FreeBSD-5.3/sys/fs/nullfs/null_subr.c
/*
* 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.
* 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: src/sys/fs/nullfs/null_subr.c,v 1.43 2004/07/10 21:20:11 marcel Exp $
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <fs/nullfs/null.h>
#define LOG2_SIZEVNODE 8 /* 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;
struct mtx null_hashmtx;
static MALLOC_DEFINE(M_NULLFSHASH, "NULLFS hash", "NULLFS hash table");
MALLOC_DEFINE(M_NULLFSNODE, "NULLFS node", "NULLFS vnode private part");
static struct vnode * null_hashget(struct mount *, struct vnode *);
static struct vnode * null_hashins(struct mount *, struct null_node *);
/*
* Initialise cache headers
*/
int
nullfs_init(vfsp)
struct vfsconf *vfsp;
{
NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */
null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash);
mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF);
return (0);
}
int
nullfs_uninit(vfsp)
struct vfsconf *vfsp;
{
mtx_destroy(&null_hashmtx);
free(null_node_hashtbl, M_NULLFSHASH);
return (0);
}
/*
* Return a VREF'ed alias for lower vnode if already exists, else 0.
* Lower vnode should be locked on entry and will be left locked on exit.
*/
static struct vnode *
null_hashget(mp, lowervp)
struct mount *mp;
struct vnode *lowervp;
{
struct thread *td = curthread; /* 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:
mtx_lock(&null_hashmtx);
LIST_FOREACH(a, hd, null_hash) {
if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
vp = NULLTOV(a);
mtx_lock(&vp->v_interlock);
/*
* Don't block if nullfs vnode is being recycled.
* We already hold a lock on the lower vnode, thus
* waiting might deadlock against the thread
* recycling the nullfs vnode or another thread
* in vrele() waiting for the vnode lock.
*/
if ((vp->v_iflag & VI_XLOCK) != 0) {
VI_UNLOCK(vp);
continue;
}
mtx_unlock(&null_hashmtx);
/*
* We need vget for the VXLOCK
* stuff, but we don't want to lock
* the lower node.
*/
if (vget(vp, LK_EXCLUSIVE | LK_THISLAYER | LK_INTERLOCK, td))
goto loop;
return (vp);
}
}
mtx_unlock(&null_hashmtx);
return (NULLVP);
}
/*
* Act like null_hashget, but add passed null_node to hash if no existing
* node found.
*/
static struct vnode *
null_hashins(mp, xp)
struct mount *mp;
struct null_node *xp;
{
struct thread *td = curthread; /* XXX */
struct null_node_hashhead *hd;
struct null_node *oxp;
struct vnode *ovp;
hd = NULL_NHASH(xp->null_lowervp);
loop:
mtx_lock(&null_hashmtx);
LIST_FOREACH(oxp, hd, null_hash) {
if (oxp->null_lowervp == xp->null_lowervp &&
NULLTOV(oxp)->v_mount == mp) {
ovp = NULLTOV(oxp);
mtx_lock(&ovp->v_interlock);
/*
* Don't block if nullfs vnode is being recycled.
* We already hold a lock on the lower vnode, thus
* waiting might deadlock against the thread
* recycling the nullfs vnode or another thread
* in vrele() waiting for the vnode lock.
*/
if ((ovp->v_iflag & VI_XLOCK) != 0) {
VI_UNLOCK(ovp);
continue;
}
mtx_unlock(&null_hashmtx);
if (vget(ovp, LK_EXCLUSIVE | LK_THISLAYER | LK_INTERLOCK, td))
goto loop;
return (ovp);
}
}
LIST_INSERT_HEAD(hd, xp, null_hash);
mtx_unlock(&null_hashmtx);
return (NULLVP);
}
/*
* Make a new or get existing nullfs node.
* Vp is the alias vnode, lowervp is the lower vnode.
*
* The lowervp assumed to be locked and having "spare" reference. This routine
* vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
* the caller's "spare" reference to created nullfs vnode.
*/
int
null_nodeget(mp, lowervp, vpp)
struct mount *mp;
struct vnode *lowervp;
struct vnode **vpp;
{
struct thread *td = curthread; /* XXX */
struct null_node *xp;
struct vnode *vp;
int error;
/* Lookup the hash firstly */
*vpp = null_hashget(mp, lowervp);
if (*vpp != NULL) {
vrele(lowervp);
return (0);
}
/*
* We do not serialize vnode creation, instead we will check for
* duplicates later, when adding new vnode to hash.
*
* Note that duplicate can only appear in hash if the lowervp is
* locked LK_SHARED.
*/
/*
* 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_NULLFSNODE, M_WAITOK);
error = getnewvnode("null", mp, null_vnodeop_p, &vp);
if (error) {
FREE(xp, M_NULLFSNODE);
return (error);
}
xp->null_vnode = vp;
xp->null_lowervp = lowervp;
xp->null_pending_locks = 0;
xp->null_drain_wakeup = 0;
vp->v_type = lowervp->v_type;
vp->v_data = xp;
/*
* From NetBSD:
* Now lock the new node. We rely on the fact that we were passed
* a locked vnode. If the lower node is exporting a struct lock
* (v_vnlock != NULL) then we just set the upper v_vnlock to the
* lower one, and both are now locked. If the lower node is exporting
* NULL, then we copy that up and manually lock the new vnode.
*/
vp->v_vnlock = lowervp->v_vnlock;
error = VOP_LOCK(vp, LK_EXCLUSIVE | LK_THISLAYER, td);
if (error)
panic("null_nodeget: can't lock new vnode\n");
/*
* Atomically insert our new node into the hash or vget existing
* if someone else has beaten us to it.
*/
*vpp = null_hashins(mp, xp);
if (*vpp != NULL) {
vrele(lowervp);
VOP_UNLOCK(vp, LK_THISLAYER, td);
vp->v_vnlock = NULL;
xp->null_lowervp = NULL;
vrele(vp);
return (0);
}
/*
* XXX We take extra vref just to workaround UFS's XXX:
* UFS can vrele() vnode in VOP_CLOSE() in some cases. Luckily, this
* can only happen if v_usecount == 1. To workaround, we just don't
* let v_usecount be 1, it will be 2 or more.
*/
VREF(lowervp);
*vpp = vp;
return (0);
}
/*
* Remove node from hash.
*/
void
null_hashrem(xp)
struct null_node *xp;
{
mtx_lock(&null_hashmtx);
LIST_REMOVE(xp, null_hash);
mtx_unlock(&null_hashmtx);
}
#ifdef DIAGNOSTIC
#ifdef KDB
#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 (vrefcnt(a->null_lowervp) < 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), vrefcnt(NULLTOV(a)),
a->null_lowervp, vrefcnt(a->null_lowervp),
fil, lno);
#endif
return a->null_lowervp;
}
#endif