bsd/miscfs/nullfs/null_subr.c

   1 /*
   2  * Copyright (c) 2006 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_OSREFERENCE_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
  10  * License may not be used to create, or enable the creation or
  11  * redistribution of, unlawful or unlicensed copies of an Apple operating
  12  * system, or to circumvent, violate, or enable the circumvention or
  13  * violation of, any terms of an Apple operating system software license
  14  * agreement.
  15  *
  16  * Please obtain a copy of the License at
  17  * http://www.opensource.apple.com/apsl/ and read it before using this
  18  * file.
  19  *
  20  * The Original Code and all software distributed under the License are
  21  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  22  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  23  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  25  * Please see the License for the specific language governing rights and
  26  * limitations under the License.
  27  *
  28  * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
  29  */
  30 /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
  31 /*
  32  * Copyright (c) 1992, 1993
  33  *      The Regents of the University of California.  All rights reserved.
  34  *
  35  * This code is derived from software donated to Berkeley by
  36  * Jan-Simon Pendry.
  37  *
  38  * Redistribution and use in source and binary forms, with or without
  39  * modification, are permitted provided that the following conditions
  40  * are met:
  41  * 1. Redistributions of source code must retain the above copyright
  42  *    notice, this list of conditions and the following disclaimer.
  43  * 2. Redistributions in binary form must reproduce the above copyright
  44  *    notice, this list of conditions and the following disclaimer in the
  45  *    documentation and/or other materials provided with the distribution.
  46  * 3. All advertising materials mentioning features or use of this software
  47  *    must display the following acknowledgement:
  48  *      This product includes software developed by the University of
  49  *      California, Berkeley and its contributors.
  50  * 4. Neither the name of the University nor the names of its contributors
  51  *    may be used to endorse or promote products derived from this software
  52  *    without specific prior written permission.
  53  *
  54  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  55  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  56  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  57  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  58  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  59  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  60  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  61  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  62  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  63  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  64  * SUCH DAMAGE.
  65  *
  66  *      @(#)null_subr.c 8.7 (Berkeley) 5/14/95
  67  *
  68  *      null_subr.c     8.4 (Berkeley) 1/21/94
  69  */
  70
  71 #include <sys/param.h>
  72 #include <sys/systm.h>
  73 #include <sys/proc.h>
  74 #include <sys/time.h>
  75 #include <sys/types.h>
  76 #include <sys/vnode.h>
  77 #include <sys/mount_internal.h>
  78 #include <sys/namei.h>
  79 #include <sys/malloc.h>
  80 #include <sys/ubc.h>
  81 #include <miscfs/nullfs/null.h>
  82
  83 #define LOG2_SIZEVNODE 7                /* log2(sizeof struct vnode) */
  84 #define NNULLNODECACHE 16
  85
  86 /*
  87  * Null layer cache:
  88  * Each cache entry holds a reference to the lower vnode
  89  * along with a pointer to the alias vnode.  When an
  90  * entry is added the lower vnode is vnode_get'd.  When the
  91  * alias is removed the lower vnode is vnode_put'd.
  92  */
  93
  94 #define NULL_NHASH(vp) \
  95         (&null_node_hashtbl[(((u_long)vp)>>LOG2_SIZEVNODE) & null_node_hash])
  96 LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
  97 u_long null_node_hash;
  98
  99 /*
 100  * Initialise cache headers
 101  */
 102 nullfs_init()
 103 {
 104
 105 #ifdef NULLFS_DIAGNOSTIC
 106         printf("nullfs_init\n");                /* printed during system boot */
 107 #endif
 108         null_node_hashtbl = hashinit(NNULLNODECACHE, M_CACHE, &null_node_hash);
 109 }
 110
 111 /*
 112  * Return a vnode_get'ed alias for lower vnode if already exists, else 0.
 113  */
 114 static struct vnode *
 115 null_node_find(mp, lowervp)
 116         struct mount *mp;
 117         struct vnode *lowervp;
 118 {
 119         struct proc *p = curproc;       /* XXX */
 120         struct null_node_hashhead *hd;
 121         struct null_node *a;
 122         struct vnode *vp;
 123
 124         /*
 125          * Find hash base, and then search the (two-way) linked
 126          * list looking for a null_node structure which is referencing
 127          * the lower vnode.  If found, the increment the null_node
 128          * reference count (but NOT the lower vnode's vnode_get counter).
 129          */
 130         hd = NULL_NHASH(lowervp);
 131 loop:
 132         for (a = hd->lh_first; a != 0; a = a->null_hash.le_next) {
 133                 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
 134                         vp = NULLTOV(a);
 135
 136                         if (vnode_get(vp)) {
 137                                 printf ("null_node_find: vget failed.\n");
 138                                 goto loop;
 139                         };
 140                         return (vp);
 141                 }
 142         }
 143
 144         return NULL;
 145 }
 146
 147
 148 /*
 149  * Make a new null_node node.
 150  * Vp is the alias vnode, lofsvp is the lower vnode.
 151  * Maintain a reference to (lowervp).
 152  */
 153 static int
 154 null_node_alloc(mp, lowervp, vpp)
 155         struct mount *mp;
 156         struct vnode *lowervp;
 157         struct vnode **vpp;
 158 {
 159         struct null_node_hashhead *hd;
 160         struct null_node *xp;
 161         struct vnode *othervp, *vp;
 162         int error;
 163
 164         MALLOC(xp, struct null_node *, sizeof(struct null_node), M_TEMP, M_WAITOK);
 165         if (error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp)) {
 166                 FREE(xp, M_TEMP);
 167                 return (error);
 168         }
 169         vp = *vpp;
 170
 171         vp->v_type = lowervp->v_type;
 172         xp->null_vnode = vp;
 173         vp->v_data = xp;
 174         xp->null_lowervp = lowervp;
 175         /*
 176          * Before we insert our new node onto the hash chains,
 177          * check to see if someone else has beaten us to it.
 178          */
 179         if (othervp = null_node_find(lowervp)) {
 180                 FREE(xp, M_TEMP);
 181                 vp->v_type = VBAD;      /* node is discarded */
 182                 vp->v_usecount = 0;     /* XXX */
 183                 vp->v_data = 0; /* prevent access to freed data */
 184                 *vpp = othervp;
 185                 return 0;
 186         };
 187         if (vp->v_type == VREG)
 188                 ubc_info_init(vp);
 189         vnode_get(lowervp);   /* Extra vnode_get will be vnode_put'd in null_node_create */
 190         hd = NULL_NHASH(lowervp);
 191         LIST_INSERT_HEAD(hd, xp, null_hash);
 192         return 0;
 193 }
 194
 195
 196 /*
 197  * Try to find an existing null_node vnode refering
 198  * to it, otherwise make a new null_node vnode which
 199  * contains a reference to the lower vnode.
 200  */
 201 int
 202 null_node_create(mp, lowervp, newvpp)
 203         struct mount *mp;
 204         struct vnode *lowervp;
 205         struct vnode **newvpp;
 206 {
 207         struct vnode *aliasvp;
 208
 209         if (aliasvp = null_node_find(mp, lowervp)) {
 210                 /*
 211                  * null_node_find has taken another reference
 212                  * to the alias vnode.
 213                  */
 214 #ifdef NULLFS_DIAGNOSTIC
 215                 vprint("null_node_create: exists", NULLTOV(ap));
 216 #endif
 217                 /* vnode_get(aliasvp); --- done in null_node_find */
 218         } else {
 219                 int error;
 220
 221                 /*
 222                  * Get new vnode.
 223                  */
 224 #ifdef NULLFS_DIAGNOSTIC
 225                 printf("null_node_create: create new alias vnode\n");
 226 #endif
 227
 228                 /*
 229                  * Make new vnode reference the null_node.
 230                  */
 231                 if (error = null_node_alloc(mp, lowervp, &aliasvp))
 232                         return error;
 233
 234                 /*
 235                  * aliasvp is already vnode_get'd by getnewvnode()
 236                  */
 237         }
 238
 239         vnode_put(lowervp);
 240
 241 #if DIAGNOSTIC
 242         if (lowervp->v_usecount < 1) {
 243                 /* Should never happen... */
 244                 vprint ("null_node_create: alias ", aliasvp);
 245                 vprint ("null_node_create: lower ", lowervp);
 246                 panic ("null_node_create: lower has 0 usecount.");
 247         };
 248 #endif
 249
 250 #ifdef NULLFS_DIAGNOSTIC
 251         vprint("null_node_create: alias", aliasvp);
 252         vprint("null_node_create: lower", lowervp);
 253 #endif
 254
 255         *newvpp = aliasvp;
 256         return (0);
 257 }
 258 #ifdef NULLFS_DIAGNOSTIC
 259 struct vnode *
 260 null_checkvp(vp, fil, lno)
 261         struct vnode *vp;
 262         char *fil;
 263         int lno;
 264 {
 265         struct null_node *a = VTONULL(vp);
 266 #ifdef notyet
 267         /*
 268          * Can't do this check because vnop_reclaim runs
 269          * with a funny vop vector.
 270          */
 271         if (vp->v_op != null_vnodeop_p) {
 272                 printf ("null_checkvp: on non-null-node\n");
 273                 while (null_checkvp_barrier) /*WAIT*/ ;
 274                 panic("null_checkvp");
 275         };
 276 #endif
 277         if (a->null_lowervp == NULL) {
 278                 /* Should never happen */
 279                 int i; u_long *p;
 280                 printf("vp = %x, ZERO ptr\n", vp);
 281                 for (p = (u_long *) a, i = 0; i < 8; i++)
 282                         printf(" %x", p[i]);
 283                 printf("\n");
 284                 /* wait for debugger */
 285                 while (null_checkvp_barrier) /*WAIT*/ ;
 286                 panic("null_checkvp");
 287         }
 288         if (a->null_lowervp->v_usecount < 1) {
 289                 int i; u_long *p;
 290                 printf("vp = %x, unref'ed lowervp\n", vp);
 291                 for (p = (u_long *) a, i = 0; i < 8; i++)
 292                         printf(" %x", p[i]);
 293                 printf("\n");
 294                 /* wait for debugger */
 295                 while (null_checkvp_barrier) /*WAIT*/ ;
 296                 panic ("null with unref'ed lowervp");
 297         };
 298 #ifdef notyet
 299         printf("null %x/%d -> %x/%d [%s, %d]\n",
 300                 NULLTOV(a), NULLTOV(a)->v_usecount,
 301                 a->null_lowervp, a->null_lowervp->v_usecount,
 302                 fil, lno);
 303 #endif
 304         return a->null_lowervp;
 305 }
 306 #endif