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