# HG changeset patch # User Eric Blake # Date 1316188763 21600 # Node ID 814138b4cfed153cbb2433ac7f55462ce98cea85 # Parent 44827bcbe6ca469770d3920c33fc5d084f3febc0 fdatasync: new module 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 diff --git a/ChangeLog b/ChangeLog --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,19 @@ +2011-09-16 Eric Blake + + 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 test-fsync: enhance tests diff --git a/MODULES.html.sh b/MODULES.html.sh --- a/MODULES.html.sh +++ b/MODULES.html.sh @@ -2356,6 +2356,7 @@ func_module fclose func_module fcntl-h func_module fcntl + func_module fdatasync func_module flock func_module fopen func_module fprintf-posix diff --git a/doc/posix-functions/fdatasync.texi b/doc/posix-functions/fdatasync.texi --- a/doc/posix-functions/fdatasync.texi +++ b/doc/posix-functions/fdatasync.texi @@ -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 diff --git a/lib/fdatasync.c b/lib/fdatasync.c new file mode 100644 --- /dev/null +++ b/lib/fdatasync.c @@ -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 . */ + +#include +#include + +int +fdatasync (int fd) +{ + return fsync (fd); +} diff --git a/lib/unistd.in.h b/lib/unistd.in.h --- a/lib/unistd.in.h +++ b/lib/unistd.in.h @@ -484,8 +484,27 @@ #endif +#if @GNULIB_FDATASYNC@ +/* Synchronize changes to a file. + Return 0 if successful, otherwise -1 and errno set. + See POSIX:2001 specification + . */ +# 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 to a file. +/* Synchronize changes, including metadata, to a file. Return 0 if successful, otherwise -1 and errno set. See POSIX:2001 specification . */ diff --git a/m4/fdatasync.m4 b/m4/fdatasync.m4 new file mode 100644 --- /dev/null +++ b/m4/fdatasync.m4 @@ -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 +]) diff --git a/m4/unistd_h.m4 b/m4/unistd_h.m4 --- a/m4/unistd_h.m4 +++ b/m4/unistd_h.m4 @@ -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 @@ # 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 @@ 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 @@ 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]) diff --git a/modules/fdatasync b/modules/fdatasync new file mode 100644 --- /dev/null +++ b/modules/fdatasync @@ -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 $HAVE_FDATASYNC = 0; then + AC_LIBOBJ([fdatasync]) +fi +gl_UNISTD_MODULE_INDICATOR([fdatasync]) + +Makefile.am: + +Include: + + +License: +LGPLv2+ + +Maintainer: +Eric Blake diff --git a/modules/fdatasync-tests b/modules/fdatasync-tests new file mode 100644 --- /dev/null +++ b/modules/fdatasync-tests @@ -0,0 +1,13 @@ +Files: +tests/test-fdatasync.c +tests/signature.h +tests/macros.h + +Depends-on: +errno + +configure.ac: + +Makefile.am: +TESTS += test-fdatasync +check_PROGRAMS += test-fdatasync diff --git a/modules/fsync b/modules/fsync --- a/modules/fsync +++ b/modules/fsync @@ -1,5 +1,5 @@ Description: -fsync(2) function: synchronize writes to a file. +fsync(2) function: synchronize writes, including metadata, to a file. Files: lib/fsync.c diff --git a/modules/unistd b/modules/unistd --- a/modules/unistd +++ b/modules/unistd @@ -39,6 +39,7 @@ -e 's/@''GNULIB_FACCESSAT''@/$(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 @@ -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' \ diff --git a/tests/test-fdatasync.c b/tests/test-fdatasync.c new file mode 100644 --- /dev/null +++ b/tests/test-fdatasync.c @@ -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 . */ + +#include + +#include + +#include "signature.h" +SIGNATURE_CHECK (fdatasync, int, (int)); + +#include +#include + +#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; +}