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 <linux/mount.h>
  16 #include "hostfs.h"
  17 #include "init.h"
  18 #include "kern.h"
  19
  20 struct hostfs_inode_info {
  21         char *host_filename;
  22         int fd;
  23         int 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 int hostfs_d_delete(struct dentry *dentry)
  35 {
  36         return 1;
  37 }
  38
  39 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 = HOSTFS_I(parent->d_inode)->host_filename;
 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         /*
 135          * The non-int inode fields are copied into ints by stat_file and
 136          * then copied into the inode because passing the actual pointers
 137          * in and having them treated as int * breaks on big-endian machines
 138          */
 139         int err;
 140         int i_mode, i_nlink, i_blksize;
 141         unsigned long long i_size;
 142         unsigned long long i_ino;
 143         unsigned long long i_blocks;
 144
 145         err = stat_file(name, &i_ino, &i_mode, &i_nlink, &ino->i_uid,
 146                         &ino->i_gid, &i_size, &ino->i_atime, &ino->i_mtime,
 147                         &ino->i_ctime, &i_blksize, &i_blocks, -1);
 148         if (err)
 149                 return err;
 150
 151         ino->i_ino = i_ino;
 152         ino->i_mode = i_mode;
 153         ino->i_nlink = i_nlink;
 154         ino->i_size = i_size;
 155         ino->i_blocks = i_blocks;
 156         return 0;
 157 }
 158
 159 static char *follow_link(char *link)
 160 {
 161         int len, n;
 162         char *name, *resolved, *end;
 163
 164         len = 64;
 165         while (1) {
 166                 n = -ENOMEM;
 167                 name = kmalloc(len, GFP_KERNEL);
 168                 if (name == NULL)
 169                         goto out;
 170
 171                 n = do_readlink(link, name, len);
 172                 if (n < len)
 173                         break;
 174                 len *= 2;
 175                 kfree(name);
 176         }
 177         if (n < 0)
 178                 goto out_free;
 179
 180         if (*name == '/')
 181                 return name;
 182
 183         end = strrchr(link, '/');
 184         if (end == NULL)
 185                 return name;
 186
 187         *(end + 1) = '\0';
 188         len = strlen(link) + strlen(name) + 1;
 189
 190         resolved = kmalloc(len, GFP_KERNEL);
 191         if (resolved == NULL) {
 192                 n = -ENOMEM;
 193                 goto out_free;
 194         }
 195
 196         sprintf(resolved, "%s%s", link, name);
 197         kfree(name);
 198         kfree(link);
 199         return resolved;
 200
 201  out_free:
 202         kfree(name);
 203  out:
 204         return ERR_PTR(n);
 205 }
 206
 207 static int hostfs_read_inode(struct inode *ino)
 208 {
 209         char *name;
 210         int err = 0;
 211
 212         /*
 213          * Unfortunately, we are called from iget() when we don't have a dentry
 214          * allocated yet.
 215          */
 216         if (list_empty(&ino->i_dentry))
 217                 goto out;
 218
 219         err = -ENOMEM;
 220         name = inode_name(ino, 0);
 221         if (name == NULL)
 222                 goto out;
 223
 224         if (file_type(name, NULL, NULL) == OS_TYPE_SYMLINK) {
 225                 name = follow_link(name);
 226                 if (IS_ERR(name)) {
 227                         err = PTR_ERR(name);
 228                         goto out;
 229                 }
 230         }
 231
 232         err = read_name(ino, name);
 233         kfree(name);
 234  out:
 235         return err;
 236 }
 237
 238 static struct inode *hostfs_iget(struct super_block *sb)
 239 {
 240         struct inode *inode;
 241         long ret;
 242
 243         inode = iget_locked(sb, 0);
 244         if (!inode)
 245                 return ERR_PTR(-ENOMEM);
 246         if (inode->i_state & I_NEW) {
 247                 ret = hostfs_read_inode(inode);
 248                 if (ret < 0) {
 249                         iget_failed(inode);
 250                         return ERR_PTR(ret);
 251                 }
 252                 unlock_new_inode(inode);
 253         }
 254         return inode;
 255 }
 256
 257 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 258 {
 259         /*
 260          * do_statfs uses struct statfs64 internally, but the linux kernel
 261          * struct statfs still has 32-bit versions for most of these fields,
 262          * so we convert them here
 263          */
 264         int err;
 265         long long f_blocks;
 266         long long f_bfree;
 267         long long f_bavail;
 268         long long f_files;
 269         long long f_ffree;
 270
 271         err = do_statfs(HOSTFS_I(dentry->d_sb->s_root->d_inode)->host_filename,
 272                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 273                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 274                         &sf->f_namelen, sf->f_spare);
 275         if (err)
 276                 return err;
 277         sf->f_blocks = f_blocks;
 278         sf->f_bfree = f_bfree;
 279         sf->f_bavail = f_bavail;
 280         sf->f_files = f_files;
 281         sf->f_ffree = f_ffree;
 282         sf->f_type = HOSTFS_SUPER_MAGIC;
 283         return 0;
 284 }
 285
 286 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 287 {
 288         struct hostfs_inode_info *hi;
 289
 290         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 291         if (hi == NULL)
 292                 return NULL;
 293
 294         *hi = ((struct hostfs_inode_info) { .host_filename      = NULL,
 295                                             .fd                 = -1,
 296                                             .mode               = 0 });
 297         inode_init_once(&hi->vfs_inode);
 298         return &hi->vfs_inode;
 299 }
 300
 301 static void hostfs_delete_inode(struct inode *inode)
 302 {
 303         truncate_inode_pages(&inode->i_data, 0);
 304         if (HOSTFS_I(inode)->fd != -1) {
 305                 close_file(&HOSTFS_I(inode)->fd);
 306                 HOSTFS_I(inode)->fd = -1;
 307         }
 308         clear_inode(inode);
 309 }
 310
 311 static void hostfs_destroy_inode(struct inode *inode)
 312 {
 313         kfree(HOSTFS_I(inode)->host_filename);
 314
 315         /*
 316          * XXX: This should not happen, probably. The check is here for
 317          * additional safety.
 318          */
 319         if (HOSTFS_I(inode)->fd != -1) {
 320                 close_file(&HOSTFS_I(inode)->fd);
 321                 printk(KERN_DEBUG "Closing host fd in .destroy_inode\n");
 322         }
 323
 324         kfree(HOSTFS_I(inode));
 325 }
 326
 327 static int hostfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 328 {
 329         struct inode *root = vfs->mnt_sb->s_root->d_inode;
 330         const char *root_path = HOSTFS_I(root)->host_filename;
 331         size_t offset = strlen(root_ino) + 1;
 332
 333         if (strlen(root_path) > offset)
 334                 seq_printf(seq, ",%s", root_path + offset);
 335
 336         return 0;
 337 }
 338
 339 static const struct super_operations hostfs_sbops = {
 340         .alloc_inode    = hostfs_alloc_inode,
 341         .drop_inode     = generic_delete_inode,
 342         .delete_inode   = hostfs_delete_inode,
 343         .destroy_inode  = hostfs_destroy_inode,
 344         .statfs         = hostfs_statfs,
 345         .show_options   = hostfs_show_options,
 346 };
 347
 348 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 349 {
 350         void *dir;
 351         char *name;
 352         unsigned long long next, ino;
 353         int error, len;
 354
 355         name = dentry_name(file->f_path.dentry, 0);
 356         if (name == NULL)
 357                 return -ENOMEM;
 358         dir = open_dir(name, &error);
 359         kfree(name);
 360         if (dir == NULL)
 361                 return -error;
 362         next = file->f_pos;
 363         while ((name = read_dir(dir, &next, &ino, &len)) != NULL) {
 364                 error = (*filldir)(ent, name, len, file->f_pos,
 365                                    ino, DT_UNKNOWN);
 366                 if (error) break;
 367                 file->f_pos = next;
 368         }
 369         close_dir(dir);
 370         return 0;
 371 }
 372
 373 int hostfs_file_open(struct inode *ino, struct file *file)
 374 {
 375         char *name;
 376         int mode = 0, r = 0, w = 0, fd;
 377
 378         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 379         if ((mode & HOSTFS_I(ino)->mode) == mode)
 380                 return 0;
 381
 382         /*
 383          * The file may already have been opened, but with the wrong access,
 384          * so this resets things and reopens the file with the new access.
 385          */
 386         if (HOSTFS_I(ino)->fd != -1) {
 387                 close_file(&HOSTFS_I(ino)->fd);
 388                 HOSTFS_I(ino)->fd = -1;
 389         }
 390
 391         HOSTFS_I(ino)->mode |= mode;
 392         if (HOSTFS_I(ino)->mode & FMODE_READ)
 393                 r = 1;
 394         if (HOSTFS_I(ino)->mode & FMODE_WRITE)
 395                 w = 1;
 396         if (w)
 397                 r = 1;
 398
 399         name = dentry_name(file->f_path.dentry, 0);
 400         if (name == NULL)
 401                 return -ENOMEM;
 402
 403         fd = open_file(name, r, w, append);
 404         kfree(name);
 405         if (fd < 0)
 406                 return fd;
 407         FILE_HOSTFS_I(file)->fd = fd;
 408
 409         return 0;
 410 }
 411
 412 int hostfs_fsync(struct file *file, struct dentry *dentry, int datasync)
 413 {
 414         return fsync_file(HOSTFS_I(dentry->d_inode)->fd, datasync);
 415 }
 416
 417 static const struct file_operations hostfs_file_fops = {
 418         .llseek         = generic_file_llseek,
 419         .read           = do_sync_read,
 420         .splice_read    = generic_file_splice_read,
 421         .aio_read       = generic_file_aio_read,
 422         .aio_write      = generic_file_aio_write,
 423         .write          = do_sync_write,
 424         .mmap           = generic_file_mmap,
 425         .open           = hostfs_file_open,
 426         .release        = NULL,
 427         .fsync          = hostfs_fsync,
 428 };
 429
 430 static const struct file_operations hostfs_dir_fops = {
 431         .llseek         = generic_file_llseek,
 432         .readdir        = hostfs_readdir,
 433         .read           = generic_read_dir,
 434 };
 435
 436 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 437 {
 438         struct address_space *mapping = page->mapping;
 439         struct inode *inode = mapping->host;
 440         char *buffer;
 441         unsigned long long base;
 442         int count = PAGE_CACHE_SIZE;
 443         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 444         int err;
 445
 446         if (page->index >= end_index)
 447                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 448
 449         buffer = kmap(page);
 450         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 451
 452         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 453         if (err != count) {
 454                 ClearPageUptodate(page);
 455                 goto out;
 456         }
 457
 458         if (base > inode->i_size)
 459                 inode->i_size = base;
 460
 461         if (PageError(page))
 462                 ClearPageError(page);
 463         err = 0;
 464
 465  out:
 466         kunmap(page);
 467
 468         unlock_page(page);
 469         return err;
 470 }
 471
 472 int hostfs_readpage(struct file *file, struct page *page)
 473 {
 474         char *buffer;
 475         long long start;
 476         int err = 0;
 477
 478         start = (long long) page->index << PAGE_CACHE_SHIFT;
 479         buffer = kmap(page);
 480         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 481                         PAGE_CACHE_SIZE);
 482         if (err < 0)
 483                 goto out;
 484
 485         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 486
 487         flush_dcache_page(page);
 488         SetPageUptodate(page);
 489         if (PageError(page)) ClearPageError(page);
 490         err = 0;
 491  out:
 492         kunmap(page);
 493         unlock_page(page);
 494         return err;
 495 }
 496
 497 int hostfs_write_begin(struct file *file, struct address_space *mapping,
 498                         loff_t pos, unsigned len, unsigned flags,
 499                         struct page **pagep, void **fsdata)
 500 {
 501         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 502
 503         *pagep = __grab_cache_page(mapping, index);
 504         if (!*pagep)
 505                 return -ENOMEM;
 506         return 0;
 507 }
 508
 509 int hostfs_write_end(struct file *file, struct address_space *mapping,
 510                         loff_t pos, unsigned len, unsigned copied,
 511                         struct page *page, void *fsdata)
 512 {
 513         struct inode *inode = mapping->host;
 514         void *buffer;
 515         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 516         int err;
 517
 518         buffer = kmap(page);
 519         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 520         kunmap(page);
 521
 522         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 523                 SetPageUptodate(page);
 524
 525         /*
 526          * If err > 0, write_file has added err to pos, so we are comparing
 527          * i_size against the last byte written.
 528          */
 529         if (err > 0 && (pos > inode->i_size))
 530                 inode->i_size = pos;
 531         unlock_page(page);
 532         page_cache_release(page);
 533
 534         return err;
 535 }
 536
 537 static const struct address_space_operations hostfs_aops = {
 538         .writepage      = hostfs_writepage,
 539         .readpage       = hostfs_readpage,
 540         .set_page_dirty = __set_page_dirty_nobuffers,
 541         .write_begin    = hostfs_write_begin,
 542         .write_end      = hostfs_write_end,
 543 };
 544
 545 static int init_inode(struct inode *inode, struct dentry *dentry)
 546 {
 547         char *name;
 548         int type, err = -ENOMEM;
 549         int maj, min;
 550         dev_t rdev = 0;
 551
 552         if (dentry) {
 553                 name = dentry_name(dentry, 0);
 554                 if (name == NULL)
 555                         goto out;
 556                 type = file_type(name, &maj, &min);
 557                 /* Reencode maj and min with the kernel encoding.*/
 558                 rdev = MKDEV(maj, min);
 559                 kfree(name);
 560         }
 561         else type = OS_TYPE_DIR;
 562
 563         err = 0;
 564         if (type == OS_TYPE_SYMLINK)
 565                 inode->i_op = &page_symlink_inode_operations;
 566         else if (type == OS_TYPE_DIR)
 567                 inode->i_op = &hostfs_dir_iops;
 568         else inode->i_op = &hostfs_iops;
 569
 570         if (type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
 571         else inode->i_fop = &hostfs_file_fops;
 572
 573         if (type == OS_TYPE_SYMLINK)
 574                 inode->i_mapping->a_ops = &hostfs_link_aops;
 575         else inode->i_mapping->a_ops = &hostfs_aops;
 576
 577         switch (type) {
 578         case OS_TYPE_CHARDEV:
 579                 init_special_inode(inode, S_IFCHR, rdev);
 580                 break;
 581         case OS_TYPE_BLOCKDEV:
 582                 init_special_inode(inode, S_IFBLK, rdev);
 583                 break;
 584         case OS_TYPE_FIFO:
 585                 init_special_inode(inode, S_IFIFO, 0);
 586                 break;
 587         case OS_TYPE_SOCK:
 588                 init_special_inode(inode, S_IFSOCK, 0);
 589                 break;
 590         }
 591  out:
 592         return err;
 593 }
 594
 595 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 596                   struct nameidata *nd)
 597 {
 598         struct inode *inode;
 599         char *name;
 600         int error, fd;
 601
 602         inode = hostfs_iget(dir->i_sb);
 603         if (IS_ERR(inode)) {
 604                 error = PTR_ERR(inode);
 605                 goto out;
 606         }
 607
 608         error = init_inode(inode, dentry);
 609         if (error)
 610                 goto out_put;
 611
 612         error = -ENOMEM;
 613         name = dentry_name(dentry, 0);
 614         if (name == NULL)
 615                 goto out_put;
 616
 617         fd = file_create(name,
 618                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 619                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 620                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 621         if (fd < 0)
 622                 error = fd;
 623         else error = read_name(inode, name);
 624
 625         kfree(name);
 626         if (error)
 627                 goto out_put;
 628
 629         HOSTFS_I(inode)->fd = fd;
 630         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 631         d_instantiate(dentry, inode);
 632         return 0;
 633
 634  out_put:
 635         iput(inode);
 636  out:
 637         return error;
 638 }
 639
 640 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 641                              struct nameidata *nd)
 642 {
 643         struct inode *inode;
 644         char *name;
 645         int err;
 646
 647         inode = hostfs_iget(ino->i_sb);
 648         if (IS_ERR(inode)) {
 649                 err = PTR_ERR(inode);
 650                 goto out;
 651         }
 652
 653         err = init_inode(inode, dentry);
 654         if (err)
 655                 goto out_put;
 656
 657         err = -ENOMEM;
 658         name = dentry_name(dentry, 0);
 659         if (name == NULL)
 660                 goto out_put;
 661
 662         err = read_name(inode, name);
 663         kfree(name);
 664         if (err == -ENOENT) {
 665                 iput(inode);
 666                 inode = NULL;
 667         }
 668         else if (err)
 669                 goto out_put;
 670
 671         d_add(dentry, inode);
 672         dentry->d_op = &hostfs_dentry_ops;
 673         return NULL;
 674
 675  out_put:
 676         iput(inode);
 677  out:
 678         return ERR_PTR(err);
 679 }
 680
 681 static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
 682 {
 683         char *file;
 684         int len;
 685
 686         file = inode_name(ino, dentry->d_name.len + 1);
 687         if (file == NULL)
 688                 return NULL;
 689         strcat(file, "/");
 690         len = strlen(file);
 691         strncat(file, dentry->d_name.name, dentry->d_name.len);
 692         file[len + dentry->d_name.len] = '\0';
 693         return file;
 694 }
 695
 696 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 697 {
 698         char *from_name, *to_name;
 699         int err;
 700
 701         if ((from_name = inode_dentry_name(ino, from)) == NULL)
 702                 return -ENOMEM;
 703         to_name = dentry_name(to, 0);
 704         if (to_name == NULL) {
 705                 kfree(from_name);
 706                 return -ENOMEM;
 707         }
 708         err = link_file(to_name, from_name);
 709         kfree(from_name);
 710         kfree(to_name);
 711         return err;
 712 }
 713
 714 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 715 {
 716         char *file;
 717         int err;
 718
 719         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 720                 return -ENOMEM;
 721         if (append)
 722                 return -EPERM;
 723
 724         err = unlink_file(file);
 725         kfree(file);
 726         return err;
 727 }
 728
 729 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 730 {
 731         char *file;
 732         int err;
 733
 734         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 735                 return -ENOMEM;
 736         err = make_symlink(file, to);
 737         kfree(file);
 738         return err;
 739 }
 740
 741 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 742 {
 743         char *file;
 744         int err;
 745
 746         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 747                 return -ENOMEM;
 748         err = do_mkdir(file, mode);
 749         kfree(file);
 750         return err;
 751 }
 752
 753 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 754 {
 755         char *file;
 756         int err;
 757
 758         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 759                 return -ENOMEM;
 760         err = do_rmdir(file);
 761         kfree(file);
 762         return err;
 763 }
 764
 765 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 766 {
 767         struct inode *inode;
 768         char *name;
 769         int err;
 770
 771         inode = hostfs_iget(dir->i_sb);
 772         if (IS_ERR(inode)) {
 773                 err = PTR_ERR(inode);
 774                 goto out;
 775         }
 776
 777         err = init_inode(inode, dentry);
 778         if (err)
 779                 goto out_put;
 780
 781         err = -ENOMEM;
 782         name = dentry_name(dentry, 0);
 783         if (name == NULL)
 784                 goto out_put;
 785
 786         init_special_inode(inode, mode, dev);
 787         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 788         if (err)
 789                 goto out_free;
 790
 791         err = read_name(inode, name);
 792         kfree(name);
 793         if (err)
 794                 goto out_put;
 795
 796         d_instantiate(dentry, inode);
 797         return 0;
 798
 799  out_free:
 800         kfree(name);
 801  out_put:
 802         iput(inode);
 803  out:
 804         return err;
 805 }
 806
 807 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 808                   struct inode *to_ino, struct dentry *to)
 809 {
 810         char *from_name, *to_name;
 811         int err;
 812
 813         if ((from_name = inode_dentry_name(from_ino, from)) == NULL)
 814                 return -ENOMEM;
 815         if ((to_name = inode_dentry_name(to_ino, to)) == NULL) {
 816                 kfree(from_name);
 817                 return -ENOMEM;
 818         }
 819         err = rename_file(from_name, to_name);
 820         kfree(from_name);
 821         kfree(to_name);
 822         return err;
 823 }
 824
 825 int hostfs_permission(struct inode *ino, int desired, struct nameidata *nd)
 826 {
 827         char *name;
 828         int r = 0, w = 0, x = 0, err;
 829
 830         if (desired & MAY_READ) r = 1;
 831         if (desired & MAY_WRITE) w = 1;
 832         if (desired & MAY_EXEC) x = 1;
 833         name = inode_name(ino, 0);
 834         if (name == NULL)
 835                 return -ENOMEM;
 836
 837         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 838             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 839                 err = 0;
 840         else
 841                 err = access_file(name, r, w, x);
 842         kfree(name);
 843         if (!err)
 844                 err = generic_permission(ino, desired, NULL);
 845         return err;
 846 }
 847
 848 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 849 {
 850         struct hostfs_iattr attrs;
 851         char *name;
 852         int err;
 853
 854         int fd = HOSTFS_I(dentry->d_inode)->fd;
 855
 856         err = inode_change_ok(dentry->d_inode, attr);
 857         if (err)
 858                 return err;
 859
 860         if (append)
 861                 attr->ia_valid &= ~ATTR_SIZE;
 862
 863         attrs.ia_valid = 0;
 864         if (attr->ia_valid & ATTR_MODE) {
 865                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 866                 attrs.ia_mode = attr->ia_mode;
 867         }
 868         if (attr->ia_valid & ATTR_UID) {
 869                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 870                 attrs.ia_uid = attr->ia_uid;
 871         }
 872         if (attr->ia_valid & ATTR_GID) {
 873                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 874                 attrs.ia_gid = attr->ia_gid;
 875         }
 876         if (attr->ia_valid & ATTR_SIZE) {
 877                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 878                 attrs.ia_size = attr->ia_size;
 879         }
 880         if (attr->ia_valid & ATTR_ATIME) {
 881                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 882                 attrs.ia_atime = attr->ia_atime;
 883         }
 884         if (attr->ia_valid & ATTR_MTIME) {
 885                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 886                 attrs.ia_mtime = attr->ia_mtime;
 887         }
 888         if (attr->ia_valid & ATTR_CTIME) {
 889                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 890                 attrs.ia_ctime = attr->ia_ctime;
 891         }
 892         if (attr->ia_valid & ATTR_ATIME_SET) {
 893                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 894         }
 895         if (attr->ia_valid & ATTR_MTIME_SET) {
 896                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 897         }
 898         name = dentry_name(dentry, 0);
 899         if (name == NULL)
 900                 return -ENOMEM;
 901         err = set_attr(name, &attrs, fd);
 902         kfree(name);
 903         if (err)
 904                 return err;
 905
 906         return inode_setattr(dentry->d_inode, attr);
 907 }
 908
 909 static const struct inode_operations hostfs_iops = {
 910         .create         = hostfs_create,
 911         .link           = hostfs_link,
 912         .unlink         = hostfs_unlink,
 913         .symlink        = hostfs_symlink,
 914         .mkdir          = hostfs_mkdir,
 915         .rmdir          = hostfs_rmdir,
 916         .mknod          = hostfs_mknod,
 917         .rename         = hostfs_rename,
 918         .permission     = hostfs_permission,
 919         .setattr        = hostfs_setattr,
 920 };
 921
 922 static const struct inode_operations hostfs_dir_iops = {
 923         .create         = hostfs_create,
 924         .lookup         = hostfs_lookup,
 925         .link           = hostfs_link,
 926         .unlink         = hostfs_unlink,
 927         .symlink        = hostfs_symlink,
 928         .mkdir          = hostfs_mkdir,
 929         .rmdir          = hostfs_rmdir,
 930         .mknod          = hostfs_mknod,
 931         .rename         = hostfs_rename,
 932         .permission     = hostfs_permission,
 933         .setattr        = hostfs_setattr,
 934 };
 935
 936 int hostfs_link_readpage(struct file *file, struct page *page)
 937 {
 938         char *buffer, *name;
 939         int err;
 940
 941         buffer = kmap(page);
 942         name = inode_name(page->mapping->host, 0);
 943         if (name == NULL)
 944                 return -ENOMEM;
 945         err = do_readlink(name, buffer, PAGE_CACHE_SIZE);
 946         kfree(name);
 947         if (err == PAGE_CACHE_SIZE)
 948                 err = -E2BIG;
 949         else if (err > 0) {
 950                 flush_dcache_page(page);
 951                 SetPageUptodate(page);
 952                 if (PageError(page)) ClearPageError(page);
 953                 err = 0;
 954         }
 955         kunmap(page);
 956         unlock_page(page);
 957         return err;
 958 }
 959
 960 static const struct address_space_operations hostfs_link_aops = {
 961         .readpage       = hostfs_link_readpage,
 962 };
 963
 964 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 965 {
 966         struct inode *root_inode;
 967         char *host_root_path, *req_root = d;
 968         int err;
 969
 970         sb->s_blocksize = 1024;
 971         sb->s_blocksize_bits = 10;
 972         sb->s_magic = HOSTFS_SUPER_MAGIC;
 973         sb->s_op = &hostfs_sbops;
 974
 975         /* NULL is printed as <NULL> by sprintf: avoid that. */
 976         if (req_root == NULL)
 977                 req_root = "";
 978
 979         err = -ENOMEM;
 980         host_root_path = kmalloc(strlen(root_ino) + 1
 981                                  + strlen(req_root) + 1, GFP_KERNEL);
 982         if (host_root_path == NULL)
 983                 goto out;
 984
 985         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 986
 987         root_inode = hostfs_iget(sb);
 988         if (IS_ERR(root_inode)) {
 989                 err = PTR_ERR(root_inode);
 990                 goto out_free;
 991         }
 992
 993         err = init_inode(root_inode, NULL);
 994         if (err)
 995                 goto out_put;
 996
 997         HOSTFS_I(root_inode)->host_filename = host_root_path;
 998         /*
 999          * Avoid that in the error path, iput(root_inode) frees again
1000          * host_root_path through hostfs_destroy_inode!
1001          */
1002         host_root_path = NULL;
1003
1004         err = -ENOMEM;
1005         sb->s_root = d_alloc_root(root_inode);
1006         if (sb->s_root == NULL)
1007                 goto out_put;
1008
1009         err = hostfs_read_inode(root_inode);
1010         if (err) {
1011                 /* No iput in this case because the dput does that for us */
1012                 dput(sb->s_root);
1013                 sb->s_root = NULL;
1014                 goto out;
1015         }
1016
1017         return 0;
1018
1019 out_put:
1020         iput(root_inode);
1021 out_free:
1022         kfree(host_root_path);
1023 out:
1024         return err;
1025 }
1026
1027 static int hostfs_read_sb(struct file_system_type *type,
1028                           int flags, const char *dev_name,
1029                           void *data, struct vfsmount *mnt)
1030 {
1031         return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
1032 }
1033
1034 static struct file_system_type hostfs_type = {
1035         .owner          = THIS_MODULE,
1036         .name           = "hostfs",
1037         .get_sb         = hostfs_read_sb,
1038         .kill_sb        = kill_anon_super,
1039         .fs_flags       = 0,
1040 };
1041
1042 static int __init init_hostfs(void)
1043 {
1044         return register_filesystem(&hostfs_type);
1045 }
1046
1047 static void __exit exit_hostfs(void)
1048 {
1049         unregister_filesystem(&hostfs_type);
1050 }
1051
1052 module_init(init_hostfs)
1053 module_exit(exit_hostfs)
1054 MODULE_LICENSE("GPL");