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         char *host_filename;
  23         int fd;
  24         fmode_t mode;
  25         struct inode vfs_inode;
  26 };
  27
  28 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  29 {
  30         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
  31 }
  32
  33 #define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)
  34
  35 static int hostfs_d_delete(struct dentry *dentry)
  36 {
  37         return 1;
  38 }
  39
  40 static const struct dentry_operations hostfs_dentry_ops = {
  41         .d_delete               = hostfs_d_delete,
  42 };
  43
  44 /* Changed in hostfs_args before the kernel starts running */
  45 static char *root_ino = "";
  46 static int append = 0;
  47
  48 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
  49
  50 static const struct inode_operations hostfs_iops;
  51 static const struct inode_operations hostfs_dir_iops;
  52 static const struct address_space_operations hostfs_link_aops;
  53
  54 #ifndef MODULE
  55 static int __init hostfs_args(char *options, int *add)
  56 {
  57         char *ptr;
  58
  59         ptr = strchr(options, ',');
  60         if (ptr != NULL)
  61                 *ptr++ = '\0';
  62         if (*options != '\0')
  63                 root_ino = options;
  64
  65         options = ptr;
  66         while (options) {
  67                 ptr = strchr(options, ',');
  68                 if (ptr != NULL)
  69                         *ptr++ = '\0';
  70                 if (*options != '\0') {
  71                         if (!strcmp(options, "append"))
  72                                 append = 1;
  73                         else printf("hostfs_args - unsupported option - %s\n",
  74                                     options);
  75                 }
  76                 options = ptr;
  77         }
  78         return 0;
  79 }
  80
  81 __uml_setup("hostfs=", hostfs_args,
  82 "hostfs=<root dir>,<flags>,...\n"
  83 "    This is used to set hostfs parameters.  The root directory argument\n"
  84 "    is used to confine all hostfs mounts to within the specified directory\n"
  85 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
  86 "    mount anything on the host that's accessible to the user that's running\n"
  87 "    it.\n"
  88 "    The only flag currently supported is 'append', which specifies that all\n"
  89 "    files opened by hostfs will be opened in append mode.\n\n"
  90 );
  91 #endif
  92
  93 static char *dentry_name(struct dentry *dentry, int extra)
  94 {
  95         struct dentry *parent;
  96         char *root, *name;
  97         int len;
  98
  99         len = 0;
 100         parent = dentry;
 101         while (parent->d_parent != parent) {
 102                 len += parent->d_name.len + 1;
 103                 parent = parent->d_parent;
 104         }
 105
 106         root = HOSTFS_I(parent->d_inode)->host_filename;
 107         len += strlen(root);
 108         name = kmalloc(len + extra + 1, GFP_KERNEL);
 109         if (name == NULL)
 110                 return NULL;
 111
 112         name[len] = '\0';
 113         parent = dentry;
 114         while (parent->d_parent != parent) {
 115                 len -= parent->d_name.len + 1;
 116                 name[len] = '/';
 117                 strncpy(&name[len + 1], parent->d_name.name,
 118                         parent->d_name.len);
 119                 parent = parent->d_parent;
 120         }
 121         strncpy(name, root, strlen(root));
 122         return name;
 123 }
 124
 125 static char *inode_name(struct inode *ino, int extra)
 126 {
 127         struct dentry *dentry;
 128
 129         dentry = list_entry(ino->i_dentry.next, struct dentry, d_alias);
 130         return dentry_name(dentry, extra);
 131 }
 132
 133 static int read_name(struct inode *ino, char *name)
 134 {
 135         /*
 136          * The non-int inode fields are copied into ints by stat_file and
 137          * then copied into the inode because passing the actual pointers
 138          * in and having them treated as int * breaks on big-endian machines
 139          */
 140         int err;
 141         int i_mode, i_nlink, i_blksize;
 142         unsigned long long i_size;
 143         unsigned long long i_ino;
 144         unsigned long long i_blocks;
 145
 146         err = stat_file(name, &i_ino, &i_mode, &i_nlink, &ino->i_uid,
 147                         &ino->i_gid, &i_size, &ino->i_atime, &ino->i_mtime,
 148                         &ino->i_ctime, &i_blksize, &i_blocks, -1);
 149         if (err)
 150                 return err;
 151
 152         ino->i_ino = i_ino;
 153         ino->i_mode = i_mode;
 154         ino->i_nlink = i_nlink;
 155         ino->i_size = i_size;
 156         ino->i_blocks = i_blocks;
 157         return 0;
 158 }
 159
 160 static char *follow_link(char *link)
 161 {
 162         int len, n;
 163         char *name, *resolved, *end;
 164
 165         len = 64;
 166         while (1) {
 167                 n = -ENOMEM;
 168                 name = kmalloc(len, GFP_KERNEL);
 169                 if (name == NULL)
 170                         goto out;
 171
 172                 n = hostfs_do_readlink(link, name, len);
 173                 if (n < len)
 174                         break;
 175                 len *= 2;
 176                 kfree(name);
 177         }
 178         if (n < 0)
 179                 goto out_free;
 180
 181         if (*name == '/')
 182                 return name;
 183
 184         end = strrchr(link, '/');
 185         if (end == NULL)
 186                 return name;
 187
 188         *(end + 1) = '\0';
 189         len = strlen(link) + strlen(name) + 1;
 190
 191         resolved = kmalloc(len, GFP_KERNEL);
 192         if (resolved == NULL) {
 193                 n = -ENOMEM;
 194                 goto out_free;
 195         }
 196
 197         sprintf(resolved, "%s%s", link, name);
 198         kfree(name);
 199         kfree(link);
 200         return resolved;
 201
 202  out_free:
 203         kfree(name);
 204  out:
 205         return ERR_PTR(n);
 206 }
 207
 208 static int hostfs_read_inode(struct inode *ino)
 209 {
 210         char *name;
 211         int err = 0;
 212
 213         /*
 214          * Unfortunately, we are called from iget() when we don't have a dentry
 215          * allocated yet.
 216          */
 217         if (list_empty(&ino->i_dentry))
 218                 goto out;
 219
 220         err = -ENOMEM;
 221         name = inode_name(ino, 0);
 222         if (name == NULL)
 223                 goto out;
 224
 225         if (file_type(name, NULL, NULL) == OS_TYPE_SYMLINK) {
 226                 name = follow_link(name);
 227                 if (IS_ERR(name)) {
 228                         err = PTR_ERR(name);
 229                         goto out;
 230                 }
 231         }
 232
 233         err = read_name(ino, name);
 234         kfree(name);
 235  out:
 236         return err;
 237 }
 238
 239 static struct inode *hostfs_iget(struct super_block *sb)
 240 {
 241         struct inode *inode;
 242         long ret;
 243
 244         inode = iget_locked(sb, 0);
 245         if (!inode)
 246                 return ERR_PTR(-ENOMEM);
 247         if (inode->i_state & I_NEW) {
 248                 ret = hostfs_read_inode(inode);
 249                 if (ret < 0) {
 250                         iget_failed(inode);
 251                         return ERR_PTR(ret);
 252                 }
 253                 unlock_new_inode(inode);
 254         }
 255         return inode;
 256 }
 257
 258 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 259 {
 260         /*
 261          * do_statfs uses struct statfs64 internally, but the linux kernel
 262          * struct statfs still has 32-bit versions for most of these fields,
 263          * so we convert them here
 264          */
 265         int err;
 266         long long f_blocks;
 267         long long f_bfree;
 268         long long f_bavail;
 269         long long f_files;
 270         long long f_ffree;
 271
 272         err = do_statfs(HOSTFS_I(dentry->d_sb->s_root->d_inode)->host_filename,
 273                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 274                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 275                         &sf->f_namelen, sf->f_spare);
 276         if (err)
 277                 return err;
 278         sf->f_blocks = f_blocks;
 279         sf->f_bfree = f_bfree;
 280         sf->f_bavail = f_bavail;
 281         sf->f_files = f_files;
 282         sf->f_ffree = f_ffree;
 283         sf->f_type = HOSTFS_SUPER_MAGIC;
 284         return 0;
 285 }
 286
 287 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 288 {
 289         struct hostfs_inode_info *hi;
 290
 291         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 292         if (hi == NULL)
 293                 return NULL;
 294
 295         *hi = ((struct hostfs_inode_info) { .host_filename      = NULL,
 296                                             .fd                 = -1,
 297                                             .mode               = 0 });
 298         inode_init_once(&hi->vfs_inode);
 299         return &hi->vfs_inode;
 300 }
 301
 302 static void hostfs_delete_inode(struct inode *inode)
 303 {
 304         truncate_inode_pages(&inode->i_data, 0);
 305         if (HOSTFS_I(inode)->fd != -1) {
 306                 close_file(&HOSTFS_I(inode)->fd);
 307                 HOSTFS_I(inode)->fd = -1;
 308         }
 309         clear_inode(inode);
 310 }
 311
 312 static void hostfs_destroy_inode(struct inode *inode)
 313 {
 314         kfree(HOSTFS_I(inode)->host_filename);
 315
 316         /*
 317          * XXX: This should not happen, probably. The check is here for
 318          * additional safety.
 319          */
 320         if (HOSTFS_I(inode)->fd != -1) {
 321                 close_file(&HOSTFS_I(inode)->fd);
 322                 printk(KERN_DEBUG "Closing host fd in .destroy_inode\n");
 323         }
 324
 325         kfree(HOSTFS_I(inode));
 326 }
 327
 328 static int hostfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 329 {
 330         struct inode *root = vfs->mnt_sb->s_root->d_inode;
 331         const char *root_path = HOSTFS_I(root)->host_filename;
 332         size_t offset = strlen(root_ino) + 1;
 333
 334         if (strlen(root_path) > offset)
 335                 seq_printf(seq, ",%s", root_path + offset);
 336
 337         return 0;
 338 }
 339
 340 static const struct super_operations hostfs_sbops = {
 341         .alloc_inode    = hostfs_alloc_inode,
 342         .drop_inode     = generic_delete_inode,
 343         .delete_inode   = hostfs_delete_inode,
 344         .destroy_inode  = hostfs_destroy_inode,
 345         .statfs         = hostfs_statfs,
 346         .show_options   = hostfs_show_options,
 347 };
 348
 349 int hostfs_readdir(struct file *file, void *ent, filldir_t filldir)
 350 {
 351         void *dir;
 352         char *name;
 353         unsigned long long next, ino;
 354         int error, len;
 355
 356         name = dentry_name(file->f_path.dentry, 0);
 357         if (name == NULL)
 358                 return -ENOMEM;
 359         dir = open_dir(name, &error);
 360         kfree(name);
 361         if (dir == NULL)
 362                 return -error;
 363         next = file->f_pos;
 364         while ((name = read_dir(dir, &next, &ino, &len)) != NULL) {
 365                 error = (*filldir)(ent, name, len, file->f_pos,
 366                                    ino, DT_UNKNOWN);
 367                 if (error) break;
 368                 file->f_pos = next;
 369         }
 370         close_dir(dir);
 371         return 0;
 372 }
 373
 374 int hostfs_file_open(struct inode *ino, struct file *file)
 375 {
 376         char *name;
 377         fmode_t mode = 0;
 378         int r = 0, w = 0, fd;
 379
 380         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 381         if ((mode & HOSTFS_I(ino)->mode) == mode)
 382                 return 0;
 383
 384         /*
 385          * The file may already have been opened, but with the wrong access,
 386          * so this resets things and reopens the file with the new access.
 387          */
 388         if (HOSTFS_I(ino)->fd != -1) {
 389                 close_file(&HOSTFS_I(ino)->fd);
 390                 HOSTFS_I(ino)->fd = -1;
 391         }
 392
 393         HOSTFS_I(ino)->mode |= mode;
 394         if (HOSTFS_I(ino)->mode & FMODE_READ)
 395                 r = 1;
 396         if (HOSTFS_I(ino)->mode & FMODE_WRITE)
 397                 w = 1;
 398         if (w)
 399                 r = 1;
 400
 401         name = dentry_name(file->f_path.dentry, 0);
 402         if (name == NULL)
 403                 return -ENOMEM;
 404
 405         fd = open_file(name, r, w, append);
 406         kfree(name);
 407         if (fd < 0)
 408                 return fd;
 409         FILE_HOSTFS_I(file)->fd = fd;
 410
 411         return 0;
 412 }
 413
 414 int hostfs_fsync(struct file *file, int datasync)
 415 {
 416         return fsync_file(HOSTFS_I(file->f_mapping->host)->fd, datasync);
 417 }
 418
 419 static const struct file_operations hostfs_file_fops = {
 420         .llseek         = generic_file_llseek,
 421         .read           = do_sync_read,
 422         .splice_read    = generic_file_splice_read,
 423         .aio_read       = generic_file_aio_read,
 424         .aio_write      = generic_file_aio_write,
 425         .write          = do_sync_write,
 426         .mmap           = generic_file_mmap,
 427         .open           = hostfs_file_open,
 428         .release        = NULL,
 429         .fsync          = hostfs_fsync,
 430 };
 431
 432 static const struct file_operations hostfs_dir_fops = {
 433         .llseek         = generic_file_llseek,
 434         .readdir        = hostfs_readdir,
 435         .read           = generic_read_dir,
 436 };
 437
 438 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 439 {
 440         struct address_space *mapping = page->mapping;
 441         struct inode *inode = mapping->host;
 442         char *buffer;
 443         unsigned long long base;
 444         int count = PAGE_CACHE_SIZE;
 445         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 446         int err;
 447
 448         if (page->index >= end_index)
 449                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 450
 451         buffer = kmap(page);
 452         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 453
 454         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 455         if (err != count) {
 456                 ClearPageUptodate(page);
 457                 goto out;
 458         }
 459
 460         if (base > inode->i_size)
 461                 inode->i_size = base;
 462
 463         if (PageError(page))
 464                 ClearPageError(page);
 465         err = 0;
 466
 467  out:
 468         kunmap(page);
 469
 470         unlock_page(page);
 471         return err;
 472 }
 473
 474 int hostfs_readpage(struct file *file, struct page *page)
 475 {
 476         char *buffer;
 477         long long start;
 478         int err = 0;
 479
 480         start = (long long) page->index << PAGE_CACHE_SHIFT;
 481         buffer = kmap(page);
 482         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 483                         PAGE_CACHE_SIZE);
 484         if (err < 0)
 485                 goto out;
 486
 487         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 488
 489         flush_dcache_page(page);
 490         SetPageUptodate(page);
 491         if (PageError(page)) ClearPageError(page);
 492         err = 0;
 493  out:
 494         kunmap(page);
 495         unlock_page(page);
 496         return err;
 497 }
 498
 499 int hostfs_write_begin(struct file *file, struct address_space *mapping,
 500                         loff_t pos, unsigned len, unsigned flags,
 501                         struct page **pagep, void **fsdata)
 502 {
 503         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 504
 505         *pagep = grab_cache_page_write_begin(mapping, index, flags);
 506         if (!*pagep)
 507                 return -ENOMEM;
 508         return 0;
 509 }
 510
 511 int hostfs_write_end(struct file *file, struct address_space *mapping,
 512                         loff_t pos, unsigned len, unsigned copied,
 513                         struct page *page, void *fsdata)
 514 {
 515         struct inode *inode = mapping->host;
 516         void *buffer;
 517         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 518         int err;
 519
 520         buffer = kmap(page);
 521         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 522         kunmap(page);
 523
 524         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 525                 SetPageUptodate(page);
 526
 527         /*
 528          * If err > 0, write_file has added err to pos, so we are comparing
 529          * i_size against the last byte written.
 530          */
 531         if (err > 0 && (pos > inode->i_size))
 532                 inode->i_size = pos;
 533         unlock_page(page);
 534         page_cache_release(page);
 535
 536         return err;
 537 }
 538
 539 static const struct address_space_operations hostfs_aops = {
 540         .writepage      = hostfs_writepage,
 541         .readpage       = hostfs_readpage,
 542         .set_page_dirty = __set_page_dirty_nobuffers,
 543         .write_begin    = hostfs_write_begin,
 544         .write_end      = hostfs_write_end,
 545 };
 546
 547 static int init_inode(struct inode *inode, struct dentry *dentry)
 548 {
 549         char *name;
 550         int type, err = -ENOMEM;
 551         int maj, min;
 552         dev_t rdev = 0;
 553
 554         if (dentry) {
 555                 name = dentry_name(dentry, 0);
 556                 if (name == NULL)
 557                         goto out;
 558                 type = file_type(name, &maj, &min);
 559                 /* Reencode maj and min with the kernel encoding.*/
 560                 rdev = MKDEV(maj, min);
 561                 kfree(name);
 562         }
 563         else type = OS_TYPE_DIR;
 564
 565         err = 0;
 566         if (type == OS_TYPE_SYMLINK)
 567                 inode->i_op = &page_symlink_inode_operations;
 568         else if (type == OS_TYPE_DIR)
 569                 inode->i_op = &hostfs_dir_iops;
 570         else inode->i_op = &hostfs_iops;
 571
 572         if (type == OS_TYPE_DIR) inode->i_fop = &hostfs_dir_fops;
 573         else inode->i_fop = &hostfs_file_fops;
 574
 575         if (type == OS_TYPE_SYMLINK)
 576                 inode->i_mapping->a_ops = &hostfs_link_aops;
 577         else inode->i_mapping->a_ops = &hostfs_aops;
 578
 579         switch (type) {
 580         case OS_TYPE_CHARDEV:
 581                 init_special_inode(inode, S_IFCHR, rdev);
 582                 break;
 583         case OS_TYPE_BLOCKDEV:
 584                 init_special_inode(inode, S_IFBLK, rdev);
 585                 break;
 586         case OS_TYPE_FIFO:
 587                 init_special_inode(inode, S_IFIFO, 0);
 588                 break;
 589         case OS_TYPE_SOCK:
 590                 init_special_inode(inode, S_IFSOCK, 0);
 591                 break;
 592         }
 593  out:
 594         return err;
 595 }
 596
 597 int hostfs_create(struct inode *dir, struct dentry *dentry, int mode,
 598                   struct nameidata *nd)
 599 {
 600         struct inode *inode;
 601         char *name;
 602         int error, fd;
 603
 604         inode = hostfs_iget(dir->i_sb);
 605         if (IS_ERR(inode)) {
 606                 error = PTR_ERR(inode);
 607                 goto out;
 608         }
 609
 610         error = init_inode(inode, dentry);
 611         if (error)
 612                 goto out_put;
 613
 614         error = -ENOMEM;
 615         name = dentry_name(dentry, 0);
 616         if (name == NULL)
 617                 goto out_put;
 618
 619         fd = file_create(name,
 620                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 621                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 622                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 623         if (fd < 0)
 624                 error = fd;
 625         else error = read_name(inode, name);
 626
 627         kfree(name);
 628         if (error)
 629                 goto out_put;
 630
 631         HOSTFS_I(inode)->fd = fd;
 632         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 633         d_instantiate(dentry, inode);
 634         return 0;
 635
 636  out_put:
 637         iput(inode);
 638  out:
 639         return error;
 640 }
 641
 642 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 643                              struct nameidata *nd)
 644 {
 645         struct inode *inode;
 646         char *name;
 647         int err;
 648
 649         inode = hostfs_iget(ino->i_sb);
 650         if (IS_ERR(inode)) {
 651                 err = PTR_ERR(inode);
 652                 goto out;
 653         }
 654
 655         err = init_inode(inode, dentry);
 656         if (err)
 657                 goto out_put;
 658
 659         err = -ENOMEM;
 660         name = dentry_name(dentry, 0);
 661         if (name == NULL)
 662                 goto out_put;
 663
 664         err = read_name(inode, name);
 665         kfree(name);
 666         if (err == -ENOENT) {
 667                 iput(inode);
 668                 inode = NULL;
 669         }
 670         else if (err)
 671                 goto out_put;
 672
 673         d_add(dentry, inode);
 674         dentry->d_op = &hostfs_dentry_ops;
 675         return NULL;
 676
 677  out_put:
 678         iput(inode);
 679  out:
 680         return ERR_PTR(err);
 681 }
 682
 683 static char *inode_dentry_name(struct inode *ino, struct dentry *dentry)
 684 {
 685         char *file;
 686         int len;
 687
 688         file = inode_name(ino, dentry->d_name.len + 1);
 689         if (file == NULL)
 690                 return NULL;
 691         strcat(file, "/");
 692         len = strlen(file);
 693         strncat(file, dentry->d_name.name, dentry->d_name.len);
 694         file[len + dentry->d_name.len] = '\0';
 695         return file;
 696 }
 697
 698 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 699 {
 700         char *from_name, *to_name;
 701         int err;
 702
 703         if ((from_name = inode_dentry_name(ino, from)) == NULL)
 704                 return -ENOMEM;
 705         to_name = dentry_name(to, 0);
 706         if (to_name == NULL) {
 707                 kfree(from_name);
 708                 return -ENOMEM;
 709         }
 710         err = link_file(to_name, from_name);
 711         kfree(from_name);
 712         kfree(to_name);
 713         return err;
 714 }
 715
 716 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 717 {
 718         char *file;
 719         int err;
 720
 721         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 722                 return -ENOMEM;
 723         if (append)
 724                 return -EPERM;
 725
 726         err = unlink_file(file);
 727         kfree(file);
 728         return err;
 729 }
 730
 731 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 732 {
 733         char *file;
 734         int err;
 735
 736         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 737                 return -ENOMEM;
 738         err = make_symlink(file, to);
 739         kfree(file);
 740         return err;
 741 }
 742
 743 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, int mode)
 744 {
 745         char *file;
 746         int err;
 747
 748         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 749                 return -ENOMEM;
 750         err = do_mkdir(file, mode);
 751         kfree(file);
 752         return err;
 753 }
 754
 755 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 756 {
 757         char *file;
 758         int err;
 759
 760         if ((file = inode_dentry_name(ino, dentry)) == NULL)
 761                 return -ENOMEM;
 762         err = do_rmdir(file);
 763         kfree(file);
 764         return err;
 765 }
 766
 767 int hostfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 768 {
 769         struct inode *inode;
 770         char *name;
 771         int err;
 772
 773         inode = hostfs_iget(dir->i_sb);
 774         if (IS_ERR(inode)) {
 775                 err = PTR_ERR(inode);
 776                 goto out;
 777         }
 778
 779         err = init_inode(inode, dentry);
 780         if (err)
 781                 goto out_put;
 782
 783         err = -ENOMEM;
 784         name = dentry_name(dentry, 0);
 785         if (name == NULL)
 786                 goto out_put;
 787
 788         init_special_inode(inode, mode, dev);
 789         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 790         if (err)
 791                 goto out_free;
 792
 793         err = read_name(inode, name);
 794         kfree(name);
 795         if (err)
 796                 goto out_put;
 797
 798         d_instantiate(dentry, inode);
 799         return 0;
 800
 801  out_free:
 802         kfree(name);
 803  out_put:
 804         iput(inode);
 805  out:
 806         return err;
 807 }
 808
 809 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 810                   struct inode *to_ino, struct dentry *to)
 811 {
 812         char *from_name, *to_name;
 813         int err;
 814
 815         if ((from_name = inode_dentry_name(from_ino, from)) == NULL)
 816                 return -ENOMEM;
 817         if ((to_name = inode_dentry_name(to_ino, to)) == NULL) {
 818                 kfree(from_name);
 819                 return -ENOMEM;
 820         }
 821         err = rename_file(from_name, to_name);
 822         kfree(from_name);
 823         kfree(to_name);
 824         return err;
 825 }
 826
 827 int hostfs_permission(struct inode *ino, int desired)
 828 {
 829         char *name;
 830         int r = 0, w = 0, x = 0, err;
 831
 832         if (desired & MAY_READ) r = 1;
 833         if (desired & MAY_WRITE) w = 1;
 834         if (desired & MAY_EXEC) x = 1;
 835         name = inode_name(ino, 0);
 836         if (name == NULL)
 837                 return -ENOMEM;
 838
 839         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 840             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 841                 err = 0;
 842         else
 843                 err = access_file(name, r, w, x);
 844         kfree(name);
 845         if (!err)
 846                 err = generic_permission(ino, desired, NULL);
 847         return err;
 848 }
 849
 850 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 851 {
 852         struct inode *inode = dentry->d_inode;
 853         struct hostfs_iattr attrs;
 854         char *name;
 855         int err;
 856
 857         int fd = HOSTFS_I(inode)->fd;
 858
 859         err = inode_change_ok(inode, attr);
 860         if (err)
 861                 return err;
 862
 863         if (append)
 864                 attr->ia_valid &= ~ATTR_SIZE;
 865
 866         attrs.ia_valid = 0;
 867         if (attr->ia_valid & ATTR_MODE) {
 868                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 869                 attrs.ia_mode = attr->ia_mode;
 870         }
 871         if (attr->ia_valid & ATTR_UID) {
 872                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 873                 attrs.ia_uid = attr->ia_uid;
 874         }
 875         if (attr->ia_valid & ATTR_GID) {
 876                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 877                 attrs.ia_gid = attr->ia_gid;
 878         }
 879         if (attr->ia_valid & ATTR_SIZE) {
 880                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 881                 attrs.ia_size = attr->ia_size;
 882         }
 883         if (attr->ia_valid & ATTR_ATIME) {
 884                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 885                 attrs.ia_atime = attr->ia_atime;
 886         }
 887         if (attr->ia_valid & ATTR_MTIME) {
 888                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 889                 attrs.ia_mtime = attr->ia_mtime;
 890         }
 891         if (attr->ia_valid & ATTR_CTIME) {
 892                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 893                 attrs.ia_ctime = attr->ia_ctime;
 894         }
 895         if (attr->ia_valid & ATTR_ATIME_SET) {
 896                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 897         }
 898         if (attr->ia_valid & ATTR_MTIME_SET) {
 899                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 900         }
 901         name = dentry_name(dentry, 0);
 902         if (name == NULL)
 903                 return -ENOMEM;
 904         err = set_attr(name, &attrs, fd);
 905         kfree(name);
 906         if (err)
 907                 return err;
 908
 909         if ((attr->ia_valid & ATTR_SIZE) &&
 910             attr->ia_size != i_size_read(inode)) {
 911                 int error;
 912
 913                 error = vmtruncate(inode, attr->ia_size);
 914                 if (err)
 915                         return err;
 916         }
 917
 918         setattr_copy(inode, attr);
 919         mark_inode_dirty(inode);
 920         return 0;
 921 }
 922
 923 static const struct inode_operations hostfs_iops = {
 924         .create         = hostfs_create,
 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 static const struct inode_operations hostfs_dir_iops = {
 937         .create         = hostfs_create,
 938         .lookup         = hostfs_lookup,
 939         .link           = hostfs_link,
 940         .unlink         = hostfs_unlink,
 941         .symlink        = hostfs_symlink,
 942         .mkdir          = hostfs_mkdir,
 943         .rmdir          = hostfs_rmdir,
 944         .mknod          = hostfs_mknod,
 945         .rename         = hostfs_rename,
 946         .permission     = hostfs_permission,
 947         .setattr        = hostfs_setattr,
 948 };
 949
 950 int hostfs_link_readpage(struct file *file, struct page *page)
 951 {
 952         char *buffer, *name;
 953         int err;
 954
 955         buffer = kmap(page);
 956         name = inode_name(page->mapping->host, 0);
 957         if (name == NULL)
 958                 return -ENOMEM;
 959         err = hostfs_do_readlink(name, buffer, PAGE_CACHE_SIZE);
 960         kfree(name);
 961         if (err == PAGE_CACHE_SIZE)
 962                 err = -E2BIG;
 963         else if (err > 0) {
 964                 flush_dcache_page(page);
 965                 SetPageUptodate(page);
 966                 if (PageError(page)) ClearPageError(page);
 967                 err = 0;
 968         }
 969         kunmap(page);
 970         unlock_page(page);
 971         return err;
 972 }
 973
 974 static const struct address_space_operations hostfs_link_aops = {
 975         .readpage       = hostfs_link_readpage,
 976 };
 977
 978 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 979 {
 980         struct inode *root_inode;
 981         char *host_root_path, *req_root = d;
 982         int err;
 983
 984         sb->s_blocksize = 1024;
 985         sb->s_blocksize_bits = 10;
 986         sb->s_magic = HOSTFS_SUPER_MAGIC;
 987         sb->s_op = &hostfs_sbops;
 988         sb->s_maxbytes = MAX_LFS_FILESIZE;
 989
 990         /* NULL is printed as <NULL> by sprintf: avoid that. */
 991         if (req_root == NULL)
 992                 req_root = "";
 993
 994         err = -ENOMEM;
 995         host_root_path = kmalloc(strlen(root_ino) + 1
 996                                  + strlen(req_root) + 1, GFP_KERNEL);
 997         if (host_root_path == NULL)
 998                 goto out;
 999
1000         sprintf(host_root_path, "%s/%s", root_ino, req_root);
1001
1002         root_inode = hostfs_iget(sb);
1003         if (IS_ERR(root_inode)) {
1004                 err = PTR_ERR(root_inode);
1005                 goto out_free;
1006         }
1007
1008         err = init_inode(root_inode, NULL);
1009         if (err)
1010                 goto out_put;
1011
1012         HOSTFS_I(root_inode)->host_filename = host_root_path;
1013         /*
1014          * Avoid that in the error path, iput(root_inode) frees again
1015          * host_root_path through hostfs_destroy_inode!
1016          */
1017         host_root_path = NULL;
1018
1019         err = -ENOMEM;
1020         sb->s_root = d_alloc_root(root_inode);
1021         if (sb->s_root == NULL)
1022                 goto out_put;
1023
1024         err = hostfs_read_inode(root_inode);
1025         if (err) {
1026                 /* No iput in this case because the dput does that for us */
1027                 dput(sb->s_root);
1028                 sb->s_root = NULL;
1029                 goto out;
1030         }
1031
1032         return 0;
1033
1034 out_put:
1035         iput(root_inode);
1036 out_free:
1037         kfree(host_root_path);
1038 out:
1039         return err;
1040 }
1041
1042 static int hostfs_read_sb(struct file_system_type *type,
1043                           int flags, const char *dev_name,
1044                           void *data, struct vfsmount *mnt)
1045 {
1046         return get_sb_nodev(type, flags, data, hostfs_fill_sb_common, mnt);
1047 }
1048
1049 static struct file_system_type hostfs_type = {
1050         .owner          = THIS_MODULE,
1051         .name           = "hostfs",
1052         .get_sb         = hostfs_read_sb,
1053         .kill_sb        = kill_anon_super,
1054         .fs_flags       = 0,
1055 };
1056
1057 static int __init init_hostfs(void)
1058 {
1059         return register_filesystem(&hostfs_type);
1060 }
1061
1062 static void __exit exit_hostfs(void)
1063 {
1064         unregister_filesystem(&hostfs_type);
1065 }
1066
1067 module_init(init_hostfs)
1068 module_exit(exit_hostfs)
1069 MODULE_LICENSE("GPL");