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