core: provide infra to make any xlator pass-through

updates: #304

Change-Id: If6a13d2e56b195390a386d720103a882e077f66c
Signed-off-by: Amar Tumballi <amarts@redhat.com>

3 files changed, 41 insertions, 12 deletions

diff --git a/libglusterfs/src/stack.h b/libglusterfs/src/stack.h
index e7d0b3ff7f4..87fbef9e3c9 100644
--- a/libglusterfs/src/stack.h
+++ b/libglusterfs/src/stack.h
@@ -258,6 +258,7 @@ STACK_RESET (call_stack_t *stack)
                 xlator_t     *old_THIS = NULL;                          \
                 xlator_t     *next_xl = obj;                            \
                 typeof(fn)    next_xl_fn = fn;                          \
+                int opn = get_fop_index_from_fn((next_xl), (fn));       \
                                                                         \
                 frame->this = next_xl;                                  \
                 frame->wind_to = #fn;                                   \
@@ -269,13 +270,15 @@ STACK_RESET (call_stack_t *stack)
                               frame->root, old_THIS->name,              \
                               THIS->name);                              \
                 /* Need to capture counts at leaf node */               \
-                if (!next_xl->children) {                               \
-                        int op = get_fop_index_from_fn((next_xl), (fn)); \
-                        GF_ATOMIC_INC (next_xl->stats.total.metrics[op].fop); \
-                        GF_ATOMIC_INC (next_xl->stats.interval.metrics[op].fop); \
+                if (!next_xl->pass_through && !next_xl->children) {     \
+                        GF_ATOMIC_INC (next_xl->stats.total.metrics[opn].fop); \
+                        GF_ATOMIC_INC (next_xl->stats.interval.metrics[opn].fop); \
                         GF_ATOMIC_INC (next_xl->stats.total.count);     \
                         GF_ATOMIC_INC (next_xl->stats.interval.count);  \
                 }                                                       \
+                if (next_xl->pass_through) {                            \
+                        next_xl_fn = (void *)*((&next_xl->pass_through_fops->stat) + (opn - 1)); \
+                }                                                       \
                 next_xl_fn (frame, next_xl, params);                    \
                 THIS = old_THIS;                                        \
         } while (0)
@@ -298,6 +301,7 @@ STACK_RESET (call_stack_t *stack)
         do {                                                            \
                 call_frame_t *_new = NULL;                              \
                 xlator_t     *old_THIS = NULL;                          \
+                typeof(fn)    next_xl_fn = fn;                          \
                                                                         \
                 _new = mem_get0 (frame->root->pool->frame_mem_pool);    \
                 if (!_new) {                                            \
@@ -332,11 +336,15 @@ STACK_RESET (call_stack_t *stack)
                 if (obj->ctx->measure_latency)                          \
                         timespec_now (&_new->begin);                    \
                 _new->op = get_fop_index_from_fn ((_new->this), (fn));  \
-                GF_ATOMIC_INC (obj->stats.total.metrics[_new->op].fop); \
-                GF_ATOMIC_INC (obj->stats.interval.metrics[_new->op].fop); \
-                GF_ATOMIC_INC (obj->stats.total.count);                 \
-                GF_ATOMIC_INC (obj->stats.interval.count);              \
-                fn (_new, obj, params);                                 \
+                if (!obj->pass_through) {                               \
+                        GF_ATOMIC_INC (obj->stats.total.metrics[_new->op].fop); \
+                        GF_ATOMIC_INC (obj->stats.interval.metrics[_new->op].fop); \
+                        GF_ATOMIC_INC (obj->stats.total.count);         \
+                        GF_ATOMIC_INC (obj->stats.interval.count);      \
+                } else {                                                \
+                        next_xl_fn = (void *)*((&obj->pass_through_fops->stat) + (_new->op - 1)); \
+                }                                                       \
+                next_xl_fn (_new, obj, params);                         \
                 THIS = old_THIS;                                        \
         } while (0)
 
diff --git a/libglusterfs/src/xlator.c b/libglusterfs/src/xlator.c
index 4071a7c0569..466be5e3a3a 100644
--- a/libglusterfs/src/xlator.c
+++ b/libglusterfs/src/xlator.c
@@ -15,9 +15,11 @@
 #include "defaults.h"
 #include "libglusterfs-messages.h"
 
-#define SET_DEFAULT_FOP(fn) do {			\
-                if (!xl->fops->fn)			\
-                        xl->fops->fn = default_##fn;	\
+#define SET_DEFAULT_FOP(fn) do {                                        \
+                if (!xl->fops->fn)                                      \
+                        xl->fops->fn = default_##fn;                    \
+                if (!xl->pass_through_fops->fn)                         \
+                        xl->pass_through_fops->fn = default_##fn;       \
         } while (0)
 
 #define SET_DEFAULT_CBK(fn) do {			\
@@ -54,6 +56,9 @@ fill_defaults (xlator_t *xl)
                 return;
         }
 
+        if (!xl->pass_through_fops)
+                xl->pass_through_fops = default_fops;
+
         SET_DEFAULT_FOP (create);
         SET_DEFAULT_FOP (open);
         SET_DEFAULT_FOP (stat);
@@ -386,6 +391,13 @@ int xlator_dynload_newway (xlator_t *xl)
                               xl->name);
         }
 
+        xl->pass_through_fops = xlapi->pass_through_fops;
+        if (!xl->pass_through_fops) {
+                gf_msg_trace ("xlator", 0, "%s: method missing (pass_through_fops), "
+                              "falling back to default",
+                              xl->name);
+        }
+
         vol_opt = GF_CALLOC (1, sizeof (volume_opt_list_t),
                              gf_common_mt_volume_opt_list_t);
         if (!vol_opt) {
diff --git a/libglusterfs/src/xlator.h b/libglusterfs/src/xlator.h
index bfab57a0133..b03998d36af 100644
--- a/libglusterfs/src/xlator.h
+++ b/libglusterfs/src/xlator.h
@@ -1039,6 +1039,10 @@ struct _xlator {
 
         /* identifier: a full string which can unique identify the xlator */
         char *identifier;
+
+        /* Is this pass_through? */
+        gf_boolean_t   pass_through;
+        struct xlator_fops    *pass_through_fops;
 };
 
 typedef struct {
@@ -1123,6 +1127,11 @@ typedef struct {
         /* dumpops: a structure again, with methods to dump the details.
            optional. */
         struct xlator_dumpops  *dumpops;
+
+        /* struct pass_through_fops: optional. provides all the filesystem
+           operations which should be used if the xlator is marked as pass_through */
+        /* by default, the default_fops would be used */
+        struct xlator_fops *pass_through_fops;
 } xlator_api_t;
 
 #define xlator_has_parent(xl) (xl->parents != NULL)