NetBSD/sys/miscfs/nullfs/null_subr.c

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1996-10-13 06:21:25 +04:00
/* $NetBSD: null_subr.c,v 1.8 1996/10/13 02:21:33 christos Exp $ */
/*
* 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.
*
* from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp
* @(#)null_subr.c 8.4 (Berkeley) 1/21/94
*/
#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/specfs/specdev.h>
#include <miscfs/nullfs/null.h>
#define LOG2_SIZEVNODE 7 /* log2(sizeof struct vnode) */
#define NNULLNODECACHE 16
/*
* 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.
*/
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#define NULL_NHASH(vp) \
(&null_node_hashtbl[(((u_long)vp)>>LOG2_SIZEVNODE) & null_node_hash])
LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
u_long null_node_hash;
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void nullfs_init __P((void));
static struct vnode *
null_node_find __P((struct mount *, struct vnode *));
static int
null_node_alloc __P((struct mount *, struct vnode *, struct vnode **));
/*
* Initialise cache headers
*/
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void
nullfs_init()
{
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#ifdef NULLFS_DIAGNOSTIC
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printf("nullfs_init\n"); /* printed during system boot */
#endif
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null_node_hashtbl = hashinit(NNULLNODECACHE, M_CACHE, &null_node_hash);
}
/*
* 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;
{
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struct null_node_hashhead *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).
*/
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hd = NULL_NHASH(lowervp);
loop:
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for (a = hd->lh_first; a != 0; a = a->null_hash.le_next) {
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)) {
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printf ("null_node_find: vget failed.\n");
goto loop;
};
return (vp);
}
}
return NULL;
}
/*
* Make a new null_node node.
* Vp is the alias vnode, lowervp 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;
{
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struct null_node_hashhead *hd;
struct null_node *xp;
struct vnode *vp, *nvp;
int error;
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extern int (**dead_vnodeop_p) __P((void *));
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if ((error = getnewvnode(VT_NULL, mp, null_vnodeop_p, &vp)) != 0)
return (error);
vp->v_type = lowervp->v_type;
MALLOC(xp, struct null_node *, sizeof(struct null_node), M_TEMP,
M_WAITOK);
if (vp->v_type == VBLK || vp->v_type == VCHR) {
MALLOC(vp->v_specinfo, struct specinfo *,
sizeof(struct specinfo), M_VNODE, M_WAITOK);
vp->v_rdev = lowervp->v_rdev;
}
vp->v_data = xp;
xp->null_vnode = vp;
xp->null_lowervp = lowervp;
xp->null_flags = 0;
#ifdef DIAGNOSTIC
xp->null_pid = -1;
xp->null_lockpc = xp->null_lockpc2 = 0;
#endif
/*
* 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.)
*/
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if ((nvp = null_node_find(mp, lowervp)) != NULL) {
*vpp = nvp;
/* free the substructures we've allocated. */
FREE(xp, M_TEMP);
if (vp->v_type == VBLK || vp->v_type == VCHR)
FREE(vp->v_specinfo, M_VNODE);
vp->v_type = VBAD; /* node is discarded */
vp->v_op = dead_vnodeop_p; /* so ops will still work */
vrele(vp); /* get rid of it. */
return (0);
}
/*
* XXX if it's a device node, it needs to be checkalias()ed.
* however, for locking reasons, that's just not possible.
* so we have to do most of the dirty work inline. Note that
* this is a limited case; we know that there's going to be
* an alias, and we know that that alias will be a "real"
* device node, i.e. not tagged VT_NON.
*/
if (vp->v_type == VBLK || vp->v_type == VCHR) {
struct vnode *cvp, **cvpp;
cvpp = &speclisth[SPECHASH(vp->v_rdev)];
loop:
for (cvp = *cvpp; cvp; cvp = cvp->v_specnext) {
if (vp->v_rdev != cvp->v_rdev ||
vp->v_type != cvp->v_type)
continue;
/*
* Alias, but not in use, so flush it out.
*/
if (cvp->v_usecount == 0) {
vgone(cvp);
goto loop;
}
if (vget(cvp, 0)) /* can't lock; will die! */
goto loop;
break;
}
vp->v_hashchain = cvpp;
vp->v_specnext = *cvpp;
vp->v_specflags = 0;
*cvpp = vp;
#ifdef DIAGNOSTIC
if (cvp == NULLVP)
panic("null_node_alloc: no alias for device");
#endif
vp->v_flag |= VALIASED;
cvp->v_flag |= VALIASED;
vrele(cvp);
}
/* XXX end of transmogrified checkalias() */
*vpp = vp;
VREF(lowervp); /* Extra VREF will be vrele'd in null_node_create */
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hd = NULL_NHASH(lowervp);
LIST_INSERT_HEAD(hd, xp, null_hash);
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.
*
* >>> we assume that the lower node is already locked upon entry, so we mark
* the upper node as locked too (if caller requests it). <<<
*/
int
null_node_create(mp, lowervp, newvpp, takelock)
struct mount *mp;
struct vnode *lowervp;
struct vnode **newvpp;
int takelock;
{
struct vnode *aliasvp;
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if ((aliasvp = null_node_find(mp, lowervp)) != NULL) {
/*
* null_node_find has taken another reference
* to the alias vnode.
*/
#ifdef NULLFS_DIAGNOSTIC
vprint("null_node_create: exists", aliasvp);
#endif
/* VREF(aliasvp); --- done in null_node_find */
} else {
int error;
/*
* Get new vnode.
*/
#ifdef NULLFS_DIAGNOSTIC
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printf("null_node_create: create new alias vnode\n");
#endif
/*
* Make new vnode reference the null_node.
*/
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if ((error = null_node_alloc(mp, lowervp, &aliasvp)) != 0)
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", aliasvp);
panic("null_node_create: lower has 0 usecount.");
};
#endif
#ifdef NULLFS_DIAGNOSTIC
vprint("null_node_create: alias", aliasvp);
#endif
/* lower node was locked: mark it as locked and take
upper layer lock */
VTONULL(aliasvp)->null_flags |= NULL_LLOCK;
if (takelock)
VOP_LOCK(aliasvp);
*newvpp = aliasvp;
return (0);
}
#ifdef notyet
#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) {
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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;
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printf("vp = %x, ZERO ptr\n", vp);
for (p = (u_long *) a, i = 0; i < 8; i++)
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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;
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printf("vp = %x, unref'ed lowervp\n", vp);
for (p = (u_long *) a, i = 0; i < 8; i++)
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printf(" %x", p[i]);
printf("\n");
/* wait for debugger */
while (null_checkvp_barrier) /*WAIT*/ ;
panic ("null with unref'ed lowervp");
};
#ifdef notyet
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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
#endif