fs/overlayfs/super.c

   1 /*
   2  *
   3  * Copyright (C) 2011 Novell Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 as published by
   7  * the Free Software Foundation.
   8  */
   9
  10 #include <uapi/linux/magic.h>
  11 #include <linux/fs.h>
  12 #include <linux/namei.h>
  13 #include <linux/xattr.h>
  14 #include <linux/mount.h>
  15 #include <linux/parser.h>
  16 #include <linux/module.h>
  17 #include <linux/statfs.h>
  18 #include <linux/seq_file.h>
  19 #include <linux/posix_acl_xattr.h>
  20 #include "overlayfs.h"
  21
  22 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
  23 MODULE_DESCRIPTION("Overlay filesystem");
  24 MODULE_LICENSE("GPL");
  25
  26
  27 struct ovl_dir_cache;
  28
  29 #define OVL_MAX_STACK 500
  30
  31 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
  32 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
  33 MODULE_PARM_DESC(ovl_redirect_dir_def,
  34                  "Default to on or off for the redirect_dir feature");
  35
  36 static bool ovl_redirect_always_follow =
  37         IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
  38 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
  39                    bool, 0644);
  40 MODULE_PARM_DESC(ovl_redirect_always_follow,
  41                  "Follow redirects even if redirect_dir feature is turned off");
  42
  43 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
  44 module_param_named(index, ovl_index_def, bool, 0644);
  45 MODULE_PARM_DESC(ovl_index_def,
  46                  "Default to on or off for the inodes index feature");
  47
  48 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
  49 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
  50 MODULE_PARM_DESC(ovl_nfs_export_def,
  51                  "Default to on or off for the NFS export feature");
  52
  53 static void ovl_entry_stack_free(struct ovl_entry *oe)
  54 {
  55         unsigned int i;
  56
  57         for (i = 0; i < oe->numlower; i++)
  58                 dput(oe->lowerstack[i].dentry);
  59 }
  60
  61 static void ovl_dentry_release(struct dentry *dentry)
  62 {
  63         struct ovl_entry *oe = dentry->d_fsdata;
  64
  65         if (oe) {
  66                 ovl_entry_stack_free(oe);
  67                 kfree_rcu(oe, rcu);
  68         }
  69 }
  70
  71 static int ovl_check_append_only(struct inode *inode, int flag)
  72 {
  73         /*
  74          * This test was moot in vfs may_open() because overlay inode does
  75          * not have the S_APPEND flag, so re-check on real upper inode
  76          */
  77         if (IS_APPEND(inode)) {
  78                 if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
  79                         return -EPERM;
  80                 if (flag & O_TRUNC)
  81                         return -EPERM;
  82         }
  83
  84         return 0;
  85 }
  86
  87 static struct dentry *ovl_d_real(struct dentry *dentry,
  88                                  const struct inode *inode,
  89                                  unsigned int open_flags, unsigned int flags)
  90 {
  91         struct dentry *real;
  92         int err;
  93
  94         if (flags & D_REAL_UPPER)
  95                 return ovl_dentry_upper(dentry);
  96
  97         if (!d_is_reg(dentry)) {
  98                 if (!inode || inode == d_inode(dentry))
  99                         return dentry;
 100                 goto bug;
 101         }
 102
 103         if (open_flags) {
 104                 err = ovl_open_maybe_copy_up(dentry, open_flags);
 105                 if (err)
 106                         return ERR_PTR(err);
 107         }
 108
 109         real = ovl_dentry_upper(dentry);
 110         if (real && (!inode || inode == d_inode(real))) {
 111                 if (!inode) {
 112                         err = ovl_check_append_only(d_inode(real), open_flags);
 113                         if (err)
 114                                 return ERR_PTR(err);
 115                 }
 116                 return real;
 117         }
 118
 119         real = ovl_dentry_lower(dentry);
 120         if (!real)
 121                 goto bug;
 122
 123         /* Handle recursion */
 124         real = d_real(real, inode, open_flags, 0);
 125
 126         if (!inode || inode == d_inode(real))
 127                 return real;
 128 bug:
 129         WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
 130              inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
 131         return dentry;
 132 }
 133
 134 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 135 {
 136         struct ovl_entry *oe = dentry->d_fsdata;
 137         unsigned int i;
 138         int ret = 1;
 139
 140         for (i = 0; i < oe->numlower; i++) {
 141                 struct dentry *d = oe->lowerstack[i].dentry;
 142
 143                 if (d->d_flags & DCACHE_OP_REVALIDATE) {
 144                         ret = d->d_op->d_revalidate(d, flags);
 145                         if (ret < 0)
 146                                 return ret;
 147                         if (!ret) {
 148                                 if (!(flags & LOOKUP_RCU))
 149                                         d_invalidate(d);
 150                                 return -ESTALE;
 151                         }
 152                 }
 153         }
 154         return 1;
 155 }
 156
 157 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
 158 {
 159         struct ovl_entry *oe = dentry->d_fsdata;
 160         unsigned int i;
 161         int ret = 1;
 162
 163         for (i = 0; i < oe->numlower; i++) {
 164                 struct dentry *d = oe->lowerstack[i].dentry;
 165
 166                 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
 167                         ret = d->d_op->d_weak_revalidate(d, flags);
 168                         if (ret <= 0)
 169                                 break;
 170                 }
 171         }
 172         return ret;
 173 }
 174
 175 static const struct dentry_operations ovl_dentry_operations = {
 176         .d_release = ovl_dentry_release,
 177         .d_real = ovl_d_real,
 178 };
 179
 180 static const struct dentry_operations ovl_reval_dentry_operations = {
 181         .d_release = ovl_dentry_release,
 182         .d_real = ovl_d_real,
 183         .d_revalidate = ovl_dentry_revalidate,
 184         .d_weak_revalidate = ovl_dentry_weak_revalidate,
 185 };
 186
 187 static struct kmem_cache *ovl_inode_cachep;
 188
 189 static struct inode *ovl_alloc_inode(struct super_block *sb)
 190 {
 191         struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);
 192
 193         if (!oi)
 194                 return NULL;
 195
 196         oi->cache = NULL;
 197         oi->redirect = NULL;
 198         oi->version = 0;
 199         oi->flags = 0;
 200         oi->__upperdentry = NULL;
 201         oi->lower = NULL;
 202         mutex_init(&oi->lock);
 203
 204         return &oi->vfs_inode;
 205 }
 206
 207 static void ovl_i_callback(struct rcu_head *head)
 208 {
 209         struct inode *inode = container_of(head, struct inode, i_rcu);
 210
 211         kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
 212 }
 213
 214 static void ovl_destroy_inode(struct inode *inode)
 215 {
 216         struct ovl_inode *oi = OVL_I(inode);
 217
 218         dput(oi->__upperdentry);
 219         iput(oi->lower);
 220         kfree(oi->redirect);
 221         ovl_dir_cache_free(inode);
 222         mutex_destroy(&oi->lock);
 223
 224         call_rcu(&inode->i_rcu, ovl_i_callback);
 225 }
 226
 227 static void ovl_free_fs(struct ovl_fs *ofs)
 228 {
 229         unsigned i;
 230
 231         dput(ofs->indexdir);
 232         dput(ofs->workdir);
 233         if (ofs->workdir_locked)
 234                 ovl_inuse_unlock(ofs->workbasedir);
 235         dput(ofs->workbasedir);
 236         if (ofs->upperdir_locked)
 237                 ovl_inuse_unlock(ofs->upper_mnt->mnt_root);
 238         mntput(ofs->upper_mnt);
 239         for (i = 0; i < ofs->numlower; i++) {
 240                 mntput(ofs->lower_layers[i].mnt);
 241                 free_anon_bdev(ofs->lower_layers[i].pseudo_dev);
 242         }
 243         kfree(ofs->lower_layers);
 244
 245         kfree(ofs->config.lowerdir);
 246         kfree(ofs->config.upperdir);
 247         kfree(ofs->config.workdir);
 248         kfree(ofs->config.redirect_mode);
 249         if (ofs->creator_cred)
 250                 put_cred(ofs->creator_cred);
 251         kfree(ofs);
 252 }
 253
 254 static void ovl_put_super(struct super_block *sb)
 255 {
 256         struct ovl_fs *ofs = sb->s_fs_info;
 257
 258         ovl_free_fs(ofs);
 259 }
 260
 261 /* Sync real dirty inodes in upper filesystem (if it exists) */
 262 static int ovl_sync_fs(struct super_block *sb, int wait)
 263 {
 264         struct ovl_fs *ofs = sb->s_fs_info;
 265         struct super_block *upper_sb;
 266         int ret;
 267
 268         if (!ofs->upper_mnt)
 269                 return 0;
 270
 271         /*
 272          * If this is a sync(2) call or an emergency sync, all the super blocks
 273          * will be iterated, including upper_sb, so no need to do anything.
 274          *
 275          * If this is a syncfs(2) call, then we do need to call
 276          * sync_filesystem() on upper_sb, but enough if we do it when being
 277          * called with wait == 1.
 278          */
 279         if (!wait)
 280                 return 0;
 281
 282         upper_sb = ofs->upper_mnt->mnt_sb;
 283
 284         down_read(&upper_sb->s_umount);
 285         ret = sync_filesystem(upper_sb);
 286         up_read(&upper_sb->s_umount);
 287
 288         return ret;
 289 }
 290
 291 /**
 292  * ovl_statfs
 293  * @sb: The overlayfs super block
 294  * @buf: The struct kstatfs to fill in with stats
 295  *
 296  * Get the filesystem statistics.  As writes always target the upper layer
 297  * filesystem pass the statfs to the upper filesystem (if it exists)
 298  */
 299 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 300 {
 301         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 302         struct dentry *root_dentry = dentry->d_sb->s_root;
 303         struct path path;
 304         int err;
 305
 306         ovl_path_real(root_dentry, &path);
 307
 308         err = vfs_statfs(&path, buf);
 309         if (!err) {
 310                 buf->f_namelen = ofs->namelen;
 311                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
 312         }
 313
 314         return err;
 315 }
 316
 317 /* Will this overlay be forced to mount/remount ro? */
 318 static bool ovl_force_readonly(struct ovl_fs *ofs)
 319 {
 320         return (!ofs->upper_mnt || !ofs->workdir);
 321 }
 322
 323 static const char *ovl_redirect_mode_def(void)
 324 {
 325         return ovl_redirect_dir_def ? "on" : "off";
 326 }
 327
 328 /**
 329  * ovl_show_options
 330  *
 331  * Prints the mount options for a given superblock.
 332  * Returns zero; does not fail.
 333  */
 334 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 335 {
 336         struct super_block *sb = dentry->d_sb;
 337         struct ovl_fs *ofs = sb->s_fs_info;
 338
 339         seq_show_option(m, "lowerdir", ofs->config.lowerdir);
 340         if (ofs->config.upperdir) {
 341                 seq_show_option(m, "upperdir", ofs->config.upperdir);
 342                 seq_show_option(m, "workdir", ofs->config.workdir);
 343         }
 344         if (ofs->config.default_permissions)
 345                 seq_puts(m, ",default_permissions");
 346         if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
 347                 seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
 348         if (ofs->config.index != ovl_index_def)
 349                 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
 350         if (ofs->config.nfs_export != ovl_nfs_export_def)
 351                 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
 352                                                 "on" : "off");
 353         return 0;
 354 }
 355
 356 static int ovl_remount(struct super_block *sb, int *flags, char *data)
 357 {
 358         struct ovl_fs *ofs = sb->s_fs_info;
 359
 360         if (!(*flags & SB_RDONLY) && ovl_force_readonly(ofs))
 361                 return -EROFS;
 362
 363         return 0;
 364 }
 365
 366 static const struct super_operations ovl_super_operations = {
 367         .alloc_inode    = ovl_alloc_inode,
 368         .destroy_inode  = ovl_destroy_inode,
 369         .drop_inode     = generic_delete_inode,
 370         .put_super      = ovl_put_super,
 371         .sync_fs        = ovl_sync_fs,
 372         .statfs         = ovl_statfs,
 373         .show_options   = ovl_show_options,
 374         .remount_fs     = ovl_remount,
 375 };
 376
 377 enum {
 378         OPT_LOWERDIR,
 379         OPT_UPPERDIR,
 380         OPT_WORKDIR,
 381         OPT_DEFAULT_PERMISSIONS,
 382         OPT_REDIRECT_DIR,
 383         OPT_INDEX_ON,
 384         OPT_INDEX_OFF,
 385         OPT_NFS_EXPORT_ON,
 386         OPT_NFS_EXPORT_OFF,
 387         OPT_ERR,
 388 };
 389
 390 static const match_table_t ovl_tokens = {
 391         {OPT_LOWERDIR,                  "lowerdir=%s"},
 392         {OPT_UPPERDIR,                  "upperdir=%s"},
 393         {OPT_WORKDIR,                   "workdir=%s"},
 394         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
 395         {OPT_REDIRECT_DIR,              "redirect_dir=%s"},
 396         {OPT_INDEX_ON,                  "index=on"},
 397         {OPT_INDEX_OFF,                 "index=off"},
 398         {OPT_NFS_EXPORT_ON,             "nfs_export=on"},
 399         {OPT_NFS_EXPORT_OFF,            "nfs_export=off"},
 400         {OPT_ERR,                       NULL}
 401 };
 402
 403 static char *ovl_next_opt(char **s)
 404 {
 405         char *sbegin = *s;
 406         char *p;
 407
 408         if (sbegin == NULL)
 409                 return NULL;
 410
 411         for (p = sbegin; *p; p++) {
 412                 if (*p == '\\') {
 413                         p++;
 414                         if (!*p)
 415                                 break;
 416                 } else if (*p == ',') {
 417                         *p = '\0';
 418                         *s = p + 1;
 419                         return sbegin;
 420                 }
 421         }
 422         *s = NULL;
 423         return sbegin;
 424 }
 425
 426 static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
 427 {
 428         if (strcmp(mode, "on") == 0) {
 429                 config->redirect_dir = true;
 430                 /*
 431                  * Does not make sense to have redirect creation without
 432                  * redirect following.
 433                  */
 434                 config->redirect_follow = true;
 435         } else if (strcmp(mode, "follow") == 0) {
 436                 config->redirect_follow = true;
 437         } else if (strcmp(mode, "off") == 0) {
 438                 if (ovl_redirect_always_follow)
 439                         config->redirect_follow = true;
 440         } else if (strcmp(mode, "nofollow") != 0) {
 441                 pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
 442                        mode);
 443                 return -EINVAL;
 444         }
 445
 446         return 0;
 447 }
 448
 449 static int ovl_parse_opt(char *opt, struct ovl_config *config)
 450 {
 451         char *p;
 452
 453         config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
 454         if (!config->redirect_mode)
 455                 return -ENOMEM;
 456
 457         while ((p = ovl_next_opt(&opt)) != NULL) {
 458                 int token;
 459                 substring_t args[MAX_OPT_ARGS];
 460
 461                 if (!*p)
 462                         continue;
 463
 464                 token = match_token(p, ovl_tokens, args);
 465                 switch (token) {
 466                 case OPT_UPPERDIR:
 467                         kfree(config->upperdir);
 468                         config->upperdir = match_strdup(&args[0]);
 469                         if (!config->upperdir)
 470                                 return -ENOMEM;
 471                         break;
 472
 473                 case OPT_LOWERDIR:
 474                         kfree(config->lowerdir);
 475                         config->lowerdir = match_strdup(&args[0]);
 476                         if (!config->lowerdir)
 477                                 return -ENOMEM;
 478                         break;
 479
 480                 case OPT_WORKDIR:
 481                         kfree(config->workdir);
 482                         config->workdir = match_strdup(&args[0]);
 483                         if (!config->workdir)
 484                                 return -ENOMEM;
 485                         break;
 486
 487                 case OPT_DEFAULT_PERMISSIONS:
 488                         config->default_permissions = true;
 489                         break;
 490
 491                 case OPT_REDIRECT_DIR:
 492                         kfree(config->redirect_mode);
 493                         config->redirect_mode = match_strdup(&args[0]);
 494                         if (!config->redirect_mode)
 495                                 return -ENOMEM;
 496                         break;
 497
 498                 case OPT_INDEX_ON:
 499                         config->index = true;
 500                         break;
 501
 502                 case OPT_INDEX_OFF:
 503                         config->index = false;
 504                         break;
 505
 506                 case OPT_NFS_EXPORT_ON:
 507                         config->nfs_export = true;
 508                         break;
 509
 510                 case OPT_NFS_EXPORT_OFF:
 511                         config->nfs_export = false;
 512                         break;
 513
 514                 default:
 515                         pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
 516                         return -EINVAL;
 517                 }
 518         }
 519
 520         /* Workdir is useless in non-upper mount */
 521         if (!config->upperdir && config->workdir) {
 522                 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 523                         config->workdir);
 524                 kfree(config->workdir);
 525                 config->workdir = NULL;
 526         }
 527
 528         return ovl_parse_redirect_mode(config, config->redirect_mode);
 529 }
 530
 531 #define OVL_WORKDIR_NAME "work"
 532 #define OVL_INDEXDIR_NAME "index"
 533
 534 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 535                                          const char *name, bool persist)
 536 {
 537         struct inode *dir =  ofs->workbasedir->d_inode;
 538         struct vfsmount *mnt = ofs->upper_mnt;
 539         struct dentry *work;
 540         int err;
 541         bool retried = false;
 542         bool locked = false;
 543
 544         inode_lock_nested(dir, I_MUTEX_PARENT);
 545         locked = true;
 546
 547 retry:
 548         work = lookup_one_len(name, ofs->workbasedir, strlen(name));
 549
 550         if (!IS_ERR(work)) {
 551                 struct iattr attr = {
 552                         .ia_valid = ATTR_MODE,
 553                         .ia_mode = S_IFDIR | 0,
 554                 };
 555
 556                 if (work->d_inode) {
 557                         err = -EEXIST;
 558                         if (retried)
 559                                 goto out_dput;
 560
 561                         if (persist)
 562                                 goto out_unlock;
 563
 564                         retried = true;
 565                         ovl_workdir_cleanup(dir, mnt, work, 0);
 566                         dput(work);
 567                         goto retry;
 568                 }
 569
 570                 err = ovl_create_real(dir, work,
 571                                       &(struct cattr){.mode = S_IFDIR | 0},
 572                                       NULL, true);
 573                 if (err)
 574                         goto out_dput;
 575
 576                 /*
 577                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
 578                  *
 579                  * a) success (there was a POSIX ACL xattr and was removed)
 580                  * b) -ENODATA (there was no POSIX ACL xattr)
 581                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
 582                  *
 583                  * There are various other error values that could effectively
 584                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
 585                  * if the xattr name is too long), but the set of filesystems
 586                  * allowed as upper are limited to "normal" ones, where checking
 587                  * for the above two errors is sufficient.
 588                  */
 589                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
 590                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 591                         goto out_dput;
 592
 593                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
 594                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 595                         goto out_dput;
 596
 597                 /* Clear any inherited mode bits */
 598                 inode_lock(work->d_inode);
 599                 err = notify_change(work, &attr, NULL);
 600                 inode_unlock(work->d_inode);
 601                 if (err)
 602                         goto out_dput;
 603         } else {
 604                 err = PTR_ERR(work);
 605                 goto out_err;
 606         }
 607 out_unlock:
 608         if (locked)
 609                 inode_unlock(dir);
 610
 611         return work;
 612
 613 out_dput:
 614         dput(work);
 615 out_err:
 616         pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
 617                 ofs->config.workdir, name, -err);
 618         work = NULL;
 619         goto out_unlock;
 620 }
 621
 622 static void ovl_unescape(char *s)
 623 {
 624         char *d = s;
 625
 626         for (;; s++, d++) {
 627                 if (*s == '\\')
 628                         s++;
 629                 *d = *s;
 630                 if (!*s)
 631                         break;
 632         }
 633 }
 634
 635 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 636 {
 637         int err = -EINVAL;
 638
 639         if (!*name) {
 640                 pr_err("overlayfs: empty lowerdir\n");
 641                 goto out;
 642         }
 643         err = kern_path(name, LOOKUP_FOLLOW, path);
 644         if (err) {
 645                 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
 646                 goto out;
 647         }
 648         err = -EINVAL;
 649         if (ovl_dentry_weird(path->dentry)) {
 650                 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
 651                 goto out_put;
 652         }
 653         if (!d_is_dir(path->dentry)) {
 654                 pr_err("overlayfs: '%s' not a directory\n", name);
 655                 goto out_put;
 656         }
 657         return 0;
 658
 659 out_put:
 660         path_put_init(path);
 661 out:
 662         return err;
 663 }
 664
 665 static int ovl_mount_dir(const char *name, struct path *path)
 666 {
 667         int err = -ENOMEM;
 668         char *tmp = kstrdup(name, GFP_KERNEL);
 669
 670         if (tmp) {
 671                 ovl_unescape(tmp);
 672                 err = ovl_mount_dir_noesc(tmp, path);
 673
 674                 if (!err)
 675                         if (ovl_dentry_remote(path->dentry)) {
 676                                 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
 677                                        tmp);
 678                                 path_put_init(path);
 679                                 err = -EINVAL;
 680                         }
 681                 kfree(tmp);
 682         }
 683         return err;
 684 }
 685
 686 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
 687                              const char *name)
 688 {
 689         struct kstatfs statfs;
 690         int err = vfs_statfs(path, &statfs);
 691
 692         if (err)
 693                 pr_err("overlayfs: statfs failed on '%s'\n", name);
 694         else
 695                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
 696
 697         return err;
 698 }
 699
 700 static int ovl_lower_dir(const char *name, struct path *path,
 701                          struct ovl_fs *ofs, int *stack_depth, bool *remote)
 702 {
 703         int err;
 704
 705         err = ovl_mount_dir_noesc(name, path);
 706         if (err)
 707                 goto out;
 708
 709         err = ovl_check_namelen(path, ofs, name);
 710         if (err)
 711                 goto out_put;
 712
 713         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
 714
 715         if (ovl_dentry_remote(path->dentry))
 716                 *remote = true;
 717
 718         /*
 719          * The inodes index feature and NFS export need to encode and decode
 720          * file handles, so they require that all layers support them.
 721          */
 722         if ((ofs->config.nfs_export ||
 723              (ofs->config.index && ofs->config.upperdir)) &&
 724             !ovl_can_decode_fh(path->dentry->d_sb)) {
 725                 ofs->config.index = false;
 726                 ofs->config.nfs_export = false;
 727                 pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
 728                         name);
 729         }
 730
 731         return 0;
 732
 733 out_put:
 734         path_put_init(path);
 735 out:
 736         return err;
 737 }
 738
 739 /* Workdir should not be subdir of upperdir and vice versa */
 740 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 741 {
 742         bool ok = false;
 743
 744         if (workdir != upperdir) {
 745                 ok = (lock_rename(workdir, upperdir) == NULL);
 746                 unlock_rename(workdir, upperdir);
 747         }
 748         return ok;
 749 }
 750
 751 static unsigned int ovl_split_lowerdirs(char *str)
 752 {
 753         unsigned int ctr = 1;
 754         char *s, *d;
 755
 756         for (s = d = str;; s++, d++) {
 757                 if (*s == '\\') {
 758                         s++;
 759                 } else if (*s == ':') {
 760                         *d = '\0';
 761                         ctr++;
 762                         continue;
 763                 }
 764                 *d = *s;
 765                 if (!*s)
 766                         break;
 767         }
 768         return ctr;
 769 }
 770
 771 static int __maybe_unused
 772 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 773                         struct dentry *dentry, struct inode *inode,
 774                         const char *name, void *buffer, size_t size)
 775 {
 776         return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
 777 }
 778
 779 static int __maybe_unused
 780 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 781                         struct dentry *dentry, struct inode *inode,
 782                         const char *name, const void *value,
 783                         size_t size, int flags)
 784 {
 785         struct dentry *workdir = ovl_workdir(dentry);
 786         struct inode *realinode = ovl_inode_real(inode);
 787         struct posix_acl *acl = NULL;
 788         int err;
 789
 790         /* Check that everything is OK before copy-up */
 791         if (value) {
 792                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 793                 if (IS_ERR(acl))
 794                         return PTR_ERR(acl);
 795         }
 796         err = -EOPNOTSUPP;
 797         if (!IS_POSIXACL(d_inode(workdir)))
 798                 goto out_acl_release;
 799         if (!realinode->i_op->set_acl)
 800                 goto out_acl_release;
 801         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
 802                 err = acl ? -EACCES : 0;
 803                 goto out_acl_release;
 804         }
 805         err = -EPERM;
 806         if (!inode_owner_or_capable(inode))
 807                 goto out_acl_release;
 808
 809         posix_acl_release(acl);
 810
 811         /*
 812          * Check if sgid bit needs to be cleared (actual setacl operation will
 813          * be done with mounter's capabilities and so that won't do it for us).
 814          */
 815         if (unlikely(inode->i_mode & S_ISGID) &&
 816             handler->flags == ACL_TYPE_ACCESS &&
 817             !in_group_p(inode->i_gid) &&
 818             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
 819                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
 820
 821                 err = ovl_setattr(dentry, &iattr);
 822                 if (err)
 823                         return err;
 824         }
 825
 826         err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
 827         if (!err)
 828                 ovl_copyattr(ovl_inode_real(inode), inode);
 829
 830         return err;
 831
 832 out_acl_release:
 833         posix_acl_release(acl);
 834         return err;
 835 }
 836
 837 static int ovl_own_xattr_get(const struct xattr_handler *handler,
 838                              struct dentry *dentry, struct inode *inode,
 839                              const char *name, void *buffer, size_t size)
 840 {
 841         return -EOPNOTSUPP;
 842 }
 843
 844 static int ovl_own_xattr_set(const struct xattr_handler *handler,
 845                              struct dentry *dentry, struct inode *inode,
 846                              const char *name, const void *value,
 847                              size_t size, int flags)
 848 {
 849         return -EOPNOTSUPP;
 850 }
 851
 852 static int ovl_other_xattr_get(const struct xattr_handler *handler,
 853                                struct dentry *dentry, struct inode *inode,
 854                                const char *name, void *buffer, size_t size)
 855 {
 856         return ovl_xattr_get(dentry, inode, name, buffer, size);
 857 }
 858
 859 static int ovl_other_xattr_set(const struct xattr_handler *handler,
 860                                struct dentry *dentry, struct inode *inode,
 861                                const char *name, const void *value,
 862                                size_t size, int flags)
 863 {
 864         return ovl_xattr_set(dentry, inode, name, value, size, flags);
 865 }
 866
 867 static const struct xattr_handler __maybe_unused
 868 ovl_posix_acl_access_xattr_handler = {
 869         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 870         .flags = ACL_TYPE_ACCESS,
 871         .get = ovl_posix_acl_xattr_get,
 872         .set = ovl_posix_acl_xattr_set,
 873 };
 874
 875 static const struct xattr_handler __maybe_unused
 876 ovl_posix_acl_default_xattr_handler = {
 877         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 878         .flags = ACL_TYPE_DEFAULT,
 879         .get = ovl_posix_acl_xattr_get,
 880         .set = ovl_posix_acl_xattr_set,
 881 };
 882
 883 static const struct xattr_handler ovl_own_xattr_handler = {
 884         .prefix = OVL_XATTR_PREFIX,
 885         .get = ovl_own_xattr_get,
 886         .set = ovl_own_xattr_set,
 887 };
 888
 889 static const struct xattr_handler ovl_other_xattr_handler = {
 890         .prefix = "", /* catch all */
 891         .get = ovl_other_xattr_get,
 892         .set = ovl_other_xattr_set,
 893 };
 894
 895 static const struct xattr_handler *ovl_xattr_handlers[] = {
 896 #ifdef CONFIG_FS_POSIX_ACL
 897         &ovl_posix_acl_access_xattr_handler,
 898         &ovl_posix_acl_default_xattr_handler,
 899 #endif
 900         &ovl_own_xattr_handler,
 901         &ovl_other_xattr_handler,
 902         NULL
 903 };
 904
 905 static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
 906 {
 907         struct vfsmount *upper_mnt;
 908         int err;
 909
 910         err = ovl_mount_dir(ofs->config.upperdir, upperpath);
 911         if (err)
 912                 goto out;
 913
 914         /* Upper fs should not be r/o */
 915         if (sb_rdonly(upperpath->mnt->mnt_sb)) {
 916                 pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
 917                 err = -EINVAL;
 918                 goto out;
 919         }
 920
 921         err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
 922         if (err)
 923                 goto out;
 924
 925         err = -EBUSY;
 926         if (ovl_inuse_trylock(upperpath->dentry)) {
 927                 ofs->upperdir_locked = true;
 928         } else if (ofs->config.index) {
 929                 pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
 930                 goto out;
 931         } else {
 932                 pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
 933         }
 934
 935         upper_mnt = clone_private_mount(upperpath);
 936         err = PTR_ERR(upper_mnt);
 937         if (IS_ERR(upper_mnt)) {
 938                 pr_err("overlayfs: failed to clone upperpath\n");
 939                 goto out;
 940         }
 941
 942         /* Don't inherit atime flags */
 943         upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
 944         ofs->upper_mnt = upper_mnt;
 945         err = 0;
 946 out:
 947         return err;
 948 }
 949
 950 static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
 951 {
 952         struct vfsmount *mnt = ofs->upper_mnt;
 953         struct dentry *temp;
 954         int err;
 955
 956         err = mnt_want_write(mnt);
 957         if (err)
 958                 return err;
 959
 960         ofs->workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
 961         if (!ofs->workdir)
 962                 goto out;
 963
 964         /*
 965          * Upper should support d_type, else whiteouts are visible.  Given
 966          * workdir and upper are on same fs, we can do iterate_dir() on
 967          * workdir. This check requires successful creation of workdir in
 968          * previous step.
 969          */
 970         err = ovl_check_d_type_supported(workpath);
 971         if (err < 0)
 972                 goto out;
 973
 974         /*
 975          * We allowed this configuration and don't want to break users over
 976          * kernel upgrade. So warn instead of erroring out.
 977          */
 978         if (!err)
 979                 pr_warn("overlayfs: upper fs needs to support d_type.\n");
 980
 981         /* Check if upper/work fs supports O_TMPFILE */
 982         temp = ovl_do_tmpfile(ofs->workdir, S_IFREG | 0);
 983         ofs->tmpfile = !IS_ERR(temp);
 984         if (ofs->tmpfile)
 985                 dput(temp);
 986         else
 987                 pr_warn("overlayfs: upper fs does not support tmpfile.\n");
 988
 989         /*
 990          * Check if upper/work fs supports trusted.overlay.* xattr
 991          */
 992         err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
 993         if (err) {
 994                 ofs->noxattr = true;
 995                 ofs->config.index = false;
 996                 pr_warn("overlayfs: upper fs does not support xattr, falling back to index=off.\n");
 997                 err = 0;
 998         } else {
 999                 vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE);
1000         }
1001
1002         /* Check if upper/work fs supports file handles */
1003         if (ofs->config.index &&
1004             !ovl_can_decode_fh(ofs->workdir->d_sb)) {
1005                 ofs->config.index = false;
1006                 pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
1007         }
1008
1009         /* NFS export of r/w mount depends on index */
1010         if (ofs->config.nfs_export && !ofs->config.index) {
1011                 pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n");
1012                 ofs->config.nfs_export = false;
1013         }
1014
1015 out:
1016         mnt_drop_write(mnt);
1017         return err;
1018 }
1019
1020 static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
1021 {
1022         int err;
1023         struct path workpath = { };
1024
1025         err = ovl_mount_dir(ofs->config.workdir, &workpath);
1026         if (err)
1027                 goto out;
1028
1029         err = -EINVAL;
1030         if (upperpath->mnt != workpath.mnt) {
1031                 pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
1032                 goto out;
1033         }
1034         if (!ovl_workdir_ok(workpath.dentry, upperpath->dentry)) {
1035                 pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
1036                 goto out;
1037         }
1038
1039         err = -EBUSY;
1040         if (ovl_inuse_trylock(workpath.dentry)) {
1041                 ofs->workdir_locked = true;
1042         } else if (ofs->config.index) {
1043                 pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
1044                 goto out;
1045         } else {
1046                 pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
1047         }
1048
1049         ofs->workbasedir = dget(workpath.dentry);
1050         err = ovl_make_workdir(ofs, &workpath);
1051         if (err)
1052                 goto out;
1053
1054         err = 0;
1055 out:
1056         path_put(&workpath);
1057
1058         return err;
1059 }
1060
1061 static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
1062                             struct path *upperpath)
1063 {
1064         struct vfsmount *mnt = ofs->upper_mnt;
1065         int err;
1066
1067         err = mnt_want_write(mnt);
1068         if (err)
1069                 return err;
1070
1071         /* Verify lower root is upper root origin */
1072         err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
1073                                 true);
1074         if (err) {
1075                 pr_err("overlayfs: failed to verify upper root origin\n");
1076                 goto out;
1077         }
1078
1079         ofs->indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
1080         if (ofs->indexdir) {
1081                 /*
1082                  * Verify upper root is exclusively associated with index dir.
1083                  * Older kernels stored upper fh in "trusted.overlay.origin"
1084                  * xattr. If that xattr exists, verify that it is a match to
1085                  * upper dir file handle. In any case, verify or set xattr
1086                  * "trusted.overlay.upper" to indicate that index may have
1087                  * directory entries.
1088                  */
1089                 if (ovl_check_origin_xattr(ofs->indexdir)) {
1090                         err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
1091                                                 upperpath->dentry, true, false);
1092                         if (err)
1093                                 pr_err("overlayfs: failed to verify index dir 'origin' xattr\n");
1094                 }
1095                 err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
1096                 if (err)
1097                         pr_err("overlayfs: failed to verify index dir 'upper' xattr\n");
1098
1099                 /* Cleanup bad/stale/orphan index entries */
1100                 if (!err)
1101                         err = ovl_indexdir_cleanup(ofs);
1102         }
1103         if (err || !ofs->indexdir)
1104                 pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1105
1106 out:
1107         mnt_drop_write(mnt);
1108         return err;
1109 }
1110
1111 static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack,
1112                                 unsigned int numlower)
1113 {
1114         int err;
1115         unsigned int i;
1116
1117         err = -ENOMEM;
1118         ofs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
1119                                     GFP_KERNEL);
1120         if (ofs->lower_layers == NULL)
1121                 goto out;
1122         for (i = 0; i < numlower; i++) {
1123                 struct vfsmount *mnt;
1124                 dev_t dev;
1125
1126                 err = get_anon_bdev(&dev);
1127                 if (err) {
1128                         pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
1129                         goto out;
1130                 }
1131
1132                 mnt = clone_private_mount(&stack[i]);
1133                 err = PTR_ERR(mnt);
1134                 if (IS_ERR(mnt)) {
1135                         pr_err("overlayfs: failed to clone lowerpath\n");
1136                         free_anon_bdev(dev);
1137                         goto out;
1138                 }
1139                 /*
1140                  * Make lower layers R/O.  That way fchmod/fchown on lower file
1141                  * will fail instead of modifying lower fs.
1142                  */
1143                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1144
1145                 ofs->lower_layers[ofs->numlower].mnt = mnt;
1146                 ofs->lower_layers[ofs->numlower].pseudo_dev = dev;
1147                 ofs->lower_layers[ofs->numlower].idx = i + 1;
1148                 ofs->numlower++;
1149
1150                 /* Check if all lower layers are on same sb */
1151                 if (i == 0)
1152                         ofs->same_sb = mnt->mnt_sb;
1153                 else if (ofs->same_sb != mnt->mnt_sb)
1154                         ofs->same_sb = NULL;
1155         }
1156         err = 0;
1157 out:
1158         return err;
1159 }
1160
1161 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1162                                             struct ovl_fs *ofs)
1163 {
1164         int err;
1165         char *lowertmp, *lower;
1166         struct path *stack = NULL;
1167         unsigned int stacklen, numlower = 0, i;
1168         bool remote = false;
1169         struct ovl_entry *oe;
1170
1171         err = -ENOMEM;
1172         lowertmp = kstrdup(ofs->config.lowerdir, GFP_KERNEL);
1173         if (!lowertmp)
1174                 goto out_err;
1175
1176         err = -EINVAL;
1177         stacklen = ovl_split_lowerdirs(lowertmp);
1178         if (stacklen > OVL_MAX_STACK) {
1179                 pr_err("overlayfs: too many lower directories, limit is %d\n",
1180                        OVL_MAX_STACK);
1181                 goto out_err;
1182         } else if (!ofs->config.upperdir && stacklen == 1) {
1183                 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
1184                 goto out_err;
1185         } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
1186                    ofs->config.redirect_follow) {
1187                 pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
1188                 ofs->config.nfs_export = false;
1189         }
1190
1191         err = -ENOMEM;
1192         stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
1193         if (!stack)
1194                 goto out_err;
1195
1196         err = -EINVAL;
1197         lower = lowertmp;
1198         for (numlower = 0; numlower < stacklen; numlower++) {
1199                 err = ovl_lower_dir(lower, &stack[numlower], ofs,
1200                                     &sb->s_stack_depth, &remote);
1201                 if (err)
1202                         goto out_err;
1203
1204                 lower = strchr(lower, '\0') + 1;
1205         }
1206
1207         err = -EINVAL;
1208         sb->s_stack_depth++;
1209         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1210                 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1211                 goto out_err;
1212         }
1213
1214         err = ovl_get_lower_layers(ofs, stack, numlower);
1215         if (err)
1216                 goto out_err;
1217
1218         err = -ENOMEM;
1219         oe = ovl_alloc_entry(numlower);
1220         if (!oe)
1221                 goto out_err;
1222
1223         for (i = 0; i < numlower; i++) {
1224                 oe->lowerstack[i].dentry = dget(stack[i].dentry);
1225                 oe->lowerstack[i].layer = &ofs->lower_layers[i];
1226         }
1227
1228         if (remote)
1229                 sb->s_d_op = &ovl_reval_dentry_operations;
1230         else
1231                 sb->s_d_op = &ovl_dentry_operations;
1232
1233 out:
1234         for (i = 0; i < numlower; i++)
1235                 path_put(&stack[i]);
1236         kfree(stack);
1237         kfree(lowertmp);
1238
1239         return oe;
1240
1241 out_err:
1242         oe = ERR_PTR(err);
1243         goto out;
1244 }
1245
1246 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
1247 {
1248         struct path upperpath = { };
1249         struct dentry *root_dentry;
1250         struct ovl_entry *oe;
1251         struct ovl_fs *ofs;
1252         struct cred *cred;
1253         int err;
1254
1255         err = -ENOMEM;
1256         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
1257         if (!ofs)
1258                 goto out;
1259
1260         ofs->creator_cred = cred = prepare_creds();
1261         if (!cred)
1262                 goto out_err;
1263
1264         ofs->config.index = ovl_index_def;
1265         ofs->config.nfs_export = ovl_nfs_export_def;
1266         err = ovl_parse_opt((char *) data, &ofs->config);
1267         if (err)
1268                 goto out_err;
1269
1270         err = -EINVAL;
1271         if (!ofs->config.lowerdir) {
1272                 if (!silent)
1273                         pr_err("overlayfs: missing 'lowerdir'\n");
1274                 goto out_err;
1275         }
1276
1277         sb->s_stack_depth = 0;
1278         sb->s_maxbytes = MAX_LFS_FILESIZE;
1279         if (ofs->config.upperdir) {
1280                 if (!ofs->config.workdir) {
1281                         pr_err("overlayfs: missing 'workdir'\n");
1282                         goto out_err;
1283                 }
1284
1285                 err = ovl_get_upper(ofs, &upperpath);
1286                 if (err)
1287                         goto out_err;
1288
1289                 err = ovl_get_workdir(ofs, &upperpath);
1290                 if (err)
1291                         goto out_err;
1292
1293                 if (!ofs->workdir)
1294                         sb->s_flags |= SB_RDONLY;
1295
1296                 sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
1297                 sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
1298
1299         }
1300         oe = ovl_get_lowerstack(sb, ofs);
1301         err = PTR_ERR(oe);
1302         if (IS_ERR(oe))
1303                 goto out_err;
1304
1305         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1306         if (!ofs->upper_mnt)
1307                 sb->s_flags |= SB_RDONLY;
1308         else if (ofs->upper_mnt->mnt_sb != ofs->same_sb)
1309                 ofs->same_sb = NULL;
1310
1311         if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
1312                 err = ovl_get_indexdir(ofs, oe, &upperpath);
1313                 if (err)
1314                         goto out_free_oe;
1315
1316                 /* Force r/o mount with no index dir */
1317                 if (!ofs->indexdir) {
1318                         dput(ofs->workdir);
1319                         ofs->workdir = NULL;
1320                         sb->s_flags |= SB_RDONLY;
1321                 }
1322
1323         }
1324
1325         /* Show index=off in /proc/mounts for forced r/o mount */
1326         if (!ofs->indexdir) {
1327                 ofs->config.index = false;
1328                 if (ofs->upper_mnt && ofs->config.nfs_export) {
1329                         pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n");
1330                         ofs->config.nfs_export = false;
1331                 }
1332         }
1333
1334         if (ofs->config.nfs_export)
1335                 sb->s_export_op = &ovl_export_operations;
1336
1337         /* Never override disk quota limits or use reserved space */
1338         cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1339
1340         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1341         sb->s_op = &ovl_super_operations;
1342         sb->s_xattr = ovl_xattr_handlers;
1343         sb->s_fs_info = ofs;
1344         sb->s_flags |= SB_POSIXACL | SB_NOREMOTELOCK;
1345
1346         err = -ENOMEM;
1347         root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1348         if (!root_dentry)
1349                 goto out_free_oe;
1350
1351         root_dentry->d_fsdata = oe;
1352
1353         mntput(upperpath.mnt);
1354         if (upperpath.dentry) {
1355                 ovl_dentry_set_upper_alias(root_dentry);
1356                 if (ovl_is_impuredir(upperpath.dentry))
1357                         ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1358         }
1359
1360         /* Root is always merge -> can have whiteouts */
1361         ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1362         ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
1363                        ovl_dentry_lower(root_dentry));
1364
1365         sb->s_root = root_dentry;
1366
1367         return 0;
1368
1369 out_free_oe:
1370         ovl_entry_stack_free(oe);
1371         kfree(oe);
1372 out_err:
1373         path_put(&upperpath);
1374         ovl_free_fs(ofs);
1375 out:
1376         return err;
1377 }
1378
1379 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
1380                                 const char *dev_name, void *raw_data)
1381 {
1382         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
1383 }
1384
1385 static struct file_system_type ovl_fs_type = {
1386         .owner          = THIS_MODULE,
1387         .name           = "overlay",
1388         .mount          = ovl_mount,
1389         .kill_sb        = kill_anon_super,
1390 };
1391 MODULE_ALIAS_FS("overlay");
1392
1393 static void ovl_inode_init_once(void *foo)
1394 {
1395         struct ovl_inode *oi = foo;
1396
1397         inode_init_once(&oi->vfs_inode);
1398 }
1399
1400 static int __init ovl_init(void)
1401 {
1402         int err;
1403
1404         ovl_inode_cachep = kmem_cache_create("ovl_inode",
1405                                              sizeof(struct ovl_inode), 0,
1406                                              (SLAB_RECLAIM_ACCOUNT|
1407                                               SLAB_MEM_SPREAD|SLAB_ACCOUNT),
1408                                              ovl_inode_init_once);
1409         if (ovl_inode_cachep == NULL)
1410                 return -ENOMEM;
1411
1412         err = register_filesystem(&ovl_fs_type);
1413         if (err)
1414                 kmem_cache_destroy(ovl_inode_cachep);
1415
1416         return err;
1417 }
1418
1419 static void __exit ovl_exit(void)
1420 {
1421         unregister_filesystem(&ovl_fs_type);
1422
1423         /*
1424          * Make sure all delayed rcu free inodes are flushed before we
1425          * destroy cache.
1426          */
1427         rcu_barrier();
1428         kmem_cache_destroy(ovl_inode_cachep);
1429
1430 }
1431
1432 module_init(ovl_init);
1433 module_exit(ovl_exit);