/*      $NetBSD: null_vfsops.c,v 1.101 2023/02/06 10:32:58 hannken Exp $        */

/*
* Copyright (c) 1999 National Aeronautics & Space Administration
* All rights reserved.
*
* This software was written by William Studenmund of the
* Numerical Aerospace Simulation Facility, NASA Ames Research Center.
*
* 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.
* 3. Neither the name of the National Aeronautics & Space Administration
*    nor the names of its contributors may be used to endorse or promote
*    products derived from this software without specific prior written
*    permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
* ``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 ADMINISTRATION OR CONTRIB-
* UTORS 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.
*/

/*
* Copyright (c) 1992, 1993, 1995
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software donated to Berkeley by
* Jan-Simon Pendry.
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
*      from: Id: lofs_vfsops.c,v 1.9 1992/05/30 10:26:24 jsp Exp
*      from: @(#)lofs_vfsops.c 1.2 (Berkeley) 6/18/92
*      @(#)null_vfsops.c       8.7 (Berkeley) 5/14/95
*/

/*
* Null file-system: VFS operations.
*
* See null_vnops.c for a description.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: null_vfsops.c,v 1.101 2023/02/06 10:32:58 hannken Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/module.h>

#include <miscfs/nullfs/null.h>
#include <miscfs/genfs/layer_extern.h>

MODULE(MODULE_CLASS_VFS, null, "layerfs");

VFS_PROTOS(nullfs);

int
nullfs_mount(struct mount *mp, const char *path, void *data, size_t *data_len)
{
       struct vnode *lowerrootvp, *vp;
       struct null_args *args = data;
       struct null_mount *nmp;
       struct layer_mount *lmp;
       struct pathbuf *pb;
       struct nameidata nd;
       int error;

       if (args == NULL)
               return EINVAL;
       if (*data_len < sizeof(*args))
               return EINVAL;

       if (mp->mnt_flag & MNT_GETARGS) {
               lmp = MOUNTTOLAYERMOUNT(mp);
               if (lmp == NULL)
                       return EIO;
               args->la.target = NULL;
               *data_len = sizeof(*args);
               return 0;
       }

       /* Update is not supported. */
       if (mp->mnt_flag & MNT_UPDATE)
               return EOPNOTSUPP;

       /* Find the lower vnode and lock it. */
       error = pathbuf_copyin(args->la.target, &pb);
       if (error) {
               return error;
       }
       NDINIT(&nd, LOOKUP, FOLLOW|LOCKLEAF, pb);
       if ((error = namei(&nd)) != 0) {
               pathbuf_destroy(pb);
               return error;
       }
       lowerrootvp = nd.ni_vp;
       pathbuf_destroy(pb);

       /* Create the mount point. */
       nmp = kmem_zalloc(sizeof(struct null_mount), KM_SLEEP);
       mp->mnt_data = nmp;
       mp->mnt_iflag |= lowerrootvp->v_mount->mnt_iflag & IMNT_MPSAFE;
       mp->mnt_iflag |= lowerrootvp->v_mount->mnt_iflag & IMNT_SHRLOOKUP;

       /*
        * Make sure that the mount point is sufficiently initialized
        * that the node create call will work.
        */
       vfs_getnewfsid(mp);
       error = vfs_set_lowermount(mp, lowerrootvp->v_mount);
       if (error) {
               vput(lowerrootvp);
               kmem_free(nmp, sizeof(struct null_mount));
               return error;
       }

       nmp->nullm_size = sizeof(struct null_node);
       nmp->nullm_tag = VT_NULL;
       nmp->nullm_bypass = layer_bypass;
       nmp->nullm_vnodeop_p = null_vnodeop_p;

       /* Setup a null node for root vnode. */
       VOP_UNLOCK(lowerrootvp);
       error = layer_node_create(mp, lowerrootvp, &vp);
       if (error) {
               vrele(lowerrootvp);
               kmem_free(nmp, sizeof(struct null_mount));
               return error;
       }
       /*
        * Keep a held reference to the root vnode.  It will be released on
        * umount.  Note: nullfs is MP-safe.
        */
       vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
       vp->v_vflag |= VV_ROOT;
       nmp->nullm_rootvp = vp;
       VOP_UNLOCK(vp);

       error = set_statvfs_info(path, UIO_USERSPACE, args->la.target,
           UIO_USERSPACE, mp->mnt_op->vfs_name, mp, curlwp);
       if (error)
               return error;

       if (mp->mnt_lower->mnt_flag & MNT_LOCAL)
               mp->mnt_flag |= MNT_LOCAL;
       return 0;
}

int
nullfs_unmount(struct mount *mp, int mntflags)
{
       struct null_mount *nmp = MOUNTTONULLMOUNT(mp);
       struct vnode *null_rootvp = nmp->nullm_rootvp;
       int error, flags = 0;

       if (mntflags & MNT_FORCE)
               flags |= FORCECLOSE;

       if (vrefcnt(null_rootvp) > 1 && (mntflags & MNT_FORCE) == 0)
               return EBUSY;

       if ((error = vflush(mp, null_rootvp, flags)) != 0)
               return error;

       /* Eliminate all activity and release the vnode. */
       vgone(null_rootvp);

       /* Finally, destroy the mount point structures. */
       kmem_free(mp->mnt_data, sizeof(struct null_mount));
       mp->mnt_data = NULL;
       return 0;
}

extern const struct vnodeopv_desc null_vnodeop_opv_desc;

const struct vnodeopv_desc * const nullfs_vnodeopv_descs[] = {
       &null_vnodeop_opv_desc,
       NULL,
};

struct vfsops nullfs_vfsops = {
       .vfs_name = MOUNT_NULL,
       .vfs_min_mount_data = sizeof (struct null_args),
       .vfs_mount = nullfs_mount,
       .vfs_start = layerfs_start,
       .vfs_unmount = nullfs_unmount,
       .vfs_root = layerfs_root,
       .vfs_quotactl = layerfs_quotactl,
       .vfs_statvfs = layerfs_statvfs,
       .vfs_sync = layerfs_sync,
       .vfs_loadvnode = layerfs_loadvnode,
       .vfs_vget = layerfs_vget,
       .vfs_fhtovp = layerfs_fhtovp,
       .vfs_vptofh = layerfs_vptofh,
       .vfs_init = layerfs_init,
       .vfs_done = layerfs_done,
       .vfs_snapshot = layerfs_snapshot,
       .vfs_extattrctl = vfs_stdextattrctl,
       .vfs_suspendctl = layerfs_suspendctl,
       .vfs_renamelock_enter = layerfs_renamelock_enter,
       .vfs_renamelock_exit = layerfs_renamelock_exit,
       .vfs_fsync = (void *)eopnotsupp,
       .vfs_opv_descs = nullfs_vnodeopv_descs
};

SYSCTL_SETUP(nullfs_sysctl_setup, "nullfs sysctl")
{

       sysctl_createv(clog, 0, NULL, NULL,
           CTLFLAG_PERMANENT,
           CTLTYPE_NODE, "null",
           SYSCTL_DESCR("Loopback file system"),
           NULL, 0, NULL, 0,
           CTL_VFS, 9, CTL_EOL);
       /*
        * XXX the "9" above could be dynamic, thereby eliminating
        * one more instance of the "number to vfs" mapping problem,
        * but "9" is the order as taken from sys/mount.h
        */
}

static int
null_modcmd(modcmd_t cmd, void *arg)
{
       int error;

       switch (cmd) {
       case MODULE_CMD_INIT:
               error = vfs_attach(&nullfs_vfsops);
               if (error != 0)
                       break;
               break;
       case MODULE_CMD_FINI:
               error = vfs_detach(&nullfs_vfsops);
               if (error != 0)
                       break;
               break;
       default:
               error = ENOTTY;
               break;
       }
       return error;
}

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