703069c0e9
shutdown). There are still problems with device access and a PR will be filed. - Kill checkalias(). Allow multiple vnodes to reference a single device. - Don't play dangerous tricks with block vnodes to ensure that only one vnode can describe a block device. Instead, prohibit concurrent opens of block devices. As a bonus remove the unreliable code that prevents multiple file system mounts on the same device. It's no longer needed. - Track opens by vnode and by device. Issue cdev_close() when the last open goes away, instead of abusing vnode::v_usecount to tell if the device is open.
414 lines
12 KiB
C
414 lines
12 KiB
C
/* $NetBSD: layer_subr.c,v 1.25 2008/01/24 17:32:55 ad Exp $ */
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/*
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* Copyright (c) 1999 National Aeronautics & Space Administration
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* All rights reserved.
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*
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* This software was written by William Studenmund of the
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* Numerical Aerospace Simulation Facility, NASA Ames Research Center.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the National Aeronautics & Space Administration
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* nor the names of its contributors may be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB-
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* UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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* OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software donated to Berkeley by
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* Jan-Simon Pendry.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp
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* @(#)null_subr.c 8.7 (Berkeley) 5/14/95
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.25 2008/01/24 17:32:55 ad Exp $");
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/proc.h>
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#include <sys/time.h>
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#include <sys/vnode.h>
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#include <sys/mount.h>
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#include <sys/namei.h>
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#include <sys/kmem.h>
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#include <sys/malloc.h>
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#include <miscfs/specfs/specdev.h>
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#include <miscfs/genfs/layer.h>
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#include <miscfs/genfs/layer_extern.h>
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#define NLAYERNODECACHE 16
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#ifdef LAYERFS_DIAGNOSTIC
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int layerfs_debug = 1;
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#endif
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/*
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* layer cache:
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* Each cache entry holds a reference to the lower vnode
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* along with a pointer to the alias vnode. When an
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* entry is added the lower vnode is VREF'd. When the
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* alias is removed the lower vnode is vrele'd.
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*/
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/*
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* Initialise cache headers
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*/
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void
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layerfs_init()
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{
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#ifdef LAYERFS_DIAGNOSTIC
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if (layerfs_debug)
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printf("layerfs_init\n"); /* printed during system boot */
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#endif
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}
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/*
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* Free global resources of layerfs.
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*/
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void
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layerfs_done()
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{
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#ifdef LAYERFS_DIAGNOSTIC
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if (layerfs_debug)
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printf("layerfs_done\n"); /* printed on layerfs detach */
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#endif
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}
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/*
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* Return a locked, VREF'ed alias for lower vnode if already exists, else NULL.
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* The layermp's hashlock must be held on entry.
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* It will be held upon return iff we return NULL.
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*/
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struct vnode *
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layer_node_find(mp, lowervp)
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struct mount *mp;
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struct vnode *lowervp;
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{
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struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
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struct layer_node_hashhead *hd;
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struct layer_node *a;
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struct vnode *vp;
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int error;
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/*
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* Find hash base, and then search the (two-way) linked
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* list looking for a layer_node structure which is referencing
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* the lower vnode. If found, the increment the layer_node
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* reference count (but NOT the lower vnode's VREF counter)
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* and return the vnode locked.
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*/
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hd = LAYER_NHASH(lmp, lowervp);
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loop:
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LIST_FOREACH(a, hd, layer_hash) {
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if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) {
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vp = LAYERTOV(a);
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mutex_enter(&vp->v_interlock);
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/*
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* If we find a node being cleaned out, then
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* ignore it and continue. A thread trying to
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* clean out the extant layer vnode needs to
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* acquire the shared lock (i.e. the lower
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* vnode's lock), which our caller already holds.
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* To allow the cleaning to succeed the current
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* thread must make progress. So, for a brief
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* time more than one vnode in a layered file
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* system may refer to a single vnode in the
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* lower file system.
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*/
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if ((vp->v_iflag & VI_XLOCK) != 0) {
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mutex_exit(&vp->v_interlock);
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continue;
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}
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mutex_exit(&lmp->layerm_hashlock);
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/*
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* We must not let vget() try to lock the layer
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* vp, since the lower vp is already locked and
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* locking the layer vp will involve locking
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* the lower vp (whether or not they actually
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* share a lock). Instead, take the layer vp's
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* lock separately afterward, but only if it
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* does not share the lower vp's lock.
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*/
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error = vget(vp, LK_INTERLOCK | LK_NOWAIT);
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if (error) {
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kpause("layerfs", false, 1, NULL);
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mutex_enter(&lmp->layerm_hashlock);
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goto loop;
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}
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LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error);
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return (vp);
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}
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}
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return NULL;
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}
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/*
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* Make a new layer_node node.
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* Vp is the alias vnode, lowervp is the lower vnode.
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* Maintain a reference to lowervp.
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*/
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int
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layer_node_alloc(mp, lowervp, vpp)
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struct mount *mp;
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struct vnode *lowervp;
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struct vnode **vpp;
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{
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struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
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struct layer_node_hashhead *hd;
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struct layer_node *xp;
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struct vnode *vp, *nvp;
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int error;
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extern int (**dead_vnodeop_p)(void *);
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error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp);
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if (error != 0)
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return (error);
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vp->v_type = lowervp->v_type;
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mutex_enter(&vp->v_interlock);
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vp->v_iflag |= VI_LAYER;
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mutex_exit(&vp->v_interlock);
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xp = kmem_alloc(lmp->layerm_size, KM_SLEEP);
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if (xp == NULL) {
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ungetnewvnode(vp);
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return ENOMEM;
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}
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if (vp->v_type == VBLK || vp->v_type == VCHR) {
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spec_node_init(vp, lowervp->v_rdev);
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}
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vp->v_data = xp;
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vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) |
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(lowervp->v_vflag & VV_MPSAFE);
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xp->layer_vnode = vp;
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xp->layer_lowervp = lowervp;
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xp->layer_flags = 0;
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/*
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* Before we insert our new node onto the hash chains,
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* check to see if someone else has beaten us to it.
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* (We could have slept in MALLOC.)
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*/
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mutex_enter(&lmp->layerm_hashlock);
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if ((nvp = layer_node_find(mp, lowervp)) != NULL) {
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*vpp = nvp;
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/* free the substructures we've allocated. */
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kmem_free(xp, lmp->layerm_size);
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if (vp->v_type == VBLK || vp->v_type == VCHR)
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spec_node_destroy(vp);
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vp->v_type = VBAD; /* node is discarded */
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vp->v_op = dead_vnodeop_p; /* so ops will still work */
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vrele(vp); /* get rid of it. */
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return (0);
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}
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/*
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* Now lock the new node. We rely on the fact that we were passed
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* a locked vnode. If the lower node is exporting a struct lock
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* (v_vnlock != NULL) then we just set the upper v_vnlock to the
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* lower one, and both are now locked. If the lower node is exporting
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* NULL, then we copy that up and manually lock the upper node.
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*
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* LAYERFS_UPPERLOCK already has the test, so we use it after copying
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* up the v_vnlock from below.
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*/
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vp->v_vnlock = lowervp->v_vnlock;
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LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error);
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KASSERT(error == 0);
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/*
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* Insert the new node into the hash.
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* Add a reference to the lower node.
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*/
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*vpp = vp;
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VREF(lowervp);
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hd = LAYER_NHASH(lmp, lowervp);
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LIST_INSERT_HEAD(hd, xp, layer_hash);
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uvm_vnp_setsize(vp, 0);
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mutex_exit(&lmp->layerm_hashlock);
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return (0);
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}
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/*
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* Try to find an existing layer_node vnode refering
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* to it, otherwise make a new layer_node vnode which
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* contains a reference to the lower vnode.
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*
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* >>> we assume that the lower node is already locked upon entry, so we
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* propagate the lock state to upper node <<
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*/
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int
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layer_node_create(mp, lowervp, newvpp)
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struct mount *mp;
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struct vnode *lowervp;
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struct vnode **newvpp;
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{
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struct vnode *aliasvp;
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struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
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mutex_enter(&lmp->layerm_hashlock);
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aliasvp = layer_node_find(mp, lowervp);
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if (aliasvp != NULL) {
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/*
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* layer_node_find has taken another reference
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* to the alias vnode and moved the lock holding to
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* aliasvp
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*/
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#ifdef LAYERFS_DIAGNOSTIC
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if (layerfs_debug)
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vprint("layer_node_create: exists", aliasvp);
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#endif
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} else {
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int error;
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mutex_exit(&lmp->layerm_hashlock);
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/*
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* Get new vnode.
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*/
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#ifdef LAYERFS_DIAGNOSTIC
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if (layerfs_debug)
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printf("layer_node_create: create new alias vnode\n");
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#endif
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/*
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* Make new vnode reference the layer_node.
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*/
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if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0)
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return error;
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/*
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* aliasvp is already VREF'd by getnewvnode()
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*/
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}
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/*
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* Now that we have VREF'd the upper vnode, release the reference
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* to the lower node. The existence of the layer_node retains one
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* reference to the lower node.
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*/
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vrele(lowervp);
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#ifdef DIAGNOSTIC
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if (lowervp->v_usecount < 1) {
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/* Should never happen... */
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vprint("layer_node_create: alias", aliasvp);
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vprint("layer_node_create: lower", lowervp);
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panic("layer_node_create: lower has 0 usecount.");
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}
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#endif
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#ifdef LAYERFS_DIAGNOSTIC
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if (layerfs_debug)
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vprint("layer_node_create: alias", aliasvp);
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#endif
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*newvpp = aliasvp;
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return (0);
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}
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#ifdef LAYERFS_DIAGNOSTIC
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struct vnode *
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layer_checkvp(vp, fil, lno)
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struct vnode *vp;
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const char *fil;
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int lno;
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{
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struct layer_node *a = VTOLAYER(vp);
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#ifdef notyet
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/*
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* Can't do this check because vop_reclaim runs
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* with a funny vop vector.
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*
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* WRS - no it doesnt...
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*/
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if (vp->v_op != layer_vnodeop_p) {
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printf ("layer_checkvp: on non-layer-node\n");
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#ifdef notyet
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while (layer_checkvp_barrier) /*WAIT*/ ;
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#endif
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panic("layer_checkvp");
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};
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#endif
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if (a->layer_lowervp == NULL) {
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/* Should never happen */
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int i; u_long *p;
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printf("vp = %p, ZERO ptr\n", vp);
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for (p = (u_long *) a, i = 0; i < 8; i++)
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printf(" %lx", p[i]);
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printf("\n");
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/* wait for debugger */
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panic("layer_checkvp");
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}
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if (a->layer_lowervp->v_usecount < 1) {
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int i; u_long *p;
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printf("vp = %p, unref'ed lowervp\n", vp);
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for (p = (u_long *) a, i = 0; i < 8; i++)
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printf(" %lx", p[i]);
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printf("\n");
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/* wait for debugger */
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panic ("layer with unref'ed lowervp");
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};
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#ifdef notnow
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printf("layer %p/%d -> %p/%d [%s, %d]\n",
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LAYERTOV(a), LAYERTOV(a)->v_usecount,
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a->layer_lowervp, a->layer_lowervp->v_usecount,
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fil, lno);
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#endif
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return a->layer_lowervp;
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}
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#endif
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