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