FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_lookup.c

     /*
      * 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. 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        8.4 (Berkeley) 2/16/94
     * $FreeBSD: src/sys/kern/vfs_lookup.c,v 1.38.2.3 2001/08/31 19:36:49 dillon Exp $
     */
    
    #include "opt_ktrace.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/vnode.h>
    #include <sys/mount.h>
    #include <sys/filedesc.h>
    #include <sys/proc.h>
    #include <sys/namei.h>
    #include <sys/sysctl.h>
    
    #ifdef KTRACE
    #include <sys/ktrace.h>
    #endif
    
    #include <vm/vm_zone.h>
    
    int varsym_enable = 0;
    SYSCTL_INT(_vfs, OID_AUTO, varsym_enable, CTLFLAG_RW, &varsym_enable, 0,
                "Enable Variant Symlinks");
    
    /*
     * OLD API FUNCTION
     *
     * Relookup a path name component.  This function is only used by the
     * old API *_rename() code under very specific conditions.  CNP_LOCKPARENT
     * must be set in the cnp.  dvp must be unlocked on entry and will be left
     * unlocked if an error occurs.
     *
     * The returned *vpp will be NULL if an error occurs.  Note that no error
     * will occur (error == 0) for CREATE requests on a non-existant target, but
     * *vpp will be NULL in that case.  Both dvp and *vpp (if not NULL) will be
     * locked in the no-error case.   No additional references are made to dvp,
     * only the locking state changes.
     */
    int
    relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
    {
            int rdonly;                     /* lookup read-only flag bit */
            int error = 0;
    
            /*
             * Setup: break out flag bits into variables.
             */
            KKASSERT(cnp->cn_flags & CNP_LOCKPARENT);
            KKASSERT(cnp->cn_flags & CNP_PDIRUNLOCK);
            vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
            cnp->cn_flags &= ~CNP_PDIRUNLOCK;
    
            *vpp = NULL;
            rdonly = cnp->cn_flags & CNP_RDONLY;
    
            /*
             * Search a new directory.
             */
    
            /*
             * Degenerate lookups (e.g. "/", "..", derived from "/.", etc)
             * are not allowed.
             */
            if (cnp->cn_nameptr[0] == '\0') {
                   error = EISDIR;
                   goto bad;
           }
           if (cnp->cn_flags & CNP_ISDOTDOT)
                   panic ("relookup: lookup on dot-dot");
   
           /*
            * We now have a segment name to search for, and a directory to search.
            */
           if ((error = VOP_OLD_LOOKUP(dvp, vpp, cnp)) != 0) {
                   KASSERT(*vpp == NULL, ("leaf should be empty"));
                   if (error != EJUSTRETURN)
                           goto bad;
                   /*
                    * If creating and at end of pathname, then can consider
                    * allowing file to be created.
                    */
                   if (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.
                    */
                   return (0);
           }
   
           /*
            * Check for symbolic link
            */
           KASSERT((*vpp)->v_type != VLNK || !(cnp->cn_flags & CNP_FOLLOW),
               ("relookup: symlink found."));
   
           /*
            * Disallow directory write attempts on read-only file systems.
            */
           if (rdonly && (cnp->cn_nameiop == NAMEI_DELETE || 
                           cnp->cn_nameiop == NAMEI_RENAME)) {
                   error = EROFS;
                   goto bad;
           }
           KKASSERT((cnp->cn_flags & CNP_PDIRUNLOCK) == 0);
           return (0);
   
   bad:
           if ((cnp->cn_flags & CNP_PDIRUNLOCK) == 0) {
                   cnp->cn_flags |= CNP_PDIRUNLOCK;
                   vn_unlock(dvp);
           }
           if (*vpp) {
                   vput(*vpp);
                   *vpp = NULL;
           }
           return (error);
   }
   

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