 652 MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
 653 MODULE_DESCRIPTION("scalable flash filesystem");