Index: configure.in
===================================================================
--- configure.in	(Revision 10235)
+++ configure.in	(Arbeitskopie)
@@ -2465,6 +2465,7 @@
 if test x"$samba_cv_HAVE_MMAP" = x"yes"; then
     AC_DEFINE(HAVE_MMAP,1,[Whether mmap works])
 fi
+AC_CHECK_FUNCS(msync)
 
 AC_CACHE_CHECK([for fcntl locking],samba_cv_HAVE_FCNTL_LOCK,[
 AC_TRY_RUN([#include "${srcdir-.}/tests/fcntl_lock.c"],
Index: tdb/tdb.c
===================================================================
--- tdb/tdb.c	(Revision 10235)
+++ tdb/tdb.c	(Arbeitskopie)
@@ -144,7 +144,25 @@
 
 #ifdef HAVE_MMAP
 	if (tdb->map_ptr) {
-		int ret = munmap(tdb->map_ptr, tdb->map_size);
+		int ret;
+#ifdef HAVE_MSYNC
+		if (tdb->flags & TDB_MSYNC) {
+			/* At least on Linux 2.4 and 2.6 there appears to be
+			 * the problem that without this call data might never
+			 * make it to disk. I've seen cases where new mappings
+			 * in winbindd_idmap of days ago have never made it
+			 * after a crash, and there have been reports that
+			 * even normally shutting down processes loses mmap'ed
+			 * info. "use mmap = no" helps, but also makes stuff
+			 * slower. This is a hack to sync the persistent
+			 * databases (without CLEAR_IF_FIRST) before
+			 * closing. It seems to solve some cases. Maybe we
+			 * have to expand it to an msync after every real
+			 * unlock. -- vl */
+			msync(tdb->map_ptr, tdb->map_size, MS_SYNC);
+		}
+#endif
+		ret = munmap(tdb->map_ptr, tdb->map_size);
 		if (ret != 0)
 			return ret;
 	}
@@ -1924,6 +1942,11 @@
 			goto fail;
 	}
 
+	if ((tdb->flags & TDB_CLEAR_IF_FIRST) == 0) {
+		/* This is a persistent database, so better ensure this goes
+		 * to disk. */
+		tdb->flags |= TDB_MSYNC;
+	}
 
  internal:
 	/* Internal (memory-only) databases skip all the code above to
Index: tdb/tdb.h
===================================================================
--- tdb/tdb.h	(Revision 10235)
+++ tdb/tdb.h	(Arbeitskopie)
@@ -55,6 +55,7 @@
 #define TDB_NOLOCK   4 /* don't do any locking */
 #define TDB_NOMMAP   8 /* don't use mmap */
 #define TDB_CONVERT 16 /* convert endian (internal use) */
+#define TDB_MSYNC   32 /* Sync after unlock */
 #define TDB_BIGENDIAN 32 /* header is big-endian (internal use) */
 
 #define TDB_ERRCODE(code, ret) ((tdb->ecode = (code)), ret)