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