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