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.\" $FreeBSD: src/share/man/man9/VOP_FSYNC.9,v 1.6.2.2 2001/12/17 11:30:18 ru Exp $
.\"
.Dd September 14, 2021
.Dt VOP_FSYNC 9
.Os
.Sh NAME
.Nm VOP_FDATASYNC ,
.Nm VOP_FSYNC
.Nd flush filesystem buffers for a file
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fn VOP_FDATASYNC "struct vnode *vp" "int waitfor" "int flags"
.Ft int
.Fn VOP_FSYNC "struct vnode *vp" "int waitfor" "int flags"
.Sh DESCRIPTION
This call flushes any dirty filesystem buffers for the file.
It is used to implement the
.Xr sync 2
and
.Xr fsync 2
system calls.
.Pp
Its arguments are:
.Bl -tag -width waitfor
.It Ar vp
the vnode of the file.
.It Ar waitfor
whether the function should do data, meta-data updates or be full-synchronous.
.It Ar flags
are additional flags to be passed to the filesystem specific
.Xr fsync 2
function.
.El
.Pp
The argument
.Fa waitfor
can use the following flags:
.Bl -tag -width ".Dv MNT_NOWAIT"
.It Dv MNT_NOWAIT
is for an asynchronous data pass and a meta-data pass as well.
.It Dv MNT_LAZY
means a limited amount of data from dirty buffers and a full meta-data synchronization pass.
.It Dv MNT_WAIT
will make
.Xr syncer 4
try to do a full synchronization pass.
That is, a meta-data pass and multiple data passes.
.El
.Pp
The argument
.Fa flags
is to specify additional flags passed to the filesystem specific
.Xr fsync 2
call.
The only supported flag at the moment is
.Dv VOP_FSYNC_SYSCALL
which indicates the file synchronization was requested from userland.
.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 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 filesystem is full.
.It Bq Er EDQUOT
Quota exceeded.
.El
.Sh SEE ALSO
.Xr syncer 4 ,
.Xr vnode 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .