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/seq_file.h>
  15 #include "hostfs.h"
  16 #include "init.h"
  17 #include "kern.h"
  18
  19 struct hostfs_inode_info {
  20         char *host_filename;
  21         int fd;
  22         int mode;
  23         struct inode vfs_inode;
  24 };
  25
  26 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  27 {
  28         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
  29 }
  30
  31 #define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)
  32
  33 int hostfs_d_delete(struct dentry *dentry)
  34 {
  35         return 1;
  36 }
  37
  38 struct dentry_operations hostfs_dentry_ops = {
  39         .d_delete               = hostfs_d_delete,
  40 };
  41
  42 /* Changed in hostfs_args before the kernel starts running */
  43 static char *root_ino = "";
  44 static int append = 0;
  45
  46 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
  47
  48 static const struct inode_operations hostfs_iops;
  49 static const struct inode_operations hostfs_dir_iops;
  50 static const struct address_space_operations hostfs_link_aops;
  51
  52 #ifndef MODULE
  53 static int __init hostfs_args(char *options, int *add)
  54 {
  55         char *ptr;
  56
  57         ptr = strchr(options, ',');
  58         if (ptr != NULL)
  59                 *ptr++ = '\0';
  60         if (*options != '\0')
  61                 root_ino = options;
  62
  63         options = ptr;
  64         while (options) {
  65                 ptr = strchr(options, ',');
  66                 if (ptr != NULL)
  67                         *ptr++ = '\0';
  68                 if (*options != '\0') {
  69                         if (!strcmp(options, "append"))
  70                                 append = 1;
  71                         else printf("hostfs_args - unsupported option - %s\n",
  72                                     options);
  73                 }
  74                 options = ptr;
  75         }
  76         return 0;
  77 }
  78
  79 __uml_setup("hostfs=", hostfs_args,
  80 "hostfs=<root dir>,<flags>,...\n"
  81 "    This is used to set hostfs parameters.  The root directory argument\n"
  82 "    is used to confine all hostfs mounts to within the specified directory\n"
  83 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
  84 "    mount anything on the host that's accessible to the user that's running\n"
  85 "    it.\n"
  86 "    The only flag currently supported is 'append', which specifies that all\n"
  87 "    files opened by hostfs will be opened in append mode.\n\n"
  88 );
  89 #endif
  90
  91 static char *dentry_name(struct dentry *dentry, int extra)
  92 {
  93         struct dentry *parent;
  94         char *root, *name;
  95         int len;
  96
  97         len = 0;
  98         parent = dentry;
  99         while (parent->d_parent != parent) {
 100                 len += parent->d_name.len + 1;
 101                 parent = parent->d_parent;
 102         }
 103
 104         root = HOSTFS_I(parent->d_inode)->host_filename;
 105         len += strlen(root);
 106         name = kmalloc(len + extra + 1, GFP_KERNEL);
 107         if (name == NULL)
 108                 return NULL;
 109
 110         name[len] = '\0';
 111         parent = dentry;
 112         while (parent->d_parent != parent) {
 113                 len -= parent->d_name.len + 1;
 114                 name[len] = '/';
 115                 strncpy(&name[len + 1], parent->d_name.name,
 116                         parent->d_name.len);
 117                 parent = parent->d_parent;
 118         }
 119         strncpy(name, root, strlen(root));
 120         return name;
 121 }
 122
 123 static char *inode_name(struct inode *ino, int extra)
 124 {
 125         struct dentry *dentry;
 126
 127         dentry = list_entry(ino->i_dentry.next, struct dentry, d_alias);
 128         return dentry_name(dentry, extra);
 129 }
 130
 131 static int read_name(struct inode *ino, char *name)
 132 {
 133         /*
 134          * The non-int inode fields are copied into ints by stat_file and
 135          * then copied into the inode because passing the actual pointers
 136          * in and having them treated as int * breaks on big-endian machines
 137          */
 138         int err;
 139         int i_mode, i_nlink, i_blksize;
 140         unsigned long long i_size;
 141         unsigned long long i_ino;
 142         unsigned long long i_blocks;
 143
 144         err = stat_file(name, &i_ino, &i_mode, &i_nlink, &ino->i_uid,
 145                         &ino->i_gid, &i_size, &ino->i_atime, &ino->i_mtime,
 146                         &ino->i_ctime, &i_blksize, &i_blocks, -1);
 147         if (err)
 148                 return err;
 149
 150         ino->i_ino = i_ino;
 151         ino->i_mode = i_mode;
 152         ino->i_nlink = i_nlink;
 153         ino->i_size = i_size;
 154         ino->i_blocks = i_blocks;
 155         return 0;
 156 }
 157
 158 static char *follow_link(char *link)
 159 {
 160         int len, n;
 161         char *name, *resolved, *end;
 162
 163         len = 64;
 164         while (1) {
 165                 n = -ENOMEM;
 166                 name = kmalloc(len, GFP_KERNEL);
 167                 if (name == NULL)
 168                         goto out;
 169
 170                 n = do_readlink(link, name, len);
 171                 if (n < len)
 172                         break;
 173                 len *= 2;
 174                 kfree(name);
 175         }
 176         if (n < 0)
 177                 goto out_free;
 178
 179         if (*name == '/')
 180                 return name;
 181
 182         end = strrchr(link, '/');
 183         if (end == NULL)
 184                 return name;
 185
 186         *(end + 1) = '\0';
 187         len = strlen(link) + strlen(name) + 1;
 188
 189         resolved = kmalloc(len, GFP_KERNEL);
 190         if (resolved == NULL) {
 191                 n = -ENOMEM;
 192                 goto out_free;
 193         }
 194
 195         sprintf(resolved, "%s%s", link, name);
 196         kfree(name);
 197         kfree(link);
 198         return resolved;
 199
 200  out_free:
 201         kfree(name);
 202  out:
 203         return ERR_PTR(n);
 204 }
 205
 206 static int hostfs_read_inode(struct inode *ino)
 207 {
 208         char *name;
 209         int err = 0;
 210
 211         /*
 212          * Unfortunately, we are called from iget() when we don't have a dentry
 213          * allocated yet.
 214          */
 215         if (list_empty(&ino->i_dentry))
 216                 goto out;
 217
 218         err = -ENOMEM;
 219         name = inode_name(ino, 0);
 220         if (name == NULL)
 221                 goto out;
 222
 223         if (file_type(name, NULL, NULL) == OS_TYPE_SYMLINK) {
 224                 name = follow_link(name);
 225                 if (IS_ERR(name)) {
 226                         err = PTR_ERR(name);
 227                         goto out;
 228                 }
 229         }
 230
 231         err = read_name(ino, name);
 232         kfree(name);
 233  out:
 234         return err;
 235 }
 236
 237 static struct inode *hostfs_iget(struct super_block *sb)
 238 {
 239         struct inode *inode;
 240         long ret;
 241
 242         inode = iget_locked(sb, 0);
 243         if (!inode)
 244                 return ERR_PTR(-ENOMEM);
 245         if (inode->i_state & I_NEW) {
 246                 ret = hostfs_read_inode(inode);
 247                 if (ret < 0) {
 248                         iget_failed(inode);
 249                         return ERR_PTR(ret);
 250                 }
 251                 unlock_new_inode(inode);
 252         }
 253         return inode;
 254 }
 255
 256 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 257 {
 258         /*
 259          * do_statfs uses struct statfs64 internally, but the linux kernel
 260          * struct statfs still has 32-bit versions for most of these fields,
 261          * so we convert them here
 262          */
 263         int err;
 264         long long f_blocks;
 265         long long f_bfree;
 266         long long f_bavail;
 267         long long f_files;
 268         long long f_ffree;
 269
 270         err = do_statfs(HOSTFS_I(dentry->d_sb->s_root->d_inode)->host_filename,
 271                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 272                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 273                         &sf->f_namelen, sf->f_spare);
 274         if (err)
 275                 return err;
 276         sf->f_blocks = f_blocks;
 277         sf->f_bfree = f_bfree;
 278         sf->f_bavail = f_bavail;
 279         sf->f_files = f_files;
 280         sf->f_ffree = f_ffree;
 281         sf->f_type = HOSTFS_SUPER_MAGIC;
 282         return 0;
 283 }
 284
 285 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 286 {
 287         struct hostfs_inode_info *hi;
 288
 289         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 290         if (hi == NULL)
 291                 return NULL;
 292
 293         *hi = ((struct hostfs_inode_info) { .host_filename      = NULL,
 294                                             .fd                 = -1,
 295                                             .mode               = 0 });
 296         inode_init_once(&hi->vfs_inode);
 297         return &hi->vfs_inode;
 298 }
 299
 300 static void hostfs_delete_inode(struct inode *inode)
 301 {
 302         truncate_inode_pages(&inode->i_data, 0);
 303         if (HOSTFS_I(inode)->fd != -1) {
 304                 close_file(&HOSTFS_I(inode)->fd);
 305                 HOSTFS_I(inode)->fd = -1;
 306         }
 307         clear_inode(inode);
 308 }
 309
 310 static void hostfs_destroy_inode(struct inode *inode)
 311 {
 312         kfree(HOSTFS_I(inode)->host_filename);
 313
 314         /*
 315          * XXX: This should not happen, probably. The check is here for
 316          * additional safety.
 317          */
 318         if (HOSTFS_I(inode)->fd != -1) {
 319                 close_file(&HOSTFS_I(inode)->fd);
 320                 printk(KERN_DEBUG "Closing host fd in .destroy_inode\n");
 321         }
 322
 323         kfree(HOSTFS_I(inode));
 324 }
 325
 326 static int hostfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 327 {
 328         struct inode *root = vfs->mnt_sb->s_root->d_inode;
 329         const char *root_path = HOSTFS_I(root)->host_filename;
 330         size_t offset = strlen(root_ino) + 1;
 331
 332         if (strlen(root_path) > offset)
 333                 seq_printf(seq, ",%s", root_path + offset);
 334
 335         return 0;
 336 }
 337
 338 static const struct super_operations hostfs_sbops = {
 339         .alloc_inode    = hostfs_alloc_inode,
 340         .drop_inode     = generic_delete_inode,
 341         .delete_inode   = hostfs_delete_inode,
 342         .destroy_inode  = hostfs_destroy_inode,
 343         .statfs         = hostfs_statfs,
 344         .show_options   = hostfs_show_options,
 345 };
 346
 347 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 348 {
 349         void *dir;
 350         char *name;
 351         unsigned long long next, ino;
 352         int error, len;
 353
 354         name = dentry_name(file->f_path.dentry, 0);
 355         if (name == NULL)
 356                 return -ENOMEM;
 357         dir = open_dir(name, &error);
 358         kfree(name);
 359         if (dir == NULL)
 360                 return -error;
 361         next = file->f_pos;
 362         while ((name = read_dir(dir, &next, &ino, &len)) != NULL) {
 363                 error = (*filldir)(ent, name, len, file->f_pos,
 364                                    ino, DT_UNKNOWN);
 365                 if (error) break;
 366                 file->f_pos = next;
 367         }
 368         close_dir(dir);
 369         return 0;
 370 }
 371
 372 int hostfs_file_open(struct inode *ino, struct file *file)
 373 {
 374         char *name;
 375         int mode = 0, r = 0, w = 0, fd;
 376
 377         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 378         if ((mode & HOSTFS_I(ino)->mode) == mode)
 379                 return 0;
 380
 381         /*
 382          * The file may already have been opened, but with the wrong access,
 383          * so this resets things and reopens the file with the new access.
 384          */
 385         if (HOSTFS_I(ino)->fd != -1) {
 386                 close_file(&HOSTFS_I(ino)->fd);
 387                 HOSTFS_I(ino)->fd = -1;
 388         }
 389
 390         HOSTFS_I(ino)->mode |= mode;
 391         if (HOSTFS_I(ino)->mode & FMODE_READ)
 392                 r = 1;
 393         if (HOSTFS_I(ino)->mode & FMODE_WRITE)
 394                 w = 1;
 395         if (w)
 396                 r = 1;
 397
 398         name = dentry_name(file->f_path.dentry, 0);
 399         if (name == NULL)
 400                 return -ENOMEM;
 401
 402         fd = open_file(name, r, w, append);
 403         kfree(name);
 404         if (fd < 0)
 405                 return fd;
 406         FILE_HOSTFS_I(file)->fd = fd;
 407
 408         return 0;
 409 }
 410
 411 int hostfs_fsync(struct file *file, struct dentry *dentry, int datasync)
 412 {
 413         return fsync_file(HOSTFS_I(dentry->d_inode)->fd, datasync);
 414 }
 415
 416 static const struct file_operations hostfs_file_fops = {
 417         .llseek         = generic_file_llseek,
 418         .read           = do_sync_read,
 419         .splice_read    = generic_file_splice_read,
 420         .aio_read       = generic_file_aio_read,
 421         .aio_write      = generic_file_aio_write,
 422         .write          = do_sync_write,
 423         .mmap           = generic_file_mmap,
 424         .open           = hostfs_file_open,
 425         .release        = NULL,
 426         .fsync          = hostfs_fsync,
 427 };
 428
 429 static const struct file_operations hostfs_dir_fops = {
 430         .llseek         = generic_file_llseek,
 431         .readdir        = hostfs_readdir,
 432         .read           = generic_read_dir,
 433 };
 434
 435 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 436 {
 437         struct address_space *mapping = page->mapping;
 438         struct inode *inode = mapping->host;
 439         char *buffer;
 440         unsigned long long base;
 441         int count = PAGE_CACHE_SIZE;
 442         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 443         int err;
 444
 445         if (page->index >= end_index)
 446                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 447
 448         buffer = kmap(page);
 449         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 450
 451         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 452         if (err != count) {
 453                 ClearPageUptodate(page);
 454                 goto out;
 455         }
 456
 457         if (base > inode->i_size)
 458                 inode->i_size = base;
 459
 460         if (PageError(page))
 461                 ClearPageError(page);
 462         err = 0;
 463
 464  out:
 465         kunmap(page);
 466
 467         unlock_page(page);
 468         return err;
 469 }
 470
 471 int hostfs_readpage(struct file *file, struct page *page)
 472 {
 473         char *buffer;
 474         long long start;
 475         int err = 0;
 476
 477         start = (long long) page->index << PAGE_CACHE_SHIFT;
 478         buffer = kmap(page);
 479         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 480                         PAGE_CACHE_SIZE);
 481         if (err < 0)
 482                 goto out;
 483
 484         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 485
 486         flush_dcache_page(page);
 487         SetPageUptodate(page);
 488         if (PageError(page)) ClearPageError(page);
 489         err = 0;
 490  out:
 491         kunmap(page);
 492         unlock_page(page);
 493         return err;
 494 }
 495
 496 int hostfs_write_begin(struct file *file, struct address_space *mapping,
 497                         loff_t pos, unsigned len, unsigned flags,
 498                         struct page **pagep, void **fsdata)
 499 {
 500         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 501
 502         *pagep = __grab_cache_page(mapping, index);
 503         if (!*pagep)
 504                 return -ENOMEM;
 505         return 0;
 506 }
 507
 508 int hostfs_write_end(struct file *file, struct address_space *mapping,
 509                         loff_t pos, unsigned len, unsigned copied,
 510                         struct page *page, void *fsdata)
 511 {
 512         struct inode *inode = mapping->host;
 513         void *buffer;
 514         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 515         int err;
 516
 517         buffer = kmap(page);
 518         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 519         kunmap(page);
 520
 521         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 522                 SetPageUptodate(page);
 523
 524         /*
 525          * If err > 0, write_file has added err to pos, so we are comparing
 526          * i_size against the last byte written.
 527          */
 528         if (err > 0 && (pos > inode->i_size))
 529                 inode->i_size = pos;
 530         unlock_page(page);
 531         page_cache_release(page);
 532
 533         return err;
 534 }
 535
 536 static const struct address_space_operations hostfs_aops = {
 537         .writepage      = hostfs_writepage,
 538         .readpage       = hostfs_readpage,
 539         .set_page_dirty = __set_page_dirty_nobuffers,
 540         .write_begin    = hostfs_write_begin,
 541         .write_end      = hostfs_write_end,
 542 };
 543
 544 static int init_inode(struct inode *inode, struct dentry *dentry)
 545 {
 546         char *name;
 547         int type, err = -ENOMEM;
 548         int maj, min;
 549         dev_t rdev = 0;
 550
 551         if (dentry) {
 552                 name = dentry_name(dentry, 0);
 553                 if (name == NULL)
 554                         goto out;
 555                 type = file_type(name, &maj, &min);
 556                 /* Reencode maj and min with the kernel encoding.*/
 557                 rdev = MKDEV(maj, min);
 558                 kfree(name);
 559         }
 560         else type = OS_TYPE_DIR;
 561
 562         err = 0;
 563         if (type == OS_TYPE_SYMLINK)
 564                 inode->i_op = &page_symlink_inode_operations;
 565         else if (type == OS_TYPE_DIR)
 566                 inode->i_op = &hostfs_dir_iops;
 567         else inode->i_op = &hostfs_iops;
 568
 569         if (type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
 570         else inode->i_fop = &hostfs_file_fops;
 571
 572         if (type == OS_TYPE_SYMLINK)
 573                 inode->i_mapping->a_ops = &hostfs_link_aops;
 574         else inode->i_mapping->a_ops = &hostfs_aops;
 575
 576         switch (type) {
 577         case OS_TYPE_CHARDEV:
 578                 init_special_inode(inode, S_IFCHR, rdev);
 579                 break;
 580         case OS_TYPE_BLOCKDEV:
 581                 init_special_inode(inode, S_IFBLK, rdev);
 582                 break;
 583         case OS_TYPE_FIFO:
 584                 init_special_inode(inode, S_IFIFO, 0);
 585                 break;
 586         case OS_TYPE_SOCK:
 587                 init_special_inode(inode, S_IFSOCK, 0);
 588                 break;
 589         }
 590  out:
 591         return err;
 592 }
 593
 594 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 595                   struct nameidata *nd)
 596 {
 597         struct inode *inode;
 598         char *name;
 599         int error, fd;
 600
 601         inode = hostfs_iget(dir->i_sb);
 602         if (IS_ERR(inode)) {
 603                 error = PTR_ERR(inode);
 604                 goto out;
 605         }
 606
 607         error = init_inode(inode, dentry);
 608         if (error)
 609                 goto out_put;
 610
 611         error = -ENOMEM;
 612         name = dentry_name(dentry, 0);
 613         if (name == NULL)
 614                 goto out_put;
 615
 616         fd = file_create(name,
 617                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 618                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 619                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 620         if (fd < 0)
 621                 error = fd;
 622         else error = read_name(inode, name);
 623
 624         kfree(name);
 625         if (error)
 626                 goto out_put;
 627
 628         HOSTFS_I(inode)->fd = fd;
 629         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 630         d_instantiate(dentry, inode);
 631         return 0;
 632
 633  out_put:
 634         iput(inode);
 635  out:
 636         return error;
 637 }
 638
 639 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 640                              struct nameidata *nd)
 641 {
 642         struct inode *inode;
 643         char *name;
 644         int err;
 645
 646         inode = hostfs_iget(ino->i_sb);
 647         if (IS_ERR(inode)) {
 648                 err = PTR_ERR(inode);
 649                 goto out;
 650         }
 651
 652         err = init_inode(inode, dentry);
 653         if (err)
 654                 goto out_put;
 655
 656         err = -ENOMEM;
 657         name = dentry_name(dentry, 0);
 658         if (name == NULL)
 659                 goto out_put;
 660
 661         err = read_name(inode, name);
 662         kfree(name);
 663         if (err == -ENOENT) {
 664                 iput(inode);
 665                 inode = NULL;
 666         }
 667         else if (err)
 668                 goto out_put;
 669
 670         d_add(dentry, inode);
 671         dentry->d_op = &hostfs_dentry_ops;
 672         return NULL;
 673
 674  out_put:
 675         iput(inode);
 676  out:
 677         return ERR_PTR(err);
 678 }
 679
 680 static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
 681 {
 682         char *file;
 683         int len;
 684
 685         file = inode_name(ino, dentry->d_name.len + 1);
 686         if (file == NULL)
 687                 return NULL;
 688         strcat(file, "/");
 689         len = strlen(file);
 690         strncat(file, dentry->d_name.name, dentry->d_name.len);
 691         file[len + dentry->d_name.len] = '\0';
 692         return file;
 693 }
 694
 695 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 696 {
 697         char *from_name, *to_name;
 698         int err;
 699
 700         if ((from_name = inode_dentry_name(ino, from)) == NULL)
 701                 return -ENOMEM;
 702         to_name = dentry_name(to, 0);
 703         if (to_name == NULL) {
 704                 kfree(from_name);
 705                 return -ENOMEM;
 706         }
 707         err = link_file(to_name, from_name);
 708         kfree(from_name);
 709         kfree(to_name);
 710         return err;
 711 }
 712
 713 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 714 {
 715         char *file;
 716         int err;
 717
 718         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 719                 return -ENOMEM;
 720         if (append)
 721                 return -EPERM;
 722
 723         err = unlink_file(file);
 724         kfree(file);
 725         return err;
 726 }
 727
 728 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 729 {
 730         char *file;
 731         int err;
 732
 733         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 734                 return -ENOMEM;
 735         err = make_symlink(file, to);
 736         kfree(file);
 737         return err;
 738 }
 739
 740 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 741 {
 742         char *file;
 743         int err;
 744
 745         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 746                 return -ENOMEM;
 747         err = do_mkdir(file, mode);
 748         kfree(file);
 749         return err;
 750 }
 751
 752 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 753 {
 754         char *file;
 755         int err;
 756
 757         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 758                 return -ENOMEM;
 759         err = do_rmdir(file);
 760         kfree(file);
 761         return err;
 762 }
 763
 764 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 765 {
 766         struct inode *inode;
 767         char *name;
 768         int err;
 769
 770         inode = hostfs_iget(dir->i_sb);
 771         if (IS_ERR(inode)) {
 772                 err = PTR_ERR(inode);
 773                 goto out;
 774         }
 775
 776         err = init_inode(inode, dentry);
 777         if (err)
 778                 goto out_put;
 779
 780         err = -ENOMEM;
 781         name = dentry_name(dentry, 0);
 782         if (name == NULL)
 783                 goto out_put;
 784
 785         init_special_inode(inode, mode, dev);
 786         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 787         if (err)
 788                 goto out_free;
 789
 790         err = read_name(inode, name);
 791         kfree(name);
 792         if (err)
 793                 goto out_put;
 794
 795         d_instantiate(dentry, inode);
 796         return 0;
 797
 798  out_free:
 799         kfree(name);
 800  out_put:
 801         iput(inode);
 802  out:
 803         return err;
 804 }
 805
 806 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 807                   struct inode *to_ino, struct dentry *to)
 808 {
 809         char *from_name, *to_name;
 810         int err;
 811
 812         if ((from_name = inode_dentry_name(from_ino, from)) == NULL)
 813                 return -ENOMEM;
 814         if ((to_name = inode_dentry_name(to_ino, to)) == NULL) {
 815                 kfree(from_name);
 816                 return -ENOMEM;
 817         }
 818         err = rename_file(from_name, to_name);
 819         kfree(from_name);
 820         kfree(to_name);
 821         return err;
 822 }
 823
 824 int hostfs_permission(struct inode *ino, int desired, struct nameidata *nd)
 825 {
 826         char *name;
 827         int r = 0, w = 0, x = 0, err;
 828
 829         if (desired & MAY_READ) r = 1;
 830         if (desired & MAY_WRITE) w = 1;
 831         if (desired & MAY_EXEC) x = 1;
 832         name = inode_name(ino, 0);
 833         if (name == NULL)
 834                 return -ENOMEM;
 835
 836         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 837             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 838                 err = 0;
 839         else
 840                 err = access_file(name, r, w, x);
 841         kfree(name);
 842         if (!err)
 843                 err = generic_permission(ino, desired, NULL);
 844         return err;
 845 }
 846
 847 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 848 {
 849         struct hostfs_iattr attrs;
 850         char *name;
 851         int err;
 852
 853         int fd = HOSTFS_I(dentry->d_inode)->fd;
 854
 855         err = inode_change_ok(dentry->d_inode, attr);
 856         if (err)
 857                 return err;
 858
 859         if (append)
 860                 attr->ia_valid &= ~ATTR_SIZE;
 861
 862         attrs.ia_valid = 0;
 863         if (attr->ia_valid & ATTR_MODE) {
 864                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 865                 attrs.ia_mode = attr->ia_mode;
 866         }
 867         if (attr->ia_valid & ATTR_UID) {
 868                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 869                 attrs.ia_uid = attr->ia_uid;
 870         }
 871         if (attr->ia_valid & ATTR_GID) {
 872                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 873                 attrs.ia_gid = attr->ia_gid;
 874         }
 875         if (attr->ia_valid & ATTR_SIZE) {
 876                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 877                 attrs.ia_size = attr->ia_size;
 878         }
 879         if (attr->ia_valid & ATTR_ATIME) {
 880                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 881                 attrs.ia_atime = attr->ia_atime;
 882         }
 883         if (attr->ia_valid & ATTR_MTIME) {
 884                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 885                 attrs.ia_mtime = attr->ia_mtime;
 886         }
 887         if (attr->ia_valid & ATTR_CTIME) {
 888                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 889                 attrs.ia_ctime = attr->ia_ctime;
 890         }
 891         if (attr->ia_valid & ATTR_ATIME_SET) {
 892                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 893         }
 894         if (attr->ia_valid & ATTR_MTIME_SET) {
 895                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 896         }
 897         name = dentry_name(dentry, 0);
 898         if (name == NULL)
 899                 return -ENOMEM;
 900         err = set_attr(name, &attrs, fd);
 901         kfree(name);
 902         if (err)
 903                 return err;
 904
 905         return inode_setattr(dentry->d_inode, attr);
 906 }
 907
 908 static const struct inode_operations hostfs_iops = {
 909         .create         = hostfs_create,
 910         .link           = hostfs_link,
 911         .unlink         = hostfs_unlink,
 912         .symlink        = hostfs_symlink,
 913         .mkdir          = hostfs_mkdir,
 914         .rmdir          = hostfs_rmdir,
 915         .mknod          = hostfs_mknod,
 916         .rename         = hostfs_rename,
 917         .permission     = hostfs_permission,
 918         .setattr        = hostfs_setattr,
 919 };
 920
 921 static const struct inode_operations hostfs_dir_iops = {
 922         .create         = hostfs_create,
 923         .lookup         = hostfs_lookup,
 924         .link           = hostfs_link,
 925         .unlink         = hostfs_unlink,
 926         .symlink        = hostfs_symlink,
 927         .mkdir          = hostfs_mkdir,
 928         .rmdir          = hostfs_rmdir,
 929         .mknod          = hostfs_mknod,
 930         .rename         = hostfs_rename,
 931         .permission     = hostfs_permission,
 932         .setattr        = hostfs_setattr,
 933 };
 934
 935 int hostfs_link_readpage(struct file *file, struct page *page)
 936 {
 937         char *buffer, *name;
 938         int err;
 939
 940         buffer = kmap(page);
 941         name = inode_name(page->mapping->host, 0);
 942         if (name == NULL)
 943                 return -ENOMEM;
 944         err = do_readlink(name, buffer, PAGE_CACHE_SIZE);
 945         kfree(name);
 946         if (err == PAGE_CACHE_SIZE)
 947                 err = -E2BIG;
 948         else if (err > 0) {
 949                 flush_dcache_page(page);
 950                 SetPageUptodate(page);
 951                 if (PageError(page)) ClearPageError(page);
 952                 err = 0;
 953         }
 954         kunmap(page);
 955         unlock_page(page);
 956         return err;
 957 }
 958
 959 static const struct address_space_operations hostfs_link_aops = {
 960         .readpage       = hostfs_link_readpage,
 961 };
 962
 963 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 964 {
 965         struct inode *root_inode;
 966         char *host_root_path, *req_root = d;
 967         int err;
 968
 969         sb->s_blocksize = 1024;
 970         sb->s_blocksize_bits = 10;
 971         sb->s_magic = HOSTFS_SUPER_MAGIC;
 972         sb->s_op = &hostfs_sbops;
 973
 974         /* NULL is printed as <NULL> by sprintf: avoid that. */
 975         if (req_root == NULL)
 976                 req_root = "";
 977
 978         err = -ENOMEM;
 979         host_root_path = kmalloc(strlen(root_ino) + 1
 980                                  + strlen(req_root) + 1, GFP_KERNEL);
 981         if (host_root_path == NULL)
 982                 goto out;
 983
 984         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 985
 986         root_inode = hostfs_iget(sb);
 987         if (IS_ERR(root_inode)) {
 988                 err = PTR_ERR(root_inode);
 989                 goto out_free;
 990         }
 991
 992         err = init_inode(root_inode, NULL);
 993         if (err)
 994                 goto out_put;
 995
 996         HOSTFS_I(root_inode)->host_filename = host_root_path;
 997         /*
 998          * Avoid that in the error path, iput(root_inode) frees again
 999          * host_root_path through hostfs_destroy_inode!
1000          */
1001         host_root_path = NULL;
1002
1003         err = -ENOMEM;
1004         sb->s_root = d_alloc_root(root_inode);
1005         if (sb->s_root == NULL)
1006                 goto out_put;
1007
1008         err = hostfs_read_inode(root_inode);
1009         if (err) {
1010                 /* No iput in this case because the dput does that for us */
1011                 dput(sb->s_root);
1012                 sb->s_root = NULL;
1013                 goto out;
1014         }
1015
1016         return 0;
1017
1018 out_put:
1019         iput(root_inode);
1020 out_free:
1021         kfree(host_root_path);
1022 out:
1023         return err;
1024 }
1025
1026 static int hostfs_read_sb(struct file_system_type *type,
1027                           int flags, const char *dev_name,
1028                           void *data, struct vfsmount *mnt)
1029 {
1030         return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
1031 }
1032
1033 static struct file_system_type hostfs_type = {
1034         .owner          = THIS_MODULE,
1035         .name           = "hostfs",
1036         .get_sb         = hostfs_read_sb,
1037         .kill_sb        = kill_anon_super,
1038         .fs_flags       = 0,
1039 };
1040
1041 static int __init init_hostfs(void)
1042 {
1043         return register_filesystem(&hostfs_type);
1044 }
1045
1046 static void __exit exit_hostfs(void)
1047 {
1048         unregister_filesystem(&hostfs_type);
1049 }
1050
1051 module_init(init_hostfs)
1052 module_exit(exit_hostfs)
1053 MODULE_LICENSE("GPL");