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6c8ded0015
Since non-doomed unionfs vnodes always share their primary lock with either the lower or upper vnode, any forwarded call to the base FS which transiently drops that upper or lower vnode lock may result in the unionfs vnode becoming completely unlocked during that transient window. The unionfs vnode may then become doomed by a concurrent forced unmount, which can lead to either or both of the following: --Complete loss of the unionfs lock: in the process of being doomed, the unionfs vnode switches back to the default vnode lock, so even if the base FS VOP reacquires the upper/lower vnode lock, that no longer translates into the unionfs vnode being relocked. This will then violate that caller's locking assumptions as well as various assertions that are enabled with DEBUG_VFS_LOCKS. --Complete less of reference on the upper/lower vnode: the caller normally holds a reference on the unionfs vnode, while the unionfs vnode in turn holds references on the upper/lower vnodes. But in the course of being doomed, the unionfs vnode will drop the latter set of references, which can effectively lead to the base FS VOP executing with no references at all on its vnode, violating the assumption that vnodes can't be recycled during these calls and (if lucky) violating various assertions in the base FS. Fix this by adding two new functions, unionfs_forward_vop_start_pair() and unionfs_forward_vop_finish_pair(), which are intended to bookend any forwarded VOP which may transiently unlock the relevant vnode(s). These functions are currently only applied to VOPs that modify file state (and require vnode reference and lock state to be identical at call entry and exit), as the common reason for transiently dropping locks is to update filesystem metadata. Reviewed by: olce Tested by: pho MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D44076
192 lines
7.2 KiB
C
192 lines
7.2 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1994 The Regents of the University of California.
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* Copyright (c) 1994 Jan-Simon Pendry.
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* Copyright (c) 2005, 2006 Masanori Ozawa <ozawa@ongs.co.jp>, ONGS Inc.
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* Copyright (c) 2006 Daichi Goto <daichi@freebsd.org>
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* 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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#ifdef _KERNEL
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/* copy method of attr from lower to upper */
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typedef enum _unionfs_copymode {
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UNIONFS_TRADITIONAL = 0,
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UNIONFS_TRANSPARENT,
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UNIONFS_MASQUERADE
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} unionfs_copymode;
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/* whiteout policy of upper layer */
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typedef enum _unionfs_whitemode {
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UNIONFS_WHITE_ALWAYS = 0,
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UNIONFS_WHITE_WHENNEEDED
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} unionfs_whitemode;
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struct unionfs_mount {
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struct mount *um_lowermp; /* MNT_REFed lower mount object */
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struct mount *um_uppermp; /* MNT_REFed upper mount object */
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struct vnode *um_lowervp; /* VREFed once */
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struct vnode *um_uppervp; /* VREFed once */
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struct vnode *um_rootvp; /* ROOT vnode */
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struct mount_upper_node um_lower_link; /* node in lower FS list of uppers */
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struct mount_upper_node um_upper_link; /* node in upper FS list of uppers */
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unionfs_copymode um_copymode;
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unionfs_whitemode um_whitemode;
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uid_t um_uid;
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gid_t um_gid;
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u_short um_udir;
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u_short um_ufile;
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};
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/* unionfs status list */
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struct unionfs_node_status {
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LIST_ENTRY(unionfs_node_status) uns_list; /* Status list */
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pid_t uns_pid; /* current process id */
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int uns_node_flag; /* uns flag */
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int uns_lower_opencnt; /* open count of lower */
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int uns_upper_opencnt; /* open count of upper */
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int uns_lower_openmode; /* open mode of lower */
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int uns_readdir_status; /* read status of readdir */
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};
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/* union node status flags */
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#define UNS_OPENL_4_READDIR 0x01 /* open lower layer for readdir */
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/* A cache of vnode references */
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struct unionfs_node {
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struct vnode *un_lowervp; /* lower side vnode */
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struct vnode *un_uppervp; /* upper side vnode */
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struct vnode *un_dvp; /* parent unionfs vnode */
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struct vnode *un_vnode; /* Back pointer */
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LIST_HEAD(, unionfs_node_status) un_unshead;
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/* unionfs status head */
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LIST_HEAD(unionfs_node_hashhead, unionfs_node) *un_hashtbl;
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/* dir vnode hash table */
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union {
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LIST_ENTRY(unionfs_node) un_hash; /* hash list entry */
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STAILQ_ENTRY(unionfs_node) un_rele; /* deferred release list */
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};
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char *un_path; /* path */
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int un_pathlen; /* strlen of path */
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int un_flag; /* unionfs node flag */
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};
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/*
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* unionfs node flags
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* It needs the vnode with exclusive lock, when changing the un_flag variable.
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*/
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#define UNIONFS_OPENEXTL 0x01 /* openextattr (lower) */
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#define UNIONFS_OPENEXTU 0x02 /* openextattr (upper) */
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extern struct vop_vector unionfs_vnodeops;
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static inline struct unionfs_node *
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unionfs_check_vnode(struct vnode *vp, const char *file __unused,
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int line __unused)
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{
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/*
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* unionfs_lock() needs the NULL check here, as it explicitly
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* handles the case in which the vnode has been vgonel()'ed.
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*/
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KASSERT(vp->v_op == &unionfs_vnodeops || vp->v_data == NULL,
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("%s:%d: non-unionfs vnode %p", file, line, vp));
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return ((struct unionfs_node *)vp->v_data);
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}
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#define MOUNTTOUNIONFSMOUNT(mp) ((struct unionfs_mount *)((mp)->mnt_data))
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#define VTOUNIONFS(vp) unionfs_check_vnode(vp, __FILE__, __LINE__)
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#define UNIONFSTOV(xp) ((xp)->un_vnode)
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int unionfs_init(struct vfsconf *);
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int unionfs_uninit(struct vfsconf *);
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int unionfs_nodeget(struct mount *, struct vnode *, struct vnode *,
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struct vnode *, struct vnode **, struct componentname *);
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void unionfs_noderem(struct vnode *);
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void unionfs_get_node_status(struct unionfs_node *, struct thread *,
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struct unionfs_node_status **);
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void unionfs_tryrem_node_status(struct unionfs_node *,
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struct unionfs_node_status *);
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int unionfs_check_rmdir(struct vnode *, struct ucred *, struct thread *td);
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int unionfs_copyfile(struct unionfs_node *, int, struct ucred *,
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struct thread *);
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void unionfs_create_uppervattr_core(struct unionfs_mount *, struct vattr *,
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struct vattr *, struct thread *);
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int unionfs_create_uppervattr(struct unionfs_mount *, struct vnode *,
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struct vattr *, struct ucred *, struct thread *);
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int unionfs_mkshadowdir(struct unionfs_mount *, struct vnode *,
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struct unionfs_node *, struct componentname *, struct thread *);
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int unionfs_mkwhiteout(struct vnode *, struct vnode *,
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struct componentname *, struct thread *, char *, int);
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int unionfs_relookup(struct vnode *, struct vnode **,
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struct componentname *, struct componentname *, struct thread *,
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char *, int, u_long);
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int unionfs_relookup_for_create(struct vnode *, struct componentname *,
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struct thread *);
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int unionfs_relookup_for_delete(struct vnode *, struct componentname *,
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struct thread *);
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int unionfs_relookup_for_rename(struct vnode *, struct componentname *,
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struct thread *);
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void unionfs_forward_vop_start_pair(struct vnode *, int *,
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struct vnode *, int *);
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bool unionfs_forward_vop_finish_pair(struct vnode *, struct vnode *, int,
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struct vnode *, struct vnode *, int);
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static inline void
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unionfs_forward_vop_start(struct vnode *basevp, int *lkflags)
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{
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unionfs_forward_vop_start_pair(basevp, lkflags, NULL, NULL);
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}
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static inline bool
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unionfs_forward_vop_finish(struct vnode *unionvp, struct vnode *basevp,
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int lkflags)
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{
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return (unionfs_forward_vop_finish_pair(unionvp, basevp, lkflags,
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NULL, NULL, 0));
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}
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#define UNIONFSVPTOLOWERVP(vp) (VTOUNIONFS(vp)->un_lowervp)
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#define UNIONFSVPTOUPPERVP(vp) (VTOUNIONFS(vp)->un_uppervp)
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#ifdef MALLOC_DECLARE
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MALLOC_DECLARE(M_UNIONFSNODE);
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MALLOC_DECLARE(M_UNIONFSPATH);
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#endif
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#ifdef UNIONFS_DEBUG
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#define UNIONFSDEBUG(format, args...) printf(format ,## args)
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#else
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#define UNIONFSDEBUG(format, args...)
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#endif /* UNIONFS_DEBUG */
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#endif /* _KERNEL */
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