target/linux/generic/patches-3.6/100-overlayfs.patch

   1 diff -Nur -x .git vfs-4cbe5a5/Documentation/filesystems/Locking vfs-3d5a648/Documentation/filesystems/Locking
   2 --- vfs-4cbe5a5/Documentation/filesystems/Locking       2012-09-01 19:39:58.000000000 +0200
   3 +++ vfs-3d5a648/Documentation/filesystems/Locking       2012-09-05 16:35:20.000000000 +0200
   4 @@ -64,6 +64,7 @@
   5         int (*atomic_open)(struct inode *, struct dentry *,
   6                                 struct file *, unsigned open_flag,
   7                                 umode_t create_mode, int *opened);
   8 +       int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
   9
  10  locking rules:
  11         all may block
  12 @@ -92,6 +93,7 @@
  13  fiemap:                no
  14  update_time:   no
  15  atomic_open:   yes
  16 +dentry_open:   no
  17
  18         Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
  19  victim.
  20 diff -Nur -x .git vfs-4cbe5a5/Documentation/filesystems/overlayfs.txt vfs-3d5a648/Documentation/filesystems/overlayfs.txt
  21 --- vfs-4cbe5a5/Documentation/filesystems/overlayfs.txt 1970-01-01 01:00:00.000000000 +0100
  22 +++ vfs-3d5a648/Documentation/filesystems/overlayfs.txt 2012-09-05 16:35:20.000000000 +0200
  23 @@ -0,0 +1,199 @@
  24 +Written by: Neil Brown <neilb@suse.de>
  25 +
  26 +Overlay Filesystem
  27 +==================
  28 +
  29 +This document describes a prototype for a new approach to providing
  30 +overlay-filesystem functionality in Linux (sometimes referred to as
  31 +union-filesystems).  An overlay-filesystem tries to present a
  32 +filesystem which is the result over overlaying one filesystem on top
  33 +of the other.
  34 +
  35 +The result will inevitably fail to look exactly like a normal
  36 +filesystem for various technical reasons.  The expectation is that
  37 +many use cases will be able to ignore these differences.
  38 +
  39 +This approach is 'hybrid' because the objects that appear in the
  40 +filesystem do not all appear to belong to that filesystem.  In many
  41 +cases an object accessed in the union will be indistinguishable
  42 +from accessing the corresponding object from the original filesystem.
  43 +This is most obvious from the 'st_dev' field returned by stat(2).
  44 +
  45 +While directories will report an st_dev from the overlay-filesystem,
  46 +all non-directory objects will report an st_dev from the lower or
  47 +upper filesystem that is providing the object.  Similarly st_ino will
  48 +only be unique when combined with st_dev, and both of these can change
  49 +over the lifetime of a non-directory object.  Many applications and
  50 +tools ignore these values and will not be affected.
  51 +
  52 +Upper and Lower
  53 +---------------
  54 +
  55 +An overlay filesystem combines two filesystems - an 'upper' filesystem
  56 +and a 'lower' filesystem.  When a name exists in both filesystems, the
  57 +object in the 'upper' filesystem is visible while the object in the
  58 +'lower' filesystem is either hidden or, in the case of directories,
  59 +merged with the 'upper' object.
  60 +
  61 +It would be more correct to refer to an upper and lower 'directory
  62 +tree' rather than 'filesystem' as it is quite possible for both
  63 +directory trees to be in the same filesystem and there is no
  64 +requirement that the root of a filesystem be given for either upper or
  65 +lower.
  66 +
  67 +The lower filesystem can be any filesystem supported by Linux and does
  68 +not need to be writable.  The lower filesystem can even be another
  69 +overlayfs.  The upper filesystem will normally be writable and if it
  70 +is it must support the creation of trusted.* extended attributes, and
  71 +must provide valid d_type in readdir responses, at least for symbolic
  72 +links - so NFS is not suitable.
  73 +
  74 +A read-only overlay of two read-only filesystems may use any
  75 +filesystem type.
  76 +
  77 +Directories
  78 +-----------
  79 +
  80 +Overlaying mainly involves directories.  If a given name appears in both
  81 +upper and lower filesystems and refers to a non-directory in either,
  82 +then the lower object is hidden - the name refers only to the upper
  83 +object.
  84 +
  85 +Where both upper and lower objects are directories, a merged directory
  86 +is formed.
  87 +
  88 +At mount time, the two directories given as mount options are combined
  89 +into a merged directory:
  90 +
  91 +  mount -t overlayfs overlayfs -olowerdir=/lower,upperdir=/upper /overlay
  92 +
  93 +Then whenever a lookup is requested in such a merged directory, the
  94 +lookup is performed in each actual directory and the combined result
  95 +is cached in the dentry belonging to the overlay filesystem.  If both
  96 +actual lookups find directories, both are stored and a merged
  97 +directory is created, otherwise only one is stored: the upper if it
  98 +exists, else the lower.
  99 +
 100 +Only the lists of names from directories are merged.  Other content
 101 +such as metadata and extended attributes are reported for the upper
 102 +directory only.  These attributes of the lower directory are hidden.
 103 +
 104 +whiteouts and opaque directories
 105 +--------------------------------
 106 +
 107 +In order to support rm and rmdir without changing the lower
 108 +filesystem, an overlay filesystem needs to record in the upper filesystem
 109 +that files have been removed.  This is done using whiteouts and opaque
 110 +directories (non-directories are always opaque).
 111 +
 112 +The overlay filesystem uses extended attributes with a
 113 +"trusted.overlay."  prefix to record these details.
 114 +
 115 +A whiteout is created as a symbolic link with target
 116 +"(overlay-whiteout)" and with xattr "trusted.overlay.whiteout" set to "y".
 117 +When a whiteout is found in the upper level of a merged directory, any
 118 +matching name in the lower level is ignored, and the whiteout itself
 119 +is also hidden.
 120 +
 121 +A directory is made opaque by setting the xattr "trusted.overlay.opaque"
 122 +to "y".  Where the upper filesystem contains an opaque directory, any
 123 +directory in the lower filesystem with the same name is ignored.
 124 +
 125 +readdir
 126 +-------
 127 +
 128 +When a 'readdir' request is made on a merged directory, the upper and
 129 +lower directories are each read and the name lists merged in the
 130 +obvious way (upper is read first, then lower - entries that already
 131 +exist are not re-added).  This merged name list is cached in the
 132 +'struct file' and so remains as long as the file is kept open.  If the
 133 +directory is opened and read by two processes at the same time, they
 134 +will each have separate caches.  A seekdir to the start of the
 135 +directory (offset 0) followed by a readdir will cause the cache to be
 136 +discarded and rebuilt.
 137 +
 138 +This means that changes to the merged directory do not appear while a
 139 +directory is being read.  This is unlikely to be noticed by many
 140 +programs.
 141 +
 142 +seek offsets are assigned sequentially when the directories are read.
 143 +Thus if
 144 +  - read part of a directory
 145 +  - remember an offset, and close the directory
 146 +  - re-open the directory some time later
 147 +  - seek to the remembered offset
 148 +
 149 +there may be little correlation between the old and new locations in
 150 +the list of filenames, particularly if anything has changed in the
 151 +directory.
 152 +
 153 +Readdir on directories that are not merged is simply handled by the
 154 +underlying directory (upper or lower).
 155 +
 156 +
 157 +Non-directories
 158 +---------------
 159 +
 160 +Objects that are not directories (files, symlinks, device-special
 161 +files etc.) are presented either from the upper or lower filesystem as
 162 +appropriate.  When a file in the lower filesystem is accessed in a way
 163 +the requires write-access, such as opening for write access, changing
 164 +some metadata etc., the file is first copied from the lower filesystem
 165 +to the upper filesystem (copy_up).  Note that creating a hard-link
 166 +also requires copy_up, though of course creation of a symlink does
 167 +not.
 168 +
 169 +The copy_up may turn out to be unnecessary, for example if the file is
 170 +opened for read-write but the data is not modified.
 171 +
 172 +The copy_up process first makes sure that the containing directory
 173 +exists in the upper filesystem - creating it and any parents as
 174 +necessary.  It then creates the object with the same metadata (owner,
 175 +mode, mtime, symlink-target etc.) and then if the object is a file, the
 176 +data is copied from the lower to the upper filesystem.  Finally any
 177 +extended attributes are copied up.
 178 +
 179 +Once the copy_up is complete, the overlay filesystem simply
 180 +provides direct access to the newly created file in the upper
 181 +filesystem - future operations on the file are barely noticed by the
 182 +overlay filesystem (though an operation on the name of the file such as
 183 +rename or unlink will of course be noticed and handled).
 184 +
 185 +
 186 +Non-standard behavior
 187 +---------------------
 188 +
 189 +The copy_up operation essentially creates a new, identical file and
 190 +moves it over to the old name.  The new file may be on a different
 191 +filesystem, so both st_dev and st_ino of the file may change.
 192 +
 193 +Any open files referring to this inode will access the old data and
 194 +metadata.  Similarly any file locks obtained before copy_up will not
 195 +apply to the copied up file.
 196 +
 197 +On a file opened with O_RDONLY fchmod(2), fchown(2), futimesat(2) and
 198 +fsetxattr(2) will fail with EROFS.
 199 +
 200 +If a file with multiple hard links is copied up, then this will
 201 +"break" the link.  Changes will not be propagated to other names
 202 +referring to the same inode.
 203 +
 204 +Symlinks in /proc/PID/ and /proc/PID/fd which point to a non-directory
 205 +object in overlayfs will not contain valid absolute paths, only
 206 +relative paths leading up to the filesystem's root.  This will be
 207 +fixed in the future.
 208 +
 209 +Some operations are not atomic, for example a crash during copy_up or
 210 +rename will leave the filesystem in an inconsistent state.  This will
 211 +be addressed in the future.
 212 +
 213 +Changes to underlying filesystems
 214 +---------------------------------
 215 +
 216 +Offline changes, when the overlay is not mounted, are allowed to either
 217 +the upper or the lower trees.
 218 +
 219 +Changes to the underlying filesystems while part of a mounted overlay
 220 +filesystem are not allowed.  If the underlying filesystem is changed,
 221 +the behavior of the overlay is undefined, though it will not result in
 222 +a crash or deadlock.
 223 diff -Nur -x .git vfs-4cbe5a5/Documentation/filesystems/vfs.txt vfs-3d5a648/Documentation/filesystems/vfs.txt
 224 --- vfs-4cbe5a5/Documentation/filesystems/vfs.txt       2012-09-01 19:39:58.000000000 +0200
 225 +++ vfs-3d5a648/Documentation/filesystems/vfs.txt       2012-09-05 16:35:20.000000000 +0200
 226 @@ -363,6 +363,7 @@
 227         int (*atomic_open)(struct inode *, struct dentry *,
 228                                 struct file *, unsigned open_flag,
 229                                 umode_t create_mode, int *opened);
 230 +       int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
 231  };
 232
 233  Again, all methods are called without any locks being held, unless
 234 @@ -692,6 +693,12 @@
 235         but instead uses bmap to find out where the blocks in the file
 236         are and uses those addresses directly.
 237
 238 +  dentry_open: this is an alternative to f_op->open(), the difference is that
 239 +       this method may open a file not necessarily originating from the same
 240 +       filesystem as the one i_op->open() was called on.  It may be
 241 +       useful for stacking filesystems which want to allow native I/O directly
 242 +       on underlying files.
 243 +
 244
 245    invalidatepage: If a page has PagePrivate set, then invalidatepage
 246          will be called when part or all of the page is to be removed
 247 diff -Nur -x .git vfs-4cbe5a5/fs/ecryptfs/main.c vfs-3d5a648/fs/ecryptfs/main.c
 248 --- vfs-4cbe5a5/fs/ecryptfs/main.c      2012-09-01 19:39:58.000000000 +0200
 249 +++ vfs-3d5a648/fs/ecryptfs/main.c      2012-09-05 16:35:20.000000000 +0200
 250 @@ -565,6 +565,13 @@
 251         s->s_maxbytes = path.dentry->d_sb->s_maxbytes;
 252         s->s_blocksize = path.dentry->d_sb->s_blocksize;
 253         s->s_magic = ECRYPTFS_SUPER_MAGIC;
 254 +       s->s_stack_depth = path.dentry->d_sb->s_stack_depth + 1;
 255 +
 256 +       rc = -EINVAL;
 257 +       if (s->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
 258 +               printk(KERN_ERR "eCryptfs: maximum fs stacking depth exceeded\n");
 259 +               goto out_free;
 260 +       }
 261
 262         inode = ecryptfs_get_inode(path.dentry->d_inode, s);
 263         rc = PTR_ERR(inode);
 264 diff -Nur -x .git vfs-4cbe5a5/fs/internal.h vfs-3d5a648/fs/internal.h
 265 --- vfs-4cbe5a5/fs/internal.h   2012-09-01 19:39:58.000000000 +0200
 266 +++ vfs-3d5a648/fs/internal.h   2012-09-05 16:35:20.000000000 +0200
 267 @@ -42,11 +42,6 @@
 268  extern void __init chrdev_init(void);
 269
 270  /*
 271 - * namei.c
 272 - */
 273 -extern int __inode_permission(struct inode *, int);
 274 -
 275 -/*
 276   * namespace.c
 277   */
 278  extern int copy_mount_options(const void __user *, unsigned long *);
 279 diff -Nur -x .git vfs-4cbe5a5/fs/Kconfig vfs-3d5a648/fs/Kconfig
 280 --- vfs-4cbe5a5/fs/Kconfig      2012-09-01 19:39:58.000000000 +0200
 281 +++ vfs-3d5a648/fs/Kconfig      2012-09-05 16:35:20.000000000 +0200
 282 @@ -67,6 +67,7 @@
 283
 284  source "fs/autofs4/Kconfig"
 285  source "fs/fuse/Kconfig"
 286 +source "fs/overlayfs/Kconfig"
 287
 288  config CUSE
 289         tristate "Character device in Userspace support"
 290 diff -Nur -x .git vfs-4cbe5a5/fs/Makefile vfs-3d5a648/fs/Makefile
 291 --- vfs-4cbe5a5/fs/Makefile     2012-09-01 19:39:58.000000000 +0200
 292 +++ vfs-3d5a648/fs/Makefile     2012-09-05 16:35:20.000000000 +0200
 293 @@ -106,6 +106,7 @@
 294  obj-$(CONFIG_AUTOFS4_FS)       += autofs4/
 295  obj-$(CONFIG_ADFS_FS)          += adfs/
 296  obj-$(CONFIG_FUSE_FS)          += fuse/
 297 +obj-$(CONFIG_OVERLAYFS_FS)     += overlayfs/
 298  obj-$(CONFIG_UDF_FS)           += udf/
 299  obj-$(CONFIG_SUN_OPENPROMFS)   += openpromfs/
 300  obj-$(CONFIG_OMFS_FS)          += omfs/
 301 diff -Nur -x .git vfs-4cbe5a5/fs/namei.c vfs-3d5a648/fs/namei.c
 302 --- vfs-4cbe5a5/fs/namei.c      2012-09-01 19:39:58.000000000 +0200
 303 +++ vfs-3d5a648/fs/namei.c      2012-09-05 16:35:20.000000000 +0200
 304 @@ -348,6 +348,7 @@
 305
 306         return security_inode_permission(inode, mask);
 307  }
 308 +EXPORT_SYMBOL(__inode_permission);
 309
 310  /**
 311   * sb_permission - Check superblock-level permissions
 312 @@ -2822,9 +2823,12 @@
 313         error = may_open(&nd->path, acc_mode, open_flag);
 314         if (error)
 315                 goto out;
 316 -       file->f_path.mnt = nd->path.mnt;
 317 -       error = finish_open(file, nd->path.dentry, NULL, opened);
 318 -       if (error) {
 319 +
 320 +       BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
 321 +       error = vfs_open(&nd->path, file, current_cred());
 322 +       if (!error) {
 323 +               *opened |= FILE_OPENED;
 324 +       } else {
 325                 if (error == -EOPENSTALE)
 326                         goto stale_open;
 327                 goto out;
 328 diff -Nur -x .git vfs-4cbe5a5/fs/namespace.c vfs-3d5a648/fs/namespace.c
 329 --- vfs-4cbe5a5/fs/namespace.c  2012-09-01 19:39:58.000000000 +0200
 330 +++ vfs-3d5a648/fs/namespace.c  2012-09-05 16:35:20.000000000 +0200
 331 @@ -1387,6 +1387,24 @@
 332         release_mounts(&umount_list);
 333  }
 334
 335 +struct vfsmount *clone_private_mount(struct path *path)
 336 +{
 337 +       struct mount *old_mnt = real_mount(path->mnt);
 338 +       struct mount *new_mnt;
 339 +
 340 +       if (IS_MNT_UNBINDABLE(old_mnt))
 341 +               return ERR_PTR(-EINVAL);
 342 +
 343 +       down_read(&namespace_sem);
 344 +       new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
 345 +       up_read(&namespace_sem);
 346 +       if (!new_mnt)
 347 +               return ERR_PTR(-ENOMEM);
 348 +
 349 +       return &new_mnt->mnt;
 350 +}
 351 +EXPORT_SYMBOL_GPL(clone_private_mount);
 352 +
 353  int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
 354                    struct vfsmount *root)
 355  {
 356 diff -Nur -x .git vfs-4cbe5a5/fs/open.c vfs-3d5a648/fs/open.c
 357 --- vfs-4cbe5a5/fs/open.c       2012-09-01 19:39:58.000000000 +0200
 358 +++ vfs-3d5a648/fs/open.c       2012-09-05 16:35:20.000000000 +0200
 359 @@ -787,8 +787,7 @@
 360                 return ERR_PTR(error);
 361
 362         f->f_flags = flags;
 363 -       f->f_path = *path;
 364 -       error = do_dentry_open(f, NULL, cred);
 365 +       error = vfs_open(path, f, cred);
 366         if (!error) {
 367                 error = open_check_o_direct(f);
 368                 if (error) {
 369 @@ -803,6 +802,26 @@
 370  }
 371  EXPORT_SYMBOL(dentry_open);
 372
 373 +/**
 374 + * vfs_open - open the file at the given path
 375 + * @path: path to open
 376 + * @filp: newly allocated file with f_flag initialized
 377 + * @cred: credentials to use
 378 + */
 379 +int vfs_open(const struct path *path, struct file *filp,
 380 +            const struct cred *cred)
 381 +{
 382 +       struct inode *inode = path->dentry->d_inode;
 383 +
 384 +       if (inode->i_op->dentry_open)
 385 +               return inode->i_op->dentry_open(path->dentry, filp, cred);
 386 +       else {
 387 +               filp->f_path = *path;
 388 +               return do_dentry_open(filp, NULL, cred);
 389 +       }
 390 +}
 391 +EXPORT_SYMBOL(vfs_open);
 392 +
 393  static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 394  {
 395         struct fdtable *fdt = files_fdtable(files);
 396 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/copy_up.c vfs-3d5a648/fs/overlayfs/copy_up.c
 397 --- vfs-4cbe5a5/fs/overlayfs/copy_up.c  1970-01-01 01:00:00.000000000 +0100
 398 +++ vfs-3d5a648/fs/overlayfs/copy_up.c  2012-09-05 16:35:20.000000000 +0200
 399 @@ -0,0 +1,385 @@
 400 +/*
 401 + *
 402 + * Copyright (C) 2011 Novell Inc.
 403 + *
 404 + * This program is free software; you can redistribute it and/or modify it
 405 + * under the terms of the GNU General Public License version 2 as published by
 406 + * the Free Software Foundation.
 407 + */
 408 +
 409 +#include <linux/fs.h>
 410 +#include <linux/slab.h>
 411 +#include <linux/file.h>
 412 +#include <linux/splice.h>
 413 +#include <linux/xattr.h>
 414 +#include <linux/security.h>
 415 +#include <linux/uaccess.h>
 416 +#include <linux/sched.h>
 417 +#include "overlayfs.h"
 418 +
 419 +#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
 420 +
 421 +static int ovl_copy_up_xattr(struct dentry *old, struct dentry *new)
 422 +{
 423 +       ssize_t list_size, size;
 424 +       char *buf, *name, *value;
 425 +       int error;
 426 +
 427 +       if (!old->d_inode->i_op->getxattr ||
 428 +           !new->d_inode->i_op->getxattr)
 429 +               return 0;
 430 +
 431 +       list_size = vfs_listxattr(old, NULL, 0);
 432 +       if (list_size <= 0) {
 433 +               if (list_size == -EOPNOTSUPP)
 434 +                       return 0;
 435 +               return list_size;
 436 +       }
 437 +
 438 +       buf = kzalloc(list_size, GFP_KERNEL);
 439 +       if (!buf)
 440 +               return -ENOMEM;
 441 +
 442 +       error = -ENOMEM;
 443 +       value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL);
 444 +       if (!value)
 445 +               goto out;
 446 +
 447 +       list_size = vfs_listxattr(old, buf, list_size);
 448 +       if (list_size <= 0) {
 449 +               error = list_size;
 450 +               goto out_free_value;
 451 +       }
 452 +
 453 +       for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
 454 +               size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX);
 455 +               if (size <= 0) {
 456 +                       error = size;
 457 +                       goto out_free_value;
 458 +               }
 459 +               error = vfs_setxattr(new, name, value, size, 0);
 460 +               if (error)
 461 +                       goto out_free_value;
 462 +       }
 463 +
 464 +out_free_value:
 465 +       kfree(value);
 466 +out:
 467 +       kfree(buf);
 468 +       return error;
 469 +}
 470 +
 471 +static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 472 +{
 473 +       struct file *old_file;
 474 +       struct file *new_file;
 475 +       int error = 0;
 476 +
 477 +       if (len == 0)
 478 +               return 0;
 479 +
 480 +       old_file = ovl_path_open(old, O_RDONLY);
 481 +       if (IS_ERR(old_file))
 482 +               return PTR_ERR(old_file);
 483 +
 484 +       new_file = ovl_path_open(new, O_WRONLY);
 485 +       if (IS_ERR(new_file)) {
 486 +               error = PTR_ERR(new_file);
 487 +               goto out_fput;
 488 +       }
 489 +
 490 +       /* FIXME: copy up sparse files efficiently */
 491 +       while (len) {
 492 +               loff_t offset = new_file->f_pos;
 493 +               size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
 494 +               long bytes;
 495 +
 496 +               if (len < this_len)
 497 +                       this_len = len;
 498 +
 499 +               if (signal_pending_state(TASK_KILLABLE, current)) {
 500 +                       error = -EINTR;
 501 +                       break;
 502 +               }
 503 +
 504 +               bytes = do_splice_direct(old_file, &offset, new_file, this_len,
 505 +                                SPLICE_F_MOVE);
 506 +               if (bytes <= 0) {
 507 +                       error = bytes;
 508 +                       break;
 509 +               }
 510 +
 511 +               len -= bytes;
 512 +       }
 513 +
 514 +       fput(new_file);
 515 +out_fput:
 516 +       fput(old_file);
 517 +       return error;
 518 +}
 519 +
 520 +static char *ovl_read_symlink(struct dentry *realdentry)
 521 +{
 522 +       int res;
 523 +       char *buf;
 524 +       struct inode *inode = realdentry->d_inode;
 525 +       mm_segment_t old_fs;
 526 +
 527 +       res = -EINVAL;
 528 +       if (!inode->i_op->readlink)
 529 +               goto err;
 530 +
 531 +       res = -ENOMEM;
 532 +       buf = (char *) __get_free_page(GFP_KERNEL);
 533 +       if (!buf)
 534 +               goto err;
 535 +
 536 +       old_fs = get_fs();
 537 +       set_fs(get_ds());
 538 +       /* The cast to a user pointer is valid due to the set_fs() */
 539 +       res = inode->i_op->readlink(realdentry,
 540 +                                   (char __user *)buf, PAGE_SIZE - 1);
 541 +       set_fs(old_fs);
 542 +       if (res < 0) {
 543 +               free_page((unsigned long) buf);
 544 +               goto err;
 545 +       }
 546 +       buf[res] = '\0';
 547 +
 548 +       return buf;
 549 +
 550 +err:
 551 +       return ERR_PTR(res);
 552 +}
 553 +
 554 +static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
 555 +{
 556 +       struct iattr attr = {
 557 +               .ia_valid =
 558 +                    ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
 559 +               .ia_atime = stat->atime,
 560 +               .ia_mtime = stat->mtime,
 561 +       };
 562 +
 563 +       return notify_change(upperdentry, &attr);
 564 +}
 565 +
 566 +static int ovl_set_mode(struct dentry *upperdentry, umode_t mode)
 567 +{
 568 +       struct iattr attr = {
 569 +               .ia_valid = ATTR_MODE,
 570 +               .ia_mode = mode,
 571 +       };
 572 +
 573 +       return notify_change(upperdentry, &attr);
 574 +}
 575 +
 576 +static int ovl_copy_up_locked(struct dentry *upperdir, struct dentry *dentry,
 577 +                             struct path *lowerpath, struct kstat *stat,
 578 +                             const char *link)
 579 +{
 580 +       int err;
 581 +       struct path newpath;
 582 +       umode_t mode = stat->mode;
 583 +
 584 +       /* Can't properly set mode on creation because of the umask */
 585 +       stat->mode &= S_IFMT;
 586 +
 587 +       ovl_path_upper(dentry, &newpath);
 588 +       WARN_ON(newpath.dentry);
 589 +       newpath.dentry = ovl_upper_create(upperdir, dentry, stat, link);
 590 +       if (IS_ERR(newpath.dentry))
 591 +               return PTR_ERR(newpath.dentry);
 592 +
 593 +       if (S_ISREG(stat->mode)) {
 594 +               err = ovl_copy_up_data(lowerpath, &newpath, stat->size);
 595 +               if (err)
 596 +                       goto err_remove;
 597 +       }
 598 +
 599 +       err = ovl_copy_up_xattr(lowerpath->dentry, newpath.dentry);
 600 +       if (err)
 601 +               goto err_remove;
 602 +
 603 +       mutex_lock(&newpath.dentry->d_inode->i_mutex);
 604 +       if (!S_ISLNK(stat->mode))
 605 +               err = ovl_set_mode(newpath.dentry, mode);
 606 +       if (!err)
 607 +               err = ovl_set_timestamps(newpath.dentry, stat);
 608 +       mutex_unlock(&newpath.dentry->d_inode->i_mutex);
 609 +       if (err)
 610 +               goto err_remove;
 611 +
 612 +       ovl_dentry_update(dentry, newpath.dentry);
 613 +
 614 +       /*
 615 +        * Easiest way to get rid of the lower dentry reference is to
 616 +        * drop this dentry.  This is neither needed nor possible for
 617 +        * directories.
 618 +        */
 619 +       if (!S_ISDIR(stat->mode))
 620 +               d_drop(dentry);
 621 +
 622 +       return 0;
 623 +
 624 +err_remove:
 625 +       if (S_ISDIR(stat->mode))
 626 +               vfs_rmdir(upperdir->d_inode, newpath.dentry);
 627 +       else
 628 +               vfs_unlink(upperdir->d_inode, newpath.dentry);
 629 +
 630 +       dput(newpath.dentry);
 631 +
 632 +       return err;
 633 +}
 634 +
 635 +/*
 636 + * Copy up a single dentry
 637 + *
 638 + * Directory renames only allowed on "pure upper" (already created on
 639 + * upper filesystem, never copied up).  Directories which are on lower or
 640 + * are merged may not be renamed.  For these -EXDEV is returned and
 641 + * userspace has to deal with it.  This means, when copying up a
 642 + * directory we can rely on it and ancestors being stable.
 643 + *
 644 + * Non-directory renames start with copy up of source if necessary.  The
 645 + * actual rename will only proceed once the copy up was successful.  Copy
 646 + * up uses upper parent i_mutex for exclusion.  Since rename can change
 647 + * d_parent it is possible that the copy up will lock the old parent.  At
 648 + * that point the file will have already been copied up anyway.
 649 + */
 650 +static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 651 +                          struct path *lowerpath, struct kstat *stat)
 652 +{
 653 +       int err;
 654 +       struct kstat pstat;
 655 +       struct path parentpath;
 656 +       struct dentry *upperdir;
 657 +       const struct cred *old_cred;
 658 +       struct cred *override_cred;
 659 +       char *link = NULL;
 660 +
 661 +       ovl_path_upper(parent, &parentpath);
 662 +       upperdir = parentpath.dentry;
 663 +
 664 +       err = vfs_getattr(parentpath.mnt, parentpath.dentry, &pstat);
 665 +       if (err)
 666 +               return err;
 667 +
 668 +       if (S_ISLNK(stat->mode)) {
 669 +               link = ovl_read_symlink(lowerpath->dentry);
 670 +               if (IS_ERR(link))
 671 +                       return PTR_ERR(link);
 672 +       }
 673 +
 674 +       err = -ENOMEM;
 675 +       override_cred = prepare_creds();
 676 +       if (!override_cred)
 677 +               goto out_free_link;
 678 +
 679 +       override_cred->fsuid = stat->uid;
 680 +       override_cred->fsgid = stat->gid;
 681 +       /*
 682 +        * CAP_SYS_ADMIN for copying up extended attributes
 683 +        * CAP_DAC_OVERRIDE for create
 684 +        * CAP_FOWNER for chmod, timestamp update
 685 +        * CAP_FSETID for chmod
 686 +        * CAP_MKNOD for mknod
 687 +        */
 688 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 689 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 690 +       cap_raise(override_cred->cap_effective, CAP_FOWNER);
 691 +       cap_raise(override_cred->cap_effective, CAP_FSETID);
 692 +       cap_raise(override_cred->cap_effective, CAP_MKNOD);
 693 +       old_cred = override_creds(override_cred);
 694 +
 695 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
 696 +       if (ovl_path_type(dentry) != OVL_PATH_LOWER) {
 697 +               err = 0;
 698 +       } else {
 699 +               err = ovl_copy_up_locked(upperdir, dentry, lowerpath,
 700 +                                        stat, link);
 701 +               if (!err) {
 702 +                       /* Restore timestamps on parent (best effort) */
 703 +                       ovl_set_timestamps(upperdir, &pstat);
 704 +               }
 705 +       }
 706 +
 707 +       mutex_unlock(&upperdir->d_inode->i_mutex);
 708 +
 709 +       revert_creds(old_cred);
 710 +       put_cred(override_cred);
 711 +
 712 +out_free_link:
 713 +       if (link)
 714 +               free_page((unsigned long) link);
 715 +
 716 +       return err;
 717 +}
 718 +
 719 +int ovl_copy_up(struct dentry *dentry)
 720 +{
 721 +       int err;
 722 +
 723 +       err = 0;
 724 +       while (!err) {
 725 +               struct dentry *next;
 726 +               struct dentry *parent;
 727 +               struct path lowerpath;
 728 +               struct kstat stat;
 729 +               enum ovl_path_type type = ovl_path_type(dentry);
 730 +
 731 +               if (type != OVL_PATH_LOWER)
 732 +                       break;
 733 +
 734 +               next = dget(dentry);
 735 +               /* find the topmost dentry not yet copied up */
 736 +               for (;;) {
 737 +                       parent = dget_parent(next);
 738 +
 739 +                       type = ovl_path_type(parent);
 740 +                       if (type != OVL_PATH_LOWER)
 741 +                               break;
 742 +
 743 +                       dput(next);
 744 +                       next = parent;
 745 +               }
 746 +
 747 +               ovl_path_lower(next, &lowerpath);
 748 +               err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
 749 +               if (!err)
 750 +                       err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
 751 +
 752 +               dput(parent);
 753 +               dput(next);
 754 +       }
 755 +
 756 +       return err;
 757 +}
 758 +
 759 +/* Optimize by not copying up the file first and truncating later */
 760 +int ovl_copy_up_truncate(struct dentry *dentry, loff_t size)
 761 +{
 762 +       int err;
 763 +       struct kstat stat;
 764 +       struct path lowerpath;
 765 +       struct dentry *parent = dget_parent(dentry);
 766 +
 767 +       err = ovl_copy_up(parent);
 768 +       if (err)
 769 +               goto out_dput_parent;
 770 +
 771 +       ovl_path_lower(dentry, &lowerpath);
 772 +       err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
 773 +       if (err)
 774 +               goto out_dput_parent;
 775 +
 776 +       if (size < stat.size)
 777 +               stat.size = size;
 778 +
 779 +       err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
 780 +
 781 +out_dput_parent:
 782 +       dput(parent);
 783 +       return err;
 784 +}
 785 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/dir.c vfs-3d5a648/fs/overlayfs/dir.c
 786 --- vfs-4cbe5a5/fs/overlayfs/dir.c      1970-01-01 01:00:00.000000000 +0100
 787 +++ vfs-3d5a648/fs/overlayfs/dir.c      2012-09-05 16:35:20.000000000 +0200
 788 @@ -0,0 +1,604 @@
 789 +/*
 790 + *
 791 + * Copyright (C) 2011 Novell Inc.
 792 + *
 793 + * This program is free software; you can redistribute it and/or modify it
 794 + * under the terms of the GNU General Public License version 2 as published by
 795 + * the Free Software Foundation.
 796 + */
 797 +
 798 +#include <linux/fs.h>
 799 +#include <linux/namei.h>
 800 +#include <linux/xattr.h>
 801 +#include <linux/security.h>
 802 +#include <linux/cred.h>
 803 +#include "overlayfs.h"
 804 +
 805 +static const char *ovl_whiteout_symlink = "(overlay-whiteout)";
 806 +
 807 +static int ovl_whiteout(struct dentry *upperdir, struct dentry *dentry)
 808 +{
 809 +       int err;
 810 +       struct dentry *newdentry;
 811 +       const struct cred *old_cred;
 812 +       struct cred *override_cred;
 813 +
 814 +       /* FIXME: recheck lower dentry to see if whiteout is really needed */
 815 +
 816 +       err = -ENOMEM;
 817 +       override_cred = prepare_creds();
 818 +       if (!override_cred)
 819 +               goto out;
 820 +
 821 +       /*
 822 +        * CAP_SYS_ADMIN for setxattr
 823 +        * CAP_DAC_OVERRIDE for symlink creation
 824 +        * CAP_FOWNER for unlink in sticky directory
 825 +        */
 826 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 827 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 828 +       cap_raise(override_cred->cap_effective, CAP_FOWNER);
 829 +       override_cred->fsuid = GLOBAL_ROOT_UID;
 830 +       override_cred->fsgid = GLOBAL_ROOT_GID;
 831 +       old_cred = override_creds(override_cred);
 832 +
 833 +       newdentry = lookup_one_len(dentry->d_name.name, upperdir,
 834 +                                  dentry->d_name.len);
 835 +       err = PTR_ERR(newdentry);
 836 +       if (IS_ERR(newdentry))
 837 +               goto out_put_cred;
 838 +
 839 +       /* Just been removed within the same locked region */
 840 +       WARN_ON(newdentry->d_inode);
 841 +
 842 +       err = vfs_symlink(upperdir->d_inode, newdentry, ovl_whiteout_symlink);
 843 +       if (err)
 844 +               goto out_dput;
 845 +
 846 +       ovl_dentry_version_inc(dentry->d_parent);
 847 +
 848 +       err = vfs_setxattr(newdentry, ovl_whiteout_xattr, "y", 1, 0);
 849 +       if (err)
 850 +               vfs_unlink(upperdir->d_inode, newdentry);
 851 +
 852 +out_dput:
 853 +       dput(newdentry);
 854 +out_put_cred:
 855 +       revert_creds(old_cred);
 856 +       put_cred(override_cred);
 857 +out:
 858 +       if (err) {
 859 +               /*
 860 +                * There's no way to recover from failure to whiteout.
 861 +                * What should we do?  Log a big fat error and... ?
 862 +                */
 863 +               printk(KERN_ERR "overlayfs: ERROR - failed to whiteout '%s'\n",
 864 +                      dentry->d_name.name);
 865 +       }
 866 +
 867 +       return err;
 868 +}
 869 +
 870 +static struct dentry *ovl_lookup_create(struct dentry *upperdir,
 871 +                                       struct dentry *template)
 872 +{
 873 +       int err;
 874 +       struct dentry *newdentry;
 875 +       struct qstr *name = &template->d_name;
 876 +
 877 +       newdentry = lookup_one_len(name->name, upperdir, name->len);
 878 +       if (IS_ERR(newdentry))
 879 +               return newdentry;
 880 +
 881 +       if (newdentry->d_inode) {
 882 +               const struct cred *old_cred;
 883 +               struct cred *override_cred;
 884 +
 885 +               /* No need to check whiteout if lower parent is non-existent */
 886 +               err = -EEXIST;
 887 +               if (!ovl_dentry_lower(template->d_parent))
 888 +                       goto out_dput;
 889 +
 890 +               if (!S_ISLNK(newdentry->d_inode->i_mode))
 891 +                       goto out_dput;
 892 +
 893 +               err = -ENOMEM;
 894 +               override_cred = prepare_creds();
 895 +               if (!override_cred)
 896 +                       goto out_dput;
 897 +
 898 +               /*
 899 +                * CAP_SYS_ADMIN for getxattr
 900 +                * CAP_FOWNER for unlink in sticky directory
 901 +                */
 902 +               cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 903 +               cap_raise(override_cred->cap_effective, CAP_FOWNER);
 904 +               old_cred = override_creds(override_cred);
 905 +
 906 +               err = -EEXIST;
 907 +               if (ovl_is_whiteout(newdentry))
 908 +                       err = vfs_unlink(upperdir->d_inode, newdentry);
 909 +
 910 +               revert_creds(old_cred);
 911 +               put_cred(override_cred);
 912 +               if (err)
 913 +                       goto out_dput;
 914 +
 915 +               dput(newdentry);
 916 +               newdentry = lookup_one_len(name->name, upperdir, name->len);
 917 +               if (IS_ERR(newdentry)) {
 918 +                       ovl_whiteout(upperdir, template);
 919 +                       return newdentry;
 920 +               }
 921 +
 922 +               /*
 923 +                * Whiteout just been successfully removed, parent
 924 +                * i_mutex is still held, there's no way the lookup
 925 +                * could return positive.
 926 +                */
 927 +               WARN_ON(newdentry->d_inode);
 928 +       }
 929 +
 930 +       return newdentry;
 931 +
 932 +out_dput:
 933 +       dput(newdentry);
 934 +       return ERR_PTR(err);
 935 +}
 936 +
 937 +struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
 938 +                               struct kstat *stat, const char *link)
 939 +{
 940 +       int err;
 941 +       struct dentry *newdentry;
 942 +       struct inode *dir = upperdir->d_inode;
 943 +
 944 +       newdentry = ovl_lookup_create(upperdir, dentry);
 945 +       if (IS_ERR(newdentry))
 946 +               goto out;
 947 +
 948 +       switch (stat->mode & S_IFMT) {
 949 +       case S_IFREG:
 950 +               err = vfs_create(dir, newdentry, stat->mode, NULL);
 951 +               break;
 952 +
 953 +       case S_IFDIR:
 954 +               err = vfs_mkdir(dir, newdentry, stat->mode);
 955 +               break;
 956 +
 957 +       case S_IFCHR:
 958 +       case S_IFBLK:
 959 +       case S_IFIFO:
 960 +       case S_IFSOCK:
 961 +               err = vfs_mknod(dir, newdentry, stat->mode, stat->rdev);
 962 +               break;
 963 +
 964 +       case S_IFLNK:
 965 +               err = vfs_symlink(dir, newdentry, link);
 966 +               break;
 967 +
 968 +       default:
 969 +               err = -EPERM;
 970 +       }
 971 +       if (err) {
 972 +               if (ovl_dentry_is_opaque(dentry))
 973 +                       ovl_whiteout(upperdir, dentry);
 974 +               dput(newdentry);
 975 +               newdentry = ERR_PTR(err);
 976 +       } else if (WARN_ON(!newdentry->d_inode)) {
 977 +               /*
 978 +                * Not quite sure if non-instantiated dentry is legal or not.
 979 +                * VFS doesn't seem to care so check and warn here.
 980 +                */
 981 +               dput(newdentry);
 982 +               newdentry = ERR_PTR(-ENOENT);
 983 +       }
 984 +
 985 +out:
 986 +       return newdentry;
 987 +
 988 +}
 989 +
 990 +static int ovl_set_opaque(struct dentry *upperdentry)
 991 +{
 992 +       int err;
 993 +       const struct cred *old_cred;
 994 +       struct cred *override_cred;
 995 +
 996 +       override_cred = prepare_creds();
 997 +       if (!override_cred)
 998 +               return -ENOMEM;
 999 +
1000 +       /* CAP_SYS_ADMIN for setxattr of "trusted" namespace */
1001 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1002 +       old_cred = override_creds(override_cred);
1003 +       err = vfs_setxattr(upperdentry, ovl_opaque_xattr, "y", 1, 0);
1004 +       revert_creds(old_cred);
1005 +       put_cred(override_cred);
1006 +
1007 +       return err;
1008 +}
1009 +
1010 +static int ovl_remove_opaque(struct dentry *upperdentry)
1011 +{
1012 +       int err;
1013 +       const struct cred *old_cred;
1014 +       struct cred *override_cred;
1015 +
1016 +       override_cred = prepare_creds();
1017 +       if (!override_cred)
1018 +               return -ENOMEM;
1019 +
1020 +       /* CAP_SYS_ADMIN for removexattr of "trusted" namespace */
1021 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
1022 +       old_cred = override_creds(override_cred);
1023 +       err = vfs_removexattr(upperdentry, ovl_opaque_xattr);
1024 +       revert_creds(old_cred);
1025 +       put_cred(override_cred);
1026 +
1027 +       return err;
1028 +}
1029 +
1030 +static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
1031 +                        struct kstat *stat)
1032 +{
1033 +       int err;
1034 +       enum ovl_path_type type;
1035 +       struct path realpath;
1036 +
1037 +       type = ovl_path_real(dentry, &realpath);
1038 +       err = vfs_getattr(realpath.mnt, realpath.dentry, stat);
1039 +       if (err)
1040 +               return err;
1041 +
1042 +       stat->dev = dentry->d_sb->s_dev;
1043 +       stat->ino = dentry->d_inode->i_ino;
1044 +
1045 +       /*
1046 +        * It's probably not worth it to count subdirs to get the
1047 +        * correct link count.  nlink=1 seems to pacify 'find' and
1048 +        * other utilities.
1049 +        */
1050 +       if (type == OVL_PATH_MERGE)
1051 +               stat->nlink = 1;
1052 +
1053 +       return 0;
1054 +}
1055 +
1056 +static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
1057 +                            const char *link)
1058 +{
1059 +       int err;
1060 +       struct dentry *newdentry;
1061 +       struct dentry *upperdir;
1062 +       struct inode *inode;
1063 +       struct kstat stat = {
1064 +               .mode = mode,
1065 +               .rdev = rdev,
1066 +       };
1067 +
1068 +       err = -ENOMEM;
1069 +       inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
1070 +       if (!inode)
1071 +               goto out;
1072 +
1073 +       err = ovl_copy_up(dentry->d_parent);
1074 +       if (err)
1075 +               goto out_iput;
1076 +
1077 +       upperdir = ovl_dentry_upper(dentry->d_parent);
1078 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1079 +
1080 +       newdentry = ovl_upper_create(upperdir, dentry, &stat, link);
1081 +       err = PTR_ERR(newdentry);
1082 +       if (IS_ERR(newdentry))
1083 +               goto out_unlock;
1084 +
1085 +       ovl_dentry_version_inc(dentry->d_parent);
1086 +       if (ovl_dentry_is_opaque(dentry) && S_ISDIR(mode)) {
1087 +               err = ovl_set_opaque(newdentry);
1088 +               if (err) {
1089 +                       vfs_rmdir(upperdir->d_inode, newdentry);
1090 +                       ovl_whiteout(upperdir, dentry);
1091 +                       goto out_dput;
1092 +               }
1093 +       }
1094 +       ovl_dentry_update(dentry, newdentry);
1095 +       ovl_copyattr(newdentry->d_inode, inode);
1096 +       d_instantiate(dentry, inode);
1097 +       inode = NULL;
1098 +       newdentry = NULL;
1099 +       err = 0;
1100 +
1101 +out_dput:
1102 +       dput(newdentry);
1103 +out_unlock:
1104 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1105 +out_iput:
1106 +       iput(inode);
1107 +out:
1108 +       return err;
1109 +}
1110 +
1111 +static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1112 +                     bool excl)
1113 +{
1114 +       return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
1115 +}
1116 +
1117 +static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1118 +{
1119 +       return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
1120 +}
1121 +
1122 +static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
1123 +                    dev_t rdev)
1124 +{
1125 +       return ovl_create_object(dentry, mode, rdev, NULL);
1126 +}
1127 +
1128 +static int ovl_symlink(struct inode *dir, struct dentry *dentry,
1129 +                        const char *link)
1130 +{
1131 +       return ovl_create_object(dentry, S_IFLNK, 0, link);
1132 +}
1133 +
1134 +static int ovl_do_remove(struct dentry *dentry, bool is_dir)
1135 +{
1136 +       int err;
1137 +       enum ovl_path_type type;
1138 +       struct path realpath;
1139 +       struct dentry *upperdir;
1140 +
1141 +       err = ovl_copy_up(dentry->d_parent);
1142 +       if (err)
1143 +               return err;
1144 +
1145 +       upperdir = ovl_dentry_upper(dentry->d_parent);
1146 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1147 +       type = ovl_path_real(dentry, &realpath);
1148 +       if (type != OVL_PATH_LOWER) {
1149 +               err = -ESTALE;
1150 +               if (realpath.dentry->d_parent != upperdir)
1151 +                       goto out_d_drop;
1152 +
1153 +               /* FIXME: create whiteout up front and rename to target */
1154 +
1155 +               if (is_dir)
1156 +                       err = vfs_rmdir(upperdir->d_inode, realpath.dentry);
1157 +               else
1158 +                       err = vfs_unlink(upperdir->d_inode, realpath.dentry);
1159 +               if (err)
1160 +                       goto out_d_drop;
1161 +
1162 +               ovl_dentry_version_inc(dentry->d_parent);
1163 +       }
1164 +
1165 +       if (type != OVL_PATH_UPPER || ovl_dentry_is_opaque(dentry))
1166 +               err = ovl_whiteout(upperdir, dentry);
1167 +
1168 +       /*
1169 +        * Keeping this dentry hashed would mean having to release
1170 +        * upperpath/lowerpath, which could only be done if we are the
1171 +        * sole user of this dentry.  Too tricky...  Just unhash for
1172 +        * now.
1173 +        */
1174 +out_d_drop:
1175 +       d_drop(dentry);
1176 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1177 +
1178 +       return err;
1179 +}
1180 +
1181 +static int ovl_unlink(struct inode *dir, struct dentry *dentry)
1182 +{
1183 +       return ovl_do_remove(dentry, false);
1184 +}
1185 +
1186 +
1187 +static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
1188 +{
1189 +       int err;
1190 +       enum ovl_path_type type;
1191 +
1192 +       type = ovl_path_type(dentry);
1193 +       if (type != OVL_PATH_UPPER) {
1194 +               err = ovl_check_empty_and_clear(dentry, type);
1195 +               if (err)
1196 +                       return err;
1197 +       }
1198 +
1199 +       return ovl_do_remove(dentry, true);
1200 +}
1201 +
1202 +static int ovl_link(struct dentry *old, struct inode *newdir,
1203 +                   struct dentry *new)
1204 +{
1205 +       int err;
1206 +       struct dentry *olddentry;
1207 +       struct dentry *newdentry;
1208 +       struct dentry *upperdir;
1209 +       struct inode *newinode;
1210 +
1211 +       err = ovl_copy_up(old);
1212 +       if (err)
1213 +               goto out;
1214 +
1215 +       err = ovl_copy_up(new->d_parent);
1216 +       if (err)
1217 +               goto out;
1218 +
1219 +       upperdir = ovl_dentry_upper(new->d_parent);
1220 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
1221 +       newdentry = ovl_lookup_create(upperdir, new);
1222 +       err = PTR_ERR(newdentry);
1223 +       if (IS_ERR(newdentry))
1224 +               goto out_unlock;
1225 +
1226 +       olddentry = ovl_dentry_upper(old);
1227 +       err = vfs_link(olddentry, upperdir->d_inode, newdentry);
1228 +       if (!err) {
1229 +               if (WARN_ON(!newdentry->d_inode)) {
1230 +                       dput(newdentry);
1231 +                       err = -ENOENT;
1232 +                       goto out_unlock;
1233 +               }
1234 +               newinode = ovl_new_inode(old->d_sb, newdentry->d_inode->i_mode,
1235 +                               new->d_fsdata);
1236 +               if (!newinode)
1237 +                       goto link_fail;
1238 +               ovl_copyattr(upperdir->d_inode, newinode);
1239 +
1240 +               ovl_dentry_version_inc(new->d_parent);
1241 +               ovl_dentry_update(new, newdentry);
1242 +
1243 +               d_instantiate(new, newinode);
1244 +       } else {
1245 +link_fail:
1246 +               if (ovl_dentry_is_opaque(new))
1247 +                       ovl_whiteout(upperdir, new);
1248 +               dput(newdentry);
1249 +       }
1250 +out_unlock:
1251 +       mutex_unlock(&upperdir->d_inode->i_mutex);
1252 +out:
1253 +       return err;
1254 +
1255 +}
1256 +
1257 +static int ovl_rename(struct inode *olddir, struct dentry *old,
1258 +                       struct inode *newdir, struct dentry *new)
1259 +{
1260 +       int err;
1261 +       enum ovl_path_type old_type;
1262 +       enum ovl_path_type new_type;
1263 +       struct dentry *old_upperdir;
1264 +       struct dentry *new_upperdir;
1265 +       struct dentry *olddentry;
1266 +       struct dentry *newdentry;
1267 +       struct dentry *trap;
1268 +       bool old_opaque;
1269 +       bool new_opaque;
1270 +       bool new_create = false;
1271 +       bool is_dir = S_ISDIR(old->d_inode->i_mode);
1272 +
1273 +       /* Don't copy up directory trees */
1274 +       old_type = ovl_path_type(old);
1275 +       if (old_type != OVL_PATH_UPPER && is_dir)
1276 +               return -EXDEV;
1277 +
1278 +       if (new->d_inode) {
1279 +               new_type = ovl_path_type(new);
1280 +
1281 +               if (new_type == OVL_PATH_LOWER && old_type == OVL_PATH_LOWER) {
1282 +                       if (ovl_dentry_lower(old)->d_inode ==
1283 +                           ovl_dentry_lower(new)->d_inode)
1284 +                               return 0;
1285 +               }
1286 +               if (new_type != OVL_PATH_LOWER && old_type != OVL_PATH_LOWER) {
1287 +                       if (ovl_dentry_upper(old)->d_inode ==
1288 +                           ovl_dentry_upper(new)->d_inode)
1289 +                               return 0;
1290 +               }
1291 +
1292 +               if (new_type != OVL_PATH_UPPER &&
1293 +                   S_ISDIR(new->d_inode->i_mode)) {
1294 +                       err = ovl_check_empty_and_clear(new, new_type);
1295 +                       if (err)
1296 +                               return err;
1297 +               }
1298 +       } else {
1299 +               new_type = OVL_PATH_UPPER;
1300 +       }
1301 +
1302 +       err = ovl_copy_up(old);
1303 +       if (err)
1304 +               return err;
1305 +
1306 +       err = ovl_copy_up(new->d_parent);
1307 +       if (err)
1308 +               return err;
1309 +
1310 +       old_upperdir = ovl_dentry_upper(old->d_parent);
1311 +       new_upperdir = ovl_dentry_upper(new->d_parent);
1312 +
1313 +       trap = lock_rename(new_upperdir, old_upperdir);
1314 +
1315 +       olddentry = ovl_dentry_upper(old);
1316 +       newdentry = ovl_dentry_upper(new);
1317 +       if (newdentry) {
1318 +               dget(newdentry);
1319 +       } else {
1320 +               new_create = true;
1321 +               newdentry = ovl_lookup_create(new_upperdir, new);
1322 +               err = PTR_ERR(newdentry);
1323 +               if (IS_ERR(newdentry))
1324 +                       goto out_unlock;
1325 +       }
1326 +
1327 +       err = -ESTALE;
1328 +       if (olddentry->d_parent != old_upperdir)
1329 +               goto out_dput;
1330 +       if (newdentry->d_parent != new_upperdir)
1331 +               goto out_dput;
1332 +       if (olddentry == trap)
1333 +               goto out_dput;
1334 +       if (newdentry == trap)
1335 +               goto out_dput;
1336 +
1337 +       old_opaque = ovl_dentry_is_opaque(old);
1338 +       new_opaque = ovl_dentry_is_opaque(new) || new_type != OVL_PATH_UPPER;
1339 +
1340 +       if (is_dir && !old_opaque && new_opaque) {
1341 +               err = ovl_set_opaque(olddentry);
1342 +               if (err)
1343 +                       goto out_dput;
1344 +       }
1345 +
1346 +       err = vfs_rename(old_upperdir->d_inode, olddentry,
1347 +                        new_upperdir->d_inode, newdentry);
1348 +
1349 +       if (err) {
1350 +               if (new_create && ovl_dentry_is_opaque(new))
1351 +                       ovl_whiteout(new_upperdir, new);
1352 +               if (is_dir && !old_opaque && new_opaque)
1353 +                       ovl_remove_opaque(olddentry);
1354 +               goto out_dput;
1355 +       }
1356 +
1357 +       if (old_type != OVL_PATH_UPPER || old_opaque)
1358 +               err = ovl_whiteout(old_upperdir, old);
1359 +       if (is_dir && old_opaque && !new_opaque)
1360 +               ovl_remove_opaque(olddentry);
1361 +
1362 +       if (old_opaque != new_opaque)
1363 +               ovl_dentry_set_opaque(old, new_opaque);
1364 +
1365 +       ovl_dentry_version_inc(old->d_parent);
1366 +       ovl_dentry_version_inc(new->d_parent);
1367 +
1368 +out_dput:
1369 +       dput(newdentry);
1370 +out_unlock:
1371 +       unlock_rename(new_upperdir, old_upperdir);
1372 +       return err;
1373 +}
1374 +
1375 +const struct inode_operations ovl_dir_inode_operations = {
1376 +       .lookup         = ovl_lookup,
1377 +       .mkdir          = ovl_mkdir,
1378 +       .symlink        = ovl_symlink,
1379 +       .unlink         = ovl_unlink,
1380 +       .rmdir          = ovl_rmdir,
1381 +       .rename         = ovl_rename,
1382 +       .link           = ovl_link,
1383 +       .setattr        = ovl_setattr,
1384 +       .create         = ovl_create,
1385 +       .mknod          = ovl_mknod,
1386 +       .permission     = ovl_permission,
1387 +       .getattr        = ovl_dir_getattr,
1388 +       .setxattr       = ovl_setxattr,
1389 +       .getxattr       = ovl_getxattr,
1390 +       .listxattr      = ovl_listxattr,
1391 +       .removexattr    = ovl_removexattr,
1392 +};
1393 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/inode.c vfs-3d5a648/fs/overlayfs/inode.c
1394 --- vfs-4cbe5a5/fs/overlayfs/inode.c    1970-01-01 01:00:00.000000000 +0100
1395 +++ vfs-3d5a648/fs/overlayfs/inode.c    2012-09-05 16:35:20.000000000 +0200
1396 @@ -0,0 +1,372 @@
1397 +/*
1398 + *
1399 + * Copyright (C) 2011 Novell Inc.
1400 + *
1401 + * This program is free software; you can redistribute it and/or modify it
1402 + * under the terms of the GNU General Public License version 2 as published by
1403 + * the Free Software Foundation.
1404 + */
1405 +
1406 +#include <linux/fs.h>
1407 +#include <linux/slab.h>
1408 +#include <linux/xattr.h>
1409 +#include "overlayfs.h"
1410 +
1411 +int ovl_setattr(struct dentry *dentry, struct iattr *attr)
1412 +{
1413 +       struct dentry *upperdentry;
1414 +       int err;
1415 +
1416 +       if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry))
1417 +               err = ovl_copy_up_truncate(dentry, attr->ia_size);
1418 +       else
1419 +               err = ovl_copy_up(dentry);
1420 +       if (err)
1421 +               return err;
1422 +
1423 +       upperdentry = ovl_dentry_upper(dentry);
1424 +
1425 +       if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
1426 +               attr->ia_valid &= ~ATTR_MODE;
1427 +
1428 +       mutex_lock(&upperdentry->d_inode->i_mutex);
1429 +       err = notify_change(upperdentry, attr);
1430 +       if (!err)
1431 +               ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
1432 +       mutex_unlock(&upperdentry->d_inode->i_mutex);
1433 +
1434 +       return err;
1435 +}
1436 +
1437 +static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
1438 +                        struct kstat *stat)
1439 +{
1440 +       struct path realpath;
1441 +
1442 +       ovl_path_real(dentry, &realpath);
1443 +       return vfs_getattr(realpath.mnt, realpath.dentry, stat);
1444 +}
1445 +
1446 +int ovl_permission(struct inode *inode, int mask)
1447 +{
1448 +       struct ovl_entry *oe;
1449 +       struct dentry *alias = NULL;
1450 +       struct inode *realinode;
1451 +       struct dentry *realdentry;
1452 +       bool is_upper;
1453 +       int err;
1454 +
1455 +       if (S_ISDIR(inode->i_mode)) {
1456 +               oe = inode->i_private;
1457 +       } else if (mask & MAY_NOT_BLOCK) {
1458 +               return -ECHILD;
1459 +       } else {
1460 +               /*
1461 +                * For non-directories find an alias and get the info
1462 +                * from there.
1463 +                */
1464 +               alias = d_find_any_alias(inode);
1465 +               if (WARN_ON(!alias))
1466 +                       return -ENOENT;
1467 +
1468 +               oe = alias->d_fsdata;
1469 +       }
1470 +
1471 +       realdentry = ovl_entry_real(oe, &is_upper);
1472 +
1473 +       /* Careful in RCU walk mode */
1474 +       realinode = ACCESS_ONCE(realdentry->d_inode);
1475 +       if (!realinode) {
1476 +               WARN_ON(!(mask & MAY_NOT_BLOCK));
1477 +               err = -ENOENT;
1478 +               goto out_dput;
1479 +       }
1480 +
1481 +       if (mask & MAY_WRITE) {
1482 +               umode_t mode = realinode->i_mode;
1483 +
1484 +               /*
1485 +                * Writes will always be redirected to upper layer, so
1486 +                * ignore lower layer being read-only.
1487 +                *
1488 +                * If the overlay itself is read-only then proceed
1489 +                * with the permission check, don't return EROFS.
1490 +                * This will only happen if this is the lower layer of
1491 +                * another overlayfs.
1492 +                *
1493 +                * If upper fs becomes read-only after the overlay was
1494 +                * constructed return EROFS to prevent modification of
1495 +                * upper layer.
1496 +                */
1497 +               err = -EROFS;
1498 +               if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
1499 +                   (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
1500 +                       goto out_dput;
1501 +       }
1502 +
1503 +       err = __inode_permission(realinode, mask);
1504 +out_dput:
1505 +       dput(alias);
1506 +       return err;
1507 +}
1508 +
1509 +
1510 +struct ovl_link_data {
1511 +       struct dentry *realdentry;
1512 +       void *cookie;
1513 +};
1514 +
1515 +static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
1516 +{
1517 +       void *ret;
1518 +       struct dentry *realdentry;
1519 +       struct inode *realinode;
1520 +
1521 +       realdentry = ovl_dentry_real(dentry);
1522 +       realinode = realdentry->d_inode;
1523 +
1524 +       if (WARN_ON(!realinode->i_op->follow_link))
1525 +               return ERR_PTR(-EPERM);
1526 +
1527 +       ret = realinode->i_op->follow_link(realdentry, nd);
1528 +       if (IS_ERR(ret))
1529 +               return ret;
1530 +
1531 +       if (realinode->i_op->put_link) {
1532 +               struct ovl_link_data *data;
1533 +
1534 +               data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
1535 +               if (!data) {
1536 +                       realinode->i_op->put_link(realdentry, nd, ret);
1537 +                       return ERR_PTR(-ENOMEM);
1538 +               }
1539 +               data->realdentry = realdentry;
1540 +               data->cookie = ret;
1541 +
1542 +               return data;
1543 +       } else {
1544 +               return NULL;
1545 +       }
1546 +}
1547 +
1548 +static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
1549 +{
1550 +       struct inode *realinode;
1551 +       struct ovl_link_data *data = c;
1552 +
1553 +       if (!data)
1554 +               return;
1555 +
1556 +       realinode = data->realdentry->d_inode;
1557 +       realinode->i_op->put_link(data->realdentry, nd, data->cookie);
1558 +       kfree(data);
1559 +}
1560 +
1561 +static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
1562 +{
1563 +       struct path realpath;
1564 +       struct inode *realinode;
1565 +
1566 +       ovl_path_real(dentry, &realpath);
1567 +       realinode = realpath.dentry->d_inode;
1568 +
1569 +       if (!realinode->i_op->readlink)
1570 +               return -EINVAL;
1571 +
1572 +       touch_atime(&realpath);
1573 +
1574 +       return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
1575 +}
1576 +
1577 +
1578 +static bool ovl_is_private_xattr(const char *name)
1579 +{
1580 +       return strncmp(name, "trusted.overlay.", 14) == 0;
1581 +}
1582 +
1583 +int ovl_setxattr(struct dentry *dentry, const char *name,
1584 +                const void *value, size_t size, int flags)
1585 +{
1586 +       int err;
1587 +       struct dentry *upperdentry;
1588 +
1589 +       if (ovl_is_private_xattr(name))
1590 +               return -EPERM;
1591 +
1592 +       err = ovl_copy_up(dentry);
1593 +       if (err)
1594 +               return err;
1595 +
1596 +       upperdentry = ovl_dentry_upper(dentry);
1597 +       return  vfs_setxattr(upperdentry, name, value, size, flags);
1598 +}
1599 +
1600 +ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
1601 +                    void *value, size_t size)
1602 +{
1603 +       if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
1604 +           ovl_is_private_xattr(name))
1605 +               return -ENODATA;
1606 +
1607 +       return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
1608 +}
1609 +
1610 +ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
1611 +{
1612 +       ssize_t res;
1613 +       int off;
1614 +
1615 +       res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
1616 +       if (res <= 0 || size == 0)
1617 +               return res;
1618 +
1619 +       if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
1620 +               return res;
1621 +
1622 +       /* filter out private xattrs */
1623 +       for (off = 0; off < res;) {
1624 +               char *s = list + off;
1625 +               size_t slen = strlen(s) + 1;
1626 +
1627 +               BUG_ON(off + slen > res);
1628 +
1629 +               if (ovl_is_private_xattr(s)) {
1630 +                       res -= slen;
1631 +                       memmove(s, s + slen, res - off);
1632 +               } else {
1633 +                       off += slen;
1634 +               }
1635 +       }
1636 +
1637 +       return res;
1638 +}
1639 +
1640 +int ovl_removexattr(struct dentry *dentry, const char *name)
1641 +{
1642 +       int err;
1643 +       struct path realpath;
1644 +       enum ovl_path_type type;
1645 +
1646 +       if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
1647 +           ovl_is_private_xattr(name))
1648 +               return -ENODATA;
1649 +
1650 +       type = ovl_path_real(dentry, &realpath);
1651 +       if (type == OVL_PATH_LOWER) {
1652 +               err = vfs_getxattr(realpath.dentry, name, NULL, 0);
1653 +               if (err < 0)
1654 +                       return err;
1655 +
1656 +               err = ovl_copy_up(dentry);
1657 +               if (err)
1658 +                       return err;
1659 +
1660 +               ovl_path_upper(dentry, &realpath);
1661 +       }
1662 +
1663 +       return vfs_removexattr(realpath.dentry, name);
1664 +}
1665 +
1666 +static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
1667 +                                 struct dentry *realdentry)
1668 +{
1669 +       if (type != OVL_PATH_LOWER)
1670 +               return false;
1671 +
1672 +       if (special_file(realdentry->d_inode->i_mode))
1673 +               return false;
1674 +
1675 +       if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
1676 +               return false;
1677 +
1678 +       return true;
1679 +}
1680 +
1681 +static int ovl_dentry_open(struct dentry *dentry, struct file *file,
1682 +                   const struct cred *cred)
1683 +{
1684 +       int err;
1685 +       struct path realpath;
1686 +       enum ovl_path_type type;
1687 +
1688 +       type = ovl_path_real(dentry, &realpath);
1689 +       if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
1690 +               if (file->f_flags & O_TRUNC)
1691 +                       err = ovl_copy_up_truncate(dentry, 0);
1692 +               else
1693 +                       err = ovl_copy_up(dentry);
1694 +               if (err)
1695 +                       return err;
1696 +
1697 +               ovl_path_upper(dentry, &realpath);
1698 +       }
1699 +
1700 +       return vfs_open(&realpath, file, cred);
1701 +}
1702 +
1703 +static const struct inode_operations ovl_file_inode_operations = {
1704 +       .setattr        = ovl_setattr,
1705 +       .permission     = ovl_permission,
1706 +       .getattr        = ovl_getattr,
1707 +       .setxattr       = ovl_setxattr,
1708 +       .getxattr       = ovl_getxattr,
1709 +       .listxattr      = ovl_listxattr,
1710 +       .removexattr    = ovl_removexattr,
1711 +       .dentry_open    = ovl_dentry_open,
1712 +};
1713 +
1714 +static const struct inode_operations ovl_symlink_inode_operations = {
1715 +       .setattr        = ovl_setattr,
1716 +       .follow_link    = ovl_follow_link,
1717 +       .put_link       = ovl_put_link,
1718 +       .readlink       = ovl_readlink,
1719 +       .getattr        = ovl_getattr,
1720 +       .setxattr       = ovl_setxattr,
1721 +       .getxattr       = ovl_getxattr,
1722 +       .listxattr      = ovl_listxattr,
1723 +       .removexattr    = ovl_removexattr,
1724 +};
1725 +
1726 +struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
1727 +                           struct ovl_entry *oe)
1728 +{
1729 +       struct inode *inode;
1730 +
1731 +       inode = new_inode(sb);
1732 +       if (!inode)
1733 +               return NULL;
1734 +
1735 +       mode &= S_IFMT;
1736 +
1737 +       inode->i_ino = get_next_ino();
1738 +       inode->i_mode = mode;
1739 +       inode->i_flags |= S_NOATIME | S_NOCMTIME;
1740 +
1741 +       switch (mode) {
1742 +       case S_IFDIR:
1743 +               inode->i_private = oe;
1744 +               inode->i_op = &ovl_dir_inode_operations;
1745 +               inode->i_fop = &ovl_dir_operations;
1746 +               break;
1747 +
1748 +       case S_IFLNK:
1749 +               inode->i_op = &ovl_symlink_inode_operations;
1750 +               break;
1751 +
1752 +       case S_IFREG:
1753 +       case S_IFSOCK:
1754 +       case S_IFBLK:
1755 +       case S_IFCHR:
1756 +       case S_IFIFO:
1757 +               inode->i_op = &ovl_file_inode_operations;
1758 +               break;
1759 +
1760 +       default:
1761 +               WARN(1, "illegal file type: %i\n", mode);
1762 +               iput(inode);
1763 +               inode = NULL;
1764 +       }
1765 +
1766 +       return inode;
1767 +
1768 +}
1769 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/Kconfig vfs-3d5a648/fs/overlayfs/Kconfig
1770 --- vfs-4cbe5a5/fs/overlayfs/Kconfig    1970-01-01 01:00:00.000000000 +0100
1771 +++ vfs-3d5a648/fs/overlayfs/Kconfig    2012-09-05 16:35:20.000000000 +0200
1772 @@ -0,0 +1,4 @@
1773 +config OVERLAYFS_FS
1774 +       tristate "Overlay filesystem support"
1775 +       help
1776 +         Add support for overlay filesystem.
1777 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/Makefile vfs-3d5a648/fs/overlayfs/Makefile
1778 --- vfs-4cbe5a5/fs/overlayfs/Makefile   1970-01-01 01:00:00.000000000 +0100
1779 +++ vfs-3d5a648/fs/overlayfs/Makefile   2012-09-05 16:35:20.000000000 +0200
1780 @@ -0,0 +1,7 @@
1781 +#
1782 +# Makefile for the overlay filesystem.
1783 +#
1784 +
1785 +obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o
1786 +
1787 +overlayfs-objs := super.o inode.o dir.o readdir.o copy_up.o
1788 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/overlayfs.h vfs-3d5a648/fs/overlayfs/overlayfs.h
1789 --- vfs-4cbe5a5/fs/overlayfs/overlayfs.h        1970-01-01 01:00:00.000000000 +0100
1790 +++ vfs-3d5a648/fs/overlayfs/overlayfs.h        2012-09-05 16:35:20.000000000 +0200
1791 @@ -0,0 +1,70 @@
1792 +/*
1793 + *
1794 + * Copyright (C) 2011 Novell Inc.
1795 + *
1796 + * This program is free software; you can redistribute it and/or modify it
1797 + * under the terms of the GNU General Public License version 2 as published by
1798 + * the Free Software Foundation.
1799 + */
1800 +
1801 +struct ovl_entry;
1802 +
1803 +enum ovl_path_type {
1804 +       OVL_PATH_UPPER,
1805 +       OVL_PATH_MERGE,
1806 +       OVL_PATH_LOWER,
1807 +};
1808 +
1809 +extern const char *ovl_opaque_xattr;
1810 +extern const char *ovl_whiteout_xattr;
1811 +extern const struct dentry_operations ovl_dentry_operations;
1812 +
1813 +enum ovl_path_type ovl_path_type(struct dentry *dentry);
1814 +u64 ovl_dentry_version_get(struct dentry *dentry);
1815 +void ovl_dentry_version_inc(struct dentry *dentry);
1816 +void ovl_path_upper(struct dentry *dentry, struct path *path);
1817 +void ovl_path_lower(struct dentry *dentry, struct path *path);
1818 +enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
1819 +struct dentry *ovl_dentry_upper(struct dentry *dentry);
1820 +struct dentry *ovl_dentry_lower(struct dentry *dentry);
1821 +struct dentry *ovl_dentry_real(struct dentry *dentry);
1822 +struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper);
1823 +bool ovl_dentry_is_opaque(struct dentry *dentry);
1824 +void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
1825 +bool ovl_is_whiteout(struct dentry *dentry);
1826 +void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
1827 +struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
1828 +                         unsigned int flags);
1829 +struct file *ovl_path_open(struct path *path, int flags);
1830 +
1831 +struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
1832 +                               struct kstat *stat, const char *link);
1833 +
1834 +/* readdir.c */
1835 +extern const struct file_operations ovl_dir_operations;
1836 +int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type);
1837 +
1838 +/* inode.c */
1839 +int ovl_setattr(struct dentry *dentry, struct iattr *attr);
1840 +int ovl_permission(struct inode *inode, int mask);
1841 +int ovl_setxattr(struct dentry *dentry, const char *name,
1842 +                const void *value, size_t size, int flags);
1843 +ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
1844 +                    void *value, size_t size);
1845 +ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
1846 +int ovl_removexattr(struct dentry *dentry, const char *name);
1847 +
1848 +struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
1849 +                           struct ovl_entry *oe);
1850 +static inline void ovl_copyattr(struct inode *from, struct inode *to)
1851 +{
1852 +       to->i_uid = from->i_uid;
1853 +       to->i_gid = from->i_gid;
1854 +}
1855 +
1856 +/* dir.c */
1857 +extern const struct inode_operations ovl_dir_inode_operations;
1858 +
1859 +/* copy_up.c */
1860 +int ovl_copy_up(struct dentry *dentry);
1861 +int ovl_copy_up_truncate(struct dentry *dentry, loff_t size);
1862 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/readdir.c vfs-3d5a648/fs/overlayfs/readdir.c
1863 --- vfs-4cbe5a5/fs/overlayfs/readdir.c  1970-01-01 01:00:00.000000000 +0100
1864 +++ vfs-3d5a648/fs/overlayfs/readdir.c  2012-09-05 16:35:20.000000000 +0200
1865 @@ -0,0 +1,566 @@
1866 +/*
1867 + *
1868 + * Copyright (C) 2011 Novell Inc.
1869 + *
1870 + * This program is free software; you can redistribute it and/or modify it
1871 + * under the terms of the GNU General Public License version 2 as published by
1872 + * the Free Software Foundation.
1873 + */
1874 +
1875 +#include <linux/fs.h>
1876 +#include <linux/slab.h>
1877 +#include <linux/namei.h>
1878 +#include <linux/file.h>
1879 +#include <linux/xattr.h>
1880 +#include <linux/rbtree.h>
1881 +#include <linux/security.h>
1882 +#include <linux/cred.h>
1883 +#include "overlayfs.h"
1884 +
1885 +struct ovl_cache_entry {
1886 +       const char *name;
1887 +       unsigned int len;
1888 +       unsigned int type;
1889 +       u64 ino;
1890 +       bool is_whiteout;
1891 +       struct list_head l_node;
1892 +       struct rb_node node;
1893 +};
1894 +
1895 +struct ovl_readdir_data {
1896 +       struct rb_root *root;
1897 +       struct list_head *list;
1898 +       struct list_head *middle;
1899 +       struct dentry *dir;
1900 +       int count;
1901 +       int err;
1902 +};
1903 +
1904 +struct ovl_dir_file {
1905 +       bool is_real;
1906 +       bool is_cached;
1907 +       struct list_head cursor;
1908 +       u64 cache_version;
1909 +       struct list_head cache;
1910 +       struct file *realfile;
1911 +};
1912 +
1913 +static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
1914 +{
1915 +       return container_of(n, struct ovl_cache_entry, node);
1916 +}
1917 +
1918 +static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
1919 +                                                   const char *name, int len)
1920 +{
1921 +       struct rb_node *node = root->rb_node;
1922 +       int cmp;
1923 +
1924 +       while (node) {
1925 +               struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
1926 +
1927 +               cmp = strncmp(name, p->name, len);
1928 +               if (cmp > 0)
1929 +                       node = p->node.rb_right;
1930 +               else if (cmp < 0 || len < p->len)
1931 +                       node = p->node.rb_left;
1932 +               else
1933 +                       return p;
1934 +       }
1935 +
1936 +       return NULL;
1937 +}
1938 +
1939 +static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
1940 +                                                  u64 ino, unsigned int d_type)
1941 +{
1942 +       struct ovl_cache_entry *p;
1943 +
1944 +       p = kmalloc(sizeof(*p) + len + 1, GFP_KERNEL);
1945 +       if (p) {
1946 +               char *name_copy = (char *) (p + 1);
1947 +               memcpy(name_copy, name, len);
1948 +               name_copy[len] = '\0';
1949 +               p->name = name_copy;
1950 +               p->len = len;
1951 +               p->type = d_type;
1952 +               p->ino = ino;
1953 +               p->is_whiteout = false;
1954 +       }
1955 +
1956 +       return p;
1957 +}
1958 +
1959 +static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
1960 +                                 const char *name, int len, u64 ino,
1961 +                                 unsigned int d_type)
1962 +{
1963 +       struct rb_node **newp = &rdd->root->rb_node;
1964 +       struct rb_node *parent = NULL;
1965 +       struct ovl_cache_entry *p;
1966 +
1967 +       while (*newp) {
1968 +               int cmp;
1969 +               struct ovl_cache_entry *tmp;
1970 +
1971 +               parent = *newp;
1972 +               tmp = ovl_cache_entry_from_node(*newp);
1973 +               cmp = strncmp(name, tmp->name, len);
1974 +               if (cmp > 0)
1975 +                       newp = &tmp->node.rb_right;
1976 +               else if (cmp < 0 || len < tmp->len)
1977 +                       newp = &tmp->node.rb_left;
1978 +               else
1979 +                       return 0;
1980 +       }
1981 +
1982 +       p = ovl_cache_entry_new(name, len, ino, d_type);
1983 +       if (p == NULL)
1984 +               return -ENOMEM;
1985 +
1986 +       list_add_tail(&p->l_node, rdd->list);
1987 +       rb_link_node(&p->node, parent, newp);
1988 +       rb_insert_color(&p->node, rdd->root);
1989 +
1990 +       return 0;
1991 +}
1992 +
1993 +static int ovl_fill_lower(void *buf, const char *name, int namelen,
1994 +                           loff_t offset, u64 ino, unsigned int d_type)
1995 +{
1996 +       struct ovl_readdir_data *rdd = buf;
1997 +       struct ovl_cache_entry *p;
1998 +
1999 +       rdd->count++;
2000 +       p = ovl_cache_entry_find(rdd->root, name, namelen);
2001 +       if (p) {
2002 +               list_move_tail(&p->l_node, rdd->middle);
2003 +       } else {
2004 +               p = ovl_cache_entry_new(name, namelen, ino, d_type);
2005 +               if (p == NULL)
2006 +                       rdd->err = -ENOMEM;
2007 +               else
2008 +                       list_add_tail(&p->l_node, rdd->middle);
2009 +       }
2010 +
2011 +       return rdd->err;
2012 +}
2013 +
2014 +static void ovl_cache_free(struct list_head *list)
2015 +{
2016 +       struct ovl_cache_entry *p;
2017 +       struct ovl_cache_entry *n;
2018 +
2019 +       list_for_each_entry_safe(p, n, list, l_node)
2020 +               kfree(p);
2021 +
2022 +       INIT_LIST_HEAD(list);
2023 +}
2024 +
2025 +static int ovl_fill_upper(void *buf, const char *name, int namelen,
2026 +                         loff_t offset, u64 ino, unsigned int d_type)
2027 +{
2028 +       struct ovl_readdir_data *rdd = buf;
2029 +
2030 +       rdd->count++;
2031 +       return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
2032 +}
2033 +
2034 +static inline int ovl_dir_read(struct path *realpath,
2035 +                              struct ovl_readdir_data *rdd, filldir_t filler)
2036 +{
2037 +       struct file *realfile;
2038 +       int err;
2039 +
2040 +       realfile = ovl_path_open(realpath, O_RDONLY | O_DIRECTORY);
2041 +       if (IS_ERR(realfile))
2042 +               return PTR_ERR(realfile);
2043 +
2044 +       do {
2045 +               rdd->count = 0;
2046 +               rdd->err = 0;
2047 +               err = vfs_readdir(realfile, filler, rdd);
2048 +               if (err >= 0)
2049 +                       err = rdd->err;
2050 +       } while (!err && rdd->count);
2051 +       fput(realfile);
2052 +
2053 +       return 0;
2054 +}
2055 +
2056 +static void ovl_dir_reset(struct file *file)
2057 +{
2058 +       struct ovl_dir_file *od = file->private_data;
2059 +       enum ovl_path_type type = ovl_path_type(file->f_path.dentry);
2060 +
2061 +       if (ovl_dentry_version_get(file->f_path.dentry) != od->cache_version) {
2062 +               list_del_init(&od->cursor);
2063 +               ovl_cache_free(&od->cache);
2064 +               od->is_cached = false;
2065 +       }
2066 +       WARN_ON(!od->is_real && type != OVL_PATH_MERGE);
2067 +       if (od->is_real && type == OVL_PATH_MERGE) {
2068 +               fput(od->realfile);
2069 +               od->realfile = NULL;
2070 +               od->is_real = false;
2071 +       }
2072 +}
2073 +
2074 +static int ovl_dir_mark_whiteouts(struct ovl_readdir_data *rdd)
2075 +{
2076 +       struct ovl_cache_entry *p;
2077 +       struct dentry *dentry;
2078 +       const struct cred *old_cred;
2079 +       struct cred *override_cred;
2080 +
2081 +       override_cred = prepare_creds();
2082 +       if (!override_cred) {
2083 +               ovl_cache_free(rdd->list);
2084 +               return -ENOMEM;
2085 +       }
2086 +
2087 +       /*
2088 +        * CAP_SYS_ADMIN for getxattr
2089 +        * CAP_DAC_OVERRIDE for lookup
2090 +        */
2091 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
2092 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
2093 +       old_cred = override_creds(override_cred);
2094 +
2095 +       mutex_lock(&rdd->dir->d_inode->i_mutex);
2096 +       list_for_each_entry(p, rdd->list, l_node) {
2097 +               if (p->type != DT_LNK)
2098 +                       continue;
2099 +
2100 +               dentry = lookup_one_len(p->name, rdd->dir, p->len);
2101 +               if (IS_ERR(dentry))
2102 +                       continue;
2103 +
2104 +               p->is_whiteout = ovl_is_whiteout(dentry);
2105 +               dput(dentry);
2106 +       }
2107 +       mutex_unlock(&rdd->dir->d_inode->i_mutex);
2108 +
2109 +       revert_creds(old_cred);
2110 +       put_cred(override_cred);
2111 +
2112 +       return 0;
2113 +}
2114 +
2115 +static inline int ovl_dir_read_merged(struct path *upperpath,
2116 +                                     struct path *lowerpath,
2117 +                                     struct ovl_readdir_data *rdd)
2118 +{
2119 +       int err;
2120 +       struct rb_root root = RB_ROOT;
2121 +       struct list_head middle;
2122 +
2123 +       rdd->root = &root;
2124 +       if (upperpath->dentry) {
2125 +               rdd->dir = upperpath->dentry;
2126 +               err = ovl_dir_read(upperpath, rdd, ovl_fill_upper);
2127 +               if (err)
2128 +                       goto out;
2129 +
2130 +               err = ovl_dir_mark_whiteouts(rdd);
2131 +               if (err)
2132 +                       goto out;
2133 +       }
2134 +       /*
2135 +        * Insert lowerpath entries before upperpath ones, this allows
2136 +        * offsets to be reasonably constant
2137 +        */
2138 +       list_add(&middle, rdd->list);
2139 +       rdd->middle = &middle;
2140 +       err = ovl_dir_read(lowerpath, rdd, ovl_fill_lower);
2141 +       list_del(&middle);
2142 +out:
2143 +       rdd->root = NULL;
2144 +
2145 +       return err;
2146 +}
2147 +
2148 +static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
2149 +{
2150 +       struct list_head *l;
2151 +       loff_t off;
2152 +
2153 +       l = od->cache.next;
2154 +       for (off = 0; off < pos; off++) {
2155 +               if (l == &od->cache)
2156 +                       break;
2157 +               l = l->next;
2158 +       }
2159 +       list_move_tail(&od->cursor, l);
2160 +}
2161 +
2162 +static int ovl_readdir(struct file *file, void *buf, filldir_t filler)
2163 +{
2164 +       struct ovl_dir_file *od = file->private_data;
2165 +       int res;
2166 +
2167 +       if (!file->f_pos)
2168 +               ovl_dir_reset(file);
2169 +
2170 +       if (od->is_real) {
2171 +               res = vfs_readdir(od->realfile, filler, buf);
2172 +               file->f_pos = od->realfile->f_pos;
2173 +
2174 +               return res;
2175 +       }
2176 +
2177 +       if (!od->is_cached) {
2178 +               struct path lowerpath;
2179 +               struct path upperpath;
2180 +               struct ovl_readdir_data rdd = { .list = &od->cache };
2181 +
2182 +               ovl_path_lower(file->f_path.dentry, &lowerpath);
2183 +               ovl_path_upper(file->f_path.dentry, &upperpath);
2184 +
2185 +               res = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
2186 +               if (res) {
2187 +                       ovl_cache_free(rdd.list);
2188 +                       return res;
2189 +               }
2190 +
2191 +               od->cache_version = ovl_dentry_version_get(file->f_path.dentry);
2192 +               od->is_cached = true;
2193 +
2194 +               ovl_seek_cursor(od, file->f_pos);
2195 +       }
2196 +
2197 +       while (od->cursor.next != &od->cache) {
2198 +               int over;
2199 +               loff_t off;
2200 +               struct ovl_cache_entry *p;
2201 +
2202 +               p = list_entry(od->cursor.next, struct ovl_cache_entry, l_node);
2203 +               off = file->f_pos;
2204 +               if (!p->is_whiteout) {
2205 +                       over = filler(buf, p->name, p->len, off, p->ino,
2206 +                                     p->type);
2207 +                       if (over)
2208 +                               break;
2209 +               }
2210 +               file->f_pos++;
2211 +               list_move(&od->cursor, &p->l_node);
2212 +       }
2213 +
2214 +       return 0;
2215 +}
2216 +
2217 +static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
2218 +{
2219 +       loff_t res;
2220 +       struct ovl_dir_file *od = file->private_data;
2221 +
2222 +       mutex_lock(&file->f_dentry->d_inode->i_mutex);
2223 +       if (!file->f_pos)
2224 +               ovl_dir_reset(file);
2225 +
2226 +       if (od->is_real) {
2227 +               res = vfs_llseek(od->realfile, offset, origin);
2228 +               file->f_pos = od->realfile->f_pos;
2229 +       } else {
2230 +               res = -EINVAL;
2231 +
2232 +               switch (origin) {
2233 +               case SEEK_CUR:
2234 +                       offset += file->f_pos;
2235 +                       break;
2236 +               case SEEK_SET:
2237 +                       break;
2238 +               default:
2239 +                       goto out_unlock;
2240 +               }
2241 +               if (offset < 0)
2242 +                       goto out_unlock;
2243 +
2244 +               if (offset != file->f_pos) {
2245 +                       file->f_pos = offset;
2246 +                       if (od->is_cached)
2247 +                               ovl_seek_cursor(od, offset);
2248 +               }
2249 +               res = offset;
2250 +       }
2251 +out_unlock:
2252 +       mutex_unlock(&file->f_dentry->d_inode->i_mutex);
2253 +
2254 +       return res;
2255 +}
2256 +
2257 +static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
2258 +                        int datasync)
2259 +{
2260 +       struct ovl_dir_file *od = file->private_data;
2261 +
2262 +       /* May need to reopen directory if it got copied up */
2263 +       if (!od->realfile) {
2264 +               struct path upperpath;
2265 +
2266 +               ovl_path_upper(file->f_path.dentry, &upperpath);
2267 +               od->realfile = ovl_path_open(&upperpath, O_RDONLY);
2268 +               if (IS_ERR(od->realfile))
2269 +                       return PTR_ERR(od->realfile);
2270 +       }
2271 +
2272 +       return vfs_fsync_range(od->realfile, start, end, datasync);
2273 +}
2274 +
2275 +static int ovl_dir_release(struct inode *inode, struct file *file)
2276 +{
2277 +       struct ovl_dir_file *od = file->private_data;
2278 +
2279 +       list_del(&od->cursor);
2280 +       ovl_cache_free(&od->cache);
2281 +       if (od->realfile)
2282 +               fput(od->realfile);
2283 +       kfree(od);
2284 +
2285 +       return 0;
2286 +}
2287 +
2288 +static int ovl_dir_open(struct inode *inode, struct file *file)
2289 +{
2290 +       struct path realpath;
2291 +       struct file *realfile;
2292 +       struct ovl_dir_file *od;
2293 +       enum ovl_path_type type;
2294 +
2295 +       od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
2296 +       if (!od)
2297 +               return -ENOMEM;
2298 +
2299 +       type = ovl_path_real(file->f_path.dentry, &realpath);
2300 +       realfile = ovl_path_open(&realpath, file->f_flags);
2301 +       if (IS_ERR(realfile)) {
2302 +               kfree(od);
2303 +               return PTR_ERR(realfile);
2304 +       }
2305 +       INIT_LIST_HEAD(&od->cache);
2306 +       INIT_LIST_HEAD(&od->cursor);
2307 +       od->is_cached = false;
2308 +       od->realfile = realfile;
2309 +       od->is_real = (type != OVL_PATH_MERGE);
2310 +       file->private_data = od;
2311 +
2312 +       return 0;
2313 +}
2314 +
2315 +const struct file_operations ovl_dir_operations = {
2316 +       .read           = generic_read_dir,
2317 +       .open           = ovl_dir_open,
2318 +       .readdir        = ovl_readdir,
2319 +       .llseek         = ovl_dir_llseek,
2320 +       .fsync          = ovl_dir_fsync,
2321 +       .release        = ovl_dir_release,
2322 +};
2323 +
2324 +static int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
2325 +{
2326 +       int err;
2327 +       struct path lowerpath;
2328 +       struct path upperpath;
2329 +       struct ovl_cache_entry *p;
2330 +       struct ovl_readdir_data rdd = { .list = list };
2331 +
2332 +       ovl_path_upper(dentry, &upperpath);
2333 +       ovl_path_lower(dentry, &lowerpath);
2334 +
2335 +       err = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
2336 +       if (err)
2337 +               return err;
2338 +
2339 +       err = 0;
2340 +
2341 +       list_for_each_entry(p, list, l_node) {
2342 +               if (p->is_whiteout)
2343 +                       continue;
2344 +
2345 +               if (p->name[0] == '.') {
2346 +                       if (p->len == 1)
2347 +                               continue;
2348 +                       if (p->len == 2 && p->name[1] == '.')
2349 +                               continue;
2350 +               }
2351 +               err = -ENOTEMPTY;
2352 +               break;
2353 +       }
2354 +
2355 +       return err;
2356 +}
2357 +
2358 +static int ovl_remove_whiteouts(struct dentry *dir, struct list_head *list)
2359 +{
2360 +       struct path upperpath;
2361 +       struct dentry *upperdir;
2362 +       struct ovl_cache_entry *p;
2363 +       const struct cred *old_cred;
2364 +       struct cred *override_cred;
2365 +       int err;
2366 +
2367 +       ovl_path_upper(dir, &upperpath);
2368 +       upperdir = upperpath.dentry;
2369 +
2370 +       override_cred = prepare_creds();
2371 +       if (!override_cred)
2372 +               return -ENOMEM;
2373 +
2374 +       /*
2375 +        * CAP_DAC_OVERRIDE for lookup and unlink
2376 +        * CAP_SYS_ADMIN for setxattr of "trusted" namespace
2377 +        * CAP_FOWNER for unlink in sticky directory
2378 +        */
2379 +       cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
2380 +       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
2381 +       cap_raise(override_cred->cap_effective, CAP_FOWNER);
2382 +       old_cred = override_creds(override_cred);
2383 +
2384 +       err = vfs_setxattr(upperdir, ovl_opaque_xattr, "y", 1, 0);
2385 +       if (err)
2386 +               goto out_revert_creds;
2387 +
2388 +       mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
2389 +       list_for_each_entry(p, list, l_node) {
2390 +               struct dentry *dentry;
2391 +               int ret;
2392 +
2393 +               if (!p->is_whiteout)
2394 +                       continue;
2395 +
2396 +               dentry = lookup_one_len(p->name, upperdir, p->len);
2397 +               if (IS_ERR(dentry)) {
2398 +                       printk(KERN_WARNING
2399 +                           "overlayfs: failed to lookup whiteout %.*s: %li\n",
2400 +                           p->len, p->name, PTR_ERR(dentry));
2401 +                       continue;
2402 +               }
2403 +               ret = vfs_unlink(upperdir->d_inode, dentry);
2404 +               dput(dentry);
2405 +               if (ret)
2406 +                       printk(KERN_WARNING
2407 +                           "overlayfs: failed to unlink whiteout %.*s: %i\n",
2408 +                           p->len, p->name, ret);
2409 +       }
2410 +       mutex_unlock(&upperdir->d_inode->i_mutex);
2411 +
2412 +out_revert_creds:
2413 +       revert_creds(old_cred);
2414 +       put_cred(override_cred);
2415 +
2416 +       return err;
2417 +}
2418 +
2419 +int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type)
2420 +{
2421 +       int err;
2422 +       LIST_HEAD(list);
2423 +
2424 +       err = ovl_check_empty_dir(dentry, &list);
2425 +       if (!err && type == OVL_PATH_MERGE)
2426 +               err = ovl_remove_whiteouts(dentry, &list);
2427 +
2428 +       ovl_cache_free(&list);
2429 +
2430 +       return err;
2431 +}
2432 diff -Nur -x .git vfs-4cbe5a5/fs/overlayfs/super.c vfs-3d5a648/fs/overlayfs/super.c
2433 --- vfs-4cbe5a5/fs/overlayfs/super.c    1970-01-01 01:00:00.000000000 +0100
2434 +++ vfs-3d5a648/fs/overlayfs/super.c    2012-09-05 16:35:20.000000000 +0200
2435 @@ -0,0 +1,685 @@
2436 +/*
2437 + *
2438 + * Copyright (C) 2011 Novell Inc.
2439 + *
2440 + * This program is free software; you can redistribute it and/or modify it
2441 + * under the terms of the GNU General Public License version 2 as published by
2442 + * the Free Software Foundation.
2443 + */
2444 +
2445 +#include <linux/fs.h>
2446 +#include <linux/namei.h>
2447 +#include <linux/xattr.h>
2448 +#include <linux/security.h>
2449 +#include <linux/mount.h>
2450 +#include <linux/slab.h>
2451 +#include <linux/parser.h>
2452 +#include <linux/module.h>
2453 +#include <linux/cred.h>
2454 +#include <linux/sched.h>
2455 +#include <linux/statfs.h>
2456 +#include <linux/seq_file.h>
2457 +#include "overlayfs.h"
2458 +
2459 +MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
2460 +MODULE_DESCRIPTION("Overlay filesystem");
2461 +MODULE_LICENSE("GPL");
2462 +
2463 +#define OVERLAYFS_SUPER_MAGIC 0x794c764f
2464 +
2465 +struct ovl_config {
2466 +       char *lowerdir;
2467 +       char *upperdir;
2468 +};
2469 +
2470 +/* private information held for overlayfs's superblock */
2471 +struct ovl_fs {
2472 +       struct vfsmount *upper_mnt;
2473 +       struct vfsmount *lower_mnt;
2474 +       long lower_namelen;
2475 +       /* pathnames of lower and upper dirs, for show_options */
2476 +       struct ovl_config config;
2477 +};
2478 +
2479 +/* private information held for every overlayfs dentry */
2480 +struct ovl_entry {
2481 +       /*
2482 +        * Keep "double reference" on upper dentries, so that
2483 +        * d_delete() doesn't think it's OK to reset d_inode to NULL.
2484 +        */
2485 +       struct dentry *__upperdentry;
2486 +       struct dentry *lowerdentry;
2487 +       union {
2488 +               struct {
2489 +                       u64 version;
2490 +                       bool opaque;
2491 +               };
2492 +               struct rcu_head rcu;
2493 +       };
2494 +};
2495 +
2496 +const char *ovl_whiteout_xattr = "trusted.overlay.whiteout";
2497 +const char *ovl_opaque_xattr = "trusted.overlay.opaque";
2498 +
2499 +
2500 +enum ovl_path_type ovl_path_type(struct dentry *dentry)
2501 +{
2502 +       struct ovl_entry *oe = dentry->d_fsdata;
2503 +
2504 +       if (oe->__upperdentry) {
2505 +               if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode))
2506 +                       return OVL_PATH_MERGE;
2507 +               else
2508 +                       return OVL_PATH_UPPER;
2509 +       } else {
2510 +               return OVL_PATH_LOWER;
2511 +       }
2512 +}
2513 +
2514 +static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
2515 +{
2516 +       struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
2517 +       smp_read_barrier_depends();
2518 +       return upperdentry;
2519 +}
2520 +
2521 +void ovl_path_upper(struct dentry *dentry, struct path *path)
2522 +{
2523 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
2524 +       struct ovl_entry *oe = dentry->d_fsdata;
2525 +
2526 +       path->mnt = ofs->upper_mnt;
2527 +       path->dentry = ovl_upperdentry_dereference(oe);
2528 +}
2529 +
2530 +void ovl_path_lower(struct dentry *dentry, struct path *path)
2531 +{
2532 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
2533 +       struct ovl_entry *oe = dentry->d_fsdata;
2534 +
2535 +       path->mnt = ofs->lower_mnt;
2536 +       path->dentry = oe->lowerdentry;
2537 +}
2538 +
2539 +enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
2540 +{
2541 +
2542 +       enum ovl_path_type type = ovl_path_type(dentry);
2543 +
2544 +       if (type == OVL_PATH_LOWER)
2545 +               ovl_path_lower(dentry, path);
2546 +       else
2547 +               ovl_path_upper(dentry, path);
2548 +
2549 +       return type;
2550 +}
2551 +
2552 +struct dentry *ovl_dentry_upper(struct dentry *dentry)
2553 +{
2554 +       struct ovl_entry *oe = dentry->d_fsdata;
2555 +
2556 +       return ovl_upperdentry_dereference(oe);
2557 +}
2558 +
2559 +struct dentry *ovl_dentry_lower(struct dentry *dentry)
2560 +{
2561 +       struct ovl_entry *oe = dentry->d_fsdata;
2562 +
2563 +       return oe->lowerdentry;
2564 +}
2565 +
2566 +struct dentry *ovl_dentry_real(struct dentry *dentry)
2567 +{
2568 +       struct ovl_entry *oe = dentry->d_fsdata;
2569 +       struct dentry *realdentry;
2570 +
2571 +       realdentry = ovl_upperdentry_dereference(oe);
2572 +       if (!realdentry)
2573 +               realdentry = oe->lowerdentry;
2574 +
2575 +       return realdentry;
2576 +}
2577 +
2578 +struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
2579 +{
2580 +       struct dentry *realdentry;
2581 +
2582 +       realdentry = ovl_upperdentry_dereference(oe);
2583 +       if (realdentry) {
2584 +               *is_upper = true;
2585 +       } else {
2586 +               realdentry = oe->lowerdentry;
2587 +               *is_upper = false;
2588 +       }
2589 +       return realdentry;
2590 +}
2591 +
2592 +bool ovl_dentry_is_opaque(struct dentry *dentry)
2593 +{
2594 +       struct ovl_entry *oe = dentry->d_fsdata;
2595 +       return oe->opaque;
2596 +}
2597 +
2598 +void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
2599 +{
2600 +       struct ovl_entry *oe = dentry->d_fsdata;
2601 +       oe->opaque = opaque;
2602 +}
2603 +
2604 +void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
2605 +{
2606 +       struct ovl_entry *oe = dentry->d_fsdata;
2607 +
2608 +       WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
2609 +       WARN_ON(oe->__upperdentry);
2610 +       BUG_ON(!upperdentry->d_inode);
2611 +       smp_wmb();
2612 +       oe->__upperdentry = dget(upperdentry);
2613 +}
2614 +
2615 +void ovl_dentry_version_inc(struct dentry *dentry)
2616 +{
2617 +       struct ovl_entry *oe = dentry->d_fsdata;
2618 +
2619 +       WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
2620 +       oe->version++;
2621 +}
2622 +
2623 +u64 ovl_dentry_version_get(struct dentry *dentry)
2624 +{
2625 +       struct ovl_entry *oe = dentry->d_fsdata;
2626 +
2627 +       WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
2628 +       return oe->version;
2629 +}
2630 +
2631 +bool ovl_is_whiteout(struct dentry *dentry)
2632 +{
2633 +       int res;
2634 +       char val;
2635 +
2636 +       if (!dentry)
2637 +               return false;
2638 +       if (!dentry->d_inode)
2639 +               return false;
2640 +       if (!S_ISLNK(dentry->d_inode->i_mode))
2641 +               return false;
2642 +
2643 +       res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1);
2644 +       if (res == 1 && val == 'y')
2645 +               return true;
2646 +
2647 +       return false;
2648 +}
2649 +
2650 +static bool ovl_is_opaquedir(struct dentry *dentry)
2651 +{
2652 +       int res;
2653 +       char val;
2654 +
2655 +       if (!S_ISDIR(dentry->d_inode->i_mode))
2656 +               return false;
2657 +
2658 +       res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1);
2659 +       if (res == 1 && val == 'y')
2660 +               return true;
2661 +
2662 +       return false;
2663 +}
2664 +
2665 +static void ovl_entry_free(struct rcu_head *head)
2666 +{
2667 +       struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu);
2668 +       kfree(oe);
2669 +}
2670 +
2671 +static void ovl_dentry_release(struct dentry *dentry)
2672 +{
2673 +       struct ovl_entry *oe = dentry->d_fsdata;
2674 +
2675 +       if (oe) {
2676 +               dput(oe->__upperdentry);
2677 +               dput(oe->__upperdentry);
2678 +               dput(oe->lowerdentry);
2679 +               call_rcu(&oe->rcu, ovl_entry_free);
2680 +       }
2681 +}
2682 +
2683 +const struct dentry_operations ovl_dentry_operations = {
2684 +       .d_release = ovl_dentry_release,
2685 +};
2686 +
2687 +static struct ovl_entry *ovl_alloc_entry(void)
2688 +{
2689 +       return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
2690 +}
2691 +
2692 +static inline struct dentry *ovl_lookup_real(struct dentry *dir,
2693 +                                            struct qstr *name)
2694 +{
2695 +       struct dentry *dentry;
2696 +
2697 +       mutex_lock(&dir->d_inode->i_mutex);
2698 +       dentry = lookup_one_len(name->name, dir, name->len);
2699 +       mutex_unlock(&dir->d_inode->i_mutex);
2700 +
2701 +       if (IS_ERR(dentry)) {
2702 +               if (PTR_ERR(dentry) == -ENOENT)
2703 +                       dentry = NULL;
2704 +       } else if (!dentry->d_inode) {
2705 +               dput(dentry);
2706 +               dentry = NULL;
2707 +       }
2708 +       return dentry;
2709 +}
2710 +
2711 +static int ovl_do_lookup(struct dentry *dentry)
2712 +{
2713 +       struct ovl_entry *oe;
2714 +       struct dentry *upperdir;
2715 +       struct dentry *lowerdir;
2716 +       struct dentry *upperdentry = NULL;
2717 +       struct dentry *lowerdentry = NULL;
2718 +       struct inode *inode = NULL;
2719 +       int err;
2720 +
2721 +       err = -ENOMEM;
2722 +       oe = ovl_alloc_entry();
2723 +       if (!oe)
2724 +               goto out;
2725 +
2726 +       upperdir = ovl_dentry_upper(dentry->d_parent);
2727 +       lowerdir = ovl_dentry_lower(dentry->d_parent);
2728 +
2729 +       if (upperdir) {
2730 +               upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
2731 +               err = PTR_ERR(upperdentry);
2732 +               if (IS_ERR(upperdentry))
2733 +                       goto out_put_dir;
2734 +
2735 +               if (lowerdir && upperdentry &&
2736 +                   (S_ISLNK(upperdentry->d_inode->i_mode) ||
2737 +                    S_ISDIR(upperdentry->d_inode->i_mode))) {
2738 +                       const struct cred *old_cred;
2739 +                       struct cred *override_cred;
2740 +
2741 +                       err = -ENOMEM;
2742 +                       override_cred = prepare_creds();
2743 +                       if (!override_cred)
2744 +                               goto out_dput_upper;
2745 +
2746 +                       /* CAP_SYS_ADMIN needed for getxattr */
2747 +                       cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
2748 +                       old_cred = override_creds(override_cred);
2749 +
2750 +                       if (ovl_is_opaquedir(upperdentry)) {
2751 +                               oe->opaque = true;
2752 +                       } else if (ovl_is_whiteout(upperdentry)) {
2753 +                               dput(upperdentry);
2754 +                               upperdentry = NULL;
2755 +                               oe->opaque = true;
2756 +                       }
2757 +                       revert_creds(old_cred);
2758 +                       put_cred(override_cred);
2759 +               }
2760 +       }
2761 +       if (lowerdir && !oe->opaque) {
2762 +               lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
2763 +               err = PTR_ERR(lowerdentry);
2764 +               if (IS_ERR(lowerdentry))
2765 +                       goto out_dput_upper;
2766 +       }
2767 +
2768 +       if (lowerdentry && upperdentry &&
2769 +           (!S_ISDIR(upperdentry->d_inode->i_mode) ||
2770 +            !S_ISDIR(lowerdentry->d_inode->i_mode))) {
2771 +               dput(lowerdentry);
2772 +               lowerdentry = NULL;
2773 +               oe->opaque = true;
2774 +       }
2775 +
2776 +       if (lowerdentry || upperdentry) {
2777 +               struct dentry *realdentry;
2778 +
2779 +               realdentry = upperdentry ? upperdentry : lowerdentry;
2780 +               err = -ENOMEM;
2781 +               inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
2782 +                                     oe);
2783 +               if (!inode)
2784 +                       goto out_dput;
2785 +               ovl_copyattr(realdentry->d_inode, inode);
2786 +       }
2787 +
2788 +       if (upperdentry)
2789 +               oe->__upperdentry = dget(upperdentry);
2790 +
2791 +       if (lowerdentry)
2792 +               oe->lowerdentry = lowerdentry;
2793 +
2794 +       dentry->d_fsdata = oe;
2795 +       dentry->d_op = &ovl_dentry_operations;
2796 +       d_add(dentry, inode);
2797 +
2798 +       return 0;
2799 +
2800 +out_dput:
2801 +       dput(lowerdentry);
2802 +out_dput_upper:
2803 +       dput(upperdentry);
2804 +out_put_dir:
2805 +       kfree(oe);
2806 +out:
2807 +       return err;
2808 +}
2809 +
2810 +struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
2811 +                         unsigned int flags)
2812 +{
2813 +       int err = ovl_do_lookup(dentry);
2814 +
2815 +       if (err)
2816 +               return ERR_PTR(err);
2817 +
2818 +       return NULL;
2819 +}
2820 +
2821 +struct file *ovl_path_open(struct path *path, int flags)
2822 +{
2823 +       path_get(path);
2824 +       return dentry_open(path, flags, current_cred());
2825 +}
2826 +
2827 +static void ovl_put_super(struct super_block *sb)
2828 +{
2829 +       struct ovl_fs *ufs = sb->s_fs_info;
2830 +
2831 +       if (!(sb->s_flags & MS_RDONLY))
2832 +               mnt_drop_write(ufs->upper_mnt);
2833 +
2834 +       mntput(ufs->upper_mnt);
2835 +       mntput(ufs->lower_mnt);
2836 +
2837 +       kfree(ufs->config.lowerdir);
2838 +       kfree(ufs->config.upperdir);
2839 +       kfree(ufs);
2840 +}
2841 +
2842 +static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
2843 +{
2844 +       int flags = *flagsp;
2845 +       struct ovl_fs *ufs = sb->s_fs_info;
2846 +
2847 +       /* When remounting rw or ro, we need to adjust the write access to the
2848 +        * upper fs.
2849 +        */
2850 +       if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
2851 +               /* No change to readonly status */
2852 +               return 0;
2853 +
2854 +       if (flags & MS_RDONLY) {
2855 +               mnt_drop_write(ufs->upper_mnt);
2856 +               return 0;
2857 +       } else
2858 +               return mnt_want_write(ufs->upper_mnt);
2859 +}
2860 +
2861 +/**
2862 + * ovl_statfs
2863 + * @sb: The overlayfs super block
2864 + * @buf: The struct kstatfs to fill in with stats
2865 + *
2866 + * Get the filesystem statistics.  As writes always target the upper layer
2867 + * filesystem pass the statfs to the same filesystem.
2868 + */
2869 +static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
2870 +{
2871 +       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
2872 +       struct dentry *root_dentry = dentry->d_sb->s_root;
2873 +       struct path path;
2874 +       int err;
2875 +
2876 +       ovl_path_upper(root_dentry, &path);
2877 +
2878 +       err = vfs_statfs(&path, buf);
2879 +       if (!err) {
2880 +               buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
2881 +               buf->f_type = OVERLAYFS_SUPER_MAGIC;
2882 +       }
2883 +
2884 +       return err;
2885 +}
2886 +
2887 +/**
2888 + * ovl_show_options
2889 + *
2890 + * Prints the mount options for a given superblock.
2891 + * Returns zero; does not fail.
2892 + */
2893 +static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
2894 +{
2895 +       struct super_block *sb = dentry->d_sb;
2896 +       struct ovl_fs *ufs = sb->s_fs_info;
2897 +
2898 +       seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
2899 +       seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
2900 +       return 0;
2901 +}
2902 +
2903 +static const struct super_operations ovl_super_operations = {
2904 +       .put_super      = ovl_put_super,
2905 +       .remount_fs     = ovl_remount_fs,
2906 +       .statfs         = ovl_statfs,
2907 +       .show_options   = ovl_show_options,
2908 +};
2909 +
2910 +enum {
2911 +       Opt_lowerdir,
2912 +       Opt_upperdir,
2913 +       Opt_err,
2914 +};
2915 +
2916 +static const match_table_t ovl_tokens = {
2917 +       {Opt_lowerdir,                  "lowerdir=%s"},
2918 +       {Opt_upperdir,                  "upperdir=%s"},
2919 +       {Opt_err,                       NULL}
2920 +};
2921 +
2922 +static int ovl_parse_opt(char *opt, struct ovl_config *config)
2923 +{
2924 +       char *p;
2925 +
2926 +       config->upperdir = NULL;
2927 +       config->lowerdir = NULL;
2928 +
2929 +       while ((p = strsep(&opt, ",")) != NULL) {
2930 +               int token;
2931 +               substring_t args[MAX_OPT_ARGS];
2932 +
2933 +               if (!*p)
2934 +                       continue;
2935 +
2936 +               token = match_token(p, ovl_tokens, args);
2937 +               switch (token) {
2938 +               case Opt_upperdir:
2939 +                       kfree(config->upperdir);
2940 +                       config->upperdir = match_strdup(&args[0]);
2941 +                       if (!config->upperdir)
2942 +                               return -ENOMEM;
2943 +                       break;
2944 +
2945 +               case Opt_lowerdir:
2946 +                       kfree(config->lowerdir);
2947 +                       config->lowerdir = match_strdup(&args[0]);
2948 +                       if (!config->lowerdir)
2949 +                               return -ENOMEM;
2950 +                       break;
2951 +
2952 +               default:
2953 +                       return -EINVAL;
2954 +               }
2955 +       }
2956 +       return 0;
2957 +}
2958 +
2959 +static int ovl_fill_super(struct super_block *sb, void *data, int silent)
2960 +{
2961 +       struct path lowerpath;
2962 +       struct path upperpath;
2963 +       struct inode *root_inode;
2964 +       struct dentry *root_dentry;
2965 +       struct ovl_entry *oe;
2966 +       struct ovl_fs *ufs;
2967 +       struct kstatfs statfs;
2968 +       int err;
2969 +
2970 +       err = -ENOMEM;
2971 +       ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
2972 +       if (!ufs)
2973 +               goto out;
2974 +
2975 +       err = ovl_parse_opt((char *) data, &ufs->config);
2976 +       if (err)
2977 +               goto out_free_ufs;
2978 +
2979 +       err = -EINVAL;
2980 +       if (!ufs->config.upperdir || !ufs->config.lowerdir) {
2981 +               printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
2982 +               goto out_free_config;
2983 +       }
2984 +
2985 +       oe = ovl_alloc_entry();
2986 +       if (oe == NULL)
2987 +               goto out_free_config;
2988 +
2989 +       err = kern_path(ufs->config.upperdir, LOOKUP_FOLLOW, &upperpath);
2990 +       if (err)
2991 +               goto out_free_oe;
2992 +
2993 +       err = kern_path(ufs->config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
2994 +       if (err)
2995 +               goto out_put_upperpath;
2996 +
2997 +       err = -ENOTDIR;
2998 +       if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
2999 +           !S_ISDIR(lowerpath.dentry->d_inode->i_mode))
3000 +               goto out_put_lowerpath;
3001 +
3002 +       err = vfs_statfs(&lowerpath, &statfs);
3003 +       if (err) {
3004 +               printk(KERN_ERR "overlayfs: statfs failed on lowerpath\n");
3005 +               goto out_put_lowerpath;
3006 +       }
3007 +       ufs->lower_namelen = statfs.f_namelen;
3008 +
3009 +       sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth,
3010 +                               lowerpath.mnt->mnt_sb->s_stack_depth) + 1;
3011 +
3012 +       err = -EINVAL;
3013 +       if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
3014 +               printk(KERN_ERR "overlayfs: maximum fs stacking depth exceeded\n");
3015 +               goto out_put_lowerpath;
3016 +       }
3017 +
3018 +
3019 +       ufs->upper_mnt = clone_private_mount(&upperpath);
3020 +       err = PTR_ERR(ufs->upper_mnt);
3021 +       if (IS_ERR(ufs->upper_mnt)) {
3022 +               printk(KERN_ERR "overlayfs: failed to clone upperpath\n");
3023 +               goto out_put_lowerpath;
3024 +       }
3025 +
3026 +       ufs->lower_mnt = clone_private_mount(&lowerpath);
3027 +       err = PTR_ERR(ufs->lower_mnt);
3028 +       if (IS_ERR(ufs->lower_mnt)) {
3029 +               printk(KERN_ERR "overlayfs: failed to clone lowerpath\n");
3030 +               goto out_put_upper_mnt;
3031 +       }
3032 +
3033 +       /*
3034 +        * Make lower_mnt R/O.  That way fchmod/fchown on lower file
3035 +        * will fail instead of modifying lower fs.
3036 +        */
3037 +       ufs->lower_mnt->mnt_flags |= MNT_READONLY;
3038 +
3039 +       /* If the upper fs is r/o, we mark overlayfs r/o too */
3040 +       if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)
3041 +               sb->s_flags |= MS_RDONLY;
3042 +
3043 +       if (!(sb->s_flags & MS_RDONLY)) {
3044 +               err = mnt_want_write(ufs->upper_mnt);
3045 +               if (err)
3046 +                       goto out_put_lower_mnt;
3047 +       }
3048 +
3049 +       err = -ENOMEM;
3050 +       root_inode = ovl_new_inode(sb, S_IFDIR, oe);
3051 +       if (!root_inode)
3052 +               goto out_drop_write;
3053 +
3054 +       root_dentry = d_make_root(root_inode);
3055 +       if (!root_dentry)
3056 +               goto out_drop_write;
3057 +
3058 +       mntput(upperpath.mnt);
3059 +       mntput(lowerpath.mnt);
3060 +
3061 +       oe->__upperdentry = dget(upperpath.dentry);
3062 +       oe->lowerdentry = lowerpath.dentry;
3063 +
3064 +       root_dentry->d_fsdata = oe;
3065 +       root_dentry->d_op = &ovl_dentry_operations;
3066 +
3067 +       sb->s_magic = OVERLAYFS_SUPER_MAGIC;
3068 +       sb->s_op = &ovl_super_operations;
3069 +       sb->s_root = root_dentry;
3070 +       sb->s_fs_info = ufs;
3071 +
3072 +       return 0;
3073 +
3074 +out_drop_write:
3075 +       if (!(sb->s_flags & MS_RDONLY))
3076 +               mnt_drop_write(ufs->upper_mnt);
3077 +out_put_lower_mnt:
3078 +       mntput(ufs->lower_mnt);
3079 +out_put_upper_mnt:
3080 +       mntput(ufs->upper_mnt);
3081 +out_put_lowerpath:
3082 +       path_put(&lowerpath);
3083 +out_put_upperpath:
3084 +       path_put(&upperpath);
3085 +out_free_oe:
3086 +       kfree(oe);
3087 +out_free_config:
3088 +       kfree(ufs->config.lowerdir);
3089 +       kfree(ufs->config.upperdir);
3090 +out_free_ufs:
3091 +       kfree(ufs);
3092 +out:
3093 +       return err;
3094 +}
3095 +
3096 +static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
3097 +                               const char *dev_name, void *raw_data)
3098 +{
3099 +       return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
3100 +}
3101 +
3102 +static struct file_system_type ovl_fs_type = {
3103 +       .owner          = THIS_MODULE,
3104 +       .name           = "overlayfs",
3105 +       .mount          = ovl_mount,
3106 +       .kill_sb        = kill_anon_super,
3107 +};
3108 +
3109 +static int __init ovl_init(void)
3110 +{
3111 +       return register_filesystem(&ovl_fs_type);
3112 +}
3113 +
3114 +static void __exit ovl_exit(void)
3115 +{
3116 +       unregister_filesystem(&ovl_fs_type);
3117 +}
3118 +
3119 +module_init(ovl_init);
3120 +module_exit(ovl_exit);
3121 diff -Nur -x .git vfs-4cbe5a5/fs/splice.c vfs-3d5a648/fs/splice.c
3122 --- vfs-4cbe5a5/fs/splice.c     2012-09-01 19:39:58.000000000 +0200
3123 +++ vfs-3d5a648/fs/splice.c     2012-09-05 16:35:20.000000000 +0200
3124 @@ -1308,6 +1308,7 @@
3125
3126         return ret;
3127  }
3128 +EXPORT_SYMBOL(do_splice_direct);
3129
3130  static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
3131                                struct pipe_inode_info *opipe,
3132 diff -Nur -x .git vfs-4cbe5a5/include/linux/fs.h vfs-3d5a648/include/linux/fs.h
3133 --- vfs-4cbe5a5/include/linux/fs.h      2012-09-01 19:39:58.000000000 +0200
3134 +++ vfs-3d5a648/include/linux/fs.h      2012-09-05 16:35:20.000000000 +0200
3135 @@ -505,6 +505,12 @@
3136   */
3137  #include <linux/quota.h>
3138
3139 +/*
3140 + * Maximum number of layers of fs stack.  Needs to be limited to
3141 + * prevent kernel stack overflow
3142 + */
3143 +#define FILESYSTEM_MAX_STACK_DEPTH 2
3144 +
3145  /**
3146   * enum positive_aop_returns - aop return codes with specific semantics
3147   *
3148 @@ -1578,6 +1584,11 @@
3149
3150         /* Being remounted read-only */
3151         int s_readonly_remount;
3152 +
3153 +       /*
3154 +        * Indicates how deep in a filesystem stack this SB is
3155 +        */
3156 +       int s_stack_depth;
3157  };
3158
3159  /* superblock cache pruning functions */
3160 @@ -1835,6 +1846,7 @@
3161         int (*atomic_open)(struct inode *, struct dentry *,
3162                            struct file *, unsigned open_flag,
3163                            umode_t create_mode, int *opened);
3164 +       int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
3165  } ____cacheline_aligned;
3166
3167  struct seq_file;
3168 @@ -2199,6 +2211,7 @@
3169  extern struct file *filp_open(const char *, int, umode_t);
3170  extern struct file *file_open_root(struct dentry *, struct vfsmount *,
3171                                    const char *, int);
3172 +extern int vfs_open(const struct path *, struct file *, const struct cred *);
3173  extern struct file * dentry_open(const struct path *, int, const struct cred *);
3174  extern int filp_close(struct file *, fl_owner_t id);
3175  extern char * getname(const char __user *);
3176 @@ -2402,6 +2415,7 @@
3177  #endif
3178  extern int notify_change(struct dentry *, struct iattr *);
3179  extern int inode_permission(struct inode *, int);
3180 +extern int __inode_permission(struct inode *, int);
3181  extern int generic_permission(struct inode *, int);
3182
3183  static inline bool execute_ok(struct inode *inode)
3184 diff -Nur -x .git vfs-4cbe5a5/include/linux/mount.h vfs-3d5a648/include/linux/mount.h
3185 --- vfs-4cbe5a5/include/linux/mount.h   2012-09-01 19:39:58.000000000 +0200
3186 +++ vfs-3d5a648/include/linux/mount.h   2012-09-05 16:35:20.000000000 +0200
3187 @@ -66,6 +66,9 @@
3188  extern void mnt_unpin(struct vfsmount *mnt);
3189  extern int __mnt_is_readonly(struct vfsmount *mnt);
3190
3191 +struct path;
3192 +extern struct vfsmount *clone_private_mount(struct path *path);
3193 +
3194  struct file_system_type;
3195  extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
3196                                       int flags, const char *name,
3197 diff -Nur -x .git vfs-4cbe5a5/MAINTAINERS vfs-3d5a648/MAINTAINERS
3198 --- vfs-4cbe5a5/MAINTAINERS     2012-09-01 19:39:58.000000000 +0200
3199 +++ vfs-3d5a648/MAINTAINERS     2012-09-05 16:35:20.000000000 +0200
3200 @@ -5103,6 +5103,13 @@
3201  F:     include/scsi/osd_*
3202  F:     fs/exofs/
3203
3204 +OVERLAYFS FILESYSTEM
3205 +M:     Miklos Szeredi <miklos@szeredi.hu>
3206 +L:     linux-fsdevel@vger.kernel.org
3207 +S:     Supported
3208 +F:     fs/overlayfs/*
3209 +F:     Documentation/filesystems/overlayfs.txt
3210 +
3211  P54 WIRELESS DRIVER
3212  M:     Christian Lamparter <chunkeey@googlemail.com>
3213  L:     linux-wireless@vger.kernel.org