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/version.h>
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/slab.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/blkdev.h>
  17 #include <linux/list.h>
  18 #include <linux/root_dev.h>
  19 #include <linux/statfs.h>
  20 #include <linux/kdev_t.h>
  21 #include <asm/uaccess.h>
  22 #include "hostfs.h"
  23 #include "kern_util.h"
  24 #include "kern.h"
  25 #include "user_util.h"
  26 #include "2_5compat.h"
  27 #include "init.h"
  28
  29 struct hostfs_inode_info {
  30         char *host_filename;
  31         int fd;
  32         int mode;
  33         struct inode vfs_inode;
  34 };
  35
  36 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  37 {
  38         return(list_entry(inode, struct hostfs_inode_info, vfs_inode));
  39 }
  40
  41 #define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_dentry->d_inode)
  42
  43 int hostfs_d_delete(struct dentry *dentry)
  44 {
  45         return(1);
  46 }
  47
  48 struct dentry_operations hostfs_dentry_ops = {
  49         .d_delete               = hostfs_d_delete,
  50 };
  51
  52 /* Changed in hostfs_args before the kernel starts running */
  53 static char *root_ino = "/";
  54 static int append = 0;
  55
  56 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
  57
  58 static struct inode_operations hostfs_iops;
  59 static struct inode_operations hostfs_dir_iops;
  60 static struct address_space_operations hostfs_link_aops;
  61
  62 #ifndef MODULE
  63 static int __init hostfs_args(char *options, int *add)
  64 {
  65         char *ptr;
  66
  67         ptr = strchr(options, ',');
  68         if(ptr != NULL)
  69                 *ptr++ = '\0';
  70         if(*options != '\0')
  71                 root_ino = options;
  72
  73         options = ptr;
  74         while(options){
  75                 ptr = strchr(options, ',');
  76                 if(ptr != NULL)
  77                         *ptr++ = '\0';
  78                 if(*options != '\0'){
  79                         if(!strcmp(options, "append"))
  80                                 append = 1;
  81                         else printf("hostfs_args - unsupported option - %s\n",
  82                                     options);
  83                 }
  84                 options = ptr;
  85         }
  86         return(0);
  87 }
  88
  89 __uml_setup("hostfs=", hostfs_args,
  90 "hostfs=<root dir>,<flags>,...\n"
  91 "    This is used to set hostfs parameters.  The root directory argument\n"
  92 "    is used to confine all hostfs mounts to within the specified directory\n"
  93 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
  94 "    mount anything on the host that's accessible to the user that's running\n"
  95 "    it.\n"
  96 "    The only flag currently supported is 'append', which specifies that all\n"
  97 "    files opened by hostfs will be opened in append mode.\n\n"
  98 );
  99 #endif
 100
 101 static char *dentry_name(struct dentry *dentry, int extra)
 102 {
 103         struct dentry *parent;
 104         char *root, *name;
 105         int len;
 106
 107         len = 0;
 108         parent = dentry;
 109         while(parent->d_parent != parent){
 110                 len += parent->d_name.len + 1;
 111                 parent = parent->d_parent;
 112         }
 113
 114         root = HOSTFS_I(parent->d_inode)->host_filename;
 115         len += strlen(root);
 116         name = kmalloc(len + extra + 1, GFP_KERNEL);
 117         if(name == NULL) return(NULL);
 118
 119         name[len] = '\0';
 120         parent = dentry;
 121         while(parent->d_parent != parent){
 122                 len -= parent->d_name.len + 1;
 123                 name[len] = '/';
 124                 strncpy(&name[len + 1], parent->d_name.name,
 125                         parent->d_name.len);
 126                 parent = parent->d_parent;
 127         }
 128         strncpy(name, root, strlen(root));
 129         return(name);
 130 }
 131
 132 static char *inode_name(struct inode *ino, int extra)
 133 {
 134         struct dentry *dentry;
 135
 136         dentry = list_entry(ino->i_dentry.next, struct dentry, d_alias);
 137         return(dentry_name(dentry, extra));
 138 }
 139
 140 static int read_name(struct inode *ino, char *name)
 141 {
 142         /* The non-int inode fields are copied into ints by stat_file and
 143          * then copied into the inode because passing the actual pointers
 144          * in and having them treated as int * breaks on big-endian machines
 145          */
 146         int err;
 147         int i_mode, i_nlink, i_blksize;
 148         unsigned long long i_size;
 149         unsigned long long i_ino;
 150         unsigned long long i_blocks;
 151
 152         err = stat_file(name, &i_ino, &i_mode, &i_nlink, &ino->i_uid,
 153                         &ino->i_gid, &i_size, &ino->i_atime, &ino->i_mtime,
 154                         &ino->i_ctime, &i_blksize, &i_blocks);
 155         if(err)
 156                 return(err);
 157
 158         ino->i_ino = i_ino;
 159         ino->i_mode = i_mode;
 160         ino->i_nlink = i_nlink;
 161         ino->i_size = i_size;
 162         ino->i_blksize = i_blksize;
 163         ino->i_blocks = i_blocks;
 164         if((ino->i_sb->s_dev == ROOT_DEV) && (ino->i_uid == getuid()))
 165                 ino->i_uid = 0;
 166         return(0);
 167 }
 168
 169 static char *follow_link(char *link)
 170 {
 171         int len, n;
 172         char *name, *resolved, *end;
 173
 174         len = 64;
 175         while(1){
 176                 n = -ENOMEM;
 177                 name = kmalloc(len, GFP_KERNEL);
 178                 if(name == NULL)
 179                         goto out;
 180
 181                 n = do_readlink(link, name, len);
 182                 if(n < len)
 183                         break;
 184                 len *= 2;
 185                 kfree(name);
 186         }
 187         if(n < 0)
 188                 goto out_free;
 189
 190         if(*name == '/')
 191                 return(name);
 192
 193         end = strrchr(link, '/');
 194         if(end == NULL)
 195                 return(name);
 196
 197         *(end + 1) = '\0';
 198         len = strlen(link) + strlen(name) + 1;
 199
 200         resolved = kmalloc(len, GFP_KERNEL);
 201         if(resolved == NULL){
 202                 n = -ENOMEM;
 203                 goto out_free;
 204         }
 205
 206         sprintf(resolved, "%s%s", link, name);
 207         kfree(name);
 208         kfree(link);
 209         return(resolved);
 210
 211  out_free:
 212         kfree(name);
 213  out:
 214         return(ERR_PTR(n));
 215 }
 216
 217 static int read_inode(struct inode *ino)
 218 {
 219         char *name;
 220         int err = 0;
 221
 222         /* Unfortunately, we are called from iget() when we don't have a dentry
 223          * allocated yet.
 224          */
 225         if(list_empty(&ino->i_dentry))
 226                 goto out;
 227
 228         err = -ENOMEM;
 229         name = inode_name(ino, 0);
 230         if(name == NULL)
 231                 goto out;
 232
 233         if(file_type(name, NULL, NULL) == OS_TYPE_SYMLINK){
 234                 name = follow_link(name);
 235                 if(IS_ERR(name)){
 236                         err = PTR_ERR(name);
 237                         goto out;
 238                 }
 239         }
 240
 241         err = read_name(ino, name);
 242         kfree(name);
 243  out:
 244         return(err);
 245 }
 246
 247 int hostfs_statfs(struct super_block *sb, struct kstatfs *sf)
 248 {
 249         /* do_statfs uses struct statfs64 internally, but the linux kernel
 250          * struct statfs still has 32-bit versions for most of these fields,
 251          * so we convert them here
 252          */
 253         int err;
 254         long long f_blocks;
 255         long long f_bfree;
 256         long long f_bavail;
 257         long long f_files;
 258         long long f_ffree;
 259
 260         err = do_statfs(HOSTFS_I(sb->s_root->d_inode)->host_filename,
 261                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 262                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 263                         &sf->f_namelen, sf->f_spare);
 264         if(err) return(err);
 265         sf->f_blocks = f_blocks;
 266         sf->f_bfree = f_bfree;
 267         sf->f_bavail = f_bavail;
 268         sf->f_files = f_files;
 269         sf->f_ffree = f_ffree;
 270         sf->f_type = HOSTFS_SUPER_MAGIC;
 271         return(0);
 272 }
 273
 274 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 275 {
 276         struct hostfs_inode_info *hi;
 277
 278         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 279         if(hi == NULL)
 280                 return(NULL);
 281
 282         *hi = ((struct hostfs_inode_info) { .host_filename      = NULL,
 283                                             .fd                 = -1,
 284                                             .mode               = 0 });
 285         inode_init_once(&hi->vfs_inode);
 286         return(&hi->vfs_inode);
 287 }
 288
 289 static void hostfs_delete_inode(struct inode *inode)
 290 {
 291         if(HOSTFS_I(inode)->fd != -1) {
 292                 close_file(&HOSTFS_I(inode)->fd);
 293                 HOSTFS_I(inode)->fd = -1;
 294         }
 295         clear_inode(inode);
 296 }
 297
 298 static void hostfs_destroy_inode(struct inode *inode)
 299 {
 300         if(HOSTFS_I(inode)->host_filename)
 301                 kfree(HOSTFS_I(inode)->host_filename);
 302
 303         /*XXX: This should not happen, probably. The check is here for
 304          * additional safety.*/
 305         if(HOSTFS_I(inode)->fd != -1) {
 306                 close_file(&HOSTFS_I(inode)->fd);
 307                 printk(KERN_DEBUG "Closing host fd in .destroy_inode\n");
 308         }
 309
 310         kfree(HOSTFS_I(inode));
 311 }
 312
 313 static void hostfs_read_inode(struct inode *inode)
 314 {
 315         read_inode(inode);
 316 }
 317
 318 static struct super_operations hostfs_sbops = {
 319         .alloc_inode    = hostfs_alloc_inode,
 320         .drop_inode     = generic_delete_inode,
 321         .delete_inode   = hostfs_delete_inode,
 322         .destroy_inode  = hostfs_destroy_inode,
 323         .read_inode     = hostfs_read_inode,
 324         .statfs         = hostfs_statfs,
 325 };
 326
 327 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 328 {
 329         void *dir;
 330         char *name;
 331         unsigned long long next, ino;
 332         int error, len;
 333
 334         name = dentry_name(file->f_dentry, 0);
 335         if(name == NULL) return(-ENOMEM);
 336         dir = open_dir(name, &error);
 337         kfree(name);
 338         if(dir == NULL) return(-error);
 339         next = file->f_pos;
 340         while((name = read_dir(dir, &next, &ino, &len)) != NULL){
 341                 error = (*filldir)(ent, name, len, file->f_pos,
 342                                    ino, DT_UNKNOWN);
 343                 if(error) break;
 344                 file->f_pos = next;
 345         }
 346         close_dir(dir);
 347         return(0);
 348 }
 349
 350 int hostfs_file_open(struct inode *ino, struct file *file)
 351 {
 352         char *name;
 353         int mode = 0, r = 0, w = 0, fd;
 354
 355         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 356         if((mode & HOSTFS_I(ino)->mode) == mode)
 357                 return(0);
 358
 359         /* The file may already have been opened, but with the wrong access,
 360          * so this resets things and reopens the file with the new access.
 361          */
 362         if(HOSTFS_I(ino)->fd != -1){
 363                 close_file(&HOSTFS_I(ino)->fd);
 364                 HOSTFS_I(ino)->fd = -1;
 365         }
 366
 367         HOSTFS_I(ino)->mode |= mode;
 368         if(HOSTFS_I(ino)->mode & FMODE_READ)
 369                 r = 1;
 370         if(HOSTFS_I(ino)->mode & FMODE_WRITE)
 371                 w = 1;
 372         if(w)
 373                 r = 1;
 374
 375         name = dentry_name(file->f_dentry, 0);
 376         if(name == NULL)
 377                 return(-ENOMEM);
 378
 379         fd = open_file(name, r, w, append);
 380         kfree(name);
 381         if(fd < 0) return(fd);
 382         FILE_HOSTFS_I(file)->fd = fd;
 383
 384         return(0);
 385 }
 386
 387 int hostfs_fsync(struct file *file, struct dentry *dentry, int datasync)
 388 {
 389         return(0);
 390 }
 391
 392 static struct file_operations hostfs_file_fops = {
 393         .llseek         = generic_file_llseek,
 394         .read           = generic_file_read,
 395         .sendfile       = generic_file_sendfile,
 396         .aio_read       = generic_file_aio_read,
 397         .aio_write      = generic_file_aio_write,
 398         .readv          = generic_file_readv,
 399         .writev         = generic_file_writev,
 400         .write          = generic_file_write,
 401         .mmap           = generic_file_mmap,
 402         .open           = hostfs_file_open,
 403         .release        = NULL,
 404         .fsync          = hostfs_fsync,
 405 };
 406
 407 static struct file_operations hostfs_dir_fops = {
 408         .llseek         = generic_file_llseek,
 409         .readdir        = hostfs_readdir,
 410         .read           = generic_read_dir,
 411 };
 412
 413 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 414 {
 415         struct address_space *mapping = page->mapping;
 416         struct inode *inode = mapping->host;
 417         char *buffer;
 418         unsigned long long base;
 419         int count = PAGE_CACHE_SIZE;
 420         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 421         int err;
 422
 423         if (page->index >= end_index)
 424                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 425
 426         buffer = kmap(page);
 427         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 428
 429         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 430         if(err != count){
 431                 ClearPageUptodate(page);
 432                 goto out;
 433         }
 434
 435         if (base > inode->i_size)
 436                 inode->i_size = base;
 437
 438         if (PageError(page))
 439                 ClearPageError(page);
 440         err = 0;
 441
 442  out:
 443         kunmap(page);
 444
 445         unlock_page(page);
 446         return err;
 447 }
 448
 449 int hostfs_readpage(struct file *file, struct page *page)
 450 {
 451         char *buffer;
 452         long long start;
 453         int err = 0;
 454
 455         start = (long long) page->index << PAGE_CACHE_SHIFT;
 456         buffer = kmap(page);
 457         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 458                         PAGE_CACHE_SIZE);
 459         if(err < 0) goto out;
 460
 461         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 462
 463         flush_dcache_page(page);
 464         SetPageUptodate(page);
 465         if (PageError(page)) ClearPageError(page);
 466         err = 0;
 467  out:
 468         kunmap(page);
 469         unlock_page(page);
 470         return(err);
 471 }
 472
 473 int hostfs_prepare_write(struct file *file, struct page *page,
 474                          unsigned int from, unsigned int to)
 475 {
 476         char *buffer;
 477         long long start, tmp;
 478         int err;
 479
 480         start = (long long) page->index << PAGE_CACHE_SHIFT;
 481         buffer = kmap(page);
 482         if(from != 0){
 483                 tmp = start;
 484                 err = read_file(FILE_HOSTFS_I(file)->fd, &tmp, buffer,
 485                                 from);
 486                 if(err < 0) goto out;
 487         }
 488         if(to != PAGE_CACHE_SIZE){
 489                 start += to;
 490                 err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer + to,
 491                                 PAGE_CACHE_SIZE - to);
 492                 if(err < 0) goto out;
 493         }
 494         err = 0;
 495  out:
 496         kunmap(page);
 497         return(err);
 498 }
 499
 500 int hostfs_commit_write(struct file *file, struct page *page, unsigned from,
 501                  unsigned to)
 502 {
 503         struct address_space *mapping = page->mapping;
 504         struct inode *inode = mapping->host;
 505         char *buffer;
 506         long long start;
 507         int err = 0;
 508
 509         start = (long long) (page->index << PAGE_CACHE_SHIFT) + from;
 510         buffer = kmap(page);
 511         err = write_file(FILE_HOSTFS_I(file)->fd, &start, buffer + from,
 512                          to - from);
 513         if(err > 0) err = 0;
 514         if(!err && (start > inode->i_size))
 515                 inode->i_size = start;
 516
 517         kunmap(page);
 518         return(err);
 519 }
 520
 521 static struct address_space_operations hostfs_aops = {
 522         .writepage      = hostfs_writepage,
 523         .readpage       = hostfs_readpage,
 524         .set_page_dirty = __set_page_dirty_nobuffers,
 525         .prepare_write  = hostfs_prepare_write,
 526         .commit_write   = hostfs_commit_write
 527 };
 528
 529 static int init_inode(struct inode *inode, struct dentry *dentry)
 530 {
 531         char *name;
 532         int type, err = -ENOMEM;
 533         int maj, min;
 534         dev_t rdev = 0;
 535
 536         if(dentry){
 537                 name = dentry_name(dentry, 0);
 538                 if(name == NULL)
 539                         goto out;
 540                 type = file_type(name, &maj, &min);
 541                 /*Reencode maj and min with the kernel encoding.*/
 542                 rdev = MKDEV(maj, min);
 543                 kfree(name);
 544         }
 545         else type = OS_TYPE_DIR;
 546
 547         err = 0;
 548         if(type == OS_TYPE_SYMLINK)
 549                 inode->i_op = &page_symlink_inode_operations;
 550         else if(type == OS_TYPE_DIR)
 551                 inode->i_op = &hostfs_dir_iops;
 552         else inode->i_op = &hostfs_iops;
 553
 554         if(type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
 555         else inode->i_fop = &hostfs_file_fops;
 556
 557         if(type == OS_TYPE_SYMLINK)
 558                 inode->i_mapping->a_ops = &hostfs_link_aops;
 559         else inode->i_mapping->a_ops = &hostfs_aops;
 560
 561         switch (type) {
 562         case OS_TYPE_CHARDEV:
 563                 init_special_inode(inode, S_IFCHR, rdev);
 564                 break;
 565         case OS_TYPE_BLOCKDEV:
 566                 init_special_inode(inode, S_IFBLK, rdev);
 567                 break;
 568         case OS_TYPE_FIFO:
 569                 init_special_inode(inode, S_IFIFO, 0);
 570                 break;
 571         case OS_TYPE_SOCK:
 572                 init_special_inode(inode, S_IFSOCK, 0);
 573                 break;
 574         }
 575  out:
 576         return(err);
 577 }
 578
 579 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 580                  struct nameidata *nd)
 581 {
 582         struct inode *inode;
 583         char *name;
 584         int error, fd;
 585
 586         error = -ENOMEM;
 587         inode = iget(dir->i_sb, 0);
 588         if(inode == NULL) goto out;
 589
 590         error = init_inode(inode, dentry);
 591         if(error)
 592                 goto out_put;
 593
 594         error = -ENOMEM;
 595         name = dentry_name(dentry, 0);
 596         if(name == NULL)
 597                 goto out_put;
 598
 599         fd = file_create(name,
 600                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 601                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 602                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 603         if(fd < 0)
 604                 error = fd;
 605         else error = read_name(inode, name);
 606
 607         kfree(name);
 608         if(error)
 609                 goto out_put;
 610
 611         HOSTFS_I(inode)->fd = fd;
 612         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 613         d_instantiate(dentry, inode);
 614         return(0);
 615
 616  out_put:
 617         iput(inode);
 618  out:
 619         return(error);
 620 }
 621
 622 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 623                             struct nameidata *nd)
 624 {
 625         struct inode *inode;
 626         char *name;
 627         int err;
 628
 629         err = -ENOMEM;
 630         inode = iget(ino->i_sb, 0);
 631         if(inode == NULL)
 632                 goto out;
 633
 634         err = init_inode(inode, dentry);
 635         if(err)
 636                 goto out_put;
 637
 638         err = -ENOMEM;
 639         name = dentry_name(dentry, 0);
 640         if(name == NULL)
 641                 goto out_put;
 642
 643         err = read_name(inode, name);
 644         kfree(name);
 645         if(err == -ENOENT){
 646                 iput(inode);
 647                 inode = NULL;
 648         }
 649         else if(err)
 650                 goto out_put;
 651
 652         d_add(dentry, inode);
 653         dentry->d_op = &hostfs_dentry_ops;
 654         return(NULL);
 655
 656  out_put:
 657         iput(inode);
 658  out:
 659         return(ERR_PTR(err));
 660 }
 661
 662 static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
 663 {
 664         char *file;
 665         int len;
 666
 667         file = inode_name(ino, dentry->d_name.len + 1);
 668         if(file == NULL) return(NULL);
 669         strcat(file, "/");
 670         len = strlen(file);
 671         strncat(file, dentry->d_name.name, dentry->d_name.len);
 672         file[len + dentry->d_name.len] = '\0';
 673         return(file);
 674 }
 675
 676 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 677 {
 678         char *from_name, *to_name;
 679         int err;
 680
 681         if((from_name = inode_dentry_name(ino, from)) == NULL)
 682                 return(-ENOMEM);
 683         to_name = dentry_name(to, 0);
 684         if(to_name == NULL){
 685                 kfree(from_name);
 686                 return(-ENOMEM);
 687         }
 688         err = link_file(to_name, from_name);
 689         kfree(from_name);
 690         kfree(to_name);
 691         return(err);
 692 }
 693
 694 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 695 {
 696         char *file;
 697         int err;
 698
 699         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 700         if(append)
 701                 return(-EPERM);
 702
 703         err = unlink_file(file);
 704         kfree(file);
 705         return(err);
 706 }
 707
 708 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 709 {
 710         char *file;
 711         int err;
 712
 713         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 714         err = make_symlink(file, to);
 715         kfree(file);
 716         return(err);
 717 }
 718
 719 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 720 {
 721         char *file;
 722         int err;
 723
 724         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 725         err = do_mkdir(file, mode);
 726         kfree(file);
 727         return(err);
 728 }
 729
 730 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 731 {
 732         char *file;
 733         int err;
 734
 735         if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
 736         err = do_rmdir(file);
 737         kfree(file);
 738         return(err);
 739 }
 740
 741 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 742 {
 743         struct inode *inode;
 744         char *name;
 745         int err = -ENOMEM;
 746
 747         inode = iget(dir->i_sb, 0);
 748         if(inode == NULL)
 749                 goto out;
 750
 751         err = init_inode(inode, dentry);
 752         if(err)
 753                 goto out_put;
 754
 755         err = -ENOMEM;
 756         name = dentry_name(dentry, 0);
 757         if(name == NULL)
 758                 goto out_put;
 759
 760         init_special_inode(inode, mode, dev);
 761         err = do_mknod(name, mode, dev);
 762         if(err)
 763                 goto out_free;
 764
 765         err = read_name(inode, name);
 766         kfree(name);
 767         if(err)
 768                 goto out_put;
 769
 770         d_instantiate(dentry, inode);
 771         return(0);
 772
 773  out_free:
 774         kfree(name);
 775  out_put:
 776         iput(inode);
 777  out:
 778         return(err);
 779 }
 780
 781 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 782                   struct inode *to_ino, struct dentry *to)
 783 {
 784         char *from_name, *to_name;
 785         int err;
 786
 787         if((from_name = inode_dentry_name(from_ino, from)) == NULL)
 788                 return(-ENOMEM);
 789         if((to_name = inode_dentry_name(to_ino, to)) == NULL){
 790                 kfree(from_name);
 791                 return(-ENOMEM);
 792         }
 793         err = rename_file(from_name, to_name);
 794         kfree(from_name);
 795         kfree(to_name);
 796         return(err);
 797 }
 798
 799 void hostfs_truncate(struct inode *ino)
 800 {
 801         not_implemented();
 802 }
 803
 804 int hostfs_permission(struct inode *ino, int desired, struct nameidata *nd)
 805 {
 806         char *name;
 807         int r = 0, w = 0, x = 0, err;
 808
 809         if (desired & MAY_READ) r = 1;
 810         if (desired & MAY_WRITE) w = 1;
 811         if (desired & MAY_EXEC) x = 1;
 812         name = inode_name(ino, 0);
 813         if (name == NULL) return(-ENOMEM);
 814
 815         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 816                         S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 817                 err = 0;
 818         else
 819                 err = access_file(name, r, w, x);
 820         kfree(name);
 821         if(!err)
 822                 err = generic_permission(ino, desired, NULL);
 823         return err;
 824 }
 825
 826 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 827 {
 828         struct hostfs_iattr attrs;
 829         char *name;
 830         int err;
 831
 832         err = inode_change_ok(dentry->d_inode, attr);
 833         if (err)
 834                 return err;
 835
 836         if(append)
 837                 attr->ia_valid &= ~ATTR_SIZE;
 838
 839         attrs.ia_valid = 0;
 840         if(attr->ia_valid & ATTR_MODE){
 841                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 842                 attrs.ia_mode = attr->ia_mode;
 843         }
 844         if(attr->ia_valid & ATTR_UID){
 845                 if((dentry->d_inode->i_sb->s_dev == ROOT_DEV) &&
 846                    (attr->ia_uid == 0))
 847                         attr->ia_uid = getuid();
 848                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 849                 attrs.ia_uid = attr->ia_uid;
 850         }
 851         if(attr->ia_valid & ATTR_GID){
 852                 if((dentry->d_inode->i_sb->s_dev == ROOT_DEV) &&
 853                    (attr->ia_gid == 0))
 854                         attr->ia_gid = getgid();
 855                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 856                 attrs.ia_gid = attr->ia_gid;
 857         }
 858         if(attr->ia_valid & ATTR_SIZE){
 859                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 860                 attrs.ia_size = attr->ia_size;
 861         }
 862         if(attr->ia_valid & ATTR_ATIME){
 863                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 864                 attrs.ia_atime = attr->ia_atime;
 865         }
 866         if(attr->ia_valid & ATTR_MTIME){
 867                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 868                 attrs.ia_mtime = attr->ia_mtime;
 869         }
 870         if(attr->ia_valid & ATTR_CTIME){
 871                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 872                 attrs.ia_ctime = attr->ia_ctime;
 873         }
 874         if(attr->ia_valid & ATTR_ATIME_SET){
 875                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 876         }
 877         if(attr->ia_valid & ATTR_MTIME_SET){
 878                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 879         }
 880         name = dentry_name(dentry, 0);
 881         if(name == NULL) return(-ENOMEM);
 882         err = set_attr(name, &attrs);
 883         kfree(name);
 884         if(err)
 885                 return(err);
 886
 887         return(inode_setattr(dentry->d_inode, attr));
 888 }
 889
 890 int hostfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 891            struct kstat *stat)
 892 {
 893         generic_fillattr(dentry->d_inode, stat);
 894         return(0);
 895 }
 896
 897 static struct inode_operations hostfs_iops = {
 898         .create         = hostfs_create,
 899         .link           = hostfs_link,
 900         .unlink         = hostfs_unlink,
 901         .symlink        = hostfs_symlink,
 902         .mkdir          = hostfs_mkdir,
 903         .rmdir          = hostfs_rmdir,
 904         .mknod          = hostfs_mknod,
 905         .rename         = hostfs_rename,
 906         .truncate       = hostfs_truncate,
 907         .permission     = hostfs_permission,
 908         .setattr        = hostfs_setattr,
 909         .getattr        = hostfs_getattr,
 910 };
 911
 912 static struct inode_operations hostfs_dir_iops = {
 913         .create         = hostfs_create,
 914         .lookup         = hostfs_lookup,
 915         .link           = hostfs_link,
 916         .unlink         = hostfs_unlink,
 917         .symlink        = hostfs_symlink,
 918         .mkdir          = hostfs_mkdir,
 919         .rmdir          = hostfs_rmdir,
 920         .mknod          = hostfs_mknod,
 921         .rename         = hostfs_rename,
 922         .truncate       = hostfs_truncate,
 923         .permission     = hostfs_permission,
 924         .setattr        = hostfs_setattr,
 925         .getattr        = hostfs_getattr,
 926 };
 927
 928 int hostfs_link_readpage(struct file *file, struct page *page)
 929 {
 930         char *buffer, *name;
 931         long long start;
 932         int err;
 933
 934         start = page->index << PAGE_CACHE_SHIFT;
 935         buffer = kmap(page);
 936         name = inode_name(page->mapping->host, 0);
 937         if(name == NULL) return(-ENOMEM);
 938         err = do_readlink(name, buffer, PAGE_CACHE_SIZE);
 939         kfree(name);
 940         if(err == PAGE_CACHE_SIZE)
 941                 err = -E2BIG;
 942         else if(err > 0){
 943                 flush_dcache_page(page);
 944                 SetPageUptodate(page);
 945                 if (PageError(page)) ClearPageError(page);
 946                 err = 0;
 947         }
 948         kunmap(page);
 949         unlock_page(page);
 950         return(err);
 951 }
 952
 953 static struct address_space_operations hostfs_link_aops = {
 954         .readpage       = hostfs_link_readpage,
 955 };
 956
 957 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 958 {
 959         struct inode *root_inode;
 960         char *name, *data = d;
 961         int err;
 962
 963         sb->s_blocksize = 1024;
 964         sb->s_blocksize_bits = 10;
 965         sb->s_magic = HOSTFS_SUPER_MAGIC;
 966         sb->s_op = &hostfs_sbops;
 967
 968         if((data == NULL) || (*data == '\0'))
 969                 data = root_ino;
 970
 971         err = -ENOMEM;
 972         name = kmalloc(strlen(data) + 1, GFP_KERNEL);
 973         if(name == NULL)
 974                 goto out;
 975
 976         strcpy(name, data);
 977
 978         root_inode = iget(sb, 0);
 979         if(root_inode == NULL)
 980                 goto out_free;
 981
 982         err = init_inode(root_inode, NULL);
 983         if(err)
 984                 goto out_put;
 985
 986         HOSTFS_I(root_inode)->host_filename = name;
 987
 988         err = -ENOMEM;
 989         sb->s_root = d_alloc_root(root_inode);
 990         if(sb->s_root == NULL)
 991                 goto out_put;
 992
 993         err = read_inode(root_inode);
 994         if(err){
 995                 /* No iput in this case because the dput does that for us */
 996                 dput(sb->s_root);
 997                 sb->s_root = NULL;
 998                 goto out_free;
 999         }
1000
1001         return(0);
1002
1003  out_put:
1004         iput(root_inode);
1005  out_free:
1006         kfree(name);
1007  out:
1008         return(err);
1009 }
1010
1011 static struct super_block *hostfs_read_sb(struct file_system_type *type,
1012                                              int flags, const char *dev_name,
1013                                              void *data)
1014 {
1015         return(get_sb_nodev(type, flags, data, hostfs_fill_sb_common));
1016 }
1017
1018 static struct file_system_type hostfs_type = {
1019         .owner          = THIS_MODULE,
1020         .name           = "hostfs",
1021         .get_sb         = hostfs_read_sb,
1022         .kill_sb        = kill_anon_super,
1023         .fs_flags       = 0,
1024 };
1025
1026 static int __init init_hostfs(void)
1027 {
1028         return(register_filesystem(&hostfs_type));
1029 }
1030
1031 static void __exit exit_hostfs(void)
1032 {
1033         unregister_filesystem(&hostfs_type);
1034 }
1035
1036 module_init(init_hostfs)
1037 module_exit(exit_hostfs)
1038 MODULE_LICENSE("GPL");
1039
1040 /*
1041  * Overrides for Emacs so that we follow Linus's tabbing style.
1042  * Emacs will notice this stuff at the end of the file and automatically
1043  * adjust the settings for this buffer only.  This must remain at the end
1044  * of the file.
1045  * ---------------------------------------------------------------------------
1046  * Local variables:
1047  * c-file-style: "linux"
1048  * End:
1049  */