/*      $NetBSD: vfs_hooks.c,v 1.9 2024/12/07 02:27:38 riastradh Exp $  */

/*-
* Copyright (c) 2005 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Julio M. Merino Vidal.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

/*
* VFS hooks.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_hooks.c,v 1.9 2024/12/07 02:27:38 riastradh Exp $");

#include <sys/param.h>

#include <sys/errno.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/queue.h>
#include <sys/sdt.h>

LIST_HEAD(vfs_hooks_head, vfs_hooks) vfs_hooks_head =
   LIST_HEAD_INITIALIZER(vfs_hooks_head);

kmutex_t vfs_hooks_lock;

void
vfs_hooks_init(void)
{

       mutex_init(&vfs_hooks_lock, MUTEX_DEFAULT, IPL_NONE);
}

int
vfs_hooks_attach(struct vfs_hooks *vfs_hooks)
{

       mutex_enter(&vfs_hooks_lock);
       LIST_INSERT_HEAD(&vfs_hooks_head, vfs_hooks, vfs_hooks_list);
       mutex_exit(&vfs_hooks_lock);

       return 0;
}

int
vfs_hooks_detach(struct vfs_hooks *vfs_hooks)
{
       struct vfs_hooks *hp;
       int ret = 0;

       mutex_enter(&vfs_hooks_lock);
       LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) {
               if (hp == vfs_hooks) {
                       LIST_REMOVE(hp, vfs_hooks_list);
                       break;
               }
       }
       if (hp == NULL)
               ret = SET_ERROR(ESRCH);
       mutex_exit(&vfs_hooks_lock);

       return ret;
}

/*
* Macro to be used in one of the vfs_hooks_* function for hooks that
* return an error code.  Calls will stop as soon as one of the hooks
* fails.
*/
#define VFS_HOOKS_W_ERROR(func, fargs, hook, hargs)                     \
int                                                                     \
func fargs                                                              \
{                                                                       \
       int error;                                                      \
       struct vfs_hooks *hp;                                           \
                                                                       \
       error = EJUSTRETURN;                                            \
                                                                       \
       mutex_enter(&vfs_hooks_lock);                                   \
       LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) {             \
               if (hp-> hook != NULL) {                                \
                       error = hp-> hook hargs;                        \
                       if (error != 0)                                 \
                               break;                                  \
               }                                                       \
       }                                                               \
       mutex_exit(&vfs_hooks_lock);                                    \
                                                                       \
       return error;                                                   \
}

/*
* Macro to be used in one of the vfs_hooks_* function for hooks that
* do not return any error code.  All hooks will be executed
* unconditionally.
*/
#define VFS_HOOKS_WO_ERROR(func, fargs, hook, hargs)                    \
void                                                                    \
func fargs                                                              \
{                                                                       \
       struct vfs_hooks *hp;                                           \
                                                                       \
       mutex_enter(&vfs_hooks_lock);                                   \
       LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) {             \
               if (hp-> hook != NULL)                                  \
                       hp-> hook hargs;                                \
       }                                                               \
       mutex_exit(&vfs_hooks_lock);                                    \
}

/*
* Routines to iterate over VFS hooks lists and execute them.
*/

VFS_HOOKS_WO_ERROR(vfs_hooks_unmount, (struct mount *mp), vh_unmount, (mp));
VFS_HOOKS_W_ERROR(vfs_hooks_reexport, (struct mount *mp, const char *path, void *data), vh_reexport, (mp, path, data));