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 *filp, void *dirent, filldir_t filldir)
 149 {
 150         struct inode *i = file_inode(filp);
 151         struct romfs_inode ri;
 152         unsigned long offset, maxoff;
 153         int j, ino, nextfh;
 154         int stored = 0;
 155         char fsname[ROMFS_MAXFN];       /* XXX dynamic? */
 156         int ret;
 157
 158         maxoff = romfs_maxsize(i->i_sb);
 159
 160         offset = filp->f_pos;
 161         if (!offset) {
 162                 offset = i->i_ino & ROMFH_MASK;
 163                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 164                 if (ret < 0)
 165                         goto out;
 166                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 167         }
 168
 169         /* Not really failsafe, but we are read-only... */
 170         for (;;) {
 171                 if (!offset || offset >= maxoff) {
 172                         offset = maxoff;
 173                         filp->f_pos = offset;
 174                         goto out;
 175                 }
 176                 filp->f_pos = offset;
 177
 178                 /* Fetch inode info */
 179                 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
 180                 if (ret < 0)
 181                         goto out;
 182
 183                 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
 184                                       sizeof(fsname) - 1);
 185                 if (j < 0)
 186                         goto out;
 187
 188                 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
 189                 if (ret < 0)
 190                         goto out;
 191                 fsname[j] = '\0';
 192
 193                 ino = offset;
 194                 nextfh = be32_to_cpu(ri.next);
 195                 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
 196                         ino = be32_to_cpu(ri.spec);
 197                 if (filldir(dirent, fsname, j, offset, ino,
 198                             romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0)
 199                         goto out;
 200
 201                 stored++;
 202                 offset = nextfh & ROMFH_MASK;
 203         }
 204
 205 out:
 206         return stored;
 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;
 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                         goto out0;
 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                         break;
 249
 250                 /* next entry */
 251                 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
 252         }
 253
 254         /* Hard link handling */
 255         if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 256                 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
 257
 258         inode = romfs_iget(dir->i_sb, offset);
 259         if (IS_ERR(inode)) {
 260                 ret = PTR_ERR(inode);
 261                 goto error;
 262         }
 263         goto outi;
 264
 265         /*
 266          * it's a bit funky, _lookup needs to return an error code
 267          * (negative) or a NULL, both as a dentry.  ENOENT should not
 268          * be returned, instead we need to create a negative dentry by
 269          * d_add(dentry, NULL); and return 0 as no error.
 270          * (Although as I see, it only matters on writable file
 271          * systems).
 272          */
 273 out0:
 274         inode = NULL;
 275 outi:
 276         d_add(dentry, inode);
 277         ret = 0;
 278 error:
 279         return ERR_PTR(ret);
 280 }
 281
 282 static const struct file_operations romfs_dir_operations = {
 283         .read           = generic_read_dir,
 284         .readdir        = romfs_readdir,
 285         .llseek         = default_llseek,
 286 };
 287
 288 static const struct inode_operations romfs_dir_inode_operations = {
 289         .lookup         = romfs_lookup,
 290 };
 291
 292 /*
 293  * get a romfs inode based on its position in the image (which doubles as the
 294  * inode number)
 295  */
 296 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
 297 {
 298         struct romfs_inode_info *inode;
 299         struct romfs_inode ri;
 300         struct inode *i;
 301         unsigned long nlen;
 302         unsigned nextfh;
 303         int ret;
 304         umode_t mode;
 305
 306         /* we might have to traverse a chain of "hard link" file entries to get
 307          * to the actual file */
 308         for (;;) {
 309                 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
 310                 if (ret < 0)
 311                         goto error;
 312
 313                 /* XXX: do romfs_checksum here too (with name) */
 314
 315                 nextfh = be32_to_cpu(ri.next);
 316                 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
 317                         break;
 318
 319                 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
 320         }
 321
 322         /* determine the length of the filename */
 323         nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
 324         if (IS_ERR_VALUE(nlen))
 325                 goto eio;
 326
 327         /* get an inode for this image position */
 328         i = iget_locked(sb, pos);
 329         if (!i)
 330                 return ERR_PTR(-ENOMEM);
 331
 332         if (!(i->i_state & I_NEW))
 333                 return i;
 334
 335         /* precalculate the data offset */
 336         inode = ROMFS_I(i);
 337         inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
 338         inode->i_dataoffset = pos + inode->i_metasize;
 339
 340         set_nlink(i, 1);                /* Hard to decide.. */
 341         i->i_size = be32_to_cpu(ri.size);
 342         i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
 343         i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
 344
 345         /* set up mode and ops */
 346         mode = romfs_modemap[nextfh & ROMFH_TYPE];
 347
 348         switch (nextfh & ROMFH_TYPE) {
 349         case ROMFH_DIR:
 350                 i->i_size = ROMFS_I(i)->i_metasize;
 351                 i->i_op = &romfs_dir_inode_operations;
 352                 i->i_fop = &romfs_dir_operations;
 353                 if (nextfh & ROMFH_EXEC)
 354                         mode |= S_IXUGO;
 355                 break;
 356         case ROMFH_REG:
 357                 i->i_fop = &romfs_ro_fops;
 358                 i->i_data.a_ops = &romfs_aops;
 359                 if (i->i_sb->s_mtd)
 360                         i->i_data.backing_dev_info =
 361                                 i->i_sb->s_mtd->backing_dev_info;
 362                 if (nextfh & ROMFH_EXEC)
 363                         mode |= S_IXUGO;
 364                 break;
 365         case ROMFH_SYM:
 366                 i->i_op = &page_symlink_inode_operations;
 367                 i->i_data.a_ops = &romfs_aops;
 368                 mode |= S_IRWXUGO;
 369                 break;
 370         default:
 371                 /* depending on MBZ for sock/fifos */
 372                 nextfh = be32_to_cpu(ri.spec);
 373                 init_special_inode(i, mode, MKDEV(nextfh >> 16,
 374                                                   nextfh & 0xffff));
 375                 break;
 376         }
 377
 378         i->i_mode = mode;
 379
 380         unlock_new_inode(i);
 381         return i;
 382
 383 eio:
 384         ret = -EIO;
 385 error:
 386         printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
 387         return ERR_PTR(ret);
 388 }
 389
 390 /*
 391  * allocate a new inode
 392  */
 393 static struct inode *romfs_alloc_inode(struct super_block *sb)
 394 {
 395         struct romfs_inode_info *inode;
 396         inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
 397         return inode ? &inode->vfs_inode : NULL;
 398 }
 399
 400 /*
 401  * return a spent inode to the slab cache
 402  */
 403 static void romfs_i_callback(struct rcu_head *head)
 404 {
 405         struct inode *inode = container_of(head, struct inode, i_rcu);
 406         kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
 407 }
 408
 409 static void romfs_destroy_inode(struct inode *inode)
 410 {
 411         call_rcu(&inode->i_rcu, romfs_i_callback);
 412 }
 413
 414 /*
 415  * get filesystem statistics
 416  */
 417 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 418 {
 419         struct super_block *sb = dentry->d_sb;
 420         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 421
 422         buf->f_type = ROMFS_MAGIC;
 423         buf->f_namelen = ROMFS_MAXFN;
 424         buf->f_bsize = ROMBSIZE;
 425         buf->f_bfree = buf->f_bavail = buf->f_ffree;
 426         buf->f_blocks =
 427                 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
 428         buf->f_fsid.val[0] = (u32)id;
 429         buf->f_fsid.val[1] = (u32)(id >> 32);
 430         return 0;
 431 }
 432
 433 /*
 434  * remounting must involve read-only
 435  */
 436 static int romfs_remount(struct super_block *sb, int *flags, char *data)
 437 {
 438         *flags |= MS_RDONLY;
 439         return 0;
 440 }
 441
 442 static const struct super_operations romfs_super_ops = {
 443         .alloc_inode    = romfs_alloc_inode,
 444         .destroy_inode  = romfs_destroy_inode,
 445         .statfs         = romfs_statfs,
 446         .remount_fs     = romfs_remount,
 447 };
 448
 449 /*
 450  * checksum check on part of a romfs filesystem
 451  */
 452 static __u32 romfs_checksum(const void *data, int size)
 453 {
 454         const __be32 *ptr = data;
 455         __u32 sum;
 456
 457         sum = 0;
 458         size >>= 2;
 459         while (size > 0) {
 460                 sum += be32_to_cpu(*ptr++);
 461                 size--;
 462         }
 463         return sum;
 464 }
 465
 466 /*
 467  * fill in the superblock
 468  */
 469 static int romfs_fill_super(struct super_block *sb, void *data, int silent)
 470 {
 471         struct romfs_super_block *rsb;
 472         struct inode *root;
 473         unsigned long pos, img_size;
 474         const char *storage;
 475         size_t len;
 476         int ret;
 477
 478 #ifdef CONFIG_BLOCK
 479         if (!sb->s_mtd) {
 480                 sb_set_blocksize(sb, ROMBSIZE);
 481         } else {
 482                 sb->s_blocksize = ROMBSIZE;
 483                 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
 484         }
 485 #endif
 486
 487         sb->s_maxbytes = 0xFFFFFFFF;
 488         sb->s_magic = ROMFS_MAGIC;
 489         sb->s_flags |= MS_RDONLY | MS_NOATIME;
 490         sb->s_op = &romfs_super_ops;
 491
 492         /* read the image superblock and check it */
 493         rsb = kmalloc(512, GFP_KERNEL);
 494         if (!rsb)
 495                 return -ENOMEM;
 496
 497         sb->s_fs_info = (void *) 512;
 498         ret = romfs_dev_read(sb, 0, rsb, 512);
 499         if (ret < 0)
 500                 goto error_rsb;
 501
 502         img_size = be32_to_cpu(rsb->size);
 503
 504         if (sb->s_mtd && img_size > sb->s_mtd->size)
 505                 goto error_rsb_inval;
 506
 507         sb->s_fs_info = (void *) img_size;
 508
 509         if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
 510             img_size < ROMFH_SIZE) {
 511                 if (!silent)
 512                         printk(KERN_WARNING "VFS:"
 513                                " Can't find a romfs filesystem on dev %s.\n",
 514                                sb->s_id);
 515                 goto error_rsb_inval;
 516         }
 517
 518         if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
 519                 printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
 520                        sb->s_id);
 521                 goto error_rsb_inval;
 522         }
 523
 524         storage = sb->s_mtd ? "MTD" : "the block layer";
 525
 526         len = strnlen(rsb->name, ROMFS_MAXFN);
 527         if (!silent)
 528                 printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
 529                        (unsigned) len, (unsigned) len, rsb->name, storage);
 530
 531         kfree(rsb);
 532         rsb = NULL;
 533
 534         /* find the root directory */
 535         pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
 536
 537         root = romfs_iget(sb, pos);
 538         if (IS_ERR(root))
 539                 goto error;
 540
 541         sb->s_root = d_make_root(root);
 542         if (!sb->s_root)
 543                 goto error;
 544
 545         return 0;
 546
 547 error:
 548         return -EINVAL;
 549 error_rsb_inval:
 550         ret = -EINVAL;
 551 error_rsb:
 552         kfree(rsb);
 553         return ret;
 554 }
 555
 556 /*
 557  * get a superblock for mounting
 558  */
 559 static struct dentry *romfs_mount(struct file_system_type *fs_type,
 560                         int flags, const char *dev_name,
 561                         void *data)
 562 {
 563         struct dentry *ret = ERR_PTR(-EINVAL);
 564
 565 #ifdef CONFIG_ROMFS_ON_MTD
 566         ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
 567 #endif
 568 #ifdef CONFIG_ROMFS_ON_BLOCK
 569         if (ret == ERR_PTR(-EINVAL))
 570                 ret = mount_bdev(fs_type, flags, dev_name, data,
 571                                   romfs_fill_super);
 572 #endif
 573         return ret;
 574 }
 575
 576 /*
 577  * destroy a romfs superblock in the appropriate manner
 578  */
 579 static void romfs_kill_sb(struct super_block *sb)
 580 {
 581 #ifdef CONFIG_ROMFS_ON_MTD
 582         if (sb->s_mtd) {
 583                 kill_mtd_super(sb);
 584                 return;
 585         }
 586 #endif
 587 #ifdef CONFIG_ROMFS_ON_BLOCK
 588         if (sb->s_bdev) {
 589                 kill_block_super(sb);
 590                 return;
 591         }
 592 #endif
 593 }
 594
 595 static struct file_system_type romfs_fs_type = {
 596         .owner          = THIS_MODULE,
 597         .name           = "romfs",
 598         .mount          = romfs_mount,
 599         .kill_sb        = romfs_kill_sb,
 600         .fs_flags       = FS_REQUIRES_DEV,
 601 };
 602
 603 /*
 604  * inode storage initialiser
 605  */
 606 static void romfs_i_init_once(void *_inode)
 607 {
 608         struct romfs_inode_info *inode = _inode;
 609
 610         inode_init_once(&inode->vfs_inode);
 611 }
 612
 613 /*
 614  * romfs module initialisation
 615  */
 616 static int __init init_romfs_fs(void)
 617 {
 618         int ret;
 619
 620         printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
 621
 622         romfs_inode_cachep =
 623                 kmem_cache_create("romfs_i",
 624                                   sizeof(struct romfs_inode_info), 0,
 625                                   SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
 626                                   romfs_i_init_once);
 627
 628         if (!romfs_inode_cachep) {
 629                 printk(KERN_ERR
 630                        "ROMFS error: Failed to initialise inode cache\n");
 631                 return -ENOMEM;
 632         }
 633         ret = register_filesystem(&romfs_fs_type);
 634         if (ret) {
 635                 printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");
 636                 goto error_register;
 637         }
 638         return 0;
 639
 640 error_register:
 641         kmem_cache_destroy(romfs_inode_cachep);
 642         return ret;
 643 }
 644
 645 /*
 646  * romfs module removal
 647  */
 648 static void __exit exit_romfs_fs(void)
 649 {
 650         unregister_filesystem(&romfs_fs_type);
 651         /*
 652          * Make sure all delayed rcu free inodes are flushed before we
 653          * destroy cache.
 654          */
 655         rcu_barrier();
 656         kmem_cache_destroy(romfs_inode_cachep);
 657 }
 658
 659 module_init(init_romfs_fs);
 660 module_exit(exit_romfs_fs);
 661
 662 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
 663 MODULE_AUTHOR("Red Hat, Inc.");
 664 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */