fs/unionfs/union_subr.c

/*-
 * Copyright (c) 1994 Jan-Simon Pendry
 * Copyright (c) 1994
 *	The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2005, 2006 Masanori Ozawa <ozawa@ongs.co.jp>, ONGS Inc.
 * Copyright (c) 2006 Daichi Goto <daichi@freebsd.org>
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *	@(#)union_subr.c	8.20 (Berkeley) 5/20/95
 * $FreeBSD$
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/dirent.h>
#include <sys/fcntl.h>
#include <sys/filedesc.h>
#include <sys/stat.h>
#include <sys/resourcevar.h>

#ifdef MAC
#include <sys/mac.h>
#endif

#include <vm/uma.h>

#include <fs/unionfs/union.h>

#define	NUNIONFSNODECACHE 32

#define	UNIONFS_NHASH(upper, lower) \
	(&unionfs_node_hashtbl[(((uintptr_t)upper + (uintptr_t)lower) >> 8) & unionfs_node_hash])

static LIST_HEAD(unionfs_node_hashhead, unionfs_node) *unionfs_node_hashtbl;
static u_long	unionfs_node_hash;
struct mtx	unionfs_hashmtx;

static MALLOC_DEFINE(M_UNIONFSHASH, "UNIONFS hash", "UNIONFS hash table");
MALLOC_DEFINE(M_UNIONFSNODE, "UNIONFS node", "UNIONFS vnode private part");
MALLOC_DEFINE(M_UNIONFSPATH, "UNIONFS path", "UNIONFS path private part");

/*
 * Initialize cache headers
 */
int
unionfs_init(struct vfsconf *vfsp)
{
	UNIONFSDEBUG("unionfs_init\n");	/* printed during system boot */
	unionfs_node_hashtbl = hashinit(NUNIONFSNODECACHE, M_UNIONFSHASH, &unionfs_node_hash);
	mtx_init(&unionfs_hashmtx, "unionfs", NULL, MTX_DEF);

	return (0);
}

/*
 * Destroy cache headers
 */
int
unionfs_uninit(struct vfsconf *vfsp)
{
	mtx_destroy(&unionfs_hashmtx);
	free(unionfs_node_hashtbl, M_UNIONFSHASH);
	return (0);
}

/*
 * Return a VREF'ed alias for unionfs vnode if already exists, else 0.
 */
static struct vnode *
unionfs_hashget(struct mount *mp, struct vnode *uppervp,
		struct vnode *lowervp, struct vnode *dvp, char *path,
		int lkflags, struct thread *td)
{
	struct unionfs_node_hashhead *hd;
	struct unionfs_node *unp;
	struct vnode   *vp;
	int error;

	if (lkflags & LK_TYPE_MASK)
		lkflags |= LK_RETRY;
	hd = UNIONFS_NHASH(uppervp, lowervp);

	mtx_lock(&unionfs_hashmtx);
	LIST_FOREACH(unp, hd, un_hash) {
		if (unp->un_uppervp == uppervp &&
		    unp->un_lowervp == lowervp &&
		    unp->un_dvp == dvp &&
		    UNIONFSTOV(unp)->v_mount == mp &&
		    (!path || !(unp->un_path) || !strcmp(unp->un_path, path))) {
			vp = UNIONFSTOV(unp);
			VI_LOCK(vp);
			mtx_unlock(&unionfs_hashmtx);
			/*
			 * We need to clear the OWEINACT flag here as this
			 * may lead vget() to try to lock our vnode which is
			 * already locked via vp.
			 */
			vp->v_iflag &= ~VI_OWEINACT;
			error = vget(vp, LK_INTERLOCK, td);
			if (error != 0)
				panic("unionfs_hashget: vget error %d", error);
			if (lkflags & LK_TYPE_MASK)
				vn_lock(vp, lkflags, td);
			return (vp);
		}
	}

	mtx_unlock(&unionfs_hashmtx);

	return (NULLVP);
}

/*
 * Act like unionfs_hashget, but add passed unionfs_node to hash if no existing
 * node found.
 */
static struct vnode *
unionfs_hashins(struct mount *mp, struct unionfs_node *uncp,
		char *path, int lkflags, struct thread *td)
{
	struct unionfs_node_hashhead *hd;
	struct unionfs_node *unp;
	struct vnode   *vp;
	int error;

	if (lkflags & LK_TYPE_MASK)
		lkflags |= LK_RETRY;
	hd = UNIONFS_NHASH(uncp->un_uppervp, uncp->un_lowervp);

	mtx_lock(&unionfs_hashmtx);
	LIST_FOREACH(unp, hd, un_hash) {
		if (unp->un_uppervp == uncp->un_uppervp &&
		    unp->un_lowervp == uncp->un_lowervp &&
		    unp->un_dvp == uncp->un_dvp &&
		    UNIONFSTOV(unp)->v_mount == mp &&
		    (!path || !(unp->un_path) || !strcmp(unp->un_path, path))) {
			vp = UNIONFSTOV(unp);
			VI_LOCK(vp);
			mtx_unlock(&unionfs_hashmtx);
			vp->v_iflag &= ~VI_OWEINACT;
			error = vget(vp, LK_INTERLOCK, td);
			if (error)
				panic("unionfs_hashins: vget error %d", error);
			if (lkflags & LK_TYPE_MASK)
				vn_lock(vp, lkflags, td);
			return (vp);
		}
	}

	LIST_INSERT_HEAD(hd, uncp, un_hash);
	uncp->un_flag |= UNIONFS_CACHED;
	mtx_unlock(&unionfs_hashmtx);

	return (NULLVP);
}

/*
 * Make a new or get existing unionfs node.
 *
 * uppervp and lowervp should be unlocked. Because if new unionfs vnode is
 * locked, uppervp or lowervp is locked too. In order to prevent dead lock,
 * you should not lock plurality simultaneously.
 */
int
unionfs_nodeget(struct mount *mp, struct vnode *uppervp,
		struct vnode *lowervp, struct vnode *dvp,
		struct vnode **vpp, struct componentname *cnp,
		struct thread *td)
{
	struct unionfs_mount *ump;
	struct unionfs_node *unp;
	struct vnode   *vp;
	int		error;
	int		lkflags;
	char	       *path;

	ump = MOUNTTOUNIONFSMOUNT(mp);
	lkflags = (cnp ? cnp->cn_lkflags : 0);
	path = (cnp ? cnp->cn_nameptr : "");

	if (uppervp == NULLVP && lowervp == NULLVP)
		panic("unionfs_nodeget: upper and lower is null");

	/* If it has no ISLASTCN flag, path check is skipped. */
	if (!cnp || !(cnp->cn_flags & ISLASTCN))
		path = NULL;

	/* Lookup the hash first. */
	*vpp = unionfs_hashget(mp, uppervp, lowervp, dvp, path, lkflags, td);
	if (*vpp != NULLVP)
		return (0);

	if ((uppervp == NULLVP || ump->um_uppervp != uppervp) ||
	    (lowervp == NULLVP || ump->um_lowervp != lowervp)) {
		if (dvp == NULLVP)
			return (EINVAL);
	}

	/*
	 * Do the MALLOC before the getnewvnode since doing so afterward
	 * might cause a bogus v_data pointer to get dereferenced elsewhere
	 * if MALLOC should block.
	 */
	MALLOC(unp, struct unionfs_node *, sizeof(struct unionfs_node),
	    M_UNIONFSNODE, M_WAITOK | M_ZERO);

	error = getnewvnode("unionfs", mp, &unionfs_vnodeops, &vp);
	if (error) {
		FREE(unp, M_UNIONFSNODE);
		return (error);
	}
	error = insmntque(vp, mp);	/* XXX: Too early for mpsafe fs */
	if (error != 0) {
		FREE(unp, M_UNIONFSNODE);
		return (error);
	}
	if (dvp != NULLVP)
		vref(dvp);
	if (uppervp != NULLVP)
		vref(uppervp);
	if (lowervp != NULLVP)
		vref(lowervp);

	unp->un_vnode = vp;
	unp->un_uppervp = uppervp;
	unp->un_lowervp = lowervp;
	unp->un_dvp = dvp;
	if (uppervp != NULLVP)
		vp->v_vnlock = uppervp->v_vnlock;
	else
		vp->v_vnlock = lowervp->v_vnlock;

	if (cnp) {
		unp->un_path = (char *)
		    malloc(cnp->cn_namelen +1, M_UNIONFSPATH, M_WAITOK | M_ZERO);
		bcopy(cnp->cn_nameptr, unp->un_path, cnp->cn_namelen);
		unp->un_path[cnp->cn_namelen] = '\0';
	}
	vp->v_type = (uppervp != NULLVP ? uppervp->v_type : lowervp->v_type);
	vp->v_data = unp;

	if ((uppervp != NULLVP && ump->um_uppervp == uppervp) &&
	    (lowervp != NULLVP && ump->um_lowervp == lowervp))
		vp->v_vflag |= VV_ROOT;

	*vpp = unionfs_hashins(mp, unp, path, lkflags, td);
	if (*vpp != NULLVP) {
		if (dvp != NULLVP)
			vrele(dvp);
		if (uppervp != NULLVP)
			vrele(uppervp);
		if (lowervp != NULLVP)
			vrele(lowervp);

		unp->un_uppervp = NULLVP;
		unp->un_lowervp = NULLVP;
		unp->un_dvp = NULLVP;
		vrele(vp);

		return (0);
	}

	if (lkflags & LK_TYPE_MASK)
		vn_lock(vp, lkflags | LK_RETRY, td);

	*vpp = vp;

	return (0);
}

/*
 * Remove node from hash.
 */
void
unionfs_hashrem(struct vnode *vp, struct thread *td)
{
	int		vfslocked;
	struct unionfs_node *unp;
	struct unionfs_node_status *unsp, *unsp_tmp;
	struct vnode   *lvp;
	struct vnode   *uvp;

	/*
	 * Use the interlock to protect the clearing of v_data to
	 * prevent faults in unionfs_lock().
	 */
	VI_LOCK(vp);
	unp = VTOUNIONFS(vp);
	lvp = unp->un_lowervp;
	uvp = unp->un_uppervp;
	unp->un_lowervp = unp->un_uppervp = NULLVP;

	vp->v_vnlock = &(vp->v_lock);
	vp->v_data = NULL;
	lockmgr(vp->v_vnlock, LK_EXCLUSIVE | LK_INTERLOCK, VI_MTX(vp), td);
	if (lvp != NULLVP)
		VOP_UNLOCK(lvp, 0, td);
	if (uvp != NULLVP)
		VOP_UNLOCK(uvp, 0, td);

	mtx_lock(&unionfs_hashmtx);
	if (unp->un_flag & UNIONFS_CACHED) {
		LIST_REMOVE(unp, un_hash);
		unp->un_flag &= ~UNIONFS_CACHED;
	}
	mtx_unlock(&unionfs_hashmtx);
	vp->v_object = NULL;

	if (lvp != NULLVP) {
		vfslocked = VFS_LOCK_GIANT(lvp->v_mount);
		vrele(lvp);
		VFS_UNLOCK_GIANT(vfslocked);
	}
	if (uvp != NULLVP) {
		vfslocked = VFS_LOCK_GIANT(uvp->v_mount);
		vrele(uvp);
		VFS_UNLOCK_GIANT(vfslocked);
	}
	if (unp->un_dvp != NULLVP) {
		vfslocked = VFS_LOCK_GIANT(unp->un_dvp->v_mount);
		vrele(unp->un_dvp);
		VFS_UNLOCK_GIANT(vfslocked);
		unp->un_dvp = NULLVP;
	}
	if (unp->un_path) {
		free(unp->un_path, M_UNIONFSPATH);
		unp->un_path = NULL;
	}

	LIST_FOREACH_SAFE(unsp, &(unp->un_unshead), uns_list, unsp_tmp) {
		LIST_REMOVE(unsp, uns_list);
		free(unsp, M_TEMP);
	}
	FREE(unp, M_UNIONFSNODE);
}

/*
 * Get the unionfs node status.
 * You need exclusive lock this vnode.
 */
void
unionfs_get_node_status(struct unionfs_node *unp, struct thread *td,
			struct unionfs_node_status **unspp)
{
	struct unionfs_node_status *unsp;

	KASSERT(NULL != unspp, ("null pointer"));
	ASSERT_VOP_ELOCKED(UNIONFSTOV(unp), "unionfs_get_node_status");

	LIST_FOREACH(unsp, &(unp->un_unshead), uns_list) {
		if (unsp->uns_tid == td->td_tid) {
			*unspp = unsp;
			return;
		}
	}

	/* create a new unionfs node status */
	MALLOC(unsp, struct unionfs_node_status *,
	    sizeof(struct unionfs_node_status), M_TEMP, M_WAITOK | M_ZERO);

	unsp->uns_tid = td->td_tid;
	LIST_INSERT_HEAD(&(unp->un_unshead), unsp, uns_list);

	*unspp = unsp;
}

/*
 * Remove the unionfs node status, if you can.
 * You need exclusive lock this vnode.
 */
void
unionfs_tryrem_node_status(struct unionfs_node *unp, struct thread *td,
			   struct unionfs_node_status *unsp)
{
	KASSERT(NULL != unsp, ("null pointer"));
	ASSERT_VOP_ELOCKED(UNIONFSTOV(unp), "unionfs_get_node_status");

	if (0 < unsp->uns_lower_opencnt || 0 < unsp->uns_upper_opencnt)
		return;

	LIST_REMOVE(unsp, uns_list);
	free(unsp, M_TEMP);
}

/*
 * Create upper node attr.
 */
void
unionfs_create_uppervattr_core(struct unionfs_mount *ump,
			       struct vattr *lva,
			       struct vattr *uva,
			       struct thread *td)
{
	VATTR_NULL(uva);
	uva->va_type = lva->va_type;
	uva->va_atime = lva->va_atime;
	uva->va_mtime = lva->va_mtime;
	uva->va_ctime = lva->va_ctime;

	switch (ump->um_copymode) {
	case UNIONFS_TRANSPARENT:
		uva->va_mode = lva->va_mode;
		uva->va_uid = lva->va_uid;
		uva->va_gid = lva->va_gid;
		break;
	case UNIONFS_MASQUERADE:
		if (ump->um_uid == lva->va_uid) {
			uva->va_mode = lva->va_mode & 077077;
			uva->va_mode |= (lva->va_type == VDIR ? ump->um_udir : ump->um_ufile) & 0700;
			uva->va_uid = lva->va_uid;
			uva->va_gid = lva->va_gid;
		} else {
			uva->va_mode = (lva->va_type == VDIR ? ump->um_udir : ump->um_ufile);
			uva->va_uid = ump->um_uid;
			uva->va_gid = ump->um_gid;
		}
		break;
	default:		/* UNIONFS_TRADITIONAL */
		FILEDESC_SLOCK(td->td_proc->p_fd);
		uva->va_mode = 0777 & ~td->td_proc->p_fd->fd_cmask;
		FILEDESC_SUNLOCK(td->td_proc->p_fd);
		uva->va_uid = ump->um_uid;
		uva->va_gid = ump->um_gid;
		break;
	}
}

/*
 * Create upper node attr.
 */
int
unionfs_create_uppervattr(struct unionfs_mount *ump,
			  struct vnode *lvp,
			  struct vattr *uva,
			  struct ucred *cred,
			  struct thread *td)
{
	int		error;
	struct vattr	lva;

	if ((error = VOP_GETATTR(lvp, &lva, cred, td)))
		return (error);

	unionfs_create_uppervattr_core(ump, &lva, uva, td);

	return (error);
}

/*
 * relookup
 *
 * dvp should be locked on entry and will be locked on return.
 *
 * If an error is returned, *vpp will be invalid, otherwise it will hold a
 * locked, referenced vnode. If *vpp == dvp then remember that only one
 * LK_EXCLUSIVE lock is held.
 */
static int
unionfs_relookup(struct vnode *dvp, struct vnode **vpp,
		 struct componentname *cnp, struct componentname *cn,
		 struct thread *td, char *path, int pathlen, u_long nameiop)
{
	int	error;

	cn->cn_namelen = pathlen;
	cn->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
	bcopy(path, cn->cn_pnbuf, pathlen);
	cn->cn_pnbuf[pathlen] = '\0';

	cn->cn_nameiop = nameiop;
	cn->cn_flags = (LOCKPARENT | LOCKLEAF | HASBUF | SAVENAME | ISLASTCN);
	cn->cn_lkflags = LK_EXCLUSIVE;
	cn->cn_thread = td;
	cn->cn_cred = cnp->cn_cred;

	cn->cn_nameptr = cn->cn_pnbuf;
	cn->cn_consume = cnp->cn_consume;

	if (nameiop == DELETE)
		cn->cn_flags |= (cnp->cn_flags & (DOWHITEOUT | SAVESTART));
	else if (RENAME == nameiop)
		cn->cn_flags |= (cnp->cn_flags & SAVESTART);

	vref(dvp);
	VOP_UNLOCK(dvp, 0, td);

	if ((error = relookup(dvp, vpp, cn))) {
		uma_zfree(namei_zone, cn->cn_pnbuf);
		cn->cn_flags &= ~HASBUF;
		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, td);
	} else
		vrele(dvp);

	return (error);
}

/*
 * relookup for CREATE namei operation.
 *
 * dvp is unionfs vnode. dvp should be locked.
 *
 * If it called 'unionfs_copyfile' function by unionfs_link etc,
 * VOP_LOOKUP information is broken.
 * So it need relookup in order to create link etc.
 */
int
unionfs_relookup_for_create(struct vnode *dvp, struct componentname *cnp,
			    struct thread *td)
{
	int	error;
	struct vnode *udvp;
	struct vnode *vp;
	struct componentname cn;

	udvp = UNIONFSVPTOUPPERVP(dvp);
	vp = NULLVP;

	error = unionfs_relookup(udvp, &vp, cnp, &cn, td, cnp->cn_nameptr,
	    strlen(cnp->cn_nameptr), CREATE);
	if (error)
		return (error);

	if (vp != NULLVP) {
		if (udvp == vp)
			vrele(vp);
		else
			vput(vp);

		error = EEXIST;
	}

	if (cn.cn_flags & HASBUF) {
		uma_zfree(namei_zone, cn.cn_pnbuf);
		cn.cn_flags &= ~HASBUF;
	}

	if (!error) {
		cn.cn_flags |= (cnp->cn_flags & HASBUF);
		cnp->cn_flags = cn.cn_flags;
	}

	return (error);
}

/*
 * relookup for DELETE namei operation.
 *
 * dvp is unionfs vnode. dvp should be locked.
 */
int
unionfs_relookup_for_delete(struct vnode *dvp, struct componentname *cnp,
			    struct thread *td)
{
	int	error;
	struct vnode *udvp;
	struct vnode *vp;
	struct componentname cn;

	udvp = UNIONFSVPTOUPPERVP(dvp);
	vp = NULLVP;

	error = unionfs_relookup(udvp, &vp, cnp, &cn, td, cnp->cn_nameptr,
	    strlen(cnp->cn_nameptr), DELETE);
	if (error)
		return (error);

	if (vp == NULLVP)
		error = ENOENT;
	else {
		if (udvp == vp)
			vrele(vp);
		else
			vput(vp);
	}

	if (cn.cn_flags & HASBUF) {
		uma_zfree(namei_zone, cn.cn_pnbuf);
		cn.cn_flags &= ~HASBUF;
	}

	if (!error) {
		cn.cn_flags |= (cnp->cn_flags & HASBUF);
		cnp->cn_flags = cn.cn_flags;
	}

	return (error);
}

/*
 * relookup for RENAME namei operation.
 *
 * dvp is unionfs vnode. dvp should be locked.
 */
int
unionfs_relookup_for_rename(struct vnode *dvp, struct componentname *cnp,
			    struct thread *td)
{
	int error;
	struct vnode *udvp;
	struct vnode *vp;
	struct componentname cn;

	udvp = UNIONFSVPTOUPPERVP(dvp);
	vp = NULLVP;

	error = unionfs_relookup(udvp, &vp, cnp, &cn, td, cnp->cn_nameptr,
	    strlen(cnp->cn_nameptr), RENAME);
	if (error)
		return (error);

	if (vp != NULLVP) {
		if (udvp == vp)
			vrele(vp);
		else
			vput(vp);
	}

	if (cn.cn_flags & HASBUF) {
		uma_zfree(namei_zone, cn.cn_pnbuf);
		cn.cn_flags &= ~HASBUF;
	}

	if (!error) {
		cn.cn_flags |= (cnp->cn_flags & HASBUF);
		cnp->cn_flags = cn.cn_flags;
	}

	return (error);

}

/*
 * Update the unionfs_node.
 *
 * uvp is new locked upper vnode. unionfs vnode's lock will be exchanged to the
 * uvp's lock and lower's lock will be unlocked.
 */
static void
unionfs_node_update(struct unionfs_node *unp, struct vnode *uvp,
		    struct thread *td)
{
	int		count, lockcnt;
	struct vnode   *vp;
	struct vnode   *lvp;

	vp = UNIONFSTOV(unp);
	lvp = unp->un_lowervp;

	/*
	 * lock update
	 */
	VI_LOCK(vp);
	unp->un_uppervp = uvp;
	vp->v_vnlock = uvp->v_vnlock;
	lockcnt = lvp->v_vnlock->lk_exclusivecount;
	if (lockcnt <= 0)
		panic("unionfs: no exclusive lock");
	VI_UNLOCK(vp);
	for (count = 1; count < lockcnt; count++)
		vn_lock(uvp, LK_EXCLUSIVE | LK_CANRECURSE | LK_RETRY, td);

	/*
	 * cache update
	 */
	mtx_lock(&unionfs_hashmtx);
	if (unp->un_flag & UNIONFS_CACHED)
		LIST_REMOVE(unp, un_hash);
	LIST_INSERT_HEAD(UNIONFS_NHASH(uvp, lvp), unp, un_hash);
	unp->un_flag |= UNIONFS_CACHED;
	mtx_unlock(&unionfs_hashmtx);
}

/*
 * Create a new shadow dir.
 *
 * udvp should be locked on entry and will be locked on return.
 *
 * If no error returned, unp will be updated.
 */
int
unionfs_mkshadowdir(struct unionfs_mount *ump, struct vnode *udvp,
		    struct unionfs_node *unp, struct componentname *cnp,
		    struct thread *td)
{
	int		error;
	struct vnode   *lvp;
	struct vnode   *uvp;
	struct vattr	va;
	struct vattr	lva;
	struct componentname cn;
	struct mount   *mp;
	struct ucred   *cred;
	struct ucred   *credbk;
	struct uidinfo *rootinfo;

	if (unp->un_uppervp != NULLVP)
		return (EEXIST);

	lvp = unp->un_lowervp;
	uvp = NULLVP;
	credbk = cnp->cn_cred;

	/* Authority change to root */
	rootinfo = uifind((uid_t)0);
	cred = crdup(cnp->cn_cred);
	chgproccnt(cred->cr_ruidinfo, 1, 0);
	change_euid(cred, rootinfo);
	change_ruid(cred, rootinfo);
	change_svuid(cred, (uid_t)0);
	uifree(rootinfo);
	cnp->cn_cred = cred;

	memset(&cn, 0, sizeof(cn));

	if ((error = VOP_GETATTR(lvp, &lva, cnp->cn_cred, td)))
		goto unionfs_mkshadowdir_abort;

	if ((error = unionfs_relookup(udvp, &uvp, cnp, &cn, td, cnp->cn_nameptr, cnp->cn_namelen, CREATE)))
		goto unionfs_mkshadowdir_abort;
	if (uvp != NULLVP) {
		if (udvp == uvp)
			vrele(uvp);
		else
			vput(uvp);

		error = EEXIST;
		goto unionfs_mkshadowdir_free_out;
	}

	if ((error = vn_start_write(udvp, &mp, V_WAIT | PCATCH)))
		goto unionfs_mkshadowdir_free_out;
	if ((error = VOP_LEASE(udvp, td, cn.cn_cred, LEASE_WRITE))) {
		vn_finished_write(mp);
		goto unionfs_mkshadowdir_free_out;
	}
	unionfs_create_uppervattr_core(ump, &lva, &va, td);

	error = VOP_MKDIR(udvp, &uvp, &cn, &va);

	if (!error) {
		unionfs_node_update(unp, uvp, td);

		/*
		 * XXX The bug which cannot set uid/gid was corrected.
		 * Ignore errors.
		 */
		va.va_type = VNON;
		VOP_SETATTR(uvp, &va, cn.cn_cred, td);
	}
	vn_finished_write(mp);

unionfs_mkshadowdir_free_out:
	if (cn.cn_flags & HASBUF) {
		uma_zfree(namei_zone, cn.cn_pnbuf);
		cn.cn_flags &= ~HASBUF;
	}

unionfs_mkshadowdir_abort:
	cnp->cn_cred = credbk;
	chgproccnt(cred->cr_ruidinfo, -1, 0);
	crfree(cred);

	return (error);
}

/*
 * Create a new whiteout.
 *
 * dvp should be locked on entry and will be locked on return.
 */
int
unionfs_mkwhiteout(struct vnode *dvp, struct componentname *cnp,
		   struct thread *td, char *path)
{
	int		error;
	struct vnode   *wvp;
	struct componentname cn;
	struct mount   *mp;

	if (path == NULL)
		path = cnp->cn_nameptr;

	wvp = NULLVP;
	if ((error = unionfs_relookup(dvp, &wvp, cnp, &cn, td, path, strlen(path), CREATE)))
		return (error);
	if (wvp != NULLVP) {
		if (cn.cn_flags & HASBUF) {
			uma_zfree(namei_zone, cn.cn_pnbuf);
			cn.cn_flags &= ~HASBUF;
		}
		if (dvp == wvp)
			vrele(wvp);
		else
			vput(wvp);

		return (EEXIST);
	}

	if ((error = vn_start_write(dvp, &mp, V_WAIT | PCATCH)))
		goto unionfs_mkwhiteout_free_out;
	if (!(error = VOP_LEASE(dvp, td, td->td_ucred, LEASE_WRITE)))
		error = VOP_WHITEOUT(dvp, &cn, CREATE);

	vn_finished_write(mp);

unionfs_mkwhiteout_free_out:
	if (cn.cn_flags & HASBUF) {
		uma_zfree(namei_zone, cn.cn_pnbuf);
		cn.cn_flags &= ~HASBUF;
	}

	return (error);
}

/*
 * Create a new vnode for create a new shadow file.
 *
 * If an error is returned, *vpp will be invalid, otherwise it will hold a
 * locked, referenced and opened vnode.
 *
 * unp is never updated.
 */
static int
unionfs_vn_create_on_upper(struct vnode **vpp, struct vnode *udvp,
			   struct unionfs_node *unp, struct vattr *uvap,
			   struct thread *td)
{
	struct unionfs_mount *ump;
	struct vnode   *vp;
	struct vnode   *lvp;
	struct ucred   *cred;
	struct vattr	lva;
	int		fmode;
	int		error;
	struct componentname cn;

	ump = MOUNTTOUNIONFSMOUNT(UNIONFSTOV(unp)->v_mount);
	vp = NULLVP;
	lvp = unp->un_lowervp;
	cred = td->td_ucred;
	fmode = FFLAGS(O_WRONLY | O_CREAT | O_TRUNC | O_EXCL);
	error = 0;

	if ((error = VOP_GETATTR(lvp, &lva, cred, td)) != 0)
		return (error);
	unionfs_create_uppervattr_core(ump, &lva, uvap, td);

	if (unp->un_path == NULL)
		panic("unionfs: un_path is null");

	cn.cn_namelen = strlen(unp->un_path);
	cn.cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK);
	bcopy(unp->un_path, cn.cn_pnbuf, cn.cn_namelen + 1);
	cn.cn_nameiop = CREATE;
	cn.cn_flags = (LOCKPARENT | LOCKLEAF | HASBUF | SAVENAME | ISLASTCN);
	cn.cn_lkflags = LK_EXCLUSIVE;
	cn.cn_thread = td;
	cn.cn_cred = cred;
	cn.cn_nameptr = cn.cn_pnbuf;
	cn.cn_consume = 0;

	vref(udvp);
	if ((error = relookup(udvp, &vp, &cn)) != 0)
		goto unionfs_vn_create_on_upper_free_out2;
	vrele(udvp);

	if (vp != NULLVP) {
		if (vp == udvp)
			vrele(vp);
		else
			vput(vp);
		error = EEXIST;
		goto unionfs_vn_create_on_upper_free_out1;
	}

	if ((error = VOP_LEASE(udvp, td, cred, LEASE_WRITE)) != 0)
		goto unionfs_vn_create_on_upper_free_out1;

	if ((error = VOP_CREATE(udvp, &vp, &cn, uvap)) != 0)
		goto unionfs_vn_create_on_upper_free_out1;

	if ((error = VOP_OPEN(vp, fmode, cred, td, -1)) != 0) {
		vput(vp);
		goto unionfs_vn_create_on_upper_free_out1;
	}
	vp->v_writecount++;
	*vpp = vp;

unionfs_vn_create_on_upper_free_out1:
	VOP_UNLOCK(udvp, 0, td);

unionfs_vn_create_on_upper_free_out2:
	if (cn.cn_flags & HASBUF) {
		uma_zfree(namei_zone, cn.cn_pnbuf);
		cn.cn_flags &= ~HASBUF;
	}

	return (error);
}

/*
 * Copy from lvp to uvp.
 *
 * lvp and uvp should be locked and opened on entry and will be locked and
 * opened on return.
 */
static int
unionfs_copyfile_core(struct vnode *lvp, struct vnode *uvp,
		      struct ucred *cred, struct thread *td)
{
	int		error;
	off_t		offset;
	int		count;
	int		bufoffset;
	char           *buf;
	struct uio	uio;
	struct iovec	iov;

	error = 0;
	memset(&uio, 0, sizeof(uio));

	uio.uio_td = td;
	uio.uio_segflg = UIO_SYSSPACE;
	uio.uio_offset = 0;

	if ((error = VOP_LEASE(lvp, td, cred, LEASE_READ)) != 0)
		return (error);
	if ((error = VOP_LEASE(uvp, td, cred, LEASE_WRITE)) != 0)
		return (error);
	buf = malloc(MAXBSIZE, M_TEMP, M_WAITOK);

	while (error == 0) {
		offset = uio.uio_offset;

		uio.uio_iov = &iov;
		uio.uio_iovcnt = 1;
		iov.iov_base = buf;
		iov.iov_len = MAXBSIZE;
		uio.uio_resid = iov.iov_len;
		uio.uio_rw = UIO_READ;

		if ((error = VOP_READ(lvp, &uio, 0, cred)) != 0)
			break;
		if ((count = MAXBSIZE - uio.uio_resid) == 0)
			break;

		bufoffset = 0;
		while (bufoffset < count) {
			uio.uio_iov = &iov;
			uio.uio_iovcnt = 1;
			iov.iov_base = buf + bufoffset;
			iov.iov_len = count - bufoffset;
			uio.uio_offset = offset + bufoffset;
			uio.uio_resid = iov.iov_len;
			uio.uio_rw = UIO_WRITE;

			if ((error = VOP_WRITE(uvp, &uio, 0, cred)) != 0)
				break;

			bufoffset += (count - bufoffset) - uio.uio_resid;
		}

		uio.uio_offset = offset + bufoffset;
	}

	free(buf, M_TEMP);

	return (error);
}

/*
 * Copy file from lower to upper.
 *
 * If you need copy of the contents, set 1 to docopy. Otherwise, set 0 to
 * docopy.
 *
 * If no error returned, unp will be updated.
 */
int
unionfs_copyfile(struct unionfs_node *unp, int docopy, struct ucred *cred,
		 struct thread *td)
{
	int		error;
	struct mount   *mp;
	struct vnode   *udvp;
	struct vnode   *lvp;
	struct vnode   *uvp;
	struct vattr	uva;

	lvp = unp->un_lowervp;
	uvp = NULLVP;

	if ((UNIONFSTOV(unp)->v_mount->mnt_flag & MNT_RDONLY))
		return (EROFS);
	if (unp->un_dvp == NULLVP)
		return (EINVAL);
	if (unp->un_uppervp != NULLVP)
		return (EEXIST);
	udvp = VTOUNIONFS(unp->un_dvp)->un_uppervp;
	if (udvp == NULLVP)
		return (EROFS);
	if ((udvp->v_mount->mnt_flag & MNT_RDONLY))
		return (EROFS);

	error = VOP_ACCESS(lvp, VREAD, cred, td);
	if (error != 0)
		return (error);

	if ((error = vn_start_write(udvp, &mp, V_WAIT | PCATCH)) != 0)
		return (error);
	error = unionfs_vn_create_on_upper(&uvp, udvp, unp, &uva, td);
	if (error != 0) {
		vn_finished_write(mp);
		return (error);
	}

	if (docopy != 0) {
		error = VOP_OPEN(lvp, FREAD, cred, td, -1);
		if (error == 0) {
			error = unionfs_copyfile_core(lvp, uvp, cred, td);
			VOP_CLOSE(lvp, FREAD, cred, td);
		}
	}
	VOP_CLOSE(uvp, FWRITE, cred, td);
	uvp->v_writecount--;

	vn_finished_write(mp);

	if (error == 0) {
		/* Reset the attributes. Ignore errors. */
		uva.va_type = VNON;
		VOP_SETATTR(uvp, &uva, cred, td);
	}

	unionfs_node_update(unp, uvp, td);

	return (error);
}

/*
 * It checks whether vp can rmdir. (check empty)
 *
 * vp is unionfs vnode.
 * vp should be locked.
 */
int
unionfs_check_rmdir(struct vnode *vp, struct ucred *cred, struct thread *td)
{
	int		error;
	int		eofflag;
	int		lookuperr;
	struct vnode   *uvp;
	struct vnode   *lvp;
	struct vnode   *tvp;
	struct vattr	va;
	struct componentname cn;
	/*
	 * The size of buf needs to be larger than DIRBLKSIZ.
	 */
	char		buf[256 * 6];
	struct dirent  *dp;
	struct dirent  *edp;
	struct uio	uio;
	struct iovec	iov;

	ASSERT_VOP_ELOCKED(vp, "unionfs_check_rmdir");

	eofflag = 0;
	uvp = UNIONFSVPTOUPPERVP(vp);
	lvp = UNIONFSVPTOLOWERVP(vp);

	/* check opaque */
	if ((error = VOP_GETATTR(uvp, &va, cred, td)) != 0)
		return (error);
	if (va.va_flags & OPAQUE)
		return (0);

	/* open vnode */
	if ((error = VOP_OPEN(vp, FREAD, cred, td, -1)) != 0)
		return (error);

	uio.uio_rw = UIO_READ;
	uio.uio_segflg = UIO_SYSSPACE;
	uio.uio_td = td;
	uio.uio_offset = 0;

#ifdef MAC
	error = mac_check_vnode_readdir(td->td_ucred, lvp);
#endif
	while (!error && !eofflag) {
		iov.iov_base = buf;
		iov.iov_len = sizeof(buf);
		uio.uio_iov = &iov;
		uio.uio_iovcnt = 1;
		uio.uio_resid = iov.iov_len;

		error = VOP_READDIR(lvp, &uio, cred, &eofflag, NULL, NULL);
		if (error)
			break;

		edp = (struct dirent*)&buf[sizeof(buf) - uio.uio_resid];
		for (dp = (struct dirent*)buf; !error && dp < edp;
		     dp = (struct dirent*)((caddr_t)dp + dp->d_reclen)) {
			if (dp->d_type == DT_WHT ||
			    (dp->d_namlen == 1 && dp->d_name[0] == '.') ||
			    (dp->d_namlen == 2 && !bcmp(dp->d_name, "..", 2)))
				continue;

			cn.cn_namelen = dp->d_namlen;
			cn.cn_pnbuf = NULL;
			cn.cn_nameptr = dp->d_name;
			cn.cn_nameiop = LOOKUP;
			cn.cn_flags = (LOCKPARENT | LOCKLEAF | SAVENAME | RDONLY | ISLASTCN);
			cn.cn_lkflags = LK_EXCLUSIVE;
			cn.cn_thread = td;
			cn.cn_cred = cred;
			cn.cn_consume = 0;

			/*
			 * check entry in lower.
			 * Sometimes, readdir function returns
			 * wrong entry.
			 */
			lookuperr = VOP_LOOKUP(lvp, &tvp, &cn);

			if (!lookuperr)
				vput(tvp);
			else
				continue; /* skip entry */

			/*
			 * check entry
			 * If it has no exist/whiteout entry in upper,
			 * directory is not empty.
			 */
			cn.cn_flags = (LOCKPARENT | LOCKLEAF | SAVENAME | RDONLY | ISLASTCN);
			lookuperr = VOP_LOOKUP(uvp, &tvp, &cn);

			if (!lookuperr)
				vput(tvp);

			/* ignore exist or whiteout entry */
			if (!lookuperr ||
			    (lookuperr == ENOENT && (cn.cn_flags & ISWHITEOUT)))
				continue;

			error = ENOTEMPTY;
		}
	}

	/* close vnode */
	VOP_CLOSE(vp, FREAD, cred, td);

	return (error);
}

#ifdef DIAGNOSTIC

struct vnode   *
unionfs_checkuppervp(struct vnode *vp, char *fil, int lno)
{
	struct unionfs_node *unp;

	unp = VTOUNIONFS(vp);

#ifdef notyet
	if (vp->v_op != unionfs_vnodeop_p) {
		printf("unionfs_checkuppervp: on non-unionfs-node.\n");
#ifdef KDB
		kdb_enter("unionfs_checkuppervp: on non-unionfs-node.\n");
#endif
		panic("unionfs_checkuppervp");
	};
#endif
	return (unp->un_uppervp);
}

struct vnode   *
unionfs_checklowervp(struct vnode *vp, char *fil, int lno)
{
	struct unionfs_node *unp;

	unp = VTOUNIONFS(vp);

#ifdef notyet
	if (vp->v_op != unionfs_vnodeop_p) {
		printf("unionfs_checklowervp: on non-unionfs-node.\n");
#ifdef KDB
		kdb_enter("unionfs_checklowervp: on non-unionfs-node.\n");
#endif
		panic("unionfs_checklowervp");
	};
#endif
	return (unp->un_lowervp);
}
#endif