NetBSD-5.0.2/sys/miscfs/genfs/layer_subr.c
/* $NetBSD: layer_subr.c,v 1.25 2008/01/24 17:32:55 ad Exp $ */
/*
* Copyright (c) 1999 National Aeronautics & Space Administration
* All rights reserved.
*
* This software was written by William Studenmund of the
* Numerical Aerospace Simulation Facility, NASA Ames Research Center.
*
* 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. Neither the name of the National Aeronautics & Space Administration
* 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 NATIONAL AERONAUTICS & SPACE ADMINISTRATION
* ``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 ADMINISTRATION OR CONTRIB-
* UTORS 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.
*/
/*
* 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. 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 8.7 (Berkeley) 5/14/95
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.25 2008/01/24 17:32:55 ad Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/kmem.h>
#include <sys/malloc.h>
#include <miscfs/specfs/specdev.h>
#include <miscfs/genfs/layer.h>
#include <miscfs/genfs/layer_extern.h>
#define NLAYERNODECACHE 16
#ifdef LAYERFS_DIAGNOSTIC
int layerfs_debug = 1;
#endif
/*
* 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.
*/
/*
* Initialise cache headers
*/
void
layerfs_init()
{
#ifdef LAYERFS_DIAGNOSTIC
if (layerfs_debug)
printf("layerfs_init\n"); /* printed during system boot */
#endif
}
/*
* Free global resources of layerfs.
*/
void
layerfs_done()
{
#ifdef LAYERFS_DIAGNOSTIC
if (layerfs_debug)
printf("layerfs_done\n"); /* printed on layerfs detach */
#endif
}
/*
* Return a locked, VREF'ed alias for lower vnode if already exists, else NULL.
* The layermp's hashlock must be held on entry.
* It will be held upon return iff we return NULL.
*/
struct vnode *
layer_node_find(mp, lowervp)
struct mount *mp;
struct vnode *lowervp;
{
struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
struct layer_node_hashhead *hd;
struct layer_node *a;
struct vnode *vp;
int error;
/*
* Find hash base, and then search the (two-way) linked
* list looking for a layer_node structure which is referencing
* the lower vnode. If found, the increment the layer_node
* reference count (but NOT the lower vnode's VREF counter)
* and return the vnode locked.
*/
hd = LAYER_NHASH(lmp, lowervp);
loop:
LIST_FOREACH(a, hd, layer_hash) {
if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) {
vp = LAYERTOV(a);
mutex_enter(&vp->v_interlock);
/*
* If we find a node being cleaned out, then
* ignore it and continue. A thread trying to
* clean out the extant layer vnode needs to
* acquire the shared lock (i.e. the lower
* vnode's lock), which our caller already holds.
* To allow the cleaning to succeed the current
* thread must make progress. So, for a brief
* time more than one vnode in a layered file
* system may refer to a single vnode in the
* lower file system.
*/
if ((vp->v_iflag & VI_XLOCK) != 0) {
mutex_exit(&vp->v_interlock);
continue;
}
mutex_exit(&lmp->layerm_hashlock);
/*
* We must not let vget() try to lock the layer
* vp, since the lower vp is already locked and
* locking the layer vp will involve locking
* the lower vp (whether or not they actually
* share a lock). Instead, take the layer vp's
* lock separately afterward, but only if it
* does not share the lower vp's lock.
*/
error = vget(vp, LK_INTERLOCK | LK_NOWAIT);
if (error) {
kpause("layerfs", false, 1, NULL);
mutex_enter(&lmp->layerm_hashlock);
goto loop;
}
LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error);
return (vp);
}
}
return NULL;
}
/*
* Make a new layer_node node.
* Vp is the alias vnode, lowervp is the lower vnode.
* Maintain a reference to lowervp.
*/
int
layer_node_alloc(mp, lowervp, vpp)
struct mount *mp;
struct vnode *lowervp;
struct vnode **vpp;
{
struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
struct layer_node_hashhead *hd;
struct layer_node *xp;
struct vnode *vp, *nvp;
int error;
extern int (**dead_vnodeop_p)(void *);
error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp);
if (error != 0)
return (error);
vp->v_type = lowervp->v_type;
mutex_enter(&vp->v_interlock);
vp->v_iflag |= VI_LAYER;
mutex_exit(&vp->v_interlock);
xp = kmem_alloc(lmp->layerm_size, KM_SLEEP);
if (xp == NULL) {
ungetnewvnode(vp);
return ENOMEM;
}
if (vp->v_type == VBLK || vp->v_type == VCHR) {
spec_node_init(vp, lowervp->v_rdev);
}
vp->v_data = xp;
vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) |
(lowervp->v_vflag & VV_MPSAFE);
xp->layer_vnode = vp;
xp->layer_lowervp = lowervp;
xp->layer_flags = 0;
/*
* 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.)
*/
mutex_enter(&lmp->layerm_hashlock);
if ((nvp = layer_node_find(mp, lowervp)) != NULL) {
*vpp = nvp;
/* free the substructures we've allocated. */
kmem_free(xp, lmp->layerm_size);
if (vp->v_type == VBLK || vp->v_type == VCHR)
spec_node_destroy(vp);
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);
}
/*
* 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 upper node.
*
* LAYERFS_UPPERLOCK already has the test, so we use it after copying
* up the v_vnlock from below.
*/
vp->v_vnlock = lowervp->v_vnlock;
LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error);
KASSERT(error == 0);
/*
* Insert the new node into the hash.
* Add a reference to the lower node.
*/
*vpp = vp;
VREF(lowervp);
hd = LAYER_NHASH(lmp, lowervp);
LIST_INSERT_HEAD(hd, xp, layer_hash);
uvm_vnp_setsize(vp, 0);
mutex_exit(&lmp->layerm_hashlock);
return (0);
}
/*
* Try to find an existing layer_node vnode refering
* to it, otherwise make a new layer_node vnode which
* contains a reference to the lower vnode.
*
* >>> we assume that the lower node is already locked upon entry, so we
* propagate the lock state to upper node <<
*/
int
layer_node_create(mp, lowervp, newvpp)
struct mount *mp;
struct vnode *lowervp;
struct vnode **newvpp;
{
struct vnode *aliasvp;
struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
mutex_enter(&lmp->layerm_hashlock);
aliasvp = layer_node_find(mp, lowervp);
if (aliasvp != NULL) {
/*
* layer_node_find has taken another reference
* to the alias vnode and moved the lock holding to
* aliasvp
*/
#ifdef LAYERFS_DIAGNOSTIC
if (layerfs_debug)
vprint("layer_node_create: exists", aliasvp);
#endif
} else {
int error;
mutex_exit(&lmp->layerm_hashlock);
/*
* Get new vnode.
*/
#ifdef LAYERFS_DIAGNOSTIC
if (layerfs_debug)
printf("layer_node_create: create new alias vnode\n");
#endif
/*
* Make new vnode reference the layer_node.
*/
if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0)
return error;
/*
* aliasvp is already VREF'd by getnewvnode()
*/
}
/*
* Now that we have VREF'd the upper vnode, release the reference
* to the lower node. The existence of the layer_node retains one
* reference to the lower node.
*/
vrele(lowervp);
#ifdef DIAGNOSTIC
if (lowervp->v_usecount < 1) {
/* Should never happen... */
vprint("layer_node_create: alias", aliasvp);
vprint("layer_node_create: lower", lowervp);
panic("layer_node_create: lower has 0 usecount.");
}
#endif
#ifdef LAYERFS_DIAGNOSTIC
if (layerfs_debug)
vprint("layer_node_create: alias", aliasvp);
#endif
*newvpp = aliasvp;
return (0);
}
#ifdef LAYERFS_DIAGNOSTIC
struct vnode *
layer_checkvp(vp, fil, lno)
struct vnode *vp;
const char *fil;
int lno;
{
struct layer_node *a = VTOLAYER(vp);
#ifdef notyet
/*
* Can't do this check because vop_reclaim runs
* with a funny vop vector.
*
* WRS - no it doesnt...
*/
if (vp->v_op != layer_vnodeop_p) {
printf ("layer_checkvp: on non-layer-node\n");
#ifdef notyet
while (layer_checkvp_barrier) /*WAIT*/ ;
#endif
panic("layer_checkvp");
};
#endif
if (a->layer_lowervp == NULL) {
/* Should never happen */
int i; u_long *p;
printf("vp = %p, ZERO ptr\n", vp);
for (p = (u_long *) a, i = 0; i < 8; i++)
printf(" %lx", p[i]);
printf("\n");
/* wait for debugger */
panic("layer_checkvp");
}
if (a->layer_lowervp->v_usecount < 1) {
int i; u_long *p;
printf("vp = %p, unref'ed lowervp\n", vp);
for (p = (u_long *) a, i = 0; i < 8; i++)
printf(" %lx", p[i]);
printf("\n");
/* wait for debugger */
panic ("layer with unref'ed lowervp");
};
#ifdef notnow
printf("layer %p/%d -> %p/%d [%s, %d]\n",
LAYERTOV(a), LAYERTOV(a)->v_usecount,
a->layer_lowervp, a->layer_lowervp->v_usecount,
fil, lno);
#endif
return a->layer_lowervp;
}
#endif