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Annotation of kernel/bsd/miscfs/nullfs/null_subr.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            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 <miscfs/nullfs/null.h>
        !            76: 
        !            77: #define LOG2_SIZEVNODE 7               /* log2(sizeof struct vnode) */
        !            78: #define        NNULLNODECACHE 16
        !            79: 
        !            80: /*
        !            81:  * Null layer cache:
        !            82:  * Each cache entry holds a reference to the lower vnode
        !            83:  * along with a pointer to the alias vnode.  When an
        !            84:  * entry is added the lower vnode is VREF'd.  When the
        !            85:  * alias is removed the lower vnode is vrele'd.
        !            86:  */
        !            87: 
        !            88: #define        NULL_NHASH(vp) \
        !            89:        (&null_node_hashtbl[(((u_long)vp)>>LOG2_SIZEVNODE) & null_node_hash])
        !            90: LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
        !            91: u_long null_node_hash;
        !            92: 
        !            93: /*
        !            94:  * Initialise cache headers
        !            95:  */
        !            96: nullfs_init()
        !            97: {
        !            98: 
        !            99: #ifdef NULLFS_DIAGNOSTIC
        !           100:        printf("nullfs_init\n");                /* printed during system boot */
        !           101: #endif
        !           102:        null_node_hashtbl = hashinit(NNULLNODECACHE, M_CACHE, &null_node_hash);
        !           103: }
        !           104: 
        !           105: /*
        !           106:  * Return a VREF'ed alias for lower vnode if already exists, else 0.
        !           107:  */
        !           108: static struct vnode *
        !           109: null_node_find(mp, lowervp)
        !           110:        struct mount *mp;
        !           111:        struct vnode *lowervp;
        !           112: {
        !           113:        struct proc *p = curproc;       /* XXX */
        !           114:        struct null_node_hashhead *hd;
        !           115:        struct null_node *a;
        !           116:        struct vnode *vp;
        !           117: 
        !           118:        /*
        !           119:         * Find hash base, and then search the (two-way) linked
        !           120:         * list looking for a null_node structure which is referencing
        !           121:         * the lower vnode.  If found, the increment the null_node
        !           122:         * reference count (but NOT the lower vnode's VREF counter).
        !           123:         */
        !           124:        hd = NULL_NHASH(lowervp);
        !           125: loop:
        !           126:        for (a = hd->lh_first; a != 0; a = a->null_hash.le_next) {
        !           127:                if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
        !           128:                        vp = NULLTOV(a);
        !           129:                        /*
        !           130:                         * We need vget for the VXLOCK
        !           131:                         * stuff, but we don't want to lock
        !           132:                         * the lower node.
        !           133:                         */
        !           134:                        if (vget(vp, 0, p)) {
        !           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:        if (error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp))
        !           163:                return (error);
        !           164:        vp = *vpp;
        !           165: 
        !           166:        MALLOC(xp, struct null_node *, sizeof(struct null_node), M_TEMP, M_WAITOK);
        !           167:        vp->v_type = lowervp->v_type;
        !           168:        xp->null_vnode = vp;
        !           169:        vp->v_data = xp;
        !           170:        xp->null_lowervp = lowervp;
        !           171:        /*
        !           172:         * Before we insert our new node onto the hash chains,
        !           173:         * check to see if someone else has beaten us to it.
        !           174:         * (We could have slept in MALLOC.)
        !           175:         */
        !           176:        if (othervp = null_node_find(lowervp)) {
        !           177:                FREE(xp, M_TEMP);
        !           178:                vp->v_type = VBAD;      /* node is discarded */
        !           179:                vp->v_usecount = 0;     /* XXX */
        !           180:                *vpp = othervp;
        !           181:                return 0;
        !           182:        };
        !           183:        VREF(lowervp);   /* Extra VREF will be vrele'd in null_node_create */
        !           184:        hd = NULL_NHASH(lowervp);
        !           185:        LIST_INSERT_HEAD(hd, xp, null_hash);
        !           186:        return 0;
        !           187: }
        !           188: 
        !           189: 
        !           190: /*
        !           191:  * Try to find an existing null_node vnode refering
        !           192:  * to it, otherwise make a new null_node vnode which
        !           193:  * contains a reference to the lower vnode.
        !           194:  */
        !           195: int
        !           196: null_node_create(mp, lowervp, newvpp)
        !           197:        struct mount *mp;
        !           198:        struct vnode *lowervp;
        !           199:        struct vnode **newvpp;
        !           200: {
        !           201:        struct vnode *aliasvp;
        !           202: 
        !           203:        if (aliasvp = null_node_find(mp, lowervp)) {
        !           204:                /*
        !           205:                 * null_node_find has taken another reference
        !           206:                 * to the alias vnode.
        !           207:                 */
        !           208: #ifdef NULLFS_DIAGNOSTIC
        !           209:                vprint("null_node_create: exists", NULLTOV(ap));
        !           210: #endif
        !           211:                /* VREF(aliasvp); --- done in null_node_find */
        !           212:        } else {
        !           213:                int error;
        !           214: 
        !           215:                /*
        !           216:                 * Get new vnode.
        !           217:                 */
        !           218: #ifdef NULLFS_DIAGNOSTIC
        !           219:                printf("null_node_create: create new alias vnode\n");
        !           220: #endif
        !           221: 
        !           222:                /*
        !           223:                 * Make new vnode reference the null_node.
        !           224:                 */
        !           225:                if (error = null_node_alloc(mp, lowervp, &aliasvp))
        !           226:                        return error;
        !           227: 
        !           228:                /*
        !           229:                 * aliasvp is already VREF'd by getnewvnode()
        !           230:                 */
        !           231:        }
        !           232: 
        !           233:        vrele(lowervp);
        !           234: 
        !           235: #if DIAGNOSTIC
        !           236:        if (lowervp->v_usecount < 1) {
        !           237:                /* Should never happen... */
        !           238:                vprint ("null_node_create: alias ", aliasvp);
        !           239:                vprint ("null_node_create: lower ", lowervp);
        !           240:                panic ("null_node_create: lower has 0 usecount.");
        !           241:        };
        !           242: #endif
        !           243: 
        !           244: #ifdef NULLFS_DIAGNOSTIC
        !           245:        vprint("null_node_create: alias", aliasvp);
        !           246:        vprint("null_node_create: lower", lowervp);
        !           247: #endif
        !           248: 
        !           249:        *newvpp = aliasvp;
        !           250:        return (0);
        !           251: }
        !           252: #ifdef NULLFS_DIAGNOSTIC
        !           253: struct vnode *
        !           254: null_checkvp(vp, fil, lno)
        !           255:        struct vnode *vp;
        !           256:        char *fil;
        !           257:        int lno;
        !           258: {
        !           259:        struct null_node *a = VTONULL(vp);
        !           260: #ifdef notyet
        !           261:        /*
        !           262:         * Can't do this check because vop_reclaim runs
        !           263:         * with a funny vop vector.
        !           264:         */
        !           265:        if (vp->v_op != null_vnodeop_p) {
        !           266:                printf ("null_checkvp: on non-null-node\n");
        !           267:                while (null_checkvp_barrier) /*WAIT*/ ;
        !           268:                panic("null_checkvp");
        !           269:        };
        !           270: #endif
        !           271:        if (a->null_lowervp == NULL) {
        !           272:                /* Should never happen */
        !           273:                int i; u_long *p;
        !           274:                printf("vp = %x, ZERO ptr\n", vp);
        !           275:                for (p = (u_long *) a, i = 0; i < 8; i++)
        !           276:                        printf(" %x", p[i]);
        !           277:                printf("\n");
        !           278:                /* wait for debugger */
        !           279:                while (null_checkvp_barrier) /*WAIT*/ ;
        !           280:                panic("null_checkvp");
        !           281:        }
        !           282:        if (a->null_lowervp->v_usecount < 1) {
        !           283:                int i; u_long *p;
        !           284:                printf("vp = %x, unref'ed lowervp\n", vp);
        !           285:                for (p = (u_long *) a, i = 0; i < 8; i++)
        !           286:                        printf(" %x", p[i]);
        !           287:                printf("\n");
        !           288:                /* wait for debugger */
        !           289:                while (null_checkvp_barrier) /*WAIT*/ ;
        !           290:                panic ("null with unref'ed lowervp");
        !           291:        };
        !           292: #ifdef notyet
        !           293:        printf("null %x/%d -> %x/%d [%s, %d]\n",
        !           294:                NULLTOV(a), NULLTOV(a)->v_usecount,
        !           295:                a->null_lowervp, a->null_lowervp->v_usecount,
        !           296:                fil, lno);
        !           297: #endif
        !           298:        return a->null_lowervp;
        !           299: }
        !           300: #endif

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