root/fs/romfs/super.c

DEFINITIONS

1. romfs_readpage
2. romfs_readdir
3. romfs_lookup
4. romfs_iget
5. romfs_alloc_inode
6. romfs_free_inode
7. romfs_statfs
8. romfs_reconfigure
9. romfs_checksum
10. romfs_fill_super
11. romfs_get_tree
12. romfs_init_fs_context
13. romfs_kill_sb
14. romfs_i_init_once
15. init_romfs_fs
16. exit_romfs_fs

   1 /* Block- or MTD-based romfs
   2  *
   3  * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * Derived from: ROMFS file system, Linux implementation
   7  *
   8  * Copyright © 1997-1999  Janos Farkas <chexum@shadow.banki.hu>
   9  *
  10  * Using parts of the minix filesystem
  11  * Copyright © 1991, 1992  Linus Torvalds
  12  *
  13  * and parts of the affs filesystem additionally
  14  * Copyright © 1993  Ray Burr
  15  * Copyright © 1996  Hans-Joachim Widmaier
  16  *
  17  * Changes
  18  *                                      Changed for 2.1.19 modules
  19  *      Jan 1997                        Initial release
  20  *      Jun 1997                        2.1.43+ changes
  21  *                                      Proper page locking in readpage
  22  *                                      Changed to work with 2.1.45+ fs
  23  *      Jul 1997                        Fixed follow_link
  24  *                      2.1.47
  25  *                                      lookup shouldn't return -ENOENT
  26  *                                      from Horst von Brand:
  27  *                                        fail on wrong checksum
  28  *                                        double unlock_super was possible
  29  *                                        correct namelen for statfs
  30  *                                      spotted by Bill Hawes:
  31  *                                        readlink shouldn't iput()
  32  *      Jun 1998        2.1.106         from Avery Pennarun: glibc scandir()
  33  *                                        exposed a problem in readdir
  34  *                      2.1.107         code-freeze spellchecker run
  35  *      Aug 1998                        2.1.118+ VFS changes
  36  *      Sep 1998        2.1.122         another VFS change (follow_link)
  37  *      Apr 1999        2.2.7           no more EBADF checking in
  38  *                                        lookup/readdir, use ERR_PTR
  39  *      Jun 1999        2.3.6           d_alloc_root use changed
  40  *                      2.3.9           clean up usage of ENOENT/negative
  41  *                                        dentries in lookup
  42  *                                      clean up page flags setting
  43  *                                        (error, uptodate, locking) in
  44  *                                        in readpage
  45  *                                      use init_special_inode for
  46  *                                        fifos/sockets (and streamline) in
  47  *                                        read_inode, fix _ops table order
  48  *      Aug 1999        2.3.16          __initfunc() => __init change
  49  *      Oct 1999        2.3.24          page->owner hack obsoleted
  50  *      Nov 1999        2.3.27          2.3.25+ page->offset => index change
  51  *
  52  *
  53  * This program is free software; you can redistribute it and/or
  54  * modify it under the terms of the GNU General Public Licence
  55  * as published by the Free Software Foundation; either version
  56  * 2 of the Licence, or (at your option) any later version.
  57  */
  58 
  59 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  60 
  61 #include <linux/module.h>
  62 #include <linux/string.h>
  63 #include <linux/fs.h>
  64 #include <linux/time.h>
  65 #include <linux/slab.h>
  66 #include <linux/init.h>
  67 #include <linux/blkdev.h>
  68 #include <linux/fs_context.h>
  69 #include <linux/mount.h>
  70 #include <linux/namei.h>
  71 #include <linux/statfs.h>
  72 #include <linux/mtd/super.h>
  73 #include <linux/ctype.h>
  74 #include <linux/highmem.h>
  75 #include <linux/pagemap.h>
  76 #include <linux/uaccess.h>
  77 #include <linux/major.h>
  78 #include "internal.h"
  79 
  80 static struct kmem_cache *romfs_inode_cachep;
  81 
  82 static const umode_t romfs_modemap[8] = {
  83         0,                      /* hard link */
  84         S_IFDIR  | 0644,        /* directory */
  85         S_IFREG  | 0644,        /* regular file */
  86         S_IFLNK  | 0777,        /* symlink */
  87         S_IFBLK  | 0600,        /* blockdev */
  88         S_IFCHR  | 0600,        /* chardev */
  89         S_IFSOCK | 0644,        /* socket */
  90         S_IFIFO  | 0644         /* FIFO */
  91 };
  92 
  93 static const unsigned char romfs_dtype_table[] = {
  94         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
  95 };
  96 
  97 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
  98 
  99 /*
 100  * read a page worth of data from the image
 101  */
 102 static int romfs_readpage(struct file *file, struct page *page)
 103 {
 104         struct inode *inode = page->mapping->host;
 105         loff_t offset, size;
 106         unsigned long fillsize, pos;
 107         void *buf;
 108         int ret;
 109 
 110         buf = kmap(page);
 111         if (!buf)
 112                 return -ENOMEM;
 113 
 114         /* 32 bit warning -- but not for us :) */
 115         offset = page_offset(page);
 116         size = i_size_read(inode);
 117         fillsize = 0;
 118         ret = 0;
 119         if (offset < size) {
 120                 size -= offset;
 121                 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
 122 
 123                 pos = ROMFS_I(inode)->i_dataoffset + offset;
 124 
 125                 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
 126                 if (ret < 0) {
 127                         SetPageError(page);
 128                         fillsize = 0;
 129                         ret = -EIO;
 130                 }
 131         }
 132 
 133         if (fillsize < PAGE_SIZE)
 134                 memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
 135         if (ret == 0)
 136                 SetPageUptodate(page);
 137 
 138         flush_dcache_page(page);
 139         kunmap(page);
 140         unlock_page(page);
 141         return ret;
 142 }
 143 
 144 static const struct address_space_operations romfs_aops = {
 145         .readpage       = romfs_readpage
 146 };
 147 
 148 /*
 149  * read the entries from a directory
 150  */
 151 static int romfs_readdir(struct file *file, struct dir_context *ctx)
 152 {
 153         struct inode *i = file_inode(file);
 154         struct romfs_inode ri;
 155         unsigned long offset, maxoff;
 156         int j, ino, nextfh;
 157         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 158         int ret;
 159 
 160         maxoff = romfs_maxsize(i->i_sb);
 161 
 162         offset = ctx->pos;
 163         if (!offset) {
 164                 offset = i->i_ino & ROMFH_MASK;
 165                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 166                 if (ret < 0)
 167                         goto out;
 168                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 169         }
 170 
 171         /* Not really failsafe, but we are read-only... */
 172         for (;;) {
 173                 if (!offset || offset >= maxoff) {
 174                         offset = maxoff;
 175                         ctx->pos = offset;
 176                         goto out;
 177                 }
 178                 ctx->pos = offset;
 179 
 180                 /* Fetch inode info */
 181                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 182                 if (ret < 0)
 183                         goto out;
 184 
 185                 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
 186                                       sizeof(fsname) - 1);
 187                 if (j < 0)
 188                         goto out;
 189 
 190                 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
 191                 if (ret < 0)
 192                         goto out;
 193                 fsname[j] = '\0';
 194 
 195                 ino = offset;
 196                 nextfh = be32_to_cpu(ri.next);
 197                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 198                         ino = be32_to_cpu(ri.spec);
 199                 if (!dir_emit(ctx, fsname, j, ino,
 200                             romfs_dtype_table[nextfh & ROMFH_TYPE]))
 201                         goto out;
 202 
 203                 offset = nextfh & ROMFH_MASK;
 204         }
 205 out:
 206         return 0;
 207 }
 208 
 209 /*
 210  * look up an entry in a directory
 211  */
 212 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 213                                    unsigned int flags)
 214 {
 215         unsigned long offset, maxoff;
 216         struct inode *inode = NULL;
 217         struct romfs_inode ri;
 218         const char *name;               /* got from dentry */
 219         int len, ret;
 220 
 221         offset = dir->i_ino & ROMFH_MASK;
 222         ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
 223         if (ret < 0)
 224                 goto error;
 225 
 226         /* search all the file entries in the list starting from the one
 227          * pointed to by the directory's special data */
 228         maxoff = romfs_maxsize(dir->i_sb);
 229         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 230 
 231         name = dentry->d_name.name;
 232         len = dentry->d_name.len;
 233 
 234         for (;;) {
 235                 if (!offset || offset >= maxoff)
 236                         break;
 237 
 238                 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
 239                 if (ret < 0)
 240                         goto error;
 241 
 242                 /* try to match the first 16 bytes of name */
 243                 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
 244                                        len);
 245                 if (ret < 0)
 246                         goto error;
 247                 if (ret == 1) {
 248                         /* Hard link handling */
 249                         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 250                                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 251                         inode = romfs_iget(dir->i_sb, offset);
 252                         break;
 253                 }
 254 
 255                 /* next entry */
 256                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 257         }
 258 
 259         return d_splice_alias(inode, dentry);
 260 error:
 261         return ERR_PTR(ret);
 262 }
 263 
 264 static const struct file_operations romfs_dir_operations = {
 265         .read           = generic_read_dir,
 266         .iterate_shared = romfs_readdir,
 267         .llseek         = generic_file_llseek,
 268 };
 269 
 270 static const struct inode_operations romfs_dir_inode_operations = {
 271         .lookup         = romfs_lookup,
 272 };
 273 
 274 /*
 275  * get a romfs inode based on its position in the image (which doubles as the
 276  * inode number)
 277  */
 278 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
 279 {
 280         struct romfs_inode_info *inode;
 281         struct romfs_inode ri;
 282         struct inode *i;
 283         unsigned long nlen;
 284         unsigned nextfh;
 285         int ret;
 286         umode_t mode;
 287 
 288         /* we might have to traverse a chain of "hard link" file entries to get
 289          * to the actual file */
 290         for (;;) {
 291                 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
 292                 if (ret < 0)
 293                         goto error;
 294 
 295                 /* XXX: do romfs_checksum here too (with name) */
 296 
 297                 nextfh = be32_to_cpu(ri.next);
 298                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 299                         break;
 300 
 301                 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
 302         }
 303 
 304         /* determine the length of the filename */
 305         nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
 306         if (IS_ERR_VALUE(nlen))
 307                 goto eio;
 308 
 309         /* get an inode for this image position */
 310         i = iget_locked(sb, pos);
 311         if (!i)
 312                 return ERR_PTR(-ENOMEM);
 313 
 314         if (!(i->i_state & I_NEW))
 315                 return i;
 316 
 317         /* precalculate the data offset */
 318         inode = ROMFS_I(i);
 319         inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
 320         inode->i_dataoffset = pos + inode->i_metasize;
 321 
 322         set_nlink(i, 1);                /* Hard to decide.. */
 323         i->i_size = be32_to_cpu(ri.size);
 324         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
 325         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
 326 
 327         /* set up mode and ops */
 328         mode = romfs_modemap[nextfh & ROMFH_TYPE];
 329 
 330         switch (nextfh & ROMFH_TYPE) {
 331         case ROMFH_DIR:
 332                 i->i_size = ROMFS_I(i)->i_metasize;
 333                 i->i_op = &romfs_dir_inode_operations;
 334                 i->i_fop = &romfs_dir_operations;
 335                 if (nextfh & ROMFH_EXEC)
 336                         mode |= S_IXUGO;
 337                 break;
 338         case ROMFH_REG:
 339                 i->i_fop = &romfs_ro_fops;
 340                 i->i_data.a_ops = &romfs_aops;
 341                 if (nextfh & ROMFH_EXEC)
 342                         mode |= S_IXUGO;
 343                 break;
 344         case ROMFH_SYM:
 345                 i->i_op = &page_symlink_inode_operations;
 346                 inode_nohighmem(i);
 347                 i->i_data.a_ops = &romfs_aops;
 348                 mode |= S_IRWXUGO;
 349                 break;
 350         default:
 351                 /* depending on MBZ for sock/fifos */
 352                 nextfh = be32_to_cpu(ri.spec);
 353                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
 354                                                   nextfh & 0xffff));
 355                 break;
 356         }
 357 
 358         i->i_mode = mode;
 359 
 360         unlock_new_inode(i);
 361         return i;
 362 
 363 eio:
 364         ret = -EIO;
 365 error:
 366         pr_err("read error for inode 0x%lx\n", pos);
 367         return ERR_PTR(ret);
 368 }
 369 
 370 /*
 371  * allocate a new inode
 372  */
 373 static struct inode *romfs_alloc_inode(struct super_block *sb)
 374 {
 375         struct romfs_inode_info *inode;
 376 
 377         inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 378         return inode ? &inode->vfs_inode : NULL;
 379 }
 380 
 381 /*
 382  * return a spent inode to the slab cache
 383  */
 384 static void romfs_free_inode(struct inode *inode)
 385 {
 386         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 387 }
 388 
 389 /*
 390  * get filesystem statistics
 391  */
 392 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 393 {
 394         struct super_block *sb = dentry->d_sb;
 395         u64 id = 0;
 396 
 397         /* When calling huge_encode_dev(),
 398          * use sb->s_bdev->bd_dev when,
 399          *   - CONFIG_ROMFS_ON_BLOCK defined
 400          * use sb->s_dev when,
 401          *   - CONFIG_ROMFS_ON_BLOCK undefined and
 402          *   - CONFIG_ROMFS_ON_MTD defined
 403          * leave id as 0 when,
 404          *   - CONFIG_ROMFS_ON_BLOCK undefined and
 405          *   - CONFIG_ROMFS_ON_MTD undefined
 406          */
 407         if (sb->s_bdev)
 408                 id = huge_encode_dev(sb->s_bdev->bd_dev);
 409         else if (sb->s_dev)
 410                 id = huge_encode_dev(sb->s_dev);
 411 
 412         buf->f_type = ROMFS_MAGIC;
 413         buf->f_namelen = ROMFS_MAXFN;
 414         buf->f_bsize = ROMBSIZE;
 415         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 416         buf->f_blocks =
 417                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
 418         buf->f_fsid.val[0] = (u32)id;
 419         buf->f_fsid.val[1] = (u32)(id >> 32);
 420         return 0;
 421 }
 422 
 423 /*
 424  * remounting must involve read-only
 425  */
 426 static int romfs_reconfigure(struct fs_context *fc)
 427 {
 428         sync_filesystem(fc->root->d_sb);
 429         fc->sb_flags |= SB_RDONLY;
 430         return 0;
 431 }
 432 
 433 static const struct super_operations romfs_super_ops = {
 434         .alloc_inode    = romfs_alloc_inode,
 435         .free_inode     = romfs_free_inode,
 436         .statfs         = romfs_statfs,
 437 };
 438 
 439 /*
 440  * checksum check on part of a romfs filesystem
 441  */
 442 static __u32 romfs_checksum(const void *data, int size)
 443 {
 444         const __be32 *ptr = data;
 445         __u32 sum;
 446 
 447         sum = 0;
 448         size >>= 2;
 449         while (size > 0) {
 450                 sum += be32_to_cpu(*ptr++);
 451                 size--;
 452         }
 453         return sum;
 454 }
 455 
 456 /*
 457  * fill in the superblock
 458  */
 459 static int romfs_fill_super(struct super_block *sb, struct fs_context *fc)
 460 {
 461         struct romfs_super_block *rsb;
 462         struct inode *root;
 463         unsigned long pos, img_size;
 464         const char *storage;
 465         size_t len;
 466         int ret;
 467 
 468 #ifdef CONFIG_BLOCK
 469         if (!sb->s_mtd) {
 470                 sb_set_blocksize(sb, ROMBSIZE);
 471         } else {
 472                 sb->s_blocksize = ROMBSIZE;
 473                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
 474         }
 475 #endif
 476 
 477         sb->s_maxbytes = 0xFFFFFFFF;
 478         sb->s_magic = ROMFS_MAGIC;
 479         sb->s_flags |= SB_RDONLY | SB_NOATIME;
 480         sb->s_time_min = 0;
 481         sb->s_time_max = 0;
 482         sb->s_op = &romfs_super_ops;
 483 
 484 #ifdef CONFIG_ROMFS_ON_MTD
 485         /* Use same dev ID from the underlying mtdblock device */
 486         if (sb->s_mtd)
 487                 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
 488 #endif
 489         /* read the image superblock and check it */
 490         rsb = kmalloc(512, GFP_KERNEL);
 491         if (!rsb)
 492                 return -ENOMEM;
 493 
 494         sb->s_fs_info = (void *) 512;
 495         ret = romfs_dev_read(sb, 0, rsb, 512);
 496         if (ret < 0)
 497                 goto error_rsb;
 498 
 499         img_size = be32_to_cpu(rsb->size);
 500 
 501         if (sb->s_mtd && img_size > sb->s_mtd->size)
 502                 goto error_rsb_inval;
 503 
 504         sb->s_fs_info = (void *) img_size;
 505 
 506         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
 507             img_size < ROMFH_SIZE) {
 508                 if (!(fc->sb_flags & SB_SILENT))
 509                         errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n",
 510                                sb->s_id);
 511                 goto error_rsb_inval;
 512         }
 513 
 514         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
 515                 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
 516                 goto error_rsb_inval;
 517         }
 518 
 519         storage = sb->s_mtd ? "MTD" : "the block layer";
 520 
 521         len = strnlen(rsb->name, ROMFS_MAXFN);
 522         if (!(fc->sb_flags & SB_SILENT))
 523                 pr_notice("Mounting image '%*.*s' through %s\n",
 524                           (unsigned) len, (unsigned) len, rsb->name, storage);
 525 
 526         kfree(rsb);
 527         rsb = NULL;
 528 
 529         /* find the root directory */
 530         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 531 
 532         root = romfs_iget(sb, pos);
 533         if (IS_ERR(root))
 534                 return PTR_ERR(root);
 535 
 536         sb->s_root = d_make_root(root);
 537         if (!sb->s_root)
 538                 return -ENOMEM;
 539 
 540         return 0;
 541 
 542 error_rsb_inval:
 543         ret = -EINVAL;
 544 error_rsb:
 545         kfree(rsb);
 546         return ret;
 547 }
 548 
 549 /*
 550  * get a superblock for mounting
 551  */
 552 static int romfs_get_tree(struct fs_context *fc)
 553 {
 554         int ret = -EINVAL;
 555 
 556 #ifdef CONFIG_ROMFS_ON_MTD
 557         ret = get_tree_mtd(fc, romfs_fill_super);
 558 #endif
 559 #ifdef CONFIG_ROMFS_ON_BLOCK
 560         if (ret == -EINVAL)
 561                 ret = get_tree_bdev(fc, romfs_fill_super);
 562 #endif
 563         return ret;
 564 }
 565 
 566 static const struct fs_context_operations romfs_context_ops = {
 567         .get_tree       = romfs_get_tree,
 568         .reconfigure    = romfs_reconfigure,
 569 };
 570 
 571 /*
 572  * Set up the filesystem mount context.
 573  */
 574 static int romfs_init_fs_context(struct fs_context *fc)
 575 {
 576         fc->ops = &romfs_context_ops;
 577         return 0;
 578 }
 579 
 580 /*
 581  * destroy a romfs superblock in the appropriate manner
 582  */
 583 static void romfs_kill_sb(struct super_block *sb)
 584 {
 585 #ifdef CONFIG_ROMFS_ON_MTD
 586         if (sb->s_mtd) {
 587                 kill_mtd_super(sb);
 588                 return;
 589         }
 590 #endif
 591 #ifdef CONFIG_ROMFS_ON_BLOCK
 592         if (sb->s_bdev) {
 593                 kill_block_super(sb);
 594                 return;
 595         }
 596 #endif
 597 }
 598 
 599 static struct file_system_type romfs_fs_type = {
 600         .owner          = THIS_MODULE,
 601         .name           = "romfs",
 602         .init_fs_context = romfs_init_fs_context,
 603         .kill_sb        = romfs_kill_sb,
 604         .fs_flags       = FS_REQUIRES_DEV,
 605 };
 606 MODULE_ALIAS_FS("romfs");
 607 
 608 /*
 609  * inode storage initialiser
 610  */
 611 static void romfs_i_init_once(void *_inode)
 612 {
 613         struct romfs_inode_info *inode = _inode;
 614 
 615         inode_init_once(&inode->vfs_inode);
 616 }
 617 
 618 /*
 619  * romfs module initialisation
 620  */
 621 static int __init init_romfs_fs(void)
 622 {
 623         int ret;
 624 
 625         pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
 626 
 627         romfs_inode_cachep =
 628                 kmem_cache_create("romfs_i",
 629                                   sizeof(struct romfs_inode_info), 0,
 630                                   SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
 631                                   SLAB_ACCOUNT, romfs_i_init_once);
 632 
 633         if (!romfs_inode_cachep) {
 634                 pr_err("Failed to initialise inode cache\n");
 635                 return -ENOMEM;
 636         }
 637         ret = register_filesystem(&romfs_fs_type);
 638         if (ret) {
 639                 pr_err("Failed to register filesystem\n");
 640                 goto error_register;
 641         }
 642         return 0;
 643 
 644 error_register:
 645         kmem_cache_destroy(romfs_inode_cachep);
 646         return ret;
 647 }
 648 
 649 /*
 650  * romfs module removal
 651  */
 652 static void __exit exit_romfs_fs(void)
 653 {
 654         unregister_filesystem(&romfs_fs_type);
 655         /*
 656          * Make sure all delayed rcu free inodes are flushed before we
 657          * destroy cache.
 658          */
 659         rcu_barrier();
 660         kmem_cache_destroy(romfs_inode_cachep);
 661 }
 662 
 663 module_init(init_romfs_fs);
 664 module_exit(exit_romfs_fs);
 665 
 666 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
 667 MODULE_AUTHOR("Red Hat, Inc.");
 668 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */