1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)msync.2 8.2 (Berkeley) 6/21/94 33.\" $FreeBSD$ 34.\" 35.Dd June 21, 1994 36.Dt MSYNC 2 37.Os 38.Sh NAME 39.Nm msync 40.Nd synchronize a mapped region 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In sys/mman.h 45.Ft int 46.Fn msync "void *addr" "size_t len" "int flags" 47.Sh DESCRIPTION 48The 49.Fn msync 50system call 51writes any modified pages back to the file system and updates 52the file modification time. 53If 54.Fa len 55is 0, all modified pages within the region containing 56.Fa addr 57will be flushed; 58if 59.Fa len 60is non-zero, only those pages containing 61.Fa addr 62and 63.Fa len-1 64succeeding locations will be examined. 65The 66.Fa flags 67argument may be specified as follows: 68.Pp 69.Bl -tag -width ".Dv MS_INVALIDATE" -compact 70.It Dv MS_ASYNC 71Return immediately 72.It Dv MS_SYNC 73Perform synchronous writes 74.It Dv MS_INVALIDATE 75Invalidate all cached data 76.El 77.Sh RETURN VALUES 78.Rv -std msync 79.Sh ERRORS 80The 81.Fn msync 82system call 83will fail if: 84.Bl -tag -width Er 85.It Bq Er EBUSY 86Some or all of the pages in the specified region are locked and 87.Dv MS_INVALIDATE 88is specified. 89.It Bq Er EINVAL 90The 91.Fa addr 92argument 93is not a multiple of the hardware page size. 94.It Bq Er EINVAL 95The 96.Fa len 97argument 98is too large or negative. 99.It Bq Er EINVAL 100The 101.Fa flags 102argument 103was both MS_ASYNC and MS_INVALIDATE. 104Only one of these flags is allowed. 105.El 106.Sh SEE ALSO 107.Xr madvise 2 , 108.Xr mincore 2 , 109.Xr mlock 2 , 110.Xr mprotect 2 , 111.Xr munmap 2 112.Sh HISTORY 113The 114.Fn msync 115system call first appeared in 116.Bx 4.4 . 117.Sh BUGS 118The 119.Fn msync 120system call is obsolete since 121.Bx 122implements a coherent file system buffer cache. 123However, it may be used to associate dirty VM pages with file system 124buffers and thus cause them to be flushed to physical media sooner 125rather than later. 126