/*
 * 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.
 *
 *      @(#)null_vfsops.c       8.2 (Berkeley) 1/21/94
 *
 * @(#)lofs_vfsops.c    1.2 (Berkeley) 6/18/92
 * $FreeBSD: src/sys/miscfs/nullfs/null_vfsops.c,v 1.35.2.3 2001/07/26 20:37:11 iedowse Exp $
 * $DragonFly: src/sys/vfs/nullfs/null_vfsops.c,v 1.31 2008/09/17 21:44:25 dillon Exp $
 */

/*
 * Null Layer
 * (See null_vnops.c for a description of what this does.)
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namecache.h>
#include <sys/nlookup.h>
#include <sys/mountctl.h>
#include <sys/sysctl.h>
#include "null.h"

extern struct vop_ops null_vnode_vops;

static MALLOC_DEFINE(M_NULLFSMNT, "NULLFS mount", "NULLFS mount structure");

SYSCTL_NODE(_vfs, OID_AUTO, nullfs, CTLFLAG_RD, 0, "NULLFS filesystem");

static int nullfs_debug;
TUNABLE_INT("vfs.nullfs.debug", &nullfs_debug);
SYSCTL_INT(_vfs_nullfs, OID_AUTO, debug, CTLFLAG_RW,
           &nullfs_debug, 0, "nullfs debugging");

static int      nullfs_root(struct mount *mp, struct vnode **vpp);
static int      nullfs_statfs(struct mount *mp, struct statfs *sbp,
                                struct ucred *cred);

/*
 * Mount null layer
 */
static int
nullfs_mount(struct mount *mp, char *path, caddr_t data, struct ucred *cred)
{
        int error = 0;
        struct null_args args;
        struct vnode *rootvp;
        struct null_mount *xmp;
        size_t size;
        struct nlookupdata nd;
        fhandle_t fh;

        NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);

        /*
         * Get argument
         */
        error = copyin(data, (caddr_t)&args, sizeof(struct null_args));
        if (error)
                return (error);

        /*
         * XXX: Should we process mount export info ?
         * If not, returning zero here is enough as the actual ro/rw update is
         * being done in sys_mount().
         */
        if (mp->mnt_flag & MNT_UPDATE) {
                xmp = MOUNTTONULLMOUNT(mp);
                error = vfs_export(mp, &xmp->export, &args.export);
                return (error);
        }

        /*
         * Find lower node
         */
        rootvp = NULL;
        error = nlookup_init(&nd, args.target, UIO_USERSPACE, NLC_FOLLOW);
        if (error)
                goto fail1;
        error = nlookup(&nd);
        if (error)
                goto fail2;
        error = cache_vget(&nd.nl_nch, nd.nl_cred, LK_EXCLUSIVE, &rootvp);
        if (error)
                goto fail2;

        xmp = (struct null_mount *) kmalloc(sizeof(struct null_mount),
                                M_NULLFSMNT, M_WAITOK | M_ZERO);

        /*
         * Save reference to underlying FS
         *
         * As lite stacking enters the scene, the old way of doing this
         * -- via the vnode -- is not good enough anymore.  Use the
         * underlying filesystem's namecache handle as our mount point
         * root, adjusting the mount to point to us. 
         *
         * NCF_ISMOUNTPT is normally set on the mount point, but we also
         * want to set it on the base directory being mounted to prevent
         * that directory from being destroyed out from under the nullfs
         * mount. 
         *
         * The forwarding mount pointer (xmp->nullm_vfs) must be set to
         * the actual target filesystem.  If the target filesystem was
         * resolved via a nullfs mount nd.nl_nch.mount will be pointing
         * to the nullfs mount structure instead of the target filesystem,
         * which would otherwise cause the mount VOPS and VFSOPS to recurse
         * endlessly.  If we are mounting via a nullfs mount we inherit
         * its read-only state, if set.
         */
        xmp->nullm_vfs = nd.nl_nch.mount;
        if (xmp->nullm_vfs != rootvp->v_mount) {
                if (xmp->nullm_vfs->mnt_flag & MNT_RDONLY)
                        mp->mnt_flag |= MNT_RDONLY;
                if (xmp->nullm_vfs->mnt_flag & MNT_NOEXEC)
                        mp->mnt_flag |= MNT_NOEXEC;
                xmp->nullm_vfs = rootvp->v_mount;
        }

        /*
         * ncmountpt is the parent glue.  When mounting a nullfs via a nullfs
         * we retain the parent nullfs to create a unique chain tuple.
         */
        mp->mnt_ncmountpt = nd.nl_nch;
        cache_changemount(&mp->mnt_ncmountpt, mp);
        mp->mnt_ncmountpt.ncp->nc_flag |= NCF_ISMOUNTPT;
        cache_unlock(&mp->mnt_ncmountpt);
        cache_zero(&nd.nl_nch);
        nlookup_done(&nd);

        vfs_add_vnodeops(mp, &null_vnode_vops, &mp->mnt_vn_norm_ops);

        vn_unlock(rootvp);              /* leave reference intact */

        /*
         * Keep a held reference to the root vnode.
         * It is vrele'd in nullfs_unmount.
         */
        xmp->nullm_rootvp = rootvp;
        /*
         * XXX What's the proper safety condition for querying
         * the underlying mount? Is this flag tuning necessary
         * at all?
         */
        if (xmp->nullm_vfs->mnt_flag & MNT_LOCAL)
                mp->mnt_flag |= MNT_LOCAL;
        mp->mnt_data = (qaddr_t) xmp;

        /*
         * Mount path
         */
        copyinstr(args.target, mp->mnt_stat.f_mntfromname, MNAMELEN - 1, &size);

        /*
         * Try to create a unique but non-random fsid for the nullfs to
         * allow it to be exported via NFS.  Use a combination of the
         * FH for the nullfs root in the underlying filesystem and a
         * CRC of the null mount path.
         *
         * Use val[1] so as not to interfere with the generally unique
         * val[0].
         */
        bzero(&fh, sizeof(fh));
        fh.fh_fsid = rootvp->v_mount->mnt_stat.f_fsid;

        if (VFS_VPTOFH(rootvp, &fh.fh_fid) == 0) {
                if (nullfs_debug)
                        kprintf("(A)");
                vfs_setfsid(mp, &fh.fh_fsid);
        } else {
                if (nullfs_debug)
                        kprintf("(B)");
                vfs_getnewfsid(mp);
        }
        fh.fh_fsid.val[1] ^= crc32(mp->mnt_stat.f_mntfromname, size);

        if (nullfs_debug) {
                kprintf("NULLFS FSID %08x.%08x -> %08x.%08x (%*.*s)\n",
                        rootvp->v_mount->mnt_stat.f_fsid.val[0],
                        rootvp->v_mount->mnt_stat.f_fsid.val[1],
                        fh.fh_fsid.val[0],
                        fh.fh_fsid.val[1],
                        (int)size, (int)size, mp->mnt_stat.f_mntfromname);
        }

        bzero(mp->mnt_stat.f_mntfromname + size, MNAMELEN - size);
        nullfs_statfs(mp, &mp->mnt_stat, cred);
        NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
                mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntfromname);

        bzero(mp->mnt_stat.f_mntonname, MNAMELEN);
        if (path != NULL) {
                (void) copyinstr(path, mp->mnt_stat.f_mntonname, MNAMELEN - 1,
                        &size);
        }

        /*
         * Set NCALIASED so unmount won't complain about namecache refs
         * still existing.
         *
         * All NULLFS operations are MPSAFE, though it will be short-lived
         * if the underlying filesystem is not.
         *
         * NOTE: There is no syncer thread for nullfs (flagged in vfsops)
         */
        mp->mnt_kern_flag |= MNTK_NCALIASED | MNTK_ALL_MPSAFE;

        return (0);
fail2:
        nlookup_done(&nd);
fail1:
        return (error);
}

/*
 * Free reference to null layer
 */
static int
nullfs_unmount(struct mount *mp, int mntflags)
{
        struct null_mount *xmp;

        NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);

        /*
         * Throw away the null_mount structure
         */
        xmp = (void *)mp->mnt_data;
        mp->mnt_data = 0;
        if (xmp->nullm_rootvp) {
                vrele(xmp->nullm_rootvp);
                xmp->nullm_rootvp = NULL;
        }
        kfree(xmp, M_NULLFSMNT);
        return 0;
}

static int
nullfs_root(struct mount *mp, struct vnode **vpp)
{
        struct vnode *vp;
        int error;

        NULLFSDEBUG("nullfs_root(mp = %p, vp = %p)\n", (void *)mp,
            (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);

        /*
         * Return locked reference to root.
         */
        vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
        error = vget(vp, LK_EXCLUSIVE | LK_RETRY);
        if (error == 0)
                *vpp = vp;
        return (error);
}

static int
nullfs_quotactl(struct mount *mp, int cmd, uid_t uid, caddr_t arg,
                struct ucred *cred)
{
        return VFS_QUOTACTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, uid, arg, cred);
}

static int
nullfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
{
        int error;
        struct statfs mstat;

        NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p)\n", (void *)mp,
            (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);

        bzero(&mstat, sizeof(mstat));

        error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, &mstat, cred);
        if (error)
                return (error);

        /* now copy across the "interesting" information and fake the rest */
        sbp->f_type = mstat.f_type;
        sbp->f_flags = mstat.f_flags;
        sbp->f_bsize = mstat.f_bsize;
        sbp->f_iosize = mstat.f_iosize;
        sbp->f_blocks = mstat.f_blocks;
        sbp->f_bfree = mstat.f_bfree;
        sbp->f_bavail = mstat.f_bavail;
        sbp->f_files = mstat.f_files;
        sbp->f_ffree = mstat.f_ffree;
        if (sbp != &mp->mnt_stat) {
                bcopy(&mp->mnt_stat.f_fsid, &sbp->f_fsid, sizeof(sbp->f_fsid));
                bcopy(mp->mnt_stat.f_mntfromname, sbp->f_mntfromname, MNAMELEN);
                bcopy(mp->mnt_stat.f_mntonname, sbp->f_mntonname, MNAMELEN);
        }
        return (0);
}

/*
 * Implement NFS export tracking
 */
static int
nullfs_checkexp(struct mount *mp, struct sockaddr *nam, int *extflagsp,
                struct ucred **credanonp)
{
        struct null_mount *xmp = (void *)mp->mnt_data;
        struct netcred *np;
        int error;

        np = vfs_export_lookup(mp, &xmp->export, nam);
        if (np) {
                *extflagsp = np->netc_exflags;
                *credanonp = &np->netc_anon;
                error = 0;
        } else {
                error = EACCES;
        }
        return(error);
#if 0
        return VFS_CHECKEXP(MOUNTTONULLMOUNT(mp)->nullm_vfs, nam, 
                extflagsp, credanonp);
#endif
}

int
nullfs_export(struct mount *mp, int op, const struct export_args *export)
{
        struct null_mount *xmp = (void *)mp->mnt_data;
        int error;

        switch(op) {
        case MOUNTCTL_SET_EXPORT:
                error = vfs_export(mp, &xmp->export, export);
                break;
        default:
                error = EOPNOTSUPP;
                break;
        }
        return(error);
}

/*
 * Pass through file handle conversion functions.
 */
static int
nullfs_vptofh(struct vnode *vp, struct fid *fhp)
{
        return VFS_VPTOFH(vp, fhp);
}

/*
 * Pass through file handle conversion functions.
 *
 * NOTE: currently only HAMMER uses rootvp.  HAMMER uses rootvp only
 * to enforce PFS isolation.
 */
static int
nullfs_fhtovp(struct mount *mp, struct vnode *rootvp,
              struct fid *fhp, struct vnode **vpp)
{
        struct null_mount *xmp = MOUNTTONULLMOUNT(mp);

        return VFS_FHTOVP(xmp->nullm_vfs, xmp->nullm_rootvp, fhp, vpp);
}

static int                        
nullfs_extattrctl(struct mount *mp, int cmd, struct vnode *vp,
                  int attrnamespace, const char *attrname, struct ucred *cred)
{
        return VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd,
                              vp, attrnamespace, attrname, cred);
}

static void
nullfs_ncpgen_set(struct mount *mp, struct namecache *ncp)
{
        struct null_mount *xmp = MOUNTTONULLMOUNT(mp);

        VFS_NCPGEN_SET(xmp->nullm_vfs, ncp);
}


static int
nullfs_ncpgen_test(struct mount *mp, struct namecache *ncp)
{
        struct null_mount *xmp = MOUNTTONULLMOUNT(mp);

        return VFS_NCPGEN_TEST(xmp->nullm_vfs, ncp);
}

static int
nullfs_modifying(struct mount *mp)
{
        struct null_mount *xmp = MOUNTTONULLMOUNT(mp);
        int error;

        if (mp->mnt_flag & MNT_RDONLY)
                error = EROFS;
        else if (xmp->nullm_vfs)
                error = VFS_MODIFYING(xmp->nullm_vfs);
        else
                error = 0;
        return error;
}

static struct vfsops null_vfsops = {
        .vfs_flags =            VFSOPSF_NOSYNCERTHR,
        .vfs_mount =            nullfs_mount,
        .vfs_unmount =          nullfs_unmount,
        .vfs_root =             nullfs_root,
        .vfs_quotactl =         nullfs_quotactl,
        .vfs_statfs =           nullfs_statfs,
        .vfs_extattrctl =       nullfs_extattrctl,
        .vfs_fhtovp =           nullfs_fhtovp,
        .vfs_vptofh =           nullfs_vptofh,
        .vfs_ncpgen_set =       nullfs_ncpgen_set,
        .vfs_ncpgen_test =      nullfs_ncpgen_test,
        .vfs_checkexp =         nullfs_checkexp,
        .vfs_modifying =        nullfs_modifying
};

VFS_SET(null_vfsops, null, VFCF_LOOPBACK | VFCF_MPSAFE);
MODULE_VERSION(null, 1);