sys/fs/adosfs/adlookup.c

   1 /*      $NetBSD: adlookup.c,v 1.12 2009/03/14 21:04:23 dsl 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 1.12 2009/03/14 21:04:23 dsl 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  *      parent pvp locked.
  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  */
  64 int
  65 adosfs_lookup(void *v)
  66 {
  67         struct vop_lookup_args /* {
  68                 struct vnode *a_dvp;
  69                 struct vnode **a_vpp;
  70                 struct componentname *a_cnp;
  71         } */ *sp = v;
  72         int nameiop, last, flags, error, nocache, i;
  73         struct componentname *cnp;
  74         struct vnode **vpp;     /* place to store result */
  75         struct anode *ap;       /* anode to find */
  76         struct vnode *vdp;      /* vnode of search dir */
  77         struct anode *adp;      /* anode of search dir */
  78         kauth_cred_t ucp;       /* lookup credentials */
  79         u_long bn, plen, hval;
  80         const u_char *pelt;
  81
  82 #ifdef ADOSFS_DIAGNOSTIC
  83         advopprint(sp);
  84 #endif
  85         cnp = sp->a_cnp;
  86         vdp = sp->a_dvp;
  87         adp = VTOA(vdp);
  88         vpp = sp->a_vpp;
  89         *vpp = NULL;
  90         ucp = cnp->cn_cred;
  91         nameiop = cnp->cn_nameiop;
  92         flags = cnp->cn_flags;
  93         last = flags & ISLASTCN;
  94         pelt = (const u_char *)cnp->cn_nameptr;
  95         plen = cnp->cn_namelen;
  96         nocache = 0;
  97
  98         /*
  99          * Check accessiblity of directory.
 100          */
 101         if ((error = VOP_ACCESS(vdp, VEXEC, ucp)) != 0)
 102                 return (error);
 103
 104         if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
 105             (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
 106                 return (EROFS);
 107
 108         /*
 109          * Before tediously performing a linear scan of the directory,
 110          * check the name cache to see if the directory/name pair
 111          * we are looking for is known already.
 112          */
 113         if ((error = cache_lookup(vdp, vpp, cnp)) >= 0)
 114                 return (error);
 115
 116         /*
 117          * fake a '.'
 118          */
 119         if (plen == 1 && pelt[0] == '.') {
 120                 /* see special cases in prologue. */
 121                 *vpp = vdp;
 122                 goto found;
 123         }
 124         /*
 125          * fake a ".."
 126          */
 127         if (flags & ISDOTDOT) {
 128                 if (vdp->v_type == VDIR && (vdp->v_vflag & VV_ROOT))
 129                         panic("adosfs .. attempted through root");
 130                 /*
 131                  * cannot get `..' while `vdp' is locked
 132                  * e.g. procA holds lock on `..' and waits for `vdp'
 133                  * we wait for `..' and hold lock on `vdp'. deadlock.
 134                  * because `vdp' may have been achieved through symlink
 135                  * fancy detection code that decreases the race
 136                  * window size is not reasonably possible.
 137                  *
 138                  * basically unlock the parent, try and lock the child (..)
 139                  * if that fails relock the parent (ignoring error) and
 140                  * fail.  Otherwise we have the child (..), attempt to
 141                  * relock the parent.  If that fails unlock the child (..)
 142                  * and fail. Otherwise we have succeded.
 143                  *
 144                  */
 145                 VOP_UNLOCK(vdp, 0); /* race */
 146                 error = VFS_VGET(vdp->v_mount, (ino_t)adp->pblock, vpp);
 147                 vn_lock(vdp, LK_EXCLUSIVE | LK_RETRY);
 148                 if (error) {
 149                         *vpp = NULL;
 150                         return (error);
 151                 }
 152                 goto found_lockdone;
 153         }
 154
 155         /*
 156          * hash the name and grab the first block in chain
 157          * then walk the chain. if chain has not been fully
 158          * walked before, track the count in `tabi'
 159          */
 160         hval = adoshash(pelt, plen, adp->ntabent, IS_INTER(adp->amp));
 161         bn = adp->tab[hval];
 162         i = min(adp->tabi[hval], 0);
 163         while (bn != 0) {
 164                 if ((error = VFS_VGET(vdp->v_mount, (ino_t)bn, vpp
 165                                       )) != 0) {
 166 #ifdef ADOSFS_DIAGNOSTIC
 167                         printf("[aget] %d)", error);
 168 #endif
 169                         return(error);
 170                 }
 171                 ap = VTOA(*vpp);
 172                 if (i <= 0) {
 173                         if (--i < adp->tabi[hval])
 174                                 adp->tabi[hval] = i;
 175                         /*
 176                          * last header in chain lock count down by
 177                          * negating it to positive
 178                          */
 179                         if (ap->hashf == 0) {
 180 #ifdef DEBUG
 181                                 if (i != adp->tabi[hval])
 182                                         panic("adlookup: wrong chain count");
 183 #endif
 184                                 adp->tabi[hval] = -adp->tabi[hval];
 185                         }
 186                 }
 187                 if (strmatch(pelt, plen, ap->name, strlen(ap->name),
 188                     IS_INTER(adp->amp)))
 189                         goto found;
 190                 bn = ap->hashf;
 191                 vput(*vpp);
 192         }
 193         *vpp = NULL;
 194         /*
 195          * not found
 196          */
 197         if ((nameiop == CREATE || nameiop == RENAME) && last) {
 198
 199                 if (vdp->v_mount->mnt_flag & MNT_RDONLY)
 200                         return (EROFS);
 201
 202                 if ((error = VOP_ACCESS(vdp, VWRITE, ucp)) != 0) {
 203 #ifdef ADOSFS_DIAGNOSTIC
 204                         printf("[VOP_ACCESS] %d)", error);
 205 #endif
 206                         return (error);
 207                 }
 208                 cnp->cn_nameiop |= SAVENAME;
 209 #ifdef ADOSFS_DIAGNOSTIC
 210                 printf("EJUSTRETURN)");
 211 #endif
 212                 return(EJUSTRETURN);
 213         }
 214         if ((cnp->cn_flags & MAKEENTRY) && nameiop != CREATE)
 215                 cache_enter(vdp, NULL, cnp);
 216 #ifdef ADOSFS_DIAGNOSTIC
 217         printf("ENOENT)");
 218 #endif
 219         return(ENOENT);
 220
 221 found:
 222         if (nameiop == DELETE && last)  {
 223                 if ((error = VOP_ACCESS(vdp, VWRITE, ucp)) != 0) {
 224                         if (vdp != *vpp)
 225                                 vput(*vpp);
 226                         *vpp = NULL;
 227                         return (error);
 228                 }
 229                 nocache = 1;
 230         }
 231         if (nameiop == RENAME && last) {
 232                 if (vdp == *vpp)
 233                         return(EISDIR);
 234                 if ((error = VOP_ACCESS(vdp, VWRITE, ucp)) != 0) {
 235                         vput(*vpp);
 236                         *vpp = NULL;
 237                         return (error);
 238                 }
 239                 cnp->cn_flags |= SAVENAME;
 240                 nocache = 1;
 241         }
 242         if (vdp == *vpp)
 243                 vref(vdp);
 244 found_lockdone:
 245         if ((cnp->cn_flags & MAKEENTRY) && nocache == 0)
 246                 cache_enter(vdp, *vpp, cnp);
 247
 248 #ifdef ADOSFS_DIAGNOSTIC
 249         printf("0)\n");
 250 #endif
 251         return(0);
 252 }