fs/hostfs/hostfs_kern.c

   1 /*
   2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  *
   5  * Ported the filesystem routines to 2.5.
   6  * 2003-02-10 Petr Baudis <pasky@ucw.cz>
   7  */
   8
   9 #include <linux/fs.h>
  10 #include <linux/magic.h>
  11 #include <linux/module.h>
  12 #include <linux/mm.h>
  13 #include <linux/pagemap.h>
  14 #include <linux/statfs.h>
  15 #include <linux/slab.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/mount.h>
  18 #include <linux/namei.h>
  19 #include "hostfs.h"
  20 #include <init.h>
  21 #include <kern.h>
  22
  23 struct hostfs_inode_info {
  24         int fd;
  25         fmode_t mode;
  26         struct inode vfs_inode;
  27 };
  28
  29 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
  30 {
  31         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
  32 }
  33
  34 #define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
  35
  36 /* Changed in hostfs_args before the kernel starts running */
  37 static char *root_ino = "";
  38 static int append = 0;
  39
  40 static const struct inode_operations hostfs_iops;
  41 static const struct inode_operations hostfs_dir_iops;
  42 static const struct inode_operations hostfs_link_iops;
  43
  44 #ifndef MODULE
  45 static int __init hostfs_args(char *options, int *add)
  46 {
  47         char *ptr;
  48
  49         ptr = strchr(options, ',');
  50         if (ptr != NULL)
  51                 *ptr++ = '\0';
  52         if (*options != '\0')
  53                 root_ino = options;
  54
  55         options = ptr;
  56         while (options) {
  57                 ptr = strchr(options, ',');
  58                 if (ptr != NULL)
  59                         *ptr++ = '\0';
  60                 if (*options != '\0') {
  61                         if (!strcmp(options, "append"))
  62                                 append = 1;
  63                         else printf("hostfs_args - unsupported option - %s\n",
  64                                     options);
  65                 }
  66                 options = ptr;
  67         }
  68         return 0;
  69 }
  70
  71 __uml_setup("hostfs=", hostfs_args,
  72 "hostfs=<root dir>,<flags>,...\n"
  73 "    This is used to set hostfs parameters.  The root directory argument\n"
  74 "    is used to confine all hostfs mounts to within the specified directory\n"
  75 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
  76 "    mount anything on the host that's accessible to the user that's running\n"
  77 "    it.\n"
  78 "    The only flag currently supported is 'append', which specifies that all\n"
  79 "    files opened by hostfs will be opened in append mode.\n\n"
  80 );
  81 #endif
  82
  83 static char *__dentry_name(struct dentry *dentry, char *name)
  84 {
  85         char *p = dentry_path_raw(dentry, name, PATH_MAX);
  86         char *root;
  87         size_t len;
  88
  89         root = dentry->d_sb->s_fs_info;
  90         len = strlen(root);
  91         if (IS_ERR(p)) {
  92                 __putname(name);
  93                 return NULL;
  94         }
  95         strlcpy(name, root, PATH_MAX);
  96         if (len > p - name) {
  97                 __putname(name);
  98                 return NULL;
  99         }
 100         if (p > name + len) {
 101                 char *s = name + len;
 102                 while ((*s++ = *p++) != '\0')
 103                         ;
 104         }
 105         return name;
 106 }
 107
 108 static char *dentry_name(struct dentry *dentry)
 109 {
 110         char *name = __getname();
 111         if (!name)
 112                 return NULL;
 113
 114         return __dentry_name(dentry, name);
 115 }
 116
 117 static char *inode_name(struct inode *ino)
 118 {
 119         struct dentry *dentry;
 120         char *name;
 121
 122         dentry = d_find_alias(ino);
 123         if (!dentry)
 124                 return NULL;
 125
 126         name = dentry_name(dentry);
 127
 128         dput(dentry);
 129
 130         return name;
 131 }
 132
 133 static char *follow_link(char *link)
 134 {
 135         int len, n;
 136         char *name, *resolved, *end;
 137
 138         len = 64;
 139         while (1) {
 140                 n = -ENOMEM;
 141                 name = kmalloc(len, GFP_KERNEL);
 142                 if (name == NULL)
 143                         goto out;
 144
 145                 n = hostfs_do_readlink(link, name, len);
 146                 if (n < len)
 147                         break;
 148                 len *= 2;
 149                 kfree(name);
 150         }
 151         if (n < 0)
 152                 goto out_free;
 153
 154         if (*name == '/')
 155                 return name;
 156
 157         end = strrchr(link, '/');
 158         if (end == NULL)
 159                 return name;
 160
 161         *(end + 1) = '\0';
 162         len = strlen(link) + strlen(name) + 1;
 163
 164         resolved = kmalloc(len, GFP_KERNEL);
 165         if (resolved == NULL) {
 166                 n = -ENOMEM;
 167                 goto out_free;
 168         }
 169
 170         sprintf(resolved, "%s%s", link, name);
 171         kfree(name);
 172         kfree(link);
 173         return resolved;
 174
 175  out_free:
 176         kfree(name);
 177  out:
 178         return ERR_PTR(n);
 179 }
 180
 181 static struct inode *hostfs_iget(struct super_block *sb)
 182 {
 183         struct inode *inode = new_inode(sb);
 184         if (!inode)
 185                 return ERR_PTR(-ENOMEM);
 186         return inode;
 187 }
 188
 189 int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
 190 {
 191         /*
 192          * do_statfs uses struct statfs64 internally, but the linux kernel
 193          * struct statfs still has 32-bit versions for most of these fields,
 194          * so we convert them here
 195          */
 196         int err;
 197         long long f_blocks;
 198         long long f_bfree;
 199         long long f_bavail;
 200         long long f_files;
 201         long long f_ffree;
 202
 203         err = do_statfs(dentry->d_sb->s_fs_info,
 204                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
 205                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
 206                         &sf->f_namelen);
 207         if (err)
 208                 return err;
 209         sf->f_blocks = f_blocks;
 210         sf->f_bfree = f_bfree;
 211         sf->f_bavail = f_bavail;
 212         sf->f_files = f_files;
 213         sf->f_ffree = f_ffree;
 214         sf->f_type = HOSTFS_SUPER_MAGIC;
 215         return 0;
 216 }
 217
 218 static struct inode *hostfs_alloc_inode(struct super_block *sb)
 219 {
 220         struct hostfs_inode_info *hi;
 221
 222         hi = kmalloc(sizeof(*hi), GFP_KERNEL);
 223         if (hi == NULL)
 224                 return NULL;
 225         hi->fd = -1;
 226         hi->mode = 0;
 227         inode_init_once(&hi->vfs_inode);
 228         return &hi->vfs_inode;
 229 }
 230
 231 static void hostfs_evict_inode(struct inode *inode)
 232 {
 233         truncate_inode_pages(&inode->i_data, 0);
 234         clear_inode(inode);
 235         if (HOSTFS_I(inode)->fd != -1) {
 236                 close_file(&HOSTFS_I(inode)->fd);
 237                 HOSTFS_I(inode)->fd = -1;
 238         }
 239 }
 240
 241 static void hostfs_i_callback(struct rcu_head *head)
 242 {
 243         struct inode *inode = container_of(head, struct inode, i_rcu);
 244         kfree(HOSTFS_I(inode));
 245 }
 246
 247 static void hostfs_destroy_inode(struct inode *inode)
 248 {
 249         call_rcu(&inode->i_rcu, hostfs_i_callback);
 250 }
 251
 252 static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
 253 {
 254         const char *root_path = root->d_sb->s_fs_info;
 255         size_t offset = strlen(root_ino) + 1;
 256
 257         if (strlen(root_path) > offset)
 258                 seq_printf(seq, ",%s", root_path + offset);
 259
 260         return 0;
 261 }
 262
 263 static const struct super_operations hostfs_sbops = {
 264         .alloc_inode    = hostfs_alloc_inode,
 265         .destroy_inode  = hostfs_destroy_inode,
 266         .evict_inode    = hostfs_evict_inode,
 267         .statfs         = hostfs_statfs,
 268         .show_options   = hostfs_show_options,
 269 };
 270
 271 int hostfs_readdir(struct file *file, struct dir_context *ctx)
 272 {
 273         void *dir;
 274         char *name;
 275         unsigned long long next, ino;
 276         int error, len;
 277         unsigned int type;
 278
 279         name = dentry_name(file->f_path.dentry);
 280         if (name == NULL)
 281                 return -ENOMEM;
 282         dir = open_dir(name, &error);
 283         __putname(name);
 284         if (dir == NULL)
 285                 return -error;
 286         next = ctx->pos;
 287         while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
 288                 if (!dir_emit(ctx, name, len, ino, type))
 289                         break;
 290                 ctx->pos = next;
 291         }
 292         close_dir(dir);
 293         return 0;
 294 }
 295
 296 int hostfs_file_open(struct inode *ino, struct file *file)
 297 {
 298         static DEFINE_MUTEX(open_mutex);
 299         char *name;
 300         fmode_t mode = 0;
 301         int err;
 302         int r = 0, w = 0, fd;
 303
 304         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
 305         if ((mode & HOSTFS_I(ino)->mode) == mode)
 306                 return 0;
 307
 308         mode |= HOSTFS_I(ino)->mode;
 309
 310 retry:
 311         if (mode & FMODE_READ)
 312                 r = 1;
 313         if (mode & FMODE_WRITE)
 314                 w = 1;
 315         if (w)
 316                 r = 1;
 317
 318         name = dentry_name(file->f_path.dentry);
 319         if (name == NULL)
 320                 return -ENOMEM;
 321
 322         fd = open_file(name, r, w, append);
 323         __putname(name);
 324         if (fd < 0)
 325                 return fd;
 326
 327         mutex_lock(&open_mutex);
 328         /* somebody else had handled it first? */
 329         if ((mode & HOSTFS_I(ino)->mode) == mode) {
 330                 mutex_unlock(&open_mutex);
 331                 return 0;
 332         }
 333         if ((mode | HOSTFS_I(ino)->mode) != mode) {
 334                 mode |= HOSTFS_I(ino)->mode;
 335                 mutex_unlock(&open_mutex);
 336                 close_file(&fd);
 337                 goto retry;
 338         }
 339         if (HOSTFS_I(ino)->fd == -1) {
 340                 HOSTFS_I(ino)->fd = fd;
 341         } else {
 342                 err = replace_file(fd, HOSTFS_I(ino)->fd);
 343                 close_file(&fd);
 344                 if (err < 0) {
 345                         mutex_unlock(&open_mutex);
 346                         return err;
 347                 }
 348         }
 349         HOSTFS_I(ino)->mode = mode;
 350         mutex_unlock(&open_mutex);
 351
 352         return 0;
 353 }
 354
 355 static int hostfs_file_release(struct inode *inode, struct file *file)
 356 {
 357         filemap_write_and_wait(inode->i_mapping);
 358
 359         return 0;
 360 }
 361
 362 int hostfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 363 {
 364         struct inode *inode = file->f_mapping->host;
 365         int ret;
 366
 367         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 368         if (ret)
 369                 return ret;
 370
 371         mutex_lock(&inode->i_mutex);
 372         ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
 373         mutex_unlock(&inode->i_mutex);
 374
 375         return ret;
 376 }
 377
 378 static const struct file_operations hostfs_file_fops = {
 379         .llseek         = generic_file_llseek,
 380         .read           = do_sync_read,
 381         .splice_read    = generic_file_splice_read,
 382         .aio_read       = generic_file_aio_read,
 383         .aio_write      = generic_file_aio_write,
 384         .write          = do_sync_write,
 385         .mmap           = generic_file_mmap,
 386         .open           = hostfs_file_open,
 387         .release        = hostfs_file_release,
 388         .fsync          = hostfs_fsync,
 389 };
 390
 391 static const struct file_operations hostfs_dir_fops = {
 392         .llseek         = generic_file_llseek,
 393         .iterate        = hostfs_readdir,
 394         .read           = generic_read_dir,
 395 };
 396
 397 int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 398 {
 399         struct address_space *mapping = page->mapping;
 400         struct inode *inode = mapping->host;
 401         char *buffer;
 402         unsigned long long base;
 403         int count = PAGE_CACHE_SIZE;
 404         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 405         int err;
 406
 407         if (page->index >= end_index)
 408                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 409
 410         buffer = kmap(page);
 411         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 412
 413         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 414         if (err != count) {
 415                 ClearPageUptodate(page);
 416                 goto out;
 417         }
 418
 419         if (base > inode->i_size)
 420                 inode->i_size = base;
 421
 422         if (PageError(page))
 423                 ClearPageError(page);
 424         err = 0;
 425
 426  out:
 427         kunmap(page);
 428
 429         unlock_page(page);
 430         return err;
 431 }
 432
 433 int hostfs_readpage(struct file *file, struct page *page)
 434 {
 435         char *buffer;
 436         long long start;
 437         int err = 0;
 438
 439         start = (long long) page->index << PAGE_CACHE_SHIFT;
 440         buffer = kmap(page);
 441         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 442                         PAGE_CACHE_SIZE);
 443         if (err < 0)
 444                 goto out;
 445
 446         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 447
 448         flush_dcache_page(page);
 449         SetPageUptodate(page);
 450         if (PageError(page)) ClearPageError(page);
 451         err = 0;
 452  out:
 453         kunmap(page);
 454         unlock_page(page);
 455         return err;
 456 }
 457
 458 int hostfs_write_begin(struct file *file, struct address_space *mapping,
 459                         loff_t pos, unsigned len, unsigned flags,
 460                         struct page **pagep, void **fsdata)
 461 {
 462         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 463
 464         *pagep = grab_cache_page_write_begin(mapping, index, flags);
 465         if (!*pagep)
 466                 return -ENOMEM;
 467         return 0;
 468 }
 469
 470 int hostfs_write_end(struct file *file, struct address_space *mapping,
 471                         loff_t pos, unsigned len, unsigned copied,
 472                         struct page *page, void *fsdata)
 473 {
 474         struct inode *inode = mapping->host;
 475         void *buffer;
 476         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 477         int err;
 478
 479         buffer = kmap(page);
 480         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 481         kunmap(page);
 482
 483         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 484                 SetPageUptodate(page);
 485
 486         /*
 487          * If err > 0, write_file has added err to pos, so we are comparing
 488          * i_size against the last byte written.
 489          */
 490         if (err > 0 && (pos > inode->i_size))
 491                 inode->i_size = pos;
 492         unlock_page(page);
 493         page_cache_release(page);
 494
 495         return err;
 496 }
 497
 498 static const struct address_space_operations hostfs_aops = {
 499         .writepage      = hostfs_writepage,
 500         .readpage       = hostfs_readpage,
 501         .set_page_dirty = __set_page_dirty_nobuffers,
 502         .write_begin    = hostfs_write_begin,
 503         .write_end      = hostfs_write_end,
 504 };
 505
 506 static int read_name(struct inode *ino, char *name)
 507 {
 508         dev_t rdev;
 509         struct hostfs_stat st;
 510         int err = stat_file(name, &st, -1);
 511         if (err)
 512                 return err;
 513
 514         /* Reencode maj and min with the kernel encoding.*/
 515         rdev = MKDEV(st.maj, st.min);
 516
 517         switch (st.mode & S_IFMT) {
 518         case S_IFLNK:
 519                 ino->i_op = &hostfs_link_iops;
 520                 break;
 521         case S_IFDIR:
 522                 ino->i_op = &hostfs_dir_iops;
 523                 ino->i_fop = &hostfs_dir_fops;
 524                 break;
 525         case S_IFCHR:
 526         case S_IFBLK:
 527         case S_IFIFO:
 528         case S_IFSOCK:
 529                 init_special_inode(ino, st.mode & S_IFMT, rdev);
 530                 ino->i_op = &hostfs_iops;
 531                 break;
 532
 533         default:
 534                 ino->i_op = &hostfs_iops;
 535                 ino->i_fop = &hostfs_file_fops;
 536                 ino->i_mapping->a_ops = &hostfs_aops;
 537         }
 538
 539         ino->i_ino = st.ino;
 540         ino->i_mode = st.mode;
 541         set_nlink(ino, st.nlink);
 542         i_uid_write(ino, st.uid);
 543         i_gid_write(ino, st.gid);
 544         ino->i_atime = st.atime;
 545         ino->i_mtime = st.mtime;
 546         ino->i_ctime = st.ctime;
 547         ino->i_size = st.size;
 548         ino->i_blocks = st.blocks;
 549         return 0;
 550 }
 551
 552 int hostfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 553                   bool excl)
 554 {
 555         struct inode *inode;
 556         char *name;
 557         int error, fd;
 558
 559         inode = hostfs_iget(dir->i_sb);
 560         if (IS_ERR(inode)) {
 561                 error = PTR_ERR(inode);
 562                 goto out;
 563         }
 564
 565         error = -ENOMEM;
 566         name = dentry_name(dentry);
 567         if (name == NULL)
 568                 goto out_put;
 569
 570         fd = file_create(name,
 571                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 572                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 573                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 574         if (fd < 0)
 575                 error = fd;
 576         else
 577                 error = read_name(inode, name);
 578
 579         __putname(name);
 580         if (error)
 581                 goto out_put;
 582
 583         HOSTFS_I(inode)->fd = fd;
 584         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 585         d_instantiate(dentry, inode);
 586         return 0;
 587
 588  out_put:
 589         iput(inode);
 590  out:
 591         return error;
 592 }
 593
 594 struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 595                              unsigned int flags)
 596 {
 597         struct inode *inode;
 598         char *name;
 599         int err;
 600
 601         inode = hostfs_iget(ino->i_sb);
 602         if (IS_ERR(inode)) {
 603                 err = PTR_ERR(inode);
 604                 goto out;
 605         }
 606
 607         err = -ENOMEM;
 608         name = dentry_name(dentry);
 609         if (name == NULL)
 610                 goto out_put;
 611
 612         err = read_name(inode, name);
 613
 614         __putname(name);
 615         if (err == -ENOENT) {
 616                 iput(inode);
 617                 inode = NULL;
 618         }
 619         else if (err)
 620                 goto out_put;
 621
 622         d_add(dentry, inode);
 623         return NULL;
 624
 625  out_put:
 626         iput(inode);
 627  out:
 628         return ERR_PTR(err);
 629 }
 630
 631 int hostfs_link(struct dentry *to, struct inode *ino, struct dentry *from)
 632 {
 633         char *from_name, *to_name;
 634         int err;
 635
 636         if ((from_name = dentry_name(from)) == NULL)
 637                 return -ENOMEM;
 638         to_name = dentry_name(to);
 639         if (to_name == NULL) {
 640                 __putname(from_name);
 641                 return -ENOMEM;
 642         }
 643         err = link_file(to_name, from_name);
 644         __putname(from_name);
 645         __putname(to_name);
 646         return err;
 647 }
 648
 649 int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 650 {
 651         char *file;
 652         int err;
 653
 654         if (append)
 655                 return -EPERM;
 656
 657         if ((file = dentry_name(dentry)) == NULL)
 658                 return -ENOMEM;
 659
 660         err = unlink_file(file);
 661         __putname(file);
 662         return err;
 663 }
 664
 665 int hostfs_symlink(struct inode *ino, struct dentry *dentry, const char *to)
 666 {
 667         char *file;
 668         int err;
 669
 670         if ((file = dentry_name(dentry)) == NULL)
 671                 return -ENOMEM;
 672         err = make_symlink(file, to);
 673         __putname(file);
 674         return err;
 675 }
 676
 677 int hostfs_mkdir(struct inode *ino, struct dentry *dentry, umode_t mode)
 678 {
 679         char *file;
 680         int err;
 681
 682         if ((file = dentry_name(dentry)) == NULL)
 683                 return -ENOMEM;
 684         err = do_mkdir(file, mode);
 685         __putname(file);
 686         return err;
 687 }
 688
 689 int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 690 {
 691         char *file;
 692         int err;
 693
 694         if ((file = dentry_name(dentry)) == NULL)
 695                 return -ENOMEM;
 696         err = do_rmdir(file);
 697         __putname(file);
 698         return err;
 699 }
 700
 701 static int hostfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
 702 {
 703         struct inode *inode;
 704         char *name;
 705         int err;
 706
 707         inode = hostfs_iget(dir->i_sb);
 708         if (IS_ERR(inode)) {
 709                 err = PTR_ERR(inode);
 710                 goto out;
 711         }
 712
 713         err = -ENOMEM;
 714         name = dentry_name(dentry);
 715         if (name == NULL)
 716                 goto out_put;
 717
 718         init_special_inode(inode, mode, dev);
 719         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 720         if (!err)
 721                 goto out_free;
 722
 723         err = read_name(inode, name);
 724         __putname(name);
 725         if (err)
 726                 goto out_put;
 727         if (err)
 728                 goto out_put;
 729
 730         d_instantiate(dentry, inode);
 731         return 0;
 732
 733  out_free:
 734         __putname(name);
 735  out_put:
 736         iput(inode);
 737  out:
 738         return err;
 739 }
 740
 741 int hostfs_rename(struct inode *from_ino, struct dentry *from,
 742                   struct inode *to_ino, struct dentry *to)
 743 {
 744         char *from_name, *to_name;
 745         int err;
 746
 747         if ((from_name = dentry_name(from)) == NULL)
 748                 return -ENOMEM;
 749         if ((to_name = dentry_name(to)) == NULL) {
 750                 __putname(from_name);
 751                 return -ENOMEM;
 752         }
 753         err = rename_file(from_name, to_name);
 754         __putname(from_name);
 755         __putname(to_name);
 756         return err;
 757 }
 758
 759 int hostfs_permission(struct inode *ino, int desired)
 760 {
 761         char *name;
 762         int r = 0, w = 0, x = 0, err;
 763
 764         if (desired & MAY_NOT_BLOCK)
 765                 return -ECHILD;
 766
 767         if (desired & MAY_READ) r = 1;
 768         if (desired & MAY_WRITE) w = 1;
 769         if (desired & MAY_EXEC) x = 1;
 770         name = inode_name(ino);
 771         if (name == NULL)
 772                 return -ENOMEM;
 773
 774         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 775             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 776                 err = 0;
 777         else
 778                 err = access_file(name, r, w, x);
 779         __putname(name);
 780         if (!err)
 781                 err = generic_permission(ino, desired);
 782         return err;
 783 }
 784
 785 int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 786 {
 787         struct inode *inode = dentry->d_inode;
 788         struct hostfs_iattr attrs;
 789         char *name;
 790         int err;
 791
 792         int fd = HOSTFS_I(inode)->fd;
 793
 794         err = inode_change_ok(inode, attr);
 795         if (err)
 796                 return err;
 797
 798         if (append)
 799                 attr->ia_valid &= ~ATTR_SIZE;
 800
 801         attrs.ia_valid = 0;
 802         if (attr->ia_valid & ATTR_MODE) {
 803                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 804                 attrs.ia_mode = attr->ia_mode;
 805         }
 806         if (attr->ia_valid & ATTR_UID) {
 807                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 808                 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
 809         }
 810         if (attr->ia_valid & ATTR_GID) {
 811                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 812                 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
 813         }
 814         if (attr->ia_valid & ATTR_SIZE) {
 815                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 816                 attrs.ia_size = attr->ia_size;
 817         }
 818         if (attr->ia_valid & ATTR_ATIME) {
 819                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 820                 attrs.ia_atime = attr->ia_atime;
 821         }
 822         if (attr->ia_valid & ATTR_MTIME) {
 823                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 824                 attrs.ia_mtime = attr->ia_mtime;
 825         }
 826         if (attr->ia_valid & ATTR_CTIME) {
 827                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 828                 attrs.ia_ctime = attr->ia_ctime;
 829         }
 830         if (attr->ia_valid & ATTR_ATIME_SET) {
 831                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 832         }
 833         if (attr->ia_valid & ATTR_MTIME_SET) {
 834                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 835         }
 836         name = dentry_name(dentry);
 837         if (name == NULL)
 838                 return -ENOMEM;
 839         err = set_attr(name, &attrs, fd);
 840         __putname(name);
 841         if (err)
 842                 return err;
 843
 844         if ((attr->ia_valid & ATTR_SIZE) &&
 845             attr->ia_size != i_size_read(inode))
 846                 truncate_setsize(inode, attr->ia_size);
 847
 848         setattr_copy(inode, attr);
 849         mark_inode_dirty(inode);
 850         return 0;
 851 }
 852
 853 static const struct inode_operations hostfs_iops = {
 854         .permission     = hostfs_permission,
 855         .setattr        = hostfs_setattr,
 856 };
 857
 858 static const struct inode_operations hostfs_dir_iops = {
 859         .create         = hostfs_create,
 860         .lookup         = hostfs_lookup,
 861         .link           = hostfs_link,
 862         .unlink         = hostfs_unlink,
 863         .symlink        = hostfs_symlink,
 864         .mkdir          = hostfs_mkdir,
 865         .rmdir          = hostfs_rmdir,
 866         .mknod          = hostfs_mknod,
 867         .rename         = hostfs_rename,
 868         .permission     = hostfs_permission,
 869         .setattr        = hostfs_setattr,
 870 };
 871
 872 static void *hostfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 873 {
 874         char *link = __getname();
 875         if (link) {
 876                 char *path = dentry_name(dentry);
 877                 int err = -ENOMEM;
 878                 if (path) {
 879                         err = hostfs_do_readlink(path, link, PATH_MAX);
 880                         if (err == PATH_MAX)
 881                                 err = -E2BIG;
 882                         __putname(path);
 883                 }
 884                 if (err < 0) {
 885                         __putname(link);
 886                         link = ERR_PTR(err);
 887                 }
 888         } else {
 889                 link = ERR_PTR(-ENOMEM);
 890         }
 891
 892         nd_set_link(nd, link);
 893         return NULL;
 894 }
 895
 896 static void hostfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
 897 {
 898         char *s = nd_get_link(nd);
 899         if (!IS_ERR(s))
 900                 __putname(s);
 901 }
 902
 903 static const struct inode_operations hostfs_link_iops = {
 904         .readlink       = generic_readlink,
 905         .follow_link    = hostfs_follow_link,
 906         .put_link       = hostfs_put_link,
 907 };
 908
 909 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 910 {
 911         struct inode *root_inode;
 912         char *host_root_path, *req_root = d;
 913         int err;
 914
 915         sb->s_blocksize = 1024;
 916         sb->s_blocksize_bits = 10;
 917         sb->s_magic = HOSTFS_SUPER_MAGIC;
 918         sb->s_op = &hostfs_sbops;
 919         sb->s_d_op = &simple_dentry_operations;
 920         sb->s_maxbytes = MAX_LFS_FILESIZE;
 921
 922         /* NULL is printed as <NULL> by sprintf: avoid that. */
 923         if (req_root == NULL)
 924                 req_root = "";
 925
 926         err = -ENOMEM;
 927         sb->s_fs_info = host_root_path =
 928                 kmalloc(strlen(root_ino) + strlen(req_root) + 2, GFP_KERNEL);
 929         if (host_root_path == NULL)
 930                 goto out;
 931
 932         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 933
 934         root_inode = new_inode(sb);
 935         if (!root_inode)
 936                 goto out;
 937
 938         err = read_name(root_inode, host_root_path);
 939         if (err)
 940                 goto out_put;
 941
 942         if (S_ISLNK(root_inode->i_mode)) {
 943                 char *name = follow_link(host_root_path);
 944                 if (IS_ERR(name))
 945                         err = PTR_ERR(name);
 946                 else
 947                         err = read_name(root_inode, name);
 948                 kfree(name);
 949                 if (err)
 950                         goto out_put;
 951         }
 952
 953         err = -ENOMEM;
 954         sb->s_root = d_make_root(root_inode);
 955         if (sb->s_root == NULL)
 956                 goto out;
 957
 958         return 0;
 959
 960 out_put:
 961         iput(root_inode);
 962 out:
 963         return err;
 964 }
 965
 966 static struct dentry *hostfs_read_sb(struct file_system_type *type,
 967                           int flags, const char *dev_name,
 968                           void *data)
 969 {
 970         return mount_nodev(type, flags, data, hostfs_fill_sb_common);
 971 }
 972
 973 static void hostfs_kill_sb(struct super_block *s)
 974 {
 975         kill_anon_super(s);
 976         kfree(s->s_fs_info);
 977 }
 978
 979 static struct file_system_type hostfs_type = {
 980         .owner          = THIS_MODULE,
 981         .name           = "hostfs",
 982         .mount          = hostfs_read_sb,
 983         .kill_sb        = hostfs_kill_sb,
 984         .fs_flags       = 0,
 985 };
 986 MODULE_ALIAS_FS("hostfs");
 987
 988 static int __init init_hostfs(void)
 989 {
 990         return register_filesystem(&hostfs_type);
 991 }
 992
 993 static void __exit exit_hostfs(void)
 994 {
 995         unregister_filesystem(&hostfs_type);
 996 }
 997
 998 module_init(init_hostfs)
 999 module_exit(exit_hostfs)
1000 MODULE_LICENSE("GPL");