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vfs_hooks.c revision 1.4 
      1 /*	$NetBSD: vfs_hooks.c,v 1.4 2008/05/10 02:26:09 rumble 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 1.4 2008/05/10 02:26:09 rumble 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()
     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 = 0;							\
    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 args;				\
    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