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fdatasync: new module

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At least libvirt would like to use the lighter-weight fdatasync
on platforms where it is supported, while still guaranteeing full
sync (via the heavy-weight fsync fallback) on all platforms.

I've got an open question to the Austin Group, since the POSIX 2008
wording is self-contradictory (unlike fsync, fdatasync requires
EBADF on non-writable fds, but still mentions that read() errors
must be propagated).  I can see how fsync() would affect atime after
read() while fdatasync() can skip that, explaining why fdatasync()
might have the EBADF requirement, but on the other hand, that prevents
an implementation (like ours) where fdatasync is a straight alias of
fsync.  At any rate, glibc allows fdatasync on read-only fds.

* modules/fsync (Description): Document difference to fdatasync.
* modules/fdatasync: New module.
* m4/fdatasync.m4 (gl_FUNC_FDATASYNC): New file.
* lib/fdatasync.c (fdatasync): Likewise.
* m4/unistd_h.m4 (gl_UNISTD_H, gl_UNISTD_H_DEFAULTS): Set up
defaults.
* modules/unistd (Makefile.am): Set witnesses.
* lib/unistd.in.h (fdatasync): Declare.
* MODULES.html.sh: Document it.
* doc/posix-functions/fdatasync.texi (fdatasync): Likewise.
* modules/fdatasync-tests: New test.
* tests/test-fdatasync.c: Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eric Blake
2011-09-16 09:59:23 -06:00
parent 9a0a67e426
commit 64da7b6c00
12 changed files with 193 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
ChangeLog
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@@ -1,3 +1,19 @@
2011-09-16 Eric Blake <eblake@redhat.com>
fdatasync: new module
* modules/fsync (Description): Document difference to fdatasync.
* modules/fdatasync: New module.
* m4/fdatasync.m4 (gl_FUNC_FDATASYNC): New file.
* lib/fdatasync.c (fdatasync): Likewise.
* m4/unistd_h.m4 (gl_UNISTD_H, gl_UNISTD_H_DEFAULTS): Set up
defaults.
* modules/unistd (Makefile.am): Set witnesses.
* lib/unistd.in.h (fdatasync): Declare.
* MODULES.html.sh: Document it.
* doc/posix-functions/fdatasync.texi (fdatasync): Likewise.
* modules/fdatasync-tests: New test.
* tests/test-fdatasync.c: Likewise.
2011-09-16 Eric Blake <eblake@redhat.com>
test-fsync: enhance tests

1
MODULES.html.sh
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@@ -2356,6 +2356,7 @@ func_all_modules ()
func_module fclose
func_module fcntl-h
func_module fcntl
func_module fdatasync
func_module flock
func_module fopen
func_module fprintf-posix

10
doc/posix-functions/fdatasync.texi
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@@ -4,15 +4,15 @@
POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/fdatasync.html}
Gnulib module: ---
Gnulib module: fdatasync
Portability problems fixed by Gnulib:
@itemize
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
MacOS X 10.5, FreeBSD 6.0, OpenBSD 3.8, Minix 3.1.8, IRIX 5.3, Solaris 2.4, mingw, MSVC 9, Interix 3.5, BeOS.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@end itemize

25
lib/fdatasync.c Normal file
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@@ -0,0 +1,25 @@
/* Emulate fdatasync on platforms that lack it.
Copyright (C) 2011 Free Software Foundation, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
#include <unistd.h>
int
fdatasync (int fd)
{
return fsync (fd);
}

21
lib/unistd.in.h
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@@ -484,8 +484,27 @@ _GL_WARN_ON_USE (fchownat, "fchownat is not portable - "
#endif
#if @GNULIB_FSYNC@
#if @GNULIB_FDATASYNC@
/* Synchronize changes to a file.
Return 0 if successful, otherwise -1 and errno set.
See POSIX:2001 specification
<http://www.opengroup.org/susv3xsh/fdatasync.html>. */
# if !@HAVE_FDATASYNC@
_GL_FUNCDECL_SYS (fdatasync, int, (int fd));
# endif
_GL_CXXALIAS_SYS (fdatasync, int, (int fd));
_GL_CXXALIASWARN (fdatasync);
#elif defined GNULIB_POSIXCHECK
# undef fdatasync
# if HAVE_RAW_DECL_FDATASYNC
_GL_WARN_ON_USE (fdatasync, "fdatasync is unportable - "
"use gnulib module fdatasync for portability");
# endif
#endif
#if @GNULIB_FSYNC@
/* Synchronize changes, including metadata, to a file.
Return 0 if successful, otherwise -1 and errno set.
See POSIX:2001 specification
<http://www.opengroup.org/susv3xsh/fsync.html>. */

14
m4/fdatasync.m4 Normal file
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@@ -0,0 +1,14 @@
# fdatasync.m4 serial 1
dnl Copyright (C) 2008-2011 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
AC_DEFUN([gl_FUNC_FDATASYNC],
[
AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
AC_CHECK_FUNCS_ONCE([fdatasync])
if test $ac_cv_func_fdatasync = no; then
HAVE_FDATASYNC=0
fi
])

6
m4/unistd_h.m4
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@@ -1,4 +1,4 @@
# unistd_h.m4 serial 58
# unistd_h.m4 serial 59
dnl Copyright (C) 2006-2011 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -40,7 +40,7 @@ AC_DEFUN([gl_UNISTD_H],
# endif
#endif
]], [chown dup2 dup3 environ euidaccess faccessat fchdir fchownat
fsync ftruncate getcwd getdomainname getdtablesize getgroups
fdatasync fsync ftruncate getcwd getdomainname getdtablesize getgroups
gethostname getlogin getlogin_r getpagesize getusershell setusershell
endusershell group_member lchown link linkat lseek pipe pipe2 pread pwrite
readlink readlinkat rmdir sleep symlink symlinkat ttyname_r unlink unlinkat
@@ -67,6 +67,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
GNULIB_FACCESSAT=0; AC_SUBST([GNULIB_FACCESSAT])
GNULIB_FCHDIR=0; AC_SUBST([GNULIB_FCHDIR])
GNULIB_FCHOWNAT=0; AC_SUBST([GNULIB_FCHOWNAT])
GNULIB_FDATASYNC=0; AC_SUBST([GNULIB_FDATASYNC])
GNULIB_FSYNC=0; AC_SUBST([GNULIB_FSYNC])
GNULIB_FTRUNCATE=0; AC_SUBST([GNULIB_FTRUNCATE])
GNULIB_GETCWD=0; AC_SUBST([GNULIB_GETCWD])
@@ -110,6 +111,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
HAVE_FACCESSAT=1; AC_SUBST([HAVE_FACCESSAT])
HAVE_FCHDIR=1; AC_SUBST([HAVE_FCHDIR])
HAVE_FCHOWNAT=1; AC_SUBST([HAVE_FCHOWNAT])
HAVE_FDATASYNC=1; AC_SUBST([HAVE_FDATASYNC])
HAVE_FSYNC=1; AC_SUBST([HAVE_FSYNC])
HAVE_FTRUNCATE=1; AC_SUBST([HAVE_FTRUNCATE])
HAVE_GETDTABLESIZE=1; AC_SUBST([HAVE_GETDTABLESIZE])

28
modules/fdatasync Normal file
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@@ -0,0 +1,28 @@
Description:
fdatasync(2) function: synchronize writes to a file.
Files:
lib/fdatasync.c
m4/fdatasync.m4
Depends-on:
fsync
unistd
configure.ac:
gl_FUNC_FDATASYNC
if test $HAVE_FDATASYNC = 0; then
AC_LIBOBJ([fdatasync])
fi
gl_UNISTD_MODULE_INDICATOR([fdatasync])
Makefile.am:
Include:
<unistd.h>
License:
LGPLv2+
Maintainer:
Eric Blake

13
modules/fdatasync-tests Normal file
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@@ -0,0 +1,13 @@
Files:
tests/test-fdatasync.c
tests/signature.h
tests/macros.h
Depends-on:
errno
configure.ac:
Makefile.am:
TESTS += test-fdatasync
check_PROGRAMS += test-fdatasync

2
modules/fsync
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@@ -1,5 +1,5 @@
Description:
fsync(2) function: synchronize writes to a file.
fsync(2) function: synchronize writes, including metadata, to a file.
Files:
lib/fsync.c

2
modules/unistd
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@@ -39,6 +39,7 @@ unistd.h: unistd.in.h $(top_builddir)/config.status $(CXXDEFS_H) $(ARG_NONNULL_H
-e 's/@''GNULIB_FACCESSAT''@/$(GNULIB_FACCESSAT)/g' \
-e 's/@''GNULIB_FCHDIR''@/$(GNULIB_FCHDIR)/g' \
-e 's/@''GNULIB_FCHOWNAT''@/$(GNULIB_FCHOWNAT)/g' \
-e 's/@''GNULIB_FDATASYNC''@/$(GNULIB_FDATASYNC)/g' \
-e 's/@''GNULIB_FSYNC''@/$(GNULIB_FSYNC)/g' \
-e 's/@''GNULIB_FTRUNCATE''@/$(GNULIB_FTRUNCATE)/g' \
-e 's/@''GNULIB_GETCWD''@/$(GNULIB_GETCWD)/g' \
@@ -82,6 +83,7 @@ unistd.h: unistd.in.h $(top_builddir)/config.status $(CXXDEFS_H) $(ARG_NONNULL_H
-e 's|@''HAVE_FACCESSAT''@|$(HAVE_FACCESSAT)|g' \
-e 's|@''HAVE_FCHDIR''@|$(HAVE_FCHDIR)|g' \
-e 's|@''HAVE_FCHOWNAT''@|$(HAVE_FCHOWNAT)|g' \
-e 's|@''HAVE_FDATASYNC''@|$(HAVE_FDATASYNC)|g' \
-e 's|@''HAVE_FSYNC''@|$(HAVE_FSYNC)|g' \
-e 's|@''HAVE_FTRUNCATE''@|$(HAVE_FTRUNCATE)|g' \
-e 's|@''HAVE_GETDTABLESIZE''@|$(HAVE_GETDTABLESIZE)|g' \

64
tests/test-fdatasync.c Normal file
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@@ -0,0 +1,64 @@
/* Test of fdatasync() function.
Copyright (C) 2008-2011 Free Software Foundation, Inc.
This program is free software: 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 3 of the License, or
(at your option) any later version.
This program 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 program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
#include <unistd.h>
#include "signature.h"
SIGNATURE_CHECK (fdatasync, int, (int));
#include <errno.h>
#include <fcntl.h>
#include "macros.h"
int
main (void)
{
int fd;
const char *file = "test-fdatasync.txt";
if (fdatasync (STDOUT_FILENO) != 0)
{
ASSERT (errno == EINVAL /* POSIX */
|| errno == ENOTSUP /* seen on MacOS X 10.5 */
|| errno == EBADF /* seen on AIX 7.1 */
);
}
errno = 0;
ASSERT (fdatasync (-1) == -1);
ASSERT (errno == EBADF);
fd = open (file, O_WRONLY|O_CREAT|O_TRUNC, 0644);
ASSERT (0 <= fd);
ASSERT (write (fd, "hello", 5) == 5);
ASSERT (fdatasync (fd) == 0);
ASSERT (close (fd) == 0);
#if 0
/* POSIX is self-contradictory on whether fdatasync must fail on
read-only file descriptors. Glibc allows it, as does our
implementation if fsync allows it. */
fd = open (file, O_RDONLY);
ASSERT (0 <= fd);
errno = 0;
ASSERT (fdatasync (fd) == -1);
ASSERT (errno == EBADF);
ASSERT (close (fd) == 0);
#endif
ASSERT (unlink (file) == 0);
return 0;
}