target/linux/generic/patches-3.2/100-overlayfs_v11.patch

   1 --- /dev/null
   2 +++ b/Documentation/filesystems/overlayfs.txt
   3 @@ -0,0 +1,199 @@
   4 +Written by: Neil Brown <neilb@suse.de>
   5 +
   6 +Overlay Filesystem
   7 +==================
   8 +
   9 +This document describes a prototype for a new approach to providing
  10 +overlay-filesystem functionality in Linux (sometimes referred to as
  11 +union-filesystems).  An overlay-filesystem tries to present a
  12 +filesystem which is the result over overlaying one filesystem on top
  13 +of the other.
  14 +
  15 +The result will inevitably fail to look exactly like a normal
  16 +filesystem for various technical reasons.  The expectation is that
  17 +many use cases will be able to ignore these differences.
  18 +
  19 +This approach is 'hybrid' because the objects that appear in the
  20 +filesystem do not all appear to belong to that filesystem.  In many
  21 +cases an object accessed in the union will be indistinguishable
  22 +from accessing the corresponding object from the original filesystem.
  23 +This is most obvious from the 'st_dev' field returned by stat(2).
  24 +
  25 +While directories will report an st_dev from the overlay-filesystem,
  26 +all non-directory objects will report an st_dev from the lower or
  27 +upper filesystem that is providing the object.  Similarly st_ino will
  28 +only be unique when combined with st_dev, and both of these can change
  29 +over the lifetime of a non-directory object.  Many applications and
  30 +tools ignore these values and will not be affected.
  31 +
  32 +Upper and Lower
  33 +---------------
  34 +
  35 +An overlay filesystem combines two filesystems - an 'upper' filesystem
  36 +and a 'lower' filesystem.  When a name exists in both filesystems, the
  37 +object in the 'upper' filesystem is visible while the object in the
  38 +'lower' filesystem is either hidden or, in the case of directories,
  39 +merged with the 'upper' object.
  40 +
  41 +It would be more correct to refer to an upper and lower 'directory
  42 +tree' rather than 'filesystem' as it is quite possible for both
  43 +directory trees to be in the same filesystem and there is no
  44 +requirement that the root of a filesystem be given for either upper or
  45 +lower.
  46 +
  47 +The lower filesystem can be any filesystem supported by Linux and does
  48 +not need to be writable.  The lower filesystem can even be another
  49 +overlayfs.  The upper filesystem will normally be writable and if it
  50 +is it must support the creation of trusted.* extended attributes, and
  51 +must provide valid d_type in readdir responses, at least for symbolic
  52 +links - so NFS is not suitable.
  53 +
  54 +A read-only overlay of two read-only filesystems may use any
  55 +filesystem type.
  56 +
  57 +Directories
  58 +-----------
  59 +
  60 +Overlaying mainly involved directories.  If a given name appears in both
  61 +upper and lower filesystems and refers to a non-directory in either,
  62 +then the lower object is hidden - the name refers only to the upper
  63 +object.
  64 +
  65 +Where both upper and lower objects are directories, a merged directory
  66 +is formed.
  67 +
  68 +At mount time, the two directories given as mount options are combined
  69 +into a merged directory:
  70 +
  71 +  mount -t overlayfs overlayfs -olowerdir=/lower,upperdir=/upper /overlay
  72 +
  73 +Then whenever a lookup is requested in such a merged directory, the
  74 +lookup is performed in each actual directory and the combined result
  75 +is cached in the dentry belonging to the overlay filesystem.  If both
  76 +actual lookups find directories, both are stored and a merged
  77 +directory is created, otherwise only one is stored: the upper if it
  78 +exists, else the lower.
  79 +
  80 +Only the lists of names from directories are merged.  Other content
  81 +such as metadata and extended attributes are reported for the upper
  82 +directory only.  These attributes of the lower directory are hidden.
  83 +
  84 +whiteouts and opaque directories
  85 +--------------------------------
  86 +
  87 +In order to support rm and rmdir without changing the lower
  88 +filesystem, an overlay filesystem needs to record in the upper filesystem
  89 +that files have been removed.  This is done using whiteouts and opaque
  90 +directories (non-directories are always opaque).
  91 +
  92 +The overlay filesystem uses extended attributes with a
  93 +"trusted.overlay."  prefix to record these details.
  94 +
  95 +A whiteout is created as a symbolic link with target
  96 +"(overlay-whiteout)" and with xattr "trusted.overlay.whiteout" set to "y".
  97 +When a whiteout is found in the upper level of a merged directory, any
  98 +matching name in the lower level is ignored, and the whiteout itself
  99 +is also hidden.
 100 +
 101 +A directory is made opaque by setting the xattr "trusted.overlay.opaque"
 102 +to "y".  Where the upper filesystem contains an opaque directory, any
 103 +directory in the lower filesystem with the same name is ignored.
 104 +
 105 +readdir
 106 +-------
 107 +
 108 +When a 'readdir' request is made on a merged directory, the upper and
 109 +lower directories are each read and the name lists merged in the
 110 +obvious way (upper is read first, then lower - entries that already
 111 +exist are not re-added).  This merged name list is cached in the
 112 +'struct file' and so remains as long as the file is kept open.  If the
 113 +directory is opened and read by two processes at the same time, they
 114 +will each have separate caches.  A seekdir to the start of the
 115 +directory (offset 0) followed by a readdir will cause the cache to be
 116 +discarded and rebuilt.
 117 +
 118 +This means that changes to the merged directory do not appear while a
 119 +directory is being read.  This is unlikely to be noticed by many
 120 +programs.
 121 +
 122 +seek offsets are assigned sequentially when the directories are read.
 123 +Thus if
 124 +  - read part of a directory
 125 +  - remember an offset, and close the directory
 126 +  - re-open the directory some time later
 127 +  - seek to the remembered offset
 128 +
 129 +there may be little correlation between the old and new locations in
 130 +the list of filenames, particularly if anything has changed in the
 131 +directory.
 132 +
 133 +Readdir on directories that are not merged is simply handled by the
 134 +underlying directory (upper or lower).
 135 +
 136 +
 137 +Non-directories
 138 +---------------
 139 +
 140 +Objects that are not directories (files, symlinks, device-special
 141 +files etc.) are presented either from the upper or lower filesystem as
 142 +appropriate.  When a file in the lower filesystem is accessed in a way
 143 +the requires write-access, such as opening for write access, changing
 144 +some metadata etc., the file is first copied from the lower filesystem
 145 +to the upper filesystem (copy_up).  Note that creating a hard-link
 146 +also requires copy_up, though of course creation of a symlink does
 147 +not.
 148 +
 149 +The copy_up may turn out to be unnecessary, for example if the file is
 150 +opened for read-write but the data is not modified.
 151 +
 152 +The copy_up process first makes sure that the containing directory
 153 +exists in the upper filesystem - creating it and any parents as
 154 +necessary.  It then creates the object with the same metadata (owner,
 155 +mode, mtime, symlink-target etc.) and then if the object is a file, the
 156 +data is copied from the lower to the upper filesystem.  Finally any
 157 +extended attributes are copied up.
 158 +
 159 +Once the copy_up is complete, the overlay filesystem simply
 160 +provides direct access to the newly created file in the upper
 161 +filesystem - future operations on the file are barely noticed by the
 162 +overlay filesystem (though an operation on the name of the file such as
 163 +rename or unlink will of course be noticed and handled).
 164 +
 165 +
 166 +Non-standard behavior
 167 +---------------------
 168 +
 169 +The copy_up operation essentially creates a new, identical file and
 170 +moves it over to the old name.  The new file may be on a different
 171 +filesystem, so both st_dev and st_ino of the file may change.
 172 +
 173 +Any open files referring to this inode will access the old data and
 174 +metadata.  Similarly any file locks obtained before copy_up will not
 175 +apply to the copied up file.
 176 +
 177 +On a file is opened with O_RDONLY fchmod(2), fchown(2), futimesat(2)
 178 +and fsetxattr(2) will fail with EROFS.
 179 +
 180 +If a file with multiple hard links is copied up, then this will
 181 +"break" the link.  Changes will not be propagated to other names
 182 +referring to the same inode.
 183 +
 184 +Symlinks in /proc/PID/ and /proc/PID/fd which point to a non-directory
 185 +object in overlayfs will not contain vaid absolute paths, only
 186 +relative paths leading up to the filesystem's root.  This will be
 187 +fixed in the future.
 188 +
 189 +Some operations are not atomic, for example a crash during copy_up or
 190 +rename will leave the filesystem in an inconsitent state.  This will
 191 +be addressed in the future.
 192 +
 193 +Changes to underlying filesystems
 194 +---------------------------------
 195 +
 196 +Offline changes, when the overlay is not mounted, are allowed to either
 197 +the upper or the lower trees.
 198 +
 199 +Changes to the underlying filesystems while part of a mounted overlay
 200 +filesystem are not allowed.  If the underlying filesystem is changed,
 201 +the behavior of the overlay is undefined, though it will not result in
 202 +a crash or deadlock.
 203 --- a/MAINTAINERS
 204 +++ b/MAINTAINERS
 205 @@ -4901,6 +4901,13 @@ F:       drivers/scsi/osd/
 206  F:     include/scsi/osd_*
 207  F:     fs/exofs/
 208
 209 +OVERLAYFS FILESYSTEM
 210 +M:     Miklos Szeredi <miklos@szeredi.hu>
 211 +L:     linux-fsdevel@vger.kernel.org
 212 +S:     Supported
 213 +F:     fs/overlayfs/*
 214 +F:     Documentation/filesystems/overlayfs.txt
 215 +
 216  P54 WIRELESS DRIVER
 217  M:     Christian Lamparter <chunkeey@googlemail.com>
 218  L:     linux-wireless@vger.kernel.org
 219 --- a/fs/Kconfig
 220 +++ b/fs/Kconfig
 221 @@ -63,6 +63,7 @@ source "fs/quota/Kconfig"
 222
 223  source "fs/autofs4/Kconfig"
 224  source "fs/fuse/Kconfig"
 225 +source "fs/overlayfs/Kconfig"
 226
 227  config CUSE
 228         tristate "Character device in Userspace support"
 229 --- a/fs/Makefile
 230 +++ b/fs/Makefile
 231 @@ -104,6 +104,7 @@ obj-$(CONFIG_QNX4FS_FS)             += qnx4/
 232  obj-$(CONFIG_AUTOFS4_FS)       += autofs4/
 233  obj-$(CONFIG_ADFS_FS)          += adfs/
 234  obj-$(CONFIG_FUSE_FS)          += fuse/
 235 +obj-$(CONFIG_OVERLAYFS_FS)     += overlayfs/
 236  obj-$(CONFIG_UDF_FS)           += udf/
 237  obj-$(CONFIG_SUN_OPENPROMFS)   += openpromfs/
 238  obj-$(CONFIG_OMFS_FS)          += omfs/
 239 --- a/fs/ecryptfs/main.c
 240 +++ b/fs/ecryptfs/main.c
 241 @@ -544,6 +544,13 @@ static struct dentry *ecryptfs_mount(str
 242         s->s_maxbytes = path.dentry->d_sb->s_maxbytes;
 243         s->s_blocksize = path.dentry->d_sb->s_blocksize;
 244         s->s_magic = ECRYPTFS_SUPER_MAGIC;
 245 +       s->s_stack_depth = path.dentry->d_sb->s_stack_depth + 1;
 246 +
 247 +       rc = -EINVAL;
 248 +       if (s->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
 249 +               printk(KERN_ERR "eCryptfs: maximum fs stacking depth exceeded\n");
 250 +               goto out_free;
 251 +       }
 252
 253         inode = ecryptfs_get_inode(path.dentry->d_inode, s);
 254         rc = PTR_ERR(inode);
 255 --- a/fs/namespace.c
 256 +++ b/fs/namespace.c
 257 @@ -1492,6 +1492,23 @@ void drop_collected_mounts(struct vfsmou
 258         release_mounts(&umount_list);
 259  }
 260
 261 +struct vfsmount *clone_private_mount(struct path *path)
 262 +{
 263 +       struct vfsmount *mnt;
 264 +
 265 +       if (IS_MNT_UNBINDABLE(path->mnt))
 266 +               return ERR_PTR(-EINVAL);
 267 +
 268 +       down_read(&namespace_sem);
 269 +       mnt = clone_mnt(path->mnt, path->dentry, CL_PRIVATE);
 270 +       up_read(&namespace_sem);
 271 +       if (!mnt)
 272 +               return ERR_PTR(-ENOMEM);
 273 +
 274 +       return mnt;
 275 +}
 276 +EXPORT_SYMBOL_GPL(clone_private_mount);
 277 +
 278  int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
 279                    struct vfsmount *root)
 280  {
 281 --- a/fs/open.c
 282 +++ b/fs/open.c
 283 @@ -644,8 +644,7 @@ static inline int __get_file_write_acces
 284         return error;
 285  }
 286
 287 -static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 288 -                                       struct file *f,
 289 +static struct file *__dentry_open(struct path *path, struct file *f,
 290                                         int (*open)(struct inode *, struct file *),
 291                                         const struct cred *cred)
 292  {
 293 @@ -653,15 +652,16 @@ static struct file *__dentry_open(struct
 294         struct inode *inode;
 295         int error;
 296
 297 +       path_get(path);
 298         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 299                                 FMODE_PREAD | FMODE_PWRITE;
 300
 301         if (unlikely(f->f_flags & O_PATH))
 302                 f->f_mode = FMODE_PATH;
 303
 304 -       inode = dentry->d_inode;
 305 +       inode = path->dentry->d_inode;
 306         if (f->f_mode & FMODE_WRITE) {
 307 -               error = __get_file_write_access(inode, mnt);
 308 +               error = __get_file_write_access(inode, path->mnt);
 309                 if (error)
 310                         goto cleanup_file;
 311                 if (!special_file(inode->i_mode))
 312 @@ -669,8 +669,7 @@ static struct file *__dentry_open(struct
 313         }
 314
 315         f->f_mapping = inode->i_mapping;
 316 -       f->f_path.dentry = dentry;
 317 -       f->f_path.mnt = mnt;
 318 +       f->f_path = *path;
 319         f->f_pos = 0;
 320         file_sb_list_add(f, inode->i_sb);
 321
 322 @@ -727,7 +726,7 @@ cleanup_all:
 323                          * here, so just reset the state.
 324                          */
 325                         file_reset_write(f);
 326 -                       mnt_drop_write(mnt);
 327 +                       mnt_drop_write(path->mnt);
 328                 }
 329         }
 330         file_sb_list_del(f);
 331 @@ -735,8 +734,7 @@ cleanup_all:
 332         f->f_path.mnt = NULL;
 333  cleanup_file:
 334         put_filp(f);
 335 -       dput(dentry);
 336 -       mntput(mnt);
 337 +       path_put(path);
 338         return ERR_PTR(error);
 339  }
 340
 341 @@ -762,14 +760,14 @@ cleanup_file:
 342  struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
 343                 int (*open)(struct inode *, struct file *))
 344  {
 345 +       struct path path = { .dentry = dentry, .mnt = nd->path.mnt };
 346         const struct cred *cred = current_cred();
 347
 348         if (IS_ERR(nd->intent.open.file))
 349                 goto out;
 350         if (IS_ERR(dentry))
 351                 goto out_err;
 352 -       nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
 353 -                                            nd->intent.open.file,
 354 +       nd->intent.open.file = __dentry_open(&path, nd->intent.open.file,
 355                                              open, cred);
 356  out:
 357         return nd->intent.open.file;
 358 @@ -798,10 +796,17 @@ struct file *nameidata_to_filp(struct na
 359
 360         /* Has the filesystem initialised the file for us? */
 361         if (filp->f_path.dentry == NULL) {
 362 -               path_get(&nd->path);
 363 -               filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
 364 -                                    NULL, cred);
 365 +               struct inode *inode = nd->path.dentry->d_inode;
 366 +
 367 +               if (inode->i_op->open) {
 368 +                       int flags = filp->f_flags;
 369 +                       put_filp(filp);
 370 +                       filp = inode->i_op->open(nd->path.dentry, flags, cred);
 371 +               } else {
 372 +                       filp = __dentry_open(&nd->path, filp, NULL, cred);
 373 +               }
 374         }
 375 +
 376         return filp;
 377  }
 378
 379 @@ -812,26 +817,45 @@ struct file *nameidata_to_filp(struct na
 380  struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 381                          const struct cred *cred)
 382  {
 383 -       int error;
 384 -       struct file *f;
 385 -
 386 -       validate_creds(cred);
 387 +       struct path path = { .dentry = dentry, .mnt = mnt };
 388 +       struct file *ret;
 389
 390         /* We must always pass in a valid mount pointer. */
 391         BUG_ON(!mnt);
 392
 393 -       error = -ENFILE;
 394 +       ret = vfs_open(&path, flags, cred);
 395 +       path_put(&path);
 396 +
 397 +       return ret;
 398 +}
 399 +EXPORT_SYMBOL(dentry_open);
 400 +
 401 +/**
 402 + * vfs_open - open the file at the given path
 403 + * @path: path to open
 404 + * @flags: open flags
 405 + * @cred: credentials to use
 406 + *
 407 + * Open the file.  If successful, the returned file will have acquired
 408 + * an additional reference for path.
 409 + */
 410 +struct file *vfs_open(struct path *path, int flags, const struct cred *cred)
 411 +{
 412 +       struct file *f;
 413 +       struct inode *inode = path->dentry->d_inode;
 414 +
 415 +       validate_creds(cred);
 416 +
 417 +       if (inode->i_op->open)
 418 +               return inode->i_op->open(path->dentry, flags, cred);
 419         f = get_empty_filp();
 420 -       if (f == NULL) {
 421 -               dput(dentry);
 422 -               mntput(mnt);
 423 -               return ERR_PTR(error);
 424 -       }
 425 +       if (f == NULL)
 426 +               return ERR_PTR(-ENFILE);
 427
 428         f->f_flags = flags;
 429 -       return __dentry_open(dentry, mnt, f, NULL, cred);
 430 +       return __dentry_open(path, f, NULL, cred);
 431  }
 432 -EXPORT_SYMBOL(dentry_open);
 433 +EXPORT_SYMBOL(vfs_open);
 434
 435  static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 436  {
 437 --- /dev/null
 438 +++ b/fs/overlayfs/Kconfig
 439 @@ -0,0 +1,4 @@
 440 +config OVERLAYFS_FS
 441 +       tristate "Overlay filesystem support"
 442 +       help
 443 +         Add support for overlay filesystem.
 444 --- /dev/null
 445 +++ b/fs/overlayfs/Makefile
 446 @@ -0,0 +1,7 @@
 447 +#
 448 +# Makefile for the overlay filesystem.
 449 +#
 450 +
 451 +obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o
 452 +
 453 +overlayfs-objs := super.o inode.o dir.o readdir.o copy_up.o
 454 --- /dev/null
 455 +++ b/fs/overlayfs/copy_up.c
 456 @@ -0,0 +1,383 @@
 457 +/*
 458 + *
 459 + * Copyright (C) 2011 Novell Inc.
 460 + *
 461 + * This program is free software; you can redistribute it and/or modify it
 462 + * under the terms of the GNU General Public License version 2 as published by
 463 + * the Free Software Foundation.
 464 + */
 465 +
 466 +#include <linux/fs.h>
 467 +#include <linux/slab.h>
 468 +#include <linux/file.h>
 469 +#include <linux/splice.h>
 470 +#include <linux/xattr.h>
 471 +#include <linux/security.h>
 472 +#include <linux/uaccess.h>
 473 +#include "overlayfs.h"
 474 +
 475 +#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
 476 +
 477 +static int ovl_copy_up_xattr(struct dentry *old, struct dentry *new)
 478 +{
 479 +       ssize_t list_size, size;
 480 +       char *buf, *name, *value;
 481 +       int error;
 482 +
 483 +       if (!old->d_inode->i_op->getxattr ||
 484 +           !new->d_inode->i_op->getxattr)
 485 +               return 0;
 486 +
 487 +       list_size = vfs_listxattr(old, NULL, 0);
 488 +       if (list_size <= 0) {
 489 +               if (list_size == -EOPNOTSUPP)
 490 +                       return 0;
 491 +               return list_size;
 492 +       }
 493 +
 494 +       buf = kzalloc(list_size, GFP_KERNEL);
 495 +       if (!buf)
 496 +               return -ENOMEM;
 497 +
 498 +       error = -ENOMEM;
 499 +       value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL);
 500 +       if (!value)
 501 +               goto out;
 502 +
 503 +       list_size = vfs_listxattr(old, buf, list_size);
 504 +       if (list_size <= 0) {
 505 +               error = list_size;
 506 +               goto out_free_value;
 507 +       }
 508 +
 509 +       for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
 510 +               size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX);
 511 +               if (size <= 0) {
 512 +                       error = size;
 513 +                       goto out_free_value;
 514 +               }
 515 +               error = vfs_setxattr(new, name, value, size, 0);
 516 +               if (error)
 517 +                       goto out_free_value;
 518 +       }
 519 +
 520 +out_free_value:
 521 +       kfree(value);
 522 +out:
 523 +       kfree(buf);
 524 +       return error;
 525 +}
 526 +
 527 +static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 528 +{
 529 +       struct file *old_file;
 530 +       struct file *new_file;
 531 +       int error = 0;
 532 +
 533 +       if (len == 0)
 534 +               return 0;
 535 +
 536 +       old_file = vfs_open(old, O_RDONLY, current_cred());
 537 +       if (IS_ERR(old_file))
 538 +               return PTR_ERR(old_file);
 539 +
 540 +       new_file = vfs_open(new, O_WRONLY, current_cred());
 541 +       if (IS_ERR(new_file)) {
 542 +               error = PTR_ERR(new_file);
 543 +               goto out_fput;
 544 +       }
 545 +
 546 +       /* FIXME: copy up sparse files efficiently */
 547 +       while (len) {
 548 +               loff_t offset = new_file->f_pos;
 549 +               size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
 550 +               long bytes;
 551 +
 552 +               if (len < this_len)
 553 +                       this_len = len;
 554 +
 555 +               if (signal_pending_state(TASK_KILLABLE, current)) {
 556 +                       error = -EINTR;
 557 +                       break;
 558 +               }
 559 +
 560 +               bytes = do_splice_direct(old_file, &offset, new_file, this_len,
 561 +                                SPLICE_F_MOVE);
 562 +               if (bytes <= 0) {
 563 +                       error = bytes;
 564 +                       break;
 565 +               }
 566 +
 567 +               len -= bytes;
 568 +       }
 569 +
 570 +       fput(new_file);
 571 +out_fput:
 572 +       fput(old_file);
 573 +       return error;
 574 +}
 575 +
 576 +static char *ovl_read_symlink(struct dentry *realdentry)
 577 +{
 578 +       int res;
 579 +       char *buf;
 580 +       struct inode *inode = realdentry->d_inode;
 581 +       mm_segment_t old_fs;
 582 +
 583 +       res = -EINVAL;
 584 +       if (!inode->i_op->readlink)
 585 +               goto err;
 586 +
 587 +       res = -ENOMEM;
 588 +       buf = (char *) __get_free_page(GFP_KERNEL);
 589 +       if (!buf)
 590 +               goto err;
 591 +
 592 +       old_fs = get_fs();
 593 +       set_fs(get_ds());
 594 +       /* The cast to a user pointer is valid due to the set_fs() */
 595 +       res = inode->i_op->readlink(realdentry,
 596 +                                   (char __user *)buf, PAGE_SIZE - 1);
 597 +       set_fs(old_fs);
 598 +       if (res < 0) {
 599 +               free_page((unsigned long) buf);
 600 +               goto err;
 601 +       }
 602 +       buf[res] = '\0';
 603 +
 604 +       return buf;
 605 +
 606 +err:
 607 +       return ERR_PTR(res);
 608 +}
 609 +
 610 +static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
 611 +{
 612 +       struct iattr attr = {
 613 +               .ia_valid = ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
 614 +               .ia_atime = stat->atime,
 615 +               .ia_mtime = stat->mtime,
 616 +       };
 617 +
 618 +       return notify_change(upperdentry, &attr);
 619 +}
 620 +
 621 +static int ovl_set_mode(struct dentry *upperdentry, umode_t mode)
 622 +{
 623 +       struct iattr attr = {
 624 +               .ia_valid = ATTR_MODE,
 625 +               .ia_mode = mode,
 626 +       };
 627 +
 628 +       return notify_change(upperdentry, &attr);
 629 +}
 630 +
 631 +static int ovl_copy_up_locked(struct dentry *upperdir, struct dentry *dentry,
 632 +                             struct path *lowerpath, struct kstat *stat,
 633 +                             const char *link)
 634 +{
 635 +       int err;
 636 +       struct path newpath;
 637 +       umode_t mode = stat->mode;
 638 +
 639 +       /* Can't properly set mode on creation because of the umask */
 640 +       stat->mode &= S_IFMT;
 641 +
 642 +       ovl_path_upper(dentry, &newpath);
 643 +       WARN_ON(newpath.dentry);
 644 +       newpath.dentry = ovl_upper_create(upperdir, dentry, stat, link);
 645 +       if (IS_ERR(newpath.dentry))
 646 +               return PTR_ERR(newpath.dentry);
 647 +
 648 +       if (S_ISREG(stat->mode)) {
 649 +               err = ovl_copy_up_data(lowerpath, &newpath, stat->size);
 650 +               if (err)
 651 +                       goto err_remove;
 652 +       }
 653 +
 654 +       err = ovl_copy_up_xattr(lowerpath->dentry, newpath.dentry);
 655 +       if (err)
 656 +               goto err_remove;
 657 +
 658 +       mutex_lock(&newpath.dentry->d_inode->i_mutex);
 659 +       if (!S_ISLNK(stat->mode))
 660 +               err = ovl_set_mode(newpath.dentry, mode);
 661 +       if (!err)
 662 +               err = ovl_set_timestamps(newpath.dentry, stat);
 663 +       mutex_unlock(&newpath.dentry->d_inode->i_mutex);
 664 +       if (err)
 665 +               goto err_remove;
 666 +
 667 +       ovl_dentry_update(dentry, newpath.dentry);
 668 +
 669 +       /*
 670 +        * Easiest way to get rid of the lower dentry reference is to
 671 +        * drop this dentry.  This is neither needed nor possible for
 672 +        * directories.
 673 +        */
 674 +       if (!S_ISDIR(stat->mode))
 675 +               d_drop(dentry);
 676 +
 677 +       return 0;
 678 +
 679 +err_remove:
 680 +       if (S_ISDIR(stat->mode))
 681 +               vfs_rmdir(upperdir->d_inode, newpath.dentry);
 682 +       else
 683 +               vfs_unlink(upperdir->d_inode, newpath.dentry);
 684 +
 685 +       dput(newpath.dentry);
 686 +
 687 +       return err;
 688 +}
 689 +
 690 +/*
 691 + * Copy up a single dentry
 692 + *
 693 + * Directory renames only allowed on "pure upper" (already created on
 694 + * upper filesystem, never copied up).  Directories which are on lower or
 695 + * are merged may not be renamed.  For these -EXDEV is returned and
 696 + * userspace has to deal with it.  This means, when copying up a
 697 + * directory we can rely on it and ancestors being stable.
 698 + *
 699 + * Non-directory renames start with copy up of source if necessary.  The
 700 + * actual rename will only proceed once the copy up was successful.  Copy
 701 + * up uses upper parent i_mutex for exclusion.  Since rename can change
 702 + * d_parent it is possible that the copy up will lock the old parent.  At
 703 + * that point the file will have already been copied up anyway.
 704 + */
 705 +static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 706 +                          struct path *lowerpath, struct kstat *stat)
 707 +{
 708 +       int err;
 709 +       struct kstat pstat;
 710 +       struct path parentpath;
 711 +       struct dentry *upperdir;
 712 +       const struct cred *old_cred;
 713 +       struct cred *override_cred;
 714 +       char *link = NULL;
 715 +
 716 +       ovl_path_upper(parent, &parentpath);
 717 +       upperdir = parentpath.dentry;
 718 +
 719 +       err = vfs_getattr(parentpath.mnt, parentpath.dentry, &pstat);
 720 +       if (err)
 721 +               return err;
 722 +
 723 +       if (S_ISLNK(stat->mode)) {
 724 +               link = ovl_read_symlink(lowerpath->dentry);
 725 +               if (IS_ERR(link))
 726 +                       return PTR_ERR(link);
 727 +       }
 728 +
 729 +       err = -ENOMEM;
 730 +       override_cred = prepare_creds();
 731 +       if (!override_cred)
 732 +               goto out_free_link;
 733 +
 734 +       override_cred->fsuid = stat->uid;
 735 +       override_cred->fsgid = stat->gid;
 736 +       /*
 737 +        * CAP_SYS_ADMIN for copying up extended attributes
 738 +        * CAP_DAC_OVERRIDE for create
 739 +        * CAP_FOWNER for chmod, timestamp update
 740 +        * CAP_FSETID for chmod
 741 +        * CAP_MKNOD for mknod
 742 +        */
 743 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 744 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 745 +       cap_raise(override_cred->cap_effective, CAP_FOWNER);
 746 +       cap_raise(override_cred->cap_effective, CAP_FSETID);
 747 +       cap_raise(override_cred->cap_effective, CAP_MKNOD);
 748 +       old_cred = override_creds(override_cred);
 749 +
 750 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
 751 +       if (ovl_path_type(dentry) != OVL_PATH_LOWER) {
 752 +               err = 0;
 753 +       } else {
 754 +               err = ovl_copy_up_locked(upperdir, dentry, lowerpath,
 755 +                                        stat, link);
 756 +               if (!err) {
 757 +                       /* Restore timestamps on parent (best effort) */
 758 +                       ovl_set_timestamps(upperdir, &pstat);
 759 +               }
 760 +       }
 761 +
 762 +       mutex_unlock(&upperdir->d_inode->i_mutex);
 763 +
 764 +       revert_creds(old_cred);
 765 +       put_cred(override_cred);
 766 +
 767 +out_free_link:
 768 +       if (link)
 769 +               free_page((unsigned long) link);
 770 +
 771 +       return err;
 772 +}
 773 +
 774 +int ovl_copy_up(struct dentry *dentry)
 775 +{
 776 +       int err;
 777 +
 778 +       err = 0;
 779 +       while (!err) {
 780 +               struct dentry *next;
 781 +               struct dentry *parent;
 782 +               struct path lowerpath;
 783 +               struct kstat stat;
 784 +               enum ovl_path_type type = ovl_path_type(dentry);
 785 +
 786 +               if (type != OVL_PATH_LOWER)
 787 +                       break;
 788 +
 789 +               next = dget(dentry);
 790 +               /* find the topmost dentry not yet copied up */
 791 +               for (;;) {
 792 +                       parent = dget_parent(next);
 793 +
 794 +                       type = ovl_path_type(parent);
 795 +                       if (type != OVL_PATH_LOWER)
 796 +                               break;
 797 +
 798 +                       dput(next);
 799 +                       next = parent;
 800 +               }
 801 +
 802 +               ovl_path_lower(next, &lowerpath);
 803 +               err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
 804 +               if (!err)
 805 +                       err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
 806 +
 807 +               dput(parent);
 808 +               dput(next);
 809 +       }
 810 +
 811 +       return err;
 812 +}
 813 +
 814 +/* Optimize by not copying up the file first and truncating later */
 815 +int ovl_copy_up_truncate(struct dentry *dentry, loff_t size)
 816 +{
 817 +       int err;
 818 +       struct kstat stat;
 819 +       struct path lowerpath;
 820 +       struct dentry *parent = dget_parent(dentry);
 821 +
 822 +       err = ovl_copy_up(parent);
 823 +       if (err)
 824 +               goto out_dput_parent;
 825 +
 826 +       ovl_path_lower(dentry, &lowerpath);
 827 +       err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
 828 +       if (err)
 829 +               goto out_dput_parent;
 830 +
 831 +       if (size < stat.size)
 832 +               stat.size = size;
 833 +
 834 +       err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
 835 +
 836 +out_dput_parent:
 837 +       dput(parent);
 838 +       return err;
 839 +}
 840 --- /dev/null
 841 +++ b/fs/overlayfs/dir.c
 842 @@ -0,0 +1,596 @@
 843 +/*
 844 + *
 845 + * Copyright (C) 2011 Novell Inc.
 846 + *
 847 + * This program is free software; you can redistribute it and/or modify it
 848 + * under the terms of the GNU General Public License version 2 as published by
 849 + * the Free Software Foundation.
 850 + */
 851 +
 852 +#include <linux/fs.h>
 853 +#include <linux/namei.h>
 854 +#include <linux/xattr.h>
 855 +#include <linux/security.h>
 856 +#include "overlayfs.h"
 857 +
 858 +static const char *ovl_whiteout_symlink = "(overlay-whiteout)";
 859 +
 860 +static int ovl_whiteout(struct dentry *upperdir, struct dentry *dentry)
 861 +{
 862 +       int err;
 863 +       struct dentry *newdentry;
 864 +       const struct cred *old_cred;
 865 +       struct cred *override_cred;
 866 +
 867 +       /* FIXME: recheck lower dentry to see if whiteout is really needed */
 868 +
 869 +       err = -ENOMEM;
 870 +       override_cred = prepare_creds();
 871 +       if (!override_cred)
 872 +               goto out;
 873 +
 874 +       /*
 875 +        * CAP_SYS_ADMIN for setxattr
 876 +        * CAP_DAC_OVERRIDE for symlink creation
 877 +        * CAP_FOWNER for unlink in sticky directory
 878 +        */
 879 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 880 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 881 +       cap_raise(override_cred->cap_effective, CAP_FOWNER);
 882 +       override_cred->fsuid = 0;
 883 +       override_cred->fsgid = 0;
 884 +       old_cred = override_creds(override_cred);
 885 +
 886 +       newdentry = lookup_one_len(dentry->d_name.name, upperdir,
 887 +                                  dentry->d_name.len);
 888 +       err = PTR_ERR(newdentry);
 889 +       if (IS_ERR(newdentry))
 890 +               goto out_put_cred;
 891 +
 892 +       /* Just been removed within the same locked region */
 893 +       WARN_ON(newdentry->d_inode);
 894 +
 895 +       err = vfs_symlink(upperdir->d_inode, newdentry, ovl_whiteout_symlink);
 896 +       if (err)
 897 +               goto out_dput;
 898 +
 899 +       ovl_dentry_version_inc(dentry->d_parent);
 900 +
 901 +       err = vfs_setxattr(newdentry, ovl_whiteout_xattr, "y", 1, 0);
 902 +       if (err)
 903 +               vfs_unlink(upperdir->d_inode, newdentry);
 904 +
 905 +out_dput:
 906 +       dput(newdentry);
 907 +out_put_cred:
 908 +       revert_creds(old_cred);
 909 +       put_cred(override_cred);
 910 +out:
 911 +       if (err) {
 912 +               /*
 913 +                * There's no way to recover from failure to whiteout.
 914 +                * What should we do?  Log a big fat error and... ?
 915 +                */
 916 +               printk(KERN_ERR "overlayfs: ERROR - failed to whiteout '%s'\n",
 917 +                      dentry->d_name.name);
 918 +       }
 919 +
 920 +       return err;
 921 +}
 922 +
 923 +static struct dentry *ovl_lookup_create(struct dentry *upperdir,
 924 +                                       struct dentry *template)
 925 +{
 926 +       int err;
 927 +       struct dentry *newdentry;
 928 +       struct qstr *name = &template->d_name;
 929 +
 930 +       newdentry = lookup_one_len(name->name, upperdir, name->len);
 931 +       if (IS_ERR(newdentry))
 932 +               return newdentry;
 933 +
 934 +       if (newdentry->d_inode) {
 935 +               const struct cred *old_cred;
 936 +               struct cred *override_cred;
 937 +
 938 +               /* No need to check whiteout if lower parent is non-existent */
 939 +               err = -EEXIST;
 940 +               if (!ovl_dentry_lower(template->d_parent))
 941 +                       goto out_dput;
 942 +
 943 +               if (!S_ISLNK(newdentry->d_inode->i_mode))
 944 +                       goto out_dput;
 945 +
 946 +               err = -ENOMEM;
 947 +               override_cred = prepare_creds();
 948 +               if (!override_cred)
 949 +                       goto out_dput;
 950 +
 951 +               /*
 952 +                * CAP_SYS_ADMIN for getxattr
 953 +                * CAP_FOWNER for unlink in sticky directory
 954 +                */
 955 +               cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 956 +               cap_raise(override_cred->cap_effective, CAP_FOWNER);
 957 +               old_cred = override_creds(override_cred);
 958 +
 959 +               err = -EEXIST;
 960 +               if (ovl_is_whiteout(newdentry))
 961 +                       err = vfs_unlink(upperdir->d_inode, newdentry);
 962 +
 963 +               revert_creds(old_cred);
 964 +               put_cred(override_cred);
 965 +               if (err)
 966 +                       goto out_dput;
 967 +
 968 +               dput(newdentry);
 969 +               newdentry = lookup_one_len(name->name, upperdir, name->len);
 970 +               if (IS_ERR(newdentry)) {
 971 +                       ovl_whiteout(upperdir, template);
 972 +                       return newdentry;
 973 +               }
 974 +
 975 +               /*
 976 +                * Whiteout just been successfully removed, parent
 977 +                * i_mutex is still held, there's no way the lookup
 978 +                * could return positive.
 979 +                */
 980 +               WARN_ON(newdentry->d_inode);
 981 +       }
 982 +
 983 +       return newdentry;
 984 +
 985 +out_dput:
 986 +       dput(newdentry);
 987 +       return ERR_PTR(err);
 988 +}
 989 +
 990 +struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
 991 +                               struct kstat *stat, const char *link)
 992 +{
 993 +       int err;
 994 +       struct dentry *newdentry;
 995 +       struct inode *dir = upperdir->d_inode;
 996 +
 997 +       newdentry = ovl_lookup_create(upperdir, dentry);
 998 +       if (IS_ERR(newdentry))
 999 +               goto out;
1000 +
1001 +       switch (stat->mode & S_IFMT) {
1002 +       case S_IFREG:
1003 +               err = vfs_create(dir, newdentry, stat->mode, NULL);
1004 +               break;
1005 +
1006 +       case S_IFDIR:
1007 +               err = vfs_mkdir(dir, newdentry, stat->mode);
1008 +               break;
1009 +
1010 +       case S_IFCHR:
1011 +       case S_IFBLK:
1012 +       case S_IFIFO:
1013 +       case S_IFSOCK:
1014 +               err = vfs_mknod(dir, newdentry, stat->mode, stat->rdev);
1015 +               break;
1016 +
1017 +       case S_IFLNK:
1018 +               err = vfs_symlink(dir, newdentry, link);
1019 +               break;
1020 +
1021 +       default:
1022 +               err = -EPERM;
1023 +       }
1024 +       if (err) {
1025 +               if (ovl_dentry_is_opaque(dentry))
1026 +                       ovl_whiteout(upperdir, dentry);
1027 +               dput(newdentry);
1028 +               newdentry = ERR_PTR(err);
1029 +       } else if (WARN_ON(!newdentry->d_inode)) {
1030 +               /*
1031 +                * Not quite sure if non-instantiated dentry is legal or not.
1032 +                * VFS doesn't seem to care so check and warn here.
1033 +                */
1034 +               dput(newdentry);
1035 +               newdentry = ERR_PTR(-ENOENT);
1036 +       }
1037 +
1038 +out:
1039 +       return newdentry;
1040 +
1041 +}
1042 +
1043 +static int ovl_set_opaque(struct dentry *upperdentry)
1044 +{
1045 +       int err;
1046 +       const struct cred *old_cred;
1047 +       struct cred *override_cred;
1048 +
1049 +       override_cred = prepare_creds();
1050 +       if (!override_cred)
1051 +               return -ENOMEM;
1052 +
1053 +       /* CAP_SYS_ADMIN for setxattr of "trusted" namespace */
1054 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1055 +       old_cred = override_creds(override_cred);
1056 +       err = vfs_setxattr(upperdentry, ovl_opaque_xattr, "y", 1, 0);
1057 +       revert_creds(old_cred);
1058 +       put_cred(override_cred);
1059 +
1060 +       return err;
1061 +}
1062 +
1063 +static int ovl_remove_opaque(struct dentry *upperdentry)
1064 +{
1065 +       int err;
1066 +       const struct cred *old_cred;
1067 +       struct cred *override_cred;
1068 +
1069 +       override_cred = prepare_creds();
1070 +       if (!override_cred)
1071 +               return -ENOMEM;
1072 +
1073 +       /* CAP_SYS_ADMIN for removexattr of "trusted" namespace */
1074 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1075 +       old_cred = override_creds(override_cred);
1076 +       err = vfs_removexattr(upperdentry, ovl_opaque_xattr);
1077 +       revert_creds(old_cred);
1078 +       put_cred(override_cred);
1079 +
1080 +       return err;
1081 +}
1082 +
1083 +static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
1084 +                        struct kstat *stat)
1085 +{
1086 +       int err;
1087 +       enum ovl_path_type type;
1088 +       struct path realpath;
1089 +
1090 +       type = ovl_path_real(dentry, &realpath);
1091 +       err = vfs_getattr(realpath.mnt, realpath.dentry, stat);
1092 +       if (err)
1093 +               return err;
1094 +
1095 +       stat->dev = dentry->d_sb->s_dev;
1096 +       stat->ino = dentry->d_inode->i_ino;
1097 +
1098 +       /*
1099 +        * It's probably not worth it to count subdirs to get the
1100 +        * correct link count.  nlink=1 seems to pacify 'find' and
1101 +        * other utilities.
1102 +        */
1103 +       if (type == OVL_PATH_MERGE)
1104 +               stat->nlink = 1;
1105 +
1106 +       return 0;
1107 +}
1108 +
1109 +static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
1110 +                            const char *link)
1111 +{
1112 +       int err;
1113 +       struct dentry *newdentry;
1114 +       struct dentry *upperdir;
1115 +       struct inode *inode;
1116 +       struct kstat stat = {
1117 +               .mode = mode,
1118 +               .rdev = rdev,
1119 +       };
1120 +
1121 +       err = -ENOMEM;
1122 +       inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
1123 +       if (!inode)
1124 +               goto out;
1125 +
1126 +       err = ovl_copy_up(dentry->d_parent);
1127 +       if (err)
1128 +               goto out_iput;
1129 +
1130 +       upperdir = ovl_dentry_upper(dentry->d_parent);
1131 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1132 +
1133 +       newdentry = ovl_upper_create(upperdir, dentry, &stat, link);
1134 +       err = PTR_ERR(newdentry);
1135 +       if (IS_ERR(newdentry))
1136 +               goto out_unlock;
1137 +
1138 +       ovl_dentry_version_inc(dentry->d_parent);
1139 +       if (ovl_dentry_is_opaque(dentry) && S_ISDIR(mode)) {
1140 +               err = ovl_set_opaque(newdentry);
1141 +               if (err) {
1142 +                       vfs_rmdir(upperdir->d_inode, newdentry);
1143 +                       ovl_whiteout(upperdir, dentry);
1144 +                       goto out_dput;
1145 +               }
1146 +       }
1147 +       ovl_dentry_update(dentry, newdentry);
1148 +       d_instantiate(dentry, inode);
1149 +       inode = NULL;
1150 +       newdentry = NULL;
1151 +       err = 0;
1152 +
1153 +out_dput:
1154 +       dput(newdentry);
1155 +out_unlock:
1156 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1157 +out_iput:
1158 +       iput(inode);
1159 +out:
1160 +       return err;
1161 +}
1162 +
1163 +static int ovl_create(struct inode *dir, struct dentry *dentry, int mode,
1164 +                       struct nameidata *nd)
1165 +{
1166 +       return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
1167 +}
1168 +
1169 +static int ovl_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1170 +{
1171 +       return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
1172 +}
1173 +
1174 +static int ovl_mknod(struct inode *dir, struct dentry *dentry, int mode,
1175 +                      dev_t rdev)
1176 +{
1177 +       return ovl_create_object(dentry, mode, rdev, NULL);
1178 +}
1179 +
1180 +static int ovl_symlink(struct inode *dir, struct dentry *dentry,
1181 +                        const char *link)
1182 +{
1183 +       return ovl_create_object(dentry, S_IFLNK, 0, link);
1184 +}
1185 +
1186 +static int ovl_do_remove(struct dentry *dentry, bool is_dir)
1187 +{
1188 +       int err;
1189 +       enum ovl_path_type type;
1190 +       struct path realpath;
1191 +       struct dentry *upperdir;
1192 +
1193 +       err = ovl_copy_up(dentry->d_parent);
1194 +       if (err)
1195 +               return err;
1196 +
1197 +       upperdir = ovl_dentry_upper(dentry->d_parent);
1198 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1199 +       type = ovl_path_real(dentry, &realpath);
1200 +       if (type != OVL_PATH_LOWER) {
1201 +               err = -ESTALE;
1202 +               if (realpath.dentry->d_parent != upperdir)
1203 +                       goto out_d_drop;
1204 +
1205 +               /* FIXME: create whiteout up front and rename to target */
1206 +
1207 +               if (is_dir)
1208 +                       err = vfs_rmdir(upperdir->d_inode, realpath.dentry);
1209 +               else
1210 +                       err = vfs_unlink(upperdir->d_inode, realpath.dentry);
1211 +               if (err)
1212 +                       goto out_d_drop;
1213 +
1214 +               ovl_dentry_version_inc(dentry->d_parent);
1215 +       }
1216 +
1217 +       if (type != OVL_PATH_UPPER || ovl_dentry_is_opaque(dentry))
1218 +               err = ovl_whiteout(upperdir, dentry);
1219 +
1220 +       /*
1221 +        * Keeping this dentry hashed would mean having to release
1222 +        * upperpath/lowerpath, which could only be done if we are the
1223 +        * sole user of this dentry.  Too tricky...  Just unhash for
1224 +        * now.
1225 +        */
1226 +out_d_drop:
1227 +       d_drop(dentry);
1228 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1229 +
1230 +       return err;
1231 +}
1232 +
1233 +static int ovl_unlink(struct inode *dir, struct dentry *dentry)
1234 +{
1235 +       return ovl_do_remove(dentry, false);
1236 +}
1237 +
1238 +
1239 +static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
1240 +{
1241 +       int err;
1242 +       enum ovl_path_type type;
1243 +
1244 +       type = ovl_path_type(dentry);
1245 +       if (type != OVL_PATH_UPPER) {
1246 +               err = ovl_check_empty_and_clear(dentry, type);
1247 +               if (err)
1248 +                       return err;
1249 +       }
1250 +
1251 +       return ovl_do_remove(dentry, true);
1252 +}
1253 +
1254 +static int ovl_link(struct dentry *old, struct inode *newdir,
1255 +                   struct dentry *new)
1256 +{
1257 +       int err;
1258 +       struct dentry *olddentry;
1259 +       struct dentry *newdentry;
1260 +       struct dentry *upperdir;
1261 +
1262 +       err = ovl_copy_up(old);
1263 +       if (err)
1264 +               goto out;
1265 +
1266 +       err = ovl_copy_up(new->d_parent);
1267 +       if (err)
1268 +               goto out;
1269 +
1270 +       upperdir = ovl_dentry_upper(new->d_parent);
1271 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1272 +       newdentry = ovl_lookup_create(upperdir, new);
1273 +       err = PTR_ERR(newdentry);
1274 +       if (IS_ERR(newdentry))
1275 +               goto out_unlock;
1276 +
1277 +       olddentry = ovl_dentry_upper(old);
1278 +       err = vfs_link(olddentry, upperdir->d_inode, newdentry);
1279 +       if (!err) {
1280 +               if (WARN_ON(!newdentry->d_inode)) {
1281 +                       dput(newdentry);
1282 +                       err = -ENOENT;
1283 +                       goto out_unlock;
1284 +               }
1285 +
1286 +               ovl_dentry_version_inc(new->d_parent);
1287 +               ovl_dentry_update(new, newdentry);
1288 +
1289 +               ihold(old->d_inode);
1290 +               d_instantiate(new, old->d_inode);
1291 +       } else {
1292 +               if (ovl_dentry_is_opaque(new))
1293 +                       ovl_whiteout(upperdir, new);
1294 +               dput(newdentry);
1295 +       }
1296 +out_unlock:
1297 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1298 +out:
1299 +       return err;
1300 +
1301 +}
1302 +
1303 +static int ovl_rename(struct inode *olddir, struct dentry *old,
1304 +                       struct inode *newdir, struct dentry *new)
1305 +{
1306 +       int err;
1307 +       enum ovl_path_type old_type;
1308 +       enum ovl_path_type new_type;
1309 +       struct dentry *old_upperdir;
1310 +       struct dentry *new_upperdir;
1311 +       struct dentry *olddentry;
1312 +       struct dentry *newdentry;
1313 +       struct dentry *trap;
1314 +       bool old_opaque;
1315 +       bool new_opaque;
1316 +       bool new_create = false;
1317 +       bool is_dir = S_ISDIR(old->d_inode->i_mode);
1318 +
1319 +       /* Don't copy up directory trees */
1320 +       old_type = ovl_path_type(old);
1321 +       if (old_type != OVL_PATH_UPPER && is_dir)
1322 +               return -EXDEV;
1323 +
1324 +       if (new->d_inode) {
1325 +               new_type = ovl_path_type(new);
1326 +
1327 +               if (new_type == OVL_PATH_LOWER && old_type == OVL_PATH_LOWER) {
1328 +                       if (ovl_dentry_lower(old)->d_inode ==
1329 +                           ovl_dentry_lower(new)->d_inode)
1330 +                               return 0;
1331 +               }
1332 +               if (new_type != OVL_PATH_LOWER && old_type != OVL_PATH_LOWER) {
1333 +                       if (ovl_dentry_upper(old)->d_inode ==
1334 +                           ovl_dentry_upper(new)->d_inode)
1335 +                               return 0;
1336 +               }
1337 +
1338 +               if (new_type != OVL_PATH_UPPER &&
1339 +                   S_ISDIR(new->d_inode->i_mode)) {
1340 +                       err = ovl_check_empty_and_clear(new, new_type);
1341 +                       if (err)
1342 +                               return err;
1343 +               }
1344 +       } else {
1345 +               new_type = OVL_PATH_UPPER;
1346 +       }
1347 +
1348 +       err = ovl_copy_up(old);
1349 +       if (err)
1350 +               return err;
1351 +
1352 +       err = ovl_copy_up(new->d_parent);
1353 +       if (err)
1354 +               return err;
1355 +
1356 +       old_upperdir = ovl_dentry_upper(old->d_parent);
1357 +       new_upperdir = ovl_dentry_upper(new->d_parent);
1358 +
1359 +       trap = lock_rename(new_upperdir, old_upperdir);
1360 +
1361 +       olddentry = ovl_dentry_upper(old);
1362 +       newdentry = ovl_dentry_upper(new);
1363 +       if (newdentry) {
1364 +               dget(newdentry);
1365 +       } else {
1366 +               new_create = true;
1367 +               newdentry = ovl_lookup_create(new_upperdir, new);
1368 +               err = PTR_ERR(newdentry);
1369 +               if (IS_ERR(newdentry))
1370 +                       goto out_unlock;
1371 +       }
1372 +
1373 +       err = -ESTALE;
1374 +       if (olddentry->d_parent != old_upperdir)
1375 +               goto out_dput;
1376 +       if (newdentry->d_parent != new_upperdir)
1377 +               goto out_dput;
1378 +       if (olddentry == trap)
1379 +               goto out_dput;
1380 +       if (newdentry == trap)
1381 +               goto out_dput;
1382 +
1383 +       old_opaque = ovl_dentry_is_opaque(old);
1384 +       new_opaque = ovl_dentry_is_opaque(new) || new_type != OVL_PATH_UPPER;
1385 +
1386 +       if (is_dir && !old_opaque && new_opaque) {
1387 +               err = ovl_set_opaque(olddentry);
1388 +               if (err)
1389 +                       goto out_dput;
1390 +       }
1391 +
1392 +       err = vfs_rename(old_upperdir->d_inode, olddentry,
1393 +                        new_upperdir->d_inode, newdentry);
1394 +
1395 +       if (err) {
1396 +               if (new_create && ovl_dentry_is_opaque(new))
1397 +                       ovl_whiteout(new_upperdir, new);
1398 +               if (is_dir && !old_opaque && new_opaque)
1399 +                       ovl_remove_opaque(olddentry);
1400 +               goto out_dput;
1401 +       }
1402 +
1403 +       if (old_type != OVL_PATH_UPPER || old_opaque)
1404 +               err = ovl_whiteout(old_upperdir, old);
1405 +       if (is_dir && old_opaque && !new_opaque)
1406 +               ovl_remove_opaque(olddentry);
1407 +
1408 +       if (old_opaque != new_opaque)
1409 +               ovl_dentry_set_opaque(old, new_opaque);
1410 +
1411 +       ovl_dentry_version_inc(old->d_parent);
1412 +       ovl_dentry_version_inc(new->d_parent);
1413 +
1414 +out_dput:
1415 +       dput(newdentry);
1416 +out_unlock:
1417 +       unlock_rename(new_upperdir, old_upperdir);
1418 +       return err;
1419 +}
1420 +
1421 +const struct inode_operations ovl_dir_inode_operations = {
1422 +       .lookup         = ovl_lookup,
1423 +       .mkdir          = ovl_mkdir,
1424 +       .symlink        = ovl_symlink,
1425 +       .unlink         = ovl_unlink,
1426 +       .rmdir          = ovl_rmdir,
1427 +       .rename         = ovl_rename,
1428 +       .link           = ovl_link,
1429 +       .setattr        = ovl_setattr,
1430 +       .create         = ovl_create,
1431 +       .mknod          = ovl_mknod,
1432 +       .permission     = ovl_permission,
1433 +       .getattr        = ovl_dir_getattr,
1434 +       .setxattr       = ovl_setxattr,
1435 +       .getxattr       = ovl_getxattr,
1436 +       .listxattr      = ovl_listxattr,
1437 +       .removexattr    = ovl_removexattr,
1438 +};
1439 --- /dev/null
1440 +++ b/fs/overlayfs/inode.c
1441 @@ -0,0 +1,383 @@
1442 +/*
1443 + *
1444 + * Copyright (C) 2011 Novell Inc.
1445 + *
1446 + * This program is free software; you can redistribute it and/or modify it
1447 + * under the terms of the GNU General Public License version 2 as published by
1448 + * the Free Software Foundation.
1449 + */
1450 +
1451 +#include <linux/fs.h>
1452 +#include <linux/slab.h>
1453 +#include <linux/xattr.h>
1454 +#include "overlayfs.h"
1455 +
1456 +int ovl_setattr(struct dentry *dentry, struct iattr *attr)
1457 +{
1458 +       struct dentry *upperdentry;
1459 +       int err;
1460 +
1461 +       if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry))
1462 +               err = ovl_copy_up_truncate(dentry, attr->ia_size);
1463 +       else
1464 +               err = ovl_copy_up(dentry);
1465 +       if (err)
1466 +               return err;
1467 +
1468 +       upperdentry = ovl_dentry_upper(dentry);
1469 +
1470 +       if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
1471 +               attr->ia_valid &= ~ATTR_MODE;
1472 +
1473 +       mutex_lock(&upperdentry->d_inode->i_mutex);
1474 +       err = notify_change(upperdentry, attr);
1475 +       mutex_unlock(&upperdentry->d_inode->i_mutex);
1476 +
1477 +       return err;
1478 +}
1479 +
1480 +static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
1481 +                        struct kstat *stat)
1482 +{
1483 +       struct path realpath;
1484 +
1485 +       ovl_path_real(dentry, &realpath);
1486 +       return vfs_getattr(realpath.mnt, realpath.dentry, stat);
1487 +}
1488 +
1489 +int ovl_permission(struct inode *inode, int mask)
1490 +{
1491 +       struct ovl_entry *oe;
1492 +       struct dentry *alias = NULL;
1493 +       struct inode *realinode;
1494 +       struct dentry *realdentry;
1495 +       bool is_upper;
1496 +       int err;
1497 +
1498 +       if (S_ISDIR(inode->i_mode)) {
1499 +               oe = inode->i_private;
1500 +       } else if (mask & MAY_NOT_BLOCK) {
1501 +               return -ECHILD;
1502 +       } else {
1503 +               /*
1504 +                * For non-directories find an alias and get the info
1505 +                * from there.
1506 +                */
1507 +               spin_lock(&inode->i_lock);
1508 +               if (WARN_ON(list_empty(&inode->i_dentry))) {
1509 +                       spin_unlock(&inode->i_lock);
1510 +                       return -ENOENT;
1511 +               }
1512 +               alias = list_entry(inode->i_dentry.next, struct dentry, d_alias);
1513 +               dget(alias);
1514 +               spin_unlock(&inode->i_lock);
1515 +               oe = alias->d_fsdata;
1516 +       }
1517 +
1518 +       realdentry = ovl_entry_real(oe, &is_upper);
1519 +
1520 +       /* Careful in RCU walk mode */
1521 +       realinode = ACCESS_ONCE(realdentry->d_inode);
1522 +       if (!realinode) {
1523 +               WARN_ON(!(mask & MAY_NOT_BLOCK));
1524 +               err = -ENOENT;
1525 +               goto out_dput;
1526 +       }
1527 +
1528 +       if (mask & MAY_WRITE) {
1529 +               umode_t mode = realinode->i_mode;
1530 +
1531 +               /*
1532 +                * Writes will always be redirected to upper layer, so
1533 +                * ignore lower layer being read-only.
1534 +                *
1535 +                * If the overlay itself is read-only then proceed
1536 +                * with the permission check, don't return EROFS.
1537 +                * This will only happen if this is the lower layer of
1538 +                * another overlayfs.
1539 +                *
1540 +                * If upper fs becomes read-only after the overlay was
1541 +                * constructed return EROFS to prevent modification of
1542 +                * upper layer.
1543 +                */
1544 +               err = -EROFS;
1545 +               if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
1546 +                   (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
1547 +                       goto out_dput;
1548 +
1549 +               /*
1550 +                * Nobody gets write access to an immutable file.
1551 +                */
1552 +               err = -EACCES;
1553 +               if (IS_IMMUTABLE(realinode))
1554 +                       goto out_dput;
1555 +       }
1556 +
1557 +       if (realinode->i_op->permission)
1558 +               err = realinode->i_op->permission(realinode, mask);
1559 +       else
1560 +               err = generic_permission(realinode, mask);
1561 +out_dput:
1562 +       dput(alias);
1563 +       return err;
1564 +}
1565 +
1566 +
1567 +struct ovl_link_data {
1568 +       struct dentry *realdentry;
1569 +       void *cookie;
1570 +};
1571 +
1572 +static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
1573 +{
1574 +       void *ret;
1575 +       struct dentry *realdentry;
1576 +       struct inode *realinode;
1577 +
1578 +       realdentry = ovl_dentry_real(dentry);
1579 +       realinode = realdentry->d_inode;
1580 +
1581 +       if (WARN_ON(!realinode->i_op->follow_link))
1582 +               return ERR_PTR(-EPERM);
1583 +
1584 +       ret = realinode->i_op->follow_link(realdentry, nd);
1585 +       if (IS_ERR(ret))
1586 +               return ret;
1587 +
1588 +       if (realinode->i_op->put_link) {
1589 +               struct ovl_link_data *data;
1590 +
1591 +               data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
1592 +               if (!data) {
1593 +                       realinode->i_op->put_link(realdentry, nd, ret);
1594 +                       return ERR_PTR(-ENOMEM);
1595 +               }
1596 +               data->realdentry = realdentry;
1597 +               data->cookie = ret;
1598 +
1599 +               return data;
1600 +       } else {
1601 +               return NULL;
1602 +       }
1603 +}
1604 +
1605 +static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
1606 +{
1607 +       struct inode *realinode;
1608 +       struct ovl_link_data *data = c;
1609 +
1610 +       if (!data)
1611 +               return;
1612 +
1613 +       realinode = data->realdentry->d_inode;
1614 +       realinode->i_op->put_link(data->realdentry, nd, data->cookie);
1615 +       kfree(data);
1616 +}
1617 +
1618 +static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
1619 +{
1620 +       struct path realpath;
1621 +       struct inode *realinode;
1622 +
1623 +       ovl_path_real(dentry, &realpath);
1624 +       realinode = realpath.dentry->d_inode;
1625 +
1626 +       if (!realinode->i_op->readlink)
1627 +               return -EINVAL;
1628 +
1629 +       touch_atime(realpath.mnt, realpath.dentry);
1630 +
1631 +       return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
1632 +}
1633 +
1634 +
1635 +static bool ovl_is_private_xattr(const char *name)
1636 +{
1637 +       return strncmp(name, "trusted.overlay.", 14) == 0;
1638 +}
1639 +
1640 +int ovl_setxattr(struct dentry *dentry, const char *name,
1641 +                const void *value, size_t size, int flags)
1642 +{
1643 +       int err;
1644 +       struct dentry *upperdentry;
1645 +
1646 +       if (ovl_is_private_xattr(name))
1647 +               return -EPERM;
1648 +
1649 +       err = ovl_copy_up(dentry);
1650 +       if (err)
1651 +               return err;
1652 +
1653 +       upperdentry = ovl_dentry_upper(dentry);
1654 +       return  vfs_setxattr(upperdentry, name, value, size, flags);
1655 +}
1656 +
1657 +ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
1658 +                    void *value, size_t size)
1659 +{
1660 +       if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
1661 +           ovl_is_private_xattr(name))
1662 +               return -ENODATA;
1663 +
1664 +       return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
1665 +}
1666 +
1667 +ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
1668 +{
1669 +       ssize_t res;
1670 +       int off;
1671 +
1672 +       res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
1673 +       if (res <= 0 || size == 0)
1674 +               return res;
1675 +
1676 +       if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
1677 +               return res;
1678 +
1679 +       /* filter out private xattrs */
1680 +       for (off = 0; off < res;) {
1681 +               char *s = list + off;
1682 +               size_t slen = strlen(s) + 1;
1683 +
1684 +               BUG_ON(off + slen > res);
1685 +
1686 +               if (ovl_is_private_xattr(s)) {
1687 +                       res -= slen;
1688 +                       memmove(s, s + slen, res - off);
1689 +               } else {
1690 +                       off += slen;
1691 +               }
1692 +       }
1693 +
1694 +       return res;
1695 +}
1696 +
1697 +int ovl_removexattr(struct dentry *dentry, const char *name)
1698 +{
1699 +       int err;
1700 +       struct path realpath;
1701 +       enum ovl_path_type type;
1702 +
1703 +       if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
1704 +           ovl_is_private_xattr(name))
1705 +               return -ENODATA;
1706 +
1707 +       type = ovl_path_real(dentry, &realpath);
1708 +       if (type == OVL_PATH_LOWER) {
1709 +               err = vfs_getxattr(realpath.dentry, name, NULL, 0);
1710 +               if (err < 0)
1711 +                       return err;
1712 +
1713 +               err = ovl_copy_up(dentry);
1714 +               if (err)
1715 +                       return err;
1716 +
1717 +               ovl_path_upper(dentry, &realpath);
1718 +       }
1719 +
1720 +       return vfs_removexattr(realpath.dentry, name);
1721 +}
1722 +
1723 +static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
1724 +                                 struct dentry *realdentry)
1725 +{
1726 +       if (type != OVL_PATH_LOWER)
1727 +               return false;
1728 +
1729 +       if (special_file(realdentry->d_inode->i_mode))
1730 +               return false;
1731 +
1732 +       if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
1733 +               return false;
1734 +
1735 +       return true;
1736 +}
1737 +
1738 +static struct file *ovl_open(struct dentry *dentry, int flags,
1739 +                            const struct cred *cred)
1740 +{
1741 +       int err;
1742 +       struct path realpath;
1743 +       enum ovl_path_type type;
1744 +
1745 +       type = ovl_path_real(dentry, &realpath);
1746 +       if (ovl_open_need_copy_up(flags, type, realpath.dentry)) {
1747 +               if (flags & O_TRUNC)
1748 +                       err = ovl_copy_up_truncate(dentry, 0);
1749 +               else
1750 +                       err = ovl_copy_up(dentry);
1751 +               if (err)
1752 +                       return ERR_PTR(err);
1753 +
1754 +               ovl_path_upper(dentry, &realpath);
1755 +       }
1756 +
1757 +       return vfs_open(&realpath, flags, cred);
1758 +}
1759 +
1760 +static const struct inode_operations ovl_file_inode_operations = {
1761 +       .setattr        = ovl_setattr,
1762 +       .permission     = ovl_permission,
1763 +       .getattr        = ovl_getattr,
1764 +       .setxattr       = ovl_setxattr,
1765 +       .getxattr       = ovl_getxattr,
1766 +       .listxattr      = ovl_listxattr,
1767 +       .removexattr    = ovl_removexattr,
1768 +       .open           = ovl_open,
1769 +};
1770 +
1771 +static const struct inode_operations ovl_symlink_inode_operations = {
1772 +       .setattr        = ovl_setattr,
1773 +       .follow_link    = ovl_follow_link,
1774 +       .put_link       = ovl_put_link,
1775 +       .readlink       = ovl_readlink,
1776 +       .getattr        = ovl_getattr,
1777 +       .setxattr       = ovl_setxattr,
1778 +       .getxattr       = ovl_getxattr,
1779 +       .listxattr      = ovl_listxattr,
1780 +       .removexattr    = ovl_removexattr,
1781 +};
1782 +
1783 +struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
1784 +                           struct ovl_entry *oe)
1785 +{
1786 +       struct inode *inode;
1787 +
1788 +       inode = new_inode(sb);
1789 +       if (!inode)
1790 +               return NULL;
1791 +
1792 +       mode &= S_IFMT;
1793 +
1794 +       inode->i_ino = get_next_ino();
1795 +       inode->i_mode = mode;
1796 +       inode->i_flags |= S_NOATIME | S_NOCMTIME;
1797 +
1798 +       switch (mode) {
1799 +       case S_IFDIR:
1800 +               inode->i_private = oe;
1801 +               inode->i_op = &ovl_dir_inode_operations;
1802 +               inode->i_fop = &ovl_dir_operations;
1803 +               break;
1804 +
1805 +       case S_IFLNK:
1806 +               inode->i_op = &ovl_symlink_inode_operations;
1807 +               break;
1808 +
1809 +       case S_IFREG:
1810 +       case S_IFSOCK:
1811 +       case S_IFBLK:
1812 +       case S_IFCHR:
1813 +       case S_IFIFO:
1814 +               inode->i_op = &ovl_file_inode_operations;
1815 +               break;
1816 +
1817 +       default:
1818 +               WARN(1, "illegal file type: %i\n", mode);
1819 +               inode = NULL;
1820 +       }
1821 +
1822 +       return inode;
1823 +
1824 +}
1825 --- /dev/null
1826 +++ b/fs/overlayfs/overlayfs.h
1827 @@ -0,0 +1,63 @@
1828 +/*
1829 + *
1830 + * Copyright (C) 2011 Novell Inc.
1831 + *
1832 + * This program is free software; you can redistribute it and/or modify it
1833 + * under the terms of the GNU General Public License version 2 as published by
1834 + * the Free Software Foundation.
1835 + */
1836 +
1837 +struct ovl_entry;
1838 +
1839 +enum ovl_path_type {
1840 +       OVL_PATH_UPPER,
1841 +       OVL_PATH_MERGE,
1842 +       OVL_PATH_LOWER,
1843 +};
1844 +
1845 +extern const char *ovl_opaque_xattr;
1846 +extern const char *ovl_whiteout_xattr;
1847 +extern const struct dentry_operations ovl_dentry_operations;
1848 +
1849 +enum ovl_path_type ovl_path_type(struct dentry *dentry);
1850 +u64 ovl_dentry_version_get(struct dentry *dentry);
1851 +void ovl_dentry_version_inc(struct dentry *dentry);
1852 +void ovl_path_upper(struct dentry *dentry, struct path *path);
1853 +void ovl_path_lower(struct dentry *dentry, struct path *path);
1854 +enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
1855 +struct dentry *ovl_dentry_upper(struct dentry *dentry);
1856 +struct dentry *ovl_dentry_lower(struct dentry *dentry);
1857 +struct dentry *ovl_dentry_real(struct dentry *dentry);
1858 +struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper);
1859 +bool ovl_dentry_is_opaque(struct dentry *dentry);
1860 +void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
1861 +bool ovl_is_whiteout(struct dentry *dentry);
1862 +void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
1863 +struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
1864 +                         struct nameidata *nd);
1865 +
1866 +struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
1867 +                               struct kstat *stat, const char *link);
1868 +
1869 +/* readdir.c */
1870 +extern const struct file_operations ovl_dir_operations;
1871 +int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type);
1872 +
1873 +/* inode.c */
1874 +int ovl_setattr(struct dentry *dentry, struct iattr *attr);
1875 +int ovl_permission(struct inode *inode, int mask);
1876 +int ovl_setxattr(struct dentry *dentry, const char *name,
1877 +                const void *value, size_t size, int flags);
1878 +ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
1879 +                    void *value, size_t size);
1880 +ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
1881 +int ovl_removexattr(struct dentry *dentry, const char *name);
1882 +
1883 +struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
1884 +                           struct ovl_entry *oe);
1885 +/* dir.c */
1886 +extern const struct inode_operations ovl_dir_inode_operations;
1887 +
1888 +/* copy_up.c */
1889 +int ovl_copy_up(struct dentry *dentry);
1890 +int ovl_copy_up_truncate(struct dentry *dentry, loff_t size);
1891 --- /dev/null
1892 +++ b/fs/overlayfs/readdir.c
1893 @@ -0,0 +1,559 @@
1894 +/*
1895 + *
1896 + * Copyright (C) 2011 Novell Inc.
1897 + *
1898 + * This program is free software; you can redistribute it and/or modify it
1899 + * under the terms of the GNU General Public License version 2 as published by
1900 + * the Free Software Foundation.
1901 + */
1902 +
1903 +#include <linux/fs.h>
1904 +#include <linux/slab.h>
1905 +#include <linux/namei.h>
1906 +#include <linux/file.h>
1907 +#include <linux/xattr.h>
1908 +#include <linux/rbtree.h>
1909 +#include <linux/security.h>
1910 +#include "overlayfs.h"
1911 +
1912 +struct ovl_cache_entry {
1913 +       const char *name;
1914 +       unsigned int len;
1915 +       unsigned int type;
1916 +       u64 ino;
1917 +       bool is_whiteout;
1918 +       struct list_head l_node;
1919 +       struct rb_node node;
1920 +};
1921 +
1922 +struct ovl_readdir_data {
1923 +       struct rb_root *root;
1924 +       struct list_head *list;
1925 +       struct list_head *middle;
1926 +       struct dentry *dir;
1927 +       int count;
1928 +       int err;
1929 +};
1930 +
1931 +struct ovl_dir_file {
1932 +       bool is_real;
1933 +       bool is_cached;
1934 +       struct list_head cursor;
1935 +       u64 cache_version;
1936 +       struct list_head cache;
1937 +       struct file *realfile;
1938 +};
1939 +
1940 +static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
1941 +{
1942 +       return container_of(n, struct ovl_cache_entry, node);
1943 +}
1944 +
1945 +static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
1946 +                                                   const char *name, int len)
1947 +{
1948 +       struct rb_node *node = root->rb_node;
1949 +       int cmp;
1950 +
1951 +       while (node) {
1952 +               struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
1953 +
1954 +               cmp = strncmp(name, p->name, len);
1955 +               if (cmp > 0)
1956 +                       node = p->node.rb_right;
1957 +               else if (cmp < 0 || len < p->len)
1958 +                       node = p->node.rb_left;
1959 +               else
1960 +                       return p;
1961 +       }
1962 +
1963 +       return NULL;
1964 +}
1965 +
1966 +static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
1967 +                                                  u64 ino, unsigned int d_type)
1968 +{
1969 +       struct ovl_cache_entry *p;
1970 +
1971 +       p = kmalloc(sizeof(*p) + len + 1, GFP_KERNEL);
1972 +       if (p) {
1973 +               char *name_copy = (char *) (p + 1);
1974 +               memcpy(name_copy, name, len);
1975 +               name_copy[len] = '\0';
1976 +               p->name = name_copy;
1977 +               p->len = len;
1978 +               p->type = d_type;
1979 +               p->ino = ino;
1980 +               p->is_whiteout = false;
1981 +       }
1982 +
1983 +       return p;
1984 +}
1985 +
1986 +static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
1987 +                                 const char *name, int len, u64 ino,
1988 +                                 unsigned int d_type)
1989 +{
1990 +       struct rb_node **newp = &rdd->root->rb_node;
1991 +       struct rb_node *parent = NULL;
1992 +       struct ovl_cache_entry *p;
1993 +
1994 +       while (*newp) {
1995 +               int cmp;
1996 +               struct ovl_cache_entry *tmp;
1997 +
1998 +               parent = *newp;
1999 +               tmp = ovl_cache_entry_from_node(*newp);
2000 +               cmp = strncmp(name, tmp->name, len);
2001 +               if (cmp > 0)
2002 +                       newp = &tmp->node.rb_right;
2003 +               else if (cmp < 0 || len < tmp->len)
2004 +                       newp = &tmp->node.rb_left;
2005 +               else
2006 +                       return 0;
2007 +       }
2008 +
2009 +       p = ovl_cache_entry_new(name, len, ino, d_type);
2010 +       if (p == NULL)
2011 +               return -ENOMEM;
2012 +
2013 +       list_add_tail(&p->l_node, rdd->list);
2014 +       rb_link_node(&p->node, parent, newp);
2015 +       rb_insert_color(&p->node, rdd->root);
2016 +
2017 +       return 0;
2018 +}
2019 +
2020 +static int ovl_fill_lower(void *buf, const char *name, int namelen,
2021 +                           loff_t offset, u64 ino, unsigned int d_type)
2022 +{
2023 +       struct ovl_readdir_data *rdd = buf;
2024 +       struct ovl_cache_entry *p;
2025 +
2026 +       rdd->count++;
2027 +       p = ovl_cache_entry_find(rdd->root, name, namelen);
2028 +       if (p) {
2029 +               list_move_tail(&p->l_node, rdd->middle);
2030 +       } else {
2031 +               p = ovl_cache_entry_new(name, namelen, ino, d_type);
2032 +               if (p == NULL)
2033 +                       rdd->err = -ENOMEM;
2034 +               else
2035 +                       list_add_tail(&p->l_node, rdd->middle);
2036 +       }
2037 +
2038 +       return rdd->err;
2039 +}
2040 +
2041 +static void ovl_cache_free(struct list_head *list)
2042 +{
2043 +       struct ovl_cache_entry *p;
2044 +       struct ovl_cache_entry *n;
2045 +
2046 +       list_for_each_entry_safe(p, n, list, l_node)
2047 +               kfree(p);
2048 +
2049 +       INIT_LIST_HEAD(list);
2050 +}
2051 +
2052 +static int ovl_fill_upper(void *buf, const char *name, int namelen,
2053 +                         loff_t offset, u64 ino, unsigned int d_type)
2054 +{
2055 +       struct ovl_readdir_data *rdd = buf;
2056 +
2057 +       rdd->count++;
2058 +       return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
2059 +}
2060 +
2061 +static inline int ovl_dir_read(struct path *realpath,
2062 +                              struct ovl_readdir_data *rdd, filldir_t filler)
2063 +{
2064 +       struct file *realfile;
2065 +       int err;
2066 +
2067 +       realfile = vfs_open(realpath, O_RDONLY | O_DIRECTORY, current_cred());
2068 +       if (IS_ERR(realfile))
2069 +               return PTR_ERR(realfile);
2070 +
2071 +       do {
2072 +               rdd->count = 0;
2073 +               rdd->err = 0;
2074 +               err = vfs_readdir(realfile, filler, rdd);
2075 +               if (err >= 0)
2076 +                       err = rdd->err;
2077 +       } while (!err && rdd->count);
2078 +       fput(realfile);
2079 +
2080 +       return 0;
2081 +}
2082 +
2083 +static void ovl_dir_reset(struct file *file)
2084 +{
2085 +       struct ovl_dir_file *od = file->private_data;
2086 +       enum ovl_path_type type = ovl_path_type(file->f_path.dentry);
2087 +
2088 +       if (ovl_dentry_version_get(file->f_path.dentry) != od->cache_version) {
2089 +               list_del_init(&od->cursor);
2090 +               ovl_cache_free(&od->cache);
2091 +               od->is_cached = false;
2092 +       }
2093 +       WARN_ON(!od->is_real && type != OVL_PATH_MERGE);
2094 +       if (od->is_real && type == OVL_PATH_MERGE) {
2095 +               fput(od->realfile);
2096 +               od->realfile = NULL;
2097 +               od->is_real = false;
2098 +       }
2099 +}
2100 +
2101 +static int ovl_dir_mark_whiteouts(struct ovl_readdir_data *rdd)
2102 +{
2103 +       struct ovl_cache_entry *p;
2104 +       struct dentry *dentry;
2105 +       const struct cred *old_cred;
2106 +       struct cred *override_cred;
2107 +
2108 +       override_cred = prepare_creds();
2109 +       if (!override_cred) {
2110 +               ovl_cache_free(rdd->list);
2111 +               return -ENOMEM;
2112 +       }
2113 +
2114 +       /*
2115 +        * CAP_SYS_ADMIN for getxattr
2116 +        * CAP_DAC_OVERRIDE for lookup
2117 +        */
2118 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
2119 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
2120 +       old_cred = override_creds(override_cred);
2121 +
2122 +       mutex_lock(&rdd->dir->d_inode->i_mutex);
2123 +       list_for_each_entry(p, rdd->list, l_node) {
2124 +               if (p->type != DT_LNK)
2125 +                       continue;
2126 +
2127 +               dentry = lookup_one_len(p->name, rdd->dir, p->len);
2128 +               if (IS_ERR(dentry))
2129 +                       continue;
2130 +
2131 +               p->is_whiteout = ovl_is_whiteout(dentry);
2132 +               dput(dentry);
2133 +       }
2134 +       mutex_unlock(&rdd->dir->d_inode->i_mutex);
2135 +
2136 +       revert_creds(old_cred);
2137 +       put_cred(override_cred);
2138 +
2139 +       return 0;
2140 +}
2141 +
2142 +static inline int ovl_dir_read_merged(struct path *upperpath, struct path *lowerpath,
2143 +                              struct ovl_readdir_data *rdd)
2144 +{
2145 +       int err;
2146 +       struct rb_root root = RB_ROOT;
2147 +       struct list_head middle;
2148 +
2149 +       rdd->root = &root;
2150 +       if (upperpath->dentry) {
2151 +               rdd->dir = upperpath->dentry;
2152 +               err = ovl_dir_read(upperpath, rdd, ovl_fill_upper);
2153 +               if (err)
2154 +                       goto out;
2155 +
2156 +               err = ovl_dir_mark_whiteouts(rdd);
2157 +               if (err)
2158 +                       goto out;
2159 +       }
2160 +       /*
2161 +        * Insert lowerpath entries before upperpath ones, this allows
2162 +        * offsets to be reasonably constant
2163 +        */
2164 +       list_add(&middle, rdd->list);
2165 +       rdd->middle = &middle;
2166 +       err = ovl_dir_read(lowerpath, rdd, ovl_fill_lower);
2167 +       list_del(&middle);
2168 +out:
2169 +       rdd->root = NULL;
2170 +
2171 +       return err;
2172 +}
2173 +
2174 +static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
2175 +{
2176 +       struct list_head *l;
2177 +       loff_t off;
2178 +
2179 +       l = od->cache.next;
2180 +       for (off = 0; off < pos; off++) {
2181 +               if (l == &od->cache)
2182 +                       break;
2183 +               l = l->next;
2184 +       }
2185 +       list_move_tail(&od->cursor, l);
2186 +}
2187 +
2188 +static int ovl_readdir(struct file *file, void *buf, filldir_t filler)
2189 +{
2190 +       struct ovl_dir_file *od = file->private_data;
2191 +       int res;
2192 +
2193 +       if (!file->f_pos)
2194 +               ovl_dir_reset(file);
2195 +
2196 +       if (od->is_real) {
2197 +               res = vfs_readdir(od->realfile, filler, buf);
2198 +               file->f_pos = od->realfile->f_pos;
2199 +
2200 +               return res;
2201 +       }
2202 +
2203 +       if (!od->is_cached) {
2204 +               struct path lowerpath;
2205 +               struct path upperpath;
2206 +               struct ovl_readdir_data rdd = { .list = &od->cache };
2207 +
2208 +               ovl_path_lower(file->f_path.dentry, &lowerpath);
2209 +               ovl_path_upper(file->f_path.dentry, &upperpath);
2210 +
2211 +               res = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
2212 +               if (res) {
2213 +                       ovl_cache_free(rdd.list);
2214 +                       return res;
2215 +               }
2216 +
2217 +               od->cache_version = ovl_dentry_version_get(file->f_path.dentry);
2218 +               od->is_cached = true;
2219 +
2220 +               ovl_seek_cursor(od, file->f_pos);
2221 +       }
2222 +
2223 +       while (od->cursor.next != &od->cache) {
2224 +               int over;
2225 +               loff_t off;
2226 +               struct ovl_cache_entry *p;
2227 +
2228 +               p = list_entry(od->cursor.next, struct ovl_cache_entry, l_node);
2229 +               off = file->f_pos;
2230 +               if (!p->is_whiteout) {
2231 +                       over = filler(buf, p->name, p->len, off, p->ino, p->type);
2232 +                       if (over)
2233 +                               break;
2234 +               }
2235 +               file->f_pos++;
2236 +               list_move(&od->cursor, &p->l_node);
2237 +       }
2238 +
2239 +       return 0;
2240 +}
2241 +
2242 +static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
2243 +{
2244 +       loff_t res;
2245 +       struct ovl_dir_file *od = file->private_data;
2246 +
2247 +       mutex_lock(&file->f_dentry->d_inode->i_mutex);
2248 +       if (!file->f_pos)
2249 +               ovl_dir_reset(file);
2250 +
2251 +       if (od->is_real) {
2252 +               res = vfs_llseek(od->realfile, offset, origin);
2253 +               file->f_pos = od->realfile->f_pos;
2254 +       } else {
2255 +               res = -EINVAL;
2256 +
2257 +               switch (origin) {
2258 +               case SEEK_CUR:
2259 +                       offset += file->f_pos;
2260 +                       break;
2261 +               case SEEK_SET:
2262 +                       break;
2263 +               default:
2264 +                       goto out_unlock;
2265 +               }
2266 +               if (offset < 0)
2267 +                       goto out_unlock;
2268 +
2269 +               if (offset != file->f_pos) {
2270 +                       file->f_pos = offset;
2271 +                       if (od->is_cached)
2272 +                               ovl_seek_cursor(od, offset);
2273 +               }
2274 +               res = offset;
2275 +       }
2276 +out_unlock:
2277 +       mutex_unlock(&file->f_dentry->d_inode->i_mutex);
2278 +
2279 +       return res;
2280 +}
2281 +
2282 +static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
2283 +                        int datasync)
2284 +{
2285 +       struct ovl_dir_file *od = file->private_data;
2286 +
2287 +       /* May need to reopen directory if it got copied up */
2288 +       if (!od->realfile) {
2289 +               struct path upperpath;
2290 +
2291 +               ovl_path_upper(file->f_path.dentry, &upperpath);
2292 +               od->realfile = vfs_open(&upperpath, O_RDONLY, current_cred());
2293 +               if (IS_ERR(od->realfile))
2294 +                       return PTR_ERR(od->realfile);
2295 +       }
2296 +
2297 +       return vfs_fsync_range(od->realfile, start, end, datasync);
2298 +}
2299 +
2300 +static int ovl_dir_release(struct inode *inode, struct file *file)
2301 +{
2302 +       struct ovl_dir_file *od = file->private_data;
2303 +
2304 +       list_del(&od->cursor);
2305 +       ovl_cache_free(&od->cache);
2306 +       if (od->realfile)
2307 +               fput(od->realfile);
2308 +       kfree(od);
2309 +
2310 +       return 0;
2311 +}
2312 +
2313 +static int ovl_dir_open(struct inode *inode, struct file *file)
2314 +{
2315 +       struct path realpath;
2316 +       struct file *realfile;
2317 +       struct ovl_dir_file *od;
2318 +       enum ovl_path_type type;
2319 +
2320 +       od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
2321 +       if (!od)
2322 +               return -ENOMEM;
2323 +
2324 +       type = ovl_path_real(file->f_path.dentry, &realpath);
2325 +       realfile = vfs_open(&realpath, file->f_flags, current_cred());
2326 +       if (IS_ERR(realfile)) {
2327 +               kfree(od);
2328 +               return PTR_ERR(realfile);
2329 +       }
2330 +       INIT_LIST_HEAD(&od->cache);
2331 +       INIT_LIST_HEAD(&od->cursor);
2332 +       od->is_cached = false;
2333 +       od->realfile = realfile;
2334 +       od->is_real = (type != OVL_PATH_MERGE);
2335 +       file->private_data = od;
2336 +
2337 +       return 0;
2338 +}
2339 +
2340 +const struct file_operations ovl_dir_operations = {
2341 +       .read           = generic_read_dir,
2342 +       .open           = ovl_dir_open,
2343 +       .readdir        = ovl_readdir,
2344 +       .llseek         = ovl_dir_llseek,
2345 +       .fsync          = ovl_dir_fsync,
2346 +       .release        = ovl_dir_release,
2347 +};
2348 +
2349 +static int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
2350 +{
2351 +       int err;
2352 +       struct path lowerpath;
2353 +       struct path upperpath;
2354 +       struct ovl_cache_entry *p;
2355 +       struct ovl_readdir_data rdd = { .list = list };
2356 +
2357 +       ovl_path_upper(dentry, &upperpath);
2358 +       ovl_path_lower(dentry, &lowerpath);
2359 +
2360 +       err = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
2361 +       if (err)
2362 +               return err;
2363 +
2364 +       err = 0;
2365 +
2366 +       list_for_each_entry(p, list, l_node) {
2367 +               if (p->is_whiteout)
2368 +                       continue;
2369 +
2370 +               if (p->name[0] == '.') {
2371 +                       if (p->len == 1)
2372 +                               continue;
2373 +                       if (p->len == 2 && p->name[1] == '.')
2374 +                               continue;
2375 +               }
2376 +               err = -ENOTEMPTY;
2377 +               break;
2378 +       }
2379 +
2380 +       return err;
2381 +}
2382 +
2383 +static int ovl_remove_whiteouts(struct dentry *dir, struct list_head *list)
2384 +{
2385 +       struct path upperpath;
2386 +       struct dentry *upperdir;
2387 +       struct ovl_cache_entry *p;
2388 +       const struct cred *old_cred;
2389 +       struct cred *override_cred;
2390 +       int err;
2391 +
2392 +       ovl_path_upper(dir, &upperpath);
2393 +       upperdir = upperpath.dentry;
2394 +
2395 +       override_cred = prepare_creds();
2396 +       if (!override_cred)
2397 +               return -ENOMEM;
2398 +
2399 +       /*
2400 +        * CAP_DAC_OVERRIDE for lookup and unlink
2401 +        * CAP_SYS_ADMIN for setxattr of "trusted" namespace
2402 +        * CAP_FOWNER for unlink in sticky directory
2403 +        */
2404 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
2405 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
2406 +       cap_raise(override_cred->cap_effective, CAP_FOWNER);
2407 +       old_cred = override_creds(override_cred);
2408 +
2409 +       err = vfs_setxattr(upperdir, ovl_opaque_xattr, "y", 1, 0);
2410 +       if (err)
2411 +               goto out_revert_creds;
2412 +
2413 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
2414 +       list_for_each_entry(p, list, l_node) {
2415 +               struct dentry *dentry;
2416 +               int ret;
2417 +
2418 +               if (!p->is_whiteout)
2419 +                       continue;
2420 +
2421 +               dentry = lookup_one_len(p->name, upperdir, p->len);
2422 +               if (IS_ERR(dentry)) {
2423 +                       printk(KERN_WARNING "overlayfs: failed to lookup whiteout %.*s: %li\n", p->len, p->name, PTR_ERR(dentry));
2424 +                       continue;
2425 +               }
2426 +               ret = vfs_unlink(upperdir->d_inode, dentry);
2427 +               dput(dentry);
2428 +               if (ret)
2429 +                       printk(KERN_WARNING "overlayfs: failed to unlink whiteout %.*s: %i\n", p->len, p->name, ret);
2430 +       }
2431 +       mutex_unlock(&upperdir->d_inode->i_mutex);
2432 +
2433 +out_revert_creds:
2434 +       revert_creds(old_cred);
2435 +       put_cred(override_cred);
2436 +
2437 +       return err;
2438 +}
2439 +
2440 +int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type)
2441 +{
2442 +       int err;
2443 +       LIST_HEAD(list);
2444 +
2445 +       err = ovl_check_empty_dir(dentry, &list);
2446 +       if (!err && type == OVL_PATH_MERGE)
2447 +               err = ovl_remove_whiteouts(dentry, &list);
2448 +
2449 +       ovl_cache_free(&list);
2450 +
2451 +       return err;
2452 +}
2453 --- /dev/null
2454 +++ b/fs/overlayfs/super.c
2455 @@ -0,0 +1,656 @@
2456 +/*
2457 + *
2458 + * Copyright (C) 2011 Novell Inc.
2459 + *
2460 + * This program is free software; you can redistribute it and/or modify it
2461 + * under the terms of the GNU General Public License version 2 as published by
2462 + * the Free Software Foundation.
2463 + */
2464 +
2465 +#include <linux/fs.h>
2466 +#include <linux/namei.h>
2467 +#include <linux/xattr.h>
2468 +#include <linux/security.h>
2469 +#include <linux/mount.h>
2470 +#include <linux/slab.h>
2471 +#include <linux/parser.h>
2472 +#include <linux/module.h>
2473 +#include <linux/seq_file.h>
2474 +#include "overlayfs.h"
2475 +
2476 +MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
2477 +MODULE_DESCRIPTION("Overlay filesystem");
2478 +MODULE_LICENSE("GPL");
2479 +
2480 +struct ovl_config {
2481 +       char *lowerdir;
2482 +       char *upperdir;
2483 +};
2484 +
2485 +/* private information held for overlayfs's superblock */
2486 +struct ovl_fs {
2487 +       struct vfsmount *upper_mnt;
2488 +       struct vfsmount *lower_mnt;
2489 +       /* pathnames of lower and upper dirs, for show_options */
2490 +       struct ovl_config config;
2491 +};
2492 +
2493 +/* private information held for every overlayfs dentry */
2494 +struct ovl_entry {
2495 +       /*
2496 +        * Keep "double reference" on upper dentries, so that
2497 +        * d_delete() doesn't think it's OK to reset d_inode to NULL.
2498 +        */
2499 +       struct dentry *__upperdentry;
2500 +       struct dentry *lowerdentry;
2501 +       union {
2502 +               struct {
2503 +                       u64 version;
2504 +                       bool opaque;
2505 +               };
2506 +               struct rcu_head rcu;
2507 +       };
2508 +};
2509 +
2510 +const char *ovl_whiteout_xattr = "trusted.overlay.whiteout";
2511 +const char *ovl_opaque_xattr = "trusted.overlay.opaque";
2512 +
2513 +
2514 +enum ovl_path_type ovl_path_type(struct dentry *dentry)
2515 +{
2516 +       struct ovl_entry *oe = dentry->d_fsdata;
2517 +
2518 +       if (oe->__upperdentry) {
2519 +               if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode))
2520 +                       return OVL_PATH_MERGE;
2521 +               else
2522 +                       return OVL_PATH_UPPER;
2523 +       } else {
2524 +               return OVL_PATH_LOWER;
2525 +       }
2526 +}
2527 +
2528 +static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
2529 +{
2530 +       struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
2531 +       smp_read_barrier_depends();
2532 +       return upperdentry;
2533 +}
2534 +
2535 +void ovl_path_upper(struct dentry *dentry, struct path *path)
2536 +{
2537 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
2538 +       struct ovl_entry *oe = dentry->d_fsdata;
2539 +
2540 +       path->mnt = ofs->upper_mnt;
2541 +       path->dentry = ovl_upperdentry_dereference(oe);
2542 +}
2543 +
2544 +void ovl_path_lower(struct dentry *dentry, struct path *path)
2545 +{
2546 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
2547 +       struct ovl_entry *oe = dentry->d_fsdata;
2548 +
2549 +       path->mnt = ofs->lower_mnt;
2550 +       path->dentry = oe->lowerdentry;
2551 +}
2552 +
2553 +enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
2554 +{
2555 +
2556 +       enum ovl_path_type type = ovl_path_type(dentry);
2557 +
2558 +       if (type == OVL_PATH_LOWER)
2559 +               ovl_path_lower(dentry, path);
2560 +       else
2561 +               ovl_path_upper(dentry, path);
2562 +
2563 +       return type;
2564 +}
2565 +
2566 +struct dentry *ovl_dentry_upper(struct dentry *dentry)
2567 +{
2568 +       struct ovl_entry *oe = dentry->d_fsdata;
2569 +
2570 +       return ovl_upperdentry_dereference(oe);
2571 +}
2572 +
2573 +struct dentry *ovl_dentry_lower(struct dentry *dentry)
2574 +{
2575 +       struct ovl_entry *oe = dentry->d_fsdata;
2576 +
2577 +       return oe->lowerdentry;
2578 +}
2579 +
2580 +struct dentry *ovl_dentry_real(struct dentry *dentry)
2581 +{
2582 +       struct ovl_entry *oe = dentry->d_fsdata;
2583 +       struct dentry *realdentry;
2584 +
2585 +       realdentry = ovl_upperdentry_dereference(oe);
2586 +       if (!realdentry)
2587 +               realdentry = oe->lowerdentry;
2588 +
2589 +       return realdentry;
2590 +}
2591 +
2592 +struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
2593 +{
2594 +       struct dentry *realdentry;
2595 +
2596 +       realdentry = ovl_upperdentry_dereference(oe);
2597 +       if (realdentry) {
2598 +               *is_upper = true;
2599 +       } else {
2600 +               realdentry = oe->lowerdentry;
2601 +               *is_upper = false;
2602 +       }
2603 +       return realdentry;
2604 +}
2605 +
2606 +bool ovl_dentry_is_opaque(struct dentry *dentry)
2607 +{
2608 +       struct ovl_entry *oe = dentry->d_fsdata;
2609 +       return oe->opaque;
2610 +}
2611 +
2612 +void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
2613 +{
2614 +       struct ovl_entry *oe = dentry->d_fsdata;
2615 +       oe->opaque = opaque;
2616 +}
2617 +
2618 +void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
2619 +{
2620 +       struct ovl_entry *oe = dentry->d_fsdata;
2621 +
2622 +       WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
2623 +       WARN_ON(oe->__upperdentry);
2624 +       BUG_ON(!upperdentry->d_inode);
2625 +       smp_wmb();
2626 +       oe->__upperdentry = dget(upperdentry);
2627 +}
2628 +
2629 +void ovl_dentry_version_inc(struct dentry *dentry)
2630 +{
2631 +       struct ovl_entry *oe = dentry->d_fsdata;
2632 +
2633 +       WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
2634 +       oe->version++;
2635 +}
2636 +
2637 +u64 ovl_dentry_version_get(struct dentry *dentry)
2638 +{
2639 +       struct ovl_entry *oe = dentry->d_fsdata;
2640 +
2641 +       WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
2642 +       return oe->version;
2643 +}
2644 +
2645 +bool ovl_is_whiteout(struct dentry *dentry)
2646 +{
2647 +       int res;
2648 +       char val;
2649 +
2650 +       if (!dentry)
2651 +               return false;
2652 +       if (!dentry->d_inode)
2653 +               return false;
2654 +       if (!S_ISLNK(dentry->d_inode->i_mode))
2655 +               return false;
2656 +
2657 +       res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1);
2658 +       if (res == 1 && val == 'y')
2659 +               return true;
2660 +
2661 +       return false;
2662 +}
2663 +
2664 +static bool ovl_is_opaquedir(struct dentry *dentry)
2665 +{
2666 +       int res;
2667 +       char val;
2668 +
2669 +       if (!S_ISDIR(dentry->d_inode->i_mode))
2670 +               return false;
2671 +
2672 +       res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1);
2673 +       if (res == 1 && val == 'y')
2674 +               return true;
2675 +
2676 +       return false;
2677 +}
2678 +
2679 +static void ovl_entry_free(struct rcu_head *head)
2680 +{
2681 +       struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu);
2682 +       kfree(oe);
2683 +}
2684 +
2685 +static void ovl_dentry_release(struct dentry *dentry)
2686 +{
2687 +       struct ovl_entry *oe = dentry->d_fsdata;
2688 +
2689 +       if (oe) {
2690 +               dput(oe->__upperdentry);
2691 +               dput(oe->__upperdentry);
2692 +               dput(oe->lowerdentry);
2693 +               call_rcu(&oe->rcu, ovl_entry_free);
2694 +       }
2695 +}
2696 +
2697 +const struct dentry_operations ovl_dentry_operations = {
2698 +       .d_release = ovl_dentry_release,
2699 +};
2700 +
2701 +static struct ovl_entry *ovl_alloc_entry(void)
2702 +{
2703 +       return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
2704 +}
2705 +
2706 +static inline struct dentry *ovl_lookup_real(struct dentry *dir, struct qstr *name)
2707 +{
2708 +       struct dentry *dentry;
2709 +
2710 +       mutex_lock(&dir->d_inode->i_mutex);
2711 +       dentry = lookup_one_len(name->name, dir, name->len);
2712 +       mutex_unlock(&dir->d_inode->i_mutex);
2713 +
2714 +       if (IS_ERR(dentry)) {
2715 +               if (PTR_ERR(dentry) == -ENOENT)
2716 +                       dentry = NULL;
2717 +       } else if (!dentry->d_inode) {
2718 +               dput(dentry);
2719 +               dentry = NULL;
2720 +       }
2721 +       return dentry;
2722 +}
2723 +
2724 +static int ovl_do_lookup(struct dentry *dentry)
2725 +{
2726 +       struct ovl_entry *oe;
2727 +       struct dentry *upperdir;
2728 +       struct dentry *lowerdir;
2729 +       struct dentry *upperdentry = NULL;
2730 +       struct dentry *lowerdentry = NULL;
2731 +       struct inode *inode = NULL;
2732 +       int err;
2733 +
2734 +       err = -ENOMEM;
2735 +       oe = ovl_alloc_entry();
2736 +       if (!oe)
2737 +               goto out;
2738 +
2739 +       upperdir = ovl_dentry_upper(dentry->d_parent);
2740 +       lowerdir = ovl_dentry_lower(dentry->d_parent);
2741 +
2742 +       if (upperdir) {
2743 +               upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
2744 +               err = PTR_ERR(upperdentry);
2745 +               if (IS_ERR(upperdentry))
2746 +                       goto out_put_dir;
2747 +
2748 +               if (lowerdir && upperdentry &&
2749 +                   (S_ISLNK(upperdentry->d_inode->i_mode) ||
2750 +                    S_ISDIR(upperdentry->d_inode->i_mode))) {
2751 +                       const struct cred *old_cred;
2752 +                       struct cred *override_cred;
2753 +
2754 +                       err = -ENOMEM;
2755 +                       override_cred = prepare_creds();
2756 +                       if (!override_cred)
2757 +                               goto out_dput_upper;
2758 +
2759 +                       /* CAP_SYS_ADMIN needed for getxattr */
2760 +                       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
2761 +                       old_cred = override_creds(override_cred);
2762 +
2763 +                       if (ovl_is_opaquedir(upperdentry)) {
2764 +                               oe->opaque = true;
2765 +                       } else if (ovl_is_whiteout(upperdentry)) {
2766 +                               dput(upperdentry);
2767 +                               upperdentry = NULL;
2768 +                               oe->opaque = true;
2769 +                       }
2770 +                       revert_creds(old_cred);
2771 +                       put_cred(override_cred);
2772 +               }
2773 +       }
2774 +       if (lowerdir && !oe->opaque) {
2775 +               lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
2776 +               err = PTR_ERR(lowerdentry);
2777 +               if (IS_ERR(lowerdentry))
2778 +                       goto out_dput_upper;
2779 +       }
2780 +
2781 +       if (lowerdentry && upperdentry &&
2782 +           (!S_ISDIR(upperdentry->d_inode->i_mode) ||
2783 +            !S_ISDIR(lowerdentry->d_inode->i_mode))) {
2784 +               dput(lowerdentry);
2785 +               lowerdentry = NULL;
2786 +               oe->opaque = true;
2787 +       }
2788 +
2789 +       if (lowerdentry || upperdentry) {
2790 +               struct dentry *realdentry;
2791 +
2792 +               realdentry = upperdentry ? upperdentry : lowerdentry;
2793 +               err = -ENOMEM;
2794 +               inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, oe);
2795 +               if (!inode)
2796 +                       goto out_dput;
2797 +       }
2798 +
2799 +       if (upperdentry)
2800 +               oe->__upperdentry = dget(upperdentry);
2801 +
2802 +       if (lowerdentry)
2803 +               oe->lowerdentry = lowerdentry;
2804 +
2805 +       dentry->d_fsdata = oe;
2806 +       dentry->d_op = &ovl_dentry_operations;
2807 +       d_add(dentry, inode);
2808 +
2809 +       return 0;
2810 +
2811 +out_dput:
2812 +       dput(lowerdentry);
2813 +out_dput_upper:
2814 +       dput(upperdentry);
2815 +out_put_dir:
2816 +       kfree(oe);
2817 +out:
2818 +       return err;
2819 +}
2820 +
2821 +struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
2822 +                         struct nameidata *nd)
2823 +{
2824 +       int err = ovl_do_lookup(dentry);
2825 +
2826 +       if (err)
2827 +               return ERR_PTR(err);
2828 +
2829 +       return NULL;
2830 +}
2831 +
2832 +static void ovl_put_super(struct super_block *sb)
2833 +{
2834 +       struct ovl_fs *ufs = sb->s_fs_info;
2835 +
2836 +       if (!(sb->s_flags & MS_RDONLY))
2837 +               mnt_drop_write(ufs->upper_mnt);
2838 +
2839 +       mntput(ufs->upper_mnt);
2840 +       mntput(ufs->lower_mnt);
2841 +
2842 +       kfree(ufs->config.lowerdir);
2843 +       kfree(ufs->config.upperdir);
2844 +       kfree(ufs);
2845 +}
2846 +
2847 +static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
2848 +{
2849 +       int flags = *flagsp;
2850 +       struct ovl_fs *ufs = sb->s_fs_info;
2851 +
2852 +       /* When remounting rw or ro, we need to adjust the write access to the
2853 +        * upper fs.
2854 +        */
2855 +       if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
2856 +               /* No change to readonly status */
2857 +               return 0;
2858 +
2859 +       if (flags & MS_RDONLY) {
2860 +               mnt_drop_write(ufs->upper_mnt);
2861 +               return 0;
2862 +       } else
2863 +               return mnt_want_write(ufs->upper_mnt);
2864 +}
2865 +
2866 +/**
2867 + * ovl_statfs
2868 + * @sb: The overlayfs super block
2869 + * @buf: The struct kstatfs to fill in with stats
2870 + *
2871 + * Get the filesystem statistics.  As writes always target the upper layer
2872 + * filesystem pass the statfs to the same filesystem.
2873 + */
2874 +static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
2875 +{
2876 +       struct dentry *root_dentry = dentry->d_sb->s_root;
2877 +       struct path path;
2878 +       ovl_path_upper(root_dentry, &path);
2879 +
2880 +       if (!path.dentry->d_sb->s_op->statfs)
2881 +               return -ENOSYS;
2882 +       return path.dentry->d_sb->s_op->statfs(path.dentry, buf);
2883 +}
2884 +
2885 +/**
2886 + * ovl_show_options
2887 + *
2888 + * Prints the mount options for a given superblock.
2889 + * Returns zero; does not fail.
2890 + */
2891 +static int ovl_show_options(struct seq_file *m, struct vfsmount *mnt)
2892 +{
2893 +       struct super_block *sb = mnt->mnt_sb;
2894 +       struct ovl_fs *ufs = sb->s_fs_info;
2895 +
2896 +       seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
2897 +       seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
2898 +       return 0;
2899 +}
2900 +
2901 +static const struct super_operations ovl_super_operations = {
2902 +       .put_super      = ovl_put_super,
2903 +       .remount_fs     = ovl_remount_fs,
2904 +       .statfs         = ovl_statfs,
2905 +       .show_options   = ovl_show_options,
2906 +};
2907 +
2908 +enum {
2909 +       Opt_lowerdir,
2910 +       Opt_upperdir,
2911 +       Opt_err,
2912 +};
2913 +
2914 +static const match_table_t ovl_tokens = {
2915 +       {Opt_lowerdir,                  "lowerdir=%s"},
2916 +       {Opt_upperdir,                  "upperdir=%s"},
2917 +       {Opt_err,                       NULL}
2918 +};
2919 +
2920 +static int ovl_parse_opt(char *opt, struct ovl_config *config)
2921 +{
2922 +       char *p;
2923 +
2924 +       config->upperdir = NULL;
2925 +       config->lowerdir = NULL;
2926 +
2927 +       while ((p = strsep(&opt, ",")) != NULL) {
2928 +               int token;
2929 +               substring_t args[MAX_OPT_ARGS];
2930 +
2931 +               if (!*p)
2932 +                       continue;
2933 +
2934 +               token = match_token(p, ovl_tokens, args);
2935 +               switch (token) {
2936 +               case Opt_upperdir:
2937 +                       kfree(config->upperdir);
2938 +                       config->upperdir = match_strdup(&args[0]);
2939 +                       if (!config->upperdir)
2940 +                               return -ENOMEM;
2941 +                       break;
2942 +
2943 +               case Opt_lowerdir:
2944 +                       kfree(config->lowerdir);
2945 +                       config->lowerdir = match_strdup(&args[0]);
2946 +                       if (!config->lowerdir)
2947 +                               return -ENOMEM;
2948 +                       break;
2949 +
2950 +               default:
2951 +                       return -EINVAL;
2952 +               }
2953 +       }
2954 +       return 0;
2955 +}
2956 +
2957 +static int ovl_fill_super(struct super_block *sb, void *data, int silent)
2958 +{
2959 +       struct path lowerpath;
2960 +       struct path upperpath;
2961 +       struct inode *root_inode;
2962 +       struct dentry *root_dentry;
2963 +       struct ovl_entry *oe;
2964 +       struct ovl_fs *ufs;
2965 +       int err;
2966 +
2967 +       err = -ENOMEM;
2968 +       ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
2969 +       if (!ufs)
2970 +               goto out;
2971 +
2972 +       err = ovl_parse_opt((char *) data, &ufs->config);
2973 +       if (err)
2974 +               goto out_free_ufs;
2975 +
2976 +       err = -EINVAL;
2977 +       if (!ufs->config.upperdir || !ufs->config.lowerdir) {
2978 +               printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
2979 +               goto out_free_config;
2980 +       }
2981 +
2982 +       oe = ovl_alloc_entry();
2983 +       if (oe == NULL)
2984 +               goto out_free_config;
2985 +
2986 +       root_inode = ovl_new_inode(sb, S_IFDIR, oe);
2987 +       if (!root_inode)
2988 +               goto out_free_oe;
2989 +
2990 +       err = kern_path(ufs->config.upperdir, LOOKUP_FOLLOW, &upperpath);
2991 +       if (err)
2992 +               goto out_put_root;
2993 +
2994 +       err = kern_path(ufs->config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
2995 +       if (err)
2996 +               goto out_put_upperpath;
2997 +
2998 +       err = -ENOTDIR;
2999 +       if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
3000 +           !S_ISDIR(lowerpath.dentry->d_inode->i_mode))
3001 +               goto out_put_lowerpath;
3002 +
3003 +       sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth,
3004 +                               lowerpath.mnt->mnt_sb->s_stack_depth) + 1;
3005 +
3006 +       err = -EINVAL;
3007 +       if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
3008 +               printk(KERN_ERR "overlayfs: maximum fs stacking depth exceeded\n");
3009 +               goto out_put_lowerpath;
3010 +       }
3011 +
3012 +
3013 +       ufs->upper_mnt = clone_private_mount(&upperpath);
3014 +       err = PTR_ERR(ufs->upper_mnt);
3015 +       if (IS_ERR(ufs->upper_mnt)) {
3016 +               printk(KERN_ERR "overlayfs: failed to clone upperpath\n");
3017 +               goto out_put_lowerpath;
3018 +       }
3019 +
3020 +       ufs->lower_mnt = clone_private_mount(&lowerpath);
3021 +       err = PTR_ERR(ufs->lower_mnt);
3022 +       if (IS_ERR(ufs->lower_mnt)) {
3023 +               printk(KERN_ERR "overlayfs: failed to clone lowerpath\n");
3024 +               goto out_put_upper_mnt;
3025 +       }
3026 +
3027 +       /*
3028 +        * Make lower_mnt R/O.  That way fchmod/fchown on lower file
3029 +        * will fail instead of modifying lower fs.
3030 +        */
3031 +       ufs->lower_mnt->mnt_flags |= MNT_READONLY;
3032 +
3033 +       /* If the upper fs is r/o, we mark overlayfs r/o too */
3034 +       if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)
3035 +               sb->s_flags |= MS_RDONLY;
3036 +
3037 +       if (!(sb->s_flags & MS_RDONLY)) {
3038 +               err = mnt_want_write(ufs->upper_mnt);
3039 +               if (err)
3040 +                       goto out_put_lower_mnt;
3041 +       }
3042 +
3043 +       err = -ENOMEM;
3044 +       root_dentry = d_alloc_root(root_inode);
3045 +       if (!root_dentry)
3046 +               goto out_drop_write;
3047 +
3048 +       mntput(upperpath.mnt);
3049 +       mntput(lowerpath.mnt);
3050 +
3051 +       oe->__upperdentry = dget(upperpath.dentry);
3052 +       oe->lowerdentry = lowerpath.dentry;
3053 +
3054 +       root_dentry->d_fsdata = oe;
3055 +       root_dentry->d_op = &ovl_dentry_operations;
3056 +
3057 +       sb->s_op = &ovl_super_operations;
3058 +       sb->s_root = root_dentry;
3059 +       sb->s_fs_info = ufs;
3060 +
3061 +       return 0;
3062 +
3063 +out_drop_write:
3064 +       if (!(sb->s_flags & MS_RDONLY))
3065 +               mnt_drop_write(ufs->upper_mnt);
3066 +out_put_lower_mnt:
3067 +       mntput(ufs->lower_mnt);
3068 +out_put_upper_mnt:
3069 +       mntput(ufs->upper_mnt);
3070 +out_put_lowerpath:
3071 +       path_put(&lowerpath);
3072 +out_put_upperpath:
3073 +       path_put(&upperpath);
3074 +out_put_root:
3075 +       iput(root_inode);
3076 +out_free_oe:
3077 +       kfree(oe);
3078 +out_free_config:
3079 +       kfree(ufs->config.lowerdir);
3080 +       kfree(ufs->config.upperdir);
3081 +out_free_ufs:
3082 +       kfree(ufs);
3083 +out:
3084 +       return err;
3085 +}
3086 +
3087 +static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
3088 +                               const char *dev_name, void *raw_data)
3089 +{
3090 +       return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
3091 +}
3092 +
3093 +static struct file_system_type ovl_fs_type = {
3094 +       .owner          = THIS_MODULE,
3095 +       .name           = "overlayfs",
3096 +       .mount          = ovl_mount,
3097 +       .kill_sb        = kill_anon_super,
3098 +};
3099 +
3100 +static int __init ovl_init(void)
3101 +{
3102 +       return register_filesystem(&ovl_fs_type);
3103 +}
3104 +
3105 +static void __exit ovl_exit(void)
3106 +{
3107 +       unregister_filesystem(&ovl_fs_type);
3108 +}
3109 +
3110 +module_init(ovl_init);
3111 +module_exit(ovl_exit);
3112 --- a/fs/splice.c
3113 +++ b/fs/splice.c
3114 @@ -1300,6 +1300,7 @@ long do_splice_direct(struct file *in, l
3115
3116         return ret;
3117  }
3118 +EXPORT_SYMBOL(do_splice_direct);
3119
3120  static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
3121                                struct pipe_inode_info *opipe,
3122 --- a/include/linux/fs.h
3123 +++ b/include/linux/fs.h
3124 @@ -482,6 +482,12 @@ struct iattr {
3125   */
3126  #include <linux/quota.h>
3127
3128 +/*
3129 + * Maximum number of layers of fs stack.  Needs to be limited to
3130 + * prevent kernel stack overflow
3131 + */
3132 +#define FILESYSTEM_MAX_STACK_DEPTH 2
3133 +
3134  /**
3135   * enum positive_aop_returns - aop return codes with specific semantics
3136   *
3137 @@ -1482,6 +1488,11 @@ struct super_block {
3138         int cleancache_poolid;
3139
3140         struct shrinker s_shrink;       /* per-sb shrinker handle */
3141 +
3142 +       /*
3143 +        * Indicates how deep in a filesystem stack this SB is
3144 +        */
3145 +       int s_stack_depth;
3146  };
3147
3148  /* superblock cache pruning functions */
3149 @@ -1639,6 +1650,7 @@ struct inode_operations {
3150         void (*truncate_range)(struct inode *, loff_t, loff_t);
3151         int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
3152                       u64 len);
3153 +       struct file *(*open)(struct dentry *, int flags, const struct cred *);
3154  } ____cacheline_aligned;
3155
3156  struct seq_file;
3157 @@ -2059,6 +2071,7 @@ extern long do_sys_open(int dfd, const c
3158  extern struct file *filp_open(const char *, int, int);
3159  extern struct file *file_open_root(struct dentry *, struct vfsmount *,
3160                                    const char *, int);
3161 +extern struct file *vfs_open(struct path *, int flags, const struct cred *);
3162  extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
3163                                  const struct cred *);
3164  extern int filp_close(struct file *, fl_owner_t id);
3165 --- a/include/linux/mount.h
3166 +++ b/include/linux/mount.h
3167 @@ -100,6 +100,9 @@ extern void mnt_pin(struct vfsmount *mnt
3168  extern void mnt_unpin(struct vfsmount *mnt);
3169  extern int __mnt_is_readonly(struct vfsmount *mnt);
3170
3171 +struct path;
3172 +extern struct vfsmount *clone_private_mount(struct path *path);
3173 +
3174  extern struct vfsmount *do_kern_mount(const char *fstype, int flags,
3175                                       const char *name, void *data);
3176