Release 4.10 fs/overlayfs/dir.c

/*
 *
 * 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/cred.h>
#include <linux/module.h>
#include <linux/posix_acl.h>
#include <linux/posix_acl_xattr.h>
#include <linux/atomic.h>
#include <linux/ratelimit.h>
#include "overlayfs.h"


static unsigned short ovl_redirect_max = 256;
module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
MODULE_PARM_DESC(ovl_redirect_max,
		 "Maximum length of absolute redirect xattr value");



void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
{
	int err;

	dget(wdentry);
	if (d_is_dir(wdentry))
		err = ovl_do_rmdir(wdir, wdentry);
	else
		err = ovl_do_unlink(wdir, wdentry);
	dput(wdentry);

	if (err) {
		pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
		       wdentry, err);
	}
}

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david howells
david howells
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struct dentry *ovl_lookup_temp(struct dentry *workdir, struct dentry *dentry)
{
	struct dentry *temp;
	char name[20];
	static atomic_t temp_id = ATOMIC_INIT(0);

	/* counter is allowed to wrap, since temp dentries are ephemeral */
	snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));

	temp = lookup_one_len(name, workdir, strlen(name));
	if (!IS_ERR(temp) && temp->d_inode) {
		pr_err("overlayfs: workdir/%s already exists\n", name);
		dput(temp);
		temp = ERR_PTR(-EIO);
	}

	return temp;
}

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richard weinberger
richard weinberger
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/* caller holds i_mutex on workdir */


static struct dentry *ovl_whiteout(struct dentry *workdir,
				   struct dentry *dentry)
{
	int err;
	struct dentry *whiteout;
	struct inode *wdir = workdir->d_inode;

	whiteout = ovl_lookup_temp(workdir, dentry);
	if (IS_ERR(whiteout))
		return whiteout;

	err = ovl_do_whiteout(wdir, whiteout);
	if (err) {
		dput(whiteout);
		whiteout = ERR_PTR(err);
	}

	return whiteout;
}

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int ovl_create_real(struct inode *dir, struct dentry *newdentry,
		    struct cattr *attr, struct dentry *hardlink, bool debug)
{
	int err;

	if (newdentry->d_inode)
		return -ESTALE;

	if (hardlink) {
		err = ovl_do_link(hardlink, dir, newdentry, debug);
	} else {
		switch (attr->mode & S_IFMT) {
		case S_IFREG:
			err = ovl_do_create(dir, newdentry, attr->mode, debug);
			break;

		case S_IFDIR:
			err = ovl_do_mkdir(dir, newdentry, attr->mode, debug);
			break;

		case S_IFCHR:
		case S_IFBLK:
		case S_IFIFO:
		case S_IFSOCK:
			err = ovl_do_mknod(dir, newdentry,
					   attr->mode, attr->rdev, debug);
			break;

		case S_IFLNK:
			err = ovl_do_symlink(dir, newdentry, attr->link, debug);
			break;

		default:
			err = -EPERM;
		}
	}
	if (!err && 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.
                 */
		err = -ENOENT;
	}
	return err;
}

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static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
{
	int err;

	err = ovl_do_setxattr(upperdentry, OVL_XATTR_OPAQUE, "y", 1, 0);
	if (!err)
		ovl_dentry_set_opaque(dentry);

	return err;
}

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hujianyang
hujianyang
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static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
			 struct kstat *stat)
{
	int err;
	enum ovl_path_type type;
	struct path realpath;
	const struct cred *old_cred;

	type = ovl_path_real(dentry, &realpath);
	old_cred = ovl_override_creds(dentry->d_sb);
	err = vfs_getattr(&realpath, stat);
	revert_creds(old_cred);
	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 (OVL_TYPE_MERGE(type))
		stat->nlink = 1;

	return 0;
}

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vivek goyal
vivek goyal
20
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/* Common operations required to be done after creation of file on upper */


static void ovl_instantiate(struct dentry *dentry, struct inode *inode,
			    struct dentry *newdentry, bool hardlink)
{
	ovl_dentry_version_inc(dentry->d_parent);
	ovl_dentry_update(dentry, newdentry);
	if (!hardlink) {
		ovl_inode_update(inode, d_inode(newdentry));
		ovl_copyattr(newdentry->d_inode, inode);
	} else {
		WARN_ON(ovl_inode_real(inode, NULL) != d_inode(newdentry));
		inc_nlink(inode);
	}
	d_instantiate(dentry, inode);
}

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vivek goyal
vivek goyal
51
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45.74%
2
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94
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3
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static bool ovl_type_merge(struct dentry *dentry)
{
	return OVL_TYPE_MERGE(ovl_path_type(dentry));
}

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amir goldstein
amir goldstein
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20
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static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
			    struct cattr *attr, struct dentry *hardlink)
{
	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
	struct inode *udir = upperdir->d_inode;
	struct dentry *newdentry;
	int err;

	if (!hardlink && !IS_POSIXACL(udir))
		attr->mode &= ~current_umask();

	inode_lock_nested(udir, I_MUTEX_PARENT);
	newdentry = lookup_one_len(dentry->d_name.name, upperdir,
				   dentry->d_name.len);
	err = PTR_ERR(newdentry);
	if (IS_ERR(newdentry))
		goto out_unlock;
	err = ovl_create_real(udir, newdentry, attr, hardlink, false);
	if (err)
		goto out_dput;

	if (ovl_type_merge(dentry->d_parent)) {
		/* Setting opaque here is just an optimization, allow to fail */
		ovl_set_opaque(dentry, newdentry);
	}

	ovl_instantiate(dentry, inode, newdentry, !!hardlink);
	newdentry = NULL;
out_dput:
	dput(newdentry);
out_unlock:
	inode_unlock(udir);
	return err;
}

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165
85.94%
3
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amir goldstein
amir goldstein
19
9.90%
1
14.29%
al viro
al viro
6
3.12%
2
28.57%
vivek goyal
vivek goyal
2
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1
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7
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static int ovl_lock_rename_workdir(struct dentry *workdir,
				   struct dentry *upperdir)
{
	/* Workdir should not be the same as upperdir */
	if (workdir == upperdir)
		goto err;

	/* Workdir should not be subdir of upperdir and vice versa */
	if (lock_rename(workdir, upperdir) != NULL)
		goto err_unlock;

	return 0;

err_unlock:
	unlock_rename(workdir, upperdir);
err:
	pr_err("overlayfs: failed to lock workdir+upperdir\n");
	return -EIO;
}

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static struct dentry *ovl_clear_empty(struct dentry *dentry,
				      struct list_head *list)
{
	struct dentry *workdir = ovl_workdir(dentry);
	struct inode *wdir = workdir->d_inode;
	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
	struct inode *udir = upperdir->d_inode;
	struct path upperpath;
	struct dentry *upper;
	struct dentry *opaquedir;
	struct kstat stat;
	int err;

	if (WARN_ON(!workdir))
		return ERR_PTR(-EROFS);

	err = ovl_lock_rename_workdir(workdir, upperdir);
	if (err)
		goto out;

	ovl_path_upper(dentry, &upperpath);
	err = vfs_getattr(&upperpath, &stat);
	if (err)
		goto out_unlock;

	err = -ESTALE;
	if (!S_ISDIR(stat.mode))
		goto out_unlock;
	upper = upperpath.dentry;
	if (upper->d_parent->d_inode != udir)
		goto out_unlock;

	opaquedir = ovl_lookup_temp(workdir, dentry);
	err = PTR_ERR(opaquedir);
	if (IS_ERR(opaquedir))
		goto out_unlock;

	err = ovl_create_real(wdir, opaquedir,
			      &(struct cattr){.mode = stat.mode}, NULL, true);
	if (err)
		goto out_dput;

	err = ovl_copy_xattr(upper, opaquedir);
	if (err)
		goto out_cleanup;

	err = ovl_set_opaque(dentry, opaquedir);
	if (err)
		goto out_cleanup;

	inode_lock(opaquedir->d_inode);
	err = ovl_set_attr(opaquedir, &stat);
	inode_unlock(opaquedir->d_inode);
	if (err)
		goto out_cleanup;

	err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
	if (err)
		goto out_cleanup;

	ovl_cleanup_whiteouts(upper, list);
	ovl_cleanup(wdir, upper);
	unlock_rename(workdir, upperdir);

	/* dentry's upper doesn't match now, get rid of it */
	d_drop(dentry);

	return opaquedir;

out_cleanup:
	ovl_cleanup(wdir, opaquedir);
out_dput:
	dput(opaquedir);
out_unlock:
	unlock_rename(workdir, upperdir);
out:
	return ERR_PTR(err);
}

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368
96.59%
3
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2
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381
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5
100.00%



static struct dentry *ovl_check_empty_and_clear(struct dentry *dentry)
{
	int err;
	struct dentry *ret = NULL;
	enum ovl_path_type type = ovl_path_type(dentry);
	LIST_HEAD(list);

	err = ovl_check_empty_dir(dentry, &list);
	if (err) {
		ret = ERR_PTR(err);
		goto out_free;
	}

	/*
         * When removing an empty opaque directory, then it makes no sense to
         * replace it with an exact replica of itself.
         *
         * If no upperdentry then skip clearing whiteouts.
         *
         * Can race with copy-up, since we don't hold the upperdir mutex.
         * Doesn't matter, since copy-up can't create a non-empty directory
         * from an empty one.
         */
	if (OVL_TYPE_UPPER(type) && OVL_TYPE_MERGE(type))
		ret = ovl_clear_empty(dentry, &list);

out_free:
	ovl_cache_free(&list);

	return ret;
}

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static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
			     const struct posix_acl *acl)
{
	void *buffer;
	size_t size;
	int err;

	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
		return 0;

	size = posix_acl_to_xattr(NULL, acl, NULL, 0);
	buffer = kmalloc(size, GFP_KERNEL);
	if (!buffer)
		return -ENOMEM;

	size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
	err = size;
	if (err < 0)
		goto out_free;

	err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
out_free:
	kfree(buffer);
	return err;
}

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static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
				    struct cattr *cattr,
				    struct dentry *hardlink)
{
	struct dentry *workdir = ovl_workdir(dentry);
	struct inode *wdir = workdir->d_inode;
	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
	struct inode *udir = upperdir->d_inode;
	struct dentry *upper;
	struct dentry *newdentry;
	int err;
	struct posix_acl *acl, *default_acl;

	if (WARN_ON(!workdir))
		return -EROFS;

	if (!hardlink) {
		err = posix_acl_create(dentry->d_parent->d_inode,
				       &cattr->mode, &default_acl, &acl);
		if (err)
			return err;
	}

	err = ovl_lock_rename_workdir(workdir, upperdir);
	if (err)
		goto out;

	newdentry = ovl_lookup_temp(workdir, dentry);
	err = PTR_ERR(newdentry);
	if (IS_ERR(newdentry))
		goto out_unlock;

	upper = lookup_one_len(dentry->d_name.name, upperdir,
			       dentry->d_name.len);
	err = PTR_ERR(upper);
	if (IS_ERR(upper))
		goto out_dput;

	err = ovl_create_real(wdir, newdentry, cattr, hardlink, true);
	if (err)
		goto out_dput2;

	/*
         * mode could have been mutilated due to umask (e.g. sgid directory)
         */
	if (!hardlink &&
	    !S_ISLNK(cattr->mode) &&
	    newdentry->d_inode->i_mode != cattr->mode) {
		struct iattr attr = {
			.ia_valid = ATTR_MODE,
			.ia_mode = cattr->mode,
                };
		inode_lock(newdentry->d_inode);
		err = notify_change(newdentry, &attr, NULL);
		inode_unlock(newdentry->d_inode);
		if (err)
			goto out_cleanup;
	}
	if (!hardlink) {
		err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
					acl);
		if (err)
			goto out_cleanup;

		err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
					default_acl);
		if (err)
			goto out_cleanup;
	}

	if (!hardlink && S_ISDIR(cattr->mode)) {
		err = ovl_set_opaque(dentry, newdentry);
		if (err)
			goto out_cleanup;

		err = ovl_do_rename(wdir, newdentry, udir, upper,
				    RENAME_EXCHANGE);
		if (err)
			goto out_cleanup;

		ovl_cleanup(wdir, upper);
	} else {
		err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
		if (err)
			goto out_cleanup;
	}
	ovl_instantiate(dentry, inode, newdentry, !!hardlink);
	newdentry = NULL;
out_dput2:
	dput(upper);
out_dput:
	dput(newdentry);
out_unlock:
	unlock_rename(workdir, upperdir);
out:
	if (!hardlink) {
		posix_acl_release(acl);
		posix_acl_release(default_acl);
	}
	return err;

out_cleanup:
	ovl_cleanup(wdir, newdentry);
	goto out_dput2;
}

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503
98.05%
6
75.00%
al viro
al viro
8
1.56%
1
12.50%
vivek goyal
vivek goyal
2
0.39%
1
12.50%
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513
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8
100.00%



static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
			      struct cattr *attr, struct dentry *hardlink)
{
	int err;
	const struct cred *old_cred;
	struct cred *override_cred;

	err = ovl_copy_up(dentry->d_parent);
	if (err)
		return err;

	old_cred = ovl_override_creds(dentry->d_sb);
	err = -ENOMEM;
	override_cred = prepare_creds();
	if (override_cred) {
		override_cred->fsuid = inode->i_uid;
		override_cred->fsgid = inode->i_gid;
		if (!hardlink) {
			err = security_dentry_create_files_as(dentry,
					attr->mode, &dentry->d_name, old_cred,
					override_cred);
			if (err) {
				put_cred(override_cred);
				goto out_revert_creds;
			}
		}
		put_cred(override_creds(override_cred));
		put_cred(override_cred);

		if (!ovl_dentry_is_whiteout(dentry))
			err = ovl_create_upper(dentry, inode, attr,
						hardlink);
		else
			err = ovl_create_over_whiteout(dentry, inode, attr,
							hardlink);
	}
out_revert_creds:
	revert_creds(old_cred);
	if (!err) {
		struct inode *realinode = d_inode(ovl_dentry_upper(dentry));

		WARN_ON(inode->i_mode != realinode->i_mode);
		WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
		WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
	}
	return err;
}

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miklos szeredi
175
68.09%
5
55.56%
vivek goyal
vivek goyal
73
28.40%
2
22.22%
al viro
al viro
5
1.95%
1
11.11%
antonio murdaca
antonio murdaca
4
1.56%
1
11.11%
Total
257
100.00%
9
100.00%



static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
			     const char *link)
{
	int err;
	struct inode *inode;
	struct cattr attr = {
		.rdev = rdev,
		.link = link,
        };

	err = ovl_want_write(dentry);
	if (err)
		goto out;

	err = -ENOMEM;
	inode = ovl_new_inode(dentry->d_sb, mode, rdev);
	if (!inode)
		goto out_drop_write;

	inode_init_owner(inode, dentry->d_parent->d_inode, mode);
	attr.mode = inode->i_mode;

	err = ovl_create_or_link(dentry, inode, &attr, NULL);
	if (err)
		iput(inode);

out_drop_write:
	ovl_drop_write(dentry);
out:
	return err;
}

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133
93.66%
3
75.00%
al viro
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9
6.34%
1
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142
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4
100.00%



static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
		      bool excl)
{
	return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
}

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40
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static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
	return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
}

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37
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static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
		     dev_t rdev)
{
	/* Don't allow creation of "whiteout" on overlay */
	if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
		return -EPERM;

	return ovl_create_object(dentry, mode, rdev, NULL);
}

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50
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static int ovl_symlink(struct inode *dir, struct dentry *dentry,
		       const char *link)
{
	return ovl_create_object(dentry, S_IFLNK, 0, link);
}

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1
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1
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static int ovl_link(struct dentry *old, struct inode *newdir,
		    struct dentry *new)
{
	int err;
	struct inode *inode;

	err = ovl_want_write(old);
	if (err)
		goto out;

	err = ovl_copy_up(old);
	if (err)
		goto out_drop_write;

	inode = d_inode(old);
	ihold(inode);

	err = ovl_create_or_link(new, inode, NULL, ovl_dentry_upper(old));
	if (err)
		iput(inode);

out_drop_write:
	ovl_drop_write(old);
out:
	return err;
}

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106
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106
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2
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static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
{
	struct dentry *workdir = ovl_workdir(dentry);
	struct inode *wdir = workdir->d_inode;
	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
	struct inode *udir = upperdir->d_inode;
	struct dentry *whiteout;
	struct dentry *upper;
	struct dentry *opaquedir = NULL;
	int err;
	int flags = 0;

	if (WARN_ON(!workdir))
		return -EROFS;

	if (is_dir) {
		opaquedir = ovl_check_empty_and_clear(dentry);
		err = PTR_ERR(opaquedir);
		if (IS_ERR(opaquedir))
			goto out;
	}

	err = ovl_lock_rename_workdir(workdir, upperdir);
	if (err)
		goto out_dput;

	upper = lookup_one_len(dentry->d_name.name, upperdir,
			       dentry->d_name.len);
	err = PTR_ERR(upper);
	if (IS_ERR(upper))
		goto out_unlock;

	err = -ESTALE;
	if ((opaquedir && upper != opaquedir) ||
	    (!opaquedir && ovl_dentry_upper(dentry) &&
	     upper != ovl_dentry_upper(dentry))) {
		goto out_dput_upper;
	}

	whiteout = ovl_whiteout(workdir, dentry);
	err = PTR_ERR(whiteout);
	if (IS_ERR(whiteout))
		goto out_dput_upper;

	if (d_is_dir(upper))
		flags = RENAME_EXCHANGE;

	err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
	if (err)
		goto kill_whiteout;
	if (flags)
		ovl_cleanup(