fs/hostfs/hostfs_kern.c

   1 /*
   2  * Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  *
   5  * Ported the filesystem routines to 2.5.
   6  * 2003-02-10 Petr Baudis <pasky@ucw.cz>
   7  */
   8
   9 #include <linux/stddef.h>
  10 #include <linux/fs.h>
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/slab.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/blkdev.h>
  16 #include <linux/list.h>
  17 #include <linux/statfs.h>
  18 #include <linux/kdev_t.h>
  19 #include <asm/uaccess.h>
  20 #include "hostfs.h"
  21 #include "kern_util.h"
  22 #include "kern.h"
  23 #include "user_util.h"
  24 #include "init.h"
  25
  26 struct hostfs_inode_info {
  27         char *host_filename;
  28         int fd;
  29         int mode;
  30         struct inode vfs_inode;
  31 };
  32
  33 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  34 {
  35         return(list_entry(inode, struct hostfs_inode_info, vfs_inode));
  36 }
  37
  38 #define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)
  39
  40 int hostfs_d_delete(struct dentry *dentry)
  41 {
  42         return(1);
  43 }
  44
  45 struct dentry_operations hostfs_dentry_ops = {
  46         .d_delete               = hostfs_d_delete,
  47 };
  48
  49 /* Changed in hostfs_args before the kernel starts running */
  50 static char *root_ino = "/";
  51 static int append = 0;
  52
  53 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
  54
  55 static const struct inode_operations hostfs_iops;
  56 static const struct inode_operations hostfs_dir_iops;
  57 static const struct address_space_operations hostfs_link_aops;
  58
  59 #ifndef MODULE
  60 static int __init hostfs_args(char *options, int *add)
  61 {
  62         char *ptr;
  63
  64         ptr = strchr(options, ',');
  65         if(ptr != NULL)
  66                 *ptr++ = '\0';
  67         if(*options != '\0')
  68                 root_ino = options;
  69
  70         options = ptr;
  71         while(options){
  72                 ptr = strchr(options, ',');
  73                 if(ptr != NULL)
  74                         *ptr++ = '\0';
  75                 if(*options != '\0'){
  76                         if(!strcmp(options, "append"))
  77                                 append = 1;
  78                         else printf("hostfs_args - unsupported option - %s\n",
  79                                     options);
  80                 }
  81                 options = ptr;
  82         }
  83         return(0);
  84 }
  85
  86 __uml_setup("hostfs=", hostfs_args,
  87 "hostfs=<root dir>,<flags>,...\n"
  88 "    This is used to set hostfs parameters.  The root directory argument\n"
  89 "    is used to confine all hostfs mounts to within the specified directory\n"
  90 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
  91 "    mount anything on the host that's accessible to the user that's running\n"
  92 "    it.\n"
  93 "    The only flag currently supported is 'append', which specifies that all\n"
  94 "    files opened by hostfs will be opened in append mode.\n\n"
  95 );
  96 #endif
  97
  98 static char *dentry_name(struct dentry *dentry, int extra)
  99 {
 100         struct dentry *parent;
 101         char *root, *name;
 102         int len;
 103
 104         len = 0;
 105         parent = dentry;
 106         while(parent->d_parent != parent){
 107                 len += parent->d_name.len + 1;
 108                 parent = parent->d_parent;
 109         }
 110
 111         root = HOSTFS_I(parent->d_inode)->host_filename;
 112         len += strlen(root);
 113         name = kmalloc(len + extra + 1, GFP_KERNEL);
 114         if(name == NULL) return(NULL);
 115
 116         name[len] = '\0';
 117         parent = dentry;
 118         while(parent->d_parent != parent){
 119                 len -= parent->d_name.len + 1;
 120                 name[len] = '/';
 121                 strncpy(&name[len + 1], parent->d_name.name,
 122                         parent->d_name.len);
 123                 parent = parent->d_parent;
 124         }
 125         strncpy(name, root, strlen(root));
 126         return(name);
 127 }
 128
 129 static char *inode_name(struct inode *ino, int extra)
 130 {
 131         struct dentry *dentry;
 132
 133         dentry = list_entry(ino->i_dentry.next, struct dentry, d_alias);
 134         return(dentry_name(dentry, extra));
 135 }
 136
 137 static int read_name(struct inode *ino, char *name)
 138 {
 139         /* The non-int inode fields are copied into ints by stat_file and
 140          * then copied into the inode because passing the actual pointers
 141          * in and having them treated as int * breaks on big-endian machines
 142          */
 143         int err;
 144         int i_mode, i_nlink, i_blksize;
 145         unsigned long long i_size;
 146         unsigned long long i_ino;
 147         unsigned long long i_blocks;
 148
 149         err = stat_file(name, &i_ino, &i_mode, &i_nlink, &ino->i_uid,
 150                         &ino->i_gid, &i_size, &ino->i_atime, &ino->i_mtime,
 151                         &ino->i_ctime, &i_blksize, &i_blocks);
 152         if(err)
 153                 return(err);
 154
 155         ino->i_ino = i_ino;
 156         ino->i_mode = i_mode;
 157         ino->i_nlink = i_nlink;
 158         ino->i_size = i_size;
 159         ino->i_blocks = i_blocks;
 160         return(0);
 161 }
 162
 163 static char *follow_link(char *link)
 164 {
 165         int len, n;
 166         char *name, *resolved, *end;
 167
 168         len = 64;
 169         while(1){
 170                 n = -ENOMEM;
 171                 name = kmalloc(len, GFP_KERNEL);
 172                 if(name == NULL)
 173                         goto out;
 174
 175                 n = do_readlink(link, name, len);
 176                 if(n < len)
 177                         break;
 178                 len *= 2;
 179                 kfree(name);
 180         }
 181         if(n < 0)
 182                 goto out_free;
 183
 184         if(*name == '/')
 185                 return(name);
 186
 187         end = strrchr(link, '/');
 188         if(end == NULL)
 189                 return(name);
 190
 191         *(end + 1) = '\0';
 192         len = strlen(link) + strlen(name) + 1;
 193
 194         resolved = kmalloc(len, GFP_KERNEL);
 195         if(resolved == NULL){
 196                 n = -ENOMEM;
 197                 goto out_free;
 198         }
 199
 200         sprintf(resolved, "%s%s", link, name);
 201         kfree(name);
 202         kfree(link);
 203         return(resolved);
 204
 205  out_free:
 206         kfree(name);
 207  out:
 208         return(ERR_PTR(n));
 209 }
 210
 211 static int read_inode(struct inode *ino)
 212 {
 213         char *name;
 214         int err = 0;
 215
 216         /* Unfortunately, we are called from iget() when we don't have a dentry
 217          * allocated yet.
 218          */
 219         if(list_empty(&ino->i_dentry))
 220                 goto out;
 221
 222         err = -ENOMEM;
 223         name = inode_name(ino, 0);
 224         if(name == NULL)
 225                 goto out;
 226
 227         if(file_type(name, NULL, NULL) == OS_TYPE_SYMLINK){
 228                 name = follow_link(name);
 229                 if(IS_ERR(name)){
 230                         err = PTR_ERR(name);
 231                         goto out;
 232                 }
 233         }
 234
 235         err = read_name(ino, name);
 236         kfree(name);
 237  out:
 238         return(err);
 239 }
 240
 241 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 242 {
 243         /* do_statfs uses struct statfs64 internally, but the linux kernel
 244          * struct statfs still has 32-bit versions for most of these fields,
 245          * so we convert them here
 246          */
 247         int err;
 248         long long f_blocks;
 249         long long f_bfree;
 250         long long f_bavail;
 251         long long f_files;
 252         long long f_ffree;
 253
 254         err = do_statfs(HOSTFS_I(dentry->d_sb->s_root->d_inode)->host_filename,
 255                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 256                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 257                         &sf->f_namelen, sf->f_spare);
 258         if(err) return(err);
 259         sf->f_blocks = f_blocks;
 260         sf->f_bfree = f_bfree;
 261         sf->f_bavail = f_bavail;
 262         sf->f_files = f_files;
 263         sf->f_ffree = f_ffree;
 264         sf->f_type = HOSTFS_SUPER_MAGIC;
 265         return(0);
 266 }
 267
 268 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 269 {
 270         struct hostfs_inode_info *hi;
 271
 272         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 273         if(hi == NULL)
 274                 return(NULL);
 275
 276         *hi = ((struct hostfs_inode_info) { .host_filename      = NULL,
 277                                             .fd                 = -1,
 278                                             .mode               = 0 });
 279         inode_init_once(&hi->vfs_inode);
 280         return(&hi->vfs_inode);
 281 }
 282
 283 static void hostfs_delete_inode(struct inode *inode)
 284 {
 285         truncate_inode_pages(&inode->i_data, 0);
 286         if(HOSTFS_I(inode)->fd != -1) {
 287                 close_file(&HOSTFS_I(inode)->fd);
 288                 HOSTFS_I(inode)->fd = -1;
 289         }
 290         clear_inode(inode);
 291 }
 292
 293 static void hostfs_destroy_inode(struct inode *inode)
 294 {
 295         kfree(HOSTFS_I(inode)->host_filename);
 296
 297         /*XXX: This should not happen, probably. The check is here for
 298          * additional safety.*/
 299         if(HOSTFS_I(inode)->fd != -1) {
 300                 close_file(&HOSTFS_I(inode)->fd);
 301                 printk(KERN_DEBUG "Closing host fd in .destroy_inode\n");
 302         }
 303
 304         kfree(HOSTFS_I(inode));
 305 }
 306
 307 static void hostfs_read_inode(struct inode *inode)
 308 {
 309         read_inode(inode);
 310 }
 311
 312 static const struct super_operations hostfs_sbops = {
 313         .alloc_inode    = hostfs_alloc_inode,
 314         .drop_inode     = generic_delete_inode,
 315         .delete_inode   = hostfs_delete_inode,
 316         .destroy_inode  = hostfs_destroy_inode,
 317         .read_inode     = hostfs_read_inode,
 318         .statfs         = hostfs_statfs,
 319 };
 320
 321 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 322 {
 323         void *dir;
 324         char *name;
 325         unsigned long long next, ino;
 326         int error, len;
 327
 328         name = dentry_name(file->f_path.dentry, 0);
 329         if(name == NULL) return(-ENOMEM);
 330         dir = open_dir(name, &error);
 331         kfree(name);
 332         if(dir == NULL) return(-error);
 333         next = file->f_pos;
 334         while((name = read_dir(dir, &next, &ino, &len)) != NULL){
 335                 error = (*filldir)(ent, name, len, file->f_pos,
 336                                    ino, DT_UNKNOWN);
 337                 if(error) break;
 338                 file->f_pos = next;
 339         }
 340         close_dir(dir);
 341         return(0);
 342 }
 343
 344 int hostfs_file_open(struct inode *ino, struct file *file)
 345 {
 346         char *name;
 347         int mode = 0, r = 0, w = 0, fd;
 348
 349         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 350         if((mode & HOSTFS_I(ino)->mode) == mode)
 351                 return(0);
 352
 353         /* The file may already have been opened, but with the wrong access,
 354          * so this resets things and reopens the file with the new access.
 355          */
 356         if(HOSTFS_I(ino)->fd != -1){
 357                 close_file(&HOSTFS_I(ino)->fd);
 358                 HOSTFS_I(ino)->fd = -1;
 359         }
 360
 361         HOSTFS_I(ino)->mode |= mode;
 362         if(HOSTFS_I(ino)->mode & FMODE_READ)
 363                 r = 1;
 364         if(HOSTFS_I(ino)->mode & FMODE_WRITE)
 365                 w = 1;
 366         if(w)
 367                 r = 1;
 368
 369         name = dentry_name(file->f_path.dentry, 0);
 370         if(name == NULL)
 371                 return(-ENOMEM);
 372
 373         fd = open_file(name, r, w, append);
 374         kfree(name);
 375         if(fd < 0) return(fd);
 376         FILE_HOSTFS_I(file)->fd = fd;
 377
 378         return(0);
 379 }
 380
 381 int hostfs_fsync(struct file *file, struct dentry *dentry, int datasync)
 382 {
 383         return fsync_file(HOSTFS_I(dentry->d_inode)->fd, datasync);
 384 }
 385
 386 static const struct file_operations hostfs_file_fops = {
 387         .llseek         = generic_file_llseek,
 388         .read           = do_sync_read,
 389         .sendfile       = generic_file_sendfile,
 390         .aio_read       = generic_file_aio_read,
 391         .aio_write      = generic_file_aio_write,
 392         .write          = do_sync_write,
 393         .mmap           = generic_file_mmap,
 394         .open           = hostfs_file_open,
 395         .release        = NULL,
 396         .fsync          = hostfs_fsync,
 397 };
 398
 399 static const struct file_operations hostfs_dir_fops = {
 400         .llseek         = generic_file_llseek,
 401         .readdir        = hostfs_readdir,
 402         .read           = generic_read_dir,
 403 };
 404
 405 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 406 {
 407         struct address_space *mapping = page->mapping;
 408         struct inode *inode = mapping->host;
 409         char *buffer;
 410         unsigned long long base;
 411         int count = PAGE_CACHE_SIZE;
 412         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 413         int err;
 414
 415         if (page->index >= end_index)
 416                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 417
 418         buffer = kmap(page);
 419         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 420
 421         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 422         if(err != count){
 423                 ClearPageUptodate(page);
 424                 goto out;
 425         }
 426
 427         if (base > inode->i_size)
 428                 inode->i_size = base;
 429
 430         if (PageError(page))
 431                 ClearPageError(page);
 432         err = 0;
 433
 434  out:
 435         kunmap(page);
 436
 437         unlock_page(page);
 438         return err;
 439 }
 440
 441 int hostfs_readpage(struct file *file, struct page *page)
 442 {
 443         char *buffer;
 444         long long start;
 445         int err = 0;
 446
 447         start = (long long) page->index << PAGE_CACHE_SHIFT;
 448         buffer = kmap(page);
 449         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 450                         PAGE_CACHE_SIZE);
 451         if(err < 0) goto out;
 452
 453         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 454
 455         flush_dcache_page(page);
 456         SetPageUptodate(page);
 457         if (PageError(page)) ClearPageError(page);
 458         err = 0;
 459  out:
 460         kunmap(page);
 461         unlock_page(page);
 462         return(err);
 463 }
 464
 465 int hostfs_prepare_write(struct file *file, struct page *page,
 466                          unsigned int from, unsigned int to)
 467 {
 468         char *buffer;
 469         long long start, tmp;
 470         int err;
 471
 472         start = (long long) page->index << PAGE_CACHE_SHIFT;
 473         buffer = kmap(page);
 474         if(from != 0){
 475                 tmp = start;
 476                 err = read_file(FILE_HOSTFS_I(file)->fd, &tmp, buffer,
 477                                 from);
 478                 if(err < 0) goto out;
 479         }
 480         if(to != PAGE_CACHE_SIZE){
 481                 start += to;
 482                 err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer + to,
 483                                 PAGE_CACHE_SIZE - to);
 484                 if(err < 0) goto out;
 485         }
 486         err = 0;
 487  out:
 488         kunmap(page);
 489         return(err);
 490 }
 491
 492 int hostfs_commit_write(struct file *file, struct page *page, unsigned from,
 493                  unsigned to)
 494 {
 495         struct address_space *mapping = page->mapping;
 496         struct inode *inode = mapping->host;
 497         char *buffer;
 498         long long start;
 499         int err = 0;
 500
 501         start = (((long long) page->index) << PAGE_CACHE_SHIFT) + from;
 502         buffer = kmap(page);
 503         err = write_file(FILE_HOSTFS_I(file)->fd, &start, buffer + from,
 504                          to - from);
 505         if(err > 0) err = 0;
 506
 507         /* Actually, if !err, write_file has added to-from to start, so, despite
 508          * the appearance, we are comparing i_size against the _last_ written
 509          * location, as we should. */
 510
 511         if(!err && (start > inode->i_size))
 512                 inode->i_size = start;
 513
 514         kunmap(page);
 515         return(err);
 516 }
 517
 518 static const struct address_space_operations hostfs_aops = {
 519         .writepage      = hostfs_writepage,
 520         .readpage       = hostfs_readpage,
 521         .set_page_dirty = __set_page_dirty_nobuffers,
 522         .prepare_write  = hostfs_prepare_write,
 523         .commit_write   = hostfs_commit_write
 524 };
 525
 526 static int init_inode(struct inode *inode, struct dentry *dentry)
 527 {
 528         char *name;
 529         int type, err = -ENOMEM;
 530         int maj, min;
 531         dev_t rdev = 0;
 532
 533         if(dentry){
 534                 name = dentry_name(dentry, 0);
 535                 if(name == NULL)
 536                         goto out;
 537                 type = file_type(name, &maj, &min);
 538                 /*Reencode maj and min with the kernel encoding.*/
 539                 rdev = MKDEV(maj, min);
 540                 kfree(name);
 541         }
 542         else type = OS_TYPE_DIR;
 543
 544         err = 0;
 545         if(type == OS_TYPE_SYMLINK)
 546                 inode->i_op = &page_symlink_inode_operations;
 547         else if(type == OS_TYPE_DIR)
 548                 inode->i_op = &hostfs_dir_iops;
 549         else inode->i_op = &hostfs_iops;
 550
 551         if(type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
 552         else inode->i_fop = &hostfs_file_fops;
 553
 554         if(type == OS_TYPE_SYMLINK)
 555                 inode->i_mapping->a_ops = &hostfs_link_aops;
 556         else inode->i_mapping->a_ops = &hostfs_aops;
 557
 558         switch (type) {
 559         case OS_TYPE_CHARDEV:
 560                 init_special_inode(inode, S_IFCHR, rdev);
 561                 break;
 562         case OS_TYPE_BLOCKDEV:
 563                 init_special_inode(inode, S_IFBLK, rdev);
 564                 break;
 565         case OS_TYPE_FIFO:
 566                 init_special_inode(inode, S_IFIFO, 0);
 567                 break;
 568         case OS_TYPE_SOCK:
 569                 init_special_inode(inode, S_IFSOCK, 0);
 570                 break;
 571         }
 572  out:
 573         return(err);
 574 }
 575
 576 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 577                  struct nameidata *nd)
 578 {
 579         struct inode *inode;
 580         char *name;
 581         int error, fd;
 582
 583         error = -ENOMEM;
 584         inode = iget(dir->i_sb, 0);
 585         if(inode == NULL) goto out;
 586
 587         error = init_inode(inode, dentry);
 588         if(error)
 589                 goto out_put;
 590
 591         error = -ENOMEM;
 592         name = dentry_name(dentry, 0);
 593         if(name == NULL)
 594                 goto out_put;
 595
 596         fd = file_create(name,
 597                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 598                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 599                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 600         if(fd < 0)
 601                 error = fd;
 602         else error = read_name(inode, name);
 603
 604         kfree(name);
 605         if(error)
 606                 goto out_put;
 607
 608         HOSTFS_I(inode)->fd = fd;
 609         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 610         d_instantiate(dentry, inode);
 611         return(0);
 612
 613  out_put:
 614         iput(inode);
 615  out:
 616         return(error);
 617 }
 618
 619 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 620                             struct nameidata *nd)
 621 {
 622         struct inode *inode;
 623         char *name;
 624         int err;
 625
 626         err = -ENOMEM;
 627         inode = iget(ino->i_sb, 0);
 628         if(inode == NULL)
 629                 goto out;
 630
 631         err = init_inode(inode, dentry);
 632         if(err)
 633                 goto out_put;
 634
 635         err = -ENOMEM;
 636         name = dentry_name(dentry, 0);
 637         if(name == NULL)
 638                 goto out_put;
 639
 640         err = read_name(inode, name);
 641         kfree(name);
 642         if(err == -ENOENT){
 643                 iput(inode);
 644                 inode = NULL;
 645         }
 646         else if(err)
 647                 goto out_put;
 648
 649         d_add(dentry, inode);
 650         dentry->d_op = &hostfs_dentry_ops;
 651         return(NULL);
 652
 653  out_put:
 654         iput(inode);
 655  out:
 656         return(ERR_PTR(err));
 657 }
 658
 659 static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
 660 {
 661         char *file;
 662         int len;
 663
 664         file = inode_name(ino, dentry->d_name.len + 1);
 665         if(file == NULL) return(NULL);
 666         strcat(file, "/");
 667         len = strlen(file);
 668         strncat(file, dentry->d_name.name, dentry->d_name.len);
 669         file[len + dentry->d_name.len] = '\0';
 670         return(file);
 671 }
 672
 673 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 674 {
 675         char *from_name, *to_name;
 676         int err;
 677
 678         if((from_name = inode_dentry_name(ino, from)) == NULL)
 679                 return(-ENOMEM);
 680         to_name = dentry_name(to, 0);
 681         if(to_name == NULL){
 682                 kfree(from_name);
 683                 return(-ENOMEM);
 684         }
 685         err = link_file(to_name, from_name);
 686         kfree(from_name);
 687         kfree(to_name);
 688         return(err);
 689 }
 690
 691 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 692 {
 693         char *file;
 694         int err;
 695
 696         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 697         if(append)
 698                 return(-EPERM);
 699
 700         err = unlink_file(file);
 701         kfree(file);
 702         return(err);
 703 }
 704
 705 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 706 {
 707         char *file;
 708         int err;
 709
 710         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 711         err = make_symlink(file, to);
 712         kfree(file);
 713         return(err);
 714 }
 715
 716 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 717 {
 718         char *file;
 719         int err;
 720
 721         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 722         err = do_mkdir(file, mode);
 723         kfree(file);
 724         return(err);
 725 }
 726
 727 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 728 {
 729         char *file;
 730         int err;
 731
 732         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 733         err = do_rmdir(file);
 734         kfree(file);
 735         return(err);
 736 }
 737
 738 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 739 {
 740         struct inode *inode;
 741         char *name;
 742         int err = -ENOMEM;
 743
 744         inode = iget(dir->i_sb, 0);
 745         if(inode == NULL)
 746                 goto out;
 747
 748         err = init_inode(inode, dentry);
 749         if(err)
 750                 goto out_put;
 751
 752         err = -ENOMEM;
 753         name = dentry_name(dentry, 0);
 754         if(name == NULL)
 755                 goto out_put;
 756
 757         init_special_inode(inode, mode, dev);
 758         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 759         if(err)
 760                 goto out_free;
 761
 762         err = read_name(inode, name);
 763         kfree(name);
 764         if(err)
 765                 goto out_put;
 766
 767         d_instantiate(dentry, inode);
 768         return(0);
 769
 770  out_free:
 771         kfree(name);
 772  out_put:
 773         iput(inode);
 774  out:
 775         return(err);
 776 }
 777
 778 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 779                   struct inode *to_ino, struct dentry *to)
 780 {
 781         char *from_name, *to_name;
 782         int err;
 783
 784         if((from_name = inode_dentry_name(from_ino, from)) == NULL)
 785                 return(-ENOMEM);
 786         if((to_name = inode_dentry_name(to_ino, to)) == NULL){
 787                 kfree(from_name);
 788                 return(-ENOMEM);
 789         }
 790         err = rename_file(from_name, to_name);
 791         kfree(from_name);
 792         kfree(to_name);
 793         return(err);
 794 }
 795
 796 int hostfs_permission(struct inode *ino, int desired, struct nameidata *nd)
 797 {
 798         char *name;
 799         int r = 0, w = 0, x = 0, err;
 800
 801         if (desired & MAY_READ) r = 1;
 802         if (desired & MAY_WRITE) w = 1;
 803         if (desired & MAY_EXEC) x = 1;
 804         name = inode_name(ino, 0);
 805         if (name == NULL) return(-ENOMEM);
 806
 807         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 808                         S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 809                 err = 0;
 810         else
 811                 err = access_file(name, r, w, x);
 812         kfree(name);
 813         if(!err)
 814                 err = generic_permission(ino, desired, NULL);
 815         return err;
 816 }
 817
 818 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 819 {
 820         struct hostfs_iattr attrs;
 821         char *name;
 822         int err;
 823
 824         err = inode_change_ok(dentry->d_inode, attr);
 825         if (err)
 826                 return err;
 827
 828         if(append)
 829                 attr->ia_valid &= ~ATTR_SIZE;
 830
 831         attrs.ia_valid = 0;
 832         if(attr->ia_valid & ATTR_MODE){
 833                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 834                 attrs.ia_mode = attr->ia_mode;
 835         }
 836         if(attr->ia_valid & ATTR_UID){
 837                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 838                 attrs.ia_uid = attr->ia_uid;
 839         }
 840         if(attr->ia_valid & ATTR_GID){
 841                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 842                 attrs.ia_gid = attr->ia_gid;
 843         }
 844         if(attr->ia_valid & ATTR_SIZE){
 845                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 846                 attrs.ia_size = attr->ia_size;
 847         }
 848         if(attr->ia_valid & ATTR_ATIME){
 849                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 850                 attrs.ia_atime = attr->ia_atime;
 851         }
 852         if(attr->ia_valid & ATTR_MTIME){
 853                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 854                 attrs.ia_mtime = attr->ia_mtime;
 855         }
 856         if(attr->ia_valid & ATTR_CTIME){
 857                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 858                 attrs.ia_ctime = attr->ia_ctime;
 859         }
 860         if(attr->ia_valid & ATTR_ATIME_SET){
 861                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 862         }
 863         if(attr->ia_valid & ATTR_MTIME_SET){
 864                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 865         }
 866         name = dentry_name(dentry, 0);
 867         if(name == NULL) return(-ENOMEM);
 868         err = set_attr(name, &attrs);
 869         kfree(name);
 870         if(err)
 871                 return(err);
 872
 873         return(inode_setattr(dentry->d_inode, attr));
 874 }
 875
 876 int hostfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 877            struct kstat *stat)
 878 {
 879         generic_fillattr(dentry->d_inode, stat);
 880         return(0);
 881 }
 882
 883 static const struct inode_operations hostfs_iops = {
 884         .create         = hostfs_create,
 885         .link           = hostfs_link,
 886         .unlink         = hostfs_unlink,
 887         .symlink        = hostfs_symlink,
 888         .mkdir          = hostfs_mkdir,
 889         .rmdir          = hostfs_rmdir,
 890         .mknod          = hostfs_mknod,
 891         .rename         = hostfs_rename,
 892         .permission     = hostfs_permission,
 893         .setattr        = hostfs_setattr,
 894         .getattr        = hostfs_getattr,
 895 };
 896
 897 static const struct inode_operations hostfs_dir_iops = {
 898         .create         = hostfs_create,
 899         .lookup         = hostfs_lookup,
 900         .link           = hostfs_link,
 901         .unlink         = hostfs_unlink,
 902         .symlink        = hostfs_symlink,
 903         .mkdir          = hostfs_mkdir,
 904         .rmdir          = hostfs_rmdir,
 905         .mknod          = hostfs_mknod,
 906         .rename         = hostfs_rename,
 907         .permission     = hostfs_permission,
 908         .setattr        = hostfs_setattr,
 909         .getattr        = hostfs_getattr,
 910 };
 911
 912 int hostfs_link_readpage(struct file *file, struct page *page)
 913 {
 914         char *buffer, *name;
 915         int err;
 916
 917         buffer = kmap(page);
 918         name = inode_name(page->mapping->host, 0);
 919         if(name == NULL) return(-ENOMEM);
 920         err = do_readlink(name, buffer, PAGE_CACHE_SIZE);
 921         kfree(name);
 922         if(err == PAGE_CACHE_SIZE)
 923                 err = -E2BIG;
 924         else if(err > 0){
 925                 flush_dcache_page(page);
 926                 SetPageUptodate(page);
 927                 if (PageError(page)) ClearPageError(page);
 928                 err = 0;
 929         }
 930         kunmap(page);
 931         unlock_page(page);
 932         return(err);
 933 }
 934
 935 static const struct address_space_operations hostfs_link_aops = {
 936         .readpage       = hostfs_link_readpage,
 937 };
 938
 939 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 940 {
 941         struct inode *root_inode;
 942         char *name, *data = d;
 943         int err;
 944
 945         sb->s_blocksize = 1024;
 946         sb->s_blocksize_bits = 10;
 947         sb->s_magic = HOSTFS_SUPER_MAGIC;
 948         sb->s_op = &hostfs_sbops;
 949
 950         if((data == NULL) || (*data == '\0'))
 951                 data = root_ino;
 952
 953         err = -ENOMEM;
 954         name = kmalloc(strlen(data) + 1, GFP_KERNEL);
 955         if(name == NULL)
 956                 goto out;
 957
 958         strcpy(name, data);
 959
 960         root_inode = iget(sb, 0);
 961         if(root_inode == NULL)
 962                 goto out_free;
 963
 964         err = init_inode(root_inode, NULL);
 965         if(err)
 966                 goto out_put;
 967
 968         HOSTFS_I(root_inode)->host_filename = name;
 969
 970         err = -ENOMEM;
 971         sb->s_root = d_alloc_root(root_inode);
 972         if(sb->s_root == NULL)
 973                 goto out_put;
 974
 975         err = read_inode(root_inode);
 976         if(err){
 977                 /* No iput in this case because the dput does that for us */
 978                 dput(sb->s_root);
 979                 sb->s_root = NULL;
 980                 goto out_free;
 981         }
 982
 983         return(0);
 984
 985  out_put:
 986         iput(root_inode);
 987  out_free:
 988         kfree(name);
 989  out:
 990         return(err);
 991 }
 992
 993 static int hostfs_read_sb(struct file_system_type *type,
 994                           int flags, const char *dev_name,
 995                           void *data, struct vfsmount *mnt)
 996 {
 997         return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
 998 }
 999
1000 static struct file_system_type hostfs_type = {
1001         .owner          = THIS_MODULE,
1002         .name           = "hostfs",
1003         .get_sb         = hostfs_read_sb,
1004         .kill_sb        = kill_anon_super,
1005         .fs_flags       = 0,
1006 };
1007
1008 static int __init init_hostfs(void)
1009 {
1010         return(register_filesystem(&hostfs_type));
1011 }
1012
1013 static void __exit exit_hostfs(void)
1014 {
1015         unregister_filesystem(&hostfs_type);
1016 }
1017
1018 module_init(init_hostfs)
1019 module_exit(exit_hostfs)
1020 MODULE_LICENSE("GPL");
1021
1022 /*
1023  * Overrides for Emacs so that we follow Linus's tabbing style.
1024  * Emacs will notice this stuff at the end of the file and automatically
1025  * adjust the settings for this buffer only.  This must remain at the end
1026  * of the file.
1027  * ---------------------------------------------------------------------------
1028  * Local variables:
1029  * c-file-style: "linux"
1030  * End:
1031  */