sys/kern/vfs_cwd.c

   1 /*      $NetBSD: vfs_cwd.c,v 1.2 2009/09/24 06:14:22 yamt 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 1.2 2009/09/24 06:14:22 yamt 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 }