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VOP_FSYNC.9
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.\" -*- nroff -*-
.\"
.\" Copyright (c) 1996 Doug Rabson
.\"
.\" All rights reserved.
.\"
.\" Copyright (c) 2019 The FreeBSD Foundation
.\"
.\" Portions of this documentation were written by BFF Storage Systems under
.\" sponsorship from the FreeBSD Foundation.
.\"
.\" This program is free software.
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
.\"
.Dd March 22, 2019
.Dt VOP_FSYNC 9
.Os
.Sh NAME
.Nm VOP_FDATASYNC ,
.Nm VOP_FSYNC
.Nd flush file system buffers for a file
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fn VOP_FDATASYNC "struct vnode *vp" "struct thread *td"
.Ft int
.Fn VOP_FSYNC "struct vnode *vp" "int waitfor" "struct thread *td"
.Sh DESCRIPTION
.Fn VOP_FSYNC
ensures that a file can be recovered to its current state following a crash.
That typically requires flushing the file's dirty buffers, its inode, and
possibly other filesystem metadata to persistent media.
.Fn VOP_FSYNC
is used to implement the
.Xr sync 2
and
.Xr fsync 2
system calls.
.Pp
Its arguments are:
.Bl -tag -width waitfor
.It Fa vp
The vnode of the file.
.It Fa waitfor
Whether the function should wait for I/O to complete.
Possible values are:
.Bl -tag -width MNT_NOWAIT
.It Dv MNT_WAIT
Synchronously wait for I/O to complete.
.It Dv MNT_NOWAIT
Start all I/O, but do not wait for it.
.It Dv MNT_LAZY
Push data not written by file system syncer.
.El
.It Fa td
The calling thread.
.El
.Pp
.Fn VOP_FDATASYNC
is similar, but it does not require that all of the file's metadata be flushed.
It only requires that the file's data be recoverable after a crash.
That implies that the data itself must be flushed to disk, as well as some
metadata such as the file's size but not necessarily its attributes.
.Fn VOP_FDATASYNC
should always wait for I/O to complete, as if called with
.Dv MNT_WAIT .
.Fn VOP_FDATASYNC
is used to implement
.Xr fdatasync 2 .
.Sh LOCKS
The vnode should be exclusively locked on entry, and stays locked on return.
.Sh RETURN VALUES
Zero is returned if the call is successful, otherwise an appropriate
error code is returned.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ENOSPC
The file system is full.
.It Bq Er EDQUOT
Quota exceeded.
.El
.Sh SEE ALSO
.Xr vnode 9
.Sh AUTHORS
This manual page was written by
.An Doug Rabson .