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/blkdev.h>
  15 #include <linux/mtd/mtd.h>
  16 #include <linux/statfs.h>
  17 #include <linux/buffer_head.h>
  18
  19 static DEFINE_MUTEX(emergency_mutex);
  20 static struct page *emergency_page;
  21
  22 struct page *emergency_read_begin(struct address_space *mapping, pgoff_t index)
  23 {
  24         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
  25         struct page *page;
  26         int err;
  27
  28         page = read_cache_page(mapping, index, filler, NULL);
  29         if (page)
  30                 return page;
  31
  32         /* No more pages available, switch to emergency page */
  33         printk(KERN_INFO"Logfs: Using emergency page\n");
  34         mutex_lock(&emergency_mutex);
  35         err = filler(NULL, emergency_page);
  36         if (err) {
  37                 mutex_unlock(&emergency_mutex);
  38                 printk(KERN_EMERG"Logfs: Error reading emergency page\n");
  39                 return ERR_PTR(err);
  40         }
  41         return emergency_page;
  42 }
  43
  44 void emergency_read_end(struct page *page)
  45 {
  46         if (page == emergency_page)
  47                 mutex_unlock(&emergency_mutex);
  48         else
  49                 page_cache_release(page);
  50 }
  51
  52 static void dump_segfile(struct super_block *sb)
  53 {
  54         struct logfs_super *super = logfs_super(sb);
  55         struct logfs_segment_entry se;
  56         u32 segno;
  57
  58         for (segno = 0; segno < super->s_no_segs; segno++) {
  59                 logfs_get_segment_entry(sb, segno, &se);
  60                 printk("%3x: %6x %8x", segno, be32_to_cpu(se.ec_level),
  61                                 be32_to_cpu(se.valid));
  62                 if (++segno < super->s_no_segs) {
  63                         logfs_get_segment_entry(sb, segno, &se);
  64                         printk(" %6x %8x", be32_to_cpu(se.ec_level),
  65                                         be32_to_cpu(se.valid));
  66                 }
  67                 if (++segno < super->s_no_segs) {
  68                         logfs_get_segment_entry(sb, segno, &se);
  69                         printk(" %6x %8x", be32_to_cpu(se.ec_level),
  70                                         be32_to_cpu(se.valid));
  71                 }
  72                 if (++segno < super->s_no_segs) {
  73                         logfs_get_segment_entry(sb, segno, &se);
  74                         printk(" %6x %8x", be32_to_cpu(se.ec_level),
  75                                         be32_to_cpu(se.valid));
  76                 }
  77                 printk("\n");
  78         }
  79 }
  80
  81 /*
  82  * logfs_crash_dump - dump debug information to device
  83  *
  84  * The LogFS superblock only occupies part of a segment.  This function will
  85  * write as much debug information as it can gather into the spare space.
  86  */
  87 void logfs_crash_dump(struct super_block *sb)
  88 {
  89         dump_segfile(sb);
  90 }
  91
  92 /*
  93  * TODO: move to lib/string.c
  94  */
  95 /**
  96  * memchr_inv - Find a character in an area of memory.
  97  * @s: The memory area
  98  * @c: The byte to search for
  99  * @n: The size of the area.
 100  *
 101  * returns the address of the first character other than @c, or %NULL
 102  * if the whole buffer contains just @c.
 103  */
 104 void *memchr_inv(const void *s, int c, size_t n)
 105 {
 106         const unsigned char *p = s;
 107         while (n-- != 0)
 108                 if ((unsigned char)c != *p++)
 109                         return (void *)(p - 1);
 110
 111         return NULL;
 112 }
 113
 114 /*
 115  * FIXME: There should be a reserve for root, similar to ext2.
 116  */
 117 int logfs_statfs(struct dentry *dentry, struct kstatfs *stats)
 118 {
 119         struct super_block *sb = dentry->d_sb;
 120         struct logfs_super *super = logfs_super(sb);
 121
 122         stats->f_type           = LOGFS_MAGIC_U32;
 123         stats->f_bsize          = sb->s_blocksize;
 124         stats->f_blocks         = super->s_size >> LOGFS_BLOCK_BITS >> 3;
 125         stats->f_bfree          = super->s_free_bytes >> sb->s_blocksize_bits;
 126         stats->f_bavail         = super->s_free_bytes >> sb->s_blocksize_bits;
 127         stats->f_files          = 0;
 128         stats->f_ffree          = 0;
 129         stats->f_namelen        = LOGFS_MAX_NAMELEN;
 130         return 0;
 131 }
 132
 133 static int logfs_sb_set(struct super_block *sb, void *_super)
 134 {
 135         struct logfs_super *super = _super;
 136
 137         sb->s_fs_info = super;
 138         sb->s_mtd = super->s_mtd;
 139         sb->s_bdev = super->s_bdev;
 140         if (sb->s_bdev)
 141                 sb->s_bdi = &bdev_get_queue(sb->s_bdev)->backing_dev_info;
 142         if (sb->s_mtd)
 143                 sb->s_bdi = sb->s_mtd->backing_dev_info;
 144         return 0;
 145 }
 146
 147 static int logfs_sb_test(struct super_block *sb, void *_super)
 148 {
 149         struct logfs_super *super = _super;
 150         struct mtd_info *mtd = super->s_mtd;
 151
 152         if (mtd && sb->s_mtd == mtd)
 153                 return 1;
 154         if (super->s_bdev && sb->s_bdev == super->s_bdev)
 155                 return 1;
 156         return 0;
 157 }
 158
 159 static void set_segment_header(struct logfs_segment_header *sh, u8 type,
 160                 u8 level, u32 segno, u32 ec)
 161 {
 162         sh->pad = 0;
 163         sh->type = type;
 164         sh->level = level;
 165         sh->segno = cpu_to_be32(segno);
 166         sh->ec = cpu_to_be32(ec);
 167         sh->gec = cpu_to_be64(segno);
 168         sh->crc = logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4);
 169 }
 170
 171 static void logfs_write_ds(struct super_block *sb, struct logfs_disk_super *ds,
 172                 u32 segno, u32 ec)
 173 {
 174         struct logfs_super *super = logfs_super(sb);
 175         struct logfs_segment_header *sh = &ds->ds_sh;
 176         int i;
 177
 178         memset(ds, 0, sizeof(*ds));
 179         set_segment_header(sh, SEG_SUPER, 0, segno, ec);
 180
 181         ds->ds_ifile_levels     = super->s_ifile_levels;
 182         ds->ds_iblock_levels    = super->s_iblock_levels;
 183         ds->ds_data_levels      = super->s_data_levels; /* XXX: Remove */
 184         ds->ds_segment_shift    = super->s_segshift;
 185         ds->ds_block_shift      = sb->s_blocksize_bits;
 186         ds->ds_write_shift      = super->s_writeshift;
 187         ds->ds_filesystem_size  = cpu_to_be64(super->s_size);
 188         ds->ds_segment_size     = cpu_to_be32(super->s_segsize);
 189         ds->ds_bad_seg_reserve  = cpu_to_be32(super->s_bad_seg_reserve);
 190         ds->ds_feature_incompat = cpu_to_be64(super->s_feature_incompat);
 191         ds->ds_feature_ro_compat= cpu_to_be64(super->s_feature_ro_compat);
 192         ds->ds_feature_compat   = cpu_to_be64(super->s_feature_compat);
 193         ds->ds_feature_flags    = cpu_to_be64(super->s_feature_flags);
 194         ds->ds_root_reserve     = cpu_to_be64(super->s_root_reserve);
 195         ds->ds_speed_reserve    = cpu_to_be64(super->s_speed_reserve);
 196         journal_for_each(i)
 197                 ds->ds_journal_seg[i] = cpu_to_be32(super->s_journal_seg[i]);
 198         ds->ds_magic            = cpu_to_be64(LOGFS_MAGIC);
 199         ds->ds_crc = logfs_crc32(ds, sizeof(*ds),
 200                         LOGFS_SEGMENT_HEADERSIZE + 12);
 201 }
 202
 203 static int write_one_sb(struct super_block *sb,
 204                 struct page *(*find_sb)(struct super_block *sb, u64 *ofs))
 205 {
 206         struct logfs_super *super = logfs_super(sb);
 207         struct logfs_disk_super *ds;
 208         struct logfs_segment_entry se;
 209         struct page *page;
 210         u64 ofs;
 211         u32 ec, segno;
 212         int err;
 213
 214         page = find_sb(sb, &ofs);
 215         if (!page)
 216                 return -EIO;
 217         ds = page_address(page);
 218         segno = seg_no(sb, ofs);
 219         logfs_get_segment_entry(sb, segno, &se);
 220         ec = be32_to_cpu(se.ec_level) >> 4;
 221         ec++;
 222         logfs_set_segment_erased(sb, segno, ec, 0);
 223         logfs_write_ds(sb, ds, segno, ec);
 224         err = super->s_devops->write_sb(sb, page);
 225         page_cache_release(page);
 226         return err;
 227 }
 228
 229 int logfs_write_sb(struct super_block *sb)
 230 {
 231         struct logfs_super *super = logfs_super(sb);
 232         int err;
 233
 234         /* First superblock */
 235         err = write_one_sb(sb, super->s_devops->find_first_sb);
 236         if (err)
 237                 return err;
 238
 239         /* Last superblock */
 240         err = write_one_sb(sb, super->s_devops->find_last_sb);
 241         if (err)
 242                 return err;
 243         return 0;
 244 }
 245
 246 static int ds_cmp(const void *ds0, const void *ds1)
 247 {
 248         size_t len = sizeof(struct logfs_disk_super);
 249
 250         /* We know the segment headers differ, so ignore them */
 251         len -= LOGFS_SEGMENT_HEADERSIZE;
 252         ds0 += LOGFS_SEGMENT_HEADERSIZE;
 253         ds1 += LOGFS_SEGMENT_HEADERSIZE;
 254         return memcmp(ds0, ds1, len);
 255 }
 256
 257 static int logfs_recover_sb(struct super_block *sb)
 258 {
 259         struct logfs_super *super = logfs_super(sb);
 260         struct logfs_disk_super _ds0, *ds0 = &_ds0;
 261         struct logfs_disk_super _ds1, *ds1 = &_ds1;
 262         int err, valid0, valid1;
 263
 264         /* read first superblock */
 265         err = wbuf_read(sb, super->s_sb_ofs[0], sizeof(*ds0), ds0);
 266         if (err)
 267                 return err;
 268         /* read last superblock */
 269         err = wbuf_read(sb, super->s_sb_ofs[1], sizeof(*ds1), ds1);
 270         if (err)
 271                 return err;
 272         valid0 = logfs_check_ds(ds0) == 0;
 273         valid1 = logfs_check_ds(ds1) == 0;
 274
 275         if (!valid0 && valid1) {
 276                 printk(KERN_INFO"First superblock is invalid - fixing.\n");
 277                 return write_one_sb(sb, super->s_devops->find_first_sb);
 278         }
 279         if (valid0 && !valid1) {
 280                 printk(KERN_INFO"Last superblock is invalid - fixing.\n");
 281                 return write_one_sb(sb, super->s_devops->find_last_sb);
 282         }
 283         if (valid0 && valid1 && ds_cmp(ds0, ds1)) {
 284                 printk(KERN_INFO"Superblocks don't match - fixing.\n");
 285                 return logfs_write_sb(sb);
 286         }
 287         /* If neither is valid now, something's wrong.  Didn't we properly
 288          * check them before?!? */
 289         BUG_ON(!valid0 && !valid1);
 290         return 0;
 291 }
 292
 293 static int logfs_make_writeable(struct super_block *sb)
 294 {
 295         int err;
 296
 297         err = logfs_open_segfile(sb);
 298         if (err)
 299                 return err;
 300
 301         /* Repair any broken superblock copies */
 302         err = logfs_recover_sb(sb);
 303         if (err)
 304                 return err;
 305
 306         /* Check areas for trailing unaccounted data */
 307         err = logfs_check_areas(sb);
 308         if (err)
 309                 return err;
 310
 311         /* Do one GC pass before any data gets dirtied */
 312         logfs_gc_pass(sb);
 313
 314         /* after all initializations are done, replay the journal
 315          * for rw-mounts, if necessary */
 316         err = logfs_replay_journal(sb);
 317         if (err)
 318                 return err;
 319
 320         return 0;
 321 }
 322
 323 static int logfs_get_sb_final(struct super_block *sb, struct vfsmount *mnt)
 324 {
 325         struct logfs_super *super = logfs_super(sb);
 326         struct inode *rootdir;
 327         int err;
 328
 329         /* root dir */
 330         rootdir = logfs_iget(sb, LOGFS_INO_ROOT);
 331         if (IS_ERR(rootdir))
 332                 goto fail;
 333
 334         sb->s_root = d_alloc_root(rootdir);
 335         if (!sb->s_root)
 336                 goto fail2;
 337
 338         super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
 339         if (!super->s_erase_page)
 340                 goto fail2;
 341         memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);
 342
 343         /* FIXME: check for read-only mounts */
 344         err = logfs_make_writeable(sb);
 345         if (err)
 346                 goto fail3;
 347
 348         log_super("LogFS: Finished mounting\n");
 349         simple_set_mnt(mnt, sb);
 350         return 0;
 351
 352 fail3:
 353         __free_page(super->s_erase_page);
 354 fail2:
 355         iput(rootdir);
 356 fail:
 357         iput(logfs_super(sb)->s_master_inode);
 358         return -EIO;
 359 }
 360
 361 int logfs_check_ds(struct logfs_disk_super *ds)
 362 {
 363         struct logfs_segment_header *sh = &ds->ds_sh;
 364
 365         if (ds->ds_magic != cpu_to_be64(LOGFS_MAGIC))
 366                 return -EINVAL;
 367         if (sh->crc != logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4))
 368                 return -EINVAL;
 369         if (ds->ds_crc != logfs_crc32(ds, sizeof(*ds),
 370                                 LOGFS_SEGMENT_HEADERSIZE + 12))
 371                 return -EINVAL;
 372         return 0;
 373 }
 374
 375 static struct page *find_super_block(struct super_block *sb)
 376 {
 377         struct logfs_super *super = logfs_super(sb);
 378         struct page *first, *last;
 379
 380         first = super->s_devops->find_first_sb(sb, &super->s_sb_ofs[0]);
 381         if (!first || IS_ERR(first))
 382                 return NULL;
 383         last = super->s_devops->find_last_sb(sb, &super->s_sb_ofs[1]);
 384         if (!last || IS_ERR(first)) {
 385                 page_cache_release(first);
 386                 return NULL;
 387         }
 388
 389         if (!logfs_check_ds(page_address(first))) {
 390                 page_cache_release(last);
 391                 return first;
 392         }
 393
 394         /* First one didn't work, try the second superblock */
 395         if (!logfs_check_ds(page_address(last))) {
 396                 page_cache_release(first);
 397                 return last;
 398         }
 399
 400         /* Neither worked, sorry folks */
 401         page_cache_release(first);
 402         page_cache_release(last);
 403         return NULL;
 404 }
 405
 406 static int __logfs_read_sb(struct super_block *sb)
 407 {
 408         struct logfs_super *super = logfs_super(sb);
 409         struct page *page;
 410         struct logfs_disk_super *ds;
 411         int i;
 412
 413         page = find_super_block(sb);
 414         if (!page)
 415                 return -EIO;
 416
 417         ds = page_address(page);
 418         super->s_size = be64_to_cpu(ds->ds_filesystem_size);
 419         super->s_root_reserve = be64_to_cpu(ds->ds_root_reserve);
 420         super->s_speed_reserve = be64_to_cpu(ds->ds_speed_reserve);
 421         super->s_bad_seg_reserve = be32_to_cpu(ds->ds_bad_seg_reserve);
 422         super->s_segsize = 1 << ds->ds_segment_shift;
 423         super->s_segmask = (1 << ds->ds_segment_shift) - 1;
 424         super->s_segshift = ds->ds_segment_shift;
 425         sb->s_blocksize = 1 << ds->ds_block_shift;
 426         sb->s_blocksize_bits = ds->ds_block_shift;
 427         super->s_writesize = 1 << ds->ds_write_shift;
 428         super->s_writeshift = ds->ds_write_shift;
 429         super->s_no_segs = super->s_size >> super->s_segshift;
 430         super->s_no_blocks = super->s_segsize >> sb->s_blocksize_bits;
 431         super->s_feature_incompat = be64_to_cpu(ds->ds_feature_incompat);
 432         super->s_feature_ro_compat = be64_to_cpu(ds->ds_feature_ro_compat);
 433         super->s_feature_compat = be64_to_cpu(ds->ds_feature_compat);
 434         super->s_feature_flags = be64_to_cpu(ds->ds_feature_flags);
 435
 436         journal_for_each(i)
 437                 super->s_journal_seg[i] = be32_to_cpu(ds->ds_journal_seg[i]);
 438
 439         super->s_ifile_levels = ds->ds_ifile_levels;
 440         super->s_iblock_levels = ds->ds_iblock_levels;
 441         super->s_data_levels = ds->ds_data_levels;
 442         super->s_total_levels = super->s_ifile_levels + super->s_iblock_levels
 443                 + super->s_data_levels;
 444         page_cache_release(page);
 445         return 0;
 446 }
 447
 448 static int logfs_read_sb(struct super_block *sb, int read_only)
 449 {
 450         struct logfs_super *super = logfs_super(sb);
 451         int ret;
 452
 453         super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
 454         if (!super->s_btree_pool)
 455                 return -ENOMEM;
 456
 457         btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
 458         btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
 459         btree_init_mempool32(&super->s_shadow_tree.segment_map,
 460                         super->s_btree_pool);
 461
 462         ret = logfs_init_mapping(sb);
 463         if (ret)
 464                 return ret;
 465
 466         ret = __logfs_read_sb(sb);
 467         if (ret)
 468                 return ret;
 469
 470         if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
 471                 return -EIO;
 472         if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
 473                         !read_only)
 474                 return -EIO;
 475
 476         mutex_init(&super->s_dirop_mutex);
 477         mutex_init(&super->s_object_alias_mutex);
 478         INIT_LIST_HEAD(&super->s_freeing_list);
 479
 480         ret = logfs_init_rw(sb);
 481         if (ret)
 482                 return ret;
 483
 484         ret = logfs_init_areas(sb);
 485         if (ret)
 486                 return ret;
 487
 488         ret = logfs_init_gc(sb);
 489         if (ret)
 490                 return ret;
 491
 492         ret = logfs_init_journal(sb);
 493         if (ret)
 494                 return ret;
 495
 496         return 0;
 497 }
 498
 499 static void logfs_kill_sb(struct super_block *sb)
 500 {
 501         struct logfs_super *super = logfs_super(sb);
 502
 503         log_super("LogFS: Start unmounting\n");
 504         /* Alias entries slow down mount, so evict as many as possible */
 505         sync_filesystem(sb);
 506         logfs_write_anchor(sb);
 507
 508         /*
 509          * From this point on alias entries are simply dropped - and any
 510          * writes to the object store are considered bugs.
 511          */
 512         super->s_flags |= LOGFS_SB_FLAG_SHUTDOWN;
 513         log_super("LogFS: Now in shutdown\n");
 514         generic_shutdown_super(sb);
 515
 516         BUG_ON(super->s_dirty_used_bytes || super->s_dirty_free_bytes);
 517
 518         logfs_cleanup_gc(sb);
 519         logfs_cleanup_journal(sb);
 520         logfs_cleanup_areas(sb);
 521         logfs_cleanup_rw(sb);
 522         if (super->s_erase_page)
 523                 __free_page(super->s_erase_page);
 524         super->s_devops->put_device(sb);
 525         logfs_mempool_destroy(super->s_btree_pool);
 526         logfs_mempool_destroy(super->s_alias_pool);
 527         kfree(super);
 528         log_super("LogFS: Finished unmounting\n");
 529 }
 530
 531 int logfs_get_sb_device(struct file_system_type *type, int flags,
 532                 struct mtd_info *mtd, struct block_device *bdev,
 533                 const struct logfs_device_ops *devops, struct vfsmount *mnt)
 534 {
 535         struct logfs_super *super;
 536         struct super_block *sb;
 537         int err = -ENOMEM;
 538         static int mount_count;
 539
 540         log_super("LogFS: Start mount %x\n", mount_count++);
 541         super = kzalloc(sizeof(*super), GFP_KERNEL);
 542         if (!super)
 543                 goto err0;
 544
 545         super->s_mtd    = mtd;
 546         super->s_bdev   = bdev;
 547         err = -EINVAL;
 548         sb = sget(type, logfs_sb_test, logfs_sb_set, super);
 549         if (IS_ERR(sb))
 550                 goto err0;
 551
 552         if (sb->s_root) {
 553                 /* Device is already in use */
 554                 err = 0;
 555                 simple_set_mnt(mnt, sb);
 556                 goto err0;
 557         }
 558
 559         super->s_devops = devops;
 560
 561         /*
 562          * sb->s_maxbytes is limited to 8TB.  On 32bit systems, the page cache
 563          * only covers 16TB and the upper 8TB are used for indirect blocks.
 564          * On 64bit system we could bump up the limit, but that would make
 565          * the filesystem incompatible with 32bit systems.
 566          */
 567         sb->s_maxbytes  = (1ull << 43) - 1;
 568         sb->s_op        = &logfs_super_operations;
 569         sb->s_flags     = flags | MS_NOATIME;
 570
 571         err = logfs_read_sb(sb, sb->s_flags & MS_RDONLY);
 572         if (err)
 573                 goto err1;
 574
 575         sb->s_flags |= MS_ACTIVE;
 576         err = logfs_get_sb_final(sb, mnt);
 577         if (err)
 578                 goto err1;
 579         return 0;
 580
 581 err1:
 582         deactivate_locked_super(sb);
 583         return err;
 584 err0:
 585         kfree(super);
 586         //devops->put_device(sb);
 587         return err;
 588 }
 589
 590 static int logfs_get_sb(struct file_system_type *type, int flags,
 591                 const char *devname, void *data, struct vfsmount *mnt)
 592 {
 593         ulong mtdnr;
 594
 595         if (!devname)
 596                 return logfs_get_sb_bdev(type, flags, devname, mnt);
 597         if (strncmp(devname, "mtd", 3))
 598                 return logfs_get_sb_bdev(type, flags, devname, mnt);
 599
 600         {
 601                 char *garbage;
 602                 mtdnr = simple_strtoul(devname+3, &garbage, 0);
 603                 if (*garbage)
 604                         return -EINVAL;
 605         }
 606
 607         return logfs_get_sb_mtd(type, flags, mtdnr, mnt);
 608 }
 609
 610 static struct file_system_type logfs_fs_type = {
 611         .owner          = THIS_MODULE,
 612         .name           = "logfs",
 613         .get_sb         = logfs_get_sb,
 614         .kill_sb        = logfs_kill_sb,
 615         .fs_flags       = FS_REQUIRES_DEV,
 616
 617 };
 618
 619 static int __init logfs_init(void)
 620 {
 621         int ret;
 622
 623         emergency_page = alloc_pages(GFP_KERNEL, 0);
 624         if (!emergency_page)
 625                 return -ENOMEM;
 626
 627         ret = logfs_compr_init();
 628         if (ret)
 629                 goto out1;
 630
 631         ret = logfs_init_inode_cache();
 632         if (ret)
 633                 goto out2;
 634
 635         return register_filesystem(&logfs_fs_type);
 636 out2:
 637         logfs_compr_exit();
 638 out1:
 639         __free_pages(emergency_page, 0);
 640         return ret;
 641 }
 642
 643 static void __exit logfs_exit(void)
 644 {
 645         unregister_filesystem(&logfs_fs_type);
 646         logfs_destroy_inode_cache();
 647         logfs_compr_exit();
 648         __free_pages(emergency_page, 0);
 649 }
 650
 651 module_init(logfs_init);
 652 module_exit(logfs_exit);
 653
 654 MODULE_LICENSE("GPL v2");
 655 MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
 656 MODULE_DESCRIPTION("scalable flash filesystem");