FreeBSD/Linux Kernel Cross Reference
sys/nfsclient/nfs_vnops.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.
     *
     *      @(#)nfs_vnops.c 8.16 (Berkeley) 5/27/95
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /*
     * vnode op calls for Sun NFS version 2 and 3
     */
    
    #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/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/fifofs/fifo.h>
    
    #include <rpc/rpcclnt.h>
    
    #include <nfs/rpcv2.h>
    #include <nfs/nfsproto.h>
    #include <nfsclient/nfs.h>
    #include <nfsclient/nfsnode.h>
    #include <nfsclient/nfsmount.h>
    #include <nfsclient/nfs_lock.h>
    #include <nfs/xdr_subs.h>
    #include <nfsclient/nfsm_subs.h>
    
    #include <net/if.h>
    #include <netinet/in.h>
    #include <netinet/in_var.h>
    
    /* Defs */
    #define TRUE    1
    #define FALSE   0
    
    /*
     * 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_flush(struct vnode *, int, struct thread *,
                       int);
   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_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  int     nfs_lookitup(struct vnode *, const 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;
   
   /*
    * Global vfs data structures for nfs
    */
   struct vop_vector nfs_vnodeops = {
           .vop_default =          &default_vnodeops,
           .vop_access =           nfs_access,
           .vop_advlock =          nfs_advlock,
           .vop_close =            nfs_close,
           .vop_create =           nfs_create,
           .vop_fsync =            nfs_fsync,
           .vop_getattr =          nfs_getattr,
           .vop_getpages =         nfs_getpages,
           .vop_putpages =         nfs_putpages,
           .vop_inactive =         nfs_inactive,
           .vop_lease =            VOP_NULL,
           .vop_link =             nfs_link,
           .vop_lookup =           nfs_lookup,
           .vop_mkdir =            nfs_mkdir,
           .vop_mknod =            nfs_mknod,
           .vop_open =             nfs_open,
           .vop_print =            nfs_print,
           .vop_read =             nfs_read,
           .vop_readdir =          nfs_readdir,
           .vop_readlink =         nfs_readlink,
           .vop_reclaim =          nfs_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 =            nfs_write,
   };
   
   struct vop_vector nfs_fifoops = {
           .vop_default =          &fifo_specops,
           .vop_access =           nfsspec_access,
           .vop_close =            nfsfifo_close,
           .vop_fsync =            nfs_fsync,
           .vop_getattr =          nfs_getattr,
           .vop_inactive =         nfs_inactive,
           .vop_print =            nfs_print,
           .vop_read =             nfsfifo_read,
           .vop_reclaim =          nfs_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, const char *name, int namelen,
                                 struct ucred *cred, struct thread *td);
   static int      nfs_renamerpc(struct vnode *fdvp, const char *fnameptr,
                                 int fnamelen, struct vnode *tdvp,
                                 const char *tnameptr, int tnamelen,
                                 struct ucred *cred, struct thread *td);
   static int      nfs_renameit(struct vnode *sdvp, struct componentname *scnp,
                                struct sillyrename *sp);
   
   /*
    * Global variables
    */
   struct mtx      nfs_iod_mtx;
   struct proc     *nfs_iodwant[NFS_MAXASYNCDAEMON];
   struct nfsmount *nfs_iodmount[NFS_MAXASYNCDAEMON];
   int              nfs_numasync = 0;
   #define DIRHDSIZ        (sizeof (struct dirent) - (MAXNAMLEN + 1))
   
   SYSCTL_DECL(_vfs_nfs);
   
   static int      nfsaccess_cache_timeout = NFS_MAXATTRTIMO;
   SYSCTL_INT(_vfs_nfs, OID_AUTO, access_cache_timeout, CTLFLAG_RW,
              &nfsaccess_cache_timeout, 0, "NFS ACCESS cache timeout");
   
   static int      nfsv3_commit_on_close = 0;
   SYSCTL_INT(_vfs_nfs, OID_AUTO, nfsv3_commit_on_close, CTLFLAG_RW,
              &nfsv3_commit_on_close, 0, "write+commit on close, else only write");
   
   static int      nfs_clean_pages_on_close = 1;
   SYSCTL_INT(_vfs_nfs, OID_AUTO, clean_pages_on_close, CTLFLAG_RW,
              &nfs_clean_pages_on_close, 0, "NFS clean dirty pages on close");
   
   int nfs_directio_enable = 0;
   SYSCTL_INT(_vfs_nfs, OID_AUTO, nfs_directio_enable, CTLFLAG_RW,
              &nfs_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 nfs_directio_allow_mmap = 1;
   SYSCTL_INT(_vfs_nfs, OID_AUTO, nfs_directio_allow_mmap, CTLFLAG_RW,
              &nfs_directio_allow_mmap, 0, "Enable mmaped IO on file with O_DIRECT opens");
   
   #if 0
   SYSCTL_INT(_vfs_nfs, OID_AUTO, access_cache_hits, CTLFLAG_RD,
              &nfsstats.accesscache_hits, 0, "NFS ACCESS cache hit count");
   
   SYSCTL_INT(_vfs_nfs, OID_AUTO, access_cache_misses, CTLFLAG_RD,
              &nfsstats.accesscache_misses, 0, "NFS ACCESS cache miss count");
   #endif
   
   #define NFSV3ACCESS_ALL (NFSV3ACCESS_READ | NFSV3ACCESS_MODIFY          \
                            | NFSV3ACCESS_EXTEND | NFSV3ACCESS_EXECUTE     \
                            | NFSV3ACCESS_DELETE | NFSV3ACCESS_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
    * nfs_iod_mtx : 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
   nfs3_access_otw(struct vnode *vp, int wmode, struct thread *td,
       struct ucred *cred)
   {
           const int v3 = 1;
           u_int32_t *tl;
           int error = 0, attrflag;
   
           struct mbuf *mreq, *mrep, *md, *mb;
           caddr_t bpos, dpos;
           u_int32_t rmode;
           struct nfsnode *np = VTONFS(vp);
   
           nfsstats.rpccnt[NFSPROC_ACCESS]++;
           mreq = nfsm_reqhead(vp, NFSPROC_ACCESS, NFSX_FH(v3) + NFSX_UNSIGNED);
           mb = mreq;
           bpos = mtod(mb, caddr_t);
           nfsm_fhtom(vp, v3);
           tl = nfsm_build(u_int32_t *, NFSX_UNSIGNED);
           *tl = txdr_unsigned(wmode);
           nfsm_request(vp, NFSPROC_ACCESS, td, cred);
           nfsm_postop_attr(vp, attrflag);
           if (!error) {
                   tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                   rmode = fxdr_unsigned(u_int32_t, *tl);
                   mtx_lock(&np->n_mtx);
                   np->n_mode = rmode;
                   np->n_modeuid = cred->cr_uid;
                   np->n_modestamp = time_second;
                   mtx_unlock(&np->n_mtx);
           }
           m_freem(mrep);
   nfsmout:
           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;
           u_int32_t mode, wmode;
           int v3 = NFS_ISV3(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_mode & VWRITE) && (vp->v_mount->mnt_flag & MNT_RDONLY)) {
                   switch (vp->v_type) {
                   case VREG:
                   case VDIR:
                   case VLNK:
                           return (EROFS);
                   default:
                           break;
                   }
           }
           /*
            * For nfs v3, 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 (v3) {
                   if (ap->a_mode & VREAD)
                           mode = NFSV3ACCESS_READ;
                   else
                           mode = 0;
                   if (vp->v_type != VDIR) {
                           if (ap->a_mode & VWRITE)
                                   mode |= (NFSV3ACCESS_MODIFY | NFSV3ACCESS_EXTEND);
                           if (ap->a_mode & VEXEC)
                                   mode |= NFSV3ACCESS_EXECUTE;
                   } else {
                           if (ap->a_mode & VWRITE)
                                   mode |= (NFSV3ACCESS_MODIFY | NFSV3ACCESS_EXTEND |
                                            NFSV3ACCESS_DELETE);
                           if (ap->a_mode & VEXEC)
                                   mode |= NFSV3ACCESS_LOOKUP;
                   }
                   /* XXX safety belt, only make blanket request if caching */
                   if (nfsaccess_cache_timeout > 0) {
                           wmode = NFSV3ACCESS_READ | NFSV3ACCESS_MODIFY |
                                   NFSV3ACCESS_EXTEND | NFSV3ACCESS_EXECUTE |
                                   NFSV3ACCESS_DELETE | NFSV3ACCESS_LOOKUP;
                   } else {
                           wmode = mode;
                   }
   
                   /*
                    * Does our cached result allow us to give a definite yes to
                    * this request?
                    */
                   mtx_lock(&np->n_mtx);
                   if ((time_second < (np->n_modestamp + nfsaccess_cache_timeout)) &&
                       (ap->a_cred->cr_uid == np->n_modeuid) &&
                       ((np->n_mode & mode) == mode)) {
                           nfsstats.accesscache_hits++;
                   } else {
                           /*
                            * Either a no, or a don't know.  Go to the wire.
                            */
                           nfsstats.accesscache_misses++;
                           mtx_unlock(&np->n_mtx);
                           error = nfs3_access_otw(vp, wmode, ap->a_td,ap->a_cred);
                           mtx_lock(&np->n_mtx);
                           if (!error) {
                                   if ((np->n_mode & mode) != mode) {
                                           error = EACCES;
                                   }
                           }
                   }
                   mtx_unlock(&np->n_mtx);
                   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_mode & 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 = nfs_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 = nfs_readdirrpc(vp, &auio, ap->a_cred);
                                   free(bp, M_TEMP);
                           } else if (vp->v_type == VLNK)
                                   error = nfs_readlinkrpc(vp, &auio, ap->a_cred);
                           else
                                   error = EACCES;
                   } else
                           mtx_unlock(&np->n_mtx);
                   return (error);
           }
   }
   
   int nfs_otw_getattr_avoid = 0;
   
   /*
    * 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);
   
           /*
            * Get a valid lease. If cached data is stale, flush it.
            */
           mtx_lock(&np->n_mtx);
           if (np->n_flag & NMODIFIED) {
                   mtx_unlock(&np->n_mtx);                 
                   error = nfs_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                   if (error == EINTR || error == EIO)
                           return (error);
                   np->n_attrstamp = 0;
                   if (vp->v_type == VDIR)
                           np->n_direofoffset = 0;
                   error = VOP_GETATTR(vp, &vattr, ap->a_cred, ap->a_td);
                   if (error)
                           return (error);
                   mtx_lock(&np->n_mtx);
                   np->n_mtime = vattr.va_mtime;
                   mtx_unlock(&np->n_mtx);
           } else {
                   struct thread *td = curthread;
   
                   if (np->n_ac_ts_syscalls != td->td_syscalls ||
                       np->n_ac_ts_tid != td->td_tid || 
                       td->td_proc == NULL ||
                       np->n_ac_ts_pid != td->td_proc->p_pid) {
                           np->n_attrstamp = 0;
                   }
                   mtx_unlock(&np->n_mtx);                                         
                   error = VOP_GETATTR(vp, &vattr, ap->a_cred, ap->a_td);
                   if (error)
                           return (error);
                   mtx_lock(&np->n_mtx);
                   if (NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime)) {
                           if (vp->v_type == VDIR)
                                   np->n_direofoffset = 0;
                           mtx_unlock(&np->n_mtx);
                           error = nfs_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                           if (error == EINTR || error == EIO) {
                                   return (error);
                           }
                           mtx_lock(&np->n_mtx);
                           np->n_mtime = vattr.va_mtime;
                   }
                   mtx_unlock(&np->n_mtx);
           }
           /*
            * If the object has >= 1 O_DIRECT active opens, we disable caching.
            */
           if (nfs_directio_enable && (fmode & O_DIRECT) && (vp->v_type == VREG)) {
                   if (np->n_directio_opens == 0) {
                           error = nfs_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                           if (error)
                                   return (error);
                           mtx_lock(&np->n_mtx);
                           np->n_flag |= NNONCACHE;
                           mtx_unlock(&np->n_mtx);
                   }
                   np->n_directio_opens++;
           }
           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 nfs_flush() to
    *                     a 1 would force a commit operation, if it is felt a
    *                     commit is necessary now.
    */
   /* ARGSUSED */
   static int
   nfs_close(struct vop_close_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           struct nfsnode *np = VTONFS(vp);
           int error = 0;
           int fmode = ap->a_fflag;
   
           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.
                        */
                       int cm = nfsv3_commit_on_close ? 1 : 0;
                       error = nfs_flush(vp, MNT_WAIT, ap->a_td, cm);
                       /* np->n_flag &= ~NMODIFIED; */
                   } else
                       error = nfs_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.
                */
               np->n_attrstamp = 0;
               if (np->n_flag & NWRITEERR) {
                   np->n_flag &= ~NWRITEERR;
                   error = np->n_error;
               }
               mtx_unlock(&np->n_mtx);
           }
           if (nfs_directio_enable)
                   KASSERT((np->n_directio_asyncwr == 0),
                           ("nfs_close: dirty unflushed (%d) directio buffers\n",
                            np->n_directio_asyncwr));
           if (nfs_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);
           }
           return (error);
   }
   
   /*
    * nfs getattr call from vfs.
    */
   static int
   nfs_getattr(struct vop_getattr_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           struct nfsnode *np = VTONFS(vp);
           caddr_t bpos, dpos;
           int error = 0;
           struct mbuf *mreq, *mrep, *md, *mb;
           int v3 = NFS_ISV3(vp);
   
           /*
            * 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 (nfs_getattrcache(vp, ap->a_vap) == 0)
                   goto nfsmout;
           if (v3 && nfsaccess_cache_timeout > 0) {
                   nfsstats.accesscache_misses++;
                   nfs3_access_otw(vp, NFSV3ACCESS_ALL, ap->a_td, ap->a_cred);
                   if (nfs_getattrcache(vp, ap->a_vap) == 0)
                           goto nfsmout;
           }
           nfsstats.rpccnt[NFSPROC_GETATTR]++;
           mreq = nfsm_reqhead(vp, NFSPROC_GETATTR, NFSX_FH(v3));
           mb = mreq;
           bpos = mtod(mb, caddr_t);
           nfsm_fhtom(vp, v3);
           nfsm_request(vp, NFSPROC_GETATTR, ap->a_td, ap->a_cred);
           if (!error) {
                   nfsm_loadattr(vp, ap->a_vap);
           }
           m_freem(mrep);
   nfsmout:
           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 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 || (vap->va_vaflags & VA_MARK_ATIME))
                   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)) {
                   error = EROFS;
                   goto out;
           }
           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 = nfs_meta_setsize(vp, ap->a_cred, 
                                                    ap->a_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 = nfs_vinvalbuf(vp, 0, ap->a_td, 1);
                               else
                                   error = nfs_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
                               if (error) {
                                   vnode_pager_setsize(vp, tsize);
                                   goto out;
                               }
                           } else
                               mtx_unlock(&np->n_mtx);
                           /*
                            * np->n_size has already been set to vap->va_size
                            * in nfs_meta_setsize(). We must set it again since
                            * nfs_loadattrcache() could be called through
                            * nfs_meta_setsize() and could modify np->n_size.
                            */
                           mtx_lock(&np->n_mtx);
                           np->n_vattr.va_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 = nfs_vinvalbuf(vp, V_SAVE, ap->a_td, 1)) != 0 &&
                               (error == EINTR || error == EIO))
                                   return error;
                   } else
                           mtx_unlock(&np->n_mtx);
           }
           error = nfs_setattrrpc(vp, vap, ap->a_cred, ap->a_td);
           if (error && vap->va_size != VNOVAL) {
                   mtx_lock(&np->n_mtx);
                   np->n_size = np->n_vattr.va_size = tsize;
                   vnode_pager_setsize(vp, tsize);
                   mtx_unlock(&np->n_mtx);
           }
   out:
           return (error);
   }
   
   /*
    * Do an nfs setattr rpc.
    */
   static int
   nfs_setattrrpc(struct vnode *vp, struct vattr *vap, struct ucred *cred,
       struct thread *td)
   {
           struct nfsv2_sattr *sp;
           struct nfsnode *np = VTONFS(vp);
           caddr_t bpos, dpos;
           u_int32_t *tl;
           int error = 0, wccflag = NFSV3_WCCRATTR;
           struct mbuf *mreq, *mrep, *md, *mb;
           int v3 = NFS_ISV3(vp);
   
           nfsstats.rpccnt[NFSPROC_SETATTR]++;
           mreq = nfsm_reqhead(vp, NFSPROC_SETATTR, NFSX_FH(v3) + NFSX_SATTR(v3));
           mb = mreq;
           bpos = mtod(mb, caddr_t);
           nfsm_fhtom(vp, v3);
           if (v3) {
                   nfsm_v3attrbuild(vap, TRUE);
                   tl = nfsm_build(u_int32_t *, NFSX_UNSIGNED);
                   *tl = nfs_false;
           } else {
                   sp = nfsm_build(struct nfsv2_sattr *, NFSX_V2SATTR);
                   if (vap->va_mode == (mode_t)VNOVAL)
                           sp->sa_mode = nfs_xdrneg1;
                   else
                           sp->sa_mode = vtonfsv2_mode(vp->v_type, vap->va_mode);
                   if (vap->va_uid == (uid_t)VNOVAL)
                           sp->sa_uid = nfs_xdrneg1;
                   else
                           sp->sa_uid = txdr_unsigned(vap->va_uid);
                   if (vap->va_gid == (gid_t)VNOVAL)
                           sp->sa_gid = nfs_xdrneg1;
                   else
                           sp->sa_gid = txdr_unsigned(vap->va_gid);
                   sp->sa_size = txdr_unsigned(vap->va_size);
                   txdr_nfsv2time(&vap->va_atime, &sp->sa_atime);
                   txdr_nfsv2time(&vap->va_mtime, &sp->sa_mtime);
           }
           nfsm_request(vp, NFSPROC_SETATTR, td, cred);
           if (v3) {
                   np->n_modestamp = 0;
                   nfsm_wcc_data(vp, wccflag);
           } else
                   nfsm_loadattr(vp, NULL);
           m_freem(mrep);
   nfsmout:
           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;
           int flags = cnp->cn_flags;
           struct vnode *newvp;
           struct nfsmount *nmp;
           caddr_t bpos, dpos;
           struct mbuf *mreq, *mrep, *md, *mb;
           long len;
           nfsfh_t *fhp;
           struct nfsnode *np;
           int error = 0, attrflag, fhsize;
           int v3 = NFS_ISV3(dvp);
           struct thread *td = cnp->cn_thread;
           
           *vpp = NULLVP;
           if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
               (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
                   return (EROFS);
           if (dvp->v_type != VDIR)
                   return (ENOTDIR);
           nmp = VFSTONFS(dvp->v_mount);
           np = VTONFS(dvp);
           if ((error = VOP_ACCESS(dvp, VEXEC, cnp->cn_cred, td)) != 0) {
                   *vpp = NULLVP;
                   return (error);
           }
           if ((error = cache_lookup(dvp, vpp, cnp)) && error != ENOENT) {
                   struct vattr vattr;
   
                   newvp = *vpp;
                   if (!VOP_GETATTR(newvp, &vattr, cnp->cn_cred, td)
                    && vattr.va_ctime.tv_sec == VTONFS(newvp)->n_ctime) {
                        nfsstats.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;
           }
           error = 0;
           newvp = NULLVP;
           nfsstats.lookupcache_misses++;
           nfsstats.rpccnt[NFSPROC_LOOKUP]++;
           len = cnp->cn_namelen;
           mreq = nfsm_reqhead(dvp, NFSPROC_LOOKUP,
                   NFSX_FH(v3) + NFSX_UNSIGNED + nfsm_rndup(len));
           mb = mreq;
           bpos = mtod(mb, caddr_t);
           nfsm_fhtom(dvp, v3);
           nfsm_strtom(cnp->cn_nameptr, len, NFS_MAXNAMLEN);
           nfsm_request(dvp, NFSPROC_LOOKUP, cnp->cn_thread, cnp->cn_cred);
           if (error) {
                   if (v3) {
                           nfsm_postop_attr(dvp, attrflag);
                           m_freem(mrep);
                   }
                   goto nfsmout;
           }
           nfsm_getfh(fhp, fhsize, v3);
   
           /*
            * Handle RENAME case...
            */
           if (cnp->cn_nameiop == RENAME && (flags & ISLASTCN)) {
                   if (NFS_CMPFH(np, fhp, fhsize)) {
                           m_freem(mrep);
                           return (EISDIR);
                   }
                   error = nfs_nget(dvp->v_mount, fhp, fhsize, &np, LK_EXCLUSIVE);
                   if (error) {
                           m_freem(mrep);
                           return (error);
                   }
                   newvp = NFSTOV(np);
                   if (v3) {
                           nfsm_postop_attr(newvp, attrflag);
                           nfsm_postop_attr(dvp, attrflag);
                   } else
                           nfsm_loadattr(newvp, NULL);
                   *vpp = newvp;
                   m_freem(mrep);
                   cnp->cn_flags |= SAVENAME;
                   return (0);
           }
   
           if (flags & ISDOTDOT) {
                   VOP_UNLOCK(dvp, 0, td);
                   error = nfs_nget(dvp->v_mount, fhp, fhsize, &np, cnp->cn_lkflags);
                   vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, td);
                   if (error)
                           return (error);
                   newvp = NFSTOV(np);
           } else if (NFS_CMPFH(np, fhp, fhsize)) {
                   VREF(dvp);
                   newvp = dvp;
           } else {
                   error = nfs_nget(dvp->v_mount, fhp, fhsize, &np, cnp->cn_lkflags);
                   if (error) {
                           m_freem(mrep);
                           return (error);
                   }
                   newvp = NFSTOV(np);
           }
           if (v3) {
                   nfsm_postop_attr(newvp, attrflag);
                   nfsm_postop_attr(dvp, attrflag);
           } else
                   nfsm_loadattr(newvp, NULL);
           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.va_ctime.tv_sec;
                   cache_enter(dvp, newvp, cnp);
           }
           *vpp = newvp;
           m_freem(mrep);
   nfsmout:
           if (error) {
                   if (newvp != NULLVP) {
                           vput(newvp);
                           *vpp = NULLVP;
                   }
                   if ((cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME) &&
                       (flags & ISLASTCN) && error == ENOENT) {
                           if (dvp->v_mount->mnt_flag & MNT_RDONLY)
                                   error = EROFS;
                           else
                                   error = EJUSTRETURN;
                   }
                   if (cnp->cn_nameiop != LOOKUP && (flags & ISLASTCN))
                           cnp->cn_flags |= SAVENAME;
           }
           return (error);
   }
   
   /*
    * nfs read call.
    * Just call nfs_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 (nfs_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 (nfs_bioread(vp, ap->a_uio, 0, ap->a_cred));
  }
  
  /*
   * Do a readlink rpc.
   * Called by nfs_doio() from below the buffer cache.
   */
  int
  nfs_readlinkrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred)
  {
          caddr_t bpos, dpos;
          int error = 0, len, attrflag;
          struct mbuf *mreq, *mrep, *md, *mb;
          int v3 = NFS_ISV3(vp);
  
          nfsstats.rpccnt[NFSPROC_READLINK]++;
          mreq = nfsm_reqhead(vp, NFSPROC_READLINK, NFSX_FH(v3));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(vp, v3);
          nfsm_request(vp, NFSPROC_READLINK, uiop->uio_td, cred);
          if (v3)
                  nfsm_postop_attr(vp, attrflag);
          if (!error) {
                  nfsm_strsiz(len, NFS_MAXPATHLEN);
                  if (len == NFS_MAXPATHLEN) {
                          struct nfsnode *np = VTONFS(vp);
                          mtx_lock(&np->n_mtx);
                          if (np->n_size && np->n_size < NFS_MAXPATHLEN)
                                  len = np->n_size;
                          mtx_unlock(&np->n_mtx);
                  }
                  nfsm_mtouio(uiop, len);
          }
          m_freem(mrep);
  nfsmout:
          return (error);
  }
  
  /*
   * nfs read rpc call
   * Ditto above
   */
  int
  nfs_readrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred)
  {
          u_int32_t *tl;
          caddr_t bpos, dpos;
          struct mbuf *mreq, *mrep, *md, *mb;
          struct nfsmount *nmp;
          int error = 0, len, retlen, tsiz, eof, attrflag;
          int v3 = NFS_ISV3(vp);
          int rsize;
  
  #ifndef nolint
          eof = 0;
  #endif
          nmp = VFSTONFS(vp->v_mount);
          tsiz = uiop->uio_resid;
          mtx_lock(&nmp->nm_mtx);
          if (uiop->uio_offset + tsiz > nmp->nm_maxfilesize) {
                  mtx_unlock(&nmp->nm_mtx);
                  return (EFBIG);
          }
          rsize = nmp->nm_rsize;
          mtx_unlock(&nmp->nm_mtx);
          while (tsiz > 0) {
                  nfsstats.rpccnt[NFSPROC_READ]++;
                  len = (tsiz > rsize) ? rsize : tsiz;
                  mreq = nfsm_reqhead(vp, NFSPROC_READ, NFSX_FH(v3) + NFSX_UNSIGNED * 3);
                  mb = mreq;
                  bpos = mtod(mb, caddr_t);
                  nfsm_fhtom(vp, v3);
                  tl = nfsm_build(u_int32_t *, NFSX_UNSIGNED * 3);
                  if (v3) {
                          txdr_hyper(uiop->uio_offset, tl);
                          *(tl + 2) = txdr_unsigned(len);
                  } else {
                          *tl++ = txdr_unsigned(uiop->uio_offset);
                          *tl++ = txdr_unsigned(len);
                          *tl = 0;
                  }
                  nfsm_request(vp, NFSPROC_READ, uiop->uio_td, cred);
                  if (v3) {
                          nfsm_postop_attr(vp, attrflag);
                          if (error) {
                                  m_freem(mrep);
                                  goto nfsmout;
                          }
                          tl = nfsm_dissect(u_int32_t *, 2 * NFSX_UNSIGNED);
                          eof = fxdr_unsigned(int, *(tl + 1));
                  } else {
                          nfsm_loadattr(vp, NULL);
                  }
                  nfsm_strsiz(retlen, rsize);
                  nfsm_mtouio(uiop, retlen);
                  m_freem(mrep);
                  tsiz -= retlen;
                  if (v3) {
                          if (eof || retlen == 0) {
                                  tsiz = 0;
                          }
                  } else if (retlen < len) {
                          tsiz = 0;
                  }
          }
  nfsmout:
          return (error);
  }
  
  /*
   * nfs write call
   */
  int
  nfs_writerpc(struct vnode *vp, struct uio *uiop, struct ucred *cred,
               int *iomode, int *must_commit)
  {
          u_int32_t *tl;
          int32_t backup;
          caddr_t bpos, dpos;
          struct mbuf *mreq, *mrep, *md, *mb;
          struct nfsmount *nmp = VFSTONFS(vp->v_mount);
          int error = 0, len, tsiz, wccflag = NFSV3_WCCRATTR, rlen, commit;
          int v3 = NFS_ISV3(vp), committed = NFSV3WRITE_FILESYNC;
          int wsize;
          
  #ifndef DIAGNOSTIC
          if (uiop->uio_iovcnt != 1)
                  panic("nfs: writerpc iovcnt > 1");
  #endif
          *must_commit = 0;
          tsiz = uiop->uio_resid;
          mtx_lock(&nmp->nm_mtx);
          if (uiop->uio_offset + tsiz > nmp->nm_maxfilesize) {
                  mtx_unlock(&nmp->nm_mtx);               
                  return (EFBIG);
          }
          wsize = nmp->nm_wsize;
          mtx_unlock(&nmp->nm_mtx);
          while (tsiz > 0) {
                  nfsstats.rpccnt[NFSPROC_WRITE]++;
                  len = (tsiz > wsize) ? wsize : tsiz;
                  mreq = nfsm_reqhead(vp, NFSPROC_WRITE,
                          NFSX_FH(v3) + 5 * NFSX_UNSIGNED + nfsm_rndup(len));
                  mb = mreq;
                  bpos = mtod(mb, caddr_t);
                  nfsm_fhtom(vp, v3);
                  if (v3) {
                          tl = nfsm_build(u_int32_t *, 5 * NFSX_UNSIGNED);
                          txdr_hyper(uiop->uio_offset, tl);
                          tl += 2;
                          *tl++ = txdr_unsigned(len);
                          *tl++ = txdr_unsigned(*iomode);
                          *tl = txdr_unsigned(len);
                  } else {
                          u_int32_t x;
  
                          tl = nfsm_build(u_int32_t *, 4 * NFSX_UNSIGNED);
                          /* Set both "begin" and "current" to non-garbage. */
                          x = txdr_unsigned((u_int32_t)uiop->uio_offset);
                          *tl++ = x;      /* "begin offset" */
                          *tl++ = x;      /* "current offset" */
                          x = txdr_unsigned(len);
                          *tl++ = x;      /* total to this offset */
                          *tl = x;        /* size of this write */
                  }
                  nfsm_uiotom(uiop, len);
                  nfsm_request(vp, NFSPROC_WRITE, uiop->uio_td, cred);
                  if (v3) {
                          wccflag = NFSV3_WCCCHK;
                          nfsm_wcc_data(vp, wccflag);
                          if (!error) {
                                  tl = nfsm_dissect(u_int32_t *, 2 * NFSX_UNSIGNED
                                          + NFSX_V3WRITEVERF);
                                  rlen = fxdr_unsigned(int, *tl++);
                                  if (rlen == 0) {
                                          error = NFSERR_IO;
                                          m_freem(mrep);
                                          break;
                                  } else if (rlen < len) {
                                          backup = len - rlen;
                                          uiop->uio_iov->iov_base =
                                              (char *)uiop->uio_iov->iov_base -
                                              backup;
                                          uiop->uio_iov->iov_len += backup;
                                          uiop->uio_offset -= backup;
                                          uiop->uio_resid += backup;
                                          len = rlen;
                                  }
                                  commit = fxdr_unsigned(int, *tl++);
  
                                  /*
                                   * Return the lowest committment level
                                   * obtained by any of the RPCs.
                                   */
                                  if (committed == NFSV3WRITE_FILESYNC)
                                          committed = commit;
                                  else if (committed == NFSV3WRITE_DATASYNC &&
                                          commit == NFSV3WRITE_UNSTABLE)
                                          committed = commit;
                                  mtx_lock(&nmp->nm_mtx);
                                  if ((nmp->nm_state & NFSSTA_HASWRITEVERF) == 0){
                                      bcopy((caddr_t)tl, (caddr_t)nmp->nm_verf,
                                          NFSX_V3WRITEVERF);
                                      nmp->nm_state |= NFSSTA_HASWRITEVERF;
                                  } else if (bcmp((caddr_t)tl,
                                      (caddr_t)nmp->nm_verf, NFSX_V3WRITEVERF)) {
                                      *must_commit = 1;
                                      bcopy((caddr_t)tl, (caddr_t)nmp->nm_verf,
                                          NFSX_V3WRITEVERF);
                                  }
                                  mtx_unlock(&nmp->nm_mtx);
                          }
                  } else {
                          nfsm_loadattr(vp, NULL);
                  }
                  if (wccflag) {
                          mtx_lock(&(VTONFS(vp))->n_mtx);
                          VTONFS(vp)->n_mtime = VTONFS(vp)->n_vattr.va_mtime;
                          mtx_unlock(&(VTONFS(vp))->n_mtx);
                  }
                  m_freem(mrep);
                  if (error)
                          break;
                  tsiz -= len;
          }
  nfsmout:
          if (vp->v_mount->mnt_kern_flag & MNTK_ASYNC)
                  committed = NFSV3WRITE_FILESYNC;
          *iomode = committed;
          if (error)
                  uiop->uio_resid = tsiz;
          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 nfsv2_sattr *sp;
          u_int32_t *tl;
          struct vnode *newvp = NULL;
          struct nfsnode *np = NULL;
          struct vattr vattr;
          caddr_t bpos, dpos;
          int error = 0, wccflag = NFSV3_WCCRATTR, gotvp = 0;
          struct mbuf *mreq, *mrep, *md, *mb;
          u_int32_t rdev;
          int v3 = NFS_ISV3(dvp);
  
          if (vap->va_type == VCHR || vap->va_type == VBLK)
                  rdev = txdr_unsigned(vap->va_rdev);
          else if (vap->va_type == VFIFO || vap->va_type == VSOCK)
                  rdev = nfs_xdrneg1;
          else {
                  return (EOPNOTSUPP);
          }
          if ((error = VOP_GETATTR(dvp, &vattr, cnp->cn_cred, cnp->cn_thread)) != 0) {
                  return (error);
          }
          nfsstats.rpccnt[NFSPROC_MKNOD]++;
          mreq = nfsm_reqhead(dvp, NFSPROC_MKNOD, NFSX_FH(v3) + 4 * NFSX_UNSIGNED +
                  + nfsm_rndup(cnp->cn_namelen) + NFSX_SATTR(v3));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(dvp, v3);
          nfsm_strtom(cnp->cn_nameptr, cnp->cn_namelen, NFS_MAXNAMLEN);
          if (v3) {
                  tl = nfsm_build(u_int32_t *, NFSX_UNSIGNED);
                  *tl++ = vtonfsv3_type(vap->va_type);
                  nfsm_v3attrbuild(vap, FALSE);
                  if (vap->va_type == VCHR || vap->va_type == VBLK) {
                          tl = nfsm_build(u_int32_t *, 2 * NFSX_UNSIGNED);
                          *tl++ = txdr_unsigned(umajor(vap->va_rdev));
                          *tl = txdr_unsigned(uminor(vap->va_rdev));
                  }
          } else {
                  sp = nfsm_build(struct nfsv2_sattr *, NFSX_V2SATTR);
                  sp->sa_mode = vtonfsv2_mode(vap->va_type, vap->va_mode);
                  sp->sa_uid = nfs_xdrneg1;
                  sp->sa_gid = nfs_xdrneg1;
                  sp->sa_size = rdev;
                  txdr_nfsv2time(&vap->va_atime, &sp->sa_atime);
                  txdr_nfsv2time(&vap->va_mtime, &sp->sa_mtime);
          }
          nfsm_request(dvp, NFSPROC_MKNOD, cnp->cn_thread, cnp->cn_cred);
          if (!error) {
                  nfsm_mtofh(dvp, newvp, v3, gotvp);
                  if (!gotvp) {
                          if (newvp) {
                                  vput(newvp);
                                  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 (v3)
                  nfsm_wcc_data(dvp, wccflag);
          m_freem(mrep);
  nfsmout:
          if (error) {
                  if (newvp)
                          vput(newvp);
          } else {
                  if (cnp->cn_flags & MAKEENTRY)
                          cache_enter(dvp, newvp, cnp);
                  *vpp = newvp;
          }
          mtx_lock(&(VTONFS(dvp))->n_mtx);
          VTONFS(dvp)->n_flag |= NMODIFIED;
          if (!wccflag)
                  VTONFS(dvp)->n_attrstamp = 0;
          mtx_unlock(&(VTONFS(dvp))->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 nfsv2_sattr *sp;
          u_int32_t *tl;
          struct nfsnode *np = NULL;
          struct vnode *newvp = NULL;
          caddr_t bpos, dpos;
          int error = 0, wccflag = NFSV3_WCCRATTR, gotvp = 0, fmode = 0;
          struct mbuf *mreq, *mrep, *md, *mb;
          struct vattr vattr;
          int v3 = NFS_ISV3(dvp);
  
          /*
           * 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, cnp->cn_thread)) != 0) {
                  return (error);
          }
          if (vap->va_vaflags & VA_EXCLUSIVE)
                  fmode |= O_EXCL;
  again:
          nfsstats.rpccnt[NFSPROC_CREATE]++;
          mreq = nfsm_reqhead(dvp, NFSPROC_CREATE, NFSX_FH(v3) + 2 * NFSX_UNSIGNED +
                  nfsm_rndup(cnp->cn_namelen) + NFSX_SATTR(v3));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(dvp, v3);
          nfsm_strtom(cnp->cn_nameptr, cnp->cn_namelen, NFS_MAXNAMLEN);
          if (v3) {
                  tl = nfsm_build(u_int32_t *, NFSX_UNSIGNED);
                  if (fmode & O_EXCL) {
                          *tl = txdr_unsigned(NFSV3CREATE_EXCLUSIVE);
                          tl = nfsm_build(u_int32_t *, NFSX_V3CREATEVERF);
  #ifdef INET
                          if (!TAILQ_EMPTY(&in_ifaddrhead))
                                  *tl++ = IA_SIN(TAILQ_FIRST(&in_ifaddrhead))->sin_addr.s_addr;
                          else
  #endif
                                  *tl++ = create_verf;
                          *tl = ++create_verf;
                  } else {
                          *tl = txdr_unsigned(NFSV3CREATE_UNCHECKED);
                          nfsm_v3attrbuild(vap, FALSE);
                  }
          } else {
                  sp = nfsm_build(struct nfsv2_sattr *, NFSX_V2SATTR);
                  sp->sa_mode = vtonfsv2_mode(vap->va_type, vap->va_mode);
                  sp->sa_uid = nfs_xdrneg1;
                  sp->sa_gid = nfs_xdrneg1;
                  sp->sa_size = 0;
                  txdr_nfsv2time(&vap->va_atime, &sp->sa_atime);
                  txdr_nfsv2time(&vap->va_mtime, &sp->sa_mtime);
          }
          nfsm_request(dvp, NFSPROC_CREATE, cnp->cn_thread, cnp->cn_cred);
          if (!error) {
                  nfsm_mtofh(dvp, newvp, v3, gotvp);
                  if (!gotvp) {
                          if (newvp) {
                                  vput(newvp);
                                  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 (v3)
                  nfsm_wcc_data(dvp, wccflag);
          m_freem(mrep);
  nfsmout:
          if (error) {
                  if (v3 && (fmode & O_EXCL) && error == NFSERR_NOTSUPP) {
                          fmode &= ~O_EXCL;
                          goto again;
                  }
                  if (newvp)
                          vput(newvp);
          } else if (v3 && (fmode & O_EXCL)) {
                  /*
                   * We are normally called with only a partially initialized
                   * VAP.  Since the NFSv3 spec says that 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 = nfs_setattrrpc(newvp, vap, cnp->cn_cred, cnp->cn_thread);
                  if (error)
                          vput(newvp);
          }
          if (!error) {
                  if (cnp->cn_flags & MAKEENTRY)
                          cache_enter(dvp, newvp, cnp);
                  *ap->a_vpp = newvp;
          }
          mtx_lock(&(VTONFS(dvp))->n_mtx);
          VTONFS(dvp)->n_flag |= NMODIFIED;
          if (!wccflag)
                  VTONFS(dvp)->n_attrstamp = 0;
          mtx_unlock(&(VTONFS(dvp))->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;
  
  #ifndef DIAGNOSTIC
          if ((cnp->cn_flags & HASBUF) == 0)
                  panic("nfs_remove: no name");
          if (vrefcnt(vp) < 1)
                  panic("nfs_remove: bad v_usecount");
  #endif
          if (vp->v_type == VDIR)
                  error = EPERM;
          else if (vrefcnt(vp) == 1 || (np->n_sillyrename &&
              VOP_GETATTR(vp, &vattr, cnp->cn_cred, cnp->cn_thread) == 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 = nfs_vinvalbuf(vp, 0, cnp->cn_thread, 1);
                  /* Do the rpc */
                  if (error != EINTR && error != EIO)
                          error = nfs_removerpc(dvp, 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);
          np->n_attrstamp = 0;
          return (error);
  }
  
  /*
   * nfs file remove rpc called from nfs_inactive
   */
  int
  nfs_removeit(struct sillyrename *sp)
  {
          /*
           * 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, sp->s_name, sp->s_namlen, sp->s_cred,
                  NULL));
  }
  
  /*
   * Nfs remove rpc, called from nfs_remove() and nfs_removeit().
   */
  static int
  nfs_removerpc(struct vnode *dvp, const char *name, int namelen,
      struct ucred *cred, struct thread *td)
  {
          caddr_t bpos, dpos;
          int error = 0, wccflag = NFSV3_WCCRATTR;
          struct mbuf *mreq, *mrep, *md, *mb;
          int v3 = NFS_ISV3(dvp);
  
          nfsstats.rpccnt[NFSPROC_REMOVE]++;
          mreq = nfsm_reqhead(dvp, NFSPROC_REMOVE,
                  NFSX_FH(v3) + NFSX_UNSIGNED + nfsm_rndup(namelen));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(dvp, v3);
          nfsm_strtom(name, namelen, NFS_MAXNAMLEN);
          nfsm_request(dvp, NFSPROC_REMOVE, td, cred);
          if (v3)
                  nfsm_wcc_data(dvp, wccflag);
          m_freem(mrep);
  nfsmout:
          mtx_lock(&(VTONFS(dvp))->n_mtx);
          VTONFS(dvp)->n_flag |= NMODIFIED;
          if (!wccflag)
                  VTONFS(dvp)->n_attrstamp = 0;
          mtx_unlock(&(VTONFS(dvp))->n_mtx);
          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;
          int error;
  
  #ifndef DIAGNOSTIC
          if ((tcnp->cn_flags & HASBUF) == 0 ||
              (fcnp->cn_flags & HASBUF) == 0)
                  panic("nfs_rename: no name");
  #endif
          /* 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) {
                  nfs_printf("nfs_rename: fvp == tvp (can't happen)\n");
                  error = 0;
                  goto out;
          }
          if ((error = vn_lock(fvp, LK_EXCLUSIVE, fcnp->cn_thread)) != 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, fcnp->cn_thread);
          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, fcnp->cn_nameptr, fcnp->cn_namelen,
                  tdvp, tcnp->cn_nameptr, tcnp->cn_namelen, tcnp->cn_cred,
                  tcnp->cn_thread);
  
          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 componentname *scnp,
      struct sillyrename *sp)
  {
  
          return (nfs_renamerpc(sdvp, scnp->cn_nameptr, scnp->cn_namelen, sdvp,
              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, const char *fnameptr, int fnamelen,
      struct vnode *tdvp, const char *tnameptr, int tnamelen, struct ucred *cred,
      struct thread *td)
  {
          caddr_t bpos, dpos;
          int error = 0, fwccflag = NFSV3_WCCRATTR, twccflag = NFSV3_WCCRATTR;
          struct mbuf *mreq, *mrep, *md, *mb;
          int v3 = NFS_ISV3(fdvp);
  
          nfsstats.rpccnt[NFSPROC_RENAME]++;
          mreq = nfsm_reqhead(fdvp, NFSPROC_RENAME,
                  (NFSX_FH(v3) + NFSX_UNSIGNED)*2 + nfsm_rndup(fnamelen) +
                  nfsm_rndup(tnamelen));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(fdvp, v3);
          nfsm_strtom(fnameptr, fnamelen, NFS_MAXNAMLEN);
          nfsm_fhtom(tdvp, v3);
          nfsm_strtom(tnameptr, tnamelen, NFS_MAXNAMLEN);
          nfsm_request(fdvp, NFSPROC_RENAME, td, cred);
          if (v3) {
                  nfsm_wcc_data(fdvp, fwccflag);
                  nfsm_wcc_data(tdvp, twccflag);
          }
          m_freem(mrep);
  nfsmout:
          mtx_lock(&(VTONFS(fdvp))->n_mtx);
          VTONFS(fdvp)->n_flag |= NMODIFIED;
          mtx_unlock(&(VTONFS(fdvp))->n_mtx);
          mtx_lock(&(VTONFS(tdvp))->n_mtx);
          VTONFS(tdvp)->n_flag |= NMODIFIED;
          mtx_unlock(&(VTONFS(tdvp))->n_mtx);
          if (!fwccflag)
                  VTONFS(fdvp)->n_attrstamp = 0;
          if (!twccflag)
                  VTONFS(tdvp)->n_attrstamp = 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;
          caddr_t bpos, dpos;
          int error = 0, wccflag = NFSV3_WCCRATTR, attrflag = 0;
          struct mbuf *mreq, *mrep, *md, *mb;
          int v3;
  
          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);
  
          v3 = NFS_ISV3(vp);
          nfsstats.rpccnt[NFSPROC_LINK]++;
          mreq = nfsm_reqhead(vp, NFSPROC_LINK,
                  NFSX_FH(v3)*2 + NFSX_UNSIGNED + nfsm_rndup(cnp->cn_namelen));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(vp, v3);
          nfsm_fhtom(tdvp, v3);
          nfsm_strtom(cnp->cn_nameptr, cnp->cn_namelen, NFS_MAXNAMLEN);
          nfsm_request(vp, NFSPROC_LINK, cnp->cn_thread, cnp->cn_cred);
          if (v3) {
                  nfsm_postop_attr(vp, attrflag);
                  nfsm_wcc_data(tdvp, wccflag);
          }
          m_freem(mrep);
  nfsmout:
          mtx_lock(&(VTONFS(tdvp))->n_mtx);
          VTONFS(tdvp)->n_flag |= NMODIFIED;
          mtx_unlock(&(VTONFS(tdvp))->n_mtx);
          if (!attrflag)
                  VTONFS(vp)->n_attrstamp = 0;
          if (!wccflag)
                  VTONFS(tdvp)->n_attrstamp = 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 nfsv2_sattr *sp;
          caddr_t bpos, dpos;
          int slen, error = 0, wccflag = NFSV3_WCCRATTR, gotvp;
          struct mbuf *mreq, *mrep, *md, *mb;
          struct vnode *newvp = NULL;
          int v3 = NFS_ISV3(dvp);
  
          nfsstats.rpccnt[NFSPROC_SYMLINK]++;
          slen = strlen(ap->a_target);
          mreq = nfsm_reqhead(dvp, NFSPROC_SYMLINK, NFSX_FH(v3) + 2*NFSX_UNSIGNED +
              nfsm_rndup(cnp->cn_namelen) + nfsm_rndup(slen) + NFSX_SATTR(v3));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(dvp, v3);
          nfsm_strtom(cnp->cn_nameptr, cnp->cn_namelen, NFS_MAXNAMLEN);
          if (v3) {
                  nfsm_v3attrbuild(vap, FALSE);
          }
          nfsm_strtom(ap->a_target, slen, NFS_MAXPATHLEN);
          if (!v3) {
                  sp = nfsm_build(struct nfsv2_sattr *, NFSX_V2SATTR);
                  sp->sa_mode = vtonfsv2_mode(VLNK, vap->va_mode);
                  sp->sa_uid = nfs_xdrneg1;
                  sp->sa_gid = nfs_xdrneg1;
                  sp->sa_size = nfs_xdrneg1;
                  txdr_nfsv2time(&vap->va_atime, &sp->sa_atime);
                  txdr_nfsv2time(&vap->va_mtime, &sp->sa_mtime);
          }
  
          /*
           * Issue the NFS request and get the rpc response.
           *
           * Only NFSv3 responses returning an error of 0 actually return
           * a file handle that can be converted into newvp without having
           * to do an extra lookup rpc.
           */
          nfsm_request(dvp, NFSPROC_SYMLINK, cnp->cn_thread, cnp->cn_cred);
          if (v3) {
                  if (error == 0)
                          nfsm_mtofh(dvp, newvp, v3, gotvp);
                  nfsm_wcc_data(dvp, wccflag);
          }
  
          /*
           * out code jumps -> here, mrep is also freed.
           */
  
          m_freem(mrep);
  nfsmout:
  
          /*
           * 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.
           */
          if (error == 0 && newvp == NULL) {
                  struct nfsnode *np = NULL;
  
                  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);
          } else {
                  *ap->a_vpp = newvp;
          }
          mtx_lock(&(VTONFS(dvp))->n_mtx);
          VTONFS(dvp)->n_flag |= NMODIFIED;
          mtx_unlock(&(VTONFS(dvp))->n_mtx);
          if (!wccflag)
                  VTONFS(dvp)->n_attrstamp = 0;
          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 nfsv2_sattr *sp;
          int len;
          struct nfsnode *np = NULL;
          struct vnode *newvp = NULL;
          caddr_t bpos, dpos;
          int error = 0, wccflag = NFSV3_WCCRATTR;
          int gotvp = 0;
          struct mbuf *mreq, *mrep, *md, *mb;
          struct vattr vattr;
          int v3 = NFS_ISV3(dvp);
  
          if ((error = VOP_GETATTR(dvp, &vattr, cnp->cn_cred, cnp->cn_thread)) != 0) {
                  return (error);
          }
          len = cnp->cn_namelen;
          nfsstats.rpccnt[NFSPROC_MKDIR]++;
          mreq = nfsm_reqhead(dvp, NFSPROC_MKDIR,
            NFSX_FH(v3) + NFSX_UNSIGNED + nfsm_rndup(len) + NFSX_SATTR(v3));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(dvp, v3);
          nfsm_strtom(cnp->cn_nameptr, len, NFS_MAXNAMLEN);
          if (v3) {
                  nfsm_v3attrbuild(vap, FALSE);
          } else {
                  sp = nfsm_build(struct nfsv2_sattr *, NFSX_V2SATTR);
                  sp->sa_mode = vtonfsv2_mode(VDIR, vap->va_mode);
                  sp->sa_uid = nfs_xdrneg1;
                  sp->sa_gid = nfs_xdrneg1;
                  sp->sa_size = nfs_xdrneg1;
                  txdr_nfsv2time(&vap->va_atime, &sp->sa_atime);
                  txdr_nfsv2time(&vap->va_mtime, &sp->sa_mtime);
          }
          nfsm_request(dvp, NFSPROC_MKDIR, cnp->cn_thread, cnp->cn_cred);
          if (!error)
                  nfsm_mtofh(dvp, newvp, v3, gotvp);
          if (v3)
                  nfsm_wcc_data(dvp, wccflag);
          m_freem(mrep);
  nfsmout:
          mtx_lock(&(VTONFS(dvp))->n_mtx);
          VTONFS(dvp)->n_flag |= NMODIFIED;
          mtx_unlock(&(VTONFS(dvp))->n_mtx);
          if (!wccflag)
                  VTONFS(dvp)->n_attrstamp = 0;
          if (error == 0 && newvp == NULL) {
                  error = nfs_lookitup(dvp, cnp->cn_nameptr, len, 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);
          } else
                  *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;
          caddr_t bpos, dpos;
          int error = 0, wccflag = NFSV3_WCCRATTR;
          struct mbuf *mreq, *mrep, *md, *mb;
          int v3 = NFS_ISV3(dvp);
  
          if (dvp == vp)
                  return (EINVAL);
          nfsstats.rpccnt[NFSPROC_RMDIR]++;
          mreq = nfsm_reqhead(dvp, NFSPROC_RMDIR,
                  NFSX_FH(v3) + NFSX_UNSIGNED + nfsm_rndup(cnp->cn_namelen));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(dvp, v3);
          nfsm_strtom(cnp->cn_nameptr, cnp->cn_namelen, NFS_MAXNAMLEN);
          nfsm_request(dvp, NFSPROC_RMDIR, cnp->cn_thread, cnp->cn_cred);
          if (v3)
                  nfsm_wcc_data(dvp, wccflag);
          m_freem(mrep);
  nfsmout:
          mtx_lock(&(VTONFS(dvp))->n_mtx);
          VTONFS(dvp)->n_flag |= NMODIFIED;
          mtx_unlock(&(VTONFS(dvp))->n_mtx);
          if (!wccflag)
                  VTONFS(dvp)->n_attrstamp = 0;
          cache_purge(dvp);
          cache_purge(vp);
          /*
           * 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, uio->uio_td) == 0) {
                          mtx_lock(&np->n_mtx);
                          if (!NFS_TIMESPEC_COMPARE(&np->n_mtime, &vattr.va_mtime)) {
                                  mtx_unlock(&np->n_mtx);
                                  nfsstats.direofcache_hits++;
                                  goto out;
                          } else
                                  mtx_unlock(&np->n_mtx);
                  }
          }
  
          /*
           * Call nfs_bioread() to do the real work.
           */
          tresid = uio->uio_resid;
          error = nfs_bioread(vp, uio, 0, ap->a_cred);
  
          if (!error && uio->uio_resid == tresid) {
                  nfsstats.direofcache_misses++;
          }
  out:
          return (error);
  }
  
  /*
   * Readdir rpc call.
   * Called from below the buffer cache by nfs_doio().
   */
  int
  nfs_readdirrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred)
  {
          int len, left;
          struct dirent *dp = NULL;
          u_int32_t *tl;
          caddr_t cp;
          nfsuint64 *cookiep;
          caddr_t bpos, dpos;
          struct mbuf *mreq, *mrep, *md, *mb;
          nfsuint64 cookie;
          struct nfsmount *nmp = VFSTONFS(vp->v_mount);
          struct nfsnode *dnp = VTONFS(vp);
          u_quad_t fileno;
          int error = 0, tlen, more_dirs = 1, blksiz = 0, bigenough = 1;
          int attrflag;
          int v3 = NFS_ISV3(vp);
  
  #ifndef DIAGNOSTIC
          if (uiop->uio_iovcnt != 1 || (uiop->uio_offset & (DIRBLKSIZ - 1)) ||
                  (uiop->uio_resid & (DIRBLKSIZ - 1)))
                  panic("nfs readdirrpc bad uio");
  #endif
  
          /*
           * If there is no cookie, assume directory was stale.
           */
          nfs_dircookie_lock(dnp);
          cookiep = nfs_getcookie(dnp, uiop->uio_offset, 0);
          if (cookiep) {
                  cookie = *cookiep;
                  nfs_dircookie_unlock(dnp);
          } else {
                  nfs_dircookie_unlock(dnp);              
                  return (NFSERR_BAD_COOKIE);
          }
  
          /*
           * Loop around doing readdir rpc's of size nm_readdirsize
           * truncated to a multiple of DIRBLKSIZ.
           * The stopping criteria is EOF or buffer full.
           */
          while (more_dirs && bigenough) {
                  nfsstats.rpccnt[NFSPROC_READDIR]++;
                  mreq = nfsm_reqhead(vp, NFSPROC_READDIR, NFSX_FH(v3) +
                          NFSX_READDIR(v3));
                  mb = mreq;
                  bpos = mtod(mb, caddr_t);
                  nfsm_fhtom(vp, v3);
                  if (v3) {
                          tl = nfsm_build(u_int32_t *, 5 * NFSX_UNSIGNED);
                          *tl++ = cookie.nfsuquad[0];
                          *tl++ = cookie.nfsuquad[1];
                          mtx_lock(&dnp->n_mtx);
                          *tl++ = dnp->n_cookieverf.nfsuquad[0];
                          *tl++ = dnp->n_cookieverf.nfsuquad[1];
                          mtx_unlock(&dnp->n_mtx);
                  } else {
                          tl = nfsm_build(u_int32_t *, 2 * NFSX_UNSIGNED);
                          *tl++ = cookie.nfsuquad[0];
                  }
                  *tl = txdr_unsigned(nmp->nm_readdirsize);
                  nfsm_request(vp, NFSPROC_READDIR, uiop->uio_td, cred);
                  if (v3) {
                          nfsm_postop_attr(vp, attrflag);
                          if (!error) {
                                  tl = nfsm_dissect(u_int32_t *,
                                      2 * NFSX_UNSIGNED);
                                  mtx_lock(&dnp->n_mtx);
                                  dnp->n_cookieverf.nfsuquad[0] = *tl++;
                                  dnp->n_cookieverf.nfsuquad[1] = *tl;
                                  mtx_unlock(&dnp->n_mtx);
                          } else {
                                  m_freem(mrep);
                                  goto nfsmout;
                          }
                  }
                  tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                  more_dirs = fxdr_unsigned(int, *tl);
  
                  /* loop thru the dir entries, doctoring them to 4bsd form */
                  while (more_dirs && bigenough) {
                          if (v3) {
                                  tl = nfsm_dissect(u_int32_t *,
                                      3 * NFSX_UNSIGNED);
                                  fileno = fxdr_hyper(tl);
                                  len = fxdr_unsigned(int, *(tl + 2));
                          } else {
                                  tl = nfsm_dissect(u_int32_t *,
                                      2 * NFSX_UNSIGNED);
                                  fileno = fxdr_unsigned(u_quad_t, *tl++);
                                  len = fxdr_unsigned(int, *tl);
                          }
                          if (len <= 0 || len > NFS_MAXNAMLEN) {
                                  error = EBADRPC;
                                  m_freem(mrep);
                                  goto nfsmout;
                          }
                          tlen = nfsm_rndup(len);
                          if (tlen == len)
                                  tlen += 4;      /* To ensure null termination */
                          left = DIRBLKSIZ - blksiz;
                          if ((tlen + DIRHDSIZ) > left) {
                                  dp->d_reclen += left;
                                  uiop->uio_iov->iov_base =
                                      (char *)uiop->uio_iov->iov_base + left;
                                  uiop->uio_iov->iov_len -= left;
                                  uiop->uio_offset += left;
                                  uiop->uio_resid -= left;
                                  blksiz = 0;
                          }
                          if ((tlen + DIRHDSIZ) > uiop->uio_resid)
                                  bigenough = 0;
                          if (bigenough) {
                                  dp = (struct dirent *)uiop->uio_iov->iov_base;
                                  dp->d_fileno = (int)fileno;
                                  dp->d_namlen = len;
                                  dp->d_reclen = tlen + DIRHDSIZ;
                                  dp->d_type = DT_UNKNOWN;
                                  blksiz += dp->d_reclen;
                                  if (blksiz == DIRBLKSIZ)
                                          blksiz = 0;
                                  uiop->uio_offset += DIRHDSIZ;
                                  uiop->uio_resid -= DIRHDSIZ;
                                  uiop->uio_iov->iov_base =
                                      (char *)uiop->uio_iov->iov_base + DIRHDSIZ;
                                  uiop->uio_iov->iov_len -= DIRHDSIZ;
                                  nfsm_mtouio(uiop, len);
                                  cp = uiop->uio_iov->iov_base;
                                  tlen -= len;
                                  *cp = '\0';     /* null terminate */
                                  uiop->uio_iov->iov_base =
                                      (char *)uiop->uio_iov->iov_base + tlen;
                                  uiop->uio_iov->iov_len -= tlen;
                                  uiop->uio_offset += tlen;
                                  uiop->uio_resid -= tlen;
                          } else
                                  nfsm_adv(nfsm_rndup(len));
                          if (v3) {
                                  tl = nfsm_dissect(u_int32_t *,
                                      3 * NFSX_UNSIGNED);
                          } else {
                                  tl = nfsm_dissect(u_int32_t *,
                                      2 * NFSX_UNSIGNED);
                          }
                          if (bigenough) {
                                  cookie.nfsuquad[0] = *tl++;
                                  if (v3)
                                          cookie.nfsuquad[1] = *tl++;
                          } else if (v3)
                                  tl += 2;
                          else
                                  tl++;
                          more_dirs = fxdr_unsigned(int, *tl);
                  }
                  /*
                   * If at end of rpc data, get the eof boolean
                   */
                  if (!more_dirs) {
                          tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                          more_dirs = (fxdr_unsigned(int, *tl) == 0);
                  }
                  m_freem(mrep);
          }
          /*
           * Fill last record, iff any, out to a multiple of DIRBLKSIZ
           * by increasing d_reclen for the last record.
           */
          if (blksiz > 0) {
                  left = DIRBLKSIZ - blksiz;
                  dp->d_reclen += left;
                  uiop->uio_iov->iov_base =
                      (char *)uiop->uio_iov->iov_base + left;
                  uiop->uio_iov->iov_len -= left;
                  uiop->uio_offset += left;
                  uiop->uio_resid -= left;
          }
  
          /*
           * We are now either at the end of the directory or have filled the
           * block.
           */
          if (bigenough)
                  dnp->n_direofoffset = uiop->uio_offset;
          else {
                  if (uiop->uio_resid > 0)
                          nfs_printf("EEK! readdirrpc resid > 0\n");
                  nfs_dircookie_lock(dnp);
                  cookiep = nfs_getcookie(dnp, uiop->uio_offset, 1);
                  *cookiep = cookie;
                  nfs_dircookie_unlock(dnp);
          }
  nfsmout:
          return (error);
  }
  
  /*
   * NFS V3 readdir plus RPC. Used in place of nfs_readdirrpc().
   */
  int
  nfs_readdirplusrpc(struct vnode *vp, struct uio *uiop, struct ucred *cred)
  {
          int len, left;
          struct dirent *dp;
          u_int32_t *tl;
          caddr_t cp;
          struct vnode *newvp;
          nfsuint64 *cookiep;
          caddr_t bpos, dpos, dpossav1, dpossav2;
          struct mbuf *mreq, *mrep, *md, *mb, *mdsav1, *mdsav2;
          struct nameidata nami, *ndp = &nami;
          struct componentname *cnp = &ndp->ni_cnd;
          nfsuint64 cookie;
          struct nfsmount *nmp = VFSTONFS(vp->v_mount);
          struct nfsnode *dnp = VTONFS(vp), *np;
          nfsfh_t *fhp;
          u_quad_t fileno;
          int error = 0, tlen, more_dirs = 1, blksiz = 0, doit, bigenough = 1, i;
          int attrflag, fhsize;
  
  #ifndef nolint
          dp = NULL;
  #endif
  #ifndef DIAGNOSTIC
          if (uiop->uio_iovcnt != 1 || (uiop->uio_offset & (DIRBLKSIZ - 1)) ||
                  (uiop->uio_resid & (DIRBLKSIZ - 1)))
                  panic("nfs readdirplusrpc bad uio");
  #endif
          ndp->ni_dvp = vp;
          newvp = NULLVP;
  
          /*
           * If there is no cookie, assume directory was stale.
           */
          nfs_dircookie_lock(dnp);
          cookiep = nfs_getcookie(dnp, uiop->uio_offset, 0);
          if (cookiep) {
                  cookie = *cookiep;
                  nfs_dircookie_unlock(dnp);
          } else {
                  nfs_dircookie_unlock(dnp);
                  return (NFSERR_BAD_COOKIE);
          }
          /*
           * Loop around doing readdir rpc's of size nm_readdirsize
           * truncated to a multiple of DIRBLKSIZ.
           * The stopping criteria is EOF or buffer full.
           */
          while (more_dirs && bigenough) {
                  nfsstats.rpccnt[NFSPROC_READDIRPLUS]++;
                  mreq = nfsm_reqhead(vp, NFSPROC_READDIRPLUS,
                          NFSX_FH(1) + 6 * NFSX_UNSIGNED);
                  mb = mreq;
                  bpos = mtod(mb, caddr_t);
                  nfsm_fhtom(vp, 1);
                  tl = nfsm_build(u_int32_t *, 6 * NFSX_UNSIGNED);
                  *tl++ = cookie.nfsuquad[0];
                  *tl++ = cookie.nfsuquad[1];
                  mtx_lock(&dnp->n_mtx);
                  *tl++ = dnp->n_cookieverf.nfsuquad[0];
                  *tl++ = dnp->n_cookieverf.nfsuquad[1];
                  mtx_unlock(&dnp->n_mtx);
                  *tl++ = txdr_unsigned(nmp->nm_readdirsize);
                  *tl = txdr_unsigned(nmp->nm_rsize);
                  nfsm_request(vp, NFSPROC_READDIRPLUS, uiop->uio_td, cred);
                  nfsm_postop_attr(vp, attrflag);
                  if (error) {
                          m_freem(mrep);
                          goto nfsmout;
                  }
                  tl = nfsm_dissect(u_int32_t *, 3 * NFSX_UNSIGNED);
                  mtx_lock(&dnp->n_mtx);
                  dnp->n_cookieverf.nfsuquad[0] = *tl++;
                  dnp->n_cookieverf.nfsuquad[1] = *tl++;
                  mtx_unlock(&dnp->n_mtx);
                  more_dirs = fxdr_unsigned(int, *tl);
  
                  /* loop thru the dir entries, doctoring them to 4bsd form */
                  while (more_dirs && bigenough) {
                          tl = nfsm_dissect(u_int32_t *, 3 * NFSX_UNSIGNED);
                          fileno = fxdr_hyper(tl);
                          len = fxdr_unsigned(int, *(tl + 2));
                          if (len <= 0 || len > NFS_MAXNAMLEN) {
                                  error = EBADRPC;
                                  m_freem(mrep);
                                  goto nfsmout;
                          }
                          tlen = nfsm_rndup(len);
                          if (tlen == len)
                                  tlen += 4;      /* To ensure null termination*/
                          left = DIRBLKSIZ - blksiz;
                          if ((tlen + DIRHDSIZ) > left) {
                                  dp->d_reclen += left;
                                  uiop->uio_iov->iov_base =
                                      (char *)uiop->uio_iov->iov_base + left;
                                  uiop->uio_iov->iov_len -= left;
                                  uiop->uio_offset += left;
                                  uiop->uio_resid -= left;
                                  blksiz = 0;
                          }
                          if ((tlen + DIRHDSIZ) > uiop->uio_resid)
                                  bigenough = 0;
                          if (bigenough) {
                                  dp = (struct dirent *)uiop->uio_iov->iov_base;
                                  dp->d_fileno = (int)fileno;
                                  dp->d_namlen = len;
                                  dp->d_reclen = tlen + DIRHDSIZ;
                                  dp->d_type = DT_UNKNOWN;
                                  blksiz += dp->d_reclen;
                                  if (blksiz == DIRBLKSIZ)
                                          blksiz = 0;
                                  uiop->uio_offset += DIRHDSIZ;
                                  uiop->uio_resid -= DIRHDSIZ;
                                  uiop->uio_iov->iov_base =
                                      (char *)uiop->uio_iov->iov_base + DIRHDSIZ;
                                  uiop->uio_iov->iov_len -= DIRHDSIZ;
                                  cnp->cn_nameptr = uiop->uio_iov->iov_base;
                                  cnp->cn_namelen = len;
                                  nfsm_mtouio(uiop, len);
                                  cp = uiop->uio_iov->iov_base;
                                  tlen -= len;
                                  *cp = '\0';
                                  uiop->uio_iov->iov_base =
                                      (char *)uiop->uio_iov->iov_base + tlen;
                                  uiop->uio_iov->iov_len -= tlen;
                                  uiop->uio_offset += tlen;
                                  uiop->uio_resid -= tlen;
                          } else
                                  nfsm_adv(nfsm_rndup(len));
                          tl = nfsm_dissect(u_int32_t *, 3 * NFSX_UNSIGNED);
                          if (bigenough) {
                                  cookie.nfsuquad[0] = *tl++;
                                  cookie.nfsuquad[1] = *tl++;
                          } else
                                  tl += 2;
  
                          /*
                           * Since the attributes are before the file handle
                           * (sigh), we must skip over the attributes and then
                           * come back and get them.
                           */
                          attrflag = fxdr_unsigned(int, *tl);
                          if (attrflag) {
                              dpossav1 = dpos;
                              mdsav1 = md;
                              nfsm_adv(NFSX_V3FATTR);
                              tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                              doit = fxdr_unsigned(int, *tl);
                              /*
                               * Skip loading the attrs for "..". There's a 
                               * race between loading the attrs here and 
                               * lookups that look for the directory currently
                               * being read (in the parent). We try to acquire
                               * the exclusive lock on ".." here, owning the 
                               * lock on the directory being read. Lookup will
                               * hold the lock on ".." and try to acquire the 
                               * lock on the directory being read.
                               * 
                               * There are other ways of fixing this, one would
                               * be to do a trylock on the ".." vnode and skip
                               * loading the attrs on ".." if it happens to be 
                               * locked by another process. But skipping the
                               * attrload on ".." seems the easiest option.
                               */
                              if (strcmp(dp->d_name, "..") == 0) {
                                      doit = 0;
                                      /*
                                       * We've already skipped over the attrs, 
                                       * skip over the filehandle. And store d_type
                                       * as VDIR.
                                       */
                                      tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                                      i = fxdr_unsigned(int, *tl);
                                      nfsm_adv(nfsm_rndup(i));
                                      dp->d_type = IFTODT(VTTOIF(VDIR));
                              }       
                              if (doit) {
                                  nfsm_getfh(fhp, fhsize, 1);
                                  if (NFS_CMPFH(dnp, fhp, fhsize)) {
                                      VREF(vp);
                                      newvp = vp;
                                      np = dnp;
                                  } else {
                                      error = nfs_nget(vp->v_mount, fhp,
                                          fhsize, &np, LK_EXCLUSIVE);
                                      if (error)
                                          doit = 0;
                                      else
                                          newvp = NFSTOV(np);
                                  }
                              }
                              if (doit && bigenough) {
                                  dpossav2 = dpos;
                                  dpos = dpossav1;
                                  mdsav2 = md;
                                  md = mdsav1;
                                  nfsm_loadattr(newvp, NULL);
                                  dpos = dpossav2;
                                  md = mdsav2;
                                  dp->d_type =
                                      IFTODT(VTTOIF(np->n_vattr.va_type));
                                  ndp->ni_vp = newvp;
                                  /* Update n_ctime, so subsequent lookup doesn't purge entry */
                                  np->n_ctime = np->n_vattr.va_ctime.tv_sec;
                                  cache_enter(ndp->ni_dvp, ndp->ni_vp, cnp);
                              }
                          } else {
                              /* Just skip over the file handle */
                              tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                              i = fxdr_unsigned(int, *tl);
                              if (i) {
                                      tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                                      fhsize = fxdr_unsigned(int, *tl);
                                      nfsm_adv(nfsm_rndup(fhsize));
                              }
                          }
                          if (newvp != NULLVP) {
                              if (newvp == vp)
                                  vrele(newvp);
                              else
                                  vput(newvp);
                              newvp = NULLVP;
                          }
                          tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                          more_dirs = fxdr_unsigned(int, *tl);
                  }
                  /*
                   * If at end of rpc data, get the eof boolean
                   */
                  if (!more_dirs) {
                          tl = nfsm_dissect(u_int32_t *, NFSX_UNSIGNED);
                          more_dirs = (fxdr_unsigned(int, *tl) == 0);
                  }
                  m_freem(mrep);
          }
          /*
           * Fill last record, iff any, out to a multiple of DIRBLKSIZ
           * by increasing d_reclen for the last record.
           */
          if (blksiz > 0) {
                  left = DIRBLKSIZ - blksiz;
                  dp->d_reclen += left;
                  uiop->uio_iov->iov_base =
                      (char *)uiop->uio_iov->iov_base + left;
                  uiop->uio_iov->iov_len -= left;
                  uiop->uio_offset += left;
                  uiop->uio_resid -= left;
          }
  
          /*
           * We are now either at the end of the directory or have filled the
           * block.
           */
          if (bigenough)
                  dnp->n_direofoffset = uiop->uio_offset;
          else {
                  if (uiop->uio_resid > 0)
                          nfs_printf("EEK! readdirplusrpc resid > 0\n");
                  nfs_dircookie_lock(dnp);
                  cookiep = nfs_getcookie(dnp, uiop->uio_offset, 1);
                  *cookiep = cookie;
                  nfs_dircookie_unlock(dnp);
          }
  nfsmout:
          if (newvp != NULLVP) {
                  if (newvp == vp)
                          vrele(newvp);
                  else
                          vput(newvp);
                  newvp = NULLVP;
          }
          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);
  #ifndef DIAGNOSTIC
          if (vp->v_type == VDIR)
                  panic("nfs: sillyrename dir");
  #endif
          MALLOC(sp, struct sillyrename *, sizeof (struct sillyrename),
                  M_NFSREQ, M_WAITOK);
          sp->s_cred = crhold(cnp->cn_cred);
          sp->s_dvp = dvp;
          sp->s_removeit = nfs_removeit;
          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, 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_NFSREQ);
          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, const char *name, int len, struct ucred *cred,
      struct thread *td, struct nfsnode **npp)
  {
          struct vnode *newvp = NULL;
          struct nfsnode *np, *dnp = VTONFS(dvp);
          caddr_t bpos, dpos;
          int error = 0, fhlen, attrflag;
          struct mbuf *mreq, *mrep, *md, *mb;
          nfsfh_t *nfhp;
          int v3 = NFS_ISV3(dvp);
  
          nfsstats.rpccnt[NFSPROC_LOOKUP]++;
          mreq = nfsm_reqhead(dvp, NFSPROC_LOOKUP,
                  NFSX_FH(v3) + NFSX_UNSIGNED + nfsm_rndup(len));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(dvp, v3);
          nfsm_strtom(name, len, NFS_MAXNAMLEN);
          nfsm_request(dvp, NFSPROC_LOOKUP, td, cred);
          if (npp && !error) {
                  nfsm_getfh(nfhp, fhlen, v3);
                  if (*npp) {
                      np = *npp;
                      if (np->n_fhsize > NFS_SMALLFH && fhlen <= NFS_SMALLFH) {
                          free((caddr_t)np->n_fhp, M_NFSBIGFH);
                          np->n_fhp = &np->n_fh;
                      } else if (np->n_fhsize <= NFS_SMALLFH && fhlen>NFS_SMALLFH)
                          np->n_fhp =(nfsfh_t *)malloc(fhlen, M_NFSBIGFH, M_WAITOK);
                      bcopy((caddr_t)nfhp, (caddr_t)np->n_fhp, fhlen);
                      np->n_fhsize = fhlen;
                      newvp = NFSTOV(np);
                  } else if (NFS_CMPFH(dnp, nfhp, fhlen)) {
                      VREF(dvp);
                      newvp = dvp;
                  } else {
                      error = nfs_nget(dvp->v_mount, nfhp, fhlen, &np, LK_EXCLUSIVE);
                      if (error) {
                          m_freem(mrep);
                          return (error);
                      }
                      newvp = NFSTOV(np);
                  }
                  if (v3) {
                          nfsm_postop_attr(newvp, attrflag);
                          if (!attrflag && *npp == NULL) {
                                  m_freem(mrep);
                                  if (newvp == dvp)
                                          vrele(newvp);
                                  else
                                          vput(newvp);
                                  return (ENOENT);
                          }
                  } else
                          nfsm_loadattr(newvp, NULL);
          }
          m_freem(mrep);
  nfsmout:
          if (npp && *npp == NULL) {
                  if (error) {
                          if (newvp) {
                                  if (newvp == dvp)
                                          vrele(newvp);
                                  else
                                          vput(newvp);
                          }
                  } else
                          *npp = np;
          }
          return (error);
  }
  
  /*
   * Nfs Version 3 commit rpc
   */
  int
  nfs_commit(struct vnode *vp, u_quad_t offset, int cnt, struct ucred *cred,
             struct thread *td)
  {
          u_int32_t *tl;
          struct nfsmount *nmp = VFSTONFS(vp->v_mount);
          caddr_t bpos, dpos;
          int error = 0, wccflag = NFSV3_WCCRATTR;
          struct mbuf *mreq, *mrep, *md, *mb;
  
          mtx_lock(&nmp->nm_mtx);
          if ((nmp->nm_state & NFSSTA_HASWRITEVERF) == 0) {
                  mtx_unlock(&nmp->nm_mtx);
                  return (0);
          }
          mtx_unlock(&nmp->nm_mtx);
          nfsstats.rpccnt[NFSPROC_COMMIT]++;
          mreq = nfsm_reqhead(vp, NFSPROC_COMMIT, NFSX_FH(1));
          mb = mreq;
          bpos = mtod(mb, caddr_t);
          nfsm_fhtom(vp, 1);
          tl = nfsm_build(u_int32_t *, 3 * NFSX_UNSIGNED);
          txdr_hyper(offset, tl);
          tl += 2;
          *tl = txdr_unsigned(cnt);
          nfsm_request(vp, NFSPROC_COMMIT, td, cred);
          nfsm_wcc_data(vp, wccflag);
          if (!error) {
                  tl = nfsm_dissect(u_int32_t *, NFSX_V3WRITEVERF);
                  if (bcmp((caddr_t)nmp->nm_verf, (caddr_t)tl,
                          NFSX_V3WRITEVERF)) {
                          bcopy((caddr_t)tl, (caddr_t)nmp->nm_verf,
                                  NFSX_V3WRITEVERF);
                          error = NFSERR_STALEWRITEVERF;
                  }
          }
          m_freem(mrep);
  nfsmout:
          return (error);
  }
  
  /*
   * Strategy routine.
   * For async requests when nfsiod(s) are running, queue the request by
   * calling nfs_asyncio(), otherwise just all nfs_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));
          KASSERT(BUF_REFCNT(bp) > 0, ("nfs_strategy: buffer %p not locked", 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 ||
              nfs_asyncio(VFSTONFS(ap->a_vp->v_mount), bp, NOCRED, curthread))
                  (void)nfs_doio(ap->a_vp, bp, cr, curthread);
          return (0);
  }
  
  /*
   * fsync vnode op. Just call nfs_flush() with commit == 1.
   */
  /* ARGSUSED */
  static int
  nfs_fsync(struct vop_fsync_args *ap)
  {
          return (nfs_flush(ap->a_vp, ap->a_waitfor, ap->a_td, 1));
  }
  
  /*
   * Flush all the blocks associated with a vnode.
   *      Walk through the buffer pool and push any dirty pages
   *      associated with the vnode.
   */
  static int
  nfs_flush(struct vnode *vp, int waitfor, struct thread *td,
      int commit)
  {
          struct nfsnode *np = VTONFS(vp);
          struct buf *bp;
          int i;
          struct buf *nbp;
          struct nfsmount *nmp = VFSTONFS(vp->v_mount);
          int s, error = 0, slptimeo = 0, slpflag = 0, retv, bvecpos;
          int passone = 1;
          u_quad_t off, endoff, toff;
          struct ucred* wcred = NULL;
          struct buf **bvec = NULL;
  #ifndef NFS_COMMITBVECSIZ
  #define NFS_COMMITBVECSIZ       20
  #endif
          struct buf *bvec_on_stack[NFS_COMMITBVECSIZ];
          int bvecsize = 0, bveccount;
  
          if (nmp->nm_flag & NFSMNT_INT)
                  slpflag = PCATCH;
          if (!commit)
                  passone = 0;
          /*
           * 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, nfs_writebp() is called to do the
           * job.
           */
  again:
          off = (u_quad_t)-1;
          endoff = 0;
          bvecpos = 0;
          if (NFS_ISV3(vp) && commit) {
                  s = splbio();
                  if (bvec != NULL && bvec != bvec_on_stack)
                          free(bvec, M_TEMP);
                  /*
                   * Count up how many buffers waiting for a commit.
                   */
                  bveccount = 0;
                  VI_LOCK(vp);
                  TAILQ_FOREACH_SAFE(bp, &vp->v_bufobj.bo_dirty.bv_hd, b_bobufs, nbp) {
                          if (BUF_REFCNT(bp) == 0 &&
                              (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.
                           */
                          VI_UNLOCK(vp);
                          bvec = (struct buf **)
                                  malloc(bveccount * sizeof(struct buf *),
                                         M_TEMP, M_NOWAIT);
                          VI_LOCK(vp);
                          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, &vp->v_bufobj.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;
                          }
                          VI_UNLOCK(vp);
                          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);
  
                          VI_LOCK(vp);
                          /*
                           * 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;
                  }
                  splx(s);
                  VI_UNLOCK(vp);
          }
          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 = nfs_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 = nfs_commit(vp, off, (int)size,
                                                    bp->b_wcred, td);
                                  if (retv) break;
                          }
                  }
  
                  if (retv == NFSERR_STALEWRITEVERF)
                          nfs_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
                                   */
                                  s = splbio();
                                  bufobj_wref(&vp->v_bufobj);
                                  bp->b_flags |= B_ASYNC;
                                  bundirty(bp);
                                  bp->b_flags &= ~B_DONE;
                                  bp->b_ioflags &= ~BIO_ERROR;
                                  bp->b_dirtyoff = bp->b_dirtyend = 0;
                                  splx(s);
                                  bufdone(bp);
                          }
                  }
          }
  
          /*
           * Start/do any write(s) that are required.
           */
  loop:
          s = splbio();
          VI_LOCK(vp);
          TAILQ_FOREACH_SAFE(bp, &vp->v_bufobj.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,
                              VI_MTX(vp), "nfsfsync", slpflag, slptimeo);
                          splx(s);
                          if (error == 0) {
                                  BUF_UNLOCK(bp);
                                  goto loop;
                          }
                          if (error == ENOLCK)
                                  goto loop;
                          if (nfs_sigintr(nmp, NULL, 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;
                  }
                  VI_UNLOCK(vp);
                  bremfree(bp);
                  if (passone || !commit)
                      bp->b_flags |= B_ASYNC;
                  else
                      bp->b_flags |= B_ASYNC;
                  splx(s);
                  bwrite(bp);
                  if (nfs_sigintr(nmp, NULL, td)) {
                          error = EINTR;
                          goto done;
                  }
                  goto loop;
          }
          splx(s);
          if (passone) {
                  passone = 0;
                  VI_UNLOCK(vp);
                  goto again;
          }
          if (waitfor == MNT_WAIT) {
                  while (vp->v_bufobj.bo_numoutput) {
                          error = bufobj_wwait(&vp->v_bufobj, slpflag, slptimeo);
                          if (error) {
                              VI_UNLOCK(vp);
                              error = nfs_sigintr(nmp, NULL, td);
                              if (error)
                                  goto done;
                              if (slpflag == PCATCH) {
                                  slpflag = 0;
                                  slptimeo = 2 * hz;
                              }
                              VI_LOCK(vp);
                          }
                  }
                  if (vp->v_bufobj.bo_dirty.bv_cnt != 0 && commit) {
                          VI_UNLOCK(vp);
                          goto loop;
                  }
                  /*
                   * Wait for all the async IO requests to drain
                   */
                  VI_UNLOCK(vp);
                  mtx_lock(&np->n_mtx);
                  while (np->n_directio_asyncwr > 0) {
                          np->n_flag |= NFSYNCWAIT;
                          error = nfs_msleep(td, (caddr_t)&np->n_directio_asyncwr,
                                             &np->n_mtx, slpflag | (PRIBIO + 1), 
                                             "nfsfsync", 0);
                          if (error) {
                                  if (nfs_sigintr(nmp, (struct nfsreq *)0, td)) {
                                          mtx_unlock(&np->n_mtx);
                                          error = EINTR;  
                                          goto done;
                                  }
                          }
                  }
                  mtx_unlock(&np->n_mtx);
          } else
                  VI_UNLOCK(vp);
          mtx_lock(&np->n_mtx);
          if (np->n_flag & NWRITEERR) {
                  error = np->n_error;
                  np->n_flag &= ~NWRITEERR;
          }
          if (commit && vp->v_bufobj.bo_dirty.bv_cnt == 0 &&
              vp->v_bufobj.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);
          return (error);
  }
  
  /*
   * NFS advisory byte-level locks.
   */
  static int
  nfs_advlock(struct vop_advlock_args *ap)
  {
          int error;
          
          mtx_lock(&Giant);
          if ((VFSTONFS(ap->a_vp->v_mount)->nm_flag & NFSMNT_NOLOCKD) != 0) {
                  struct nfsnode *np = VTONFS(ap->a_vp);
  
                  error = lf_advlock(ap, &(np->n_lockf), np->n_size);
                  goto out;
          }
          error = nfs_dolock(ap);
  out:    
          mtx_unlock(&Giant);
          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);
  
          nfs_printf("\tfileid %ld fsid 0x%x",
             np->n_vattr.va_fileid, np->n_vattr.va_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
  nfs_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
  
          if (BUF_REFCNT(bp) == 0)
                  panic("bwrite: buffer is not locked???");
  
          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;
          mode_t mode = ap->a_mode;
          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 ((mode & 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, ap->a_td);
          if (error)
                  goto out;
          error  = vaccess(vp->v_type, vap->va_mode, vap->va_uid, vap->va_gid,
                           mode, 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, ap->a_td);
                          goto out;
                  }
          }
          mtx_unlock(&np->n_mtx);
  out:
          return (fifo_specops.vop_close(ap));
  }
  
  /*
   * Just call nfs_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 (nfs_writebp(bp, 1, curthread));
  }
  
  struct buf_ops buf_ops_nfs = {
          .bop_name       =       "buf_ops_nfs",
          .bop_write      =       nfs_bwrite,
          .bop_strategy   =       bufstrategy,
          .bop_sync       =       bufsync,
          .bop_bdflush    =       bufbdflush,
  };