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