core: add dispatch table for init/fini

This adds a layer of indirection so that derivative translators such as
NUFA and switch can refer to the parent's init/fini (in both cases DHT's)
without having to create stub functions.

Change-Id: I1af1fea70a9ddd2aa20485af7ae65f9660f19dd6
BUG: 924490
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/4709
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>

2 files changed, 27 insertions, 10 deletions

diff --git a/libglusterfs/src/xlator.c b/libglusterfs/src/xlator.c
index 9bde4fa8f6c..da5501b2cfa 100644
--- a/libglusterfs/src/xlator.c
+++ b/libglusterfs/src/xlator.c
@@ -183,7 +183,7 @@ xlator_dynload (xlator_t *xl)
         char              *name = NULL;
         void              *handle = NULL;
         volume_opt_list_t *vol_opt = NULL;
-
+        class_methods_t   *vtbl = NULL;
 
         GF_VALIDATE_OR_GOTO ("xlator", xl, out);
 
@@ -218,16 +218,28 @@ xlator_dynload (xlator_t *xl)
                 goto out;
         }
 
-        if (!(*VOID(&xl->init) = dlsym (handle, "init"))) {
-                gf_log ("xlator", GF_LOG_WARNING, "dlsym(init) on %s",
-                        dlerror ());
-                goto out;
-        }
+        /*
+         * If class_methods exists, its contents override any definitions of
+         * init or fini for that translator.  Otherwise, we fall back to the
+         * older method of looking for init and fini directly.
+         */
+        vtbl = dlsym(handle,"class_methods");
+        if (vtbl) {
+                xl->init = vtbl->init;
+                xl->fini = vtbl->fini;
+        }
+        else {
+                if (!(*VOID(&xl->init) = dlsym (handle, "init"))) {
+                        gf_log ("xlator", GF_LOG_WARNING, "dlsym(init) on %s",
+                                dlerror ());
+                        goto out;
+                }
 
-        if (!(*VOID(&(xl->fini)) = dlsym (handle, "fini"))) {
-                gf_log ("xlator", GF_LOG_WARNING, "dlsym(fini) on %s",
-                        dlerror ());
-                goto out;
+                if (!(*VOID(&(xl->fini)) = dlsym (handle, "fini"))) {
+                        gf_log ("xlator", GF_LOG_WARNING, "dlsym(fini) on %s",
+                                dlerror ());
+                        goto out;
+                }
         }
 
         if (!(*VOID(&(xl->notify)) = dlsym (handle, "notify"))) {
diff --git a/libglusterfs/src/xlator.h b/libglusterfs/src/xlator.h
index 607f0dcecee..2567fc70c48 100644
--- a/libglusterfs/src/xlator.h
+++ b/libglusterfs/src/xlator.h
@@ -827,6 +827,11 @@ struct _xlator {
         gf_boolean_t        is_autoloaded;
 };
 
+typedef struct {
+        int32_t (*init) (xlator_t *this);
+        void    (*fini) (xlator_t *this);
+} class_methods_t;
+
 #define xlator_has_parent(xl) (xl->parents != NULL)
 
 #define XLATOR_NOTIFY(_xl, params ...)          \