tier/ctr: Solving DB Lock issue due to write contention from db connections

Problem: The DB on the brick is been accessed by CTR, for write and
tier migrator, for read and write. The write from tier migrator is reseting
the heat counters after a cycle. Since we are using sqlite, two connections
trying to write would cause a db lock contention. As a result CTR used to fail
to update the db.

Solution: Using the same db connection of CTR for reseting the heat counters.
1) Introducted a new IPC FOP for CTR
2) After the query do a ipc syncop to the underlying client xlator associated
   to the brick.
3) CTR in brick will catch the IPC FOP and cleat the heat counters.

Change-Id: I53306bfc08dcdba479deb4ccc154896521336150
BUG: 1260730
Signed-off-by: Joseph Fernandes <josferna@redhat.com>
Reviewed-on: http://review.gluster.org/12031
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Dan Lambright <dlambrig@redhat.com>
Tested-by: Dan Lambright <dlambrig@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/xlators/cluster/dht/src/tier.h b/xlators/cluster/dht/src/tier.h
index 88fb7844dad..76ff27d5932 100644
--- a/xlators/cluster/dht/src/tier.h
+++ b/xlators/cluster/dht/src/tier.h
@@ -31,6 +31,7 @@
 #define TIMER_SECS 3600
 
 #include "gfdb_data_store.h"
+#include "gfdb_sqlite3.h"
 #include <ctype.h>
 #include <sys/stat.h>
 
@@ -56,10 +57,16 @@ typedef struct _gfdb_brick_dict_info {
         query_cbk_args_t       *_query_cbk_args;
 } _gfdb_brick_dict_info_t;
 
+typedef struct brick_list {
+        xlator_t          *xlator;
+        char              *brick_db_path;
+        struct list_head  list;
+} brick_list_t;
+
 typedef struct _dm_thread_args {
         xlator_t                *this;
         gf_defrag_info_t        *defrag;
-        dict_t                  *brick_list;
+        struct list_head        *brick_list;
         int                     freq_time;
         int                     return_value;
 } promotion_args_t, demotion_args_t;