target/linux/generic/patches-2.6.39/100-overlayfs.patch

   1 --- a/include/linux/fs.h
   2 +++ b/include/linux/fs.h
   3 @@ -1594,6 +1594,7 @@ struct inode_operations {
   4         void (*truncate_range)(struct inode *, loff_t, loff_t);
   5         int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
   6                       u64 len);
   7 +       struct file *(*open)(struct dentry *, int flags, const struct cred *);
   8  } ____cacheline_aligned;
   9
  10  struct seq_file;
  11 @@ -1988,6 +1989,7 @@ extern long do_sys_open(int dfd, const c
  12  extern struct file *filp_open(const char *, int, int);
  13  extern struct file *file_open_root(struct dentry *, struct vfsmount *,
  14                                    const char *, int);
  15 +extern struct file *vfs_open(struct path *, int flags, const struct cred *);
  16  extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
  17                                  const struct cred *);
  18  extern int filp_close(struct file *, fl_owner_t id);
  19 --- a/fs/open.c
  20 +++ b/fs/open.c
  21 @@ -666,8 +666,7 @@ static inline int __get_file_write_acces
  22         return error;
  23  }
  24
  25 -static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
  26 -                                       struct file *f,
  27 +static struct file *__dentry_open(struct path *path, struct file *f,
  28                                         int (*open)(struct inode *, struct file *),
  29                                         const struct cred *cred)
  30  {
  31 @@ -675,15 +674,16 @@ static struct file *__dentry_open(struct
  32         struct inode *inode;
  33         int error;
  34
  35 +       path_get(path);
  36         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
  37                                 FMODE_PREAD | FMODE_PWRITE;
  38
  39         if (unlikely(f->f_flags & O_PATH))
  40                 f->f_mode = FMODE_PATH;
  41
  42 -       inode = dentry->d_inode;
  43 +       inode = path->dentry->d_inode;
  44         if (f->f_mode & FMODE_WRITE) {
  45 -               error = __get_file_write_access(inode, mnt);
  46 +               error = __get_file_write_access(inode, path->mnt);
  47                 if (error)
  48                         goto cleanup_file;
  49                 if (!special_file(inode->i_mode))
  50 @@ -691,8 +691,7 @@ static struct file *__dentry_open(struct
  51         }
  52
  53         f->f_mapping = inode->i_mapping;
  54 -       f->f_path.dentry = dentry;
  55 -       f->f_path.mnt = mnt;
  56 +       f->f_path = *path;
  57         f->f_pos = 0;
  58         file_sb_list_add(f, inode->i_sb);
  59
  60 @@ -745,7 +744,7 @@ cleanup_all:
  61                          * here, so just reset the state.
  62                          */
  63                         file_reset_write(f);
  64 -                       mnt_drop_write(mnt);
  65 +                       mnt_drop_write(path->mnt);
  66                 }
  67         }
  68         file_sb_list_del(f);
  69 @@ -753,8 +752,7 @@ cleanup_all:
  70         f->f_path.mnt = NULL;
  71  cleanup_file:
  72         put_filp(f);
  73 -       dput(dentry);
  74 -       mntput(mnt);
  75 +       path_put(path);
  76         return ERR_PTR(error);
  77  }
  78
  79 @@ -780,14 +778,14 @@ cleanup_file:
  80  struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
  81                 int (*open)(struct inode *, struct file *))
  82  {
  83 +       struct path path = { .dentry = dentry, .mnt = nd->path.mnt };
  84         const struct cred *cred = current_cred();
  85
  86         if (IS_ERR(nd->intent.open.file))
  87                 goto out;
  88         if (IS_ERR(dentry))
  89                 goto out_err;
  90 -       nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
  91 -                                            nd->intent.open.file,
  92 +       nd->intent.open.file = __dentry_open(&path, nd->intent.open.file,
  93                                              open, cred);
  94  out:
  95         return nd->intent.open.file;
  96 @@ -816,10 +814,17 @@ struct file *nameidata_to_filp(struct na
  97
  98         /* Has the filesystem initialised the file for us? */
  99         if (filp->f_path.dentry == NULL) {
 100 -               path_get(&nd->path);
 101 -               filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
 102 -                                    NULL, cred);
 103 +               struct inode *inode = nd->path.dentry->d_inode;
 104 +
 105 +               if (inode->i_op->open) {
 106 +                       int flags = filp->f_flags;
 107 +                       put_filp(filp);
 108 +                       filp = inode->i_op->open(nd->path.dentry, flags, cred);
 109 +               } else {
 110 +                       filp = __dentry_open(&nd->path, filp, NULL, cred);
 111 +               }
 112         }
 113 +
 114         return filp;
 115  }
 116
 117 @@ -830,26 +835,45 @@ struct file *nameidata_to_filp(struct na
 118  struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 119                          const struct cred *cred)
 120  {
 121 -       int error;
 122 -       struct file *f;
 123 -
 124 -       validate_creds(cred);
 125 +       struct path path = { .dentry = dentry, .mnt = mnt };
 126 +       struct file *ret;
 127
 128         /* We must always pass in a valid mount pointer. */
 129         BUG_ON(!mnt);
 130
 131 -       error = -ENFILE;
 132 +       ret = vfs_open(&path, flags, cred);
 133 +       path_put(&path);
 134 +
 135 +       return ret;
 136 +}
 137 +EXPORT_SYMBOL(dentry_open);
 138 +
 139 +/**
 140 + * vfs_open - open the file at the given path
 141 + * @path: path to open
 142 + * @flags: open flags
 143 + * @cred: credentials to use
 144 + *
 145 + * Open the file.  If successful, the returned file will have acquired
 146 + * an additional reference for path.
 147 + */
 148 +struct file *vfs_open(struct path *path, int flags, const struct cred *cred)
 149 +{
 150 +       struct file *f;
 151 +       struct inode *inode = path->dentry->d_inode;
 152 +
 153 +       validate_creds(cred);
 154 +
 155 +       if (inode->i_op->open)
 156 +               return inode->i_op->open(path->dentry, flags, cred);
 157         f = get_empty_filp();
 158 -       if (f == NULL) {
 159 -               dput(dentry);
 160 -               mntput(mnt);
 161 -               return ERR_PTR(error);
 162 -       }
 163 +       if (f == NULL)
 164 +               return ERR_PTR(-ENFILE);
 165
 166         f->f_flags = flags;
 167 -       return __dentry_open(dentry, mnt, f, NULL, cred);
 168 +       return __dentry_open(path, f, NULL, cred);
 169  }
 170 -EXPORT_SYMBOL(dentry_open);
 171 +EXPORT_SYMBOL(vfs_open);
 172
 173  static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 174  {
 175 --- a/fs/splice.c
 176 +++ b/fs/splice.c
 177 @@ -1296,6 +1296,7 @@ long do_splice_direct(struct file *in, l
 178
 179         return ret;
 180  }
 181 +EXPORT_SYMBOL(do_splice_direct);
 182
 183  static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
 184                                struct pipe_inode_info *opipe,
 185 --- a/fs/namespace.c
 186 +++ b/fs/namespace.c
 187 @@ -1494,6 +1494,23 @@ void drop_collected_mounts(struct vfsmou
 188         release_mounts(&umount_list);
 189  }
 190
 191 +struct vfsmount *clone_private_mount(struct path *path)
 192 +{
 193 +       struct vfsmount *mnt;
 194 +
 195 +       if (IS_MNT_UNBINDABLE(path->mnt))
 196 +               return ERR_PTR(-EINVAL);
 197 +
 198 +       down_read(&namespace_sem);
 199 +       mnt = clone_mnt(path->mnt, path->dentry, CL_PRIVATE);
 200 +       up_read(&namespace_sem);
 201 +       if (!mnt)
 202 +               return ERR_PTR(-ENOMEM);
 203 +
 204 +       return mnt;
 205 +}
 206 +EXPORT_SYMBOL_GPL(clone_private_mount);
 207 +
 208  int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
 209                    struct vfsmount *root)
 210  {
 211 --- a/include/linux/mount.h
 212 +++ b/include/linux/mount.h
 213 @@ -100,6 +100,9 @@ extern void mnt_pin(struct vfsmount *mnt
 214  extern void mnt_unpin(struct vfsmount *mnt);
 215  extern int __mnt_is_readonly(struct vfsmount *mnt);
 216
 217 +struct path;
 218 +extern struct vfsmount *clone_private_mount(struct path *path);
 219 +
 220  extern struct vfsmount *do_kern_mount(const char *fstype, int flags,
 221                                       const char *name, void *data);
 222
 223 --- /dev/null
 224 +++ b/fs/overlayfs/overlayfs.c
 225 @@ -0,0 +1,2414 @@
 226 +#include <linux/fs.h>
 227 +#include <linux/namei.h>
 228 +#include <linux/sched.h>
 229 +#include <linux/fs_struct.h>
 230 +#include <linux/file.h>
 231 +#include <linux/xattr.h>
 232 +#include <linux/security.h>
 233 +#include <linux/device_cgroup.h>
 234 +#include <linux/mount.h>
 235 +#include <linux/splice.h>
 236 +#include <linux/slab.h>
 237 +#include <linux/parser.h>
 238 +#include <linux/module.h>
 239 +#include <linux/uaccess.h>
 240 +#include <linux/rbtree.h>
 241 +
 242 +MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
 243 +MODULE_DESCRIPTION("Overlay filesystem");
 244 +MODULE_LICENSE("GPL");
 245 +
 246 +#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
 247 +
 248 +struct ovl_fs {
 249 +       struct vfsmount *upper_mnt;
 250 +       struct vfsmount *lower_mnt;
 251 +};
 252 +
 253 +struct ovl_entry {
 254 +       struct dentry *__upperdentry;
 255 +       struct dentry *lowerdentry;
 256 +       union {
 257 +               struct {
 258 +                       u64 version;
 259 +                       bool opaque;
 260 +               };
 261 +               struct rcu_head rcu;
 262 +       };
 263 +};
 264 +
 265 +static const char *ovl_whiteout_xattr = "trusted.overlay.whiteout";
 266 +static const char *ovl_opaque_xattr = "trusted.overlay.opaque";
 267 +static const char *ovl_whiteout_symlink = "(overlay-whiteout)";
 268 +
 269 +enum ovl_path_type {
 270 +       OVL_PATH_UPPER,
 271 +       OVL_PATH_MERGE,
 272 +       OVL_PATH_LOWER,
 273 +};
 274 +
 275 +static enum ovl_path_type ovl_path_type(struct dentry *dentry)
 276 +{
 277 +       struct ovl_entry *oe = dentry->d_fsdata;
 278 +
 279 +       if (oe->__upperdentry) {
 280 +               if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode))
 281 +                       return OVL_PATH_MERGE;
 282 +               else
 283 +                       return OVL_PATH_UPPER;
 284 +       } else {
 285 +               return OVL_PATH_LOWER;
 286 +       }
 287 +}
 288 +
 289 +static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
 290 +{
 291 +       struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
 292 +       smp_read_barrier_depends();
 293 +       return upperdentry;
 294 +}
 295 +
 296 +static void ovl_path_upper(struct dentry *dentry, struct path *path)
 297 +{
 298 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 299 +       struct ovl_entry *oe = dentry->d_fsdata;
 300 +
 301 +       path->mnt = ofs->upper_mnt;
 302 +       path->dentry = ovl_upperdentry_dereference(oe);
 303 +}
 304 +
 305 +static void ovl_path_lower(struct dentry *dentry, struct path *path)
 306 +{
 307 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 308 +       struct ovl_entry *oe = dentry->d_fsdata;
 309 +
 310 +       path->mnt = ofs->lower_mnt;
 311 +       path->dentry = oe->lowerdentry;
 312 +}
 313 +
 314 +static enum ovl_path_type ovl_path_real(struct dentry *dentry,
 315 +                                       struct path *path)
 316 +{
 317 +
 318 +       enum ovl_path_type type = ovl_path_type(dentry);
 319 +
 320 +       if (type == OVL_PATH_LOWER)
 321 +               ovl_path_lower(dentry, path);
 322 +       else
 323 +               ovl_path_upper(dentry, path);
 324 +
 325 +       return type;
 326 +}
 327 +
 328 +static struct dentry *ovl_dentry_upper(struct dentry *dentry)
 329 +{
 330 +       struct ovl_entry *oe = dentry->d_fsdata;
 331 +
 332 +       return ovl_upperdentry_dereference(oe);
 333 +}
 334 +
 335 +static struct dentry *ovl_dentry_lower(struct dentry *dentry)
 336 +{
 337 +       struct ovl_entry *oe = dentry->d_fsdata;
 338 +
 339 +       return oe->lowerdentry;
 340 +}
 341 +
 342 +static struct dentry *ovl_dentry_real(struct dentry *dentry)
 343 +{
 344 +       struct ovl_entry *oe = dentry->d_fsdata;
 345 +       struct dentry *realdentry;
 346 +
 347 +       realdentry = ovl_upperdentry_dereference(oe);
 348 +       if (!realdentry)
 349 +               realdentry = oe->lowerdentry;
 350 +
 351 +       return realdentry;
 352 +}
 353 +
 354 +static bool ovl_dentry_is_opaque(struct dentry *dentry)
 355 +{
 356 +       struct ovl_entry *oe = dentry->d_fsdata;
 357 +       return oe->opaque;
 358 +}
 359 +
 360 +static void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
 361 +{
 362 +       struct ovl_entry *oe = dentry->d_fsdata;
 363 +       oe->opaque = opaque;
 364 +}
 365 +
 366 +static void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
 367 +{
 368 +       struct ovl_entry *oe = dentry->d_fsdata;
 369 +
 370 +       WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
 371 +       WARN_ON(oe->__upperdentry);
 372 +       smp_wmb();
 373 +       oe->__upperdentry = upperdentry;
 374 +}
 375 +
 376 +static void ovl_dentry_version_inc(struct dentry *dentry)
 377 +{
 378 +       struct ovl_entry *oe = dentry->d_fsdata;
 379 +
 380 +       WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
 381 +       oe->version++;
 382 +}
 383 +
 384 +static u64 ovl_dentry_version_get(struct dentry *dentry)
 385 +{
 386 +       struct ovl_entry *oe = dentry->d_fsdata;
 387 +
 388 +       WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
 389 +       return oe->version;
 390 +}
 391 +
 392 +static bool ovl_is_whiteout(struct dentry *dentry)
 393 +{
 394 +       int res;
 395 +       char val;
 396 +
 397 +       if (!dentry)
 398 +               return false;
 399 +       if (!dentry->d_inode)
 400 +               return false;
 401 +       if (!S_ISLNK(dentry->d_inode->i_mode))
 402 +               return false;
 403 +
 404 +       res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1);
 405 +       if (res == 1 && val == 'y')
 406 +               return true;
 407 +
 408 +       return false;
 409 +}
 410 +
 411 +static bool ovl_is_opaquedir(struct dentry *dentry)
 412 +{
 413 +       int res;
 414 +       char val;
 415 +
 416 +       if (!S_ISDIR(dentry->d_inode->i_mode))
 417 +               return false;
 418 +
 419 +       res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1);
 420 +       if (res == 1 && val == 'y')
 421 +               return true;
 422 +
 423 +       return false;
 424 +}
 425 +
 426 +struct ovl_cache_entry {
 427 +       const char *name;
 428 +       unsigned int len;
 429 +       unsigned int type;
 430 +       u64 ino;
 431 +       bool is_whiteout;
 432 +       struct list_head l_node;
 433 +       struct rb_node node;
 434 +};
 435 +
 436 +struct ovl_readdir_data {
 437 +       struct rb_root *root;
 438 +       struct list_head *list;
 439 +       struct list_head *middle;
 440 +       struct dentry *dir;
 441 +       int count;
 442 +       int err;
 443 +};
 444 +
 445 +struct ovl_dir_file {
 446 +       bool is_real;
 447 +       bool is_cached;
 448 +       struct list_head cursor;
 449 +       u64 cache_version;
 450 +       struct list_head cache;
 451 +       struct file *realfile;
 452 +};
 453 +
 454 +static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
 455 +{
 456 +       return container_of(n, struct ovl_cache_entry, node);
 457 +}
 458 +
 459 +static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
 460 +                                                   const char *name, int len)
 461 +{
 462 +       struct rb_node *node = root->rb_node;
 463 +       int cmp;
 464 +
 465 +       while (node) {
 466 +               struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
 467 +
 468 +               cmp = strncmp(name, p->name, len);
 469 +               if (cmp > 0)
 470 +                       node = p->node.rb_right;
 471 +               else if (cmp < 0 || len < p->len)
 472 +                       node = p->node.rb_left;
 473 +               else
 474 +                       return p;
 475 +       }
 476 +
 477 +       return NULL;
 478 +}
 479 +
 480 +static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
 481 +                                                  u64 ino, unsigned int d_type)
 482 +{
 483 +       struct ovl_cache_entry *p;
 484 +
 485 +       p = kmalloc(sizeof(*p) + len + 1, GFP_KERNEL);
 486 +       if (p) {
 487 +               char *name_copy = (char *) (p + 1);
 488 +               memcpy(name_copy, name, len);
 489 +               name_copy[len] = '\0';
 490 +               p->name = name_copy;
 491 +               p->len = len;
 492 +               p->type = d_type;
 493 +               p->ino = ino;
 494 +               p->is_whiteout = false;
 495 +       }
 496 +
 497 +       return p;
 498 +}
 499 +
 500 +static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
 501 +                                 const char *name, int len, u64 ino,
 502 +                                 unsigned int d_type)
 503 +{
 504 +       struct rb_node **newp = &rdd->root->rb_node;
 505 +       struct rb_node *parent = NULL;
 506 +       struct ovl_cache_entry *p;
 507 +
 508 +       while (*newp) {
 509 +               int cmp;
 510 +               struct ovl_cache_entry *tmp;
 511 +
 512 +               parent = *newp;
 513 +               tmp = ovl_cache_entry_from_node(*newp);
 514 +               cmp = strncmp(name, tmp->name, len);
 515 +               if (cmp > 0)
 516 +                       newp = &tmp->node.rb_right;
 517 +               else if (cmp < 0 || len < tmp->len)
 518 +                       newp = &tmp->node.rb_left;
 519 +               else
 520 +                       return 0;
 521 +       }
 522 +
 523 +       p = ovl_cache_entry_new(name, len, ino, d_type);
 524 +       if (p == NULL)
 525 +               return -ENOMEM;
 526 +
 527 +       list_add_tail(&p->l_node, rdd->list);
 528 +       rb_link_node(&p->node, parent, newp);
 529 +       rb_insert_color(&p->node, rdd->root);
 530 +
 531 +       return 0;
 532 +}
 533 +
 534 +static int ovl_fill_lower(void *buf, const char *name, int namelen,
 535 +                           loff_t offset, u64 ino, unsigned int d_type)
 536 +{
 537 +       struct ovl_readdir_data *rdd = buf;
 538 +       struct ovl_cache_entry *p;
 539 +
 540 +       rdd->count++;
 541 +       p = ovl_cache_entry_find(rdd->root, name, namelen);
 542 +       if (p) {
 543 +               list_move_tail(&p->l_node, rdd->middle);
 544 +       } else {
 545 +               p = ovl_cache_entry_new(name, namelen, ino, d_type);
 546 +               if (p == NULL)
 547 +                       rdd->err = -ENOMEM;
 548 +               else
 549 +                       list_add_tail(&p->l_node, rdd->middle);
 550 +       }
 551 +
 552 +       return rdd->err;
 553 +}
 554 +
 555 +static void ovl_cache_free(struct list_head *list)
 556 +{
 557 +       struct ovl_cache_entry *p;
 558 +       struct ovl_cache_entry *n;
 559 +
 560 +       list_for_each_entry_safe(p, n, list, l_node)
 561 +               kfree(p);
 562 +
 563 +       INIT_LIST_HEAD(list);
 564 +}
 565 +
 566 +static int ovl_fill_upper(void *buf, const char *name, int namelen,
 567 +                         loff_t offset, u64 ino, unsigned int d_type)
 568 +{
 569 +       struct ovl_readdir_data *rdd = buf;
 570 +
 571 +       rdd->count++;
 572 +       return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
 573 +}
 574 +
 575 +static int ovl_dir_read(struct path *realpath, struct ovl_readdir_data *rdd,
 576 +                         filldir_t filler)
 577 +{
 578 +       struct file *realfile;
 579 +       int err;
 580 +
 581 +       realfile = vfs_open(realpath, O_RDONLY | O_DIRECTORY, current_cred());
 582 +       if (IS_ERR(realfile))
 583 +               return PTR_ERR(realfile);
 584 +
 585 +       do {
 586 +               rdd->count = 0;
 587 +               rdd->err = 0;
 588 +               err = vfs_readdir(realfile, filler, rdd);
 589 +               if (err >= 0)
 590 +                       err = rdd->err;
 591 +       } while (!err && rdd->count);
 592 +       fput(realfile);
 593 +
 594 +       return 0;
 595 +}
 596 +
 597 +static void ovl_dir_reset(struct file *file)
 598 +{
 599 +       struct ovl_dir_file *od = file->private_data;
 600 +       enum ovl_path_type type = ovl_path_type(file->f_path.dentry);
 601 +
 602 +       if (ovl_dentry_version_get(file->f_path.dentry) != od->cache_version) {
 603 +               list_del_init(&od->cursor);
 604 +               ovl_cache_free(&od->cache);
 605 +               od->is_cached = false;
 606 +       }
 607 +       WARN_ON(!od->is_real && type != OVL_PATH_MERGE);
 608 +       if (od->is_real && type == OVL_PATH_MERGE) {
 609 +               fput(od->realfile);
 610 +               od->realfile = NULL;
 611 +               od->is_real = false;
 612 +       }
 613 +}
 614 +
 615 +static int ovl_dir_mark_whiteouts(struct ovl_readdir_data *rdd)
 616 +{
 617 +       struct ovl_cache_entry *p;
 618 +       struct dentry *dentry;
 619 +       const struct cred *old_cred;
 620 +       struct cred *override_cred;
 621 +
 622 +       override_cred = prepare_creds();
 623 +       if (!override_cred) {
 624 +               ovl_cache_free(rdd->list);
 625 +               return -ENOMEM;
 626 +       }
 627 +
 628 +       /*
 629 +        * CAP_SYS_ADMIN for getxattr
 630 +        * CAP_DAC_OVERRIDE for lookup
 631 +        */
 632 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 633 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 634 +       old_cred = override_creds(override_cred);
 635 +
 636 +       mutex_lock(&rdd->dir->d_inode->i_mutex);
 637 +       list_for_each_entry(p, rdd->list, l_node) {
 638 +               if (p->type != DT_LNK)
 639 +                       continue;
 640 +
 641 +               dentry = lookup_one_len(p->name, rdd->dir, p->len);
 642 +               if (IS_ERR(dentry))
 643 +                       continue;
 644 +
 645 +               p->is_whiteout = ovl_is_whiteout(dentry);
 646 +               dput(dentry);
 647 +       }
 648 +       mutex_unlock(&rdd->dir->d_inode->i_mutex);
 649 +
 650 +       revert_creds(old_cred);
 651 +       put_cred(override_cred);
 652 +
 653 +       return 0;
 654 +}
 655 +
 656 +static int ovl_dir_read_merged(struct path *upperpath, struct path *lowerpath,
 657 +                              struct ovl_readdir_data *rdd)
 658 +{
 659 +       int err;
 660 +       struct rb_root root = RB_ROOT;
 661 +       struct list_head middle;
 662 +
 663 +       rdd->root = &root;
 664 +       if (upperpath->dentry) {
 665 +               rdd->dir = upperpath->dentry;
 666 +               err = ovl_dir_read(upperpath, rdd, ovl_fill_upper);
 667 +               if (err)
 668 +                       goto out;
 669 +
 670 +               err = ovl_dir_mark_whiteouts(rdd);
 671 +               if (err)
 672 +                       goto out;
 673 +       }
 674 +       /*
 675 +        * Insert lowerpath entries before upperpath ones, this allows
 676 +        * offsets to be reasonably constant
 677 +        */
 678 +       list_add(&middle, rdd->list);
 679 +       rdd->middle = &middle;
 680 +       err = ovl_dir_read(lowerpath, rdd, ovl_fill_lower);
 681 +       list_del(&middle);
 682 +out:
 683 +       rdd->root = NULL;
 684 +
 685 +       return err;
 686 +}
 687 +
 688 +static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
 689 +{
 690 +       struct list_head *l;
 691 +       loff_t off;
 692 +
 693 +       l = od->cache.next;
 694 +       for (off = 0; off < pos; off++) {
 695 +               if (l == &od->cache)
 696 +                       break;
 697 +               l = l->next;
 698 +       }
 699 +       list_move_tail(&od->cursor, l);
 700 +}
 701 +
 702 +static int ovl_readdir(struct file *file, void *buf, filldir_t filler)
 703 +{
 704 +       struct ovl_dir_file *od = file->private_data;
 705 +       int res;
 706 +
 707 +       if (!file->f_pos)
 708 +               ovl_dir_reset(file);
 709 +
 710 +       if (od->is_real) {
 711 +               res = vfs_readdir(od->realfile, filler, buf);
 712 +               file->f_pos = od->realfile->f_pos;
 713 +
 714 +               return res;
 715 +       }
 716 +
 717 +       if (!od->is_cached) {
 718 +               struct path lowerpath;
 719 +               struct path upperpath;
 720 +               struct ovl_readdir_data rdd = { .list = &od->cache };
 721 +
 722 +               ovl_path_lower(file->f_path.dentry, &lowerpath);
 723 +               ovl_path_upper(file->f_path.dentry, &upperpath);
 724 +
 725 +               res = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
 726 +               if (res) {
 727 +                       ovl_cache_free(rdd.list);
 728 +                       return res;
 729 +               }
 730 +
 731 +               od->cache_version = ovl_dentry_version_get(file->f_path.dentry);
 732 +               od->is_cached = true;
 733 +
 734 +               ovl_seek_cursor(od, file->f_pos);
 735 +       }
 736 +
 737 +       while (od->cursor.next != &od->cache) {
 738 +               int over;
 739 +               loff_t off;
 740 +               struct ovl_cache_entry *p;
 741 +
 742 +               p = list_entry(od->cursor.next, struct ovl_cache_entry, l_node);
 743 +               off = file->f_pos;
 744 +               file->f_pos++;
 745 +               list_move(&od->cursor, &p->l_node);
 746 +
 747 +               if (p->is_whiteout)
 748 +                       continue;
 749 +
 750 +               over = filler(buf, p->name, p->len, off, p->ino, p->type);
 751 +               if (over)
 752 +                       break;
 753 +       }
 754 +
 755 +       return 0;
 756 +}
 757 +
 758 +static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
 759 +{
 760 +       loff_t res;
 761 +       struct ovl_dir_file *od = file->private_data;
 762 +
 763 +       mutex_lock(&file->f_dentry->d_inode->i_mutex);
 764 +       if (!file->f_pos)
 765 +               ovl_dir_reset(file);
 766 +
 767 +       if (od->is_real) {
 768 +               res = vfs_llseek(od->realfile, offset, origin);
 769 +               file->f_pos = od->realfile->f_pos;
 770 +       } else {
 771 +               res = -EINVAL;
 772 +
 773 +               switch (origin) {
 774 +               case SEEK_CUR:
 775 +                       offset += file->f_pos;
 776 +                       break;
 777 +               case SEEK_SET:
 778 +                       break;
 779 +               default:
 780 +                       goto out_unlock;
 781 +               }
 782 +               if (offset < 0)
 783 +                       goto out_unlock;
 784 +
 785 +               if (offset != file->f_pos) {
 786 +                       file->f_pos = offset;
 787 +                       if (od->is_cached)
 788 +                               ovl_seek_cursor(od, offset);
 789 +               }
 790 +               res = offset;
 791 +       }
 792 +out_unlock:
 793 +       mutex_unlock(&file->f_dentry->d_inode->i_mutex);
 794 +
 795 +       return res;
 796 +}
 797 +
 798 +static int ovl_dir_fsync(struct file *file, int datasync)
 799 +{
 800 +       struct ovl_dir_file *od = file->private_data;
 801 +
 802 +       /* May need to reopen directory if it got copied up */
 803 +       if (!od->realfile) {
 804 +               struct path upperpath;
 805 +
 806 +               ovl_path_upper(file->f_path.dentry, &upperpath);
 807 +               od->realfile = vfs_open(&upperpath, O_RDONLY, current_cred());
 808 +               if (IS_ERR(od->realfile))
 809 +                       return PTR_ERR(od->realfile);
 810 +       }
 811 +
 812 +       return vfs_fsync(od->realfile, datasync);
 813 +}
 814 +
 815 +static int ovl_dir_release(struct inode *inode, struct file *file)
 816 +{
 817 +       struct ovl_dir_file *od = file->private_data;
 818 +
 819 +       list_del(&od->cursor);
 820 +       ovl_cache_free(&od->cache);
 821 +       if (od->realfile)
 822 +               fput(od->realfile);
 823 +       kfree(od);
 824 +
 825 +       return 0;
 826 +}
 827 +
 828 +static int ovl_dir_open(struct inode *inode, struct file *file)
 829 +{
 830 +       struct path realpath;
 831 +       struct file *realfile;
 832 +       struct ovl_dir_file *od;
 833 +       enum ovl_path_type type;
 834 +
 835 +       od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
 836 +       if (!od)
 837 +               return -ENOMEM;
 838 +
 839 +       type = ovl_path_real(file->f_path.dentry, &realpath);
 840 +       realfile = vfs_open(&realpath, file->f_flags, current_cred());
 841 +       if (IS_ERR(realfile)) {
 842 +               kfree(od);
 843 +               return PTR_ERR(realfile);
 844 +       }
 845 +       INIT_LIST_HEAD(&od->cache);
 846 +       INIT_LIST_HEAD(&od->cursor);
 847 +       od->is_cached = false;
 848 +       od->realfile = realfile;
 849 +       od->is_real = (type != OVL_PATH_MERGE);
 850 +       file->private_data = od;
 851 +
 852 +       return 0;
 853 +}
 854 +
 855 +static const struct file_operations ovl_dir_operations = {
 856 +       .read           = generic_read_dir,
 857 +       .open           = ovl_dir_open,
 858 +       .readdir        = ovl_readdir,
 859 +       .llseek         = ovl_dir_llseek,
 860 +       .fsync          = ovl_dir_fsync,
 861 +       .release        = ovl_dir_release,
 862 +};
 863 +
 864 +static const struct inode_operations ovl_dir_inode_operations;
 865 +
 866 +static void ovl_entry_free(struct rcu_head *head)
 867 +{
 868 +       struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu);
 869 +       kfree(oe);
 870 +}
 871 +
 872 +static void ovl_dentry_release(struct dentry *dentry)
 873 +{
 874 +       struct ovl_entry *oe = dentry->d_fsdata;
 875 +
 876 +       if (oe) {
 877 +               dput(oe->__upperdentry);
 878 +               dput(oe->lowerdentry);
 879 +               call_rcu(&oe->rcu, ovl_entry_free);
 880 +       }
 881 +}
 882 +
 883 +static const struct dentry_operations ovl_dentry_operations = {
 884 +       .d_release = ovl_dentry_release,
 885 +};
 886 +
 887 +static struct dentry *ovl_lookup_real(struct dentry *dir, struct qstr *name)
 888 +{
 889 +       struct dentry *dentry;
 890 +
 891 +       mutex_lock(&dir->d_inode->i_mutex);
 892 +       dentry = lookup_one_len(name->name, dir, name->len);
 893 +       mutex_unlock(&dir->d_inode->i_mutex);
 894 +
 895 +       if (IS_ERR(dentry)) {
 896 +               if (PTR_ERR(dentry) == -ENOENT)
 897 +                       dentry = NULL;
 898 +       } else if (!dentry->d_inode) {
 899 +               dput(dentry);
 900 +               dentry = NULL;
 901 +       }
 902 +       return dentry;
 903 +}
 904 +
 905 +static struct ovl_entry *ovl_alloc_entry(void)
 906 +{
 907 +       return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
 908 +}
 909 +
 910 +static struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
 911 +                                  struct ovl_entry *oe);
 912 +
 913 +static int ovl_whiteout(struct dentry *upperdir, struct dentry *dentry)
 914 +{
 915 +       int err;
 916 +       struct dentry *newdentry;
 917 +       const struct cred *old_cred;
 918 +       struct cred *override_cred;
 919 +
 920 +       /* FIXME: recheck lower dentry to see if whiteout is really needed */
 921 +
 922 +       err = -ENOMEM;
 923 +       override_cred = prepare_creds();
 924 +       if (!override_cred)
 925 +               goto out;
 926 +
 927 +       /*
 928 +        * CAP_SYS_ADMIN for setxattr
 929 +        * CAP_DAC_OVERRIDE for symlink creation
 930 +        */
 931 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 932 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 933 +       override_cred->fsuid = 0;
 934 +       override_cred->fsgid = 0;
 935 +       old_cred = override_creds(override_cred);
 936 +
 937 +       newdentry = lookup_one_len(dentry->d_name.name, upperdir,
 938 +                                  dentry->d_name.len);
 939 +       err = PTR_ERR(newdentry);
 940 +       if (IS_ERR(newdentry))
 941 +               goto out_put_cred;
 942 +
 943 +       /* Just been removed within the same locked region */
 944 +       WARN_ON(newdentry->d_inode);
 945 +
 946 +       err = vfs_symlink(upperdir->d_inode, newdentry, ovl_whiteout_symlink);
 947 +       if (err)
 948 +               goto out_dput;
 949 +
 950 +       ovl_dentry_version_inc(dentry->d_parent);
 951 +
 952 +       err = vfs_setxattr(newdentry, ovl_whiteout_xattr, "y", 1, 0);
 953 +       if (err)
 954 +               vfs_unlink(upperdir->d_inode, newdentry);
 955 +
 956 +out_dput:
 957 +       dput(newdentry);
 958 +out_put_cred:
 959 +       revert_creds(old_cred);
 960 +       put_cred(override_cred);
 961 +out:
 962 +       if (err) {
 963 +               /*
 964 +                * There's no way to recover from failure to whiteout.
 965 +                * What should we do?  Log a big fat error and... ?
 966 +                */
 967 +               printk(KERN_ERR "overlayfs: ERROR - failed to whiteout '%s'\n",
 968 +                      dentry->d_name.name);
 969 +       }
 970 +
 971 +       return err;
 972 +}
 973 +
 974 +static struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 975 +                                  struct nameidata *nd)
 976 +{
 977 +       struct ovl_entry *oe;
 978 +       struct dentry *upperdir;
 979 +       struct dentry *lowerdir;
 980 +       struct dentry *upperdentry = NULL;
 981 +       struct dentry *lowerdentry = NULL;
 982 +       struct inode *inode = NULL;
 983 +       int err;
 984 +
 985 +       err = -ENOMEM;
 986 +       oe = ovl_alloc_entry();
 987 +       if (!oe)
 988 +               goto out;
 989 +
 990 +       upperdir = ovl_dentry_upper(dentry->d_parent);
 991 +       lowerdir = ovl_dentry_lower(dentry->d_parent);
 992 +
 993 +       if (upperdir) {
 994 +               upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
 995 +               err = PTR_ERR(upperdentry);
 996 +               if (IS_ERR(upperdentry))
 997 +                       goto out_put_dir;
 998 +
 999 +               if (lowerdir && upperdentry &&
1000 +                   (S_ISLNK(upperdentry->d_inode->i_mode) ||
1001 +                    S_ISDIR(upperdentry->d_inode->i_mode))) {
1002 +                       const struct cred *old_cred;
1003 +                       struct cred *override_cred;
1004 +
1005 +                       err = -ENOMEM;
1006 +                       override_cred = prepare_creds();
1007 +                       if (!override_cred)
1008 +                               goto out_dput_upper;
1009 +
1010 +                       /* CAP_SYS_ADMIN needed for getxattr */
1011 +                       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1012 +                       old_cred = override_creds(override_cred);
1013 +
1014 +                       if (ovl_is_opaquedir(upperdentry)) {
1015 +                               oe->opaque = true;
1016 +                       } else if (ovl_is_whiteout(upperdentry)) {
1017 +                               dput(upperdentry);
1018 +                               upperdentry = NULL;
1019 +                               oe->opaque = true;
1020 +                       }
1021 +                       revert_creds(old_cred);
1022 +                       put_cred(override_cred);
1023 +               }
1024 +       }
1025 +       if (lowerdir && !oe->opaque) {
1026 +               lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
1027 +               err = PTR_ERR(lowerdentry);
1028 +               if (IS_ERR(lowerdentry))
1029 +                       goto out_dput_upper;
1030 +       }
1031 +
1032 +       if (lowerdentry && upperdentry &&
1033 +           (!S_ISDIR(upperdentry->d_inode->i_mode) ||
1034 +            !S_ISDIR(lowerdentry->d_inode->i_mode))) {
1035 +               dput(lowerdentry);
1036 +               lowerdentry = NULL;
1037 +               oe->opaque = true;
1038 +       }
1039 +
1040 +       if (lowerdentry || upperdentry) {
1041 +               struct dentry *realdentry;
1042 +
1043 +               realdentry = upperdentry ? upperdentry : lowerdentry;
1044 +               err = -ENOMEM;
1045 +               inode = ovl_new_inode(dir->i_sb, realdentry->d_inode->i_mode, oe);
1046 +               if (!inode)
1047 +                       goto out_dput;
1048 +       }
1049 +
1050 +       if (upperdentry)
1051 +               oe->__upperdentry = upperdentry;
1052 +
1053 +       if (lowerdentry)
1054 +               oe->lowerdentry = lowerdentry;
1055 +
1056 +       dentry->d_fsdata = oe;
1057 +       dentry->d_op = &ovl_dentry_operations;
1058 +       d_add(dentry, inode);
1059 +
1060 +       return NULL;
1061 +
1062 +out_dput:
1063 +       dput(lowerdentry);
1064 +out_dput_upper:
1065 +       dput(upperdentry);
1066 +out_put_dir:
1067 +       kfree(oe);
1068 +out:
1069 +       return ERR_PTR(err);
1070 +}
1071 +
1072 +static int ovl_copy_up_xattr(struct dentry *old, struct dentry *new)
1073 +{
1074 +       ssize_t list_size, size;
1075 +       char *buf, *name, *value;
1076 +       int error;
1077 +
1078 +       if (!old->d_inode->i_op->getxattr ||
1079 +           !new->d_inode->i_op->getxattr)
1080 +               return 0;
1081 +
1082 +       list_size = vfs_listxattr(old, NULL, 0);
1083 +       if (list_size <= 0) {
1084 +               if (list_size == -EOPNOTSUPP)
1085 +                       return 0;
1086 +               return list_size;
1087 +       }
1088 +
1089 +       buf = kzalloc(list_size, GFP_KERNEL);
1090 +       if (!buf)
1091 +               return -ENOMEM;
1092 +
1093 +       error = -ENOMEM;
1094 +       value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL);
1095 +       if (!value)
1096 +               goto out;
1097 +
1098 +       list_size = vfs_listxattr(old, buf, list_size);
1099 +       if (list_size <= 0) {
1100 +               error = list_size;
1101 +               goto out_free_value;
1102 +       }
1103 +
1104 +       for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
1105 +               size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX);
1106 +               if (size <= 0) {
1107 +                       error = size;
1108 +                       goto out_free_value;
1109 +               }
1110 +               error = vfs_setxattr(new, name, value, size, 0);
1111 +               if (error)
1112 +                       goto out_free_value;
1113 +       }
1114 +
1115 +out_free_value:
1116 +       kfree(value);
1117 +out:
1118 +       kfree(buf);
1119 +       return error;
1120 +}
1121 +
1122 +static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
1123 +{
1124 +       struct file *old_file;
1125 +       struct file *new_file;
1126 +       int error = 0;
1127 +
1128 +       if (len == 0)
1129 +               return 0;
1130 +
1131 +       old_file = vfs_open(old, O_RDONLY, current_cred());
1132 +       if (IS_ERR(old_file))
1133 +               return PTR_ERR(old_file);
1134 +
1135 +       new_file = vfs_open(new, O_WRONLY, current_cred());
1136 +       if (IS_ERR(new_file)) {
1137 +               error = PTR_ERR(new_file);
1138 +               goto out_fput;
1139 +       }
1140 +
1141 +       /* FIXME: copy up sparse files efficiently */
1142 +       while (len) {
1143 +               loff_t offset = new_file->f_pos;
1144 +               size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
1145 +               long bytes;
1146 +
1147 +               if (len < this_len)
1148 +                       this_len = len;
1149 +
1150 +               if (signal_pending_state(TASK_KILLABLE, current)) {
1151 +                       error = -EINTR;
1152 +                       break;
1153 +               }
1154 +
1155 +               bytes = do_splice_direct(old_file, &offset, new_file, this_len,
1156 +                                SPLICE_F_MOVE);
1157 +               if (bytes <= 0) {
1158 +                       error = bytes;
1159 +                       break;
1160 +               }
1161 +
1162 +               len -= bytes;
1163 +       }
1164 +
1165 +       fput(new_file);
1166 +out_fput:
1167 +       fput(old_file);
1168 +       return error;
1169 +}
1170 +
1171 +static struct dentry *ovl_lookup_create(struct dentry *upperdir,
1172 +                                       struct dentry *template)
1173 +{
1174 +       int err;
1175 +       struct dentry *newdentry;
1176 +       struct qstr *name = &template->d_name;
1177 +
1178 +       newdentry = lookup_one_len(name->name, upperdir, name->len);
1179 +       if (IS_ERR(newdentry))
1180 +               return newdentry;
1181 +
1182 +       if (newdentry->d_inode) {
1183 +               const struct cred *old_cred;
1184 +               struct cred *override_cred;
1185 +
1186 +               /* No need to check whiteout if lower parent is non-existent */
1187 +               err = -EEXIST;
1188 +               if (!ovl_dentry_lower(template->d_parent))
1189 +                       goto out_dput;
1190 +
1191 +               if (!S_ISLNK(newdentry->d_inode->i_mode))
1192 +                       goto out_dput;
1193 +
1194 +               err = -ENOMEM;
1195 +               override_cred = prepare_creds();
1196 +               if (!override_cred)
1197 +                       goto out_dput;
1198 +
1199 +               /*
1200 +                * CAP_SYS_ADMIN for getxattr
1201 +                * CAP_FOWNER for unlink in sticky directory
1202 +                */
1203 +               cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1204 +               cap_raise(override_cred->cap_effective, CAP_FOWNER);
1205 +               old_cred = override_creds(override_cred);
1206 +
1207 +               err = -EEXIST;
1208 +               if (ovl_is_whiteout(newdentry))
1209 +                       err = vfs_unlink(upperdir->d_inode, newdentry);
1210 +
1211 +               revert_creds(old_cred);
1212 +               put_cred(override_cred);
1213 +               if (err)
1214 +                       goto out_dput;
1215 +
1216 +               dput(newdentry);
1217 +               newdentry = lookup_one_len(name->name, upperdir, name->len);
1218 +               if (IS_ERR(newdentry)) {
1219 +                       ovl_whiteout(upperdir, template);
1220 +                       return newdentry;
1221 +               }
1222 +
1223 +               /*
1224 +                * Whiteout just been successfully removed, parent
1225 +                * i_mutex is still held, there's no way the lookup
1226 +                * could return positive.
1227 +                */
1228 +               WARN_ON(newdentry->d_inode);
1229 +       }
1230 +
1231 +       return newdentry;
1232 +
1233 +out_dput:
1234 +       dput(newdentry);
1235 +       return ERR_PTR(err);
1236 +}
1237 +
1238 +static struct dentry *ovl_upper_create(struct dentry *upperdir,
1239 +                                      struct dentry *dentry,
1240 +                                      struct kstat *stat, const char *link)
1241 +{
1242 +       int err;
1243 +       struct dentry *newdentry;
1244 +       struct inode *dir = upperdir->d_inode;
1245 +
1246 +       newdentry = ovl_lookup_create(upperdir, dentry);
1247 +       if (IS_ERR(newdentry))
1248 +               goto out;
1249 +
1250 +       switch (stat->mode & S_IFMT) {
1251 +       case S_IFREG:
1252 +               err = vfs_create(dir, newdentry, stat->mode, NULL);
1253 +               break;
1254 +
1255 +       case S_IFDIR:
1256 +               err = vfs_mkdir(dir, newdentry, stat->mode);
1257 +               break;
1258 +
1259 +       case S_IFCHR:
1260 +       case S_IFBLK:
1261 +       case S_IFIFO:
1262 +       case S_IFSOCK:
1263 +               err = vfs_mknod(dir, newdentry, stat->mode, stat->rdev);
1264 +               break;
1265 +
1266 +       case S_IFLNK:
1267 +               err = vfs_symlink(dir, newdentry, link);
1268 +               break;
1269 +
1270 +       default:
1271 +               err = -EPERM;
1272 +       }
1273 +       if (err) {
1274 +               if (ovl_dentry_is_opaque(dentry))
1275 +                       ovl_whiteout(upperdir, dentry);
1276 +               dput(newdentry);
1277 +               newdentry = ERR_PTR(err);
1278 +       }
1279 +
1280 +out:
1281 +       return newdentry;
1282 +
1283 +}
1284 +
1285 +static char *ovl_read_symlink(struct dentry *realdentry)
1286 +{
1287 +       int res;
1288 +       char *buf;
1289 +       struct inode *inode = realdentry->d_inode;
1290 +       mm_segment_t old_fs;
1291 +
1292 +       res = -EINVAL;
1293 +       if (!inode->i_op->readlink)
1294 +               goto err;
1295 +
1296 +       res = -ENOMEM;
1297 +       buf = (char *) __get_free_page(GFP_KERNEL);
1298 +       if (!buf)
1299 +               goto err;
1300 +
1301 +       old_fs = get_fs();
1302 +       set_fs(get_ds());
1303 +       /* The cast to a user pointer is valid due to the set_fs() */
1304 +       res = inode->i_op->readlink(realdentry,
1305 +                                   (char __user *)buf, PAGE_SIZE - 1);
1306 +       set_fs(old_fs);
1307 +       if (res < 0) {
1308 +               free_page((unsigned long) buf);
1309 +               goto err;
1310 +       }
1311 +       buf[res] = '\0';
1312 +
1313 +       return buf;
1314 +
1315 +err:
1316 +       return ERR_PTR(res);
1317 +}
1318 +
1319 +static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
1320 +{
1321 +       struct iattr attr = {
1322 +               .ia_valid = ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
1323 +               .ia_atime = stat->atime,
1324 +               .ia_mtime = stat->mtime,
1325 +       };
1326 +
1327 +       return notify_change(upperdentry, &attr);
1328 +}
1329 +
1330 +static int ovl_set_mode(struct dentry *upperdentry, umode_t mode)
1331 +{
1332 +       struct iattr attr = {
1333 +               .ia_valid = ATTR_MODE,
1334 +               .ia_mode = mode,
1335 +       };
1336 +
1337 +       return notify_change(upperdentry, &attr);
1338 +}
1339 +
1340 +static int ovl_set_opaque(struct dentry *upperdentry)
1341 +{
1342 +       int err;
1343 +       const struct cred *old_cred;
1344 +       struct cred *override_cred;
1345 +
1346 +       override_cred = prepare_creds();
1347 +       if (!override_cred)
1348 +               return -ENOMEM;
1349 +
1350 +       /* CAP_SYS_ADMIN for setxattr of "trusted" namespace */
1351 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1352 +       old_cred = override_creds(override_cred);
1353 +       err = vfs_setxattr(upperdentry, ovl_opaque_xattr, "y", 1, 0);
1354 +       revert_creds(old_cred);
1355 +       put_cred(override_cred);
1356 +
1357 +       return err;
1358 +}
1359 +
1360 +static int ovl_remove_opaque(struct dentry *upperdentry)
1361 +{
1362 +       int err;
1363 +       const struct cred *old_cred;
1364 +       struct cred *override_cred;
1365 +
1366 +       override_cred = prepare_creds();
1367 +       if (!override_cred)
1368 +               return -ENOMEM;
1369 +
1370 +       /* CAP_SYS_ADMIN for removexattr of "trusted" namespace */
1371 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1372 +       old_cred = override_creds(override_cred);
1373 +       err = vfs_removexattr(upperdentry, ovl_opaque_xattr);
1374 +       revert_creds(old_cred);
1375 +       put_cred(override_cred);
1376 +
1377 +       return err;
1378 +}
1379 +
1380 +static int ovl_copy_up_locked(struct dentry *upperdir, struct dentry *dentry,
1381 +                             struct path *lowerpath, struct kstat *stat,
1382 +                             const char *link)
1383 +{
1384 +       int err;
1385 +       struct path newpath;
1386 +       umode_t mode = stat->mode;
1387 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
1388 +
1389 +       /* Can't properly set mode on creation because of the umask */
1390 +       stat->mode &= S_IFMT;
1391 +
1392 +       newpath.mnt = ofs->upper_mnt;
1393 +       newpath.dentry = ovl_upper_create(upperdir, dentry, stat, link);
1394 +       if (IS_ERR(newpath.dentry)) {
1395 +               err = PTR_ERR(newpath.dentry);
1396 +
1397 +               /* Already copied up? */
1398 +               if (err == -EEXIST && ovl_path_type(dentry) != OVL_PATH_LOWER)
1399 +                       return 0;
1400 +
1401 +               return err;
1402 +       }
1403 +
1404 +       if (S_ISREG(stat->mode)) {
1405 +               err = ovl_copy_up_data(lowerpath, &newpath, stat->size);
1406 +               if (err)
1407 +                       goto err_remove;
1408 +       }
1409 +
1410 +       err = ovl_copy_up_xattr(lowerpath->dentry, newpath.dentry);
1411 +       if (err)
1412 +               goto err_remove;
1413 +
1414 +       mutex_lock(&newpath.dentry->d_inode->i_mutex);
1415 +       if (!S_ISLNK(stat->mode))
1416 +               err = ovl_set_mode(newpath.dentry, mode);
1417 +       if (!err)
1418 +               err = ovl_set_timestamps(newpath.dentry, stat);
1419 +       mutex_unlock(&newpath.dentry->d_inode->i_mutex);
1420 +       if (err)
1421 +               goto err_remove;
1422 +
1423 +       ovl_dentry_update(dentry, newpath.dentry);
1424 +
1425 +       /*
1426 +        * Easiest way to get rid of the lower dentry reference is to
1427 +        * drop this dentry.  This is neither needed nor possible for
1428 +        * directories.
1429 +        */
1430 +       if (!S_ISDIR(stat->mode))
1431 +               d_drop(dentry);
1432 +
1433 +       return 0;
1434 +
1435 +err_remove:
1436 +       if (S_ISDIR(stat->mode))
1437 +               vfs_rmdir(upperdir->d_inode, newpath.dentry);
1438 +       else
1439 +               vfs_unlink(upperdir->d_inode, newpath.dentry);
1440 +
1441 +       dput(newpath.dentry);
1442 +
1443 +       return err;
1444 +}
1445 +
1446 +static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
1447 +                          struct path *lowerpath, struct kstat *stat)
1448 +{
1449 +       int err;
1450 +       struct kstat pstat;
1451 +       struct path parentpath;
1452 +       struct dentry *upperdir;
1453 +       const struct cred *old_cred;
1454 +       struct cred *override_cred;
1455 +       char *link = NULL;
1456 +
1457 +       ovl_path_upper(parent, &parentpath);
1458 +       upperdir = parentpath.dentry;
1459 +
1460 +       err = vfs_getattr(parentpath.mnt, parentpath.dentry, &pstat);
1461 +       if (err)
1462 +               return err;
1463 +
1464 +       if (S_ISLNK(stat->mode)) {
1465 +               link = ovl_read_symlink(lowerpath->dentry);
1466 +               if (IS_ERR(link))
1467 +                       return PTR_ERR(link);
1468 +       }
1469 +
1470 +       err = -ENOMEM;
1471 +       override_cred = prepare_creds();
1472 +       if (!override_cred)
1473 +               goto out_free_link;
1474 +
1475 +       override_cred->fsuid = stat->uid;
1476 +       override_cred->fsgid = stat->gid;
1477 +       /*
1478 +        * CAP_SYS_ADMIN for copying up extended attributes
1479 +        * CAP_DAC_OVERRIDE for create
1480 +        * CAP_FOWNER for chmod, timestamp update
1481 +        * CAP_FSETID for chmod
1482 +        * CAP_MKNOD for mknod
1483 +        */
1484 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1485 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
1486 +       cap_raise(override_cred->cap_effective, CAP_FOWNER);
1487 +       cap_raise(override_cred->cap_effective, CAP_FSETID);
1488 +       cap_raise(override_cred->cap_effective, CAP_MKNOD);
1489 +       old_cred = override_creds(override_cred);
1490 +
1491 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1492 +       /*
1493 +        * Using upper filesystem locking to protect against copy up
1494 +        * racing with rename (rename means the copy up was already
1495 +        * successful).
1496 +        */
1497 +       if (dentry->d_parent != parent) {
1498 +               WARN_ON((ovl_path_type(dentry) == OVL_PATH_LOWER));
1499 +               err = 0;
1500 +       } else {
1501 +               err = ovl_copy_up_locked(upperdir, dentry, lowerpath,
1502 +                                        stat, link);
1503 +               if (!err) {
1504 +                       /* Restore timestamps on parent (best effort) */
1505 +                       ovl_set_timestamps(upperdir, &pstat);
1506 +               }
1507 +       }
1508 +
1509 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1510 +
1511 +       revert_creds(old_cred);
1512 +       put_cred(override_cred);
1513 +
1514 +out_free_link:
1515 +       if (link)
1516 +               free_page((unsigned long) link);
1517 +
1518 +       return err;
1519 +}
1520 +
1521 +static int ovl_copy_up(struct dentry *dentry)
1522 +{
1523 +       int err;
1524 +
1525 +       err = 0;
1526 +       while (!err) {
1527 +               struct dentry *next;
1528 +               struct dentry *parent;
1529 +               struct path lowerpath;
1530 +               struct kstat stat;
1531 +               enum ovl_path_type type = ovl_path_type(dentry);
1532 +
1533 +               if (type != OVL_PATH_LOWER)
1534 +                       break;
1535 +
1536 +               next = dget(dentry);
1537 +               /* find the topmost dentry not yet copied up */
1538 +               for (;;) {
1539 +                       parent = dget_parent(next);
1540 +
1541 +                       type = ovl_path_type(parent);
1542 +                       if (type != OVL_PATH_LOWER)
1543 +                               break;
1544 +
1545 +                       dput(next);
1546 +                       next = parent;
1547 +               }
1548 +
1549 +               ovl_path_lower(next, &lowerpath);
1550 +               err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
1551 +               if (!err)
1552 +                       err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
1553 +
1554 +               dput(parent);
1555 +               dput(next);
1556 +       }
1557 +
1558 +       return err;
1559 +}
1560 +
1561 +/* Optimize by not copying up the file first and truncating later */
1562 +static int ovl_copy_up_truncate(struct dentry *dentry, loff_t size)
1563 +{
1564 +       int err;
1565 +       struct kstat stat;
1566 +       struct path lowerpath;
1567 +       struct dentry *parent = dget_parent(dentry);
1568 +
1569 +       err = ovl_copy_up(parent);
1570 +       if (err)
1571 +               goto out_dput_parent;
1572 +
1573 +       ovl_path_lower(dentry, &lowerpath);
1574 +       err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
1575 +       if (err)
1576 +               goto out_dput_parent;
1577 +
1578 +       if (size < stat.size)
1579 +               stat.size = size;
1580 +
1581 +       err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
1582 +
1583 +out_dput_parent:
1584 +       dput(parent);
1585 +       return err;
1586 +}
1587 +
1588 +static int ovl_setattr(struct dentry *dentry, struct iattr *attr)
1589 +{
1590 +       struct dentry *upperdentry;
1591 +       int err;
1592 +
1593 +       if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry))
1594 +               err = ovl_copy_up_truncate(dentry, attr->ia_size);
1595 +       else
1596 +               err = ovl_copy_up(dentry);
1597 +       if (err)
1598 +               return err;
1599 +
1600 +       upperdentry = ovl_dentry_upper(dentry);
1601 +
1602 +       if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
1603 +               attr->ia_valid &= ~ATTR_MODE;
1604 +
1605 +       mutex_lock(&upperdentry->d_inode->i_mutex);
1606 +       err = notify_change(upperdentry, attr);
1607 +       mutex_unlock(&upperdentry->d_inode->i_mutex);
1608 +
1609 +       return err;
1610 +}
1611 +
1612 +static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
1613 +                        struct kstat *stat)
1614 +{
1615 +       struct path realpath;
1616 +
1617 +       ovl_path_real(dentry, &realpath);
1618 +       return vfs_getattr(realpath.mnt, realpath.dentry, stat);
1619 +}
1620 +
1621 +static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
1622 +                        struct kstat *stat)
1623 +{
1624 +       int err;
1625 +       enum ovl_path_type type;
1626 +       struct path realpath;
1627 +
1628 +       type = ovl_path_real(dentry, &realpath);
1629 +       err = vfs_getattr(realpath.mnt, realpath.dentry, stat);
1630 +       if (err)
1631 +               return err;
1632 +
1633 +       stat->dev = dentry->d_sb->s_dev;
1634 +       stat->ino = dentry->d_inode->i_ino;
1635 +
1636 +       /*
1637 +        * It's probably not worth it to count subdirs to get the
1638 +        * correct link count.  nlink=1 seems to pacify 'find' and
1639 +        * other utilities.
1640 +        */
1641 +       if (type == OVL_PATH_MERGE)
1642 +               stat->nlink = 1;
1643 +
1644 +       return 0;
1645 +}
1646 +
1647 +static int ovl_permission(struct inode *inode, int mask, unsigned int flags)
1648 +{
1649 +       struct ovl_entry *oe;
1650 +       struct dentry *alias = NULL;
1651 +       struct inode *realinode;
1652 +       struct dentry *realdentry;
1653 +       bool is_upper;
1654 +       int err;
1655 +
1656 +       if (S_ISDIR(inode->i_mode)) {
1657 +               oe = inode->i_private;
1658 +       } else if (flags & IPERM_FLAG_RCU) {
1659 +               return -ECHILD;
1660 +       } else {
1661 +               /*
1662 +                * For non-directories find an alias and get the info
1663 +                * from there.
1664 +                */
1665 +               spin_lock(&inode->i_lock);
1666 +               if (WARN_ON(list_empty(&inode->i_dentry))) {
1667 +                       spin_unlock(&inode->i_lock);
1668 +                       return -ENOENT;
1669 +               }
1670 +               alias = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1671 +               dget(alias);
1672 +               spin_unlock(&inode->i_lock);
1673 +               oe = alias->d_fsdata;
1674 +       }
1675 +
1676 +       realdentry = ovl_upperdentry_dereference(oe);
1677 +       is_upper = true;
1678 +       if (!realdentry) {
1679 +               realdentry = oe->lowerdentry;
1680 +               is_upper = false;
1681 +       }
1682 +
1683 +       /* Careful in RCU walk mode */
1684 +       realinode = ACCESS_ONCE(realdentry->d_inode);
1685 +       if (!realinode) {
1686 +               WARN_ON(!(flags & IPERM_FLAG_RCU));
1687 +               return -ENOENT;
1688 +       }
1689 +
1690 +       if (mask & MAY_WRITE) {
1691 +               umode_t mode = realinode->i_mode;
1692 +
1693 +               /*
1694 +                * Writes will always be redirected to upper layer, so
1695 +                * ignore lower layer being read-only.
1696 +                */
1697 +               err = -EROFS;
1698 +               if (is_upper && IS_RDONLY(realinode) &&
1699 +                   (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
1700 +                       goto out_dput;
1701 +
1702 +               /*
1703 +                * Nobody gets write access to an immutable file.
1704 +                */
1705 +               err = -EACCES;
1706 +               if (IS_IMMUTABLE(realinode))
1707 +                       goto out_dput;
1708 +       }
1709 +
1710 +       if (realinode->i_op->permission)
1711 +               err = realinode->i_op->permission(realinode, mask, flags);
1712 +       else
1713 +               err = generic_permission(realinode, mask, flags,
1714 +                                        realinode->i_op->check_acl);
1715 +out_dput:
1716 +       dput(alias);
1717 +       return err;
1718 +}
1719 +
1720 +static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
1721 +                            const char *link)
1722 +{
1723 +       int err;
1724 +       struct dentry *newdentry;
1725 +       struct dentry *upperdir;
1726 +       struct inode *inode;
1727 +       struct kstat stat = {
1728 +               .mode = mode,
1729 +               .rdev = rdev,
1730 +       };
1731 +
1732 +       err = -ENOMEM;
1733 +       inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
1734 +       if (!inode)
1735 +               goto out;
1736 +
1737 +       err = ovl_copy_up(dentry->d_parent);
1738 +       if (err)
1739 +               goto out_iput;
1740 +
1741 +       upperdir = ovl_dentry_upper(dentry->d_parent);
1742 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1743 +
1744 +       newdentry = ovl_upper_create(upperdir, dentry, &stat, link);
1745 +       err = PTR_ERR(newdentry);
1746 +       if (IS_ERR(newdentry))
1747 +               goto out_unlock;
1748 +
1749 +       ovl_dentry_version_inc(dentry->d_parent);
1750 +       if (ovl_dentry_is_opaque(dentry) && S_ISDIR(mode)) {
1751 +               err = ovl_set_opaque(newdentry);
1752 +               if (err) {
1753 +                       vfs_rmdir(upperdir->d_inode, newdentry);
1754 +                       ovl_whiteout(upperdir, dentry);
1755 +                       goto out_dput;
1756 +               }
1757 +       }
1758 +       ovl_dentry_update(dentry, newdentry);
1759 +       d_instantiate(dentry, inode);
1760 +       inode = NULL;
1761 +       newdentry = NULL;
1762 +       err = 0;
1763 +
1764 +out_dput:
1765 +       dput(newdentry);
1766 +out_unlock:
1767 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1768 +out_iput:
1769 +       iput(inode);
1770 +out:
1771 +       return err;
1772 +}
1773 +
1774 +static int ovl_create(struct inode *dir, struct dentry *dentry, int mode,
1775 +                       struct nameidata *nd)
1776 +{
1777 +       return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
1778 +}
1779 +
1780 +static int ovl_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1781 +{
1782 +       return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
1783 +}
1784 +
1785 +static int ovl_mknod(struct inode *dir, struct dentry *dentry, int mode,
1786 +                      dev_t rdev)
1787 +{
1788 +       return ovl_create_object(dentry, mode, rdev, NULL);
1789 +}
1790 +
1791 +static int ovl_symlink(struct inode *dir, struct dentry *dentry,
1792 +                        const char *link)
1793 +{
1794 +       return ovl_create_object(dentry, S_IFLNK, 0, link);
1795 +}
1796 +
1797 +struct ovl_link_data {
1798 +       struct dentry *realdentry;
1799 +       void *cookie;
1800 +};
1801 +
1802 +static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
1803 +{
1804 +       void *ret;
1805 +       struct dentry *realdentry;
1806 +       struct inode *realinode;
1807 +
1808 +       realdentry = ovl_dentry_real(dentry);
1809 +       realinode = realdentry->d_inode;
1810 +
1811 +       if (WARN_ON(!realinode->i_op->follow_link))
1812 +               return ERR_PTR(-EPERM);
1813 +
1814 +       ret = realinode->i_op->follow_link(realdentry, nd);
1815 +       if (IS_ERR(ret))
1816 +               return ret;
1817 +
1818 +       if (realinode->i_op->put_link) {
1819 +               struct ovl_link_data *data;
1820 +
1821 +               data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
1822 +               if (!data) {
1823 +                       realinode->i_op->put_link(realdentry, nd, ret);
1824 +                       return ERR_PTR(-ENOMEM);
1825 +               }
1826 +               data->realdentry = realdentry;
1827 +               data->cookie = ret;
1828 +
1829 +               return data;
1830 +       } else {
1831 +               return NULL;
1832 +       }
1833 +}
1834 +
1835 +static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
1836 +{
1837 +       struct inode *realinode;
1838 +       struct ovl_link_data *data = c;
1839 +
1840 +       if (!data)
1841 +               return;
1842 +
1843 +       realinode = data->realdentry->d_inode;
1844 +       realinode->i_op->put_link(data->realdentry, nd, data->cookie);
1845 +       kfree(data);
1846 +}
1847 +
1848 +static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
1849 +{
1850 +       struct path realpath;
1851 +       struct inode *realinode;
1852 +
1853 +       ovl_path_real(dentry, &realpath);
1854 +       realinode = realpath.dentry->d_inode;
1855 +
1856 +       if (!realinode->i_op->readlink)
1857 +               return -EINVAL;
1858 +
1859 +       touch_atime(realpath.mnt, realpath.dentry);
1860 +
1861 +       return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
1862 +}
1863 +
1864 +static int ovl_do_remove(struct dentry *dentry, bool is_dir)
1865 +{
1866 +       int err;
1867 +       enum ovl_path_type type;
1868 +       struct path realpath;
1869 +       struct dentry *upperdir;
1870 +
1871 +       err = ovl_copy_up(dentry->d_parent);
1872 +       if (err)
1873 +               return err;
1874 +
1875 +       upperdir = ovl_dentry_upper(dentry->d_parent);
1876 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1877 +       type = ovl_path_real(dentry, &realpath);
1878 +       if (type != OVL_PATH_LOWER) {
1879 +               err = -ESTALE;
1880 +               if (realpath.dentry->d_parent != upperdir)
1881 +                       goto out_d_drop;
1882 +
1883 +               if (is_dir)
1884 +                       err = vfs_rmdir(upperdir->d_inode, realpath.dentry);
1885 +               else
1886 +                       err = vfs_unlink(upperdir->d_inode, realpath.dentry);
1887 +               if (err)
1888 +                       goto out_d_drop;
1889 +
1890 +               ovl_dentry_version_inc(dentry->d_parent);
1891 +       }
1892 +
1893 +       if (type != OVL_PATH_UPPER || ovl_dentry_is_opaque(dentry))
1894 +               err = ovl_whiteout(upperdir, dentry);
1895 +
1896 +       /*
1897 +        * Keeping this dentry hashed would mean having to release
1898 +        * upperpath/lowerpath, which could only be done if we are the
1899 +        * sole user of this dentry.  Too tricky...  Just unhash for
1900 +        * now.
1901 +        */
1902 +out_d_drop:
1903 +       d_drop(dentry);
1904 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1905 +
1906 +       return err;
1907 +}
1908 +
1909 +static int ovl_unlink(struct inode *dir, struct dentry *dentry)
1910 +{
1911 +       return ovl_do_remove(dentry, false);
1912 +}
1913 +
1914 +static int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
1915 +{
1916 +       int err;
1917 +       struct path lowerpath;
1918 +       struct path upperpath;
1919 +       struct ovl_cache_entry *p;
1920 +       struct ovl_readdir_data rdd = { .list = list };
1921 +
1922 +       ovl_path_upper(dentry, &upperpath);
1923 +       ovl_path_lower(dentry, &lowerpath);
1924 +
1925 +       err = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
1926 +       if (err)
1927 +               return err;
1928 +
1929 +       err = 0;
1930 +
1931 +       list_for_each_entry(p, list, l_node) {
1932 +               if (p->is_whiteout)
1933 +                       continue;
1934 +
1935 +               if (p->name[0] == '.') {
1936 +                       if (p->len == 1)
1937 +                               continue;
1938 +                       if (p->len == 2 && p->name[1] == '.')
1939 +                               continue;
1940 +               }
1941 +               err = -ENOTEMPTY;
1942 +               break;
1943 +       }
1944 +
1945 +       return err;
1946 +}
1947 +
1948 +static int ovl_remove_whiteouts(struct dentry *dir, struct list_head *list)
1949 +{
1950 +       struct path upperpath;
1951 +       struct dentry *upperdir;
1952 +       struct ovl_cache_entry *p;
1953 +       const struct cred *old_cred;
1954 +       struct cred *override_cred;
1955 +       int ret = 0;
1956 +
1957 +       ovl_path_upper(dir, &upperpath);
1958 +       upperdir = upperpath.dentry;
1959 +
1960 +       override_cred = prepare_creds();
1961 +       if (!override_cred)
1962 +               return -ENOMEM;
1963 +
1964 +       /*
1965 +        * CAP_DAC_OVERRIDE for lookup and unlink
1966 +        */
1967 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
1968 +       old_cred = override_creds(override_cred);
1969 +
1970 +       mutex_lock(&upperdir->d_inode->i_mutex);
1971 +       list_for_each_entry(p, list, l_node) {
1972 +               if (p->is_whiteout) {
1973 +                       struct dentry *dentry;
1974 +
1975 +                       dentry = lookup_one_len(p->name, upperdir, p->len);
1976 +                       if (IS_ERR(dentry)) {
1977 +                               ret = PTR_ERR(dentry);
1978 +                               break;
1979 +                       }
1980 +                       ret = vfs_unlink(upperdir->d_inode, dentry);
1981 +                       dput(dentry);
1982 +                       if (ret)
1983 +                               break;
1984 +               }
1985 +       }
1986 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1987 +
1988 +       revert_creds(old_cred);
1989 +       put_cred(override_cred);
1990 +
1991 +       return ret;
1992 +}
1993 +
1994 +static int ovl_check_empty_and_clear(struct dentry *dentry,
1995 +                                    enum ovl_path_type type)
1996 +{
1997 +       int err;
1998 +       LIST_HEAD(list);
1999 +
2000 +       err = ovl_check_empty_dir(dentry, &list);
2001 +       if (!err && type == OVL_PATH_MERGE)
2002 +               err = ovl_remove_whiteouts(dentry, &list);
2003 +
2004 +       ovl_cache_free(&list);
2005 +
2006 +       return err;
2007 +}
2008 +
2009 +static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
2010 +{
2011 +       int err;
2012 +       enum ovl_path_type type;
2013 +
2014 +       type = ovl_path_type(dentry);
2015 +       if (type != OVL_PATH_UPPER) {
2016 +               err = ovl_check_empty_and_clear(dentry, type);
2017 +               if (err)
2018 +                       return err;
2019 +       }
2020 +
2021 +       return ovl_do_remove(dentry, true);
2022 +}
2023 +
2024 +static int ovl_link(struct dentry *old, struct inode *newdir,
2025 +                   struct dentry *new)
2026 +{
2027 +       int err;
2028 +       struct dentry *olddentry;
2029 +       struct dentry *newdentry;
2030 +       struct dentry *upperdir;
2031 +
2032 +       err = ovl_copy_up(old);
2033 +       if (err)
2034 +               goto out;
2035 +
2036 +       err = ovl_copy_up(new->d_parent);
2037 +       if (err)
2038 +               goto out;
2039 +
2040 +       upperdir = ovl_dentry_upper(new->d_parent);
2041 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
2042 +       newdentry = ovl_lookup_create(upperdir, new);
2043 +       err = PTR_ERR(newdentry);
2044 +       if (IS_ERR(newdentry))
2045 +               goto out_unlock;
2046 +
2047 +       olddentry = ovl_dentry_upper(old);
2048 +       err = vfs_link(olddentry, upperdir->d_inode, newdentry);
2049 +       if (!err) {
2050 +               ovl_dentry_version_inc(new->d_parent);
2051 +               ovl_dentry_update(new, newdentry);
2052 +
2053 +               ihold(old->d_inode);
2054 +               d_instantiate(new, old->d_inode);
2055 +       } else {
2056 +               if (ovl_dentry_is_opaque(new))
2057 +                       ovl_whiteout(upperdir, new);
2058 +               dput(newdentry);
2059 +       }
2060 +out_unlock:
2061 +       mutex_unlock(&upperdir->d_inode->i_mutex);
2062 +out:
2063 +       return err;
2064 +
2065 +}
2066 +
2067 +static int ovl_rename(struct inode *olddir, struct dentry *old,
2068 +                       struct inode *newdir, struct dentry *new)
2069 +{
2070 +       int err;
2071 +       enum ovl_path_type old_type;
2072 +       struct dentry *old_upperdir;
2073 +       struct dentry *new_upperdir;
2074 +       struct dentry *olddentry;
2075 +       struct dentry *newdentry;
2076 +       struct dentry *trap;
2077 +       bool old_opaque;
2078 +       bool new_opaque;
2079 +       bool is_dir = S_ISDIR(old->d_inode->i_mode);
2080 +
2081 +       /* Don't copy up directory trees */
2082 +       old_type = ovl_path_type(old);
2083 +       if (old_type != OVL_PATH_UPPER && is_dir)
2084 +               return -EXDEV;
2085 +
2086 +       if (new->d_inode) {
2087 +               enum ovl_path_type new_type;
2088 +
2089 +               new_type = ovl_path_type(new);
2090 +
2091 +               if (new_type == OVL_PATH_LOWER && old_type == OVL_PATH_LOWER) {
2092 +                       if (ovl_dentry_lower(old)->d_inode ==
2093 +                           ovl_dentry_lower(new)->d_inode)
2094 +                               return 0;
2095 +               }
2096 +               if (new_type != OVL_PATH_LOWER && old_type != OVL_PATH_LOWER) {
2097 +                       if (ovl_dentry_upper(old)->d_inode ==
2098 +                           ovl_dentry_upper(new)->d_inode)
2099 +                               return 0;
2100 +               }
2101 +
2102 +               if (new_type != OVL_PATH_UPPER &&
2103 +                   S_ISDIR(new->d_inode->i_mode)) {
2104 +                       err = ovl_check_empty_and_clear(new, new_type);
2105 +                       if (err)
2106 +                               return err;
2107 +               }
2108 +       }
2109 +
2110 +       err = ovl_copy_up(old);
2111 +       if (err)
2112 +               return err;
2113 +
2114 +       err = ovl_copy_up(new->d_parent);
2115 +       if (err)
2116 +               return err;
2117 +
2118 +       old_upperdir = ovl_dentry_upper(old->d_parent);
2119 +       new_upperdir = ovl_dentry_upper(new->d_parent);
2120 +
2121 +       trap = lock_rename(new_upperdir, old_upperdir);
2122 +
2123 +       olddentry = ovl_dentry_upper(old);
2124 +       newdentry = ovl_dentry_upper(new);
2125 +       if (newdentry) {
2126 +               dget(newdentry);
2127 +       } else {
2128 +               newdentry = ovl_lookup_create(new_upperdir, new);
2129 +               err = PTR_ERR(newdentry);
2130 +               if (IS_ERR(newdentry))
2131 +                       goto out_unlock;
2132 +       }
2133 +
2134 +       err = -ESTALE;
2135 +       if (olddentry->d_parent != old_upperdir)
2136 +               goto out_dput;
2137 +       if (newdentry->d_parent != new_upperdir)
2138 +               goto out_dput;
2139 +       if (olddentry == trap)
2140 +               goto out_dput;
2141 +       if (newdentry == trap)
2142 +               goto out_dput;
2143 +
2144 +       old_opaque = ovl_dentry_is_opaque(old);
2145 +       new_opaque = ovl_dentry_is_opaque(new) ||
2146 +               ovl_path_type(new) != OVL_PATH_UPPER;
2147 +
2148 +       if (is_dir && !old_opaque && new_opaque) {
2149 +               err = ovl_set_opaque(olddentry);
2150 +               if (err)
2151 +                       goto out_dput;
2152 +       }
2153 +
2154 +       err = vfs_rename(old_upperdir->d_inode, olddentry,
2155 +                        new_upperdir->d_inode, newdentry);
2156 +
2157 +       if (err) {
2158 +               if (ovl_dentry_is_opaque(new))
2159 +                       ovl_whiteout(new_upperdir, new);
2160 +               if (is_dir && !old_opaque && new_opaque)
2161 +                       ovl_remove_opaque(olddentry);
2162 +               goto out_dput;
2163 +       }
2164 +
2165 +       if (old_type != OVL_PATH_UPPER || old_opaque)
2166 +               err = ovl_whiteout(old_upperdir, old);
2167 +       if (is_dir && old_opaque && !new_opaque)
2168 +               ovl_remove_opaque(olddentry);
2169 +
2170 +       if (old_opaque != new_opaque)
2171 +               ovl_dentry_set_opaque(old, new_opaque);
2172 +
2173 +       ovl_dentry_version_inc(old->d_parent);
2174 +       ovl_dentry_version_inc(new->d_parent);
2175 +
2176 +out_dput:
2177 +       dput(newdentry);
2178 +out_unlock:
2179 +       unlock_rename(new_upperdir, old_upperdir);
2180 +       return err;
2181 +}
2182 +
2183 +static bool ovl_is_private_xattr(const char *name)
2184 +{
2185 +       return strncmp(name, "trusted.overlay.", 14) == 0;
2186 +}
2187 +
2188 +static int ovl_setxattr(struct dentry *dentry, const char *name,
2189 +                         const void *value, size_t size, int flags)
2190 +{
2191 +       int err;
2192 +       struct dentry *upperdentry;
2193 +
2194 +       if (ovl_is_private_xattr(name))
2195 +               return -EPERM;
2196 +
2197 +       err = ovl_copy_up(dentry);
2198 +       if (err)
2199 +               return err;
2200 +
2201 +       upperdentry = ovl_dentry_upper(dentry);
2202 +       return  vfs_setxattr(upperdentry, name, value, size, flags);
2203 +}
2204 +
2205 +static ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
2206 +                             void *value, size_t size)
2207 +{
2208 +       if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
2209 +           ovl_is_private_xattr(name))
2210 +               return -ENODATA;
2211 +
2212 +       return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
2213 +}
2214 +
2215 +static ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
2216 +{
2217 +       ssize_t res;
2218 +       int off;
2219 +
2220 +       res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
2221 +       if (res <= 0 || size == 0)
2222 +               return res;
2223 +
2224 +       if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
2225 +               return res;
2226 +
2227 +       /* filter out private xattrs */
2228 +       for (off = 0; off < res;) {
2229 +               char *s = list + off;
2230 +               size_t slen = strlen(s) + 1;
2231 +
2232 +               BUG_ON(off + slen > res);
2233 +
2234 +               if (ovl_is_private_xattr(s)) {
2235 +                       res -= slen;
2236 +                       memmove(s, s + slen, res - off);
2237 +               } else {
2238 +                       off += slen;
2239 +               }
2240 +       }
2241 +
2242 +       return res;
2243 +}
2244 +
2245 +static int ovl_removexattr(struct dentry *dentry, const char *name)
2246 +{
2247 +       int err;
2248 +       struct path realpath;
2249 +       enum ovl_path_type type;
2250 +
2251 +       if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
2252 +           ovl_is_private_xattr(name))
2253 +               return -ENODATA;
2254 +
2255 +       type = ovl_path_real(dentry, &realpath);
2256 +       if (type == OVL_PATH_LOWER) {
2257 +               err = vfs_getxattr(realpath.dentry, name, NULL, 0);
2258 +               if (err < 0)
2259 +                       return err;
2260 +
2261 +               err = ovl_copy_up(dentry);
2262 +               if (err)
2263 +                       return err;
2264 +
2265 +               ovl_path_upper(dentry, &realpath);
2266 +       }
2267 +
2268 +       return vfs_removexattr(realpath.dentry, name);
2269 +}
2270 +
2271 +static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
2272 +                                 struct dentry *realdentry)
2273 +{
2274 +       if (type != OVL_PATH_LOWER)
2275 +               return false;
2276 +
2277 +       if (special_file(realdentry->d_inode->i_mode))
2278 +               return false;
2279 +
2280 +       if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
2281 +               return false;
2282 +
2283 +       return true;
2284 +}
2285 +
2286 +static struct file *ovl_open(struct dentry *dentry, int flags,
2287 +                            const struct cred *cred)
2288 +{
2289 +       int err;
2290 +       struct path realpath;
2291 +       enum ovl_path_type type;
2292 +
2293 +       type = ovl_path_real(dentry, &realpath);
2294 +       if (ovl_open_need_copy_up(flags, type, realpath.dentry)) {
2295 +               if (flags & O_TRUNC)
2296 +                       err = ovl_copy_up_truncate(dentry, 0);
2297 +               else
2298 +                       err = ovl_copy_up(dentry);
2299 +               if (err)
2300 +                       return ERR_PTR(err);
2301 +
2302 +               ovl_path_upper(dentry, &realpath);
2303 +       }
2304 +
2305 +       return vfs_open(&realpath, flags, cred);
2306 +}
2307 +
2308 +static const struct inode_operations ovl_dir_inode_operations = {
2309 +       .lookup         = ovl_lookup,
2310 +       .mkdir          = ovl_mkdir,
2311 +       .symlink        = ovl_symlink,
2312 +       .unlink         = ovl_unlink,
2313 +       .rmdir          = ovl_rmdir,
2314 +       .rename         = ovl_rename,
2315 +       .link           = ovl_link,
2316 +       .setattr        = ovl_setattr,
2317 +       .create         = ovl_create,
2318 +       .mknod          = ovl_mknod,
2319 +       .permission     = ovl_permission,
2320 +       .getattr        = ovl_dir_getattr,
2321 +       .setxattr       = ovl_setxattr,
2322 +       .getxattr       = ovl_getxattr,
2323 +       .listxattr      = ovl_listxattr,
2324 +       .removexattr    = ovl_removexattr,
2325 +};
2326 +
2327 +static const struct inode_operations ovl_file_inode_operations = {
2328 +       .setattr        = ovl_setattr,
2329 +       .permission     = ovl_permission,
2330 +       .getattr        = ovl_getattr,
2331 +       .setxattr       = ovl_setxattr,
2332 +       .getxattr       = ovl_getxattr,
2333 +       .listxattr      = ovl_listxattr,
2334 +       .removexattr    = ovl_removexattr,
2335 +       .open           = ovl_open,
2336 +};
2337 +
2338 +static const struct inode_operations ovl_symlink_inode_operations = {
2339 +       .setattr        = ovl_setattr,
2340 +       .follow_link    = ovl_follow_link,
2341 +       .put_link       = ovl_put_link,
2342 +       .readlink       = ovl_readlink,
2343 +       .getattr        = ovl_getattr,
2344 +       .setxattr       = ovl_setxattr,
2345 +       .getxattr       = ovl_getxattr,
2346 +       .listxattr      = ovl_listxattr,
2347 +       .removexattr    = ovl_removexattr,
2348 +};
2349 +
2350 +static struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
2351 +                                  struct ovl_entry *oe)
2352 +{
2353 +       struct inode *inode;
2354 +
2355 +       inode = new_inode(sb);
2356 +       if (!inode)
2357 +               return NULL;
2358 +
2359 +       mode &= S_IFMT;
2360 +
2361 +       inode->i_ino = get_next_ino();
2362 +       inode->i_mode = mode;
2363 +       inode->i_flags |= S_NOATIME | S_NOCMTIME;
2364 +
2365 +       switch (mode) {
2366 +       case S_IFDIR:
2367 +               inode->i_private = oe;
2368 +               inode->i_op = &ovl_dir_inode_operations;
2369 +               inode->i_fop = &ovl_dir_operations;
2370 +               break;
2371 +
2372 +       case S_IFLNK:
2373 +               inode->i_op = &ovl_symlink_inode_operations;
2374 +               break;
2375 +
2376 +       case S_IFREG:
2377 +       case S_IFSOCK:
2378 +       case S_IFBLK:
2379 +       case S_IFCHR:
2380 +       case S_IFIFO:
2381 +               inode->i_op = &ovl_file_inode_operations;
2382 +               break;
2383 +
2384 +       default:
2385 +               WARN(1, "illegal file type: %i\n", mode);
2386 +               inode = NULL;
2387 +       }
2388 +
2389 +       return inode;
2390 +
2391 +}
2392 +
2393 +static void ovl_put_super(struct super_block *sb)
2394 +{
2395 +       struct ovl_fs *ufs = sb->s_fs_info;
2396 +
2397 +       if (!(sb->s_flags & MS_RDONLY))
2398 +               mnt_drop_write(ufs->upper_mnt);
2399 +
2400 +       mntput(ufs->upper_mnt);
2401 +       mntput(ufs->lower_mnt);
2402 +
2403 +       kfree(ufs);
2404 +}
2405 +
2406 +static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
2407 +{
2408 +       int flags = *flagsp;
2409 +       struct ovl_fs *ufs = sb->s_fs_info;
2410 +
2411 +       /* When remounting rw or ro, we need to adjust the write access to the
2412 +        * upper fs.
2413 +        */
2414 +       if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
2415 +               /* No change to readonly status */
2416 +               return 0;
2417 +
2418 +       if (flags & MS_RDONLY) {
2419 +               mnt_drop_write(ufs->upper_mnt);
2420 +               return 0;
2421 +       } else
2422 +               return mnt_want_write(ufs->upper_mnt);
2423 +}
2424 +
2425 +/**
2426 + * ovl_statfs
2427 + * @sb: The overlayfs super block
2428 + * @buf: The struct kstatfs to fill in with stats
2429 + *
2430 + * Get the filesystem statistics.  As writes always target the upper layer
2431 + * filesystem pass the statfs to the same filesystem.
2432 + */
2433 +static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
2434 +{
2435 +       struct dentry *root_dentry = dentry->d_sb->s_root;
2436 +       struct path path;
2437 +       ovl_path_upper(root_dentry, &path);
2438 +
2439 +       if (!path.dentry->d_sb->s_op->statfs)
2440 +               return -ENOSYS;
2441 +       return path.dentry->d_sb->s_op->statfs(path.dentry, buf);
2442 +}
2443 +
2444 +static const struct super_operations ovl_super_operations = {
2445 +       .put_super      = ovl_put_super,
2446 +       .remount_fs     = ovl_remount_fs,
2447 +       .statfs         = ovl_statfs,
2448 +};
2449 +
2450 +struct ovl_config {
2451 +       char *lowerdir;
2452 +       char *upperdir;
2453 +};
2454 +
2455 +enum {
2456 +       Opt_lowerdir,
2457 +       Opt_upperdir,
2458 +       Opt_err,
2459 +};
2460 +
2461 +static const match_table_t ovl_tokens = {
2462 +       {Opt_lowerdir,                  "lowerdir=%s"},
2463 +       {Opt_upperdir,                  "upperdir=%s"},
2464 +       {Opt_err,                       NULL}
2465 +};
2466 +
2467 +static int ovl_parse_opt(char *opt, struct ovl_config *config)
2468 +{
2469 +       char *p;
2470 +
2471 +       config->upperdir = NULL;
2472 +       config->lowerdir = NULL;
2473 +
2474 +       while ((p = strsep(&opt, ",")) != NULL) {
2475 +               int token;
2476 +               substring_t args[MAX_OPT_ARGS];
2477 +
2478 +               if (!*p)
2479 +                       continue;
2480 +
2481 +               token = match_token(p, ovl_tokens, args);
2482 +               switch (token) {
2483 +               case Opt_upperdir:
2484 +                       kfree(config->upperdir);
2485 +                       config->upperdir = match_strdup(&args[0]);
2486 +                       if (!config->upperdir)
2487 +                               return -ENOMEM;
2488 +                       break;
2489 +
2490 +               case Opt_lowerdir:
2491 +                       kfree(config->lowerdir);
2492 +                       config->lowerdir = match_strdup(&args[0]);
2493 +                       if (!config->lowerdir)
2494 +                               return -ENOMEM;
2495 +                       break;
2496 +
2497 +               default:
2498 +                       return -EINVAL;
2499 +               }
2500 +       }
2501 +       return 0;
2502 +}
2503 +
2504 +static int ovl_fill_super(struct super_block *sb, void *data, int silent)
2505 +{
2506 +       struct path lowerpath;
2507 +       struct path upperpath;
2508 +       struct inode *root_inode;
2509 +       struct dentry *root_dentry;
2510 +       struct ovl_entry *oe;
2511 +       struct ovl_fs *ufs;
2512 +       struct ovl_config config;
2513 +       int err;
2514 +
2515 +       err = ovl_parse_opt((char *) data, &config);
2516 +       if (err)
2517 +               goto out;
2518 +
2519 +       err = -EINVAL;
2520 +       if (!config.upperdir || !config.lowerdir) {
2521 +               printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
2522 +               goto out_free_config;
2523 +       }
2524 +
2525 +       err = -ENOMEM;
2526 +       ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
2527 +       if (!ufs)
2528 +               goto out_free_config;
2529 +
2530 +       oe = ovl_alloc_entry();
2531 +       if (oe == NULL)
2532 +               goto out_free_ufs;
2533 +
2534 +       root_inode = ovl_new_inode(sb, S_IFDIR, oe);
2535 +       if (!root_inode)
2536 +               goto out_free_oe;
2537 +
2538 +       err = kern_path(config.upperdir, LOOKUP_FOLLOW, &upperpath);
2539 +       if (err)
2540 +               goto out_put_root;
2541 +
2542 +       err = kern_path(config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
2543 +       if (err)
2544 +               goto out_put_upperpath;
2545 +
2546 +       err = -ENOTDIR;
2547 +       if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
2548 +           !S_ISDIR(lowerpath.dentry->d_inode->i_mode))
2549 +               goto out_put_lowerpath;
2550 +
2551 +       ufs->upper_mnt = clone_private_mount(&upperpath);
2552 +       err = PTR_ERR(ufs->upper_mnt);
2553 +       if (IS_ERR(ufs->upper_mnt)) {
2554 +               printk(KERN_ERR "overlayfs: failed to clone upperpath\n");
2555 +               goto out_put_lowerpath;
2556 +       }
2557 +
2558 +       ufs->lower_mnt = clone_private_mount(&lowerpath);
2559 +       err = PTR_ERR(ufs->lower_mnt);
2560 +       if (IS_ERR(ufs->lower_mnt)) {
2561 +               printk(KERN_ERR "overlayfs: failed to clone lowerpath\n");
2562 +               goto out_put_upper_mnt;
2563 +       }
2564 +
2565 +       if (!(sb->s_flags & MS_RDONLY)) {
2566 +               err = mnt_want_write(ufs->upper_mnt);
2567 +               if (err)
2568 +                       goto out_put_lower_mnt;
2569 +       }
2570 +
2571 +       err = -ENOMEM;
2572 +       root_dentry = d_alloc_root(root_inode);
2573 +       if (!root_dentry)
2574 +               goto out_drop_write;
2575 +
2576 +       mntput(upperpath.mnt);
2577 +       mntput(lowerpath.mnt);
2578 +
2579 +       oe->__upperdentry = upperpath.dentry;
2580 +       oe->lowerdentry = lowerpath.dentry;
2581 +
2582 +       root_dentry->d_fsdata = oe;
2583 +       root_dentry->d_op = &ovl_dentry_operations;
2584 +
2585 +       sb->s_op = &ovl_super_operations;
2586 +       sb->s_root = root_dentry;
2587 +       sb->s_fs_info = ufs;
2588 +
2589 +       return 0;
2590 +
2591 +out_drop_write:
2592 +       if (!(sb->s_flags & MS_RDONLY))
2593 +               mnt_drop_write(ufs->upper_mnt);
2594 +out_put_lower_mnt:
2595 +       mntput(ufs->lower_mnt);
2596 +out_put_upper_mnt:
2597 +       mntput(ufs->upper_mnt);
2598 +out_put_lowerpath:
2599 +       path_put(&lowerpath);
2600 +out_put_upperpath:
2601 +       path_put(&upperpath);
2602 +out_put_root:
2603 +       iput(root_inode);
2604 +out_free_oe:
2605 +       kfree(oe);
2606 +out_free_ufs:
2607 +       kfree(ufs);
2608 +out_free_config:
2609 +       kfree(config.lowerdir);
2610 +       kfree(config.upperdir);
2611 +out:
2612 +       return err;
2613 +}
2614 +
2615 +static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
2616 +                               const char *dev_name, void *raw_data)
2617 +{
2618 +       return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
2619 +}
2620 +
2621 +static struct file_system_type ovl_fs_type = {
2622 +       .owner          = THIS_MODULE,
2623 +       .name           = "overlayfs",
2624 +       .mount          = ovl_mount,
2625 +       .kill_sb        = kill_anon_super,
2626 +};
2627 +
2628 +static int __init ovl_init(void)
2629 +{
2630 +       return register_filesystem(&ovl_fs_type);
2631 +}
2632 +
2633 +static void __exit ovl_exit(void)
2634 +{
2635 +       unregister_filesystem(&ovl_fs_type);
2636 +}
2637 +
2638 +module_init(ovl_init);
2639 +module_exit(ovl_exit);
2640 --- a/fs/Kconfig
2641 +++ b/fs/Kconfig
2642 @@ -63,6 +63,7 @@ source "fs/quota/Kconfig"
2643
2644  source "fs/autofs4/Kconfig"
2645  source "fs/fuse/Kconfig"
2646 +source "fs/overlayfs/Kconfig"
2647
2648  config CUSE
2649         tristate "Character device in Userspace support"
2650 --- a/fs/Makefile
2651 +++ b/fs/Makefile
2652 @@ -105,6 +105,7 @@ obj-$(CONFIG_QNX4FS_FS)             += qnx4/
2653  obj-$(CONFIG_AUTOFS4_FS)       += autofs4/
2654  obj-$(CONFIG_ADFS_FS)          += adfs/
2655  obj-$(CONFIG_FUSE_FS)          += fuse/
2656 +obj-$(CONFIG_OVERLAYFS_FS)     += overlayfs/
2657  obj-$(CONFIG_UDF_FS)           += udf/
2658  obj-$(CONFIG_SUN_OPENPROMFS)   += openpromfs/
2659  obj-$(CONFIG_OMFS_FS)          += omfs/
2660 --- /dev/null
2661 +++ b/fs/overlayfs/Kconfig
2662 @@ -0,0 +1,4 @@
2663 +config OVERLAYFS_FS
2664 +       tristate "Overlay filesystem support"
2665 +       help
2666 +         Add support for overlay filesystem.
2667 --- /dev/null
2668 +++ b/fs/overlayfs/Makefile
2669 @@ -0,0 +1,5 @@
2670 +#
2671 +# Makefile for the overlay filesystem.
2672 +#
2673 +
2674 +obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o
2675 --- /dev/null
2676 +++ b/Documentation/filesystems/overlayfs.txt
2677 @@ -0,0 +1,163 @@
2678 +Written by: Neil Brown <neilb@suse.de>
2679 +
2680 +Overlay Filesystem
2681 +==================
2682 +
2683 +This document describes a prototype for a new approach to providing
2684 +overlay-filesystem functionality in Linux (sometimes referred to as
2685 +union-filesystems).  An overlay-filesystem tries to present a
2686 +filesystem which is the result over overlaying one filesystem on top
2687 +of the other.
2688 +
2689 +The result will inevitably fail to look exactly like a normal
2690 +filesystem for various technical reasons.  The expectation is that
2691 +many use cases will be able to ignore these differences.
2692 +
2693 +This approach is 'hybrid' because the objects that appear in the
2694 +filesystem do not all appear to belong to that filesystem.  In many
2695 +cases an object accessed in the union will be indistinguishable
2696 +from accessing the corresponding object from the original filesystem.
2697 +This is most obvious from the 'st_dev' field returned by stat(2).
2698 +
2699 +While directories will report an st_dev from the overlay-filesystem,
2700 +all non-directory objects will report an st_dev from the lower or
2701 +upper filesystem that is providing the object.  Similarly st_ino will
2702 +only be unique when combined with st_dev, and both of these can change
2703 +over the lifetime of a non-directory object.  Many applications and
2704 +tools ignore these values and will not be affected.
2705 +
2706 +Upper and Lower
2707 +---------------
2708 +
2709 +An overlay filesystem combines two filesystems - an 'upper' filesystem
2710 +and a 'lower' filesystem.  When a name exists in both filesystems, the
2711 +object in the 'upper' filesystem is visible while the object in the
2712 +'lower' filesystem is either hidden or, in the case of directories,
2713 +merged with the 'upper' object.
2714 +
2715 +It would be more correct to refer to an upper and lower 'directory
2716 +tree' rather than 'filesystem' as it is quite possible for both
2717 +directory trees to be in the same filesystem and there is no
2718 +requirement that the root of a filesystem be given for either upper or
2719 +lower.
2720 +
2721 +The lower filesystem can be any filesystem supported by Linux and does
2722 +not need to be writable.  The lower filesystem can even be another
2723 +overlayfs.  The upper filesystem will normally be writable and if it
2724 +is it must support the creation of trusted.* extended attributes, and
2725 +must provide valid d_type in readdir responses, at least for symbolic
2726 +links - so NFS is not suitable.
2727 +
2728 +A read-only overlay of two read-only filesystems may use any
2729 +filesystem type.
2730 +
2731 +Directories
2732 +-----------
2733 +
2734 +Overlaying mainly involved directories.  If a given name appears in both
2735 +upper and lower filesystems and refers to a non-directory in either,
2736 +then the lower object is hidden - the name refers only to the upper
2737 +object.
2738 +
2739 +Where both upper and lower objects are directories, a merged directory
2740 +is formed.
2741 +
2742 +At mount time, the two directories given as mount options are combined
2743 +into a merged directory.  Then whenever a lookup is requested in such
2744 +a merged directory, the lookup is performed in each actual directory
2745 +and the combined result is cached in the dentry belonging to the overlay
2746 +filesystem.  If both actual lookups find directories, both are stored
2747 +and a merged directory is created, otherwise only one is stored: the
2748 +upper if it exists, else the lower.
2749 +
2750 +Only the lists of names from directories are merged.  Other content
2751 +such as metadata and extended attributes are reported for the upper
2752 +directory only.  These attributes of the lower directory are hidden.
2753 +
2754 +whiteouts and opaque directories
2755 +--------------------------------
2756 +
2757 +In order to support rm and rmdir without changing the lower
2758 +filesystem, an overlay filesystem needs to record in the upper filesystem
2759 +that files have been removed.  This is done using whiteouts and opaque
2760 +directories (non-directories are always opaque).
2761 +
2762 +The overlay filesystem uses extended attributes with a
2763 +"trusted.overlay."  prefix to record these details.
2764 +
2765 +A whiteout is created as a symbolic link with target
2766 +"(overlay-whiteout)" and with xattr "trusted.overlay.whiteout" set to "y".
2767 +When a whiteout is found in the upper level of a merged directory, any
2768 +matching name in the lower level is ignored, and the whiteout itself
2769 +is also hidden.
2770 +
2771 +A directory is made opaque by setting the xattr "trusted.overlay.opaque"
2772 +to "y".  Where the upper filesystem contains an opaque directory, any
2773 +directory in the lower filesystem with the same name is ignored.
2774 +
2775 +readdir
2776 +-------
2777 +
2778 +When a 'readdir' request is made on a merged directory, the upper and
2779 +lower directories are each read and the name lists merged in the
2780 +obvious way (upper is read first, then lower - entries that already
2781 +exist are not re-added).  This merged name list is cached in the
2782 +'struct file' and so remains as long as the file is kept open.  If the
2783 +directory is opened and read by two processes at the same time, they
2784 +will each have separate caches.  A seekdir to the start of the
2785 +directory (offset 0) followed by a readdir will cause the cache to be
2786 +discarded and rebuilt.
2787 +
2788 +This means that changes to the merged directory do not appear while a
2789 +directory is being read.  This is unlikely to be noticed by many
2790 +programs.
2791 +
2792 +seek offsets are assigned sequentially when the directories are read.
2793 +Thus if
2794 +  - read part of a directory
2795 +  - remember an offset, and close the directory
2796 +  - re-open the directory some time later
2797 +  - seek to the remembered offset
2798 +
2799 +there may be little correlation between the old and new locations in
2800 +the list of filenames, particularly if anything has changed in the
2801 +directory.
2802 +
2803 +Readdir on directories that are not merged is simply handled by the
2804 +underlying directory (upper or lower).
2805 +
2806 +
2807 +Non-directories
2808 +---------------
2809 +
2810 +Objects that are not directories (files, symlinks, device-special
2811 +files etc.) are presented either from the upper or lower filesystem as
2812 +appropriate.  When a file in the lower filesystem is accessed in a way
2813 +the requires write-access, such as opening for write access, changing
2814 +some metadata etc., the file is first copied from the lower filesystem
2815 +to the upper filesystem (copy_up).  Note that creating a hard-link
2816 +also requires copy_up, though of course creation of a symlink does
2817 +not.
2818 +
2819 +The copy_up process first makes sure that the containing directory
2820 +exists in the upper filesystem - creating it and any parents as
2821 +necessary.  It then creates the object with the same metadata (owner,
2822 +mode, mtime, symlink-target etc.) and then if the object is a file, the
2823 +data is copied from the lower to the upper filesystem.  Finally any
2824 +extended attributes are copied up.
2825 +
2826 +Once the copy_up is complete, the overlay filesystem simply
2827 +provides direct access to the newly created file in the upper
2828 +filesystem - future operations on the file are barely noticed by the
2829 +overlay filesystem (though an operation on the name of the file such as
2830 +rename or unlink will of course be noticed and handled).
2831 +
2832 +Changes to underlying filesystems
2833 +---------------------------------
2834 +
2835 +Offline changes, when the overlay is not mounted, are allowed to either
2836 +the upper or the lower trees.
2837 +
2838 +Changes to the underlying filesystems while part of a mounted overlay
2839 +filesystem are not allowed.  This is not yet enforced, but will be in
2840 +the future.