/*
* 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 8.7 (Berkeley) 5/14/95
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/malloc.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.
*/
#define NULL_NHASH(vp) \
(&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
static u_long null_node_hash;
static int null_node_alloc __P((struct mount *mp, struct vnode *lowervp,
struct vnode **vpp));
static struct vnode *
null_node_find __P((struct mount *mp, struct vnode *lowervp));
/*
* Initialise cache headers
*/
int
nullfs_init(vfsp)
struct vfsconf *vfsp;
{
#ifdef DEBUG
printf("nullfs_init\n"); /* printed during system boot */
#endif
null_node_hashtbl = hashinit(NNULLNODECACHE, M_CACHE, &null_node_hash);
return (0);
}
/*
* 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 proc *p = curproc; /* XXX */
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).
*/
hd = NULL_NHASH(lowervp);
loop:
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, p)) {
printf ("null_node_find: vget failed.\n");
goto loop;
};
return (vp);
}
}
return NULLVP;
}
/*
* 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_hashhead *hd;
struct null_node *xp;
struct vnode *othervp, *vp;
int error;
/*
* Do the MALLOC before the getnewvnode since doing so afterward
* might cause a bogus v_data pointer to get dereferenced
* elsewhere if MALLOC should block.
*/
MALLOC(xp, struct null_node *, sizeof(struct null_node), M_TEMP, M_WAITOK);
error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp);
if (error) {
FREE(xp, M_TEMP);
return (error);
}
vp = *vpp;
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.)
*/
othervp = null_node_find(mp, lowervp);
if (othervp) {
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_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.
*/
int
null_node_create(mp, lowervp, newvpp)
struct mount *mp;
struct vnode *lowervp;
struct vnode **newvpp;
{
struct vnode *aliasvp;
aliasvp = null_node_find(mp, lowervp);
if (aliasvp) {
/*
* null_node_find has taken another reference
* to the alias vnode.
*/
#ifdef DEBUG
vprint("null_node_create: exists", aliasvp);
#endif
/* VREF(aliasvp); --- done in null_node_find */
} else {
int error;
/*
* Get new vnode.
*/
#ifdef DEBUG
printf("null_node_create: create new alias vnode\n");
#endif
/*
* Make new vnode reference the null_node.
*/
error = null_node_alloc(mp, lowervp, &aliasvp);
if (error)
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);
vprint ("null_node_create: lower ", lowervp);
panic ("null_node_create: lower has 0 usecount.");
};
#endif
#ifdef DEBUG
vprint("null_node_create: alias", aliasvp);
vprint("null_node_create: lower", lowervp);
#endif
*newvpp = aliasvp;
return (0);
}
#ifdef DIAGNOSTIC
#include "opt_ddb.h"
#ifdef DDB
#define null_checkvp_barrier 1
#else
#define null_checkvp_barrier 0
#endif
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 == NULLVP) {
/* Should never happen */
int i; u_long *p;
printf("vp = %p, ZERO ptr\n", (void *)vp);
for (p = (u_long *) a, i = 0; i < 8; i++)
printf(" %lx", 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 = %p, unref'ed lowervp\n", (void *)vp);
for (p = (u_long *) a, i = 0; i < 8; i++)
printf(" %lx", 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
