check for fsync().

2009-03-17  Sven Neumann  <sven@sven>

	* configure.in: check for fsync().

	* libgimpconfig/gimpconfigwriter.c 
(gimp_config_writer_close_file):
	fsync temporary file if destination file exists.


svn path=/trunk/; revision=28172

ChangeLog

@@ -1,3 +1,10 @@
+2009-03-17  Sven Neumann  <sven@sven>
+
+	* configure.in: check for fsync().
+
+	* libgimpconfig/gimpconfigwriter.c (gimp_config_writer_close_file):
+	fsync temporary file if destination file exists.
+
 2009-03-17  Tor Lillqvist  <tml@iki.fi>
 
 	* libgimpconfig/gimpconfigwriter.c

configure.in

@@ -401,8 +401,10 @@ AC_FUNC_VPRINTF
 AC_FUNC_ALLOCA
 
 # check some more funcs
+AC_CHECK_FUNCS(fsync)
 AC_CHECK_FUNCS(difftime mmap)
 
+
 AM_BINRELOC
 
 

libgimpconfig/gimpconfigwriter.c

@@ -664,6 +664,31 @@ gimp_config_writer_close_file (GimpConfigWriter  *writer,
       return FALSE;
     }
 
+#ifdef HAVE_FSYNC
+  /* If the final destination exists, we want to sync the newly written
+   * file to ensure the data is on disk when we rename over the destination.
+   * otherwise if we get a system crash we can lose both the new and the
+   * old file on some filesystems. (I.E. those that don't guarantee the
+   * data is written to the disk before the metadata.)
+   */
+  if (writer->tmpname && g_file_test (writer->filename, G_FILE_TEST_EXISTS))
+    {
+      if (fsync (writer->fd) != 0)
+        {
+          g_set_error (error, GIMP_CONFIG_ERROR, GIMP_CONFIG_ERROR_WRITE,
+                       _("Error writing to temporary file for '%s': %s\n"
+                         "The original file has not been touched."),
+                       gimp_filename_to_utf8 (writer->filename),
+                       g_strerror (errno));
+
+          close (writer->fd);
+          g_unlink (writer->tmpname);
+
+          return FALSE;
+        }
+    }
+#endif
+
   if (close (writer->fd) != 0)
     {
       if (writer->tmpname)