fs/overlayfs/dir.c - kernel/lockdown - Git at Google

 /*
  *
  * 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 "overlayfs.h"

 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);
 	}
 }

 struct dentry *ovl_lookup_temp(struct dentry *workdir, struct dentry *dentry)
 {
 	struct dentry *temp;
 	char name[20];

 	snprintf(name, sizeof(name), "#%lx", (unsigned long) dentry);

 	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;
 }

 /* 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;
 }

 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
 		    struct kstat *stat, const char *link,
 		    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 (stat->mode & S_IFMT) {
 		case S_IFREG:
 			err = ovl_do_create(dir, newdentry, stat->mode, debug);
 			break;

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

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

 		case S_IFLNK:
 			err = ovl_do_symlink(dir, newdentry, 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;
 }

 static int ovl_set_opaque(struct dentry *upperdentry)
 {
 	return ovl_do_setxattr(upperdentry, OVL_XATTR_OPAQUE, "y", 1, 0);
 }

 static void ovl_remove_opaque(struct dentry *upperdentry)
 {
 	int err;

 	err = ovl_do_removexattr(upperdentry, OVL_XATTR_OPAQUE);
 	if (err) {
 		pr_warn("overlayfs: failed to remove opaque from '%s' (%i)\n",
 			upperdentry->d_name.name, 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, 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 (OVL_TYPE_MERGE(type))
 		stat->nlink = 1;

 	return 0;
 }

 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 			    struct kstat *stat, const char *link,
 			    struct dentry *hardlink)
 {
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 	struct inode *udir = upperdir->d_inode;
 	struct dentry *newdentry;
 	int err;

 	mutex_lock_nested(&udir->i_mutex, 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, stat, link, hardlink, false);
 	if (err)
 		goto out_dput;

 	ovl_dentry_version_inc(dentry->d_parent);
 	ovl_dentry_update(dentry, newdentry);
 	ovl_copyattr(newdentry->d_inode, inode);
 	d_instantiate(dentry, inode);
 	newdentry = NULL;
 out_dput:
 	dput(newdentry);
 out_unlock:
 	mutex_unlock(&udir->i_mutex);
 	return err;
 }

 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;
 }

 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, &stat, NULL, NULL, true);
 	if (err)
 		goto out_dput;

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

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

 	mutex_lock(&opaquedir->d_inode->i_mutex);
 	err = ovl_set_attr(opaquedir, &stat);
 	mutex_unlock(&opaquedir->d_inode->i_mutex);
 	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);
 }

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

 	err = ovl_check_empty_dir(dentry, &list);
 	if (err)
 		ret = ERR_PTR(err);
 	else {
 		/*
 		 * 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_dentry_upper(dentry))
 			ret = ovl_clear_empty(dentry, &list);
 	}

 	ovl_cache_free(&list);

 	return ret;
 }

 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 				    struct kstat *stat, const char *link,
 				    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;

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

 	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, stat, link, hardlink, true);
 	if (err)
 		goto out_dput2;

 	if (S_ISDIR(stat->mode)) {
 		err = ovl_set_opaque(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_dentry_version_inc(dentry->d_parent);
 	ovl_dentry_update(dentry, newdentry);
 	ovl_copyattr(newdentry->d_inode, inode);
 	d_instantiate(dentry, inode);
 	newdentry = NULL;
 out_dput2:
 	dput(upper);
 out_dput:
 	dput(newdentry);
 out_unlock:
 	unlock_rename(workdir, upperdir);
 out:
 	return err;

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

 static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev,
 			      const char *link, struct dentry *hardlink)
 {
 	int err;
 	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;

 	if (!ovl_dentry_is_opaque(dentry)) {
 		err = ovl_create_upper(dentry, inode, &stat, link, hardlink);
 	} else {
 		const struct cred *old_cred;
 		struct cred *override_cred;

 		err = -ENOMEM;
 		override_cred = prepare_creds();
 		if (!override_cred)
 			goto out_iput;

 		/*
 		 * CAP_SYS_ADMIN for setting opaque xattr
 		 * CAP_DAC_OVERRIDE for create in workdir, rename
 		 * CAP_FOWNER for removing whiteout from sticky dir
 		 */
 		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);
 		old_cred = override_creds(override_cred);

 		err = ovl_create_over_whiteout(dentry, inode, &stat, link,
 					       hardlink);

 		revert_creds(old_cred);
 		put_cred(override_cred);
 	}

 	if (!err)
 		inode = NULL;
 out_iput:
 	iput(inode);
 out:
 	return err;
 }

 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 			     const char *link)
 {
 	int err;

 	err = ovl_want_write(dentry);
 	if (!err) {
 		err = ovl_create_or_link(dentry, mode, rdev, link, NULL);
 		ovl_drop_write(dentry);
 	}

 	return err;
 }

 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);
 }

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

 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);
 }

 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_link(struct dentry *old, struct inode *newdir,
 		    struct dentry *new)
 {
 	int err;
 	struct dentry *upper;

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

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

 	upper = ovl_dentry_upper(old);
 	err = ovl_create_or_link(new, upper->d_inode->i_mode, 0, NULL, upper);

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

 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;

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

 	if (is_dir) {
 		if (OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
 			opaquedir = ovl_check_empty_and_clear(dentry);
 			err = PTR_ERR(opaquedir);
 			if (IS_ERR(opaquedir))
 				goto out;
 		} else {
 			LIST_HEAD(list);

 			/*
 			 * When removing an empty opaque directory, then it
 			 * makes no sense to replace it with an exact replica of
 			 * itself.  But emptiness still needs to be checked.
 			 */
 			err = ovl_check_empty_dir(dentry, &list);
 			ovl_cache_free(&list);
 			if (err)
 				goto out;
 		}
 	}

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

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

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

 		err = ovl_do_rename(wdir, whiteout, udir, upper, 0);
 		dput(upper);
 		if (err)
 			goto kill_whiteout;
 	} else {
 		int flags = 0;

 		if (opaquedir)
 			upper = opaquedir;
 		err = -ESTALE;
 		if (upper->d_parent != upperdir)
 			goto kill_whiteout;

 		if (is_dir)
 			flags |= RENAME_EXCHANGE;

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

 		if (is_dir)
 			ovl_cleanup(wdir, upper);
 	}
 	ovl_dentry_version_inc(dentry->d_parent);
 out_d_drop:
 	d_drop(dentry);
 	dput(whiteout);
 out_unlock:
 	unlock_rename(workdir, upperdir);
 out_dput:
 	dput(opaquedir);
 out:
 	return err;

 kill_whiteout:
 	ovl_cleanup(wdir, whiteout);
 	goto out_d_drop;
 }

 static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 {
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 	struct inode *dir = upperdir->d_inode;
 	struct dentry *upper = ovl_dentry_upper(dentry);
 	int err;

 	mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
 	err = -ESTALE;
 	if (upper->d_parent == upperdir) {
 		/* Don't let d_delete() think it can reset d_inode */
 		dget(upper);
 		if (is_dir)
 			err = vfs_rmdir(dir, upper);
 		else
 			err = vfs_unlink(dir, upper, NULL);
 		dput(upper);
 		ovl_dentry_version_inc(dentry->d_parent);
 	}

 	/*
 	 * 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.
 	 */
 	d_drop(dentry);
 	mutex_unlock(&dir->i_mutex);

 	return err;
 }

 static inline int ovl_check_sticky(struct dentry *dentry)
 {
 	struct inode *dir = ovl_dentry_real(dentry->d_parent)->d_inode;
 	struct inode *inode = ovl_dentry_real(dentry)->d_inode;

 	if (check_sticky(dir, inode))
 		return -EPERM;

 	return 0;
 }

 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 {
 	enum ovl_path_type type;
 	int err;

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

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

 	err = ovl_copy_up(dentry->d_parent);
 	if (err)
 		goto out_drop_write;

 	type = ovl_path_type(dentry);
 	if (OVL_TYPE_PURE_UPPER(type)) {
 		err = ovl_remove_upper(dentry, is_dir);
 	} else {
 		const struct cred *old_cred;
 		struct cred *override_cred;

 		err = -ENOMEM;
 		override_cred = prepare_creds();
 		if (!override_cred)
 			goto out_drop_write;

 		/*
 		 * CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
 		 * CAP_DAC_OVERRIDE for create in workdir, rename
 		 * CAP_FOWNER for removing whiteout from sticky dir
 		 * CAP_FSETID for chmod of opaque dir
 		 * CAP_CHOWN for chown of opaque dir
 		 */
 		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_CHOWN);
 		old_cred = override_creds(override_cred);

 		err = ovl_remove_and_whiteout(dentry, is_dir);

 		revert_creds(old_cred);
 		put_cred(override_cred);
 	}
 out_drop_write:
 	ovl_drop_write(dentry);
 out:
 	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)
 {
 	return ovl_do_remove(dentry, true);
 }

 static int ovl_rename2(struct inode *olddir, struct dentry *old,
 		       struct inode *newdir, struct dentry *new,
 		       unsigned int flags)
 {
 	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 cleanup_whiteout = false;
 	bool overwrite = !(flags & RENAME_EXCHANGE);
 	bool is_dir = d_is_dir(old);
 	bool new_is_dir = false;
 	struct dentry *opaquedir = NULL;
 	const struct cred *old_cred = NULL;
 	struct cred *override_cred = NULL;

 	err = -EINVAL;
 	if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
 		goto out;

 	flags &= ~RENAME_NOREPLACE;

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

 	/* Don't copy up directory trees */
 	old_type = ovl_path_type(old);
 	err = -EXDEV;
 	if (OVL_TYPE_MERGE_OR_LOWER(old_type) && is_dir)
 		goto out;

 	if (new->d_inode) {
 		err = ovl_check_sticky(new);
 		if (err)
 			goto out;

 		if (d_is_dir(new))
 			new_is_dir = true;

 		new_type = ovl_path_type(new);
 		err = -EXDEV;
 		if (!overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir)
 			goto out;

 		err = 0;
 		if (!OVL_TYPE_UPPER(new_type) && !OVL_TYPE_UPPER(old_type)) {
 			if (ovl_dentry_lower(old)->d_inode ==
 			    ovl_dentry_lower(new)->d_inode)
 				goto out;
 		}
 		if (OVL_TYPE_UPPER(new_type) && OVL_TYPE_UPPER(old_type)) {
 			if (ovl_dentry_upper(old)->d_inode ==
 			    ovl_dentry_upper(new)->d_inode)
 				goto out;
 		}
 	} else {
 		if (ovl_dentry_is_opaque(new))
 			new_type = __OVL_PATH_UPPER;
 		else
 			new_type = __OVL_PATH_UPPER | __OVL_PATH_PURE;
 	}

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

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

 	err = ovl_copy_up(new->d_parent);
 	if (err)
 		goto out_drop_write;
 	if (!overwrite) {
 		err = ovl_copy_up(new);
 		if (err)
 			goto out_drop_write;
 	}

 	old_opaque = !OVL_TYPE_PURE_UPPER(old_type);
 	new_opaque = !OVL_TYPE_PURE_UPPER(new_type);

 	if (old_opaque || new_opaque) {
 		err = -ENOMEM;
 		override_cred = prepare_creds();
 		if (!override_cred)
 			goto out_drop_write;

 		/*
 		 * CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
 		 * CAP_DAC_OVERRIDE for create in workdir
 		 * CAP_FOWNER for removing whiteout from sticky dir
 		 * CAP_FSETID for chmod of opaque dir
 		 * CAP_CHOWN for chown of opaque dir
 		 */
 		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_CHOWN);
 		old_cred = override_creds(override_cred);
 	}

 	if (overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir) {
 		opaquedir = ovl_check_empty_and_clear(new);
 		err = PTR_ERR(opaquedir);
 		if (IS_ERR(opaquedir)) {
 			opaquedir = NULL;
 			goto out_revert_creds;
 		}
 	}

 	if (overwrite) {
 		if (old_opaque) {
 			if (new->d_inode || !new_opaque) {
 				/* Whiteout source */
 				flags |= RENAME_WHITEOUT;
 			} else {
 				/* Switch whiteouts */
 				flags |= RENAME_EXCHANGE;
 			}
 		} else if (is_dir && !new->d_inode && new_opaque) {
 			flags |= RENAME_EXCHANGE;
 			cleanup_whiteout = true;
 		}
 	}

 	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) {
 		if (opaquedir) {
 			newdentry = opaquedir;
 			opaquedir = NULL;
 		} else {
 			dget(newdentry);
 		}
 	} else {
 		new_create = true;
 		newdentry = lookup_one_len(new->d_name.name, new_upperdir,
 					   new->d_name.len);
 		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;

 	if (is_dir && !old_opaque && new_opaque) {
 		err = ovl_set_opaque(olddentry);
 		if (err)
 			goto out_dput;
 	}
 	if (!overwrite && new_is_dir && old_opaque && !new_opaque) {
 		err = ovl_set_opaque(newdentry);
 		if (err)
 			goto out_dput;
 	}

 	if (old_opaque || new_opaque) {
 		err = ovl_do_rename(old_upperdir->d_inode, olddentry,
 				    new_upperdir->d_inode, newdentry,
 				    flags);
 	} else {
 		/* No debug for the plain case */
 		BUG_ON(flags & ~RENAME_EXCHANGE);
 		err = vfs_rename(old_upperdir->d_inode, olddentry,
 				 new_upperdir->d_inode, newdentry,
 				 NULL, flags);
 	}

 	if (err) {
 		if (is_dir && !old_opaque && new_opaque)
 			ovl_remove_opaque(olddentry);
 		if (!overwrite && new_is_dir && old_opaque && !new_opaque)
 			ovl_remove_opaque(newdentry);
 		goto out_dput;
 	}

 	if (is_dir && old_opaque && !new_opaque)
 		ovl_remove_opaque(olddentry);
 	if (!overwrite && new_is_dir && !old_opaque && new_opaque)
 		ovl_remove_opaque(newdentry);

 	if (old_opaque != new_opaque) {
 		ovl_dentry_set_opaque(old, new_opaque);
 		if (!overwrite)
 			ovl_dentry_set_opaque(new, old_opaque);
 	}

 	if (cleanup_whiteout)
 		ovl_cleanup(old_upperdir->d_inode, newdentry);

 	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);
 out_revert_creds:
 	if (old_opaque || new_opaque) {
 		revert_creds(old_cred);
 		put_cred(override_cred);
 	}
 out_drop_write:
 	ovl_drop_write(old);
 out:
 	dput(opaquedir);
 	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,
 	.rename2	= ovl_rename2,
 	.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,
 };
	/*
	*
	* 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 "overlayfs.h"

	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);
	}
	}

	struct dentry ovl_lookup_temp(struct dentry workdir, struct dentry *dentry)
	{
	struct dentry *temp;
	char name[20];

	snprintf(name, sizeof(name), "#%lx", (unsigned long) dentry);

	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;
	}

	/* 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;
	}

	int ovl_create_real(struct inode dir, struct dentry newdentry,
	struct kstat stat, const char link,
	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 (stat->mode & S_IFMT) {
	case S_IFREG:
	err = ovl_do_create(dir, newdentry, stat->mode, debug);
	break;

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

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

	case S_IFLNK:
	err = ovl_do_symlink(dir, newdentry, 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;
	}

	static int ovl_set_opaque(struct dentry *upperdentry)
	{
	return ovl_do_setxattr(upperdentry, OVL_XATTR_OPAQUE, "y", 1, 0);
	}

	static void ovl_remove_opaque(struct dentry *upperdentry)
	{
	int err;

	err = ovl_do_removexattr(upperdentry, OVL_XATTR_OPAQUE);
	if (err) {
	pr_warn("overlayfs: failed to remove opaque from '%s' (%i)\n",
	upperdentry->d_name.name, 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, 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 (OVL_TYPE_MERGE(type))
	stat->nlink = 1;

	return 0;
	}

	static int ovl_create_upper(struct dentry dentry, struct inode inode,
	struct kstat stat, const char link,
	struct dentry *hardlink)
	{
	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
	struct inode *udir = upperdir->d_inode;
	struct dentry *newdentry;
	int err;

	mutex_lock_nested(&udir->i_mutex, 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, stat, link, hardlink, false);
	if (err)
	goto out_dput;

	ovl_dentry_version_inc(dentry->d_parent);
	ovl_dentry_update(dentry, newdentry);
	ovl_copyattr(newdentry->d_inode, inode);
	d_instantiate(dentry, inode);
	newdentry = NULL;
	out_dput:
	dput(newdentry);
	out_unlock:
	mutex_unlock(&udir->i_mutex);
	return err;
	}

	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;
	}

	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, &stat, NULL, NULL, true);
	if (err)
	goto out_dput;

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

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

	mutex_lock(&opaquedir->d_inode->i_mutex);
	err = ovl_set_attr(opaquedir, &stat);
	mutex_unlock(&opaquedir->d_inode->i_mutex);
	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);
	}

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

	err = ovl_check_empty_dir(dentry, &list);
	if (err)
	ret = ERR_PTR(err);
	else {
	/*
	* 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_dentry_upper(dentry))
	ret = ovl_clear_empty(dentry, &list);
	}

	ovl_cache_free(&list);

	return ret;
	}

	static int ovl_create_over_whiteout(struct dentry dentry, struct inode inode,
	struct kstat stat, const char link,
	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;

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

	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, stat, link, hardlink, true);
	if (err)
	goto out_dput2;

	if (S_ISDIR(stat->mode)) {
	err = ovl_set_opaque(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_dentry_version_inc(dentry->d_parent);
	ovl_dentry_update(dentry, newdentry);
	ovl_copyattr(newdentry->d_inode, inode);
	d_instantiate(dentry, inode);
	newdentry = NULL;
	out_dput2:
	dput(upper);
	out_dput:
	dput(newdentry);
	out_unlock:
	unlock_rename(workdir, upperdir);
	out:
	return err;

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

	static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev,
	const char link, struct dentry hardlink)
	{
	int err;
	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;

	if (!ovl_dentry_is_opaque(dentry)) {
	err = ovl_create_upper(dentry, inode, &stat, link, hardlink);
	} else {
	const struct cred *old_cred;
	struct cred *override_cred;

	err = -ENOMEM;
	override_cred = prepare_creds();
	if (!override_cred)
	goto out_iput;

	/*
	* CAP_SYS_ADMIN for setting opaque xattr
	* CAP_DAC_OVERRIDE for create in workdir, rename
	* CAP_FOWNER for removing whiteout from sticky dir
	*/
	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);
	old_cred = override_creds(override_cred);

	err = ovl_create_over_whiteout(dentry, inode, &stat, link,
	hardlink);

	revert_creds(old_cred);
	put_cred(override_cred);
	}

	if (!err)
	inode = NULL;
	out_iput:
	iput(inode);
	out:
	return err;
	}

	static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
	const char *link)
	{
	int err;

	err = ovl_want_write(dentry);
	if (!err) {
	err = ovl_create_or_link(dentry, mode, rdev, link, NULL);
	ovl_drop_write(dentry);
	}

	return err;
	}

	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);
	}

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

	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);
	}

	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_link(struct dentry old, struct inode newdir,
	struct dentry *new)
	{
	int err;
	struct dentry *upper;

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

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

	upper = ovl_dentry_upper(old);
	err = ovl_create_or_link(new, upper->d_inode->i_mode, 0, NULL, upper);

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

	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;

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

	if (is_dir) {
	if (OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
	opaquedir = ovl_check_empty_and_clear(dentry);
	err = PTR_ERR(opaquedir);
	if (IS_ERR(opaquedir))
	goto out;
	} else {
	LIST_HEAD(list);

	/*
	* When removing an empty opaque directory, then it
	* makes no sense to replace it with an exact replica of
	* itself. But emptiness still needs to be checked.
	*/
	err = ovl_check_empty_dir(dentry, &list);
	ovl_cache_free(&list);
	if (err)
	goto out;
	}
	}

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

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

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

	err = ovl_do_rename(wdir, whiteout, udir, upper, 0);
	dput(upper);
	if (err)
	goto kill_whiteout;
	} else {
	int flags = 0;

	if (opaquedir)
	upper = opaquedir;
	err = -ESTALE;
	if (upper->d_parent != upperdir)
	goto kill_whiteout;

	if (is_dir)
	flags \|= RENAME_EXCHANGE;

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

	if (is_dir)
	ovl_cleanup(wdir, upper);
	}
	ovl_dentry_version_inc(dentry->d_parent);
	out_d_drop:
	d_drop(dentry);
	dput(whiteout);
	out_unlock:
	unlock_rename(workdir, upperdir);
	out_dput:
	dput(opaquedir);
	out:
	return err;

	kill_whiteout:
	ovl_cleanup(wdir, whiteout);
	goto out_d_drop;
	}

	static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
	{
	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
	struct inode *dir = upperdir->d_inode;
	struct dentry *upper = ovl_dentry_upper(dentry);
	int err;

	mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
	err = -ESTALE;
	if (upper->d_parent == upperdir) {
	/* Don't let d_delete() think it can reset d_inode */
	dget(upper);
	if (is_dir)
	err = vfs_rmdir(dir, upper);
	else
	err = vfs_unlink(dir, upper, NULL);
	dput(upper);
	ovl_dentry_version_inc(dentry->d_parent);
	}

	/*
	* 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.
	*/
	d_drop(dentry);
	mutex_unlock(&dir->i_mutex);

	return err;
	}

	static inline int ovl_check_sticky(struct dentry *dentry)
	{
	struct inode *dir = ovl_dentry_real(dentry->d_parent)->d_inode;
	struct inode *inode = ovl_dentry_real(dentry)->d_inode;

	if (check_sticky(dir, inode))
	return -EPERM;

	return 0;
	}

	static int ovl_do_remove(struct dentry *dentry, bool is_dir)
	{
	enum ovl_path_type type;
	int err;

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

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

	err = ovl_copy_up(dentry->d_parent);
	if (err)
	goto out_drop_write;

	type = ovl_path_type(dentry);
	if (OVL_TYPE_PURE_UPPER(type)) {
	err = ovl_remove_upper(dentry, is_dir);
	} else {
	const struct cred *old_cred;
	struct cred *override_cred;

	err = -ENOMEM;
	override_cred = prepare_creds();
	if (!override_cred)
	goto out_drop_write;

	/*
	* CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
	* CAP_DAC_OVERRIDE for create in workdir, rename
	* CAP_FOWNER for removing whiteout from sticky dir
	* CAP_FSETID for chmod of opaque dir
	* CAP_CHOWN for chown of opaque dir
	*/
	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_CHOWN);
	old_cred = override_creds(override_cred);

	err = ovl_remove_and_whiteout(dentry, is_dir);

	revert_creds(old_cred);
	put_cred(override_cred);
	}
	out_drop_write:
	ovl_drop_write(dentry);
	out:
	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)
	{
	return ovl_do_remove(dentry, true);
	}

	static int ovl_rename2(struct inode olddir, struct dentry old,
	struct inode newdir, struct dentry new,
	unsigned int flags)
	{
	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 cleanup_whiteout = false;
	bool overwrite = !(flags & RENAME_EXCHANGE);
	bool is_dir = d_is_dir(old);
	bool new_is_dir = false;
	struct dentry *opaquedir = NULL;
	const struct cred *old_cred = NULL;
	struct cred *override_cred = NULL;

	err = -EINVAL;
	if (flags & ~(RENAME_EXCHANGE \| RENAME_NOREPLACE))
	goto out;

	flags &= ~RENAME_NOREPLACE;

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

	/* Don't copy up directory trees */
	old_type = ovl_path_type(old);
	err = -EXDEV;
	if (OVL_TYPE_MERGE_OR_LOWER(old_type) && is_dir)
	goto out;

	if (new->d_inode) {
	err = ovl_check_sticky(new);
	if (err)
	goto out;

	if (d_is_dir(new))
	new_is_dir = true;

	new_type = ovl_path_type(new);
	err = -EXDEV;
	if (!overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir)
	goto out;

	err = 0;
	if (!OVL_TYPE_UPPER(new_type) && !OVL_TYPE_UPPER(old_type)) {
	if (ovl_dentry_lower(old)->d_inode ==
	ovl_dentry_lower(new)->d_inode)
	goto out;
	}
	if (OVL_TYPE_UPPER(new_type) && OVL_TYPE_UPPER(old_type)) {
	if (ovl_dentry_upper(old)->d_inode ==
	ovl_dentry_upper(new)->d_inode)
	goto out;
	}
	} else {
	if (ovl_dentry_is_opaque(new))
	new_type = __OVL_PATH_UPPER;
	else
	new_type = __OVL_PATH_UPPER \| __OVL_PATH_PURE;
	}

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

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

	err = ovl_copy_up(new->d_parent);
	if (err)
	goto out_drop_write;
	if (!overwrite) {
	err = ovl_copy_up(new);
	if (err)
	goto out_drop_write;
	}

	old_opaque = !OVL_TYPE_PURE_UPPER(old_type);
	new_opaque = !OVL_TYPE_PURE_UPPER(new_type);

	if (old_opaque \|\| new_opaque) {
	err = -ENOMEM;
	override_cred = prepare_creds();
	if (!override_cred)
	goto out_drop_write;

	/*
	* CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
	* CAP_DAC_OVERRIDE for create in workdir
	* CAP_FOWNER for removing whiteout from sticky dir
	* CAP_FSETID for chmod of opaque dir
	* CAP_CHOWN for chown of opaque dir
	*/
	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_CHOWN);
	old_cred = override_creds(override_cred);
	}

	if (overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir) {
	opaquedir = ovl_check_empty_and_clear(new);
	err = PTR_ERR(opaquedir);
	if (IS_ERR(opaquedir)) {
	opaquedir = NULL;
	goto out_revert_creds;
	}
	}

	if (overwrite) {
	if (old_opaque) {
	if (new->d_inode \|\| !new_opaque) {
	/* Whiteout source */
	flags \|= RENAME_WHITEOUT;
	} else {
	/* Switch whiteouts */
	flags \|= RENAME_EXCHANGE;
	}
	} else if (is_dir && !new->d_inode && new_opaque) {
	flags \|= RENAME_EXCHANGE;
	cleanup_whiteout = true;
	}
	}

	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) {
	if (opaquedir) {
	newdentry = opaquedir;
	opaquedir = NULL;
	} else {
	dget(newdentry);
	}
	} else {
	new_create = true;
	newdentry = lookup_one_len(new->d_name.name, new_upperdir,
	new->d_name.len);
	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;

	if (is_dir && !old_opaque && new_opaque) {
	err = ovl_set_opaque(olddentry);
	if (err)
	goto out_dput;
	}
	if (!overwrite && new_is_dir && old_opaque && !new_opaque) {
	err = ovl_set_opaque(newdentry);
	if (err)
	goto out_dput;
	}

	if (old_opaque \|\| new_opaque) {
	err = ovl_do_rename(old_upperdir->d_inode, olddentry,
	new_upperdir->d_inode, newdentry,
	flags);
	} else {
	/* No debug for the plain case */
	BUG_ON(flags & ~RENAME_EXCHANGE);
	err = vfs_rename(old_upperdir->d_inode, olddentry,
	new_upperdir->d_inode, newdentry,
	NULL, flags);
	}

	if (err) {
	if (is_dir && !old_opaque && new_opaque)
	ovl_remove_opaque(olddentry);
	if (!overwrite && new_is_dir && old_opaque && !new_opaque)
	ovl_remove_opaque(newdentry);
	goto out_dput;
	}

	if (is_dir && old_opaque && !new_opaque)
	ovl_remove_opaque(olddentry);
	if (!overwrite && new_is_dir && !old_opaque && new_opaque)
	ovl_remove_opaque(newdentry);

	if (old_opaque != new_opaque) {
	ovl_dentry_set_opaque(old, new_opaque);
	if (!overwrite)
	ovl_dentry_set_opaque(new, old_opaque);
	}

	if (cleanup_whiteout)
	ovl_cleanup(old_upperdir->d_inode, newdentry);

	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);
	out_revert_creds:
	if (old_opaque \|\| new_opaque) {
	revert_creds(old_cred);
	put_cred(override_cred);
	}
	out_drop_write:
	ovl_drop_write(old);
	out:
	dput(opaquedir);
	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,
	.rename2 = ovl_rename2,
	.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,
	};