fs/cramfs/inode.c

   1 /*
   2  * Compressed rom filesystem for Linux.
   3  *
   4  * Copyright (C) 1999 Linus Torvalds.
   5  *
   6  * This file is released under the GPL.
   7  */
   8
   9 /*
  10  * These are the VFS interfaces to the compressed rom filesystem.
  11  * The actual compression is based on zlib, see the other files.
  12  */
  13
  14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16 #include <linux/module.h>
  17 #include <linux/fs.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/init.h>
  20 #include <linux/string.h>
  21 #include <linux/blkdev.h>
  22 #include <linux/slab.h>
  23 #include <linux/vfs.h>
  24 #include <linux/mutex.h>
  25 #include <uapi/linux/cramfs_fs.h>
  26 #include <asm/uaccess.h>
  27
  28 #include "internal.h"
  29
  30 /*
  31  * cramfs super-block data in memory
  32  */
  33 struct cramfs_sb_info {
  34         unsigned long magic;
  35         unsigned long size;
  36         unsigned long blocks;
  37         unsigned long files;
  38         unsigned long flags;
  39 };
  40
  41 static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
  42 {
  43         return sb->s_fs_info;
  44 }
  45
  46 static const struct super_operations cramfs_ops;
  47 static const struct inode_operations cramfs_dir_inode_operations;
  48 static const struct file_operations cramfs_directory_operations;
  49 static const struct address_space_operations cramfs_aops;
  50
  51 static DEFINE_MUTEX(read_mutex);
  52
  53
  54 /* These macros may change in future, to provide better st_ino semantics. */
  55 #define OFFSET(x)       ((x)->i_ino)
  56
  57 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
  58 {
  59         if (!cino->offset)
  60                 return offset + 1;
  61         if (!cino->size)
  62                 return offset + 1;
  63
  64         /*
  65          * The file mode test fixes buggy mkcramfs implementations where
  66          * cramfs_inode->offset is set to a non zero value for entries
  67          * which did not contain data, like devices node and fifos.
  68          */
  69         switch (cino->mode & S_IFMT) {
  70         case S_IFREG:
  71         case S_IFDIR:
  72         case S_IFLNK:
  73                 return cino->offset << 2;
  74         default:
  75                 break;
  76         }
  77         return offset + 1;
  78 }
  79
  80 static struct inode *get_cramfs_inode(struct super_block *sb,
  81         const struct cramfs_inode *cramfs_inode, unsigned int offset)
  82 {
  83         struct inode *inode;
  84         static struct timespec zerotime;
  85
  86         inode = iget_locked(sb, cramino(cramfs_inode, offset));
  87         if (!inode)
  88                 return ERR_PTR(-ENOMEM);
  89         if (!(inode->i_state & I_NEW))
  90                 return inode;
  91
  92         switch (cramfs_inode->mode & S_IFMT) {
  93         case S_IFREG:
  94                 inode->i_fop = &generic_ro_fops;
  95                 inode->i_data.a_ops = &cramfs_aops;
  96                 break;
  97         case S_IFDIR:
  98                 inode->i_op = &cramfs_dir_inode_operations;
  99                 inode->i_fop = &cramfs_directory_operations;
 100                 break;
 101         case S_IFLNK:
 102                 inode->i_op = &page_symlink_inode_operations;
 103                 inode->i_data.a_ops = &cramfs_aops;
 104                 break;
 105         default:
 106                 init_special_inode(inode, cramfs_inode->mode,
 107                                 old_decode_dev(cramfs_inode->size));
 108         }
 109
 110         inode->i_mode = cramfs_inode->mode;
 111         i_uid_write(inode, cramfs_inode->uid);
 112         i_gid_write(inode, cramfs_inode->gid);
 113
 114         /* if the lower 2 bits are zero, the inode contains data */
 115         if (!(inode->i_ino & 3)) {
 116                 inode->i_size = cramfs_inode->size;
 117                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
 118         }
 119
 120         /* Struct copy intentional */
 121         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
 122         /* inode->i_nlink is left 1 - arguably wrong for directories,
 123            but it's the best we can do without reading the directory
 124            contents.  1 yields the right result in GNU find, even
 125            without -noleaf option. */
 126
 127         unlock_new_inode(inode);
 128
 129         return inode;
 130 }
 131
 132 /*
 133  * We have our own block cache: don't fill up the buffer cache
 134  * with the rom-image, because the way the filesystem is set
 135  * up the accesses should be fairly regular and cached in the
 136  * page cache and dentry tree anyway..
 137  *
 138  * This also acts as a way to guarantee contiguous areas of up to
 139  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
 140  * worry about end-of-buffer issues even when decompressing a full
 141  * page cache.
 142  */
 143 #define READ_BUFFERS (2)
 144 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 145 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 146
 147 /*
 148  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 149  * data that takes up more space than the original and with unlucky
 150  * alignment.
 151  */
 152 #define BLKS_PER_BUF_SHIFT      (2)
 153 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 154 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
 155
 156 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 157 static unsigned buffer_blocknr[READ_BUFFERS];
 158 static struct super_block * buffer_dev[READ_BUFFERS];
 159 static int next_buffer;
 160
 161 /*
 162  * Returns a pointer to a buffer containing at least LEN bytes of
 163  * filesystem starting at byte offset OFFSET into the filesystem.
 164  */
 165 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
 166 {
 167         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 168         struct page *pages[BLKS_PER_BUF];
 169         unsigned i, blocknr, buffer;
 170         unsigned long devsize;
 171         char *data;
 172
 173         if (!len)
 174                 return NULL;
 175         blocknr = offset >> PAGE_CACHE_SHIFT;
 176         offset &= PAGE_CACHE_SIZE - 1;
 177
 178         /* Check if an existing buffer already has the data.. */
 179         for (i = 0; i < READ_BUFFERS; i++) {
 180                 unsigned int blk_offset;
 181
 182                 if (buffer_dev[i] != sb)
 183                         continue;
 184                 if (blocknr < buffer_blocknr[i])
 185                         continue;
 186                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
 187                 blk_offset += offset;
 188                 if (blk_offset + len > BUFFER_SIZE)
 189                         continue;
 190                 return read_buffers[i] + blk_offset;
 191         }
 192
 193         devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
 194
 195         /* Ok, read in BLKS_PER_BUF pages completely first. */
 196         for (i = 0; i < BLKS_PER_BUF; i++) {
 197                 struct page *page = NULL;
 198
 199                 if (blocknr + i < devsize) {
 200                         page = read_mapping_page(mapping, blocknr + i, NULL);
 201                         /* synchronous error? */
 202                         if (IS_ERR(page))
 203                                 page = NULL;
 204                 }
 205                 pages[i] = page;
 206         }
 207
 208         for (i = 0; i < BLKS_PER_BUF; i++) {
 209                 struct page *page = pages[i];
 210                 if (page) {
 211                         wait_on_page_locked(page);
 212                         if (!PageUptodate(page)) {
 213                                 /* asynchronous error */
 214                                 page_cache_release(page);
 215                                 pages[i] = NULL;
 216                         }
 217                 }
 218         }
 219
 220         buffer = next_buffer;
 221         next_buffer = NEXT_BUFFER(buffer);
 222         buffer_blocknr[buffer] = blocknr;
 223         buffer_dev[buffer] = sb;
 224
 225         data = read_buffers[buffer];
 226         for (i = 0; i < BLKS_PER_BUF; i++) {
 227                 struct page *page = pages[i];
 228                 if (page) {
 229                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 230                         kunmap(page);
 231                         page_cache_release(page);
 232                 } else
 233                         memset(data, 0, PAGE_CACHE_SIZE);
 234                 data += PAGE_CACHE_SIZE;
 235         }
 236         return read_buffers[buffer] + offset;
 237 }
 238
 239 static void cramfs_kill_sb(struct super_block *sb)
 240 {
 241         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 242         kill_block_super(sb);
 243         kfree(sbi);
 244 }
 245
 246 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 247 {
 248         sync_filesystem(sb);
 249         *flags |= MS_RDONLY;
 250         return 0;
 251 }
 252
 253 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 254 {
 255         int i;
 256         struct cramfs_super super;
 257         unsigned long root_offset;
 258         struct cramfs_sb_info *sbi;
 259         struct inode *root;
 260
 261         sb->s_flags |= MS_RDONLY;
 262
 263         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 264         if (!sbi)
 265                 return -ENOMEM;
 266         sb->s_fs_info = sbi;
 267
 268         /* Invalidate the read buffers on mount: think disk change.. */
 269         mutex_lock(&read_mutex);
 270         for (i = 0; i < READ_BUFFERS; i++)
 271                 buffer_blocknr[i] = -1;
 272
 273         /* Read the first block and get the superblock from it */
 274         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 275         mutex_unlock(&read_mutex);
 276
 277         /* Do sanity checks on the superblock */
 278         if (super.magic != CRAMFS_MAGIC) {
 279                 /* check for wrong endianness */
 280                 if (super.magic == CRAMFS_MAGIC_WEND) {
 281                         if (!silent)
 282                                 pr_err("wrong endianness\n");
 283                         return -EINVAL;
 284                 }
 285
 286                 /* check at 512 byte offset */
 287                 mutex_lock(&read_mutex);
 288                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 289                 mutex_unlock(&read_mutex);
 290                 if (super.magic != CRAMFS_MAGIC) {
 291                         if (super.magic == CRAMFS_MAGIC_WEND && !silent)
 292                                 pr_err("wrong endianness\n");
 293                         else if (!silent)
 294                                 pr_err("wrong magic\n");
 295                         return -EINVAL;
 296                 }
 297         }
 298
 299         /* get feature flags first */
 300         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 301                 pr_err("unsupported filesystem features\n");
 302                 return -EINVAL;
 303         }
 304
 305         /* Check that the root inode is in a sane state */
 306         if (!S_ISDIR(super.root.mode)) {
 307                 pr_err("root is not a directory\n");
 308                 return -EINVAL;
 309         }
 310         /* correct strange, hard-coded permissions of mkcramfs */
 311         super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
 312
 313         root_offset = super.root.offset << 2;
 314         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 315                 sbi->size=super.size;
 316                 sbi->blocks=super.fsid.blocks;
 317                 sbi->files=super.fsid.files;
 318         } else {
 319                 sbi->size=1<<28;
 320                 sbi->blocks=0;
 321                 sbi->files=0;
 322         }
 323         sbi->magic=super.magic;
 324         sbi->flags=super.flags;
 325         if (root_offset == 0)
 326                 pr_info("empty filesystem");
 327         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 328                  ((root_offset != sizeof(struct cramfs_super)) &&
 329                   (root_offset != 512 + sizeof(struct cramfs_super))))
 330         {
 331                 pr_err("bad root offset %lu\n", root_offset);
 332                 return -EINVAL;
 333         }
 334
 335         /* Set it all up.. */
 336         sb->s_op = &cramfs_ops;
 337         root = get_cramfs_inode(sb, &super.root, 0);
 338         if (IS_ERR(root))
 339                 return PTR_ERR(root);
 340         sb->s_root = d_make_root(root);
 341         if (!sb->s_root)
 342                 return -ENOMEM;
 343         return 0;
 344 }
 345
 346 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 347 {
 348         struct super_block *sb = dentry->d_sb;
 349         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 350
 351         buf->f_type = CRAMFS_MAGIC;
 352         buf->f_bsize = PAGE_CACHE_SIZE;
 353         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 354         buf->f_bfree = 0;
 355         buf->f_bavail = 0;
 356         buf->f_files = CRAMFS_SB(sb)->files;
 357         buf->f_ffree = 0;
 358         buf->f_fsid.val[0] = (u32)id;
 359         buf->f_fsid.val[1] = (u32)(id >> 32);
 360         buf->f_namelen = CRAMFS_MAXPATHLEN;
 361         return 0;
 362 }
 363
 364 /*
 365  * Read a cramfs directory entry.
 366  */
 367 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
 368 {
 369         struct inode *inode = file_inode(file);
 370         struct super_block *sb = inode->i_sb;
 371         char *buf;
 372         unsigned int offset;
 373
 374         /* Offset within the thing. */
 375         if (ctx->pos >= inode->i_size)
 376                 return 0;
 377         offset = ctx->pos;
 378         /* Directory entries are always 4-byte aligned */
 379         if (offset & 3)
 380                 return -EINVAL;
 381
 382         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 383         if (!buf)
 384                 return -ENOMEM;
 385
 386         while (offset < inode->i_size) {
 387                 struct cramfs_inode *de;
 388                 unsigned long nextoffset;
 389                 char *name;
 390                 ino_t ino;
 391                 umode_t mode;
 392                 int namelen;
 393
 394                 mutex_lock(&read_mutex);
 395                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 396                 name = (char *)(de+1);
 397
 398                 /*
 399                  * Namelengths on disk are shifted by two
 400                  * and the name padded out to 4-byte boundaries
 401                  * with zeroes.
 402                  */
 403                 namelen = de->namelen << 2;
 404                 memcpy(buf, name, namelen);
 405                 ino = cramino(de, OFFSET(inode) + offset);
 406                 mode = de->mode;
 407                 mutex_unlock(&read_mutex);
 408                 nextoffset = offset + sizeof(*de) + namelen;
 409                 for (;;) {
 410                         if (!namelen) {
 411                                 kfree(buf);
 412                                 return -EIO;
 413                         }
 414                         if (buf[namelen-1])
 415                                 break;
 416                         namelen--;
 417                 }
 418                 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
 419                         break;
 420
 421                 ctx->pos = offset = nextoffset;
 422         }
 423         kfree(buf);
 424         return 0;
 425 }
 426
 427 /*
 428  * Lookup and fill in the inode data..
 429  */
 430 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 431 {
 432         unsigned int offset = 0;
 433         struct inode *inode = NULL;
 434         int sorted;
 435
 436         mutex_lock(&read_mutex);
 437         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 438         while (offset < dir->i_size) {
 439                 struct cramfs_inode *de;
 440                 char *name;
 441                 int namelen, retval;
 442                 int dir_off = OFFSET(dir) + offset;
 443
 444                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 445                 name = (char *)(de+1);
 446
 447                 /* Try to take advantage of sorted directories */
 448                 if (sorted && (dentry->d_name.name[0] < name[0]))
 449                         break;
 450
 451                 namelen = de->namelen << 2;
 452                 offset += sizeof(*de) + namelen;
 453
 454                 /* Quick check that the name is roughly the right length */
 455                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 456                         continue;
 457
 458                 for (;;) {
 459                         if (!namelen) {
 460                                 inode = ERR_PTR(-EIO);
 461                                 goto out;
 462                         }
 463                         if (name[namelen-1])
 464                                 break;
 465                         namelen--;
 466                 }
 467                 if (namelen != dentry->d_name.len)
 468                         continue;
 469                 retval = memcmp(dentry->d_name.name, name, namelen);
 470                 if (retval > 0)
 471                         continue;
 472                 if (!retval) {
 473                         inode = get_cramfs_inode(dir->i_sb, de, dir_off);
 474                         break;
 475                 }
 476                 /* else (retval < 0) */
 477                 if (sorted)
 478                         break;
 479         }
 480 out:
 481         mutex_unlock(&read_mutex);
 482         if (IS_ERR(inode))
 483                 return ERR_CAST(inode);
 484         d_add(dentry, inode);
 485         return NULL;
 486 }
 487
 488 static int cramfs_readpage(struct file *file, struct page * page)
 489 {
 490         struct inode *inode = page->mapping->host;
 491         u32 maxblock;
 492         int bytes_filled;
 493         void *pgdata;
 494
 495         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 496         bytes_filled = 0;
 497         pgdata = kmap(page);
 498
 499         if (page->index < maxblock) {
 500                 struct super_block *sb = inode->i_sb;
 501                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 502                 u32 start_offset, compr_len;
 503
 504                 start_offset = OFFSET(inode) + maxblock*4;
 505                 mutex_lock(&read_mutex);
 506                 if (page->index)
 507                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
 508                                 4);
 509                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
 510                         start_offset);
 511                 mutex_unlock(&read_mutex);
 512
 513                 if (compr_len == 0)
 514                         ; /* hole */
 515                 else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
 516                         pr_err("bad compressed blocksize %u\n",
 517                                 compr_len);
 518                         goto err;
 519                 } else {
 520                         mutex_lock(&read_mutex);
 521                         bytes_filled = cramfs_uncompress_block(pgdata,
 522                                  PAGE_CACHE_SIZE,
 523                                  cramfs_read(sb, start_offset, compr_len),
 524                                  compr_len);
 525                         mutex_unlock(&read_mutex);
 526                         if (unlikely(bytes_filled < 0))
 527                                 goto err;
 528                 }
 529         }
 530
 531         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 532         flush_dcache_page(page);
 533         kunmap(page);
 534         SetPageUptodate(page);
 535         unlock_page(page);
 536         return 0;
 537
 538 err:
 539         kunmap(page);
 540         ClearPageUptodate(page);
 541         SetPageError(page);
 542         unlock_page(page);
 543         return 0;
 544 }
 545
 546 static const struct address_space_operations cramfs_aops = {
 547         .readpage = cramfs_readpage
 548 };
 549
 550 /*
 551  * Our operations:
 552  */
 553
 554 /*
 555  * A directory can only readdir
 556  */
 557 static const struct file_operations cramfs_directory_operations = {
 558         .llseek         = generic_file_llseek,
 559         .read           = generic_read_dir,
 560         .iterate        = cramfs_readdir,
 561 };
 562
 563 static const struct inode_operations cramfs_dir_inode_operations = {
 564         .lookup         = cramfs_lookup,
 565 };
 566
 567 static const struct super_operations cramfs_ops = {
 568         .remount_fs     = cramfs_remount,
 569         .statfs         = cramfs_statfs,
 570 };
 571
 572 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
 573         int flags, const char *dev_name, void *data)
 574 {
 575         return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
 576 }
 577
 578 static struct file_system_type cramfs_fs_type = {
 579         .owner          = THIS_MODULE,
 580         .name           = "cramfs",
 581         .mount          = cramfs_mount,
 582         .kill_sb        = cramfs_kill_sb,
 583         .fs_flags       = FS_REQUIRES_DEV,
 584 };
 585 MODULE_ALIAS_FS("cramfs");
 586
 587 static int __init init_cramfs_fs(void)
 588 {
 589         int rv;
 590
 591         rv = cramfs_uncompress_init();
 592         if (rv < 0)
 593                 return rv;
 594         rv = register_filesystem(&cramfs_fs_type);
 595         if (rv < 0)
 596                 cramfs_uncompress_exit();
 597         return rv;
 598 }
 599
 600 static void __exit exit_cramfs_fs(void)
 601 {
 602         cramfs_uncompress_exit();
 603         unregister_filesystem(&cramfs_fs_type);
 604 }
 605
 606 module_init(init_cramfs_fs)
 607 module_exit(exit_cramfs_fs)
 608 MODULE_LICENSE("GPL");