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         strncpy(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         char *name;
 306         fmode_t mode = 0;
 307         int r = 0, w = 0, fd;
 308
 309         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 310         if ((mode & HOSTFS_I(ino)->mode) == mode)
 311                 return 0;
 312
 313         /*
 314          * The file may already have been opened, but with the wrong access,
 315          * so this resets things and reopens the file with the new access.
 316          */
 317         if (HOSTFS_I(ino)->fd != -1) {
 318                 close_file(&HOSTFS_I(ino)->fd);
 319                 HOSTFS_I(ino)->fd = -1;
 320         }
 321
 322         HOSTFS_I(ino)->mode |= mode;
 323         if (HOSTFS_I(ino)->mode & FMODE_READ)
 324                 r = 1;
 325         if (HOSTFS_I(ino)->mode & FMODE_WRITE)
 326                 w = 1;
 327         if (w)
 328                 r = 1;
 329
 330         name = dentry_name(file->f_path.dentry);
 331         if (name == NULL)
 332                 return -ENOMEM;
 333
 334         fd = open_file(name, r, w, append);
 335         __putname(name);
 336         if (fd < 0)
 337                 return fd;
 338         FILE_HOSTFS_I(file)->fd = fd;
 339
 340         return 0;
 341 }
 342
 343 int hostfs_fsync(struct file *file, int datasync)
 344 {
 345         return fsync_file(HOSTFS_I(file->f_mapping->host)->fd, datasync);
 346 }
 347
 348 static const struct file_operations hostfs_file_fops = {
 349         .llseek         = generic_file_llseek,
 350         .read           = do_sync_read,
 351         .splice_read    = generic_file_splice_read,
 352         .aio_read       = generic_file_aio_read,
 353         .aio_write      = generic_file_aio_write,
 354         .write          = do_sync_write,
 355         .mmap           = generic_file_mmap,
 356         .open           = hostfs_file_open,
 357         .release        = NULL,
 358         .fsync          = hostfs_fsync,
 359 };
 360
 361 static const struct file_operations hostfs_dir_fops = {
 362         .llseek         = generic_file_llseek,
 363         .readdir        = hostfs_readdir,
 364         .read           = generic_read_dir,
 365 };
 366
 367 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 368 {
 369         struct address_space *mapping = page->mapping;
 370         struct inode *inode = mapping->host;
 371         char *buffer;
 372         unsigned long long base;
 373         int count = PAGE_CACHE_SIZE;
 374         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 375         int err;
 376
 377         if (page->index >= end_index)
 378                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 379
 380         buffer = kmap(page);
 381         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 382
 383         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 384         if (err != count) {
 385                 ClearPageUptodate(page);
 386                 goto out;
 387         }
 388
 389         if (base > inode->i_size)
 390                 inode->i_size = base;
 391
 392         if (PageError(page))
 393                 ClearPageError(page);
 394         err = 0;
 395
 396  out:
 397         kunmap(page);
 398
 399         unlock_page(page);
 400         return err;
 401 }
 402
 403 int hostfs_readpage(struct file *file, struct page *page)
 404 {
 405         char *buffer;
 406         long long start;
 407         int err = 0;
 408
 409         start = (long long) page->index << PAGE_CACHE_SHIFT;
 410         buffer = kmap(page);
 411         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 412                         PAGE_CACHE_SIZE);
 413         if (err < 0)
 414                 goto out;
 415
 416         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 417
 418         flush_dcache_page(page);
 419         SetPageUptodate(page);
 420         if (PageError(page)) ClearPageError(page);
 421         err = 0;
 422  out:
 423         kunmap(page);
 424         unlock_page(page);
 425         return err;
 426 }
 427
 428 int hostfs_write_begin(struct file *file, struct address_space *mapping,
 429                         loff_t pos, unsigned len, unsigned flags,
 430                         struct page **pagep, void **fsdata)
 431 {
 432         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 433
 434         *pagep = grab_cache_page_write_begin(mapping, index, flags);
 435         if (!*pagep)
 436                 return -ENOMEM;
 437         return 0;
 438 }
 439
 440 int hostfs_write_end(struct file *file, struct address_space *mapping,
 441                         loff_t pos, unsigned len, unsigned copied,
 442                         struct page *page, void *fsdata)
 443 {
 444         struct inode *inode = mapping->host;
 445         void *buffer;
 446         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 447         int err;
 448
 449         buffer = kmap(page);
 450         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 451         kunmap(page);
 452
 453         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 454                 SetPageUptodate(page);
 455
 456         /*
 457          * If err > 0, write_file has added err to pos, so we are comparing
 458          * i_size against the last byte written.
 459          */
 460         if (err > 0 && (pos > inode->i_size))
 461                 inode->i_size = pos;
 462         unlock_page(page);
 463         page_cache_release(page);
 464
 465         return err;
 466 }
 467
 468 static const struct address_space_operations hostfs_aops = {
 469         .writepage      = hostfs_writepage,
 470         .readpage       = hostfs_readpage,
 471         .set_page_dirty = __set_page_dirty_nobuffers,
 472         .write_begin    = hostfs_write_begin,
 473         .write_end      = hostfs_write_end,
 474 };
 475
 476 static int read_name(struct inode *ino, char *name)
 477 {
 478         dev_t rdev;
 479         struct hostfs_stat st;
 480         int err = stat_file(name, &st, -1);
 481         if (err)
 482                 return err;
 483
 484         /* Reencode maj and min with the kernel encoding.*/
 485         rdev = MKDEV(st.maj, st.min);
 486
 487         switch (st.mode & S_IFMT) {
 488         case S_IFLNK:
 489                 ino->i_op = &hostfs_link_iops;
 490                 break;
 491         case S_IFDIR:
 492                 ino->i_op = &hostfs_dir_iops;
 493                 ino->i_fop = &hostfs_dir_fops;
 494                 break;
 495         case S_IFCHR:
 496         case S_IFBLK:
 497         case S_IFIFO:
 498         case S_IFSOCK:
 499                 init_special_inode(ino, st.mode & S_IFMT, rdev);
 500                 ino->i_op = &hostfs_iops;
 501                 break;
 502
 503         default:
 504                 ino->i_op = &hostfs_iops;
 505                 ino->i_fop = &hostfs_file_fops;
 506                 ino->i_mapping->a_ops = &hostfs_aops;
 507         }
 508
 509         ino->i_ino = st.ino;
 510         ino->i_mode = st.mode;
 511         ino->i_nlink = st.nlink;
 512         ino->i_uid = st.uid;
 513         ino->i_gid = st.gid;
 514         ino->i_atime = st.atime;
 515         ino->i_mtime = st.mtime;
 516         ino->i_ctime = st.ctime;
 517         ino->i_size = st.size;
 518         ino->i_blocks = st.blocks;
 519         return 0;
 520 }
 521
 522 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 523                   struct nameidata *nd)
 524 {
 525         struct inode *inode;
 526         char *name;
 527         int error, fd;
 528
 529         inode = hostfs_iget(dir->i_sb);
 530         if (IS_ERR(inode)) {
 531                 error = PTR_ERR(inode);
 532                 goto out;
 533         }
 534
 535         error = -ENOMEM;
 536         name = dentry_name(dentry);
 537         if (name == NULL)
 538                 goto out_put;
 539
 540         fd = file_create(name,
 541                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 542                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 543                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 544         if (fd < 0)
 545                 error = fd;
 546         else
 547                 error = read_name(inode, name);
 548
 549         __putname(name);
 550         if (error)
 551                 goto out_put;
 552
 553         HOSTFS_I(inode)->fd = fd;
 554         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 555         d_instantiate(dentry, inode);
 556         return 0;
 557
 558  out_put:
 559         iput(inode);
 560  out:
 561         return error;
 562 }
 563
 564 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 565                              struct nameidata *nd)
 566 {
 567         struct inode *inode;
 568         char *name;
 569         int err;
 570
 571         inode = hostfs_iget(ino->i_sb);
 572         if (IS_ERR(inode)) {
 573                 err = PTR_ERR(inode);
 574                 goto out;
 575         }
 576
 577         err = -ENOMEM;
 578         name = dentry_name(dentry);
 579         if (name == NULL)
 580                 goto out_put;
 581
 582         err = read_name(inode, name);
 583
 584         __putname(name);
 585         if (err == -ENOENT) {
 586                 iput(inode);
 587                 inode = NULL;
 588         }
 589         else if (err)
 590                 goto out_put;
 591
 592         d_add(dentry, inode);
 593         dentry->d_op = &hostfs_dentry_ops;
 594         return NULL;
 595
 596  out_put:
 597         iput(inode);
 598  out:
 599         return ERR_PTR(err);
 600 }
 601
 602 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 603 {
 604         char *from_name, *to_name;
 605         int err;
 606
 607         if ((from_name = dentry_name(from)) == NULL)
 608                 return -ENOMEM;
 609         to_name = dentry_name(to);
 610         if (to_name == NULL) {
 611                 __putname(from_name);
 612                 return -ENOMEM;
 613         }
 614         err = link_file(to_name, from_name);
 615         __putname(from_name);
 616         __putname(to_name);
 617         return err;
 618 }
 619
 620 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 621 {
 622         char *file;
 623         int err;
 624
 625         if ((file = dentry_name(dentry)) == NULL)
 626                 return -ENOMEM;
 627         if (append)
 628                 return -EPERM;
 629
 630         err = unlink_file(file);
 631         __putname(file);
 632         return err;
 633 }
 634
 635 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 636 {
 637         char *file;
 638         int err;
 639
 640         if ((file = dentry_name(dentry)) == NULL)
 641                 return -ENOMEM;
 642         err = make_symlink(file, to);
 643         __putname(file);
 644         return err;
 645 }
 646
 647 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 648 {
 649         char *file;
 650         int err;
 651
 652         if ((file = dentry_name(dentry)) == NULL)
 653                 return -ENOMEM;
 654         err = do_mkdir(file, mode);
 655         __putname(file);
 656         return err;
 657 }
 658
 659 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 660 {
 661         char *file;
 662         int err;
 663
 664         if ((file = dentry_name(dentry)) == NULL)
 665                 return -ENOMEM;
 666         err = do_rmdir(file);
 667         __putname(file);
 668         return err;
 669 }
 670
 671 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 672 {
 673         struct inode *inode;
 674         char *name;
 675         int err;
 676
 677         inode = hostfs_iget(dir->i_sb);
 678         if (IS_ERR(inode)) {
 679                 err = PTR_ERR(inode);
 680                 goto out;
 681         }
 682
 683         err = -ENOMEM;
 684         name = dentry_name(dentry);
 685         if (name == NULL)
 686                 goto out_put;
 687
 688         init_special_inode(inode, mode, dev);
 689         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 690         if (!err)
 691                 goto out_free;
 692
 693         err = read_name(inode, name);
 694         __putname(name);
 695         if (err)
 696                 goto out_put;
 697         if (err)
 698                 goto out_put;
 699
 700         d_instantiate(dentry, inode);
 701         return 0;
 702
 703  out_free:
 704         __putname(name);
 705  out_put:
 706         iput(inode);
 707  out:
 708         return err;
 709 }
 710
 711 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 712                   struct inode *to_ino, struct dentry *to)
 713 {
 714         char *from_name, *to_name;
 715         int err;
 716
 717         if ((from_name = dentry_name(from)) == NULL)
 718                 return -ENOMEM;
 719         if ((to_name = dentry_name(to)) == NULL) {
 720                 __putname(from_name);
 721                 return -ENOMEM;
 722         }
 723         err = rename_file(from_name, to_name);
 724         __putname(from_name);
 725         __putname(to_name);
 726         return err;
 727 }
 728
 729 int hostfs_permission(struct inode *ino, int desired)
 730 {
 731         char *name;
 732         int r = 0, w = 0, x = 0, err;
 733
 734         if (desired & MAY_READ) r = 1;
 735         if (desired & MAY_WRITE) w = 1;
 736         if (desired & MAY_EXEC) x = 1;
 737         name = inode_name(ino);
 738         if (name == NULL)
 739                 return -ENOMEM;
 740
 741         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 742             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 743                 err = 0;
 744         else
 745                 err = access_file(name, r, w, x);
 746         __putname(name);
 747         if (!err)
 748                 err = generic_permission(ino, desired, NULL);
 749         return err;
 750 }
 751
 752 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 753 {
 754         struct inode *inode = dentry->d_inode;
 755         struct hostfs_iattr attrs;
 756         char *name;
 757         int err;
 758
 759         int fd = HOSTFS_I(inode)->fd;
 760
 761         err = inode_change_ok(inode, attr);
 762         if (err)
 763                 return err;
 764
 765         if (append)
 766                 attr->ia_valid &= ~ATTR_SIZE;
 767
 768         attrs.ia_valid = 0;
 769         if (attr->ia_valid & ATTR_MODE) {
 770                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 771                 attrs.ia_mode = attr->ia_mode;
 772         }
 773         if (attr->ia_valid & ATTR_UID) {
 774                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 775                 attrs.ia_uid = attr->ia_uid;
 776         }
 777         if (attr->ia_valid & ATTR_GID) {
 778                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 779                 attrs.ia_gid = attr->ia_gid;
 780         }
 781         if (attr->ia_valid & ATTR_SIZE) {
 782                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 783                 attrs.ia_size = attr->ia_size;
 784         }
 785         if (attr->ia_valid & ATTR_ATIME) {
 786                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 787                 attrs.ia_atime = attr->ia_atime;
 788         }
 789         if (attr->ia_valid & ATTR_MTIME) {
 790                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 791                 attrs.ia_mtime = attr->ia_mtime;
 792         }
 793         if (attr->ia_valid & ATTR_CTIME) {
 794                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 795                 attrs.ia_ctime = attr->ia_ctime;
 796         }
 797         if (attr->ia_valid & ATTR_ATIME_SET) {
 798                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 799         }
 800         if (attr->ia_valid & ATTR_MTIME_SET) {
 801                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 802         }
 803         name = dentry_name(dentry);
 804         if (name == NULL)
 805                 return -ENOMEM;
 806         err = set_attr(name, &attrs, fd);
 807         __putname(name);
 808         if (err)
 809                 return err;
 810
 811         if ((attr->ia_valid & ATTR_SIZE) &&
 812             attr->ia_size != i_size_read(inode)) {
 813                 int error;
 814
 815                 error = vmtruncate(inode, attr->ia_size);
 816                 if (err)
 817                         return err;
 818         }
 819
 820         setattr_copy(inode, attr);
 821         mark_inode_dirty(inode);
 822         return 0;
 823 }
 824
 825 static const struct inode_operations hostfs_iops = {
 826         .create         = hostfs_create,
 827         .link           = hostfs_link,
 828         .unlink         = hostfs_unlink,
 829         .symlink        = hostfs_symlink,
 830         .mkdir          = hostfs_mkdir,
 831         .rmdir          = hostfs_rmdir,
 832         .mknod          = hostfs_mknod,
 833         .rename         = hostfs_rename,
 834         .permission     = hostfs_permission,
 835         .setattr        = hostfs_setattr,
 836 };
 837
 838 static const struct inode_operations hostfs_dir_iops = {
 839         .create         = hostfs_create,
 840         .lookup         = hostfs_lookup,
 841         .link           = hostfs_link,
 842         .unlink         = hostfs_unlink,
 843         .symlink        = hostfs_symlink,
 844         .mkdir          = hostfs_mkdir,
 845         .rmdir          = hostfs_rmdir,
 846         .mknod          = hostfs_mknod,
 847         .rename         = hostfs_rename,
 848         .permission     = hostfs_permission,
 849         .setattr        = hostfs_setattr,
 850 };
 851
 852 static void *hostfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 853 {
 854         char *link = __getname();
 855         if (link) {
 856                 char *path = dentry_name(dentry);
 857                 int err = -ENOMEM;
 858                 if (path) {
 859                         int err = hostfs_do_readlink(path, link, PATH_MAX);
 860                         if (err == PATH_MAX)
 861                                 err = -E2BIG;
 862                         __putname(path);
 863                 }
 864                 if (err < 0) {
 865                         __putname(link);
 866                         link = ERR_PTR(err);
 867                 }
 868         } else {
 869                 link = ERR_PTR(-ENOMEM);
 870         }
 871
 872         nd_set_link(nd, link);
 873         return NULL;
 874 }
 875
 876 static void hostfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
 877 {
 878         char *s = nd_get_link(nd);
 879         if (!IS_ERR(s))
 880                 __putname(s);
 881 }
 882
 883 static const struct inode_operations hostfs_link_iops = {
 884         .readlink       = generic_readlink,
 885         .follow_link    = hostfs_follow_link,
 886         .put_link       = hostfs_put_link,
 887 };
 888
 889 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 890 {
 891         struct inode *root_inode;
 892         char *host_root_path, *req_root = d;
 893         int err;
 894
 895         sb->s_blocksize = 1024;
 896         sb->s_blocksize_bits = 10;
 897         sb->s_magic = HOSTFS_SUPER_MAGIC;
 898         sb->s_op = &hostfs_sbops;
 899         sb->s_maxbytes = MAX_LFS_FILESIZE;
 900
 901         /* NULL is printed as <NULL> by sprintf: avoid that. */
 902         if (req_root == NULL)
 903                 req_root = "";
 904
 905         err = -ENOMEM;
 906         sb->s_fs_info = host_root_path =
 907                 kmalloc(strlen(root_ino) + strlen(req_root) + 2, GFP_KERNEL);
 908         if (host_root_path == NULL)
 909                 goto out;
 910
 911         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 912
 913         root_inode = new_inode(sb);
 914         if (!root_inode)
 915                 goto out;
 916
 917         err = read_name(root_inode, host_root_path);
 918         if (err)
 919                 goto out_put;
 920
 921         if (S_ISLNK(root_inode->i_mode)) {
 922                 char *name = follow_link(host_root_path);
 923                 if (IS_ERR(name))
 924                         err = PTR_ERR(name);
 925                 else
 926                         err = read_name(root_inode, name);
 927                 kfree(name);
 928                 if (err)
 929                         goto out_put;
 930         }
 931
 932         err = -ENOMEM;
 933         sb->s_root = d_alloc_root(root_inode);
 934         if (sb->s_root == NULL)
 935                 goto out_put;
 936
 937         return 0;
 938
 939 out_put:
 940         iput(root_inode);
 941 out:
 942         return err;
 943 }
 944
 945 static int hostfs_read_sb(struct file_system_type *type,
 946                           int flags, const char *dev_name,
 947                           void *data, struct vfsmount *mnt)
 948 {
 949         return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
 950 }
 951
 952 static void hostfs_kill_sb(struct super_block *s)
 953 {
 954         kill_anon_super(s);
 955         kfree(s->s_fs_info);
 956 }
 957
 958 static struct file_system_type hostfs_type = {
 959         .owner          = THIS_MODULE,
 960         .name           = "hostfs",
 961         .get_sb         = hostfs_read_sb,
 962         .kill_sb        = hostfs_kill_sb,
 963         .fs_flags       = 0,
 964 };
 965
 966 static int __init init_hostfs(void)
 967 {
 968         return register_filesystem(&hostfs_type);
 969 }
 970
 971 static void __exit exit_hostfs(void)
 972 {
 973         unregister_filesystem(&hostfs_type);
 974 }
 975
 976 module_init(init_hostfs)
 977 module_exit(exit_hostfs)
 978 MODULE_LICENSE("GPL");