File synchronization fixes.

* admin/CPP-DEFINES (BSD_SYSTEM, HAVE_FSYNC): Remove.
* admin/merge-gnulib (GNULIB_MODULES): Add fsync, fdatasync.
* configure.ac (BSD_SYSTEM, BSD_SYSTEM_AHB): Remove; no longer needed.
(fsync): Remove check; now done by gnulib.
* lib/fdatasync.c, lib/fsync.c, m4/fdatasync.m4, m4/fsync.m4:
New files, from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* lib-src/Makefile.in (LIB_FDATASYNC): New macro.
(emacsclient${EXEEXT}): Use it.
* lib-src/emacsclient.c (main): Use fdatasync, not fsync, since we don't
care about metadata.  Keep trying if interrupted.
* lib-src/movemail.c (main, popmail): Don't worry about BSD_SYSTEM, since
fsync is available everywhere (or there is a substitute).  Don't
report an error if fsync returns EINVAL.
* nt/inc/ms-w32.h (fdatasync): New macro, suggested by Eli Zaretskii.
* src/Makefile.in (LIB_FDATASYNC): New macro.
(LIBES): Use it.
* src/conf_post.h (BSD_SYSTEM, BSD_SYSTEM_AHB): Remove; no longer needed.
* src/fileio.c (Fwrite_region, write_region_inhibit_fsync):
Don't worry about HAVE_FSYNC, since a substitute fsync is
available if the system lacks one.
(Fwrite_regin): Retry fsync if interrupted.

Fixes: debbugs:13944

23 files changed, 273 insertions, 76 deletions

diff --git a/ChangeLog b/ChangeLog
index 2ac8ec1de5..2fcd7c7711 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2013-03-13  Paul Eggert  <[email protected]>
 
+	File synchronization fixes (Bug#13944).
+	* configure.ac (BSD_SYSTEM, BSD_SYSTEM_AHB): Remove; no longer needed.
+	(fsync): Remove check; now done by gnulib.
+	* lib/fdatasync.c, lib/fsync.c, m4/fdatasync.m4, m4/fsync.m4:
+	New files, from gnulib.
+	* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
+
 	Merge from gnulib, incorporating:
 	2013-03-13 putenv: port to Solaris 10
 	2013-03-12 mktime: fix configure typo
diff --git a/admin/CPP-DEFINES b/admin/CPP-DEFINES
index da8dec5a0f..c11c3c3b48 100644
--- a/admin/CPP-DEFINES
+++ b/admin/CPP-DEFINES
@@ -9,7 +9,6 @@ documented in config.in, and this file would not be necessary.
 
 AIX
 _AIX
-BSD_SYSTEM
 CYGWIN		Compiling the Cygwin port.
 __CYGWIN__	Ditto
 GNU_LINUX
@@ -149,7 +148,6 @@ HAVE_FORK
 HAVE_FREEIFADDRS
 HAVE_FREETYPE
 HAVE_FSEEKO
-HAVE_FSYNC
 HAVE_FUTIMENS
 HAVE_FUTIMES
 HAVE_FUTIMESAT
diff --git a/admin/ChangeLog b/admin/ChangeLog
index a0fd90e0d1..fcc339c17c 100644
--- a/admin/ChangeLog
+++ b/admin/ChangeLog
@@ -1,3 +1,9 @@
+2013-03-13  Paul Eggert  <[email protected]>
+
+	File synchronization fixes (Bug#13944).
+	* CPP-DEFINES (BSD_SYSTEM, HAVE_FSYNC): Remove.
+	* merge-gnulib (GNULIB_MODULES): Add fsync, fdatasync.
+
 2013-03-11  Paul Eggert  <[email protected]>
 
 	* notes/unicode: Improve notes about Emacs source file encoding.
diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index b43f2bd9bb..100749191f 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -29,7 +29,8 @@ GNULIB_MODULES='
   alloca-opt c-ctype c-strcase
   careadlinkat close-stream crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512
   dtoastr dtotimespec dup2 environ execinfo faccessat
-  fcntl-h fdopendir filemode fstatat getloadavg getopt-gnu gettime gettimeofday
+  fcntl-h fdatasync fdopendir filemode fstatat fsync
+  getloadavg getopt-gnu gettime gettimeofday
   ignore-value intprops largefile lstat
   manywarnings memrchr mktime
   pselect pthread_sigmask putenv readlink readlinkat
diff --git a/configure.ac b/configure.ac
index aed625e44a..0d1f31032a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2872,7 +2872,7 @@ select getpagesize setlocale \
 utimes getrlimit setrlimit shutdown getaddrinfo \
 strsignal setitimer \
 sendto recvfrom getsockname getpeername getifaddrs freeifaddrs \
-gai_strerror mkstemp getline getdelim fsync sync \
+gai_strerror mkstemp getline getdelim sync \
 difftime posix_memalign \
 getpwent endpwent getgrent endgrent \
 touchlock \
@@ -3774,7 +3774,6 @@ esac
 
 dnl Define symbols to identify the version of Unix this is.
 dnl Define all the symbols that apply correctly.
-AH_TEMPLATE(BSD_SYSTEM, [Define if the system is compatible with BSD 4.2.])
 AH_TEMPLATE(DOS_NT, [Define if the system is MS DOS or MS Windows.])
 AH_TEMPLATE(MSDOS, [Define if the system is MS DOS.])
 AH_TEMPLATE(USG, [Define if the system is compatible with System III.])
@@ -3798,30 +3797,12 @@ case $opsys in
     ;;
 
   darwin)
-    dnl BSD4_3 and BSD4_4 are already defined in sys/param.h.
-    AC_DEFINE(BSD_SYSTEM, [])
-    dnl More specific than the above two.  We cannot use __APPLE__ as this
-    dnl may not be defined on non-OSX Darwin, and we cannot define DARWIN
-    dnl here because Panther and lower CoreFoundation.h uses DARWIN to
+    dnl Not __APPLE__, as this may not be defined on non-OSX Darwin.
+    dnl Not DARWIN, because Panther and lower CoreFoundation.h use DARWIN to
     dnl distinguish OS X from pure Darwin.
     AC_DEFINE(DARWIN_OS, [], [Define if the system is Darwin.])
     ;;
 
-  freebsd)
-    dnl Hack to avoid calling AC_PREPROC_IFELSE multiple times.
-    dnl Would not be needed with autoconf >= 2.67, where the
-    dnl preprocessed output is accessible in "conftest.i".
-    AC_DEFINE(BSD_SYSTEM_AHB, 1, [Define if AH_BOTTOM should change BSD_SYSTEM.])
-    ;;
-
-  gnu | netbsd | openbsd )
-    AC_PREPROC_IFELSE([AC_LANG_PROGRAM([[
-#ifndef BSD_SYSTEM
-# error "BSD_SYSTEM not defined"
-#endif
-    ]], [[]])], [], AC_DEFINE(BSD_SYSTEM, 43) )
-    ;;
-
   gnu-linux | gnu-kfreebsd )
     AC_DEFINE(USG, [])
     AC_DEFINE(GNU_LINUX, [], [Define if ths system is compatible with GNU/Linux.])
@@ -4185,15 +4166,8 @@ case "$opsys" in
    LD_SWITCH_SYSTEM_TEMACS="-fno-pie -prebind $libs_nsgui -Xlinker -headerpad -Xlinker $headerpad_extra"
 
    ## This is here because src/Makefile.in did some extra fiddling around
-   ## with LD_SWITCH_SYSTEM.  The cpp logic was:
-   ##   #ifndef LD_SWITCH_SYSTEM
-   ##   #if !defined (__GNUC__) && ((defined (BSD_SYSTEM) && !defined (COFF)))
-   ## Since all the *bsds define LD_SWITCH_SYSTEM, this simplifies to:
-   ## not using gcc, darwin.
-   ## Because this was done in src/Makefile.in, the resulting part of
-   ## LD_SWITCH_SYSTEM was not used in configure (ie, in ac_link).
-   ## It therefore seems cleaner to put this in LD_SWITCH_SYSTEM_TEMACS,
-   ## rather than LD_SWITCH_SYSTEM.
+   ## with LD_SWITCH_SYSTEM.  It seems cleaner to put this in
+   ## LD_SWITCH_SYSTEM_TEMACS instead,
    test "x$LD_SWITCH_SYSTEM" = "x" && test "x$GCC" != "xyes" && \
      LD_SWITCH_SYSTEM_TEMACS="-X $LD_SWITCH_SYSTEM_TEMACS"
    ;;
diff --git a/lib-src/ChangeLog b/lib-src/ChangeLog
index 6ecfb283ff..d8ec057942 100644
--- a/lib-src/ChangeLog
+++ b/lib-src/ChangeLog
@@ -1,5 +1,14 @@
 2013-03-13  Paul Eggert  <[email protected]>
 
+	File synchronization fixes (Bug#13944).
+	* Makefile.in (LIB_FDATASYNC): New macro.
+	(emacsclient${EXEEXT}): Use it.
+	* emacsclient.c (main): Use fdatasync, not fsync, since we don't
+	care about metadata.  Keep trying if interrupted.
+	* movemail.c (main, popmail): Don't worry about BSD_SYSTEM, since
+	fsync is available everywhere (or there is a substitute).  Don't
+	report an error if fsync returns EINVAL.
+
 	Static checking by Sun C 5.12.
 	* etags.c (analyse_regex): Omit unreachable code.
 
diff --git a/lib-src/Makefile.in b/lib-src/Makefile.in
index 8a6960ee2f..7069af9767 100644
--- a/lib-src/Makefile.in
+++ b/lib-src/Makefile.in
@@ -161,6 +161,8 @@ LIBRESOLV=@LIBRESOLV@
 LIBS_MAIL=@LIBS_MAIL@
 ## empty or -lrt or -lposix4 if HAVE_CLOCK_GETTIME
 LIB_CLOCK_GETTIME = @LIB_CLOCK_GETTIME@
+## empty or -lrt or -lposix4 if HAVE_FDATASYNC
+LIB_FDATASYNC = @LIB_FDATASYNC@
 
 ## Extra libraries to use when linking movemail.
 LIBS_MOVE = $(LIBS_MAIL) $(KRB4LIB) $(DESLIB) $(KRB5LIB) $(CRYPTOLIB) \
@@ -334,7 +336,7 @@ pop.o: ${srcdir}/pop.c ${srcdir}/../lib/min-max.h $(config_h)
 emacsclient${EXEEXT}: ${srcdir}/emacsclient.c $(config_h)
 	$(CC) ${ALL_CFLAGS} ${srcdir}/emacsclient.c \
 	   -DVERSION="\"${version}\"" \
-	   $(LOADLIBES) -o emacsclient
+	   $(LOADLIBES) $(LIB_FDATASYNC) -o emacsclient
 
 hexl${EXEEXT}: ${srcdir}/hexl.c $(config_h)
 	$(CC) ${ALL_CFLAGS} ${srcdir}/hexl.c $(LOADLIBES) -o hexl
diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index 6feaf18ba6..898e8d69b0 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -1724,7 +1724,8 @@ main (int argc, char **argv)
       needlf = 2;
     }
   fflush (stdout);
-  fsync (1);
+  while (fdatasync (1) != 0 && errno == EINTR)
+    continue;
 
   /* Now, wait for an answer and print any messages.  */
   while (exit_status == EXIT_SUCCESS)
@@ -1825,7 +1826,8 @@ main (int argc, char **argv)
   if (needlf)
     printf ("\n");
   fflush (stdout);
-  fsync (1);
+  while (fdatasync (1) != 0 && errno == EINTR)
+    continue;
 
   if (rl < 0)
     exit_status = EXIT_FAILURE;
diff --git a/lib-src/movemail.c b/lib-src/movemail.c
index 190937d762..81ac8aa187 100644
--- a/lib-src/movemail.c
+++ b/lib-src/movemail.c
@@ -466,10 +466,8 @@ main (int argc, char **argv)
 	  }
       }
 
-#ifdef BSD_SYSTEM
-      if (fsync (outdesc) < 0)
+      if (fsync (outdesc) != 0 && errno != EINVAL)
 	pfatal_and_delete (outname);
-#endif
 
       /* Prevent symlink attacks truncating other users' mailboxes */
       if (setregid (-1, real_gid) < 0)
@@ -750,21 +748,14 @@ popmail (char *mailbox, char *outfile, int preserve, char *password, int reverse
 	}
     }
 
-  /* On AFS, a call to write only modifies the file in the local
-   *     workstation's AFS cache.  The changes are not written to the server
-   *      until a call to fsync or close is made.  Users with AFS home
-   *      directories have lost mail when over quota because these checks were
-   *      not made in previous versions of movemail. */
-
-#ifdef BSD_SYSTEM
-  if (fsync (mbfi) < 0)
+  if (fsync (mbfi) != 0 && errno != EINVAL)
     {
       error ("Error in fsync: %s", strerror (errno), 0);
+      close (mbfi);
       return EXIT_FAILURE;
     }
-#endif
 
-  if (close (mbfi) == -1)
+  if (close (mbfi) != 0)
     {
       error ("Error in close: %s", strerror (errno), 0);
       return EXIT_FAILURE;
diff --git a/lib/fdatasync.c b/lib/fdatasync.c
new file mode 100644
index 0000000000..8f9bf15a52
--- /dev/null
+++ b/lib/fdatasync.c
@@ -0,0 +1,27 @@
+/* Emulate fdatasync on platforms that lack it.
+
+   Copyright (C) 2011-2013 Free Software Foundation, Inc.
+
+   This library 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 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
+   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)
+{
+  /* This does more work than strictly necessary, but is the best we
+     can do portably.  */
+  return fsync (fd);
+}
diff --git a/lib/fsync.c b/lib/fsync.c
new file mode 100644
index 0000000000..8a1a975049
--- /dev/null
+++ b/lib/fsync.c
@@ -0,0 +1,83 @@
+/* Emulate fsync on platforms that lack it, primarily Windows and
+   cross-compilers like MinGW.
+
+   This is derived from sqlite3 sources.
+   http://www.sqlite.org/cvstrac/rlog?f=sqlite/src/os_win.c
+   http://www.sqlite.org/copyright.html
+
+   Written by Richard W.M. Jones <rjones.at.redhat.com>
+
+   Copyright (C) 2008-2013 Free Software Foundation, Inc.
+
+   This library 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 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
+   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>
+
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+
+/* FlushFileBuffers */
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+
+# include <errno.h>
+
+/* Get _get_osfhandle.  */
+# include "msvc-nothrow.h"
+
+int
+fsync (int fd)
+{
+  HANDLE h = (HANDLE) _get_osfhandle (fd);
+  DWORD err;
+
+  if (h == INVALID_HANDLE_VALUE)
+    {
+      errno = EBADF;
+      return -1;
+    }
+
+  if (!FlushFileBuffers (h))
+    {
+      /* Translate some Windows errors into rough approximations of Unix
+       * errors.  MSDN is useless as usual - in this case it doesn't
+       * document the full range of errors.
+       */
+      err = GetLastError ();
+      switch (err)
+        {
+        case ERROR_ACCESS_DENIED:
+          /* For a read-only handle, fsync should succeed, even though we have
+             no way to sync the access-time changes.  */
+          return 0;
+
+          /* eg. Trying to fsync a tty. */
+        case ERROR_INVALID_HANDLE:
+          errno = EINVAL;
+          break;
+
+        default:
+          errno = EIO;
+        }
+      return -1;
+    }
+
+  return 0;
+}
+
+#else /* !Windows */
+
+# error "This platform lacks fsync function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib."
+
+#endif /* !Windows */
diff --git a/lib/gnulib.mk b/lib/gnulib.mk
index c130cbc65b..4b754ec21d 100644
--- a/lib/gnulib.mk
+++ b/lib/gnulib.mk
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=dup --avoid=errno --avoid=fchdir --avoid=fcntl --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=sigprocmask --avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt c-ctype c-strcase careadlinkat close-stream crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl-h fdopendir filemode fstatat getloadavg getopt-gnu gettime gettimeofday ignore-value intprops largefile lstat manywarnings memrchr mktime pselect pthread_sigmask putenv readlink readlinkat sig2str socklen stat-time stdalign stdarg stdbool stdio strftime strtoimax strtoumax symlink sys_stat sys_time time timer-time timespec-add timespec-sub unsetenv utimens warnings
+# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=dup --avoid=errno --avoid=fchdir --avoid=fcntl --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=sigprocmask --avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt c-ctype c-strcase careadlinkat close-stream crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl-h fdatasync fdopendir filemode fstatat fsync getloadavg getopt-gnu gettime gettimeofday ignore-value intprops largefile lstat manywarnings memrchr mktime pselect pthread_sigmask putenv readlink readlinkat sig2str socklen stat-time stdalign stdarg stdbool stdio strftime strtoimax strtoumax symlink sys_stat sys_time time timer-time timespec-add timespec-sub unsetenv utimens warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
@@ -297,6 +297,15 @@ EXTRA_DIST += fcntl.in.h
 
 ## end   gnulib module fcntl-h
 
+## begin gnulib module fdatasync
+
+
+EXTRA_DIST += fdatasync.c
+
+EXTRA_libgnu_a_SOURCES += fdatasync.c
+
+## end   gnulib module fdatasync
+
 ## begin gnulib module fdopendir
 
 
@@ -332,6 +341,15 @@ EXTRA_libgnu_a_SOURCES += at-func.c fstatat.c
 
 ## end   gnulib module fstatat
 
+## begin gnulib module fsync
+
+
+EXTRA_DIST += fsync.c
+
+EXTRA_libgnu_a_SOURCES += fsync.c
+
+## end   gnulib module fsync
+
 ## begin gnulib module getgroups
 
 if gl_GNULIB_ENABLED_getgroups
diff --git a/m4/fdatasync.m4 b/m4/fdatasync.m4
new file mode 100644
index 0000000000..551c0d9ff4
--- /dev/null
+++ b/m4/fdatasync.m4
@@ -0,0 +1,32 @@
+# fdatasync.m4 serial 4
+dnl Copyright (C) 2008-2013 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])
+
+  dnl Using AC_CHECK_FUNCS_ONCE would break our subsequent AC_SEARCH_LIBS
+  AC_CHECK_DECLS_ONCE([fdatasync])
+  LIB_FDATASYNC=
+  AC_SUBST([LIB_FDATASYNC])
+
+  if test $ac_cv_have_decl_fdatasync = no; then
+    HAVE_DECL_FDATASYNC=0
+    dnl Mac OS X 10.7 has fdatasync but does not declare it.
+    AC_CHECK_FUNCS([fdatasync])
+    if test $ac_cv_func_fdatasync = no; then
+      HAVE_FDATASYNC=0
+    fi
+  else
+    dnl Solaris <= 2.6 has fdatasync() in libposix4.
+    dnl Solaris 7..10 has it in librt.
+    gl_saved_libs=$LIBS
+    AC_SEARCH_LIBS([fdatasync], [rt posix4],
+                   [test "$ac_cv_search_fdatasync" = "none required" ||
+                    LIB_FDATASYNC=$ac_cv_search_fdatasync])
+    LIBS=$gl_saved_libs
+  fi
+])
diff --git a/m4/fsync.m4 b/m4/fsync.m4
new file mode 100644
index 0000000000..43f51528d6
--- /dev/null
+++ b/m4/fsync.m4
@@ -0,0 +1,17 @@
+# fsync.m4 serial 2
+dnl Copyright (C) 2008-2013 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_FSYNC],
+[
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  AC_CHECK_FUNCS_ONCE([fsync])
+  if test $ac_cv_func_fsync = no; then
+    HAVE_FSYNC=0
+  fi
+])
+
+# Prerequisites of lib/fsync.c.
+AC_DEFUN([gl_PREREQ_FSYNC], [:])
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 6c3012d827..d304f10b76 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -63,10 +63,12 @@ AC_DEFUN([gl_EARLY],
   # Code from module extern-inline:
   # Code from module faccessat:
   # Code from module fcntl-h:
+  # Code from module fdatasync:
   # Code from module fdopendir:
   # Code from module filemode:
   # Code from module fpending:
   # Code from module fstatat:
+  # Code from module fsync:
   # Code from module getgroups:
   # Code from module getloadavg:
   # Code from module getopt-gnu:
@@ -187,6 +189,11 @@ AC_DEFUN([gl_INIT],
   gl_MODULE_INDICATOR([faccessat])
   gl_UNISTD_MODULE_INDICATOR([faccessat])
   gl_FCNTL_H
+  gl_FUNC_FDATASYNC
+  if test $HAVE_FDATASYNC = 0; then
+    AC_LIBOBJ([fdatasync])
+  fi
+  gl_UNISTD_MODULE_INDICATOR([fdatasync])
   gl_FUNC_FDOPENDIR
   if test $HAVE_FDOPENDIR = 0 || test $REPLACE_FDOPENDIR = 1; then
     AC_LIBOBJ([fdopendir])
@@ -204,6 +211,12 @@ AC_DEFUN([gl_INIT],
     AC_LIBOBJ([fstatat])
   fi
   gl_SYS_STAT_MODULE_INDICATOR([fstatat])
+  gl_FUNC_FSYNC
+  if test $HAVE_FSYNC = 0; then
+    AC_LIBOBJ([fsync])
+    gl_PREREQ_FSYNC
+  fi
+  gl_UNISTD_MODULE_INDICATOR([fsync])
   gl_GETLOADAVG
   if test $HAVE_GETLOADAVG = 0; then
     AC_LIBOBJ([getloadavg])
@@ -743,12 +756,14 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/execinfo.in.h
   lib/faccessat.c
   lib/fcntl.in.h
+  lib/fdatasync.c
   lib/fdopendir.c
   lib/filemode.c
   lib/filemode.h
   lib/fpending.c
   lib/fpending.h
   lib/fstatat.c
+  lib/fsync.c
   lib/ftoastr.c
   lib/ftoastr.h
   lib/getgroups.c
@@ -842,10 +857,12 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/faccessat.m4
   m4/fcntl-o.m4
   m4/fcntl_h.m4
+  m4/fdatasync.m4
   m4/fdopendir.m4
   m4/filemode.m4
   m4/fpending.m4
   m4/fstatat.m4
+  m4/fsync.m4
   m4/getgroups.m4
   m4/getloadavg.m4
   m4/getopt.m4
diff --git a/nt/ChangeLog b/nt/ChangeLog
index dcda682cfc..48c1cb8bc8 100644
--- a/nt/ChangeLog
+++ b/nt/ChangeLog
@@ -1,3 +1,8 @@
+2013-03-13  Paul Eggert  <[email protected]>
+
+	File synchronization fixes (Bug#13944).
+	* inc/ms-w32.h (fdatasync): New macro, suggested by Eli Zaretskii.
+
 2013-03-05  Paul Eggert  <[email protected]>
 
 	FILE's lock is now always .#FILE and may be a regular file (Bug#13807).
diff --git a/nt/inc/ms-w32.h b/nt/inc/ms-w32.h
index 9473fbe3ca..1240239089 100644
--- a/nt/inc/ms-w32.h
+++ b/nt/inc/ms-w32.h
@@ -220,6 +220,7 @@ extern int sys_unlink (const char *);
 /* Map to MSVC names.  */
 #define execlp    _execlp
 #define execvp    _execvp
+#define fdatasync _commit
 #define fdopen	  _fdopen
 #ifndef fileno
 #define fileno	  _fileno
diff --git a/src/ChangeLog b/src/ChangeLog
index ae6fe86f66..d328d0a74c 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2013-03-13  Paul Eggert  <[email protected]>
+
+	File synchronization fixes (Bug#13944).
+	* Makefile.in (LIB_FDATASYNC): New macro.
+	(LIBES): Use it.
+	* conf_post.h (BSD_SYSTEM, BSD_SYSTEM_AHB): Remove; no longer needed.
+	* fileio.c (Fwrite_region, write_region_inhibit_fsync):
+	Don't worry about HAVE_FSYNC, since a substitute fsync is
+	available if the system lacks one.
+	(Fwrite_regin): Retry fsync if interrupted.
+
 2013-03-13  Eli Zaretskii  <[email protected]>
 
 	* w32term.c (w32_read_socket): If we Emacs frame is being
diff --git a/src/Makefile.in b/src/Makefile.in
index b2034a3379..31de9714c6 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -139,6 +139,7 @@ M17N_FLT_LIBS = @M17N_FLT_LIBS@
 
 LIB_CLOCK_GETTIME=@LIB_CLOCK_GETTIME@
 LIB_EACCESS=@LIB_EACCESS@
+LIB_FDATASYNC=@LIB_FDATASYNC@
 LIB_TIMER_TIME=@LIB_TIMER_TIME@
 
 DBUS_CFLAGS = @DBUS_CFLAGS@
@@ -391,7 +392,7 @@ ALLOBJS = $(VMLIMIT_OBJ) $(obj) $(otherobj)
 LIBES = $(LIBS) $(W32_LIBS) $(LIBS_GNUSTEP) $(LIBX_BASE) $(LIBIMAGE) \
    $(LIBX_OTHER) $(LIBSOUND) \
    $(RSVG_LIBS) $(IMAGEMAGICK_LIBS) $(LIB_CLOCK_GETTIME) \
-   $(LIB_EACCESS) $(LIB_TIMER_TIME) $(DBUS_LIBS) \
+   $(LIB_EACCESS) $(LIB_FDATASYNC) $(LIB_TIMER_TIME) $(DBUS_LIBS) \
    $(LIB_EXECINFO) \
    $(LIBXML2_LIBS) $(LIBGPM) $(LIBRESOLV) $(LIBS_SYSTEM) \
    $(LIBS_TERMCAP) $(GETLOADAVG_LIBS) $(SETTINGS_LIBS) $(LIBSELINUX_LIBS) \
diff --git a/src/conf_post.h b/src/conf_post.h
index 6c9747a436..5cb385d902 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -44,19 +44,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 # define __has_attribute(a) 0 /* non-clang */
 #endif
 
-/* This silences a few compilation warnings on FreeBSD.  */
-#ifdef BSD_SYSTEM_AHB
-#undef BSD_SYSTEM_AHB
-#undef BSD_SYSTEM
-#if __FreeBSD__ == 1
-#define BSD_SYSTEM 199103
-#elif __FreeBSD__ == 2
-#define BSD_SYSTEM 199306
-#elif __FreeBSD__ >= 3
-#define BSD_SYSTEM 199506
-#endif
-#endif
-
 #ifdef DARWIN_OS
 #ifdef emacs
 #define malloc unexec_malloc
diff --git a/src/fileio.c b/src/fileio.c
index 8937f7ca47..724250c8aa 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -4959,20 +4959,23 @@ This calls `write-region-annotate-functions' at the start, and
 
   immediate_quit = 0;
 
-#ifdef HAVE_FSYNC
   /* fsync appears to change the modtime on BSD4.2.
      Disk full in NFS may be reported here.  */
   /* mib says that closing the file will try to write as fast as NFS can do
      it, and that means the fsync here is not crucial for autosave files.  */
-  if (!auto_saving && !write_region_inhibit_fsync && fsync (desc) < 0)
+  if (!auto_saving && !write_region_inhibit_fsync)
     {
-      /* If fsync fails with EINTR, don't treat that as serious.  Also
+      /* Transfer data and metadata to disk, retrying if interrupted.  Also,
 	 ignore EINVAL which happens when fsync is not supported on this
 	 file.  */
-      if (errno != EINTR && errno != EINVAL)
-	ok = 0, save_errno = errno;
+      while (fsync (desc) != 0)
+	if (errno != EINTR)
+	  {
+	    if (errno != EINVAL)
+	      ok = 0, save_errno = errno;
+	    break;
+	  }
     }
-#endif
 
   modtime = invalid_emacs_time ();
   if (visiting)
@@ -6046,13 +6049,11 @@ in the buffer; this is the default behavior, because the auto-save
 file is usually more useful if it contains the deleted text.  */);
   Vauto_save_include_big_deletions = Qnil;
 
-#ifdef HAVE_FSYNC
   DEFVAR_BOOL ("write-region-inhibit-fsync", write_region_inhibit_fsync,
 	       doc: /* Non-nil means don't call fsync in `write-region'.
 This variable affects calls to `write-region' as well as save commands.
 A non-nil value may result in data loss!  */);
   write_region_inhibit_fsync = 0;
-#endif
 
   DEFVAR_BOOL ("delete-by-moving-to-trash", delete_by_moving_to_trash,
                doc: /* Specifies whether to use the system's trash can.
diff --git a/src/filelock.c b/src/filelock.c
index 32992896c2..f17d3182ea 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -437,6 +437,14 @@ create_lock_file (char *lfname, char *lock_info_str, bool force)
 	  if (emacs_write (fd, lock_info_str, lock_info_len) != lock_info_len
 	      || (need_fchmod && fchmod (fd, world_readable) != 0))
 	    err = errno;
+	  else
+	    while (fsync (fd) != 0)
+	      if (errno != EINTR)
+		{
+		  if (errno != EINVAL)
+		    err = errno;
+		  break;
+		}
 	  if (emacs_close (fd) != 0)
 	    err = errno;
 	  if (!err && rename_lock_file (nonce, lfname, force) != 0)
diff --git a/src/sysdep.c b/src/sysdep.c
index b99f179210..bff11fc9f7 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -1289,10 +1289,9 @@ reset_sys_modes (struct tty_display_info *tty_out)
   if (tty_out->terminal->reset_terminal_modes_hook)
     tty_out->terminal->reset_terminal_modes_hook (tty_out->terminal);
 
-#ifdef BSD_SYSTEM
   /* Avoid possible loss of output when changing terminal modes.  */
-  fsync (fileno (tty_out->output));
-#endif
+  while (fdatasync (fileno (tty_out->output)) != 0 && errno == EINTR)
+    continue;
 
 #ifndef DOS_NT
 #ifdef F_SETOWN