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layer_subr.c revision 1.25
      1  1.25        ad /*	$NetBSD: layer_subr.c,v 1.25 2008/01/24 17:32:55 ad Exp $	*/
      2   1.1  wrstuden 
      3   1.1  wrstuden /*
      4   1.1  wrstuden  * Copyright (c) 1999 National Aeronautics & Space Administration
      5   1.1  wrstuden  * All rights reserved.
      6   1.1  wrstuden  *
      7   1.1  wrstuden  * This software was written by William Studenmund of the
      8   1.8       wiz  * Numerical Aerospace Simulation Facility, NASA Ames Research Center.
      9   1.1  wrstuden  *
     10   1.1  wrstuden  * Redistribution and use in source and binary forms, with or without
     11   1.1  wrstuden  * modification, are permitted provided that the following conditions
     12   1.1  wrstuden  * are met:
     13   1.1  wrstuden  * 1. Redistributions of source code must retain the above copyright
     14   1.1  wrstuden  *    notice, this list of conditions and the following disclaimer.
     15   1.1  wrstuden  * 2. Redistributions in binary form must reproduce the above copyright
     16   1.1  wrstuden  *    notice, this list of conditions and the following disclaimer in the
     17   1.1  wrstuden  *    documentation and/or other materials provided with the distribution.
     18   1.5     soren  * 3. Neither the name of the National Aeronautics & Space Administration
     19   1.1  wrstuden  *    nor the names of its contributors may be used to endorse or promote
     20   1.1  wrstuden  *    products derived from this software without specific prior written
     21   1.1  wrstuden  *    permission.
     22   1.1  wrstuden  *
     23   1.1  wrstuden  * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
     24   1.1  wrstuden  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     25   1.1  wrstuden  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     26   1.1  wrstuden  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB-
     27   1.1  wrstuden  * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
     28   1.1  wrstuden  * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     29   1.1  wrstuden  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     30   1.1  wrstuden  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     31   1.1  wrstuden  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     32   1.1  wrstuden  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     33   1.1  wrstuden  * POSSIBILITY OF SUCH DAMAGE.
     34   1.1  wrstuden  */
     35   1.1  wrstuden /*
     36   1.1  wrstuden  * Copyright (c) 1992, 1993
     37   1.1  wrstuden  *	The Regents of the University of California.  All rights reserved.
     38   1.1  wrstuden  *
     39   1.1  wrstuden  * This code is derived from software donated to Berkeley by
     40   1.1  wrstuden  * Jan-Simon Pendry.
     41   1.1  wrstuden  *
     42   1.1  wrstuden  * Redistribution and use in source and binary forms, with or without
     43   1.1  wrstuden  * modification, are permitted provided that the following conditions
     44   1.1  wrstuden  * are met:
     45   1.1  wrstuden  * 1. Redistributions of source code must retain the above copyright
     46   1.1  wrstuden  *    notice, this list of conditions and the following disclaimer.
     47   1.1  wrstuden  * 2. Redistributions in binary form must reproduce the above copyright
     48   1.1  wrstuden  *    notice, this list of conditions and the following disclaimer in the
     49   1.1  wrstuden  *    documentation and/or other materials provided with the distribution.
     50  1.15       agc  * 3. Neither the name of the University nor the names of its contributors
     51   1.1  wrstuden  *    may be used to endorse or promote products derived from this software
     52   1.1  wrstuden  *    without specific prior written permission.
     53   1.1  wrstuden  *
     54   1.1  wrstuden  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     55   1.1  wrstuden  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     56   1.1  wrstuden  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     57   1.1  wrstuden  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     58   1.1  wrstuden  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     59   1.1  wrstuden  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     60   1.1  wrstuden  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     61   1.1  wrstuden  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     62   1.1  wrstuden  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     63   1.1  wrstuden  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     64   1.1  wrstuden  * SUCH DAMAGE.
     65   1.1  wrstuden  *
     66   1.1  wrstuden  *	from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp
     67   1.1  wrstuden  *	@(#)null_subr.c	8.7 (Berkeley) 5/14/95
     68   1.1  wrstuden  */
     69   1.9     lukem 
     70   1.9     lukem #include <sys/cdefs.h>
     71  1.25        ad __KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.25 2008/01/24 17:32:55 ad Exp $");
     72   1.1  wrstuden 
     73   1.1  wrstuden #include <sys/param.h>
     74   1.1  wrstuden #include <sys/systm.h>
     75   1.1  wrstuden #include <sys/proc.h>
     76   1.1  wrstuden #include <sys/time.h>
     77   1.1  wrstuden #include <sys/vnode.h>
     78   1.1  wrstuden #include <sys/mount.h>
     79   1.1  wrstuden #include <sys/namei.h>
     80  1.23        ad #include <sys/kmem.h>
     81   1.1  wrstuden #include <sys/malloc.h>
     82  1.23        ad 
     83   1.1  wrstuden #include <miscfs/specfs/specdev.h>
     84   1.1  wrstuden #include <miscfs/genfs/layer.h>
     85   1.1  wrstuden #include <miscfs/genfs/layer_extern.h>
     86   1.1  wrstuden 
     87   1.1  wrstuden #define	NLAYERNODECACHE 16
     88   1.1  wrstuden 
     89  1.16       erh #ifdef LAYERFS_DIAGNOSTIC
     90  1.16       erh int layerfs_debug = 1;
     91  1.16       erh #endif
     92  1.16       erh 
     93   1.1  wrstuden /*
     94   1.1  wrstuden  * layer cache:
     95   1.1  wrstuden  * Each cache entry holds a reference to the lower vnode
     96   1.1  wrstuden  * along with a pointer to the alias vnode.  When an
     97   1.1  wrstuden  * entry is added the lower vnode is VREF'd.  When the
     98   1.1  wrstuden  * alias is removed the lower vnode is vrele'd.
     99   1.1  wrstuden  */
    100   1.1  wrstuden 
    101   1.1  wrstuden /*
    102   1.1  wrstuden  * Initialise cache headers
    103   1.1  wrstuden  */
    104   1.1  wrstuden void
    105   1.1  wrstuden layerfs_init()
    106   1.1  wrstuden {
    107   1.6  jdolecek #ifdef LAYERFS_DIAGNOSTIC
    108  1.16       erh 	if (layerfs_debug)
    109  1.16       erh 		printf("layerfs_init\n");		/* printed during system boot */
    110   1.6  jdolecek #endif
    111   1.6  jdolecek }
    112   1.1  wrstuden 
    113   1.6  jdolecek /*
    114   1.6  jdolecek  * Free global resources of layerfs.
    115   1.6  jdolecek  */
    116   1.6  jdolecek void
    117   1.6  jdolecek layerfs_done()
    118   1.6  jdolecek {
    119   1.1  wrstuden #ifdef LAYERFS_DIAGNOSTIC
    120  1.16       erh 	if (layerfs_debug)
    121  1.16       erh 		printf("layerfs_done\n");		/* printed on layerfs detach */
    122   1.1  wrstuden #endif
    123   1.1  wrstuden }
    124   1.1  wrstuden 
    125   1.1  wrstuden /*
    126  1.21       chs  * Return a locked, VREF'ed alias for lower vnode if already exists, else NULL.
    127  1.21       chs  * The layermp's hashlock must be held on entry.
    128  1.21       chs  * It will be held upon return iff we return NULL.
    129   1.1  wrstuden  */
    130   1.1  wrstuden struct vnode *
    131   1.1  wrstuden layer_node_find(mp, lowervp)
    132   1.1  wrstuden 	struct mount *mp;
    133   1.1  wrstuden 	struct vnode *lowervp;
    134   1.1  wrstuden {
    135   1.1  wrstuden 	struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
    136   1.1  wrstuden 	struct layer_node_hashhead *hd;
    137   1.1  wrstuden 	struct layer_node *a;
    138   1.1  wrstuden 	struct vnode *vp;
    139  1.21       chs 	int error;
    140   1.1  wrstuden 
    141   1.1  wrstuden 	/*
    142   1.1  wrstuden 	 * Find hash base, and then search the (two-way) linked
    143   1.1  wrstuden 	 * list looking for a layer_node structure which is referencing
    144   1.1  wrstuden 	 * the lower vnode.  If found, the increment the layer_node
    145   1.1  wrstuden 	 * reference count (but NOT the lower vnode's VREF counter)
    146   1.1  wrstuden 	 * and return the vnode locked.
    147   1.1  wrstuden 	 */
    148   1.1  wrstuden 	hd = LAYER_NHASH(lmp, lowervp);
    149   1.1  wrstuden loop:
    150  1.21       chs 	LIST_FOREACH(a, hd, layer_hash) {
    151   1.1  wrstuden 		if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) {
    152   1.1  wrstuden 			vp = LAYERTOV(a);
    153  1.24        ad 			mutex_enter(&vp->v_interlock);
    154   1.1  wrstuden 			/*
    155  1.24        ad 			 * If we find a node being cleaned out, then
    156  1.24        ad 			 * ignore it and continue.  A thread trying to
    157  1.24        ad 			 * clean out the extant layer vnode needs to
    158  1.24        ad 			 * acquire the shared lock (i.e. the lower
    159  1.24        ad 			 * vnode's lock), which our caller already holds.
    160  1.24        ad 			 * To allow the cleaning to succeed the current
    161  1.24        ad 			 * thread must make progress.  So, for a brief
    162  1.24        ad 			 * time more than one vnode in a layered file
    163  1.24        ad 			 * system may refer to a single vnode in the
    164  1.24        ad 			 * lower file system.
    165   1.1  wrstuden 			 */
    166  1.24        ad 			if ((vp->v_iflag & VI_XLOCK) != 0) {
    167  1.24        ad 				mutex_exit(&vp->v_interlock);
    168  1.24        ad 				continue;
    169  1.24        ad 			}
    170  1.22        ad 			mutex_exit(&lmp->layerm_hashlock);
    171  1.24        ad 			/*
    172  1.24        ad 			 * We must not let vget() try to lock the layer
    173  1.24        ad 			 * vp, since the lower vp is already locked and
    174  1.24        ad 			 * locking the layer vp will involve locking
    175  1.24        ad 			 * the lower vp (whether or not they actually
    176  1.24        ad 			 * share a lock).  Instead, take the layer vp's
    177  1.24        ad 			 * lock separately afterward, but only if it
    178  1.24        ad 			 * does not share the lower vp's lock.
    179  1.24        ad 			 */
    180  1.24        ad 			error = vget(vp, LK_INTERLOCK | LK_NOWAIT);
    181  1.21       chs 			if (error) {
    182  1.24        ad 				kpause("layerfs", false, 1, NULL);
    183  1.22        ad 				mutex_enter(&lmp->layerm_hashlock);
    184   1.1  wrstuden 				goto loop;
    185  1.21       chs 			}
    186  1.21       chs 			LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error);
    187   1.1  wrstuden 			return (vp);
    188   1.1  wrstuden 		}
    189   1.1  wrstuden 	}
    190   1.1  wrstuden 	return NULL;
    191   1.1  wrstuden }
    192   1.1  wrstuden 
    193   1.1  wrstuden 
    194   1.1  wrstuden /*
    195   1.1  wrstuden  * Make a new layer_node node.
    196   1.1  wrstuden  * Vp is the alias vnode, lowervp is the lower vnode.
    197   1.1  wrstuden  * Maintain a reference to lowervp.
    198   1.1  wrstuden  */
    199   1.1  wrstuden int
    200   1.1  wrstuden layer_node_alloc(mp, lowervp, vpp)
    201   1.1  wrstuden 	struct mount *mp;
    202   1.1  wrstuden 	struct vnode *lowervp;
    203   1.1  wrstuden 	struct vnode **vpp;
    204   1.1  wrstuden {
    205   1.1  wrstuden 	struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
    206   1.1  wrstuden 	struct layer_node_hashhead *hd;
    207   1.1  wrstuden 	struct layer_node *xp;
    208   1.1  wrstuden 	struct vnode *vp, *nvp;
    209   1.1  wrstuden 	int error;
    210  1.17   xtraeme 	extern int (**dead_vnodeop_p)(void *);
    211   1.1  wrstuden 
    212  1.23        ad 	error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp);
    213  1.23        ad 	if (error != 0)
    214   1.1  wrstuden 		return (error);
    215   1.1  wrstuden 	vp->v_type = lowervp->v_type;
    216  1.23        ad 	mutex_enter(&vp->v_interlock);
    217  1.22        ad 	vp->v_iflag |= VI_LAYER;
    218  1.23        ad 	mutex_exit(&vp->v_interlock);
    219   1.1  wrstuden 
    220  1.23        ad 	xp = kmem_alloc(lmp->layerm_size, KM_SLEEP);
    221  1.23        ad 	if (xp == NULL) {
    222  1.23        ad 		ungetnewvnode(vp);
    223  1.23        ad 		return ENOMEM;
    224  1.23        ad 	}
    225   1.1  wrstuden 	if (vp->v_type == VBLK || vp->v_type == VCHR) {
    226  1.25        ad 		spec_node_init(vp, lowervp->v_rdev);
    227   1.1  wrstuden 	}
    228   1.1  wrstuden 
    229   1.1  wrstuden 	vp->v_data = xp;
    230  1.23        ad 	vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) |
    231  1.23        ad 	    (lowervp->v_vflag & VV_MPSAFE);
    232   1.1  wrstuden 	xp->layer_vnode = vp;
    233   1.1  wrstuden 	xp->layer_lowervp = lowervp;
    234   1.1  wrstuden 	xp->layer_flags = 0;
    235  1.21       chs 
    236   1.1  wrstuden 	/*
    237   1.1  wrstuden 	 * Before we insert our new node onto the hash chains,
    238   1.1  wrstuden 	 * check to see if someone else has beaten us to it.
    239   1.1  wrstuden 	 * (We could have slept in MALLOC.)
    240   1.1  wrstuden 	 */
    241  1.22        ad 	mutex_enter(&lmp->layerm_hashlock);
    242   1.1  wrstuden 	if ((nvp = layer_node_find(mp, lowervp)) != NULL) {
    243   1.1  wrstuden 		*vpp = nvp;
    244   1.1  wrstuden 
    245   1.1  wrstuden 		/* free the substructures we've allocated. */
    246  1.23        ad 		kmem_free(xp, lmp->layerm_size);
    247   1.1  wrstuden 		if (vp->v_type == VBLK || vp->v_type == VCHR)
    248  1.25        ad 			spec_node_destroy(vp);
    249   1.1  wrstuden 
    250   1.1  wrstuden 		vp->v_type = VBAD;		/* node is discarded */
    251   1.1  wrstuden 		vp->v_op = dead_vnodeop_p;	/* so ops will still work */
    252   1.1  wrstuden 		vrele(vp);			/* get rid of it. */
    253   1.1  wrstuden 		return (0);
    254   1.1  wrstuden 	}
    255   1.1  wrstuden 
    256   1.1  wrstuden 	/*
    257   1.1  wrstuden 	 * Now lock the new node. We rely on the fact that we were passed
    258   1.1  wrstuden 	 * a locked vnode. If the lower node is exporting a struct lock
    259   1.1  wrstuden 	 * (v_vnlock != NULL) then we just set the upper v_vnlock to the
    260   1.1  wrstuden 	 * lower one, and both are now locked. If the lower node is exporting
    261   1.1  wrstuden 	 * NULL, then we copy that up and manually lock the upper node.
    262   1.1  wrstuden 	 *
    263   1.1  wrstuden 	 * LAYERFS_UPPERLOCK already has the test, so we use it after copying
    264   1.1  wrstuden 	 * up the v_vnlock from below.
    265   1.1  wrstuden 	 */
    266   1.1  wrstuden 
    267   1.1  wrstuden 	vp->v_vnlock = lowervp->v_vnlock;
    268   1.1  wrstuden 	LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error);
    269  1.21       chs 	KASSERT(error == 0);
    270   1.1  wrstuden 
    271   1.1  wrstuden 	/*
    272  1.21       chs 	 * Insert the new node into the hash.
    273  1.21       chs 	 * Add a reference to the lower node.
    274   1.1  wrstuden 	 */
    275   1.1  wrstuden 
    276   1.1  wrstuden 	*vpp = vp;
    277  1.21       chs 	VREF(lowervp);
    278   1.1  wrstuden 	hd = LAYER_NHASH(lmp, lowervp);
    279   1.1  wrstuden 	LIST_INSERT_HEAD(hd, xp, layer_hash);
    280   1.7       chs 	uvm_vnp_setsize(vp, 0);
    281  1.22        ad 	mutex_exit(&lmp->layerm_hashlock);
    282   1.1  wrstuden 	return (0);
    283   1.1  wrstuden }
    284   1.1  wrstuden 
    285   1.1  wrstuden 
    286   1.1  wrstuden /*
    287   1.1  wrstuden  * Try to find an existing layer_node vnode refering
    288   1.1  wrstuden  * to it, otherwise make a new layer_node vnode which
    289   1.1  wrstuden  * contains a reference to the lower vnode.
    290   1.1  wrstuden  *
    291   1.1  wrstuden  * >>> we assume that the lower node is already locked upon entry, so we
    292   1.1  wrstuden  * propagate the lock state to upper node <<
    293   1.1  wrstuden  */
    294   1.1  wrstuden int
    295   1.1  wrstuden layer_node_create(mp, lowervp, newvpp)
    296   1.1  wrstuden 	struct mount *mp;
    297   1.1  wrstuden 	struct vnode *lowervp;
    298   1.1  wrstuden 	struct vnode **newvpp;
    299   1.1  wrstuden {
    300   1.1  wrstuden 	struct vnode *aliasvp;
    301   1.1  wrstuden 	struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
    302   1.1  wrstuden 
    303  1.22        ad 	mutex_enter(&lmp->layerm_hashlock);
    304  1.21       chs 	aliasvp = layer_node_find(mp, lowervp);
    305  1.21       chs 	if (aliasvp != NULL) {
    306   1.1  wrstuden 		/*
    307   1.1  wrstuden 		 * layer_node_find has taken another reference
    308   1.1  wrstuden 		 * to the alias vnode and moved the lock holding to
    309   1.1  wrstuden 		 * aliasvp
    310   1.1  wrstuden 		 */
    311   1.1  wrstuden #ifdef LAYERFS_DIAGNOSTIC
    312  1.16       erh 		if (layerfs_debug)
    313  1.16       erh 			vprint("layer_node_create: exists", aliasvp);
    314   1.1  wrstuden #endif
    315   1.1  wrstuden 	} else {
    316   1.1  wrstuden 		int error;
    317   1.1  wrstuden 
    318  1.22        ad 		mutex_exit(&lmp->layerm_hashlock);
    319  1.21       chs 
    320   1.1  wrstuden 		/*
    321   1.1  wrstuden 		 * Get new vnode.
    322   1.1  wrstuden 		 */
    323   1.1  wrstuden #ifdef LAYERFS_DIAGNOSTIC
    324  1.16       erh 		if (layerfs_debug)
    325  1.16       erh 			printf("layer_node_create: create new alias vnode\n");
    326   1.1  wrstuden #endif
    327   1.1  wrstuden 
    328   1.1  wrstuden 		/*
    329   1.1  wrstuden 		 * Make new vnode reference the layer_node.
    330   1.1  wrstuden 		 */
    331   1.1  wrstuden 		if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0)
    332   1.1  wrstuden 			return error;
    333   1.1  wrstuden 
    334   1.1  wrstuden 		/*
    335   1.1  wrstuden 		 * aliasvp is already VREF'd by getnewvnode()
    336   1.1  wrstuden 		 */
    337   1.1  wrstuden 	}
    338   1.1  wrstuden 
    339   1.1  wrstuden 	/*
    340   1.1  wrstuden 	 * Now that we have VREF'd the upper vnode, release the reference
    341  1.19       wiz 	 * to the lower node. The existence of the layer_node retains one
    342   1.1  wrstuden 	 * reference to the lower node.
    343   1.1  wrstuden 	 */
    344   1.1  wrstuden 	vrele(lowervp);
    345   1.1  wrstuden 
    346   1.1  wrstuden #ifdef DIAGNOSTIC
    347   1.1  wrstuden 	if (lowervp->v_usecount < 1) {
    348   1.1  wrstuden 		/* Should never happen... */
    349   1.1  wrstuden 		vprint("layer_node_create: alias", aliasvp);
    350   1.1  wrstuden 		vprint("layer_node_create: lower", lowervp);
    351   1.1  wrstuden 		panic("layer_node_create: lower has 0 usecount.");
    352  1.21       chs 	}
    353   1.1  wrstuden #endif
    354   1.1  wrstuden 
    355   1.1  wrstuden #ifdef LAYERFS_DIAGNOSTIC
    356  1.16       erh 	if (layerfs_debug)
    357  1.16       erh 		vprint("layer_node_create: alias", aliasvp);
    358   1.1  wrstuden #endif
    359   1.1  wrstuden 	*newvpp = aliasvp;
    360   1.1  wrstuden 	return (0);
    361   1.1  wrstuden }
    362   1.1  wrstuden 
    363  1.16       erh #ifdef LAYERFS_DIAGNOSTIC
    364   1.1  wrstuden struct vnode *
    365   1.1  wrstuden layer_checkvp(vp, fil, lno)
    366   1.1  wrstuden 	struct vnode *vp;
    367  1.16       erh 	const char *fil;
    368   1.1  wrstuden 	int lno;
    369   1.1  wrstuden {
    370   1.1  wrstuden 	struct layer_node *a = VTOLAYER(vp);
    371   1.1  wrstuden #ifdef notyet
    372   1.1  wrstuden 	/*
    373   1.1  wrstuden 	 * Can't do this check because vop_reclaim runs
    374   1.1  wrstuden 	 * with a funny vop vector.
    375   1.1  wrstuden 	 *
    376   1.1  wrstuden 	 * WRS - no it doesnt...
    377   1.1  wrstuden 	 */
    378   1.1  wrstuden 	if (vp->v_op != layer_vnodeop_p) {
    379   1.1  wrstuden 		printf ("layer_checkvp: on non-layer-node\n");
    380   1.1  wrstuden #ifdef notyet
    381   1.1  wrstuden 		while (layer_checkvp_barrier) /*WAIT*/ ;
    382   1.1  wrstuden #endif
    383   1.1  wrstuden 		panic("layer_checkvp");
    384   1.1  wrstuden 	};
    385   1.1  wrstuden #endif
    386   1.1  wrstuden 	if (a->layer_lowervp == NULL) {
    387   1.1  wrstuden 		/* Should never happen */
    388   1.1  wrstuden 		int i; u_long *p;
    389   1.1  wrstuden 		printf("vp = %p, ZERO ptr\n", vp);
    390   1.1  wrstuden 		for (p = (u_long *) a, i = 0; i < 8; i++)
    391   1.1  wrstuden 			printf(" %lx", p[i]);
    392   1.1  wrstuden 		printf("\n");
    393   1.1  wrstuden 		/* wait for debugger */
    394   1.1  wrstuden 		panic("layer_checkvp");
    395   1.1  wrstuden 	}
    396   1.1  wrstuden 	if (a->layer_lowervp->v_usecount < 1) {
    397   1.1  wrstuden 		int i; u_long *p;
    398   1.1  wrstuden 		printf("vp = %p, unref'ed lowervp\n", vp);
    399   1.1  wrstuden 		for (p = (u_long *) a, i = 0; i < 8; i++)
    400   1.1  wrstuden 			printf(" %lx", p[i]);
    401   1.1  wrstuden 		printf("\n");
    402   1.1  wrstuden 		/* wait for debugger */
    403   1.1  wrstuden 		panic ("layer with unref'ed lowervp");
    404   1.1  wrstuden 	};
    405   1.1  wrstuden #ifdef notnow
    406   1.1  wrstuden 	printf("layer %p/%d -> %p/%d [%s, %d]\n",
    407   1.1  wrstuden 	        LAYERTOV(a), LAYERTOV(a)->v_usecount,
    408   1.1  wrstuden 		a->layer_lowervp, a->layer_lowervp->v_usecount,
    409   1.1  wrstuden 		fil, lno);
    410   1.1  wrstuden #endif
    411   1.1  wrstuden 	return a->layer_lowervp;
    412   1.1  wrstuden }
    413  1.16       erh #endif
    414