bc855512c8
that they set v->v_vnlock. This is true for all filesystems in the tree. - Remove all uses of LK_THISLAYER. If the lower layer is locked, the null layer is locked. We only use vget() to get a reference now. null essentially does no locking. This fixes LOOKUP_SHARED with nullfs. - Remove the special LK_DRAIN considerations, I do not believe this is needed now as LK_DRAIN doesn't destroy the lower vnode's lock, and it's hardly used anymore. - Add one well commented hack to prevent the lowervp from going away while we're in it's VOP_LOCK routine. This can only happen if we're forcibly unmounted while some callers are waiting in the lock. In this case the lowervp could be recycled after we drop our last ref in null_reclaim(). Prevent this with a vhold().
82 lines
2.9 KiB
C
82 lines
2.9 KiB
C
/*-
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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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* 4. 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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* @(#)null.h 8.3 (Berkeley) 8/20/94
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*
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* $FreeBSD$
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*/
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struct null_mount {
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struct mount *nullm_vfs;
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struct vnode *nullm_rootvp; /* Reference to root null_node */
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};
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#ifdef _KERNEL
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/*
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* A cache of vnode references
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*/
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struct null_node {
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LIST_ENTRY(null_node) null_hash; /* Hash list */
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struct vnode *null_lowervp; /* VREFed once */
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struct vnode *null_vnode; /* Back pointer */
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};
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#define MOUNTTONULLMOUNT(mp) ((struct null_mount *)((mp)->mnt_data))
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#define VTONULL(vp) ((struct null_node *)(vp)->v_data)
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#define NULLTOV(xp) ((xp)->null_vnode)
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int nullfs_init(struct vfsconf *vfsp);
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int nullfs_uninit(struct vfsconf *vfsp);
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int null_nodeget(struct mount *mp, struct vnode *target, struct vnode **vpp);
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void null_hashrem(struct null_node *xp);
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int null_bypass(struct vop_generic_args *ap);
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#ifdef DIAGNOSTIC
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struct vnode *null_checkvp(struct vnode *vp, char *fil, int lno);
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#define NULLVPTOLOWERVP(vp) null_checkvp((vp), __FILE__, __LINE__)
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#else
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#define NULLVPTOLOWERVP(vp) (VTONULL(vp)->null_lowervp)
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#endif
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extern struct vop_vector null_vnodeops;
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#ifdef MALLOC_DECLARE
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MALLOC_DECLARE(M_NULLFSNODE);
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#endif
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#ifdef NULLFS_DEBUG
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#define NULLFSDEBUG(format, args...) printf(format ,## args)
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#else
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#define NULLFSDEBUG(format, args...)
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#endif /* NULLFS_DEBUG */
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#endif /* _KERNEL */
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