libglusterfs: Fix volume_options_t struct

The volume_options_t struct was modified and a new member was introduced
in the middle of the struct. This caused GD2 to crash when it tried to
read the volume options. The new member has been moved to the end of the
struct to correct this.

And a note has been added to notify developers on how to modify this
struct, and the xlator_api_t struct.

Updates: gluster/glusterfs#302

Change-Id: I2e9899ec10516be29c7e9d574da53be8ec17a99e
Signed-off-by: Kaushal M <kaushal@redhat.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/libglusterfs/src/xlator.h b/libglusterfs/src/xlator.h
index 0e50bef1cb6..bfab57a0133 100644
--- a/libglusterfs/src/xlator.h
+++ b/libglusterfs/src/xlator.h
@@ -1052,6 +1052,10 @@ typedef struct {
 /* This would be the only structure which needs to be exported by
    the translators. For the backward compatibility, in 4.x series
    even the old exported fields will be supported */
+/* XXX: This struct is in use by GD2, and hence SHOULD NOT be modified.
+ * If the struct must be modified, see instructions at the comment with
+ * GD2MARKER below.
+ */
 typedef struct {
         /* op_version: will be used by volume generation logic to figure
            out whether to insert it in graph or no, based on cluster's
@@ -1075,6 +1079,13 @@ typedef struct {
            volume file, then that should be defined here. optional. */
         volume_option_t *options;
 
+        /* XXX: GD2MARKER
+         * If a new member that needs to be visible to GD2 is introduced,
+         * add it above this comment.
+         * Any other new members need to be added below this comment, or at the
+         * end of the struct
+         */
+
         /* init(): mandatory method, will be called during the
            graph initialization */
         int32_t (*init) (xlator_t *this);