/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1994, 1995 The Regents of the University of California.
 * Copyright (c) 1994, 1995 Jan-Simon Pendry.
 * Copyright (c) 2005, 2006, 2012 Masanori Ozawa <ozawa@ongs.co.jp>, ONGS Inc.
 * Copyright (c) 2006, 2012 Daichi Goto <daichi@freebsd.org>
 * 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kdb.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/stat.h>

#include <fs/unionfs/union.h>

static MALLOC_DEFINE(M_UNIONFSMNT, "UNIONFS mount", "UNIONFS mount structure");

static vfs_fhtovp_t     unionfs_fhtovp;
static vfs_checkexp_t   unionfs_checkexp;
static vfs_mount_t      unionfs_domount;
static vfs_quotactl_t   unionfs_quotactl;
static vfs_root_t       unionfs_root;
static vfs_sync_t       unionfs_sync;
static vfs_statfs_t     unionfs_statfs;
static vfs_unmount_t    unionfs_unmount;
static vfs_vget_t       unionfs_vget;
static vfs_extattrctl_t unionfs_extattrctl;

static struct vfsops unionfs_vfsops;

/*
 * Mount unionfs layer.
 */
static int
unionfs_domount(struct mount *mp)
{
        struct vnode   *lowerrootvp;
        struct vnode   *upperrootvp;
        struct vnode   *lvp1;
        struct vnode   *lvp2;
        struct unionfs_mount *ump;
        char           *target;
        char           *tmp;
        char           *ep;
        struct nameidata nd, *ndp;
        struct vattr    va;
        unionfs_copymode copymode;
        unionfs_whitemode whitemode;
        int             below;
        int             error;
        int             len;
        uid_t           uid;
        gid_t           gid;
        u_short         udir;
        u_short         ufile;

        UNIONFSDEBUG("unionfs_mount(mp = %p)\n", mp);

        error = 0;
        below = 0;
        uid = 0;
        gid = 0;
        udir = 0;
        ufile = 0;
        copymode = UNIONFS_TRANSPARENT; /* default */
        whitemode = UNIONFS_WHITE_ALWAYS;
        ndp = &nd;

        if (mp->mnt_flag & MNT_ROOTFS) {
                vfs_mount_error(mp, "Cannot union mount root filesystem");
                return (EOPNOTSUPP);
        }

        /*
         * Update is a no operation.
         */
        if (mp->mnt_flag & MNT_UPDATE) {
                vfs_mount_error(mp, "unionfs does not support mount update");
                return (EOPNOTSUPP);
        }

        /*
         * Get argument
         */
        error = vfs_getopt(mp->mnt_optnew, "target", (void **)&target, &len);
        if (error)
                error = vfs_getopt(mp->mnt_optnew, "from", (void **)&target,
                    &len);
        if (error || target[len - 1] != '\0') {
                vfs_mount_error(mp, "Invalid target");
                return (EINVAL);
        }
        if (vfs_getopt(mp->mnt_optnew, "below", NULL, NULL) == 0)
                below = 1;
        if (vfs_getopt(mp->mnt_optnew, "udir", (void **)&tmp, NULL) == 0) {
                if (tmp != NULL)
                        udir = (mode_t)strtol(tmp, &ep, 8);
                if (tmp == NULL || *ep) {
                        vfs_mount_error(mp, "Invalid udir");
                        return (EINVAL);
                }
                udir &= S_IRWXU | S_IRWXG | S_IRWXO;
        }
        if (vfs_getopt(mp->mnt_optnew, "ufile", (void **)&tmp, NULL) == 0) {
                if (tmp != NULL)
                        ufile = (mode_t)strtol(tmp, &ep, 8);
                if (tmp == NULL || *ep) {
                        vfs_mount_error(mp, "Invalid ufile");
                        return (EINVAL);
                }
                ufile &= S_IRWXU | S_IRWXG | S_IRWXO;
        }
        /* check umask, uid and gid */
        if (udir == 0 && ufile != 0)
                udir = ufile;
        if (ufile == 0 && udir != 0)
                ufile = udir;

        vn_lock(mp->mnt_vnodecovered, LK_SHARED | LK_RETRY);
        error = VOP_GETATTR(mp->mnt_vnodecovered, &va, mp->mnt_cred);
        if (!error) {
                if (udir == 0)
                        udir = va.va_mode;
                if (ufile == 0)
                        ufile = va.va_mode;
                uid = va.va_uid;
                gid = va.va_gid;
        }
        VOP_UNLOCK(mp->mnt_vnodecovered);
        if (error)
                return (error);

        if (mp->mnt_cred->cr_ruid == 0) {       /* root only */
                if (vfs_getopt(mp->mnt_optnew, "uid", (void **)&tmp,
                    NULL) == 0) {
                        if (tmp != NULL)
                                uid = (uid_t)strtol(tmp, &ep, 10);
                        if (tmp == NULL || *ep) {
                                vfs_mount_error(mp, "Invalid uid");
                                return (EINVAL);
                        }
                }
                if (vfs_getopt(mp->mnt_optnew, "gid", (void **)&tmp,
                    NULL) == 0) {
                        if (tmp != NULL)
                                gid = (gid_t)strtol(tmp, &ep, 10);
                        if (tmp == NULL || *ep) {
                                vfs_mount_error(mp, "Invalid gid");
                                return (EINVAL);
                        }
                }
                if (vfs_getopt(mp->mnt_optnew, "copymode", (void **)&tmp,
                    NULL) == 0) {
                        if (tmp == NULL) {
                                vfs_mount_error(mp, "Invalid copymode");
                                return (EINVAL);
                        } else if (strcasecmp(tmp, "traditional") == 0)
                                copymode = UNIONFS_TRADITIONAL;
                        else if (strcasecmp(tmp, "transparent") == 0)
                                copymode = UNIONFS_TRANSPARENT;
                        else if (strcasecmp(tmp, "masquerade") == 0)
                                copymode = UNIONFS_MASQUERADE;
                        else {
                                vfs_mount_error(mp, "Invalid copymode");
                                return (EINVAL);
                        }
                }
                if (vfs_getopt(mp->mnt_optnew, "whiteout", (void **)&tmp,
                    NULL) == 0) {
                        if (tmp == NULL) {
                                vfs_mount_error(mp, "Invalid whiteout mode");
                                return (EINVAL);
                        } else if (strcasecmp(tmp, "always") == 0)
                                whitemode = UNIONFS_WHITE_ALWAYS;
                        else if (strcasecmp(tmp, "whenneeded") == 0)
                                whitemode = UNIONFS_WHITE_WHENNEEDED;
                        else {
                                vfs_mount_error(mp, "Invalid whiteout mode");
                                return (EINVAL);
                        }
                }
        }
        /* If copymode is UNIONFS_TRADITIONAL, uid/gid is mounted user. */
        if (copymode == UNIONFS_TRADITIONAL) {
                uid = mp->mnt_cred->cr_ruid;
                gid = mp->mnt_cred->cr_rgid;
        }

        UNIONFSDEBUG("unionfs_mount: uid=%d, gid=%d\n", uid, gid);
        UNIONFSDEBUG("unionfs_mount: udir=0%03o, ufile=0%03o\n", udir, ufile);
        UNIONFSDEBUG("unionfs_mount: copymode=%d\n", copymode);

        /*
         * Find upper node
         */
        NDINIT(ndp, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE, target);
        if ((error = namei(ndp)))
                return (error);

        NDFREE_PNBUF(ndp);

        /* get root vnodes */
        lowerrootvp = mp->mnt_vnodecovered;
        upperrootvp = ndp->ni_vp;
        KASSERT(lowerrootvp != NULL, ("%s: NULL lower root vp", __func__));
        KASSERT(upperrootvp != NULL, ("%s: NULL upper root vp", __func__));

        /* create unionfs_mount */
        ump = malloc(sizeof(struct unionfs_mount), M_UNIONFSMNT,
            M_WAITOK | M_ZERO);

        /*
         * Save reference
         */
        if (below) {
                VOP_UNLOCK(upperrootvp);
                vn_lock(lowerrootvp, LK_EXCLUSIVE | LK_RETRY);
                ump->um_lowervp = upperrootvp;
                ump->um_uppervp = lowerrootvp;
        } else {
                ump->um_lowervp = lowerrootvp;
                ump->um_uppervp = upperrootvp;
        }
        ump->um_rootvp = NULL;
        ump->um_uid = uid;
        ump->um_gid = gid;
        ump->um_udir = udir;
        ump->um_ufile = ufile;
        ump->um_copymode = copymode;
        ump->um_whitemode = whitemode;

        mp->mnt_data = ump;

        /*
         * Copy upper layer's RDONLY flag.
         */
        mp->mnt_flag |= ump->um_uppervp->v_mount->mnt_flag & MNT_RDONLY;

        /*
         * Unlock the node
         */
        VOP_UNLOCK(ump->um_uppervp);

        /*
         * Detect common cases in which constructing a unionfs hierarchy
         * would produce deadlock (or failed locking assertions) upon
         * use of the resulting unionfs vnodes.  This typically happens
         * when the requested upper and lower filesytems (which themselves
         * may be unionfs instances and/or nullfs aliases) end up resolving
         * to the same base-layer files.  Note that this is not meant to be
         * an exhaustive check of all possible deadlock-producing scenarios.
         */
        lvp1 = lvp2 = NULL;
        VOP_GETLOWVNODE(ump->um_lowervp, &lvp1, FREAD);
        VOP_GETLOWVNODE(ump->um_uppervp, &lvp2, FREAD);
        if (lvp1 != NULL && lvp1 == lvp2)
                error = EDEADLK;
        if (lvp1 != NULL)
                vrele(lvp1);
        if (lvp2 != NULL)
                vrele(lvp2);

        /*
         * Get the unionfs root vnode.
         */
        if (error == 0) {
                error = unionfs_nodeget(mp, ump->um_uppervp, ump->um_lowervp,
                    NULL, &(ump->um_rootvp), NULL);
        }
        if (error != 0) {
                vrele(upperrootvp);
                free(ump, M_UNIONFSMNT);
                mp->mnt_data = NULL;
                return (error);
        }
        KASSERT(ump->um_rootvp != NULL, ("rootvp cannot be NULL"));
        KASSERT((ump->um_rootvp->v_vflag & VV_ROOT) != 0,
            ("%s: rootvp without VV_ROOT", __func__));

        /*
         * Do not release the namei() reference on upperrootvp until after
         * we attempt to register the upper mounts.  A concurrent unmount
         * of the upper or lower FS may have caused unionfs_nodeget() to
         * create a unionfs node with a NULL upper or lower vp and with
         * no reference held on upperrootvp or lowerrootvp.
         * vfs_register_upper() should subsequently fail, which is what
         * we want, but we must ensure neither underlying vnode can be
         * reused until that happens.  We assume the caller holds a reference
         * to lowerrootvp as it is the mount's covered vnode.
         */
        ump->um_lowermp = vfs_register_upper_from_vp(ump->um_lowervp, mp,
            &ump->um_lower_link);
        ump->um_uppermp = vfs_register_upper_from_vp(ump->um_uppervp, mp,
            &ump->um_upper_link);

        vrele(upperrootvp);

        if (ump->um_lowermp == NULL || ump->um_uppermp == NULL) {
                if (ump->um_lowermp != NULL)
                        vfs_unregister_upper(ump->um_lowermp, &ump->um_lower_link);
                if (ump->um_uppermp != NULL)
                        vfs_unregister_upper(ump->um_uppermp, &ump->um_upper_link);
                vflush(mp, 1, FORCECLOSE, curthread);
                free(ump, M_UNIONFSMNT);
                mp->mnt_data = NULL;
                return (ENOENT);
        }

        /*
         * Specify that the covered vnode lock should remain held while
         * lookup() performs the cross-mount walk.  This prevents a lock-order
         * reversal between the covered vnode lock (which is also locked by
         * unionfs_lock()) and the mountpoint's busy count.  Without this,
         * unmount will lock the covered vnode lock (directly through the
         * covered vnode) and wait for the busy count to drain, while a
         * concurrent lookup will increment the busy count and then may lock
         * the covered vnode lock (indirectly through unionfs_lock()).
         *
         * Note that this is only needed for the 'below' case in which the
         * upper vnode is also the covered vnode, because unionfs_lock()
         * only locks the upper vnode as long as both lower and upper vnodes
         * are present (which they will always be for the unionfs mount root).
         */
        if (below) {
                vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
                mp->mnt_vnodecovered->v_vflag |= VV_CROSSLOCK;
                VOP_UNLOCK(mp->mnt_vnodecovered);
        }

        MNT_ILOCK(mp);
        if ((ump->um_lowermp->mnt_flag & MNT_LOCAL) != 0 &&
            (ump->um_uppermp->mnt_flag & MNT_LOCAL) != 0)
                mp->mnt_flag |= MNT_LOCAL;
        mp->mnt_kern_flag |= MNTK_NOMSYNC | MNTK_UNIONFS |
            (ump->um_uppermp->mnt_kern_flag & MNTK_SHARED_WRITES);
        MNT_IUNLOCK(mp);

        /*
         * Get new fsid
         */
        vfs_getnewfsid(mp);

        snprintf(mp->mnt_stat.f_mntfromname, MNAMELEN, "<%s>:%s",
            below ? "below" : "above", target);

        UNIONFSDEBUG("unionfs_mount: from %s, on %s\n",
            mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);

        return (0);
}

/*
 * Free reference to unionfs layer
 */
static int
unionfs_unmount(struct mount *mp, int mntflags)
{
        struct unionfs_mount *ump;
        int             error;
        int             num;
        int             freeing;
        int             flags;

        UNIONFSDEBUG("unionfs_unmount: mp = %p\n", mp);

        ump = MOUNTTOUNIONFSMOUNT(mp);
        flags = 0;

        if (mntflags & MNT_FORCE)
                flags |= FORCECLOSE;

        /* vflush (no need to call vrele) */
        for (freeing = 0; (error = vflush(mp, 1, flags, curthread)) != 0;) {
                num = mp->mnt_nvnodelistsize;
                if (num == freeing)
                        break;
                freeing = num;
        }

        if (error)
                return (error);

        vn_lock(mp->mnt_vnodecovered, LK_EXCLUSIVE | LK_RETRY | LK_CANRECURSE);
        mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK;
        VOP_UNLOCK(mp->mnt_vnodecovered);
        vfs_unregister_upper(ump->um_lowermp, &ump->um_lower_link);
        vfs_unregister_upper(ump->um_uppermp, &ump->um_upper_link);
        free(ump, M_UNIONFSMNT);
        mp->mnt_data = NULL;

        return (0);
}

static int
unionfs_root(struct mount *mp, int flags, struct vnode **vpp)
{
        struct unionfs_mount *ump;
        struct vnode *vp;

        ump = MOUNTTOUNIONFSMOUNT(mp);
        vp = ump->um_rootvp;

        UNIONFSDEBUG("unionfs_root: rootvp=%p locked=%x\n",
            vp, VOP_ISLOCKED(vp));

        vref(vp);
        if (flags & LK_TYPE_MASK)
                vn_lock(vp, flags);

        *vpp = vp;

        return (0);
}

static int
unionfs_quotactl(struct mount *mp, int cmd, uid_t uid, void *arg,
    bool *mp_busy)
{
        struct mount *uppermp;
        struct unionfs_mount *ump;
        int error;
        bool unbusy;

        ump = MOUNTTOUNIONFSMOUNT(mp);
        /*
         * Issue a volatile load of um_uppermp here, as the mount may be
         * torn down after we call vfs_unbusy().
         */
        uppermp = atomic_load_ptr(&ump->um_uppermp);
        KASSERT(*mp_busy == true, ("upper mount not busy"));
        /*
         * See comment in sys_quotactl() for an explanation of why the
         * lower mount needs to be busied by the caller of VFS_QUOTACTL()
         * but may be unbusied by the implementation.  We must unbusy
         * the upper mount for the same reason; otherwise a namei lookup
         * issued by the VFS_QUOTACTL() implementation could traverse the
         * upper mount and deadlock.
         */
        vfs_unbusy(mp);
        *mp_busy = false;
        unbusy = true;
        error = vfs_busy(uppermp, 0);
        /*
         * Writing is always performed to upper vnode.
         */
        if (error == 0)
                error = VFS_QUOTACTL(uppermp, cmd, uid, arg, &unbusy);
        if (unbusy)
                vfs_unbusy(uppermp);

        return (error);
}

static int
unionfs_statfs(struct mount *mp, struct statfs *sbp)
{
        struct unionfs_mount *ump;
        struct statfs   *mstat;
        uint64_t        lbsize;
        int             error;

        ump = MOUNTTOUNIONFSMOUNT(mp);

        UNIONFSDEBUG("unionfs_statfs(mp = %p, lvp = %p, uvp = %p)\n",
            mp, ump->um_lowervp, ump->um_uppervp);

        mstat = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK | M_ZERO);

        error = VFS_STATFS(ump->um_lowermp, mstat);
        if (error) {
                free(mstat, M_STATFS);
                return (error);
        }

        /* now copy across the "interesting" information and fake the rest */
        sbp->f_blocks = mstat->f_blocks;
        sbp->f_files = mstat->f_files;

        lbsize = mstat->f_bsize;

        error = VFS_STATFS(ump->um_uppermp, mstat);
        if (error) {
                free(mstat, M_STATFS);
                return (error);
        }

        /*
         * The FS type etc is copy from upper vfs.
         * (write able vfs have priority)
         */
        sbp->f_type = mstat->f_type;
        sbp->f_flags = mstat->f_flags;
        sbp->f_bsize = mstat->f_bsize;
        sbp->f_iosize = mstat->f_iosize;

        if (mstat->f_bsize != lbsize)
                sbp->f_blocks = ((off_t)sbp->f_blocks * lbsize) /
                    mstat->f_bsize;

        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;

        free(mstat, M_STATFS);
        return (0);
}

static int
unionfs_sync(struct mount *mp, int waitfor)
{
        /* nothing to do */
        return (0);
}

static int
unionfs_vget(struct mount *mp, ino_t ino, int flags, struct vnode **vpp)
{
        return (EOPNOTSUPP);
}

static int
unionfs_fhtovp(struct mount *mp, struct fid *fidp, int flags,
    struct vnode **vpp)
{
        return (EOPNOTSUPP);
}

static int
unionfs_checkexp(struct mount *mp, struct sockaddr *nam, uint64_t *extflagsp,
    struct ucred **credanonp, int *numsecflavors, int *secflavors)
{
        return (EOPNOTSUPP);
}

static int
unionfs_extattrctl(struct mount *mp, int cmd, struct vnode *filename_vp,
    int namespace, const char *attrname)
{
        struct unionfs_mount *ump;
        struct unionfs_node *unp;

        ump = MOUNTTOUNIONFSMOUNT(mp);
        unp = VTOUNIONFS(filename_vp);

        if (unp->un_uppervp != NULL) {
                return (VFS_EXTATTRCTL(ump->um_uppermp, cmd,
                    unp->un_uppervp, namespace, attrname));
        } else {
                return (VFS_EXTATTRCTL(ump->um_lowermp, cmd,
                    unp->un_lowervp, namespace, attrname));
        }
}

static struct vfsops unionfs_vfsops = {
        .vfs_checkexp =         unionfs_checkexp,
        .vfs_extattrctl =       unionfs_extattrctl,
        .vfs_fhtovp =           unionfs_fhtovp,
        .vfs_init =             unionfs_init,
        .vfs_mount =            unionfs_domount,
        .vfs_quotactl =         unionfs_quotactl,
        .vfs_root =             unionfs_root,
        .vfs_statfs =           unionfs_statfs,
        .vfs_sync =             unionfs_sync,
        .vfs_uninit =           unionfs_uninit,
        .vfs_unmount =          unionfs_unmount,
        .vfs_vget =             unionfs_vget,
};

VFS_SET(unionfs_vfsops, unionfs, VFCF_LOOPBACK);