MFC r221436:

[FreeBSD/stable/8.git] / sys / fs / nfsclient / nfs_clvnops.c

/*-
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Rick Macklem at The University of Guelph.
 *
 * 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.
 * 4. 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 nfs_vnops.c        8.16 (Berkeley) 5/27/95
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 * vnode op calls for Sun NFS version 2, 3 and 4
 */

#include "opt_inet.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/resourcevar.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/jail.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/namei.h>
#include <sys/socket.h>
#include <sys/vnode.h>
#include <sys/dirent.h>
#include <sys/fcntl.h>
#include <sys/lockf.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/signalvar.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>

#include <fs/nfs/nfsport.h>
#include <fs/nfsclient/nfsnode.h>
#include <fs/nfsclient/nfsmount.h>
#include <fs/nfsclient/nfs.h>

#include <net/if.h>
#include <netinet/in.h>
#include <netinet/in_var.h>

#include <nfs/nfs_lock.h>

/* Defs */
#define TRUE    1
#define FALSE   0

extern struct nfsstats newnfsstats;
extern int nfsrv_useacl;
MALLOC_DECLARE(M_NEWNFSREQ);

/*
 * Ifdef for FreeBSD-current merged buffer cache. It is unfortunate that these
 * calls are not in getblk() and brelse() so that they would not be necessary
 * here.
 */
#ifndef B_VMIO
#define vfs_busy_pages(bp, f)
#endif

static vop_read_t       nfsfifo_read;
static vop_write_t      nfsfifo_write;
static vop_close_t      nfsfifo_close;
static int      nfs_setattrrpc(struct vnode *, struct vattr *, struct ucred *,
                    struct thread *);
static vop_lookup_t     nfs_lookup;
static vop_create_t     nfs_create;
static vop_mknod_t      nfs_mknod;
static vop_open_t       nfs_open;
static vop_pathconf_t   nfs_pathconf;
static vop_close_t      nfs_close;
static vop_access_t     nfs_access;
static vop_getattr_t    nfs_getattr;
static vop_setattr_t    nfs_setattr;
static vop_read_t       nfs_read;
static vop_fsync_t      nfs_fsync;
static vop_remove_t     nfs_remove;
static vop_link_t       nfs_link;
static vop_rename_t     nfs_rename;
static vop_mkdir_t      nfs_mkdir;
static vop_rmdir_t      nfs_rmdir;
static vop_symlink_t    nfs_symlink;
static vop_readdir_t    nfs_readdir;
static vop_strategy_t   nfs_strategy;
static vop_lock1_t      nfs_lock1;
static  int     nfs_lookitup(struct vnode *, char *, int,
                    struct ucred *, struct thread *, struct nfsnode **);
static  int     nfs_sillyrename(struct vnode *, struct vnode *,
                    struct componentname *);
static vop_access_t     nfsspec_access;
static vop_readlink_t   nfs_readlink;
static vop_print_t      nfs_print;
static vop_advlock_t    nfs_advlock;
static vop_advlockasync_t nfs_advlockasync;
static vop_getacl_t nfs_getacl;
static vop_setacl_t nfs_setacl;

/*
 * Global vfs data structures for nfs
 */
struct vop_vector newnfs_vnodeops = {
        .vop_default =          &default_vnodeops,
        .vop_access =           nfs_access,
        .vop_advlock =          nfs_advlock,
        .vop_advlockasync =     nfs_advlockasync,
        .vop_close =            nfs_close,
        .vop_create =           nfs_create,
        .vop_fsync =            nfs_fsync,
        .vop_getattr =          nfs_getattr,
        .vop_getpages =         ncl_getpages,
        .vop_putpages =         ncl_putpages,
        .vop_inactive =         ncl_inactive,
        .vop_link =             nfs_link,
        .vop_lock1 =            nfs_lock1,
        .vop_lookup =           nfs_lookup,
        .vop_mkdir =            nfs_mkdir,
        .vop_mknod =            nfs_mknod,
        .vop_open =             nfs_open,
        .vop_pathconf =         nfs_pathconf,
        .vop_print =            nfs_print,
        .vop_read =             nfs_read,
        .vop_readdir =          nfs_readdir,
        .vop_readlink =         nfs_readlink,
        .vop_reclaim =          ncl_reclaim,
        .vop_remove =           nfs_remove,
        .vop_rename =           nfs_rename,
        .vop_rmdir =            nfs_rmdir,
        .vop_setattr =          nfs_setattr,
        .vop_strategy =         nfs_strategy,
        .vop_symlink =          nfs_symlink,
        .vop_write =            ncl_write,
        .vop_getacl =           nfs_getacl,
        .vop_setacl =           nfs_setacl,
};

struct vop_vector newnfs_fifoops = {
        .vop_default =          &fifo_specops,
        .vop_access =           nfsspec_access,
        .vop_close =            nfsfifo_close,
        .vop_fsync =            nfs_fsync,
        .vop_getattr =          nfs_getattr,
        .vop_inactive =         ncl_inactive,
        .vop_print =            nfs_print,
        .vop_read =             nfsfifo_read,
        .vop_reclaim =          ncl_reclaim,
        .vop_setattr =          nfs_setattr,
        .vop_write =            nfsfifo_write,
};

static int nfs_mknodrpc(struct vnode *dvp, struct vnode **vpp,
    struct componentname *cnp, struct vattr *vap);
static int nfs_removerpc(struct vnode *dvp, struct vnode *vp, char *name,
    int namelen, struct ucred *cred, struct thread *td);
static int nfs_renamerpc(struct vnode *fdvp, struct vnode *fvp,
    char *fnameptr, int fnamelen, struct vnode *tdvp, struct vnode *tvp,
    char *tnameptr, int tnamelen, struct ucred *cred, struct thread *td);
static int nfs_renameit(struct vnode *sdvp, struct vnode *svp,
    struct componentname *scnp, struct sillyrename *sp);

/*
 * Global variables
 */
#define DIRHDSIZ        (sizeof (struct dirent) - (MAXNAMLEN + 1))

SYSCTL_DECL(_vfs_newnfs);

static int      nfsaccess_cache_timeout = NFS_MAXATTRTIMO;
SYSCTL_INT(_vfs_newnfs, OID_AUTO, access_cache_timeout, CTLFLAG_RW,
           &nfsaccess_cache_timeout, 0, "NFS ACCESS cache timeout");

static int      nfs_prime_access_cache = 0;
SYSCTL_INT(_vfs_newnfs, OID_AUTO, prime_access_cache, CTLFLAG_RW,
           &nfs_prime_access_cache, 0,
           "Prime NFS ACCESS cache when fetching attributes");

static int      newnfs_commit_on_close = 0;
SYSCTL_INT(_vfs_newnfs, OID_AUTO, commit_on_close, CTLFLAG_RW,
    &newnfs_commit_on_close, 0, "write+commit on close, else only write");

static int      nfs_clean_pages_on_close = 1;
SYSCTL_INT(_vfs_newnfs, OID_AUTO, clean_pages_on_close, CTLFLAG_RW,
           &nfs_clean_pages_on_close, 0, "NFS clean dirty pages on close");

int newnfs_directio_enable = 0;
SYSCTL_INT(_vfs_newnfs, OID_AUTO, nfs_directio_enable, CTLFLAG_RW,
           &newnfs_directio_enable, 0, "Enable NFS directio");

/*
 * This sysctl allows other processes to mmap a file that has been opened
 * O_DIRECT by a process.  In general, having processes mmap the file while
 * Direct IO is in progress can lead to Data Inconsistencies.  But, we allow
 * this by default to prevent DoS attacks - to prevent a malicious user from
 * opening up files O_DIRECT preventing other users from mmap'ing these
 * files.  "Protected" environments where stricter consistency guarantees are
 * required can disable this knob.  The process that opened the file O_DIRECT
 * cannot mmap() the file, because mmap'ed IO on an O_DIRECT open() is not
 * meaningful.
 */
int newnfs_directio_allow_mmap = 1;
SYSCTL_INT(_vfs_newnfs, OID_AUTO, nfs_directio_allow_mmap, CTLFLAG_RW,
           &newnfs_directio_allow_mmap, 0, "Enable mmaped IO on file with O_DIRECT opens");

#if 0
SYSCTL_INT(_vfs_newnfs, OID_AUTO, access_cache_hits, CTLFLAG_RD,
           &newnfsstats.accesscache_hits, 0, "NFS ACCESS cache hit count");

SYSCTL_INT(_vfs_newnfs, OID_AUTO, access_cache_misses, CTLFLAG_RD,
           &newnfsstats.accesscache_misses, 0, "NFS ACCESS cache miss count");
#endif

#define NFSACCESS_ALL (NFSACCESS_READ | NFSACCESS_MODIFY                \
                         | NFSACCESS_EXTEND | NFSACCESS_EXECUTE \
                         | NFSACCESS_DELETE | NFSACCESS_LOOKUP)

/*
 * SMP Locking Note :
 * The list of locks after the description of the lock is the ordering
 * of other locks acquired with the lock held.
 * np->n_mtx : Protects the fields in the nfsnode.
       VM Object Lock
       VI_MTX (acquired indirectly)
 * nmp->nm_mtx : Protects the fields in the nfsmount.
       rep->r_mtx
 * ncl_iod_mutex : Global lock, protects shared nfsiod state.
 * nfs_reqq_mtx : Global lock, protects the nfs_reqq list.
       nmp->nm_mtx
       rep->r_mtx
 * rep->r_mtx : Protects the fields in an nfsreq.
 */

static int
nfs34_access_otw(struct vnode *vp, int wmode, struct thread *td,
    struct ucred *cred, u_int32_t *retmode)
{
        int error = 0, attrflag, i, lrupos;
        u_int32_t rmode;
        struct nfsnode *np = VTONFS(vp);
        struct nfsvattr nfsva;

        error = nfsrpc_accessrpc(vp, wmode, cred, td, &nfsva, &attrflag,
            &rmode, NULL);
        if (attrflag)
                (void) nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0, 1);
        if (!error) {
                lrupos = 0;
                mtx_lock(&np->n_mtx);
                for (i = 0; i < NFS_ACCESSCACHESIZE; i++) {
                        if (np->n_accesscache[i].uid == cred->cr_uid) {
                                np->n_accesscache[i].mode = rmode;
                                np->n_accesscache[i].stamp = time_second;
                                break;
                        }
                        if (i > 0 && np->n_accesscache[i].stamp <
                            np->n_accesscache[lrupos].stamp)
                                lrupos = i;
                }
                if (i == NFS_ACCESSCACHESIZE) {
                        np->n_accesscache[lrupos].uid = cred->cr_uid;
                        np->n_accesscache[lrupos].mode = rmode;
                        np->n_accesscache[lrupos].stamp = time_second;
                }
                mtx_unlock(&np->n_mtx);
                if (retmode != NULL)
                        *retmode = rmode;
        } else if (NFS_ISV4(vp)) {
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        }
        return (error);
}

/*
 * nfs access vnode op.
 * For nfs version 2, just return ok. File accesses may fail later.
 * For nfs version 3, use the access rpc to check accessibility. If file modes
 * are changed on the server, accesses might still fail later.
 */
static int
nfs_access(struct vop_access_args *ap)
{
        struct vnode *vp = ap->a_vp;
        int error = 0, i, gotahit;
        u_int32_t mode, wmode, rmode;
        int v34 = NFS_ISV34(vp);
        struct nfsnode *np = VTONFS(vp);

        /*
         * Disallow write attempts on filesystems mounted read-only;
         * unless the file is a socket, fifo, or a block or character
         * device resident on the filesystem.
         */
        if ((ap->a_accmode & (VWRITE | VAPPEND | VWRITE_NAMED_ATTRS |
            VDELETE_CHILD | VWRITE_ATTRIBUTES | VDELETE | VWRITE_ACL |
            VWRITE_OWNER)) != 0 && (vp->v_mount->mnt_flag & MNT_RDONLY) != 0) {
                switch (vp->v_type) {
                case VREG:
                case VDIR:
                case VLNK:
                        return (EROFS);
                default:
                        break;
                }
        }
        /*
         * For nfs v3 or v4, check to see if we have done this recently, and if
         * so return our cached result instead of making an ACCESS call.
         * If not, do an access rpc, otherwise you are stuck emulating
         * ufs_access() locally using the vattr. This may not be correct,
         * since the server may apply other access criteria such as
         * client uid-->server uid mapping that we do not know about.
         */
        if (v34) {
                if (ap->a_accmode & VREAD)
                        mode = NFSACCESS_READ;
                else
                        mode = 0;
                if (vp->v_type != VDIR) {
                        if (ap->a_accmode & VWRITE)
                                mode |= (NFSACCESS_MODIFY | NFSACCESS_EXTEND);
                        if (ap->a_accmode & VAPPEND)
                                mode |= NFSACCESS_EXTEND;
                        if (ap->a_accmode & VEXEC)
                                mode |= NFSACCESS_EXECUTE;
                        if (ap->a_accmode & VDELETE)
                                mode |= NFSACCESS_DELETE;
                } else {
                        if (ap->a_accmode & VWRITE)
                                mode |= (NFSACCESS_MODIFY | NFSACCESS_EXTEND);
                        if (ap->a_accmode & VAPPEND)
                                mode |= NFSACCESS_EXTEND;
                        if (ap->a_accmode & VEXEC)
                                mode |= NFSACCESS_LOOKUP;
                        if (ap->a_accmode & VDELETE)
                                mode |= NFSACCESS_DELETE;
                        if (ap->a_accmode & VDELETE_CHILD)
                                mode |= NFSACCESS_MODIFY;
                }
                /* XXX safety belt, only make blanket request if caching */
                if (nfsaccess_cache_timeout > 0) {
                        wmode = NFSACCESS_READ | NFSACCESS_MODIFY |
                                NFSACCESS_EXTEND | NFSACCESS_EXECUTE |
                                NFSACCESS_DELETE | NFSACCESS_LOOKUP;
                } else {
                        wmode = mode;
                }

                /*
                 * Does our cached result allow us to give a definite yes to
                 * this request?
                 */
                gotahit = 0;
                mtx_lock(&np->n_mtx);
                for (i = 0; i < NFS_ACCESSCACHESIZE; i++) {
                        if (ap->a_cred->cr_uid == np->n_accesscache[i].uid) {
                            if (time_second < (np->n_accesscache[i].stamp
                                + nfsaccess_cache_timeout) &&
                                (np->n_accesscache[i].mode & mode) == mode) {
                                NFSINCRGLOBAL(newnfsstats.accesscache_hits);
                                gotahit = 1;
                            }
                            break;
                        }
                }
                mtx_unlock(&np->n_mtx);
                if (gotahit == 0) {
                        /*
                         * Either a no, or a don't know.  Go to the wire.
                         */
                        NFSINCRGLOBAL(newnfsstats.accesscache_misses);
                        error = nfs34_access_otw(vp, wmode, ap->a_td,
                            ap->a_cred, &rmode);
                        if (!error &&
                            (rmode & mode) != mode)
                                error = EACCES;
                }
                return (error);
        } else {
                if ((error = nfsspec_access(ap)) != 0) {
                        return (error);
                }
                /*
                 * Attempt to prevent a mapped root from accessing a file
                 * which it shouldn't.  We try to read a byte from the file
                 * if the user is root and the file is not zero length.
                 * After calling nfsspec_access, we should have the correct
                 * file size cached.
                 */
                mtx_lock(&np->n_mtx);
                if (ap->a_cred->cr_uid == 0 && (ap->a_accmode & VREAD)
                    && VTONFS(vp)->n_size > 0) {
                        struct iovec aiov;
                        struct uio auio;
                        char buf[1];

                        mtx_unlock(&np->n_mtx);
                        aiov.iov_base = buf;
                        aiov.iov_len = 1;
                        auio.uio_iov = &aiov;
                        auio.uio_iovcnt = 1;
                        auio.uio_offset = 0;
                        auio.uio_resid = 1;
                        auio.uio_segflg = UIO_SYSSPACE;
                        auio.uio_rw = UIO_READ;
                        auio.uio_td = ap->a_td;

                        if (vp->v_type == VREG)
                                error = ncl_readrpc(vp, &auio, ap->a_cred);
                        else if (vp->v_type == VDIR) {
                                char* bp;
                                bp = malloc(NFS_DIRBLKSIZ, M_TEMP, M_WAITOK);
                                aiov.iov_base = bp;
                                aiov.iov_len = auio.uio_resid = NFS_DIRBLKSIZ;
                                error = ncl_readdirrpc(vp, &auio, ap->a_cred,
                                    ap->a_td);
                                free(bp, M_TEMP);
                        } else if (vp->v_type == VLNK)
                                error = ncl_readlinkrpc(vp, &auio, ap->a_cred);
                        else
                                error = EACCES;
                } else
                        mtx_unlock(&np->n_mtx);
                return (error);
        }
}


/*
 * nfs open vnode op
 * Check to see if the type is ok
 * and that deletion is not in progress.
 * For paged in text files, you will need to flush the page cache
 * if consistency is lost.
 */
/* ARGSUSED */
static int
nfs_open(struct vop_open_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);
        struct vattr vattr;
        int error;
        int fmode = ap->a_mode;

        if (vp->v_type != VREG && vp->v_type != VDIR && vp->v_type != VLNK)
                return (EOPNOTSUPP);

        /*
         * For NFSv4, we need to do the Open Op before cache validation,
         * so that we conform to RFC3530 Sec. 9.3.1.
         */
        if (NFS_ISV4(vp)) {
                error = nfsrpc_open(vp, fmode, ap->a_cred, ap->a_td);
                if (error) {
                        error = nfscl_maperr(ap->a_td, error, (uid_t)0,
                            (gid_t)0);
                        return (error);
                }
        }

        /*
         * Now, if this Open will be doing reading, re-validate/flush the
         * cache, so that Close/Open coherency is maintained.
         */
        mtx_lock(&np->n_mtx);
        if (np->n_flag & NMODIFIED) {
                mtx_unlock(&np->n_mtx);
                error = ncl_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                if (error == EINTR || error == EIO) {
                        if (NFS_ISV4(vp))
                                (void) nfsrpc_close(vp, 0, ap->a_td);
                        return (error);
                }
                mtx_lock(&np->n_mtx);
                np->n_attrstamp = 0;
                if (vp->v_type == VDIR)
                        np->n_direofoffset = 0;
                mtx_unlock(&np->n_mtx);
                error = VOP_GETATTR(vp, &vattr, ap->a_cred);
                if (error) {
                        if (NFS_ISV4(vp))
                                (void) nfsrpc_close(vp, 0, ap->a_td);
                        return (error);
                }
                mtx_lock(&np->n_mtx);
                np->n_mtime = vattr.va_mtime;
                if (NFS_ISV4(vp))
                        np->n_change = vattr.va_filerev;
        } else {
                mtx_unlock(&np->n_mtx);
                error = VOP_GETATTR(vp, &vattr, ap->a_cred);
                if (error) {
                        if (NFS_ISV4(vp))
                                (void) nfsrpc_close(vp, 0, ap->a_td);
                        return (error);
                }
                mtx_lock(&np->n_mtx);
                if ((NFS_ISV4(vp) && np->n_change != vattr.va_filerev) ||
                    NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime)) {
                        if (vp->v_type == VDIR)
                                np->n_direofoffset = 0;
                        mtx_unlock(&np->n_mtx);
                        error = ncl_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                        if (error == EINTR || error == EIO) {
                                if (NFS_ISV4(vp))
                                        (void) nfsrpc_close(vp, 0, ap->a_td);
                                return (error);
                        }
                        mtx_lock(&np->n_mtx);
                        np->n_mtime = vattr.va_mtime;
                        if (NFS_ISV4(vp))
                                np->n_change = vattr.va_filerev;
                }
        }

        /*
         * If the object has >= 1 O_DIRECT active opens, we disable caching.
         */
        if (newnfs_directio_enable && (fmode & O_DIRECT) &&
            (vp->v_type == VREG)) {
                if (np->n_directio_opens == 0) {
                        mtx_unlock(&np->n_mtx);
                        error = ncl_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                        if (error) {
                                if (NFS_ISV4(vp))
                                        (void) nfsrpc_close(vp, 0, ap->a_td);
                                return (error);
                        }
                        mtx_lock(&np->n_mtx);
                        np->n_flag |= NNONCACHE;
                }
                np->n_directio_opens++;
        }
        mtx_unlock(&np->n_mtx);
        vnode_create_vobject(vp, vattr.va_size, ap->a_td);
        return (0);
}

/*
 * nfs close vnode op
 * What an NFS client should do upon close after writing is a debatable issue.
 * Most NFS clients push delayed writes to the server upon close, basically for
 * two reasons:
 * 1 - So that any write errors may be reported back to the client process
 *     doing the close system call. By far the two most likely errors are
 *     NFSERR_NOSPC and NFSERR_DQUOT to indicate space allocation failure.
 * 2 - To put a worst case upper bound on cache inconsistency between
 *     multiple clients for the file.
 * There is also a consistency problem for Version 2 of the protocol w.r.t.
 * not being able to tell if other clients are writing a file concurrently,
 * since there is no way of knowing if the changed modify time in the reply
 * is only due to the write for this client.
 * (NFS Version 3 provides weak cache consistency data in the reply that
 *  should be sufficient to detect and handle this case.)
 *
 * The current code does the following:
 * for NFS Version 2 - play it safe and flush/invalidate all dirty buffers
 * for NFS Version 3 - flush dirty buffers to the server but don't invalidate
 *                     or commit them (this satisfies 1 and 2 except for the
 *                     case where the server crashes after this close but
 *                     before the commit RPC, which is felt to be "good
 *                     enough". Changing the last argument to ncl_flush() to
 *                     a 1 would force a commit operation, if it is felt a
 *                     commit is necessary now.
 * for NFS Version 4 - flush the dirty buffers and commit them, if
 *                     nfscl_mustflush() says this is necessary.
 *                     It is necessary if there is no write delegation held,
 *                     in order to satisfy open/close coherency.
 *                     If the file isn't cached on local stable storage,
 *                     it may be necessary in order to detect "out of space"
 *                     errors from the server, if the write delegation
 *                     issued by the server doesn't allow the file to grow.
 */
/* ARGSUSED */
static int
nfs_close(struct vop_close_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);
        struct nfsvattr nfsva;
        struct ucred *cred;
        int error = 0, ret, localcred = 0;
        int fmode = ap->a_fflag;

        if ((vp->v_mount->mnt_kern_flag & MNTK_UNMOUNTF))
                return (0);
        /*
         * During shutdown, a_cred isn't valid, so just use root.
         */
        if (ap->a_cred == NOCRED) {
                cred = newnfs_getcred();
                localcred = 1;
        } else {
                cred = ap->a_cred;
        }
        if (vp->v_type == VREG) {
            /*
             * Examine and clean dirty pages, regardless of NMODIFIED.
             * This closes a major hole in close-to-open consistency.
             * We want to push out all dirty pages (and buffers) on
             * close, regardless of whether they were dirtied by
             * mmap'ed writes or via write().
             */
            if (nfs_clean_pages_on_close && vp->v_object) {
                VM_OBJECT_LOCK(vp->v_object);
                vm_object_page_clean(vp->v_object, 0, 0, 0);
                VM_OBJECT_UNLOCK(vp->v_object);
            }
            mtx_lock(&np->n_mtx);
            if (np->n_flag & NMODIFIED) {
                mtx_unlock(&np->n_mtx);
                if (NFS_ISV3(vp)) {
                    /*
                     * Under NFSv3 we have dirty buffers to dispose of.  We
                     * must flush them to the NFS server.  We have the option
                     * of waiting all the way through the commit rpc or just
                     * waiting for the initial write.  The default is to only
                     * wait through the initial write so the data is in the
                     * server's cache, which is roughly similar to the state
                     * a standard disk subsystem leaves the file in on close().
                     *
                     * We cannot clear the NMODIFIED bit in np->n_flag due to
                     * potential races with other processes, and certainly
                     * cannot clear it if we don't commit.
                     * These races occur when there is no longer the old
                     * traditional vnode locking implemented for Vnode Ops.
                     */
                    int cm = newnfs_commit_on_close ? 1 : 0;
                    error = ncl_flush(vp, MNT_WAIT, cred, ap->a_td, cm, 0);
                    /* np->n_flag &= ~NMODIFIED; */
                } else if (NFS_ISV4(vp)) { 
                        if (nfscl_mustflush(vp) != 0) {
                                int cm = newnfs_commit_on_close ? 1 : 0;
                                error = ncl_flush(vp, MNT_WAIT, cred, ap->a_td,
                                    cm, 0);
                                /*
                                 * as above w.r.t races when clearing
                                 * NMODIFIED.
                                 * np->n_flag &= ~NMODIFIED;
                                 */
                        }
                } else
                    error = ncl_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                mtx_lock(&np->n_mtx);
            }
            /* 
             * Invalidate the attribute cache in all cases.
             * An open is going to fetch fresh attrs any way, other procs
             * on this node that have file open will be forced to do an 
             * otw attr fetch, but this is safe.
             * --> A user found that their RPC count dropped by 20% when
             *     this was commented out and I can't see any requirement
             *     for it, so I've disabled it when negative lookups are
             *     enabled. (What does this have to do with negative lookup
             *     caching? Well nothing, except it was reported by the
             *     same user that needed negative lookup caching and I wanted
             *     there to be a way to disable it to see if it
             *     is the cause of some caching/coherency issue that might
             *     crop up.)
             */
            if (VFSTONFS(vp->v_mount)->nm_negnametimeo == 0)
                    np->n_attrstamp = 0;
            if (np->n_flag & NWRITEERR) {
                np->n_flag &= ~NWRITEERR;
                error = np->n_error;
            }
            mtx_unlock(&np->n_mtx);
        }

        if (NFS_ISV4(vp)) {
                /*
                 * Get attributes so "change" is up to date.
                 */
                if (error == 0 && nfscl_mustflush(vp) != 0) {
                        ret = nfsrpc_getattr(vp, cred, ap->a_td, &nfsva,
                            NULL);
                        if (!ret) {
                                np->n_change = nfsva.na_filerev;
                                (void) nfscl_loadattrcache(&vp, &nfsva, NULL,
                                    NULL, 0, 0);
                        }
                }

                /*
                 * and do the close.
                 */
                ret = nfsrpc_close(vp, 0, ap->a_td);
                if (!error && ret)
                        error = ret;
                if (error)
                        error = nfscl_maperr(ap->a_td, error, (uid_t)0,
                            (gid_t)0);
        }
        if (newnfs_directio_enable)
                KASSERT((np->n_directio_asyncwr == 0),
                        ("nfs_close: dirty unflushed (%d) directio buffers\n",
                         np->n_directio_asyncwr));
        if (newnfs_directio_enable && (fmode & O_DIRECT) && (vp->v_type == VREG)) {
                mtx_lock(&np->n_mtx);
                KASSERT((np->n_directio_opens > 0), 
                        ("nfs_close: unexpectedly value (0) of n_directio_opens\n"));
                np->n_directio_opens--;
                if (np->n_directio_opens == 0)
                        np->n_flag &= ~NNONCACHE;
                mtx_unlock(&np->n_mtx);
        }
        if (localcred)
                NFSFREECRED(cred);
        return (error);
}

/*
 * nfs getattr call from vfs.
 */
static int
nfs_getattr(struct vop_getattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct thread *td = curthread;  /* XXX */
        struct nfsnode *np = VTONFS(vp);
        int error = 0;
        struct nfsvattr nfsva;
        struct vattr *vap = ap->a_vap;
        struct vattr vattr;

        /*
         * Update local times for special files.
         */
        mtx_lock(&np->n_mtx);
        if (np->n_flag & (NACC | NUPD))
                np->n_flag |= NCHG;
        mtx_unlock(&np->n_mtx);
        /*
         * First look in the cache.
         */
        if (ncl_getattrcache(vp, &vattr) == 0) {
                vap->va_type = vattr.va_type;
                vap->va_mode = vattr.va_mode;
                vap->va_nlink = vattr.va_nlink;
                vap->va_uid = vattr.va_uid;
                vap->va_gid = vattr.va_gid;
                vap->va_fsid = vattr.va_fsid;
                vap->va_fileid = vattr.va_fileid;
                vap->va_size = vattr.va_size;
                vap->va_blocksize = vattr.va_blocksize;
                vap->va_atime = vattr.va_atime;
                vap->va_mtime = vattr.va_mtime;
                vap->va_ctime = vattr.va_ctime;
                vap->va_gen = vattr.va_gen;
                vap->va_flags = vattr.va_flags;
                vap->va_rdev = vattr.va_rdev;
                vap->va_bytes = vattr.va_bytes;
                vap->va_filerev = vattr.va_filerev;
                /*
                 * Get the local modify time for the case of a write
                 * delegation.
                 */
                nfscl_deleggetmodtime(vp, &vap->va_mtime);
                return (0);
        }

        if (NFS_ISV34(vp) && nfs_prime_access_cache &&
            nfsaccess_cache_timeout > 0) {
                NFSINCRGLOBAL(newnfsstats.accesscache_misses);
                nfs34_access_otw(vp, NFSACCESS_ALL, td, ap->a_cred, NULL);
                if (ncl_getattrcache(vp, ap->a_vap) == 0) {
                        nfscl_deleggetmodtime(vp, &ap->a_vap->va_mtime);
                        return (0);
                }
        }
        error = nfsrpc_getattr(vp, ap->a_cred, td, &nfsva, NULL);
        if (!error)
                error = nfscl_loadattrcache(&vp, &nfsva, vap, NULL, 0, 0);
        if (!error) {
                /*
                 * Get the local modify time for the case of a write
                 * delegation.
                 */
                nfscl_deleggetmodtime(vp, &vap->va_mtime);
        } else if (NFS_ISV4(vp)) {
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        }
        return (error);
}

/*
 * nfs setattr call.
 */
static int
nfs_setattr(struct vop_setattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);
        struct thread *td = curthread;  /* XXX */
        struct vattr *vap = ap->a_vap;
        int error = 0;
        u_quad_t tsize;

#ifndef nolint
        tsize = (u_quad_t)0;
#endif

        /*
         * Setting of flags and marking of atimes are not supported.
         */
        if (vap->va_flags != VNOVAL)
                return (EOPNOTSUPP);

        /*
         * Disallow write attempts if the filesystem is mounted read-only.
         */
        if ((vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
            vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
            vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL) &&
            (vp->v_mount->mnt_flag & MNT_RDONLY))
                return (EROFS);
        if (vap->va_size != VNOVAL) {
                switch (vp->v_type) {
                case VDIR:
                        return (EISDIR);
                case VCHR:
                case VBLK:
                case VSOCK:
                case VFIFO:
                        if (vap->va_mtime.tv_sec == VNOVAL &&
                            vap->va_atime.tv_sec == VNOVAL &&
                            vap->va_mode == (mode_t)VNOVAL &&
                            vap->va_uid == (uid_t)VNOVAL &&
                            vap->va_gid == (gid_t)VNOVAL)
                                return (0);             
                        vap->va_size = VNOVAL;
                        break;
                default:
                        /*
                         * Disallow write attempts if the filesystem is
                         * mounted read-only.
                         */
                        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                                return (EROFS);
                        /*
                         *  We run vnode_pager_setsize() early (why?),
                         * we must set np->n_size now to avoid vinvalbuf
                         * V_SAVE races that might setsize a lower
                         * value.
                         */
                        mtx_lock(&np->n_mtx);
                        tsize = np->n_size;
                        mtx_unlock(&np->n_mtx);
                        error = ncl_meta_setsize(vp, ap->a_cred, td,
                            vap->va_size);
                        mtx_lock(&np->n_mtx);
                        if (np->n_flag & NMODIFIED) {
                            tsize = np->n_size;
                            mtx_unlock(&np->n_mtx);
                            if (vap->va_size == 0)
                                error = ncl_vinvalbuf(vp, 0, td, 1);
                            else
                                error = ncl_vinvalbuf(vp, V_SAVE, td, 1);
                            if (error) {
                                vnode_pager_setsize(vp, tsize);
                                return (error);
                            }
                            /*
                             * Call nfscl_delegmodtime() to set the modify time
                             * locally, as required.
                             */
                            nfscl_delegmodtime(vp);
                        } else
                            mtx_unlock(&np->n_mtx);
                        /*
                         * np->n_size has already been set to vap->va_size
                         * in ncl_meta_setsize(). We must set it again since
                         * nfs_loadattrcache() could be called through
                         * ncl_meta_setsize() and could modify np->n_size.
                         */
                        mtx_lock(&np->n_mtx);
                        np->n_vattr.na_size = np->n_size = vap->va_size;
                        mtx_unlock(&np->n_mtx);
                };
        } else {
                mtx_lock(&np->n_mtx);
                if ((vap->va_mtime.tv_sec != VNOVAL || vap->va_atime.tv_sec != VNOVAL) && 
                    (np->n_flag & NMODIFIED) && vp->v_type == VREG) {
                        mtx_unlock(&np->n_mtx);
                        if ((error = ncl_vinvalbuf(vp, V_SAVE, td, 1)) != 0 &&
                            (error == EINTR || error == EIO))
                                return (error);
                } else
                        mtx_unlock(&np->n_mtx);
        }
        error = nfs_setattrrpc(vp, vap, ap->a_cred, td);
        if (error && vap->va_size != VNOVAL) {
                mtx_lock(&np->n_mtx);
                np->n_size = np->n_vattr.na_size = tsize;
                vnode_pager_setsize(vp, tsize);
                mtx_unlock(&np->n_mtx);
        }
        return (error);
}

/*
 * Do an nfs setattr rpc.
 */
static int
nfs_setattrrpc(struct vnode *vp, struct vattr *vap, struct ucred *cred,
    struct thread *td)
{
        struct nfsnode *np = VTONFS(vp);
        int error, ret, attrflag, i;
        struct nfsvattr nfsva;

        if (NFS_ISV34(vp)) {
                mtx_lock(&np->n_mtx);
                for (i = 0; i < NFS_ACCESSCACHESIZE; i++)
                        np->n_accesscache[i].stamp = 0;
                np->n_flag |= NDELEGMOD;
                mtx_unlock(&np->n_mtx);
        }
        error = nfsrpc_setattr(vp, vap, NULL, cred, td, &nfsva, &attrflag,
            NULL);
        if (attrflag) {
                ret = nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0, 1);
                if (ret && !error)
                        error = ret;
        }
        if (error && NFS_ISV4(vp))
                error = nfscl_maperr(td, error, vap->va_uid, vap->va_gid);
        return (error);
}

/*
 * nfs lookup call, one step at a time...
 * First look in cache
 * If not found, unlock the directory nfsnode and do the rpc
 */
static int
nfs_lookup(struct vop_lookup_args *ap)
{
        struct componentname *cnp = ap->a_cnp;
        struct vnode *dvp = ap->a_dvp;
        struct vnode **vpp = ap->a_vpp;
        struct mount *mp = dvp->v_mount;
        int flags = cnp->cn_flags;
        struct vnode *newvp;
        struct nfsmount *nmp;
        struct nfsnode *np, *newnp;
        int error = 0, attrflag, dattrflag, ltype;
        struct thread *td = cnp->cn_thread;
        struct nfsfh *nfhp;
        struct nfsvattr dnfsva, nfsva;
        struct vattr vattr;
        struct timespec dmtime;
        
        *vpp = NULLVP;
        if ((flags & ISLASTCN) && (mp->mnt_flag & MNT_RDONLY) &&
            (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
                return (EROFS);
        if (dvp->v_type != VDIR)
                return (ENOTDIR);
        nmp = VFSTONFS(mp);
        np = VTONFS(dvp);

        /* For NFSv4, wait until any remove is done. */
        mtx_lock(&np->n_mtx);
        while (NFSHASNFSV4(nmp) && (np->n_flag & NREMOVEINPROG)) {
                np->n_flag |= NREMOVEWANT;
                (void) msleep((caddr_t)np, &np->n_mtx, PZERO, "nfslkup", 0);
        }
        mtx_unlock(&np->n_mtx);

        if ((error = VOP_ACCESS(dvp, VEXEC, cnp->cn_cred, td)) != 0)
                return (error);
        error = cache_lookup(dvp, vpp, cnp);
        if (error > 0 && error != ENOENT)
                return (error);
        if (error == -1) {
                /*
                 * We only accept a positive hit in the cache if the
                 * change time of the file matches our cached copy.
                 * Otherwise, we discard the cache entry and fallback
                 * to doing a lookup RPC.
                 *
                 * To better handle stale file handles and attributes,
                 * clear the attribute cache of this node if it is a
                 * leaf component, part of an open() call, and not
                 * locally modified before fetching the attributes.
                 * This should allow stale file handles to be detected
                 * here where we can fall back to a LOOKUP RPC to
                 * recover rather than having nfs_open() detect the
                 * stale file handle and failing open(2) with ESTALE.
                 */
                newvp = *vpp;
                newnp = VTONFS(newvp);
                if (!(nmp->nm_flag & NFSMNT_NOCTO) &&
                    (flags & (ISLASTCN | ISOPEN)) == (ISLASTCN | ISOPEN) &&
                    !(newnp->n_flag & NMODIFIED)) {
                        mtx_lock(&newnp->n_mtx);
                        newnp->n_attrstamp = 0;
                        mtx_unlock(&newnp->n_mtx);
                }
                if (nfscl_nodeleg(newvp, 0) == 0 ||
                    (VOP_GETATTR(newvp, &vattr, cnp->cn_cred) == 0 &&
                    timespeccmp(&vattr.va_ctime, &newnp->n_ctime, ==))) {
                        NFSINCRGLOBAL(newnfsstats.lookupcache_hits);
                        if (cnp->cn_nameiop != LOOKUP &&
                            (flags & ISLASTCN))
                                cnp->cn_flags |= SAVENAME;
                        return (0);
                }
                cache_purge(newvp);
                if (dvp != newvp)
                        vput(newvp);
                else 
                        vrele(newvp);
                *vpp = NULLVP;
        } else if (error == ENOENT) {
                if (dvp->v_iflag & VI_DOOMED)
                        return (ENOENT);
                /*
                 * We only accept a negative hit in the cache if the
                 * modification time of the parent directory matches
                 * our cached copy.  Otherwise, we discard all of the
                 * negative cache entries for this directory. We also
                 * only trust -ve cache entries for less than
                 * nm_negative_namecache_timeout seconds.
                 */
                if ((u_int)(ticks - np->n_dmtime_ticks) <
                    (nmp->nm_negnametimeo * hz) &&
                    VOP_GETATTR(dvp, &vattr, cnp->cn_cred) == 0 &&
                    timespeccmp(&vattr.va_mtime, &np->n_dmtime, ==)) {
                        NFSINCRGLOBAL(newnfsstats.lookupcache_hits);
                        return (ENOENT);
                }
                cache_purge_negative(dvp);
                mtx_lock(&np->n_mtx);
                timespecclear(&np->n_dmtime);
                mtx_unlock(&np->n_mtx);
        }

        /*
         * Cache the modification time of the parent directory in case
         * the lookup fails and results in adding the first negative
         * name cache entry for the directory.  Since this is reading
         * a single time_t, don't bother with locking.  The
         * modification time may be a bit stale, but it must be read
         * before performing the lookup RPC to prevent a race where
         * another lookup updates the timestamp on the directory after
         * the lookup RPC has been performed on the server but before
         * n_dmtime is set at the end of this function.
         */
        dmtime = np->n_vattr.na_mtime;
        error = 0;
        newvp = NULLVP;
        NFSINCRGLOBAL(newnfsstats.lookupcache_misses);
        error = nfsrpc_lookup(dvp, cnp->cn_nameptr, cnp->cn_namelen,
            cnp->cn_cred, td, &dnfsva, &nfsva, &nfhp, &attrflag, &dattrflag,
            NULL);
        if (dattrflag)
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        if (error) {
                if (newvp != NULLVP) {
                        vput(newvp);
                        *vpp = NULLVP;
                }

                if (error != ENOENT) {
                        if (NFS_ISV4(dvp))
                                error = nfscl_maperr(td, error, (uid_t)0,
                                    (gid_t)0);
                        return (error);
                }

                /* The requested file was not found. */
                if ((cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME) &&
                    (flags & ISLASTCN)) {
                        /*
                         * XXX: UFS does a full VOP_ACCESS(dvp,
                         * VWRITE) here instead of just checking
                         * MNT_RDONLY.
                         */
                        if (mp->mnt_flag & MNT_RDONLY)
                                return (EROFS);
                        cnp->cn_flags |= SAVENAME;
                        return (EJUSTRETURN);
                }

                if ((cnp->cn_flags & MAKEENTRY) && cnp->cn_nameiop != CREATE) {
                        /*
                         * Maintain n_dmtime as the modification time
                         * of the parent directory when the oldest -ve
                         * name cache entry for this directory was
                         * added.  If a -ve cache entry has already
                         * been added with a newer modification time
                         * by a concurrent lookup, then don't bother
                         * adding a cache entry.  The modification
                         * time of the directory might have changed
                         * due to the file this lookup failed to find
                         * being created.  In that case a subsequent
                         * lookup would incorrectly use the entry
                         * added here instead of doing an extra
                         * lookup.
                         */
                        mtx_lock(&np->n_mtx);
                        if (timespeccmp(&np->n_dmtime, &dmtime, <=)) {
                                if (!timespecisset(&np->n_dmtime)) {
                                        np->n_dmtime = dmtime;
                                        np->n_dmtime_ticks = ticks;
                                }
                                mtx_unlock(&np->n_mtx);
                                cache_enter(dvp, NULL, cnp);
                        } else
                                mtx_unlock(&np->n_mtx);
                }
                return (ENOENT);
        }

        /*
         * Handle RENAME case...
         */
        if (cnp->cn_nameiop == RENAME && (flags & ISLASTCN)) {
                if (NFS_CMPFH(np, nfhp->nfh_fh, nfhp->nfh_len)) {
                        FREE((caddr_t)nfhp, M_NFSFH);
                        return (EISDIR);
                }
                error = nfscl_nget(mp, dvp, nfhp, cnp, td, &np, NULL,
                    LK_EXCLUSIVE);
                if (error)
                        return (error);
                newvp = NFSTOV(np);
                if (attrflag)
                        (void) nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
                *vpp = newvp;
                cnp->cn_flags |= SAVENAME;
                return (0);
        }

        if (flags & ISDOTDOT) {
                ltype = VOP_ISLOCKED(dvp);
                error = vfs_busy(mp, MBF_NOWAIT);
                if (error != 0) {
                        vfs_ref(mp);
                        VOP_UNLOCK(dvp, 0);
                        error = vfs_busy(mp, 0);
                        vn_lock(dvp, ltype | LK_RETRY);
                        vfs_rel(mp);
                        if (error == 0 && (dvp->v_iflag & VI_DOOMED)) {
                                vfs_unbusy(mp);
                                error = ENOENT;
                        }
                        if (error != 0)
                                return (error);
                }
                VOP_UNLOCK(dvp, 0);
                error = nfscl_nget(mp, dvp, nfhp, cnp, td, &np, NULL,
                    cnp->cn_lkflags);
                if (error == 0)
                        newvp = NFSTOV(np);
                vfs_unbusy(mp);
                if (newvp != dvp)
                        vn_lock(dvp, ltype | LK_RETRY);
                if (dvp->v_iflag & VI_DOOMED) {
                        if (error == 0) {
                                if (newvp == dvp)
                                        vrele(newvp);
                                else
                                        vput(newvp);
                        }
                        error = ENOENT;
                }
                if (error != 0)
                        return (error);
                if (attrflag)
                        (void) nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
        } else if (NFS_CMPFH(np, nfhp->nfh_fh, nfhp->nfh_len)) {
                FREE((caddr_t)nfhp, M_NFSFH);
                VREF(dvp);
                newvp = dvp;
                if (attrflag)
                        (void) nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
        } else {
                error = nfscl_nget(mp, dvp, nfhp, cnp, td, &np, NULL,
                    cnp->cn_lkflags);
                if (error)
                        return (error);
                newvp = NFSTOV(np);
                if (attrflag)
                        (void) nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
                else if ((flags & (ISLASTCN | ISOPEN)) == (ISLASTCN | ISOPEN) &&
                    !(np->n_flag & NMODIFIED)) {                        
                        /*
                         * Flush the attribute cache when opening a
                         * leaf node to ensure that fresh attributes
                         * are fetched in nfs_open() since we did not
                         * fetch attributes from the LOOKUP reply.
                         */
                        mtx_lock(&np->n_mtx);
                        np->n_attrstamp = 0;
                        mtx_unlock(&np->n_mtx);
                }
        }
        if (cnp->cn_nameiop != LOOKUP && (flags & ISLASTCN))
                cnp->cn_flags |= SAVENAME;
        if ((cnp->cn_flags & MAKEENTRY) &&
            (cnp->cn_nameiop != DELETE || !(flags & ISLASTCN))) {
                np->n_ctime = np->n_vattr.na_vattr.va_ctime;
                cache_enter(dvp, newvp, cnp);
        }
        *vpp = newvp;
        return (0);
}

/*
 * nfs read call.
 * Just call ncl_bioread() to do the work.
 */
static int
nfs_read(struct vop_read_args *ap)
{
        struct vnode *vp = ap->a_vp;

        switch (vp->v_type) {
        case VREG:
                return (ncl_bioread(vp, ap->a_uio, ap->a_ioflag, ap->a_cred));
        case VDIR:
                return (EISDIR);
        default:
                return (EOPNOTSUPP);
        }
}

/*
 * nfs readlink call
 */
static int
nfs_readlink(struct vop_readlink_args *ap)
{
        struct vnode *vp = ap->a_vp;

        if (vp->v_type != VLNK)
                return (EINVAL);
        return (ncl_bioread(vp, ap->a_uio, 0, ap->a_cred));
}

/*
 * Do a readlink rpc.
 * Called by ncl_doio() from below the buffer cache.
 */
int
ncl_readlinkrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred)
{
        int error, ret, attrflag;
        struct nfsvattr nfsva;

        error = nfsrpc_readlink(vp, uiop, cred, uiop->uio_td, &nfsva,
            &attrflag, NULL);
        if (attrflag) {
                ret = nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0, 1);
                if (ret && !error)
                        error = ret;
        }
        if (error && NFS_ISV4(vp))
                error = nfscl_maperr(uiop->uio_td, error, (uid_t)0, (gid_t)0);
        return (error);
}

/*
 * nfs read rpc call
 * Ditto above
 */
int
ncl_readrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred)
{
        int error, ret, attrflag;
        struct nfsvattr nfsva;

        error = nfsrpc_read(vp, uiop, cred, uiop->uio_td, &nfsva, &attrflag,
            NULL);
        if (attrflag) {
                ret = nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0, 1);
                if (ret && !error)
                        error = ret;
        }
        if (error && NFS_ISV4(vp))
                error = nfscl_maperr(uiop->uio_td, error, (uid_t)0, (gid_t)0);
        return (error);
}

/*
 * nfs write call
 */
int
ncl_writerpc(struct vnode *vp, struct uio *uiop, struct ucred *cred,
    int *iomode, int *must_commit, int called_from_strategy)
{
        struct nfsvattr nfsva;
        int error = 0, attrflag, ret;
        u_char verf[NFSX_VERF];
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);

        *must_commit = 0;
        error = nfsrpc_write(vp, uiop, iomode, verf, cred,
            uiop->uio_td, &nfsva, &attrflag, NULL, called_from_strategy);
        NFSLOCKMNT(nmp);
        if (!error && NFSHASWRITEVERF(nmp) &&
            NFSBCMP(verf, nmp->nm_verf, NFSX_VERF)) {
                *must_commit = 1;
                NFSBCOPY(verf, nmp->nm_verf, NFSX_VERF);
        }
        NFSUNLOCKMNT(nmp);
        if (attrflag) {
                if (VTONFS(vp)->n_flag & ND_NFSV4)
                        ret = nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 1,
                            1);
                else
                        ret = nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0,
                            1);
                if (ret && !error)
                        error = ret;
        }
        if (vp->v_mount->mnt_kern_flag & MNTK_ASYNC)
                *iomode = NFSWRITE_FILESYNC;
        if (error && NFS_ISV4(vp))
                error = nfscl_maperr(uiop->uio_td, error, (uid_t)0, (gid_t)0);
        return (error);
}

/*
 * nfs mknod rpc
 * For NFS v2 this is a kludge. Use a create rpc but with the IFMT bits of the
 * mode set to specify the file type and the size field for rdev.
 */
static int
nfs_mknodrpc(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
    struct vattr *vap)
{
        struct nfsvattr nfsva, dnfsva;
        struct vnode *newvp = NULL;
        struct nfsnode *np = NULL, *dnp;
        struct nfsfh *nfhp;
        struct vattr vattr;
        int error = 0, attrflag, dattrflag;
        u_int32_t rdev;

        if (vap->va_type == VCHR || vap->va_type == VBLK)
                rdev = vap->va_rdev;
        else if (vap->va_type == VFIFO || vap->va_type == VSOCK)
                rdev = 0xffffffff;
        else
                return (EOPNOTSUPP);
        if ((error = VOP_GETATTR(dvp, &vattr, cnp->cn_cred)))
                return (error);
        error = nfsrpc_mknod(dvp, cnp->cn_nameptr, cnp->cn_namelen, vap,
            rdev, vap->va_type, cnp->cn_cred, cnp->cn_thread, &dnfsva,
            &nfsva, &nfhp, &attrflag, &dattrflag, NULL);
        if (!error) {
                if (!nfhp)
                        (void) nfsrpc_lookup(dvp, cnp->cn_nameptr,
                            cnp->cn_namelen, cnp->cn_cred, cnp->cn_thread,
                            &dnfsva, &nfsva, &nfhp, &attrflag, &dattrflag,
                            NULL);
                if (nfhp)
                        error = nfscl_nget(dvp->v_mount, dvp, nfhp, cnp,
                            cnp->cn_thread, &np, NULL, LK_EXCLUSIVE);
        }
        if (dattrflag)
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        if (!error) {
                newvp = NFSTOV(np);
                if (attrflag != 0) {
                        error = nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
                        if (error != 0)
                                vput(newvp);
                }
        }
        if (!error) {
                if ((cnp->cn_flags & MAKEENTRY))
                        cache_enter(dvp, newvp, cnp);
                *vpp = newvp;
        } else if (NFS_ISV4(dvp)) {
                error = nfscl_maperr(cnp->cn_thread, error, vap->va_uid,
                    vap->va_gid);
        }
        dnp = VTONFS(dvp);
        mtx_lock(&dnp->n_mtx);
        dnp->n_flag |= NMODIFIED;
        if (!dattrflag)
                dnp->n_attrstamp = 0;
        mtx_unlock(&dnp->n_mtx);
        return (error);
}

/*
 * nfs mknod vop
 * just call nfs_mknodrpc() to do the work.
 */
/* ARGSUSED */
static int
nfs_mknod(struct vop_mknod_args *ap)
{
        return (nfs_mknodrpc(ap->a_dvp, ap->a_vpp, ap->a_cnp, ap->a_vap));
}

static u_long create_verf;
/*
 * nfs file create call
 */
static int
nfs_create(struct vop_create_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vattr *vap = ap->a_vap;
        struct componentname *cnp = ap->a_cnp;
        struct nfsnode *np = NULL, *dnp;
        struct vnode *newvp = NULL;
        struct nfsmount *nmp;
        struct nfsvattr dnfsva, nfsva;
        struct nfsfh *nfhp;
        nfsquad_t cverf;
        int error = 0, attrflag, dattrflag, fmode = 0;
        struct vattr vattr;

        /*
         * Oops, not for me..
         */
        if (vap->va_type == VSOCK)
                return (nfs_mknodrpc(dvp, ap->a_vpp, cnp, vap));

        if ((error = VOP_GETATTR(dvp, &vattr, cnp->cn_cred)))
                return (error);
        if (vap->va_vaflags & VA_EXCLUSIVE)
                fmode |= O_EXCL;
        dnp = VTONFS(dvp);
        nmp = VFSTONFS(vnode_mount(dvp));
again:
        /* For NFSv4, wait until any remove is done. */
        mtx_lock(&dnp->n_mtx);
        while (NFSHASNFSV4(nmp) && (dnp->n_flag & NREMOVEINPROG)) {
                dnp->n_flag |= NREMOVEWANT;
                (void) msleep((caddr_t)dnp, &dnp->n_mtx, PZERO, "nfscrt", 0);
        }
        mtx_unlock(&dnp->n_mtx);

#ifdef INET
        CURVNET_SET(CRED_TO_VNET(cnp->cn_cred));
        IN_IFADDR_RLOCK();
        if (!TAILQ_EMPTY(&V_in_ifaddrhead))
                cverf.lval[0] = IA_SIN(TAILQ_FIRST(&V_in_ifaddrhead))->sin_addr.s_addr;
        else
#endif
                cverf.lval[0] = create_verf;
#ifdef INET
        IN_IFADDR_RUNLOCK();
        CURVNET_RESTORE();
#endif
        cverf.lval[1] = ++create_verf;
        error = nfsrpc_create(dvp, cnp->cn_nameptr, cnp->cn_namelen,
            vap, cverf, fmode, cnp->cn_cred, cnp->cn_thread, &dnfsva, &nfsva,
            &nfhp, &attrflag, &dattrflag, NULL);
        if (!error) {
                if (nfhp == NULL)
                        (void) nfsrpc_lookup(dvp, cnp->cn_nameptr,
                            cnp->cn_namelen, cnp->cn_cred, cnp->cn_thread,
                            &dnfsva, &nfsva, &nfhp, &attrflag, &dattrflag,
                            NULL);
                if (nfhp != NULL)
                        error = nfscl_nget(dvp->v_mount, dvp, nfhp, cnp,
                            cnp->cn_thread, &np, NULL, LK_EXCLUSIVE);
        }
        if (dattrflag)
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        if (!error) {
                newvp = NFSTOV(np);
                if (attrflag)
                        error = nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
        }
        if (error) {
                if (newvp != NULL) {
                        vput(newvp);
                        newvp = NULL;
                }
                if (NFS_ISV34(dvp) && (fmode & O_EXCL) &&
                    error == NFSERR_NOTSUPP) {
                        fmode &= ~O_EXCL;
                        goto again;
                }
        } else if (NFS_ISV34(dvp) && (fmode & O_EXCL)) {
                if (nfscl_checksattr(vap, &nfsva)) {
                        /*
                         * We are normally called with only a partially
                         * initialized VAP. Since the NFSv3 spec says that
                         * the server may use the file attributes to
                         * store the verifier, the spec requires us to do a
                         * SETATTR RPC. FreeBSD servers store the verifier in
                         * atime, but we can't really assume that all servers
                         * will so we ensure that our SETATTR sets both atime
                         * and mtime.
                         */
                        if (vap->va_mtime.tv_sec == VNOVAL)
                                vfs_timestamp(&vap->va_mtime);
                        if (vap->va_atime.tv_sec == VNOVAL)
                                vap->va_atime = vap->va_mtime;
                        error = nfsrpc_setattr(newvp, vap, NULL, cnp->cn_cred,
                            cnp->cn_thread, &nfsva, &attrflag, NULL);
                        if (error && (vap->va_uid != (uid_t)VNOVAL ||
                            vap->va_gid != (gid_t)VNOVAL)) {
                                /* try again without setting uid/gid */
                                vap->va_uid = (uid_t)VNOVAL;
                                vap->va_gid = (uid_t)VNOVAL;
                                error = nfsrpc_setattr(newvp, vap, NULL, 
                                    cnp->cn_cred, cnp->cn_thread, &nfsva,
                                    &attrflag, NULL);
                        }
                        if (attrflag)
                                (void) nfscl_loadattrcache(&newvp, &nfsva, NULL,
                                    NULL, 0, 1);
                }
        }
        if (!error) {
                if (cnp->cn_flags & MAKEENTRY)
                        cache_enter(dvp, newvp, cnp);
                *ap->a_vpp = newvp;
        } else if (NFS_ISV4(dvp)) {
                error = nfscl_maperr(cnp->cn_thread, error, vap->va_uid,
                    vap->va_gid);
        }
        mtx_lock(&dnp->n_mtx);
        dnp->n_flag |= NMODIFIED;
        if (!dattrflag)
                dnp->n_attrstamp = 0;
        mtx_unlock(&dnp->n_mtx);
        return (error);
}

/*
 * nfs file remove call
 * To try and make nfs semantics closer to ufs semantics, a file that has
 * other processes using the vnode is renamed instead of removed and then
 * removed later on the last close.
 * - If v_usecount > 1
 *        If a rename is not already in the works
 *           call nfs_sillyrename() to set it up
 *     else
 *        do the remove rpc
 */
static int
nfs_remove(struct vop_remove_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vnode *dvp = ap->a_dvp;
        struct componentname *cnp = ap->a_cnp;
        struct nfsnode *np = VTONFS(vp);
        int error = 0;
        struct vattr vattr;

        KASSERT((cnp->cn_flags & HASBUF) != 0, ("nfs_remove: no name"));
        KASSERT(vrefcnt(vp) > 0, ("nfs_remove: bad v_usecount"));
        if (vp->v_type == VDIR)
                error = EPERM;
        else if (vrefcnt(vp) == 1 || (np->n_sillyrename &&
            VOP_GETATTR(vp, &vattr, cnp->cn_cred) == 0 &&
            vattr.va_nlink > 1)) {
                /*
                 * Purge the name cache so that the chance of a lookup for
                 * the name succeeding while the remove is in progress is
                 * minimized. Without node locking it can still happen, such
                 * that an I/O op returns ESTALE, but since you get this if
                 * another host removes the file..
                 */
                cache_purge(vp);
                /*
                 * throw away biocache buffers, mainly to avoid
                 * unnecessary delayed writes later.
                 */
                error = ncl_vinvalbuf(vp, 0, cnp->cn_thread, 1);
                /* Do the rpc */
                if (error != EINTR && error != EIO)
                        error = nfs_removerpc(dvp, vp, cnp->cn_nameptr,
                            cnp->cn_namelen, cnp->cn_cred, cnp->cn_thread);
                /*
                 * Kludge City: If the first reply to the remove rpc is lost..
                 *   the reply to the retransmitted request will be ENOENT
                 *   since the file was in fact removed
                 *   Therefore, we cheat and return success.
                 */
                if (error == ENOENT)
                        error = 0;
        } else if (!np->n_sillyrename)
                error = nfs_sillyrename(dvp, vp, cnp);
        mtx_lock(&np->n_mtx);
        np->n_attrstamp = 0;
        mtx_unlock(&np->n_mtx);
        return (error);
}

/*
 * nfs file remove rpc called from nfs_inactive
 */
int
ncl_removeit(struct sillyrename *sp, struct vnode *vp)
{
        /*
         * Make sure that the directory vnode is still valid.
         * XXX we should lock sp->s_dvp here.
         */
        if (sp->s_dvp->v_type == VBAD)
                return (0);
        return (nfs_removerpc(sp->s_dvp, vp, sp->s_name, sp->s_namlen,
            sp->s_cred, NULL));
}

/*
 * Nfs remove rpc, called from nfs_remove() and ncl_removeit().
 */
static int
nfs_removerpc(struct vnode *dvp, struct vnode *vp, char *name,
    int namelen, struct ucred *cred, struct thread *td)
{
        struct nfsvattr dnfsva;
        struct nfsnode *dnp = VTONFS(dvp);
        int error = 0, dattrflag;

        mtx_lock(&dnp->n_mtx);
        dnp->n_flag |= NREMOVEINPROG;
        mtx_unlock(&dnp->n_mtx);
        error = nfsrpc_remove(dvp, name, namelen, vp, cred, td, &dnfsva,
            &dattrflag, NULL);
        mtx_lock(&dnp->n_mtx);
        if ((dnp->n_flag & NREMOVEWANT)) {
                dnp->n_flag &= ~(NREMOVEWANT | NREMOVEINPROG);
                mtx_unlock(&dnp->n_mtx);
                wakeup((caddr_t)dnp);
        } else {
                dnp->n_flag &= ~NREMOVEINPROG;
                mtx_unlock(&dnp->n_mtx);
        }
        if (dattrflag)
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        mtx_lock(&dnp->n_mtx);
        dnp->n_flag |= NMODIFIED;
        if (!dattrflag)
                dnp->n_attrstamp = 0;
        mtx_unlock(&dnp->n_mtx);
        if (error && NFS_ISV4(dvp))
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        return (error);
}

/*
 * nfs file rename call
 */
static int
nfs_rename(struct vop_rename_args *ap)
{
        struct vnode *fvp = ap->a_fvp;
        struct vnode *tvp = ap->a_tvp;
        struct vnode *fdvp = ap->a_fdvp;
        struct vnode *tdvp = ap->a_tdvp;
        struct componentname *tcnp = ap->a_tcnp;
        struct componentname *fcnp = ap->a_fcnp;
        struct nfsnode *fnp = VTONFS(ap->a_fvp);
        struct nfsnode *tdnp = VTONFS(ap->a_tdvp);
        struct nfsv4node *newv4 = NULL;
        int error;

        KASSERT((tcnp->cn_flags & HASBUF) != 0 &&
            (fcnp->cn_flags & HASBUF) != 0, ("nfs_rename: no name"));
        /* Check for cross-device rename */
        if ((fvp->v_mount != tdvp->v_mount) ||
            (tvp && (fvp->v_mount != tvp->v_mount))) {
                error = EXDEV;
                goto out;
        }

        if (fvp == tvp) {
                ncl_printf("nfs_rename: fvp == tvp (can't happen)\n");
                error = 0;
                goto out;
        }
        if ((error = vn_lock(fvp, LK_EXCLUSIVE)) != 0)
                goto out;

        /*
         * We have to flush B_DELWRI data prior to renaming
         * the file.  If we don't, the delayed-write buffers
         * can be flushed out later after the file has gone stale
         * under NFSV3.  NFSV2 does not have this problem because
         * ( as far as I can tell ) it flushes dirty buffers more
         * often.
         * 
         * Skip the rename operation if the fsync fails, this can happen
         * due to the server's volume being full, when we pushed out data
         * that was written back to our cache earlier. Not checking for
         * this condition can result in potential (silent) data loss.
         */
        error = VOP_FSYNC(fvp, MNT_WAIT, fcnp->cn_thread);
        VOP_UNLOCK(fvp, 0);
        if (!error && tvp)
                error = VOP_FSYNC(tvp, MNT_WAIT, tcnp->cn_thread);
        if (error)
                goto out;

        /*
         * If the tvp exists and is in use, sillyrename it before doing the
         * rename of the new file over it.
         * XXX Can't sillyrename a directory.
         */
        if (tvp && vrefcnt(tvp) > 1 && !VTONFS(tvp)->n_sillyrename &&
                tvp->v_type != VDIR && !nfs_sillyrename(tdvp, tvp, tcnp)) {
                vput(tvp);
                tvp = NULL;
        }

        error = nfs_renamerpc(fdvp, fvp, fcnp->cn_nameptr, fcnp->cn_namelen,
            tdvp, tvp, tcnp->cn_nameptr, tcnp->cn_namelen, tcnp->cn_cred,
            tcnp->cn_thread);

        if (error == 0 && NFS_ISV4(tdvp)) {
                /*
                 * For NFSv4, check to see if it is the same name and
                 * replace the name, if it is different.
                 */
                MALLOC(newv4, struct nfsv4node *,
                    sizeof (struct nfsv4node) +
                    tdnp->n_fhp->nfh_len + tcnp->cn_namelen - 1,
                    M_NFSV4NODE, M_WAITOK);
                mtx_lock(&tdnp->n_mtx);
                mtx_lock(&fnp->n_mtx);
                if (fnp->n_v4 != NULL && fvp->v_type == VREG &&
                    (fnp->n_v4->n4_namelen != tcnp->cn_namelen ||
                      NFSBCMP(tcnp->cn_nameptr, NFS4NODENAME(fnp->n_v4),
                      tcnp->cn_namelen) ||
                      tdnp->n_fhp->nfh_len != fnp->n_v4->n4_fhlen ||
                      NFSBCMP(tdnp->n_fhp->nfh_fh, fnp->n_v4->n4_data,
                        tdnp->n_fhp->nfh_len))) {
#ifdef notdef
{ char nnn[100]; int nnnl;
nnnl = (tcnp->cn_namelen < 100) ? tcnp->cn_namelen : 99;
bcopy(tcnp->cn_nameptr, nnn, nnnl);
nnn[nnnl] = '\0';
printf("ren replace=%s\n",nnn);
}
#endif
                        FREE((caddr_t)fnp->n_v4, M_NFSV4NODE);
                        fnp->n_v4 = newv4;
                        newv4 = NULL;
                        fnp->n_v4->n4_fhlen = tdnp->n_fhp->nfh_len;
                        fnp->n_v4->n4_namelen = tcnp->cn_namelen;
                        NFSBCOPY(tdnp->n_fhp->nfh_fh, fnp->n_v4->n4_data,
                            tdnp->n_fhp->nfh_len);
                        NFSBCOPY(tcnp->cn_nameptr,
                            NFS4NODENAME(fnp->n_v4), tcnp->cn_namelen);
                }
                mtx_unlock(&tdnp->n_mtx);
                mtx_unlock(&fnp->n_mtx);
                if (newv4 != NULL)
                        FREE((caddr_t)newv4, M_NFSV4NODE);
        }

        if (fvp->v_type == VDIR) {
                if (tvp != NULL && tvp->v_type == VDIR)
                        cache_purge(tdvp);
                cache_purge(fdvp);
        }

out:
        if (tdvp == tvp)
                vrele(tdvp);
        else
                vput(tdvp);
        if (tvp)
                vput(tvp);
        vrele(fdvp);
        vrele(fvp);
        /*
         * Kludge: Map ENOENT => 0 assuming that it is a reply to a retry.
         */
        if (error == ENOENT)
                error = 0;
        return (error);
}

/*
 * nfs file rename rpc called from nfs_remove() above
 */
static int
nfs_renameit(struct vnode *sdvp, struct vnode *svp, struct componentname *scnp,
    struct sillyrename *sp)
{

        return (nfs_renamerpc(sdvp, svp, scnp->cn_nameptr, scnp->cn_namelen,
            sdvp, NULL, sp->s_name, sp->s_namlen, scnp->cn_cred,
            scnp->cn_thread));
}

/*
 * Do an nfs rename rpc. Called from nfs_rename() and nfs_renameit().
 */
static int
nfs_renamerpc(struct vnode *fdvp, struct vnode *fvp, char *fnameptr,
    int fnamelen, struct vnode *tdvp, struct vnode *tvp, char *tnameptr,
    int tnamelen, struct ucred *cred, struct thread *td)
{
        struct nfsvattr fnfsva, tnfsva;
        struct nfsnode *fdnp = VTONFS(fdvp);
        struct nfsnode *tdnp = VTONFS(tdvp);
        int error = 0, fattrflag, tattrflag;

        error = nfsrpc_rename(fdvp, fvp, fnameptr, fnamelen, tdvp, tvp,
            tnameptr, tnamelen, cred, td, &fnfsva, &tnfsva, &fattrflag,
            &tattrflag, NULL, NULL);
        mtx_lock(&fdnp->n_mtx);
        fdnp->n_flag |= NMODIFIED;
        if (fattrflag != 0) {
                mtx_unlock(&fdnp->n_mtx);
                (void) nfscl_loadattrcache(&fdvp, &fnfsva, NULL, NULL, 0, 1);
        } else {
                fdnp->n_attrstamp = 0;
                mtx_unlock(&fdnp->n_mtx);
        }
        mtx_lock(&tdnp->n_mtx);
        tdnp->n_flag |= NMODIFIED;
        if (tattrflag != 0) {
                mtx_unlock(&tdnp->n_mtx);
                (void) nfscl_loadattrcache(&tdvp, &tnfsva, NULL, NULL, 0, 1);
        } else {
                tdnp->n_attrstamp = 0;
                mtx_unlock(&tdnp->n_mtx);
        }
        if (error && NFS_ISV4(fdvp))
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        return (error);
}

/*
 * nfs hard link create call
 */
static int
nfs_link(struct vop_link_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vnode *tdvp = ap->a_tdvp;
        struct componentname *cnp = ap->a_cnp;
        struct nfsnode *np, *tdnp;
        struct nfsvattr nfsva, dnfsva;
        int error = 0, attrflag, dattrflag;

        if (vp->v_mount != tdvp->v_mount) {
                return (EXDEV);
        }

        /*
         * Push all writes to the server, so that the attribute cache
         * doesn't get "out of sync" with the server.
         * XXX There should be a better way!
         */
        VOP_FSYNC(vp, MNT_WAIT, cnp->cn_thread);

        error = nfsrpc_link(tdvp, vp, cnp->cn_nameptr, cnp->cn_namelen,
            cnp->cn_cred, cnp->cn_thread, &dnfsva, &nfsva, &attrflag,
            &dattrflag, NULL);
        tdnp = VTONFS(tdvp);
        mtx_lock(&tdnp->n_mtx);
        tdnp->n_flag |= NMODIFIED;
        if (dattrflag != 0) {
                mtx_unlock(&tdnp->n_mtx);
                (void) nfscl_loadattrcache(&tdvp, &dnfsva, NULL, NULL, 0, 1);
        } else {
                tdnp->n_attrstamp = 0;
                mtx_unlock(&tdnp->n_mtx);
        }
        if (attrflag)
                (void) nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0, 1);
        else {
                np = VTONFS(vp);
                mtx_lock(&np->n_mtx);
                np->n_attrstamp = 0;
                mtx_unlock(&np->n_mtx);
        }
        /*
         * If negative lookup caching is enabled, I might as well
         * add an entry for this node. Not necessary for correctness,
         * but if negative caching is enabled, then the system
         * must care about lookup caching hit rate, so...
         */
        if (VFSTONFS(vp->v_mount)->nm_negnametimeo != 0 &&
            (cnp->cn_flags & MAKEENTRY))
                cache_enter(tdvp, vp, cnp);
        if (error && NFS_ISV4(vp))
                error = nfscl_maperr(cnp->cn_thread, error, (uid_t)0,
                    (gid_t)0);
        return (error);
}

/*
 * nfs symbolic link create call
 */
static int
nfs_symlink(struct vop_symlink_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vattr *vap = ap->a_vap;
        struct componentname *cnp = ap->a_cnp;
        struct nfsvattr nfsva, dnfsva;
        struct nfsfh *nfhp;
        struct nfsnode *np = NULL, *dnp;
        struct vnode *newvp = NULL;
        int error = 0, attrflag, dattrflag, ret;

        vap->va_type = VLNK;
        error = nfsrpc_symlink(dvp, cnp->cn_nameptr, cnp->cn_namelen,
            ap->a_target, vap, cnp->cn_cred, cnp->cn_thread, &dnfsva,
            &nfsva, &nfhp, &attrflag, &dattrflag, NULL);
        if (nfhp) {
                ret = nfscl_nget(dvp->v_mount, dvp, nfhp, cnp, cnp->cn_thread,
                    &np, NULL, LK_EXCLUSIVE);
                if (!ret)
                        newvp = NFSTOV(np);
                else if (!error)
                        error = ret;
        }
        if (newvp != NULL) {
                if (attrflag)
                        (void) nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
        } else if (!error) {
                /*
                 * If we do not have an error and we could not extract the
                 * newvp from the response due to the request being NFSv2, we
                 * have to do a lookup in order to obtain a newvp to return.
                 */
                error = nfs_lookitup(dvp, cnp->cn_nameptr, cnp->cn_namelen,
                    cnp->cn_cred, cnp->cn_thread, &np);
                if (!error)
                        newvp = NFSTOV(np);
        }
        if (error) {
                if (newvp)
                        vput(newvp);
                if (NFS_ISV4(dvp))
                        error = nfscl_maperr(cnp->cn_thread, error,
                            vap->va_uid, vap->va_gid);
        } else {
                /*
                 * If negative lookup caching is enabled, I might as well
                 * add an entry for this node. Not necessary for correctness,
                 * but if negative caching is enabled, then the system
                 * must care about lookup caching hit rate, so...
                 */
                if (VFSTONFS(dvp->v_mount)->nm_negnametimeo != 0 &&
                    (cnp->cn_flags & MAKEENTRY))
                        cache_enter(dvp, newvp, cnp);
                *ap->a_vpp = newvp;
        }

        dnp = VTONFS(dvp);
        mtx_lock(&dnp->n_mtx);
        dnp->n_flag |= NMODIFIED;
        if (dattrflag != 0) {
                mtx_unlock(&dnp->n_mtx);
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        } else {
                dnp->n_attrstamp = 0;
                mtx_unlock(&dnp->n_mtx);
        }
        return (error);
}

/*
 * nfs make dir call
 */
static int
nfs_mkdir(struct vop_mkdir_args *ap)
{
        struct vnode *dvp = ap->a_dvp;
        struct vattr *vap = ap->a_vap;
        struct componentname *cnp = ap->a_cnp;
        struct nfsnode *np = NULL, *dnp;
        struct vnode *newvp = NULL;
        struct vattr vattr;
        struct nfsfh *nfhp;
        struct nfsvattr nfsva, dnfsva;
        int error = 0, attrflag, dattrflag, ret;

        if ((error = VOP_GETATTR(dvp, &vattr, cnp->cn_cred)) != 0)
                return (error);
        vap->va_type = VDIR;
        error = nfsrpc_mkdir(dvp, cnp->cn_nameptr, cnp->cn_namelen,
            vap, cnp->cn_cred, cnp->cn_thread, &dnfsva, &nfsva, &nfhp,
            &attrflag, &dattrflag, NULL);
        dnp = VTONFS(dvp);
        mtx_lock(&dnp->n_mtx);
        dnp->n_flag |= NMODIFIED;
        if (dattrflag != 0) {
                mtx_unlock(&dnp->n_mtx);
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        } else {
                dnp->n_attrstamp = 0;
                mtx_unlock(&dnp->n_mtx);
        }
        if (nfhp) {
                ret = nfscl_nget(dvp->v_mount, dvp, nfhp, cnp, cnp->cn_thread,
                    &np, NULL, LK_EXCLUSIVE);
                if (!ret) {
                        newvp = NFSTOV(np);
                        if (attrflag)
                           (void) nfscl_loadattrcache(&newvp, &nfsva, NULL,
                                NULL, 0, 1);
                } else if (!error)
                        error = ret;
        }
        if (!error && newvp == NULL) {
                error = nfs_lookitup(dvp, cnp->cn_nameptr, cnp->cn_namelen,
                    cnp->cn_cred, cnp->cn_thread, &np);
                if (!error) {
                        newvp = NFSTOV(np);
                        if (newvp->v_type != VDIR)
                                error = EEXIST;
                }
        }
        if (error) {
                if (newvp)
                        vput(newvp);
                if (NFS_ISV4(dvp))
                        error = nfscl_maperr(cnp->cn_thread, error,
                            vap->va_uid, vap->va_gid);
        } else {
                /*
                 * If negative lookup caching is enabled, I might as well
                 * add an entry for this node. Not necessary for correctness,
                 * but if negative caching is enabled, then the system
                 * must care about lookup caching hit rate, so...
                 */
                if (VFSTONFS(dvp->v_mount)->nm_negnametimeo != 0 &&
                    (cnp->cn_flags & MAKEENTRY))
                        cache_enter(dvp, newvp, cnp);
                *ap->a_vpp = newvp;
        }
        return (error);
}

/*
 * nfs remove directory call
 */
static int
nfs_rmdir(struct vop_rmdir_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vnode *dvp = ap->a_dvp;
        struct componentname *cnp = ap->a_cnp;
        struct nfsnode *dnp;
        struct nfsvattr dnfsva;
        int error, dattrflag;

        if (dvp == vp)
                return (EINVAL);
        error = nfsrpc_rmdir(dvp, cnp->cn_nameptr, cnp->cn_namelen,
            cnp->cn_cred, cnp->cn_thread, &dnfsva, &dattrflag, NULL);
        dnp = VTONFS(dvp);
        mtx_lock(&dnp->n_mtx);
        dnp->n_flag |= NMODIFIED;
        if (dattrflag != 0) {
                mtx_unlock(&dnp->n_mtx);
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        } else {
                dnp->n_attrstamp = 0;
                mtx_unlock(&dnp->n_mtx);
        }

        cache_purge(dvp);
        cache_purge(vp);
        if (error && NFS_ISV4(dvp))
                error = nfscl_maperr(cnp->cn_thread, error, (uid_t)0,
                    (gid_t)0);
        /*
         * Kludge: Map ENOENT => 0 assuming that you have a reply to a retry.
         */
        if (error == ENOENT)
                error = 0;
        return (error);
}

/*
 * nfs readdir call
 */
static int
nfs_readdir(struct vop_readdir_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);
        struct uio *uio = ap->a_uio;
        int tresid, error = 0;
        struct vattr vattr;
        
        if (vp->v_type != VDIR) 
                return(EPERM);

        /*
         * First, check for hit on the EOF offset cache
         */
        if (np->n_direofoffset > 0 && uio->uio_offset >= np->n_direofoffset &&
            (np->n_flag & NMODIFIED) == 0) {
                if (VOP_GETATTR(vp, &vattr, ap->a_cred) == 0) {
                        mtx_lock(&np->n_mtx);
                        if ((NFS_ISV4(vp) && np->n_change == vattr.va_filerev) ||
                            !NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime)) {
                                mtx_unlock(&np->n_mtx);
                                NFSINCRGLOBAL(newnfsstats.direofcache_hits);
                                return (0);
                        } else
                                mtx_unlock(&np->n_mtx);
                }
        }

        /*
         * Call ncl_bioread() to do the real work.
         */
        tresid = uio->uio_resid;
        error = ncl_bioread(vp, uio, 0, ap->a_cred);

        if (!error && uio->uio_resid == tresid)
                NFSINCRGLOBAL(newnfsstats.direofcache_misses);
        return (error);
}

/*
 * Readdir rpc call.
 * Called from below the buffer cache by ncl_doio().
 */
int
ncl_readdirrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred,
    struct thread *td)
{
        struct nfsvattr nfsva;
        nfsuint64 *cookiep, cookie;
        struct nfsnode *dnp = VTONFS(vp);
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int error = 0, eof, attrflag;

        KASSERT(uiop->uio_iovcnt == 1 &&
            (uiop->uio_offset & (DIRBLKSIZ - 1)) == 0 &&
            (uiop->uio_resid & (DIRBLKSIZ - 1)) == 0,
            ("nfs readdirrpc bad uio"));

        /*
         * If there is no cookie, assume directory was stale.
         */
        ncl_dircookie_lock(dnp);
        cookiep = ncl_getcookie(dnp, uiop->uio_offset, 0);
        if (cookiep) {
                cookie = *cookiep;
                ncl_dircookie_unlock(dnp);
        } else {
                ncl_dircookie_unlock(dnp);              
                return (NFSERR_BAD_COOKIE);
        }

        if (NFSHASNFSV3(nmp) && !NFSHASGOTFSINFO(nmp))
                (void)ncl_fsinfo(nmp, vp, cred, td);

        error = nfsrpc_readdir(vp, uiop, &cookie, cred, td, &nfsva,
            &attrflag, &eof, NULL);
        if (attrflag)
                (void) nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0, 1);

        if (!error) {
                /*
                 * We are now either at the end of the directory or have filled
                 * the block.
                 */
                if (eof)
                        dnp->n_direofoffset = uiop->uio_offset;
                else {
                        if (uiop->uio_resid > 0)
                                ncl_printf("EEK! readdirrpc resid > 0\n");
                        ncl_dircookie_lock(dnp);
                        cookiep = ncl_getcookie(dnp, uiop->uio_offset, 1);
                        *cookiep = cookie;
                        ncl_dircookie_unlock(dnp);
                }
        } else if (NFS_ISV4(vp)) {
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        }
        return (error);
}

/*
 * NFS V3 readdir plus RPC. Used in place of ncl_readdirrpc().
 */
int
ncl_readdirplusrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred,
    struct thread *td)
{
        struct nfsvattr nfsva;
        nfsuint64 *cookiep, cookie;
        struct nfsnode *dnp = VTONFS(vp);
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int error = 0, attrflag, eof;

        KASSERT(uiop->uio_iovcnt == 1 &&
            (uiop->uio_offset & (DIRBLKSIZ - 1)) == 0 &&
            (uiop->uio_resid & (DIRBLKSIZ - 1)) == 0,
            ("nfs readdirplusrpc bad uio"));

        /*
         * If there is no cookie, assume directory was stale.
         */
        ncl_dircookie_lock(dnp);
        cookiep = ncl_getcookie(dnp, uiop->uio_offset, 0);
        if (cookiep) {
                cookie = *cookiep;
                ncl_dircookie_unlock(dnp);
        } else {
                ncl_dircookie_unlock(dnp);
                return (NFSERR_BAD_COOKIE);
        }

        if (NFSHASNFSV3(nmp) && !NFSHASGOTFSINFO(nmp))
                (void)ncl_fsinfo(nmp, vp, cred, td);
        error = nfsrpc_readdirplus(vp, uiop, &cookie, cred, td, &nfsva,
            &attrflag, &eof, NULL);
        if (attrflag)
                (void) nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0, 1);

        if (!error) {
                /*
                 * We are now either at end of the directory or have filled the
                 * the block.
                 */
                if (eof)
                        dnp->n_direofoffset = uiop->uio_offset;
                else {
                        if (uiop->uio_resid > 0)
                                ncl_printf("EEK! readdirplusrpc resid > 0\n");
                        ncl_dircookie_lock(dnp);
                        cookiep = ncl_getcookie(dnp, uiop->uio_offset, 1);
                        *cookiep = cookie;
                        ncl_dircookie_unlock(dnp);
                }
        } else if (NFS_ISV4(vp)) {
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        }
        return (error);
}

/*
 * Silly rename. To make the NFS filesystem that is stateless look a little
 * more like the "ufs" a remove of an active vnode is translated to a rename
 * to a funny looking filename that is removed by nfs_inactive on the
 * nfsnode. There is the potential for another process on a different client
 * to create the same funny name between the nfs_lookitup() fails and the
 * nfs_rename() completes, but...
 */
static int
nfs_sillyrename(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
{
        struct sillyrename *sp;
        struct nfsnode *np;
        int error;
        short pid;
        unsigned int lticks;

        cache_purge(dvp);
        np = VTONFS(vp);
        KASSERT(vp->v_type != VDIR, ("nfs: sillyrename dir"));
        MALLOC(sp, struct sillyrename *, sizeof (struct sillyrename),
            M_NEWNFSREQ, M_WAITOK);
        sp->s_cred = crhold(cnp->cn_cred);
        sp->s_dvp = dvp;
        VREF(dvp);

        /* 
         * Fudge together a funny name.
         * Changing the format of the funny name to accomodate more 
         * sillynames per directory.
         * The name is now changed to .nfs.<ticks>.<pid>.4, where ticks is 
         * CPU ticks since boot.
         */
        pid = cnp->cn_thread->td_proc->p_pid;
        lticks = (unsigned int)ticks;
        for ( ; ; ) {
                sp->s_namlen = sprintf(sp->s_name, 
                                       ".nfs.%08x.%04x4.4", lticks, 
                                       pid);
                if (nfs_lookitup(dvp, sp->s_name, sp->s_namlen, sp->s_cred,
                                 cnp->cn_thread, NULL))
                        break;
                lticks++;
        }
        error = nfs_renameit(dvp, vp, cnp, sp);
        if (error)
                goto bad;
        error = nfs_lookitup(dvp, sp->s_name, sp->s_namlen, sp->s_cred,
                cnp->cn_thread, &np);
        np->n_sillyrename = sp;
        return (0);
bad:
        vrele(sp->s_dvp);
        crfree(sp->s_cred);
        free((caddr_t)sp, M_NEWNFSREQ);
        return (error);
}

/*
 * Look up a file name and optionally either update the file handle or
 * allocate an nfsnode, depending on the value of npp.
 * npp == NULL  --> just do the lookup
 * *npp == NULL --> allocate a new nfsnode and make sure attributes are
 *                      handled too
 * *npp != NULL --> update the file handle in the vnode
 */
static int
nfs_lookitup(struct vnode *dvp, char *name, int len, struct ucred *cred,
    struct thread *td, struct nfsnode **npp)
{
        struct vnode *newvp = NULL, *vp;
        struct nfsnode *np, *dnp = VTONFS(dvp);
        struct nfsfh *nfhp, *onfhp;
        struct nfsvattr nfsva, dnfsva;
        struct componentname cn;
        int error = 0, attrflag, dattrflag;
        u_int hash;

        error = nfsrpc_lookup(dvp, name, len, cred, td, &dnfsva, &nfsva,
            &nfhp, &attrflag, &dattrflag, NULL);
        if (dattrflag)
                (void) nfscl_loadattrcache(&dvp, &dnfsva, NULL, NULL, 0, 1);
        if (npp && !error) {
                if (*npp != NULL) {
                    np = *npp;
                    vp = NFSTOV(np);
                    /*
                     * For NFSv4, check to see if it is the same name and
                     * replace the name, if it is different.
                     */
                    if (np->n_v4 != NULL && nfsva.na_type == VREG &&
                        (np->n_v4->n4_namelen != len ||
                         NFSBCMP(name, NFS4NODENAME(np->n_v4), len) ||
                         dnp->n_fhp->nfh_len != np->n_v4->n4_fhlen ||
                         NFSBCMP(dnp->n_fhp->nfh_fh, np->n_v4->n4_data,
                         dnp->n_fhp->nfh_len))) {
#ifdef notdef
{ char nnn[100]; int nnnl;
nnnl = (len < 100) ? len : 99;
bcopy(name, nnn, nnnl);
nnn[nnnl] = '\0';
printf("replace=%s\n",nnn);
}
#endif
                            FREE((caddr_t)np->n_v4, M_NFSV4NODE);
                            MALLOC(np->n_v4, struct nfsv4node *,
                                sizeof (struct nfsv4node) +
                                dnp->n_fhp->nfh_len + len - 1,
                                M_NFSV4NODE, M_WAITOK);
                            np->n_v4->n4_fhlen = dnp->n_fhp->nfh_len;
                            np->n_v4->n4_namelen = len;
                            NFSBCOPY(dnp->n_fhp->nfh_fh, np->n_v4->n4_data,
                                dnp->n_fhp->nfh_len);
                            NFSBCOPY(name, NFS4NODENAME(np->n_v4), len);
                    }
                    hash = fnv_32_buf(nfhp->nfh_fh, nfhp->nfh_len,
                        FNV1_32_INIT);
                    onfhp = np->n_fhp;
                    /*
                     * Rehash node for new file handle.
                     */
                    vfs_hash_rehash(vp, hash);
                    np->n_fhp = nfhp;
                    if (onfhp != NULL)
                        FREE((caddr_t)onfhp, M_NFSFH);
                    newvp = NFSTOV(np);
                } else if (NFS_CMPFH(dnp, nfhp->nfh_fh, nfhp->nfh_len)) {
                    FREE((caddr_t)nfhp, M_NFSFH);
                    VREF(dvp);
                    newvp = dvp;
                } else {
                    cn.cn_nameptr = name;
                    cn.cn_namelen = len;
                    error = nfscl_nget(dvp->v_mount, dvp, nfhp, &cn, td,
                        &np, NULL, LK_EXCLUSIVE);
                    if (error)
                        return (error);
                    newvp = NFSTOV(np);
                }
                if (!attrflag && *npp == NULL) {
                        if (newvp == dvp)
                                vrele(newvp);
                        else
                                vput(newvp);
                        return (ENOENT);
                }
                if (attrflag)
                        (void) nfscl_loadattrcache(&newvp, &nfsva, NULL, NULL,
                            0, 1);
        }
        if (npp && *npp == NULL) {
                if (error) {
                        if (newvp) {
                                if (newvp == dvp)
                                        vrele(newvp);
                                else
                                        vput(newvp);
                        }
                } else
                        *npp = np;
        }
        if (error && NFS_ISV4(dvp))
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        return (error);
}

/*
 * Nfs Version 3 and 4 commit rpc
 */
int
ncl_commit(struct vnode *vp, u_quad_t offset, int cnt, struct ucred *cred,
   struct thread *td)
{
        struct nfsvattr nfsva;
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int error, attrflag;
        u_char verf[NFSX_VERF];

        mtx_lock(&nmp->nm_mtx);
        if ((nmp->nm_state & NFSSTA_HASWRITEVERF) == 0) {
                mtx_unlock(&nmp->nm_mtx);
                return (0);
        }
        mtx_unlock(&nmp->nm_mtx);
        error = nfsrpc_commit(vp, offset, cnt, cred, td, verf, &nfsva,
            &attrflag, NULL);
        if (!error) {
                if (NFSBCMP((caddr_t)nmp->nm_verf, verf, NFSX_VERF)) {
                        NFSBCOPY(verf, (caddr_t)nmp->nm_verf, NFSX_VERF);
                        error = NFSERR_STALEWRITEVERF;
                }
                if (!error && attrflag)
                        (void) nfscl_loadattrcache(&vp, &nfsva, NULL, NULL,
                            0, 1);
        } else if (NFS_ISV4(vp)) {
                error = nfscl_maperr(td, error, (uid_t)0, (gid_t)0);
        }
        return (error);
}

/*
 * Strategy routine.
 * For async requests when nfsiod(s) are running, queue the request by
 * calling ncl_asyncio(), otherwise just all ncl_doio() to do the
 * request.
 */
static int
nfs_strategy(struct vop_strategy_args *ap)
{
        struct buf *bp = ap->a_bp;
        struct ucred *cr;

        KASSERT(!(bp->b_flags & B_DONE),
            ("nfs_strategy: buffer %p unexpectedly marked B_DONE", bp));
        BUF_ASSERT_HELD(bp);

        if (bp->b_iocmd == BIO_READ)
                cr = bp->b_rcred;
        else
                cr = bp->b_wcred;

        /*
         * If the op is asynchronous and an i/o daemon is waiting
         * queue the request, wake it up and wait for completion
         * otherwise just do it ourselves.
         */
        if ((bp->b_flags & B_ASYNC) == 0 ||
            ncl_asyncio(VFSTONFS(ap->a_vp->v_mount), bp, NOCRED, curthread))
                (void) ncl_doio(ap->a_vp, bp, cr, curthread, 1);
        return (0);
}

/*
 * fsync vnode op. Just call ncl_flush() with commit == 1.
 */
/* ARGSUSED */
static int
nfs_fsync(struct vop_fsync_args *ap)
{
        return (ncl_flush(ap->a_vp, ap->a_waitfor, NULL, ap->a_td, 1, 0));
}

/*
 * Flush all the blocks associated with a vnode.
 *      Walk through the buffer pool and push any dirty pages
 *      associated with the vnode.
 * If the called_from_renewthread argument is TRUE, it has been called
 * from the NFSv4 renew thread and, as such, cannot block indefinitely
 * waiting for a buffer write to complete.
 */
int
ncl_flush(struct vnode *vp, int waitfor, struct ucred *cred, struct thread *td,
    int commit, int called_from_renewthread)
{
        struct nfsnode *np = VTONFS(vp);
        struct buf *bp;
        int i;
        struct buf *nbp;
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int error = 0, slptimeo = 0, slpflag = 0, retv, bvecpos;
        int passone = 1, trycnt = 0;
        u_quad_t off, endoff, toff;
        struct ucred* wcred = NULL;
        struct buf **bvec = NULL;
        struct bufobj *bo;
#ifndef NFS_COMMITBVECSIZ
#define NFS_COMMITBVECSIZ       20
#endif
        struct buf *bvec_on_stack[NFS_COMMITBVECSIZ];
        int bvecsize = 0, bveccount;

        if (called_from_renewthread != 0)
                slptimeo = hz;
        if (nmp->nm_flag & NFSMNT_INT)
                slpflag = NFS_PCATCH;
        if (!commit)
                passone = 0;
        bo = &vp->v_bufobj;
        /*
         * A b_flags == (B_DELWRI | B_NEEDCOMMIT) block has been written to the
         * server, but has not been committed to stable storage on the server
         * yet. On the first pass, the byte range is worked out and the commit
         * rpc is done. On the second pass, ncl_writebp() is called to do the
         * job.
         */
again:
        off = (u_quad_t)-1;
        endoff = 0;
        bvecpos = 0;
        if (NFS_ISV34(vp) && commit) {
                if (bvec != NULL && bvec != bvec_on_stack)
                        free(bvec, M_TEMP);
                /*
                 * Count up how many buffers waiting for a commit.
                 */
                bveccount = 0;
                BO_LOCK(bo);
                TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
                        if (!BUF_ISLOCKED(bp) &&
                            (bp->b_flags & (B_DELWRI | B_NEEDCOMMIT))
                                == (B_DELWRI | B_NEEDCOMMIT))
                                bveccount++;
                }
                /*
                 * Allocate space to remember the list of bufs to commit.  It is
                 * important to use M_NOWAIT here to avoid a race with nfs_write.
                 * If we can't get memory (for whatever reason), we will end up
                 * committing the buffers one-by-one in the loop below.
                 */
                if (bveccount > NFS_COMMITBVECSIZ) {
                        /*
                         * Release the vnode interlock to avoid a lock
                         * order reversal.
                         */
                        BO_UNLOCK(bo);
                        bvec = (struct buf **)
                                malloc(bveccount * sizeof(struct buf *),
                                       M_TEMP, M_NOWAIT);
                        BO_LOCK(bo);
                        if (bvec == NULL) {
                                bvec = bvec_on_stack;
                                bvecsize = NFS_COMMITBVECSIZ;
                        } else
                                bvecsize = bveccount;
                } else {
                        bvec = bvec_on_stack;
                        bvecsize = NFS_COMMITBVECSIZ;
                }
                TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
                        if (bvecpos >= bvecsize)
                                break;
                        if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL)) {
                                nbp = TAILQ_NEXT(bp, b_bobufs);
                                continue;
                        }
                        if ((bp->b_flags & (B_DELWRI | B_NEEDCOMMIT)) !=
                            (B_DELWRI | B_NEEDCOMMIT)) {
                                BUF_UNLOCK(bp);
                                nbp = TAILQ_NEXT(bp, b_bobufs);
                                continue;
                        }
                        BO_UNLOCK(bo);
                        bremfree(bp);
                        /*
                         * Work out if all buffers are using the same cred
                         * so we can deal with them all with one commit.
                         *
                         * NOTE: we are not clearing B_DONE here, so we have
                         * to do it later on in this routine if we intend to
                         * initiate I/O on the bp.
                         *
                         * Note: to avoid loopback deadlocks, we do not
                         * assign b_runningbufspace.
                         */
                        if (wcred == NULL)
                                wcred = bp->b_wcred;
                        else if (wcred != bp->b_wcred)
                                wcred = NOCRED;
                        vfs_busy_pages(bp, 1);

                        BO_LOCK(bo);
                        /*
                         * bp is protected by being locked, but nbp is not
                         * and vfs_busy_pages() may sleep.  We have to
                         * recalculate nbp.
                         */
                        nbp = TAILQ_NEXT(bp, b_bobufs);

                        /*
                         * A list of these buffers is kept so that the
                         * second loop knows which buffers have actually
                         * been committed. This is necessary, since there
                         * may be a race between the commit rpc and new
                         * uncommitted writes on the file.
                         */
                        bvec[bvecpos++] = bp;
                        toff = ((u_quad_t)bp->b_blkno) * DEV_BSIZE +
                                bp->b_dirtyoff;
                        if (toff < off)
                                off = toff;
                        toff += (u_quad_t)(bp->b_dirtyend - bp->b_dirtyoff);
                        if (toff > endoff)
                                endoff = toff;
                }
                BO_UNLOCK(bo);
        }
        if (bvecpos > 0) {
                /*
                 * Commit data on the server, as required.
                 * If all bufs are using the same wcred, then use that with
                 * one call for all of them, otherwise commit each one
                 * separately.
                 */
                if (wcred != NOCRED)
                        retv = ncl_commit(vp, off, (int)(endoff - off),
                                          wcred, td);
                else {
                        retv = 0;
                        for (i = 0; i < bvecpos; i++) {
                                off_t off, size;
                                bp = bvec[i];
                                off = ((u_quad_t)bp->b_blkno) * DEV_BSIZE +
                                        bp->b_dirtyoff;
                                size = (u_quad_t)(bp->b_dirtyend
                                                  - bp->b_dirtyoff);
                                retv = ncl_commit(vp, off, (int)size,
                                                  bp->b_wcred, td);
                                if (retv) break;
                        }
                }

                if (retv == NFSERR_STALEWRITEVERF)
                        ncl_clearcommit(vp->v_mount);

                /*
                 * Now, either mark the blocks I/O done or mark the
                 * blocks dirty, depending on whether the commit
                 * succeeded.
                 */
                for (i = 0; i < bvecpos; i++) {
                        bp = bvec[i];
                        bp->b_flags &= ~(B_NEEDCOMMIT | B_CLUSTEROK);
                        if (retv) {
                                /*
                                 * Error, leave B_DELWRI intact
                                 */
                                vfs_unbusy_pages(bp);
                                brelse(bp);
                        } else {
                                /*
                                 * Success, remove B_DELWRI ( bundirty() ).
                                 *
                                 * b_dirtyoff/b_dirtyend seem to be NFS
                                 * specific.  We should probably move that
                                 * into bundirty(). XXX
                                 */
                                bufobj_wref(bo);
                                bp->b_flags |= B_ASYNC;
                                bundirty(bp);
                                bp->b_flags &= ~B_DONE;
                                bp->b_ioflags &= ~BIO_ERROR;
                                bp->b_dirtyoff = bp->b_dirtyend = 0;
                                bufdone(bp);
                        }
                }
        }

        /*
         * Start/do any write(s) that are required.
         */
loop:
        BO_LOCK(bo);
        TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
                if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL)) {
                        if (waitfor != MNT_WAIT || passone)
                                continue;

                        error = BUF_TIMELOCK(bp,
                            LK_EXCLUSIVE | LK_SLEEPFAIL | LK_INTERLOCK,
                            BO_MTX(bo), "nfsfsync", slpflag, slptimeo);
                        if (error == 0) {
                                BUF_UNLOCK(bp);
                                goto loop;
                        }
                        if (error == ENOLCK) {
                                error = 0;
                                goto loop;
                        }
                        if (called_from_renewthread != 0) {
                                /*
                                 * Return EIO so the flush will be retried
                                 * later.
                                 */
                                error = EIO;
                                goto done;
                        }
                        if (newnfs_sigintr(nmp, td)) {
                                error = EINTR;
                                goto done;
                        }
                        if (slpflag & PCATCH) {
                                slpflag = 0;
                                slptimeo = 2 * hz;
                        }
                        goto loop;
                }
                if ((bp->b_flags & B_DELWRI) == 0)
                        panic("nfs_fsync: not dirty");
                if ((passone || !commit) && (bp->b_flags & B_NEEDCOMMIT)) {
                        BUF_UNLOCK(bp);
                        continue;
                }
                BO_UNLOCK(bo);
                bremfree(bp);
                if (passone || !commit)
                    bp->b_flags |= B_ASYNC;
                else
                    bp->b_flags |= B_ASYNC;
                bwrite(bp);
                if (newnfs_sigintr(nmp, td)) {
                        error = EINTR;
                        goto done;
                }
                goto loop;
        }
        if (passone) {
                passone = 0;
                BO_UNLOCK(bo);
                goto again;
        }
        if (waitfor == MNT_WAIT) {
                while (bo->bo_numoutput) {
                        error = bufobj_wwait(bo, slpflag, slptimeo);
                        if (error) {
                            BO_UNLOCK(bo);
                            if (called_from_renewthread != 0) {
                                /*
                                 * Return EIO so that the flush will be
                                 * retried later.
                                 */
                                error = EIO;
                                goto done;
                            }
                            error = newnfs_sigintr(nmp, td);
                            if (error)
                                goto done;
                            if (slpflag & PCATCH) {
                                slpflag = 0;
                                slptimeo = 2 * hz;
                            }
                            BO_LOCK(bo);
                        }
                }
                if (bo->bo_dirty.bv_cnt != 0 && commit) {
                        BO_UNLOCK(bo);
                        goto loop;
                }
                /*
                 * Wait for all the async IO requests to drain
                 */
                BO_UNLOCK(bo);
                mtx_lock(&np->n_mtx);
                while (np->n_directio_asyncwr > 0) {
                        np->n_flag |= NFSYNCWAIT;
                        error = newnfs_msleep(td, &np->n_directio_asyncwr,
                            &np->n_mtx, slpflag | (PRIBIO + 1), 
                            "nfsfsync", 0);
                        if (error) {
                                if (newnfs_sigintr(nmp, td)) {
                                        mtx_unlock(&np->n_mtx);
                                        error = EINTR;  
                                        goto done;
                                }
                        }
                }
                mtx_unlock(&np->n_mtx);
        } else
                BO_UNLOCK(bo);
        mtx_lock(&np->n_mtx);
        if (np->n_flag & NWRITEERR) {
                error = np->n_error;
                np->n_flag &= ~NWRITEERR;
        }
        if (commit && bo->bo_dirty.bv_cnt == 0 &&
            bo->bo_numoutput == 0 && np->n_directio_asyncwr == 0)
                np->n_flag &= ~NMODIFIED;
        mtx_unlock(&np->n_mtx);
done:
        if (bvec != NULL && bvec != bvec_on_stack)
                free(bvec, M_TEMP);
        if (error == 0 && commit != 0 && waitfor == MNT_WAIT &&
            (bo->bo_dirty.bv_cnt != 0 || bo->bo_numoutput != 0 ||
             np->n_directio_asyncwr != 0) && trycnt++ < 5) {
                /* try, try again... */
                passone = 1;
                wcred = NULL;
                bvec = NULL;
                bvecsize = 0;
printf("try%d\n", trycnt);
                goto again;
        }
        return (error);
}

/*
 * NFS advisory byte-level locks.
 */
static int
nfs_advlock(struct vop_advlock_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct ucred *cred;
        struct nfsnode *np = VTONFS(ap->a_vp);
        struct proc *p = (struct proc *)ap->a_id;
        struct thread *td = curthread;  /* XXX */
        struct vattr va;
        int ret, error = EOPNOTSUPP;
        u_quad_t size;
        
        if (NFS_ISV4(vp) && (ap->a_flags & F_POSIX)) {
                cred = p->p_ucred;
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                if (vp->v_iflag & VI_DOOMED) {
                        VOP_UNLOCK(vp, 0);
                        return (EBADF);
                }

                /*
                 * If this is unlocking a write locked region, flush and
                 * commit them before unlocking. This is required by
                 * RFC3530 Sec. 9.3.2.
                 */
                if (ap->a_op == F_UNLCK &&
                    nfscl_checkwritelocked(vp, ap->a_fl, cred, td))
                        (void) ncl_flush(vp, MNT_WAIT, cred, td, 1, 0);

                /*
                 * Loop around doing the lock op, while a blocking lock
                 * must wait for the lock op to succeed.
                 */
                do {
                        ret = nfsrpc_advlock(vp, np->n_size, ap->a_op,
                            ap->a_fl, 0, cred, td);
                        if (ret == NFSERR_DENIED && (ap->a_flags & F_WAIT) &&
                            ap->a_op == F_SETLK) {
                                VOP_UNLOCK(vp, 0);
                                error = nfs_catnap(PZERO | PCATCH, ret,
                                    "ncladvl");
                                if (error)
                                        return (EINTR);
                                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                                if (vp->v_iflag & VI_DOOMED) {
                                        VOP_UNLOCK(vp, 0);
                                        return (EBADF);
                                }
                        }
                } while (ret == NFSERR_DENIED && (ap->a_flags & F_WAIT) &&
                     ap->a_op == F_SETLK);
                if (ret == NFSERR_DENIED) {
                        VOP_UNLOCK(vp, 0);
                        return (EAGAIN);
                } else if (ret == EINVAL || ret == EBADF || ret == EINTR) {
                        VOP_UNLOCK(vp, 0);
                        return (ret);
                } else if (ret != 0) {
                        VOP_UNLOCK(vp, 0);
                        return (EACCES);
                }

                /*
                 * Now, if we just got a lock, invalidate data in the buffer
                 * cache, as required, so that the coherency conforms with
                 * RFC3530 Sec. 9.3.2.
                 */
                if (ap->a_op == F_SETLK) {
                        if ((np->n_flag & NMODIFIED) == 0) {
                                np->n_attrstamp = 0;
                                ret = VOP_GETATTR(vp, &va, cred);
                        }
                        if ((np->n_flag & NMODIFIED) || ret ||
                            np->n_change != va.va_filerev) {
                                (void) ncl_vinvalbuf(vp, V_SAVE, td, 1);
                                np->n_attrstamp = 0;
                                ret = VOP_GETATTR(vp, &va, cred);
                                if (!ret) {
                                        np->n_mtime = va.va_mtime;
                                        np->n_change = va.va_filerev;
                                }
                        }
                }
                VOP_UNLOCK(vp, 0);
                return (0);
        } else if (!NFS_ISV4(vp)) {
                error = vn_lock(vp, LK_SHARED);
                if (error)
                        return (error);
                if ((VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NOLOCKD) != 0) {
                        size = VTONFS(vp)->n_size;
                        VOP_UNLOCK(vp, 0);
                        error = lf_advlock(ap, &(vp->v_lockf), size);
                } else {
                        if (nfs_advlock_p != NULL)
                                error = nfs_advlock_p(ap);
                        else {
                                VOP_UNLOCK(vp, 0);
                                error = ENOLCK;
                        }
                }
        }
        return (error);
}

/*
 * NFS advisory byte-level locks.
 */
static int
nfs_advlockasync(struct vop_advlockasync_args *ap)
{
        struct vnode *vp = ap->a_vp;
        u_quad_t size;
        int error;
        
        if (NFS_ISV4(vp))
                return (EOPNOTSUPP);
        error = vn_lock(vp, LK_SHARED);
        if (error)
                return (error);
        if ((VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NOLOCKD) != 0) {
                size = VTONFS(vp)->n_size;
                VOP_UNLOCK(vp, 0);
                error = lf_advlockasync(ap, &(vp->v_lockf), size);
        } else {
                VOP_UNLOCK(vp, 0);
                error = EOPNOTSUPP;
        }
        return (error);
}

/*
 * Print out the contents of an nfsnode.
 */
static int
nfs_print(struct vop_print_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);

        ncl_printf("\tfileid %ld fsid 0x%x",
           np->n_vattr.na_fileid, np->n_vattr.na_fsid);
        if (vp->v_type == VFIFO)
                fifo_printinfo(vp);
        printf("\n");
        return (0);
}

/*
 * This is the "real" nfs::bwrite(struct buf*).
 * We set B_CACHE if this is a VMIO buffer.
 */
int
ncl_writebp(struct buf *bp, int force __unused, struct thread *td)
{
        int s;
        int oldflags = bp->b_flags;
#if 0
        int retv = 1;
        off_t off;
#endif

        BUF_ASSERT_HELD(bp);

        if (bp->b_flags & B_INVAL) {
                brelse(bp);
                return(0);
        }

        bp->b_flags |= B_CACHE;

        /*
         * Undirty the bp.  We will redirty it later if the I/O fails.
         */

        s = splbio();
        bundirty(bp);
        bp->b_flags &= ~B_DONE;
        bp->b_ioflags &= ~BIO_ERROR;
        bp->b_iocmd = BIO_WRITE;

        bufobj_wref(bp->b_bufobj);
        curthread->td_ru.ru_oublock++;
        splx(s);

        /*
         * Note: to avoid loopback deadlocks, we do not
         * assign b_runningbufspace.
         */
        vfs_busy_pages(bp, 1);

        BUF_KERNPROC(bp);
        bp->b_iooffset = dbtob(bp->b_blkno);
        bstrategy(bp);

        if( (oldflags & B_ASYNC) == 0) {
                int rtval = bufwait(bp);

                if (oldflags & B_DELWRI) {
                        s = splbio();
                        reassignbuf(bp);
                        splx(s);
                }
                brelse(bp);
                return (rtval);
        }

        return (0);
}

/*
 * nfs special file access vnode op.
 * Essentially just get vattr and then imitate iaccess() since the device is
 * local to the client.
 */
static int
nfsspec_access(struct vop_access_args *ap)
{
        struct vattr *vap;
        struct ucred *cred = ap->a_cred;
        struct vnode *vp = ap->a_vp;
        accmode_t accmode = ap->a_accmode;
        struct vattr vattr;
        int error;

        /*
         * Disallow write attempts on filesystems mounted read-only;
         * unless the file is a socket, fifo, or a block or character
         * device resident on the filesystem.
         */
        if ((accmode & VWRITE) && (vp->v_mount->mnt_flag & MNT_RDONLY)) {
                switch (vp->v_type) {
                case VREG:
                case VDIR:
                case VLNK:
                        return (EROFS);
                default:
                        break;
                }
        }
        vap = &vattr;
        error = VOP_GETATTR(vp, vap, cred);
        if (error)
                goto out;
        error  = vaccess(vp->v_type, vap->va_mode, vap->va_uid, vap->va_gid,
            accmode, cred, NULL);
out:
        return error;
}

/*
 * Read wrapper for fifos.
 */
static int
nfsfifo_read(struct vop_read_args *ap)
{
        struct nfsnode *np = VTONFS(ap->a_vp);
        int error;

        /*
         * Set access flag.
         */
        mtx_lock(&np->n_mtx);
        np->n_flag |= NACC;
        getnanotime(&np->n_atim);
        mtx_unlock(&np->n_mtx);
        error = fifo_specops.vop_read(ap);
        return error;   
}

/*
 * Write wrapper for fifos.
 */
static int
nfsfifo_write(struct vop_write_args *ap)
{
        struct nfsnode *np = VTONFS(ap->a_vp);

        /*
         * Set update flag.
         */
        mtx_lock(&np->n_mtx);
        np->n_flag |= NUPD;
        getnanotime(&np->n_mtim);
        mtx_unlock(&np->n_mtx);
        return(fifo_specops.vop_write(ap));
}

/*
 * Close wrapper for fifos.
 *
 * Update the times on the nfsnode then do fifo close.
 */
static int
nfsfifo_close(struct vop_close_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);
        struct vattr vattr;
        struct timespec ts;

        mtx_lock(&np->n_mtx);
        if (np->n_flag & (NACC | NUPD)) {
                getnanotime(&ts);
                if (np->n_flag & NACC)
                        np->n_atim = ts;
                if (np->n_flag & NUPD)
                        np->n_mtim = ts;
                np->n_flag |= NCHG;
                if (vrefcnt(vp) == 1 &&
                    (vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
                        VATTR_NULL(&vattr);
                        if (np->n_flag & NACC)
                                vattr.va_atime = np->n_atim;
                        if (np->n_flag & NUPD)
                                vattr.va_mtime = np->n_mtim;
                        mtx_unlock(&np->n_mtx);
                        (void)VOP_SETATTR(vp, &vattr, ap->a_cred);
                        goto out;
                }
        }
        mtx_unlock(&np->n_mtx);
out:
        return (fifo_specops.vop_close(ap));
}

/*
 * Just call ncl_writebp() with the force argument set to 1.
 *
 * NOTE: B_DONE may or may not be set in a_bp on call.
 */
static int
nfs_bwrite(struct buf *bp)
{

        return (ncl_writebp(bp, 1, curthread));
}

struct buf_ops buf_ops_newnfs = {
        .bop_name       =       "buf_ops_nfs",
        .bop_write      =       nfs_bwrite,
        .bop_strategy   =       bufstrategy,
        .bop_sync       =       bufsync,
        .bop_bdflush    =       bufbdflush,
};

/*
 * Cloned from vop_stdlock(), and then the ugly hack added.
 */
static int
nfs_lock1(struct vop_lock1_args *ap)
{
        struct vnode *vp = ap->a_vp;
        int error = 0;

        /*
         * Since vfs_hash_get() calls vget() and it will no longer work
         * for FreeBSD8 with flags == 0, I can only think of this horrible
         * hack to work around it. I call vfs_hash_get() with LK_EXCLOTHER
         * and then handle it here. All I want for this case is a v_usecount
         * on the vnode to use for recovery, while another thread might
         * hold a lock on the vnode. I have the other threads blocked, so
         * there isn't any race problem.
         */
        if ((ap->a_flags & LK_TYPE_MASK) == LK_EXCLOTHER) {
                if ((ap->a_flags & LK_INTERLOCK) == 0)
                        panic("ncllock1");
                if ((vp->v_iflag & VI_DOOMED))
                        error = ENOENT;
                VI_UNLOCK(vp);
                return (error);
        }
        return (_lockmgr_args(vp->v_vnlock, ap->a_flags, VI_MTX(vp),
            LK_WMESG_DEFAULT, LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, ap->a_file,
            ap->a_line));
}

static int
nfs_getacl(struct vop_getacl_args *ap)
{
        int error;

        if (ap->a_type != ACL_TYPE_NFS4)
                return (EOPNOTSUPP);
        error = nfsrpc_getacl(ap->a_vp, ap->a_cred, ap->a_td, ap->a_aclp,
            NULL);
        if (error > NFSERR_STALE) {
                (void) nfscl_maperr(ap->a_td, error, (uid_t)0, (gid_t)0);
                error = EPERM;
        }
        return (error);
}

static int
nfs_setacl(struct vop_setacl_args *ap)
{
        int error;

        if (ap->a_type != ACL_TYPE_NFS4)
                return (EOPNOTSUPP);
        error = nfsrpc_setacl(ap->a_vp, ap->a_cred, ap->a_td, ap->a_aclp,
            NULL);
        if (error > NFSERR_STALE) {
                (void) nfscl_maperr(ap->a_td, error, (uid_t)0, (gid_t)0);
                error = EPERM;
        }
        return (error);
}

/*
 * Return POSIX pathconf information applicable to nfs filesystems.
 */
static int
nfs_pathconf(struct vop_pathconf_args *ap)
{
        struct nfsv3_pathconf pc;
        struct nfsvattr nfsva;
        struct vnode *vp = ap->a_vp;
        struct thread *td = curthread;
        int attrflag, error;

        if (NFS_ISV34(vp)) {
                error = nfsrpc_pathconf(vp, &pc, td->td_ucred, td, &nfsva,
                    &attrflag, NULL);
                if (attrflag != 0)
                        (void) nfscl_loadattrcache(&vp, &nfsva, NULL, NULL, 0,
                            1);
                if (error != 0)
                        return (error);
        } else {
                /* For NFSv2, just fake them. */
                pc.pc_linkmax = LINK_MAX;
                pc.pc_namemax = NFS_MAXNAMLEN;
                pc.pc_notrunc = 1;
                pc.pc_chownrestricted = 1;
                pc.pc_caseinsensitive = 0;
                pc.pc_casepreserving = 1;
                error = 0;
        }
        switch (ap->a_name) {
        case _PC_LINK_MAX:
                *ap->a_retval = pc.pc_linkmax;
                break;
        case _PC_NAME_MAX:
                *ap->a_retval = pc.pc_namemax;
                break;
        case _PC_PATH_MAX:
                *ap->a_retval = PATH_MAX;
                break;
        case _PC_PIPE_BUF:
                *ap->a_retval = PIPE_BUF;
                break;
        case _PC_CHOWN_RESTRICTED:
                *ap->a_retval = pc.pc_chownrestricted;
                break;
        case _PC_NO_TRUNC:
                *ap->a_retval = pc.pc_notrunc;
                break;
        case _PC_ACL_EXTENDED:
                *ap->a_retval = 0;
                break;
        case _PC_ACL_NFS4:
                if (NFS_ISV4(vp) && nfsrv_useacl != 0 && attrflag != 0 &&
                    NFSISSET_ATTRBIT(&nfsva.na_suppattr, NFSATTRBIT_ACL))
                        *ap->a_retval = 1;
                else
                        *ap->a_retval = 0;
                break;
        case _PC_ACL_PATH_MAX:
                if (NFS_ISV4(vp))
                        *ap->a_retval = ACL_MAX_ENTRIES;
                else
                        *ap->a_retval = 3;
                break;
        case _PC_MAC_PRESENT:
                *ap->a_retval = 0;
                break;
        case _PC_ASYNC_IO:
                /* _PC_ASYNC_IO should have been handled by upper layers. */
                KASSERT(0, ("_PC_ASYNC_IO should not get here"));
                error = EINVAL;
                break;
        case _PC_PRIO_IO:
                *ap->a_retval = 0;
                break;
        case _PC_SYNC_IO:
                *ap->a_retval = 0;
                break;
        case _PC_ALLOC_SIZE_MIN:
                *ap->a_retval = vp->v_mount->mnt_stat.f_bsize;
                break;
        case _PC_FILESIZEBITS:
                if (NFS_ISV34(vp))
                        *ap->a_retval = 64;
                else
                        *ap->a_retval = 32;
                break;
        case _PC_REC_INCR_XFER_SIZE:
                *ap->a_retval = vp->v_mount->mnt_stat.f_iosize;
                break;
        case _PC_REC_MAX_XFER_SIZE:
                *ap->a_retval = -1; /* means ``unlimited'' */
                break;
        case _PC_REC_MIN_XFER_SIZE:
                *ap->a_retval = vp->v_mount->mnt_stat.f_iosize;
                break;
        case _PC_REC_XFER_ALIGN:
                *ap->a_retval = PAGE_SIZE;
                break;
        case _PC_SYMLINK_MAX:
                *ap->a_retval = NFS_MAXPATHLEN;
                break;

        default:
                error = EINVAL;
                break;
        }
        return (error);
}