fs/hostfs/hostfs_kern.c

   1 /*
   2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  *
   5  * Ported the filesystem routines to 2.5.
   6  * 2003-02-10 Petr Baudis <pasky@ucw.cz>
   7  */
   8
   9 #include <linux/fs.h>
  10 #include <linux/module.h>
  11 #include <linux/mm.h>
  12 #include <linux/pagemap.h>
  13 #include <linux/statfs.h>
  14 #include <linux/slab.h>
  15 #include <linux/seq_file.h>
  16 #include <linux/mount.h>
  17 #include "hostfs.h"
  18 #include "init.h"
  19 #include "kern.h"
  20
  21 struct hostfs_inode_info {
  22         int fd;
  23         fmode_t mode;
  24         struct inode vfs_inode;
  25 };
  26
  27 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  28 {
  29         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
  30 }
  31
  32 #define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)
  33
  34 static int hostfs_d_delete(struct dentry *dentry)
  35 {
  36         return 1;
  37 }
  38
  39 static const struct dentry_operations hostfs_dentry_ops = {
  40         .d_delete               = hostfs_d_delete,
  41 };
  42
  43 /* Changed in hostfs_args before the kernel starts running */
  44 static char *root_ino = "";
  45 static int append = 0;
  46
  47 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
  48
  49 static const struct inode_operations hostfs_iops;
  50 static const struct inode_operations hostfs_dir_iops;
  51 static const struct address_space_operations hostfs_link_aops;
  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, int extra)
  93 {
  94         struct dentry *parent;
  95         char *root, *name;
  96         int len;
  97
  98         len = 0;
  99         parent = dentry;
 100         while (parent->d_parent != parent) {
 101                 len += parent->d_name.len + 1;
 102                 parent = parent->d_parent;
 103         }
 104
 105         root = parent->d_sb->s_fs_info;
 106         len += strlen(root);
 107         name = kmalloc(len + extra + 1, GFP_KERNEL);
 108         if (name == NULL)
 109                 return NULL;
 110
 111         name[len] = '\0';
 112         parent = dentry;
 113         while (parent->d_parent != parent) {
 114                 len -= parent->d_name.len + 1;
 115                 name[len] = '/';
 116                 strncpy(&name[len + 1], parent->d_name.name,
 117                         parent->d_name.len);
 118                 parent = parent->d_parent;
 119         }
 120         strncpy(name, root, strlen(root));
 121         return name;
 122 }
 123
 124 static char *inode_name(struct inode *ino, int extra)
 125 {
 126         struct dentry *dentry;
 127
 128         dentry = list_entry(ino->i_dentry.next, struct dentry, d_alias);
 129         return dentry_name(dentry, extra);
 130 }
 131
 132 static int read_name(struct inode *ino, char *name)
 133 {
 134         struct hostfs_stat st;
 135         int err = stat_file(name, &st, -1);
 136         if (err)
 137                 return err;
 138
 139         ino->i_ino = st.ino;
 140         ino->i_mode = st.mode;
 141         ino->i_nlink = st.nlink;
 142         ino->i_uid = st.uid;
 143         ino->i_gid = st.gid;
 144         ino->i_atime = st.atime;
 145         ino->i_mtime = st.mtime;
 146         ino->i_ctime = st.ctime;
 147         ino->i_size = st.size;
 148         ino->i_blocks = st.blocks;
 149         return 0;
 150 }
 151
 152 static char *follow_link(char *link)
 153 {
 154         int len, n;
 155         char *name, *resolved, *end;
 156
 157         len = 64;
 158         while (1) {
 159                 n = -ENOMEM;
 160                 name = kmalloc(len, GFP_KERNEL);
 161                 if (name == NULL)
 162                         goto out;
 163
 164                 n = hostfs_do_readlink(link, name, len);
 165                 if (n < len)
 166                         break;
 167                 len *= 2;
 168                 kfree(name);
 169         }
 170         if (n < 0)
 171                 goto out_free;
 172
 173         if (*name == '/')
 174                 return name;
 175
 176         end = strrchr(link, '/');
 177         if (end == NULL)
 178                 return name;
 179
 180         *(end + 1) = '\0';
 181         len = strlen(link) + strlen(name) + 1;
 182
 183         resolved = kmalloc(len, GFP_KERNEL);
 184         if (resolved == NULL) {
 185                 n = -ENOMEM;
 186                 goto out_free;
 187         }
 188
 189         sprintf(resolved, "%s%s", link, name);
 190         kfree(name);
 191         kfree(link);
 192         return resolved;
 193
 194  out_free:
 195         kfree(name);
 196  out:
 197         return ERR_PTR(n);
 198 }
 199
 200 static struct inode *hostfs_iget(struct super_block *sb)
 201 {
 202         struct inode *inode = new_inode(sb);
 203         if (!inode)
 204                 return ERR_PTR(-ENOMEM);
 205         return inode;
 206 }
 207
 208 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 209 {
 210         /*
 211          * do_statfs uses struct statfs64 internally, but the linux kernel
 212          * struct statfs still has 32-bit versions for most of these fields,
 213          * so we convert them here
 214          */
 215         int err;
 216         long long f_blocks;
 217         long long f_bfree;
 218         long long f_bavail;
 219         long long f_files;
 220         long long f_ffree;
 221
 222         err = do_statfs(dentry->d_sb->s_fs_info,
 223                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 224                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 225                         &sf->f_namelen, sf->f_spare);
 226         if (err)
 227                 return err;
 228         sf->f_blocks = f_blocks;
 229         sf->f_bfree = f_bfree;
 230         sf->f_bavail = f_bavail;
 231         sf->f_files = f_files;
 232         sf->f_ffree = f_ffree;
 233         sf->f_type = HOSTFS_SUPER_MAGIC;
 234         return 0;
 235 }
 236
 237 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 238 {
 239         struct hostfs_inode_info *hi;
 240
 241         hi = kzalloc(sizeof(*hi), GFP_KERNEL);
 242         if (hi == NULL)
 243                 return NULL;
 244         hi->fd = -1;
 245         inode_init_once(&hi->vfs_inode);
 246         return &hi->vfs_inode;
 247 }
 248
 249 static void hostfs_evict_inode(struct inode *inode)
 250 {
 251         truncate_inode_pages(&inode->i_data, 0);
 252         end_writeback(inode);
 253         if (HOSTFS_I(inode)->fd != -1) {
 254                 close_file(&HOSTFS_I(inode)->fd);
 255                 HOSTFS_I(inode)->fd = -1;
 256         }
 257 }
 258
 259 static void hostfs_destroy_inode(struct inode *inode)
 260 {
 261         kfree(HOSTFS_I(inode));
 262 }
 263
 264 static int hostfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 265 {
 266         const char *root_path = vfs->mnt_sb->s_fs_info;
 267         size_t offset = strlen(root_ino) + 1;
 268
 269         if (strlen(root_path) > offset)
 270                 seq_printf(seq, ",%s", root_path + offset);
 271
 272         return 0;
 273 }
 274
 275 static const struct super_operations hostfs_sbops = {
 276         .alloc_inode    = hostfs_alloc_inode,
 277         .destroy_inode  = hostfs_destroy_inode,
 278         .evict_inode    = hostfs_evict_inode,
 279         .statfs         = hostfs_statfs,
 280         .show_options   = hostfs_show_options,
 281 };
 282
 283 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 284 {
 285         void *dir;
 286         char *name;
 287         unsigned long long next, ino;
 288         int error, len;
 289
 290         name = dentry_name(file->f_path.dentry, 0);
 291         if (name == NULL)
 292                 return -ENOMEM;
 293         dir = open_dir(name, &error);
 294         kfree(name);
 295         if (dir == NULL)
 296                 return -error;
 297         next = file->f_pos;
 298         while ((name = read_dir(dir, &next, &ino, &len)) != NULL) {
 299                 error = (*filldir)(ent, name, len, file->f_pos,
 300                                    ino, DT_UNKNOWN);
 301                 if (error) break;
 302                 file->f_pos = next;
 303         }
 304         close_dir(dir);
 305         return 0;
 306 }
 307
 308 int hostfs_file_open(struct inode *ino, struct file *file)
 309 {
 310         char *name;
 311         fmode_t mode = 0;
 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         /*
 319          * The file may already have been opened, but with the wrong access,
 320          * so this resets things and reopens the file with the new access.
 321          */
 322         if (HOSTFS_I(ino)->fd != -1) {
 323                 close_file(&HOSTFS_I(ino)->fd);
 324                 HOSTFS_I(ino)->fd = -1;
 325         }
 326
 327         HOSTFS_I(ino)->mode |= mode;
 328         if (HOSTFS_I(ino)->mode & FMODE_READ)
 329                 r = 1;
 330         if (HOSTFS_I(ino)->mode & FMODE_WRITE)
 331                 w = 1;
 332         if (w)
 333                 r = 1;
 334
 335         name = dentry_name(file->f_path.dentry, 0);
 336         if (name == NULL)
 337                 return -ENOMEM;
 338
 339         fd = open_file(name, r, w, append);
 340         kfree(name);
 341         if (fd < 0)
 342                 return fd;
 343         FILE_HOSTFS_I(file)->fd = fd;
 344
 345         return 0;
 346 }
 347
 348 int hostfs_fsync(struct file *file, int datasync)
 349 {
 350         return fsync_file(HOSTFS_I(file->f_mapping->host)->fd, datasync);
 351 }
 352
 353 static const struct file_operations hostfs_file_fops = {
 354         .llseek         = generic_file_llseek,
 355         .read           = do_sync_read,
 356         .splice_read    = generic_file_splice_read,
 357         .aio_read       = generic_file_aio_read,
 358         .aio_write      = generic_file_aio_write,
 359         .write          = do_sync_write,
 360         .mmap           = generic_file_mmap,
 361         .open           = hostfs_file_open,
 362         .release        = NULL,
 363         .fsync          = hostfs_fsync,
 364 };
 365
 366 static const struct file_operations hostfs_dir_fops = {
 367         .llseek         = generic_file_llseek,
 368         .readdir        = hostfs_readdir,
 369         .read           = generic_read_dir,
 370 };
 371
 372 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 373 {
 374         struct address_space *mapping = page->mapping;
 375         struct inode *inode = mapping->host;
 376         char *buffer;
 377         unsigned long long base;
 378         int count = PAGE_CACHE_SIZE;
 379         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 380         int err;
 381
 382         if (page->index >= end_index)
 383                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 384
 385         buffer = kmap(page);
 386         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 387
 388         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 389         if (err != count) {
 390                 ClearPageUptodate(page);
 391                 goto out;
 392         }
 393
 394         if (base > inode->i_size)
 395                 inode->i_size = base;
 396
 397         if (PageError(page))
 398                 ClearPageError(page);
 399         err = 0;
 400
 401  out:
 402         kunmap(page);
 403
 404         unlock_page(page);
 405         return err;
 406 }
 407
 408 int hostfs_readpage(struct file *file, struct page *page)
 409 {
 410         char *buffer;
 411         long long start;
 412         int err = 0;
 413
 414         start = (long long) page->index << PAGE_CACHE_SHIFT;
 415         buffer = kmap(page);
 416         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 417                         PAGE_CACHE_SIZE);
 418         if (err < 0)
 419                 goto out;
 420
 421         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 422
 423         flush_dcache_page(page);
 424         SetPageUptodate(page);
 425         if (PageError(page)) ClearPageError(page);
 426         err = 0;
 427  out:
 428         kunmap(page);
 429         unlock_page(page);
 430         return err;
 431 }
 432
 433 int hostfs_write_begin(struct file *file, struct address_space *mapping,
 434                         loff_t pos, unsigned len, unsigned flags,
 435                         struct page **pagep, void **fsdata)
 436 {
 437         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 438
 439         *pagep = grab_cache_page_write_begin(mapping, index, flags);
 440         if (!*pagep)
 441                 return -ENOMEM;
 442         return 0;
 443 }
 444
 445 int hostfs_write_end(struct file *file, struct address_space *mapping,
 446                         loff_t pos, unsigned len, unsigned copied,
 447                         struct page *page, void *fsdata)
 448 {
 449         struct inode *inode = mapping->host;
 450         void *buffer;
 451         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 452         int err;
 453
 454         buffer = kmap(page);
 455         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 456         kunmap(page);
 457
 458         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 459                 SetPageUptodate(page);
 460
 461         /*
 462          * If err > 0, write_file has added err to pos, so we are comparing
 463          * i_size against the last byte written.
 464          */
 465         if (err > 0 && (pos > inode->i_size))
 466                 inode->i_size = pos;
 467         unlock_page(page);
 468         page_cache_release(page);
 469
 470         return err;
 471 }
 472
 473 static const struct address_space_operations hostfs_aops = {
 474         .writepage      = hostfs_writepage,
 475         .readpage       = hostfs_readpage,
 476         .set_page_dirty = __set_page_dirty_nobuffers,
 477         .write_begin    = hostfs_write_begin,
 478         .write_end      = hostfs_write_end,
 479 };
 480
 481 static void init_inode(struct inode *inode, char *path)
 482 {
 483         int type;
 484         int maj, min;
 485         dev_t rdev = 0;
 486
 487         type = file_type(path, &maj, &min);
 488         /* Reencode maj and min with the kernel encoding.*/
 489         rdev = MKDEV(maj, min);
 490
 491         if (type == OS_TYPE_SYMLINK)
 492                 inode->i_op = &page_symlink_inode_operations;
 493         else if (type == OS_TYPE_DIR)
 494                 inode->i_op = &hostfs_dir_iops;
 495         else inode->i_op = &hostfs_iops;
 496
 497         if (type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
 498         else inode->i_fop = &hostfs_file_fops;
 499
 500         if (type == OS_TYPE_SYMLINK)
 501                 inode->i_mapping->a_ops = &hostfs_link_aops;
 502         else inode->i_mapping->a_ops = &hostfs_aops;
 503
 504         switch (type) {
 505         case OS_TYPE_CHARDEV:
 506                 init_special_inode(inode, S_IFCHR, rdev);
 507                 break;
 508         case OS_TYPE_BLOCKDEV:
 509                 init_special_inode(inode, S_IFBLK, rdev);
 510                 break;
 511         case OS_TYPE_FIFO:
 512                 init_special_inode(inode, S_IFIFO, 0);
 513                 break;
 514         case OS_TYPE_SOCK:
 515                 init_special_inode(inode, S_IFSOCK, 0);
 516                 break;
 517         }
 518 }
 519
 520 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 521                   struct nameidata *nd)
 522 {
 523         struct inode *inode;
 524         char *name;
 525         int error, fd;
 526
 527         inode = hostfs_iget(dir->i_sb);
 528         if (IS_ERR(inode)) {
 529                 error = PTR_ERR(inode);
 530                 goto out;
 531         }
 532
 533         error = -ENOMEM;
 534         name = dentry_name(dentry, 0);
 535         if (name == NULL)
 536                 goto out_put;
 537
 538         fd = file_create(name,
 539                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 540                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 541                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 542         if (fd < 0) {
 543                 error = fd;
 544         } else {
 545                 error = read_name(inode, name);
 546                 init_inode(inode, name);
 547         }
 548
 549         kfree(name);
 550         if (error)
 551                 goto out_put;
 552
 553         HOSTFS_I(inode)->fd = fd;
 554         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 555         d_instantiate(dentry, inode);
 556         return 0;
 557
 558  out_put:
 559         iput(inode);
 560  out:
 561         return error;
 562 }
 563
 564 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 565                              struct nameidata *nd)
 566 {
 567         struct inode *inode;
 568         char *name;
 569         int err;
 570
 571         inode = hostfs_iget(ino->i_sb);
 572         if (IS_ERR(inode)) {
 573                 err = PTR_ERR(inode);
 574                 goto out;
 575         }
 576
 577         err = -ENOMEM;
 578         name = dentry_name(dentry, 0);
 579         if (name == NULL)
 580                 goto out_put;
 581
 582         err = read_name(inode, name);
 583         init_inode(inode, name);
 584
 585         kfree(name);
 586         if (err == -ENOENT) {
 587                 iput(inode);
 588                 inode = NULL;
 589         }
 590         else if (err)
 591                 goto out_put;
 592
 593         d_add(dentry, inode);
 594         dentry->d_op = &hostfs_dentry_ops;
 595         return NULL;
 596
 597  out_put:
 598         iput(inode);
 599  out:
 600         return ERR_PTR(err);
 601 }
 602
 603 static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
 604 {
 605         char *file;
 606         int len;
 607
 608         file = inode_name(ino, dentry->d_name.len + 1);
 609         if (file == NULL)
 610                 return NULL;
 611         strcat(file, "/");
 612         len = strlen(file);
 613         strncat(file, dentry->d_name.name, dentry->d_name.len);
 614         file[len + dentry->d_name.len] = '\0';
 615         return file;
 616 }
 617
 618 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 619 {
 620         char *from_name, *to_name;
 621         int err;
 622
 623         if ((from_name = inode_dentry_name(ino, from)) == NULL)
 624                 return -ENOMEM;
 625         to_name = dentry_name(to, 0);
 626         if (to_name == NULL) {
 627                 kfree(from_name);
 628                 return -ENOMEM;
 629         }
 630         err = link_file(to_name, from_name);
 631         kfree(from_name);
 632         kfree(to_name);
 633         return err;
 634 }
 635
 636 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 637 {
 638         char *file;
 639         int err;
 640
 641         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 642                 return -ENOMEM;
 643         if (append)
 644                 return -EPERM;
 645
 646         err = unlink_file(file);
 647         kfree(file);
 648         return err;
 649 }
 650
 651 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 652 {
 653         char *file;
 654         int err;
 655
 656         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 657                 return -ENOMEM;
 658         err = make_symlink(file, to);
 659         kfree(file);
 660         return err;
 661 }
 662
 663 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 664 {
 665         char *file;
 666         int err;
 667
 668         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 669                 return -ENOMEM;
 670         err = do_mkdir(file, mode);
 671         kfree(file);
 672         return err;
 673 }
 674
 675 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 676 {
 677         char *file;
 678         int err;
 679
 680         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 681                 return -ENOMEM;
 682         err = do_rmdir(file);
 683         kfree(file);
 684         return err;
 685 }
 686
 687 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 688 {
 689         struct inode *inode;
 690         char *name;
 691         int err;
 692
 693         inode = hostfs_iget(dir->i_sb);
 694         if (IS_ERR(inode)) {
 695                 err = PTR_ERR(inode);
 696                 goto out;
 697         }
 698
 699         err = -ENOMEM;
 700         name = dentry_name(dentry, 0);
 701         if (name == NULL)
 702                 goto out_put;
 703
 704         init_special_inode(inode, mode, dev);
 705         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 706         if (err)
 707                 goto out_free;
 708
 709         err = read_name(inode, name);
 710         init_inode(inode, name);
 711         if (err)
 712                 goto out_put;
 713         kfree(name);
 714         if (err)
 715                 goto out_put;
 716
 717         d_instantiate(dentry, inode);
 718         return 0;
 719
 720  out_free:
 721         kfree(name);
 722  out_put:
 723         iput(inode);
 724  out:
 725         return err;
 726 }
 727
 728 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 729                   struct inode *to_ino, struct dentry *to)
 730 {
 731         char *from_name, *to_name;
 732         int err;
 733
 734         if ((from_name = inode_dentry_name(from_ino, from)) == NULL)
 735                 return -ENOMEM;
 736         if ((to_name = inode_dentry_name(to_ino, to)) == NULL) {
 737                 kfree(from_name);
 738                 return -ENOMEM;
 739         }
 740         err = rename_file(from_name, to_name);
 741         kfree(from_name);
 742         kfree(to_name);
 743         return err;
 744 }
 745
 746 int hostfs_permission(struct inode *ino, int desired)
 747 {
 748         char *name;
 749         int r = 0, w = 0, x = 0, err;
 750
 751         if (desired & MAY_READ) r = 1;
 752         if (desired & MAY_WRITE) w = 1;
 753         if (desired & MAY_EXEC) x = 1;
 754         name = inode_name(ino, 0);
 755         if (name == NULL)
 756                 return -ENOMEM;
 757
 758         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 759             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 760                 err = 0;
 761         else
 762                 err = access_file(name, r, w, x);
 763         kfree(name);
 764         if (!err)
 765                 err = generic_permission(ino, desired, NULL);
 766         return err;
 767 }
 768
 769 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 770 {
 771         struct inode *inode = dentry->d_inode;
 772         struct hostfs_iattr attrs;
 773         char *name;
 774         int err;
 775
 776         int fd = HOSTFS_I(inode)->fd;
 777
 778         err = inode_change_ok(inode, attr);
 779         if (err)
 780                 return err;
 781
 782         if (append)
 783                 attr->ia_valid &= ~ATTR_SIZE;
 784
 785         attrs.ia_valid = 0;
 786         if (attr->ia_valid & ATTR_MODE) {
 787                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 788                 attrs.ia_mode = attr->ia_mode;
 789         }
 790         if (attr->ia_valid & ATTR_UID) {
 791                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 792                 attrs.ia_uid = attr->ia_uid;
 793         }
 794         if (attr->ia_valid & ATTR_GID) {
 795                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 796                 attrs.ia_gid = attr->ia_gid;
 797         }
 798         if (attr->ia_valid & ATTR_SIZE) {
 799                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 800                 attrs.ia_size = attr->ia_size;
 801         }
 802         if (attr->ia_valid & ATTR_ATIME) {
 803                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 804                 attrs.ia_atime = attr->ia_atime;
 805         }
 806         if (attr->ia_valid & ATTR_MTIME) {
 807                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 808                 attrs.ia_mtime = attr->ia_mtime;
 809         }
 810         if (attr->ia_valid & ATTR_CTIME) {
 811                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 812                 attrs.ia_ctime = attr->ia_ctime;
 813         }
 814         if (attr->ia_valid & ATTR_ATIME_SET) {
 815                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 816         }
 817         if (attr->ia_valid & ATTR_MTIME_SET) {
 818                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 819         }
 820         name = dentry_name(dentry, 0);
 821         if (name == NULL)
 822                 return -ENOMEM;
 823         err = set_attr(name, &attrs, fd);
 824         kfree(name);
 825         if (err)
 826                 return err;
 827
 828         if ((attr->ia_valid & ATTR_SIZE) &&
 829             attr->ia_size != i_size_read(inode)) {
 830                 int error;
 831
 832                 error = vmtruncate(inode, attr->ia_size);
 833                 if (err)
 834                         return err;
 835         }
 836
 837         setattr_copy(inode, attr);
 838         mark_inode_dirty(inode);
 839         return 0;
 840 }
 841
 842 static const struct inode_operations hostfs_iops = {
 843         .create         = hostfs_create,
 844         .link           = hostfs_link,
 845         .unlink         = hostfs_unlink,
 846         .symlink        = hostfs_symlink,
 847         .mkdir          = hostfs_mkdir,
 848         .rmdir          = hostfs_rmdir,
 849         .mknod          = hostfs_mknod,
 850         .rename         = hostfs_rename,
 851         .permission     = hostfs_permission,
 852         .setattr        = hostfs_setattr,
 853 };
 854
 855 static const struct inode_operations hostfs_dir_iops = {
 856         .create         = hostfs_create,
 857         .lookup         = hostfs_lookup,
 858         .link           = hostfs_link,
 859         .unlink         = hostfs_unlink,
 860         .symlink        = hostfs_symlink,
 861         .mkdir          = hostfs_mkdir,
 862         .rmdir          = hostfs_rmdir,
 863         .mknod          = hostfs_mknod,
 864         .rename         = hostfs_rename,
 865         .permission     = hostfs_permission,
 866         .setattr        = hostfs_setattr,
 867 };
 868
 869 int hostfs_link_readpage(struct file *file, struct page *page)
 870 {
 871         char *buffer, *name;
 872         int err;
 873
 874         buffer = kmap(page);
 875         name = inode_name(page->mapping->host, 0);
 876         if (name == NULL)
 877                 return -ENOMEM;
 878         err = hostfs_do_readlink(name, buffer, PAGE_CACHE_SIZE);
 879         kfree(name);
 880         if (err == PAGE_CACHE_SIZE)
 881                 err = -E2BIG;
 882         else if (err > 0) {
 883                 flush_dcache_page(page);
 884                 SetPageUptodate(page);
 885                 if (PageError(page)) ClearPageError(page);
 886                 err = 0;
 887         }
 888         kunmap(page);
 889         unlock_page(page);
 890         return err;
 891 }
 892
 893 static const struct address_space_operations hostfs_link_aops = {
 894         .readpage       = hostfs_link_readpage,
 895 };
 896
 897 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 898 {
 899         struct inode *root_inode;
 900         char *host_root_path, *req_root = d;
 901         int err;
 902
 903         sb->s_blocksize = 1024;
 904         sb->s_blocksize_bits = 10;
 905         sb->s_magic = HOSTFS_SUPER_MAGIC;
 906         sb->s_op = &hostfs_sbops;
 907         sb->s_maxbytes = MAX_LFS_FILESIZE;
 908
 909         /* NULL is printed as <NULL> by sprintf: avoid that. */
 910         if (req_root == NULL)
 911                 req_root = "";
 912
 913         err = -ENOMEM;
 914         sb->s_fs_info = host_root_path =
 915                 kmalloc(strlen(root_ino) + strlen(req_root) + 2, GFP_KERNEL);
 916         if (host_root_path == NULL)
 917                 goto out;
 918
 919         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 920
 921         root_inode = new_inode(sb);
 922         if (!root_inode)
 923                 goto out;
 924
 925         root_inode->i_op = &hostfs_dir_iops;
 926         root_inode->i_fop = &hostfs_dir_fops;
 927
 928         if (file_type(host_root_path, NULL, NULL) == OS_TYPE_SYMLINK) {
 929                 char *name = follow_link(host_root_path);
 930                 if (IS_ERR(name))
 931                         err = PTR_ERR(name);
 932                 else
 933                         err = read_name(root_inode, name);
 934                 kfree(name);
 935         } else {
 936                 err = read_name(root_inode, host_root_path);
 937         }
 938         if (err)
 939                 goto out_put;
 940
 941         err = -ENOMEM;
 942         sb->s_root = d_alloc_root(root_inode);
 943         if (sb->s_root == NULL)
 944                 goto out_put;
 945
 946         return 0;
 947
 948 out_put:
 949         iput(root_inode);
 950 out:
 951         return err;
 952 }
 953
 954 static int hostfs_read_sb(struct file_system_type *type,
 955                           int flags, const char *dev_name,
 956                           void *data, struct vfsmount *mnt)
 957 {
 958         return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
 959 }
 960
 961 static void hostfs_kill_sb(struct super_block *s)
 962 {
 963         kill_anon_super(s);
 964         kfree(s->s_fs_info);
 965 }
 966
 967 static struct file_system_type hostfs_type = {
 968         .owner          = THIS_MODULE,
 969         .name           = "hostfs",
 970         .get_sb         = hostfs_read_sb,
 971         .kill_sb        = hostfs_kill_sb,
 972         .fs_flags       = 0,
 973 };
 974
 975 static int __init init_hostfs(void)
 976 {
 977         return register_filesystem(&hostfs_type);
 978 }
 979
 980 static void __exit exit_hostfs(void)
 981 {
 982         unregister_filesystem(&hostfs_type);
 983 }
 984
 985 module_init(init_hostfs)
 986 module_exit(exit_hostfs)
 987 MODULE_LICENSE("GPL");