path: root/sys/kern/vfs_vnops.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.
 *
 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
 * Copyright (c) 2013, 2014 The FreeBSD Foundation
 *
 * Portions of this software were developed by Konstantin Belousov
 * under sponsorship from the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)vfs_vnops.c	8.2 (Berkeley) 1/21/94
 */

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

#include "opt_hwpmc_hooks.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/disk.h>
#include <sys/fail.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/kdb.h>
#include <sys/ktr.h>
#include <sys/stat.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/filio.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/prng.h>
#include <sys/sx.h>
#include <sys/sleepqueue.h>
#include <sys/sysctl.h>
#include <sys/ttycom.h>
#include <sys/conf.h>
#include <sys/syslog.h>
#include <sys/unistd.h>
#include <sys/user.h>

#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>

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

#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif

static fo_rdwr_t	vn_read;
static fo_rdwr_t	vn_write;
static fo_rdwr_t	vn_io_fault;
static fo_truncate_t	vn_truncate;
static fo_ioctl_t	vn_ioctl;
static fo_poll_t	vn_poll;
static fo_kqfilter_t	vn_kqfilter;
static fo_stat_t	vn_statfile;
static fo_close_t	vn_closefile;
static fo_mmap_t	vn_mmap;
static fo_fallocate_t	vn_fallocate;

struct 	fileops vnops = {
	.fo_read = vn_io_fault,
	.fo_write = vn_io_fault,
	.fo_truncate = vn_truncate,
	.fo_ioctl = vn_ioctl,
	.fo_poll = vn_poll,
	.fo_kqfilter = vn_kqfilter,
	.fo_stat = vn_statfile,
	.fo_close = vn_closefile,
	.fo_chmod = vn_chmod,
	.fo_chown = vn_chown,
	.fo_sendfile = vn_sendfile,
	.fo_seek = vn_seek,
	.fo_fill_kinfo = vn_fill_kinfo,
	.fo_mmap = vn_mmap,
	.fo_fallocate = vn_fallocate,
	.fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
};

const u_int io_hold_cnt = 16;
static int vn_io_fault_enable = 1;
SYSCTL_INT(_debug, OID_AUTO, vn_io_fault_enable, CTLFLAG_RWTUN,
    &vn_io_fault_enable, 0, "Enable vn_io_fault lock avoidance");
static int vn_io_fault_prefault = 0;
SYSCTL_INT(_debug, OID_AUTO, vn_io_fault_prefault, CTLFLAG_RWTUN,
    &vn_io_fault_prefault, 0, "Enable vn_io_fault prefaulting");
static int vn_io_pgcache_read_enable = 1;
SYSCTL_INT(_debug, OID_AUTO, vn_io_pgcache_read_enable, CTLFLAG_RWTUN,
    &vn_io_pgcache_read_enable, 0,
    "Enable copying from page cache for reads, avoiding fs");
static u_long vn_io_faults_cnt;
SYSCTL_ULONG(_debug, OID_AUTO, vn_io_faults, CTLFLAG_RD,
    &vn_io_faults_cnt, 0, "Count of vn_io_fault lock avoidance triggers");

static int vfs_allow_read_dir = 0;
SYSCTL_INT(_security_bsd, OID_AUTO, allow_read_dir, CTLFLAG_RW,
    &vfs_allow_read_dir, 0,
    "Enable read(2) of directory by root for filesystems that support it");

/*
 * Returns true if vn_io_fault mode of handling the i/o request should
 * be used.
 */
static bool
do_vn_io_fault(struct vnode *vp, struct uio *uio)
{
	struct mount *mp;

	return (uio->uio_segflg == UIO_USERSPACE && vp->v_type == VREG &&
	    (mp = vp->v_mount) != NULL &&
	    (mp->mnt_kern_flag & MNTK_NO_IOPF) != 0 && vn_io_fault_enable);
}

/*
 * Structure used to pass arguments to vn_io_fault1(), to do either
 * file- or vnode-based I/O calls.
 */
struct vn_io_fault_args {
	enum {
		VN_IO_FAULT_FOP,
		VN_IO_FAULT_VOP
	} kind;
	struct ucred *cred;
	int flags;
	union {
		struct fop_args_tag {
			struct file *fp;
			fo_rdwr_t *doio;
		} fop_args;
		struct vop_args_tag {
			struct vnode *vp;
		} vop_args;
	} args;
};

static int vn_io_fault1(struct vnode *vp, struct uio *uio,
    struct vn_io_fault_args *args, struct thread *td);

int
vn_open(struct nameidata *ndp, int *flagp, int cmode, struct file *fp)
{
	struct thread *td = ndp->ni_cnd.cn_thread;

	return (vn_open_cred(ndp, flagp, cmode, 0, td->td_ucred, fp));
}

static uint64_t
open2nameif(int fmode, u_int vn_open_flags)
{
	uint64_t res;

	res = ISOPEN | LOCKLEAF;
	if ((fmode & O_BENEATH) != 0)
		res |= BENEATH;
	if ((fmode & O_RESOLVE_BENEATH) != 0)
		res |= RBENEATH;
	if ((vn_open_flags & VN_OPEN_NOAUDIT) == 0)
		res |= AUDITVNODE1;
	if ((vn_open_flags & VN_OPEN_NOCAPCHECK) != 0)
		res |= NOCAPCHECK;
	return (res);
}

/*
 * Common code for vnode open operations via a name lookup.
 * Lookup the vnode and invoke VOP_CREATE if needed.
 * Check permissions, and call the VOP_OPEN or VOP_CREATE routine.
 *
 * Note that this does NOT free nameidata for the successful case,
 * due to the NDINIT being done elsewhere.
 */
int
vn_open_cred(struct nameidata *ndp, int *flagp, int cmode, u_int vn_open_flags,
    struct ucred *cred, struct file *fp)
{
	struct vnode *vp;
	struct mount *mp;
	struct thread *td = ndp->ni_cnd.cn_thread;
	struct vattr vat;
	struct vattr *vap = &vat;
	int fmode, error;

restart:
	fmode = *flagp;
	if ((fmode & (O_CREAT | O_EXCL | O_DIRECTORY)) == (O_CREAT |
	    O_EXCL | O_DIRECTORY))
		return (EINVAL);
	else if ((fmode & (O_CREAT | O_DIRECTORY)) == O_CREAT) {
		ndp->ni_cnd.cn_nameiop = CREATE;
		ndp->ni_cnd.cn_flags = open2nameif(fmode, vn_open_flags);
		/*
		 * Set NOCACHE to avoid flushing the cache when
		 * rolling in many files at once.
		 *
		 * Set NC_KEEPPOSENTRY to keep positive entries if they already
		 * exist despite NOCACHE.
		 */
		ndp->ni_cnd.cn_flags |= LOCKPARENT | NOCACHE | NC_KEEPPOSENTRY;
		if ((fmode & O_EXCL) == 0 && (fmode & O_NOFOLLOW) == 0)
			ndp->ni_cnd.cn_flags |= FOLLOW;
		if ((vn_open_flags & VN_OPEN_INVFS) == 0)
			bwillwrite();
		if ((error = namei(ndp)) != 0)
			return (error);
		if (ndp->ni_vp == NULL) {
			VATTR_NULL(vap);
			vap->va_type = VREG;
			vap->va_mode = cmode;
			if (fmode & O_EXCL)
				vap->va_vaflags |= VA_EXCLUSIVE;
			if (vn_start_write(ndp->ni_dvp, &mp, V_NOWAIT) != 0) {
				NDFREE(ndp, NDF_ONLY_PNBUF);
				vput(ndp->ni_dvp);
				if ((error = vn_start_write(NULL, &mp,
				    V_XSLEEP | PCATCH)) != 0)
					return (error);
				NDREINIT(ndp);
				goto restart;
			}
			if ((vn_open_flags & VN_OPEN_NAMECACHE) != 0)
				ndp->ni_cnd.cn_flags |= MAKEENTRY;
#ifdef MAC
			error = mac_vnode_check_create(cred, ndp->ni_dvp,
			    &ndp->ni_cnd, vap);
			if (error == 0)
#endif
				error = VOP_CREATE(ndp->ni_dvp, &ndp->ni_vp,
						   &ndp->ni_cnd, vap);
			vput(ndp->ni_dvp);
			vn_finished_write(mp);
			if (error) {
				NDFREE(ndp, NDF_ONLY_PNBUF);
				if (error == ERELOOKUP) {
					NDREINIT(ndp);
					goto restart;
				}
				return (error);
			}
			fmode &= ~O_TRUNC;
			vp = ndp->ni_vp;
		} else {
			if (ndp->ni_dvp == ndp->ni_vp)
				vrele(ndp->ni_dvp);
			else
				vput(ndp->ni_dvp);
			ndp->ni_dvp = NULL;
			vp = ndp->ni_vp;
			if (fmode & O_EXCL) {
				error = EEXIST;
				goto bad;
			}
			if (vp->v_type == VDIR) {
				error = EISDIR;
				goto bad;
			}
			fmode &= ~O_CREAT;
		}
	} else {
		ndp->ni_cnd.cn_nameiop = LOOKUP;
		ndp->ni_cnd.cn_flags = open2nameif(fmode, vn_open_flags);
		ndp->ni_cnd.cn_flags |= (fmode & O_NOFOLLOW) != 0 ? NOFOLLOW :
		    FOLLOW;
		if ((fmode & FWRITE) == 0)
			ndp->ni_cnd.cn_flags |= LOCKSHARED;
		if ((error = namei(ndp)) != 0)
			return (error);
		vp = ndp->ni_vp;
	}
	error = vn_open_vnode(vp, fmode, cred, td, fp);
	if (error)
		goto bad;
	*flagp = fmode;
	return (0);
bad:
	NDFREE(ndp, NDF_ONLY_PNBUF);
	vput(vp);
	*flagp = fmode;
	ndp->ni_vp = NULL;
	return (error);
}

static int
vn_open_vnode_advlock(struct vnode *vp, int fmode, struct file *fp)
{
	struct flock lf;
	int error, lock_flags, type;

	ASSERT_VOP_LOCKED(vp, "vn_open_vnode_advlock");
	if ((fmode & (O_EXLOCK | O_SHLOCK)) == 0)
		return (0);
	KASSERT(fp != NULL, ("open with flock requires fp"));
	if (fp->f_type != DTYPE_NONE && fp->f_type != DTYPE_VNODE)
		return (EOPNOTSUPP);

	lock_flags = VOP_ISLOCKED(vp);
	VOP_UNLOCK(vp);

	lf.l_whence = SEEK_SET;
	lf.l_start = 0;
	lf.l_len = 0;
	lf.l_type = (fmode & O_EXLOCK) != 0 ? F_WRLCK : F_RDLCK;
	type = F_FLOCK;
	if ((fmode & FNONBLOCK) == 0)
		type |= F_WAIT;
	error = VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, type);
	if (error == 0)
		fp->f_flag |= FHASLOCK;

	vn_lock(vp, lock_flags | LK_RETRY);
	if (error == 0 && VN_IS_DOOMED(vp))
		error = ENOENT;
	return (error);
}

/*
 * Common code for vnode open operations once a vnode is located.
 * Check permissions, and call the VOP_OPEN routine.
 */
int
vn_open_vnode(struct vnode *vp, int fmode, struct ucred *cred,
    struct thread *td, struct file *fp)
{
	accmode_t accmode;
	int error;

	if (vp->v_type == VLNK)
		return (EMLINK);
	if (vp->v_type == VSOCK)
		return (EOPNOTSUPP);
	if (vp->v_type != VDIR && fmode & O_DIRECTORY)
		return (ENOTDIR);
	accmode = 0;
	if (fmode & (FWRITE | O_TRUNC)) {
		if (vp->v_type == VDIR)
			return (EISDIR);
		accmode |= VWRITE;
	}
	if (fmode & FREAD)
		accmode |= VREAD;
	if (fmode & FEXEC)
		accmode |= VEXEC;
	if ((fmode & O_APPEND) && (fmode & FWRITE))
		accmode |= VAPPEND;
#ifdef MAC
	if (fmode & O_CREAT)
		accmode |= VCREAT;
	if (fmode & O_VERIFY)
		accmode |= VVERIFY;
	error = mac_vnode_check_open(cred, vp, accmode);
	if (error)
		return (error);

	accmode &= ~(VCREAT | VVERIFY);
#endif
	if ((fmode & O_CREAT) == 0 && accmode != 0) {
		error = VOP_ACCESS(vp, accmode, cred, td);
		if (error != 0)
			return (error);
	}
	if (vp->v_type == VFIFO && VOP_ISLOCKED(vp) != LK_EXCLUSIVE)
		vn_lock(vp, LK_UPGRADE | LK_RETRY);
	error = VOP_OPEN(vp, fmode, cred, td, fp);
	if (error != 0)
		return (error);

	error = vn_open_vnode_advlock(vp, fmode, fp);
	if (error == 0 && (fmode & FWRITE) != 0) {
		error = VOP_ADD_WRITECOUNT(vp, 1);
		if (error == 0) {
			CTR3(KTR_VFS, "%s: vp %p v_writecount increased to %d",
			     __func__, vp, vp->v_writecount);
		}
	}

	/*
	 * Error from advlock or VOP_ADD_WRITECOUNT() still requires
	 * calling VOP_CLOSE() to pair with earlier VOP_OPEN().
	 * Arrange for that by having fdrop() to use vn_closefile().
	 */
	if (error != 0) {
		fp->f_flag |= FOPENFAILED;
		fp->f_vnode = vp;
		if (fp->f_ops == &badfileops) {
			fp->f_type = DTYPE_VNODE;
			fp->f_ops = &vnops;
		}
		vref(vp);
	}

	ASSERT_VOP_LOCKED(vp, "vn_open_vnode");
	return (error);

}

/*
 * Check for write permissions on the specified vnode.
 * Prototype text segments cannot be written.
 * It is racy.
 */
int
vn_writechk(struct vnode *vp)
{

	ASSERT_VOP_LOCKED(vp, "vn_writechk");
	/*
	 * If there's shared text associated with
	 * the vnode, try to free it up once.  If
	 * we fail, we can't allow writing.
	 */
	if (VOP_IS_TEXT(vp))
		return (ETXTBSY);

	return (0);
}

/*
 * Vnode close call
 */
static int
vn_close1(struct vnode *vp, int flags, struct ucred *file_cred,
    struct thread *td, bool keep_ref)
{
	struct mount *mp;
	int error, lock_flags;

	if (vp->v_type != VFIFO && (flags & FWRITE) == 0 &&
	    MNT_EXTENDED_SHARED(vp->v_mount))
		lock_flags = LK_SHARED;
	else
		lock_flags = LK_EXCLUSIVE;

	vn_start_write(vp, &mp, V_WAIT);
	vn_lock(vp, lock_flags | LK_RETRY);
	AUDIT_ARG_VNODE1(vp);
	if ((flags & (FWRITE | FOPENFAILED)) == FWRITE) {
		VOP_ADD_WRITECOUNT_CHECKED(vp, -1);
		CTR3(KTR_VFS, "%s: vp %p v_writecount decreased to %d",
		    __func__, vp, vp->v_writecount);
	}
	error = VOP_CLOSE(vp, flags, file_cred, td);
	if (keep_ref)
		VOP_UNLOCK(vp);
	else
		vput(vp);
	vn_finished_write(mp);
	return (error);
}

int
vn_close(struct vnode *vp, int flags, struct ucred *file_cred,
    struct thread *td)
{

	return (vn_close1(vp, flags, file_cred, td, false));
}

/*
 * Heuristic to detect sequential operation.
 */
static int
sequential_heuristic(struct uio *uio, struct file *fp)
{
	enum uio_rw rw;

	ASSERT_VOP_LOCKED(fp->f_vnode, __func__);

	rw = uio->uio_rw;
	if (fp->f_flag & FRDAHEAD)
		return (fp->f_seqcount[rw] << IO_SEQSHIFT);

	/*
	 * Offset 0 is handled specially.  open() sets f_seqcount to 1 so
	 * that the first I/O is normally considered to be slightly
	 * sequential.  Seeking to offset 0 doesn't change sequentiality
	 * unless previous seeks have reduced f_seqcount to 0, in which
	 * case offset 0 is not special.
	 */
	if ((uio->uio_offset == 0 && fp->f_seqcount[rw] > 0) ||
	    uio->uio_offset == fp->f_nextoff[rw]) {
		/*
		 * f_seqcount is in units of fixed-size blocks so that it
		 * depends mainly on the amount of sequential I/O and not
		 * much on the number of sequential I/O's.  The fixed size
		 * of 16384 is hard-coded here since it is (not quite) just
		 * a magic size that works well here.  This size is more
		 * closely related to the best I/O size for real disks than
		 * to any block size used by software.
		 */
		if (uio->uio_resid >= IO_SEQMAX * 16384)
			fp->f_seqcount[rw] = IO_SEQMAX;
		else {
			fp->f_seqcount[rw] += howmany(uio->uio_resid, 16384);
			if (fp->f_seqcount[rw] > IO_SEQMAX)
				fp->f_seqcount[rw] = IO_SEQMAX;
		}
		return (fp->f_seqcount[rw] << IO_SEQSHIFT);
	}

	/* Not sequential.  Quickly draw-down sequentiality. */
	if (fp->f_seqcount[rw] > 1)
		fp->f_seqcount[rw] = 1;
	else
		fp->f_seqcount[rw] = 0;
	return (0);
}

/*
 * Package up an I/O request on a vnode into a uio and do it.
 */
int
vn_rdwr(enum uio_rw rw, struct vnode *vp, void *base, int len, off_t offset,
    enum uio_seg segflg, int ioflg, struct ucred *active_cred,
    struct ucred *file_cred, ssize_t *aresid, struct thread *td)
{
	struct uio auio;
	struct iovec aiov;
	struct mount *mp;
	struct ucred *cred;
	void *rl_cookie;
	struct vn_io_fault_args args;
	int error, lock_flags;

	if (offset < 0 && vp->v_type != VCHR)
		return (EINVAL);
	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 = td;
	error = 0;

	if ((ioflg & IO_NODELOCKED) == 0) {
		if ((ioflg & IO_RANGELOCKED) == 0) {
			if (rw == UIO_READ) {
				rl_cookie = vn_rangelock_rlock(vp, offset,
				    offset + len);
			} else if ((ioflg & IO_APPEND) != 0) {
				rl_cookie = vn_rangelock_wlock(vp, 0, OFF_MAX);
			} else {
				rl_cookie = vn_rangelock_wlock(vp, offset,
				    offset + len);
			}
		} else
			rl_cookie = NULL;
		mp = NULL;
		if (rw == UIO_WRITE) { 
			if (vp->v_type != VCHR &&
			    (error = vn_start_write(vp, &mp, V_WAIT | PCATCH))
			    != 0)
				goto out;
			if (MNT_SHARED_WRITES(mp) ||
			    ((mp == NULL) && MNT_SHARED_WRITES(vp->v_mount)))
				lock_flags = LK_SHARED;
			else
				lock_flags = LK_EXCLUSIVE;
		} else
			lock_flags = LK_SHARED;
		vn_lock(vp, lock_flags | LK_RETRY);
	} else
		rl_cookie = NULL;

	ASSERT_VOP_LOCKED(vp, "IO_NODELOCKED with no vp lock held");
#ifdef MAC
	if ((ioflg & IO_NOMACCHECK) == 0) {
		if (rw == UIO_READ)
			error = mac_vnode_check_read(active_cred, file_cred,
			    vp);
		else
			error = mac_vnode_check_write(active_cred, file_cred,
			    vp);
	}
#endif
	if (error == 0) {
		if (file_cred != NULL)
			cred = file_cred;
		else
			cred = active_cred;
		if (do_vn_io_fault(vp, &auio)) {
			args.kind = VN_IO_FAULT_VOP;
			args.cred = cred;
			args.flags = ioflg;
			args.args.vop_args.vp = vp;
			error = vn_io_fault1(vp, &auio, &args, td);
		} else if (rw == UIO_READ) {
			error = VOP_READ(vp, &auio, ioflg, cred);
		} else /* if (rw == UIO_WRITE) */ {
			error = VOP_WRITE(vp, &auio, ioflg, cred);
		}
	}
	if (aresid)
		*aresid = auio.uio_resid;
	else
		if (auio.uio_resid && error == 0)
			error = EIO;
	if ((ioflg & IO_NODELOCKED) == 0) {
		VOP_UNLOCK(vp);
		if (mp != NULL)
			vn_finished_write(mp);
	}
 out:
	if (rl_cookie != NULL)
		vn_rangelock_unlock(vp, rl_cookie);
	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 kern_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).
 */
int
vn_rdwr_inchunks(enum uio_rw rw, struct vnode *vp, void *base, size_t len,
    off_t offset, enum uio_seg segflg, int ioflg, struct ucred *active_cred,
    struct ucred *file_cred, size_t *aresid, struct thread *td)
{
	int error = 0;
	ssize_t iaresid;

	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 (rw != UIO_READ && vp->v_type == VREG)
			bwillwrite();
		iaresid = 0;
		error = vn_rdwr(rw, vp, base, chunk, offset, segflg,
		    ioflg, active_cred, file_cred, &iaresid, td);
		len -= chunk;	/* aresid calc already includes length */
		if (error)
			break;
		offset += chunk;
		base = (char *)base + chunk;
		kern_yield(PRI_USER);
	} while (len);
	if (aresid)
		*aresid = len + iaresid;
	return (error);
}

#if OFF_MAX <= LONG_MAX
off_t
foffset_lock(struct file *fp, int flags)
{
	volatile short *flagsp;
	off_t res;
	short state;

	KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));

	if ((flags & FOF_NOLOCK) != 0)
		return (atomic_load_long(&fp->f_offset));

	/*
	 * According to McKusick the vn lock was protecting f_offset here.
	 * It is now protected by the FOFFSET_LOCKED flag.
	 */
	flagsp = &fp->f_vnread_flags;
	if (atomic_cmpset_acq_16(flagsp, 0, FOFFSET_LOCKED))
		return (atomic_load_long(&fp->f_offset));

	sleepq_lock(&fp->f_vnread_flags);
	state = atomic_load_16(flagsp);
	for (;;) {
		if ((state & FOFFSET_LOCKED) == 0) {
			if (!atomic_fcmpset_acq_16(flagsp, &state,
			    FOFFSET_LOCKED))
				continue;
			break;
		}
		if ((state & FOFFSET_LOCK_WAITING) == 0) {
			if (!atomic_fcmpset_acq_16(flagsp, &state,
			    state | FOFFSET_LOCK_WAITING))
				continue;
		}
		DROP_GIANT();
		sleepq_add(&fp->f_vnread_flags, NULL, "vofflock", 0, 0);
		sleepq_wait(&fp->f_vnread_flags, PUSER -1);
		PICKUP_GIANT();
		sleepq_lock(&fp->f_vnread_flags);
		state = atomic_load_16(flagsp);
	}
	res = atomic_load_long(&fp->f_offset);
	sleepq_release(&fp->f_vnread_flags);
	return (res);
}

void
foffset_unlock(struct file *fp, off_t val, int flags)
{
	volatile short *flagsp;
	short state;

	KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));

	if ((flags & FOF_NOUPDATE) == 0)
		atomic_store_long(&fp->f_offset, val);
	if ((flags & FOF_NEXTOFF_R) != 0)
		fp->f_nextoff[UIO_READ] = val;
	if ((flags & FOF_NEXTOFF_W) != 0)
		fp->f_nextoff[UIO_WRITE] = val;

	if ((flags & FOF_NOLOCK) != 0)
		return;

	flagsp = &fp->f_vnread_flags;
	state = atomic_load_16(flagsp);
	if ((state & FOFFSET_LOCK_WAITING) == 0 &&
	    atomic_cmpset_rel_16(flagsp, state, 0))
		return;

	sleepq_lock(&fp->f_vnread_flags);
	MPASS((fp->f_vnread_flags & FOFFSET_LOCKED) != 0);
	MPASS((fp->f_vnread_flags & FOFFSET_LOCK_WAITING) != 0);
	fp->f_vnread_flags = 0;
	sleepq_broadcast(&fp->f_vnread_flags, SLEEPQ_SLEEP, 0, 0);
	sleepq_release(&fp->f_vnread_flags);
}
#else
off_t
foffset_lock(struct file *fp, int flags)
{
	struct mtx *mtxp;
	off_t res;

	KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));

	mtxp = mtx_pool_find(mtxpool_sleep, fp);
	mtx_lock(mtxp);
	if ((flags & FOF_NOLOCK) == 0) {
		while (fp->f_vnread_flags & FOFFSET_LOCKED) {
			fp->f_vnread_flags |= FOFFSET_LOCK_WAITING;
			msleep(&fp->f_vnread_flags, mtxp, PUSER -1,
			    "vofflock", 0);
		}
		fp->f_vnread_flags |= FOFFSET_LOCKED;
	}
	res = fp->f_offset;
	mtx_unlock(mtxp);
	return (res);
}

void
foffset_unlock(struct file *fp, off_t val, int flags)
{
	struct mtx *mtxp;

	KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));

	mtxp = mtx_pool_find(mtxpool_sleep, fp);
	mtx_lock(mtxp);
	if ((flags & FOF_NOUPDATE) == 0)
		fp->f_offset = val;
	if ((flags & FOF_NEXTOFF_R) != 0)
		fp->f_nextoff[UIO_READ] = val;
	if ((flags & FOF_NEXTOFF_W) != 0)
		fp->f_nextoff[UIO_WRITE] = val;
	if ((flags & FOF_NOLOCK) == 0) {
		KASSERT((fp->f_vnread_flags & FOFFSET_LOCKED) != 0,
		    ("Lost FOFFSET_LOCKED"));
		if (fp->f_vnread_flags & FOFFSET_LOCK_WAITING)
			wakeup(&fp->f_vnread_flags);
		fp->f_vnread_flags = 0;
	}
	mtx_unlock(mtxp);
}
#endif

void
foffset_lock_uio(struct file *fp, struct uio *uio, int flags)
{

	if ((flags & FOF_OFFSET) == 0)
		uio->uio_offset = foffset_lock(fp, flags);
}

void
foffset_unlock_uio(struct file *fp, struct uio *uio, int flags)
{

	if ((flags & FOF_OFFSET) == 0)
		foffset_unlock(fp, uio->uio_offset, flags);
}

static int
get_advice(struct file *fp, struct uio *uio)
{
	struct mtx *mtxp;
	int ret;

	ret = POSIX_FADV_NORMAL;
	if (fp->f_advice == NULL || fp->f_vnode->v_type != VREG)
		return (ret);

	mtxp = mtx_pool_find(mtxpool_sleep, fp);
	mtx_lock(mtxp);
	if (fp->f_advice != NULL &&
	    uio->uio_offset >= fp->f_advice->fa_start &&
	    uio->uio_offset + uio->uio_resid <= fp->f_advice->fa_end)
		ret = fp->f_advice->fa_advice;
	mtx_unlock(mtxp);
	return (ret);
}

int
vn_read_from_obj(struct vnode *vp, struct uio *uio)
{
	vm_object_t obj;
	vm_page_t ma[io_hold_cnt + 2];
	off_t off, vsz;
	ssize_t resid;
	int error, i, j;

	MPASS(uio->uio_resid <= ptoa(io_hold_cnt + 2));
	obj = atomic_load_ptr(&vp->v_object);
	if (obj == NULL)
		return (EJUSTRETURN);

	/*
	 * Depends on type stability of vm_objects.
	 */
	vm_object_pip_add(obj, 1);
	if ((obj->flags & OBJ_DEAD) != 0) {
		/*
		 * Note that object might be already reused from the
		 * vnode, and the OBJ_DEAD flag cleared.  This is fine,
		 * we recheck for DOOMED vnode state after all pages
		 * are busied, and retract then.
		 *
		 * But we check for OBJ_DEAD to ensure that we do not
		 * busy pages while vm_object_terminate_pages()
		 * processes the queue.
		 */
		error = EJUSTRETURN;
		goto out_pip;
	}

	resid = uio->uio_resid;
	off = uio->uio_offset;
	for (i = 0; resid > 0; i++) {
		MPASS(i < io_hold_cnt + 2);
		ma[i] = vm_page_grab_unlocked(obj, atop(off),
		    VM_ALLOC_NOCREAT | VM_ALLOC_SBUSY | VM_ALLOC_IGN_SBUSY |
		    VM_ALLOC_NOWAIT);
		if (ma[i] == NULL)
			break;

		/*
		 * Skip invalid pages.  Valid mask can be partial only
		 * at EOF, and we clip later.
		 */
		if (vm_page_none_valid(ma[i])) {
			vm_page_sunbusy(ma[i]);
			break;
		}

		resid -= PAGE_SIZE;
		off += PAGE_SIZE;
	}
	if (i == 0) {
		error = EJUSTRETURN;
		goto out_pip;
	}

	/*
	 * Check VIRF_DOOMED after we busied our pages.  Since
	 * vgonel() terminates the vnode' vm_object, it cannot
	 * process past pages busied by us.
	 */
	if (VN_IS_DOOMED(vp)) {
		error = EJUSTRETURN;
		goto out;
	}

	resid = PAGE_SIZE - (uio->uio_offset & PAGE_MASK) + ptoa(i - 1);
	if (resid > uio->uio_resid)
		resid = uio->uio_resid;

	/*
	 * Unlocked read of vnp_size is safe because truncation cannot
	 * pass busied page.  But we load vnp_size into a local
	 * variable so that possible concurrent extension does not
	 * break calculation.
	 */
#if defined(__powerpc__) && !defined(__powerpc64__)
	vsz = obj->un_pager.vnp.vnp_size;
#else
	vsz = atomic_load_64(&obj->un_pager.vnp.vnp_size);
#endif
	if (uio->uio_offset + resid > vsz)
		resid = vsz - uio->uio_offset;

	error = vn_io_fault_pgmove(ma, uio->uio_offset & PAGE_MASK, resid, uio);

out:
	for (j = 0; j < i; j++) {
		if (error == 0)
			vm_page_reference(ma[j]);
		vm_page_sunbusy(ma[j]);
	}
out_pip:
	vm_object_pip_wakeup(obj);
	if (error != 0)
		return (error);
	return (uio->uio_resid == 0 ? 0 : EJUSTRETURN);
}

/*
 * File table vnode read routine.
 */
static int
vn_read(struct file *fp, struct uio *uio, struct ucred *active_cred, int flags,
    struct thread *td)
{
	struct vnode *vp;
	off_t orig_offset;
	int error, ioflag;
	int advice;

	KASSERT(uio->uio_td == td, ("uio_td %p is not td %p",
	    uio->uio_td, td));
	KASSERT(flags & FOF_OFFSET, ("No FOF_OFFSET"));
	vp = fp->f_vnode;
	ioflag = 0;
	if (fp->f_flag & FNONBLOCK)
		ioflag |= IO_NDELAY;
	if (fp->f_flag & O_DIRECT)
		ioflag |= IO_DIRECT;

	/*
	 * Try to read from page cache.  VIRF_DOOMED check is racy but
	 * allows us to avoid unneeded work outright.
	 */
	if (vn_io_pgcache_read_enable && !mac_vnode_check_read_enabled() &&
	    (vn_irflag_read(vp) & (VIRF_DOOMED | VIRF_PGREAD)) == VIRF_PGREAD) {
		error = VOP_READ_PGCACHE(vp, uio, ioflag, fp->f_cred);
		if (error == 0) {
			fp->f_nextoff[UIO_READ] = uio->uio_offset;
			return (0);
		}
		if (error != EJUSTRETURN)
			return (error);
	}

	advice = get_advice(fp, uio);
	vn_lock(vp, LK_SHARED | LK_RETRY);

	switch (advice) {
	case POSIX_FADV_NORMAL:
	case POSIX_FADV_SEQUENTIAL:
	case POSIX_FADV_NOREUSE:
		ioflag |= sequential_heuristic(uio, fp);
		break;
	case POSIX_FADV_RANDOM:
		/* Disable read-ahead for random I/O. */
		break;
	}
	orig_offset = uio->uio_offset;

#ifdef MAC
	error = mac_vnode_check_read(active_cred, fp->f_cred, vp);
	if (error == 0)
#endif
		error = VOP_READ(vp, uio, ioflag, fp->f_cred);
	fp->f_nextoff[UIO_READ] = uio->uio_offset;
	VOP_UNLOCK(vp);
	if (error == 0 && advice == POSIX_FADV_NOREUSE &&
	    orig_offset != uio->uio_offset)
		/*
		 * Use POSIX_FADV_DONTNEED to flush pages and buffers
		 * for the backing file after a POSIX_FADV_NOREUSE
		 * read(2).
		 */
		error = VOP_ADVISE(vp, orig_offset, uio->uio_offset - 1,
		    POSIX_FADV_DONTNEED);
	return (error);
}

/*
 * File table vnode write routine.
 */
static int
vn_write(struct file *fp, struct uio *uio, struct ucred *active_cred, int flags,
    struct thread *td)
{
	struct vnode *vp;
	struct mount *mp;
	off_t orig_offset;
	int error, ioflag, lock_flags;
	int advice;

	KASSERT(uio->uio_td == td, ("uio_td %p is not td %p",
	    uio->uio_td, td));
	KASSERT(flags & FOF_OFFSET, ("No FOF_OFFSET"));
	vp = fp->f_vnode;
	if (vp->v_type == VREG)
		bwillwrite();
	ioflag = IO_UNIT;
	if (vp->v_type == VREG && (fp->f_flag & O_APPEND))
		ioflag |= IO_APPEND;
	if (fp->f_flag & FNONBLOCK)
		ioflag |= IO_NDELAY;
	if (fp->f_flag & O_DIRECT)
		ioflag |= IO_DIRECT;
	if ((fp->f_flag & O_FSYNC) ||
	    (vp->v_mount && (vp->v_mount->mnt_flag & MNT_SYNCHRONOUS)))
		ioflag |= IO_SYNC;
	/*
	 * For O_DSYNC we set both IO_SYNC and IO_DATASYNC, so that VOP_WRITE()
	 * implementations that don't understand IO_DATASYNC fall back to full
	 * O_SYNC behavior.
	 */
	if (fp->f_flag & O_DSYNC)
		ioflag |= IO_SYNC | IO_DATASYNC;
	mp = NULL;
	if (vp->v_type != VCHR &&
	    (error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
		goto unlock;

	advice = get_advice(fp, uio);

	if (MNT_SHARED_WRITES(mp) ||
	    (mp == NULL && MNT_SHARED_WRITES(vp->v_mount))) {
		lock_flags = LK_SHARED;
	} else {
		lock_flags = LK_EXCLUSIVE;
	}

	vn_lock(vp, lock_flags | LK_RETRY);
	switch (advice) {
	case POSIX_FADV_NORMAL:
	case POSIX_FADV_SEQUENTIAL:
	case POSIX_FADV_NOREUSE:
		ioflag |= sequential_heuristic(uio, fp);
		break;
	case POSIX_FADV_RANDOM:
		/* XXX: Is this correct? */
		break;
	}
	orig_offset = uio->uio_offset;

#ifdef MAC
	error = mac_vnode_check_write(active_cred, fp->f_cred, vp);
	if (error == 0)
#endif
		error = VOP_WRITE(vp, uio, ioflag, fp->f_cred);
	fp->f_nextoff[UIO_WRITE] = uio->uio_offset;
	VOP_UNLOCK(vp);
	if (vp->v_type != VCHR)
		vn_finished_write(mp);
	if (error == 0 && advice == POSIX_FADV_NOREUSE &&
	    orig_offset != uio->uio_offset)
		/*
		 * Use POSIX_FADV_DONTNEED to flush pages and buffers
		 * for the backing file after a POSIX_FADV_NOREUSE
		 * write(2).
		 */
		error = VOP_ADVISE(vp, orig_offset, uio->uio_offset - 1,
		    POSIX_FADV_DONTNEED);
unlock:
	return (error);
}

/*
 * The vn_io_fault() is a wrapper around vn_read() and vn_write() to
 * prevent the following deadlock:
 *
 * Assume that the thread A reads from the vnode vp1 into userspace
 * buffer buf1 backed by the pages of vnode vp2.  If a page in buf1 is
 * currently not resident, then system ends up with the call chain
 *   vn_read() -> VOP_READ(vp1) -> uiomove() -> [Page Fault] ->
 *     vm_fault(buf1) -> vnode_pager_getpages(vp2) -> VOP_GETPAGES(vp2)
 * which establishes lock order vp1->vn_lock, then vp2->vn_lock.
 * If, at the same time, thread B reads from vnode vp2 into buffer buf2
 * backed by the pages of vnode vp1, and some page in buf2 is not
 * resident, we get a reversed order vp2->vn_lock, then vp1->vn_lock.
 *
 * To prevent the lock order reversal and deadlock, vn_io_fault() does
 * not allow page faults to happen during VOP_READ() or VOP_WRITE().
 * Instead, it first tries to do the whole range i/o with pagefaults
 * disabled. If all pages in the i/o buffer are resident and mapped,
 * VOP will succeed (ignoring the genuine filesystem errors).
 * Otherwise, we get back EFAULT, and vn_io_fault() falls back to do
 * i/o in chunks, with all pages in the chunk prefaulted and held
 * using vm_fault_quick_hold_pages().
 *
 * Filesystems using this deadlock avoidance scheme should use the
 * array of the held pages from uio, saved in the curthread->td_ma,
 * instead of doing uiomove().  A helper function
 * vn_io_fault_uiomove() converts uiomove request into
 * uiomove_fromphys() over td_ma array.
 *
 * Since vnode locks do not cover the whole i/o anymore, rangelocks
 * make the current i/o request atomic with respect to other i/os and
 * truncations.
 */

/*
 * Decode vn_io_fault_args and perform the corresponding i/o.
 */
static int
vn_io_fault_doio(struct vn_io_fault_args *args, struct uio *uio,
    struct thread *td)
{
	int error, save;

	error = 0;
	save = vm_fault_disable_pagefaults();
	switch (args->kind) {
	case VN_IO_FAULT_FOP:
		error = (args->args.fop_args.doio)(args->args.fop_args.fp,
		    uio, args->cred, args->flags, td);
		break;
	case VN_IO_FAULT_VOP:
		if (uio->uio_rw == UIO_READ) {
			error = VOP_READ(args->args.vop_args.vp, uio,
			    args->flags, args->cred);
		} else if (uio->uio_rw == UIO_WRITE) {
			error = VOP_WRITE(args->args.vop_args.vp, uio,
			    args->flags, args->cred);
		}
		break;
	default:
		panic("vn_io_fault_doio: unknown kind of io %d %d",
		    args->kind, uio->uio_rw);
	}
	vm_fault_enable_pagefaults(save);
	return (error);
}

static int
vn_io_fault_touch(char *base, const struct uio *uio)
{
	int r;

	r = fubyte(base);
	if (r == -1 || (uio->uio_rw == UIO_READ && subyte(base, r) == -1))
		return (EFAULT);
	return (0);
}

static int
vn_io_fault_prefault_user(const struct uio *uio)
{
	char *base;
	const struct iovec *iov;
	size_t len;
	ssize_t resid;
	int error, i;

	KASSERT(uio->uio_segflg == UIO_USERSPACE,
	    ("vn_io_fault_prefault userspace"));

	error = i = 0;
	iov = uio->uio_iov;
	resid = uio->uio_resid;
	base = iov->iov_base;
	len = iov->iov_len;
	while (resid > 0) {
		error = vn_io_fault_touch(base, uio);
		if (error != 0)
			break;
		if (len < PAGE_SIZE) {
			if (len != 0) {
				error = vn_io_fault_touch(base + len - 1, uio);
				if (error != 0)
					break;
				resid -= len;
			}
			if (++i >= uio->uio_iovcnt)
				break;
			iov = uio->uio_iov + i;
			base = iov->iov_base;
			len = iov->iov_len;
		} else {
			len -= PAGE_SIZE;
			base += PAGE_SIZE;
			resid -= PAGE_SIZE;
		}
	}
	return (error);
}

/*
 * Common code for vn_io_fault(), agnostic to the kind of i/o request.
 * Uses vn_io_fault_doio() to make the call to an actual i/o function.
 * Used from vn_rdwr() and vn_io_fault(), which encode the i/o request
 * into args and call vn_io_fault1() to handle faults during the user
 * mode buffer accesses.
 */
static int
vn_io_fault1(struct vnode *vp, struct uio *uio, struct vn_io_fault_args *args,
    struct thread *td)
{
	vm_page_t ma[io_hold_cnt + 2];
	struct uio *uio_clone, short_uio;
	struct iovec short_iovec[1];
	vm_page_t *prev_td_ma;
	vm_prot_t prot;
	vm_offset_t addr, end;
	size_t len, resid;
	ssize_t adv;
	int error, cnt, saveheld, prev_td_ma_cnt;

	if (vn_io_fault_prefault) {
		error = vn_io_fault_prefault_user(uio);
		if (error != 0)
			return (error); /* Or ignore ? */
	}

	prot = uio->uio_rw == UIO_READ ? VM_PROT_WRITE : VM_PROT_READ;

	/*
	 * The UFS follows IO_UNIT directive and replays back both
	 * uio_offset and uio_resid if an error is encountered during the
	 * operation.  But, since the iovec may be already advanced,
	 * uio is still in an inconsistent state.
	 *
	 * Cache a copy of the original uio, which is advanced to the redo
	 * point using UIO_NOCOPY below.
	 */
	uio_clone = cloneuio(uio);
	resid = uio->uio_resid;

	short_uio.uio_segflg = UIO_USERSPACE;
	short_uio.uio_rw = uio->uio_rw;
	short_uio.uio_td = uio->uio_td;

	error = vn_io_fault_doio(args, uio, td);
	if (error != EFAULT)
		goto out;

	atomic_add_long(&vn_io_faults_cnt, 1);
	uio_clone->uio_segflg = UIO_NOCOPY;
	uiomove(NULL, resid - uio->uio_resid, uio_clone);
	uio_clone->uio_segflg = uio->uio_segflg;

	saveheld = curthread_pflags_set(TDP_UIOHELD);
	prev_td_ma = td->td_ma;
	prev_td_ma_cnt = td->td_ma_cnt;

	while (uio_clone->uio_resid != 0) {
		len = uio_clone->uio_iov->iov_len;
		if (len == 0) {
			KASSERT(uio_clone->uio_iovcnt >= 1,
			    ("iovcnt underflow"));
			uio_clone->uio_iov++;
			uio_clone->uio_iovcnt--;
			continue;
		}
		if (len > ptoa(io_hold_cnt))
			len = ptoa(io_hold_cnt);
		addr = (uintptr_t)uio_clone->uio_iov->iov_base;
		end = round_page(addr + len);
		if (end < addr) {
			error = EFAULT;
			break;
		}
		cnt = atop(end - trunc_page(addr));
		/*
		 * A perfectly misaligned address and length could cause
		 * both the start and the end of the chunk to use partial
		 * page.  +2 accounts for such a situation.
		 */
		cnt = vm_fault_quick_hold_pages(&td->td_proc->p_vmspace->vm_map,
		    addr, len, prot, ma, io_hold_cnt + 2);
		if (cnt == -1) {
			error = EFAULT;
			break;
		}
		short_uio.uio_iov = &short_iovec[0];
		short_iovec[0].iov_base = (void *)addr;
		short_uio.uio_iovcnt = 1;
		short_uio.uio_resid = short_iovec[0].iov_len = len;
		short_uio.uio_offset = uio_clone->uio_offset;
		td->td_ma = ma;
		td->td_ma_cnt = cnt;

		error = vn_io_fault_doio(args, &short_uio, td);
		vm_page_unhold_pages(ma, cnt);
		adv = len - short_uio.uio_resid;

		uio_clone->uio_iov->iov_base =
		    (char *)uio_clone->uio_iov->iov_base + adv;
		uio_clone->uio_iov->iov_len -= adv;
		uio_clone->uio_resid -= adv;
		uio_clone->uio_offset += adv;

		uio->uio_resid -= adv;
		uio->uio_offset += adv;

		if (error != 0 || adv == 0)
			break;
	}
	td->td_ma = prev_td_ma;
	td->td_ma_cnt = prev_td_ma_cnt;
	curthread_pflags_restore(saveheld);
out:
	free(uio_clone, M_IOV);
	return (error);
}

static int
vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred,
    int flags, struct thread *td)
{
	fo_rdwr_t *doio;
	struct vnode *vp;
	void *rl_cookie;
	struct vn_io_fault_args args;
	int error;

	doio = uio->uio_rw == UIO_READ ? vn_read : vn_write;
	vp = fp->f_vnode;

	/*
	 * The ability to read(2) on a directory has historically been
	 * allowed for all users, but this can and has been the source of
	 * at least one security issue in the past.  As such, it is now hidden
	 * away behind a sysctl for those that actually need it to use it, and
	 * restricted to root when it's turned on to make it relatively safe to
	 * leave on for longer sessions of need.
	 */
	if (vp->v_type == VDIR) {
		KASSERT(uio->uio_rw == UIO_READ,
		    ("illegal write attempted on a directory"));
		if (!vfs_allow_read_dir)
			return (EISDIR);
		if ((error = priv_check(td, PRIV_VFS_READ_DIR)) != 0)
			return (EISDIR);
	}

	foffset_lock_uio(fp, uio, flags);
	if (do_vn_io_fault(vp, uio)) {
		args.kind = VN_IO_FAULT_FOP;
		args.args.fop_args.fp = fp;
		args.args.fop_args.doio = doio;
		args.cred = active_cred;
		args.flags = flags | FOF_OFFSET;
		if (uio->uio_rw == UIO_READ) {
			rl_cookie = vn_rangelock_rlock(vp, uio->uio_offset,
			    uio->uio_offset + uio->uio_resid);
		} else if ((fp->f_flag & O_APPEND) != 0 ||
		    (flags & FOF_OFFSET) == 0) {
			/* For appenders, punt and lock the whole range. */
			rl_cookie = vn_rangelock_wlock(vp, 0, OFF_MAX);
		} else {
			rl_cookie = vn_rangelock_wlock(vp, uio->uio_offset,
			    uio->uio_offset + uio->uio_resid);
		}
		error = vn_io_fault1(vp, uio, &args, td);
		vn_rangelock_unlock(vp, rl_cookie);
	} else {
		error = doio(fp, uio, active_cred, flags | FOF_OFFSET, td);
	}
	foffset_unlock_uio(fp, uio, flags);
	return (error);
}

/*
 * Helper function to perform the requested uiomove operation using
 * the held pages for io->uio_iov[0].iov_base buffer instead of
 * copyin/copyout.  Access to the pages with uiomove_fromphys()
 * instead of iov_base prevents page faults that could occur due to
 * pmap_collect() invalidating the mapping created by
 * vm_fault_quick_hold_pages(), or pageout daemon, page laundry or
 * object cleanup revoking the write access from page mappings.
 *
 * Filesystems specified MNTK_NO_IOPF shall use vn_io_fault_uiomove()
 * instead of plain uiomove().
 */
int
vn_io_fault_uiomove(char *data, int xfersize, struct uio *uio)
{
	struct uio transp_uio;
	struct iovec transp_iov[1];
	struct thread *td;
	size_t adv;
	int error, pgadv;

	td = curthread;
	if ((td->td_pflags & TDP_UIOHELD) == 0 ||
	    uio->uio_segflg != UIO_USERSPACE)
		return (uiomove(data, xfersize, uio));

	KASSERT(uio->uio_iovcnt == 1, ("uio_iovcnt %d", uio->uio_iovcnt));
	transp_iov[0].iov_base = data;
	transp_uio.uio_iov = &transp_iov[0];
	transp_uio.uio_iovcnt = 1;
	if (xfersize > uio->uio_resid)
		xfersize = uio->uio_resid;
	transp_uio.uio_resid = transp_iov[0].iov_len = xfersize;
	transp_uio.uio_offset = 0;
	transp_uio.uio_segflg = UIO_SYSSPACE;
	/*
	 * Since transp_iov points to data, and td_ma page array
	 * corresponds to original uio->uio_iov, we need to invert the
	 * direction of the i/o operation as passed to
	 * uiomove_fromphys().
	 */
	switch (uio->uio_rw) {
	case UIO_WRITE:
		transp_uio.uio_rw = UIO_READ;
		break;
	case UIO_READ:
		transp_uio.uio_rw = UIO_WRITE;
		break;
	}
	transp_uio.uio_td = uio->uio_td;
	error = uiomove_fromphys(td->td_ma,
	    ((vm_offset_t)uio->uio_iov->iov_base) & PAGE_MASK,
	    xfersize, &transp_uio);
	adv = xfersize - transp_uio.uio_resid;
	pgadv =
	    (((vm_offset_t)uio->uio_iov->iov_base + adv) >> PAGE_SHIFT) -
	    (((vm_offset_t)uio->uio_iov->iov_base) >> PAGE_SHIFT);
	td->td_ma += pgadv;
	KASSERT(td->td_ma_cnt >= pgadv, ("consumed pages %d %d", td->td_ma_cnt,
	    pgadv));
	td->td_ma_cnt -= pgadv;
	uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + adv;
	uio->uio_iov->iov_len -= adv;
	uio->uio_resid -= adv;
	uio->uio_offset += adv;
	return (error);
}

int
vn_io_fault_pgmove(vm_page_t ma[], vm_offset_t offset, int xfersize,
    struct uio *uio)
{
	struct thread *td;
	vm_offset_t iov_base;
	int cnt, pgadv;

	td = curthread;
	if ((td->td_pflags & TDP_UIOHELD) == 0 ||
	    uio->uio_segflg != UIO_USERSPACE)
		return (uiomove_fromphys(ma, offset, xfersize, uio));

	KASSERT(uio->uio_iovcnt == 1, ("uio_iovcnt %d", uio->uio_iovcnt));
	cnt = xfersize > uio->uio_resid ? uio->uio_resid : xfersize;
	iov_base = (vm_offset_t)uio->uio_iov->iov_base;
	switch (uio->uio_rw) {
	case UIO_WRITE:
		pmap_copy_pages(td->td_ma, iov_base & PAGE_MASK, ma,
		    offset, cnt);
		break;
	case UIO_READ:
		pmap_copy_pages(ma, offset, td->td_ma, iov_base & PAGE_MASK,
		    cnt);
		break;
	}
	pgadv = ((iov_base + cnt) >> PAGE_SHIFT) - (iov_base >> PAGE_SHIFT);
	td->td_ma += pgadv;
	KASSERT(td->td_ma_cnt >= pgadv, ("consumed pages %d %d", td->td_ma_cnt,
	    pgadv));
	td->td_ma_cnt -= pgadv;
	uio->uio_iov->iov_base = (char *)(iov_base + cnt);
	uio->uio_iov->iov_len -= cnt;
	uio->uio_resid -= cnt;
	uio->uio_offset += cnt;
	return (0);
}

/*
 * File table truncate routine.
 */
static int
vn_truncate(struct file *fp, off_t length, struct ucred *active_cred,
    struct thread *td)
{
	struct mount *mp;
	struct vnode *vp;
	void *rl_cookie;
	int error;

	vp = fp->f_vnode;

retry:
	/*
	 * Lock the whole range for truncation.  Otherwise split i/o
	 * might happen partly before and partly after the truncation.
	 */
	rl_cookie = vn_rangelock_wlock(vp, 0, OFF_MAX);
	error = vn_start_write(vp, &mp, V_WAIT | PCATCH);
	if (error)
		goto out1;
	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	AUDIT_ARG_VNODE1(vp);
	if (vp->v_type == VDIR) {
		error = EISDIR;
		goto out;
	}
#ifdef MAC
	error = mac_vnode_check_write(active_cred, fp->f_cred, vp);
	if (error)
		goto out;
#endif
	error = vn_truncate_locked(vp, length, (fp->f_flag & O_FSYNC) != 0,
	    fp->f_cred);
out:
	VOP_UNLOCK(vp);
	vn_finished_write(mp);
out1:
	vn_rangelock_unlock(vp, rl_cookie);
	if (error == ERELOOKUP)
		goto retry;
	return (error);
}

/*
 * Truncate a file that is already locked.
 */
int
vn_truncate_locked(struct vnode *vp, off_t length, bool sync,
    struct ucred *cred)
{
	struct vattr vattr;
	int error;

	error = VOP_ADD_WRITECOUNT(vp, 1);
	if (error == 0) {
		VATTR_NULL(&vattr);
		vattr.va_size = length;
		if (sync)
			vattr.va_vaflags |= VA_SYNC;
		error = VOP_SETATTR(vp, &vattr, cred);
		VOP_ADD_WRITECOUNT_CHECKED(vp, -1);
	}
	return (error);
}

/*
 * File table vnode stat routine.
 */
static int
vn_statfile(struct file *fp, struct stat *sb, struct ucred *active_cred,
    struct thread *td)
{
	struct vnode *vp = fp->f_vnode;
	int error;

	vn_lock(vp, LK_SHARED | LK_RETRY);
	error = VOP_STAT(vp, sb, active_cred, fp->f_cred, td);
	VOP_UNLOCK(vp);

	return (error);
}

/*
 * File table vnode ioctl routine.
 */
static int
vn_ioctl(struct file *fp, u_long com, void *data, struct ucred *active_cred,
    struct thread *td)
{
	struct vattr vattr;
	struct vnode *vp;
	struct fiobmap2_arg *bmarg;
	int error;

	vp = fp->f_vnode;
	switch (vp->v_type) {
	case VDIR:
	case VREG:
		switch (com) {
		case FIONREAD:
			vn_lock(vp, LK_SHARED | LK_RETRY);
			error = VOP_GETATTR(vp, &vattr, active_cred);
			VOP_UNLOCK(vp);
			if (error == 0)
				*(int *)data = vattr.va_size - fp->f_offset;
			return (error);
		case FIOBMAP2:
			bmarg = (struct fiobmap2_arg *)data;
			vn_lock(vp, LK_SHARED | LK_RETRY);
#ifdef MAC
			error = mac_vnode_check_read(active_cred, fp->f_cred,
			    vp);
			if (error == 0)
#endif
				error = VOP_BMAP(vp, bmarg->bn, NULL,
				    &bmarg->bn, &bmarg->runp, &bmarg->runb);
			VOP_UNLOCK(vp);
			return (error);
		case FIONBIO:
		case FIOASYNC:
			return (0);
		default:
			return (VOP_IOCTL(vp, com, data, fp->f_flag,
			    active_cred, td));
		}
		break;
	case VCHR:
		return (VOP_IOCTL(vp, com, data, fp->f_flag,
		    active_cred, td));
	default:
		return (ENOTTY);
	}
}

/*
 * File table vnode poll routine.
 */
static int
vn_poll(struct file *fp, int events, struct ucred *active_cred,
    struct thread *td)
{
	struct vnode *vp;
	int error;

	vp = fp->f_vnode;
#if defined(MAC) || defined(AUDIT)
	if (AUDITING_TD(td) || mac_vnode_check_poll_enabled()) {
		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
		AUDIT_ARG_VNODE1(vp);
		error = mac_vnode_check_poll(active_cred, fp->f_cred, vp);
		VOP_UNLOCK(vp);
		if (error != 0)
			return (error);
	}
#endif
	error = VOP_POLL(vp, events, fp->f_cred, td);
	return (error);
}

/*
 * Acquire the requested lock and then check for validity.  LK_RETRY
 * permits vn_lock to return doomed vnodes.
 */
static int __noinline
_vn_lock_fallback(struct vnode *vp, int flags, const char *file, int line,
    int error)
{

	KASSERT((flags & LK_RETRY) == 0 || error == 0,
	    ("vn_lock: error %d incompatible with flags %#x", error, flags));

	if (error == 0)
		VNASSERT(VN_IS_DOOMED(vp), vp, ("vnode not doomed"));

	if ((flags & LK_RETRY) == 0) {
		if (error == 0) {
			VOP_UNLOCK(vp);
			error = ENOENT;
		}
		return (error);
	}

	/*
	 * LK_RETRY case.
	 *
	 * Nothing to do if we got the lock.
	 */
	if (error == 0)
		return (0);

	/*
	 * Interlock was dropped by the call in _vn_lock.
	 */
	flags &= ~LK_INTERLOCK;
	do {
		error = VOP_LOCK1(vp, flags, file, line);
	} while (error != 0);
	return (0);
}

int
_vn_lock(struct vnode *vp, int flags, const char *file, int line)
{
	int error;

	VNASSERT((flags & LK_TYPE_MASK) != 0, vp,
	    ("vn_lock: no locktype (%d passed)", flags));
	VNPASS(vp->v_holdcnt > 0, vp);
	error = VOP_LOCK1(vp, flags, file, line);
	if (__predict_false(error != 0 || VN_IS_DOOMED(vp)))
		return (_vn_lock_fallback(vp, flags, file, line, error));
	return (0);
}

/*
 * File table vnode close routine.
 */
static int
vn_closefile(struct file *fp, struct thread *td)
{
	struct vnode *vp;
	struct flock lf;
	int error;
	bool ref;

	vp = fp->f_vnode;
	fp->f_ops = &badfileops;
	ref= (fp->f_flag & FHASLOCK) != 0 && fp->f_type == DTYPE_VNODE;

	error = vn_close1(vp, fp->f_flag, fp->f_cred, td, ref);

	if (__predict_false(ref)) {
		lf.l_whence = SEEK_SET;
		lf.l_start = 0;
		lf.l_len = 0;
		lf.l_type = F_UNLCK;
		(void) VOP_ADVLOCK(vp, fp, F_UNLCK, &lf, F_FLOCK);
		vrele(vp);
	}
	return (error);
}

/*
 * Preparing to start a filesystem write operation. If the operation is
 * permitted, then we bump the count of operations in progress and
 * proceed. If a suspend request is in progress, we wait until the
 * suspension is over, and then proceed.
 */
static int
vn_start_write_refed(struct mount *mp, int flags, bool mplocked)
{
	struct mount_pcpu *mpcpu;
	int error, mflags;

	if (__predict_true(!mplocked) && (flags & V_XSLEEP) == 0 &&
	    vfs_op_thread_enter(mp, mpcpu)) {
		MPASS((mp->mnt_kern_flag & MNTK_SUSPEND) == 0);
		vfs_mp_count_add_pcpu(mpcpu, writeopcount, 1);
		vfs_op_thread_exit(mp, mpcpu);
		return (0);
	}

	if (mplocked)
		mtx_assert(MNT_MTX(mp), MA_OWNED);
	else
		MNT_ILOCK(mp);

	error = 0;

	/*
	 * Check on status of suspension.
	 */
	if ((curthread->td_pflags & TDP_IGNSUSP) == 0 ||
	    mp->mnt_susp_owner != curthread) {
		mflags = ((mp->mnt_vfc->vfc_flags & VFCF_SBDRY) != 0 ?
		    (flags & PCATCH) : 0) | (PUSER - 1);
		while ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0) {
			if (flags & V_NOWAIT) {
				error = EWOULDBLOCK;
				goto unlock;
			}
			error = msleep(&mp->mnt_flag, MNT_MTX(mp), mflags,
			    "suspfs", 0);
			if (error)
				goto unlock;
		}
	}
	if (flags & V_XSLEEP)
		goto unlock;
	mp->mnt_writeopcount++;
unlock:
	if (error != 0 || (flags & V_XSLEEP) != 0)
		MNT_REL(mp);
	MNT_IUNLOCK(mp);
	return (error);
}

int
vn_start_write(struct vnode *vp, struct mount **mpp, int flags)
{
	struct mount *mp;
	int error;

	KASSERT((flags & V_MNTREF) == 0 || (*mpp != NULL && vp == NULL),
	    ("V_MNTREF requires mp"));

	error = 0;
	/*
	 * If a vnode is provided, get and return the mount point that
	 * to which it will write.
	 */
	if (vp != NULL) {
		if ((error = VOP_GETWRITEMOUNT(vp, mpp)) != 0) {
			*mpp = NULL;
			if (error != EOPNOTSUPP)
				return (error);
			return (0);
		}
	}
	if ((mp = *mpp) == NULL)
		return (0);

	/*
	 * VOP_GETWRITEMOUNT() returns with the mp refcount held through
	 * a vfs_ref().
	 * As long as a vnode is not provided we need to acquire a
	 * refcount for the provided mountpoint too, in order to
	 * emulate a vfs_ref().
	 */
	if (vp == NULL && (flags & V_MNTREF) == 0)
		vfs_ref(mp);

	return (vn_start_write_refed(mp, flags, false));
}

/*
 * Secondary suspension. Used by operations such as vop_inactive
 * routines that are needed by the higher level functions. These
 * are allowed to proceed until all the higher level functions have
 * completed (indicated by mnt_writeopcount dropping to zero). At that
 * time, these operations are halted until the suspension is over.
 */
int
vn_start_secondary_write(struct vnode *vp, struct mount **mpp, int flags)
{
	struct mount *mp;
	int error;

	KASSERT((flags & V_MNTREF) == 0 || (*mpp != NULL && vp == NULL),
	    ("V_MNTREF requires mp"));

 retry:
	if (vp != NULL) {
		if ((error = VOP_GETWRITEMOUNT(vp, mpp)) != 0) {
			*mpp = NULL;
			if (error != EOPNOTSUPP)
				return (error);
			return (0);
		}
	}
	/*
	 * If we are not suspended or have not yet reached suspended
	 * mode, then let the operation proceed.
	 */
	if ((mp = *mpp) == NULL)
		return (0);

	/*
	 * VOP_GETWRITEMOUNT() returns with the mp refcount held through
	 * a vfs_ref().
	 * As long as a vnode is not provided we need to acquire a
	 * refcount for the provided mountpoint too, in order to
	 * emulate a vfs_ref().
	 */
	MNT_ILOCK(mp);
	if (vp == NULL && (flags & V_MNTREF) == 0)
		MNT_REF(mp);
	if ((mp->mnt_kern_flag & (MNTK_SUSPENDED | MNTK_SUSPEND2)) == 0) {
		mp->mnt_secondary_writes++;
		mp->mnt_secondary_accwrites++;
		MNT_IUNLOCK(mp);
		return (0);
	}
	if (flags & V_NOWAIT) {
		MNT_REL(mp);
		MNT_IUNLOCK(mp);
		return (EWOULDBLOCK);
	}
	/*
	 * Wait for the suspension to finish.
	 */
	error = msleep(&mp->mnt_flag, MNT_MTX(mp), (PUSER - 1) | PDROP |
	    ((mp->mnt_vfc->vfc_flags & VFCF_SBDRY) != 0 ? (flags & PCATCH) : 0),
	    "suspfs", 0);
	vfs_rel(mp);
	if (error == 0)
		goto retry;
	return (error);
}

/*
 * Filesystem write operation has completed. If we are suspending and this
 * operation is the last one, notify the suspender that the suspension is
 * now in effect.
 */
void
vn_finished_write(struct mount *mp)
{
	struct mount_pcpu *mpcpu;
	int c;

	if (mp == NULL)
		return;

	if (vfs_op_thread_enter(mp, mpcpu)) {
		vfs_mp_count_sub_pcpu(mpcpu, writeopcount, 1);
		vfs_mp_count_sub_pcpu(mpcpu, ref, 1);
		vfs_op_thread_exit(mp, mpcpu);
		return;
	}

	MNT_ILOCK(mp);
	vfs_assert_mount_counters(mp);
	MNT_REL(mp);
	c = --mp->mnt_writeopcount;
	if (mp->mnt_vfs_ops == 0) {
		MPASS((mp->mnt_kern_flag & MNTK_SUSPEND) == 0);
		MNT_IUNLOCK(mp);
		return;
	}
	if (c < 0)
		vfs_dump_mount_counters(mp);
	if ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0 && c == 0)
		wakeup(&mp->mnt_writeopcount);
	MNT_IUNLOCK(mp);
}

/*
 * Filesystem secondary write operation has completed. If we are
 * suspending and this operation is the last one, notify the suspender
 * that the suspension is now in effect.
 */
void
vn_finished_secondary_write(struct mount *mp)
{
	if (mp == NULL)
		return;
	MNT_ILOCK(mp);
	MNT_REL(mp);
	mp->mnt_secondary_writes--;
	if (mp->mnt_secondary_writes < 0)
		panic("vn_finished_secondary_write: neg cnt");
	if ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0 &&
	    mp->mnt_secondary_writes <= 0)
		wakeup(&mp->mnt_secondary_writes);
	MNT_IUNLOCK(mp);
}

/*
 * Request a filesystem to suspend write operations.
 */
int
vfs_write_suspend(struct mount *mp, int flags)
{
	int error;

	vfs_op_enter(mp);

	MNT_ILOCK(mp);
	vfs_assert_mount_counters(mp);
	if (mp->mnt_susp_owner == curthread) {
		vfs_op_exit_locked(mp);
		MNT_IUNLOCK(mp);
		return (EALREADY);
	}
	while (mp->mnt_kern_flag & MNTK_SUSPEND)
		msleep(&mp->mnt_flag, MNT_MTX(mp), PUSER - 1, "wsuspfs", 0);

	/*
	 * Unmount holds a write reference on the mount point.  If we
	 * own busy reference and drain for writers, we deadlock with
	 * the reference draining in the unmount path.  Callers of
	 * vfs_write_suspend() must specify VS_SKIP_UNMOUNT if
	 * vfs_busy() reference is owned and caller is not in the
	 * unmount context.
	 */
	if ((flags & VS_SKIP_UNMOUNT) != 0 &&
	    (mp->mnt_kern_flag & MNTK_UNMOUNT) != 0) {
		vfs_op_exit_locked(mp);
		MNT_IUNLOCK(mp);
		return (EBUSY);
	}

	mp->mnt_kern_flag |= MNTK_SUSPEND;
	mp->mnt_susp_owner = curthread;
	if (mp->mnt_writeopcount > 0)
		(void) msleep(&mp->mnt_writeopcount, 
		    MNT_MTX(mp), (PUSER - 1)|PDROP, "suspwt", 0);
	else
		MNT_IUNLOCK(mp);
	if ((error = VFS_SYNC(mp, MNT_SUSPEND)) != 0) {
		vfs_write_resume(mp, 0);
		/* vfs_write_resume does vfs_op_exit() for us */
	}
	return (error);
}

/*
 * Request a filesystem to resume write operations.
 */
void
vfs_write_resume(struct mount *mp, int flags)
{

	MNT_ILOCK(mp);
	if ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0) {
		KASSERT(mp->mnt_susp_owner == curthread, ("mnt_susp_owner"));
		mp->mnt_kern_flag &= ~(MNTK_SUSPEND | MNTK_SUSPEND2 |
				       MNTK_SUSPENDED);
		mp->mnt_susp_owner = NULL;
		wakeup(&mp->mnt_writeopcount);
		wakeup(&mp->mnt_flag);
		curthread->td_pflags &= ~TDP_IGNSUSP;
		if ((flags & VR_START_WRITE) != 0) {
			MNT_REF(mp);
			mp->mnt_writeopcount++;
		}
		MNT_IUNLOCK(mp);
		if ((flags & VR_NO_SUSPCLR) == 0)
			VFS_SUSP_CLEAN(mp);
		vfs_op_exit(mp);
	} else if ((flags & VR_START_WRITE) != 0) {
		MNT_REF(mp);
		vn_start_write_refed(mp, 0, true);
	} else {
		MNT_IUNLOCK(mp);
	}
}

/*
 * Helper loop around vfs_write_suspend() for filesystem unmount VFS
 * methods.
 */
int
vfs_write_suspend_umnt(struct mount *mp)
{
	int error;

	KASSERT((curthread->td_pflags & TDP_IGNSUSP) == 0,
	    ("vfs_write_suspend_umnt: recursed"));

	/* dounmount() already called vn_start_write(). */
	for (;;) {
		vn_finished_write(mp);
		error = vfs_write_suspend(mp, 0);
		if (error != 0) {
			vn_start_write(NULL, &mp, V_WAIT);
			return (error);
		}
		MNT_ILOCK(mp);
		if ((mp->mnt_kern_flag & MNTK_SUSPENDED) != 0)
			break;
		MNT_IUNLOCK(mp);
		vn_start_write(NULL, &mp, V_WAIT);
	}
	mp->mnt_kern_flag &= ~(MNTK_SUSPENDED | MNTK_SUSPEND2);
	wakeup(&mp->mnt_flag);
	MNT_IUNLOCK(mp);
	curthread->td_pflags |= TDP_IGNSUSP;
	return (0);
}

/*
 * Implement kqueues for files by translating it to vnode operation.
 */
static int
vn_kqfilter(struct file *fp, struct knote *kn)
{

	return (VOP_KQFILTER(fp->f_vnode, kn));
}

/*
 * Simplified in-kernel wrapper calls for extended attribute access.
 * Both calls pass in a NULL credential, authorizing as "kernel" access.
 * Set IO_NODELOCKED in ioflg if the vnode is already locked.
 */
int
vn_extattr_get(struct vnode *vp, int ioflg, int attrnamespace,
    const char *attrname, int *buflen, char *buf, struct thread *td)
{
	struct uio	auio;
	struct iovec	iov;
	int	error;

	iov.iov_len = *buflen;
	iov.iov_base = buf;

	auio.uio_iov = &iov;
	auio.uio_iovcnt = 1;
	auio.uio_rw = UIO_READ;
	auio.uio_segflg = UIO_SYSSPACE;
	auio.uio_td = td;
	auio.uio_offset = 0;
	auio.uio_resid = *buflen;

	if ((ioflg & IO_NODELOCKED) == 0)
		vn_lock(vp, LK_SHARED | LK_RETRY);

	ASSERT_VOP_LOCKED(vp, "IO_NODELOCKED with no vp lock held");

	/* authorize attribute retrieval as kernel */
	error = VOP_GETEXTATTR(vp, attrnamespace, attrname, &auio, NULL, NULL,
	    td);

	if ((ioflg & IO_NODELOCKED) == 0)
		VOP_UNLOCK(vp);

	if (error == 0) {
		*buflen = *buflen - auio.uio_resid;
	}

	return (error);
}

/*
 * XXX failure mode if partially written?
 */
int
vn_extattr_set(struct vnode *vp, int ioflg, int attrnamespace,
    const char *attrname, int buflen, char *buf, struct thread *td)
{
	struct uio	auio;
	struct iovec	iov;
	struct mount	*mp;
	int	error;

	iov.iov_len = buflen;
	iov.iov_base = buf;

	auio.uio_iov = &iov;
	auio.uio_iovcnt = 1;
	auio.uio_rw = UIO_WRITE;
	auio.uio_segflg = UIO_SYSSPACE;
	auio.uio_td = td;
	auio.uio_offset = 0;
	auio.uio_resid = buflen;

	if ((ioflg & IO_NODELOCKED) == 0) {
		if ((error = vn_start_write(vp, &mp, V_WAIT)) != 0)
			return (error);
		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	}

	ASSERT_VOP_LOCKED(vp, "IO_NODELOCKED with no vp lock held");

	/* authorize attribute setting as kernel */
	error = VOP_SETEXTATTR(vp, attrnamespace, attrname, &auio, NULL, td);

	if ((ioflg & IO_NODELOCKED) == 0) {
		vn_finished_write(mp);
		VOP_UNLOCK(vp);
	}

	return (error);
}

int
vn_extattr_rm(struct vnode *vp, int ioflg, int attrnamespace,
    const char *attrname, struct thread *td)
{
	struct mount	*mp;
	int	error;

	if ((ioflg & IO_NODELOCKED) == 0) {
		if ((error = vn_start_write(vp, &mp, V_WAIT)) != 0)
			return (error);
		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	}

	ASSERT_VOP_LOCKED(vp, "IO_NODELOCKED with no vp lock held");

	/* authorize attribute removal as kernel */
	error = VOP_DELETEEXTATTR(vp, attrnamespace, attrname, NULL, td);
	if (error == EOPNOTSUPP)
		error = VOP_SETEXTATTR(vp, attrnamespace, attrname, NULL,
		    NULL, td);

	if ((ioflg & IO_NODELOCKED) == 0) {
		vn_finished_write(mp);
		VOP_UNLOCK(vp);
	}

	return (error);
}

static int
vn_get_ino_alloc_vget(struct mount *mp, void *arg, int lkflags,
    struct vnode **rvp)
{

	return (VFS_VGET(mp, *(ino_t *)arg, lkflags, rvp));
}

int
vn_vget_ino(struct vnode *vp, ino_t ino, int lkflags, struct vnode **rvp)
{

	return (vn_vget_ino_gen(vp, vn_get_ino_alloc_vget, &ino,
	    lkflags, rvp));
}

int
vn_vget_ino_gen(struct vnode *vp, vn_get_ino_t alloc, void *alloc_arg,
    int lkflags, struct vnode **rvp)
{
	struct mount *mp;
	int ltype, error;

	ASSERT_VOP_LOCKED(vp, "vn_vget_ino_get");
	mp = vp->v_mount;
	ltype = VOP_ISLOCKED(vp);
	KASSERT(ltype == LK_EXCLUSIVE || ltype == LK_SHARED,
	    ("vn_vget_ino: vp not locked"));
	error = vfs_busy(mp, MBF_NOWAIT);
	if (error != 0) {
		vfs_ref(mp);
		VOP_UNLOCK(vp);
		error = vfs_busy(mp, 0);
		vn_lock(vp, ltype | LK_RETRY);
		vfs_rel(mp);
		if (error != 0)
			return (ENOENT);
		if (VN_IS_DOOMED(vp)) {
			vfs_unbusy(mp);
			return (ENOENT);
		}
	}
	VOP_UNLOCK(vp);
	error = alloc(mp, alloc_arg, lkflags, rvp);
	vfs_unbusy(mp);
	if (error != 0 || *rvp != vp)
		vn_lock(vp, ltype | LK_RETRY);
	if (VN_IS_DOOMED(vp)) {
		if (error == 0) {
			if (*rvp == vp)
				vunref(vp);
			else
				vput(*rvp);
		}
		error = ENOENT;
	}
	return (error);
}

int
vn_rlimit_fsize(const struct vnode *vp, const struct uio *uio,
    struct thread *td)
{

	if (vp->v_type != VREG || td == NULL)
		return (0);
	if ((uoff_t)uio->uio_offset + uio->uio_resid >
	    lim_cur(td, RLIMIT_FSIZE)) {
		PROC_LOCK(td->td_proc);
		kern_psignal(td->td_proc, SIGXFSZ);
		PROC_UNLOCK(td->td_proc);
		return (EFBIG);
	}
	return (0);
}

int
vn_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
    struct thread *td)
{
	struct vnode *vp;

	vp = fp->f_vnode;
#ifdef AUDIT
	vn_lock(vp, LK_SHARED | LK_RETRY);
	AUDIT_ARG_VNODE1(vp);
	VOP_UNLOCK(vp);
#endif
	return (setfmode(td, active_cred, vp, mode));
}

int
vn_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
    struct thread *td)
{
	struct vnode *vp;

	vp = fp->f_vnode;
#ifdef AUDIT
	vn_lock(vp, LK_SHARED | LK_RETRY);
	AUDIT_ARG_VNODE1(vp);
	VOP_UNLOCK(vp);
#endif
	return (setfown(td, active_cred, vp, uid, gid));
}

void
vn_pages_remove(struct vnode *vp, vm_pindex_t start, vm_pindex_t end)
{
	vm_object_t object;

	if ((object = vp->v_object) == NULL)
		return;
	VM_OBJECT_WLOCK(object);
	vm_object_page_remove(object, start, end, 0);
	VM_OBJECT_WUNLOCK(object);
}

int
vn_bmap_seekhole(struct vnode *vp, u_long cmd, off_t *off, struct ucred *cred)
{
	struct vattr va;
	daddr_t bn, bnp;
	uint64_t bsize;
	off_t noff;
	int error;

	KASSERT(cmd == FIOSEEKHOLE || cmd == FIOSEEKDATA,
	    ("Wrong command %lu", cmd));

	if (vn_lock(vp, LK_SHARED) != 0)
		return (EBADF);
	if (vp->v_type != VREG) {
		error = ENOTTY;
		goto unlock;
	}
	error = VOP_GETATTR(vp, &va, cred);
	if (error != 0)
		goto unlock;
	noff = *off;
	if (noff >= va.va_size) {
		error = ENXIO;
		goto unlock;
	}
	bsize = vp->v_mount->mnt_stat.f_iosize;
	for (bn = noff / bsize; noff < va.va_size; bn++, noff += bsize -
	    noff % bsize) {
		error = VOP_BMAP(vp, bn, NULL, &bnp, NULL, NULL);
		if (error == EOPNOTSUPP) {
			error = ENOTTY;
			goto unlock;
		}
		if ((bnp == -1 && cmd == FIOSEEKHOLE) ||
		    (bnp != -1 && cmd == FIOSEEKDATA)) {
			noff = bn * bsize;
			if (noff < *off)
				noff = *off;
			goto unlock;
		}
	}
	if (noff > va.va_size)
		noff = va.va_size;
	/* noff == va.va_size. There is an implicit hole at the end of file. */
	if (cmd == FIOSEEKDATA)
		error = ENXIO;
unlock:
	VOP_UNLOCK(vp);
	if (error == 0)
		*off = noff;
	return (error);
}

int
vn_seek(struct file *fp, off_t offset, int whence, struct thread *td)
{
	struct ucred *cred;
	struct vnode *vp;
	struct vattr vattr;
	off_t foffset, size;
	int error, noneg;

	cred = td->td_ucred;
	vp = fp->f_vnode;
	foffset = foffset_lock(fp, 0);
	noneg = (vp->v_type != VCHR);
	error = 0;
	switch (whence) {
	case L_INCR:
		if (noneg &&
		    (foffset < 0 ||
		    (offset > 0 && foffset > OFF_MAX - offset))) {
			error = EOVERFLOW;
			break;
		}
		offset += foffset;
		break;
	case L_XTND:
		vn_lock(vp, LK_SHARED | LK_RETRY);
		error = VOP_GETATTR(vp, &vattr, cred);
		VOP_UNLOCK(vp);
		if (error)
			break;

		/*
		 * If the file references a disk device, then fetch
		 * the media size and use that to determine the ending
		 * offset.
		 */
		if (vattr.va_size == 0 && vp->v_type == VCHR &&
		    fo_ioctl(fp, DIOCGMEDIASIZE, &size, cred, td) == 0)
			vattr.va_size = size;
		if (noneg &&
		    (vattr.va_size > OFF_MAX ||
		    (offset > 0 && vattr.va_size > OFF_MAX - offset))) {
			error = EOVERFLOW;
			break;
		}
		offset += vattr.va_size;
		break;
	case L_SET:
		break;
	case SEEK_DATA:
		error = fo_ioctl(fp, FIOSEEKDATA, &offset, cred, td);
		if (error == ENOTTY)
			error = EINVAL;
		break;
	case SEEK_HOLE:
		error = fo_ioctl(fp, FIOSEEKHOLE, &offset, cred, td);
		if (error == ENOTTY)
			error = EINVAL;
		break;
	default:
		error = EINVAL;
	}
	if (error == 0 && noneg && offset < 0)
		error = EINVAL;
	if (error != 0)
		goto drop;
	VFS_KNOTE_UNLOCKED(vp, 0);
	td->td_uretoff.tdu_off = offset;
drop:
	foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
	return (error);
}

int
vn_utimes_perm(struct vnode *vp, struct vattr *vap, struct ucred *cred,
    struct thread *td)
{
	int error;

	/*
	 * Grant permission if the caller is the owner of the file, or
	 * the super-user, or has ACL_WRITE_ATTRIBUTES permission on
	 * on the file.  If the time pointer is null, then write
	 * permission on the file is also sufficient.
	 *
	 * From NFSv4.1, draft 21, 6.2.1.3.1, Discussion of Mask Attributes:
	 * A user having ACL_WRITE_DATA or ACL_WRITE_ATTRIBUTES
	 * will be allowed to set the times [..] to the current
	 * server time.
	 */
	error = VOP_ACCESSX(vp, VWRITE_ATTRIBUTES, cred, td);
	if (error != 0 && (vap->va_vaflags & VA_UTIMES_NULL) != 0)
		error = VOP_ACCESS(vp, VWRITE, cred, td);
	return (error);
}

int
vn_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
{
	struct vnode *vp;
	int error;

	if (fp->f_type == DTYPE_FIFO)
		kif->kf_type = KF_TYPE_FIFO;
	else
		kif->kf_type = KF_TYPE_VNODE;
	vp = fp->f_vnode;
	vref(vp);
	FILEDESC_SUNLOCK(fdp);
	error = vn_fill_kinfo_vnode(vp, kif);
	vrele(vp);
	FILEDESC_SLOCK(fdp);
	return (error);
}

static inline void
vn_fill_junk(struct kinfo_file *kif)
{
	size_t len, olen;

	/*
	 * Simulate vn_fullpath returning changing values for a given
	 * vp during e.g. coredump.
	 */
	len = (arc4random() % (sizeof(kif->kf_path) - 2)) + 1;
	olen = strlen(kif->kf_path);
	if (len < olen)
		strcpy(&kif->kf_path[len - 1], "$");
	else
		for (; olen < len; olen++)
			strcpy(&kif->kf_path[olen], "A");
}

int
vn_fill_kinfo_vnode(struct vnode *vp, struct kinfo_file *kif)
{
	struct vattr va;
	char *fullpath, *freepath;
	int error;

	kif->kf_un.kf_file.kf_file_type = vntype_to_kinfo(vp->v_type);
	freepath = NULL;
	fullpath = "-";
	error = vn_fullpath(vp, &fullpath, &freepath);
	if (error == 0) {
		strlcpy(kif->kf_path, fullpath, sizeof(kif->kf_path));
	}
	if (freepath != NULL)
		free(freepath, M_TEMP);

	KFAIL_POINT_CODE(DEBUG_FP, fill_kinfo_vnode__random_path,
		vn_fill_junk(kif);
	);

	/*
	 * Retrieve vnode attributes.
	 */
	va.va_fsid = VNOVAL;
	va.va_rdev = NODEV;
	vn_lock(vp, LK_SHARED | LK_RETRY);
	error = VOP_GETATTR(vp, &va, curthread->td_ucred);
	VOP_UNLOCK(vp);
	if (error != 0)
		return (error);
	if (va.va_fsid != VNOVAL)
		kif->kf_un.kf_file.kf_file_fsid = va.va_fsid;
	else
		kif->kf_un.kf_file.kf_file_fsid =
		    vp->v_mount->mnt_stat.f_fsid.val[0];
	kif->kf_un.kf_file.kf_file_fsid_freebsd11 =
	    kif->kf_un.kf_file.kf_file_fsid; /* truncate */
	kif->kf_un.kf_file.kf_file_fileid = va.va_fileid;
	kif->kf_un.kf_file.kf_file_mode = MAKEIMODE(va.va_type, va.va_mode);
	kif->kf_un.kf_file.kf_file_size = va.va_size;
	kif->kf_un.kf_file.kf_file_rdev = va.va_rdev;
	kif->kf_un.kf_file.kf_file_rdev_freebsd11 =
	    kif->kf_un.kf_file.kf_file_rdev; /* truncate */
	return (0);
}

int
vn_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t size,
    vm_prot_t prot, vm_prot_t cap_maxprot, int flags, vm_ooffset_t foff,
    struct thread *td)
{
#ifdef HWPMC_HOOKS
	struct pmckern_map_in pkm;
#endif
	struct mount *mp;
	struct vnode *vp;
	vm_object_t object;
	vm_prot_t maxprot;
	boolean_t writecounted;
	int error;

#if defined(COMPAT_FREEBSD7) || defined(COMPAT_FREEBSD6) || \
    defined(COMPAT_FREEBSD5) || defined(COMPAT_FREEBSD4)
	/*
	 * POSIX shared-memory objects are defined to have
	 * kernel persistence, and are not defined to support
	 * read(2)/write(2) -- or even open(2).  Thus, we can
	 * use MAP_ASYNC to trade on-disk coherence for speed.
	 * The shm_open(3) library routine turns on the FPOSIXSHM
	 * flag to request this behavior.
	 */
	if ((fp->f_flag & FPOSIXSHM) != 0)
		flags |= MAP_NOSYNC;
#endif
	vp = fp->f_vnode;

	/*
	 * Ensure that file and memory protections are
	 * compatible.  Note that we only worry about
	 * writability if mapping is shared; in this case,
	 * current and max prot are dictated by the open file.
	 * XXX use the vnode instead?  Problem is: what
	 * credentials do we use for determination? What if
	 * proc does a setuid?
	 */
	mp = vp->v_mount;
	if (mp != NULL && (mp->mnt_flag & MNT_NOEXEC) != 0) {
		maxprot = VM_PROT_NONE;
		if ((prot & VM_PROT_EXECUTE) != 0)
			return (EACCES);
	} else
		maxprot = VM_PROT_EXECUTE;
	if ((fp->f_flag & FREAD) != 0)
		maxprot |= VM_PROT_READ;
	else if ((prot & VM_PROT_READ) != 0)
		return (EACCES);

	/*
	 * If we are sharing potential changes via MAP_SHARED and we
	 * are trying to get write permission although we opened it
	 * without asking for it, bail out.
	 */
	if ((flags & MAP_SHARED) != 0) {
		if ((fp->f_flag & FWRITE) != 0)
			maxprot |= VM_PROT_WRITE;
		else if ((prot & VM_PROT_WRITE) != 0)
			return (EACCES);
	} else {
		maxprot |= VM_PROT_WRITE;
		cap_maxprot |= VM_PROT_WRITE;
	}
	maxprot &= cap_maxprot;

	/*
	 * For regular files and shared memory, POSIX requires that
	 * the value of foff be a legitimate offset within the data
	 * object.  In particular, negative offsets are invalid.
	 * Blocking negative offsets and overflows here avoids
	 * possible wraparound or user-level access into reserved
	 * ranges of the data object later.  In contrast, POSIX does
	 * not dictate how offsets are used by device drivers, so in
	 * the case of a device mapping a negative offset is passed
	 * on.
	 */
	if (
#ifdef _LP64
	    size > OFF_MAX ||
#endif
	    foff > OFF_MAX - size)
		return (EINVAL);

	writecounted = FALSE;
	error = vm_mmap_vnode(td, size, prot, &maxprot, &flags, vp,
	    &foff, &object, &writecounted);
	if (error != 0)
		return (error);
	error = vm_mmap_object(map, addr, size, prot, maxprot, flags, object,
	    foff, writecounted, td);
	if (error != 0) {
		/*
		 * If this mapping was accounted for in the vnode's
		 * writecount, then undo that now.
		 */
		if (writecounted)
			vm_pager_release_writecount(object, 0, size);
		vm_object_deallocate(object);
	}
#ifdef HWPMC_HOOKS
	/* Inform hwpmc(4) if an executable is being mapped. */
	if (PMC_HOOK_INSTALLED(PMC_FN_MMAP)) {
		if ((prot & VM_PROT_EXECUTE) != 0 && error == 0) {
			pkm.pm_file = vp;
			pkm.pm_address = (uintptr_t) *addr;
			PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_MMAP, (void *) &pkm);
		}
	}
#endif
	return (error);
}

void
vn_fsid(struct vnode *vp, struct vattr *va)
{
	fsid_t *f;

	f = &vp->v_mount->mnt_stat.f_fsid;
	va->va_fsid = (uint32_t)f->val[1];
	va->va_fsid <<= sizeof(f->val[1]) * NBBY;
	va->va_fsid += (uint32_t)f->val[0];
}

int
vn_fsync_buf(struct vnode *vp, int waitfor)
{
	struct buf *bp, *nbp;
	struct bufobj *bo;
	struct mount *mp;
	int error, maxretry;

	error = 0;
	maxretry = 10000;     /* large, arbitrarily chosen */
	mp = NULL;
	if (vp->v_type == VCHR) {
		VI_LOCK(vp);
		mp = vp->v_rdev->si_mountpt;
		VI_UNLOCK(vp);
	}
	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 (waitfor != MNT_WAIT)
				continue;
			if (BUF_LOCK(bp,
			    LK_EXCLUSIVE | LK_INTERLOCK | LK_SLEEPFAIL,
			    BO_LOCKPTR(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);
		}
		if (maxretry < 1000)
			pause("dirty", hz < 1000 ? 1 : hz / 1000);
		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 (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)
					break;
			if ((mp != NULL && mp->mnt_secondary_writes > 0) ||
			    (error == 0 && --maxretry >= 0))
				goto loop1;
			if (error == 0)
				error = EAGAIN;
		}
	}
	BO_UNLOCK(bo);
	if (error != 0)
		vn_printf(vp, "fsync: giving up on dirty (error = %d) ", error);

	return (error);
}

/*
 * Copies a byte range from invp to outvp.  Calls VOP_COPY_FILE_RANGE()
 * or vn_generic_copy_file_range() after rangelocking the byte ranges,
 * to do the actual copy.
 * vn_generic_copy_file_range() is factored out, so it can be called
 * from a VOP_COPY_FILE_RANGE() call as well, but handles vnodes from
 * different file systems.
 */
int
vn_copy_file_range(struct vnode *invp, off_t *inoffp, struct vnode *outvp,
    off_t *outoffp, size_t *lenp, unsigned int flags, struct ucred *incred,
    struct ucred *outcred, struct thread *fsize_td)
{
	int error;
	size_t len;
	uint64_t uval;

	len = *lenp;
	*lenp = 0;		/* For error returns. */
	error = 0;

	/* Do some sanity checks on the arguments. */
	if (invp->v_type == VDIR || outvp->v_type == VDIR)
		error = EISDIR;
	else if (*inoffp < 0 || *outoffp < 0 ||
	    invp->v_type != VREG || outvp->v_type != VREG)
		error = EINVAL;
	if (error != 0)
		goto out;

	/* Ensure offset + len does not wrap around. */
	uval = *inoffp;
	uval += len;
	if (uval > INT64_MAX)
		len = INT64_MAX - *inoffp;
	uval = *outoffp;
	uval += len;
	if (uval > INT64_MAX)
		len = INT64_MAX - *outoffp;
	if (len == 0)
		goto out;

	/*
	 * If the two vnode are for the same file system, call
	 * VOP_COPY_FILE_RANGE(), otherwise call vn_generic_copy_file_range()
	 * which can handle copies across multiple file systems.
	 */
	*lenp = len;
	if (invp->v_mount == outvp->v_mount)
		error = VOP_COPY_FILE_RANGE(invp, inoffp, outvp, outoffp,
		    lenp, flags, incred, outcred, fsize_td);
	else
		error = vn_generic_copy_file_range(invp, inoffp, outvp,
		    outoffp, lenp, flags, incred, outcred, fsize_td);
out:
	return (error);
}

/*
 * Test len bytes of data starting at dat for all bytes == 0.
 * Return true if all bytes are zero, false otherwise.
 * Expects dat to be well aligned.
 */
static bool
mem_iszero(void *dat, int len)
{
	int i;
	const u_int *p;
	const char *cp;

	for (p = dat; len > 0; len -= sizeof(*p), p++) {
		if (len >= sizeof(*p)) {
			if (*p != 0)
				return (false);
		} else {
			cp = (const char *)p;
			for (i = 0; i < len; i++, cp++)
				if (*cp != '\0')
					return (false);
		}
	}
	return (true);
}

/*
 * Look for a hole in the output file and, if found, adjust *outoffp
 * and *xferp to skip past the hole.
 * *xferp is the entire hole length to be written and xfer2 is how many bytes
 * to be written as 0's upon return.
 */
static off_t
vn_skip_hole(struct vnode *outvp, off_t xfer2, off_t *outoffp, off_t *xferp,
    off_t *dataoffp, off_t *holeoffp, struct ucred *cred)
{
	int error;
	off_t delta;

	if (*holeoffp == 0 || *holeoffp <= *outoffp) {
		*dataoffp = *outoffp;
		error = VOP_IOCTL(outvp, FIOSEEKDATA, dataoffp, 0, cred,
		    curthread);
		if (error == 0) {
			*holeoffp = *dataoffp;
			error = VOP_IOCTL(outvp, FIOSEEKHOLE, holeoffp, 0, cred,
			    curthread);
		}
		if (error != 0 || *holeoffp == *dataoffp) {
			/*
			 * Since outvp is unlocked, it may be possible for
			 * another thread to do a truncate(), lseek(), write()
			 * creating a hole at startoff between the above
			 * VOP_IOCTL() calls, if the other thread does not do
			 * rangelocking.
			 * If that happens, *holeoffp == *dataoffp and finding
			 * the hole has failed, so disable vn_skip_hole().
			 */
			*holeoffp = -1;	/* Disable use of vn_skip_hole(). */
			return (xfer2);
		}
		KASSERT(*dataoffp >= *outoffp,
		    ("vn_skip_hole: dataoff=%jd < outoff=%jd",
		    (intmax_t)*dataoffp, (intmax_t)*outoffp));
		KASSERT(*holeoffp > *dataoffp,
		    ("vn_skip_hole: holeoff=%jd <= dataoff=%jd",
		    (intmax_t)*holeoffp, (intmax_t)*dataoffp));
	}

	/*
	 * If there is a hole before the data starts, advance *outoffp and
	 * *xferp past the hole.
	 */
	if (*dataoffp > *outoffp) {
		delta = *dataoffp - *outoffp;
		if (delta >= *xferp) {
			/* Entire *xferp is a hole. */
			*outoffp += *xferp;
			*xferp = 0;
			return (0);
		}
		*xferp -= delta;
		*outoffp += delta;
		xfer2 = MIN(xfer2, *xferp);
	}

	/*
	 * If a hole starts before the end of this xfer2, reduce this xfer2 so
	 * that the write ends at the start of the hole.
	 * *holeoffp should always be greater than *outoffp, but for the
	 * non-INVARIANTS case, check this to make sure xfer2 remains a sane
	 * value.
	 */
	if (*holeoffp > *outoffp && *holeoffp < *outoffp + xfer2)
		xfer2 = *holeoffp - *outoffp;
	return (xfer2);
}

/*
 * Write an xfer sized chunk to outvp in blksize blocks from dat.
 * dat is a maximum of blksize in length and can be written repeatedly in
 * the chunk.
 * If growfile == true, just grow the file via vn_truncate_locked() instead
 * of doing actual writes.
 * If checkhole == true, a hole is being punched, so skip over any hole
 * already in the output file.
 */
static int
vn_write_outvp(struct vnode *outvp, char *dat, off_t outoff, off_t xfer,
    u_long blksize, bool growfile, bool checkhole, struct ucred *cred)
{
	struct mount *mp;
	off_t dataoff, holeoff, xfer2;
	int error, lckf;

	/*
	 * Loop around doing writes of blksize until write has been completed.
	 * Lock/unlock on each loop iteration so that a bwillwrite() can be
	 * done for each iteration, since the xfer argument can be very
	 * large if there is a large hole to punch in the output file.
	 */
	error = 0;
	holeoff = 0;
	do {
		xfer2 = MIN(xfer, blksize);
		if (checkhole) {
			/*
			 * Punching a hole.  Skip writing if there is
			 * already a hole in the output file.
			 */
			xfer2 = vn_skip_hole(outvp, xfer2, &outoff, &xfer,
			    &dataoff, &holeoff, cred);
			if (xfer == 0)
				break;
			if (holeoff < 0)
				checkhole = false;
			KASSERT(xfer2 > 0, ("vn_write_outvp: xfer2=%jd",
			    (intmax_t)xfer2));
		}
		bwillwrite();
		mp = NULL;
		error = vn_start_write(outvp, &mp, V_WAIT);
		if (error != 0)
			break;
		if (growfile) {
			error = vn_lock(outvp, LK_EXCLUSIVE);
			if (error == 0) {
				error = vn_truncate_locked(outvp, outoff + xfer,
				    false, cred);
				VOP_UNLOCK(outvp);
			}
		} else {
			if (MNT_SHARED_WRITES(mp))
				lckf = LK_SHARED;
			else
				lckf = LK_EXCLUSIVE;
			error = vn_lock(outvp, lckf);
			if (error == 0) {
				error = vn_rdwr(UIO_WRITE, outvp, dat, xfer2,
				    outoff, UIO_SYSSPACE, IO_NODELOCKED,
				    curthread->td_ucred, cred, NULL, curthread);
				outoff += xfer2;
				xfer -= xfer2;
				VOP_UNLOCK(outvp);
			}
		}
		if (mp != NULL)
			vn_finished_write(mp);
	} while (!growfile && xfer > 0 && error == 0);
	return (error);
}

/*
 * Copy a byte range of one file to another.  This function can handle the
 * case where invp and outvp are on different file systems.
 * It can also be called by a VOP_COPY_FILE_RANGE() to do the work, if there
 * is no better file system specific way to do it.
 */
int
vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
    struct vnode *outvp, off_t *outoffp, size_t *lenp, unsigned int flags,
    struct ucred *incred, struct ucred *outcred, struct thread *fsize_td)
{
	struct vattr va;
	struct mount *mp;
	struct uio io;
	off_t startoff, endoff, xfer, xfer2;
	u_long blksize;
	int error, interrupted;
	bool cantseek, readzeros, eof, lastblock;
	ssize_t aresid;
	size_t copylen, len, rem, savlen;
	char *dat;
	long holein, holeout;

	holein = holeout = 0;
	savlen = len = *lenp;
	error = 0;
	interrupted = 0;
	dat = NULL;

	error = vn_lock(invp, LK_SHARED);
	if (error != 0)
		goto out;
	if (VOP_PATHCONF(invp, _PC_MIN_HOLE_SIZE, &holein) != 0)
		holein = 0;
	VOP_UNLOCK(invp);

	mp = NULL;
	error = vn_start_write(outvp, &mp, V_WAIT);
	if (error == 0)
		error = vn_lock(outvp, LK_EXCLUSIVE);
	if (error == 0) {
		/*
		 * If fsize_td != NULL, do a vn_rlimit_fsize() call,
		 * now that outvp is locked.
		 */
		if (fsize_td != NULL) {
			io.uio_offset = *outoffp;
			io.uio_resid = len;
			error = vn_rlimit_fsize(outvp, &io, fsize_td);
			if (error != 0)
				error = EFBIG;
		}
		if (VOP_PATHCONF(outvp, _PC_MIN_HOLE_SIZE, &holeout) != 0)
			holeout = 0;
		/*
		 * Holes that are past EOF do not need to be written as a block
		 * of zero bytes.  So, truncate the output file as far as
		 * possible and then use va.va_size to decide if writing 0
		 * bytes is necessary in the loop below.
		 */
		if (error == 0)
			error = VOP_GETATTR(outvp, &va, outcred);
		if (error == 0 && va.va_size > *outoffp && va.va_size <=
		    *outoffp + len) {
#ifdef MAC
			error = mac_vnode_check_write(curthread->td_ucred,
			    outcred, outvp);
			if (error == 0)
#endif
				error = vn_truncate_locked(outvp, *outoffp,
				    false, outcred);
			if (error == 0)
				va.va_size = *outoffp;
		}
		VOP_UNLOCK(outvp);
	}
	if (mp != NULL)
		vn_finished_write(mp);
	if (error != 0)
		goto out;

	/*
	 * Set the blksize to the larger of the hole sizes for invp and outvp.
	 * If hole sizes aren't available, set the blksize to the larger 
	 * f_iosize of invp and outvp.
	 * This code expects the hole sizes and f_iosizes to be powers of 2.
	 * This value is clipped at 4Kbytes and 1Mbyte.
	 */
	blksize = MAX(holein, holeout);

	/* Clip len to end at an exact multiple of hole size. */
	if (blksize > 1) {
		rem = *inoffp % blksize;
		if (rem > 0)
			rem = blksize - rem;
		if (len - rem > blksize)
			len = savlen = rounddown(len - rem, blksize) + rem;
	}

	if (blksize <= 1)
		blksize = MAX(invp->v_mount->mnt_stat.f_iosize,
		    outvp->v_mount->mnt_stat.f_iosize);
	if (blksize < 4096)
		blksize = 4096;
	else if (blksize > 1024 * 1024)
		blksize = 1024 * 1024;
	dat = malloc(blksize, M_TEMP, M_WAITOK);

	/*
	 * If VOP_IOCTL(FIOSEEKHOLE) works for invp, use it and FIOSEEKDATA
	 * to find holes.  Otherwise, just scan the read block for all 0s
	 * in the inner loop where the data copying is done.
	 * Note that some file systems such as NFSv3, NFSv4.0 and NFSv4.1 may
	 * support holes on the server, but do not support FIOSEEKHOLE.
	 */
	eof = false;
	while (len > 0 && error == 0 && !eof && interrupted == 0) {
		endoff = 0;			/* To shut up compilers. */
		cantseek = true;
		startoff = *inoffp;
		copylen = len;

		/*
		 * Find the next data area.  If there is just a hole to EOF,
		 * FIOSEEKDATA should fail and then we drop down into the
		 * inner loop and create the hole on the outvp file.
		 * (I do not know if any file system will report a hole to
		 *  EOF via FIOSEEKHOLE, but I am pretty sure FIOSEEKDATA
		 *  will fail for those file systems.)
		 *
		 * For input files that don't support FIOSEEKDATA/FIOSEEKHOLE,
		 * the code just falls through to the inner copy loop.
		 */
		error = EINVAL;
		if (holein > 0)
			error = VOP_IOCTL(invp, FIOSEEKDATA, &startoff, 0,
			    incred, curthread);
		if (error == 0) {
			endoff = startoff;
			error = VOP_IOCTL(invp, FIOSEEKHOLE, &endoff, 0,
			    incred, curthread);
			/*
			 * Since invp is unlocked, it may be possible for
			 * another thread to do a truncate(), lseek(), write()
			 * creating a hole at startoff between the above
			 * VOP_IOCTL() calls, if the other thread does not do
			 * rangelocking.
			 * If that happens, startoff == endoff and finding
			 * the hole has failed, so set an error.
			 */
			if (error == 0 && startoff == endoff)
				error = EINVAL; /* Any error. Reset to 0. */
		}
		if (error == 0) {
			if (startoff > *inoffp) {
				/* Found hole before data block. */
				xfer = MIN(startoff - *inoffp, len);
				if (*outoffp < va.va_size) {
					/* Must write 0s to punch hole. */
					xfer2 = MIN(va.va_size - *outoffp,
					    xfer);
					memset(dat, 0, MIN(xfer2, blksize));
					error = vn_write_outvp(outvp, dat,
					    *outoffp, xfer2, blksize, false,
					    holeout > 0, outcred);
				}

				if (error == 0 && *outoffp + xfer >
				    va.va_size && xfer == len)
					/* Grow last block. */
					error = vn_write_outvp(outvp, dat,
					    *outoffp, xfer, blksize, true,
					    false, outcred);
				if (error == 0) {
					*inoffp += xfer;
					*outoffp += xfer;
					len -= xfer;
					if (len < savlen)
						interrupted = sig_intr();
				}
			}
			copylen = MIN(len, endoff - startoff);
			cantseek = false;
		} else {
			cantseek = true;
			startoff = *inoffp;
			copylen = len;
			error = 0;
		}

		xfer = blksize;
		if (cantseek) {
			/*
			 * Set first xfer to end at a block boundary, so that
			 * holes are more likely detected in the loop below via
			 * the for all bytes 0 method.
			 */
			xfer -= (*inoffp % blksize);
		}
		/* Loop copying the data block. */
		while (copylen > 0 && error == 0 && !eof && interrupted == 0) {
			if (copylen < xfer)
				xfer = copylen;
			error = vn_lock(invp, LK_SHARED);
			if (error != 0)
				goto out;
			error = vn_rdwr(UIO_READ, invp, dat, xfer,
			    startoff, UIO_SYSSPACE, IO_NODELOCKED,
			    curthread->td_ucred, incred, &aresid,
			    curthread);
			VOP_UNLOCK(invp);
			lastblock = false;
			if (error == 0 && aresid > 0) {
				/* Stop the copy at EOF on the input file. */
				xfer -= aresid;
				eof = true;
				lastblock = true;
			}
			if (error == 0) {
				/*
				 * Skip the write for holes past the initial EOF
				 * of the output file, unless this is the last
				 * write of the output file at EOF.
				 */
				readzeros = cantseek ? mem_iszero(dat, xfer) :
				    false;
				if (xfer == len)
					lastblock = true;
				if (!cantseek || *outoffp < va.va_size ||
				    lastblock || !readzeros)
					error = vn_write_outvp(outvp, dat,
					    *outoffp, xfer, blksize,
					    readzeros && lastblock &&
					    *outoffp >= va.va_size, false,
					    outcred);
				if (error == 0) {
					*inoffp += xfer;
					startoff += xfer;
					*outoffp += xfer;
					copylen -= xfer;
					len -= xfer;
					if (len < savlen)
						interrupted = sig_intr();
				}
			}
			xfer = blksize;
		}
	}
out:
	*lenp = savlen - len;
	free(dat, M_TEMP);
	return (error);
}

static int
vn_fallocate(struct file *fp, off_t offset, off_t len, struct thread *td)
{
	struct mount *mp;
	struct vnode *vp;
	off_t olen, ooffset;
	int error;
#ifdef AUDIT
	int audited_vnode1 = 0;
#endif

	vp = fp->f_vnode;
	if (vp->v_type != VREG)
		return (ENODEV);

	/* Allocating blocks may take a long time, so iterate. */
	for (;;) {
		olen = len;
		ooffset = offset;

		bwillwrite();
		mp = NULL;
		error = vn_start_write(vp, &mp, V_WAIT | PCATCH);
		if (error != 0)
			break;
		error = vn_lock(vp, LK_EXCLUSIVE);
		if (error != 0) {
			vn_finished_write(mp);
			break;
		}
#ifdef AUDIT
		if (!audited_vnode1) {
			AUDIT_ARG_VNODE1(vp);
			audited_vnode1 = 1;
		}
#endif
#ifdef MAC
		error = mac_vnode_check_write(td->td_ucred, fp->f_cred, vp);
		if (error == 0)
#endif
			error = VOP_ALLOCATE(vp, &offset, &len);
		VOP_UNLOCK(vp);
		vn_finished_write(mp);

		if (olen + ooffset != offset + len) {
			panic("offset + len changed from %jx/%jx to %jx/%jx",
			    ooffset, olen, offset, len);
		}
		if (error != 0 || len == 0)
			break;
		KASSERT(olen > len, ("Iteration did not make progress?"));
		maybe_yield();
	}

	return (error);
}

static u_long vn_lock_pair_pause_cnt;
SYSCTL_ULONG(_debug, OID_AUTO, vn_lock_pair_pause, CTLFLAG_RD,
    &vn_lock_pair_pause_cnt, 0,
    "Count of vn_lock_pair deadlocks");

u_int vn_lock_pair_pause_max;
SYSCTL_UINT(_debug, OID_AUTO, vn_lock_pair_pause_max, CTLFLAG_RW,
    &vn_lock_pair_pause_max, 0,
    "Max ticks for vn_lock_pair deadlock avoidance sleep");

static void
vn_lock_pair_pause(const char *wmesg)
{
	atomic_add_long(&vn_lock_pair_pause_cnt, 1);
	pause(wmesg, prng32_bounded(vn_lock_pair_pause_max));
}

/*
 * Lock pair of vnodes vp1, vp2, avoiding lock order reversal.
 * vp1_locked indicates whether vp1 is exclusively locked; if not, vp1
 * must be unlocked.  Same for vp2 and vp2_locked.  One of the vnodes
 * can be NULL.
 *
 * The function returns with both vnodes exclusively locked, and
 * guarantees that it does not create lock order reversal with other
 * threads during its execution.  Both vnodes could be unlocked
 * temporary (and reclaimed).
 */
void
vn_lock_pair(struct vnode *vp1, bool vp1_locked, struct vnode *vp2,
    bool vp2_locked)
{
	int error;

	if (vp1 == NULL && vp2 == NULL)
		return;
	if (vp1 != NULL) {
		if (vp1_locked)
			ASSERT_VOP_ELOCKED(vp1, "vp1");
		else
			ASSERT_VOP_UNLOCKED(vp1, "vp1");
	} else {
		vp1_locked = true;
	}
	if (vp2 != NULL) {
		if (vp2_locked)
			ASSERT_VOP_ELOCKED(vp2, "vp2");
		else
			ASSERT_VOP_UNLOCKED(vp2, "vp2");
	} else {
		vp2_locked = true;
	}
	if (!vp1_locked && !vp2_locked) {
		vn_lock(vp1, LK_EXCLUSIVE | LK_RETRY);
		vp1_locked = true;
	}

	for (;;) {
		if (vp1_locked && vp2_locked)
			break;
		if (vp1_locked && vp2 != NULL) {
			if (vp1 != NULL) {
				error = VOP_LOCK1(vp2, LK_EXCLUSIVE | LK_NOWAIT,
				    __FILE__, __LINE__);
				if (error == 0)
					break;
				VOP_UNLOCK(vp1);
				vp1_locked = false;
				vn_lock_pair_pause("vlp1");
			}
			vn_lock(vp2, LK_EXCLUSIVE | LK_RETRY);
			vp2_locked = true;
		}
		if (vp2_locked && vp1 != NULL) {
			if (vp2 != NULL) {
				error = VOP_LOCK1(vp1, LK_EXCLUSIVE | LK_NOWAIT,
				    __FILE__, __LINE__);
				if (error == 0)
					break;
				VOP_UNLOCK(vp2);
				vp2_locked = false;
				vn_lock_pair_pause("vlp2");
			}
			vn_lock(vp1, LK_EXCLUSIVE | LK_RETRY);
			vp1_locked = true;
		}
	}
	if (vp1 != NULL)
		ASSERT_VOP_ELOCKED(vp1, "vp1 ret");
	if (vp2 != NULL)
		ASSERT_VOP_ELOCKED(vp2, "vp2 ret");
}