afr: add arbitration support

Add logic in afr to work in conjunction with the arbiter xlator when a
replica 3 arbiter volume is created. More specifically, this patch:

* Enables full locks for afr data transaction for such volumes.
* Removes the upfront marking of pending xattrs at the time of pre-op
  and defer it to post-op. (This is an arbiter independent change and is made for all afr transactions.)
* After pre-op stage, check if we can proceed with the fop stage without
  ending up in split-brain by examining the changelog xattrs.
* Unwinds the fop with failure if only one source was available at the
   time of pre-op and the fop happened to fail on particular source brick.
* Skips data self-heal if arbiter brick is the only source available.
* Adds the arbiter-count option to the shd graph.

This patch is a part of the arbiter logic implementation for 3 way AFR
details of which can be found at http://review.gluster.org/#/c/9656/

Change-Id: I9603db9d04de5626eb2f4d8d959ef5b46113561d
BUG: 1199985
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: http://review.gluster.org/10258
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/xlators/cluster/afr/src/afr-inode-write.c b/xlators/cluster/afr/src/afr-inode-write.c
index f712166e44d..f9fde44e9e4 100644
--- a/xlators/cluster/afr/src/afr-inode-write.c
+++ b/xlators/cluster/afr/src/afr-inode-write.c
@@ -37,7 +37,7 @@
 #include "protocol-common.h"
 
 #include "afr-transaction.h"
-
+#include "afr-self-heal.h"
 
 static void
 __afr_inode_write_finalize (call_frame_t *frame, xlator_t *this)
@@ -97,6 +97,8 @@ __afr_inode_write_finalize (call_frame_t *frame, xlator_t *this)
 			}
 		}
 	}
+
+        afr_txn_arbitrate_fop_cbk (frame, this);
 }
 
 
@@ -342,6 +344,7 @@ afr_do_writev (call_frame_t *frame, xlator_t *this)
 {
         call_frame_t    *transaction_frame = NULL;
         afr_local_t     *local             = NULL;
+        afr_private_t   *priv              = NULL;
         int             ret   = -1;
         int             op_errno = ENOMEM;
 
@@ -350,6 +353,7 @@ afr_do_writev (call_frame_t *frame, xlator_t *this)
                 goto out;
 
         local = frame->local;
+        priv = this->private;
         transaction_frame->local = local;
 	frame->local = NULL;
 
@@ -379,6 +383,12 @@ afr_do_writev (call_frame_t *frame, xlator_t *this)
                 local->transaction.start   = local->cont.writev.offset;
                 local->transaction.len     = iov_length (local->cont.writev.vector,
                                                          local->cont.writev.count);
+
+                /*Lock entire file to avoid network split brains.*/
+                if (priv->arbiter_count == 1) {
+                        local->transaction.start   = 0;
+                        local->transaction.len     = 0;
+                }
         }
 
         ret = afr_transaction (transaction_frame, this, AFR_DATA_TRANSACTION);