BSD 4.4 Lite Kernel Sources

1 files changed, 1495 insertions, 0 deletions

diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c
new file mode 100644
index 000000000000..96327b0922d4
--- /dev/null
+++ b/sys/fs/unionfs/union_vnops.c
@@ -0,0 +1,1495 @@
+/*
+ * Copyright (c) 1992, 1993, 1994 The Regents of the University of California.
+ * Copyright (c) 1992, 1993, 1994 Jan-Simon Pendry.
+ * All rights reserved.
+ *
+ * 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.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 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_vnops.c	8.6 (Berkeley) 2/17/94
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/proc.h>
+#include <sys/file.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/vnode.h>
+#include <sys/mount.h>
+#include <sys/namei.h>
+#include <sys/malloc.h>
+#include <sys/buf.h>
+#include <sys/queue.h>
+#include <miscfs/union/union.h>
+
+#define FIXUP(un) { \
+	if (((un)->un_flags & UN_ULOCK) == 0) { \
+		union_fixup(un); \
+	} \
+}
+
+static void
+union_fixup(un)
+	struct union_node *un;
+{
+
+	VOP_LOCK(un->un_uppervp);
+	un->un_flags |= UN_ULOCK;
+}
+
+static int
+union_lookup1(udvp, dvp, vpp, cnp)
+	struct vnode *udvp;
+	struct vnode *dvp;
+	struct vnode **vpp;
+	struct componentname *cnp;
+{
+	int error;
+	struct vnode *tdvp;
+	struct mount *mp;
+
+	/*
+	 * If stepping up the directory tree, check for going
+	 * back across the mount point, in which case do what
+	 * lookup would do by stepping back down the mount
+	 * hierarchy.
+	 */
+	if (cnp->cn_flags & ISDOTDOT) {
+		for (;;) {
+			/*
+			 * Don't do the NOCROSSMOUNT check
+			 * at this level.  By definition,
+			 * union fs deals with namespaces, not
+			 * filesystems.
+			 */
+			if ((dvp->v_flag & VROOT) == 0)
+				break;
+
+			tdvp = dvp;
+			dvp = dvp->v_mount->mnt_vnodecovered;
+			vput(tdvp);
+			VREF(dvp);
+			VOP_LOCK(dvp);
+		}
+	}
+
+        error = VOP_LOOKUP(dvp, &tdvp, cnp);
+	if (error)
+		return (error);
+
+	/*
+	 * The parent directory will have been unlocked, unless lookup
+	 * found the last component.  In which case, re-lock the node
+	 * here to allow it to be unlocked again (phew) in union_lookup.
+	 */
+	if (dvp != tdvp && !(cnp->cn_flags & ISLASTCN))
+		VOP_LOCK(dvp);
+
+	dvp = tdvp;
+
+	/*
+	 * Lastly check if the current node is a mount point in
+	 * which case walk up the mount hierarchy making sure not to
+	 * bump into the root of the mount tree (ie. dvp != udvp).
+	 */
+	while (dvp != udvp && (dvp->v_type == VDIR) &&
+	       (mp = dvp->v_mountedhere)) {
+
+		if (mp->mnt_flag & MNT_MLOCK) {
+			mp->mnt_flag |= MNT_MWAIT;
+			sleep((caddr_t) mp, PVFS);
+			continue;
+		}
+
+		if (error = VFS_ROOT(mp, &tdvp)) {
+			vput(dvp);
+			return (error);
+		}
+
+		vput(dvp);
+		dvp = tdvp;
+	}
+
+	*vpp = dvp;
+	return (0);
+}
+
+int
+union_lookup(ap)
+	struct vop_lookup_args /* {
+		struct vnodeop_desc *a_desc;
+		struct vnode *a_dvp;
+		struct vnode **a_vpp;
+		struct componentname *a_cnp;
+	} */ *ap;
+{
+	int error;
+	int uerror, lerror;
+	struct vnode *uppervp, *lowervp;
+	struct vnode *upperdvp, *lowerdvp;
+	struct vnode *dvp = ap->a_dvp;
+	struct union_node *dun = VTOUNION(dvp);
+	struct componentname *cnp = ap->a_cnp;
+	int lockparent = cnp->cn_flags & LOCKPARENT;
+	int rdonly = cnp->cn_flags & RDONLY;
+	struct union_mount *um = MOUNTTOUNIONMOUNT(dvp->v_mount);
+	struct ucred *saved_cred;
+
+	cnp->cn_flags |= LOCKPARENT;
+
+	upperdvp = dun->un_uppervp;
+	lowerdvp = dun->un_lowervp;
+	uppervp = NULLVP;
+	lowervp = NULLVP;
+
+	/*
+	 * do the lookup in the upper level.
+	 * if that level comsumes additional pathnames,
+	 * then assume that something special is going
+	 * on and just return that vnode.
+	 */
+	if (upperdvp) {
+		FIXUP(dun);
+		uerror = union_lookup1(um->um_uppervp, upperdvp,
+					&uppervp, cnp);
+		/*if (uppervp == upperdvp)
+			dun->un_flags |= UN_KLOCK;*/
+
+		if (cnp->cn_consume != 0) {
+			*ap->a_vpp = uppervp;
+			if (!lockparent)
+				cnp->cn_flags &= ~LOCKPARENT;
+			return (uerror);
+		}
+	} else {
+		uerror = ENOENT;
+	}
+
+	/*
+	 * in a similar way to the upper layer, do the lookup
+	 * in the lower layer.   this time, if there is some
+	 * component magic going on, then vput whatever we got
+	 * back from the upper layer and return the lower vnode
+	 * instead.
+	 */
+	if (lowerdvp) {
+		int nameiop;
+
+		VOP_LOCK(lowerdvp);
+
+		/*
+		 * Only do a LOOKUP on the bottom node, since
+		 * we won't be making changes to it anyway.
+		 */
+		nameiop = cnp->cn_nameiop;
+		cnp->cn_nameiop = LOOKUP;
+		if (um->um_op == UNMNT_BELOW) {
+			saved_cred = cnp->cn_cred;
+			cnp->cn_cred = um->um_cred;
+		}
+		lerror = union_lookup1(um->um_lowervp, lowerdvp,
+				&lowervp, cnp);
+		if (um->um_op == UNMNT_BELOW)
+			cnp->cn_cred = saved_cred;
+		cnp->cn_nameiop = nameiop;
+
+		if (lowervp != lowerdvp)
+			VOP_UNLOCK(lowerdvp);
+
+		if (cnp->cn_consume != 0) {
+			if (uppervp) {
+				if (uppervp == upperdvp)
+					vrele(uppervp);
+				else
+					vput(uppervp);
+				uppervp = NULLVP;
+			}
+			*ap->a_vpp = lowervp;
+			if (!lockparent)
+				cnp->cn_flags &= ~LOCKPARENT;
+			return (lerror);
+		}
+	} else {
+		lerror = ENOENT;
+	}
+
+	if (!lockparent)
+		cnp->cn_flags &= ~LOCKPARENT;
+
+	/*
+	 * at this point, we have uerror and lerror indicating
+	 * possible errors with the lookups in the upper and lower
+	 * layers.  additionally, uppervp and lowervp are (locked)
+	 * references to existing vnodes in the upper and lower layers.
+	 *
+	 * there are now three cases to consider.
+	 * 1. if both layers returned an error, then return whatever
+	 *    error the upper layer generated.
+	 *
+	 * 2. if the top layer failed and the bottom layer succeeded
+	 *    then two subcases occur.
+	 *    a.  the bottom vnode is not a directory, in which
+	 *	  case just return a new union vnode referencing
+	 *	  an empty top layer and the existing bottom layer.
+	 *    b.  the bottom vnode is a directory, in which case
+	 *	  create a new directory in the top-level and
+	 *	  continue as in case 3.
+	 *
+	 * 3. if the top layer succeeded then return a new union
+	 *    vnode referencing whatever the new top layer and
+	 *    whatever the bottom layer returned.
+	 */
+
+	*ap->a_vpp = NULLVP;
+
+	/* case 1. */
+	if ((uerror != 0) && (lerror != 0)) {
+		return (uerror);
+	}
+
+	/* case 2. */
+	if (uerror != 0 /* && (lerror == 0) */ ) {
+		if (lowervp->v_type == VDIR) { /* case 2b. */
+			dun->un_flags &= ~UN_ULOCK;
+			VOP_UNLOCK(upperdvp);
+			uerror = union_mkshadow(um, upperdvp, cnp, &uppervp);
+			VOP_LOCK(upperdvp);
+			dun->un_flags |= UN_ULOCK;
+
+			if (uerror) {
+				if (lowervp) {
+					vput(lowervp);
+					lowervp = NULLVP;
+				}
+				return (uerror);
+			}
+		}
+	}
+
+	if (lowervp)
+		VOP_UNLOCK(lowervp);
+
+	error = union_allocvp(ap->a_vpp, dvp->v_mount, dvp, upperdvp, cnp,
+			      uppervp, lowervp);
+
+	if (error) {
+		if (uppervp)
+			vput(uppervp);
+		if (lowervp)
+			vrele(lowervp);
+	} else {
+		if (*ap->a_vpp != dvp)
+			if (!lockparent || !(cnp->cn_flags & ISLASTCN))
+				VOP_UNLOCK(dvp);
+	}
+
+	return (error);
+}
+
+int
+union_create(ap)
+	struct vop_create_args /* {
+		struct vnode *a_dvp;
+		struct vnode **a_vpp;
+		struct componentname *a_cnp;
+		struct vattr *a_vap;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_dvp);
+	struct vnode *dvp = un->un_uppervp;
+
+	if (dvp) {
+		int error;
+		struct vnode *vp;
+
+		FIXUP(un);
+
+		VREF(dvp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_dvp);
+		error = VOP_CREATE(dvp, &vp, ap->a_cnp, ap->a_vap);
+		if (error)
+			return (error);
+
+		error = union_allocvp(
+				ap->a_vpp,
+				ap->a_dvp->v_mount,
+				ap->a_dvp,
+				NULLVP,
+				ap->a_cnp,
+				vp,
+				NULLVP);
+		if (error)
+			vput(vp);
+		return (error);
+	}
+
+	vput(ap->a_dvp);
+	return (EROFS);
+}
+
+int
+union_mknod(ap)
+	struct vop_mknod_args /* {
+		struct vnode *a_dvp;
+		struct vnode **a_vpp;
+		struct componentname *a_cnp;
+		struct vattr *a_vap;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_dvp);
+	struct vnode *dvp = un->un_uppervp;
+
+	if (dvp) {
+		int error;
+		struct vnode *vp;
+
+		FIXUP(un);
+
+		VREF(dvp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_dvp);
+		error = VOP_MKNOD(dvp, &vp, ap->a_cnp, ap->a_vap);
+		if (error)
+			return (error);
+
+		if (vp) {
+			error = union_allocvp(
+					ap->a_vpp,
+					ap->a_dvp->v_mount,
+					ap->a_dvp,
+					NULLVP,
+					ap->a_cnp,
+					vp,
+					NULLVP);
+			if (error)
+				vput(vp);
+		}
+		return (error);
+	}
+
+	vput(ap->a_dvp);
+	return (EROFS);
+}
+
+int
+union_open(ap)
+	struct vop_open_args /* {
+		struct vnodeop_desc *a_desc;
+		struct vnode *a_vp;
+		int a_mode;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_vp);
+	struct vnode *tvp;
+	int mode = ap->a_mode;
+	struct ucred *cred = ap->a_cred;
+	struct proc *p = ap->a_p;
+	int error;
+
+	/*
+	 * If there is an existing upper vp then simply open that.
+	 */
+	tvp = un->un_uppervp;
+	if (tvp == NULLVP) {
+		/*
+		 * If the lower vnode is being opened for writing, then
+		 * copy the file contents to the upper vnode and open that,
+		 * otherwise can simply open the lower vnode.
+		 */
+		tvp = un->un_lowervp;
+		if ((ap->a_mode & FWRITE) && (tvp->v_type == VREG)) {
+			struct vnode *vp;
+			int i;
+
+			/*
+			 * Open the named file in the upper layer.  Note that
+			 * the file may have come into existence *since* the
+			 * lookup was done, since the upper layer may really
+			 * be a loopback mount of some other filesystem...
+			 * so open the file with exclusive create and barf if
+			 * it already exists.
+			 * XXX - perhaps should re-lookup the node (once more
+			 * with feeling) and simply open that.  Who knows.
+			 */
+			error = union_vn_create(&vp, un, p);
+			if (error)
+				return (error);
+
+			/* at this point, uppervp is locked */
+			union_newupper(un, vp);
+			un->un_flags |= UN_ULOCK;
+
+			/*
+			 * Now, if the file is being opened with truncation,
+			 * then the (new) upper vnode is ready to fly,
+			 * otherwise the data from the lower vnode must be
+			 * copied to the upper layer first.  This only works
+			 * for regular files (check is made above).
+			 */
+			if ((mode & O_TRUNC) == 0) {
+				/*
+				 * XXX - should not ignore errors
+				 * from VOP_CLOSE
+				 */
+				VOP_LOCK(tvp);
+				error = VOP_OPEN(tvp, FREAD, cred, p);
+				if (error == 0) {
+					error = union_copyfile(p, cred,
+						       tvp, un->un_uppervp);
+					VOP_UNLOCK(tvp);
+					(void) VOP_CLOSE(tvp, FREAD);
+				} else {
+					VOP_UNLOCK(tvp);
+				}
+
+#ifdef UNION_DIAGNOSTIC
+				if (!error)
+					uprintf("union: copied up %s\n",
+								un->un_path);
+#endif
+			}
+
+			un->un_flags &= ~UN_ULOCK;
+			VOP_UNLOCK(un->un_uppervp);
+			union_vn_close(un->un_uppervp, FWRITE, cred, p);
+			VOP_LOCK(un->un_uppervp);
+			un->un_flags |= UN_ULOCK;
+
+			/*
+			 * Subsequent IOs will go to the top layer, so
+			 * call close on the lower vnode and open on the
+			 * upper vnode to ensure that the filesystem keeps
+			 * its references counts right.  This doesn't do
+			 * the right thing with (cred) and (FREAD) though.
+			 * Ignoring error returns is not righ, either.
+			 */
+			for (i = 0; i < un->un_openl; i++) {
+				(void) VOP_CLOSE(tvp, FREAD);
+				(void) VOP_OPEN(un->un_uppervp, FREAD, cred, p);
+			}
+			un->un_openl = 0;
+
+			if (error == 0)
+				error = VOP_OPEN(un->un_uppervp, mode, cred, p);
+			return (error);
+		}
+
+		/*
+		 * Just open the lower vnode
+		 */
+		un->un_openl++;
+		VOP_LOCK(tvp);
+		error = VOP_OPEN(tvp, mode, cred, p);
+		VOP_UNLOCK(tvp);
+
+		return (error);
+	}
+
+	FIXUP(un);
+
+	error = VOP_OPEN(tvp, mode, cred, p);
+
+	return (error);
+}
+
+int
+union_close(ap)
+	struct vop_close_args /* {
+		struct vnode *a_vp;
+		int  a_fflag;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_vp);
+	struct vnode *vp;
+
+	if (un->un_uppervp) {
+		vp = un->un_uppervp;
+	} else {
+#ifdef UNION_DIAGNOSTIC
+		if (un->un_openl <= 0)
+			panic("union: un_openl cnt");
+#endif
+		--un->un_openl;
+		vp = un->un_lowervp;
+	}
+
+	return (VOP_CLOSE(vp, ap->a_fflag, ap->a_cred, ap->a_p));
+}
+
+/*
+ * Check access permission on the union vnode.
+ * The access check being enforced is to check
+ * against both the underlying vnode, and any
+ * copied vnode.  This ensures that no additional
+ * file permissions are given away simply because
+ * the user caused an implicit file copy.
+ */
+int
+union_access(ap)
+	struct vop_access_args /* {
+		struct vnodeop_desc *a_desc;
+		struct vnode *a_vp;
+		int a_mode;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_vp);
+	int error = EACCES;
+	struct vnode *vp;
+
+	if (vp = un->un_uppervp) {
+		FIXUP(un);
+		return (VOP_ACCESS(vp, ap->a_mode, ap->a_cred, ap->a_p));
+	}
+
+	if (vp = un->un_lowervp) {
+		VOP_LOCK(vp);
+		error = VOP_ACCESS(vp, ap->a_mode, ap->a_cred, ap->a_p);
+		if (error == 0) {
+			struct union_mount *um = MOUNTTOUNIONMOUNT(vp->v_mount);
+
+			if (um->um_op == UNMNT_BELOW)
+				error = VOP_ACCESS(vp, ap->a_mode,
+						um->um_cred, ap->a_p);
+		}
+		VOP_UNLOCK(vp);
+		if (error)
+			return (error);
+	}
+
+	return (error);
+}
+
+/*
+ *  We handle getattr only to change the fsid.
+ */
+int
+union_getattr(ap)
+	struct vop_getattr_args /* {
+		struct vnode *a_vp;
+		struct vattr *a_vap;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+	int error;
+	struct union_node *un = VTOUNION(ap->a_vp);
+	struct vnode *vp = un->un_uppervp;
+	struct vattr *vap;
+	struct vattr va;
+
+
+	/*
+	 * Some programs walk the filesystem hierarchy by counting
+	 * links to directories to avoid stat'ing all the time.
+	 * This means the link count on directories needs to be "correct".
+	 * The only way to do that is to call getattr on both layers
+	 * and fix up the link count.  The link count will not necessarily
+	 * be accurate but will be large enough to defeat the tree walkers.
+	 */
+
+	vap = ap->a_vap;
+
+	vp = un->un_uppervp;
+	if (vp != NULLVP) {
+		FIXUP(un);
+		error = VOP_GETATTR(vp, vap, ap->a_cred, ap->a_p);
+		if (error)
+			return (error);
+	}
+
+	if (vp == NULLVP) {
+		vp = un->un_lowervp;
+	} else if (vp->v_type == VDIR) {
+		vp = un->un_lowervp;
+		vap = &va;
+	} else {
+		vp = NULLVP;
+	}
+
+	if (vp != NULLVP) {
+		VOP_LOCK(vp);
+		error = VOP_GETATTR(vp, vap, ap->a_cred, ap->a_p);
+		VOP_UNLOCK(vp);
+		if (error)
+			return (error);
+	}
+
+	if ((vap != ap->a_vap) && (vap->va_type == VDIR))
+		ap->a_vap->va_nlink += vap->va_nlink;
+
+	vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0];
+	return (0);
+}
+
+int
+union_setattr(ap)
+	struct vop_setattr_args /* {
+		struct vnode *a_vp;
+		struct vattr *a_vap;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_vp);
+	int error;
+
+	/*
+	 * Handle case of truncating lower object to zero size,
+	 * by creating a zero length upper object.  This is to
+	 * handle the case of open with O_TRUNC and O_CREAT.
+	 */
+	if ((un->un_uppervp == NULLVP) &&
+	    /* assert(un->un_lowervp != NULLVP) */
+	    (un->un_lowervp->v_type == VREG) &&
+	    (ap->a_vap->va_size == 0)) {
+		struct vnode *vp;
+
+		error = union_vn_create(&vp, un, ap->a_p);
+		if (error)
+			return (error);
+
+		/* at this point, uppervp is locked */
+		union_newupper(un, vp);
+
+		VOP_UNLOCK(vp);
+		union_vn_close(un->un_uppervp, FWRITE, ap->a_cred, ap->a_p);
+		VOP_LOCK(vp);
+		un->un_flags |= UN_ULOCK;
+	}
+
+	/*
+	 * Try to set attributes in upper layer,
+	 * otherwise return read-only filesystem error.
+	 */
+	if (un->un_uppervp != NULLVP) {
+		FIXUP(un);
+		error = VOP_SETATTR(un->un_uppervp, ap->a_vap,
+					ap->a_cred, ap->a_p);
+	} else {
+		error = EROFS;
+	}
+
+	return (error);
+}
+
+int
+union_read(ap)
+	struct vop_read_args /* {
+		struct vnode *a_vp;
+		struct uio *a_uio;
+		int  a_ioflag;
+		struct ucred *a_cred;
+	} */ *ap;
+{
+	int error;
+	struct vnode *vp = OTHERVP(ap->a_vp);
+	int dolock = (vp == LOWERVP(ap->a_vp));
+
+	if (dolock)
+		VOP_LOCK(vp);
+	else
+		FIXUP(VTOUNION(ap->a_vp));
+	error = VOP_READ(vp, ap->a_uio, ap->a_ioflag, ap->a_cred);
+	if (dolock)
+		VOP_UNLOCK(vp);
+
+	return (error);
+}
+
+int
+union_write(ap)
+	struct vop_read_args /* {
+		struct vnode *a_vp;
+		struct uio *a_uio;
+		int  a_ioflag;
+		struct ucred *a_cred;
+	} */ *ap;
+{
+	int error;
+	struct vnode *vp = OTHERVP(ap->a_vp);
+	int dolock = (vp == LOWERVP(ap->a_vp));
+
+	if (dolock)
+		VOP_LOCK(vp);
+	else
+		FIXUP(VTOUNION(ap->a_vp));
+	error = VOP_WRITE(vp, ap->a_uio, ap->a_ioflag, ap->a_cred);
+	if (dolock)
+		VOP_UNLOCK(vp);
+
+	return (error);
+}
+
+int
+union_ioctl(ap)
+	struct vop_ioctl_args /* {
+		struct vnode *a_vp;
+		int  a_command;
+		caddr_t  a_data;
+		int  a_fflag;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+
+	return (VOP_IOCTL(OTHERVP(ap->a_vp), ap->a_command, ap->a_data,
+				ap->a_fflag, ap->a_cred, ap->a_p));
+}
+
+int
+union_select(ap)
+	struct vop_select_args /* {
+		struct vnode *a_vp;
+		int  a_which;
+		int  a_fflags;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+
+	return (VOP_SELECT(OTHERVP(ap->a_vp), ap->a_which, ap->a_fflags,
+				ap->a_cred, ap->a_p));
+}
+
+int
+union_mmap(ap)
+	struct vop_mmap_args /* {
+		struct vnode *a_vp;
+		int  a_fflags;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap;
+{
+
+	return (VOP_MMAP(OTHERVP(ap->a_vp), ap->a_fflags,
+				ap->a_cred, ap->a_p));
+}
+
+int
+union_fsync(ap)
+	struct vop_fsync_args /* {
+		struct vnode *a_vp;
+		struct ucred *a_cred;
+		int  a_waitfor;
+		struct proc *a_p;
+	} */ *ap;
+{
+	int error = 0;
+	struct vnode *targetvp = OTHERVP(ap->a_vp);
+
+	if (targetvp) {
+		int dolock = (targetvp == LOWERVP(ap->a_vp));
+
+		if (dolock)
+			VOP_LOCK(targetvp);
+		else
+			FIXUP(VTOUNION(ap->a_vp));
+		error = VOP_FSYNC(targetvp, ap->a_cred,
+					ap->a_waitfor, ap->a_p);
+		if (dolock)
+			VOP_UNLOCK(targetvp);
+	}
+
+	return (error);
+}
+
+int
+union_seek(ap)
+	struct vop_seek_args /* {
+		struct vnode *a_vp;
+		off_t  a_oldoff;
+		off_t  a_newoff;
+		struct ucred *a_cred;
+	} */ *ap;
+{
+
+	return (VOP_SEEK(OTHERVP(ap->a_vp), ap->a_oldoff, ap->a_newoff, ap->a_cred));
+}
+
+int
+union_remove(ap)
+	struct vop_remove_args /* {
+		struct vnode *a_dvp;
+		struct vnode *a_vp;
+		struct componentname *a_cnp;
+	} */ *ap;
+{
+	int error;
+	struct union_node *dun = VTOUNION(ap->a_dvp);
+	struct union_node *un = VTOUNION(ap->a_vp);
+
+	if (dun->un_uppervp && un->un_uppervp) {
+		struct vnode *dvp = dun->un_uppervp;
+		struct vnode *vp = un->un_uppervp;
+
+		FIXUP(dun);
+		VREF(dvp);
+		dun->un_flags |= UN_KLOCK;
+		vput(ap->a_dvp);
+		FIXUP(un);
+		VREF(vp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_vp);
+
+		error = VOP_REMOVE(dvp, vp, ap->a_cnp);
+		if (!error)
+			union_removed_upper(un);
+
+		/*
+		 * XXX: should create a whiteout here
+		 */
+	} else {
+		/*
+		 * XXX: should create a whiteout here
+		 */
+		vput(ap->a_dvp);
+		vput(ap->a_vp);
+		error = EROFS;
+	}
+
+	return (error);
+}
+
+int
+union_link(ap)
+	struct vop_link_args /* {
+		struct vnode *a_vp;
+		struct vnode *a_tdvp;
+		struct componentname *a_cnp;
+	} */ *ap;
+{
+	int error;
+	struct union_node *dun = VTOUNION(ap->a_vp);
+	struct union_node *un = VTOUNION(ap->a_tdvp);
+
+	if (dun->un_uppervp && un->un_uppervp) {
+		struct vnode *dvp = dun->un_uppervp;
+		struct vnode *vp = un->un_uppervp;
+
+		FIXUP(dun);
+		VREF(dvp);
+		dun->un_flags |= UN_KLOCK;
+		vput(ap->a_vp);
+		FIXUP(un);
+		VREF(vp);
+		vrele(ap->a_tdvp);
+
+		error = VOP_LINK(dvp, vp, ap->a_cnp);
+	} else {
+		/*
+		 * XXX: need to copy to upper layer
+		 * and do the link there.
+		 */
+		vput(ap->a_vp);
+		vrele(ap->a_tdvp);
+		error = EROFS;
+	}
+
+	return (error);
+}
+
+int
+union_rename(ap)
+	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;
+{
+	int error;
+
+	struct vnode *fdvp = ap->a_fdvp;
+	struct vnode *fvp = ap->a_fvp;
+	struct vnode *tdvp = ap->a_tdvp;
+	struct vnode *tvp = ap->a_tvp;
+
+	if (fdvp->v_op == union_vnodeop_p) {	/* always true */
+		struct union_node *un = VTOUNION(fdvp);
+		if (un->un_uppervp == NULLVP) {
+			error = EROFS;
+			goto bad;
+		}
+
+		FIXUP(un);
+		fdvp = un->un_uppervp;
+		VREF(fdvp);
+		vrele(ap->a_fdvp);
+	}
+
+	if (fvp->v_op == union_vnodeop_p) {	/* always true */
+		struct union_node *un = VTOUNION(fvp);
+		if (un->un_uppervp == NULLVP) {
+			error = EROFS;
+			goto bad;
+		}
+
+		FIXUP(un);
+		fvp = un->un_uppervp;
+		VREF(fvp);
+		vrele(ap->a_fvp);
+	}
+
+	if (tdvp->v_op == union_vnodeop_p) {
+		struct union_node *un = VTOUNION(tdvp);
+		if (un->un_uppervp == NULLVP) {
+			error = EROFS;
+			goto bad;
+		}
+
+		tdvp = un->un_uppervp;
+		VREF(tdvp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_tdvp);
+	}
+
+	if (tvp && tvp->v_op == union_vnodeop_p) {
+		struct union_node *un = VTOUNION(tvp);
+		if (un->un_uppervp == NULLVP) {
+			error = EROFS;
+			goto bad;
+		}
+
+		tvp = un->un_uppervp;
+		VREF(tvp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_tvp);
+	}
+
+	return (VOP_RENAME(fdvp, fvp, ap->a_fcnp, tdvp, tvp, ap->a_tcnp));
+
+bad:
+	vrele(fdvp);
+	vrele(fvp);
+	vput(tdvp);
+	if (tvp)
+		vput(tvp);
+
+	return (error);
+}
+
+int
+union_mkdir(ap)
+	struct vop_mkdir_args /* {
+		struct vnode *a_dvp;
+		struct vnode **a_vpp;
+		struct componentname *a_cnp;
+		struct vattr *a_vap;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_dvp);
+	struct vnode *dvp = un->un_uppervp;
+
+	if (dvp) {
+		int error;
+		struct vnode *vp;
+
+		FIXUP(un);
+		VREF(dvp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_dvp);
+		error = VOP_MKDIR(dvp, &vp, ap->a_cnp, ap->a_vap);
+		if (error)
+			return (error);
+
+		error = union_allocvp(
+				ap->a_vpp,
+				ap->a_dvp->v_mount,
+				ap->a_dvp,
+				NULLVP,
+				ap->a_cnp,
+				vp,
+				NULLVP);
+		if (error)
+			vput(vp);
+		return (error);
+	}
+
+	vput(ap->a_dvp);
+	return (EROFS);
+}
+
+int
+union_rmdir(ap)
+	struct vop_rmdir_args /* {
+		struct vnode *a_dvp;
+		struct vnode *a_vp;
+		struct componentname *a_cnp;
+	} */ *ap;
+{
+	int error;
+	struct union_node *dun = VTOUNION(ap->a_dvp);
+	struct union_node *un = VTOUNION(ap->a_vp);
+
+	if (dun->un_uppervp && un->un_uppervp) {
+		struct vnode *dvp = dun->un_uppervp;
+		struct vnode *vp = un->un_uppervp;
+
+		FIXUP(dun);
+		VREF(dvp);
+		dun->un_flags |= UN_KLOCK;
+		vput(ap->a_dvp);
+		FIXUP(un);
+		VREF(vp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_vp);
+
+		error = VOP_RMDIR(dvp, vp, ap->a_cnp);
+		if (!error)
+			union_removed_upper(un);
+
+		/*
+		 * XXX: should create a whiteout here
+		 */
+	} else {
+		/*
+		 * XXX: should create a whiteout here
+		 */
+		vput(ap->a_dvp);
+		vput(ap->a_vp);
+		error = EROFS;
+	}
+
+	return (error);
+}
+
+int
+union_symlink(ap)
+	struct vop_symlink_args /* {
+		struct vnode *a_dvp;
+		struct vnode **a_vpp;
+		struct componentname *a_cnp;
+		struct vattr *a_vap;
+		char *a_target;
+	} */ *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_dvp);
+	struct vnode *dvp = un->un_uppervp;
+
+	if (dvp) {
+		int error;
+		struct vnode *vp;
+		struct mount *mp = ap->a_dvp->v_mount;
+
+		FIXUP(un);
+		VREF(dvp);
+		un->un_flags |= UN_KLOCK;
+		vput(ap->a_dvp);
+		error = VOP_SYMLINK(dvp, &vp, ap->a_cnp,
+					ap->a_vap, ap->a_target);
+		*ap->a_vpp = NULLVP;
+		return (error);
+	}
+
+	vput(ap->a_dvp);
+	return (EROFS);
+}
+
+/*
+ * union_readdir works in concert with getdirentries and
+ * readdir(3) to provide a list of entries in the unioned
+ * directories.  getdirentries is responsible for walking
+ * down the union stack.  readdir(3) is responsible for
+ * eliminating duplicate names from the returned data stream.
+ */
+int
+union_readdir(ap)
+	struct vop_readdir_args /* {
+		struct vnodeop_desc *a_desc;
+		struct vnode *a_vp;
+		struct uio *a_uio;
+		struct ucred *a_cred;
+	} */ *ap;
+{
+	int error = 0;
+	struct union_node *un = VTOUNION(ap->a_vp);
+
+	if (un->un_uppervp) {
+		FIXUP(un);
+		error = VOP_READDIR(un->un_uppervp, ap->a_uio, ap->a_cred);
+	}
+
+	return (error);
+}
+
+int
+union_readlink(ap)
+	struct vop_readlink_args /* {
+		struct vnode *a_vp;
+		struct uio *a_uio;
+		struct ucred *a_cred;
+	} */ *ap;
+{
+	int error;
+	struct vnode *vp = OTHERVP(ap->a_vp);
+	int dolock = (vp == LOWERVP(ap->a_vp));
+
+	if (dolock)
+		VOP_LOCK(vp);
+	else
+		FIXUP(VTOUNION(ap->a_vp));
+	error = VOP_READLINK(vp, ap->a_uio, ap->a_cred);
+	if (dolock)
+		VOP_UNLOCK(vp);
+
+	return (error);
+}
+
+int
+union_abortop(ap)
+	struct vop_abortop_args /* {
+		struct vnode *a_dvp;
+		struct componentname *a_cnp;
+	} */ *ap;
+{
+	int error;
+	struct vnode *vp = OTHERVP(ap->a_dvp);
+	struct union_node *un = VTOUNION(ap->a_dvp);
+	int islocked = un->un_flags & UN_LOCKED;
+	int dolock = (vp == LOWERVP(ap->a_dvp));
+
+	if (islocked) {
+		if (dolock)
+			VOP_LOCK(vp);
+		else
+			FIXUP(VTOUNION(ap->a_dvp));
+	}
+	error = VOP_ABORTOP(vp, ap->a_cnp);
+	if (islocked && dolock)
+		VOP_UNLOCK(vp);
+
+	return (error);
+}
+
+int
+union_inactive(ap)
+	struct vop_inactive_args /* {
+		struct vnode *a_vp;
+	} */ *ap;
+{
+
+	/*
+	 * Do nothing (and _don't_ bypass).
+	 * Wait to vrele lowervp until reclaim,
+	 * so that until then our union_node is in the
+	 * cache and reusable.
+	 *
+	 * NEEDSWORK: Someday, consider inactive'ing
+	 * the lowervp and then trying to reactivate it
+	 * with capabilities (v_id)
+	 * like they do in the name lookup cache code.
+	 * That's too much work for now.
+	 */
+
+#ifdef UNION_DIAGNOSTIC
+	struct union_node *un = VTOUNION(ap->a_vp);
+
+	if (un->un_flags & UN_LOCKED)
+		panic("union: inactivating locked node");
+#endif
+
+	return (0);
+}
+
+int
+union_reclaim(ap)
+	struct vop_reclaim_args /* {
+		struct vnode *a_vp;
+	} */ *ap;
+{
+
+	union_freevp(ap->a_vp);
+
+	return (0);
+}
+
+int
+union_lock(ap)
+	struct vop_lock_args *ap;
+{
+	struct vnode *vp = ap->a_vp;
+	struct union_node *un;
+
+start:
+	while (vp->v_flag & VXLOCK) {
+		vp->v_flag |= VXWANT;
+		sleep((caddr_t)vp, PINOD);
+	}
+
+	un = VTOUNION(vp);
+
+	if (un->un_uppervp) {
+		if ((un->un_flags & UN_ULOCK) == 0) {
+			un->un_flags |= UN_ULOCK;
+			VOP_LOCK(un->un_uppervp);
+		}
+#ifdef DIAGNOSTIC
+		if (un->un_flags & UN_KLOCK)
+			panic("union: dangling upper lock");
+#endif
+	}
+
+	if (un->un_flags & UN_LOCKED) {
+#ifdef DIAGNOSTIC
+		if (curproc && un->un_pid == curproc->p_pid &&
+			    un->un_pid > -1 && curproc->p_pid > -1)
+			panic("union: locking against myself");
+#endif
+		un->un_flags |= UN_WANT;
+		sleep((caddr_t) &un->un_flags, PINOD);
+		goto start;
+	}
+
+#ifdef DIAGNOSTIC
+	if (curproc)
+		un->un_pid = curproc->p_pid;
+	else
+		un->un_pid = -1;
+#endif
+
+	un->un_flags |= UN_LOCKED;
+	return (0);
+}
+
+int
+union_unlock(ap)
+	struct vop_lock_args *ap;
+{
+	struct union_node *un = VTOUNION(ap->a_vp);
+
+#ifdef DIAGNOSTIC
+	if ((un->un_flags & UN_LOCKED) == 0)
+		panic("union: unlock unlocked node");
+	if (curproc && un->un_pid != curproc->p_pid &&
+			curproc->p_pid > -1 && un->un_pid > -1)
+		panic("union: unlocking other process's union node");
+#endif
+
+	un->un_flags &= ~UN_LOCKED;
+
+	if ((un->un_flags & (UN_ULOCK|UN_KLOCK)) == UN_ULOCK)
+		VOP_UNLOCK(un->un_uppervp);
+
+	un->un_flags &= ~(UN_ULOCK|UN_KLOCK);
+
+	if (un->un_flags & UN_WANT) {
+		un->un_flags &= ~UN_WANT;
+		wakeup((caddr_t) &un->un_flags);
+	}
+
+#ifdef DIAGNOSTIC
+	un->un_pid = 0;
+#endif
+
+	return (0);
+}
+
+int
+union_bmap(ap)
+	struct vop_bmap_args /* {
+		struct vnode *a_vp;
+		daddr_t  a_bn;
+		struct vnode **a_vpp;
+		daddr_t *a_bnp;
+		int *a_runp;
+	} */ *ap;
+{
+	int error;
+	struct vnode *vp = OTHERVP(ap->a_vp);
+	int dolock = (vp == LOWERVP(ap->a_vp));
+
+	if (dolock)
+		VOP_LOCK(vp);
+	else
+		FIXUP(VTOUNION(ap->a_vp));
+	error = VOP_BMAP(vp, ap->a_bn, ap->a_vpp, ap->a_bnp, ap->a_runp);
+	if (dolock)
+		VOP_UNLOCK(vp);
+
+	return (error);
+}
+
+int
+union_print(ap)
+	struct vop_print_args /* {
+		struct vnode *a_vp;
+	} */ *ap;
+{
+	struct vnode *vp = ap->a_vp;
+
+	printf("\ttag VT_UNION, vp=%x, uppervp=%x, lowervp=%x\n",
+			vp, UPPERVP(vp), LOWERVP(vp));
+	return (0);
+}
+
+int
+union_islocked(ap)
+	struct vop_islocked_args /* {
+		struct vnode *a_vp;
+	} */ *ap;
+{
+
+	return ((VTOUNION(ap->a_vp)->un_flags & UN_LOCKED) ? 1 : 0);
+}
+
+int
+union_pathconf(ap)
+	struct vop_pathconf_args /* {
+		struct vnode *a_vp;
+		int a_name;
+		int *a_retval;
+	} */ *ap;
+{
+	int error;
+	struct vnode *vp = OTHERVP(ap->a_vp);
+	int dolock = (vp == LOWERVP(ap->a_vp));
+
+	if (dolock)
+		VOP_LOCK(vp);
+	else
+		FIXUP(VTOUNION(ap->a_vp));
+	error = VOP_PATHCONF(vp, ap->a_name, ap->a_retval);
+	if (dolock)
+		VOP_UNLOCK(vp);
+
+	return (error);
+}
+
+int
+union_advlock(ap)
+	struct vop_advlock_args /* {
+		struct vnode *a_vp;
+		caddr_t  a_id;
+		int  a_op;
+		struct flock *a_fl;
+		int  a_flags;
+	} */ *ap;
+{
+
+	return (VOP_ADVLOCK(OTHERVP(ap->a_vp), ap->a_id, ap->a_op,
+				ap->a_fl, ap->a_flags));
+}
+
+
+/*
+ * XXX - vop_strategy must be hand coded because it has no
+ * vnode in its arguments.
+ * This goes away with a merged VM/buffer cache.
+ */
+int
+union_strategy(ap)
+	struct vop_strategy_args /* {
+		struct buf *a_bp;
+	} */ *ap;
+{
+	struct buf *bp = ap->a_bp;
+	int error;
+	struct vnode *savedvp;
+
+	savedvp = bp->b_vp;
+	bp->b_vp = OTHERVP(bp->b_vp);
+
+#ifdef DIAGNOSTIC
+	if (bp->b_vp == NULLVP)
+		panic("union_strategy: nil vp");
+	if (((bp->b_flags & B_READ) == 0) &&
+	    (bp->b_vp == LOWERVP(savedvp)))
+		panic("union_strategy: writing to lowervp");
+#endif
+
+	error = VOP_STRATEGY(bp);
+	bp->b_vp = savedvp;
+
+	return (error);
+}
+
+/*
+ * Global vfs data structures
+ */
+int (**union_vnodeop_p)();
+struct vnodeopv_entry_desc union_vnodeop_entries[] = {
+	{ &vop_default_desc, vn_default_error },
+	{ &vop_lookup_desc, union_lookup },		/* lookup */
+	{ &vop_create_desc, union_create },		/* create */
+	{ &vop_mknod_desc, union_mknod },		/* mknod */
+	{ &vop_open_desc, union_open },			/* open */
+	{ &vop_close_desc, union_close },		/* close */
+	{ &vop_access_desc, union_access },		/* access */
+	{ &vop_getattr_desc, union_getattr },		/* getattr */
+	{ &vop_setattr_desc, union_setattr },		/* setattr */
+	{ &vop_read_desc, union_read },			/* read */
+	{ &vop_write_desc, union_write },		/* write */
+	{ &vop_ioctl_desc, union_ioctl },		/* ioctl */
+	{ &vop_select_desc, union_select },		/* select */
+	{ &vop_mmap_desc, union_mmap },			/* mmap */
+	{ &vop_fsync_desc, union_fsync },		/* fsync */
+	{ &vop_seek_desc, union_seek },			/* seek */
+	{ &vop_remove_desc, union_remove },		/* remove */
+	{ &vop_link_desc, union_link },			/* link */
+	{ &vop_rename_desc, union_rename },		/* rename */
+	{ &vop_mkdir_desc, union_mkdir },		/* mkdir */
+	{ &vop_rmdir_desc, union_rmdir },		/* rmdir */
+	{ &vop_symlink_desc, union_symlink },		/* symlink */
+	{ &vop_readdir_desc, union_readdir },		/* readdir */
+	{ &vop_readlink_desc, union_readlink },		/* readlink */
+	{ &vop_abortop_desc, union_abortop },		/* abortop */
+	{ &vop_inactive_desc, union_inactive },		/* inactive */
+	{ &vop_reclaim_desc, union_reclaim },		/* reclaim */
+	{ &vop_lock_desc, union_lock },			/* lock */
+	{ &vop_unlock_desc, union_unlock },		/* unlock */
+	{ &vop_bmap_desc, union_bmap },			/* bmap */
+	{ &vop_strategy_desc, union_strategy },		/* strategy */
+	{ &vop_print_desc, union_print },		/* print */
+	{ &vop_islocked_desc, union_islocked },		/* islocked */
+	{ &vop_pathconf_desc, union_pathconf },		/* pathconf */
+	{ &vop_advlock_desc, union_advlock },		/* advlock */
+#ifdef notdef
+	{ &vop_blkatoff_desc, union_blkatoff },		/* blkatoff */
+	{ &vop_valloc_desc, union_valloc },		/* valloc */
+	{ &vop_vfree_desc, union_vfree },		/* vfree */
+	{ &vop_truncate_desc, union_truncate },		/* truncate */
+	{ &vop_update_desc, union_update },		/* update */
+	{ &vop_bwrite_desc, union_bwrite },		/* bwrite */
+#endif
+	{ (struct vnodeop_desc*)NULL, (int(*)())NULL }
+};
+struct vnodeopv_desc union_vnodeop_opv_desc =
+	{ &union_vnodeop_p, union_vnodeop_entries };