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 #include <linux/module.h>
  15 #include <linux/fs.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/init.h>
  18 #include <linux/string.h>
  19 #include <linux/blkdev.h>
  20 #include <linux/cramfs_fs.h>
  21 #include <linux/slab.h>
  22 #include <linux/cramfs_fs_sb.h>
  23 #include <linux/buffer_head.h>
  24 #include <linux/vfs.h>
  25 #include <asm/semaphore.h>
  26
  27 #include <asm/uaccess.h>
  28
  29 static struct super_operations cramfs_ops;
  30 static struct inode_operations cramfs_dir_inode_operations;
  31 static struct file_operations cramfs_directory_operations;
  32 static struct address_space_operations cramfs_aops;
  33
  34 static DECLARE_MUTEX(read_mutex);
  35
  36
  37 /* These two macros may change in future, to provide better st_ino
  38    semantics. */
  39 #define CRAMINO(x)      ((x)->offset?(x)->offset<<2:1)
  40 #define OFFSET(x)       ((x)->i_ino)
  41
  42 static struct inode *get_cramfs_inode(struct super_block *sb, struct cramfs_inode * cramfs_inode)
  43 {
  44         struct inode * inode = new_inode(sb);
  45         static struct timespec zerotime;
  46
  47         if (inode) {
  48                 inode->i_mode = cramfs_inode->mode;
  49                 inode->i_uid = cramfs_inode->uid;
  50                 inode->i_size = cramfs_inode->size;
  51                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
  52                 inode->i_blksize = PAGE_CACHE_SIZE;
  53                 inode->i_gid = cramfs_inode->gid;
  54                 /* Struct copy intentional */
  55                 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
  56                 inode->i_ino = CRAMINO(cramfs_inode);
  57                 /* inode->i_nlink is left 1 - arguably wrong for directories,
  58                    but it's the best we can do without reading the directory
  59                    contents.  1 yields the right result in GNU find, even
  60                    without -noleaf option. */
  61                 insert_inode_hash(inode);
  62                 if (S_ISREG(inode->i_mode)) {
  63                         inode->i_fop = &generic_ro_fops;
  64                         inode->i_data.a_ops = &cramfs_aops;
  65                 } else if (S_ISDIR(inode->i_mode)) {
  66                         inode->i_op = &cramfs_dir_inode_operations;
  67                         inode->i_fop = &cramfs_directory_operations;
  68                 } else if (S_ISLNK(inode->i_mode)) {
  69                         inode->i_op = &page_symlink_inode_operations;
  70                         inode->i_data.a_ops = &cramfs_aops;
  71                 } else {
  72                         inode->i_size = 0;
  73                         inode->i_blocks = 0;
  74                         init_special_inode(inode, inode->i_mode,
  75                                 old_decode_dev(cramfs_inode->size));
  76                 }
  77         }
  78         return inode;
  79 }
  80
  81 /*
  82  * We have our own block cache: don't fill up the buffer cache
  83  * with the rom-image, because the way the filesystem is set
  84  * up the accesses should be fairly regular and cached in the
  85  * page cache and dentry tree anyway..
  86  *
  87  * This also acts as a way to guarantee contiguous areas of up to
  88  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
  89  * worry about end-of-buffer issues even when decompressing a full
  90  * page cache.
  91  */
  92 #define READ_BUFFERS (2)
  93 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
  94 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
  95
  96 /*
  97  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
  98  * data that takes up more space than the original and with unlucky
  99  * alignment.
 100  */
 101 #define BLKS_PER_BUF_SHIFT      (2)
 102 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 103 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
 104
 105 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 106 static unsigned buffer_blocknr[READ_BUFFERS];
 107 static struct super_block * buffer_dev[READ_BUFFERS];
 108 static int next_buffer;
 109
 110 /*
 111  * Returns a pointer to a buffer containing at least LEN bytes of
 112  * filesystem starting at byte offset OFFSET into the filesystem.
 113  */
 114 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
 115 {
 116         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 117         struct page *pages[BLKS_PER_BUF];
 118         unsigned i, blocknr, buffer, unread;
 119         unsigned long devsize;
 120         char *data;
 121
 122         if (!len)
 123                 return NULL;
 124         blocknr = offset >> PAGE_CACHE_SHIFT;
 125         offset &= PAGE_CACHE_SIZE - 1;
 126
 127         /* Check if an existing buffer already has the data.. */
 128         for (i = 0; i < READ_BUFFERS; i++) {
 129                 unsigned int blk_offset;
 130
 131                 if (buffer_dev[i] != sb)
 132                         continue;
 133                 if (blocknr < buffer_blocknr[i])
 134                         continue;
 135                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
 136                 blk_offset += offset;
 137                 if (blk_offset + len > BUFFER_SIZE)
 138                         continue;
 139                 return read_buffers[i] + blk_offset;
 140         }
 141
 142         devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
 143
 144         /* Ok, read in BLKS_PER_BUF pages completely first. */
 145         unread = 0;
 146         for (i = 0; i < BLKS_PER_BUF; i++) {
 147                 struct page *page = NULL;
 148
 149                 if (blocknr + i < devsize) {
 150                         page = read_cache_page(mapping, blocknr + i,
 151                                 (filler_t *)mapping->a_ops->readpage,
 152                                 NULL);
 153                         /* synchronous error? */
 154                         if (IS_ERR(page))
 155                                 page = NULL;
 156                 }
 157                 pages[i] = page;
 158         }
 159
 160         for (i = 0; i < BLKS_PER_BUF; i++) {
 161                 struct page *page = pages[i];
 162                 if (page) {
 163                         wait_on_page_locked(page);
 164                         if (!PageUptodate(page)) {
 165                                 /* asynchronous error */
 166                                 page_cache_release(page);
 167                                 pages[i] = NULL;
 168                         }
 169                 }
 170         }
 171
 172         buffer = next_buffer;
 173         next_buffer = NEXT_BUFFER(buffer);
 174         buffer_blocknr[buffer] = blocknr;
 175         buffer_dev[buffer] = sb;
 176
 177         data = read_buffers[buffer];
 178         for (i = 0; i < BLKS_PER_BUF; i++) {
 179                 struct page *page = pages[i];
 180                 if (page) {
 181                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
 182                         kunmap(page);
 183                         page_cache_release(page);
 184                 } else
 185                         memset(data, 0, PAGE_CACHE_SIZE);
 186                 data += PAGE_CACHE_SIZE;
 187         }
 188         return read_buffers[buffer] + offset;
 189 }
 190
 191 static void cramfs_put_super(struct super_block *sb)
 192 {
 193         kfree(sb->s_fs_info);
 194         sb->s_fs_info = NULL;
 195 }
 196
 197 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
 198 {
 199         *flags |= MS_RDONLY;
 200         return 0;
 201 }
 202
 203 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 204 {
 205         int i;
 206         struct cramfs_super super;
 207         unsigned long root_offset;
 208         struct cramfs_sb_info *sbi;
 209         struct inode *root;
 210
 211         sb->s_flags |= MS_RDONLY;
 212
 213         sbi = kmalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 214         if (!sbi)
 215                 return -ENOMEM;
 216         sb->s_fs_info = sbi;
 217         memset(sbi, 0, sizeof(struct cramfs_sb_info));
 218
 219         /* Invalidate the read buffers on mount: think disk change.. */
 220         down(&read_mutex);
 221         for (i = 0; i < READ_BUFFERS; i++)
 222                 buffer_blocknr[i] = -1;
 223
 224         /* Read the first block and get the superblock from it */
 225         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
 226         up(&read_mutex);
 227
 228         /* Do sanity checks on the superblock */
 229         if (super.magic != CRAMFS_MAGIC) {
 230                 /* check at 512 byte offset */
 231                 down(&read_mutex);
 232                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 233                 up(&read_mutex);
 234                 if (super.magic != CRAMFS_MAGIC) {
 235                         if (!silent)
 236                                 printk(KERN_ERR "cramfs: wrong magic\n");
 237                         goto out;
 238                 }
 239         }
 240
 241         /* get feature flags first */
 242         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
 243                 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
 244                 goto out;
 245         }
 246
 247         /* Check that the root inode is in a sane state */
 248         if (!S_ISDIR(super.root.mode)) {
 249                 printk(KERN_ERR "cramfs: root is not a directory\n");
 250                 goto out;
 251         }
 252         root_offset = super.root.offset << 2;
 253         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
 254                 sbi->size=super.size;
 255                 sbi->blocks=super.fsid.blocks;
 256                 sbi->files=super.fsid.files;
 257         } else {
 258                 sbi->size=1<<28;
 259                 sbi->blocks=0;
 260                 sbi->files=0;
 261         }
 262         sbi->magic=super.magic;
 263         sbi->flags=super.flags;
 264         if (root_offset == 0)
 265                 printk(KERN_INFO "cramfs: empty filesystem");
 266         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 267                  ((root_offset != sizeof(struct cramfs_super)) &&
 268                   (root_offset != 512 + sizeof(struct cramfs_super))))
 269         {
 270                 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
 271                 goto out;
 272         }
 273
 274         /* Set it all up.. */
 275         sb->s_op = &cramfs_ops;
 276         root = get_cramfs_inode(sb, &super.root);
 277         if (!root)
 278                 goto out;
 279         sb->s_root = d_alloc_root(root);
 280         if (!sb->s_root) {
 281                 iput(root);
 282                 goto out;
 283         }
 284         return 0;
 285 out:
 286         kfree(sbi);
 287         sb->s_fs_info = NULL;
 288         return -EINVAL;
 289 }
 290
 291 static int cramfs_statfs(struct super_block *sb, struct kstatfs *buf)
 292 {
 293         buf->f_type = CRAMFS_MAGIC;
 294         buf->f_bsize = PAGE_CACHE_SIZE;
 295         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 296         buf->f_bfree = 0;
 297         buf->f_bavail = 0;
 298         buf->f_files = CRAMFS_SB(sb)->files;
 299         buf->f_ffree = 0;
 300         buf->f_namelen = CRAMFS_MAXPATHLEN;
 301         return 0;
 302 }
 303
 304 /*
 305  * Read a cramfs directory entry.
 306  */
 307 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 308 {
 309         struct inode *inode = filp->f_dentry->d_inode;
 310         struct super_block *sb = inode->i_sb;
 311         char *buf;
 312         unsigned int offset;
 313         int copied;
 314
 315         /* Offset within the thing. */
 316         offset = filp->f_pos;
 317         if (offset >= inode->i_size)
 318                 return 0;
 319         /* Directory entries are always 4-byte aligned */
 320         if (offset & 3)
 321                 return -EINVAL;
 322
 323         buf = kmalloc(256, GFP_KERNEL);
 324         if (!buf)
 325                 return -ENOMEM;
 326
 327         copied = 0;
 328         while (offset < inode->i_size) {
 329                 struct cramfs_inode *de;
 330                 unsigned long nextoffset;
 331                 char *name;
 332                 ino_t ino;
 333                 mode_t mode;
 334                 int namelen, error;
 335
 336                 down(&read_mutex);
 337                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);
 338                 name = (char *)(de+1);
 339
 340                 /*
 341                  * Namelengths on disk are shifted by two
 342                  * and the name padded out to 4-byte boundaries
 343                  * with zeroes.
 344                  */
 345                 namelen = de->namelen << 2;
 346                 memcpy(buf, name, namelen);
 347                 ino = CRAMINO(de);
 348                 mode = de->mode;
 349                 up(&read_mutex);
 350                 nextoffset = offset + sizeof(*de) + namelen;
 351                 for (;;) {
 352                         if (!namelen) {
 353                                 kfree(buf);
 354                                 return -EIO;
 355                         }
 356                         if (buf[namelen-1])
 357                                 break;
 358                         namelen--;
 359                 }
 360                 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
 361                 if (error)
 362                         break;
 363
 364                 offset = nextoffset;
 365                 filp->f_pos = offset;
 366                 copied++;
 367         }
 368         kfree(buf);
 369         return 0;
 370 }
 371
 372 /*
 373  * Lookup and fill in the inode data..
 374  */
 375 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 376 {
 377         unsigned int offset = 0;
 378         int sorted;
 379
 380         down(&read_mutex);
 381         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 382         while (offset < dir->i_size) {
 383                 struct cramfs_inode *de;
 384                 char *name;
 385                 int namelen, retval;
 386
 387                 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);
 388                 name = (char *)(de+1);
 389
 390                 /* Try to take advantage of sorted directories */
 391                 if (sorted && (dentry->d_name.name[0] < name[0]))
 392                         break;
 393
 394                 namelen = de->namelen << 2;
 395                 offset += sizeof(*de) + namelen;
 396
 397                 /* Quick check that the name is roughly the right length */
 398                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 399                         continue;
 400
 401                 for (;;) {
 402                         if (!namelen) {
 403                                 up(&read_mutex);
 404                                 return ERR_PTR(-EIO);
 405                         }
 406                         if (name[namelen-1])
 407                                 break;
 408                         namelen--;
 409                 }
 410                 if (namelen != dentry->d_name.len)
 411                         continue;
 412                 retval = memcmp(dentry->d_name.name, name, namelen);
 413                 if (retval > 0)
 414                         continue;
 415                 if (!retval) {
 416                         struct cramfs_inode entry = *de;
 417                         up(&read_mutex);
 418                         d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
 419                         return NULL;
 420                 }
 421                 /* else (retval < 0) */
 422                 if (sorted)
 423                         break;
 424         }
 425         up(&read_mutex);
 426         d_add(dentry, NULL);
 427         return NULL;
 428 }
 429
 430 static int cramfs_readpage(struct file *file, struct page * page)
 431 {
 432         struct inode *inode = page->mapping->host;
 433         u32 maxblock, bytes_filled;
 434         void *pgdata;
 435
 436         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 437         bytes_filled = 0;
 438         if (page->index < maxblock) {
 439                 struct super_block *sb = inode->i_sb;
 440                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
 441                 u32 start_offset, compr_len;
 442
 443                 start_offset = OFFSET(inode) + maxblock*4;
 444                 down(&read_mutex);
 445                 if (page->index)
 446                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
 447                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
 448                 up(&read_mutex);
 449                 pgdata = kmap(page);
 450                 if (compr_len == 0)
 451                         ; /* hole */
 452                 else {
 453                         down(&read_mutex);
 454                         bytes_filled = cramfs_uncompress_block(pgdata,
 455                                  PAGE_CACHE_SIZE,
 456                                  cramfs_read(sb, start_offset, compr_len),
 457                                  compr_len);
 458                         up(&read_mutex);
 459                 }
 460         } else
 461                 pgdata = kmap(page);
 462         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
 463         kunmap(page);
 464         flush_dcache_page(page);
 465         SetPageUptodate(page);
 466         unlock_page(page);
 467         return 0;
 468 }
 469
 470 static struct address_space_operations cramfs_aops = {
 471         .readpage = cramfs_readpage
 472 };
 473
 474 /*
 475  * Our operations:
 476  */
 477
 478 /*
 479  * A directory can only readdir
 480  */
 481 static struct file_operations cramfs_directory_operations = {
 482         .llseek         = generic_file_llseek,
 483         .read           = generic_read_dir,
 484         .readdir        = cramfs_readdir,
 485 };
 486
 487 static struct inode_operations cramfs_dir_inode_operations = {
 488         .lookup         = cramfs_lookup,
 489 };
 490
 491 static struct super_operations cramfs_ops = {
 492         .put_super      = cramfs_put_super,
 493         .remount_fs     = cramfs_remount,
 494         .statfs         = cramfs_statfs,
 495 };
 496
 497 static struct super_block *cramfs_get_sb(struct file_system_type *fs_type,
 498         int flags, const char *dev_name, void *data)
 499 {
 500         return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
 501 }
 502
 503 static struct file_system_type cramfs_fs_type = {
 504         .owner          = THIS_MODULE,
 505         .name           = "cramfs",
 506         .get_sb         = cramfs_get_sb,
 507         .kill_sb        = kill_block_super,
 508         .fs_flags       = FS_REQUIRES_DEV,
 509 };
 510
 511 static int __init init_cramfs_fs(void)
 512 {
 513         cramfs_uncompress_init();
 514         return register_filesystem(&cramfs_fs_type);
 515 }
 516
 517 static void __exit exit_cramfs_fs(void)
 518 {
 519         cramfs_uncompress_exit();
 520         unregister_filesystem(&cramfs_fs_type);
 521 }
 522
 523 module_init(init_cramfs_fs)
 524 module_exit(exit_cramfs_fs)
 525 MODULE_LICENSE("GPL");