206 lines
6.6 KiB
Groff
206 lines
6.6 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 1998, 1999 Eivind Eklund
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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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.\"
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.\" If you integrate this manpage in another OS, I'd appreciate a note
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.\" - eivind@FreeBSD.org
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 16, 1998
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.Os
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.Dt NAMEI 9
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.Sh NAME
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.Nm namei ,
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.Nm NDINIT
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.Nd convert pathname to a pointer to a locked vnode.
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/namei.h>
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.Ft int
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.Fn namei "struct nameidata *ndp"
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.Ft void
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.Fn NDINIT "struct nameidata *ndp" "int operation" "int operflags" "int segflag" "const char *path" "struct proc *proc"
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.Fn NDFREE "struct nameidata *ndp" "int operflags"
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.Sh DESCRIPTION
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.Fn namei
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is used to get from a pathname to a vnode for the object.
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This is a necessity to start doing VFS operations. The vnode
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returned will have its reference count increased; when you're through
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with it, you have to release it using either
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.Xr vrele 9
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or
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.Xr vput 9 ,
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depending on whether you specified the LOCKLEAF flag or not.
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.Pp
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To initialize the nameidata struct, you usually use
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.Fn NDINIT .
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It takes the following arguments:
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.Pp
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.Bl -tag -width nameidatap
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.It Ar nameidatap
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pointer to the struct nameidata to initialize
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.It Ar operation
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The operation to have
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.Fn namei
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do. The relevant operations are
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.Dv LOOKUP ,
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.Dv CREATE ,
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.Dv DELETE ,
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and
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.Dv RENAME .
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The latter three are just setup for those
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effects; just calling
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.Fn namei
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will not result in
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.Fn VOP_RENAME
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being called.
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.It Ar operflags
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Operation flags. Several of these can be effective at the same time.
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.It Ar segflag
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Segment indicator. This tells if the name of the object is in
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userspace (UIO_USERSPACE) or in the kernel address space (UIO_SYSSPACE).
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.It Ar path
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Pointer to pathname buffer (the file or directory name that will be
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looked up)
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.It Ar proc
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Which process context to use for the
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.Fn namei
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locks.
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.El
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.Sh NAMEI OPERATION FLAGS
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.Fn namei
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takes the following set of 'operation flags' that influence
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how it operates:
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.Bl -tag -width WANTPARENT
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.It Dv LOCKLEAF
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Lock vnode on return. This is a full lock of the vnode; you'll have to use
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.Xr VOP_UNLOCK 9
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to release the lock (or use
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.Xr vput 9
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to release the lock and do a
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.Xr vrele 9 ,
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all in one).
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.It Dv LOCKPARENT
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Make
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.Fn namei
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also return the parent (directory) vnode (in nd.ni_dvp),
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in locked state, unless the dvp is identical to the vp, in which case the dvp
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is not locked per se (but may be locked due to LOCKLEAF).
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If you get a lock, remember to release the lock (using
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.Xr vput 9
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or
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.Xr VOP_UNLOCK 9
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and
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.Xr vrele 9 . )
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.It Dv WANTPARENT
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Make
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.Fn namei
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also return the parent (directory) vnode, in unlocked
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state. Remember to release it (using
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.Xr vrele 9 . )
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.It Dv NOCACHE
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Avoid
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.Fn namei
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creating this entry in the namecache if it is not
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already present. Normally
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.Fn namei
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will add entries to the name cache
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if they're not already there.
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.It Dv FOLLOW
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With this flag,
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.Fn namei
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will follow the symbolic link if the last part
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of the path supplied is a symbolic link (i.e., it will return a vnode
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for whatever the link points at, instead for the link itself).
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.It Dv NOOBJ
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Do not call
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.Fn vfs_object_create
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for the returned vnode even if it is
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just a VREG and we're able to (ie, it is locked).
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.It Dv NOFOLLOW
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Do not follow symbolic links (pseudo).
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This flag is not looked for by the actual code, which looks for
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FOLLOW.
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NOFOLLOW is used to indicate to the source code reader that symlinks
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are intentionally not followed.
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.El
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.Sh ALLOCATED ELEMENTS
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.Bl -tag -width WANTPARENT
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.It Dv ni_startdir
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Where we did lookup relative to.
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In the normal case, this is either the current directory or the root.
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It is the current directory if the name passed in doesn't start with /
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and we have not gone through any symlinks with an absolute path, and
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the root otherwise.
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.Pp
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In this case, it is is only used by lookup(), and should not be
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considered valid after a call to namei().
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.Pp
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If SAVESTART is set, this is set to the same as ni_dvp, with an extra
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VREF().
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.Pp
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To block NDFREE from releasing ni_startdir when it is set, use the
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flag NDF_NO_STARTDIR_RELE.
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.It Dv ni_dvp
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The directory vp for the directory the object we're looking up is in.
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This is available on successful return if LOCKPARENT or WANTPARENT is
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set. It is locked if LOCKPARENT is set. Freeing this in NDFREE can
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be inhibited by NDF_NO_DVP_RELE, NDF_NO_DVP_PUT, or NDF_NO_DVP_UNLOCK
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(with the obvious effects).
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.It Dv ni_vp
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The vp for the target of the of the pathname exists, NULL otherwise.
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The vp is returned with increased reference count (VREF'ed). If
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LOCKLEAF is set, it is also locked.
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.Pp
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Freeing this in NDFREE can be inhibited by NDF_NO_VP_RELE,
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NDF_NO_VP_PUT, or NDF_NO_VP_UNLOCK (with the obvious effects).
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.It Dv ni_cnd.cn_pnbuf
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Path name buffer. This is allocated through zalloc(namei_zone)
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and freed through zfree(namei_zone, ...).
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.Pp
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This is available to the caller (who must free it using
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.Xr NDFREE 9 )
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if SAVESTART or SAVENAME is set.
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To free only the ni_cnd.cn_pnbuf, there is a special flags NDF_ONLY_PNBUF.
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To not free the cnd, use the flag ND_NO_FREE_PNBUF.
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.El
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.Sh BUGS
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LOCKPARENT does not always result in parent vp being locked (see details in
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description).
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This results in complications everywhere LOCKPARENT is used.
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In order to solve this for the cases that include both LOCKPARENT and LOCKLEAF,
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it will be necessary to go to recursive locking.
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.Sh SEE ALSO
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.Xr VFS 9 ,
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.Xr vnode 9 ,
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.Pa src/sys/kern/vfs_lookup.c
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.Sh AUTHORS
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This man page was written by
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.An Eivind Eklund .
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