text: /*-
   * Copyright (c) 1989, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * This code is derived from software contributed
   * to Berkeley by John Heidemann of the UCLA Ficus project.
   *
   * Source: * @(#)i405_init.c 2.10 92/04/27 UCLA Ficus project
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 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.
   */
  
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD: release/9.1.0/sys/kern/vfs_default.c 237351 2012-06-21 03:58:10Z mckusick $");
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/bio.h>
  #include <sys/buf.h>
  #include <sys/conf.h>
  #include <sys/event.h>
  #include <sys/kernel.h>
  #include <sys/limits.h>
  #include <sys/lock.h>
  #include <sys/lockf.h>
  #include <sys/malloc.h>
  #include <sys/mount.h>
  #include <sys/mutex.h>
  #include <sys/namei.h>
  #include <sys/fcntl.h>
  #include <sys/unistd.h>
  #include <sys/vnode.h>
  #include <sys/dirent.h>
  #include <sys/poll.h>
  
  #include <security/mac/mac_framework.h>
  
  #include <vm/vm.h>
  #include <vm/vm_object.h>
  #include <vm/vm_extern.h>
  #include <vm/pmap.h>
  #include <vm/vm_map.h>
  #include <vm/vm_page.h>
  #include <vm/vm_pager.h>
  #include <vm/vnode_pager.h>
  
  static int	vop_nolookup(struct vop_lookup_args *);
  static int	vop_norename(struct vop_rename_args *);
  static int	vop_nostrategy(struct vop_strategy_args *);
  static int	get_next_dirent(struct vnode *vp, struct dirent **dpp,
  				char *dirbuf, int dirbuflen, off_t *off,
  				char **cpos, int *len, int *eofflag,
  				struct thread *td);
  static int	dirent_exists(struct vnode *vp, const char *dirname,
  			      struct thread *td);
  
  #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
  
  /*
   * This vnode table stores what we want to do if the filesystem doesn't
   * implement a particular VOP.
   *
   * If there is no specific entry here, we will return EOPNOTSUPP.
   *
   * Note that every filesystem has to implement either vop_access
   * or vop_accessx; failing to do so will result in immediate crash
   * due to stack overflow, as vop_stdaccess() calls vop_stdaccessx(),
   * which calls vop_stdaccess() etc.
   */
  
  struct vop_vector default_vnodeops = {
  	.vop_default =		NULL,
  	.vop_bypass =		VOP_EOPNOTSUPP,
  
  	.vop_access =		vop_stdaccess,
  	.vop_accessx =		vop_stdaccessx,
  	.vop_advise =		vop_stdadvise,
  	.vop_advlock =		vop_stdadvlock,
  	.vop_advlockasync =	vop_stdadvlockasync,
  	.vop_advlockpurge =	vop_stdadvlockpurge,
  	.vop_allocate =		vop_stdallocate,
  	.vop_bmap =		vop_stdbmap,
  	.vop_close =		VOP_NULL,
  	.vop_fsync =		VOP_NULL,
  	.vop_getpages =		vop_stdgetpages,
  	.vop_getwritemount = 	vop_stdgetwritemount,
  	.vop_inactive =		VOP_NULL,
  	.vop_ioctl =		VOP_ENOTTY,
  	.vop_kqfilter =		vop_stdkqfilter,
  	.vop_islocked =		vop_stdislocked,
  	.vop_lock1 =		vop_stdlock,
  	.vop_lookup =		vop_nolookup,
  	.vop_open =		VOP_NULL,
  	.vop_pathconf =		VOP_EINVAL,
  	.vop_poll =		vop_nopoll,
  	.vop_putpages =		vop_stdputpages,
  	.vop_readlink =		VOP_EINVAL,
  	.vop_rename =		vop_norename,
  	.vop_revoke =		VOP_PANIC,
  	.vop_strategy =		vop_nostrategy,
  	.vop_unlock =		vop_stdunlock,
  	.vop_vptocnp =		vop_stdvptocnp,
  	.vop_vptofh =		vop_stdvptofh,
  	.vop_unp_bind =		vop_stdunp_bind,
  	.vop_unp_connect =	vop_stdunp_connect,
  	.vop_unp_detach =	vop_stdunp_detach,
  };
  
  /*
   * Series of placeholder functions for various error returns for
   * VOPs.
   */
  
  int
  vop_eopnotsupp(struct vop_generic_args *ap)
  {
  	/*
  	printf("vop_notsupp[%s]\n", ap->a_desc->vdesc_name);
  	*/
  
  	return (EOPNOTSUPP);
  }
  
  int
  vop_ebadf(struct vop_generic_args *ap)
  {
  
  	return (EBADF);
  }
  
  int
  vop_enotty(struct vop_generic_args *ap)
  {
  
  	return (ENOTTY);
  }
  
  int
  vop_einval(struct vop_generic_args *ap)
  {
  
  	return (EINVAL);
  }
  
  int
  vop_enoent(struct vop_generic_args *ap)
  {
  
  	return (ENOENT);
  }
  
  int
  vop_null(struct vop_generic_args *ap)
  {
  
  	return (0);
  }
  
  /*
   * Helper function to panic on some bad VOPs in some filesystems.
   */
  int
  vop_panic(struct vop_generic_args *ap)
  {
  
  	panic("filesystem goof: vop_panic[%s]", ap->a_desc->vdesc_name);
  }
  
  /*
   * vop_std<something> and vop_no<something> are default functions for use by
   * filesystems that need the "default reasonable" implementation for a
   * particular operation.
   *
   * The documentation for the operations they implement exists (if it exists)
   * in the VOP_<SOMETHING>(9) manpage (all uppercase).
   */
  
  /*
   * Default vop for filesystems that do not support name lookup
   */
  static int
  vop_nolookup(ap)
  	struct vop_lookup_args /* {
  		struct vnode *a_dvp;
  		struct vnode **a_vpp;
  		struct componentname *a_cnp;
  	} */ *ap;
  {
  
  	*ap->a_vpp = NULL;
  	return (ENOTDIR);
  }
  
  /*
   * vop_norename:
   *
   * Handle unlock and reference counting for arguments of vop_rename
   * for filesystems that do not implement rename operation.
   */
  static int
  vop_norename(struct vop_rename_args *ap)
  {
  
  	vop_rename_fail(ap);
  	return (EOPNOTSUPP);
  }
  
  /*
   *	vop_nostrategy:
   *
   *	Strategy routine for VFS devices that have none.
   *
   *	BIO_ERROR and B_INVAL must be cleared prior to calling any strategy
   *	routine.  Typically this is done for a BIO_READ strategy call.
   *	Typically B_INVAL is assumed to already be clear prior to a write
   *	and should not be cleared manually unless you just made the buffer
   *	invalid.  BIO_ERROR should be cleared either way.
   */
  
  static int
  vop_nostrategy (struct vop_strategy_args *ap)
  {
  	printf("No strategy for buffer at %p\n", ap->a_bp);
  	vprint("vnode", ap->a_vp);
  	ap->a_bp->b_ioflags |= BIO_ERROR;
  	ap->a_bp->b_error = EOPNOTSUPP;
  	bufdone(ap->a_bp);
  	return (EOPNOTSUPP);
  }
  
  static int
  get_next_dirent(struct vnode *vp, struct dirent **dpp, char *dirbuf,
  		int dirbuflen, off_t *off, char **cpos, int *len,
  		int *eofflag, struct thread *td)
  {
  	int error, reclen;
  	struct uio uio;
  	struct iovec iov;
  	struct dirent *dp;
  
  	KASSERT(VOP_ISLOCKED(vp), ("vp %p is not locked", vp));
  	KASSERT(vp->v_type == VDIR, ("vp %p is not a directory", vp));
  
  	if (*len == 0) {
  		iov.iov_base = dirbuf;
  		iov.iov_len = dirbuflen;
  
  		uio.uio_iov = &iov;
  		uio.uio_iovcnt = 1;
  		uio.uio_offset = *off;
  		uio.uio_resid = dirbuflen;
  		uio.uio_segflg = UIO_SYSSPACE;
  		uio.uio_rw = UIO_READ;
  		uio.uio_td = td;
  
  		*eofflag = 0;
  
  #ifdef MAC
  		error = mac_vnode_check_readdir(td->td_ucred, vp);
  		if (error == 0)
  #endif
  			error = VOP_READDIR(vp, &uio, td->td_ucred, eofflag,
  		    		NULL, NULL);
  		if (error)
  			return (error);
  
  		*off = uio.uio_offset;
  
  		*cpos = dirbuf;
  		*len = (dirbuflen - uio.uio_resid);
  
  		if (*len == 0)
  			return (ENOENT);
  	}
  
  	dp = (struct dirent *)(*cpos);
  	reclen = dp->d_reclen;
  	*dpp = dp;
  
  	/* check for malformed directory.. */
  	if (reclen < DIRENT_MINSIZE)
  		return (EINVAL);
  
  	*cpos += reclen;
  	*len -= reclen;
  
  	return (0);
  }
  
  /*
   * Check if a named file exists in a given directory vnode.
   */
  static int
  dirent_exists(struct vnode *vp, const char *dirname, struct thread *td)
  {
  	char *dirbuf, *cpos;
  	int error, eofflag, dirbuflen, len, found;
  	off_t off;
  	struct dirent *dp;
  	struct vattr va;
  
  	KASSERT(VOP_ISLOCKED(vp), ("vp %p is not locked", vp));
  	KASSERT(vp->v_type == VDIR, ("vp %p is not a directory", vp));
  
  	found = 0;
  
  	error = VOP_GETATTR(vp, &va, td->td_ucred);
  	if (error)
  		return (found);
  
  	dirbuflen = DEV_BSIZE;
  	if (dirbuflen < va.va_blocksize)
  		dirbuflen = va.va_blocksize;
  	dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
  
  	off = 0;
  	len = 0;
  	do {
  		error = get_next_dirent(vp, &dp, dirbuf, dirbuflen, &off,
  					&cpos, &len, &eofflag, td);
  		if (error)
  			goto out;
  
  		if ((dp->d_type != DT_WHT) &&
  		    !strcmp(dp->d_name, dirname)) {
  			found = 1;
  			goto out;
  		}
  	} while (len > 0 || !eofflag);
  
  out:
  	free(dirbuf, M_TEMP);
  	return (found);
  }
  
  int
  vop_stdaccess(struct vop_access_args *ap)
  {
  
  	KASSERT((ap->a_accmode & ~(VEXEC | VWRITE | VREAD | VADMIN |
  	    VAPPEND)) == 0, ("invalid bit in accmode"));
  
  	return (VOP_ACCESSX(ap->a_vp, ap->a_accmode, ap->a_cred, ap->a_td));
  }
  
  int
  vop_stdaccessx(struct vop_accessx_args *ap)
  {
  	int error;
  	accmode_t accmode = ap->a_accmode;
  
  	error = vfs_unixify_accmode(&accmode);
  	if (error != 0)
  		return (error);
  
  	if (accmode == 0)
  		return (0);
  
  	return (VOP_ACCESS(ap->a_vp, accmode, ap->a_cred, ap->a_td));
  }
  
  /*
   * Advisory record locking support
   */
  int
  vop_stdadvlock(struct vop_advlock_args *ap)
  {
  	struct vnode *vp;
  	struct ucred *cred;
  	struct vattr vattr;
  	int error;
  
  	vp = ap->a_vp;
  	cred = curthread->td_ucred;
  	vn_lock(vp, LK_SHARED | LK_RETRY);
  	error = VOP_GETATTR(vp, &vattr, cred);
  	VOP_UNLOCK(vp, 0);
  	if (error)
  		return (error);
  
  	return (lf_advlock(ap, &(vp->v_lockf), vattr.va_size));
  }
  
  int
  vop_stdadvlockasync(struct vop_advlockasync_args *ap)
  {
  	struct vnode *vp;
  	struct ucred *cred;
  	struct vattr vattr;
  	int error;
  
  	vp = ap->a_vp;
  	cred = curthread->td_ucred;
  	vn_lock(vp, LK_SHARED | LK_RETRY);
  	error = VOP_GETATTR(vp, &vattr, cred);
  	VOP_UNLOCK(vp, 0);
  	if (error)
  		return (error);
  
  	return (lf_advlockasync(ap, &(vp->v_lockf), vattr.va_size));
  }
  
  int
  vop_stdadvlockpurge(struct vop_advlockpurge_args *ap)
  {
  	struct vnode *vp;
  
  	vp = ap->a_vp;
  	lf_purgelocks(vp, &vp->v_lockf);
  	return (0);
  }
  
  /*
   * vop_stdpathconf:
   *
   * Standard implementation of POSIX pathconf, to get information about limits
   * for a filesystem.
   * Override per filesystem for the case where the filesystem has smaller
   * limits.
   */
  int
  vop_stdpathconf(ap)
  	struct vop_pathconf_args /* {
  	struct vnode *a_vp;
  	int a_name;
  	int *a_retval;
  	} */ *ap;
  {
  
  	switch (ap->a_name) {
  		case _PC_NAME_MAX:
  			*ap->a_retval = NAME_MAX;
  			return (0);
  		case _PC_PATH_MAX:
  			*ap->a_retval = PATH_MAX;
  			return (0);
  		case _PC_LINK_MAX:
  			*ap->a_retval = LINK_MAX;
  			return (0);
  		case _PC_MAX_CANON:
  			*ap->a_retval = MAX_CANON;
  			return (0);
  		case _PC_MAX_INPUT:
  			*ap->a_retval = MAX_INPUT;
  			return (0);
  		case _PC_PIPE_BUF:
  			*ap->a_retval = PIPE_BUF;
  			return (0);
  		case _PC_CHOWN_RESTRICTED:
  			*ap->a_retval = 1;
  			return (0);
  		case _PC_VDISABLE:
  			*ap->a_retval = _POSIX_VDISABLE;
  			return (0);
  		default:
  			return (EINVAL);
  	}
  	/* NOTREACHED */
  }
  
  /*
   * Standard lock, unlock and islocked functions.
   */
  int
  vop_stdlock(ap)
  	struct vop_lock1_args /* {
  		struct vnode *a_vp;
  		int a_flags;
  		char *file;
  		int line;
  	} */ *ap;
  {
  	struct vnode *vp = ap->a_vp;
  
  	return (_lockmgr_args(vp->v_vnlock, ap->a_flags, VI_MTX(vp),
  	    LK_WMESG_DEFAULT, LK_PRIO_DEFAULT, LK_TIMO_DEFAULT, ap->a_file,
  	    ap->a_line));
  }
  
  /* See above. */
  int
  vop_stdunlock(ap)
  	struct vop_unlock_args /* {
  		struct vnode *a_vp;
  		int a_flags;
  	} */ *ap;
  {
  	struct vnode *vp = ap->a_vp;
  
  	return (lockmgr(vp->v_vnlock, ap->a_flags | LK_RELEASE, VI_MTX(vp)));
  }
  
  /* See above. */
  int
  vop_stdislocked(ap)
  	struct vop_islocked_args /* {
  		struct vnode *a_vp;
  	} */ *ap;
  {
  
  	return (lockstatus(ap->a_vp->v_vnlock));
  }
  
  /*
   * Return true for select/poll.
   */
  int
  vop_nopoll(ap)
  	struct vop_poll_args /* {
  		struct vnode *a_vp;
  		int  a_events;
  		struct ucred *a_cred;
  		struct thread *a_td;
  	} */ *ap;
  {
  
  	return (poll_no_poll(ap->a_events));
  }
  
  /*
   * Implement poll for local filesystems that support it.
   */
  int
  vop_stdpoll(ap)
  	struct vop_poll_args /* {
  		struct vnode *a_vp;
  		int  a_events;
  		struct ucred *a_cred;
  		struct thread *a_td;
  	} */ *ap;
  {
  	if (ap->a_events & ~POLLSTANDARD)
  		return (vn_pollrecord(ap->a_vp, ap->a_td, ap->a_events));
  	return (ap->a_events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
  }
  
  /*
   * Return our mount point, as we will take charge of the writes.
   */
  int
  vop_stdgetwritemount(ap)
  	struct vop_getwritemount_args /* {
  		struct vnode *a_vp;
  		struct mount **a_mpp;
  	} */ *ap;
  {
  	struct mount *mp;
  
  	/*
  	 * XXX Since this is called unlocked we may be recycled while
  	 * attempting to ref the mount.  If this is the case or mountpoint
  	 * will be set to NULL.  We only have to prevent this call from
  	 * returning with a ref to an incorrect mountpoint.  It is not
  	 * harmful to return with a ref to our previous mountpoint.
  	 */
  	mp = ap->a_vp->v_mount;
  	if (mp != NULL) {
  		vfs_ref(mp);
  		if (mp != ap->a_vp->v_mount) {
  			vfs_rel(mp);
  			mp = NULL;
  		}
  	}
  	*(ap->a_mpp) = mp;
  	return (0);
  }
  
  /* XXX Needs good comment and VOP_BMAP(9) manpage */
  int
  vop_stdbmap(ap)
  	struct vop_bmap_args /* {
  		struct vnode *a_vp;
  		daddr_t  a_bn;
  		struct bufobj **a_bop;
  		daddr_t *a_bnp;
  		int *a_runp;
  		int *a_runb;
  	} */ *ap;
  {
  
  	if (ap->a_bop != NULL)
  		*ap->a_bop = &ap->a_vp->v_bufobj;
  	if (ap->a_bnp != NULL)
  		*ap->a_bnp = ap->a_bn * btodb(ap->a_vp->v_mount->mnt_stat.f_iosize);
  	if (ap->a_runp != NULL)
  		*ap->a_runp = 0;
  	if (ap->a_runb != NULL)
  		*ap->a_runb = 0;
  	return (0);
  }
  
  int
  vop_stdfsync(ap)
  	struct vop_fsync_args /* {
  		struct vnode *a_vp;
  		struct ucred *a_cred;
  		int a_waitfor;
  		struct thread *a_td;
  	} */ *ap;
  {
  	struct vnode *vp = ap->a_vp;
  	struct buf *bp;
  	struct bufobj *bo;
  	struct buf *nbp;
  	int error = 0;
  	int maxretry = 1000;     /* large, arbitrarily chosen */
  
  	bo = &vp->v_bufobj;
  	BO_LOCK(bo);
  loop1:
  	/*
  	 * MARK/SCAN initialization to avoid infinite loops.
  	 */
          TAILQ_FOREACH(bp, &bo->bo_dirty.bv_hd, b_bobufs) {
                  bp->b_vflags &= ~BV_SCANNED;
  		bp->b_error = 0;
  	}
  
  	/*
  	 * Flush all dirty buffers associated with a vnode.
  	 */
  loop2:
  	TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
  		if ((bp->b_vflags & BV_SCANNED) != 0)
  			continue;
  		bp->b_vflags |= BV_SCANNED;
  		if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL)) {
  			if (ap->a_waitfor != MNT_WAIT)
  				continue;
  			if (BUF_LOCK(bp,
  			    LK_EXCLUSIVE | LK_INTERLOCK | LK_SLEEPFAIL,
  			    BO_MTX(bo)) != 0) {
  				BO_LOCK(bo);
  				goto loop1;
  			}
  			BO_LOCK(bo);
  		}
  		BO_UNLOCK(bo);
  		KASSERT(bp->b_bufobj == bo,
  		    ("bp %p wrong b_bufobj %p should be %p",
  		    bp, bp->b_bufobj, bo));
  		if ((bp->b_flags & B_DELWRI) == 0)
  			panic("fsync: not dirty");
  		if ((vp->v_object != NULL) && (bp->b_flags & B_CLUSTEROK)) {
  			vfs_bio_awrite(bp);
  		} else {
  			bremfree(bp);
  			bawrite(bp);
  		}
  		BO_LOCK(bo);
  		goto loop2;
  	}
  
  	/*
  	 * If synchronous the caller expects us to completely resolve all
  	 * dirty buffers in the system.  Wait for in-progress I/O to
  	 * complete (which could include background bitmap writes), then
  	 * retry if dirty blocks still exist.
  	 */
  	if (ap->a_waitfor == MNT_WAIT) {
  		bufobj_wwait(bo, 0, 0);
  		if (bo->bo_dirty.bv_cnt > 0) {
  			/*
  			 * If we are unable to write any of these buffers
  			 * then we fail now rather than trying endlessly
  			 * to write them out.
  			 */
  			TAILQ_FOREACH(bp, &bo->bo_dirty.bv_hd, b_bobufs)
  				if ((error = bp->b_error) == 0)
  					continue;
  			if (error == 0 && --maxretry >= 0)
  				goto loop1;
  			error = EAGAIN;
  		}
  	}
  	BO_UNLOCK(bo);
  	if (error == EAGAIN)
  		vprint("fsync: giving up on dirty", vp);
  
  	return (error);
  }
  
  /* XXX Needs good comment and more info in the manpage (VOP_GETPAGES(9)). */
  int
  vop_stdgetpages(ap)
  	struct vop_getpages_args /* {
  		struct vnode *a_vp;
  		vm_page_t *a_m;
  		int a_count;
  		int a_reqpage;
  		vm_ooffset_t a_offset;
  	} */ *ap;
  {
  
  	return vnode_pager_generic_getpages(ap->a_vp, ap->a_m,
  	    ap->a_count, ap->a_reqpage);
  }
  
  int
  vop_stdkqfilter(struct vop_kqfilter_args *ap)
  {
  	return vfs_kqfilter(ap);
  }
  
  /* XXX Needs good comment and more info in the manpage (VOP_PUTPAGES(9)). */
  int
  vop_stdputpages(ap)
  	struct vop_putpages_args /* {
  		struct vnode *a_vp;
  		vm_page_t *a_m;
  		int a_count;
  		int a_sync;
  		int *a_rtvals;
  		vm_ooffset_t a_offset;
  	} */ *ap;
  {
  
  	return vnode_pager_generic_putpages(ap->a_vp, ap->a_m, ap->a_count,
  	     ap->a_sync, ap->a_rtvals);
  }
  
  int
  vop_stdvptofh(struct vop_vptofh_args *ap)
  {
  	return (EOPNOTSUPP);
  }
  
  int
  vop_stdvptocnp(struct vop_vptocnp_args *ap)
  {
  	struct vnode *vp = ap->a_vp;
  	struct vnode **dvp = ap->a_vpp;
  	struct ucred *cred = ap->a_cred;
  	char *buf = ap->a_buf;
  	int *buflen = ap->a_buflen;
  	char *dirbuf, *cpos;
  	int i, error, eofflag, dirbuflen, flags, locked, len, covered;
  	off_t off;
  	ino_t fileno;
  	struct vattr va;
  	struct nameidata nd;
  	struct thread *td;
  	struct dirent *dp;
  	struct vnode *mvp;
  
  	i = *buflen;
  	error = 0;
  	covered = 0;
  	td = curthread;
  
  	if (vp->v_type != VDIR)
  		return (ENOENT);
  
  	error = VOP_GETATTR(vp, &va, cred);
  	if (error)
  		return (error);
  
  	VREF(vp);
  	locked = VOP_ISLOCKED(vp);
  	VOP_UNLOCK(vp, 0);
  	NDINIT_ATVP(&nd, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE,
  	    "..", vp, td);
  	flags = FREAD;
  	error = vn_open_cred(&nd, &flags, 0, VN_OPEN_NOAUDIT, cred, NULL);
  	if (error) {
  		vn_lock(vp, locked | LK_RETRY);
  		return (error);
  	}
  	NDFREE(&nd, NDF_ONLY_PNBUF);
  
  	mvp = *dvp = nd.ni_vp;
  
  	if (vp->v_mount != (*dvp)->v_mount &&
  	    ((*dvp)->v_vflag & VV_ROOT) &&
  	    ((*dvp)->v_mount->mnt_flag & MNT_UNION)) {
  		*dvp = (*dvp)->v_mount->mnt_vnodecovered;
  		VREF(mvp);
  		VOP_UNLOCK(mvp, 0);
  		vn_close(mvp, FREAD, cred, td);
  		VREF(*dvp);
  		vn_lock(*dvp, LK_EXCLUSIVE | LK_RETRY);
  		covered = 1;
  	}
  
  	fileno = va.va_fileid;
  
  	dirbuflen = DEV_BSIZE;
  	if (dirbuflen < va.va_blocksize)
  		dirbuflen = va.va_blocksize;
  	dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
  
  	if ((*dvp)->v_type != VDIR) {
  		error = ENOENT;
  		goto out;
  	}
  
  	off = 0;
  	len = 0;
  	do {
  		/* call VOP_READDIR of parent */
  		error = get_next_dirent(*dvp, &dp, dirbuf, dirbuflen, &off,
  					&cpos, &len, &eofflag, td);
  		if (error)
  			goto out;
  
  		if ((dp->d_type != DT_WHT) &&
  		    (dp->d_fileno == fileno)) {
  			if (covered) {
  				VOP_UNLOCK(*dvp, 0);
  				vn_lock(mvp, LK_EXCLUSIVE | LK_RETRY);
  				if (dirent_exists(mvp, dp->d_name, td)) {
  					error = ENOENT;
  					VOP_UNLOCK(mvp, 0);
  					vn_lock(*dvp, LK_EXCLUSIVE | LK_RETRY);
  					goto out;
  				}
  				VOP_UNLOCK(mvp, 0);
  				vn_lock(*dvp, LK_EXCLUSIVE | LK_RETRY);
  			}
  			i -= dp->d_namlen;
  
  			if (i < 0) {
  				error = ENOMEM;
  				goto out;
  			}
  			bcopy(dp->d_name, buf + i, dp->d_namlen);
  			error = 0;
  			goto out;
  		}
  	} while (len > 0 || !eofflag);
  	error = ENOENT;
  
  out:
  	free(dirbuf, M_TEMP);
  	if (!error) {
  		*buflen = i;
  		vref(*dvp);
  	}
  	if (covered) {
  		vput(*dvp);
  		vrele(mvp);
  	} else {
  		VOP_UNLOCK(mvp, 0);
  		vn_close(mvp, FREAD, cred, td);
  	}
  	vn_lock(vp, locked | LK_RETRY);
  	return (error);
  }
  
  int
  vop_stdallocate(struct vop_allocate_args *ap)
  {
  #ifdef __notyet__
  	struct statfs sfs;
  #endif
  	struct iovec aiov;
  	struct vattr vattr, *vap;
  	struct uio auio;
  	off_t fsize, len, cur, offset;
  	uint8_t *buf;
  	struct thread *td;
  	struct vnode *vp;
  	size_t iosize;
  	int error;
  
  	buf = NULL;
  	error = 0;
  	td = curthread;
  	vap = &vattr;
  	vp = ap->a_vp;
  	len = *ap->a_len;
  	offset = *ap->a_offset;
  
  	error = VOP_GETATTR(vp, vap, td->td_ucred);
  	if (error != 0)
  		goto out;
  	fsize = vap->va_size;
  	iosize = vap->va_blocksize;
  	if (iosize == 0)
  		iosize = BLKDEV_IOSIZE;
  	if (iosize > MAXPHYS)
  		iosize = MAXPHYS;
  	buf = malloc(iosize, M_TEMP, M_WAITOK);
  
  #ifdef __notyet__
  	/*
  	 * Check if the filesystem sets f_maxfilesize; if not use
  	 * VOP_SETATTR to perform the check.
  	 */
  	error = VFS_STATFS(vp->v_mount, &sfs, td);
  	if (error != 0)
  		goto out;
  	if (sfs.f_maxfilesize) {
  		if (offset > sfs.f_maxfilesize || len > sfs.f_maxfilesize ||
  		    offset + len > sfs.f_maxfilesize) {
  			error = EFBIG;
  			goto out;
  		}
  	} else
  #endif
  	if (offset + len > vap->va_size) {
  		/*
  		 * Test offset + len against the filesystem's maxfilesize.
  		 */
  		VATTR_NULL(vap);
  		vap->va_size = offset + len;
  		error = VOP_SETATTR(vp, vap, td->td_ucred);
  		if (error != 0)
  			goto out;
  		VATTR_NULL(vap);
  		vap->va_size = fsize;
  		error = VOP_SETATTR(vp, vap, td->td_ucred);
  		if (error != 0)
  			goto out;
  	}
  
  	for (;;) {
  		/*
  		 * Read and write back anything below the nominal file
  		 * size.  There's currently no way outside the filesystem
  		 * to know whether this area is sparse or not.
  		 */
  		cur = iosize;
  		if ((offset % iosize) != 0)
  			cur -= (offset % iosize);
  		if (cur > len)
  			cur = len;
  		if (offset < fsize) {
  			aiov.iov_base = buf;
  			aiov.iov_len = cur;
  			auio.uio_iov = &aiov;
  			auio.uio_iovcnt = 1;
  			auio.uio_offset = offset;
  			auio.uio_resid = cur;
  			auio.uio_segflg = UIO_SYSSPACE;
  			auio.uio_rw = UIO_READ;
  			auio.uio_td = td;
  			error = VOP_READ(vp, &auio, 0, td->td_ucred);
  			if (error != 0)
  				break;
  			if (auio.uio_resid > 0) {
  				bzero(buf + cur - auio.uio_resid,
  				    auio.uio_resid);
  			}
  		} else {
  			bzero(buf, cur);
  		}
  
  		aiov.iov_base = buf;
  		aiov.iov_len = cur;
  		auio.uio_iov = &aiov;
  		auio.uio_iovcnt = 1;
  		auio.uio_offset = offset;
  		auio.uio_resid = cur;
  		auio.uio_segflg = UIO_SYSSPACE;
  		auio.uio_rw = UIO_WRITE;
  		auio.uio_td = td;
  
  		error = VOP_WRITE(vp, &auio, 0, td->td_ucred);
  		if (error != 0)
  			break;
  
  		len -= cur;
  		offset += cur;
  		if (len == 0)
  			break;
  		if (should_yield())
  			break;
  	}
  
   out:
  	*ap->a_len = len;
  	*ap->a_offset = offset;
  	free(buf, M_TEMP);
  	return (error);
  }
  
  int
  vop_stdadvise(struct vop_advise_args *ap)
  {
  	struct vnode *vp;
  	off_t start, end;
  	int error, vfslocked;
  
  	vp = ap->a_vp;
  	switch (ap->a_advice) {
  	case POSIX_FADV_WILLNEED:
  		/*
  		 * Do nothing for now.  Filesystems should provide a
  		 * custom method which starts an asynchronous read of
  		 * the requested region.
  		 */
  		error = 0;
  		break;
  	case POSIX_FADV_DONTNEED:
  		/*
  		 * Flush any open FS buffers and then remove pages
  		 * from the backing VM object.  Using vinvalbuf() here
  		 * is a bit heavy-handed as it flushes all buffers for
  		 * the given vnode, not just the buffers covering the
  		 * requested range.
  		 */
  		error = 0;
  		vfslocked = VFS_LOCK_GIANT(vp->v_mount);
  		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  		if (vp->v_iflag & VI_DOOMED) {
  			VOP_UNLOCK(vp, 0);
  			VFS_UNLOCK_GIANT(vfslocked);
  			break;
  		}
  		vinvalbuf(vp, V_CLEANONLY, 0, 0);
  		if (vp->v_object != NULL) {
  			start = trunc_page(ap->a_start);
  			end = round_page(ap->a_end);
  			VM_OBJECT_LOCK(vp->v_object);
  			vm_object_page_cache(vp->v_object, OFF_TO_IDX(start),
  			    OFF_TO_IDX(end));
  			VM_OBJECT_UNLOCK(vp->v_object);
  		}
  		VOP_UNLOCK(vp, 0);
  		VFS_UNLOCK_GIANT(vfslocked);
  		break;
  	default:
  		error = EINVAL;
  		break;
  	}
  	return (error);
  }
  
  int
  vop_stdunp_bind(struct vop_unp_bind_args *ap)
  {
  
  	ap->a_vp->v_socket = ap->a_socket;
  	return (0);
  }
  
  int
  vop_stdunp_connect(struct vop_unp_connect_args *ap)
  {
  
  	*ap->a_socket = ap->a_vp->v_socket;
  	return (0);
  }
  
  int
  vop_stdunp_detach(struct vop_unp_detach_args *ap)
  {
  
  	ap->a_vp->v_socket = NULL;
  	return (0);
  }
  
  /*
   * vfs default ops
   * used to fill the vfs function table to get reasonable default return values.
   */
  int
  vfs_stdroot (mp, flags, vpp)
  	struct mount *mp;
  	int flags;
  	struct vnode **vpp;
  {
  
  	return (EOPNOTSUPP);
  }
  
  int
  vfs_stdstatfs (mp, sbp)
  	struct mount *mp;
  	struct statfs *sbp;
  {
  
  	return (EOPNOTSUPP);
  }
  
  int
  vfs_stdquotactl (mp, cmds, uid, arg)
  	struct mount *mp;
  	int cmds;
  	uid_t uid;
  	void *arg;
  {
  
  	return (EOPNOTSUPP);
  }
  
  int
  vfs_stdsync(mp, waitfor)
  	struct mount *mp;
  	int waitfor;
  {
  	struct vnode *vp, *mvp;
  	struct thread *td;
  	int error, lockreq, allerror = 0;
  
  	td = curthread;
  	lockreq = LK_EXCLUSIVE | LK_INTERLOCK;
  	if (waitfor != MNT_WAIT)
  		lockreq |= LK_NOWAIT;
  	/*
  	 * Force stale buffer cache information to be flushed.
  	 */
  loop:
  	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
  		if (vp->v_bufobj.bo_dirty.bv_cnt == 0) {
  			VI_UNLOCK(vp);
  			continue;
  		}
  		if ((error = vget(vp, lockreq, td)) != 0) {
  			if (error == ENOENT) {
  				MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
  				goto loop;
  			}
  			continue;
  		}
  		error = VOP_FSYNC(vp, waitfor, td);
  		if (error)
  			allerror = error;
  		vput(vp);
  	}
  	return (allerror);
  }
  
  int
  vfs_stdnosync (mp, waitfor)
  	struct mount *mp;
  	int waitfor;
  {
  
  	return (0);
  }
  
  int
  vfs_stdvget (mp, ino, flags, vpp)
  	struct mount *mp;
  	ino_t ino;
  	int flags;
  	struct vnode **vpp;
  {
  
  	return (EOPNOTSUPP);
  }
  
  int
  vfs_stdfhtovp (mp, fhp, flags, vpp)
  	struct mount *mp;
  	struct fid *fhp;
  	int flags;
  	struct vnode **vpp;
  {
  
  	return (EOPNOTSUPP);
  }
  
  int
  vfs_stdinit (vfsp)
  	struct vfsconf *vfsp;
  {
  
  	return (0);
  }
  
  int
  vfs_stduninit (vfsp)
  	struct vfsconf *vfsp;
  {
  
  	return(0);
  }
  
  int
  vfs_stdextattrctl(mp, cmd, filename_vp, attrnamespace, attrname)
  	struct mount *mp;
  	int cmd;
  	struct vnode *filename_vp;
  	int attrnamespace;
  	const char *attrname;
  {
  
  	if (filename_vp != NULL)
  		VOP_UNLOCK(filename_vp, 0);
  	return (EOPNOTSUPP);
  }
  
  int
  vfs_stdsysctl(mp, op, req)
  	struct mount *mp;
  	fsctlop_t op;
  	struct sysctl_req *req;
  {
  
  	return (EOPNOTSUPP);
  }
  
  /* end of vfs default ops */
  