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_i_callback(struct rcu_head *head)
 251 {
 252         struct inode *inode = container_of(head, struct inode, i_rcu);
 253         INIT_LIST_HEAD(&inode->i_dentry);
 254         kfree(HOSTFS_I(inode));
 255 }
 256
 257 static void hostfs_destroy_inode(struct inode *inode)
 258 {
 259         call_rcu(&inode->i_rcu, hostfs_i_callback);
 260 }
 261
 262 static int hostfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 263 {
 264         const char *root_path = vfs->mnt_sb->s_fs_info;
 265         size_t offset = strlen(root_ino) + 1;
 266
 267         if (strlen(root_path) > offset)
 268                 seq_printf(seq, ",%s", root_path + offset);
 269
 270         return 0;
 271 }
 272
 273 static const struct super_operations hostfs_sbops = {
 274         .alloc_inode    = hostfs_alloc_inode,
 275         .destroy_inode  = hostfs_destroy_inode,
 276         .evict_inode    = hostfs_evict_inode,
 277         .statfs         = hostfs_statfs,
 278         .show_options   = hostfs_show_options,
 279 };
 280
 281 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 282 {
 283         void *dir;
 284         char *name;
 285         unsigned long long next, ino;
 286         int error, len;
 287
 288         name = dentry_name(file->f_path.dentry);
 289         if (name == NULL)
 290                 return -ENOMEM;
 291         dir = open_dir(name, &error);
 292         __putname(name);
 293         if (dir == NULL)
 294                 return -error;
 295         next = file->f_pos;
 296         while ((name = read_dir(dir, &next, &ino, &len)) != NULL) {
 297                 error = (*filldir)(ent, name, len, file->f_pos,
 298                                    ino, DT_UNKNOWN);
 299                 if (error) break;
 300                 file->f_pos = next;
 301         }
 302         close_dir(dir);
 303         return 0;
 304 }
 305
 306 int hostfs_file_open(struct inode *ino, struct file *file)
 307 {
 308         static DEFINE_MUTEX(open_mutex);
 309         char *name;
 310         fmode_t mode = 0;
 311         int err;
 312         int r = 0, w = 0, fd;
 313
 314         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 315         if ((mode & HOSTFS_I(ino)->mode) == mode)
 316                 return 0;
 317
 318         mode |= HOSTFS_I(ino)->mode;
 319
 320 retry:
 321         if (mode & FMODE_READ)
 322                 r = 1;
 323         if (mode & FMODE_WRITE)
 324                 w = 1;
 325         if (w)
 326                 r = 1;
 327
 328         name = dentry_name(file->f_path.dentry);
 329         if (name == NULL)
 330                 return -ENOMEM;
 331
 332         fd = open_file(name, r, w, append);
 333         __putname(name);
 334         if (fd < 0)
 335                 return fd;
 336
 337         mutex_lock(&open_mutex);
 338         /* somebody else had handled it first? */
 339         if ((mode & HOSTFS_I(ino)->mode) == mode) {
 340                 mutex_unlock(&open_mutex);
 341                 return 0;
 342         }
 343         if ((mode | HOSTFS_I(ino)->mode) != mode) {
 344                 mode |= HOSTFS_I(ino)->mode;
 345                 mutex_unlock(&open_mutex);
 346                 close_file(&fd);
 347                 goto retry;
 348         }
 349         if (HOSTFS_I(ino)->fd == -1) {
 350                 HOSTFS_I(ino)->fd = fd;
 351         } else {
 352                 err = replace_file(fd, HOSTFS_I(ino)->fd);
 353                 close_file(&fd);
 354                 if (err < 0) {
 355                         mutex_unlock(&open_mutex);
 356                         return err;
 357                 }
 358         }
 359         HOSTFS_I(ino)->mode = mode;
 360         mutex_unlock(&open_mutex);
 361
 362         return 0;
 363 }
 364
 365 int hostfs_fsync(struct file *file, int datasync)
 366 {
 367         return fsync_file(HOSTFS_I(file->f_mapping->host)->fd, datasync);
 368 }
 369
 370 static const struct file_operations hostfs_file_fops = {
 371         .llseek         = generic_file_llseek,
 372         .read           = do_sync_read,
 373         .splice_read    = generic_file_splice_read,
 374         .aio_read       = generic_file_aio_read,
 375         .aio_write      = generic_file_aio_write,
 376         .write          = do_sync_write,
 377         .mmap           = generic_file_mmap,
 378         .open           = hostfs_file_open,
 379         .release        = NULL,
 380         .fsync          = hostfs_fsync,
 381 };
 382
 383 static const struct file_operations hostfs_dir_fops = {
 384         .llseek         = generic_file_llseek,
 385         .readdir        = hostfs_readdir,
 386         .read           = generic_read_dir,
 387 };
 388
 389 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 390 {
 391         struct address_space *mapping = page->mapping;
 392         struct inode *inode = mapping->host;
 393         char *buffer;
 394         unsigned long long base;
 395         int count = PAGE_CACHE_SIZE;
 396         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 397         int err;
 398
 399         if (page->index >= end_index)
 400                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 401
 402         buffer = kmap(page);
 403         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 404
 405         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 406         if (err != count) {
 407                 ClearPageUptodate(page);
 408                 goto out;
 409         }
 410
 411         if (base > inode->i_size)
 412                 inode->i_size = base;
 413
 414         if (PageError(page))
 415                 ClearPageError(page);
 416         err = 0;
 417
 418  out:
 419         kunmap(page);
 420
 421         unlock_page(page);
 422         return err;
 423 }
 424
 425 int hostfs_readpage(struct file *file, struct page *page)
 426 {
 427         char *buffer;
 428         long long start;
 429         int err = 0;
 430
 431         start = (long long) page->index << PAGE_CACHE_SHIFT;
 432         buffer = kmap(page);
 433         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 434                         PAGE_CACHE_SIZE);
 435         if (err < 0)
 436                 goto out;
 437
 438         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 439
 440         flush_dcache_page(page);
 441         SetPageUptodate(page);
 442         if (PageError(page)) ClearPageError(page);
 443         err = 0;
 444  out:
 445         kunmap(page);
 446         unlock_page(page);
 447         return err;
 448 }
 449
 450 int hostfs_write_begin(struct file *file, struct address_space *mapping,
 451                         loff_t pos, unsigned len, unsigned flags,
 452                         struct page **pagep, void **fsdata)
 453 {
 454         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 455
 456         *pagep = grab_cache_page_write_begin(mapping, index, flags);
 457         if (!*pagep)
 458                 return -ENOMEM;
 459         return 0;
 460 }
 461
 462 int hostfs_write_end(struct file *file, struct address_space *mapping,
 463                         loff_t pos, unsigned len, unsigned copied,
 464                         struct page *page, void *fsdata)
 465 {
 466         struct inode *inode = mapping->host;
 467         void *buffer;
 468         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 469         int err;
 470
 471         buffer = kmap(page);
 472         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 473         kunmap(page);
 474
 475         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 476                 SetPageUptodate(page);
 477
 478         /*
 479          * If err > 0, write_file has added err to pos, so we are comparing
 480          * i_size against the last byte written.
 481          */
 482         if (err > 0 && (pos > inode->i_size))
 483                 inode->i_size = pos;
 484         unlock_page(page);
 485         page_cache_release(page);
 486
 487         return err;
 488 }
 489
 490 static const struct address_space_operations hostfs_aops = {
 491         .writepage      = hostfs_writepage,
 492         .readpage       = hostfs_readpage,
 493         .set_page_dirty = __set_page_dirty_nobuffers,
 494         .write_begin    = hostfs_write_begin,
 495         .write_end      = hostfs_write_end,
 496 };
 497
 498 static int read_name(struct inode *ino, char *name)
 499 {
 500         dev_t rdev;
 501         struct hostfs_stat st;
 502         int err = stat_file(name, &st, -1);
 503         if (err)
 504                 return err;
 505
 506         /* Reencode maj and min with the kernel encoding.*/
 507         rdev = MKDEV(st.maj, st.min);
 508
 509         switch (st.mode & S_IFMT) {
 510         case S_IFLNK:
 511                 ino->i_op = &hostfs_link_iops;
 512                 break;
 513         case S_IFDIR:
 514                 ino->i_op = &hostfs_dir_iops;
 515                 ino->i_fop = &hostfs_dir_fops;
 516                 break;
 517         case S_IFCHR:
 518         case S_IFBLK:
 519         case S_IFIFO:
 520         case S_IFSOCK:
 521                 init_special_inode(ino, st.mode & S_IFMT, rdev);
 522                 ino->i_op = &hostfs_iops;
 523                 break;
 524
 525         default:
 526                 ino->i_op = &hostfs_iops;
 527                 ino->i_fop = &hostfs_file_fops;
 528                 ino->i_mapping->a_ops = &hostfs_aops;
 529         }
 530
 531         ino->i_ino = st.ino;
 532         ino->i_mode = st.mode;
 533         ino->i_nlink = st.nlink;
 534         ino->i_uid = st.uid;
 535         ino->i_gid = st.gid;
 536         ino->i_atime = st.atime;
 537         ino->i_mtime = st.mtime;
 538         ino->i_ctime = st.ctime;
 539         ino->i_size = st.size;
 540         ino->i_blocks = st.blocks;
 541         return 0;
 542 }
 543
 544 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 545                   struct nameidata *nd)
 546 {
 547         struct inode *inode;
 548         char *name;
 549         int error, fd;
 550
 551         inode = hostfs_iget(dir->i_sb);
 552         if (IS_ERR(inode)) {
 553                 error = PTR_ERR(inode);
 554                 goto out;
 555         }
 556
 557         error = -ENOMEM;
 558         name = dentry_name(dentry);
 559         if (name == NULL)
 560                 goto out_put;
 561
 562         fd = file_create(name,
 563                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 564                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 565                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 566         if (fd < 0)
 567                 error = fd;
 568         else
 569                 error = read_name(inode, name);
 570
 571         __putname(name);
 572         if (error)
 573                 goto out_put;
 574
 575         HOSTFS_I(inode)->fd = fd;
 576         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 577         d_instantiate(dentry, inode);
 578         return 0;
 579
 580  out_put:
 581         iput(inode);
 582  out:
 583         return error;
 584 }
 585
 586 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 587                              struct nameidata *nd)
 588 {
 589         struct inode *inode;
 590         char *name;
 591         int err;
 592
 593         inode = hostfs_iget(ino->i_sb);
 594         if (IS_ERR(inode)) {
 595                 err = PTR_ERR(inode);
 596                 goto out;
 597         }
 598
 599         err = -ENOMEM;
 600         name = dentry_name(dentry);
 601         if (name == NULL)
 602                 goto out_put;
 603
 604         err = read_name(inode, name);
 605
 606         __putname(name);
 607         if (err == -ENOENT) {
 608                 iput(inode);
 609                 inode = NULL;
 610         }
 611         else if (err)
 612                 goto out_put;
 613
 614         d_add(dentry, inode);
 615         return NULL;
 616
 617  out_put:
 618         iput(inode);
 619  out:
 620         return ERR_PTR(err);
 621 }
 622
 623 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 624 {
 625         char *from_name, *to_name;
 626         int err;
 627
 628         if ((from_name = dentry_name(from)) == NULL)
 629                 return -ENOMEM;
 630         to_name = dentry_name(to);
 631         if (to_name == NULL) {
 632                 __putname(from_name);
 633                 return -ENOMEM;
 634         }
 635         err = link_file(to_name, from_name);
 636         __putname(from_name);
 637         __putname(to_name);
 638         return err;
 639 }
 640
 641 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 642 {
 643         char *file;
 644         int err;
 645
 646         if (append)
 647                 return -EPERM;
 648
 649         if ((file = dentry_name(dentry)) == NULL)
 650                 return -ENOMEM;
 651
 652         err = unlink_file(file);
 653         __putname(file);
 654         return err;
 655 }
 656
 657 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 658 {
 659         char *file;
 660         int err;
 661
 662         if ((file = dentry_name(dentry)) == NULL)
 663                 return -ENOMEM;
 664         err = make_symlink(file, to);
 665         __putname(file);
 666         return err;
 667 }
 668
 669 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 670 {
 671         char *file;
 672         int err;
 673
 674         if ((file = dentry_name(dentry)) == NULL)
 675                 return -ENOMEM;
 676         err = do_mkdir(file, mode);
 677         __putname(file);
 678         return err;
 679 }
 680
 681 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 682 {
 683         char *file;
 684         int err;
 685
 686         if ((file = dentry_name(dentry)) == NULL)
 687                 return -ENOMEM;
 688         err = do_rmdir(file);
 689         __putname(file);
 690         return err;
 691 }
 692
 693 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 694 {
 695         struct inode *inode;
 696         char *name;
 697         int err;
 698
 699         inode = hostfs_iget(dir->i_sb);
 700         if (IS_ERR(inode)) {
 701                 err = PTR_ERR(inode);
 702                 goto out;
 703         }
 704
 705         err = -ENOMEM;
 706         name = dentry_name(dentry);
 707         if (name == NULL)
 708                 goto out_put;
 709
 710         init_special_inode(inode, mode, dev);
 711         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 712         if (!err)
 713                 goto out_free;
 714
 715         err = read_name(inode, name);
 716         __putname(name);
 717         if (err)
 718                 goto out_put;
 719         if (err)
 720                 goto out_put;
 721
 722         d_instantiate(dentry, inode);
 723         return 0;
 724
 725  out_free:
 726         __putname(name);
 727  out_put:
 728         iput(inode);
 729  out:
 730         return err;
 731 }
 732
 733 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 734                   struct inode *to_ino, struct dentry *to)
 735 {
 736         char *from_name, *to_name;
 737         int err;
 738
 739         if ((from_name = dentry_name(from)) == NULL)
 740                 return -ENOMEM;
 741         if ((to_name = dentry_name(to)) == NULL) {
 742                 __putname(from_name);
 743                 return -ENOMEM;
 744         }
 745         err = rename_file(from_name, to_name);
 746         __putname(from_name);
 747         __putname(to_name);
 748         return err;
 749 }
 750
 751 int hostfs_permission(struct inode *ino, int desired, unsigned int flags)
 752 {
 753         char *name;
 754         int r = 0, w = 0, x = 0, err;
 755
 756         if (flags & IPERM_FLAG_RCU)
 757                 return -ECHILD;
 758
 759         if (desired & MAY_READ) r = 1;
 760         if (desired & MAY_WRITE) w = 1;
 761         if (desired & MAY_EXEC) x = 1;
 762         name = inode_name(ino);
 763         if (name == NULL)
 764                 return -ENOMEM;
 765
 766         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 767             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 768                 err = 0;
 769         else
 770                 err = access_file(name, r, w, x);
 771         __putname(name);
 772         if (!err)
 773                 err = generic_permission(ino, desired, flags, NULL);
 774         return err;
 775 }
 776
 777 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 778 {
 779         struct inode *inode = dentry->d_inode;
 780         struct hostfs_iattr attrs;
 781         char *name;
 782         int err;
 783
 784         int fd = HOSTFS_I(inode)->fd;
 785
 786         err = inode_change_ok(inode, attr);
 787         if (err)
 788                 return err;
 789
 790         if (append)
 791                 attr->ia_valid &= ~ATTR_SIZE;
 792
 793         attrs.ia_valid = 0;
 794         if (attr->ia_valid & ATTR_MODE) {
 795                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 796                 attrs.ia_mode = attr->ia_mode;
 797         }
 798         if (attr->ia_valid & ATTR_UID) {
 799                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 800                 attrs.ia_uid = attr->ia_uid;
 801         }
 802         if (attr->ia_valid & ATTR_GID) {
 803                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 804                 attrs.ia_gid = attr->ia_gid;
 805         }
 806         if (attr->ia_valid & ATTR_SIZE) {
 807                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 808                 attrs.ia_size = attr->ia_size;
 809         }
 810         if (attr->ia_valid & ATTR_ATIME) {
 811                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 812                 attrs.ia_atime = attr->ia_atime;
 813         }
 814         if (attr->ia_valid & ATTR_MTIME) {
 815                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 816                 attrs.ia_mtime = attr->ia_mtime;
 817         }
 818         if (attr->ia_valid & ATTR_CTIME) {
 819                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 820                 attrs.ia_ctime = attr->ia_ctime;
 821         }
 822         if (attr->ia_valid & ATTR_ATIME_SET) {
 823                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 824         }
 825         if (attr->ia_valid & ATTR_MTIME_SET) {
 826                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 827         }
 828         name = dentry_name(dentry);
 829         if (name == NULL)
 830                 return -ENOMEM;
 831         err = set_attr(name, &attrs, fd);
 832         __putname(name);
 833         if (err)
 834                 return err;
 835
 836         if ((attr->ia_valid & ATTR_SIZE) &&
 837             attr->ia_size != i_size_read(inode)) {
 838                 int error;
 839
 840                 error = vmtruncate(inode, attr->ia_size);
 841                 if (err)
 842                         return err;
 843         }
 844
 845         setattr_copy(inode, attr);
 846         mark_inode_dirty(inode);
 847         return 0;
 848 }
 849
 850 static const struct inode_operations hostfs_iops = {
 851         .create         = hostfs_create,
 852         .link           = hostfs_link,
 853         .unlink         = hostfs_unlink,
 854         .symlink        = hostfs_symlink,
 855         .mkdir          = hostfs_mkdir,
 856         .rmdir          = hostfs_rmdir,
 857         .mknod          = hostfs_mknod,
 858         .rename         = hostfs_rename,
 859         .permission     = hostfs_permission,
 860         .setattr        = hostfs_setattr,
 861 };
 862
 863 static const struct inode_operations hostfs_dir_iops = {
 864         .create         = hostfs_create,
 865         .lookup         = hostfs_lookup,
 866         .link           = hostfs_link,
 867         .unlink         = hostfs_unlink,
 868         .symlink        = hostfs_symlink,
 869         .mkdir          = hostfs_mkdir,
 870         .rmdir          = hostfs_rmdir,
 871         .mknod          = hostfs_mknod,
 872         .rename         = hostfs_rename,
 873         .permission     = hostfs_permission,
 874         .setattr        = hostfs_setattr,
 875 };
 876
 877 static void *hostfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 878 {
 879         char *link = __getname();
 880         if (link) {
 881                 char *path = dentry_name(dentry);
 882                 int err = -ENOMEM;
 883                 if (path) {
 884                         err = hostfs_do_readlink(path, link, PATH_MAX);
 885                         if (err == PATH_MAX)
 886                                 err = -E2BIG;
 887                         __putname(path);
 888                 }
 889                 if (err < 0) {
 890                         __putname(link);
 891                         link = ERR_PTR(err);
 892                 }
 893         } else {
 894                 link = ERR_PTR(-ENOMEM);
 895         }
 896
 897         nd_set_link(nd, link);
 898         return NULL;
 899 }
 900
 901 static void hostfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
 902 {
 903         char *s = nd_get_link(nd);
 904         if (!IS_ERR(s))
 905                 __putname(s);
 906 }
 907
 908 static const struct inode_operations hostfs_link_iops = {
 909         .readlink       = generic_readlink,
 910         .follow_link    = hostfs_follow_link,
 911         .put_link       = hostfs_put_link,
 912 };
 913
 914 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 915 {
 916         struct inode *root_inode;
 917         char *host_root_path, *req_root = d;
 918         int err;
 919
 920         sb->s_blocksize = 1024;
 921         sb->s_blocksize_bits = 10;
 922         sb->s_magic = HOSTFS_SUPER_MAGIC;
 923         sb->s_op = &hostfs_sbops;
 924         sb->s_d_op = &hostfs_dentry_ops;
 925         sb->s_maxbytes = MAX_LFS_FILESIZE;
 926
 927         /* NULL is printed as <NULL> by sprintf: avoid that. */
 928         if (req_root == NULL)
 929                 req_root = "";
 930
 931         err = -ENOMEM;
 932         sb->s_fs_info = host_root_path =
 933                 kmalloc(strlen(root_ino) + strlen(req_root) + 2, GFP_KERNEL);
 934         if (host_root_path == NULL)
 935                 goto out;
 936
 937         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 938
 939         root_inode = new_inode(sb);
 940         if (!root_inode)
 941                 goto out;
 942
 943         err = read_name(root_inode, host_root_path);
 944         if (err)
 945                 goto out_put;
 946
 947         if (S_ISLNK(root_inode->i_mode)) {
 948                 char *name = follow_link(host_root_path);
 949                 if (IS_ERR(name))
 950                         err = PTR_ERR(name);
 951                 else
 952                         err = read_name(root_inode, name);
 953                 kfree(name);
 954                 if (err)
 955                         goto out_put;
 956         }
 957
 958         err = -ENOMEM;
 959         sb->s_root = d_alloc_root(root_inode);
 960         if (sb->s_root == NULL)
 961                 goto out_put;
 962
 963         return 0;
 964
 965 out_put:
 966         iput(root_inode);
 967 out:
 968         return err;
 969 }
 970
 971 static struct dentry *hostfs_read_sb(struct file_system_type *type,
 972                           int flags, const char *dev_name,
 973                           void *data)
 974 {
 975         return mount_nodev(type, flags, data, hostfs_fill_sb_common);
 976 }
 977
 978 static void hostfs_kill_sb(struct super_block *s)
 979 {
 980         kill_anon_super(s);
 981         kfree(s->s_fs_info);
 982 }
 983
 984 static struct file_system_type hostfs_type = {
 985         .owner          = THIS_MODULE,
 986         .name           = "hostfs",
 987         .mount          = hostfs_read_sb,
 988         .kill_sb        = hostfs_kill_sb,
 989         .fs_flags       = 0,
 990 };
 991
 992 static int __init init_hostfs(void)
 993 {
 994         return register_filesystem(&hostfs_type);
 995 }
 996
 997 static void __exit exit_hostfs(void)
 998 {
 999         unregister_filesystem(&hostfs_type);
1000 }
1001
1002 module_init(init_hostfs)
1003 module_exit(exit_hostfs)
1004 MODULE_LICENSE("GPL");