Implement fdatasync() as a wrapper around fsync()

ok guenther, deraadt, jmc

4 files changed, 55 insertions, 12 deletions

diff --git a/lib/libc/gen/Makefile.inc b/lib/libc/gen/Makefile.inc
index 64d8df708c3..e39258c979b 100644
--- a/lib/libc/gen/Makefile.inc
+++ b/lib/libc/gen/Makefile.inc
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile.inc,v 1.58 2012/09/15 20:59:38 miod Exp $
+#	$OpenBSD: Makefile.inc,v 1.59 2013/04/15 16:38:21 matthew Exp $
 
 # gen sources
 .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/gen ${LIBCSRCDIR}/gen
@@ -6,7 +6,8 @@
 SRCS+=  alarm.c assert.c auth_subr.c authenticate.c \
         basename.c clock.c closedir.c confstr.c ctermid.c ctype_.c \
         daemon.c devname.c dirfd.c dirname.c disklabel.c elf_hash.c err.c \
-        errx.c errlist.c errno.c exec.c fnmatch.c fpclassify.c frexp.c \
+        errx.c errlist.c errno.c exec.c \
+        fdatasync.c fnmatch.c fpclassify.c frexp.c \
         fstab.c ftok.c fts.c ftw.c getbsize.c getcap.c getcwd.c \
         getdomainname.c getgrent.c getgrouplist.c gethostname.c \
         getloadavg.c getlogin.c getmntinfo.c getnetgrent.c getpagesize.c \
diff --git a/lib/libc/gen/fdatasync.c b/lib/libc/gen/fdatasync.c
new file mode 100644
index 00000000000..26612123a2c
--- /dev/null
+++ b/lib/libc/gen/fdatasync.c
@@ -0,0 +1,13 @@
+/*	$OpenBSD: fdatasync.c,v 1.1 2013/04/15 16:38:21 matthew Exp $ */
+/*
+ * Written by Matthew Dempsky, 2013.
+ * Public domain.
+ */
+
+#include <unistd.h>
+
+int
+fdatasync(int fd)
+{
+	return (fsync(fd));
+}
diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc
index 0bd51eecbc5..a22d4bf77e6 100644
--- a/lib/libc/sys/Makefile.inc
+++ b/lib/libc/sys/Makefile.inc
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile.inc,v 1.109 2013/02/03 10:38:40 miod Exp $
+#	$OpenBSD: Makefile.inc,v 1.110 2013/04/15 16:38:21 matthew Exp $
 #	$NetBSD: Makefile.inc,v 1.35 1995/10/16 23:49:07 jtc Exp $
 #	@(#)Makefile.inc	8.1 (Berkeley) 6/17/93
 
@@ -210,6 +210,7 @@ MLINKS+=clock_gettime.2 clock_settime.2
 MLINKS+=dup.2 dup2.2
 MLINKS+=execve.2 exect.2
 MLINKS+=fhopen.2 fhstat.2 fhopen.2 fhstatfs.2
+MLINKS+=fsync.2 fdatasync.2
 MLINKS+=getgid.2 getegid.2
 MLINKS+=getitimer.2 setitimer.2
 MLINKS+=getitimer.2 timeradd.3
diff --git a/lib/libc/sys/fsync.2 b/lib/libc/sys/fsync.2
index 166f852f7d6..1684c49dcfa 100644
--- a/lib/libc/sys/fsync.2
+++ b/lib/libc/sys/fsync.2
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: fsync.2,v 1.10 2013/03/31 22:11:26 guenther Exp $
+.\"	$OpenBSD: fsync.2,v 1.11 2013/04/15 16:38:21 matthew Exp $
 .\"	$NetBSD: fsync.2,v 1.4 1995/02/27 12:32:38 cgd Exp $
 .\"
 .\" Copyright (c) 1983, 1993
@@ -30,34 +30,50 @@
 .\"
 .\"     @(#)fsync.2	8.1 (Berkeley) 6/4/93
 .\"
-.Dd $Mdocdate: March 31 2013 $
+.Dd $Mdocdate: April 15 2013 $
 .Dt FSYNC 2
 .Os
 .Sh NAME
-.Nm fsync
+.Nm fsync ,
+.Nm fdatasync
 .Nd "synchronize a file's in-core state with that on disk"
 .Sh SYNOPSIS
 .Fd #include <unistd.h>
 .Ft int
 .Fn fsync "int fd"
+.Ft int
+.Fn fdatasync "int fd"
 .Sh DESCRIPTION
+The
 .Fn fsync
-causes all modified data and attributes of
+function causes all modified data and attributes of
 .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
+function is similar to
 .Fn fsync
+except that it only guarantees modified data
+.Pq and metadata necessary to read that data
+is committed to storage.
+Other file modifications may be left unsynchronized.
+.Pp
+.Fn fsync
+and
+.Fn fdatasync
 should be used by programs that require a file to be in a known state,
 for example, in building a simple transaction facility.
 .Sh RETURN VALUES
-A 0 value is returned on success.
-A \-1 value indicates an error.
+.Rv -std fsync fdatasync
 .Sh ERRORS
 The
 .Fn fsync
-fails if:
+and
+.Fn fdatasync
+functions fail if:
 .Bl -tag -width Er
 .It Bq Er EBADF
 .Fa fd
@@ -74,10 +90,22 @@ An I/O error occurred while reading from or writing to the file system.
 .Sh STANDARDS
 The
 .Fn fsync
-function conforms to
+and
+.Fn fdatasync
+functions conform to
 .St -p1003.1-2008 .
 .Sh HISTORY
 The
 .Fn fsync
-function call appeared in
+function appeared in
 .Bx 4.2 .
+The
+.Fn fdatasync
+function appeared in
+.Ox 5.4 .
+.Sh BUGS
+The
+.Fn fdatasync
+function is currently a wrapper around
+.Fn fsync ,
+so it synchronizes more state than necessary.