bsd/miscfs/nullfs/null_subr.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
  26 /*
  27  * Copyright (c) 1992, 1993
  28  *      The Regents of the University of California.  All rights reserved.
  29  *
  30  * This code is derived from software donated to Berkeley by
  31  * Jan-Simon Pendry.
  32  *
  33  * Redistribution and use in source and binary forms, with or without
  34  * modification, are permitted provided that the following conditions
  35  * are met:
  36  * 1. Redistributions of source code must retain the above copyright
  37  *    notice, this list of conditions and the following disclaimer.
  38  * 2. Redistributions in binary form must reproduce the above copyright
  39  *    notice, this list of conditions and the following disclaimer in the
  40  *    documentation and/or other materials provided with the distribution.
  41  * 3. All advertising materials mentioning features or use of this software
  42  *    must display the following acknowledgement:
  43  *      This product includes software developed by the University of
  44  *      California, Berkeley and its contributors.
  45  * 4. Neither the name of the University nor the names of its contributors
  46  *    may be used to endorse or promote products derived from this software
  47  *    without specific prior written permission.
  48  *
  49  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  50  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  51  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  52  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  53  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  54  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  55  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  56  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  57  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  58  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  59  * SUCH DAMAGE.
  60  *
  61  *      @(#)null_subr.c 8.7 (Berkeley) 5/14/95
  62  *
  63  *      null_subr.c     8.4 (Berkeley) 1/21/94
  64  */
  65
  66 #include <sys/param.h>
  67 #include <sys/systm.h>
  68 #include <sys/proc.h>
  69 #include <sys/time.h>
  70 #include <sys/types.h>
  71 #include <sys/vnode.h>
  72 #include <sys/mount.h>
  73 #include <sys/namei.h>
  74 #include <sys/malloc.h>
  75 #include <sys/ubc.h>
  76 #include <miscfs/nullfs/null.h>
  77
  78 #define LOG2_SIZEVNODE 7                /* log2(sizeof struct vnode) */
  79 #define NNULLNODECACHE 16
  80
  81 /*
  82  * Null layer cache:
  83  * Each cache entry holds a reference to the lower vnode
  84  * along with a pointer to the alias vnode.  When an
  85  * entry is added the lower vnode is VREF'd.  When the
  86  * alias is removed the lower vnode is vrele'd.
  87  */
  88
  89 #define NULL_NHASH(vp) \
  90         (&null_node_hashtbl[(((u_long)vp)>>LOG2_SIZEVNODE) & null_node_hash])
  91 LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
  92 u_long null_node_hash;
  93
  94 /*
  95  * Initialise cache headers
  96  */
  97 nullfs_init()
  98 {
  99
 100 #ifdef NULLFS_DIAGNOSTIC
 101         printf("nullfs_init\n");                /* printed during system boot */
 102 #endif
 103         null_node_hashtbl = hashinit(NNULLNODECACHE, M_CACHE, &null_node_hash);
 104 }
 105
 106 /*
 107  * Return a VREF'ed alias for lower vnode if already exists, else 0.
 108  */
 109 static struct vnode *
 110 null_node_find(mp, lowervp)
 111         struct mount *mp;
 112         struct vnode *lowervp;
 113 {
 114         struct proc *p = curproc;       /* XXX */
 115         struct null_node_hashhead *hd;
 116         struct null_node *a;
 117         struct vnode *vp;
 118
 119         /*
 120          * Find hash base, and then search the (two-way) linked
 121          * list looking for a null_node structure which is referencing
 122          * the lower vnode.  If found, the increment the null_node
 123          * reference count (but NOT the lower vnode's VREF counter).
 124          */
 125         hd = NULL_NHASH(lowervp);
 126 loop:
 127         for (a = hd->lh_first; a != 0; a = a->null_hash.le_next) {
 128                 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
 129                         vp = NULLTOV(a);
 130                         /*
 131                          * We need vget for the VXLOCK
 132                          * stuff, but we don't want to lock
 133                          * the lower node.
 134                          */
 135                         if (vget(vp, 0, p)) {
 136                                 printf ("null_node_find: vget failed.\n");
 137                                 goto loop;
 138                         };
 139                         return (vp);
 140                 }
 141         }
 142
 143         return NULL;
 144 }
 145
 146
 147 /*
 148  * Make a new null_node node.
 149  * Vp is the alias vnode, lofsvp is the lower vnode.
 150  * Maintain a reference to (lowervp).
 151  */
 152 static int
 153 null_node_alloc(mp, lowervp, vpp)
 154         struct mount *mp;
 155         struct vnode *lowervp;
 156         struct vnode **vpp;
 157 {
 158         struct null_node_hashhead *hd;
 159         struct null_node *xp;
 160         struct vnode *othervp, *vp;
 161         int error;
 162
 163         MALLOC(xp, struct null_node *, sizeof(struct null_node), M_TEMP, M_WAITOK);
 164         if (error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp)) {
 165                 FREE(xp, M_TEMP);
 166                 return (error);
 167         }
 168         vp = *vpp;
 169
 170         vp->v_type = lowervp->v_type;
 171         xp->null_vnode = vp;
 172         vp->v_data = xp;
 173         xp->null_lowervp = lowervp;
 174         /*
 175          * Before we insert our new node onto the hash chains,
 176          * check to see if someone else has beaten us to it.
 177          */
 178         if (othervp = null_node_find(lowervp)) {
 179                 FREE(xp, M_TEMP);
 180                 vp->v_type = VBAD;      /* node is discarded */
 181                 vp->v_usecount = 0;     /* XXX */
 182                 vp->v_data = 0; /* prevent access to freed data */
 183                 *vpp = othervp;
 184                 return 0;
 185         };
 186         if (vp->v_type == VREG)
 187                 ubc_info_init(vp);
 188         VREF(lowervp);   /* Extra VREF will be vrele'd in null_node_create */
 189         hd = NULL_NHASH(lowervp);
 190         LIST_INSERT_HEAD(hd, xp, null_hash);
 191         return 0;
 192 }
 193
 194
 195 /*
 196  * Try to find an existing null_node vnode refering
 197  * to it, otherwise make a new null_node vnode which
 198  * contains a reference to the lower vnode.
 199  */
 200 int
 201 null_node_create(mp, lowervp, newvpp)
 202         struct mount *mp;
 203         struct vnode *lowervp;
 204         struct vnode **newvpp;
 205 {
 206         struct vnode *aliasvp;
 207
 208         if (aliasvp = null_node_find(mp, lowervp)) {
 209                 /*
 210                  * null_node_find has taken another reference
 211                  * to the alias vnode.
 212                  */
 213 #ifdef NULLFS_DIAGNOSTIC
 214                 vprint("null_node_create: exists", NULLTOV(ap));
 215 #endif
 216                 /* VREF(aliasvp); --- done in null_node_find */
 217         } else {
 218                 int error;
 219
 220                 /*
 221                  * Get new vnode.
 222                  */
 223 #ifdef NULLFS_DIAGNOSTIC
 224                 printf("null_node_create: create new alias vnode\n");
 225 #endif
 226
 227                 /*
 228                  * Make new vnode reference the null_node.
 229                  */
 230                 if (error = null_node_alloc(mp, lowervp, &aliasvp))
 231                         return error;
 232
 233                 /*
 234                  * aliasvp is already VREF'd by getnewvnode()
 235                  */
 236         }
 237
 238         vrele(lowervp);
 239
 240 #if DIAGNOSTIC
 241         if (lowervp->v_usecount < 1) {
 242                 /* Should never happen... */
 243                 vprint ("null_node_create: alias ", aliasvp);
 244                 vprint ("null_node_create: lower ", lowervp);
 245                 panic ("null_node_create: lower has 0 usecount.");
 246         };
 247 #endif
 248
 249 #ifdef NULLFS_DIAGNOSTIC
 250         vprint("null_node_create: alias", aliasvp);
 251         vprint("null_node_create: lower", lowervp);
 252 #endif
 253
 254         *newvpp = aliasvp;
 255         return (0);
 256 }
 257 #ifdef NULLFS_DIAGNOSTIC
 258 struct vnode *
 259 null_checkvp(vp, fil, lno)
 260         struct vnode *vp;
 261         char *fil;
 262         int lno;
 263 {
 264         struct null_node *a = VTONULL(vp);
 265 #ifdef notyet
 266         /*
 267          * Can't do this check because vop_reclaim runs
 268          * with a funny vop vector.
 269          */
 270         if (vp->v_op != null_vnodeop_p) {
 271                 printf ("null_checkvp: on non-null-node\n");
 272                 while (null_checkvp_barrier) /*WAIT*/ ;
 273                 panic("null_checkvp");
 274         };
 275 #endif
 276         if (a->null_lowervp == NULL) {
 277                 /* Should never happen */
 278                 int i; u_long *p;
 279                 printf("vp = %x, ZERO ptr\n", vp);
 280                 for (p = (u_long *) a, i = 0; i < 8; i++)
 281                         printf(" %x", p[i]);
 282                 printf("\n");
 283                 /* wait for debugger */
 284                 while (null_checkvp_barrier) /*WAIT*/ ;
 285                 panic("null_checkvp");
 286         }
 287         if (a->null_lowervp->v_usecount < 1) {
 288                 int i; u_long *p;
 289                 printf("vp = %x, unref'ed lowervp\n", vp);
 290                 for (p = (u_long *) a, i = 0; i < 8; i++)
 291                         printf(" %x", p[i]);
 292                 printf("\n");
 293                 /* wait for debugger */
 294                 while (null_checkvp_barrier) /*WAIT*/ ;
 295                 panic ("null with unref'ed lowervp");
 296         };
 297 #ifdef notyet
 298         printf("null %x/%d -> %x/%d [%s, %d]\n",
 299                 NULLTOV(a), NULLTOV(a)->v_usecount,
 300                 a->null_lowervp, a->null_lowervp->v_usecount,
 301                 fil, lno);
 302 #endif
 303         return a->null_lowervp;
 304 }
 305 #endif