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/magic.h>
  11 #include <linux/module.h>
  12 #include <linux/mm.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/statfs.h>
  15 #include <linux/slab.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/mount.h>
  18 #include <linux/namei.h>
  19 #include "hostfs.h"
  20 #include <init.h>
  21 #include <kern.h>
  22
  23 struct hostfs_inode_info {
  24         int fd;
  25         fmode_t mode;
  26         struct inode vfs_inode;
  27         struct mutex open_mutex;
  28 };
  29
  30 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  31 {
  32         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
  33 }
  34
  35 #define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
  36
  37 /* Changed in hostfs_args before the kernel starts running */
  38 static char *root_ino = "";
  39 static int append = 0;
  40
  41 static const struct inode_operations hostfs_iops;
  42 static const struct inode_operations hostfs_dir_iops;
  43 static const struct inode_operations hostfs_link_iops;
  44
  45 #ifndef MODULE
  46 static int __init hostfs_args(char *options, int *add)
  47 {
  48         char *ptr;
  49
  50         ptr = strchr(options, ',');
  51         if (ptr != NULL)
  52                 *ptr++ = '\0';
  53         if (*options != '\0')
  54                 root_ino = options;
  55
  56         options = ptr;
  57         while (options) {
  58                 ptr = strchr(options, ',');
  59                 if (ptr != NULL)
  60                         *ptr++ = '\0';
  61                 if (*options != '\0') {
  62                         if (!strcmp(options, "append"))
  63                                 append = 1;
  64                         else printf("hostfs_args - unsupported option - %s\n",
  65                                     options);
  66                 }
  67                 options = ptr;
  68         }
  69         return 0;
  70 }
  71
  72 __uml_setup("hostfs=", hostfs_args,
  73 "hostfs=<root dir>,<flags>,...\n"
  74 "    This is used to set hostfs parameters.  The root directory argument\n"
  75 "    is used to confine all hostfs mounts to within the specified directory\n"
  76 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
  77 "    mount anything on the host that's accessible to the user that's running\n"
  78 "    it.\n"
  79 "    The only flag currently supported is 'append', which specifies that all\n"
  80 "    files opened by hostfs will be opened in append mode.\n\n"
  81 );
  82 #endif
  83
  84 static char *__dentry_name(struct dentry *dentry, char *name)
  85 {
  86         char *p = dentry_path_raw(dentry, name, PATH_MAX);
  87         char *root;
  88         size_t len;
  89
  90         root = dentry->d_sb->s_fs_info;
  91         len = strlen(root);
  92         if (IS_ERR(p)) {
  93                 __putname(name);
  94                 return NULL;
  95         }
  96
  97         /*
  98          * This function relies on the fact that dentry_path_raw() will place
  99          * the path name at the end of the provided buffer.
 100          */
 101         BUG_ON(p + strlen(p) + 1 != name + PATH_MAX);
 102
 103         strlcpy(name, root, PATH_MAX);
 104         if (len > p - name) {
 105                 __putname(name);
 106                 return NULL;
 107         }
 108
 109         if (p > name + len)
 110                 strcpy(name + len, p);
 111
 112         return name;
 113 }
 114
 115 static char *dentry_name(struct dentry *dentry)
 116 {
 117         char *name = __getname();
 118         if (!name)
 119                 return NULL;
 120
 121         return __dentry_name(dentry, name);
 122 }
 123
 124 static char *inode_name(struct inode *ino)
 125 {
 126         struct dentry *dentry;
 127         char *name;
 128
 129         dentry = d_find_alias(ino);
 130         if (!dentry)
 131                 return NULL;
 132
 133         name = dentry_name(dentry);
 134
 135         dput(dentry);
 136
 137         return name;
 138 }
 139
 140 static char *follow_link(char *link)
 141 {
 142         int len, n;
 143         char *name, *resolved, *end;
 144
 145         name = __getname();
 146         if (!name) {
 147                 n = -ENOMEM;
 148                 goto out_free;
 149         }
 150
 151         n = hostfs_do_readlink(link, name, PATH_MAX);
 152         if (n < 0)
 153                 goto out_free;
 154         else if (n == PATH_MAX) {
 155                 n = -E2BIG;
 156                 goto out_free;
 157         }
 158
 159         if (*name == '/')
 160                 return name;
 161
 162         end = strrchr(link, '/');
 163         if (end == NULL)
 164                 return name;
 165
 166         *(end + 1) = '\0';
 167         len = strlen(link) + strlen(name) + 1;
 168
 169         resolved = kmalloc(len, GFP_KERNEL);
 170         if (resolved == NULL) {
 171                 n = -ENOMEM;
 172                 goto out_free;
 173         }
 174
 175         sprintf(resolved, "%s%s", link, name);
 176         __putname(name);
 177         kfree(link);
 178         return resolved;
 179
 180  out_free:
 181         __putname(name);
 182         return ERR_PTR(n);
 183 }
 184
 185 static struct inode *hostfs_iget(struct super_block *sb)
 186 {
 187         struct inode *inode = new_inode(sb);
 188         if (!inode)
 189                 return ERR_PTR(-ENOMEM);
 190         return inode;
 191 }
 192
 193 static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 194 {
 195         /*
 196          * do_statfs uses struct statfs64 internally, but the linux kernel
 197          * struct statfs still has 32-bit versions for most of these fields,
 198          * so we convert them here
 199          */
 200         int err;
 201         long long f_blocks;
 202         long long f_bfree;
 203         long long f_bavail;
 204         long long f_files;
 205         long long f_ffree;
 206
 207         err = do_statfs(dentry->d_sb->s_fs_info,
 208                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 209                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 210                         &sf->f_namelen);
 211         if (err)
 212                 return err;
 213         sf->f_blocks = f_blocks;
 214         sf->f_bfree = f_bfree;
 215         sf->f_bavail = f_bavail;
 216         sf->f_files = f_files;
 217         sf->f_ffree = f_ffree;
 218         sf->f_type = HOSTFS_SUPER_MAGIC;
 219         return 0;
 220 }
 221
 222 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 223 {
 224         struct hostfs_inode_info *hi;
 225
 226         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 227         if (hi == NULL)
 228                 return NULL;
 229         hi->fd = -1;
 230         hi->mode = 0;
 231         inode_init_once(&hi->vfs_inode);
 232         mutex_init(&hi->open_mutex);
 233         return &hi->vfs_inode;
 234 }
 235
 236 static void hostfs_evict_inode(struct inode *inode)
 237 {
 238         truncate_inode_pages_final(&inode->i_data);
 239         clear_inode(inode);
 240         if (HOSTFS_I(inode)->fd != -1) {
 241                 close_file(&HOSTFS_I(inode)->fd);
 242                 HOSTFS_I(inode)->fd = -1;
 243         }
 244 }
 245
 246 static void hostfs_i_callback(struct rcu_head *head)
 247 {
 248         struct inode *inode = container_of(head, struct inode, i_rcu);
 249         kfree(HOSTFS_I(inode));
 250 }
 251
 252 static void hostfs_destroy_inode(struct inode *inode)
 253 {
 254         call_rcu(&inode->i_rcu, hostfs_i_callback);
 255 }
 256
 257 static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
 258 {
 259         const char *root_path = root->d_sb->s_fs_info;
 260         size_t offset = strlen(root_ino) + 1;
 261
 262         if (strlen(root_path) > offset)
 263                 seq_printf(seq, ",%s", root_path + offset);
 264
 265         if (append)
 266                 seq_puts(seq, ",append");
 267
 268         return 0;
 269 }
 270
 271 static const struct super_operations hostfs_sbops = {
 272         .alloc_inode    = hostfs_alloc_inode,
 273         .destroy_inode  = hostfs_destroy_inode,
 274         .evict_inode    = hostfs_evict_inode,
 275         .statfs         = hostfs_statfs,
 276         .show_options   = hostfs_show_options,
 277 };
 278
 279 static int hostfs_readdir(struct file *file, struct dir_context *ctx)
 280 {
 281         void *dir;
 282         char *name;
 283         unsigned long long next, ino;
 284         int error, len;
 285         unsigned int type;
 286
 287         name = dentry_name(file->f_path.dentry);
 288         if (name == NULL)
 289                 return -ENOMEM;
 290         dir = open_dir(name, &error);
 291         __putname(name);
 292         if (dir == NULL)
 293                 return -error;
 294         next = ctx->pos;
 295         while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
 296                 if (!dir_emit(ctx, name, len, ino, type))
 297                         break;
 298                 ctx->pos = next;
 299         }
 300         close_dir(dir);
 301         return 0;
 302 }
 303
 304 static int hostfs_open(struct inode *ino, struct file *file)
 305 {
 306         char *name;
 307         fmode_t mode;
 308         int err;
 309         int r, w, fd;
 310
 311         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 312         if ((mode & HOSTFS_I(ino)->mode) == mode)
 313                 return 0;
 314
 315         mode |= HOSTFS_I(ino)->mode;
 316
 317 retry:
 318         r = w = 0;
 319
 320         if (mode & FMODE_READ)
 321                 r = 1;
 322         if (mode & FMODE_WRITE)
 323                 r = w = 1;
 324
 325         name = dentry_name(file->f_path.dentry);
 326         if (name == NULL)
 327                 return -ENOMEM;
 328
 329         fd = open_file(name, r, w, append);
 330         __putname(name);
 331         if (fd < 0)
 332                 return fd;
 333
 334         mutex_lock(&HOSTFS_I(ino)->open_mutex);
 335         /* somebody else had handled it first? */
 336         if ((mode & HOSTFS_I(ino)->mode) == mode) {
 337                 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
 338                 close_file(&fd);
 339                 return 0;
 340         }
 341         if ((mode | HOSTFS_I(ino)->mode) != mode) {
 342                 mode |= HOSTFS_I(ino)->mode;
 343                 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
 344                 close_file(&fd);
 345                 goto retry;
 346         }
 347         if (HOSTFS_I(ino)->fd == -1) {
 348                 HOSTFS_I(ino)->fd = fd;
 349         } else {
 350                 err = replace_file(fd, HOSTFS_I(ino)->fd);
 351                 close_file(&fd);
 352                 if (err < 0) {
 353                         mutex_unlock(&HOSTFS_I(ino)->open_mutex);
 354                         return err;
 355                 }
 356         }
 357         HOSTFS_I(ino)->mode = mode;
 358         mutex_unlock(&HOSTFS_I(ino)->open_mutex);
 359
 360         return 0;
 361 }
 362
 363 static int hostfs_file_release(struct inode *inode, struct file *file)
 364 {
 365         filemap_write_and_wait(inode->i_mapping);
 366
 367         return 0;
 368 }
 369
 370 static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
 371                         int datasync)
 372 {
 373         struct inode *inode = file->f_mapping->host;
 374         int ret;
 375
 376         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 377         if (ret)
 378                 return ret;
 379
 380         mutex_lock(&inode->i_mutex);
 381         ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
 382         mutex_unlock(&inode->i_mutex);
 383
 384         return ret;
 385 }
 386
 387 static const struct file_operations hostfs_file_fops = {
 388         .llseek         = generic_file_llseek,
 389         .read           = new_sync_read,
 390         .splice_read    = generic_file_splice_read,
 391         .read_iter      = generic_file_read_iter,
 392         .write_iter     = generic_file_write_iter,
 393         .write          = new_sync_write,
 394         .mmap           = generic_file_mmap,
 395         .open           = hostfs_open,
 396         .release        = hostfs_file_release,
 397         .fsync          = hostfs_fsync,
 398 };
 399
 400 static const struct file_operations hostfs_dir_fops = {
 401         .llseek         = generic_file_llseek,
 402         .iterate        = hostfs_readdir,
 403         .read           = generic_read_dir,
 404         .open           = hostfs_open,
 405         .fsync          = hostfs_fsync,
 406 };
 407
 408 static int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 409 {
 410         struct address_space *mapping = page->mapping;
 411         struct inode *inode = mapping->host;
 412         char *buffer;
 413         unsigned long long base;
 414         int count = PAGE_CACHE_SIZE;
 415         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 416         int err;
 417
 418         if (page->index >= end_index)
 419                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 420
 421         buffer = kmap(page);
 422         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 423
 424         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 425         if (err != count) {
 426                 ClearPageUptodate(page);
 427                 goto out;
 428         }
 429
 430         if (base > inode->i_size)
 431                 inode->i_size = base;
 432
 433         if (PageError(page))
 434                 ClearPageError(page);
 435         err = 0;
 436
 437  out:
 438         kunmap(page);
 439
 440         unlock_page(page);
 441         return err;
 442 }
 443
 444 static int hostfs_readpage(struct file *file, struct page *page)
 445 {
 446         char *buffer;
 447         long long start;
 448         int bytes_read, ret;
 449
 450         start = (long long) page->index << PAGE_CACHE_SHIFT;
 451         buffer = kmap(page);
 452         bytes_read = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 453                         PAGE_CACHE_SIZE);
 454         if (bytes_read < 0) {
 455                 ret = bytes_read;
 456                 goto out;
 457         }
 458
 459         memset(buffer + bytes_read, 0, PAGE_CACHE_SIZE - bytes_read);
 460
 461         flush_dcache_page(page);
 462         SetPageUptodate(page);
 463         if (PageError(page)) ClearPageError(page);
 464         ret = 0;
 465  out:
 466         kunmap(page);
 467         unlock_page(page);
 468         return ret;
 469 }
 470
 471 static int hostfs_write_begin(struct file *file, struct address_space *mapping,
 472                               loff_t pos, unsigned len, unsigned flags,
 473                               struct page **pagep, void **fsdata)
 474 {
 475         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 476
 477         *pagep = grab_cache_page_write_begin(mapping, index, flags);
 478         if (!*pagep)
 479                 return -ENOMEM;
 480         return 0;
 481 }
 482
 483 static int hostfs_write_end(struct file *file, struct address_space *mapping,
 484                             loff_t pos, unsigned len, unsigned copied,
 485                             struct page *page, void *fsdata)
 486 {
 487         struct inode *inode = mapping->host;
 488         void *buffer;
 489         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 490         int err;
 491
 492         buffer = kmap(page);
 493         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 494         kunmap(page);
 495
 496         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 497                 SetPageUptodate(page);
 498
 499         /*
 500          * If err > 0, write_file has added err to pos, so we are comparing
 501          * i_size against the last byte written.
 502          */
 503         if (err > 0 && (pos > inode->i_size))
 504                 inode->i_size = pos;
 505         unlock_page(page);
 506         page_cache_release(page);
 507
 508         return err;
 509 }
 510
 511 static const struct address_space_operations hostfs_aops = {
 512         .writepage      = hostfs_writepage,
 513         .readpage       = hostfs_readpage,
 514         .set_page_dirty = __set_page_dirty_nobuffers,
 515         .write_begin    = hostfs_write_begin,
 516         .write_end      = hostfs_write_end,
 517 };
 518
 519 static int read_name(struct inode *ino, char *name)
 520 {
 521         dev_t rdev;
 522         struct hostfs_stat st;
 523         int err = stat_file(name, &st, -1);
 524         if (err)
 525                 return err;
 526
 527         /* Reencode maj and min with the kernel encoding.*/
 528         rdev = MKDEV(st.maj, st.min);
 529
 530         switch (st.mode & S_IFMT) {
 531         case S_IFLNK:
 532                 ino->i_op = &hostfs_link_iops;
 533                 break;
 534         case S_IFDIR:
 535                 ino->i_op = &hostfs_dir_iops;
 536                 ino->i_fop = &hostfs_dir_fops;
 537                 break;
 538         case S_IFCHR:
 539         case S_IFBLK:
 540         case S_IFIFO:
 541         case S_IFSOCK:
 542                 init_special_inode(ino, st.mode & S_IFMT, rdev);
 543                 ino->i_op = &hostfs_iops;
 544                 break;
 545         case S_IFREG:
 546                 ino->i_op = &hostfs_iops;
 547                 ino->i_fop = &hostfs_file_fops;
 548                 ino->i_mapping->a_ops = &hostfs_aops;
 549                 break;
 550         default:
 551                 return -EIO;
 552         }
 553
 554         ino->i_ino = st.ino;
 555         ino->i_mode = st.mode;
 556         set_nlink(ino, st.nlink);
 557         i_uid_write(ino, st.uid);
 558         i_gid_write(ino, st.gid);
 559         ino->i_atime = st.atime;
 560         ino->i_mtime = st.mtime;
 561         ino->i_ctime = st.ctime;
 562         ino->i_size = st.size;
 563         ino->i_blocks = st.blocks;
 564         return 0;
 565 }
 566
 567 static int hostfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 568                          bool excl)
 569 {
 570         struct inode *inode;
 571         char *name;
 572         int error, fd;
 573
 574         inode = hostfs_iget(dir->i_sb);
 575         if (IS_ERR(inode)) {
 576                 error = PTR_ERR(inode);
 577                 goto out;
 578         }
 579
 580         error = -ENOMEM;
 581         name = dentry_name(dentry);
 582         if (name == NULL)
 583                 goto out_put;
 584
 585         fd = file_create(name,
 586                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 587                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 588                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 589         if (fd < 0)
 590                 error = fd;
 591         else
 592                 error = read_name(inode, name);
 593
 594         __putname(name);
 595         if (error)
 596                 goto out_put;
 597
 598         HOSTFS_I(inode)->fd = fd;
 599         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 600         d_instantiate(dentry, inode);
 601         return 0;
 602
 603  out_put:
 604         iput(inode);
 605  out:
 606         return error;
 607 }
 608
 609 static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 610                                     unsigned int flags)
 611 {
 612         struct inode *inode;
 613         char *name;
 614         int err;
 615
 616         inode = hostfs_iget(ino->i_sb);
 617         if (IS_ERR(inode)) {
 618                 err = PTR_ERR(inode);
 619                 goto out;
 620         }
 621
 622         err = -ENOMEM;
 623         name = dentry_name(dentry);
 624         if (name == NULL)
 625                 goto out_put;
 626
 627         err = read_name(inode, name);
 628
 629         __putname(name);
 630         if (err == -ENOENT) {
 631                 iput(inode);
 632                 inode = NULL;
 633         }
 634         else if (err)
 635                 goto out_put;
 636
 637         d_add(dentry, inode);
 638         return NULL;
 639
 640  out_put:
 641         iput(inode);
 642  out:
 643         return ERR_PTR(err);
 644 }
 645
 646 static int hostfs_link(struct dentry *to, struct inode *ino,
 647                        struct dentry *from)
 648 {
 649         char *from_name, *to_name;
 650         int err;
 651
 652         if ((from_name = dentry_name(from)) == NULL)
 653                 return -ENOMEM;
 654         to_name = dentry_name(to);
 655         if (to_name == NULL) {
 656                 __putname(from_name);
 657                 return -ENOMEM;
 658         }
 659         err = link_file(to_name, from_name);
 660         __putname(from_name);
 661         __putname(to_name);
 662         return err;
 663 }
 664
 665 static int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 666 {
 667         char *file;
 668         int err;
 669
 670         if (append)
 671                 return -EPERM;
 672
 673         if ((file = dentry_name(dentry)) == NULL)
 674                 return -ENOMEM;
 675
 676         err = unlink_file(file);
 677         __putname(file);
 678         return err;
 679 }
 680
 681 static int hostfs_symlink(struct inode *ino, struct dentry *dentry,
 682                           const char *to)
 683 {
 684         char *file;
 685         int err;
 686
 687         if ((file = dentry_name(dentry)) == NULL)
 688                 return -ENOMEM;
 689         err = make_symlink(file, to);
 690         __putname(file);
 691         return err;
 692 }
 693
 694 static int hostfs_mkdir(struct inode *ino, struct dentry *dentry, umode_t mode)
 695 {
 696         char *file;
 697         int err;
 698
 699         if ((file = dentry_name(dentry)) == NULL)
 700                 return -ENOMEM;
 701         err = do_mkdir(file, mode);
 702         __putname(file);
 703         return err;
 704 }
 705
 706 static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 707 {
 708         char *file;
 709         int err;
 710
 711         if ((file = dentry_name(dentry)) == NULL)
 712                 return -ENOMEM;
 713         err = do_rmdir(file);
 714         __putname(file);
 715         return err;
 716 }
 717
 718 static int hostfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
 719 {
 720         struct inode *inode;
 721         char *name;
 722         int err;
 723
 724         inode = hostfs_iget(dir->i_sb);
 725         if (IS_ERR(inode)) {
 726                 err = PTR_ERR(inode);
 727                 goto out;
 728         }
 729
 730         err = -ENOMEM;
 731         name = dentry_name(dentry);
 732         if (name == NULL)
 733                 goto out_put;
 734
 735         init_special_inode(inode, mode, dev);
 736         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 737         if (!err)
 738                 goto out_free;
 739
 740         err = read_name(inode, name);
 741         __putname(name);
 742         if (err)
 743                 goto out_put;
 744         if (err)
 745                 goto out_put;
 746
 747         d_instantiate(dentry, inode);
 748         return 0;
 749
 750  out_free:
 751         __putname(name);
 752  out_put:
 753         iput(inode);
 754  out:
 755         return err;
 756 }
 757
 758 static int hostfs_rename2(struct inode *old_dir, struct dentry *old_dentry,
 759                           struct inode *new_dir, struct dentry *new_dentry,
 760                           unsigned int flags)
 761 {
 762         char *old_name, *new_name;
 763         int err;
 764
 765         if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
 766                 return -EINVAL;
 767
 768         old_name = dentry_name(old_dentry);
 769         if (old_name == NULL)
 770                 return -ENOMEM;
 771         new_name = dentry_name(new_dentry);
 772         if (new_name == NULL) {
 773                 __putname(old_name);
 774                 return -ENOMEM;
 775         }
 776         if (!flags)
 777                 err = rename_file(old_name, new_name);
 778         else
 779                 err = rename2_file(old_name, new_name, flags);
 780
 781         __putname(old_name);
 782         __putname(new_name);
 783         return err;
 784 }
 785
 786 static int hostfs_permission(struct inode *ino, int desired)
 787 {
 788         char *name;
 789         int r = 0, w = 0, x = 0, err;
 790
 791         if (desired & MAY_NOT_BLOCK)
 792                 return -ECHILD;
 793
 794         if (desired & MAY_READ) r = 1;
 795         if (desired & MAY_WRITE) w = 1;
 796         if (desired & MAY_EXEC) x = 1;
 797         name = inode_name(ino);
 798         if (name == NULL)
 799                 return -ENOMEM;
 800
 801         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 802             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 803                 err = 0;
 804         else
 805                 err = access_file(name, r, w, x);
 806         __putname(name);
 807         if (!err)
 808                 err = generic_permission(ino, desired);
 809         return err;
 810 }
 811
 812 static int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 813 {
 814         struct inode *inode = dentry->d_inode;
 815         struct hostfs_iattr attrs;
 816         char *name;
 817         int err;
 818
 819         int fd = HOSTFS_I(inode)->fd;
 820
 821         err = inode_change_ok(inode, attr);
 822         if (err)
 823                 return err;
 824
 825         if (append)
 826                 attr->ia_valid &= ~ATTR_SIZE;
 827
 828         attrs.ia_valid = 0;
 829         if (attr->ia_valid & ATTR_MODE) {
 830                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 831                 attrs.ia_mode = attr->ia_mode;
 832         }
 833         if (attr->ia_valid & ATTR_UID) {
 834                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 835                 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
 836         }
 837         if (attr->ia_valid & ATTR_GID) {
 838                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 839                 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
 840         }
 841         if (attr->ia_valid & ATTR_SIZE) {
 842                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 843                 attrs.ia_size = attr->ia_size;
 844         }
 845         if (attr->ia_valid & ATTR_ATIME) {
 846                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 847                 attrs.ia_atime = attr->ia_atime;
 848         }
 849         if (attr->ia_valid & ATTR_MTIME) {
 850                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 851                 attrs.ia_mtime = attr->ia_mtime;
 852         }
 853         if (attr->ia_valid & ATTR_CTIME) {
 854                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 855                 attrs.ia_ctime = attr->ia_ctime;
 856         }
 857         if (attr->ia_valid & ATTR_ATIME_SET) {
 858                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 859         }
 860         if (attr->ia_valid & ATTR_MTIME_SET) {
 861                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 862         }
 863         name = dentry_name(dentry);
 864         if (name == NULL)
 865                 return -ENOMEM;
 866         err = set_attr(name, &attrs, fd);
 867         __putname(name);
 868         if (err)
 869                 return err;
 870
 871         if ((attr->ia_valid & ATTR_SIZE) &&
 872             attr->ia_size != i_size_read(inode))
 873                 truncate_setsize(inode, attr->ia_size);
 874
 875         setattr_copy(inode, attr);
 876         mark_inode_dirty(inode);
 877         return 0;
 878 }
 879
 880 static const struct inode_operations hostfs_iops = {
 881         .permission     = hostfs_permission,
 882         .setattr        = hostfs_setattr,
 883 };
 884
 885 static const struct inode_operations hostfs_dir_iops = {
 886         .create         = hostfs_create,
 887         .lookup         = hostfs_lookup,
 888         .link           = hostfs_link,
 889         .unlink         = hostfs_unlink,
 890         .symlink        = hostfs_symlink,
 891         .mkdir          = hostfs_mkdir,
 892         .rmdir          = hostfs_rmdir,
 893         .mknod          = hostfs_mknod,
 894         .rename2        = hostfs_rename2,
 895         .permission     = hostfs_permission,
 896         .setattr        = hostfs_setattr,
 897 };
 898
 899 static void *hostfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 900 {
 901         char *link = __getname();
 902         if (link) {
 903                 char *path = dentry_name(dentry);
 904                 int err = -ENOMEM;
 905                 if (path) {
 906                         err = hostfs_do_readlink(path, link, PATH_MAX);
 907                         if (err == PATH_MAX)
 908                                 err = -E2BIG;
 909                         __putname(path);
 910                 }
 911                 if (err < 0) {
 912                         __putname(link);
 913                         link = ERR_PTR(err);
 914                 }
 915         } else {
 916                 link = ERR_PTR(-ENOMEM);
 917         }
 918
 919         nd_set_link(nd, link);
 920         return NULL;
 921 }
 922
 923 static void hostfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
 924 {
 925         char *s = nd_get_link(nd);
 926         if (!IS_ERR(s))
 927                 __putname(s);
 928 }
 929
 930 static const struct inode_operations hostfs_link_iops = {
 931         .readlink       = generic_readlink,
 932         .follow_link    = hostfs_follow_link,
 933         .put_link       = hostfs_put_link,
 934 };
 935
 936 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 937 {
 938         struct inode *root_inode;
 939         char *host_root_path, *req_root = d;
 940         int err;
 941
 942         sb->s_blocksize = 1024;
 943         sb->s_blocksize_bits = 10;
 944         sb->s_magic = HOSTFS_SUPER_MAGIC;
 945         sb->s_op = &hostfs_sbops;
 946         sb->s_d_op = &simple_dentry_operations;
 947         sb->s_maxbytes = MAX_LFS_FILESIZE;
 948
 949         /* NULL is printed as <NULL> by sprintf: avoid that. */
 950         if (req_root == NULL)
 951                 req_root = "";
 952
 953         err = -ENOMEM;
 954         sb->s_fs_info = host_root_path =
 955                 kmalloc(strlen(root_ino) + strlen(req_root) + 2, GFP_KERNEL);
 956         if (host_root_path == NULL)
 957                 goto out;
 958
 959         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 960
 961         root_inode = new_inode(sb);
 962         if (!root_inode)
 963                 goto out;
 964
 965         err = read_name(root_inode, host_root_path);
 966         if (err)
 967                 goto out_put;
 968
 969         if (S_ISLNK(root_inode->i_mode)) {
 970                 char *name = follow_link(host_root_path);
 971                 if (IS_ERR(name))
 972                         err = PTR_ERR(name);
 973                 else
 974                         err = read_name(root_inode, name);
 975                 kfree(name);
 976                 if (err)
 977                         goto out_put;
 978         }
 979
 980         err = -ENOMEM;
 981         sb->s_root = d_make_root(root_inode);
 982         if (sb->s_root == NULL)
 983                 goto out;
 984
 985         return 0;
 986
 987 out_put:
 988         iput(root_inode);
 989 out:
 990         return err;
 991 }
 992
 993 static struct dentry *hostfs_read_sb(struct file_system_type *type,
 994                           int flags, const char *dev_name,
 995                           void *data)
 996 {
 997         return mount_nodev(type, flags, data, hostfs_fill_sb_common);
 998 }
 999
1000 static void hostfs_kill_sb(struct super_block *s)
1001 {
1002         kill_anon_super(s);
1003         kfree(s->s_fs_info);
1004 }
1005
1006 static struct file_system_type hostfs_type = {
1007         .owner          = THIS_MODULE,
1008         .name           = "hostfs",
1009         .mount          = hostfs_read_sb,
1010         .kill_sb        = hostfs_kill_sb,
1011         .fs_flags       = 0,
1012 };
1013 MODULE_ALIAS_FS("hostfs");
1014
1015 static int __init init_hostfs(void)
1016 {
1017         return register_filesystem(&hostfs_type);
1018 }
1019
1020 static void __exit exit_hostfs(void)
1021 {
1022         unregister_filesystem(&hostfs_type);
1023 }
1024
1025 module_init(init_hostfs)
1026 module_exit(exit_hostfs)
1027 MODULE_LICENSE("GPL");