kernel NFS - Fix another deadlock in the readdirplus code

[dragonfly.git] / sys / kern / vfs_vnops.c

/*
 * Copyright (c) 1982, 1986, 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 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.
 *
 *      @(#)vfs_vnops.c 8.2 (Berkeley) 1/21/94
 * $FreeBSD: src/sys/kern/vfs_vnops.c,v 1.87.2.13 2002/12/29 18:19:53 dillon Exp $
 * $DragonFly: src/sys/kern/vfs_vnops.c,v 1.58 2008/06/28 17:59:49 dillon Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/proc.h>
#include <sys/priv.h>
#include <sys/mount.h>
#include <sys/nlookup.h>
#include <sys/vnode.h>
#include <sys/buf.h>
#include <sys/filio.h>
#include <sys/ttycom.h>
#include <sys/conf.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>

#include <sys/thread2.h>
#include <sys/mplock2.h>

static int vn_closefile (struct file *fp);
static int vn_ioctl (struct file *fp, u_long com, caddr_t data,
                struct ucred *cred, struct sysmsg *msg);
static int vn_read (struct file *fp, struct uio *uio, 
                struct ucred *cred, int flags);
static int vn_poll (struct file *fp, int events, struct ucred *cred);
static int vn_kqfilter (struct file *fp, struct knote *kn);
static int vn_statfile (struct file *fp, struct stat *sb, struct ucred *cred);
static int vn_write (struct file *fp, struct uio *uio, 
                struct ucred *cred, int flags);

struct fileops vnode_fileops = {
        .fo_read = vn_read,
        .fo_write = vn_write,
        .fo_ioctl = vn_ioctl,
        .fo_poll = vn_poll,
        .fo_kqfilter = vn_kqfilter,
        .fo_stat = vn_statfile,
        .fo_close = vn_closefile,
        .fo_shutdown = nofo_shutdown
};

/*
 * Common code for vnode open operations.  Check permissions, and call
 * the VOP_NOPEN or VOP_NCREATE routine.
 *
 * The caller is responsible for setting up nd with nlookup_init() and
 * for cleaning it up with nlookup_done(), whether we return an error
 * or not.
 *
 * On success nd->nl_open_vp will hold a referenced and, if requested,
 * locked vnode.  A locked vnode is requested via NLC_LOCKVP.  If fp
 * is non-NULL the vnode will be installed in the file pointer.
 *
 * NOTE: The vnode is referenced just once on return whether or not it
 * is also installed in the file pointer.
 */
int
vn_open(struct nlookupdata *nd, struct file *fp, int fmode, int cmode)
{
        struct vnode *vp;
        struct ucred *cred = nd->nl_cred;
        struct vattr vat;
        struct vattr *vap = &vat;
        int error;

        /*
         * Certain combinations are illegal
         */
        if ((fmode & (FWRITE | O_TRUNC)) == O_TRUNC)
                return(EACCES);

        /*
         * Lookup the path and create or obtain the vnode.  After a
         * successful lookup a locked nd->nl_nch will be returned.
         *
         * The result of this section should be a locked vnode.
         *
         * XXX with only a little work we should be able to avoid locking
         * the vnode if FWRITE, O_CREAT, and O_TRUNC are *not* set.
         */
        nd->nl_flags |= NLC_OPEN;
        if (fmode & O_APPEND)
                nd->nl_flags |= NLC_APPEND;
        if (fmode & O_TRUNC)
                nd->nl_flags |= NLC_TRUNCATE;
        if (fmode & FREAD)
                nd->nl_flags |= NLC_READ;
        if (fmode & FWRITE)
                nd->nl_flags |= NLC_WRITE;
        if ((fmode & O_EXCL) == 0 && (fmode & O_NOFOLLOW) == 0)
                nd->nl_flags |= NLC_FOLLOW;

        if (fmode & O_CREAT) {
                /*
                 * CONDITIONAL CREATE FILE CASE
                 *
                 * Setting NLC_CREATE causes a negative hit to store
                 * the negative hit ncp and not return an error.  Then
                 * nc_error or nc_vp may be checked to see if the ncp 
                 * represents a negative hit.  NLC_CREATE also requires
                 * write permission on the governing directory or EPERM
                 * is returned.
                 */
                nd->nl_flags |= NLC_CREATE;
                nd->nl_flags |= NLC_REFDVP;
                bwillinode(1);
                error = nlookup(nd);
        } else {
                /*
                 * NORMAL OPEN FILE CASE
                 */
                error = nlookup(nd);
        }

        if (error)
                return (error);

        /*
         * split case to allow us to re-resolve and retry the ncp in case
         * we get ESTALE.
         */
again:
        if (fmode & O_CREAT) {
                if (nd->nl_nch.ncp->nc_vp == NULL) {
                        if ((error = ncp_writechk(&nd->nl_nch)) != 0)
                                return (error);
                        VATTR_NULL(vap);
                        vap->va_type = VREG;
                        vap->va_mode = cmode;
                        if (fmode & O_EXCL)
                                vap->va_vaflags |= VA_EXCLUSIVE;
                        error = VOP_NCREATE(&nd->nl_nch, nd->nl_dvp, &vp,
                                            nd->nl_cred, vap);
                        if (error)
                                return (error);
                        fmode &= ~O_TRUNC;
                        /* locked vnode is returned */
                } else {
                        if (fmode & O_EXCL) {
                                error = EEXIST;
                        } else {
                                error = cache_vget(&nd->nl_nch, cred, 
                                                    LK_EXCLUSIVE, &vp);
                        }
                        if (error)
                                return (error);
                        fmode &= ~O_CREAT;
                }
        } else {
                error = cache_vget(&nd->nl_nch, cred, LK_EXCLUSIVE, &vp);
                if (error)
                        return (error);
        }

        /*
         * We have a locked vnode and ncp now.  Note that the ncp will
         * be cleaned up by the caller if nd->nl_nch is left intact.
         */
        if (vp->v_type == VLNK) {
                error = EMLINK;
                goto bad;
        }
        if (vp->v_type == VSOCK) {
                error = EOPNOTSUPP;
                goto bad;
        }
        if ((fmode & O_CREAT) == 0) {
                if (fmode & (FWRITE | O_TRUNC)) {
                        if (vp->v_type == VDIR) {
                                error = EISDIR;
                                goto bad;
                        }
                        error = vn_writechk(vp, &nd->nl_nch);
                        if (error) {
                                /*
                                 * Special stale handling, re-resolve the
                                 * vnode.
                                 */
                                if (error == ESTALE) {
                                        vput(vp);
                                        vp = NULL;
                                        cache_setunresolved(&nd->nl_nch);
                                        error = cache_resolve(&nd->nl_nch, cred);
                                        if (error == 0)
                                                goto again;
                                }
                                goto bad;
                        }
                }
        }
        if (fmode & O_TRUNC) {
                vn_unlock(vp);                          /* XXX */
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);   /* XXX */
                VATTR_NULL(vap);
                vap->va_size = 0;
                error = VOP_SETATTR(vp, vap, cred);
                if (error)
                        goto bad;
        }

        /*
         * Setup the fp so VOP_OPEN can override it.  No descriptor has been
         * associated with the fp yet so we own it clean.  
         *
         * f_nchandle inherits nl_nch.  This used to be necessary only for
         * directories but now we do it unconditionally so f*() ops
         * such as fchmod() can access the actual namespace that was
         * used to open the file.
         */
        if (fp) {
                if (nd->nl_flags & NLC_APPENDONLY)
                        fmode |= FAPPENDONLY;
                fp->f_nchandle = nd->nl_nch;
                cache_zero(&nd->nl_nch);
                cache_unlock(&fp->f_nchandle);
        }

        /*
         * Get rid of nl_nch.  vn_open does not return it (it returns the
         * vnode or the file pointer).  Note: we can't leave nl_nch locked
         * through the VOP_OPEN anyway since the VOP_OPEN may block, e.g.
         * on /dev/ttyd0
         */
        if (nd->nl_nch.ncp)
                cache_put(&nd->nl_nch);

        error = VOP_OPEN(vp, fmode, cred, fp);
        if (error) {
                /*
                 * setting f_ops to &badfileops will prevent the descriptor
                 * code from trying to close and release the vnode, since
                 * the open failed we do not want to call close.
                 */
                if (fp) {
                        fp->f_data = NULL;
                        fp->f_ops = &badfileops;
                }
                goto bad;
        }

#if 0
        /*
         * Assert that VREG files have been setup for vmio.
         */
        KASSERT(vp->v_type != VREG || vp->v_object != NULL,
                ("vn_open: regular file was not VMIO enabled!"));
#endif

        /*
         * Return the vnode.  XXX needs some cleaning up.  The vnode is
         * only returned in the fp == NULL case.
         */
        if (fp == NULL) {
                nd->nl_open_vp = vp;
                nd->nl_vp_fmode = fmode;
                if ((nd->nl_flags & NLC_LOCKVP) == 0)
                        vn_unlock(vp);
        } else {
                vput(vp);
        }
        return (0);
bad:
        if (vp)
                vput(vp);
        return (error);
}

int
vn_opendisk(const char *devname, int fmode, struct vnode **vpp)
{
        struct vnode *vp;
        int error;

        if (strncmp(devname, "/dev/", 5) == 0)
                devname += 5;
        if ((vp = getsynthvnode(devname)) == NULL) {
                error = ENODEV;
        } else {
                error = VOP_OPEN(vp, fmode, proc0.p_ucred, NULL);
                vn_unlock(vp);
                if (error) {
                        vrele(vp);
                        vp = NULL;
                }
        }
        *vpp = vp;
        return (error);
}

/*
 * Check for write permissions on the specified vnode.  nch may be NULL.
 */
int
vn_writechk(struct vnode *vp, struct nchandle *nch)
{
        /*
         * If there's shared text associated with
         * the vnode, try to free it up once.  If
         * we fail, we can't allow writing.
         */
        if (vp->v_flag & VTEXT)
                return (ETXTBSY);

        /*
         * If the vnode represents a regular file, check the mount
         * point via the nch.  This may be a different mount point
         * then the one embedded in the vnode (e.g. nullfs).
         *
         * We can still write to non-regular files (e.g. devices)
         * via read-only mounts.
         */
        if (nch && nch->ncp && vp->v_type == VREG)
                return (ncp_writechk(nch));
        return (0);
}

/*
 * Check whether the underlying mount is read-only.  The mount point 
 * referenced by the namecache may be different from the mount point
 * used by the underlying vnode in the case of NULLFS, so a separate
 * check is needed.
 */
int
ncp_writechk(struct nchandle *nch)
{
        if (nch->mount && (nch->mount->mnt_flag & MNT_RDONLY))
                return (EROFS);
        return(0);
}

/*
 * Vnode close call
 *
 * MPSAFE
 */
int
vn_close(struct vnode *vp, int flags)
{
        int error;

        error = vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        if (error == 0) {
                error = VOP_CLOSE(vp, flags);
                vn_unlock(vp);
        }
        vrele(vp);
        return (error);
}

/*
 * Sequential heuristic.
 *
 * MPSAFE (f_seqcount and f_nextoff are allowed to race)
 */
static __inline
int
sequential_heuristic(struct uio *uio, struct file *fp)
{
        /*
         * Sequential heuristic - detect sequential operation
         *
         * NOTE: SMP: We allow f_seqcount updates to race.
         */
        if ((uio->uio_offset == 0 && fp->f_seqcount > 0) ||
            uio->uio_offset == fp->f_nextoff) {
                int tmpseq = fp->f_seqcount;

                tmpseq += (uio->uio_resid + BKVASIZE - 1) / BKVASIZE;
                if (tmpseq > IO_SEQMAX)
                        tmpseq = IO_SEQMAX;
                fp->f_seqcount = tmpseq;
                return(fp->f_seqcount << IO_SEQSHIFT);
        }

        /*
         * Not sequential, quick draw-down of seqcount
         *
         * NOTE: SMP: We allow f_seqcount updates to race.
         */
        if (fp->f_seqcount > 1)
                fp->f_seqcount = 1;
        else
                fp->f_seqcount = 0;
        return(0);
}

/*
 * get - lock and return the f_offset field.
 * set - set and unlock the f_offset field.
 *
 * These routines serve the dual purpose of serializing access to the
 * f_offset field (at least on i386) and guaranteeing operational integrity
 * when multiple read()ers and write()ers are present on the same fp.
 *
 * MPSAFE
 */
static __inline off_t
vn_get_fpf_offset(struct file *fp)
{
        u_int   flags;
        u_int   nflags;

        /*
         * Shortcut critical path.
         */
        flags = fp->f_flag & ~FOFFSETLOCK;
        if (atomic_cmpset_int(&fp->f_flag, flags, flags | FOFFSETLOCK))
                return(fp->f_offset);

        /*
         * The hard way
         */
        for (;;) {
                flags = fp->f_flag;
                if (flags & FOFFSETLOCK) {
                        nflags = flags | FOFFSETWAKE;
                        tsleep_interlock(&fp->f_flag, 0);
                        if (atomic_cmpset_int(&fp->f_flag, flags, nflags))
                                tsleep(&fp->f_flag, PINTERLOCKED, "fpoff", 0);
                } else {
                        nflags = flags | FOFFSETLOCK;
                        if (atomic_cmpset_int(&fp->f_flag, flags, nflags))
                                break;
                }
        }
        return(fp->f_offset);
}

/*
 * MPSAFE
 */
static __inline void
vn_set_fpf_offset(struct file *fp, off_t offset)
{
        u_int   flags;
        u_int   nflags;

        /*
         * We hold the lock so we can set the offset without interference.
         */
        fp->f_offset = offset;

        /*
         * Normal release is already a reasonably critical path.
         */
        for (;;) {
                flags = fp->f_flag;
                nflags = flags & ~(FOFFSETLOCK | FOFFSETWAKE);
                if (atomic_cmpset_int(&fp->f_flag, flags, nflags)) {
                        if (flags & FOFFSETWAKE)
                                wakeup(&fp->f_flag);
                        break;
                }
        }
}

/*
 * MPSAFE
 */
static __inline off_t
vn_poll_fpf_offset(struct file *fp)
{
#if defined(__x86_64__) || !defined(SMP)
        return(fp->f_offset);
#else
        off_t off = vn_get_fpf_offset(fp);
        vn_set_fpf_offset(fp, off);
        return(off);
#endif
}

/*
 * Package up an I/O request on a vnode into a uio and do it.
 *
 * MPSAFE
 */
int
vn_rdwr(enum uio_rw rw, struct vnode *vp, caddr_t base, int len,
        off_t offset, enum uio_seg segflg, int ioflg, 
        struct ucred *cred, int *aresid)
{
        struct uio auio;
        struct iovec aiov;
        struct ccms_lock ccms_lock;
        int error;

        if ((ioflg & IO_NODELOCKED) == 0)
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        aiov.iov_base = base;
        aiov.iov_len = len;
        auio.uio_resid = len;
        auio.uio_offset = offset;
        auio.uio_segflg = segflg;
        auio.uio_rw = rw;
        auio.uio_td = curthread;
        ccms_lock_get_uio(&vp->v_ccms, &ccms_lock, &auio);
        if (rw == UIO_READ) {
                error = VOP_READ(vp, &auio, ioflg, cred);
        } else {
                error = VOP_WRITE(vp, &auio, ioflg, cred);
        }
        ccms_lock_put(&vp->v_ccms, &ccms_lock);
        if (aresid)
                *aresid = auio.uio_resid;
        else
                if (auio.uio_resid && error == 0)
                        error = EIO;
        if ((ioflg & IO_NODELOCKED) == 0)
                vn_unlock(vp);
        return (error);
}

/*
 * Package up an I/O request on a vnode into a uio and do it.  The I/O
 * request is split up into smaller chunks and we try to avoid saturating
 * the buffer cache while potentially holding a vnode locked, so we 
 * check bwillwrite() before calling vn_rdwr().  We also call uio_yield()
 * to give other processes a chance to lock the vnode (either other processes
 * core'ing the same binary, or unrelated processes scanning the directory).
 *
 * MPSAFE
 */
int
vn_rdwr_inchunks(enum uio_rw rw, struct vnode *vp, caddr_t base, int len,
                 off_t offset, enum uio_seg segflg, int ioflg,
                 struct ucred *cred, int *aresid)
{
        int error = 0;

        do {
                int chunk;

                /*
                 * Force `offset' to a multiple of MAXBSIZE except possibly
                 * for the first chunk, so that filesystems only need to
                 * write full blocks except possibly for the first and last
                 * chunks.
                 */
                chunk = MAXBSIZE - (uoff_t)offset % MAXBSIZE;

                if (chunk > len)
                        chunk = len;
                if (vp->v_type == VREG) {
                        switch(rw) {
                        case UIO_READ:
                                bwillread(chunk);
                                break;
                        case UIO_WRITE:
                                bwillwrite(chunk);
                                break;
                        }
                }
                error = vn_rdwr(rw, vp, base, chunk, offset, segflg,
                                ioflg, cred, aresid);
                len -= chunk;   /* aresid calc already includes length */
                if (error)
                        break;
                offset += chunk;
                base += chunk;
                uio_yield();
        } while (len);
        if (aresid)
                *aresid += len;
        return (error);
}

/*
 * File pointers can no longer get ripped up by revoke so
 * we don't need to lock access to the vp.
 *
 * f_offset updates are not guaranteed against multiple readers
 *
 * MPSAFE
 */
static int
vn_read(struct file *fp, struct uio *uio, struct ucred *cred, int flags)
{
        struct ccms_lock ccms_lock;
        struct vnode *vp;
        int error, ioflag;

        KASSERT(uio->uio_td == curthread,
                ("uio_td %p is not td %p", uio->uio_td, curthread));
        vp = (struct vnode *)fp->f_data;

        ioflag = 0;
        if (flags & O_FBLOCKING) {
                /* ioflag &= ~IO_NDELAY; */
        } else if (flags & O_FNONBLOCKING) {
                ioflag |= IO_NDELAY;
        } else if (fp->f_flag & FNONBLOCK) {
                ioflag |= IO_NDELAY;
        }
        if (flags & O_FBUFFERED) {
                /* ioflag &= ~IO_DIRECT; */
        } else if (flags & O_FUNBUFFERED) {
                ioflag |= IO_DIRECT;
        } else if (fp->f_flag & O_DIRECT) {
                ioflag |= IO_DIRECT;
        }
        if ((flags & O_FOFFSET) == 0 && (vp->v_flag & VNOTSEEKABLE) == 0)
                uio->uio_offset = vn_get_fpf_offset(fp);
        vn_lock(vp, LK_SHARED | LK_RETRY);
        ioflag |= sequential_heuristic(uio, fp);

        ccms_lock_get_uio(&vp->v_ccms, &ccms_lock, uio);
        error = VOP_READ(vp, uio, ioflag, cred);
        ccms_lock_put(&vp->v_ccms, &ccms_lock);
        fp->f_nextoff = uio->uio_offset;
        vn_unlock(vp);
        if ((flags & O_FOFFSET) == 0 && (vp->v_flag & VNOTSEEKABLE) == 0)
                vn_set_fpf_offset(fp, uio->uio_offset);
        return (error);
}

/*
 * MPSAFE
 */
static int
vn_write(struct file *fp, struct uio *uio, struct ucred *cred, int flags)
{
        struct ccms_lock ccms_lock;
        struct vnode *vp;
        int error, ioflag;

        KASSERT(uio->uio_td == curthread,
                ("uio_td %p is not p %p", uio->uio_td, curthread));
        vp = (struct vnode *)fp->f_data;

        ioflag = IO_UNIT;
        if (vp->v_type == VREG &&
           ((fp->f_flag & O_APPEND) || (flags & O_FAPPEND))) {
                ioflag |= IO_APPEND;
        }

        if (flags & O_FBLOCKING) {
                /* ioflag &= ~IO_NDELAY; */
        } else if (flags & O_FNONBLOCKING) {
                ioflag |= IO_NDELAY;
        } else if (fp->f_flag & FNONBLOCK) {
                ioflag |= IO_NDELAY;
        }
        if (flags & O_FBUFFERED) {
                /* ioflag &= ~IO_DIRECT; */
        } else if (flags & O_FUNBUFFERED) {
                ioflag |= IO_DIRECT;
        } else if (fp->f_flag & O_DIRECT) {
                ioflag |= IO_DIRECT;
        }
        if (flags & O_FASYNCWRITE) {
                /* ioflag &= ~IO_SYNC; */
        } else if (flags & O_FSYNCWRITE) {
                ioflag |= IO_SYNC;
        } else if (fp->f_flag & O_FSYNC) {
                ioflag |= IO_SYNC;
        }

        if (vp->v_mount && (vp->v_mount->mnt_flag & MNT_SYNCHRONOUS))
                ioflag |= IO_SYNC;
        if ((flags & O_FOFFSET) == 0)
                uio->uio_offset = vn_get_fpf_offset(fp);
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        ioflag |= sequential_heuristic(uio, fp);
        ccms_lock_get_uio(&vp->v_ccms, &ccms_lock, uio);
        error = VOP_WRITE(vp, uio, ioflag, cred);
        ccms_lock_put(&vp->v_ccms, &ccms_lock);
        fp->f_nextoff = uio->uio_offset;
        vn_unlock(vp);
        if ((flags & O_FOFFSET) == 0)
                vn_set_fpf_offset(fp, uio->uio_offset);
        return (error);
}

/*
 * MPSAFE
 */
static int
vn_statfile(struct file *fp, struct stat *sb, struct ucred *cred)
{
        struct vnode *vp;
        int error;

        vp = (struct vnode *)fp->f_data;
        error = vn_stat(vp, sb, cred);
        return (error);
}

/*
 * MPSAFE
 */
int
vn_stat(struct vnode *vp, struct stat *sb, struct ucred *cred)
{
        struct vattr vattr;
        struct vattr *vap;
        int error;
        u_short mode;
        cdev_t dev;

        vap = &vattr;
        error = VOP_GETATTR(vp, vap);
        if (error)
                return (error);

        /*
         * Zero the spare stat fields
         */
        sb->st_lspare = 0;
        sb->st_qspare1 = 0;
        sb->st_qspare2 = 0;

        /*
         * Copy from vattr table
         */
        if (vap->va_fsid != VNOVAL)
                sb->st_dev = vap->va_fsid;
        else
                sb->st_dev = vp->v_mount->mnt_stat.f_fsid.val[0];
        sb->st_ino = vap->va_fileid;
        mode = vap->va_mode;
        switch (vap->va_type) {
        case VREG:
                mode |= S_IFREG;
                break;
        case VDATABASE:
                mode |= S_IFDB;
                break;
        case VDIR:
                mode |= S_IFDIR;
                break;
        case VBLK:
                mode |= S_IFBLK;
                break;
        case VCHR:
                mode |= S_IFCHR;
                break;
        case VLNK:
                mode |= S_IFLNK;
                /* This is a cosmetic change, symlinks do not have a mode. */
                if (vp->v_mount->mnt_flag & MNT_NOSYMFOLLOW)
                        sb->st_mode &= ~ACCESSPERMS;    /* 0000 */
                else
                        sb->st_mode |= ACCESSPERMS;     /* 0777 */
                break;
        case VSOCK:
                mode |= S_IFSOCK;
                break;
        case VFIFO:
                mode |= S_IFIFO;
                break;
        default:
                return (EBADF);
        }
        sb->st_mode = mode;
        if (vap->va_nlink > (nlink_t)-1)
                sb->st_nlink = (nlink_t)-1;
        else
                sb->st_nlink = vap->va_nlink;
        sb->st_uid = vap->va_uid;
        sb->st_gid = vap->va_gid;
        sb->st_rdev = dev2udev(vp->v_rdev);
        sb->st_size = vap->va_size;
        sb->st_atimespec = vap->va_atime;
        sb->st_mtimespec = vap->va_mtime;
        sb->st_ctimespec = vap->va_ctime;

        /*
         * A VCHR and VBLK device may track the last access and last modified
         * time independantly of the filesystem.  This is particularly true
         * because device read and write calls may bypass the filesystem.
         */
        if (vp->v_type == VCHR || vp->v_type == VBLK) {
                dev = vp->v_rdev;
                if (dev != NULL) {
                        if (dev->si_lastread) {
                                sb->st_atimespec.tv_sec = dev->si_lastread;
                                sb->st_atimespec.tv_nsec = 0;
                        }
                        if (dev->si_lastwrite) {
                                sb->st_atimespec.tv_sec = dev->si_lastwrite;
                                sb->st_atimespec.tv_nsec = 0;
                        }
                }
        }

        /*
         * According to www.opengroup.org, the meaning of st_blksize is 
         *   "a filesystem-specific preferred I/O block size for this 
         *    object.  In some filesystem types, this may vary from file
         *    to file"
         * Default to PAGE_SIZE after much discussion.
         */

        if (vap->va_type == VREG) {
                sb->st_blksize = vap->va_blocksize;
        } else if (vn_isdisk(vp, NULL)) {
                /*
                 * XXX this is broken.  If the device is not yet open (aka
                 * stat() call, aka v_rdev == NULL), how are we supposed
                 * to get a valid block size out of it?
                 */
                dev = vp->v_rdev;

                sb->st_blksize = dev->si_bsize_best;
                if (sb->st_blksize < dev->si_bsize_phys)
                        sb->st_blksize = dev->si_bsize_phys;
                if (sb->st_blksize < BLKDEV_IOSIZE)
                        sb->st_blksize = BLKDEV_IOSIZE;
        } else {
                sb->st_blksize = PAGE_SIZE;
        }
        
        sb->st_flags = vap->va_flags;

        error = priv_check_cred(cred, PRIV_VFS_GENERATION, 0);
        if (error)
                sb->st_gen = 0;
        else
                sb->st_gen = (u_int32_t)vap->va_gen;

        sb->st_blocks = vap->va_bytes / S_BLKSIZE;
        return (0);
}

/*
 * MPALMOSTSAFE - acquires mplock
 */
static int
vn_ioctl(struct file *fp, u_long com, caddr_t data, struct ucred *ucred,
         struct sysmsg *msg)
{
        struct vnode *vp = ((struct vnode *)fp->f_data);
        struct vnode *ovp;
        struct vattr vattr;
        int error;
        off_t size;

        switch (vp->v_type) {
        case VREG:
        case VDIR:
                if (com == FIONREAD) {
                        error = VOP_GETATTR(vp, &vattr);
                        if (error)
                                break;
                        size = vattr.va_size;
                        if ((vp->v_flag & VNOTSEEKABLE) == 0)
                                size -= vn_poll_fpf_offset(fp);
                        if (size > 0x7FFFFFFF)
                                size = 0x7FFFFFFF;
                        *(int *)data = size;
                        error = 0;
                        break;
                }
                if (com == FIOASYNC) {                          /* XXX */
                        error = 0;                              /* XXX */
                        break;
                }
                /* fall into ... */
        default:
#if 0
                return (ENOTTY);
#endif
        case VFIFO:
        case VCHR:
        case VBLK:
                if (com == FIODTYPE) {
                        if (vp->v_type != VCHR && vp->v_type != VBLK) {
                                error = ENOTTY;
                                break;
                        }
                        *(int *)data = dev_dflags(vp->v_rdev) & D_TYPEMASK;
                        error = 0;
                        break;
                }
                error = VOP_IOCTL(vp, com, data, fp->f_flag, ucred, msg);
                if (error == 0 && com == TIOCSCTTY) {
                        struct proc *p = curthread->td_proc;
                        struct session *sess;

                        if (p == NULL) {
                                error = ENOTTY;
                                break;
                        }

                        get_mplock();
                        sess = p->p_session;
                        /* Do nothing if reassigning same control tty */
                        if (sess->s_ttyvp == vp) {
                                error = 0;
                                rel_mplock();
                                break;
                        }

                        /* Get rid of reference to old control tty */
                        ovp = sess->s_ttyvp;
                        vref(vp);
                        sess->s_ttyvp = vp;
                        if (ovp)
                                vrele(ovp);
                        rel_mplock();
                }
                break;
        }
        return (error);
}

/*
 * MPSAFE
 */
static int
vn_poll(struct file *fp, int events, struct ucred *cred)
{
        int error;

        error = VOP_POLL(((struct vnode *)fp->f_data), events, cred);
        return (error);
}

/*
 * Check that the vnode is still valid, and if so
 * acquire requested lock.
 */
int
#ifndef DEBUG_LOCKS
vn_lock(struct vnode *vp, int flags)
#else
debug_vn_lock(struct vnode *vp, int flags, const char *filename, int line)
#endif
{
        int error;
        
        do {
#ifdef  DEBUG_LOCKS
                vp->filename = filename;
                vp->line = line;
                error = debuglockmgr(&vp->v_lock, flags,
                                     "vn_lock", filename, line);
#else
                error = lockmgr(&vp->v_lock, flags);
#endif
                if (error == 0)
                        break;
        } while (flags & LK_RETRY);

        /*
         * Because we (had better!) have a ref on the vnode, once it
         * goes to VRECLAIMED state it will not be recycled until all
         * refs go away.  So we can just check the flag.
         */
        if (error == 0 && (vp->v_flag & VRECLAIMED)) {
                lockmgr(&vp->v_lock, LK_RELEASE);
                error = ENOENT;
        }
        return (error);
}

/*
 * MPSAFE
 */
void
vn_unlock(struct vnode *vp)
{
        lockmgr(&vp->v_lock, LK_RELEASE);
}

/*
 * MPSAFE
 */
int
vn_islocked(struct vnode *vp)
{
        return (lockstatus(&vp->v_lock, curthread));
}

/*
 * Return the lock status of a vnode and unlock the vnode
 * if we owned the lock.  This is not a boolean, if the
 * caller cares what the lock status is the caller must
 * check the various possible values.
 *
 * This only unlocks exclusive locks held by the caller,
 * it will NOT unlock shared locks (there is no way to
 * tell who the shared lock belongs to).
 *
 * MPSAFE
 */
int
vn_islocked_unlock(struct vnode *vp)
{
        int vpls;

        vpls = lockstatus(&vp->v_lock, curthread);
        if (vpls == LK_EXCLUSIVE)
                lockmgr(&vp->v_lock, LK_RELEASE);
        return(vpls);
}

/*
 * Restore a vnode lock that we previously released via
 * vn_islocked_unlock().  This is a NOP if we did not
 * own the original lock.
 *
 * MPSAFE
 */
void
vn_islocked_relock(struct vnode *vp, int vpls)
{
        int error;

        if (vpls == LK_EXCLUSIVE)
                error = lockmgr(&vp->v_lock, vpls);
}

/*
 * MPSAFE
 */
static int
vn_closefile(struct file *fp)
{
        int error;

        fp->f_ops = &badfileops;
        error = vn_close(((struct vnode *)fp->f_data), fp->f_flag);
        return (error);
}

/*
 * MPSAFE
 */
static int
vn_kqfilter(struct file *fp, struct knote *kn)
{
        int error;

        error = VOP_KQFILTER(((struct vnode *)fp->f_data), kn);
        return (error);
}