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.TH "D_LOOKUP" "9" "17 July 2003" "" ""

.SH NAME
d_lookup \- search for a dentry
.SH SYNOPSIS
.sp
\fB
.sp
struct dentry * d_lookup  (struct dentry * \fIparent\fB, struct qstr * \fIname\fB);
\fR
.SH "ARGUMENTS"
.TP
\fB\fIparent\fB\fR
parent dentry
.TP
\fB\fIname\fB\fR
qstr of name we wish to find
.SH "DESCRIPTION"
.PP
Searches the children of the parent dentry for the name in question. If
the dentry is found its reference count is incremented and the dentry
is returned. The caller must use d_put to free the entry when it has
finished using it. NULL is returned on failure.
.PP
__d_lookup is dcache_lock free. The hash list is protected using RCU.
Memory barriers are used while updating and doing lockless traversal. 
To avoid races with d_move while rename is happening, d_move_count is 
used. 
.PP
Overflows in \fBmemcmp\fR, while d_move, are avoided by keeping the length
and name pointer in one structure pointed by d_qstr.
.PP
\fBrcu_read_lock\fR and \fBrcu_read_unlock\fR are used to disable preemption while
lookup is going on.
.PP
d_lru list is not updated, which can leave non-zero d_count dentries
around in d_lru list.
.PP
\fBd_lookup\fR is protected against the concurrent renames in some unrelated
directory using the seqlockt_t rename_lock.
.SH "ABOUT THIS DOCUMENT"
.PP
This documentation is free software; you can redistribute
it and/or modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later
version.
.PP
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
.PP
You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
MA 02111-1307 USA
.PP
For more details see the file COPYING in the source
distribution of Linux.
.PP
If you have comments on the formatting of this manpage, then please contact
Michael Still (mikal@stillhq.com).
.PP
This documentation was generated with kernel version 2.5.72.