adlookup.c

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    1 /*      $NetBSD: adlookup.c,v 1.6 2005/02/26 22:58:54 perry Exp $       */
    2 
    3 /*
    4  * Copyright (c) 1994 Christian E. Hopps
    5  * Copyright (c) 1996 Matthias Scheler
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. All advertising materials mentioning features or use of this software
   17  *    must display the following acknowledgement:
   18  *      This product includes software developed by Christian E. Hopps.
   19  * 4. The name of the author may not be used to endorse or promote products
   20  *    derived from this software without specific prior written permission
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __KERNEL_RCSID(0, "$NetBSD: adlookup.c,v 1.6 2005/02/26 22:58:54 perry Exp $");
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/vnode.h>
   40 #include <sys/namei.h>
   41 #include <sys/mount.h>
   42 #include <sys/time.h>
   43 #include <sys/queue.h>
   44 #include <fs/adosfs/adosfs.h>
   45 
   46 #ifdef ADOSFS_EXACTMATCH
   47 #define strmatch(s1, l1, s2, l2, i) \
   48     ((l1) == (l2) && memcmp((s1), (s2), (l1)) == 0)
   49 #else
   50 #define strmatch(s1, l1, s2, l2, i) \
   51     ((l1) == (l2) && adoscaseequ((s1), (s2), (l1), (i)))
   52 #endif
   53 
   54 /*
   55  * adosfs lookup. enters with:
   56  * pvp (parent vnode) referenced and locked.
   57  * exit with:
   58  *      target vp referenced and locked.
   59  *      unlock pvp unless LOCKPARENT and at end of search.
   60  * special cases:
   61  *      pvp == vp, just ref pvp, pvp already holds a ref and lock from
   62  *          caller, this will not occur with RENAME or CREATE.
   63  *      LOOKUP always unlocks parent if last element. (not now!?!?)
   64  */
   65 int
   66 adosfs_lookup(v)
   67         void *v;
   68 {
   69         struct vop_lookup_args /* {
   70                 struct vnode *a_dvp;
   71                 struct vnode **a_vpp;
   72                 struct componentname *a_cnp;
   73         } */ *sp = v;
   74         int nameiop, last, lockp, wantp, flags, error, nocache, i;
   75         struct componentname *cnp;
   76         struct vnode **vpp;     /* place to store result */
   77         struct anode *ap;       /* anode to find */
   78         struct vnode *vdp;      /* vnode of search dir */
   79         struct anode *adp;      /* anode of search dir */
   80         struct ucred *ucp;      /* lookup credentials */
   81         u_long bn, plen, hval;
   82         const u_char *pelt;
   83 
   84 #ifdef ADOSFS_DIAGNOSTIC
   85         advopprint(sp);
   86 #endif
   87         cnp = sp->a_cnp;
   88         vdp = sp->a_dvp;
   89         adp = VTOA(vdp);
   90         vpp = sp->a_vpp;
   91         *vpp = NULL;
   92         ucp = cnp->cn_cred;
   93         nameiop = cnp->cn_nameiop;
   94         cnp->cn_flags &= ~PDIRUNLOCK;
   95         flags = cnp->cn_flags;
   96         last = flags & ISLASTCN;
   97         lockp = flags & LOCKPARENT;
   98         wantp = flags & (LOCKPARENT | WANTPARENT);
   99         pelt = (const u_char *)cnp->cn_nameptr;
  100         plen = cnp->cn_namelen;
  101         nocache = 0;
  102 
  103         /*
  104          * Check accessiblity of directory.
  105          */
  106         if ((error = VOP_ACCESS(vdp, VEXEC, ucp, cnp->cn_proc)) != 0)
  107                 return (error);
  108 
  109         if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
  110             (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
  111                 return (EROFS);
  112 
  113         /*
  114          * Before tediously performing a linear scan of the directory,
  115          * check the name cache to see if the directory/name pair
  116          * we are looking for is known already.
  117          */
  118         if ((error = cache_lookup(vdp, vpp, cnp)) >= 0)
  119                 return (error);
  120 
  121         /*
  122          * fake a '.'
  123          */
  124         if (plen == 1 && pelt[0] == '.') {
  125                 /* see special cases in prologue. */
  126                 *vpp = vdp;
  127                 goto found;
  128         }
  129         /*
  130          * fake a ".."
  131          */
  132         if (flags & ISDOTDOT) {
  133                 if (vdp->v_type == VDIR && (vdp->v_flag & VROOT))
  134                         panic("adosfs .. attempted through root");
  135                 /*
  136                  * cannot get `..' while `vdp' is locked
  137                  * e.g. procA holds lock on `..' and waits for `vdp'
  138                  * we wait for `..' and hold lock on `vdp'. deadlock.
  139                  * because `vdp' may have been achieved through symlink
  140                  * fancy detection code that decreases the race
  141                  * window size is not reasonably possible.
  142                  *
  143                  * basically unlock the parent, try and lock the child (..)
  144                  * if that fails relock the parent (ignoring error) and
  145                  * fail.  Otherwise we have the child (..) if this is the
  146                  * last and the caller requested LOCKPARENT, attempt to
  147                  * relock the parent.  If that fails unlock the child (..)
  148                  * and fail. Otherwise we have succeded.
  149                  *
  150                  */
  151                 VOP_UNLOCK(vdp, 0); /* race */
  152                 cnp->cn_flags |= PDIRUNLOCK;
  153                 if ((error = VFS_VGET(vdp->v_mount,
  154                                       (ino_t)adp->pblock, vpp)) != 0) {
  155                         if (vn_lock(vdp, LK_EXCLUSIVE | LK_RETRY) == 0)
  156                                 cnp->cn_flags &= ~PDIRUNLOCK;
  157                 } else if (last && lockp ) {
  158                     if ((error = vn_lock(vdp, LK_EXCLUSIVE))) {
  159                         vput(*vpp);
  160                     } else {
  161                         cnp->cn_flags &= ~PDIRUNLOCK;
  162                     }
  163                 }
  164                 if (error) {
  165                         *vpp = NULL;
  166                         return (error);
  167                 }
  168                 goto found_lockdone;
  169         }
  170 
  171         /*
  172          * hash the name and grab the first block in chain
  173          * then walk the chain. if chain has not been fully
  174          * walked before, track the count in `tabi'
  175          */
  176         hval = adoshash(pelt, plen, adp->ntabent, IS_INTER(adp->amp));
  177         bn = adp->tab[hval];
  178         i = min(adp->tabi[hval], 0);
  179         while (bn != 0) {
  180                 if ((error = VFS_VGET(vdp->v_mount, (ino_t)bn, vpp)) != 0) {
  181 #ifdef ADOSFS_DIAGNOSTIC
  182                         printf("[aget] %d)", error);
  183 #endif
  184                         /* XXX check to unlock parent possibly? */
  185                         return(error);
  186                 }
  187                 ap = VTOA(*vpp);
  188                 if (i <= 0) {
  189                         if (--i < adp->tabi[hval])
  190                                 adp->tabi[hval] = i;
  191                         /*
  192                          * last header in chain lock count down by
  193                          * negating it to positive
  194                          */
  195                         if (ap->hashf == 0) {
  196 #ifdef DEBUG
  197                                 if (i != adp->tabi[hval])
  198                                         panic("adlookup: wrong chain count");
  199 #endif
  200                                 adp->tabi[hval] = -adp->tabi[hval];
  201                         }
  202                 }
  203                 if (strmatch(pelt, plen, ap->name, strlen(ap->name),
  204                     IS_INTER(adp->amp)))
  205                         goto found;
  206                 bn = ap->hashf;
  207                 vput(*vpp);
  208         }
  209         *vpp = NULL;
  210         /*
  211          * not found
  212          */
  213         if ((nameiop == CREATE || nameiop == RENAME) && last) {
  214 
  215                 if (vdp->v_mount->mnt_flag & MNT_RDONLY)
  216                         return (EROFS);
  217 
  218                 if ((error = VOP_ACCESS(vdp, VWRITE, ucp, cnp->cn_proc)) != 0) {
  219 #ifdef ADOSFS_DIAGNOSTIC
  220                         printf("[VOP_ACCESS] %d)", error);
  221 #endif
  222                         return (error);
  223                 }
  224                 if (lockp == 0) {
  225                         VOP_UNLOCK(vdp, 0);
  226                         cnp->cn_flags |= PDIRUNLOCK;
  227                 }
  228                 cnp->cn_nameiop |= SAVENAME;
  229 #ifdef ADOSFS_DIAGNOSTIC
  230                 printf("EJUSTRETURN)");
  231 #endif
  232                 return(EJUSTRETURN);
  233         }
  234         if ((cnp->cn_flags & MAKEENTRY) && nameiop != CREATE)
  235                 cache_enter(vdp, NULL, cnp);
  236 #ifdef ADOSFS_DIAGNOSTIC
  237         printf("ENOENT)");
  238 #endif
  239         return(ENOENT);
  240 
  241 found:
  242         if (nameiop == DELETE && last)  {
  243                 if ((error = VOP_ACCESS(vdp, VWRITE, ucp, cnp->cn_proc)) != 0) {
  244                         if (vdp != *vpp)
  245                                 vput(*vpp);
  246                         *vpp = NULL;
  247                         return (error);
  248                 }
  249                 nocache = 1;
  250         }
  251         if (nameiop == RENAME && wantp && last) {
  252                 if (vdp == *vpp)
  253                         return(EISDIR);
  254                 if ((error = VOP_ACCESS(vdp, VWRITE, ucp, cnp->cn_proc)) != 0) {
  255                         vput(*vpp);
  256                         *vpp = NULL;
  257                         return (error);
  258                 }
  259                 cnp->cn_flags |= SAVENAME;
  260                 nocache = 1;
  261         }
  262         if (vdp == *vpp)
  263                 VREF(vdp);
  264         else if (lockp == 0 || last == 0) {
  265                 VOP_UNLOCK(vdp, 0);
  266                 cnp->cn_flags |= PDIRUNLOCK;
  267         }
  268 found_lockdone:
  269         if ((cnp->cn_flags & MAKEENTRY) && nocache == 0)
  270                 cache_enter(vdp, *vpp, cnp);
  271 
  272 #ifdef ADOSFS_DIAGNOSTIC
  273         printf("0)\n");
  274 #endif
  275         return(0);
  276 }
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FreeBSD/Linux Kernel Cross Reference sys/fs/adosfs/adlookup.c

FreeBSD/Linux Kernel Cross Reference
sys/fs/adosfs/adlookup.c
