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.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (c) 1995 Michael Chastain (mec@shell.portal.com), 15 April 1995.
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.\" Modified Fri Jan 31 16:14:33 1997 by Eric S. Raymond <esr@thyrsus.com>
.\"
.TH BDFLUSH 2 "15 April 1995" "Linux 1.2.4" "Linux Programmer's Manual"
.SH NAME
bdflush \- start, flush, or tune buffer-dirty-flush daemon
.SH SYNOPSIS
.nf
.BI "int bdflush(int" " func, " "long *" "address);"
.BI "int bdflush(int" " func, " "long" " data);"
.fi
.SH DESCRIPTION
.B bdflush
starts, flushes, or tunes the buffer-dirty-flush daemon.
Only the super-user may call
.BR bdflush .
.PP
If
.I func
is negative or 0, and no daemon has been started, then
.B bdflush
enters the daemon code and never returns.
.PP
If
.I func
is 1,
some dirty buffers are written to disk.
.PP
If
.I func
is 2 or more and is even (low bit is 0), then
.I address
is the address of a long word,
and the tuning parameter numbered
.RI "(" "func" "\-2)/2"
is returned to the caller in that address.
.PP
If
.I func
is 3 or more and is odd (low bit is 1), then
.I data
is a long word,
and the kernel sets tuning parameter numbered
.RI "(" "func" "\-3)/2"
to that value.
.PP
The set of parameters, their values, and their legal ranges
are defined in the kernel source file
.IR fs/buffer.c .
.SH "RETURN VALUE"
If
.I func
is negative or 0 and the daemon successfully starts,
.B bdflush
never returns.
Otherwise, the return value is 0 on success and \-1 on failure, with
.I errno
set to indicate the error.
.SH ERRORS
.TP
.B EPERM
Caller is not super-user.
.TP
.B EFAULT
.I address
points outside your accessible address space.
.TP
.B EBUSY
An attempt was made to enter the daemon code after
another process has already entered.
.TP
.B EINVAL
An attempt was made to read or write an invalid parameter number,
or to write an invalid value to a parameter.
.SH "CONFORMING TO"
\fBbdflush\fP is Linux specific and should not be used in programs
intended to be portable.
.SH "SEE ALSO"
.BR fsync (2),
.BR sync (2),
.BR update (8),
.BR sync (8)
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