195 lines
5.2 KiB
Groff
195 lines
5.2 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 1996 Doug Rabson
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.\"
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.\" All rights reserved.
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.\"
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.\" This program is free software.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 27, 2017
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.Dt VOP_LOOKUP 9
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.Os
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.Sh NAME
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.Nm VOP_LOOKUP
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.Nd lookup a component of a pathname
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/vnode.h
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.In sys/namei.h
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.Ft int
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.Fn VOP_LOOKUP "struct vnode *dvp" "struct vnode **vpp" "struct componentname *cnp"
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.Sh DESCRIPTION
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This entry point looks up a single pathname component in a given directory.
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.Pp
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Its arguments are:
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.Bl -tag -width vpp
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.It Fa dvp
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The locked vnode of the directory to search.
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.It Fa vpp
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The address of a variable where the resulting locked vnode should be stored.
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.It Fa cnp
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The pathname component to be searched for.
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.El
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.Pp
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.Fa Cnp
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is a pointer to a componentname structure defined as follows:
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.Bd -literal
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struct componentname {
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/*
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* Arguments to lookup.
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*/
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u_long cn_nameiop; /* namei operation */
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u_long cn_flags; /* flags to namei */
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struct thread *cn_thread; /* thread requesting lookup */
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struct ucred *cn_cred; /* credentials */
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/*
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* Shared between lookup and commit routines.
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*/
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char *cn_pnbuf; /* pathname buffer */
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char *cn_nameptr; /* pointer to looked up name */
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long cn_namelen; /* length of looked up component */
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u_long cn_hash; /* hash value of looked up name */
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};
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.Ed
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.Pp
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Convert a component of a pathname into a pointer to a locked vnode.
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This is a very central and rather complicated routine.
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If the file system is not maintained in a strict tree hierarchy,
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this can result in a deadlock situation.
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.Pp
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The
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.Fa cnp->cn_nameiop
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argument is
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.Dv LOOKUP ,
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.Dv CREATE ,
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.Dv RENAME ,
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or
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.Dv DELETE
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depending on the intended use of the object.
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When
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.Dv CREATE ,
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.Dv RENAME ,
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or
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.Dv DELETE
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is specified, information usable in
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creating, renaming, or deleting a directory entry may be calculated.
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.Pp
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Overall outline of VOP_LOOKUP:
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.Bd -ragged -offset indent
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Check accessibility of directory.
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Look for name in cache, if found, then return name.
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Search for name in directory, goto to found or notfound as appropriate.
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.Ed
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.Pp
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notfound:
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.Bd -ragged -offset indent
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If creating or renaming and at end of pathname,
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return
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.Er EJUSTRETURN ,
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leaving info on available slots else return
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.Er ENOENT .
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.Ed
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.Pp
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found:
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.Bd -ragged -offset indent
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If at end of path and deleting, return information to allow delete.
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If at end of path and renaming, lock target
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inode and return info to allow rename.
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If not at end, add name to cache; if at end and neither creating
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nor deleting, add name to cache.
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.Ed
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.Sh LOCKS
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The directory,
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.Fa dvp
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should be locked on entry.
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If an error (note: the return value
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.Er EJUSTRETURN
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is not considered an error)
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is detected, it will be returned locked.
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Otherwise, it will be unlocked unless both
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.Dv LOCKPARENT
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and
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.Dv ISLASTCN
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are specified in
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.Fa cnp->cn_flags .
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If an entry is found in the directory, it will be returned locked.
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.Sh RETURN VALUES
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Zero is returned with
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.Fa *vpp
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set to the locked vnode of the file if the component is found.
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If the component being searched for is ".", then the vnode just has
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an extra reference added to it with
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.Xr vref 9 .
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The caller must take care to release the locks appropriately in this
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case.
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.Pp
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If the component is not found and the operation is
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.Dv CREATE
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or
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.Dv RENAME ,
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the flag
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.Dv ISLASTCN
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is specified and the operation would succeed, the special return value
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.Er EJUSTRETURN
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is returned.
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Otherwise, an appropriate error code is returned.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er ENOTDIR
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The vnode
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.Fa dvp
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does not represent a directory.
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.It Bq Er ENOENT
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The component
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.Fa dvp
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was not found in this directory.
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.It Bq Er EACCES
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Access for the specified operation is denied.
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.It Bq Er EJUSTRETURN
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A
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.Dv CREATE
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or
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.Dv RENAME
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operation would be successful.
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.El
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.Sh SEE ALSO
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.Xr vnode 9 ,
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.Xr VOP_ACCESS 9 ,
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.Xr VOP_CREATE 9 ,
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.Xr VOP_MKDIR 9 ,
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.Xr VOP_MKNOD 9 ,
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.Xr VOP_RENAME 9 ,
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.Xr VOP_SYMLINK 9
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.Sh HISTORY
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The function
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.Nm
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appeared in
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.Bx 4.3 .
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.Sh AUTHORS
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This manual page was written by
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.An Doug Rabson ,
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with some text from comments in
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.Pa ufs_lookup.c .
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