.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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.\" $FreeBSD$
.\"
.Dd July 8, 2001
.Dt VFS_BUSY 9
.Os
.Sh NAME
.Nm vfs_busy
.Nd "marks a mount point as busy"
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft int
.Fn vfs_busy "struct mount *mp" "int flags" "struct mtx *interlkp" "struct proc *p"
.Sh DESCRIPTION
The
.Fn vfs_busy
function marks a mount point as busy.
The purpose of this
function is to synchronize access to a mount point.
It also delays unmounting by sleeping on
.Fa mp
if the
.Dv MNTK_UNMOUNT
flag is set in
.Fa mp->mnt_kern_flag
and the
.Dv LK_NOWAIT
flag is
.Em not
set.
.Pp
Its arguments are:
.Bl -tag -width ".Fa interlkp"
.It Fa mp
The mount point to busy.
.It Fa flags
Flags controlling how
.Fn vfs_busy
should act.
.Bl -tag -width ".Dv LK_NOWAIT"
.It Dv LK_NOWAIT
do not sleep if
.Dv MNTK_UNMOUNT
is set.
.El
.It Fa interlkp
The interlock mutex for
.Fa mp->mount_lock .
If there is any chance
the mount point is being unmounted and
.Dv LK_NOWAIT
is not set then
interlock must be valid locked mutex.
.It Fa p
The process responsible for this call.
.El
.Sh LOCKS
If
.Fa interlkp
is a valid pointer it must be locked on entry,
and it will not be unlocked even in the case of an error.
.Sh RETURN VALUES
A 0 value is returned on success.
If the mount point is being
unmounted
.Er ENOENT
will always be returned.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ENOENT
The mount point is being unmounted
.Dv ( MNTK_UNMOUNT
is set).
.El
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .