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cd9660_lookup.c

/*    $OpenBSD: cd9660_lookup.c,v 1.11 2003/06/02 23:28:05 millert Exp $      */
/*    $NetBSD: cd9660_lookup.c,v 1.18 1997/05/08 16:19:59 mycroft Exp $ */

/*-
 * Copyright (c) 1989, 1993, 1994
 *    The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley
 * by Pace Willisson (pace@blitz.com).  The Rock Ridge Extension
 * Support code is derived from software contributed to Berkeley
 * by Atsushi Murai (amurai@spec.co.jp).
 *
 * 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.
 *
 *    from: @(#)ufs_lookup.c  7.33 (Berkeley) 5/19/91
 *
 *    @(#)cd9660_lookup.c     8.5 (Berkeley) 12/5/94
 */

#include <sys/param.h>
#include <sys/namei.h>
#include <sys/buf.h>
#include <sys/file.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/systm.h>

#include <isofs/cd9660/iso.h>
#include <isofs/cd9660/cd9660_extern.h>
#include <isofs/cd9660/cd9660_node.h>
#include <isofs/cd9660/iso_rrip.h>
#include <isofs/cd9660/cd9660_rrip.h>

struct      nchstats iso_nchstats;

/*
 * Convert a component of a pathname into a pointer to a locked inode.
 * This is a very central and rather complicated routine.
 * If the file system is not maintained in a strict tree hierarchy,
 * this can result in a deadlock situation (see comments in code below).
 *
 * 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 and the target of the pathname
 * exists, lookup returns both the target and its parent directory locked.
 * When creating or renaming and LOCKPARENT is specified, the target may
 * not be ".".  When deleting and LOCKPARENT is specified, the target may
 * be "."., but the caller must check to ensure it does an vrele and iput
 * instead of two iputs.
 *
 * Overall outline of cd9660_lookup:
 *
 *    check accessibility of directory
 *    look for name in cache, if found, then if at end of path
 *      and deleting or creating, drop it, else return name
 *    search for name in directory, to found or notfound
 * notfound:
 *    if creating, return locked directory, leaving info on available slots
 *    else return error
 * found:
 *    if at end of path and deleting, return information to allow delete
 *    if at end of path and rewriting (RENAME and LOCKPARENT), lock target
 *      inode and return info to allow rewrite
 *    if not at end, add name to cache; if at end and neither creating
 *      nor deleting, add name to cache
 *
 * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode unlocked.
 */
int
cd9660_lookup(v)
      void *v;
{
      struct vop_lookup_args /* {
            struct vnode *a_dvp;
            struct vnode **a_vpp;
            struct componentname *a_cnp;
      } */ *ap = v;
      register struct vnode *vdp;   /* vnode for directory being searched */
      register struct iso_node *dp; /* inode for directory being searched */
      register struct iso_mnt *imp; /* file system that directory is in */
      struct buf *bp;               /* a buffer of directory entries */
      struct iso_directory_record *ep = NULL;
                              /* the current directory entry */
      int entryoffsetinblock;       /* offset of ep in bp's buffer */
      int saveoffset = -1;          /* offset of last directory entry in dir */
      int numdirpasses;       /* strategy for directory search */
      doff_t endsearch;       /* offset to end directory search */
      struct vnode *pdp;            /* saved dp during symlink work */
      struct vnode *tdp;            /* returned by cd9660_vget_internal */
      u_long bmask;                 /* block offset mask */
      int lockparent;               /* 1 => lockparent flag is set */
      int wantparent;               /* 1 => wantparent or lockparent flag */
      int error;
      ino_t ino = 0;
      int reclen;
      u_short namelen;
      char altname[NAME_MAX];
      int res;
      int assoc, len;
      char *name;
      struct vnode **vpp = ap->a_vpp;
      struct componentname *cnp = ap->a_cnp;
      struct ucred *cred = cnp->cn_cred;
      int flags;
      int nameiop = cnp->cn_nameiop;
      struct proc *p = cnp->cn_proc;

      cnp->cn_flags &= ~PDIRUNLOCK;
      flags = cnp->cn_flags;

      bp = NULL;
      *vpp = NULL;
      vdp = ap->a_dvp;
      dp = VTOI(vdp);
      imp = dp->i_mnt;
      lockparent = flags & LOCKPARENT;
      wantparent = flags & (LOCKPARENT|WANTPARENT);
      
      /*
       * Check accessiblity of directory.
       */
      if ((error = VOP_ACCESS(vdp, VEXEC, cred, cnp->cn_proc)) != 0)
            return (error);

      if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
          (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
            return (EROFS);
      
      /*
       * We now have a segment name to search for, and a directory to search.
       *
       * Before tediously performing a linear scan of the directory,
       * check the name cache to see if the directory/name pair
       * we are looking for is known already.
       */
      if ((error = cache_lookup(vdp, vpp, cnp)) >= 0)
            return (error);

      len = cnp->cn_namelen;
      name = cnp->cn_nameptr;
      /*
       * A leading `=' means, we are looking for an associated file
       */
      assoc = (imp->iso_ftype != ISO_FTYPE_RRIP && *name == ASSOCCHAR);
      if (assoc) {
            len--;
            name++;
      }
      
      /*
       * If there is cached information on a previous search of
       * this directory, pick up where we last left off.
       * We cache only lookups as these are the most common
       * and have the greatest payoff. Caching CREATE has little
       * benefit as it usually must search the entire directory
       * to determine that the entry does not exist. Caching the
       * location of the last DELETE or RENAME has not reduced
       * profiling time and hence has been removed in the interest
       * of simplicity.
       */
      bmask = imp->im_bmask;
      if (nameiop != LOOKUP || dp->i_diroff == 0 ||
          dp->i_diroff > dp->i_size) {
            entryoffsetinblock = 0;
            dp->i_offset = 0;
            numdirpasses = 1;
      } else {
            dp->i_offset = dp->i_diroff;
            if ((entryoffsetinblock = dp->i_offset & bmask) &&
                (error = cd9660_bufatoff(dp, (off_t)dp->i_offset, NULL, 
                  &bp)))
                        return (error);
            numdirpasses = 2;
            iso_nchstats.ncs_2passes++;
      }
      endsearch = dp->i_size;
      
searchloop:
      while (dp->i_offset < endsearch) {
            /*
             * If offset is on a block boundary,
             * read the next directory block.
             * Release previous if it exists.
             */
            if ((dp->i_offset & bmask) == 0) {
                  if (bp != NULL)
                        brelse(bp);
                  error = cd9660_bufatoff(dp, (off_t)dp->i_offset,
                                   NULL, &bp);
                  if (error)
                        return (error);
                  entryoffsetinblock = 0;
            }
            /*
             * Get pointer to next entry.
             */
            ep = (struct iso_directory_record *)
                  ((char *)bp->b_data + entryoffsetinblock);
            
            reclen = isonum_711(ep->length);
            if (reclen == 0) {
                  /* skip to next block, if any */
                  dp->i_offset =
                      (dp->i_offset & ~bmask) + imp->logical_block_size;
                  continue;
            }
            
            if (reclen < ISO_DIRECTORY_RECORD_SIZE)
                  /* illegal entry, stop */
                  break;
            
            if (entryoffsetinblock + reclen > imp->logical_block_size)
                  /* entries are not allowed to cross boundaries */
                  break;
            
            namelen = isonum_711(ep->name_len);
            
            if (reclen < ISO_DIRECTORY_RECORD_SIZE + namelen)
                  /* illegal entry, stop */
                  break;
            
            /*
             * Check for a name match.
             */
            switch (imp->iso_ftype) {
            default:
                  if ((!(isonum_711(ep->flags)&4)) == !assoc) {
                        if ((len == 1
                             && *name == '.')
                            || (flags & ISDOTDOT)) {
                              if (namelen == 1
                                  && ep->name[0] == ((flags & ISDOTDOT) ? 1 : 0)) {
                                    /*
                                     * Save directory entry's inode number and
                                     * release directory buffer.
                                     */
                                    dp->i_ino = isodirino(ep, imp);
                                    goto found;
                              }
                              if (namelen != 1
                                  || ep->name[0] != 0)
                                    goto notfound;
                        } else if (!(res = isofncmp(name, len, 
                            ep->name, namelen, imp->joliet_level))) {
                              if (isonum_711(ep->flags)&2)
                                    ino = isodirino(ep, imp);
                              else
                                    ino = dbtob(bp->b_blkno)
                                          + entryoffsetinblock;
                              saveoffset = dp->i_offset;
                        } else if (ino)
                              goto foundino;
#ifdef      NOSORTBUG   /* On some CDs directory entries are not sorted correctly */
                        else if (res < 0)
                              goto notfound;
                        else if (res > 0 && numdirpasses == 2)
                              numdirpasses++;
#endif
                  }
                  break;
            case ISO_FTYPE_RRIP:
                  if (isonum_711(ep->flags)&2)
                        ino = isodirino(ep, imp);
                  else
                        ino = dbtob(bp->b_blkno) + entryoffsetinblock;
                  dp->i_ino = ino;
                  cd9660_rrip_getname(ep,altname,&namelen,&dp->i_ino,imp);
                  if (namelen == cnp->cn_namelen
                      && !bcmp(name,altname,namelen))
                        goto found;
                  ino = 0;
                  break;
            }
            dp->i_offset += reclen;
            entryoffsetinblock += reclen;
      }
      if (ino) {
foundino:
            dp->i_ino = ino;
            if (saveoffset != dp->i_offset) {
                  if (lblkno(imp, dp->i_offset) !=
                      lblkno(imp, saveoffset)) {
                        if (bp != NULL)
                              brelse(bp);
                        if ((error = cd9660_bufatoff(dp,
                                  (off_t)saveoffset, NULL, &bp)) != 0)
                              return (error);
                  }
                  entryoffsetinblock = saveoffset & bmask;
                  ep = (struct iso_directory_record *)
                        ((char *)bp->b_data + entryoffsetinblock);
                  dp->i_offset = saveoffset;
            }
            goto found;
      }
notfound:
      /*
       * If we started in the middle of the directory and failed
       * to find our target, we must check the beginning as well.
       */
      if (numdirpasses == 2) {
            numdirpasses--;
            dp->i_offset = 0;
            endsearch = dp->i_diroff;
            goto searchloop;
      }
      if (bp != NULL)
            brelse(bp);

      /*
       * Insert name into cache (as non-existent) if appropriate.
       */
      if (cnp->cn_flags & MAKEENTRY)
            cache_enter(vdp, *vpp, cnp);
      if (nameiop == CREATE || nameiop == RENAME)
            return (EJUSTRETURN);
      return (ENOENT);
      
found:
      if (numdirpasses == 2)
            iso_nchstats.ncs_pass2++;
      
      /*
       * Found component in pathname.
       * If the final component of path name, save information
       * in the cache as to where the entry was found.
       */
      if ((flags & ISLASTCN) && nameiop == LOOKUP)
            dp->i_diroff = dp->i_offset;
      
      /*
       * Step through the translation in the name.  We do not `iput' the
       * directory because we may need it again if a symbolic link
       * is relative to the current directory.  Instead we save it
       * unlocked as "pdp".  We must get the target inode before unlocking
       * the directory to insure that the inode will not be removed
       * before we get it.  We prevent deadlock by always fetching
       * inodes from the root, moving down the directory tree. Thus
       * when following backward pointers ".." we must unlock the
       * parent directory before getting the requested directory.
       * There is a potential race condition here if both the current
       * and parent directories are removed before the `iget' for the
       * inode associated with ".." returns.  We hope that this occurs
       * infrequently since we cannot avoid this race condition without
       * implementing a sophisticated deadlock detection algorithm.
       * Note also that this simple deadlock detection scheme will not
       * work if the file system has any hard links other than ".."
       * that point backwards in the directory structure.
       */
      pdp = vdp;
      /*
       * If ino is different from dp->i_ino,
       * it's a relocated directory.
       */
      if (flags & ISDOTDOT) {
            brelse(bp);
            VOP_UNLOCK(pdp, 0, p);  /* race to get the inode */
            cnp->cn_flags |= PDIRUNLOCK;
            error = cd9660_vget_internal(vdp->v_mount, dp->i_ino, &tdp,
                      dp->i_ino != ino, NULL);
            if (error) {
                  if (vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY, p) == 0)
                        cnp->cn_flags &= ~PDIRUNLOCK;
                  return (error);
            }
            if (lockparent && (flags & ISLASTCN)) {
                  if ((error = vn_lock(pdp, LK_EXCLUSIVE, p))) {
                        vput(tdp);
                        return (error);
                  }
                  cnp->cn_flags &= ~PDIRUNLOCK;
            }
            *vpp = tdp;
      } else if (dp->i_number == dp->i_ino) {
            brelse(bp);
            VREF(vdp);  /* we want ourself, ie "." */
            *vpp = vdp;
      } else {
            error = cd9660_vget_internal(vdp->v_mount, dp->i_ino, &tdp,
                                   dp->i_ino != ino, ep);
            brelse(bp);
            if (error)
                  return (error);
            if (!lockparent || !(flags & ISLASTCN)) {
                  VOP_UNLOCK(pdp, 0, p);
                  cnp->cn_flags |= PDIRUNLOCK;
            }
            *vpp = tdp;
      }
      
      /*
       * Insert name into cache if appropriate.
       */
      if (cnp->cn_flags & MAKEENTRY)
            cache_enter(vdp, *vpp, cnp);
      return (0);
}

/*
 * Return buffer with the contents of block "offset" from the beginning of
 * directory "ip".  If "res" is non-zero, fill it in with a pointer to the
 * remaining space in the directory.
 */
int
cd9660_bufatoff(struct iso_node *ip, off_t offset, char **res, 
    struct buf **bpp)
{
      struct iso_mnt *imp;
      struct buf *bp;
      daddr_t lbn;
      int bsize, error;
      struct vnode *vp = ITOV(ip);

      imp = ip->i_mnt;
      lbn = lblkno(imp, offset);
      bsize = blksize(imp, ip, lbn);
      
      if ((error = bread(vp, lbn, bsize, NOCRED, &bp)) != 0) {
            brelse(bp);
            *bpp = NULL;
            return (error);
      }
      if (res)
            *res = (char *)bp->b_data + blkoff(imp, offset);
      *bpp = bp;
      return (0);
}

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