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 static 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_final(&inode->i_data);
 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 static 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 static 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 static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
 363                         int datasync)
 364 {
 365         struct inode *inode = file->f_mapping->host;
 366         int ret;
 367
 368         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 369         if (ret)
 370                 return ret;
 371
 372         mutex_lock(&inode->i_mutex);
 373         ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
 374         mutex_unlock(&inode->i_mutex);
 375
 376         return ret;
 377 }
 378
 379 static const struct file_operations hostfs_file_fops = {
 380         .llseek         = generic_file_llseek,
 381         .splice_read    = generic_file_splice_read,
 382         .read_iter      = generic_file_read_iter,
 383         .write_iter     = generic_file_write_iter,
 384         .mmap           = generic_file_mmap,
 385         .open           = hostfs_file_open,
 386         .release        = hostfs_file_release,
 387         .fsync          = hostfs_fsync,
 388 };
 389
 390 static const struct file_operations hostfs_dir_fops = {
 391         .llseek         = generic_file_llseek,
 392         .iterate        = hostfs_readdir,
 393         .read           = generic_read_dir,
 394 };
 395
 396 static int hostfs_writepage(struct page *page, struct writeback_control *wbc)
 397 {
 398         struct address_space *mapping = page->mapping;
 399         struct inode *inode = mapping->host;
 400         char *buffer;
 401         unsigned long long base;
 402         int count = PAGE_CACHE_SIZE;
 403         int end_index = inode->i_size >> PAGE_CACHE_SHIFT;
 404         int err;
 405
 406         if (page->index >= end_index)
 407                 count = inode->i_size & (PAGE_CACHE_SIZE-1);
 408
 409         buffer = kmap(page);
 410         base = ((unsigned long long) page->index) << PAGE_CACHE_SHIFT;
 411
 412         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
 413         if (err != count) {
 414                 ClearPageUptodate(page);
 415                 goto out;
 416         }
 417
 418         if (base > inode->i_size)
 419                 inode->i_size = base;
 420
 421         if (PageError(page))
 422                 ClearPageError(page);
 423         err = 0;
 424
 425  out:
 426         kunmap(page);
 427
 428         unlock_page(page);
 429         return err;
 430 }
 431
 432 static int hostfs_readpage(struct file *file, struct page *page)
 433 {
 434         char *buffer;
 435         long long start;
 436         int err = 0;
 437
 438         start = (long long) page->index << PAGE_CACHE_SHIFT;
 439         buffer = kmap(page);
 440         err = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
 441                         PAGE_CACHE_SIZE);
 442         if (err < 0)
 443                 goto out;
 444
 445         memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
 446
 447         flush_dcache_page(page);
 448         SetPageUptodate(page);
 449         if (PageError(page)) ClearPageError(page);
 450         err = 0;
 451  out:
 452         kunmap(page);
 453         unlock_page(page);
 454         return err;
 455 }
 456
 457 static int hostfs_write_begin(struct file *file, struct address_space *mapping,
 458                               loff_t pos, unsigned len, unsigned flags,
 459                               struct page **pagep, void **fsdata)
 460 {
 461         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 462
 463         *pagep = grab_cache_page_write_begin(mapping, index, flags);
 464         if (!*pagep)
 465                 return -ENOMEM;
 466         return 0;
 467 }
 468
 469 static int hostfs_write_end(struct file *file, struct address_space *mapping,
 470                             loff_t pos, unsigned len, unsigned copied,
 471                             struct page *page, void *fsdata)
 472 {
 473         struct inode *inode = mapping->host;
 474         void *buffer;
 475         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 476         int err;
 477
 478         buffer = kmap(page);
 479         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
 480         kunmap(page);
 481
 482         if (!PageUptodate(page) && err == PAGE_CACHE_SIZE)
 483                 SetPageUptodate(page);
 484
 485         /*
 486          * If err > 0, write_file has added err to pos, so we are comparing
 487          * i_size against the last byte written.
 488          */
 489         if (err > 0 && (pos > inode->i_size))
 490                 inode->i_size = pos;
 491         unlock_page(page);
 492         page_cache_release(page);
 493
 494         return err;
 495 }
 496
 497 static const struct address_space_operations hostfs_aops = {
 498         .writepage      = hostfs_writepage,
 499         .readpage       = hostfs_readpage,
 500         .set_page_dirty = __set_page_dirty_nobuffers,
 501         .write_begin    = hostfs_write_begin,
 502         .write_end      = hostfs_write_end,
 503 };
 504
 505 static int read_name(struct inode *ino, char *name)
 506 {
 507         dev_t rdev;
 508         struct hostfs_stat st;
 509         int err = stat_file(name, &st, -1);
 510         if (err)
 511                 return err;
 512
 513         /* Reencode maj and min with the kernel encoding.*/
 514         rdev = MKDEV(st.maj, st.min);
 515
 516         switch (st.mode & S_IFMT) {
 517         case S_IFLNK:
 518                 ino->i_op = &hostfs_link_iops;
 519                 break;
 520         case S_IFDIR:
 521                 ino->i_op = &hostfs_dir_iops;
 522                 ino->i_fop = &hostfs_dir_fops;
 523                 break;
 524         case S_IFCHR:
 525         case S_IFBLK:
 526         case S_IFIFO:
 527         case S_IFSOCK:
 528                 init_special_inode(ino, st.mode & S_IFMT, rdev);
 529                 ino->i_op = &hostfs_iops;
 530                 break;
 531
 532         default:
 533                 ino->i_op = &hostfs_iops;
 534                 ino->i_fop = &hostfs_file_fops;
 535                 ino->i_mapping->a_ops = &hostfs_aops;
 536         }
 537
 538         ino->i_ino = st.ino;
 539         ino->i_mode = st.mode;
 540         set_nlink(ino, st.nlink);
 541         i_uid_write(ino, st.uid);
 542         i_gid_write(ino, st.gid);
 543         ino->i_atime = st.atime;
 544         ino->i_mtime = st.mtime;
 545         ino->i_ctime = st.ctime;
 546         ino->i_size = st.size;
 547         ino->i_blocks = st.blocks;
 548         return 0;
 549 }
 550
 551 static int hostfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 552                          bool excl)
 553 {
 554         struct inode *inode;
 555         char *name;
 556         int error, fd;
 557
 558         inode = hostfs_iget(dir->i_sb);
 559         if (IS_ERR(inode)) {
 560                 error = PTR_ERR(inode);
 561                 goto out;
 562         }
 563
 564         error = -ENOMEM;
 565         name = dentry_name(dentry);
 566         if (name == NULL)
 567                 goto out_put;
 568
 569         fd = file_create(name,
 570                          mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR,
 571                          mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP,
 572                          mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
 573         if (fd < 0)
 574                 error = fd;
 575         else
 576                 error = read_name(inode, name);
 577
 578         __putname(name);
 579         if (error)
 580                 goto out_put;
 581
 582         HOSTFS_I(inode)->fd = fd;
 583         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
 584         d_instantiate(dentry, inode);
 585         return 0;
 586
 587  out_put:
 588         iput(inode);
 589  out:
 590         return error;
 591 }
 592
 593 static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
 594                                     unsigned int flags)
 595 {
 596         struct inode *inode;
 597         char *name;
 598         int err;
 599
 600         inode = hostfs_iget(ino->i_sb);
 601         if (IS_ERR(inode)) {
 602                 err = PTR_ERR(inode);
 603                 goto out;
 604         }
 605
 606         err = -ENOMEM;
 607         name = dentry_name(dentry);
 608         if (name == NULL)
 609                 goto out_put;
 610
 611         err = read_name(inode, name);
 612
 613         __putname(name);
 614         if (err == -ENOENT) {
 615                 iput(inode);
 616                 inode = NULL;
 617         }
 618         else if (err)
 619                 goto out_put;
 620
 621         d_add(dentry, inode);
 622         return NULL;
 623
 624  out_put:
 625         iput(inode);
 626  out:
 627         return ERR_PTR(err);
 628 }
 629
 630 static int hostfs_link(struct dentry *to, struct inode *ino,
 631                        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 static 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 static int hostfs_symlink(struct inode *ino, struct dentry *dentry,
 666                           const char *to)
 667 {
 668         char *file;
 669         int err;
 670
 671         if ((file = dentry_name(dentry)) == NULL)
 672                 return -ENOMEM;
 673         err = make_symlink(file, to);
 674         __putname(file);
 675         return err;
 676 }
 677
 678 static int hostfs_mkdir(struct inode *ino, struct dentry *dentry, umode_t mode)
 679 {
 680         char *file;
 681         int err;
 682
 683         if ((file = dentry_name(dentry)) == NULL)
 684                 return -ENOMEM;
 685         err = do_mkdir(file, mode);
 686         __putname(file);
 687         return err;
 688 }
 689
 690 static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
 691 {
 692         char *file;
 693         int err;
 694
 695         if ((file = dentry_name(dentry)) == NULL)
 696                 return -ENOMEM;
 697         err = do_rmdir(file);
 698         __putname(file);
 699         return err;
 700 }
 701
 702 static int hostfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
 703 {
 704         struct inode *inode;
 705         char *name;
 706         int err;
 707
 708         inode = hostfs_iget(dir->i_sb);
 709         if (IS_ERR(inode)) {
 710                 err = PTR_ERR(inode);
 711                 goto out;
 712         }
 713
 714         err = -ENOMEM;
 715         name = dentry_name(dentry);
 716         if (name == NULL)
 717                 goto out_put;
 718
 719         init_special_inode(inode, mode, dev);
 720         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
 721         if (!err)
 722                 goto out_free;
 723
 724         err = read_name(inode, name);
 725         __putname(name);
 726         if (err)
 727                 goto out_put;
 728         if (err)
 729                 goto out_put;
 730
 731         d_instantiate(dentry, inode);
 732         return 0;
 733
 734  out_free:
 735         __putname(name);
 736  out_put:
 737         iput(inode);
 738  out:
 739         return err;
 740 }
 741
 742 static int hostfs_rename2(struct inode *old_dir, struct dentry *old_dentry,
 743                           struct inode *new_dir, struct dentry *new_dentry,
 744                           unsigned int flags)
 745 {
 746         char *old_name, *new_name;
 747         int err;
 748
 749         if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
 750                 return -EINVAL;
 751
 752         old_name = dentry_name(old_dentry);
 753         if (old_name == NULL)
 754                 return -ENOMEM;
 755         new_name = dentry_name(new_dentry);
 756         if (new_name == NULL) {
 757                 __putname(old_name);
 758                 return -ENOMEM;
 759         }
 760         if (!flags)
 761                 err = rename_file(old_name, new_name);
 762         else
 763                 err = rename2_file(old_name, new_name, flags);
 764
 765         __putname(old_name);
 766         __putname(new_name);
 767         return err;
 768 }
 769
 770 static int hostfs_permission(struct inode *ino, int desired)
 771 {
 772         char *name;
 773         int r = 0, w = 0, x = 0, err;
 774
 775         if (desired & MAY_NOT_BLOCK)
 776                 return -ECHILD;
 777
 778         if (desired & MAY_READ) r = 1;
 779         if (desired & MAY_WRITE) w = 1;
 780         if (desired & MAY_EXEC) x = 1;
 781         name = inode_name(ino);
 782         if (name == NULL)
 783                 return -ENOMEM;
 784
 785         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
 786             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
 787                 err = 0;
 788         else
 789                 err = access_file(name, r, w, x);
 790         __putname(name);
 791         if (!err)
 792                 err = generic_permission(ino, desired);
 793         return err;
 794 }
 795
 796 static int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 797 {
 798         struct inode *inode = d_inode(dentry);
 799         struct hostfs_iattr attrs;
 800         char *name;
 801         int err;
 802
 803         int fd = HOSTFS_I(inode)->fd;
 804
 805         err = inode_change_ok(inode, attr);
 806         if (err)
 807                 return err;
 808
 809         if (append)
 810                 attr->ia_valid &= ~ATTR_SIZE;
 811
 812         attrs.ia_valid = 0;
 813         if (attr->ia_valid & ATTR_MODE) {
 814                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
 815                 attrs.ia_mode = attr->ia_mode;
 816         }
 817         if (attr->ia_valid & ATTR_UID) {
 818                 attrs.ia_valid |= HOSTFS_ATTR_UID;
 819                 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
 820         }
 821         if (attr->ia_valid & ATTR_GID) {
 822                 attrs.ia_valid |= HOSTFS_ATTR_GID;
 823                 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
 824         }
 825         if (attr->ia_valid & ATTR_SIZE) {
 826                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
 827                 attrs.ia_size = attr->ia_size;
 828         }
 829         if (attr->ia_valid & ATTR_ATIME) {
 830                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
 831                 attrs.ia_atime = attr->ia_atime;
 832         }
 833         if (attr->ia_valid & ATTR_MTIME) {
 834                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
 835                 attrs.ia_mtime = attr->ia_mtime;
 836         }
 837         if (attr->ia_valid & ATTR_CTIME) {
 838                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
 839                 attrs.ia_ctime = attr->ia_ctime;
 840         }
 841         if (attr->ia_valid & ATTR_ATIME_SET) {
 842                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
 843         }
 844         if (attr->ia_valid & ATTR_MTIME_SET) {
 845                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
 846         }
 847         name = dentry_name(dentry);
 848         if (name == NULL)
 849                 return -ENOMEM;
 850         err = set_attr(name, &attrs, fd);
 851         __putname(name);
 852         if (err)
 853                 return err;
 854
 855         if ((attr->ia_valid & ATTR_SIZE) &&
 856             attr->ia_size != i_size_read(inode))
 857                 truncate_setsize(inode, attr->ia_size);
 858
 859         setattr_copy(inode, attr);
 860         mark_inode_dirty(inode);
 861         return 0;
 862 }
 863
 864 static const struct inode_operations hostfs_iops = {
 865         .permission     = hostfs_permission,
 866         .setattr        = hostfs_setattr,
 867 };
 868
 869 static const struct inode_operations hostfs_dir_iops = {
 870         .create         = hostfs_create,
 871         .lookup         = hostfs_lookup,
 872         .link           = hostfs_link,
 873         .unlink         = hostfs_unlink,
 874         .symlink        = hostfs_symlink,
 875         .mkdir          = hostfs_mkdir,
 876         .rmdir          = hostfs_rmdir,
 877         .mknod          = hostfs_mknod,
 878         .rename2        = hostfs_rename2,
 879         .permission     = hostfs_permission,
 880         .setattr        = hostfs_setattr,
 881 };
 882
 883 static void *hostfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 884 {
 885         char *link = __getname();
 886         if (link) {
 887                 char *path = dentry_name(dentry);
 888                 int err = -ENOMEM;
 889                 if (path) {
 890                         err = hostfs_do_readlink(path, link, PATH_MAX);
 891                         if (err == PATH_MAX)
 892                                 err = -E2BIG;
 893                         __putname(path);
 894                 }
 895                 if (err < 0) {
 896                         __putname(link);
 897                         link = ERR_PTR(err);
 898                 }
 899         } else {
 900                 link = ERR_PTR(-ENOMEM);
 901         }
 902
 903         nd_set_link(nd, link);
 904         return NULL;
 905 }
 906
 907 static void hostfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
 908 {
 909         char *s = nd_get_link(nd);
 910         if (!IS_ERR(s))
 911                 __putname(s);
 912 }
 913
 914 static const struct inode_operations hostfs_link_iops = {
 915         .readlink       = generic_readlink,
 916         .follow_link    = hostfs_follow_link,
 917         .put_link       = hostfs_put_link,
 918 };
 919
 920 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
 921 {
 922         struct inode *root_inode;
 923         char *host_root_path, *req_root = d;
 924         int err;
 925
 926         sb->s_blocksize = 1024;
 927         sb->s_blocksize_bits = 10;
 928         sb->s_magic = HOSTFS_SUPER_MAGIC;
 929         sb->s_op = &hostfs_sbops;
 930         sb->s_d_op = &simple_dentry_operations;
 931         sb->s_maxbytes = MAX_LFS_FILESIZE;
 932
 933         /* NULL is printed as <NULL> by sprintf: avoid that. */
 934         if (req_root == NULL)
 935                 req_root = "";
 936
 937         err = -ENOMEM;
 938         sb->s_fs_info = host_root_path =
 939                 kmalloc(strlen(root_ino) + strlen(req_root) + 2, GFP_KERNEL);
 940         if (host_root_path == NULL)
 941                 goto out;
 942
 943         sprintf(host_root_path, "%s/%s", root_ino, req_root);
 944
 945         root_inode = new_inode(sb);
 946         if (!root_inode)
 947                 goto out;
 948
 949         err = read_name(root_inode, host_root_path);
 950         if (err)
 951                 goto out_put;
 952
 953         if (S_ISLNK(root_inode->i_mode)) {
 954                 char *name = follow_link(host_root_path);
 955                 if (IS_ERR(name))
 956                         err = PTR_ERR(name);
 957                 else
 958                         err = read_name(root_inode, name);
 959                 kfree(name);
 960                 if (err)
 961                         goto out_put;
 962         }
 963
 964         err = -ENOMEM;
 965         sb->s_root = d_make_root(root_inode);
 966         if (sb->s_root == NULL)
 967                 goto out;
 968
 969         return 0;
 970
 971 out_put:
 972         iput(root_inode);
 973 out:
 974         return err;
 975 }
 976
 977 static struct dentry *hostfs_read_sb(struct file_system_type *type,
 978                           int flags, const char *dev_name,
 979                           void *data)
 980 {
 981         return mount_nodev(type, flags, data, hostfs_fill_sb_common);
 982 }
 983
 984 static void hostfs_kill_sb(struct super_block *s)
 985 {
 986         kill_anon_super(s);
 987         kfree(s->s_fs_info);
 988 }
 989
 990 static struct file_system_type hostfs_type = {
 991         .owner          = THIS_MODULE,
 992         .name           = "hostfs",
 993         .mount          = hostfs_read_sb,
 994         .kill_sb        = hostfs_kill_sb,
 995         .fs_flags       = 0,
 996 };
 997 MODULE_ALIAS_FS("hostfs");
 998
 999 static int __init init_hostfs(void)
1000 {
1001         return register_filesystem(&hostfs_type);
1002 }
1003
1004 static void __exit exit_hostfs(void)
1005 {
1006         unregister_filesystem(&hostfs_type);
1007 }
1008
1009 module_init(init_hostfs)
1010 module_exit(exit_hostfs)
1011 MODULE_LICENSE("GPL");