/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed
 * to Berkeley by John Heidemann of the UCLA Ficus project.
 *
 * 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/bio.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/event.h>
#include <sys/filio.h>
#include <sys/inotify.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/lockf.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/rwlock.h>
#include <sys/fcntl.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/dirent.h>
#include <sys/poll.h>
#include <sys/stat.h>
#include <security/audit/audit.h>
#include <sys/priv.h>

#include <security/mac/mac_framework.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vnode_pager.h>

static int      vop_nolookup(struct vop_lookup_args *);
static int      vop_norename(struct vop_rename_args *);
static int      vop_nostrategy(struct vop_strategy_args *);
static int      dirent_exists(struct vnode *vp, const char *dirname,
                              struct thread *td);

static int vop_stdis_text(struct vop_is_text_args *ap);
static int vop_stdunset_text(struct vop_unset_text_args *ap);
static int vop_stdadd_writecount(struct vop_add_writecount_args *ap);
static int vop_stdfdatasync(struct vop_fdatasync_args *ap);
static int vop_stdgetpages_async(struct vop_getpages_async_args *ap);
static int vop_stdread_pgcache(struct vop_read_pgcache_args *ap);
static int vop_stdstat(struct vop_stat_args *ap);
static int vop_stdvput_pair(struct vop_vput_pair_args *ap);
static int vop_stdgetlowvnode(struct vop_getlowvnode_args *ap);

/*
 * This vnode table stores what we want to do if the filesystem doesn't
 * implement a particular VOP.
 *
 * If there is no specific entry here, we will return EOPNOTSUPP.
 *
 * Note that every filesystem has to implement either vop_access
 * or vop_accessx; failing to do so will result in immediate crash
 * due to stack overflow, as vop_stdaccess() calls vop_stdaccessx(),
 * which calls vop_stdaccess() etc.
 */

struct vop_vector default_vnodeops = {
        .vop_default =          NULL,
        .vop_bypass =           VOP_EOPNOTSUPP,

        .vop_access =           vop_stdaccess,
        .vop_accessx =          vop_stdaccessx,
        .vop_advise =           vop_stdadvise,
        .vop_advlock =          vop_stdadvlock,
        .vop_advlockasync =     vop_stdadvlockasync,
        .vop_advlockpurge =     vop_stdadvlockpurge,
        .vop_allocate =         vop_stdallocate,
        .vop_deallocate =       vop_stddeallocate,
        .vop_bmap =             vop_stdbmap,
        .vop_close =            VOP_NULL,
        .vop_fsync =            VOP_NULL,
        .vop_stat =             vop_stdstat,
        .vop_fdatasync =        vop_stdfdatasync,
        .vop_getlowvnode =      vop_stdgetlowvnode,
        .vop_getpages =         vop_stdgetpages,
        .vop_getpages_async =   vop_stdgetpages_async,
        .vop_getwritemount =    vop_stdgetwritemount,
        .vop_inactive =         VOP_NULL,
        .vop_need_inactive =    vop_stdneed_inactive,
        .vop_inotify =          vop_stdinotify,
        .vop_inotify_add_watch = vop_stdinotify_add_watch,
        .vop_ioctl =            vop_stdioctl,
        .vop_kqfilter =         vop_stdkqfilter,
        .vop_islocked =         vop_stdislocked,
        .vop_lock1 =            vop_stdlock,
        .vop_lookup =           vop_nolookup,
        .vop_open =             VOP_NULL,
        .vop_pathconf =         VOP_EINVAL,
        .vop_poll =             vop_nopoll,
        .vop_putpages =         vop_stdputpages,
        .vop_readlink =         VOP_EINVAL,
        .vop_read_pgcache =     vop_stdread_pgcache,
        .vop_rename =           vop_norename,
        .vop_revoke =           VOP_PANIC,
        .vop_strategy =         vop_nostrategy,
        .vop_unlock =           vop_stdunlock,
        .vop_vptocnp =          vop_stdvptocnp,
        .vop_vptofh =           vop_stdvptofh,
        .vop_unp_bind =         vop_stdunp_bind,
        .vop_unp_connect =      vop_stdunp_connect,
        .vop_unp_detach =       vop_stdunp_detach,
        .vop_is_text =          vop_stdis_text,
        .vop_set_text =         vop_stdset_text,
        .vop_unset_text =       vop_stdunset_text,
        .vop_add_writecount =   vop_stdadd_writecount,
        .vop_copy_file_range =  vop_stdcopy_file_range,
        .vop_vput_pair =        vop_stdvput_pair,
        .vop_delayed_setsize =  VOP_PANIC,
};
VFS_VOP_VECTOR_REGISTER(default_vnodeops);

/*
 * Series of placeholder functions for various error returns for
 * VOPs.
 */

int
vop_eopnotsupp(struct vop_generic_args *ap)
{
        /*
        printf("vop_notsupp[%s]\n", ap->a_desc->vdesc_name);
        */

        return (EOPNOTSUPP);
}

int
vop_ebadf(struct vop_generic_args *ap)
{

        return (EBADF);
}

int
vop_enotty(struct vop_generic_args *ap)
{

        return (ENOTTY);
}

int
vop_einval(struct vop_generic_args *ap)
{

        return (EINVAL);
}

int
vop_enoent(struct vop_generic_args *ap)
{

        return (ENOENT);
}

int
vop_eagain(struct vop_generic_args *ap)
{

        return (EAGAIN);
}

int
vop_null(struct vop_generic_args *ap)
{

        return (0);
}

/*
 * Helper function to panic on some bad VOPs in some filesystems.
 */
int
vop_panic(struct vop_generic_args *ap)
{

        panic("filesystem goof: vop_panic[%s]", ap->a_desc->vdesc_name);
}

/*
 * vop_std<something> and vop_no<something> are default functions for use by
 * filesystems that need the "default reasonable" implementation for a
 * particular operation.
 *
 * The documentation for the operations they implement exists (if it exists)
 * in the VOP_<SOMETHING>(9) manpage (all uppercase).
 */

/*
 * Default vop for filesystems that do not support name lookup
 */
static int
vop_nolookup(struct vop_lookup_args *ap)
{

        *ap->a_vpp = NULL;
        return (ENOTDIR);
}

/*
 * vop_norename:
 *
 * Handle unlock and reference counting for arguments of vop_rename
 * for filesystems that do not implement rename operation.
 */
static int
vop_norename(struct vop_rename_args *ap)
{

        vop_rename_fail(ap);
        return (EOPNOTSUPP);
}

/*
 *      vop_nostrategy:
 *
 *      Strategy routine for VFS devices that have none.
 *
 *      BIO_ERROR and B_INVAL must be cleared prior to calling any strategy
 *      routine.  Typically this is done for a BIO_READ strategy call.
 *      Typically B_INVAL is assumed to already be clear prior to a write
 *      and should not be cleared manually unless you just made the buffer
 *      invalid.  BIO_ERROR should be cleared either way.
 */

static int
vop_nostrategy (struct vop_strategy_args *ap)
{
        printf("No strategy for buffer at %p\n", ap->a_bp);
        vn_printf(ap->a_vp, "vnode ");
        ap->a_bp->b_ioflags |= BIO_ERROR;
        ap->a_bp->b_error = EOPNOTSUPP;
        bufdone(ap->a_bp);
        return (EOPNOTSUPP);
}

/*
 * Check if a named file exists in a given directory vnode
 *
 * Returns 0 if the file exists, ENOENT if it doesn't, or errors returned by
 * vn_dir_next_dirent().
 */
static int
dirent_exists(struct vnode *vp, const char *dirname, struct thread *td)
{
        char *dirbuf;
        int error, eofflag;
        size_t dirbuflen, len;
        off_t off;
        struct dirent *dp;
        struct vattr va;

        ASSERT_VOP_LOCKED(vp, "vnode not locked");
        KASSERT(vp->v_type == VDIR, ("vp %p is not a directory", vp));

        error = VOP_GETATTR(vp, &va, td->td_ucred);
        if (error != 0)
                return (error);

        dirbuflen = MAX(DEV_BSIZE, GENERIC_MAXDIRSIZ);
        if (dirbuflen < va.va_blocksize)
                dirbuflen = va.va_blocksize;
        dirbuf = malloc(dirbuflen, M_TEMP, M_WAITOK);

        len = 0;
        off = 0;
        eofflag = 0;

        for (;;) {
                error = vn_dir_next_dirent(vp, td, dirbuf, dirbuflen,
                    &dp, &len, &off, &eofflag);
                if (error != 0)
                        goto out;

                if (len == 0)
                        break;

                if (dp->d_type != DT_WHT && dp->d_fileno != 0 &&
                    strcmp(dp->d_name, dirname) == 0)
                        goto out;
        }

        error = ENOENT;

out:
        free(dirbuf, M_TEMP);
        return (error);
}

int
vop_stdaccess(struct vop_access_args *ap)
{

        KASSERT((ap->a_accmode & ~(VEXEC | VWRITE | VREAD | VADMIN |
            VAPPEND)) == 0, ("invalid bit in accmode"));

        return (VOP_ACCESSX(ap->a_vp, ap->a_accmode, ap->a_cred, ap->a_td));
}

int
vop_stdaccessx(struct vop_accessx_args *ap)
{
        int error;
        accmode_t accmode = ap->a_accmode;

        error = vfs_unixify_accmode(&accmode);
        if (error != 0)
                return (error);

        if (accmode == 0)
                return (0);

        return (VOP_ACCESS(ap->a_vp, accmode, ap->a_cred, ap->a_td));
}

/*
 * Advisory record locking support
 */
int
vop_stdadvlock(struct vop_advlock_args *ap)
{
        struct vnode *vp;
        struct mount *mp;
        struct vattr vattr;
        int error;

        vp = ap->a_vp;

        /*
         * Provide atomicity of open(O_CREAT | O_EXCL | O_EXLOCK) for
         * local filesystems.  See vn_open_cred() for reciprocal part.
         */
        mp = vp->v_mount;
        if (mp != NULL && (mp->mnt_flag & MNT_LOCAL) != 0 &&
            ap->a_op == F_SETLK && (ap->a_flags & F_FIRSTOPEN) == 0) {
                VI_LOCK(vp);
                while ((vp->v_iflag & VI_FOPENING) != 0)
                        msleep(vp, VI_MTX(vp), PLOCK, "lockfo", 0);
                VI_UNLOCK(vp);
        }

        if (ap->a_fl->l_whence == SEEK_END) {
                /*
                 * The NFSv4 server must avoid doing a vn_lock() here, since it
                 * can deadlock the nfsd threads, due to a LOR.  Fortunately
                 * the NFSv4 server always uses SEEK_SET and this code is
                 * only required for the SEEK_END case.
                 */
                vn_lock(vp, LK_SHARED | LK_RETRY);
                error = VOP_GETATTR(vp, &vattr, curthread->td_ucred);
                VOP_UNLOCK(vp);
                if (error)
                        return (error);
        } else
                vattr.va_size = 0;

        return (lf_advlock(ap, &(vp->v_lockf), vattr.va_size));
}

int
vop_stdadvlockasync(struct vop_advlockasync_args *ap)
{
        struct vnode *vp;
        struct vattr vattr;
        int error;

        vp = ap->a_vp;
        if (ap->a_fl->l_whence == SEEK_END) {
                /* The size argument is only needed for SEEK_END. */
                vn_lock(vp, LK_SHARED | LK_RETRY);
                error = VOP_GETATTR(vp, &vattr, curthread->td_ucred);
                VOP_UNLOCK(vp);
                if (error)
                        return (error);
        } else
                vattr.va_size = 0;

        return (lf_advlockasync(ap, &(vp->v_lockf), vattr.va_size));
}

int
vop_stdadvlockpurge(struct vop_advlockpurge_args *ap)
{
        struct vnode *vp;

        vp = ap->a_vp;
        lf_purgelocks(vp, &vp->v_lockf);
        return (0);
}

/*
 * vop_stdpathconf:
 *
 * Standard implementation of POSIX pathconf, to get information about limits
 * for a filesystem.
 * Override per filesystem for the case where the filesystem has smaller
 * limits.
 */
int
vop_stdpathconf(struct vop_pathconf_args *ap)
{

        switch (ap->a_name) {
                case _PC_ASYNC_IO:
                        *ap->a_retval = _POSIX_ASYNCHRONOUS_IO;
                        return (0);
                case _PC_PATH_MAX:
                        *ap->a_retval = PATH_MAX;
                        return (0);
                case _PC_ACL_EXTENDED:
                case _PC_ACL_NFS4:
                case _PC_CAP_PRESENT:
                case _PC_DEALLOC_PRESENT:
                case _PC_INF_PRESENT:
                case _PC_MAC_PRESENT:
                case _PC_NAMEDATTR_ENABLED:
                case _PC_HAS_NAMEDATTR:
                case _PC_HAS_HIDDENSYSTEM:
                case _PC_CLONE_BLKSIZE:
                case _PC_CASE_INSENSITIVE:
                        *ap->a_retval = 0;
                        return (0);
                default:
                        return (EINVAL);
        }
        /* NOTREACHED */
}

/*
 * Standard lock, unlock and islocked functions.
 */
int
vop_stdlock(struct vop_lock1_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct mtx *ilk;

        ilk = VI_MTX(vp);
        return (lockmgr_lock_flags(vp->v_vnlock, ap->a_flags,
            &ilk->lock_object, ap->a_file, ap->a_line));
}

/* See above. */
int
vop_stdunlock(struct vop_unlock_args *ap)
{
        struct vnode *vp = ap->a_vp;

        return (lockmgr_unlock(vp->v_vnlock));
}

/* See above. */
int
vop_stdislocked(struct vop_islocked_args *ap)
{

        return (lockstatus(ap->a_vp->v_vnlock));
}

/*
 * Variants of the above set.
 *
 * Differences are:
 * - shared locking disablement is not supported
 * - v_vnlock pointer is not honored
 */
int
vop_lock(struct vop_lock1_args *ap)
{
        struct vnode *vp = ap->a_vp;
        int flags = ap->a_flags;
        struct mtx *ilk;

        MPASS(vp->v_vnlock == &vp->v_lock);

        if (__predict_false((flags & ~(LK_TYPE_MASK | LK_NODDLKTREAT | LK_RETRY)) != 0))
                goto other;

        switch (flags & LK_TYPE_MASK) {
        case LK_SHARED:
                return (lockmgr_slock(&vp->v_lock, flags, ap->a_file, ap->a_line));
        case LK_EXCLUSIVE:
                return (lockmgr_xlock(&vp->v_lock, flags, ap->a_file, ap->a_line));
        }
other:
        ilk = VI_MTX(vp);
        return (lockmgr_lock_flags(&vp->v_lock, flags,
            &ilk->lock_object, ap->a_file, ap->a_line));
}

int
vop_unlock(struct vop_unlock_args *ap)
{
        struct vnode *vp = ap->a_vp;

        MPASS(vp->v_vnlock == &vp->v_lock);

        return (lockmgr_unlock(&vp->v_lock));
}

int
vop_islocked(struct vop_islocked_args *ap)
{
        struct vnode *vp = ap->a_vp;

        MPASS(vp->v_vnlock == &vp->v_lock);

        return (lockstatus(&vp->v_lock));
}

/*
 * Return true for select/poll.
 */
int
vop_nopoll(struct vop_poll_args *ap)
{

        if (ap->a_events & ~POLLSTANDARD)
                return (POLLNVAL);
        return (ap->a_events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
}

/*
 * Implement poll for local filesystems that support it.
 */
int
vop_stdpoll(struct vop_poll_args *ap)
{
        if (ap->a_events & ~POLLSTANDARD)
                return (vn_pollrecord(ap->a_vp, ap->a_td, ap->a_events));
        return (ap->a_events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
}

/*
 * Return our mount point, as we will take charge of the writes.
 */
int
vop_stdgetwritemount(struct vop_getwritemount_args *ap)
{
        struct mount *mp;
        struct vnode *vp;

        /*
         * Note that having a reference does not prevent forced unmount from
         * setting ->v_mount to NULL after the lock gets released. This is of
         * no consequence for typical consumers (most notably vn_start_write)
         * since in this case the vnode is VIRF_DOOMED. Unmount might have
         * progressed far enough that its completion is only delayed by the
         * reference obtained here. The consumer only needs to concern itself
         * with releasing it.
         */
        vp = ap->a_vp;
        mp = vfs_ref_from_vp(vp);
        *(ap->a_mpp) = mp;
        return (0);
}

/*
 * If the file system doesn't implement VOP_BMAP, then return sensible defaults:
 * - Return the vnode's bufobj instead of any underlying device's bufobj
 * - Calculate the physical block number as if there were equal size
 *   consecutive blocks, but
 * - Report no contiguous runs of blocks.
 */
int
vop_stdbmap(struct vop_bmap_args *ap)
{

        if (ap->a_bop != NULL)
                *ap->a_bop = &ap->a_vp->v_bufobj;
        if (ap->a_bnp != NULL)
                *ap->a_bnp = ap->a_bn * btodb(ap->a_vp->v_mount->mnt_stat.f_iosize);
        if (ap->a_runp != NULL)
                *ap->a_runp = 0;
        if (ap->a_runb != NULL)
                *ap->a_runb = 0;
        return (0);
}

int
vop_stdfsync(struct vop_fsync_args *ap)
{

        return (vn_fsync_buf(ap->a_vp, ap->a_waitfor));
}

static int
vop_stdfdatasync(struct vop_fdatasync_args *ap)
{

        return (VOP_FSYNC(ap->a_vp, MNT_WAIT, ap->a_td));
}

int
vop_stdfdatasync_buf(struct vop_fdatasync_args *ap)
{

        return (vn_fsync_buf(ap->a_vp, MNT_WAIT));
}

/* XXX Needs good comment and more info in the manpage (VOP_GETPAGES(9)). */
int
vop_stdgetpages(struct vop_getpages_args *ap)
{

        return vnode_pager_generic_getpages(ap->a_vp, ap->a_m,
            ap->a_count, ap->a_rbehind, ap->a_rahead, NULL, NULL);
}

static int
vop_stdgetpages_async(struct vop_getpages_async_args *ap)
{
        int error;

        error = VOP_GETPAGES(ap->a_vp, ap->a_m, ap->a_count, ap->a_rbehind,
            ap->a_rahead);
        if (ap->a_iodone != NULL)
                ap->a_iodone(ap->a_arg, ap->a_m, ap->a_count, error);
        return (error);
}

int
vop_stdkqfilter(struct vop_kqfilter_args *ap)
{
        return vfs_kqfilter(ap);
}

/* XXX Needs good comment and more info in the manpage (VOP_PUTPAGES(9)). */
int
vop_stdputpages(struct vop_putpages_args *ap)
{

        return vnode_pager_generic_putpages(ap->a_vp, ap->a_m, ap->a_count,
             ap->a_sync, ap->a_rtvals);
}

int
vop_stdvptofh(struct vop_vptofh_args *ap)
{
        return (EOPNOTSUPP);
}

int
vop_stdvptocnp(struct vop_vptocnp_args *ap)
{
        struct vnode *const vp = ap->a_vp;
        struct vnode **const dvp = ap->a_vpp;
        char *buf = ap->a_buf;
        size_t *buflen = ap->a_buflen;
        char *dirbuf;
        int i = *buflen;
        int error = 0, covered = 0;
        int eofflag, flags, locked;
        size_t dirbuflen, len;
        off_t off;
        ino_t fileno;
        struct vattr va;
        struct nameidata nd;
        struct thread *const td = curthread;
        struct ucred *const cred = td->td_ucred;
        struct dirent *dp;
        struct vnode *mvp;

        if (vp->v_type != VDIR)
                return (ENOENT);

        error = VOP_GETATTR(vp, &va, cred);
        if (error)
                return (error);

        vref(vp);
        locked = VOP_ISLOCKED(vp);
        VOP_UNLOCK(vp);
        NDINIT_ATVP(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF, UIO_SYSSPACE,
            "..", vp);
        flags = FREAD;
        error = vn_open_cred(&nd, &flags, 0, VN_OPEN_NOAUDIT, cred, NULL);
        if (error) {
                vn_lock(vp, locked | LK_RETRY);
                return (error);
        }
        NDFREE_PNBUF(&nd);

        mvp = *dvp = nd.ni_vp;

        if (vp->v_mount != (*dvp)->v_mount &&
            ((*dvp)->v_vflag & VV_ROOT) &&
            ((*dvp)->v_mount->mnt_flag & MNT_UNION)) {
                *dvp = (*dvp)->v_mount->mnt_vnodecovered;
                vref(mvp);
                VOP_UNLOCK(mvp);
                vn_close(mvp, FREAD, cred, td);
                vref(*dvp);
                vn_lock(*dvp, LK_SHARED | LK_RETRY);
                covered = 1;
        }

        fileno = va.va_fileid;

        dirbuflen = MAX(DEV_BSIZE, GENERIC_MAXDIRSIZ);
        if (dirbuflen < va.va_blocksize)
                dirbuflen = va.va_blocksize;
        dirbuf = malloc(dirbuflen, M_TEMP, M_WAITOK);

        if ((*dvp)->v_type != VDIR) {
                error = ENOENT;
                goto out;
        }

        len = 0;
        off = 0;
        eofflag = 0;

        for (;;) {
                /* call VOP_READDIR of parent */
                error = vn_dir_next_dirent(*dvp, td,
                    dirbuf, dirbuflen, &dp, &len, &off, &eofflag);
                if (error != 0)
                        goto out;

                if (len == 0) {
                        error = ENOENT;
                        goto out;
                }

                if ((dp->d_type != DT_WHT) &&
                    (dp->d_fileno == fileno)) {
                        if (covered) {
                                VOP_UNLOCK(*dvp);
                                vn_lock(mvp, LK_SHARED | LK_RETRY);
                                if (dirent_exists(mvp, dp->d_name, td) == 0) {
                                        error = ENOENT;
                                        VOP_UNLOCK(mvp);
                                        vn_lock(*dvp, LK_SHARED | LK_RETRY);
                                        goto out;
                                }
                                VOP_UNLOCK(mvp);
                                vn_lock(*dvp, LK_SHARED | LK_RETRY);
                        }
                        i -= dp->d_namlen;

                        if (i < 0) {
                                error = ENOMEM;
                                goto out;
                        }
                        if (dp->d_namlen == 1 && dp->d_name[0] == '.') {
                                error = ENOENT;
                        } else {
                                bcopy(dp->d_name, buf + i, dp->d_namlen);
                                error = 0;
                        }
                        goto out;
                }
        }

out:
        free(dirbuf, M_TEMP);
        if (!error) {
                *buflen = i;
                vref(*dvp);
        }
        if (covered) {
                vput(*dvp);
                vrele(mvp);
        } else {
                VOP_UNLOCK(mvp);
                vn_close(mvp, FREAD, cred, td);
        }
        vn_lock(vp, locked | LK_RETRY);
        return (error);
}

int
vop_stdallocate(struct vop_allocate_args *ap)
{
#ifdef __notyet__
        struct statfs *sfs;
        off_t maxfilesize = 0;
#endif
        struct iovec aiov;
        struct vattr vattr, *vap;
        struct uio auio;
        off_t fsize, len, cur, offset;
        uint8_t *buf;
        struct thread *td;
        struct vnode *vp;
        size_t iosize;
        int error;

        buf = NULL;
        error = 0;
        td = curthread;
        vap = &vattr;
        vp = ap->a_vp;
        len = *ap->a_len;
        offset = *ap->a_offset;

        error = VOP_GETATTR(vp, vap, ap->a_cred);
        if (error != 0)
                goto out;
        fsize = vap->va_size;
        iosize = vap->va_blocksize;
        if (iosize == 0)
                iosize = BLKDEV_IOSIZE;
        if (iosize > maxphys)
                iosize = maxphys;
        buf = malloc(iosize, M_TEMP, M_WAITOK);

#ifdef __notyet__
        /*
         * Check if the filesystem sets f_maxfilesize; if not use
         * VOP_SETATTR to perform the check.
         */
        sfs = malloc(sizeof(struct statfs), M_STATFS, M_WAITOK);
        error = VFS_STATFS(vp->v_mount, sfs, td);
        if (error == 0)
                maxfilesize = sfs->f_maxfilesize;
        free(sfs, M_STATFS);
        if (error != 0)
                goto out;
        if (maxfilesize) {
                if (offset > maxfilesize || len > maxfilesize ||
                    offset + len > maxfilesize) {
                        error = EFBIG;
                        goto out;
                }
        } else
#endif
        if (offset + len > vap->va_size) {
                /*
                 * Test offset + len against the filesystem's maxfilesize.
                 */
                VATTR_NULL(vap);
                vap->va_size = offset + len;
                error = VOP_SETATTR(vp, vap, ap->a_cred);
                if (error != 0)
                        goto out;
                VATTR_NULL(vap);
                vap->va_size = fsize;
                error = VOP_SETATTR(vp, vap, ap->a_cred);
                if (error != 0)
                        goto out;
        }

        for (;;) {
                /*
                 * Read and write back anything below the nominal file
                 * size.  There's currently no way outside the filesystem
                 * to know whether this area is sparse or not.
                 */
                cur = iosize;
                if ((offset % iosize) != 0)
                        cur -= (offset % iosize);
                if (cur > len)
                        cur = len;
                if (offset < fsize) {
                        aiov.iov_base = buf;
                        aiov.iov_len = cur;
                        auio.uio_iov = &aiov;
                        auio.uio_iovcnt = 1;
                        auio.uio_offset = offset;
                        auio.uio_resid = cur;
                        auio.uio_segflg = UIO_SYSSPACE;
                        auio.uio_rw = UIO_READ;
                        auio.uio_td = td;
                        error = VOP_READ(vp, &auio, ap->a_ioflag, ap->a_cred);
                        if (error != 0)
                                break;
                        if (auio.uio_resid > 0) {
                                bzero(buf + cur - auio.uio_resid,
                                    auio.uio_resid);
                        }
                } else {
                        bzero(buf, cur);
                }

                aiov.iov_base = buf;
                aiov.iov_len = cur;
                auio.uio_iov = &aiov;
                auio.uio_iovcnt = 1;
                auio.uio_offset = offset;
                auio.uio_resid = cur;
                auio.uio_segflg = UIO_SYSSPACE;
                auio.uio_rw = UIO_WRITE;
                auio.uio_td = td;

                error = VOP_WRITE(vp, &auio, ap->a_ioflag, ap->a_cred);
                if (error != 0)
                        break;

                len -= cur;
                offset += cur;
                if (len == 0)
                        break;
                if (should_yield())
                        break;
        }

 out:
        *ap->a_len = len;
        *ap->a_offset = offset;
        free(buf, M_TEMP);
        return (error);
}

static int
vp_zerofill(struct vnode *vp, struct vattr *vap, off_t *offsetp, off_t *lenp,
    int ioflag, struct ucred *cred)
{
        int iosize;
        int error = 0;
        struct iovec aiov;
        struct uio auio;
        struct thread *td;
        off_t offset, len;

        iosize = vap->va_blocksize;
        td = curthread;
        offset = *offsetp;
        len = *lenp;

        if (iosize == 0)
                iosize = BLKDEV_IOSIZE;
        /* If va_blocksize is 512 bytes, iosize will be 4 kilobytes */
        iosize = min(iosize * 8, ZERO_REGION_SIZE);

        while (len > 0) {
                int xfersize = iosize;
                if (offset % iosize != 0)
                        xfersize -= offset % iosize;
                if (xfersize > len)
                        xfersize = len;

                aiov.iov_base = __DECONST(void *, zero_region);
                aiov.iov_len = xfersize;
                auio.uio_iov = &aiov;
                auio.uio_iovcnt = 1;
                auio.uio_offset = offset;
                auio.uio_resid = xfersize;
                auio.uio_segflg = UIO_SYSSPACE;
                auio.uio_rw = UIO_WRITE;
                auio.uio_td = td;

                error = VOP_WRITE(vp, &auio, ioflag, cred);
                if (error != 0) {
                        len -= xfersize - auio.uio_resid;
                        offset += xfersize - auio.uio_resid;
                        break;
                }

                len -= xfersize;
                offset += xfersize;
        }

        *offsetp = offset;
        *lenp = len;
        return (error);
}

int
vop_stddeallocate(struct vop_deallocate_args *ap)
{
        struct vnode *vp;
        off_t offset, len;
        struct ucred *cred;
        int error;
        struct vattr va;
        off_t noff, xfersize, rem;

        vp = ap->a_vp;
        offset = *ap->a_offset;
        cred = ap->a_cred;

        error = VOP_GETATTR(vp, &va, cred);
        if (error)
                return (error);

        len = omin((off_t)va.va_size - offset, *ap->a_len);
        while (len > 0) {
                noff = offset;
                error = vn_bmap_seekhole_locked(vp, FIOSEEKDATA, &noff, cred);
                if (error) {
                        if (error != ENXIO)
                                /* XXX: Is it okay to fallback further? */
                                goto out;

                        /*
                         * No more data region to be filled
                         */
                        offset += len;
                        len = 0;
                        error = 0;
                        break;
                }
                KASSERT(noff >= offset, ("FIOSEEKDATA going backward"));
                if (noff != offset) {
                        xfersize = omin(noff - offset, len);
                        len -= xfersize;
                        offset += xfersize;
                        if (len == 0)
                                break;
                }
                error = vn_bmap_seekhole_locked(vp, FIOSEEKHOLE, &noff, cred);
                if (error)
                        goto out;

                /* Fill zeroes */
                xfersize = rem = omin(noff - offset, len);
                error = vp_zerofill(vp, &va, &offset, &rem, ap->a_ioflag, cred);
                if (error) {
                        len -= xfersize - rem;
                        goto out;
                }

                len -= xfersize;
                if (should_yield())
                        break;
        }
        /* Handle the case when offset is beyond EOF */
        if (len < 0)
                len = 0;
out:
        *ap->a_offset = offset;
        *ap->a_len = len;
        return (error);
}

int
vop_stdadvise(struct vop_advise_args *ap)
{
        struct vnode *vp;
        struct bufobj *bo;
        uintmax_t bstart, bend;
        daddr_t startn, endn;
        int bsize, error;

        vp = ap->a_vp;
        switch (ap->a_advice) {
        case POSIX_FADV_WILLNEED:
                /*
                 * Do nothing for now.  Filesystems should provide a
                 * custom method which starts an asynchronous read of
                 * the requested region.
                 */
                error = 0;
                break;
        case POSIX_FADV_DONTNEED:
                error = 0;
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                if (VN_IS_DOOMED(vp)) {
                        VOP_UNLOCK(vp);
                        break;
                }

                /*
                 * Round to block boundaries (and later possibly further to
                 * page boundaries).  Applications cannot reasonably be aware
                 * of the boundaries, and the rounding must be to expand at
                 * both extremities to cover enough.  It still doesn't cover
                 * read-ahead.  For partial blocks, this gives unnecessary
                 * discarding of buffers but is efficient enough since the
                 * pages usually remain in VMIO for some time.
                 */
                bsize = vp->v_bufobj.bo_bsize;
                bstart = rounddown(ap->a_start, bsize);
                bend = ap->a_end;
                bend = roundup(bend, bsize);

                /*
                 * Deactivate pages in the specified range from the backing VM
                 * object.  Pages that are resident in the buffer cache will
                 * remain wired until their corresponding buffers are released
                 * below.
                 */
                if (vp->v_object != NULL) {
                        VM_OBJECT_RLOCK(vp->v_object);
                        vm_object_page_noreuse(vp->v_object,
                            OFF_TO_IDX(trunc_page(bstart)),
                            OFF_TO_IDX(round_page(bend)));
                        VM_OBJECT_RUNLOCK(vp->v_object);
                }

                bo = &vp->v_bufobj;
                startn = bstart / bsize;
                endn = bend / bsize;
                BO_RLOCK(bo);
                error = bnoreuselist(&bo->bo_clean, bo, startn, endn);
                if (error == 0)
                        error = bnoreuselist(&bo->bo_dirty, bo, startn, endn);
                BO_RUNLOCK(bo);
                VOP_UNLOCK(vp);
                break;
        default:
                error = EINVAL;
                break;
        }
        return (error);
}

int
vop_stdunp_bind(struct vop_unp_bind_args *ap)
{

        ap->a_vp->v_unpcb = ap->a_unpcb;
        return (0);
}

int
vop_stdunp_connect(struct vop_unp_connect_args *ap)
{

        *ap->a_unpcb = ap->a_vp->v_unpcb;
        return (0);
}

int
vop_stdunp_detach(struct vop_unp_detach_args *ap)
{

        ap->a_vp->v_unpcb = NULL;
        return (0);
}

static int
vop_stdis_text(struct vop_is_text_args *ap)
{

        return ((int)atomic_load_int(&ap->a_vp->v_writecount) < 0);
}

int
vop_stdset_text(struct vop_set_text_args *ap)
{
        struct vnode *vp;
        int n;
        bool gotref;

        vp = ap->a_vp;

        n = atomic_load_int(&vp->v_writecount);
        for (;;) {
                if (__predict_false(n > 0)) {
                        return (ETXTBSY);
                }

                /*
                 * Transition point, we may need to grab a reference on the vnode.
                 *
                 * Take the ref early As a safety measure against bogus calls
                 * to vop_stdunset_text.
                 */
                if (n == 0) {
                        gotref = false;
                        if ((vn_irflag_read(vp) & VIRF_TEXT_REF) != 0) {
                                vref(vp);
                                gotref = true;
                        }
                        if (atomic_fcmpset_int(&vp->v_writecount, &n, -1)) {
                                return (0);
                        }
                        if (gotref) {
                                vunref(vp);
                        }
                        continue;
                }

                MPASS(n < 0);
                if (atomic_fcmpset_int(&vp->v_writecount, &n, n - 1)) {
                        return (0);
                }
        }
        __assert_unreachable();
}

static int
vop_stdunset_text(struct vop_unset_text_args *ap)
{
        struct vnode *vp;
        int n;

        vp = ap->a_vp;

        n = atomic_load_int(&vp->v_writecount);
        for (;;) {
                if (__predict_false(n >= 0)) {
                        return (EINVAL);
                }

                /*
                 * Transition point, we may need to release a reference on the vnode.
                 */
                if (n == -1) {
                        if (atomic_fcmpset_int(&vp->v_writecount, &n, 0)) {
                                if ((vn_irflag_read(vp) & VIRF_TEXT_REF) != 0) {
                                        vunref(vp);
                                }
                                return (0);
                        }
                        continue;
                }

                MPASS(n < -1);
                if (atomic_fcmpset_int(&vp->v_writecount, &n, n + 1)) {
                        return (0);
                }
        }
        __assert_unreachable();
}

static __always_inline int
vop_stdadd_writecount_impl(struct vop_add_writecount_args *ap, bool handle_msync)
{
        struct vnode *vp;
        struct mount *mp __diagused;
        int n;

        vp = ap->a_vp;

#ifdef INVARIANTS
        mp = vp->v_mount;
        if (mp != NULL) {
                if (handle_msync) {
                        VNPASS((mp->mnt_kern_flag & MNTK_NOMSYNC) == 0, vp);
                } else {
                        VNPASS((mp->mnt_kern_flag & MNTK_NOMSYNC) != 0, vp);
                }
        }
#endif

        n = atomic_load_int(&vp->v_writecount);
        for (;;) {
                if (__predict_false(n < 0)) {
                        return (ETXTBSY);
                }

                VNASSERT(n + ap->a_inc >= 0, vp,
                    ("neg writecount increment %d + %d = %d", n, ap->a_inc,
                    n + ap->a_inc));
                if (n == 0) {
                        if (handle_msync) {
                                vlazy(vp);
                        }
                }

                if (atomic_fcmpset_int(&vp->v_writecount, &n, n + ap->a_inc)) {
                        return (0);
                }
        }
        __assert_unreachable();
}

int
vop_stdadd_writecount(struct vop_add_writecount_args *ap)
{

        return (vop_stdadd_writecount_impl(ap, true));
}

int
vop_stdadd_writecount_nomsync(struct vop_add_writecount_args *ap)
{

        return (vop_stdadd_writecount_impl(ap, false));
}

int
vop_stdneed_inactive(struct vop_need_inactive_args *ap)
{

        return (1);
}

int
vop_stdinotify(struct vop_inotify_args *ap)
{
        vn_inotify(ap->a_vp, ap->a_dvp, ap->a_cnp, ap->a_event, ap->a_cookie);
        return (0);
}

int
vop_stdinotify_add_watch(struct vop_inotify_add_watch_args *ap)
{
        return (vn_inotify_add_watch(ap->a_vp, ap->a_sc, ap->a_mask,
            ap->a_wdp, ap->a_td));
}

int
vop_stdioctl(struct vop_ioctl_args *ap)
{
        struct vnode *vp;
        struct vattr va;
        off_t *offp;
        int error;

        switch (ap->a_command) {
        case FIOSEEKDATA:
        case FIOSEEKHOLE:
                vp = ap->a_vp;
                error = vn_lock(vp, LK_SHARED);
                if (error != 0)
                        return (EBADF);
                if (vp->v_type == VREG)
                        error = VOP_GETATTR(vp, &va, ap->a_cred);
                else
                        error = ENOTTY;
                if (error == 0) {
                        offp = ap->a_data;
                        if (*offp < 0 || *offp >= va.va_size)
                                error = ENXIO;
                        else if (ap->a_command == FIOSEEKHOLE)
                                *offp = va.va_size;
                }
                VOP_UNLOCK(vp);
                break;
        default:
                error = ENOTTY;
                break;
        }
        return (error);
}

/*
 * vfs default ops
 * used to fill the vfs function table to get reasonable default return values.
 */
int
vfs_stdroot(struct mount *mp, int flags, struct vnode **vpp)
{

        return (EOPNOTSUPP);
}

int
vfs_stdstatfs(struct mount *mp, struct statfs *sbp)
{

        return (EOPNOTSUPP);
}

int
vfs_stdquotactl(struct mount *mp, int cmds, uid_t uid, void *arg, bool *mp_busy)
{
        return (EOPNOTSUPP);
}

int
vfs_stdsync(struct mount *mp, int waitfor)
{
        struct vnode *vp, *mvp;
        struct thread *td;
        int error, lockreq, allerror = 0;

        td = curthread;
        lockreq = LK_EXCLUSIVE | LK_INTERLOCK;
        if (waitfor != MNT_WAIT)
                lockreq |= LK_NOWAIT;
        /*
         * Force stale buffer cache information to be flushed.
         */
loop:
        MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
                if (vp->v_bufobj.bo_dirty.bv_cnt == 0) {
                        VI_UNLOCK(vp);
                        continue;
                }
                if ((error = vget(vp, lockreq)) != 0) {
                        if (error == ENOENT) {
                                MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
                                goto loop;
                        }
                        continue;
                }
                error = VOP_FSYNC(vp, waitfor, td);
                if (error)
                        allerror = error;
                vput(vp);
        }
        return (allerror);
}

int
vfs_stdnosync(struct mount *mp, int waitfor)
{

        return (0);
}

int
vop_stdcopy_file_range(struct vop_copy_file_range_args *ap)
{
        int error;

        error = vn_generic_copy_file_range(ap->a_invp, ap->a_inoffp,
            ap->a_outvp, ap->a_outoffp, ap->a_lenp, ap->a_flags, ap->a_incred,
            ap->a_outcred, ap->a_fsizetd);
        return (error);
}

int
vfs_stdvget(struct mount *mp, ino_t ino, int flags, struct vnode **vpp)
{

        return (EOPNOTSUPP);
}

int
vfs_stdfhtovp(struct mount *mp, struct fid *fhp, int flags, struct vnode **vpp)
{

        return (EOPNOTSUPP);
}

int
vfs_stdinit(struct vfsconf *vfsp)
{

        return (0);
}

int
vfs_stduninit(struct vfsconf *vfsp)
{

        return(0);
}

int
vfs_stdextattrctl(struct mount *mp, int cmd, struct vnode *filename_vp,
    int attrnamespace, const char *attrname)
{

        if (filename_vp != NULL)
                VOP_UNLOCK(filename_vp);
        return (EOPNOTSUPP);
}

int
vfs_stdsysctl(struct mount *mp, fsctlop_t op, struct sysctl_req *req)
{

        return (EOPNOTSUPP);
}

static vop_bypass_t *
bp_by_off(struct vop_vector *vop, struct vop_generic_args *a)
{

        return (*(vop_bypass_t **)((char *)vop + a->a_desc->vdesc_vop_offset));
}

int
vop_sigdefer(struct vop_vector *vop, struct vop_generic_args *a)
{
        vop_bypass_t *bp;
        int prev_stops, rc;

        bp = bp_by_off(vop, a);
        MPASS(bp != NULL);

        prev_stops = sigdeferstop(SIGDEFERSTOP_SILENT);
        rc = bp(a);
        sigallowstop(prev_stops);
        return (rc);
}

static int
vop_stdstat(struct vop_stat_args *a)
{
        struct vattr vattr;
        struct vattr *vap;
        struct vnode *vp;
        struct stat *sb;
        int error;
        u_short mode;

        vp = a->a_vp;
        sb = a->a_sb;

        error = vop_stat_helper_pre(a);
        if (error != 0)
                return (error);

        vap = &vattr;

        /*
         * Initialize defaults for new and unusual fields, so that file
         * systems which don't support these fields don't need to know
         * about them.
         */
        vap->va_birthtime.tv_sec = -1;
        vap->va_birthtime.tv_nsec = 0;
        vap->va_fsid = VNOVAL;
        vap->va_gen = 0;
        vap->va_rdev = NODEV;
        vap->va_filerev = 0;
        vap->va_bsdflags = 0;

        error = VOP_GETATTR(vp, vap, a->a_active_cred);
        if (error)
                goto out;

        /*
         * Zero the spare stat fields
         */
        bzero(sb, sizeof *sb);

        /*
         * Copy from vattr table
         */
        if (vap->va_fsid != VNOVAL)
                sb->st_dev = vap->va_fsid;
        else
                sb->st_dev = vp->v_mount->mnt_stat.f_fsid.val[0];
        sb->st_ino = vap->va_fileid;
        mode = vap->va_mode;
        switch (vap->va_type) {
        case VREG:
                mode |= S_IFREG;
                break;
        case VDIR:
                mode |= S_IFDIR;
                break;
        case VBLK:
                mode |= S_IFBLK;
                break;
        case VCHR:
                mode |= S_IFCHR;
                break;
        case VLNK:
                mode |= S_IFLNK;
                break;
        case VSOCK:
                mode |= S_IFSOCK;
                break;
        case VFIFO:
                mode |= S_IFIFO;
                break;
        default:
                error = EBADF;
                goto out;
        }
        sb->st_mode = mode;
        sb->st_nlink = vap->va_nlink;
        sb->st_uid = vap->va_uid;
        sb->st_gid = vap->va_gid;
        sb->st_rdev = vap->va_rdev;
        if (vap->va_size > OFF_MAX) {
                error = EOVERFLOW;
                goto out;
        }
        sb->st_size = vap->va_size;
        sb->st_atim.tv_sec = vap->va_atime.tv_sec;
        sb->st_atim.tv_nsec = vap->va_atime.tv_nsec;
        sb->st_mtim.tv_sec = vap->va_mtime.tv_sec;
        sb->st_mtim.tv_nsec = vap->va_mtime.tv_nsec;
        sb->st_ctim.tv_sec = vap->va_ctime.tv_sec;
        sb->st_ctim.tv_nsec = vap->va_ctime.tv_nsec;
        sb->st_birthtim.tv_sec = vap->va_birthtime.tv_sec;
        sb->st_birthtim.tv_nsec = vap->va_birthtime.tv_nsec;

        /*
         * According to www.opengroup.org, the meaning of st_blksize is
         *   "a filesystem-specific preferred I/O block size for this
         *    object.  In some filesystem types, this may vary from file
         *    to file"
         * Use minimum/default of PAGE_SIZE (e.g. for VCHR).
         */

        sb->st_blksize = max(PAGE_SIZE, vap->va_blocksize);
        sb->st_flags = vap->va_flags;
        sb->st_blocks = vap->va_bytes / S_BLKSIZE;
        sb->st_gen = vap->va_gen;
        sb->st_filerev = vap->va_filerev;
        sb->st_bsdflags = vap->va_bsdflags;
out:
        return (vop_stat_helper_post(a, error));
}

static int
vop_stdread_pgcache(struct vop_read_pgcache_args *ap __unused)
{
        return (EJUSTRETURN);
}

static int
vop_stdvput_pair(struct vop_vput_pair_args *ap)
{
        struct vnode *dvp, *vp, **vpp;

        dvp = ap->a_dvp;
        vpp = ap->a_vpp;
        vput(dvp);
        if (vpp != NULL && ap->a_unlock_vp && (vp = *vpp) != NULL)
                vput(vp);
        return (0);
}

static int
vop_stdgetlowvnode(struct vop_getlowvnode_args *ap)
{
        vref(ap->a_vp);
        *ap->a_vplp = ap->a_vp;
        return (0);
}