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                 page_cache_release(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         page_cache_release(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_alloc_root(rootdir);
 319         if (!sb->s_root) {
 320                 iput(rootdir);
 321                 goto fail;
 322         }
 323
 324         /* at that point we know that ->put_super() will be called */
 325         super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
 326         if (!super->s_erase_page)
 327                 return -ENOMEM;
 328         memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);
 329
 330         /* FIXME: check for read-only mounts */
 331         err = logfs_make_writeable(sb);
 332         if (err) {
 333                 __free_page(super->s_erase_page);
 334                 return err;
 335         }
 336
 337         log_super("LogFS: Finished mounting\n");
 338         return 0;
 339
 340 fail:
 341         iput(super->s_master_inode);
 342         iput(super->s_segfile_inode);
 343         iput(super->s_mapping_inode);
 344         return -EIO;
 345 }
 346
 347 int logfs_check_ds(struct logfs_disk_super *ds)
 348 {
 349         struct logfs_segment_header *sh = &ds->ds_sh;
 350
 351         if (ds->ds_magic != cpu_to_be64(LOGFS_MAGIC))
 352                 return -EINVAL;
 353         if (sh->crc != logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4))
 354                 return -EINVAL;
 355         if (ds->ds_crc != logfs_crc32(ds, sizeof(*ds),
 356                                 LOGFS_SEGMENT_HEADERSIZE + 12))
 357                 return -EINVAL;
 358         return 0;
 359 }
 360
 361 static struct page *find_super_block(struct super_block *sb)
 362 {
 363         struct logfs_super *super = logfs_super(sb);
 364         struct page *first, *last;
 365
 366         first = super->s_devops->find_first_sb(sb, &super->s_sb_ofs[0]);
 367         if (!first || IS_ERR(first))
 368                 return NULL;
 369         last = super->s_devops->find_last_sb(sb, &super->s_sb_ofs[1]);
 370         if (!last || IS_ERR(last)) {
 371                 page_cache_release(first);
 372                 return NULL;
 373         }
 374
 375         if (!logfs_check_ds(page_address(first))) {
 376                 page_cache_release(last);
 377                 return first;
 378         }
 379
 380         /* First one didn't work, try the second superblock */
 381         if (!logfs_check_ds(page_address(last))) {
 382                 page_cache_release(first);
 383                 return last;
 384         }
 385
 386         /* Neither worked, sorry folks */
 387         page_cache_release(first);
 388         page_cache_release(last);
 389         return NULL;
 390 }
 391
 392 static int __logfs_read_sb(struct super_block *sb)
 393 {
 394         struct logfs_super *super = logfs_super(sb);
 395         struct page *page;
 396         struct logfs_disk_super *ds;
 397         int i;
 398
 399         page = find_super_block(sb);
 400         if (!page)
 401                 return -EINVAL;
 402
 403         ds = page_address(page);
 404         super->s_size = be64_to_cpu(ds->ds_filesystem_size);
 405         super->s_root_reserve = be64_to_cpu(ds->ds_root_reserve);
 406         super->s_speed_reserve = be64_to_cpu(ds->ds_speed_reserve);
 407         super->s_bad_seg_reserve = be32_to_cpu(ds->ds_bad_seg_reserve);
 408         super->s_segsize = 1 << ds->ds_segment_shift;
 409         super->s_segmask = (1 << ds->ds_segment_shift) - 1;
 410         super->s_segshift = ds->ds_segment_shift;
 411         sb->s_blocksize = 1 << ds->ds_block_shift;
 412         sb->s_blocksize_bits = ds->ds_block_shift;
 413         super->s_writesize = 1 << ds->ds_write_shift;
 414         super->s_writeshift = ds->ds_write_shift;
 415         super->s_no_segs = super->s_size >> super->s_segshift;
 416         super->s_no_blocks = super->s_segsize >> sb->s_blocksize_bits;
 417         super->s_feature_incompat = be64_to_cpu(ds->ds_feature_incompat);
 418         super->s_feature_ro_compat = be64_to_cpu(ds->ds_feature_ro_compat);
 419         super->s_feature_compat = be64_to_cpu(ds->ds_feature_compat);
 420         super->s_feature_flags = be64_to_cpu(ds->ds_feature_flags);
 421
 422         journal_for_each(i)
 423                 super->s_journal_seg[i] = be32_to_cpu(ds->ds_journal_seg[i]);
 424
 425         super->s_ifile_levels = ds->ds_ifile_levels;
 426         super->s_iblock_levels = ds->ds_iblock_levels;
 427         super->s_data_levels = ds->ds_data_levels;
 428         super->s_total_levels = super->s_ifile_levels + super->s_iblock_levels
 429                 + super->s_data_levels;
 430         page_cache_release(page);
 431         return 0;
 432 }
 433
 434 static int logfs_read_sb(struct super_block *sb, int read_only)
 435 {
 436         struct logfs_super *super = logfs_super(sb);
 437         int ret;
 438
 439         super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
 440         if (!super->s_btree_pool)
 441                 return -ENOMEM;
 442
 443         btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
 444         btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
 445         btree_init_mempool32(&super->s_shadow_tree.segment_map,
 446                         super->s_btree_pool);
 447
 448         ret = logfs_init_mapping(sb);
 449         if (ret)
 450                 return ret;
 451
 452         ret = __logfs_read_sb(sb);
 453         if (ret)
 454                 return ret;
 455
 456         if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
 457                 return -EIO;
 458         if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
 459                         !read_only)
 460                 return -EIO;
 461
 462         ret = logfs_init_rw(sb);
 463         if (ret)
 464                 return ret;
 465
 466         ret = logfs_init_areas(sb);
 467         if (ret)
 468                 return ret;
 469
 470         ret = logfs_init_gc(sb);
 471         if (ret)
 472                 return ret;
 473
 474         ret = logfs_init_journal(sb);
 475         if (ret)
 476                 return ret;
 477
 478         return 0;
 479 }
 480
 481 static void logfs_kill_sb(struct super_block *sb)
 482 {
 483         struct logfs_super *super = logfs_super(sb);
 484
 485         log_super("LogFS: Start unmounting\n");
 486         /* Alias entries slow down mount, so evict as many as possible */
 487         sync_filesystem(sb);
 488         logfs_write_anchor(sb);
 489
 490         /*
 491          * From this point on alias entries are simply dropped - and any
 492          * writes to the object store are considered bugs.
 493          */
 494         super->s_flags |= LOGFS_SB_FLAG_SHUTDOWN;
 495         log_super("LogFS: Now in shutdown\n");
 496         generic_shutdown_super(sb);
 497
 498         BUG_ON(super->s_dirty_used_bytes || super->s_dirty_free_bytes);
 499
 500         logfs_cleanup_gc(sb);
 501         logfs_cleanup_journal(sb);
 502         logfs_cleanup_areas(sb);
 503         logfs_cleanup_rw(sb);
 504         if (super->s_erase_page)
 505                 __free_page(super->s_erase_page);
 506         super->s_devops->put_device(super);
 507         logfs_mempool_destroy(super->s_btree_pool);
 508         logfs_mempool_destroy(super->s_alias_pool);
 509         kfree(super);
 510         log_super("LogFS: Finished unmounting\n");
 511 }
 512
 513 static struct dentry *logfs_get_sb_device(struct logfs_super *super,
 514                 struct file_system_type *type, int flags)
 515 {
 516         struct super_block *sb;
 517         int err = -ENOMEM;
 518         static int mount_count;
 519
 520         log_super("LogFS: Start mount %x\n", mount_count++);
 521
 522         err = -EINVAL;
 523         sb = sget(type, logfs_sb_test, logfs_sb_set, super);
 524         if (IS_ERR(sb)) {
 525                 super->s_devops->put_device(super);
 526                 kfree(super);
 527                 return ERR_CAST(sb);
 528         }
 529
 530         if (sb->s_root) {
 531                 /* Device is already in use */
 532                 super->s_devops->put_device(super);
 533                 kfree(super);
 534                 return dget(sb->s_root);
 535         }
 536
 537         /*
 538          * sb->s_maxbytes is limited to 8TB.  On 32bit systems, the page cache
 539          * only covers 16TB and the upper 8TB are used for indirect blocks.
 540          * On 64bit system we could bump up the limit, but that would make
 541          * the filesystem incompatible with 32bit systems.
 542          */
 543         sb->s_maxbytes  = (1ull << 43) - 1;
 544         sb->s_op        = &logfs_super_operations;
 545         sb->s_flags     = flags | MS_NOATIME;
 546
 547         err = logfs_read_sb(sb, sb->s_flags & MS_RDONLY);
 548         if (err)
 549                 goto err1;
 550
 551         sb->s_flags |= MS_ACTIVE;
 552         err = logfs_get_sb_final(sb);
 553         if (err) {
 554                 deactivate_locked_super(sb);
 555                 return ERR_PTR(err);
 556         }
 557         return dget(sb->s_root);
 558
 559 err1:
 560         /* no ->s_root, no ->put_super() */
 561         iput(super->s_master_inode);
 562         iput(super->s_segfile_inode);
 563         iput(super->s_mapping_inode);
 564         deactivate_locked_super(sb);
 565         return ERR_PTR(err);
 566 }
 567
 568 static struct dentry *logfs_mount(struct file_system_type *type, int flags,
 569                 const char *devname, void *data)
 570 {
 571         ulong mtdnr;
 572         struct logfs_super *super;
 573         int err;
 574
 575         super = kzalloc(sizeof(*super), GFP_KERNEL);
 576         if (!super)
 577                 return ERR_PTR(-ENOMEM);
 578
 579         mutex_init(&super->s_dirop_mutex);
 580         mutex_init(&super->s_object_alias_mutex);
 581         INIT_LIST_HEAD(&super->s_freeing_list);
 582
 583         if (!devname)
 584                 err = logfs_get_sb_bdev(super, type, devname);
 585         else if (strncmp(devname, "mtd", 3))
 586                 err = logfs_get_sb_bdev(super, type, devname);
 587         else {
 588                 char *garbage;
 589                 mtdnr = simple_strtoul(devname+3, &garbage, 0);
 590                 if (*garbage)
 591                         err = -EINVAL;
 592                 else
 593                         err = logfs_get_sb_mtd(super, mtdnr);
 594         }
 595
 596         if (err) {
 597                 kfree(super);
 598                 return ERR_PTR(err);
 599         }
 600
 601         return logfs_get_sb_device(super, type, flags);
 602 }
 603
 604 static struct file_system_type logfs_fs_type = {
 605         .owner          = THIS_MODULE,
 606         .name           = "logfs",
 607         .mount          = logfs_mount,
 608         .kill_sb        = logfs_kill_sb,
 609         .fs_flags       = FS_REQUIRES_DEV,
 610
 611 };
 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         return register_filesystem(&logfs_fs_type);
 630 out2:
 631         logfs_compr_exit();
 632 out1:
 633         __free_pages(emergency_page, 0);
 634         return ret;
 635 }
 636
 637 static void __exit logfs_exit(void)
 638 {
 639         unregister_filesystem(&logfs_fs_type);
 640         logfs_destroy_inode_cache();
 641         logfs_compr_exit();
 642         __free_pages(emergency_page, 0);
 643 }
 644
 645 module_init(logfs_init);
 646 module_exit(logfs_exit);
 647
 648 MODULE_LICENSE("GPL v2");
 649 MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
 650 MODULE_DESCRIPTION("scalable flash filesystem");