text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   *
   * Copyright (C) 2011 Novell Inc.
   */
  
  #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(redirect_max,
  		 "Maximum length of absolute redirect xattr value");
  
  static int ovl_set_redirect(struct dentry *dentry, bool samedir);
  
  int 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("cleanup of '%pd2' failed (%i)\n",
  		       wdentry, err);
  	}
  
  	return err;
  }
  
  struct dentry *ovl_lookup_temp(struct dentry *workdir)
  {
  	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("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 ovl_fs *ofs)
  {
  	int err;
  	struct dentry *whiteout;
  	struct dentry *workdir = ofs->workdir;
  	struct inode *wdir = workdir->d_inode;
  
  	if (!ofs->whiteout) {
  		whiteout = ovl_lookup_temp(workdir);
  		if (IS_ERR(whiteout))
  			goto out;
  
  		err = ovl_do_whiteout(wdir, whiteout);
  		if (err) {
  			dput(whiteout);
  			whiteout = ERR_PTR(err);
  			goto out;
  		}
  		ofs->whiteout = whiteout;
  	}
  
  	if (ofs->share_whiteout) {
  		whiteout = ovl_lookup_temp(workdir);
  		if (IS_ERR(whiteout))
  			goto out;
  
  		err = ovl_do_link(ofs->whiteout, wdir, whiteout);
  		if (!err)
  			goto out;
  
  		if (err != -EMLINK) {
  			pr_warn("Failed to link whiteout - disabling whiteout inode sharing(nlink=%u, err=%i)\n",
  				ofs->whiteout->d_inode->i_nlink, err);
  			ofs->share_whiteout = false;
  		}
  		dput(whiteout);
  	}
  	whiteout = ofs->whiteout;
  	ofs->whiteout = NULL;
  out:
  	return whiteout;
  }
  
  /* Caller must hold i_mutex on both workdir and dir */
  int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
  			     struct dentry *dentry)
  {
  	struct inode *wdir = ofs->workdir->d_inode;
  	struct dentry *whiteout;
  	int err;
  	int flags = 0;
  
  	whiteout = ovl_whiteout(ofs);
  	err = PTR_ERR(whiteout);
  	if (IS_ERR(whiteout))
  		return err;
  
  	if (d_is_dir(dentry))
  		flags = RENAME_EXCHANGE;
  
  	err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
  	if (err)
  		goto kill_whiteout;
  	if (flags)
  		ovl_cleanup(wdir, dentry);
  
  out:
  	dput(whiteout);
  	return err;
  
  kill_whiteout:
  	ovl_cleanup(wdir, whiteout);
  	goto out;
  }
  
  static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry,
  			  umode_t mode)
  {
  	int err;
  	struct dentry *d, *dentry = *newdentry;
  
  	err = ovl_do_mkdir(dir, dentry, mode);
  	if (err)
  		return err;
  
  	if (likely(!d_unhashed(dentry)))
  		return 0;
  
  	/*
  	 * vfs_mkdir() may succeed and leave the dentry passed
  	 * to it unhashed and negative. If that happens, try to
  	 * lookup a new hashed and positive dentry.
  	 */
  	d = lookup_one_len(dentry->d_name.name, dentry->d_parent,
  			   dentry->d_name.len);
  	if (IS_ERR(d)) {
  		pr_warn("failed lookup after mkdir (%pd2, err=%i).\n",
  			dentry, err);
  		return PTR_ERR(d);
  	}
  	dput(dentry);
  	*newdentry = d;
  
  	return 0;
  }
  
  struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
  			       struct ovl_cattr *attr)
  {
  	int err;
  
  	if (IS_ERR(newdentry))
  		return newdentry;
  
  	err = -ESTALE;
  	if (newdentry->d_inode)
  		goto out;
  
  	if (attr->hardlink) {
  		err = ovl_do_link(attr->hardlink, dir, newdentry);
  	} else {
  		switch (attr->mode & S_IFMT) {
  		case S_IFREG:
  			err = ovl_do_create(dir, newdentry, attr->mode);
  			break;
  
  		case S_IFDIR:
  			/* mkdir is special... */
  			err =  ovl_mkdir_real(dir, &newdentry, attr->mode);
  			break;
  
  		case S_IFCHR:
  		case S_IFBLK:
  		case S_IFIFO:
  		case S_IFSOCK:
  			err = ovl_do_mknod(dir, newdentry, attr->mode,
  					   attr->rdev);
  			break;
  
  		case S_IFLNK:
  			err = ovl_do_symlink(dir, newdentry, attr->link);
  			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 = -EIO;
  	}
  out:
  	if (err) {
  		dput(newdentry);
  		return ERR_PTR(err);
  	}
  	return newdentry;
  }
  
  struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr)
  {
  	return ovl_create_real(d_inode(workdir), ovl_lookup_temp(workdir),
  			       attr);
  }
  
  static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
  			       int xerr)
  {
  	int err;
  
  	err = ovl_check_setxattr(dentry, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
  	if (!err)
  		ovl_dentry_set_opaque(dentry);
  
  	return err;
  }
  
  static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
  {
  	/*
  	 * Fail with -EIO when trying to create opaque dir and upper doesn't
  	 * support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
  	 * return a specific error for noxattr case.
  	 */
  	return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
  }
  
  /*
   * Common operations required to be done after creation of file on upper.
   * If @hardlink is false, then @inode is a pre-allocated inode, we may or
   * may not use to instantiate the new dentry.
   */
  static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
  			   struct dentry *newdentry, bool hardlink)
  {
  	struct ovl_inode_params oip = {
  		.upperdentry = newdentry,
  		.newinode = inode,
  	};
  
  	ovl_dir_modified(dentry->d_parent, false);
  	ovl_dentry_set_upper_alias(dentry);
  	ovl_dentry_update_reval(dentry, newdentry,
  			DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
  
  	if (!hardlink) {
  		/*
  		 * ovl_obtain_alias() can be called after ovl_create_real()
  		 * and before we get here, so we may get an inode from cache
  		 * with the same real upperdentry that is not the inode we
  		 * pre-allocated.  In this case we will use the cached inode
  		 * to instantiate the new dentry.
  		 *
  		 * XXX: if we ever use ovl_obtain_alias() to decode directory
  		 * file handles, need to use ovl_get_inode_locked() and
  		 * d_instantiate_new() here to prevent from creating two
  		 * hashed directory inode aliases.
  		 */
  		inode = ovl_get_inode(dentry->d_sb, &oip);
  		if (IS_ERR(inode))
  			return PTR_ERR(inode);
  		if (inode == oip.newinode)
  			ovl_set_flag(OVL_UPPERDATA, inode);
  	} else {
  		WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
  		dput(newdentry);
  		inc_nlink(inode);
  	}
  
  	d_instantiate(dentry, inode);
  	if (inode != oip.newinode) {
  		pr_warn_ratelimited("newly created inode found in cache (%pd2)\n",
  				    dentry);
  	}
  
  	/* Force lookup of new upper hardlink to find its lower */
  	if (hardlink)
  		d_drop(dentry);
  
  	return 0;
  }
  
  static bool ovl_type_merge(struct dentry *dentry)
  {
  	return OVL_TYPE_MERGE(ovl_path_type(dentry));
  }
  
  static bool ovl_type_origin(struct dentry *dentry)
  {
  	return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
  }
  
  static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
  			    struct ovl_cattr *attr)
  {
  	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
  	struct inode *udir = upperdir->d_inode;
  	struct dentry *newdentry;
  	int err;
  
  	if (!attr->hardlink && !IS_POSIXACL(udir))
  		attr->mode &= ~current_umask();
  
  	inode_lock_nested(udir, I_MUTEX_PARENT);
  	newdentry = ovl_create_real(udir,
  				    lookup_one_len(dentry->d_name.name,
  						   upperdir,
  						   dentry->d_name.len),
  				    attr);
  	err = PTR_ERR(newdentry);
  	if (IS_ERR(newdentry))
  		goto out_unlock;
  
  	if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
  		/* Setting opaque here is just an optimization, allow to fail */
  		ovl_set_opaque(dentry, newdentry);
  	}
  
  	err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink);
  	if (err)
  		goto out_cleanup;
  out_unlock:
  	inode_unlock(udir);
  	return err;
  
  out_cleanup:
  	ovl_cleanup(udir, newdentry);
  	dput(newdentry);
  	goto out_unlock;
  }
  
  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,
  			  STATX_BASIC_STATS, AT_STATX_SYNC_AS_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_create_temp(workdir, OVL_CATTR(stat.mode));
  	err = PTR_ERR(opaquedir);
  	if (IS_ERR(opaquedir))
  		goto out_unlock;
  
  	err = ovl_copy_xattr(dentry->d_sb, 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);
  	dput(opaquedir);
  out_unlock:
  	unlock_rename(workdir, upperdir);
  out:
  	return ERR_PTR(err);
  }
  
  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_xattr_size(acl->a_count);
  	buffer = kmalloc(size, GFP_KERNEL);
  	if (!buffer)
  		return -ENOMEM;
  
  	err = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
  	if (err < 0)
  		goto out_free;
  
  	err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
  out_free:
  	kfree(buffer);
  	return err;
  }
  
  static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
  				    struct ovl_cattr *cattr)
  {
  	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;
  	bool hardlink = !!cattr->hardlink;
  
  	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;
  
  	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 (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper)))
  		goto out_dput;
  
  	newdentry = ovl_create_temp(workdir, cattr);
  	err = PTR_ERR(newdentry);
  	if (IS_ERR(newdentry))
  		goto out_dput;
  
  	/*
  	 * 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;
  	}
  	err = ovl_instantiate(dentry, inode, newdentry, hardlink);
  	if (err)
  		goto out_cleanup;
  out_dput:
  	dput(upper);
  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);
  	dput(newdentry);
  	goto out_dput;
  }
  
  static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
  			      struct ovl_cattr *attr, bool origin)
  {
  	int err;
  	const struct cred *old_cred;
  	struct cred *override_cred;
  	struct dentry *parent = dentry->d_parent;
  
  	err = ovl_copy_up(parent);
  	if (err)
  		return err;
  
  	old_cred = ovl_override_creds(dentry->d_sb);
  
  	/*
  	 * When linking a file with copy up origin into a new parent, mark the
  	 * new parent dir "impure".
  	 */
  	if (origin) {
  		err = ovl_set_impure(parent, ovl_dentry_upper(parent));
  		if (err)
  			goto out_revert_creds;
  	}
  
  	err = -ENOMEM;
  	override_cred = prepare_creds();
  	if (override_cred) {
  		override_cred->fsuid = inode->i_uid;
  		override_cred->fsgid = inode->i_gid;
  		if (!attr->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);
  		else
  			err = ovl_create_over_whiteout(dentry, inode, attr);
  	}
  out_revert_creds:
  	revert_creds(old_cred);
  	return err;
  }
  
  static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
  			     const char *link)
  {
  	int err;
  	struct inode *inode;
  	struct ovl_cattr attr = {
  		.rdev = rdev,
  		.link = link,
  	};
  
  	err = ovl_want_write(dentry);
  	if (err)
  		goto out;
  
  	/* Preallocate inode to be used by ovl_get_inode() */
  	err = -ENOMEM;
  	inode = ovl_new_inode(dentry->d_sb, mode, rdev);
  	if (!inode)
  		goto out_drop_write;
  
  	spin_lock(&inode->i_lock);
  	inode->i_state |= I_CREATING;
  	spin_unlock(&inode->i_lock);
  
  	inode_init_owner(inode, dentry->d_parent->d_inode, mode);
  	attr.mode = inode->i_mode;
  
  	err = ovl_create_or_link(dentry, inode, &attr, false);
  	/* Did we end up using the preallocated inode? */
  	if (inode != d_inode(dentry))
  		iput(inode);
  
  out_drop_write:
  	ovl_drop_write(dentry);
  out:
  	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_set_link_redirect(struct dentry *dentry)
  {
  	const struct cred *old_cred;
  	int err;
  
  	old_cred = ovl_override_creds(dentry->d_sb);
  	err = ovl_set_redirect(dentry, false);
  	revert_creds(old_cred);
  
  	return err;
  }
  
  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;
  
  	err = ovl_copy_up(new->d_parent);
  	if (err)
  		goto out_drop_write;
  
  	if (ovl_is_metacopy_dentry(old)) {
  		err = ovl_set_link_redirect(old);
  		if (err)
  			goto out_drop_write;
  	}
  
  	err = ovl_nlink_start(old);
  	if (err)
  		goto out_drop_write;
  
  	inode = d_inode(old);
  	ihold(inode);
  
  	err = ovl_create_or_link(new, inode,
  			&(struct ovl_cattr) {.hardlink = ovl_dentry_upper(old)},
  			ovl_type_origin(old));
  	if (err)
  		iput(inode);
  
  	ovl_nlink_end(old);
  out_drop_write:
  	ovl_drop_write(old);
  out:
  	return err;
  }
  
  static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
  {
  	return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
  }
  
  static int ovl_remove_and_whiteout(struct dentry *dentry,
  				   struct list_head *list)
  {
  	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
  	struct dentry *workdir = ovl_workdir(dentry);
  	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
  	struct dentry *upper;
  	struct dentry *opaquedir = NULL;
  	int err;
  
  	if (WARN_ON(!workdir))
  		return -EROFS;
  
  	if (!list_empty(list)) {
  		opaquedir = ovl_clear_empty(dentry, list);
  		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) &&
  	     !ovl_matches_upper(dentry, upper))) {
  		goto out_dput_upper;
  	}
  
  	err = ovl_cleanup_and_whiteout(ofs, d_inode(upperdir), upper);
  	if (err)
  		goto out_d_drop;
  
  	ovl_dir_modified(dentry->d_parent, true);
  out_d_drop:
  	d_drop(dentry);
  out_dput_upper:
  	dput(upper);
  out_unlock:
  	unlock_rename(workdir, upperdir);
  out_dput:
  	dput(opaquedir);
  out:
  	return err;
  }
  
  static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
  			    struct list_head *list)
  {
  	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
  	struct inode *dir = upperdir->d_inode;
  	struct dentry *upper;
  	struct dentry *opaquedir = NULL;
  	int err;
  
  	if (!list_empty(list)) {
  		opaquedir = ovl_clear_empty(dentry, list);
  		err = PTR_ERR(opaquedir);
  		if (IS_ERR(opaquedir))
  			goto out;
  	}
  
  	inode_lock_nested(dir, I_MUTEX_PARENT);
  	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_matches_upper(dentry, upper)))
  		goto out_dput_upper;
  
  	if (is_dir)
  		err = vfs_rmdir(dir, upper);
  	else
  		err = vfs_unlink(dir, upper, NULL);
  	ovl_dir_modified(dentry->d_parent, ovl_type_origin(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.
  	 */
  	if (!err)
  		d_drop(dentry);
  out_dput_upper:
  	dput(upper);
  out_unlock:
  	inode_unlock(dir);
  	dput(opaquedir);
  out:
  	return err;
  }
  
  static bool ovl_pure_upper(struct dentry *dentry)
  {
  	return !ovl_dentry_lower(dentry) &&
  	       !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
  }
  
  static void ovl_drop_nlink(struct dentry *dentry)
  {
  	struct inode *inode = d_inode(dentry);
  	struct dentry *alias;
  
  	/* Try to find another, hashed alias */
  	spin_lock(&inode->i_lock);
  	hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
  		if (alias != dentry && !d_unhashed(alias))
  			break;
  	}
  	spin_unlock(&inode->i_lock);
  
  	/*
  	 * Changes to underlying layers may cause i_nlink to lose sync with
  	 * reality.  In this case prevent the link count from going to zero
  	 * prematurely.
  	 */
  	if (inode->i_nlink > !!alias)
  		drop_nlink(inode);
  }
  
  static int ovl_do_remove(struct dentry *dentry, bool is_dir)
  {
  	int err;
  	const struct cred *old_cred;
  	struct dentry *upperdentry;
  	bool lower_positive = ovl_lower_positive(dentry);
  	LIST_HEAD(list);
  
  	/* No need to clean pure upper removed by vfs_rmdir() */
  	if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
  		err = ovl_check_empty_dir(dentry, &list);
  		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;
  
  	err = ovl_nlink_start(dentry);
  	if (err)
  		goto out_drop_write;
  
  	old_cred = ovl_override_creds(dentry->d_sb);
  	if (!lower_positive)
  		err = ovl_remove_upper(dentry, is_dir, &list);
  	else
  		err = ovl_remove_and_whiteout(dentry, &list);
  	revert_creds(old_cred);
  	if (!err) {
  		if (is_dir)
  			clear_nlink(dentry->d_inode);
  		else
  			ovl_drop_nlink(dentry);
  	}
  	ovl_nlink_end(dentry);
  
  	/*
  	 * Copy ctime
  	 *
  	 * Note: we fail to update ctime if there was no copy-up, only a
  	 * whiteout
  	 */
  	upperdentry = ovl_dentry_upper(dentry);
  	if (upperdentry)
  		ovl_copyattr(d_inode(upperdentry), d_inode(dentry));
  
  out_drop_write:
  	ovl_drop_write(dentry);
  out:
  	ovl_cache_free(&list);
  	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 bool ovl_type_merge_or_lower(struct dentry *dentry)
  {
  	enum ovl_path_type type = ovl_path_type(dentry);
  
  	return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
  }
  
  static bool ovl_can_move(struct dentry *dentry)
  {
  	return ovl_redirect_dir(dentry->d_sb) ||
  		!d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
  }
  
  static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
  {
  	char *buf, *ret;
  	struct dentry *d, *tmp;
  	int buflen = ovl_redirect_max + 1;
  
  	if (!abs_redirect) {
  		ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
  			       GFP_KERNEL);
  		goto out;
  	}
  
  	buf = ret = kmalloc(buflen, GFP_KERNEL);
  	if (!buf)
  		goto out;
  
  	buflen--;
  	buf[buflen] = '\0';
  	for (d = dget(dentry); !IS_ROOT(d);) {
  		const char *name;
  		int thislen;
  
  		spin_lock(&d->d_lock);
  		name = ovl_dentry_get_redirect(d);
  		if (name) {
  			thislen = strlen(name);
  		} else {
  			name = d->d_name.name;
  			thislen = d->d_name.len;
  		}
  
  		/* If path is too long, fall back to userspace move */
  		if (thislen + (name[0] != '/') > buflen) {
  			ret = ERR_PTR(-EXDEV);
  			spin_unlock(&d->d_lock);
  			goto out_put;
  		}
  
  		buflen -= thislen;
  		memcpy(&buf[buflen], name, thislen);
  		spin_unlock(&d->d_lock);
  		tmp = dget_parent(d);
  
  		dput(d);
  		d = tmp;
  
  		/* Absolute redirect: finished */
  		if (buf[buflen] == '/')
  			break;
  		buflen--;
  		buf[buflen] = '/';
  	}
  	ret = kstrdup(&buf[buflen], GFP_KERNEL);
  out_put:
  	dput(d);
  	kfree(buf);
  out:
  	return ret ? ret : ERR_PTR(-ENOMEM);
  }
  
  static bool ovl_need_absolute_redirect(struct dentry *dentry, bool samedir)
  {
  	struct dentry *lowerdentry;
  
  	if (!samedir)
  		return true;
  
  	if (d_is_dir(dentry))
  		return false;
  
  	/*
  	 * For non-dir hardlinked files, we need absolute redirects
  	 * in general as two upper hardlinks could be in different
  	 * dirs. We could put a relative redirect now and convert
  	 * it to absolute redirect later. But when nlink > 1 and
  	 * indexing is on, that means relative redirect needs to be
  	 * converted to absolute during copy up of another lower
  	 * hardllink as well.
  	 *
  	 * So without optimizing too much, just check if lower is
  	 * a hard link or not. If lower is hard link, put absolute
  	 * redirect.
  	 */
  	lowerdentry = ovl_dentry_lower(dentry);
  	return (d_inode(lowerdentry)->i_nlink > 1);
  }
  
  static int ovl_set_redirect(struct dentry *dentry, bool samedir)
  {
  	int err;
  	const char *redirect = ovl_dentry_get_redirect(dentry);
  	bool absolute_redirect = ovl_need_absolute_redirect(dentry, samedir);
  
  	if (redirect && (!absolute_redirect || redirect[0] == '/'))
  		return 0;
  
  	redirect = ovl_get_redirect(dentry, absolute_redirect);
  	if (IS_ERR(redirect))
  		return PTR_ERR(redirect);
  
  	err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
  				 OVL_XATTR_REDIRECT,
  				 redirect, strlen(redirect), -EXDEV);
  	if (!err) {
  		spin_lock(&dentry->d_lock);
  		ovl_dentry_set_redirect(dentry, redirect);
  		spin_unlock(&dentry->d_lock);
  	} else {
  		kfree(redirect);
  		pr_warn_ratelimited("failed to set redirect (%i)\n",
  				    err);
  		/* Fall back to userspace copy-up */
  		err = -EXDEV;
  	}
  	return err;
  }
  
  static int ovl_rename(struct inode *olddir, struct dentry *old,
  		      struct inode *newdir, struct dentry *new,
  		      unsigned int flags)
  {
  	int err;
  	struct dentry *old_upperdir;
  	struct dentry *new_upperdir;
  	struct dentry *olddentry;
  	struct dentry *newdentry;
  	struct dentry *trap;
  	bool old_opaque;
  	bool new_opaque;
  	bool cleanup_whiteout = false;
  	bool update_nlink = false;
  	bool overwrite = !(flags & RENAME_EXCHANGE);
  	bool is_dir = d_is_dir(old);
  	bool new_is_dir = d_is_dir(new);
  	bool samedir = olddir == newdir;
  	struct dentry *opaquedir = NULL;
  	const struct cred *old_cred = NULL;
  	LIST_HEAD(list);
  
  	err = -EINVAL;
  	if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
  		goto out;
  
  	flags &= ~RENAME_NOREPLACE;
  
  	/* Don't copy up directory trees */
  	err = -EXDEV;
  	if (!ovl_can_move(old))
  		goto out;
  	if (!overwrite && !ovl_can_move(new))
  		goto out;
  
  	if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
  		err = ovl_check_empty_dir(new, &list);
  		if (err)
  			goto out;
  	}
  
  	if (overwrite) {
  		if (ovl_lower_positive(old)) {
  			if (!ovl_dentry_is_whiteout(new)) {
  				/* Whiteout source */
  				flags |= RENAME_WHITEOUT;
  			} else {
  				/* Switch whiteouts */
  				flags |= RENAME_EXCHANGE;
  			}
  		} else if (is_dir && ovl_dentry_is_whiteout(new)) {
  			flags |= RENAME_EXCHANGE;
  			cleanup_whiteout = true;
  		}
  	}
  
  	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;
  	} else if (d_inode(new)) {
  		err = ovl_nlink_start(new);
  		if (err)
  			goto out_drop_write;
  
  		update_nlink = true;
  	}
  
  	old_cred = ovl_override_creds(old->d_sb);
  
  	if (!list_empty(&list)) {
  		opaquedir = ovl_clear_empty(new, &list);
  		err = PTR_ERR(opaquedir);
  		if (IS_ERR(opaquedir)) {
  			opaquedir = NULL;
  			goto out_revert_creds;
  		}
  	}
  
  	old_upperdir = ovl_dentry_upper(old->d_parent);
  	new_upperdir = ovl_dentry_upper(new->d_parent);
  
  	if (!samedir) {
  		/*
  		 * When moving a merge dir or non-dir with copy up origin into
  		 * a new parent, we are marking the new parent dir "impure".
  		 * When ovl_iterate() iterates an "impure" upper dir, it will
  		 * lookup the origin inodes of the entries to fill d_ino.
  		 */
  		if (ovl_type_origin(old)) {
  			err = ovl_set_impure(new->d_parent, new_upperdir);
  			if (err)
  				goto out_revert_creds;
  		}
  		if (!overwrite && ovl_type_origin(new)) {
  			err = ovl_set_impure(old->d_parent, old_upperdir);
  			if (err)
  				goto out_revert_creds;
  		}
  	}
  
  	trap = lock_rename(new_upperdir, old_upperdir);
  
  	olddentry = lookup_one_len(old->d_name.name, old_upperdir,
  				   old->d_name.len);
  	err = PTR_ERR(olddentry);
  	if (IS_ERR(olddentry))
  		goto out_unlock;
  
  	err = -ESTALE;
  	if (!ovl_matches_upper(old, olddentry))
  		goto out_dput_old;
  
  	newdentry = lookup_one_len(new->d_name.name, new_upperdir,
  				   new->d_name.len);
  	err = PTR_ERR(newdentry);
  	if (IS_ERR(newdentry))
  		goto out_dput_old;
  
  	old_opaque = ovl_dentry_is_opaque(old);
  	new_opaque = ovl_dentry_is_opaque(new);
  
  	err = -ESTALE;
  	if (d_inode(new) && ovl_dentry_upper(new)) {
  		if (opaquedir) {
  			if (newdentry != opaquedir)
  				goto out_dput;
  		} else {
  			if (!ovl_matches_upper(new, newdentry))
  				goto out_dput;
  		}
  	} else {
  		if (!d_is_negative(newdentry) &&
  		    (!new_opaque || !ovl_is_whiteout(newdentry)))
  			goto out_dput;
  	}
  
  	if (olddentry == trap)
  		goto out_dput;
  	if (newdentry == trap)
  		goto out_dput;
  
  	if (olddentry->d_inode == newdentry->d_inode)
  		goto out_dput;
  
  	err = 0;
  	if (ovl_type_merge_or_lower(old))
  		err = ovl_set_redirect(old, samedir);
  	else if (is_dir && !old_opaque && ovl_type_merge(new->d_parent))
  		err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
  	if (err)
  		goto out_dput;
  
  	if (!overwrite && ovl_type_merge_or_lower(new))
  		err = ovl_set_redirect(new, samedir);
  	else if (!overwrite && new_is_dir && !new_opaque &&
  		 ovl_type_merge(old->d_parent))
  		err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
  	if (err)
  		goto out_dput;
  
  	err = ovl_do_rename(old_upperdir->d_inode, olddentry,
  			    new_upperdir->d_inode, newdentry, flags);
  	if (err)
  		goto out_dput;
  
  	if (cleanup_whiteout)
  		ovl_cleanup(old_upperdir->d_inode, newdentry);
  
  	if (overwrite && d_inode(new)) {
  		if (new_is_dir)
  			clear_nlink(d_inode(new));
  		else
  			ovl_drop_nlink(new);
  	}
  
  	ovl_dir_modified(old->d_parent, ovl_type_origin(old) ||
  			 (!overwrite && ovl_type_origin(new)));
  	ovl_dir_modified(new->d_parent, ovl_type_origin(old) ||
  			 (d_inode(new) && ovl_type_origin(new)));
  
  	/* copy ctime: */
  	ovl_copyattr(d_inode(olddentry), d_inode(old));
  	if (d_inode(new) && ovl_dentry_upper(new))
  		ovl_copyattr(d_inode(newdentry), d_inode(new));
  
  out_dput:
  	dput(newdentry);
  out_dput_old:
  	dput(olddentry);
  out_unlock:
  	unlock_rename(new_upperdir, old_upperdir);
  out_revert_creds:
  	revert_creds(old_cred);
  	if (update_nlink)
  		ovl_nlink_end(new);
  out_drop_write:
  	ovl_drop_write(old);
  out:
  	dput(opaquedir);
  	ovl_cache_free(&list);
  	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_getattr,
  	.listxattr	= ovl_listxattr,
  	.get_acl	= ovl_get_acl,
  	.update_time	= ovl_update_time,
  };
  