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

This is a backport of 12031.

> 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>

Signed-off-by: Dan Lambright <dlambrig@redhat.com>

Conflicts:
	xlators/cluster/dht/src/tier.c

Change-Id: I88aa289cdf21e216b42c3d8ccfb4e7e828b43772
BUG: 1262341
Reviewed-on: http://review.gluster.org/12161
Reviewed-by: Joseph Fernandes
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Tested-by: Dan Lambright <dlambrig@redhat.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/xlators/cluster/dht/src/tier.h b/xlators/cluster/dht/src/tier.h
index 34631b0a841..d5fbba655e5 100644
--- a/xlators/cluster/dht/src/tier.h
+++ b/xlators/cluster/dht/src/tier.h
@@ -61,10 +61,16 @@ 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;