bsd/miscfs/nullfs/null_subr.c

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