/*      $NetBSD: overlay_vfsops.c,v 1.74 2025/02/16 18:38:58 joe Exp $  */

/*
 * Copyright (c) 1999, 2000 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
 */

/*
 * Overlay Layer
 * (See overlay_vnops.c for a description of what this does.)
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: overlay_vfsops.c,v 1.74 2025/02/16 18:38:58 joe Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/module.h>
#include <miscfs/overlay/overlay.h>
#include <miscfs/genfs/layer_extern.h>

MODULE(MODULE_CLASS_VFS, overlay, "layerfs");

VFS_PROTOS(ov);

#define NOVERLAYNODECACHE       16

/*
 * Mount overlay layer
 */
int
ov_mount(struct mount *mp, const char *path, void *data, size_t *data_len)
{
        struct lwp *l = curlwp;
        int error = 0;
        struct overlay_args *args = data;
        struct vnode *lowerrootvp, *vp;
        struct overlay_mount *nmp;
        struct layer_mount *lmp;

#ifdef OVERLAYFS_DIAGNOSTIC
        printf("ov_mount(mp = %p)\n", mp);
#endif

        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 lower node
         */
        lowerrootvp = mp->mnt_vnodecovered;
        vref(lowerrootvp);
        if ((error = vn_lock(lowerrootvp, LK_EXCLUSIVE))) {
                vrele(lowerrootvp);
                return (error);
        }

        /*
         * First cut at fixing up upper mount point
         */
        nmp = kmem_zalloc(sizeof(struct overlay_mount), KM_SLEEP);

        mp->mnt_data = nmp;

        /*
         * 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 overlay_mount));
                return error;
        }

        nmp->ovm_size = sizeof (struct overlay_node);
        nmp->ovm_tag = VT_OVERLAY;
        nmp->ovm_bypass = layer_bypass;
        nmp->ovm_vnodeop_p = overlay_vnodeop_p;

        /*
         * Fix up overlay node for root vnode
         */
        VOP_UNLOCK(lowerrootvp);
        error = layer_node_create(mp, lowerrootvp, &vp);
        /*
         * Make sure the fixup worked
         */
        if (error) {
                vrele(lowerrootvp);
                kmem_free(nmp, sizeof(struct overlay_mount));
                return error;
        }

        /*
         * Keep a held reference to the root vnode.
         * It is vrele'd in ov_unmount.
         */
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        vp->v_vflag |= VV_ROOT;
        nmp->ovm_rootvp = vp;
        VOP_UNLOCK(vp);

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

        if (mp->mnt_lower->mnt_flag & MNT_LOCAL)
                mp->mnt_flag |= MNT_LOCAL;
#ifdef OVERLAYFS_DIAGNOSTIC
        printf("ov_mount: lower %s, alias at %s\n",
            mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
#endif
        return 0;
}

/*
 * Free reference to overlay layer
 */
int
ov_unmount(struct mount *mp, int mntflags)
{
        struct vnode *overlay_rootvp = MOUNTTOOVERLAYMOUNT(mp)->ovm_rootvp;
        struct overlay_mount *omp;
        int error;
        int flags = 0;

#ifdef OVERLAYFS_DIAGNOSTIC
        printf("ov_unmount(mp = %p)\n", mp);
#endif

        if (mntflags & MNT_FORCE)
                flags |= FORCECLOSE;

        if (vrefcnt(overlay_rootvp) > 1 && (mntflags & MNT_FORCE) == 0)
                return (EBUSY);
        if ((error = vflush(mp, overlay_rootvp, flags)) != 0)
                return (error);

#ifdef OVERLAYFS_DIAGNOSTIC
        vprint("alias root of lower", overlay_rootvp);
#endif
        /*
         * Blow it away for future re-use
         */
        vgone(overlay_rootvp);
        /*
         * Finally, throw away the overlay_mount structure
         */
        omp = mp->mnt_data;
        kmem_free(omp, sizeof(struct overlay_mount));
        mp->mnt_data = NULL;
        return 0;
}

extern const struct vnodeopv_desc overlay_vnodeop_opv_desc;

const struct vnodeopv_desc * const ov_vnodeopv_descs[] = {
        &overlay_vnodeop_opv_desc,
        NULL,
};

struct vfsops overlay_vfsops = {
        .vfs_name = MOUNT_OVERLAY,
        .vfs_min_mount_data = sizeof (struct overlay_args),
        .vfs_mount = ov_mount,
        .vfs_start = layerfs_start,
        .vfs_unmount = ov_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 = ov_vnodeopv_descs
};

SYSCTL_SETUP(overlay_sysctl_setup, "overlay fs sysctl")
{

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT, CTLTYPE_NODE, "overlay",
                       SYSCTL_DESCR("Overlay file system"),
                       NULL, 0, NULL, 0,
                       CTL_VFS, CTL_CREATE, CTL_EOL);
}

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

        switch (cmd) {
        case MODULE_CMD_INIT:
                error = vfs_attach(&overlay_vfsops);
                break;
        case MODULE_CMD_FINI:
                error = vfs_detach(&overlay_vfsops);
                break;
        default:
                error = ENOTTY;
                break;
        }

        return (error);
}