fs/tmpfs/tmpfs_vnops.c

/*	$NetBSD: tmpfs_vnops.c,v 1.95 2012/02/27 16:10:56 chs Exp $	*/

/*
 * Copyright (c) 2005, 2006, 2007 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Julio M. Merino Vidal, developed as part of Google's Summer of Code
 * 2005 program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * tmpfs vnode interface.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tmpfs_vnops.c,v 1.95 2012/02/27 16:10:56 chs Exp $");

#include <sys/param.h>
#include <sys/dirent.h>
#include <sys/fcntl.h>
#include <sys/event.h>
#include <sys/malloc.h>
#include <sys/namei.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/lockf.h>
#include <sys/kauth.h>

#include <uvm/uvm.h>

#include <miscfs/fifofs/fifo.h>
#include <miscfs/genfs/genfs.h>
#include <fs/tmpfs/tmpfs_vnops.h>
#include <fs/tmpfs/tmpfs.h>

/*
 * vnode operations vector used for files stored in a tmpfs file system.
 */
int (**tmpfs_vnodeop_p)(void *);
const struct vnodeopv_entry_desc tmpfs_vnodeop_entries[] = {
	{ &vop_default_desc,		vn_default_error },
	{ &vop_lookup_desc,		tmpfs_lookup },
	{ &vop_create_desc,		tmpfs_create },
	{ &vop_mknod_desc,		tmpfs_mknod },
	{ &vop_open_desc,		tmpfs_open },
	{ &vop_close_desc,		tmpfs_close },
	{ &vop_access_desc,		tmpfs_access },
	{ &vop_getattr_desc,		tmpfs_getattr },
	{ &vop_setattr_desc,		tmpfs_setattr },
	{ &vop_read_desc,		tmpfs_read },
	{ &vop_write_desc,		tmpfs_write },
	{ &vop_ioctl_desc,		tmpfs_ioctl },
	{ &vop_fcntl_desc,		tmpfs_fcntl },
	{ &vop_poll_desc,		tmpfs_poll },
	{ &vop_kqfilter_desc,		tmpfs_kqfilter },
	{ &vop_revoke_desc,		tmpfs_revoke },
	{ &vop_mmap_desc,		tmpfs_mmap },
	{ &vop_fsync_desc,		tmpfs_fsync },
	{ &vop_seek_desc,		tmpfs_seek },
	{ &vop_remove_desc,		tmpfs_remove },
	{ &vop_link_desc,		tmpfs_link },
	{ &vop_rename_desc,		tmpfs_rename },
	{ &vop_mkdir_desc,		tmpfs_mkdir },
	{ &vop_rmdir_desc,		tmpfs_rmdir },
	{ &vop_symlink_desc,		tmpfs_symlink },
	{ &vop_readdir_desc,		tmpfs_readdir },
	{ &vop_readlink_desc,		tmpfs_readlink },
	{ &vop_abortop_desc,		tmpfs_abortop },
	{ &vop_inactive_desc,		tmpfs_inactive },
	{ &vop_reclaim_desc,		tmpfs_reclaim },
	{ &vop_lock_desc,		tmpfs_lock },
	{ &vop_unlock_desc,		tmpfs_unlock },
	{ &vop_bmap_desc,		tmpfs_bmap },
	{ &vop_strategy_desc,		tmpfs_strategy },
	{ &vop_print_desc,		tmpfs_print },
	{ &vop_pathconf_desc,		tmpfs_pathconf },
	{ &vop_islocked_desc,		tmpfs_islocked },
	{ &vop_advlock_desc,		tmpfs_advlock },
	{ &vop_bwrite_desc,		tmpfs_bwrite },
	{ &vop_getpages_desc,		tmpfs_getpages },
	{ &vop_putpages_desc,		tmpfs_putpages },
	{ &vop_whiteout_desc,		tmpfs_whiteout },
	{ NULL, NULL }
};

const struct vnodeopv_desc tmpfs_vnodeop_opv_desc = {
	&tmpfs_vnodeop_p, tmpfs_vnodeop_entries
};

/*
 * tmpfs_lookup: path name traversal routine.
 *
 * Arguments: dvp (directory being searched), vpp (result),
 * cnp (component name - path).
 *
 * => Caller holds a reference and lock on dvp.
 * => We return looked-up vnode (vpp) locked, with a reference held.
 */
int
tmpfs_lookup(void *v)
{
	struct vop_lookup_args /* {
		struct vnode *a_dvp;
		struct vnode **a_vpp;
		struct componentname *a_cnp;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp, **vpp = ap->a_vpp;
	struct componentname *cnp = ap->a_cnp;
	const bool lastcn = (cnp->cn_flags & ISLASTCN) != 0;
	tmpfs_node_t *dnode, *tnode;
	tmpfs_dirent_t *de;
	int error;

	KASSERT(VOP_ISLOCKED(dvp));

	dnode = VP_TO_TMPFS_DIR(dvp);
	*vpp = NULL;

	/* Check accessibility of directory. */
	error = VOP_ACCESS(dvp, VEXEC, cnp->cn_cred);
	if (error) {
		goto out;
	}

	/*
	 * If requesting the last path component on a read-only file system
	 * with a write operation, deny it.
	 */
	if (lastcn && (dvp->v_mount->mnt_flag & MNT_RDONLY) != 0 &&
	    (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
		error = EROFS;
		goto out;
	}

	/*
	 * Avoid doing a linear scan of the directory if the requested
	 * directory/name couple is already in the cache.
	 */
	error = cache_lookup(dvp, vpp, cnp);
	if (error >= 0) {
		/* Both cache-hit or an error case. */
		goto out;
	}

	if (cnp->cn_flags & ISDOTDOT) {
		tmpfs_node_t *pnode;

		/*
		 * Lookup of ".." case.
		 */
		if (lastcn && cnp->cn_nameiop == RENAME) {
			error = EINVAL;
			goto out;
		}
		KASSERT(dnode->tn_type == VDIR);
		pnode = dnode->tn_spec.tn_dir.tn_parent;
		if (pnode == NULL) {
			error = ENOENT;
			goto out;
		}

		/*
		 * Lock the parent tn_vlock before releasing the vnode lock,
		 * and thus prevents parent from disappearing.
		 */
		mutex_enter(&pnode->tn_vlock);
		VOP_UNLOCK(dvp);

		/*
		 * Get a vnode of the '..' entry and re-acquire the lock.
		 * Release the tn_vlock.
		 */
		error = tmpfs_vnode_get(dvp->v_mount, pnode, vpp);
		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
		goto out;

	} else if (cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.') {
		/*
		 * Lookup of "." case.
		 */
		if (lastcn && cnp->cn_nameiop == RENAME) {
			error = EISDIR;
			goto out;
		}
		vref(dvp);
		*vpp = dvp;
		error = 0;
		goto done;
	}

	/*
	 * Other lookup cases: perform directory scan.
	 */
	de = tmpfs_dir_lookup(dnode, cnp);
	if (de == NULL || de->td_node == TMPFS_NODE_WHITEOUT) {
		/*
		 * The entry was not found in the directory.  This is valid
		 * if we are creating or renaming an entry and are working
		 * on the last component of the path name.
		 */
		if (lastcn && (cnp->cn_nameiop == CREATE ||
		    cnp->cn_nameiop == RENAME)) {
			error = VOP_ACCESS(dvp, VWRITE, cnp->cn_cred);
			if (error) {
				goto out;
			}
			error = EJUSTRETURN;
		} else {
			error = ENOENT;
		}
		if (de) {
			KASSERT(de->td_node == TMPFS_NODE_WHITEOUT);
			cnp->cn_flags |= ISWHITEOUT;
		}
		goto done;
	}

	tnode = de->td_node;

	/*
	 * If it is not the last path component and found a non-directory
	 * or non-link entry (which may itself be pointing to a directory),
	 * raise an error.
	 */
	if (!lastcn && tnode->tn_type != VDIR && tnode->tn_type != VLNK) {
		error = ENOTDIR;
		goto out;
	}

	/* Check the permissions. */
	if (lastcn && (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
		kauth_action_t action = 0;

		/* This is the file-system's decision. */
		if ((dnode->tn_mode & S_ISTXT) != 0 &&
		    kauth_cred_geteuid(cnp->cn_cred) != dnode->tn_uid &&
		    kauth_cred_geteuid(cnp->cn_cred) != tnode->tn_uid) {
			error = EPERM;
		} else {
			error = VOP_ACCESS(dvp, VWRITE, cnp->cn_cred);
		}

		if (cnp->cn_nameiop == DELETE) {
			action |= KAUTH_VNODE_DELETE;
		} else {
			KASSERT(cnp->cn_nameiop == RENAME);
			action |= KAUTH_VNODE_RENAME;
		}
		error = kauth_authorize_vnode(cnp->cn_cred,
		    action, *vpp, dvp, error);
		if (error) {
			goto out;
		}
	}

	/* Get a vnode for the matching entry. */
	mutex_enter(&tnode->tn_vlock);
	error = tmpfs_vnode_get(dvp->v_mount, tnode, vpp);
done:
	/*
	 * Cache the result, unless request was for creation (as it does
	 * not improve the performance).
	 */
	if ((cnp->cn_flags & MAKEENTRY) != 0 && cnp->cn_nameiop != CREATE) {
		cache_enter(dvp, *vpp, cnp);
	}
out:
	KASSERT((*vpp && VOP_ISLOCKED(*vpp)) || error);
	KASSERT(VOP_ISLOCKED(dvp));

	return error;
}

int
tmpfs_create(void *v)
{
	struct vop_create_args /* {
		struct vnode		*a_dvp;
		struct vnode		**a_vpp;
		struct componentname	*a_cnp;
		struct vattr		*a_vap;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp, **vpp = ap->a_vpp;
	struct componentname *cnp = ap->a_cnp;
	struct vattr *vap = ap->a_vap;

	KASSERT(VOP_ISLOCKED(dvp));
	KASSERT(vap->va_type == VREG || vap->va_type == VSOCK);
	return tmpfs_alloc_file(dvp, vpp, vap, cnp, NULL);
}

int
tmpfs_mknod(void *v)
{
	struct vop_mknod_args /* {
		struct vnode		*a_dvp;
		struct vnode		**a_vpp;
		struct componentname	*a_cnp;
		struct vattr		*a_vap;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp, **vpp = ap->a_vpp;
	struct componentname *cnp = ap->a_cnp;
	struct vattr *vap = ap->a_vap;
	enum vtype vt = vap->va_type;

	if (vt != VBLK && vt != VCHR && vt != VFIFO) {
		vput(dvp);
		return EINVAL;
	}
	return tmpfs_alloc_file(dvp, vpp, vap, cnp, NULL);
}

int
tmpfs_open(void *v)
{
	struct vop_open_args /* {
		struct vnode	*a_vp;
		int		a_mode;
		kauth_cred_t	a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	mode_t mode = ap->a_mode;
	tmpfs_node_t *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);
	if (node->tn_links < 1) {
		/*
		 * The file is still active, but all its names have been
		 * removed (e.g. by a "rmdir $(pwd)").  It cannot be opened
		 * any more, as it is about to be destroyed.
		 */
		return ENOENT;
	}

	/* If the file is marked append-only, deny write requests. */
	if ((node->tn_flags & APPEND) != 0 &&
	    (mode & (FWRITE | O_APPEND)) == FWRITE) {
		return EPERM;
	}
	return 0;
}

int
tmpfs_close(void *v)
{
	struct vop_close_args /* {
		struct vnode	*a_vp;
		int		a_fflag;
		kauth_cred_t	a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;

	KASSERT(VOP_ISLOCKED(vp));

	tmpfs_update(vp, NULL, NULL, NULL, UPDATE_CLOSE);
	return 0;
}

int
tmpfs_access(void *v)
{
	struct vop_access_args /* {
		struct vnode	*a_vp;
		int		a_mode;
		kauth_cred_t	a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	mode_t mode = ap->a_mode;
	kauth_cred_t cred = ap->a_cred;
	tmpfs_node_t *node = VP_TO_TMPFS_NODE(vp);
	const bool writing = (mode & VWRITE) != 0;
	int error;

	KASSERT(VOP_ISLOCKED(vp));

	/* Possible? */
	switch (vp->v_type) {
	case VDIR:
	case VLNK:
	case VREG:
		if (writing && (vp->v_mount->mnt_flag & MNT_RDONLY) != 0) {
			return EROFS;
		}
		break;
	case VBLK:
	case VCHR:
	case VSOCK:
	case VFIFO:
		break;
	default:
		return EINVAL;
	}
	if (writing && (node->tn_flags & IMMUTABLE) != 0) {
		return EPERM;
	}

	/* Permitted? */
	error = genfs_can_access(vp->v_type, node->tn_mode, node->tn_uid,
	    node->tn_gid, mode, cred);

	return kauth_authorize_vnode(cred, kauth_mode_to_action(mode), vp,
	    NULL, error);
}

int
tmpfs_getattr(void *v)
{
	struct vop_getattr_args /* {
		struct vnode	*a_vp;
		struct vattr	*a_vap;
		kauth_cred_t	a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	struct vattr *vap = ap->a_vap;
	tmpfs_node_t *node = VP_TO_TMPFS_NODE(vp);

	vattr_null(vap);

	tmpfs_update(vp, NULL, NULL, NULL, 0);

	vap->va_type = vp->v_type;
	vap->va_mode = node->tn_mode;
	vap->va_nlink = node->tn_links;
	vap->va_uid = node->tn_uid;
	vap->va_gid = node->tn_gid;
	vap->va_fsid = vp->v_mount->mnt_stat.f_fsidx.__fsid_val[0];
	vap->va_fileid = node->tn_id;
	vap->va_size = node->tn_size;
	vap->va_blocksize = PAGE_SIZE;
	vap->va_atime = node->tn_atime;
	vap->va_mtime = node->tn_mtime;
	vap->va_ctime = node->tn_ctime;
	vap->va_birthtime = node->tn_birthtime;
	vap->va_gen = TMPFS_NODE_GEN(node);
	vap->va_flags = node->tn_flags;
	vap->va_rdev = (vp->v_type == VBLK || vp->v_type == VCHR) ?
	    node->tn_spec.tn_dev.tn_rdev : VNOVAL;
	vap->va_bytes = round_page(node->tn_size);
	vap->va_filerev = VNOVAL;
	vap->va_vaflags = 0;
	vap->va_spare = VNOVAL; /* XXX */

	return 0;
}

#define GOODTIME(tv)	((tv)->tv_sec != VNOVAL || (tv)->tv_nsec != VNOVAL)
/* XXX Should this operation be atomic?  I think it should, but code in
 * XXX other places (e.g., ufs) doesn't seem to be... */
int
tmpfs_setattr(void *v)
{
	struct vop_setattr_args /* {
		struct vnode	*a_vp;
		struct vattr	*a_vap;
		kauth_cred_t	a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	struct vattr *vap = ap->a_vap;
	kauth_cred_t cred = ap->a_cred;
	lwp_t *l = curlwp;
	int error = 0;

	KASSERT(VOP_ISLOCKED(vp));

	/* Abort if any unsettable attribute is given. */
	if (vap->va_type != VNON || vap->va_nlink != VNOVAL ||
	    vap->va_fsid != VNOVAL || vap->va_fileid != VNOVAL ||
	    vap->va_blocksize != VNOVAL || GOODTIME(&vap->va_ctime) ||
	    vap->va_gen != VNOVAL || vap->va_rdev != VNOVAL ||
	    vap->va_bytes != VNOVAL) {
		return EINVAL;
	}
	if (error == 0 && (vap->va_flags != VNOVAL))
		error = tmpfs_chflags(vp, vap->va_flags, cred, l);

	if (error == 0 && (vap->va_size != VNOVAL))
		error = tmpfs_chsize(vp, vap->va_size, cred, l);

	if (error == 0 && (vap->va_uid != VNOVAL || vap->va_gid != VNOVAL))
		error = tmpfs_chown(vp, vap->va_uid, vap->va_gid, cred, l);

	if (error == 0 && (vap->va_mode != VNOVAL))
		error = tmpfs_chmod(vp, vap->va_mode, cred, l);

	if (error == 0 && (GOODTIME(&vap->va_atime) || GOODTIME(&vap->va_mtime)
	    || GOODTIME(&vap->va_birthtime))) {
		error = tmpfs_chtimes(vp, &vap->va_atime, &vap->va_mtime,
		    &vap->va_birthtime, vap->va_vaflags, cred, l);
		if (error == 0)
			return 0;
	}
	tmpfs_update(vp, NULL, NULL, NULL, 0);
	return error;
}

int
tmpfs_read(void *v)
{
	struct vop_read_args /* {
		struct vnode *a_vp;
		struct uio *a_uio;
		int a_ioflag;
		kauth_cred_t a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	struct uio *uio = ap->a_uio;
	const int ioflag = ap->a_ioflag;
	tmpfs_node_t *node;
	struct uvm_object *uobj;
	int error;

	KASSERT(VOP_ISLOCKED(vp));

	if (vp->v_type != VREG) {
		return EISDIR;
	}
	if (uio->uio_offset < 0) {
		return EINVAL;
	}

	node = VP_TO_TMPFS_NODE(vp);
	node->tn_status |= TMPFS_NODE_ACCESSED;
	uobj = node->tn_spec.tn_reg.tn_aobj;
	error = 0;

	while (error == 0 && uio->uio_resid > 0) {
		vsize_t len;

		if (node->tn_size <= uio->uio_offset) {
			break;
		}
		len = MIN(node->tn_size - uio->uio_offset, uio->uio_resid);
		if (len == 0) {
			break;
		}
		error = ubc_uiomove(uobj, uio, len, IO_ADV_DECODE(ioflag),
		    UBC_READ | UBC_PARTIALOK | UBC_UNMAP_FLAG(vp));
	}
	return error;
}

int
tmpfs_write(void *v)
{
	struct vop_write_args /* {
		struct vnode	*a_vp;
		struct uio	*a_uio;
		int		a_ioflag;
		kauth_cred_t	a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	struct uio *uio = ap->a_uio;
	const int ioflag = ap->a_ioflag;
	tmpfs_node_t *node;
	struct uvm_object *uobj;
	off_t oldsize;
	bool extended;
	int error;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);
	oldsize = node->tn_size;

	if (uio->uio_offset < 0 || vp->v_type != VREG) {
		error = EINVAL;
		goto out;
	}
	if (uio->uio_resid == 0) {
		error = 0;
		goto out;
	}
	if (ioflag & IO_APPEND) {
		uio->uio_offset = node->tn_size;
	}

	extended = uio->uio_offset + uio->uio_resid > node->tn_size;
	if (extended) {
		error = tmpfs_reg_resize(vp, uio->uio_offset + uio->uio_resid);
		if (error)
			goto out;
	}

	uobj = node->tn_spec.tn_reg.tn_aobj;
	error = 0;
	while (error == 0 && uio->uio_resid > 0) {
		vsize_t len;

		len = MIN(node->tn_size - uio->uio_offset, uio->uio_resid);
		if (len == 0) {
			break;
		}
		error = ubc_uiomove(uobj, uio, len, IO_ADV_DECODE(ioflag),
		    UBC_WRITE | UBC_UNMAP_FLAG(vp));
	}
	if (error) {
		(void)tmpfs_reg_resize(vp, oldsize);
	}

	node->tn_status |= TMPFS_NODE_ACCESSED | TMPFS_NODE_MODIFIED |
	    (extended ? TMPFS_NODE_CHANGED : 0);
	VN_KNOTE(vp, NOTE_WRITE);
out:
	if (error) {
		KASSERT(oldsize == node->tn_size);
	} else {
		KASSERT(uio->uio_resid == 0);
	}
	return error;
}

int
tmpfs_fsync(void *v)
{
	struct vop_fsync_args /* {
		struct vnode *a_vp;
		kauth_cred_t a_cred;
		int a_flags;
		off_t a_offlo;
		off_t a_offhi;
		struct lwp *a_l;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;

	/* Nothing to do.  Just update. */
	KASSERT(VOP_ISLOCKED(vp));
	tmpfs_update(vp, NULL, NULL, NULL, 0);
	return 0;
}

/*
 * tmpfs_remove: unlink a file.
 *
 * => Both directory (dvp) and file (vp) are locked.
 * => We unlock and drop the reference on both.
 */
int
tmpfs_remove(void *v)
{
	struct vop_remove_args /* {
		struct vnode *a_dvp;
		struct vnode *a_vp;
		struct componentname *a_cnp;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp, *vp = ap->a_vp;
	tmpfs_node_t *node;
	tmpfs_dirent_t *de;
	int error;

	KASSERT(VOP_ISLOCKED(dvp));
	KASSERT(VOP_ISLOCKED(vp));

	if (vp->v_type == VDIR) {
		error = EPERM;
		goto out;
	}
	node = VP_TO_TMPFS_NODE(vp);

	/* Files marked as immutable or append-only cannot be deleted. */
	if (node->tn_flags & (IMMUTABLE | APPEND)) {
		error = EPERM;
		goto out;
	}

	/* Lookup the directory entry (check the cached hint first). */
	de = tmpfs_dir_cached(node);
	if (de == NULL) {
		tmpfs_node_t *dnode = VP_TO_TMPFS_DIR(dvp);
		struct componentname *cnp = ap->a_cnp;
		de = tmpfs_dir_lookup(dnode, cnp);
	}
	KASSERT(de && de->td_node == node);

	/*
	 * Remove the entry from the directory (drops the link count) and
	 * destroy it or replace it with a whiteout.
	 * Note: the inode referred by it will not be destroyed
	 * until the vnode is reclaimed/recycled.
	 */
	tmpfs_dir_detach(dvp, de);
	if (ap->a_cnp->cn_flags & DOWHITEOUT)
		tmpfs_dir_attach(dvp, de, TMPFS_NODE_WHITEOUT);
	else
		tmpfs_free_dirent(VFS_TO_TMPFS(vp->v_mount), de);
	error = 0;
out:
	/* Drop the references and unlock the vnodes. */
	vput(vp);
	if (dvp == vp) {
		vrele(dvp);
	} else {
		vput(dvp);
	}
	return error;
}

/*
 * tmpfs_link: create a hard link.
 */
int
tmpfs_link(void *v)
{
	struct vop_link_args /* {
		struct vnode *a_dvp;
		struct vnode *a_vp;
		struct componentname *a_cnp;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp;
	vnode_t *vp = ap->a_vp;
	struct componentname *cnp = ap->a_cnp;
	tmpfs_node_t *dnode, *node;
	tmpfs_dirent_t *de;
	int error;

	KASSERT(dvp != vp);
	KASSERT(VOP_ISLOCKED(dvp));
	KASSERT(vp->v_type != VDIR);
	KASSERT(dvp->v_mount == vp->v_mount);

	dnode = VP_TO_TMPFS_DIR(dvp);
	node = VP_TO_TMPFS_NODE(vp);

	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);

	/* Check for maximum number of links limit. */
	if (node->tn_links == LINK_MAX) {
		error = EMLINK;
		goto out;
	}
	KASSERT(node->tn_links < LINK_MAX);

	/* We cannot create links of files marked immutable or append-only. */
	if (node->tn_flags & (IMMUTABLE | APPEND)) {
		error = EPERM;
		goto out;
	}

	/* Allocate a new directory entry to represent the inode. */
	error = tmpfs_alloc_dirent(VFS_TO_TMPFS(vp->v_mount),
	    cnp->cn_nameptr, cnp->cn_namelen, &de);
	if (error) {
		goto out;
	}

	/*
	 * Insert the entry into the directory.
	 * It will increase the inode link count.
	 */
	tmpfs_dir_attach(dvp, de, node);

	/* Update the timestamps and trigger the event. */
	if (node->tn_vnode) {
		VN_KNOTE(node->tn_vnode, NOTE_LINK);
	}
	node->tn_status |= TMPFS_NODE_CHANGED;
	tmpfs_update(vp, NULL, NULL, NULL, 0);
	error = 0;
out:
	VOP_UNLOCK(vp);
	vput(dvp);
	return error;
}

/*
 * tmpfs_rename: rename routine, the hairiest system call, with the
 * insane API.
 *
 * Arguments: fdvp (from-parent vnode), fvp (from-leaf), tdvp (to-parent)
 * and tvp (to-leaf), if exists (NULL if not).
 *
 * => Caller holds a reference on fdvp and fvp, they are unlocked.
 *    Note: fdvp and fvp can refer to the same object (i.e. when it is root).
 *
 * => Both tdvp and tvp are referenced and locked.  It is our responsibility
 *    to release the references and unlock them (or destroy).
 */

/*
 * First, some forward declarations of subroutines.
 */

static int tmpfs_sane_rename(struct vnode *, struct componentname *,
    struct vnode *, struct componentname *, kauth_cred_t, bool);
static int tmpfs_rename_enter(struct mount *, struct tmpfs_mount *,
    kauth_cred_t,
    struct vnode *, struct tmpfs_node *, struct componentname *,
    struct tmpfs_dirent **, struct vnode **,
    struct vnode *, struct tmpfs_node *, struct componentname *,
    struct tmpfs_dirent **, struct vnode **);
static int tmpfs_rename_enter_common(struct mount *, struct tmpfs_mount *,
    kauth_cred_t,
    struct vnode *, struct tmpfs_node *,
    struct componentname *, struct tmpfs_dirent **, struct vnode **,
    struct componentname *, struct tmpfs_dirent **, struct vnode **);
static int tmpfs_rename_enter_separate(struct mount *, struct tmpfs_mount *,
    kauth_cred_t,
    struct vnode *, struct tmpfs_node *, struct componentname *,
    struct tmpfs_dirent **, struct vnode **,
    struct vnode *, struct tmpfs_node *, struct componentname *,
    struct tmpfs_dirent **, struct vnode **);
static void tmpfs_rename_exit(struct tmpfs_mount *,
    struct vnode *, struct vnode *, struct vnode *, struct vnode *);
static int tmpfs_rename_lock_directory(struct vnode *, struct tmpfs_node *);
static int tmpfs_rename_genealogy(struct tmpfs_node *, struct tmpfs_node *,
    struct tmpfs_node **);
static int tmpfs_rename_lock(struct mount *, kauth_cred_t, int,
    struct vnode *, struct tmpfs_node *, struct componentname *, bool,
    struct tmpfs_dirent **, struct vnode **,
    struct vnode *, struct tmpfs_node *, struct componentname *, bool,
    struct tmpfs_dirent **, struct vnode **);
static void tmpfs_rename_attachdetach(struct tmpfs_mount *,
    struct vnode *, struct tmpfs_dirent *, struct vnode *,
    struct vnode *, struct tmpfs_dirent *, struct vnode *);
static int tmpfs_do_remove(struct tmpfs_mount *, struct vnode *,
    struct tmpfs_node *, struct tmpfs_dirent *, struct vnode *, kauth_cred_t);
static int tmpfs_rename_check_possible(struct tmpfs_node *,
    struct tmpfs_node *, struct tmpfs_node *, struct tmpfs_node *);
static int tmpfs_rename_check_permitted(kauth_cred_t,
    struct tmpfs_node *, struct tmpfs_node *,
    struct tmpfs_node *, struct tmpfs_node *);
static int tmpfs_remove_check_possible(struct tmpfs_node *,
    struct tmpfs_node *);
static int tmpfs_remove_check_permitted(kauth_cred_t,
    struct tmpfs_node *, struct tmpfs_node *);
static int tmpfs_check_sticky(kauth_cred_t,
    struct tmpfs_node *, struct tmpfs_node *);

int
tmpfs_rename(void *v)
{
	struct vop_rename_args  /* {
		struct vnode		*a_fdvp;
		struct vnode		*a_fvp;
		struct componentname	*a_fcnp;
		struct vnode		*a_tdvp;
		struct vnode		*a_tvp;
		struct componentname	*a_tcnp;
	} */ *ap = v;
	struct vnode *fdvp = ap->a_fdvp;
	struct vnode *fvp = ap->a_fvp;
	struct componentname *fcnp = ap->a_fcnp;
	struct vnode *tdvp = ap->a_tdvp;
	struct vnode *tvp = ap->a_tvp;
	struct componentname *tcnp = ap->a_tcnp;
	kauth_cred_t cred;
	int error;

	KASSERT(fdvp != NULL);
	KASSERT(fvp != NULL);
	KASSERT(fcnp != NULL);
	KASSERT(fcnp->cn_nameptr != NULL);
	KASSERT(tdvp != NULL);
	KASSERT(tcnp != NULL);
	KASSERT(fcnp->cn_nameptr != NULL);
	/* KASSERT(VOP_ISLOCKED(fdvp) != LK_EXCLUSIVE); */
	/* KASSERT(VOP_ISLOCKED(fvp) != LK_EXCLUSIVE); */
	KASSERT(VOP_ISLOCKED(tdvp) == LK_EXCLUSIVE);
	KASSERT((tvp == NULL) || (VOP_ISLOCKED(tvp) == LK_EXCLUSIVE));
	KASSERT(fdvp->v_type == VDIR);
	KASSERT(tdvp->v_type == VDIR);

	cred = fcnp->cn_cred;
	KASSERT(tcnp->cn_cred == cred);

	/*
	 * Sanitize our world from the VFS insanity.  Unlock the target
	 * directory and node, which are locked.  Release the children,
	 * which are referenced.  Check for rename("x", "y/."), which
	 * it is our responsibility to reject, not the caller's.  (But
	 * the caller does reject rename("x/.", "y").  Go figure.)
	 */

	VOP_UNLOCK(tdvp);
	if ((tvp != NULL) && (tvp != tdvp))
		VOP_UNLOCK(tvp);

	vrele(fvp);
	if (tvp != NULL)
		vrele(tvp);

	if (tvp == tdvp) {
		error = EINVAL;
		goto out;
	}

	error = tmpfs_sane_rename(fdvp, fcnp, tdvp, tcnp, cred, false);

out:	/*
	 * All done, whether with success or failure.  Release the
	 * directory nodes now, as the caller expects from the VFS
	 * protocol.
	 */
	vrele(fdvp);
	vrele(tdvp);

	return error;
}

/*
 * tmpfs_sane_rename: rename routine, the hairiest system call, with
 * the sane API.
 *
 * Arguments:
 *
 * . fdvp (from directory vnode),
 * . fcnp (from component name),
 * . tdvp (to directory vnode), and
 * . tcnp (to component name).
 *
 * fdvp and tdvp must be referenced and unlocked.
 */
static int
tmpfs_sane_rename(struct vnode *fdvp, struct componentname *fcnp,
    struct vnode *tdvp, struct componentname *tcnp, kauth_cred_t cred,
    bool posixly_correct)
{
	struct mount *mount;
	struct tmpfs_mount *tmpfs;
	struct tmpfs_node *fdnode, *tdnode;
	struct tmpfs_dirent *fde, *tde;
	struct vnode *fvp, *tvp;
	char *newname;
	int error;

	KASSERT(fdvp != NULL);
	KASSERT(fcnp != NULL);
	KASSERT(tdvp != NULL);
	KASSERT(tcnp != NULL);
	/* KASSERT(VOP_ISLOCKED(fdvp) != LK_EXCLUSIVE); */
	/* KASSERT(VOP_ISLOCKED(tdvp) != LK_EXCLUSIVE); */
	KASSERT(fdvp->v_type == VDIR);
	KASSERT(tdvp->v_type == VDIR);
	KASSERT(fdvp->v_mount == tdvp->v_mount);
	KASSERT((fcnp->cn_flags & ISDOTDOT) == 0);
	KASSERT((tcnp->cn_flags & ISDOTDOT) == 0);
	KASSERT((fcnp->cn_namelen != 1) || (fcnp->cn_nameptr[0] != '.'));
	KASSERT((tcnp->cn_namelen != 1) || (tcnp->cn_nameptr[0] != '.'));
	KASSERT((fcnp->cn_namelen != 2) || (fcnp->cn_nameptr[0] != '.') ||
	    (fcnp->cn_nameptr[1] != '.'));
	KASSERT((tcnp->cn_namelen != 2) || (tcnp->cn_nameptr[0] != '.') ||
	    (tcnp->cn_nameptr[1] != '.'));

	/*
	 * Pull out the tmpfs data structures.
	 */
	fdnode = VP_TO_TMPFS_NODE(fdvp);
	tdnode = VP_TO_TMPFS_NODE(tdvp);
	KASSERT(fdnode != NULL);
	KASSERT(tdnode != NULL);
	KASSERT(fdnode->tn_vnode == fdvp);
	KASSERT(tdnode->tn_vnode == tdvp);
	KASSERT(fdnode->tn_type == VDIR);
	KASSERT(tdnode->tn_type == VDIR);

	mount = fdvp->v_mount;
	KASSERT(mount != NULL);
	KASSERT(mount == tdvp->v_mount);
	/* XXX How can we be sure this stays true?  (Not that you're
	 * likely to mount a tmpfs read-only...)  */
	KASSERT((mount->mnt_flag & MNT_RDONLY) == 0);
	tmpfs = VFS_TO_TMPFS(mount);
	KASSERT(tmpfs != NULL);

	/*
	 * Decide whether we need a new name, and allocate memory for
	 * it if so.  Do this before locking anything or taking
	 * destructive actions so that we can back out safely and sleep
	 * safely.  XXX Is sleeping an issue here?  Can this just be
	 * moved into tmpfs_rename_attachdetach?
	 */
	if (tmpfs_strname_neqlen(fcnp, tcnp)) {
		newname = tmpfs_strname_alloc(tmpfs, tcnp->cn_namelen);
		if (newname == NULL) {
			error = ENOSPC;
			goto out_unlocked;
		}
	} else {
		newname = NULL;
	}

	/*
	 * Lock and look up everything.  GCC is not very clever.
	 */
	fde = tde = NULL;
	fvp = tvp = NULL;
	error = tmpfs_rename_enter(mount, tmpfs, cred,
	    fdvp, fdnode, fcnp, &fde, &fvp,
	    tdvp, tdnode, tcnp, &tde, &tvp);
	if (error)
		goto out_unlocked;

	/*
	 * Check that everything is locked and looks right.
	 */
	KASSERT(fde != NULL);
	KASSERT(fvp != NULL);
	KASSERT(fde->td_node != NULL);
	KASSERT(fde->td_node->tn_vnode == fvp);
	KASSERT(fde->td_node->tn_type == fvp->v_type);
	KASSERT((tde == NULL) == (tvp == NULL));
	KASSERT((tde == NULL) || (tde->td_node != NULL));
	KASSERT((tde == NULL) || (tde->td_node->tn_vnode == tvp));
	KASSERT((tde == NULL) || (tde->td_node->tn_type == tvp->v_type));
	KASSERT(VOP_ISLOCKED(fdvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(tdvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(fvp) == LK_EXCLUSIVE);
	KASSERT((tvp == NULL) || (VOP_ISLOCKED(tvp) == LK_EXCLUSIVE));

	/*
	 * If the source and destination are the same object, we need
	 * only at most delete the source entry.
	 */
	if (fvp == tvp) {
		KASSERT(tvp != NULL);
		if (fde->td_node->tn_type == VDIR) {
			/* XXX How can this possibly happen?  */
			error = EINVAL;
			goto out_locked;
		}
		if (!posixly_correct && (fde != tde)) {
			/* XXX Doesn't work because of locking.
			 * error = VOP_REMOVE(fdvp, fvp);
			 */
			error = tmpfs_do_remove(tmpfs, fdvp, fdnode, fde, fvp,
			    cred);
			if (error)
				goto out_locked;
		}
		goto success;
	}
	KASSERT(fde != tde);
	KASSERT(fvp != tvp);

	/*
	 * If the target exists, refuse to rename a directory over a
	 * non-directory or vice versa, or to clobber a non-empty
	 * directory.
	 */
	if (tvp != NULL) {
		KASSERT(tde != NULL);
		KASSERT(tde->td_node != NULL);
		if (fvp->v_type == VDIR && tvp->v_type == VDIR)
			error = ((tde->td_node->tn_size > 0)? ENOTEMPTY : 0);
		else if (fvp->v_type == VDIR && tvp->v_type != VDIR)
			error = ENOTDIR;
		else if (fvp->v_type != VDIR && tvp->v_type == VDIR)
			error = EISDIR;
		else
			error = 0;
		if (error)
			goto out_locked;
		KASSERT((fvp->v_type == VDIR) == (tvp->v_type == VDIR));
	}

	/*
	 * Authorize the rename.
	 */
	error = tmpfs_rename_check_possible(fdnode, fde->td_node,
	    tdnode, (tde? tde->td_node : NULL));
	if (error)
		goto out_locked;
	error = tmpfs_rename_check_permitted(cred, fdnode, fde->td_node,
	    tdnode, (tde? tde->td_node : NULL));
	error = kauth_authorize_vnode(cred, KAUTH_VNODE_DELETE, fvp, fdvp,
	    error);
	error = kauth_authorize_vnode(cred, KAUTH_VNODE_RENAME, tvp, tdvp,
	    error);
	if (error)
		goto out_locked;

	/*
	 * Everything is hunky-dory.  Shuffle the directory entries.
	 */
	tmpfs_rename_attachdetach(tmpfs, fdvp, fde, fvp, tdvp, tde, tvp);

	/*
	 * Update the directory entry's name necessary, and flag
	 * metadata updates.  A memory allocation failure here is not
	 * OK because we've already committed some changes that we
	 * can't back out at this point, and we have things locked so
	 * we can't sleep, hence the early allocation above.
	 */
	if (newname != NULL) {
		KASSERT(tcnp->cn_namelen <= TMPFS_MAXNAMLEN);

		tmpfs_strname_free(tmpfs, fde->td_name, fde->td_namelen);
		fde->td_namelen = (uint16_t)tcnp->cn_namelen;
		(void)memcpy(newname, tcnp->cn_nameptr, tcnp->cn_namelen);
		/* Commit newname and don't free it on the way out.  */
		fde->td_name = newname;
		newname = NULL;

		fde->td_node->tn_status |= TMPFS_NODE_CHANGED;
		tdnode->tn_status |= TMPFS_NODE_MODIFIED;
	}

success:
	VN_KNOTE(fvp, NOTE_RENAME);
	error = 0;

out_locked:
	tmpfs_rename_exit(tmpfs, fdvp, fvp, tdvp, tvp);

out_unlocked:
	/* KASSERT(VOP_ISLOCKED(fdvp) != LK_EXCLUSIVE); */
	/* KASSERT(VOP_ISLOCKED(tdvp) != LK_EXCLUSIVE); */
	/* KASSERT((fvp == NULL) || (VOP_ISLOCKED(fvp) != LK_EXCLUSIVE)); */
	/* KASSERT((tvp == NULL) || (VOP_ISLOCKED(tvp) != LK_EXCLUSIVE)); */

	if (newname != NULL)
		tmpfs_strname_free(tmpfs, newname, tcnp->cn_namelen);

	return error;
}

/*
 * Look up fcnp in fdnode/fdvp and store its directory entry in fde_ret
 * and the associated vnode in fvp_ret; fail if not found.  Look up
 * tcnp in tdnode/tdvp and store its directory entry in tde_ret and the
 * associated vnode in tvp_ret; store null instead if not found.  Fail
 * if anything has been mounted on any of the nodes involved.
 *
 * fdvp and tdvp must be referenced.
 *
 * On entry, nothing is locked.
 *
 * On success, everything is locked, and *fvp_ret, and *tvp_ret if
 * nonnull, are referenced.  The only pairs of vnodes that may be
 * identical are {fdvp, tdvp} and {fvp, tvp}.
 *
 * On failure, everything remains as was.
 *
 * Locking everything including the source and target nodes is
 * necessary to make sure that, e.g., link count updates are OK.  The
 * locking order is, in general, ancestor-first, matching the order you
 * need to use to look up a descendant anyway.
 */
static int
tmpfs_rename_enter(struct mount *mount, struct tmpfs_mount *tmpfs,
    kauth_cred_t cred,
    struct vnode *fdvp, struct tmpfs_node *fdnode, struct componentname *fcnp,
    struct tmpfs_dirent **fde_ret, struct vnode **fvp_ret,
    struct vnode *tdvp, struct tmpfs_node *tdnode, struct componentname *tcnp,
    struct tmpfs_dirent **tde_ret, struct vnode **tvp_ret)
{
	int error;

	KASSERT(mount != NULL);
	KASSERT(tmpfs != NULL);
	KASSERT(fdvp != NULL);
	KASSERT(fdnode != NULL);
	KASSERT(fcnp != NULL);
	KASSERT(fde_ret != NULL);
	KASSERT(fvp_ret != NULL);
	KASSERT(tdvp != NULL);
	KASSERT(tdnode != NULL);
	KASSERT(tcnp != NULL);
	KASSERT(tde_ret != NULL);
	KASSERT(tvp_ret != NULL);
	KASSERT(fdnode->tn_vnode == fdvp);
	KASSERT(tdnode->tn_vnode == tdvp);
	KASSERT(fdnode->tn_type == VDIR);
	KASSERT(tdnode->tn_type == VDIR);

	if (fdvp == tdvp) {
		KASSERT(fdnode == tdnode);
		error = tmpfs_rename_enter_common(mount, tmpfs, cred, fdvp,
		    fdnode, fcnp, fde_ret, fvp_ret, tcnp, tde_ret, tvp_ret);
	} else {
		KASSERT(fdnode != tdnode);
		error = tmpfs_rename_enter_separate(mount, tmpfs, cred,
		    fdvp, fdnode, fcnp, fde_ret, fvp_ret,
		    tdvp, tdnode, tcnp, tde_ret, tvp_ret);
	}

	if (error)
		return error;

	KASSERT(*fde_ret != NULL);
	KASSERT(*fvp_ret != NULL);
	KASSERT((*tde_ret == NULL) == (*tvp_ret == NULL));
	KASSERT((*tde_ret == NULL) || ((*tde_ret)->td_node != NULL));
	KASSERT((*tde_ret == NULL) ||
	    ((*tde_ret)->td_node->tn_vnode == *tvp_ret));
	KASSERT(VOP_ISLOCKED(fdvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(*fvp_ret) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(tdvp) == LK_EXCLUSIVE);
	KASSERT((*tvp_ret == NULL) ||
	    (VOP_ISLOCKED(*tvp_ret) == LK_EXCLUSIVE));
	KASSERT(*fvp_ret != fdvp);
	KASSERT(*fvp_ret != tdvp);
	KASSERT(*tvp_ret != fdvp);
	KASSERT(*tvp_ret != tdvp);
	return 0;
}

/*
 * Lock and look up with a common source/target directory.
 */
static int
tmpfs_rename_enter_common(struct mount *mount, struct tmpfs_mount *tmpfs,
    kauth_cred_t cred,
    struct vnode *dvp, struct tmpfs_node *dnode,
    struct componentname *fcnp,
    struct tmpfs_dirent **fde_ret, struct vnode **fvp_ret,
    struct componentname *tcnp,
    struct tmpfs_dirent **tde_ret, struct vnode **tvp_ret)
{
	struct tmpfs_dirent *fde, *tde;
	struct vnode *fvp, *tvp;
	int error;

	error = tmpfs_rename_lock_directory(dvp, dnode);
	if (error)
		goto fail0;

	/* Did we lose a race with mount?  */
	if (dvp->v_mountedhere != NULL) {
		error = EBUSY;
		goto fail1;
	}

	/* Make sure the caller may read the directory.  */
	error = VOP_ACCESS(dvp, VEXEC, cred);
	if (error)
		goto fail1;

	/*
	 * The order in which we lock the source and target nodes is
	 * irrelevant because there can only be one rename on this
	 * directory in flight at a time, and we have it locked.
	 */

	fde = tmpfs_dir_lookup(dnode, fcnp);
	if (fde == NULL) {
		error = ENOENT;
		goto fail1;
	}

	KASSERT(fde->td_node != NULL);
	/* We ruled out `.' earlier.  */
	KASSERT(fde->td_node != dnode);
	/* We ruled out `..' earlier.  */
	KASSERT(fde->td_node != dnode->tn_spec.tn_dir.tn_parent);
	mutex_enter(&fde->td_node->tn_vlock);
	error = tmpfs_vnode_get(mount, fde->td_node, &fvp);
	if (error)
		goto fail1;
	KASSERT(fvp != NULL);
	KASSERT(VOP_ISLOCKED(fvp) == LK_EXCLUSIVE);
	KASSERT(fvp != dvp);
	KASSERT(fvp->v_mount == mount);

	/* Refuse to rename a mount point.  */
	if ((fvp->v_type == VDIR) && (fvp->v_mountedhere != NULL)) {
		error = EBUSY;
		goto fail2;
	}

	tde = tmpfs_dir_lookup(dnode, tcnp);
	if (tde == NULL) {
		tvp = NULL;
	} else {
		KASSERT(tde->td_node != NULL);
		/* We ruled out `.' earlier.  */
		KASSERT(tde->td_node != dnode);
		/* We ruled out `..' earlier.  */
		KASSERT(tde->td_node != dnode->tn_spec.tn_dir.tn_parent);
		if (tde->td_node != fde->td_node) {
			mutex_enter(&tde->td_node->tn_vlock);
			error = tmpfs_vnode_get(mount, tde->td_node, &tvp);
			if (error)
				goto fail2;
			KASSERT(tvp->v_mount == mount);
			/* Refuse to rename over a mount point.  */
			if ((tvp->v_type == VDIR) &&
			    (tvp->v_mountedhere != NULL)) {
				error = EBUSY;
				goto fail3;
			}
		} else {
			tvp = fvp;
			vref(tvp);
		}
		KASSERT(tvp != NULL);
		KASSERT(VOP_ISLOCKED(tvp) == LK_EXCLUSIVE);
	}
	KASSERT(tvp != dvp);

	*fde_ret = fde;
	*fvp_ret = fvp;
	*tde_ret = tde;
	*tvp_ret = tvp;
	return 0;

fail3:	if (tvp != NULL) {
		if (tvp != fvp)
			vput(tvp);
		else
			vrele(tvp);
	}

fail2:	vput(fvp);
fail1:	VOP_UNLOCK(dvp);
fail0:	return error;
}

/*
 * Lock and look up with separate source and target directories.
 */
static int
tmpfs_rename_enter_separate(struct mount *mount, struct tmpfs_mount *tmpfs,
    kauth_cred_t cred,
    struct vnode *fdvp, struct tmpfs_node *fdnode, struct componentname *fcnp,
    struct tmpfs_dirent **fde_ret, struct vnode **fvp_ret,
    struct vnode *tdvp, struct tmpfs_node *tdnode, struct componentname *tcnp,
    struct tmpfs_dirent **tde_ret, struct vnode **tvp_ret)
{
	struct tmpfs_node *intermediate_node;
	struct tmpfs_dirent *fde, *tde;
	struct vnode *fvp, *tvp;
	int error;

	KASSERT(fdvp != tdvp);
	KASSERT(fdnode != tdnode);

#if 0				/* XXX */
	mutex_enter(&tmpfs->tm_rename_lock);
#endif

	error = tmpfs_rename_genealogy(fdnode, tdnode, &intermediate_node);
	if (error)
		goto fail;

	/*
	 * intermediate_node == NULL means fdnode is not an ancestor of
	 * tdnode.
	 */
	if (intermediate_node == NULL)
		error = tmpfs_rename_lock(mount, cred, ENOTEMPTY,
		    tdvp, tdnode, tcnp, true, &tde, &tvp,
		    fdvp, fdnode, fcnp, false, &fde, &fvp);
	else
		error = tmpfs_rename_lock(mount, cred, EINVAL,
		    fdvp, fdnode, fcnp, false, &fde, &fvp,
		    tdvp, tdnode, tcnp, true, &tde, &tvp);
	if (error)
		goto fail;

	KASSERT(fde != NULL);
	KASSERT(fde->td_node != NULL);

	/*
	 * Reject rename("foo/bar", "foo/bar/baz/quux/zot").
	 */
	if (fde->td_node == intermediate_node) {
		tmpfs_rename_exit(tmpfs, fdvp, fvp, tdvp, tvp);
		return EINVAL;
	}

	*fde_ret = fde;
	*fvp_ret = fvp;
	*tde_ret = tde;
	*tvp_ret = tvp;
	return 0;

fail:
#if 0				/* XXX */
	mutex_exit(&tmpfs->tm_rename_lock);
#endif
	return error;
}

/*
 * Unlock everything we locked for rename.
 *
 * fdvp and tdvp must be referenced.
 *
 * On entry, everything is locked, and fvp and tvp referenced.
 *
 * On exit, everything is unlocked, and fvp and tvp are released.
 */
static void
tmpfs_rename_exit(struct tmpfs_mount *tmpfs,
    struct vnode *fdvp, struct vnode *fvp,
    struct vnode *tdvp, struct vnode *tvp)
{

	KASSERT(tmpfs != NULL);
	KASSERT(fdvp != NULL);
	KASSERT(fvp != NULL);
	KASSERT(fdvp != fvp);
	KASSERT(fdvp != tvp);
	KASSERT(tdvp != tvp);
	KASSERT(tdvp != fvp);
	KASSERT(VOP_ISLOCKED(fdvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(tdvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(fvp) == LK_EXCLUSIVE);
	KASSERT((tvp == NULL) || (VOP_ISLOCKED(tvp) == LK_EXCLUSIVE));

	if (tvp != NULL) {
		if (tvp != fvp)
			vput(tvp);
		else
			vrele(tvp);
	}
	VOP_UNLOCK(tdvp);
	vput(fvp);
	if (fdvp != tdvp)
		VOP_UNLOCK(fdvp);

#if 0				/* XXX */
	if (fdvp != tdvp)
		mutex_exit(&tmpfs->tm_rename_lock);
#endif
}

/*
 * Lock a directory, but fail if it has been rmdir'd.
 *
 * vp must be referenced.
 */
static int
tmpfs_rename_lock_directory(struct vnode *vp, struct tmpfs_node *node)
{

	KASSERT(vp != NULL);
	KASSERT(node != NULL);
	KASSERT(node->tn_vnode == vp);
	KASSERT(node->tn_type == VDIR);

	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	if (node->tn_spec.tn_dir.tn_parent == NULL) {
		VOP_UNLOCK(vp);
		return ENOENT;
	}

	return 0;
}

/*
 * Analyze the genealogy of the source and target nodes.
 *
 * On success, stores in *intermediate_node_ret either the child of
 * fdnode of which tdnode is a descendant, or null if tdnode is not a
 * descendant of fdnode at all.
 *
 * fdnode and tdnode must be unlocked and referenced.  The file
 * system's rename lock must also be held, to exclude concurrent
 * changes to the file system's genealogy other than rmdir.
 *
 * XXX This causes an extra lock/unlock of tdnode in the case when
 * we're just about to lock it again before locking anything else.
 * However, changing that requires reorganizing the code to make it
 * even more horrifically obscure.
 */
static int
tmpfs_rename_genealogy(struct tmpfs_node *fdnode, struct tmpfs_node *tdnode,
    struct tmpfs_node **intermediate_node_ret)
{
	struct tmpfs_node *node = tdnode, *parent;
	int error;

	KASSERT(fdnode != NULL);
	KASSERT(tdnode != NULL);
	KASSERT(fdnode != tdnode);
	KASSERT(intermediate_node_ret != NULL);

	KASSERT(fdnode->tn_vnode != NULL);
	KASSERT(tdnode->tn_vnode != NULL);
	KASSERT(fdnode->tn_type == VDIR);
	KASSERT(tdnode->tn_type == VDIR);

	/*
	 * We need to provisionally lock tdnode->tn_vnode to keep rmdir
	 * from deleting it -- or any ancestor -- at an inopportune
	 * moment.
	 */
	error = tmpfs_rename_lock_directory(tdnode->tn_vnode, tdnode);
	if (error)
		return error;

	for (;;) {
		parent = node->tn_spec.tn_dir.tn_parent;
		KASSERT(parent != NULL);
		KASSERT(parent->tn_type == VDIR);

		/* Did we hit the root without finding fdnode?  */
		if (parent == node) {
			*intermediate_node_ret = NULL;
			break;
		}

		/* Did we find that fdnode is an ancestor?  */
		if (parent == fdnode) {
			*intermediate_node_ret = node;
			break;
		}

		/* Neither -- keep ascending the family tree.  */
		node = parent;
	}

	VOP_UNLOCK(tdnode->tn_vnode);
	return 0;
}

/*
 * Lock directories a and b, which must be distinct, and look up and
 * lock nodes a and b.  Do a first and then b.  Directory b may not be
 * an ancestor of directory a, although directory a may be an ancestor
 * of directory b.  Fail with overlap_error if node a is directory b.
 * Neither componentname may be `.' or `..'.
 *
 * a_dvp and b_dvp must be referenced.
 *
 * On entry, a_dvp and b_dvp are unlocked.
 *
 * On success,
 * . a_dvp and b_dvp are locked,
 * . *a_dirent_ret is filled with a directory entry whose node is
 *     locked and referenced,
 * . *b_vp_ret is filled with the corresponding vnode,
 * . *b_dirent_ret is filled either with null or with a directory entry
 *     whose node is locked and referenced,
 * . *b_vp is filled either with null or with the corresponding vnode,
 *     and
 * . the only pair of vnodes that may be identical is a_vp and b_vp.
 *
 * On failure, a_dvp and b_dvp are left unlocked, and *a_dirent_ret,
 * *a_vp, *b_dirent_ret, and *b_vp are left alone.
 */
static int
tmpfs_rename_lock(struct mount *mount, kauth_cred_t cred, int overlap_error,
    struct vnode *a_dvp, struct tmpfs_node *a_dnode,
    struct componentname *a_cnp, bool a_missing_ok,
    struct tmpfs_dirent **a_dirent_ret, struct vnode **a_vp_ret,
    struct vnode *b_dvp, struct tmpfs_node *b_dnode,
    struct componentname *b_cnp, bool b_missing_ok,
    struct tmpfs_dirent **b_dirent_ret, struct vnode **b_vp_ret)
{
	struct tmpfs_dirent *a_dirent, *b_dirent;
	struct vnode *a_vp, *b_vp;
	int error;

	KASSERT(a_dvp != NULL);
	KASSERT(a_dnode != NULL);
	KASSERT(a_cnp != NULL);
	KASSERT(a_dirent_ret != NULL);
	KASSERT(a_vp_ret != NULL);
	KASSERT(b_dvp != NULL);
	KASSERT(b_dnode != NULL);
	KASSERT(b_cnp != NULL);
	KASSERT(b_dirent_ret != NULL);
	KASSERT(b_vp_ret != NULL);
	KASSERT(a_dvp != b_dvp);
	KASSERT(a_dnode != b_dnode);
	KASSERT(a_dnode->tn_vnode == a_dvp);
	KASSERT(b_dnode->tn_vnode == b_dvp);
	KASSERT(a_dnode->tn_type == VDIR);
	KASSERT(b_dnode->tn_type == VDIR);
	KASSERT(a_missing_ok != b_missing_ok);

	error = tmpfs_rename_lock_directory(a_dvp, a_dnode);
	if (error)
		goto fail0;

	/* Did we lose a race with mount?  */
	if (a_dvp->v_mountedhere != NULL) {
		error = EBUSY;
		goto fail1;
	}

	/* Make sure the caller may read the directory.  */
	error = VOP_ACCESS(a_dvp, VEXEC, cred);
	if (error)
		goto fail1;

	a_dirent = tmpfs_dir_lookup(a_dnode, a_cnp);
	if (a_dirent != NULL) {
		KASSERT(a_dirent->td_node != NULL);
		/* We ruled out `.' earlier.  */
		KASSERT(a_dirent->td_node != a_dnode);
		/* We ruled out `..' earlier.  */
		KASSERT(a_dirent->td_node !=
		    a_dnode->tn_spec.tn_dir.tn_parent);
		if (a_dirent->td_node == b_dnode) {
			error = overlap_error;
			goto fail1;
		}
		mutex_enter(&a_dirent->td_node->tn_vlock);
		error = tmpfs_vnode_get(mount, a_dirent->td_node, &a_vp);
		if (error)
			goto fail1;
		KASSERT(a_vp->v_mount == mount);
		/* Refuse to rename (over) a mount point.  */
		if ((a_vp->v_type == VDIR) && (a_vp->v_mountedhere != NULL)) {
			error = EBUSY;
			goto fail2;
		}
	} else if (!a_missing_ok) {
		error = ENOENT;
		goto fail1;
	} else {
		a_vp = NULL;
	}
	KASSERT(a_vp != a_dvp);
	KASSERT(a_vp != b_dvp);

	error = tmpfs_rename_lock_directory(b_dvp, b_dnode);
	if (error)
		goto fail2;

	/* Did we lose a race with mount?  */
	if (b_dvp->v_mountedhere != NULL) {
		error = EBUSY;
		goto fail3;
	}

	/* Make sure the caller may read the directory.  */
	error = VOP_ACCESS(b_dvp, VEXEC, cred);
	if (error)
		goto fail3;

	b_dirent = tmpfs_dir_lookup(b_dnode, b_cnp);
	if (b_dirent != NULL) {
		KASSERT(b_dirent->td_node != NULL);
		/* We ruled out `.' earlier.  */
		KASSERT(b_dirent->td_node != b_dnode);
		/* We ruled out `..' earlier.  */
		KASSERT(b_dirent->td_node !=
		    b_dnode->tn_spec.tn_dir.tn_parent);
		/* b is not an ancestor of a.  */
		KASSERT(b_dirent->td_node != a_dnode);
		/* But the source and target nodes might be the same.  */
		if ((a_dirent == NULL) ||
		    (a_dirent->td_node != b_dirent->td_node)) {
			mutex_enter(&b_dirent->td_node->tn_vlock);
			error = tmpfs_vnode_get(mount, b_dirent->td_node,
			    &b_vp);
			if (error)
				goto fail3;
			KASSERT(b_vp->v_mount == mount);
			KASSERT(a_vp != b_vp);
			/* Refuse to rename (over) a mount point.  */
			if ((b_vp->v_type == VDIR) &&
			    (b_vp->v_mountedhere != NULL)) {
				error = EBUSY;
				goto fail4;
			}
		} else {
			b_vp = a_vp;
			vref(b_vp);
		}
	} else if (!b_missing_ok) {
		error = ENOENT;
		goto fail3;
	} else {
		b_vp = NULL;
	}
	KASSERT(b_vp != a_dvp);
	KASSERT(b_vp != b_dvp);

	KASSERT(VOP_ISLOCKED(a_dvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(b_dvp) == LK_EXCLUSIVE);
	KASSERT(a_missing_ok || (a_dirent != NULL));
	KASSERT(a_missing_ok || (a_dirent->td_node != NULL));
	KASSERT(b_missing_ok || (b_dirent != NULL));
	KASSERT(b_missing_ok || (b_dirent->td_node != NULL));
	KASSERT((a_dirent == NULL) || (a_dirent->td_node != NULL));
	KASSERT((a_dirent == NULL) || (a_dirent->td_node->tn_vnode == a_vp));
	KASSERT((b_dirent == NULL) || (b_dirent->td_node != NULL));
	KASSERT((b_dirent == NULL) || (b_dirent->td_node->tn_vnode == b_vp));
	KASSERT((a_vp == NULL) || (VOP_ISLOCKED(a_vp) == LK_EXCLUSIVE));
	KASSERT((b_vp == NULL) || (VOP_ISLOCKED(b_vp) == LK_EXCLUSIVE));

	*a_dirent_ret = a_dirent;
	*b_dirent_ret = b_dirent;
	*a_vp_ret = a_vp;
	*b_vp_ret = b_vp;
	return 0;

fail4:	if (b_vp != NULL) {
		KASSERT(VOP_ISLOCKED(b_vp) == LK_EXCLUSIVE);
		if (b_vp != a_vp)
			vput(b_vp);
		else
			vrele(a_vp);
	}

fail3:	KASSERT(VOP_ISLOCKED(b_dvp) == LK_EXCLUSIVE);
	VOP_UNLOCK(b_dvp);

fail2:	if (a_vp != NULL) {
		KASSERT(VOP_ISLOCKED(a_vp) == LK_EXCLUSIVE);
		vput(a_vp);
	}

fail1:	KASSERT(VOP_ISLOCKED(a_dvp) == LK_EXCLUSIVE);
	VOP_UNLOCK(a_dvp);

fail0:	/* KASSERT(VOP_ISLOCKED(a_dvp) != LK_EXCLUSIVE); */
	/* KASSERT(VOP_ISLOCKED(b_dvp) != LK_EXCLUSIVE); */
	/* KASSERT((a_vp == NULL) || (VOP_ISLOCKED(a_vp) != LK_EXCLUSIVE)); */
	/* KASSERT((b_vp == NULL) || (VOP_ISLOCKED(b_vp) != LK_EXCLUSIVE)); */
	return error;
}

/*
 * Shuffle the directory entries to move fvp from the directory fdvp
 * into the directory tdvp.  fde is fvp's directory entry in fdvp.  If
 * we are overwriting a target node, it is tvp, and tde is its
 * directory entry in tdvp.
 *
 * fdvp, fvp, tdvp, and tvp must all be locked and referenced.
 */
static void
tmpfs_rename_attachdetach(struct tmpfs_mount *tmpfs,
    struct vnode *fdvp, struct tmpfs_dirent *fde, struct vnode *fvp,
    struct vnode *tdvp, struct tmpfs_dirent *tde, struct vnode *tvp)
{

	KASSERT(tmpfs != NULL);
	KASSERT(fdvp != NULL);
	KASSERT(fde != NULL);
	KASSERT(fvp != NULL);
	KASSERT(tdvp != NULL);
	KASSERT(fde->td_node != NULL);
	KASSERT(fde->td_node->tn_vnode == fvp);
	KASSERT((tde == NULL) == (tvp == NULL));
	KASSERT((tde == NULL) || (tde->td_node != NULL));
	KASSERT((tde == NULL) || (tde->td_node->tn_vnode == tvp));
	KASSERT(VOP_ISLOCKED(fdvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(tdvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(fvp) == LK_EXCLUSIVE);
	KASSERT((tvp == NULL) || (VOP_ISLOCKED(tvp) == LK_EXCLUSIVE));

	/*
	 * If we are moving from one directory to another, detach the
	 * source entry and reattach it to the target directory.
	 */
	if (fdvp != tdvp) {
		/* tmpfs_dir_detach clobbers fde->td_node, so save it.  */
		struct tmpfs_node *fnode = fde->td_node;
		tmpfs_dir_detach(fdvp, fde);
		tmpfs_dir_attach(tdvp, fde, fnode);
	} else if (tvp == NULL) {
		/*
		 * We are changing the directory.  tmpfs_dir_attach and
		 * tmpfs_dir_detach note the events for us, but for
		 * this case we don't call them, so we must note the
		 * event explicitly.
		 */
		VN_KNOTE(fdvp, NOTE_WRITE);
	}

	/*
	 * If we are replacing an existing target entry, delete it.
	 */
	if (tde != NULL) {
		KASSERT(tvp != NULL);
		KASSERT(tde->td_node != NULL);
		KASSERT((fvp->v_type == VDIR) == (tvp->v_type == VDIR));
		if (tde->td_node->tn_type == VDIR) {
			KASSERT(tde->td_node->tn_size == 0);
			KASSERT(tde->td_node->tn_links == 2);
			/* Decrement the extra link count for `.' so
			 * the vnode will be recycled when released.  */
			tde->td_node->tn_links--;
		}
		tmpfs_dir_detach(tdvp, tde);
		tmpfs_free_dirent(tmpfs, tde);
	}
}

/*
 * Remove the entry de for the non-directory vp from the directory dvp.
 *
 * Everything must be locked and referenced.
 */
static int
tmpfs_do_remove(struct tmpfs_mount *tmpfs, struct vnode *dvp,
    struct tmpfs_node *dnode, struct tmpfs_dirent *de, struct vnode *vp,
    kauth_cred_t cred)
{
	int error;

	KASSERT(tmpfs != NULL);
	KASSERT(dvp != NULL);
	KASSERT(dnode != NULL);
	KASSERT(de != NULL);
	KASSERT(vp != NULL);
	KASSERT(dnode->tn_vnode == dvp);
	KASSERT(de->td_node != NULL);
	KASSERT(de->td_node->tn_vnode == vp);
	KASSERT(VOP_ISLOCKED(dvp) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(vp) == LK_EXCLUSIVE);

	error = tmpfs_remove_check_possible(dnode, de->td_node);
	if (error)
		return error;

	error = tmpfs_remove_check_permitted(cred, dnode, de->td_node);
	error = kauth_authorize_vnode(cred, KAUTH_VNODE_DELETE, vp, dvp,
	    error);
	if (error)
		return error;

	tmpfs_dir_detach(dvp, de);
	tmpfs_free_dirent(tmpfs, de);

	return 0;
}

/*
 * Check whether a rename is possible independent of credentials.
 *
 * Everything must be locked and referenced.
 */
static int
tmpfs_rename_check_possible(
    struct tmpfs_node *fdnode, struct tmpfs_node *fnode,
    struct tmpfs_node *tdnode, struct tmpfs_node *tnode)
{

	KASSERT(fdnode != NULL);
	KASSERT(fnode != NULL);
	KASSERT(tdnode != NULL);
	KASSERT(fdnode != fnode);
	KASSERT(tdnode != tnode);
	KASSERT(fnode != tnode);
	KASSERT(fdnode->tn_vnode != NULL);
	KASSERT(fnode->tn_vnode != NULL);
	KASSERT(tdnode->tn_vnode != NULL);
	KASSERT((tnode == NULL) || (tnode->tn_vnode != NULL));
	KASSERT(VOP_ISLOCKED(fdnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(fnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(tdnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT((tnode == NULL) ||
	    (VOP_ISLOCKED(tnode->tn_vnode) == LK_EXCLUSIVE));

	/*
	 * If fdnode is immutable, we can't write to it.  If fdnode is
	 * append-only, the only change we can make is to add entries
	 * to it.  If fnode is immutable, we can't change the links to
	 * it.  If fnode is append-only...well, this is what UFS does.
	 */
	if ((fdnode->tn_flags | fnode->tn_flags) & (IMMUTABLE | APPEND))
		return EPERM;

	/*
	 * If tdnode is immutable, we can't write to it.  If tdnode is
	 * append-only, we can add entries, but we can't change
	 * existing entries.
	 */
	if (tdnode->tn_flags & (IMMUTABLE | (tnode? APPEND : 0)))
		return EPERM;

	/*
	 * If tnode is immutable, we can't replace links to it.  If
	 * tnode is append-only...well, this is what UFS does.
	 */
	if (tnode != NULL) {
		KASSERT(tnode != NULL);
		if ((tnode->tn_flags & (IMMUTABLE | APPEND)) != 0)
			return EPERM;
	}

	return 0;
}

/*
 * Check whether a rename is permitted given our credentials.
 *
 * Everything must be locked and referenced.
 */
static int
tmpfs_rename_check_permitted(kauth_cred_t cred,
    struct tmpfs_node *fdnode, struct tmpfs_node *fnode,
    struct tmpfs_node *tdnode, struct tmpfs_node *tnode)
{
	int error;

	KASSERT(fdnode != NULL);
	KASSERT(fnode != NULL);
	KASSERT(tdnode != NULL);
	KASSERT(fdnode != fnode);
	KASSERT(tdnode != tnode);
	KASSERT(fnode != tnode);
	KASSERT(fdnode->tn_vnode != NULL);
	KASSERT(fnode->tn_vnode != NULL);
	KASSERT(tdnode->tn_vnode != NULL);
	KASSERT((tnode == NULL) || (tnode->tn_vnode != NULL));
	KASSERT(VOP_ISLOCKED(fdnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(fnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(tdnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT((tnode == NULL) ||
	    (VOP_ISLOCKED(tnode->tn_vnode) == LK_EXCLUSIVE));

	/*
	 * We need to remove or change an entry in the source directory.
	 */
	error = VOP_ACCESS(fdnode->tn_vnode, VWRITE, cred);
	if (error)
		return error;

	/*
	 * If we are changing directories, then we need to write to the
	 * target directory to add or change an entry.  Also, if fnode
	 * is a directory, we need to write to it to change its `..'
	 * entry.
	 */
	if (fdnode != tdnode) {
		error = VOP_ACCESS(tdnode->tn_vnode, VWRITE, cred);
		if (error)
			return error;
		if (fnode->tn_type == VDIR) {
			error = VOP_ACCESS(fnode->tn_vnode, VWRITE, cred);
			if (error)
				return error;
		}
	}

	error = tmpfs_check_sticky(cred, fdnode, fnode);
	if (error)
		return error;

	error = tmpfs_check_sticky(cred, tdnode, tnode);
	if (error)
		return error;

	return 0;
}

/*
 * Check whether removing node's entry in dnode is possible independent
 * of credentials.
 *
 * Everything must be locked and referenced.
 */
static int
tmpfs_remove_check_possible(struct tmpfs_node *dnode, struct tmpfs_node *node)
{

	KASSERT(dnode != NULL);
	KASSERT(dnode->tn_vnode != NULL);
	KASSERT(node != NULL);
	KASSERT(dnode != node);
	KASSERT(VOP_ISLOCKED(dnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(node->tn_vnode) == LK_EXCLUSIVE);

	/*
	 * We want to delete the entry.  If dnode is immutable, we
	 * can't write to it to delete the entry.  If dnode is
	 * append-only, the only change we can make is to add entries,
	 * so we can't delete entries.  If node is immutable, we can't
	 * change the links to it, so we can't delete the entry.  If
	 * node is append-only...well, this is what UFS does.
	 */
	if ((dnode->tn_flags | node->tn_flags) & (IMMUTABLE | APPEND))
		return EPERM;

	return 0;
}

/*
 * Check whether removing node's entry in dnode is permitted given our
 * credentials.
 *
 * Everything must be locked and referenced.
 */
static int
tmpfs_remove_check_permitted(kauth_cred_t cred,
    struct tmpfs_node *dnode, struct tmpfs_node *node)
{
	int error;

	KASSERT(dnode != NULL);
	KASSERT(dnode->tn_vnode != NULL);
	KASSERT(node != NULL);
	KASSERT(dnode != node);
	KASSERT(VOP_ISLOCKED(dnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT(VOP_ISLOCKED(node->tn_vnode) == LK_EXCLUSIVE);

	/*
	 * Check whether we are permitted to write to the source
	 * directory in order to delete an entry from it.
	 */
	error = VOP_ACCESS(dnode->tn_vnode, VWRITE, cred);
	if (error)
		return error;

	error = tmpfs_check_sticky(cred, dnode, node);
	if (error)
		return error;

	return 0;
}

/*
 * Check whether we may change an entry in a sticky directory.  If the
 * directory is sticky, the user must own either the directory or, if
 * it exists, the node, in order to change the entry.
 *
 * Everything must be locked and referenced.
 */
static int
tmpfs_check_sticky(kauth_cred_t cred,
    struct tmpfs_node *dnode, struct tmpfs_node *node)
{

	KASSERT(dnode != NULL);
	KASSERT(dnode->tn_vnode != NULL);
	KASSERT(VOP_ISLOCKED(dnode->tn_vnode) == LK_EXCLUSIVE);
	KASSERT((node == NULL) || (node->tn_vnode != NULL));
	KASSERT((node == NULL) ||
	    (VOP_ISLOCKED(dnode->tn_vnode) == LK_EXCLUSIVE));

	if (dnode->tn_mode & S_ISTXT) {
		uid_t euid = kauth_cred_geteuid(cred);
		if (euid == dnode->tn_uid)
			return 0;
		if ((node == NULL) || (euid == node->tn_uid))
			return 0;
		return EPERM;
	}

	return 0;
}

int
tmpfs_mkdir(void *v)
{
	struct vop_mkdir_args /* {
		struct vnode		*a_dvp;
		struct vnode		**a_vpp;
		struct componentname	*a_cnp;
		struct vattr		*a_vap;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp;
	vnode_t **vpp = ap->a_vpp;
	struct componentname *cnp = ap->a_cnp;
	struct vattr *vap = ap->a_vap;

	KASSERT(vap->va_type == VDIR);
	return tmpfs_alloc_file(dvp, vpp, vap, cnp, NULL);
}

int
tmpfs_rmdir(void *v)
{
	struct vop_rmdir_args /* {
		struct vnode		*a_dvp;
		struct vnode		*a_vp;
		struct componentname	*a_cnp;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp;
	vnode_t *vp = ap->a_vp;
	tmpfs_mount_t *tmp = VFS_TO_TMPFS(dvp->v_mount);
	tmpfs_node_t *dnode = VP_TO_TMPFS_DIR(dvp);
	tmpfs_node_t *node = VP_TO_TMPFS_DIR(vp);
	tmpfs_dirent_t *de;
	int error = 0;

	KASSERT(VOP_ISLOCKED(dvp));
	KASSERT(VOP_ISLOCKED(vp));
	KASSERT(node->tn_spec.tn_dir.tn_parent == dnode);

	/*
	 * Directories with more than two non-whiteout
	 * entries ('.' and '..') cannot be removed.
	 */
	if (node->tn_size > 0) {
		KASSERT(error == 0);
		TAILQ_FOREACH(de, &node->tn_spec.tn_dir.tn_dir, td_entries) {
			if (de->td_node != TMPFS_NODE_WHITEOUT) {
				error = ENOTEMPTY;
				break;
			}
		}
		if (error)
			goto out;
	}

	/* Lookup the directory entry (check the cached hint first). */
	de = tmpfs_dir_cached(node);
	if (de == NULL) {
		struct componentname *cnp = ap->a_cnp;
		de = tmpfs_dir_lookup(dnode, cnp);
	}
	KASSERT(de && de->td_node == node);

	/* Check flags to see if we are allowed to remove the directory. */
	if (dnode->tn_flags & APPEND || node->tn_flags & (IMMUTABLE | APPEND)) {
		error = EPERM;
		goto out;
	}

	/* Decrement the link count for the virtual '.' entry. */
	node->tn_links--;
	node->tn_status |= TMPFS_NODE_STATUSALL;

	/* Detach the directory entry from the directory. */
	tmpfs_dir_detach(dvp, de);

	/* Purge the cache for parent. */
	cache_purge(dvp);

	/*
	 * Destroy the directory entry or replace it with a whiteout.
	 * Note: the inode referred by it will not be destroyed
	 * until the vnode is reclaimed.
	 */
	if (ap->a_cnp->cn_flags & DOWHITEOUT)
		tmpfs_dir_attach(dvp, de, TMPFS_NODE_WHITEOUT);
	else
		tmpfs_free_dirent(tmp, de);

	/* Destroy the whiteout entries from the node. */
	while ((de = TAILQ_FIRST(&node->tn_spec.tn_dir.tn_dir)) != NULL) {
		KASSERT(de->td_node == TMPFS_NODE_WHITEOUT);
		tmpfs_dir_detach(vp, de);
		tmpfs_free_dirent(tmp, de);
	}

	KASSERT(node->tn_links == 0);
out:
	/* Release the nodes. */
	vput(dvp);
	vput(vp);
	return error;
}

int
tmpfs_symlink(void *v)
{
	struct vop_symlink_args /* {
		struct vnode		*a_dvp;
		struct vnode		**a_vpp;
		struct componentname	*a_cnp;
		struct vattr		*a_vap;
		char			*a_target;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp;
	vnode_t **vpp = ap->a_vpp;
	struct componentname *cnp = ap->a_cnp;
	struct vattr *vap = ap->a_vap;
	char *target = ap->a_target;

	KASSERT(vap->va_type == VLNK);
	return tmpfs_alloc_file(dvp, vpp, vap, cnp, target);
}

int
tmpfs_readdir(void *v)
{
	struct vop_readdir_args /* {
		struct vnode	*a_vp;
		struct uio	*a_uio;
		kauth_cred_t	a_cred;
		int		*a_eofflag;
		off_t		**a_cookies;
		int		*ncookies;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	struct uio *uio = ap->a_uio;
	int *eofflag = ap->a_eofflag;
	off_t **cookies = ap->a_cookies;
	int *ncookies = ap->a_ncookies;
	off_t startoff, cnt;
	tmpfs_node_t *node;
	int error;

	KASSERT(VOP_ISLOCKED(vp));

	/* This operation only makes sense on directory nodes. */
	if (vp->v_type != VDIR) {
		return ENOTDIR;
	}
	node = VP_TO_TMPFS_DIR(vp);
	startoff = uio->uio_offset;
	cnt = 0;
	if (node->tn_links == 0) {
		error = 0;
		goto out;
	}

	if (uio->uio_offset == TMPFS_DIRCOOKIE_DOT) {
		error = tmpfs_dir_getdotdent(node, uio);
		if (error != 0) {
			if (error == -1)
				error = 0;
			goto out;
		}
		cnt++;
	}
	if (uio->uio_offset == TMPFS_DIRCOOKIE_DOTDOT) {
		error = tmpfs_dir_getdotdotdent(node, uio);
		if (error != 0) {
			if (error == -1)
				error = 0;
			goto out;
		}
		cnt++;
	}
	error = tmpfs_dir_getdents(node, uio, &cnt);
	if (error == -1) {
		error = 0;
	}
	KASSERT(error >= 0);
out:
	if (eofflag != NULL) {
		*eofflag = (!error && uio->uio_offset == TMPFS_DIRCOOKIE_EOF);
	}
	if (error || cookies == NULL || ncookies == NULL) {
		return error;
	}

	/* Update NFS-related variables, if any. */
	off_t i, off = startoff;
	tmpfs_dirent_t *de = NULL;

	*cookies = malloc(cnt * sizeof(off_t), M_TEMP, M_WAITOK);
	*ncookies = cnt;

	for (i = 0; i < cnt; i++) {
		KASSERT(off != TMPFS_DIRCOOKIE_EOF);
		if (off != TMPFS_DIRCOOKIE_DOT) {
			if (off == TMPFS_DIRCOOKIE_DOTDOT) {
				de = TAILQ_FIRST(&node->tn_spec.tn_dir.tn_dir);
			} else if (de != NULL) {
				de = TAILQ_NEXT(de, td_entries);
			} else {
				de = tmpfs_dir_lookupbycookie(node, off);
				KASSERT(de != NULL);
				de = TAILQ_NEXT(de, td_entries);
			}
			if (de == NULL) {
				off = TMPFS_DIRCOOKIE_EOF;
			} else {
				off = tmpfs_dircookie(de);
			}
		} else {
			off = TMPFS_DIRCOOKIE_DOTDOT;
		}
		(*cookies)[i] = off;
	}
	KASSERT(uio->uio_offset == off);
	return error;
}

int
tmpfs_readlink(void *v)
{
	struct vop_readlink_args /* {
		struct vnode	*a_vp;
		struct uio	*a_uio;
		kauth_cred_t	a_cred;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	struct uio *uio = ap->a_uio;
	tmpfs_node_t *node;
	int error;

	KASSERT(VOP_ISLOCKED(vp));
	KASSERT(uio->uio_offset == 0);
	KASSERT(vp->v_type == VLNK);

	node = VP_TO_TMPFS_NODE(vp);
	error = uiomove(node->tn_spec.tn_lnk.tn_link,
	    MIN(node->tn_size, uio->uio_resid), uio);
	node->tn_status |= TMPFS_NODE_ACCESSED;

	return error;
}

int
tmpfs_inactive(void *v)
{
	struct vop_inactive_args /* {
		struct vnode *a_vp;
		bool *a_recycle;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	tmpfs_node_t *node;

	KASSERT(VOP_ISLOCKED(vp));

	node = VP_TO_TMPFS_NODE(vp);
	*ap->a_recycle = (node->tn_links == 0);
	VOP_UNLOCK(vp);

	return 0;
}

int
tmpfs_reclaim(void *v)
{
	struct vop_reclaim_args /* {
		struct vnode *a_vp;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	tmpfs_mount_t *tmp = VFS_TO_TMPFS(vp->v_mount);
	tmpfs_node_t *node = VP_TO_TMPFS_NODE(vp);
	bool racing;

	/* Disassociate inode from vnode. */
	mutex_enter(&node->tn_vlock);
	node->tn_vnode = NULL;
	vp->v_data = NULL;
	/* Check if tmpfs_vnode_get() is racing with us. */
	racing = TMPFS_NODE_RECLAIMING(node);
	mutex_exit(&node->tn_vlock);

	/*
	 * If inode is not referenced, i.e. no links, then destroy it.
	 * Note: if racing - inode is about to get a new vnode, leave it.
	 */
	if (node->tn_links == 0 && !racing) {
		tmpfs_free_node(tmp, node);
	}
	return 0;
}

int
tmpfs_pathconf(void *v)
{
	struct vop_pathconf_args /* {
		struct vnode	*a_vp;
		int		a_name;
		register_t	*a_retval;
	} */ *ap = v;
	const int name = ap->a_name;
	register_t *retval = ap->a_retval;
	int error = 0;

	switch (name) {
	case _PC_LINK_MAX:
		*retval = LINK_MAX;
		break;
	case _PC_NAME_MAX:
		*retval = TMPFS_MAXNAMLEN;
		break;
	case _PC_PATH_MAX:
		*retval = PATH_MAX;
		break;
	case _PC_PIPE_BUF:
		*retval = PIPE_BUF;
		break;
	case _PC_CHOWN_RESTRICTED:
		*retval = 1;
		break;
	case _PC_NO_TRUNC:
		*retval = 1;
		break;
	case _PC_SYNC_IO:
		*retval = 1;
		break;
	case _PC_FILESIZEBITS:
		*retval = sizeof(off_t) * CHAR_BIT;
		break;
	default:
		error = EINVAL;
	}
	return error;
}

int
tmpfs_advlock(void *v)
{
	struct vop_advlock_args /* {
		struct vnode	*a_vp;
		void *		a_id;
		int		a_op;
		struct flock	*a_fl;
		int		a_flags;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	tmpfs_node_t *node = VP_TO_TMPFS_NODE(vp);

	return lf_advlock(v, &node->tn_lockf, node->tn_size);
}

int
tmpfs_getpages(void *v)
{
	struct vop_getpages_args /* {
		struct vnode *a_vp;
		voff_t a_offset;
		struct vm_page **a_m;
		int *a_count;
		int a_centeridx;
		vm_prot_t a_access_type;
		int a_advice;
		int a_flags;
	} */ * const ap = v;
	vnode_t *vp = ap->a_vp;
	const voff_t offset = ap->a_offset;
	struct vm_page **pgs = ap->a_m;
	const int centeridx = ap->a_centeridx;
	const vm_prot_t access_type = ap->a_access_type;
	const int advice = ap->a_advice;
	const int flags = ap->a_flags;
	int error, npages = *ap->a_count;
	tmpfs_node_t *node;
	struct uvm_object *uobj;

	KASSERT(vp->v_type == VREG);
	KASSERT(mutex_owned(vp->v_interlock));

	node = VP_TO_TMPFS_NODE(vp);
	uobj = node->tn_spec.tn_reg.tn_aobj;

	/*
	 * Currently, PGO_PASTEOF is not supported.
	 */
	if (vp->v_size <= offset + (centeridx << PAGE_SHIFT)) {
		if ((flags & PGO_LOCKED) == 0)
			mutex_exit(vp->v_interlock);
		return EINVAL;
	}

	if (vp->v_size < offset + (npages << PAGE_SHIFT)) {
		npages = (round_page(vp->v_size) - offset) >> PAGE_SHIFT;
	}

	if ((flags & PGO_LOCKED) != 0)
		return EBUSY;

	if ((flags & PGO_NOTIMESTAMP) == 0) {
		if ((vp->v_mount->mnt_flag & MNT_NOATIME) == 0)
			node->tn_status |= TMPFS_NODE_ACCESSED;

		if ((access_type & VM_PROT_WRITE) != 0) {
			node->tn_status |= TMPFS_NODE_MODIFIED;
			if (vp->v_mount->mnt_flag & MNT_RELATIME)
				node->tn_status |= TMPFS_NODE_ACCESSED;
		}
	}

	/*
	 * Invoke the pager.
	 *
	 * Clean the array of pages before.  XXX: PR/32166
	 * Note that vnode lock is shared with underlying UVM object.
	 */
	if (pgs) {
		memset(pgs, 0, sizeof(struct vm_pages *) * npages);
	}
	KASSERT(vp->v_interlock == uobj->vmobjlock);

	error = (*uobj->pgops->pgo_get)(uobj, offset, pgs, &npages, centeridx,
	    access_type, advice, flags | PGO_ALLPAGES);

#if defined(DEBUG)
	if (!error && pgs) {
		for (int i = 0; i < npages; i++) {
			KASSERT(pgs[i] != NULL);
		}
	}
#endif
	return error;
}

int
tmpfs_putpages(void *v)
{
	struct vop_putpages_args /* {
		struct vnode *a_vp;
		voff_t a_offlo;
		voff_t a_offhi;
		int a_flags;
	} */ * const ap = v;
	vnode_t *vp = ap->a_vp;
	const voff_t offlo = ap->a_offlo;
	const voff_t offhi = ap->a_offhi;
	const int flags = ap->a_flags;
	tmpfs_node_t *node;
	struct uvm_object *uobj;
	int error;

	KASSERT(mutex_owned(vp->v_interlock));

	if (vp->v_type != VREG) {
		mutex_exit(vp->v_interlock);
		return 0;
	}

	node = VP_TO_TMPFS_NODE(vp);
	uobj = node->tn_spec.tn_reg.tn_aobj;

	KASSERT(vp->v_interlock == uobj->vmobjlock);
	error = (*uobj->pgops->pgo_put)(uobj, offlo, offhi, flags);

	/* XXX mtime */

	return error;
}

int
tmpfs_whiteout(void *v)
{
	struct vop_whiteout_args /* {
		struct vnode		*a_dvp;
		struct componentname	*a_cnp;
		int			a_flags;
	} */ *ap = v;
	vnode_t *dvp = ap->a_dvp;
	struct componentname *cnp = ap->a_cnp;
	const int flags = ap->a_flags;
	tmpfs_mount_t *tmp = VFS_TO_TMPFS(dvp->v_mount);
	tmpfs_dirent_t *de;
	int error;

	switch (flags) {
	case LOOKUP:
		break;
	case CREATE:
		error = tmpfs_alloc_dirent(tmp, cnp->cn_nameptr,
		    cnp->cn_namelen, &de);
		if (error)
			return error;
		tmpfs_dir_attach(dvp, de, TMPFS_NODE_WHITEOUT);
		break;
	case DELETE:
		cnp->cn_flags &= ~DOWHITEOUT; /* when in doubt, cargo cult */
		de = tmpfs_dir_lookup(VP_TO_TMPFS_DIR(dvp), cnp);
		if (de == NULL)
			return ENOENT;
		tmpfs_dir_detach(dvp, de);
		tmpfs_free_dirent(tmp, de);
		break;
	}
	return 0;
}

int
tmpfs_print(void *v)
{
	struct vop_print_args /* {
		struct vnode	*a_vp;
	} */ *ap = v;
	vnode_t *vp = ap->a_vp;
	tmpfs_node_t *node = VP_TO_TMPFS_NODE(vp);

	printf("tag VT_TMPFS, tmpfs_node %p, flags 0x%x, links %d\n"
	    "\tmode 0%o, owner %d, group %d, size %" PRIdMAX ", status 0x%x",
	    node, node->tn_flags, node->tn_links, node->tn_mode, node->tn_uid,
	    node->tn_gid, (uintmax_t)node->tn_size, node->tn_status);
	if (vp->v_type == VFIFO) {
		VOCALL(fifo_vnodeop_p, VOFFSET(vop_print), v);
	}
	printf("\n");
	return 0;
}