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, 25 insertions, 0 deletions

diff --git a/xlators/cluster/afr/src/afr-common.c b/xlators/cluster/afr/src/afr-common.c
index 8993b164b91..8fbca0b6f42 100644
--- a/xlators/cluster/afr/src/afr-common.c
+++ b/xlators/cluster/afr/src/afr-common.c
@@ -993,6 +993,17 @@ afr_local_transaction_cleanup (afr_local_t *local, xlator_t *this)
         afr_entry_lockee_cleanup (&local->internal_lock);
 
         GF_FREE (local->transaction.pre_op);
+
+        GF_FREE (local->transaction.pre_op_sources);
+        if (local->transaction.pre_op_xdata) {
+                for (i = 0; i < priv->child_count; i++) {
+                        if (!local->transaction.pre_op_xdata[i])
+                                continue;
+                        dict_unref (local->transaction.pre_op_xdata[i]);
+                }
+                GF_FREE (local->transaction.pre_op_xdata);
+        }
+
         GF_FREE (local->transaction.eager_lock);
         GF_FREE (local->transaction.fop_subvols);
         GF_FREE (local->transaction.failed_subvols);
@@ -4055,6 +4066,20 @@ afr_transaction_local_init (afr_local_t *local, xlator_t *this)
         if (!local->transaction.pre_op)
                 goto out;
 
+        if (priv->arbiter_count == 1) {
+                local->transaction.pre_op_xdata =
+                        GF_CALLOC (sizeof (*local->transaction.pre_op_xdata),
+                                   priv->child_count, gf_afr_mt_dict_t);
+                if (!local->transaction.pre_op_xdata)
+                        goto out;
+
+                local->transaction.pre_op_sources =
+                        GF_CALLOC (sizeof (*local->transaction.pre_op_sources),
+                                   priv->child_count, gf_afr_mt_char);
+                if (!local->transaction.pre_op_sources)
+                        goto out;
+        }
+
         local->transaction.fop_subvols = GF_CALLOC (sizeof (*local->transaction.fop_subvols),
 						    priv->child_count,
 						    gf_afr_mt_char);