target/linux/generic/patches-2.6.37/209-overlayfs.patch

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