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author | rgrimes <rgrimes@FreeBSD.org> | 1994-05-24 10:09:53 +0000 |
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committer | rgrimes <rgrimes@FreeBSD.org> | 1994-05-24 10:09:53 +0000 |
commit | 27464aaa8e6ad0a90df705f3dd8ea4c48ffefd04 (patch) | |
tree | 498662170037963c8b911613f2622e38efea4434 /sys/fs/nullfs/null_subr.c | |
parent | 41dbbe7dea1bb3e50798efb3ea01e967bf27364a (diff) | |
download | FreeBSD-src-27464aaa8e6ad0a90df705f3dd8ea4c48ffefd04.zip FreeBSD-src-27464aaa8e6ad0a90df705f3dd8ea4c48ffefd04.tar.gz |
BSD 4.4 Lite Kernel Sources
Diffstat (limited to 'sys/fs/nullfs/null_subr.c')
-rw-r--r-- | sys/fs/nullfs/null_subr.c | 293 |
1 files changed, 293 insertions, 0 deletions
diff --git a/sys/fs/nullfs/null_subr.c b/sys/fs/nullfs/null_subr.c new file mode 100644 index 0000000..a31723f --- /dev/null +++ b/sys/fs/nullfs/null_subr.c @@ -0,0 +1,293 @@ +/* + * Copyright (c) 1992, 1993 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software donated to Berkeley by + * Jan-Simon Pendry. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * @(#)null_subr.c 8.4 (Berkeley) 1/21/94 + * + * $Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp jsp $ + */ + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/time.h> +#include <sys/types.h> +#include <sys/vnode.h> +#include <sys/mount.h> +#include <sys/namei.h> +#include <sys/malloc.h> +#include <miscfs/nullfs/null.h> + +#define LOG2_SIZEVNODE 7 /* log2(sizeof struct vnode) */ +#define NNULLNODECACHE 16 +#define NULL_NHASH(vp) ((((u_long)vp)>>LOG2_SIZEVNODE) & (NNULLNODECACHE-1)) + +/* + * Null layer cache: + * Each cache entry holds a reference to the lower vnode + * along with a pointer to the alias vnode. When an + * entry is added the lower vnode is VREF'd. When the + * alias is removed the lower vnode is vrele'd. + */ + +/* + * Cache head + */ +struct null_node_cache { + struct null_node *ac_forw; + struct null_node *ac_back; +}; + +static struct null_node_cache null_node_cache[NNULLNODECACHE]; + +/* + * Initialise cache headers + */ +nullfs_init() +{ + struct null_node_cache *ac; +#ifdef NULLFS_DIAGNOSTIC + printf("nullfs_init\n"); /* printed during system boot */ +#endif + + for (ac = null_node_cache; ac < null_node_cache + NNULLNODECACHE; ac++) + ac->ac_forw = ac->ac_back = (struct null_node *) ac; +} + +/* + * Compute hash list for given lower vnode + */ +static struct null_node_cache * +null_node_hash(lowervp) +struct vnode *lowervp; +{ + + return (&null_node_cache[NULL_NHASH(lowervp)]); +} + +/* + * Return a VREF'ed alias for lower vnode if already exists, else 0. + */ +static struct vnode * +null_node_find(mp, lowervp) + struct mount *mp; + struct vnode *lowervp; +{ + struct null_node_cache *hd; + struct null_node *a; + struct vnode *vp; + + /* + * Find hash base, and then search the (two-way) linked + * list looking for a null_node structure which is referencing + * the lower vnode. If found, the increment the null_node + * reference count (but NOT the lower vnode's VREF counter). + */ + hd = null_node_hash(lowervp); +loop: + for (a = hd->ac_forw; a != (struct null_node *) hd; a = a->null_forw) { + if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { + vp = NULLTOV(a); + /* + * We need vget for the VXLOCK + * stuff, but we don't want to lock + * the lower node. + */ + if (vget(vp, 0)) { + printf ("null_node_find: vget failed.\n"); + goto loop; + }; + return (vp); + } + } + + return NULL; +} + + +/* + * Make a new null_node node. + * Vp is the alias vnode, lofsvp is the lower vnode. + * Maintain a reference to (lowervp). + */ +static int +null_node_alloc(mp, lowervp, vpp) + struct mount *mp; + struct vnode *lowervp; + struct vnode **vpp; +{ + struct null_node_cache *hd; + struct null_node *xp; + struct vnode *othervp, *vp; + int error; + + if (error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp)) + return (error); + vp = *vpp; + + MALLOC(xp, struct null_node *, sizeof(struct null_node), M_TEMP, M_WAITOK); + vp->v_type = lowervp->v_type; + xp->null_vnode = vp; + vp->v_data = xp; + xp->null_lowervp = lowervp; + /* + * Before we insert our new node onto the hash chains, + * check to see if someone else has beaten us to it. + * (We could have slept in MALLOC.) + */ + if (othervp = null_node_find(lowervp)) { + FREE(xp, M_TEMP); + vp->v_type = VBAD; /* node is discarded */ + vp->v_usecount = 0; /* XXX */ + *vpp = othervp; + return 0; + }; + VREF(lowervp); /* Extra VREF will be vrele'd in null_node_create */ + hd = null_node_hash(lowervp); + insque(xp, hd); + return 0; +} + + +/* + * Try to find an existing null_node vnode refering + * to it, otherwise make a new null_node vnode which + * contains a reference to the lower vnode. + */ +int +null_node_create(mp, lowervp, newvpp) + struct mount *mp; + struct vnode *lowervp; + struct vnode **newvpp; +{ + struct vnode *aliasvp; + + if (aliasvp = null_node_find(mp, lowervp)) { + /* + * null_node_find has taken another reference + * to the alias vnode. + */ +#ifdef NULLFS_DIAGNOSTIC + vprint("null_node_create: exists", NULLTOV(ap)); +#endif + /* VREF(aliasvp); --- done in null_node_find */ + } else { + int error; + + /* + * Get new vnode. + */ +#ifdef NULLFS_DIAGNOSTIC + printf("null_node_create: create new alias vnode\n"); +#endif + + /* + * Make new vnode reference the null_node. + */ + if (error = null_node_alloc(mp, lowervp, &aliasvp)) + return error; + + /* + * aliasvp is already VREF'd by getnewvnode() + */ + } + + vrele(lowervp); + +#ifdef DIAGNOSTIC + if (lowervp->v_usecount < 1) { + /* Should never happen... */ + vprint ("null_node_create: alias "); + vprint ("null_node_create: lower "); + printf ("null_node_create: lower has 0 usecount.\n"); + panic ("null_node_create: lower has 0 usecount."); + }; +#endif + +#ifdef NULLFS_DIAGNOSTIC + vprint("null_node_create: alias", aliasvp); + vprint("null_node_create: lower", lowervp); +#endif + + *newvpp = aliasvp; + return (0); +} +#ifdef NULLFS_DIAGNOSTIC +struct vnode * +null_checkvp(vp, fil, lno) + struct vnode *vp; + char *fil; + int lno; +{ + struct null_node *a = VTONULL(vp); +#ifdef notyet + /* + * Can't do this check because vop_reclaim runs + * with a funny vop vector. + */ + if (vp->v_op != null_vnodeop_p) { + printf ("null_checkvp: on non-null-node\n"); + while (null_checkvp_barrier) /*WAIT*/ ; + panic("null_checkvp"); + }; +#endif + if (a->null_lowervp == NULL) { + /* Should never happen */ + int i; u_long *p; + printf("vp = %x, ZERO ptr\n", vp); + for (p = (u_long *) a, i = 0; i < 8; i++) + printf(" %x", p[i]); + printf("\n"); + /* wait for debugger */ + while (null_checkvp_barrier) /*WAIT*/ ; + panic("null_checkvp"); + } + if (a->null_lowervp->v_usecount < 1) { + int i; u_long *p; + printf("vp = %x, unref'ed lowervp\n", vp); + for (p = (u_long *) a, i = 0; i < 8; i++) + printf(" %x", p[i]); + printf("\n"); + /* wait for debugger */ + while (null_checkvp_barrier) /*WAIT*/ ; + panic ("null with unref'ed lowervp"); + }; +#ifdef notyet + printf("null %x/%d -> %x/%d [%s, %d]\n", + NULLTOV(a), NULLTOV(a)->v_usecount, + a->null_lowervp, a->null_lowervp->v_usecount, + fil, lno); +#endif + return a->null_lowervp; +} +#endif |