initial import of NetBSD tree

1 files changed, 658 insertions, 0 deletions

diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
new file mode 100644
index 00000000000..da127e73fe6
--- /dev/null
+++ b/sys/kern/vfs_lookup.c
@@ -0,0 +1,658 @@
+/*	$NetBSD: vfs_lookup.c,v 1.15 1995/03/08 01:20:50 cgd Exp $	*/
+
+/*
+ * Copyright (c) 1982, 1986, 1989, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ * (c) UNIX System Laboratories, Inc.
+ * All or some portions of this file are derived from material licensed
+ * to the University of California by American Telephone and Telegraph
+ * Co. or Unix System Laboratories, Inc. and are reproduced herein with
+ * the permission of UNIX System Laboratories, Inc.
+ *
+ * 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.
+ *
+ *	@(#)vfs_lookup.c	8.6 (Berkeley) 11/21/94
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/syslimits.h>
+#include <sys/time.h>
+#include <sys/namei.h>
+#include <sys/vnode.h>
+#include <sys/mount.h>
+#include <sys/errno.h>
+#include <sys/malloc.h>
+#include <sys/filedesc.h>
+#include <sys/proc.h>
+
+#ifdef KTRACE
+#include <sys/ktrace.h>
+#endif
+
+/*
+ * Convert a pathname into a pointer to a locked inode.
+ *
+ * The FOLLOW flag is set when symbolic links are to be followed
+ * when they occur at the end of the name translation process.
+ * Symbolic links are always followed for all other pathname
+ * components other than the last.
+ *
+ * The segflg defines whether the name is to be copied from user
+ * space or kernel space.
+ *
+ * Overall outline of namei:
+ *
+ *	copy in name
+ *	get starting directory
+ *	while (!done && !error) {
+ *		call lookup to search path.
+ *		if symbolic link, massage name in buffer and continue
+ *	}
+ */
+int
+namei(ndp)
+	register struct nameidata *ndp;
+{
+	register struct filedesc *fdp;	/* pointer to file descriptor state */
+	register char *cp;		/* pointer into pathname argument */
+	register struct vnode *dp;	/* the directory we are searching */
+	struct iovec aiov;		/* uio for reading symbolic links */
+	struct uio auio;
+	int error, linklen;
+	struct componentname *cnp = &ndp->ni_cnd;
+
+	ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_proc->p_ucred;
+#ifdef DIAGNOSTIC
+	if (!cnp->cn_cred || !cnp->cn_proc)
+		panic ("namei: bad cred/proc");
+	if (cnp->cn_nameiop & (~OPMASK))
+		panic ("namei: nameiop contaminated with flags");
+	if (cnp->cn_flags & OPMASK)
+		panic ("namei: flags contaminated with nameiops");
+#endif
+	fdp = cnp->cn_proc->p_fd;
+
+	/*
+	 * Get a buffer for the name to be translated, and copy the
+	 * name into the buffer.
+	 */
+	if ((cnp->cn_flags & HASBUF) == 0)
+		MALLOC(cnp->cn_pnbuf, caddr_t, MAXPATHLEN, M_NAMEI, M_WAITOK);
+	if (ndp->ni_segflg == UIO_SYSSPACE)
+		error = copystr(ndp->ni_dirp, cnp->cn_pnbuf,
+			    MAXPATHLEN, &ndp->ni_pathlen);
+	else
+		error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
+			    MAXPATHLEN, &ndp->ni_pathlen);
+	if (error) {
+		free(cnp->cn_pnbuf, M_NAMEI);
+		ndp->ni_vp = NULL;
+		return (error);
+	}
+	ndp->ni_loopcnt = 0;
+#ifdef KTRACE
+	if (KTRPOINT(cnp->cn_proc, KTR_NAMEI))
+		ktrnamei(cnp->cn_proc->p_tracep, cnp->cn_pnbuf);
+#endif
+
+	/*
+	 * Get starting point for the translation.
+	 */
+	if ((ndp->ni_rootdir = fdp->fd_rdir) == NULL)
+		ndp->ni_rootdir = rootvnode;
+	dp = fdp->fd_cdir;
+	VREF(dp);
+	for (;;) {
+		/*
+		 * Check if root directory should replace current directory.
+		 * Done at start of translation and after symbolic link.
+		 */
+		cnp->cn_nameptr = cnp->cn_pnbuf;
+		if (*(cnp->cn_nameptr) == '/') {
+			vrele(dp);
+			while (*(cnp->cn_nameptr) == '/') {
+				cnp->cn_nameptr++;
+				ndp->ni_pathlen--;
+			}
+			dp = ndp->ni_rootdir;
+			VREF(dp);
+		}
+		ndp->ni_startdir = dp;
+		if (error = lookup(ndp)) {
+			FREE(cnp->cn_pnbuf, M_NAMEI);
+			return (error);
+		}
+		/*
+		 * Check for symbolic link
+		 */
+		if ((cnp->cn_flags & ISSYMLINK) == 0) {
+			if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0)
+				FREE(cnp->cn_pnbuf, M_NAMEI);
+			else
+				cnp->cn_flags |= HASBUF;
+			return (0);
+		}
+		if ((cnp->cn_flags & LOCKPARENT) && ndp->ni_pathlen == 1)
+			VOP_UNLOCK(ndp->ni_dvp);
+		if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
+			error = ELOOP;
+			break;
+		}
+		if (ndp->ni_pathlen > 1)
+			MALLOC(cp, char *, MAXPATHLEN, M_NAMEI, M_WAITOK);
+		else
+			cp = cnp->cn_pnbuf;
+		aiov.iov_base = cp;
+		aiov.iov_len = MAXPATHLEN;
+		auio.uio_iov = &aiov;
+		auio.uio_iovcnt = 1;
+		auio.uio_offset = 0;
+		auio.uio_rw = UIO_READ;
+		auio.uio_segflg = UIO_SYSSPACE;
+		auio.uio_procp = (struct proc *)0;
+		auio.uio_resid = MAXPATHLEN;
+		if (error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred)) {
+			if (ndp->ni_pathlen > 1)
+				free(cp, M_NAMEI);
+			break;
+		}
+		linklen = MAXPATHLEN - auio.uio_resid;
+		if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
+			if (ndp->ni_pathlen > 1)
+				free(cp, M_NAMEI);
+			error = ENAMETOOLONG;
+			break;
+		}
+		if (ndp->ni_pathlen > 1) {
+			bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
+			FREE(cnp->cn_pnbuf, M_NAMEI);
+			cnp->cn_pnbuf = cp;
+		} else
+			cnp->cn_pnbuf[linklen] = '\0';
+		ndp->ni_pathlen += linklen;
+		vput(ndp->ni_vp);
+		dp = ndp->ni_dvp;
+	}
+	FREE(cnp->cn_pnbuf, M_NAMEI);
+	vrele(ndp->ni_dvp);
+	vput(ndp->ni_vp);
+	ndp->ni_vp = NULL;
+	return (error);
+}
+
+/*
+ * Search a pathname.
+ * This is a very central and rather complicated routine.
+ *
+ * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
+ * The starting directory is taken from ni_startdir. The pathname is
+ * descended until done, or a symbolic link is encountered. The variable
+ * ni_more is clear if the path is completed; it is set to one if a
+ * symbolic link needing interpretation is encountered.
+ *
+ * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
+ * whether the name is to be looked up, created, renamed, or deleted.
+ * When CREATE, RENAME, or DELETE is specified, information usable in
+ * creating, renaming, or deleting a directory entry may be calculated.
+ * If flag has LOCKPARENT or'ed into it, the parent directory is returned
+ * locked. If flag has WANTPARENT or'ed into it, the parent directory is
+ * returned unlocked. Otherwise the parent directory is not returned. If
+ * the target of the pathname exists and LOCKLEAF is or'ed into the flag
+ * the target is returned locked, otherwise it is returned unlocked.
+ * When creating or renaming and LOCKPARENT is specified, the target may not
+ * be ".".  When deleting and LOCKPARENT is specified, the target may be ".".
+ * 
+ * Overall outline of lookup:
+ *
+ * dirloop:
+ *	identify next component of name at ndp->ni_ptr
+ *	handle degenerate case where name is null string
+ *	if .. and crossing mount points and on mounted filesys, find parent
+ *	call VOP_LOOKUP routine for next component name
+ *	    directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
+ *	    component vnode returned in ni_vp (if it exists), locked.
+ *	if result vnode is mounted on and crossing mount points,
+ *	    find mounted on vnode
+ *	if more components of name, do next level at dirloop
+ *	return the answer in ni_vp, locked if LOCKLEAF set
+ *	    if LOCKPARENT set, return locked parent in ni_dvp
+ *	    if WANTPARENT set, return unlocked parent in ni_dvp
+ */
+int
+lookup(ndp)
+	register struct nameidata *ndp;
+{
+	register char *cp;		/* pointer into pathname argument */
+	register struct vnode *dp = 0;	/* the directory we are searching */
+	struct vnode *tdp;		/* saved dp */
+	struct mount *mp;		/* mount table entry */
+	int docache;			/* == 0 do not cache last component */
+	int wantparent;			/* 1 => wantparent or lockparent flag */
+	int rdonly;			/* lookup read-only flag bit */
+	int error = 0;
+	struct componentname *cnp = &ndp->ni_cnd;
+
+	/*
+	 * Setup: break out flag bits into variables.
+	 */
+	wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
+	docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
+	if (cnp->cn_nameiop == DELETE ||
+	    (wantparent && cnp->cn_nameiop != CREATE))
+		docache = 0;
+	rdonly = cnp->cn_flags & RDONLY;
+	ndp->ni_dvp = NULL;
+	cnp->cn_flags &= ~ISSYMLINK;
+	dp = ndp->ni_startdir;
+	ndp->ni_startdir = NULLVP;
+	VOP_LOCK(dp);
+
+dirloop:
+	/*
+	 * Search a new directory.
+	 *
+	 * The cn_hash value is for use by vfs_cache.
+	 * The last component of the filename is left accessible via
+	 * cnp->cn_nameptr for callers that need the name. Callers needing
+	 * the name set the SAVENAME flag. When done, they assume
+	 * responsibility for freeing the pathname buffer.
+	 */
+	cnp->cn_consume = 0;
+	cnp->cn_hash = 0;
+	for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
+		cnp->cn_hash += (unsigned char)*cp;
+	cnp->cn_namelen = cp - cnp->cn_nameptr;
+	if (cnp->cn_namelen > NAME_MAX) {
+		error = ENAMETOOLONG;
+		goto bad;
+	}
+#ifdef NAMEI_DIAGNOSTIC
+	{ char c = *cp;
+	*cp = '\0';
+	printf("{%s}: ", cnp->cn_nameptr);
+	*cp = c; }
+#endif
+	ndp->ni_pathlen -= cnp->cn_namelen;
+	ndp->ni_next = cp;
+	cnp->cn_flags |= MAKEENTRY;
+	if (*cp == '\0' && docache == 0)
+		cnp->cn_flags &= ~MAKEENTRY;
+	if (cnp->cn_namelen == 2 &&
+	    cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
+		cnp->cn_flags |= ISDOTDOT;
+	else
+		cnp->cn_flags &= ~ISDOTDOT;
+	if (*ndp->ni_next == 0)
+		cnp->cn_flags |= ISLASTCN;
+	else
+		cnp->cn_flags &= ~ISLASTCN;
+
+
+	/*
+	 * Check for degenerate name (e.g. / or "")
+	 * which is a way of talking about a directory,
+	 * e.g. like "/." or ".".
+	 */
+	if (cnp->cn_nameptr[0] == '\0') {
+		if (dp->v_type != VDIR) {
+			error = ENOTDIR;
+			goto bad;
+		}
+		if (cnp->cn_nameiop != LOOKUP) {
+			error = EISDIR;
+			goto bad;
+		}
+		if (wantparent) {
+			ndp->ni_dvp = dp;
+			VREF(dp);
+		}
+		ndp->ni_vp = dp;
+		if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
+			VOP_UNLOCK(dp);
+		if (cnp->cn_flags & SAVESTART)
+			panic("lookup: SAVESTART");
+		return (0);
+	}
+
+	/*
+	 * Handle "..": two special cases.
+	 * 1. If at root directory (e.g. after chroot)
+	 *    or at absolute root directory
+	 *    then ignore it so can't get out.
+	 * 2. If this vnode is the root of a mounted
+	 *    filesystem, then replace it with the
+	 *    vnode which was mounted on so we take the
+	 *    .. in the other file system.
+	 */
+	if (cnp->cn_flags & ISDOTDOT) {
+		for (;;) {
+			if (dp == ndp->ni_rootdir || dp == rootvnode) {
+				ndp->ni_dvp = dp;
+				ndp->ni_vp = dp;
+				VREF(dp);
+				goto nextname;
+			}
+			if ((dp->v_flag & VROOT) == 0 ||
+			    (cnp->cn_flags & NOCROSSMOUNT))
+				break;
+			tdp = dp;
+			dp = dp->v_mount->mnt_vnodecovered;
+			vput(tdp);
+			VREF(dp);
+			VOP_LOCK(dp);
+		}
+	}
+
+	/*
+	 * We now have a segment name to search for, and a directory to search.
+	 */
+unionlookup:
+	ndp->ni_dvp = dp;
+	if (error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp)) {
+#ifdef DIAGNOSTIC
+		if (ndp->ni_vp != NULL)
+			panic("leaf should be empty");
+#endif
+#ifdef NAMEI_DIAGNOSTIC
+		printf("not found\n");
+#endif
+		if ((error == ENOENT) &&
+		    (dp->v_flag & VROOT) &&
+		    (dp->v_mount->mnt_flag & MNT_UNION)) {
+			tdp = dp;
+			dp = dp->v_mount->mnt_vnodecovered;
+			vput(tdp);
+			VREF(dp);
+			VOP_LOCK(dp);
+			goto unionlookup;
+		}
+
+		if (error != EJUSTRETURN)
+			goto bad;
+		/*
+		 * If creating and at end of pathname, then can consider
+		 * allowing file to be created.
+		 */
+		if (rdonly || (ndp->ni_dvp->v_mount->mnt_flag & MNT_RDONLY)) {
+			error = EROFS;
+			goto bad;
+		}
+		/*
+		 * We return with ni_vp NULL to indicate that the entry
+		 * doesn't currently exist, leaving a pointer to the
+		 * (possibly locked) directory inode in ndp->ni_dvp.
+		 */
+		if (cnp->cn_flags & SAVESTART) {
+			ndp->ni_startdir = ndp->ni_dvp;
+			VREF(ndp->ni_startdir);
+		}
+		return (0);
+	}
+#ifdef NAMEI_DIAGNOSTIC
+	printf("found\n");
+#endif
+
+	/*
+	 * Take into account any additional components consumed by
+	 * the underlying filesystem.
+	 */
+	if (cnp->cn_consume > 0) {
+		cnp->cn_nameptr += cnp->cn_consume;
+		ndp->ni_next += cnp->cn_consume;
+		ndp->ni_pathlen -= cnp->cn_consume;
+		cnp->cn_consume = 0;
+	}
+
+	dp = ndp->ni_vp;
+	/*
+	 * Check to see if the vnode has been mounted on;
+	 * if so find the root of the mounted file system.
+	 */
+	while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
+	       (cnp->cn_flags & NOCROSSMOUNT) == 0) {
+		if (mp->mnt_flag & MNT_MLOCK) {
+			mp->mnt_flag |= MNT_MWAIT;
+			sleep((caddr_t)mp, PVFS);
+			continue;
+		}
+		if (error = VFS_ROOT(dp->v_mountedhere, &tdp))
+			goto bad2;
+		vput(dp);
+		ndp->ni_vp = dp = tdp;
+	}
+
+	/*
+	 * Check for symbolic link
+	 */
+	if ((dp->v_type == VLNK) &&
+	    ((cnp->cn_flags & FOLLOW) || *ndp->ni_next == '/')) {
+		cnp->cn_flags |= ISSYMLINK;
+		return (0);
+	}
+
+nextname:
+	/*
+	 * Not a symbolic link.  If more pathname,
+	 * continue at next component, else return.
+	 */
+	if (*ndp->ni_next == '/') {
+		cnp->cn_nameptr = ndp->ni_next;
+		while (*cnp->cn_nameptr == '/') {
+			cnp->cn_nameptr++;
+			ndp->ni_pathlen--;
+		}
+		vrele(ndp->ni_dvp);
+		goto dirloop;
+	}
+	/*
+	 * Check for read-only file systems.
+	 */
+	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME) {
+		/*
+		 * Disallow directory write attempts on read-only
+		 * file systems.
+		 */
+		if (rdonly || (dp->v_mount->mnt_flag & MNT_RDONLY) ||
+		    (wantparent &&
+		     (ndp->ni_dvp->v_mount->mnt_flag & MNT_RDONLY))) {
+			error = EROFS;
+			goto bad2;
+		}
+	}
+	if (cnp->cn_flags & SAVESTART) {
+		ndp->ni_startdir = ndp->ni_dvp;
+		VREF(ndp->ni_startdir);
+	}
+	if (!wantparent)
+		vrele(ndp->ni_dvp);
+	if ((cnp->cn_flags & LOCKLEAF) == 0)
+		VOP_UNLOCK(dp);
+	return (0);
+
+bad2:
+	if ((cnp->cn_flags & LOCKPARENT) && *ndp->ni_next == '\0')
+		VOP_UNLOCK(ndp->ni_dvp);
+	vrele(ndp->ni_dvp);
+bad:
+	vput(dp);
+	ndp->ni_vp = NULL;
+	return (error);
+}
+
+/*
+ * Reacquire a path name component.
+ */
+int
+relookup(dvp, vpp, cnp)
+	struct vnode *dvp, **vpp;
+	struct componentname *cnp;
+{
+	register struct vnode *dp = 0;	/* the directory we are searching */
+	int docache;			/* == 0 do not cache last component */
+	int wantparent;			/* 1 => wantparent or lockparent flag */
+	int rdonly;			/* lookup read-only flag bit */
+	int error = 0;
+#ifdef NAMEI_DIAGNOSTIC
+	int newhash;			/* DEBUG: check name hash */
+	char *cp;			/* DEBUG: check name ptr/len */
+#endif
+
+	/*
+	 * Setup: break out flag bits into variables.
+	 */
+	wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT);
+	docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
+	if (cnp->cn_nameiop == DELETE ||
+	    (wantparent && cnp->cn_nameiop != CREATE))
+		docache = 0;
+	rdonly = cnp->cn_flags & RDONLY;
+	cnp->cn_flags &= ~ISSYMLINK;
+	dp = dvp;
+	VOP_LOCK(dp);
+
+/* dirloop: */
+	/*
+	 * Search a new directory.
+	 *
+	 * The cn_hash value is for use by vfs_cache.
+	 * The last component of the filename is left accessible via
+	 * cnp->cn_nameptr for callers that need the name. Callers needing
+	 * the name set the SAVENAME flag. When done, they assume
+	 * responsibility for freeing the pathname buffer.
+	 */
+#ifdef NAMEI_DIAGNOSTIC
+	for (newhash = 0, cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
+		newhash += (unsigned char)*cp;
+	if (newhash != cnp->cn_hash)
+		panic("relookup: bad hash");
+	if (cnp->cn_namelen != cp - cnp->cn_nameptr)
+		panic ("relookup: bad len");
+	if (*cp != 0)
+		panic("relookup: not last component");
+	printf("{%s}: ", cnp->cn_nameptr);
+#endif
+
+	/*
+	 * Check for degenerate name (e.g. / or "")
+	 * which is a way of talking about a directory,
+	 * e.g. like "/." or ".".
+	 */
+	if (cnp->cn_nameptr[0] == '\0') {
+		if (dp->v_type != VDIR) {
+			error = ENOTDIR;
+			goto bad;
+		}
+		if (cnp->cn_nameiop != LOOKUP || wantparent) {
+			error = EISDIR;
+			goto bad;
+		}
+		if (!(cnp->cn_flags & LOCKLEAF))
+			VOP_UNLOCK(dp);
+		*vpp = dp;
+		if (cnp->cn_flags & SAVESTART)
+			panic("lookup: SAVESTART");
+		return (0);
+	}
+
+	if (cnp->cn_flags & ISDOTDOT)
+		panic ("relookup: lookup on dot-dot");
+
+	/*
+	 * We now have a segment name to search for, and a directory to search.
+	 */
+	if (error = VOP_LOOKUP(dp, vpp, cnp)) {
+#ifdef DIAGNOSTIC
+		if (*vpp != NULL)
+			panic("leaf should be empty");
+#endif
+		if (error != EJUSTRETURN)
+			goto bad;
+		/*
+		 * If creating and at end of pathname, then can consider
+		 * allowing file to be created.
+		 */
+		if (rdonly || (dvp->v_mount->mnt_flag & MNT_RDONLY)) {
+			error = EROFS;
+			goto bad;
+		}
+		/* ASSERT(dvp == ndp->ni_startdir) */
+		if (cnp->cn_flags & SAVESTART)
+			VREF(dvp);
+		/*
+		 * We return with ni_vp NULL to indicate that the entry
+		 * doesn't currently exist, leaving a pointer to the
+		 * (possibly locked) directory inode in ndp->ni_dvp.
+		 */
+		return (0);
+	}
+	dp = *vpp;
+
+#ifdef DIAGNOSTIC
+	/*
+	 * Check for symbolic link
+	 */
+	if (dp->v_type == VLNK && (cnp->cn_flags & FOLLOW))
+		panic ("relookup: symlink found.\n");
+#endif
+
+	/*
+	 * Check for read-only file systems.
+	 */
+	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME) {
+		/*
+		 * Disallow directory write attempts on read-only
+		 * file systems.
+		 */
+		if (rdonly || (dp->v_mount->mnt_flag & MNT_RDONLY) ||
+		    (wantparent &&
+		     (dvp->v_mount->mnt_flag & MNT_RDONLY))) {
+			error = EROFS;
+			goto bad2;
+		}
+	}
+	/* ASSERT(dvp == ndp->ni_startdir) */
+	if (cnp->cn_flags & SAVESTART)
+		VREF(dvp);
+	
+	if (!wantparent)
+		vrele(dvp);
+	if ((cnp->cn_flags & LOCKLEAF) == 0)
+		VOP_UNLOCK(dp);
+	return (0);
+
+bad2:
+	if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN))
+		VOP_UNLOCK(dvp);
+	vrele(dvp);
+bad:
+	vput(dp);
+	*vpp = NULL;
+	return (error);
+}