d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Add fdatasync(2) man page, combined with fsync(2).

Browse Source 
Reviewed by:	emaste, rpokala, wblock
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D7522
This commit is contained in:
Konstantin Belousov 2016-08-17 10:16:42 +00:00
parent e2a18110f0
commit 174c072c00
2 changed files with 48 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
lib/libc/sys/Makefile.inc
View File

@ -366,6 +366,7 @@ MLINKS+=ffclock.2 ffclock_getcounter.2 \
ffclock.2 ffclock_getestimate.2 \
ffclock.2 ffclock_setestimate.2
MLINKS+=fhopen.2 fhstat.2 fhopen.2 fhstatfs.2
MLINKS+=fsync.2 fdatasync.2
MLINKS+=getdirentries.2 getdents.2
MLINKS+=getfh.2 lgetfh.2
MLINKS+=getgid.2 getegid.2

51
lib/libc/sys/fsync.2
View File

@ -1,5 +1,11 @@
.\" Copyright (c) 1983, 1993
.\" The Regents of the University of California. All rights reserved.
.\" Copyright (c) 2016 The FreeBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" Parts of this documentation were written by
.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
.\" from the FreeBSD Foundation.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
@ -28,40 +34,65 @@
.\" @(#)fsync.2 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd June 4, 1993
.Dd August 17, 2016
.Dt FSYNC 2
.Os
.Sh NAME
.Nm fsync
.Nm fdatasync, fsync
.Nd "synchronise changes to a file"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn fdatasync "int fd"
.Ft int
.Fn fsync "int fd"
.Sh DESCRIPTION
The
.Fn fsync
system call
causes all modified data and attributes of
causes all modified data and attributes of the file referenced by
the file descriptor
.Fa fd
to be moved to a permanent storage device.
This normally results in all in-core modified copies
of buffers for the associated file to be written to a disk.
.Pp
The
.Fn fdatasync
system call causes all modified data of
.Fa fd
to be moved to a permanent storage device.
Unlike
.Fn fsync ,
the system call does not guarantee that file attributes or
metadata necessary to access the file are committed to the permanent storage.
.Pp
The
.Fn fsync
system call
should be used by programs that require a file to be
in a known state, for example, in building a simple transaction
facility.
If the file metadata has already been committed, using
.Fn fdatasync
can be more efficient than
.Fn fsync .
.Pp
Both
.Fn fdatasync
and
.Fn fsync
calls are cancellation points.
.Sh RETURN VALUES
.Rv -std fsync
.Sh ERRORS
The
.Fn fsync
fails if:
and
.Fn fdatasync
calls fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
@ -85,3 +116,15 @@ The
.Fn fsync
system call appeared in
.Bx 4.2 .
The
.Fn fdatasync
system call appeared in
.Fx 12.0
.Sh BUGS
The
.Fn fdatasync
system call currently does not guarantee that enqueued
.Xr aio 4
requests for the file referenced by
.Fa fd
are completed before the syscall returns.