jbr/locking: Define path for lock/unlock fops in JBR

lock/unlock fops need to be handled differently than
other 'regular' fops, so as to avoid chances of deadlock
in blocking calls. This patch addresses the same in the
following manner, with a caveat.

1. On receiving the fop if the node is a follower, it
   performs the operation (irrespective of it being
   lock/unlock fop), and returns the result.

2. If the node is a leader it follows the following paths
   for lock and unlock fops:

   For lock fops :
   -> It performs the fop on itself. If it is a failure, it
      sends -ve ack to the client. If it is successful, it
      dispatches the fop to the followers.
   -> On receiving responses from the followers, it checks
      for quorum (including the leader's outcome). If
      quorum is met, it sends +ve ack to the client.
   -> If quorum is not met, then it *should* issue a rollback
      to the followers, followed by the rollback on the leader.
      It should then send -ve ack to he client.

   For unlock fops:
   -> It dispatches the fop on the followers first.
   -> On receiving responses from the followers, it performs
      the fop on itself. On completion, it checks for quorum
      (including the leader's outcome). If quorum is met, it
      sends +ve ack to the client.
   -> If quorum is not met, then it *should* issue a rollback
      on itslef, followed by the rollback on the followers.
      It should then send -ve ack to he client.

Caveat:
   -> jbr-server does not have a rollback framework yet,
      and hence this patch does not perform the rollbacks as
      discussed in the failure scenarios above. The rollback
      framework will be a different dependent patch.

Change-Id: I26961b27cb85f324c1ffeee80e82ec082ffa4465
BUG: 1333370
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/14226
Smoke: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/xlators/experimental/jbr-client/src/jbr-messages.h b/xlators/experimental/jbr-client/src/jbr-messages.h
index 61fa725d56a..626c4fd3eaa 100644
--- a/xlators/experimental/jbr-client/src/jbr-messages.h
+++ b/xlators/experimental/jbr-client/src/jbr-messages.h
@@ -102,4 +102,12 @@
  */
 #define J_MSG_QUORUM_NOT_MET                 (JBR_COMP_BASE + 9)
 
+/*!
+ * @messageid
+ * @diagnosis
+ * @recommendedaction
+ */
+#define J_MSG_LOCK_FAILURE                  (JBR_COMP_BASE + 10)
+
+
 #endif /* _JBR_MESSAGES_H_ */