--- /dev/null
+--- a/fs/open.c
++++ b/fs/open.c
+@@ -666,8 +666,7 @@ static inline int __get_file_write_acces
+ return error;
+ }
+
+-static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
+- struct file *f,
++static struct file *__dentry_open(struct path *path, struct file *f,
+ int (*open)(struct inode *, struct file *),
+ const struct cred *cred)
+ {
+@@ -675,15 +674,16 @@ static struct file *__dentry_open(struct
+ struct inode *inode;
+ int error;
+
++ path_get(path);
+ f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
+ FMODE_PREAD | FMODE_PWRITE;
+
+ if (unlikely(f->f_flags & O_PATH))
+ f->f_mode = FMODE_PATH;
+
+- inode = dentry->d_inode;
++ inode = path->dentry->d_inode;
+ if (f->f_mode & FMODE_WRITE) {
+- error = __get_file_write_access(inode, mnt);
++ error = __get_file_write_access(inode, path->mnt);
+ if (error)
+ goto cleanup_file;
+ if (!special_file(inode->i_mode))
+@@ -691,8 +691,7 @@ static struct file *__dentry_open(struct
+ }
+
+ f->f_mapping = inode->i_mapping;
+- f->f_path.dentry = dentry;
+- f->f_path.mnt = mnt;
++ f->f_path = *path;
+ f->f_pos = 0;
+ file_sb_list_add(f, inode->i_sb);
+
+@@ -745,7 +744,7 @@ cleanup_all:
+ * here, so just reset the state.
+ */
+ file_reset_write(f);
+- mnt_drop_write(mnt);
++ mnt_drop_write(path->mnt);
+ }
+ }
+ file_sb_list_del(f);
+@@ -753,8 +752,7 @@ cleanup_all:
+ f->f_path.mnt = NULL;
+ cleanup_file:
+ put_filp(f);
+- dput(dentry);
+- mntput(mnt);
++ path_put(path);
+ return ERR_PTR(error);
+ }
+
+@@ -780,14 +778,14 @@ cleanup_file:
+ struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
+ int (*open)(struct inode *, struct file *))
+ {
++ struct path path = { .dentry = dentry, .mnt = nd->path.mnt };
+ const struct cred *cred = current_cred();
+
+ if (IS_ERR(nd->intent.open.file))
+ goto out;
+ if (IS_ERR(dentry))
+ goto out_err;
+- nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
+- nd->intent.open.file,
++ nd->intent.open.file = __dentry_open(&path, nd->intent.open.file,
+ open, cred);
+ out:
+ return nd->intent.open.file;
+@@ -816,10 +814,17 @@ struct file *nameidata_to_filp(struct na
+
+ /* Has the filesystem initialised the file for us? */
+ if (filp->f_path.dentry == NULL) {
+- path_get(&nd->path);
+- filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
+- NULL, cred);
++ struct inode *inode = nd->path.dentry->d_inode;
++
++ if (inode->i_op->open) {
++ int flags = filp->f_flags;
++ put_filp(filp);
++ filp = inode->i_op->open(nd->path.dentry, flags, cred);
++ } else {
++ filp = __dentry_open(&nd->path, filp, NULL, cred);
++ }
+ }
++
+ return filp;
+ }
+
+@@ -830,26 +835,45 @@ struct file *nameidata_to_filp(struct na
+ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
+ const struct cred *cred)
+ {
+- int error;
+- struct file *f;
+-
+- validate_creds(cred);
++ struct path path = { .dentry = dentry, .mnt = mnt };
++ struct file *ret;
+
+ /* We must always pass in a valid mount pointer. */
+ BUG_ON(!mnt);
+
+- error = -ENFILE;
++ ret = vfs_open(&path, flags, cred);
++ path_put(&path);
++
++ return ret;
++}
++EXPORT_SYMBOL(dentry_open);
++
++/**
++ * vfs_open - open the file at the given path
++ * @path: path to open
++ * @flags: open flags
++ * @cred: credentials to use
++ *
++ * Open the file. If successful, the returned file will have acquired
++ * an additional reference for path.
++ */
++struct file *vfs_open(struct path *path, int flags, const struct cred *cred)
++{
++ struct file *f;
++ struct inode *inode = path->dentry->d_inode;
++
++ validate_creds(cred);
++
++ if (inode->i_op->open)
++ return inode->i_op->open(path->dentry, flags, cred);
+ f = get_empty_filp();
+- if (f == NULL) {
+- dput(dentry);
+- mntput(mnt);
+- return ERR_PTR(error);
+- }
++ if (f == NULL)
++ return ERR_PTR(-ENFILE);
+
+ f->f_flags = flags;
+- return __dentry_open(dentry, mnt, f, NULL, cred);
++ return __dentry_open(path, f, NULL, cred);
+ }
+-EXPORT_SYMBOL(dentry_open);
++EXPORT_SYMBOL(vfs_open);
+
+ static void __put_unused_fd(struct files_struct *files, unsigned int fd)
+ {
+--- a/include/linux/fs.h
++++ b/include/linux/fs.h
+@@ -1602,6 +1602,7 @@ struct inode_operations {
+ void (*truncate_range)(struct inode *, loff_t, loff_t);
+ int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
+ u64 len);
++ struct file *(*open)(struct dentry *, int flags, const struct cred *);
+ } ____cacheline_aligned;
+
+ struct seq_file;
+@@ -1996,6 +1997,7 @@ extern long do_sys_open(int dfd, const c
+ extern struct file *filp_open(const char *, int, int);
+ extern struct file *file_open_root(struct dentry *, struct vfsmount *,
+ const char *, int);
++extern struct file *vfs_open(struct path *, int flags, const struct cred *);
+ extern struct file * dentry_open(struct dentry *, struct vfsmount *, int,
+ const struct cred *);
+ extern int filp_close(struct file *, fl_owner_t id);
+--- a/fs/splice.c
++++ b/fs/splice.c
+@@ -1300,6 +1300,7 @@ long do_splice_direct(struct file *in, l
+
+ return ret;
+ }
++EXPORT_SYMBOL(do_splice_direct);
+
+ static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
+ struct pipe_inode_info *opipe,
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1494,6 +1494,23 @@ void drop_collected_mounts(struct vfsmou
+ release_mounts(&umount_list);
+ }
+
++struct vfsmount *clone_private_mount(struct path *path)
++{
++ struct vfsmount *mnt;
++
++ if (IS_MNT_UNBINDABLE(path->mnt))
++ return ERR_PTR(-EINVAL);
++
++ down_read(&namespace_sem);
++ mnt = clone_mnt(path->mnt, path->dentry, CL_PRIVATE);
++ up_read(&namespace_sem);
++ if (!mnt)
++ return ERR_PTR(-ENOMEM);
++
++ return mnt;
++}
++EXPORT_SYMBOL_GPL(clone_private_mount);
++
+ int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
+ struct vfsmount *root)
+ {
+--- a/include/linux/mount.h
++++ b/include/linux/mount.h
+@@ -100,6 +100,9 @@ extern void mnt_pin(struct vfsmount *mnt
+ extern void mnt_unpin(struct vfsmount *mnt);
+ extern int __mnt_is_readonly(struct vfsmount *mnt);
+
++struct path;
++extern struct vfsmount *clone_private_mount(struct path *path);
++
+ extern struct vfsmount *do_kern_mount(const char *fstype, int flags,
+ const char *name, void *data);
+
+--- a/fs/Kconfig
++++ b/fs/Kconfig
+@@ -63,6 +63,7 @@ source "fs/quota/Kconfig"
+
+ source "fs/autofs4/Kconfig"
+ source "fs/fuse/Kconfig"
++source "fs/overlayfs/Kconfig"
+
+ config CUSE
+ tristate "Character device in Userspace support"
+--- a/fs/Makefile
++++ b/fs/Makefile
+@@ -105,6 +105,7 @@ obj-$(CONFIG_QNX4FS_FS) += qnx4/
+ obj-$(CONFIG_AUTOFS4_FS) += autofs4/
+ obj-$(CONFIG_ADFS_FS) += adfs/
+ obj-$(CONFIG_FUSE_FS) += fuse/
++obj-$(CONFIG_OVERLAYFS_FS) += overlayfs/
+ obj-$(CONFIG_UDF_FS) += udf/
+ obj-$(CONFIG_SUN_OPENPROMFS) += openpromfs/
+ obj-$(CONFIG_OMFS_FS) += omfs/
+--- /dev/null
++++ b/fs/overlayfs/Kconfig
+@@ -0,0 +1,4 @@
++config OVERLAYFS_FS
++ tristate "Overlay filesystem support"
++ help
++ Add support for overlay filesystem.
+--- /dev/null
++++ b/fs/overlayfs/Makefile
+@@ -0,0 +1,7 @@
++#
++# Makefile for the overlay filesystem.
++#
++
++obj-$(CONFIG_OVERLAYFS_FS) += overlayfs.o
++
++overlayfs-objs := super.o inode.o dir.o readdir.o copy_up.o
+--- /dev/null
++++ b/fs/overlayfs/copy_up.c
+@@ -0,0 +1,383 @@
++/*
++ *
++ * Copyright (C) 2011 Novell Inc.
++ *
++ * This program is free software; you can redistribute it and/or modify it
++ * under the terms of the GNU General Public License version 2 as published by
++ * the Free Software Foundation.
++ */
++
++#include <linux/fs.h>
++#include <linux/slab.h>
++#include <linux/file.h>
++#include <linux/splice.h>
++#include <linux/xattr.h>
++#include <linux/security.h>
++#include <linux/uaccess.h>
++#include "overlayfs.h"
++
++#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
++
++static int ovl_copy_up_xattr(struct dentry *old, struct dentry *new)
++{
++ ssize_t list_size, size;
++ char *buf, *name, *value;
++ int error;
++
++ if (!old->d_inode->i_op->getxattr ||
++ !new->d_inode->i_op->getxattr)
++ return 0;
++
++ list_size = vfs_listxattr(old, NULL, 0);
++ if (list_size <= 0) {
++ if (list_size == -EOPNOTSUPP)
++ return 0;
++ return list_size;
++ }
++
++ buf = kzalloc(list_size, GFP_KERNEL);
++ if (!buf)
++ return -ENOMEM;
++
++ error = -ENOMEM;
++ value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL);
++ if (!value)
++ goto out;
++
++ list_size = vfs_listxattr(old, buf, list_size);
++ if (list_size <= 0) {
++ error = list_size;
++ goto out_free_value;
++ }
++
++ for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
++ size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX);
++ if (size <= 0) {
++ error = size;
++ goto out_free_value;
++ }
++ error = vfs_setxattr(new, name, value, size, 0);
++ if (error)
++ goto out_free_value;
++ }
++
++out_free_value:
++ kfree(value);
++out:
++ kfree(buf);
++ return error;
++}
++
++static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
++{
++ struct file *old_file;
++ struct file *new_file;
++ int error = 0;
++
++ if (len == 0)
++ return 0;
++
++ old_file = vfs_open(old, O_RDONLY, current_cred());
++ if (IS_ERR(old_file))
++ return PTR_ERR(old_file);
++
++ new_file = vfs_open(new, O_WRONLY, current_cred());
++ if (IS_ERR(new_file)) {
++ error = PTR_ERR(new_file);
++ goto out_fput;
++ }
++
++ /* FIXME: copy up sparse files efficiently */
++ while (len) {
++ loff_t offset = new_file->f_pos;
++ size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
++ long bytes;
++
++ if (len < this_len)
++ this_len = len;
++
++ if (signal_pending_state(TASK_KILLABLE, current)) {
++ error = -EINTR;
++ break;
++ }
++
++ bytes = do_splice_direct(old_file, &offset, new_file, this_len,
++ SPLICE_F_MOVE);
++ if (bytes <= 0) {
++ error = bytes;
++ break;
++ }
++
++ len -= bytes;
++ }
++
++ fput(new_file);
++out_fput:
++ fput(old_file);
++ return error;
++}
++
++static char *ovl_read_symlink(struct dentry *realdentry)
++{
++ int res;
++ char *buf;
++ struct inode *inode = realdentry->d_inode;
++ mm_segment_t old_fs;
++
++ res = -EINVAL;
++ if (!inode->i_op->readlink)
++ goto err;
++
++ res = -ENOMEM;
++ buf = (char *) __get_free_page(GFP_KERNEL);
++ if (!buf)
++ goto err;
++
++ old_fs = get_fs();
++ set_fs(get_ds());
++ /* The cast to a user pointer is valid due to the set_fs() */
++ res = inode->i_op->readlink(realdentry,
++ (char __user *)buf, PAGE_SIZE - 1);
++ set_fs(old_fs);
++ if (res < 0) {
++ free_page((unsigned long) buf);
++ goto err;
++ }
++ buf[res] = '\0';
++
++ return buf;
++
++err:
++ return ERR_PTR(res);
++}
++
++static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
++{
++ struct iattr attr = {
++ .ia_valid = ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
++ .ia_atime = stat->atime,
++ .ia_mtime = stat->mtime,
++ };
++
++ return notify_change(upperdentry, &attr);
++}
++
++static int ovl_set_mode(struct dentry *upperdentry, umode_t mode)
++{
++ struct iattr attr = {
++ .ia_valid = ATTR_MODE,
++ .ia_mode = mode,
++ };
++
++ return notify_change(upperdentry, &attr);
++}
++
++static int ovl_copy_up_locked(struct dentry *upperdir, struct dentry *dentry,
++ struct path *lowerpath, struct kstat *stat,
++ const char *link)
++{
++ int err;
++ struct path newpath;
++ umode_t mode = stat->mode;
++
++ /* Can't properly set mode on creation because of the umask */
++ stat->mode &= S_IFMT;
++
++ ovl_path_upper(dentry, &newpath);
++ WARN_ON(newpath.dentry);
++ newpath.dentry = ovl_upper_create(upperdir, dentry, stat, link);
++ if (IS_ERR(newpath.dentry))
++ return PTR_ERR(newpath.dentry);
++
++ if (S_ISREG(stat->mode)) {
++ err = ovl_copy_up_data(lowerpath, &newpath, stat->size);
++ if (err)
++ goto err_remove;
++ }
++
++ err = ovl_copy_up_xattr(lowerpath->dentry, newpath.dentry);
++ if (err)
++ goto err_remove;
++
++ mutex_lock(&newpath.dentry->d_inode->i_mutex);
++ if (!S_ISLNK(stat->mode))
++ err = ovl_set_mode(newpath.dentry, mode);
++ if (!err)
++ err = ovl_set_timestamps(newpath.dentry, stat);
++ mutex_unlock(&newpath.dentry->d_inode->i_mutex);
++ if (err)
++ goto err_remove;
++
++ ovl_dentry_update(dentry, newpath.dentry);
++
++ /*
++ * Easiest way to get rid of the lower dentry reference is to
++ * drop this dentry. This is neither needed nor possible for
++ * directories.
++ */
++ if (!S_ISDIR(stat->mode))
++ d_drop(dentry);
++
++ return 0;
++
++err_remove:
++ if (S_ISDIR(stat->mode))
++ vfs_rmdir(upperdir->d_inode, newpath.dentry);
++ else
++ vfs_unlink(upperdir->d_inode, newpath.dentry);
++
++ dput(newpath.dentry);
++
++ return err;
++}
++
++/*
++ * Copy up a single dentry
++ *
++ * Directory renames only allowed on "pure upper" (already created on
++ * upper filesystem, never copied up). Directories which are on lower or
++ * are merged may not be renamed. For these -EXDEV is returned and
++ * userspace has to deal with it. This means, when copying up a
++ * directory we can rely on it and ancestors being stable.
++ *
++ * Non-directory renames start with copy up of source if necessary. The
++ * actual rename will only proceed once the copy up was successful. Copy
++ * up uses upper parent i_mutex for exclusion. Since rename can change
++ * d_parent it is possible that the copy up will lock the old parent. At
++ * that point the file will have already been copied up anyway.
++ */
++static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
++ struct path *lowerpath, struct kstat *stat)
++{
++ int err;
++ struct kstat pstat;
++ struct path parentpath;
++ struct dentry *upperdir;
++ const struct cred *old_cred;
++ struct cred *override_cred;
++ char *link = NULL;
++
++ ovl_path_upper(parent, &parentpath);
++ upperdir = parentpath.dentry;
++
++ err = vfs_getattr(parentpath.mnt, parentpath.dentry, &pstat);
++ if (err)
++ return err;
++
++ if (S_ISLNK(stat->mode)) {
++ link = ovl_read_symlink(lowerpath->dentry);
++ if (IS_ERR(link))
++ return PTR_ERR(link);
++ }
++
++ err = -ENOMEM;
++ override_cred = prepare_creds();
++ if (!override_cred)
++ goto out_free_link;
++
++ override_cred->fsuid = stat->uid;
++ override_cred->fsgid = stat->gid;
++ /*
++ * CAP_SYS_ADMIN for copying up extended attributes
++ * CAP_DAC_OVERRIDE for create
++ * CAP_FOWNER for chmod, timestamp update
++ * CAP_FSETID for chmod
++ * CAP_MKNOD for mknod
++ */
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
++ cap_raise(override_cred->cap_effective, CAP_FOWNER);
++ cap_raise(override_cred->cap_effective, CAP_FSETID);
++ cap_raise(override_cred->cap_effective, CAP_MKNOD);
++ old_cred = override_creds(override_cred);
++
++ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
++ if (ovl_path_type(dentry) != OVL_PATH_LOWER) {
++ err = 0;
++ } else {
++ err = ovl_copy_up_locked(upperdir, dentry, lowerpath,
++ stat, link);
++ if (!err) {
++ /* Restore timestamps on parent (best effort) */
++ ovl_set_timestamps(upperdir, &pstat);
++ }
++ }
++
++ mutex_unlock(&upperdir->d_inode->i_mutex);
++
++ revert_creds(old_cred);
++ put_cred(override_cred);
++
++out_free_link:
++ if (link)
++ free_page((unsigned long) link);
++
++ return err;
++}
++
++int ovl_copy_up(struct dentry *dentry)
++{
++ int err;
++
++ err = 0;
++ while (!err) {
++ struct dentry *next;
++ struct dentry *parent;
++ struct path lowerpath;
++ struct kstat stat;
++ enum ovl_path_type type = ovl_path_type(dentry);
++
++ if (type != OVL_PATH_LOWER)
++ break;
++
++ next = dget(dentry);
++ /* find the topmost dentry not yet copied up */
++ for (;;) {
++ parent = dget_parent(next);
++
++ type = ovl_path_type(parent);
++ if (type != OVL_PATH_LOWER)
++ break;
++
++ dput(next);
++ next = parent;
++ }
++
++ ovl_path_lower(next, &lowerpath);
++ err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
++ if (!err)
++ err = ovl_copy_up_one(parent, next, &lowerpath, &stat);
++
++ dput(parent);
++ dput(next);
++ }
++
++ return err;
++}
++
++/* Optimize by not copying up the file first and truncating later */
++int ovl_copy_up_truncate(struct dentry *dentry, loff_t size)
++{
++ int err;
++ struct kstat stat;
++ struct path lowerpath;
++ struct dentry *parent = dget_parent(dentry);
++
++ err = ovl_copy_up(parent);
++ if (err)
++ goto out_dput_parent;
++
++ ovl_path_lower(dentry, &lowerpath);
++ err = vfs_getattr(lowerpath.mnt, lowerpath.dentry, &stat);
++ if (err)
++ goto out_dput_parent;
++
++ if (size < stat.size)
++ stat.size = size;
++
++ err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
++
++out_dput_parent:
++ dput(parent);
++ return err;
++}
+--- /dev/null
++++ b/fs/overlayfs/dir.c
+@@ -0,0 +1,607 @@
++/*
++ *
++ * Copyright (C) 2011 Novell Inc.
++ *
++ * This program is free software; you can redistribute it and/or modify it
++ * under the terms of the GNU General Public License version 2 as published by
++ * the Free Software Foundation.
++ */
++
++#include <linux/fs.h>
++#include <linux/namei.h>
++#include <linux/xattr.h>
++#include <linux/security.h>
++#include "overlayfs.h"
++
++static const char *ovl_whiteout_symlink = "(overlay-whiteout)";
++
++static struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
++ struct nameidata *nd)
++{
++ int err = ovl_do_lookup(dentry);
++
++ if (err)
++ return ERR_PTR(err);
++
++ return NULL;
++}
++
++static int ovl_whiteout(struct dentry *upperdir, struct dentry *dentry)
++{
++ int err;
++ struct dentry *newdentry;
++ const struct cred *old_cred;
++ struct cred *override_cred;
++
++ /* FIXME: recheck lower dentry to see if whiteout is really needed */
++
++ err = -ENOMEM;
++ override_cred = prepare_creds();
++ if (!override_cred)
++ goto out;
++
++ /*
++ * CAP_SYS_ADMIN for setxattr
++ * CAP_DAC_OVERRIDE for symlink creation
++ * CAP_FOWNER for unlink in sticky directory
++ */
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
++ cap_raise(override_cred->cap_effective, CAP_FOWNER);
++ override_cred->fsuid = 0;
++ override_cred->fsgid = 0;
++ old_cred = override_creds(override_cred);
++
++ newdentry = lookup_one_len(dentry->d_name.name, upperdir,
++ dentry->d_name.len);
++ err = PTR_ERR(newdentry);
++ if (IS_ERR(newdentry))
++ goto out_put_cred;
++
++ /* Just been removed within the same locked region */
++ WARN_ON(newdentry->d_inode);
++
++ err = vfs_symlink(upperdir->d_inode, newdentry, ovl_whiteout_symlink);
++ if (err)
++ goto out_dput;
++
++ ovl_dentry_version_inc(dentry->d_parent);
++
++ err = vfs_setxattr(newdentry, ovl_whiteout_xattr, "y", 1, 0);
++ if (err)
++ vfs_unlink(upperdir->d_inode, newdentry);
++
++out_dput:
++ dput(newdentry);
++out_put_cred:
++ revert_creds(old_cred);
++ put_cred(override_cred);
++out:
++ if (err) {
++ /*
++ * There's no way to recover from failure to whiteout.
++ * What should we do? Log a big fat error and... ?
++ */
++ printk(KERN_ERR "overlayfs: ERROR - failed to whiteout '%s'\n",
++ dentry->d_name.name);
++ }
++
++ return err;
++}
++
++static struct dentry *ovl_lookup_create(struct dentry *upperdir,
++ struct dentry *template)
++{
++ int err;
++ struct dentry *newdentry;
++ struct qstr *name = &template->d_name;
++
++ newdentry = lookup_one_len(name->name, upperdir, name->len);
++ if (IS_ERR(newdentry))
++ return newdentry;
++
++ if (newdentry->d_inode) {
++ const struct cred *old_cred;
++ struct cred *override_cred;
++
++ /* No need to check whiteout if lower parent is non-existent */
++ err = -EEXIST;
++ if (!ovl_dentry_lower(template->d_parent))
++ goto out_dput;
++
++ if (!S_ISLNK(newdentry->d_inode->i_mode))
++ goto out_dput;
++
++ err = -ENOMEM;
++ override_cred = prepare_creds();
++ if (!override_cred)
++ goto out_dput;
++
++ /*
++ * CAP_SYS_ADMIN for getxattr
++ * CAP_FOWNER for unlink in sticky directory
++ */
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ cap_raise(override_cred->cap_effective, CAP_FOWNER);
++ old_cred = override_creds(override_cred);
++
++ err = -EEXIST;
++ if (ovl_is_whiteout(newdentry))
++ err = vfs_unlink(upperdir->d_inode, newdentry);
++
++ revert_creds(old_cred);
++ put_cred(override_cred);
++ if (err)
++ goto out_dput;
++
++ dput(newdentry);
++ newdentry = lookup_one_len(name->name, upperdir, name->len);
++ if (IS_ERR(newdentry)) {
++ ovl_whiteout(upperdir, template);
++ return newdentry;
++ }
++
++ /*
++ * Whiteout just been successfully removed, parent
++ * i_mutex is still held, there's no way the lookup
++ * could return positive.
++ */
++ WARN_ON(newdentry->d_inode);
++ }
++
++ return newdentry;
++
++out_dput:
++ dput(newdentry);
++ return ERR_PTR(err);
++}
++
++struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
++ struct kstat *stat, const char *link)
++{
++ int err;
++ struct dentry *newdentry;
++ struct inode *dir = upperdir->d_inode;
++
++ newdentry = ovl_lookup_create(upperdir, dentry);
++ if (IS_ERR(newdentry))
++ goto out;
++
++ switch (stat->mode & S_IFMT) {
++ case S_IFREG:
++ err = vfs_create(dir, newdentry, stat->mode, NULL);
++ break;
++
++ case S_IFDIR:
++ err = vfs_mkdir(dir, newdentry, stat->mode);
++ break;
++
++ case S_IFCHR:
++ case S_IFBLK:
++ case S_IFIFO:
++ case S_IFSOCK:
++ err = vfs_mknod(dir, newdentry, stat->mode, stat->rdev);
++ break;
++
++ case S_IFLNK:
++ err = vfs_symlink(dir, newdentry, link);
++ break;
++
++ default:
++ err = -EPERM;
++ }
++ if (err) {
++ if (ovl_dentry_is_opaque(dentry))
++ ovl_whiteout(upperdir, dentry);
++ dput(newdentry);
++ newdentry = ERR_PTR(err);
++ } else if (WARN_ON(!newdentry->d_inode)) {
++ /*
++ * Not quite sure if non-instantiated dentry is legal or not.
++ * VFS doesn't seem to care so check and warn here.
++ */
++ dput(newdentry);
++ newdentry = ERR_PTR(-ENOENT);
++ }
++
++out:
++ return newdentry;
++
++}
++
++static int ovl_set_opaque(struct dentry *upperdentry)
++{
++ int err;
++ const struct cred *old_cred;
++ struct cred *override_cred;
++
++ override_cred = prepare_creds();
++ if (!override_cred)
++ return -ENOMEM;
++
++ /* CAP_SYS_ADMIN for setxattr of "trusted" namespace */
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ old_cred = override_creds(override_cred);
++ err = vfs_setxattr(upperdentry, ovl_opaque_xattr, "y", 1, 0);
++ revert_creds(old_cred);
++ put_cred(override_cred);
++
++ return err;
++}
++
++static int ovl_remove_opaque(struct dentry *upperdentry)
++{
++ int err;
++ const struct cred *old_cred;
++ struct cred *override_cred;
++
++ override_cred = prepare_creds();
++ if (!override_cred)
++ return -ENOMEM;
++
++ /* CAP_SYS_ADMIN for removexattr of "trusted" namespace */
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ old_cred = override_creds(override_cred);
++ err = vfs_removexattr(upperdentry, ovl_opaque_xattr);
++ revert_creds(old_cred);
++ put_cred(override_cred);
++
++ return err;
++}
++
++static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
++ struct kstat *stat)
++{
++ int err;
++ enum ovl_path_type type;
++ struct path realpath;
++
++ type = ovl_path_real(dentry, &realpath);
++ err = vfs_getattr(realpath.mnt, realpath.dentry, stat);
++ if (err)
++ return err;
++
++ stat->dev = dentry->d_sb->s_dev;
++ stat->ino = dentry->d_inode->i_ino;
++
++ /*
++ * It's probably not worth it to count subdirs to get the
++ * correct link count. nlink=1 seems to pacify 'find' and
++ * other utilities.
++ */
++ if (type == OVL_PATH_MERGE)
++ stat->nlink = 1;
++
++ return 0;
++}
++
++static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
++ const char *link)
++{
++ int err;
++ struct dentry *newdentry;
++ struct dentry *upperdir;
++ struct inode *inode;
++ struct kstat stat = {
++ .mode = mode,
++ .rdev = rdev,
++ };
++
++ err = -ENOMEM;
++ inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
++ if (!inode)
++ goto out;
++
++ err = ovl_copy_up(dentry->d_parent);
++ if (err)
++ goto out_iput;
++
++ upperdir = ovl_dentry_upper(dentry->d_parent);
++ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
++
++ newdentry = ovl_upper_create(upperdir, dentry, &stat, link);
++ err = PTR_ERR(newdentry);
++ if (IS_ERR(newdentry))
++ goto out_unlock;
++
++ ovl_dentry_version_inc(dentry->d_parent);
++ if (ovl_dentry_is_opaque(dentry) && S_ISDIR(mode)) {
++ err = ovl_set_opaque(newdentry);
++ if (err) {
++ vfs_rmdir(upperdir->d_inode, newdentry);
++ ovl_whiteout(upperdir, dentry);
++ goto out_dput;
++ }
++ }
++ ovl_dentry_update(dentry, newdentry);
++ d_instantiate(dentry, inode);
++ inode = NULL;
++ newdentry = NULL;
++ err = 0;
++
++out_dput:
++ dput(newdentry);
++out_unlock:
++ mutex_unlock(&upperdir->d_inode->i_mutex);
++out_iput:
++ iput(inode);
++out:
++ return err;
++}
++
++static int ovl_create(struct inode *dir, struct dentry *dentry, int mode,
++ struct nameidata *nd)
++{
++ return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
++}
++
++static int ovl_mkdir(struct inode *dir, struct dentry *dentry, int mode)
++{
++ return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
++}
++
++static int ovl_mknod(struct inode *dir, struct dentry *dentry, int mode,
++ dev_t rdev)
++{
++ return ovl_create_object(dentry, mode, rdev, NULL);
++}
++
++static int ovl_symlink(struct inode *dir, struct dentry *dentry,
++ const char *link)
++{
++ return ovl_create_object(dentry, S_IFLNK, 0, link);
++}
++
++static int ovl_do_remove(struct dentry *dentry, bool is_dir)
++{
++ int err;
++ enum ovl_path_type type;
++ struct path realpath;
++ struct dentry *upperdir;
++
++ err = ovl_copy_up(dentry->d_parent);
++ if (err)
++ return err;
++
++ upperdir = ovl_dentry_upper(dentry->d_parent);
++ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
++ type = ovl_path_real(dentry, &realpath);
++ if (type != OVL_PATH_LOWER) {
++ err = -ESTALE;
++ if (realpath.dentry->d_parent != upperdir)
++ goto out_d_drop;
++
++ /* FIXME: create whiteout up front and rename to target */
++
++ if (is_dir)
++ err = vfs_rmdir(upperdir->d_inode, realpath.dentry);
++ else
++ err = vfs_unlink(upperdir->d_inode, realpath.dentry);
++ if (err)
++ goto out_d_drop;
++
++ ovl_dentry_version_inc(dentry->d_parent);
++ }
++
++ if (type != OVL_PATH_UPPER || ovl_dentry_is_opaque(dentry))
++ err = ovl_whiteout(upperdir, dentry);
++
++ /*
++ * Keeping this dentry hashed would mean having to release
++ * upperpath/lowerpath, which could only be done if we are the
++ * sole user of this dentry. Too tricky... Just unhash for
++ * now.
++ */
++out_d_drop:
++ d_drop(dentry);
++ mutex_unlock(&upperdir->d_inode->i_mutex);
++
++ return err;
++}
++
++static int ovl_unlink(struct inode *dir, struct dentry *dentry)
++{
++ return ovl_do_remove(dentry, false);
++}
++
++
++static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
++{
++ int err;
++ enum ovl_path_type type;
++
++ type = ovl_path_type(dentry);
++ if (type != OVL_PATH_UPPER) {
++ err = ovl_check_empty_and_clear(dentry, type);
++ if (err)
++ return err;
++ }
++
++ return ovl_do_remove(dentry, true);
++}
++
++static int ovl_link(struct dentry *old, struct inode *newdir,
++ struct dentry *new)
++{
++ int err;
++ struct dentry *olddentry;
++ struct dentry *newdentry;
++ struct dentry *upperdir;
++
++ err = ovl_copy_up(old);
++ if (err)
++ goto out;
++
++ err = ovl_copy_up(new->d_parent);
++ if (err)
++ goto out;
++
++ upperdir = ovl_dentry_upper(new->d_parent);
++ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
++ newdentry = ovl_lookup_create(upperdir, new);
++ err = PTR_ERR(newdentry);
++ if (IS_ERR(newdentry))
++ goto out_unlock;
++
++ olddentry = ovl_dentry_upper(old);
++ err = vfs_link(olddentry, upperdir->d_inode, newdentry);
++ if (!err) {
++ if (WARN_ON(!newdentry->d_inode)) {
++ dput(newdentry);
++ err = -ENOENT;
++ goto out_unlock;
++ }
++
++ ovl_dentry_version_inc(new->d_parent);
++ ovl_dentry_update(new, newdentry);
++
++ ihold(old->d_inode);
++ d_instantiate(new, old->d_inode);
++ } else {
++ if (ovl_dentry_is_opaque(new))
++ ovl_whiteout(upperdir, new);
++ dput(newdentry);
++ }
++out_unlock:
++ mutex_unlock(&upperdir->d_inode->i_mutex);
++out:
++ return err;
++
++}
++
++static int ovl_rename(struct inode *olddir, struct dentry *old,
++ struct inode *newdir, struct dentry *new)
++{
++ int err;
++ enum ovl_path_type old_type;
++ enum ovl_path_type new_type;
++ struct dentry *old_upperdir;
++ struct dentry *new_upperdir;
++ struct dentry *olddentry;
++ struct dentry *newdentry;
++ struct dentry *trap;
++ bool old_opaque;
++ bool new_opaque;
++ bool new_create = false;
++ bool is_dir = S_ISDIR(old->d_inode->i_mode);
++
++ /* Don't copy up directory trees */
++ old_type = ovl_path_type(old);
++ if (old_type != OVL_PATH_UPPER && is_dir)
++ return -EXDEV;
++
++ if (new->d_inode) {
++ new_type = ovl_path_type(new);
++
++ if (new_type == OVL_PATH_LOWER && old_type == OVL_PATH_LOWER) {
++ if (ovl_dentry_lower(old)->d_inode ==
++ ovl_dentry_lower(new)->d_inode)
++ return 0;
++ }
++ if (new_type != OVL_PATH_LOWER && old_type != OVL_PATH_LOWER) {
++ if (ovl_dentry_upper(old)->d_inode ==
++ ovl_dentry_upper(new)->d_inode)
++ return 0;
++ }
++
++ if (new_type != OVL_PATH_UPPER &&
++ S_ISDIR(new->d_inode->i_mode)) {
++ err = ovl_check_empty_and_clear(new, new_type);
++ if (err)
++ return err;
++ }
++ } else {
++ new_type = OVL_PATH_UPPER;
++ }
++
++ err = ovl_copy_up(old);
++ if (err)
++ return err;
++
++ err = ovl_copy_up(new->d_parent);
++ if (err)
++ return err;
++
++ old_upperdir = ovl_dentry_upper(old->d_parent);
++ new_upperdir = ovl_dentry_upper(new->d_parent);
++
++ trap = lock_rename(new_upperdir, old_upperdir);
++
++ olddentry = ovl_dentry_upper(old);
++ newdentry = ovl_dentry_upper(new);
++ if (newdentry) {
++ dget(newdentry);
++ } else {
++ new_create = true;
++ newdentry = ovl_lookup_create(new_upperdir, new);
++ err = PTR_ERR(newdentry);
++ if (IS_ERR(newdentry))
++ goto out_unlock;
++ }
++
++ err = -ESTALE;
++ if (olddentry->d_parent != old_upperdir)
++ goto out_dput;
++ if (newdentry->d_parent != new_upperdir)
++ goto out_dput;
++ if (olddentry == trap)
++ goto out_dput;
++ if (newdentry == trap)
++ goto out_dput;
++
++ old_opaque = ovl_dentry_is_opaque(old);
++ new_opaque = ovl_dentry_is_opaque(new) || new_type != OVL_PATH_UPPER;
++
++ if (is_dir && !old_opaque && new_opaque) {
++ err = ovl_set_opaque(olddentry);
++ if (err)
++ goto out_dput;
++ }
++
++ err = vfs_rename(old_upperdir->d_inode, olddentry,
++ new_upperdir->d_inode, newdentry);
++
++ if (err) {
++ if (new_create && ovl_dentry_is_opaque(new))
++ ovl_whiteout(new_upperdir, new);
++ if (is_dir && !old_opaque && new_opaque)
++ ovl_remove_opaque(olddentry);
++ goto out_dput;
++ }
++
++ if (old_type != OVL_PATH_UPPER || old_opaque)
++ err = ovl_whiteout(old_upperdir, old);
++ if (is_dir && old_opaque && !new_opaque)
++ ovl_remove_opaque(olddentry);
++
++ if (old_opaque != new_opaque)
++ ovl_dentry_set_opaque(old, new_opaque);
++
++ ovl_dentry_version_inc(old->d_parent);
++ ovl_dentry_version_inc(new->d_parent);
++
++out_dput:
++ dput(newdentry);
++out_unlock:
++ unlock_rename(new_upperdir, old_upperdir);
++ return err;
++}
++
++const struct inode_operations ovl_dir_inode_operations = {
++ .lookup = ovl_lookup,
++ .mkdir = ovl_mkdir,
++ .symlink = ovl_symlink,
++ .unlink = ovl_unlink,
++ .rmdir = ovl_rmdir,
++ .rename = ovl_rename,
++ .link = ovl_link,
++ .setattr = ovl_setattr,
++ .create = ovl_create,
++ .mknod = ovl_mknod,
++ .permission = ovl_permission,
++ .getattr = ovl_dir_getattr,
++ .setxattr = ovl_setxattr,
++ .getxattr = ovl_getxattr,
++ .listxattr = ovl_listxattr,
++ .removexattr = ovl_removexattr,
++};
+--- /dev/null
++++ b/fs/overlayfs/inode.c
+@@ -0,0 +1,375 @@
++/*
++ *
++ * Copyright (C) 2011 Novell Inc.
++ *
++ * This program is free software; you can redistribute it and/or modify it
++ * under the terms of the GNU General Public License version 2 as published by
++ * the Free Software Foundation.
++ */
++
++#include <linux/fs.h>
++#include <linux/slab.h>
++#include <linux/xattr.h>
++#include "overlayfs.h"
++
++int ovl_setattr(struct dentry *dentry, struct iattr *attr)
++{
++ struct dentry *upperdentry;
++ int err;
++
++ if ((attr->ia_valid & ATTR_SIZE) && !ovl_dentry_upper(dentry))
++ err = ovl_copy_up_truncate(dentry, attr->ia_size);
++ else
++ err = ovl_copy_up(dentry);
++ if (err)
++ return err;
++
++ upperdentry = ovl_dentry_upper(dentry);
++
++ if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
++ attr->ia_valid &= ~ATTR_MODE;
++
++ mutex_lock(&upperdentry->d_inode->i_mutex);
++ err = notify_change(upperdentry, attr);
++ mutex_unlock(&upperdentry->d_inode->i_mutex);
++
++ return err;
++}
++
++static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
++ struct kstat *stat)
++{
++ struct path realpath;
++
++ ovl_path_real(dentry, &realpath);
++ return vfs_getattr(realpath.mnt, realpath.dentry, stat);
++}
++
++int ovl_permission(struct inode *inode, int mask, unsigned int flags)
++{
++ struct ovl_entry *oe;
++ struct dentry *alias = NULL;
++ struct inode *realinode;
++ struct dentry *realdentry;
++ bool is_upper;
++ int err;
++
++ if (S_ISDIR(inode->i_mode)) {
++ oe = inode->i_private;
++ } else if (flags & IPERM_FLAG_RCU) {
++ return -ECHILD;
++ } else {
++ /*
++ * For non-directories find an alias and get the info
++ * from there.
++ */
++ spin_lock(&inode->i_lock);
++ if (WARN_ON(list_empty(&inode->i_dentry))) {
++ spin_unlock(&inode->i_lock);
++ return -ENOENT;
++ }
++ alias = list_entry(inode->i_dentry.next, struct dentry, d_alias);
++ dget(alias);
++ spin_unlock(&inode->i_lock);
++ oe = alias->d_fsdata;
++ }
++
++ realdentry = ovl_entry_real(oe, &is_upper);
++
++ /* Careful in RCU walk mode */
++ realinode = ACCESS_ONCE(realdentry->d_inode);
++ if (!realinode) {
++ WARN_ON(!(flags & IPERM_FLAG_RCU));
++ err = -ENOENT;
++ goto out_dput;
++ }
++
++ if (mask & MAY_WRITE) {
++ umode_t mode = realinode->i_mode;
++
++ /*
++ * Writes will always be redirected to upper layer, so
++ * ignore lower layer being read-only.
++ */
++ err = -EROFS;
++ if (is_upper && IS_RDONLY(realinode) &&
++ (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
++ goto out_dput;
++
++ /*
++ * Nobody gets write access to an immutable file.
++ */
++ err = -EACCES;
++ if (IS_IMMUTABLE(realinode))
++ goto out_dput;
++ }
++
++ if (realinode->i_op->permission)
++ err = realinode->i_op->permission(realinode, mask, flags);
++ else
++ err = generic_permission(realinode, mask, flags,
++ realinode->i_op->check_acl);
++out_dput:
++ dput(alias);
++ return err;
++}
++
++
++struct ovl_link_data {
++ struct dentry *realdentry;
++ void *cookie;
++};
++
++static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
++{
++ void *ret;
++ struct dentry *realdentry;
++ struct inode *realinode;
++
++ realdentry = ovl_dentry_real(dentry);
++ realinode = realdentry->d_inode;
++
++ if (WARN_ON(!realinode->i_op->follow_link))
++ return ERR_PTR(-EPERM);
++
++ ret = realinode->i_op->follow_link(realdentry, nd);
++ if (IS_ERR(ret))
++ return ret;
++
++ if (realinode->i_op->put_link) {
++ struct ovl_link_data *data;
++
++ data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
++ if (!data) {
++ realinode->i_op->put_link(realdentry, nd, ret);
++ return ERR_PTR(-ENOMEM);
++ }
++ data->realdentry = realdentry;
++ data->cookie = ret;
++
++ return data;
++ } else {
++ return NULL;
++ }
++}
++
++static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)
++{
++ struct inode *realinode;
++ struct ovl_link_data *data = c;
++
++ if (!data)
++ return;
++
++ realinode = data->realdentry->d_inode;
++ realinode->i_op->put_link(data->realdentry, nd, data->cookie);
++ kfree(data);
++}
++
++static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
++{
++ struct path realpath;
++ struct inode *realinode;
++
++ ovl_path_real(dentry, &realpath);
++ realinode = realpath.dentry->d_inode;
++
++ if (!realinode->i_op->readlink)
++ return -EINVAL;
++
++ touch_atime(realpath.mnt, realpath.dentry);
++
++ return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
++}
++
++
++static bool ovl_is_private_xattr(const char *name)
++{
++ return strncmp(name, "trusted.overlay.", 14) == 0;
++}
++
++int ovl_setxattr(struct dentry *dentry, const char *name,
++ const void *value, size_t size, int flags)
++{
++ int err;
++ struct dentry *upperdentry;
++
++ if (ovl_is_private_xattr(name))
++ return -EPERM;
++
++ err = ovl_copy_up(dentry);
++ if (err)
++ return err;
++
++ upperdentry = ovl_dentry_upper(dentry);
++ return vfs_setxattr(upperdentry, name, value, size, flags);
++}
++
++ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
++ void *value, size_t size)
++{
++ if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
++ ovl_is_private_xattr(name))
++ return -ENODATA;
++
++ return vfs_getxattr(ovl_dentry_real(dentry), name, value, size);
++}
++
++ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
++{
++ ssize_t res;
++ int off;
++
++ res = vfs_listxattr(ovl_dentry_real(dentry), list, size);
++ if (res <= 0 || size == 0)
++ return res;
++
++ if (ovl_path_type(dentry->d_parent) != OVL_PATH_MERGE)
++ return res;
++
++ /* filter out private xattrs */
++ for (off = 0; off < res;) {
++ char *s = list + off;
++ size_t slen = strlen(s) + 1;
++
++ BUG_ON(off + slen > res);
++
++ if (ovl_is_private_xattr(s)) {
++ res -= slen;
++ memmove(s, s + slen, res - off);
++ } else {
++ off += slen;
++ }
++ }
++
++ return res;
++}
++
++int ovl_removexattr(struct dentry *dentry, const char *name)
++{
++ int err;
++ struct path realpath;
++ enum ovl_path_type type;
++
++ if (ovl_path_type(dentry->d_parent) == OVL_PATH_MERGE &&
++ ovl_is_private_xattr(name))
++ return -ENODATA;
++
++ type = ovl_path_real(dentry, &realpath);
++ if (type == OVL_PATH_LOWER) {
++ err = vfs_getxattr(realpath.dentry, name, NULL, 0);
++ if (err < 0)
++ return err;
++
++ err = ovl_copy_up(dentry);
++ if (err)
++ return err;
++
++ ovl_path_upper(dentry, &realpath);
++ }
++
++ return vfs_removexattr(realpath.dentry, name);
++}
++
++static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
++ struct dentry *realdentry)
++{
++ if (type != OVL_PATH_LOWER)
++ return false;
++
++ if (special_file(realdentry->d_inode->i_mode))
++ return false;
++
++ if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
++ return false;
++
++ return true;
++}
++
++static struct file *ovl_open(struct dentry *dentry, int flags,
++ const struct cred *cred)
++{
++ int err;
++ struct path realpath;
++ enum ovl_path_type type;
++
++ type = ovl_path_real(dentry, &realpath);
++ if (ovl_open_need_copy_up(flags, type, realpath.dentry)) {
++ if (flags & O_TRUNC)
++ err = ovl_copy_up_truncate(dentry, 0);
++ else
++ err = ovl_copy_up(dentry);
++ if (err)
++ return ERR_PTR(err);
++
++ ovl_path_upper(dentry, &realpath);
++ }
++
++ return vfs_open(&realpath, flags, cred);
++}
++
++static const struct inode_operations ovl_file_inode_operations = {
++ .setattr = ovl_setattr,
++ .permission = ovl_permission,
++ .getattr = ovl_getattr,
++ .setxattr = ovl_setxattr,
++ .getxattr = ovl_getxattr,
++ .listxattr = ovl_listxattr,
++ .removexattr = ovl_removexattr,
++ .open = ovl_open,
++};
++
++static const struct inode_operations ovl_symlink_inode_operations = {
++ .setattr = ovl_setattr,
++ .follow_link = ovl_follow_link,
++ .put_link = ovl_put_link,
++ .readlink = ovl_readlink,
++ .getattr = ovl_getattr,
++ .setxattr = ovl_setxattr,
++ .getxattr = ovl_getxattr,
++ .listxattr = ovl_listxattr,
++ .removexattr = ovl_removexattr,
++};
++
++struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
++ struct ovl_entry *oe)
++{
++ struct inode *inode;
++
++ inode = new_inode(sb);
++ if (!inode)
++ return NULL;
++
++ mode &= S_IFMT;
++
++ inode->i_ino = get_next_ino();
++ inode->i_mode = mode;
++ inode->i_flags |= S_NOATIME | S_NOCMTIME;
++
++ switch (mode) {
++ case S_IFDIR:
++ inode->i_private = oe;
++ inode->i_op = &ovl_dir_inode_operations;
++ inode->i_fop = &ovl_dir_operations;
++ break;
++
++ case S_IFLNK:
++ inode->i_op = &ovl_symlink_inode_operations;
++ break;
++
++ case S_IFREG:
++ case S_IFSOCK:
++ case S_IFBLK:
++ case S_IFCHR:
++ case S_IFIFO:
++ inode->i_op = &ovl_file_inode_operations;
++ break;
++
++ default:
++ WARN(1, "illegal file type: %i\n", mode);
++ inode = NULL;
++ }
++
++ return inode;
++
++}
+--- /dev/null
++++ b/fs/overlayfs/overlayfs.h
+@@ -0,0 +1,62 @@
++/*
++ *
++ * Copyright (C) 2011 Novell Inc.
++ *
++ * This program is free software; you can redistribute it and/or modify it
++ * under the terms of the GNU General Public License version 2 as published by
++ * the Free Software Foundation.
++ */
++
++struct ovl_entry;
++
++enum ovl_path_type {
++ OVL_PATH_UPPER,
++ OVL_PATH_MERGE,
++ OVL_PATH_LOWER,
++};
++
++extern const char *ovl_opaque_xattr;
++extern const char *ovl_whiteout_xattr;
++extern const struct dentry_operations ovl_dentry_operations;
++
++enum ovl_path_type ovl_path_type(struct dentry *dentry);
++u64 ovl_dentry_version_get(struct dentry *dentry);
++void ovl_dentry_version_inc(struct dentry *dentry);
++void ovl_path_upper(struct dentry *dentry, struct path *path);
++void ovl_path_lower(struct dentry *dentry, struct path *path);
++enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
++struct dentry *ovl_dentry_upper(struct dentry *dentry);
++struct dentry *ovl_dentry_lower(struct dentry *dentry);
++struct dentry *ovl_dentry_real(struct dentry *dentry);
++struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper);
++bool ovl_dentry_is_opaque(struct dentry *dentry);
++void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque);
++bool ovl_is_whiteout(struct dentry *dentry);
++void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
++int ovl_do_lookup(struct dentry *dentry);
++
++struct dentry *ovl_upper_create(struct dentry *upperdir, struct dentry *dentry,
++ struct kstat *stat, const char *link);
++
++/* readdir.c */
++extern const struct file_operations ovl_dir_operations;
++int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type);
++
++/* inode.c */
++int ovl_setattr(struct dentry *dentry, struct iattr *attr);
++int ovl_permission(struct inode *inode, int mask, unsigned int flags);
++int ovl_setxattr(struct dentry *dentry, const char *name,
++ const void *value, size_t size, int flags);
++ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
++ void *value, size_t size);
++ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
++int ovl_removexattr(struct dentry *dentry, const char *name);
++
++struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
++ struct ovl_entry *oe);
++/* dir.c */
++extern const struct inode_operations ovl_dir_inode_operations;
++
++/* copy_up.c */
++int ovl_copy_up(struct dentry *dentry);
++int ovl_copy_up_truncate(struct dentry *dentry, loff_t size);
+--- /dev/null
++++ b/fs/overlayfs/readdir.c
+@@ -0,0 +1,558 @@
++/*
++ *
++ * Copyright (C) 2011 Novell Inc.
++ *
++ * This program is free software; you can redistribute it and/or modify it
++ * under the terms of the GNU General Public License version 2 as published by
++ * the Free Software Foundation.
++ */
++
++#include <linux/fs.h>
++#include <linux/slab.h>
++#include <linux/namei.h>
++#include <linux/file.h>
++#include <linux/xattr.h>
++#include <linux/rbtree.h>
++#include <linux/security.h>
++#include "overlayfs.h"
++
++struct ovl_cache_entry {
++ const char *name;
++ unsigned int len;
++ unsigned int type;
++ u64 ino;
++ bool is_whiteout;
++ struct list_head l_node;
++ struct rb_node node;
++};
++
++struct ovl_readdir_data {
++ struct rb_root *root;
++ struct list_head *list;
++ struct list_head *middle;
++ struct dentry *dir;
++ int count;
++ int err;
++};
++
++struct ovl_dir_file {
++ bool is_real;
++ bool is_cached;
++ struct list_head cursor;
++ u64 cache_version;
++ struct list_head cache;
++ struct file *realfile;
++};
++
++static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
++{
++ return container_of(n, struct ovl_cache_entry, node);
++}
++
++static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
++ const char *name, int len)
++{
++ struct rb_node *node = root->rb_node;
++ int cmp;
++
++ while (node) {
++ struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
++
++ cmp = strncmp(name, p->name, len);
++ if (cmp > 0)
++ node = p->node.rb_right;
++ else if (cmp < 0 || len < p->len)
++ node = p->node.rb_left;
++ else
++ return p;
++ }
++
++ return NULL;
++}
++
++static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
++ u64 ino, unsigned int d_type)
++{
++ struct ovl_cache_entry *p;
++
++ p = kmalloc(sizeof(*p) + len + 1, GFP_KERNEL);
++ if (p) {
++ char *name_copy = (char *) (p + 1);
++ memcpy(name_copy, name, len);
++ name_copy[len] = '\0';
++ p->name = name_copy;
++ p->len = len;
++ p->type = d_type;
++ p->ino = ino;
++ p->is_whiteout = false;
++ }
++
++ return p;
++}
++
++static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
++ const char *name, int len, u64 ino,
++ unsigned int d_type)
++{
++ struct rb_node **newp = &rdd->root->rb_node;
++ struct rb_node *parent = NULL;
++ struct ovl_cache_entry *p;
++
++ while (*newp) {
++ int cmp;
++ struct ovl_cache_entry *tmp;
++
++ parent = *newp;
++ tmp = ovl_cache_entry_from_node(*newp);
++ cmp = strncmp(name, tmp->name, len);
++ if (cmp > 0)
++ newp = &tmp->node.rb_right;
++ else if (cmp < 0 || len < tmp->len)
++ newp = &tmp->node.rb_left;
++ else
++ return 0;
++ }
++
++ p = ovl_cache_entry_new(name, len, ino, d_type);
++ if (p == NULL)
++ return -ENOMEM;
++
++ list_add_tail(&p->l_node, rdd->list);
++ rb_link_node(&p->node, parent, newp);
++ rb_insert_color(&p->node, rdd->root);
++
++ return 0;
++}
++
++static int ovl_fill_lower(void *buf, const char *name, int namelen,
++ loff_t offset, u64 ino, unsigned int d_type)
++{
++ struct ovl_readdir_data *rdd = buf;
++ struct ovl_cache_entry *p;
++
++ rdd->count++;
++ p = ovl_cache_entry_find(rdd->root, name, namelen);
++ if (p) {
++ list_move_tail(&p->l_node, rdd->middle);
++ } else {
++ p = ovl_cache_entry_new(name, namelen, ino, d_type);
++ if (p == NULL)
++ rdd->err = -ENOMEM;
++ else
++ list_add_tail(&p->l_node, rdd->middle);
++ }
++
++ return rdd->err;
++}
++
++static void ovl_cache_free(struct list_head *list)
++{
++ struct ovl_cache_entry *p;
++ struct ovl_cache_entry *n;
++
++ list_for_each_entry_safe(p, n, list, l_node)
++ kfree(p);
++
++ INIT_LIST_HEAD(list);
++}
++
++static int ovl_fill_upper(void *buf, const char *name, int namelen,
++ loff_t offset, u64 ino, unsigned int d_type)
++{
++ struct ovl_readdir_data *rdd = buf;
++
++ rdd->count++;
++ return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
++}
++
++static int ovl_dir_read(struct path *realpath, struct ovl_readdir_data *rdd,
++ filldir_t filler)
++{
++ struct file *realfile;
++ int err;
++
++ realfile = vfs_open(realpath, O_RDONLY | O_DIRECTORY, current_cred());
++ if (IS_ERR(realfile))
++ return PTR_ERR(realfile);
++
++ do {
++ rdd->count = 0;
++ rdd->err = 0;
++ err = vfs_readdir(realfile, filler, rdd);
++ if (err >= 0)
++ err = rdd->err;
++ } while (!err && rdd->count);
++ fput(realfile);
++
++ return 0;
++}
++
++static void ovl_dir_reset(struct file *file)
++{
++ struct ovl_dir_file *od = file->private_data;
++ enum ovl_path_type type = ovl_path_type(file->f_path.dentry);
++
++ if (ovl_dentry_version_get(file->f_path.dentry) != od->cache_version) {
++ list_del_init(&od->cursor);
++ ovl_cache_free(&od->cache);
++ od->is_cached = false;
++ }
++ WARN_ON(!od->is_real && type != OVL_PATH_MERGE);
++ if (od->is_real && type == OVL_PATH_MERGE) {
++ fput(od->realfile);
++ od->realfile = NULL;
++ od->is_real = false;
++ }
++}
++
++static int ovl_dir_mark_whiteouts(struct ovl_readdir_data *rdd)
++{
++ struct ovl_cache_entry *p;
++ struct dentry *dentry;
++ const struct cred *old_cred;
++ struct cred *override_cred;
++
++ override_cred = prepare_creds();
++ if (!override_cred) {
++ ovl_cache_free(rdd->list);
++ return -ENOMEM;
++ }
++
++ /*
++ * CAP_SYS_ADMIN for getxattr
++ * CAP_DAC_OVERRIDE for lookup
++ */
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
++ old_cred = override_creds(override_cred);
++
++ mutex_lock(&rdd->dir->d_inode->i_mutex);
++ list_for_each_entry(p, rdd->list, l_node) {
++ if (p->type != DT_LNK)
++ continue;
++
++ dentry = lookup_one_len(p->name, rdd->dir, p->len);
++ if (IS_ERR(dentry))
++ continue;
++
++ p->is_whiteout = ovl_is_whiteout(dentry);
++ dput(dentry);
++ }
++ mutex_unlock(&rdd->dir->d_inode->i_mutex);
++
++ revert_creds(old_cred);
++ put_cred(override_cred);
++
++ return 0;
++}
++
++static int ovl_dir_read_merged(struct path *upperpath, struct path *lowerpath,
++ struct ovl_readdir_data *rdd)
++{
++ int err;
++ struct rb_root root = RB_ROOT;
++ struct list_head middle;
++
++ rdd->root = &root;
++ if (upperpath->dentry) {
++ rdd->dir = upperpath->dentry;
++ err = ovl_dir_read(upperpath, rdd, ovl_fill_upper);
++ if (err)
++ goto out;
++
++ err = ovl_dir_mark_whiteouts(rdd);
++ if (err)
++ goto out;
++ }
++ /*
++ * Insert lowerpath entries before upperpath ones, this allows
++ * offsets to be reasonably constant
++ */
++ list_add(&middle, rdd->list);
++ rdd->middle = &middle;
++ err = ovl_dir_read(lowerpath, rdd, ovl_fill_lower);
++ list_del(&middle);
++out:
++ rdd->root = NULL;
++
++ return err;
++}
++
++static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
++{
++ struct list_head *l;
++ loff_t off;
++
++ l = od->cache.next;
++ for (off = 0; off < pos; off++) {
++ if (l == &od->cache)
++ break;
++ l = l->next;
++ }
++ list_move_tail(&od->cursor, l);
++}
++
++static int ovl_readdir(struct file *file, void *buf, filldir_t filler)
++{
++ struct ovl_dir_file *od = file->private_data;
++ int res;
++
++ if (!file->f_pos)
++ ovl_dir_reset(file);
++
++ if (od->is_real) {
++ res = vfs_readdir(od->realfile, filler, buf);
++ file->f_pos = od->realfile->f_pos;
++
++ return res;
++ }
++
++ if (!od->is_cached) {
++ struct path lowerpath;
++ struct path upperpath;
++ struct ovl_readdir_data rdd = { .list = &od->cache };
++
++ ovl_path_lower(file->f_path.dentry, &lowerpath);
++ ovl_path_upper(file->f_path.dentry, &upperpath);
++
++ res = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
++ if (res) {
++ ovl_cache_free(rdd.list);
++ return res;
++ }
++
++ od->cache_version = ovl_dentry_version_get(file->f_path.dentry);
++ od->is_cached = true;
++
++ ovl_seek_cursor(od, file->f_pos);
++ }
++
++ while (od->cursor.next != &od->cache) {
++ int over;
++ loff_t off;
++ struct ovl_cache_entry *p;
++
++ p = list_entry(od->cursor.next, struct ovl_cache_entry, l_node);
++ off = file->f_pos;
++ if (!p->is_whiteout) {
++ over = filler(buf, p->name, p->len, off, p->ino, p->type);
++ if (over)
++ break;
++ }
++ file->f_pos++;
++ list_move(&od->cursor, &p->l_node);
++ }
++
++ return 0;
++}
++
++static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
++{
++ loff_t res;
++ struct ovl_dir_file *od = file->private_data;
++
++ mutex_lock(&file->f_dentry->d_inode->i_mutex);
++ if (!file->f_pos)
++ ovl_dir_reset(file);
++
++ if (od->is_real) {
++ res = vfs_llseek(od->realfile, offset, origin);
++ file->f_pos = od->realfile->f_pos;
++ } else {
++ res = -EINVAL;
++
++ switch (origin) {
++ case SEEK_CUR:
++ offset += file->f_pos;
++ break;
++ case SEEK_SET:
++ break;
++ default:
++ goto out_unlock;
++ }
++ if (offset < 0)
++ goto out_unlock;
++
++ if (offset != file->f_pos) {
++ file->f_pos = offset;
++ if (od->is_cached)
++ ovl_seek_cursor(od, offset);
++ }
++ res = offset;
++ }
++out_unlock:
++ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
++
++ return res;
++}
++
++static int ovl_dir_fsync(struct file *file, int datasync)
++{
++ struct ovl_dir_file *od = file->private_data;
++
++ /* May need to reopen directory if it got copied up */
++ if (!od->realfile) {
++ struct path upperpath;
++
++ ovl_path_upper(file->f_path.dentry, &upperpath);
++ od->realfile = vfs_open(&upperpath, O_RDONLY, current_cred());
++ if (IS_ERR(od->realfile))
++ return PTR_ERR(od->realfile);
++ }
++
++ return vfs_fsync(od->realfile, datasync);
++}
++
++static int ovl_dir_release(struct inode *inode, struct file *file)
++{
++ struct ovl_dir_file *od = file->private_data;
++
++ list_del(&od->cursor);
++ ovl_cache_free(&od->cache);
++ if (od->realfile)
++ fput(od->realfile);
++ kfree(od);
++
++ return 0;
++}
++
++static int ovl_dir_open(struct inode *inode, struct file *file)
++{
++ struct path realpath;
++ struct file *realfile;
++ struct ovl_dir_file *od;
++ enum ovl_path_type type;
++
++ od = kzalloc(sizeof(struct ovl_dir_file), GFP_KERNEL);
++ if (!od)
++ return -ENOMEM;
++
++ type = ovl_path_real(file->f_path.dentry, &realpath);
++ realfile = vfs_open(&realpath, file->f_flags, current_cred());
++ if (IS_ERR(realfile)) {
++ kfree(od);
++ return PTR_ERR(realfile);
++ }
++ INIT_LIST_HEAD(&od->cache);
++ INIT_LIST_HEAD(&od->cursor);
++ od->is_cached = false;
++ od->realfile = realfile;
++ od->is_real = (type != OVL_PATH_MERGE);
++ file->private_data = od;
++
++ return 0;
++}
++
++const struct file_operations ovl_dir_operations = {
++ .read = generic_read_dir,
++ .open = ovl_dir_open,
++ .readdir = ovl_readdir,
++ .llseek = ovl_dir_llseek,
++ .fsync = ovl_dir_fsync,
++ .release = ovl_dir_release,
++};
++
++static int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
++{
++ int err;
++ struct path lowerpath;
++ struct path upperpath;
++ struct ovl_cache_entry *p;
++ struct ovl_readdir_data rdd = { .list = list };
++
++ ovl_path_upper(dentry, &upperpath);
++ ovl_path_lower(dentry, &lowerpath);
++
++ err = ovl_dir_read_merged(&upperpath, &lowerpath, &rdd);
++ if (err)
++ return err;
++
++ err = 0;
++
++ list_for_each_entry(p, list, l_node) {
++ if (p->is_whiteout)
++ continue;
++
++ if (p->name[0] == '.') {
++ if (p->len == 1)
++ continue;
++ if (p->len == 2 && p->name[1] == '.')
++ continue;
++ }
++ err = -ENOTEMPTY;
++ break;
++ }
++
++ return err;
++}
++
++static int ovl_remove_whiteouts(struct dentry *dir, struct list_head *list)
++{
++ struct path upperpath;
++ struct dentry *upperdir;
++ struct ovl_cache_entry *p;
++ const struct cred *old_cred;
++ struct cred *override_cred;
++ int err;
++
++ ovl_path_upper(dir, &upperpath);
++ upperdir = upperpath.dentry;
++
++ override_cred = prepare_creds();
++ if (!override_cred)
++ return -ENOMEM;
++
++ /*
++ * CAP_DAC_OVERRIDE for lookup and unlink
++ * CAP_SYS_ADMIN for setxattr of "trusted" namespace
++ * CAP_FOWNER for unlink in sticky directory
++ */
++ cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ cap_raise(override_cred->cap_effective, CAP_FOWNER);
++ old_cred = override_creds(override_cred);
++
++ err = vfs_setxattr(upperdir, ovl_opaque_xattr, "y", 1, 0);
++ if (err)
++ goto out_revert_creds;
++
++ mutex_lock_nested(&upperdir->d_inode->i_mutex, I_MUTEX_PARENT);
++ list_for_each_entry(p, list, l_node) {
++ struct dentry *dentry;
++ int ret;
++
++ if (!p->is_whiteout)
++ continue;
++
++ dentry = lookup_one_len(p->name, upperdir, p->len);
++ if (IS_ERR(dentry)) {
++ printk(KERN_WARNING "overlayfs: failed to lookup whiteout %.*s: %li\n", p->len, p->name, PTR_ERR(dentry));
++ continue;
++ }
++ ret = vfs_unlink(upperdir->d_inode, dentry);
++ dput(dentry);
++ if (ret)
++ printk(KERN_WARNING "overlayfs: failed to unlink whiteout %.*s: %i\n", p->len, p->name, ret);
++ }
++ mutex_unlock(&upperdir->d_inode->i_mutex);
++
++out_revert_creds:
++ revert_creds(old_cred);
++ put_cred(override_cred);
++
++ return err;
++}
++
++int ovl_check_empty_and_clear(struct dentry *dentry, enum ovl_path_type type)
++{
++ int err;
++ LIST_HEAD(list);
++
++ err = ovl_check_empty_dir(dentry, &list);
++ if (!err && type == OVL_PATH_MERGE)
++ err = ovl_remove_whiteouts(dentry, &list);
++
++ ovl_cache_free(&list);
++
++ return err;
++}
+--- /dev/null
++++ b/fs/overlayfs/super.c
+@@ -0,0 +1,625 @@
++/*
++ *
++ * Copyright (C) 2011 Novell Inc.
++ *
++ * This program is free software; you can redistribute it and/or modify it
++ * under the terms of the GNU General Public License version 2 as published by
++ * the Free Software Foundation.
++ */
++
++#include <linux/fs.h>
++#include <linux/namei.h>
++#include <linux/xattr.h>
++#include <linux/security.h>
++#include <linux/mount.h>
++#include <linux/slab.h>
++#include <linux/parser.h>
++#include <linux/module.h>
++#include <linux/seq_file.h>
++#include "overlayfs.h"
++
++MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
++MODULE_DESCRIPTION("Overlay filesystem");
++MODULE_LICENSE("GPL");
++
++struct ovl_config {
++ char *lowerdir;
++ char *upperdir;
++};
++
++/* private information held for overlayfs's superblock */
++struct ovl_fs {
++ struct vfsmount *upper_mnt;
++ struct vfsmount *lower_mnt;
++ /* pathnames of lower and upper dirs, for show_options */
++ struct ovl_config config;
++};
++
++/* private information held for every overlayfs dentry */
++struct ovl_entry {
++ /*
++ * Keep "double reference" on upper dentries, so that
++ * d_delete() doesn't think it's OK to reset d_inode to NULL.
++ */
++ struct dentry *__upperdentry;
++ struct dentry *lowerdentry;
++ union {
++ struct {
++ u64 version;
++ bool opaque;
++ };
++ struct rcu_head rcu;
++ };
++};
++
++const char *ovl_whiteout_xattr = "trusted.overlay.whiteout";
++const char *ovl_opaque_xattr = "trusted.overlay.opaque";
++
++
++enum ovl_path_type ovl_path_type(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ if (oe->__upperdentry) {
++ if (oe->lowerdentry && S_ISDIR(dentry->d_inode->i_mode))
++ return OVL_PATH_MERGE;
++ else
++ return OVL_PATH_UPPER;
++ } else {
++ return OVL_PATH_LOWER;
++ }
++}
++
++static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
++{
++ struct dentry *upperdentry = ACCESS_ONCE(oe->__upperdentry);
++ smp_read_barrier_depends();
++ return upperdentry;
++}
++
++void ovl_path_upper(struct dentry *dentry, struct path *path)
++{
++ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ path->mnt = ofs->upper_mnt;
++ path->dentry = ovl_upperdentry_dereference(oe);
++}
++
++void ovl_path_lower(struct dentry *dentry, struct path *path)
++{
++ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ path->mnt = ofs->lower_mnt;
++ path->dentry = oe->lowerdentry;
++}
++
++enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
++{
++
++ enum ovl_path_type type = ovl_path_type(dentry);
++
++ if (type == OVL_PATH_LOWER)
++ ovl_path_lower(dentry, path);
++ else
++ ovl_path_upper(dentry, path);
++
++ return type;
++}
++
++struct dentry *ovl_dentry_upper(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ return ovl_upperdentry_dereference(oe);
++}
++
++struct dentry *ovl_dentry_lower(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ return oe->lowerdentry;
++}
++
++struct dentry *ovl_dentry_real(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++ struct dentry *realdentry;
++
++ realdentry = ovl_upperdentry_dereference(oe);
++ if (!realdentry)
++ realdentry = oe->lowerdentry;
++
++ return realdentry;
++}
++
++struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
++{
++ struct dentry *realdentry;
++
++ realdentry = ovl_upperdentry_dereference(oe);
++ if (realdentry) {
++ *is_upper = true;
++ } else {
++ realdentry = oe->lowerdentry;
++ *is_upper = false;
++ }
++ return realdentry;
++}
++
++bool ovl_dentry_is_opaque(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++ return oe->opaque;
++}
++
++void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++ oe->opaque = opaque;
++}
++
++void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ WARN_ON(!mutex_is_locked(&upperdentry->d_parent->d_inode->i_mutex));
++ WARN_ON(oe->__upperdentry);
++ BUG_ON(!upperdentry->d_inode);
++ smp_wmb();
++ oe->__upperdentry = dget(upperdentry);
++}
++
++void ovl_dentry_version_inc(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
++ oe->version++;
++}
++
++u64 ovl_dentry_version_get(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ WARN_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
++ return oe->version;
++}
++
++bool ovl_is_whiteout(struct dentry *dentry)
++{
++ int res;
++ char val;
++
++ if (!dentry)
++ return false;
++ if (!dentry->d_inode)
++ return false;
++ if (!S_ISLNK(dentry->d_inode->i_mode))
++ return false;
++
++ res = vfs_getxattr(dentry, ovl_whiteout_xattr, &val, 1);
++ if (res == 1 && val == 'y')
++ return true;
++
++ return false;
++}
++
++static bool ovl_is_opaquedir(struct dentry *dentry)
++{
++ int res;
++ char val;
++
++ if (!S_ISDIR(dentry->d_inode->i_mode))
++ return false;
++
++ res = vfs_getxattr(dentry, ovl_opaque_xattr, &val, 1);
++ if (res == 1 && val == 'y')
++ return true;
++
++ return false;
++}
++
++static void ovl_entry_free(struct rcu_head *head)
++{
++ struct ovl_entry *oe = container_of(head, struct ovl_entry, rcu);
++ kfree(oe);
++}
++
++static void ovl_dentry_release(struct dentry *dentry)
++{
++ struct ovl_entry *oe = dentry->d_fsdata;
++
++ if (oe) {
++ dput(oe->__upperdentry);
++ dput(oe->__upperdentry);
++ dput(oe->lowerdentry);
++ call_rcu(&oe->rcu, ovl_entry_free);
++ }
++}
++
++const struct dentry_operations ovl_dentry_operations = {
++ .d_release = ovl_dentry_release,
++};
++
++static struct ovl_entry *ovl_alloc_entry(void)
++{
++ return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL);
++}
++
++static struct dentry *ovl_lookup_real(struct dentry *dir, struct qstr *name)
++{
++ struct dentry *dentry;
++
++ mutex_lock(&dir->d_inode->i_mutex);
++ dentry = lookup_one_len(name->name, dir, name->len);
++ mutex_unlock(&dir->d_inode->i_mutex);
++
++ if (IS_ERR(dentry)) {
++ if (PTR_ERR(dentry) == -ENOENT)
++ dentry = NULL;
++ } else if (!dentry->d_inode) {
++ dput(dentry);
++ dentry = NULL;
++ }
++ return dentry;
++}
++
++int ovl_do_lookup(struct dentry *dentry)
++{
++ struct ovl_entry *oe;
++ struct dentry *upperdir;
++ struct dentry *lowerdir;
++ struct dentry *upperdentry = NULL;
++ struct dentry *lowerdentry = NULL;
++ struct inode *inode = NULL;
++ int err;
++
++ err = -ENOMEM;
++ oe = ovl_alloc_entry();
++ if (!oe)
++ goto out;
++
++ upperdir = ovl_dentry_upper(dentry->d_parent);
++ lowerdir = ovl_dentry_lower(dentry->d_parent);
++
++ if (upperdir) {
++ upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
++ err = PTR_ERR(upperdentry);
++ if (IS_ERR(upperdentry))
++ goto out_put_dir;
++
++ if (lowerdir && upperdentry &&
++ (S_ISLNK(upperdentry->d_inode->i_mode) ||
++ S_ISDIR(upperdentry->d_inode->i_mode))) {
++ const struct cred *old_cred;
++ struct cred *override_cred;
++
++ err = -ENOMEM;
++ override_cred = prepare_creds();
++ if (!override_cred)
++ goto out_dput_upper;
++
++ /* CAP_SYS_ADMIN needed for getxattr */
++ cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
++ old_cred = override_creds(override_cred);
++
++ if (ovl_is_opaquedir(upperdentry)) {
++ oe->opaque = true;
++ } else if (ovl_is_whiteout(upperdentry)) {
++ dput(upperdentry);
++ upperdentry = NULL;
++ oe->opaque = true;
++ }
++ revert_creds(old_cred);
++ put_cred(override_cred);
++ }
++ }
++ if (lowerdir && !oe->opaque) {
++ lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name);
++ err = PTR_ERR(lowerdentry);
++ if (IS_ERR(lowerdentry))
++ goto out_dput_upper;
++ }
++
++ if (lowerdentry && upperdentry &&
++ (!S_ISDIR(upperdentry->d_inode->i_mode) ||
++ !S_ISDIR(lowerdentry->d_inode->i_mode))) {
++ dput(lowerdentry);
++ lowerdentry = NULL;
++ oe->opaque = true;
++ }
++
++ if (lowerdentry || upperdentry) {
++ struct dentry *realdentry;
++
++ realdentry = upperdentry ? upperdentry : lowerdentry;
++ err = -ENOMEM;
++ inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode, oe);
++ if (!inode)
++ goto out_dput;
++ }
++
++ if (upperdentry)
++ oe->__upperdentry = dget(upperdentry);
++
++ if (lowerdentry)
++ oe->lowerdentry = lowerdentry;
++
++ dentry->d_fsdata = oe;
++ dentry->d_op = &ovl_dentry_operations;
++ d_add(dentry, inode);
++
++ return 0;
++
++out_dput:
++ dput(lowerdentry);
++out_dput_upper:
++ dput(upperdentry);
++out_put_dir:
++ kfree(oe);
++out:
++ return err;
++}
++
++static void ovl_put_super(struct super_block *sb)
++{
++ struct ovl_fs *ufs = sb->s_fs_info;
++
++ if (!(sb->s_flags & MS_RDONLY))
++ mnt_drop_write(ufs->upper_mnt);
++
++ mntput(ufs->upper_mnt);
++ mntput(ufs->lower_mnt);
++
++ kfree(ufs->config.lowerdir);
++ kfree(ufs->config.upperdir);
++ kfree(ufs);
++}
++
++static int ovl_remount_fs(struct super_block *sb, int *flagsp, char *data)
++{
++ int flags = *flagsp;
++ struct ovl_fs *ufs = sb->s_fs_info;
++
++ /* When remounting rw or ro, we need to adjust the write access to the
++ * upper fs.
++ */
++ if (((flags ^ sb->s_flags) & MS_RDONLY) == 0)
++ /* No change to readonly status */
++ return 0;
++
++ if (flags & MS_RDONLY) {
++ mnt_drop_write(ufs->upper_mnt);
++ return 0;
++ } else
++ return mnt_want_write(ufs->upper_mnt);
++}
++
++/**
++ * ovl_statfs
++ * @sb: The overlayfs super block
++ * @buf: The struct kstatfs to fill in with stats
++ *
++ * Get the filesystem statistics. As writes always target the upper layer
++ * filesystem pass the statfs to the same filesystem.
++ */
++static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
++{
++ struct dentry *root_dentry = dentry->d_sb->s_root;
++ struct path path;
++ ovl_path_upper(root_dentry, &path);
++
++ if (!path.dentry->d_sb->s_op->statfs)
++ return -ENOSYS;
++ return path.dentry->d_sb->s_op->statfs(path.dentry, buf);
++}
++
++/**
++ * ovl_show_options
++ *
++ * Prints the mount options for a given superblock.
++ * Returns zero; does not fail.
++ */
++static int ovl_show_options(struct seq_file *m, struct vfsmount *mnt)
++{
++ struct super_block *sb = mnt->mnt_sb;
++ struct ovl_fs *ufs = sb->s_fs_info;
++
++ seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
++ seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
++ return 0;
++}
++
++static const struct super_operations ovl_super_operations = {
++ .put_super = ovl_put_super,
++ .remount_fs = ovl_remount_fs,
++ .statfs = ovl_statfs,
++ .show_options = ovl_show_options,
++};
++
++enum {
++ Opt_lowerdir,
++ Opt_upperdir,
++ Opt_err,
++};
++
++static const match_table_t ovl_tokens = {
++ {Opt_lowerdir, "lowerdir=%s"},
++ {Opt_upperdir, "upperdir=%s"},
++ {Opt_err, NULL}
++};
++
++static int ovl_parse_opt(char *opt, struct ovl_config *config)
++{
++ char *p;
++
++ config->upperdir = NULL;
++ config->lowerdir = NULL;
++
++ while ((p = strsep(&opt, ",")) != NULL) {
++ int token;
++ substring_t args[MAX_OPT_ARGS];
++
++ if (!*p)
++ continue;
++
++ token = match_token(p, ovl_tokens, args);
++ switch (token) {
++ case Opt_upperdir:
++ kfree(config->upperdir);
++ config->upperdir = match_strdup(&args[0]);
++ if (!config->upperdir)
++ return -ENOMEM;
++ break;
++
++ case Opt_lowerdir:
++ kfree(config->lowerdir);
++ config->lowerdir = match_strdup(&args[0]);
++ if (!config->lowerdir)
++ return -ENOMEM;
++ break;
++
++ default:
++ return -EINVAL;
++ }
++ }
++ return 0;
++}
++
++static int ovl_fill_super(struct super_block *sb, void *data, int silent)
++{
++ struct path lowerpath;
++ struct path upperpath;
++ struct inode *root_inode;
++ struct dentry *root_dentry;
++ struct ovl_entry *oe;
++ struct ovl_fs *ufs;
++ int err;
++
++ err = -ENOMEM;
++ ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
++ if (!ufs)
++ goto out;
++
++ err = ovl_parse_opt((char *) data, &ufs->config);
++ if (err)
++ goto out_free_ufs;
++
++ err = -EINVAL;
++ if (!ufs->config.upperdir || !ufs->config.lowerdir) {
++ printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
++ goto out_free_config;
++ }
++
++ oe = ovl_alloc_entry();
++ if (oe == NULL)
++ goto out_free_config;
++
++ root_inode = ovl_new_inode(sb, S_IFDIR, oe);
++ if (!root_inode)
++ goto out_free_oe;
++
++ err = kern_path(ufs->config.upperdir, LOOKUP_FOLLOW, &upperpath);
++ if (err)
++ goto out_put_root;
++
++ err = kern_path(ufs->config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
++ if (err)
++ goto out_put_upperpath;
++
++ err = -ENOTDIR;
++ if (!S_ISDIR(upperpath.dentry->d_inode->i_mode) ||
++ !S_ISDIR(lowerpath.dentry->d_inode->i_mode))
++ goto out_put_lowerpath;
++
++ ufs->upper_mnt = clone_private_mount(&upperpath);
++ err = PTR_ERR(ufs->upper_mnt);
++ if (IS_ERR(ufs->upper_mnt)) {
++ printk(KERN_ERR "overlayfs: failed to clone upperpath\n");
++ goto out_put_lowerpath;
++ }
++
++ ufs->lower_mnt = clone_private_mount(&lowerpath);
++ err = PTR_ERR(ufs->lower_mnt);
++ if (IS_ERR(ufs->lower_mnt)) {
++ printk(KERN_ERR "overlayfs: failed to clone lowerpath\n");
++ goto out_put_upper_mnt;
++ }
++
++ if (!(sb->s_flags & MS_RDONLY)) {
++ err = mnt_want_write(ufs->upper_mnt);
++ if (err)
++ goto out_put_lower_mnt;
++ }
++
++ err = -ENOMEM;
++ root_dentry = d_alloc_root(root_inode);
++ if (!root_dentry)
++ goto out_drop_write;
++
++ mntput(upperpath.mnt);
++ mntput(lowerpath.mnt);
++
++ oe->__upperdentry = dget(upperpath.dentry);
++ oe->lowerdentry = lowerpath.dentry;
++
++ root_dentry->d_fsdata = oe;
++ root_dentry->d_op = &ovl_dentry_operations;
++
++ sb->s_op = &ovl_super_operations;
++ sb->s_root = root_dentry;
++ sb->s_fs_info = ufs;
++
++ return 0;
++
++out_drop_write:
++ if (!(sb->s_flags & MS_RDONLY))
++ mnt_drop_write(ufs->upper_mnt);
++out_put_lower_mnt:
++ mntput(ufs->lower_mnt);
++out_put_upper_mnt:
++ mntput(ufs->upper_mnt);
++out_put_lowerpath:
++ path_put(&lowerpath);
++out_put_upperpath:
++ path_put(&upperpath);
++out_put_root:
++ iput(root_inode);
++out_free_oe:
++ kfree(oe);
++out_free_config:
++ kfree(ufs->config.lowerdir);
++ kfree(ufs->config.upperdir);
++out_free_ufs:
++ kfree(ufs);
++out:
++ return err;
++}
++
++static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
++ const char *dev_name, void *raw_data)
++{
++ return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
++}
++
++static struct file_system_type ovl_fs_type = {
++ .owner = THIS_MODULE,
++ .name = "overlayfs",
++ .mount = ovl_mount,
++ .kill_sb = kill_anon_super,
++};
++
++static int __init ovl_init(void)
++{
++ return register_filesystem(&ovl_fs_type);
++}
++
++static void __exit ovl_exit(void)
++{
++ unregister_filesystem(&ovl_fs_type);
++}
++
++module_init(ovl_init);
++module_exit(ovl_exit);
+--- /dev/null
++++ b/Documentation/filesystems/overlayfs.txt
+@@ -0,0 +1,167 @@
++Written by: Neil Brown <neilb@suse.de>
++
++Overlay Filesystem
++==================
++
++This document describes a prototype for a new approach to providing
++overlay-filesystem functionality in Linux (sometimes referred to as
++union-filesystems). An overlay-filesystem tries to present a
++filesystem which is the result over overlaying one filesystem on top
++of the other.
++
++The result will inevitably fail to look exactly like a normal
++filesystem for various technical reasons. The expectation is that
++many use cases will be able to ignore these differences.
++
++This approach is 'hybrid' because the objects that appear in the
++filesystem do not all appear to belong to that filesystem. In many
++cases an object accessed in the union will be indistinguishable
++from accessing the corresponding object from the original filesystem.
++This is most obvious from the 'st_dev' field returned by stat(2).
++
++While directories will report an st_dev from the overlay-filesystem,
++all non-directory objects will report an st_dev from the lower or
++upper filesystem that is providing the object. Similarly st_ino will
++only be unique when combined with st_dev, and both of these can change
++over the lifetime of a non-directory object. Many applications and
++tools ignore these values and will not be affected.
++
++Upper and Lower
++---------------
++
++An overlay filesystem combines two filesystems - an 'upper' filesystem
++and a 'lower' filesystem. When a name exists in both filesystems, the
++object in the 'upper' filesystem is visible while the object in the
++'lower' filesystem is either hidden or, in the case of directories,
++merged with the 'upper' object.
++
++It would be more correct to refer to an upper and lower 'directory
++tree' rather than 'filesystem' as it is quite possible for both
++directory trees to be in the same filesystem and there is no
++requirement that the root of a filesystem be given for either upper or
++lower.
++
++The lower filesystem can be any filesystem supported by Linux and does
++not need to be writable. The lower filesystem can even be another
++overlayfs. The upper filesystem will normally be writable and if it
++is it must support the creation of trusted.* extended attributes, and
++must provide valid d_type in readdir responses, at least for symbolic
++links - so NFS is not suitable.
++
++A read-only overlay of two read-only filesystems may use any
++filesystem type.
++
++Directories
++-----------
++
++Overlaying mainly involved directories. If a given name appears in both
++upper and lower filesystems and refers to a non-directory in either,
++then the lower object is hidden - the name refers only to the upper
++object.
++
++Where both upper and lower objects are directories, a merged directory
++is formed.
++
++At mount time, the two directories given as mount options are combined
++into a merged directory:
++
++ mount -t overlayfs overlayfs -olowerdir=/lower,upperdir=/upper /overlay
++
++Then whenever a lookup is requested in such a merged directory, the
++lookup is performed in each actual directory and the combined result
++is cached in the dentry belonging to the overlay filesystem. If both
++actual lookups find directories, both are stored and a merged
++directory is created, otherwise only one is stored: the upper if it
++exists, else the lower.
++
++Only the lists of names from directories are merged. Other content
++such as metadata and extended attributes are reported for the upper
++directory only. These attributes of the lower directory are hidden.
++
++whiteouts and opaque directories
++--------------------------------
++
++In order to support rm and rmdir without changing the lower
++filesystem, an overlay filesystem needs to record in the upper filesystem
++that files have been removed. This is done using whiteouts and opaque
++directories (non-directories are always opaque).
++
++The overlay filesystem uses extended attributes with a
++"trusted.overlay." prefix to record these details.
++
++A whiteout is created as a symbolic link with target
++"(overlay-whiteout)" and with xattr "trusted.overlay.whiteout" set to "y".
++When a whiteout is found in the upper level of a merged directory, any
++matching name in the lower level is ignored, and the whiteout itself
++is also hidden.
++
++A directory is made opaque by setting the xattr "trusted.overlay.opaque"
++to "y". Where the upper filesystem contains an opaque directory, any
++directory in the lower filesystem with the same name is ignored.
++
++readdir
++-------
++
++When a 'readdir' request is made on a merged directory, the upper and
++lower directories are each read and the name lists merged in the
++obvious way (upper is read first, then lower - entries that already
++exist are not re-added). This merged name list is cached in the
++'struct file' and so remains as long as the file is kept open. If the
++directory is opened and read by two processes at the same time, they
++will each have separate caches. A seekdir to the start of the
++directory (offset 0) followed by a readdir will cause the cache to be
++discarded and rebuilt.
++
++This means that changes to the merged directory do not appear while a
++directory is being read. This is unlikely to be noticed by many
++programs.
++
++seek offsets are assigned sequentially when the directories are read.
++Thus if
++ - read part of a directory
++ - remember an offset, and close the directory
++ - re-open the directory some time later
++ - seek to the remembered offset
++
++there may be little correlation between the old and new locations in
++the list of filenames, particularly if anything has changed in the
++directory.
++
++Readdir on directories that are not merged is simply handled by the
++underlying directory (upper or lower).
++
++
++Non-directories
++---------------
++
++Objects that are not directories (files, symlinks, device-special
++files etc.) are presented either from the upper or lower filesystem as
++appropriate. When a file in the lower filesystem is accessed in a way
++the requires write-access, such as opening for write access, changing
++some metadata etc., the file is first copied from the lower filesystem
++to the upper filesystem (copy_up). Note that creating a hard-link
++also requires copy_up, though of course creation of a symlink does
++not.
++
++The copy_up process first makes sure that the containing directory
++exists in the upper filesystem - creating it and any parents as
++necessary. It then creates the object with the same metadata (owner,
++mode, mtime, symlink-target etc.) and then if the object is a file, the
++data is copied from the lower to the upper filesystem. Finally any
++extended attributes are copied up.
++
++Once the copy_up is complete, the overlay filesystem simply
++provides direct access to the newly created file in the upper
++filesystem - future operations on the file are barely noticed by the
++overlay filesystem (though an operation on the name of the file such as
++rename or unlink will of course be noticed and handled).
++
++Changes to underlying filesystems
++---------------------------------
++
++Offline changes, when the overlay is not mounted, are allowed to either
++the upper or the lower trees.
++
++Changes to the underlying filesystems while part of a mounted overlay
++filesystem are not allowed. This is not yet enforced, but will be in
++the future.
+--- a/MAINTAINERS
++++ b/MAINTAINERS
+@@ -4713,6 +4713,13 @@ F: drivers/scsi/osd/
+ F: include/scsi/osd_*
+ F: fs/exofs/
+
++OVERLAYFS FILESYSTEM
++M: Miklos Szeredi <miklos@szeredi.hu>
++L: linux-fsdevel@vger.kernel.org
++S: Supported
++F: fs/overlayfs/*
++F: Documentation/filesystems/overlayfs.txt
++
+ P54 WIRELESS DRIVER
+ M: Christian Lamparter <chunkeey@googlemail.com>
+ L: linux-wireless@vger.kernel.org
projects / openwrt / svn-archive / archive.git / blobdiff