fs/romfs/super.c

   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 #include <linux/module.h>
  60 #include <linux/string.h>
  61 #include <linux/fs.h>
  62 #include <linux/time.h>
  63 #include <linux/slab.h>
  64 #include <linux/init.h>
  65 #include <linux/blkdev.h>
  66 #include <linux/parser.h>
  67 #include <linux/mount.h>
  68 #include <linux/namei.h>
  69 #include <linux/statfs.h>
  70 #include <linux/mtd/super.h>
  71 #include <linux/ctype.h>
  72 #include <linux/highmem.h>
  73 #include <linux/pagemap.h>
  74 #include <linux/uaccess.h>
  75 #include "internal.h"
  76
  77 static struct kmem_cache *romfs_inode_cachep;
  78
  79 static const umode_t romfs_modemap[8] = {
  80         0,                      /* hard link */
  81         S_IFDIR  | 0644,        /* directory */
  82         S_IFREG  | 0644,        /* regular file */
  83         S_IFLNK  | 0777,        /* symlink */
  84         S_IFBLK  | 0600,        /* blockdev */
  85         S_IFCHR  | 0600,        /* chardev */
  86         S_IFSOCK | 0644,        /* socket */
  87         S_IFIFO  | 0644         /* FIFO */
  88 };
  89
  90 static const unsigned char romfs_dtype_table[] = {
  91         DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
  92 };
  93
  94 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
  95
  96 /*
  97  * read a page worth of data from the image
  98  */
  99 static int romfs_readpage(struct file *file, struct page *page)
 100 {
 101         struct inode *inode = page->mapping->host;
 102         loff_t offset, size;
 103         unsigned long fillsize, pos;
 104         void *buf;
 105         int ret;
 106
 107         buf = kmap(page);
 108         if (!buf)
 109                 return -ENOMEM;
 110
 111         /* 32 bit warning -- but not for us :) */
 112         offset = page_offset(page);
 113         size = i_size_read(inode);
 114         fillsize = 0;
 115         ret = 0;
 116         if (offset < size) {
 117                 size -= offset;
 118                 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
 119
 120                 pos = ROMFS_I(inode)->i_dataoffset + offset;
 121
 122                 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
 123                 if (ret < 0) {
 124                         SetPageError(page);
 125                         fillsize = 0;
 126                         ret = -EIO;
 127                 }
 128         }
 129
 130         if (fillsize < PAGE_SIZE)
 131                 memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
 132         if (ret == 0)
 133                 SetPageUptodate(page);
 134
 135         flush_dcache_page(page);
 136         kunmap(page);
 137         unlock_page(page);
 138         return ret;
 139 }
 140
 141 static const struct address_space_operations romfs_aops = {
 142         .readpage       = romfs_readpage
 143 };
 144
 145 /*
 146  * read the entries from a directory
 147  */
 148 static int romfs_readdir(struct file *file, struct dir_context *ctx)
 149 {
 150         struct inode *i = file_inode(file);
 151         struct romfs_inode ri;
 152         unsigned long offset, maxoff;
 153         int j, ino, nextfh;
 154         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 155         int ret;
 156
 157         maxoff = romfs_maxsize(i->i_sb);
 158
 159         offset = ctx->pos;
 160         if (!offset) {
 161                 offset = i->i_ino & ROMFH_MASK;
 162                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 163                 if (ret < 0)
 164                         goto out;
 165                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 166         }
 167
 168         /* Not really failsafe, but we are read-only... */
 169         for (;;) {
 170                 if (!offset || offset >= maxoff) {
 171                         offset = maxoff;
 172                         ctx->pos = offset;
 173                         goto out;
 174                 }
 175                 ctx->pos = offset;
 176
 177                 /* Fetch inode info */
 178                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 179                 if (ret < 0)
 180                         goto out;
 181
 182                 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
 183                                       sizeof(fsname) - 1);
 184                 if (j < 0)
 185                         goto out;
 186
 187                 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
 188                 if (ret < 0)
 189                         goto out;
 190                 fsname[j] = '\0';
 191
 192                 ino = offset;
 193                 nextfh = be32_to_cpu(ri.next);
 194                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 195                         ino = be32_to_cpu(ri.spec);
 196                 if (!dir_emit(ctx, fsname, j, ino,
 197                             romfs_dtype_table[nextfh & ROMFH_TYPE]))
 198                         goto out;
 199
 200                 offset = nextfh & ROMFH_MASK;
 201         }
 202 out:
 203         return 0;
 204 }
 205
 206 /*
 207  * look up an entry in a directory
 208  */
 209 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 210                                    unsigned int flags)
 211 {
 212         unsigned long offset, maxoff;
 213         struct inode *inode;
 214         struct romfs_inode ri;
 215         const char *name;               /* got from dentry */
 216         int len, ret;
 217
 218         offset = dir->i_ino & ROMFH_MASK;
 219         ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
 220         if (ret < 0)
 221                 goto error;
 222
 223         /* search all the file entries in the list starting from the one
 224          * pointed to by the directory's special data */
 225         maxoff = romfs_maxsize(dir->i_sb);
 226         offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 227
 228         name = dentry->d_name.name;
 229         len = dentry->d_name.len;
 230
 231         for (;;) {
 232                 if (!offset || offset >= maxoff)
 233                         goto out0;
 234
 235                 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
 236                 if (ret < 0)
 237                         goto error;
 238
 239                 /* try to match the first 16 bytes of name */
 240                 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
 241                                        len);
 242                 if (ret < 0)
 243                         goto error;
 244                 if (ret == 1)
 245                         break;
 246
 247                 /* next entry */
 248                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 249         }
 250
 251         /* Hard link handling */
 252         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 253                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 254
 255         inode = romfs_iget(dir->i_sb, offset);
 256         if (IS_ERR(inode)) {
 257                 ret = PTR_ERR(inode);
 258                 goto error;
 259         }
 260         goto outi;
 261
 262         /*
 263          * it's a bit funky, _lookup needs to return an error code
 264          * (negative) or a NULL, both as a dentry.  ENOENT should not
 265          * be returned, instead we need to create a negative dentry by
 266          * d_add(dentry, NULL); and return 0 as no error.
 267          * (Although as I see, it only matters on writable file
 268          * systems).
 269          */
 270 out0:
 271         inode = NULL;
 272 outi:
 273         d_add(dentry, inode);
 274         ret = 0;
 275 error:
 276         return ERR_PTR(ret);
 277 }
 278
 279 static const struct file_operations romfs_dir_operations = {
 280         .read           = generic_read_dir,
 281         .iterate        = romfs_readdir,
 282         .llseek         = default_llseek,
 283 };
 284
 285 static const struct inode_operations romfs_dir_inode_operations = {
 286         .lookup         = romfs_lookup,
 287 };
 288
 289 /*
 290  * get a romfs inode based on its position in the image (which doubles as the
 291  * inode number)
 292  */
 293 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
 294 {
 295         struct romfs_inode_info *inode;
 296         struct romfs_inode ri;
 297         struct inode *i;
 298         unsigned long nlen;
 299         unsigned nextfh;
 300         int ret;
 301         umode_t mode;
 302
 303         /* we might have to traverse a chain of "hard link" file entries to get
 304          * to the actual file */
 305         for (;;) {
 306                 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
 307                 if (ret < 0)
 308                         goto error;
 309
 310                 /* XXX: do romfs_checksum here too (with name) */
 311
 312                 nextfh = be32_to_cpu(ri.next);
 313                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 314                         break;
 315
 316                 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
 317         }
 318
 319         /* determine the length of the filename */
 320         nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
 321         if (IS_ERR_VALUE(nlen))
 322                 goto eio;
 323
 324         /* get an inode for this image position */
 325         i = iget_locked(sb, pos);
 326         if (!i)
 327                 return ERR_PTR(-ENOMEM);
 328
 329         if (!(i->i_state & I_NEW))
 330                 return i;
 331
 332         /* precalculate the data offset */
 333         inode = ROMFS_I(i);
 334         inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
 335         inode->i_dataoffset = pos + inode->i_metasize;
 336
 337         set_nlink(i, 1);                /* Hard to decide.. */
 338         i->i_size = be32_to_cpu(ri.size);
 339         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
 340         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
 341
 342         /* set up mode and ops */
 343         mode = romfs_modemap[nextfh & ROMFH_TYPE];
 344
 345         switch (nextfh & ROMFH_TYPE) {
 346         case ROMFH_DIR:
 347                 i->i_size = ROMFS_I(i)->i_metasize;
 348                 i->i_op = &romfs_dir_inode_operations;
 349                 i->i_fop = &romfs_dir_operations;
 350                 if (nextfh & ROMFH_EXEC)
 351                         mode |= S_IXUGO;
 352                 break;
 353         case ROMFH_REG:
 354                 i->i_fop = &romfs_ro_fops;
 355                 i->i_data.a_ops = &romfs_aops;
 356                 if (i->i_sb->s_mtd)
 357                         i->i_data.backing_dev_info =
 358                                 i->i_sb->s_mtd->backing_dev_info;
 359                 if (nextfh & ROMFH_EXEC)
 360                         mode |= S_IXUGO;
 361                 break;
 362         case ROMFH_SYM:
 363                 i->i_op = &page_symlink_inode_operations;
 364                 i->i_data.a_ops = &romfs_aops;
 365                 mode |= S_IRWXUGO;
 366                 break;
 367         default:
 368                 /* depending on MBZ for sock/fifos */
 369                 nextfh = be32_to_cpu(ri.spec);
 370                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
 371                                                   nextfh & 0xffff));
 372                 break;
 373         }
 374
 375         i->i_mode = mode;
 376
 377         unlock_new_inode(i);
 378         return i;
 379
 380 eio:
 381         ret = -EIO;
 382 error:
 383         printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
 384         return ERR_PTR(ret);
 385 }
 386
 387 /*
 388  * allocate a new inode
 389  */
 390 static struct inode *romfs_alloc_inode(struct super_block *sb)
 391 {
 392         struct romfs_inode_info *inode;
 393         inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 394         return inode ? &inode->vfs_inode : NULL;
 395 }
 396
 397 /*
 398  * return a spent inode to the slab cache
 399  */
 400 static void romfs_i_callback(struct rcu_head *head)
 401 {
 402         struct inode *inode = container_of(head, struct inode, i_rcu);
 403         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 404 }
 405
 406 static void romfs_destroy_inode(struct inode *inode)
 407 {
 408         call_rcu(&inode->i_rcu, romfs_i_callback);
 409 }
 410
 411 /*
 412  * get filesystem statistics
 413  */
 414 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 415 {
 416         struct super_block *sb = dentry->d_sb;
 417         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 418
 419         buf->f_type = ROMFS_MAGIC;
 420         buf->f_namelen = ROMFS_MAXFN;
 421         buf->f_bsize = ROMBSIZE;
 422         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 423         buf->f_blocks =
 424                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
 425         buf->f_fsid.val[0] = (u32)id;
 426         buf->f_fsid.val[1] = (u32)(id >> 32);
 427         return 0;
 428 }
 429
 430 /*
 431  * remounting must involve read-only
 432  */
 433 static int romfs_remount(struct super_block *sb, int *flags, char *data)
 434 {
 435         *flags |= MS_RDONLY;
 436         return 0;
 437 }
 438
 439 static const struct super_operations romfs_super_ops = {
 440         .alloc_inode    = romfs_alloc_inode,
 441         .destroy_inode  = romfs_destroy_inode,
 442         .statfs         = romfs_statfs,
 443         .remount_fs     = romfs_remount,
 444 };
 445
 446 /*
 447  * checksum check on part of a romfs filesystem
 448  */
 449 static __u32 romfs_checksum(const void *data, int size)
 450 {
 451         const __be32 *ptr = data;
 452         __u32 sum;
 453
 454         sum = 0;
 455         size >>= 2;
 456         while (size > 0) {
 457                 sum += be32_to_cpu(*ptr++);
 458                 size--;
 459         }
 460         return sum;
 461 }
 462
 463 /*
 464  * fill in the superblock
 465  */
 466 static int romfs_fill_super(struct super_block *sb, void *data, int silent)
 467 {
 468         struct romfs_super_block *rsb;
 469         struct inode *root;
 470         unsigned long pos, img_size;
 471         const char *storage;
 472         size_t len;
 473         int ret;
 474
 475 #ifdef CONFIG_BLOCK
 476         if (!sb->s_mtd) {
 477                 sb_set_blocksize(sb, ROMBSIZE);
 478         } else {
 479                 sb->s_blocksize = ROMBSIZE;
 480                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
 481         }
 482 #endif
 483
 484         sb->s_maxbytes = 0xFFFFFFFF;
 485         sb->s_magic = ROMFS_MAGIC;
 486         sb->s_flags |= MS_RDONLY | MS_NOATIME;
 487         sb->s_op = &romfs_super_ops;
 488
 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 (!silent)
 509                         printk(KERN_WARNING "VFS:"
 510                                " Can't find a romfs filesystem on dev %s.\n",
 511                                sb->s_id);
 512                 goto error_rsb_inval;
 513         }
 514
 515         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
 516                 printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
 517                        sb->s_id);
 518                 goto error_rsb_inval;
 519         }
 520
 521         storage = sb->s_mtd ? "MTD" : "the block layer";
 522
 523         len = strnlen(rsb->name, ROMFS_MAXFN);
 524         if (!silent)
 525                 printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
 526                        (unsigned) len, (unsigned) len, rsb->name, storage);
 527
 528         kfree(rsb);
 529         rsb = NULL;
 530
 531         /* find the root directory */
 532         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 533
 534         root = romfs_iget(sb, pos);
 535         if (IS_ERR(root))
 536                 goto error;
 537
 538         sb->s_root = d_make_root(root);
 539         if (!sb->s_root)
 540                 goto error;
 541
 542         return 0;
 543
 544 error:
 545         return -EINVAL;
 546 error_rsb_inval:
 547         ret = -EINVAL;
 548 error_rsb:
 549         kfree(rsb);
 550         return ret;
 551 }
 552
 553 /*
 554  * get a superblock for mounting
 555  */
 556 static struct dentry *romfs_mount(struct file_system_type *fs_type,
 557                         int flags, const char *dev_name,
 558                         void *data)
 559 {
 560         struct dentry *ret = ERR_PTR(-EINVAL);
 561
 562 #ifdef CONFIG_ROMFS_ON_MTD
 563         ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
 564 #endif
 565 #ifdef CONFIG_ROMFS_ON_BLOCK
 566         if (ret == ERR_PTR(-EINVAL))
 567                 ret = mount_bdev(fs_type, flags, dev_name, data,
 568                                   romfs_fill_super);
 569 #endif
 570         return ret;
 571 }
 572
 573 /*
 574  * destroy a romfs superblock in the appropriate manner
 575  */
 576 static void romfs_kill_sb(struct super_block *sb)
 577 {
 578 #ifdef CONFIG_ROMFS_ON_MTD
 579         if (sb->s_mtd) {
 580                 kill_mtd_super(sb);
 581                 return;
 582         }
 583 #endif
 584 #ifdef CONFIG_ROMFS_ON_BLOCK
 585         if (sb->s_bdev) {
 586                 kill_block_super(sb);
 587                 return;
 588         }
 589 #endif
 590 }
 591
 592 static struct file_system_type romfs_fs_type = {
 593         .owner          = THIS_MODULE,
 594         .name           = "romfs",
 595         .mount          = romfs_mount,
 596         .kill_sb        = romfs_kill_sb,
 597         .fs_flags       = FS_REQUIRES_DEV,
 598 };
 599 MODULE_ALIAS_FS("romfs");
 600
 601 /*
 602  * inode storage initialiser
 603  */
 604 static void romfs_i_init_once(void *_inode)
 605 {
 606         struct romfs_inode_info *inode = _inode;
 607
 608         inode_init_once(&inode->vfs_inode);
 609 }
 610
 611 /*
 612  * romfs module initialisation
 613  */
 614 static int __init init_romfs_fs(void)
 615 {
 616         int ret;
 617
 618         printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
 619
 620         romfs_inode_cachep =
 621                 kmem_cache_create("romfs_i",
 622                                   sizeof(struct romfs_inode_info), 0,
 623                                   SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
 624                                   romfs_i_init_once);
 625
 626         if (!romfs_inode_cachep) {
 627                 printk(KERN_ERR
 628                        "ROMFS error: Failed to initialise inode cache\n");
 629                 return -ENOMEM;
 630         }
 631         ret = register_filesystem(&romfs_fs_type);
 632         if (ret) {
 633                 printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");
 634                 goto error_register;
 635         }
 636         return 0;
 637
 638 error_register:
 639         kmem_cache_destroy(romfs_inode_cachep);
 640         return ret;
 641 }
 642
 643 /*
 644  * romfs module removal
 645  */
 646 static void __exit exit_romfs_fs(void)
 647 {
 648         unregister_filesystem(&romfs_fs_type);
 649         /*
 650          * Make sure all delayed rcu free inodes are flushed before we
 651          * destroy cache.
 652          */
 653         rcu_barrier();
 654         kmem_cache_destroy(romfs_inode_cachep);
 655 }
 656
 657 module_init(init_romfs_fs);
 658 module_exit(exit_romfs_fs);
 659
 660 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
 661 MODULE_AUTHOR("Red Hat, Inc.");
 662 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */