fs/hostfs/hostfs_kern.c

   1 /*
   2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.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 "init.h"
  24
  25 struct hostfs_inode_info {
  26         char *host_filename;
  27         int fd;
  28         int mode;
  29         struct inode vfs_inode;
  30 };
  31
  32 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  33 {
  34         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
  35 }
  36
  37 #define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)
  38
  39 int hostfs_d_delete(struct dentry *dentry)
  40 {
  41         return 1;
  42 }
  43
  44 struct dentry_operations hostfs_dentry_ops = {
  45         .d_delete               = hostfs_d_delete,
  46 };
  47
  48 /* Changed in hostfs_args before the kernel starts running */
  49 static char *root_ino = "";
  50 static int append = 0;
  51
  52 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
  53
  54 static const struct inode_operations hostfs_iops;
  55 static const struct inode_operations hostfs_dir_iops;
  56 static const struct address_space_operations hostfs_link_aops;
  57
  58 #ifndef MODULE
  59 static int __init hostfs_args(char *options, int *add)
  60 {
  61         char *ptr;
  62
  63         ptr = strchr(options, ',');
  64         if(ptr != NULL)
  65                 *ptr++ = '\0';
  66         if(*options != '\0')
  67                 root_ino = options;
  68
  69         options = ptr;
  70         while(options){
  71                 ptr = strchr(options, ',');
  72                 if(ptr != NULL)
  73                         *ptr++ = '\0';
  74                 if(*options != '\0'){
  75                         if(!strcmp(options, "append"))
  76                                 append = 1;
  77                         else printf("hostfs_args - unsupported option - %s\n",
  78                                     options);
  79                 }
  80                 options = ptr;
  81         }
  82         return 0;
  83 }
  84
  85 __uml_setup("hostfs=", hostfs_args,
  86 "hostfs=<root dir>,<flags>,...\n"
  87 "    This is used to set hostfs parameters.  The root directory argument\n"
  88 "    is used to confine all hostfs mounts to within the specified directory\n"
  89 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
  90 "    mount anything on the host that's accessible to the user that's running\n"
  91 "    it.\n"
  92 "    The only flag currently supported is 'append', which specifies that all\n"
  93 "    files opened by hostfs will be opened in append mode.\n\n"
  94 );
  95 #endif
  96
  97 static char *dentry_name(struct dentry *dentry, int extra)
  98 {
  99         struct dentry *parent;
 100         char *root, *name;
 101         int len;
 102
 103         len = 0;
 104         parent = dentry;
 105         while(parent->d_parent != parent){
 106                 len += parent->d_name.len + 1;
 107                 parent = parent->d_parent;
 108         }
 109
 110         root = HOSTFS_I(parent->d_inode)->host_filename;
 111         len += strlen(root);
 112         name = kmalloc(len + extra + 1, GFP_KERNEL);
 113         if(name == NULL)
 114                 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, -1);
 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)
 259                 return err;
 260         sf->f_blocks = f_blocks;
 261         sf->f_bfree = f_bfree;
 262         sf->f_bavail = f_bavail;
 263         sf->f_files = f_files;
 264         sf->f_ffree = f_ffree;
 265         sf->f_type = HOSTFS_SUPER_MAGIC;
 266         return 0;
 267 }
 268
 269 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 270 {
 271         struct hostfs_inode_info *hi;
 272
 273         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 274         if(hi == NULL)
 275                 return NULL;
 276
 277         *hi = ((struct hostfs_inode_info) { .host_filename      = NULL,
 278                                             .fd                 = -1,
 279                                             .mode               = 0 });
 280         inode_init_once(&hi->vfs_inode);
 281         return &hi->vfs_inode;
 282 }
 283
 284 static void hostfs_delete_inode(struct inode *inode)
 285 {
 286         truncate_inode_pages(&inode->i_data, 0);
 287         if(HOSTFS_I(inode)->fd != -1) {
 288                 close_file(&HOSTFS_I(inode)->fd);
 289                 HOSTFS_I(inode)->fd = -1;
 290         }
 291         clear_inode(inode);
 292 }
 293
 294 static void hostfs_destroy_inode(struct inode *inode)
 295 {
 296         kfree(HOSTFS_I(inode)->host_filename);
 297
 298         /*XXX: This should not happen, probably. The check is here for
 299          * additional safety.*/
 300         if(HOSTFS_I(inode)->fd != -1) {
 301                 close_file(&HOSTFS_I(inode)->fd);
 302                 printk(KERN_DEBUG "Closing host fd in .destroy_inode\n");
 303         }
 304
 305         kfree(HOSTFS_I(inode));
 306 }
 307
 308 static void hostfs_read_inode(struct inode *inode)
 309 {
 310         read_inode(inode);
 311 }
 312
 313 static const struct super_operations hostfs_sbops = {
 314         .alloc_inode    = hostfs_alloc_inode,
 315         .drop_inode     = generic_delete_inode,
 316         .delete_inode   = hostfs_delete_inode,
 317         .destroy_inode  = hostfs_destroy_inode,
 318         .read_inode     = hostfs_read_inode,
 319         .statfs         = hostfs_statfs,
 320 };
 321
 322 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 323 {
 324         void *dir;
 325         char *name;
 326         unsigned long long next, ino;
 327         int error, len;
 328
 329         name = dentry_name(file->f_path.dentry, 0);
 330         if(name == NULL)
 331                 return -ENOMEM;
 332         dir = open_dir(name, &error);
 333         kfree(name);
 334         if(dir == NULL)
 335                 return -error;
 336         next = file->f_pos;
 337         while((name = read_dir(dir, &next, &ino, &len)) != NULL){
 338                 error = (*filldir)(ent, name, len, file->f_pos,
 339                                    ino, DT_UNKNOWN);
 340                 if(error) break;
 341                 file->f_pos = next;
 342         }
 343         close_dir(dir);
 344         return 0;
 345 }
 346
 347 int hostfs_file_open(struct inode *ino, struct file *file)
 348 {
 349         char *name;
 350         int mode = 0, r = 0, w = 0, fd;
 351
 352         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 353         if((mode & HOSTFS_I(ino)->mode) == mode)
 354                 return 0;
 355
 356         /* The file may already have been opened, but with the wrong access,
 357          * so this resets things and reopens the file with the new access.
 358          */
 359         if(HOSTFS_I(ino)->fd != -1){
 360                 close_file(&HOSTFS_I(ino)->fd);
 361                 HOSTFS_I(ino)->fd = -1;
 362         }
 363
 364         HOSTFS_I(ino)->mode |= mode;
 365         if(HOSTFS_I(ino)->mode & FMODE_READ)
 366                 r = 1;
 367         if(HOSTFS_I(ino)->mode & FMODE_WRITE)
 368                 w = 1;
 369         if(w)
 370                 r = 1;
 371
 372         name = dentry_name(file->f_path.dentry, 0);
 373         if(name == NULL)
 374                 return -ENOMEM;
 375
 376         fd = open_file(name, r, w, append);
 377         kfree(name);
 378         if(fd < 0)
 379                 return fd;
 380         FILE_HOSTFS_I(file)->fd = fd;
 381
 382         return 0;
 383 }
 384
 385 int hostfs_fsync(struct file *file, struct dentry *dentry, int datasync)
 386 {
 387         return fsync_file(HOSTFS_I(dentry->d_inode)->fd, datasync);
 388 }
 389
 390 static const struct file_operations hostfs_file_fops = {
 391         .llseek         = generic_file_llseek,
 392         .read           = do_sync_read,
 393         .splice_read    = generic_file_splice_read,
 394         .aio_read       = generic_file_aio_read,
 395         .aio_write      = generic_file_aio_write,
 396         .write          = do_sync_write,
 397         .mmap           = generic_file_mmap,
 398         .open           = hostfs_file_open,
 399         .release        = NULL,
 400         .fsync          = hostfs_fsync,
 401 };
 402
 403 static const struct file_operations hostfs_dir_fops = {
 404         .llseek         = generic_file_llseek,
 405         .readdir        = hostfs_readdir,
 406         .read           = generic_read_dir,
 407 };
 408
 409 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 410 {
 411         struct address_space *mapping = page->mapping;
 412         struct inode *inode = mapping->host;
 413         char *buffer;
 414         unsigned long long base;
 415         int count = PAGE_CACHE_SIZE;
 416         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 417         int err;
 418
 419         if (page->index >= end_index)
 420                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 421
 422         buffer = kmap(page);
 423         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 424
 425         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 426         if(err != count){
 427                 ClearPageUptodate(page);
 428                 goto out;
 429         }
 430
 431         if (base > inode->i_size)
 432                 inode->i_size = base;
 433
 434         if (PageError(page))
 435                 ClearPageError(page);
 436         err = 0;
 437
 438  out:
 439         kunmap(page);
 440
 441         unlock_page(page);
 442         return err;
 443 }
 444
 445 int hostfs_readpage(struct file *file, struct page *page)
 446 {
 447         char *buffer;
 448         long long start;
 449         int err = 0;
 450
 451         start = (long long) page->index << PAGE_CACHE_SHIFT;
 452         buffer = kmap(page);
 453         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 454                         PAGE_CACHE_SIZE);
 455         if(err < 0) goto out;
 456
 457         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 458
 459         flush_dcache_page(page);
 460         SetPageUptodate(page);
 461         if (PageError(page)) ClearPageError(page);
 462         err = 0;
 463  out:
 464         kunmap(page);
 465         unlock_page(page);
 466         return err;
 467 }
 468
 469 int hostfs_prepare_write(struct file *file, struct page *page,
 470                          unsigned int from, unsigned int to)
 471 {
 472         char *buffer;
 473         long long start, tmp;
 474         int err;
 475
 476         start = (long long) page->index << PAGE_CACHE_SHIFT;
 477         buffer = kmap(page);
 478         if(from != 0){
 479                 tmp = start;
 480                 err = read_file(FILE_HOSTFS_I(file)->fd, &tmp, buffer,
 481                                 from);
 482                 if(err < 0) goto out;
 483         }
 484         if(to != PAGE_CACHE_SIZE){
 485                 start += to;
 486                 err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer + to,
 487                                 PAGE_CACHE_SIZE - to);
 488                 if(err < 0) goto out;
 489         }
 490         err = 0;
 491  out:
 492         kunmap(page);
 493         return err;
 494 }
 495
 496 int hostfs_commit_write(struct file *file, struct page *page, unsigned from,
 497                  unsigned to)
 498 {
 499         struct address_space *mapping = page->mapping;
 500         struct inode *inode = mapping->host;
 501         char *buffer;
 502         long long start;
 503         int err = 0;
 504
 505         start = (((long long) page->index) << PAGE_CACHE_SHIFT) + from;
 506         buffer = kmap(page);
 507         err = write_file(FILE_HOSTFS_I(file)->fd, &start, buffer + from,
 508                          to - from);
 509         if(err > 0) err = 0;
 510
 511         /* Actually, if !err, write_file has added to-from to start, so, despite
 512          * the appearance, we are comparing i_size against the _last_ written
 513          * location, as we should. */
 514
 515         if(!err && (start > inode->i_size))
 516                 inode->i_size = start;
 517
 518         kunmap(page);
 519         return err;
 520 }
 521
 522 static const struct address_space_operations hostfs_aops = {
 523         .writepage      = hostfs_writepage,
 524         .readpage       = hostfs_readpage,
 525         .set_page_dirty = __set_page_dirty_nobuffers,
 526         .prepare_write  = hostfs_prepare_write,
 527         .commit_write   = hostfs_commit_write
 528 };
 529
 530 static int init_inode(struct inode *inode, struct dentry *dentry)
 531 {
 532         char *name;
 533         int type, err = -ENOMEM;
 534         int maj, min;
 535         dev_t rdev = 0;
 536
 537         if(dentry){
 538                 name = dentry_name(dentry, 0);
 539                 if(name == NULL)
 540                         goto out;
 541                 type = file_type(name, &maj, &min);
 542                 /*Reencode maj and min with the kernel encoding.*/
 543                 rdev = MKDEV(maj, min);
 544                 kfree(name);
 545         }
 546         else type = OS_TYPE_DIR;
 547
 548         err = 0;
 549         if(type == OS_TYPE_SYMLINK)
 550                 inode->i_op = &page_symlink_inode_operations;
 551         else if(type == OS_TYPE_DIR)
 552                 inode->i_op = &hostfs_dir_iops;
 553         else inode->i_op = &hostfs_iops;
 554
 555         if(type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
 556         else inode->i_fop = &hostfs_file_fops;
 557
 558         if(type == OS_TYPE_SYMLINK)
 559                 inode->i_mapping->a_ops = &hostfs_link_aops;
 560         else inode->i_mapping->a_ops = &hostfs_aops;
 561
 562         switch (type) {
 563         case OS_TYPE_CHARDEV:
 564                 init_special_inode(inode, S_IFCHR, rdev);
 565                 break;
 566         case OS_TYPE_BLOCKDEV:
 567                 init_special_inode(inode, S_IFBLK, rdev);
 568                 break;
 569         case OS_TYPE_FIFO:
 570                 init_special_inode(inode, S_IFIFO, 0);
 571                 break;
 572         case OS_TYPE_SOCK:
 573                 init_special_inode(inode, S_IFSOCK, 0);
 574                 break;
 575         }
 576  out:
 577         return err;
 578 }
 579
 580 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 581                  struct nameidata *nd)
 582 {
 583         struct inode *inode;
 584         char *name;
 585         int error, fd;
 586
 587         error = -ENOMEM;
 588         inode = iget(dir->i_sb, 0);
 589         if(inode == NULL) goto out;
 590
 591         error = init_inode(inode, dentry);
 592         if(error)
 593                 goto out_put;
 594
 595         error = -ENOMEM;
 596         name = dentry_name(dentry, 0);
 597         if(name == NULL)
 598                 goto out_put;
 599
 600         fd = file_create(name,
 601                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 602                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 603                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 604         if(fd < 0)
 605                 error = fd;
 606         else error = read_name(inode, name);
 607
 608         kfree(name);
 609         if(error)
 610                 goto out_put;
 611
 612         HOSTFS_I(inode)->fd = fd;
 613         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 614         d_instantiate(dentry, inode);
 615         return 0;
 616
 617  out_put:
 618         iput(inode);
 619  out:
 620         return error;
 621 }
 622
 623 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 624                              struct nameidata *nd)
 625 {
 626         struct inode *inode;
 627         char *name;
 628         int err;
 629
 630         err = -ENOMEM;
 631         inode = iget(ino->i_sb, 0);
 632         if(inode == NULL)
 633                 goto out;
 634
 635         err = init_inode(inode, dentry);
 636         if(err)
 637                 goto out_put;
 638
 639         err = -ENOMEM;
 640         name = dentry_name(dentry, 0);
 641         if(name == NULL)
 642                 goto out_put;
 643
 644         err = read_name(inode, name);
 645         kfree(name);
 646         if(err == -ENOENT){
 647                 iput(inode);
 648                 inode = NULL;
 649         }
 650         else if(err)
 651                 goto out_put;
 652
 653         d_add(dentry, inode);
 654         dentry->d_op = &hostfs_dentry_ops;
 655         return NULL;
 656
 657  out_put:
 658         iput(inode);
 659  out:
 660         return ERR_PTR(err);
 661 }
 662
 663 static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
 664 {
 665         char *file;
 666         int len;
 667
 668         file = inode_name(ino, dentry->d_name.len + 1);
 669         if(file == NULL)
 670                 return NULL;
 671         strcat(file, "/");
 672         len = strlen(file);
 673         strncat(file, dentry->d_name.name, dentry->d_name.len);
 674         file[len + dentry->d_name.len] = '\0';
 675         return file;
 676 }
 677
 678 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 679 {
 680         char *from_name, *to_name;
 681         int err;
 682
 683         if((from_name = inode_dentry_name(ino, from)) == NULL)
 684                 return -ENOMEM;
 685         to_name = dentry_name(to, 0);
 686         if(to_name == NULL){
 687                 kfree(from_name);
 688                 return -ENOMEM;
 689         }
 690         err = link_file(to_name, from_name);
 691         kfree(from_name);
 692         kfree(to_name);
 693         return err;
 694 }
 695
 696 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 697 {
 698         char *file;
 699         int err;
 700
 701         if((file = inode_dentry_name(ino, dentry)) == NULL)
 702                 return -ENOMEM;
 703         if(append)
 704                 return -EPERM;
 705
 706         err = unlink_file(file);
 707         kfree(file);
 708         return err;
 709 }
 710
 711 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 712 {
 713         char *file;
 714         int err;
 715
 716         if((file = inode_dentry_name(ino, dentry)) == NULL)
 717                 return -ENOMEM;
 718         err = make_symlink(file, to);
 719         kfree(file);
 720         return err;
 721 }
 722
 723 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 724 {
 725         char *file;
 726         int err;
 727
 728         if((file = inode_dentry_name(ino, dentry)) == NULL)
 729                 return -ENOMEM;
 730         err = do_mkdir(file, mode);
 731         kfree(file);
 732         return err;
 733 }
 734
 735 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 736 {
 737         char *file;
 738         int err;
 739
 740         if((file = inode_dentry_name(ino, dentry)) == NULL)
 741                 return -ENOMEM;
 742         err = do_rmdir(file);
 743         kfree(file);
 744         return err;
 745 }
 746
 747 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 748 {
 749         struct inode *inode;
 750         char *name;
 751         int err = -ENOMEM;
 752
 753         inode = iget(dir->i_sb, 0);
 754         if(inode == NULL)
 755                 goto out;
 756
 757         err = init_inode(inode, dentry);
 758         if(err)
 759                 goto out_put;
 760
 761         err = -ENOMEM;
 762         name = dentry_name(dentry, 0);
 763         if(name == NULL)
 764                 goto out_put;
 765
 766         init_special_inode(inode, mode, dev);
 767         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 768         if(err)
 769                 goto out_free;
 770
 771         err = read_name(inode, name);
 772         kfree(name);
 773         if(err)
 774                 goto out_put;
 775
 776         d_instantiate(dentry, inode);
 777         return 0;
 778
 779  out_free:
 780         kfree(name);
 781  out_put:
 782         iput(inode);
 783  out:
 784         return err;
 785 }
 786
 787 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 788                   struct inode *to_ino, struct dentry *to)
 789 {
 790         char *from_name, *to_name;
 791         int err;
 792
 793         if((from_name = inode_dentry_name(from_ino, from)) == NULL)
 794                 return -ENOMEM;
 795         if((to_name = inode_dentry_name(to_ino, to)) == NULL){
 796                 kfree(from_name);
 797                 return -ENOMEM;
 798         }
 799         err = rename_file(from_name, to_name);
 800         kfree(from_name);
 801         kfree(to_name);
 802         return err;
 803 }
 804
 805 int hostfs_permission(struct inode *ino, int desired, struct nameidata *nd)
 806 {
 807         char *name;
 808         int r = 0, w = 0, x = 0, err;
 809
 810         if (desired & MAY_READ) r = 1;
 811         if (desired & MAY_WRITE) w = 1;
 812         if (desired & MAY_EXEC) x = 1;
 813         name = inode_name(ino, 0);
 814         if (name == NULL)
 815                 return -ENOMEM;
 816
 817         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 818                         S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 819                 err = 0;
 820         else
 821                 err = access_file(name, r, w, x);
 822         kfree(name);
 823         if(!err)
 824                 err = generic_permission(ino, desired, NULL);
 825         return err;
 826 }
 827
 828 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 829 {
 830         struct hostfs_iattr attrs;
 831         char *name;
 832         int err;
 833
 834         int fd = HOSTFS_I(dentry->d_inode)->fd;
 835
 836         err = inode_change_ok(dentry->d_inode, attr);
 837         if (err)
 838                 return err;
 839
 840         if(append)
 841                 attr->ia_valid &= ~ATTR_SIZE;
 842
 843         attrs.ia_valid = 0;
 844         if(attr->ia_valid & ATTR_MODE){
 845                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 846                 attrs.ia_mode = attr->ia_mode;
 847         }
 848         if(attr->ia_valid & ATTR_UID){
 849                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 850                 attrs.ia_uid = attr->ia_uid;
 851         }
 852         if(attr->ia_valid & ATTR_GID){
 853                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 854                 attrs.ia_gid = attr->ia_gid;
 855         }
 856         if(attr->ia_valid & ATTR_SIZE){
 857                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 858                 attrs.ia_size = attr->ia_size;
 859         }
 860         if(attr->ia_valid & ATTR_ATIME){
 861                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 862                 attrs.ia_atime = attr->ia_atime;
 863         }
 864         if(attr->ia_valid & ATTR_MTIME){
 865                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 866                 attrs.ia_mtime = attr->ia_mtime;
 867         }
 868         if(attr->ia_valid & ATTR_CTIME){
 869                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 870                 attrs.ia_ctime = attr->ia_ctime;
 871         }
 872         if(attr->ia_valid & ATTR_ATIME_SET){
 873                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 874         }
 875         if(attr->ia_valid & ATTR_MTIME_SET){
 876                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 877         }
 878         name = dentry_name(dentry, 0);
 879         if(name == NULL)
 880                 return -ENOMEM;
 881         err = set_attr(name, &attrs, fd);
 882         kfree(name);
 883         if(err)
 884                 return err;
 885
 886         return inode_setattr(dentry->d_inode, attr);
 887 }
 888
 889 int hostfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 890            struct kstat *stat)
 891 {
 892         generic_fillattr(dentry->d_inode, stat);
 893         return 0;
 894 }
 895
 896 static const struct inode_operations hostfs_iops = {
 897         .create         = hostfs_create,
 898         .link           = hostfs_link,
 899         .unlink         = hostfs_unlink,
 900         .symlink        = hostfs_symlink,
 901         .mkdir          = hostfs_mkdir,
 902         .rmdir          = hostfs_rmdir,
 903         .mknod          = hostfs_mknod,
 904         .rename         = hostfs_rename,
 905         .permission     = hostfs_permission,
 906         .setattr        = hostfs_setattr,
 907         .getattr        = hostfs_getattr,
 908 };
 909
 910 static const struct inode_operations hostfs_dir_iops = {
 911         .create         = hostfs_create,
 912         .lookup         = hostfs_lookup,
 913         .link           = hostfs_link,
 914         .unlink         = hostfs_unlink,
 915         .symlink        = hostfs_symlink,
 916         .mkdir          = hostfs_mkdir,
 917         .rmdir          = hostfs_rmdir,
 918         .mknod          = hostfs_mknod,
 919         .rename         = hostfs_rename,
 920         .permission     = hostfs_permission,
 921         .setattr        = hostfs_setattr,
 922         .getattr        = hostfs_getattr,
 923 };
 924
 925 int hostfs_link_readpage(struct file *file, struct page *page)
 926 {
 927         char *buffer, *name;
 928         int err;
 929
 930         buffer = kmap(page);
 931         name = inode_name(page->mapping->host, 0);
 932         if(name == NULL)
 933                 return -ENOMEM;
 934         err = do_readlink(name, buffer, PAGE_CACHE_SIZE);
 935         kfree(name);
 936         if(err == PAGE_CACHE_SIZE)
 937                 err = -E2BIG;
 938         else if(err > 0){
 939                 flush_dcache_page(page);
 940                 SetPageUptodate(page);
 941                 if (PageError(page)) ClearPageError(page);
 942                 err = 0;
 943         }
 944         kunmap(page);
 945         unlock_page(page);
 946         return err;
 947 }
 948
 949 static const struct address_space_operations hostfs_link_aops = {
 950         .readpage       = hostfs_link_readpage,
 951 };
 952
 953 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 954 {
 955         struct inode *root_inode;
 956         char *host_root_path, *req_root = d;
 957         int err;
 958
 959         sb->s_blocksize = 1024;
 960         sb->s_blocksize_bits = 10;
 961         sb->s_magic = HOSTFS_SUPER_MAGIC;
 962         sb->s_op = &hostfs_sbops;
 963
 964         /* NULL is printed as <NULL> by sprintf: avoid that. */
 965         if (req_root == NULL)
 966                 req_root = "";
 967
 968         err = -ENOMEM;
 969         host_root_path = kmalloc(strlen(root_ino) + 1
 970                                  + strlen(req_root) + 1, GFP_KERNEL);
 971         if(host_root_path == NULL)
 972                 goto out;
 973
 974         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 975
 976         root_inode = iget(sb, 0);
 977         if(root_inode == NULL)
 978                 goto out_free;
 979
 980         err = init_inode(root_inode, NULL);
 981         if(err)
 982                 goto out_put;
 983
 984         HOSTFS_I(root_inode)->host_filename = host_root_path;
 985         /* Avoid that in the error path, iput(root_inode) frees again
 986          * host_root_path through hostfs_destroy_inode! */
 987         host_root_path = NULL;
 988
 989         err = -ENOMEM;
 990         sb->s_root = d_alloc_root(root_inode);
 991         if(sb->s_root == NULL)
 992                 goto out_put;
 993
 994         err = read_inode(root_inode);
 995         if(err){
 996                 /* No iput in this case because the dput does that for us */
 997                 dput(sb->s_root);
 998                 sb->s_root = NULL;
 999                 goto out;
1000         }
1001
1002         return 0;
1003
1004 out_put:
1005         iput(root_inode);
1006 out_free:
1007         kfree(host_root_path);
1008 out:
1009         return err;
1010 }
1011
1012 static int hostfs_read_sb(struct file_system_type *type,
1013                           int flags, const char *dev_name,
1014                           void *data, struct vfsmount *mnt)
1015 {
1016         return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
1017 }
1018
1019 static struct file_system_type hostfs_type = {
1020         .owner          = THIS_MODULE,
1021         .name           = "hostfs",
1022         .get_sb         = hostfs_read_sb,
1023         .kill_sb        = kill_anon_super,
1024         .fs_flags       = 0,
1025 };
1026
1027 static int __init init_hostfs(void)
1028 {
1029         return register_filesystem(&hostfs_type);
1030 }
1031
1032 static void __exit exit_hostfs(void)
1033 {
1034         unregister_filesystem(&hostfs_type);
1035 }
1036
1037 module_init(init_hostfs)
1038 module_exit(exit_hostfs)
1039 MODULE_LICENSE("GPL");