sys/kern/vfs_hooks.c

   1 /*      $NetBSD: vfs_hooks.c,v 1.5 2008/11/19 18:36:07 ad Exp $ */
   2
   3 /*-
   4  * Copyright (c) 2005 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Julio M. Merino Vidal.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * VFS hooks.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 __KERNEL_RCSID(0, "$NetBSD: vfs_hooks.c,v 1.5 2008/11/19 18:36:07 ad Exp $");
  38
  39 #include <sys/param.h>
  40 #include <sys/queue.h>
  41 #include <sys/mount.h>
  42 #include <sys/mutex.h>
  43
  44 LIST_HEAD(vfs_hooks_head, vfs_hooks) vfs_hooks_head =
  45     LIST_HEAD_INITIALIZER(vfs_hooks_head);
  46
  47 kmutex_t vfs_hooks_lock;
  48
  49 void
  50 vfs_hooks_init(void)
  51 {
  52
  53         mutex_init(&vfs_hooks_lock, MUTEX_DEFAULT, IPL_NONE);
  54 }
  55
  56 int
  57 vfs_hooks_attach(struct vfs_hooks *vfs_hooks)
  58 {
  59
  60         mutex_enter(&vfs_hooks_lock);
  61         LIST_INSERT_HEAD(&vfs_hooks_head, vfs_hooks, vfs_hooks_list);
  62         mutex_exit(&vfs_hooks_lock);
  63
  64         return (0);
  65 }
  66
  67 int
  68 vfs_hooks_detach(struct vfs_hooks *vfs_hooks)
  69 {
  70         struct vfs_hooks *hp;
  71         int ret = 0;
  72
  73         mutex_enter(&vfs_hooks_lock);
  74         LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) {
  75                 if (hp == vfs_hooks) {
  76                         LIST_REMOVE(hp, vfs_hooks_list);
  77                         break;
  78                 }
  79         }
  80         if (hp == NULL)
  81                 ret = ESRCH;
  82         mutex_exit(&vfs_hooks_lock);
  83
  84         return (ret);
  85 }
  86
  87 /*
  88  * Macro to be used in one of the vfs_hooks_* function for hooks that
  89  * return an error code.  Calls will stop as soon as one of the hooks
  90  * fails.
  91  */
  92 #define VFS_HOOKS_W_ERROR(func, fargs, hook, hargs)                     \
  93 int                                                                     \
  94 func fargs                                                              \
  95 {                                                                       \
  96         int error;                                                      \
  97         struct vfs_hooks *hp;                                           \
  98                                                                         \
  99         error = EJUSTRETURN;                                            \
 100                                                                         \
 101         mutex_enter(&vfs_hooks_lock);                                   \
 102         LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) {             \
 103                 if (hp-> hook != NULL) {                                \
 104                         error = hp-> hook hargs;                        \
 105                         if (error != 0)                                 \
 106                                 break;                                  \
 107                 }                                                       \
 108         }                                                               \
 109         mutex_exit(&vfs_hooks_lock);                                    \
 110                                                                         \
 111         return error;                                                   \
 112 }
 113
 114 /*
 115  * Macro to be used in one of the vfs_hooks_* function for hooks that
 116  * do not return any error code.  All hooks will be executed
 117  * unconditionally.
 118  */
 119 #define VFS_HOOKS_WO_ERROR(func, fargs, hook, hargs)                    \
 120 void                                                                    \
 121 func fargs                                                              \
 122 {                                                                       \
 123         struct vfs_hooks *hp;                                           \
 124                                                                         \
 125         mutex_enter(&vfs_hooks_lock);                                   \
 126         LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) {             \
 127                 if (hp-> hook != NULL)                                  \
 128                         hp-> hook hargs;                                \
 129         }                                                               \
 130         mutex_exit(&vfs_hooks_lock);                                    \
 131 }
 132
 133 /*
 134  * Routines to iterate over VFS hooks lists and execute them.
 135  */
 136
 137 VFS_HOOKS_WO_ERROR(vfs_hooks_unmount, (struct mount *mp), vh_unmount, (mp));
 138 VFS_HOOKS_W_ERROR(vfs_hooks_reexport, (struct mount *mp, const char *path, void *data), vh_reexport, (mp, path, data));