[dconf] Move shmdir guessing code to common/

[Ryan Lortie <ryanl src gnome org>]

commit bece1f7488e07c2d3f2c9b978ef0065a3ab1413f
Author: Ryan Lortie <desrt desrt ca>
Date:   Sat Jul 17 12:20:33 2010 -0400

    Move shmdir guessing code to common/
    
    Increase the intelligence of the algorithm: use ~/.cache/dconf as a
    reasonable default if not on NFS.
    
    The dconf engine now has a non-blocking startup when not on NFS.

 client/Makefile.am     |    1 +
 common/Makefile.am     |    2 +
 common/dconf-shmdir.c  |   54 ++++++++++++++++++++++++++++++++++++++++++++++++
 common/dconf-shmdir.h  |    3 ++
 engine/dconf-engine.c  |    3 +-
 gsettings/Makefile.am  |    1 +
 service/Makefile.am    |   19 ++++++++--------
 service/dconf-writer.c |   14 ++++++++---
 8 files changed, 83 insertions(+), 14 deletions(-)
---
diff --git a/client/Makefile.am b/client/Makefile.am
index 8e17e7b..9dc20b6 100644
--- a/client/Makefile.am
+++ b/client/Makefile.am
@@ -26,6 +26,7 @@ dconfinclude_HEADERS = \
 
 libdconf_la_LIBADD = $(gio_LIBS)
 libdconf_la_SOURCES = \
+	../common/dconf-shmdir.c	\
 	../common/dconf-paths.c		\
 	../engine/dconf-engine.c	\
 	../gvdb/gvdb-reader.c		\
diff --git a/common/Makefile.am b/common/Makefile.am
index 7423714..0238cd1 100644
--- a/common/Makefile.am
+++ b/common/Makefile.am
@@ -2,4 +2,6 @@ dconfinclude_HEADERS = \
 	dconf-paths.h
 
 EXTRA_DIST = \
+	dconf-shmdir.h	\
+	dconf-paths.h	\
 	dconf-paths.c
diff --git a/common/dconf-shmdir.c b/common/dconf-shmdir.c
new file mode 100644
index 0000000..d94f5c3
--- /dev/null
+++ b/common/dconf-shmdir.c
@@ -0,0 +1,54 @@
+#include "dconf-shmdir.h"
+#include <sys/statfs.h>
+#include <sys/vfs.h>
+#include <errno.h>
+
+#ifndef NFS_SUPER_MAGIC
+#define NFS_SUPER_MAGIC 0x6969
+#endif
+
+static gboolean
+is_local (const gchar *filename)
+{
+  struct statfs buf;
+  gint s;
+
+  do
+    s = statfs (filename, &buf);
+  while (s < 0 && errno == EINTR);
+
+  if (s < 0 && errno == ENOENT)
+    {
+      g_mkdir_with_parents (filename, 0700);
+
+      do
+        s = statfs (filename, &buf);
+      while (s < 0 && errno == EINTR);
+    }
+
+  return s == 0 && buf.f_type != NFS_SUPER_MAGIC;
+}
+
+gchar *
+dconf_shmdir_from_environment (void)
+{
+  gchar *result;
+
+  result = g_strdup (g_getenv ("DCONF_SESSION_DIR"));
+
+  if (result == NULL)
+    {
+      const gchar *cache = g_get_user_cache_dir ();
+
+      if (is_local (cache))
+        result = g_build_filename (cache, "dconf", NULL);
+    }
+
+  if (g_mkdir_with_parents (result, 0700))
+    {
+      g_free (result);
+      result = NULL;
+    }
+
+  return result;
+}
diff --git a/common/dconf-shmdir.h b/common/dconf-shmdir.h
new file mode 100644
index 0000000..953d856
--- /dev/null
+++ b/common/dconf-shmdir.h
@@ -0,0 +1,3 @@
+#include <glib.h>
+
+gchar *dconf_shmdir_from_environment (void);
diff --git a/engine/dconf-engine.c b/engine/dconf-engine.c
index 82fcd17..43d73f2 100644
--- a/engine/dconf-engine.c
+++ b/engine/dconf-engine.c
@@ -1,5 +1,6 @@
 
 #define _XOPEN_SOURCE 600
+#include "dconf-shmdir.h"
 #include "dconf-engine.h"
 #include <gvdb-reader.h>
 #include <string.h>
@@ -26,7 +27,7 @@ dconf_engine_get_session_dir (void)
 
   if (g_once_init_enter (&initialised))
     {
-      session_dir = g_strdup (getenv ("DCONF_SESSION_DIR"));
+      session_dir = dconf_shmdir_from_environment ();
 
       if (session_dir == NULL)
         {
diff --git a/gsettings/Makefile.am b/gsettings/Makefile.am
index 2f81184..9acf7e7 100644
--- a/gsettings/Makefile.am
+++ b/gsettings/Makefile.am
@@ -7,6 +7,7 @@ libdconfsettings_la_LIBADD = $(gio_LIBS)
 libdconfsettings_la_LDFLAGS = -module -avoid-version -shared
 libdconfsettings_la_SOURCES = \
 	../engine/dconf-engine.c	\
+	../common/dconf-shmdir.c	\
 	../gvdb/gvdb-reader.c		\
 	dconfsettingsbackend.c
 
diff --git a/service/Makefile.am b/service/Makefile.am
index f5e3a70..c8ebb06 100644
--- a/service/Makefile.am
+++ b/service/Makefile.am
@@ -1,4 +1,4 @@
-AM_CFLAGS = $(gio_CFLAGS) -I$(top_srcdir)/gvdb -Wall -Wmissing-prototypes -Wwrite-strings
+AM_CFLAGS = $(gio_CFLAGS) -I$(top_srcdir)/gvdb -I$(top_srcdir)/common -Wall -Wmissing-prototypes -Wwrite-strings
 
 libexec_PROGRAMS = dconf-service
 
@@ -7,14 +7,15 @@ dbusservice_DATA = ca.desrt.dconf.service
 
 dconf_service_LDADD = $(gio_LIBS)
 dconf_service_SOURCES = \
-	../gvdb/gvdb-builder.c	\
-	../gvdb/gvdb-reader.c	\
-	dconf-interfaces.h	\
-	dconf-interfaces.c	\
-	dconf-rebuilder.h	\
-	dconf-rebuilder.c	\
-	dconf-writer.h		\
-	dconf-writer.c		\
+	../gvdb/gvdb-builder.c		\
+	../gvdb/gvdb-reader.c		\
+	../common/dconf-shmdir.c	\
+	dconf-interfaces.h		\
+	dconf-interfaces.c		\
+	dconf-rebuilder.h		\
+	dconf-rebuilder.c		\
+	dconf-writer.h			\
+	dconf-writer.c			\
 	service.c
 
 DISTCLEANFILES = ca.desrt.dconf.service
diff --git a/service/dconf-writer.c b/service/dconf-writer.c
index a165ed5..7f7ff7f 100644
--- a/service/dconf-writer.c
+++ b/service/dconf-writer.c
@@ -1,5 +1,6 @@
 #include "dconf-writer.h"
 
+#include "dconf-shmdir.h"
 #include "dconf-rebuilder.h"
 
 #include <unistd.h>
@@ -158,9 +159,14 @@ dconf_writer_init (void)
                  dconf_writer_db_dir, g_strerror (errno));
     }
 
-  dconf_writer_shm_dir = g_build_filename (cache_dir, "dconf", NULL);
+  dconf_writer_shm_dir = dconf_shmdir_from_environment ();
 
-  if (g_mkdir_with_parents (dconf_writer_shm_dir, 0700))
-    g_error ("Can not create directory '%s': %s",
-             dconf_writer_shm_dir, g_strerror (errno));
+  if (dconf_writer_shm_dir == NULL)
+    {
+      dconf_writer_shm_dir = g_build_filename (cache_dir, "dconf", NULL);
+
+      if (g_mkdir_with_parents (dconf_writer_shm_dir, 0700))
+        g_error ("Can not create directory '%s': %s",
+                 dconf_writer_shm_dir, g_strerror (errno));
+    }
 }