Add support for overlayfs and start using it

5 files changed, 41 insertions, 8 deletions

diff --git a/Makefile.am b/Makefile.am
index 8f84603..3376c41 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -9,8 +9,11 @@ etc_shell_leveldir = $(sysconfdir)/shell/level
 dhcphookdir = /etc/dhcp3/dhclient-exit-hooks.d
 enumdir = $(datadir)/enumeration
 
-AM_CFLAGS = -I src -Wall -I /usr/include/glib-2.0 -I /usr/lib/glib-2.0/include
-AM_CXXFLAGS = -I src -Wall -Werror
+if USE_OVERLAYFS
+USE_OVERLAYFS = -DUSE_OVERLAYFS=1
+endif
+AM_CFLAGS = -I src -Wall -I /usr/include/glib-2.0 -I /usr/lib/glib-2.0/include $(USE_OVERLAYFS)
+AM_CXXFLAGS = -I src -Wall -Werror $(USE_OVERLAYFS)
 AM_CXXFLAGS += -I /usr/include/glib-2.0 -I /usr/lib/glib-2.0/include
 AM_YFLAGS = -d --name-prefix=yy_`basename $* .y`_
 AM_LFLAGS = --prefix=yy_`basename $* .l`_ -olex.yy.c
diff --git a/configure.ac b/configure.ac
index 04210fd..088461a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -29,6 +29,12 @@ AC_ARG_ENABLE([nostrip],
 	[include -nostrip option during packaging]),
 	[NOSTRIP=-nostrip], [NOSTRIP=])
 
+AC_ARG_ENABLE([overlayfs],
+	AC_HELP_STRING([--enable-overlayfs],
+	[use overlayfs instead of unionfs (default is no)]),
+	[enable_overlayfs=yes], [enable_overlayfs=no])
+AM_CONDITIONAL([USE_OVERLAYFS], [test "$enable_overlayfs" != no])
+
 AC_CONFIG_FILES(
 	[Makefile]
 	[perl_dmod/Makefile]
diff --git a/debian/rules b/debian/rules
index f2c57b7..47a1d16 100755
--- a/debian/rules
+++ b/debian/rules
@@ -8,6 +8,7 @@ cfg_opts += --libdir=/usr/lib
 cfg_opts += --includedir=/usr/include
 cfg_opts += --mandir=\$${prefix}/share/man
 cfg_opts += --infodir=\$${prefix}/share/info
+cfg_opts += --enable-overlayfs
 cfg_opts += CFLAGS="$(CFLAGS)"
 cfg_opts += LDFLAGS="-Wl,-z,defs"
 cfg_opts += CXXFLAGS="$(CXXFLAGS)"
diff --git a/src/common/unionfs.c b/src/common/unionfs.c
index d8b7626..c1752ac 100644
--- a/src/common/unionfs.c
+++ b/src/common/unionfs.c
@@ -71,9 +71,20 @@ static inline void
 sys_mount_session(void)
 {
   char mopts[MAX_LENGTH_DIR_PATH * 2];
-  snprintf(mopts, MAX_LENGTH_DIR_PATH * 2, "dirs=%s=rw:%s=ro",
+  const char *fstype;
+  const char *moptfmt;
+  int local_errno;
+
+#ifdef USE_OVERLAYFS
+  fstype = "overlayfs";
+  moptfmt = "upperdir=%s,lowerdir=%s";
+#else
+  fstype = "unionfs";
+  moptfmt = "dirs=%s=rw:%s=ro";
+#endif
+  snprintf(mopts, MAX_LENGTH_DIR_PATH * 2, moptfmt,
            get_cdirp(), get_adirp());
-  if (mount("unionfs", get_mdirp(), "unionfs", 0, mopts) != 0) {
+  if (mount(fstype, get_mdirp(), fstype, 0, mopts) != 0) {
     perror("mount");
   }
 }
diff --git a/src/cstore/unionfs/cstore-unionfs.cpp b/src/cstore/unionfs/cstore-unionfs.cpp
index e21e660..c53e443 100644
--- a/src/cstore/unionfs/cstore-unionfs.cpp
+++ b/src/cstore/unionfs/cstore-unionfs.cpp
@@ -1477,14 +1477,26 @@ bool
 UnionfsCstore::do_mount(const FsPath& rwdir, const FsPath& rdir,
                         const FsPath& mdir)
 {
-  string mopts = "dirs=";
+  const char *fstype;
+  string mopts;
+
+#ifdef USE_OVERLAYFS
+  fstype = "overlayfs";
+  mopts = "upperdir=";
+  mopts += rwdir.path_cstr();
+  mopts += ",lowerdir=";
+  mopts += rdir.path_cstr();
+#else
+  fstype = "unionfs";
+  mopts = "dirs=";
   mopts += rwdir.path_cstr();
   mopts += "=rw:";
   mopts += rdir.path_cstr();
   mopts += "=ro";
-  if (mount("unionfs", mdir.path_cstr(), "unionfs", 0, mopts.c_str()) != 0) {
-    output_internal("union mount failed [%s][%s]\n",
-                    strerror(errno), mdir.path_cstr());
+#endif
+  if (mount(fstype, mdir.path_cstr(), fstype, 0, mopts.c_str()) != 0) {
+    output_internal("union mount failed [%s][%s][%s]\n",
+                    strerror(errno), mdir.path_cstr(), mopts.c_str());
     return false;
   }
   return true;