/*      $NetBSD: layer_vfsops.c,v 1.56 2022/12/09 10:33:18 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
*/

/*
* Generic layer VFS operations.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: layer_vfsops.c,v 1.56 2022/12/09 10:33:18 hannken Exp $");

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

#include <miscfs/specfs/specdev.h>
#include <miscfs/genfs/genfs.h>
#include <miscfs/genfs/layer.h>
#include <miscfs/genfs/layer_extern.h>

SYSCTL_SETUP_PROTO(sysctl_vfs_layerfs_setup);

MODULE(MODULE_CLASS_MISC, layerfs, NULL);

static int
layerfs_modcmd(modcmd_t cmd, void *arg)
{

       switch (cmd) {
       case MODULE_CMD_INIT:
               return 0;
       case MODULE_CMD_FINI:
               return 0;
       default:
               return ENOTTY;
       }
       return 0;
}

/*
* VFS start.  Nothing needed here - the start routine on the underlying
* filesystem will have been called when that filesystem was mounted.
*/
int
layerfs_start(struct mount *mp, int flags)
{

#ifdef notyet
       return VFS_START(mp->mnt_lower, flags);
#else
       return 0;
#endif
}

int
layerfs_root(struct mount *mp, int lktype, struct vnode **vpp)
{
       struct vnode *vp;

       vp = MOUNTTOLAYERMOUNT(mp)->layerm_rootvp;
       if (vp == NULL) {
               *vpp = NULL;
               return EINVAL;
       }
       /*
        * Return root vnode with locked and with a reference held.
        */
       vref(vp);
       vn_lock(vp, lktype | LK_RETRY);
       *vpp = vp;
       return 0;
}

int
layerfs_quotactl(struct mount *mp, struct quotactl_args *args)
{
       int error;

       error = vfs_busy(mp);
       if (error == 0) {
               error = VFS_QUOTACTL(mp->mnt_lower, args);
               vfs_unbusy(mp);
       }

       return error;
}

int
layerfs_statvfs(struct mount *mp, struct statvfs *sbp)
{
       struct statvfs *sbuf;
       int error;

       sbuf = kmem_zalloc(sizeof(*sbuf), KM_SLEEP);
       error = vfs_busy(mp);
       if (error == 0) {
               error = VFS_STATVFS(mp->mnt_lower, sbuf);
               vfs_unbusy(mp);
       }
       if (error) {
               goto done;
       }
       /* Copy across the relevant data and fake the rest. */
       sbp->f_flag = sbuf->f_flag;
       sbp->f_bsize = sbuf->f_bsize;
       sbp->f_frsize = sbuf->f_frsize;
       sbp->f_iosize = sbuf->f_iosize;
       sbp->f_blocks = sbuf->f_blocks;
       sbp->f_bfree = sbuf->f_bfree;
       sbp->f_bavail = sbuf->f_bavail;
       sbp->f_bresvd = sbuf->f_bresvd;
       sbp->f_files = sbuf->f_files;
       sbp->f_ffree = sbuf->f_ffree;
       sbp->f_favail = sbuf->f_favail;
       sbp->f_fresvd = sbuf->f_fresvd;
       sbp->f_namemax = sbuf->f_namemax;
       copy_statvfs_info(sbp, mp);
done:
       kmem_free(sbuf, sizeof(*sbuf));
       return error;
}

int
layerfs_sync(struct mount *mp, int waitfor,
   kauth_cred_t cred)
{

       /*
        * XXX - Assumes no data cached at layer.
        */
       return 0;
}

int
layerfs_loadvnode(struct mount *mp, struct vnode *vp,
   const void *key, size_t key_len, const void **new_key)
{
       struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
       struct vnode *lowervp;
       struct layer_node *xp;

       KASSERT(key_len == sizeof(struct vnode *));
       memcpy(&lowervp, key, key_len);

       xp = kmem_alloc(lmp->layerm_size, KM_SLEEP);

       /* Share the interlock, vmobjlock, and klist with the lower node. */
       vshareilock(vp, lowervp);
       rw_obj_hold(lowervp->v_uobj.vmobjlock);
       uvm_obj_setlock(&vp->v_uobj, lowervp->v_uobj.vmobjlock);
       vshareklist(vp, lowervp);

       vp->v_tag = lmp->layerm_tag;
       vp->v_type = lowervp->v_type;
       vp->v_op = lmp->layerm_vnodeop_p;
       if (vp->v_type == VBLK || vp->v_type == VCHR)
               spec_node_init(vp, lowervp->v_rdev);
       vp->v_data = xp;
       xp->layer_vnode = vp;
       xp->layer_lowervp = lowervp;
       xp->layer_flags = 0;
       uvm_vnp_setsize(vp, 0);

       /*  Add a reference to the lower node. */
       vref(lowervp);
       *new_key = &xp->layer_lowervp;
       return 0;
}

int
layerfs_vget(struct mount *mp, ino_t ino, int lktype, struct vnode **vpp)
{
       struct vnode *vp;
       int error;

       error = vfs_busy(mp);
       if (error == 0) {
               error = VFS_VGET(mp->mnt_lower, ino, lktype, &vp);
               vfs_unbusy(mp);
       }
       if (error) {
               *vpp = NULL;
               return error;
       }
       VOP_UNLOCK(vp);
       error = layer_node_create(mp, vp, vpp);
       if (error) {
               vrele(vp);
               *vpp = NULL;
               return error;
       }
       error = vn_lock(*vpp, lktype);
       if (error) {
               vrele(*vpp);
               *vpp = NULL;
               return error;
       }
       return 0;
}

int
layerfs_fhtovp(struct mount *mp, struct fid *fidp, int lktype,
   struct vnode **vpp)
{
       struct vnode *vp;
       int error;

       error = vfs_busy(mp);
       if (error == 0) {
               error = VFS_FHTOVP(mp->mnt_lower, fidp, lktype, &vp);
               vfs_unbusy(mp);
       }
       if (error) {
               *vpp = NULL;
               return error;
       }
       VOP_UNLOCK(vp);
       error = layer_node_create(mp, vp, vpp);
       if (error) {
               vput(vp);
               *vpp = NULL;
               return (error);
       }
       error = vn_lock(*vpp, lktype);
       if (error) {
               vrele(*vpp);
               *vpp = NULL;
               return error;
       }
       return 0;
}

int
layerfs_vptofh(struct vnode *vp, struct fid *fhp, size_t *fh_size)
{

       return VFS_VPTOFH(LAYERVPTOLOWERVP(vp), fhp, fh_size);
}

/*
* layerfs_snapshot - handle a snapshot through a layered file system
*
* At present, we do NOT support snapshotting through a layered file
* system as the ffs implementation changes v_vnlock of the snapshot
* vnodes to point to one common lock. As there is no way for us to
* absolutely pass this change up the stack, a layered file system
* would end up referencing the wrong lock.
*
* This routine serves as a central resource for this behavior; all
* layered file systems don't need to worry about the above. Also, if
* things get fixed, all layers get the benefit.
*/
int
layerfs_snapshot(struct mount *mp, struct vnode *vp,
   struct timespec *ts)
{

       return EOPNOTSUPP;
}

/*
* layerfs_suspendctl - suspend a layered file system
*
* Here we should suspend the lower file system(s) too.  At present
* this will deadlock as we don't know which to suspend first.
*
* This routine serves as a central resource for this behavior; all
* layered file systems don't need to worry about the above. Also, if
* things get fixed, all layers get the benefit.
*/
int
layerfs_suspendctl(struct mount *mp, int cmd)
{

       return genfs_suspendctl(mp, cmd);
}

SYSCTL_SETUP(sysctl_vfs_layerfs_setup, "sysctl vfs.layerfs subtree setup")
{
       const struct sysctlnode *layerfs_node = NULL;

       sysctl_createv(clog, 0, NULL, &layerfs_node,
#ifdef _MODULE
                      0,
#else
                      CTLFLAG_PERMANENT,
#endif
                      CTLTYPE_NODE, "layerfs",
                      SYSCTL_DESCR("Generic layered file system"),
                      NULL, 0, NULL, 0,
                      CTL_VFS, CTL_CREATE, CTL_EOL);

#ifdef LAYERFS_DIAGNOSTIC
       sysctl_createv(clog, 0, &layerfs_node, NULL,
#ifndef _MODULE
                      CTLFLAG_PERMANENT |
#endif
                      CTLFLAG_READWRITE,
                      CTLTYPE_INT,
                      "debug",
                      SYSCTL_DESCR("Verbose debugging messages"),
                      NULL, 0, &layerfs_debug, 0,
                      CTL_CREATE, CTL_EOL);
#endif

       /*
        * other subtrees should really be aliases to this, but since
        * they can't tell if layerfs has been instantiated yet, they
        * can't do that...not easily.  not yet.  :-)
        */
}

int
layerfs_renamelock_enter(struct mount *mp)
{

       return VFS_RENAMELOCK_ENTER(mp->mnt_lower);
}

void
layerfs_renamelock_exit(struct mount *mp)
{

       VFS_RENAMELOCK_EXIT(mp->mnt_lower);
}

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