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vfs_cwd.c revision 1.3 
      1 /*	$NetBSD: vfs_cwd.c,v 1.3 2010/01/08 11:35:10 pooka Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2008 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 /*
     30  * Current working directory.
     31  */
     32 
     33 #include <sys/cdefs.h>
     34 __KERNEL_RCSID(0, "$NetBSD: vfs_cwd.c,v 1.3 2010/01/08 11:35:10 pooka Exp $");
     35 
     36 #include <sys/param.h>
     37 #include <sys/atomic.h>
     38 #include <sys/filedesc.h>
     39 #include <sys/proc.h>
     40 #include <sys/vnode.h>
     41 
     42 static int	cwdi_ctor(void *, void *, int);
     43 static void	cwdi_dtor(void *, void *);
     44 
     45 static pool_cache_t cwdi_cache;
     46 
     47 void
     48 cwd_sys_init(void)
     49 {
     50 
     51 	cwdi_cache = pool_cache_init(sizeof(struct cwdinfo), coherency_unit,
     52 	    0, 0, "cwdi", NULL, IPL_NONE, cwdi_ctor, cwdi_dtor, NULL);
     53 	KASSERT(cwdi_cache != NULL);
     54 }
     55 
     56 /*
     57  * Create an initial cwdinfo structure, using the same current and root
     58  * directories as curproc.
     59  */
     60 struct cwdinfo *
     61 cwdinit(void)
     62 {
     63 	struct cwdinfo *cwdi;
     64 	struct cwdinfo *copy;
     65 
     66 	cwdi = pool_cache_get(cwdi_cache, PR_WAITOK);
     67 	copy = curproc->p_cwdi;
     68 
     69 	rw_enter(&copy->cwdi_lock, RW_READER);
     70 	cwdi->cwdi_cdir = copy->cwdi_cdir;
     71 	if (cwdi->cwdi_cdir)
     72 		vref(cwdi->cwdi_cdir);
     73 	cwdi->cwdi_rdir = copy->cwdi_rdir;
     74 	if (cwdi->cwdi_rdir)
     75 		vref(cwdi->cwdi_rdir);
     76 	cwdi->cwdi_edir = copy->cwdi_edir;
     77 	if (cwdi->cwdi_edir)
     78 		vref(cwdi->cwdi_edir);
     79 	cwdi->cwdi_cmask = copy->cwdi_cmask;
     80 	cwdi->cwdi_refcnt = 1;
     81 	rw_exit(&copy->cwdi_lock);
     82 
     83 	return (cwdi);
     84 }
     85 
     86 static int
     87 cwdi_ctor(void *arg, void *obj, int flags)
     88 {
     89 	struct cwdinfo *cwdi = obj;
     90 
     91 	rw_init(&cwdi->cwdi_lock);
     92 
     93 	return 0;
     94 }
     95 
     96 static void
     97 cwdi_dtor(void *arg, void *obj)
     98 {
     99 	struct cwdinfo *cwdi = obj;
    100 
    101 	rw_destroy(&cwdi->cwdi_lock);
    102 }
    103 
    104 /*
    105  * Make p2 share p1's cwdinfo.
    106  */
    107 void
    108 cwdshare(struct proc *p2)
    109 {
    110 	struct cwdinfo *cwdi;
    111 
    112 	cwdi = curproc->p_cwdi;
    113 
    114 	atomic_inc_uint(&cwdi->cwdi_refcnt);
    115 	p2->p_cwdi = cwdi;
    116 }
    117 
    118 /*
    119  * Make sure proc has only one reference to its cwdi, creating
    120  * a new one if necessary.
    121  */
    122 void
    123 cwdunshare(struct proc *p)
    124 {
    125 	struct cwdinfo *cwdi = p->p_cwdi;
    126 
    127 	if (cwdi->cwdi_refcnt > 1) {
    128 		cwdi = cwdinit();
    129 		cwdfree(p->p_cwdi);
    130 		p->p_cwdi = cwdi;
    131 	}
    132 }
    133 
    134 /*
    135  * Release a cwdinfo structure.
    136  */
    137 void
    138 cwdfree(struct cwdinfo *cwdi)
    139 {
    140 
    141 	if (atomic_dec_uint_nv(&cwdi->cwdi_refcnt) > 0)
    142 		return;
    143 
    144 	vrele(cwdi->cwdi_cdir);
    145 	if (cwdi->cwdi_rdir)
    146 		vrele(cwdi->cwdi_rdir);
    147 	if (cwdi->cwdi_edir)
    148 		vrele(cwdi->cwdi_edir);
    149 	pool_cache_put(cwdi_cache, cwdi);
    150 }
    151